Faster than a speeding bullet train

China is throttling up a 430-km/h magnetically levitated train to link Shanghai and its airport. Built in China by a trio of German companies and the Shanghai Maglev Transportation Development Co., it reaches 430 km/h (268 mi/h)-130 km/h faster than Japan's famous bullet train. And even as it goes faster than any commercial vehicle without wings, the Chinese train is smoother and quieter than Amtrak's wheel-on-rail Acela-the state of the art in the United States-which pokes along when it can at a maximum 240 km/h. After many false starts and the completion of full-scale experimental maglev systems in Japan and Germany in the 1980s, maglev in China will finally start shuffling passengers in October in a reasonably large-scale, commercial system. The trains will run from downtown Shanghai's financial district to Pudong International Airport, making a 9-minute run that will shave about 40 minutes off the typical trip time in a taxi. With three five-car trains, each carrying as many as 574 passengers, and trains leaving every 10 minutes, the US $1.2 billion system could carry more than 10 million passengers a year.     

START: A system of transportation applying rendezvous technology

START (system of transportation applying rendezvous technology) is a side-by-side rendezvous technique designed to improve the collection and transfer of passengers in a rail-guided intercity transportation system. In operation, a nonstop express train provides service between cities, while frequent-stop local trains are used to provide coverage of metropolitan areas. The local trains link up with the express trains through a side-by-side rendezvous on parallel rendezvous tracks, and transfer of passengers and cargo takes place while both trains are in motion. The START concept offers the advantage that passengers and cargo can be transferred at many points along an intercity express route without severely affecting the average speed of the intercity system.     

Energy-Efficient Mobile Data Uploading from High-Speed Trains

Recent decades have witnessed the fast development of high-speed railway systems in many countries, which have significantly shortened the travel time between distant cities. Accompanied with this convenience is the challenge for cell phone vendors to provide broadband Internet access for passengers, particularly considering the fast changing channel conditions in high-speed trains and the limited battery of cell phones, which often cannot be re-charged in trains. In this paper, inspired by the unique spatial-temporal characteristics of wireless signals along high-speed railways, we propose a novel energy-efficient scheduling approach for uploading data from cell phones, both with soft deadlines (e.g., documents) and hard deadlines (e.g., video streaming). Our solution effectively predicts the signal strength through its spatial-temporal periodicity in this new application scenario, and smartly adjusts the transmission rate to maximize the overall data transmission rate and yet conserves the energy consumption. Performance evaluation based on realistic railway scenarios and H.264 video traces demonstrate the effectiveness of our solution and its superiority as compared to the existing solutions.     

铁路旅客列车无线公用电话应用技术

据不完全统计,全国铁路每年有超过10亿人/次的客运流量,铁路列车作为运输旅客的载体蕴藏着一个潜在的、亟待开发的巨大通信市场。开发这个市场,为旅客在出行途中提供商用级的电信服务,一直是铁道部领导重视以及中国铁通探讨和研究的课题。本文对无线公用电话在旅客列车上的成功应用进行了深入研究。     

Noise performance of a precision pulsed electromagnet power supply for magnetic resonance imaging

Prepolarized magnetic resonance imaging (PMRI) uses two pulsed electromagnets to achieve high-field image quality with the benefits of low-field data acquisition. The principal challenge with all resistive MRI systems is the implementation of a highly precise magnet current supply. The noise current through the magnet is fundamentally limited by the current transducer used to provide feedback and the voltage reference used to generate the demand signal. Field instability in the main field magnet can both corrupt the received data and degrade the robustness of Carr?Purcell?Meiboom?Gill (CPMG) echo trains, which are paramount to efficient imaging in PMRI. In this work, we present the magnet control system that achieved sufficient field stability for PMRI at Prepolarized magnetic resonance imaging (PMRI) uses two pulsed electromagnets to achieve high-field image quality with the benefits of low-field data acquisition. The principal challenge with all resistive MRI systems is the implementation of a highly precise magnet current supply. The noise current through the magnet is fundamentally limited by the current transducer used to provide feedback and the voltage reference used to generate the demand signal. Field instability in the main field magnet can both corrupt the received data and degrade the robustness of Carr?Purcell?Meiboom?Gill (CPMG) echo trains, which are paramount to efficient imaging in PMRI. In this work, we present the magnet control system that achieved sufficient field stability for PMRI at $0.5/0.13$ T, identify the dominant sources of noise in the control system, examine the imaging artifacts that can occur if the field stability is insufficient, and identify how the design can be improved for better field stability, should it be required for future implementations of PMRI.     

