ParaGraph: Graph editor support for parallel programming environments

We report here on a graph editor, ParaGraph, that supports massively parallel programming. It provides a flexible mechanism for the concise specification of families of annotated graphs, addressing the problems of user annotation and scale independent graph manipulation. ParaGraph currently serves as the basis for tools supporting communication abstractions in program specification and debugging. Its foundation in an extended form of aggregate rewriting graph grammars makes its adaptation to other parallel programming environments straightforward.The Parallel Programming Environments Project at the University of Massachusetts is supported by the Office of Naval Research under Contract N000014-84-K-0647 and by the National Science Foundation under Grants DCR-8500332 and CCR-8712410.     

An examination of exergy destruction in organic Rankine cycles

The exergy topological method is used to present a quantitative estimation of the exergy destroyed in an organic Rankine cycle (ORC) operating on R113. A detailed roadmap of exergy flow is presented using an exergy wheel, and this visual representation clearly depicts the exergy accounting associated with each thermodynamic process. The analysis indicates that the evaporator accounts for maximum exergy destroyed in the ORC and the process responsible for this is the heat transfer across a finite temperature difference. In addition, the results confirm the thermodynamic superiority of the regenerative ORC over the basic ORC since regenerative heating helps offset a significant amount of exergy destroyed in the evaporator, thereby resulting in a thermodynamically more efficient process. Parameters such as thermodynamic influence coefficient and degree of thermodynamic perfection are identified as useful design metrics to assist exergy‐based design of devices. This paper also examines the impact of operating parameters such as evaporator pressure and inlet temperature of the hot gases entering the evaporator on ORC performance. It is shown that exergy destruction decreases with increasing evaporator pressure and decreasing turbine inlet temperatures. Finally, the analysis reveals the potential of the exergy topological methodology as a robust technique to identify the magnitude of irreversibilities associated with real thermodynamic processes in practical thermal systems. Copyright © 2008 John Wiley & Sons, Ltd.     

基于顺序图着色方法的地面数字电视频率指配

介绍了频率指配的数学模型和顺序图着色方法,并举例说明了顺序图着色方法在地面电视频率指配规划中的实际应用.     

Predicting metamorphic relations for testing scientific software: a machine learning approach using graph kernels

Comprehensive, automated software testing requires an oracle to check whether the output produced by a test case matches the expected behaviour of the programme. But the challenges in creating suitable oracles limit the ability to perform automated testing in some programmes, and especially in scientific software. Metamorphic testing is a method for automating the testing process for programmes without test oracles. This technique operates by checking whether the programme behaves according to properties called metamorphic relations. A metamorphic relation describes the change in output when the input is changed in a prescribed way. Unfortunately, finding the metamorphic relations satisfied by a programme or function remains a labour‐intensive task, which is generally performed by a domain expert or a programmer. In this work, we propose a machine learning approach for predicting metamorphic relations that uses a graph‐based representation of a programme to represent control flow and data dependency information. In earlier work, we found that simple features derived from such graphs provide good performance. An analysis of the features used in this earlier work led us to explore the effectiveness of several representations of those graphs using the machine learning framework of graph kernels, which provide various ways of measuring similarity between graphs. Our results show that a graph kernel that evaluates the contribution of all paths in the graph has the best accuracy and that control flow information is more useful than data dependency information. The data used in this study are available for download at http://www.cs.colostate.edu/saxs/MRpred/functions.tar.gz to help researchers in further development of metamorphic relation prediction methods. Copyright © 2015 John Wiley & Sons, Ltd.     

基于CiteSpace的国内乡村公共空间研究综述

随着国家乡村振兴战略的稳步推进,乡村建设逐渐成为发展的关键领域,公共空间作为乡村的重要组成部分,随之受到广泛的关注。以1996~2021年CNKI国内乡村公共空间研究文献为检索源,采用CiteSpace软件生成科学知识图谱,分析研究的热点与趋势。在此基础上,将现有研究按照综合性与专题性展开文献述评。研究发现：（1）近20年乡村公共空间的研究集中在空间的形态特征、保护更新、演变重构等方面,多学科研究为其提供了广阔的视角;（2）近年来乡村公共空间研究发生物质-社会-文化转向,需关注其文化属性的挖掘,尤其是非物质文化在公共空间中的呈现方式与保护利用模式;（3）乡村公共空间的分类方式多样,类别之间存在交叉重复问题,应明晰类别之间的相互关系,把握基于生产-生活-生态的复合化类型与特征;（4）在新时代快速发展背景下,创新产业与乡村发展密切相关,需进一步更新乡村公共空间的传播和利用方式,发掘其新型价值;（5）乡村公共空间重构聚焦于物质空间的建设与传统文化的保护传承,需注重结合乡村产业发展与城乡融合,构建具有地域性特征的“功能-文化-空间-机制”的重构路径。未来应搭建多学科平台,结合应用性理论探索新视角,同时运用定性定量多种研究方法,综合探索乡村公共空间研究的理论方法与体系。     

