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| 1 | Information entropy for ordinal classification显示文摘Ordinal classification plays an important role in various decision making tasks.However, little attention is paid to this type of learning tasks compared with general classification learning.Shannon information entropy and the derived measure of mutual information play a fundamental role in a number of learning algorithms including feature evaluation, selection and decision tree construction.These measures are not applicable to ordinal classification for they cannot characterize the consistency of monotonicity in ordinal classification.In this paper, we generalize Shannon's entropy to crisp ordinal classification and fuzzy ordinal classification, and show the information measures of ranking mutual information and fuzzy ranking mutual information.We discuss the properties of these measures and show that the proposed ranking mutual information and fuzzy ranking mutual information are the indexes of consistency of monotonicity in ordinal classification.In addition, the proposed indexes are used to evaluate the monotonicity degree between features and decision in the context of ordinal classification. | HU QingHua GUO MaoZu YU DaRen LIU JinFu | 2010 | Science China(Information Sciences)2010，53，6： | 29 |
| 2 | The TanSat mission: preliminary global observations显示文摘The Chinese global carbon dioxide monitoring satellite (Tan Sat) was launched successfully in December2016 and has completed its on-orbit tests and calibration. Tan Sat aims to measure the atmospheric column-averaged dry air mole fractions of carbon dioxide (XCO_2) with a precision of 4 ppm at the regional scale, and in addition, to derive global and regional CO2fluxes. Progress towards these objectives is reviewed and the first scientific results from Tan Sat measurements are presented. Tan Sat on-orbit tests indicate that the Atmospheric Carbon dioxide Grating Spectrometer is in normal working status and is beginning to produce L1B products. The preliminary Tan Sat XCO_2products have been retrieved by an algorithm and compared to NASA Orbiting Carbon Observatory-2 (OCO-2) measurements during an overlapping observation period. Furthermore, the XCO_2retrievals have been validated against eight groundsite measurement datasets from the Total Carbon Column Observing Network, for which the preliminary conclusion is that Tan Sat has met the precision design requirement, with an average bias of 2.11 ppm.The first scientific observations are presented, namely, the seasonal distributions of XCO_2over land on a global scale. | Yi Liu Jing Wang Lu Yao Xi Chen Zhaonan Cai Dongxu Yang Zengshan Yin Songyan Gu Longfei Tian Naimeng Lu Daren Lyu | 2018 | Science Bulletin2018，63，18： | 23 |
| 3 | Ozone mini-hole occurring over the Tibetan Plateau in December 2003显示文摘By analyzing the total ozone data from TOMS and ground-based observations, it is found that a large area with extremely low ozone occurred over the Tibetan Plateau during December 14-17, 2003. After correcting the bias in TOMS data, the area with the total ozone < 220 DU is found to be over 2500000 km2, and the minimum value is only 190 DU. It is the first time that an ozone mini-hole or an extremely low ozone event is found to occur over the Tibetan Plateau. | BIAN Jianchun WANG Gengchen CHEN Hongbin QI Donglin LUE Daren ZHOU Xiuji | 2006 | Chinese Science Bulletin2006，51，7： | 19 |
| 4 | First Global Carbon Dioxide Maps Produced from Tan Sat Measurements显示文摘1.The need for global carbon monitoring from space and the Tan Sat mission Global warming is a major problem,for which carbon dioxide(CO_2 )is the main greenhouse gas involved in heating the troposphere.However,the poor availability of global CO_2 measurements makes it difficult to estimate CO_2 emissions accurately.Satellite measurements would be very helpful for understanding the global CO_2 flux distribution if the CO_2 column-averaged dry-air mole fraction(XCO_2 ) | Dongxu YANG Yi LIU Zhaonan CAI Xi CHEN Lu YAO Daren LU | 2018 | Advances in Atmospheric Sciences2018，35，6： | 16 |
