Journal of South China University of Technology(Natural Science Edition)

Nonlinear Dynamic Buckling of Shallow Elastic Arch

Han Qiang Huang Huai-wei Fan Xue-jun

2010, 38(3): 1-7. doi:10.3969/j.issn.1000-565X.2010.03.001

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This paper deals with the snap-through buckling of a shallow elastic arch under dropping impacts by means of the nonlinear dynamic method. In the investigation, a nonlinear dynamic equilibrium equation is deduced based on the Hamilton principle and is then analyzed using both the single-mode and the double-mode methods. Then, the governing equation of structure responses is obtained via Galerkin＇s approach. Moreover, the charactcristics of equilibrium points of the system are discussed and the stability of system attracters and their attraction domains is analyzed. Numerical results show that the double-mode method is more accurate than the single-mode one. The single-mode method may give incorrect critical buckling conditions and dynamic responses in some conditions. In addition, the initial shape of the shallow arch greatly affects the critical conditions of snap-through buckling, and that higher arch may possess greater buckling bearing capacity.

Nonlinear FEM Analysis of Horizontal Impact Resistance of Deepwater High-Pile Foundations of Highway Bridges

Pan Fang Guo Xin-yan

2010, 38(3): 8-11，24. doi:10.3969/j.issn.1000-565X.2010.03.002

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As there have been multiple bridge collapses caused by ship impacts in China, it is important to rationally evaluate the horizontal resistance of foundations of highway bridges to ship impacts. In order to meet the require- ments of impact resistance design and evaluation, this paper proposes a nonlinear FEM-based evaluation method of the horizontal resistanee of deepwater high-pile foundations under ship impacts. Then, by analyzing the ship impact on a bridge of G325 national highway, the proposed evaluation method is compared with the calculation method presented in the national design standard. The results indicate that the proposed method is applicable to the antiimpact design of deepwater high-pile foundations of highway bridges.

Fracture Parameters of Fractal Cracks

Zhang Heng Wei De-min

2010, 38(3): 12-16. doi:10.3969/j.issn.1000-565X.2010.03.003

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In this paper, first, four parameters including the critical fracture stress, the fracture toughness, the crack extension force and the fracture energy of an infinite plate with a solitary fractal crack of mode I under one- way tension are investigated based on the fraetal geometry. Next, the boundary of the crack domain is constructed with standard Koch fractal curve, and the elastic strain energy of the plate is deduced according to the perimeter- area relationship of the fractal crack domain. Then, the critical fracture stress of the plate is obtained according to the Griffith fracture criterion, and theoretical equations of the fracture toughness, the crack extension force and the fracture energy are consequently derived, which are utilized to generalize the G criterion to the fractal crack case. Finally, numerical simulations are conducted to analyze the influences of various factors on the four above-mentioned parameters. The results indicate that the fracture toughness of the material negatively correlates with the crack length, that the relationship between the fracture toughness and the fractal dimension varies with the yardstick length, and that the fracture energy increases with the length and roughness of the crack. In addition, the growth of a crack is proved unsmooth in the paper.

Temperature Characteirsitics of Flame Ceiling Jet Generated by Fire on Train in Subway Tunnel

Mao Jun XI Yan-Hong Fan Hong-Ming

2010, 38(3): 17-24. doi:10.3969/j.issn.1000-565X.2010.03.004

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In this paper, 1：8 scale model experiments and numerical simulations were performed to analyze the temperature characteristics of flame ceiling jet generated by a fire at the head and the tail of a train in a subway tunnel. The results were then compared with those at the train center. It is found out that, if the fire occurs at the train head and tail, the maximum temperature of the flame ceiling jet appears at the location of δ= 0. 25H away from the tunnel roof, while it appears at the location of δ= 0. 18H if the fire occurs at the train center, all these being different from that of the gas ceiling jet appearing at the location of 0. 01H away from the tunnel roof; that the vertical temperature along the tunnel changes piecewise under a stable combustion state, so the maximum temperature at the fire on the train head and tail reduces parabolically, while that at the fire on the train center reduces linearly; and that, being a certain distance away from the train, the flame significantly weakens, and the maximum temperature of the flame ceiling jet exhibits an exponential decay.

