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Variation properties of ionospheric eclipse factor and ionospheric influence factor

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Progress in Natural Science:Materials International 2005年第6期15卷 573-576页

作者： ZHAO Chunmei 1,2.*, YUAN Yunbin1, OU Jikun1 and CHEN Jinping3(1. institute of Geodesy and Geophysics, chinese {2. of sciences, Wuhan 430077, china 2. Graduate School of chinese {2. of sciences, beijing 100039, china 3. department of Precision Instrument and Mechanology, tsinghua {12., beijing 100084, china) institute of Geodesy and Geophysics Chinese Academy of Sciences Wuhan 430077 China Graduate School of chinese academy of {2. Beijing 100039 China department of Precision Instrument and Mechanology Tsinghua University Beijing 100084 China

The concepts and calculation methods of ionospheric eclipse factor (IEF) and ionospheric influence factor (IFF) are further illustrated. The temporal and spacial variation properties of IEF and IFF are studied, which shows that the properties are influenced by the geographic position and season. The possibility of improving the precision of using GPS data to determine ionospheric delay based on the above variation properties is also analysed.

关键词： GPS ionospheric eclipse factor ionospheric influence factor.

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 {2.,beijing 100084,china 2.institute of Acoustics,chinese academy of sciences,beijing 100190,china department of Physics Tsinghua University Beijing China institute of Acoustics Chinese Academy of Sciences Beijing 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

Crystallization and preliminary X-ray studies of porcine kidney aminoacylase Ⅰ

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chinese Science Bulletin 1997年第20期42卷 1750-1752页

作者： ZHAOHaiyan, MENGWuyi, LIN Zhengjiong and ZHOU Haimeng1. National Laboratory of Biomacromolecules, institute of Biophysics, chinese {2. of sciences, beijing 100101, china 2. department of Biological Science and Biotechnology, tsinghua university, beijing 100084, china National Laboratory of Biomacromolecules Institute of Biophysics Chinese Academy of Sciences Beijing China department of Biological Science and Biotechnology Tsinghua University Beijing China

AMINOACYLASE Ⅰ（ACY-1）（E. C. 3. 5. 1. 14 ） participated in amino acid metabolism existingin mammalian kidney and microorganisms, and catalyzes reversible hydrolysis of acylaminoacids. ACY-1 consists of 772.amino acids, and the molecular weight is 85 500 daltons. It is adimeric metalloprotein having two Zn2. in the molecule. The nucleotide and the amino acid se-quence of porcine and human ACY-1 have been determined. The nucleotide sequence and

关键词： aminoacylase I crystallization preliminary crystallography.

Critical slope gradient for compulsory abandonment of farmland on the hilly Loess Plateau

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chinese Science Bulletin 1998年第5期43卷 409-412页

作者： TANG Keli+1, ZHANG Keli 1,2.and LEI Aling 1,3 1. institute of Soil and Water Conservation, chinese {2. of sciences, Yangling 712.00, china 2. department of Hydraulic Engineering, tsinghua university, beijing 100084, china 3. Water Resources C institute of Soil and Water Conservation Chinese Academy of Sciences Yangling China department of Hydraulic Engineering Tsinghua University Beijing China Water Resources Conservation Bureau of Yangtze River Ministry of Water Resources Wuhan China

Scientific evidence for the upper limit of farmland is proposed. Shallow gully erosion is one of erosion types distributed extensively on sloping farmland in the hilly regions of the Loess Plateau. Field observation and aerial photos interpretation, as well as laboratory experiments show that the shallow gully erosion occurring on the steeper farmland in the hilly regions of the Loess Plateau is an important factor leading to intensive erosion on slope, because of its extensive distribution and intensive runoff collection. The data on the formation, development and distribution of shallow gullies on sloping farmland indicate that critical slope gradient for shallow gully initiation ranges from 15 to 2. degrees with an average of 18.2.degrees. Therefore, it is suggested that critical slope gradient for compulsory abandonment of farmland on the hilly Loess Plateau should be kept within the critical slope gradient for shallow gully initiation to prevent shallow gully formation in order to control soil loss more effectively. But as the first step, the cultivation on the slopes with slope larger than 2. degrees where the maximum erosion occurs should be strictly forbidden.

