Table of Content

20 January 2008, Volume 44 Issue 1

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Methods of Estimation of GPS Instrumental Bias from Single Site's GPS Data and Comparative Study of Results

LI Qiang,FENG Man,ZHANG Donghe,XIAO Zuo,SHI Liqin

2008, 44(1):  149-156. 

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The major error sources of deriving TEC from GPS observational data are instrumental biases. Two methods of extracting TEC and instrumental biases based on single site's GPS observations, called Kalman filter and self adjusted cell methods respectively, are presented. TEC and instrumental biases were computed by using these two methods from GPS data at several sites in 2004. The results were analyzed respectively and then compared with each other. The results also were compared with corresponding values published by CODE (Center for Orbit Determination in Europe).Its statistical characteristics with respect to the latitude of observational site were discussed. The main results can be concluded that the proposed methods can be used to derive TEC and instrumental biases which are accuracy enough with respect to CODE's published values. The standard deviations of derived instrumental biases are related to latitudes of observational sites. For China region, based on the paper's computational results, it shows that the sites with lower latitude are related with larger deviation, which is a implication that ionosphere is more complex in low latitude area than that in mid latitude and more caution should be paid in using the assumption of simple smooth ionospheric model in lower latitude.

Review on the Synoptic Scale Meiyu Front System and Its Synoptics' Definition

ZHENG Yongguang,CHEN Jiong,GE Guoqing,HUANG Yanfang,ZHANG Chunxi

2008, 44(1):  157-164. 

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The progress on synoptic scale Meiyu front is summarized after 1930 s. The existed studies show that the structure of the Meiyu front is very complicated, and has a multiformity feature. Based on previous studies, the synoptics' definition of Meiyu front is given as: there exists a narrow rain band of thousands of kilometers long across East Asia and northwestern Pacific; the rain band advances and retreats closely related with the Asia monsoon, and the frontal surface is between warm monsoon air mass and the others; and the Meiyu frontal area is a band with high gradient of θse.

Entanglement Properties of the Fractional QuantumHall Effect on the Sphere

LIU Xuele,LI Dingping

2008, 44(1):  11-14. 

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The von Neumann entropy measure of entanglement is used to study the fractional quantum Hall effect on the sphere. Numerical results show that the FQHE on the sphere is a maximal entanglement state. While the number of particles in the system is big, the value of the entanglement (E) can be written as the function of the filling factor (ν):E～log21ν.

Experimental and Calculative Research on the Dynamic Bond-Strengthof the Interface between Steel and Cement Mortar

LI Xudong,YE Lin,LIU Kaixin

2008, 44(1):  1-5. 

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A new kind of specimen was designed and produced to research the dynamic bond-strength of the interface between steel and cement mortar experimentally and numerically. The relationship of the loading speed rate and the bond-strength of the interface between steel and cement mortar was investigated through quasi-static and impact experiments. Numerical calculation was carried out by using LS-DYNA software and Johnson-Holmquist-Cook model as the constitutive relationship of cement mortar material. By calculation the process and mechanism of the fracture of the interface under impact loading was studied and the credibility and reliability of the impact experiment method based on the SHPB experiment technique are verified. It can be concluded that the bond-strength is roughly linear with the logarithm of the loading speed rates.

Study on Reducing Divergence of the Beams Extracted from a PermanentMagnet Microwave Ion Source by Using Permanent Magnet Lens

QIAN Feng,XU Rong,GUO Zhiyu,SONG Zhizhong,YU Jinxiang,PENG Shixiang,YUAN Zhongxi,LU Yuanrong,ZHAO Jie

2008, 44(1):  6-10. 

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This paper introduces an improvement of mini permanent magnet (PM) 2.45 GHz microwave ion source's extraction system at the Institute of Heavy Ion Physics, Peking University. Through simulating and measuring, the magnetic field with or without a 10 cm long PM lens added 9 cm downstream from the PM ring of the ion source was compared. The simulations and experiments indicated that the PM lens can focus the beam effectively. Compared with solenoid lens, this method can simplify the beam transport system, save power and improve the vacuum at ion source region.

