Accelerating MR Imaging via Deep Chambolle-Pock Network
Haifeng WangJing ChengSen JiaZhilang QiuCaiyun ShiLixian ZouShi SuYuchou ChangYanjie ZhuLeslie YingDong Liang
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Compressed sensing (CS) has been introduced to accelerate data acquisition in MR Imaging. However, CS-MRI methods suffer from detail loss with large acceleration and complicated parameter selection. To address the limitations of existing CS-MRI methods, a model-driven MR reconstruction is proposed that trains a deep network, named CP-net, which is derived from the Chambolle-Pock algorithm to reconstruct the in vivo MR images of human brains from highly undersampled complex k-space data acquired on different types of MR scanners. The proposed deep network can learn the proximal operator and parameters among the Chambolle-Pock algorithm. All of the experiments show that the proposed CP-net achieves more accurate MR reconstruction results, outperforming state-of-the-art methods across various quantitative metrics.Keywords:
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Urban development is promoted in urban areas focusing on public transportation facilities such as stations, including compact cities. Stations are essential as transportation hubs, and many studies have been conducted on the relationship between stations and surrounding areas. The SPMI is a quantitative method of expressing the convenience of rail transportation, focusing on individuals and summarizing the number of stations that can be reached in a day without transfers. However, the current calculation does not consider train type and treats both individual station trains and limited express trains as equally valuable. Therefore, the value of limited express trains, which stop at fewer stations, is smaller than that of individual station trains, and the utility of such trains cannot be expressed numerically. Therefore, this study focused on the time saved by using limited express trains, etc., and proposed a method to calculate the time value of each station train, which was then used to calculate the conversion coefficient for each station train on routes in Chiba Prefecture.
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A key train plays a important role in the rail timetable. The unreasonable key trains 47 layout greatly influences the normal train-running order, thus affecting the quality of 48 the high-speed rail (HSR) timetable. This paper studies the probability produced by 49 train paths for overcoming bottlenecks, and identifies key trains in the HSR timetable, 50 that is, key trains have greater effecter on other trains and needed to pay close 51 attention to them. Moreover, under certain capacity requirements, this paper 52 calculates reasonable key trains ratio for different combinations of speed in a HSR 53 timetable. This research demonstrates that: （a） maintaining a low speed level is 54 essential for key trains in the HSR timetable; and （b） when trains of 350km/h and 55 250km/h run on the same line, the key trains (250km/h) ratio of the 56 Beijing-Shanghai HSR should be less than 10%. Currently, for the trains running on 57 the Beijing-Shanghai HSR, whose speeds are 300km/h and 250km/h, the key trains 58 (250km/h) ratio should be no more than 20%.
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This paper presents a novel approach, compressive mobile sensing, to use mobile sensors to sample and reconstruct sensing fields based on compressive sensing. Compressive sensing is an emerging research field based on the fact that a small number of linear measurements can recover a sparse signal without losing any useful information. Using compressive sensing, the signal can be recovered by a sampling rate that is much lower than the requirements from the well-known Shannon sampling theory. The proposed compressive mobile sensing approach has not only the merits of compressive sensing, but also the flexibility of different sampling densities for areas of different interests. A special measurement process makes it different from normal compressive sensing. Adopting importance sampling, compressive mobile sensing enables mobile sensors to move adaptively and acquire more samples from more important areas. A motion planning algorithm is designed based on the result of sparsity analysis to locate areas of more interests. At last, experimental results of 2-D mapping are presented as an implementation compressive mobile sensing.
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There has been much discussion of introducing express train service in urban railway transportation since the express train service was successfully launched in Seoul line 9. However the discussion is mainly focused on the infrastructure problem like how to install siding tracks or the corresponding costs. This study addresses the operational aspects in operating the express trains; for example, how to calculate of running times of express trains or headway between the trains, and then how to make up the timetable. These aspects have been found out by means of another special project. We suggest a simulation based approach to develop the mixed timetable. The approach consists of the several steps of calculating some fundamental times, adding the trains, and adjusting the arrival and departure times. The approach has some advantages that the running time and headway are automatically calculated within the simulation software so that the feasibility of timetable can be easily checked. We could yield a mixed feasible timetable of regular and express trains in the Seoul line 9 just by means of the suggested procedure.
