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Systematic distortion in cosmic microwave background maps

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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 2.7} 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 China Graduate University of Chinese academy of sciences Beijing China center for Astrophysics Tsinghua University Beijing 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

The relationship between the canonical ENSO and the phase transition of the Antarctic oscillation at the quasi-quadrennial timescale

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Acta Oceanologica Sinica 2010年第6期29卷 26-34页

作者： LIU Changzheng XUE Feng National Climate center Beijing 100081 China LASG Institute of Atmospheric Physics Chinese Academy of Sciences Beijing 100029 China

A correlation analysis is performed to investigate the relationship between El Nino-Southern Oscillation （ENSO） and the Antarctic oscillation （AAO） at the quasi-quadrennial （QQ） *** is found that the cold tongue index （CTI） and the AAO index （AAOI） are negatively correlated with about a 7-month lead-time,while they are positively correlated with about a 15-month *** further explore this relationship,complex empirical orthogonal function analysis is employed in the QQ sea level pressure （SLP） anomalies from 1951 to *** results indicate that,during the ENSO cycle,there exists one kind of global tropical wave of wavenumber 1 （GTW1） propagating *** the traveling of GTW1,the tropical SLP anomaly tends to intrude into the southern ***,three strong signals travel synchronously along the circumSouth-Pacific path,and a relatively weak signal extends eastward and poleward over the South Ocean in the Atlantic-Indian Ocean *** the propagation of these signals,the AAO phase tends to be reversed *** a result,there exists an evident lead-lag correlation between CTI and *** can be concluded that ENSO plays a key role in the phase transition of AAO at the QQ *** is also noticed that this regular relationship is only evident in the canonical ENSO events,for which sea surface temperature （SST） anomalies extend westward from the tropical eastern *** the other hand,the similar relationships are not found among those atypical ENSO events for which SST anomalies spread eastward from the central Pacific,such as the 1982.1983 ENSO event.

关键词： ENSO Antarctic oscillation the quasi-quadrennial timescale the global tropical wave of wavenumber 1

Summer Arctic sea fog

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Acta Oceanologica Sinica 2001年第2期20卷 183-196页

作者： Xie Simei, Xue Zhenhe, Jiang Dezhong, Zou Bin, Qu Shaohou (1. National Research center for Marine Environment Forecasts, beijing 100081,{2. 2. institute of Atmospheric physics, Chinese academy of sciences, beijing 10002.,{2.) Natl. Res. Ctr. for Marine Envrn. Fo Beijing 100081 China

Synchronous or quasi-synchronous sea-land-air observations were conducted using advanced sea ice, atmospheric and marine instruments during china's First Arctic Expedition. *** on the Precious data from the expedition, it was found that in the Arctic Ocean, most part of which is covered with ice or is mixed with ice, various kinds of sea fog formed such as advection fog, radiation fog and vapor fog. Each kind he its own characteristic and mechanics of creation. In the southern part of the Arctic Ocean, due to the sufficient warm and wet flow there, it is favorable for advection fog to form, which is dense and lasts a long time. On ice cap or vast floating ice, due to the strong radiation cooling effect, stable radiating fog is likely to form. In floating ice area there forms vapor fog with the appearance of masses of vapor from a boiling pot, which is different from short-lasting land fog. The study indicates that the reason why there are many kinds of sea fog form in the Arctic Ocean is because of the complicated cushion and the consequent sea-air interaction caused by the sea ice distribution and its unique physical characteristics. Sea fog is the atmospheric phenomenon of sea-air heat exchange. Especially, due to the high albedo of ice and snow surface, it is diffcult to absorb great amount of solar radiation during the polar days. Besides, ice is a poor conductor of heat; it blocks the sea-air heat exchange. The sea-air exchange is active in floating ice area where the ice is broken. The sea sends heat to the atmosphere in form of latent heat; vapor fog is a way of sea-air heat exchange influencing the climate and an indicator of the extent of the exchange. The study also indicates that the sea also transports heat to the atmosophere in form of sensible heat when vapor fog occurs.