Safety Velocity of On-Fire Train Moving in Subway Tunnel

Xi Yan-hong Mao Jun Fan Hong-ming Zhao Yao-hua Zhu Sheng

2010, 38(3): 25-30，36. doi:10.3969/j.issn.1000-565X.2010.03.005

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The safety of on-fire trains moving in subway tunnel is important to emergency rescue, and the train velocity is the key to the train safety. This paper adopts a fire prototype with a heat release rate of 0 - 10 MW to perform a model experiment of train fire in a 1 ： 8 subway tunnel model. After a similar transformation, the heat release rate of the model fire reaches 0 - 55 kW. By using n-heptane as the fuel and by adopting a frequency conversion fan to form a flow field, the motion of the train in the model tunnel is simulated, and the relationship between the wind velocity and the heat release rate, the temperature field around the train and the flame/smoke pervasion rule are in- vestigated in the conditions of variable train velocity, fire location and fire source location. Finally, by taking Beijing

Segregability Evaluation of Granular Pavement Materials

Bao Xiu-ning Zhang Xiao-ning

2010, 38(3): 31-36. doi:10.3969/j.issn.1000-565X.2010.03.006

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In order to escape the pavement destruction caused by the segregation of granular pavement materials, a segregation test was designed according to the segregation process, and a kind of four-element mineral mixture was chosen as the research object to construct a continuous diameter distribution model. Afterwards, the segregability of granular materials was obtained according to the parameters describing the material segregation. The results show that, according to the segregation degree of granular materials evaluated by the difference in diameter dispersion co- efficient, it is convenient to assess the fitness of segregated materials for pavement, and that the segregation degree of granular materials obviously increases with the average diameter and the diameter dispersion coefficient. The proposed evaluation method can also be used to analyze the segregation of asphalt mixture.

Analysis of Viscoelastic Properties of Modified Asphalt via Dynamic Mechanical Method

Zhan Xiao-li Wang Duan-yi

2010, 38(3): 37-40，52. doi:10.3969/j.issn.1000-565X.2010.03.007

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As the existing evaluation index of viscoelastic properties of asphalt is inapplicable to modified asphalt, the viscoelastic properties of both base asphah and modified asphalt are analyzed by using the dynamic mechanical method. In the investigation, the parameters describing the viscoelastic properties at different temperatures and fre- quencies are measured, and the variation laws of both Han curves and dynamic viscoelastic parameters are analyzed. The results indicate that the temperature dependence of Han curves of modified asphalt varies at different temperatures, that there exists a great difference in viscoelasitc properties between base asphalt and modified as- phalt due to the complex morphological structure of modified asphalt, and that the dynamic mechanical analysis is effective in revealing the relativity between the macroscopic mechanical properties and the microstructure of modified asphalt.

Method to Test Dynamic Modulus of Asphalt Mixture Based on Semi-Circular Specimens

Liu Yu Zhang Xiao-ning Chen Shao-xing

2010, 38(3): 41-46. doi:10.3969/j.issn.1000-565X.2010.03.008

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As the dynamic uniaxial compression modulus is difficult to use in testing pavement core, the evaluation method based on the design modulus is inapplicable to the compliance examination of pavement quality. In order to solve this problem, a test method for dynamic modulus was proposed based on semi-circular bending specimens, and the corresponding test parameters were determined. Then, the proposed method was used to test the dynamic modulus of common pavement asphalt mixture. The results show that the stress coefficient obtained via the three-di- mension finite element method is of high precision, and that the precision of the tested dynamic modulus is high enough. Moreover, it is found from the variation coefficient of the test data that the proposed method is of good sta- bility due to its weak dispersion and small repeatability deviation.

