基于有限元法的高速振动排序输送机动态性能的研究

利用三维建模软件和有限元分析手段,对振动筛完成了实体建模和动力学特性——固有特性、响应行为的分析研究,获得了振动筛自身的振动行为和响应特征。振动筛挡板自身的局部动态响应行为,可对与其接触的物料施加微小的作用力和位移载荷,这些局部作用促使物料在沿筛体运动的同时,物料会发生旋转、排序。振动筛的动态力学响应行为的研究,为进一步提高振动筛的筛分和对物料的排序性能将产生积极的作用。     

轻轨列车用缓冲器动态阻抗特性研究

目前国内是参考铁道客车的标准提出轻轨用列车缓冲器的性能指标,并据此选择轻轨列车缓冲器容量和动态阻抗特性。由于城轨车辆采用动力分散的模式,且编组很少,在正常工况下所受车钩力很小,所以参照铁道客车标准选择的缓冲器容量和动态阻抗力往往过高。采用动力学的分析方法确定了动态阻抗特性改变前后的列车纵向冲动量,提出在满足性能和安全要求的前提下,可以降低缓冲器的动态阻抗力和容量,不仅可以改善列车的纵向冲动、提高缓冲器的使用寿命,而且能够降低制造成本。     

SD模型下装备制造业技术创新发展模式研究

全球经济一体化在带来经济和社会迅猛发展的同时,也伴随着高能耗和高污染等现象,使得装备制造业的发展面临着前所未有的挑战。可持续发展理念影响着未来经济发展的模式,装备制造业提高其未来市场竞争力,关键在于提高技术创新能力。在相关概念界定的基础上,明确装备制造业技术创新模式的功能和目标,从宏、微观的视角出发,运用系统动力学研究探讨装备制造业技术创新发展模式运行过程中涉及到的效益结构、要素关系、模型构建及运行规律等,为装备制造业技术创新发展模式功能的发挥和目标的实现提供支持。     

综合多种方法识别济阳拗陷反转构造

陆相断陷湖盆陡坡带常发育多种砂体,由于其地震反射特征的特殊性,干扰了反转构造的识别。结合孤北洼陷五号桩断层带正反转褶皱和高青地区高青—平南断层正反转构造实例,分析了反转构造的地震反射特征,运用钻井资料进行地层细分和对比,声波时差进行剥蚀量的计算,流体包裹体的性质判断构造应力性质。五号桩断层带正反转褶皱地震反射特征呈现上凸下凹的外形,上部地层中间厚、两翼薄,且褶皱顶部遭受剥蚀,同相轴削蚀现象明显,下部地层保留了断陷盆地沉积充填特征;钻井资料亦显示背斜核部遭受剥蚀;声波时差随深度变化的关系曲线在剥蚀段明显错开。高青—平南断层发现了表征张性和压性环境的两类包裹体。多种方法相互约束可提高反转构造识别的准确率。     

Dynamics of social assistance: the Norwegian experience in comparative perspective

In the article we ask how long Norwegian recipients of social assistance stay on aid over an eight‐year period? We focus on the populations selected, the design of the study and how spells are recorded and measured. The data set includes nearly the entire 1995 cohort of social assistance claimants (n = 155,000), and contains individual information over eight years (1992–1999), which is the maximum length of a single continuous spell. The study combines a retrospective and a prospective multiple cohort design. The data analysis shows that there is no simple answer to our question; the answer depends on the sample selected, the design, number of spells counted and the chosen measure of central tendency. We find that median duration times vary from two months to 40 months. The conclusion is that a point‐in‐time sample has clearly the longest duration. It makes a big difference whether one measures one or more spells. Because cycling is a common phenomenon, the sum of all spell durations is much higher than that of the first continuous spell. A retrospective design severely underestimates spell durations since many spells are right‐hand censored. As there is no single, adequate answer to our initial question, it is recommended that analysts of social assistance dynamics carefully specify their sample, design and spells counted.     

新时代文化和旅游融合发展的动力、策略与路径

文化是旅游发展的重要根基,旅游是文化发展的重要载体,文旅融合既是文化和旅游互动共荣的客观需要,也是文化和旅游发展的必然趋势.新时代背景下,随着消费升级和数字经济的发展,民众对文化旅游体验的需求转向对更高级的情感和自我实现的需求.面对我国文旅融合发展过程中表现出的主体和策略不够明晰、不确定性增强等问题,需要从多维度探究文旅融合发展的动力、融合发展策略选择与路径.基于对文化和旅游互动关系,以及文旅融合机制、模式、过程及路径的研究述评,分别从文旅融合的内在动力和外在动力视角,围绕产业关联、市场需求、技术创新和政策保障四个方面剖析了文旅融合的动力;提出了放大综合效应、深挖文化内涵、提升市场竞争力、统筹协调等文旅融合发展策略,以及升级产品体系、优化业态组合、培养复合人才和完善管理体制等文旅融合路径,以推动文旅的深度融合.     

Relation of transition probabilities in the Leslie model to those from experimental cumulative distributions

Summary We explore the relationship between transition probabilities in the Leslie model and those derived from experimental cumulative distributions. The nature of the two kinds of probabilities are discussed, and a formula derived for converting from one to the other. A numerical example is given to illustrate the differences.     

Dynamics of buried seed population and seedling cohorts of two dominant weeds in a hill agroecosystem of the humid subtropics of India

Dynamics of the buried seeds and plant population of two dominant weeds, viz.,Emilia sonchifolia (Linn.) DC. andRichardsonia pilosa HBK were studied in the crop fields of Meghalaya, north-east India during radish and maize cropping and intervening fallow periods. The total buried seed population ofR. pilosa was always larger than that ofE. sonchifolia, but the germinable fraction was invariably greater in the latter. A major portion (39–41%) of the viable (germinable+dormant) seed population in both weeds was confined to the surface soil layer (0–5 cm). The viable seed population ofE. sonchifolia peaked during April, while that ofR. pilosa showed two peaks (during August and December). The survival pattern and half-lives of seedling cohorts showed, some differences in the two weed species, but both being summer annuals, their populations behaved in a similar manner by showing higher seedling recruitment (K) and survivorship (p) rates in the summer crop (maize) than in the winter crop (radish). However, the density of plants that could attain adulthood was significantly higher inE. sonchifolia thanR. pilosa which might have resulted in greater seed input of the former to the soil leading to its greater abundance in the crop fields. Supported by the University Grants Commission, New Delhi (Grants No. F. 3-37/87 SR II)     

改革开放与当代中国社会发展

当代中国的社会发展是同改革开放荣辱与共、以改革开放的途径与方式推进的。其中的体制改革是当代中国社会发展的根本内在动力 ,对外开放则是当代中国社会发展的基本外部条件 ,两者共同构成了推动中国社会发展的动力机制和基本手段。要推进 2 1世纪中国社会发展必须继续依靠改革开放并且进行改革开放的政策创新。     

城市化动力机制及其作用机理研究

本文以中国城市化的发展实践为背景,从宏观层面上总结、分析了中国城市化发展的动力机制,从经济学的角度,对改革开放以来市场经济动力机制的作用机理进行了系统的分析和研究,并提出了城市化市场经济机制作用机理的演化模型。