Generalized parton distributions of the pion

a r X i v :0712.1947v 2 [h e p -p h ] 24 D e c 2007Generalized Parton Distributions and Nucleon Form FactorsO.V.Selyugin2Momentum transfer dependence of GPDs and pro-ton form factorsOur proposal consists in the attempt tofind a simple ansatz which will be good enough to describe the form factors of the proton and neutron taking into account a number of new data that have appeared in the last years.Let us keep the simple Gaussian ansatz but using some new conditions.To support the proposal[3]and[4]we chose the t-dependence of GPDs in the formH q(x,t)=q(x)exp[a+(1−x)2x bt].(3)with the free parameters b=0.4(determined mostly by the power2of the factor1−x), a±(a+-for H and a−-for E).All these parameters werefixed by analyzing the data on the ratio of proton Pauli and Dirac form-factors.The function q(x)was taken in the same normalization pointµ2=1GeV2as in[6],which is based on the MRST2002global fit[7].In all our calculations we restricted ourselves to the contributions of u and d quarks in H q and E q with E u(x)=k u/N u(1−x)κ1u(x),E d(x)=k dmethod.The other method uses the polarized differential cross section to obtain these form factors.In our model we can obtain the results of both methods by changing the slope of E.So we examined two versions differing by the slopes a−.One can now use the information on the neutron form factors in order to choose the more realistic version.3Neutron form factorsUsing the model developed for proton we can calculate the neutron form factors.For that the isotopic invariance can be used to relate the proton GPDs to the neutron ones,Hence, we do not change any parameters and preserve the same t-dependence of GPDs as in the case of proton.Again,we take two values of the slope a−as in the case of the proton form factors with the same size,which correspond to version(I)and version(II)below.Our calculation of the G n E is shown in Fig.2a.Evidently,thefirst version is in better agreement with experimental data.Therefore, neutron data support the results obtained by polarization transfer method.This conclusion is supported by the calculations of G n M shown in Fig.2b.In this case, it is clearly seen that our parameterization normalized using the proton form-factors ratio from the polarization experiments describes these neutron data quite well.4ConclusionsThe proposed version of Gaussian t-dependence of GPDs reproduces the electromagnetic structure of the proton and neutron sufficiently well.We show that changing only the slope parameters a−of E q it is possible to obtain both the Rosenbluth and Polarization data on the ratio of Pauli and dirac electromagnetic proton form-factors.The description of neutron form-factors is essentially better with the slope parameterfitted to proton polarization transfer data.This is in accordance with the recent theoretical analysis[14].(a)(b)Figure2a.G n E(hard and dot-dashed lines correspond to version(I)and(II));experimental data from[12].Figure2b.G n M(hard and dot-dashed lines correspond to version(I)and(II));experimental data from[13].Acknowledgments We are indebted to M.Anselmino,S.V.Goloskokov,P.Kroll, E.A.Kuraev,E.Predazzi and E.Tomasi-Gustafsson for useful discussions.This work was partially supported by the Deutsche Forschungsgemeinschaft,grant436RUS113/881/0, the Russian Foundation for Basic Research(Grant03-02-16816)and the Russian Feder-ation Ministry of Education and Science(Grant MIREA2.2.2.2.6546). References[1]D.Muller et al.,Fortschr.Phys.42,101(1994);X.Ji,Phys.Rev.Lett.78,610(1998);A.V.Radyushkin,Phys.Rev,D56,5524(1997).[2]M.Burkardt,Phys.Rev.D62,071503(2000).[3]A.V.Radyushkin,Phys.Rev.D58,11400(1998).[4]M.Burkardt,Phys.Lett.B595,245(2004).[5]M.Diehl,Th Feldmann,R.Jakob and P.Kroll,Eur.Phys.J.C39,1(2005).[6]M.Guidal,M.V.Polyakov,A.V.Radyushkin,and M.Vanderhaeghen,Phys.RevD(2005).[7]A.D.Martin et al.,Phys.Lett.B531,216(2002).[8]P.Stoler,Phys.Rev.D65(2002)053013;Phys.Rev.Lett.,91,172303(2003).[9]A.F.Sill et al.,Phys.Rev.D48,29(1993).[10]S.J.Brodsky,hep-ph/0208158.[11]M.K.Jones et al.,Phys.Rev.Lett.,84,1398(2000);O.Gayou et al.,Phys.Rev.C64,038202(2001);O.Gayou et al.,Phys.Rev.Lett.,88,092301(2002);V.Punjabil et al.,Phys.Rev.C71,055202(2005).[12]B.Plaster et al.,Phys.Rev.C73,025205(2006);R.Madey,et al.,Phys.Rev.Lett.91,122002(2003);I.G.Warren,et al.,Phys.Rev.Lett.92,042301(2004).[13]S.Rock,et al.,Phys.Rev.Lett.49,1139(1982).[14]Yu.M.Bystritskiy,E.A.Kuraev and E.Tomasi-Gustafsson,Phys.Rev.C75(2007)015207.。

Single gate optimization for plastic injection moldAbstract:Abstract: This paper deals with a methodology for single gate location optimization for plastic injection mold. The objective of the gate optimization is to minimize the warpage of injection molded parts, because warpage is a crucial quality issue for most injection molded parts while it is influenced greatly by the gate location. Feature warpage is defined as the ratio of maximum displacement on the feature surface to the projected length of the feature surface to describe part warpage. The optimization is combined with the numerical simulation technology to find the optimal gate location, in which the simulated annealing algorithm is used to search for the optimum. Finally, an example is discussed in the paper and it can be concluded that the proposed method is effective.Key words: Injection mold, Gate location, Optimization, Feature warpage.INTRODUCTIONPlastic injection molding is a widely used, com- plex but highly efficient technique for producing a large variety of plastic products, particularly those with high production requirement, tight tolerance, and complex shapes. The quality of injection molded parts is a function of plastic material, part geometry, mold structure and process conditions. The most important part of an injection mold basically is the following three sets of components: cavities, gates and runners, and cooling system.Lam and Seow (2000) and Jin and Lam (2002) achieved cavity balancing by varying the wall thick- ness of the part. A balance filling process within the cavity gives an evenly distributed pressure and tem- perature which can drastically reduce the warpage of the part. But the cavity balancing is only one of the important influencing factors of part qualities. Espe- cially, the part has its functional requirements, and its thicknesses should not be varied usually.From the pointview of the injection mold design, a gate is characterized by its size and location, and the runner system by the size and layout. The gate size and runner layout are usually determined as constants. Relatively, gate locations and runner sizes are more flexible, which can be varied to influence the quality of the part. As a result, they are often the design pa- rameters for optimization.Lee and Kim (1996a) optimized the sizes of runners and gates to balance runner system for mul- tiple injection cavities. The runner balancing was described as the differences of entrance pressures for a multi-cavity mold with identical cavities, and as differences of pressures at theend of the melt flow path in each cavity for a family mold with different cavity volumes and geometries. The methodology has shown uniform pressure distributions among the cavities during the entire molding cycle of multiple cavities mold.Zhai et al.(2005a) presented the two gate loca- tion optimization of one molding cavity by an effi- cient search method based on pressure gradient (PGSS), and subsequently positioned weld lines to the desired locations by varying runner sizes for multi-gate parts (Zhai et al., 2006). As large-volume part, multiple gates are needed to shorten the maxi- mum flow path, with a corresponding decrease in injection pressure. The method is promising for de- sign of gates and runners for a single cavity with multiple gates.Many of injection molded parts are produced with one gate, whether in single cavity mold or in multiple cavities mold. Therefore, the gate location of a single gate is the most common design parameter for optimization. A shape analysis approach was pre- sented by Courbebaisse and Garcia (2002), by which the best gate location of injection molding was esti- mated. Subsequently, they developed this methodol- ogy further and applied it to single gate location op- timization of an L shape example (Courbebaisse,2005). It is easy to use and not time-consuming, while it only serves the turning of simple flat parts with uniform thickness.Pandelidis and Zou (1990) presented the opti- mization of gate location, by indirect quality measures relevant to warpage and material degradation, which is represented as weighted sum of a temperature dif- ferential term, an over-pack term, and a frictional overheating term. Warpage is influenced by the above factors, but the relationship between them is not clear. Therefore, the optimization effect is restricted by the determination of the weighting factors.Lee and Kim (1996b) developed an automated selection method of gate location, in which a set of initial gate locations were proposed by a designer and then the optimal gate was located by the adjacent node evaluation method. The conclusion to a great extent depends much on the human design er’s in tuition, because the first step of the method is based on the desi gner’s proposition. So the result is to a large ex- tent limited to the designer’s experience.Lam and Jin (2001) developed a gate location optimization method based on the minimization of the Standard Deviation of Flow Path Length (SD[L]) and Standard Deviation of Filling Time (SD[T]) during the molding filling process. Subsequently, Shen et al.(2004a; 2004b) optimized the gate location design by minimizing the weighted sum of filling pressure, filling time difference between different flow paths, temperature difference, and over-pack percentage. Zhai et al.(2005b) investigated optimal gate location with evaluation criteria of injection pressure at the end of filling. These researchers presented the objec- tive functions asperformances of injection molding filling operation, which are correlated with product qualities. But the correlation between the perform- ances and qualities is very complicated and no clear relationship has been observed between them yet. It is also difficult to select appropriate weighting factors for each term.A new objective function is presented here to evaluate the warpage of injection molded parts to optimize gate location. To measure part quality di- rectly, this investigation defines feature warpage to evaluate part warpage, which is evaluated from the “flow plus warpage” simulation outputs of Moldflow Plastics Insight (MPI) software. The objective func- tion is minimized to achieve minimum deformation in gate location optimization. Simulated annealing al- gorithm is employed to search for the optimal gate location. An example is given to illustrate the effec- tivity of the proposed optimization procedure.QUALITY MEASURES: FEATURE WARPGEDefinition of feature warp ageTo apply optimization theory to the gate design, quality measures of the part must be specified in the first instance. The term “quality” may be referred to many product properties, such as mechanical, thermal, electrical, optical, ergonomical or geometrical prop- erties. There are two types of part quality measures: direct and indirect. A model that predicts the proper- ties from numerical simulation results would be characterized as a direct quality measure. In contrast, an indirect measure of part quality is correlated with target quality, but it cannot provide a direct estimate of that quality.For warpage, the indirect quality measures in related works are one of performances of injection molding flowing behavior or weighted sum of those. The performances are presented as filling time dif- ferential along different flow paths, temperature dif- ferential, over-pack percentage, and so on. It is ob- vious that warpage is influenced by these perform- ances, but the relationship between warpage and these performances is not clear and the determination of these weighting factors is rather difficult. Therefore, the optimization with the above objective function probably will not minimize part warpage even with perfect optimization technique. Sometimes, improper weighting factors will result in absolutely wrong re- sults.Some statistical quantities calculated from the nodal displacements were characterized as direct quality measures to achieve minimum deformation in related optimization studies. The statistical quantities are usually a maximum nodal displacement, an av- erage of top 10 percentile nodal displacements, and an overall average nodal displacement (Lee and Kim,1995; 1996b). These nodal displacements are easy to obtain from the simulation results, the statistical val- ues, to some extents, representing the deformation. But the statistical displacement cannot effectively describe the deformation of the injection molded parts.In industry, designers and manufacturers usually pay more attention to the degree of part warpage on some specific features than the whole deformation of the injection molded parts. In this study, feature warpage is defined to describe the deformation of the injection parts. The feature warpage is the ratio of the maximum displacement of the feature surface to the projected length of the feature surface (Fig.1):where γ is the feature warpage, h is the maximum displacement on the feature surface deviating from the reference platform, and L is the projected length of the feature surface on a reference direction paralleling the reference platform.For complicated features (only plane feature discussed here), the feature warpage is usually sepa- rated into two constituents on the reference plane, which are represented on a 2D coordinate system:where γx, γy are the constituent feature warpages in the X, Y direction, and L x, L y are the projected lengths of the feature surface on X, Y component.Evaluation of feature wa rpageAfter the determination of target feature com- bined with corresponding reference plane and pro- jection direction, the value of L can be calculated immediately from the part with the calculating method of analytic geometry (Fig.2). L is a constant for any part on the specified feature surface and pro- jected direction. But the evaluation of h is more com- plicated than that of L.Simulation of injection molding process is a common technique to forecast the quality of part de- sign, mold design and process settings. The results of warpage simulation are expressed as the nodal de- flections on X, Y, Z component (W x, W y, W z), and the nodal displacement W. W is the vector length of vector sum of W x·i, W y·j, and W z·k, where i, j, k are the unit vectors on X, Y, Z component. The h is the maximum displacement of the nodes on the feature surface, which is correlated with the normal orientation of the reference plane, and can be derived from the results of warpage simulation.To calculate h, the deflection of ith node is evaluated firstly as follows:where W i is the deflection in the normal direction of the reference plane of ith node; W ix, W iy, W iz are the deflections on X, Y, Z component of ith node; α,β,γ are the angles of normal vector of the reference; A and B are the terminal nodes of the feature to projectingdirection (Fig.2); WA and WB are the deflections of nodes A and B:where W Ax, W Ay, W Az are the deflections on X, Y, Zcomponent of node A; W Bx, W By and W Bz are the de- flections on X, Y, Z component of node B; ωiA and ωiB are the weighting factors of the terminal node deflections calculated as follows:where L iA is the projector distance between ith node and node A. Ultimately, h is the maximum of the absolute value of W i:In industry, the inspection of the warpage is carried out with the help of a feeler gauge, while the measured part should be placed on a reference plat- form. The value of h is the maximum numerical reading of the space between the measured part sur- face and the reference platform.GATE LOCATION OPTIMIZATION PROBLEM FORMATIONThe quality term “warpag e”means the perma- nent deformation of the part, which is not caused by an applied load. It is caused by differential shrinkage throughout the part, due to the imbalance of polymer flow, packing, cooling, and crystallization.The placement of a gate in an injection mold is one of the most important variables of the total mold design. The quality of the molded part is greatly af- fected by the gate location, because it influences the manner that the plastic flows into the mold cavity. Therefore, different gate locations introduce inho- mogeneity in orientation, density, pressure, and temperature distribution, accordingly introducing different value and distribution of warpage. Therefore, gate location is a valuable design variable to minimize the injection molded part warpage. Because the cor- relation between gate location and warpage distribu- tion is to a large extent independent of the melt and mold temperature, it is assumed that the moldingconditions are kept constant in this investigation. The injection molded part warpage is quantified by the feature warpage which was discussed in the previous section.The single gate location optimization can thus be formulated as follows:Minimize:Subject to:where γ is the feature warpage; p is the injection pressure at the gate position; p0 is the allowable in- jection pressure of injection molding machine or the allowable injection pressure specified by the designer or manufacturer; X is the coordinate vector of the candidate gate locations; X i is the node on the finite element mesh model of the part for injection molding process simulation; N is the total number of nodes.In the finite element mesh model of the part, every node is a possible candidate for a gate. There- fore, the total number of the possible gate location N p is a function of the total number of nodes N and the total number of gate locations to be optimized n:In this study, only the single-gate location problem is investigated.SIMULATED ANNEALING ALGORITHMThe simulated annealing algorithm is one of the most powerful and popular meta-heuristics to solve optimization problems because of the provision of good global solutions to real-world problems. The algorithm is based upon that of Metropolis et al. (1953), which was originally proposed as a means to find an equilibrium configuration of a collection of atoms at a given temperature. The connection be- tween this algorithm and mathematical minimization was first noted by Pincus (1970), but it was Kirkpatrick et al.(1983) who proposed that it formed the basis of an optimization technique for combina- tional (and other) problems.To apply the simulated annealing method to op timization problems, the objective function f is used as an energy function E. Instead of finding a low energy configuration, the problem becomes to seek an approximate global optimal solution. The configura- tions of the values of design variables are substituted for the energy configurations of the body, and the control parameter for the process is substituted for temperature. A random number generator is used as a way of generating new values for the design variables. It is obvious that this algorithm just takes the mini- mization problems into account. Hence, while per- forming a maximization problem the objective func- tion is multiplied by (−1) to obtain a capable form.The major advantage of simulated annealing algorithm over other methods is the ability to avoid being trapped at local minima. This algorithm em- ploys a random search, which not only accepts changes that decrease objective function f, but also accepts some changes that increase it. The latter are accepted with a probability pwhere ∆f is the increase of f, k is Boltzm an’s constant, and T is a control parameter which by analogy with the original application is known as the system “tem perature”irrespective of the objective function involved.In the case of gate location optimization, the implementation of this algorithm is illustrated in Fig.3, and this algorithm is detailed as follows:(1) SA algorithm starts from an initial gate loca- tion X old with an assigned value T k of the “tempera- ture”parameter T (the “temperature” counter k is initially set to zero). Proper control parameter c (0<c<1) in annealing process and Markov chain N generateare given.(2) SA algorithm generates a new gate location X new in the neighborhood of X old and the value of the objective function f(X) is calculated.(3) The new gate location will be accepted with probability determined by the acceptance functionFig.3 The flow chart of the simulated annealing algorithmAPPLICATION AND DISCUSSIONThe application to a complex industrial part is presented in this section to illustrate the proposed quality measure and optimization methodology. The part is provided by a manufacturer, as shown in Fig.4. In this part, the flatness of basal surface is the most important profileprecision requirement. Therefore, the feature warpage is discussed on basal surface, in which reference platform is specified as a horizontal plane attached to the basal surface, and the longitu- dinal direction is specified as projected reference direction. The parameter h is the maximum basal surface deflection on the normal direction, namely the vertical direction, and the parameter L is the projected length of the basal surface to the longitudinal direc- tion.Fig.4 Industrial part provided by the manufac tur e rThe material of the part is Nylon Zytel 101L (30% EGF, DuPont Engineering Polymer). The molding conditions in the simulation are listed in T able 1. Fig.5 shows the finite element mesh model ofthe part employed in the numerical simulation. It has1469 nodes and 2492 elements. The objective func- tion, namely feature warpage, is evaluated by Eqs.(1), (3)~(6). The h is evaluated from the results of “Flow+Warp” Analysis Sequence in MPI by Eq.(1), and the L is measured on the industrial part immediately, L=20.50 mm.MPI is the most extensive software for the in- jection molding simulation, which can recommend the best gate location based on balanced flow. Gate location analysis is an effective tool for gate location design besides empirical method. For this part, the gate location analysis of MPI recommends that the best gate location is near node N7459, as shown in Fig.5. The part warpage is simulated based on this recommended gate and thus the feature warpage is evaluated: γ=5.15%, which is a great value. In trial manufacturing, part warpage is visible on the sample work piece. This is unacceptable for the manufacturer.The great warpage on basal surface is caused bythe uneven orientation distribution of the glass fiber, as shown in Fig.6a. Fig.6a shows that the glass fiber orientation changes from negative direction to posi- tive direction because of the location of the gate, par- ticularly thegreatest change of the fiber orientation appears near the gate. The great diversification of fiber orientation caused by gate location introduces serious differential shrinkage. Accordingly, the fea- ture warpage is notable and the gate location must be optimized to reduce part warpageT o optimize the gate location, the simulated an- nealing searching discussed in the section “Simulated annealing algorithm” is applied to this part. The maximum number of iterations is chosen as 30 to ensure the precision of the optimization, and the maximum number of random trials allowed for each iteration is chosen as 10 to decrease the probability of null iteration without an iterative solution. Node N7379 (Fig.5) is found to be the optimum gate loca- tion.The feature warpage is evaluated from the war- page simulation results f(X)=γ=0.97%, which is less than that of the recommended gate by MPI. And the part warpage meets the manufacturer’s requirements in trial manufacturing. Fig.6b shows the fiber orien- tation in the simulation. It is seen that the optimal gate location results in the even glass fiber orientation, and thus introduces great reduction of shrinkage differ- ence on the vertical direction along the longitudinal direction. Accordingly, the feature warpage is re- duced.CONCLUSIONFeature warpage is defined to describe the war- page of injection molded parts and is evaluated based on the numerical simulation software MPI in this investigation. The feature warpage evaluation based on numerical simulation is combined with simulated annealing algorithm to optimize the single gate loca- tion for plastic injection mold. An industrial part is taken as an example to illustrate the proposed method. The method results in an optimal gate location, by which the part is satisfactory for the manufacturer. This method is also suitable to other optimization problems for warpage minimization, such as location optimization for multiple gates, runner system bal- ancing, and option of anisotropic materials.注塑模的单浇口优化摘要：本文论述了一种单浇口位置优化注塑模具的方法。

