输送黏性介质时叶轮出口角对泵性能的影响

为了研究离心泵在输送黏性介质时,叶轮出口角对泵性能的影响,采用FLUENT软件,对2种不同叶轮出口角的 离心泵,分别在清水和5种不同黏性的油性介质下,进行数值模拟分析,预测离心泵在各工况下的水力性能。结果表明： 输送介质为清水时,增大出口角能提高扬程但会降低水力效率;介质运动黏度介于10. 80~ 65. 00 mm2／s时,增加叶轮出 口角能同时提高扬程和效率;介质运动黏度≥65. 00 1111112/S时,增加出口角不能改善其水力性能。文章研究结果能改善 离心泵的水力设计方法,确保泵的高效运行。     

船舶反弯扭螺旋桨水力特性的数值模拟与分析

运用计算流体力学方法(CFD)对船舶反弯扭螺旋桨的水力特性进行数值模拟计算,获得了螺旋桨的推力系数、扭矩系数及敞水效率等水力特性参数,与试验结果进行了比较,两者吻合良好.模拟计算提供了详细的三维流场分布,可对反弯扭桨叶的工作特性和叶梢涡、尾涡及气蚀的分布状态进行深入的分析.在叶面邻近区域采用层叠式的半结构网格以适应边界层的计算要求,在边界层外的流动区域采用非结构网格,取得了较高的计算精度.     

社会转型期弱势群体的利益表达机制探析

在20世纪90年代以来的社会转型过程中所形成的弱势群体,是和谐社会视角下的一个热点问题,也是十六届六中全会有关社会体制改革所关注的一个焦点.弱势群体的利益表达有利于政治稳定和社会和谐,有利于利益均衡和社会发展,也有利于实现社会的公平与正义.通过构建有效的弱势群体利益表达机制,使其能够拥有平等的利益表达权利,自主、理性、合法地进行利益表达,从而由权利均衡走向利益均衡,是促进弱势群体走出困境的一种有效制度安排.     

The Veils of Clio: Dimensions of a Behavioral Narratology

This paper outlines a behavior-analysis approach to the field of narratology, the study of the narrative or story, with emphasis on nonfiction stories and the processes by which such stories distort the world they describe. Stories are described in terms of (a) a behavior-analysis adaptation of Todorov''s (1977) analysis of the plots of stories in terms of states of equilibrium/disequilibrium and (b) Grant''s (2005) analysis of the structure of stories in terms of establishing operations and escape contingencies. These two sets of concepts are applied to understanding how and why stories lead to distortions of the events they report.     

State transition modeling of complex monitored health data

This article considers the analysis of complex monitored health data, where often one or several signals are reflecting the current health status that can be represented by a finite number of states, in addition to a set of covariates. In particular, we consider a novel application of a non-parametric state intensity regression method in order to study time-dependent effects of covariates on the state transition intensities. The method can handle baseline, time varying as well as dynamic covariates. Because of the non-parametric nature, the method can handle different data types and challenges under minimal assumptions. If the signal that is reflecting the current health status is of continuous nature, we propose the application of a weighted median and a hysteresis filter as data pre-processing steps in order to facilitate robust analysis. In intensity regression, covariates can be aggregated by a suitable functional form over a time history window. We propose to study the estimated cumulative regression parameters for different choices of the time history window in order to investigate short- and long-term effects of the given covariates. The proposed framework is discussed and applied to resuscitation data of newborns collected in Tanzania.     

An Empirical Test of a Neo-Malthusian Theory of Fertility Change

Some neo-Malthusians regard fertility as being kept in check by scarcities and constraints and, conversely, as being raised by economic prosperity. Since out-migration to developed countries and the receipt of food aid from developed countries relax the constraints imposed by a country’s carrying capacity, both will have a positive effect on fertility rates in developing countries. Moreover, better economic prospects will also raise fertility, all other things equal. This article provides an empirical test of these hypotheses derived from a neo-Malthusian theory of fertility change. The results fail to confirm the theory and often contradict it.

元朝野生动物保护政策及其对旅游资源保护的启示

在中国历史上,元朝统治者比较懂得爱惜野生动物。在这种思想意识的支配下,他们制定了一套完整的保护野生动物的条例和法规,详细规定了狩猎和禁猎的时间、地点及捕猎野生动物的种类,并在实践中认真贯彻执行,使元朝的野生动物保护工作走上了法制轨道,取得了明显的社会效益、经济效益和生态效益。这一切对于今天的旅游资源开发与保护仍有借鉴意义。     

Neighborhood change from the bottom Up: What are the determinants of social distance between new and prior residents?

An important source of neighborhood change occurs when there is a turnover in the housing unit due to residential mobility and the new residents differ from the prior residents based on socio-demographic characteristics (what we term social distance). Nonetheless, research has typically not asked which characteristics explain transitions with higher social distance based on a number of demographic dimensions. We explore this question using American Housing Survey data from 1985 to 2007, and focus on instances in which the prior household moved out and is replaced by a new household. We focus on four key characteristics for explaining this social distance: the type of housing unit, the age of the housing unit, the length of residence of the exiting household, and the crime and social disorder in the neighborhood. We find that transitions in the oldest housing units and for the longest tenured residents result in the greatest amount of social distance between new and prior residents, implying that these transitions are particularly important for fostering neighborhood socio-demographic change. The results imply micro-mechanisms at the household level that might help explain net change at the neighborhood level.     

Building home on a fault line: Aging out of child welfare with a serious mental health diagnosis

Youth aging out of foster care are at high risk for homelessness. This research explains how and why homelessness occurs among youth with serious mental health struggles after aging out of residential and transitional living programmes. Using a longitudinal constructivist grounded theory design, we analyse 20 in‐depth interviews exploring youth's transition experiences and perceptions of transition success within 4 months of emancipation and at 6 and 12 months postemancipation. Monthly 15‐min check‐ins prevented attrition. A three‐phase transition process was observed driven by participant desires and actions to cultivate psychological home through establishing physical home alone away from social networks. Pre‐emancipation, the promise of home was privacy and opportunity for self‐redefinition. Shortly after emancipation, home became a physical and social space to be, a valuable resource to share and a demonstration of personal transition success. However, later in the year postemancipation, maintaining physical home proves nearly impossible given the risk context. Findings speak to how and why youth aging out appear overly self‐reliant upon emancipation. Cultivating a psychological sense of home has practice implications for child welfare providers who aim to prepare youth to live independently postemancipation.     

To what extent is social security spending associated with enhanced firm-level performance? A case study of SMEs in Indonesia

Although the relationship between social protection and enterprise performance is much debated in the literature, evidence is particularly limited in the case of small and medium-sized enterprises in developing economies. Using census data from 2010 to 2014, this article examines how the provision of social security influenced business performance in Indonesia. The author finds that increased social security spending of 10 per cent is associated with a per-worker revenue gain of up to 2 per cent. Moreover, profits are not found to decrease with increased social protection coverage, suggesting that increasing worker benefits may be a worthwhile business investment.