Kinematical structure of the circumstellar environments of galactic B[e]-type stars
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一种体内构建组织工程软骨的方法1.组织工程学是一门研究如何在体内构建组织和器官的学科。
Tissue engineering is a discipline that studies how to build tissues and organs in the body.2.目前,体内构建软骨组织的方法已经取得了一定的进展。
Currently, there has been some progress in the methods of building cartilage tissue in the body.3.软骨是一种结缔组织,具有一定的韧性和弹性。
Cartilage is a type of connective tissue that has a certain toughness and elasticity.4.在体内构建软骨组织需要考虑细胞、生物材料和生物力学等因素。
Building cartilage tissue in the body requires consideration of factors such as cells, biomaterials, and biomechanics.5.一种常见的体内构建软骨组织的方法是通过干细胞移植。
A common method for building cartilage tissue in the body is through stem cell transplantation.6.干细胞具有多能性,可以分化成不同类型的细胞,如软骨细胞。
Stem cells have pluripotency and can differentiate into different types of cells, such as chondrocytes.7.干细胞移植需要将干细胞注入到受损的软骨组织中,促进软骨再生。
Stem cell transplantation involves injecting stem cells into damaged cartilage tissue to promote cartilage regeneration.8.另一种体内构建软骨组织的方法是通过生物材料支架的植入。
Investigation of crystal growthkineticsIntroductionCrystal growth is a process that involves the formation of crystal structures from a homogeneous solution or melt. The study of crystal growth kinetics is important in terms of understanding the fundamental principles underlying the processes of nucleation and crystal growth, as well as in the development and optimization of crystal growth techniques and the design of new materials.NucleationNucleation is the initial stage in crystal growth that involves the formation of small clusters or nuclei of the crystal phase in the supersaturated solution or melt. The rate of nucleation is dependent on several factors including temperature, concentration, degree of supersaturation, and the presence of seed crystals.The classical theory of nucleation postulates that the free energy required for the formation of a nucleus is proportional to the volume of the nucleus raised to the power of 2/3. This implies that the formation of larger nuclei requires much higher free energy, which in turn leads to a decrease in the rate of nucleation. Changing the crystallization conditions can affect the kinetics of nucleation, and a detailed understanding of this process is essential for controlling the formation of crystals with specific properties.Crystal GrowthOnce nuclei are formed, crystal growth proceeds through the addition of atoms or molecules to the growing crystal surface. The rate of crystal growth is dependent on the concentration of solute in the solution, temperature, and other factors such as agitation or the presence of impurities.Crystal growth can either be diffusion-controlled or surface-controlled. In diffusion-controlled growth, the rate of crystal growth is limited by the rate of diffusion of solute to the growing surface. Surface-controlled growth, on the other hand, is limited by the rate of attachment or detachment of solute molecules at the crystal surface.Crystal Growth KineticsThe kinetics of crystal growth can be described by several models, including the Avrami equation, the Ostwald–de Waele model, and the Lifshitz–Slyozov–Wagner model. These models are based on assumptions about the mechanisms of crystal growth and have different mathematical forms.The Avrami equation is one of the most widely used models for describing the kinetics of crystal growth. It is based on the assumption that the growth of crystals is a random process, and the rate of growth of a crystal is proportional to the number of crystals present in the solution or melt.The Ostwald–de Waele model assumes that crystal growth is a power-law process, and the relationship between the growth rate and the concentration of solute in the solution follows a power law. This model is particularly useful for describing the kinetics of crystal growth in systems where diffusion is the rate-limiting step.The Lifshitz–Slyozov–Wagner model is based on the assumption that crystal growth occurs through the coalescence of smaller crystals into larger ones. This model is useful for understanding the mechanisms underlying the formation of large single crystals from a solution or melt.ConclusionIn conclusion, the study of crystal growth kinetics is an important area of research that is essential for the development of new materials and the optimization of crystal growth techniques. The kinetics of nucleation and crystal growth are dependent on several factors such as temperature, concentration, and the presence of impurities, and can be described by several mathematical models. A detailed understanding of thekinetics of crystal growth is essential for controlling the formation of crystals with specific properties and for the design of new materials with novel properties.。
英文回答:The process of photosynthesis involves the intricate coordination of various cellular structures within plant cells. These structures epass the chloroplasts, thylakoid membranes, stroma, and grana. The chloroplasts, serving as the primary organelles for photosynthesis, consist of thylakoid membranes that amodate the photosystems responsible for capturing light energy, while the stroma hosts the enzymes essential for the Calvin cycle, the secondary phase of photosynthesis. Moreover, the grana,prised of stacked thylakoid membranes, play a pivotal role in facilitating the light-dependent reactions of photosynthesis.光合作用的过程涉及植物细胞内各种细胞结构的复杂协调。
这些结构通过氯仿、Thylakoid膜、石膏和颗粒。
作为光合作用的主要管子的氯聚变器由热液膜组成,该膜对负责捕捉光能的光系统产生摩擦作用,而斯特罗玛则拥有对卡尔文循环至关重要的酶,即光合作用二级。
由叠叠的Thylakoid膜制成的颗粒在促进光合作用依赖光的反应方面发挥着关键作用。
The chloroplasts have this double layer of membranes that kind of act like bodyguards for all the photosynthesis stuff inside.Inside these membranes, there are these stacks called grana where the light-dependent reactions happen. These stacks are packed with these green pigments called chlorophyll that suck up all the light energy and kick off the whole photosynthesis process. Then there's this fluid-filled space outside the stacks called the stroma, where the Calvin cycle happens. This is where the carbon dioxide gets turned into glucose with the help of enzymes and ATP that's made during the light-dependent reactions.氯仿机有一层双层膜里面所有光合作用的东西都像保镖一样在这些膜内部,有这些被称为grana的堆积物,在那里发生依赖光的反应。
Materials Science and Engineering A452–453 (2007) 284–291Creep behavior of austenitic stainless steel weldmetals as a function of ferrite contentY.Cui∗,Carl D.LundinDepartment of Materials Science and Engineering,The University of Tennessee,Knoxville,TN37996-2200,USAReceived26July2005;received in revised form17October2006;accepted18October2006AbstractFour types of modified and commercial E308H and E316H weld deposits with Ferrite Number(FN)in the range of0–5.7were investigated for creep behavior at stress levels between70and240MPa,with a range of temperature550–700◦C.After creep testing,sigma phase was found in commercial E308H and E316H creep samples,significant carbide evolution from modified E308H and E316H with0FN creep samples distribute in a random and a chain along the substructures and grain boundaries,respectively.The creep results show that,for E316H weld deposits,modified samples with0FN,even though containing microfissures,have a higher creep strength than thefissure-free commercial samples with a higher ferrite content.This can be attributed to the beneficial effect from the carbides on dislocation barriers and the detrimental effect on hard and brittle sigma formed in commercial E316H.Fissure-containing modified E308H has a lower creep strength thanfissure-free commercial sample because of the propagation paths provided byfissures and the minimal effect on the randomly distributed carbides.