Exact and simplified estimations for elastic buckling pressures of structural pipe-in-pipe cross sections under external hydrostatic pressure

Structural pipe-in-pipe cross sections have significant potential for application in offshore oil and gas production systems because they combine thermal insulation performance with structural strength and self weight in an integrated way. Such cross sections comprise inner and outer thin-walled pipes with the annulus between them fully filled by a selectable filler material to impart an appropriate combination of properties. Structural pipe-in-pipe cross sections can exhibit several different collapse mechanisms, and the basis of the preferential occurrence of one over the others is of interest. This article presents an exact analysis for predicting the elastic buckling behaviours of a structural pipe-in-pipe cross section when subjected to external hydrostatic pressure. Simplified approximations are also investigated for elastic buckling pressure and mode when the outer pipe and its contact with the filler material is considered as a pipe on an elastic foundation. Results are presented to show the variation of elastic buckling pressure with the relative elastic modulus of the filler and pipe materials, the filler thickness, and the thicknesses of the inner and outer pipes. Case studies based on realistic application scenarios are used to show that the simplified approximations are sufficiently accurate for practical structural design purposes.     

Second-order sum-frequency wave diffraction by a truncated surface-piercing cylinder in bichromatic waves

This work considers the second-order sum-frequency diffraction problem for a stationary truncated surface-piercing circular cylinder in bichromatic waves. The solution method was based on a semianalytical formulation of the second-order sum-frequency diffraction potential. The boundary conditions were properly satisfied by introducing the “locked” and the “free” wave components of the nonlinear velocity potential. The method was validated by comparing the calculated results with numerical data previously reported by other authors. Particular attention was paid to the second-order sum-frequency heave forces and the change in the wave run-up configuration due to the existence of the lower fluid domain underneath the truncated cylinder.     

The ISM Code and the ISPS Code: A critical legal analysis of two SOLAS regimes

Within the comprehensive body of law encompassed by the International Convention on Safety of Life at Sea, 1974 (SOLAS), there are two regimes that are topical and outstanding in the current maritime milieu. These are the international safety management and the international ship and port facility regimes, both characterized by two codes serving as the centre of gravity of each, namely, the ISM Code and the ISPS Code, respectively. In this article the concept of the code as a legal instrument is perused following which a critical legal analysis is carried out of the two above-mentioned Codes, including their backgrounds, the evolutionary process culminating into the regimes and their interrelationships. Several anomalies and inadequacies in the two regimes are identified but in the final analysis it is concluded that both instruments are salutary additions to the body of convention law generated by the International Maritime Organization (IMO). They will undoubtedly influence the continuing development of international law in the field of maritime safety and security.     

The place of the ISPS Code in the legal international regime

The adoption of the International Ship and Port Facility Security Code (ISPS Code) is the latest response of the international shipping community to the increasing threat posed by acts of terrorism at sea. The ACHILLE LAURO incident of 1985 showed that the traditional law against piracy was not adequate to deal with new types of unlawful acts against international shipping, especially those involving acts of terrorism. The 1988 Convention for the Suppression of Unlawful Acts against the Safety of Maritime Navigation (SUA Convention) and the technical and administrative measures adopted by the Maritime Safety Committee of IMO in 1986 and 1996 attempted to develop a broader regime to deal with unlawful acts against international shipping.However, the events of September 11, 2001 showed that additional measures were still needed to prevent terrorist attacks against ships.     

高速公路桥梁病害分析与防治

文章结合实例探讨了高速公路桥梁病害的成因 ,对桥面铺装病害、预应力混凝土梁裂缝、橡胶支座变形受损、外露混凝土局部破损等常见病害的成因进行了深入、系统的分析 ,同时提出了预防和处理措施。     

Development and Evaluation of a High Voltage Supply Unit for Electrorheological Fluid Dampers

Controllable dampers using electrorheological (ER) fluids have attracted considerable interest in recent years. They are proposed for use in semi-active suspensions for ground vehicles. The main advantages of ER fluid dampers are their fast response, ease of control, simple construction and low power requirements. This paper describes the development and testing of a high-voltage supply unit for modulating the damping force of an ER fluid damper. Experimental results on the vibration isolation characteristics of an ER fluid damper with different control strategies, obtained using a quarter-car model test rig, are also presented.     

GSM-R网络中HLR冗灾备份

HLR是GSM—R网络重要的组成部分。本文对HLR冗灾备份的组网方案及工作方式等关键内容进行了介绍。     

计算机联锁系统的辅助设计

近几年来,计算机联锁发展得很快,全路开通的车站无论在数量上还是规模上都逐年增加,这就在客观上要求我们优化设计方法,缩短设计、调试周期,为此,开发了一套针对DS6-11型计算机联锁的辅助设计软件.     

Urban form,travel time,and cost relationships with tour complexity and mode choice

The primary purpose of this study was to investigate how relative associations between travel time, costs, and land use patterns where people live and work impact modal choice and trip chaining patterns in the Central Puget Sound (Seattle) region. By using a tour-based modeling framework and highly detailed land use and travel data, this study attempts to add detail on the specific land use changes necessary to address different types of travel, and to develop a comparative framework by which the relative impact of travel time and urban form changes can be assessed. A discrete choice modeling framework adjusted for demographic factors and assessed the relative effect of travel time, costs, and urban form on mode choice and trip chaining characteristics for the three tour types. The tour based modeling approach increased the ability to understand the relative contribution of urban form, time, and costs in explaining mode choice and tour complexity for home and work related travel. Urban form at residential and employment locations, and travel time and cost were significant predictors of travel choice. Travel time was the strongest predictor of mode choice while urban form the strongest predictor of the number of stops within a tour. Results show that reductions in highway travel time are associated with less transit use and walking. Land use patterns where respondents work predicted mode choice for mid day and journey to work travel.