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Chinese Science Bulletin 2008年第21期53卷 3364-3370页

作者： luo weijun WANG ShiJie State Key Laboratory of Environmental Geochemistry Institute of Geochemistry Chinese Academy of Sciences Guiyang 550002 China

According to systemically monitoring results of oxygen(hydrogen) isotope compositions of precipita-tion,soil waters,soil CO2,cave drip waters and their corresponding speleothems in Liangfeng Cave(LFC) in Guizhou Province,Southwest China,it is found that local precipitation is the main source of soil waters and drip waters,and that the amplitudes of those δ 18O values of three waters(precipitation,soil water and drip water) decrease in turn in the observed year,which are 0‰ to -10‰, -2‰ to -9‰ and -6‰ to -8‰,***,the δ 18O values for three waters show a roughly simultaneous variation,namely,that those values are lighter in the rainy seasons,weightier in the dry seasons,and that the average δ 18O value of drip waters is about 0.3‰ weightier than that of precipitation,which is modified by surface evaporation *** also find that oxygen isotope equilibrium is reached or neared in the formation processes of speleothems in LFC system,and that it is feasible to reconstruct paleotemperature and paleoprecipitation by using δ 18O values of ***,it should be noted that surface evaporation would affect the oxygen isotope values in the study area.

关键词：贵州氧化同位素洞穴堆积物古代气候

Characteristics of strontium isotopes and their implications in the Qixing Cave of Guizhou, China

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Chinese Science Bulletin 2011年第7期56卷 670-675页

作者： ZHU XiaoLong WANG ShiJie luo weijun State Key Laboratory of Environmental Geochemistry Institute of GeochemistryChinese Academy of SciencesGuiyang 550002China Graduate University of Chinese Academy of Sciences Beijing 100049China

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 consequentl

关键词：锶同位素同位素特征贵州省中国洞穴堆积物同位素组成流动路径停留时间

Stable Carbon Isotope Variations in Cave Percolation Waters and their Implications in Four Caves of Guizhou, China

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Acta Geologica Sinica(English Edition) 2013年第5期87卷 1396-1411页

作者： luo weijun WANG Shijie XIE Xingneng ZHOU Yunchao LI Tingyu State Key Laboratory of Environmental Geochemistry Institute of GeochemistryChinese Academy of Sciences Puding Karst Ecosystem Research Station Chinese Academy of Sciences

Monitoring and sampling of main plants, soil CO2, soil water, bedrock, spring water, drip water and its corresponding speleothem were performed at four cave systems of Guizhou, Southwest China, from April 2003 to May 2004, in order to understand stable carbon isotope ratios variations of dissolved inorganic Carbon （DIC） in cave percolation waters （δ13CDIC） and their implications for paleoclimate. Stable carbon isotopic compositions and ions （Ca, Mg, Sr, SO4, CI etc.） were measured for all samples. The results indicate that there are significant differences among the δ13CDIC values from inter-cave, even inter-drip of intra-cave in the four caves. The δ13CDIC values from the Liangfeng Cave （LFC） is lightest among the four caves, where vegetation type overlying the cave is primary forest dominated by tall trees with lighter average δ13C value （-29.9‰）. And there are remarkable differences in δ13CDIC values of different drip waters in the Qixing Cave （QXC） and Jiangjun Cave （JJC）, up to 6.9‰ and 7.8‰, respectively. Further analyses show that the δ13CDIC values in cave drip waters are not only controlled by vegetation biomass overlying the cave, but also hydro-geochemical processes. Therefore, accurate interpreting of δ13C recorded in speleothems cannot be guaranteed if these effects of the above mentioned factors are not taken into consideration.

关键词： cave drip water stable carbon isotope biomass hydro-geochemistry speleothem

Three-dimensional fluorescence spectral characteristics of dissolved organic carbon in cave drip waters and their responses to environment changes: Four cave systems as an example in Guizhou Province, China

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Chinese Science Bulletin 2008年第6期53卷 884-889页

作者： XIE XingNeng WANG ShiJie ZHOU YunChao luo weijun State Key Laboratory of Environmental Geochemistry Institute of Geochemistry Chinese Academy of Sciences Guiyang 550002 China Graduate University of the Chinese Academy of Sciences Beijing 100049 China Forestry College of Guizhou University Guiyang 550025 China

Understanding the responses of fluorescence spectral characteristics of cave drip waters to modern environment and climate changes is key to the reconstructions of environmental and climatic changes using fluorescence spectral characteristics of speleothems. The fluorescence spectral characteristics of dissolved organic carbon (DOC) in four active cave systems were analyzed with a three-dimensional (3D) fluorescence spectral analysis method. We found that the fluorescence types of DOC were mainly of fulvic-like and protein-like fluorescences, both in soil waters and cave drip waters. The intensity of fulvic-like fluorescence was positively correlated with the concentrations of DOC, suggesting that the DOC of cave drip waters was derived from the overlying soil layer of a cave system. Compared with the other cave systems, the variation range of the excitation and emission wavelengths for fulvic-like fluorescence of cave drip waters in Liangfeng cave system that had forest vegetation was smaller and the excitation wavelength was longer, while its fluorescence intensity varied significantly. By contrast, the excitation and emission wavelengths and fluorescence intensity for that in Jiangjun cave system that had a scrub and tussock vegetation showed the most significant variation, while its excitation wavelength was shorter. This implies that the variation of vegetation overlying a cave appears to be a factor affecting the fluorescence spectral characteristics of cave drip waters.