© 2006 Elsevier B.V. All rights reserved.Keywords:Welding;Creep;Austenitic stainless steel;Ferrite Number;Dislocation1.IntroductionAustenitic stainless steels constitute the largest stainless fam-ily in terms of alloy type and are used in various corrosive conditions over the temperatures ranging from cryogenic to elevated[1].They are generally regarded as readily weldable materials without the risk of cracking and with considerable tolerance for variations in welding conditions.However,fully austenitic weld deposits may contain microfissures in single pass welds and in underlying weld runs reheated by subsequent passes in multipass welds.The occurrence of the microfissures can be the cause of weld rejection and may induce of prop-erty degradation of the weld metal.Hot cracking in austenitic stainless steel welds has been extensively discussed in the lit-erature,and a universal agreement,on liquidation mechanisms, have been reached among investigators[2–10].Carl D.Lundin summarized the characteristics of microfissuring in his series of articles discussing microfissure investigations.Microfissures occur primarily in ferrite-free areas along grain boundaries in the HAZ of the previous deposited weld pass.The microfis-∗Corresponding author.Tel.:+18659745299;fax:+18659740880.E-mail address:ycui1@(Y.Cui).suring tendency is enhanced by multiple thermal cycling in the HAZ[11].In addition,a low ductility region already exists in the weld metal of previously deposited weld beads from multi-pass or repair welding.This region is usually the initial location for microfissuring occurrence when the weld with a low ferrite content,under a high imposed strain that exceeds the strain tol-erance of the microstructure[9].Delta ferrite is usually required at a certain level for its beneficial effect in reducing or preventing microfissuring in austenitic stainless steel weldments[12].This level of ferrite was morefirmly established by Lundin et al.in an article documenting the ferrite-fissuring tendency of austenitic stainless steel weld metals[13].Because the microfissures are very small and not detectable at lower magnification,the Fissur-ing Bend Test method is often used to evaluate the microfissuring tendency in multipass weldments due to its favorable features most desired in a weldability test[18].Several of constitution diagrams and models have been developed to accurately predict the ferrite content in stainless steel welds[14–17].Electrode manufacturers as well as consumers often use Ferrite Number,a measure of the ferrite content,as an alloy specification in order to ensure that weldments contain a desired minimum(or maxi-mum)ferrite level.Ferrite in the austenitic stainless steel weld plays a dual role.On the one hand,it reduces the susceptibility of the weld to hot cracking and on the other hand it affects the0921-5093/$–see front matter© 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.msea.2006.10.132Y.Cui,C.D.Lundin/Materials Science and Engineering A 452–453 (2007) 284–291285creep properties for long-term service at elevated temperatures. Microfissures can be controlled to a certain extent by attention to consumable composition and purity,and welding technique, but they cannot be uniquely eradicated in real weld application because ferrite distribution is not uniform.Thus,Ferrite Num-ber and microfissures or cracks in austenitic materials generally cause the most alarm when the weldment properties are being considered such as strength,toughness,corrosion resistance and long-term service at elevated temperatures.The purpose of this study was to evaluate the creep behavior of austenitic stainless steel weld metals with and without ferrite content(fissure-free andfissure-containing).2.Experimental procedures2.1.Materials evaluationFour different weld electrodes(3.2mm diameter),com-mercial and modified E308H and E316H,were used in this investigation.Modified electrodes are those electrodes that were especially produced by adjusting the ratio of Chromium-equivalent and Nickel-equivalent in order to obtain a ferrite-free microstructure and produce microfissures.The deposit chemical compositions still meet the AWS A5.4specification,as shown in Table1.The base metal used is304stainless steel cut from bar stock.Three-layer weld pads(six beads to each layer)were pro-duced using Shielded Metal Arc(SMA)welding to permit the evaluation of microfissuring in relatively undiluted weld metal. Before welding,plates were clamped on each end to a heavy backingfixture to prevent excessive deformation during weld-ing.The deposited three-layer pad is approximately6.4mm thick,25.4mm wide and203mm long with the configuration as shown in Fig.1.The welding parameters are shown in Table2. With the pads still in the clampingfixture,the surface was milled using a0.254mm depth of cut on each pass until the surface was clear of irregularities.The pad surface was ground on a surface grinder using a12pass sequence with thefirst8passes each removing0.025mm and thefinal4passes each removing 0.013mm.After grinding,the specimens were removed from the clampingfixture and ultrasonically washed in methanol to remove all traces of cuttingfluids for Ferrite Number measure-ment and Fissure Bend Testing.The Ferrite Number was determined in the center100mm region of the ground pad,using a15intersection grid layout, with the Feritscope,as shown in Fig.2.The average Ferrite Number of commercial E316H and E308H,modified E316H and E308H are4.7,5.7,0and0,respectively.Fig.1.Schematic drawing of(a)the clampingfixture and(b)the pad configu-ration.Table2Welding parametersCurrent(A)95V oltage(V)23Travel speed(mm/min)203Number of layers3Interpass temperature(◦C)94Heat Input(kJ/mm)0.7Fig.2.Schematic diagram for Ferrite Number determination.Table1Chemical composition of weld depositsC Mn Si P S Cr Ni Mo Al Ti Co V Cu Nb N C308H0.048 1.680.490.0290.00819.789.490.160.010.010.130.0860.230.010.82 M308H0.074 1.170.410.0340.01118.3910.510.170.0040.010.0300.0800.240.010.12 C316H0.065 1.700.400.0250.00719.1011.90 2.30––––0.200.010.03 M316H0.065 1.230.430.0380.01117.4013.47 2.22––––0.150.010.13286Y.Cui,C.D.Lundin /Materials Science and EngineeringA 452–453 (2007) 284–291Fig.3.Weldment preparation and schematic drawing of creep sample.The bend fixture was used to perform the Fissure Bend Test on weld coupons to determine the microfissure distribution.The milled and surface ground weld pads were bent in tension to an angle of 120◦for detecting the microfissures present across the center 100mm of the pad surface for evaluation of microfissur-ing tendency.The number of microfissures was counted under the microscope at 100magnification.An average microfissure density of 7.9and 5.9cm −2was determined for modified E308H and E316H pads,meanwhile no microfissures were present in the commercial E308H and E316H weld pads.2.2.Creep property evaluation2.2.1.Sample preparationBefore welding,the plates were clamped on each side to a heavy backing fixture to prevent excessive distortion.All weld-ing was accomplished with the same welding conditions as those for the electrode evaluation.Fig.3shows the groove joint prepa-ration,the application of two butter layers and the sequence of the joint.All weld-metal test specimens for creep testing were extracted along the longitudinal direction from the coupon.2.2.2.Creep testingThe creep testing was conducted in constant load creep frames.Each frame contains a three-zone furnace with the power level for each zone being independently adjustable.Each furnace is controlled by a Leeds and Northrup Electromax III controller which utilizes a chromel–alumel thermocouple to monitor the temperature at the center of the middle zone.Each specimen is mounted in a testing fixture and suspended within the creep frame furnace.A chromel–alumel thermocouple wired to the center of the specimen gauge length is connected to a digi-tal temperature recorder which,in turn,is used to monitor the temperature of the specimen during testing.To minimize the convection of air through the furnace,both the top and bottomorifices of the furnace were packed with ceramic wool.At the beginning of each test,the specimens are heated to the desired temperature and stabilized before any load is applied.Loading is in uniaxial tension with a constant load throughout the test.In addition to temperature,specimen extension,measured by a dial gauge attached to the testing fixture,is also recorded as a function of time.Different stress levels between 70and 240MPa were used together with a range of temperature (550–700◦C)for creep testing of commercial and modified E308H and E316H weld deposits.3.Results and discussion 3.1.Creep testing resultsFig.4illustrates typical creep curves (strain versus time to rupture)for fissure-containing and fissure-free E316HsamplesFig.4.Typical creep curves (strain vs.time to rupture)for fissure-containing and fissure-free 316H samples under the same testing condition,117MPa and 660◦C.Y.Cui,C.D.Lundin/Materials Science and Engineering A 452–453 (2007) 284–291287Fig.5.