基于多层次模型的波函数法在凹域问题应用研究

波函数法（Wave Based Method，WBM）是近年来发展的基于间接 Trefftz 理论的结构—声辐射中频问题的一种重要方法。 WBM 函数收敛的充要条件是分析域为凸域。为提高使用 WBM 理论的应用范围和应用效率，根据多层次模型，提出了补域概念用于解决凹域问题。最后，以一个周边简支矩形薄板为例进行验证数值，计算结果表明了方法准确性和有效性。     

Fracture mechanics analysis for mooring chain links subjected to out-of-plane bending (OPB)

A fracture mechanics (FM) based investigation on the mechanism of out-of-plane bending (OPB) between mooring chain links and its effects on fatigue lives of mooring chain links are conducted. Four types of OPB problems that mooring chain links laying on the chain wheel, chain links passing over the bending shoe, chain links constraint provided by the chain hawse, and chain links constraint provided by the chain stopper are considered. Tension ranges of mooring lines are calculated based on the combined loading process induced by the motions of wave frequency (WF) and low frequency (LF). Initial cracks are assumed to propagate from surfaces of chain links and stress intensity factors are calculated in terms of stress ranges determined by a finite element (FE) analysis. The results show that fatigue lives of mooring chain links are decreased significantly due to OPB effects. In addition, the increase of the number of pockets of chain wheel mitigates OPB effects on fatigue lives of mooring chain links laying on the chain wheel, and the increase of the track diameter would reduce OPB effects on fatigue lives of mooring chain links passing over the bending shoe as well. However, for chain links constraint provided by the chain hawse, the diameter of mooring chain hawse has no significant effect on fatigue lives of the mooring chain links subject to OPB if without the abrupt change of the contact conditions between chain links and chain hawse. For mooring links constraint provided by chain stoppers considering the effect of proof loading test, fatigue lives of mooring chain links would drop significantly with the increase of interlink angles and friction coefficient.     

DP2自升式平台环网电站关键技术研究

本文依托某采用环网电站技术的具有世界领先水平的DP2多功能自升式海洋平台实船项目，对这种非常规的动力定位系统的设计难点和要点进行剖析，重点介绍了平台环网电站在过载、短路等故障或扰动情况下的故障隔离和故障穿越技术，并列举了相应的解决方案，最后通过实船验证对该解决方案进行了论证和总结，供类似项目借鉴。     

MARK III 型LNG模拟舱结构安全评估及优化设计研究

液化天然气（Liquefied Natural Gas）运输船的建造技术复杂，货物维护系统（Cargo Containment System） 种类繁多，船上 LNG 常采用低温高压的储藏方式，该方式对储舱结构强度以及货物维护系统的 变形要求非常高。本文采用有限元方法， 对根据行业规范设计的 MARK III 型 LNG 模拟舱结构进行结构 强度安全性评估，并在满足 LNG 模拟舱结构承载能力要求的基础上，对 MARK III 型 LNG 模拟舱进行结 构优化设计研究，为今后 MARK III 型 LNG 运输船的船体结构设计和优化提供可靠的技术支撑。     

Dynamic stability metrics for the container loading problem

The Container Loading Problem (CLP) literature has traditionally evaluated the dynamic stability of cargo by applying two metrics to box arrangements: the mean number of boxes supporting the items excluding those placed directly on the floor (M1) and the percentage of boxes with insufficient lateral support (M2). However, these metrics, that aim to be proxies for cargo stability during transportation, fail to translate real-world cargo conditions of dynamic stability.In this paper two new performance indicators are proposed to evaluate the dynamic stability of cargo arrangements: the number of fallen boxes (NFB) and the number of boxes within the Damage Boundary Curve fragility test (NB_DBC). Using 1500 solutions for well-known problem instances found in the literature, these new performance indicators are evaluated using a physics simulation tool (StableCargo), replacing the real-world transportation by a truck with a simulation of the dynamic behaviour of container loading arrangements.Two new dynamic stability metrics that can be integrated within any container loading algorithm are also proposed. The metrics are analytical models of the proposed stability performance indicators, computed by multiple linear regression. Pearson’s r correlation coefficient was used as an evaluation parameter for the performance of the models. The extensive computational results show that the proposed metrics are better proxies for dynamic stability in the CLP than the previous widely used metrics.     

Towards data-driven car-following models

Car following models have been studied with many diverse approaches for decades. Nowadays, technological advances have significantly improved our traffic data collection capabilities. Conventional car following models rely on mathematical formulas and are derived from traffic flow theory; a property that often makes them more restrictive. On the other hand, data-driven approaches are more flexible and allow the incorporation of additional information to the model; however, they may not provide as much insight into traffic flow theory as the traditional models. In this research, an innovative methodological framework based on a data-driven approach is proposed for the estimation of car-following models, suitable for incorporation into microscopic traffic simulation models. An existing technique, i.e. locally weighted regression (loess), is defined through an optimization problem and is employed in a novel way. The proposed methodology is demonstrated using data collected from a sequence of instrumented vehicles in Naples, Italy. Gipps’ model, one of the most extensively used car-following models, is calibrated against the same data and used as a reference benchmark. Optimization issues are raised in both cases. The obtained results suggest that data-driven car-following models could be a promising research direction.     

