共查询到20条相似文献，搜索用时 321 毫秒
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空间光学遥感器所经受的主要力学环境是在运载、发射过程中的动力学环境,尤其是遥感器所经受的各种振动载荷,它直接关系到遥感器结构的稳定性,是影响遥感器在空间能否正常工作的关键因素。采用CAE技术对空间光学遥感器进行动态刚度及动力学载荷响应分析,旨在考查空间光学遥感器抗外界干扰能力和运载、发射、试验过程抗破坏能力。研究结果表明,空间光学遥感器具有较高的刚度,能够抑制动力学环境干扰,保持良好的动态特性,空间光学遥感器方案可行。 相似文献
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Yi-Chen Yin Zhi-Long Yu Zhi-Yuan Ma Tian-Wen Zhang Yu-Yang Lu Tao Ma Fei Zhou Hong-Bin Yao Shu-Hong Yu 《国家科学评论(英文版)》2019,6(2):247
Lithium metal is one of the most promising anode materials for high-energy-density Li batteries. However, low stability caused by dendrite growth and volume change during cycling hinders its practical application. Herein, we report an ingenious design of bio-inspired low-tortuosity carbon with tunable vertical micro-channels to be used as a host to incorporate nanosized Sn/Ni alloy nucleation sites, which can guide Li metal''s plating/stripping and meanwhile accommodate the volume change. The pore sizes of the vertical channels of the carbon host can be regulated to investigate the structure–performance correlation. After compositing Li, the bio-inspired carbon host with the smallest pore size (∼14 μm) of vertical channels exhibits the lowest overpotential (∼18 mV at 1 mA cm−2), most stable tripping/plating voltage profiles, and best cycling stability (up to 500 cycles) in symmetrical cells. Notably, the carbon/Li composite anode is more rewarding than Li foil when coupled with LiFePO4 in full cells, exhibiting a much lower polarization effect, better rate capability and higher capacity retention (90.6% after 120 cycles). This novel bio-inspired design of a low-tortuosity carbon host with nanoalloy coatings may open a new avenue for fabricating advanced Li-metal batteries with high performance. 相似文献
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尽管近期大量学者验证了外部知识异质度对企业创新绩效具有倒U型曲线效应,但却没有能够厘清这一效应的内生性机制及其形成原因。本研究基于知识重构和吸收能力的视角,通过采集和分析来自江苏、浙江和上海的261个创新型样本企业问卷数据,识别外部知识异质度对企业创新绩效倒U型曲线效应的形成机制。结果表明:外部知识异质度通过促进知识重构正向影响创新绩效,却通过弱化吸收能力反向影响创新绩效;这两种效果相反的中介机制导致外部知识异质度与创新绩效之间产生了倒U型曲线关系。这一发现揭示了企业外部知识异质度对创新绩效影响的内在机理,进一步发展了主流文献的相关研究。 相似文献
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An electrochemical hexavalent chromium concentration sensor based on a microfluidic fuel cell is presented. The correlation between current density and chromium concentration is established in this report. Three related operation parameters are investigated, including pH values, temperature, and external resistance on the sensor performance. The results show that the current density increases with increasing temperature and the sensor produces a maximum regression coefficient at the catholyte pH value of 1.0. Moreover, it is found that the external resistance has a great influence on the linearity and current densities of the microfluidic sensor. Owing to the membraneless structure and the steady co-laminar flow inside the microchannel, the microfluidic sensor exhibits short response time to hexavalent chromium concentration. The laminar flow fuel cell sensor provides a new and simple method for detecting hexavalent chromium concentration in the industrial wastewater. 相似文献
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《Journal of The Franklin Institute》2017,354(11):4457-4480
Due to the hopeful application of gathering information from unreachable position, wireless sensor network creates an immense challenge for data routing to maximize the communication with more energy efficiency. In order to design the energy efficient routing, the optimization based clustering protocols are more preferred in wireless sensor network. In this paper, we have proposed competent optimization based algorithm called Fractional lion (FLION) clustering algorithm for creating the energy efficient routing path. Here, the proposed clustering algorithm is used to increase the energy and lifetime of the network nodes by selecting the rapid cluster head. In addition, we have proposed multi-objective FLION clustering algorithm to develop the new fitness function based on the five objectives like intra-cluster distance, inter-cluster distance, cluster head energy, normal nodes energy and delay. Here, the proposed fitness function is used to find the rapid cluster centroid for an efficient routing path. Finally, the performance of the proposed clustering algorithm is compared with the existing clustering algorithms such as low energy adaptive clustering hierarchy (LEACH), particle swarm optimization (PSO), artificial bee colony (ABC) and Fractional ABC clustering algorithm. The results proved that the lifetime of the wireless sensor nodes is maximized by the proposed FLION based multi-objective clustering algorithm as compared with existing protocols. 相似文献
