桶型基础在负压作用下的屈曲分析

桶型基础是一种新型的基础结构形式 ,它采用短粗圆柱薄壳结构 ,利用负压原理安装 ,当基础非常接近海床时 ,裙端在横向没有约束 ,在静水压力作用下极易产生屈曲 ,是结构最危险的状态。本文将此时的结构简化为一端固定 ,一端自由的圆柱薄壳 ,采用经典线性屈曲理论 ,通过选取轴向梁函数与周向三角形函数的组合作为屈曲挠度函数 ,得到了桶型基础在一端固定 ,另一端自由边界条件下的线弹性屈曲的解析解。同时采用工程实例进行计算 ,并与有限元计算进行了对比 ,获得了比较满意的结果。根据本文的理论方法编制的程序简单明了 ,计算方便 ,非常适合于实际工程中的预算和评估。     

基于导热反问题的双层炉膛内壁缺陷诊断

对内壁带有不规则缺陷的双层炉膛建立了二维稳态传热模型并通过有限元方法进行求解.利用外壁面的温度分布,根据共轭梯度法,通过使外壁面温度测量值和计算值之差最小化,基于导热反问题机理对内壁面的缺陷形态进行了识别.并对某焚烧炉炉膛进行了数值试验,分析了测量误差和初值选取对反演结果的影响.     

Experimental study of a suspended subsea module at different positions in the splash zone

During the lifting of submerged marine modules, the highest dynamic loads occur in the splash zone. These forces are highly dynamic and cannot easily be estimated with sufficient accuracy using simple calculations or high-fidelity computational fluid dynamics because of their irregular and complex geometries. We conducted an experimental study in a wave tank to investigate the dynamics of a large subsea module in the splash zone subject to irregular waves. The experiments were conducted using a 1:8 scale model of a subsea module, similar to that designed by Offshore Oil Engineering Co., Ltd., for the subsea pipeline from the Wenchang gas fields to the Yacheng pipeline. The model was examined at five different positions relative to the free surface, from completely above the surface to fully submerged. The resulting data are analyzed in the time and frequency domains. Spectral analysis and a dynamic effect parameter are used to analyze the dynamic loads on the subsea module. Several time-domain numerical analyses are performed with different peak periods, and the tension of the sub-slings is obtained. The experimental results for the relative forces and motions of the subsea module are presented, providing a reference for the design of other similar modules and their installation and validation data for computational modeling.     

Looking at sustainable urban mobility through a cross-assessment model within the framework of land-use and transport integration

In order to realise sustainable urban transport, it is necessary to combine different kinds of decision-making, including vision-led, plan-led and consensus-led approaches. In this paper, a cross-assessment model that supports both vision-led and consensus-led approaches is proposed as an analytical tool for developing sustainable urban transport and land use strategies for a low-carbon society. It is applied to an impact analysis of public transport and land use strategies in 2030 for all of Japan's 269 urban areas, with outcomes – including the financial balance of public transport operation, user benefits, and CO₂ emissions reduction – compared by strategy and urban area.     

The capitalization of subway access in home value: A repeat-rentals model with supply constraints in Beijing

Urban rail transit enhances accessibility of the communities it serves and often contributes to the value of local real properties. A small number of studies have gone beyond the traditional cross-sectional hedonic analysis to use repeat-sales data in the US for more robust estimation of rail transit’s impact on property value. While the empirical literature generally supports the positive capitalization of rail transit in home value, it has produced widely varied estimates and failed to incorporate the theoretical insight that more elastic housing supply would reduce the extent of local amenities’ capitalization in home value. Observing Beijing’s rapid expansion of subway lines during the late 2000s, this study uses repeat rental transactions from 2005 to 2011 to investigate how home value reacts to the change in the home’s distance to nearest subway station. Repeat-rentals estimates suggest a rent-distance elasticity of −0.02, 70% below the cross-sectional hedonic estimate. Moreover, using the unique history of state-owned enterprise relocations as instrument for intra-city variation in land supply, we find that the capitalization of subway proximity in home value is weaker where land supply is more elastic. Our findings support the significant bias caused by omitted variables in the hedonic estimates and confirm housing supply’s role in explaining the intra-city spatial variation in estimates.     