distribution的用法Distribution是英语中一个常用的词汇，它可以表示分配、分发、分布等含义。

在不同的语境下，我们可以使用不同的表达方式和搭配，来描述Distribution的不同用法和含义。

1. Distribution作为名词，表示分配、分发、分布。

例如：- The distribution of resources is a key factor in economic development.（资源的分配是经济发展的关键因素。

）- The distribution of flyers was completed ahead of schedule.（传单的分发提前完成了。

）- The distribution of wealth is highly unequal in many countries.（在许多国家，财富分配极不平等。

）2. Distribution作为动词，表示分配、分发。

例如：- The manager is responsible for distributing the workload among the team members.（经理负责将工作负担分配给团队成员。

） - The charity organization distributed food and clothing to the needy families.（慈善组织向需要帮助的家庭分发食品和衣物。

）3. Distribution还可以作为数学和统计学中的专业术语，表示概率分布、频率分布等。

例如：- The distribution of the sample data can be used to estimate the population parameters.（样本数据的分布可以用来估计总体参数。

）- The normal distribution is widely used in statistical analysis.（正态分布在统计分析中被广泛应用。

normal distributionnormal distribution, also called gaussian distribution, the most mon distribution function for independent, randomly generated variables. its familiar bell-shaped curve is ubiquitous in statistical reports, fromsurvey analysis and quality control to resource allocation.the graph of the normal distribution is characterized by two parameters: the mean, or average, which is the maximum of the graph and about which the graph is always symmetric; and the standard deviation, which determines the amount of dispersion away from the mean.a small standard deviation (pared with the mean) produces a steep graph, whereas a large standard deviation (again pared with the mean) produces a flat graph. see the figure.the normal distribution is produced by the normal density function, p(x) = e−(x−μ)2/2σ2/σsquare rootof√2π. in this exponential function e is the constant 2.71828…, is the mean, and σ is the standard deviation. the probability of a random variablefalling within any given range of values is equal to the proportion of the area enclosed under thefunction’s graph between the given values and above the x-axis. because the denominator (σsquare rootof√2π), known as the normalizing coefficient, causes the total area enclosed by the graph to be exactly equal to unity, probabilities can be obtained directlyfrom the corresponding area—i.e., an area of 0.5 corresponds to a probability of 0.5. although these areas can be determined with calculus, tables were generated in the 19th century for the special caseof = 0 and σ= 1, known as the standard normal distribution, and these tables can be used for any normal distribution after the variables are suitably rescaled by subtracting their mean and dividing by their standard deviation, (x−μ)/σ. calculators have now all but eliminated the use of such tables.for further details see probability theory.the term “gaussian distribution” refers to the german mathematician carl friedrich gauss, who first developed a two-parameter exponential function in 1809 in connection with studies of astronomical observation errors. this study led gauss to formulate his law of observational error and to advance the theory of the method of least squares approximation. another famous early application of the normal distribution was by the british physicist james clerk maxwell, who in 1859 formulated his law of distribution of molecular velocities—later generalized as the maxwell-boltzmann distribution law.the french mathematician abraham de moivre, in his doctrine of chances (1718), first noted that probabilities associated with discretely generated random variables (such as are obtained by flipping a coin or rolling a die) can be approximated by the area under the graph of an exponential function. thisresult was extended and generalized by the frenchscientist pierre-simon laplace, in his théorie analytique des probabilités(1812; “analytic theory of probability”), into the first central limit theorem, which proved that probabilities for almostall independent and identically distributed random variables converge rapidly (with sample size) to the area under an exponential function—that is, to a normal distribution. the central limit theorem permitted hitherto intractable problems, particularly those involving discrete variables, to be handled with calculus.。

CH7Nonrandom Sampling - Every unit of the population does not have the same probability of being included in the sampleRandom sampling - Every unit of the population has the same probability of being included in the sample.Random Sampling TechniquesSimple Random Sample – basis for other random sampling techniques Stratified Random SampleProportionate -- the percentage of the sample taken from each stratum is proportionate to the percentage that each stratum(層) is within the populationDisproportionate -- proportions of the strata within the sample are different than the proportions of the strata within the populationPopulation is divided into non-overlapping subpopulations called strata Researcher extracts a simple random sample from each subpopulation Stratified random sampling has the potential for reducing error Sampling error – a sample does not represent the populationStratified random sampling has the potential to match the sample closely to the population Stratified sampling is more costlyStratum should be relatively homogeneous, i.e. race, gender, religion Systematic Random SamplePopulation elements are an ordered sequence.With systematic sampling, every k th item is selected to produce a sample of size n from a population of size NSystematic sampling is evenly distributed across the frame Sample elements are selected at a constant interval, k, from the ordered sequence frame.Systematic sampling is based on the assumption that the source of the population is random Cluster (or Area) SamplingCluster sampling – involves dividing the population into non-overlapping areas Identifies the clusters that tend to be internally homogeneous Each cluster is a microcosm(縮圖) of the populationIf the cluster is too large, a second set of clusters is taken from each original cluster This is two stage samplingAdvantagesMore convenient for geographically dispersed populations Simplified administration of the surveyUnavailability of sampling frame prohibits using other random sampling methodsn =sample size N=population size k =size of selection intervalk =N nDisadvantagesStatistically less efficient when the cluster elements are similarCosts and problems of statistical analysis are greater than for simple random samplingNon-Random sampling – sampling techniques used to select elements from the population by any mechanism that does not involve a random selection processErrors:Data from nonrandom samples are not appropriate for analysis by inferential statistical methods.Sampling Error occurs when the sample is not representative of the populationNon-sampling Errors – all errors other than sampling errorsMissing Data, Recording, Data Entry, and Analysis ErrorsPoorly conceived concepts , unclear definitions, and defective questionnairesResponse errors occur when people do not know, will not say, or overstate in their answersCentral Limit Theorem(中央極限定理)Central limits theorem allows one to study populations with differently shaped distributionsCentral limits theorem creates the potential for applying the normal distribution to many problems when sample size is sufficiently largeAdvantage of Central Limits theorem is when sample data is drawn from populations not normally distributed or populations of unknown shape can also be analyzed because the sample means are normally distributed due to large sample sizesAs sample size increases, the distribution narrowsDue to the Std Dev of the meanStd Dev of mean decreases as sample size increasesZ Formula for Sample MeansSampling Distribution of PSample ProportionSampling DistributionnQ > 5 (P is the population proportion and Q = 1 - P.)The mean of the distribution is P.The standard deviation of the distribution is Z Formula for Sample Proportions.deviationstandardandmeanon withdistributinormalaisxofondistributithe,ofdeviationstandardandofmeanwithpopulationnormalafromnsizeofsamplerandomaofmeantheisxIfxxnσμσμσμ== nXXZX Xσμσμ-=-=P = Xn√(p∗q)/n。

