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301.
The forthcoming Next Generation Network (NGN) is an all IP network. Multimedia communications over IP networks are a type of bundled session communications, which cannot directly traverse Network Address Translations (NATs) and firewalls even in NGN. To solve the problem that the existing traversal methods are not suitable for service providers to set up a real system in NGN,a Distributed Broker-agent Architecture (DBA) is addressed. DBA is secure and realizable for service providers and enterprises because it is easy to set up and does not need to upgrade the existing devices like Firewalls, NATs or endpoint devices of subscribers.DBA is composed of two-layer distributed agents, the server proxies and the client agents, in which all multimedia communications use shared tunnels to carry signaling messages and media data between broker-agents, and the call signaling is encrypted over Security Socket Layer (SSL) to guarantee the security of calling. Moreover, the function model and multiplexed connection messages format of DBA are designed, which lays a basis for the protocol in the future NGN. In addition, a simple implementation based on H.323 verifyies the main function of traversing firewalls and NATs. 相似文献
302.
Zhongshan Bridge is a kind of steel arch bridge with a particular space-combined structure.The rationality of design.accuracy of theoretical calculation and reliability of transportation were studied.Its design,FEM calculation of stresses and strains,and model test were introduced in detail.The theoretical analysis and model test verified that the design was reliable and safe.The simulated stresses,rigidity and stability,which are based on the selected loading system and cross-section geometry,satisfy the related design standards.Some of the issues that need to be considered in the real bridge construction were also discussed. 相似文献
303.
NEURAL NETWORKS PREDICTION FOR SEISMIC RESPONSE OF STRUCTURE UNDER THE LEVENBERG-MARQUARDT ALGORITHM 总被引:1,自引:0,他引:1
Activecontrolandsemi activecontrolarenewapproachestoseismichazardmitigationofstructure .Whileinactivecontrolorsemi activecontrol ,mea surementofstructurestate ,transmissionandcalcu lationofsignalandinflictionofcontrolforcerequiretime ,moreover ,controlforceiscalculatedaccordingtotheseismicresponseofstructureinlastepoch ,sothecontrolforceinactivecontrolorsemi activecontrolmaybedistortedduetotime delay .Suchdistortionusuallyincreasestheseismicresponseofstructureandmakesstructuremoredangerous[1-3… 相似文献
304.
Repair and Strengthening Assessment of Existing Bridges Based on Time-Dependent Reliability Analysis
The strategy on repair and strengthening of existing bridges based on time-dependent reliability was analyzed with the maximum expected benefit as the objective function. A sample of risk-ranking decision was illustrated based on updated inspection information with 35 survival age. The effect of improvement of live loads and difference of repair methods on time-dependent reliability of existing bridges are considered. The results show that the decision method can be used in real project, with the cost of failure consequence and the risk of failure considered. 相似文献
305.
机场跑道长度可靠性设计方法 总被引:1,自引:2,他引:1
将可靠性理论引入跑道长度计算,对有关变量作了统计分析,获得了空气相对密度、风速、驾驶误差系数、着陆接地点到跑道端的距离等变量的分布规律。采用遗传算法和重要抽样法进行了跑道长度可靠度分析,提出了一种基于可靠性理论的跑道长度设计方法,对永备机场进行了可靠性评价,其平均失效概率是4 75×10-4,实际失效概率为2×10-43×10-4,两者比较接近。计算结果表明可靠性方法对跑道长度设计和安全性评价是可行的。 相似文献
306.
牟瑞芳 《西南交通大学学报(英文版)》2004,12(1):69-72
The concentration of runoff depends upon that of soil loss and the latter is assumed to be linear to the value of EI that equals the product of total storm energy E times the maximum 30-min intensity,I^30 for a given rainstorm.Usually,the maximum accumulative amount of rain for a rainstorm might bring on the maximum amount of runoff,but it does not equal the maximum erosion and not always lead the maximum concentration.Thus,the average concentration weighted by amount of runoff is somewhat unreasonable.An improvement for the calculation method of non-point source pollution load put forward by professor Li Huaien is proposed.In replacement of the weight of runoff,E1 value of a single rainstorm is introduced as a new weight.An example of Fujing Rive rwatershed shows that its application is effective. 相似文献
307.
308.
输送带安装质量控制要点 总被引:1,自引:0,他引:1
分析输送带安装过程中出现的主要问题,以施工过程中各质量控制点为节点进行控制,强化对各施工工序的管理,保证施工质量。 相似文献
309.
310.
在铁路投资项目中,资本金是一个很重要的基础数据,它不仅关系到投资各方的出资额,而且也影响最终的经济评价结果指标.本文分析了现行经济评价中资本金计算存在的问题及原因,提出了由静态总投资及资本金比例推算出动态总投资的算法,并通过案例分析比较了按静态投资算法和按动态投资算法两种情形下各投资主体出资额的变化,以及对最终经济评价... 相似文献