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Wireless Mesh network and IEEE 802 Standards

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ZTE Communications 2008年第2期6卷 7-10页

作者： Chen Linlin, Liu Naian (state key Lab of integrated Service networks , xidian university, xi’an 710071, china )

Although the wireless broadband access system is developing rapidly, its development is limited due to some disadvantages , such as small capacity of bandwidth and small coverage . The Wireless Mesh network (WMN) is one of the important technologies for 'last mile 'broadband wireless access . The WMN can integrate with multiple wireless systems , such as Wireless Local Area network (WLAN), Wireless Personal Area network (WPAN), and Wireless Metropolitan Area network (WMAN), to improve the performance of the wireless network and enlarge the coverage range . With the wide applications of the WMN, the IEEE 802 standard group is devoted to promoting the development of the WMN technology and establishing the related technical standards . At present, WMN standards have appeared in IEEE 802.11s , 802.15, 802.16, and 802.20.

关键词： Mesh WMN IEEE Wireless Mesh network and IEEE 802 Standards

Energy Transfer among Chlorophylls in Trimeric Light-harvesting Complex Ⅱ of Bryopsis corticulans

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Acta Biochimica et Biophysica Sinica 2006年第5期38卷 310-317页

作者： Su-Juan ZHANG~(1,2*)Shui-Cai WANG~2 Jun-Fang HE~2 Hui CHEN~3 1 Institute of Photonics and Photo-Technology,Northwest university,xi'an 710069,china 2 state key laboratory of Transient Optics and Photonics,xi 'an Institute of Optics and Precision Mechanics,Chinese Academy of Sciences,xi'an 710068.china 3 Laboratoty of Photosynthesis Basic Research,Institute of Botany,Chinese Academy of Sciences,Beijing 100093,china Institute of Photonics and Photo-Technology Northwest UniversityXi'an 710069 China state key laboratory of Transient Optics and Photonics Xi'an Institute of Optics and Precision Mechanics Chinese Academy of SciencesXi'an 710068 China laboratory of Photosynthesis Basic Research Institute of Botany Chinese Academy of SciencesBeijing 100093 China

A study on energy transfer among chlorophylls（Chls）in the trimeric unit of the major light-harvesting complex Ⅱ（LHC Ⅱ）from Bryopsis corriculan,was carried out using time-correlated singlephoton *** the chlorophyll Q region of LHC Ⅱ,six molecules characterized as Chlb628,Chlb646,Chlb652654,657,Chla664666,Chla674677.680and Chla682683were discriminated according to their absorption spectrumand fluorescence emission ***,excited by pulsed light of 628 nm,fluorescence kinetics spectrain the chlorophyll Q region were *** accordance with the principles of fluorescence kinetics,thesekinetics data were analyzed with a multi-exponential *** constants on energy transfer were *** overwhelming percentage of energy transfer among chlorophylls undergoes a process longer than 97picoseconds（ps）,which shows that,before transferring energy to another Chl,the excited Chl might convertenergy to vibrations of a lower state with different multiplicity（intersystem crossing）.Energy transfer at thelevel of approximately 10 ps was also obtained,which was interpreted as the excited Chls may go throughinternal conversion before transferring energy to another *** with a higher standard deviation,timeconstants at the femtosecond level can not be entirely excluded,which can be attributed to the ultrafastprocess of direct energy *** to the arrangement and direction of the dipole moment of Chls inLHC Ⅱ,the probability of these processes is *** fluorescence lifetimes of Chlb652654,657,Chla664666,Chla674677.680and Chla682683were determined to be 1.44ns,1.43 ns,636 ps and 713 ps,*** of energy dissipation in the pathway of fluorescence emission were no more than 40% in thetrimeric unit of LHC Ⅱ.These results are important for a better understanding of the relationship between thestructure and function of LHC Ⅱ.

关键词： energy transfer LHC Ⅱ transient spectrum fluorescence kinetics

NUMERICAL SIMULATION OF EXTREME WAVE GENERATION USING VOF METHOD

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Journal of Hydrodynamics 2010年第4期22卷 466-477页

作者： ZHAO xi-zeng RIAM HU Chang-hong SUN Zhao-chen Kyushu university Fukuoka Japan State Key Laboratory of Coastal and Offshore Engineering Dalian University of Technology Dalian 116024 China RIAM Kyushu University Fukuoka Japan state key laboratory of Coastal and Offshore Engineering Dalian University of Technology Dalian 116024 China

Numerical simulations of extreme wave generation are carried out by using the Volume Of Fluid（VOF） *** waves are generated based on wave focusing in a 2-D numerical *** validate the capability of the VOF-based model described in this article,the propagation of regular waves is computed and compared with the theoretical *** adjusting the phases of wave components,extreme waves are formed at given time and given position in the *** numerical results are compared with theoretical solutions and experimental *** is concluded that the present model based on the VOF technique can provide acceptably accurate numerical results to serve practical purposes.

