In this dissertation , the basic principles of the coding and decoding of ldpc codes are studied systematically , and some code - design problems such as the design of degree distribution sequences , the design of girths and the design of efficient encode - able ldpc codes are analyzed in detail . based on all these efforts , some positive results are obtained and summarized as follow : 1 本文在对低密度校验码现有理论的研究基础上，系统地分析了低密度校验码在删除信道下的纠错性能和度序列设计、低密度校验码的围长设计和快速编码设计等编码设计问题，获得了一些研究成果，主要概括为： 1
In this study , iltv - nm98a strain and iltv - wanggang strain were multiplied in chorioallantois . a pair of primers were devised according to the nucleic acid sequence of iltv tk gene and the dna of multiplied virus was used as pattern to amplify the gene of tk by polymerase chain reaction ( pcr ) . the product of pcr was linked with suitable plasmid . then , the recombined plasmid was converted to escherichia coli . the converted escherichia coli 根据已发表的iltvtk基因的核苷酸序列设计一对pcr引物，以增殖的两株iltv的dna为模板，分别对它们的tk基因进行pcr扩增。将回收的pcr产物连接到适当的质粒载体上，转化感受态大肠杆菌，通过筛选对iltvtk基因的阳性克隆进行扩增培养。
Secondly , it was . made theoretical analyses about the optimal training sequence design by the maximum likelihood estimation method and obtained the corresponding results , which were compared with the separate results derived by the minimum mean square error ( mmse ) estimation method in the other literature . at last , it was analyzed the impac 其次进行了采用最大似然( ml )估计法的最佳训练序列设计的理论分析，分别得到了有关结果，并和其他文献中采用最小均方误差( mmse )估计法的设计结果进行了分析比较，得到了有关结论。
( 2 ) we have cloned 752bp fragment of mxnrampl gene from the genomic dna of malus xiaojinensis cheng et jiang by using common pcr method with primers designed according to the conserved domain sequences of plant nramp gene families . sequence analysis suggested that the predicted amino acid sequence of this fragment has 98 % and 83 % identities to the nramp gene fragment of wheat and osnramps of rice respectively ( 2 )根据植物nramp基因家族的功能保守区序列设计引物，通过常规pcr法从小金海棠基因组dna中扩增出了mxnramp1基因的752bp的特异性产物；序列分析表明，该片段所推导的氨基酸序列与小麦nramp基因片段(杂交用的探针片段)及水稻osnramp3基因分别具有98和83的同源性。
In chapter one , the research status quo of the stream cipher including its generation and attacks are introduced , at the same time since the main design idea of the generalized self - shrinking sequences results from that of the shrinking sequences , the research status quo of the shrinking sequence is also presented in this chapter 其中第一章主要介绍了序列密码的研究现状，包括生成现状和攻击现状，另外在本章章末介绍了广义自缩序列设计思想的来源?缩减序列的研究现状。第二章介绍了广义自缩序列族的一些基本伪随机性特性，包括最小周期以及线性复杂度等结果。
In this paper , 45 e . coli strains isolated from chicken farms in sichuan province were determined to be the pathogenic e . coli by animal test . type 1 pili of 45 strains isolated was detected by msha . the pila gene of 45 avian pathogenic e . coli strains were amplified by the polymerase chain reaction ( pcr ) with primers designed according to the sequence of the pila gene in genbank . results showed that pcr was more sensitive , faster and more characteristic than msha to detect type 1 pili 本研究将从四川规模化鸡场分离鉴定、经1日龄雏鸡致病性试验得到的鸡源致病性大肠杆菌45株，采用d -甘露糖敏感血凝试验( msha )检测1型菌毛，根据genbank中公布的人源大肠杆菌1型菌毛pila基因序列设计一对引物用pcr扩增鸡源致病性大肠杆菌1型菌毛pila基因。
The coding and decoding ideas of low - density parity - check codes on graphs are systematically summarized , and the density evolution theory is introduced . the two leading factors on the performance of ldpc codes , i . e . the degree distribution sequences and the girths of these codes , are analyzed in detail ; 2 系统地阐述了低密度校验码基于图模型的编译码思想，介绍了密度进化理论，对影响低密度校验码纠错性能的两个主要因素? ?度序列设计和围长设计进行了深入分析； 2
( 3 ) 490bp cdna fragment of fe ( ii ) - transporter gene mxlrtl was cloned by using common pcr method from iron - stressed root cdna library of malus xiaojinensis cheng et jiang with primers designed according to the conserved domain sequences of plant irt gene families . then we cloned the full cdna of mxlrtl gene by race method from this library with primers designed according to the sequence of 490bp cdna fragment ( 3 )根据植物irt基因家族的功能保守区序列设计引物，首先通过常规pcr法从缺铁胁迫处理的小金海棠根系cdna文库中克隆了fe ( ) -转运蛋白基因mxirt1的490bp的片段，然后根据测序结果设计引物，通过race法从该cdna文库中克隆了mxirt1基因的cdna全长。
