Table of Content

25 January 2018, Volume 46 Issue 1

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Power & Electrical Engineering

Effect of Magnetic Nano-Fluids on CHF Characteristics of Saturated Boiling of Microchannels

LUO Xiaoping LI Haiyan TANG Yang WU Di

2018, 46(1):  1-8.  doi:10.3969/j.issn.1000-565X.2018.01.001

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The deionized water and w(Fe₃O₄) =0. 5% of magnetic nano-fluids were taken as the working fluids to perform saturated flow boiling transfer heat experiments in the three different sizes of rectangular micro-channels．And the effect on the characteristics of CHF by nano-fluids was considered mass flow rate and magnetic field in the process of the flow boiling transfer heat was explored． The experimental results shows that the CHF values of deioni-zed water and 0. 5% magnetic fluid both increase with the increased mass flow rate． And the increase of CHF value is relatively obvious when the mass flow rate is low． The CHF values of 0. 5% of magnetic nano-fluids can be in-creased by approximately 71% ～157% than deionized water when there is no magnetic field． The CHF values of 0. 5% of magnetic fluid increase with magnetic field strengthening and the increase rate is about 4% ～ 17. 4%．Compared the experimental values with the predicted values of Kosar model，the MAE values of deionized water and magnetic fluid are 25% and 30% respectively． After the modification of Kosar model，the MAE values are both less than 15%． Obviously，the prediction of the experimental results is improved．


Multiple-Relaxation-Time Lattice Boltzmann Model for Convection Heat Transfer in an Inclined Porous Media

LI Peisheng LI Wei ZHANG Ying SUN Jincong WANG Zhaotai

2018, 46(1):  9-17.  doi:10.3969/j.issn.1000-565X.2018.01.002

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A non-orthogonal multiple-relaxation-time lattice Boltzmann model is developed for simulating convection heat transfer in an inclined cavity filed with porous media at a representative elementary volume scale． The numeri-cal stability and computational efficiency of the Bhatnagar-Gross-Krook (BGK) model and the multiple relaxation model (MRT) are analyzed and compared by means of selecting the typical flow and heat transfer problems． It's found that present numerical results are well congruous with the previous results． Then simulation is performed in the convective heat transfer in inclined cavity，and the influence of porosity ε (ε =0. 4，0. 6，0. 9)，Darcy num-ber (Da =10^-4 ，10^-2 )，Ｒayleigh number (10⁴ ≤Ra≤10⁷) and inclined angle θ ( －180°≤θ≤180°) is dis-cussed on the convective heat transfer． The results indicate that the non-orthogonal MRT-LB model has good numeri-cal stability and convergence speed when low viscosity is dealt with． Average Nusselt number at hot sidewall pre-sents the symmetrical distribution of M type with the change of inclined angle and obtains the extreme value in the specific inclination interval． With the Darcy number，Rayleigh number increasing，the maximum average Nusselt number corresponding angle presents hysteresis phenomenon． The average Nusselt number discontinues change at low Ra number． The power function relation of the average Nusselt number with Ra^* number (Ra^* = DaRa) is obtained．


A Method of Smoke Exhausted under Semi-Transverse Ventilation in the Tilted Tunnel Fire

LOU Bo QIN Rifu QIU Yonghai

2018, 46(1):  18-25.  doi:10.3969/j.issn.1000-565X.2018.01.003

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The research on the method of smoke exhausted in sloping tunnels is helpful to the rescue and escape for crew in the tunnel fire． In order to explore the method of smoke exhausted in the tilted tunnel fire under the condition of semi-transverse ventilation，the numerical simulation is adopted to simulate the process of tunnel fire in this paper，and then analysing the rule of the coefficient of λ (uniformity coefficient of smoke exhaust range) and α (the thermal efficiency of smoke exhaust) in different smoke-exhaust methods． Ｒesults show that when the slope is 0. 0% ～1. 5%，the standard of smoke exhaust can control the smoke to spread effectively in the tunnel; When the slope is 1. 5% ～3. 0%，smoke along the down-slope direction can be controlled near to exhaust port due to the effect of buoyancy，so the method of unilateral smoke exhaust in the upslope direction is adopted to exhaust effectively and improve heat effi-ciency of smoke exhaust of fans; But when the slope is more than 3. 0%，the smoke exhaust rapidly escape from ex-haust port and spread to the tunnel exit because of the chimney effect which makes the smoke exhaust in the tunnel spread with tremendous speed，so longitudinal ventilation should be added to restrain the reflux of smoke exhaust in the upslope direction，which restricts the spread of the smoke exhaust more effectively．


