Table of Content

25 April 2015, Volume 43 Issue 4

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Traffic & Transportation Engineering

Detection Algorithm of Expressway Moving Objects Based on Background Subtraction

Fu Xin-sha Wang Xiang-bo Li Hai-feng Meng Qing-xin

2015, 43(4):  1-6.  doi:10.3969/j.issn.1000-565X.2015.04.001

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As the existing background subtraction algorithm is insufficient for the real-time expressway monitoring with frequent light change，an adaptive threshold determination algorithm based on the gray level is proposed． In this algorithm，the pixels of the object in the difference image are effectively classified by means of the statistical method，and the classification standard is defined as the adaptive threshold． Moreover，the gradient distribution of the difference image is used to judge the area of motion objects． Experimental results show that the proposed adap-tive threshold algorithm is effective in recognizing objects in different environments with high accuracy and stability．


Overtaking Model for Two-Lane Highway Considering Vehicle Running Characteristics

Xu Lun- hui Hu San- gen Wu Shuai Luo Qiang

2015, 43(4):  7-14 27.  doi:10.3969/j.issn.1000-565X.2015.04.002

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As the existing overtaking models often ignore the impact of vehicle running characteristics on the overta-king behavior，this paper puts forward a new mathematical model to calculate the time required for overtaking and the distance for the vehicle from its overtaking beginning to the end． In the investigation，the existing models are analyzed，the overtaking vehicles are classified according to their types，a two-lane overtaking scene is designed，and the speed limits of different road grades are taken into full consideration． Moreover，the required overtaking time and the overtaking distance of micro cars，mid-size cars and full-size cars on two-lane highway are calculated for various vehicle types with different overtaking speeds and driving speeds，and the results are compared with those obtained by the existing overtaking model． It is found that the required overtaking time and the overtaking dis-tance are both related to the vehicle type，the overtaking speed，the driving speed of the overtaking vehicle and the driving speed of the opposite vehicles; and that the proposed model helps to obtain overtaking time and distance va-rying with vehicle types because it well considers vehicle running characteristics，so that it accords better with the actual overtaking process．


Effect of Ｒeference Group on Decision of Conformity Crossing Behaviors of Pedestrians

Wu Wen-jing Luo Qing-yu Jia Hong-fei

2015, 43(4):  14-19.  doi:10.3969/j.issn.1000-565X.2015.04.003

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Conformity crossing is one of the important potential safety hazards of pedestrian traffic． In uncertain traffic environments，the conformity effect of pedestrians play an important role in the whole process of the crossing decision of individual pedestrians． In this paper，the evolution rule for the crossing or waiting of pedestrians is de-duced based on the game theory after analyzing the factors influencing the interaction crossing，and a threshold model describing the crossing behavior is constructed to quantitatively evaluate the impact degree of reference group on individual pedestrian’s decision． Moreover，the interaction between the reference group and the individual is analyzed by using an example of interaction． The results show that the effect of reference group has a significant im-pact on the pedestrians’crossing behavior． This research expands and enriches the theoretical framework and tech-nique of pedestrian behavior analysis，and provides a scientific foundation for the establishment and implementation of high-performance safety measures for the crossing of pedestrians．


Estimationof Expressway Section Travel Time Based on Correction Algorithm

2015, 43(4):  20-27.  doi:10.3969/j.issn.1000-565X.2015.04.004

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In the existing expressway toll collection systems，the estimated section travel time based on original toll records is inaccurate，which may reduce the estimation accuracy of traffic flow． In order to solve this problem，a new travel time estimation algorithm，which calculates the space-time coordinate displacement of vehicles according to the trajectory method and adjusts the travel time by taking the section length as the weight，is proposed． The algorithm is then applied to an expressway toll collection system． The results show that the proposed algorithm helps to obtain an estimated travel time close to the actual one．


Identification of Trip-Activity-Intermediate Stop Using GPS-Based Travel Survey Data

Zong Fang Wang Xiao Zhang Hui- yong Bai Yu

2015, 43(4):  28-32 40.  doi:10.3969/j.issn.1000-565X.2015.04.005

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Dealt with in this paper are the techniques for processing data and identifying trips and activities based on GPS travel survey data． In the investigation，by improving the method of stationary points，a method to identify the status based on continuous data segments is proposed，and a trip-activity identification algorithm consisting of three steps，namely dividing status segments，identifying activities and recognizing trips，is designed． Moreover，by setting the minimum dwell time as 4min，the identification of intermediate stops is performed． Finally，a compari-son is made between the results obtained by the proposed algorithm and the travel diaries reported in paper-form travel survey． It is found that the proposed algorithm is effective in identifying trips，activities and intermediate stops with high accuracy，especially the short-time intermediate stops often omitted in the paper-form travel survey．This research significantly enhances the efficiency and accuracy of travel survey and facilitates the development of urban transportation system．