(a).Creep-rupture behavior for E308H welds;(b)creep-rupture behavior for E316H welds;(c)creep-rupture behavior for commercial E308H and E316H.under the same testing conditions,117MPa and660◦C.Both curves match well up to1700h,then thefissure-containing spec-imen exhibits more secondary creep.The creep rate increases rapidly in the tertiary region that starts at approximately2% creep strain in both specimens.However,the time to rupture for fissure-containing modified316H is1000h greater than com-mercial316Hfissure-free sample.The analysis of creep test results was conducted using the Larson–Miller Parameter technique as shown in Fig.5(stress level versus LMP).It is apparent that the creep properties of modified E316H(microfissure-containing)are superior to the commercial E316H(microfissure-free)samples;meanwhile modified E308H(fissure-containing)sample shows lower creep properties than commercial E308H(fissure-free)sample.3.2.Metallurgical evaluationSamples for microstructure evaluation were extracted from fractured creep specimens and ground and polished to0.05m surfacefinish and electrolytically etched with potassium hydrox-ide to reveal the morphology of the microstructure.The etchant selection is considered to be sensitive in revealing sigma phase (colored)in austenitic stainless steel weld metals which have experienced long-term service at elevated temperature.The most successful etchant for revealing sigma phase is an electrolytic etchant containing potassium hydroxide(KOH–H2O)solution under a controlled(DC)current density and the etchant time.The solution preferentially etches sigma(relative to the austenitic grain boundaries)the color of which varies from yellow to reddish-brown under the optical microscope.Such characteristic colors and contrast made sigma phase identification[19].Fig.6shows the microstructural morphologies of modified 308H samples before and after creep testing.Before and after creep testing,the microstructure of modified308H is austenite (FN=0),as shown in Fig.6(a).For commercial308H,the as-deposited microstructures are austenite with ferrite,austenite with ferrite and sigma after creep testing as shown in Fig.6(b).Fig.6(c)shows the microstructure of modified316H.Before creep testing,the microstructure is all austenite(FN=0).Dur-ing testing,carbides evolved in the vicinity of the substructure and grain boundaries.For commercial316H(FN=4.7),the microstructure is austenite with ferrite before creep testing and austenite with ferrite and sigma(deduced from morphology and color etching)after creep testing,as shown in Fig.6(d).288Y.Cui,C.D.Lundin /Materials Science and EngineeringA 452–453 (2007) 284–291Fig.6.Microstructure of samples before and after creep testing.(a)Modified E308H (138MPa,620◦C,746h);(b)commercial E308H (138MPa,645◦C,754h);(c)modified E316H (117MPa,660◦C,3671h);(d)commercial E316H (117MPa,660◦C,2685h).The sigma phase is distributed along the substructure and grain boundaries and shows reddish-brown under the microscope.SEM microstructural morphology of commercial and modi-fied E316H samples after creep testing is presented in Fig.7as a back scattered image.The typical microstructure includes the coarse irregular-shaped secondary phase like the “islands”in the matrix in Fig.7(a)and the dark globular particles in Fig.7(b).The majority of the globular particles form,in modified E316H,along the substructure and grain boundaries and exhibit a size in the range of 0.2–0.4m while the size of the particles within the matrix is around 0.6m.EDS analysis was performed at location A for the irregular-shaped secondary phase and location B for matrix.The EDS spectra presented in Fig.8for locations A and B,respectively.The EDS results show that the irregular-shaped secondary phase contains higher Cr as compared to the matrix.In addition,the fact that these irregular-shaped secondary phasesY.Cui,C.D.Lundin /Materials Science and Engineering A 452–453 (2007) 284–291289Fig.7.SEM microstructural morphology of creep samples after testing (117MPa,660◦C),as a back scattered image (a)commercial E316H (2686h);(b)modified E316H (3671h).were stained red by potassium hydroxide etching,indicates that these are phase.Aluminum oxide presented shown in Fig.8(a)(Al and O peaks)was involved from the polishing process with alumina powder.This can be deduced from the chemicalcom-Fig.8.The EDS spectra for locations A (a)and B (b)in Fig.7(a).position (less aluminum content)and further proved by the latter X-ray diffraction pattern (no aluminum peak appears again).The EDS spectra for particles and matrix for modified E316H do not indicate large difference in chemical composition because it is hard to isolate the small particles from the matrix using EDS.3.3.X-ray diffractionTo further verify the presence of sigma phase and precipita-tion,an X-ray diffraction apparatus was employed to carry out the analysis.An electrolytic precipitate exaction technique was used to obtain the precipitates from commercial and modified E308H and E316H samples before and after creep testing.To extract particles,a known weight of a sample was placed into 10%HCl +90%methanol solution with a constant voltage of 8V referred to the platinum electrode.A centrifuge was used to separate the particles from the solution.The particles collected from the solution were cleaned using high purity methanol.Then the particles were ready for X-ray diffraction.The par-ticles extracted are weighed again and the ratio of the weight percentage of the precipitate to the matrix is obtained from the following formula [20].The results of electrolytic extraction of particles from weld deposits are shown in Table 3.R = M r(M i f )×100,where M i is the initial mass of sample,M f the final mass of sample after extraction and cleaning,M r the mass of residue and R is the residue,mass %.The X-ray diffraction (XRD)spectra were obtained in a Philips X’pert Pro Diffractometer at 45kV and 40mA.Diffrac-290Y.Cui,C.D.Lundin /Materials Science and Engineering A 452–453 (2007) 284–291Table 3Results of electrolytic extraction of particles from weld deposits Material M i (g)M f (g)M r (g)R (%)M316H bf 10.1990 5.47980.01140.242M316H af 0.57600.11140.0050 1.076C316H bf 19.946713.41840.03830.587C316H af 2.10040.27890.0360 1.976M308H bf 3.7304 2.37090.00400.294M308H af 1.96110.13190.0200 1.093C308H bf 4.7813 1.33510.00270.078C308H af1.88590.16950.00930.542tion patterns are acquired from samples in a step mode with 0.02◦step (2θ)and 4s per point over diffraction angles from 30◦to 60◦.The information from X-ray examination was recorded in the form of intensity as function of 2θ.It is evident that Cr 23C 6is the dominant precipitate with a few MnS inclusions for both commercial and modified 308H and 316H before creep testing.After creep testing most particles are Cr 23C 6and an amount of -FeCr was observed in the commercial 316H sample.This agrees with the metallographic examination on this sample.The majority particles for modified and commercial 308H as well as modified 316H are Cr 23C 6.No -FeCr was found in commer-cial E308H samples due to an insufficient amount particles to be detected using X-ray diffraction.The typical X-ray spectra of modified and commercial 316H after creep testing are shown in Fig.9.Fig.9.Typical X-ray diffraction patterns obtained from modified and commer-cial E316H weld deposits after creep testing.3.4.Mechanism analysisAccording to the results on particles extracted from weld deposits of modified E308H and E316H (FN =0),the ratio of extracted particle weight (the ratio of the particle weight to the weight dissolved in electrolytic precipitate extraction)for these two deposits pre-and post-creep testing are in the same level,around 0.2and 1%,respectively.The precipitate ratio after creep testing is much greater than that before,which means that a sig-nificant of carbides evolved after creep testing.The carbides in modified E316H are distributed in chains and those in modi-fied E308H are distributed at random.For commercial E308H and E316H,the extraction ratios are quite different.Because of molybdenum added in E316H,more carbides formed in weld deposits for E316H than E308H before creep testing.After creep testing,more sigma phase formed in E316H than E308H which results in the large difference in extraction ratio for both of these commercial weld deposits.It is to be noted that microfissures