DEFORMATION OF SOFT COLLOIDAL CRYSTALLINE STRUCTURE - THEORETICAL CONSIDERATIONS AND EXPERIMENTAL EVIDENCES BY SYNCHROTRON SMALL-ANGLE X-RAY SCATTERING ON TENSILE STRETCHED POLYMERIC LATEX FILM

Films obtained via drying a polymeric latex dispersion are normally colloidal crystalline where latex particles are packed into a face centered cubic (fcc) structure. Different from conventional atomic crystallites or hard sphere colloidal crystallites, the crystalline structure of these films is normally deformable due to the low glass transition temperature of the latex particles. Upon tensile deformation, depending on the drawing direction with respect to the normal of specific crystallographic plane, one observes different crystalline structural changes. Three typical situations where crystallographic c-axis, body diagonal or face diagonal of the fcc structure of the colloidal crystallites being parallel to the stretching direction were investigated.

Theoretical and experimental research on time-optimal trajectory planning and control of industrial robots

提出了一种用于工业机器人时间最优轨迹规划及轨迹控制的新方法，它可以确保在关节位移、速度、加速度以及二阶加速度边界值的约束下，机器人手部沿笛卡尔空间中规定路径运动的时间阳短。在这种方法中，所规划的关节轨迹都采用二次多项式加余弦函数的形式，不仅可以保证各关节运动的位移、速度 、加速度连续而且还可以保证各关节运动的二阶加速度连续。采用这种方法，既可以提高机器人的工作效率又可以延长机器人的工作寿命以PUMA560机器人为对象进行了计算机仿真和机器人实验，结果表明这种方法是正确的有效的。它为工业机器人在非线性运动学约束条件下的时间最优轨迹规划及控制问题提供了一种较好的解决方案。

Unsteady Model of Drop Marangoni Migration in Microgravity

The experiments of drop Marangoni migration have been performed by the drop shift facility of short period of 4.5 s, and the drop accelerates gradually to an asymptotic velocity during the free fall. The unsteady and axisymmetric model is developed to study the drop migration for the case of moderate Reynolds number Re = O(1), and the results are compared with the experimental ones in the present paper. Both numerical and experimental results show that the migration velocity for moderate Reynolds number is several times smaller than that given by the linear YGB theory.

Equivalent Model Of Expansion Of Cement Mortar Under Sulphate Erosion

The expansion property of cement mortar under the attack of sulfate ions is studied by experimental and theoretical methods. First, cement mortars are fabricated with the ratio of water to cement of 0.4, 0.6, and 0.8. Secondly, the expansion of specimen immerged in sulphate solution is measured at different times. Thirdly, a theoretical model of expansion of cement mortar under sulphate erosion is suggested by virtue of represent volume element method. In this model, the damage evolution due to the interaction between delayed ettringite and cement mortar is taken into account. Finally, the numerical calculation is performed. The numerical and experimental results indicate that the model perfectly describes the expansion of the cement mortar.

蒸发液层对流稳定性理论与实验研究进展

综述了蒸发液层稳定性理论分析和蒸发对流实验研究方面的最新进展．首先回顾历史上经典的单层流Marangoni不稳定性分析．利用经典的单层流模型可以很好解释无蒸发液层的稳定性特性，但是由于经典的单层流模型没有考虑蒸汽层与液层之间的动力学耦合关系，所以不能完全解释蒸发液层的Marangoni不稳定性特性．有的学者建立了考虑蒸汽层与液层的热耦合与动力学耦合关系的两层流模型，并采用了界面温度连续这样的假设．而在实验的观测中，蒸发界面处的温度是不连续的，特别是在蒸发量比较大的情况下，汽／液界面处温度跳跃很明显．由于界面温度连续假设在处于非平衡状态的系统中是不成立的，所以这些模型虽然能给出一些新的有关系统稳定性的特性，但还是不能完全解释蒸发液层的Marangoni不稳定性的特性，特别是为什么从底部冷却液层的时候，在实验中仍然能够观察到Marangoni对流涡胞的出现的原因．本文总结了前人的研究成果，同时给出了蒸发系统的动力学建模过程和实验研究方法，并对各种模型的稳定性特性进行了总结．最后，指出了现有理论中存在的问题和有待进一步研究的问题．

