汽轮机动平衡技术研究及海洋条件下转子不平衡因素分析

文章介绍了影响系数法在动平衡中的应用,并进行了实验验证;同时分析了海洋中摇摆情况及变工况的情况下对转子不平衡的影响,对于汽轮机的运行有着重要的指导作用。     

扬中市扬中夹江二桥施工技术

简要介绍了扬中市扬中夹江二桥构造,详细阐述了该桥有底钢吊箱施工高桩承台、Y型墩施工及其裂缝预防措施、下承式造桥机逐孔施工连续梁、Y型墩连续梁组合体系施工及其监控等关键施工技术,对同类型桥梁施工有借鉴意义。     

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库存在配送系统优化过程中影响甚大,过高的库存或库存不足均会对配送系统造成不良影响。研究了连锁零售配送系统的配送中心和门店的两级库存水平和订货策略问题。通过在数学解析模型的优化结果基础上,应用三维可视化离散事件仿真方法建立了在FLEXSIM软件平台上的配送系统的仿真模型,并结合约束理论与系统仿真对仿真过程进行优化,缩减了仿真方案的数量和提高了仿真的效率并得到优化的仿真方案。研究结果表明,基于整合约束理论的三维可视化仿真是可以提高仿真效率并增强仿真交互性的有效方法。     

Re-parameterization of Bézier Curves by Square Approximation with Endpoint Constraints

In order to get an approximation with better effect of parameterization of Bozier curves, we proposed a method for arc-length parameterization and the corresponding algorithms by square approximation for the discrete even de-parameterization of the curves. This method is simple and easy to implement, and the property of the approximation has no change compared with the original curve. A quantitative criterion for estimating the effect of parameterization is also built to quantitatively characterize the parameterization effect of the algorithms. As a result, the nearly arc-length parameterized curve has a smaller relative deviation using either the algorithm with point constraint at endpoints or the algorithm with point constraint plus the first derivative constraint at endpoints. Experiments show that after re-parameterization with our algorithms, the relative deviation will have at least a 20% reduction.     

盾构推进对既有隧道影响的渗流与结构耦合研究

在上海西藏南路越江隧道西线Φ11580泥水盾构近距离下穿上海地铁已建M8线隧道的过程中,通过布置在M8线内的高精度电子水准尺连续采集了大量的可靠数据,清晰地观测到了M8线上行线隧道随着盾构推进-拼装周期产生的隆沉。该文以实测数据为基础,通过渗流与结构耦合数值模拟方法,研究了西藏南路盾构穿越过程中既有M8线位移变化以及周围土体位移与孔压变化。     

Impact analysis of cordon-based congestion pricing on mode-split for a bimodal transportation network

This paper investigates the impact of cordon-based congestion pricing scheme on the mode-split of a bimodal transportation network with auto and rail travel modes. For any given toll-charge pattern, its impact on the mode-split can be estimated by solving a combined mode-split and traffic-assignment problem. Using a binary logit model for the mode-split, the combined problem is converted into a traffic-assignment problem with elastic demand. Probit-based stochastic user equilibrium (SUE) principle is adopted for this traffic-assignment problem, and a continuously distributed value of time (VOT) is assumed to convert the toll charges and transit fares into time-units. This combined mode-split and traffic-assignment problem is then formulated as a fixed-point model, which can be solved by a convergent Cost Averaging method. The combined mode-split and traffic-assignment problem is then used to analyze a multimodal toll design problem for cordon-based congestion pricing scheme, with the aim of increasing the mode-share of public transport system to a targeted level. Taking the fixed-point model as a constraint, the multimodal toll design problem is thus formulated as a mathematical programming with equilibrium constraints (MPEC) model. A genetic algorithm (GA) is employed to solve this MPEC model, which is then numerical validated by a network example.     

大规模数据并发环境下视频监控系统的研究与实现

城市轨道交通综合监控系统中的视频监控子系统与多个业务子系统共处同一个网络环境中,具有大规模数据并发特点。首先,介绍视频监控子系统所采取的策略,然后介绍基于订阅分发模型的视频数据规划,最后,重点研究视频分发过程中的负载均衡技术。在多台服务器工作的条件下,根据服务器的性能和负载等因素,提出一种基于动态测量的负载均衡技术,实验证明,该负载均衡技术可以有效地降低时延,提高系统的吞吐量,并均衡各个服务器的负载,取得良好的效果。     

用于汽车动力学实时仿真的悬架建模方法的研究

针对汽车动力学实时仿真的要求提出一种新的悬架建模方法—复合约束隔离解耦建模方法。将悬架系统视为连接车身和车轮之间的无质量复合约束,基于这个概念建立的悬架系统模型,由于实现有质量刚体的相互隔离及代数方程与微分方程的解耦,提高了模型求解效率。应用该方法建立的悬架模型,由于是面向结构的模型,因而可较为准确地描述悬架动态特性,同时由于求解效率的提高又能够满足仿真实时性的要求。     

Air transportation in a carbon constrained world: Long-term dynamics of policies and strategies for mitigating the carbon footprint of commercial aviation

With increasing demand for air transportation worldwide and decreasing marginal fuel efficiency improvements, the contribution of aviation to climate change relative to other sectors is projected to increase in the future. As a result, growing public and political pressures are likely to further target air transportation to reduce its greenhouse gas emissions. The key challenges faced by policy makers and air transportation industry stakeholders is to reduce aviation greenhouse gas emissions while sustaining mobility for passengers and time-sensitive cargo as well as meeting future demand for air transportation in developing and emerging countries. This paper examines five generic policies for reducing the emissions of commercial aviation; (1) technological efficiency improvements, (2) operational efficiency improvements, (3) use of alternative fuels, (4) demand shift and (5) carbon pricing (i.e. market-based incentives). In order to evaluate the impacts of these policies on total emissions, air transport mobility, airfares and airline profitability, a system dynamics modeling approach was used. The Global Aviation Industry Dynamics (GAID) model captures the systemic interactions and the delayed feedbacks in the air transportation system and allows scenarios testing through simulations. For this analysis, a set of 34 scenarios with various levels of aggressiveness along the five generic policies were simulated and tested. It was found that no single policy can maintain emissions levels steady while increasing projected demand for air transportation. Simulation results suggest that a combination of the proposed policies does produce results that are close to a “weak” sustainability definition of increasing supply to meet new demand needs while maintaining constant or increasing slightly emissions levels. A combination of policies that includes aggressive levels of technological and operations efficiency improvements, use of biofuels along with moderate levels of carbon pricing and short-haul demand shifts efforts achieves a 140% increase in capacity in 2024 over 2004 while only increasing emissions by 20% over 2004. In addition, airline profitability is moderately impacted (10% reduction) compared to other scenarios where profitability is reduced by over 50% which pose a threat to necessary investments and the implementation of mitigating measures to reduce CO2 emissions. This study has shown that an approach based on a portfolio of mitigating measures and policies spanning across technology and operational improvements, use of biofuels, demand shift and carbon pricing is required to transition the air transportation industry close to an operating point of environmental and mobility sustainability.     

独立需求生产批量优化问题的遗传算法实现

生产批量问题是企业生产和管理中一个常见的约束批量问题,在假定问题中各产品的需求独立,同时满足能力约束和生产平衡的条件下,建立基于独立需求的遗传算法模型,实现使生产费用、生产准备费用和库存费用综合指标最小的生产批量算法。并通过对实际问题的计算验证该模型和算法的有效性和可行性。