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15 April 2011, Volume 32 Issue 4 Previous Issue    Next Issue
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A localization algorithm based on DV-Hop and distance geometry constraints Zheng, Jun-Gang (1); Wu, Cheng-Dong (1); Chu, Hao (1); Huang, Yue (1) 2011, 32 (4):  457-459+463.  DOI: - Abstract ( 310 )   HTML   PDF (1623KB) ( 763 )   The error in the DV-Hop localization algorithm is primarily in computing the distance between unknown and anchor nodes. Using distance geometry constraints and the Cayley-Menger determinant in two-dimensional space, the distance between unknown and anchor nodes were optimized and corrected. The conditions of distance geometry constraints successfully reduced the error of distance measurements between unknown and anchor nodes, and node localization was determined using trilateration. Simulation results show that the measurement data needing correction increases with the number of anchor nodes, and that this localization algorithm accurately measures the distance between unknown and anchor nodes, thereby improving positioning accuracy of network nodes and greatly increasing the coverage rate of nodes. References | Related Articles | Metrics

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An image reconstruction algorithm based on Tikhonov and variation regularization for magnetic induction tomography Chen, Yu-Yan (1); Wang, Xu (1); Lü, Yi (1); Yang, Dan (1) 2011, 32 (4):  460-463.  DOI: - Abstract ( 442 )   HTML   PDF (1958KB) ( 699 )   A new hybrid algorithm is presented to solve the ill-conditioned inverse problem of magnetic induction tomography (MIT) and improve the quality of reconstructed images. The hybrid algorithm first produces the preliminary image region using the solution well-posedness of the Tikhonov regularization algorithm, and then obtains the final reconstructed image using the edge-preserving and sharpening property of the variation regularization algorithm. Compared with the Tikhonov regularization algorithm and the variation regularization algorithm, the hybrid algorithm overcame the numerical instability of MIT image reconstruction, accelerated the convergence speed of image reconstruction, and improved the resolving power of target conductors and the quality of the reconstructed image. Simulation results verified the effectiveness of the proposed algorithm. References | Related Articles | Metrics

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Automated classification of gait patterns based on process neural networks Wang, Fei (1); Zhang, Yu-Zhong (1); Wen, Shi-Guang (1); Wu, Cheng-Dong (1) 2011, 32 (4):  464-467+471.  DOI: - Abstract ( 505 )   HTML   PDF (1488KB) ( 1215 )   A general scheme for automated classification of gait patterns based on process neural networks is proposed to overcome limitations of the feature vector approach, including difficulty in feature selection, heavy computing load, and complexity of recognition algorithms. Initial human gait capture was done using accelerometers mounted on the lower limbs of a subject to obtain kinematic information for various gait patterns. Using a Butterworth filter, a time-series acceleration signal was processed, then fitted as a time-dependent function and presented to PNNs directly. For the capacity of arbitrary functional approximation of PNNs, the automated classification of time-series acceleration signals for different gait patterns was achieved. Furthermore, to overcome the slow convergence and localized minimum problems with the traditional gradient descent method, a particle swarm optimization algorithm was adopted to modify the weight functions and weight values of PNNs. Experimental results demonstrated the correctness and effectiveness of the proposed scheme. References | Related Articles | Metrics

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Using a Gaussian process to improve and utilize empirical mode decomposition Wen, Shi-Guang (1); Wang, Fei (1); Wu, Cheng-Dong (1); Zhang, Yu-Zhong (1) 2011, 32 (4):  468-471.  DOI: - Abstract ( 324 )   HTML   PDF (1270KB) ( 765 )   The traditional Hilbert-Huang transform (HHT) based on the envelope line calculation of the cubic spline interpolation has several drawbacks such as overshooting and endpoint oscillation. To solve this problem, a new algorithm based on Gaussian process regression is proposed to compute the envelope. Optimizing the parameters of Gaussian process regression is discussed, with improved generalization ability and interpolation precision. The algorithm effectively resolves the false frequency and endpoint oscillation problems. Gait data processing indicates that the problem of spurious frequency and endpoint oscillation can be preferably improved with a Gaussian process, and distortion of mode function was decreased. References | Related Articles | Metrics

