Table of Content

20 May 2007, Volume 43 Issue 3

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Phase Solution of Modulated Fringe Carrier Using Wavelet Transform

LI Hongju ,CHEN Huijun

2007, 43(3):  317-320. 

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The relation between the carrier frequency and the maximum of the wavelet coefficient modules is given, from which the searching ranges of the maximum amplitudes in the dimension coordinate are presented. The method reduces the difficulty of phase determination from the wavelet transform coefficient maps. The computational results show the validity of the technique, and present the influence of the carrier frequency on the processing errors of the phase solution.

Numerical Studies of Scaling Exponents in Compressible

HU Kaiheng,CHEN Kai,SHE Zhensu

2007, 43(3):  307-311. 

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Compressible turbulent channel flows at two Mach numbers (M = 0.8 and 1.3 ) are simulated by the numerical integration of the Navier, Stokes equations with a high, order compact finite difference scheme. The comparative studies of incompressible and compressible flows indicate that the effect of compressibility on the scaling exponents is small in the region near y+ = 20 and in the center while it is significant in the viscous sublayer (y+＝5.5) and the log, law region (y+≈120). Further studies on the variation of the relative scaling exponent show that the channel can be divided into four distinct zones according to their scaling behavior: viscous sublayer and lower edge of buffer layer (Ⅰ); the outer part of the buffer layer and lower part of log region (Ⅱ); the major part of the log region and lower edge of the center region (Ⅲ); and finally the other part of the center region (Ⅳ). The variation of the scaling exponents with the compressibility is the most remarkable in the zone Ⅰ and Ⅲ. Finally, it is found that the most intermittent region exactly coincides with the location of the maximum Reynolds shear stress.

Research on Energy Absorption Feature of Ring Systems

ZHAO Kai,SHEN Jianhu,LIU Kaixin,LU GuoxingYANG Jialing

2007, 43(3):  312-316. 

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The modified Split Hopkinson Pressure Bar system equipped with the high, speed camera is utilized to perform the experimental researches on the dynamic behavior of ring systems made of different materials subjected to impact loading. Correspondingly, comprehensive numerical simulations on the ring systems are conducted by the dynamic finite element software LS, DYNA. The energy absorption features of different ring systems and the influences of different parameters are discussed. The results show that the energy absorption efficiency of the ring systems is relatively high and the system is very valuable for engineering uses.

Studies of the Three, Dimensional Magnetic Null Based on Sattellite Observations in the Reconnection Region

XIAO Chijie,WANG Xiaogang,PU Zuyin,MA Zhiwei,ZHAO Hui,ZHOU Guiping,WANG Jingxiu,FU Suiyan,LIU Zhenxing

2007, 43(3):  285-295. 

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Magnetic reconnection is considered to be of crucial importance not only to space science but also to magnetically confined fusion,as well as many basic processes in astrophysics and cosmology. In general, except on a closed field line, three, dimensional (3D) magnetic reconnection occurs on the separator connecting magnetic nulls and separatrices, which are determined by the eigenvectors of the magnetic field gradient matrixes of the null pair. Due to the 3D geometric property, the null can only be detected by an at least 4, point measurement so far uniquely provided by the Cluster mission. Here the authors review the recent progresses in applying the Poincare method of magnetic null identification to find out: (1) the in situ evidences of four types of nulls (A, B, As and Bs) and their fans and spines; (2) the spatial scale of the spine structure of the null being of the order of local ion inertial length scale, suggesting that the Hall effect should be important in 3D reconnection dynamics; (3) the in situ evidence for the existence of A, B, B, As null pairs and the separator lines combining the null pairs; and (4) the existence of a lower hybrid oscillation in the immediate vicinity of the A, B separator line, which provides a possible mechanism for electron heating and acceleration in the reconnection process. It is the first in situ evidence for complete 3D reconnection geometry and associated dynamics, a crucial step toward to establish an observational framework of 3D reconnection.

A Note on Harmonic Functions

CAI Yongyong,LI Feng

2007, 43(3):  296-298. 

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An extension form of Liouville's theorem about analytic functions for general harmonic functions is proved.

