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Electroluminescent properties of three ternary europium complexes with different phenanthroline derivatives

Science china chemistry 2004年第4期47卷 326-334页

作者： BIAN Zuqiang1,2. GAO Deqing1, GUAN Min1, XIN Hao1, LI Fuyou1, HUANG Chunhui1, WANG Kezhi2.& JIN Linpei2.1. State Key Laboratory of Rare Earth Materials chemistry and Applications, Peking University, beijing 100871,{2. 2. department of chemistry, beijing Normal University, beijing 100875,{2. 1. State Key Laboratory of Rare Earth Materials chemistry and Applications Peking University 100871 Beijing China 2. department of chemistry Beijing Normal University 100875 Beijing China

Three ternary Eu(III) complexes with general formula of Eu(DBM)3LN (DBM = dibenzoylmethanate, and LN (N = 1-3 ) stand for three different 1,10-phenanthroline derivatives) have been synthesized for vacuum deposition films-based electroluminescent devices. The complex Eu(DBM)3L3 (L3 = 2.phenyl-3-[3-(carbazol-9-yl)propyl]imidazo[4,5-f]1,10-phenan-throline) was designed with an effort to combine the electron-transporting phenanthroline platform and the hole-transporting carbazole group into one molecule expecting to improve both electron and hole transporting properties simultaneously. The results show that the variation of the neutral ligands in Eu(III) mixed ligand complexes is a simple and effective approach to the improvement in the thermal stability, PL and EL properties of materials. A double-layer device with the configuration of ITO/TPD (50 nm)/Eu(DBM)3L3 (50 nm)/Mg0.9Ag0.1 (2.0 nm)/Ag (100 nm) exhibited Eu(III)-based pure red emission with a maximum brightness of 561 cd/m2.at 16 V, and an onset driving voltage of 8 V. A device with the configuration of ITO/TPD (50 nm)/[Eu(DBM)3L3 (5 nm):BCP (5 nm)]4/BCP (2. nm)/AIQ (10 nm) Mg0.9Ag0.9 (110 nm)/Ag (100 nm) gave high efficient and pure red light emission with a luminance of 1419 cd/m2. Keywords dibenzoylmethane - electroluminescence - lanthanide - N ligands

关键词： dibenzoylmethane electroluminescence lanthanide N ligands

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Investigation on extremal and critical characteristics of ignition time for H_2.O_2.combustion system and their applications

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Science china(Technological Sciences) 2009年第5期52卷 1161-1166页

作者： CHEN JianHua1,ZHANG HuiQiang2.LI ZhuoYi2.& ZHANG GuiTian1 1 School of Aerospace,North Western Polytechnical University,Xi’an 710072.china 2.department of Engineering Mechanics,{2. University,beijing 100084,china School of Aerospace North Western Polytechnical University Xi’an 710072 China department of Engineering Mechanics Tsinghua University Beijing 100084 China

The L,H and C curves in P-T phase are proposed to describe the minimal,maximal and critical char-acteristics of ignition time of H2.O2.combustion system,*** features of H2.O2.Air) com-bustion system,including explosion or not as well as the time delay to achieve its explosion status,can be well shown by explosion limits and these proposed *** curves can be described by 1.2.1=ks[Ms],(k11/k10+1)k1=ks[Ms],and 2.1=ks[Ms],respectively,which provide a physical explanation for these curves and give another way to establish *** on the contour of ignition time,the Z-type explosion limits can be explained by thermal explosion ***,the ignition distance of supersonic combustion is predicted according to the ignition time obtained in a Semenov system,which is very reasonable.

关键词： ignition time thermal explosion detailed reaction mechanism Semenov system supersonic combustion

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Effect of acid oxidization of carbon nanotube electrode on the capacitances of double layer capacitors

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Science china(Technological Sciences) 2004年第3期47卷 257-264页

作者： Li Chensha1,WANG Dazhi1,LIANG Tongxiang2.WANG Xiaofeng1 & LIANG Ji1 1. department of Mechanical Engineering, tsinghua University,{2. 100084, china 2. Institute of Nuclear Energy Technology, tsinghua University,Beijng 102.01,china tsinghua Univ Dept Mech Engn Beijing 100084 Peoples R China tsinghua Univ Inst Nucl Energy Technol Beijing 102201 Peoples R China

Polarizable electrode of electric double layer capacitor was made from carbon nanotubes. The effect of acid oxidation of electrode on the specific capacitance was studied. Oxidation removed the redundant carbon, expanded the pore size and introducedf some kinds of functional groups on the surface of CNTs. The specific capacitance of the electrodes winth organic electrolyte was increased from 2..4 to 49.6 F/g after being oxidized at a volume ratio H2.O4 to HNO3 of 3:1.

关键词： carbon nanotubes, electric double layer capacitor, specific capacitance.