关键词： Arctic sea fog vapor fog radiation fog advection fog mechanism of the creation of sea fog

Morphologies of Fe-66.7 at.%Si alloy solidified in a drop tube

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Science china(physics,Mechanics & Astronomy) 2005年第6期48卷 658-666页

作者： WANG Haiyan1,2. LIU Riping1, MA Mingzhen1, JING Qin1, LI Gong1, SUN Liling2.& WANG Wenkui1,2.1. Key Laboratory of Metastable Materials Science & Technology, Yanshan University, Qinhuangdao 066004, china 2. institute of physics, Chinese {2. of sciences, beijing 100080, china Key Laboratory of Metastable Materials Science & Technology Yanshan University Qinhuangdao China institute of physics Chinese Academy of Sciences Beijing China

Solidification of 0.1―1.0 mm diameter droplets of Fe-66.7 at.%Si alloy was achieved in a 3 m drop tube. The XRD, EDS, and SEM measurements reveal that all the droplets are composed of the primary phase α and the α+ε eutectic. With decreasing droplet diameter, the growth mode of the primary phase α changes from faceted to nonfaceted growth and the eutectic changes from needle-like to anomalous eutectic. In addition, the width of the primary phase α decreases with decreasing droplet size. The different cooling rates and undercooling levels corresponding to the samples with different sizes are responsible for the morphology changes. The cooling rates of the samples with different diameters during free fall were calculated and their effects on the microstructure formation were discussed. This kind of transition is also found inside the same sample, which is due to the larger cooling rate on the surface than at the center.

关键词： Fe-Si alloy, solidification, drop tube, undercooling.

Band gap anomaly and topological properties in lead chalcogenides

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Chinese physics B 2016年第3期25卷 27-34页

作者：聂思敏许霄琰徐刚方忠 beijing National Laboratory for condensed {2. physics and Institute of Physics Chinese Academy of Sciences Beijing 1O0190 China Collaborative Innovation center of Quantum matter Beijing 100084 China

Band gap anomaly is a well-known issue in lead chalcogenides PbX （X = S, Se, Te, Po）. Combining ab initio calculations and tight-binding （TB） method, we have studied the band evolution in PbX, and found that the band gap anomaly in PbTe is mainly related to the high on-site energy of Te 5s orbital and the large s-p hopping originated from the irregular extended distribution of Te 5s electrons. Furthermore, our calculations show that PbPo is an indirect band gap （6.5 meV） semiconductor with band inversion at L point, which clearly indicates that PbPo is a topological crystalline insulator （TCI）. The calculated mirror Chern number and surface states double confirm this conclusion.

关键词： band gap anomaly lead chalcogenides indirect band gap semiconductor topological crystallineinsulator

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. 100084, china 2. center of Quantum Information Science and Technology, Tsinghua National Laboratory for information Science and Technology, {2. 100084, china 3. institute of physics, School of sciences, {2. University of Posts and Telecommunications, {2. 100876, china) Key Laboratory for Atomic and Molecular Nanosciences and Department of Physics Tsinghua University Beijing 100084 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.

Forecasting the summer rainfall in North china using the year-to-year increment approach

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Science china Earth sciences 2009年第4期52卷 532-539页

作者： FAN Ke1, LIN MeiJing1,2.& GAO YuZhong3 1 Nansen-Zhu International Research center, institute of Atmospheric {2., Chinese academy of sciences, beijing 10002., china 2.Graduate University of the Chinese academy of sciences, beijing 100049, china 3 Heilongjiang Meteorological Administration, Harbin 150030, china Nansen-Zhu International Research center Institute of Atmospheric Physics Chinese Academy of Sciences Beijing China Graduate University of the Chinese academy of sciences Beijing China Heilongjiang Meteorological Administration Harbin China

