共查询到20条相似文献，搜索用时 93 毫秒
1.
A model of dynamic programming for repairing strategies of concrete structures during a projected service period is proposed,which takes into account the degradation in strength of components and the probability of accidental load.This model takes the safety grade of a structural system as the state variable of repairing strategies,and incorporates economic factors including expected repair cost,property loss due to structure failure,goods and material loss due to structure failure,loss of production interrupt due to structure failure,and inspection cost in decision making.It is found that the optimal repairing strategies are sensitive to the probability of accidental loads as well as the failure costs.The practicality of the model is demonstrated by an example. 相似文献
2.
in order to evaluate the seismic reliability of water distribution system and make rehabilitation decisions correspondingly, it is necessary to assess pipelines damage states and conduct functional analysis based on pipe leak- age model. When an earthquake occurred, the water distribution system kept serving with leakage. By adding a virtual node at the centre of the pipeline with leakage, an efficient approach to pressure-driven analysis was developed for simulating a variety of low relative scenarios, and a hydraulic leakage model was also built to perform hydraulic analy- sis of the water supply network with seismic damage. Then the mean-first-order-second-moment method was used to analyse the seismic serviceability of the water distribution system. According to the assessment analysis, pipes that were destroyed or in heavy leakage were isolated and repaired emergently, which improved the water supply capability of the network and would constitute the basis for enhancing seismic reliability of the system. The proposed approach to seismic reliability and rehabilitation decision analysis on water distribution system is demonstrated effective through a case study. 相似文献
3.
Water distribution networks are essential components of water supply systems. The combination of pipe structural deterioration and mechanics leads to the failure of pipelines. A physical model for estimating the pipe failure must include both the pipe deterioration model and mechanics model. Winkler pipe-soil interaction （WPSI）, an analytical mechanics model developed by Rajani and Tesfamariam （2004）, takes external and internal loads, temperature changes, loss of bedding support, and the elastoplastic effect of soil into consideration. Based on the WPSI model, a method to evaluate the elastic and plastic areas was proposed in the present study. An FEM model based on pipe-soil interaction （PSI） element was used to verify the analytical model. Sensitivity analyses indicate that the soft soil, long pipe and high temperature induced the axial plastic deformation more likely, which, however, may not occur in normal scenarios. The soft soil, pipes in small diameters, long unsupported bedding are prone to form flexural plastic area. The results show that the pipes subjected to the same loads have smaller stresses in the elastoplastic analysis than elastic analysis. The difference, however, is slight. 相似文献
4.
An accurate understanding of the condition of a pipe is important for maintaining acceptable levels of service and providing appropriate strategies for maintenance and rehabilitation in water supply systems. Many factors contribute to pipe deterioration. To consolidate information on these factors to assess the condition of water pipes, this study employed a new approach based on Bayesian configuration against pipe condition to generate factor weights. Ten pipe factors from three pipe materials （cast iron, ductile cast iron and steel） were used in this study. The factors included size, age, inner coating, outer coating, soil condition, bedding condition, trench depth, electrical recharge, the number of road lanes, material, and operational pressure. To address identification problems that arise when switching from pipe factor information to actual pipe condition, informative prior factor weight distribution based on the literature and previous knowledge of water pipe assessment was used. The influence of each factor on the results of pipe assessment was estimated. Results suggested that factors that with smaller weight values or with weights having relative stable posterior means and narrow uncertainty bounds, would have less influence on pipe conditions. The model was the most sensitive to variations of pipe age. Using numerical experiments of different factor combinations, a simplified model, excluding factors such as trench depth, electrical recharge, and the number of road lanes, is provided. The proposed Bayesian inference approach provides a more reliable assessment of pipe deterioration. 相似文献
5.
陈升霞 《延边教育学院学报》2013,(4):72-73
阅读教学犹如浩瀚的海洋,可以挖掘出无限的写作教学内容。阅读教学是目前语文课堂教学的主流形式,教师对课文的教学就是一个阅读教学,学生对课文的学习就是一种精读的过程,注重以读促写,根据教材特点,精心选择读写结合点,给学生提供有效借鉴的对象和创造的依据,及时有效地进行模仿和创造性练笔,鼓励学生自由地表达,有个性地表达,为学生打开一扇写作的窗,让学生学会写作。 相似文献
6.