关键词：中国贵州洞穴水三维荧光光谱土层类型植物类型

Temporal and spatial variations in hydrogeochemistry of cave percolation water and their implications for four caves in Guizhou, China

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Chinese Journal Of Geochemistry 2013年第2期32卷 119-129页

作者： luo weijun WANG Shijie XIE Xingneng ZHOU Yunchao LI Tingyu State Key Laboratory of Environmental Geochemistry Institute of Geochemistry Chinese Academy of Sciences Puding Karst Ecosystem Research Station Chinese Academy of Sciences

Soil water and cave drip water from four cave systems in Guizhou, Southwest China, were monitored and sampled monthly from April 2003 to May 2004 to understand spatio-temporal variations in hydro-geochemistry of cave percolation water. The results indicated that among the 5 drip water sites from the Liangfeng Cave (LFC), there were no significant differences among the hydro-geochemical parameters. In the Xiniu Cave (XNC), the drip rates were variable and responded quickly to precipitation events in the 3# (No. 3) drip site with variable water head; both bulk and variation in drip rates were smaller in the 2# with constant water head. However, in the Qixing Cave (QXC) and Jiangjun Cave (JJC), drip rates, concentrations of major ions and saturation index for calcite (SI C ) were smaller, and Mg/Ca ratios in Group I (1#, 2#, 6#, 7# and 8# in the QXC; 2# and 3# in the JJC) were larger than those in Group II (3#, 4#, 5# and 9# in the QXC; 1# and 4# in the JJC). These differences might be the result of different hydrogeological processes above the caves, which are divided into five categories based on hydro-geochemistry data. The formation of some proxies in speleothem, such as Mg/Ca, is likely to be affected by those processes.

关键词：水文地球化学洞穴滴水渗漏水化学研究贵州和空间时间石窟

An X-band 22.5°/45° digital phase shifter based on switched filter networks

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Journal of Semiconductors 2017年第6期38卷 93-96页

作者： Pengpeng Sun Hui Liu Miao Geng Rong Zhang Qi Wang weijun luo Institute of Microelectronics Chinese Academy of Sciences Beijing 100029 China University of Chinese Academy of Sciences Beijing 100049 China School of Advanced Materials and Nanotechnology Xidian University Xi'an 710049 China

The design approach and performance of a 22.5°/45°digital phase shifter based on a switched filter network for X-band phased arrays are *** the MMIC phase shifters are fabricated employing a 0.25 m gate GaAs pHEMT process and share in the same chip size of 0.82 1.06 mm^*** measurement results of the proposed phase shifters over the whole operating frequency range show that the phase shift error is less than 22.5°˙2.5°,45°˙3.5°,which shows an excellent agreement with the simulated performance,the insertion loss is within the range of 0.9–1.2 dB for the 22.5° phase shifter and 0.9–1.4 dB for the 45°phase shifter,and the input/output return loss is better than –12.5 and –11 dB *** also achieve the similar P（1dB）continuous wave power handing capability of 24.8 dBm at 10 *** phase shifters show a good phase shift error,insertion loss and return loss in the X-band（40%）,which can be employed into the wide bandwidth multi-bit digital phase shifter.

关键词： phase shifter switched filter X-band GaAs pHEMT

CO flux of soil respiration in natural recovering karst abandoned farmland in Southwest China

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Acta Geochimica 2020年第4期39卷 527-538页

作者： Yanwei Wang weijun luo Guangneng Zeng Hanling Yang Meifang Wang Yina Lyu Anyun Cheng Lin Zhang Xianli Cai Jia Chen Shijie Wang State Key Laboratory of Environmental Geochemistry Institute of GeochemistryChinese Academy of Sciences99 West Lincheng Road.Guiyang 550081Guizhou ProvinceChina University of Chinese Academy of Sciences Beijing 100049China Puding Karst Ecosystem Research Station Chinese Academy of SciencesPuding 562100China School of Chemistry and Eco-Environniental Engineering Guizhou Minzu UniversityGuiyang 550025China School of Geography and Environmental Sciences Guizhou Normal UniversityGuiyang 550025China

To estimate carbon sequestration potential in the karst area,soil respiration in a natural recovering karst abandoned farmland in Shawan,Puding,Guizhou,southwest China was continuously and automatically monitored for more than two *** results show that the CO2flux of soil respiration(2.63±1.89 lmol m^-2s-^1)is higher in the karst area than in non-karst areas under similar conditions but that regional value(1.32 lmol m-2s-1)is lower because of larger rock fragment coverage(~50%).A the same time,the temperature sensitivity of soil respiration(Q10)in this study area is significantly higher than that of non-karst areas under similar *** respiration has an obvious temporal variation,which is reflected in a significant exponential relationship between soil respiration and soil temperature,but the relationship between soil respiration and soil moisture is very *** soil respiration has an obvious spatial variation,which is likely affected by different diffusion or water-rock reaction processes.

