4GHz微波收发信机的日常维护

我台的两套4GHZ微波收发信机已经使用近20年，元器件都已老化，给日常维护工作带来很多困难。笔者根据多年的工作实践，总结了日常维护的一些经验和同行共同学习。下面从微波收发信机的收信系统、发信系统、电源系统和监控系统四部分分别介绍。

Postfix邮件队列处理与调度方法研究

电子邮件系统是Internet的一个核心应用 ,而Postifix是应用广泛的邮件系统之一。通过对Postfix邮件队列处理与调度方法的研究 ,具体分析Postfix对邮件处理的流程 ,对调整和优化Postfix系统以及利用Postfix系统建立基于Web的邮件系统提供了参考。

Implementation of a 6 GHz band TDD RF transceiver for the next generation mobile communication system

The development of a high performance wideband radio frequency （RF） transceiver used in the next generation mobile communication system is presented. The developed RF transceiver operates in the 6 to 6.3 GHz band and the channel bandwidth is up to 100 MHz. It operates in the time division duplex （TDD） mode and supports the multiple-input multipleoutput （MIMO） technique for the international mobile telecommunications （IMT）-advanced systems. The classical superheterodyne scheme is employed to achieve optimal performance. Design issues of the essential components such as low noise amplifier, power amplifier and local oscillators are described in detail. Measurement results show that the maximum linear output power of the RF transceiver is above 23 dBm, and the gain and noise figure of the low noise amplifier is around 24 dB and below 1 dB, respectively. Furthermore, the error vector magnitude （EVM） measurement shows that the performance of the developed RF transceiver is well beyond the requirements of the long term evolution （LTE）-advanced system. With up to 8 x 8 MIMO configuration, the RF transceiver supports more than a 1 Gbit/s data rate in field tests.

A Robust Decision Feedback Equalizer for ATSC DTV Receivers

Least mean square (LMS) decision feedback equalizer (DFE) is preferred as an effective solution to coping with inter-symbol interference (ISI) for ATSC digital television (DTV) receivers. In DTV transmission environment, echo delay often covers several hundreds symbols, which leads to very large-scale equalizer. One consequence of the large-scale equalizer is the very slow convergence, which combined with error propagation, inherent drawback of DFE, seriously deteriorates the performance of the receivers, especially in severe channels More working modes and corresponding robust control mechanism were given to help the equalizer converge to the stable state smoothly. Simulation results show that the improved equalizer can perform better, especially in the severe channels.

The real-time display algorithm of objects in seabed

Three-dimension electronic chart display information system (ECDIS) is one of the new developing directions of electronic navigation chart, and its real-time quality is one of the important requirements. In this paper the algorithm of simplifying triangle surface using edge contraction, which can ensure the real-time display of objects in seabed enviromnent, was put forward. The optimum contraction point was determined by the Lagrange matrix, so that the algorithm ensures that the contraction point locates on the original model, meanwhile meets the demands of least deviation. This algorithm can improve the plotting speed, and preserve the boundary character by using the fewer triangles to simulate objects.

Fraud Detection in Interoperable Information Systems

Interoperability is broad and complex subject being the most critical issue facing businesses that need to access information from multiple systems. The concept of unwanted interoperability can result in fault decision making based on counterfeit data produced by hostile interoperable system. Research in this paper is based on highway toll collection system analysis as representative of hierarchical heterogeneous systems where integration becomes more important than development due to the short time in disposal between the contract signature and implementation. Unwanted interoperability detect mechanism is presented using information collected from different information system levels.

Detection Probability Analysis of Space-Based AIS Signal by Using Geometrical Model

To analyze the detection probability of shipbome AIS （automatic identification system） signal from space, a mathematical model dependent upon three factors of message collision avoidance, power of signal received by satellite and interference ratio of signal received is presented in the paper. The altitude and footprint area of the AIS satellite are discussed to overcome the collision of messages transmitted in the different time slots fxom different SOTDMA （self organizing time division multiple access） cell areas, but arrive at the same time slot due to the different signal path lengths. The simulated result shows that compared to the normal LEO （low ear~ orbit） satellite system, on average the maximum signal coverage area and the maximum FOV （field of view） of the AIS satellite system are reduced by 74% and 38%. The majority of power of signal transmitted fi＇om shipborne 12W-power AIS transmitters located within the maximum signal coverage area may be received with the sufficient margin of power of signal by the LEO satellite, but the space-based AIS system generally suffers from the insufficient CIR （carrier to co-channel interference ratio） of signal received since around 95% pairs of message simultaneously received by satellites may not be correctly decoded. The insufficient CIR of signal received is the bottleneck for the high message detection probability. Therefore, the measure of separating the collision messages should be further taken by the space-based AIS system to increase the detection probability.

Microscopic simulation of multi-lane traffic under dynamic tolling and information feedback

To investigate drivers' lane-changing behavior under different information feedback strategies,a microscopic traffic simulation based on the cellular automaton model was made on the typical freeway with a regular lane and a high-occupancy one. A new dynamic tolling scheme in terms of the real-time traffic condition on the high-occupancy lane was further designed to enhance the whole freeway's flow throughput. The results show that the mean velocity feedback strategy is generally more efficient than the travel time feedback strategy in correctly guiding drivers' lane choice behavior. Specifically,the toll level,lane-changing rate and freeway's throughput and congestion coefficient induced by the travel time feedback strategy oscillate with larger amplitude and longer period. In addition,the dynamic tolling scheme can make the high-occupancy lane less congested and maximize the freeway's throughput when the regular-lane inflow rate is larger than 0.45.

