Study of Deformation Effects in the Charged Particle Emission from 46Ti

Effect of Freeze-Thaw Cycles on Mechanical Behavior of Compacted Fine-Grained SoilGuoyu Li, Wei Ma, Shuping Zhao, Yuncheng Mao, Yanhu MuState Key Laboratory of Frozen Soils Engineering, Cold and Arid Regions Environmental and Engineering Research Institute, Chinese Academy of Sciences, Lanzhou, Gansu, ChinaABSTRACT: A large amount of work has been conducted to study the effect of freeze-thaw cycles on the geotechnical properties of various soils. But less laboratory work has been focused on the effect of number of freeze-thaw cycles and on quantitative relationship between mechanical behavior and freeze-thaw cycles. This study undertook a series of tests including freeze-thaw (FT) (after 0, 2, 5, 11, 21, and 31 freeze-thaw cycles respectively), unconfined compression (UC) and unconsolidated-undrained triaxial compression (UUTC) tests. These tests aim to assess the influence of freeze-thaw cycles on the mechanical behavior of compacted fine-grained soil, to establish correlation between the mechanical behavior and freeze-thaw cycles, and to facilitate the prediction of changes in geotechnical properties of soil. Freeze-thaw cycles notably influence the stress-strain curve reducing the UC strength by 11%, elastic modulus by 32%, and cohesion by 84% after 31 freeze-thaw cycles in comparison with those soils unexposed to freeze-thaw. The angle of internal friction is slightly increased by 1 to 2°. The weakening and deteriorating effects of freeze-thaw on the compacted fine-grained soil are confirmed. They can provide a scientific basis for design consideration of cold-region infrastructures, and for countermeasures against frost heave and thaw settlement.KEY WORDS: Mechanical behavior, freeze-thaw, geotechnical properties, fine-grained soil, frost heave and thaw settlement.1INTRUDUCTIONRepeated freezing and thawing in cold regions strongly weathers and deteriorates the geotechnical properties of densely compacted foundation soil, e.g., change in micro-fabric and loss in strength. It thus might cause damage, and even failure of the foundation of the various man-made infrastructures such as residential buildings, roads, airstrips, pipeline and pile (Alkire and Morrison 1982).According to several laboratory tests (Kim and Daniel 1992, Othman and Benson 1993), the hydraulic permeability of compacted fine-grained soil increases following freeze-thaw cycles. The mechanism of this increase is because micro-fissuring are enlarged during freezing and thawing and because ice melting in soil matrix leaves internal large pore spaces (Chamberlain et al., 1990). Chamberlain and Gow (1979) also mentioned that fine particles might move out of large pore spaces during freezing and thawing. Eigenbrod (1996) also found that freezing and thawing leaded to densification of soft and normally-consolidated clay samples, but other studies showed the opposite to occur for dense samples. Studies showed that freeze-thaw increased density of loose soil but decreased the density of dense soils (Viklander 1998, Yao et al.2008, Li et al. 2011). This so-called dual effect of freeze-thaw process on the density has been verified by the several studies (Su et al. 2008, Wang et al. 2009, Yang et al. 2003). Considerable laboratory work has been performed to study effects of freeze-thaw cycles on geotechnical properties inducing changes in soil strength such as shear strength, elastic modulus, cohesion and internal friction angle for varying densities. Some works showed that freeze-thaw caused a decrease in strength of soils (Culley 1971, Graham and Au 1985, Yong et al. 1985, Aoyama et al. 1985, Lee et al. 1995, Simonsen et al. 2002, Qi and Ma 2006, Wang et al. 2007). However, some researchers found that the strength increased for loosely compacted soils (Ono and Mitachi 1997, Alkire and Morrison 1982). It is therefore known that dense soils tend to swell under freeze-thaw but loose soils are densified.Although a considerable amount of studies have been conducted, they have some disadvantages such as less number of freeze-thaw cycles, lack of quantitative relationship between mechanical behavior and number of freeze-thaw cycles. These limitations make it difficult to predict the developing trend of soil undergoing freezing and thawing. The effect of freeze-thaw cycles on the mechanical behavior has been tested using closed-system freeze-thaw (FT) tests, unconfined compression (UC) tests, and unconsolidated-undrained triaxial compression (UUTC) tests. These tests aim to (1) confirm the weakening effect of freeze-thaw cycles; (2) assess the changing process of the mechanical behavior under the freeze-thaw cycles; and (3) establish the quantitative relationships between them.2TESTING PROCEDUREA fine-grained soil, i.e. silty clay, was collected close to Yonydeng county, Gansu province in Northwestern China. Grain size distribution (Figure 1), liquid and plastic limits, and specific gravity were measured in the laboratory prior to the FT, UC and UUTC tests according to the Chinese standard JTG E40-2007 which resembles the ASTM Standards such as D4318–10, D2166–06, D2850–03a (MC-PRC 2007, Li et al. 2011). The liquid and plastic limits are 26.9 % and 18.7%, respectively. The specific gravity is 2.704. The Proctor compaction test following the standard D698–07 was carried out to determine the maximum dry density and the optimum water content, which are 1.91 g/cm3 and 16.1 %, respectively. The remolded cylindrical samples (125 mm in height and 61.8 mm in diameter) were densely compacted and formed by a layer-by-layer compressing devices (a steel mold). Water content and dry density of soil samples were close to the maximum and the optimum.The samples were then sealed with rubber membranes and consolidated for 24 hours for homogeneous water content. After this consolidating period, they were placed into a modelingbox and exposed to cyclic freezing and thawing in a closed system without in- or out-flow of moisture. The air temperature in the modeling box was automatically controlled and adjusted by circulating coolants (Freon or Ethylene Glycol) driven by a compressor, which varied in the range of -30 to 30 °C as shown in Figure 2. One freeze-thaw cycle lasted 24 hours, 16 hours for freezing and 8 hours for thawing. After different freeze-thaw cycles, soil samples were taken out of the box; and the UC and UUTC tests were performed to investigate the effect of freeze-thaw cycles on the changes in mechanical behavior.Figure 1: Grain-size distribution of the soil sampleFigure 2: Temperature change of air in modeling box under freeze-thaw.Soil samples preparation and testing operations were carried out conforming to the related standard JTG E40-2007 (MC-PRC 2007). Dry density of 1.81 g/cm3 and water content of 16.1% of samples were selected for various tests; their resolutions are controlled within ±1%. Three soil samples were used to perform the strain-controlled UC tests at a constant axial strain rate of 2.4% per minute while four soil samples were used to perform the UUTC tests at a constant strain rate of 1% per minute. The applied confining stress in UUTC tests is 50, 100, 200 and 300 kPa respectively. The compression tests terminate until load values decrease with increasing strain. Six groups of soil samples, being used for 0 (i.e. unexposed to freeze-thaw), 2, 5, 11, 21 and 31 freeze-thaw cycles, were used to carry out the related tests. The deformation and load were measured with MTS stress and strain sensors, respectively, with an accuracy of 0.5 % of the full scale. They were automatically recorded by data logger at a certain time interval needed to provide a complete stress-strain curve.3RESULTS FROM UC TESTS3.1Effect of freeze-thaw on unconfined compressive (UC) strengthThe results of the UC tests are given in Figures 3 to 6. Soil samples unexposed were also tested for comparison. Figure 3 shows the stress-strain curves of typical soil samples after different number of freeze-thaw cycles. The stress-strain curves consist of three stages during the strain increase: elastic, plastic, and failure stages respectively (Yang et al, 2010). Failure is taken to correspond to the maximum unconfined compressive stress attained or the stress at 15 % axial strain, whichever occur first during the performance of a test (ASTM, 2006). The soil exhibits the elastic property while the strain is relatively low below about 2% representing the straight portion of the curves. In the plastic stages, the stress-strain curve begins to bend downward with the increasing strain. This bend indicates that the weaker part in soil sample begin to yield, and even to damage. In the failure stage, the stress falls abruptly after the peak point of the curve because the soil sample begins to fail. The failure pattern is typical of brittle one.Figure 3: Stress-strain curve for soil samples after different freeze-thaw cycles.Figure 4: Change in UC strength with increasing freeze-thaw cycles.The UC strength is defined as the maximum axial compressive stress at failure or the corresponding stress at 15% strain if no maximum axial compressive stress is reached, whichever occurs first. The UC strength as a function of the freeze-thaw cycles is shown in Figure 4. The straight line shows the decreasing trend of the UC strength with the increasing freeze-thaw cycles.After 31 freeze-thaw cycles, UC strength has decreased by 11% on average. The soil sample isweakening after repeated freezing and thawing. The linear regression equation is given as follows.σf = -0.589 n+176.4 (r20.33) [1] where σf (in kPa) is the UC strength and n is the number of freeze-thaw cycles, and r2 is thecoefficient of determination. This equation can be used to predict the change in strength of thesimilar soil due to freeze-thaw cycles. This empirical relationship depends on the soil type, watercontent and dry density.3.2Effect of freeze-thaw on failure strain and elastic modulusThe strain at failure and the elastic modulus are defined as failure strain and the slope of thestraight line of the stress-strain curve respectively. They are important parameters characterizingthe mechanical behavior of soil. Figure 5 shows the response of failure strain to freeze-thawcycles. The failure strain decreases with increasing freeze-thaw cycles. It decreases by 11.2% onaverage after 31 freeze-thaw cycles. The freeze-thaw cycles progressively cause the local damagein soil samples.Figure 5: Change in failure strain with increasing freeze-thaw cycles.Figure 6: Change in elastic modulus with increasing freeze-thaw numbers.The elastic modulus progressively decreases with increasing freeze-thaw cycles (Figure 6). Itdecreases by 32% on average after 31 freeze-thaw cycles. The following linear regressionequation is found from the results:E = -0.046 n+6.07 (r20.19) [2] where E (in MPa) is the elastic modulus.According to results of the UC tests, decrease in the UC strength, elastic modulus, and failurestrain confirms the weakening effect of freeze-thaw cycles on soil.4RESULTS FROM UUTC TESTSResults of UUTC tests on samples unexposed to freeze-thaw and after 11 freeze-thaw cycles aregiven in Figures 7 to 10. The other results for different freeze-thaw cycles are summarized inTable 1 and Figure 11. Figures 7 and 8 show the stress-strain curves of the compacted fine-grained soil under varying confining stresses unexposed and exposed to freeze-thaw cycles.Figure 7: Stress-strain curve at various confining stress for samples unexposed to freeze-thaw.Figure 8: Stress-strain curve at various confining stress for samples after 11 freeze-thaw cycles.The stress-strain curve and failure pattern of the soil samples are similar to those in the UC tests.The mechanical behavior of soil samples also exhibit obvious three stages during loading. Thefailure pattern is typical of brittle failure. Moreover, the deviator stress strength, defined as themaximum deviator stress at failure at a given confining stress, for the soil samples after 11 freeze-thaw cycles is much smaller than the one for samples unexposed to freeze-thaw. In addition, soils exhibit a transition from strain-softening to strain-hardening behavior with the increasing confining stress. The freeze-thaw cycles reduce the confining stress at which the stress-strain curve transits from strain-softening to strain-hardening.Figures 9 and 10 show the Mohr strength lines for soil samples unexposed and after 11 freeze-thaw cycles, respectively. The shear stress and normal stress are denoted as τ and σ respectively. The real Mohr failure envelops are not straight lines. But they can be simplified as straight lines for convenience of analysis as following equations 3 and 4.τ = σ tan (350) + 60[3]τ = σ tan (360) + 28.8 [4]S h e a r s t r e s s (k P a )Normal stress (kPa)07006005004003002001001600120010008006004002000 Figure 9: Mohr strength line for soil samples unexposed to freeze thaw.0200400600800100012001600100200300400500600700Normal stress (kPa)S h e a r s t r e s s (k P a )Figure 10: Mohr strength line for soil samples after 11 freeze-thaw cycles.The cohesion and internal friction angle of soil samples depend on the number of freeze-thaw cycles (Table 1 and Figure 11). The cohesion, the intercept of the Mohr strength line, is considerably reduced due to freeze-thaw (Figures 9 to 11); and the internal friction angle that the strength line makes with the normal stress axial, slightly increases by 1 to 2° (Table 1). The cohesion decreases by 84% on average after 31 freeze-thaw cycles.The results from the UUTC tests show that freeze-thaw reduces the deviator stress strength, cohesion and the confining stress at which strain-softening/hardening transition occurs. Freeze-thaw cycles weaken the structure and reduce the strength of compacted fine-grained soil.Table 1: Changes in cohesion and angle of internal friction after different freeze-thaw cycles Number of freeze-thaw cycles 0 21131Cohesion (kPa)60 42.528.89.8Internal friction angle (°) 35 373636Figure 11: Cohesion as a function of the number of freeze-thaw cycles.Change in mechanical behavior is attributed to the increase in volume of the pore of soil because water volume increases by 9% when it freezes. The volume increase from water to ice makes stress on the surrounding soil particles and pushes them moving out of pore space, even separated each other. In addition, freezing always leads to some joints and fissures due to shrinkage (Othman and Benson 1993, Proskin et al. 2010, Mu et al. 2011). Following the thawing, the removed finer particles and fissures tend to re-position to their original locations. But it is very hard to fully recover for densely compacted soil. This process occurs at each freeze-thaw cycle. As a consequence, a net increase in volume and a weakening of soil sample occurs at each new freeze-thaw cycle. These microstructure variations lead to changes in mechanical properties in macroscopic scale. Concerns should be made on the weathering and weakening process of freeze-thaw to geotechnical properties of compacted fine-grained soils.5CONCLUSIONSFreeze-thaw reduces the UC strength, elastic modulus and failure strain of compacted fine-grained soil, indicating that freeze-thaw has a significantly weakening effect on the compacted soils. The degraded mechanical behavior has a close correlation with the number of freeze-thaw cycles. A correlation has been established to predict and assess the developing trend of the degradation.The results from UUTC tests confirm that repeated freeze-thaw leads to obvious decrease in deviator stress strength, cohesion, and the confining stress at which the stress-strain curve shows a transition from the strain-softening to strain-hardening.ACKNOWLEDGEMENTSThis work was supported by the Program for Innovative Research Group of Natural Science Foundation of China (Nos. No.41121061), National Key Basic Research Program of China (973 Program) (No. 2012CB026106), the Chinese Academy of Sciences (CAS) Western Project (No. KZCX2-XB2-10), Western Communications Construction Scientific and Technological Project (No. 200831800025), National Natural Science Foundation of China (Nos. 41171055, 40971046 and 41023003) and Project of the State Key Laboratory of Frozen Soils Engineering, CAS, (No. SKLFSE-ZY-03).REFERENCESAlkire, B. and Morrison, J., 1982. Change in soil structure due to freeze-thaw and repeated loading. Transportation Research Record 918: 15–22.Aoyama, K., Ogawa, S. and Fukuda, M., 1985. Temperature dependencies of mechanical properties of soil subjected to freezing and thawing. Proceedings of the 4th International Symposium on Ground Freezing, Sapporo, Japan, August 5-7, 217-222.ASTM, 2006. Standard Test Method for Unconfined Compressive Strength of Cohesive Soil.ASTM standard D2166-06. American Society for Testing and Materials (ASTM) International. Chamberlain, E., Iskander, I. and Hunsiker, S., 1990. Effect of freeze-thaw on the permeability and macrostructure of soils. Proceedings of the International Symposium on Frozen Soil Impacts on Agriculture, Range, and Forest Lands. Cold Regions Research and Engineering Laboratory, Hanover, New Hampshire, U.S.A. Special Report 90-1: 145–155. Chamberlain, E. and Gow, A., 1979. Effect of freezing and thawing on the permeability and structure of soils. Engineering Geology 13: 73–92.Culley, R., 1971. Effect of freeze-thaw cycling on stress-strain characteristics and volume change of a till subjected to repetitive loading. Canadian Geotechnical Journal 8: 359-371. Eigenbrod, K., 1996. Effects of cyclic freezing and thawing on volume changes and permeabilities of soft fine-grained soils. Canadian Geotechnical Journal 33(4): 529–537. Graham, J. and Au, V., 1985. Effects of freeze-thaw and softening on a natural clay at low stresses. Canadian Geotechnical Journal 22(1): 69–78.Kim, W. and Daniel, D., 1992. Effects of freezing on hydraulic conductivity of compacted clay.Journal of Geotechnical Engineering 118(7): 1083–1097.Lee, W., Bohra, N., Altschaeffl, A. and White, T., 1995. Resilient modulus of cohesive soils and the effect of freeze-thaw. Canadian Geotechnical Journal 32: 559-568.Li, G., Ma, W., Mu, Y., Zhou, C. and Mao, Y., 2011. Process and mechanism of impact of freezing and thawing cycle on collapse deformation of compacted loess. China Journal of Highway and Transport 24(5): 1-5.Mu, Y., Ma, W., Li, G. and Mao, Y., 2011. Quantitative analysis of impacts of freeze-thaw cycles upon microstructure of compacted loess. Chinese Journal of Geotechnical Engineering, 2011, 33(12): 1919-1925.Ministry of Communication of the People’s Republic of China (MC-PRC), 2007. Test Methods of Soil for Highway Engineering. China Communication Press, Beijing, China.Ono, T. and Mitachi, T., 1997. Computer controlled triaxial freeze-thaw-shear apparatus.Ground Freezing 97. A.A. Balkema, Rotterdam: 335–339.Othman, M. and Benson, C., 1993. Effect of freeze-thaw on the hydraulic conductivity and morphology of compacted clay. Canadian Geotechnical Journal 30(2): 236–246Proskin, S., Sego, D. and Alostaz, M., 2010. Freeze–thaw and consolidation tests on Suncor mature fine tailings (MFT). Cold Regions Science and Technology 63 (3): 110-120.Qi, J. and Ma, W., 2006. Influence of freezing-thawing on strength of overconsolidated soils.Chinese Journal of Geotechnical Engineering 28: 2082-2086.Simonsen, E., Janoo, V. and Isacsson, U., 2002. Resilient properties of unbound road materials during seasonal frost conditions. Journal of Cold Regions Engineering 16: 28-50.Su, Q., Tang, D. and Liu, S., 2008. Test on physic-mechanical properties of Qinghai-Tibet slope clay under freezing-thawing cycles. Chinese Journal of Rock Mechanics and Engineering 27(supp.1): 2990-2994.Viklander, P., 1998. Permeability and volume changes in till due to cyclic freeze-thaw. Canadian Geotechnical Journal 35(3): 471–477.Wang, D., Ma, W., Niu, Y., Chang, X. and Wen, Z., 2007. Effects of cyclic freezing and thawing on mechanical properties of Qinghai-Tibet clay. Cold regions science and technology 48(1):34-43.Wang, X., Yang, P., Wang, H. and Dai, H., 2009. Experimental study on effects of freezing and thawing on mechanical properties of clay. Chinese Journal of Geotechnical Engineering 31: 1768-1772.Yang, C., He, P., Cheng, G., Zhu, Y. and Zhao, S., 2003. Testing study on influence of freezing and thawing on dry density and water content of soil. Chinese Journal of Rock Mechanics and Engineering 22(sup.2): 2695-2699.Yang, Y., Lai, Y., Li, S. and Dong, Y., 2010. Experimental study of deformation failure and energy properties of frozen silt under triaxial compression. Rock and Soil Mechanics 31 (11): 3505-3510.Yao, Y., Qi, J. and Song, C., 2008. Influence of freeze-thaw on engineering properties of Qingzang clay. Journal of Glaciology and Geocryology 30: 165-169.Yong, R., Boonsinsuk, P. and Yin, C., 1985. Alteration of soil behavior after cyclic freezing and thawing. Proceedings of the 4th International Symposium on Ground Freezing, Sapporo, Japan, August 5-7, 217-222.。