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Incremental linear discriminate analysis based on a residual natural power method Chen, Dong-Yue (1); Wu, Cheng-Dong (1) 2011, 32 (4):  472-475+480.  DOI: - Abstract ( 248 )   HTML   PDF (584KB) ( 737 )   A new algorithm with a structure containing two incremental principal component analysis (PCA) modules is proposed to solve the incremental linear discriminate analysis (LDA) problem. A residual covariance natural power (RCNP) PCA method and lossless update equations of both a within-class scatter matrix and a covariance matrix are also proposed for accelerating convergence of the incremental LDA. Simulation results show that the proposed method provides faster convergence, and better performance in complex computations and in ease of operation compared to other incremental LDAs. References | Related Articles | Metrics

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Non-fragile robust H∞ control for linear systems with interval time-varying delay Ma, Da-Zhong (1); Wang, Zhan-Shan (1); Feng, Jian (1) 2011, 32 (4):  476-480.  DOI: - Abstract ( 290 )   HTML   PDF (186KB) ( 658 )   For time-varying delay linear systems with intervals, a new Lyapunov-Krasovskii method was presented to analyze the stability of linear systems with interval time-varying delay, and design a non-fragile robust H∞ controller. The non-fragile robust H∞ controller guaranteed the time-delay systems were asymptotically stable and satisfied a prescribed H∞ performance level. The non-fragile robust H∞ controller of linear systems with interval time-varying delay can be solved by linear matrix inequality (LMI). The effectiveness of the proposed design method was verified by simulation examples. References | Related Articles | Metrics

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An adaptive differential evolution algorithm based on a multi-population parallel Ge, Yan-Feng (1); Jin, Wen-Jing (1); Gao, Li-Qun (1); Feng, Da (1) 2011, 32 (4):  481-484.  DOI: - Abstract ( 590 )   HTML   PDF (821KB) ( 1313 )   A new adaptive differential evolution algorithm was put forward to improve search speed and avoid local optimal value. Sufficiently analyzing the characteristics of classic/adaptive mutation operators and the solution state, individuals were divided into three subgroups according to individual fitness values, thereby optimizing based on multiple populations, and different mutation operators were placed in different subpopulations. In addition, self-adaptive adjustment was introduced to adjust control parameters. Performance of the new approach was superior to other algorithms when tested on eight standard test functions. References | Related Articles | Metrics

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Chaotic phase state classification based on an improved pulse coupled neural network Jiang, Fang-Fang (1); Wang, Xu (1); Yang, Dan (1) 2011, 32 (4):  485-488.  DOI: - Abstract ( 322 )   HTML   PDF (626KB) ( 537 )   Chaotic phase state classification is a key step in utilizing chaotic systems to detect weak signals. A chaotic phase state classification method based on an improved pulse coupled neural network (PCNN) was proposed. The movement characteristics of mammalian visual cortical neurons were simulated with improved PCNN, while outputting the structural characteristics of a phase state diagram of a chaotic system. Dimensions of these characteristics were reduced using average residual error to yield real-time classification for chaotic/periodic states of the system. Sinusoidal and ECG signals were used to verify the proposed method using Lyapunov characteristic exponents. Results indicate that the method can quickly and accurately classify different chaotic phase states. References | Related Articles | Metrics

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A brain tissue extraction algorithm based on an improved C-V model Jia, Di (1); Yang, Jin-Zhu (1); Zhang, Yi-Fei (2); Yu, Ge (2) 2011, 32 (4):  489-492.  DOI: - Abstract ( 269 )   HTML   PDF (1639KB) ( 619 )   Through improving C-V model in three aspects, a new rapid and accurate method for brain tissue extraction is presented. First, segmentation speed was enhanced through improving the classical distance matrix, with the distance function convergence improved compromising accuracy. Secondly, the improved method changed the uniqueness of classical results and made the evolving lines stop at the same level gray, so spinal fluid could be wiped off, and white/gray matter was extracted more accurately. Finally, a dynamic condition for ending iteration was proposed through comparing the interval frames. This improvement changed the flaw of setting evolving times to end iteration, and improved veracity and speed. Results indicated that these improvements make brain tissue extraction more rapid and accurate, and could be helpful to doctors in making confirmed diagnoses. References | Related Articles | Metrics

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An improved SIC detection algorithm for MIMO systems Liu, Li (1); Wang, Jin-Kuan (1); Yan, Dong-Mei (1); Liu, Fu-Lai (1) 2011, 32 (4):  493-495+500.  DOI: - Abstract ( 478 )   HTML   PDF (403KB) ( 1183 )   When using successive interference cancellation (SIC) in MIMO detection, overall performance is determined by the first stages being decoded due to error propagation. To solve this problem, an improved SIC detection algorithm was proposed. For the algorithm undergoing SIC detection, an exhaustive search of initial P level signals was conducted, and accumulated metrics were calculated and arranged in order. From these were selected L signals with the smallest metrics. Then SIC algorithms were used to detect ongoing levels. Exhaustively searching initial P levels reduced frequency of coding errors and consequent error propagation and improved detection ability of the system. An appropriate trade-off between detection performance and computation complexity was obtained by adjusting P and L values. References | Related Articles | Metrics

