Table of Content

28 April 2013, Volume 47 Issue 04 Previous Issue    Next Issue

Atomic Energy Technology

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Analysis on Reconstruction Technique Using Dynamic Grids in Tomographic Gamma Scanning Method for Radioactive Waste Drum GU Wei-Guo, WANG De-Zhong, LIU Cheng, QIAN Nan 2013, 47 (04):  505-512.  Abstract ( 2792 )   Save A new image reconstruction algorithm employing dynamic grids technique was proposed for tomographic gamma scanning (TGS). The process of detection was simulated aiming at the single-point and multi-point sources in the matrix with three different densities. The results of the transmission reconstruction and emission reconstruction exhibit that the emission reconstruction error and grids number by using dynamic grids is less than that by using fixed grids in most cases respectively. Moreover, with the increase of the source position radius or the matrix density, the emission reconstruction error of fixed grids will increase, but the error still maintains the low level if dynamic grids are applied. It is indicated that the high detection accuracy is obtained for the full segment of radioactive waste drum filled with high density matrix if dynamic grids are used in TGS emission reconstruction.   References | Related Articles | Metrics

Mathematical sciences and chemical

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Droplet Oscillations under AC Electrowetting JIANG Dong-Dong, HONG Fang-Jun, ZHENG Ping 2013, 47 (04):  513-518.  Abstract ( 2780 )   Save An experimental study on droplet oscillations under AC electrowetting on dielectric (EWOD) with coplanar-electrodes configuration at different input frequencies was conducted. It was found that the droplet resonates at some specific frequencies, which agrees reasonably well with those predicted using a previous linear theoretical analysis, and the resonance modes is named Pn (n=2, 4, …). At resonance modes Pn, the droplet oscillates symmetrically with n/2 peaks appearing on the droplet surface. There exists a critical frequency between the adjacent resonance modes, at which the droplet oscillates symmetrically but very weakly, and the oscillation phase relationship between the contact line width and height of the droplet switches. At frequencies lower than this critical frequency, the contact line will form lobes whose number increases with the order of adjacent resonance mode and whose position alternates periodically in azimuthal direction through droplet spreading and receding. At frequency higher than the critical frequency, droplet oscillates asymmetrically with the transmission of ripples on the droplet surface. It is believed these asymmetric oscillations will produce more chaotic fluid flows inside the droplet than symmetric oscillations and therefore can enhance the mixing efficiency in dropletbased microfluidics.   References | Related Articles | Metrics

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Residual Strength Analysis of Thin-Walled Structures with Multiple Site Damage Based on Crack Tip Opening Angle Method HUANG Xiang-Long, ZHANG Xiao-Jing, BAI Guo-Juan, XU Wu, WANG Hai 2013, 47 (04):  519-524.  Abstract ( 1968 )   Save This paper is to validate the crack tip opening angle (CTOA) obtained from the M(T) specimens to predict the residual strength of the thinwalled structures with multiple site damage. Using ABAQUS software to build the 2D M(T) finite element model, the crack growth process was simulated by CTOA fracture criterion with plane stress model. The predicted residual strength and loadcrack extension curves are close to the experimental results, the relative error is less than 6%. But for the multiple site damage specimens, the relative error is about 20%. Then the constraint around the crack tip is improved by using plane strain core (PSC) model. The constant CTOA and PSC were used to analyze thinwalled structures with multiple cracks configuration. The predicted results have good agreement with experiment， the relative error is less than 10%. Thus, the CTOA criterion and the PSC model are useful and reliable to predict the residual strength for structures with multiple site damage. References | Related Articles | Metrics

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Direct Image Correction Algorithm for PIV Measurement of Flowfield within Circular Tube LIU Yi-Peng, HU Xue-Yu, CHEN Jia-Luo, WANG Ping-Yang, DU Chao-Hui 2013, 47 (04):  525-532.  Abstract ( 2827 )   Save  A direct image correction algorithm based on the optical principle was developed to solve flowfield distortion of particle image velocimetry(PIV) measurement within circular tube. Without the restriction of liquid saturation temperature, this method can be applied for the synchronous correction of coordinate and velocity vector, and can correctly recover the image distortion in the vicinity of tube wall. In addition, this method requires no accessorial device. A computer code was developed based on Fortran language, which can be easily applied to other cases as long as changing the relevant input parameters. The method was validated by using a uniform square grid with the max deviation of 3%. And this method can provide a satisfactory correction result for the PIV experiment of cryogenic gasliquid two phase flow.   References | Related Articles | Metrics

