Soviet and Japanese oversnow vehicles

The Soviet Union has an overwhelming need for oversnow and adverse terrain transport since by their own definition over 60% of their country is considered as Arctic. They have developed a wide range of configurations and types of vehicles to fit their production capabilities and needs. Their vehicles in general are not sophisticated but rather emphasize ease of maintenance and simplicity. Their research however is based on investigating even exotic vehicle configurations.

Japan on the other hand has limited its work to a small number of vehicles to fit their limited needs in the Northern Islands. Their research has been based mainly on the development and improvement of a snow/road track which can be used to meet their specialized military requirements.     

Thixotropy of greases and low-speed operation of rotational plastoviscometers and rolling bearings

Summary A typical property of greases, as plastic disperse systems, is their thixotropy (reversible destruction of their structure due to deformation). In relation to this, if the rate of their formation drops below a certain critical value it becomes practically very difficult or even impossible to attain steady conditions of their flow. This is observed both in rotational plastoviscometers and in rolling-contact bearings, and is manifested in more or less sharp fluctuations of the resistance moments. The critical value of the rate of deformation depends on the nature of the grease and the rigidity of the braking device or the power reserve of the drive, decreasing when these values are increased. When soap greases are deformed they become anisotropic, which, when the direction of deformation is changed, tells perceptibly on their resistance to deformation and results in fluctuations of the resistance moments in rolling bearings.     

The art of shock waves and their flowfields

The visualization of compressible flows is a mature science that has significantly contributed to many advances in fluid mechanics. Numerous visualization records have been generated, many of which are not only noteworthy for their physical content, but also for their aesthetic appeal. Images of shock waves and their flowfields, primarily obtained with density-sensitive visualization methods, not only provide valuable information about the physical mechanisms of flows, but often have the qualities of works of art. This paper reviews briefly the role of these visualizations in science and their possible position in an art environment, while trying to establish a little-explored link between the elements of compressible fluid dynamics and some features found in various works of art.      

混凝土抗折动强度及其极值研究

混凝土类不均匀脆性材料的率敏感性主要是由于混凝土的不均匀性造成的,不均匀性使得不同速率的动裂纹发展路径不同,决定了不同速率的抗折动强度不同。基于此,提出混凝土抗折动强度由砂浆与骨料的抗折静强度的加权平均值再加上惯性项组成的代数表达式,并预测混凝土材料在爆炸冲击荷载条件下的极限抗折动强度。最后通过特殊设计的单一菱形净浆骨料三点弯实验, 验证了不同加载速率时破坏裂纹的发展路径及抗折动强度变化规律。     

Fourier analysis and automated measurement of cell and fiber angular orientation distributions

This paper studies the application of the discrete Fourier transform (DFT) to predict angular orientation distributions from images of fibers and cells. Angular distributions of fibers in composites define their material properties. In biological tissues, cell and fiber orientation distributions are important since they define their mechanical properties and function.We developed a filtering scheme for the DFT to predict angular distributions accurately. The errors involved in this DFT technique and their sources were quantified through Monte Carlo simulation of computer-generated images. The knowledge of these errors allows one to verify the suitability of the method for a particular application. We found that the DFT method is most accurate for slender fibers, and propose a means to minimize errors by optimizing parameters. This method was applied to predict orientation distribution of cells and actin fibers in bio-artificial tissue constructs.     

Comparison of squeeze flow and vane rheometry for yield stress and viscous fluids

Two principal squeeze flow modes are investigated for yield stress and Newtonian materials squeezed by a constant force, F, between plates of equal or unequal diameters. In mode A, the material fills the space between the plates and is extruded at their periphery as their separation decreases. Experiments are described to measure the contribution to F from the extrudate. In mode B, all the material remains in contact with the planes of the plates as their separation decreases; there is no extrudate. The results of mode B experiments agree closely with the predictions of theory and give rheological parameters in fair agreement with those measured by the rotational vane method. The material properties and extrusion behaviour which complicate mode A experiments are discussed.     

Tricuspid Chordae Tendineae Mechanics: Insertion Site,Leaflet, and Size-Specific Analysis and Constitutive Modelling

