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1.
CHENMin LIUZuli WANGChuancong WANGYu YANGXinsheng YAOKailun 《科学通报(英文版)》2004,49(4):313-316
Bi2WTi3O12 ceramics are fabricated by the conventional solid-state reaction process. With increasing temperature the sample first has metallic behavior, then strong electrical fluctuations above 100℃, and finally exhibits stable nonlinear properties characterized by semiconductivity above 300℃ at low field (E≤100 V/mm). The Arrhenius law for electrical conductivity by thermal activation is not suitable to explain the anomalous results. XRD analysis reveals that Bi2WO6 is the main phase and Bi4Ti3O12 is the second phase. Based on the phase transition of tungsten trioxide from room temperature to about 300℃, the electrical properties of Bi2WTi3O12 ceramics can be explained. 相似文献
2.
Precipitation variability in central Himalayas and its relation to Northern Hemisphere temperature 总被引:3,自引:0,他引:3
DUAN Keqin & YAO Tandong . Cold Arid Regions Environmental Engineering ResearchInstitute Chinese Academy Sciences Lanzhou China . National Laboratory of Western China抯 Environmental Systems Lanzhou University Lanzhou China 《科学通报(英文版)》2003,48(14):1480-1482
Agriculture, industry and hydroelectric power in south Asia are heavily dependent on the performance of the summer (June to September) monsoon rainfall, which provides 75—90% of the annual rainwater over most parts of the area. A weak monsoon year generally corresponds to low crop yields. And strong monsoon usually produces abundant crops, although too much rainfall may produce devastating floods. However, modeling efforts to forecast the monsoon have met with only moderate success[1]. Prev… 相似文献
3.
Regional differences in the timing of recent air warming during the past four decades in China 总被引:3,自引:0,他引:3
Global surface temperature has dramatically increased in the past decades. It is critical to evaluate such a change using appropriate approaches. The previous studies for assessment of the change usually used overall trends of temperature series (i.e. slopes of simple linear regression of temperature versus year based on a least-square analysis) for entire study period. Temperature trends, however, differ among different periods, i.e. there are often breakpoints in the temperature series. Therefore, the overall linear trend of a temperature series may conceal some of the temporal characteristics of the temperature change. To precisely characterize the temporal and spatial patterns of air temperature change in China, we analyze the annual mean temperature series between the year of 1961–2004 for 536 meteorological stations across China, using piecewise linear regression approach. We found remarkable breakpoints in the annual mean temperature during the study period across the country. The annual mean temperature started to increase in 1984 at a rate of 0.058°C/a at the country level. The year when warming started appeared to be gradually later from the north to the south: temperature increased since the 1970s in the north (north of 40°N), and did not rise until the 1980s in most areas of the south (south of 40°N), with warming starting in 1983 in the Tibetan Plateau. The trends in annual mean temperatures showed a large spatial heterogeneity across China: a relatively small rising with a rate of 0.025–0.05°C/a in the Sichuan Basin, Central China and South China; the greatest increase in some parts of northwest China (i.e. Xinjiang) with up to a rate of 0.1°C/a; and rising at a rate of >0.05°C/a for most regions of the country. The feedbacks of cold waves and snow may be responsible for such regional differences in the timing and rates of warming in China. 相似文献
4.