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This paper reviews our work on the application of ultrafast pulsed laser micro∕nanoprocessing for the three-dimensional (3D) biomimetic modification of materials surfaces. It is shown that the artificial surfaces obtained by femtosecond-laser processing of Si in reactive gas atmosphere exhibit roughness at both micro- and nanoscales that mimics the hierarchical morphology of natural surfaces. Along with the spatial control of the topology, defining surface chemistry provides materials exhibiting notable wetting characteristics which are potentially useful for open microfluidic applications. Depending on the functional coating deposited on the laser patterned 3D structures, we can achieve artificial surfaces that are (a) of extremely low surface energy, thus water-repellent and self-cleaned, and (b) responsive, i.e., showing the ability to change their surface energy in response to different external stimuli such as light, electric field, and pH. Moreover, the behavior of different kinds of cells cultured on laser engineered substrates of various wettabilities was investigated. Experiments showed that it is possible to preferentially tune cell adhesion and growth through choosing proper combinations of surface topography and chemistry. It is concluded that the laser textured 3D micro∕nano-Si surfaces with controllability of roughness ratio and surface chemistry can advantageously serve as a novel means to elucidate the 3D cell-scaffold interactions for tissue engineering applications. 相似文献
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本文选取2011-2015年我国新能源上市公司为研究对象,采用多元回归分析方法,分别研究不同规制约束下,政府环境研发补贴对环境研发投入和环境绩效的影响。实证研究结果显示：政府环境研发补贴对企业环境绩效具有积极的促进效应,企业环境研发投入在政府环境研发补贴与企业环境绩效之间具有中介作用。具体而言,政府环境研发补贴在较高的内部规制下能够显著促进企业环境研发投入与企业环境绩效,企业环境研发投入在较高的外部规制下能够显著促进企业环境绩效;当企业面临高外部规制和高内部规制时,政府环境研发补贴对企业环境绩效的促进作用最强;当企业面临内外部规制一强一弱的制约时,相比于低外部规制和高内部规制,政府环境研发补贴在高外部规制和低内部规制下更能促进企业环境绩效的提升。本文研究结论对提升政府环境研发补贴绩效和新能源企业环境研发效率具有重要的现实意义。 相似文献
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Because of their low cost, natural abundance, environmental benignity, plentiful polymorphs, good chemical stability and excellent optical properties, TiO2 materials are of great importance in the areas of physics, chemistry and material science. Much effort has been devoted to the synthesis of TiO2 nanomaterials for various applications. Among them, mesoporous TiO2 materials, especially with hierarchically porous structures, show great potential owing to their extraordinarily high surface areas, large pore volumes, tunable pore structures and morphologies, and nanoscale effects. This review aims to provide an overview of the synthesis and applications of hierarchically mesoporous TiO2 materials. In the first section, the general synthetic strategies for hierarchically mesoporous TiO2 materials are reviewed. After that, we summarize the architectures of hierarchically mesoporous TiO2 materials, including nanofibers, nanosheets, microparticles, films, spheres, core-shell and multi-level structures. At the same time, the corresponding mechanisms and the key factors for the controllable synthesis are highlighted. Following this, the applications of hierarchically mesoporous TiO2 materials in terms of energy storage and environmental protection, including photocatalytic degradation of pollutants, photocatalytic fuel generation, photoelectrochemical water splitting, catalyst support, lithium-ion batteries and sodium-ion batteries, are discussed. Finally, we outline the challenges and future directions of research and development in this area. 相似文献
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Aaron Montero Ramon Huerta Francisco B. Rodriguez 《Journal of The Franklin Institute》2018,355(5):2951-2977
