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COLLISION OF WATER DROP ON WATER

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Acta Mechanica Sinica 1988年第4期4卷 297-304页

作者： Cai Yikun (department of physics,{2. university,International Centre for Materials physics,Academia Sinica) 1. department of physics Peking University International Centre for Materials Physics Academia Sinica Beijing China

A series of experiments are performed to study the collision of a water drop with variousimpact velocities,ranged from 0 to 600 cm/s,onto a water *** kinds of phenomena have *** of them named"penetration"and"cleavage",were observed for low impact velocity(up to100 cm/s).Their common characteristics are that no obvious disturbances on the surface were observedduring the coUiding *** no splashing jets nor obvious crater were *** penetrationwe mean that a drop fallen into water becomes a ring,which penetrates the water smoothly with a velocityof several centimeters per *** the penetrating process no obvious change of its configurationwas *** falling height corresponding to penetration is proportional to volume of the *** periodicity of the falhng heights(corresponding to penetration)was *** named"cleavage"occurs when the impact velocity is other than that corresponding topenetration,then the drop cleaves into an"inverted cauliflower"after falling below the surface of *** does not *** diffusing and slowly expanding it vanishes in the vessel water several *** two kinds of phenomena,as we know,have not been reported *** the impact velocityapproaches or exceeds 100 cm/s,the third kind of phenomena,the splash,*** diameter anddepth of the crater occuring in the case of splash,together with the time for the crater to reach itsmaximum size,and the time for the rebounding column to begin to rise are given as functions of the fallingheight of the drop.

关键词： splash water drop penetration water surface impact

Trend,seasonal and diurnal variations of atmospheric CO_2.in beijing

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Chinese Science Bulletin 2002年第24期47卷 2050-2055页

作者： WANG Yuesi, WANG Changke, GUO Xueqing, LIU Guangren & HUANG YaoLAPC, Institute of atmospheric physics, Chinese Academy of Sciences, {2. 100083, China department of Chemistry, Capital Normal {4., {2. 100037, China LAPC Institute of Atmospheric Physics Chinese Academy of Sciences Beijing China department of Chemistry Capital Normal University Beijing China

The concentration of atmospheric CO2.in beijing increased rapidly at a mean growth rate of 3.7%·a-1 from 1993 to 1995. After displaying a peak of ({2.9.7±2..9) μmol·mol-1 in 1995, it decreased slowly. Both the almost stable anthropogenic CO2.source and increasing biotic CO2.sink contribute to the drop of CO2.concentration from 1995 to 2.00. The seasonal variation of CO2.concentration exhibits a clear cycle with a maximum in winter, averaging ({2.6.8± 2..6)μmol·mol-1, and a minimum in summer, averaging (369.1±6.1)μmol·mol-1. The seasonal variation of CO2.concentration is mainly controlled by phenology. The mean diurnal variation of atmospheric CO2.concentration for a year in beijing is highly clear: daily maximum CO2.concentration usually occurs at night, but daily minimum CO2.concentration does in the daytime, with a mean diurnal difference more than 3{2.7μmol·mol-1. It has been revealed that the interannual variations of atmospheric CO2.concentration in winter and autumn regulated the

关键词： atmospheric CO2 annual variation seasonal variation diurnal variation urban environment.

FURTHER EVIDENCE FOR FA CENTERS IN BaFCL:Eu^(2.) CRYSTAL

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Chinese Chemical Letters 1993年第9期4卷 817-820页

作者： Wei CHEN department of Materials physics,{2. university of Science and Technology,{2. 100083Mian Zeng SU department of Chemistry,peking university,{2. 100871

The formation of color centers in BaFCl:Eu^(2.) crystal is studied in more de- tail and further evidence for FA centers in BaFCl:Eu^(2.)is *** creation of color centers in BaFCl:Eu^(2.)may be devided into three *** long time X-irradiation be- yond stage 1,the concentration of FA centers depends linearly on the nth(n=1,2.or 3) power of F center *** under short time X-irradiation within stage 1,the concentration dependence of FA centers on F center is *** centers are easier to create than complex *** mechanisms for color centers formation in BaFCl:Eu^(2.) are also proposed and discussed.