Port-city exhaust emission model: An application to cruise and ferry operations in Las Palmas Port

Exhaust emissions cause air pollution and climate change. The exhausts of shipboard fuel combustion are equally damaging particularly, so close to the environmentally sensitive mainland and island coasts, as well as at ports due to their urbanized character. This paper estimates, for the first time, exhaust pollutants related to cruise and ferry operations in Las Palmas Port and, in an island context. Emission assessment is based on a full bottom-up model and messages transmitted by the Automatic Identification System during 2011. Results are described as a breakdown of NOx, SOx, PM_2.5, CO and CO₂, according to ship classes, operative type and time, providing valuable information to environmental policy makers in port-city areas and islands under similar conditions. It is generally concluded that vessel traffic and passenger shipping in particular are a source of air pollution in Las Palmas Port. Emission maps confirm location of hot spots in quays assigned for cruise and ferry operations. Policy recommendations encourage regular monitoring of exhaust emissions and market-based incentives supported by details on polluting and operative profiles. On the other hand, feasibility studies are suggested for automated mooring, LNG bunkering facilities and also shore-side energy services, prioritizing berthing of shipping sectors (or sub-sectors) with the highest share of exhaust emissions once their local effects have been confirmed by a dispersion, exposure and impact assessment.     

Planning for the unexpected: The value of reserve capacity for public transport network robustness

Public transport networks (PTN) are subject to recurring service disruptions. Most studies of the robustness of PTN have focused on network topology and considered vulnerability in terms of connectivity reliability. While these studies provide insights on general design principles, there is lack of knowledge concerning the effectiveness of different strategies to reduce the impacts of disruptions. This paper proposes and demonstrates a methodology for evaluating the effectiveness of a strategic increase in capacity on alternative PTN links to mitigate the impact of unexpected network disruptions. The evaluation approach consists of two stages: identifying a set of important links and then for each identified important link, a set of capacity enhancement schemes is evaluated. The proposed method integrates stochastic supply and demand models, dynamic route choice and limited operational capacity. This dynamic agent-based modelling of network performance enables to capture cascading network effects as well as the adaptive redistribution of passenger flows. An application for the rapid PTN of Stockholm, Sweden, demonstrates how the proposed method could be applied to sequentially designed scenarios based on their performance indicators. The method presented in this paper could support policy makers and operators in prioritizing measures to increase network robustness by improving system capacity to absorb unexpected disruptions.     

Dynamic activity-travel assignment in multi-state supernetworks

The integration of activity-based modeling and dynamic traffic assignment for travel demand analysis has recently attracted ever-increasing attention. However, related studies have limitations either on the integration structure or the number of choice facets being captured. This paper proposes a formulation of dynamic activity-travel assignment (DATA) in the framework of multi-state supernetworks, in which any path through a personalized supernetwork represents a particular activity-travel pattern (ATP) at a high level of spatial and temporal detail. DATA is formulated as a discrete-time dynamic user equilibrium (DUE) problem, which is reformulated as an equivalent variational inequality (VI) problem. A generalized dynamic link disutility function is established with the accommodation of different characteristics of the links in the supernetworks. Flow constraints and non-uniqueness of equilibria are also investigated. In the proposed formulation, the choices of departure time, route, mode, activity sequence, activity and parking location are all unified into one time-dependent ATP choice. As a result, the interdependences among all these choice facets can be readily captured. A solution algorithm based on the route-swapping mechanism is adopted to find the user equilibrium. A numerical example with simulated scenarios is provided to demonstrate the advantages of the proposed approach.     

Development of control models for the planning of sustainable transportation systems

Planning of sustainable transportation systems requires integration of multiple systems while considering a holistic approach. A limited amount of research has been conducted that simultaneously considers all the transportation, economic activity, environmental and social effects. The proposed research envisages incorporating considerations related to sustainability and providing solutions to stakeholders in policy making. In this paper, a dynamic model for planning and development of sustainable transportation systems is presented. This is given by a system of three nonlinear differential equations representing the dynamics of the three independent states, namely, transportation, activity, and environmental systems. A policy scenario considering investment in energy efficient technologies and its effects on the states is discussed to assist making investment decisions. Optimal control techniques are used to design the controls. The results show that it is possible to formulate an optimal control to achieve the desired target. Numerical results, based on actual parameters, are presented to illustrate the long-term trends of the states. The methodology discussed in this paper will be helpful to decision makers in making optimal decisions. The contribution of this research work is the introduction of a systems and controls methodology to develop optimal policies for the design of sustainable systems.