计及频率约束的潜艇环肋圆柱壳优化设计研究

基于多岛遗传算法,研究了环肋圆柱壳静水压力作用下,考虑强度和稳定性约束和频率约束时质量最轻的优化设计问题,讨论了强度约束和稳定性与频率约束以及材料、几何参数对优化结果的影响.环肋圆柱壳经优化后,壳板的质量比例大约是70%,肋骨质量占30%,并且随壳体的长径比(L/R)变化不大.环肋圆柱壳的优化中,肋骨的应力约束是主要约束,肋骨应力已经非常接近许用应力标准,其他应力、局部和总体失稳压力还有一定的储备.提高材料的屈服极限,可以显著降低总质量,但是肋骨也很接近许用应力标准.     

Vertical integration and its implications to port expansion

ABSTRACT

Over the years many shipping lines have established terminal operation companies, with some set up as independent firms. However, port authorities and local governments have not always welcomed external investment and control with open arms. The economic implications and each stakeholder’s best strategies remain unclear. This study develops an analytical model in order to study the effects of vertical integration, with a focus on shipping lines’ investment in ports’ capacity. Modelling results suggest that vertical integration between terminal operator and a shipping line leads to higher port capacity, port charge, market output and consumer surplus. It also reduces delay costs. All these results suggest that vertical integration can be an important source of synergy for the maritime industry. Although vertical integration increases the participating carrier’s output at the expenses of non-integrating rival shipping firms, our numerical analysis suggests that the overall social welfare is likely to increase. Preliminary empirical tests confirm that vertically integrated ports handle more traffic volumes and are associated with better infrastructure and equipment. Therefore, port authorities and government regulators should carefully review the market competition status as well as port expansion plans.     

Assessment of investment decision in the dry bulk shipping market based on real options thinking and the shipping cycle perspective

As the dry bulk shipping market seems to have been stuck in a trough period for a long time, investors need to pay more attention to their investment strategies to survive during this period. This study aimed to find a suitable model to assess dry bulk ship investment decisions in the tough and peak periods based on real options theories. Two options, involving an abandonment option and a deferrable option, were used to define investors’ responses to the uncertainty in investment processes such as stopping or selling vessels. The option valuation was solved by using a binomial valuation model, due to data limitations. In accordance with shipping cycle theories, different volatility parameters for the tough and peak periods were calculated using a generalized autoregressive conditional heteroskedasticity (GARCH) model. The application of the real options model to a case study involving secondhand ship trading indicated its viability. According to the results of the case study, the new model has advantages over the traditional net present value (NPV) method in uncertain investment environments. Thus, the results demonstrate that the real options model is a more suitable method for use in the current dry bulk shipping market.     

中国船舶工业发展趋势及企业生产经营建议

"十二五"是中国造船业由大转强的重要战略机遇期,我国造船业面临的形势异常严峻:世界新船订单巨幅下滑,市场竞争更加激烈,原材料、人工等成本不断上涨,人民币升值压力不断加大等许多问题。面对"十二五",造船企业要抓住机遇,迎接挑战,加快推进结构调整和产业升级,掌控船舶工业未来发展的主动权。     

外资进入中国航运市场现状分析及应对策略

随着中国加入WTO,市场的不断开放,外资航运巨头加速了在中国的扩张,这给中国的航运企业很大压力和挑战,本文剖析了外资航运巨头进入中国航运市场的现状,从而提出我国航运企业的应对之策。     

关于财政性投资项目管理的思考

分析近年来财政性投资项目管理中遇到的问题,深入剖析其原因,并从法制建设、预算评审、项目管理方式和绩效评价等几个方面提出完善财政性投资项目管理的思路,为今后财政性投资项目的管理提供借鉴,以提高财政资金的使用效益。     

厚钢板疲劳裂纹扩展前缘应力状态试验与数值仿真

复杂的环境载荷不可避免地会造成海洋结构物的疲劳损伤,而高强度厚钢板典型的三向应力状态会增加结构脆性,更加缩短结构的疲劳寿命。为研究厚板裂纹前缘应力状态沿板厚方向的分布,完成了3组36 mm板厚Q370QE高强度钢的标准疲劳裂纹扩展速率试验,得到了材料参数C,m以及应力强度因子门槛值。接着,应用有限元方法分别基于线弹性分析和塑性分析计算裂纹尖端应力强度因子和裂纹尖端局部约束因子,并解释试验中裂纹前缘由倾斜趋于平直的现象。计算所得裂纹尖端应力强度因子可描述板厚中心部分裂纹前缘的应力状态,但在试件表面处结果失真,而裂纹前缘局部约束因子因考虑了厚板的厚度效应,故沿板厚方向分布的裂纹尖端局部约束因子可有效量化裂纹尖端的应力状态分布。     

Terminal investment timing decisions in a competitive setting with uncertainty using a real option approach

This paper uses a real option approach to analyze terminal investment timing decisions for situations in which a port faces competition from its rivals in an uncertain market. We propose a network model to describe carriers’ cargo routing decisions and competition among rival ports. We then transform this model into a multicommodity flow problem and use the column generation algorithm to solve it. After obtaining a port’s possible future annual revenues and the potential net present value (NPV) for its terminal construction project through the network model, we adopt the expanded NPV rule and transform the investment timing decision into an optimal stopping problem. A least squares Monte Carlo simulation algorithm is proposed to find the investing probabilities for future years. The proposed models are applied to a steel cargo terminal investment case in the Port of Bengbu in Anhui province of China. The impacts on the investing probability and the expanded NPV of changes in the demand volatility, the initial investment and the port discharging rate are analyzed to provide managerial insights for port managers.     

境外港口升级改造工程建设要点

随着亚非拉国家腹地经济的发展,升级改造类工程项目逐渐增多。结合案例,分析码头升级改造工程的制约因素及需要重点考虑的问题;对港口规划中码头规模确定、码头前沿线确定所需考虑的主要因素及滚装码头的布置形式,码头结构设计中结构稳定性、整体性所需考虑的要素及解决方案,以及施工过程中所需考虑的主要问题等进行系统的对比分析。     

Influence of local government on port investment: implications of China’s decentralized port governance system

ABSTRACT

The pursuit of better performance by the local government can influence the investment decision-making related to port expansion. This paper compares the ceilings at which the port enterprise and the local government would stop making investments. To achieve this, the benefits to the port enterprise and the local government are measured over a given time period. An empirical study investigating how a port would respond if a rival port uses a type of capacity investment strategy is conducted for two major ports in Liaoning. The time at which the local government and the port enterprise would stop making investments and the final equilibrium are developed using the data from 2010. From the empirical results, it was found that investment in port capacity contributes greatly to the local government’s performance. Meanwhile, different investment ceilings are discovered for the port enterprise and the local government. This research is meaningful for discussing the institutional relationship between the local government and the port enterprise in China’s current decentralized port governance system.

This paper is a revised and expanded version of a paper entitled ‘Port expansion mechanism in the context of political achievement of local government: a special phenomenon in China’ presented at International Association of Maritime Economists 2012 Taipei Conference during 5th September –8th September.