CHEN TianRan YU KeFu SHI Qi LI Shu Gilbert J. Price WANG Rong ZHAO MeiXia CHEN TeGu ZHAO JianXin 《科学通报(英文版)》2009,54(12):2107-2117
Coral reefs worldwide are becoming increasingly and detrimentally impacted upon by a variety of factors including significant climate changes, such as global warming and increased El Nino-Southern Oscillation activity. Generally, the persistence of coral reefs, especially at low-latitudes, is governed, in part, by sea surface temperatures not exceeding the critical limit (-30℃) at which mass mortality can occur. Thus, it is thought that corals living at high-latitudes (i.e., currently cooler sea surface temperatures) will likely respond more favourably to hypothesized future temperature increases than corals living at low-latitudes (i.e., currently warmer sea surface temperatures). Consequently, high-latitude coral communities may have the potential to act as regions of refugia for many coral species in the face of potential future global warming. The Daya Bay (22°31′--22°50′N), northern South China Sea, contains several high-latitude non-reefal coral communities and represents one of the most northerly distributions of scleractinian corals within the region. Significantly, Daya Bay has experienced dramatic warming in both air and sea surface temperatures throughout the past 50 years. In this paper, we analyze 25 years of change in the Daya Bay coral communities, based both on historic surveys and our latest 2006--2008 regional ecological surveys. Our results suggest that, contrary to predictions, there have been significant declines in coral cover within the Daya Bay during the past 25 years (i.e., 76.6% coral cover in 1983/1984 to only 15.3% coral cover by 2008). Such changes also reflect a significant shift in the most abundant coral species, from Acropora pruinosa to Favites abdita. Most of the modern coral communities became established between 15 and 30 years ago, corresponding to a period of increased winter sea surface temperature. However, very few colonies have become established within the last 15 years, despite a more intense period of warming. By taking into account additional factors, we hypothesize that direct anthropogenic impacts, rather than climatic events, have both restricted the development, and drove the decline, of Daya Bay coral communities in the last 15 years. The Daya Bay has also been subjected to occasional extreme cold events during the past 50 years, with the most recent occurring in early 2008 (13 January-13 February). During the 2008 cold event, the lowest air temperature reaches only 6.6℃, and the mean sea surface temperature for February fall to 〈 14℃, including six continuous days at 12.3℃. Significantly, the sea surface temperatures fall below the hypothesized critical lower temperature threshold (-13℃) that commonly leads to mass mortality in scleractinian coral communities. Surprisingly, our coral community surveys, conducted both before (August 2007) and after (late February 2008) the extreme 2008 cold event, demonstrate that the Daya Bay coral ecosystems are barely impacted upon during the cold period. Those observations suggest that the Daya Bay scleractinian coral communities have developed adaptations to low sea surface temperatures. Overall, our data support the hypothesis that high-latitude coral communities, such as Daya Bay, have the potential to act as areas of refugia for scleractinian corals in the advent of potential future global warming. 相似文献
5.
Characteristics of climatic trends and correlation between pan-evaporation and environmental factors in the last 40 years over China 总被引:16,自引:1,他引:16
ZUO Hongchao LI Dongliang HU Yinqiao BAO Yan & Lü Shihua Cold Arid Regions Environmental Engineering Institute Chinese Academy of Sciences Lanzhou China 《科学通报(英文版)》2005,50(12):1235-1241
Using the data observed by 62 Chinese Routine Meteorological Stations (CRMS) with long term radiation observation, the climatic trends and the relationship between pan-evaporation and its environmental factors are analyzed comprehensively. The results show that during the last 40 years, the relative humidity is uptrend in west China, downtrend in east China, and their extrema are 0.20%/a and -0.22%/a respectively; the precipitations of about 61% CRMS keep uptrend, its maximum can reach 10.52 mm/a^2 while the cloud amounts of about 79% CRMS keep downtrend slightly. About 98% CRMS display the air temperature uptrend, and the maximum is 0.11℃/a. About 76% CRMSdisplay the land surface temperature uptrend. About 87% CRMS show the daily range of temperature downtrend. The global radiations observed by about 85% CRMS and the 10 m wind speeds observed by about 77% CRMS hold downtrend. The annual pan-evaporations of about 66% CRMS hold descend trend, and the biggest descent reaches -24.9 mm/a^2. The pan-evaporation has good relationship with many environmental factors, but the relationship with the relative humidity is the best. All of the climatic trends respond to the global climate changes. 相似文献
6.
WU Yu XU Boqing 《科学通报(英文版)》2005,50(19):2153-2156
A novel two-step method for the synthesis of monoclinic titanium oxide (i.e. TiO2(B)) nanosheets is presented in this report. The method is featured by two steps: 1) synthesis of hydrogen titanate nanosheets, followed by 2) calcination of the titanate nanosheets at elevated temperatures. The hydrogen titanate nanosheets were prepared first by autoclaving anatase TiO2 powders, obtained by air cal- cining an ethanol-gel of Ti(OH)4 at 500℃, in aqueous NaOH (10 mol/L) at 150-200℃, and then by washing with hydro- chloric acid under supersonic irradiation. While sizes of the nanosheets were found to increase with increasing the temperature of the hydrothermal treatment, the calcination at 400-500℃ of the hydrogen titanate nanosheets that were synthesized at higher autoclaving temperatures (180-200℃) produced monoclinic TiO2 nanosheets with a uniform morphology. By contrast, the same calcination of the titanate nanosheets synthesized at the autoclaving temperature 180℃ led to anatase TiO2 nanoparticles. 相似文献
7.
