基于安全可靠性的多类用户交通分配模型

为探究出行安全对用户出行选择行为的影响,提出了考虑事故风险成本和旅行时间的多类用户交通分配模型。针对事故发生的随机性特征,定义了路径出行安全可靠性概念,并以此计算用户的事故风险成本预算,体现出行者的安全偏好。基于考虑事故机会和事故风险的基础事故预测模型,针对路段和交叉口的不同特征,分别定义了路段和交叉口的事故风险成本分布。构建的交叉口事故风险成本模型,体现了交叉口不同转向的事故风险成本的差异性。为了求解基于安全可靠性的多类用户交通分配模型,采用路径配流法和相继平均法设计了相应的求解算法,并通过算例分析了模型和算法的有效性。研究结果表明：安全可靠性在用户出行选择中具有重要影响。当在广义出行费用中考虑事故风险成本时,出行者会更多地选择事故风险成本较小的路径;不同风险倾向的用户会有不同的选择特征,保守型出行者倾向于选择路径事故风险成本标准差相对较小的路径,即事故风险成本波动小的路径,而中立型出行者倾向于选择事故风险成本均值相对较低的路径;考虑交叉口的事故风险成本与否会直接影响流量分配结果,即路径交叉口数量和转向的差异性同样会影响出行者的选择。所提出的模型对于客流预测和网络安全评价与管理具有潜在的应用价值。     

铌磷半钢在中磷铸铁闸瓦中应用的研究

本文通过对用铌磷半钢配制的中磷闸瓦的金相组织、力学性能、物理性能和摩擦-磨损特性的研究及其实际运行,证明:其质量指标和使用性能完全满足 TB1159-76标准,并超过普通中磷闸瓦的技术水平;可使中磷铸铁闸瓦的原材料成本降低10%左右.     

A conceptual framework of individual activity program generation

The research in this paper attempts to better understand the process by which activities are generated at an individual level. Activity-based travel analyses have gained popularity in recent years because they recognize the complexity of activity behavior and view travel as a derivative of this behavior. Most activity-based studies have focused on the spatial and temporal linkage of trips; that is, the scheduling of activities. They consider the agenda of activities for participation, and associated attributes of the activity participation (such as mode to activity and location of activity performance), as predetermined. This paper develops a comprehensive conceptual framework of the relatively unexplored area of activity agenda generation. Such a framework will be valuable in empirical modeling of activity generation behavior. A subsequent paper focuses on translating a part of this conceptual framework into an empirical model.     

A cross-section analysis of stock returns: The case of shipping firms

This paper undertakes an analysis of the determinants of the cross-section of expected stock returns of 19 shipping companies listed in the US, Norway, Stockholm and London. Various factors, including company stock market beta, divided yield, and financial leverage have been identified in the finance literature as determinants of share price performance. We capitalize on these findings and add one more industry specific factor, the average age of the company's fleet, to quantitatively analyse the determinants of the performance of shipping shock returns. We use the Fama-MacBeth methodology to empirically test whether the five factors above have a significant effect on shipping stocks' performance. Our results indicate that the industry specific factor (the average age of the fleet) plus financial leverage, are significant in explaining shipping stocks' returns, wheras the stock market beta and the dividend yield are far less significant.     

Passive Repulsive MagLev: Concept and Experimental Demonstration

A simple demonstrator for a magnetic levitation vehicle (MagLev) based on repulsive suspension forces generated by permanent magnets is presented. The lateral and yaw motions are stabilized using controlled electromagnets. A mathematical model, aimed mainly at defining the control strategy, has been developed and then experimentally validated using the demonstrator. Two different control strategies have been tested, namely a zero position error and a zero average current control strategy. Both proved to grant a stable behaviour and to effectively counteract external force disturbances. This demonstrator will be used in future research on MagLev vehicles but also on magnetic suspensions in general.     

Deterring the dauntless—appraising the effects of naval deterrence against the Somali piracy

This article considers whether the Somali pirates were deterred by the naval task forces between the years 2009 and 2013. By disaggregating data and using previously unpublished records regarding the naval operations, two areas of operations are identified as potential periods of deterrence. The article uses a model of asymmetric deterrence to study the outcomes and equilibria of the navy-pirate interaction. It is found that the naval operations eventually did deter the Somali pirates in the Gulf of Aden, but that this objective was not met in the Somali Basin. It is concluded that the operational focus on the Gulf of Aden coupled with the fact that the area is relatively smaller than the Somali Basin enabled the naval credibility, thus effectively denying the pirates access to the sea. Conversely, limited attention by the naval units and the long Somali southern coast with its open waters impeded naval control in the Somali Basin. In connection to these findings some conclusions regarding naval deterrence are discussed.     

