18 July 2011, Volume 29 Issue 20

    

Articles

• Select all
  |

Articles
• Select
  Investigation of a Folding Wing Aircraft Using Dynamic Analysis Simulation and Experimental Method

  ZHANG Wei;GUO Xiaoguang;CAO Dongxing

  . 2011, 29(20): 18-22. https://doi.org/10.3981/j.issn.1000-7857.2011.20.001

  Abstract ( ) Download PDF ( ) HTML   Knowledge map   Save

  The flight characteristics of a folding wing aircraft are investigated and on this basis, a full-size folding wing aircraft is designed. The aircraft's modes and dynamic characteristics are analyzed by use of CAE software Abaqus. It is shown that when the folding angle is smaller than 90 degree, the wing's third and fourth order modes are of bend-torsion-coupled. Thus in the subsonic conditions, the wing would likely be in the flutter state. A folding wing aircraft model is designed. A number of flight characters are obtained by using the model, and it is shown that the focus point of the aircraft moves forward because of its high sweepback angle, thus the aircraft would be more stable.
• Select
  Design of Multi-axle Vehicle Steering Control System and Simulation Based on Fuzzy Adaptive PID Controller

  WEN Guilin;HAN Wangli;ZHOU Bing

  . 2011, 29(20): 23-26. https://doi.org/10.3981/j.issn.1000-7857.2011.20.002

  Abstract ( ) Download PDF ( ) HTML   Knowledge map   Save

  A 2-DOF model of the five-axle all terrain crane with some simplifications is proposed, and based on the assumption of zero side-slip angle of mass center and the proportional control strategy, the function relating the angles of the rear and the front axles, and the velocity are derived. With some simplifications with respect to the proportional valve and the cylinder, a mathematical model of the steering system in Matlab/Simulink is established. In order to overcome the weakness of the traditional PID controller, a fuzzy adaptive PID controller of the rear axle steering angle is built in Matlab by using its fuzzy logic control toolbox. Through the real-time determination of the PID parameters, a high control precision is achieved. A steady state cornering simulation is carried out under 25km/h, and the comparison of the simulation and theoretical values shows that the fuzzy adaptive PID controller works well, with quick system response and good following performance.
• Select
  Genetic Algorithms for Machining Task Scheduling

  LI Haolin;DING Shangjie

  . 2011, 29(20): 27-30. https://doi.org/10.3981/j.issn.1000-7857.2011.20.003

  Abstract ( ) Download PDF ( ) HTML   Knowledge map   Save

  Production scheduling is one of the key technologies for the automatic control system, and is able to influence the desired economic benefits. The purpose of the scheduling is to shorten the manufacturing cycle, to improve the utilization of resources, and to ensure the production task that would be finished in time. Based on the genetic algorithm method, the problems of production scheduling in the workshop are solved. The distribution of the processing tool is considered as a primary constraint during the process, and the order of working process is also considered. The order crossover (OX) methods and sequence variation method are used to complete the genetic variation process. The scheduling is combined with the tool management in the algorithm; therefore the result is much closer to the actual situation. The system is able to complete the production scheduling and cutting tools distribution according to the manufacturing task and task rank. The interface for the operator is also programmed to make sure the system could be used in the daily work. The computational results show that it is effective, and the scheduling results are optimized. The system mainly possesses task arrangement, production scheduling, and cutting tools management functions.
• Select
  Coulomb Blockade Effect in Coupled Mesoscopic Capacitance and Inductance Circuit

  ZHANG Yuqiang;CAI Shaohong;

  . 2011, 29(20): 31-34. https://doi.org/10.3981/j.issn.1000-7857.2011.20.004

  Abstract ( ) Download PDF ( ) HTML   Knowledge map   Save

  In view of the discreteness of electric charges in coupled mesoscopic capacitance and inductance circuit, the Coulomb blockade effect is studied by means of the classical Lagrangian canonical transformation and the finite-difference Schrödinger equation. The results show that Coulomb blockade effect is not only related with the component parameters of each circuit, but also with the coupling parameters,which would serve as an insight to understand the characteristics of the quantum in mesoscopic fields. This paper provides a theoretical basis for design of the micro-nano circuits and devices.
• Select
  Electrical and Optical properties of CdS, ZnO_1-xS_x: A First Principle Study