Transceiver Optimization for Multi-Antenna Device-to-Device Communications

It has been shown that the deployment of device-to-device(D2D) communication in cellular systems can provide better support for local services. However, improper design of the hybrid system may cause severe interference between cellular and D2D links. In this paper, we consider transceiver design for the system employing multiple antennas to mitigate the interference. The precoder and decoder matrices are optimized in terms of sum mean squared error(MSE) and capacity, respectively. For the MSE minimization problem, we present an alternative transceiver optimization algorithm. While for the non-convex capacity maximization problem, we decompose the primal problem into a sequence of standard convex quadratic programs for efficient optimization. The evaluation of our proposed algorithms for performance enhancement of the entire D2D integrated cellular system is carried out through simulations.

ITERATIVE RECEIVER FOR OFDM SYSTEMS BASED ON SEMI-BLIND CHANNEL ESTIMATION

In this paper we propose two iterative algorithms of joint channel estimation and symbol detection for Orthogonal Frequency Division Multiplexing (OFDM) systems. In which, superimposed pilot scheme is adopted and an initial Channel State Information (CSI) is obtained by employing a first-order statistic. In each subsequent iteration, we propose two algorithms to update the CSI. The Mean Square Error (MSE) of channel estimation and Bit Error Rate (BER) performance are given and simulation results demonstrate that the iterative algorithm using method B has good perform-ance approaching the ideal condition.

Therapeutic effect in patients with coronary heart disease based on information analysis from Traditional Chinese Medicine four diagnostic methods

OBJECTIVE:To study information gained by Traditional Chinese Medicine(TCM)four diagnostic methods and characteristics of syndrome development before and after treatment in patients with coronary heart disease,and to probe into assessment indexes of therapeutic effects with distinctive TCM features.METHODS:Information from the four diagnostic methods before and after treatment in 100 patients with coronary heart disease was collected using the TCM interrogation scale,a pulse condition instrument,a tongue-face diagnosis instrument,anda voice diagnosis information collection system.Changes in the four diagnostic method results from before and after treatment were analyzed with frequency analysis and t-test methods.RESULTS:Before treatment,deficiency syndrome complicated with hyperactivity of pathogenic factors was most common.After treatment,deficiency syndrome was most common.This change from complex syndromes to single syndromes indicates disease and syndrome alleviation.Frequencies of symptoms gained by interrogation after treatment for syndrome of deficiency of heart-Qi,syndrome of deficiency of heart-Yin,and turbid phlegm syndrome were all less severe than those before treatment.Parameters of face color,color on all sub-regions of tongue,color of tongue fur,septic and greasy fur,and lip color after treatment all had significant changes.After treatment,part of the voice diagnosis parameters in the deficiency of heart-Yin and turbid phlegm syndromes had significant changes,but no significant changes were found in the deficiency of heart-Qi syndrome.CONCLUSION:Use of the TCM four diagnostic methods can provide an effective basis forTCM syndrome diagnosis,observation of development of state of illness,and evaluation of clinical therapeutic effects.

Experiment study of ATP system for free-space optical communications

To meet the requirement of high tracking angular accuracy for the acquisition, tracking, and pointing (ATP) subsystem of the free-space optical communication, and provide the basis for the further optical communication between maritime mobile platforms, the experimental system, which executing part for the fine tracking is voice coil motor with high frequency and good performance for error compensation, is established, and the whole system can be controlled by personal computer. A series of experiments has been done for the simulation target of different uniform speed, and the data of tracking error for fine tracking and coarse tracking are collected, analyzed and evaluateds separately, and the real-time optical power of communication laser is also collected. The result shows that standard deviation for ATP system tracking error increases with the increase of target speed, while the range of tracking error appears to be no order. Furthermore, communication link can be hold for a long time.

A flexible receiver with fiber optical parametric amplifier in OCDMA-FSO communication system

A new receiver is proposed, which uses the fiber optical parametric amplifier(FOPA) in optical code division multiple access(OCDMA) over free space optic(FSO) communication system. The noise tolerance as the performance index in this receiver is derived. The receiver can not only improve the noise tolerance but also change the pump data conveniently for adapting to the length variation of the coding sequence under a complex and fast-changing weather condition. The influence of different factors on the noise tolerance is analyzed, and a significant improvement of about 18.77 d B for the noise tolerance can be achieved when the pump power and the length of coding sequence are 5 W and 256, respectively.

SPECIAL ISSUE： DISTRIBUTION OF NATIONAL INCOME IN A TRANSITIONAL ECONOMY Labor income shares （LIS） in economic development： an empirical study based on China＇s sectoral-level data

Empirical study of sectoral-level change in LIS in China reveals that change in industry structure is synchronous and positively correlated with LIS in different sectors of the economy, intensifying overall LIS fluctuations. Our analysis of LIS based on data from the major sectors of China＇s economy show that, relative to 1993, the increase in LIS in 1996 was largely due to the increased proportion of LIS in secondary industry. Relative to 1996, the fall in LIS in 2003 was closely related to the fall in the proportion of primary industry in the overall economy. The year 2004 was unusual in that it witnessed a dramatic fall in overall LIS level. The primary reason for the fall was a change in statistical definition that led to a significant reduction in LIS in the secondary and tertiary sectors. There were huge variations in LIS level among different regions. However, with the passage of time, the regional disparities are gradually being reduced. This is also closely connected to changes in industry structure and within-sector LIS fluctuations.

A Situation Analysis of Combined Two Chinese Enterprises Income Tax Systems in One

In terms of policies to Chinese enterprises income tax system, especially nowadays two income tax systems within domestic and foreign enterprises, their weakness is becoming more and more apparent. In order to perfect China＇s future tax system, it is supposed to combine the two income tax systems within domestic and foreign enterprises.