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Calculation of light emission in sonoluminescence

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Science china(Physics,Mechanics & Astronomy) 2009年第4期52卷 593-601页

作者： LI ChaoHui1 & AN Yu1,2.1 department of Physics,tsinghua University,{2. 100084,china 2.Institute of Acoustics,Chinese Academy of Sciences,{2. 100190,china department of Physics Tsinghua University Beijing 100084 China Institute of Acoustics Chinese Academy of Sciences Beijing 100190 China

We modify a uniform model of single bubble sonoluminescence,in which heat diffusion,water vapor diffusion and chemical reactions are included to describe the bubble dynamics,and the processes of electron-atom bremsstrahlung,electron-ion bremsstrahlung and recombination radiation,radiative attachment of electrons to atoms and molecules,line emissions of OH radicals and Na atoms are taken into account to calculate the light emission. With this model,we compute the light pulse width,the photon number per flash,the continuum and line spectra and the gas species as the products of chemical reactions,and try to compare with all the experimental data available. We obtain good agreement with the observations of Ar and Xe bubbles in many cases,but fail to match the experimental data of the photon number per flash. We also find that for He bubble the computed photon number is always too small to interpret the observations.

关键词： sonoluminescence bremsstrahlung radiative attachment line spectrum collision broadening

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Microwave-assisted reaction of peptide formation by amino acid with phosphate:Exploration of the most possible channels for the origin of life

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Science china chemistry 2006年第4期49卷 351-356页

作者： HU Rong1, TIAN Jinping2.& YIN Yingwu2.3 1. College of chemistry & Environment Protection Engineering, Southwest University for Nationalities, Chengdu 610041, china 2. TH-UNIS Insight Co., Ltd., {2. 100085, china 3. Key Laboratory of Bioorganic Phosphorus chemistry & Chemical Biology, Ministry of Education, department of chemistry, tsinghua University, beijing 100084, china 1. College of chemistry & Environment Protection Engineering Southwest University for Nationalities Chengdu 610041 China 2. TH-UNIS Insight Co. Ltd. Beijing 100085 China 3. Key Laboratory of Bioorganic Phosphorus chemistry & Chemical Biology Ministry of Education Department of Chemistry Tsinghua University Beijing 100084 China

Microwave-assisted reaction of peptide formation by amino acids with phosphate was studied. The results showed that the products were a mixture of peptides containing dipeptide, oc- tapeptides and cyclic peptides, which could be obtained in a short time. Polyphosphate was also produced synchronously by the intermolecular condensation of phosphate. The polymerization de- gree reached 99% (pyrophosphate 64%, trimetaphosphate 35%) after 2.h at 2.0℃ under microwave irradiation. The intermediates of the mixed anhydrides formed by the intermolecular condensation of phosphates and glycin were determined by ESI-MS. Peptides were also produced by the reaction of amino acids with trimetaphosphate in aqueous solution. The conversion degree of valine reached 46.5% even at room temperature. The cyclic process of peptide formation and phosphate polymeri- zation, regeneration and utilization in amino acids-phosphate system under microwave irradiation was detected and proved. Peptides could be continually formed only by inputting energy into this system. The above recycle may be the most possible process for primitive peptide formation in the origin of life.

关键词： microwave, phosphate, amino acid, peptide, origin of life.

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Influence of magnetic current on the ground state entanglement in an isotropic transverse XY chain

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Progress in Natural Science:Materials International 2007年第10期17卷 1147-1151页

作者： Liu Dan1,2., Zhang Yong3 and Long Guilu1,2.1. Key Laboratory for Atomic and Molecular NanoSciences, and department of Physics, tsinghua University,{2., china 2. Center of Quantum Information Science and Technology, tsinghua National Laboratory for information Science and Technology,{2., china 3. Institute of Physics, School of Sciences, beijing University of Posts and Telecommunications, beijing 100876, china) Key Laboratory for Atomic and Molecular NanoSciences and Department of Physics Tsinghua University Beijing 100084 China Center of Quantum Information Science and Technology Tsinghua National Laboratory for information Science and Technology Beijing 100084 China Institute of Physics School of Sciences Beijing University of Posts and Telecommunications Beijing 100876 China

We study the ground state entanglement in a three-qubit XY chain under the influence of a magnetization current. It is found that the ground state changes from a W state to a disentangled state as the magnetic field varies. When the Lagrange multiplier λ>3, namely under a strong magnetic current, the ground state holds onto a W state for a large range of the magnetic field strength. A phase transition to the magnetization-current phase occurs under a certain condition.

关键词： Heisenberg-XY chain magnetic-current phase transition.

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SOME PROPERTIES OF LSQR FOR LARGE SPARSE LINEAR LEAST SQUARES PROBLEMS

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Journal of Systems Science & Complexity 2010年第4期23卷 815-821页

作者： Zhongxiao JIA department of Mathematical Sciences,tsinghua University,{2. 100084,china. department of Mathematical Sciences Tsinghua University

It is well-known that many Krylov solvers for linear systems,eigenvalue problems,andsingular value decomposition problems have very simple and elegant formulas for residual *** not only allow us to further understand the methods theoretically but also can be usedas cheap stopping criteria without forming approximate solutions and residuals at each step beforeconvergence takes *** for large sparse linear least squares problems is based on the Lanczosbidiagonalization process and is a Krylov ***,there has not yet been an analogouslyelegant formula for residual *** paper derives such kind of *** addition,the authorgets some other properties of LSQR and its mathematically equivalent CGLS.