重型车湿式桥非线性传动能量流耗分析

重型车湿式桥传动系统能量流动与损耗研究是车辆经济性、安全性及动力性的基础。现有研究主要简单分析单工况下齿轮箱的能量损耗,缺乏复杂工况下基于人车路的传动系统能量流耗精细综合研究。针对典型重型车辆循环作业下的湿式桥传动系统能量流耗进行综合分析,建立不同能量损耗类型的数学模型。考虑车辆循环作业能量流耗影响因素,基于键合图理论分析总成及系统能量流耗情况后,建立整个传动系统的能量流耗模型。此动力学模型与实车试验数据结合不但可以研究一般工况下的人车路湿式桥非线性能量流耗,还可以分析驱动滑转、制动滑移、转弯、轮荷及重心转移等复杂工况,这为今后研究和精确实车复杂工况下的能量流耗情况提供了一套可行的方法。     

基于因子图优化的激光SLAM

为提高基于激光雷达的同步定位和建图(simultaneous localization and mapping,SLAM)精度,提出一种基于因子图的高效率、高精度的激光雷达SLAM框架。采用一种基于滑动窗口的因子图方法,将当前帧进行帧间匹配得到相对位姿,按照一定规则选出关键帧,将关键帧与全局地图进行匹配得到绝对位姿;构建一个因子图,将得到的连续帧之间的相对位姿与关键帧的绝对位姿作为优化因子,机器人的位姿作为状态节点放入因子图中进行位姿优化,得到高频率的机器人位姿以及全局一致的环境地图。结果表明：该算法能够减小误差的累积,具有更高的定位精度。     

Fast accessing Web3D contents using lightweight progressive meshes

Accessing Web3D contents is relatively slow through Internet under limited bandwidth. Preprocessing of 3D models can certainly alleviate the problem, such as 3D compression and progressive meshes (PM). But none of them considers the similarity between components of a 3D model, so that we could take advantage of this to further improve the efficiency. This paper proposes a similarity‐aware data reduction method together with PM, called lightweight progressive meshes (LPM). LPM aims to excavate similar components in a 3D model, generates PM representation of each component left after removing redundant components, and organizes all the processed data using a structure called lightweight scene graph. The proposed LPM possesses four significant advantages. First, it can minimize the file size of 3D model dramatically without almost any precision loss. Because of this, minimal data is delivered. Second, PM enables the delivery to be progressive, so called streaming. Third, when rendering at client side, due to lightweight scene graph, decompression is not necessary and instanced rendering is fully exerted. Fourth, it is extremely efficient and effective under very limited bandwidth, especially when delivering large 3D scenes. Performance on real data justifies the effectiveness of our LPM, which improves the state‐of‐the‐art in accessing Web3D contents. Copyright © 2015 John Wiley & Sons, Ltd.     

基于KM算法投切事件匹配的负荷辨识方法

负荷投切事件是关联负荷分类、辨识的一个重要依据,为了能够准确的实现非侵入式负荷投切过程的辨识,提出一种基于KM算法投切事件匹配的非侵入式负荷辨识方法。在该方法中,首先采用一种功率曲线拟合逼近的方式进行负荷事件检测,并利用投切稳态特征建立用电设备投入和切除特征的概率分布模型。同时,考虑到负荷投入事件和切除事件数量不对等情况,将负荷事件与数据库负荷进行匹配,并采用加权优化的KM算法寻找最佳解,从而实现负荷投入和切除的正确匹配辨识。最后,在真实的测试场景并结合REDD数据集进行实验,结果表明文中方法能对负荷投切事件进行有效匹配辨识,为实现能耗细分奠定了基础。