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The organization works of passenger train operation for large scale urban rail transit during the earlier stage of construction should be designed according to the organization of running the express trains and the slow trains.This method may create an excellent hardware environment for operation departments to raise their service level.The division of running the express trains and the slow trains is aimed at running slow trains to satisfy therequirement of passengers along the rail lines up and down the trains, while running express trains to satisfy the requirement of the long legspassengers up and down the trains between the surrounding cities and the surrounding cities with the central city. The basic service purpose of urban rail transit is aimed at to satisfy the requirement of different travelling distances and to shorten the travelling times.
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The highlight in developing new high-performance trains in Europe has often been on extreme high-speed trains. However, since the cost for new infrastructure adapted to these trains is extremely high, there is now a growing interest for more flexible vehicles offering, at a low price, high performance, efficient space utilisation and high comfort. These trains are a prerequisite for achieving an efficient passenger train system. The paper describes adequate requirements on parameters essential to train effectiveness. At first the average speed of the train has been derived as functions of power, tractive effort and maximum speed for certain well defined travelling conditions. It is then discussed how the average speed and other parameters like energy consumption per passenger and the train weight per seat can be influenced by new designs and new technical solutions.
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In this paper, communication with and inside trains is analysed. Existing communication links to trains are exemplified. A semi-automated planning tool for basic calculations of the positions of base stations is shown. It is detailed, how this tool may simplify the planning process for different usage scenarios. In addition, the distribution of signals inside and between the train's coaches is described. Both together can be used for cost calculations for operators intending to offer a certain service to train passengers. An outlook towards future use of communication inside trains is given at the end.
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Genetic algorithm based on conflict detecting for solving departure time domains of passenger trains
In passenger train operations, it is imperative that timetables are well planned to achieve the highest levels of efficiency and safety. The departure time domain of passenger trains serves as the framework and core component of the train timetable, determining a rough plan for passenger trains, which eventually impacts the overall performance of the train operations. The goal of the departure time domain of passenger trains is to satisfy the passenger's expected arrival/departure times. This paper developed a departure time domain for passenger trains under the constrained receiving and dispatching capacities of arrival–departure tracks in a railway station. A genetic algorithm was proposed based on strategies of conflict detecting in order to calculate an optimal arrival and departure time domain for the trains. The proposed model and algorithm were implemented in an experimental network at Chengdu Station in China with 52 pairs of trains; the results showed that all trains met the expectations of the passengers with the capacities of the arrival–departure tracks. The model and algorithm developed in this paper could also serve to resolve the problem of departure time domain of passenger trains in an entire railway network.
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Abstract – In this paper, simulation models, created in the OpenTrack simulation tool, were used to compare the proposed timetable with a variant in which all trains from and Lazarevac would be extended to Belgrade Center. This paper aims to analyze the effects of the increasing number of trains on part of Belgrade railway junction from Resnik to Belgrade Center. The results have shown that the section from Dedinje junction to Resnik has more than enough capacity for the increased number of trains. Also, the simulation results show us that when the number of trains increases by 40%, BG trains can operate without or with acceptable delays. Keywords – railway, simulation, BG voz, OpenTrack.
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As an important mode of railcar operation,multi-block trains play the role of reducing accumulation time,cutting down shunting on the way and speeding car movement.However,the complexity and particularity attract few domestic specialists and scholars.So,this paper firstly expounds the meaning and characteristics of multi-block trains.Then based on optimal theories of the train formation plan of one-block trains,car-hour savings of two cases in which multi-block trains are formed respectively are analyzed in detail.With utilization of the step function,the 0-1 programming model is constructed to optimize the train formation plan of multi-block trains at technical service stations.The objective is to maximize the technical benefit,which is regarded with the working conditions of multi-block trains.Finally,the paper gives a numerical example,which proves the effectiveness of the model,and interprets its speciality and applicability.
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