统计学中英文对照表2008—03—21 11:39Absolutedeviation,绝对离差Absolutenumber,绝对数Absoluteresiduals，绝对残差Accelerationarray，加速度立体阵Accelerationinanarbitrarydirection,任意方向上的加速度Accelerationnormal,法向加速度Accelerationspacedimension，加速度空间的维数Accelerationtangential,切向加速度Accelerationvector，加速度向量Acceptablehypothesis,可接受假设Accumulation,累积Accuracy,准确度Actualfrequency，实际频数Adaptiveestimator,自适应估计量Addition,相加Additiontheorem，加法定理Additivity，可加性Adjustedrate,调整率Adjustedvalue，校正值Admissibleerror,容许误差Aggregation,聚集性Alternativehypothesis,备择假设Amonggroups，组间Amounts,总量Analysisofcorrelation，相关分析Analysisofcovariance，协方差分析Analysisofregression，回归分析Analysisoftimeseries,时间序列分析Analysisofvariance,方差分析Angulartransformation,角转换ANOVA（analysisofvariance）,方差分析ANOVAModels,方差分析模型Arcing，弧/弧旋Arcsinetransformation，反正弦变换Areaunderthecurve，曲线面积AREG，评估从一个时间点到下一个时间点回归相关时的误差ARIMA，季节和非季节性单变量模型的极大似然估计Arithmeticgridpaper，算术格纸Arithmeticmean,算术平均数Arrheniusrelation，艾恩尼斯关系Assessingfit，拟合的评估Associativelaws，结合律Asymmetricdistribution,非对称分布Asymptoticbias,渐近偏倚Asymptoticefficiency，渐近效率Asymptoticvariance,渐近方差Attributablerisk，归因危险度Attributedata,属性资料Attribution,属性Autocorrelation，自相关Autocorrelationofresiduals，残差的自相关Average，平均数Averageconfidenceintervallength，平均置信区间长度Averagegrowthrate，平均增长率Barchart,条形图Bargraph,条形图Baseperiod,基期Bayes’theorem，Bayes定理Bell-shapedcurve，钟形曲线Bernoullidistribution，伯努力分布Best-trimestimator，最好切尾估计量Bias,偏性Binarylogisticregression,二元逻辑斯蒂回归Binomialdistribution，二项分布Bisquare，双平方BivariateCorrelate，二变量相关Bivariatenormaldistribution，双变量正态分布Bivariatenormalpopulation，双变量正态总体Biweightinterval,双权区间BiweightM—estimator,双权M估计量Block，区组/配伍组BMDP(Biomedicalcomputerprograms）,BMDP统计软件包Boxplots，箱线图/箱尾图Breakdownbound,崩溃界/崩溃点Canonicalcorrelation,典型相关Caption，纵标目Case—controlstudy，病例对照研究Categoricalvariable,分类变量Catenary,悬链线Cauchydistribution,柯西分布Cause-and—effectrelationship,因果关系Cell,单元Censoring,终检Centerofsymmetry,对称中心Centeringandscaling,中心化和定标Centraltendency,集中趋势Centralvalue，中心值CHAID—χ2AutomaticInteractionDetector，卡方自动交互检测Chance，机遇Chanceerror,随机误差Chancevariable，随机变量Characteristicequation,特征方程Characteristicroot，特征根Characteristicvector，特征向量Chebshevcriterionoffit,拟合的切比雪夫准则Chernofffaces，切尔诺夫脸谱图Chi—squaretest，卡方检验/χ2检验Choleskeydecomposition,乔洛斯基分解Circlechart，圆图Classinterval，组距Classmid—value,组中值Classupperlimit,组上限Classifiedvariable,分类变量Clusteranalysis，聚类分析Clustersampling,整群抽样Code，代码Codeddata，编码数据Coding，编码Coefficientofcontingency,列联系数Coefficientofdetermination，决定系数Coefficientofmultiplecorrelation，多重相关系数Coefficientofpartialcorrelation,偏相关系数Coefficientofproduction-momentcorrelation,积差相关系数Coefficientofrankcorrelation，等级相关系数Coefficientofregression，回归系数Coefficientofskewness,偏度系数Coefficientofvariation,变异系数Cohortstudy，队列研究Column，列Columneffect，列效应Columnfactor,列因素Combinationpool,合并Combinativetable,组合表Commonfactor,共性因子Commonregressioncoefficient,公共回归系数Commonvalue，共同值Commonvariance,公共方差Commonvariation，公共变异Communalityvariance,共性方差Comparability，可比性Comparisonofbathes,批比较Comparisonvalue,比较值Compartmen**＊el，分部模型Compassion，伸缩Complementofanevent，补事件Completeassociation，完全正相关Completedissociation,完全不相关Completestatistics,完备统计量Completelyrandomizeddesign，完全随机化设计Compositeevent,联合事件Compositeevents，复合事件Concavity，凹性Conditionalexpectation，条件期望Conditionallikelihood，条件似然Conditionalprobability,条件概率Conditionallylinear，依条件线性Confidenceinterval，置信区间Confidencelimit,置信限Confidencelowerlimit,置信下限Confidenceupperlimit，置信上限ConfirmatoryFactorAnalysis，验证性因子分析Confirmatoryresearch,证实性实验研究Confoundingfactor,混杂因素Conjoint，联合分析Consistency,相合性Consistencycheck,一致性检验Consistentasymptoticallynormalestimate,相合渐近正态估计Consistentestimate，相合估计Constrainednonlinearregression，受约束非线性回归Constraint，约束Contaminateddistribution,污染分布ContaminatedGausssian，污染高斯分布Contaminatednormaldistribution,污染正态分布Contamination，污染Contaminationmodel，污染模型Contingencytable,列联表Contour，边界线Contributionrate,贡献率Control，对照Controlledexperiments，对照实验Conventionaldepth,常规深度Convolution，卷积Correctedfactor,校正因子Correctedmean,校正均值Correctioncoefficient，校正系数Correctness，正确性Correlationcoefficient,相关系数Correlationindex,相关指数Correspondence，对应Counting,计数Counts，计数/频数Covariance，协方差Covariant，共变CoxRegression,Cox回归Criteriaforfitting,拟合准则Criteriaofleastsquares,最小二乘准则Criticalratio，临界比Criticalregion,拒绝域Criticalvalue,临界值Cross-overdesign,交叉设计Cross-sectionanalysis，横断面分析Cross-sectionsurvey，横断面调查Crosstabs，交叉表Cross—tabulationtable,复合表Cuberoot，立方根Cumulativedistributionfunction,分布函数Cumulativeprobability,累计概率Curvature,曲率/弯曲Curvature，曲率Curvefit，曲线拟和Curvefitting,曲线拟合Curvilinearregression,曲线回归Curvilinearrelation，曲线关系Cut-and-trymethod，尝试法Cycle，周期Cyclist，周期性Dtest，D检验Dataacquisition，资料收集Databank，数据库Datacapacity，数据容量Datadeficiencies,数据缺乏Datahandling,数据处理Datamanipulation，数据处理Dataprocessing，数据处理Datareduction，数据缩减Dataset,数据集Datasources，数据来源Datatransformation，数据变换Datavalidity，数据有效性Data—in，数据输入Data—out，数据输出Deadtime,停滞期Degreeoffreedom，自由度Degreeofprecision，精密度Degreeofreliability，可靠性程度Degression,递减Densityfunction,密度函数Densityofdatapoints，数据点的密度Dependentvariable,应变量/依变量/因变量Dependentvariable,因变量Depth,深度Derivativematrix，导数矩阵Derivative-freemethods，无导数方法Design,设计Determinacy，确定性Determinant，行列式Determinant,决定因素Deviation,离差Deviationfromaverage,离均差Diagnosticplot，诊断图Dichotomousvariable,二分变量Differentialequation,微分方程Directstandardization,直接标准化法Discretevariable，离散型变量DISCRIMINANT，判断Discriminantanalysis，判别分析Discriminantcoefficient，判别系数Discriminantfunction，判别值Dispersion,散布/分散度Disproportional，不成比例的Disproportionatesub-classnumbers,不成比例次级组含量Distributionfree,分布无关性/免分布Distributionshape，分布形状Distribution-freemethod,任意分布法Distributivelaws,分配律Disturbance,随机扰动项Doseresponsecurve，剂量反应曲线Doubleblindmethod,双盲法Doubleblindtrial,双盲试验Doubleexponentialdistribution,双指数分布Doublelogarithmic,双对数Downwardrank,降秩Dual-spaceplot,对偶空间图DUD，无导数方法Duncan'snewmultiplerangemethod,新复极差法/Duncan新法Effect，实验效应Eigenvalue，特征值Eigenvector,特征向量Ellipse，椭圆Empiricaldistribution，经验分布Empiricalprobability，经验概率单位Enumerationdata，计数资料Equalsun—classnumber，相等次级组含量Equallylikely,等可能Equivariance,同变性Error，误差/错误Errorofestimate,估计误差ErrortypeI，第一类错误ErrortypeII,第二类错误Es＊＊＊,被估量Estimatederrormeansquares,估计误差均方Estimatederrorsumofsquares,估计误差平方和Euclideandistance，欧式距离Event,事件Event，事件Exceptionaldatapoint，异常数据点Expectationplane，期望平面Expectationsurface,期望曲面Expectedvalues，期望值Experiment,实验Experimentalsampling,试验抽样Experimentalunit,试验单位Explanatoryvariable,说明变量Exploratorydataanalysis,探索性数据分析ExploreSummarize，探索—摘要Exponentialcurve,指数曲线Exponentialgrowth,指数式增长EXSMOOTH，指数平滑方法Extendedfit,扩充拟合Extraparameter,附加参数Extrapolation，外推法Extremeobservation，末端观测值Extremes，极端值/极值Fdistribution，F分布Ftest,F检验Factor,因素/因子Factoranalysis，因子分析FactorAnalysis，因子分析Factorscore，因子得分Factorial，阶乘Factorialdesign,析因试验设计Falsenegative,假阴性Falsenegativeerror，假阴性错误Familyofdistributions,分布族Familyofestimators，估计量族Fanning，扇面Fatalityrate，病死率Fieldinvestigation,现场调查Fieldsurvey，现场调查Finitepopulation，有限总体Finite—sample，有限样本Firstderivative,一阶导数Firstprincipalcomponent，第一主成分Firstquartile，第一四分位数Fisherinformation,费雪信息量Fittedvalue,拟合值Fittingacurve,曲线拟合Fixedbase，定基Fluctuation，随机起伏Forecast，预测Fourfoldtable,四格表Fourth，四分点Fractionblow，左侧比率Fractionalerror,相对误差Frequency，频率Frequencypolygon,频数多边图Frontierpoint,界限点Functionrelationship,泛函关系Gammadistribution，伽玛分布Gaussincrement,高斯增量Gaussiandistribution，高斯分布/正态分布Gauss—Newtonincrement,高斯-牛顿增量Generalcensus,全面普查GENLOG(Generalizedlinermodels)，广义线性模型Geometricmean,几何平均数Gini’smeandifference，基尼均差GLM(Generallinermodels）,通用线性模型Goodnessoffit,拟和优度/配合度Gradientofdeterminant,行列式的梯度Graeco-Latinsquare,希腊拉丁方Grandmean,总均值Grosserrors，重大错误Gross—errorsensitivity，大错敏感度Groupaverages,分组平均Groupeddata,分组资料Guessedmean，假定平均数Half—life，半衰期HampelM-estimators，汉佩尔M估计量Happenstance，偶然事件Harmonicmean，调和均数Hazardfunction，风险均数Hazardrate,风险率Heading,标目Heavy—taileddistribution，重尾分布Hessianarray，海森立体阵Heterogeneity,不同质Heterogeneityofvariance,方差不齐Hierarchicalclassification,组内分组Hierarchicalclusteringmethod,系统聚类法High—leveragepoint，高杠杆率点HILOGLINEAR，多维列联表的层次对数线性模型Hinge,折叶点Histogram,直方图Historicalcohortstudy，历史性队列研究Holes，空洞HOMALS,多重响应分析Homogeneityofvariance,方差齐性Homogeneitytest,齐性检验HuberM-estimators,休伯M估计量Hyperbola,双曲线Hypothesistesting，假设检验Hypotheticaluniverse,假设总体Impossibleevent，不可能事件Independence，独立性Independentvariable,自变量Index,指标/指数Indirectstandardization，间接标准化法Individual,个体Inferenceband，推断带Infinitepopulation,无限总体Infinitelygreat,无穷大Infinitelysmall，无穷小Influencecurve,影响曲线Informationcapacity，信息容量Initialcondition,初始条件Initialestimate,初始估计值Initiallevel,最初水平Interaction，交互作用Interactionterms，交互作用项Intercept,截距Interpolation,内插法Interquartilerange，四分位距Intervalestimation，区间估计Intervalsofequalprobability，等概率区间Intrinsiccurvature,固有曲率Invariance,不变性Inversematrix,逆矩阵Inverseprobability，逆概率Inversesinetransformation，反正弦变换Iteration,迭代Jacobiandeterminant,雅可比行列式Jointdistributionfunction，分布函数Jointprobability，联合概率Jointprobabilitydistribution,联合概率分布Kmeansmethod,逐步聚类法Kaplan—Meier，评估事件的时间长度Kaplan—Merierchart,Kaplan-Merier图Kendall'srankcorrelation，Kendall等级相关Kinetic，动力学Kolmogorov—Smirnovetest，柯尔莫哥洛夫-斯米尔诺夫检验KruskalandWallistest，Kruskal及Wallis检验/多样本的秩和检验/H检验Kurtosis，峰度Lackoffit，失拟Ladderofpowers,幂阶梯Lag,滞后Largesample，大样本Largesampletest,大样本检验Latinsquare，拉丁方Latinsquaredesign，拉丁方设计Leakage,泄漏Leastfavorableconfiguration,最不利构形Leastfavorabledistribution,最不利分布Leastsignificantdifference，最小显著差法Leastsquaremethod，最小二乘法Least-absolute-residualsestimates，最小绝对残差估计Least-absolute-residualsfit，最小绝对残差拟合Least—absolute—residualsline,最小绝对残差线Legend，图例L—estimator,L估计量L-estimatoroflocation，位置L估计量L—estimatorofscale，尺度L估计量Level，水平Lifeexpectance,预期期望寿命Lifetable，寿命表Lifetablemethod，生命表法Light—taileddistribution，轻尾分布Likelihoodfunction，似然函数Likelihoodratio，似然比linegraph,线图Linearcorrelation，直线相关Linearequation，线性方程Linearprogramming,线性规划Linearregression,直线回归LinearRegression,线性回归Lineartrend，线性趋势Loading,载荷Locationandscaleequivariance，位置尺度同变性Locationequivariance,位置同变性Locationinvariance,位置不变性Locationscalefamily,位置尺度族Logranktest，时序检验Logarithmiccurve，对数曲线Logarithmicnormaldistribution，对数正态分布Logarithmicscale,对数尺度Logarithmictransformation,对数变换Logiccheck,逻辑检查Logisticdistribution，逻辑斯特分布Logittransformation,Logit转换LOGLINEAR，多维列联表通用模型Lognormaldistribution，对数正态分布Lostfunction，损失函数Lowcorrelation，低度相关Lowerlimit，下限Lowest—attainedvariance，最小可达方差LSD,最小显著差法的简称Lurkingvariable,潜在变量Main effect，主效应Major heading，主辞标目Marginal density function,边缘密度函数Marginal probability，边缘概率Marginal probability distribution,边缘概率分布Matched data，配对资料Matched distribution，匹配过分布Matching of distribution，分布的匹配Matching of transformation,变换的匹配Mathematical expectation,数学期望Mathematical model，数学模型Maximum L—estimator,极大极小L 估计量Maximum likelihood method,最大似然法Mean，均数Mean squares between groups,组间均方Mean squares within group，组内均方Means （Compare means），均值-均值比较Median,中位数Median effective dose，半数效量Median lethal dose,半数致死量Median polish，中位数平滑Median test，中位数检验Minimal sufficient statistic,最小充分统计量Minimum distance estimation，最小距离估计Minimum effective dose，最小有效量Minimum lethal dose，最小致死量Minimum variance estimator,最小方差估计量MINITAB,统计软件包Minor heading，宾词标目Missing data，缺失值Model specification,模型的确定Modeling Statistics ，模型统计Models for outliers，离群值模型Modifying the model,模型的修正Modulus of continuity，连续性模Morbidity,发病率Most favorable configuration,最有利构形Multidimensional Scaling （ASCAL),多维尺度/多维标度Multinomial Logistic Regression ，多项逻辑斯蒂回归Multiple comparison，多重比较Multiple correlation ，复相关Multiple covariance,多元协方差Multiple linear regression,多元线性回归Multiple response ,多重选项Multiple solutions，多解Multiplication theorem,乘法定理Multiresponse，多元响应Multi-stage sampling,多阶段抽样Multivariate T distribution,多元T分布Mutual exclusive,互不相容Mutual independence，互相独立Natural boundary，自然边界Natural dead,自然死亡Natural zero，自然零Negative correlation，负相关Negative linear correlation,负线性相关Negatively skewed，负偏Newman-Keuls method,q检验NK method,q检验No statistical significance,无统计意义Nominal variable,名义变量Nonconstancy of variability,变异的非定常性Nonlinear regression，非线性相关Nonparametric statistics,非参数统计Nonparametric test,非参数检验Nonparametric tests，非参数检验Normal deviate,正态离差Normal distribution,正态分布Normal equation，正规方程组Normal ranges，正常范围Normal value,正常值Nuisance parameter,多余参数/讨厌参数Null hypothesis，无效假设Numerical variable，数值变量Objective function，目标函数Observation unit，观察单位Observed value，观察值One sided test,单侧检验One—way analysis of variance，单因素方差分析Oneway ANOVA ，单因素方差分析Open sequential trial,开放型序贯设计Optrim,优切尾Optrim efficiency，优切尾效率Order statistics,顺序统计量Ordered categories，有序分类Ordinal logistic regression ，序数逻辑斯蒂回归Ordinal variable，有序变量Orthogonal basis,正交基Orthogonal design,正交试验设计Orthogonality conditions,正交条件ORTHOPLAN，正交设计Outlier cutoffs,离群值截断点Outliers，极端值OVERALS ,多组变量的非线性正规相关Overshoot,迭代过度Paired design,配对设计Paired sample,配对样本Pairwise slopes，成对斜率Parabola，抛物线Parallel tests，平行试验Parameter,参数Parametric statistics，参数统计Parametric test,参数检验Partial correlation,偏相关Partial regression,偏回归Partial sorting，偏排序Partials residuals，偏残差Pattern,模式Pearson curves,皮尔逊曲线Peeling,退层Percent bar graph,百分条形图Percentage，百分比Percentile,百分位数Percentile curves,百分位曲线Periodicity，周期性Permutation,排列P-estimator,P估计量Pie graph，饼图Pitman estimator，皮特曼估计量Pivot，枢轴量Planar，平坦Planar assumption,平面的假设PLANCARDS，生成试验的计划卡Point estimation,点估计Poisson distribution，泊松分布Polishing，平滑Polled standard deviation，合并标准差Polled variance,合并方差Polygon，多边图Polynomial，多项式Polynomial curve，多项式曲线Population,总体Population attributable risk,人群归因危险度Positive correlation，正相关Positively skewed,正偏Posterior distribution，后验分布Power of a test，检验效能Precision，精密度Predicted value，预测值Preliminary analysis，预备性分析Principal component analysis,主成分分析Prior distribution，先验分布Prior probability，先验概率Probabilistic model，概率模型probability,概率Probability density，概率密度Product moment,乘积矩/协方差Profile trace,截面迹图Proportion,比/构成比Proportion allocation in stratified random sampling,按比例分层随机抽样Proportionate,成比例Proportionate sub-class numbers，成比例次级组含量Prospective study,前瞻性调查Proximities，亲近性Pseudo F test,近似F检验Pseudo model，近似模型Pseudosigma，伪标准差Purposive sampling,有目的抽样QR decomposition,QR分解Quadratic approximation,二次近似Qualitative classification，属性分类Qualitative method,定性方法Quantile—quantile plot，分位数-分位数图/Q-Q图Quantitative analysis，定量分析Quartile，四分位数Quick Cluster，快速聚类Radix sort，基数排序Random allocation,随机化分组Random blocks design,随机区组设计Random event,随机事件Randomization，随机化Range，极差/全距Rank correlation，等级相关Rank sum test,秩和检验Rank test,秩检验Ranked data，等级资料Rate,比率Ratio，比例Raw data，原始资料Raw residual,原始残差Rayleigh’s test，雷氏检验R ayleigh’s Z，雷氏Z值Reciprocal，倒数Reciprocal transformation,倒数变换Recording,记录Redescending estimators，回降估计量Reducing dimensions,降维Re—expression，重新表达Reference set,标准组Region of acceptance，接受域Regression coefficient，回归系数Regression sum of square，回归平方和Rejection point,拒绝点Relative dispersion，相对离散度Relative number,相对数Reliability，可靠性Reparametrization,重新设置参数Replication，重复Report Summaries，报告摘要Residual sum of square,剩余平方和Resistance，耐抗性Resistant line，耐抗线Resistant technique，耐抗技术R—estimator of location,位置R估计量R—estimator of scale,尺度R估计量Retrospective study,回顾性调查Ridge trace,岭迹Ridit analysis,Ridit分析Rotation,旋转Rounding，舍入Row,行Row effects，行效应Row factor,行因素RXC table，RXC表Sample,样本Sample regression coefficient,样本回归系数Sample size,样本量Sample standard deviation，样本标准差Sampling error，抽样误差SAS（Statistical analysis system ），SAS统计软件包Scale，尺度/量表Scatter diagram，散点图Schematic plot，示意图/简图Score test，计分检验Screening，筛检SEASON,季节分析Second derivative,二阶导数Second principal component,第二主成分SEM (Structural equation modeling)，结构化方程模型Semi—logarithmic graph,半对数图Semi-logarithmic paper，半对数格纸Sensitivity curve,敏感度曲线Sequential analysis，贯序分析Sequential data set,顺序数据集Sequential design,贯序设计Sequential method,贯序法Sequential test，贯序检验法Serial tests，系列试验Short-cut method，简捷法Sigmoid curve，S形曲线Sign function,正负号函数Sign test,符号检验Signed rank,符号秩Significance test，显著性检验Significant figure,有效数字Simple cluster sampling，简单整群抽样Simple correlation，简单相关Simple random sampling,简单随机抽样Simple regression,简单回归simple table，简单表Sine estimator，正弦。

Characterization of Nanoparticle SizeDistribution纳米颗粒的粒径分布特征纳米颗粒大多是尺寸在1~100纳米之间的颗粒状物质，其大小不仅对于颗粒的光学、电学、磁学等性质具有很大的影响，而且也对其在生命科学和医学方面的应用产生了极大的影响。

