检索结果-南通市图书馆

Systematic distortion in cosmic microwave background maps

在线全文

学校读者我要写书评

暂无评论

Science china(Physics,Mechanics & Astronomy) 2009年第5期52卷 804-808页

作者： LIU Hao 1,3 &LI TiPei 1,2 1key laboratory of Particle Astrophysics,Institute of High energy Physics,chinese academy of sciences,beijing 100049,china 2Center for Astrophysics,Tsinghua University,beijing 100084,china 3 Graduate University of chinese academy of sciences,beijing 100049,china key laboratory of Particle Astrophysics Institute of High Energy Physics Chinese Academy of Sciences Beijing 100049 China Center for Astrophysics Tsinghua University Beijing 100084 China Graduate University of chinese academy of sciences Beijing 100049 China

To minimize instrumentally the induced systematic errors,cosmic microwave background(CMB)anisotropy experiments measure temperature differences across the sky using pairs of horn antennas, temperature map is recovered from temperature difference obtained in sky survey through a map-making *** inspect and calibrate residual systematic errors in the recovered temperature maps is important as most previous studies of cosmology are based on these *** analyzing pixel-ring coupling and latitude dependence of CMB temperatures,we find notable systematic devia- tion from CMB Gaussianity in released Wilkinson Microwave Anisotropy Probe(WMAP)*** detected deviation cannot be explained by the best-fit LCDM cosmological model at a confidence level above 99%and cannot be ignored for a precision cosmology study.

关键词： cosmology cosmic microwave background methods data analysis

Study on the atmospheric photochemical reaction of CF_3 radicals using ultraviolet photoelectron and photoionization mass spectrometer

在线全文

学校读者我要写书评

暂无评论

Science china Chemistry 2008年第4期51卷 316-321页

作者： YAO Li1,2, DU Lin1,2, YIN Shi1,2 & GE MaoFa1 1 beijing National laboratory for Molecular sciences (BNLMS), State key laboratory for Structural Chemistry of Unstable and Stable Species, Institute of Chemistry, chinese academy of sciences, beijing 100080, china 2 Graduate University of chinese academy of sciences, beijing 100080, china 1. beijing National laboratory for Molecular sciences (BNLMS) State Key Laboratory for Structural Chemistry of Unstable and Stable Species Institute of Chemistry Chinese Academy of Sciences Beijing 100080 China 2. Graduate University of chinese academy of sciences Beijing 100080 China

A study of the atmospheric photochemical reaction of CF3 radical with CO and O2 was performed by using a homemade ultraviolet photoelectron spectrometer-photoionization mass spectrometer (PES- PIMS). The electronic structures and mechanism of ionization and dissociation of CF3OC(O)OOC(O)- OCF3 were investigated. It was indicated that the two bands on the photoelectron spectrum of CF3OC(O)OOC(O)OCF3 are the result of ionization of an electron from a lone pair of oxygen and a fluo- rine lone pair of CF3 group. The outermost electrons reside in the oxygen lone pair. The experimental and theoretical first vertical ionization energy is 13.21 and 13.178 eV, respectively, with the PES and OVGF method. They are in good agreement. The photo ionization and dissociation processes were discussed with the help of theoretical calculations and PES-PIMS experiment. After ionization, the parent ions prefer the dissociation of the C-O bond and giving the fragments CF3OCO+ and CF3+. It demonstrated that the ultraviolet photoelectron and photoionization mass spectrometer could be ap- plied widely in the study of atmospheric photochemical reaction.

关键词： photochemical reaction CF3 radical ultraviolet photoelectron and photoionization mass spectroscopy transient species

A 12-bit multichannel ADC for pixel detectors in particle physics and nuclear imaging

在线全文

学校读者我要写书评

暂无评论

Science china(Technological sciences) 2010年第5期53卷 1208-1214页

作者： WEI Wei1,2,3,WANG Zheng1,3 & ZHAO JingWei1,3 1 Institute of High energy Physics,chinese academy of sciences,beijing 100049,china 2 Graduate University of chinese academy of sciences,beijing 100049,china 3 key Lab of Nuclear Detection Technology and Nuclear Electronics of chinese academy of sciences,beijing 100049,china 1. Institute of High energy Physics Chinese Academy of Sciences Beijing 100049 China2. Graduate University of Chinese Academy of Sciences Beijing 100049 China3. Key Lab of Nuclear Detection Technology and Nuclear Electronics of Chinese Academy of Sciences Beijing 100049 China

Modern pixel detectors in nuclear and particle physics experiments and also in nuclear imaging,starve for highly integrated application specified integrated circuit(ASIC),whereas in china the study of ASIC still stays far away from practical *** lack of ASIC strictly limits the research and development of domestic high energy physics field.A 12-bit multichannel ADC designed for high density readout is introduced as a major candidate for solution.A precise model is discussed and the simulation fully agrees with the model,which indicates a key principle of *** is performed according to the given rule,and novel layout techniques are carried *** results in all aspects are also obtained,showing an excellent real performance,which satisfies the practical requirement.