  ZHANG Haixia;CHU Xingli;WANG Tianxing

  . 2011, 29(20): 35-40. https://doi.org/10.3981/j.issn.1000-7857.2011.20.005

  Abstract ( ) Download PDF ( ) HTML   Knowledge map   Save

  In this paper, the electronic structure and optical properties of zinc blend-type compounds CdS and ZnO_1-xS_x (x=0, 0.25, 0.5, 0.75, 1) are numerically analyzed by means of the plane wave ultrasoft pseudo-potential method with the generalized gradient approximation (GGA) under the density functional theory (DFT). The lattice parameters, the band structure, the density of states and the optical conductivity are obtained. The optical properties including the dielectric function, the conductivity, the absorption spectrum and the energy-loss spectrum are discussed. It shows that the zinc blend-type compounds CdS and ZnO_1-xS_x are both direct band gap materials; the crystal constants increase with the quantity of S doping ZnO; the ZnO_1-xS_x has a wider band gap than CdS and can be expected to provide a high quality buffer layer for high efficiency Cu(In_1-xGa_x)Se₂ (CIGSe) solar cells by improving the surface quality of absorption layer and decreasing the absorption loss.
• Select
  Charging Characteristics of Short-pulse Discharges in Different Inter-electrode Regions

  MI Junfeng;HAO Chengxiang;ZHAN Xiaoping;WANG Mingtao

  . 2011, 29(20): 41-44. https://doi.org/10.3981/j.issn.1000-7857.2011.20.006

  Abstract ( ) Download PDF ( ) HTML   Knowledge map   Save

  Experiments of charging particles by short-pulse discharges were carried out under different voltages and the charge number on drops was measured by Millikan cell with and without a diversion cylinder. The results show that without the diversion cylinder, the charge number on drops increases with the increase of the voltage, while both the short-pulse voltages are lower than the broken-down voltage. The charge number on drops reaches the maximum when the short-pulse voltage is equal to the broken-down voltage. But when the short-pulse voltage is higher than broken-down voltage, the charge number on drops is decreased. However, when the diversion cylinder is present, the neutralization phenomenon could be avoided in the plasma region. The charge number on drops is higher than that in case without the diversion cylinder. But it is not beneficial to charging to use the diversion cylinder when the applied voltages are lower than the broken-down voltage. At the same time, the influence of the cylinder diameter on the charging on drops is studied and it is indicated that it is the best for charging of the short-pulse discharge when the diameter of the diversion cylinder is 2cm.
• Select
  Influencing Factors of the Anaerobic Phosphorus Release From Aerobic Activated Sludge in Low-Temperature A²/O Process

  LI Jianzheng;GUO Yaqiong;HE Junguo;JIN Yu;

  . 2011, 29(20): 45-48. https://doi.org/10.3981/j.issn.1000-7857.2011.20.007

  Abstract ( ) Download PDF ( ) HTML   Knowledge map   Save

  To enhance the phosphorus removal in the low-temperature A²/O wastewater treatment process, an anaerobic phosphorus release tank is attached to the aerobic treating process, and the control parameters of the tank are analyzed. The results show that the anaerobic phosphorus release of aerobic activated sludge from the secondary clarifier effectively improves the TP removal efficiency of the low-temperature A²/O process, and the COD removal is at the same time enhanced. In order to meet the demand for the carbon source of the anaerobic phosphorus release, raw water should be put into the anaerobic phosphorus release tank and mixed with the fresh sludge from the secondary clarifier in a volume ratio of 1:1, with a sludge load of 0.015-0.02g COD/g MLSS. For an sequencing batch process, the optimum sludge retention time is 14h, while in a continuous flow process it is 12h. NO₃^- would significantly inhibit the anaerobic phosphorus release, so its concentration should be controlled within 5mg/L. The intermittent slow blend is suggested to improve the efficiency of anaerobic phosphorus release.
• Select
  A Mothod of Hemming Roll-in Control