因此，对纳米颗粒的粒径分布进行表征是极其关键的。

纳米颗粒粒径分布的特征纳米材料的粒径通常具有一定的分布，因此，粒子的尺寸分散性是表征纳米颗粒粒径分布的主要参数。

通常情况下，颗粒的尺寸分散性由不同尺寸之间的标准差来表征。

分散平均粒径则由粒径分布曲线上的面积或体积平均计算得出。

粒径分布的形状通常是根据粒度分布函数来描述的。

在纳米科技领域，对颗粒粒径的分布特征进行准确的描述是至关重要的，因为这是评估纳米颗粒材料性能和行为的必要条件。

实际上，纳米颗粒的性质随着其粒径的改变而发生根本性的变化。

相同材料的纳米结构可能会表现出非常不同的性质，因此，需要对纳米颗粒的粒径分布进行深入的研究和分析。

表征纳米颗粒尺寸分布的方法目前，常用的纳米颗粒尺寸分布表征方法通常是静态光散射和动态光散射。

光散射是表征颗粒粒径的最常见的技术之一，它通过测量样品分散液中颗粒散射光的强度和角度信息，计算得出颗粒粒径和粒径分布。

颗粒与光子的相互作用形成可观察的光学信号，因此，这些方法可以在不破坏样品的情况下实现纳米颗粒的表征。

另一方面，离子束散射和扫描电子显微镜也可以用于表征纳米颗粒尺寸分布，但是这些技术一般需要相对较高的成本和更复杂的操作，因此通常用于对纳米颗粒进行更详细的分析。

粒径分布的独特性质对纳米颗粒尺寸分布进行表征的关键在于了解其独特性质和特征。

常见的尺寸分布特征包括单峰分布和双峰分布。

单峰分布通常表明样品中存在一种纳米颗粒的种类，而双峰分布则表明存在两种或以上的颗粒种类。

此外，颗粒粒径分布的宽度也是表征其性质的关键参数之一。

如果样品中的颗粒粒径分布很广，则说明该样品中包含了多种颗粒种类或者存在着一定程度的聚合。

美国连续束电子加速器的能量升级到12Ge V 的科学与实验设备石　宗　仁(中国原子能科学研究院　北京　102413)摘　要 驱动美国托马斯杰斐逊国家加速器装置(Thomas Jeffers on Nati onal Accelerat or Facility,简称JLab )的能量升级到12GeV 的科学是研究胶子激发和色禁闭的起因,研究原子核的构件核子是如何由夸克和胶子构成的,研究原子核的结构及寻找新物理等的一门科学.实验设备是12Ge V 的加速器、各种超导磁谱仪及极化靶等.在能量为12Ge V 的加速器中,将采用深度遍举过程和极化实验.关键词 胶子激发,色禁闭,普适的部分子分布,连续束电子加速器,超导磁谱仪,深度遍举过程,极化The exper i m ent a l equi p mentfor the 12GeV upgrade of CEBAF a t J LabSH I Zong 2Ren(China Institute of A to m ic Energy,B eijing 102413,China )Abstract The upgrade at JLab of the continuous electr on beam accelerator facility to 12GeV was based on the requirements for research on gluonic excitations and the origin of quark confinement,how nucleons are built up fr om quarks and gluons,the structure of nuclei,and new physics .The upgraded experi mental equipment includes the 12GeV accelerator,superconducting magnetic s pectr ometers and polarized targets .Keywords gluonic excitations,color confinement,generalized parton distributi ons,continuous electr on beam accelerator,superconducting magnetic s pectr ometer,deep exclusive p rocesses,polarizati on2006-03-10收到初稿,2006-04-28修回　Email:zrshi@iris .ciae .ac .cn1　引言核物理学是一门研究原子核性质及其结构的基础科学,是核工程的物理基础,是研究物质起源和演化的基础,也是研究星际燃料来源的基础,是理论与实验紧密结合、不断深入和发展、需要长期研究的科学.它在国防、能源、医学、材料分析及其改性、环境科学和空间探索等方面都已发挥了重要的作用.在21世纪,核物理学将面临新的机遇和挑战.美国将核物理学作为国家级的科学,是美国技术大厦的支柱之一,也是培养人材的摇篮.在1979年,美国能源部和美国国家自然科学基金委员会的核科学咨询委员会第一次制定了核科学的长远规划LRP (a Long range p lan for nuclear science ),它评估过去、展望和计划未来.在随后的1983、1989、1996和2002年都做过LRP .在1989年的LRP [1]中,将标准模型(standard model,简称S M )作为核物理学的理论基础,其中强相互作用理论是量子色动力学(quantu m chr omo dyna m ics,QCD )它标志了核物理学新的里程碑.在文献[1]中,也明确地提出了原子核组成的四个层次:原子核类似于有表面振动和集体转动的液滴;原子核由核子组成;原子核由核子、介子和核子激发态等强子组成,也称为介子-重子模型(mes 2on-bary on model);原子核由夸克和胶子组成等.前两个层次构成了低能核物理.前三个层次统称传统核物理(conventi onal nuclear physics).在夸克和胶子的层次上研究强子和原子核的性质称为现代核物理(conte mporary nuclear physics).在2002年的LRP[2]中,明确地提出现代核物理包含5个科学目标:(1)核子的QCD结构及其相互作用;(2)原子核的结构及其稳定性;(3)高能量密度的QCD及热核物质的性质;(4)在核天体中元素的起源及物质的演化;(5)寻求新物理.美国托马斯杰斐逊国家加速器装置(Thomas Jeffers on Nati onal Accelerat or Facility,简称JLab)是基于第一、第二和第五个科学目标.总之,现代核物理以标准模型为理论基础,在夸克和胶子的层次上研究核物质的性质.当前研究非微扰QCD、色禁闭(col or confin ment)机制以及QCD 真空的结构是重要的科学任务.它的研究内容已经大大地超出了传统的范围.当然,人们最终希望用QCD统一地描述强子和原子核及其在各种极端条件下核物质的性质,它将是21世纪核物理学面临的机遇和挑战.为此,对构成核物理实验的炮弹(入射粒子束)、靶、探测器、电子学线路和数据获取及其处理程序,以及实验方法等都提出了新的要求.首先,人们需要多种类型的加速器,以提供参于电磁、弱和强相互作用的高品质的多种初级和次级粒子束(初级的如电子、质子和重离子,次级的如γ射线、反质子和中微子等),从而探知强子的电磁、弱和强相互作用方面的结构及极端条件下核物质的性质.其中高品质电子加速器具有头等重要的作用.这是由于电磁相互作用在理论上清楚,可微扰计算,大多数反应是单步过程,具有远高于弱相互作用的强度,以及通过调节电子转移四动量的平方(Q2)可改变空间和时间分辨率等优点.借改变Q2,能够观察到在核子内组分夸克模型CQM(constituent quark model)和部分子模型(part on model)之间以及在原子核内4个层次及其间的过渡性质.在1956年,Hofstadter等人[3]通过电子弹性散射,测量了质子内部的电荷和电流分布,说明了质子不是点粒子,而是有结构的,由此Hofstadter获得了诺贝尔奖;在1968年,Friedman等人[4]在斯坦福直线加速器中心(Stanf ord linear accelerat or center, S LAC)通过电子深度非弹散射(deep inelastic scat2 tering,D I S)发现了质子内部有后来称为夸克的微小颗粒存在,为此获得了诺贝尔奖;Prescott等人[5,6]利用极化电子-非极化靶,测量电子极化不对称度,证明了弱相互作用中存在中性流;在1983,年欧洲合作组Aubert等人[7]利用电子在原子核上的D I S,发现了原子核的结构不同于自由核子集体的结构,它称为E MC效应;A sh man等人[8]利用极化电子-极化靶,测量极化不对称度,发现了夸克对质子自旋的贡献约20%,而相对论CQM预言约70%,这是著名的至今仍在研究的热门课题“自旋危机”(s p in cri2 sis).大量事实已证明,电子是研究强子和原子核性质的强有力的探针.在虚光子携带能量等于零的B reit框架中,虚光子的波长λ=h/(2πQ),Q越大,λ越小,空间分辨率也越高.用高能量的电子能获得大的Q值.由于反应截面反比于Q n,一般n=4,所以Q越大,截面越小,为补偿小截面,需要强束流.实验上,由于需要采用对夸克和胶子场算符矩阵元灵敏的遍举和极化测量,所以分别要求电子束流的占空因子(duty fac2 t or)～100%(也称连续束),以及电子自旋具有取向的极化束.总之,需要高能、强流、极化和连续束的电子加速器.现在,J lab具有6Ge V、强流、极化、连续电子束的加速器装置(continuos electr on bea m accelerat or fa2 cility,简称CE BAF).随着QCD的进展,如色禁闭的流管模型被第一原理的格点(lattice)规范QCD计算所证实,新的包含丰富强子结构信息的普适的部分子分布(generalized part on distributi ons,GP D)理论的出现等,驱使人们采用12Ge V或更高能量的CE2 BAF.目前,由于技术上的成熟,将6Ge V提高到12Ge V是现实的,预计2010年即可实现.12Ge V将为人们提供新的运动学的区域,打开许多新的前所未有的研究窗口,以及在已有的运动学区域提供统计不确定度小的实验数据.在12Ge V,将采用深度遍举过程DEP(deep exclusive p r ocesse)和极化实验.本文第2节介绍驱动12Ge V的核科学,第3节是JLab的发展历史,加速器和超导磁谱仪等的现状和未来,在结束语中简单地介绍国际上在核物理方面正在筹建的大型加速器.在附录Ⅰ,简要地介绍了S M和QCD,在附录Ⅱ,介绍了实验上相关的问题:遍举和极化测量,运动学变量和反应类型,观测量和因子化定理等.本文主要参考了JLab在2004年6月的“CE BAF12Ge V改进的科学和实验装置的预概念设计报告”[9],及有关的文献.2　驱动12Ge V 的核科学胶子激发和色禁闭的起因、原子核构件是如何由夸克和胶子构成的、原子核物理和检验对称性及寻找新物理等四个方面的科学动机驱动了12GeV.下面分别叙述它们,但着重说明前两个.2.1　胶子激发和色禁闭的起因通过研究胶子的性质及其在强子中的作用,能得出色禁闭的起因,而寻找和研究含有胶子自由度的混合介子(hybrids )则是重要的手段.在JLab 新建的D 厅里,胶子激发(gluonic excitati ons )合作组(简称Glue X 组)将通过线极化的实光子与核子相互作用产生混合介子,利用密封性的谱仪测量混合介子的各种衰变产物.实验上将得到普通介子、轻夸克的混合介子、胶球(glueball )、介子分子态(mes on -mes on molecules )的质量谱,特别是奇异混合介子的质量谱[9,10].2.1.1　流管-色禁闭的起因早在1970年,Na mbu Y 在芝加哥大学没有发表的报告中,谈到在粒子内部夸克是由弦联系在一起的.在1985年,Isgur 和Pat on [11]提出了胶子的流管(gluonic flux -tube )模型.在1995年,Bali 等人[12]用格点QCD 计算表明,介子中的正反价夸克间形成了由胶子构成的流管.图1表示出量子电动力学QE D 和QCD 的场线和力同介子的正反价夸克间距的关系.图的上部分显示出QED 单位面积的电力线数和力反比于r 2,而势能将反比于r ,r 越大,势能越小.图的下部分显示出QCD 单位面积的色力线数和力与r 无关,势能将随r 线性增加,r 越大,势能越大.QCD 和QE D 的性质截然不同.色禁闭起源于流管的形成,GlueX 实验将检验它是否正确.2.1.2　普通介子的JPC根据CQM ,在夸克和反夸克构成的普通介子中,胶子自由度被冻结了,普通介子用qq _表示.qq _的总角动量J =L +S,宇称量子数P =(-1)L +1,电荷共轭量子数C =(-1)L +S.其中L 是正反夸克的相对轨道角动量;总自旋S =s 1+s 2,s 1和s 2分别是等于1/2的正反夸克的自旋.当L =S =0时,J PC=0-+,对应于九重赝标量介子(p seudoscalar mes on )π、η、η′和K;当L =0,S =1时,J PC =1--,对应于九重矢量介子(vect or mes on )ρ、ω、<和K 3.图1　在QCD 和QED 中的场线和力同正反价夸克间距的关系具有整数自旋J 、宇称P =(-1)J的称为自然宇称的粒子,P =(-1)J +1的称为非自然宇称的粒子.自然性(naturality )量子数τ=P (-1)J,自然宇称和非自然宇称粒子的τ分别为+1和-1.赝标量介子的τ=-1,矢量介子的τ=+1.2.1.3　混合介子的J PCHCQM 不能描述用qq _g 表示的混合介子,它的存在表明,在低能QCD 有价胶子自由度.流管基态的角动量L ′=0,最低的胶子集体激发态是L ′=1,它相当流管的顺时针和逆时针的两种转动态,两者的线性组合构成了J PC G =1-+和1+-的退化态.J PC与J PCG 耦合可得到qq _g 的J PCH ,见表1.从表1能够看出,J PC G 与L =S =0的J PC耦合产生的J PCH =1--和1++,在S =1的J PC中有其副本.J PCG 与S =1的JPC耦合产生的J PCH 有两类:一类是τ=-1,如0-+,2-+,1+-,…,在S =0的J PC 中有其副本;另一类τ=+1,如1-+,0+-,2+-,…,在J PC中没有副本.J PCH 与J PC相同的称为普通的qq _g,不同的称为奇异(exotic )的qq _g .由此得出,奇异的qq _g 能够通过S =1的矢量介子的胶子集体激发产生,但不能通过S =0的赝标量介子产生.在高能,由于光子可看作是由自旋平行的虚的正2反夸克构成的矢量介子,所以它能够产生奇异的qq _g .在表1也列出了L ≠0的J PCH .由于普通的qq _g 与qq _能够产生组态混合,所以实验上很难区分两者.如果在实验上找到了奇异的qq _g,如J PCH =1-+,那么qq _g 就被唯一的确定了.格点QCD 已经预言了轻夸克qq _g 的谱及其衰变方式,表1　J PC 和J PCHSL012JPC00-+1+-2-+11--(0,1,2)++(1,2,3)--J PCH01--,1++(0,1,2)++,(0,1,2)--(1,2,3)--,(1,2,3)++1(0,1,2)-+,(0,1,2)+-(1;0,1,2;1,2,3)+-,(1;0,1,2;1,2,3)-+(0,1,2;1,2,3;2,3,4)-+,(0,1,2;1,2,3;2,3,4)+-式,其中最低的1-+的奇异q q _g 质量为1.9—2.0Ge V.图2表示在2.7Ge V /c2以下的q q _、胶球、q q _g和介子分子态的质量谱.从图可以看出,在1.3—2.7Ge V /c2的区间,除奇异qq _g 具有0+-、1-+、2+-量子数外,其他的都没有,所以实验上找到具有此量子数的介子就是奇异的qq _g.图2　普通介子、胶球、混合介子和分子态的质量谱2.1.4　光致反应除光子等效矢量介子外,由于能够得到高品质、高强度、线极化的光子束,所以用光致反应产生qq _g,特别是奇异的qq _g,是有效和现实的.光致反应γ↑N →X ↑N ′,s =(p γ+p p )2,(1)t =(p γ-p X )2,(2)其中X 是具有确定J P的qq _g;↑表示γ射线是线极化的,及在实验上测量X 的极化;N 和N ′分别是初态核子和末态重子;洛伦兹标量s 和t 分别是在质心系的能量和四动量转移,称为Mandelstam 变量.在图3的t 道反应中,当没有重子数交换时,可以通过交换介子或坡密子(pomer on )等实现.在小t 时,主要是交换π+[13].实验上光子和核子靶分别是线极化和非极化的,测量反冲核子(但不测其极化)并测量X 衰变产物的角分布.通过角分布能够导出X 的极化方向和极化度.当交换坡密子时反应截面σ与随s 无关;当交换介子时,σ随s 增大而减少,σ与t 满足指数衰减关系:σ～e -α│t │.图3　光致产生混合介子的t 道反应2.1.5　线极化光子使用线极化光子的意义在于通过测量X 的极化,如果交换粒子的自然性知道了,就能知道X 的自然性,反之亦然;X 的极化方向与光子的线极化方向是相互关联的,并与X 的自然性有关.线极化光子的波函数为│x 〉=(│-1〉-│+1〉)/2,(3)│y 〉=i (│-1〉+│+1〉)/2,(4)其中│-1〉和│+1〉分别是左和右手圆极化光子的本征态.在光子和X 的三动量方向构成的产生平面里,│x 〉和│y 〉分别是在其内和与其垂直的线极化光子.由于|x 〉和|y 〉分别是左和右圆极化光子的差与和,所以它们对应的幅度分别是〈J X λX |T |J γλγ,J ex λex 〉与〈J X λX |T |J γ-λγ,J ex λex 〉的差与和.J ex 和λex 分别是交换粒子粒子的角动量和螺旋性.螺旋性定义为粒子自旋在其运动方向上的投影,其取值为-s 至s .在相互作用顶点,根据宇称和角动量守恒,〈J X λX |T |J γλγ,J exλex 〉∞τ〈J X -λX |T |J γ-λγ,J ex -λex 〉[14,15],其中τ=τX τex .从测量X 的极化,可判定τ=+1或τ=-1,于是如果X 的τX 知道了,交换粒子的τex 就知道了,反之亦然.当t 道交换π+时,如果τX =-1,X 的线极化方向与光子的线极化方向平行;如果τX =+1,X 的线极化方向与光子的线极化方向垂直[13].非极化和圆极化光子不具备这种性质.2.1.6　分波分析分析实验数据的重要工具是分波分析P WA (partial wave analysis ).