New Parallel Interference Cancellation Scheme for DS／CDMA Systems

This paper proposes a new multi-stage parallel interference cancellation scheme by modifying the conventional multi-stage parallel interference canceller (PIC). At each stage, it first converts the interference-cancelled outputs from previous stage into the a prior information, in terms of which the bit mean values are computed and the multi-access interferenee (MAI) for each user is evaluated, and then an interferenee cancellation is performed to obtain further interference suppression. To reduce the implementation complexity, wegive an approximation expression for bit mean value. The performance over AWGN channel is analyzed and compared to the conventional PIC. The user number K= 7 and spreading factor N= 13 are chosen as simulation parameters. The computer simulation results show that the proposed PIC has better performance than the conventional PIC both with 2 interference cancellation (IC) stages, at bit error rate of 10^-3 , for example, about 3 dB performance gain is obtained by using the proposed PIC. It is also shown that our proposed PIC with 1-stage is superior to the conventional PIC with 2-stage in performance, which is of practical value because PIC with fewer stages can bring about shorter processing delay.     

Effect of bromization on the propertises of a series of substituted 1,8,15,22—tetra（2,4—ditertbutylphenoxy） phthalocyanines

A series of 1,8,15,22-tetra(2,4-ditertbutylphen-oxy) phthalocyanines [α-（oAr）4PcM,M1=(H)2,M2=Pd,M3=Cu,M4=Zn,M5=Pb] were synthesized in this study.Each compound was bromized in two kinds of solvent.One is the solvent mixture of 1,1,2-trichloroethane and water,the other is 1,1,2-trichloroethane alone.The effects of solvent,bromine excess added and reaction duration on the bromization reaction were studied.The shift of maximum absorbance wave-length both is solution and in solid thin film was investigated comparatively,discovering that both were bathochromism but the former was more.TG data showed that the temperature of thermal decomposition decreased continuously with the increase of numbers of bromine.Finally,the fragments produced during the bromization of (OAr)4PcPb in 1,1,2-trichloroethane were characterized by GC/MS.Based on the electronic structure,the possible mechanism of decomposition of these compounds was presented and discussed.     

The c-myc coding DNA sequences of cyprinids （Teleostei： Cypriniformes）： Implications for phylogeny

The family Cyprinidae is one of the largest fish families in the world, which is widely distributed in East Asian, with obvious difference in characteristic size among species. The phylogeneUc analysis of cyprinid taxa based on the functionally important genes can help to understand the speciation and functional divergence of the Cyprinidae. The c-myc gene is an important gene regulating individual growth. In the present study, the sequence variations of the cyprinid c-myc gene and their phylogenetic significance were analyzed. The 41 complete sequences of the c-myc gene were obtained from cyprinids and outgroups through PCR amplification and clone. The coding DNA sequences of the c-myc gene were used to infer molecular phylogenetic relationships within the Cyprinidae. Myxocyprinus asiaticus （Catostomidae）, Misgurnus anguillicaudatus （CobiUdae） and Hemimyzon sinensis （Homalopteridae） were assigned to the outgroup taxa. Phylogenetic analyses using maximum parsimony （MP）, maximum likelihood （ML）, and Bayesian retrieved similar topology. Within the Cyprinidae, Leuciscini and Barbini formed the monophyletic lineage respectively with high nodal supports. Leuciscini comprises Xenocyprinae, CuItrinae, East Asian species of Leuciscinae and Danioninae, Gobioninae and Acheilognathinae, and Barbini contains Schizothoracinae, Barbinae, Cyprininae and Labeoninae. Danio rerio, D. myersi and Rasbora trilineata were supposed to separate from Leuciscinae and Barbini and to form another lineage. The positions of some Danioninae species were still unresolved. Analyses of both amino acid variation with parsimony information and two high variation regions indicated that there is no correlation between variations of single amino acid or high variation regions and characteristic size of cyprinids. In addition, the species with smaller size were usually found to be basal within clades in the tree, which might be the results of the adaptation to the primitive ecology and survival pressure.     

