Journal of Northeastern University(Natural Science)

Amended Harmony Search Algorithm for Solving Spacecraft Optimal Rendezvous Problem

WANG Hao， OUYANG Hai-bin， GAO Li-qun

2015, 36 (7): 913-917. DOI: 10.12068/j.issn.1005-3026.2015.07.001

Abstract ( 733 )

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A hybrid index of fuel-time on the basis of C-W equations was built for the spacecraft optimal rendezvous problem， and an amended harmony search (AHS) algorithm was proposed to solve this problem. In the AHS algorithm， a global uniform learning operation was presented that the guidance of the current global best harmony was utilized and the pitch adjusting operation was replaced， resulting in the enhancement of the balance between the global search and local search. The PAR was dynamically adjusted to adapt the search process of algorithm. Several optimal rendezvous cases were used to test the effectiveness of AHS algorithm， and it was verified by the numerical results that correct satisfied results could be obtained with the proposed AHS algorithm， which is better than that of the other algorithms.

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Soft Sensor for Determination of Dynamic Fluid Levels Based on Enhanced Just-in-Time Learning Algorithm

WANG Tong， GAO Xian-wen， LIU Wen-fang

2015, 36 (7): 918-922. DOI: 10.12068/j.issn.1005-3026.2015.07.002

Abstract ( 1110 )

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When soft sensor model is used to predict dynamic fluid levels in oil production， it will gradually degenerate during the process， resulting in the larger deviation of prediction results and the difficulties to be used in practical oilfield production. To solve this problem， a new just-in-time model based on the similarity of subspaces was proposed to realize adaptive dynamic updates for a prediction model of dynamic fluid level. According to the production data， the similarity of subspaces was calculated to improve the accuracy of selecting modeling samples. Two memory parameters were designed to change the update method in traditional just-in-time learning model， which could reduce the amount of calculation and improve the prediction accuracy of dynamic fluid level. Compared with the traditional just-in-time learning algorithm， the improved method has better measurement accuracy and adaptation for the prediction of dynamic fluid levels. The example showed that the proposed method was fitted in with the standard of oil production and could be applied to actual production.

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Global Path Planning Based on Improved Ant Colony Optimization Algorithm for Geometry

LIU Jie， YAN Qing-dong， MA Yue， TANG Zheng-hua

2015, 36 (7): 923-928. DOI: 10.12068/j.issn.1005-3026.2015.07.003

Abstract ( 874 )

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The improved ant colony algorithm and path geometry optimization were applied to solve the global path planning problem of mobile robot. The obstacle performance was combined in the proposed algorithm to establish the workspace model of the robot. By setting the initial pheromone， the ant searching speed was accelerated， and through the adaptive pheromone mechanism， the interference problem of initial pheromone to the specific map was solved. In addition， the pros and cons of the path planning were screened by setting the adaptive path length. It was also proposed that the pheromone spreading strategy was decided by the path length. Meanwhile， according to the principle of geometry， the planning path was optimized to accelerate the convergence speed of the optimal solution. The effectiveness and universal application of the proposed algorithm was demonstrated by the simulation results. In the random environment map， the optimal path could be rapidly obtained with the proposed algorithm.

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Cost Oriented Virtualized Resource Optimization Allocation for SBS

ZHANG Bin， ZHU Meng-xiao， ZHAO Xiu-tao， ZHANG Chang-sheng

2015, 36 (7): 929-933. DOI: 10.12068/j.issn.1005-3026.2015.07.004

Abstract ( 738 )

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When deploying applications in cloud environments， there are few researches on the optimal resource allocation for cloud applications described as service based software systems (SBS). To solve the problem， resource configuration (RC) was defined， and a method for identifying all the RCs of any component services was proposed. Based on this， the resource allocation for SBS was modeled as combination optimization of RCs， and a genetic algorithm (GA) with improved cross operator and mutation operator was presented to solve the optimization model. Effectiveness of the model was proved by the experiment results， and it was showed that the proposed GA converged fast. In addition， similar optimal solutions could be obtained by the GA with linear programing， and it was more efficiency to deal with larger problem.