螺旋性的反应幅度能够多极展开:T λ3λ4;λ1λ2=16πρJ ≥μ(2J +1)T J λ3λ4;λ1λ2(s )d Jλλ′(θs ),(5)λ=λ1-λ2,λ′=λ3-λ4,m =max (|λ|,|λ′|),其中T Jλ3λ4;λ1λ2是分波的系数;λ1、λ2、λ3和λ4分别是光子、N 、X 和N ′的螺旋性;J 是分波的阶数;d J λλ′(θs )是转动矩阵,d J 00(θs )=P J(θs );在质心坐标系中,λ和λ′分别是碰撞前后总角动量在运动方向上的投影.通过拟合角分布和各种极化观测量,确定分波系数,然后得到共振参数及J PC等.P WA 具有固有的缺点:当增加分波时,强分波串到弱分波,这种现象称为Dannachie 的连续模糊性或称泄漏.为了减少泄漏,建立密封性、质量分辨好、允许高计数率、对各种衰变方式灵敏、效率随角度变化均匀的探测器是必要的.D 厅的探测器正是根据这些要求设计的.2.2原子核构件核子的基本结构核子是原子核的基本构件,它的质量、自旋及相互作用性质直接取决于其内部的夸克和胶子的运动,它可用附录(Ⅰ)的(1)式描述,研究核子结构是QCD 的突出任务.在1994年以后,Muller [16],J i [17]和Radyush 2kin [18]等人提出了新的普适于硬的遍举过程的GP D ,这些过程如:深度虚光子的康普顿散射DVCS (deep ly virtual Co mp t on scattering ),ep →ep γ;深度虚介子产生过程DVMP (deep ly virtual mes on p r oduc 2ti on ),ep →epm;深度虚光子的双轻子产生,ep →ep ll 等.DVCS 和DVMP 的手袋(handbag )见图4,从DVCS 的手袋图看出,电子发射的虚光子γ3从质子击出一个夸克,高速夸克传播距离z 发射实光子γ后返回质子.在DVMP 中,高速夸克发射的胶子转变成正反夸克对qq _,其中q 返回质子,q _与被击中的夸克形成赝标量或矢量介子.GP D 打开了新的研究非微扰QCD 的窗口.它是图4　DVCS 和DVMP 的手袋图形状因子FF (for m fact or )、部分子分布函数P DF(part on distributi on functi ons )、分布幅度的统一.它给出了许多新的预言:夸克轨道角动量同GP D 的关系;矢量介子产生反应对胶子灵敏;冲击参数分布能够给出纵向动量比例x 和冲击参数b ⊥关联的三维图像,称为核子的断层扫描[19];通过DVCS 和BH (Bethe -Heitler )相干项可以得到反应幅度的相位参数,实现强子的全息照相[20];GP D 的二次矩是引力理论中的能量-动量张量形状因子等.由于它包含了丰富的强子结构信息,所以利用12Ge V 测量GP D 是重点之一.在12Ge V ,通过单举、半单举和遍举及极化测量,研究价夸克极化的P DF 、微扰QCD 的组分标度、强子螺旋性守恒、核子自旋结构、横动量相关的分布函数、高级t w ist 效应、普适的G DH (gerasi m ov drell hearn )求和规则、夸克-强子二重性等广泛的课题.2.2.1　GP D在硬反应(hard reacti on )中,夸克场算符[21]为O (x )=1/4π・∫d z -exp (xP +z -)q _(-z /2)Γi W [-z /2,z /2]q (z /2)|z +=0,z =0,(6)Γi =γ+,γ+γ5,σ+jγ5,W [-z /2,z /2]=P exp (-i g ・∫d sz μA μ(sz )),其中P +是强子动量的正分量;xP +是激活夸克动量的正分量,x =(x i +x f )/2,x i 和x f 分别是初、末态激活夸克携带强子正动量的比例;γ+、γ+γ5、σ+j γ5分别是矢量、轴矢量和张量的D irac 算符;q _(-z /2)和q (z /2)分别是在位置-z /2和z /2的共轭夸克和夸克的场算符;W ils on 连线W 保证了算符的规范不变性,积分从-z /2到z /2,A μ是胶子场.当取光锥规范时,Aμ=0,W ils on 连线等于1.算符O (x )是用光锥坐标表示的,光锥坐标定义为,υ±=υ0±υ3,υ=(υ1,υ2);夸克q 与其共轭夸克q _的间距,即虚光子吸收点和光子或介子的发射点的间距z 满足光锥条件:z 2=2z +z --z 2=0(1/Q 2),z +～M x B /Q 2,z -～1/M x B .夸克场算符的强子矩阵元为F i (x,ξ,t )=∫d z-/4πexp (xP +z -)〈p ′,s ′|q _(-z /2)Γi q (z /2)|p,s 〉,(7)其中p,s 和p ′,s ′分别表示初、末态强子的动量和自旋的极化.在弹性散射、D I S 和DEP 中,矩阵元分别对应:z =0,p ′≠p ;z ≠0,p ′=p 和z ≠0,p ′≠p 三种情况.z =0和z ≠0分别称为局部和非局部算符.矩阵元可用矢量、轴矢量和张量的基展开,在t w ist -2的层次上,Γi =γ+,F i (x,ξ,t,Q 2)=1/2P +[H (x,ξ,t )u_γ+u +E (x,ξ,t )u _(i σ+αΔα/2m )u ],(8)Γi =γ+γ5,F i (x,ξ,t,Q 2)=1/2P +[H _(x,ξ,t )u _γ+γ5u +E _(x,ξ,t )u _(γ5Δ+/2m )u ],(9)Γi =σ+j γ5,F i (x,ξ,t,Q 2) =-i /2P+[H T (x,ξ,t )u _σ+jγ5u + H _T (x,ξ,t )u _(ε+j αβΔαP β/m 2)u +E T (x,ξ,t )u _(ε+jαβΔαγβ/2m )u +E _T (x,ξ,t )u _(ε+jαβP αγβ/m )u ],(10)其中2P +=(p ′+p )+,2ξ=(x f -x i )=(p ′-p )+/P +,t =Δ2,Δ=p ′-p .H 、E 和H _、E _分别是自旋平均和螺旋性相关的手征偶(chiral even )的GP D,H T 、H _T 、E T 和E _T 分别是横向自旋相关的手征奇(chiralodd )的GP D,共8个GP D.它们是洛伦兹标量x 、ξ、t和Q 2的函数.在B j orken 极限,ξ=x B /(2-x B ).ξ和x 的范围在-1和1之间.-ξ≥x ≥-1、-ξ≤x ≤ξ和ξ≤x ≤1分别是反夸克区、中心区和夸克区,中心区的GP D 是强子内部存在介子的概率.对于胶子可写成类似的算符和GP D[22].DVCS 对夸克味量子数不灵敏,其反应截面∝Q-4.在DVMP 中,产生的赝标量介子选H _和E _及其对自旋灵敏,矢量介子选择H 和E 及其对自旋不灵敏,DVMP 的反应截面∝Q -6[23].(1)GP D 同P DF 和FF 的关系P DF 是GP D 在ξ=t =0的极限,即H (x,0,0)=f 1(x ),H _(x,0,0)=g 1(x ),H T (x,0,0)=h 1(x ),(11)其中f 1(x )、g 1(x )和h 1(x )分别是在非极化、纵向和横向极化的核子中存在相应极化的夸克具有x 的概率.实验上f 1(x )和g 1(x )已经测量了.由于h 1(x )是手征奇的,实验上很难测量,人们正期待德国GSI 未来极化质子和反质子的对撞实验.定义GP D 的Mellin 矩=∫d xxn -1GP D.它将非局部夸克和胶子的场算符转换成局部算符,便于用格点QC D 计算.核子电磁的FF 可表示成n =1的矩,F 1(t )=∑e q∫d xH q(x,ξt )F 2(t )=∑eq∫d xE q(x,ξ,t )(12)轴矢量和张量FF 同GP D 有类似的关系.在实光子的康普顿散射中,相应的FF 是GP D 的n =0的矩:R V (t )=∑e q ∫d x 1xH q(x,ξ,t ),R T (t )=∑e q∫d x 1xE q (x,ξ,t ),R A (t )=∑eq∫d x 1xH _q(x,ξ,t ),(13)所有的积分限从-1到+1.(2)季向东的求和规则当n =2时得到季向东[17]的求和规则:J q =12Δρq -L q =12∫1-1x d x[H q (x,ξ,0)+E q(x,ξ,0)],(14)其中J q、Δρq 和L q 分别是味q 夸克的总角动量、自旋和轨道角动量.通过测量H q 和E q能够计算出J q ,扣出从D I S 实验得到的Δρq ,可求出L q.最新的测量结果表明,胶子对核子自旋的贡献很小[24],所以L q对解答自旋危机是十分关键的.(3)冲击参数分布冲击参数分布I P D (i m pact para meter distribu 2ti on )是在ξ=0,Δ⊥≠0,Δ∥=0时的GP D 的富利叶变换[21].如自旋平均的I P Dh (x,b ⊥)=∫d 2Δexp (i b ⊥Δ⊥)H (x,ξ=0,Δ⊥)/(2π)2,(15)其中b ⊥是相对横动量中心R ⊥=ρi x i r i ⊥的距离,x k 和r k ⊥分别是第k 个部分子的纵向动量及其横向位置.8个GP D 对应的I P D 具有概率解释.在图5,从左至右,FF 是二维b ⊥的函数,P DF 是一维x 的函数,I P D 则将两者联立起来得到三维分布.测量核子的I P D 将使人们对核子结构有突破性的认识.图5　FF 、P DF 和I P D的关系图6　在非极化和横向X 方向极化质子中非极化夸克的I P D (4)I P D 的极化效应从I P D 得到了两种新的极化效应[25]:第一,在横向X 方向极化的核子中,味q 非极化的密度q X (x,b ⊥)不是轴对称的,并在Y 方向移位.它可写城如下形式:q X (x,b ⊥)=q (x,b ⊥)-5/5b Y [E q (x,b ⊥)]/2M 4π2,E q (x,b ⊥)=∫d 2Δ⊥E q (x,0,-Δ⊥)ex p (-i b ⊥Δ⊥)(16)其中q (x,b ⊥)是在非极化核子中的非极化夸克的I P D.在图6左侧的两个图分别是在非极化和X 方向极化的质子中,纵向动量x =0.5的u 夸克的I P D ,非极化时I P D 是轴对称的,极化时I P D 是非轴对称的,并在Y 方向移位.在图6右侧的两个图分别是d 夸克对应的I P D.d 夸克比u 夸克的变形大,两者的移位方向相反.平均移位和方向正比于该夸克的反常磁矩k q 及其符号,平均移位可表示成:d q Y =∫d x ∫d 2b ⊥q (x,b ⊥)b Y =1/(2M )∫d xE q (x,0,0)=k q /2M,(17)其中M 是核子的质量,d qY ～0.2f m.第二,在非极化的核子中,味q 的夸克横向极化的密度分布q i (x,b ⊥)=-s i e ij9/9b j [2H _q (x,b _)+E T (x,b ⊥)]/2M 4π2,(18)其中s 是夸克自旋的分量,i,j =X 或Y .q i (x,b ⊥)具有类似的变形.在文献[26]中,明确地给出了I P D 与横动量相关的时间反演不守恒的P DF 的关系:f ⊥1T ∴-E ′,h ⊥1∴-(E ′T +2H _″T ),h ⊥1T ∴2H _″T ,其中f ′=(5/5b 2)f,f ″=(5/5b 2)2f .I P D 极化效应说明了SS A起源于夸克密度分布变形和位移,它是强子自旋物理的焦点之一,并有待实验上的验证.(5)GP D 的测量方法实验上将采用两类遍举极化实验测量GP D.第一类利用高Q 2的弹性散射和共振跃迁、高-t 值的康普顿散射和高-t 值及低Q 2的电产生介子等反应得到相应的FF,它们同GP D 的关系见(12)和(13)式.反应概图分别表示在图7中的(a ),(b ),(c )和(d ).在图7(a )中,核子内的一个价夸克吸收入射的虚(实)光子后,立刻返回核子,并迅速地将其能动量传递给其他的价夸克,最后核子获得了能动量;在图7(b )中,高能动量的夸克返回核子,使核子处在激发态;在图7(c )和7(d )中,高能动量的夸克飞行距离z 后放射一个实光子或介子并返回核子.第一类测量将约束GP D 在高-t值和小b ⊥的行为.第二类是利用高Q 2和小-t 值的DVCS 和DV MP 等直接地测量GP D (见图4).图7　形状因子反应的概图2.2.2　大Q2物理大Q2物理的内容很多,主要是研究从非微扰向微扰的过渡.以μpG p E/G p M同Q2关系为例说明J lab的重要成果及大Q2的必要.在e↑p→ep′↑弹性极化迁移反应中,在单光子交换下,质子电磁形状因子的比G p E/G p M正比于反冲质子p′的横向和纵极化度P T和P L,G p E/G p M=-P T/P L・(E+E′)tan(θ/2)(2M)-1,(19)其中E和E′是入射和出射电子的能量,θ是入射和出射电子间的夹角.在图8中,绿点表示μpG p E/G p M,它随着Q2增大线性地减少,说明在质子内电荷和电流的分布不同[27,28],其中μp是质子的磁矩.过去通过非极化的Rosenbluth分离方法得到的μpG p E/G p M在1. 0附近,说明电荷和电流的分布相同.极化和非极化两种实验方法得出两种截然不同的结论,在实验和理论上产生了极大的反响.在实验上,JLab再次用Rosenbluth方法测量说明过去的结果是正确的.在理论上,Guichon等人[29]提出了除单光子交换外还有双光子交换,双光子交换部分对非极化的结果贡献大,对极化的贡献小.目前,实验上正在测量单-双光子交换在电子散射中的比例.现在需要知道Q2等于多少μpG p E/G p M才能达到微扰QCD的预言值?在12Ge V,Q2可达14Ge V2. 2.2.3　大x物理从图12对DVCS的运动学复盖范围能够看出,强流12Ge V为研究大x物理提供了新的机遇.根据大量非极化质子的实验数据,在x=0.5—1.0的区域,海夸克(sea quark)的贡献可以忽略,是一个纯的价夸克区.在该区,目的是研究价夸克和胶子的动力学,从而检验S U(6)对称的价夸克模型、S U(6)破缺、微扰QCD的强子螺旋性守恒等理论.另外,为高能强子-强子碰撞和寻找新粒子及新物理提供数据.过去在x>0.3的区域,由于价夸克的分布概率也很小,所以实验数据很少,即便有,数据的不确定度也很图8　GpE/GpM同Q2的关系大,不能鉴别理论模型.图9显示出中子纵向极化不对称A n1同x的关系,绿点是6Ge V的数据,红点是A 厅计划测量的数据[30].图9　A n1同x的关系2.3　原子核物理原子核物理分为研究原子核本身性质和将原子核作为研究QCD的实验室等两个方面.前者研究强子在核介质中的改性,核子-介子自由度在什么标度是可靠的,核子-介子自由度如何过渡到夸克-胶子自由度,核子-核子相互作用中的长程(>2f m)张量力和短程排斥力的QCD基础等;后者研究色透明性,夸克强子化的时空特性,高密度夸克分布的性质等.图10表示出在原子核内两个核子重迭的概率很高,在重叠区域核子密度达到～5—10倍于正常值,它为研究高密度和夸克部分去禁闭及中子星的性质提供了难得的条件.实验上通过测量x >1的P DF 能够认识高密度的性质.图10　在原子核内两个核子重迭2.4　检验对称性和寻找新的标准模型JLab 将通过Pri m akoff 效应测量轻的赝标量介子π0,η,η′→γγ的衰变宽度和跃迁形状因子,研究手征自发破缺和手征反常[31].世界上,通过极高能的反应寻找新粒子及新相互作用力,和在低能比较S M 预言的参数与测量值的偏离等两种方法检验S M 和寻求新物理.JLab 将通过低能宇称不守恒的电弱相干散射测量质子的弱荷,以及电弱混合角sin 2θW与S M 预言相比较.3　美国托马斯杰斐逊国家加速器装置(简称JLab )的状况 JLab 属于美国能源部,由美国东南大学研究协会管理.它是NS AC 在1979年的LRP 中优先推荐建造的占空因子为100%、能量为4Ge V 的电子加速器,于1987年在V iginia Ne wport Ne ws 建造,它是工作在液氦温度的超导铌射频共振腔加速电子的直线加速器,该加速器于1994年夏运行,在1996年电子能量提高到6Ge V.在2010年电子能量将达到12Ge V ,以后能量提高到24Ge V 也是可能的.目前,JLab 的CE 2BAF 是世界上最大的超导射频直线加速器,它的束流品质超过了其他连续电子束加速器.除初级电子束外,通过纵向极化电子在重金属上的韧致辐射和在薄片晶体上的相干韧致辐射,分别产生圆极化和线极化的实光子.韧致辐射后的电子在磁偶极场的作用下偏转到电子焦面探测器,电子信号与光子反应产物信号符合,从电子能量能够确定对应光子的能量,这种光子称为标记光子.在20世纪90年代初,世界上出现了连续束电子加速器,如德国Mainz 大学的0.85Ge V 的MAM I (Mainz M icr otr on ),美国M I T 大学的1.1Ge V 的Bates 、德国Bonn 大学的3.5Ge V 的E LS A (Electr on Stretcher Accelerat or )及荷兰N I KHEF (Nati onal I nsti 2tute f or Nuclear Physics and H igh -Energy Physics )的0.9Ge V 的AmPS (Am sterda m Pulse Stretcher ).除MA 2M I 是电子感应方式实现连续束外,其余都是贮存拉长环(st orage /stretcher )方式.目前,N I KHEF 已关闭,Bates 于2005年结束了核物理计划,MAM I 的能量将提高到1.5Ge V ,ELS A 还在运行.3.1　加速器6Ge V 和未来12Ge V CE BAF 的结构和实验厅的布局见图11.经预直线加速器,能量为45Me V 的电子注入到80m 长的超导直线加速段,能量达到0.56Ge V ,经弧形轨道arc 进入另一个80m 的超导直线加速段,能量达1.12Ge V.在2个直线加速段回转5次,电子能量达到5.6Ge V.在A 、B 、C 3个实验厅能同时工作,并各自可以工作在不同的电子能量,能量分别是1.1、2.2、3.3、4.4和5.6Ge V.其束流品质为:平均束流强度I =200μA,发散度ε～2×10-9m ・rad,能散度σE /E =2×10-5.用极化的激光照射拉伸或非拉伸的Ga A s 光阴极,通过光电效应产生纵向极化度P e=70%—85%的电子.光子的能量及其分辨率分别为E γ<6GeV 和ΔE γ/E γ=10-3.电子的纵向极化度利用莫特(Mott )、Moller 和康普顿散射极化仪测量.图11　JLab 加速器的结构和实验厅的布局美国核科学家在建造4Ge V 时,就认识到其能量是低的,因而在直线加速段的隧道内留有一定的空间.刚开始运行时,即1994年,就酝酿提高能量的物理和需要的设备.在2001年2月,形成了之《驱动。