Research on Energy Spread of RFQ Accelerator in AMS

LIU Kexin,GUO Zhiyu,YAN Xueqing,LU Yuanrong,FANG Jiaxun,CHEN Jia'er

2008, 44(1):  15-18. 

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Using RFQ as the main accelerator is a possible way to make AMS more compact. It is most important to reduce the energy spread of RFQ accelerator. Based on a theoretical analysis of the energy spread of RFQ shaper section, simulation by using computer code RFQDYN shows that an energy spread of 0.4% can be obtained by optimizing RFQ parameters.

The Metal-Semiconductor Junction of Indium and Nb Doped SrTiO₃

WANG Shiqi,MA Yubin

2008, 44(1):  19-22. 

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The metal-semiconductor junction of indium and Nb doped SrTiO₃ were fabricated. The current-voltage of the junction were obtained by three terminals method. In the junction of 0.05 wt.% doped Nb-STO, the effect factor n derived from negative voltage are in range 1.05-1.10 and almost independent of temperature. The junctions both show non-linear I-V characteristic.The contact between Indium and Nb-STO could not be treated as Ohmic contact, even in high doped Nb-STO.

Study on Intense Pulsed Ion Beam Mixing of Ni/Ti and Al/Ti Systems

SHANG Yijun,YAN Sha,LE Xiaoyun,ZHAO Weijiang,WANG Yugang,XUE Jianming

2008, 44(1):  23-27. 

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The intense pulsed ion beam (IPIB) mixing effect of Ni/Ti and Al/Ti systems are studied. Compared with common ion beam, it is obvious that the mixing layers formed by IPIB irradiation are thicker, and the mixing rate is much higher. However, the IPIB mixing effects are various for different film/substrate systems because of their different thermodynamic properties. During IPIB irradiation, film material lost seriously, especially for the samples with big differences in their film and substrate thermal dynamic parameters. Two IPIB mixing mechanisms which are distinct from common ion beam mixing are discussed and the reason of mass loss of film materials are analyzed.

Quantum Local Theory of Two-Photon Interference by a Nonlocal Double Slits

WANG Ruopeng,ZHANG Huirong

2008, 44(1):  28-30. 

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The authors shows a quantum local theory that can explain the interference experiment which is designed based on the nonlocal double slits experiment. The theoretical results are consistent with the experimental data perfectly.

A Low Power Pipeline FFT Processor Based on Data Statistical Characteristics

ZHANG Shiqun,YU Dunshan,SHENG Shimin

2008, 44(1):  31-36. 

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A low power FFT (Fast Fourier Transform) processor based on Single-path Delay Feedback (SDF) architecture is proposed. Power optimization strategy based on statistical characteristics of input data is applied in the design. Both the advantages and the drawbacks of this strategy are analyzed in detail, and solutions to overcome the drawbacks are addressed. An experimental 64-point FFT processor model is implemented in SMIC 0.18 μm CMOS technology, and for given input signals, 15% power reduction can be achieved.

A Novel Compound Conditions Recognition Algorithm in Decompilation

WEI Tao,MAO Jian,ZOU Wei

2008, 44(1):  37-43. 

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A novel recognition algorithm is proposed. Compared with previous works, the algorithm is deterministic rather than heuristic, and it does not use complicated data structures. The new algorithm is more accurate than typical current approaches; furthermore, the new method has been applied to several real-world binaries, and experimental results validate such theoretical analysis.

The VLSI Implementation of Intra Prediction in H.264/AVC

ZHU Zhongping,FENG Jianhua,Cao Xixin

2008, 44(1):  44-48. 

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An intra prediction circuit in H.264/AVC is implemented. By choosing variable circuit path and reusing adders, the authors implement all the prediction modes except plane prediction mode with low cost. Synthesized by SMIC 0.18 μm CMOS technology, the total gates is about 4000, the critical path delay is 5.7 ns.