关键词： Karst critical zone Abandoned land Soil respiration Carbon cycle

A Ku band internally matched high power GaN HEMT amplifier with over 30%of PAE

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Journal of Semiconductors 2012年第1期33卷 52-55页

作者： Ge Qin Chen xiaojuan luo weijun Yuan Tingting Pu Yan Liu Xinyu Key Laboratory of Microwave Devices&Integrated Circuits Institute of Microelectronics Chinese Academy of SciencesBeijing 100029China

We report a high power Ku band internally matched power amplifier （IMPA） with high power added efficiency （PAE） using 0.3 μm A1GaN/GaN high electron mobility transistors （HEMTs） on 6H-SiC substrate. The intemal matching circuit is designed to achieve high power output for the developed devices with a gate width of 4 mm. To improve the bandwidth of the amplifier, a T type pre-matching network is used at the input and output circuits, respectively. After optimization by a three-dimensional electromagnetic （3D-EM） simulator, the amplifier demonstrates a maximum output power of 42.5 dBm （17.8 W）, PAE of 30% to 36.4% and linear gain of 7 to 9.3 dB over 13.8-14.3 GHz under a 10% duty cycle pulse condition when operated at Vas = 30 V and Vgs = -4 V. At such a power level and PAE, the amplifier exhibits a power density of 4.45 W/mm.

关键词： Ku-band A1GaN/GaN HEMTs IMPA output power PAE

Can soil remediation agents synergistically mitigate rice Cd content and CH_(4)emission from karst paddies?

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Acta Geochimica 2024年第6期43卷 1123-1132页

作者： Wangbiao Lu Guangneng Zeng weijun luo Jiangju Song Maofei Ni Shuangqin Guo Qi Zhang Chengling Huang Cheng Yang Haijun Du Shijie Wang College of Eco-Environmental Engineering Guizhou Minzu UniversityGuiyang 550025China State Key Laboratory of Environmental Geochemistry Institute of GeochemistryChinese Academy of SciencesGuiyang 550081China Puding Karst Ecosystem Research Station Chinese Academy of SciencesPuding 562100China School of Chemical Engineering Guizhou Minzu UniversityGuiyang 550025China

Rice(Oryza sativa L.)paddies are increasingly threatened by cadmium(Cd)pollution,and potentially serve as CH_(4)emitters to the *** agents widely mitigate Cd pollution in paddy soil,however,we know little about their regulations on CH_(4)***,via adding biochar(B),sulfhydryl-modified palygorskite(SMP),and selenium foliar fertilizer(SFF),we conducted a pot experiment to investigate soil and rice Cd contents together with in-situ CH_(4)f *** to CK,the addition of SMP,SFF,and B-SMP reduced Cd in brown rice by 25%to 50%,25%,and 50%to 75%,*** 7%B,7%B-0.01%SMP,and SFF reduced CH_(4)emissions by 8.46%,5.30%,and 4.11%,***_(4)emission increased gradually along the growing season,with the cumulative CH_(4)fluxes ranging between 338.82 and 619.13 kg hm^(-2).Our results highlight that mixed 7%B-0.01%SMP and SFF showed collaborative eff ects on Cd remediation and CH_(4)*** study reveals the feasibility of reducing Cd pollution and CH_(4)emission in karst rice paddies,which hopes to supplement the knowledge of collaborative controls on soil remediation and carbon emission.

关键词： Cd content CH_(4) flux Remediation agents Synergistical effect Rice paddy

High performance 1 mm AlGaN/GaN HEMT based on SiC substrate

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Frontiers of Electrical and Electronic Engineering in China 2008年第1期3卷 120-122页

作者： weijun luo Xiaojuan CHEN Chengzhan LI Xinyu LIU Zhijing HE Ke WEI Xiaoxin LIANG Xiaoliang WANG Institute of Semiconductors Chinese Academy of SciencesBeijing 100083China Institute of Microelectronics Chinese Academy of SciencesBeijing 100083China

This is our first report on the high performance 1 mm AlGaN/GaN high electron mobility transistor(HEMT)which was developed using home-made AlGaN/GaN epitaxy structures based on SiC ***-organic chemical vapor deposition(MOCVD)was used to generate the epitaxy *** experiments show that the device has a gate length of 0.8 mm exhibiting drain current density of 1.16 A/mm,transconductance of 241 ms/mm,a gate-drain break-down voltage larger than 80 V,maximum current gain frequency of 20 GHz and maximum power gain frequency of 28 *** addition,the power gain under the continues wave condition is 14.2 dB with a power density of 4.1 W/mm,while under the pulsed wave condition,power gain reaches 14.4 dB with power density at 5.2 W/***,the two-port network impedance characteristics display great potential in microwave application.

关键词： AlGaN/GaN high electron mobility transistor(HEMT) microwave power power gain