共查询到20条相似文献，搜索用时 109 毫秒
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为了研究车辆在桥面上行驰过程中突然刹车对桥梁产生的冲击振动的影响,考虑了车轮处的摩擦力与刹车制动力共同作用时移动质量模型对车桥的耦合振动现象进行数值模拟。对于工程中常用的变截面箱梁,推导了平面内呈线性和抛物线形变化时的质量阵,采用Romberg数值积分方法得到刚度矩阵中的系数项。对于变速行驰在桥面上的车辆出现紧急刹车的现象,考虑了车轮与桥面间的摩擦并引入冲击系数模拟刹车力对桥面的作用,探讨了摩擦系数与冲击系数对车桥耦合振动的影响。 相似文献
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《Journal of The Franklin Institute》2023,360(12):8339-8362
This paper addresses the problem of controlling a wave energy converter (WEC) susceptible to faults in its braking subsystems, characterized through nonlinear damping. By considering the necessity of robust trajectory tracking related to the sea waves for maximizing the converted energy, one aims to preserve such a trajectory in the presence of faults to avoid physical damage in the structure of the WEC. To achieve this objective, this paper proposes a fault-tolerant control (FTC) that combines two systems: (i) a novel nonlinear servocompensator (NSC) and (ii) a fault diagnosis subsystem (FD). The NSC is based on a variable structure control that generalizes the internal model principle for robust tracking. The reference signal is computed from real-time measurements of the irregular sea waves. The FD subsystem estimates the faults related to the wear of the brakes via an unknown input observer. Due to its independent performance from the FD, the global scheme can be considered as a passive FTC. By considering the faulty model of a WEC based on the Archimedes wave swing prototype, theoretical formulation and the convergence proof are given for the NSC and the FD. The performance of the proposed design is verified with numerical simulations of the WEC with the incidence of irregular sea waves under different fault scenarios in the upper and lower brakes. 相似文献
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《Journal of The Franklin Institute》2022,359(16):8497-8521
In order to improve the response speed and control precision of the braking system with parameters uncertainty and nonlinear friction, a braking-by-wire system based on the electromagnetic direct-drive valve and a novel cascade control algorithm was proposed in this paper. An electromagnetic linear actuator directly drives the valve spool and rapidly adjusts the pressure of braking wheel cylinders. A dynamic model of electromagnetic direct-drive valve considering improved LuGre dynamic friction is established. A novel cascade control algorithm with an outside loop pressure fuzzy controller and an inside loop electromagnetic direct-drive valve position controller was proposed. An adaptive integral robust inside loop controller is designed by combining friction compensation adaptive control law, linear feedback, and integral robust control. The uncertainty parameters and the friction state are estimated online. The stability of the cascade controller is proved by the Lyapunov method. Then a multi-objective opitimizemization design method of control parameters is proposed, which combines a multi-objective game theory and a technique for order preference by similarity to ideal solution (TOPSIS) based on entropy weight. The results show that the pressurization time of cascade control is less than 0.09 s under the 15 MPa step target signal. The control precision is improved effectively by the cascade controller under the ARTEMIS condition. 相似文献
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This article investigates the organisational conditions for service encounter-based innovation. Its focus is on the initial crucial part of the innovation process during which ideas/new practises are developed by front-line employees and integrated in the organisation. The article argues that service encounter-based innovation varies among service organisations because of different organisational conditions. This is illustrated in a multiple comparative case study of 11 Scandinavian service organisations. A model of conditions for service encounter-based innovation is developed based on the theoretical discussions and the case study. The model suggests how and why some service organisations derive innovation benefits from service-encounters while others do not. Thus, the article provides new and important knowledge concerning user-driven innovation in services. 相似文献
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本文较详细地分析了情报科学产生以来的历史;探讨了当今这门学科为什么出现衰微的原因,分析了情报科学理论研究为什么不能取得进展的若干因素,并提出了一些加强理论研究的建议。 相似文献
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如何在资源约束条件下实现初创企业的产品创新一直是学界和商界关注的焦点。本文首先介绍了创业决策逻辑理论中的目标导向和手段导向的特征,通过案例分析分别探讨了锤子和小米两个初创企业产品创新流程决策,并以理论模型对比了两种决策理论在实践中的适用性和局限性。研究结果表明,锤子手机的研发过程体现了目标导向的特征,而小米手机的研发过程体现了手段导向的特征。本研究认为,创业更多是介于精密计划和非系统性试错之间,目标导向和手段导向逻辑的适用性取决于不确定情境下创业者战略决策的权变性,权变性影响了企业资源的整合和创业机会的识别;初创企业在发展早期比较适合采取目标导向逻辑进行决策,通过提高资源整合效率,能加快创业机会的识别,而手段导向的作用更多体现在产品创新后期,随着产品的约束性条件不断演化,创业者通过保持资源整合的柔性来持续识别新的创业机会,产品创新是外界环境各种约束性条件不断迭代而成的结果。 相似文献
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基于博弈论的企业人力资本投资理论——一个文献综述 总被引：2，自引：0，他引：2
从博弈论的视角,对该理论在企业通用性人力资本投资行为的博弈解释、专用性人力资本投资过程中的激励约束问题以及人力资本投资水平国际差异的不同博弈解释等三个方面的研究成果进行了较系统的阐述,最后指出了有待进一步研究的问题和方向。 相似文献
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Bin Zhou 《Journal of The Franklin Institute》2018,355(15):7246-7280