In water distribution systems, water leakage from cracked water pipes is a major concern for water providers. Generally, the relationship between the leakage rate and the water pressure can be modeled by a power function developed from the orifice equation. This paper presents an approximate solution for the computation of the steady-state leakage rate through a longitudinal line crack of a water distribution pipe considering the surrounding soil properties. The derived solution agrees well with results of numerical simulations. Compared with the traditional models, the new solution allows assessment of all the parameters that related with leakage including the pressure head inside the pipe, hydraulic conductivity, crack size and its position, and pipe size and its depth. 相似文献
7.
Pressure pipes are widely used in modern industry with some in potentially dangerous situations of explosion and impact. The security problems of these pipes when subjected to impact have attracted a lot of attention. A non-linear numerical model has therefore been developed to investigate the dynamic behavior of pressure pipes subjected to high-velocity impact. A high strain rate effect on the pipe response is considered here and the fluid and pipe interaction is modeled to include the coupling effect between the deformation of the pipe and its internal pressure. Low-velocity and high-velocity impact experimental results are used to verify the numerical model, and a reasonable agreement between the numerical and experimental results has been achieved. The effects on the dynamic behavior of the pipes of the nose shape of the projectile, the diameter of the spherical projectile, and the pipe wall thickness and internal pressure, are investigated quantitatively. During high-velocity impacts, the increase of pressure in the pipes decreases their resistance to perforation. A rise in internal pressure increases the elastic resistance of the pipes toward impacts without crack formation. 相似文献
8.
Hua ZHU Bo ZHUAN Jin-jun TAN Rong-hua HONG 《浙江大学学报(A卷英文版)》2008,9(3):410-415
This paper focuses on the heat transfer performance of semi-open heat pipe which is a new type of heat pipe. After analyzing its condensation heat transfer mechanisms theoretically, several semi-open heat pipes in different length ratios and upper hole diameters are studied experimentally and compared with the same dimensions closed heat pipes. Experimental results show that the heat transfer performance of semi-open heat pipe becomes better by increasing heat transfer rate. At the first transitional point, the heat transfer performance of semi-open heat pipe approaches the level of the closed heat pipe. It is suitable to choose upper small hole about 1 mm in diameter and length ratio larger than 0.6 for the semi-open heat pipe. 相似文献
9.
桩基础施工是否顺利,将对主体工程的施工产生较大影响,特别在管桩施工中,往往因为施工时造成的桩头或桩身损坏,不得不进行设计修改,影响主体工程的进度,增加施工成本,因此科学合理的修复方法,对保证工程质量、加快进度、减少成本很有必要。 相似文献
10.
高层建筑机械防烟系统可靠性故障树分析 总被引：1，自引：0，他引：1
卜增文 《深圳职业技术学院学报》2003,2(3):14-17
从可靠性的基本原理出发，用FTA方法对高层建筑机械防烟系统的组成单元进行了分析，建立其故障树和数学模型，对所建故障树进行了定性分析和定量计算。分析和计算了机械防烟系统故障的各种可能组合方式以及系统部件重要度，据此可以判断系统各个部件故障的发生概率，便于采取相应的预防或纠正措施，从而在设计阶段就可以控制系统的可靠度。 相似文献
11.
周平南 《实验室研究与探索》2004,23(11):14-16
针对DUNHAM-BUSH冷水机组冷凝器的泄漏问题，开展了失效冷凝器铜管的宏观和微观分析。研究结果表明，冷凝器铜管的工艺缺陷不是造成失效的主要原因，铜管内大量沉积物的产生是造成冷凝器泄漏的主要原因。 相似文献
12.
