Table of Content

20 January 2006, Volume 42 Issue 1

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An Evaluation on Wind Environment Around Skyscrapers

JIANG Yujun,SANG Jianguo,ZHANG Boyin

2006, 42(1):  68-73. 

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An evaluation on the wind environment around skyscrapers was made according to some experiments. Due to the analysis on the experimental data and numerical simulation results, some local highvelocity areas will appear in winter. In order to guarantee the pedestrian safety in strong wind conditions, some countermeasures need to be taken.

RF Structure Design of a 201.5 MHz Deuteron RFQ Accelerator

ZHANG Chuan,GUO Zhiyu,Alwin Schempp,CHEN Jiaer,FANG Jiaxun

2006, 42(1):  74-77. 

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A 201.5MHz, 2.0MeV, 50mA deuteron Radio Frequency Quadrupole (RFQ) accelerator is proposed as the neutron generator for the Peking University (PKU) Neutron Experiment Facility. For the good performance at the frequency ~ 200MHz, the 4-rod resonator structure is chosen. Also, the mini-vane-type electrode is adopted for convenient water-cooling. The total RF structure design studies are performed by one of the most reliable 3D electromagnetic field simulation software, CST Microwave Studio^®, with attentions to meet the demands of lowest dipole effect as well as minimum RF power consumption. The detail optimization methods and results are presented.

An Nonlinear Time Series Analysis Method for Reconstruction of Sea Surface Temperature (SST) Anomalies

ZHOU Baiyan,LI Xiaodong

2006, 42(1):  78-82. 

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A nonlinear time series analysis method has been used for reconstruction of sea surface temperature (SST) anomalies. The method involves principal components analysis, phase space reconstruction and least squares estimate. It differs from traditional linear fitting methods in the way that temporal information is used instead of spatial information. The method is demonstrated on CZ model data and proves to be a success.

Ultrafast Photonic Crystal All-optical Switching

GONG Qihuang,HU Xiaoyong

2006, 42(1):  11-17. 

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As a novel and artificial photonic material, photonic crystal possesses unique photonic bandgap properties and can manipulate the propagation states of photons. Photonic crystal is important basis for the integrated photonic devices, such as all-optical switching. The methods of the realization of photonic crystal switching and the progresses of the study of ultrafast photonic crystal all-optical switching are discussed.

Some Hot Topics in Attachment Theory -- Comment on Hu & Meng

LI Tonggui

2006, 42(1):  18-25. 

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The article by Hu & Meng (2003) serves to remind important virtues of assessing attachment in Chinese infants. In this commentary, the author further develops the potential contributions of this approach. After introducing some important topics of attachment theory, such as internal working models, measurement on attachment, cultural differences of attachment, and intergenerational transmission, the author argues that the distinctions in some attachment behaviors of Chinese infants may not be due to culturalenvironmental and familyparenting factors, as Hu & Meng (2003) claimed. It is reasonable that these distinctions might be caused by intergenerational transmission of attachment.

Obstruction Sets, Quasi-Hyperbolicity and Linear Transversality

WEN Lan,GAN Shaobo

2006, 42(1):  1-10. 

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The authors give a quick account for the theory of quasi-hyperbolicity and linear transversality, due independently to Mañé, Sacker-Sell, and Selgrade. In the last section the authors explain the correspondence between this theory and the obstruction sets theory of Liao. In fact this account serves also as an illustration of Liao's theory.

Solar Wind Origin in Coronal Funnels: An Introduction of the Article Published in Science, Vol 308, 2005

ZHAO Liang

2006, 42(1):  26-28. 

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"Solar wind origin in coronal funnels", written by Prof. Chuanyi Tu et al., was published as a research article in Science on April 22 of 2005. Based on the observation of SOHO spacecraft and fore-free magnetic model, this article indicated the coronal altitude and magnetic structure where the solar wind originates. The background of the study of solar wind and the scientific idea and methods used in the article is introduced. Finally the conclusion of the article is explained.

Oblique Derivative Problems for Quasilinear Degenerate Elliptic Equations of Second Order

WEN Guochun

2006, 42(1):  29-34. 

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The present work deals with oblique derivative problems for second order quasilinear elliptic equations with parabolic degeneracy.Firstly the formulation of the problems and estimates of solutions of the problems for the equations are given, and then the uniqueness and existence of solutions for the above problems are proved by the complex analytic method.

Harmonic Morphisms into Almost Hermitian Manifolds

YE Pingkai,MO Xiaohuan,SUN Fang

2006, 42(1):  35-40. 

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M→N be a horizontally conformal map from a Riemannian manifold M to an almost Hermitian manifold. The authors express the tension field of Φ in terms of the dilation of Φ and the Lee form of N, which lead to a test for Φ to be a harmonic morphism. Some results on transfer of structures involving a Watson type result are given.

Theoretical Study on the Surface Core-Level Eigen-Energy Shifts of Ca(100)

XUN Kun,ZHAO Zizheng

2006, 42(1):  47-50. 

