石南油田多相流管线工艺计算模型的选择

运用不同的模型对石南油田的一条多相流管线的压降进行了计算,与实测值相比,计算结果均不理想。因此针对该多相流管线提出了一种新的组合模型,经计算比较,该模型对石南多相流管线有足够的精度,能满足工程上的要求。     

基于模型修正的实体车-桥耦合分析系统建立及验证

为将梁格法车-桥耦合分析系统提升至同时考虑结构整体响应及局部应力分析的精细化实体车-桥耦合分析系统,首先,基于最小势能原理推导八节点六面体实体有限单元列式,采用等参插值确定单元的协调位移,引入Wilson非协调位移模式,消除一阶单元在弯曲变形分析中的剪切自锁,提高单元的分析精度和计算效率;采用静/动力分析算例对所构造非协调八节点六面体单元（ICH8）的准确性进行验证;其次,基于车轮与桥面接触实体单元间的位移协调和力的平衡关系,采用非线性分离迭代法建立实体车-桥耦合分析系统,编制自主研发的精细化分析模块;再次,融合Monte-Carlo灵敏度分析与遗传算法构建桥梁实体有限元模型修正方法,并借助现场静载测试结果对目标桥梁实体有限元模型进行修正;最后,联合修正的桥梁实体有限元模型与跑车工况测试结果验证所建立实体车-桥耦合分析系统的准确性。结果表明：由所建立的实体车-桥耦合分析系统得到的桥梁动力响应与实测响应吻合良好,从而验证了该分析系统的可靠性。借助所建立的实体车-桥耦合分析系统,不仅可实现时域内桥梁结构的整体内力分析,同时还可实现桥梁结构的局部应力分析,包括局部构件的应力分布和应力集中等,对当前车-桥耦合振动领域分析工具具有一定的改进和提升。     

A risk-based first-principles approach to assessing green seas loading on the hatch covers of bulk carriers in extreme weather conditions

This paper aims to present and explain the work undertaken at the SSRC on the Safety of Bulk Carriers in extreme weather conditions over the past 3 years, to draw conclusions deriving there from, concerning key influencing design, operational and environmental parameters and to offer recommendations regarding the rule development process and on the way forward considering research, development and implementation to ship design and operation with the view to improving the safety of these ships cost-effectively. In severe storms, hatch covers of low freeboard vessels such as bulk carriers are the first-line of protection against flooding. Present methods of hatch covers design are still empirical because impact loads due to green seas and structural behaviour due to this type of loads have not been examined, hence not known accurately. The loading due to green seas is implicitly non-linear and, as model test results demonstrated, bulk carriers in extreme conditions are exposed to significant loads, which in some cases exceed current design standards. Since the consequences of hatch cover failure are potentially catastrophic, the risk of this happening should be quantified in probabilistic terms as required by modern safety standards. To this end, the paper aims to propose and implement a methodology for estimating probabilities of deck wetness and impact loads due to green seas as a function of key design and operational parameters.     

我国高等职业教育办学模式的探讨

办学模式改革已成为高职教育模式改革的重点。教育行政主导模式、行业主导模式、市场主导模式是目前办学模式的三大主要类型,三种模式的互动决定了社会化办学将成为我国高职教育办学模式的未来走向。     

汽车无级变速传动（CVT）建模与仿真

从实时控制的角度出发，建立了汽车的无级变速传动夹紧力控制，速比控制及整车动态模型，基于这一动态模型，仿真计算了汽车在起步与行驶阻力变化时的动态调节过程，为进一步研究无级变速传动控制规律和进行电控系统设计提供必要的前期工作基础。     

城市轨道交通安全体系的前向引导与后向完善

通过大邱地铁火灾的案例分析指出,导致灾害的主要原因可归结为:一是前向引导不足,即建设期间遗留的安全隐患以及运营安全体系筹划工作的欠缺;二是后向完善缺乏,即涣散的运营管理.其中,前向引导不足是火灾发生的主因;后向完善的缺乏导致火灾迅速蔓延,造成伤亡惨重.城市轨道交通员工必须牢记"安全第一"的使命与宗旨,树立"建设、运营一盘棋"的整体观念,增强前向引导与后向完善的工作意识,努力建立起可靠的城市轨道交通安全体系.     

公路隧道模型试验相似材料试验研究

满足相似关系的模型材料是模型试验的基础.在调研相似材料研究现状的基础上,通过大量的配比试验研制出满足相似条件的模型材料,该相似材料是以重晶石粉、石英砂作为骨料,松香、酒精溶液作为胶结剂.材料力学试验表明,材料具有容重大、泊松比基本满足软岩的要求、抗压强度和弹性模量低、力学性能稳定、可重复使用等特点.     

Multi-agent model predictive control of signaling split in urban traffic networks

The operation of large dynamic systems such as urban traffic networks remains a challenge in control engineering to a great extent due to their sheer size, intrinsic complexity, and nonlinear behavior. Recently, control engineers have looked for unconventional means for modeling and control of complex dynamic systems, in particular the technology of multi-agent systems whose appeal stems from their composite nature, flexibility, and scalability. This paper contributes to this evolving technology by proposing a framework for multi-agent control of linear dynamic systems, which decomposes a centralized model predictive control problem into a network of coupled, but small sub-problems that are solved by the distributed agents. Theoretical results ensure convergence of the distributed iterations to a globally optimal solution. The framework is applied to the signaling split control of traffic networks. Experiments conducted with simulation software indicate that the multi-agent framework attains performance comparable to conventional control. The main advantages of the multi-agent framework are its graceful extension and localized reconfiguration, which require adjustments only in the control strategies of the agents in the vicinity.     

城市道路隧道通风井形式对通风效果的影响

文章基于某隧道工程实例,通过模型试验方法研究了通风井型隧道处于交通阻滞时通风井的通风效果。研究结果表明:当隧道仅凭借车辆低速运动产生的交通风进行自然通风时,通风井处于周期性进、排风转换状态且通风量较低;当采用射流风机与交通风相结合使通风井处于常排风状态时,矩形通风井的排风量随横截面当量直径增大而增大,通风井排风量随通风井倾斜角度减小而增大。     

Retrospect and prospect for subarea travel demand modeling: an empirical study

Abstract

At present, customized subarea models have been widely used in local transportation planning throughout the USA. A subarea model's biggest strengths lie in its more detailed and accurate modeling outputs which better meet local planning requirements. In addition, a subarea model can substantially reduce database size and model running time. In spite of these advantages, subarea models remain quite weak in modeling transit projects, smart growth measures, air quality conformity, and other areas. In addition to evaluating subarea models, this paper uses the Irvine Transportation Analysis Model (ITAM) as an empirical case of subarea model to illustrate the remedial procedures in maintaining its consistency with the regional model of the Orange County Transportation Analysis Model (OCTAM). Looking into the future, subarea models face both opportunities and challenges. More GIS applications, travel surveys, micro-simulation software utilization, and modeling improvements are expected to be incorporated into the subarea modeling process.