共查询到20条相似文献，搜索用时 15 毫秒
1.
Ahmadreza Argha Li Li Steven W. Su Hung Nguyen 《Journal of The Franklin Institute》2018,355(14):6191-6214
This paper proposes a framework for the design of sparsely distributed output feedback discrete-time sliding mode control (ODSMC) for interconnected systems. The major target here is to develop an observer based discrete-time sliding mode controller employing a sparsely distributed control network structure in which local controllers exploit some other sub-systems’ information as well as its own local information. As the local controllers/observers have access to some other sub-systems’ states, the control performance will be improved and the applicability region will be widened compared to the decentralised structure. As the first step, a stability condition is derived for the overall closed-loop system obtained from applying ODSMC to the underlying interconnected system, by assuming a priori known structure for the control/observer network. The developed LMI based controller design scheme provides the possibility to employ different information patterns such as fully distributed, sparsely distributed and decentralised patterns. In the second step, we propose a methodology to identify a sparse control/observer network structure with the least possible number of communication links that satisfies the stability condition given in the first step. The boundedness of the obtained overall closed-loop system is analysed and a bound is derived for the augmented system state which includes the closed-loop system state and the switching function. 相似文献
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动物都需要认识和学习外界环境因素,并根据价值与风险做出抉择与行动;社会动物还必须有社会认知、共情、社会交往等社会行为能力;而人类有发达的自我认知、逻辑推演、意识、语言等能力。动物认知能力的好坏,决定了动物在野外是否能够成功觅食、躲避天敌、繁衍后代;而人类认知能力,则决定了个人的人生轨迹、自我价值实现乃至对社会的贡献。所有这些认知行为都是由神经细胞的功能来决定,其神经基础是脑科学的核心问题,也是人类认识自身的终极挑战。经过多年的研究,神经科学已经揭示了认知行为神经基础的一些基本原理:不同认知行为是由脑内不同的神经环路负责,需要各脑区内的局部神经环路与脑区间长程神经环路的协同工作;学习与记忆是许多认知功能的必要基础,这是由神经细胞之间突触联结的强度与结构的可塑性介导;神经调质(例如多巴胺)可以在多个尺度上调节神经网络的活动与可塑性,从而调控认知行为。文章聚焦在感知觉、学习与记忆、抉择、社会行为、意识和运动控制等方面,对认知功能的神经基础进行了概述。我们认为,未来神经科学需要结合介观和微观尺度的研究,对认知行为的神经基础进行系统与深入的阐明。在介观层面,科学家们需要描绘脑区之间细胞类型特异性的联结图谱;绘制认知功能的大脑功能图谱;利用因果性手段、揭示认知功能的核心脑区;操控不同脑区及脑区间联结的活动,进而观察认知行为的改变和其他参与环路的活动变化,从而获得脑整体动态规律。在微观层面,需要阐明不同脑区有哪些特定类型的神经元;揭示不同类型神经元是如何参与特定认知功能的;解析不同类型的神经元是如何联结以及这些联结是如何在认知行为中发生动态改变的。这些介观与微观研究将为理解宏观认知行为的神经基础提供重要线索,对于破解人类智能这一终极奥秘具有重要意义。同时,揭示认知行为的神经机制还是治疗脑疾病的必要基础,而且有助于推动脑启发(Brain Inspired)的智能技术的发展。 相似文献
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《Information processing & management》2022,59(3):102901
Deep learning methods have been widely applied for disease diagnosis on resting-state fMRI (rs-fMRI) data, but they are incapable of investigating global relationships between different brain regions as well as ignoring the interpretability. To address these issues, this paper presents a new graph neural network framework for brain disease diagnosis via jointly learning global relationships and selecting the most discriminative brain regions. Specifically, we first design a self-attention structure learning to capture the global interactions between brain regions for achieving diagnosis effectiveness, and theoretically integrate a feature selection method to reduce the noise influence as well as achieve interpretability. Experiment results on three neurological diseases datasets show the effectiveness of our method, compared to the comparison methods, in terms of diagnostic performance and interpretability. 相似文献
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基于模体的科学家合作网络基元特征分析 总被引：2，自引：0，他引：2
基于复杂网络构建科学家合作网络并分析其全局结构特征,是理解科学家间合作机制的重要手段和研究热点。实际上,辨识其局部结构可以进一步增进对合作机制的理解。基于复杂网络局部结构研究的前沿理念和方法——模体,构建并辨析若干大型科学家合作网络的基元特征:模体特性、子图浓度以及子图自下而上的组合机制。研究表明不同领域科学家合作网络的模体与反模体形式具有共性特征,网络的子图相对浓度则因不同领域科学家之间合作强度及网络发展程度差异而具有不同的分布特征。此外,科学家合作网络具有相似的自下而上构建机制。研究提供了基于模体的科学家合作网络结构辨识方法。 相似文献
5.