Control of On-Ramp of Annular Expressways Based on Priority Entrance

Tian Sheng Xu Lun-hui Liao Ran-kun Yang Ya-zao

2010, 38(3): 47-52. doi:10.3969/j.issn.1000-565X.2010.03.009

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In order to overcome the traffic congestion due to the traffic demand for urban expressways that exceeds the traffic supply, the benefit of priority entrance is analyzed by fully considering the requirements of vehicles for priority entrance on the on-ramp of urban expressways, and an on-ramp control strategy based on the priority en- trance is proposed, which permits vehicles with top priority to drive into urban expressways in a peak traffic condi- tion. Moreover, an algorithm of priority entrance for the annular road sections of urban expressways is presented, and the corresponding numerical example is conducted. The results indicate that the proposed strategy is applicable to on-ramp control and helps to raise the use efficiency of roads because it can prevent vehicles with lower priority from entering urban expressways.

Coordinated Scheduling Model of Traffic Modes in Comprehensive Passenger Transport Hub

Zong Fang Wang Lin-hong Jia Hong-fei

2010, 38(3): 53-57，63. doi:10.3969/j.issn.1000-565X.2010.03.010

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Proposed in this paper is a coordinated scheduling model of different traffic modes in a comprehensive passenger transport hub, with the minimum passenger cost as the optimization objective, the departure intervals of different modes （subway, light rail and bus） as the decision variables and with the vehicle configuration and trans- portation capacity matching as the constraint conditions. Then, by using the genetic algorithm toolbox in Matlab, the model is solved and is finally verified with the survey data in Xizhimen transportation hub in Beijing. The re- suits indicate that, after the coordinated scheduling, the passenger cost greatly reduces, and that the proposed model effectively solves the scheduling problem of comprehensive passenger transport hub.

Heuristic Algorithm to Solve Vehicle Routing Problem with Split Pickups and Deliveries

Yang Ya-zao Jin Wen-zhou Hao Xiao-ni Tian Sheng

2010, 38(3): 58-63. doi:10.3969/j.issn.1000-565X.2010.03.011

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Heuristic Algorithm to Solve Vehicle Routing Problem with Split Pickups and DeliveriesYang Ya-zao, Jin Wen-zhou, Hao Xiao-ni, Tian Sheng 1. School of Business Administration, South China University of Technology, Guangzhou 510640, Guangdong, China; 2. School of Civil Engineering and Transportation, South China University of Technology, Guangzhou 510640, Guangdong, ChinaAbstract:In order to save the transportation cost and improve the efficiency of logistics services, the vehicle rou- ting problem with split pickups and deliveries is investigated. According to the characteristics of this problem, that is, multiple visits for a certain task point or for the same task point by a certain vehicle are allowed, a three-phase heuristic algorithm, which splits the demands of pickups and deliveries at some task points and minimizes the total driving distance of vehicles, is proposed. Numerical results show that the proposed algorithm helps to obtain reaso- nable vehicle routings, especially with the case of total delivery amount being greater than total pickup amount.

Route Planning of Public Transit for Regional Evacuation Based on Time-Expanded Network

CuiJian-xun An Shi Cui Na

2010, 38(3): 64-69. doi:10.3969/j.issn.1000-565X.2010.03.012

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This paper deals with the route planning of public transit in urban road network for regional evacuation in emergency. In the investigation, first, the public transit evacuation system is modeled by using a time-expanded network. Next, a discrete and dynamic network flow model to minimize the total evacuation time is established, which transforms the route planning problem into a mixed integer programming （MILP） one. Then, a heuristic ta- bu-based search algorithm is designed to find out a high-efficiency solution to the route planning. Finally, a case study is conducted for the central road network of Changchun City in China, and the difference between the accurate results obtained from CPLEX9.0 and the approximate ones obtained from the tabu-based search algorithm is re- vealed. Numerical results indicate that the proposed time-expanded network-based model effectively represents the dynamic property of public transit evacuation system, and that the tabu-based algorithm reaches a compromise between the solving efficiency and the accuracy.

