混响室场均匀性的FEKO仿真

介绍了混响室的基本原理和主要参数,阐述了混响室场均匀性校准的步骤和场均匀性标准偏差的计算方法.利用FEKO软件对混响室建模,进行最低可用频率处的场均匀性校准的仿真,计算工作区8个位置的电场,得到场标准偏差.仿真结果表明,混响室在200 MHz的场均匀性完全符合标准IEC61000-4-21的规定,电场均匀性标准偏差小于3.66 dB.     

电磁混响室的性能校准

介绍了电磁兼容测试中常用到的混响室技术,并讨论了混响室的校准方法。利用E场探头和对数周期天线对混响室性能进行了测试,确定了混响室的性能系数,如ACF,IL等和工作区场的均匀度。     

源搅拌混响室天线布置方式实验研究

根据谐振腔理论,分析了理想情况下影响源搅拌混响室性能的主要因素.通过实验方法,对提出的两种源搅拌方案从场均匀性和统计特性两方面进行分析.经过对采样数据处理可知,在一定数量采样值的情况下,这两种方式都可以实现较好的场均匀性,同时借助K-S拟合对测量值的统计特性进行了分析,结果表明源搅拌混响室的一维场分布服从瑞利分布,通过...     

天线反射对混波室场均匀性校准的影响

场均匀性是混波室的重要指标,但其在校准中会受天线反射的影响。首先计算分析了混波室经验最低使用频率与体积的关系,通过增加体积降低最低使用频率会增加成本;然后介绍了混波室场均匀性校准程序,最后通过实验分析得出,混波室搅拌器搅动会影响发射天线驻波比,由此导致归一化因子不同混波室场强归一化标准偏差不同,甚至会影响混波室最低使用频率。     

多通道温度测量整体校准系统仿真分析

为了实现低温风洞等设备高精度温度场测量目的 ,需要综合考虑温度传感器、连接电缆、调理放大器、数据采集系统以及环境等各种因素产生的综合误差,设计一套在低温范围内对温度测量系统进行整体全回路原位校准装置;针对整体全回路原位校准装置在准度、温度场均匀性、温度场稳定性等各方面的高精度要求,在装置方案设计完成后,对其核心部分隔热校准腔进行了热力学仿真计算,对其主体三层结构型式、绝热技术、引线密封方式、温度场均匀性保证措施等进行了模拟计算,并建立了实验平台对仿真结果进行了实际验证和方案优化;仿真和实验验证结果证明,低温温度测量系统整体校准装置所采用的设计方案能够满足一次校准通道数11路和在77～323 K温度范围内温度准度50 mK、有效温度场均匀性50 mK等技术指标要求.     

温度继电器温度特性自动检测方法研究及应用

为了实现温度继电器温度特性的自动检测,论文从应用角度出发,论述了一种基于空气测定法的简单实用、精度高的自动检测系统.该系统设计了电阻加热炉来模拟检测温场,并通过较长时间的预热和用鼓风机实现检测温场的空气流动,显著提高了温度均匀性,采用模糊算法按照设定的控温曲线对温场温度进行控制.在该系统中,还提出了电阻加热炉炉丝按功率分组策略,大大改善了电炉性能;并采取整体最小二乘法误差校准,有效地提高了系统检测精度.     

改进敏感场的电容层析成像图像重建算法

针对电容层析成像系统中敏感场的“软场”特性,提出了一种基于成像敏感场灵敏度均值滤波的Landweber图像重建算法。该算法是通过模板卷积的方式对敏感场灵敏度进行邻域平均,降低靠近极板区域的灵敏度,提高管道中心区域的灵敏度,部分消除了因敏感场不均匀对图像重建质量的影响,提高图像重建精度。仿真结果表明,该算法在图像重建精度和收敛速度上均优于传统的Landweber图像重建算法。     

基于局部区域拟合模型的磁共振图像分割与偏移估计算法

磁共振(MR)图像的灰度通常是不均匀的,这种不均匀性是由于成像设备的缺陷导致产生了一种光滑的偏移场.一般的基于灰度统计特性的分割算法都是假设目标区域和背景区域图像的灰度分别是一致的,因此该类算法不能很好地应用于磁共振图像的分割.提出一种基于局部拟合模型的磁共振图像分割与偏移估计算法:利用图像的局部区域的灰度特性建立恢复...     

温度继电器温度特性检测系统的研制

为了实现温度继电器温度特性的检测,本文从应用角度出发,论述了一种基于空气测定法的简单实用、高精度的自动检测系统.本系统设计了电阻加热炉来模拟实现检测温场,并通过较长时间的预热和在试验腔的检测段放置孔板显著提高了温度均匀性,采用模糊算法按照设定的控温曲线对温场温度进行控制.在该系统中,还提出了电阻加热炉炉丝按功率分组策略,大大改善了电炉性能;并采取整体最小二乘法误差校准,有效提高了系统检测精度.     

基于相关性的快速体绘制研究

光线投射法是三维直接体绘制算法中的一种最基本方法,但简单的光线投射算法存在采样效率低和绘制速度慢的缺点。本文充分利用对象空间与图像空间的各种相关性,利用 对象空间中数据场的相关性,对采样点处的均匀性区域采用正方体进行度量,并以此来确定采样步长,在射线方向上采用自适应的采样方式,避免在采样点周围均匀性区域中中重复地进行采样,大大地提高了三维数据场的绘制速度。     

煤矿井下安全监控分站的设计及其仿真实现

为了设计一种具有低成本、低功耗、易操作、功能强且可靠性高的煤矿井下安全分站,针对煤矿安全生产实际,文章提出了采用MCS-51系列单片机为核心、具有CAN总线通信接口的煤矿井下安全监控分站的设计方案;首先给出煤矿井下安全监控分站的整体构架设计,然后着重阐述模拟量输入信号处理系统的设计过程,最后说明单片机最小系统及其键盘、显示、报警、通信等各个组成部分的设计;为验证设计方案的可行性与有效性,使用Proteus软件对设计内容进行仿真验证,设计的煤矿井下安全监控分站具有瓦斯、温度等模拟量参数超标报警功能和电机开停、风门开闭等开关量指示功能;仿真结果表明:设计的煤矿井下安全监控分站具有一定的实际应用价值.     

