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多级环境下基于非定常/定常流混合分析的叶片颤振预报方法 被引量:3
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作者 黄秀全 张翔 张恒铭 《工程热物理学报》 EI CAS CSCD 北大核心 2014年第7期1304-1308,共5页
发展了多级叶轮机环境下应用于叶片颤振预报的非定常流/定常流混合分析方法。对于叶片颤振预报,采用了基于能量法的单向耦合方法。非定常流计算采用了高效的频域谐波方法,定常流计算采用了时间推进方法。在非定常流和定常流交界面,发展... 发展了多级叶轮机环境下应用于叶片颤振预报的非定常流/定常流混合分析方法。对于叶片颤振预报,采用了基于能量法的单向耦合方法。非定常流计算采用了高效的频域谐波方法,定常流计算采用了时间推进方法。在非定常流和定常流交界面,发展了基于滤波技术的无反射混合平面方法。本文发展的叶片颤振预报方法,忽略了叶排干涉非定常流对叶片颤振稳定性的非线性影响,但包含了多级定常基础流动效应。通过对某二级风扇的颤振预测验证了该方法的有效性。 展开更多
关键词 叶片颤振 频域谐波方法 非定常流 混合分析 多级环境
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Chinese Wall策略及其在多级安全环境中的扩展 被引量:8
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作者 秦超 陈钟 段云所 《北京大学学报(自然科学版)》 CAS CSCD 北大核心 2002年第3期369-374,共6页
ChineseWall安全策略因不同于BLP的动态特性而备受人们关注 ,但Brewer和Nash定义的ChineseWall策略只适用一定的应用范围 ,没有考虑普遍存在的多级访问控制的限制条件。本文主要结合多级安全环境 ,分析研究具有多级访问控制环境的Chines... ChineseWall安全策略因不同于BLP的动态特性而备受人们关注 ,但Brewer和Nash定义的ChineseWall策略只适用一定的应用范围 ,没有考虑普遍存在的多级访问控制的限制条件。本文主要结合多级安全环境 ,分析研究具有多级访问控制环境的ChineseWall策略的扩展实现。根据该环境中的ChineseWall的利益冲突处理表现为数据聚合问题 ,利用数据标签的格级标定 ,提出一种基于历史访问库和利益冲突聚合链表的安全策略实现方法。 展开更多
关键词 CHINESE Wall策略 数据聚合 格级 历史访问库 多级安全环境 计算机
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确定应力模型在离心压缩机级流场模拟的应用 被引量:3
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作者 高丽敏 李晓军 +1 位作者 高杰 刘波 《机械工程学报》 EI CAS CSCD 北大核心 2011年第2期166-172,共7页
在求解多级叶轮机械流场的定常计算方法中,ADAMCZYK提出的通道平均方法比混合界面方法更为严格也更为复杂,方程中的确定应力项反映了级环境下流场非定常性的时均效应。然而,与雷诺平均方程一样,通道平均方程本身也没包含足够的信息来确... 在求解多级叶轮机械流场的定常计算方法中,ADAMCZYK提出的通道平均方法比混合界面方法更为严格也更为复杂,方程中的确定应力项反映了级环境下流场非定常性的时均效应。然而,与雷诺平均方程一样,通道平均方程本身也没包含足够的信息来确定它的解。基于简化的通道平均方程,建立适合离心压缩机动静相干非定常的半经验确定应力模型,替代重叠区域方法来计算确定应力的方法,结合界面处理方法,发展预测离心压缩机级环境下包含动/静相干周期性非定常流场的时均效应的定常计算方法。采用确定应力模型及混合界面两种方法对两台离心压缩机级内的流场进行计算,两种方法计算时间相当。与混合界面方法相比,由于考虑了非定常流动的时均效应,确定应力模型方法得到的流场分布与试验测量更加吻合;而且确定应力的引入在一定程度上能补偿'人工掺混'带来的影响,采用确定应力模型能够得到更真实的流场。 展开更多
关键词 通道平均 N-S 方程 多级环境 确定应力 离心压缩机
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The Super-population Bridges the Habitat Diversity and Biodiversity 被引量:3
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作者 李天星 《Agricultural Science & Technology》 CAS 2009年第6期11-14,19,共5页
There is another way for new species to invade former settlers' habitats and successfully settle there; it is demonstrated that the su- per-population, which plays a key role in changing the world-wide environment, c... There is another way for new species to invade former settlers' habitats and successfully settle there; it is demonstrated that the su- per-population, which plays a key role in changing the world-wide environment, can create many new microhabitats in the old habitat, it is these new microhabitats that make new species easily come into the old habitat and settle there without fierce competition with former settlers. In other words, the super-population lead to the differentiation of the worldwide environment, lead to the environmental diversity in the biosphere. Through the differentiation of the environment the super-population produces many new microhabitats for new species, the appearance of many new microhabitats make it possible for new species to coexist with former settlers in the biosphere. The cqexistence of new species with former settlers or with new species' "ancestors" results in the increaseing in the biodiversity of the biosphere. The super-population is the founder of many new environments on the earth, it bridges the habitat diversity and the biodiversity. Now It is easy to explain the phenomenon that new species sometimes coexist with former settlers and even depend on former settlers in the biosphere rather than fierce competition between them. 展开更多
关键词 Super-population MICROHABITAT Habitat diversity Species diversity BIODIVERSITY
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Competitive location problem of multi-level pickup point considering cooperative coverage 被引量:2
