A compact LTCC branch-line coupler UsingModified-T equivalent-circuit modelfor transmission line

In this letter, a compact branch-line coupler is proposed by making good use of the three-dimensional layout capability of the low-temperature co-fired ceramic (LTCC) substrate. This branch-line coupler is accomplished by using lumped-inductors and lumped-capacitors to realize the modified-T equivalent-circuit model for the transmission line so that the circuit size may drastically be reduced. Specifically, a very compact LTCC branch-line coupler with a size of 0.079/spl lambda//spl times/0.0717/spl lambda/ is implemented and carefully examined, where /spl lambda/ is the wavelength of the multilayer structure at the operating frequency f/sub 0/.     

新型多用途钻杆打磨机

国内目前对钻杆接头飞边打磨和对钻杆接头除锈均采用人工方法，存在打磨质量不稳定、效率低、工人劳动强度大等缺点。开发的多用途钻杆打磨机已应用于打磨石油钻杆接头飞边、钻杆接头除锈工艺，该技术可以大幅度提高打磨生产效率，打磨钻杆飞边质量稳定，钻杆接头表面除锈效果好。该设备的自动化程度高，操作简单，维护方便，可改善工人的劳动环境。     

Accelerated wear testing with a microfabricated surface to evaluate the lubrication ability of biomolecules on polyethylene

Wear of ultrahigh‐molecular‐weight polyethylene (UHMWPE) and wear‐particle‐induced osteolysis and bone resorption are the major factors causing the failure of total joint replacements. It is feasible to improve the lubrication and reduce the wear of artificial joints. We need further understanding of the lubrication mechanism of the synovial fluid. The objective of this study is to evaluate the lubricating ability of three major components in the synovial fluid: albumin, globulin, and phospholipids. An accelerated wear testing procedure in which UHMWPE is rubbed against a microfabricated surface with controlled asperities has been developed to evaluate the lubrication behavior. An analysis of the wear particle dimensions and wear amount of the tests has provided insights for comparing their lubrication performance. It is concluded that the presence of biomolecules at the articulating interface may reduce friction. A higher concentration of a biological lubricant leads to a decrease in the wear particle width. In addition, in combination with the wear results and mechanical analysis, the roles of individual biomolecules contributing to friction and wear at the articulating interface are discussed. These results can help us to identify the role of the biomolecules in the boundary lubrication of artificial joints, and further development of lubricating additives for artificial joints may be feasible. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Water bamboo husk reinforced poly(lactic acid) green composites

The water bamboo husk is one of major agricultural wastes in Taiwan. In this study, the powder obtained from the water bamboo husk was added to poly(lactic acid) (PLA) to form novel reinforced biodegradable composites. Morphologies, mechanical properties, and heat resistance of these water bamboo powder reinforced composites were investigated. The results indicate that the char yields were increased as plant powder was incorporated to PLA. In addition, the mechanical properties were also enhanced due to the addition of powders. The increments of storage moduli of PLA were about 50–200%. Moreover, the increments of loss moduli of PLA were about 70–200%. On the other hand, the T_g of PLA was slightly decreased by the addition of powder, and this may improve the brittle characteristics of PLA. Furthermore, this type of reinforced PLA would be more environmental friendly than the artificial additive‐reinforced one. POLYM. ENG. SCI., 2008. © 2008 Society of Plastics Engineers     

Intelligent control of doubly‐fed induction generator systems using PIDNNs

An intelligent control for a stand‐alone doubly‐fed induction generator (DFIG) system using a proportional‐integral‐derivative neural network (PIDNN) is proposed in this study. This system can be applied as a stand‐alone power supply system or as the emergency power system when the electricity grid fails for all sub‐synchronous, synchronous, and super‐synchronous conditions. The rotor side converter is controlled using field‐oriented control to produce 3‐phase stator voltages with constant magnitude and frequency at different rotor speeds. Moreover, the grid side converter, which is also controlled using field‐oriented control, is primarily implemented to maintain the magnitude of the DC‐link voltage. Furthermore, the intelligent PIDNN controller is proposed for both the rotor and grid side converters to improve the transient and steady‐state responses of the DFIG system for different operating conditions. Both the network structure and online learning algorithm are introduced in detail. Finally, the feasibility of the proposed control scheme is verified through experimentation. Copyright © 2011 John Wiley and Sons Asia Pte Ltd and Chinese Automatic Control Society     

物流企业多式联运合作伙伴优选

在遵循物流企业多式联运合作伙伴选择的原则基础上,通过定性与定量综合分析,采用层次分析法和熵权法获得综合评价仅重,基于PROMETGEE-Ⅱ法对联运合作伙伴进行排序,建立相应的评价指标体系模型.通过算例分析证明,该模型具有可操作和实用性.     