Variations of organic carbon isotopic composition and its environmental significance during the last glacial on western Chinese Loess Plateau 总被引:8,自引:0,他引:8
CHEN Fahu RAO Zhiguo ZHANG Jiawu JIN Ming MA Jianying 《科学通报(英文版)》2006,51(13):1593-1602
The last glacial period is characterized by a cold and dry climate with low atmospheric CO2 concentration. The relatively arid climate and low CO2 concentration are favorable to the growth of C4 plants, but the low temperature limits the development of th… 相似文献
8.
This study analyzes the changes in glacier zones and snow composition of Glacier No.1 in the Tianshan Mountains of China since 1961,and their possible relations with climate.It is found that precipitation dominated the snow composition and that air temperature and precipitation controlled the distribution of glacier zones,but interannual change in precipitation had a relatively large effect on glacier zones and snow composition during 1963–1981 (P10) and 1963–1989 (P11).However,during 1982–2007 (P20) and 19... 相似文献
9.
CUI Zhijiu YANG Jianqiang ZHANG Wei ZHAO Liang & XIE Youyu . College of Environmental Sciences Peking University Beijing China . State Key Laboratory of Loess Quaternary Geology ChineseAcademy of Sciences Shaanxi China . Geographic Science Resource Research Institute Chinese Acad-emy of Sciences Beijing China 《科学通报(英文版)》2004,49(11):1177-1184
Deep sea deposits, ice cores and loess deposits have been used extensively and successfully, to study global climatic changes. Since permafrost is a consequence of cold climates, indicators of permafrost can also be used to reconstruct ancient climates in certain areas during certain periods. The recent discovery of large areas of ice wedge networks, and determination of their ages, have enabled us to locate the southern boundary of the permafrost that ex-isted in China about 20 thousand years… 相似文献
10.
The Mg/Sr ratio in a stalagmite,whic is directly proportinonal to DMg/Ca,the solid-liquid distribution coefficient of Mg,is proposed as a geochemical thermometer to estimate paleotemperature changes,The paleotemperature change in eastern Beijing over the past 3000 years has been reconstructed by using this thermometer in the stalagmite ZFFS-1 from Jingdong Cave,The records can be divided into two periods:3000-2000 aBP,cool and wet ,the air temperature averaging 9.8℃;and 2000aBP-present, hot and dry,the air temperature being 1℃ higher than the mean value (11.7℃) of the past 3000 years ,During 500-200 aBP,the air temperature was about 1.2℃ lower than that of the present,corresponding to the Little Ice Age Europe Like δ^18O and δ^C ,Mg/Sr (or DMg/Ca) reflects and obviously warming trend of the past 200 years,These results are supported by historic recods. 相似文献
11.
ZHENG Bin SHI Chunhua CHEN Yuejuan 《科学通报(英文版)》2006,51(14):1761-1765
As one of the important green-house gases, methane in the stratosphere affects the stratospheric processes of radiation, dynamics and chemistry, even the tropo-spheric circulation through interactions between the stratosphere and the troposphere. To a gre… 相似文献
12.
Simulated and reconstructed winter temperature in the eastern China during the last millennium 总被引:7,自引:2,他引:7
LIU Jian H. Storch CHEN Xing E. Zorita ZHENG Jingyun WANG Sumin 《科学通报(英文版)》2005,50(24):2872-2877
Since the 1990s, under the auspicious impetus of two international research programs, the “Past Global Changes” (PAGES) and the “Climate Variability and Pre- dictability” (CLIVAR), massive research work has been carried out on climate and environment changes over the past 2000 years[1-3]. But majority of the studies has been centered on obtaining various kinds of climatic proxy data (such as historical documents, tree rings, ice cores, lake cores) and focused on the reconstruction of… 相似文献
13.