decrease creep resis-tance for E308H because of the propagation paths provided by fissures and the reduced benefit effect of the randomly dis-tributed carbides.However,for commercial E316H,sigma phase formed along the grain boundaries due to the higher ferrite and Mo content (the extent of sigmatizion is greater than for commercial 308H).Since the sigma phase is hard and brittle it promotes secondary cracking between the sigma phase and austenite in the matrix under the stress.For modified E316H (fissure-containing),carbides are distributed in a chain of dis-crete globular M 23C 6at the substructure and grain boundaries.This morphology benefits creep-rupture life.The mechanisms causing creep are complex and not fully understood,but dislocation climb is thought to be important.To observe the morphology related to carbides and disloca-tion,a Hitachi 800H type transmission electron microscope was employed.The sample for TEM evaluation extracted from the transverse section of modified E316H sample after creep test,at 45◦along the loading axis.The chemical thinning was per-formed by using a type Tenupo-3dual electrolytic polishing equipment with a solution of 5%perchloric acid in methanol.Fig.10shows the typical TEM microstructural morphology of modified E316H after creep testing under 70MPa,700◦C and 4560h.From the metallurgraphy evaluation and particle extraction ratio,the concentration of the evolved carbides in the modified E316creep sample is high.At such high con-centrations,the precipitates may interact with the dislocation cooperatively rather than individually.Dislocations are multi-plied and locked by the fine precipitate formed in austenite.It is evident that bonding of dislocation to the precipitates will be much stronger than it would be to an “atmosphere”.The precip-itates nucleated at dislocations most effectively retard slip.With increasing plastic deformation,the intersection of dislocations with each other grows to form a network as a forest of disloca-tions.Because of the particles in the forest,any slip dislocation does not travel far before it intersects other dislocations passing through its slip plane at various angles.The particles make the movement of the entangled dislocations through the lattice more difficult.When part of the dislocation in the forest is locked,it isY.Cui,C.D.Lundin/Materials Science and Engineering A 452–453 (2007) 284–291291Fig.10.Typical TEM microstructural morphology of modified E316H after creep testing under70MPa,700◦C and4560h.hard to move entire network.This results in the density of dislo-cations on one side of a particle wall higher than the other side. It is not quite understood that why carbides distributed in a chain of discrete globular precipitates in the E316H weld metal,but in a random order in E308H weld deposits when both FNs are pared to the effect of microfissures and sigma phase in E316H and E308H weld deposits,it is concluded that secondary cracking caused by sigma phase is a main factor in effecting creep properties for E316H deposits,and the microfissures to E308H deposits.4.Conclusions1.The creep test results revealed that modified E316H with0FN(fissure-containing deposits)have superior creep resistance, followed by commercial E316H and E308H,the modified 308H with0FN(fissure-containing)samples showed the poorest performance.2.M23C6carbides evolved from modified E308H and E316Hweld coupons after creep testing when their Ferrite Numbers are0in as-welded samples.The majority of the carbides in modified316H(FN=0)in the range of0.2–0.4m dis-tributed in a chain of discrete globular M23C6along the substructure and grain boundaries while the carbides in mod-ified E308H weld coupons(FN=0)are distributed in a random order.3.Sigma phase can be detected in commercial E316H andE308H samples after the creep tests.More sigma phaseformed in commercial E316H weld deposits than commercial E308H because of the difference in molybdenum content.4.Carbides evolved in a chain effectively retard the movementof dislocation which results in the higher creep properties of modified E316Hfissure-containing sample thanfissure-free.Fissure-containing modified E308H has a lower creep strength thanfissure-free commercial sample because of the propagation paths provided byfissures and the reduced effect on the randomly distributed carbides.5.Creep strength of austenitic stainless weld metals is as a func-tion of ferrite:secondary cracking caused by sigma phase (high ferrite content)is a main factor in effecting creep prop-erties for E316H deposits,and the microfissures to E308H deposits(low ferrite content).AcknowledgementsThe author acknowledges thefinancial support from the Welding Research Council.The authors are grateful to Dr.D.J. Kotecki(The Lincoln Electric Co.)and Mr.Frank Lake(ESAB) for supplying the electrodes.References[1]J.R.Davis,Stainless Steels,ASM Specialty Handbook,ASM International,1996.[2]J.C.Borland,R.N.Younger,Br.Weld.J.8(1960)22–59.[3]R.G.Bake,Br.Weld.J.15(1968)283–295.[4]R.G.Baker,R.P.Newman,Met.Construct.Br.Weld.J.1(1969)1–4.[5]A.M.Rirrer,W.F.Savage,Metall.Trans.A17A(1986)727–737.[6]H.Thielsch,Weld.Eng.52(1967)80–85.[7]T.G.Gooch,J.Honeycomb,Met.Construct.9(1970)375–380.[8]C.D.Lundin,D.F.Spond,Weld.J.55(1976)356s–366s.[9]C.D.Lundin,Weld.J.8(1980)226s–232s.[10]R.Nakkalil,N.L.Richards,M.C.Chaturvedi,Metall.Trans.A24A(1993)1169–1179.[11]C.D.Lundin,C.P.D.Chou,Weld.J.64(1985)113s–118s.[12]F.C.Hull,Weld.J.46(1967)339s–409s.[13]C.D.Lundin,W.T.DeLong,D.F.Spond,Weld.J.54(1975)241s–246s.[14]A.L.Schaeffler,Met.Prog.56(1949)680–680B.[15]W.T.DeLog,Weld.J.53(1974)273s–286s.[16]D.J.Kotecki,T.A.Siewert,Weld.J.71(1992)171s–178s.[17]J.M.Vitek,S.A.David,C.R.Hinman,Weld.J.82(2003)10s–17s,and43s–50s.[18]C.D.Lundin,W.T.DeLong,D.F.Spond,Weld.J.55(1976)145s–151s.[19]L.Patel,The effect of carbon on the formation of sigma phase inaustenitic stainless steel,Master Thesis,The University of Tennessee,1981, p.81.[20]ASTM Designation:E963-95,Standard Practice for Electrolytic Extractionof Phase from Ni and Ni–Fe Base Superalloys Using a Hydrochloric-Mehanol Electrolyte.。
Inverse ManipulatorKinematicsAlgebraic solution by reduction to polynomialOutline2 Introduction IntroductionIntroductionThe Inverse kinematic is the basis of robot trajectory planning and control.5IntroductionExample :6Algebraic solution by reduction to polynomialOutline7SolvabilitySolvabilityFor the 6 DOF Puma 560 manipulator,we have:How to find the 6 joint variablesHere we might have 12 equations to solve for 6 independent variables. Constraints should be utilized.6 equations for 6 unknown variables9SolvabilityDifficulty: these 6 equations are nonlinear and transcendental equations.obtain the solution.whereSolvability11SolvabilitySolvabilityThe dexterous workspace is only one point(the origin). The There is no dexterous workspace. The reachable SolvabilityFor most industry robots, there is limitation for the joint variable range, thus the workspace is reduced.Only one attainable orientationIf a manipulator has less than 6 DOF, it can’t attain general goal position and orientation in 3D space.Workspace also depends on the tool-frame transformation.Solvability15There might be multiple solution in solving kinematic equations.Two possible solution for the same position and orientation.How to choose possible solution?Solvability” solution.The number of solutions depends on the number of and the allowable ranges of motion of the joints, also, it can be a function of other link parameters (link length, link twist, link offset, joint angle).Solvability2. Multiple solutions17The PUMA 560 can reach certain goals with 8different solutions.