Adaptive bit allocation algorithm in an orphogonal frequency division multiplexing system of cognitive radio     

SU Jian huan  FENG Wen jiang  HE Qi wen  ZOU Qi ping 《保鲜与加工》2008,(10):1185-1188

An orphogonal frequency division multiplexing(OFDM) based cognitive radio architecture was designed to meet the transmission requirements of a cognitive radio system. After finishing the allocation of subtransmission, and keeping BER within the limit that ensures service quality, an adaptive bit allocation method was proposed to allocate the bit and energy of subtransmission dynamically. The total power for launching needed reached its minimum (or SNR per bit reached its maximum). Compared with the fixed bit allocation method, the proposed method is simpler, decreases the system transmission power, and has better BER performance.  相似文献   

Handling performace evaluation of a vehicle stability control system based on a driver model     

HE Yan song  LI Xing quan  XU Zhong ming 《保鲜与加工》2008,(10):1098-1102

By combining a driver model, a vehicle system dynamics model, and a vehicle lateral stability control system, the performance of the driver vehicle road closed loop system through a pylon course slalom test was simulated. The simulation was done in accordance with the GB/T6323.1-94 standard. Vehicle stability control system effectiveness was evaluated by measuring the mean maximum yaw rate and the mean maximum steering wheel angle. The simulation results showed the slalom test value with lateral stability control was approximately 4% higher than without a stability control system. This indicates the controlling system improves vehicle handling stability.  相似文献   

Deforming mechanisms in a non mandrel drawing process of an aluminum tube from circular to rectangular cross section     

QUAN Guo zheng  ZHOU Jie  AI Bai sheng  TONG Ying 《保鲜与加工》2008,(6):593-597

An elasto plastic finite element method (FEM) was used to study the deforming mechanisms of an aluminum tube drawn without a mandrel from a circular to a rectangular cross section. The simplified dynamics model and FE model of the non mandrel drawing process were established based on the FEM software deform 3D and simulations subsequently performed. Based on the simulation results, the influence of different semi die angles on the drawing load was summarized, and the proper values were found. As for the blank instability during the drawing process, the tangential stress distribution rule along the rectangle sides was acquired. The drawing die sizing section then was modified with a camber angle of 178° to eliminate instability. The touch boundary and touch stress distribution during drawing process also were analyzed. The aluminum tube produced by the optimized drawing die possesses eligible dimensions and smooth inner surfaces.  相似文献   

Energy transmission process of combustion flame radiation in the tuyeres and raceways of blast furnaces     

ZHANG Xing lan  OU YANG Qi  WEN Liang yin  BAI Chen guang 《保鲜与加工》2008,(12):1337-1341

We developed a process model of flame beam transmission using pulverized coal powder and coke combustion in a raceway. We employed a Monte Carlo computation method equation based on charge couple devrce(CCD) target heat flow distribution for radiation heat transfer. We explored the factors impacting radiation transmission. Based on these, a three dimensional reconstruction was analyzed at varying coke particle concentrations. This model provided an effective method to produce on line monitoring of raceway working states.  相似文献   

A new method for calculating the vacancy formation energy of typical structure metals     

ZHANG Xi yan  ZHAO Xin chun  JIA Chong  LIU Qing 《保鲜与加工》2008,(12):1342-1345

Based on the model proposed by Tiwari and Patil, we improved the calculation method for surface energy, and calculated the vacancy formation energy for typical metals such as fcc, bcc and hcp metals. The calculated results and experimental values agree with each other when an energy modification coefficient is introduced. The energy modification coefficients of fcc, bcc and hcp metals are 1.292, 1.265 and 1.357, respectively. The proposed method can calculate and predict the vacancy formation energy of metals efficiently.  相似文献   

optimizing the CO2 supercritical fluid extraction process of isoflavone from Soybean by uniform design     

