The spatial distribution estimation of Interference temperature based on kriging method in cognitive radio

In order to resolve the problems of the traditional interference temperature estimation methods, such as unclear spatial characteristics, inaccurate estimation of spatial distribution, and the insufficient use of spectrum resources, this paper proposes an estimation method which utilizes the interference temperature sample values obtained by wireless sensors distribute in space to estimate the interference temperature in the total area. This method makes use of the geo-statistical interpolation method of Kriging to calculate the interference temperature data and obtain the 3-dimensional distribution of the interference temperature in the area. Kriging interpolation method is based on the variogram and structure analysis theory, makes optimal estimation of the variables in area. Simulation results demonstrate that the proposed method can estimate the spatial distribution of interference temperature in the interested area more accurately and the spatial spectrum utilization is improved.     

Group based DBF MUD in CDMA mobile communication system

For the CDMA wireless cellular communication system, a new methodology is proposed to combine digital beamforming (DBF) with multi user detection (MUD) technology which harnesses the co channel interference mitigation and obtains better performance. The proposed approach assigns all the users within a cell into separated groups according to their direction of arrival (DOA). Then, only one DBF branch is employed for a singular group so that the main lobe is steered to the desired users in the group and nulls are directed to the mobile stations in other group. Furthermore, inter group interference is degraded by MUD following the DBF. The new strategy simplifies the weight vector calculation and solves the unorthogonal channel problem. Additionally, it decreases the bit error rate. The analysis and simulation illustrate the fruits of the new mechanism.     

A blind adaptive reduced-rank receiver for ultra-wideband communication systems

A low-complexity blind adaptive receiver for ultra-wideband (UWB) systems in the presence of both multiple access interference (MAI) and inter symbol interference (ISI) is proposed, which is composed of two stages. In the first stage, a reduced-rank algorithm based on the multi-stage Wiener filter (MSWF) is considered to suppress the MAI and extract multi-path components. Channel estimation using the projection approximation subspace tracking with deflation (PASTd) algorithm and multi-path combining are then performed to further enhance the signal to interference plus noise ratio (SINR) of the desired user in the second stage. The simulation results show that the proposed receiver exhibits reasonably good bit error ratio (BER) performance compared with those of matched filter, conventional Rake receiver, decorrelating Rake receiver and adaptive receiver based on constant modulus algorithm (CMA). Moreover, it has faster convergence speed and less complexity.     

EEG Signal Denoising Based on Wavelet Transform

The article focuses on the method of noise cancellation for EEG signal. The method of notch filter is discussed. According to the frequency of noise and the principle of notch filter, the design result of the notch filter and the denoised signal are presented. Then, the analysis of EEG signal are proposed based on wavelet transform (WT) and noise cancellation using WT. Wavelet transform is a multi-resolution time-frequency analysis method. It can decompose mixed signal into signals at different frequency bands. The EEG signal is analyzed and denoised using WT, then the results are presented respectively. Comparing the experiment results shows that WT can detect and process noise in the EEG signal effectively.     

The Application of Narrowband Interference Suppression in Direct Sequence Spread Spectrum

In order to improve the system effect, it is necessary take the technique of digital signal process to suppress interference, because of the finite gain and the narrow-band interference in system of direct sequence spread spectrum. The authors design a new filter structure improving on tunable digital heterodyne adaptive notch filters. This filter can adaptively track the interference frequency and control the bandwidth and depth of notch, which has the excellent agility and utility. The experiment proves this method overcomes limitation of other interference suppressions, hardly weaken the system performances, enhances the stability of the filter system, and can quickly track the interference frequency.     

Study of Acquisition in a Rake Receiver Based on Digital Matched-filter

The Rake receiver based on digital matched filter(DMF) is studied extensively in order to investigate the performance of the PN code acquisition.By using the state transition diagram,the authors derive the analytic expressions of the mean acquisition time of the Rake receiver based on DMF over frequency-selective channel.Numerical analysis is also given.It is shown that the proposed Rake receiver based on DMF can accelerate the process of PN code acquisition.Because there are many resolved multipath components over frequency-selective channel,the detection probability of Rake receiver is larger than the conventional receiver.If more fingers of Rake receiver are available,then the mean acquisition time is longer and the threshold of detector can be set more widely.     