+Due to the limits of joints range, some of these 8 solutions could be inaccessible.SolvabilitySolvabilityAlgebraic solution by reduction to polynomial Outline20Manipulator Subspace21workspace is a portion of an n‐DOF subspacesubspace : planeworkspace : a subset of the plane{workspace} ⊂{subspace} ⊂{space}Manipulator Subspaceof a manipulator?Giving an expression for a manipulator’s wrist frame {w}to be free to take on all possible values.Manipulator SubspaceThe subspace of is given by:233R planar manipulatorAs are allowed to take on arbitrary values, the subspace is generatedNOTE : Link lengths and joints limits restrict the workspace of the manipulator to be a subset of this subspace.Algebraic solution by reduction to polynomial Outline24Algebraic vs. GeometricGiven the transformation matrix, solved for25Algebraic vs. GeometricD-H TableAlgebraic vs. GeometricThe transformation matrix can be computed viaand we haveAlgebraic vs. GeometricSpecification of the goal points can be accomplished by specifying three parameters: ..The transformation is assumed to have the following structurewhereThe above four nonlinear equations are used to solve for (unknown)Algebraic vs. GeometricThe parameters is How to solve for according thefollowing equations:Algebraic vs. Geometric1.Algebraic solution 30The is the only unknown parameter.Algebraic vs. GeometricStep1.In the solution algorithm, the above constraintshould be checked to determine whether a solution exist or not. If the constrain is not Algebraic vs. Geometric1.Algebraic solution Here, the choice of signs in the solution of corresponds to Algebraic vs. Geometric33Based on the solution of , we can get:whereAlgebraic vs. Geometricwe haveAlgebraic vs. GeometricNote:If a choice of sign is made in the solution of ,it will affect and thus affectStep5. Based on the fact that The solution of can be obtained.Algebraic vs. Geometric36solved for by using the tools of plane geometry.can utilize plane geometry directly to find a solution.Algebraic vs. Geometricconsidering the solid triangle, the “” can be applied to solve for as:37PossibleconfigurationThe other possible solution can be obtained by settingAlgebraic vs. Geometric2. Geometric solutionTo solve for , we find the express for angleand .38and can be solved via:then can be solved as:Algebraic vs. Geometric39the solution of can Algebraic solution by reduction to polynomial Outline40Algebraic solution by reduction to polynomialexpression in terms of a single variable.This is a very important geometric substitution used often in solving kinematic equations. These substitution convert transcendental equations into polynomial equations in Algebraic solution by reduction to polynomialGiven a transcendental equation try to solve for42Solutions:(when )Algebraic solution by reduction to polynomial Outline43Inverse manipulator kinematicsThe Unimation Puma 560 Industry Robot44Inverse manipulator kinematicsReview : D-H table45Inverse manipulator kinematicsReview : Transformation of each link.46Inverse manipulator kinematicsReview : Transformation of all link47whereInverse manipulator kinematics: Given the goal point and orientation specified by:(Known: Numerical value)Solve forInverse manipulator kinematics Separating out 1 unknown parameter How to solve ?Inverse manipulator kinematics2. Inverting to be obtain50 whereInverse manipulator kinematicsCheck the (2,4) elements on both sides ,we have Inverse manipulator kinematicsIntroduce the trigonometric(三角恒等变换) substitutions:52whereThen it can be obtained that:Inverse manipulator kinematics3. The left side of the following equation is known53Inverse manipulator kinematicsTaking square of the above two equations, and adding the results together, it can be obtained thatInverse manipulator kinematicsThe above equation depends only on , then similar steps can be followed to solve for as:4. Consider the following equationhave been solved, but is unknownInverse manipulator kinematics56Eq.(3.11) in Chapter3Check elements (1,4) and (2,4) on both sides, we haveInverse manipulator kinematics 57Inverse manipulator kinematics585. Now the left side of the following equation is knownEq.(3.11) in Chapter3Check the elements (1,3) and (3,3), it can be obtained thatInverse manipulator kinematics ca can be solved as:Case2.,The manipulator is in a singular configurationas axis 4 and 6 line up and cause the same motion of the last link of the robot. Thus is chosen arbitrarily.Inverse manipulator kinematics606. Consider the following equation again:andCheck the elements (1,3) and (3,3), it can be obtained thatInverse manipulator kinematics 61Hence, we can solve for as7. Applying the same method one more time, we havewhereCheck the elements (3,1) and (1,1), it can be obtained thatInverse manipulator kinematics62Thus we can solve for aswe can obtain eight sets of possible solutions, some of them will be discarded due to the joint angle limitsInverse manipulator kinematics63Summary1、原则:等号两端的矩阵中对应元素相等,列出相关方)、从含变量少的左边开始,如,向右递推,直到)、选择等号左边或右边矩阵中等于常数或仅含有一个变量的元素,列出相应元素对应的方程或方程组。
【神圣几何】金字塔科技金字塔让人类着迷了数千年。
正如雷格·米勒(Reg Miler)在《金字塔真相》这本书中写到的,其中最为著名的埃及大金字塔仍是世界上最大的未解之谜。
而金字塔科技很可能始于数百世纪前的远古时代。
PYRAMIDS HAVE FASCINATED HUMAN KIND FOR THOUSANDS OF YEARS. ONE OF THE MOST FAMOUS, THE GREAT PYRAMID, REMAINS THE WORLDS GREATEST UNSOLVED MYSTERY AS REG MILER PUTS IT IN HIS BOOK, PYRAMID TRUTH. PYRAMID TECHNOLOGY BEGAN PROBABLY HUNDREDS OF CENTURIES AGO.金字塔技术被推入现代社会始于20世纪20年代,捷克斯洛伐克人卡尔·德巴尔(Karl Derbal)因发明了金字塔型的剃须刀片打磨器而获得了专利。
到了40、50年代出现了另一个进展,当著名心理学家威廉·赖希(Wilhelm Reich)提出的奥根效应(Orgone effect)被应用到金字塔科技时,极大的增强了这些技术的多功能疗愈和排毒效果。
It got its first real push into modern society in the 1920s, when Karl Derbal of Czechoslovakia, received a patent for the pyramids used as a razor blade sharpener. Then another development occurred in the 1940s to 1950s, when Wilhelm Reich discovered the Orgone effect which, when applied to pyramid technologies, greatly enhanced the multipurpose healing and detoxification effect of pyramids.我们都知道金字塔很特别。
a r X i v :a s t r o -p h /0308087v 1 6 A u g 2003Astronomy &Astrophysics manuscript no.zickgraf February 2,2008(DOI:will be inserted by hand later)Kinematical structure of the circumstellar environments ofgalactic B[e]-type stars ⋆F.-J.ZickgrafHamburger Sternwarte,Gojenbergsweg 112,21029Hamburg,GermanyReceived date;accepted dateAbstract.High resolution line profiles are presented for selected forbidden and permitted emission lines of a sample of galactic B[e]-type stars.The spectral resolution corresponds to 5-7km s −1with the exception of some line profiles which were observed with a resolution of 9-13km s −1.All H αprofiles are characterized by a narrow split or single emission component with a width of ∼150−250km s −1(FWHM)and broad wings with a full width of ∼1000−2000km s −1.The H αprofiles can be classified into three groups:double-peaked profiles representing the majority,single-peaked emission-line profiles,and normal P Cygni-type profiles.Likewise,the forbidden lines exhibit in most cases double-peaked profiles.In particular,the majority of starsshows split [O I ]λ6300˚A.Double-peaked profiles are also found in several stars for [N II ]λ6583˚A and [Fe II ]λ7155˚A although these lines in many stars exhibit single-peaked emission profiles.The split forbidden line profiles have peak separations of as little as ∼10km s −1,and were therefore only discernible for the first time in the high-resolution spectra.The ratio of violet to red emission peak intensities,V /R ,is predominantly smaller or equal to 1.Theoretical profiles were calculated for the optically thin case.A latitude-dependent stellar wind with a radial expansion and a velocity decreasing from the pole to the equator was adopted.This configuration can produce split line profiles if viewed under some angle with respect to the line of sight.In addition an equatorial dust ring with various optical depths was assumed.It can explain line asymmetries observed in some stars.Moreover,the V /R ratios can be understood in terms of this model.The comparison of the observed line profiles with the models thus confirms the assumption of disk-like line-formation regions as commonly adopted for B[e]-type stars.Key words.Stars:circumstellar matter –Stars:early-type –Stars:emission-line,Be –Stars:mass-loss1.IntroductionThe class of B[e]-type stars is characterized by the B[e]phe-nomenon (Lamers et al.1998).This term summarizes the pres-ence of strong Balmer emission lines,narrow permitted and forbidden low-excitation emission lines of Fe II ,[Fe II ]and [O I ],and in particular a strong near to mid-IR excess.It is attributed to hot circumstellar dust (T dust ∼1000K)and is a distinguishing characteristic with respect to other classes of peculiar emission-line stars.The presence of dust requires re-gions of high density and a temperature low enough to allow dust condensation.A recent review of the properties of this still enigmatic class of emission-line stars was given by Zickgraf (1998)during the first workshop dedicated entirely to this type of stars (Hubert &Jaschek 1998).It was shown that although B[e]-type stars share the mentioned properties,indicating very similar physical conditions in their circumstellar environments with regard to temperature,density,and velocity,they form by2 F.