Spar平台垂荡板设计中的关键问题

Spar平台是一种适宜于深海石油的开采、生产、处理加工和储存的平台结构形式。垂荡板是影响Truss Spar和Cell Spar垂荡性能的关键构件。垂荡板的性能及设计已是国际Spar工程和研究的热点之一。介绍了影响Spar平台垂荡板性能的主要因素,以及典型的垂荡板结构和主要载荷。     

Influence of FRP wrapping techniques on the compressive behavior of concrete prisms

Results of an experimental investigation on the compressive behavior of concrete prisms with square cross-section, externally wrapped with carbon fiber reinforced plastic (CFRP) sheets are presented. The effects of the following parameters were analyzed: local reinforcement at the corners and continuous layers; horizontal and vertical discontinuous strips; number of continuous layers—length of specimens.An analytical model is proposed to determine the maximum bearing capacity of compressed concrete members with square cross-section and externally wrapped with FRP for the different configurations examined, and also able to consider the strength reduction with the length increase of concrete members. Analytical results are then compared with the experimental data available in the literature, showing good agreement.     

Contact control for grasping a non-cooperative satellite by a space robot

Multibody System Dynamics - In this paper, the contact control problem of a space robot to grasp a non-cooperative satellite is investigated in detail, and a new capture control strategy is...     

Topology optimization of pressure structures based on regional contour tracking technology

This article presents a new computational approach to solve the design-dependent loading problem in topology optimization of pressure structures. A simple algorithm based on digital image processing and regional contour tracking technology is proposed that generates the appropriate loading surface during the topology evolution. First, the topological layout produced during the optimization process is transformed into a compact image. Then, the regional contour tracking technology is used to represent the boundary of objects and extract pressure loading elements. At last, the pressures are transferred directly to corresponding element nodes. Due to the semi-automatically determined endpoints of the loading boundaries, the current scheme can deal with structures loaded by pressure from outside the domain, as well as pressure completely contained within the domain. Also, the calculation of the load sensitivities can be avoided in the current scheme. As a simple alternative computational strategy for compliance topology optimization of pressure structures, the current scheme is stable, flexible and efficient. Representative numerical examples are presented to show the validity and advantages of the proposed scheme. Especially, the design of closed containers and storage tanks indicates that it works well for the topology optimization of pressure structures.     

Definition and experimental evaluation of the smoke “confinement velocity” in tunnel fires

An experimental study is carried out on a reduced scale tunnel model (scale reduction is 1:20). The main objective is to evaluate the longitudinal velocity induced into a tunnel when a fire plume continuously released is confined and extracted between two exhaust vents located on both sides of the fire source. For the experimental simulations, fire-induced smoke is simulated by an air and helium mix release. Smoke flow is symmetrical as regards the fire location and experiments are realized for an half tunnel with only one vent activated downstream the source. The vent extraction flow rate is step by step increased and the length of the stratified smoke layer downstream the vent as well as the longitudinal fresh air flow induced, are measured. A confinement velocity is then associated to the minimum value of the longitudinal air flow needed to prevent the smoke layer propagation downstream the vent. This velocity is evaluated for several values of the fire heat release rate and finally compared with the corresponding critical velocity obtained for a longitudinal ventilation system.     

Thermal effects in H2O and CO2 assisted direct carbon solid oxide fuel cells

Thermal effects in a H₂O and CO₂ assisted tubular direct carbon solid oxide fuel cell (DC-SOFC) are numerically investigated. Parametric simulations are further conducted to study the effects of operating potential, the distance between carbon and anode, inlet gas temperature, and anode inlet gas flow rate on the thermal behaviors of the fuel cell. It is found that the fuel cell with H₂O as gasification agent performs considerably better than the cell with CO₂ as gasification agent in all cases. It is also found that the temperature field of the fuel cell is highly uneven. The breakdown of the heat sources in the fuel cell shows that the H₂O assisted DC-SOFC has much higher heat generation and consumption than the CO₂ assisted cell. Interestingly, a thermal neutral voltage is observed, at which no heating or cooling of the cell is needed. In addition, the distance between the anode and the carbon layer is required to be as small as possible, which improves the temperature uniformity of the fuel cell. The results of this study demonstrates the importance of thermal effects in DC-SOFCs and form a solid foundation for DC-SOFC thermal management.     

立柱式钻井平台内孤立波载荷尺度效应研究

在海洋内孤立波作用下,立柱式钻井平台会产生大幅度的运动响应,影响钻井平台的作业效率与安全,其中平台内孤立波载荷的准确预测是关键。为此,以3类内孤立波理论(KdV、eKdV和MCC)的适用性条件为依据,通过构建两层流体中内孤立波对立柱式钻井平台强非线性作用的数值模拟方法,结合模型试验分析了立柱式钻井平台内孤立波载荷的尺度效应。结果表明,在大尺度条件下采用Morison公式和傅汝德-克雷洛夫公式分别计算内孤立波的水平力和垂向力仍然是可行的。此外,内孤立波载荷模型试验中,立柱式钻井平台内孤立波水平力及垂向力的尺度效应因流体黏性影响的不同而产生差异,受黏性影响较大的水平力尺度效应显著,而受黏性影响较弱的垂向力的尺度效应较弱,可以忽略。      

Optimizing Passenger Flow Control and Bus‐Bridging Service for Commuting Metro Lines

Oversaturated conditions are often observed during peak‐hour periods, especially for commuting metro lines serving as a corridor connecting suburb and urban areas due to its unidirectional passenger flow pattern. System operators are concerned about the amount of passengers accumulated inside station and at platform when train service cannot meet the travel demand. In this article, we tackle the metro system congestion issue and develop a compound strategy integrating passenger flow control and bus‐bridging service, to mitigate overcrowded situation. A two‐stage mathematical modeling procedure is proposed. Stage 1 determines the stations and time periods for taking passenger flow control strategy. Stage 2 identifies the optimal bus‐bridging services. Mixed integer linear programming models are developed to find the demand‐responsive flow control pattern and bus‐bridging services. The proposed passenger flow control and bus‐bridging strategy is applied to a commuting metro line in Shanghai. The results show that the proposed strategy is effective in reducing the number of stranded passengers, releasing the overcrowding pressure, and improving passengers’ satisfaction.     

西非多点系泊FPSO波频运动预报研究

应用三维势流理论及非线性时域动力耦合分析方法,针对西非深水海域的一座多点系泊浮式生产储油装置(FPSO),在涌浪海洋环境下对其进行了时域耦合计算和频域短期预报计算,并与模型试验结果进行了对比,较好地预报了该FPSO的波频运动性能,包括垂荡、横摇和纵摇,从而为我国深水海洋工程方案设计研究提供了技术储备.     

Scale Effect on the Shrinkage Characteristics of a Spherical Cavity in Stressed Grain

An analytical method is presented to investigate the scale effect on the shrinkage rate and the healing history of a spherical cavity in a stressed grain. The results show that the scale effect on the shrinkage rate of a spherical cavity in a stressed grain gradually increases as the spherical cavity shrinks. Because of the influence of a small-scale parameter from the nonlocal elastic theory, a spherical cavity in stressed grain does not eliminate completely through only lattice diffusion. The result may give a reference to reveal the healing mechanism of the damage defects in grains under hydrostatic pressures.