论“一颗印”民居及其所体现的建筑文化

"一颗印"是云南最典型的民居住屋形式,属于合院系住屋,融合了云南特有的民族文化和环境因素,成为地方性文化的载体与外在表现,集中体现出我国的传统主流文化、环境观念、审美情趣的特征,是研究云南建筑发展与演变的有力实证,它的传承与更新对当代建筑设计创作有着非常积极的意义。     

项目教学法在房屋建筑学课程设计中的应用

以房屋建筑学课程设计实训课程改革为例,阐述项目教学法的学习情景设计、学习情境实施、教学效果分析以及应该注意的问题。探索如何在该门课程的教学中采用项目教学法,以充分发掘学生的创造潜能,提高学生解决实际问题的综合能力。     

低电平扫描电流高强辐射场试验方法研究

低电平扫描电流试验(LLSC)是飞机高强辐射场(HIRF)试验的一部分,其实质是在2~400 MHz 频段 内对飞机进行电磁辐照,以确定外部HIRF 环境与设备线束感应电流之间的传递函数。基于RTCA/ DO-160G 和SAE ARP5583A 标准建立HIRF 测试环境,通过对AC312E 直升机开展低电平扫描电流试验,得到了线束传递函数随频 率、天线极化方式、电磁辐照方向、线束布置的变化规律并分析了其影响机理。结果表明:发射天线以不同极化方式 辐照机体时,不同布置的线束其传递函数有一定差别;发射天线以垂直极化在0°方向辐照时,行李舱附近右发动机 控制单元(EECUR)线束的传递函数比位于驾驶舱的座舱显示器(MFD)线束的传递函数要小;发射天线以垂直极化 方式在不同方向辐照机体时,EECUR 线束在某些频段下在右侧90°方向辐照比左侧270°方向辐照的传递函数要大。 所得结论可为直升机适航符合性验证和低电平扫描电流试验的开展提供参考与支撑。     

A Multi‐Autonomous Underwater Vehicle System for Autonomous Tracking of Marine Life

This paper presents a multi‐autonomous underwater vehicle system capable of cooperatively and autonomously tracking and following marine targets (i.e., fish) tagged with an acoustic transmitter. The AUVs have been equipped with stereo‐hydrophones that receive signals broadcasted by the acoustic transmitter tags to enable real‐time calculation of bearing‐to‐tag and distance‐to‐tag measurements. These measurements are shared between AUVs via acoustic modem and fused within each AUV's particle filter for estimating the target's position. The AUVs use a leader/follower multi‐AUV control system to enable the AUVs to drive toward the estimated target state by following collision‐free paths. Once within the local area of the target, the AUVs circumnavigate the target state until it moves to another area. The system builds on previous work by incorporating a new SmartTag package that can be attached to an individual's dorsal fin. The SmartTag houses a full inertial measurement unit (INU), video logger, acoustic transmitter, and timed release mechanism. After real‐time AUV tracking experiments, the SmartTag is recovered. Logged IMU data are fused with logged AUV‐obtained acoustic tag measurements within a particle filter to improve state estimation accuracy. This improvement is validated through a series of multi‐AUV shark and boat tracking experiments conducted at Santa Catalina Island, California. When compared with previous work that did not use the SmartTag package, results demonstrated a decrease in mean position estimation error of 25–75%, tag orientation estimation errors dropped from 80° to 30° , the sensitivity of mean position error with respect to distance to the tag was less by a factor of 50, and the sensitivity of mean position error with respect to acoustic signal reception frequency to the tag was 25 times less. These statistics demonstrate a large improvement in the system's robustness when the SmartTag package is used.