Climate change is a significant and rapidly growing global issue that is having major impacts on the environment, economy, and human health. The effects of climate change are wide-ranging and can be felt across the world, with consequences including extreme weather events, rising sea levels, and changes in ecosystems. In this essay, we will explore the various effects of climate change and their implications for our planet.One of the most visible effects of climate change is the increased frequency and intensity of extreme weather events. Heatwaves, droughts, hurricanes, and heavy rainfall are becoming more common, leading to widespread devastation and loss of life. These extreme weather events are particularly harmful to vulnerable populations and have a significant economic impact, as infrastructure and agriculture are often damaged or destroyed.Rising sea levels are another consequence of climate change, driven by the melting of polar ice caps and glaciers. As sea levels continue to rise, coastal areas and low-lying islands are at risk of being inundated, leading to displacement of communities and loss of valuable land. Additionally, saltwater intrusion into coastal aquifers can contaminate freshwater sources, impacting both human and ecological systems.Changes in ecosystems are also a significant effect of climate change, with shifts in temperature and precipitation patterns altering habitats and disrupting species' life cycles. This can lead to loss of biodiversity, as some species are unable to adapt to changing conditions and face extinction. In addition, thespread of invasive species and diseases can further destabilize ecosystems, leading to negative impacts on agriculture and food security.The effects of climate change extend beyond the environment and into the realm of human health. Rising temperatures can exacerbate air pollution and worsen respiratory conditions, while changes in precipitation patterns can lead to waterborne diseases and food insecurity. Additionally, extreme weather events can cause physical injury and mental health issues, particularly for those who are displaced or directly impacted by disasters.The economic impact of climate change is substantial, with costs associated with extreme weather events, loss of infrastructure, and damage to agriculture and fisheries. This can strain national economies and lead to increased poverty and inequality, particularly in developing countries that lack the resources to adapt to and mitigate the effects of climate change.In response to the effects of climate change, it is crucial that we take action to reduce our greenhouse gas emissions and adapt to the changes that are already occurring. This includes transitioning to renewable energy sources, improving energy efficiency, and implementing policies to reduce deforestation and promote sustainable land use. Additionally, it is important to invest in climate-resilient infrastructure and technologies, and to support vulnerable communities in adapting to the impacts of climate change.In conclusion, the effects of climate change are far-reaching and have significant implications for the environment, economy, and human health.Addressing this global challenge requires urgent and coordinated action at all levels, from individual efforts to national and international policies. By working together to mitigate the effects of climate change and adapt to its impacts, we can build a more sustainable and resilient future for our planet.。

A Thesis Submitted in Partial Fulfillment of the Requirementsfor the Degree for the Master of EngineeringDynamic Analysis and Vibration Sensing of Thin-Wall Annular WorkpieceCandidate : Liu WuguangMajor : Mechatronic EngineeringSupervisor : Prof. Lee Kok-MengAssoc. Prof. Guo JiajieHuazhong University of Science & TechnologyWuhan , Hubei 430074, P.R.ChinaMay, 2015独创性声明本人声明所呈交的学位论文是我个人在导师指导下进行的研究工作及取得的研究成果。

尽我所知，除文中已经标明引用的内容外，本论文不包含任何其他个人或集体已经发表或撰写过的研究成果。

对本文的研究做出贡献的个人和集体，均已在文中以明确方式标明。

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保密□，在年解密后适用本授权书。

本论文属于不保密□。

（请在以上方框内打“√”）学位论文作者签名：指导教师签名：日期：年月日日期：年月日华中科技大学硕士学位论文摘要薄壁零部件（如航空发动机压气机盘）在加工时易受装夹力、切削力等因素影响，时空分布的工件变形和振动会导致加工质量和精度降低。

中文摘要摘要镁合金室温下绝对强度低和塑性变形能力较差是阻碍其广泛应用的瓶颈问题。

滑移和孪生是镁合金重要的塑性变形机制，由于室温下只能开启有限的滑移系，所以孪生对塑性变形的协调变得十分重要。

孪晶结构镁合金中的退火强化是近年来发现的一个有趣的现象，即，通过预变形和中间退火处理可以让固溶原子偏聚在孪晶界上产生钉扎作用，使孪晶在后续变形过程中的长大受到抑制，从而起到强化作用。

然而，孪晶界被钉扎后，合金在后续变形过程中的组织演变规律尚缺乏研究。

对孪晶结构镁合金组织演变规律的探讨有助于更深入的理解孪生变形机制，为调控孪生行为提供科学依据。

本课题选取了Nd原子百分比为0.03%（1#）和0.18%（2#）的两种Mg-Nd 合金，研究对比中间退火后孪晶在进一步变形过程中的演变规律。

对上述合金挤压棒材先进行预压缩得到预变形样品，然后对一部分样品在200℃下退火6h后做再压缩实验，另一部分样品不进行退火直接做再压缩实验。

采用电子背散射技术（EBSD）原位观察研究孪晶的演变，统计分析了孪晶的特征参量，包括孪晶的数量和体积分数、孪晶形核和长大的施密特因子，以及孪晶形核和长大对孪生过程的贡献等，并探讨了中间退火和合金元素对孪晶演变的影响规律。

