熔锥光纤定向耦合理论

提出了一种分析熔锥光纤定向耦合器及其衍生器件的新数理模型。通过把基模场的高斯理论发展到双包层光纤,并采用正态分布函数来描述耦合区的几何形态,较为完善清晰地反映了模场及边界的渐变特性。导出了本地标量场耦合系数的简洁解析式及其矢量修正式。具体器件的理论计算与实验相符较好。     

A new procedure for steepest ascent

The procedure of steepest ascent consists of performing a sequence of sets of trials. Each set of trials is obtained as a result of proceeding sequentially along the path of maximum increase in response. Until now there has been no formal stopping rule, When response values are subject to random error, the decision to stop can be premature due to a “false” drop in the observed response.

A new stopping rule procedure for steepest ascent is intro-duced that takes into account the random error variation in response values. The new procedure protects against taking too many observations when the true mean response is decreasing, it also protects against stopping. prematurely when the true mean response is increasing, A numerical example is given which illus-trates the method.     

圆管分层层流的流动规律

从流体力学中NOS 方程出发,建立了圆管两相分层层流流动的数学模型。通过两相分层层流的相互作用的流体力学分析,提出了两相流动界面的耦合条件,从而得到了一组完整描述两相圆管分层流的数学方程,再通过数值求解分层流的数学方程,得到了对工程实际应用有重要价值的流动规律。应用圆管两相分层层流的流动规律,可以实现高粘流体的高效率输送, ,其节能效果十分明显。     

Effect of Brief Staff‐Assisted Career Service Delivery on Drop‐In Clients

Brief staff‐assisted career counseling services based on cognitive information processing theory were evaluated using 138 drop‐in clients who completed pre‐ and postintervention self‐report measures of knowledge about next steps, confidence in making next steps, and anxiety about career concerns. Significant changes occurred in each dimension and were significantly associated with the quality of career adviser interaction. Participants rated the experience as highly positive. Decreases in anxiety about career concerns were unrelated to the intervention. Implications include that a brief service delivery model yields positive outcomes for many clients but requires adjustments in organizational culture, physical environment, practitioner approaches, and client expectations. Future research should examine relational variables related to decreased anxiety with a brief service delivery model, the degree to which this approach works with specific career needs, and client attributes leading to successful versus unsuccessful outcomes with this model.     

带锯条掉齿前后横向振动位移及主频率变化规律

以MJ345A型木工带锯机为研究对象,在空载下利用振动分析仪和振动信号采集、处理、分析软件对带锯条的横向振动进行测试及信号采集,通过锯条横向振动位移、自功率谱分析,找出不同条件下锯条振动位移和主振型频率的变化规律.通过正交试验分析可知：锯轮主轴转速是对锯条横向振动位移影响最为显著的因素,其次为锯条张紧力,皮带张紧力为不明显因素.对带锯条掉齿前后的分析表明：如果测定带锯条横向振动位移范围在0.56~0.68μm,振动主频率范围在450~465 Hz,则说明锯条已经产生至少2个掉齿,为保证带锯机锯切安全及锯切质量需要及时更换新的带锯条;明确了带锯条掉齿前后横向振动位移、频率的变化规律.研究结果可为实际生产中充分合理利用带锯条,防止加工质量严重下降和危害人身安全事故的发生,适时更换锯条提供前期试验基础和判断的初步依据.     

坚持行政合理性原则有效控制行政自由裁量权

行政自由裁量权是行政权力的重要组成部分 ,行政合理性原则是行政法治的一项基本原则。通过采取权力对权力有效控制的方法约束政府的行政行为 ,这在依法行政的实践过程中突出体现出来     

有先行者优势的确定性网络

提出了一个确定性网络模型.模型考虑了新生成节点有不同的强弱状态,用节点度刻画节点的强弱,即强节点的度比较大.通过解析计算,得到了网络的特征系数,其特点是幂律度分布、大集聚系数和幂律簇度相关性,即模型生成了一个无标度层次网络.认为网络是无标度的是由于其生成方式上的特点,越早生成的节点拥有的度越大,这与BA(Barabási-Albert)无标度网络生长方式相似.如果节点度代表了个体拥有的资源、能力及社会关系等,那么越早生成的节点度越大,恰好对应于占先策略,即先行者优势.     

American crime drops: Investigating the breaks,dips and drops in temporal homicide

ObjectivesWhile a great deal of attention has been given to the 1990s crime drop, less is known about the more recent decline in homicide rates that occurred in several large U.S. cities. This paper aims to explore whether these represent two distinct drops via statistical evidence of structural breaks in longitudinal homicide trends and explore potentially differing explanations for the two declines. Methods: Using homicide data on a large sample of U.S. cities from 1990 to 2011, we test for structural breaks in temporal homicide rates. Combining census data and a time series approach, we also examine the role structural features, demographic shifts, and crime control strategies played in the changes in homicide rates over time. Results: Statistical evidence demonstrates two structural breaks in homicide trends, with one trend reflecting the 1990s crime drop (1994–2002) and another trend capturing a second decline (2007–2011). Time series analysis confirms previous research findings about the contributions of structural conditions (e.g., disadvantage) and crime control strategies (e.g., police force size) to the crime drop of the 1990s, but these factors cannot account for the more recent drop with the exception of police presence. Conclusions: Although both structural conditions and crime control strategies are critical to the longitudinal trends in homicide rates over the entire span from 1990 to 2011, different factors account for these two distinct temporal trends.     

羊毛细度候选基因的研究进展

随着分子生物学的快速发展,各种分子标记技术在许多领域得到了广泛的应用。羊毛细度一直以来是制约我国羊毛产品的主要因素,本文论述了用KAP和KRT基因作为羊毛细度候选基因的理论依据,并阐述通过PCR-SSCP分子标记的方法对羊毛细度进行分析的可能性。     

水滴蒸发的理论分析与蒸发时间的研究

对水滴的蒸发进行了理论分析和研究，并进一步讨论了蒸发时间与水滴直径、水滴速度以及介质温度之间的变化规律，为水滴群的进一步研究奠定了基础。