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261.
采用气相色谱-质谱联用技术,首次对木果楝叶子和果实挥发油进行了成分分析,从木果楝叶子和果实分别鉴定出了33和36种化合物,分别占挥发油的99.11%和97.63%.两个部位中挥发油化学组成各有异同,但其主要成分均是倍半萜类化合物b-桉叶烯和γ-桉叶烯.本研究结果可为木果楝的综合开发利用提供理论依据.  相似文献   
262.
中国西北干旱区土地退化与生态建设问题   总被引:7,自引:0,他引:7       下载免费PDF全文
郑度 《自然杂志》2007,29(1):7-7
本文阐述了西北干旱区自然环境的基本特点,讨论了土地退化中土地沙漠化、土地盐渍化和草地退化问题。指出生态建设应当尊重自然,不宜大面积植树造林,采取生态修复措施和建立自然保护区有助于环境整治与生态建设。在区域发展中应当重视土地与水资源的合理开发利用以及区域间环境与发展协调等问题。  相似文献   
263.
为了实现在石油工业地质研究中用先进的网络系统管理前磁信息数据,使用面向Agent的软件工程方法——Gaia方法详细分析了油田前磁信息数字化信息管理系统,建立了该系统的分析模型和设计模型,将Gaia和OAA的系统分析与设计方法应用在基于Multi Agent前磁信息处理系统中.本文应用Gaia的分析方法建立了系统的角色模型,在此基础上构建了基于Multi Agent前磁信息数据处理整体框架体系,该体系也可基于异构平台的数据环境.  相似文献   
264.
The presence of several high affinity binding sites on human serum albumin (HSA) makes it a possible target for many drugs. This study is designed to examine the effect of aloe-emodin on HSA by fluo-rescence, CD spectroscopy and molecular modeling. The results of fluorescence measurements sug-gested that the hydrophobic interaction was the predominant intermolecular force stabilizing the AE-HSA complex, which was in good agreement with the result of molecular modeling study. And the enthalpy change ΔH0 and the entropy change ΔS0 were calculated to be -7.041 kJ·mol-1 and 76.619 J·mol-1·K-1 according to the Van't Hoff equation. The alterations of protein secondary structure in the presence of AE in aqueous solution were quantitatively calculated from CD spectra, and the content of α-helices obviously increased.  相似文献   
265.
Large quantities of di-tert-butyl peroxide (DTBP) have been emitted into the troposphere due to human activities. Its role in the atmospheric photochemical reaction has not been understood. This study presents the results of the photochemical reactions of DTBP and NOx, which have been simulated in a self-made smog chamber under the temperature of (29±1)℃. Both the wall decays of ozone and NO2 could be neglected, compared to the results in simulative experiments. The effective intensity of UV light used in the experiments was 1.28×10-3 s-1, which was expressed by the rate constant of NO2 photolysis in purified air. The reaction mechanism was proposed according to our results and reports of other researchers. The maximum values of incremental reactivity (IR) in the three simulative ex- periments were 9.53×10-2, 5.23×10-2 and 3.78×10-2, respectively. The incremental reactivity decreased with the increase of initial concentrations of DTBP. The IR value of DTBP obtained in this study was comparable to that of acetylene reported in our previous research.  相似文献   
266.
本文主要通过Win32汇编语言编写的一个窗口程序,解释了Windows操作系统的多任务结构和它的消息处理机制,从Windows原理来理解面向对象编程的原理,并对Windows内部的API函数作了相应的分析,在此基础上,通过调用多个API函数实现窗口程序的编写。  相似文献   
267.
山西铝土矿资源开发利用的建议   总被引:1,自引:0,他引:1  
介绍了山西铝土矿资源特征,分析了山西铝土矿资源开发利用的现状,并针对存在的问题,提出了相关的建议.  相似文献   
268.
Interest in the forming mechanism of sediment waves increases recently because of its significance on submarine engineering, sedimentary dynamics and hydrocarbon reservoir prediction in deep water. In this paper, the time-averaged continuity equations and Reynolds-averaged Navier-Stokes equations are applied in the numerical simulation of fluid dynamics. The modeling results are used to illuminate the effects of topography on turbidity current and explore the origin of submarine sediment waves. The research results show that (1) deposition occurs firstly at the lower ramp due to the deceleration of fluid, increase of density, loss of flow capacity and longer duration of flow passage; (2) density increase at the upslope due to the local jam results in velocity decrease and pressure increase; (3) sediment waves begin to be formed and migrated toward upstream in an area far away from the source with in- crease of the turbidity events; (4) deposition becomes more slowly with decrease of grain sizes, but the shape and sequences of these deposits are controlled by topography, not grain size.  相似文献   
269.
The interior Radon transform arises from a limited data problem in computerized tomography. The corresponding operator R is investigated as a mapping between wightedL 2-spaces. Our result is the explicit construction of a singular value decomposition for R. This immediately leads to an inversion formula by series expansion and range characterizations. Foundation item: Supported by the Foundation of the Ministry of Education of China and the Science Foundation of Wuhan University Biography: WANG Jin-ping (1963-), male, Ph.D candidate, Research interests are in numerical solution of singular integral equation and integral transformation.  相似文献   
270.
Two new sorts of fiber optic sensor are designed.Firstly, the variation of refractive index of resin surrounding the embedded fiber optic was mean to observed by measuring the speckle spatial spectrum at the end-face of the fiber optic.Secondly, it is proposed to measuring the change of thickness of the laminate by using fiber optic microbend attenuation.The experiment results measured by the fiber optic sensors are given.The first sort of sensor was found to be able to detect the viscosity process of the resin matrix during cure process includeing the minimum point of viscosity, the gelation point and the end point of cure process; the second sort of sensor could detect the course of change of the thickness of composite laminate pressed by operation pressure.It is benefit for us to optimize the operation technology and to establish the intelligent monitoring system about curing process of composites for the reason that the viscosity process and the change course of the thickness of laminate can be monitored.  相似文献   
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