| 5 | Spatiotemporal spectrum and momentum flux of the stratospheric gravity waves generated by a typhoon显示文摘The simulation results of Typhoon Matsa (2005) by using the Weather Research and Forecasting (WRF) model show that pronounced stratospheric gravity waves (GWs) are generated in the vicinity of the typhoon. Using the model output, we investigate the spatial structures and the temporal variations of the GWs through a three dimensional (3-d) spectral analysis, i.e. the spectrum with respect to two horizontal wavenumbers and frequency. We further derive the momentum flux carried by the GWs. Spectral investigation results show that the power spectral density (PSD) of the GWs exhibits a single-peaked spectrum, which consists primarily of a distinct spectrum at horizontal wavelength of ~1000km, time period of 12-18h, and vertical wavelength of 7-9km. This spectrum is different from the spectra of GWs generated by deep convections disclosed by the previous researches. Both the PSD and momentum flux spectrum are prominent in positive k h portion, which is consistent with the fact that the GWs propagate in the upstream of mean flow. Large momentum flux is found to be associated with the GWs, and the net zonal momentum flux is 0.7845×10 3 Pa at 20km height, which can account for ~26% of the momentum flux that is required in driving the QBO phenomenon. | CHEN Dan CHEN ZeYu Lü DaRen | 2013 | Science China Earth Sciences2013，56，1： | 15 |
| 6 | First China ocean reflection experiment using coastal GNSS-R显示文摘It is a new way for oceanographic remote sensing using the GNSS-Reflection technique. Sea waves, tides and sea surface wind can be obtained by analyzing the direct and reflected GPS signals from sea surface. It has become an advanced field concerned by many researchers. In this paper the first China Ocean Reflection Experiment (CORE) with the coastal GNSS-R in the southeast is reported and the method to retrieve oceanographic parameters with the direct and reflected GPS signals is studied. The primary retrievals of Significant Wave Height (SWH) are presented and also compared with the meas-urements from Ultrasonic Wave Gauge (UWG) in situ. | WANG Xin SUN Qiang ZHANG XunXie LU DaRen SHAO LianJun HU Xiong RUFFINI Giulio DUNNE Stephen FRANCOIS Soulat | 2008 | Chinese Science Bulletin2008，53，7： | 15 |
| 7 | Simulation of the stratospheric gravity waves generated by the Typhoon Matsa in 2005显示文摘The generation of stratospheric gravity waves(GWs) due to typhoon is simulated by using a meso-scale model(WRF) with a typhoon case,the Matsa in 2005.An 8-day model run that covers the major stages of the Matsa's development reproduces the key features of the typhoon.For example,good agreements in the typhoon's track,the intensity,and the spiral clouds,as well as mean state of stratosphere,are seen between the simulation results and the observation.Simulation results clearly show that with typhoon propagates northwestward,pronounced stratospheric GWs are generated continuously in the vicinity of Matsa.The GWs exhibit the typical curve-like wave fronts away from the Typhoon Matsa,and propagate preferentially in the upstream of the background winds.These characteristics reflect that the stratospheric GWs are closely associated with the typhoon,and thus the GWs are referred to as Tropical Cyclone related Gravity Waves(TC-GWs).The results also show that these waves should have a rather large horizontal scale so that the outmost wave fronts can be seen at the distance of ~1000 km to the typhoon center in the horizontal plane of 20 km.This is consistent with the phenomenon of stratospheric TC-GWs with ~1000 km horizontal scale disclosed by the previous observational analysis results. | CHEN Dan CHEN ZeYu Lü DaRen | 2012 | Science China Earth Sciences2012，55，4： | 12 |
| 8 | Statistics of gravity waves in the lower stratosphere over Beijing based on high vertical resolution radiosonde显示文摘The seasonal variation of inertia gravity-wave activity in the lower stratosphere (17―24 km) over Beijing is studied based on the high vertical resolution radionsonde observa- tions (from December 2001 to February 2003) of Beijing Observatory (116°28′E, 39°48′N). Some of the important gravity-wave parameters, such as intrinsic frequency, and propagation direction, are estimated according to the polarized relation among gravity-wave wind components and temperature. Time series of wave energy show that the largest wave amplitudes occur during the winter and the least during the summer, and the average of the KE:PE ratios is about 2.6. Zonal and meridional wind perturbations have almost the same roots of mean variances, which shows that the wave energy in the lower stratosphere is isotropic horizontally. The motion and tem- perature fields are dominated by waves with vertical wavelengths of 1.5―3 km, which occupy above 80% samples, with a mean value of about 2.3 km. The horizontal wavelengths are mainly distributed between 100―800 km, averaging 445 km. The ratio of the mean horizontal to vertical wavelength is about 200:1, which indicates that the wave propagates nearly horizontally, with a very small vertical angle. The intrinsic frequency is estimated by fitting a polarized ellipse to the wind perturbations after band-filtering waves with a wavelength of 1.5―3 km, and the results show that the intrinsic frequency is dominated by 1f―3.5f, with an averaging value of 2f, corre- sponding to an intrinsic time period of 9 hours. Wave energy is found to propagate mainly upward, and in the horizontal direction, there is clear azimuthal anisotropy, with predominate northwest propagation against the prevailing wind. | BIAN Jianchun CHEN Hongbin LU Daren | 2005 | Science China Earth Sciences2005，48，9： | 12 |