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A Query Expansion Method Based on Search Log and Local Context

ZHANG Shu-bo， MA An-xiang， ZHANG Bin， SUN Da-ming

2015, 36 (7): 933-936. DOI: 10.12068/j.issn.1005-3026.2015.07.005

Abstract ( 766 )

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When search logs encounter over sparse and timeliness problems，the quality of extensions cannot be guaranteed by the query expansion methods based on the search log， resulting in the impossibility to meet the needs of timeliness information. A query expansion method based on the search log and local context was introduced. By exploring relationships between user queries and relevant documents in search logs， candidate expansion terms were extracted， and local contexts from related documents were concentrated to extract words with higher frequencies and timeliness. By considering query performances and timeliness of expansions， expansions with higher qualities were provided with this method. Experimental results showed that precisions and recalls could be effectively improved， and better query performance to original queries could be obtained.

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Calculation Model of Temperature Field and Its Deviation Analysis for Hot Rolled Strip

JIANG Lian-yun， YUAN Guo， WU Di， WANG Guo-dong

2015, 36 (7): 937-941. DOI: 10.12068/j.issn.1005-3026.2015.07.006

Abstract ( 780 )

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Temperature field of hot rolled strip was calculated according to the partial differential equation of heat conduction and the boundary and initial condition， and the lumped parameter analysis method which neglects temperature gradient along the thickness. The equations of relative deviation for the two temperature calculation models， assuming the former was accurate， were obtained， and the equations were calculated by Matlab. The application range of temperature calculation model obtained by lumped parameter analysis method were obtained. The ranges of Biot were 0～0.1008， 0～0.1361 and 0～0.9593 for the central， 1/4 and surface of strip， respectively， when the relative deviation was less than 5%， and the ranges of Biot were 0～0.2033， 0～0.2782 and 0～1.4974 for the central， 1/4 and surface of strip， respectively， when the relative deviation was less than 10%.

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Modeling and Simulation of Thin Aluminum Cold Rolling with Work Roll Edge Contact

GUAN Jian-long， HE An-rui， SUN Wen-quan

2015, 36 (7): 942-946. DOI: 10.12068/j.issn.1005-3026.2015.07.007

Abstract ( 575 )

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A deformation model of roll system in aluminum cold rolling mill applied to online control in the actual production， was established by elastic cantilever beam method and the influence function method processing ideas. The influences of working roll edge contact on the forces acting on the roll system and the cross-sectional shape of aluminum strip in the process of thin aluminum strip rolled by cold rolling mill were studied. The simulation study of different inlet strip thickness， bending force and the contact state of working roll were carried out. The results showed that the contact force of working roll edge increases with the increasing thickness of the entrance， and decreases with the increase of the bending force. When the working roll edge contacts with rolling mill， the difference between outlet strip crown and lateral thickness is less than the non-contact rolling， and this process is useful to reduce edge drop. However， as it reduces the regulatory capacity of the aluminum rolling mill for the edge plate， it should be avoided.

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Effect of Low Basicity Dephosphorization Slag in BOF Slagless Steelmaking

HE Xiao-fei， WANG Xin-hua， LIANG Xiu-lan， LI Hai-bo

2015, 36 (7): 947-952. DOI: 10.12068/j.issn.1005-3026.2015.07.008

Abstract ( 797 )

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Based on SGRS technology， the effect of low basicity dephosphorization (De-P) slag in BOF slagless steelmaking was studied. According to the mass balance of slagless steelmaking， the lower the basicity of De-P slag is， the more CaO will be recycled and the more desilicication of liquid steel will be attained. At the same time， the experimental results show that， with the decrease of De-P slag basicity， the slag melting performance is gradually improved， leading to the beneficial outcomes of increasing the deslagging quantity and reducing the metallic iron content in De-P slag. When the basicity of De-P slag is 1.2-1.8， the hemisphere temperature of De-P slag could be controlled below 1380℃， the free CaO content of De-P slag could be controlled at around 0.7%， and the amount of BOF deslagging in the end of De-P stage could be controlled more than 8t (210t BOF) or 5t (100t BOF).

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Evaluation of Blast Furnace Operation Profile Based on Principal Component Analysis (PCA)

YAN Bing-ji， ZHANG Jian-liang， GUO Hong-wei， CAO Ying-jie

2015, 36 (7): 952-956. DOI: 10.12068/j.issn.1005-3026.2015.07.009

Abstract ( 591 )

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Aiming at solving the existing problems that there are many indexes used in operation profile evaluation and there are many overlaps among them， an improved method based on principal component analysis (PCA) was proposed. The method can generate three new core indicators from traditional indexes in operation profile evaluation (coke ratio， coal ratio， comprehensive coke ratio， utilization coefficient and the silicon content in hot metal). The new core indicators are independent of each other in space， and can represent the original ones. The above problems are thus solved. The improved model of operation profile evaluation was developed and applied to No.1 1780m³ blast furnace in Guofeng Steel， and the main categories of operation profile of the blast furnace were determined and evaluated.