Background: Tricuspid valve chordae tendineae play a vital role in our cardiovascular system. They function as “parachute cords” to the tricuspid leaflets to prevent prolapse during systole. However, in contrast to the tricuspid annulus and leaflets, the tricuspid chordae tendineae have received little attention. Few previous studies have described their mechanics and their structure-function relationship. Objective: In this study, we aimed to quantify the mechanics of tricuspid chordae tendineae based on their leaflet of origin, insertion site, and size. Methods: Specifically, we uniaxially stretched 53 tricuspid chordae tendineae from sheep and recorded their stress-strain behavior. We also analyzed the microstructure of the tricuspid chordae tendineae based on two-photon microscopy and histology. Finally, we compared eight different hyperelastic constitutive models and their ability to fit our data. Results: We found that tricuspid chordae tendineae are highly organized collageneous tissues, which are populated with cells throughout their thickness. In uniaxial stretching, this microstructure causes the classic J-shaped nonlinear stress-strain response known from other collageneous tissues. We found differences in stiffness between tricuspid chordae tendineae from the anterior, posterior, or septal leaflets only at small strains. Similarly, we found significant differences based on their insertion site or size also only at small strains. Of the models we fit to our data, we recommend the Ogden two-parameter model. This model fit the data excellently and required a minimal number of parameters. For future use, we identified and reported the Ogden material parameters for an average data set. Conclusion: The data presented in this study help to explain the mechanics and structure-function relationship of tricuspid chordae tendineae and provide a model recommendation (with parameters) for use in computational simulations of the tricuspid valve.

     

Consumer perspectives on genetic testing, research and services for ethnoculturally diverse populations

A panel of individuals from diverse ethnocultural backgrounds and representing a variety of genetic disorders presented their consumer perspectives on genetic programs, testing and services. Their remarks emphasized how misunderstanding and miscommunication between health care professionals and many of the populations for whom they provide services can lead to unfilled genetic service needs. Panelists recommended that health care professionals become more aware and knowledgeable about the diversity of customs, beliefs and cultures of those receiving their services. Only by building a foundation of trust and mutual respect will genetic testing, research and services become more accessible to individuals from diverse populations, their families and their communities.     

Self-adjustment mechanisms and their application for orthosis design

Medical orthoses aim at guiding anatomical joints along their natural trajectories while preventing pathological movements, especially in case of trauma or injuries. The motions that take place between bone surfaces have complex kinematics. These so-called arthrokinematic motions exhibit axes that move both in translation and rotation. Traditionally, orthoses are carefully adjusted and positioned such that their kinematics approximate the arthrokinematic movements as closely as possible in order to protect the joint. Adjustment procedures are typically long and tedious. We suggest in this paper another approach. We propose mechanisms having intrinsic self-aligning properties. They are designed such that their main axis self-adjusts with respect to the joint’s physiological axis during motion. When connected to a limb, their movement becomes homokinetic and they have the property of automatically minimizing internal stresses. The study is performed here in the planar case focusing on the most important component of the arthrokinematic motions of a knee joint.     

Hollow spherical titanium dioxide nanoparticles for energy and environmental applications

Hollow spherical titanium dioxide(TiO_2) nanoparticles possess unique properties toward energy and environmental applications,because of the intrinsic properties of TiO_2 and benefits induced by their hollow structure.A detailed understanding of TiO_2 hollow spheres will promote their use in sustainable energy and environmental applications.This perspective details current methods for synthesizing hollow spherical TiO_2 nanoparticles,and their performance in dye-sensitized solar cells,photocatalysts,and batteries.This perspective will promote the design and innovative thinking on the application of hollow spherical metal oxide nanoparticles.     

THE BOUNDED EXTERMINATION AND STABILITY OF MUTUAL INTERFERENCE SYSTEM OF FOUR－DIMENSIONAL SPECIES

ＴＨＥＢＯＵＮＤＥＤＥＸＴＥＲＭＩＮＡＴＩＯＮＡＮＤＳＴＡＢＩＬＩＴＹＯＦＭＵＴＵＡＬＩＮＴＥＲＦＥＲＥＮＣＥＳＹＳＴＥＭＯＦＦＯＵＲ－ＤＩＭＥＮＳＩＯＮＡＬＳＰＥＣＩＥＳＨｏｕＧａｎ－ｓｈｅｎｇ（侯赣生）（Ｄｅｐｌ．ｏｆＰｈｙｓｉｃｓ,Ｊｉａｎｇｘ...     

多尺度模拟与计算研究进展

简要介绍了多尺问题与研究方法.重点论述了两类常见多尺度问题的模拟计算方法与研究进展,分析了各自的优缺点和使用范围.对现有研究的局限性和存在的问题进行分析,指出了进一步研究多尺度模拟与计算的必要性.介绍了求解含有孤立缺陷问题的非局部准连续体法,MAAD等方法以及求解基于微观模型本构模拟问题的局部连续体法、HMM等方法.文章对多尺度模拟与计算的前景进行展望,提出了一些亟待解决的问题.     

Mechanical deformations of carbon nanorings: a study by molecular dynamics and nonlocal continuum mechanics

Understanding of the elastic deformation behaviours of recently synthesised carbon nanorings (CNRs) is crucial in guiding their future applications, because the strain engineering provides an efficient means to modify their physical and chemical properties. In this paper, by using molecular dynamics simulations and nonlocal continuum mechanics models, we study the elastic deformations of CNRs with three different molecular structures, i.e., cycloparaphenylenes (CPPs), [4]cyclochrysenylenes and cyclacenes. Our results show that, compared to other two types of CNRs, CPPs have the smallest mechanical stiffness, which is attributed to the influence of numerous weak connecting carbon–carbon bonds existing between their component benzene rings. In addition to the molecular structure, the elastic deformation behaviours of CNRs are also found to strongly depend on the size. Specifically, the compressive stiffness of CNRs is found to increase as their size (radius) decreases. Meanwhile, the size reduction of CNRs can trigger the anisotropy of their compressive stiffness and can also aggravate the influence of small-scale effects on their elastic deformation behaviours, which can significantly reduce the compressive stiffness.