Influences of built environment characteristics and individual factors on commuting distance: A multilevel mixture hazard modeling approach

Concerns over transportation energy consumption and green-household gas (GHG) emissions have prompted a growing body of research into the influence of built environment on travel behavior. Studies on the relationship between land use and travel behavior are often at a certain aggregated spatial unit such as traffic analysis zone (TAZ), spatial issues occur among individuals clustered within a zone because of the locational effects. However, recognition of the spatial issues in travel modeling was not sufficiently investigated yet. The object of this study is twofold. First, a multilevel hazard model was applied to accommodate the spatial context in which individuals generate commuting distance. Second, this research provides additional insights into examine the effects of socio-demographics and built environment on commuting distance. Using Washington metropolitan area as the case, the built environment measures were calculated for each TAZ. To estimate the model parameters, the robust maximum likelihood estimation method for a partial function was used, and the model results confirmed the important roles that played by the TAZ and individual level factors in influencing commuting distance. Meanwhile, a comparison among the general multilevel model, single level and multilevel hazard models was conducted. The results suggest that application of the multilevel hazard-based model obtains significant improvements over traditional model. The significant spatial heterogeneity parameter indicates that it is necessary to accommodate the spatial issues in the context of commuting distance. The results are expected to give urban planners a better understanding on how the TAZ and individual level factors influence the commuting distance, and consequently develop targeted countermeasures.     

关于北方内陆河流水资源开发利用问题初探

本文对北方河流开发问题进行研究,从最大程度利用现有已建水利枢纽工程的调节能力,兴建新的水利工程,在满足下游生态水量的情况下,研究增加流域水土开发规模的可能性。     

高速铁路隧道壁吸声材料降噪效果仿真分析

应用SYSNOISE软件建立列车-隧道-隧道内壁吸音板结构的二维边界元模型,研究隧道内壁吸声结构不同铺设方案下的降噪效果。根据高速铁路列车通过时隧道内壁吸声结构不同铺设面积、铺设位置等因素,分析其对列车通过时噪声的降噪效果,并综合考虑工程经济性等因素,计算4个较为典型的隧道内壁吸声结构的铺设方案。计算结果表明:在隧道内壁全部铺设吸声材料的情况下,铺设隧道吸声结构对隧道内声压级的降噪效果约为14.3dB。随着隧道内壁吸声材料铺设面积的增加,隧道内的降噪效果越好。在计算选取的4个方案中,内壁整体铺设方案降噪效果最佳,内壁部分铺设方案降噪效果最差,两者的组合方案降噪效果适中,实际工程应用中应综合各方面因素对降噪方案进行选取。     

谈非规则相邻车站的信号联锁设计

针对相邻车站的特殊接轨方式,论述如何划分信号联锁分界点,围绕分界点如何进行信号联锁关系设计,最终实现债权明确、安全可靠和使用方便等功能。     

轨道交通建设影响下土地利用性质空间分异的组合预测模型

在先验数据有限且存在不确定因素情形下，为解决城市轨道交通沿线土地利用性质空间分异的预测问题，提出一种基于系统云灰色模型和马尔可夫链的组合预测模型。采用系统云灰色模型，使用较少量的历史数据完成城市轨道交通沿线各类性质用地面积变化曲线的粗略拟合；借助马尔可夫链进行系统状态划分，通过缩小预测区间以提高预测精确度；运用组合预测模型，对2003-2015年南京市轨道交通1号线主要吸引范围内土地利用性质的空间分异进行了预测分析。计算结果表明：轨道交通建设加剧了城市土地利用性质的空间分异，其周边各种性质的土地利用面积变化趋势呈现出非平稳随机过程特性；轨道交通建设对不同性质土地利用的影响方式与影响强度各不相同，其中，对居住用地具有强烈的吸引作用，对公建用地吸引作用不明显，对工业用地具有明显的排斥作用。