Installation strength analysis of subsea flowline jumpers

Subsea flowline jumper (FJ) is basic connection component for the wet oil tree, the subsea pipeline and the riser base, playing an irreplaceable role in the subsea production system. During the installation of FJ, collisions often happen between FJ and other equipment, which may cause serious damage. Besides, as the operating water depth increases, the demand for the installation equipments like the crane and winch will increase. The research of deepwater FJ installation in China is still in the primary stage, so an installation method for deepwater FJ is proposed in this paper. Finite element models of a typical M-shape FJ installation system were built to simulate the installation procedures. Analysis results showed that the installation steps designed for the FJ are feasible and valid for deepwater FJ. In order to ensure the safety of the installation process, the collision-sensitive analysis for the FJ was conducted, and results show that it is necessary to set the pick up speed at a proper value, in order to avoid collision in installation process. Besides, the mechanical characteristics of FJ during the installation were investigated under a range of environmental conditions and it was found that the maximum stress of the FJ always happens at its central position. The basic requirements for the installation equipment were also obtained through the analysis of the main installation steps.     

Using system dynamics in maritime economics: an endogenous decision model for shipowners in the dry bulk sector

In this paper, we consider the benefits of applying system dynamics in maritime economics. We build an endogenous shipowners' model for the dry bulk sector, incorporating both the decision process of individual shipowners and traditional shipping market conditions. The aim is to arrive at a simulation tool that can be used for a variety of applications, both for teaching/learning and for research purposes. Within the endogenous shipping model, we can distinguish between the strategic and the tactical choices shipowners face. As an application, we focus explicitly on a strategic decision-making process that is relevant to any shipowner, i.e. the sale of a vessel. System dynamics seems to be a tool well-suited for the detailed modelling of strategic and operational behaviour in the maritime business.     

中巴喀喇昆仑公路冰川灾害

中巴公路穿越西喀喇昆仑-喜马拉雅山系的冰缘地带,沿线冰川活跃,冰川消融与进退等引发各类地质灾害,严重损毁公路,危及公路安全.中巴公路灾害防治是中巴公路改扩建工程的目标,科学防灾减灾需要掌握中巴公路沿线冰川及冰川灾害的形成及发展规律.通过野外调查、定点观测、文献检索与遥感解译等研究手段发现,独特的地形地貌、丰沛的夏季降雪、险峻的地形落差、山地气候波动等环境因素孕育大量跃动型冰川,具有长期萎缩与间歇跃动、同期不同步、夏季累积型和悬冰川的活动特征.中巴公路沿线可区分为四大活动性冰川群,洪扎河谷(Hunza River)一带的帕苏幕士塔格山冰川群(Pasu Mustaghs)最为活跃.中巴公路冰川灾害可分为冰川灾害与冰川地质灾害两大类别,10个类型.其中,冰湖溃决、冰川泥石流的治理是工程上主要面临的防治问题.     

如何在治堵大环境下进行公交线路提速

2013年浙江省各市开展全面治堵工作,其中提高公共交通的服务水平是交通治堵的重点工作,也是城市交通可持续发展的必经之路。公交服务水平的提高不仅追求量的发展,还要保证质的提升,而对公交线路进行提速就是提升公交服务品质的途径之一。本文在城市交通治堵的大环境下,利用治堵的压力和动力,借机调动大量资源,从公交系统内和公交系统外全面、系统、科学地对温州运量最大的前20条线路进行提速。通过方案的逐步落实,3条提速线路效果明显,城市交通也得到进一步改善。     

The importance of being early

This research quantifies the relationship between the cost of earliness and lateness by empirically observing commute trips from two different sources. The first empirical analysis uses individual level travel survey data from six metropolitan regions while the second analysis uses traffic data from the Twin Cities freeway network. The analysis conducted in this research provides a method to estimate the ratio of the costs of earliness to lateness for different datasets. This can be a useful tool for traffic engineers and planners, to assist them in the development and implementation of improved control strategies for congested cities. The results also corroborates the hypothesis of earliness being less expensive than lateness and show that the finding holds steady over time and across different regions and levels.     