| 9 | Monitoring Carbon Dioxide from Space:Retrieval Algorithm and Flux Inversion Based on GOSAT Data and Using CarbonTracker-China显示文摘Monitoring atmospheric carbon dioxide(CO_2) from space-borne state-of-the-art hyperspectral instruments can provide a high precision global dataset to improve carbon flux estimation and reduce the uncertainty of climate projection. Here, we introduce a carbon flux inversion system for estimating carbon flux with satellite measurements under the support of 'The Strategic Priority Research Program of the Chinese Academy of Sciences—Climate Change: Carbon Budget and Relevant Issues'. The carbon flux inversion system is composed of two separate parts: the Institute of Atmospheric Physics Carbon Dioxide Retrieval Algorithm for Satellite Remote Sensing(IAPCAS), and Carbon Tracker-China(CT-China), developed at the Chinese Academy of Sciences. The Greenhouse gases Observing SATellite(GOSAT) measurements are used in the carbon flux inversion experiment. To improve the quality of the IAPCAS-GOSAT retrieval, we have developed a post-screening and bias correction method, resulting in 25%–30% of the data remaining after quality control. Based on these data, the seasonal variation of XCO_2(column-averaged CO_2dry-air mole fraction) is studied, and a strong relation with vegetation cover and population is identified. Then, the IAPCAS-GOSAT XCO_2 product is used in carbon flux estimation by CT-China. The net ecosystem CO_2 exchange is-0.34 Pg C yr^(-1)(±0.08 Pg C yr^(-1)), with a large error reduction of 84%, which is a significant improvement on the error reduction when compared with in situ-only inversion. | Dongxu YANG Huifang ZHANG Yi LIU Baozhang CHEN Zhaonan CAI Daren Lü | 2017 | Advances in Atmospheric Sciences2017，34，8： | 9 |
| 10 | High power all-fiberized and narrow-bandwidth MOPA system by tandem pumping strategy for thermally induced mode instability suppression显示文摘An all-fiberized and narrow-bandwidth master oscillator power amplification(MOPA) system with record output power of 4 kW level and slope efficiency of 78% is demonstrated. Tandem pumping strategy is tentatively introduced into the narrow-bandwidth MOPA system for thermally induced mode instability(TMI) suppression. The stimulated Brillouin scattering(SBS) effect is balanced by simply using one-stage phase modulation technique. With different phase modulation signals, SBS limited output powers of 336 W, 1.2 kW and 3.94 kW are respectively achieved with spectral bandwidths accounting for 90% power of ~0.025, 0.17 and ~0.89 nm. Compared with our previous 976 nm pumping system, TMI threshold is overall boosted to be >5 times in which tandem pumping increases the TMI threshold of >3times. The beam quality(M~2 factor) of the output laser is well within 1.5 below the TMI threshold while it is ultimately saturated to be 1.86 with the influence of TMI at maximal output power. Except for SBS and TMI, stimulated Raman scattering(SRS) effect will be another challenge for further power scaling. In such a high power MOPA system, multidetrimental effects(SBS, SRS and TMI) will coexist and may be mutual-coupled, which could provide a well platform for further comprehensively investigating and optimizing the high power, narrow-bandwidth fiber amplifiers. | Pengfei Ma Hu Xiao Daren Meng Wei Liu Rumao Tao Jinyong Leng Yanxing Ma Rongtao Su Pu Zhou Zejin Liu | 2018 | High Power Laser Science and Engineering2018，6，4： | 9 |
| 11 | Atmospheric Profiling Synthetic Observation System in Tibet显示文摘1.Introduction The Atmosphere Profiling Synthetic Observation System(APSOS)is the first ground-based facility for profiling atmospheric variables and multiple constituents in the whole(neutral)atmosphere from the surface up to the lower thermosphere.It enables simultaneous observations and extensive studies of the atmospheric vertical structure and | Daren LU Weilin PAN Yinan WANG | 2018 | Advances in Atmospheric Sciences2018，35，3： | 8 |
| 12 | The structure of instantaneous frequencies of periodic analytic signals显示文摘In this paper, the structure of analytic signals is investigated by means of the relation between analytic signals and functions in the Hardy space. It is shown that an analytic signal is made up of two parts, one depending on the amplitude of the signal and another on the boundary value of an inner function. Based on this result, properties of the instantaneous frequencies of these two parts are studied, and it is found that negative instantaneous frequencies are caused by the amplitude of a signal. Finally, such conditions that an analytic signal is of positive instantaneous frequency are presented. | Tan LiHui Yang LiHua Huang DaRen | 2010 | Science China Mathematics2010，53，2： | 7 |