Division of Highway Network Hierarchy Based on Weighted Complex Network

Deng Ya-juan Wang Huan Du Ruo Hu Shao-rong

2015, 43(4):  33-40.  doi:10.3969/j.issn.1000-565X.2015.04.006

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In order to divide the highway network hierarchy reasonably，first，both the complex network theory and the dual topology method are adopted to abstract highway sections into different nodes． Then，the weights of the nodes are calculated by considering the traffic volume and the coherence degree，and a weighted adjacency matrix based on the gravity model is obtained． Moreover，the importance degree，closeness and betweenness of the nodes are calculated with the help of Matlab，the comprehensive weight of the nodes is obtained by means of the variation coefficient method，and the nodes satisfying the mileage requirement are filtrated by setting the planed annual mile-age as the control variable． Finally，a classification of highway network hierarchy is performed based on the fuzzy clustering of the filtrated nodes． The results show that the application of complex network theory to the classification of highway network hierarchy helps to obtain the mileage and space distribution of each highway grade，which bene-fits the level improvement of road networks．


Conversion of Dynamic Axle Load on Asphalt Pavement Considering Friction Coefficient

Han Ding Shen Fei Li Ling- lin

2015, 43(4):  41-47.  doi:10.3969/j.issn.1000-565X.2015.04.007

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In order to investigate the dynamic axle load conversion in complex conditions，the dynamic response of as-phalt pavement subjected to moving load is analyzed，the validity of the numerical calculation and the influence of vehi-cle characteristics are discussed，and a conversion formula of the dynamic axle load is set up． Then，based on the two-dimension Lamb problem，the effectiveness of the numerical calculation is verified，and a three-dimension dynamic nu-merical model of asphalt pavement with rigid base is established to analyze the effects of vehicle speed，road surface fric-tion coefficient and axle load． The results show that，when the vehicle moves at a constant speed，both the axle load and the road surface friction coefficient remarkably influence the dynamic response of pavement; and that the conversion co-efficient of the dynamic axle load considering the friction coefficient is significantly greater than that of the static axle
load． Moreover，it is found that the three-dimension finite element model，which takes into consideration various affec-
ting factors of the vehicle and the asphalt pavement，accords well with the actual stress state of asphalt pavement struc-
ture; and that the presented conversion formula is feasible in improving the current design specifications．


Adaptability of Small-Resistance Fasteners on Long-Span Continuous Bridge of Heavy Haul Railway

Dai Gong-lian Zhu Jun-pu Yan Bin

2015, 43(4):  48-55.  doi:10.3969/j.issn.1000-565X.2015.04.008

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In order to reveal the influence of the layout of small resistance fasteners on the distribution of longitudi-nal force loaded on the continuously-welded rail of continuous bridge of heavy haul railway，a recognized method to analyze the rail-bridge interaction is adopted，and a spatial integrated finite element model，which takes into con-sideration the adjacent multi-span simply-supported beams，is established to describe the continuously-welded rail of a (60 +100 +60)m continuous bridge of the heavy haul railway with an axle load of 30t． Afterwards，based on the comparison of some layout plans of small-resistance fasteners，the influences of such design parameters as fas-tener resistance，substructure stiffness，loading mode and braking force ratio are discussed． The results show that(1) when small-resistance fasteners are only laid on the continuous beam，the rail stress as well as the horizontal force at pier top is rather small，and the broken seam value of the rail can be reduced at the same time; (2) the in-fluence of longitudinal resistance of small-resistance fasteners on the rail stress is up to 11． 2%; (3) when small-resistance fasteners are laid on the continuous bridge，the rapid displacement between the rail and the beam be-comes the main controlling index，and the longitudinal stiffness limit at the brake pier top of a 100m-span continu-ous bridge reaches 3000 kN/cm; and (4) both the loading mode and the braking force ratio greatly influence the displacement between the rail and the beam，so that an accurate braking force ratio should be determined by tests．


Simulation of Structure Falling Slamming Process Affected by Air Cushion and Wind