Financial lessons from Asian experience in constructing and operating high speed train networks

A serious interest in high speed train has been increasing all over the world. However, recent experiences in Asian countries show that high speed rail projects are not financially viable even in areas seemingly favorable to rail operations. Considering the existing intensive highway and airline network, putting public subsidies to high speed rail projects are barely justifiable from a purely economic point of view. What is required of any government which contemplates high speed rail construction as a policy option is to show taxpayers the cost/revenues difference between constructing a high speed rail line and expanding a capacity of other means, before proceeding.     

Uncertain benefits: Application of Bayesian melding to the Alaskan Way Viaduct in Seattle

Uncertainty is inherent in major infrastructure projects, but public decision-making for such projects ignores it. We investigate the uncertainty about the future effects of tearing down the Alaskan Way Viaduct in downtown Seattle, using an integrated model of housing, jobs, land use and transportation, on outcomes including average commute times. Our methodology combines the urban simulation model UrbanSim with the regional transportation model. We assess uncertainty using Bayesian melding, yielding a full predictive distribution of average commute times on 22 different routes in 2020. Of these routes, 14 do not include the viaduct and eight do. For the 14 base routes that do not include the viaduct, the predictive distributions overlap substantially, and so there is no indication that removing the viaduct would increase commute times for these routes. For each of the eight routes that do include the viaduct, the 95% predictive interval for the difference in average travel times between the two scenarios includes zero, so there is not strong statistical support for the conclusion that removing the viaduct would lead to any increase in travel times. However, the median predicted increase is positive for each of these routes, with an average of 6 min, suggesting that there may be some measurable increase in travel time for drivers that use the viaduct as a core component of their commute.     

Wave impact underneath horizontal decks

The problem of water impact on a fixed horizontal platform deck from regular incident waves was studied. Two-dimensional potential flow was assumed, and the resulting boundary-value problem was solved by three alternative numerical methods, a method based on a generalization of the impact theory by Wagner, and two different nonlinear boundary-element methods. The Wagner-based method used a von Karman approach during the water exit phase, i.e., when the wetted surface decreases. Experiments of the impact on an idealized platform deck have been performed to validate the theory. Comparisons show that the Wagner-based method yields good results for the water entry phase, when the wetted deck area increases, but poor results when the wetted area diminishes. The boundary-element methods compare well with experiments for the entire impact process. A Kutta condition is necessary at the aft body–free surface intersection during water exit and when the flow separates from the aft edge. Gravity effects matter for the water exit phase.     

Evaluation of marine radar as an ocean-wave-field detector through full numerical simulation

The importance of ocean waves parameters (propagation direction, mean period, significant wave height, etc.) is related to several aspects of a ships safety, efficiency in operation, routing, design, and maintenance. However, some available methods for obtaining those parameters have data limitations and inconvenient aspects. In severe weather conditions, an ocean-wave-field detector is necessary. This can provide two-dimensional ocean-wave-field information directly. Among other conventional methods, ship-borne wave radar has the ability to function as such a detector, and some researchers have tried to develop practical systems. A numerical approach using plan position indicator (PPI) images from conventional marine radars is proposed to retrieve valuable information from the ocean waves. A three-dimensional Fourier transform is applied to a set of consecutive radar PPI images to perform spectrum analysis. The removal of undesired elements in the spectrum is achieved by applying a hi-pass filter to remove static components, and by comparing the data with the expected dispersion shell to correct for nonocean-wave power. Numerical experiments under controlled conditions using simulated PPI images were performed through numerical simulations based on theoretical ocean-wave equations. The results include a comparison between the original wave parameters used in the simulation and the values retrieved from the spectrum analysis.