China Academy of Railway Sciences

Beijing, China

China Academy of Railway Sciences

Beijing, China
Time filter
Source Type

Liu J.,China Academy of Railway Sciences
International Conference on Advanced Communication Technology, ICACT | Year: 2017

At present, the user experience provided by smart mobile terminals is limited to the battery capacity. This paper focuses on how to improve the energy efficiency of terminals in OFDMA-based wireless multicast systems with frequency-selective channels. We assume that multicast terminals can switch to sleep mode during the transmission of some OFDM symbols according to their OFDMA frame-level quality of service (QoS) requirements. Based on it, we combine resource allocation with terminal sleeping mechanism, and propose a new resource allocation problem model. The task is to minimize the total time when terminals are in receive mode through jointly optimizing the subcarrier allocation for different multicast terminals and the power allocation between different subcarriers, which is a NP-hard problem. To adapt to the needs of real-time applications, we separate subcarrier and power allocation, and propose a low-complexity suboptimal algorithm for this problem. Performance evaluations are conducted in homogenous and heterogeneous networks respectively. Simulation results show that compared with traditional multicast and unicast, our proposed method reduce the total energy consumption of terminals significantly with the same QoS requirements of terminals guaranteed. Additionally, the advantage of our proposed method over traditional multicast diminishes with the increase of the maximum transmission power, and increase with the number of multicast terminals and OFDM symbols in an OFDMA frame. © 2017 Global IT Research Institute - GiRI.

Yu Z.,China Academy of Railway Sciences
MATEC Web of Conferences | Year: 2017

A model is used to examine the influence of chemical composition on the vaporization rate of LNG during spreading. Calculations have been performed whereby the vaporization rate of the LNG mixtures has been compared to the vaporization of pure methane under the initial conditions. The detailed results indicate that the vaporization rate LNG mixture is different to that of pure methane. LNG as the liquid mixture gets rich in ethane and isobaric latent heat increases rapidly, leading to the rate vaporization of LNG decrease in compared to pure methane. © The Authors, published by EDP Sciences.

Zheng X.,China Academy of Railway Sciences
Zhongguo Tiedao Kexue/China Railway Science | Year: 2017

In order to further study polymer grouting uplift technology for repairing the settlement of ballastless track structure for high speed railway, by simulating the gravity back pressure at the uplift of ballastless track structure, the expansion characteristics of polymer grouting material cured under pressure and the mechanical properties of its consolidated body were investigated. The foam structure of consolidated body was analyzed by scanning electron microscope (SEM). Results reveal that, under the condition of back pressure forming, the expansive force of polymer grouting material is basically zero before rise time (0~10 s). It increases rapidly from rise time to surface drying time (10~20 s) and approximately tends to be stable after surface drying time (20 s). The expansive force of polymer grouting material grows with the increasing amount of polymer grouting. Meanwhile, the density of its consolidated body increases and the foam occupied volume reduces. Both the compressive strength and elastic modulus of consolidated body increase linearly. By adjusting the injection amount of polymer grouting material, the needed uplift force can be achieved for ballastless track with different restraining forces. The stress of the consolidated body of in-service polymer grouting material cured under pressure is in the elastic stage. The elastic modulus of consolidated body is equivalent to that of the graded crushed stone on subgrade bed surface and can together bear the load. © 2017, Editorial Department of China Railway Science. All right reserved.

Sun J.,China Academy of Railway Sciences
Zhongguo Tiedao Kexue/China Railway Science | Year: 2017

Taking the following two examples, the multi span continuous bridge in two ends of XinWeiNan Railway Station in Zheng-Xi passenger dedicated line and seamless turnout on variable width bridge, we use general finite element software MIDAS/CIVIL to establish finite element model of single and crossing line seamless turnout and bridge on Weinan North Railway Station bridge. The Interaction of seamless turnout and bridge under the action of temperature field is studied. Results illustrate that under the action of temperature load, the longitudinal displacement of single and crossing line turnout rail is much larger than the transverse displacement. The maximum lateral displacement is between 1 to 2 mm and the maximum longitudinal displacement is between 20 to 30 mm, but both of them are less than the rail displacement allowed value of 40 mm, having a large residual quantity. The maximum temperature longitudinal force of single and crossing line turnout rail is 1 303 and 1 340 kN, all occur in 20 m range near continuous beam crevice. So, regional monitoring and maintenance should be strengthened in order to prevent the rail expansion in summer and rail breakage in winter. A proper reduction of fastening resistance in beam crevice is advised. The transverse displacement of single and crossing line turnout beam are very close and smaller, the maximum values are 2.7 and 2.8 mm. Their longitudinal displacement has large difference, the maximum values are 5.3 and 26.8 mm, which are all located at beam end. The rail temperature deformation of seamless turnout has little influence on longitudinal, transverse displacement of bridge. The deformation of bridge is caused by the beam average temperature rise. In conclusion, the influence of temperature force of turnout should not be focused too much in bridge maintenance and repair process. © 2017, Editorial Department of China Railway Science. All right reserved.