Application of Singular Value Decomposition to Pattern Recognition of Partial Discharge in Cable

NIU Haiqing WU Juzhuo GUO Shaofeng

2018, 46(1):  26-32.  doi:10.3969/j.issn.1000-565X.2018.01.004

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Aiming at pattern recognition of on-line partial discharge (PD) monitoring，the wavelet packet coeffi-cient matrix is constructed on the basis of wavelet packet decomposition of de-noised PD signal after the wavelet packet decomposition of de-noised partial discharge signal is done． Then，by the singular value decomposition of the wavelet packet coefficient matrix，the singular value energy percentage is defined as the feature vector of the partial discharge signal． Two classifications of the supportive vector machine are extended to multi one by M-ary al-gorithm，and the particle swarm optimization algorithm is used to optimize the parameters of supportive vector ma-chine． Finally，input is regarded as the feature vectors，supportive vector machines are used to recognize 4 kinds of discharge signals，and a comparison of recognition effect is made by means of BP neural network． The results show that the feature vector of the singular value energy percentage can reflect the characteristics of the original signal well． Based on supportive vector machines，the discharge signals can be effectively identified with a 95% average recognition rate． And with the increase of decomposition scale，the average recognition rate of 4 kinds of discharge signal increases，but the increment decreases． Supportive vector machine and BP neural network can well identify 4 kinds of discharge signals，and the former has a better recognition effect．


The Neutral Point Potential Regulation of Three-Level Inverter Based on the Deadbeat Control Algorithm

YAO Yuan KANG Longyun ZHANG Zhi FENG Yuanbin CHENG Jiancai

2018, 46(1):  33-40.  doi:10.3969/j.issn.1000-565X.2018.01.005

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In this paper an exploration is performed into midpoint potential migration of NPC three-level inverter and the midpoint potential fluctuation． On the basis of the analysis of the voltage vectors and the midpoint potential，a mathematical model is constructed under the deadbeat control framework． In order to keep the ability to fix the drifted midpoint potential，the virtual voltage vector method is employed． In the proposed algorithm，the vectors applied to modify the midpoint potential are evaluated accordingly． Compared with the conventional algorithm，the time needed to fix the midpoint potential is decreased in this proposed algorithm，and the ability to fix the midpoint potential is in-sensitive to the modulation index． Moreover，the proposed algorithm can eliminate the oscillation of the midpoint po-tential． The validity of the proposed algorithm is verified by the simulation and experiments．


Traffic & Transportation Engineering

Thrust Characteristics of Ducted Propeller under the Effects of Cavities

WU Jiaming ZHANG Enwei ZHONG Le

2018, 46(1):  41-49.  doi:10.3969/j.issn.1000-565X.2018.01.006

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The numerical model based on dynamic and sliding mesh technique combined with cavitation model is applied to simulate the hydrodynamic behavior of a ducted propeller running at high rotating velocity in a linear mo-tion on the effects of cavitation，the growth and development of cavitation of the propeller in a linear motion are ob-served，the cavity effects on surrounding flow fields and propeller thrust when the propeller is in a linear motion are investigated，and the influences of different rotating velocities and linear velocities on thrust characteristics of the ducted propeller in cavitation environment are analyzed． Ｒesults indicate that (1) the growth and development of cavitation on the propeller blade and the hydrodynamic behavior variations caused by the cavitation can be simulated objectively with the numerical approach combined with cavitation model when the propeller is at high rotating velo-city; (2) the maximum relative error between numerical and experimental results with cavity effects is smaller than that without cavity effect，the higher the advanced velocity or the rotating velocity is，the more significant the diffe-rence exists between them; (3) the effects of cavitation on the hydrodynamic characteristics are not only confined to suction surface，but also on high pressure blade surface．