关键词： hilly region of Loess Plateau upper limitation for farmland shallow gully erosion erosion dynamic.

Plant protein kinase genes induced by drought, high salt and cold stresses

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chinese Science Bulletin 2000年第13期45卷 1153-1157页

作者： LIU Qiang , ZHANG Yong & Chen Shouyi1. Deparlmenl of Biological Science and Biotechnology, tsinghua university, {2. 100084, china 2. department of Biological Science and Biotechnology, Slate Key Laboratory of Biomembrane and Membrane Biotechnology, tsinghua university, {2. 100084, china 3. institute of Genetics, {12. academy of sciences, {2. 100101, china department of Biological Science and Biotechnology Tsinghua University Beijing China department of Biological Science and Biotechnology State Key Laboratory of Biomembrane and Membrane Biotechnology Tsinghua University Beijing China institute of Genetics Chinese Academy of Sciences Beijing China

Drought, high salt and cold are three different kinds of environment stresses that severely influence the growth, development and productivity of crops. They all decrease the water state of plant cells, and consequently result in the harm of plant from water deficit. Several genes encoding protein kinases and induced by drought, high salt and low temperature have been isolated from Arabidopsis. These protein kinases include receptor protein kinase (RPK), MAP kinases, ribosomal-protein kinases and transcription-regulation protein kinase. The expression features of these genes and the regulatory roles of these protein kinases in stress response and signal transduction are discussed.

关键词： protein kinase environment stress signal transduction gene expression.

New evidence for lack of CMB power on large scales

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Science china(Physics,Mechanics & Astronomy) 2010年第3期53卷 567-570页

作者： LIU Hao1 & LI TiPei1,2.3 1 Key Laboratory of Particle Astrophysics, institute of High Energy Physics, chinese {2. of sciences, beijing 100049, china 2.department of Physics & Center for Astrophysics, tsinghua university, beijing 100084, china 3 department of Engineering Physics & Center for Astrophysics, tsinghua university, beijing 100084, china Key Laboratory of Particle Astrophysics Institute of High Energy Physics Chinese Academy of Sciences department of Physics & Center for Astrophysics Tsinghua University department of Engineering Physics & Center for Astrophysics Tsinghua University

A digitalized temperature map is recovered from the first light sky survey image published by the Planck team, from which an angular power spectrum of the cosmic microwave background (CMB) is derived. The amplitudes of the low multipoles (low-l) measured from the preliminary Planck power spectrum are significantly lower than those reported by the WMAP team. Possible systematical effects are far from enough to explain the observed low-l differences.

关键词： cosmology cosmic microwave background data analysis

A land surface model incorporated with soil freeze/thaw and its application in GAME/Tibet

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Science china Earth sciences 2006年第12期49卷 1311-1322页

作者： HU Heping1, YE Baisheng2. ZHOU Yuhua3 & TIAN Fuqiang1 1. department of Hydraulic Engineering, tsinghua {2., beijing 100084, china 2. Cold and Arid Regions Environmental and Engineering Research institute, chinese academy of sciences, Lanzhou 730000, china 3. department of Civil Engineering, Massachusetts institute of Technology, USA department of Hydraulic Engineering Tsinghua University Beijing China Cold and Arid Regions Environmental and Engineering Research institute Chinese Academy of Sciences Lanzhou China department of Civil Engineering Massachusetts Institute of Technology USA

Land surface process is of great importance in global climate change, moisture and heat exchange in the interface of the earth and atmosphere, human impacts on the environment and eco- system, etc. Soil freeze/thaw plays an important role in cold land surface processes. In this work the diurnal freeze/thaw effects on energy partition in the context of GAME/Tibet are studied. A sophisti- cated land surface model is developed, the particular aspect of which is its physical consideration of soil freeze/thaw and vapor flux. The simultaneous water and heat transfer soil sub-model not only reflects the water flow from unfrozen zone to frozen fringe in freezing/thawing soil, but also demon- strates the change of moisture and temperature field induced by vapor flux from high temperature zone to low temperature zone, which makes the model applicable for various circumstances. The modified Picard numerical method is employed to help with the water balance and convergence of the numerical scheme. Finally, the model is applied to analyze the diurnal energy and water cycle char- acteristics over the Tibetan Plateau using the Game/Tibet datasets observed in May and July of 1998. Heat and energy transfer simulation shows that: (i) There exists a negative feedback mechanism between soil freeze/thaw and soil temperature/ground heat flux; (ii) during freezing period all three heat fluxes do not vary apparently, in spite of the fact that the negative soil temperature is higher than that not considering soil freeze; (iii) during thawing period, ground heat flux increases, and sensible heat flux decreases, but latent heat flux does not change much; and (iv) during freezing period, soil temperature decreases, though ground heat flux increases.