A Note on Compound Poisson Distributions

ZHANG Bo,QI Yongcheng

2007, 43(3):  299-301. 

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The infinite composition and decomposition properties of compound Poisson distributions are demonstrated. It covers the classical results of Gerber H.U.

A Fast Mesh Generation Algorithm with Point, by, Point Delaunay Insertion

LI Shuixiang,CHEN Bin,ZHAO Liang,LIU Yuewu

2007, 43(3):  302-306. 

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A grouped double link data structure corresponding to element inserting coefficient (EIC) is presented to eliminate the search for the maximum EIC element in the point, by, point center insertion algorithm. Adjacency search, double linked element list, random direction search, adjacency rotation, and heredity of geometrical quantities are applied to increase the efficiency of mesh generation. The relationship between the computing time and the number of generated elements is nearly linear and the time complexity is O(N^1.05),N, where N is the number of elements. Example shows the generating rate of this algorithm is above 50?000 tetrahedrons per second on an AMD Athlon 3200+(2.0?GHz) personal computer.

Theoretical Interpretation of Experimental Results on Four, Photon de Broglie Wavelength Measurement

YANG Zhi,WANG Ruopeng

2007, 43(3):  321-324. 

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Experimental results of four, photon de Broglie wavelength measurement are analyzed based on a local description for the quantum state and optical field of photon pairs generated from spontaneous parametric down, conversion (SPDC). The agreement between the theoretical results and reported experimental is found.

A Numerical Study of the Intensification Mechanism of Typhoon LEO over South China Sea (1999)

ZHU Xiaojin,ZHANG Qinghong

2007, 43(3):  325-329. 

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High, resolution numerical simulation scheme is used to study the physical mechanism of the intensification of Typhoon LEO (1999), which develops from a tropical storm in South Chine Sea. The results show the transition from a tropical storm to a typhoon is caused by convective bursts near the storm center. The convective condensation heating effect helps to form a warm core and also a cyclonic circulation at upper levels. The merger of mesoscale vortices or the injection of mesoscale vortices to the storm center at lower levels might be the trigger of convective bursts.

Influence of Biomass Burning in South Asia on Lower Tropospheric Ozone Concentration over Kunming

ZHENG Yongguang,CHEN Jiong,ZHU Peijun,CHAN Loyin,CHAN Chuenyu,QIN Yu

2007, 43(3):  330-337. 

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Ozone enhancement was observed in the lower troposphere over Kunming on 21 March 2001 using electrochemical concentration cell ozonesondes. The influence of the biomass burning in South Asia on ozone concentration in the lower troposphere over Kunming is analyzed, based on NCEP reanalysis, Total Column Ozone, numerical simulation of MM5, AI from TOMS, and aerosol optical depths from MODIS. It is shown that the enhancement of ozone in the lower troposphere over Kunming is due to biomass burning emissions in South Asia. TOMS AI images and the atmospheric background circulations suggest that biomass burning plumes in South Asia are transported to Kunming and cause the enhancement of ozone concentrations in the lower troposphere.

Enhanced Tunneling Magnetoresistance in Fe₃O₄ Nanopowder Compact Coated with SiO₂

SONG Pengyun,WANG JunfengYAN Huijuan

2007, 43(3):  338-342. 

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Fe₃O₄ is considered to be half metal nature and has a comparatively high Curie temperature of 858 K compared with other metal oxides, which makes it more attractive in spin, electronic application. The extrinsic magnetoresistance of Fe₃O₄ has been studied extensively, however, so far few progress is acheieved. Here, a new way is given to obtain higher MR. Fe₃O₄ nanospheres with the average diameter of about 200 nm is prepared and coated by SiO₂, which forms a shell of several nms. The nanopowder with SiO₂ shells, which serves as grain boundaries, is pressed and then sintered into compacts, which show enhanced MR. At different temperatures MR curves of compacts with SiO₂ and without SiO₂ differ much, and the former display a linear respond at high field range, which is interpreted as the existance of insulating SiO₂ grain boundaries.

The Relationship between the Tropical Cyclone Frequency over the South Asian Marginal Seas and Tropospheric Wind Variations

ZHANG Xin,QIAN Weihong

2007, 43(3):  383-389. 