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A chaotic image encryption algorithm based on image correlation Zhang, Wei (1); Zhu, Zhi-Liang (2); Yu, Hai (2) 2011, 32 (4):  496-500.  DOI: - Abstract ( 262 )   HTML   PDF (1371KB) ( 888 )   Considering the high correlation among adjacent pixels, a "divide and conquer" algorithm was proposed for four adjacent pixels to improve the permutation phase of traditional chaotic encryption schemes. Adjacent pixels were first separated, and then the four groups of separated pixels were permutated using "cat maps" of the four groups having different parameters, followed by reconstruction and diffusion. Simulations results indicated that, when security of the encryption algorithm could be guaranteed, permutation and encryption time decreased. References | Related Articles | Metrics

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An interactive object segmentation algorithm for a region-based active contour Song, Chun-He (1); Zhao, Hai (1); Jing, Wei (1); Zhu, Hong-Bo (1) 2011, 32 (4):  501-504.  DOI: - Abstract ( 294 )   HTML   PDF (806KB) ( 624 )   Research was conducted on object segmentation of the interactive information comprising prior knowledge between user and system. An interactive object segmentation algorithm was proposed based on an active contour without an edge (CV) and the prior shape. Due to imprecision in the prior shape user inputs, a weighted pix algorithm based on gradient and Laplace was introduced. To overcome problems with object contour shrink, a new area actuator was introduced. The proposed algorithm did not need a prior knowledge model obtained by training based on accurate prior knowledge. The user only needed to choose an approximate region of object segmentation, and the algorithm was able to segment the region. Given the selected gray scale levels, the iterative frequency was only about 26.4% of the basic CV model. References | Related Articles | Metrics

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Structure and micromechanical properties of a weld joint using steel with low sensitivity to weld cracking Lan, Liang-Yun (1); Qiu, Chun-Lin (1); Zhao, De-Wen (1); Gao, Xiu-Hua (1) 2011, 32 (4):  505-508.  DOI: - Abstract ( 285 )   HTML   PDF (1961KB) ( 839 )   Submerged arc welding technology was used to weld a steel plate with low susceptibility to weld cracking, and microstructure observation, conventional Vickers microhardness and nanoindentation examination were conducted in the heat affected zone (HAZ). The results show that a coarse grained HAZ mainly consisted of coarse granular bainite. Owing to a large number of nanoprecipitates and higher dislocation density, the higher microhardness and nanohardness were obtained in the coarse grained HAZ. The weld zone and fine grained HAZ mainly consisted of acicular ferrite plus proeutectoid ferrite and quasi-polygonal ferrite, respectively, and their nanohardness and modulus of elasticity were both less than that of the coarse grained HAZ. The greatest strength was observed in the coarse grained HAZ. The coarse granular bainite may diminish impact toughness, causing localized brittle fractures in the head of the coarse grained HAZ. References | Related Articles | Metrics

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Casting strip character of twin-roll casted 3% Si non-oriented silicon steel Zhang, Ting (1); Zhang, Xiao-Ming (1); Zhang, Qiong (1); Guo, Zhi-Yuan (1) 2011, 32 (4):  509-511+515.  DOI: - Abstract ( 509 )   HTML   PDF (1508KB) ( 545 )   Given the lengthy production cycle, high energy consumption, and other shortcomings of the traditional process for producing silicon steel, a twin-roll casting process was used to produce 3%Si non-oriented silicon steel casting strips. MEM, SEM, and TEM were used to compare micro-structure, texture, and precipitate characteristics of a casting strip containing 0.6%Al with another containing 0.9%Al. The structure of 3%Si non-oriented silicon steel produced by the twin-roll casting process was a uniform isoaxial grain, with average grain size approximate 300 μm. Texture of the strip altered significantly with changes in Al mass fraction. Texture intensity of {100} in the cast strip with 0.9%Al was 7-fold stronger than with random texture. Precipitates were AIN and MnS with maximum size about 500 and 50 nm, respectively. References | Related Articles | Metrics