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Verification of the Calculation of Acoustic Field with Typical Bottom Based on Parabolic Equation in Scaled Tank Experiment ZHU Han-Hao, PU Sheng-Chun, ZHANG Hai-Gang, LIU Wei, AN Xu-Dong 2013, 47 (04):  532-537.  Abstract ( 2142 )   Save In order to research the calculation of acoustic field based on parabolic equation (PE), a simulation experiment was carried out to analyze the underwater sound propagation with elastic bottom. In the test, a polyvinyl chloride (PVC) slab is used to simulate the elastic bottom, and the transmission losses for two types of seabed, including horizontal and sloping, are measured in an anechoic tank. In the simulation, PE method is used to calculate the horizontal seabed model, and the inclined is calculated with the coordinate mapping PE method. The accuracy of the two PE methods was verified by the agreement between the numerical simulation and the results of the measured experimental data. References | Related Articles | Metrics

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Numerical Simulation of Ship Bubbly Wake Based on Population Balance Model FU Hui-Ping 2013, 47 (04):  538-543.  Abstract ( 3016 )   Save Firstly, the bubbly wake around a model-scaled KRISO container ship KCS was numerically simulated based on the Euler two-fluid(ETF) model with uniform bubble size. Then the bubbles were divided into a few size groups, and the ship bubbly wake was numerically simulated again based on a discrete population balance model(PBM). The size distribution characteristics of bubbles such as number density and volume fraction of each size were derived. The effects of initial uniform bubble size and the size groups on the wake were researched through the analysis of mean Sauter diameters. The results show that the big bubbles aggregate on the ship wall, while small bubbles on the free surface; the ETF results can be used as the initial value of PBM; the more close the uniform ETF bubble size to the mean Sauter diameter, the more easy the PBM computation converges.   References | Related Articles | Metrics

Energy and Power Engineering

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The Effect of Cooling Structure on the Output Performance of  Automobile Exhaust Thermoelectric Generator QUAN Rui-a, TANG Xin-Feng-a, QUAN Shu-Hai-b, c , HUANG Liang-b 2013, 47 (04):  544-549.  Abstract ( 2006 )   Save To maximize the temperature difference of automobile exhaust thermoelectric generator(AETEG), based on the same hot source and different loads of engine, the open circuit voltage and maximum power of AETEG with unitary, singlecolumn and independent cold source structure were experimented, the effect of those different cold source structures on the output performance of AETEG was compared and analyzed. The results indicate that the output performance can be greatly enhanced with the optimized cold source structure, the effect of independent cold source structure is the most superior, singlecolumn cold source structure takes the second place, while the unitary cold source structure is the worst, the contact between the cold side of single thermoelectric module and its corresponding cold source is tighter, and the temperature difference is much larger when cold source structure is of independent miniaturization.   References | Related Articles | Metrics

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Design and Efficiency of Photovoltaic-Thermoelectric Power Generator with Negative Feedback Characteristic YANG Jing-Jing-1, LIU Yong-Sheng-1, FANG Wen-Jian-1, FANG Jin-1, PENG Lin-1, YANG Zheng-Long-2, GAO Tian-1, GU Min-An-1 2013, 47 (04):  550-554.  Abstract ( 2395 )   Save The output power of solar cell decreases with the increase of temperature, while the output power of semiconductor thermoelectric power generation module increases with the increase of temperature difference. Based on their output power vs. temperature relationship mentioned above, an optimal system of photovoltaicthermoelectric power generation was designed by using chimney effect,  which possesses a negative feedback characteristic. By analysis, it can be seen that the out power adds 4.3W by using thermoelectric module, and photovoltaic cell power increases 6.9% in the system. This method can raise energy efficiency to 12.06%, which is higher 1.42% than that by natural cooling method. Moreover, the system reduces emissions of NOx 9.7 kg, CO2 742.9 kg, SO2 9.6 kg during the apparatus lifecycle. At the same time,  this system maintains temperature difference at 22 ℃ between photovoltaic cells and environment, which increases the solar cells life span. References | Related Articles | Metrics

