Journal of Xi'an Jiaotong University 

About: Journal of Xi'an Jiaotong University is an academic journal. The journal publishes majorly in the area(s): China & Heat transfer. It has an ISSN identifier of 0253-987X. Over the lifetime, 1166 publications have been published receiving 2597 citations.

Direct Numerical Simulation of Turbulent Flow and Heat Transfer in a Square Duct Rotating along Its Spanwise Direction

Abstract: Turbulent flow and heat transfer in a square duct rotating along its spanwise direction is investigated by direct numerical simulation.The spatial terms in the governing equations are discretized by second-order central difference scheme and the time terms are discretized by the Adams-Bashforth scheme.The influence of rotation on the streamwise velocity,crosswise velocity and the mean temperature is analyzed.The results show that the mean velocity and the mean turbulent kinetic energy decreases with the increase of rotation number when the centrifugal buoyancy force is neglected.The mean turbulent kinetic energy of Roτ=1.5 decreases by 15 percent compared with that of Roτ=0.If the effect of the centrifugal buoyancy force is taken into account,for the radially outwards flow,the mean velocity and turbulent kinetic energy increase with rotation number compared with those without the effect of centrifugal force,and the results are converse for the flow radially inwards.It is found that the mean turbulent kinetic energy increases by 17 percent for the radially outwards flow at Roτ=1.5 compared with that of Grτ,L=0,but it decreases by 43 percent for the flow radially inwards.

Loess and Environment

Abstract: The loess highland, which lies on the land surface of the earth where human beings lived in the past and are living at present, is one of origin of the national culture of China. It is one of the three archive banks of contemporary climate environment. When carrying out research taking the contemporary sand storm as a reference to the formation process of loess, the loess highland is a huge natural laboratory. In the study of the loess highland made by Chinese geologists, the cipher of the loess highland has been decoded on six larger scales, thus recognizing in depth the situation of global geological change of mankind. Viewing from the present record, the human global change must be an accelerated global change but we are able to control its speed and scale so as to obtain reasonable sustainable development. 

A Roberts' Adaptive Edge Detection Method

Abstract: An adaptive edge detection method is proposed for the sensitivity to noise and given threshold of existing Roberts algorithmsThe basic principle of the Roberts algorithm is used and the direction of the detection is expandedThe algorithm generates automatically adaptive threshold according to the mean value of the 3×3 area pixels around the detecting pixel and the property of people's visionIt not only can keep advantages of existing Roberts algorithm such as parallel process,fast calculation speed and the comparatively thin edge,but also can play a certain part in restraining noiseBecause the edge detected by Roberts algorithm is comparatively thick,and the efficiency of the edge-thin algorithm is lower,the edge-thin algorithm is analyzed and improvedThe improved algorithm detects the edge of the image where there exists noise,filters the fake edge,then thins the edge of the image,and finally gets the single pixel edgeBy comparing the test results of the adaptive edge detection algorithm with those of the existing Roberts algorithm,the adaptive edge detection method can generate automatically adaptive threshold,improves the performance in getting detailed-edge and restraining noise

An Improved Weighted Centroid Location Algorithm

Abstract: A weighted centroid location algorithm is proposed to improve location precision by using received signal strength indication(RSSI)ratio(RR-WCL).In the RR-WCL algorithm,the anchor nodes send their own information periodically,and the unknown nodes only record the RSSI mean values sent from the same anchor node.When the number of beacon messages that an unknown node received is larger than the threshold,the unknown node will establish a collection of anchor nodes,a collection of signal strength and a collection of anchor nodes'locations.Then the RSSI ratios received from anchor nodes are used as weights to determine the position of an unknown node.The results obtained from simulation and real-system experiments show that the environment has little impact on the performance of locating.Moreover,there is an improvement of 6.4% to 37.25% in location precision compared with the centroid location algorithm and 5.12% to 11.23% in location precision compared with the weighted centroid location algorithm when the number of anchor nodes increases.

Independent Component Analysis and Manifold Learning with Applications to Fault Diagnosis of VSC-HVDC Systems

Abstract: A fault diagnosis scheme for voltage source converter-high voltage direct current transmission(VSC-HVDC) system is proposed based on the independent component analysis(ICA) and the locally linear embedding(LLE) in the present work.The measured signals in the VSC-HVDC can not be used directly to detect system fault due to the heavy inference noise.The FastICA is hence employed to eliminate the disturbed noise and recover the fault sources from the measured DC line voltage and current observation signals.Then the LLE algorithm is applied to extract distinct characteristics hiding in the recovered fault signals.To enhance the fault pattern recognition,the support vector machine(SVM) is adopted to learn the relationship between the fault features and the system operation conditions.The ability of the proposed ICA-LLE method to detect VSC-HVDC system fault is evaluated with the simulated data.The analysis results demonstrate the feasibility and effectiveness.The distinguished features of the fault signals,such as AC line-to-line fault and AC line-to-ground fault,and the compound faults,can be extracted efficiently and then isolated in the 3-D feature space correctly.The classification rate of the SVM with the proposed scheme is increased by 20% compared with LLE.