EQUIVALENT MODEL OF EXPANSION OF CEMENT MORTAR UNDER SULPHATE EROSION

The expansion property of cement mortar under the attack of sulfate ions is studied by experimental and theoretical methods. First, cement mortars are fabricated with the ratio of water to cement of 0.4, 0.6, and 0.8. Secondly, the expansion of specimen immerged in sulphate solution is measured at different times. Thirdly, a theoretical model of expansion of cement mortar under sulphate erosion is suggested by virtue of represent volume element method. In this model, the damage evolution due to the interaction between delayed ettringite and cement mortar is taken into account. Finally, the numerical calculation is performed. The numerical and experimental results indicate that the model perfectly describes the expansion of the cement mortar.

Optimized phase pupil masks for extended depths of field

By properly designing a phase pupil mask to modulate or encode the optical images and then digitally restoring them, one can greatly extend the depth of field and improve image quality. The original works done by Dowski and Cathey introduce the use of a cubic phase pupil mask to extend the depth of field. The theoretical and experimental researches all verified its effectiveness. In this paper, we suggest the use of an exponential phase pupil mask to extend the depth of field. This phase mask has two variable parameters for designing to control the shape of the mask so as to modulate the wave-front more flexible. We employ an optimization procedure based on the Fisher information metric to obtain the optimum values of the parameters for the exponential and the cubic masks, respectively. A series of performance comparisons between these two optimized phase masks in extending the depth of field are then done. The results show that the exponential phase mask provide slight advantage to the cubic one in several aspects. (c) 2006 Elsevier B.V. All rights reserved.

Thermally induced evolution of phase transformations in gas hydrate sediment

Thermally induced evolution of phase transformations is a basic physical-chemical process in the dissociation of gas hydrate in sediment (GHS). Heat transfer leads to the weakening of the bed soil and the simultaneous establishment of a time varying stress field accompanied by seepage of fluids and deformation of the soil. As a consequence, ground failure could occur causing engineering damage or/and environmental disaster. This paper presents a simplified analysis of the thermal process by assuming that thermal conduction can be decoupled from the flow and deformation process. It is further assumed that phase transformations take place instantaneously. Analytical and numerical results are given for several examples of simplified geometry. Experiments using Tetra-hydro-furan hydrate sediments were carried out in our laboratory to check the theory. By comparison, the theoretical, numerical and experimental results on the evolution of dissociation fronts and temperature in the sediment are found to be in good agreement.

问题之间共性关系的意识水平对平面几何解题迁移的影响

Transfer of learning is one of the major concepts in educational psychology. As cognitive psychology develops, many researchers have found that transfer plays an important part in problem solving, and the awareness of the similarity of related problems is important in transfer. So they become more interested in researching the problem of transfer. But in the literature of transfer research, it has been found that many researchers do not hold identical conclusions about the influence of awareness of related problems during problem solving transfer. This dissertation is written on the basic of much of sub-research work, such as looking up literature concerning transfer of problem solving research, comparing the results of research work done recently and experimental researches. The author of this dissertation takes middle school students as subjects, geometry as materials, and adopts factorial design in his experiments. The influence of awareness of related problems on problem solving transfer is examined from three dimensions which are the degree of difficulty of transfer problems, the level of awareness of related problems and the characteristics of subjects themselves. Five conclusions have been made after the experimental research: (1) During the process of geometry problem solving, the level of awareness of related problems is one of the major factors that influence the effect of problem solving transfer. (2) Either more difficult or more easy of the transfer problems will hinder the influence of awareness of related problems during problem solving transfer, and the degree of difficulty of the transfer problems have interactions with the level of awareness of related problems in affecting transfer. (3) During geometry problems solving transfer, the level of awareness of related problems has interactions with the degree of student achievement. Compared with the students who have lower achievement, the influence of the level of the awareness is bigger in the students who have higher achievement. (4) There is positive correlation between geometry achievement and reasoning ability of the middle school students. The student who has higher reasoning ability has higher geometry achievement, while the level of awareness is raised, the transfer achievement of both can be raised significantly. (5) There is positive correlation between geometry achievement and cognitive style of the middle school students. The student who has independent field tendency of cognitive style has higher geometry achievement, while the level of awareness is raised, the transfer achievement of both can be raised significantly. At the end of the dissertation, the researcher offers two proposals concerning Geometry teaching on the basis of the research findings.

