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941.
The strontium isotopic compositions (87Sr/86Sr) of samples including soils, bedrock, soil waters, drip waters and their corresponding speleothems in the Qixing Cave (QXC), Guizhou Province, China, were systemically measured and analyzed. The results indicate that there are significant Sr isotopic differences among samples. The mean 87Sr/86Sr ratios in drip water for the samples 1#, 4# and 9# were 0.709568, 0.709139 and 0.708761, respectively, which possibly result from different flow paths, residence times, and other hydrogeological processes in the unsaturated zone overlying QXC. Meanwhile, levels of 40.8%, 57.6% and 72.4% of Sr in drip waters for 1#, 4# and 9#, respectively, were derived from bedrock dissolution, which was calculated by the mixture model of the two end-members (soil and bedrock). There is, however, no positive correlation between the relative proportion from bedrock dissolution (δ13C value is 1.8‰) and drip water δ13CDIC values. The mean drip water δ13CDIC value in 1# is the heaviest (–4.5‰) with the lowest contribution rate of bedrock dissolution, whereas the value in 9# is the lightest (–9.3‰) with the highest contribution rate of bedrock dissolution. The proportion from host rock dissolution in 4# is higher than that in 1# and lower than that in 9#, while its mean drip water δ13CDIC value (–8.6‰) is higher than that of 9# and lower than that for 1#. This suggests that the prior calcite precipitation (PCP) processes in the unsaturated zone overlying the cave are responsible for the δ13CDIC value differences between different drip waters, and not bedrock dissolution. Furthermore, this study also demonstrates that the 87Sr/86Sr ratios of speleothems in the 1# and 4# mainly reflect the variation in the relative proportions from the soil system (soil water) and bedrock dissolution overlying the cave. It is, therefore, feasible to use the strontium isotopic signals of speleothems as an indicator for soil chemical weathering intensity, and consequently as a monsoon proxy in the study area. 相似文献
942.
BREED Dan 《科学通报(英文版)》2011,56(1):76-83
The Real-Time Four-Dimensional Data Assimilation (RT-FDDA) system is used for orographic snowpack enhancement.The model has three nested domains with the grid spacing of 18,6 and 2 km.To evaluate the simulations of winter orographic clouds and precipitation,comparisons are made between model simulations and observations to determine how the model simulates the cloud distribution,cloud height,cloud vertical profiles and snow precipitation.The simulated results of the 02:00 UTC cycling with 2-km resolution are used in the comparison.The observations include SNOTEL,ceilometer,sounding and satellite data,from the ground to air.The verification of these observations indicates that the Weather Research and Forecast (WRF) RT-FDDA system provides good simulations.It is better to use data within the forecast period of 2-16 h simulations.Although the horizontal wind component near the ground has some bias,and the simulated clouds are a little higher and have a little more coverage than observed,the simulated precipitation is a little weaker than observed.The results of the comparison show that the WRF RT-FDDA model provides good simulations and can be used in orographic cloud seeding. 相似文献
943.
Coalbed methane (CBM) accumulation models include continuous gas accumulation and staged gas accumulation.However,studied on the geochemical characteristics and indices to evaluate staged accumulation CBM are lacking.This study for the first time obtained the carbon and hydrogen isotopic compositions of methane and ethane generated at different evolution stages using thermal simulation of samples prepared by treating an herbaceous swamp peat at different temperatures.The results showed that the carbon isotopic compositions of methane and ethane were obviously affected by the thermal evolution level of the starting sample,while the hydrogen isotopic compositions were closely related to the maturity of gases.The carbon and hydrogen isotopic compositions of gases generated by coal-forming organic matter with Ro values from 1.2%,1.7%,2.4%,3.2% and 3.7% to 5.2% were determinated.The relationship between Ro values and the carbon and hydrogen isotopic compositions of gases generated by coal-forming organic matter at different evolution stages as well as the carbon or hydrogen isotopic relationships between methane and ethane were established.The results provide a scientific basis for studying the genesis of CBM generated at different maturity intervals and understanding the geochemical characteristics of staged accumulation CBM.These results were applied to a case study on CBM from the southern Qinshui basin,and it was found that the CBM accumulated after the Middle Jurassic and was characteristic of staged gas accumulation.This is consistent with the result of geological studies,and further showed that the results of thermal simulation experiments are very important for evaluating the genesis of natural CBM. 相似文献
944.
Angular dependent NEXAFS study of the molecular orientation of PTCDA multilayers on Au (111) surface
CAO Liang ZHANG WenHua HAN YuYan CHEN TieXin ZHENG ZhiYuan WAN Li XU FaQiang IBRAHIM Kurash QIAN HaiJie WANG JiaOu 《科学通报(英文版)》2011,56(33):3575-3577
The molecular orientation of perylene-3,4,9,10-tetracarboxylic acid dianhydride (PTCDA) multilayers adsorbed on Au (111) surface has been investigated using angular dependent O K-edge near edge X-ray absorption fine structure (NEXAFS) spectroscopy. The significant angular dependence of important resonant structures (π* and σ*) reveals that PTCDA molecules adopt an ordered geometry on the substrate surface. The average tilt angle of the PTCDA molecular planes is 27°±10° from the Au (111) surface. 相似文献
945.
946.
SUN Ke XIE Liang JU Yu WU XuMing HOU Jie HAN Wei WANG Xin MAN JiangWei LIU Yu YUAN HaiQing LUO ZhenAo XIONG Shang & ZHU NingHua State Key Laboratory on Integrated Optoelectronics 《科学通报(英文版)》2011,(32):3486-3492
A compact fiber-optic diode-laser sensor system for measuring relative humidity is studied. In such a system, a distributed feedback laser lasing near 1877 nm is used as light source while a high-precision Pt resistance as temperature sensor, an accuracy of 0.1% relative-humidity can be achieved. The laser sensor system is able to lock to the absorption peak and calculate the density of water vapor without any additional reference measurements. Using programs built in to the microcontroller unit, the laser system can switch functions between direct measurement at high density and second-harmonic detection at low density. The system can switch between the two modes automatically and work in a wide dynamic range. 相似文献
947.