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Study on Calcination of Szaibelyite and Calcium Carbonate Mixture for Magnesium Extraction

PENG Jian-ping， WANG Yao-wu， ZHU Gang-li， FENG Nai-xiang

2015, 36 (7): 957-961. DOI: 10.12068/j.issn.1005-3026.2015.07.010

Abstract ( 618 )

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Calcination of szaibelyite and calcium carbonate mixtures and extraction of magnesium from the calcined products by vacuum aluminothermic reduction were experimentally studied. The effects of calcium carbonate addition， forming pressure and calcination temperature on phases in the calcination products， the burning loss ratio of the mixtures and reduction ratio of magnesium oxide were discussed. The results indicated that most of the MgO were replaced from Mg₃B₂O₆ and Mg₂B₂O₅ by CaO during the calcination process of the mixtures. Moreover， the formation of Ca₁₂Al₁₄O₃₃ favored the reduction of MgO. Although it was favorable for the formation of Ca₃B₂O₆， higher forming pressure caused lower burning loss ratio of the mixture and lower reduction ratio of MgO. The reduction ratio of MgO was greater than 85% when the mixture with m_○Ca/m_○s = 1.9 was formed at 90MPa and then calcinated at 1100°C for 120min.

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Numerical Simulation on Flow Characteristics of Self-stirring Reactor Driven by Pressure Energy

ZHANG Zi-mu， LYU Chao， ZHAO Qiu-yue， LIU Yan

2015, 36 (7): 962-965. DOI: 10.12068/j.issn.1005-3026.2015.07.011

Abstract ( 587 )

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A new kind of self-stirring tubular reactor was presented and numerical simulation approach was adopted to investigate the flow characteristics in the novel self-stirring leaching reactor. With the same agitation speed， the influence of inlet flow rate on fluid flow in the reactor was studied. The results show that， in different inlet flow conditions， the flow velocity distribution was uniform in the axial direction， but the velocities of fluids in inlet and outlet regions were higher due to the disturbance action， and the velocity in the outlet region was lower than that in the inlet region. In the radial direction， the velocity near the wall was higher and that close to the agitating shaft was lower， which shows that the impeller blade tip made a greater effect on fluid. The circulation flow in the reactor with stirring forms more easily under the flow rate of 8.3m/s.

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Preparation of Lanthanum Hydroxide by Spray Pyrolysis of Lanthanum Chloride

BIAN Xue， WANG Zhen-feng， WANG Jin-yu， WU Wen-yuan

2015, 36 (7): 966-969. DOI: 10.12068/j.issn.1005-3026.2015.07.012

Abstract ( 812 )

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Using H₂O₂ as auxiliary reagent， the preparation of lanthanum hydroxide by spray pyrolysis of lanthanum chloride was studied. The thermodynamic principle was used to calculate the starting temperature of lanthanum chloride reaction with H₂O₂， and it is 288℃. The effect of pyrolysis temperature，LaCl₃ solution concentration， H₂O₂addition and carrier gas pressure on the conversion ratio of La(OH)₃ was experimentally studied. The Cl concent analysis， XRD and SEM indicate that the optimum conditions for the pyrolysis are temperature of 600℃， LaCl₃ solution concentration of 400g/L， H₂O₂ addition of 5% and carrier gas pressure of 0.4MPa， resulting in the conversion of 99.96% with debris shape La(OH)₃.