Zhu Liang-sheng Yu Long-fei Zhang Shan-ju Li Jian-hua

2015, 43(4):  56-62 68.  doi:10.3969/j.issn.1000-565X.2015.04.009

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As the air cushion and the wind both greatly affect the falling process of marine structures from the sky into the water，this paper proposes an air-solid coupled mathematical model to describe the falling slamming process of 3D complex structures． In the investigation，the falling mechanism of structures is analyzed，the air damping and the 6DOF (Degree of Freedom) motion characteristics are fully taken into consideration，and the three-dimension transient N-S equation，the turbulence dynamic equation，the energy equation and the rigid 6DOF kinematic equa-tion are comprehensively adopted． The proposed model is then applied to numerically simulate the falling slamming process of a structure from the air into the water，and the results are compared with those obtained by the physical model，finding that the proposed model is effective in simulating the falling slamming process． Moreover，from the simulated results obtained at different falling heights or in different wind blow environments，it is found that (1) the existence of air cushion changes not only the structure slamming speed but also the pressure distribution; (2) the slamming may result in a temperature rise of the air cushion; and (3) the wind blow changes the falling pose of structures and makes the structures fall from the air with a“zigzag”pose and then slam into the water．


Approximate Analytical Solution of Large-Amplitude Ship Rolling Motion Based on MLP

Liu Ya-chong Hu An-kang Han Feng-lei Wang Chun-hui

2015, 43(4):  63-68.  doi:10.3969/j.issn.1000-565X.2015.04.04.010

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An approximate analytical solution with a certain precision helps to construct a link between ship rolling motion features and hull parameters，which is convenient for analyzing the influence of hull parameters on the rol-ling motion and stability． In this paper，by taking into consideration the nonlinearity of damping and restoring mo-ments，an equation describing the ship rolling motion in regular waves is established． Then，in order to overcome the limitations of weak nonlinearity，the modified Lindstedt-Poincare method (MLP) is adopted to obtain the per-turbation solution of the established rolling motion equation，and the analytical solution in still water which is accu-rate to the second order and the analytical solution in regular wave which is accurate to the first order are both ob-tained． Finally，the correctness of the approximate analytical solution is verified by an example solved respectively via the MLP method and the numerical algorithm．


MDO Modeling of Ships Based on Design Structure Matrix

Liu Qiang Feng Bai-wei Liu Zu-yuan

2015, 43(4):  69-77.  doi:10.3969/j.issn.1000-565X.2015.04.011

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In order to reduce the coupling degree of the MDO (Multidisciplinary Design Optimization) model of ships，and thus to indirectly improve the optimization efficiency，a remodeling method for modeling is proposed based on a relation information flow-based clustering algorithm． In this algorithm，an exponential function is used as the substitution of the linear function to improve the theoretical hypothesis and the calculation method，and the co-ding of the algorithm is also modified． Moreover，two assessment indexes，namely the proportion of relation weight in the interior of the clustering and the BUS clustering scale，are proposed for comparison． Finally，a conceptual model of a 5400TEU container ship in the early conceptual design is used to illustrate the proposed modeling method．The results verify the feasibility of the method in ship modeling．


Power & Electrical Engineering

Fractional-Order Sensorless Control of Permanent Magnet Synchronous Motor

Chen Si-yi Pi You-guo

2015, 43(4):  78-84 94.  doi:10.3969/j.issn.1000-565X.2015.04.012

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As the control system without position sensors for the permanent magnet synchronous motor is of low con-trol accuracy at low or zero speed，a subsection control strategy with both the separately-controlled startup and the self-controlledoperation is proposed． In this strategy，when the system is in the separately-controlled startup stage，the machine can be started or stopped smoothly by injecting a stable rotating magnetic field into stator windings．However，when the system is in the self-controlled operation stage，a fractional-order sliding mode observer and a fractional-order model areboth introduced to ensure the smooth transition between the two control stages in the sen-sorlesscontrol system． Then，the response curves of the sensorlesscontrol system respectively with fractional-order sliding mode observerand integral-order sliding mode observer are obtained via simulation and experiments． The re-sults show that the proposed algorithm not only implements smooth startup of the machine but also effectively re-duces the chattering in the switching process． Thus，a higher integrated control performance is achieved．


Investigation into Tripping Characteristics of Low-Voltage Release Under Voltage Sag Based on Large-Scale Experimental

Ouyang Sen Liu Ping Li Xiang

2015, 43(4):  85-94.  doi:10.3969/j.issn.1000-565X.2015.04.013

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According to the GB/T17626． 11—2008 and the correlated research results at home and abroad，an ex-perimental scheme was proposed to explore the tripping characteristics of low-voltage release under voltage sag，and the corresponding experimental platform was constructed． With this platform，large-scale experiments of 10 com-monly-used low-voltage releases were carried out at different voltage sag amplitudes，durations and phases，finding that the amplitude，the duration and the phase collectively determine the tripping characteristicsof low-voltage re-lease under voltage sag． Moreover，the experimental results were extremely treated and a curve fitting was per-formed to explore the function relationship between the amplitude and the duration at different phases，as well as the function relationship between the phase and the duration at different amplitudes． Thus，a tripping model of low-voltage release under voltage sag is successfully established．