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Application of Water-Based Nano-Fluid in Copper Wire Flat Heat Pipe with Mesh Structure LI Shuang-Shuang, MA Qi, LIU Zhen-Hua 2013, 47 (04):  555-559.  Abstract ( 2224 )   Save The heat transfer characteristics of a novel flat heat pipe, the copper wire-bonded and mesh screen flat heat pipe ,were investigated experimentally. The effect of various working pressures, nano-fluid concentration and working fluids which include deionized water and waterbased copper nanofluids on copper wire-bonded and mesh screen flat heat pipe was analyzed. Besides, the performance was compared to that of copper wire-bonded flat heat pipe. The results show that nanofluid under low-pressure conditions can significantly improve the heat transfer characteristics of heat pipe and is a new working medium which can be applied to flat heat pipe. The overall thermal performances of new heat pipe are superior to those of copper wire-bonded flat heat pipe, the thermal resistance reduces distinctly and the maximum power increases obviously.   References | Related Articles | Metrics

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Analysis of Geothermal Power Generation by Total Flow System with Binary Cycle WANG Xin-Yue-1, YU Yue-Feng-1, HU Da-2, CHEN Liang-Le-2, MIN Cheng-Hao-2, DONG Zheng-Wen-2 2013, 47 (04):  560-564.  Abstract ( 3534 )   Save A total flow system with binary cycle was used in geothermal power generation with low-medium temperature, and compared with flash system. The optimal flash temperature was derived theoretically. Different parts of the total flow system with binary cycle were analyzed with the exergy loss, so as to propose the direction of reducing the exergy loss and optimizing the system which is reducing the minimum temperature difference of hot side and cold side of heat exchanger. Under the given condition, these two plants were calculated according to their system models. As shown by the calculation result, the maximum total capacity of total flow system with binary cycle is higher than that of the flash system by 12.7%. The power of the total flow system with binary cycle increases with the rise of the evaporation temperature of the organic fluid, and the power of the flash system firstly increases and then decreases while the flash pressure rises up. References | Related Articles | Metrics

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Analysis on Combustion Flame of a Stirling Engine by Using Ethanol as Fuel ZHOU Xiao-Li, CHEN Xiao-Ling, ZHANG Wu-Gao, YU Chao 2013, 47 (04):  565-571.  Abstract ( 2442 )   Save The performance of a Stirling engine is closely related with the quality of combustion. Visual test bench is adopted, by using a highspeed camera to photograph combustion flame, the effect of gas ejector on the stability and the shape of ethanol flame was analyzed. According to the relationship between RGB and combustion mode in different ways, the change of combustion mode when ejected air is participating in combustion was studied. The results show that, with suitable amount of ejecting air, the stability of the flame is improved apparently, and the length of the flame is shortened, the fullness of the flame is increased significantly, and the mode of combustion becomes half premixed and halfdiffusion combustion.   References | Related Articles | Metrics

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Investigation on Dewetting Dynamics of Thin Liquid Film Containing Insoluble Surfactant LI Chun-Xi, SHEN Lei, YE Xue-Min, TONG Jia-Lin 2013, 47 (04):  572-578.  Abstract ( 2866 )   Save  Under slip boundary conditions, the dewetting of thin liquid films in the presence of insoluble surfactant monolayer was considered. Coupled nonlinear governing equations for the film thickness and surfactant concentration based on boundary layer theory were employed. The dewetting evolution of films was simulated using PDECOL program and the numerical results were presented, while the effects of characteristic parameters on dewetting process were discussed. The results show that the impact of Marangoni effect on the change rate of films thickness is not significant in vertical direction, the change rate of films thickness is dominated by disjoining pressure and capillary stress. The influence of Marangoni number M on static dewetted structures is not significant, and decreasing capillary number C will suppress the dewetting phenomenon effectively. Increasing slip coefficient β will accelerate the dewetting process and shorten the dewetted structures. Increasing equilibrium film thickness lc will lessen the deformation degree of surface and thereby lead the film thickness to be stabilized.   References | Related Articles | Metrics

