Correlating the internal length in strain gradient plasticity theory with the microstructure of material

The internal length is the governing parameter in strain gradient theories which among other things have been used successfully to interpret size effects at the microscale. Physically, the internal length is supposed to be related with the microstructure of the material and evolves during the deformation. Based on Taylor hardening law, we propose a power-law relationship to describe the evolution of the variable internal length with strain. Then, the classical Fleck–Hutchinson strain gradient theory is extended with a strain-dependent internal length, and the generalized Fleck–Hutchinson theory is confirmed here, by comparing our model predictions to recent experimental data on tension and torsion of thin wires with varying diameter and grain size. Our work suggests that the internal length is a configuration-dependent parameter, closely related to dislocation characteristics and grain size, as well as sample geometry when this affects either the underlying microstructure or the ductility of the material.     

New experimental test of strain-gradient plasticity theory: metal foil sandwich structures in flexure

Experimental tests of strain-gradient plasticity theory rely on studies of the size effect (smaller is stronger) in micromechanical testing. The plastic strain gradient is varied by varying the size of the specimen. This confounds the direct effects of the size and the effects of the strain gradient. We propose experiments on foil sandwich structures in which these parameters are separated. Preliminary results suggest that it is the foil thickness that determines the strength, not the strain gradient.     

Psychological state and psychological strain in relation to infertility

The purpose of the study was to explore the relationship between psychological state and perceived strain in relation to fertility problems. Couples presenting at an infertility clinic completed, on two occasions seven months apart, a series of standardized measures to assess psychopathology. In addition, they completed a weekly diary rating their mood state or distress/strain over a period of 22 weeks, during which investigations and treatment were taking place. Little evidence of psychopathology was found in the sample; the weekly diaries also suggested a general lack of distress/strain, even in response to medical investigations and diagnosis. The results are discussed in the light of wide individual variations in ratings obtained from the diaries. Participants with high distress/strain scores tended to have significantly higher initial scores on the psychometric measures administered. Participants with high distress/strain scores were also more likely to show a further significant increase in distress/strain scores in relation to diagnostic information. It is argued that a task for future research is to determine the characteristics of those couples who are likely to experience difficulty in coping with the strain of infertility investigations so that counselling resources and support services can be most effectively targeted. © 1998 John Wiley & Sons, Ltd.     

Intrasession and intersession habituation in mice: From inbred strain variability to linkage analysis

When placed in a novel environment, mice tend to explore for a period of time, and then reduce the level of exploration. This reduction in locomotor or exploratory behavior is known as habituation and can occur within a single session or across sessions, respectively, termed intrasession and intersession habituation. Recent research indicates that there is a genetic component to habituation behavior and that some of the genes involved differ between the two types of habituation. The genetic evidence also suggests that intrasession habituation and intersession habituation are measuring somewhat different conceptual entities and with more such evidence may eventually help us understand the different pathways involved. Some of the genetic methods and tools used to unravel the roles of specific genes in both types of habituation are outlined here, with examples from the literature, as well as new data, to illustrate that this seemingly simple behavior is actually very complicated in terms of genetics. Evidence to date suggests that a number of genetic regions play roles in one or both types of habituation, and further research will be necessary to determine the specific genes involved.     

新世纪20年国内假设检验及其关联问题的方法学研究

新世纪20年来国内假设检验方法学研究内容可分为如下几类: 零假设显著性检验的不足、p值的使用问题、心理学研究的可重复性问题、效应量、检验力、等效性检验、其他与假设检验关联的研究。零假设显著性检验已经发展成一套组合流程: 为了保证检验力和节省成本, 实验研究需要做先验检验力分析预估样本容量, 但问卷超过160人在传统统计中就没有必要这样做。当拒绝零假设时, 应当结合效应量做出结论。当不拒绝零假设时, 需要报告后验检验力; 如果效应量中或大而检验力不够高, 则可增加被试再行分析, 但这一过程应主动披露, 报告最后的实际p值并对可能犯的第一类错误率做出评估。