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Study on Crystallization and Solidification Behaviors of CaO-SiO₂-Al₂O₃ Mold Slags with Hot Thermocouple Technique

ZHOU Zhen-yu， TANG Ping， WEN Guang-hua， LIU Qiang

2015, 36 (7): 970-975. DOI: 10.12068/j.issn.1005-3026.2015.07.013

Abstract ( 633 )

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A mold slag based on CaO-SiO₂-Al₂O₃ system was designed for casting high-aluminum peritectic steels. Single hot thermocouple technique (SHTT) was applied to study the impact of w(CaO)/w(Al₂O₃) on crystallization behaviors. Double hot thermocouple technique (DHTT) was used to simulate the formation of slag film and define the impact of w(CaO)/w(Al₂O₃) on solidification fraction. The results show that the slags can be divided into two groups according to crystallization characters: the group with w(CaO)/w(Al₂O₃) higher than 1.30 (Group Ⅱ) has a higher tendency of crystallization than that with w(CaO)/w(Al₂O₃) lower 1.30 (Group Ⅰ). Cuspidine (Group Ⅰ) and dicalcium silicate (Group Ⅱ) were precipitated respectively in these two groups during isothermal process. As the w(CaO)/w(Al₂O₃) increased， the crystallization tendency increased sharply which causes the solidification fraction in slag film increased. The slags were also compared with industrial slag used for casting common peritectic steels， showing that the slags with w(CaO)/w(Al₂O₃)≤1.30 have similar properties with industrial slag. The designed CaO-SiO₂-Al₂O₃slag can be used in casting high-aluminum peritectic steels.

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Magnetic Separation and Enrichment of Rough Chromite Concentrate from the Ramu Laterite Project

LIU San-ping， CHANG Yong-feng， LU Dian-kun， JIANG Kai-xi

2015, 36 (7): 976-980. DOI: 10.12068/j.issn.1005-3026.2015.07.014

Abstract ( 612 )

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As the existence of chromium related spinel ores may cause serious wear on the pipe and autoclave during the pipe transportation and high pressure acid leaching procedure， it is necessary to remove the chromium containing minerals from the nickeliferrous laterite ore from Ramu， Papua New Guinea. The main problem in the beneficiation of chromite in the Ramu project is that the w(Cr₂O₃):w(FeO) of chromite concentrate is merely 2.3， which can not meet the standard of metallurgical chromite product. This paper presents the results of detailed characterization of process mineralogy and magnetic separation of rough chromite concentrate obtained from tabling separation procedure of the Ramu project. The screen classification and purification tests show that the w(Cr₂O₃):w(FeO) of the rough chromite concentrate could be further enhanced by eliminating the fines and other gangue minerals. The magnetic separation of the +0.074mm rough chromite concentrate increased the w(Cr₂O₃):w(FeO) to 2.59 with 63.89% recovery of chromium.

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Economic Benefit Between Autonomous Power and Purchasing Power from State Grid in Iron and Steel Enterprises

LIU Jing-yu， CHAI Shao-xuan， CHANG Yong

2015, 36 (7): 980-984. DOI: 10.12068/j.issn.1005-3026.2015.07.015

Abstract ( 775 )

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In view of the current price relationship between autonomous power and state grid power in iron and steel enterprises， an optimal economic management model of autonomous power plant was established using the method of economic planning. The optimal production and distribution plan of enterprise and the optimal power purchasing scheme considering the peak-valley power prices were discussed by solving the enterprise’s profit maximum function. The optimal schemes and results show that the level of the enterprise’s benefit has relationships mainly with the buying-power unit profit contribution after resale， the power supply unit profit and the quantity of power sale to grid. It is encouraged that， more outsourcing and less autonomous power is used as far as possible at the valley price of grid power， and more autonomous and less outsourcing power is used as far as possible and surplus electricity is saled online at the peak price of grid power.

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Probability Distribution Prediction of Milling Error Generated by Tool and Artifact Coupling Deviation Based on Monte-Carlo Method

ZHANG Yi-min， CAO Hui， HUANG Xian-zhen

2015, 36 (7): 985-990. DOI: 10.12068/j.issn.1005-3026.2015.07.016

Abstract ( 657 )

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The milling force calculation model was established based on the theory of bevel cutting， and the milling force was obtained. The bend function of thin plate deformation was built， and the milling error in milling process of tool-workpiece coupling deformation was obtained based on the combination of tool deformation. Neural network fitting method was adopted to obtain the function relationship between the input milling parameters and the output maximum milling error. Considering the influence on metal cutting by the parameters of tool， material， workpiece and working condition， the input parameters were sampled by the Monte-Carlo method. The parameter samples were substituted into the function model which was fitted by neural network， and the milling error samples were obtained. Then a probability distribution prediction method of milling error was put forward by analyzing the probability characteristics of the milling error. It was closer to actual than the deterministic calculation of milling error.

