筑路机械租赁合同签订应注意的问题

对公路工程施工中租赁双方合同条款订立、机械租赁的计费方法、租金结算、机械运输、维修、合同责任、机械租赁的优越性进行了介绍,并给出了租用过程中遇到问题的解决方法以及采取的防范措施,可以为类似工程的施工单位提供借鉴。     

损伤局部性方法研究进展

本文综述了应用力学研究所的教师、博士后人员和研究生们将损伤局部性方法 (LDA)用于娇变损伤和低周疲劳损伤分析以及细观损伤测量中的研究成果。展望了 损伤局部性方法进一步发展的前景。      

搭板加筋路基处理路桥过渡段差异沉降研究

针对路桥过渡段因路基与桥台沉降差较大而产生的桥头跳车现象,文中利用FLAC3D软件建立了桥头结构与搭板加筋路基的分析模型,对比分析搭板长度与土工格栅层数、模量对路桥过渡段差异沉降的影响,结果表明,搭板可以有效避免路桥连接处的错台现象,但易引起二次跳车现象的发生;搭板加筋路基可以有效减小路桥过渡段差异沉降,避免二次跳车现象的发生,提高行车舒适度;布置土工格栅的效果主要体现在路基与地基交界处;格栅模量的增加可以减小道路沉降。     

湛江港航道会船区设置方案研究

随着航运的快速发展,大型船舶通过进出港航道占用航道时间越来越长,在进港航道设置会船区是十分必要的。现行规范中对于会船区的有关规定及计算尚不明确。针对湛江港航道里程长、规模大、通航环境复杂的客观实际,在对现状船型尺度调研的基础上,分析了拟建会船区的水深、波浪、流速条件。提出了30万、15万t不同船舶组合通航方案,并计算了统一断面与复式断面两种形式下的航道通航宽度,确定会船区长度、宽度、转弯半径、设计底高程等参数,选取了水深良好、位置恰当的会船区平面布置方案。     

洋山深水港进港航道人工开挖段回淤特征

为保障洋山深水港的正常运营,近年来进港航道每年都会开展维护性疏浚。基于2017—2019年期间的水深资料,统计分析了航道人工开挖段的浅区分布与回淤特征。结果表明:在常风天航道回淤呈现"春夏冲淤基本平衡且局部冲刷,秋冬淤积为主"的季节变化规律;台风天航道回淤较为明显,淤积程度主要与台风风力和移动路径有关。结合水文资料初步探讨了航道回淤原因,为洋山进港航道今后的疏浚施工安排提供技术支撑。     

界牌枢纽船闸引航道优化设计

针对界牌枢纽改建船闸工程上、下游引航道口门区横流超标的问题,通过调整引航道分水墙长度与挂板高程,通过水流条件试验,得到合理可行的引航道平面优化布置方案;针对下游引航道地质条件突变、原设计采用的混合式结构不再适用的问题,通过进行重力式结构与重力墩+挂板结构的经济技术比选,确定更改方案。结果表明,重力式结构的抗船舶撞击能力强且施工简单,增加投资略高,可作为推荐方案。     

Investigating scalability in population synthesis: a comparative approach

In this paper, we investigate the influence of scalability on the accuracy of different synthetic populations using both fitting and generation-based approaches. Most activity-based models need a base-year synthetic population of agents with various attributes. However, when several attributes need to be synthesized, the accuracy of the synthetic population may decrease due to the mixed effects of scalability and dimensionality. We analyze two population synthesis methods for different levels of scalability, i.e. two to five attributes and different sample sizes – 10%, 25% and 50%. Results reveal that the simulation-based approach is more stable than Iterative Proportional Fitting (IPF) when the number of attributes increases. However, IPF is less sensitive to changes in sample size when compared to the simulation-based approach. We also demonstrate the importance of choosing the appropriate metric to validate the synthetic populations as the trends in terms of RMSE/MAE are different from those of SRMSE.     

波浪对二层海水中的直立圆弧形透空防波堤的绕射

基于二层海水的微幅波绕射理论,应用特征函数展开法,推导了在二层海水中波浪对直立圆弧形透空防波堤绕射的波势解析解,并据此分别计算了作用于防波堤的表面波与内波载荷以及最大波面分布。计算结果表明:在防波堤结构表面适度布孔既可以明显减小所受到的表面波与内波载荷,又可改变绕射水波的最大波面分布。而表面波与内波各自作用于防波堤上的无量纲最大波浪载荷可能具有相同量级,说明内波作用不可忽视。海况与波浪条件以及防波堤几何条件等因素的相对变化对波浪的绕射均有一定影响,而表面波与内波在波浪作用的变化规律上存在一定差异。     

Port competition with accessibility and congestion: a theoretical framework and literature review on empirical studies

This review interprets recent studies of the interactions between the competition of gateway seaports and the accessibility of landside transportation links to inland regions. Port competition is treated as part of a rivalry between two transportation chains. This article identifies the main modeling approaches and defines the different types of hinterland access systems described in the literature. A general theoretical framework is then proposed to incorporate those key components. The importance of the proposed framework is revealed by comparing and extending results from the literature. Major assumptions that need further empirical verification are identified and discussed, and related empirical studies are reviewed. Finally, avenues for further research are discussed.     

The coopetition game in international liner shipping

In maritime freight transportation, carriers build collaborative relationships with other carriers while competing with each other to optimize their own profits. In such a scenario, a game of coopetition is formed. We formulate a nonlinear mixed-integer problem to determine the optimal levels of coopetition for a single company and embed the resulting problem into a general game theoretic framework. A diagonalization algorithm that incorporates an ascent direction search technique is developed to effectively evaluate the game. The numerical results show that carriers choose similar coopetition levels to maximize their profits, and the coopetition game can reach equilibrium under general conditions.