Taming the dragons-designing danger out of the Hong Kong MTR

The Hong Kong mass transit railway (MTR) was designed to have four routes, of which three are in service so far. It has 39 km of double track and 37 stations and carries up to 90000 passengers per hour in each direction under crush conditions. Design of the system is therefore vital in terms of safety and the stations, trains and power supplies are discussed while considering this aspect     

A probability inequality for band-limited pulse trains

Band-limited pulse trains derived from a discrete stochastic process are considered. An upper bound is obtained for the average probability that the magnitude of the departure of the instantaneous signal value from the mean signal value exceedslambdatimes the standard deviation, as a function oflambda. This upper bound is useful in the analysis and prediction of intersymbol interference, quantizing errors, and digit errors in digital data communication systems.     

A Procedure for Decomposing the Myoelectric Signal Into Its Constituent Action Potentials-Part II: Execution and Test for Accuracy

The scheme for decomposing a myoelectric signal into its constituent motor unit action potential trains described in the paper [3] requires interaction from the human operator. In this paper, guidelines to be employed by the operator in assisting the computerized algorithms in identifying (classifying) a motor unit action potential are presented. The accuracy of the decomposition scheme was evaluated by decomposing a mathematically synthesized myoelectric signal. This signal was constructed by linearly superimposing eight mathematically generated motor unit action potential trains along with Gaussian noise. A skilled operator was able to decompose this signal with an accuracy of 99.8 percent, incurring one error in a total of 435 classifications. The decomposition reproducibility was evaluated by having two experienced operators independently decompose the same record of empirically obtained myoelectric signal. Their results were in total agreement for 479 motor unit action potential classifications belonging to five motor unit action potential trains. Up to eight motor unit action potential trains have been decomposed from one myoelectric signal.     

Comprehensive drive train efficiency analysis of hybrid electric and fuel cell vehicles based on motor-controller efficiency modeling

From the point of view of overall hybrid electric vehicle (HEV) and fuel cell vehicle (FCV) drive train efficiency, the research focus is mainly on the efficiency analysis of the power train components, which prove to be an integral part of modern HEV and FCV drive trains. The critical portion of any HEV electrical system consists of a power electronic converter (inverter) and a suitable traction motor. Thus, the efficiency analysis of the inverter/motor is of prime importance for the calculation of the overall efficiency of the drive trains. This paper aims at modeling the efficiencies of the traction motor/controller through efficiency maps. Efficiency maps are a convenient way to represent motor drive systems of large and complex systems, like that of a HEV. The paper uses the advanced vehicle simulator (ADVISOR) software for the simulations of a large-sized car, similar to a Chevy Lumina, over the urban dynamometer-driving schedule and highway fuel economy test drive cycles. Furthermore, the paper investigates the traction motor efficiency maps and consequent overall drive train efficiencies of commercially available Honda Insight and Toyota Prius HEVs. In all the case studies, the aim is to analyze the overall drive train efficiency over the city and highway drive cycles based on the inverter/motor efficiency maps.     

Mobile Hotspot Network System for High‐Speed Railway Communications Using Millimeter Waves

We propose a millimeter wave (MMW)‐based mobile hotspot network (MHN) system for application in high‐speed railways that is capable of supporting a peak backhaul link throughput of 1 Gbps per train at 400 km/h. The MHN system can be implemented in subways and high‐speed trains to support passengers with smart devices and provide access to the Internet. The proposed system can overcome the inherent high path loss in MMW through system designs and high antenna gains. We present a simulation of the system performance that shows that a fixed beamforming strategy can provide high signal‐to‐interference‐plus‐noise‐ratio similar to those of an adaptive beamforming strategy, with the exception of 15% of the train path in which the network can use link adaptation with low‐order modulation formats or trigger a handover to maintain the connection. We also demonstrate the feasibility of the MHN system using a test bed deployed in Seoul subway line 8. The backhaul link throughput varies instantaneously between 200 Mbps and 500 Mbps depending on the SNR variations while the train is running. During the field trial, the smartphones used could make connections through offloading.     