  YUAN Pengfei;ZHANG Zhaochun;WU Caiting;WANG Zhuang;LIU Zhao;CAO Guihua;XUE Jing

  . 2011, 29(20): 49-52. https://doi.org/10.3981/j.issn.1000-7857.2011.20.008

  Abstract ( ) Download PDF ( ) HTML   Knowledge map   Save

  Optimzation methods are applied to sheet metal hemming. For the determination of parameters that influence the roll-in, an approximation Hemming model is proposed, to be used with optimization methods. The small area of sheet metal hemming lead to low efficiency, while the approximation hemming model can solve the problem, which make hemming model optimization possible. And the approximation hemming model based certain optimization method offer a new method to control the roll-in in hemming.
• Select
  Adaptive Friction Compensation for 2-DOF Tracking System

  WANG Hongru;WANG Jianzhong

  . 2011, 29(20): 53-56. https://doi.org/10.3981/j.issn.1000-7857.2011.20.009

  Abstract ( ) Download PDF ( ) HTML   Knowledge map   Save

  In order to eliminate nonlinear effects of friction on 2-DOF tracking system and to improve its position-tracking accuracy, a novel adaptive friction compensation algorithm is proposed. Based on nonlinear characteristics of friction, a LuGre dynamic friction model is adopted to characterize friction in the 2-DOF tracking system. In this method, unknown parameters for the LuGre model are estimated in the manner of off-line; friction state and the inconstant parameters are estimated by using nonlinear observers and self-adaptive law. A Lyapunov-like argument proves the asymptotic stability of the whole closed-loop system. Experimental results indicate that the proposed method could effectively alleviate the influences of friction when the 2-DOF tracking system works with a lower speed, and could improve tracking accuracy for the 2-DOF tracking system accordingly.
• Select
  Ductility Design Based on the Bonded Prestressed Concrete Frame Beams

  SONG Xiaohong;FAN Qinxin

  . 2011, 29(20): 57-62. https://doi.org/10.3981/j.issn.1000-7857.2011.20.010

  Abstract ( ) Download PDF ( ) HTML   Knowledge map   Save

  Combined with the large span, heavy load, stability, durability, and high requirement for fire prevention and anti-corrosion, the optimized structure should be a post-tensioned bonded prestressed concrete frame structure, and the overall structure has good mechanical properties. Starting from three macro directions of analysis model establishment, the crack control, and bearing capacity calculation, the detail design process for long-span posted-tensioned bonded prestressed beams is introduced. Some problems, such as degree of the relative height of equivalent compression zone, partial presstressing ratio, rate of tension reinforcing steel bar, and non-prestressed reinforcement area ratio, are discussed and the treatments are put forward. As indicating in the results, for developing a reasonable tension construction scheme, some construction measures for the core areas of tension are suggested, and the design experience could be referred to similar engineering projects.
• Select
  Effect of Coronatine on Internode Elongation and Yield Characters of Maize