Robustness Analysis Model of Urban Transit Networks

Duan Hou-li Li Zhi-heng Zhang Yi

2010, 38(3): 70-75，81. doi:10.3969/j.issn.1000-565X.2010.03.013

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The analysis of robustness, an important performance index of urban transit networks, helps to well evaluate and optimize the measures of urban transit systems. In this paper, first, three models of urban transit systems respectively for the original transit network, the transit station network and the transit line network are established based on the bipartite graph model, and a robustness index of the topology structure of urban transit networks is de- fined. Then, a fast algorithm is proposed for the robustness analysis of large-scale networks. Finally, the robustness of the three established models is analyzed, with Beijing transit system under random and intentional attacks as an example. The results indicate that, compared with the random network, the urban transit network is not sensitive to the random attack, but somewhat sensitive to degree-based and betweenness-based attack.

Coordinated Development of Traffic Between Central City and New Urban Districts and Corresponding Evaluation

Ma Shu-hong Zhou Wei Wang Yuan-qing

2010, 38(3): 76-81. doi:10.3969/j.issn.1000-565X.2010.03.014

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At present, most cities in China are in rapid expansion by constructing new urban districts. At the same time, the traffic problem becomes more and more serious. From the viewpoint of system theory, this paper proposes the basic concept of the coordinated development of the traffic between central cities and new urban districts, analy- zes the basic requirements of the coordinated development in the aspects of technical coordination, benefit coordina- tion, system coordination and function coordination, and builds up two evaluation index systems to respectively de- scribe the internal and the external coordinated transport sub-systems. Moreover, an evaluation model correspon- ding to the basic concept and the evaluation index systems is constructed to evaluate the coordinated development of traffic between a central city and its new urban districts. Finally, by using the traffic between Xi＇an and Gaoling, which is found primarily coordinated but trends to grow, as an example, the correctness of the proposed theory and methods is verified.

Robust Optimization Model of Fleet Planning Decision Under Demand Uncertainty

Yang Qiu-ping Xie Xin-lian Su Chen

2010, 38(3): 82-88. doi:10.3969/j.issn.1000-565X.2010.03.015

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This paper deals with the fleet planning decision in complex and uncertain circumstances. In the investigation, first, the existing methods and basic characteristics of fleet planning are analyzed. Next, by combining the ship deployment optimization with the fleet development, a deterministic model of fleet planning with muhimode in- vestment, which mee.ts the actual demands of the complex market, is established. Then, by introducing the robust optimization approach based on scenario analysis and by using a scenario set with given probability to describe the uncertainty of market demands, the deterministic model is extended to a robust optimization model considering vari- ous uncertain factors. The new model, possessing strong robustness, considers not only the demand uncertainty but also various complex practical issues-the ship operating outcome, the enterprise investment capability, the buil- ding of new ships, the purchase or sale of second-hand ships and the ship chartering. Finally, by using a shipping enterprise as an example, the robust optimization model is compared with the deterministic one. The results indicate that the robust model helps to obtain relatively conservative solution and is effective in guaranteeing the robustness of fleet planning decision.

Selection of Kernel Input Features and Evaluation Rules for Transient Stability Assessment

Guan Lin Zheng Chuan-cai Wang Lu Zhang Xiao-qiang Wang Tong-wen

2010, 38(3): 89-94，100. doi:10.3969/j.issn.1000-565X.2010.03.016

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This paper deals with two key issuses of the artificial intelligence （AI） -based transient stability assess- ment （TSA） of power system, namely the selection of kernel input features and the stability-related evaluation mo- del. In the investigation, first, data-driven feature selection method and rule extraction algorithm are proposed. Then, the key features are evaluated and the transient stability rules are made from the training samples. During the feature selection, a genetic algorithm-based k-nearest neighbor （GA-knn） is used to assess the input features. Du- ring the rule extraction, a mining algorithm of classification and association rules is followed to form the rules of transient stability assessment. The proposed method is then applied to both the New England 10-machine 39-bus and the 3-machine 9-bus systems, and the results are compared and analyzed. It is found out that the selected ker- nel features from 53 candidates and the obtained rules are adapted for the two test power systems. However in the stability boundary, evaluation rules are complex and specific.