-J.Zickgraf:Circumstellar environments of galactic B[e]-type starsin the Magellanic Clouds(MCs).These observations strongly suggested that the stellar winds can be described by a two-component model.In this picture a cool and dense equatorial wind emerging from a single star is responsible for the for-mation of the narrow low-excitation emission lines.It is also supposed to be the site of dust formation.The polar region is dominated by a hot and fast expanding OB star wind with the high wind velocities observed normally for stars of this type.A similar model had been proposed earlier by Swings(1973a) for the galactic B[e]-type star HD45677also based on spectro-scopic observations.In contrast to the post-main sequence MC sgB[e]s it seems to be a(near)main-sequence object.Likewise, the pre-main sequence Herbig Ae/Be stars are supposed to pos-sess circumstellar disks.Disk-like circumstellar environments could also be caused by binarity.Apart from objects belonging to the subclass of symB[e]several B[e]stars have in fact been shown to be com-ponents of a binary system.In the SMC two B[e]supergiants, Hen S18and R4,were found to possess lower mass com-panions(Zickgraf et al.1989,1996).Likewise,in the Milky Way a couple of B[e]stars were found to be binaries,e.g. MWC623(Zickgraf&Stahl1989),AS381(Miroshnichenko et al.2002a),and CI Cam(=MWC84).Further instances are possibly MWC349A(Hofmann et al.2002)and MWC342 (Miroshnichenko&Corporon1999).It is,however,not clear whether in these objects the B[e]phenomenon itself is actually caused by their binary nature.For some objects this seems not to be the case.In Hen S18,R4,and MWC623the B[e]phe-nomenon can be ascribed to the B star component in the binary systems.These B[e]stars behave like single stars(Zickgraf et al.1989,1996,Zickgraf2001).AS381on the other hand shows signs of mass transfer suggesting that interaction could play a role in the occurence of the B[e]phenomenon in this object(Miroshnichenko et al.2002a).At this time the role of binarity is thus controversial.Spectroscopic studies showed that the low-excitation lines attributed to the disks are narrow and thus indicative for low wind velocities in the line forming region.Typically, line widths(FWHM)of the order of less than∼100km s−1 to300km s−1are observed(e.g.Swings&Andrillat1981, Zickgraf et al.1986).Given the early spectral types of the un-derlying stars such small wind velocities are unusual.In the case of stars viewed edge-on the direct investiga-tion of the velocity structure of the disk winds is possible by studying absorption lines formed in the disk.This method was used by Zickgraf et al.(1996)to study three B[e]supergiants in the MCs using satellite UV spectroscopy.The observations of UV resonance lines showed that the disk winds are in fact very slow,at least in the case of massive supergiants.The expansion velocities measured were of the order of70-100km s−1,i.e. typically a factor of10less than usually observed for stars of similar spectral type.This may also hold for members of other B[e]star classes.For viewing angles deviating from edge-on one can make use of the low-excitation emission lines to study the kinematics of the disk winds.Of particular interest are lines from forbidden transitions because they are optically thin.Therefore radiation transfer does not complicate the interpretation of the line in-Table1.Observed sample of B[e]-type stars.References forspectral types are:WS85=Wolf&Stahl(1985),McG88= McGregor et al.(1988),WW89=Winkler&Wolf(1989), LeB89=Le Bertre et al.(1989),Th´e94=Th´e et al.(1994), Sw73=Swings(1973a),C99=Clark et al.(1999),Lei77= Leibowitz1977),L98=Lamers et al.(1998),Isr96=Israelian et al.(1996),Drew97=Drew et al.(1997).star spec.class.references tensities and profiles.Furthermore,the forbidden lines should form at a large distance from the central star.Hence,in the case of a radially accelerated outflow(as e.g.the usually adopted β-type velocity law)the radial velocity component in the line forming region should have reached the terminal wind speed. Because of the small velocities involved the investigation of the emission-line profiles requires high spectral resolution.If one aims at a resolution of about1/10of the terminal velocity a spectral resolution of about∼5−10km s−1is necessary for the wind velocities measured e.g.by Zickgraf et al.(1996)forB[e]supergiants.In order to study the disk winds using emission-line pro-files a sample of galactic B[e]-type stars listed in Table1was observed with high spectral resolution.In Sect.2the observa-tions are described.The observed line profiles are described in Sect.3.The density conditions in the line formation region of the forbidden lines are discussed in Sect.4.The role of rotation and expansion is investigated in Sect.5.In Sect.6model cal-culations of optically thin line profiles are presented and com-pared with the observed lines.Finally,conclusions are given in Sect.7.The Appendix contains the observational data in Sects.A and B,and remarks on individual stars in Sect.C.An atlas of the high-resolution spectra is presented in Sect.D1.F.-J.Zickgraf:Circumstellar environments of galactic B[e]-type stars3 Table3.Lines observed with CES in1986(+)and in1988(×).star Hα+[N II][O I][Fe II][Fe II]Fe II Fe II He I+Na I Dλ6300˚Aλ7155˚Aλ4287˚Aλ6456˚Aλ4549/56˚Aλ5876˚ATable4.Lines observed at Calar Alto Observatory.Coud´e observations with a resolution of45000are indicated by the letter”h”, coud´e observations obtained with the lower resolution of23000are indicated by”m”.Supplementary observations with FOCES are denoted by the letter“F”.star Hα+[N II][N II][O I][Fe II]He I+Na I D He Iλ6583˚Aλ6300˚Aλ7155˚Aλ5876˚A&λ6678˚A2.Observations and data reductionThe spectroscopic observations were carried out in1986and1988with the Coud´e Echelle Spectrometer(CES)at the1.4mCAT at ESO,La Silla,and in1987with the coud´e spec-trograph at the2.2m telescope at the Centro AstronomicoHispano Aleman(CAHA)on Calar Alto,Spain.For a fewstars with incomplete coud´e data the observations were sup-plemented by echelle spectra obtained with FOCES at CalarAlto Observatory in June2000and February2002.The journalof observations is given in Table2.Due to the small spectral coverage of about≃30−60˚Aprovided by the coud´e spectrographs strong emission linescharacteristic for B[e]-type stars were selected and the ob-served wavelength ranges adjusted around these lines.In Tabs.3and4the observed lines are listed for each studied object.During the1987observing run on Calar Alto the northern B[e]-type star MWC623was included in the sample.The resultson this star have been presented already by Zickgraf&Stahl(1989)and Zickgraf(2001)and are therefore omitted here.The CES spectra were collected during two campaigns inNovember1986and March1988.The short camera of thespectrograph was equipped with a RCA CCD(ESO CCD#8,4 F.-J.Zickgraf:Circumstellar environments of galactic B[e]-type starsTable2.Journal of observations.date wavel.range spectral res.instrument[˚A]R=λ/∆λchip with24µm pixel size.With a diaphragm diameter of 200µm and an entrance slit width of180µm a spectral resolu-tion of34000was achieved,i.e.9km s−1.A full discussion of the FOCES spectra will be given elsewhere(Zickgraf2003,in preparation).Here only the lines observed also with the coud´e spectrographs will be considered.During all observing campaigns wavelength calibration was obtained with Th-Ar lamps.Forflatfielding built-in lamps were used.The coud´e spectra were reduced by application of standard procedures(bias subtraction,flat-fielding,wavelength calibration,normalization)of the ESO-MIDAS image process-ing software package,context longslit.For the FOCES data the ESO-MIDAS context echelle was used.All spectra werefinally rebinned to heliocentric wavelengths.The spectra in the red spectral region are strongly affected by narrow telluric absorption features.To correct for these lines,the normalized spectra were divided by the normalized spectrum of a hot comparison star with a line free continuum or with possible photospheric lines removed during the normal-ization procedure.For the Hαlines the correction spectrum was created from the object spectra themselves.First each spec-trum was smoothed.Then the original spectrum