  WEI Xiaoyi;ZHANG Mingcai;LI Zhaohu;DUAN Liusheng

  . 2011, 29(20): 63-67. https://doi.org/10.3981/j.issn.1000-7857.2011.20.011

  Abstract ( ) Download PDF ( ) HTML   Knowledge map   Save

  Maize hybrid Zhengdan 958 was tested, with the treatment of 0.001, 0.01, 0.1 and 1μmol/L coronatine (COR), and with water as control (CK). Agronomic traits, physiological indexes and yield characters were measured to study the effect of coronatine on internode elongations in maize. The results show that with the increase of the concentration of coronatine, the plant height, the ear height and the internode length are decreased. The plant height, the ear height and the internode length of the 2nd to 8th internodes with the treatment of 0.01, 0.1 and 1μmol/L COR are smaller than those of CK, and the differences are in a significant or highly significant level. With the increase of the concentration of coronatine, the activities of indole acetic acid oxidase (IAAO), phenylalanine ammonia lyase (PAL) and peroxidase (POD) of the elongated internodes are significantly increased. Except for the 0.001μmol/L COR treatment, the enzymatic activities of IAAO, PAL and POD with the treatment of 0.01, 0.1 and 1μmol/L COR are higher than those of CK, and the differences are in a highly significant level. Compared with those of CK, the ear length, the kernels per row, the ear weight, the grain weight per ear and the yield with the treatment of 0.001 and 0.01μmol/L COR are significantly or highly significantly increased. With the increase of concentrations of coronatine, these traits see decreasing trends, which shows that low concentrations of coronatine would increase the maize production. On the whole, the optimal concentration of coronatine should be 0.01μmol/L, which could suppress the internode elongation and increase the production. Therefore, the coronatine has a good prospect to serve as a retardant in maize.
• Select
  An Assessment of the Impact of Climatics Condition on Wheat Pests Outbreak and Diseases Spread

  ZENG Juan;JIANG Yuying;HUO Zhiguo

  . 2011, 29(20): 68-72. https://doi.org/10.3981/j.issn.1000-7857.2011.20.012

  Abstract ( ) Download PDF ( ) HTML   Knowledge map   Save

  This paper gives a comprehensive analysis and assessment of the impact of climatic conditions on wheat pest outbreak and disease spread, to find out the mechanism how abnormal weather and climate affects the pest and disease occurrence. Reliable data were collected via continuous field monitoring and observation in 20 main wheat-planting provinces, and are related to the climatic traits and meteorologic disasters in the whole development stage of winter wheat during 2009-2010. These year's data are compared with those of past normal years. It is indicated that the unusural meteorologic events, such as the sudden and sharp drop of temperature at the beginning of winter and the long-lasting abnormal low temperature in spring in northern and eastern wheat zones, and historically rare drought through autumn, winter and spring in south-western wheat zones, would postpone the stage of wheat pests and diseases with remarkable diversification of each kind. Wheat stripe rust is restricted to a smaller range and in less serious grade. Wheat sharp spot and wheat powdery mildew occur in a massive area and on a medium grade. Wheat scab and aphids break out seriously at the heading stage; nevertheless wheat mites are lighter than a mid-size one at the former stage. It is concluded that the key stage and the weather elements are different for different pests and diseases, as the bases for classification and focus for forecast. In order to improve the forecast and assessment, it is important to pay attention to weather conditions in both broad and particular areas and for both long and short periods, using the "classification" and "focus" methods.
• Select
  A Heat Resistance Model of Aqueous Film Forming Foam

  WU Xiangjun;ZHANG Guanghui;SU Xiaobo

  . 2011, 29(20): 73-79. https://doi.org/10.3981/j.issn.1000-7857.2011.20.013

  Abstract ( ) Download PDF ( ) HTML   Knowledge map   Save

  Aqueous Film Forming Foam (AFFF) fire extinguisher is the most effective firefighting system for large scale oil fire on big warship deck. The heat resistance effect is one of the primary extinguishing mechanism of AFFF as the extinguishing agent. When the AFFF film layer is formed on the surface of fire, its spreading effect will continually feed AFFF from outside; and due to the heat radiation of the fire, AFFF continues to ablate inside. The presence of the ablation process makes AFFF thinner, the thermal resistance capacity will decrease. When the fuel under the AFFF reaches a flash point, the fuel may be re-ignited, due to the air inside of the AFFF. To improve the AFFF extinguishing efficacy, a quantitative analysis of the flame retardant properties of AFFF and the distribution of the temperature field in the AFFF thermal invironment is of great significance. In this paper, a solid-state ablation model is proposed, and, based on this model, a steady-state ablation model of AFFF is established, combinating the ablation characteristics of AFFF and some assumptions, concerning AFFF density, ablation rate and the components rate of model. The temperature distribution within AFFF can be obtained through simulations. The result of simulation is lower than the experimental result, with an error of within 10%. The model can be used to calculate the AFFF flux for oil fire per area on the warship deck.