基于日照阴影识别的桁式拱肋三维温度场模拟方法

为精确高效地识别桁式拱肋的阴影分布范围并准确计算日照温度场，在传统三维温度场计算方法的基础上，引入三角形重心坐标及栅格加速结构，形成一套高效三维温度场模拟方法。首先，将光线追踪技术的阴影识别算法嵌入ABAQUS软件的自定义热源(DFLUX)子程序，实现了三维日照温度场的数值模拟，给出了详细的计算流程并验证了该方法的准确性；其次，选取高效的相交算法与合理的栅格划分方式解决了复杂结构桥梁阴影识别计算量庞大、计算效率低下的问题；最后，利用该方法计算了桁式拱肋的日照温度场并量化了温度效应。结果表明：提出的模拟方法可以实现阴影的精确识别与结构三维温度场的准确计算，通过引入基于栅格加速结构的三角形重心坐标法可以有效减少阴影识别的计算量，显著提升计算效率;日照阴影对桁式拱肋温度场及温度效应的影响不容忽视，考虑日照阴影后：下弦杆温度纵向波动十分显著，且波动幅度随着太阳辐射强度的增强逐渐增加，相邻的光照、阴影区域最大温差达13.0 ℃,拱肋竖向位移减小19%，上弦管上缘应力最大增加12.9 MPa，下弦管上缘由受压状态转变为受拉状态，应力差值达39.1 MPa;桁式拱肋的日照温度效应十分突出,日照温度作用下拱顶位移变化幅度达76 mm，较钢管混凝土拱肋拱圈施工允许误差大26 mm,最大温度应力达58.7 MPa，为恒载效应的3倍，叠加温度效应后钢管最大初应力为110 MPa，为空管稳定承载应力的32%;提出的模拟方法在桁式拱肋日照温度效应分析中得到了成功应用，亦可应用于大跨复杂结构的施工线形精细化控制、健康监测数据的温度响应分离及结构损伤识别中的温度模态频率剔除等多个场景。     

功效系数法在水泥稳定材料配合比设计中的应用

水泥稳定材料的配合比设计方法主要考虑技术指标,对经济指标关注很少。对满足强度要求的多个配合比设计方案,将价格也作为考察指标之一,运用功效系数法加以评价和优化,获得性价比最佳的配合比设计方案,既能保证质量,又可节约工程成本,并总结出一种多指标权衡的配合比设计评价和优化方法。     

Explaining “peak car” with economic variables

Many western countries have seen a plateau and subsequent decrease of car travel during the 21st century. What has generated particular interest and debate is the statement that the development cannot be explained by changes in traditional explanatory factors such as GDP and fuel prices. Instead, it has been argued, the observed trends are indications of substantial changes in lifestyles, preferences and attitudes to car travel; what we are experiencing is not just a temporary plateau, but a true “peak car”. However, this study shows that the traditional variables GDP and fuel price are in fact sufficient to explain the observed trends in car traffic in all the countries included in our study: the United States, France, the United Kingdom, Sweden and (to a large extent) Australia and Germany. We argue that the importance of the fuel price increases in the early 2000s has been underappreciated in the studies that shaped the later debate. Results also indicate that GDP elasticities tend to decrease with rising GDP, and that fuel price elasticities tend to increase at high price levels and during periods of rapid price increases.     

Collective public-transport tickets and anticipated majority choice: A model of student tickets

In Germany, many universities have student tickets that are bargained for between student representatives and public transport companies, approved by referendum, and mandatory for all students. They allow the use of public transport at no additional cost. I analyze such a scenario in a theoretical model as an example of a flat-rate ticket for public transport which is implemented by majority decision. The mandatory character of the ticket reduces transaction costs like marketing and ticket inspection, reducing the ticket price and thus the students’ commuting expenses. However, there is a countervailing effect. Students face and rationally expect zero marginal monetary commuting costs, so that new students choose a place of residence which is relatively far from the university. This in turn raises the equilibrium ticket price. It may even be the case that students would be better off if such a ticket had never existed. Nonetheless, they always vote for it in referenda, because accepting the high price is optimal given their place of residence. After laying out the model, I analyze an optimal policy, which consists, for example, of subsidizing student dorms at an efficient distance to the city center.     

城市轨道交通新建线路对沿线住宅价格增值的时空效应

定量分析城市轨道交通对沿线土地价值的影响，是通过土地价值捕获将外部效益内部化， 解决中国新型城镇化过程中城市轨道交通财务可持续的关键问题。本文在开源数据环境下，获 取2011—2016年北京市二手房交易数据，采用特征价格模型(HPM)分析北京城市轨道交通新建 线路对沿线住宅价格增值的时空效应。研究表明：与全局常参数的多元线性回归模型(MLR)、空 间滞后模型(SLM)、空间误差模型(SEM)和空间杜宾模型(SDM)相比，局部变参数的地理加权回归 模型(GWR)拟合效果更优，可以更好地消除残差的空间效应，刻画轨道交通与土地价值关系的空 间异质性。城市轨道交通带来的可达性提升对沿线80%以上住宅小区的房价具有显著的正效 应，住宅价格增值比率随地铁站距离递远递减，且具有显著的空间异质性。轨道交通对住宅价格 的影响在空间上具有网络化效应，新建线路不仅会改变周边房价，对城轨网络其他位置的住宅也 具有影响。城市轨道交通对住宅价格的影响范围为1 km，在该范围内，住宅价格受到的增值效应 在 2011—2016 年基本稳定，约为 3%；受新线直接影响区域的住宅价格会产生相对更大的提升 (0.02%~0.22%)。     

Is car drivers’ response to congestion charging schemes based on the correct perception of price signals?

This paper deals with the question of whether the capability of car drivers to estimate the cost of a new hypothetical, highly differentiated congestion charge influences their decision to change travel behaviour. The analysis makes use of an integrated choice and latent variable model (ICLV) which merges classic choice models with the structural equation approach (SEM) for latent variables. This hybrid model improves the explanatory power considerably compared with a conventional discrete choice model. The results suggest that charge complexity decreases the resistance in considering behavioural changes. Car drivers tend to avoid a travel option where the price is not known beforehand, a phenomenon known as ambiguity avoidance.     

选举交互模型下的股市权益定价

运用停时理论及粒子选举交互作用系统,建立了一个包含两类投资者的股票价格模型,用以描述证券市场的单只证券价格过程波动的统计特性.基于统计分析方法,证明了标准化随机价格过程收敛于相应Black-Scholes模型的分布.讨论了该价格过程模型下的欧式未定权益的定价和套期保值问题.     

基于灰色关联分析的房地产价格估算研究

房地产开发价格确定的准确与否直接影响项目开发利润的大小,更会关系到项目的成功与失败.结合房地产开发的特点,在充分考虑房地产价格影响因素的基础上,利用已建类似项目的价格建立灰色关联分析模型,估算出拟建项目房地产价格,并结合实例进行了阐述.     

集装箱航运市场运力供需与运价分析模型

根据船舶集装箱运输生产的航速和箱位两个要素，定义了以每天每箱位投入燃油数和箱位数为自变量的航运生产函数；推导出集装箱航运市场供方根据需求的变化而调整产量的扩张路径；推导出供方短期单位总成本，并求出边际成本曲线，即供应函数。结果表明，在大范围内，边际成本对需求相对较不敏感，运价相对稳定，但当船队已完全利用，边际成本及船东要求的运价上升很快。