We study in this paper solutions to several kinds of linear bimatrix equations arising from pole assignment and stability analysis of complex-valued linear systems, which have several potential applications in control theory, particularly, can be used to model second-order linear systems in a very dense manner. These linear bimatrix equations include generalized Sylvester bimatrix equations, Sylvester bimatrix equations, Stein bimatrix equations, and Lyapunov bimatrix equations. Complete and explicit solutions are provided in terms of the bimatrices that are coefficients of the equations/systems. The obtained solutions are then used to solve the full state feedback pole assignment problem for complex-valued linear system. For a special case of complex-valued linear systems, the so-called antilinear system, the solutions are also used to solve the so-called anti-preserving (the closed-loop system is still an antilinear system) and normalization (the closed-loop system is a normal linear system) problems. Second-order linear systems, particularly, the spacecraft rendezvous control system, are used to demonstrate the obtained theoretical results. 相似文献
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Arjan van Rooij 《Research Policy》2005,34(6):836-851
This article analyses markets for technology from a buyer's perspective: the question why firms acquire technology is the central research question. An in-depth historical case study of a chemical company is confronted with systematic and economic research. The acquisition of complete plants by the particular firm under study is explained and several factors are proposed which may help further research on markets for technology. 相似文献
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针对轧制塑性加工中轧件金属发生塑性变形的特点,本文经过理论分析,实验验证,建立一个新的摩擦机理：滚-滑摩擦机理。 相似文献
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以索尔曼提出的学科教学知识为理论基础,以重点本科院校的一名具有三十几年教龄的资深英语教师为个案．通过课堂观察、录像、采访、学生问卷等形式,发现该教师关于学生的知识包括五个方面,关于学生的知识的形成受四大因素的影响。 相似文献
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通过对国外有关文献的分析,说明为什么要对M ayer的连续融资假设进行进一步讨论,运用博弈论的方法对该假设进行理论分析,推导出在两阶段项目中不同类型的公司之间存在分离均衡,并运用国内市场的数据对连续融资假设进行实证分析。得出扩展连续融资假设与可转债的有效期限应等于项目周期的推论,并对推论进行实证以及对实证结果提出自己的解释。 相似文献
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本文基于探索性案例研究方法，探讨开放式创新实施的情境、实施路径和效应，在深入分析创新情境、开放式创新和创新能力的动态变化轨迹基础上，试图构建一个“创新情境--开放式创新--创新能力”的整合分析模型。依据这一研究框架，文章对在开放式创新方面有代表的海尔集团作了2009-2018年纵向案例研究。本文研究丰富了开放式创新的内核，从作用于创新链的节点、交易逻辑和类型等三方面诠释了开放式创新的内涵；定义了开放式创新的类型，提出从驱动力、创新链开放节点、交易逻辑、知识流、卷入的创新资源、沟通方式、沟通频率和核心特征等8个维度定义开放式创新，可划分为内部依赖-内向型、主导参与-内向型、主导参与-双向型、社群共创-双向型4种类型。研究结论发现，由技术控制力和创新活跃度反映的创新情境是决定开放式创新模式选择的依据，开放式创新是一个依据企业面临环境和战略选择发生的连续的、动态的创新资源吸引、整合、利用、释放和扩散过程，随着创新情境越来越有利，开放式创新依次经历内部依赖-内向型、主导参与-内向型、主导参与-双向型、社群共创-双向型4个阶段，与之对应的创新能力则沿着“技术创新能力-整合创新能力-生态创新能力”的路径演化。本文的理论贡献在于：丰富了开放式创新的内核，定义了开放式创新的类型，并基于创新情境、开放式创新与创新能力动态演化路径提出了COC模型，为企业如何实施开放式创新提供了理论支撑和实践指导。 相似文献
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CELIA T. ROMM NAVA PLISKIN 《The Information Society》2013,29(3):207-226
Few studies have attempted to link e-mail use to power and politics. The purpose of this article is to offer some initial evidence and analysis of e-mail's role in organizational power and politics. To frame the discussion, the article reviews the relevant writings on power and politics. The review is concluded with a theoretical critique that suggests that contextual and, particularly, temporal aspects should be incorporated into research on power and politics in organizations. To demonstrate how an analysis based on temporal aspects can be undertaken, a case study that outlines the use of e-mail for power and politics in a university is presented. The discussion and conclusions sections synthesize the analysis by demonstrating that what was interpreted by many organization members at the early stages of the conflict as a ''battle of the sexes'' can be seen (and, indeed, was interpreted by many organization members at the later stages of the conflict) as an elaborate exercise in misinformation created by top management to further its political objectives. The article concludes with a discussion of the implications from this case to e-mail research and practice. 相似文献
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人体生物摩擦学的基础科学问题 总被引：2，自引：0，他引：2
人体的生物摩擦副包含头发、皮肤、眼睛、味觉、牙齿、关节、心脏
、血液等,它们
对人体健康和康复质量具有重要影响。本文对人体生物摩擦学的特点、生物摩擦学行为对人
体生命质量的影响、人体生物摩擦学的科学问题进行了探讨,提出了人体内植物“少磨损、
低危害”的生物摩擦学质量概念,以及实现这个目标所需要的NBIC摩擦学融合技术,即Nano
tribology,Biotribology,Implants materials, Coating technology四方面相互交叉融
合产生的摩擦学新技术。 相似文献
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It is often argued that small–medium enterprises (SMEs) do not manage knowledge the same way as large firms, but may need appropriate approaches to capture and exploit external knowledge effectively. This paper compares two opposite approaches to knowledge management (KM): one is called ‘deliberate’ or ‘planned’, and the other ‘emergent’. These approaches are analysed with reference to the management of knowledge pertaining to client–supplier relationships, which are particularly important in the case of small companies providing knowledge-intensive business services (KIBS). A case study of a small KIBS company is illustrated, which has developed two different projects, based on different approaches to KM, for managing knowledge referring to clients. The case shows that, for a small company, an emergent approach to KM can be more suitable than a deliberate one for managing such knowledge. The implications of this result for KM research and practice are then examined. 相似文献