Acta Scientiarum Naturalium Universitatis Pekinensis

The Research of Transient Characteristics of Thin Wire Antennas

YU Zhefeng,ZHOU Lezhu,BAN Yongling,WANG Pai

2004, 40(3): 341-345.

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FDTD (Finite Difference Time Domain) method was used to numerically simulate the transient radiating and scattering characteristics of thin wire antennas. The effects of other antennas on the radiation characteristics of thin wire antenna are analyzed when the antenna is fed by an electromagnetic pulse. The scattering characteristics of thin wire antennas are also analyzed when they are illuminated by an electromagnetic pulse. The required distances between different antennas are given when MIMO (Multiple Input Multiple Output) system is applied to the field of UWB (ultra wideband).

Numerical Study of Power Transient in Backward Pumped Raman Amplifier

ZHENG Lei,CHEN Zhangyuan,TANG Wenjing,WU Deming,XU Anshi

2004, 40(3): 346-350.

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It is observed that the amplitude of the power transient overshoot depends on the gain of the amplifier when the input signal power is the constant. The other system parameters, such as the input pump power and fiber length, have no effects on it.

Assembly of Carbon Nanotube onto Scanning Tunneling Microscope Tips

TIAN Yang,WANG Jingyun,PENG Lianmao

2004, 40(3): 351-354.

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Carbon nanotubes have attracted much attention as new probe tips for Atomic Force Microscopy due to their tiny diameter and excellent mechanical properties. In this paper, a new method was developed to assemble a carbon nanotube onto a tungsten tip. This tip was then used as probe of Scanning Tunneling Microscopy and got clear step image of high ordered pyrolytic graphite (HOPG) surface.

Active Measurement-Based Admission Control

YI Na,JIN Ye,LIANG Qinglin

2004, 40(3): 355-360.

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Admission control is required to determine whether new connections should be admitted to network to guarantee the quality of service (QoS) for data transmission. This paper proposes a new active measurement-based admission control (AMBAC) method to guarantee the QoS in IP network. The basic idea of this method is: the ingress router actively sends probe packets to egress router and the egress router makes the admission control by monitoring the received probe packets. The proposed method is fully scalable and has less response time. The simulation results show that AMBAC can strictly guarantee the QoS of data transmission and effectively improve the utilization of network resource.

Hybrid ARQ for LDPC-Coded System

XUE Yingjian,XIANG Haige

2004, 40(3): 361-366.

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For the detected error words by the LDPC decoder, the characteristics of code bits reliability information is investigated. An efficient novel hybrid automatic repeat request (HARQ) scheme is proposed for system coded with Low-Density Parity Check (LDPC) codes. Compared with the Reliability-based hybrid ARQ (RB-HARQ), the new HARQ scheme outperforms the RB-HARQ in consideration of the bit transmission power for the requesting messages in the backward transmission channel. Simulation results show that the new H-ARQ scheme is more practical than RB-HARQ.

Characteristics Analysis of the Fiber Optic Gyroscope with Double Fiber Ring Resonators

ZHU Shuguang,XU Anshi,LI Zhengbin,WU Deming,WANG Dapeng

2004, 40(3): 367-371.

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A new fiber optic gyroscope (FOG) structure was put forwarded by authors. Based on the comparison with the traditional single-fiber-ring FOG, the important characteristics and advantages of the FOG with new structure are given. Furthermore, with detailed formula derivation and computation, the resonance conditions and resonance output characteristics of fiber optic ring resonators with or without welding point were presented.

Mining Maximal Moving Sequential Patterns in Mobile Environment

MA Shuai,TANG Shiwei,YANG Dongqing,WANG Tengjiao,GAO Jun

2004, 40(3): 379-387.

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Mining moving sequential patterns has great significance for effective and efficient location management in wireless communication systems. Mining moving sequential patterns is different from mining conventional sequential patterns, firstly it needs to consider much about the time factor in moving sequences; secondly it cares about what the next moving is for mobile user, so items must be successive in mining moving sequential patterns. A novel technique to mine moving sequential patterns is proposed. A clustering method is introduced to preprocess the original moving histories into moving sequences, whose main role is to discretize the time attribute. And then an efficient method, called PrefixTree, is presented to mine the moving sequences. Performance study shows that PrefixTree outperforms Revised PrefixSpan-2, which is revised to mine moving sequences, in mining large moving sequence databases.

XCODE: An Extensible Component Description Language for System Software

TENG Qiming,CHEN Xiangqun

2004, 40(3): 388-396.

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Components can be identified from various abstraction levels and can be of different granularities. The components for system software have special challenges for description purpose due to their inherent non-functional attributes and special attributes related to the peculiar role of an operating system. They often exhibit different forms during different phases of the development process of an embedded operating system. An extensible component description language named “XCODE was presented here. As a XML-based language, XCODE can be envisioned various usage scenarios. It provides an extensible, tool independent, royalty-free approach to describe various aspects of components during Compile-Time, Link-Time and Run-Time.