研究结果表明：①对于经过中间退火的1#合金孪晶演变过程，再压缩后孪晶的体积分数增加量为14%，其中形核的贡献为14%，长大的贡献为86%。

再压缩过程中孪生变形由孪晶长大主导。

孪晶形核的数量分数为24%，孪晶长大的数量分数为38%。

孪晶形核的平均施密特因子（SF）为0.35，孪晶长大的平均SF为0.47。

孪晶形核的SF主要分布在0.4-0.3范围内，孪晶形核的SF等级主要是R1和R2等级（R1~R6分别对应于孪晶六个变体中最大~最小的等级），孪晶长大的SF主要分布在0.5-0.4范围内，孪晶长大的SF等级主要是R1和R2等级。

②对于不经中间退火的1#合金孪晶演变过程，再压缩后孪晶的体积分数增加量为22%，其中形核的贡献为59%，长大的贡献为41%。

机械英语试题及答案详解一、选择题1. The term "mechanical engineering" refers to the application of engineering principles to:A. Chemical processesB. Electrical systemsC. Design and manufacture of machinesD. Software development答案：C2. What is the primary function of a bearing in a mechanical system?A. To convert energyB. To reduce frictionC. To increase efficiencyD. To absorb heat答案：B3. The process of converting a rough workpiece into a finished part is known as:A. MachiningB. WeldingC. CastingD. Forging答案：A二、填空题4. The formula for calculating the force exerted by a springis known as ________.答案：Hooke's Law5. In mechanical design, the term ________ refers to thestudy of the forces and moments acting on a body.答案：Statics6. The unit of pressure in the International System of Units (SI) is ________.答案：Pascal (Pa)三、简答题7. Explain the difference between static and dynamic friction.答案：Static friction is the force that must be overcometo start moving an object at rest, while dynamic friction is the force that opposes the motion of an object that isalready moving.8. Describe the purpose of a gear in a mechanical system.答案：A gear is used to transmit motion and force from one part of a system to another, often changing the speed and/or direction of the motion.四、计算题9. A hydraulic press has a piston with an area of 0.02 m². If the pressure applied to the piston is 5 MPa, calculate the force exerted by the piston.答案：Force = P ressure × Area = 5 × 10⁶ Pa × 0.02 m²= 100,000 N10. A lever is balanced when the product of the effort force and its distance from the fulcrum is equal to the product of the load force and its distance from the fulcrum. If the effort force is 300 N and the load force is 1200 N, and the effort is applied 2 m from the fulcrum, calculate the distance from the fulcrum to the load.答案：Let the distance from the fulcrum to the load be\( x \). According to the principle of levers, \( 300 N\times 2 m = 1200 N \times x \). Solving for \( x \) gives\( x = \frac{300 N \times 2 m}{1200 N} = 0.5 m \).五、论述题11. Discuss the importance of mechanical vibrations in the context of machinery operation and maintenance.答案：Mechanical vibrations are crucial in machinery for several reasons. They can indicate the health of a machine, with abnormal vibrations often signaling a problem such as imbalance, misalignment, or wear. Monitoring vibrations can help in predictive maintenance, preventing breakdowns and extending the life of machinery.12. Explain the concept of stress concentration in mechanical components and its implications.答案：Stress concentration occurs in mechanical components where the stress is higher than the average stress due to geometrical discontinuities or material defects. This can lead to premature failure of the component under load, as the high-stress areas are more susceptible to fatigue and cracking. Designing to minimize stress concentrations and using materials with good fatigue resistance can mitigate these effects.。

剑桥雅思阅读解析8(test2)店铺为大家整理收集了剑桥雅思阅读8真题解析：test2阅读原文解析，希望对各位考生的备考有所帮助,祝每位烤鸭考试顺利，都能取得好成绩!剑桥雅思阅读8原文(test2)READING PASSAGE 1You should spend about 20 minutes on Questions 1-13, which are based on Reading Passage 1 below.Sheet glass manufacture:the float processGlass, which has been made since the time of the Mesopotamians and Egyptians, is little more than a mixture of sand, soda ash and lime. When heated to about 1500 degrees Celsius (℃) this becomes a molten mass that hardens when slowly cooled. The first successful method for making clear, flat glass involved spinning. This method was very effective as the glass had not touched any surfaces between being soft and becoming hard, so it stayed perfectly unblemished, with a 'fire finish'. However, the process took a long time and was labour intensive.Nevertheless, demand for flat glass was very high and glassmakers across the world were looking for a method of making it continuously. The first continuous ribbon process involved squeezing molten glass through two hot rollers, similar to an old mangle. This allowed glass of virtually any thickness to be made non-stop, but the rollers would leave both sides of the glass marked, and these would then need to be ground and polished. This part of the process rubbed away around 20 per cent of the glass, and the machines were very expensive.The float process for making flat glass was invented by Alistair Pilkington. This process allows the manufacture of clear, tinted and coated glass for buildings, and clear and tinted glass for vehicles. Pilkington had been experimenting with improving the melting process, and in 1952 he had the idea of using a bed of molten metal to form the flat glass, eliminating altogether the need for rollers within the float bath. The metal had to melt at a temperature less than the hardening point of glass (about 600℃), but could not boil at a temperature below the temperature of the molten glass (about 1500℃). The best meta l for the job was tin.The rest of the concept relied on gravity, which guaranteed that the surface of the molten metal was perfectly flat and horizontal. Consequently, when pouring molten glass onto the molten tin, the underside of the glass would also be perfectly flat. If the glass were kept hot enough, it would flow over the molten tin until the top surface was also flat, horizontal and perfectly parallel to the bottom surface. Once the glass cooled to 604℃ or less it was too hard to mark and could be transported out of the cooling zone by rollers. The glass settled to a thickness of six millimetres because of surface tension interactions between the glass and the tin. By fortunate coincidence, 60 per cent of the flat glass market at that time was for six-millimetre glass.Pilkington built a pilot plant in 1953 and by 1955 he had convinced his company to build a full-scale plant. However, it took 14 months of non-stop production, costing the company ￡100,000 a month, before the plant produced any usable glass. Furthermore, once they succeeded in making marketable flat glass, the machine was turned off for a service to prepare it for years of continuous production. When it started up again it took another four months to get the process right again. They finallysucceeded in 1959 and there are now float plants all over the world, with each able to produce around 1000 tons of glass every day, non-stop for around 15 years.Float plants today make glass of near optical quality. Several processes —melting, refining, homogenising —take place simultaneously in the 2000 tonnes of molten glass in the furnace. They occur in separate zones in a complex glass flow driven by high temperatures. It adds up to a continuous melting process, lasting as long as 50 hours, that delivers glass smoothly and continuously to the float bath, and from there to a coating zone and finally a heat treatment zone, where stresses formed during cooling are relieved.The principle of float glass is unchanged since the 1950s. However, the product has changed dramatically, from a single thickness of 6.8 mm to a range from sub-millimetre to 25 mm, from a ribbon frequently marred by inclusions and bubbles to almost optical perfection. To ensure the highest quality, inspection takes place at every stage. Occasionally, a bubble is not removed during refining, a sand grain refuses to melt, a tremor in the tin puts ripples into the glass ribbon. Automated on-line inspection does two things. Firstly, it reveals process faults upstream that can be corrected. Inspection technology allows more than 100 million measurements a second to be made across the ribbon, locating flaws the unaided eye would be unable to see. Secondly, it enables computers downstream to steer cutters around flaws.Float glass is sold by the square metre, and at the final stage computers translate customer requirements into patterns of cuts designed to minimise waste.Questions 1-8Complete the table and diagram below.Choose NO MORE THAN TWO WORDS from the passage for each answer.Write your answers in boxes 1-8 on your answer sheet.Early methods of producing flat glassMethod Advantages Disadvantages1............Glass remained2........... ? Slow3.............RibbonCould produce glass sheets of varying 4.............non-stop process ? Glass was 5...........20% of glass rubbed awayMachines were expensive图片11Questions 9-13Do the following statements agree with the information given in Reading Passage 1?In boxes 9-13 on your answer sheet, writeTRUE if the statement agrees with the informationFALSE if the statement contradicts the informationNOT GIVEN if there is no information on this9 The metal used in the float process had to have specific properties.10 Pilkington invested some of his own money in his float plant.11 Pilkington’s first full-scale plant was an instant commercial success.12 The process invented by Pilkington has now beenimproved.13 Computers are better than humans at detecting faults in glass.READING PASSAGE 2You should spend about 20 minutes on Questions 14-26, which are based on Reading Passage 2 on the following pages.Question 14-17Reading passage 2 has six paragraphs, A-F.Choose the correct heading for paragraphs B and D-F from the list of headings below.Write the correct number, i-ix, in boxes 14-17 on your answer sheet.List of Headingsi Predicting climatic changesii The relevance of the Little Ice Age todayiii How cities contribute to climate change.iv Human impact on the climatev How past climatic conditions can be determinedvi A growing need for weather recordsvii A study covering a thousand yearsviii People have always responded to climate changeix Enough food at lastExample AnswerParagraph A Viii14 Paragraph BExample AnswerParagraph C V15 Paragraph D16 Paragraph E17 Paragraph FTHE LITTLE ICE AGEA This book will provide a detailed examination of the Little Ice Age and other climatic shifts, but, before I embark on that, let me provide a historical context. We tend to think of climate — as opposed to weather — as something unchanging, yet humanity has been at the mercy of climate change for its entire existence, with at least eight glacial episodes in the past 730,000 years. Our ancestors adapted to the universal but irregular global warming since the end of the last great Ice Age, around 10,000 years ago, with dazzling opportunism. They developed strategies for surviving harsh drought cycles, decades of heavy rainfall or unaccustomed cold; adopted agriculture and stock-raising, which revolutionised human life; and founded the world's first pre-industrial civilisations in Egypt, Mesopotamia and the Americas. But the price of sudden climate change, in famine, disease and suffering, was often high.B The Little Ice Age lasted from roughly 1300 until the middle of the nineteenth century. Only two centuries ago, Europe experienced a cycle of bitterly cold winters; mountain glaciers in the Swiss Alps were the lowest in recorded memory, and pack ice surrounded Iceland for much of the year. The climatic events of the Little Ice Age did more than help shape the modern world. They are the deeply important context for the current unprecedented global warming. The Little Ice Age was far from a deep freeze, however; rather an irregular seesaw of rapid climatic shifts, few lasting more than a quarter-century, driven by complex and still little understood interactions between the atmosphere and the ocean. The seesaw brought cycles of intensely cold winters and easterly winds, then switched abruptly to years of heavy spring and early summer rains, mild winters,and frequent Atlantic storms, or to periods of droughts, light northeasterly winds, and summer heat waves.C Reconstructing the climate changes of the past is extremely difficult, because systematic weather observations began only a few centuries ago, in Europe and North America. Records from India and tropical Africa are even more recent. For the time before records began, we have only 'proxy records' reconstructed largely from tree rings and ice cores, supplemented by a few incomplete written accounts. We now have hundreds of tree-ring records from throughout the northern hemisphere, and many from south of the equator, too, amplified with a growing body of temperature data from ice cores drilled in Antarctica, Greenland, the Peruvian Andes, and other locations, we are close to a knowledge of annual summer and winter temperature variations over much of the northern hemisphere going back 600 years.D This book is a narrative history of climatic shifts during the past ten centuries, and some of the ways in which people in Europe adapted to them. Part One describes the Medieval Warm Period, roughly 900 to 1200. During these three centuries, Norse voyagers from Northern Europe explored northern seas, settled Greenland, and visited North America. It was not a time of uniform warmth, for then, as always since the Great Ice Age, there were constant shifts in rainfall and temperature. Mean European temperatures were about the same as today, perhaps slightly cooler.E It is known that the Little Ice Age cooling began in Greenland and the Arctic in about 1200. As the Arctic ice pack spread southward, Norse voyages to the west were rerouted into the open Atlantic, then ended altogether. Storminess increased in the North Atlantic and North Sea. Colder, much wetter weatherdescended on Europe between 1315 and 1319, when thousands perished in a continent-wide famine. By 1400, the weather had become decidedly more unpredictable and stormier, with sudden shifts and lower temperatures that culminated in the cold decades of the late sixteenth century. Fish were a vital commodity in growing towns and cities, where food supplies were a constant concern. Dried cod and herring were already the staples of the European fish trade, but changes in water temperatures forced fishing fleets to work further offshore. The Basques, Dutch, and English developed the first offshore fishing boats adapted to a colder and stormier Atlantic. A gradual agricultural revolution in northern Europe stemmed from concerns over food supplies at a time of rising populations. The revolution involved intensive commercial farming and the growing of animal fodder on land not previously used for crops. The increased productivity from farmland made some countries self-sufficient in grain and livestock and offered effective protection against famine.F Global temperatures began to rise slowly after 1850, with the beginning of the Modern Warm Period. There was a vast migration from Europe by land-hungry farmers and others, to which the famine caused by the Irish potato blight contributed, to North America, Australia, New Zealand, and southern Africa. Millions of hectares of forest and woodland fell before the newcomers' axes between 1850 and 1890, as intensive European farming methods expanded across the world. The unprecedented land clearance released vast quantities of carbon dioxide into the atmosphere, triggering for the first time humanly caused global warming. Temperatures climbed more rapidly in the twentieth century as the use of fossil fuels proliferated and greenhouse gas levels continued to soar. The rise has been even steeper since theearly 1980s. The Little Ice Age has given way to a new climatic regime, marked by prolonged and steady warming. At the same time, extreme weather events like Category 5 hurricanes are becoming more frequent.Questions 18-22Complete the summary using the list of words, A-I, below.Write the correct letter, A-I, in boxes 18-22 on your answer sheet.Weather during the Little Ice AgeDocumentation of past weather conditions is limited: our main sources of knowledge of conditions in the distant past are 18...........and 19.................. We can deduce that the Little Ice Age was a time of 20.............. , rather than of consistent freezing. Within it there were some periods of very cold winters, other of 21...............and heavy rain, and yet others that saw 22................with no rain at all.A climatic shiftsB ice coresC tree ringsD glaciersE interactionsF weather observationsG heat waves H storms I written accountsQuestions 23-26Classify the following events as occurring during theA Medieval Warm PeriodB Little Ice AgeC Modern Warm PeriodWrite the correct letter, A, B or C, in boxes 23-26 on your answer sheet.23 Many Europeans started farming abroad.24 The cutting down of trees began to affect the climate.25 Europeans discovered other lands.26 Changes took place in fishing patterns.READING PASSAGE 3You should spend about 20 minutes on Questions 27-40, which are based on Reading Passage 3 on the following pages.Questions 27-32Reading Passage 3 has six paragraphs, A-F.Choose the correct heading for each paragraph from the list of headings below.Write the correct number, i-viii, in boxes 27-32 on your answer sheet.List of Headingsi The difficulties of talking about smellsii The role of smell in personal relationshipsiii Future studies into smelliv The relationship between the brain and the nosev The interpretation of smells as a factor in defining groups vi Why our sense of smell is not appreciatedvii Smell is our superior senseviii The relationship between smell and feelings27 paragraph A28 paragraph B29 paragraph C30 paragraph D31 paragraph E32 paragraph FThe meaning and power of smellThe sense of smell, or olfaction, is powerful. Odours affect us on a physical, psychological and social level. For the most part, however, we breathe in the aromas which surround us without being consciously aware of their importance to us. It is only when the faculty of smell is impaired for some reason that we begin torealise the essential role the sense of smell plays in our sense of well-beingA A survey conducted by Anthony Synott at Montreal's Concordia University asked participants to comment on how important smell was to them in their lives. It became apparent that smell can evoke strong emotional responses. A scent associated with a good experience can bring a rush of joy, while a foul odour or one associated with a bad memory may make us grimace with disgust. Respondents to the survey noted that many of their olfactory likes and dislikes were based on emotional associations. Such associations can be powerful enough so that odours that we would generally label unpleasant become agreeable, and those that we would generally consider fragrant become disagreeable for particular individuals. The perception of smell, therefore, consists not only of the sensation of the odours themselves, but of the experiences and emotions associated with them.B Odours are also essential cues in social bonding. One respondent to the survey believed that there is no true emotional bonding without touching and smelling a loved one. In fact, infants recognise the odours of their mothers soon after birth and adults can often identify their children or spouses by scent. In one well-known test, women and men were able to distinguish by smell alone clothing worn by their marriage partners from similar clothing worn by other people. Most of the subjects would probably never have given much thought to odour as a cue for identifying family members before being involved in the test, but as the experiment revealed, even when not consciously considered, smells register.C In spite of its importance to our emotional and sensorylives, smell is probably the most undervalued sense in many cultures. The reason often given for the low regard in which smell is held is that, in comparison with its importance among animals, the human sense of smell is feeble and undeveloped. While it is true that the olfactory powers of humans are nothing like as fine as those possessed by certain animals, they are still remarkably acute. Our noses are able to recognise thousands of smells, and to perceive odours which are present only in extremely small quantities.D Smell, however, is a highly elusive phenomenon. Odours, unlike colours, for instance, cannot be named in many languages because the specific vocabulary simply doesn't exist. ‘It smells like…,’ we have to say when describing an odour, struggling to express our olfactory experience. Nor can odours be recorded: there is no effective way to either capture or store them over time. In the realm of olfaction, we must make do with descriptions and recollections. This has implications for olfactory research.E Most of the research on smell undertaken to date has been of a physical scientific nature. Significant advances have been made in the understanding of the biological and chemical nature of olfaction, but many fundamental questions have yet to be answered. Researchers have still to decide whether smell is one sense or two — one responding to odours proper and the other registering odourless chemicals in the air. Other unanswered questions are whether the nose is the only part of the body affected by odours, and how smells can be measured objectively given the non-physical components. Questions like these mean that interest in the psychology of smell is inevitably set to play an increasingly important role for researchers.F However, smell is not simply a biological and psychologicalphenomenon. Smell is cultural, hence it is a social and historical phenomenon. Odours are invested with cultural values: smells that are considered to be offensive in some cultures may be perfectly acceptable in others. Therefore, our sense of smell is a means of, and model for, interacting with the world. Different smells can provide us with intimate and emotionally charged experiences and the value that we attach to these experiences is interiorised by the members of society in a deeply personal way. Importantly, our commonly held feelings about smells can help distinguish us from other cultures. The study of the cultural history of smell is, therefore, in a very real sense, an investigation into the essence of human culture.Questions 33-36Choose the correct letter, A, B, C or D.Write the correct letter in boxes 33-36 on your answer sheet.33 According to the introduction, we become aware of the importance of smell whenA we discover a new smell.B we experience a powerful smell.C our ability to smell is damaged.D we are surrounded by odours.34 The experiment described in paragraph BA shows how we make use of smell without realising it.B demonstrates that family members have a similar smell.C proves that a sense of smell is learnt.D compares the sense of smell in males and females.35 What is the write doing in paragraph C?A supporting other researchB making a proposalC rejecting a common beliefD describing limitations36 What does the write suggest about the study of smell in the atmosphere in paragraph E?A The measurement of smell is becoming more accurate.B Researchers believe smell is a purely physical reaction.C Most smells are inoffensive.D Smell is yet to be defined.Questions 37-40Complete the sentences below.Choose ONE WORD ONLY from the passage for each answer.Write your answers in boxes 37-40 on your answer sheet.37 Tests have shown that odours can help people recognise the.......... belonging to their husbands and wives.38 Certain linguistic groups may have difficulty describing smell because they lack the appropriate ................ .39 The sense of smell may involve response to................ which do not smell, in addition to obvious odours.40 Odours regarded as unpleasant in certain.................are not regarded as unpleasant in others.剑桥雅思阅读8原文参考译文(test2)PASSAGE 1 参考译文：玻璃板制造：浮法工艺早在美索不达米亚时期和古埃及时期人们就开始制造玻璃，当时制作出的玻璃只不过是沙子、碳酸钠和石灰的混合物而已。