REN Yan rong  CHEN Xiao lin  LI Xiao bo 《保鲜与加工》2008,(11):1333-1336

A supercritical CO2 fluid extraction (SFE) method was developed to extract isoflavone. A uniform design was used to investigate the effect of the extraction pressure, extraction time, extraction temperature, and medicinal materials granularity on isoflavone extraction efficiency. The optimum conditions of extraction were as follows: 45 MPa extraction pressure, 50 ℃ extraction temperature, 4 h extraction time, 40 eyes medicinal materials granularity, and the extraction efficiency was (0.361±0.012)%.  相似文献   

conductivity of a TiO2 cathode in the FFC process and analysis of its influencing factors     

LI Ze quan  BAI Chen guang  CHEN Xiao liang  TAO Chang yuan 《保鲜与加工》2008,(11):1323-1326

The conductivity of a TiO2 cathode in the FFC process was studied by sintering and electrolyzing experiments. Sintered TiO2 cathode and electrochemical reduction of TiO2 were measured using X ray diffraction. Results show that changing the energy band structure of TiO2 via high temperature sintering can cause electric conduction vacancy. An electric double layer can be formed in molten salt. Ionization of oxygen atoms leads to formation of TiO2 x ionic structures. The ions infiltrate to the electrode in molten salt, increasing the number of conduction ions. The electrolyzing process proceeds smoothly, based on the integrated mechanism of activating the TiO2 cathode. The activated TiO2 cathode can be obtained by forming electric conduction vacancy at high temperature sintering, the TiO2 x ionic structure by electric double layer, and ions infiltrating to the interior of the electrode.  相似文献   

The effect of moisture content on the tendency of coal to combust spontaneously     

JIANG De yi  LI Lin  BEAMISH B Basil 《保鲜与加工》2008,(12):1451-1454

The self heating of coal is influenced by many factors, but mainly it involves exothermic reactions between reactive sites in the coal and oxygen from the air. Moisture affects the nature of the radical sites where oxidation occurs, and affects the tendency of coal to combust spontaneously. Adiabatic tests show the coal self heating rate increases as the moisture content increases. At approximately 40% to 50% of the moisture holding capacity of the coal, the self heating rate becomes measurable. Above this critical level of moisture content, the heat produced by oxidation is dissipated by moisture evaporation and coal self heating is significantly delayed.  相似文献   

Impact of chloride ion on undegradable landfill leachate treatment by electrochemical oxidation     

LIU Yong  LIU Dan  ZHAO Shi lin  ZHANG Ai ping  LI Rui zhen 《保鲜与加工》2008,(12):1430-1435

We investigated the removal effects of chloride ion on treating organic substances with electrolysis using leachate from semi aerobic bioreactors. The experimental results show that, under the given conditions, the removal efficiency of refractory organic substances increases with rising initial chloride ion concentration in leachate. The impact of chloride ion on removal efficiency mainly is influenced by the initial chloride ion concentration and the chemical oxygen demand (COD) in leachate. The impact of chloride ion on the specific electric consumption of removal COD is obvious when the initial chloride ion concentration is lower. No obvious change of this impact is observed when the chloride ion concentration exceeds 125 g/L. Meanwhile, the more obvious impact of initial chloride ion concentration on organic substance removal is observed when the COD concentration in leachate is lower.  相似文献   

Stress wave effect in numerical simulation on rock breaking under high pressure water jet   总被引：1，自引：0，他引：1  

SI Hu  WANG Dan dan  LI Xiao hong 《保鲜与加工》2008,(8):942-945

The evolvement of rock damage struck by a high pressure water jet is characterized by nonlinear properties, thus making it a complicated dynamic problem. Based on a nonlinear finite element and elastic plasticity theory, a computational model was established. The dynamic load striking the rock by a high pressure water jet was simulated by the dynamic contact method. Furthermore, the propagation of a stress wave in the same rock was simulated at different impact velocities. The results show that the propagation velocity of a stress wave is proportional to the impact velocity of the high pressure water jet. The effects of a stress wave in sandstone and coal impacted by high pressure water jets of the same velocity were simulated.The effect of a stress wave in coal was stronger than in sandstone, while the region of propagation of stress wave in coal was smaller.  相似文献