球形容器角变形及其局部应力的一个理论分析

本文利用解析方法，建立了球形容器角变形的一些几何关系式与局部应力的分析表达式；求得了一个简明而且实用的应力集中系数公式，表明应力集中不仅依赖于角变形量，而且随径厚比的平方根的增加而增加。     

Preliminaries to the body-cover theory of pitch control

Preliminary theoretical and empirical work suggest that increased thyroarytenoid muscle activity may either increase or decrease fundamental frequency, depending on cricothyroid muscle activity and a new cross-sectional area parameter. This parameter is defined as the ratio of muscular tissue in vibration to total tissue in vibration. Canine laryngeal nerves were stimulated to measure vocal-fold length changes. These data, combined with previously reported tissue density, passive stress, and passive frequency data, were used to construct a set of curves predicting canine fundamental frequency from thyroarytenoid and cricothyroid muscle activity and the area ratio. The results suggest that high cricothyroid muscle activity and small area ratios tend to cause fundamental frequency lowering with increased thyroarytenoid muscle activity.     

On the use of acoustic birefringence to determine components of plane stress

To assess the integrity of a structure containing a (known) flaw, it is necessary to know the stresses acting on the flaw. Many common structural elements (e.g. beams and plates) are subjected to either true plane stress or generalized plane stress. For either of these cases, there are three in-plane stresses (one shear stress and two normal stresses) to be determined in general.In this paper, we consider the application of the acoustic birefringence method to generalized plane stress states, where the thickness-averaged values of the shear and normal stresses are sought. It is shown that the times-of-flight are thickness-averaged effects, whereas the polarization directions depend upon local values of stress. Consequently, when the symmetric (axial) component of the stresses dominates the antisymmetric (bending) component, the acoustic birefringence method can be used to determine all three stresses, if the boundary conditions are known. For unknown boundary conditions, the normal stresses can be determined to within arbitrary functions.Problems arise in using the normal incidence technique when either the shear stress vanishes, or the symmetric (membrane) components of generalized plane stress do not dominate the bending components. In the former case, the thickness-averaged difference in normal stresses can be obtained, provided that the birefringence in the unstressed state is known. In the latter case, the (averaged) difference in normal stresses can be obtained by measuring time-of-flight differences of off-axis SH-waves propagating in the planes of material symmetry of the plate.     

Protection of mitochondrial integrity from oxidative stress by selenium-containing glutathione transferase

The antioxidant activity of a novel artificial glutathione peroxidase-like enzyme, selenium-containing glutathione 5-transferase from Lucilia cuprina (seleno-LuGST1-1), was studied by using a ferrous sulfate/ascorbate-induced mitochondrial damage model system. Swelling of mitochondria, lipid peroxidation, and cytochrome-c oxidase activity were selected to evaluate the preservation of mitochondrial integrity in this system. Seleno-LuGST1-1 could effectively protect the mitochondria against oxidative damage in a dose-dependent manner and exhibited both higher catalytic activity and greater antioxidant ability than the classic mimic, 2-phenyl-1,2-benziososelenazol-3(2H)-one (Ebselen). This novel artificial biocatalyst therefore may have great protential for pharmacologic application in the treatment of reactive oxygen species-related diseases.     

Rheologische Eigenschaften gesunder Synovialflüssigkeiten

Zusammenfassung Die rheologischen Eigenschaften gesunder menschlicher Gelenksflüssigkeiten im Geschwindigkeitsgefällebereich vonD = 10^–3-10³ s^–1 wurden untersucht. Es wurden die Scherviskosität und die erste Normalspannungsdifferenz gemessen. Gesunde Synovialflüssigkeiten besitzen hohe Anfangsviskosität (~40 Pa · s) und zeigen eine starke Abhängigkeit vom Geschwindigkeitsgefälle. Der SchermodulG ist im Gegensatz zu pathologischen Proben niedrig und über weite Bereiche konstant. Die längsten Relaxationszeiten betragen 5–10 s. Die kritische Konzentration, bei der Netzwerkbildung einsetzt, beträgt 0,75 10^–3 g/ml. Die Proben lassen sich zu einer Masterkurve vereinigen, die als verallgemeinertes Fließgesetz für gesunde Synovia aufgefaßt werden kann. Eine Untersuchung über die zeitliche Abhängigkeit der post-mortem-Synovia zeigt, daß innerhalb von 12 Stunden keine nennenswerten Veränderungen eintreten.

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The rheology of healthy human synovial fluids has been investigated at a shear-rate between 10^–3-10³ s^–1. Shear viscosity and first normal-stress difference were measured. Healthy synovial fluids show high zero-shear viscosity (about 40 Pa · s) and a strong shear rate dependence. The modulusG is constant over a large range, in contrast to pathological samples. The longest relaxation times are 5–10 s. The critical concentrationc _cr , at which entanglement occurs is about 0.75 10^–3 g/ml. The samples can be represented by a master-curve, which may be regarded as the constitutive equation of healthy synovial fluids. An investigation of the time dependency of synovial fluids indicated no changes within 12 hours post mortem.

Herrn Prof. Dr. DDr. h. c. O. Kratky zum 80. Geburtstag mit den besten Wünschen gewidmet.     

螺栓材料应力与声速、温度关系的测定

基于应力－超声波速度关系方法已用于螺栓轴向应力的测量。而声速与被测材料的许多物理因素有关，如弹性模量，密度与温度。本文介绍了用于分析超声波速度－应力－温度三者关系的实验与计算方法，并给出了三种金属材料的结果。检测的质量。     

Analysis of Digital Lateral Shearing Interferometer

A new method is proposed for reconstructing wavefront from discretely sampled interferogram data obtained by a digital lateral shearing interferometer. Assumptions applied in the conventional methods are not used and reconstruction error caused by the difference between the amount of shear and the sampling interval can be removed. System error and the influence of the discrete sampling, which limit accuracy of the tested results of the lateral shearing interferometer, are analyzed.     

Stress in aerogel during depressurization of autoclave: II. Silica gels

Although supercritical drying avoids the capillary stresses that tend to warp and crack xerogels, there are other sources of stress that interfere with the preparation of monolithic aerogels. In this paper, we present experimental results showing that there is a limit to the rate at which the pressure can be released from the autoclave without causing cracking, and that the maximum rate decreases as the gel size increases. Using an analysis developed in a companion paper, the stresses generated during depressurization are compared to the modulus of rupture of our aerogels. The calculations require knowledge of the pressure-dependence of the density of the vapor (ethanol, in our experiments), as well as the permeability and modulus of the gel network. Measurements of those properties were performed on a series of silica gels made under basic and neutral conditions. We find that the calculated stresses are large enough to account for the cracking of our gels at high rates of depressurization; moreover, the predicted dependence of stress on gel diameter is in agreement with experiment.     

复合材料中加捻纤维束的预应力效应

利用加捻纤维束的力学性能,可以制成预应力复合材料.在不受外力的情况下,这种复合材料的基体受压应力的控制.当有拉伸力作用的时候,材料所受的拉应力值会大大减少,这样,利用这种现象可以提高纤维增强复合材料的抗拉强度.本文将分析连续的加捻纤维束受拉状况并考虑到材料固化后产生的残余应力的影响.这种方法所产生的预应力取决于纤维束的加捻程度.本文将给出计算这种预应力的方法,而且还提供加捻纤维束产生预应力的光弹测试结果以及这种纤维预应力复合材料的纤维破坏的特征.