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The first principles all-electron linearized augmented plane wave film method in the local density functional approximation is employed to investigate the electronic structure of the seven-layer Ca(100) slab system. The partial valence charges in muffin-tin spheres for various atom types, the layer projected local state densities of valence band, and the centroid shifts of 3d, 4s and 4p bands are given. The calculation shows that the core-level eigen-energies for surface atom are about 0.55eV lower than those of central atom, which can be attributed to the contribution of both the spill-out of s, p-like valence charge to vacuum and the narrowed of surface atom 3d band originated from the reduction of coordinate.

A Genetic Algorithm Assisted Beam Tracking and Forming

LI Lei,ZHU Bocheng,ZHOU Lezhu,GONG Zhonglin

2006, 42(1):  110-115. 

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A genetic algorithm assisted beam tracking and forming is applied to solve the problem of tracking a continuous moving signal while suppressing a strong fixed interference. An improved binary coding method is proposed, which introduces several parameters to control the solution precision and search space efficiently. The convergence and reliability of this algorithm are given much consideration. The simulation results show that the algorithm is able to track a fast moving signal while suppressing a fixed interference.

Stepping-Forward Impulse Method

ZHAO Zhen,LIU Caishan,CHEN Bin

2006, 42(1):  41-46. 

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The complexity of tangential movements during impact is one of main characteristics for multi-rigid-body systems. A general numerical method for impulse problems of 2D rigid body systems is introduced. The method inherits the invariance of configuration of dynamic system during impact. It discretizes impact process into multi-steps. A little impuse increment is permitted in each step and the mode of sticking or sliding must be judged before every step increment. This method can solve the impact problems properly and efficiently due to collision or inconsistency for multi-rigid-body systems.

Fabrication and Application of Gallium Nitride-Based Two-Dimensional Octagonal Photonic Quasicrystals

ZHANG Zhensheng,ZHANG Bei,XU Jun,JING Guangyin

2006, 42(1):  51-54. 

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In order to solve the general problem of low extraction efficiency of conventional semiconductor light emitting diodes (LED), Gallium nitride (GaN)-based two-dimensional octagonal photonic quasicrystals (2D-8PQCs) structures were firstly fabricated and successfully applied on the GaN-based emitters by means of focused ion beam (FIB) etching. When the diameter of holes and air filling factor of 2D8PQC are 600nm and 30% respectively, the enhancement factor of the surface light extraction efficiency of the 2D-8PQC was achieved as high as 2.5 under current injection. The effects of 2D-8PQCs on the emitters were studied by the measurements of microscopic electrical luminescence and emitting images. It confirmes that the guided modes are blocked and coupled out into radiation modes by the 2D-8PQCs. The surface light extraction is consequently enhanced. It provides a promising way of the application of 2D-PQC to GaN-based light emitters.

Study on the Structure and Evolvement of Atmospheric Boundary Layer of Frontal Fogs in Spring and Winter at Southern Suburb of Beijing

WANG Kai,ZHANG Hongsheng,WANG Qiang,LI Fuyu,CHEN Jiayi

2006, 42(1):  55-60. 

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The structure of the profiles of wind velocity, temperature and humidity during the formation and dissipation of foggy periods in spring and winter are studied by using the observational data in atmospheric boundary layer obtained in the southern of Beijing in 1999. The relationship between the physical process of the formation and dissipation of the fog and the meteorological factors, such as maximum value of wind speed, PBL height, is pointed out. The physical process of the fog development affecting evolution process of atmospheric boundary layer is discussed. Thus, a physical background for improving the fog prediction accuracy and artificial dispersal is provided.

Streaming 3D Terrain over Network

MA Zhigang,ZHANG Kai,WANG Guoping,DONG Shihai

2006, 42(1):  116-120. 

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Internet-based navigating of large-cale terrain environments is an important aspect of distribute virtual reality applications such as flight simulations and military maneuver, but currently is restricted by the limited network bandwidth. The authors exploit the potential of terrain as stream media and propose a new data lay-out that facilitates network transmission. By taking advantage of the regularity of DEM, terrain data are organized into multiple progressive compressed streams. Runtime network throughput is effectively reduced by intra- and inter-frame coherence. Coupled with carefully designed transmission scheme, the algorithm is decreased and can accommodate to dynamically changed network bandwidth.

A Study on the Dry Intrusion of Air Flows from the Lower Stratosphere in a Cyclone Development

ZHANG Wei,TAO Zuyu,HU Yongyun,WANG Hongqing,HUANG Wei

2006, 42(1):  61-67. 

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The developing process of a cyclone over the Yellow Sea is simulated with the numerical model MM5. The model output are demonstrated using visual software, LiveView, which is a five dimension visualization system for large data sets. Using this visual system, the authors are able to study the dry intrusion of air flows from the lower stratosphere and to analyze the reason of its occurrence and its effects on such a fast developing cyclone in detail. Horizontal and vertical cross sections are presented to reveal the thermal and kinetic structures of the dry intrusion. Air parcel motions during the dry intrusion are extensively studied with the technique of trajectory analysis. The mechanism of the occurrence of the dry intrusion and its connection with the cyclone development are discussed. The results suggest that dry intrusion is an important factor in influencing on this cyclone development.

