自动闭塞区段增设接近离去停电表示电路

用继电器的空闲接点组成停电表示电路。当车站设备停电时,在控制台上给出区间的占用表示,便于人员监督列车的运行。     

基于GSM-R无线网络实现车-地通信的CTCS-3级列控系统分析

着重阐述基于GSM-R无线网络的车-地通信如何实现地面设备之无线闭塞中心子系统与车载设备连接,如何确保无线闭塞中心子系统发送行车许可和临时限速等控车指令实现高速列车的无线指挥,以及如何完成无线闭塞中心实时接收车载设备动态信息的无线反馈。     

A macroscopic loading model for time-varying pedestrian flows in public walking areas

A macroscopic loading model applicable to time-dependent and congested pedestrian flows in public walking areas is proposed. Building on the continuum theory of pedestrian flows and the cell transmission model for car traffic, an isotropic framework is developed that can describe the simultaneous and potentially conflicting propagation of multiple pedestrian groups. The model is formulated at the aggregate level and thus computationally cheap, which is advantageous for studying large-scale problems. A detailed analysis of several basic flow patterns including counter- and cross flows, as well as two generic scenarios involving a corner- and a bottleneck flow is carried out. Various behavioral patterns ranging from disciplined queueing to impatient jostling can be realistically reproduced. Following a systematic model calibration, two case studies involving a Swiss railway station and a Dutch bottleneck flow experiment are presented. A comparison with the social force model and pedestrian tracking data shows a good performance of the proposed model with respect to predictions of travel time and density.     

小型水面船舶惯导系统标校方法初探

介绍水面船舶安装惯导系统的重要性和惯导系统标校的实施环境及通常方法。分析小型水面船舶在惯导标校上的特殊性,并针对小型水面船舶惯导系统的标校给出了两种方案建议。     

Time-domain structural analysis during block turnover and lifting using 2D flexible multibody dynamics

Ship construction involves the assembly of several blocks on a dock. When a block is lifted using a crane, it undergoes deformation. Until now, structural analysis has been applied in a few cases to evaluate the stress on such blocks. Therefore, this study proposes an evaluation method for time-domain stress using 2D flexible multibody dynamics. We adopt the discrete Euler-Lagrange equation to achieve robustness during the numerical integration of problems that involve high stiffness. We formulate the equations of motion of 2D shell elements based on the absolute nodal coordinate formulation, which is an efficient analysis technique for nonlinear and large deformation cases. We also derive the two types of kinematic constraints (ball and fixed joints) between the rigid and shell element, which can be attached to an arbitrary point. Based on the theories, we develop the program to build models, including 2D flexible multibody dynamics and several joints, and to solve the equations of motion efficiently. As a result, it is successfully applied to the dynamic analysis of the block turnover by a gantry crane and the block lifting by a floating crane. The von-Mises stresses that change over time are compared to the maximum yield stress and analyzed according to the wave direction.     

Does traffic-related calibration of car-following models provide accurate estimations of vehicle emissions?

Fuel consumption or pollutant emissions can be assessed by coupling a microscopic traffic flow model with an instantaneous emission model. Traffic models are usually calibrated using goodness of fit indicators related to the traffic behavior. Thus, this paper investigates how such a calibration influences the accuracy of fuel consumption and NOx and PM estimations. Two traffic models are investigated: Newell and Gipps. It appears that the Gipps model provides the closest simulated trajectories when compared to real ones. Interestingly, a reverse ranking is observed for fuel consumption, NOx and PM emissions. For both models, the emissions of single vehicles are very sensitive to the calibration. This is confirmed by a global sensitivity analysis of the Gipps model that shows that non-optimal parameters significantly increase the variance of the outputs. Fortunately, this is no longer the case when emissions are calculated for a group of many vehicles. Indeed, the mean errors for platoons are close to 10% for the Gipps model and always lower than 4% for the Newell model. Another interesting property is that optimal parameters for each vehicle can be replaced by the mean values with no discrepancy for the Newell model and low discrepancies for the Gipps model when calculating the different emission outputs. Finally, this study presents preliminary results that show that multi-objective calibration methods are certainly the best direction for future works on the Gipps model. Indeed, the accuracy of vehicle emissions can be highly improved with negligible counterparts on the traffic model accuracy.     