反应气氛对铝热还原氧化钛合成氮化钛的影响

研究在流动氮气和埋炭条件下铝热还原氮化TiO2的反应过程,借助于X射线衍射(XRD)和扫描电子显微镜(SEM)分别测试和观察两种气氛中不同温度下处理后产物的物相组成和显微结构。结果显示,与流动氮气氛下一样,在埋炭气氛下采用铝热还原氮化法可以制备氮化钛复相材料,但处理气氛明显影响着铝热反应的程度及产物的形貌,在埋炭条件下处理后的产物中氮化钛含量、晶粒大小、晶格常数明显低于流动氮气氛下处理产物中上述各项值;热力学计算发现埋炭条件下铝除参与铝热还原反应外,还与炭粉床中氧发生反应,使参与铝热反应的金属铝不足,造成产物中有剩余的金红石存在。     

遗传学教学的改革与实践

遗传学是农科院校的一门核心基础课，也是生物科学的重要基础学科，近年来遗传学及其相关学科的研究进展很快，为使遗传学课程教学适库这一形势，获得良好的教学效果，就必须加强遗传学课程的改革，加强实践环节。文章从遗樗学教学大纲修订、多媒体辅助对教学改革及自主性实验教学改革等方面对我们在遗传学教学改革的一些做法和成效进行了介绍和分析，以期进一步促进我们遗传学教学水平的提高。     

聚醚胺的合成及催化性能研究

报导二氯三甘醇与过量乙二胺反应，生成１，１４－二氨基－６，９－二氧杂－３，１２－二氯杂十四烷（Ｉ），并完全甲基化得叔胺化合物：２，５，１４，１７－四甲基－８，１１－二氧杂－２，５，１４，１７－四氮杂十八烷（ＩＩ），将（Ｉ）接到到氯甲基聚苯乙烯大孔树脂上，并完全甲基化得高分子支载聚醚胺（ＩＩＩ），（ＩＩ），（ＩＩＩ）作相转移催化剂催化ｎ－Ｃ８Ｈ１７Ｂｒ与Ｋ１或与ＫＯＡ反应，结果表明，（ＩＩ）、（ＩＩ     

碎米桠的开发利用研究

碎米桠Rabdosia rubescens(Hemsl.)Hara系唇形科香茶菜属植物,分布于河南省南部山地.从其叶中分离鉴定出两种新二萜成份:碎米粒甲素和乙素(即Xin dongninA和B).总含量0.25%左右.药理研究证明,具有较强的抑菌作用和抗肿瘤能力,是一个很有开发利用价值的药用植物.     

On the Hejek-Renyi Inequality

In this paper we give an elementary and unified proof of the Hajek-Renyi inequality, and get a general version of this inequality which not only covers the all known results but also derives some new results.     

改善工艺指标,防止锅炉结垢

本文分析了贵州铝厂锅炉锅内水磷酸盐加药流程 ,指出了该工艺存在的主要问题是 :不能同时对几台运行的锅炉加药 ,因而难于控制锅内水中 PO4 -3的浓度在规定的范围 5 - 15 mg/l以内 ,从而导致锅炉结垢 ,蒸汽污染等问题。经过多年生产实践 ,我们对磷酸盐的加药流程及设备进行了技术改造 ,使得该系统能同时对几台运行的锅炉加药 ,并重新选择了运行可靠的加药泵 ,从而确保了均匀加药。经过一年多的生产运行表明 ,改造后的流程能比较好地控制锅内水中 PO-3 4的浓度在 7- 9mg/l,用药量降低了 5 0 % ;蒸汽中的钠含量由原来的 2 30 - 2 70 mg/l降低为 70 - 80 mg/l,且设备基本上无新结垢 ,经济效益十分显著