县域土地利用数量结构与功能特征关联方法探讨

基于土地利用数量结构与功能特征对应变换关系,选取相关定量指标,以安徽省含山县为例,探讨县域土地利用数量结构与功能特征关联分析方法。结果表明:定量分析具有可行性,操作性强,较为简便。一定程度上,多样性、均匀度景观生态综合功能指标与组合类型数呈同向关联,而优势度与其呈反向关联,经济密度、人口密度社会经济综合功能指标与土地利用程度、建设用地区位指数呈同向关联。

山地红枣林地滴灌水分运移规律试验研究

在米脂山地微灌枣树示范基地研究了一定流量范围、不同灌水量条件下,地表滴灌水分在水平和垂直方向上的运移规律及滴灌结束后的水分再分布特征。试验结果表明:在流量稳定条件下,湿润体的水平和垂直扩散距离均与时间有显著的幂函数关系;在4.6~5.0 L/h的流量范围内,湿润体的水平和垂直扩散距离与灌水量也存在显著的幂函数关系;滴灌停止后24 h内的土壤湿润体扩散很大,湿润体平均含水量降低很快,24 h后的扩散较小,平均含水量下降较小,确定滴灌停止后24 h时的湿润体特征值可作为滴灌系统设计的依据。

低分子有机酸对辣椒生长发育及叶片活性氧代谢的影响

采用盆栽试验与室内分析相结合的方法,研究了6种低分子有机酸和一种有机酸盐对辣椒生长发育和叶片活性氧代谢的影响。结果表明:柠檬酸、乙酰丙酸和有机酸钾处理不仅可显著提高辣椒根系干质量,增加辣椒vC含量,而且提高了辣椒的产量。甲酸、柠檬酸、乙酰丙酸和有机酸钾处理使根系活力比对照分别提高83%、93.8%、96.75%和99.5%。柠檬酸、乙酰丙酸和有机酸钾处理提高了辣椒叶片的SOD和POD活性,降低了膜脂过氧化产物MDA含量,延缓了叶片衰老。但是低分子有机酸处理对CAT活性的影响较小。

生物法提取桑皮纤维漂白工艺的研究与优化

研究生物法提取桑皮纤维的最佳漂白工艺。【方法】采用回归正交组合设计,研究了碱(NaOH)用量、漂白剂(H2O2)用量、水料比、漂白温度及漂白时间对生物法提取桑皮纤维漂白的技术参数。【结果】(1)各因子对纤维白度的影响程度依次为:漂白温度>漂白时间>碱用量>漂白剂用量>水料比,漂白温度是漂白过程中的关键控制因素。(2)因子交互效应分析显示,碱用量与漂白温度、漂白剂用量与漂白时间、料水比与漂白时间通过互作产生了增白效应。【结论】通过对纤维白度模型的优化,得到的最佳漂白工艺参数为:碱用量2.05 g/L,漂白剂用量6%,水料比16.7∶1,漂白温度112℃,漂白时间125 min。在最佳工艺参数条件下,纤维白度可达75.0以上,经反复试验验证,该工艺正确可行。

子午岭地区植被演替过程中土壤养分及酶活性特征研究

选择植被自然恢复不同年限的阳坡梁坡地作为研究对象,采用时空互代法研究子午岭地区植被恢复过程中土壤养分和酶活性的变化。结果表明,植被恢复140 a内,不同土层土壤有机质含量、全氮含量、蔗糖酶活性、脲酶活性、碱性磷酸酶活性和过氧化氢酶活性增加,且表土层(0~20 cm)土壤养分含量和酶活性高于下层土壤(20~40 cm)。以裸露地为对照,土壤0~20 cm土层,有机质含量、全氮含量、蔗糖酶活性、脲酶活性、碱性磷酸酶活性和过氧化氢酶活性分别增加了23.8%~534.9%、9.3%~300.0%、213.6%~521.5%、40.4%~286.5%、22.7%~232.2%和3.2%~22.4%,土壤速效磷含量呈现波动变化,过氧化氢酶活性变化幅度比其他三种酶低。土壤有机质含量与全氮、速效磷含量密切相关;土壤蔗糖酶与土壤有机质、全氮均为极显著的相关关系(0.930/0.918);土壤脲酶活性与全氮含量相关系数最高(0.804);土壤碱性磷酸酶活性与有机质、全氮含量都呈极显著相关(0.977/0.984);土壤过氧化氢酶活性与全氮含量极显著相关,相关系数达0.996。

黄土丘陵区不同植被恢复模式对土壤酶活性的影响

为了解侵蚀环境下植被恢复对土壤酶活性的影响,以典型侵蚀环境黄土丘陵区纸坊沟流域生态恢复30a植被长期定位试验点为研究对象,选取坡耕地为参照,分析了植被恢复过程中土壤脲酶、磷酸酶、蔗糖酶、淀粉酶、纤维素酶、过氧化氢酶、多酚氧化酶及理化性质的演变特征。结果表明,黄土丘陵区的坡耕地由于不合理的人为干扰,土壤理化性质和酶活性较弱,通过植被恢复可以有效的改善土壤肥力,不同恢复模式对土壤酶活性和肥力的改善作用不同,恢复30a,脲酶活性增加33%～213%,磷酸酶活性增加275%～394%,蔗糖酶活性增加70%～210%,纤维素酶活性增加24%～48%,过氧化氢酶增加32%～96%,多酚氧化酶降低23%～29%,淀粉酶变化规律不同。不同植被恢复模式其生物特性不同,对土壤酶活性影响也不同。相关性分析说明磷酸酶、蔗糖酶、纤维素酶和多酚氧化酶与其它因子相关性相对较强,可以作为评价土壤质量的生物学指标。