Method for precise controlling of the at shift control system

The shift comfort and efficiency of Automatic Transmission in vehicle are highly influenced by the pressure of the clutch shift control system, especially by the electro-hydraulic clutch subsystem. In this paper, the new design principles of electro-hydraulic clutch systems developed and modeled in detail, the clutch-to-clutch control system is analyzed in three time intervals: oil filled phase, changing phase of clutch torque and synchronous phase of clutch speed. The demand pressures for the engaged clutches calculated in each phase and is precisely built up by using fuzzy slide mode control, the time of hydraulic pressure building-up is very sensitive to the dither current in simulation. All control parameters are optimized by Cosimulation between software Simulink and SimulationX. Finally, the optimal algorithm of the clutch shift control is written into the transmission control unit of a testing vehicle. The testing results show that the suggested control strategy is effective.     

Microbial community structure in the marginal ice zone of the Bellingshausen Sea

Phytoplankton, bacteria and microzooplankton were investigated on a transect in the Bellingshausen Sea during the ice melt period in November–December 1992. The transect along the 85°W meridian comprised seven stations that progressed from solid pack-ice (70°S), through melting ice into open water (67°S). The abundance, biomass and taxonomic composition were determined for each component of the microbial community. The phytoplankton was mostly dominated by diatoms, particularly small (<20 μm) species. Diatom abundance ranged from 66 000 cells l⁻¹ under the ice to 410 000 cells l⁻¹ in open water. Phytoplankton biomass varied from <1 to 167 mg C m⁻³, with diatoms comprising 89–95% of the total biomass in open water and autotrophic nanoflagellates comprising 57% under the ice. The standing stocks of autotrophs in the mixed layer ranged from 95 mg C m⁻² under the pack-ice to 9478 mg C m⁻² in open waters. Bacterial abundance in ice-covered and open water stations varied from 1.1 to 5.5×10⁸ cells l⁻¹. Bacterial biomass ranged from 2.4 mg C m⁻³ under pack-ice to an average of 14 mg C m⁻³ in open water. The microzooplankton consisted mainly of aloricate oligotrich ciliates and heterotrophic dinoflagellates and these were most abundant in open waters. Their biomass varied between 0.2 and 54 mg C m⁻³ with a minimum at depth under the ice and maximum in open surface waters. Microheterotrophic standing stocks varied between 396 mg C m⁻² under pack-ice and 3677 mg C m⁻² in the open waters. The standing stocks of the total microbial community increased consistently from 491 mg C m⁻² at the ice station to 13 155 mg C m⁻² in open waters, reflecting the productive response of the community to ice-melt. The composition of the microbial community also shifted markedly from one dominated by heterotrophs (82% of microbial stocks) at the ice station to one dominated by autotrophs (73% of microbial stocks) in the open water. Our estimates suggest that the microbial community comprised >100% of the total particulate organic carbon (POC) under the ice and 62–66% of the measured POC in the open waters.     

Hydrodynamics study of a BCF mode bioinspired robotic-fish underwater vehicle using Lighthill’s slender body model

This paper investigates the hydrodynamic characteristics of the rectilinear motion of a robotic fish underwater vehicle. This 2-joint, 3-link multibody vehicle model is biologically inspired by a body caudal fin carangiform fish propulsion mechanism. Navier–Stokes equations are used to compute the unsteady flow fields generated due to the interaction between the vehicle and the surrounding incompressible and Newtonian fluid (water) environment. The NACA 0014 airfoil aerodynamic profile has been designed to boost the swimming efficiency by reducing drag as the vehicle undergoes an undulatory/oscillatory motion. Using the Lighthill slender body model, a traveling wave mathematical function is defined to undulate the robotic fish posterior (caudal) region while the motion tracking is carried out by dynamic meshing technique. The results obtained show that though the net lift force approaches to zero, the net thrust or negative drag coefficient maintains a finite value dependent on kinematic parameters like tail beat frequency (TBF) and amplitude span (AS) at a given propulsive wavelength and the forward velocity of the vehicle. The results reveal the effects of TBF and AS on the coefficient of drag friction and the thrust force. Drag coefficients obtained from the simulations are compared and validated with the experimental results. The hydrodynamic results are found to be similar to the kinematic study results and suggest that TBF and AS play the most effective roles in the bioinspired propulsion technique. Relation of these parameters with propelling thrust force and forward velocity is also in conjunction over a given range of TBF and AS values.