Improved Catastrophic Genetic Algorithm and Its Application to Reactive Power Optimization

Jiang Jin-liang Lin Guang-ming Ouyang Sen Zeng Jiang

2010, 38(3): 95-100. doi:10.3969/j.issn.1000-565X.2010.03.017

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In order to resolve the issues of prematurity and instability of catastrophic genetic algorithm （CGA）, an improved CGA （ICGA） is proposed, and an improved catastrophic operator related to the generation number is de- signed. Moreover, considering both the global performance and the convergence speed, two probability algorithms respectively for the crossover related to the generation number and for the mutation related to the fitness are de- signed. The proposed ICGA is finally applied to the reactive power optimization of the IEEE 14-bus and the IEEE 30-bus systems. The results show that ICGA is applicable to the reactive power optimization of power system due to its good global performance and high convergence speed.

Generation Investment Decision-Making at the Change of Electricity Market and CO2 Emission Policy

Liu Guo-zhong Wen Fu-shuan Dong Zhao-yang

2010, 38(3): 101-108. doi:10.3969/j.issn.1000-565X.2010.03.018

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In order to reveal the effects of CO2 emission policy and some other uncertain factors in the operation process on the investment decision-making of thermal power plants, a mathematical model considering the variations of the uncertain factors is established, and a new methodological framework of generation investment decision-ma- king is developed based on the option game theory. Then, on the assumption that the generation investment in different generation companies are performed sequentially, a solution based on the Barraquand-Martineau （B-M） option pricing model is presented. Finally, the proposed method is illustrated by a simulation. Numerical results indicate that the proposed framework well considers multiple uncertain factors and simulates the dynamic game process of thermal power plants in the planning period in stochastically-varied market environments.

Application of Intelligent Agent-Based Simulation to Electricity Market

Wang Ye-ping Yang Yan ring Zhao-xia Chen Hao-yong Chen Tian-en

2010, 38(3): 109-113，122. doi:10.3969/j.issn.1000-565X.2010.03.019

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The intelligent agent-based simulation has become a novel and powerful tool in the study of electricity market. This paper deals with the construction of a simulation system of electricity market. In the investigation, first, the intelligent-agent learning algorithms suitable for simulating the strategic bidding of electricity firms are in- troduced. Next, the applications of the VRE-learning algorithm, the Q-learning algorithm and the greedy algorithm to the simulation system are illustrated, and the corresponding implementation frameworks are proposed. Then, the techniques for the learning algotrithms to handle the convergence of agent bidding are discussed. Finally, an exam- pie is performed to test the effectiveness of the intelligent agent-based simulation. The results indicate that the intel- ligent-agent learning algorithms are capable of simulating the rational bidding behavior of electricity firms.

Experimental Investigation into Micro-Scale Diffusion Flame of Liquid Ethanol Affected by Magnetic Field

Yang Ze-liang Chen Shao-you Gan Yun-hua Zhao Jian-jian

2010, 38(3): 114-117. doi:10.3969/j.issn.1000-565X.2010.03.020

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In this paper, the effects of magnetic induction intensity on the height, temperature and stable flow range of the micro-scale diffusion flame of liquid ethanol were experimentally investigated. The results show that, in a fixed magnetic field, the flame height decreases, while the flame temperature increases and the stable flow range expands. All these phenomena are due to the effect of fixed magnetic field on the ions and ion clusters in incomplete combustion.

Application of Intelligent Agent-Based Simulation to Electricity Market

Wang Shi-Yong Li Di Chen Chao

2010, 38(3): 118-122. doi:10.3969/j.issn.1000-565X.2010.03.021

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The intelligent agent-based simulation has become a novel and powerful tool in the study of electricity market. This paper deals with the construction of a simulation system of electricity market. In the investigation, first, the intelligent-agent learning algorithms suitable for simulating the strategic bidding of electricity firms are in- troduced. Next, the applications of the VRE-learning algorithm, the Q-learning algorithm and the greedy algorithm to the simulation system are illustrated, and the corresponding implementation frameworks are proposed. Then, the techniques for the learning algotrithms to handle the convergence of agent bidding are discussed. Finally, an exam- ple is performed to test the effectiveness of the intelligent agent-based simulation. The results indicate that the intel- ligent-agent learning algorithms are capable of simulating the rational bidding behavior of electricity firms.