一种CMOS折叠结构ADC中的失调抵消技术

CMOS折叠预放电路的失凋是限制CMOS折叠结构A／D转换器实现高分辨率应用的主要原因之一．文中提出差分对的动态匹配技术改善了折叠预放电路的失调，从而为研制CMOS工艺中的高分辨率折叠结构A／D转换器提供了一种可行方案，并给出了MATLAB和电路仿真的实验结果．

CMOS/SOI 4Kb SRAM总剂量辐照实验

研究了CMOS/SOI 4Kb静态随机存储器的抗总剂量辐照性能。CMOS/SOI 4Kb静态随机存储器采用1K * 4的并行结构体纱，其地址取数时间为30ns，芯片尺寸为3.6mm * 3.84mm；在工作电压为3V时，CMOS/SOI 4Kb静态随机存储器抗总剂量高达5 * 10~5R(Si)，能较好地满足军用和航天领域的要求。

Electro-mass multi odor sensor

For an olfactory sensor or electronic nose the task is not only to detect the object concentration, but also to recognize it. It is well known that all the elements can be identified by their charge to mass ratio e+/m. We tried to use this principle for molecular recognition. Two kinds of sensors are used simultaneously in testing. One is Quartz Crystal Microbalance (QCM) for detecting the change in mass, the other is Interdigital Electrode (IE) for detecting the change in conduction. In this paper the principle and the feasibility of this method are reported. The preliminary results on the recognition of alcohols are presented. The multisensor can be used as an instrument for research on material properties and kinetic process as well.

Structural evaluation of polycrystalline silicon thin films by hot-wire-assisted PECVD

Tungsten wires were introduced into a plasma-enhanced chemical vapor deposition (PECVD) system as a catalyzer: we name this technique 'hot-wire-assisted PECVD' (HW-PECVD). Under constant deposition pressure (p(g)), gas flow ratio and catalyzer position, the effects of the hot wire temperature (T-f) on the structural properties of the poly-Si films have been characterized by X-ray diffraction (XRD), Raman scattering and Fourier-transform infrared (FTIR) spectroscopy. Compared with conventional PECVD, the grain size, crystalline volume fraction (X-e) and deposition rate were all enhanced when a high T-f was used. The best poly-Si film exhibits a preferential (220) orientation, with a full width at half-maximum (FWHM) of 0.2 degrees. The Si-Si TO peak of the Raman scattering spectrum is located at 519.8 cm(-1) with a FWHM of 7.1 cm(-1). The X-c is 0.93. These improvements are mainly the result of promotion of the dissociation of SiH4 and an increase in the atomic H concentration in the gas phase. (C) 2001 Elsevier Science B.V. All rights reserved.

High-quality metamorphic HEMT grown on GaAs substrates by MBE

Metamorphic high electron mobility transistor (M-HEMT) structures have been grown on GaAs substrates by molecular beam epitaxy (MBE). Linearly graded and the step-graded InGaAs and InAlAs buffet layers hal e been compared, and TEM, PL and low-temperature Hall have been used to analyze the properties of the buffer layers and the M-HEMT structure. For a single-delta-doped M-HEMT structure with an In0.53Ga0.47As channel layer and a 0.8 mum step-graded InAlAs buffer layer, room-temperature mobility of 9000 cm(2)/V s and a sheet electron density as high as 3.6 x 10(12)/cm(2) are obtained. These results are nearly equivalent to those obtained for the same structure grown on an InP substrate. A basic M-HEMT device with 1 mum gate was fabricated, and g(m) is larger than 400 mS/mm. (C) 2001 Elsevier Science B.V. All rights reserved.

Influence of interdot electronic coupling on photoluminescence spectra of self-assembled InAs/GaAs quantum dots

The influence of interdot electronic coupling on photoluminescence (PL) spectra of self-assembled InAs/GaAs quantum dots (QDs) has been systematically investigated combining with the measurement of transmission electron microscopy. The experimentally observed fast red-shift of PL energy and an anomalous reduction of the linewidth with increasing temperature indicate that the QD ensemble can be regarded as a coupled system. The study of multilayer vertically coupled QD structures shows that a red-shift of PL peak energy and a reduction of PL linewidth are expected as the number of QD layers is increased. On the other hand, two layer QDs with different sizes have been grown according to the mechanism of a vertically correlated arrangement. However, only one PL peak related to the large QD ensemble has been observed due to the strong coupling in InAs pairs. A new possible mechanism to reduce the PL linewidth of QD ensemble is also discussed.