Ch 2 Overview of Engineering MechanicsAs we look around us we see a world full of ‘things’: machines, devices, tools; things that we have designed, 当我们环顾四周，我们可以看到充满物质的世界：机器，仪器，工具：这些被我设计、建造和使用过built and used; things made of wood, metals, ceramics, and plastics. We know from experience that some 的东西：这些东西是由木头，金属，陶瓷和塑料做成。

我们从经验可以知道一些东西比别的东things are better than others; they last longer, cost less, are quieter, look better, or are easier to use.比别的东西好：他们比较耐用，低成本，安静，看起来好点，或者使用比较简单。

Ideally, however, every such item has been designed according to some set of ‘functional requirements; as 不管怎么样，最理想的是这样一个东西都是被设计者所认为的那样根据某些“使用要求”设计出来的。

perceived by the designers—that is, it has been designed so as to answer the question, ‘Exactly what function也就是说他的设计是为了回答这些问题，确切的说它应该执行怎么样的功should it perform?’ In the world of engineering, the major function frequently is to support some type of 能？在工程的领域里，最主要的功能是经常支持一些由于重力，惯性，压力等作用产loading due to weight, inertia, pressure etc. From the beams in our homes to the wings of an airplane, there 生的荷载。

应变速率英语The concept of strain rate, central to materials science and engineering, refers to the rate of change of strain with respect to time. It is a crucial parameter that governs the mechanical behavior of materials under dynamic loading conditions. Understanding strain rate in the context of materials' response to external forces is essential for predicting and optimizing material performance in various applications.In the English language, the term "strain rate" is often used interchangeably with "rate of strain" or "strain rate of change." These terms describe the same phenomenon: how quickly a material deforms when subjected to external forces. The importance of strain rate lies in its ability to influence material properties such as strength, ductility, and toughness. For instance, metals and polymers often exhibit higher strength and lower ductility at higher strain rates, due to the faster accumulation of microstructural changes within the material.The study of strain rate effects is particularly relevant in dynamic loading scenarios such as impacttesting, ballistic impact, and explosive shock waves. In these situations, the duration of loading is short, and the strain rates can be extremely high. Materials musttherefore possess sufficient resistance to failure under these extreme conditions to ensure safe and reliable performance.In addition to its application in materials testing, strain rate analysis is also employed in other fields such as geophysics and civil engineering. For instance, thestudy of earthquake-resistant structures often involves understanding how materials behave at high strain rates. Similarly, in geophysics, strain rate analysis is used to investigate the deformation and flow of rocks and soils within the Earth's crust.Moreover, strain rate has implications for materials processing techniques such as metalworking, plastic molding, and glassblowing. By controlling the rate of deformation during these processes, manufacturers can achieve desired material properties and dimensional accuracy.In summary, strain rate is a fundamental concept in materials science and engineering that has wide-rangingapplications across multiple fields. Its significance liesin its ability to govern material behavior under dynamic loading conditions, influencing properties such as strength, ductility, and toughness. By understanding and manipulating strain rate, we can optimize material performance in a diverse range of applications, from automotive safety systems to earthquake-resistant infrastructure.**应变速率与材料行为：英语语境下的科学现象探索** 在材料科学和工程领域，应变速率是一个核心概念，它指的是应变随时间变化的速率。