Automation Technique, Computer Technology

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A Binary-String-Set-Based Algebraic Framework for Policy Composition LIU Chen-Yan-1, 2 , PAN Li-1, 2 , ZI Xiao-Chao-2 2013, 47 (04):  579-583.  Abstract ( 2345 )   Save A new algebraic framework was proposed for merging the algebraic model with the implementation mechanism. In this framework, the policy is converted into logic pattern by defining new binary string/binary string set and constructing a new set of operation rules. Depending on that, an algorithm named rotate-combination is issued to solve the problem of order-sensitivity and rule-redundancy in MTBDD mechanism. By deriving the semantic operators and formulating the policies composition as expressions of the algebra, a new model was set. Furthermore, an analysis of the time complexity and simulation results were given to demonstrate the effectiveness of the framework, and its performance is better than that of the MTBDD-based mechanism.   References | Related Articles | Metrics

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Prediction of User’s Retweet Behavior in Social Network XIE Jing, LIU Gong-Shen, SU Bo, MENG Kui 2013, 47 (04):  583-588.  Abstract ( 3732 )   Save Based on the tweet’s topic and user’s characteristics on Sina Weibo, a prediction algorithm for user’s retweet behavior in social network was proposed. Firstly, use mutual information theory to extract features from retweeted users’ tweet content. Compute the relevance between extracted features and given user’s tweet content to predict the user’s retweet behavior. Then study the relationship between user’s retweet behavior and user’s other characteristics such as gender, number of friends, number of followers, and number of tweets to select proper user characterization. Use user characterization and Bayesian model to predict a given user’s retweet probability. Combining the results from the above two methods to make a final prediction of user’s retweet behavior on a tweet with given topic. The prediction algorithm is of great significance in studying the spread of internet public opinion and microblogging marketing. References | Related Articles | Metrics

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Visual Force Measurement Using Pseudo Zernike Moment Invariants HU Wen-1, LIU Hong-Tao-1, HU Chun-2, FAN Ming-Xia-3, MO Jin-Qiu-1, WANG Shi-Gang-1 2013, 47 (04):  589-593.  Abstract ( 2458 )   Save  A new visual force measurement method was proposed to measure applied forces through analyzing pseudo Zernike moment invariants. First, a feature vector of pseudo Zernike moment invariants is used to describe the deformed microgripper shape in microassembly. This description indicates a function between the applied force and the feature vector of moment invariants. Then, a training set is established, where the input and the output represent the feature vector of moment invariants and the corresponding known applied force, respectively. Finally, a support vector machine (SVM) compares the feature vectors in the testing set with those ones in the training set, implements multiclass classification and estimates unknown applied forces in the testing set. The experiments on four different microcantilevers validate the proposed method.   References | Related Articles | Metrics

Aeronautics & Astronautics

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Processing Method for  Hilbert-Huang Transform End Effects Self-Adaptive Endpoint-Phase Sinusoidal Extension LI Fang-Xi, CHEN Gui-Ming, LIU Xi-Liang, ZHANG Qian, LI Sheng-Chao 2013, 47 (04):  594-601.  Abstract ( 2749 )   Save  For the Hilbert-Huang Transform(HHT) endpoint effect problem, a self-adaptive method of endpoint-phase sinusoidal extension was presented. This method adaptively adds sinusoidal extension function of phase, amplitude and frequency to improve decomposition precision according to the data trend near the end. Then the object function to represent empirical mode decomposition(EMD) performance was introduced to satisfy the pertinence precision between intrinsic mode function(IMF) and original signal and low iterations of EMD. The boundary extension parameter decomposition is an adaptive process with better practicability. The simulation and example of hydraulic system show that this approach can not only solve HHT end effect, but also improve EMD decomposition precision with less filtration and reduce Hilbert spectrum end effect. Finally, it can extract the fault characteristics of gear pump vibration signal and get a good application effect.   References | Related Articles | Metrics

Automation Technique, Computer Technology

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A Method for Cucumber Identification Based on Iterative -RELIEF and Relevance Vector Machine JIN Li-Zuan, TU Jun, LIU Cheng-Liang 2013, 47 (04):  602-606.  Abstract ( 2111 )   Save To satisfy the requirement of real-time processing and identification accuracy, a method based on iterative-RELIEF relevance vector machine was proposed. In this method, information of image samples is brought into the module of iterative-RELIEF algorithm, which exports a weight for every feature. Then, the information of image samples with weights is brought into the training module of relevance vector machine (RVM). As a result, an image classifier is made, which can be used to predict the classes of unknown pixels of a image containing a cucumber. In the experiment, the rate of right identification is up to 80% or more, while the rate of false identification is lower than 27%, and the ratio of the two is up to 3.0 or more.   References | Related Articles | Metrics