Optimization-based assisted calibration of traffic simulation models

Use of traffic simulation has increased in recent decades; and this high-fidelity modelling, along with moving vehicle animation, has allowed transportation decisions to be made with better confidence. During this time, traffic engineers have been encouraged to embrace the process of calibration, in which steps are taken to reconcile simulated and field-observed performance. According to international surveys, experts, and conventional wisdom, existing (non-automated) methods of calibration have been difficult or inadequate. There has been extensive research on improved calibration methods, but many of these efforts have not produced the flexibility and practicality required by real-world engineers. With this in mind, a patent-pending (US 61/859,819) architecture for software-assisted calibration was developed to maximize practicality, flexibility, and ease-of-use. This architecture is called SASCO (i.e. Sensitivity Analysis, Self-Calibration, and Optimization). The original optimization method within SASCO was based on “directed brute force” (DBF) searching; performing exhaustive evaluation of alternatives in a discrete, user-defined search space. Simultaneous Perturbation Stochastic Approximation (SPSA) has also gained favor as an efficient method for optimizing computationally expensive, “black-box” traffic simulations, and was also implemented within SASCO. This paper uses synthetic and real-world case studies to assess the qualities of DBF and SPSA, so they can be applied in the right situations. SPSA was found to be the fastest method, which is important when calibrating numerous inputs, but DBF was more reliable. Additionally DBF was better than SPSA for sensitivity analysis, and for calibrating complex inputs. Regardless of which optimization method is selected, the SASCO architecture appears to offer a new and practice-ready level of calibration efficiency.     

An enhanced SPSA algorithm for the calibration of Dynamic Traffic Assignment models

Simultaneous perturbation stochastic approximation (SPSA) is an efficient and well established optimization method that approximates gradients from successive objective function evaluations. It is especially attractive for high-dimensional problems and has been successfully applied to the calibration of Dynamic Traffic Assignment (DTA) models. This paper presents an enhanced SPSA algorithm, called Weighted SPSA (W-SPSA), which incorporates the information of spatial and temporal correlation in a traffic network to limit the impact of noise and improve convergence and robustness. W-SPSA appears to outperform the original SPSA algorithm by reducing the noise generated by uncorrelated measurements in the gradient approximation, especially for DTA models of sparsely correlated large-scale networks and a large number of time intervals. Comparisons between SPSA and W-SPSA have been performed through rigorous synthetic tests and the application of W-SPSA for the calibration of real world DTA networks is demonstrated with a case study of the entire expressway network in Singapore.     

NTO型沥青燃烧炉检测精度的试验分析

结合吉林省长松高速公路施工检测的具体实践,分别进行消石灰单质、空白集料以及自拌ATB-25沥青混合料燃烧试验对燃烧法进行标定,得出了添加消石灰混合料和SMA混合料油石比的修正值,提高了沥青混凝土施工检测的精度,对今后利用燃烧法进行沥青混合料油石比检测结果的标定具有借鉴意义。     

EGR系统在SNH4102型柴油机中的标定试验

EGR系统是治理内燃机排放污染物Nq的有效方法之一,在PTO台架上对SNH4102型柴油机EGR系统进行标定试验,采用真空度控制EGR阀开度,实现EGR系统的调节。在柴油机额定转速下,将测功器开至100％,75％,50％,10％;在最大扭矩下,将测功器开至100％,75％,50％;及怠速工况下,找到EGR阀最佳开度,完成EGR系统的标定;并通过NHA-501型废气分析仪和FLB-100不透光式烟度计等测量排放物的含量。结果表明：在SNH4102型柴油机台架试验中,EGR系统对于NOx的控制有明显的效果,对CO和HC等排放物的抑制作用不明显。