背应力英文术语In the realm of engineering and physics, the term "back stress" refers to a residual stress that opposes the direction of the applied load. This concept is particularly significant in the study of materials and their mechanical properties, as it influences how materials deform under stress and recover once the stress is removed.Back stress is a key factor in the phenomenon known as Bauschinger effect, where the yield strength of a material in compression becomes different from the yield strength in tension after a plastic deformation has occurred. This effect is named after the German engineer Johann Bauschinger, who first described it in the late 19th century.Understanding back stress is crucial for predicting the behavior of materials under cyclic loading, which is common in many industrial applications. For instance, metal components in machinery or structures are often subjected to repeated loading and unloading cycles, leading to what is known as fatigue. The accumulation of back stress during these cycles can lead to unexpected failures if not properly accounted for in the design process.In metallurgy, back stress plays a role in work hardening, also known as strain hardening, where a metal becomes stronger and harder after being plastically deformed. This is due to the increase in dislocation density within the metal's crystal structure, which creates an internal back stress that opposes further dislocation movement.Moreover, back stress is a critical consideration in the field of plasticity theory, which deals with the permanent deformation of materials. The mathematical modeling of back stress involves complex equations that describe how materials yield and flow under various stress states. These models are essential for engineers to design safe and reliable products.In summary, back stress is a fundamental concept in the study of material science and engineering. It affects how materials respond to external loads, their strength, and their durability. A thorough understanding of back stress and its implications is necessaryfor the development of advanced materials and the design of structures and components that can withstand the demands of modern engineering challenges.The study of back stress is not only limited to metals but also extends to polymers, composites, and other materials. Each material exhibits unique back stress characteristics, influenced by its microstructure, composition, and processing history. Researchers continue to explore the effects of back stress on new materials, seeking to enhance their performance for various applications.In the aerospace industry, for example, the control of back stress is vital for the development of lightweight yet strong materials that can endure the extreme conditions of flight. Similarly, in the automotive industry, understanding back stress contributes to the creation of vehicles that are both fuel-efficient and safe.In conclusion, back stress is a complex but essential aspect of material behavior. Its study and application are integral to the advancement of technology and the improvement of our daily lives through better, more resilient materials and products. As research progresses, our grasp of back stress and its management will continue to evolve, leading to innovations that will shape the future of engineering and design. 。

带大隔板爆炸成型弹丸战斗部药型罩结构研究祖旭东;黄正祥;朱传胜【摘要】An analytical model for calculating the collapse velocity of a liner element under the impact of Mach wave is proposed based on the characteristics of detonation wave transmitting in a charge embedded wave shaper of explosively formed projectile ( EFP ) to research the liner configuration. The theoretical results show that, local thickening of the liner top can reduce the collapse velocity of the top element significantly and avoid the damage at the nose of the EFP;the overmuch increment of the thickness of the liner top leads to droplets and hollows,and is adverse to the stability and the penetration capability of the EFP. The simulations reveal that, the EFP initial velocity and length-diameter ratio are barely decreased due to thickening the top of the liner;the thickness increment between 12 . 5％ and 25 . 0％ can inhibit the damage at the nose of the EFP and avoid droplets and hollows. The X-ray results are identical to the simulation results reasonably well.%为研究爆炸成型弹丸(EFP)药型罩结构,基于爆轰波在有大直径隔板的EFP装药结构中的传播特性,建立了马赫波作用下罩顶微元压垮速度理论计算模型.理论计算结果表明,药型罩顶部局部加厚可以显著地降低罩顶微元压垮速度,避免EFP头部断裂;当厚度增加量过大时会导致EFP头部出现射滴和包心,对EFP飞行稳定性和侵彻威力造成负面影响.数值模拟结果表明,罩顶局部加厚不会显著降低EFP速度和长径比;当罩顶局部厚度增加量为12.5％～25.0％时,既能避免EFP头部断裂,又能避免EFP头部出现射滴和包心.对带隔板EFP战斗部进行了X光实验,实验结果验证了数值模拟结果的正确性.【期刊名称】《南京理工大学学报（自然科学版）》【年(卷),期】2017(041)006【总页数】5页(P676-680)【关键词】爆炸力学;爆炸成型弹丸;战斗部;药型罩;马赫波;隔板【作者】祖旭东;黄正祥;朱传胜【作者单位】南京理工大学机械工程学院,江苏南京210094;南京理工大学机械工程学院,江苏南京210094;南京理工大学机械工程学院,江苏南京210094【正文语种】中文【中图分类】TJ303.4与射流相比,爆炸成型弹丸(Explosively formed projectile,EFP)具有对炸高不敏感、反应装甲对其影响小、侵彻后效大等优点,已经应用于多种反装甲武器系统中。

高中英语哲学思考单选题50题1. Philosophy is the search for ______ and understanding of the nature of reality and human existence.A. wisdomB. knowledgeC. intelligenceD. experience答案：A。

本题考查词汇辨析。

“wisdom”意为“智慧”，哲学是对现实本质和人类存在的智慧的追寻和理解；“knowledge”侧重于“知识”；“intelligence”指“智力”；“experience”是“经验”。

哲学更强调的是智慧的探寻，A 选项最符合题意。

2. In philosophy, the concept of 'truth' is often ______ and debated.A. exploredB. ignoredC. rememberedD. forgotten答案：A。

“explore”意为“探索”，在哲学中，“真理”的概念常常被探索和争论；“ignore”是“忽视”；“remember”是“记得”；“forget”是“忘记”。

哲学中会对真理的概念进行探索，A 选项符合语境。

3. One of the fundamental questions in philosophy is whether we have ______ will or if our actions are determined by external factors.A. freeB. limitedC. controlledD. forced答案：A。

“free will”意为“自由意志”，哲学中的一个基本问题是我们是否有自由意志，还是我们的行为由外部因素决定；“limited”是“有限的”；“controlled”是“受控制的”；“forced”是“被迫的”。

Deforestation Causes and Effects Deforestation is a critical environmental issue that has far-reaching causes and effects. The primary cause of deforestation is human activity, including logging, agriculture, and urbanization. These activities result in the clearing of large areas of forests, leading to numerous negative effects on the environment, wildlife, and human populations. In this response, I will explore the causes and effects of deforestation from various perspectives, shedding light on the urgency of addressing this pressing issue. From an environmental perspective,deforestation has devastating consequences on the Earth's ecosystems. Forests play a crucial role in regulating the climate by absorbing carbon dioxide from the atmosphere. When trees are cut down, this natural carbon sink is compromised, leading to increased greenhouse gas emissions and contributing to climate change. Furthermore, deforestation disrupts the water cycle, leading to soil erosion, decreased water quality, and disrupted rainfall patterns. This, in turn, affects the biodiversity of the forests, leading to the loss of countless plant and animal species. From a wildlife perspective, deforestation poses a significant threat to numerous species that call the forests their home. As their natural habitats are destroyed, many animals are forced to migrate to new areas, leading to increased competition for resources and heightened risk of extinction. Deforestation also fragments habitats, making it difficult for wildlife to find food, shelter, and mates. This can lead to a decline in population numbers and genetic diversity, further jeopardizing the survival of many species. From a human perspective, deforestation has wide-ranging social and economic impacts. Many indigenous communities rely on forests for their livelihoods, including food, medicine, and shelter. When these forests are cleared, these communities lose not only their homes but also their cultural heritage and traditional knowledge. Additionally, deforestation can lead to soil degradation, making it challenging for farmers to grow crops and sustain their livelihoods. This can result in food insecurity and poverty, further exacerbating social inequalities. Furthermore, deforestation contributes to the loss of ecosystem services that are vital for human well-being. Forests play a crucial role in regulating the water cycle, preventing soil erosion, and providing clean air and water. When these services are compromised, humanpopulations are at greater risk of natural disasters, such as floods and landslides, and are more susceptible to air and water pollution. Additionally, the loss of forests can impact industries that rely on forest resources, such as timber and paper production, leading to economic instability and job loss in these sectors. In conclusion, deforestation is a complex issue with far-reaching causes and effects that impact the environment, wildlife, and human populations. Addressing this issue requires a multi-faceted approach that considers the social, economic, and environmental dimensions of deforestation. By raising awareness, implementing sustainable land management practices, and supporting conservation efforts, we can work towards mitigating the causes and effects of deforestation and preserving the invaluable benefits that forests provide to the planet and all its inhabitants.。

Scientists studying the effects of various phenomena play a crucial role in expanding our understanding of the natural world, human behavior, and the complex interplay between different variables. This process involves systematic investigation, data collection, analysis, and interpretation to draw meaningful conclusions. Let's explore the broader concept of scientists studying the effects of different factors and delve into the methodologies, significance, and challenges associated with such studies.### **Introduction:**Scientists engaging in the study of effects often aim to uncover causal relationships, identify patterns, or understand the impact of certain factors on a given system. This exploration encompasses a wide range of disciplines, including physics, chemistry, biology, psychology, environmental science, and social sciences. The effects being studied can be diverse, ranging from the microscopic level of particles to the macroscopic level of ecosystems or human societies.### **Methodologies in Studying Effects:**1. **Experimental Design:**- **Controlled Experiments:** Scientists often use controlled experiments to isolate specific variables and observe their effects systematically. This involves manipulating one variable while keeping others constant.2. **Observational Studies:**-**Longitudinal Studies:** Researchers track subjects over an extended period to observe changes and identify potential causative factors.- **Cross-Sectional Studies:** Examining a diverse group at a single point in time to uncover correlations and associations.3. **Field Studies:**-**Ecological Studies:** Scientists study effects within natural environments, observing interactions between organisms and their surroundings.-**Social Science Field Studies:** Researchers may conduct surveys or interviews to understand the effects of social, economic, or cultural factors on individuals or communities.4. **Computer Modeling:**- **Simulation Studies:** Scientists use computer models to simulate real-world scenarios, allowing them to predict and analyze potential effects without real-world experimentation.### **Significance of Studying Effects:**1. **Scientific Advancement:**- **New Discoveries:** Research on the effects of various factors often leads to the discovery of new phenomena, principles, or relationships.-**Advancement of Knowledge:** Building on existing knowledge, scientists contribute to the continuous advancement of their respective fields.2. **Problem Solving:**- **Environmental Solutions:** Studying the effects of human activities on the environment aids in developing strategies for sustainable resource use and conservation.- **Medical Breakthroughs:** Understanding the effects of drugs, diseases, and lifestyle on health contributes to medical advancements and improved healthcare.3. **Policy Formulation:**-**Informed Decision-Making:** Governments and organizations use scientific studies to formulate policies addressing societal issues, such as public health, education, and environmental protection.-**Risk Assessment:** Studying the effects of potential hazards helps in assessing and mitigating risks to human health and safety.4. **Technological Innovation:**- **Materials Science:** Studying the effects of different materials on each other contributes to the development of new materials with enhanced properties.-**Engineering Advancements:** Understanding the effects of forces, temperature, and other factors on structures and systems informs engineering practices and innovations.### **Challenges in Studying Effects:**1. **Complexity of Systems:**-**Interconnected Variables:** Natural systems are often complex, with numerous interconnected variables. Isolating the effect of one variable while keeping others constant can be challenging.2. **Ethical Considerations:**- **Human Subjects:** In social and medical studies, ethical considerations, such as informed consent and the potential for harm, must be carefully addressed.-**Environmental Impact:** Researchers studying ecological effects must consider the potential impact of their studies on the environment.3. **Resource Limitations:**-**Financial Constraints:** Conducting comprehensive studies requires financial resources for equipment, personnel, and data analysis.- **Time Constraints:** Longitudinal studies, in particular, can be time-consuming, requiring sustained funding and commitment.4. **Data Interpretation:**-**Statistical Challenges:** Interpreting data and drawing meaningful conclusions require statistical expertise to avoid misinterpretation or bias.- **Correlation vs. Causation:** Distinguishing between correlation and causation is critical to avoid drawing incorrect causal relationships.### **Case Study: Studying the Effects of Climate Change:**Consider a case study where scientists are studying the effects of climate change:1. **Methodology:**- **Observational Studies:** Scientists analyze long-term climate data, including temperature records, sea-level measurements, and ice core samples.-**Computer Modeling:** Climate scientists use sophisticated models to simulate future climate scenarios based on different emission scenarios.2. **Significance:**- **Policy Impact:** Findings contribute to global efforts to mitigate climate change, shaping international agreements and policy decisions.-**Environmental Awareness:** Studying the effects raises public awareness of climate change impacts, fostering environmentally conscious behaviors.3. **Challenges:**- **Data Uncertainty:** Climate systems are intricate, and uncertainties in data interpretation can pose challenges in predicting future scenarios.- **Global Collaboration:** Studying a phenomenon as pervasive as climate change requires international collaboration and coordination.### **Conclusion:**In conclusion, scientists studying the effects of various factors contribute significantly to human knowledge, technological innovation, and policy formulation across diverse disciplines. The methodologies employed, the significance of their findings, and the challenges they face vary depending on the field of study. Despite challenges, the pursuit of understanding the effects of different variables remains integral to scientific progress and addressing global challenges.。