关键词： extreme wave Volume Of Fluid (VOF) wave focusing wave tank regular wave

The dust emission law in the wind erosion process on soil surface

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Science china(Physics,Mechanics & Astronomy) 2009年第2期52卷 258-269页

作者： xiNG Mao1 & GUO LieJin2 1 Mining Technology Institute, Taiyuan university of Technology, Taiyuan 030024, china 2 state key laboratory of Multiphase Flow in Power Engineering, xi’an Jiaotong university, xi’an 710049, china Mining Technology Institute Taiyuan University of Technology Taiyuan 030024 China state key laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong University Xi’an 710049 China

The dust emission models to date cannot describe the relation between the transport rate of different sized grains and their grain size composition in soil surface, so Aeolian grain transport on a soil-like bed composed of fine sand and silt powder was measured in a wind tunnel. Six types of soil-like beds with different silt fractions have been tested in this experiment. The mass flux profiles of silt dust and sand grains are much different due to their different motion modes. Analysis of the vertical distribution of the powder and sand grains reveals that for a given soil bed, the ratio of the horizontal dust flux to the horizontal sand flux is directly proportional to their mass ratio in the bed. The dust flux is closely linked to the sand flux by the bombardment mechanism. For a given wind velocity and grain size of the bed, the slopes of the vertical mass flux profiles of sand grains larger than 100 μm are nearly equal in a log-linear plot and the ratio between the fraction of transport rate of each size group to the whole transport rate and the mass fraction of each size group in the bed is a constant only dependent on grain size. With this law, the transport rate of dust and different sized grains can be related with the grain size composition in the soil surface.

关键词： wind erosion dust transport rate grain size

Finite element simulation on the deep drawing of titanium thin-walled surface part

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Rare Metals 2010年第1期29卷 108-113页

作者： GAO Enzhi, LI Hongwei, KOU Hongchao, CHANG Hui, LI Jinshan, and ZHOU Lian state key laboratory of Solidification Processing, Northwestern Polytechnical university, xi’an 710072, china state key laboratory of Solidification Processing Northwestern Polytechnical University

The deep drawing of titanium thin-walled surface part was simulated based on a self-developed three-dimensional finite element model. After an investigation on forming rules, a virtual orthogonal experimental design was adopted to determine the significance of processing parameters, such as die radius, blank holder force, and friction coefficient, on the forming process. The distributions of thickness and equivalent plastic strain of the drawn part were evaluated. The results show that die radius has a relative major influence on the deep drawing process, followed by friction coefficient and blank holder force.

关键词： deep drawing titanium alloy finite element simulation orthogonal experiment processing parameters

ERASED-CHASE DECODING FOR RS-CODED MPSK SIGNALING OVER A RAYLEIGH FADING CHANNEL

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Journal of Electronics(china) 2007年第3期24卷 296-300页

作者： Xu Chaojun Sun Yue Wang xinmei state key Lab. of integrated Service networks Xidian University Xi＇an 710071 China

In this paper,a novel dual-metric,the maximum and minimum Squared Euclidean Distance Increment (SEDI) brought by changing the hard decision symbol,is introduced to measure the reli-ability of the received M-ary Phase Shift keying (MPSK) symbols over a Rayleigh fading channel. Based on the dual-metric,a Chase-type soft decoding algorithm,which is called erased-Chase algorithm,is developed for Reed-Solomon (RS) coded MPSK schemes. The proposed algorithm treats the unre-liable symbols with small maximum SEDI as erasures,and tests the non-erased unreliable symbols with small minimum SEDI as the Chase-2 algorithm does. By introducing optimality test into the decoding procedure,much more reduction in the decoding complexity can be achieved. Simulation results of the RS(63,42,22)-coded 8-PSK scheme over a Rayleigh fading channel show that the proposed algorithm provides a very efficient tradeoff between the decoding complexity and the error performance. Finally,an adaptive scheme for the number of erasures is introduced into the decoding algorithm.