Analysis and Solution for Frequency Tracking Degradation of Phase-Locked Loop of Piezoelectric Transducers

Wu Jian Dong Hui-juan Zhang Guang-yu

2010, 38(3): 123-128. doi:10.3969/j.issn.1000-565X.2010.03.022

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In the uhrasonic order to improve the precision and reliability of frequency tracking of piezoelectric transducers during drilling of carbon-fiber composites, four kinds of tracking degradations of the traditional phase-locked loop （PLL） system, namely the lock losing, the mis-tracking, the dead lock and the large tracking error, are ana- lyzed based on the equivalent circuit of piezoelectric transducers. Then, the reasons for the degradations are ex- plained, finding out that to counteract the static capacitance is the only way to overcoming the degradation. Accor- dingly, a PLL frequency tracking technique based on the static capacitance compensation is proposed, by which the transducer is equivalent to an ideal LCR serial resonance circuit, thus the tracking degradations being effectively solved. Experimental results show that, by using the proposed technique, the frequency tracking precision of trans- ducer mechanical resonance is higher than -20 - 10 Hz, that the mis-tracking and the dead lock are effectively overcome, and that the tracking bandwidth is up to 6 kHz.

CFD Investigation into Pressure Loss of Single-Cylinder Engine Muffler

Zhang De-man Li Shun-ming Men Xiu-hua

2010, 38(3): 129-132. doi:10.3969/j.issn.1000-565X.2010.03.023

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In this paper, first, the pulse pressure signal at the entrance of a single-cylinder engine muffler was measured. Next, based on the physical structure of the muffler, a simulation model of the muffler was constructed. Then, by considering the exhaust characteristics of the single-cylinder engine, a method was proposed to determine the critical conditions according to the effective pulse pressure. Moreover, the distribution of pressure loss in the muffler was simulated based on the computational fluid dynamics （CFD） , and the simulated results were used to discover the parts with large pressure loss in the muffler, with some measures being taken to improve the internal structure of the muffler. Finally, in the same operation conditions, the entrance pressure signal of the improved muffler was measured and simulated. The results indicate that the pressure loss in the improved muffler falls remarkably and distributes more regularly.

A Vaccine-Symbiosis Clonal Selection Algorithm for Mixed-Model Scheduling on Assembly Lines

Liu Ran Lou Pel-huang Tang Dun-bing Yang Lei

2010, 38(3): 133-137，142. doi:10.3969/j.issn.1000-565X.2010.03.024

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In order to solve the scheduling optimization problem in mixed-model assembly lines, a multi-objective vaccine eoevolution elonal selection algorithm is proposed, and the vaccine population and the corresponding popu- lation operations are designed to interact and coevolve with the antibody population, thus greatly improving the per- formance of the algorithm. Then, according to the discrete feature of the scheduling optimization problem, the anti- body affinity is evaluated from the phenotype and the genotype. Moreover, according to the antibody quality and the evolutionary generations, the adaptive mutation rate is designed, and multiple local optimizations are executed in each iteration process to improve the convergence rate of the algorithm. The results of two series of experiments show that, as compared with other three multi-objective optimization algorithms, the proposed algorithm is of high efficiency and superiority.

Resolution of Acoustic Perceptual Difference Between Multitone and Narrow-Band White Noise

Xie Zhi-wen Che Hong-feng

2010, 38(3): 138-142. doi:10.3969/j.issn.1000-565X.2010.03.025

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The acoustic perceptual difference between the muhitone with 5, 10, 20, 30, 50 and 100 components and the narrow-band white noise in the same critical band is resolved for the 10 critical bands of 3, 5, 7, 9, 11, 13, 15, 17, 19 and 21. The results show that the perceptual difference between muhitone and narrow-band white noise becomes more and more difficult to resolve with the increase in the number of frequency components, and that, at a certain number of frequency components, the multitone with high frequency is closer to the narrow-band white noise. The results also reflect human ears＇ ability of distinguishing frequency, that is, the frequency resolu- tion of human ears is related to the critical band. The higher the critical band index, the worse the frequency reso- lution of ears, and the closer the muhitone to the narrow-band white noise.