Short-Term Forecasting of Subway Traffic Based on K-Nearest Neighbour Pattern Matching

LIN Peiqun CHEN Litian LEI Yongwei

2018, 46(1):  50-57.  doi:10.3969/j.issn.1000-565X.2018.01.007

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In order to forecast the subway traffic accurately and better the vehicle scheduling and site management，a short-term forecasting of subway traffic based on K-nearest neighbour pattern matching is proposed． By analyzing the subway traffic data，it is found that the day passenger flow development mode of subway has a certain law．Thus，an adaptive K acquisition algorithm based on the calculation of error rate is proposed，it can improve the uni-versality of the prediction algorithm by automatically obtaining the appropriate K． Finally，Guangzhou South Rail-way Station is taken as an example for the case study． The experimental results show that the method proposed is applicable to the subway passenger flow forecast of two different modes of traffic-holidays and non-holidays，its ave-rage prediction accuracy is about 90%． It can be seen that this method has a good application value．


ptimizing Last Train Timetable for Urban Rail Transit Based on Dynamic Accessibility

YAO Enjian LIU Wenting LIU Shasha YANG Yang

2018, 46(1):  58-65.  doi:10.3969/j.issn.1000-565X.2018.01.008

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The research of urban rail transit dynamic accessibility and last train timetable is the basis for optimizing the transfer between last trains in different lines and maximizing transportation benefits． First，urban rail transit dy-namic accessibility is defined from three dimensions such as stations，transit lines，and the whole network，based on the static network topology and dynamic passenger flow． Second，dynamic accessibility indicators of Guangzhou rail transit network is evaluated through assigning the dynamic passenger flow data to the whole network． Finally，aiming at maximizing dynamic accessibility，a last train optimizing model is proposed，taking into consideration the departure time constraint of the last trains for all lines，and a genetic algorithm is applied to solve the optimization problem． Taking Guangzhou subway network for the case study，the analysis shows that static accessibility and dy-namic accessibility of Guangzhou rail transit network increased by 20. 29% and 10. 97percentage points respectively after the adjustment of the last train timetable，which indicates that the optimized last train timetable can effectively improve transport capacity．


A Construction Approach Based on Kinematic Simulation Environment for Networked Intelligent Vehicles

CHAI Linguo CAI Baigen SHANGGUAN Wei WANG Jian WANG Huashen

2018, 46(1):  66-77.  doi:10.3969/j.issn.1000-565X.2018.01.009

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A novel approach based on kinematic simulation environment of networked intelligent vehicle is proposed in this paper． Functionality relevant to kinematics of networked intelligent vehicles can be verified via simulation on the basis of proposed approach． Intersections are adopted as the main elements composing the road network and all the roads are classed as connection between two different intersections． Properties of intersections and vehicles are defined and approaches of realization for vehicle kinematic models in the simulation environment are designed． Ve-hicle-positioning deviation based on Gaussian distribution is given and uniform and Ｒayleigh distribution on the ba-sis of communication delay in the process of simulation are introduced to enhance the simulation reality． A series of simulation is conducted to prove the reliability of the simulation environment． Vehicle delay presents the same tend-ency to HCM 1994 vehicle delay model in different volumes to capacity ratio． The distribution of distance between two vehicles when pre-warning is generated is subject to the uncertainty models． A slot-based intersection control method is implemented so that the approach to kinematic function of networked intelligent vehicle is verified．


