08 December 2011, Volume 29 Issue 34

    

• Select all
  |

Articles
• Select
  Optimization of Fourth-order Compact Finite Difference Triangular Scheme and Its Initial Applications

  LIU Xiao;WANG Xiaoguang;LI Wenqiang

  . 2011, 29(34): 20-26. https://doi.org/10.3981/j.issn.1000-7857.2011.34.002

  Abstract ( ) Download PDF ( ) HTML   Knowledge map   Save

  In order to improve the precision and resolution of a numerical scheme used to solve the complex scientific and engineering problems, it is necessary for difference scheme to resolve wave numbers with as high precision as possible. Based on this idea, a triangular compact finite difference scheme with fourth-order accuracy and high resolution is proposed. On one hand, this compact scheme could be efficiently solved by the algorithms which are recently developed to solve the (cyclic) triangular equations, therefore, the first derivation could be efficiently calculated by the optimized compact difference scheme with higher resolution and less amount of calculation; on the other hand, it has a maximum accuracy wave number of 2.5761, comparing with that of 1.13097 by using traditional schemes. In short, the optimized compact difference scheme is more appropriate to simulate small scale fluctuations in fluid dynamics. Numerical computation experiments illustrate that(1) even though the optimized scheme is still fourth-order, it has a smaller error than that of traditional fourth-order compact finite difference, especially for the small scale fluctuations; (2) for the problems involving traveling wave, the optimized scheme is able to simulate wave propagation behavior more accurately. Both the theoretical analysis and numerical experiments indicate that the optimized compact finite difference scheme is more appropriate to resolve the problems with small scale fluctuations.
• Select
  Simulation of the Characteristics of Pyrolysis and Combustion on Typical Fire Scene of Plywood by Thermogravimetric Analysis

  YUE Hailing

  . 2011, 29(34): 27-30. https://doi.org/10.3981/j.issn.1000-7857.2011.34.003

  Abstract ( ) Download PDF ( ) HTML   Knowledge map   Save

  Pyrolysis and combustion process of combustible materials is the initial stage of fire, which has greatly influence on the development of fire. Through changing atmosphere in the halfway, the pyrolysis and combustion properties of plywood were studied by using a thermogravimetric analyzer in nitrogen under constant temperature conditions. The result indicates that effect of transforming atmosphere on the pyrolysis is little before the end of the first stage of plywood pyrolysis. In the second phase of plywood pyrolysis, atmosphere changing from air to nitrogen, the trend of weight loss is along with the trend of nitrogen atmosphere. After changing from nitrogen atmosphere to air atmosphere, pyrolysis rapidly accelerates, and final rate of weight loss is the same as that in air atmosphere.
• Select
  Numerical Simulation and In-situ Measurements of Reinforced Floor in Controlling Floor Heave of Soft Rock Roadway

  LI Xibing;HE Tao;YAO Jinrui;MA Chunde;HE Zhongguo

  . 2011, 29(34): 31-36. https://doi.org/10.3981/j.issn.1000-7857.2011.34.004

  Abstract ( ) Download PDF ( ) HTML   Knowledge map   Save

  With the increase of depth in mining engineering, many support difficulties occurred in main development and preparation roadways in Maluping mining area of Guizhou Kailin Group. Traditional support technologies and measures failed to work. Problems in terms of the safety of the permanent roadways such as roof falling, rib spalling and floor heaving were often found, to require repetitive rebuilding work. To control and prevent the severe destruction of the surrounding rocks in the deep red shale roadway of Maluping mining area, in-situ investigations and theoretical analysis were carried out and an approach was put forward to control the floor heave by strengthening the floor. Meanwhile, three new improved support schemes were adopted on the basis of the original support scheme. The original scheme and these three improved schemes were simulated by using 3DEC, a discrete element code, and then in-situ tests were performed in a 100m long experimental roadway. Simulation results indicate that floor anchors can be used to control the floor heave by cutting the plastic sliding line located in floor corners. An improvement of floor toughness, integrity and bearing ability against the bulking pressure of rocks was achieved by placing steel meshes on the concrete floor. The in-situ test data show that the combined support scheme would reduce the floor heave by 83%, which has solved the support problem in Kailin Mine, that had been affecting the mine production for a long time.
• Select
  Superposition Features of Air Flow's Changes in a Mine Ventilation System