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Dimension-Reduced Incremental Harmonic Balance Method for Multi-span Rubbing Rotor System

YAO Hong-liang， CONG Yan， XU Qi， WEN Bang-chun

2015, 36 (7): 991-995. DOI: 10.12068/j.issn.1005-3026.2015.07.017

Abstract ( 666 )

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The finite element model of multi-span rubbing rotor system has a large number of degrees of freedom，which affects the efficiency of the numerical simulation seriously. To overcome this problem and remain the accuracy of numerical simulation at the same time， a new dimension-reduced incremental harmonic balance method combining the fixed interface component mode synthesis method was presented. Firstly， the degree of freedom was reduced by the fixed interface component mode synthesis method， and then the incremental harmonic balance method was applied to obtain the stable state response of the dimension-reduced system， and at last the response of the original rotor system can be obtained. The method can not only get the stable state solution directly， but also be combined with the arc-length method to obtain the unstable state response. The results show that a two-span rotor system can reach good accuracy and high efficiency with few dominant modes.

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Rapid Extraction of Feature Points and Experimental Research on Blade Section Curve

LIU Jia，ZHAO Ji， YANG Xu， ZHANG Liang

2015, 36 (7): 996-1000. DOI: 10.12068/j.issn.1005-3026.2015.07.018

Abstract ( 525 )

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For the problem of improving the measuring efficiency in blade machining process， a new method was proposed for extracting feature points， which was based on the curvature mutation of blade section curve. According to the monotonicity of discrete points integral curve， section curve was classified into the curvature smooth region and curvature mutation region. The basis feature points were selected by the curvature of discrete points and the character of region. B-spline was structured to approximate the original curve. The extraction of feature points was completed when the Hausdorff distance between the constructed B-spline and original curve met preset error value. Calculations and experimental results showed that the density of feature points are related to curvature variation of section curve. When error is set as 0.05mm， the average compression rate can reach 98% and average computation time is 103 seconds. Comparing to the traditional method， it can convergence to preset error value quickly. The proposed method is potentially useful for improving measuring efficiency of blade.

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Analysis of Elastohydrodynamic Lubrication Friction of Rolling Element Bearing

ZHANG Yu， XIE Li-yang， HU Zhi-yong， ZHANG Xiao-chen

2015, 36 (7): 1000-1004. DOI: 10.12068/j.issn.1005-3026.2015.07.019

Abstract ( 746 )

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Based on a set of full non-Newtonian elastohydrodynamic lubrication (EHL) point contact numerical simulation method， the steady and transient EHL characteristics at ball element and raceway elliptical contact in deep groove ball bearing were investigated. According to the results of film pressure and thickness， the effects of surface roughness， surface geometrical morphology (rough surface heights)， slide-to-roll ratio， contact load and rolling velocity on the friction coefficient of deep groove ball bearing were discussed. The results show that the effect of surface roughness on the friction coefficient is negligible， while different surface geometrical morphologies have weak influence on the friction coefficient. The friction coefficient increases with the increase of slide-to-roll ratio and the improvement of the contact force and rolling speed lead to the increase of the friction coefficient.

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Simulation of Temperature in Micro Mill-Grinding Based on Single-Edge Single-Grit Orthogonal Cutting

GONG Ya-dong， WANG Chao， FAN Zhi-guang， TAN Xue-fei

2015, 36 (7): 1005-1009. DOI: 10.12068/j.issn.1005-3026.2015.07.020

Abstract ( 603 )

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The single-edge single-grit orthogonal cutting model was developed， and the finite element simulation of micro mill-grinding was accomplished using the arbitrary Lagarangian Eulerian (ALE) method. The distribution and variation of temperature fields in the cutting process were analyzed. For the grinding of abrasive grains on the rear face， its effect on processing temperature was investigated. Temperature zones were defined according to the heat sources distribution， and the temperature change law of each temperature zone was analyzed. The simulation results show that the maximum temperature during processing is located at the abrasive grinding zone and the zone adjacent to the cutting edge. The temperature change law of each temperature zone in micro mill-grinding is the same as that in micro milling except for abrasive grinding zone. Grinding of the grit on rear face leads to temperature rise of all zones during processing. And the closer from the grinding zone， the larger the temperature rise is.