Neural processing layers built on divergent connectivity patterns display two types of stimulus-dependent responses: neurons that react to a few stimuli, specialists, and other ones that respond to a wide range of inputs, generalists. Specialists are essential for the discrimination of stimuli and generalists extract common and generic properties from them. This neural heterogeneity could have emerged because of animal adaptation to the environment. Thus, we suggest that there is a relationship between the percentage of specialists and generalists and the stimulus complexity. In order to study this possible relationship, we use patterns with different complexities in a bio-inspired neural network and calculate their classification errors for different ratios of these types of neurons. This study shows that, when the complexity of the stimuli is low, the minimum classification error is achieved with almost any specialist-generalist ratio. Thus, in this case, the role of these neurons during pattern recognition is unspecific. When this complexity is intermediate, both are needed to minimize the classification error, usually in a similar proportion. For increasing stimulus complexity, the importance of generalists decreases, until their relevance is fully nullified when the complexity is high. Therefore, if we adjust the specialist-generalist ratio to the complexity of patterns, we can build more effective neural networks for pattern recognition. Finally, we propose an estimation of stimulus complexity based on the proportion of these types of neurons observed by neural recordings. This offers the possibility to evaluate the stimulus complexity to which animals are adapted. 相似文献
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To address the growing energy demands of sustainable development, it is crucial to develop new materials that can improve the efficiency of energy storage systems. Hierarchically structured porous materials have shown their great potential for energy storage applications owing to their large accessible space, high surface area, low density, excellent accommodation capability with volume and thermal variation, variable chemical compositions and well controlled and interconnected hierarchical porosity at different length scales. Porous hierarchy benefits electron and ion transport, and mass diffusion and exchange. The electrochemical behavior of hierarchically structured porous materials varies with different pore parameters. Understanding their relationship can lead to the defined and accurate design of highly efficient hierarchically structured porous materials to enhance further their energy storage performance. In this review, we take the characteristic parameters of the hierarchical pores as the survey object to summarize the recent progress on hierarchically structured porous materials for energy storage. This is the first of this kind exclusively to survey the performance of hierarchically structured porous materials from different porous characteristics. For those who are not familiar with hierarchically structured porous materials, a series of very significant synthesis strategies of hierarchically structured porous materials are firstly and briefly reviewed. This will be beneficial for those who want to quickly obtain useful reference information about the synthesis strategies of new hierarchically structured porous materials to improve their performance in energy storage. The effect of different organizational, structural and geometric parameters of porous hierarchy on their electrochemical behavior is then deeply discussed. We outline the existing problems and development challenges of hierarchically structured porous materials that need to be addressed in renewable energy applications. We hope that this review can stimulate strong intuition into the design and application of new hierarchically structured porous materials in energy storage and other fields. 相似文献
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本文立足于资源配置视角,从整体上将创业战略导向、高管团队垂直对差异与创业绩效纳入统一理论框架,剖析了三者变量之间的作用机理和影响关系模式,并进一步选取我国中小企业板2006－2010年上市公司作为样本进行实证检验。聚类分析结果表明,样本公司创业战略导向存在三种不同的结构维度：“内部研发”型、“外部投资”型,以及“内部研发＋外部投资”型,但大多偏好“外部投资”型创业战略导向。层次回归分析结果表明：其一,创业战略导向会对成长性和盈利性绩效会产生差异性影响,不过分组层次回归结果却进一步揭示,“内部研发”型创业战略导向尚未对企业成长性绩效产生显著影响;其二,高管团队垂直对差异会对成长性和盈利性绩效产生显著调节效应,不过年龄和任期垂直对差异仅部分产生调节效应。本文的研究结论对于高管团队培育、公司治理结构和机制优化以及研发投资方向选择等具有积极的启示作用。 相似文献
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知识网络结构及其对知知识管理的启示 总被引：5，自引：0，他引：5