关键词： CGLS krylov subspace lanczos bidiagonalization least squares lsqr normal equations.

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Numerical simulation of air-water two-phase flow over stepped spillways

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Science china(Technological Sciences) 2006年第6期49卷 674-684页

作者： CHENG Xiangju1, CHEN Yongcan1 & LUO Lin2.1. department of Hydraulic Engineering, tsinghua University,{2., china 2. State Key Laboratory of Hydraulics and Mountain River Engineering, Sichuan University, Chengdu 610065, china department of Hydraulic Engineering Tsinghua University Beijing 100084 China State Key Laboratory of Hydraulics Mountain River Engineering Sichuan University Chengdu 610065 China

Stepped spillways for significant energy dissipation along the chute have gained interest; popularity among researchers; dam engineers. Due to the complexity of air-water two-phase flow over stepped spillways, the finite volume computational fluid dynamics module of the FLUENT software was used to simulate the main characteristics of the flow. Adopting the RNG k- turbulence model, the mixture flow model for air-water two-phase flow was used to simulate the flow field over stepped spillway with the PISO arithmetic technique. The numerical result successfully reproduced the complex flow over a stepped spillway of an experiment case, including the interaction between entrained air bubbles; cavity recirculation in the skimming flow regime, velocity distribution; the pressure profiles on the step surface as well. The result is helpful for understanding the detailed information about energy dissipation over stepped spillways.

关键词： stepped spillway, mixture model, RNG k-εmodel, air-water two-phase flow.

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Droplet creator based on electrowetting-on-dielectric for lab on a chip

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Science china(Technological Sciences) 2006年第2期49卷 248-256页

作者： ZENG Xuefeng1, YUE Ruifeng1, WU Jiangang1, HU Huan1, DONG Liang1, WANG Zheyao1, HE Feng2.& LIU Litian1 1. Institute of Microelectronics, tsinghua University, beijing 100084,{2. 2. department of Engineering Mechanics, tsinghua University, beijing 100084,{2. 1. Institute of Microelectronics Tsinghua University Beijing 100084 China 2. department of Engineering Mechanics Tsinghua University Beijing 100084 China

Electrowetting-on-dielectric (EWOD) is to directly control the wettability of liquids on the solid surface by applying the electric potential to the microelectrode array under the dielectric layer. The prototype of the EWOD droplet creator with the sandwiched structure is used: the droplet is sandwiched between the top and bottom plates; the bot- tom plate consists of silicon used as the substrate of the microelectrode array, nitride sili- con film deposited by low pressure chemical vapor deposition as the dielectric layer and the fluorocarbon polymer film deposited by inductively coupled plasma chemical vapor deposition as the hydrophobic layer; and the top plate is the transparent electrode covered with the hydrophobic layer. To obtain the required minimum voltage, the process and the criterion of creating droplets are analyzed. At the voltage of 35 V the deionized water droplet surrounded in silicone oil is successfully created.

关键词： micro total analysis system, electrowetting-on-dielectric, creation and control of droplets, inductively coupled plasma chemical vapor deposition.

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Gas kinetic algorithm for flows in Poiseuille-like microchannels using Boltzmann model equation

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Science china(Physics,Mechanics & Astronomy) 2005年第4期48卷 496-512页

作者： LI Zhihui1,2. ZHANG Hanxin1 & FU Song2.⒈ National Laboratory for CFD, Hypervelocity Aerodynamics Institute,china Aerodynamics Research and Development Center,Mianyang 62.000,china 2.{2. of Engineering Mechanics,tsinghua University,beijing 100084,china 1. National Laboratory for CFD Hypervelocity Aerodynamics Institute China Aerodynamics Research and Development Center 621000 Mianyang China 2. department of Engineering Mechanics Tsinghua University 100084 Beijing China

The gas-kinetic unified algorithm using Boltzmann model equation have been extended and developed to solve the micro-scale gas flows in Poiseuille-like micro-channels from Micro-Electro-Mechanical Systems (MEMS). The numerical modeling of the gas kinetic boundary conditions suitable for micro-scale gas flows is presented. To test the present method, the classical Couette flows with various Knudsen numbers, the gas flows from short microchannels like plane Poiseuille and the pressure-driven gas flows in two-dimensional short microchannels have been simulated and compared with the approximate solutions of the Boltzmann equation, the related DSMC results, the modified N-S solutions with slip-flow boundary theory, the gas-kinetic BGK-Burnett solutions and the experimental data. The comparisons show that the present gas-kinetic numerical algorithm using the mesoscopic Boltzmann simplified velocity distribution function equation can effectively simulate and reveal the gas flows in microchannels. The numerical experience indicates that this method may be a powerful tool in the numerical simulation of micro-scale gas flows from MEMS.

关键词： Boltzmann model equation, discrete velocity ordinate method, finite-difference scheme, Couette flow, Poiseuille flow, gas flow in short-microchannel.

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