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The Synthesis Method of Eight-Bar Linkage Based on Solution Region Synthesis Theory

CUI Guang-zhen， HAN Jian-you， YANG Tong

2015, 36 (7): 1010-1014. DOI: 10.12068/j.issn.1005-3026.2015.07.021

Abstract ( 640 )

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An approach to synthesize a 1-DOF eight-bar linkage was given based on solution region synthesis theory. Firstly， the 4-positions of a 4R open chain were found by analyzing the design requirements. Secondly， for synthesizing the eight-bar linkage， three RR links were added to the 4R open chain. Meanwhile， the solution region could be built by the solution curves， which were gotten when RR links were added. Finally， the feasible solution region was gotten by removing the linkages， which did not meet the design requirements. The designers could directly and accurately choose the linkage from the feasible solution region， and solved the problem of blind choice. The example shows that the solution region theory and method offers a simple and effective way for the rapid design of an eight-bar linkage with meeting the requirements.

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Modeling of the Compound Digging Force of Hydraulic Excavator Based on Resistance Characteristics

CHEN Jin， REN Zhi-gui， LYU Liang， YONG Bin

2015, 36 (7): 1015-1019. DOI: 10.12068/j.issn.1005-3026.2015.07.022

Abstract ( 616 )

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The compound digging force concept was proposed based on the digging process in actual operation conditions of the composite motion of three hydraulic cylinders. According to the main function of boom， arm and bucket， the restricted conditions of the compound digging force were determined. The value range of orientation angle was up to the resistance angle and the difference angle. The calculating model of compound digging force was established based on a compound digging force hypothesis， which is changing gradually with the orientation angle. Taking a 36 t backhoe hydraulic excavator as an example， the validity of the hypothesis was proved. Taking the actual digging trajectory and the digging resistance obtained by testing as the reference， the calculating results of the existing theoretical digging force model were compared with that of the actual one. The comparative results indicate that the model can exactly estimate the real compound digging ability of the excavator. In this way， it can provide evaluation criterion and calculation basis to optimal design and strength analysis of the excavator working device.

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Flotation Behavior of Chalcopyrite and Molybdenite in the Presence of 2，3-Disulfanylbutanedioic Acid

LI Ming-yang， WEI De-zhou， CUI Bao-yu， LUO Na

2015, 36 (7): 1020-1024. DOI: 10.12068/j.issn.1005-3026.2015.07.023

Abstract ( 649 )

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The effect of 2， 3-disulfanylbutanedioic acid (DMSA) on the flotability of chalcopyrite and molybdenite with kerosene as a collector was investigated. The interaction mechanism between the DMSA and minerals was explored via Zeta potential analysis and quantum-chemistry calculation. Flotation results showed that DMSA has strong depression effect on chalcopyrite but slightly inhibition effect on molybdenite. Optimal separation efficiency is obtained when DMSA concentrate was only 1/9~1/13 of sodium sulphide. According to the results of Zeta potential test， DMSA adsorbs both on chalcopyrite and molybdenite surface， but the adsorption ability of DMSA on chalcopyrite surface is much stronger than that on molybdenite. The results of quantum-chemistry calculation indicated that electrochemical reaction only occurs between DMSA and chalcopyrite but not between DMSA and molybdenite.

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Research on Magnetic Properties of Oolitic Hematite Roasted by Suspension Roasting Furnace

WANG Ru， HAN Yue-xin， LI Yan-jun， ZHANG Yu-shu

2015, 36 (7): 1024-1028. DOI: 10.12068/j.issn.1005-3026.2015.07.024

Abstract ( 735 )

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Suspension roasting test result of oolitic hematite from west part of Hubei province was investigated. The effects of reduction temperature， reduction time， oxidation temperature， particle size on the magnetic properties and phase composition of reduced iron ore were investigated by using vibrating sample magnetometer， X-ray diffraction， Mssbauer spectrometer. The results show that magnetic properties of iron ore enhanced obviously after suspension roasting and directly proportional to the content of strong magnetic iron minerals. Both the magnetization intensity and magnetic susceptibility of reduced ore increased with increase of reduction temperature when reduction temperature range from 550℃ to 650℃. However， when reduction temperature rose to over 700℃， both the magnetization intensity and magnetic susceptibility decreased accordingly. The magnetization intensity and magnetic susceptibility of reduced ore increased with reduction time extending. The content of γ-Fe₂O₃ in roasted ore increased with the increase of oxidation temperature and reached the maximum value when oxidation temperature was at 350℃. When particle size is smaller than 15μm， the magnetization intensity and magnetic susceptibility of particle decreased with the decrease of particle size， while remenance and corecivity of particle increased correspondingly.