Sea surface temperature record from the north of the East China Sea since late Holocene 总被引:2,自引:0,他引:2
Using the alkenone paleotemperature index U37^k, a high-resolution sea surface temperature (SST) record since 3600 a BP was reconstructed from the mud area in the north of the East China Sea. Combining with the grain size distribution curve of sensitive grain size group, which may reflect the East Asia Winter Monsoon activity, the palaeoenvironmental evolution cycle throughout the late Holocene in the area was obtained. The marine environment evolution during the last 3600 years displays a five-stage trend. (1) Temperature descending period from 0.85 cal. ka BP to present. The maximum temperature decrease amplitude is 2℃. The winter monsoon intensified and 'Little Ice Age' were recorded in this period. (2) Warming period from 1.90 to 0.85 cal. ka BP. The mean temperature increase amplitude is 0.8℃. The Sui-Tang warming period was recorded at about 0.85--1.35 cal. ka BP and a prominent cooling event was recorded at 1.4 cal. ka BP in this period. (3) Temperature descending period from 2.55 to 1.90 cal. ka BP. Temperature cooling amplitude is 0.9℃. This period is coincident with an integrated temperature circle recorded in the Antarctic ice core, with the temperature changes from a slow cooling stage to a rapid warming stage. (4) Temperature comparatively stable with a little ascending period from 3.2 to 2.55 cal. ka BP. Temperature warming amplitude is 0.3℃. This period is coincident with the temperature fluctuant ascending period recorded in Antarctic ice core. (5) Temperature comparatively stable with little descending period from 3.6 to 3.2 cal. ka BP. This period corresponds with the temperature fluctuant cooling period recorded in Antarctic ice core. Basically, those five periods were coincident with the Antarctic ice core record. During the global cooling stage, the SST change in the continental shelf sea can be adjusted simultaneously. 相似文献
14.
Conclusions We have studied C60 films grown on Ni3Co(111) single-crystalline substrate using hotwall diffusion method. The XRD and SEM results show that high-quality C60 (111) singlecrystalline film with grain size of ∼ 1 μm can be obtained at the substrate temperature of 150 ° C. Due to the
strong interfacial interaction between C60 and Ni3Co(111) substrates, temperature has much more influence on the orientation of the film than that of the film grown on nonmetallic
substrates. The film grown at 100 ° C has a weak orientational order and the film grown at 200 ° C is randomly oriented. 相似文献
15.
To quantify the impact of urbanization on changes in observed surface air temperature and extremes, a homogenized dataset of daily mean, maximum and minimum temperature (Trn, Trnax and Train) observations at 20 stations in Greater Beijing (GBJ) from 1978 to 2008 is analyzed. In contrast with previous studies, a cluster analysis is done to objectively classify observing stations into four categories (urbanized, suburban, rural and mountain), which is checked with remote-sensing night-light images since the 1990s. At urbanized sites, there is an added warming trend in annual mean Tm representing an average of 10.9% (up to 18.4% or 0.12℃/decade at the most strongly influenced site) of overall warming. Corresponding contributions for Train are 12.7% (up to 20.8% or 0.19℃/decade) and 24% for diurnal temperature range DTR (up to 37.4% or 0.149℃/decade) over the last three dec- ades. Although it has not had a significant impact on daytime records (Tmax), urbanization has enhanced the increasing (decreasing) trend of extremely warm (cold) nights by an average of 12.7% or 2.07 d/decade (29.0% or 5.06 d/decade) at the urbanized sites since the 1970s. 相似文献
16.
Using historical records on first and last frost and snow, spring cultivation, David peach blossom, autumn crop harvest, grade
of sea freeze and change in northern citrus boundary, we reconstructed temperature change during 601–920 AD. The mean temperature
of the winter half-year (October to April) over Central East China during this period was about −0.22°C higher than that of
the present (1961–2000 AD mean). During 601–820 AD, mean temperature was about −0.52°C higher than the present. During 821–920
AD, the mean temperature was 0.42°C lower than the present. The temperature fluctuations were characterized by a maximum amplitude
of 1.05°C at the centennial scale, 1.38°C at the 50–year scale, 2.02°C at the 30-year scale, and 2.3°C at the 20-year scale.