An Estimate of the Length of Diagnostics Tests

The diagnosis of digital systems can be conveniently modelled as the recognition of distinct binary error-free patterns, Specifically, if for a given fault condition, the pass or fail responses to a set of applied tests are recorded as a column of a matrix M, a test schedule of length k is a subset of the rows of M which preserves column distinguishability. Since the determination of a minimal test schedule is a formidable problem for moderately complex networks, it appears desirable to have guidlines for the evaluation of heuristically or suboptimally computed test schedules. One such guideline is the median kmin of the minimal test schedule kmin over the set of all binary matrices M: while in general [log2m] ? kmin ? m - 1, this paper shows that kmin < [2 log2m], that is, for most practical cases, kmin is much closer to the lower bound [log2m] than to the upper bound (m - 1).     

At the crossroads in air-traffic control III. View from the cockpit?reactions of some pilots, automatic flight management, flight-control systems, airborne CAS, `moving map' displays, `three-dimensional' area navigation, and others

Control of air traffic from the ground is only half the story?the airborne electronic equipment, displays, instrumentation, and human response are necessary to complete the loop in any practicable system. A few versions of collision-avoidance systems are entirely under airborne control. Based upon experience, pilots are wary of the hazards at certain major airports; in approaching other terminals, however, they have a sense of confidence that is inspired by the existence of the latest ATC equipment and facilities that afford a high degree of safety to pilots, passengers, and aircraft.     

Scheduling of uniform multidimensional systems under resourceconstraints

Multidimensional (MD) systems are widely used to model scientific applications such as image processing, geophysical signal processing, and fluid dynamics. Such systems, usually, contain repetitive groups of operations represented by nested loops. The optimization of such loops, considering processing resource constraints, is required in order to improve their computational time. Most of the existing static scheduling mechanisms, used in the high-level synthesis of very large scale integration (VLSI) architectures, do not consider the parallelism inherent to the multidimensional characteristics of the problem. This paper explores the basic properties of MD loop pipelining and presents two novel techniques, multidimensional rotation scheduling and push-up scheduling, able to achieve the shortest possible schedule length. These new techniques transform a multidimensional data flow graph representing the problem, while assigning the loop operations to a schedule table. The multidimensional rotation scheduling is an iterative “heuristic” method, depending upon user input, while the push-up scheduling algorithm is able to compute the new schedule in polynomial time. The optimal resulting schedule length and the efficiency of the algorithms are demonstrated by a series of practical experiments     

Parameterized Scheduling of Topological Patterns in Signal Processing Dataflow Graphs

In recent work, a graphical modeling construct called “topological patterns” has been shown to enable concise representation and direct analysis of repetitive dataflow graph sub-structures in the context of design methods and tools for digital signal processing systems (Sane et al. 2010). In this paper, we present a formal design method for specifying topological patterns and deriving parameterized schedules from such patterns based on a novel schedule model called the scalable schedule tree. The approach represents an important class of parameterized schedule structures in a form that is intuitive for representation and efficient for code generation. Through application case studies involving image processing and wireless communications, we demonstrate our methods for topological pattern representation, scalable schedule tree derivation, and associated dataflow graph code generation.     

