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901.
This paper deduces the expression of the Schottky contact capacitance of AlGaN/AlN/GaN high electron mobility transistors (HEMTs), which will help to understand the electron depleting process. Some material parameters related with capacitance--voltage profiling are given in the expression. Detailed analysis of the forward-biased capacitance has been carried on. The gate capacitance of undoped AlGaN/AlN/GaN HEMT will fall under forward bias. If a rising profile is obviously observed, the donor-like impurity or trap is possibly introduced in the barrier. 相似文献
902.
天山南麓山前平原土壤盐分空间异质性对植物群落组成及结构的影响 总被引:2,自引:1,他引:1
将轮台天山南麓山前平原中下部自北至南分为4个地貌带:洪水剥蚀带、溢出带、三角洲带及两河交汇区带。并以土壤电导作为积盐程度的指标,分析了天山南麓山前平原4个地貌带土壤盐的分布特征:溢出带和三角洲带土壤盐分含量高,两端洪水剥蚀带和两河交汇区带盐分含量低。物种多样性及物种组成分析结果表明,自北至南物种多样性及物种数量都在下降,洪水剥蚀带主要为柽柳群落、琵琶柴群落,溢出带主要为柽柳群落、盐节木群落、盐角草群落,三角洲带及两河交汇区均为柽柳群落。通过相关性分析,土壤盐分与群落物种多样性相关性不显著。但是,土壤盐渍化的变化明显影响到植物群落物种组成的变化、群落类型的空间分布和演替。 相似文献
903.
Based on the analysis and study of mineral composition, structure, and major and trace elements, this paper deals with element geochemical characteristics and transformation from primary ore into oxidized ore in the Erzhe gold deposit, Sichuan. Some grounds are provided to constrain the transformation of primary ore to oxidized ore. 相似文献
904.
电磁波和弹性波的复反射函数无论从数学表达形式上,还是从物理意义上都有一定的相似性。通过对拟地震解释法中反射系数qn的求取,将频率测深曲线转换成vp-t0曲线及时间剖面,并对均匀介质及2层、3层、4层断面的理论模型和实例做了正反演计算。结果表明,频率测深拟地震解释法作为一种新的解释手段具有较好的应用前景。 相似文献
905.
Ice-core samples from Upper Fremont Glacier (UFG), Wyoming, were used as proxy records for the chemical composition of atmospheric
deposition. Results of analysis of the ice-core samples for stable isotopes of nitrogen (δ15N, ) and sulfur (δ34S, ), as well as and deposition rates from the late-1940s thru the early-1990s, were used to enhance and extend existing National Atmospheric
Deposition Program/National Trends Network (NADP/NTN) data in western Wyoming. The most enriched δ34S value in the UFG ice-core samples coincided with snow deposited during the 1980 eruption of Mt. St. Helens, Washington.
The remaining δ34S values were similar to the isotopic composition of coal from southern Wyoming. The δ15N values in ice-core samples representing a similar period of snow deposition were negative, ranging from -5.9 to -3.2 ‰ and
all fall within the δ15N values expected from vehicle emissions. Ice-core nitrate and sulfate deposition data reflect the sharply increasing U.S.
emissions data from 1950 to the mid-1970s. 相似文献
906.
NILANJAN DASGUPTA TARITWAN PAL JOYDEEP SEN TAMOGHNO GHOSH 《Journal of Earth System Science》2011,120(4):617-626
The study involves the characterization of pegmatoidal granite, southeast of Beawar, Ajmer district, Rajasthan. Earlier researchers
had described this granite as part of the BGC, basement to the Bhim Group of the Delhi Super Group rocks. However, the present
study indicates that it is younger than the rocks of Bhim Group of South Delhi Fold Belt, into which it is intrusive. The
intrusion is structurally controlled and the outcrop pattern is phacolithic. The granite had intruded post-D2 deformation of the Delhi orogeny along the axial planes of D2 folds. The intrusion has also resulted in the formation of a contact aureole about the calc gneisses. 相似文献
907.
渤海湾盆地石炭纪—二叠纪煤的有机组分红外光谱研究 总被引:1,自引:0,他引:1
通过对渤海湾盆地石炭纪-二叠纪煤中主要有机组分进行显微傅里叶红外分析,揭示了孢子体,角质体,树脂体及基质镜质体等有机组分化学组成,结构的特点和对油气形成贡献的差异。结果表明,角质体,树脂体和孢子体都具有富氢指数高,富氧指数低的特点,但树脂体对油气生成的贡献更大而且时间较早,孢子体较差而且时间较晚,就基质镜质体而言,晚石炭世太原组(C2t)煤比早二叠世山西组(P1s)煤富氢指数高,富脂链参数也大,表 相似文献
908.
Alexandre Lisboa Lago Vagner Roberto Elis Welitom Rodrigues Borges Giovanni Chaves Penner 《Environmental Geology》2009,58(2):407-417
Geophysics has been shown to be effective in identifying areas contaminated by waste disposal, contributing to the greater efficiency of soundings programs and the installation of monitoring wells. In the study area, four trenches were constructed with a total volume of about 25,000 m3. They were almost totally filled with re-refined lubricating oil waste for approximately 25 years. No protection liners were used in the bottoms and laterals of the disposal trenches. The purpose of this work is to evaluate the potential of the resistivity and ground penetrating radar (GPR) methods in characterizing the contamination of this lubricant oil waste disposal area in Ribeirão Preto, SP, situated on the geological domain of the basalt spills of the Serra Geral Formation and the sandstones of the Botucatu Formation. Geophysical results were shown in 2D profiles. The geophysical methods used enabled the identification of geophysical anomalies, which characterized the contamination produced by the trenches filled with lubricant oil waste. Conductive anomalies (smaller than 185 Ωm) immediately below the trenches suggest the action of bacteria in the hydrocarbons, as has been observed in several sites contaminated by hydrocarbons in previously reported cases in the literature. It was also possible to define the geometry of the trenches, as evidenced by the GPR method. Direct sampling (chemical analysis of the soil and the water in the monitoring well) confirmed the contamination. In the soil analysis, low concentrations of several polycyclic aromatic hydrocarbons (PAHs) were found, mainly naphthalene and phenanthrene. In the water samples, an analysis verified contamination of the groundwater by lead (Pb). The geophysical methods used in the investigation provided an excellent tool for environmental characterization in this study of a lubricant oil waste disposal area, and could be applied in the study of similar areas. 相似文献
909.
910.