检索结果-南通市图书馆

Acceleration of C_2^+-C_8^+ Clusters to MeV Energies

在线全文

学校读者我要写书评

暂无评论

Chinese journal of nuclear physics 1995年第1期17卷 49-51页

作者： Shen Ding-yu Jiang dong-xing Wang Xue-mei Li Shuo-zhong Qian Xing (department of Technical Physics,peking university,beijing 100871) peking Univ Beijing China

Beams of C2+-C8+ clusters have been accelerated to 3 MeV in 1.7 MV *** beam intensity of small C-cluster is large enough for some physical *** gas density in the stripper cell is an important parameter for obtainingma... 详细信息

关键词： Carbon cluster Stripping Dissociation

SYNTHESIS OF DIACETYLENE-CONTAINING COPOLYESTERS AND THEIR DFFECT ON ELECTRO-OPTICAL PROPERTIES OF LIQUID CRYSTALS

在线全文

学校读者我要写书评

暂无评论

Chinese Journal of Polymer Science 1999年第2期17卷 193-196页

作者： Xiao-fang Chen Yao-wen Bai Yu-guo Ma Chen-hui Wang dong Zhang Xin-hua Wan Qi-feng Zhou department of Polymer Science and Engineering, College of Chemistry, peking university, beijing 100871, china 北京大学化学院北京 100871 北京大学化学院北京

Some diacetylene-containing copolyesters with different ratios of dipropargyl 1,10-decanate anddipropargyl terephthalate were synthesized. Properties of these copolymers were characterized by differentialscanning calorimetry and polarizing optical microscopy. The copolymer could be cross-linked easily by UVirradiation in a liquid crystal matrix without adding any photoinitiator. The preliminary studies showed thatthe diacetylene-containing polymer network can assist liquid crystal molecules to align with the externalelectric field, thus reducing the response time of display devices.

关键词： Diacetylene-containing copolyesters Polymer-stabilized liquid crystals Electo-optical of liquid crystals

A Discussion on Evolution of Microstructures and Influence Factors during Continuous Rolling of Compact Strip Production

在线全文

学校读者我要写书评

暂无评论

Journal of Materials Science & Technology 2004年第3期20卷 274-278页

作者： Hongbo dong Yonglin KANG Hao YU department of Materials Processing and Controlling, university of Science and Technology beijing, beijing 100083, china Dept. of Mat. Proc. and Control Univ. of Sci. and Technol. Beijing Beijing 100083 China

The evolution of microstructures and influence factors of ultrathin hot strips of low carbon steel produced by compactstrip production (CSP) techniques were investigated. The steel blocking samples of CSP six-passes were obtained,and microstructures at the different positions of workpiece for each pass were studied. At the same time, anexplicit finite element technique was used to reveal the continuous rolling process. By combining experiment resultswith simulation analysis, the effects of plastic strain, temperature, precipitation and interval time on evolution andrefinement of crystal grains have been investigated. The results are useful for the development of high strength hotstrips.

关键词： CSP Microstructure Strain Temperature Precipitation

A novel extended Kalman filter for a class of nonlinear systems

在线全文

学校读者我要写书评

暂无评论

Progress in Natural Science:Materials International 2006年第9期16卷 912-918页

作者： dong Zhe and YOU Zheng (department of Precision Instrument and Mechanology, Tsinghua university, beijing 100084, china) [a]department of Precision Instrument and Mechanology Tsinghua University Beijing China

Estimation of the state variables of nonlinear systems is one of the fundamental and significant problems in control and signal processing. A new extended Kalman filtering approach for a class of nonlinear discrete-time systems in engineering is presented in this paper. In contrast to the celebrated extended Kalman filter (EKF), there is no linearization operation in the design procedure of the filter, and the parameters of the filter are obtained through minimizing a proper upper bound of the mean-square estimation error. Simulation results show that this filter can provide higher estimation precision than that provided by the EKF.

关键词： nonlinear systems state estimation Kalman filtering.

VARIABLE NON-UNIFORM QUANTIZED BELIEF PROPAGATION ALGORITHM FOR LDPC DECODING

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Journal of Electronics(china) 2008年第4期25卷 539-543页

作者： Liu Binbin Bai dong Mei Shunliang department of Electronic Engineering Tsinghua University Beijing 100084 China department of Electronics Peking University Beijing 100871 China

Non-uniform quantization for messages in Low-Density Parity-Check(LDPC)decoding canreduce implementation complexity and mitigate performance *** the distribution of messagesvaries in the iterative *** letter proposes a variable non-uniform quantized Belief Propaga-tion(BP)*** BP decoding is analyzed by density evolution with Gaussian *** the probability density of messages can be well approximated by Gaussian distribution,by theunbiased estimation of variance,the distribution of messages can be tracked during the *** non-uniform quantization scheme can be optimized to minimize the *** resultsshow that the variable non-uniform quantization scheme can achieve better error rate performance andfaster decoding convergence than the conventional non-uniform quantization and uniform quantizationschemes.