基于2016年北京市、江苏省、陕西省三个重要区域的高校专利权转移数据,运用社会网络分析方法和多元回归模型,探索不同区域高校科技成果转化的网络结构和影响因素。研究表明,三个重要地区高校科技成果均在本地实现了较高的转化量,其中江苏省在本地的转化率超过了50%;三个重要地区高校均趋向于在经济活力高、创新水平较高的区域进行科技成果转化活动;影响各个区域高校科技成果转化的因素存在着一些差异,不能一概而论。不同发展模式和经济水平的区域要依据自身发展特点,选取合适的参照对象,有针对性的采取一定的措施来刺激本地高校专利的发明和转让。 相似文献
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跨区域产学协同创新网络是一个由区域、区域间合作关系构成的合作网络,以及知识元素、知识元素间组合关系构成的知识网络共同构成的依存型多层网络。利用1997—2017年我国跨区域产学联合申请专利数据进行实证分析,结果表明：区域在合作网络中的中心性、结构洞和知识网络的多样性、组合机会显著正向影响跨区域协同创新绩效;知识网络的多样性负向调节区域在合作网络中的中心性和结构洞对跨区域协同创新绩效的影响作用;知识网络的组合机会负向调节区域在合作网络中的结构洞对跨区域协同创新绩效的影响作用。因此,区域创新中应充分利用产学主体的合作网络优势位置和知识网络优质资源,为跨区域资源共享和价值共创提供不竭动力。 相似文献
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The brain network is notably cost-efficient, while the fundamental physical and dynamic mechanisms underlying its economical optimization in network structure and activity have not been determined. In this study, we investigate the intricate cost-efficient interplay between structure and dynamics in biologically plausible spatial modular neuronal network models. We observe that critical avalanche states from excitation-inhibition balance under modular network topology with less wiring cost can also achieve lower costs in firing but with strongly enhanced response sensitivity to stimuli. We derive mean-field equations that govern the macroscopic network dynamics through a novel approximate theory. The mechanism of low firing cost and stronger response in the form of critical avalanches is explained as a proximity to a Hopf bifurcation of the modules when increasing their connection density. Our work reveals the generic mechanism underlying the cost-efficient modular organization and critical dynamics widely observed in neural systems, providing insights into brain-inspired efficient computational designs. 相似文献
9.
在考虑创新采纳个体之间交互作用所产生的局部网络效应基础上,运用微观扩散模型研究创新扩散。仿真分析表明,复杂社会网络结构、局部网络效应强度以及创新采纳个体自身偏好异质性共同决定创新扩散的过程。复杂社会网络结构影响创新扩散的程度和速度,即使局部网络效应强度很强,也有可能因为网络结构的影响而导致创新扩散最终失败;采纳个体偏好异质性对创新扩散的影响并不确定,当局部网络效应较弱时,偏好异质性越高越有利于创新扩散。与之相反,当局部网络效应较强时,偏好异质性则会抑制创新扩散,且异质性对创新扩散的影响也会随着复杂社会网络结构的差异而呈现不同模式。 相似文献
10.
在考虑局部网络效应基础上,从多种技术同时扩散的视角出发,采用仿真模型分析消费者交互作用对网络外部性市场技术演化的影响。研究表明:消费者交互作用所形成的聚集效应是驱动网络外部性市场技术演化的重要因素,在一定程度上决定了技术演化的均衡结果呈现为赢家通吃或多种技术共存。聚集效应使得消费者选择出现"局部偏差",即采用的技术并非是整体市场中占有率最高的。当消费者交互作用的聚集效应越强,技术演化均衡结果往往是多种互不兼容技术共存;当消费者交互作用的聚集效应越弱,技术演化则趋向于赢家通吃。此外,这种聚集效应还会影响企业扩大安装基础和加强市场沟通这两种技术竞争策略的效果。 相似文献
11.
