现代有轨电车无接触网供电方案比较分析

现代有轨电车以“中低运量、准快速、低碳、人文、高效”的特点越来越受到国内各级城市的青睐。由于接触网对城市景观,尤其是敏感区域的影响较大,为进一步体现与城市景观的融合,其供电方式逐步由接触网向无接触网发展。无触网供电方案种类很多,且各自的技术特点不尽相同。文章在分析世界上各种无触网供电方案技术特征的基础上,对其进行了综合比较,为有轨电车项目的无触网供电方案的合理选择提供了决策依据。     

投资组合有效边界的图解分析

从均值-方差理论的角度出发，通过投资组合有效边界的数学模型，讨论仅包含3项资产的投资组合在不同资产比例分配下的期望收益和方差，得出不同情形下等收益率线和等方差线的切点连线(临界线)的不同图形表示，从而确定投资组合有效边界在E-V平面图上为一系列相连的抛物线段．从等方差线上所有投资组合的总风险小于单个投资的风险而得出风险分散的结论．     

广义凸集值映射优化问题的强有效解

在局部凸Hausdorff拓扑向量空间中,研究了集值优化问题的强有效解.首先,在广义锥次似凸集值映射下,获得了集值优化问题的强有效解的标量化的特性,最后,获得了带广义不等式约束集值优化问题的强有效解的La-grange型最优性条件.     

供应链中经销商的风险协调作用

论证了供应链中风险中性的经销商能够协调零售商面临的风险．为了减少供应链中零售商的风险、增加供应链效益，经销商会提供一份对指经销商和零售商双方都有益的合同选择单给零售商．风险厌恶型的零售商从中能够得到满意的合同，同时可使经销商的期望利润最大化，零售商也会因此增加订购数量，从而获得最大期望价值．     

高海拔特长隧道低压低氧环境施工控制技术研究——供氧技术标准、关键通风技术、施工人员组织、施工装备效率

为解决高海拔地区低压和低氧环境带来的隧道施工供氧、通风等技术难题,采用现场试验及测试的方法,对高海拔隧道施工人员缺氧状况、供氧效果、机械排污量等进行研究,结合理论推导及数值计算,得到如下结果:人体的缺氧危险等级分为严重缺氧(Ⅰ)、缺氧(Ⅱ)、存在缺氧危险(Ⅲ)和不缺氧(Ⅳ)4级;基于肺泡氧分压与氧气体积分数关系的不同缺氧等级下的氧气体积分数控制标准;不同海拔CO体积分数控制标准模型;基于风管开口处流量理论的风管漏风率海拔修正系数计算公式;风机风压、功率的海拔修正系数公式;考虑人体劳动的平均能量代谢率海拔修正系数的不同海拔下施工人员劳动强度指数及强度等级。     

Forecasting electricity demand of electric vehicles by analyzing consumers’ charging patterns

The spread of electric vehicles (EVs) and their increasing demand for electricity has placed a greater burden on electricity generation and the power grid. In particular, the problem of whether to expand the electricity power stations and distribution facilities due to the construction of EV charging stations is emerging as an immediate issue. To effectively meet the demand for additional electricity while ensuring the stability of the power grid, there is a need to accurately predict the charging demands for EVs. Therefore, this study estimates the changes in electricity charging demand based on consumer preferences for EVs, charging time of day, and types of electric vehicle supply equipment (EVSE) and elucidates the matters to be considered for constructing EV infrastructure. The results show that consumers mainly preferred charging during the evening. However, when we considered different types of EVSEs (public and private) in the analysis, people preferred to charge at public EVSEs during the day. During peak load time, people tended to prefer charging using fast public EVSEs, which shows that consumers considered the tradeoffs between the full charge time and the price for charging. Based on these findings, this study provides key political implications for policy makers to consider in taking preemptive measures to adjust the electricity supply infrastructure.     

Kink in the intermodal supply chain: interorganizational relations in the port economy

The intermodal logistics supply chain is designed to move goods from the point of production to the point of consumption as quickly and as cheaply as possible. The ability to accomplish this objective has allowed for the wholesale geographic relocation and offshoring of basic manufacturing and assembly. As a chain of linked and integrated organizations characterized by sequential interdependence, interorganizational relations play a key role in determining the level of integration and seamlessness. Yet there is one critical interorganizational link in the chain that deviates from this vision. This is the relationship between the shipping container terminal and drayage trucking operations which is better described as a form of intermodal disintegration. The weakness in this link of the supply chain is explained by the divergent industrial structures and labor market conditions, the unique nature of the transaction, and the externalization of costs to subordinate workers.     

Transitioning to energy efficient vehicles: An analysis of the potential rebound effects and subsequent impact upon emissions

Given the shift toward energy efficient vehicles (EEVs) in recent years, it is important that the effects of this transition are properly examined. This paper investigates some of these effects by analyzing annual kilometers traveled (AKT) of private vehicle owners in Stockholm in 2008. The difference in emissions associated with EEV adoption is estimated, along with the effect of a congestion-pricing exemption for EEVs on vehicle usage. Propensity score matching is used to compare AKT rates of different vehicle owner groups based on the treatments of: EEV ownership and commuting across the cordon, controlling for confounding factors such as demographics. Through this procedure, rebound effects are identified, with some EEV owners found to have driven up to 12.2% further than non-EEV owners. Although some of these differences could be attributed to the congestion-pricing exemption, the results were not statistically significant. Overall, taking into account lifecycle emissions of each fuel type, average EEV emissions were 50.5% less than average non-EEV emissions, with this reduction in emissions offset by 2.0% due to rebound effects. Although it is important for policy-makers to consider the potential for unexpected negative effects in similar transitions, the overall benefit of greatly reduced emissions appears to outweigh any rebound effects present in this case study.     

车载信号电源同步切除同步供电设计方案

针对信号设备维护人员提出的"车载信号设备首尾应同步断电、同步供电"需求,为方便维修及维护,缩短故障时延,设计了车载信号设备首尾同步供电、同步切除方案,任意一端均可操作执行。     

铁路电力与信号设备供电匹配性分析

铁路工程中由于信号电源屏与供电系统开关电流整定不匹配,经常导致事故时开关越级跳闸。通过分析信号负荷的特点及信号、电力两专业对信号负荷电流的计算过程,发现二者所遵循的标准以及对系数的取值存在差异。电力专业计算结果更接近于实际,而信号专业计算结果偏大,造成电流整定不匹配。通过分析开关的保护特性,提出对于信号负荷占变压器容量比重较小时,信号机房配电开关采用隔离型,信号电源屏进线开关与变电所开关实现选择性保护的配电方案;信号负荷占变压器容量比重较大时,电力供电设远动功能,便于快速恢复供电。此方案已在多个工程中采用。