高压交直流同塔输电线路无线电干扰与可听噪声的计算

为了寻求一种适合交直流同塔架设线路的无线电干扰与可听噪声计算方法，从理论上分析了混合线路表面场强的特点，利用线性叠加原理求出混合线路表面场强，并结合晴天和雨天对交流和直流线路电晕程度的不同影响，提出在同一种天气状况下计算交直流线路无线电干扰与可听噪声。用3种计算无线电干扰与可听噪声的方法，分晴天和雨天情况进行计算比较，结果表明3种方法中BPA修正公式计算值最大，该方法可视为目前计算交直流同塔线路无线电干扰与可听噪声的有效方法。     

Application of frequency shifting in truncating substructure low order normal modes

A method to cutoff substructure low order normal modes in component mode synthesis is proposed. Frequency shifting technique is introduced in substructure free vibration differential equation. Quasi-static constraint mode is taken into coordinate transformation and the contribution of substructure low order normal modes to system middle frequency modes is reduced,thus substructure low order normal modes truncation is achieved. This technique is used to compute dynamic characteristics of a body-in-white FEM mode in the frequency band of 160~190 Hz. The results show that compared with traditional component mode synthesis,which keeps 1 836 normal modes,this method only needs 297 normal modes and saves 27.7% calculation time. It means frequency shifting technique can improve the computational efficiency for middle frequency band dynamic characteristics of complex structure.     

Experimental Analysis of Seismic Performance of Strengthening Frame-supported Reinforced Concrete Masonry Short-leg Shear Wall Structure Damaged by Earthquake Using the Sub-structure Pseudo-dynamic Test

Based on the damage assessment and strengthening scheme of the full-scale model which is the three-floor frame-supported reinforced concrete masonry short-leg shear wall structure, the strengthened model is tested using the substructure pseudo-dynamic testing method. The applicability of the proposed strengthening technique for the building damaged by earthquake is discussed. Thus, the seismic performance of the strengthened model is proposed to seek the strengthening technique for the structure damaged by earthquake, and it provides important reference for the post-disaster reconstruction after Wenchuan earthquake.     

ANALYSIS OF THE TIME HISTORY RESPONSE FOR LARGE STRUCTURE UNDER THE ACTION OF IMPULSIVE LOADING USING STEP-BY-STEP REDUCED DYNAMIC-STIFFNESS COMPOSITION METHOD

In this paper, a dynamic substructure method for analysing the transient response of the large structure is proposed. The method is based or, the combination of the reduced dynamic-stiffness composition method and the step-by-stop integration method. Its main feature is that the computational effort may be reduced significantly. Several examples are given to prove its reliability, effectiveness and accuracy.     

The study on EMI principle and suppression method of vehicle ignition system

Vehicle ignition system is the main electromagnetic interference source. Electromagnetic radiation produced by ignition system will produce the interference to electromagnetic environment around. It is necessary to study the electromagnetic interference (EMI) principle, noise paths and suppression method. We analyze the electromagnetic interference principle of ignition system, and harness trouble-shooting related to electromagnetic interference is also tested. Results show that the spark discharge between spark plug electrodes is the main interference source in ignition system. Then, the paths of conducted interference and the reason of radiated emission are discussed in detail. Finally, two kinds of power supply cord EMI filters are designed and implemented on the basis of analysis results. Experimental results indicate that the filter can reduce the noise of power-wire in broadband range. Simultaneously, the radiation emission performance from power wire is also reduced observably. The proposed mixing filter has been demonstrated in this paper to perform satisfactorily with excellent effectiveness in suppression of conducted EMI from 10 MHz to 110 MHz, and the object car can also pass the EMC standard tests.     

A data selection method applied to on-line drift compensation for gas sensors

A new data culling and labeling method is proposed to avoid misleading outcomes caused by multi-state samples during drift compensation process. This method culls data by the curve slops of gas sensor array response and labels data by comparing input samples with the memories of pattern recognition algorithm to avoid occurrence of misleading results. Experiments show the method combined with on-line drift compensation algorithm can estimate sample-states automatically and increase the recognizing accuracy from 37.5% to 100%.     

Rosenbrock-based coupled time integration method and its convergence analysis

Real-time substructring testing is under rapid development. is a hybrid computational-experimental technique, and its challenge is to ensure that the numerical substructure and the experimental substructure interact in real time, which requires efficient numerical integration methods. With this mind, based on the Rosenbrock real-time integrator, a coupled time integration method is proposed which enables completely parallel computation. By virtue of a Single-DoF split-mass test problem, stability and accuracy analyses are performed theoretically for the coupled method. Moreover, numerical simulations on a Three-DoF split-mass system are conducted to further investigate the convergence and other properties of the coupled method. The theoretical analysis and the numerical simulations reveal that the method exhibits favourable stability and second order accuracy. Compared with direct time integration methods, the proposed method is more suitable for Real-Time Substructuring Tests of complicated structures and relevant hybrid simulations.     

