石油天然气长输管线用钢新进展

本文介绍了１９９０年以来国外在石油天然气长输管线用钢方面的最新成果，以获得较低的强度和韧性匹配为目的经轧后加速冷却工艺后的钢的强度的预测和控制；具有优良抗氢致裂纹的含硼、微碳、低硫、Ｎｂ－Ｔｉ微合金化、Ｘ６５－Ｘ８０级管线钢的开发，满足于特殊性能要求的ＴｉＯ处理技术及Ｘ８０级ＴｉＯ细化晶粒钢、低硬度和低屈强比钢，以及复合板加工耐腐蚀钢管的生产。     

电子商务对企业集团营销手段的影响

介绍了电子商务，以及目前电子商务的发展趋势及对社会的影响，特别阐述了蓬勃发展的电子商务对企业集团的经营环境与手段的影响。     

Computer-aided analysis of double drift region impatt diode

The results calculated by computer for the double drift region IMPATT diode oscillator on the 8 mm waveband are reported in this paper. A comparison between single and double drift devices concerning the power output and efficiency is given. The effect of doping profile, current density and RF voltage on the performances of these devices have also been investigated. The theoretical data of these double drift IMPATT oscillator and amplifier are provided.     

Possibilities and problems with the use of models as a communication tool in water resource management

Politicians and policy-makers, as well as modellers, often nurses an expectation that model derived results is an objective source of information that can be used to support decisions. However, several prerequisites have to be dealt with in order to ensure that models can be used as legitimate and efficient tools in water resource management. Based on empirical material from recent studies on the use of models in stakeholder dialogues, mainly focusing on catchment nutrient transport, two central problems are identified: (a) Models are laden with choices and thus depend on assumptions and priorities of modellers. (b) There are several factors that influence ability and willingness of stakeholders (as information recovers) to criticize or accept results of the modelling exercise. Recognized factors likely to influence stakeholders' acceptance of model derived results include issues at stake, stakeholders' ability to criticize model derived information, and their trust in the institutions that have developed or applied the used models. Identified prerequisites for successful use of models in integrated water resource management include: consideration of user relevance, awareness of and preparedness to handle constraints linked to communication of model-based results, transparency of used models and data and of involved uncertainties, mutual respect between experts and stakeholders and between involved stakeholder groups, a robust institutional network, and sufficient time for dialogues. Development and use of strategies for participatory modelling, based on a continuous dialogue between experts and stakeholders is recommended as a way to facilitate that the prerequisites for a successful use of models in water resource management are fulfilled.     

Enhanced Oil Recovery: The Synthesis of Anthraquinone [1, 2-C] Alkylisoxazole

Anthraquinone [1, 2-C] methylisoxazole is synthesized from 2-ethylanthraquinone through nitration and treating with oleum. The different methods of 2-ethylanthraquinone nitrated were discussed. The optimum conditions were determined. The structure of the product was confirmed by MS and ¹H NMR.     

An analytical study on the thermal characteristics of flat-plate and evacuated solar collectors

In this study, we highlighted differences in the standards used in performance tests of solar collectors. We analyzed testing results for different types of solar collectors to determine the effects of the collector area and mass flow rate, which were not necessarily consistent across all tests. Our analysis showed that the factor,F′ (τα), including collector efficiency factor (F′), could be correlated with the flow rate or area regardless of the collector type. Moreover, the collector loss coefficient (F′U _L ) per flow rate or area for an evacuated collector was less that of a flat-plate collector; this was also correlated with the flow rate or area, regardless of the type of evacuated collector. As a result of this analysis, we propose a modified heat loss coefficient that includes the effects of all parameters that can be considered in a performance test and show that this coefficient could better describe the thermal characteristics of various types of solar collectors.     

A Class of POCA Distributions For rapid fading variations

Polydorou and Capsalis [1] pioneered the concept of POCA distribution to study the statistical behavior of the fast fading characteristics in an indoor environment under the assumption of finite number of scatters. In this note, we derive a comprehensive class of formulas for the POCA distribution to help better statistical modeling of the fast fading characteristics. The calculations involve use of several special functions and their properties.     

初至波走时层析成像中的正则化方法

 波场的等效性、观测数据的有限性和观测误差等因素导致地球物理反演本身具有严重的多解性，降低这种多解性的一种重要途径就是对反演过程进行约束。传统的初至波走时层析成像方法，通常是在外部对模型空间施加显式的约束和平滑处理，这样就会破坏模型参数与传播算子之间的相关性，难以达到有效利用先验信息的目的, 甚至会影响反演的稳定性。针对这一问题，本文将先验信息分为三类，在此基础上阐述了通过正则化手段将各种先验信息纳入到反演方程当中，替代传统的外部约束模式。理论试验结果表明，正则化方法比外部约束方法有效地提高了反演的精度和分辨率；将该正则化方法应用于实际二维资料处理，也得到了比较好的反演结果。     

嵌入式数控操作系统与任务模块划分研究

采用嵌入式计算机技术构建数控系统是实现开放式数控的重要方式。研究分析了系统中操作系统实时性实现和数控功能划分2个关键性技术。选择RT-Linux作为嵌入式操作系统,在此平台上根据操作系统特点和数控任务实时性和多任务要求,划分了数控任务模块,并对其优先级和相互间数据交换进行了设计。