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作者 Han Xun Zhang Jin Zeng Qian 《Journal of Southeast University(English Edition)》 EI CAS 2019年第1期111-117,共7页
To occupy a greater market share in terminal distribution, companies are urged to make full use of cooperative coverage formed with brand effect and information sharing in the layout of pickup points. Based on the div... To occupy a greater market share in terminal distribution, companies are urged to make full use of cooperative coverage formed with brand effect and information sharing in the layout of pickup points. Based on the diversity of pickup points, the piecewise function, signal intensity function and probability function are introduced. Meanwhile, considering the effect of distance satisfaction and cooperation coverage on customer behavior, the location model of the pickup point under competitive environments is established. The genetic algorithm is used to solve the problem, and the effectiveness of the model and algorithm is verified by a case. The results show that the sensitivity of weighted demand coverages to budget decreases gradually. The maximum weighted demand coverage increases at first and then decreases with the increase of the signal threshold, and there is a positive correlation with the change of the actual demand coverage to the senior customers, but it is negatively related to the intermediate and primary customers. When the number of high-level pickup points in a competitive enterprise is small, the advantage of the target enterprise is more significant. Through comparison, the cooperative coverage model is better than the non-cooperative coverage model, in terms of the weighted demand coverage, the construction cost and the attention paid to the important customers. 展开更多
关键词 pickup point cooperative coverage multi-level facility layout competitive conditions genetic algorithm
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An Interconnected Multi-Plane Multi-Stage Fault-Tolerant On-Board Switching Fabric 被引量:1
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作者 LIU Kai YAN Jian +1 位作者 CHEN Xiang LU Jianhua 《China Communications》 SCIE CSCD 2015年第2期74-83,共10页
The harsh space radiation environment compromises the reliability of an on-board switching fabric by leading to cross-point and switching element(SE)faults.Different from traditional faulttolerant switching fabrics on... The harsh space radiation environment compromises the reliability of an on-board switching fabric by leading to cross-point and switching element(SE)faults.Different from traditional faulttolerant switching fabrics only taking crosspoint faults into account,a novel Input and Output Parallel Clos network,referred to as the(p_1,p_2)-IOPClos,is proposed to tolerate both cross-point and SE faults.In the(p_1,p_2)-IOPClos,there are p_1 and p_2 expanded parallel switching planes in the input and output stages,respectively.The multiple input/output switching planes are interconnected through the middle stage to provide multiple paths in each stage by which the network throughput can be increased remarkably.Furthermore,the network reliability of the(p_1,p_2)-IOPClos under the above both kinds of faults is analyzed.The corresponding implementation cost is also presented along with the network size.Both theoretical analysis and numerical results indicate that the(p_1,p_2)-IOPClos outperforms traditional Clos-type networks at reliability,while has less implementation cost than the multi-plane Clos network. 展开更多
关键词 on-board switching fabric clos network reliability
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DPTSV:A Dynamic Priority Task Scheduling Strategy for TSS Deadlock Based on Value Evaluation 被引量:2
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作者 ZHAO Bo XIANG Shuang +1 位作者 AN Yang TAO Wei 《China Communications》 SCIE CSCD 2016年第1期161-175,共15页
