Some Discussion On the Calculation of the Discrete Fourier Transform(DFT)

In the field of signal analyies for time frequency, the DFT is a familiar term. Especially,when its efficient algorithm FFT given, the other operations in signal analyses are also usually translated to DFT as soon as possible so as to enhance the calculating speed. But in our exploning the virtual instrument for time frequency analyzing, two sorts of formulas to calculate DFT and its inverse transform (IDFT) are found. These results are in different value of operation from different signal analysts or from different instruments for time frequency analyzing, their physical meaning are also not clear enough.The period extent theory some previous document based on when defined DFT is firstly expatiated. Then, separately with future defining coefficient method and analogy evolvement method, the authors argue that, based on the period extent theory, it is more rational to calculate DFT with the formula given. A shortage is pointed out and corrected is appeared in some previous documents when having given the formula of DFT. The improper view is also clarified that the reason why there are two sorts of formulas is make by custom.The rationality of the authors view with three examples is visually verified in the end.     

Improvement and simulation on direct torque control system of permanent magnet synchronous motor

To solve the problems of large flux, torque ripple and inconstant inverter switching frequency in conventional direct torque control (DTC), a space vector modulation (SVM) technique is introduced to the conventional PMSM-DTC system and analyzed thoroughly based on the mathematical model. This novel control method which enjoys the advantages of VC and DTC has only one easy adjustable PI regulator and is easy to realize. The simulation verifies that this control system is capable of effectively improving the steady state performance and keeping the excellent dynamic performance of the PMSM-DTC system simultaneously and remain the switching frequency constant.     

Order Tracking Method Based on Time-Frequency Analysis

The fault character of moving parts of rotating machinery most time is speed related. The method of order spectrum analysis is more efficient than usual frequency analysis.Two general methods for realizing order tracking are discussed, and a new order tracking method based on time-frequency analysis is proposed. The time frequency order tracking method only depends on software for order tracking, which is a strong supplement to traditional methods, and specially satisfied the require of virtual instruments, so there is a good prospect for its using.     

Application on Extracting Feature in State Monitoring and Fault Diagnosis

With the development and application of information and internet and virtual instrument technology ,the virtual globular company based on internet arises .To study remote state monitoring, remote fault detection and diagnosis about large scale, complicated and integrative equipment become very important. In the whole fault diagnosis system , the detecting ,data acquisition is original ,processing; transform and extracting features with the signal detected is a key factor. The theories and methods used in mechanical fault diagnosis is stated. The application of signal process and its feature extracting methods is introduced which are time domain, frequency domain and time frequency domain analysis, in state monitoring and fault diagnosis with its signal analysis. The processing method of random time variant special signal is given also.     

Binary phase only filter based watermarking combined with discrete wavelet transform

The binary phase only filter (BPOF) based digital image watermarking combined with a discrete wavelet transform (DWT) was proposed. Firstly, the DWT transform was applied to an image. Then, the discrete Fourier transform (DFT) was applied to the low frequency subband of the DWT transform. Next, the phase information of the DFT was binarized to obtain the BPOF, which would be taken as the watermark and embedded into the corresponding magnitude. Compared to applying the DFT transform to the whole image and embedding the BPOF watermark in the entire frequency range, or in the low frequency range, the watermark robustness in JPEG compression is improved significantly while maintaining the watermark imperceptibility and detection efficiency. This method may be used to demonstrate the authenticity and integrity of an image. The simulation experiments demonstrate the efficiency of this method.     

Performance Analysis of Anti-CW Interference in MC-CDMA Systems

The multicarrier-code division multiple access (MC-CDMA),which is the combination of direct sequence CDMA (DS-CDMA) and orthogonal frequency division multiplexing (OFDM) techniques, offers various advantages over single-carrier CDMA system. Some of the advantages are that MC-CDMA systems possess can remove the intersymbol interference (ISI) and enhance narrow-band interference suppression capabilities. So the MC-CDMA technique becomes a focus in the field of mobile communication. The authors introduce the typical MC-CDMA system model, discuss the decision statisticalvariable in Rayleigh fading channel included the CW interference, and give the expressions of probability of error in uplink. An approach is proposed with Modified Equal Gain Combining (MEGC) to decrease the effect of CW interference. Theoretical analysis and numerical results show that the anti-CW interference performance of MC-CDMA system can be improved used the MEGC approach.     

