共查询到20条相似文献，搜索用时 687 毫秒
1.
Probability density function (PDF) method is proposed for analysing the structure of the reconstructed attractor in computing the correlation dimensions of RR intervals of ten normal old men.PDF contains important information about the spatial distribution of the phase points in the reconstructed attractor.To the best of our knowledge, it is the first time that the PDF method is put forward for the analysis of the reconstructed attractor structure.Numerical simulations demonstrate that the cardiac systems of healthy old men are about 6-6.5 dimensional complex dynamical systems.It is found that PDF is not symmetrically distributed when time delay is small, while PDF satisfies Gaussian distribution when time delay is big enough.A cluster effect mechanism is presented to explain this phenomenon.By studying the shape of PDFs, that the roles played by time delay are more important than embedding dimension in the reconstruction is clearly indicated.Results have demonstrated that the PDF method represents a promising numerical approach for the observation of the reconstructed attractor structure and may provide more information and new diagnostic potential of the analyzed cardiac system. 相似文献
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To find the optimal routing is always an important topic in wireless sensor networks （WSNs）. Considering a WSN where the nodes have limited energy, we propose a novel Energy^＊Delay model based on ant algorithms （＂E＆D ANTS＂ for short） to minimize the time delay in transferring a fixed number of data packets in an energy-constrained manner in one round. Our goal is not only to maximize the lifetime of the network but also to provide real-time data transmission services. However, because of the tradeoff of energy and delay in wireless network systems, the reinforcement learning （RL） algorithm is introduced to train the model. In this survey, the paradigm of E＆D ANTS is explicated and compared to other ant-based routing algorithms like AntNet and AntChain about the issues of routing information, routing overhead and adaptation. Simulation results show that our method performs about seven times better than AntNet and also outperforms AntChain by more than 150% in terms of energy cost and delay per round. 相似文献
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1 Ｉｎｔｒｏｄｕｃｔｉｏｎ Ｉｔｉｓｗｅｌｌｋｎｏｗｎｔｈａｔｎ ＧａＡｓａｎｄａｎｕｍｂｅｒｏｆｏｔｈｅｒｃｏｍｐｏｕｎｄｓｅｍｉｃｏｎｄｕｃｔｏｒｓｃａｎｅｘｈｉｂｉｔｓｅｌｆ ｓｕｓｔａｉｎｅｄｃｕｒｒｅｎｔｏｓｃｉｌｌａｔｉｏｎｓｉｎｔｈｅｍｉｃｒｏｗａｖｅｒａｎｇｅｗｈｅｎｔｈｅａｐｐｌｉｅｄｄｒｉｆｔｆｉｅｌｄｅｘｃｅｅｄｓｔｈｅｃｈａｒａｃｔｅｒｉｓｔｉｃｔｈｒｅｓｈｏｌｄｖａｌｕｅ .Ｓｅｍｉｃｏｎｄｕｃｔｏｒｓａｒｅａｐｐｒｏｐｒｉａｔｅｍａｔｅｒｉａｌｓｆｏｒｕｎｄｅｒｓｔａｎ… 相似文献
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电容层析成像是检测封闭空间内部不同介电常数物质分布的有效技术手段。常见的电容层析成像系统被测对象直径一般为10 cm左右,电容检测电路的工作电压一般不超过20 Vpp。当ECT系统应用在粮仓等大尺寸的对象上时,需要提高激励电压以较高的灵敏度和分辨率,从而获得良好重建图像。文章介绍了高压激励电容层析成像系统的结构,给出了内置8极板电容传感器阵列的详细参数,并介绍了几种典型的分布模型的重建图像和误差数据。实验表明：本文所设计的高压电容层析成像系统具有良好的图像重建能力。 相似文献
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时空索引技术是近年来地理信息系统领域的研究热点,如何有机结合空间和时间信息,提高查询效率是重中之重。本文构建了飘浮模型的时空索引机制,以三层数据查询结构保证时空的有效结合。同时,创新的采用影像与矢量数据配准的方式共同作为数据源,降低系统成本,增加直观效果。实践表明该索引机制可以有效提高查询效率,基于该模型的校园地理信息平台运行效果良好。 相似文献
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The flooding distance is an important parameter in the design and evaluation of a routing protocol,which is related not only to the delay time in the route discovery,but also to the stability and reliability of the route.In this paper, the average flooding distance (AFD) for a mobile ad hoc network (MANET) in a random graph model was given based on the dynamic source routing (DSR) protocol.The influence of spatial reuse on the AFD was also studied.Compared with that in the model without the spatial reuse,the AFD in the model with the spatial reuse has much smaller value,when the connetivity probability between nodes in the network is small and when the number of reused times is large.This means that the route discovery with the spatial reuse is much more effective. 相似文献