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An Improved Total Variation-Based Image Fusion Algorithm   HAO Min-Hui, LIU Zhe, ZHANG Yong-Liang, ZHANG He-Ni 2013, 47 (04):  607-612.  Abstract ( 2639 )   Save Considering the total variation-based algorithm for image fusion has block effects when fusing multi-focus images, the notion of feature representation in conjunction with principal component analysis was used for improvement. The improved approach prevents independent block transform from happening. The experimental results show that the proposed algorithm can resolve the problem of block effects efficiently, and it also outperforms the discrete wavelet transform based algorithm when focusing on noisy image. Key words： References | Related Articles | Metrics

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An Improved Kriging Approximation and Its Application to Shape Design Optimization of Torpedo WEN Qing-Guo, SONG Bao-Wei, WANG Peng, WANG Si-Ling 2013, 47 (04):  613-618.  Abstract ( 2168 )   Save Sample augmentation  could improve the accuracy of the Kriging models under small samples. It adds additional data to the original samples, the augmented samples are used to build the Kriging model. There are two methods to create the additional samples. The first one uses maximum likelihood estimation (MLE), the other uses minimum means squared error (MSE). The MLE process is too strict to provide enough additional useful information, the augmented samples are exceedingly close to the original samples. The minimum MSE process gets new samples with available information to the original database, the accuracy of the Kriging model under the augmented samples is improved. The minimum MSE process can solve the problem about constructing the high accuracy Kriging models under small samples. Finally, a torpedo shape design optimization was carried out with the technique, and the Kriging model using the minimum MSE process shows its high precision and reliability.  References | Related Articles | Metrics

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An Enhanced Hybrid Genetic Algorithm for the Capacitated Arc Routing Problem   LIU Tian-Tang, JIANG Zhi-Bin, HU Hong-Tao, LIU Ran 2013, 47 (04):  619-625.  Abstract ( 2205 )   Save In order to solve the NP-hard capacitated arc routing problem (CARP) in acceptable time, an enhance hybrid genetic algorithm (EHGA) was proposed. The enhanced local search (ELS) was used within a genetic algorithm (GA) framework to intensify the search. Binary tournament replacement and population management strategy were proposed when population was updated. The CARP benchmark instances were tested. The results show that EHGA outperforms memetic algorithm (MA), and is effective to solve the CARP.   References | Related Articles | Metrics

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Sensor Allocation Based on the Maximum Error in Thermal Monitoring for Microprocessors   QIU Geng, LI Xin, RONG Meng-Tian, LIU Tao 2013, 47 (04):  626-629.  Abstract ( 1754 )   Save A new singular value-awared method of solving and sensor allocation strategy were proposed for the temperature sensors embedded in microprocessors as to monitor the thermal behavior. The strategy discussed how many temperature sensors we need at least to satisfy the max error to be allowed by using of improved dual clustering algorithm. The experimental results indicate the superiority of the technique and confirm that it can calculate the minimum number of sensors with the max error allowed in widely used microprocessor architecture. Much less sensors are used compared with the k-means cluster algorithm.   References | Related Articles | Metrics

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Drift Suppression in Motion Estimation Based on B-Spline Fitting of Vertical Profile LIU Hong-Tao, JIANG Ru-Yi, HU Wen, MO Jin-Qiu, WANG Shi-Gang 2013, 47 (04):  630-634.  Abstract ( 2238 )   Save In vehicle motion estimation using visual odometry, drift accumulated from errors in relative measurement is a big problem. This paper put forward a new drift suppression method based on dynamic tracking by B-spline fitting of vertical road profile. When a vehicle is driving tightly on the surface of a road, the motion trajectory will have the same shape as the vertical road profile. Thus tracking of the vertical road profile can be used to suppress the drift value for motion estimation using visual odometry. As vertical road profile tracking and motion estimation are not synchronous, a fixedlag Kalman drift suppressor was established. The experiment validates the effectiveness of the method suggested for drift suppression in visual odometry.   References | Related Articles | Metrics

