检索结果-南通市图书馆

RANDOM COPOLYMER OF PROPYLENE OXIDE AND ETHYLENE OXIDE PREPARED BY DOUBLE METAL CYANIDE COMPLEX CATALYST

在线全文

学校读者我要写书评

暂无评论

Chinese Journal of Polymer Science 2002年第5期20卷 453-459页

作者： Yi-jun Huang Guo-rong Qi Guan-xi Chen department of Polymer Science and Engineering, Zhejiang university Hangzhou 31002.,{2. Zhejiang Univ Dept Polymer Sci & Engn Hangzhou 310027 Peoples R China

Copolymerization of propylene oxide (PO) and ethylene oxide (EO) using double metal cyanide (DMC) complex as the catalyst was carried out. The structure of random copolymers was confirmed by C-13-NMR and IR spectra. H-1-NMR analysis shows that the EO content in the copolymer is the same as that in the initial monomer feed. Moderate molecular weight copolymers with various EO content were obtained and their values of molecular weight distribution (MWD) fell in the range of 1.2.-1.55. It was found that the molecular weight of copolymers is controlled by the mass ratio of EO+PO to initiator moles used, The reaction rate as well as polymer yield decrease with increasing EO content in the feed composition.

关键词： propylene oxide ethylene oxide double metal cyanide complex

CYP2.1 Pst Ⅰ/Rsa Ⅰ polymorphism and colorectal cancer risk:A meta-analysis

在线全文

学校读者我要写书评

暂无评论

World Journal of Gastroenterology 2010年第23期16卷 2949-2953页

作者： Guo-Wu Zhou,Jia Hu,Qiang Li department of Respiration,Changhai Hospital,Second Military Medical university,Shanghai 2.0433,{2. department of Oncology,Changhai Hospital,Second Military Medical university,Shanghai 2.0433,{2. department of Respiration Changhai Hospital Second Military Medical University Shanghai 200433 China.

AIM:To clarify the association between CYP2.1 PstⅠ/RsaⅠ polymorphism and susceptibility to colorectal ***:A meta-analysis based on 10 eligible casecontrol studies involving 4979 cases and 6012.controls was carried out to summarize the data on the association between CYP2.1 RsaⅠ/PstⅠ polymorphism and colorectal cancer ***:In comparison of the homozygote c2.2.and c2.carriers(c1c2.+ c2.2. and the homozygous wild-type genotype(c1c1),no association was found between CYP2.1 RsaⅠ/PstⅠ polymorphism and colorectal cancer risk [odds ratio(OR)=1.2.(95% CI:0.93-1.66) for c2.2.OR = 1.02.95% CI:0.88-1.19) for c2.carriers].In stratif ied analysis,Caucasians with c2.2.homozygote appeared to have an increased risk of colorectal cancer(OR=2.67,95% CI:1.03-6.89,P=0.043),no signif icant associations were found in other ***:c2.2.homozygote of CYP2.1 PstⅠ/RsaⅠ polymorphism may be associated with the increased risk of colorectal cancer in Caucasians,which needs further investigations.

关键词： Cytochrome P450 2.1 PstⅠ/RsaⅠ polymorphism Colorectal cancer Cancer susceptibility Metaanalysis

Ab initio molecular dynamics simulation of the atom packing and density of Al-Ni amorphous alloys

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Science china(Technological Sciences) 2010年第12期53卷 3175-3182页

作者： YU ChunYan1, HUI XiDong1, CHEN XiaoHua1, LIU XingJun1, LIN DeYe1, LIU ZiKui2.& CHEN GuoLiang1 1 State Key Laboratory for Advanced Metals and Materials, university of Science and Technology Beijing, Beijing 100083, china 2.{2. of Materials Science and Engineering, Pennsylvania State university, university Park, PA 16802. USA 1. State Key Laboratory for Advanced Metals and Materials University of Science and Technology Beijing Beijing 100083 China2. Department of Materials Science and Engineering Pennsylvania State University University Park PA 16802 USA