Research and Implementation of GPGPU Accelerated Audio Mixing Algorithm for Multi-Party Collaboration

SHENG Xiangzhi,SHAN Baosong

2008, 44(1):  49-54. 

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A GPGPU accelerated audio mixing algorithm for multi-party collaboration namely GAM is introduced. The mixing is performed by pixel shader. To minimize time used while buffer switching, traditional mixing algorithm was rearranged to a two-pass rendering. By vertex shader, the projection of 3-D model was moved between the passes. So multiple functions resulting different sized output set were performed on one render buffer without multiple shader executions on one pixel. The audio units to be mixed were inputted in one texture to remedy the issue that the I/O bandwidth of GPGPU was not match to the computational capacity of GPGPU. The experimental result shows that the GAM algorithm achieves high performance contrasting to CPU-based algorithms on mainstream hardware.

A Low-Leakage Pipelined Instruction Cache Design

SUN Hanxin,WANG Xiaoyin,TONG Dong,CHENG Xu

2008, 44(1):  55-61. 

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Pipelined level one instruction cache (PIL1) has been proposed to improve instruction fetch bandwidth in high frequency processor. However, few researches in the literature have focused on reducing the leakage power in PIL1. Here,the authors observe that the PIL1 structure naturally lends itself to provide inherent leakage power saving opportunities. Based on this observation, the authors propose to manage cache line activities according to the demand of the fetch address, which activates only the requested line and keeps others in low-voltage mode, thereby saving leakage power effectively. Simulation results demonstrate that the PIL1 leakage power is reduced by an average of 77.3%. Meanwhile, the performance degradation is only 0.32% and no timing overhead is induced.

A Low Pass Filter with Adjustable Bandwidth for MEMS Capacitive Accelerometer Readout Circuit

CHEN Jianghua,XIANG Bin,MO Bangxian,WANG Zhanfei,NI Xuewen

2008, 44(1):  98-102. 

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This paper describes a low-pass filter with adjustable bandwidth range from 100 Hz to 8 kHz for MEMS capacitive accelerometer readout circuit. The signals with their frequencies lower than 500 Hz are filtered through the switched-capacitor low-pass filter, while those higher than 500 Hz are filtered through the continuous-time one. This low-pass filter was implemented with 1.2 μm 2P2M N-well CMOS process. Problems such as charge injection and clock feedthrough caused by turning off swithes are analyzed and solved in this design. The optimal switch sequence helps eliminate the nonlinearity caused by the charge injection; the addition of dummy switches to sensitive nodes caused by the clock feedthrough can greatly reduce the coupled charge; and the use of high PSRR folded cascode differential input stage can restrain the interference from the power supply. The circuit performance, therefore, has been greatly improved.

A Study of Accuracy of Time Domain Integral Equation Methods for Analysis of Broadband Electromagnetic Scattering

WANG Pai,XIA Mingyao,ZHOU Lezhu

2008, 44(1):  62-66. 

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The accuracy of time domain integral equation (TDIE) methods for broadband electromagnetic scattering problems is studied. The impacts of different choice of temporal basis functions on the accuracy of the induced surface current,scattered far-field and radar cross-section (RCS) are examined. Numerical results show that: for closed scatterers, time domain combined field integral equations (TDCFIE) must be employed to suppress the resonant disturbance; whereas the induced currents and far-fields in time domain look accurate, the RCS defined in frequency domain may deviate obviously, which suggests that RCS could be the best quantity for accuracy checking.

A Method for Modeling and Realizing SelfAdaptive Software Architecture

FENG Yaodong,HUANG Gang,MEI Hong

2008, 44(1):  67-76. 

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The authors present an architecture-based approach to self-adaptive systems, called self-adaptive software architecture (SASA). To guarantee the general applicability, the authors synthesize a set of popular and/or sophisticated methods in architecture based software engineering, including the quality related architecture analysis methods for identifying why and when to change, the quality driven architecture design methods for deciding what to change, the architectural description language with dynamisms for recording the above knowledge, and the runtime software architecture for executing the designed adaptations. The approach is demonstrated on Java 2 Platform Enterprise Edition (J2EE).

