CO_2、NH_3对YBa_2Cu_3O_(7-x)的结构及超导电性的影响

以热重分析(TGA)、电阻测量和X射线衍射分析等方法,研究了CO_2与NH_3对YBa_2Cu_3O_(7-x)超导体结构稳定性及超导,电性的影响。当温度低于373K时,CO_2对YBa_2Cu_3O(7-x)的结构和超导电性无影响;当温度为523K时,CO_2使YBa_2Cu_3O_(7-x)的Tc下降;温度高于703K时,CO_2将很快破坏YBa_2Cu_3O_(7-x)的结构,并产生化学反应,生成新的化合物,在CO_2中存在的O_2与N_2对YBa_2Cu_3O(7-x)与CO_2的反应及反应产物的影响有较大差异。NH_3对YBa_2Cu_3O(7-x)结构稳定性的影响不大。     

Intrafamilial conflict and emotional well-being: a population based study among Icelandic adolescents

Objectives

During intrafamilial conflicts children are often innocent bystanders, caught in the crossfire. In such situations, they are at increased risk to become directly involved in abusive verbal behavior of the perpetrator, and exposed to being shouted or yelled at, threatened, rejected and even physically abused. The present study has two main objectives: (1) ascertain a national base rate of intrafamilial conflicts and physical violence at home among Icelandic adolescents; and (2) to investigate the association of witnessing and/or having been a part of intrafamilial conflict or physical violence at home with variables that relate to mental health and well-being.

Methods

The participants were 3,515 students, 14- and 15-year-old, in the national compulsory school system in Iceland. As a part of the 2003 ESPAD survey, each pupil was asked about experiences of severe verbal arguments and physical violence at home as well as their background, behaviors, and mental health assessed with the use of tested measurement scales such as the Symptom Distress Checklist 90 (SCL-90) and the Rosenberg Self-Esteem Scale.

Results

About 22% of the participants stated that they had witnessed a severe verbal argument between parents and 34% stated that they had been involved in a severe verbal argument with parents. This rate was slightly higher for girls compared to boys. All together 7% of adolescents had witnessed physical violence at home where an adult was involved and 6% of the participants stated that they had experiences of being involved in physical violence at home where an adult was involved. Witnessing or being involved in severe verbal arguments at home and/or witnessing or being involved in physical violence with an adult was significantly associated with greater levels of depression, anger, and anxiety, and negatively related with self-esteem (p < 0.01).

Conclusions

Many adolescents in Iceland witness severe parental verbal arguments or physical violence between adults in their homes and some are directly involved in such acts. It affects their long-term emotional and behavioral development and well-being.

Practice implications

Preventive measures have to be implemented at an early age and should include, but not be limited to, information on disciplining and upbringing of children and the negative impact of intrafamilial conflicts on the long-term health of their children. Due attention should be given to the health and well-being of children where such violence is known to occur.     

一类神经网络的指数稳定性分析

避免构造Lyapunov函数的困难,运用广义Dahlquist数方法研究了一类神经网络模型平衡点的存在唯一性和指数稳定性,在没有假设激活函数具有可微性、有界性的条件下,得出新的判据。     

松花江(吉林省段)流域经济系统稳定性演变态势

基于对稳定性的认识和理解,以压力、敏感性和响应等稳定性要素构建流域经济系统稳定性评价指标体系和评价模型,对松花江（吉林省段）流域经济系统稳定性演变特征进行分析。结果如下。1）从压力得分来看,松花江（吉林省段）流域经济系统压力具有显著的空间分异特征。2）从敏感性得分来看,流域内吉林市、松原市和白城市自身经济系统内部结构和功能不尽合理,一定程度说明松花江（吉林省段）流域的经济结构合理性较差。3）从响应得分来看,松花江（吉林省段）流域经济系统响应总体呈现出由流域自上而下依次降低的特征。4）从稳定性得分来看,松花江（吉林省段）流域经济系统稳定性具有明显的中心-外围特征,并且区域间差异程度不断扩大,尤其是长春市和白城市之间。今后经济发展过程不仅要巩固流域核心城市的优势地位,更要加快流域边缘城市的发展,注重经济发展的质量和效率,避免差距进一步扩大。     

普通高校乒乓球课学生击球稳定性的影响因素

对普通高校乒乓球课影响学生击球稳定性的众多因素进行多维分析,结果表明:影响学生击球稳定性的主要因子是:动作结构因子、旋转理解因子、发力方式因子、外在客观因子,并据此提出了提高学生击球的稳定性,有利于激发学生学习的积极性,从而提高教学效率。     

世界优秀跳远、三级跳远运动员竞技表现稳定性的对比研究

以奥运会、世界锦标赛跳远、三级跳远前8名运动员为研究对象。运用文献资料法、统计法、比较法和归纳法,对决赛过程中成功率、各轮次最优成绩的频数、有效成绩的稳定性(变异系数)等反映跳跃远度项目竞技表现过程稳定性的参数进行分析。结果表明:成功率总体趋势是逐渐下降,前3轮成功率相对高于后3轮,三级跳远的成功率普遍高于跳远的成功率;男子跳远运动员最优成绩较多的是在后3轮创造的,女子跳远运动员最优成绩大多在前3轮创造的,且统计检验的结果非常显著,男、女三级跳远运动员最优成绩多在前3轮创造;跳远运动员前8名有效成绩的平均变异系数差异不大,三级跳远前8名有效成绩的平均变异系数有一定的个体差异,但该类项目总体稳定性较好,跳远比三级跳远更为稳定。     

核心稳定性研究历史与现状

核心稳定性是一个广泛应用于包括健康和医学领域在内的多领域的常见术语,科学文献中有关核心稳定性定义的表述各不相同。通过对“核心”的位置、核心稳定性中的稳定性的定义、核心稳定性的构成的分析,确定人体“核心”的位置,探讨“核心稳定性”中的“稳定性”的内涵,分析核心稳定性的生物力学原理。     

弧圈球技术集击球稳健性和威胁性于一体的物理分析

运用物理方法,从弧圈球对乒乓球运行的速度、弧线形状、弧线高度、弧线方向等的影响,以及和球台、球拍作用的效果进行分析,揭示了孤圈球技术集击球稳健性和威胁性于一体的物理原因.     

散货船优化积载的数学模型及其应用

为寻求散货船的最佳航次积载方案,在满足船体强度、稳性和吃水差约束的条件下,建立侧重于船体强度状况的散货船优化积载通用非线性数学模型.基于通用优化模型求解软件LINGO和散货船装载软件SEACOS给出一个完整的计算实例,验证数学模型.此项研究为各类船舶实现自动优化积载奠定理论基础,对提高各类货船运力、改善船舶耐波性、延长船舶寿命、确保船舶安全都具有实用价值.     

2009—2010年国外数字资源长期保存模式分析及启示

对2009—2010年国外数字资源长期保存项目的分析发现,数字资源保存模式对数字资源保存活动的开展具有积极的引导与评估作用。我国数字资源长期保存工作应注意:作为组织者,建立和健全一套行之有效的方针政策与做出正确的决策是其首当其冲的任务,实现与合作者之间的良好沟通与合作是开展数字资源保存项目的基础,获得或者募集资金是开展工作的先决条件;在技术环节上,要充分考虑到被保存资源的客观状态,利用现有技术进行保存,并且要充分考虑到资源前后格式上的变化及未来资源所处的技术环境;在维护与评估上,积累经验并正确评估是十分必要的。