关键词： Reed-Solomon (RS) codes Coded M-ary Phase Shift keying (MPSK) Rayleigh fading Dual-metric Chase decoding

Aging assessment of large generator insulation based on PD measurements

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Progress in Natural Science:Materials International 2005年第11期15卷 1035-1043页

作者： YUE Bo, CHEN xiaolin, CHENG Yonghong and xiE Hengkun (state key laboratory of Electrical Insulation and Power Equipment, xi'an Jiaotong university, xi'an 710049, china Graduate School at Shenzhen, Tsinghua university, Shenzhen 518055, china Department of Electrical Engineering, Tsinghua university, Beijing 100084, china) state key laboratory of Electrical Insulation and Power Equipment Xi''an Jiaotong University Xi''an 710049 China. Graduate School Shenzhen Tsinghua University Shenzhen 518055 China. Department of Electrical Engineering Tsinghua University Beijing 100084 China

The statistical parameters of phase resolved partial discharge (PD) distribution and ultra-wideband (UWB) characteristics of PD pulse are proposed for aging assessment of large generator insulation. Multi-stress aging tests of the model generator stator bar specimens were performed and PD measurements were conducted using both digital PD detector with frequency ranging from 40 kHz to 400 kHz and UWB PD detector with bandwidth from 10 MHz to 3 GHz at different aging stages. The test results show that the skewness and UWB frequency characteristics of PD can be taken as the characterization parameters for aging assessment of generator insulation. Furthermore, the measurement results of real generator stator bars show that these methods based on statistical parameters and UWB characteristics of PD are prospective for aging assessment and residual lifetime estimation of large generator stator insulation.

关键词： partial discharge stator insulation multi-stress accelerated aging statistical parameters ultra-wideband aging assessment.

Experimental Investigation and Numerical Simulation of the Grain Size Evolution during Isothermal Forging of a TC6 Alloy

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Journal of Materials Science & Technology 2005年第2期21卷 155-160页

作者： Miaoquan LI, Shankun XUE, Aiming xiONG and Shenghui CHEN state key laboratory of Solidification Processing, School of Materials Science and Engineering, Northwestern Polytechnical university, xi’an 710072, china state key laboratory of Solidification Processing School of Materials Science and Engineering Northwestern PolytechnicalUniversity Xi'an 710072 China

Hot compression was conducted at a Thermecmaster-Z simulator, at deformation temperatures of 800-1040℃, with strain rates of 0.001-50 s-1 and height reduction of 50%. Grain size of the prior α phase was measured with a Leica LABOR-LUX12MFS/ST microscope to which QUANTIMET 500 software for image analysis for quantitative metallography was linked. According to the present experimental data, a constitutive relationship for a TC6 alloy and a model for grain size of the prior a phase were established based on the Arrhenius' equation and the Yada's equation, respectively. By finite element (FE) simulation, deformation distribution was determined for isothermal forging of a TC6 aerofoil blade at temperatures of 860-940℃ and hammer velocities of 9-3000.0 mm/min. Meanwhile, the grain size of the prior α phase is simulated during isothermal forging of the TC6 aerofoil blade, by combining FE outputs with the present grain size model. The present results illustrate the grain size and its distribution in the prior α phase during the isothermal forging of the TC6 aerofoil blade. The simulated results show that the height reduction, deformation temperature, and hammer velocity have significant effects on distribution of the equivalent strain and the grain size of the prior α phase.

关键词： Titanium alloy Isothermal forging Grain size Model Finite element (FE) simulation

Phase-selection and metastable phase formation in highly undercooled eutectic Ni78.6Si21.4alloys

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Progress in Natural Science:Materials International 2006年第3期16卷 287-291页

作者： LU Yiping, YANG Gencang, YANG Changlin, WANG Haipeng and ZHOU Yaohe (state key laboratory of Solidification Processing, Northwestern Polytechnical university, xi'an 710072, china Department of Applied Physics, Northwestern Polytechnical university, xi'an 710072, china) [a]state key laboratory of Solidification Processing Northwestern Polytechnical University Xi'an China [b]Department of Applied Physics Northwestern Polytechnical University Xi'an China

A large undercooling (250 K) was achieved in eutectic Ni78.6 Si21.4 melt by the combination of molten-glass denucleation and cyclic superheating. The metastable phase formation process in the bulk undercooled eutectic Ni78.6 Si21.4 melts was investigated. With the increase of undercooling, different metastable phases form in eutectic Ni78.6 Si21.4 melts and part of these metastable phases can be kept at room temperature through slow post-solidification. Under large undercooling, the metastable phases β2-Ni3Si, Ni31Si12 and Ni3Si2 were identified. Especially, the Ni3Si2 phase was obtained in eutectic Ni78.6 Si21.4 alloy for the first time. Based on the principle of free energy minimum and transient nucleation theory, the solidification behavior of melts was analyzed with regard to the metastable phase formation when the melts were in highly undercooled state.

关键词： undercooling molten-glass metastable phase rapid solidification.