| 13 | Simulation of the stratosphere-troposphere exchange process in a typical cold vortex over Northeast China显示文摘A mesoscale weather research and forecasting(WRF)model was used to simulate a cold vortex that developed over Northeast China during June 19–23,2010.The simulation used high vertical resolution to reproduce the key features of the cold vortex development.Characteristics of the associated stratosphere-troposphere exchange(STE),specifically the spatiotemporal distribution of the cross-tropopause mass flux(CTF),were investigated using the Wei formula.The simulation results showed that the net mass exchange induced by the cold vortex was controlled by stratosphere-to-troposphere transport(STT)processes.In the pre-formation stage of the cold vortex(i.e.,the development of the trough and ridge),active exchange was evident.Over the lifecycle of the cold vortex,STT processes prevailed at the rear of the trough and moving vortex,whereas troposphere-to-stratosphere transport(TST)processes prevailed at the front end.This spatial pattern was caused by temporal fluctuations of the tropopause.However,because of the cancellation of the upward flux by the downward flux,the contribution of the tropopause fluctuation term to the net mass exchange was only minor.In this case,horizontal motion dominated the net mass exchange.The time evolution of the CTF exhibited three characteristics:(1)the predominance of the STT during the pre-formation stage;(2)the formation and development of the cold vortex,in which the CTF varied in a fluctuating pattern from TST to STT to TST;and(3)the prevalence of the STT during the decay stage. | CHEN Dan Lü DaRen CHEN ZeYu | 2014 | Science China Earth Sciences2014，57，7： | 7 |
| 14 | Advances in the Researches in Middle and Upper Atmosphere in 2006—2008显示文摘This paper summarizes the research results obtained by Chinese scientists and/or through international collaborations in 2006—2008.Specifically,this paper focus on the research fields in the middle and upper atmosphere,including developments in facilities and instruments,and the advancements in scientific issues. | CHEN Zeyu CHEN Hongbin CHEN Wen LU Daren | 2008 | 空间科学学报2008，28，5： | 6 |
| 15 | Advances in the Studies of the Middle and Upper Atmosphere in 2004 - 2006显示文摘This paper summarizes the research results obtained by Chinese scientists and/or through international collaborations during 2004 to 2006. Within the context of COSPAR, the progresses in the studies of the middle and upper atmosphere in China in the past two years are introduced with focusing the developments in facilities and instruments, and the advancements in scientific issues, e.g., dynamics related processes, atmospheric constituents, and the coupling with the lower atmosphere. | CHEN Zeyu LIU Renqiang CHEN Hongbin CHEN Wen LU Daren XU Jiyao HU Xiong | 2006 | 空间科学学报2006，26，z1： | 6 |
| 16 | Change of NO_2 column density over Beijing from satellite measurement during the Beijing 2008 Olympic Games显示文摘The effect of the air quality ensuring measures for the Beijing 2008 Olympic Games in reducing air pollution during the game period is assessed using the tropospheric NO2 column density retrieved from Ozone Monitoring Instrument onboard AURA satel- lite. The basic method of the assessment is the comparison of the NO2 column densities during the game period with that during the corresponding period of 2005?2007 for the Beijing area, and the comparison among Beijing and neighbouring cities Tianjin and Tangshan, which are of similar situation in air pollution of NO2 in recent years. The images of tropospheric NO2 column den- sities over Northern China during the Beijing 2008 Olympic Games show the remarkable effect of the air quality ensuring meas- ures in reducing NO2 pollution: the tropospheric NO2 column density in Beijing is much lower than that in Tianjin and Tangshan, while there were very similar values in the three large cities during the same period of the last three years. About 40% reduction in tropospheric NO2 column density over the Beijing area is obtained from the assessment during July to August, 2008, a key period of air quality ensuring measures for the Beijing 2008 Olympic Games. | YU Huan WANG PuCai ZONG XueMei LI Xin LU DaRen | 2010 | Chinese Science Bulletin2010，55，3： | 6 |