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The climatically character of wind vectors at 100 hPa and 850 hPa level and the relationship between the tropical easterly current at the 100 hPa level and trop ical cyclone numbers in low and high frequency years were analyzed by using the data of NCEP/NCAR reanalysis and the tropical cyclone data from JTWC(Joint Typho on Warning Center) over the Arabian Sea,Bay of Bengal and the South China Sea during the period 19581998.The result shows that a high positive correlation be tween tropical easterly current and the number of tropical cyclone is found in the Arabian Sea,Bay of Bengal.However,such a positive correlation is not found in South China Sea.Because South China Sea is at the southeast of South Asia high,the domination of meridional wind makes the relationship between tropical cycl one numbers and the merridional wind at the 100 hPa level is higher than it between tropical cyclone numbers and tropical easterly.

A Novel ESD Clamp Protection Circuit with Low Leakage Current and High Latch, up Immunity

WANG Yuan,JIA,Song,ZHANG Ganggang,CHEN Zhongjian,JI Lijiu

2007, 43(3):  400-404. 

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A novel ESD clamp protection circuit named gate, controlled SCR cascade diode string (gcSCR, CDS) is proposed. Compared with the traditional CDS device, this novel structure has a high ESD performance due to its low leakage current and low turn, on resistance by inserting a SCR transistor. A gate, controlled PMOS transistor is also used to immunize its latch, up effects. This new structure is performed in 0.35?μm CMOS process. The measured results show that it has a low leakage current about 12nA and a high ESD robustness above 8kV.

Effects of Urban Buildings on 3-Dimensional PBL Structures: WRF Simulation Study

CHEN Jiong,ZHENG Yongguang,DENG Liantang

2007, 43(3):  343-350. 

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The Urban Boundary Layer Parameterization(UBP) is developed to describe the dynamic and thermal effects of urban buildings on boundary, layer meteorological fields. The UBP is incorporated into the Weather Research and Forecasting(WRF) model, and is used to simulate the summer meteorological fields and Plantary Boundary Layer(PBL) structures in the Beijing area. Results show that the UBP scheme produces winds and temperatures at the surface layer that is more consistent with the observations than that simulated using the Mellor, Yamada, Janjic(MYJ) scheme. The UBP scheme gives weaker winds and a stronger hot, island effect than that by the MYJ scheme. Anthropogenic heating has little effects on the 2, meter temperature during daytime because turbulent diffusion is strong enough to transport heat to higher levels. It is concluded that the UBP scheme improves the simulation of the surface, layer meteorological fields in urban area, and that the description of the urban canopy, layer structures is more rational.

Numerical Simulations of Summer Precipitation in China during 1951, 2000 Using a Regional Climate Model

HUANG Jianbin,ZHU Jinhong,LI Zhenhua

2007, 43(3):  351-357. 

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In order to test the capability of the high, resolution regional climate model RegCM3, simulations of summer precipitation in China between 1951 and 2000 are carried out. In these simulations, NCEP/NCAR (National Center for Environmental Prediction and National Center for Atmospheric Research) reanalysis data are used as initial and boundary conditions. The model domain covers the whole China and surrounding areas, and centers at 32.5°N, 95°E. It has 160 and 95 grids in zonal and meridional directions, respectively, with a grid space of 60?km. The Fritsch & Chapper of Grell scheme is employed. Monfthly sea surface temperatures used are GISST2.3b from the Hadley Center. Simulations are carried out from May 1 to September 1 for each year. Analysis of precipitation focuses on the period of June, July, August. In order to test results, simulated results and observations are converted into grid data with 1° latitude multiply by 1° longitude. Seasonal and total rainfalls are compared with observations from 160 stations by the National Climate Center (NCC) to validate the model's performance in simulating the climatological mean and interannual variations of the summer precipitation. Main results are: (1) for the climatological mean precipitation over China, the simulated rainfall is close to observations, much better than that from NCEP/NCAR reanalysis data. (2) for the spatial distribution of precipitation anomalies, the simulated results over the Northeastern part of China are better than over other parts, and the simulated precipitations in the valley of the Yellow River and the Yangtze are the worst; (3) for the temporal evolution, the simulated results display decadal variations, and the simulated results over the 1960's and 1990's are better and stable, however, the results over the 1970's and 1980's show large variations; (4) simulated precipitation over the 1970's and 1980's is poor, heavier than observations, suggesting that the model is unable to generate observed decadal variations.