Al-Ni alloys have better glass forming ability (GFA) than other Al-based alloys. However, the relationship among the atomic arrangement, glass transition, packing density and composition hasn’t been systematically studied. In this paper the ab initio molecular dynamics simulation (AIMD) was performed on the atom packing and density of AlxNi100-x (x=80, 83, 85, 86, 87 and 90) alloys. The pair correlation function and Voronoi tessellation indicated that there are obvious topological and chemical short-range orders in these alloys. The topological structure consists of Al-centered icosahedra like and Ni-centered tri-capped trigonal prism (TTP) like polyhedra. There is strong chemical short-range ordering between Al and Ni atoms indicated by the bond-length of Al-Ni pair shorter than the sum of the radii of Al and Ni atoms, which increases with the increasing of Ni content. It is shown that the densities of amorphous alloys don’t agree with the linear law with a peak at x=85. Based on the features of the structure and density, it is concluded that Al-Ni alloys at x=84–86 have high GFA, which can be extended to multi-component Al-based alloys.

关键词： AIMD Al-Ni alloys density short-range order chemical short-range order

在线全文

学校读者我要写书评

暂无评论

基于居民实际支出数据的稳健性分析

天津师范大学学报（社会科学版） 2005年第1期25卷 23-28页

作者：孙宪华郭亚帆天津财经大学统计学系天津300222

统计作为一种科学原理和技术,对社会经济起着举足轻重的工具性作用。然而,传统的统计量在许多情况下都不具有很强的代表性,需要运用像切尾均值、茎叶图、M-估计量等多种稳健统计方法方可更全面、更准确、更清晰地反映居民支出总体的实... 详细信息

统计作为一种科学原理和技术,对社会经济起着举足轻重的工具性作用。然而,传统的统计量在许多情况下都不具有很强的代表性,需要运用像切尾均值、茎叶图、M-估计量等多种稳健统计方法方可更全面、更准确、更清晰地反映居民支出总体的实际水平和分布情况。

关键词：居民支出稳健性茎叶图 M-估计量

The origin and development of " Zuo Bridges

在线全文

学校读者我要写书评

暂无评论

西南师范大学学报（自然科学版） 1995年第4期20卷 387-393页

作者： Liao Boqin(department of Physics, Southwest china {2. university , Chongqing 630715)

Ｔｈｅｏｒｉｇｉｎａｎｄｄｅｖｅｌｏｐｍｅｎｔｏｆ＂ＺｕｏＢｒｉｄｇｅｓ＂ＬｉａｏＢｏｑｉｎ（ＤｅｐａｒｔｍｅｎｔｏｆＰｈｙｓｉｃｓ，ＳｏｕｔｈｗｅｓｔＣｈｉｎａＮｏｒｍａｌＵｎｉｖｅｒｓｉｔｙ，Ｃｈｏｎｇｑｉｎｇ６... 详细信息

Ｔｈｅｏｒｉｇｉｎａｎｄｄｅｖｅｌｏｐｍｅｎｔｏｆ＂ＺｕｏＢｒｉｄｇｅｓ＂ＬｉａｏＢｏｑｉｎ（ＤｅｐａｒｔｍｅｎｔｏｆＰｈｙｓｉｃｓ，ＳｏｕｔｈｗｅｓｔＣｈｉｎａＮｏｒｍａｌＵｎｉｖｅｒｓｉｔｙ，Ｃｈｏｎｇｑｉｎｇ６３０７１５）Ｔｈｅｏｒｉｇｉｎａｎ...

关键词：索桥桥梁起源发展

china: A COUNTRY OF THE THIRD WORLD OR THE THIRD GREAT POWER?

在线全文

学校读者我要写书评

暂无评论

Journal of Geographical Sciences 1996年第3期6卷 84-88页

作者： Hu Zhaoliang(department of geography, Peking {2., Beijing 100871People’s Republic of china)Soon-Cheol MoonSeoul National {2., Seoul, Korea

In 1990, World Bank and IMF calculated china's GDP with Purchasing Power Parity (PPP). World Bank estimated it at 1,950 U.S dollars and IMF did it at 1,300. According to this figure, china ranked next to U.S. and Japan in the world. This result has created a dispute whether china is a country of the Third World or the third great power. For explaining this question, measuring system of the PPP and traditional exchange rate must be exanined first.