RNA干扰及其植物抗病毒应用

【研究目的】RNA干扰(RNA interference,RNAi)是分子生物学研究领域的一项新兴技术,在动植物的遗传改良、功能基因组、基因治疗等研究中广泛应用;【方法】它是指一些小的双链RNA分子介导的、序列特异的转录后基因沉默现象;【结果】本文就RNA干扰的作用机制、RNA干扰与植物病毒间的互作以及RNA干扰表达载体构建的一些研究进展进行了综述;【结论】随着RNAi研究的进一步深入,RNAi必将成为遗传育种工作者培育抗病毒植物的有力手段,促进植物抗病育种的发展。     

Novel method for fault line selection in arc suppression coils system using transient energy

In order to overcome low sensitivity of the protection based on transient components when the faulty voltage passes zero, regarding arc suppression coill branch as a healthy feeder line, using the relation of its transient energy and all feeders of transient energy amounting to zero, this paper presents an improved fault line selection method in arc suppression coils system using transient energy. This method has no requirements of detection fault close angle and pre setting, has a good anti interference ability and adaptability to various faults occurred in the systems with arc suppression coils. Large amount of digital simulation results show that the proposed method is effective and reliable.     

基于广义谐振理论的输电线路中波无源干扰谐振频率预测

现有IEEE（institute of electrical and electronics engineers）标准,目前只能明确0.5~1.7 MHz有限频段的输电线路无源干扰谐振机理。为拓展输电线路无源干扰谐振的研究频率,引入广义谐振理论,提出了一种基于电磁场能量平衡的干扰谐振频率预测构想。将大尺度空间下输电线路铁塔阵列及天线等效为广义封闭系统,从而基于复坡印廷定理,推导了电磁开放系统广义谐振因子的表达式,求解得到的广义谐振因子零值点为无源干扰谐振频点。该方法由于避开了传统将铁塔等效为半波天线的局限,因此可以实现中波频段无源干扰谐振预测。采用IEEE标准算例进行验证,结果表明：1.7 MHz频率以下,基于广义谐振理论的无源干扰谐振频率预测值和缩比模型实测值最大误差不超过±0.169 MHz。     

“增阻降流”苹果修剪理论创建及应用研究

为给苹果早、丰、稳产修剪技术提供新的理论支撑,笔者以苹果树体结构图为试材,依据物理学的电路原理创新性地提出并定性论证了一套更深层次的剪枝理论。该理论包含3个要点：（1）“增阻降流”修剪法可使苹果树早、丰、稳产;（2）根茎以上任何枝,疏则增阻（树阻）,截则降阻（树阻）;（3）疏除基部同枝轴低阻大型枝比高阻小型枝树阻增幅大。此外,还对该理论进行了具体解释,并于2004-2010年进行了该理论的应用试验。结果表明：幼龄期苹果园应用此理论后,13个品种中的4个品种定植第2年开花株率即达75%,另外9个品种为50%,进入初果期比常规管理提早1~2年;盛果期富士园应用本理论,6年单产平均49203 kg/hm2,比对照园提高54.4%,大小年指数介于6.1%~18.6%,可评价为“丰产、稳产园”,而对照园大小年指数介于121.8%~428.8%,属于严重变产园,且单产在2008、2009年有下滑趋势。由上可见,“增阻降流”修剪理论在实现苹果早、丰、稳产方面,效果显著。     

Simple and High Performance Timing Synchronization in OFDM System

One ML timing offset estimation method for orthogonal frequency-division multiplexing(OFDM) systems is presented.The performance of our timing offset estimator are compared to that of H.Minn's estimator in terms of estimator variance error in both AWGN channel and multipath fading channel. Because no performance floor exists under high SNR condition,the new estimator can get more accurate estimation result with low computational complexity even under multipath fading environment.     

RNA干涉机制的研究进展及植物学意义

RNA干涉(RNAi)是指由双链RNA(dsRNA)引起的序列特异性基因沉默,其中small RNA(siRNA和microRNA)在RNA干涉机制中起关键作用。本文综述了RNAi中siRNA和microRNA分别介导的作用机制,RNAi在植物中的研究现状,主要包括转基因植物中的RNA干涉和植物病毒诱导的RNA干涉等方面的研究概况。评述了RNAi在植物学研究中的意义,主要包括功能基因的研究、转基因植物的研究及植物抗病性研究。     

A New Algorithm for Open Conductor Faults in Power Systems with Variable Structures

A new method to calculate electric values of unsymmetrical open conductorfaults in power systems with variable structures and parameters is proposed. All the fault componentsof nodal voltage or branch current and the equivalent parameters of open port for each sequence net-work can be obtained rapidly. The method presented here is much more understandable in contrast tothose available, and meanwhile the amount of calculations is greatly reduced. Its effectiveness hasbeen verified by numerical examples.