  YAN Zhenguo;FAN Jingdao;WANG Honggang

  . 2011, 29(34): 37-40. https://doi.org/10.3981/j.issn.1000-7857.2011.34.005

  Abstract ( ) Download PDF ( ) HTML   Knowledge map   Save

  The linear superposition principle applies where the governing equations of a physical problem are linear. Keeping other factors unchanged, in a ventilation system, the change of the air flow has a non-linear relation with that of the air resistance, and thus the linear superposition principle does not apply directly. Based on the Taylor's expansion, however, the superposition feature can apply to some extent for the changes of the air flow and the air resistance in a ventilation system by the linearization of the non linear equations, which means that in a ventilation system the variations of the air resistance of different parts can approximately be added up to calculate the air flow variation when the changes of air resistances are relatively small. The error of such kind of superposition increases with the expanded range of air resistance's variations. The superposition feature of a ventilation system is important for the evaluation and identification of the air flow's fluctuations. For a large and complex ventilation network, however, the application of the superposition method requires further studies.
• Select
  Simulation of Digital Exploration Process and Its Application in Surface Mine

  LIU Guangwei;BAI Runcai;ZHAO Hao

  . 2011, 29(34): 41-44. https://doi.org/10.3981/j.issn.1000-7857.2011.34.006

  Abstract ( ) Download PDF ( ) HTML   Knowledge map   Save

  A new method is proposed to simulate the 3D digital mining in surface mine, by driving the template to slice the integrated solid model continually with the benches being united and the position displayed. Based on the 3D terrain model and the 3D geological model of surface mine, the mining template is determined by the actual production situation of surface mine, to implement the simulation of surface mining by moving these templates to slice 3D models. Volume classification of rock and coal can be determined by solid modeling and boolean operation between solids, and then the mining plan is determined. The engineer may choose the best design from several planned designs. The proposed method improves the speed and the quality of long term design planning by virsualizing the digital exploration process.
• Select
  Numerical Simulation of Film Cooling Efficiency at Different Blow Ratios

  CHEN Wei;DONG Ruoling;SHI Honghui;WANG Chunjuan;ZHANG Xiaodong

  . 2011, 29(34): 45-49. https://doi.org/10.3981/j.issn.1000-7857.2011.34.007

  Abstract ( ) Download PDF ( ) HTML   Knowledge map   Save

  Numerical simulations were carried out to verify the influence of blow ratios on the film cooling effectiveness. With the blow ratio M taking values of 0.5, 1.0, 1.5, 2.0, numerical simulations were carried out on the fluid flows and heat transfers in a cylindrical hole and a fan-shaped hole. By using the realizable k-ε turbulence model with an enhanced wall function, based on the bulk flow control, the three-dimensional steady incompressible N-S equations and the method of SIMPLEC, the mean flow velocity at the exit of the hole and the temperature of the cooled wall were calculated to analyze the film cooling effectiveness. Different blowing ratios were compared on the influence of the film cooling effectiveness. The results indicate that when the blow ratio increases, the jet tends to lift off the wall. Within the scope of this study, in the near field of the hole, for the cylindrical hole, the blow ratio has no obvious effect on the film cooling effectiveness, however, for the fan-shaped hole, the film cooling effectiveness increases with the blow ratio. As the jet goes downstream of the flow direction, for the fan-shaped hole, the jet coverage area increases while for the cylindrical hole, a back-flow is found and the film cooling effectiveness is enhanced around the near downstream field but decreased in the far downstream field. Thus the cooling effectiveness does not change monotonously with the blowing ratio for the cylindrical hole, but for the fan-shaped hole, the film cooling effectiveness increases with the blow ratio.
• Select
  Design Requirements for Construction Machinery Maintainability Based on QFD