供水管网中的节点流量具有不确定性,为了研究节点流量不确定性对供水管网漏损定位能力的影响,建立供水管网节点流量分布在不同条件下的需求分布水力模型。一种是供水管网中各节点平均分配流入量的均匀模型,另一种是在供水管网各节点按需分配流入量的分配模型,比较两种需求分布模型的漏损定位性能。利用加权最小二乘算法完成供水管网水力模型的漏损定位,加权最小二乘算法具有模型精度高和计算效率高的优点,该方法通过计算供水管网中监测值与水力模型模拟值的差异,判断是否发生漏损,并能准确定位漏损节点。最后通过实例证明供水管网节点流量的不确定性对供水管网漏损定位性能有突出影响。 相似文献
13.
继电保护设备是一种重要的电力二次设备,继电保护装置分为继电保护装置本体和二次回路．文章通过对继电保护装置本体应用软／硬件失效模型进行风险评估,对二次回路应用故障树模型进行分析,建立了继电保护系统失效模型,该模型能够帮助电力自动化系统较准确地判断出系统的故障率和运行可靠性． 相似文献
14.
针对电路故障测试过程中存在故障难以定位和修复的问题,提出了一种基于功能重构的故障修复方法。该方法使用全集测试集对被测电路进行精确测试,以测试向量中的响应值与实际电路中的响应结果进行对比,实现对故障的精确定位。当被测电路的所有故障信息被收集后,采用功能重构的原理对出现故障的电路进行修复,在实现功能修复同时,降低了故障修复难度。文章给出了这种故障检测与功能重构的总体实现框图,并分别对模拟电路和数字电路的故障详细阐述了功能重构的方法。 相似文献
15.
程敏珍 《福建工程学院学报》2007,5(4):340-343
收集建筑消防系统实际运行资料,分析影响建筑消防系统正常运行的因素;通过建立故障树和数学模型,利用故障树分析法对系统运行过程可能产生的故障进行定性和定量分析,确定系统可靠度和各故障因素的概率重要度,据此判定系统中事故频发的环节,为改善系统运行和提高系统的可靠性能提供理论依据. 相似文献
16.
Dong-fang Hu Zheng-liang Huang Jing-yuan Sun Jing-dai Wang Zu-wei Liao Bin-bo Jiang Jian Yang Yong-rong Yang 《浙江大学学报(A卷英文版)》2017,18(3):212-224
The effect of a gradual contraction pipe (GCP) on gas-liquid flow in a circular-sectioned horizontal to vertical 90° duct bend was investigated by computational fluid dynamics (CFD) simulation. The hydrodynamics of gas-liquid flow in 90° duct bends with and without a GCP in the vertical section were compared using a 3D steady Eulerian-Eulerian approach. The predicted static pressure in the vertical section of the pipes and the pressure drop in the whole pipe were consistent with experimental data. Results of simulations showed that liquid could distribute more uniformly at the exit of the pipe with a GCP. The increased uniformity was accompanied by an increase in pressure drop by a factor of less than 10% compared to the pipe without a GCP. The position of minimum pressure in the bend was changed by the GCP. A GCP can alter the trajectories of the fluid and secondary flow. As a result, the fluid can quickly reach a steady state downstream from the bend. 相似文献
17.
液压系统中的泄漏是一个不可忽视的重要问题。本文主要利用化整为零的思路,去分析系统中液压泵、液压阀等关键元件工作中的泄漏问题及其排除方法。最后,经过汇总统一得出一个液压系统泄漏的逻辑诊断流程图。 相似文献
18.
19.
软件构件的出现提高了软件生产的效率,同时做为SOA的核心技术的ESB提供了综合、灵活而且一致的集成方法。本文在这两种技术的基础上,提出了一种基于ESB的构件开发模式。利用该开发模式,可以快速高效地建立柔性、健壮性、鲁棒性较好的服务构件,并使构件的装配和部署进一步简化,从装配和部署角度提高软件开发的整体速度。该开发模式对各行业领域的软件和构件开发都具有实际的参考价值。 相似文献
20.
EXPERIMENTAL STUDY ON SEMI-OPEN HEAT PIPES AND ITS APPLICATIONS 总被引：4，自引：0，他引：4
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