关键词： Low-Density Parity-Check (LDPC) codes Iterative decoding Belief Propagation (BP) Non-uniform quantization

Thermodynamic Assessment of Reactions between Yttrium and Tramp Elements in Petroleum Pipe Steel

在线全文

学校读者我要写书评

暂无评论

International Journal of Minerals,Metallurgy and Materials 1998年第4期12卷 219-222页

作者： Aixue Sha Luren dong Shangyi Li( Metallurgy School, university of Science and Technology beijing, beijing 1 00083, china)(Science and Technology department, Metallurgical Industry Bureau of china, beijing 100711, china) Metallurgy School University of Science and Technology Beijing Beijing 100083 China Science and Technology department Metallurgical Industry Bureau of China Beijing 100711 China

In the thermodynamic evaluation Y was selected as a typical heavy rare earth metal for reducing the detrmental effects of tramp elements in the petroleum pipe steel. The possibilities of reactions between Y and trampelements such as Sn, Sb, As, etc. after deoxidation and desulphurization were estimated by calculating the Gibbsfree energies of formation. The equilibrium content of Y for eliminating the detrimental effects of tramp elements inthe steel was recommended from the results of thermodynamic calculation.

关键词： rare earth metals tramp elements thermodynamic calculation

Factors influencing intercellular spaces in the rat esophageal epithelium

在线全文

学校读者我要写书评

暂无评论

World Journal of Gastroenterology 2010年第9期16卷 1063-1069页

作者： dong-Hong Zhang,Li-Ya Zhou,Xiu-Yun dong,Rong-Li Cui,Yan Xue,San-Ren Lin,department of Gastroenterology,peking university Third Hospital,beijing 100191,china department of Gastroenterology Peking University Third Hospital No. 49 Huayuanbei Road Beijing 100191 China. liyazhou@***

AIM:To evaluate the effect of acute stress,hydrochloric acid,ethanol,aspirin,and prednisolone on the intercellular spaces of the esophageal ***:Part -RESULTS:(1) The f ive damaging factors produced no lesions or inflammation in esophageal mucosa of rats under either gross or routine histological *** epithelial intercellular space diameters in stress and aspirin groups were significantly greater,nearly three or two-fold respectively,than those in their corresponding control groups (stress model:0.38 ± 0.05 μm vs 0.13 ± 0.02 μm,P 0.05;ethanol model:0.25 ± 0.10 μm vs 0.19 ± 0.05 μm,P > 0.05;prednisolone model:0.20 ± 0.03 μm vs 0.14 ± 0.03 μm,P > 0.05);and (2) No significant difference in the intercellular space diameters was observed between the group pretreated with esomeprazole and the control group,in both the stress and aspirin models (stress model:0.35 ± 0.05 μm vs 0.37 ± 0.05 μm,P > 0.05;aspirin model:0.24 ± 0.02 μm vs 0.27 ± 0.03 μm,P > 0.05).CONCLUSION:Acute stress and aspirin can induce DIS of the esophageal epithelium in rats,and it is not correlated with acid reflux.

关键词： Esophagus Dilated intercellular spaces Stress,acute Aspirin Reflux,acid

Measurement of Monomer Reactivity Ratios of D,L-3-Methylglycolide with Glycolide or D,L-Lactide

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

Chinese Chemical Letters 2000年第9期11卷 815-818页

作者： Chang Ming dong Kun Yuan QIU Zhong Wei GU Xin De FENG department of Polymer Science and Engineering, College of Chemistry and Molecular Engineering, peking university, beijing 100871 National Research Institute for Family Planning, beijing 100081 peking Univ Coll Chem & Mol Engn Dept Polymer Sci & Engn Beijing 100871 Peoples R China Natl Res Inst Family Plannning Beijing 100081 Peoples R China

For monomer reactivity ratios study, the copolymerization of D,L-3-methylglycolide (MG) with glycolide (GA) or D,L-lactide (LA) was carried out in bulk to a certain low conversion in the presence of stannous octoate at 140 degrees C. The copolymer compositions were determined by H-1 NMR spectroscopy. The monomer reactivity ratios were evaluated by Fineman-Ross method, Kelen-Tudos method and linear least-squares method. The monomer reactivity ratios of D,L-3-methylglycolide and glycolide or D,L-lactide are r(mg)= 0.73, r(ga)= 1.47; r(mg)= 1.71, r(la)= 0.92, respectively.

关键词： D,L-3-methylglycolide glycolide D,L-lactide ring-opening copolymerization monomer reactivity ratios

HIGH TEMPERATURE OXIDATION AND STRUCTURE OF SCALE AND WHISKERS FOR Fe-Ni-Cr SEALING ALLOYS

在线全文

学校读者我要写书评

暂无评论

Acta Metallurgica Sinica(English Letters) 1993年第8期6卷 147-150页

作者： dong Zhili MA Jusheng TANG Xiangyun YOU Liang Tsinghua university,beijing,china lecturer department of Materials Science and Engineering,Tsinghua university,beijing 100084,china Tsinghua Univ Beijing China

The oxidation rate,the growth,morphology and structure of oxide scale and whiskers for Fe-Ni-Cr sealing alloys in H_2-H_2O atmosphere at high temperatures have been studied. The growth rate of scale is controlled by *... 详细信息

关键词： oxidation oxide scale oxide whisker Fe-Ni-Cr sealing alloy