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Effect of additional load on the performance and microstructure of 2124 alloy Quan, Li-Wei (1); Zhao, Gang (1); Tian, Ni (1) 2011, 32 (4):  512-515.  DOI: - Abstract ( 220 )   HTML   PDF (613KB) ( 599 )   Microstructure and performance were investigated on aged 2124 alloy at 190 and 170°C with or without added load by means of TEM, tensile testing. Due to dislocations providing enough misfits for the nucleation of S phases, equivalent S phase distribution in various directions was obtained. Load did not significantly impact preferential orientation of the S phase. However, length of the S phase in aged samples with load was shorter than that without load. Load had no significant impact on preferential orientation and length of GPB. Growth rate of the S phase aged at 190°C was faster than that at 170°C with load. Because of a large amount of fine S phase precipitation, yield strength of the aged alloy with load was larger than that without load. References | Related Articles | Metrics

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Optimizing speed feedforward compensation of a hot strip mill laminar cooling system Zhang, Dian-Hua (1); Liu, En-Yang (1); Liu, Wei-Dong (2); Liu, Xiao-Feng (2) 2011, 32 (4):  516-519.  DOI: - Abstract ( 393 )   HTML   PDF (883KB) ( 590 )   Equipment and mathematical models of a hot strip mill laminar cooling control system were described. Mathematical models of the system consist of models for air cooling, laminar cooling, feedback control, and self-learning. The original laminar cooling system was unable to effectively handle the relatively large changes in strip speed in the cooling area, thereby significantly compromising coiling temperature control accuracy. Speed feedforward compensation was proposed to achieve more adequate coiling temperature control. Improved speed feedforward compensation methods are provided in the process automation system and in the basic automation system. The optimized laminar cooling system was stable and reliable with high control precision, and metallurgical properties of the product were improved significantly, thereby laying a foundation for users to develop new products. References | Related Articles | Metrics

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Thermal field simulation of in-mold continuous casting of rectangular blooms Li, Xiao-Bin (1); Ding, Hua (1); Tang, Zheng-You (1); He, Ji-Cheng (2) 2011, 32 (4):  520-523+532.  DOI: - Abstract ( 290 )   HTML   PDF (1848KB) ( 548 )   A mathematical model describing the in-mold temperature contour for a GCr15 rectangular bloom was determined using FEM. Temperature-dependent thermophysical parameters along with average heat flow, transient heat flow, and corner air gap in boundary conditions were used to study temperature contour and billet shell thickness of rectangular blooms under different boundary conditions. Simulation experiments indicated that the temperature range with an average heat flow boundary was wider than that with transient heat flow when not considering the air gap. With the air gap, however, the ranges were similar. Corner air gap only affected the temperature of the corner region, while the core, wide face center, and narrow face center regions were not affected. Corner shell thickness with an air gap was 6 to 7 mm narrower than the one without air gap, and the hot spot area appeared 30 mm away from the corner. References | Related Articles | Metrics

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Activity calculation model for a slag system consisting of CaO-SiO2- Al2O3-FeO-CaF2- La2O3-Nb2O5- TiO2 Zhang, Bo (1); Jiang, Mao-Fa (1); Qi, Jie (1); Liu, Cheng-Jun (1) 2011, 32 (4):  524-528.  DOI: - Abstract ( 290 )   HTML   PDF (1727KB) ( 1072 )   Given the theory governing the molecular ionic structure of slag, a model was determined for calculating activity of an eight-element slag system consisting of CaO-SiO2- Al2O3-FeO-CaF2- La2O3-Nb2O5- TiO2. The activity change of components containing niobium, rare earth elements, or titanium was calculated and analyzed. Activity calculated by the model conformed well to experimental data. The component containing niobium were mainly FeO · Nb2O5, those containing lanthanum were mainly La2O3 and La2O3 · Al2O3, and the components containing titanium were mainly 2FeO · TiO2 and FeO · TiO2. As FeO mass fraction in the slag decreased, the niobium component changed from FeO · Nb2O5 to CaO · Nb2O5, while the titanium component changed from 2FeO · TiO2 and FeO · TiO2 to TiO2. w(CaO)/w(SiO2) was an important factor influencing activity of the components containing niobium or titanium at low levels of FeO mass fraction. Activity of 2CaO · Nb2O5 and CaO · TiO2 markedly increased with the increasing w(CaO)/w(SiO2). References | Related Articles | Metrics