View-based model-driven architecture for enhancing maintainability of data access services

In modern service-oriented architectures, database access is done by a special type of services, the so-called data access services (DAS). Though, particularly in data-intensive applications, using and developing DAS are very common today, the link between the DAS and their implementation, e.g. a layer of data access objects (DAOs) encapsulating the database queries, still is not sufficiently elaborated, yet. As a result, as the number of DAS grows, finding the desired DAS for reuse and/or associated documentation can become an impossible task. In this paper we focus on bridging this gap between the DAS and their implementation by presenting a view-based, model-driven data access architecture (VMDA) managing models of the DAS, DAOs and database queries in a queryable manner. Our models support tailored views of different stakeholders and are scalable with all types of DAS implementations. In this paper we show that our view-based and model driven architecture approach can enhance software development productivity and maintainability by improving DAS documentation. Moreover, our VMDA opens a wide range of applications such as evaluating DAS usage for DAS performance optimization. Furthermore, we provide tool support and illustrate the applicability of our VMDA in a large-scale case study. Finally, we quantitatively prove that our approach performs with acceptable response times.     

A pragmatic multi-method investigation of discrepant technological events: Coping,attributions, and ‘accidental’ learning

Discrepant technological events or situations that entail a problem, a misunderstanding or a difficulty with the Information Technology (IT) being employed, are common in the workplace, and can lead to frustration and avoidance behaviors. Little is known, however, about how individuals cope with these events. This paper examines these events by using a multi-method pragmatic approach informed by coping theory. The results of two studies – a critical incident study and an experiment – serve to build and test, respectively, a theoretical model that posits that individuals use a variety of strategies when dealing with these events: they experience negative emotions, make external attributions, and adopt engagement coping strategies directed at solving the event, eventually switching to a disengagement coping strategy when they feel they have no control over the situation. Furthermore, users’ efforts may result in ‘accidental’ learning as they try to overcome the discrepant IT events through engagement coping. The paper ends with a discussion of the results in light of existing literature, future opportunities for research, and implications for practice.     

The Distributed Time-Triggered Simulation Scheme: Core Principles and Supporting Execution Engine

Distributed real-time simulation is a young technology field but its practice is under increasing demands. In recent years the author and his collaborators have been establishing a new approach called the distributed time-triggered simulation (DTS) scheme which is conceptually simple and easy to use but widely applicable. The concept was initiated in the course of developing a new-generation object-oriented real-time programming scheme called the time-triggered message-triggered object (TMO) programming scheme. Some fundamental issues inherent in distributed real-time simulation that were learned during recent experimental studies are discussed along with some approaches for resolving the issues. An execution engine developed to support both the TMOs engaged in control computation and the TMOs engaged in DTS is also discussed along with its possible extensions that will enable significantly larger-scale DTSs.     

Software-Konfigurationsmanagement in großen Softwareprojekten

Zusammenfassung Mit zunehmender Größe der Softwaresysteme verschärfen sich die für die Software-Herstellung typischen Probleme: Beherrschen großer Objektmengen, Erhalten der Systemkonsistenz, Kontrolle der ständigen Änderungseinflüsse und Gewährleisten einer langen Lebensdauer. Die Disziplin Konfigurationsmanagement bildet den methodischen Ansatz, diese Probleme besser zu beherrschen. Software-Konfigurationsmanagement faßt die Herstellung von Softwaresystemen als eine Abfolge von kontrollierten Änderungen an gesicherten Zwischen- und Endergebnissen auf. Dargestellt werden die Objekte und Funktionen des Software-Konfigurationsmanagements sowie die hierfür in großen Software-Projekten benötigten Methoden, Instanzen und Hilfsmittel.     

Information for Authors

正http://www.zju.edu.cn/jzus http://www.springerlink.com Aim The Journals of Zhejiang University-SCIENCE(A/B/C)are edited by the international board of distinguished Chinese and foreign scientists,and are aimed to present the latest developments and achievements in scientific research in China and     

Editorial:Brain-machine interface(BMI) and cyborg intelligence

正Brain-machine interfaces(BMIs)aim at building a direct communication pathway between the brain and an external device,and represent an area of research where significant progress has been made during the past decade.Based on BMIs,mind information can be read out by neural signals to control     

Information for Authors

正http://www.zju.edu.cn/jzus http://www.springerlink.com Aim The Journals of Zhejiang University-SCIENCE(A/B/C)are edited by the international board of distinguished Chinese and foreign scientists,and are aimed to present the latest developments and achievements in scientific research in China and overseas to the world’s scientific circles,especially to stimulate     

SCIENCE CHINA Information Sciences SUBJECT INDEX TO VOLUME 57(2014)

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Information for Authors

正http://www.zju.edu.cn/jzus http://www.springerlink.com Aim The Journals of Zhejiang University-SCIENCE(A/B/C)are edited by the international board of distinguished Chinese and foreign scientists,and are aimed to present the latest developments and achievements in scientific research in China and overseas to the world’s scientific circles,especially to stimulate