was divided by the smoothed spectrum.Thefinal correction spectrum was then created by averaging several of these individual spectra observed during the same night as the spectrum to be corrected.The observed spectral sections are displayed in the Appendix in Figs.D.1to D.8together with remarks on the in-dividual objects in Sect.C.For Hαsee Fig.1.3.Observed line profilesIn the following the observed characteristics of the line profiles are summarized.Table A.1in the Appendix lists relevant line parameters.Measurements of heliocentric radial velocities are also listed in the Appendix in Table B.1.The profiles of Hα, of He I emission lines,and of the forbidden lines rebinned on a velocity scale are displayed in Figs.13and2a,b.The line profiles can be categorized into four groups:–group1:normal P Cygni-type line profiles with an absorp-tion component reaching below the continuum on the violet side of the profile and an emission component on the red side,–group2:single-peaked pure emission lines without absorp-tion components,–group3:double-peaked emission lines with a central or al-most central absorption component,or at least an intensity dip on one of the lineflanks,–group4:absorption lines.These profile groups correspond to Beals types I,V,III,and VII-VIII,respectively,defined by Beals(1955).The profile types of the observed lines are summarized in Table5.3.1.HαprofilesA general characteristic of all Hαprofiles displayed in Fig.1is that they exhibit a narrow single or split emission component with a full width at half maximum(FWHM)of about3-5˚A, i.e.∼150−250km s−1,and broad wings on both sides of the emission component extending up to typically∼20−25˚A,i.e.∼1000km s−1.These wings are generally ascribed to electron scattering(e.g.Zickgraf et al.1986).Only one star,CPD−52◦9243,shows a P Cygni profile which resembles the“normal”(group1)profile type.Hen485 in1988and MWC1055may also be classed with group1,al-though the absorption components do not reach below the con-tinuum level.The Hαprofiles of four stars,MWC84,MWC137, MWC297,and Hen230,fall into group2,which exhibits pure emission line profiles.The FWHM is of the order of3-5˚A. Note,however,that the lines are not symmetric.The asymme-try is particularly pronounced in the case of MWC84.Most of the investigated stars belong to group3exhibiting double-peaked Hαemission lines.In all of the eleven cases of this group the blue emission peak is weaker than the red peak. In no case the central absorption components reaches below the continuum level.For the peculiar line profiles of HD45677and MWC645see Sect.C.For several stars Hαwas observed more than once.The profiles are plotted in Fig.1:MWC137in1987(solid line) and in2002(dashed line);MWC342in1987(solid line)and in2000(dashed line);MWC939in1987(solid line)and1988 (dashed line),the profile observed in2000is indistinguish-able that of1988;MWC1055in1987(solid line)and2000 (dashed line);HD87643in1986(solid line)and1988(dashed line);Hen485in1986(solid line)and1988(dashed line).ForHen485(see text).malized to the peakflux.From bottom to top the profiles of[O I]λ6300A,[Fe II]λ7155A,[N II]λ6583A,and[S III]λ6312A are plotted with shifts in relative intensity of0,0.75,1.5,and2.25,respectively.the line observed in2002is shown.3.2.2.[N II]linesThe wavelength region around[N II]λ6583˚A is displayed in Fig.D.2.In two stars,CPD−52◦9243and HD87643,the [N II]line is absent.The lines visible in the spectra of these stars aroundλ6585˚A are probably due to Fe IIλ6586.69˚A. Heliocentric radial velocities are v rad=−72km s−1for CPD−52◦9243and v rad=−18km s−1for HD87643.In MWC1055[N II]is only weakly discernible.The majority of stars,however,exhibits clearly visible,in many cases strong, [N II]λ6583˚A emission.Eight stars show double-peak profiles. Hen1191shows a sloping line top inclined towards the red side similar to the[O I]line of Hen230,however with a weak peak on the blue edge.Due to this feature the line was classified type 3.Eight stars exhibit single-peaked emission lines.However,in two of these cases,respectively,the profiles were observed with the lower resolution of23000and34000.They are labelled “e”and”f”in Table5.Note that each of these stars shows a double-peaked(type3)[O I]profile.3.2.3.[Fe II]The spectral section with[Fe II]λ7155˚A is shown in Fig.D.3. Note for that CD−24◦5721the forbiddden lines[Fe II]λλ4287, 4276˚A were observed instead of the red line(Fig.D.4).In five cases the[Fe II]profiles are double-peaked similar to[O I]. However,contrary to[O I]the majority of objects,i.e.10,ex-hibits single-peaked profiles,2of them on a resolution level of 9km s−1.3.2.4.[S III]linesThe[S III]λ6312˚A lines are displayed in Fig.D.1.Only four stars exhibit this higher-excitation emission line,i.e.MWC17, MWC84,MWC137,and MWC349A.In MWC137it is very weak and not much can be said about its profile.The[S III] line of MWC84is also weak.The strongest[S III]was found in MWC349A.3.2.5.Fe II linesFor only half of the sample permitted Fe II lines were observed, mostly Fe IIλ6456˚A,but also Fe II lines around4550˚A for a few stars instead.The wavelength region around Fe IIλ6456˚A is displayed in Fig.D.5.Three of the observed stars exhibit single-peak emission lines.Four stars show double-peaked pro-files.For Hen485the double-peak structure is only weakly in-dicated.CPD−52◦9243is the only star showing a P Cygni pro-file of group1.CD−24◦5721is exceptional.This star shows narrow absorption lines(Fig.D.6).The lines identified in the observed spectral sections of this star are listed in Table C.1.3.2.6.Na I D linesThe lines of the Na I D doublet are shown in Fig.D.7.The spectral section shown in thisfigure also contains the line of He Iλ5876˚A(see below).Most stars clearly show circumstel-lar Na I emission.Only4of the14observed stars do not show an emission component of the doublet.In most cases the ab-sorption components are blends of multiple narrow absorptionF.-J.Zickgraf:Circumstellar environments of galactic B[e]-type stars9 Table5.Classification of the line profile types of the programme stars into groups1to4:1=normal P Cygni profile,2=single-peaked emission line,3=double-peaked emission line,4=absorption line.Additional classification codes are:?=weak line, no further classification possible,0=no line visible,–=not observed.For class3a minus or plus sign denotes objects with V/R≤1.0or V/R>1.0,respectively.For Na I D no group is listed because of the confusion due to interstellar absorption components.For this doublet only the presence of emission(“em”)or pure absorption(“abs”)is indicated.star Hα[O I][Fe II][N II][S III]Fe II He I Na I Da:Fe IIλ6586c:He Iλ6678in emissiond:He Iλ6678possible blue shifted absorption componente:observed with R=23000f:observed with FOCESlines which are very likely mainly due to interstellar absorp-tion.This makes it difficult to detect circumstellar absorption features.Because of this problem only the overall appearance of emission or absorption is listed in Table5.Exceptions are CPD−52◦9243and possibly Hen485,cf.Sect.C.18and C.14. Heliocentric radial velocities of the absorption components are listed in Table B.2.3.3.He I linesThe He Iλ5876˚A lines are displayed in Fig.D.7.They appear in all four varieties of profile types.However,only one star exhibits a clear P Cyg profile of type1,namely MWC300.In CPD−57◦2874an emission component seems to partlyfill in the absorption component.Two stars show split type3profiles andfive stars single-peaked emission profiles.Six stars show an absorption line.For four stars no observation of He Iλ5876˚A were obtained.In MWC137strong variability was found be-tween1987and2002.The He I line changed from absorption to emission(cf.Sect.C.3).3.4.SummaryAn important result of the observations presented here is the detection of one or more double-peaked emission lines in many objects(cf.Table5).Actually,15,possibly16,of the18objects show at least one line with a double-peaked profile.This profile type is found for both,permitted and forbidden lines,but not necessarily for each line of a particular star.Eleven of the18 objects have split Hαprofiles.Split forbidden lines are found in13objects.Twelve stars exhibit split[O I]lines.The frac-tion of split lines of[N II]and[Fe II]is smaller.Only8of18 stars exhibit split[N II]lines,and5of17stars have split[Fe II] lines.There are only2cases where Hαis double-peaked, but all forbidden lines are single-peaked emission lines.These are HD87643and MWC300.According to Oudmaijer et al. (1998),and Wolf&Stahl(1985and Winkler&Wolf(1989), respectively,they belong to the B[e]supergiants and are most likely viewed under intermediate to pole-on inclination angles. Note,however,that the nature of these stars still is controver-sially discussed(see also Sect.C.5).A remarkable feature of the double-peaked profiles is that most,i.e.,∼85%,of the observed lines have an intensity ratio of the violet to red component of V/R≤1.Of the43detected type3lines only8show a V/R ratio larger than1.These are 6of26forbidden,and2of16permitted lines(cf.Table A.1). The latter are all Fe II lines.4.Density conditions in the forbidden-lineforming zoneThe interpretation of the observed line profiles might be com-plicated by the fact that the sample of B[e]-type stars is not ho-mogeneous with respect to the intrinsic object characteristics. The discussion by Lamers et al.