A regional approach to study technology transfer through foreign direct investment: The electronics industry in two Mexican regions 总被引：1，自引：0，他引：1
Ramón Padilla-Pérez 《Research Policy》2008,37(5):849-860
This paper develops a conceptual framework and presents empirical evidence to examine technology transfer from foreign direct investment (FDI) to host regions, from a systemic perspective that integrates micro- (the firm) and meso (the region)-level analyses. This approach helps identify four different levels at which technology transfer may occur. Comprehensive fieldwork in Mexico was undertaken to collect evidence of an FDI-led, large industry (electronics) in two regions. The empirical evidence collected in this research shows that technology transfer derived from FDI may impact diverse actors of the host region (local firms, universities, research centres, industry associations), but also that its occurrence is neither automatic nor homogenous across regions. 相似文献
12.
基于社会网络理论和制度理论,构建网络嵌入、制度环境和区域创新能力的理论模型。利用中国30个省份2005—2016年间的面板数据,探索了国际网络嵌入和本地网络嵌入对区域创新能力的影响机制,以及制度环境的调节作用。结果显示：国际网络嵌入促进了区域创新能力,而本地网络嵌入与区域创新能力之间存在倒U型关系。本地网络嵌入和国际网络嵌入之间存在交互效应,共同促进区域创新能力提升,且国际网络嵌入表现出对本地嵌入的替代性。市场化水平增强了国际网络嵌入对区域创新能力的正向作用,同时削弱了本地网络嵌入与区域创新能力之间的倒U型关系;东中西部地区发展的不平衡也导致了多重网络嵌入与区域创新能力关系的差异。 相似文献
13.
利用我国31个省区2006-2010年技术市场成交合同数据,运用社会网络分析和GIS空间分析方法,研究了区域间技术转移的网络结构及空间分布特征。结果表明:(1)2006年以来,我国省际技术转移活动越来越密切和频繁,随着各区域技术实力及区域间技术差距的变化,技术转移网络以北京为中心的"核心—边缘"结构有逐步削弱的趋势。(2)大宗技术转移以北京为核心向其他区域扩散,受地理距离的约束较小;整体技术转移表现为空间聚集(分散)形态各异的几个区域板块,地理距离在各区域板块演变中的作用存在一定差异。(3)随着各区域及其邻近区域技术实力的变化,区域间技术转移的实现路径表现为由"弱—弱"子群转变为"强—弱"子群或"弱—强"子群,最后发展为地理邻近且良性互动的"强—强"子群。 相似文献
14.
Social networks provide individuals with diverse or redundant information depending on the network structure. Both types of information offer advantages for generating new ideas. At the same time, network structure and network content are independent. As a result, two individuals with the same network position can access diverse or redundant content from their social peers. In this study, we investigate the function of social networks in innovative endeavors given individuals’ different kinds of information accessing behavior. In accordance with previous research, we argue that individuals with a broker status access more diverse information through non-redundant network structures and develop, on average, more novel ideas. We further propose that redundancy in content complements brokers’ structural non-redundancy by providing familiar knowledge elements and therefore interpretability, while non-redundancy in both content and structure leads to information overload. Thus, we hypothesize that brokers accessing more information depth, and independently, less information breadth generate newer ideas. To test our hypotheses, we collected data from a popular online maker community containing 18,146 ideas, 19,919 profiles, and 52,663 comments. We used topic modeling (Latent Dirichlet Allocation) to extract hidden knowledge elements and social network analysis to identify brokers. In line with our hypotheses, we find that information depth (breadth) strengthens (weakens) a favorable broker position. These findings have implications for the literature on idea generation in social networks and household sector innovation. 相似文献
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16.
Xiangyong Chen Jinde Cao Ju H. Park Tingwen Huang Jianlong Qiu 《Journal of The Franklin Institute》2018,355(5):2892-2911
By considering network transmission mode, this paper addresses the finite-time multi-switching synchronization problem for two kinds of multiple chaotic systems. For multiple same-order chaotic systems, we construct the general switching rules and analyze the existence of switching cases. The presented schemes guarantee the states of each derive system to be finite-timely synchronized with the desired states of every respond system in the different transmission paths and switching sequences. For multiple different order chaotic systems, we analyze a special multi-switching hybrid synchronization behavior, where part of the states are completely synchronized and the others belong to combination synchronization. Moveover, the easily verifiable criterion is derived for such synchronization. Finally, numerical examples are given to show the effectiveness of the presented theoretical results. 相似文献
17.