关键词： third world economic growth GDP china

Ultra-Broad-Band LiNbO3 Electro-Optic Modulators with Novel Complex Electrode

在线全文

学校读者我要写书评

暂无评论

Chinese Journal of Lasers 2000年第2期9卷 128-133页

作者： ZHOU Weiqin WU Boyu PENG Jihu GU Jinghua HU Jinyang (department of Electronic Engineering, Tsinghua university, Beijing 100084,{2.) 清华大学北京 100084

The characteristics of Z- cut LiNbO3optical modulators with novel complex electrode are discussed by using the finite element method （FEM） and studied experimentally in this paper. The travelling wave electrode consists of upper and lower parts. It can easily realize phase velocity matching between microwave and optical wave and drastically reduce microwave electrode loss. An electrooptic modulator with larger than 100 GHz bandwidth and half wave voltage 6 V is designed, fabricated and measured. Vπis 5. 1 V and the attenuation coefficient ac is 0. 3 dB/(cm· GHz1/2.. The experimental results show that the modulator has great potentiality for expanding bandwidth.

关键词： electro-optic medulator LiNbO3 modulator travelling wave electrode complex electrode

Research progress in studies on the coalbed gas geochemistry

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Progress in Natural Science:Materials International 2006年第3期16卷 215-220页

作者： TAO Mingxin (College of Resources Sciences & Technology, Beijing normal university, Beijing 100875,{2. Key Laboratory of Gas Geochemistry, Institute of Geology and Geophysics, Chinese Academy of Sciences, Lanzhou 730000,{2.) [a]College of Resources Sciences & Technology Beijing Normal University Beijing China [b]Key Laboratory of Gas Geochemistry Institute of Geology and Geophysics Lanzhou China

The current situation of geochemical studies on coalbed gas is reviewed in this paper. Generally, coalbed gas is composi-tionally dominated by methane with δ13C1 values ranging approximately from - 80‰ to - 10‰. However, few isotopic studies have been carried out on other components of coalbed gas except for hydrogen and carbon dioxide, whose δDCH4 values available for utilization vary from - 333‰ to - 117‰, and δ13CCO2.values from - 2.. 4‰ to + 18. 6‰. Two major types of coalbed gas, thermogenic gas and secondary biogenic gas, have been identified, and there are also some other classification criteria. Compared with conventional natural gases, coalbed gas has a wide distribution range of δ13C1 and δ13CCO2.values, especially possessing some extremely heavy values. Current problems that remain unsolved in the coalbed gas geochemistry include the variation mechanism, controlling factors and application of carbon and hydrogen isotopes of methane, the relation between the values of δ13C1 and Ro, the systematic classification scheme and criterion of genetic types, and the application of the coalbed gas geochemistry in evaluating target districts of the coalbed gas exploration.

关键词： coalbed gas geochemistry isotopic composition genetic type novel resource.

含磷稠环8,9,16,17-四脱氢-6,14-二硫羰基-6,14-二巯基-7,8,15,16-四氮-5,13-二氧-6,14-二磷杂二苯并[a,h]蒽烷吡啶盐及其衍生物的合成和结构

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

化学学报 1987年第10期45卷 987-992页

作者：陈其杰金淑娟缪方明王瑾玲南开大学元素有机化学研究所天津师范大学化学系天津师范大学化学系天津

本文报道标题化合物及其十一个衍生物的合成方法,测定了该盐及其若干衍生物的分子和晶体结构,并对衍生物的性质、氢核磁共振谱和质谱进行了讨论.

关键词：晶体结构化合物结晶构造固体结构二苯并 a,h 化学学报分子磷杂实测值分子离子峰异形体电子轰击质谱脱氢脱气射线衍射计算值 ppm 产率含磷