Chapter 11 Geographical Distribution Present distribution cannot be accounted for by differences in physical conditions. Importance of barriers. Affinity of the productions of the same continent. Centres of creation. Means of dispersal, by changes of climate and of the level of the land, and by occasional means. Dispersal during the Glacial period co-extensive with the world.In considering the distribution of organic beings over the face of the globe, the first great fact which strikes us is, that neither the similarity nor the dissimilarity of the inhabitants of various regions can be accounted for by their climatal and other physical conditions. Of late, almost every author who has studied the subject has come to this conclusion. The case of America alone would almost suffice to prove itstruth: for if we exclude the northern parts where the circumpolar land is almost continuous, all authors agree that one of the most fundamental divisions in geographical distribution is that between the New and Old Worlds; yet if we travel over the vast American continent, from the central parts of the United States to its extreme southern point, we meet with the most diversified conditions; the most humid districts, arid deserts, lofty mountains, grassy plains, forests, marshes, lakes, and great rivers, under almost every temperature. There is hardly a climate or condition in the Old World which cannot be paralleled in the New--at least as closely as the same species generally require; for it is a most rare case to find a group of organisms confined to any small spot, having conditions peculiar in only a slight degree; for instance, small areas in the Old World could be pointed out hotter thanany in the New World, yet these are not inhabited by a peculiar fauna or flora. Notwithstanding this parallelism in the conditions of the Old and New Worlds, how widely different are their living productions!In the southern hemisphere, if we compare large tracts of land in Australia, South Africa, and western South America, between latitudes 25 deg and 35 deg, we shall find parts extremely similar in all their conditions, yet it would not be possible to point out three faunas and floras more utterly dissimilar. Or again we may compare the productions of South America south of lat. 35 deg with those north of 25 deg, which consequently inhabit a considerably different climate, and they will be found incomparably more closely related to each other, than they are to the productions of Australia or Africa under nearly the same climate. Analogous facts could be givenwith respect to the inhabitants of the sea.A second great fact which strikes us in our general review is, that barriers of any kind, or obstacles to free migration, are related in a close and important manner to the differences between the productions of various regions. We see this in the great difference of nearly all the terrestrial productions of the New and Old Worlds, excepting in the northern parts, where the land almost joins, and where, under a slightly different climate, there might have been free migration for the northern temperate forms, as there now is for the strictly arctic productions. We see the same fact in the great difference between the inhabitants of Australia, Africa, and South America under the same latitude: for these countries are almost as much isolated from each other as is possible. On each continent, also, we see the same fact; for on the opposite sides of lofty andcontinuous mountain-ranges, and of great deserts, and sometimes even of large rivers, we find different productions; though as mountain chains, deserts, etc., are not as impassable, or likely to have endured so long as the oceans separating continents, the differences are very inferior in degree to those characteristic of distinct continents.Turning to the sea, we find the same law. No two marine faunas are more distinct, with hardly a fish, shell, or crab in common, than those of the eastern and western shores of South and Central America; yet these great faunas are separated only by the narrow, but impassable, isthmus of Panama. Westward of the shores of America, a wide space of open ocean extends, with not an island as a halting-place for emigrants; here we have a barrier of another kind, and as soon as this is passed we meet in the eastern islands of the Pacific, with another and totallydistinct fauna. So that here three marine faunas range far northward and southward, in parallel lines not far from each other, under corresponding climates; but from being separated from each other by impassable barriers, either of land or open sea, they are wholly distinct. On the other hand, proceeding still further westward from the eastern islands of the tropical parts of the Pacific, we encounter no impassable barriers, and we have innumerable islands as halting-places, until after travelling over a hemisphere we come to the shores of Africa; and over this vast space we meet with no well-defined and distinct marine faunas. Although hardly one shell, crab or fish is common to the above-named three approximate faunas of Eastern and Western America and the eastern Pacific islands, yet many fish range from the Pacific into the Indian Ocean, and many shells are common to the eastern islands of the Pacificand the eastern shores of Africa, on almost exactly opposite meridians of longitude.A third great fact, partly included in the foregoing statements, is the affinity of the productions of the same continent or sea, though the species themselves are distinct at different points and stations. It is a law of the widest generality, and every continent offers innumerable instances. Nevertheless the naturalist in travelling, for instance, from north to south never fails to be struck by the manner in which successive groups of beings, specifically distinct, yet clearly related, replace each other. He hears from closely allied, yet distinct kinds of birds, notes nearly similar, and sees their nests similarly constructed, but not quite alike, with eggs coloured in nearly the same manner. The plains near the Straits of Magellan are inhabited by one species of Rhea(American ostrich), and northward the plains of La Plata by another species of the same genus; and not by a true ostrich or emeu, like those found in Africa and Australia under the same latitude. On these same plains of La Plata, we see the agouti and bizcacha, animals having nearly the same habits as our hares and rabbits and belonging to the same order of Rodents, but they plainly display an American type of structure. We ascend the lofty peaks of the Cordillera and we find an alpine species of bizcacha; we look to the waters, and we do not find the beaver or musk-rat, but the coypu and capybara, rodents of the American type. Innumerable other instances could be given. If we look to the islands off the American shore, however much they may differ in geological structure, the inhabitants, though they may be all peculiar species, are essentially American. We may look back to past ages, as shown in the last chapter, and wefind American types then prevalent on the American continent and in the American seas. We see in these facts some deep organic bond, prevailing throughout space and time, over the same areas of land and water, and independent of their physical conditions. The naturalist must feel little curiosity, who is not led to inquire what this bond is.This bond, on my theory, is simply inheritance, that cause which alone, as far as we positively know, produces organisms quite like, or, as we see in the case of varieties nearly like each other. The dissimilarity of the inhabitants of different regions may be attributed to modification through natural selection, and in a quite subordinate degree to the direct influence of different physical conditions. The degree of dissimilarity will depend on the migration of the more dominant forms of life from one region into another having been effectedwith more or less ease, at periods more or less remote;--on the nature and number of the former immigrants;--and on their action and reaction, in their mutual struggles for life;--the relation of organism to organism being, as I have already often remarked, the most important of all relations. Thus the high importance of barriers comes into play by checking migration; as does time for the slow process of modification through natural selection. Widely-ranging species, abounding in individuals, which have already triumphed over many competitors in their own widely-extended homes will have the best chance of seizing on new places, when they spread into new countries. In their new homes they will be exposed to new conditions, and will frequently undergo further modification and improvement; and thus they will become still further victorious, and will produce groups of modified descendants.On this principle of inheritance with modification, we can understand how it is that sections of genera, whole genera, and even families are confined to the same areas, as is so commonly and notoriously the case.I believe, as was remarked in the last chapter, in no law of necessary development. As the variability of each species is an independent property, and will be taken advantage of by natural selection, only so far as it profits the individual in its complex struggle for life, so the degree of modification in different species will be no uniform quantity. If, for instance, a number of species, which stand in direct competition with each other, migrate in a body into a new and afterwards isolated country, they will be little liable to modification; for neither migration nor isolation in themselves can do anything. These principles come into playonly by bringing organisms into new relations with each other, and in a lesser degree with the surrounding physical conditions. As we have seen in the last chapter that some forms have retained nearly the same character from an enormously remote geological period, so certain species have migrated over vast spaces, and have not become greatly modified.On these views, it is obvious, that the several species of the same genus, though inhabiting the most distant quarters of the world, must originally have proceeded from the same source, as they have descended from the same progenitor. In the case of those species, which have undergone during whole geological periods but little modification, there is not much difficulty in believing that they may have migrated from the same region; for during the vast geographical and climatal changes which will have supervened since ancient times, almost any amount ofmigration is possible. But in many other cases, in which we have reason to believe that the species of a genus have been produced within comparatively recent times, there is great difficulty on this head. It is also obvious that the individuals of the same species, though now inhabiting distant and isolated regions, must have proceeded from one spot, where their parents were first produced: for, as explained in the last chapter, it is incredible that individuals identically the same should ever have been produced through natural selection from parents specifically distinct.We are thus brought to the question which has been largely discussed by naturalists, namely, whether species have been created at one or more points of the earth's surface. Undoubtedly there are very many cases of extreme difficulty, in understanding how the same species could possibly havemigrated from some one point to the several distant and isolated points, where now found. Nevertheless the simplicity of the view that each species was first produced within a single region captivates the mind. He who rejects it, rejects the vera causa of ordinary generation with subsequent migration, and calls in the agency of a miracle. It is universally admitted, that in most cases the area inhabited by a species is continuous; and when a plant or animal inhabits two points so distant from each other, or with an interval of such a nature, that the space could not be easily passed over by migration, the fact is given as something remarkable and exceptional. The capacity of migrating across the sea is more distinctly limited in terrestrial mammals, than perhaps in any other organic beings; and, accordingly, we find no inexplicable cases of the same mammal inhabiting distant points of the world. No geologistwill feel any difficulty in such cases as Great Britain having been formerly united to Europe, and consequently possessing the same quadrupeds. But if the same species can be produced at two separate points, why do we not find a single mammal common to Europe and Australia or South America? The conditions of life are nearly the same, so that a multitude of European animals and plants have become naturalised in America and Australia; and some of the aboriginal plants are identically the same at these distant points of the northern and southern hemispheres? The answer, as I believe, is, that mammals have not been able to migrate, whereas some plants, from their varied means of dispersal, have migrated across the vast and broken interspace. The great and striking influence which barriers of every kind have had on distribution, is intelligible only on the view that the great majority of species have been produced on one sidealone, and have not been able to migrate to the other side. Some few families, many sub-families, very many genera, and a still greater number of sections of genera are confined to a single region; and it has been observed by several naturalists, that the most natural genera, or those genera in which the species are most closely related to each other, are generally local, or confined to one area. What a strange anomaly it would be, if, when coming one step lower in the series, to the individuals of the same species, a directly opposite rule prevailed; and species were not local, but had been produced in two or more distinct areas!Hence it seems to me, as it has to many other naturalists, that the view of each species having been produced in one area alone, and having subsequently migrated from that area as far as its powers of migration and subsistence under past andpresent conditions permitted, is the most probable. Undoubtedly many cases occur, in which we cannot explain how the same species could have passed from one point to the other. But the geographical and climatal changes, which have certainly occurred within recent geological times, must have interrupted or rendered discontinuous the formerly continuous range of many species. So that we are reduced to consider whether the exceptions to continuity of range are so numerous and of so grave a nature, that we ought to give up the belief, rendered probable by general considerations, that each species has been produced within one area, and has migrated thence as far as it could. It would be hopelessly tedious to discuss all the exceptional cases of the same species, now living at distant and separated points; nor do I for a moment pretend that any explanation could be offered of many such cases. But after somepreliminary remarks, I will discuss a few of the most striking classes of facts; namely, the existence of the same species on the summits of distant mountain-ranges, and at distant points in the arctic and antarctic regions; and secondly (in the following chapter), the wide distribution of freshwater productions; and thirdly, the occurrence of the same terrestrial species on islands and on the mainland, though separated by hundreds of miles of open sea. If the existence of the same species at distant and isolated points of the earth's surface, can in many instances be explained on the view of each species having migrated from a single birthplace; then, considering our ignorance with respect to former climatal and geographical changes and various occasional means of transport, the belief that this has been the universal law, seems to me incomparably the safest.In discussing this subject, we shall be enabled at the same time to consider a point equally important for us, namely, whether the several distinct species of a genus, which on my theory have all descended from a common progenitor, can have migrated (undergoing modification during some part of their migration) from the area inhabited by their progenitor. If it can be shown to be almost invariably the case, that a region, of which most of its inhabitants are closely related to, or belong to the same genera with the species of a second region, has probably received at some former period immigrants from this other region, my theory will be strengthened; for we can clearly understand, on the principle of modification, why the inhabitants of a region should be related to those of another region, whence it has been stocked. A volcanic island, for instance, upheaved and formed at the distance of a few hundredsof miles from a continent, would probably receive from it in the course of time a few colonists, and their descendants, though modified, would still be plainly related by inheritance to the inhabitants of the continent. Cases of this nature are common, and are, as we shall hereafter more fully see, inexplicable on the theory of independent creation. This view of the relation of species in one region to those in another, does not differ much (by substituting the word variety for species) from that lately advanced in an ingenious paper by Mr. Wallace, in which he concludes, that "every species has come into existence coincident both in space and time with apre-existing closely allied species." And I now know from correspondence, that this coincidence he attributes to generation with modification.The previous remarks on "single and multiple centres ofcreation" do not directly bear on another alliedquestion,--namely whether all the individuals of the same species have descended from a single pair, or single hermaphrodite, or whether, as some authors suppose, from many individuals simultaneously created. With those organic beings which never intercross (if such exist), the species, on my theory, must have descended from a succession of improved varieties, which will never have blended with other individuals or varieties, but will have supplanted each other; so that, at each successive stage of modification and improvement, all the individuals of each variety will have descended from a single parent. But in the majority of cases, namely, with all organisms which habitually unite for each birth, or which often intercross, I believe that during the slow process of modification the individuals of the species will have been keptnearly uniform by intercrossing; so that many individuals will have gone on simultaneously changing, and the whole amount of modification will not have been due, at each stage, to descent from a single parent. To illustrate what I mean: our English racehorses differ slightly from the horses of every other breed; but they do not owe their difference and superiority to descent from any single pair, but to continued care in selecting and training many individuals during many generations.Before discussing the three classes of facts, which I have selected as presenting the greatest amount of difficulty on the theory of "single centres of creation," I must say a few words on the means of dispersal.MEANS OF DISPERSAL.Sir C. Lyell and other authors have ably treated this subject. I can give here only the briefest abstract of the moreimportant facts. Change of climate must have had a powerful influence on migration: a region when its climate was different may have been a high road for migration, but now be impassable;I shall, however, presently have to discuss this branch of the subject in some detail. Changes of level in the land must also have been highly influential: a narrow isthmus now separates two marine faunas; submerge it, or let it formerly have been submerged, and the two faunas will now blend or may formerly have blended: where the sea now extends, land may at a former period have connected islands or possibly even continents together, and thus have allowed terrestrial productions to pass from one to the other. No geologist will dispute that great mutations of level have occurred within the period of existing organisms. Edward Forbes insisted that all the islands in the Atlantic must recently have been connected with Europe orAfrica, and Europe likewise with America. Other authors have thus hypothetically bridged over every ocean, and have united almost every island to some mainland. If indeed the arguments used by Forbes are to be trusted, it must be admitted that scarcely a single island exists which has not recently been united to some continent. This view cuts the Gordian knot of the dispersal of the same species to the most distant points, and removes many a difficulty: but to the best of my judgment we are not authorized in admitting such enormous geographical changes within the period of existing species. It seems to me that we have abundant evidence of great oscillations of level in our continents; but not of such vast changes in their position and extension, as to have united them within the recent period to each other and to the several intervening oceanic islands. I freely admit the former existence of many islands,now buried beneath the sea, which may have served as halting places for plants and for many animals during their migration. In the coral-producing oceans such sunken islands are now marked, as I believe, by rings of coral or atolls standing over them. Whenever it is fully admitted, as I believe it will some day be, that each species has proceeded from a single birthplace, and when in the course of time we know something definite about the means of distribution, we shall be enabled to speculate with security on the former extension of the land. But I do not believe that it will ever be proved that within the recent period continents which are now quite separate, have been continuously, or almost continuously, united with each other, and with the many existing oceanic islands. Several facts in distribution,--such as the great difference in the marine faunas on the opposite sides of almost every continent,--theclose relation of the tertiary inhabitants of several lands and even seas to their present inhabitants,--a certain degree of relation (as we shall hereafter see) between the distribution of mammals and the depth of the sea,--these and other such facts seem to me opposed to the admission of such prodigious geographical revolutions within the recent period, as are necessitated on the view advanced by Forbes and admitted by his many followers. The nature and relative proportions of the inhabitants of oceanic islands likewise seem to me opposed to the belief of their former continuity with continents. Nor does their almost universally volcanic composition favour the admission that they are the wrecks of sunken continents;--if they had originally existed as mountain-ranges on the land, some at least of the islands would have been formed, like other mountain-summits, of granite, metamorphic schists, oldfossiliferous or other such rocks, instead of consisting of mere piles of volcanic matter.I must now say a few words on what are called accidental means, but which more properly might be called occasional means of distribution. I shall here confine myself to plants. In botanical works, this or that plant is stated to be ill adapted for wide dissemination; but for transport across the sea, the greater or less facilities may be said to be almost wholly unknown. Until I tried, with Mr. Berkeley's aid, a few experiments, it was not even known how far seeds could resist the injurious action of sea-water. To my surprise I found that out of 87 kinds, 64 germinated after an immersion of 28 days, and a few survived an immersion of 137 days. For convenience sake I chiefly tried small seeds, without the capsule or fruit; and as all of these sank in a few days, they could not be floatedacross wide spaces of the sea, whether or not they were injured by the salt-water. Afterwards I tried some larger fruits, capsules, etc., and some of these floated for a long time. It is well known what a difference there is in the buoyancy of green and seasoned timber; and it occurred to me that floods might wash down plants or branches, and that these might be dried on the banks, and then by a fresh rise in the stream be washed into the sea. Hence I was led to dry stems and branches of 94 plants with ripe fruit, and to place them on sea water. The majority sank quickly, but some which whilst green floated for a very short time, when dried floated much longer; for instance, ripe hazel-nuts sank immediately, but when dried, they floated for 90 days and afterwards when planted they germinated; an asparagus plant with ripe berries floated for 23 days, when dried it floated for 85 days, and the seeds afterwardsgerminated: the ripe seeds of Helosciadium sank in two days, when dried they floated for above 90 days, and afterwards germinated. Altogether out of the 94 dried plants, 18 floated for above 28 days, and some of the 18 floated for a very much longer period. So that as 64/87 seeds germinated after an immersion of 28 days; and as 18/94 plants with ripe fruit (but not all the same species as in the foregoing experiment) floated, after being dried, for above 28 days, as far as we may infer anything from these scanty facts, we may conclude that the seeds of 14/100 plants of any country might be floated by sea-currents during 28 days, and would retain their power of germination. In Johnston's Physical Atlas, the average rate of the several Atlantic currents is 33 miles per diem (some currents running at the rate of 60 miles per diem); on this average, the seeds of 14/100 plants belonging to one country might be floatedacross 924 miles of sea to another country; and when stranded, if blown to a favourable spot by an inland gale, they would germinate.Subsequently to my experiments, M. Martens tried similar ones, but in a much better manner, for he placed the seeds in a box in the actual sea, so that they were alternately wet and exposed to the air like really floating plants. He tried 98 seeds, mostly different from mine; but he chose many large fruits and likewise seeds from plants which live near the sea; and this would have favoured the average length of their flotation and of their resistance to the injurious action of the salt-water. On the other hand he did not previously dry the plants or branches with the fruit; and this, as we have seen, would have caused some of them to have floated much longer. The result was that 18/98 of his seeds floated for 42 days, and werethen capable of germination. But I do not doubt that plants exposed to the waves would float for a less time than those protected from violent movement as in our experiments. Therefore it would perhaps be safer to assume that the seeds of about 10/100 plants of a flora, after having been dried, could be floated across a space of sea 900 miles in width, and would then germinate. The fact of the larger fruits often floating longer than the small, is interesting; as plants with large seeds or fruit could hardly be transported by any other means; and Alph. de Candolle has shown that such plants generally have restricted ranges.But seeds may be occasionally transported in another manner. Drift timber is thrown up on most islands, even on those in the midst of the widest oceans; and the natives of the coral-islands in the Pacific, procure stones for their tools, solely from theroots of drifted trees, these stones being a valuable royal tax.I find on examination, that when irregularly shaped stones are embedded in the roots of trees, small parcels of earth are very frequently enclosed in their interstices and behind them,--so perfectly that not a particle could be washed away in the longest transport: out of one small portion of earth thus COMPLETELY enclosed by wood in an oak about 50 years old, three dicotyledonous plants germinated: I am certain of the accuracy of this observation. Again, I can show that the carcasses of birds, when floating on the sea, sometimes escape being immediately devoured; and seeds of many kinds in the crops of floating birds long retain their vitality: peas and vetches, for instance, are killed by even a few days' immersion in sea-water; but some taken out of the crop of a pigeon, which had floated on artificial salt-water for 30 days, to my surprise。