关键词： FA FURTHER EVIDENCE FOR FA CENTERS IN BaFCL CRYSTAL

Soil Properties in Two Soil Profiles from Terraces of the Nam Co Lake in Tibet,China

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Journal of Mountain Science 2009年第4期6卷 354-361页

作者： WANG Liqiang YI Chaolu Brigitta Sehiitt LIU Kexin ZHOU Liping Institute of Tibetan Plateau Research Chinese Academy of Sciences Beijing 100085 China department of Physical Geography Freie University of Berlin Berlin12249 Germany State Key Laboratory of Nuclear physics and Technology Peking University Beijing 100871 China College of Urban and Environmental Sciences Peking University Beijing100871 China

This article investigates the soil properties in two soil profiles from the terraces of the Nam Co Lake in Tibet,China. Profile 1,with a slope aspect to east,is 37 m,and profile 2.to southwest,is 32.m above the lake level. Twelve and nine layers were identified in profile 1 and profile 2.respectively,based on the color,texture,structure,moisture content,presence of carbonate,and root density. Grain sizes and measurements of water content,total organic carbon,total inorganic carbon,total carbon,pH value and electrical conductivity were all analyzed for each sample. The results show that soil is poorly developed because of sparse vegetation coverage and weak chemical weathering in the cold and arid area. The results also indicate that the soil properties are different between the two profiles and suggest that soil is better developed in profile 1 than in profile 2. These differences are ascribed to the dissimilarity of landform,vegetation and timing. Profile 1 faces to east as compared with profile 2.facing to southwest and gets less insolation and therefore less evaporation. Thus,vegetation grows better in profile 1 than in profile 2. Radiocarbon dating and OSL dating show that profile 1 underwent a longer soil forming process than profile 2.which is helpful for the soil development in profile 1.

关键词： Soil property Soil genesis Environmental change Marine isotope stage 3 (MIS 3)

On Hoava-Lifshitz cosmology

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Chinese physics C 2011年第5期35卷 429-435页

作者： CHEN Bin1) department of physics, and State Key Laboratory of Nuclear physics and Technology, peking university, {4. 100871, China department of physics and State Key Laboratory of Nuclear Physics and Technology Peking University

We give a brief overview of the Horava-Lifshitz-gravity theory, its modifications and its implications in cosmology. In particular, we discuss the various issues on the gravitational scalar mode, including its decoupling, its role as inflaton and its stability. Our analysis shows that the scalar mode could decouple naturally at λ = 1 due to the extra gauge symmetry. On the other hand, the fact that the scalar mode becomes ghost when 1/3 〈 λ 〈 1 is a real challenge to the theory. We try to overcome this problem by modifying the action such that the RG flow lies outside the problematic region. We discuss the cosmological implications of the theory.

关键词： Horava-Lifshitz-gravity cosmology ghost

Zircon and apatite fission track analyses on mineralization ages and tectonic activities of Tuwu-Yandong porphyry copper deposit in northern Xinjiang, China

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Science China Earth Sciences 2007年第12期50卷 1787-1795页

作者： YUAN WanMing1,BAO ZengKuan2.DONG JinQuan2.GUO ZhaoJie3 & DENG Jun1 1 State Key Laboratory of Geological Processes and Mineral Resources,China university of Geosciences,beijing100083,China 2.Laboratory of Nuclear Analysis Techniques,Institute of High Energy {2.,Chinese Academy of Sciences,beijing 100039,China 3 {4. of Geology,peking university,beijing 100871,China 1. State Key Laboratory of Geological Processes and Mineral Resources China University of Geosciences Beijing 100083 China 2. Laboratory of Nuclear Analysis Techniques Institute of High Energy Physics Chinese Academy of Sciences Beijing 100039 China 3. department of Geology Peking University Beijing 100871 China

The mineralization ages reported in the past in the Tuwu-Yandong copper district not only are different,but also fall into the Hercynian *** study has achieved 9 zircon and 7 apatite fission track analysis *** zircon fission track ages range from 158 Ma to 2.9 Ma and the apatite ages are between 64.Ma and 14. *** mineralization accords with the regional tectonics in the copper *** consider that the zircon fission track age could reveal the mineralization age based on annealing zone temperature of 14.―300℃ and retention temperature of ～2.0℃ for zircon fission track,and metallogenetic temperature of 12.―350℃ in this ore *** three mineralization epochs have been identified,i.e.,2.9―2.6 Ma,2.2.2.0 Ma and 165―158 Ma,and indicate occurrence of the min-eralization in the Indosinian and Yanshan *** to apatite fission track ages,the three tectonic-mineralizing epochs are 14.―132.Ma,109―97 Ma and 64.Ma,which means age at about 100℃ after the *** three epochs lasted 14. Ma,108 Ma and about 100 Ma from ～2.0℃ to ～100℃ and trend decrease from early to *** is shown by the fission track modeling that this district underwent three stages of geological thermal histories,stable in Cretaceous and cooling both before Cretaceous and after 2. Ma.