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Modeling the radiative properties of Gaussian rough surfaces Cai, Jiu-Ju (1); Wang, Ai-Hua (1) 2011, 32 (4):  529-532.  DOI: - Abstract ( 502 )   HTML   PDF (818KB) ( 670 )   The radiative properties of two different materials surfaces with one-dimensional microscale Gaussian roughness were numerically investigated with an FDTD (finite-difference time-domain) method and near-to-far-field transformation. Calculated results were compared with those from other two approaches. The bi-directional reflectivity peak decreased gradually and eventually disappeared with increasing perfectly electric conductor (PEC) surface RMS (root mean square) roughness. The retroreflection became evident as the ratio of RMS roughness to surface correlation distance increased. Given identical surface characteristics, the overall trend of the bi-directional reflectivity was the same for both PEC and silicon surfaces although the latter was much lower than the former. The reflection of the PEC surface became more like a mirror surface as incident angle increased. References | Related Articles | Metrics

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Electromagnetic field and Joule heating of an electroslag remelting process with two series-connected electrodes Wang, Fang (1); Li, Bao-Kuan (1) 2011, 32 (4):  533-536.  DOI: - Abstract ( 343 )   HTML   PDF (1956KB) ( 571 )   A 3D finite element model was developed to analyze magnetic field, electromagnetic force, current density, and the Joule heating field for electrodes, slag, and ingots in an electroslag remelting process with two series-connected electrodes. The proximity effect dominated in the two-electrode ESR system, while the skin effect was important in the single electrode system. Maximum current distribution occurred on the interior of two series-connected electrodes in the slag and 20 to 25% of total current went through the ingot. Maximum Joule heating was at the bottom interior of the slag electrode. Investigating the various parameters indicated that if current frequency exceeded 35 Hz, current density in the inner electrode tended towards a linear distribution. Maximum Joule heating in the slag increased with increasing electrode immersion depth and decreasing of slag cap thickness. References | Related Articles | Metrics

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Use of a comprehensive analytical approach for water modeling of an asymmetrical two-strand tundish Lei, Hong (1); Zhao, Yan (2); Xing, Guo-Cheng (3); Sun, Zhong-Qiang (3) 2011, 32 (4):  537-540+553.  DOI: - Abstract ( 297 )   HTML   PDF (1112KB) ( 760 )   If a classic combined approach is used to analyze the residue time distribution (RTD) curve in a tundish, the volume ratio of the dead zone in the multi-strand tundish sometimes is negative. In addressing this problem, a comprehensive analytical approach was used to pre-treat the RTD curve of each strand in the multi-strand tundish to get the characteristic RTD curve, and then a classic combined approach was used to treat the characteristic RTD curve, with the whole characteristic parameters obtained to determine fluid flow in the multi-strand tundish. The water model result for the RTD curve of an asymmetrical two-strand tundish showed that the negative volume ratio of the dead zone appeared with Sahai's revised approach. Mean residence time is the key parameter to estimate the similarity of flow characteristics of each strand in the multi-strand tundish. The minimum mean residence time for each strand is the key parameter to investigate the fluid flow in the multi-strand tundish. References | Related Articles | Metrics

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Simulating heat of formation in a TiAl alloy Jin, Hak-Son (1); Du, An (1) 2011, 32 (4):  541-544.  DOI: - Abstract ( 304 )   HTML   PDF (495KB) ( 606 )   The MAEAM model describing the constant ratio of electron density was adjusted, and the phase structure of each component ratio was taken into account based on phase diagrams. Heat of formation of a TiAl alloy was calculated using MAEAM theory. The calculation result yielded change trends consistent with results using the Miedema theory. In order to evaluate the reliability of the proposed calculation method, the heat of formation of NiAl alloys and FeAl alloys was calculated. Calculation results agreed with experimental values and the first principle calculation results. References | Related Articles | Metrics

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Numerical simulation of the temperature field in rubber composites during cord fracture Liu, Jun (1); Liu, Xiao-Po (1); Fang, Qing-Hong (2); Huang, Bao-Zong (1) 2011, 32 (4):  545-548.  DOI: - Abstract ( 292 )   HTML   PDF (1064KB) ( 541 )   A two dimensional computation model was established by using FEM for unidirectional cord reinforced rubber composites. Given cord fracture and debonding slippage, the transient temperature field of rubber composites was simulated under cyclic loading to determine the effect of cord debonding slip friction on heat generation lag time. Temperature rose dramatically with cord fracture, while debonding slip friction caused a much lower temperature increase. The high temperature range increase caused by local stress concentration with cord fracture is an important factor affecting material failure. These results provide a valuable reference for the design of rubber composites products. References | Related Articles | Metrics