Study of Evapotranspiration Processes Simulationin Arid and Semi, Arid Regions

LIU Shuhua,YU Fei,LIU Heping,ZHANG Chenyi,LIANG Fuming,WANG Jianhua

2007, 43(3):  359-366. 

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An integrated and flexible numerical model has been established to simulate and study the evaporation, transpiration and evapotranspiration mechanism of moisture on land, surface with complex vegetative cover. To better simulate this process, the authors apply some reasonable modifications to the parameterization of edaphic process too. The model is used to simulate the process of Zhangye station during IOP2 of HEIFE, and the results are generally in good agreement with observations. It indicates that the model developed can be used to study the interaction between land surface and atmospheric boundary layer over arid and semi, arid regions. Thus it can be used on evaluating the environment and shaping measures for sustainable development.

A Rotation Invariant 3D Shape Descriptor

XIN Guyu,ZHA Hongbin

2007, 43(3):  428-433. 

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A novel method is proposed to construct 3D shape descriptors by extracting rotation invariants of 3D models. In this method, a 3D model is firstly represented as a collection of spherical functions by using Hadamard transforms, and then the rotation invariants of the spherical functions are extracted by spherical harmonic decomposition. The method can avoid information, loss in the process of representing 3D models by the spherical functions. A shape similarity measure is defined on the extracted rotation invariants. A large amount of experiment results verified that this 3D shape descriptor performs better than some others.

Phase Transitions and Superconductivity Related to Structural Blocks in YBCNO

ZHANG Li,WANG Yongzhong,YU Jing

2007, 43(3):  367-374. 

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The YBa₂Cu_3-xNi_xO_7-δ (x=0, 0.05, 0.10, 0.15, 0.20, 0.25) (YBCNO), polycrystalline samples, synthesized by solid state reaction technique, were characterized by thermogravimetry, differential scanning calorimatry, DC magnetization measurement, temperature dependent X, ray diffraction and Rietveld refinement. It is observed there are two phase transitions at about 400?℃ and 850?℃ in each sample before melting, respectively. By careful measurement it shows the amounts of weight loss and endotherm, along with T_c, decrease with the dopant increasing when phase transitions occurred. Combining the mechanism of oxygen diffusion with the block model in YBCO,the mechanism of the phase transitions can be explained as follows: the phase transition at 400?℃ comes directly from O(1) in the rock salt block, and corresponds to the beginning of O, T; the phase transition at 850?℃　corresponds to the end of O, T, when O(2) and O(3) of Cu(2), O plain are rearranged and a few oxygen enter O(1) site of Cu(1), O plain through O(4) bridge atom, and at last escape from the crystal cell. Thus the phase transition at 850?℃ is related with the pervoskite block. Refined results confirmed this point. The calculation of the combinative energy between rock salt block and perovskite block shows that with Ni content increasing, the higher the combinative energy, the lower the T_c. The results demonstrate that the structural blocks uniquely influence the superconductivity and thermal properties.

Intensity Variation of Influence Factors on Floating Dust in the Tarim Basin

MA Yu,WANG Xu,KANG Fengqin

2007, 43(3):  375-382. 

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Based on daily observation data from 27 meteorological stations in the peripheral regions of Tarim Basin from 1961 to 2003, the authors sort out 40 meteorological factors and show the existence of consistency among the analogical meteorological factors with correlation analysis. 15 among the 40 factors, such as daily mean and 6, hour variation of sea level pressure, air temperature and wind speed, daily mean of relative humidity, daily precipitation and daily maximum depth of frozen soil, are considered having influences on floating dust weathers, while others are neglected due to their self, consistencies. The degree of correlations between these 15 factors and floating dust weathers has significant changes from one month to another. Analyses of multivariate linear regression show significant seasonal changes. At 08:00, 14:00 temperature variation and daily, mean relative humidity are the dominant factors of influencing on floating dust weathers in all seasons. At 14:00, 20:00 in spring and summer, pressure variation is the secondary factor. At 08:00, 14:00 in autumn variation of wind speed is important. Daily, mean wind speed is important in all seasons, with more prominent influences in spring and winter.