项目名称：近海工程混凝土结构性能评估与修复加固关键技术完成人：陈达，侯利军，廖迎娣，江朝华，欧阳峰，庄宁，冯兴国，俞小彤，李晓宇完成单位：河海大学成果类别：应用类项目简介：该项目“近海工程混凝土结构性能评估与修复加固关键技术”，所属水利工程科学技术领域，该成果主要应用于码头、桥梁、水闸、防波堤等近海工程混凝土结构性能评估与修复加固。

近海工程混凝土结构所处环境复杂，不仅遭受海洋环境高盐、高湿、甚至高温和干湿交替等物理化学作用，而且长期处于风、浪、流耦合荷载作用，其耐久性和力学性能退化速度与程度显著高于普通环境，在运行一定年限后常常发生较为严重的钢筋锈蚀、混凝土开裂和剥落等劣化现象，严重影响结构的安全运行。

因此，建立近海环境混凝土结构性能评估方法、开发高效可靠的修复加固技术，是近海工程领域迫切需要解决的关键难题，对结构安全评估与耐久性提升具有重要意义。

该项目依托5项国家自然科学基金、水利部公益性行业科研专项等基金项目，围绕近海工程混凝土性能评估和修复加固进行了深入研究，并开发了集修复加固材料、施工工艺和施工装备于一体的成套修复加固技术。

该项目成果主要分为三部分：（1）研究了海洋干湿交替和硫酸盐侵蚀耦合作用对混凝土物理、力学性能的影响，建立了化学-力学-物理过程多场耦合本构模型，为近海混凝土结构性能评估提供理论模型；研究了荷载与氯盐腐蚀耦合作用下钢筋的锈蚀机理，揭示了荷载对钢筋/混凝土界面破坏、钢筋去钝化以及温度、湿度对钢筋锈蚀的影响效应，构建了钢筋锈蚀剩余寿命预测模型，为混凝土结构运行维护和修复加固设计提供依据。

（2）研发了适用于近海环境混凝土修复的高性能纤维水泥基材料，提出了修复材料配合比定量化优化方案，以及修复材料与既有混凝土的粘结设计方法；提出并试验验证了不锈钢钢筋修复加固锈蚀碳钢钢筋的方案，纠正了通常认为不锈钢钢筋会加速碳钢钢筋锈蚀的观念；开发了锈蚀率定量测定装置和自发电外加电流钢筋锈蚀防护装置，解决了混凝土和钢筋高效修复加固难题。

考证热现象英文作文英文：When it comes to the study of heat phenomenon, thereare a lot of interesting things to explore. As for me, I am particularly interested in the concept of thermal equilibrium. This is the state where two objects that arein contact with each other have the same temperature. It is a very important concept in thermodynamics.One of the most fascinating things about thermal equilibrium is that it is a fundamental law of nature. Itis impossible for two objects to be in contact with each other and not reach thermal equilibrium. This is because heat always flows from hotter objects to colder objects. So, if two objects are at different temperatures and in contact with each other, heat will flow from the hotter object to the colder object until they both reach the same temperature.Another interesting thing about thermal equilibrium is that it can be used to measure temperature. For example, if you have a thermometer and you want to measure the temperature of a liquid, you can place the thermometer in the liquid and wait until it reaches thermal equilibrium with the liquid. Once the thermometer and the liquid are at the same temperature, you can read the temperature off the thermometer.Overall, the study of heat phenomenon is a fascinating field with many interesting concepts to explore. Whether you are interested in thermal equilibrium, heat transfer, or any other aspect of thermodynamics, there is always something new to learn and discover.中文：谈到热现象的研究，有很多有趣的事情可以探索。

