作序

The external prefaces come into being for the literature of narrate function.

外序的生成是建立在种种具有叙述作意功用的文献基础之上的。

The article presents the developing condition of PWM and SVPWM first.Then the theory of SVPWM is discussed in detail.The SVPWM is based on the thought of magnetic chain tracking.It makes the ideal magnetic chain circle of three-phased sysmmetry electric motor supplied by three-phased sysmmetry sine wave voltage for basis,uses the practical magnetic chain vector formed by the different switch modes of three-phased inverter to track the basic magnetic chain circle.During the course of tracking,the inverter changes the switch modes properly to form the PWM waves.Then the modulation wave of SVPWM is analyzed in detail.The modulation wave of SVPWM is implicit,but the analogous modulation wave in A-B-C axis needs to be calculated in order to expose the internal relation of SVPWM and SPWM.That is to show the implicit modulation wave of SVPWM. SVPWM actually is a transformed SPWM ruly sampled by the modulation wave which is injected by the zero prefaces based on space vectors.

本文首先对脉宽调制技术的发展现状进行了综述，在此基础上分析了电压空间矢量脉宽调制技术的发展现状；接着对空间电压矢量脉宽调制技术的基本原理进行了详细的分析和推导，SVPWM是基于磁链追踪的思想，它以三相对称正弦波电压供电下三相对称电动机定子理想磁链圆为基准，由三相逆变器不同开关模式下所形成的实际磁链矢量来追踪基准磁链圆的，在追踪的过程中，逆变器的开关模式作适当的切换，从而形成PWM波；然后详细分析了电压空间矢量脉宽调制技术的调制波，虽然SVPWM法的调制波是隐含的，但是为了揭示SVPWM法与SPWM法的内在联系，需要求出SVPWM在A-B-C坐标系上的等效调制波，也就是将SVPWM的隐含调制波显化；SVPWM实质是一种基于空间矢量在三相正弦波中注入了零序分量的调制波进行规则采样的一种变形SPWM。

Maoshixu mainly taken poetic license with history method, the "Book of Songs" All articles from the perspective of the historical background to explain Although there when the far-fetched, but others made a clear judgments on the poetic.

毛诗序主要采取以史证诗的方法，对《诗经》各篇均从历史背景中给予解释，虽有时牵强，但有的则对诗意作了明晰的判断。

This print asks Mr Wei Xumin to make " of one " foreword talk simply overall experience, as a result he says " me unexpectedly Buddhist templeput on the brakes does not live, write into an article ", the title of the article cries " defeat since Shui Qiongyun aurelian change butterfly ", in modesty deep accumulate poetic flavour and thought.

本刊请魏恤民先生作一&序&简单谈谈总体感受，结果他说&我竟刹不住，写成了一篇文章&，文章的题目叫《水穷云起破蛹化蝶》，谦虚中深蕴诗意和思想。

In this study, 2 individuals carrying RHD positive, D antigen negative allele (with exon 1 and 10 of RHD) and their mRNA were investigated by using reverse transcriptase PCR and sequencing through one pair of specific primers for 5′- and 3′-non-coding region of RHD, taking a Rh-positive sample as control.

本文分别针对RHD基因mRNA的5′-和3′-非编码区设计一对特异性引物，通过逆转录PCR和cDNA测序，分析2例RHD基因阳性（拥有第1和第10外显子）、D抗原表型阴性个体的全长mRNA/cDNA序列，同时以1例正常Rh阳性个体作对照。

On the other hand, the more important thing is because the urban housing is a kind of heterogeneity products.

另一方面，更重要的是由于城市住房是一种异质性产品。

Climate histogram is the fall that collects place measure calm value, cent serves as cross axle for a few equal interval, the area that the frequency that the value appears according to place is accumulated and becomes will be determined inside each interval, discharge the graph that rise with post, also be called histogram.

气候直方图是将所收集的降水量测定值，分为几个相等的区间作为横轴，并将各区间内所测定值依所出现的次数累积而成的面积，用柱子排起来的图形，也叫做柱状图。