Ma C.,China Academy of Railway Sciences
Zhongguo Tiedao Kexue/China Railway Science | Year: 2017

To control the converter with high power level and low switching frequency, the mathematical model of double-phase dual four quadrant converter (4QC) is established for analyzing the electrical characteristics of converter main circuit. Considering the line resistor, a double closed-loop control method, which includes a voltage outer loop and a current inner loop, is introduced to control the modulation voltage of 4QC. A carrier phase shifting method based on doubling control frequency is proposed, which can reduce lower order harmonics on traction power network side without extra hardware device, combining with Sine Pulse Width Modulation (SPWM) technology, it can also control converters with various switching frequencies. Based on the platform with TMS320F28335 DSP chip, a control software which consists of initializing program, serial communication service program and periodic interrupt program is designed, and is verified on a back-to-back power-fed test bed. Test results demonstrate that, controlled by the proposed control methods for 4QC, the converter with high power-level and low switching frequency shows a smooth change of current during start-up, can operate with full load and unity power factor during traction and braking modes. During the test, the ripple wave of intermediate voltage is small, the input current acts without any abnormity, the lower order harmonics on the power network side and THD are also dramatically decreased. © 2017, Editorial Department of China Railway Science. All right reserved.

Bai L.,China Academy of Railway Sciences
Proceedings - 2016 International Conference on Network and Information Systems for Computers, ICNISC 2016 | Year: 2017

Along with the large scale construction of urban rail transit and the application of computer science in the transportation industry, the reasonable, accurate urban rail transit passenger flow prediction has important significance for the line construction benefit analysis, transportation scheme evaluation, passengers monitoring, and emergency response and so on. This paper studies the current integrated prediction method and calculation model system, analyzes the National Day holiday passenger flow data characteristic of Guangzhou Metro Line 5, and proposes a passenger flow prediction method combined the time series model and regression model. And then the results through experiment and demonstration shows that the model can obtain the better forecast precision. This algorithm has strong practical significance for urban rail transit passenger flow short-term and abnormal forecast. © 2016 IEEE.

Luo X.,China Academy of Railway Sciences | He F.,China Railway Southeast Research Institute Co.
Modern Tunnelling Technology | Year: 2014

Water bursts are one of the most serious geological disasters that can occur during the construction of long deep-buried tunnels, and their occurrences are closely related to the aquifer ahead of the working face or outside the free face. In this paper, the causes of water burst occurrences in long deep-buried tunnels are analyzed. Five kinds of structures and models are systematically presented: a highly fractured zone at upper wall of an uncemented and water-rich compressive fault; an uncemented and water-rich tensional fault zone; an uncemented and water-rich faulted bedding plane (a closely jointed rock mass); water-filling karst; and an underground water-bearing syncline structure and its water burst model. Moreover, disasters that occurred in five kinds of structures are analyzed through examples.

Li Q.,Beijing Jiaotong University | Ren S.,China Academy of Railway Sciences
IEEE Transactions on Instrumentation and Measurement | Year: 2012

Discrete surface defects impact the riding quality and safety of a railway system. However, it is a challenge to inspect such defects in a vision system because of illumination inequality and the variation of reflection property of rail surfaces. This paper puts forward a real-time visual inspection system (VIS) for discrete surface defects. VIS first acquires a rail image by the image acquisition system, and then, it cuts the subimage of rail track by the track extraction algorithm. Subsequently, VIS enhances the contrast of the rail image using the local normalization (LN) method, which is nonlinear and illumination independent. At last, VIS detects defects using the defect localization based on projection profile (DLBP), which is robust to noise and very fast. Our experimental results demonstrate that VIS detects the Type-II defects with a recall of 93.10% and Type-I defects with a recall of 80.41%, and the proposed LN method and DLBP algorithm are better than the related well-established approaches. Furthermore, VIS is very fast with a linear computational time complexity, and it can be in real time to run on a 216-km/h test train under our experimental setup. © 1963-2012 IEEE.

China Academy of Railway Sciences | Date: 2012-08-28

A ballastless track system comprises a base; a track slab arranged above the base; a poured-field layer arranged between the base and the track slab, the poured-field layer being formed by filling self-compacting concrete, emulsified asphalt cement mortar or resin mortar, and the inside of the poured-field layer being of a steel bar structure; a connecting piece, the first end of the connecting piece extending into the track slab, and the second end of the connecting piece extending into the poured-field layer; and two rows of rail-seat arranged on the track slab in parallel; and rails arranged on the rail-seat. The ballastless track system is high in reliability, good in durability, and easy in construction and maintenance.

China Academy of Railway Sciences | Date: 2011-12-15

Provided in the disclosure is a pre-stressed concrete track slab of slab-type ballast-less track, which includes a slab body (1), on which fastening embedded casings (4) are arranged. At least one row of longitudinal common steel bars (11) and at least one row of transverse common steel bars (12) are arranged in the slab body (1) along a length direction and a width direction. The longitudinal common steel bars (11) are insulated from the transverse common steel bars (12). At least one row of longitudinal pre-stressed steel bars (7) and at least one row of transverse pre-stressed steel bars (6) are fastened in the slab body (1) along the length direction and the width direction through anchor backing plates and fastener devices (8). In the pre-stress directions of the longitudinal pre-stressed steel bars (7) and the transverse pre-stressed steel bars (6), it is post-tensioned in both directions or it is pre-tensioned in one direction and post-tensioned in the other direction. Limiting structures (5) and grounding terminals (10) are also arranged on the slab body (1). The pre-stressed concrete track slab has the characteristics of light structural dead weight, small structure height, low manufacturing cost and deformation resistance.

Loading China Academy of Railway Sciences collaborators
Loading China Academy of Railway Sciences collaborators