英语专业八级考试TEM-8阅读理解练习册（1）(英语专业2012级)UNIT 1Text AEvery minute of every day, what ecologist生态学家James Carlton calls a global ―conveyor belt‖, redistributes ocean organisms生物.It’s planetwide biological disruption生物的破坏that scientists have barely begun to understand.Dr. Carlton —an oceanographer at Williams College in Williamstown,Mass.—explains that, at any given moment, ―There are several thousand marine species traveling… in the ballast water of ships.‖ These creatures move from coastal waters where they fit into the local web of life to places where some of them could tear that web apart. This is the larger dimension of the infamous无耻的，邪恶的invasion of fish-destroying, pipe-clogging zebra mussels有斑马纹的贻贝.Such voracious贪婪的invaders at least make their presence known. What concerns Carlton and his fellow marine ecologists is the lack of knowledge about the hundreds of alien invaders that quietly enter coastal waters around the world every day. Many of them probably just die out. Some benignly亲切地，仁慈地—or even beneficially — join the local scene. But some will make trouble.In one sense, this is an old story. Organisms have ridden ships for centuries. They have clung to hulls and come along with cargo. What’s new is the scale and speed of the migrations made possible by the massive volume of ship-ballast water压载水— taken in to provide ship stability—continuously moving around the world…Ships load up with ballast water and its inhabitants in coastal waters of one port and dump the ballast in another port that may be thousands of kilometers away. A single load can run to hundreds of gallons. Some larger ships take on as much as 40 million gallons. The creatures that come along tend to be in their larva free-floating stage. When discharged排出in alien waters they can mature into crabs, jellyfish水母, slugs鼻涕虫，蛞蝓, and many other forms.Since the problem involves coastal species, simply banning ballast dumps in coastal waters would, in theory, solve it. Coastal organisms in ballast water that is flushed into midocean would not survive. Such a ban has worked for North American Inland Waterway. But it would be hard to enforce it worldwide. Heating ballast water or straining it should also halt the species spread. But before any such worldwide regulations were imposed, scientists would need a clearer view of what is going on.The continuous shuffling洗牌of marine organisms has changed the biology of the sea on a global scale. It can have devastating effects as in the case of the American comb jellyfish that recently invaded the Black Sea. It has destroyed that sea’s anchovy鳀鱼fishery by eating anchovy eggs. It may soon spread to western and northern European waters.The maritime nations that created the biological ―conveyor belt‖ should support a coordinated international effort to find out what is going on and what should be done about it. (456 words)1.According to Dr. Carlton, ocean organism‟s are_______.A.being moved to new environmentsB.destroying the planetC.succumbing to the zebra musselD.developing alien characteristics2.Oceanographers海洋学家are concerned because_________.A.their knowledge of this phenomenon is limitedB.they believe the oceans are dyingC.they fear an invasion from outer-spaceD.they have identified thousands of alien webs3.According to marine ecologists, transplanted marinespecies____________.A.may upset the ecosystems of coastal watersB.are all compatible with one anotherC.can only survive in their home watersD.sometimes disrupt shipping lanes4.The identified cause of the problem is_______.A.the rapidity with which larvae matureB. a common practice of the shipping industryC. a centuries old speciesD.the world wide movement of ocean currents5.The article suggests that a solution to the problem__________.A.is unlikely to be identifiedB.must precede further researchC.is hypothetically假设地，假想地easyD.will limit global shippingText BNew …Endangered‟ List Targets Many US RiversIt is hard to think of a major natural resource or pollution issue in North America today that does not affect rivers.Farm chemical runoff残渣, industrial waste, urban storm sewers, sewage treatment, mining, logging, grazing放牧,military bases, residential and business development, hydropower水力发电,loss of wetlands. The list goes on.Legislation like the Clean Water Act and Wild and Scenic Rivers Act have provided some protection, but threats continue.The Environmental Protection Agency (EPA) reported yesterday that an assessment of 642,000 miles of rivers and streams showed 34 percent in less than good condition. In a major study of the Clean Water Act, the Natural Resources Defense Council last fall reported that poison runoff impairs损害more than 125,000 miles of rivers.More recently, the NRDC and Izaak Walton League warned that pollution and loss of wetlands—made worse by last year’s flooding—is degrading恶化the Mississippi River ecosystem.On Tuesday, the conservation group保护组织American Rivers issued its annual list of 10 ―endangered‖ and 20 ―threatened‖ rivers in 32 states, the District of Colombia, and Canada.At the top of the list is the Clarks Fork of the Yellowstone River, whereCanadian mining firms plan to build a 74-acre英亩reservoir水库，蓄水池as part of a gold mine less than three miles from Yellowstone National Park. The reservoir would hold the runoff from the sulfuric acid 硫酸used to extract gold from crushed rock.―In the event this tailings pond failed, the impact to th e greater Yellowstone ecosystem would be cataclysmic大变动的，灾难性的and the damage irreversible不可逆转的.‖ Sen. Max Baucus of Montana, chairman of the Environment and Public Works Committee, wrote to Noranda Minerals Inc., an owner of the ― New World Mine‖.Last fall, an EPA official expressed concern about the mine and its potential impact, especially the plastic-lined storage reservoir. ― I am unaware of any studies evaluating how a tailings pond尾矿池，残渣池could be maintained to ensure its structural integrity forev er,‖ said Stephen Hoffman, chief of the EPA’s Mining Waste Section. ―It is my opinion that underwater disposal of tailings at New World may present a potentially significant threat to human health and the environment.‖The results of an environmental-impact statement, now being drafted by the Forest Service and Montana Department of State Lands, could determine the mine’s future…In its recent proposal to reauthorize the Clean Water Act, the Clinton administration noted ―dramatically improved water quality since 1972,‖ when the act was passed. But it also reported that 30 percent of riverscontinue to be degraded, mainly by silt泥沙and nutrients from farm and urban runoff, combined sewer overflows, and municipal sewage城市污水. Bottom sediments沉积物are contaminated污染in more than 1,000 waterways, the administration reported in releasing its proposal in January. Between 60 and 80 percent of riparian corridors (riverbank lands) have been degraded.As with endangered species and their habitats in forests and deserts, the complexity of ecosystems is seen in rivers and the effects of development----beyond the obvious threats of industrial pollution, municipal waste, and in-stream diversions改道to slake消除the thirst of new communities in dry regions like the Southwes t…While there are many political hurdles障碍ahead, reauthorization of the Clean Water Act this year holds promise for US rivers. Rep. Norm Mineta of California, who chairs the House Committee overseeing the bill, calls it ―probably the most important env ironmental legislation this Congress will enact.‖ (553 words)6.According to the passage, the Clean Water Act______.A.has been ineffectiveB.will definitely be renewedC.has never been evaluatedD.was enacted some 30 years ago7.“Endangered” rivers are _________.A.catalogued annuallyB.less polluted than ―threatened rivers‖C.caused by floodingD.adjacent to large cities8.The “cataclysmic” event referred to in paragraph eight would be__________.A. fortuitous偶然的，意外的B. adventitious外加的，偶然的C. catastrophicD. precarious不稳定的，危险的9. The owners of the New World Mine appear to be______.A. ecologically aware of the impact of miningB. determined to construct a safe tailings pondC. indifferent to the concerns voiced by the EPAD. willing to relocate operations10. The passage conveys the impression that_______.A. Canadians are disinterested in natural resourcesB. private and public environmental groups aboundC. river banks are erodingD. the majority of US rivers are in poor conditionText CA classic series of experiments to determine the effects ofoverpopulation on communities of rats was reported in February of 1962 in an article in Scientific American. The experiments were conducted by a psychologist, John B. Calhoun and his associates. In each of these experiments, an equal number of male and female adult rats were placed in an enclosure and given an adequate supply of food, water, and other necessities. The rat populations were allowed to increase. Calhoun knew from experience approximately how many rats could live in the enclosures without experiencing stress due to overcrowding. He allowed the population to increase to approximately twice this number. Then he stabilized the population by removing offspring that were not dependent on their mothers. He and his associates then carefully observed and recorded behavior in these overpopulated communities. At the end of their experiments, Calhoun and his associates were able to conclude that overcrowding causes a breakdown in the normal social relationships among rats, a kind of social disease. The rats in the experiments did not follow the same patterns of behavior as rats would in a community without overcrowding.The females in the rat population were the most seriously affected by the high population density: They showed deviant异常的maternal behavior; they did not behave as mother rats normally do. In fact, many of the pups幼兽，幼崽, as rat babies are called, died as a result of poor maternal care. For example, mothers sometimes abandoned their pups,and, without their mothers' care, the pups died. Under normal conditions, a mother rat would not leave her pups alone to die. However, the experiments verified that in overpopulated communities, mother rats do not behave normally. Their behavior may be considered pathologically 病理上，病理学地diseased.The dominant males in the rat population were the least affected by overpopulation. Each of these strong males claimed an area of the enclosure as his own. Therefore, these individuals did not experience the overcrowding in the same way as the other rats did. The fact that the dominant males had adequate space in which to live may explain why they were not as seriously affected by overpopulation as the other rats. However, dominant males did behave pathologically at times. Their antisocial behavior consisted of attacks on weaker male,female, and immature rats. This deviant behavior showed that even though the dominant males had enough living space, they too were affected by the general overcrowding in the enclosure.Non-dominant males in the experimental rat communities also exhibited deviant social behavior. Some withdrew completely; they moved very little and ate and drank at times when the other rats were sleeping in order to avoid contact with them. Other non-dominant males were hyperactive; they were much more active than is normal, chasing other rats and fighting each other. This segment of the rat population, likeall the other parts, was affected by the overpopulation.The behavior of the non-dominant males and of the other components of the rat population has parallels in human behavior. People in densely populated areas exhibit deviant behavior similar to that of the rats in Calhoun's experiments. In large urban areas such as New York City, London, Mexican City, and Cairo, there are abandoned children. There are cruel, powerful individuals, both men and women. There are also people who withdraw and people who become hyperactive. The quantity of other forms of social pathology such as murder, rape, and robbery also frequently occur in densely populated human communities. Is the principal cause of these disorders overpopulation? Calhoun’s experiments suggest that it might be. In any case, social scientists and city planners have been influenced by the results of this series of experiments.11. Paragraph l is organized according to__________.A. reasonsB. descriptionC. examplesD. definition12．Calhoun stabilized the rat population_________.A. when it was double the number that could live in the enclosure without stressB. by removing young ratsC. at a constant number of adult rats in the enclosureD. all of the above are correct13.W hich of the following inferences CANNOT be made from theinformation inPara. 1?A. Calhoun's experiment is still considered important today.B. Overpopulation causes pathological behavior in rat populations.C. Stress does not occur in rat communities unless there is overcrowding.D. Calhoun had experimented with rats before.14. Which of the following behavior didn‟t happen in this experiment?A. All the male rats exhibited pathological behavior.B. Mother rats abandoned their pups.C. Female rats showed deviant maternal behavior.D. Mother rats left their rat babies alone.15. The main idea of the paragraph three is that __________.A. dominant males had adequate living spaceB. dominant males were not as seriously affected by overcrowding as the otherratsC. dominant males attacked weaker ratsD. the strongest males are always able to adapt to bad conditionsText DThe first mention of slavery in the statutes法令，法规of the English colonies of North America does not occur until after 1660—some forty years after the importation of the first Black people. Lest we think that existed in fact before it did in law, Oscar and Mary Handlin assure us, that the status of B lack people down to the 1660’s was that of servants. A critique批判of the Handlins’ interpretation of why legal slavery did not appear until the 1660’s suggests that assumptions about the relation between slavery and racial prejudice should be reexamined, and that explanation for the different treatment of Black slaves in North and South America should be expanded.The Handlins explain the appearance of legal slavery by arguing that, during the 1660’s, the position of white servants was improving relative to that of black servants. Thus, the Handlins contend, Black and White servants, heretofore treated alike, each attained a different status. There are, however, important objections to this argument. First, the Handlins cannot adequately demonstrate that t he White servant’s position was improving, during and after the 1660’s; several acts of the Maryland and Virginia legislatures indicate otherwise. Another flaw in the Handlins’ interpretation is their assumption that prior to the establishment of legal slavery there was no discrimination against Black people. It is true that before the 1660’s Black people were rarely called slaves. But this shouldnot overshadow evidence from the 1630’s on that points to racial discrimination without using the term slavery. Such discrimination sometimes stopped short of lifetime servitude or inherited status—the two attributes of true slavery—yet in other cases it included both. The Handlins’ argument excludes the real possibility that Black people in the English colonies were never treated as the equals of White people.The possibility has important ramifications后果，影响.If from the outset Black people were discriminated against, then legal slavery should be viewed as a reflection and an extension of racial prejudice rather than, as many historians including the Handlins have argued, the cause of prejudice. In addition, the existence of discrimination before the advent of legal slavery offers a further explanation for the harsher treatment of Black slaves in North than in South America. Freyre and Tannenbaum have rightly argued that the lack of certain traditions in North America—such as a Roman conception of slavery and a Roman Catholic emphasis on equality— explains why the treatment of Black slaves was more severe there than in the Spanish and Portuguese colonies of South America. But this cannot be the whole explanation since it is merely negative, based only on a lack of something. A more compelling令人信服的explanation is that the early and sometimes extreme racial discrimination in the English colonies helped determine the particular nature of the slavery that followed. (462 words)16. Which of the following is the most logical inference to be drawn from the passage about the effects of “several acts of the Maryland and Virginia legislatures” (Para.2) passed during and after the 1660‟s?A. The acts negatively affected the pre-1660’s position of Black as wellas of White servants.B. The acts had the effect of impairing rather than improving theposition of White servants relative to what it had been before the 1660’s.C. The acts had a different effect on the position of white servants thandid many of the acts passed during this time by the legislatures of other colonies.D. The acts, at the very least, caused the position of White servants toremain no better than it had been before the 1660’s.17. With which of the following statements regarding the status ofBlack people in the English colonies of North America before the 1660‟s would the author be LEAST likely to agree?A. Although black people were not legally considered to be slaves,they were often called slaves.B. Although subject to some discrimination, black people had a higherlegal status than they did after the 1660’s.C. Although sometimes subject to lifetime servitude, black peoplewere not legally considered to be slaves.D. Although often not treated the same as White people, black people,like many white people, possessed the legal status of servants.18. According to the passage, the Handlins have argued which of thefollowing about the relationship between racial prejudice and the institution of legal slavery in the English colonies of North America?A. Racial prejudice and the institution of slavery arose simultaneously.B. Racial prejudice most often the form of the imposition of inheritedstatus, one of the attributes of slavery.C. The source of racial prejudice was the institution of slavery.D. Because of the influence of the Roman Catholic Church, racialprejudice sometimes did not result in slavery.19. The passage suggests that the existence of a Roman conception ofslavery in Spanish and Portuguese colonies had the effect of _________.A. extending rather than causing racial prejudice in these coloniesB. hastening the legalization of slavery in these colonies.C. mitigating some of the conditions of slavery for black people in these coloniesD. delaying the introduction of slavery into the English colonies20. The author considers the explanation put forward by Freyre andTannenbaum for the treatment accorded B lack slaves in the English colonies of North America to be _____________.A. ambitious but misguidedB. valid有根据的but limitedC. popular but suspectD. anachronistic过时的，时代错误的and controversialUNIT 2Text AThe sea lay like an unbroken mirror all around the pine-girt, lonely shores of Orr’s Island. Tall, kingly spruce s wore their regal王室的crowns of cones high in air, sparkling with diamonds of clear exuded gum流出的树胶; vast old hemlocks铁杉of primeval原始的growth stood darkling in their forest shadows, their branches hung with long hoary moss久远的青苔;while feathery larches羽毛般的落叶松,turned to brilliant gold by autumn frosts, lighted up the darker shadows of the evergreens. It was one of those hazy朦胧的, calm, dissolving days of Indian summer, when everything is so quiet that the fainest kiss of the wave on the beach can be heard, and white clouds seem to faint into the blue of the sky, and soft swathing一长条bands of violet vapor make all earth look dreamy, and give to the sharp, clear-cut outlines of the northern landscape all those mysteries of light and shade which impart such tenderness to Italian scenery.The funeral was over,--- the tread鞋底的花纹/ 踏of many feet, bearing the heavy burden of two broken lives, had been to the lonely graveyard, and had come back again,--- each footstep lighter and more unconstrained不受拘束的as each one went his way from the great old tragedy of Death to the common cheerful of Life.The solemn black clock stood swaying with its eternal ―tick-tock, tick-tock,‖ in the kitchen of the brown house on Orr’s Island. There was there that sense of a stillness that can be felt,---such as settles down on a dwelling住处when any of its inmates have passed through its doors for the last time, to go whence they shall not return. The best room was shut up and darkened, with only so much light as could fall through a little heart-shaped hole in the window-shutter,---for except on solemn visits, or prayer-meetings or weddings, or funerals, that room formed no part of the daily family scenery.The kitchen was clean and ample, hearth灶台, and oven on one side, and rows of old-fashioned splint-bottomed chairs against the wall. A table scoured to snowy whiteness, and a little work-stand whereon lay the Bible, the Missionary Herald, and the Weekly Christian Mirror, before named, formed the principal furniture. One feature, however, must not be forgotten, ---a great sea-chest水手用的储物箱,which had been the companion of Zephaniah through all the countries of the earth. Old, and battered破旧的，磨损的, and unsightly难看的it looked, yet report said that there was good store within which men for the most part respect more than anything else; and, indeed it proved often when a deed of grace was to be done--- when a woman was suddenly made a widow in a coast gale大风，狂风, or a fishing-smack小渔船was run down in the fogs off the banks, leaving in some neighboring cottage a family of orphans,---in all such cases, the opening of this sea-chest was an event of good omen 预兆to the bereaved丧亲者;for Zephaniah had a large heart and a large hand, and was apt有…的倾向to take it out full of silver dollars when once it went in. So the ark of the covenant约柜could not have been looked on with more reverence崇敬than the neighbours usually showed to Captain Pennel’s sea-chest.1. The author describes Orr‟s Island in a(n)______way.A.emotionally appealing, imaginativeB.rational, logically preciseC.factually detailed, objectiveD.vague, uncertain2.According to the passage, the “best room”_____.A.has its many windows boarded upB.has had the furniture removedC.is used only on formal and ceremonious occasionsD.is the busiest room in the house3.From the description of the kitchen we can infer that thehouse belongs to people who_____.A.never have guestsB.like modern appliancesC.are probably religiousD.dislike housework4.The passage implies that_______.A.few people attended the funeralB.fishing is a secure vocationC.the island is densely populatedD.the house belonged to the deceased5.From the description of Zephaniah we can see thathe_________.A.was physically a very big manB.preferred the lonely life of a sailorC.always stayed at homeD.was frugal and saved a lotText BBasic to any understanding of Canada in the 20 years after the Second World War is the country' s impressive population growth. For every three Canadians in 1945, there were over five in 1966. In September 1966 Canada's population passed the 20 million mark. Most of this surging growth came from natural increase. The depression of the 1930s and the war had held back marriages, and the catching-up process began after 1945. The baby boom continued through the decade of the 1950s, producing a population increase of nearly fifteen percent in the five years from 1951 to 1956. This rate of increase had been exceeded only once before in Canada's history, in the decade before 1911 when the prairies were being settled. Undoubtedly, the good economic conditions of the 1950s supported a growth in the population, but the expansion also derived from a trend toward earlier marriages and an increase in the average size of families; In 1957 the Canadian birth rate stood at 28 per thousand, one of the highest in the world. After the peak year of 1957, thebirth rate in Canada began to decline. It continued falling until in 1966 it stood at the lowest level in 25 years. Partly this decline reflected the low level of births during the depression and the war, but it was also caused by changes in Canadian society. Young people were staying at school longer, more women were working; young married couples were buying automobiles or houses before starting families; rising living standards were cutting down the size of families. It appeared that Canada was once more falling in step with the trend toward smaller families that had occurred all through theWestern world since the time of the Industrial Revolution. Although the growth in Canada’s population had slowed down by 1966 (the cent), another increase in the first half of the 1960s was only nine percent), another large population wave was coming over the horizon. It would be composed of the children of the children who were born during the period of the high birth rate prior to 1957.6. What does the passage mainly discuss?A. Educational changes in Canadian society.B. Canada during the Second World War.C. Population trends in postwar Canada.D. Standards of living in Canada.7. According to the passage, when did Canada's baby boom begin?A. In the decade after 1911.B. After 1945.C. During the depression of the 1930s.D. In 1966.8. The author suggests that in Canada during the 1950s____________.A. the urban population decreased rapidlyB. fewer people marriedC. economic conditions were poorD. the birth rate was very high9. When was the birth rate in Canada at its lowest postwar level?A. 1966.B. 1957.C. 1956.D. 1951.10. The author mentions all of the following as causes of declines inpopulation growth after 1957 EXCEPT_________________.A. people being better educatedB. people getting married earlierC. better standards of livingD. couples buying houses11.I t can be inferred from the passage that before the IndustrialRevolution_______________.A. families were largerB. population statistics were unreliableC. the population grew steadilyD. economic conditions were badText CI was just a boy when my father brought me to Harlem for the first time, almost 50 years ago. We stayed at the hotel Theresa, a grand brick structure at 125th Street and Seventh avenue. Once, in the hotel restaurant, my father pointed out Joe Louis. He even got Mr. Brown, the hotel manager, to introduce me to him, a bit punchy强力的but still champ焦急as fast as I was concerned.Much has changed since then. Business and real estate are booming. Some say a new renaissance is under way. Others decry责难what they see as outside forces running roughshod肆意践踏over the old Harlem. New York meant Harlem to me, and as a young man I visited it whenever I could. But many of my old haunts are gone. The Theresa shut down in 1966. National chains that once ignored Harlem now anticipate yuppie money and want pieces of this prime Manhattan real estate. So here I am on a hot August afternoon, sitting in a Starbucks that two years ago opened a block away from the Theresa, snatching抓取，攫取at memories between sips of high-priced coffee. I am about to open up a piece of the old Harlem---the New York Amsterdam News---when a tourist。