Path Following Control of Intelligent Vehicles Considering Lateral Stability

LIN Fen NI Lanqing ZHAO Youqun ZHANG Huada ZHANG Huiqi WANG Kaizheng

2018, 46(1):  78-84.  doi:10.3969/j.issn.1000-565X.2018.01.010

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For the problem of path following in autonomous vehicles，the traditional position deviation control me-thod used to neglect the dynamic stability of vehicle． To solve this problem，a control method taking into account the lateral stability of path-following is proposed． Firstly，2-DOF vehicle dynamics model and path-following error model are established． Secondly，taking into consideration the position of vehicle and the state of vehicle dynamics，the desired yaw rate is generated through the use of the back-stepping feedback dominance back-stepping (FDB)．After that，an integrated control strategy of active front steering (AFS) and direct yaw moment control (DYC) based on LQT (linear quadratic tracker) are designed． Next，the ideal control inputs (front wheel angle and yaw moment) are obtained，and the desired yaw rate and sideslip angle is thus tracked accurately． Finally the proposed method is verified in the Simulink environment． The simulation results show that the proposed control method has good lateral stability in path tracking． Compared with the method without considering the lateral stability，the me-thod proposed has higher tracking accuracy in the process of path tracking，the sideslip angle of the vehicle is smal-ler，and the yaw rate can better track the desired value．


Comprehensive Performance Optimization of PHEV Considering CVT Ｒatio Jumping in Mode Switching Process

QIN Datong LIU Xingyuan LUO Song

2018, 46(1):  85-90,111.  doi:10.3969/j.issn.1000-565X.2018.01.011

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Aimed at the single motor plug-in hybrid electric vehicle with CVT，an optimal control strategy for vehi-cle comprehensive performance is proposed． The CVT target speed ratio of each working mode is obtained through the optimization of system efficiency so that the vehicle energy consumption is improved． In order to solve the pro-blem of the vehicle ride comfort variation caused by the change of target speed ratio in mode switching，the vehicle ride comfort is adopted for improvement by limiting the change rate of CVT speed ratio，which，however，will pro-duce an effect on the speed of a car in its desired speed following． Therefore，by using PID controller which com-pensates the motor torque，a weighting function formed by the fuel economy，ride comfort and speed following is constructed，the parameters of PID controller based on Genetic Algorithm are optimized under the New Europe Dri-ving Cycle and multi-objective comprehensive evaluation through comparison between and analysis of the simulation results of a vehicle is conducted． The simulation results demonstrate that the method can effectively improve the ve-hicle comprehensive performance，including fuel economy，ride comfort and speed following．


Study on the Influence of Anisotropy Air Voids Structure in Porous Asphalt Mixture on Seepage Characteristics

XIAO Xin ZHANG Xiaoning

2018, 46(1):  91-96.  doi:10.3969/j.issn.1000-565X.2018.01.012

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In order to study the influence of anisotropy air voids structure in porous asphalt mixture on seepage characteristics，the theory of Darcy Law was adopted． Air voids micro-distribution characteristics of porous asphalt mixture are obtained on the basis of industrial CT，seepage flow numerical model of porous asphalt mixture is estab-lished and the internal flow characteristics of water within porous asphalt mixture are analyzed by the finite volume method． In the meantime，a cuboid test-piece is designed as a representative volume element to describe the anisot-ropy permeability performance of the porous asphalt mixture． The results demonstrate that the porous asphalt mix-ture features an uneven distribution in light of air voids，denser connecting air voids and larger area per single air void in horizontal direction than that in vertical direction． The results also indicate that because of the anisotropy of air voids，the permeability performance of the mixture sample also features anisotropy，the permeability coefficients in two horizontal directions tend to be very close，which are about two times those of the vertical directions． Thus in terms of the analysis of the permeability performance，the porous asphalt mixture can be considered as isotropy hori-zontally or as anisotropy when analyzed both horizontally and vertically．


Computer Science & Technology

A Fast Iris Image Reconstruction Algorithm using LLE and PSO

WO Yan WU Jiaqian

2018, 46(1):  97-102.  doi:10.3969/j.issn.1000-565X.2018.01.013

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Because of its efficient identification performance, Iriscode has been widely used in iris recognition systems. With the emphasis on biosafety security, how to reconstruct the iris image from Iriscode to judge the safety of iris recognition system has become a research hotspot. In this paper, we analyze the problem of reconstructing iris images from Iriscode, construct an iris reconstruction optimization model and propose a two-stage fast iris reconstruction algorithm. We regard the process of extracting Iriscode as the dimensionality reduction process. In the first stage, some inexact iris reconstruction images are reconstructed according to the neighborhood of the given Iriscode using locally linear embedding algorithm. In the second stage, we use the particle swarm optimization algorithm and the inexact iris images obtained in the previous stages as the initial particle to perform the iterative search to search the accurate result. Experiments show that the reconstructed iris images obtained by the proposed algorithm can achieve the purpose of forging attack through the iris recognition system. Compared to other reconstruction algorithms, there is an increase in time consuming and accept rate of the reconstructed image.