农业龙头企业农产品质量控制评价体系的研究

近年来,食品安全事件频繁发生,农产品质量问题备受关注,农产品是与人类健康联系最紧密的消费品,改善农产品质量势在必行。本研究以农业龙头企业农产品的质量控制为研究对象,从农产品的料供应质量控制、企业主体质量控制、政府及消费者的质量控制三个角度入手,构建相应的评价指标。评价指标的选取充分考虑了农业龙头企业的特点与农产品质量控制的特殊性,应用层次分析法,选出了5个一级评价指标：农民（基地）农产品质量控制、企业内部农产品质量控制、市场竞争优势、政府的质量监控、消费者的质量监控,以及细化的二级指标。农业龙头企业可以选择模糊评价法对几年的指标进行综合评价,分析企业农产品质量控制的优点与不足,不断提高农产品质量与管理。     

Flowmeter Based Virtual Instrument

The flowmeter based virtual instrument is a new test instrument, which has more advantages than the traditional flowmeter. This flowmeter is based on Qin's model. Apply to the flowrate measurement realm the virtual instrument technique. The design method has been introduced from hardware, software and panel, modelize the different flowrate measure way, with the virtual instrument's figural calculation and show to replace the traditional flowrate measurement, realize multi-threading long-distance flowrate measure easily.     

PCI Bus Card and Its Applications in the Virtual Instrument

This paper analyses the PCI bus features, and introduces several developing tolls and the techniques, including PCI controller IC, driver development software and the key points of designing PCI cards with the main focus on IC S5933 and driver development software WinDriver. An example in the virtual instrument-a random signal generator, consisting of PCI card and software, is also given. DDS is realized by software, through the high transfer speed of PCI bus. The signal generator can produce sin, noise, frequency sweep and others complex waves. It can be used to adjust the wave, frequency, amplitude, phase and precision conveniently and accurately.     

Great Capacity of Data Logger Based on Virtual Instrument Technology

The Data Logger is an important secondary-instrument,which can be applied to automatic monitor and control system,and high speed local data acquisition for later analysis.The Virtual Great Capacity of Data Logger based on virtual instrument technology is a new instrument which has more advantages than the traditional Data Logger.The design method has been introduced from three ways,which includes system principle, hardware configuration and programming design, and an application example is given.This Data Logger is low cost,easy to take,also easy to operate.It can be widely used in many of actual applications.     

Better subcarrier bases for powerline communication system

To solve the frequency dispersive feature in powerline channel, the quthors analyzed the anti-interference performance of modulation schemes with different subcarrier bases, and use orthogonal wavelet packet as subcarrier base instead of sine base in OFDM to suppress multi-path effect and frequency selective fading by its orthogonality in powerline channel. Through experiment, performances of wavelet packet modulation with different wavelet packets and OFDM are analyzed. Experiment results indicate that when the SNR has reached a certain level, orthogonal wavelet packet modulation has better performance than bi-orthogonal wavelet packet and sine base.     

玉米自交系选型留雄保纯繁殖程序及群体遗传学分析

把玉米自交系繁殖纳入回交群体模式,设计了玉米自交系选型留雄（确立轮回亲本群）保纯繁殖程序,在Ｍｏ１７保纯繁殖实践中应用收到良好效果,优越性突出。运用群体遗传学原理,通过回交群体遗传分析,揭示了群体基因与基因型及其频率等参数取决于基因型的基因对数与世代数,总趋势是随世代的推移,逐步回归最终用一于其轮回亲本群的规律,对玉米自交系选型留雄保纯繁殖程序予以有力的理论支持。     

SIMULATION STUDY OF ACTIVE POWER DISTORTION COMPENSATOR

In this paper, the effectes of modulation index, modulation frequency, modulation method and LPF parameters on current-fed active compensator arc studied by using digital simulation and the performances of voltage-fed active compensator are compared with those of the current-fed active compensator.     

Development of Virtual Sweep Signal Source

A new kind of virtual sweep signal source which can be used to output specific sweep signal according to(users') configuration and can be widely applied to frequency characteristics measurement in the field of mechanics,electrics and electronics,is developed by using Dot Net software engineering technique,C/S architecture and general data acquisition platform.The virtual instruments not only make up the intrinsic defect of traditional instruments based on hardware components in high performance,remote control and data processing,but also indicate the powerful life and nice future of virtual instrument technologies.     

Virtual Logistics and Its Development

The research of virtual logistics is a front task in the field of logistics management research. This paper explains the meaning of the virtual logistics and virtual logistics organization in detail based on the analysis on various existing concepts of them, introduces the actuality of the research concerning virtual logistics. Then a three dimensionality research framework and major research contents of virtual logistics are proposed. Four development directions of virtual logistics research and corresponding research emphases are pointed out.     

