Slow‐fast dynamics in a model of population and resource growth

Models of the interaction of population, the economy, and the environment often contain nonlinear functional relationships and variables that move at different speeds. These properties foster apparent unpredictabilities in system behaviour. Using a simple deterministic model of demographic, economic and environmental interactions we illustrate the usefulness of geometric singular perturbation theory in environmental population economics. In contrast to local stability analysis, the theory of slow‐fast dynamics helps to gain new insights into the global behaviour of the system. In particular, the knowledge of the basins of attraction of the stationary states enables one to determine the regions of sustainable future paths of resources and population.     

Transcending Differences: Using Concrete Subject-Matter in Heterogeneous Groups

ABSTRACT

The need to conduct social group work with heterogeneous members is a reality. Yet the social work literature does not offer much guidance in how to work with diverse groups of people. This paper illustrates a method of social group work that utilizes tangible and palpable subject matter as a therapeutic vehicle to create strong group cohesion with heterogeneous group members. It aims to explain how and why using non-personal subjects as the heart of the group helps people connect to themselves, to the world and to each other in a personal way. The examples given are from two groups that are very different in their compositions and very different from each other. One is a psycho-educational group at a Continuing Day Treatment Program for severely and persistently mentally ill elderly and the other is a group with adolescent and pre-adolescent females in a community center. Four benefits of using this method of social group work are outlined.     

水力喷射压裂孔内压力分布研究

水力喷射压裂工艺是集水力射孔和压裂一体的新型油田增产技术。在室内实验基础上， 运用流体力学计算方法， 对水力喷射压裂孔道内压力场进行计算， 得到了井下水力射流在地层孔道内的压力及速度分布， 揭示了喷嘴空间位置、 喷嘴数量、 孔道形状、 喷嘴压降和喷嘴直径对孔道压力的影响规律。结果表明：高速射流之间具有很强的独立性， 喷嘴空间位置和喷嘴数量不会影响孔道内压力； 水力射流在不同形状孔道内产生的压力相同； 孔道压力随喷嘴压降和喷嘴直径的增大而增加。     

重庆市汽车产业可持续发展动力机制分析

运用系统动力学理论,构建重庆汽车产业可持续发展的系统动力学模型,分析汽车产业可持续发展的动力机制,并运用重庆汽车产业相关数据进行仿真分析,寻找影响重庆汽车产业可持续发展的主要问题和关键因素.研究表明:技术创新、政府、环境与市场是重庆市汽车产业可持续发展的三大驱动力,而随着产学研合作力度的不断增大,产学研合作力度对企业创新能力的促进作用却越来越小,且提高汽车产业的市场集中度不能有效提高企业的创新能力.     

An online estimation scheme for a Hull–White model with HMM-driven parameters

This paper considers the implementation of a mean-reverting interest rate model with Markov-modulated parameters. Hidden Markov model filtering techniques in Elliott (1994, Automatica, 30:1399–1408) and Elliott et al. (1995, Hidden Markov Models: Estimation and Control. Springer, New York) are employed to obtain optimal estimates of the model parameters via recursive filters of auxiliary quantities of the observation process. Algorithms are developed and implemented on a financial dataset of 30-day Canadian Treasury bill yields. We also provide standard errors for the model parameter estimates. Our analysis shows that within the dataset and period studied, a model with two regimes is sufficient to describe the interest rate dynamics on the basis of very small prediction errors and the Akaike information criterion.     

自旋器件中的自旋动力学:微波领域应用的新兴科学(英文)

自旋电子学指通过控制和利用电子自旋(而不是电荷)获得一系列新颖性能的研究领域。自旋电子器件已经成功地应用于计算机硬盘驱动器和磁性随机存储器,对IT行业的发展产生了深远的影响。这些应用都是基于自旋极化传输效应,即具有固定自旋取向的电子穿过磁性异质结所发生的相关效应。目前,在将微波和自旋极化传输联系起来的自旋器件中的自旋动力学研究,为研制尺寸远远小于微波波长的新型微波器件提供了巨大的潜能。在这篇综述中,首先简单地介绍了自旋器件的概念;接着研究了微波实验来研究自旋电子器件的微波辅助翻转和自旋泵浦现象。前者将能够开发出高密度的计算机硬盘,而后者,结合直接电子检测技术,将能够实现小型化的无源微波探测器。     

The Take Over of Parent-Child Dynamics in a Supervisory Relationship: Identifying the Role Transformation

The literature on supervision discusses processes occurring in the supervisor-supervisee relationship that are similar to, and have parallels in, a parent-child relationship. This slipping from the one type of relationship into the other can interfere with the process of supervision. This shift to the supervisee feeling like a child and the supervisor like a parent is liable to be the natural outcome of transference and counter-transference. The aim of this paper is to examine the pseudo-parental role of the supervisor, in order to make supervisors more aware of, and alert to, the possibility that their supervision of young workers may slip into a parent-child mode, to identify critical points where parental feelings may intrude on supervision, and to suggest a useful support model that can help prevent this intrusion.     

耐温耐盐聚合物堵剂的制备及性能研究

针对高温高矿化度地质条件特点，合成了对苯乙烯磺酸钠–2–丙烯酰胺基–2–甲基丙磺酸–膨润土聚合物堵剂。采用不同浓度盐溶液、使用温度及时间评价其耐盐耐温性能，优化了携带液体系，采用岩芯模拟实验考察堵剂封堵效果及耐冲刷性能。结果表明：该堵剂在80130 ℃恒温放置60 d 后树脂的吸水率和强度基本保持不变，树脂耐温性能良好；在质量分数30% 的模拟盐水溶液中吸水率仍可达12.00 g
g..1，树脂的耐盐性能良好；树脂在含水40% 的乳化油中3 h 不膨胀；岩芯实验测定聚合物堵剂在高渗和中渗通道中封堵率达到99.96% 和96.41%，经30 PV 水长期冲刷封堵率仍可达95.12% 和94.43%。     

抗温抗盐聚合物降滤失剂的研制及其作用机制

针对当前国内外超高温水基钻井液滤失性及高温稳定性调控难点，新研制出抗240 ℃高温、抗盐聚合物降滤失剂HTP–1。热重分析表明，HTP–1 分子链热解温度达320 ℃以上，热稳定性强；在各种钻井液基浆中的降滤失作用评价结果表明，HTP–1 在钻井液中具有优异的抗高温（240 ℃）抗盐（饱和）、抗钙（0.5%）降滤失作用，优于国内外同类产品。通过吸附实验、粒度分布测量、胶体稳定性测试和泥饼压缩性测试等手段，探讨了HTP–1 的降滤失作用机理：（1）在粘土颗粒上的吸附量大且吸附牢固，受矿化度、pH 值和温度的影响小；（2）老化（240 ℃/16 h）前后均能明显改善泥饼可压缩性，降低其渗透率；（3）增强钻井液体系的胶体稳定性，改善其中的颗粒粒径级配。     

产业成长的系统动力学分析

产业成长贯穿着自组织思想和机制,许多人在研究中都描述了这种成长的内在规律性和机制。科学与哲学中的自组织理念阐述了这种演化的动力,产业成长是一个产业在国民经济中所存在的延续过程,其动力存在的微观基础——企业、产品或市场、技术周期性的变化规律。