关键词： mineralization age, tectonic epoch, fission track, zircon, apatite, Tuwu-Yandong, Xinjiang

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

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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,{2. university,{4. 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

Beams of C2./sub>+-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 obtainingmaximum Cm+ cluster beam.

关键词： Carbon cluster Stripping Dissociation

Progress in studies of the climate of humid period and the impacts of changing precession in early-mid Holocene

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Progress in Natural Science:Materials International 2008年第12期18卷 1459-1464页

作者： Jianbin Huang~a Shaowu Wang~a Xinyu Wen~a Bao Yang~b a department of atmospheric Sciences,School of {2.,peking {4.,beijing 100871,China b Laboratory for Desert and Desertification,Cold and Arid Regions Environmental and Engineering Research Institute,Chinese Academy of Sciences,Lanzhou 730000,China [a]department of atmospheric Sciences School of Physics Peking University Beijing 100871 China [b]Laboratory for Desert and Desertification Cold and Arid Regions Environmental and Engineering Research Institute Chinese Academy of Sciences Lanzhou 730000 China

Studies on the climate of humid period and the impacts of changing precession in the early-mid Holocene are reviewed in this paper. High-resolution proxy data indicated that the African Humid Period,strong summer monsoon from the Arabian Sea to South Asia, northward migration of ITCZ (lntertropical Convergence Zone) over the northern South America,and the humid period of China appeared in 10.5-5.5 kaBP,10.0-6.0 kaBP,10.5 5.4.kaBP,and 11.0-8.0 kaBP,*** studies proved that summer inso- lation over the Northern Hemisphere increased following the changes of precession in the early Holocene,which increased the land-sea temperature contrasts,intensified the summer monsoon circulation in the Northern Hemisphere,and finally induced a humid climate over the area under the influence of summer ***,modeling results underestimated the increase of precipitation and the degree of northward extension of monsoon rain belt compared with palaeo-environmental *** discrepancies between the modeling results and the palaeo-environmental data may be associated with the changes of North Atlantic circulation,sea ice and veg- etation ***,climate of the humid period was not stable,in which several droughts were inlaid on centennial *** this review,perspectives for further studies of the climate change of the humid period in the early-mid Holocene are also proposed.

关键词： Holocene Humid period Precession Summer monsoon

A Parameterization of Bowen Ratio with Respect to Soil Moisture Availability

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Advances in atmospheric Sciences 1995年第4期12卷 449-474页

作者： Ye Zhuojia and Roger A. Pielke (Institute of atmospheric physics, Chinese Academy of Sciences, {2. 10002., China)(Colorado State university, {4. of atmospheric Science, Fort Collins, Colorado 8052., USA) Institute of atmospheric physics ChineseAcademyof Scienced Colorado Stateuniversity Department of Atmospheric Science

The Bowen ratio (B) is impacted by 5 environmental elements: soil moisture availabillity, m, the ratio of resistances between atmosphere and soil pores, atmospheric relative humidity, h,atmospheric stability, △T, and enviD ronment temperature. These impacts have been investigated over diverse surfaces, including bare soil, free water surface, and vegetation covered land, using an analytical approach. It was concluded that: (a) B is not a continuous function. The singularity exists at the condition αhcb = h, occurring preferably in the following conditions f weak turbulence, stable stratified stability, dry soil, and humid air, where hcb, defined by Eq.(11) is a critical variable. The existence of a singularity makes the dependence of B on the five variables very complicated. The value of B approaches being inversely proportional to m under the conditions m≥mfc (the soil capacity) and / *** proportional coefficient changes with season and latitude with relatively high values in winter and over the poles; (b) B is nearly independent of during the day. The impact of m on B is much larger as compared to that of on B; (c) when h increases, the absolute value of B also increases; (d) over bare soil,when the absolute surface net radiation increases, the absolute value of B will increase. The impact of RN on B is larger at night than during the day, and (e) over plant canopy, the singularity and the dependdes of B on m,rα, and h are modified as compared to that over bare *** (i) during the daytime unstable condition, m exerts an even stronger impact on B; at night, however,B changes are weak in response to the change in m; (ii) the value of B is much more sensitive in response to the changes of turbulent intensity; (iii) the B response to the variation of h over a vegetation covered area is weaker; and (iv) the singularity exists at the condition hcp=h instead of αhcb=h as over bare soil, where hcp is defined by Eq.({2.). The formulas derived over bare soil also hol

关键词： Bowen ratio parameterization Soil moisture availability Plant canopy