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Dynamic analysis of a giant magnetostrictive actuator at varying temperature Yuan, Hui-Qun (1); Wu, Wen-Bo (1); Li, Ying (1); Li, Dong (1) 2011, 32 (4):  549-553.  DOI: - Abstract ( 291 )   HTML   PDF (2388KB) ( 573 )   A simple dynamic model was established to determine the effect of temperature on vibratory response of the giant magnetostrictive actuator, resulting in a differential equation of motion containing terms of temperature. Under known magnetization intensity, the effect of temperature and pre-stress on vibratory response was discussed, and a coefficient of temperature dependent displacement response determined. The resonance solution caused by giant magnetostrictive nonlinearity was derived, and the effect of temperature on resonance factors discussed. Simulation results indicated that magneto-thermo-mechanical coupled nonlinearity greatly affected vibratory response of the actuator, and that temperature should be considered in analysis and design of the actuator. References | Related Articles | Metrics

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Simulating the excavating track of a excavator robot using an adaptive neural-fuzzy inference system Wang, Fu-Bin (1); Liu, Jie (1); Jiao, Chun-Wang (1); Chen, Zhi-Kun (2) 2011, 32 (4):  554-558.  DOI: - Abstract ( 332 )   HTML   PDF (1292KB) ( 860 )   To improve tracking pattern control accuracy of the working parts of a hydraulic excavator robot, analysis was conducted on the working parts which were simplified into the two-dimensional robotic arm composed of arm and bucket and two joints. When establishing an inverse kinematics model, terminal position and orientation space of the bucket and joint space and cylinder space of the working parts should relate to the tracking pattern and should control the excavator robot in each space. To improve precision in tracking the desired pattern, two adaptive neural-fuzzy inference systems (ANFIS) were used to determine inverse mapping relations between the x and y joint coordinates and joint angle, and an ANFIS inverse mapping model was established. I/O curve data of inverse mapping was selected to train ANFIS structure, with an I/O mapping curve of a fuzzy model used to obtain a corresponding joint angle based on a given desired excavation trace. Finally, the proposed fuzzy model was used to trace an expected motion pattern, and simulation results showed that tracking precision met actual demands. References | Related Articles | Metrics

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Analysis and experimental investigation of factors affecting control characteristics of line inverted pendulum systems Luo, Zhong (1); Shi, Zhi-Yong (1); Hu, Peng (1); Liu, Hong-Yi (1) 2011, 32 (4):  559-562.  DOI: - Abstract ( 346 )   HTML   PDF (1595KB) ( 748 )   Given the relationship between parameters of the mechanical parts and initial angle of an inverted pendulum, control parameters and a structural model of an inverted pendulum system was set up for a typical experimental system of nonlinear, strong coupling, and multi-input/output control, with its operational principles described. The relationship between control parameters of the optimum control strategy and the parameters of the mechanical parts was analyzed. The equation describing effect of the initial angle as well as the effect of system control parameters on parameters of the mechanical parts was determined. Results of combined experiments indicated that factors affecting system control error included tooth belt power transmission error, dolly and rocker arm inertia, and friction between tooth belt and sprocket. These results provide theory and methods for control of inverted pendulum systems as well as for analysis and design of and other related system. References | Related Articles | Metrics

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Moving mesh based transient simulation of rolling piston compressor pump chamber flow Yue, Xiang-Ji (1); Ba, De-Chun (1); Su, Zheng-Yu (2); Zhang, Yu (1) 2011, 32 (4):  563-566.  DOI: - Abstract ( 358 )   HTML   PDF (1754KB) ( 667 )   Using a moving mesh method, a three-dimensional transient numerical simulation model for a rolling piston compressor chamber was established. Compared with a theoretical work cycle, the numerical results indicated that the model reflected the main process of a rolling piston compressor, and can be used to study a pump chamber flow field. Gas flow in a pump chamber was simulated, providing considerable detailed information of the pump chamber flow field. Flow phenomena and flow field in the pump chamber were analyzed, and primary characteristics of the flow field during compressor intake, compression, and exhaust were determined. The results provide a basis for structural optimization and further study in rolling piston compressors. References | Related Articles | Metrics