Adaptive Watermarking Based on Localized Perceptual Quality Evaluation

ZHU Xinshan,TANG Zhi

2008, 44(1):  77-86. 

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To seek the good tradeoff between robustness and unobtrusiveness, the cover data is divided into nonoverlapping blocks and an independent distortion situation is assigned to each block, which is called localized quality evaluation. Two specific implementations applying the Signal to Noise Ratio and Watson's visual model as the quality metrics are respectively achieved in the sense of maximizing the detection value. And the corresponding upper limits are derived under the given distortion constraints. Then, some practical adjustment strategies of those relative parameters are provided. The approach also introduces an improved linear correlation detector using side information and analyzes its performance mathematically. A lot of experimental results show the presented schemes obtain very significant performance improvement in terms of image transparency and robustness.

Doubly Selective Channel Estimation Based on Fractional Basis Expansion Model

LIU Yingnan,JIANG Wei,YAO Chunguang,WANG Wujun,LIANG Qinglin

2008, 44(1):  87-92. 

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By analyzing the relationship between basis expansion model (BEM) and Doppler spectrum, the authors propose a scheme based on fractional BEM for the estimation of doubly selective channel parameters. When the receiver detects the maximum frequency of Doppler-spread, the frequency of BEM is modified by a factor of 1/K, and improved mean-square error of channel can be obtained.

LDPC-SPC Product Codes

QIAO Hua,LIN Guangrong,WANG Da,DONG Mingke,XIANG Haige

2008, 44(1):  93-97. 

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LDPC-SPC codes is introduced. LDPC-SPC codes choose LDPC codes as horizontal codes and single parity check (SPC) codes as vertical codes. Some decoding algorithms are also given, including algorithms based on hard decision and soft decision. By these algorithms, each bit of every LDPC code can get extrinsic messages from other LDPC code words to help LDPC decoder decode successfully. Based on the LDPC code which is half rate and 8064 bits long, a LDPC-SPC code is constructed. Simulation results show that the LDPC-SPC codes can lower the error floor of the LDPC codes and have better BER (Bit Error Ratio) performance. When BER is 10-7, the performance of the LDPC-SPC codes is 0.3 dB better than the LDPC codes.

Boehmite Nanowires Formation from Porous Anodic Alumina Membrane

YANG Xin,WANG Jingyun,PAN Huayong

2008, 44(1):  103-107. 

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High purity alumina foils were used as raw material. Based on porous anodic aluminium oxide membrane (AAO), the pivotal intermediate product, boehmite nanowires were successfully synthesized by an efficient hydrothermal method. The whole reaction process was very simple and avoids the superfluous impurities. The characteristic length of the products was 60 nm and the diameter of them is about 2-5 nm. By the comparative experiments, it could be concluded that the multiporous structure of AAO was the key reason for synthesizing boehmite nanowires by this method.

Urbanization Effects on Local Climate in Shenyang in Recent 47 Years

MA Mingmin,JIANG Xiaoyan,LIU Shuhua ZHANG Jing

2008, 44(1):  108-114. 

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Based on the meteorological data from five weather stations of Shenyang during 1959-2005, the change trends and characteristics of the temperature, precipitation, relative humidity, wind speed of urban and rural areas of Shenyang are analyzed. The effect of urbanization on local climate in Shenyang is discussed. The results show that: 1 in recent 47 years, the temperature of Shenyang has increased remarkably, with the most obvious warming occurring in winter and spring, and a little warming trend in summer. Meanwhile, the warming trend of rural areas increases slightly faster than that of urban areas. 2 The change trends of precipitation, relative humidity, wind speed of Shenyang decreases mostly, of which wind speed decreases most and precipitation decreases least. Compared with relative humidity and wind speed, the seasonal change trend of precipitation is complex, with a little increase in winter. The analysis indicates that the development of urbanization in Shenyang has a serious effect on local climate, especially on the climate of rural areas. Furthermore, the effect of urbanization on temperature and wind speed is more obvious and direct than that on relative humidity and precipitation.

