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.     

生物法处理生活污水脱氮除磷效果分析

通过对铁道部无锡干部培训基地（以下简称培训基地）的生活污水的生物法处理效果观察，探析兼氧／好氧生物处理系统的脱氮除磷原理并对影响处理效果因素进行分析。     

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.     

Effect of Connecting the Front and Rear Air Suspensions of a Vehicle on the Transmissibility of Road Undulation Inputs

Airsprings have been used for vehicle suspensions over the last 40 years. They are mostly used as independent suspensions. Analysis of air springs available in literature is mostly limited to a single-degree-of-freedom system or a two-degrees-of-freedom system only in the translation mode. This paper deals with a model of a vehicle where the front and the rear springs are connected by a capillary tube. A two-degrees-of-freedom model having motion in bounce and pitch mode is presented. Equations of mass flow are linearized on the assumption of small variations in volume and pressure. Expressions for the transmissibility and the phase angle in the bounce and the pitch mode are derived. Road inputs to the front and the rear axles are assumed to be identical except for a phase difference between them. The effect of the capillary flow coefficient and that of the phase angle between the front and the rear axle excitation are studied. It is shown that an optimum value of the capillary flow coefficient exists which minimizes the transmissibility of motion in both modes over the entire frequency range. It is also observed that a phase angle of 180 degrees presents ideal transmissibility characteristics. Thus, a promising application of air springs for a vehicle suspension is presented.     

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.

Fatigue design for plug/ring type gas welded joints of sts301l including welding residual stresses

This paper presents a fatigue design method for plug and ring type gas welded joints, which incorporates welding residual stress effects. A non-linear finite element analysis (FEA) was first performed to simulate the gas welding process. The numerically predicted residual stresses of the gas welds were then compared to experimental results measured using a hole drilling method. In order to evaluate the fatigue strength of the plug and ring type gas welded joints, a stress amplitude (σ _a ) _R taling the welding residual stress of the gas weld into account was introduced and is based on a modified Goodman equation incorporating the effect of the residual stress. Using the stress amplitude (σ _a ) _R , the ΔP-N _f relations obtained from fatigue tests for plug and ring type gas welded joints having various dimensions and shapes were systematically rearranged into (σ _a ) _R -N _f relations. It was found that the proposed stress amplitude (σ _a ) _R could provide a systematic and reasonable fatigue design criterion for the plug and ring type gas welded joints.