1 Case study of seismic hazard assessment in underground coal mining using passive tomography2 A Novel Experimental Technique to Simulate Pillar Burst in Laboratory3 A Microseismic Method for Dynamic Warning of Rockburst Development Processes in Tunnels4 Influence of specimen height-to-width ratio on the strainburst characteristics of Tianhu granite under true-triaxial unloading conditions5 Transient characters of energy changes induced by blasting excavation of deep-buried tunnels6 Rockburst characteristics and microseismic monitoring of deep-buried tunnels for Jinping II Hydropower Station7 Microseismic multi-parameter characteristics of rockburst hazard induced by hard roof fall and high stress concentration8 Fracture Angle Analysis of Rock Burst Faulting Planes Based on True-Triaxial Experiment9 Mitigation of rock burst events by blasting techniques during deep-tunnel excavation10 Numerical simulation of pressure relief in hard coal seam by water jet cutting11 Predicting rockburst tendency based on fuzzy matter-element model12 Forecasting of rockbursts in deep underground engineering based on abstraction ant colony clustering algorithm13 Rockburst laboratory tests database - Application of data mining techniques14 Observation of rock fragment ejection in post-failure response15 A system to mitigate deep mine tremor effects in the design of civil infrastructure16 Risk evaluation of rock burst through theory of static and dynamic stresses superposition17 Acoustic emission during different-type inter-block movements18 Analysis of damage to underground workings and their supports caused by dynamic phenomena19 Influence of Geostress Orientation on Fracture Response of Deep Underground Cavity Subjected to Dynamic Loading20 A New Rockburst Proneness Index Based on Energy Principle21 The Risk Analysis Applied to Deep Tunnels Design-El Teniente New Mine Level Access Tunnels, Chile22 Fractal Dimension of Fracture Surface in Rock Material after High Temperature23 Numerical Investigation of Rockburst Effect of Shock Wave on Underground Roadway24 The Mechanism and Application of Deep-Hole Precracking Blasting on Rockburst Prevention25 Sectional velocity model for microseismic source location in tunnels26 Fan-structure shear rupture mechanism as a source of shear rupture rockbursts27 Hands-on experience of safe and efficient ore mining in Siberia28 ROCKBURST HAZARD ASSESSMENT IN BEDDED ROCK MASS: LABORATORY TESTS OF ROCK SAMPLES AND NUMERICAL CALCULATIONS29 PREDICTIVE REGRESSION MODELS OF MONTHLY SEISMIC ENERGY EMISSIONS INDUCED BY LONGWALL MINING30 Numerical simulation of rock-burst relief and prevention by water-jet cutting31 Microseismic and acoustic emission effect on gas outburst hazard triggered by shock wave: a case study32 Damage initiation and propagation assessed from stress-induced microseismic events during a mine-by test in the Opalinus Clay33 Distinct element analysis of unstable shear failure of rock discontinuities in undergroundmining conditions34 Coalescence of two parallel pre-existing surface cracks in granite35 Analysis of statistic parameters of geoacoustic monitoring data for the Antey uranium deposit36 Estimation of rockburst wall-rock velocity invoked by slab flexure sources in deep tunnels37 Spatial structure evolution of overlying strata and inducing mechanism of rockburst in coal mine38 Investigating the dynamic-load demand on support systems using passive monitoring data39 Influence of Unloading Rate on the Strainburst Characteristics of Beishan Granite Under True-Triaxial Unloading Conditions40 Influence of Mining and Retaining Parameters on Evolution of Hazard Rockburst in Strip-pillar Mining41 Improvement and application technology of long bedding borehole rig in rockburst seam at headentry and tailentry42 Research OfRockburst Prediction and Control Technology43 Prediction of Classification of Rock Burst Risk Based on Genetic Algorithms with SVM44 Case histories of rock engineering projects in China45 Impact of destress blasting on stress field development ahead of a hardcoal longwall face46 A review of ground support systems performance subjected to dynamic loading47 Rockburst Disaster Prediction of Isolated Coal Pillar by Electromagnetic Radiation Based on Frictional Effect48 Numerical simulation study on the delay of rockburst based on rock mass stress release rate49 Modeling of Rockburst by Elastoplastic Damage Theory at Finite Strains50 In-situ stress measurement and surrounding rock stability analysis of The Gaoligong Mountain tunnel51 Research on plane strain model test of rockburst of underground cavern in hard brittle rockmass52 Geomechanical assessment of mining conditions in the Khingansk manganese ore body53 Localization of deformation and prognostibility of rock failure54 Rockburst disaster prediction of isolated coal pillar by electromagnetic radiation based on frictional effect.55 Comprehensive prediction of rockburst in high-speed railway tunnel56 Orifices Stress Concentration Study by Static and Dynamic Combination Loads57 Study On Application Of The Mine Anti-impact And Energy-absorption Device58 Rockburst dangerous area dividing in Guo-tun deep mine59 Rock mass damage induced by rockbursts occurring on tunnel floors: a case study of two tunnels at the Jinping II Hydropower Station60 Towards an understanding of dynamic demand on ground support61 Dynamic shearing failure mechanism and threshold based on true-triaxialrockburst experiment62 Investigation of unloading rockburst test based on acoustic emission63 Microseismic frequency-spectrum evolutionary rule of rockburst triggered by roof fall64 Seismic energy distribution and hazard assessment in underground coal mines using statistical energy analysis65 Laboratory study of unloading rate effects on rockburst66 Kinetics of Seismic Emission in Coal Mines in Kuzbass67 A potential method of containing rockburst damage and enhancing safety using a sacrificial layer68 The effect of loading rate on the behavior of samples composed of coal and rock69 Knowledge-based and data-driven fuzzy modeling for rockburst prediction70 Long-hole destress blasting for rockburst control during deep underground coal mining71 Rockmass damage development following two extremely intense rockbursts in deep tunnels at Jinping II hydropower station, southwestern China72 Studies on temporal and spatial variation of microseismic activities in a deep metal mine73 Principles of rock support in burst-prone ground74 Mechanical-electromagnetic transformations in rocks on failure75 Prediction of underground engineering disasters based on comprehensive analysis of in-situ stress measurements and geological conditions76 Prediction of rockburst classification using Random Forest77 Neural network estimation of rockburst damage severity based on engineering cases78 Correlation between time-delayed rockburst and blasting disturbance in deep-buried tunnel79 Security risk assessment of rockburst in the process of tunnel excavation by drilling and blasting method in deep-buried hard rock80 Frequency fractal feature of microseismic events in the process of immediate rockburst in deep tunnel81 Rockburst risk analysis based on microseismic monitoring in deep-buried tunnel with TBM excavation82 Dynamic rock failure and its containment-a Gordian Knot design problem83 Relationship of fault-slip rockburst with seismic waves84 Mine seismicity of Vorkuta coal mines85 The Research of Rockburst Hazards of Linglong Gold Mine Base on The Relationship of Impact Energy and Confining Pressure86 Study on rockburst intensity prediction based on efficacy coefficient method87 The mechanisms and consequences of strong mining tremors that occur in Polish hard coal and copper mines88 Critical energy and mine rockburst potential89 Large scale field tests of rock bolts and high-tensile steel wire mesh subjected to dynamic loading90 Control of rockburst risk in hard coal longwall mining - A case study91 The estimation of the effectiveness of torpedo blasting based on an analysis of focal mechanisms of induced mining tremors in the Bielszowice coal mine92 Shotcrete Support of a Ventilation Shaft in Hard Rock93 Research on Characteristic of Rockburst& Rules of Microseismic Monitoring at Headrace Tunnels in Jinping II Hydropower Station94 Rockburst Behaviors of Beishan Granite Subjected to Instantaneous Unloading95 The Affection of Ke of Coal Seam on Strata Behavior96 Consideration of stress and structural influence on high stress response in deep tunnelling - the Olmos Tunnel, Peru97 A MODEL OF ROCK MASS FRACTURING AHEAD OF THE LONGWALL FACE AS A CONSEQUENCEOF INTENSITY OF EXPLOITATION98 The basic assumptions of the quantitative version of the Comprehensive Method of Rockburst Hazard Evaluation99 Study on Influences of Reserving Coal Battlement along Goaf Tunnels on Rockburst100 Energy sources of rockbursts搜索关键词：rock-burst单词总个数：1308平均单词个数：13.08名词结构：79个，占比79%复合机构：21个，占比21%完整句：7个，占比7%疑问句：2个，占比2%。

残余应力英语Residual stress represents the distribution of stress in a material that is not at equilibrium. This type of stress is especially prevalent in manufacturing, where it arises from the processes of machining, welding, and heat treatment. Residual stress can have significant effects on theproperties and performance of materials, including their strength, fatigue life, and fracture toughness.The origins of residual stress can be multifaceted and complex, often arising from the unequal heating and coolingof a material. This type of stress can also arise from the mechanical deformation of a material, which may lead to local stress concentrations and dislocations. In many cases, the effects of residual stress can be relatively mild and not cause significant problems. However, in other cases, residual stress can lead to the premature failure of a component or structure.There are a variety of techniques available to measure and analyze residual stress in materials. These range from X-ray diffraction and neutron diffraction to hole drilling and the curvature method. These methods allow for the accurate determination of residual stress within a material, enabling improvements to be made in the design and manufacturing of components and structures.In conclusion, residual stress is a critical issue for materials science and engineering. The development of methods to understand, measure, and control residual stress is important for the successful design and production of manycomponents and structures. As the complexity of modern materials and manufacturing processes continues to increase, the study of residual stress will only become more important.。

Crosslinking improves elongation at break1、IntroductionIn the fields of materials science and engineering, the fracture elongation of materials is an important indicator for measuring their toughness and durability. Many researchers have been exploring ways to improve this performance by altering the microstructure and chemical composition of materials. Recently, studies have shown that crosslinking methods can improve the fracture elongation of materials, which has broad application prospects.2、Crosslinking methodCrosslinking is a chemical process in which linear or network structured macromolecular chains are connected together to enhance the strength and toughness of a material. Common crosslinking methods include radiation crosslinking, chemical crosslinking, and thermal crosslinking. These methods have altered the internal structure of the material to varying degrees, making it more resilient and durable.3、Mechanism for improving elongation at breakThrough cross-linking methods, the molecular chains of the material are strengthened and connected, which enables the material to better disperse and absorb energy when subjected to external stress. In addition, crosslinking also improves the plasticity and toughness of the material, allowing it to better adapt to the external environment during deformation. These factors work together to significantly improve the fracture elongation of the material.4、Experimental Results and DiscussionIn a recent study, we employed radiation crosslinking to improve the fracture elongation of a polymer material. The experimental results indicate that the cross-linked material exhibits significant advantages in terms of fracture elongation. Compared with untreated materials, its fracture elongation has increased by nearly 30%. In addition, we also found that with the increase of crosslinking degree, the toughness of the material was significantly improved.5、ConclusionThis study indicates that crosslinking methods can improve the fracture elongation of materials. This discovery has important guiding significance for the development of new high-strength and high toughness materials. In the future, we will continue to conduct in-depth research on the effects of different crosslinking methods on material properties, in order to discover more new materials with application prospects.交联提高断裂伸长率一、引言在材料科学和工程领域，材料的断裂伸长率是衡量其韧性和耐久性的重要指标。