组织中知识的基本载体互相联结,形成组织的内部知识网络;与组织外部的知识载体进行物质和信息交换,形成组织的外部知识网络．组织内外部知识网络的结构影响组织绩效．从知识网络结构的一个方面,即网络闭合性角度展开研究,提出了知识管理的三个原则和三个方法,前者包括提高内部网络的闭合性、降低外部网络的闭合性以及平衡两者关系,后者包括知识载体网络化、知识网络模块化和外部知识获取行为制度化． 相似文献
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开放性有利于企业获取更多的创新机会,但开放式创新过程中也需要考虑独占性损失的风险,因为独占性对企业创新新颖性和效率等绩效存在重要的影响。本研究旨在剖析独占性机制和开放性对创新漏斗不同阶段的创新绩效的影响。整合企业跨界搜索理论与知识保护理论,基于332家广东省制造业企业的问卷调查数据,探讨开放性与独占性机制对创新漏斗不同阶段的创新绩效影响。研究发现：正式独占性机制的使用负向影响创新漏斗创意形成阶段的创新效率,半正式独占性机制的使用有利于提升创新漏斗创意形成阶段的创新效率,而非正式独占性机制则有助于创新漏斗创意形成和新产品开发与商业化阶段的创新新颖性的提升;另外,创新新颖性通过创新漏斗整个阶段的横向合作开放性来解释,尤其是与高校科研院所的合作,与竞争对手合作开放性对新产品开发与商业化阶段的创新新颖性积极正相关,而垂直合作开放性则对新产品开发与商业化阶段的创新效率具有正相关关系。 相似文献
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在供给侧结构性改革下,产品创新是科创企业实现持续发展、高质量发展及跨越式发展的关键。然而,如何激发科创企业产品创新却尚未明晰。战略人力资源管理的构型观与权变观为这一问题解决提供了思路。本文以400余家科创企业为案例样本,运用模糊集定性比较分析方法,以动机、能力、机会三个层面的战略人力资源管理构件为条件,从生命周期视角构建了产品创新的实现过程模型。研究发现：（1）初创期科创企业存在驱动高产品创新的一种路径;发展期科创企业存在五种路径,并分布于三类科创企业中;成熟期科创企业存在四种路径,并分布于两类科创企业中。（2）机会层构件是成熟期科创企业实现高产品创新的必要条件;而在初创期与发展期,任何构件均不能成为实现高产品创新的必要条件。（3）在初创期,战略人力资源管理构件并不能对高产品创新起到决定性作用;在发展期与成熟期,机会层与动机层的交互效应对驱动高产品创新更加重要。（4）从企业生命周期纵向对比来看,战略人力资源管理构件的核心作用发挥主要遵循着从无到有、从动机层到机会层的发展逻辑。本文研究结论有助于深化不同生命周期阶段科创企业对战略人力资源管理构件组合的重要性认识,并为寻求多种更佳乃至最佳的产品创新驱动路径提供启示。 相似文献
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《Journal of The Franklin Institute》2023,360(12):8973-8996
In this paper, the measurement outlier-resistant target tracking problem is investigated in wireless sensor networks (WSNs) with energy harvesting constraints. Each WSN node can acquire energy stochastically from surroundings. No matter whether the WSN node acquires energy or not, the WSN node’s measurement can be transmitted if the energy amount of the WSN node is greater than zero. In such a case, the sensor energy-induced missing measurement (SE-IMM) phenomenon may occur. The objective of this paper is to develop a solution for the considered target tracking problem by devising the filter including a saturation constraint such that, in the simultaneous presence of outliers and the SE-IMM phenomenon, the tracking performance can meet the given performance index. Firstly, the relation between the energy level of the WSN node and its probability distribution is computed recursively. Then, an upper bound of the tracking error covariance is derived which is minimized by appropriately choosing the filter parameter. Finally, the feasibility of the proposed target tracking scheme is validated by conducting a set of comparative experiments and the relationship between the energy of the WSN node and the tracking performance is also disclosed. 相似文献
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Jinpeng Wu Shun-Chang Liu Zongbao Li Shuo Wang Ding-Jiang Xue Yuan Lin Jin-Song Hu 《国家科学评论(英文版)》2021,8(8)
Metal halide perovskite solar cells (PSCs) have seen an extremely rapid rise in power conversion efficiencies in the past few years. However, the commercialization of this class of emerging materials still faces serious challenges, one of which is the instability against external stimuli such as moisture, heat and irradiation. Much focus has deservedly been placed on understanding the different origins of intrinsic instability and thereby enhancing their stability. Among these, tensile strain in perovskite films is an important source of instability that cannot be overcome using conventionally extrinsic stabilization approaches such as encapsulation. Here we review recent progress in the understanding of the origin of strain in perovskites as well as its corresponding characterization methods, and their impacts on the physical properties of perovskites and the performance of PSCs including efficiency and stability. We then summarize the latest advances in strain-regulation strategies that improve the intrinsic stability of perovskites and photovoltaic devices. Finally, we provide a perspective on how to make further progress in stable and high-efficiency PSCs via strain engineering. 相似文献
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从技术创新联盟的特定情境出发,将知识整合机制分为独立整合机制和合作整合机制两个维度,分析并强调了它们对创新绩效的正向影响作用。基于多重理论视角,识别并研究了任务不确定性、联盟关系不确定性(联盟依赖和联盟冲突)以及外部环境不确定性对这两种整合机制的影响,认为独立型、合作型知识整合机制在这些前导变量和创新绩效之间起中介作用,并给出了相关命题和研究框架。 相似文献
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研究了在异构分簇无线传感器网络中,如何优化簇内节点的通信半径,从而最小化网络的总能耗.定义节点的能量消耗模型为E=a(dα+c)、网络半径为 R 、层数为 K .对节点通信半径不可调的网络,证明了α=2、c≤4R2时,或α=4、c≤4R2、K≤ 6 R时,最小化网络总能耗的簇内节点通信半径的上界为 α c/(α-1) .对于节点通信半径可调的网络,在α=2时,提出了自内而外依次最小化每层簇内节点的平均能耗来确定节点通信半径的算法. 相似文献