Theoretical Analysis of the Electromagnetic Leakage Coming from Symmetric Transmission Line with Insert of Unbalanced Loads

TIAN Fang,GONG Zhonglin

2007, 43(3):  390-394. 

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This paper analyzed the electromagnetic leakage mechanisms of a symmetric transmission line and cable with insert of unbalanced loads. The electromagnetic leakage comes from the point, chaining the unbalanced loads. The electromagnetic leakages of the two cases above are simulated and compared by using a hybrid method which is formed by the combination of circuit, FEM and subcell, FDTD methods.

Efficient VLSI Design and Implementation of Decimation Filter for 2^nd ΣΔ A/D Converter

PENG Chungan,YU Dunshan,SHANG Tianxiu,SHENG Shimin

2007, 43(3):  395-399. 

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The authors describes an efficient design and implementation of a decimation filter for high resolution 2nd ΣΔ A/D converter. A new universal multiplier, free VLSI structure is proposed to implement 2, time decimation for half band filters and a high, order invsinc corrector filter, the whole filter is realized without any multiplier or RAM or ROM, and the 2nd ΣΔ A/D converter reaches a 16, bit resolution with low cost.

Schema Merging Study with Semantic Relationships of Schema Elements

WANG Hongding,TAN Shaohua,TANG Shiwei,YANG Dongqing,TONG Yunhai

2007, 43(3):  405-411. 

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Data integration has been a long, standing challenge for the database study communities, and construction global schemas is one of the most important problems in data integration research. This paper first analyzes the semantic relationships of schema elements, and based on those semantic relationships of schema elements, it proposes a method to schema merging with the results of schema matching. Different from previous methods, it extracts schemas from data dictionaries of data sources directly. Moreover, rules of schema elements merging are given corresponding to their semantic relationships. By using data dictionaries, not conceptual models, the method is more applicable and effective than the previous ones.

Improving the Field Emission Properties of a Graphite Paste Film by Nitrogen Ion Bombardment

WANG Weiwei,SUN HuiYU,LigangZHANG,Gengmin

2007, 43(3):  412-416. 

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The field emission properties of a graphite paste film were found to have been greatly improved by nitrogen ion bombardment. The bombardment transformed the graphite surface into an array of graphite cones with a ～108cm^-2 tip density. XPS measurement showed that plenty of nitrogen had been injected into the graphite film and there existed a large number of sp2 bonds. Field emission test demonstrated that the distribution of the emission sites in the post, bombardment film was much more dense and uniform than that of the original one. The maximum current density of 1.65mA/cm² was also achieved, which was much higher than that of the pre, treatment sample.

Realization of 6, Tap Finite Impulse Response Interpolation Filter for H.264/AVC Encoder

WANG Qingchun,CAO Xixin,LU Weijun,HE XiaoyanCAO Jian

2007, 43(3):  417-420. 

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It is proposed that four hardware architectures of 6, tap finite impulse response interpolation filter for the design of H.264/AVC encoder (SOC). Moreover, based on comparative analysis of Synopsys Design Compiler to implement the hardware at the same constraint, an efficient half pixel interpolation filter (6, tap FIR) architecture had been given finally.

CMOS Combinational Circuit Leakage Power Reduction Using Genetic Algorit

ZHAO Xiaoying,YI Jiangfang,TONG Dong,CHENG Xu

2007, 43(3):  421-427. 

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A leakage power reduction platform for CMOS combinational circuits by means of input vector control is presented. Genetic algorithm is used for searching minimum leakage vector and circuit status difference is used as fitness function. Experimental results show that this circuit status difference based genetic algorithm can achieve satisfied leakage power reduction, and runtime is reasonable. This method has no requirement for HSpice simulation and independent from target technology library.