(1998)showed that the con-nection between the different classes of B[e]-type stars is the10 F.-J.Zickgraf:Circumstellar environments of galactic B[e]-type starsuniformity of the B[e]phenomenon which calls for invoking a common cause for its occurence in different environments.In the following we will therefore take the view of looking primar-ily at the B[e]phenomenon itself rather than at specific object classes.The forbidden-lines in the spectra of B[e]-type stars are dominated by lines of low-excitation ions of neutral or singly ionized metals.Higher excitation lines like [S III ]are rare.This indicates that the temperaturein thelineemittingregion is about 104K (Lamers et al.1998).The forbidden lines probe the outer low-density zone of the line formation region.A measure for the maximum density in this region is the critical density,N cr ,for which downward collisional and radiative rates are equal.In the approximation of a 2-level ion with upper level u and lower level l it is given by N cr =A ulΩ(u,l )T2(2)with the collision strength Ω(u,l ),the statistical weight g u andthe electron temperature T .According to Viotti (1976)Ω(u,l )is given byΩ(u,l )≈0.2λ4g u A ul(3)with the wavelength λin microns.For [Fe II ](14F)λ7155˚Athis leads to N cr ≃2.2108cm −3for T e =104K.The critical den-sities are summarized in Table 6.Table 6.Critical densities,N cr ,of the observed forbidden lines for an electron temperature of T e =104K,and total ion-ization energies,χ,for the production of the respective ion (Cox 2000).The last line gives D 0=N 0/N cr for a density N 0=1011cm −3at r =1R ⋆.ion [O I ][Fe II ][N II ][S III ]lineλ6300˚Aλ7155˚Aλ6583˚Aλ6312˚AThe forbidden lines not only differ with respect to the crit-ical density but also have different ionisation potentials.Theionisation energy necessary to form Fe II is 7.9eV .For N II an energy of 14.53eV is required.With χ=33.70eV S III has the highest ionisation energy of the observed forbidden lines.Hence,the forbidden lines probe a density interval of about three orders of magnitude,∼105-108cm −3,and a range of ionisation from neutral,[O I ],to [S III ]with an ionisation po-tential of ∼34eV .5.Disk wind:radial expansion vs.rotationA spherically symmetric and radially expanding wind is ex-pected to form flat-topped profiles if the lines are optically thin.This has already been shown by Beals (1931).The forbidden lines in particular form at large distances from the central star where the wind has reached the terminal velocity (see below).A constant velocity wind is expected to form box-shaped lines if the emissivity is constant throughout the emitting volume.In the observed sample of B[e]-type stars there is just one case,CPD −57◦2874,where a line profile comes close to flat-topped,however not box-shaped.This is the line [O I ]λ6300of this object.The vast majority of the observed profiles are clearly different from flat-topped and therefore are inconsis-tent with a spherically symmetric and optically thin line for-mation region.Deviations from flat-topped profiles could be produced in the case of spherical symmetry by additional ex-tinction due to dust distributed evenly throughout the line for-mation region.This has been discussed e.g by Appenzeller et al.(1984)for T Tauri stars.However,the profile shape expected for this configuration is not observed in any of the B[e]-type stars of the sample presented here.The polarimetric observa-tions and the forbidden line profiles therefore strongly indicate that the B[e]phenomenon is correlated with an anisotropic dis-tribution of the circumstellar matter.Split profiles of H αsimilar to those shown in Fig.1are fre-quently found in classical Be stars,although the H αequivalent widths in these stars are usually much smaller than in B[e]-type stars and the underlying photospheric absorption component is often discernible.The double-peaked Be star profiles are gener-ally assigned to a disk-like geometry of the line forming region in connection with rotation.Mihalas &Conti (1980)discussed the formation of Beals type III,i.e.type 3,line profiles in the context of the combi-nation of rotation and expansion in a disk-like circumstellar environment.Adding expansion could in particular explain the blueshifted absorption components of H αand the V/R ratios smaller than 1.It would introduce an asymmetry of the line profiles by shifting the central reversals towards shorter wave-lengths as observed for most B[e]-type stars.For the forbidden lines,however,this mechanism would not work because the lines are optically thin and therefore absorption does not con-tribute.Nevertheless,the combination of expansion and rota-tion could at least explain the observed double-peaked profiles of H α.The double-peaked profiles of the optically thin lines could quite naturally be produced in rotating disks as shown e.g.by P¨o llitsch (1981).Keplerian disks could for example ex-ist around binary B[e]stars (see Sect.1).The profiles calcu-lated by P¨o llitsch display,however,two emission peaks withV/R=1due to the axial symmetry.Profiles of this type found only in a few cases,e.g.[S III]of MWC349A,[N II] CPD−57◦2874,[N II]and[Fe II]of MWC939,and[O I] CD−24◦5721and CPD−57◦2874.However,the majority double-peak lines has V/R<1including other lines of mentioned stars.It is therefore not obvious that rotation is likely explanation for the double-peaked profiles.Rather, line profiles seem to be determined by radial outflow.Let us assume as an example a disk-like configurationa rotational velocity v0at1R⋆of v0=300km s−1and constant radial expansion velocity of v exp.Angulartum conservation requires v rot(r)=v0R⋆/r.Hence at distance of10R⋆the rotation velocity would have droppedures the solid line designates a ratio of line widths of1.The observed line widths may help to better understand the possible role of expansion and rotation.In a disk-like circum-stellar environment in which rotation dominates over expansion the forbidden lines are expected to be narrower than the permit-ted lines because the rotational velocity decreases outwards.If rotation is negligible compared to the expansion velocity of a wind accelerated outwards the forbidden lines should have a larger width than the permitted lines.The latter are formed in the accelerating inner wind zone.The forbidden lines originate at large distance from the star where the wind has reached the terminal velocity.In Figs.5and6the FWHM of[O I]λ6300˚A is plotted ver-sus the FWHM of Hαand He I,respectively.They clearly showThe comparison of the line widths of the forbidden lines shown in Fig.7reveals a correlation which is consistent with the assumption that the velocity in the line forming region is constant,and hence that rotation is not important far from the central star.With few exceptions the[O I]line is approx-imately as broad as the[Fe II]line.For[N II]the result is similar,however,with larger scatter.The comparison of[N II] and[Fe II]displayed in the lower left panel of Fig.7shows four stars with broader[Fe II]than[N II].Note that in two of these cases,MWC137and MWC1055,the lines are very weak and the line widths are uncertain.Only Hen485and CPD−57◦2874show significantly broader[Fe II]than[N II]. The general trend is towards equal widths or smaller widths for[Fe II].The comparison with[S III]is not meaningful and therefore not shown because only three stars exhibit this line, i.e.MWC17,MWC137,and MWC349A.Inspecting the line。