A Bulk Micromachined Relay with Lateral Contact and Isolation Structure

YANG Zhenchuan,LI Ting,HAO Yilong,WU Guoying

2004, 40(3): 397-401.

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A bulk micromachined relay with lateral contact and isolation structure is presented. The relay is fabricated with glass/silicon wafer bonding and deep reactive ion etching (DRIE) process. Refilled polysilicon trenches are used as isolation structure. It is laterally driven with electrostatic actuator. The threshold voltage of the relay is simulated using Reduced Order Modeling (ROM) methods provided by a general finite element simulator, ANSYS^TM. The simulated result and experimental result are compared and discussed.

High Performance Linear 288×4 CMOS Readout Integrated Circuit with Time-Delay-Integration

GAO Jun,LU Wengao,LIU Jing,TANG Ju,CUI Wentao,ZHAO Baoying,CHEN Zhongjian,JI Lijiu

2004, 40(3): 402-406.

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A high performance CMOS linear 288×4 readout integrated circuit (ROIC) is detailed in this paper. It is a large-scale mixed-signal circuit with time-delay integration (TDI) function to enhance the signal to noise ratio (S/N), and defective element deselection (DED) function to decrease the probability of bad columns. The other features include adjustable integration time, multi gain, bidirection of TDI scan, super-sample, and electrical test. Digital I/O ports aredesigned to control its work mode. It is fabricated using 1.2μm double poly double metal (DPDM) CMOS technology. The measured power consume is about 24mW at 5V supply.

A New MD Statistical Noise Improvement Algorithm for Dose Effect Simulation

SHI Xiaokang,SHI Hao,YU Min,HUANG Ru,ZHANG Xing

2004, 40(3): 407-411.

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A new method for the acceleration of MD (molecular dynamics) simulation of ion implantation into crystalline targets is presented. The READE (Rare Event Algorithm with Dose Effect) method can well speed up the MD simulation of ion implantation with dose effect. As a result, the time required performing a simulation with high precision and dose effect is drastically reduced. And many details producing statistical noise in simulation is involved in the READE and help it to be more reasonable and reliable.

Extracting the Interface Trap Density Using the Proportional Difference Method from the Output Characteristic of NMOSFET

ZHANG Heqiu,XU Mingzhen,TAN Changhua

2004, 40(3): 417-423.

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The threshold voltage and the peak of proportional difference for MOSFET devices will change after the uniform high electric field stress. This is the effect of traps generated during the stress. In this paper, the threshold voltage, the peak of proportional difference and the interface trap density of NMOSFET are extracted from the output characteristic by the proportional difference method. The relationship between the threshold voltage and the peak of proportional difference, and between the interface trap density and stress time are also acquired. The method is also applicable to the PMOSFET. This is a simple, quick technique. And the data can be analyzed during the process of measuring.

A Multi-Layer Charge-Pump Phase-Locked Loop Behavioral Model

FENG Wennan,LIU Ling,CHEN Zhongjian,JI Lijiu

2004, 40(3): 424-431.

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A novel multi-layer Charge-Pump Phase-Locked Loop (CP-PLL) behavioral model is presented in this paper. In contrast to conventional CP-PLL models, the multi-layer model offers great flexibility of trading off the speed and accuracy of simulation by describing the ideal and nonideal characteristics in separated layers that can be configured individually. Also with a specific layer the approach provides the ability of carrying out noise simulation in time domain. The multi-layer model is built in Verilog-A and simulated by Spectre^TM. A simulation speed up factor of 20 to 99 is achieved with reasonable loss of accuracy.

Nodal Model Simulation of an Accelerometer

XIAO Zhiyong,YANG Zhenchuan,ZHANG Haixia,HAO Yilong

2004, 40(3): 432-436.

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A capacitive accelerometer is simulated using the basic nodal model of components such as beam, plate mass, lumped mass, gap, squeeze film damper and anchor, which are implemented under ZeniVDE^TM. The simulation includes static, time domain and frequency domain simulation. The simulation result is in good coincidence with the experiment result and simulation result of ANSYS, a general FEA simulator.

An Output Buffer Amplifier Used in Detection Circuit of Micro Sensor

Lv Zhijun,NI Xuewen,MO Bangxian,XIANG Bin

2004, 40(3): 437-443.

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An output buffer amplifier with compact structure used in detection circuit of micro sensor is presented. The op amp contains a constant-gm rail-to-rail input stage and a simple classAB output stage and its output resistor is low. The simulation and measurement show that the output buffer amplifier could well be used in detection circuit.

Designment and Implementation of a Computer Aided Speech Training System for Deaf Children

LIU Huadong,WU Xihong,CHI Huisheng

2004, 40(3): 444-450.

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The main work of this paper is to apply speech signal processing and speech recognition technologies in speech training for deaf children, and a computer aided speech training system suited for deaf children is designed and implemented. The system is divided into three modules, basic training, articulation training and intelligibility training, which is in the fashion of visual feedback of speech features. Based on the characteristic of deaf childrens speech training and the relation between acoustical feature and physiological feature, the contrast training method and object training method are proposed. The clinical evaluation was carried out in China Rehabilitation Research Center for Deaf Children and got a good result in second and third grade kindergarten. The experimental results show that it is effective for the contrast training method and object training method to correct the deaf childrens voice disorder and articulation disorder.

