直流车辆用蓄能器

直流车辆用文中所述的蓄能器能在显著降低功率消耗的同时,又在节能方面迈出了重要一步,而且车辆可在局部无接触导线区运行.样车试验证实了这些设想.     

鼠~(75)Se—亚硒酸钠的药物动力学研究

本文给大、小白鼠注射~(75)Se-亚硒酸钠,研究了硒的药物动力学变化及各种因素的影响。结果表明:硒在大、小鼠体内的药物动力学符合二室开放模型,不同给药途径无明显影响;硒经胃吸收良好,体内分布以肝肾最高,其次为血液、肺、脾、胃肠、心脏等。机体摄入多量以至中毒量硒以后,各组织通过延缓吸收、增加排泄来缓解硒浓度,过量未排泄的硒则进入血细胞内储存。给低硒动物硒制剂后,各组织通过加快吸收,延缓排泄而有效地保留硒。本实验阐明了硒的代谢动力学规律,为硒的临床应用提供了实验依据。     

Transnational corporations; problems for study in the new international order of maritime shipping

This paper examines what is becoming the new order of maritime shipping, the transnational corporation. By combining the flags of convenience with crews of convenience, these corporations have become entiitcs with an existence above and beyond the nation-state in which they operate. Factors contributing to and problems resulting from this maritime structure are discussed. Possible resons for scholarly neglect of this area in the U.S.A. are suggested.     

Canadian container ports: how have they fared? How will they do?

Between 1980 and 1989 container TEUs handled at all world ports increased by a factor of 2.11. On the East Coast of North America, the growth factor was only 1.69; on the West Coast, 2.23. These growth factors, when multiplied by the 1980 TEU volume at individual North American ports, give 1989 expected performance levels for the ports. Comparing the expected performance to the actual, it is found in the Canadian context that the big winner is Vancouver; the big loser is Saint John. Halifax and Montreal have outperformed their nearest US East Coast rivals but have not performed as well as southern ports on the Altantic Seaboard. These and other comparisons are made in order to describe how Canadian container ports have performed in the decade of the 1980s. The paper then speculates on how the ports will do in the future, based on a discussion of five factors: port facilities; inland transportation connections; shipping lines serving the ports; demand for container shipping; and legal arrangements between the United States and Canada.     

High Speed Stability for Rail Vehicles Considering Varying Conicity and Creep Coefficients

The critical or hunting speed of solid axle rail vehicles is known to be a strong function of primary suspension stiffness, wheel/rail profile geometry (conicity and gravitational stiffness), wheel/rail friction forces (creep coefficients), bogie/carbody inertia properties, and secondary suspension design. This paper deals with the problem of maximizing the critical speed through design of the primary and secondary suspension but with control only over the range of wheel/rail geometry and friction characteristics. For example, the conicity may varie from .05 to .3 and the linear creep coefficients from 25% to 100% of the predicted Kalker values.

It is shown that the maximum critical speed is greatly limited by the wheel/rail geometry and friction variations. It is also shown that, when lateral curving and ride quality are considered, the best design approach is to select an intermediate primary longitudinal stiffness, to limit the lowest value of conicity (e.g. to .1 or .2) by wheel profile redesign, increasing the secondary yaw damping value (yaw relaxation) and optimizing the primary and secondary lateral stiffness.     

Automated transit vehicle size considerations

Synthesis of cost-effective transit alternatives using automated vehicles requires consideration of a wide range of factors that are moot in determination of the optimum size of manually driven vehicles where the need to amortize driver wages dominates the economics. Discussions of many of these factors have appeared in previous papers. This article brings them together into consideration of one specific system characteristic: the optimum automated-transit-vehicle size.     

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.     

Dynamic transit scheduling under efficiency constraints

The problem of dynamic transit scheduling is addressed, and a method for transient and steady-state solutions is developed. The dynamic demand-supply formulation employed is based on previously calibrated disaggregate demand specifications. The existence and feasibility of solutions are examined, and stability conditions are derived. Numerical examples for both urban and rural conditions are given. The new methodology does not require time-series endogenous data but only initial conditions to provide long- or short-term scheduling plans. Futhermore, it takes into account passenger demand fluctuations and explicitly deals with management responsiveness and time lags in implementing scheduling decisions. Owing to its dynamic nature the methodology can be used as a design tool in transit scheduling and for assessing the effects of time-varying exogenous events such as gasoline price fluctuations, transport budget restrictions and other contingencies.     

The process of capital investment at US public portst

It is virtually impossible for a US public port authority to be totally proactive in its behaviour since there are too many major factors that affect its future that cannot be controlled or even anticipated by the port staff. Conversely, it is also virtually impossible for a public port authority to be totally reactive since the time window between decision and implementation often exceeds the time window of opportunity. For a public port authority to maintain long-term viability, it must constantly review the facilities it owns, the services it offers, and the source of the revenues it generates. This on-going review should determine how well the Port is adhering to its mission and accomplishing its goals and objectives as set out in the Port's strategic plan. Today, a major management challenge for any viable Port is prioritizing goals and maintaining a policy that ensures clear focus on the highest priority goals. Determining priorities amongst capital projects should be high on the list of any public port authority. This paper provides an overview of the decision-making processes used by American public port authorities in evaluating new capital projects and, we hope, an insight into processes for determining the desirability of expanding, contracting, or terminating present facilities and services.     

变频调速系统中正弦绕组电机的谐波分析

本文从典型的电压型逆变器输出的六阶梯电压波形和电流型逆变器输出的方波形电流出发,分析在不同时间谐波供馈到异步电机时,在正弦绕组电批及普通绕组电机中所产生的一系列空间磁场谐波幅值的相对变化,以及所有这些谐波在正弦绕组电机中被消除或抑制的情况,为在 PWM 调制及电流型变频器多重化技术应用中消除某一确定谐波的影响提供了依据