G factor G 因素G factor 一般因素G periodG period G 期G score 年级分数G tolerance G 耐力G 期 G 期GA 总平均数gab 空谈GABA γ 氨基丁酸gabble 急促不清的说话gabby 健谈的gaby 傻子GAD 泛焦虑症gad 游荡gaffe 失礼gag reflex 咽反射gage 量规Gagne s accumulative learning theory 加涅的累积学习论Gagne s hierarchy of learning 加涅的学习层次Gagne s hierarchy system of learning 加涅的学习层次系统Gagne s learning model 加涅的学习模型Gagne s learning outcome variety 加涅的学习结果种类Gagne s stages of learning 加涅的学习阶段Gagne s theory of instruction 加涅的教学论gaiety 快乐gain 增益gain experience 获得经验gain from illness 因病得益gaining new insights through restudying the old material 温故知新gainsharing 收入分成gain loss hypothesis 得失说gain loss model 得失模型gain loss theory 得失论gait 步态galactochloral 半乳糖氯醛galactosemia 半乳糖血galeanthropia 变猫妄想Galen s doctrine of temperament 盖伦气质学说galeophilia 爱猫癖gall 恐吓Gallup polls 盖洛普民意测验Gallup s public opinion poll 盖洛普民意测验Galton bar 高尔顿横木Galton Questionnaire 高尔顿问卷Galton whistle 高尔顿音笛Galton s law 高氏定律Galton s tube 高尔顿音笛Galton s whistle 高尔顿音笛Galton Watson process 高华二氏步骤高华二氏步骤galvanic current 电流galvanic reflex 电反射galvanic shock 电休克galvanic skin reflex 皮电反射galvanic skin response 皮电反应galvanic skin response apparatus 皮电反应仪galvanic stimulation 电刺激galvanocontractility 电流收缩性galvanogustometer 电味觉计galvanohypnotism 电催眠galvanometer 电流计galvanonervous 电流神经的galvanotropism 向电性gam 交际gambler 赌博者gambler s fallacy 赌博者的错误gambling 赌博gambling focus 赌胜性聚焦gambling house 赌场game 游戏game against nature 反自然博奕game against society 反社会博奕game of adult infant 成人 婴儿游戏成人 婴儿 戏game of dialogue 对话游戏game theory 博奕论gamenomania 求婚狂gamester 赌棍gamete 生殖细胞game with rules 规则游戏gamin 流浪儿gaming 赌博gamma distribution γ分布gamma fiber γ纤维gamma motor neuron γ运动神经元γ运动神经原gamma movement γ运动gamma rhythm γ节律gamma aminobutyric acid γ 氨基丁酸gamophobia 婚姻恐怖症gang 帮派gang 团伙gang age 帮团年龄gang behavior 帮派行为gangland 黑社会ganglia 神经节ganglia coeliaca 腹腔神经节ganglia lumbalia 腰腔神经节ganglia thoracalia 胸腔神经节ganglia trunci sympathici 交感干神经节交感 神经节gangliocyte 神经节细胞gangliolytic 神经节阻滞的ganglion 神经节ganglion basal 基底神经节ganglion cell 神经节细胞ganglion cell layer 神经节细胞层ganglion cerebral 脑丘ganglion ciliare 睫状脑神经节ganglion collaterale 副神经节ganglion cordis 心脏脑神经节ganglion geniculi 膝状脑神经节ganglion hypogastrium 腹下神经节ganglion neuron 节神经元ganglion oculare 眼神经节ganglion oticum 耳神经节ganglion prevertebral 椎前神经节ganglion spinale 脊神经节ganglion splanchnicum 内脏脑神经节ganglion sympathetic 交感神经节ganglionic blocking agent 神经节阻滞剂神经节阻滞剂ganglionic cell 神经节细胞ganglionic crest 神经节脊ganglionic layer 神经节层ganglionic neuron 神经节原ganglionoplegic 神经节阻滞的ganglioside 神经节苷脂ganja 印度大麻Ganser symptom 甘塞尔症状Ganser syndrome 甘塞尔综合症Ganser s twilight state 甘塞尔昏暗状态甘塞尔昏暗状态gaol 监狱gaolbird 囚犯gaol break 越狱gap 间断garbage 不准确数据garbage 垃圾Garcia effect 加萨效应gargalanesthesia 痒感缺失gargalesthesia 痒感gargoylism 脂肪软骨营养不良garrulity 喋喋不休GAS 一般适应综合症gas chromatography 气体分色法gasconade 夸口gasometer 气量计gasometry 气体定量法gasping center 喘息中枢gastralgia 胃痛gastric 胃的gastric anacidity 胃酸缺乏gastrin 促胃液素gastroduodenitis 胃十二指肠炎gastroduodenoscopy 胃十二指肠镜检gastroduodenostomy 胃十二指肠吻合术胃十二指肠吻合术gastrointestinal disorder 肠胃失调gastrointestinal hormones 肠胃激素gastrointestinal reaction 胃肠反应gastrointestinal system 肠胃系统gastrone 抑胃分泌素gastronome 美食家gastrorrhoea 胃液分泌过多gastroscope 胃窥镜gastroscopy 胃镜检查gastrosis 胃病gastrospasm 胃痉挛gastrospiry 吞气症gastroxynsis 胃酸过多症gastrula 原肠胚gate cell 闸门细胞gate control theory 闸门控制说gate control theory of pain 痛的闸门控制说gatekeeper 社会观察人员Gates Reading Readiness Test 盖茨阅读准备测验Gates Mckillop Reading Diagnostic Tests 盖麦二氏阅读鉴定测验Gates MacGinitie Reading Test 盖麦二氏阅读测验gateway 途径gather 收集gather data 收集数据gather experience 积累经验gather information 收集信息gating mechanism 闸门机制gatism 大小便失禁gauge 规范Gauss curve 高斯曲线Gauss distribution 高斯分布Gauss lens system 高斯透镜系统Gaussian curve 高斯曲线Gaussian probability distribution 高斯概率分布Gaza s operation 神经支切断术gaze 凝视GCA 地面控制进场GCI 普通认知指数gear ratio 传动比Geist Picture Interest Inventory 盖氏图画式兴趣量表gelasmus 憨笑Gelb effect 杰尔贝效应geld 阉割gelded 阉割了的Gelineau s syndrome 发作性睡眠Gelor lens system 塞洛尔透镜系统gelototherapy 欢笑疗法geminus 双生子gender consistency 性别一致性gender constancy 性别恒定性gender identity 性别认定gender identity disorder 性别认定障碍性别认定疾病gender role 性别角色gender stability 性别固定gender typing 性别特征形成gene 基因gene action 基因作用gene activation 基因活化gene activity 基因活性gene amplification 基因增殖gene balance 基因平衡gene conversion 基因转换gene copy 基因拷贝gene dosage 基因量gene duplication 基因复制gene expression 基因表达gene interaction 基因相互作用gene mutation 基因突变gene mutation rate 基因突变率gene order 基因序列gene recombination 基因重组gene replication 基因复制gene substitution 基因替代gene theory 基因学说genealogical table 系谱表genealogy 家系genecology 种群生态学geneogenous 先天性的general 一般的general ability 一般能力general ability test 一般能力测验general abnormality factor 一般异常因素一般 常因素general achievement test 一般成就测验普通成就测验general activity 一般活动general adaptation syndrome 一般适应综合症general amnesia 概括性遗忘general amnesia 全面性遗忘general anesthesia 全身麻醉general anxiety 一般性焦虑General Anxiety Scale 一般焦虑量表General Aptitude Test Battery 一般能力倾向测验普通文书测验general attention 一般注意general attitude type 一般态度型general average 总平均数general birth rate 一般出生率general census 全面普查general characteristic 一般特性general cognitive index 普通认知指数general concept 一般概念general condensed summary 要点说明general cortex 一般皮质general death rate 一般死亡率general didactics 普通教授学general diffused lighting 漫射照明general disturbance 整体性失调General Educational Development Tests 普通教育发展测验general factor 一般因素General Health Questionnaire 普通健康问卷general homology 一般相应general hunger 一般饥饿general intelligence 一般智力general intelligence factor 一般智力因素普通智慧因素general investigation 普查general knowledge 一般知识general lighting 一般照明general linguistics 普通语言学general mean 总平均数general measure 一般测量general measure of reliability 可靠性一般测量general mental ability 一般心理能力general methodology 普通方法学general microbiology 普通微生物学general mood of society 社会风气general paralysis of insane 麻痹性痴呆general paresis 轻瘫general phisical examination 一般身体检查general physiology 普通生理学general problem solver 通用问题解答general problem solver procedure 通用问题解决程序general process of reading comprehension 阅读理解的一般过程general psychology 普通心理学General Psychology and Experimental Psychology 普通心理与实验心理general range 一般范围general reaction 全身反应general reference group theory 一般参照组理论general sensation 全身感觉general sensory 一般感觉general sensory area 一般感觉区general sexual dysfunction 普遍性功能障碍general sociology 普通社会学general survey 普查general system 统摄系统general system theory 一般系统论general transfer 一般迁移general trend 一般趋势general will 共同意志generality 一般性generalizability theory 概化理论概化理论generalization 泛化generalization 类化generalization gradient 泛化梯度generalization hypothesis 泛化假说generalization of image 形象概括generalization of problem 课题的类化generalization of subject matter 教材的概括generalize 普遍化generalized anxiety disorder 泛焦虑症generalized epilepsy 全部性癫痫generalized expectancy 类化预期generalized imitation 类化模仿generalized least squares estimator 一般化最小二乘推定量generalized log series 类化对数数列generalized other 类化的他人generalized reinforce 类化强化物generalized seizure 普遍性发作generalized sexual inhibition 普遍性功能抑制generalized trait 类化特质generalized transduction 普通性传导generalized goal tension 类化目标扩张类化目标扩张generalizing abstraction 概括抽象generalizing assimilation 概识同化generate 生育generate test method 生成检验法generating structure 生成结构generation 生育generation gap 代沟generation interval 世代间隙generation discrimination theory 生成 辨别理论generative center 发生中心generative grammar 衍生语法generative organs 生殖器官generative power 生殖力generative semantics 生成语义学generative theory 生成理论generative transformational grammar 生成转换语法generativity 繁殖generativity vs stagnation conflict 创建与休怠冲突generator 发生器generator electrical potential 发生器电位发生器电位generator potential 启动电位generic 一般的generic coefficient 种属系数generic condition 一般条件generosity effect 宽容效应genesclinic 偏性遗传genesis 发生genetic assimilation 遗传同化genetic banks 物种遗传库genetic block 遗传性阻碍genetic carrier 遗传载体genetic code 遗传密码genetic complement 遗传互补genetic complex 遗传综体genetic constitution 遗传素质genetic continuity 遗传连续性genetic control 遗传控制genetic copying 遗传复制genetic correlation 遗传相关genetic counseling 遗传咨询genetic definition 发生论定义genetic differences 遗传差异genetic disorder 遗传性障碍genetic dominance 遗传支配性genetic dominant traits 遗传的显性特征遗传的显性特徵genetic drift 遗传漂变genetic effect of radiation 遗传辐射效应遗传辐射效应genetic element 遗传成份genetic engineer 遗传工程学家genetic engineering 遗传工程genetic epistemology 发生认识论genetic equilibrium 遗传平衡genetic factor 遗传因子genetic feedback 遗传反馈genetic gain 遗传获得量genetic guidance 遗传辅导genetic homeostasis 遗传稳态genetic information 遗传信息genetic limitation 遗传限度genetic load 遗传负荷genetic mark 遗传标记genetic material 遗传物质genetic method 发生法genetic obesity 遗传型肥胖症genetic potential 遗传潜力genetic predeterminism 遗传决定论genetic psychology 发生心理学genetic recessive traits 遗传的隐性特征遗传的隐性特徵genetic relationship 亲缘关系genetic sequence 发生次序genetic stability 遗传稳定性genetic statistics 遗传统计genetic surgery 遗传手术genetic synecology 群落发生学genetic theory 发生说genetic theory of language 语言天赋论语言天赋论genetic transcription 基因转录genetic variant 遗传性变型genetic variation 遗传性变异genetical mark 遗传标记genetical population 遗传群体genetics 遗传学genetous 先天的Geneva school 日内瓦学派gene environment interaction 基因遗传相互作用genic 基因的genic interaction 基因相互作用genic material 遗传物质genic value 基因值geniculate body 膝状体geniculocortical system 膝状体皮质系genital 生殖器的genital character 性征期性格genital disorder 性器失调genital locomotor stage 性运动期genital phase 性器期genital stage 性征期genital zone 性感区genitalia 外生殖器genitality 生殖力genius 天才genocatachresia 色情倒错genocide 种族灭绝genocopy 拟遗传型genome 基因组genome mutation 基因组突变genomotive 隐性动机genomotive 原生性动机genopathy 基因病genophobia 性事恐怖症genotype 遗传型genotype environment correlation 遗传 环境相关genotype environment interaction 遗传 环境互应genotypic control 遗传型控制genotypic environment 遗传型环境genotypic milieu 遗传背景genovariation 基因变异gens 氏族gentle 高贵的gentleman 有教养的人genu 膝genuflect 屈膝genuine epilepsy 真性癫痫genuine hallucination 真性幻觉genuineness 真挚genus 类genus homo 人属geographical environment 地理环境geometric average 几何平均数geometric construction 几何构造geometric distance model 几何距离模式几何距离模式geometric distribution 几何分布geometric figure 几何图形geometric horopter 几何视野单像区geometric mean 几何平均数geometric method 几何平均法geometric model 几何模型geometric series 几何级数geometrical concept 几何概念geometrical optical illusion 几何光学错觉geometrical progression 几何级数geometry 几何学geometry design 绘几何形geophagia 食土癖geophagist 食土癖者geopsychology 地理心理学gephyrophobia 过桥恐怖症geratology 老年医学gereology 老年学geriatric medicine 老年医学geriatric psychiatry 老年精神医学geriatric psychology 老年心理学geriatrics 老年病学geriopsychosis 老年精神病Gerlach s network 格拉赫网germ cell 生殖细胞germinal period 胚胎期germination inhibitor 萌发抑制作用gerocomia 老年保健gerontic 老年的gerontogenesis 老年发生gerontolinguistics 老年语言学Gerontological Apperception Test 老年统觉测验gerontological psychology 老年心理学gerontology 老年学gerontophile 亲老人癖gerontophile 嗜耄癖gerontophilia 爱恋老人gerontophilia 嗜耄癖者gerontopia 老视geropsychiatry 老年精神医学geropsychology 老年心理学Gerstmann s syndrome 格斯特曼综合症格斯特曼徵候 Gesell Development Scale 格塞尔发展量表Gesell Development Schedules 格塞尔发展测量表Gesell Development Test 格塞尔发展测验格塞尔学前测验Gesell developmental norm 格塞尔发展常模Gestal laws of organization 组织完形法则Gestalt 格式塔Gestalt 完形Gestalt Completion Test 完形补足测验Gestalt factor 完形因素Gestalt laws of perceptual organization 知觉组织完形法则Gestalt principles of organization 格式塔组织原则Gestalt psychology 格式塔心理学Gestalt psychology 完形心理学完形心理学Gestalt psychotherapy 完形心理治疗法完形心理治疗法Gestalt quality 形质Gestalt Review 格式塔评论Gestalt theory 完形理论Gestalt theory of learning 学习的完形说学习的完形说Gestalt therapy 完形治疗法Gestaltests 完形心理学派Gestaltism 完形主义gestation 受孕gesticulate 姿态表达gestural language 手势语gesture 手势gesture 姿态gesture language 手势语get away with 侥幸做成GH 生长激素ghetto 犹太人区ghost 幽灵ghost word 造出来的字giant baby 巨大儿giantism 巨人症gibberish 言语凌乱gibberish aphasia 呓语性失语Gibson effect 吉卜生错觉效应giddiness 晕眩gift 天资gifted 天才gifted child 超常儿童giftedness 天才giftedness 资赋优异giftie 才能gigantism 巨人症Gilles de la Tourette s syndrome 图雷特综合症Gilmore Oral Reading Test 吉尔摩朗诵测验Gittinger personality assessment system theory 盖氏人格评估系统学说盖氏人格评估系统学说glamor 魅力glamour 魅力gland 腺glandula 腺glandulae 腺glandulae olfactoriae 嗅腺glandular endocrinica 内分泌腺glandular gustatoria 味觉腺glandular integumentaria 皮肤腺glandular optica 视神经节腺glandular theory 腺体理论glandular thyreoidea 甲状腺glare 眩目glare index 眩光指数glare recovery time 眩光视觉恢复时间眩光视觉恢 时间glare recovery time curve 眩光视觉恢复时间曲线glass sensation 玻璃感觉glassy eyed 目光呆滞的glaucoma 青光眼glaucosis 青光眼盲glia 神经胶质glial 神经胶质的glial cell 胶质细胞glial membrane 神经胶膜glial tissue 神经胶质组织glide 滑音glide illusion 下滑错觉glider 滑翔gliding model 滑动模型glimmer 模糊感觉gliosis 神经胶质变性global 全体的global 整体的global aphasia 完全失语症global convergence 全局收敛global focusing 总体聚焦global learning 全部学习global learning 整体学习global method 全体法globe thermometer 黑球温度计globus hysterics 癔病球感globus pallidus 苍白球glomeruli caudales 尾小球glossal 舌的glossolalia 荒诞言语glossolalia 语言含混glossology 语言学glossopharyngeal 舌咽的glossopharyngeal nerve 舌咽神经glossopharyngeus 舌咽肌glossophobia 言语恐怖症glossosynthesis 造语症glottis 声门glove anesthesia 手套型感觉丧失症glower 怒视GLU 谷胺酸glucagon 抗胰岛素glucostatic theory 葡萄糖恒定理论glutamic acid 谷胺酸glutethimide 苯乙派啶酮glutton 贪食者gluttony 暴饮暴食GLY 甘胺酸glycine 甘胺酸glycogen 糖原glycogeusia 甘味症glycometabolism 糖代谢gnosia 直觉gnosis 感悟go bankrupt 破产goal 目标goal activities 目标活动goal analysis 目标分析goal behavior 目标行为goal directness 目标指向性goal discrepancy 目标差goal discrepancy score 目标差评分goal effectiveness 目标有效性goal frustration 目标挫折goal gradient 目标等级goal gradient hypothesis 目标等级假说目标等级假说goal object 目的物goal orientation 目标定向goal response 目的性反应goal set 目标定势goal setting 目标设定goal setting theory 目标设定理论goal setting training 目标设定训练goal situation 目标情境goal stimulus 目标刺激goals of crime 犯罪目的goals of sports collective 运动集体目标运动集体目标goal cognition theory of learning 学习的目的认知说goal directed behavior 目标导向行为目标导向行为goal directed learning 有目的的学习有目的的学习goal directed motivation 目标导向动机目标导向动机goal directed response 目标指向反应目标指向反应goal directed thinking 目的指向性思维目的指向性思考goal limited adjustment therapy 有限目标适应治疗法goal orientation 目标定向goal orientation conflict 目标定向冲突目标定向 突goal oriented 目标定向性goal seeking behavior 目标寻求行为目标寻求行为goggles 护目镜golden section 黄金分割Goldmann perimeter 高尔顿曼视野计Golgi method 高尔吉法Golgi type Ⅰ cell 高尔吉Ⅰ型细胞Golgi type Ⅱ cell 高尔吉Ⅱ型细胞Golgi Mazzoni s corpuscle 高尔吉 马祖尼小体Goltz s theory 戈尔茨学说gonad 性腺gonadal hormone 性激素gonadogenesis 性腺发生gonadoinhibitory 性腺抑制gonadopathy 性腺病gonadopause 性腺机能丧失gonadotherapy 性激素疗法gonadotrophic 促性腺的gonadotrophic hormone 促性腺激素gonadotropin 促性腺激素goniocraniometry 颅角测量法goniometer 测角器good figure 良型good me 良我good or evil 性可善可恶论good points 优点good sense 判断力强good shape 良形Goodenough Draw a Man Test 谷氏画人测验Goodenough Harris Drawing Test 谷哈二氏画人测验Goodman model 古德曼模式Goodman Kruskal s coefficient of predicta bility 古 克二氏预测系数goodness 德行goodness 优良goodness of fit 符合度goodness of fit test 适合度考验goodness of mind 良心good boy nice girl orientation 乖孩子取向good boy nice girl stage 乖孩子期good poor analysis G P分析good poor analysis 上位 下位分析goofball 镇静剂goon 怪人goosy 神经质的Gordon Occupational Check List 高登职业检核表Gordon Personal Inventory 高登个性量表Gordon Personal Profile 高登个人侧面图Gordon s reflex 戈登反射Gordon s sign 戈登症Gordon s technique 高登法gorge 暴食gorilla 大猩猩gossip 流言Gottschaldt Test 哥德沙尔特嵌入图形测验Gottstein s fibers 哥特斯坦纤维Gough Adjective Check List 高夫形容词检核表Gough model 高夫模式govern 统治govern oneself 克制government 支配关系governor meridian 督脉Gower s syndrome 高尔综合症gowster 吸毒者go or no go task 去或不去作业GPA 计点平均成绩GPAS 盖氏人格评估系统学说GPC rules 形 音转换规则GPIGPS 通用问题解答GRgradation 等级gradation 梯变grade 年级grade by sized 按大小分级grade differential 等级差别grade distribution 年级分配grade equivalent 等级当等grade equivalent scale 等级当等量表grade estimation 等级评定grade norm 年级常模grade scale 年级量表grade score 年级分数grade series 等级系列graded potential 级量电位graded response items 分级式作答试题分级式作答试题grader potential 渐变电位grade point average 计点平均成绩grade skipping 跳级gradient 递变度gradient analysis 梯度分析gradient descent 梯度下降gradient of generalization 类化递变gradient of reinforcement 强化递变gradient of stimulus generalization 刺激类化递变gradient of texture 结构递变gradient of texture density 结构密度递变gradient preference 梯度适应gradient search 递变度搜索grading 分等级gradual advance 渐升gradual decline 渐降gradualness 循序性gradualness of development 发展渐进说发展渐进说Graduate Record Examination 研究生入学考试graduated system of punishment 分级惩罚制graduation of curve 曲线修匀graffito pollution 涂写污染grammar 语法grammatical ellipsis 文法上的省略grammatical rules 语法规则grammatical structure 语法结构grammatical structure understanding 语法结构理解grammaticality 符合语法规则grand average 总平均数grand mal 癫痫大发作grand mean 总平均grandeur delusion 夸大妄想grandfather complex 祖父情结grandiloquence 夸大grandiosity 夸大grandmother 溺爱Granit Harper s law 格热尼特 哈伯律grant 准予granular cell 颗粒细胞granuloblast 成粒细胞grapevine 传闻graph 图表graph analysis 图解分析graph theory 图论grapheme phoneme conversion rules 形 音转换规则graphic analysis 图解分析graphic collection 图象归类graphic display 图示graphic expression 图示graphic individuality 书法个性graphic method 图示法graphic presentation 图像显示graphic psychology 版画心理学graphic rating scale 图示评定量表graphic record 图示法graphic representation 图示graphic symbol 图示符号graphical displays 图形显示器graphical representation 图形表象graphoanalysis 书写分析graphocatharsis 书写疏泄法graphokinesthetic 书写动觉的graphology 笔迹学graphology 字相学graphomania 书写狂graphomotor 书写运动的graphomotor aphasia 书写性失语graphomotor test 书写肌动测验graphopathology 书写病理学graphophobia 书写恐怖症graphorrhea 涂写癖graphorrhes 书写错乱graphospasm 书写痉挛Grashey s aphasia 格拉希氏失语症Grashey s aphasia 遗忘性失语症grasp 抓握grasping 贪婪的grasping reflex 抓握反射grass widow 离婚女子grass widower 离婚男子Grassmann s law 格拉斯曼定律grassroots 基础gratification 满足感grating 光栅gravamen 冤情Graves Design Judgment Test 格雷夫设计判断测验Graves disease 格氏病graviceptor 重力受纳器gravid 妊娠的gravidity 妊娠gravid puerperal psychosis 孕 产期精神病gravimeter 比重计gravimetric 比重测定的gravitation 重力gravitational receptor 重力感受器gravity effect 重力影响gravity free condition 失重状态gray matter 灰质Gray Oral Reading Test 格雷朗读测验格雷朗读测验greatest limit 最大极限greatest measure 最大数值great man theory 伟人论great man theory of history 历史伟人论历史伟人论great man theory of leadership 领袖伟人论great man theory of leadership 伟人领导论Greco Latin square design 希腊拉丁方阵设计greed 贪婪green 绿green blindness 绿色盲green vision 绿幻视gregarious instinct 群集本能gregarious personality 合群人格gregariousness 合群性gregariousness 群集性grey area 次贫地区grey market 半黑市grey matter 灰质grey reticular 灰质网grey reticular formation 灰质网状结构灰质网状结构grey scale 灰度标尺grid seminar 方格训练grid stereoscope 栅栏实体镜grief 悲伤grievance 牢骚grievance procedure 苦情处理制度grimace 愁眉苦脸grip diameter 手抓握径grip strength 握力grisly 吓人的gritty 勇敢的grizzle 诉苦groan 呻吟grooming 修饰grooming behavior 修饰行为grooming interpersonal conflict 整饰人际冲突Groos theory of play 格鲁斯游戏理论groovy 常规的gross 粗大的gross 总的gross figures 总数gross motor movements 大运动动作gross motor skill learning 粗大运动技能学习gross score 总分数Gros Schultze method 格罗斯 斯查尔茨法ground 背景ground 基础ground transportation 地面运输grounded theory 扎根理论grounding 基础训练groundless 无根据ground based flight 地面模拟飞行ground controlled approach 地面控制进场group 群体group 团体Group & Organization Management 群体与组织管理group acceptance 团体接纳group aggression 团体侵犯group analytic 群体分析group analytic therapy 集体分析治疗Group Assessment of Interpersonal Traits 人际特质小组评量group atmosphere 群体气氛group atmosphere 团体气氛group attack 团体攻击group average method 群平均法group behavior 团体行为group behavior modification 团体行为矫正group belongingness 群体从属性group boundary 团体界限group characteristics 团体特性group classification 群体分类group climate 团体气氛group cohesion 团体凝聚力group cohesiveness 群体凝聚性group communication network 团体联络网group composition 团体组成group congruence 群体协调一致group consciousness 团体意识group constitutional determinants 群体构造化要素group consumers 集体消费者group contagion 团体感染group counseling 团体咨询group data 分类资料group decision 团体决定group decision making 团体决策group delinquent reaction 群体犯罪反应 体犯罪反应group delusion 群体幻觉group demography 群体人口统计学group development 团体发展group difference 团体差异group dimension 团体维度group discussion 集体讨论group discussion interview 集体讨论面谈group discussion method 群体讨论法group discussion test 群体讨论测查group dynamics 团体动力学Group Dynamics Theorygroup ecology 群体生态学group effect 群体效率group emotional identification 群体情绪认同group error 分组误差group evaluation 团体评价group experience 团体经验group experiment 团体实验group factor 群体因素group fallacy 群体谬误group feeling 团体感group formation 群体形成group function 群体功能group goal 团体目标group guidance 团体辅导group hypnosis 集体催眠group identification 团体认同group identity 团体同一性group incentive 团体激励group instruction method 小组教学法group integration 团体统合group integrative determinants 团体统合要素group integrator 群体协调器group intelligence test 团体智力测验group interaction theory 团体互动理论团体互动理论group interval 组距group interview 团体访谈group interview method 小组交谈法group interview test 团体访谈测查Group Inventory for Finding Creative Talent 创造性天才团体测验group leadership 集体领导group marriage 群婚group measurement method 团体测量法团体测量法group mind 集团精神group mind 群体心理group mind theory 群体心理理论group morale 团体士气group norm 群体规范group norm 小组常模group normative analysis 团体范围分析团体范围分析group observation 团体观察法group of behavioral sampling 行为样组行为样组group of classes 组群group of images 意象群group order ranking 小组顺序排列法group oriented 团体取向group participation 集体参与group performance 集体业绩group performance theory 团体绩效理论团体绩效理论Group Personality Projective Test 团体个性投射测验group play therapy 集体游戏疗法group polarization 群体极化group polarization effect 群体极化效应群体极化效应group polarization phenomenon 群体极化现象group pressure 群体压力group pressure toward uniformity 群体齐一性压力group problem solving 团体问题解决团体问题解决group process 团体历程group productivity 团体生产性group psychology 群体心理学group psychotherapy 团体心理疗法group regulation 群体调节group risk taking 团体冒险group role 团体角色Group Rorschach Test 团体罗尔沙赫测验group sampling 分组抽样group sampling 集体抽样group schedule 团体表格group selection 群体选择group self preference 群体自我偏爱group size 团体大小group socialization 团体社会化group solidarity 团结一致group spirit 团队精神group star 群星group stress 集体应激group structure 团体结构group study 团体研究group suggestion 群体暗示group superego 团体超我group syntality 群体个性group test 团体测验group theory 群体理论group therapy 团体治疗法group thinking 团体思维group training 集体训练group types 群体类型group unity 群体团结group variation 集群变异group work 团体工作Group Z Test 团体Z测验grouped 分组grouped data 分组数据grouped frequency distribution 分组次数分布grouped measures 分组量数grouped observation 分组观测值grouped table 分组表grouping 分组grouping by ability 能力分组grouping error 分组误差grouping habit 集合习性grouping item 分组项目grouping of controls 控制器分组grouping of data 资料归类groupment 群体性groupshift 群体转移groupthink 集体思考group centered leader 团体中心领袖团体中心领袖group factor theory 群因素论group relations theory 团体关系论grown up 成人growth 成长growth 生长growth center 成长中心growth curve 生长曲线growth hormone 生长激素growth motivation 成长动机growth need 成长需要growth of population 人口增长growth pains 成长痛growth pattern 生长模式growth period 发育期growth periodicity 发育周期性growth phase 发育周期growth ratio 生长比率growth spurt 生长陡增growth stage 生长阶段growth promoting hormone 生长激素Gruber s test 格鲁伯试验grudge 妒忌GSR 皮电反应GT 概化理论概化理论GTH 促性腺激素guardian 监护人guardianship 监护guess 猜测guessed average 假定平均数guessing correction formula 猜测纠正公式guesstimate 瞎猜guesswork 猜测Guess Who Test 猜人测验guess who technique 猜人法guidance 辅导guidance function of test 测验的指导功能guidance learning 指导学习guidance of self study 自学辅导guidance services 辅导服务guide 指导guide specifications 指导性规范guided daydream 导向白日梦guided discovery learning 有指导的发现学习guided fantasy 导向幻想guided participation 引导参与guiding idea 主导观念。