  GUO Pengfei;ZHENG Huaizhou;YU Chunfeng;ZHAO Yongpeng

  . 2011, 29(34): 50-53. https://doi.org/10.3981/j.issn.1000-7857.2011.34.008

  Abstract ( ) Download PDF ( ) HTML   Knowledge map   Save

  The design for maintainability is important in the construction machinery, and the identification of the design requirements of construction machinery maintainability is the pre-requirement. Firstly, the paper briefly discusses the QFD method, especially, the basic makeup of HoQ. Secondly, the analysis process of the design requirements of construction machinery maintainability based on QFD is discussed, mainly including six steps: analyzing the clients' maintainable requirements, evaluating the weight of each requirement, determining the design index of maintainability, constructing the design index matrix, constructing the design index and maintainable requirements matrix, and forming the design index weight matrix of maintainability. Lastly, through analyzing the design requirements of one bulldozer maintainability based QFD, the importance sequence of maintainability design indexes is obtained, as in the order: the disassembly-assembly character, the modularization, the standardization, the compactness, the accessability and the easiness to identify. It is shown that the analysis of design requirements of construction machinery maintainability based on QFD can effectively solve the problems of complexity and uncertainty in the analysis process and evaluate the design requirements of maintainability by integrating qualitative analysis with quantitative analysis, with a high practical value.
• Select
  Data Acquisition and Analysis System for Country Region Geological Hazards Based on ArcEngine

  ZOU Qiang;ZHANG Wenjun;SHUI Wei;WANG Weihong

  . 2011, 29(34): 54-58. https://doi.org/10.3981/j.issn.1000-7857.2011.34.009

  Abstract ( ) Download PDF ( ) HTML   Knowledge map   Save

  Regional geological surveys are a basic work for disaster prevention and mitigation management. Based on the actual field survey and the geological hazard analysis, the GIS technique, the database technique and the multi-sources data technique are applied to acquire and analyze the geological hazard information, as a bottleneck in the regional geological hazard investigation. According to the geological industry standard, the characteristics of geological hazards are analyzed, and the heterogeneous data sources including the basic geographic data, the hazard feature data and the correlative multimedia data are normalized. Moreover, the connections are marked for special data and hazard characteristic data. Consequently, a special topic database is built for geological hazards by the ArcSDE and SQL Server management platform. And then, with ArcGIS's open development environment, the data acquisition and analysis system for the county regional geological hazards is successfully constructed by the Visual Studio.Net(C#) and ArcEngine technology. The software system, consisting of function modules of the map operation, the information importing and editing, the inquiry statistics, the hazard analysis and evaluation, the mapping output, can meet the demands of the geological hazard data acquisition and analysis. Furthermore, the above work not only provides a computer platform for rapidly acquiring and scientifically managing the geological hazard information, but also offers a technical support for the regional hazard analysis.
• Select
  Dual Buck PV Inverter Based on Current Hysteresis Control

  YUE Zhou

  . 2011, 29(34): 59-63. https://doi.org/10.3981/j.issn.1000-7857.2011.34.010

  Abstract ( ) Download PDF ( ) HTML   Knowledge map   Save

  The inverter is one of the core equipment in a photovoltaic system. To improve the reliability and stability of the inverter, to obtain an ideal sinusoidal output voltage and to optimize the performance of the inverter, a novel two-buck PV inverter is proposed in this paper. The DC / AC inverter principle and the control scheme are discussed. The fixed-width two-state ring adjustable hysteresis current control strategy is adopted. The paper gives an in-depth analysis of a two-state hysteresis current control of inverter, the inverter input-output relationship, the use of the double-loop control of the basic design of hysteresis current control method. Matlab simulations show that the control strategy is simple, and the effective use of the control system will bring about a good steady-state and the dynamic characteristics of the output voltage waveform are good, which would enjoy a practical value.
• Select
  Creation Fastigium Types and Interevent Time Distributions of Three Artists