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Analyzing the factors affecting ball screw pair contact deformation Wang, Dan (1); Wang, Wen-Zhu (1); Sun, Zhi-Li (1); Zhou, Liang (1) 2011, 32 (4):  567-570.  DOI: - Abstract ( 286 )   HTML   PDF (1963KB) ( 759 )   The principal curvature radius of a ball screw pair was calculated using the structural parameters of the ball screw pair, and the curvilinear relationship between helix angle, contact angle, and principal curvature was plotted. Based on Hertz contact theory, contact deformation of the ball screw pair was calculated. Contact stiffness was then investigated using the relationship between contact angle, helix angle, and contact deformation. Calculated contact deformation values were verified with ANSYS FEM. The results demonstrated the validity of the theory. Contact characteristics of ball screw pairs can be effectively improved by increasing helix angle and contact angle. References | Related Articles | Metrics

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Finite element analysis of thermal characteristics of the spindle assembly and headstock for a numerical control lathe Zhang, Yao-Man (1); Liu, Qi-Wei (2) 2011, 32 (4):  571-574.  DOI: - Abstract ( 320 )   HTML   PDF (1453KB) ( 979 )   The effect of thermal properties on performance was determined for the headstock of a CNC lathe. Based on the factors needed for finite element analysis (FEA), an FEA model of the headstock was established, with the constant temperature field distribution and thermal equilibrium time of the headstock simulated and calculated. Under conditions of heat and structure load, the temperature field and thermal deformation of the headstock were calculated using a thermal and structure coupling technique, and heat distortion trends of the spindle assembly and headstock were analyzed. Results indicated that hot asymmetry affected machine processing performance and provide a foundation for optimization design of spindle assembly and thermal error compensation. References | Related Articles | Metrics

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Application of a new collector in reverse flotation of hematite Liu, Wen-Gang (1); Wei, De-Zhou (1); Cui, Bao-Yu (1); Huang, Fu-Yan (1) 2011, 32 (4):  575-578.  DOI: - Abstract ( 266 )   HTML   PDF (1936KB) ( 534 )   Use of N-dodecylethylenediamine (ND) in reverse flotation of hematite was investigated for separation of artificially mixed and actual iron ores. ND effectively separated quartz from hematite when the mass ratio of hematite to quartz was 1:1 and 3:2. At pulp pH of 7.27, 40 mg/L collector and 3.33 mg/L starch yielded product with 60.36% and 61.20% iron, respectively. In room temperature separation trials with actual ore, product containing 66.72% iron and a 93.46% iron recovery were obtained by subjecting iron ore at 95.42% -0.045 mm granularity in the presence of 200 g/t ND, 400 g/t sodium hydroxide, and 200 g/t starch to a coarse sorting, a fine sorting, and two scavenging operations. References | Related Articles | Metrics

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An algorithm for matching adjacent sections of complex ore bodies Chen, Xiao-Qing (1); Ren, Feng-Yu (1); Zhang, Guo-Jian (1); Ding, Hang-Xing (1) 2011, 32 (4):  579-582.  DOI: - Abstract ( 320 )   HTML   PDF (784KB) ( 590 )   A three-dimensional prismoid was formed by connecting adjacent sections of ore body into a three-dimensional visualization model of deposits to show the ore body shape. An algorithm for matching adjacent sections of an ore body was studied. Polygonal sections were first matched to address the question of which piece to fit where. Secondly, the characteristic vertices of the polygons were given an approximate match up. Finally, the original polygons were cut into several parts by these characteristic vertices. A matching relationship between upper and lower sections was determined and the surface model of the ore bodies was formed through triangulation. Actual mining practice verified that this algorithm is fast and accurate in matching complex ore bodies, and is unaffected by size, rotation, and transformation of the polygon. References | Related Articles | Metrics

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Analyzing the sedimentary system of sandstone-type uranium deposits in the Pingzhuang basin Chen, Xiao-Hong (1); Gong, En-Pu (1); Zhao, Zhong-Hua (1); Yang, Fu (2) 2011, 32 (4):  583-586.  DOI: - Abstract ( 231 )   HTML   PDF (1644KB) ( 576 )   Based on former research findings, sedimentary system characteristics and potential uranium mineralization sections of the upper Sunjiawan formation of the late cretaceous located near Heishui were analyzed using principles of sedimentology, well logging geology, and stratigraphy. Results indicated that the Heishui area is in the formative stage of the upper Sunjiawan formation and is not located at the center of the Pingzhuang basin but lies on the edge of the basin. The sedimentary base level experienced a cycle in which elevation occurred during the early stage, a high point was reached in mid stage, and a drop off during the late stage. During this period, alluvial braided channel deposits were favorable to uranium mineralization. References | Related Articles | Metrics

