磷酸酯/Fe3+ 型油基冻胶压裂液性能研究

针对磷酸酯/Al3+ 交联的油基压裂液交联速度慢，交联剂溶解性慢、稳定性差和价格高等缺点，首次对磷酸酯/Fe3+ 交联的油基压裂液体系进行了研究。通过对铁交联剂体系的优化，筛选一种磷酸酯/Fe3+ 交联的新型交联剂体系，并对磷酸酯/Fe3+ 油基冻胶压裂液性能进行了评价。结果表明：采用30%Fe2(SO4)3+15% 二乙醇胺+55% 水制备的新型交联剂体系，直接与磷酸酯混合即可形成油基冻胶，其性能不受放置时间的影响，交联速度快，成胶性能好，10 min 就可达到最大黏度；压裂液的抗温抗剪切性能高，与常规铝交联剂体系比较，压裂液成胶速度提高了20 倍，压裂液的抗温能力由原来100 ℃提高到135 ℃，并且压裂液的破胶性和滤失性等性能均能达到压裂施工的要求。     

DBF系统的通道校正技术

描述了影响DBF系统特性的主要因素,研究了阵元间互耦对自适应方向图旁瓣和零深的影响及校正方法,讨论了在DBF阵中校正接收通道幅、相误差和I/Q支路正交误差的技术途径。计算机模拟和测试证明,按照所述方法进行校正可以得到满意的结果。另外,为了减小I/Q支路产生正交误差,建议采用中频直接采样和数字化的接收机方案。     

Community-based household waste management: Lessons learnt from EXNORA's ‘zero waste management’ scheme in two South Indian cities

This paper presents two case studies on the efforts by a community-based organisation to promote a sustainable integrated waste management system in Indian mega cities. This effort was initiated in 1989 by a local non-governmental organisation (NGO) called EXNORA and is based on a ‘zero waste management scheme’ set up, run and financed by the residents themselves. As this model has been widely quoted as successful, the study aims at learning from two communities implementing this model.Results are reported from a survey of the two schemes that used various tools to assess both their performance and sustainability in selected residential areas of two Indian cities, Chennai and Hyderabad. The results indicate limited success of the schemes both in saving a significant fraction of the generated waste from dumping, and in rehabilitating the local poor. However, they show that motivated individuals can successfully set up and manage waste collection systems that lead to overall environmental improvements. The differences in the two schemes reflect how the local assets and contexts impact on the success of the scheme. The scheme in a rich neighbourhood of Hyderabad was less ambitious in its overall objectives and focussed on the provision of a waste management service, using the opportunity to provide local employment to a socially deprived fraction of the population. The scheme in a middle-class area of Chennai, although pioneering in its approach, suffered from diseconomies of scale and lack of social integration, making it less viable in the medium to long term. Both schemes suffered from a lack of community involvement, motivation and political support, which threatens the long-term sustainability of the enterprise. The research concludes that the role that communities can realistically play in management of their own waste depends on the local context. The system advocated by EXNORA seems to require significant local resources, and political and technical support which are hard to find and sustain without strong local leaders. Another model set up in the city of Visakhapatnam is finally introduced as an alternative. This is based on triangular contracts between the municipality, the residents and micro-enterprises and may provide a good solution in dealing with the technical and commercial aspects which communities find difficult.     

服装制板、打板在实践应用中的探索

从服装企业生产的角度,阐述了服装制板、打板在生产实践中的具体应用。并结合实践经验,分析总结了针对不同情况与要求如何快速、准确、合理地制板、打板,以便为服装生产企业提供优质、方便、快捷的技术服务,促进服装企业的快速发展。     

内开槽螺纹波导冷腔色散特性模拟研究

根据螺纹波导中模式间的耦合方程组及冷腔色散方程进行了数值计算,分析了2个模式的相互耦合机理。基于圆柱形波导中线性极化TE11模式存在极化简并的特性,将线极化TE11脉冲作为1个探针,采用粒子模拟软件对该腔体进行了3维冷腔模拟;并将模拟结果与数值计算结果进行了比较,两者基本一致。通过计算机模拟得出了混合模式的电场等位线分布图,结合色散方程数值计算分析了内开槽螺纹几何特性变化对波导色散特性的影响规律。     

On an adaptive version of the Metropolis–Hastings algorithm with independent proposal distribution

In this paper, we present a general formulation of an algorithm, the adaptive independent chain (AIC), that was introduced in a special context in Gåsemyr et al . [ Methodol. Comput. Appl. Probab. 3 (2001)]. The algorithm aims at producing samples from a specific target distribution Π, and is an adaptive, non-Markovian version of the Metropolis–Hastings independent chain. A certain parametric class of possible proposal distributions is fixed, and the parameters of the proposal distribution are updated periodically on the basis of the recent history of the chain, thereby obtaining proposals that get ever closer to Π. We show that under certain conditions, the algorithm produces an exact sample from Π in a finite number of iterations, and hence that it converges to Π. We also present another adaptive algorithm, the componentwise adaptive independent chain (CAIC), which may be an alternative in particular in high dimensions. The CAIC may be regarded as an adaptive approximation to the Gibbs sampler updating parametric approximations to the conditionals of Π.     

Role of informal sector recycling in waste management in developing countries

Many thousands of people in developing country cities depend on recycling materials from waste for their livelihoods. With the focus of the Millennium Development Goals on poverty reduction, and of waste strategies on improving recycling rates, one of the major challenges in solid waste management in developing countries is how best to work with this informal sector to improve their livelihoods, working conditions and efficiency in recycling.The general characteristics of informal recycling are reviewed, highlighting both positive and negative aspects. Despite the health and social problems associated with informal recycling, it provides significant economic benefits that need to be retained. Experience shows that it can be highly counterproductive to establish new formal waste recycling systems without taking into account informal systems that already exist. The preferred option is to integrate the informal sector into waste management planning, building on their practices and experience, while working to improve efficiency and the living and working conditions of those involved. Issues associated with integrating informal recycling into the formal waste management sector are discussed.     

引导大学生进行英语成功阅读的方法探索

为落实教育部颁布的《高校英语专业教学大纲》的要求,提高英语语言学习性阅读或语言应用性阅读的能力,就必须有效地引导学生成功阅读。要进行成功阅读,就要打好基础,坚持循序渐进、量的原则,要讲究阅读的方法;要在教学中特别注意研究语义单位关系,借以提高阅读的效率。     

试论19世纪60年代～70年代东疆地区封禁政策的危机--兼谈"移民实边"思想的产生

19世纪60年代～70年代东疆地区封禁政策的危机,主要表现在沙俄的军事侵略威胁、朝鲜流民问题的冲击、东北边疆防御力量的空前削弱三个方面。清廷为了摆脱这一危机而苦苦摸索,移民实边思想便是这一摸索的产物。     

设计素描的四种基本功

设计素描作为学习设计的一门基础课程,通过观察方法、思维方式、表现形式、立体观念和细节刻画四个方面的介绍说明设计素描对于学习产品设计的重要性.