     

On art,science, beauty and the experimentalist

Comments are made on the concepts of beauty and art, and their relationship with physical phenomena. Experimental physicists have means at their disposal to produce objects of art just as the painter uses oil and the sculptor uses marble to produce objects of art. Several new photographs of “log-art” or artistic science are shown.     

Assessment of family cancer history collection and utilization in patient care

OBJECTIVES: This study was conducted to determine whether patients and accompanying persons visiting the Gynecologic Oncology Clinic were aware if a family cancer history was recorded and utilized in their medical care; whether they were aware of the importance of a family cancer history, and whether they would like to learn more about familial cancer. METHODS: Sixteen- and 17-item self-report questionnaires were administered to patients and their accompanying persons, respectively, who were visiting the Gynecologic Oncology Clinic. All responses were anonymous. RESULTS: Two hundred forty-four patient questionnaires and 114 accompanying person questionnaires were completed. Seventy-eight percent of the patients and 70% of the accompanying persons replied that a physician had inquired about their family history of cancer. Only 40% of those patients and 70% of those accompanying persons (31 and 49% of total patients and accompanying persons, respectively) replied that the inquiry was by their family physician. Sixty-seven percent of these patients and 63% of these accompanying persons reported that a written record was made of the family history. Thirty-one percent of the patients and 28% of accompanying persons knew that their family cancer history information had been used to aid in their medical care. Eighty-eight percent of the patients and 83% of the accompanying persons reported the occurrence of at least one relative with cancer; however, only 44% of the patients and 35% of the accompanying persons replied that a health care provider had ever provided teaching about the importance of a family cancer history. Seventy-five percent of the patients and 73% of the accompanying persons indicated that they would like to learn more about hereditary cancer and cancer genetics. CONCLUSIONS: This study demonstrates that patients desire information about cancer genetics and hereditary cancer. Therefore, health care providers should provide better education and information to their patients as well as improve their family history-taking skills.     

Hollow spherical titanium dioxide nanoparticles for energy and environmental applications

Hollow spherical titanium dioxide (TiO₂) nanoparticles possess unique properties toward energy and environmental applications, because of the intrinsic properties of TiO₂ and benefits induced by their hollow structure. A detailed understanding of TiO₂ hollow spheres will promote their use in sustainable energy and environmental applications. This perspective details current methods for synthesizing hollow spherical TiO₂ nanoparticles, and their performance in dye-sensitized solar cells, photocatalysts, and batteries. This perspective will promote the design and innovative thinking on the application of hollow spherical metal oxide nanoparticles.     

On pressure and thermal flux in gas-mixture flows and in two-phase flows

To begin with, two different definitions of pressure, thermal flux, etc. in the diffusion model and two-fluid model are given. Then the physical interpretations of the pressure and the thermal flux are provided by introducing the momentum and energy fluxes,M and ε, through a surface dS in the flow field. The quantities defined in the diffusion model are suggested when the motion of the mixture is studied as a whole, while the quantities defined in the two-fluid model are suggested when the motion of individual species is studied. The collision pressure and thermal flux in dense gas-mixtures are also discussed in detail, i.e. their origin, their expressions in the momentum and energy equations, and their distinctions from the normal partial pressure and thermal flux. A gas-particle flow can be treated as a flow of dense gas-mixtures. The long-standing controversy whether the “inertial coupling term” should exist in the momentum equation can be clarified by the two different definitions of pressure.     

Shadow Waves: Entropies and Interactions for Delta and Singular Shocks

This paper deals with two key problems for delta (or singular) shock solutions to systems of conservation laws: that of their entropy admissibility conditions (which is connected to the notorious uniqueness problem) and that of their interaction. We choose to represent systems of conservation laws by nets of functions which are piecewise constant (or constant with respect only to the space variable), here called shadow waves. All the calculations can then be done on each element of such nets using only the usual Rankine–Hugoniot conditions. A 3 × 3 pressureless gas dynamics model is the main example in the paper.     

Bifurcations and Attractor-Repeller Splittings of Non-Saddle Sets

This paper is devoted to the study of some aspects of the stability theory of flows. In particular, we study Morse decompositions induced by non-saddle sets, including their corresponding Morse equations, attractor-repeller splittings of non-saddle sets and bifurcations originated by implosions of the basin of attraction of asymptotically stable fixed points. We also characterize the non-saddle sets of the plane in terms of the Euler characteristic of their region of influence.