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Laboratory experiments on the process of rock tunnel failure and its particle flow numerical simulation Wang, Shu-Hong (1); Xu, Yuan (1); Zhang, Lun (2); Zhang, Min-Si (1) 2011, 32 (4):  587-590.  DOI: - Abstract ( 276 )   HTML   PDF (1575KB) ( 800 )   Based on previous jointed model tests and numerical simulation studies, several groups of material compression tests were designed on joint models with holes, and model experimental processes were simulated with particle flow code software (PFC2D). Tallies of the stress-strain curve and numerical simulation curve were taken as selection criterion of PFC mesomechanics parameters in the model experiment. After that, the failure process of jointed rockmass with holes was simulated by the mesomechanics parameters to reappear. The failure process and mechanism of jointed rockmass with holes are discussed. The entire process was divided into four stages, including the linear elastic stage, the early crack stage, the peak stage, and post-peak stage. This failure mechanism can reasonably predict the failure mode of the actual engineering and evaluate the stability of engineering rockmass. References | Related Articles | Metrics

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Multi-objective robust operation model for a supply chain with credit period uncertainty Yu, Li-Ping (1); Xu, Jia-Wang (2); Huang, Xiao-Yuan (1) 2011, 32 (4):  591-594+599.  DOI: - Abstract ( 292 )   HTML   PDF (1480KB) ( 708 )   The effect of trade credit on supply chain product and cash flow was determined, with variations in the credit period described by using an interval uncertainty method. A multi-objective robust operation model was established using a robust linear programming approach in an uncertain credit period for a multi-product and multi-period supply chain involving one producer and one supplier. A numerical example was used to verify the proposed model, and the optimum robust operating strategy was determined for worst case supply chain conditions during an uncertain credit period. When robust measures were adopted in the objectives of supply chain coordination and profit was maximized for all participants, the effect of credit period uncertainty on objective values decreased significantly. References | Related Articles | Metrics

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A method for evaluating intellectual capital while considering interaction context Suo, Wei-Lan (1); Fan, Zhi-Ping (1); Jia, Lu (1) 2011, 32 (4):  595-599.  DOI: - Abstract ( 220 )   HTML   PDF (1645KB) ( 477 )   Intellectual capital dimensions and their components were first finalized, with interaction analysis conducted to solve the problem of intellectual capital evaluation given the context of interaction. An evaluation method for intellectual capital was then proposed considering the interaction context. TAC (two-additive choquet) integral operator was used to calculate the dimensional evaluation values and the overall evaluation value in the proposed method. Furthermore, the contribution of dimensions to the overall evaluation value was clarified through an elucidation operation, so that decision makers can determine the performance of intellectual capital and manage it effectively. An example was used to illustrate the practicality and effectiveness of the proposed method. References | Related Articles | Metrics

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IPA-based service quality evaluation Zhang, Xiao (1); Fan, Zhi-Ping (1); Fang, Fang (1); Zheng, Wen (2) 2011, 32 (4):  600-603+608.  DOI: - Abstract ( 582 )   HTML   PDF (1433KB) ( 754 )   Given existing problems with service quality evaluation, a criterion system of service quality was devised, and service quality was evaluated based on the idea and methodology of importance-performance analysis (IPA). The service quality evaluation process utilized initial evaluation information obtained by customer questionnaires. Criterion performance was then calculated from the evaluation information. Next, taking into account the causal relationship between criterion importance and criterion performance in service quality evaluation, criterion importance was computed by constructing a BP neural network. Evaluation results were analyzed using IPA. An example is provided to show the feasibility and validity of the proposed method. References | Related Articles | Metrics

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Analyzing characteristics of the complex network of stock risk during unilateral decline of the Shanghai stock market Zhang, Ding (1); Zhuang, Xin-Tian (1) 2011, 32 (4):  604-608.  DOI: - Abstract ( 276 )   HTML   PDF (508KB) ( 589 )   Short-term stock risk was simulated with a VaR array. An undirected and unweighted stock short-term risk network was built taking stocks from the Shanghai stock market, with the correlation of the VaR arrays of stocks used as boundaries. Then, the topological structure of the network was analyzed utilizing the theories and methodology of complex networks. The complex network of short-term risk of stocks had a small-world effect with a scale-free property at specified times, though in most cases the scale-free characteristic was not observed. Under conditions of unilateral decline, price fluctuations for individual stocks was relatively high, although the mutual risk impact of each stock was lower. In a shorter term, the difference in losses between holding different stocks was relatively large, while over the longer term, the difference was smaller. References | Related Articles | Metrics