Statistical Relation Research between Cloud Liquid Water Content and Cloud Optical Thickness from Multiple Observations

LIU Xiaochun,MAO Jietai

2008, 44(1):  115-120. 

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Comparisons of the integrated liquid water content from a ground-based microwave radiometer and PMS observations with the Cloud Optical Thickness (COT) of EOS/MODIS cloud products are carried out, respectively. Two equations are obtained for describing the relationship between cloud liquid water content and COT. Results show that the two slopes of fits are very close, and the former equation is better than the latter.The equation is applied to calculate cloud liquid water content at given time, and the results are compared with Water Path of MODIS. It shows that they have great agreement in layers under stratus cloud.

Retrieval of Atmospheric Total Water Vapor with MODIS Near Infrared Measurements

LI Honglin,LI Wanbiao

2008, 44(1):  121-128. 

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Retrieving atmospheric water vapor from remote sensing data is very important in such aspects as water circulation, global climatic change, weather forecast and atmosphere correction. Considering the scanning angle of the sensor, the two-band ratio method for retrieval of atmospheric total water vapor is developed by moderate-resolution imaging spectro-radiometer(MODIS) near infrared measurements. The RMS error compared to radiosonde observation is 0.29 g/cm2, and the correlation coefficient is 92%. The comparison of the monthly mean total water vapor distribution shows that the retrieval water vapor field is in good agreement with that of the MODIS product.

Geometric Method for Determining Cloud-Top Heightfrom Stereoscopic Observation

HUANG Lei,L Shenghui,ZHANG Yan,WANG Hongqing

2008, 44(1):  129-134. 

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A new and accurate method based on cloud movements, spherical and plane triangular relationships of satellites, earth's core, projected-cloud and true-cloud for determining cloud-top height is developed. Synthetic stereo images from a single satellite are used to test this method. It is demonstrated that the cloud-top height can be determined from stereoscopic measurements of geo-synchronous satellites with vertical accuracy of approximately 500 m. Error analysis of 1-pixel incorrect match was presented.

Footprint Analysis for a Stagnant Air Pollution Episode in Beijing

CAI Xuhui,CHOU Jingyao,SONG Yu,YOU Chunhua

2008, 44(1):  135-141. 

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A typical stagnant air pollution episode happened during October 1 to 10, 2004 in Beijing. Using the method of footprint analysis and the monitoring data for major pollutant (PM10 in this period, detailed process and the source-area of potential influence in this episode were analyzed. Results illustrate that: 1 the diurnal variation of PM10 concentration differs significantly from usual case, and high concentration appeares in the afternoons and evenings, 2 the horizontal distribution of PM10 concentration has a pattern as “the higher in the south and the lower in the north”, and 3 the development of the episode is accompanied with obviously extending of the footprint 100-200 km to the southwest of Beijing, suggesting that source emission from the southwest may contribute significantly to this heavy pollution episode.

The Computation of Topological Relations among Composite Regions with Broad Boundaries Based on Relation Matrix

DU Shihong,QIN Qiming,WANG Qiao,GUO Luo

2008, 44(1):  142-148. 

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The topological relations between simple regions with broad boundaries (BBRs) can be modeled by the extended 9-intersection model and be computed out easily, while the relations between composite BBRs are more complex than the relations between simple ones. Therefore, in order to query and analyze topological relations between composite BBRs in computer environment, a computational method is needed. Based on the relation of composite BBRs and their simple BBRs, an approach is proposed to compute the topological relations between composite BBRs from the relations between simple ones. The computation approach makes that the extended 9-intersection is no longer a conceptual model, but a computational model, which is helpful to query and analyze the topological relations between BBRs.