SVC-MERS-Based Voltage Control ofAsynchronous Generator Set in Wind Power Generation System

Wei Ye-wen Kang Long-yun Huang Zhi-zhen Qi Ru-jun

2015, 43(4):  95-103 125.  doi:10.3969/j.issn.1000-565X.2015.04.014

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Although asynchronous generator is of simple structure，low cost and high operation reliability，its output voltage is sensitive to load fluctuation． In order to solve this problem，the voltage unbalance caused by the output power change of asynchronous generator is analyzed，the conventional phase shift control and indirect voltage con-trol schemes are improved，and a direct voltage control scheme，which adopts a novel continuous reactive power compensator SVC-MERS to stabilize the output voltage，is proposed． Then，some simulations are performed to veri-fy the effectiveness of the proposed scheme in broadening the running range and improving the current quality． Fi-nally，a simulated SVC-MERS test platform，which supplies a reactive power up to 7． 66kvar，is constructed to test the voltage stabilization performance of the asynchronous generator set． As compared with STATCOM，the proposed device is of simpler structure and less switching loss benefited from the adoption of power frequency control．


Hierarchical Coordinated Control of Islanded Wind-Diesel-Battery Microgrid for Improving Power Quality

Ma Yi-wei Yang Ping Wang Yue-wu Zhao Zhuo-li

2015, 43(4):  104-111.  doi:10.3969/j.issn.1000-565X.2015.04.015

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As the high-penetration intermittent microsource and the frequently-switched load may impact the opera-tion stability of islanded microgrids，a hierarchical coordinated control scheme based on different time scales，which takes into full consideration the control characteristics of both the diesel generator and the battery storage system，is proposed． In this scheme，a primary controller based on the battery storage system and a secondary controller based on the diesel generator are designed to improve the stability of voltage and frequency of islanded microgrids in diffe-rent time scales． Moreover，in order to resist smaller and faster random system net-load disturbances，a modified droop controller with P-f and Q-V controls of the battery storage system is proposed，which helps to improve the sta-bility of system voltage and frequency． At the same time，in order to resist bigger and slower system net-load dis-turbances，a PI controller and an auxiliary reactive power compensator are presented for the diesel generator，which helps to implement the isochronous control of system frequency and voltage and to further restore the system opera-tion stability． The feasibility and effectiveness of the proposed method is finally verified by the analysis of Dong’ao islanded wind-diesel-battery microgrid operated in various conditions．


Influence of Illumination Probability of Photovoltaic System on Voltage of Power Distribution Networks

Chen Xu Yang Yu-yao Zhang Yong-jun Ye Lin-hao

2015, 43(4):  112-118.  doi:10.3969/j.issn.1000-565X.2015.04.016

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In order to explore the reactive voltage characteristics of power distribution networks affected by the grid-connected photovoltaic (PV) system，a probabilistic distribution model of PV power generation system is estab-lished based on the Beta-distribution of solar irradiance． Then，by taking into consideration the probabilistic impact of solar radiance on the output of PV power generation system，the PV outputs in three typical weather conditions，namely a low cloudiness day，a cloudless day and a partly cloudy day，are simulated，and the probabilistic output of PV power generation system in continuous time sections is obtained，which is used to perform the power flow cal-culation in turn． Moreover，the calculated power flow is compared with that obtained by using the constant power model． Finally，an example is given to analyze the laws of voltage distribution and voltage amplitude fluctuation in grid-connected PV distribution networks． The results also show that，as compared with the conventional constant power model，the established probabilistic model reflects the randomness and volatility of PV output better．


Feasibility Study on Energy Harvesting Around AC Transmission Line Based on Electric Potential

Zhao Dong-sheng Dai Dong Deng Hong-lei Li Li-cheng Zhai Shao-lei Cao Min

2015, 43(4):  119-125.  doi:10.3969/j.issn.1000-565X.2015.04.017

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Proposed in this paper is a method of utilizing a capacitive transducer to harvest the electric potential energy stored in the space around the AC transmission line，which helps to supply power to the on-line -monitoring system installed on a transmission tower． First，the circuit model of the potential energy-harvesting system and the relationship between the load resistance and the output power are analyzed，and a way to harvesting the maximum energy is presented． Then，the electric field distribution at the tower head of a 500kV AC double-loop transmission line is simulated，and the places suitable for transducer installation are determined． Finally，an experiment is con-ducted by adopting a capacitive transducer with a radius of 40cm and an interval of 15cm，and about 5mJ of energy is obtained at 50kV in 24s，which means that the capacitive transducer can afford an output power of 208 μW to meet the minimum power limit of wireless sensor nodes． In practically application，there is higher operating voltage compared with the experiment，by utilizing the high-intensity electric field efficiently on the tower with optimized capacitive transducer，enough energy will be harvested to power the on-line -monitoring system．