There were four peaks warmer than today (601–620 AD, mean of 1°C higher temperature; 641–660 AD, 1.44°C; 701–720 AD, 0.88°C;
781–800 AD, 0.65°C). Three cold periods were in 741–760, 821–840, and 881–900 AD, the mean temperature of which was 0.37–0.87°C
lower than the present. 相似文献
17.
Estimation on the response of glaciers in China to the global warming in the 21st century 总被引:17,自引:0,他引:17
Glaciers in China can be categorized into 3 types, i.e. the maritime (temperate) type, sub-continental (sub-polar) type and extreme Continental (polar) type, which take 22%, 46% and 32% of the total existing glacier area (59 406 km2) respectively. Researches indicate that glaciers of the three types show different response patterns to the global warming. Since the Maxima of the Little Ice Age (the 17th century), air temperature has risen at a magnitude of 1.3℃on average and the glacier area decreased corresponds to 20% of the present total glacier area in western China. it is estimated that air temperature rise in the 2030s, 2070s and 2100s will be of the order of 0.4-1.2, 1.2-2.7 and 2.1-4.0 K in western China. With these scenarios, glaciers in China will suffer from further shrinkage by 12%, 28% and 45% by the 2030s, 2070s and 2100s. The uncertainties may account for 30%-67% in 2100 in China. 相似文献
18.
Branched glycerol dialkyl glycerol tetraethers (GDGTs) were analyzed in peat samples taken from the Zoigê grassland, located on the eastern margin of the Qinghai-Tibetan Plateau. The mean annual air temperature (MAAT) and pH in the 210 Pb-dating peat core were reconstructed based on the cyclization of branched tetraethers (CBT) and methylation of branched tetraethers (MBT) indices for the last 150 years. The results showed that the MAAT and pH values involved three stages of variation over the last 150 year... 相似文献
19.
Modern systematics and environmental significance of stable isotopic variations in Wanxiang Cave, Wudu, Gansu, China 总被引:1,自引:1,他引:1
KathleenR.Johnson LvnnInaram ZHANGXinli VVANGSumin PANGFushun LONGLude 《科学通报(英文版)》2004,49(15):1649-1652
This paper presents the stable isotopic compositions from the cave dripwater and actively forming soda straw stalactites collected from Wanxiang Cave, Wudu, Gansu, located on the Qinghai-Tibetan Plateau and Loess Plateau transition zone, China. The δ^18Odw and δDdw of dripwater samples in the cave plot directly on the local MWL, constructed by using GNIP data from 3 sites surrounding the cave regions (Lanzhou, Xi‘an, and Chengdu), the nearest site to the cave, suggesting that there is a close relationship be-tween the δ^18Odw of the cave water and the δ^18O of the pre-cipitations. Using the measured δ^18Odw and δ^18Omc values from the mid-farthest parts from the cave entrance and the carbonate paleotemperature equation, the calculated temperatures range from 8.9 to 12.4℃, with the mean value of 10.7℃ and the temperature calculated at 8 locations in the farthest part of the cave is in the range of 10.I--12.4℃, with the mean value of 11.5℃, being consistent with the survey value(10.99℃)in the cave, slightly lower than the mean annual temperature (14.4℃) in Wudu. This suggests that modern speleothems are forming under isotopic equilibrium and their isotopic composition accurately reflects the mean annual temperature at the surface, indicating that the isotopic composition of the modern speleothems records local temperature change with credibility. 相似文献
20.
Distribution of methane and its homologues in low-layer atmosphere over eastern China and seas 总被引:1,自引:0,他引:1
Fulin Huang Xunhua Zhang Xianghua Xia Zuji Qiang Changgong Lin Yingkai Zhang 《科学通报(英文版)》1998,43(22):1902-1902
Systematic, fixed_point and long observations and sample testing make clear distributions of methane and the homologues in the low_layer air over eastern China and sea areas. Within about 250 km from epicenter of moderate and strong earthquakes, oil_gas areas have methane concentration anomaly and CO\-2 anomaly in the low_layer atmosphere around the earthquakes, have a temperature increase by 1-6℃ at the occurrence of moderate and strong earthquakes and indicate that concentration anomaly of methane family in the low_layer air can be used as an important index for petroleum geochemical exploration. 相似文献