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Speech Enhancement Based on Chinese Restaurant Process LEI Ju- Yang 2013, 47 (04):  635-639.  Abstract ( 3094 )   Save Aiming to the problem of speech enhancement from colored noise, the Chinese restaurant process mixture model (referred to as CRPMM) was introduced to modeling the distribution of noise. Markov sampling chains can be conveniently extended, where the latent variables are distributed according to a Chinese restaurant process. The updating form of joint probability of parametric variables and the latent variables were built related to block sampling. This method can approximate the posterior distribution of noise on space exactly, incorporating Kalman filtering technique. The simulation results and the experimental result of speech enhancement show that the infinite block sampling technique data-driving can adapt new modes, and a higher efficiency can be achieved for speech enhancement.   References | Related Articles | Metrics

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Design and Motion Description of a Hybrid Self-Reconfigurable Robot YU Jiang-1, FEI Yan-Qiong-1, YANG Wei-1, LOU Xiao-Chun-2 2013, 47 (04):  640-643.  Abstract ( 2085 )   Save A new hybrid self-reconfigurable modular robot which is composed of several triangular columnar master-slave modular was designed. The basic module consists of a master module and a slave module. There are three main drive motors and corresponding gears in each master module, and two drive motor in each slave module. Based on the structure of the connection ports, the analysis of the connection ports’ motion was given. The description of the basic spatial configuration of the self-reconfigurable modular robot was given based on the geometric characteristics of the basic module. Then the simulation of the self-reconfigurable robot changed from line to hexagon was given. The results show that the construct of the modular robot is compact and effective.   References | Related Articles | Metrics

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Automated Negotiation Decision Model Based on Classifier Fusion PENG Yan-Bin-1, ZHENG Zhi-Jun-1, YU Cheng-Bo-2, LI Ji-Ming-3 2013, 47 (04):  644-649.  Abstract ( 2724 )   Save Due to the confidentiality of information in e-commerce environment, negotiation participants can not get opponent’s negotiation preferences, thereby affecting the negotiation performance. To solve this, an automated negotiation decision model based on classifier fusion was proposed. The model incorporates support vector machine and Bayesian classifier by combining the advantages of both, improving the effect of classification learning of negotiation preferences. Based on accurate estimation of opponent’s negotiation preference, a particle swarm optimization algorithm was used to search the optimal counter proposal. The experimental data show that the new method is better than the single classifier, and can maintain a high total negotiation utility in the noisy small scale training set.   References | Related Articles | Metrics

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Scheduling Algorithm of Dual-Arm Multi-cluster Tools with Residency Constraints SHI Xiao-Ming, ZHOU Bing-Hai 2013, 47 (04):  650-655.  Abstract ( 2506 )   Save According to characteristics of the cluster tools, a problem domain of the scheduling was supposed and defined, and a scheduling algorithm of dual-arm muti-cluster tools with residence constraints was presented as well. A decomposition method is utilized to this algorithm to break multi-cluster tools into several independent single-cluster ones, meanwhile, a free-conflict constraint scheduling algorithm is presented with an objective of minimizing the fundamental period of the current wafers. Simulated experiments were designed to evaluate the proposed algorithm. The results indicate that the proposed algorithm is valid to schedule the wafers on the multi-cluster tools.   References | Related Articles | Metrics

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The Critical Stroke Model of Anchoring-Extending Gastrointestinal Micro Robot and Its Experimental Study LIN Wei, YAN Guo-Zheng 2013, 47 (04):  656-662.  Abstract ( 1967 )   Save To obtain the main parameters range of the anchoring-extending gastrointestinal micro robot, the critical step model was deduced by using the hyperelastic stress-stain constitutive model, which describes the biomechanical behavior of the intestinal tract. For extending mechanism, according to the relation factor of the speed and resistance force in the critical step model, a smooth signal cabin robot model was used in experiments, with in vitro small intestine of various diameters; for anchoring mechanism, a legged robot model was used to test the anchoring force in difference leg length. The experimental result is returned to the model to export some robot design guidelines. Finally, a robot prototype was used in an in-vitro experiment to validate the critical stroke model. Key words： References | Related Articles | Metrics

