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为更好地控制集装箱滚装船门框结构的安装精度,以45000t集装箱滚装船中只包含水密门结构的分段为例进行水密门精度控制研究。通过研究该分段的建造方式,改进分段的建造工艺,合理安排门框结构在分段建造过程中的安装顺序,进而缩减结构变形;同时,利用精度测量仪器进行跟踪测量,保证始终把精度控制在有效范围内。对焊接过程中采用的焊接方法进行研究,改进焊接工艺,采取逐步退焊法控制焊接热量,进而减少焊接变形。通过对分段水密门门框结构的安装工艺及焊接工艺进行研究,将理论与实践相结合,总结出一套行之有效的建造工艺,确保分段门框结构安装精度得到有效控制,保证水密门的性能,为该系列船后续的分段建造提供参考。 相似文献
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The focus of this paper is on the productive efficiency of ports. We estimate a directional technology distance function using parametric techniques to analyze the production technology and technical efficiency of a set of Spanish Port Authorities observed over the period 1993–2012. Technical inefficiency is conceived as the ability of ports to simultaneously expand a given output and contract variable inputs while maintaining quasi-fixed inputs and other outputs constant. Thus, for containerized cargo we address the following question: Given the amount of quasi-fixed inputs used by the firm and given the volume of the other outputs (liquids, solids, non-containerized cargo and passenger traffic), could ports increase their containerized merchandise while simultaneously reducing their variable inputs? Similar questions are asked for solid bulk and non-containerized general cargo. Our results show evidence of technical inefficiency among the ports in our sample. In particular, if the ports operated efficiently, we find that containerized cargo could be expanded by an average of over 6.4%, with an equivalent reduction in variable inputs. Solid bulk cargo and general non-containerized cargo could be increased by 4.1% and 6.1% respectively, with corresponding reductions in variable inputs. An implication of our results is that there is ample scope for specialization on the part of ports with no increase in infrastructure costs. Given that large investments in infrastructure have been made in Spanish port over the last decade, this opens the possibility of moving towards a management model based on taking advantage of existing capacity rather than new investments. 相似文献
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In a variety of applications of traffic flow, including traffic simulation, real-time estimation and prediction, one requires a probabilistic model of traffic flow. The usual approach to constructing such models involves the addition of random noise terms to deterministic equations, which could lead to negative traffic densities and mean dynamics that are inconsistent with the original deterministic dynamics. This paper offers a new stochastic model of traffic flow that addresses these issues. The source of randomness in the proposed model is the uncertainty inherent in driver gap choice, which is represented by random state dependent vehicle time headways. A wide range of time headway distributions is allowed. From the random time headways, counting processes are defined, which represent cumulative flows across cell boundaries in a discrete space and continuous time conservation framework. We show that our construction implicitly ensures non-negativity of traffic densities and that the fluid limit of the stochastic model is consistent with cell transmission model (CTM) based deterministic dynamics. 相似文献
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《运输规划与技术》2012,35(8):868-880
ABSTRACTAnalysis of elevator traffic in high rise buildings is critical to the performance evaluation of elevator group control systems (EGCS). Elevator dispatching methods or parking algorithms in an EGCS can be designed or modified according to analyses of traffic flow. However, interpretation of traffic flow based solely on numerical data may not be explicit and transparent for EGCS experts as well as for other non-expert building administration. In this study, we present a model for visualization and analysis of elevator traffic. First, we present an alternative approach for traffic analysis which we call route visualization. In the proposed approach, we initially decompose elevator traffic into its component parts and investigate each component independently. Then, using superposition of components we obtain a reconstructed model of overall traffic. This modeling approach provides component-based traffic analysis and representation of routes with intensities through data visualization. In the second part we introduce a multi-dimensional analysis of time parameters in ECGS. This approach provides a comparative analysis of several control algorithms such as dispatch or park algorithms for different combinations of traffic components. 相似文献
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文中对低温设备温差应力循环所产生的疲劳失效事故进行了分析,目的是防止低温储罐在使用中出现疲劳破坏。文中通过对失效低温设备断口形貌特征的勘察,采用断口分析、焊接缺陷分析、温差应力循环与疲劳载荷分析的方法,得出了低温液体储罐设备在使用中易出现疲劳失效模式的结论。同时,从设计结构、施焊控制、安全泄放装置维护等方面,对低温液体储罐疲劳失效提出了预防措施。 相似文献
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富水砂层中暗挖隧道施工沉降控制技术 总被引:1,自引:1,他引:0
富水砂层中暗挖隧道施工是地铁施工中的一大难点,常常因沉降过大而引发安全事故。在深圳地铁安-侨区间隧道工程中,通过洞内帷幕注浆、水平旋喷桩、地表井点降水等辅助措施做到了超前控制,在解决隧道开挖安全问题的同时有效地减少了沉降量;施工过程中严格执行了"管超前、短进尺、强支护、早封闭、勤量测"的方针,控制了时空效应,解决了富水砂层中暗挖隧道沉降过大的问题。文章重点分析了沉降原因及控制沉降的关键技术和有效措施。 相似文献