A Constant Time Algorithm for MST on RMESH

CHEN Peng,HUO Jinjian,ZHANG Li'ang

2006, 42(1):  83-88. 

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A constant time algorithm for minimum spanning tree problem on a n²×mn² RMESH is introduced. Based on the conclusion of simulating RMESH by PRAM, there is an O(logn) algorithm for MST on PRAM. The time complexity of these algorithms is the best so far.

Fabrication of Nitrogen-Doped Carbon Nanotube Arrays and Their Field Emission Properties

CHAI Yang,YU Ligang,WANG Mingsheng,ZHANG Qifeng,WU Jinlei

2006, 42(1):  89-92. 

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Carbon nanotube (CNT) arrays have been produced on silicon substrate by an one-step route based on the pyrolysis of mixture of the ferrocene and melamine under well-chosen synthesis condition. Transmission electron microscope (TEM) and scanning electron microscope (SEM) studies showed the products were all multi-walled CNTs that are about 50nm in diameter and about 15μm in length, growing outward separately and perpendicularly to the substrate. X-ray photoelectron spectroscopy (XPS) and TEM studies revealed that the CNTs were nitrogen-doped. Field emission measurement suggested that the nitrogen-doped CNT arrays begin to emit electron at electric field of 1.60V/μm, and field emission images exhibited the high emission sites density.

An Improved Bit and Power Allocation Algorithm for OFDM Systems

XUE Jinyin,JIAO Bingli

2006, 42(1):  93-98. 

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A new iterative method is proposed to overcome vibration in adaptive power and bit loading algorithms for wireless OFDM systems. The method is introduced into rate adaptive (RA) algorithms aiming at maximization of data rate under the constraint of total transmit power and bit error rate. Then two improved RA algorithms, named water-filling RA (WF-RA) and equalpower RA (EP-RA) algorithm respectively, are proposed. Simulation results show the improved WF-RA algorithm has approximately the same throughput as the optimal solution and the improved EP-RA algorithm has a lower computational complexity compared to the previous ones. Finally, the performance degradation due to imperfect channel state information is discussed.

Study of Hanoi Tower Problem with Multi-Pegs

LIU Duo,DAI Yiqi

2006, 42(1):  99-102. 

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The authors investigate the Hanoi Tower problem with multipegs more than three. Based on the idea of dynamic programming, the recursion formula of the least number of movements necessary for this problem is presented. The direct formula of the least number of movements necessary for this problem is given and proved by triple mathematical induction and pure combinatorics.

ArithRegion - An Index Structure on Compressed XML Data

BAO Xiaoyuan,TANG Shiwei,WU Ling,YANG Dongqing,SONG Zaisheng,WANG Tengjiao

2006, 42(1):  103-109. 

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Even XML is used as a popular data exchange standard over Internet and Intranet, its space expansion makes the transmitting and storing of XML data very expensive in terms of resources because of adding tags to every different semantic content unit. After compressed, its size will be much smaller, but how to evaluate query efficiently and directly based on the compressed data is still a necessary work. The authors propose an XML index structure using B+ tree as its' backbone structure, on compressed data which is resulted from revert arithmetic compression, ArithRegion. Queries as the form of //element₁/element₂/…/elment_m can be evaluated efficiently using ArithRegion.

Simulation of High Voltage Unit (HVU) in Particle Radiation Detector (PRD)

CHANG Guoping,CHEN Hongfei,ZOU Jiqing

2006, 42(1):  121-126. 

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High voltage is provided by High Voltage Unit (HVU) to guarantee the normal working of the Particle Radiation Detector (PRD), which is on board the China-Brazil Earth Resource Satellite (CBERS). Firstly an overview of PRD, especially on its function in space exploration, is given, then the basic principles of HVU and a theoretical analysis and data simulation to its Pulse and Energy-Exchange Part, which is the most essential part in HVU, is made. From the data simulation, the feasibility of the steady work of HVU and the wobbling feature of its output voltage with the change of other parameters can be theoretically obtained. Finally, its probable future use and improvement are discussed.

Stateful Security Alert Correlation by Dynamic Bayesian Plan Graph

XU Hui,FENG Jinwen,YE Zhiyuan

2006, 42(1):  127-132. 

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The concept of stateful alert correlation and a correlation algorithm based on dynamic Bayesian planning graph are proposed. Dynamic Bayesian planning graph adds dynamic Bayesian inference to based planning graph. It represents system security states explicitly and the relation between states and actions. The algorithm handles uncertain information with Bayesian inference, giving a quantitative evaluation of the security state of a system and eliminating false alarms effectively.

Innovation of Administrate System of Science-Technological Research Results in Universities

WANG Jin,ZHANG Ping,ZHOU Hui,ZHANG Ming

2006, 42(1):  133-136. 

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The authors discuss how to establish a system to administrate the science-technology research results and make it useful and helpful to facilitate the application of science-technology research results, which is in harmony with market economy. The authors also discuss how people can put into practice the pattern of administrating the science-technology research results adopted by U.S. universities and how to administrate the technology transfer in the market economy. In addition, the authors discuss the technology transfer from the perspectives of the evaluation, registration and secrecy of the science-technology research results, the application of the patent, and the protection of intelligence property.