关键词： application specified integrated circuit high density readout Wilkinson ADC multi-channel ADC

Numerical study of successive CMEs during November 4―5, 1998

在线全文

学校读者我要写书评

暂无评论

Science china(Technological sciences) 2008年第10期51卷 1600-1610页

作者： ZHOU YuFen & FENG XueShang SIGMA Weather Group, State key laboratory for Space Weather, Center for Space Science and Applied Research, chinese academy of sciences, beijing 100190, china 1. SIGMA Weather Group State Key Laboratory for Space Weather Center for Space Science and Applied Research Chinese Academy of Sciences Beijing 100190 China

We present the solar-terrestrial transit process of three successive coronal mass ejections (CMEs) of November 4―5, 1998 originating from active region 8375 by using a time-dependent three-dimensional magnetohydrodynamics (MHD) simula-tion. These CMEs interacted with each other while they were propagating in inter-planetary space and finally formed a "complex ejecta". A newly developed SIP-CESE MHD model was applied to solve MHD equations numerically. The quiet solar wind was started from Parker-like 1D solar wind solution and the magnetic field map was calculated from the solar photospheric magnetic field data. In our simulation, the ejections were initiated using pulse in the real active region 8375. The interplanetary disturbance parameters, such as speed, direction and angular size of the expanding CME, were determined from the SOHO/LASCO data with the cone-model. We discussed the three-dimensional aspects of the propagation, in-teraction and merging of the three ejections. The simulated interplanetary shocks were compared with the nearby-Earth measurement. The results showed that our simulation could reproduce and explain some of the general features observed by satellite for the "complex ejecta".

关键词： complex ejecta three-dimensional MHD simulation SIP-CESE MHD model

Nonlinear interactions between gravity waves and background winds

在线全文

学校读者我要写书评

暂无评论

Progress in Natural Science:Materials International 2007年第6期17卷 639-644页

作者： Liu Xiao1,2 and Xu Jiyao1(1. State key laboratory for Space Weather, Center for Space Science and Applied Research, chinese academy of sciences, beijing 100080, china 2. Graduate University of chinese academy of sciences, beijing 100039, china) [a]State key laboratory for Space Weather Center for Space Science and Applied Research Chinese Academy of Sciences Beijing China [b]Graduate University of chinese academy of sciences Beijing China

Using the nonlinear propagating gravity waves (GW) model in the two-dimensional compressible atmosphere and the linear GW theory, the process of GW propagation in different background winds, e.g. the direction of the background wind is opposite to (dead wind) or the same as (tail wind) the direction of the horizontal phase velocity of GW, is studied. The results show that the dead wind prolongs the vertical wavelength and accelerates GW propagation. Therefore, GW propagates up to a higher height becomes instable in a short time and eventually induces an inverse jet flow. Then, the vertical wavelength is becoming short due to the nonlinear interactions between GW and the inverse jet flow. The vertical wavelength and group velocity decrease after GW propagates into the tail wind. The initial instable time is delayed. Although most of GW is trapped in the instable region, some of GW propagates above the instable region. Compared with GW propagation in the tail wind, the nonlinear interactions between GW and the dead wind are also strong. In contrast, the linear GW theory predicts that GW can propagate freely in the dead wind. The vertical wavelength simulated by the nonlinear numerical model is different from that predicted by the linear theory greatly after GW propagates into the dead wind.

关键词： gravity waves background winds vertical group velocity vertical wavelength nonlinear interactions.

Hyperconcentrated flows as influenced by coupled wind-water processes

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Science china Earth sciences 2005年第11期48卷 1990-2000页

作者： XU Jiongxin Institute of Geographical sciences and Natural Resources Research, chinese academy of sciences key laboratory of Water Cycle and Related Land Surface Processes, chinese academy of sciences, beijing 100101, china 1. key laboratory of Water Cycle and Related Land Surface Processes Chinese Academy of Sciences Institute of Geographical Sciences and Natural Resources Research Chinese Academy of Sciences 100101 Beijing China

Using data from more than 40 rivers in the middle Yellow River basin, a study has been made of the influence of coupled wind-water processes on hyperconcentrated flows. A simple “vehicle” model has been proposed to describe hyperconcentrated flows. The liquid phase of two-phase flows is a “vehicle”, in which coarse sediment particles are carried as solid-phase. The formation and characteristics of hyperconcentrated flows are closely related with the forma-tion and characteristics of this liquid-phase and solid-phase. Surface materials and geomorphic agents of the middle Yellow River basin form some patterns of combination, which have deep influence on the formation and characteristics of liquid- and solid-phases of hyperconcentrated flows. The combination of high percentages of relatively coarse material with low percentages of fine material appears in the area predominated by the wind process, where the supply of rela-tively coarse sediment is sufficient, but the supply of relatively coarse sediment is not. The com-bination of low percentages of relatively coarse material with high percentages of fine material appears in the area predominated by the water process, where the supply of fine sediment is sufficient, but the supply of fine sediment is not. In the area predominated by coupled wind-water processes appears the combination of medium percentages of coarse and fine materials, and thus both coarse and fine sediments are in relatively sufficient supply. The manner in which the mean annual sediment concentrations of liquid- and solid-phases vary with total suspended sediment concentration is different. With the increased total suspended sediment concentration, mean annual sediment concentration of liquid-phase increased to a limit and then remained constant; however, mean annual sediment concentrations of solid-phase in-creased continuously. Thus, the magnitude of total suspended sediment concentration depends on the supply conditions of relatively coarse sedime