一种新型的认知无线电频谱空穴自适应检测算法

根据认知无线电实际频谱需求,通过对弱信号检测技术的研究,该文首次在认知无线电领域提出了一种基于三重矩阵累积估计的频谱空穴检测算法,该算法将频域块自适应滤波与矩阵重构、累积估计和频域平滑相结合实现弱信号检测。最后以QPSK调制信号为例进行了算法的计算机仿真,给出了性能分析。仿真结果表明该检测算法能够快速有效地实现弱信号检测并具有较高的检测概率,完全可以应用于认知无线电的频谱空穴检测。     

基于限制车速的安全带强制使用装置

为解决驾驶员驾驶安全性低和行驶舒适性差的问题,设计出一种新型安全带强制使用装置。采用计算机仿真模拟的方法进行研究和设计,外围的输入信号模拟发动机的加速踏板信号、转速信号和安全带佩戴情况信号,控制芯片采用飞思卡尔公司的MC9S128单片机,输出信号为输给发动机ECU的油门踏板信号和语音提示系统的控制信号。实验表明,如果驾驶员和乘客不佩戴安全带,不管驾驶员如何操作加速踏板,将车速限定在一定的人身安全的车速范围内;当需要提速时,提醒驾驶员和乘客佩戴安全带,以确保人身安全,使汽车被动安全装置更为人性化,由此提高驾车舒适性和安全性。     

一种应用于地铁站的无线乘客求助系统的研究

为了能使地铁站内乘客求助信息快速、可靠地传输,又方便系统的安装与维护,采用了单片机控制无线传输模块收发乘客求助信息的方案,并在无线收发模块之间添加中继器以增加传输的距离。进行地铁站内环境对无线信号衰减程度的分析,并设计了地铁站内无线乘客求助信息系统。该系统可以满足地铁站内环境下乘客求助信息的无线传输。     

基于变换谱相干积累的片段信号PRI检测

受自身搜索方式和目标辐射源波束调度的影响,侦察系统往往只能截获辐射源的部分信号,这为后续分选处理带来了很大挑战.针对该问题,提出了通过时PRI变换谱进行相干积累以提高真实PRI检测概率的方法.首先介绍了PRI变换法,对算法原理进行了说明;接着从理论上推导了PRI变换谱峰值与脉冲个数的关系,指出了PRI变换谱的相干积累特性,并分析了其对虚假脉冲的适应能力;最后通过仿真试验对理论分析进行了验证.仿真结果表明,文中提出的方法能够有效提高片段信号的PRI 谱峰,从而有利于提高检测概率.     

Evaluation of relative merits/demerits of different signalingschemes used at a railway station for an approaching train in IndianRailways today

Indian Railways, one of the largest railway networks in the world today, has a peculiarity that a station exists almost every 5-7 km. Most trains do not stop at all stations and run through more stations than they stop at. The speed at which the trains run through the stations, therefore, is a crucial parameter that determines the run time of a train through a section and, hence, the total throughput (or carrying capacity of the railways). Indian Railways uses several signaling schemes to enable movement of trains in a safe manner. The signaling schemes play an important role in determining the action of the driver in terms of slowing down of trains and, consequently, on the throughput of the railway system. This paper examines the different signaling schemes used currently and in the recent past by Indian Railways from the point of view of information that they present to the train driver and the impact that it has on total throughput. The signaling schemes are compared using total signal entropy presented to the driver at each stage. Apart from theoretical computation of signal entropy, results of some experiments conducted to obtain the impact of signaling schemes on run time of trains are also presented     

Performance improvements of communication-based train control (CBTC) systems with unreliable wireless networks

Communication-based train control (CBTC) uses wireless networks, such as wireless local area networks (WLANs), to transmit trains status and control commands. CBTC systems have stringent requirements for train-ground communications, as the train control system depends on the accurate, timely and reliable data over the communication links. However, since WLANs are not originally designed for high mobility environment, random packet delay and losses are inevitable in WLAN-based CBTC systems, which could result in unnecessary traction, brake or even emergency brake of trains, losses of line capacity and passenger satisfaction. In this paper, we study the impacts of random packet delay on the performance of CBTC systems, and propose a novel scheme to improve the CBTC performance by mitigating the impacts of random packet delay. Unlike the existing works that only consider a single train, we consider a group of trains in CBTC systems to improve the CBTC performance. Extensive field test and simulation results are presented. We show that the current adopted control scheme in CBTC systems needs to keep stability and performance under transmission delays through increasing the distance between trains in steady state which means cost of line capacity. By contrast, our proposed scheme can significantly improve the CBTC performance.