从构件本体强度失效看其强度计算

构件强度失效 (破坏 )的形式 (流动或断裂 )与材料的力学性质、应力状态有关 .在构件的失效 (破坏 )形式 (或强度计算 )中 ,把材料分为塑性材料和脆性材料应理解为材料处于塑性状态和脆性状态 .为此 ,按照可能发生的失效 (破坏 )形式来选择适宜的强度理论进行计算 .     

Species-diversified plant cover enhances orchard ecosystem resistance to climatic stress and soil erosion in subtropical hillside

Naturally occurring plants in agroecosystem evidently play an important role in ecosystem stability. Field studies on the ecological effects of native plants conserved in orchard and their resistance to adverse climatic stress, and soil erosion were conducted from 1998 to 2001 in a newly developed Changshan-huyou (Citrus changshan-huyou Y.B. Chang) orchard. The experimental area covered 150 ha in typical red soil hilly region in southeastern China. The experimental design was a randomized complete block with six combinations of twelve plant species with four replications. All species used were native in the orchard. Plots were 15×8 m2 and separated by 2 m buffer strips. Precipitation, soil erosion in rainstorm days and aboveground biomass of plant community when rainstorm days ended, soil temperature and moisture under various plant covers during seasonal megathermal drought period, antiscourability of soil with different root density under various simulated rainfalls were measured. Plant cover signifi     

Investigation of stressful life events in patients with systemic sclerosis

Objective: To assess the occurrence of stressful life events in the year before the initiation of systemic sclerosis. Methods: A consecutive series of 40 patients with systemic sclerosis (mean age (56.3~ 11.9) years, mean disease duration (4.3±3.1) years; 32 females and 8 males), including 28 with diffuse cutaneous scleroderma and 12 with limited cutaneous scleroderma, were evaluated. A control group of 40 healthy subjects free of systemic sclerosis also was included. Socioeconomic status was inves-tigated and Paykel's interview for recent life events (a semi-structured research interview covering 64 life events) was conducted. Results: Patients with systemic sclerosis showed higher percentages of lower education (72.5%) and working class (82.5%), and reported more stressful life events (P＜0.05), such as exits (P＜0.05), undesirable events (P＜0.01), and uncontrolled events (P＜0.001), when compared with the control. More events that had an objective negative impact (P＜0.001) were also reported in systemic sclerosis patients than in the control. These results are in accordance with a muitifactorial model of pathogenesis in systemic sclerosis. Conclusion: We reported a strong relationship between stressful life events and the initiation of systemic sclerosis. Our findings are consistent with current understanding of the extensive links of behavioral responses to stress with neurophysiological and biochemical processes.     

混凝土坝裂纹扩展算法(英文)

混凝土建筑物中的裂纹扩展追踪计算是确定结构安全度的重要手段。本文提出用虚拟裂纹单元及断裂力学准则(应变强度因子)追踪和模拟裂缝初始断裂、扩展并最终导致破坏的过程,给出一条逐段扩展的裂纹线,本方法计算结果与某些混凝土坝实测资料及模型试验结果吻合较好。     

高等职业教育德育课教学改革探讨

高等职业教育思想政治素质是最重要的素质，每位“德育”教师在了解教育对象的同时，应强调“知能统一”，“知情和谐”，注重“知能并重”，“符合需求”，做到因材施教，要认真研究，改进考试内容和形式，使其适应新的教育理念的要求。     

紧缩蛋白和免疫反应

紧缩蛋白既介导细胞的感染和转化,也介导对已感染细胞和转化细胞的紧缩反应。紧缩蛋白在机体的免疫反应中起着十分重要的作用。     

高职教师职业压力调查及建议——以湖北职业技术学院为例

以高职教师作为被试,采用分层随机抽样方式对其职业压力状况进行调查和分析,以期为高职院校树立“以人为本”的现代管理理念、营造“人本化”环境、实施科学管理提供参考和建议。     

A first order system model of fracture healing

A first order system model is proposed for simulating the influence of stress stimulation on fracture strength during fracture healing. To validate the model, the diaphyses of bilateral tibiae in 70 New Zealand rabbits were osteotomized and fixed with rigid plates and stress-relaxation plates, respectively. Stress shielding rate and ultimate bending strength of the healing bone were measured at 2 to 48 weeks postoperatively. Ratios of stress stimulation and fracture strength of the healing bone to those of intact bone were taken as the system input and output. The assumed first order system model can approximate the experimental data on fracture strength from the input of stress stimulation over time, both for the rigid plate group and the stress-relaxation plate group, with different system parameters of time constant and gain. The fitting curve indicates that the effect of mechanical stimulus occurs mainly in late stages of healing. First order system can model the stress adaptation process of fracture healing. This approach presents a simple bio-mathematical model of the relationship between stress stimulation and fracture strength, and has the potential to optimize planning of functional exercises and conduct parametric studies. Project (No. 39470698) supported by the National Natural Science Foundation of China     

‘Always ready and always well’: Exploring stress on school principals in Chile

Educational systems worldwide have increased the responsibilities and tasks of principals, seeking to improve schools’ performance. As a result, the role of principals has become increasingly challenging and stressful, having a negative impact on principals’ attraction and retention, job satisfaction as well as their mental and physical health. This paper explores how a group of 21 Chilean school principals working in the Valparaiso Region experience stress, based on individual semi-structured interviews about their subjective experiences in their role. Findings suggest that principals consider their work to be challenging, associated with several demanding situations in their schools which contribute to feeling stress. Stressors identified by principals can be organized into three groups: work-related, such as dealing with bureaucratic pressures and lack of support from municipal authorities; relationship-related, such as managing relations with a wide range of school actors and the emotional burden of interacting with them; and time-related, such as being always available to solve problems and feeling isolated in this task.     

Stress among higher education students: towards a research agenda

This article has two primary aims. Firstly, it provides a critical review of previous studies into student stress and identifies several important issues that, as yet, have not been explored. There has been no consideration of the effect of students maturing during their studies on the stress that they experience and how they cope with that stress. Secondly, the article highlights limitations in the past and present literature base, where there has been a concentration on a quantitative approach, and focus on a narrow range of subject groups. There is also a need to undertake longitudinal research to investigate individuals’ stress experiences during the period they study at university. Overall the key assertion here is that thus far research into student stress has not offered a complete account and explanation of students’ stress experiences.