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Experimental Research on Restoring Cadmium-Contaminated Soil by Using Oxalic Acid Combined with Sedum Alfredii Hance

GUO Fan-di， PAN Jun， SUN Li-na， HU Xiao-min

2015, 36 (7): 1029-1032. DOI: 10.12068/j.issn.1005-3026.2015.07.025

Abstract ( 627 )

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For studying the effect of restoring cadmium-contaminated soil by using oxalic acid elution combined with Sedum alfredii hance， a test was performed by using Sedum alfredii hance combined with oxalic acid chosen from the roots secretion of mine ecological Sedum alfredii hance as an eluent. After four times of soil elution tests were doned by using four different concentration oxalic acid solutions， it was shown that when the concentration of oxalic acid was 25mmol/L， the maximum dry weight of Sedum alfredii hance and the most abundant cadmium on the ground were obtained. The total mass removal rate was the biggest， which could arrive at 51.34%， and it was higher than the group of no elution for 35 percent points. The test results showed that the effect of restoring cadmium-contaminated soil was the best when using the 25mmol/L concentration oxalic acid combined with Sedum alfredii hance. This test results can prove that the oxalic acid combined with mine ecological Sedum alfredii hance has a significant effect in the cadmium removal to restore cadmium-contaminated soil， and the ecotype Sedum alfredii hance grows healthy as well. Scientific proof is provided for the promotion and application of the restoring technology of cadmium-contaminated soil by using oxalic acid combined with Sedum alfredii hance.

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Numerical Simulation on Methane Distribution Legularity in Deep Coal Seam Under Variable Temperatures

WEI Chen-hui， ZHU Wan-cheng， BAI Yu， GAI Di

2015, 36 (7): 1033-1036. DOI: 10.12068/j.issn.1005-3026.2015.07.026

Abstract ( 663 )

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Methane migration and distribution in deep coal seam is closely related to the coupled process among thermal， gas flow and mechanical fields. Based on the THM (thermal hydraulic mechanical)coupling model， coal seam condition and in-situ test data， numerical simulation was conducted to examine the factors affecting the distribution of methane pressure and content. It is shown that， permeability of coal seam is the main factor affecting gas pressure distribution， where the effective stress coefficient， initial porosity， elastic modulus and adsorption swelling coefficient all have important impacts on permeability. Methane content distribution is controlled by both gas pressure and coal temperature. Methane content may be overestimated without considering the coal seam temperature.

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Study on Residual Gas Content Diversity Between Soft and Hard Coal

CHEN Li-wei， YANG Tian-hong ， YANG Hong-min， ZHANG Shu-jin

2015, 36 (7): 1037-1041. DOI: 10.12068/j.issn.1005-3026.2015.07.027

Abstract ( 564 )

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For extrude coal seam with soft coal， in order to inspect more accurate gas drainage effect， residual gas content diversity between soft and hard coal must be studied. Based on gas seepage field analysis of drainage conditions， considering the comprehensive influence of the condition of soft coal on gas flow and coal seam in coal seam， through establishing the gas fluid-structure coupling equation， and combining with the initial conditions and boundary conditions of borehole gas drainage， the differences of residual gas content of soft and hard coal under the extraction condition was simulated by using the multi-physic fields coupling analysis software. The results of numerical simulation showed the residual gas content of soft coal is higher than one of hard coal under the same extraction time. It will take 180 days when gas content of soft coal is reduced to 8m³/t， but it takes 162 days for hard coal.

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Simulation Research on Antifreezing Technology of Biomass Gasification Wet Purification Device

YAN Fang， XU Kai-li，YAO Xi-wen，WANG Bei-bei

2015, 36 (7): 1042-1046. DOI: 10.12068/j.issn.1005-3026.2015.07.028

Abstract ( 536 )

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A heating method was proposed for heating of clean room by using biomass gasification device to heat air. Calculation model was built by heat transfer theory， linear equation to calculate temperature of coil outlet air and non-linear equation to calculate temperature of clean room after heating were deduced. Under condition of some biomass gasification station with 0.08m， 0.10m， 0.12m coil inner diameter， required coil length and wind speed fitting for heating were calculated. Then feasibility of this method was verified. The “Origin” software was used to make linear fitting for calculated temperature of clean room. Logarithmic function relation of clean room temperature and wind speed was determined. Then range of wind speed was confirmed， and the heating energy consumption and quantity of heat production were compared. Be compared with traditional electric heating， it could reduce energy consumption for 95% and more.