| 17 | Comparison of choroidal vessel thickness in children and adult eyes by enhanced-depth imaging optical coherence tomography imaging显示文摘AIM: To evaluate choroidal thickness, medium choroidal vessel thickness(MCVT) and large choroidal vessel thickness(LCVT) in normal children and adult subjects.METHODS: Manual measurements of subfoveal choroidal thickness(SFCT), MCVT and LCVT at subfoveal and 750 μm nasal and temporal to fovea locations were completed on enhanced-depth imaging optical coherence tomography(EDI-OCT) scans of normal children and adult subjects.RESULTS: Fifty adult and fifty-seven child subjects were included in the study(including 80 adult and 103 child eyes). Mean(±SD) SFCT of adult and children eyes in the study was 309.3±95.7 μm and 279.3±50.4 μm respectively. SFCT and subfoveal MCVT in adult eyes were significantly more than children(P=0.01 and P≤0.0001 respectively).CONCLUSION: There is choroidal thickening with associated thickening of medium choroidal vessels in adults, suggesting that there is alteration in choroidal vasculature with ageing. | Daren Hanumunthadu Jorge Ruiz-Medrano Sunila Dumpala Ayesha Jabeen Asiya Jabeen Abhilash Goud JoséM Ruiz-Moreno Jay Chhablani | 2018 | International Journal of Ophthalmology(English edition)2018，11，4： | 6 |
| 18 | Power generation and heat sink improvement characteristics of recooling cycle for thermal cracked hydrocarbon fueled scramjet显示文摘In order to further investigate how much fuel heat sink could be increased and how much power generation could be obtained by using recooling cycle for a regeneratively cooled scramjet,the energy conversion from heat to electricity and the fuel heat sink increase in recooling cycle are experimentally investigated for fuel conversion rate and components of gas cracked fuel products at different fuel temperatures.The results indicate that the total fuel heat sink(i.e.,physical+chemical+recooling) of a recooling cycle is obviously higher than the heat sink of fuel itself,and the maximum heat sink increment is as high as 0.4 MJ/kg throughout the recooling cycle.Furthermore,the cracked fuel mixture has a significant capacity of doing work.The thermodynamic power generation scheme,which adopts the cracked fuel gas mixture as the working fluid,is a potential power generation cycle,and the maximum specific power generation is about 500 kW/kg.Turbine-pump scheme using cracked fuel gas mixture is also a potential fuel feeding cycle. | BAO Wen QIN Jiang ZHOU WeiXing ZHANG Duo YU DaRen | 2011 | Science China(Technological Sciences)2011，54，4： | 6 |
| 19 | Characteristics of atmospheric aerosol optical depth variation over China in recent 30 years显示文摘This note retrieves the annual and monthly mean 0.75 urn aerosol optical depth (AOD) by using the daily direct solar radiation and sunshine duration data of 47 solar stations from 1961 to 1990. The characteristic of AOD variation over China in recent 30 years was analyzed. The results indicate that AOD increased obviously over China from 1961 to 1990. AOD increased most rapidly over the east part of Southwest China, the middle-and-lower reaches of the Yangtze River and the Tibetan Plateau. The increasing trend of AOD is also relatively distinct in North China, the Shandong Peninsula, east part of Qinghai Province, and coastal areas of Guangdong Province. However, in most parts of Northwest China and Northeast China, the increase of AOD is less significant, while in the west part of the Xinjiang Uygur Autonomous Region and some parts of Yunnan Province, AOD shows decreasing tendency. Generally, AOD reaches its maximum in spring and the minimum appears in summer. As to the linear trend, the maximum | LUO Yunfeng LU Daren HE Qing LI Weiliang ZHOU Xiuji | 2000 | Chinese Science Bulletin2000，45，14： | 6 |
| 20 | Ozone vertical variations during a typhoon derived from the OMI observations and reanalysis data显示文摘Typhoon is considered to play a key role in the dynamical exchange processes taking place between the troposphere and stratosphere.In this paper,the impact of typhoon on the ozone distribution in the upper troposphere and middle stratosphere is investigated using ozone profiles measured by Aura’s Ozone Monitoring Instrument and meteorological fields from reanalysis data.During the passage of Typhoon Hai-Tang in 2005 over the western North Pacific,low values of ozone column above 200 hPa and ozone mixing ratio between the upper troposphere and the middle stratosphere(from 200 to 50 hPa)are observed right above the typhoon’s track,a result due to the strong upward propagation of air associated with overshooting convection in typhoon.A comparative analysis of different stages of Hai-Tang suggests that in the region where typhoon has higher intensity the troposphere-to-stratosphere transport is enhanced.These results indicated that the typhoon has a significant impact on the ozone variation in the upper troposphere and the middle stratosphere. | FU YunFei XIAN Tao Lü DaRen LIU GuoSheng HENG ZhiWei SUN Liang LIU Qi WANG Yu YANG YuanJian | 2013 | Chinese Science Bulletin2013，58，32： | 5 |
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