Physics

Analysis of Nonlinear Distortion in Impulse Response Measurement of Spherical Microphone Array

Liu Yu Xie Bo-sun Mai Hai-ming Chen Jia-yan

2015, 43(4):  126-132 137.  doi:10.3969/j.issn.1000-565X.2015.04.018

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During the impulse response measurement of spherical microphone arrays，the scattering of the incident sound wave caused by the array geometry may change the harmonic proportion of signals recorded by the microphone．In this paper，two methods，one using the maximum length sequence and the other using the logarithmic sine sweep as the excitation source，were adopted to measure the impulse response，and the effect of nonlinear distortion on the measured results was analyzed． Moreover，a simulation was carried out for comparison． Simulated and measured re-sults indicate that (1) the proportion of harmonic distortion varies with the incident angle of sound source due to the scattering of incident sound wave on the spherical surface; (2) the microphone with a harmonic distortion array back onto the sound source slightly affects the output，while the microphone with a harmonic distortion array facing to the sound source greatly affects the output; and (3) in general，the measurement method based on the maximum length sequence is more sensitive to the nonlinear distortion of sound sources while the method based on the logarithmic sine sweep is more suitable for the impulse response measurement of spherical microphone arrays．


Effect of Speech Sound Pressure Level and Reverberation on Chinese Speech Ｒecongition for Foreign Students

Cui Shu-hui Peng Jian-xin

2015, 43(4):  133-137.  doi:10.3969/j.issn.1000-565X.2015.04.019

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Two room impulse responses with different reverberation time were obtained by the acoustical simulation in a classroom． The subjective Chinese speech intelligibility was evaluated by foreign students under differentspeech sound pressure level conditions． The effect of speech sound pressure level on Chinese speech intelligibility scores for foreign students in classroom was discussed． The shorter reverberation time was，the higher Chinese speech intel-ligibility scores for foreign students were under the same speech sound pressure level condition． Chinese speech in-telligibility scores first increases with the increase of speech sound pressure level under the same reverberant time condition，but the speech intelligibility scores slightly decreased with the increase of the speech sound pressure level when the sound pressure level reaches a certain value． To ensure good Chinese speech intelligibility in classroom for foreign students，a speech sound pressure level of 62 ～74 dBA should be recommended with a lower reverberation time as far as possible．


Effects of LED Lights with Different Colors on Human Electrocardiogram Under Extremely Low Illumination

Zhou Xiao-ming Xu Jia-bin Shao Zhi-dong

2015, 43(4):  138-142.  doi:10.3969/j.issn.1000-565X.2015.04.020

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On the basis of the biological equivalent theory，the control variable method is used to measure the elec-trocardiograms (ECGs) of testees under low-illumination LED lights with different colors and to explore the corre-sponding non-visual biological effect on human body’s physiological function． The results show that low-illumina-tion light source has certain effect on human electrocardiograms; and that the wavelength of low-illumination light source influences human ECG parameters． For instance，blue light significantly speeds up human heart rate while red and green lights have relatively greater effect on the depolarization and repolarization of the ventricle． Moreover，it is also found that both the depolarization time and the repolarization time increase under the illumination of these three kinds of light sources．


Heat Conduction Model of Thermoelectric Cooler and its Application to Nonuniform Heat Flux

Zhu Ren-jiang Pan Ying-jun Jiang Mao-hua Fan Si-qiang Zhang Peng

2015, 43(4):  143-148.  doi:10.3969/j.issn.1000-565X.2015.04.021

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Based on the structure and coupling characteristics of semiconductor thermoelectric cooler，the expression of inner heat source is simplified through separating the responding area of Peltier effect and Joule effect，and a new heat conduction model of thermoelectric cooler is established with the help of elliptic partial differential equation．This model is independent of the physical and geometrical parameters of the thermoelectric couple，and it only needs the standard parameters provided by the producer，so that the numerical analysis of temperature field of nonuniform heat flow can be realized at given current and boundary conditions． Then，the universality of the proposed model is verified by fitting manufacturer’s data． Moreover，with the help of this model，the three-dimension and sectional temperature field distributions in the heat dissipation system of small-size semiconductor power devices with thermoe-lectric cooler are obtained，and the common characteristics of such heat dissipation system is revealed．