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Solution to impedance distribution in electrical impedance tomography （EIT） is an ill-posed nonlinear inverse problem. It is especially difficult to reconstruct an EIT image in the center area of a measured object. Tikhonov regularization with some prior information is a sound regnlarization method for static electrical impedance tomography under the condition that some true impedance distribution information is known a priori. This paper presents a direct search method （DSM） as pretreatment of image reconstruction through which one not only can construct a regularization matrix which may locate in areas of impedance change, but also can obtain an initial impedance distribution more similar to the true impedance distribution, as well as better current modes which can better distinguish the initial distribution and the true distribution. Simulation results indicate that, by using DSM, resolution in the center area of the measured object can be improved significantly. 相似文献
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一种新的混沌系统的复合结构分析 总被引：1，自引：0，他引：1
分析了一种新的三维自治混沌系统吸引子的复合结构. 首先证明了该混沌系统存在5个平衡点, 讨论了系统的控制参数大小同平衡点稳定性之间的关系. 其次, 对吸引子在y-z平面的运动轨迹作了理论分析, 描述了吸引子存在及消失的原因. 最后, 通过对该混沌系统运动轨迹在不同控制参数作用下的计算机仿真, 揭示了涡卷数不同的混沌吸引子形成的过程. 表明该混沌系统具有复合结构, 能够演化成其他的三维自治混沌系统. 理论分析及仿真结果对分析其他具有相似结构的混沌系统具有重要的参考价值. 相似文献
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研究了一类非自治时滞微分系统的解的不变集与吸引集的存在性,得到了其解的不变集与吸引集的存在的范围. 相似文献
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中国古代官员致仕制度的法学分析 总被引：2，自引：0，他引：2
齐惠 《内蒙古大学学报(人文社会科学版)》2005,37(6):84-88
官员退休在古代称致仕，是指官员因老、病、孝养等原因交还官职，退休养老的行为。致仕制度源于礼制，在发展的过程中不断向法制化转变，但是在专制政府的权力运作中，政治权力作为一种主要的力量支配着法律的实施，以礼入法的致仕制度始终只是一个过程，最终也未能实现彻底的法制化。 相似文献
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一种伽利略信号跟踪的多路径消除方法 总被引：1，自引：0，他引：1
针对伽利略信号调制的特点,提出了一种基于滤波相关器法的多路径消除方法ELSC（early-late strobe correlator）．通过对滤波相关器法应用于伽利略E1信号的跟踪情况进行分析,发现滤波相关器法不能消除延迟为0．5个码片附近的多路径信号影响．ELSC方法通过对几个滤波相关器的叠加,能有效消除0．5个码片附近的多路径信号影响．通过仿真比较了ELSC方法和滤波相关器法对于伽利略信号的多路径误差包络．结果表明ELSC方法优于传统的滤波相关器法,不仅适用于伽利略信号的跟踪,同时也适用于GPS信号的跟踪． 相似文献
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近20年来，科学心理研究不再局限于信息加工层次上，而是扩展到包括心理的神经机制、分子机制、神经系统本质和并行分布式信息加工的多层次，而且意识问题已开始成为多学科关注的焦点；方法上相应地由以反应时方法、出声思考方法和计算机模拟方法等为主，变为以脑成像等神经科学方法、分子生物学方法、人工神经网络模拟方法和启动效应方法等为主，研究的指标也由意识外显的心理行为指标为主为为以物理、化学、生理指标和意识所不能直接外显的内隐指标为主，出现了新神经主义和新生物学主义的倾向；联合主义取代符号成为方法论思想主流；符号理论已基本被放弃，但新的理论并未建立。这其实是在“心理学科学范式”这一根本问题上发生了改变，即（智能）系统范式取代了经典原（信息加工）过程范式。 相似文献
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控制系统中的时滞现象是影响控制效果的不可忽视的因素。文章采用递归响应法对磁流变阻尼控制系统的算法进行仿真计算,分析在不同情况下递归响应法对磁流变阻尼控制系统的时滞补偿效果,并与主动控制系统进行比较。结果表明,递归响应法对磁流变阻尼控制系统有一定的补偿效果,对主动控制系统效果更加显著。 相似文献
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In tracking test,discharge is a complicated process and comparative tracking index(CTI)has wide variation.To evaluate tracking resistance,the chaos analysis of discharge current is presented based on the tracking test ofphenolic resin in accordance with IEC601 12.According to the characteristics of statistical self-similarity and complexity of discharge current,the largest Lyapunov exponent is calculated,and the 2-dimensional attractor ofdischarge current is reconstructed.Moreover,the attractors of discharge current and recurrence plots of different discharge states are reconstructed.The results indicate that the chaos attractors have different characteristics in evolutionary tracks,the topological structure and grain direction of recurrence plots show significant differences.The chaos attractor can describe the tracking process,the recurrence plot can identify the tracking state clearly,while its arithmetic is simple. 相似文献
16.