关键词： river sediment, hyperconcentrated flows, liquid-solid two-phase flows, wind process, fluvial process, Yellow River

Effects of diatoms on reproduction and growth of marine copepods

在线全文

学校读者我要写书评

暂无评论

Progress in Natural Science:Materials International 2004年第10期14卷 1-7页

作者： ZHANG Guangtao 1,2 and SUN Song 1 (1.key laboratory of Marine Ecology&Environment sciences,Institute of Oceanology,chinese academy of sciences,Qingdao266071,china 2.Graduate School,chinese academy of sciences,beijing100039,china) chinese Acad Sci Inst Oceanol Key Lab Marine Ecol & Environm Sci Qingdao 266071 Peoples R China chinese Acad Sci Grad Sch Beijing 100039 Peoples R China

Two hot spots in marine ecology,deleterious effects of diatoms and feeding selectivity of copepods,as well as new progress on these two issues achieved in the recent ten years,are *** two issues are considered correlated *** and their metabolites can induce deleterious effects on growth,reproduction and development of copepods,including increase of mortality and decrease of egg production,hatching and growth *** negative effects,resulting from either chemical toxin or nutritional defi-ciency,can be conquered in natural environments by diverse *** is therefore concluded that deleterious effects of diatoms observed in laboratory or during blooming period are only a special case that accommodation of feeding strategy of copepods is *** under-stand their feeding strategy in natural environments is a prerequisite to explaining the mechanisms of deleterious effects caused by diatoms,and makes it possible to re-evaluate the energy flow in marine ecosystems.

关键词： diatoms copepod feeding strategy reproduction deleterious effects

Graphene-based hybrid materials and their applications in energy storage and conversion

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

chinese Science Bulletin 2012年第23期57卷 2983-2994页

作者： ZHOU Ding 1,2,CUI Yi 1,2 & HAN BaoHang 1,2 1 National Center for Nanoscience and Technology,beijing 100190,china 2 State key laboratory of Transducer Technology,chinese academy of sciences,Shanghai 200050,china National Center for Nanoscience and Technology State key laboratory of Transducer Technology Chinese Academy of Sciences

Graphene attracts more and more scientists and researchers owing to its superior electronic,thermal,and mechanical *** material scientists,graphene is a kind of versatile building blocks,and considerable progress has been made in recent ***-based hybrid materials have been prepared by incorporating inorganic species and/or cross-linking of organic species through covalent and/or noncovalent *** graphene-based hybrid materials show improved or excellent performance in various *** this review,we summarize the synthesis of graphene and graphene-based hybrid materials,and their applications in energy storage and conversion.

关键词： graphene hybrid material energy storage energy conversion

Compression behavior of Zr_(41)Ti_(14)Cu_(12.5)Ni_(10)Be_(22.5) bulk metallic glass up to 24 GPa

在线全文

学校读者我要写书评

暂无评论

Science china(Physics,Mechanics & Astronomy) 2005年第3期48卷 319-324页

作者： LI Gong 1, 2 , ZHAN Zaiji 2 , LIU Jing 3 , YUN Jinku 1 , SUN Liling 2 , LIU Riping 1 , ZHANG Jun 2 & WANG Wenkui 1, 2 1. key laboratory of Metastable Materials Science and Technology, Yanshan University, Qinhuangdao 066004, china 2. Center for Condensed Matter Physics, Institute of Physics, chinese academy of sciences, beijing 100080, china 3. BSRF, Institute of High energy Physics, chinese academy of sciences, beijing 100039, china 1. key laboratory of Metastable Materials Science and Technology Yanshan University 066004 Qinhuangdao China 2. Center for Condensed Matter Physics Institute of Physics Chinese Academy of Sciences 100080 Beijing China 3. BSRF Institute of High Energy Physics Chinese Academy of Sciences 100039 Beijing China

The compression of a Zr41Ti14Cu12.5Ni10Be22.5 bulk metallic glass (BMG) is investigated at room temperature up to 24 GPa using in-situ high pressure energy dispersive X-ray diffraction with a synchrotron radiation source. The pressure-induced structural relaxation is exhibited. It is found that below about 8 GPa, the existence of excess free volume contributes to the rapid structural relaxation, which gives rise to the rapid volumetric change, and the structural relaxation results in the structural stiffness under higher pressure.

关键词： bulk metallic glass, high pressure, structural relaxation, synchrotron radiation.