Research on Video Description Based on Adaptive Frame Sampling Algorithm and Bidirectional Long Short-Term Memory

ZHANG Ｒongfeng NING Peiyang XIAO Huanhou SHI Jinglun QIU Wei

2018, 46(1):  103-111.  doi:10.3969/j.issn.1000-565X.2018.01.014

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Video to text is a new challenging task in the field of computer vision. Focusing on this technical difficulty, this paper proposes an adaptive sampling algorithms and employs the Bidirectional Long-Short Term Memory (BLSTM) model and deep BLSTM based on the video features extracting by deep Convolutional Neural Networks. Since this doubly deep networks structure can learn the spatial and temporal correlation description of the videos, it is able to obtain the global dependency information from space and time domain. Experimental results showed that by using the datasets of M-VAD and MPII-MD, the proposed framework could achieve the average score of 7.8 and 9.1 in METEOR, respectively. Comparing to the original S2VT model, the proposed method outperformed 15.7% and 28.2% by average score and it also improved the descriptions of the videos.

Transfer Learning for Classification on Imbalanced Data

CHEN Qiong XU Yangyang CHEN Linqing

2018, 46(1):  122-130.  doi:10.3969/j.issn.1000-565X.2018.01.016

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Traditional classification algorithms based on the balance data meet some challenges, when data distribution become more and more imbalanced. Transfer learning can solve the problem of imbalanced data distribution by using the relevant auxiliary data sets to compensate the imbalanced target data set. In this paper, we proposed the UnbalancedTrAdaboost(UBTA) binary classification algorithm based on TrAdaboost, which calculates the weights of weak classifiers usingthe auprc (the Area Under the Precision-Recall Curve) of different classes and updates the weights of misclassified data of different classes with different mechanisms. The AUC measure is more accurate combined with G-mean and BER when evaluated the unbalanced classification, since AUC is insensitive to changes in class distribution. The results of these three metrics indicate that, the UBTA algorithm achieves better performance for imbalanced data and classifies more minority instances with the high accuracy of majority instances.

High Accurate Contour Vision Algorithm Based on Shape Context and ICP

LIU Yu SUN Kun XIE Hongwei

2018, 46(1):  131-138，144.  doi:10.3969/j.issn.1000-565X.2018.01.017

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In order to solve the problems of high precision contour measurement with arbitrary shape, a high accurate vision algorithm is proposed based on shape context descriptor and iterative closest point (ICP). Firstly, the sub-pixel edge of workpiece is extracted by using edge extraction algorithm based on local area, then the noise is filtered out and contour is completed. Secondly, based on coarse-to-fine matching strategy, the coarse matching is performed by using shape context descriptor and the fine matching is performed by using iterative closest point for obtaining the sub-pixel accuracy contour matching. Finally, the neighbor-method is proposed to calculate the contour errors. The experimental results show that the detection accuracy of the proposed algorithm can reach to 0.5 pixel, which can meet the needs of practical application.

Research and analysis about the length of vertex-degree sequence of complex networks of Normal distribution

ZHANG Zhanying XIAO Wenjun LAI Zhengwen LI Meisheng

2018, 46(1):  139-144.  doi:10.3969/j.issn.1000-565X.2018.01.018

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Degree distribution is an important characteristic of complex network. According to analyzing the length of vertex-degree sequence ( ) of the complex network with power law distribution、exponential distribution and general degree distribution , we have found the general characteristic: the length of vertex-degree sequence of complex network is the order of ( is the number of network nodes). The paper proved the same conclusion in the complex network with normal distributions.