Zhou C.,Central South University |
Tang J.-T.,Central South University |
Ren Z.-Y.,Central South University |
Xiao X.,Central South University |
And 2 more authors.
Chinese Journal of Geophysics (Acta Geophysica Sinica) | Year: 2015
In the range 1- to 5 kHz, so called the audio magnetotelluric (AMT) 'dead band', signal power of the natural electromagnetic field has low values. It leads to the distortion of the impedance data and may cause misinterpretation. It is difficult to correct the distortion data with time series or power spectrum data processing methods. With a large number of experimental data, the Rhoplus method can be used to obtain a reasonable result. A series of AMT observation experiments were accomplished using the Phoenix MTU-5A instruments. The AMT data was recorded in different seasons and different days, some data was recorded both in day and night. On the basis of these data, firstly the distortion characteristics of AMT 'dead band' data were analyzed by using signal power, signal coherence, apparent resistivity, phase and phase tensor. Secondly the Rhoplus technique is applied to correct the distortion data. Its applicable conditions, processing scheme and key detailed techniques are presented. Finally, a large amount of data, including six sites and a test line, are provided to demonstrate the effectiveness of the method. The experiments show that the natural electromagnetic signal strength is rather low and the coherences of the orthogonal electromagnetic field components are low in the AMT 'dead band', which lead to the distortion of the impedance apparent resistivity, phase and phase tensor data. The frequency range of AMT 'dead band' distortion can be wide upto 10 k~100 Hz of which 5 k~1 kHz is most obvious generally. The effect of the distortion is closely related to the observation time and more serious in autumn and winter than summer, and more serious in the daytime than nighttime. The processing results show that when the main noise in the AMT 'dead band' is incoherent noise, the distorted data can be picked out automatically by using the coherence threshold value, and the Rhoplus method can obtain a good result that is consistent with the undistorted reference data which is observed in the night time or summer season. When the main noise in the AMT 'dead band' is coherent noise, the distorted data can be picked out manually by the interactive processing, the Rhoplus method can obtain a good result that is consistent with the undistorted reference data too. For the case of distorted data has no manifestation distinction with the undistorted data, the Rhoplus method can identify the distortion and correct it by using the high quality data in the frequency band over or under the AMT 'dead band'. For the case of distorted data has a wide distortion band and poor quality, the Rhoplus method can be effective too by using the limited high quality data at some frequencies. AMT impedance apparent resistivity, phase and phase tensor data in the so called AMT 'dead band' may distort when observations are conducted in the daytime of autumn or winter season. The distorted data can be corrected effectively by the Rhoplus method, the combined data selection strategy of the coherence threshold value and interactive processing is fast and objective, the result curves are smooth and corrected data can be basically in line with undistorted observation data. © 2015, Science Press. All right reserved.
Zhou Y.,Wuhan Naval University of Engineering |
Li H.,Wuhan Naval University of Engineering |
Wang W.,Power China Zhongnan Engineering Corporation Ltd |
Cao Q.,Wuhan Naval University of Engineering |
Zhou S.,Wuhan Naval University of Engineering
Journal of Electrical Engineering and Technology | Year: 2015
This paper presented an improved analytical method for calculating the open-circuit magnetic field in the surface-mounted permanent magnet machines accounting for slots and eccentric magnet pole. Magnetic field produced by radial and parallel permanent magnet is equivalent to that produced by surface current according to equivalent surface-current method of permanent magnet. The model is divided into two types of subdomains. The field solution of each subdomain is obtained by applying the interface and boundary conditions. The magnet field produced by equivalent surface current is superposed according to superposition principle of vector potential. The investigation shows harmonic contents of radial flux density can be reduced a lot by changing eccentric distance of eccentric magnet poles compared with conventional surface-mounted permanent-magnet machines with concentric magnet poles. The FE(finite element) results confirm the validity of the analytical results with the proposed model. © The Korean Institute of Electrical Engineers
Yuan J.,Changsha University of Science and Technology |
He Y.,Power China Zhongnan Engineering Corporation Ltd |
Liu J.,Changsha University of Science and Technology
Journal of Performance of Constructed Facilities | Year: 2016
Red clay is a common roadbed filler in China. In southern China, because of the high natural moisture content, it is hard to make enough compact clay in the process of roadbed filling construction, and it shrinks and cracks when dehydrated. This article compares the domestic regional soil properties of red clay in China, analyzing its physical properties, composition, chemical properties, and water characteristics, and the filler used in the construction of the Dongxin expressway. Swelling of the red clay packing was also observed. According to laboratory tests, field test analyses, and settlement observation tests, when using red clay as road filler, the use of a smooth bump grinding wheel and rolling of subgrade compaction works best for controlling moisture content, with the wet compaction test method within the range of ±5% of optimum moisture content. This method can ensure the strength and stability of the subgrade to provide guidance for the use of red clay in construction. © 2015 American Society of Civil Engineers.
He J.,Hunan University |
He J.,Power China Zhongnan Engineering Corporation Ltd |
Zhang J.,Hunan University |
Li G.,Hunan University |
Guo S.,Hunan University
Advances in Science and Technology of Water Resources | Year: 2016
The boundary face method (BFM), combined with a fast algorithm, was applied to transient heat conduction analysis of concrete dams during the pouring process, so as to predict the temperature distribution and its time history in concrete dams during the construction process. Using the time convolution method to compute the time integration and the Taylor series expansion method to separate the spatial variables and time variables in fundamental solutions, the spatial variable integrals can be calculated and stored at the same time, improving the calculation efficiency of the convolution integral. A case study shows that the temperature distribution obtained by the fast BFM agrees with the results of the finite element method, demonstrating the feasibility of application of the fast BFM to transient heat conduction analysis during the actual dam construction process. © 2016, Editorial Board of Advances in Science and Technology of Water Resources, Hohai University. All right reserved.
Zhou M.,Power China Zhongnan Engineering Corporation Ltd |
Dai G.-L.,Central South University
Tiedao Xuebao/Journal of the China Railway Society | Year: 2015
A finite element analysis model was established on the stability of longitudinally connected ballastless slab track on simply-supported beam bridges of high speed railway. In this model, solid finite elements were used to simulate track structure; contact elements were applied to simulate the contact constraint relationship between adjacent layers; compression bar elements were used to simulate the support of bridges to the track; nonlinear spring elements were applied to simulate the constraint of pigeonhole type lateral chock blocks on track structure. The correctness of the model was verified through theoretical calculation. On the basis of this, constraints between layers, section stiffness of mortar layer and the layout of pigeonhole type lateral chock blocks on the stability of longitudinal connected ballastless slab track were compared. The research showed that the basic assumptions of traditional stability calculating methods did not match the practical conditions, and the caculating results tended to be unsafe. The nonlinear constraint relations between layers must be calculated during the stability analysis of the track structure. The weaker the constraint between the layers was, the worse the stability of the track structure. The track structure lost its stability when the temperature of the longitudinally connected ballastless slab track rose to 18.9℃ if pigeonhole type lateral blocks were not installed. The spacing between adjacent blocks should not be more than 18.3m when the maximum permissible temperature of track structure was 30℃. The stability of track structure can be effectively improved by improving the quality of mortar layers and reducing the spacing between adjacent blocks. ©, 2015, Science Press. All right reserved.