Potential release of hydrogen fluoride from domestic coal in endemic fluorosis area in Guizhou,China 总被引:1,自引:0,他引:1
Almost half of the total rural area of Guizhou Province and many regions within the 11 adjacent provinces in southwestern China have a long history(at least 70 years) of endemic fluorosis,including dental fluorosis and osteofluorosis along with its associated deformities and disabilities.Over decades of research,this specific type of endemic fluorosis has been defined as coal-burning fluorosis,which is distinct from drinking-water fluorosis.It is generally acknowledged that indoor burning and combustion of high-fluorine coal leads to food contamination,and fluorine then enters the human body.However,the exact chemical form of fluorine during its release and transfer to the body is still unknown.In the present study,21 domestic coal samples from outcrop and semi-outcrop coal collected in five villages with fluorosis were analyzed by time-of-flight secondary ion mass spectrometry(TOF-SIMS).The total mass fraction of sulfur in the samples ranged from 0.24%-5.58% and total fluorine content ranged 90.2-149.2 mg/kg.H3O+,H2SO4+ and HSO4-were detected in the samples by TOF-SIMS,which indicated that sulfuric acid hydrate(H2SO4.H2O) was present in the samples.F-was detected in all of these,which suggested the samples contain ionic fluorine compounds.Under certain circumstances,such as heating or burning,the prevalence and coexistence of the acid(H2SO4.H2O) and base(F-) would lead to a neutralization reaction producing volatile hydrogen fluoride(HF,bp = 19.5℃).This would be the chemical form of fluorine released from the coal.Further studies using HF and SO2 test tubes on headspace gas over coal samples heated to 200℃ in the laboratory and on headspace gas over stoves or chimney tops at rural residences confirmed the release of HF. 相似文献
948.
WANG HaiPeng & WEI BingBo * Department of Applied Physics Northwestern Polytechnical University Xi’an China 《科学通报(英文版)》2011,56(32):3416-3419
Using liquid Fe 60 Cu 40 alloy as a model, the structure of liquid Fe-Cu alloy systems is investigated in the temperature range 1200 2200 K, covering a large metastable undercooled regime, to understand the phase separation of liquid Fe-Cu alloys on the atomic scale. The total pair distribution functions (PDFs) indicate that liquid Fe 60 Cu 40 alloy is ordered in the short range and disordered in the long range. If the atom types are ignored, the total atom number densities and PDFs demonstrate that the atoms are distributed homogenously in the liquid alloy. However, the segregation of Fe and Cu atoms is very obvious with decreasing temperature. The partial PDFs and coordination numbers show that the Cu and Fe atoms are not apt to get together on the atomic scale at low temperatures; this will lead to large fluctuations and phase separation in liquid Fe-Cu alloy. 相似文献
949.
A flat submerged membrane combined with a TiO 2 /UV photocatalytic reactor (FSMPR) was employed in batch mode to remove humic acid (HA). HA removal efficiency was characterized by UV 254 absorbance, UV-vis spectra, dissolved organic carbon (DOC) concentration, specific UV absorbance (SUVA), and trihalomethane formation potential (THMFP). The FSMPR process was effective in removing more than 86% of DOC and nearly 100% of UV 254 absorbance, while the THMFPs of samples were reduced to < 19 μ g/L after 150 min of treatment. In addition, changes in transmembrane pressure (TMP) with and without UV were evaluated; TiO 2 /UV was effective at controlling membrane fouling by HA. Analysis of the molecular weight (MW) distributions and three-dimensional excitation-emission matrix (EEM) fluorescence spectra of HAs revealed that the effectiveness in membrane fouling control is a result of changes in HA molecular characteristics. The TiO 2 /UV photocatalytic reactor caused the degradation of high MW, hydrophobic humic-like molecules to low MW, hydrophilic protein-like molecules, although this fraction was not completely removed during 150 min of treatment and was less responsible for membrane fouling. 相似文献
950.
The present study attempts to investigate the role of rigid claws and smooth adhesive pads in the locust Locusta migratoria manilensis,when attaching to various substrates.We measured the attachment forces on sandpaper and silicate glass plate of locusts with intact attachment system,and those with either the pretarsal claws or the tarsal pads having been entirely destroyed,to explore the role of pads and claws when a locust is walking on various substrates.To obtain information about morphological characteristics and material properties of the claws,we examined the intact and fractured claws by scanning electron microscopy,and tested the fractural force in a fracture experiment.We proposed a mechanical model for locust climbing on a slanting surface to analyze the conduction and final result of the attachment forces generated by the attachment organs on the fore-,mid-and hindlegs.Attachment forces generated by locusts with destroyed pads were similar to those generated by locusts with intact attachment system on both substrates,which presumably indicated that the claws have a significantly important role when attaching to various substrates.The result of the fracture experiment demonstrated that the claws are made of relatively stiff material,and their shear strength ranged between 39-45 MPa.Mechanical analysis of locust climbing on slanting surface showed that the force generated by the hindlegs suspended the whole body of locust up from the surface and pushed the body forward,while the midlegs steadily suspended the centre of gravity and the forelegs pulled the suspended body forward.The results obtained contribute to the further interpretation of the interaction mechanisms between insect attachment system and substrates,and supply information for designing and manufacturing slippery plates for trapping plague locusts. 相似文献