Wind Generator Stabilization with Doubly-Fed Asynchronous Machine

This paper investigates the function of doubly-fed asynchronous machine(DASM)with emphasis placed on its ability to the stabilization of the power system including wind generators.P(active power)and Q(reactive power)compensation from DASM can be regulated independently through secondary-excitation controlling.Simulation results by power system computer aided design(PSCAD)show that DASM can restore the wind-generator system to a normal operating condition rapidly even following severe transmission-line failures.Comparison studies have also been performed between wind turbine pitch control and proposed method.     

沙门一行制历因缘探讨

唐僧一行参与乃至领导了盛唐时期的皇家天文台的工作,编制了著名的《大衍历》,本文从文化角度对沙门一行制历的因缘加以考证,认为促成一行制历的原因：一是政治统治的需要,二是沙门一行的俗家家世背景,三是沙门一行的宗教身份,且三者层层递进。其中一行的宗教身份,解释了其复杂知识结构以及《大衍历》域外天文学知识的可能来源,同时一行囊天台宗和律宗的修行身份并入于密教,加上文献材料中所体现出来的道教背景,契合了玄宗朝的宗教政策,是获得玄宗信赖的重要原因。而对于沙门一行制历的缘由,对于一行宗教背景中的道教成份,也是前贤的研究所忽略的。     

Predicting the Dielectric Strength of c-C4F8 and SF6 Gas Mixtures by Monte Carlo Method

An improved Monte Carlo method was used to simulate the motion of electrons in c-C_4F_8 and SF_6 gas mixtures for pulsed townsend discharge. The electron swarm parameters such as effective ionization coefficient, [AKα-] and drift velocity over the E/N range from 280～700 Td(1Td=10-21 V·m2) were calculated by employing a set of cross sections available in literature. From the variation cure of [AKα-] with SF_6 partial pressure p, the limiting field (E/N)_lim of gas mixture at different gas content was determined. It is found that the limiting field of c-C_4F_8 and SF_6 gas mixture is higher than that of pure SF_6 at any SF_6 mixture ratio. Simulation results show excellent agreement with experiment data available in previous literature.     

Some Key Technologies of a New-type CNC Curve Grinding Machine

This paper presented a new-type CNC curve grinding machine, in order to conquer the disadvantages of conventional NC curve grinding machine and improve surface quality, dimensional accuracy and machining efficiency. The new-type grinder adopts some high and new technologies: ① the normal tracing device could make grinding wheel coincide with the normal direction of the machining points in work piece, and improve surface quality and dimensional accuracy; ② the digital image on-line recognition system could monitor machining process and compensate wheel wear in real time; ③ linear motor drive mechanism could realize the exact adjustment of the grinding head digitally and increase the machining efficiency. The math models of normal tracing and circular tolerance zone were presented. The experimental results show that the new-type CNC curve grinding machine equipped with the three devices mentioned above is easy to realize the precision grinding of any complex curve, and improve surface quality, dimensional accuracy and machining efficiency.     

Study on Distributed Motion of Self-Reconfigurable Robot Based on Local Rules

The eigenvector of a module with six adjacent module's state was constructed according to self-reconfigurable robot M-Cubes and the configuration of system was expressed with the eigenvectors of all modules.According to the configuration and motion characteristics of the modules,a 3-dimension motion rule set was provided.The rule sets of each module was run according to eigenvector of the module after the motion direction of system decided and motion rules were selected.At last,the rapid and effective motion and metamorphosis were realized in system.The rule sets are operated on three systems and the distributed motion of system is fully realized.The result of simulation shows that the 3-dimension motion rule sets has perfect applicability and extensibility.The motion steps and communication load of the modules increase with the module number in linear.     

浅谈建筑施工企业工程造价控制的若干方法

对建筑施工企业而言,建设工程项目的成本直接关系到项目的成败,关系到建筑施工企业的发展,同时也是工程竞标的主要因素。阐述了建筑施工企业工程造价控制的一些做法,诸如:合理预测工程项目的成本,抓好工程实施阶段的成本控制和做好工程实施阶段实质性管理工作。由此实现施工管理效益最大化。     

沥青混凝土路面冷再生工程中旧料结团状况的评价与控制

通过对广深高速公路旧路面回收料RAP结团状况的研究,提出了细度模数比FMR(fineness modulus ratio)这一量化评价指标,通过试验证实了该指标适合于RAP结团状况的评价,并提出了在沥青混凝土路面冷再生工程中运用该指标进行旧料结团状况控制的方法和建议.     

平原区四车道无中间分隔带公路事故预测模型研究

针对平原区四车道无中间分隔带公路,借用事故预测模型技术研究其安全特征和规律.基于该类公路安全的定性和定量分析,确定了普通路段、村庄路段、交叉口路段的分段方案,并加强了对货车等车型构成的考虑.建模结果中,交通量、自然交通量中货车比例、第一层路侧危险度、竖曲线弯曲度、横坡度、路面宽度对普通路段,交通量、折算交通量中货车比例、第一层路侧危险度对交叉口路段,交通量、加权的横坡度、路基宽度等对村庄路段的事故有显著影响.最后进行了实例分析.     

彭溪河特大桥索塔锚固区段足尺模型试验研究

介绍彭溪河特大桥索塔锚固区段足尺模型试验、张拉工艺模型试验及空间有限元仿真分析。通过模型试验与理论计算相结合的方法,研究索塔锚固区的受力状态和安全性能,并测试小半径“U”形环向预应力束预应力损失和伸长量,为优化设计及指导施工提供了可靠的依据。     

液化天然气储运中的翻滚现象及预防措施

介绍了液化天然气储运中的翻滚（涡旋）现象及预防措施,着重分析了液化天然气在储运中的翻滚机理,提出了相应的预防措施,以减少和消除翻滚现象,提高液化天然气在储运中的安全性。