摘要原子核是目前高能物理实验的一个重要研究对象。

在高能核物理实验中，原子核部分子分布函数是模拟计算各种高能反应的重要输入信息，在检验标准模型和探寻新物理的过程中起到关键作用。

本论文的目的就是通过对世界上各合作组的带电轻子－原子核（包括质子）的深度非弹性散射实验数据的QCD理论分析，来获取质子和原子核的部分子分布函数。

我们发布了质子的部分子分布函数数据库IMParton16，以及原子核的部分子分布函数数据库nIMParton16（nuclear IMParton）。

本研究包含三个主要内容。

（1）研究了核子内部部分子分布的起源问题。

我们成功地建立了夸克模型和高Q2下测量到的部分子分布之间的直接联系。

（2）研究了各种核介质效应对核子内部部分子分布的影响，以及各种核介质效应的核依赖关系。

（3）我们应用部分子重组效应修正的DGLAP方程对不同实验组的数据进行了全局χ2分析，并得到了质子和原子核的部分子分布函数。

关于部分子分布的起源问题，我们发展了动力学部分子模型，并把部分∼0.1GeV2。

在该初始标度下，我们实现子分布演化的初始标度降低到了Q2了最自然最简单的仅包含价夸克分布的非微扰输入，并且参数化非微扰输入用到的自由参数个数最少，仅有三个。

我们还发现核子内部还应存在一些超越夸克模型的少量的非微扰海夸克成分。

在核介质效应研究方面，我们计算了核子费米运动引起的原子核中核子结构函数的弥散效应，束缚核子变胖效果给出的EMC效应，以及原子核中部分子重组过程增强导致的核遮蔽效应。

我们首次发现了EMC效应的强弱与核子之间剩余强相互作用能量之间的显著的线性关联。

我们在部分子层次上系统地描述了核遮蔽效应、反遮蔽效应和EMC效应。

鉴于考虑了较为全面的核物理效应，我们全局拟合确定的原子核部分子分布函数更加准确，并且参数化核效应修正因子的核依赖关系和x依赖关系时使用的自由参数最少，仅有两个。

（与其他合作组的全局拟合相比，自由参数的个数几乎小一个数量级）。