A new approach to forecasting the year-to-year increment of rainfall in North china in July-August (JA) is proposed. DY is defined as the difference of a variable between the current year and the preceding year (year-to-year increment). NR denotes the seasonal mean precipitation rate over North china in JA. After analyzing the atmospheric circulation anomalies associated with the DY of NR, five key predictors for the DY of NR have been identified. The prediction model for the DY of NR is established by using multi-linear regression method and the NR is obtained (the current forecasted DY of NR added to the preceding observed NR). The prediction model shows a high correlation coefficient (0.8) between the simulated and the observed DY of NR throughout period 1965-1999, with an average relative root mean square error of 19% for the percentage of precipitation rate anomaly over North china. The prediction model makes a hindcast for 2.00-2.07, with an average relative root mean square error of 2.% for the percentage of precipitation rate anomaly over North china. The model reproduces the downward trend of the percentage of precipitation rate anomaly over North china during 1965-2.06. Because the current operational prediction models of the summer precipitation have average forecast scores of 60%-70%, it has been more difficult to forecast the summer rainfall over North china. Thus this new approach for predicting the year-to-year increment of the summer precipitation (and hence the summer precipitation itself) has the potential to significantly improve operational forecasting skill for summer precipitation.

关键词： annual increment North china precipitation prediction prediction skill

MOLECULAR SIMULATION STUDY ON THE CHANGE OF POLYMER STRUCTURE DURING YIELDING

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Chinese Journal of Polymer Science 2001年第5期19卷 527-529页

作者： Chen-guang Xu Tai-ning Liang Juan Sun Xiao-zhen Yang State Key Laboratory of Polymer physics and Chemistry center for Molecular Science, {2. of Chemistry Chinese academy of sciences, beijing 100080 china 中科院化学所高分子物理与化学国家重点实验室北京

A better understanding of a recently raised argument on whether there occurs a structure change during yielding has been acquired by using molecular simulation. That is, when monitoring the displacements of all atoms before and after the yield, a structure transition does occur, which is the 'atomic jump' that coordinates the amount of the atoms in the polymer and makes a large step beyond similar to0.05 nm for all those atoms. Results indicate that the complex of polymer chain packing induces the multiple atomic jumps around the yield point. This explains why polymers have a broader yielding peak.

关键词： polymer deformation yield structure transition atomic jump multiple yields

Sea surface temperature east of Australia:A predictor of tropical cyclone frequency over the western North Pacific?

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Chinese Science Bulletin 2011年第2期56卷 196-201页

作者： ZHOU BoTao 1,2.& CUI Xuan 3 1 National Climate center,china Meteorological Administration,{2. 100081,china 2.Nansen-Zhu International Research center,institute of Atmospheric physics,Chinese academy of sciences,{2. 10002.,china 3 National Meteorological center,china Meteorological Administration,{2. 100081,china National Climate center China Meteorological Administration Beijing China Nansen-Zhu International Research center Institute of Atmospheric Physics Chinese Academy of Sciences Beijing China National Meteorological center China Meteorological Administration Beijing China

The relationship between sea surface temperature (SST) east of Australia and tropical cyclone frequency over the western North Pacific (WNPTCF) is analyzed by use of observation *** WNPTCF from June to October is correlated negatively to spring SST east of *** the spring SST is in the positive phase,a cyclonic circulation anomaly in the upper troposphere and an anticyclonic circulation anomaly in the lower troposphere prevail over the western North Pacific from June to October,concurrent with an anomalous atmospheric subsidence and an enlarged vertical zonal wind *** conditions are unfavorable for tropical cyclone genesis,and thus WNPTCF *** negative phase of the spring SST east of Australia leads to more tropical cyclones over the western North *** spring SST east of Australia may give rise to simultaneous change in tropical atmospheric circulation via the teleconnection wave train,and then subsequently affect atmospheric circulation variation over the western North Pacific.

关键词：热带气旋北太平洋澳大利亚西部海面温度热带大气环流预测频率