叠前深度逆时偏移成像的并行算法研究

逆时偏移(RTM)成像波场逆推具有计算量大和运算速度慢的问题。为此,根据叠前深度RTM算法的特点,运用稳定条件、边界条件、成像条件3个要件并基于消息传递接口,提出全波波动方程叠前深度RTM成像并行算法。与传统柯西霍夫叠前深度偏移算法进行对比的结果表明,该算法能够较好地对地震数据进行偏移成像,成像效果优于传统算法并且并行速度较快。     

一种基于共享存储的叠前深度偏移并行算法

为了解决叠前深度偏移计算量巨大这个问题,人们投入了很大精力来开发高效的并行算法.就此,在对一些相关并行算法进行分析之后,根据三维叠前Kirchhoff深度偏移的特点,提出了一种基于共享存储的简化并行算法.其中Slave进程直接存储和读取射线旅行时,消息传递总量显著减少;同时合理地结合"任务池"技术与粗粒度级并行,前者确保动态负载平衡,后者使得Slave与Master之间的通信开销尽可能小.实际数据的测试结果表明,此并行算法高效且可扩展性较好.     

基于Xeon Phi平台的波动方程叠前深度偏移

波动方程叠前深度偏移适用于强横向变速介质,是一种高精度成像方法,但其巨大的计算量阻碍了该技术的应用。Xeon Phi是一种全新的高性能计算设备,为波动方程叠前深度偏移方法的推广应用提供了新的技术支持。以裂步傅里叶算子为例,介绍了面向Xeon Phi平台的偏移算法移植和优化方法,即采用offload模式将计算核函数加载到Xeon Phi设备上,在Xeon Phi协处理器上采用多线程方式,并且调整程序结构,充分利用SIMD矢量引擎提高向量化处理效率。扩展负载动态均衡的并行框架,形成了一套适用于大规模异构系统、基于Xeon Phi平台的波动方程叠前深度偏移软件。实际数据测试表明Xeon Phi平台可以极大地提高地震偏移处理效率,具有良好的可扩展性。     

基于多层次并行算法的共成像点道集抽取

研究地表区域勘探和开发,应依靠地震偏移成像算法。在地震勘探中,利用叠前深度偏移抽取的共成像点道集为修正偏移速度提供了一种工具,然而庞大的计算量严重影响生产速度。为提高数据处理速度,提出了多层次并行共成点道集抽取算法,在集群节点间利用MPI并行,每个节点内部采用OpenMP并行,从而充分发挥每个节点的运算性能。实验结果表明,基于多层次并行的共成像点道集抽取具有良好的并行加速比和并行效率,有效提高了偏移速度分析的计算效率,为地震资料处理提供了更优的并行策略,并为油气勘探提供有效参考依据。     

基于CUDA的Kirchhoff叠前时间偏移算法设计与实现*

Kirchhoff叠前时间偏移是地震数据处理中最耗时的常用模块之一。为加快计算和显示速度,针对CUDA平台多处理器流水线特性,对传统Kirchhoff叠前时间偏移算法在CUDA平台上进行了重新设计,包括基于CUDA的Kirchhoff叠前时间偏移算法、基于CUDA的纵波波动方程算法和GPU与CPU间的通信算法三个子算法。所有算法在NVIDIA GeForce 8800 GT系统上编译实现,通过对比相同数据在Intel Core2Due CPU 2.0 GHz的地震偏移,综合分析和实验结果表明,基于CUDA     

三维叠前kirchhoff深度偏移软件在并行计算机上的实现技术

文章针对三维叠前kirchhoff深度偏移过程中的成像精度和并行效率两项技术指标,进行了实用技术研究。为提高成像精度笔者开发了三种反假频算法、三种旅行时体插值方法、偏移孔径控制和振幅保真技术;为提高并行效率这里采用分治策略将叠前数据分割、成像体分块来解决处理器间负载平衡问题。采用国际通用的Marmousi模型来验证软件的正确性和实用性,选用SEG/EAGE模型进行了并行效率测试。成像深度误差小于3％,在2-8个处理器试验,并行效率平均到达80％,霍多莫尔实际资料处理取得满意效果。     

基于混合负载平衡的并行启发式搜索算法

在分析了迭代加深启发式搜索(Iterative Deepening A*)算法及其可并行性后，提出了一种新的基于混合负载平衡的并行迭代加深启发式搜索算法。该算法综合了静态负载平衡和动态负载平衡的优点，可以在多结点的并行搜索计算中获得很高的加速比和效率。给出了该算法的Java RMI实现。通过在72个结点的并行机上的试验表明，该算法可以极大地提高并行搜索算法的加速度和效率。     

基于余弦向量法的Web数据并行抓掘系统

为了提高Web海量数据的抓掘效率,引入并行机群抓掘机制。为使机群中每个计算节点的能力得到充分发挥,应用向量度量技术解决抓取任务和计算节点能力匹配的问题。对抓取任务向量、计算节点向量进行定义,提出余弦向量匹配算法,描述相关并行算法。理论分析和实验表明,基于余弦向量匹配算法的挖掘任务分配模型具有良好的分配适应性和负载平衡性。     

基于Slice的H.264并行视频编码算法

从H.264视频编码标准的特点出发,提出了基于Slice级别的H.264视频编码并行算法,该算法不仅能够保证节点间的负载平衡,减少各节点间数据的依赖关系,还充分利用了已有的计算能力。最后给出了在曙光3000上的实验结果。     

并行算法与并行机相结合的可扩展性

可扩展性是设计并行算法和高性能并行机所要考虑的一个重要问题。文中首先分析了等效率和等速度两种可扩展性评价准则,指出其优缺点,然后在分析并行计算时间的基础上提出一种新的可扩展性评价准则（等并行开销计算比可扩展性评价准则）,新准则可用来评价并行算法与并行机相结合的可扩展性。最后用该评价准则分析了两个并行算法与ＹＨ０３高性能并行机相结合的可扩展性。     

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