关键词： land surface model,soil freeze/thaw,GAME/Tibet,simultaneous liquid,vapor and heat transfer.

Numerical exploration of new features on three-dimensional transition of a cylinder wake

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Science china Mathematics 2004年第z1期47卷 69-80页

作者： LING Guocan, XIONG Jun & ZHU KeqinState Key Laboratory of Nonlinear Mechanics, institute of Mechanics, chinese {2. of sciences, beijing 100080, china department of Engineering Mechanics, tsinghua university, beijing 100084, china State Key Laboratory of Nonlinear Mechanics Institute of Mechanics Chinese Academy of Sciences Beijing China department of Engineering Mechanics Tsinghua University Beijing China

The three-dimensional transition of the wake flow behind a circular cylinder is studied in detail by direct numerical simulations using 3D incompressible N-S equations for Reynolds number ranging from 2.0 to 300. New features and vortex dynamics of the 3D transition of the wake are found and investigated. At Re = 2.0, the flow pattern is characterized by mode A instability. However, the spanwise characteristic length of the cylinder determines the transition features. Particularly for the specific spanwise characteristic length linear stable mode may dominate the wake in place of mode A and determine the spanwise phase difference of the primary vortices shedding. At Re = 2.0 and 300 it is found that the streamwise vortices evolve into a new type of mode "dual vortex pair mode" downstream. The streamwise vortex structures switch among mode A, mode B and dual vortex pair mode from near wake to downstream wake. At Re = 2.0, an independent low frequency fm in addition to the vortex shedding frequency fs is identified. Frequency coupling between fm and fs occurs. These result in the irregularity of the temporal signals and become a key feature in the transition of the wake. Based on the formation analysis of the streamwise vorticity in the vicinity of cylinder, it is suggested that mode A is caused by the emergence of the spanwise velocity due to three dimensionality of the incoming flow past the cylinder. Energy distribution on various wave numbers and the frequency variation in the wake are also described.

关键词： cylinder, wake, 3D transition, Fourier-spectral-spectral-element method, direct numerical simulation (DNS).

Two mode photon bunching effect as witness of quantum criticality in circuit QED

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Science china(Physics,Mechanics & Astronomy) 2009年第12期52卷 1898-1905页

作者： AI Qing1,WANG YingDan2.LONG Guilu1,3 & SUN ChangPu4 1 department of Physics,{2. university,beijing 100084,china 2.department of Physics,university of Basel,Klingelbergstrasse 82.4056 Basel,Switzerland 3 {2. National Laboratory for Information Science and Technology,beijing 100084,china 4 institute of Theoretical Physics,chinese academy of sciences,beijing 100080,china department of Physics Tsinghua University Beijing China department of Physics University of Basel Basel Switzerland tsinghua National Laboratory for Information Science and Technology Beijing China institute of Theoretical Physics Chinese Academy of Sciences Beijing China

We suggest a scheme to probe critical phenomena at a quantum phase transition (QPT) using the quantum correlation of two photonic modes simultaneously coupled to a critical system. As an experimentally accessible physical implementation,a circuit QED system is formed by a capacitively coupled Josephson junction qubit array interacting with one superconducting transmission line resonator (TLR). It realizes an Ising chain in the transverse field (ICTF) which interacts with the two magnetic modes propagating in the TLR. We demonstrate that in the vicinity of criticality the originally independent fields tend to display photon bunching effects due to their interaction with the ICTF. Thus,the occurrence of the QPT is reflected by the quantum characteristics of the photonic fields.

关键词： quantum phase transition photon bunching circuit QED