点的应力分析常见错误及对策

本文对学生在<材料力学>应力状态这一章学习中出现的错误进行了专题讨论与剖析,并提出了相应的对策.     

Finite element simulation of stress intensity factors in elastic-plastic crack growth

INTRODUCTION The finite element method (FEM) has been widely employed for solving linear elastic and elas-tic-plastic fracture problems. The evaluation of stress intensity factors in 2D geometries by FEM is a tech-nique widely used for non-standard crack configura-tions. Basically, there are two groups of estimation methods, those based on field extrapolation near the crack tip (Chan et al., 1970; Shih et al., 1976) and those using the energy release when the crack propagates. However…     

Consequences of school grading systems on adolescent health: evidence from a Swedish school reform

ABSTRACT

Education reforms that entail increased emphasis on high-stakes testing, assessment and grading have spread across education systems in recent decades. Critics have argued that these policies could have consequences for stress, identity, self-esteem and the overall health of pupils. However, these potentially negative consequences have rarely been investigated in a systematic and rigorous way. In this study we use a major education reform in Sweden, which introduced grades and increased the use of testing for pupils in the 6^th and 7^th school year (aged 12 to 13 years), to study the consequences of grading and assessment for health outcomes. Using data from the Health Behaviours of School-Aged Children Survey, we find that the reform increased school-related stress and reduced the academic self-esteem of pupils in the 7^th school year. This, in turn, had an indirect effect on psychosomatic symptoms and life satisfaction for these pupils. Moreover, the negative effects of the reform were generally stronger for girls, thereby widening the already troubling gender differences in health. We conclude that accountability reforms aimed at increased use of testing, assessment and grading can potentially have negative side effects on pupils’ health.     

Unified expression for failure of reinforced concrete members in bridge

INTRODUCTION Reinforced concrete elements with box section are commonly used in horizontal subsystems and in vertical support of bridge structures. The horizontal structural members normally have box section and top flange. The vertical supports of the bridge usually have a box section also. To simplify the deduction of such structural member under combined forces, the box sections without top flange are discussed here. Fig.1 shows the typical section types of reinforced concrete members.…     

离心泵叶轮结构有限元分析

叶轮是泵的核心部分,泵的性能参数:流量、扬程、效率和特性曲线的形状等均与叶轮的设计有重要关系。通过对叶轮结构进行有限元分析,准确地得到了叶轮在载荷作用下的应力,为叶轮的强度计算提供了可靠依据。     

不同抗旱品种大豆苗中脯氨酸累积的差异

研究了干旱胁迫时不同抗旱性大豆品种苗中游离脯氨酸积累与大豆抗旱性的关系．结果表明，随着水分胁迫的加强，游离脯氨酸的累积显著增加，且抗旱性强的品种在干旱胁迫的前期游离脯氨酸累积量小于抗旱性弱的品种，但深度胁迫时其累积量则明显大于抗旱性弱的品种．脯氨酸的积累可作为大豆抗旱性的筛选指标．     

Survival responses to incest: Adolescents in crisis

Twenty-seven incest victims, aged 12-18, responded to their experiences with self-destructive behaviors such as substance abuse, suicide attempts, perfectionism, isolation, or depression in attempts to alleviate stress or assert some control over helplessness created by the incest. Therapy focused on the premise that such adolescent behaviors are logical and predictable survival responses rather than simply clues to sexual abuse. Treatment goals included establishing trust, helping the victim re-define his or her role in the incest, view destructive behaviors as predictable responses, and understand that present behaviors are a continuation of these past survival responses. Such self-awareness encourages the adolescent to better manage or discontinue now inappropriate behaviors.     

大鼠梗阻性黄疸对急性胃粘膜病变的影响及洛赛克对它的预防研究

通过制作大鼠 Ｏ Ｊ和 Ａ Ｇ Ｍ Ｌ 模型,研究了 Ｏ Ｊ对 Ａ Ｇ Ｍ Ｌ 的影响及洛赛克对 Ａ Ｇ Ｍ Ｌ 的预防作用．结果表明： Ｏ Ｊ能明显加强大鼠应激下 Ａ Ｇ Ｍ Ｌ 的形成,且其 Ａ Ｇ Ｍ Ｌ 的严重性与胆道梗阻时间相关,洛赛克对 Ｏ Ｊ大鼠应激下 Ａ Ｇ Ｍ Ｌ 的形成有预防作用     

SH3603汽车驱动桥齿轮联接螺栓断裂原因及消除方法

对SH3603（35D）型矿用汽车驱动桥主减速器一、二级从动齿轮的联接螺栓断裂事故进行了疲劳断裂理论分析,找出了根本原因,并提出具体的消除方法。     

竞技运动中自我控制的反语效应

自我控制的反语效应是指处于高心理压力下的个体,努力想控制自己的心理状态,由于消极暗示（他人给予的或自我给予的）的原因,往往得到与期望相反结果的现象。本文的目的是考察关于运动技术表现失败的自我控制的反语效应。研究中,方便抽样抽取63名被试,随机分配到低压力和高压力情景中的积极暗示组、消极暗示组和控制组。结果发现,高压力下,消极暗示组更容易使被试产生自我控制的反语效应。研究结果提示：较大的比赛压力下,教练员不应对运动员消极暗示,而应是积极暗示,这样可能会有效地避免反语效应的发生。