Analysis of Effect of Torso Scattering on Near-Field Head-Related Transfer Functions by Using Perturbation Method

Yu Guang-zheng Xie Bo-sun Rao Dan

2010, 38(3): 143-147. doi:10.3969/j.issn.1000-565X.2010.03.026

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Proposed in this paper is a combination of the perturbation method and the muhipole expansion method, which is used to approximately calculate the near-field head-related transfer function （HRTF） of the snowman model and to quantitatively analyze the effects of torso scattering and reflection on HRTF. Calculated results indicate that the contribution of torso scattering to HRTF depends on not only the order and frequency of perturbation app- roximation but also the position （including the direction and the distance） of sound source; that, under the first- order perturbation approximation, the contribution of torso scattering increases with the increase in both the frequency and the azimuth of the sound source departing from the ear, and with the decrease in both the distance of the sound source from the head center and the elevation of the sound source ; that the contribution of perturbation terms with higher orders to HRTF greatly decreases with the increase in perturbation orders; and that, when the sound source distance is not less than 0. 02m and the elevation is not less than 135°, the calculation errors of the third-order perturbation approximatation are controlled within ± 1.0 dB below 20 kHz, and the contributions of the fourth-order and the higher-order scatterings are neglectable.

Virtual Auditory Replay and Broadening of Auditory Source Width

Shi Bei Xie Bo-sun

2010, 38(3): 148-155. doi:10.3969/j.issn.1000-565X.2010.03.027

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Psychoacoustic experiments are conducted to investigate the broadening and the evenness of auditory source width （ASW） when uncorrelated noise signals are reproduced by a pair of virtual loudspeakers respectively located at ±45°, ± 60°, ± 75° and ±90°, and by a pair of virtual loudspeakers and a real central loudspeaker simultaneously. Results show that： when signals are reproduced only by a pair of virtual loudspeakers, ASW can be broadened to a maximum value of about ± 70° for octave noises with a central frequency varying from 250 Hz to 1 kHz, but the maximum reaches about ±50° for pink noises. When the angle between two virtual loudspeakers is wide, ASW can not be evenly broadened and it becomes empty in middle and strong in sides. When a pair of virtual loudspeakers and a real central loudspeaker replay simultaneously, the sound pressure level of the central loudspeaker relative to virtual loudspeakers greatly affects the ASW and its evenness. ASW can be evenly broadened to a wide range by adjusting the sound pressure level of the central loudspeaker. Furthermore, theoretical calculation and test results show that there is a negative linearity between ASW and IACC （the maximum of inter-aural crosscorrelation function） only when IACC0 （the inter-aural cross-correlation value when r = 0） is greater than 0, whereas for all kinds of replay signals, the negative linearity always exists between ASW and IACC0.

Mathematical Description and Application Analysis of Principal-Agent Relationship

Deng Ze-hui

2010, 38(3): 156-161. doi:10.3969/j.issn.1000-565X.2010.03.028

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This paper deals with the principal-agent relationship, a complex function representing the relationship among different variables, and introduces the State-Space Formulation method to demonstrate its basic model and general framework. With the help of Kuhn-Tucker theory, the solution to the model is then analyzed. Afterwards, with the rural cooperative finance as an example, the application of principal-agent theory is discussed. It is con- cluded that, in the setting of risk-sharing mechanism between government and the person in charge of rural coopera- tive finance organization, the moral hazard of the person in charge and various uncertainties should be fully consi- dered. The principal-agent theory is effective in analyzing the contract relationship among different individuals and provides an approach to understanding the contract relationship.

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