This paper analyzes the threat of TCG Software Stack(TSS)/TCM Service Module(TSM) deadlock in multi-user environment such as cloud and discusses its causes and mechanism.In addition,this paper puts forward a dynamic p... This paper analyzes the threat of TCG Software Stack(TSS)/TCM Service Module(TSM) deadlock in multi-user environment such as cloud and discusses its causes and mechanism.In addition,this paper puts forward a dynamic priority task scheduling strategy based on value evaluation to handle this threat.The strategy is based on the implementation features of trusted hardware and establishes a multi-level ready queue.In this strategy,an algorithm for real-time value computing is also designed,and it can adjust the production curves of the real time value by setting parameters in different environment,thus enhancing its adaptability,which is followed by scheduling and algorithm description.This paper also implements the algorithm and carries out its performance optimization.Due to the experiment result from Intel NUC,it is shown that TSS based on advanced DPTSV is able to solve the problem of deadlock with no negative influence on performance and security in multi-user environment. 展开更多
关键词 TCG software stack/TCM service module deadlock multi-user trusted platform module real-time value
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LDPC Coding Scheme for Improving the Reliability of Multi-Level-Cell NAND Flash Memory in Radiation Environments 被引量:2
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作者 Guangjun Ge Liuguo Yin 《China Communications》 SCIE CSCD 2017年第8期10-21,共12页
Utilizing commercial off-the-shelf(COTS) components in satellites has received much attention due to the low cost. However, commercial memories suffer severe reliability problems in radiation environments. This paper ... Utilizing commercial off-the-shelf(COTS) components in satellites has received much attention due to the low cost. However, commercial memories suffer severe reliability problems in radiation environments. This paper studies the low-density parity-check(LDPC) coding scheme for improving the reliability of multi-level-cell(MLC) NAND Flash memory in radiation environments. Firstly, based on existing physical experiment works, we introduce a new error model for heavyion irradiations; secondly, we explore the optimization of writing voltage allocation to maximize the capacity of the storage channel; thirdly, we design the degree distribution of LDPC codes that is specially suitable for the proposed model; finally, we propose a joint detection-decoding scheme based on LDPC codes, which estimates the storage channel state and executes an adaptive log-likelihood ratio(LLR) calculation to achieve better performance. Simulation results show that, compared with the conventional LDPC coding scheme, the proposed scheme may almost double the lifetime of the MLC NAND Flash memory in radiation environments. 展开更多
关键词 low-density parity-check(LDPC) coding multi-level-cell(MLC) NAND Flash memory joint detection-decoding commercial off-the-shelf(COTS) components space radiation environments
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单级低速模拟轴流压气机实验台改进设计 被引量:6
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作者 刘宝杰 张帅 +2 位作者 于贤君 安广丰 付丹阳 《航空动力学报》 EI CAS CSCD 北大核心 2018年第7期1665-1675,共11页
为了使单级低速台能够更好地模拟高压压气机后面级流动,采用导叶+静子+转子+静子+导叶的五排叶片布局,适当提高轮毂比,以及采用3D打印树脂叶片,对常规三排叶片单级低速模拟大尺寸轴流压气机实验台进行了改进设计研究,并与四级重复级低... 为了使单级低速台能够更好地模拟高压压气机后面级流动,采用导叶+静子+转子+静子+导叶的五排叶片布局,适当提高轮毂比,以及采用3D打印树脂叶片,对常规三排叶片单级低速模拟大尺寸轴流压气机实验台进行了改进设计研究,并与四级重复级低速大尺寸压气机实验台的第三级结果进行了对比。结果表明:改型设计的单级低速大尺寸压气机的设计点效率达到了89.1%,流量裕度达到了32.9%,与四级重复级实验结果基本一致,而且实现了基本相似的级间参数分布,比传统单级实验台更接近高压压气机后面级的典型流动,从而可以利用该实验台成本低和周期短的优势,开展更多更深入的关于高压压气机后面级流动机理和设计方法的实验研究。 展开更多
关键词 低速模拟 单级压气机 流场测量 多级环境 三维打印
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