变性梯度凝胶电泳及其在土壤微生物生态学中的应用

变性梯度凝胶电泳（denaturing gradient gel electrophoresis,DGGE）因其具有可靠性强、易操作、可同时分析多个样品等优点,目前已经成为一种普遍的快速指纹分析分子技术,广泛应用于微生物群落组成、多样性及种群动态等研究。笔者综述了DGGE技术的基本原理和发展,以及该技术在土壤微生物生态学领域诸多方面的应用,并进一步对该技术在微生物生态学领域研究中存在的优势和局限性进行了讨论评价,最后对其应用前景进行了展望。     

虚拟植物的发展概况与应用

近三十年来,随着计算机技术的发展,虚拟植物的研究取得了显著进步,已经成为精准农业的一项核心技术,并在多个领域中得到了广泛的应用。本文概述了虚拟植物的发展历史和近年来的研究现状,并根据现有的技术缺陷分析了虚拟植物未来的发展方向,最后介绍了虚拟植物在科学实验、精准农业、教育培训和动漫影视中的实际应用。     

The role of mutations in intraspecific differentiation of groundnut (Arachis hypogaea L.)

Summary Based on morphological diversity, cultivated groundnut (Arachis hypogaea L.) is classified into two subspecies (fastigiata and hypogaea) and further into four botanical types (Spanish bunch, Valencia, Virginia bunch and Virginia runner). In a cross between two Spanish cultivars belonging to ssp. fastigiata, a true breeding variant (Dharwad early runner) sharing some characters of both the subspecies was isolated. The variant, on mutagenesis with ethyl methane sulphonate (EMS) yielded a very high frequency of mutants resembling all four botanical types. Some of the mutants produced germinal reversions to Dharwad early runner in later generations indicating genetic instability. While most of the revertants bred true, some of the mutants continued to segregate, wherein each botanical group of mutants produced all other botanical types. A detailed analysis of the breeding behaviour of mutants revealed several unusual features (such as homozygous mutations, mutation outbursts, segregation distortions, somatic mutations and multiple character mutations) that could not be explained through conventional mutation theory. In the light of these findings, the role of mutations in evolutionary differentiation of the crop and the probable mode of their origin have been discussed.     

Sustainable fisheries management in the resource periphery: The cases of Chile and New Zealand

Abstract: Chile and New Zealand both depend on their natural resource bases for their exports. This situation characterises the historical condition of the resource periphery. Despite similar processes of globalisation in their fisheries sectors since the 1970s, the ways in which public and private policies and management strategies have been brought to bear on sustaining the resource base differ considerably. In light of the strategic economic agreement between the two countries (and Singapore and Brunei) signed in 2005, these contrasts reveal that multiple options exist for countries in the resource periphery to enhance their national development by working with comparative advantages alongside competitive advantages introduced into the sector. Chile’s explosive growth in aquaculture and its low levels of public and private concern for more sustainable fisheries is contrasted with New Zealand’s more sustainable approach to natural resource management through a range of instruments and commitments. The principal conclusion is that resource periphery producers should capitalise on their natural assets, but only within the context of a sustainable strategy that promotes and enforces responsibility. The current crisis in global capture fisheries is both an opportunity and a warning in this regard.     

Intergeneric hybridization between Brassica species and Crambe abyssinica

A protocol for high frequency callus induction and plant regeneration from sunflower (Helianthus annuus L.) anthers is described. Different variables using Murashige & Skoog (MS) basal medium supplemented with 2.0 mg/l α-naphthaleneacetic acid (NAA) and 1.0 mg/l N₆-benzyladenine (BA) were tested for their ability to enhance the frequency of anther callusing and subsequent embryogenesis. Of these, agar concentration, sucrose concentration, carbohydrate source had significant effect on callusing, while differences due to incubation under dark vs light conditions, cold pretreatment of capitula for 1 to 6 days prior to anther inoculation and genotype on callusing were non-significant. However, all these factors exerted highly significant influence on embryogenesis when calli from the various media were transferred to medium supplemented with 0.1 mg/l NAA and 0.5 mg/l BA. With the procedure developed, callusing as high as 100% and embryo formation at a frequency of 44% was achieved. Although complete embryos were formed the frequency of their conversion to whole plantlets was low (14.3%). Hence, the embryogenic pathway was bypassed to obtain multiple shoots by transferring embryogenic calli with developing embryos to MS medium supplemented with 0.5 mg/l BA. Elongated shoots rooted on half-strength MS medium supplemented with 0.5 mg/l NAA. Cytological analysis of embryogenic callus and somatic embryos revealed haploids at a frequency of 30% while that of rooted plants showed haploid regenerants at a frequency of 8.3%. Nevertheless, the frequency of putative haploid plants could be enhanced through mass multiplication using nodal explants of the regenerants. This revised version was published online in August 2006 with corrections to the Cover Date.