  HE Ting;XU Xiulian;WANG Xuming

  . 2011, 29(34): 64-67. https://doi.org/10.3981/j.issn.1000-7857.2011.34.011

  Abstract ( ) Download PDF ( ) HTML   Knowledge map   Save

  In recent six years, the study of human dynamics has experienced a flourishing development. In order to verify and explore the universal human dynamics rules of artist creations, a statistical investigation on the creations of three famous artists (Xu Beihong, Feng Zikai, Liu Haisu) is performed. The results show that their interevent time distributions obey the power law as in a qualitative agreement with the known human dynamics rules in communication, visit to networks, borrowing books and order programme of movie or music. The power law exponents of the three artist interevent time distributions are exactly the same. The value is 2.14, largely deviated from those of scientist and writer interevent time distributions in literature, which indicates that while the artist creation activities do obey the universal rules of human behaviors, they have their own characteristics. It is proposed to use the so-called "enveloping curve" of the data, including the number of the works an artist created in a year, as well as the shape and the number of the creation fastigiums, in an enveloping curve form, to describe the differences of artist individual creation rules due to their personal experience. An enveloping curve is defined as a smooth curve nearest to all "higher points", to which each oscillation of the work number an artist created in a year reaches during a rising or falling process of the creation. In principle, this statistical description suits the studies of other human behaviors.
Reviews
• Select
  Research Progress of Lignocellulose Hydrolysis of Chemicals

  CHEN Li;DENG Lihua;YAN Zongcheng;WANG Honglin

  . 2011, 29(34): 68-72. https://doi.org/10.3981/j.issn.1000-7857.2011.34.012

  Abstract ( ) Download PDF ( ) HTML   Knowledge map   Save

  Lignocellulose is one of the most abundant renewable resources in the earth. Its use can effectively alleviate the dependence on fossil fuels. With its complex structure, the lignocellulose hydrolysis is a key process in the conversion of lignocellulose. This paper discusses problems of lignocellulose hydrolysis in producing sugars and compares advantages and disadvantages of various methods in doing so. Recent progresses in lignocellulose hydrolysis to produce polyol chemicals, energy chemicals and new platform chemicals are reviewed. Finally, the development prospect is discussed for related studies.
• Select
  Latest Progress in Vanadium-based SCR Aftertreatment Technology Applied to Diesel Engine

  YANG Jianjun;LI Guo;MA Jie;LIU Shuangxi;GAO Haiyang

  . 2011, 29(34): 73-79. https://doi.org/10.3891/j.issn1000-7857.2011.34.013

  Abstract ( ) Download PDF ( ) HTML   Knowledge map   Save

  The vanadium-based Selective Catalyst Reduction (SCR) aftertreatment technology is the key method for medium and heavy diesel engine to achieve the IV/V European Standard Regulation for Vehicle Pollutant. The researches on the advantages of vanadium-based SCR technology, the performance optimization and integration of the vanadium-typed catalyst with other aftertreatment technology are reviewed. Special attentions are paid to performance of NO_x conversion for the vanadium-based SCR system, the effect of the catalyst on the emission of THC, CO, and PM, the emission of greenhouse gas, the resistance to sulfur poisoning, and cost advantages. Aiming at the catalyst performance optimization, the emphases are given to the effects of catalyst volume, urea solution injection strategies, urea vaporization and distribution on the catalyst performance, as well as performance of the SCR catalyst in the cold start-up of engine. At last, the different layout of vanadium-typed catalyst with other aftertreatment is discussed. In addition, the future development in this field is explored.