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When hitting underground structures directly or exploding in rock-soil media near underground structures, the conventional weapons with large charge weight will make underground structures be subjected to strong shock vibration and cause personal casualty and damage of precision electronic equipments. The shock vibration has become one of the cardinal killing means of weapons. However, the existing methods of predicting structure shock vibration are limited evidently. In this paper the coupling coefficient of acceleration in clayey soil is obtained firstly. Subsequently based on repeated experiments of chemical explosion, after dimension analysis and by using method of multivariate stepwise regression, the calculation formulae of shock vibration acceleration for the underground structure are obtained finally. The formulae consider top and side explosion respectively, taking into account the effects of penetration depth, charge weight, distance to explosion center, rock-soil media, size of structure and buried depth. They are easy to use with high practicability and degree of confidence, and can provide credible evidence for prediction of shock vibration and vibration isolating design of underground structure. 相似文献
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该文从分析城市人才流失的原因入手,探究城市高校与企业合作所产生的积极意义,论述了依托校企合作有效缓解城市人才流失的具体策略。 相似文献
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采集2008—2012年浙江省青田县城市环境空气质量监测结果数据,对其空气质量变化趋势进行分析研究,为该县城空气质量趋势的预测提供理论依据,为当地政府环境管理的决策提供参考。 相似文献
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In petrochemical plant, the in-operation repairing is usually a repairing strategy with pressured inoperation repairing for avoiding huge economic losses caused by unplanned shutdown when some slight local leakage happens in pipes. This paper studies the effects of repairing strategies on the failure probability of the pipe systems in process industries based on the time-average fault tree approach, especially the in-operation repairing strategies including pressured in-operation repairing activities. The fault tree model can predict the effect of different repairing plans on the pipe failure probability, which is significant to the optimization of the repairing plans. At first pipes are distinguished into four states in this model, i.e., successive state, flaw state, leakage state and failure state. Then the fault tree approach, which is usually applied in the studies of dynamic equipment, is adopted to model the pipe failure. Moreover, the effect of pressured in-operation repairing is also considered in the model. In addition, this paper proposes a series of time-average parameters of the fault tree model, all of which are used to calculate node parameters of the fault tree model. At last, a practical case is calculated based on the fault tree model in a repairing activity of pipe thinning. 相似文献
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在文化消费视域下,作为文化品牌的图书馆具有鲜明的符号价值与象征意义,图书馆品牌化的过程就是对特定符号价值与象征意义的生产和消费过程。图书馆品牌承载的形象、故事、情感、价值观成为文化消费的对象,以及图书馆从工具性到文化性定位转型的关键要素。文旅融合背景下,以"悠·图书馆"为代表的城市社区图书馆通过赋予图书馆的象征价值和体验价值,并通过品牌个性、传承文化资产、开发美学价值、讲述品牌故事等品牌意义重构的实践破解城市社区图书馆发展困境。"悠·图书馆"作为重构的城市社区图书馆品牌,通过品牌象征意义、价值观、形象、故事4个层面的符号重构策略,实现城市社区图书馆品牌创新与传播。 相似文献
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Direction of spin axis and spin rate of the pitched baseball 总被引：1，自引：0，他引：1
Jinji T Sakurai S 《Sports biomechanics / International Society of Biomechanics in Sports》2006,5(2):197-214
In this study, we aimed to determine the direction of the spin axis and the spin rate of pitched baseballs and to estimate the associated aerodynamic forces. In addition, the effects of the spin axis direction and spin rate on the trajectory of a pitched baseball were evaluated. The trajectories of baseballs pitched by both a pitcher and a pitching machine were recorded using four synchronized video cameras (60 Hz) and were analyzed using direct linear transform (DLT) procedures. A polynomial function using the least squares method was used to derive the time-displacement relationship of the ball coordinates during flight for each pitch. The baseball was filmed immediately after ball release using a high-speed video camera (250 Hz), and the direction of the spin axis and the spin rate (omega) were calculated based on the positional changes of the marks on the ball. The lift coefficient was correlated closely with omegasinalpha (r = 0.860), where alpha is the angle between the spin axis and the pitching direction. The term omegasinalpha represents the vertical component of the velocity vector. The lift force, which is a result of the Magnus effect occurring because of the rotation of the ball, acts perpendicularly to the axis of rotation. The Magnus effect was found to be greatest when the angular and translational velocity vectors were perpendicular to each other, and the break of the pitched baseball became smaller as the angle between these vectors approached 0 degrees. Balls delivered from a pitching machine broke more than actual pitcher's balls. It is necessary to consider the differences when we use pitching machines in batting practice. 相似文献
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Tsutomu Harada 《Research Policy》2003,32(10):1737-1751
The purpose of this paper is to reexamine the role of gatekeeper in R&D organizations through the data collected from a midium-sized machine tool firm. Although the related literature points out (1) information gathering and (2) information transmitting functions as main roles of gatekeeper, this paper further suggests (3) knowledge transforming function that has to be executed within R&D organizations. We will argue that since the latter function often requires distinctive skills that impede information gathering activities, there emerges a three-step flow of communication instead of a two-step flow of communication. We define persons fulfilling this new role as a knowledge transformer, and related testable hypotheses are derived. The latter part of this paper proposes new measuring methods that identify knowledge transformers and test these hypotheses. 相似文献