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Integration and Application Research on Safety Evaluation Model of Complex Systems

YAO Xi-wen， TANG Gui-cheng， XU Kai-li， YAN Fang

2015, 36 (7): 1047-1051. DOI: 10.12068/j.issn.1005-3026.2015.07.029

Abstract ( 568 )

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In order to fully improve accuracy and reliability of safety assessment for complex systems， a risk evaluation model for complicated process by combining risk evaluation with HAZOP， LOPA and Bow-Tie analysis. Firstly， higher risk units in system are chosen by risk evaluation method， and detailed HAZOP analysis is conducted for such higher risk node. Secondly， LOPA is applied for scenarios with higher risk， and the residual risk level of accident is evaluated based on the semi-quantitative risk matrix， and HAZOP case library was enriched by means of LOPA; Finally， key activities to prevent the failure of IPL (independent protection layer) are identified useless working through Bow-Tie analysis， then the safety accident with heavy casualties or property damage caused by system unsafe behavior is fundamentally prevent. Taking the RFCC (residue fluid catalytic cracking) equipment in Liaohe Petrochemical Industry Company as an example， the applicability and reliability of the model were verified through field application.

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Experimental Study on Dust Concentration Distribution in Crushing Chamber

CHEN Ju-shi， JIANG Zhong-an， ZHANG Yi-kun

2015, 36 (7): 1051-1055. DOI: 10.12068/j.issn.1005-3026.2015.07.030

Abstract ( 584 )

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In order to avoid the over-limit of dust concentration in crushing chamber and to obtain the rational parameters for the design of dust removal by ventilation， according to the similarity theory and the gas-solid two-phase flow motion equation， taking 27^# crushing chamber in Xishimen Iron Mine as the background， the similarity index was deduced and a similarity model device was designed for the specific situation in the crushing chamber. Meanwhile， the dust concentration distribution was studied. The results indicated that dust concentration reached the maximum value near the mouth region in the crusher， while it gradually reduced along the radial direction in this region. The higher wind velocity and ore moisture are， the lower the dust concentration is. In addition， when ore moisture reached the value of 3.02%， the dust concentration no longer reduced. After the installation of exhaust dedusting system， the dust concentration was below 2mg/m³， and the average removal rate reached 90%.

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Influence of the Track Parameters on Vibration Characteristics of Ballastless Track

SHI Wen-bo， MIAO Lin-chang， WANG Zheng-xing， LUO Jun-hui

2015, 36 (7): 1056-1060. DOI: 10.12068/j.issn.1005-3026.2015.07.031

Abstract ( 638 )

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A nonlinear coupling model of wheel and rail was established according to the mechanical characteristic of ballastless track with elastic supporting block and the actual parameters of metro vehicle. The time-variant vertical acceleration of the rail and the sleepers can be calculated from the model， and the frequency-dependent acceleration was verified by the fast Fourier transform algorithm. A vibration power fixed by human sensitivity was introduced to quantify the vibration energy of the rail and sleepers. The impact of the parameters in the model was evaluated. The result shows the vibration energy is reduced with the increase of the stiffness and damp， meanwhile， the decrease in amplitude of the vibration energy that is resultant from the increase of the system stiffness is more prominent.

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An Empirical Study on the Preference for Geographic Proximity and Investment Performance of Venture Capital

LI Zhi-ping， LUO Guo-feng， YU Pei-li， CHEN Kai

2015, 36 (7): 1060-1064. DOI: 10.12068/j.issn.1005-3026.2015.07.032

Abstract ( 725 )

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Taking venture capital investments between 2000 and 2009 in mainland China as the research sample， regression analysis was used to explore the factors which affect the preference and performance of geographic proximity of venture capital (VC) in China. The results indicated that VC firms’ reputation and local competition status affect the preference for geographic proximity. Older， larger and more experienced VC firms with stronger IPO records exhibit less preference for geographic proximity while greater competition compels VC firms to invest distant targets. Different from the previous research abroad， no evidence was found that investment networks have any effect on the preference for geographic proximity. Abnormally， the logit regression results showed that investments of geographic proximity may lead to lower returns.

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