Transients are fundamental to ecological systems with significant implications to management, conservation and biological control. We uncover a type of transient synchronization behavior in spatial ecological networks whose local dynamics are of the chaotic, predator–prey type. In the parameter regime where there is phase synchronization among all the patches, complete synchronization (i.e. synchronization in both phase and amplitude) can arise in certain pairs of patches as determined by the network symmetry—henceforth the phenomenon of ‘synchronization within synchronization.’ Distinct patterns of complete synchronization coexist but, due to intrinsic instability or noise, each pattern is a transient and there is random, intermittent switching among the patterns in the course of time evolution. The probability distribution of the transient time is found to follow an algebraic scaling law with a divergent average transient lifetime. Based on symmetry considerations, we develop a stability analysis to understand these phenomena. The general principle of symmetry can also be exploited to explain previously discovered, counterintuitive synchronization behaviors in ecological networks. 相似文献
18.
基于交通优势度的建设用地适宜性评价与实证——以玉树地震灾区为例 总被引：4，自引：0，他引：4
任何区位的土地属性都存在分异和区别,由此形成了不同水平的建设用地适宜性。而交通设施规模及空间网络是影响土地属性与建设适宜性分异的重要因素。本文从宏观和微观两个尺度,构建了交通优势度的评价方法,宏观尺度侧重各类交通设施综合优势水平的总体评价、物理空间分析与大尺度分异特征。微观尺度采用栅格方法进行精细评价,注重地形高程和坡度等自然因素对交通优势度的修正影响,形成集人文与自然因素相结合的评价方法。然后,选择玉树地震灾区作为案例区,从地震影响区和重灾区两个空间层级,深入分析交通优势度的等级结构及空间分异。最后,根据交通优势度的分异性,分析各区位土地资源对人类社会活动的适宜性差异,尤其是充分考虑地形高程和坡度等自然因素,并以建设适宜性突出和明显的土地资源为主体,对建设适宜水平较高、空间连续且面积较大的区域进行划定,相对精准地勾勒出城镇建设、居民点选址及产业布局的适宜区位与范围。 相似文献
19.
《Information processing & management》2020,57(6):102352
Intracerebral hemorrhage (ICH) is the most serious type of stroke, which results in a high disability or mortality rate. Therefore, accurate and rapid ICH region segmentation is of great significance for clinical diagnosis and treatment of ICH. In this paper, we focus on deep neural networks to automatically segment ICH regions. Firstly, we propose an encoder-decoder convolutional neural network (ED-Net) architecture to comprehensively utilizing both the low-level and high-level semantic information. Specifically, the encoder is used to extract multi-scale semantic feature information, while the decoder integrates them to form a unified ICH feature representation. Secondly, we introduce a synthetic loss function by paying more attention to the small ICH regions to overcome the data imbalanced problem. Thirdly, to improve the clinical adaptability of the proposed model, we collect 480 patient cases with ICH from four hospitals to construct a multi-center dataset, in which each case contains the first and review CT scans. In particular, CT scans of different patients are diverse, which greatly increases the difficulty of segmentation. Finally, we evaluate ED-Net on the multi-center ICH clinical dataset from different model parameters and different loss functions. We also compare the results of ED-Net with nine state-of-the-art methods in the literature. Both quantitative and visual results have shown that ED-Net outperforms other methods by providing more accurate and stable performance. 相似文献
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《Information processing & management》2019,56(4):1376-1390
This study investigated whether or not online tourism information prompted the international tourists who visited South Korea in 2015 to visit a wide range of tourism destinations, in particular those in non-capital regions, by comparing the tourist site networks of online and offline information seeker groups. It was hypothesized that the data would confirm how well the smart tourism ecosystem has been built and contributed to South Korea's tourism industry by showing that online tourism information leads tourists to visit more geographically diverse sites. Using network analysis with big data, the results showed that the offline information seeker group had geographically wider movement patterns than the online information seekers. In other words, the offline information seeker group showed movements in various directions and frequent visits to non-capital regions as opposed to the online information seeker group, which was highly dependent on the capital region. Thus, this study suggested that current online tourism information about South Korea did not provide appropriate tourism information to fulfill the needs of international tourists. This, consequently, might interrupt the implementation of smart tourism ecosystem efforts. Based on these results, this study had highlighted the importance of delivering both regionally and contextually diverse tourism information via online information sources. 相似文献