Numerical Simulation of Pulsed Liquid Fluidized Bed and Its Experimental Validation

The pulsed liquid fluidized bed was studied using numerical simulation and experimental methods, The area-averaged two-fluid model (TFM) was used to simulate the pulsed fluidization. The bed expansion and collapse processes were simulated first and the phenomena obtained from the calculation were consistent with our previous experiments and observations. In the pulsed fluidization, the variation of bed height, the variations of particle velocity and concentration distribution were obtained and analyzed. Experiments were carried out to validate the simulation results. The pressure variation with time at different locations was measured using pressure transducers and compared with the simulated results. The variations of bed height and particle concentration distribution were recorded using a digital video camera recorder. The results were consistent with the simulation results as a whole.

The Experimental and Numerical Studies on Gas Production from Hydrate Reservoir by Depressurization

A set of experimental system to study hydrate dissociation in porous media is built and some experiments on hydrate dissociation by depressurization are carried out. A mathematical model is developed to simulate the hydrate dissociation by depressurization in hydrate-bearing porous media. The model can be used to analyze the effects of the flow of multiphase fluids, the kinetic process and endothermic process of hydrate dissociation, ice-water phase equilibrium, the variation of permeability, convection and conduction on the hydrate dissociation, and gas and water productions. The numerical results agree well with the experimental results, which validate our mathematical model. For a 3-D hydrate reservoir of Class 3, the evolutions of pressure, temperature, and saturations are elucidated and the effects of some main parameters on gas and water rates are analyzed. Numerical results show that gas can be produced effectively from hydrate reservoir in the first stage of depressurization. Then, methods such as thermal stimulation or inhibitor injection should be considered due to the energy deficiency of formation energy. The numerical results for 3-D hydrate reservoir of Class 1 show that the overlying gas hydrate zone can apparently enhance gas rate and prolong life span of gas reservoir.

Domain decomposition hybrid method for numerical simulation of bluff body flows:theoretical model and application

The discrete vortex method is not capable of precisely predicting the bluff body flow separation and the fine structure of flow field in the vicinity of the body surface. In order to make a theoretical improvement over the method and to reduce the difficulty in finite-difference solution of N-S equations at high Reynolds number, in the present paper, we suggest a new numerical simulation model and a theoretical method for domain decomposition hybrid combination of finite-difference method and vortex method. Specifically, the full flow. field is decomposed into two domains. In the region of O(R) near the body surface (R is the characteristic dimension of body), we use the finite-difference method to solve the N-S equations and in the exterior domain, we take the Lagrange-Euler vortex method. The connection and coupling conditions for flow in the two domains are established. The specific numerical scheme of this theoretical model is given. As a preliminary application, some numerical simulations for flows at Re=100 and Re-1000 about a circular cylinder are made, and compared with the finite-difference solution of N-S equations for full flow field and experimental results, and the stability of the solution against the change of the interface between the two domains is examined. The results show that the method of the present paper has the advantage of finite-difference solution for N-S equations in precisely predicting the fine structure of flow field, as well as the advantage of vortex method in efficiently computing the global characteristics of the separated flow. It saves computer time and reduces the amount of computation, as compared with pure N-S equation solution. The present method can be used for numerical simulation of bluff body flow at high Reynolds number and would exhibit even greater merit in that case.

Dynamic damage and failure in viscoplastic materials

In this paper, a dynamic damage model in ductile solids under the application of a dynamic mean tensile stress is developed. The proposed model considers void nucleation and growth as parts of the damage process under intense dynamic loading (strain rates epsilon greater than or equal to 10(3) s(-1)). The evolution equation of the ductile void has the closed form, in which work-hardening behavior, rate-dependent contribution and inertial effects are taken into account. Meanwhile, a plate impact test is performed for simulating the dynamic fracture process in LY12 aluminum alloy. The damage model is incorporated in a hydrodynamic computer code, to simulate the first few stress reverberations in the target as it spalls and postimpact porosity in the specimen. Fair agreement between computed and experimental results is obtained. Numerical analysis shows that the influence of inertial resistance on the initial void growth in the case of high loading rate can not be neglected. It is also indicated that the dynamic growth of voids is highly sensitive to the strain rates.