A Study on Prosodic Boundaries Location and Synthesized Units Selection Algorithms in Mandarin Speech Synthesis

CHENG Yong,WU Xihong,CHI Huisheng

2004, 40(3): 451-457.

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A new statistical prosodic structure model is proposed, which is based on the idea of analyzing and modeling of hierarchical stochastic properties of Chinese mandarin, where three basic levels of prosodic structure are divided as: prosodic word, prosodic phrase, prosodic phrase cluster. Meanwhile, synthesized units selection algorithms, which are suited for large-corpus-based speech synthesis, are described and discussed in this paper. The experimental results show that the proposed model is effective and high performance could be obtained.

Motion Detection for Human Bodies Basing Adaptive Background Subtraction by Using an Omnidirectional Camera

PI Wenkai,LIU Hong,ZHA Hongbin

2004, 40(3): 458-464.

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A new real-time omnidirectional vision system is proposed for tracking multiple targets in indoor environments. In this system, an omnidirectional camera is used to obtain the 360°view images of the global scene. First, it builds the background model by observing the scene without people in it. When the detecting process starts, omnidirectional images are changed into the cylindrical panoramic images, and an adaptive background subtraction method is utilized to segment the moving regions and locate the positions of human bodies. Thus, multiple human bodies can be tracked. Experimental results show that the proposed system performs well in indoor, complex environments.

SDML: A Spatial Data Mining Language for Spatial Database

GAO Tao,XIE Kunqing,MA Xiujun,CHEN Guanhua

2004, 40(3): 465-472.

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The design of SDML is on the basis of spatialSQL in spatial database, extending operators in spatial data mining while using language of data mining process model for reference. SDML can be divided into view manipulation language(VML) and model manipulation language (MML) by different steps of data mining process and objects that SDML manipulates. VML is responsible for manipulating views of data mining, while MML is for models of data mining. The thoughts and design of SDML are described in detail, and a solution is presented that use SDML for spatial generalization and spatial association, which are two typical problems in spatial data mining.

Managing User Interaction Forms on Web Pages: A Template-Base Approach

XUE Ming,LI Hongyan

2004, 40(3): 473-479.

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A metadata model called Template Model to deal with the user interaction forms on the web pages is proposed. The template model can carry the aggregation semantics of the user interaction forms and maintain it as a hierarchal structure. It is possible to reuse some of the page components to facilitate generating and maintaining large number of user interaction forms on web pages. And the template model can help to deal with the queries to these interaction forms.

An Improved DBSCAN Algorithm which is Insensitive to Input Parameters

CAI Yingkun,XIE Kunqing,MA Xiujun

2004, 40(3): 480-486.

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An improved DBSCAN algorithm is presented, which is insensitive to input parameter by discovering connected clusters. The new algorithm produces better clustering results, while maintaining the high performance of the origin algorithm at the same time. The results of experiments demonstrate that the new algorithm outperforms OPTICS.

Study of Field Emission Properties of Colloidal Graphite

WENG Bo,SONG Jiaohua,ZHANG Gengmin,ZHANG Zhaoxiang

2004, 40(3): 487-490.

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Field emission properties of colloidal graphite were investigated. The electric fields for extracting 10μA/cm² and 1mA/cm² current densities were measured to be about 5.4 and 8.8V/μm, respectively. Morphologic image of the colloidal graphite film was obtained using a scanning electron microscope. The Fowler-Nordheim model was used to analyze the obtained results. The enhancement factor of electric field was calculated to be about 4×10².

Analysis of Scattering Influence of the Material Filled in Slots on the Rotationally Symmetric Conducting Targets

HU Wei,ZHOU Lezhu,ZHU Xili,LI Mingzhi

2004, 40(3): 491-497.

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The Finite-Difference Time Domain (FDTD) algorithms of anisotropic material was used to analyze the plan wave scattering by slots on aircraft loaded with anisotropic material. This paper calculated the impact of the material filled in the slot on the scattering characteristics of the rotationally symmetric model. Numerical results showed that the backscatter could be greatly reduced by using negative unixial anisotropic media to fill in the slots of the proper width and depth at the specific position of the model.

Analysis of Near-Field Distribution and Cross-Polarization Radiation Pattern Cavity-Backed Microstrip Patch Antenna on a Uniaxial substrate

BAN Yongling,ZHOU Lezhu,YU Zhefeng,WANG Pai

2004, 40(3): 498-504.

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For the study of effects of uniaxial anisotropy in the substrate on radiation property of cavity-backed microstrip patch antenna, the hybrid method of Edge-Based finite element (Edge-Based FEM) and boundary integral (BI) is adopted to solve the tangential electric field distribution on the surface and the cross polarization radiation pattern. The computing results show that the field distribution and cross polarization pattern of microstrip antenna with different uniaxial substrate are affected only when the optic axis is along z coordinate. When the optic axis is along x, y coordinate, the effects are neglected.

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