范子荣 《雁北师范学院学报》2008,24(5)
针对电加热炉温度控制系统,研究了自适应模糊PID-Smith控制方法.该控制方法利用Smith预估算法克服纯滞后,利用模糊控制来提高系统的鲁棒性,利用PID控制来提高稳态精度.通过Matlab仿真研究,表明该控制器具有良好的稳定性和鲁棒性,对于大时间滞后的电加热炉温控系统是一种实用而简便的控制方法. 相似文献
17.
Elina Lahelma 《Gender and education》2005,17(3):305-317
In Finland more than 80% of the male population participates in military service. Going to the army is an important step in the transition to male adulthood and a period for further education. This paper explores reflections on the army of 20‐year‐old men, some of whom have it already behind them and some others with their military service forthcoming. The focus is on exploring the kinds of masculinities that are constructed when talking about experiences or expectations. The paper suggests that, when talking about the army, male bonds are established which unite men from different cultural, educational and social backgrounds, as well as different generations. This communality is discussed in relation to differences. I concentrate on the making of differences due to the formal hierarchies within the army, between men and the women who participate in military service and between Finns and immigrants in the army. The final discussion is on attitude, endurance and the construction of ‘proper’ masculinity. The paper draws from interviews of 21 young men conducted in a longitudinal, ethnographically grounded study on youth transitions. 相似文献
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X-Z聚羧酸系减水剂的性能研究 总被引：1，自引：0，他引：1
研究了以聚乙二醇系列、丙烯酸、顺酐、烯丙基磺酸钠、丙烯酸羟乙酯为原料合成的X-Z聚羧酸系减水剂对水泥水化过程及微观结构的影响,并测试了掺加减水剂的混凝土性能.结果表明,X-Z系列减水剂具有缓凝特性,能够显著延缓水泥水化的放热;可使水泥气孔细化且分布更加合理,水泥石的后期水化更充分,水化产物结构更紧密更有力量;减水率达25%,坍落度损失低,各龄期混凝土抗压强度都有较大提高.yh 相似文献
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Peer-to-peer (P2P) systems are now very popular. Current P2P systems are broadly of two kinds, structured and unstructured. The tree structured P2P systems used technologies such as distributed hash tables (DHT) and hierarchical clustering can search the required target quickly, however, in a tree, the internal node has a higher load and its leave or crash often causes a large population of its offspring's problems, so that in the highly dynamic Internet environment the tree structure may still suffer frequent breaks. On the other hand, most widely used unstructured P2P networks rely on central directory servers or massive message flooding, clearly not scalable. So, we consider both of the above systems' advantages and disadvantages and realize that in the P2P systems one node may fail easily, but that when a number of nodes organized as a set, which we call "super node", the set is robust. Super nodes can be created and updated aware of topology-aware, and used with simple protocol such as flooding or "servers" to exchange information. Furthermore the entire robust super node can be organized into exquisite tree structure. By using this overlay network architecture, P2P systems are robust, efficient, scalable and secure. The simulation results demonstrated that our architecture greatly reduces the alteration time of the structure while decreasing the average delay time, compared to the common tree structure. 相似文献