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Optimal Matching Algorithm for Heat Measuring Instrument with Platinum Resistance REN Shu-1, JI Xiao-Jun-1, DONG Hao-Ran-1, CAI Ping-1, HAN Tao-1, CHEN Le-Sheng-2, ZHOU Xian-Mei-2 2013, 47 (04):  663-666.  Abstract ( 2407 )   Save An optimal matching algorithm based on matrix computation was proposed to solve the problem of how to get the most pairs of two matched thermal resistances with the special matching roles in large amount of resistances. The algorithm can also be applied to other matching problems.  All feasible matched pairs could be got by a cycle of matrix computation. The influence factor of each feasible combination would be drawn from the pairing rate. Selected priority of each feasible combination is determined by the influence factor. The optimal screening process is based on the selected priority so as to obtain the final matching plan. Monte Carlo method was used to validate the performance of the optimal algorithm. References | Related Articles | Metrics

Aeronautics & Astronautics

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Game Theory Based Multi-UAV Cooperative Searching Model and Fast Solution Approach DU Ji-Yong-a, ZHANG Feng-Ming-b, MAO Hong-Bao-c, LIU Hua-Wei-c, YANG Ji-a 2013, 47 (04):  667-673.  Abstract ( 3542 )   Save This paper proposed a local Nash optimal based distributed search decision method in the frame of distributed model predictive control (DMPC). To consider the interaction between the UAVs, a graph theory based multi-UAVs cooperative model was constructed, which was based on artificial potential field (AFP) cooperative mechanism. It proposed a connected component based hierarchical structure that decomposes the complex optimization problem into smaller, more manageable sub-problems, to reduce the computational complex and communication burden. In this approach, a decision priority sequence is determined by node output degree. According to the decision priority, the paper proposed three decision forms: symmetry, leader-follower(LF) and symmetry-LF form. The corresponding game models were generated. The MPC and particle swarm optimization (PSO) based method was implemented to solve the individual UAV decision making. The simulations show that this is potentially a good method for solving cooperative search problem involving a large number of vehicles with robust performance.   References | Related Articles | Metrics

General Industrial Technology

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Thermal Transfer Performance of Parallel Flow Heat Exchangers under Frost Conditions LIANG Yuan-Yuan, XU Bo, CHEN Jiang-Ping 2013, 47 (04):  674-678.  Abstract ( 1963 )   Save The parallel flow heat exchanger’s thermal transfer performance under frost conditions was investigated. The heat transfer area and overall surface efficiency change as the frost grows. The airside heat transfer coefficient was also calculated using logarithmic-mean temperature difference (LMTD) method. The result shows that when the frost thickness grows to 0.4 mm, the heat transfer area decreases by 18%, and the air side surface efficiency decreases by 17.42%~24.78%. Moreover, the reduction of the heat transfer coefficient is an important cause to the decline of heat exchanger performance. The heat transfer coefficient decreases about 50% in the tests, while louver gap blockage mainly contributes to the decrease of heat transfer coefficient.   References | Related Articles | Metrics

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Development of a Low-g Micro Inertial Switch Based on Planar Rectangular Helical Spring WANG Chao, CHEN Guang-Yan, WU Jia-Li 2013, 47 (04):  679-686.  Abstract ( 2461 )   Save A low-g (1 g~30 g) micro inertial switch based on planar rectangular helical spring was developed. Single crystal silicon with perfect mechanical property was used as the structure material. The onstate threshold fomula of the inertial switch was derived with the Castigliano’s theorem and the linear elasticity theory of material mechanics. The relative error is less than 3% between the theoretic and the ANSYS simulation results. Designs of double contact points and low natural frequency of the mass-spring structure were proposed to improve the environment adaptability of the micro inertial switch. The fabrication process utilizing SOI wafer with double buried layers was carried out to improve the precision of structure parameters. The micro inertial switch was fabricated using crucial technology including KOH etching, ICP etching and spray coating. The bulk of chip is about 7 mm×7 mm×1.3 mm in size. The laboratory centrifuge tests were performed on the fabricated inertial switch to measure the on-state threshold. The test results show that the threshold value is about 6.45 g with a closed precision of 0.5 g. Amount of on-state threshold transfer caused by environment tests including random vibration test and high temperature test is less than 0.5 g, which shows that the developed inertial switch has better environment adaptability and mechanical property.   References | Related Articles | Metrics