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61.
Within Australia, there has been a recent expansion of relay working operations. To address concerns about the amount of sleep obtained by drivers in relay vans, and potential deficits in alertness associated with relay work, the current study assessed the sleep behaviour and alertness of 15 train drivers working short (<48 h) relay operations. In total, drivers obtained 8-12h of sleep during the relay trip (which took approx 40 h). Overall, they reported that they felt more alert following each sleep period. Drivers were able to sustain attention during the 10-min vigilance tasks administered before and after each shift. These findings suggest that the amount of sleep obtained in crew vans during short relay operations is sufficient to maintain alertness during the trip. They also emphasise the importance of scheduling shifts to maximise the number of sleep opportunities that occur between 2200 and 0700 h. 相似文献
62.
The determination of the direct kinematics of a parallel mechanism is a difficult problem but must be solved for practical
application. This paper presents the efficient formulation of the direct kinematics and the Jacobian of a double parallel
robot arm for velocity control. The robot arm consists of two parallel mechanisms, and a central axis that generates positional
and orientational motions independently. Given a set of lengths for the linear actuators, the direct kinematics computes the
position and orientation of the end-effector, and the Jacobian transforms the velocities of the end-effector to those of the
linear actuators. The developed formulation is implemented in a real-time control setting and its efficiency is demonstrated.
Department of Control and Instrumentation Engr. 相似文献
63.
在高速列车运行过程中,列控系统等级转换过程所用的时长和转换成功概率,直接影响列车运行安全和行车效率。利用有色Petri网对CTCS-3级列控系统和CTCS-2级列控系统之间等级转换以及典型设备故障导致降级场景分别建模,模拟等级转换过程中RBC(Radio Block Center,无线闭塞中心),车载设备,有源应答器之间的信息交互过程。分析了列车速度对等级转换实时性的要求和对转换成功概率的影响,以及突发降级的可能性,结果表明建模方法满足CTCS-3级列控系统的安全性和兼容性要求。 相似文献
64.
This paper focuses on the development of metaheuristic algorithms for the real-time traffic management problem of scheduling and routing trains in complex and busy railway networks. This key optimization problem can be formulated as a mixed integer linear program. However, since the problem is strongly NP-hard, heuristic algorithms are typically adopted in practice to compute good quality solutions in a short computation time. This paper presents a number of algorithmic improvements implemented in the AGLIBRARY optimization solver in order to improve the possibility of finding good quality solutions quickly. The optimization solver manages trains at the microscopic level of block sections and at a precision of seconds. The solver outcome is a detailed conflict-free train schedule, being able to avoid deadlock situations and to minimize train delays. The proposed algorithmic framework starts from a good initial solution for the train scheduling problem with fixed routes, obtained via a truncated branch-and-bound algorithm. Variable neighbourhood search or tabu search algorithms are then applied to improve the solution by re-routing some trains. The neighbourhood of a solution is characterized by the set of candidate trains to be re-routed and the available routes. Computational experiments are performed on railway networks from different countries and various sources of disturbance. The new algorithms often outperform a state-of-the-art tabu search algorithm and a commercial solver in terms of reduced computation times and/or train delays. 相似文献
65.
This paper proposes a two-stage optimization approach to optimize the train schedule and circulation plan with consideration of passenger demand for an urban rail transit line. A train scheduling model is based on the operation of train services, which results a mixed integer nonlinear programming problem. Moreover, a train circulation model is formulated to adjust the departure and arrival times obtained by the train scheduling model to reduce the number of trains required, which results in a mixed integer linear programming problem. The case study based on the Beijing Yizhuang line illustrates the effectiveness of the proposed model and solution approach. 相似文献
66.
论述了液化石油气铁道罐车的设计。着重介绍了设计中主要参数的确定.容器类别的划分.主要受压元件的计算和结构设计。同时也涉及了液化石油气铁道罐车与一般压力容器在设计、制造、检验及试验方面的区别。 相似文献
67.
《电子学报:英文版》2016,(4):740-745
In existing metro systems, the train ground radio communication system for different applications are deployed independently. Investing and constructing the communication infrastructures repeatedly wastes substan-tial social resources, and it brings di?culties to maintain all these infrastructures. We present the communication Quality of service (QoS) requirement for different train ground radio applications. An integrated TD-LTE based train ground radio communication system for the metro system (LTE-M) is designed next. In order to test the LTE-M system performance, an indoor testing environment is set up. The channel simulator and programmable attenua-tors are used to simulate the real metro environment. Ex-tensive test results show that the designed LTE-M system performance satisfies metro communication requirements. 相似文献
68.
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70.
王娜 《江汉石油职工大学学报》2004,17(1):56-57,60
我国的风险投资业,经过十余年发展,有了一个比较好的开端,对推动科学技术的进步和高新技术产业的发展发挥了积极作用。但还存在着诸如法规政策不完善、风险创业资本进出渠道不畅通等诸多问题。对此,有必要认真思考,总结经验,用创新发展的眼光和思路去理解和解决问题,以推动中国风险投资的发展。 相似文献