45 resultados para Hirt, Aloys, 1759-1836.
Resumo:
The mass resolved multiphoton ionization (MPI) spectra of methyl iodide were obtained in the 430-490 nm region using a time-of-flight (TOF) mass spectrometer. They have the same vibrational structure, which testifies that the fragment species, in the wavelength region under study, are from the photodissociation of multiphoton ionized molecular parent ions. Some features in the spectra are identified as three-photon excitations to 6p and 7s Rydberg states of methyl iodide. Two new vibrational structures of some Rydberg states are observed. The mechanism of ionization and dissociation is also discussed. (C) 2001 Elsevier Science B.V. All rights reserved.
Resumo:
为了探讨长白山植物区系的垂直分化特征及其与周边地区植物区系的联系,通过对以往在该地区采集的标本进行分类学鉴定,统计得出长白山共有维管束植物134科517属1323种。对这些植物从属、种两级进行统计分析,结果表明:长白山4个植被垂直带的植物区系具有明显的垂直分布格局;在整体上具有温带性质,包含有少量的热带成分,主要体现在阔叶红松林带;随海拔的升高,温带性质逐渐减弱,寒带亚寒带逐渐增强。植物区系的垂直变化反映了长白山低海拔植物区系与热带植物区系的联系,以及高海拔地段与北极成分之间的联系。
Resumo:
A novel porous material constructed from p-sulfonatocalix[4]arene molecules and a Ag-I coordination polymer has been structurally characterized. The porous supramolecular complex features a bilayer arrangement of p-sulfonatocalix[4]arene molecules linked by a Ag-I-hmt (hmt: hexamethylene- tetramine) coordination polymer through metal-ligand bonding, hydrogen bonding and host-guest interactions.
Resumo:
On the basis of the quantitative relationship among rubber processing, structure and property, the methodology of the integrated processing-structure-property analysis on rubber in-mold vulcanization is presented, and then the temporal evolution and spatial distribution characteristics of silicone rubber hot processing parameters, crosslinking structure parameters and mechanical property parameters are obtained by means of the finite element method. The present work is helpful for optimizing curing conditions, and then the design of rubber vulcanization processes according to certain requirements can be done.
Resumo:
A composite solid polymer electrolyte (SPE) of (PEO)(10)LiClO4-Al2O3 was prepared and Pt and stainless steel(SS) blocking electrodes were used for an impedance study. It was found that the semicircle in the high frequency range and the straight line in the low frequency range depend upon different blocking electrodes and polarization potentials applied in the experiments. In the equivalent circuit. two constant phase elements (CPE) have been used instead of the pure geometrical and double layer capacitances. respectively. A theoretical line calculated from their estimated values has a good correlation with the experiment data. Moreover. the equivalent circuit also can be used to explain the impedance properties of Pt and stainless steel (SS) blocking electrodes both in the high and the low frequency ranges. (C) 2001 Elsevier Science Ltd. All rights reserved.
Resumo:
以含硝基偶氮苯侧基的丙烯酸酯液晶聚合物为研究对象,利用DSC、WAXD、偏光显微镜等手段研究了分子结构对侧链液晶聚合物结晶行为的影响.结果表明:丙烯酸酯类液晶聚合物的晶区是由介晶基团的规整排列形成的,大分子主链和柔性间隔基不参与结晶.随着柔性间隔基长度的增加,晶区分子排列有序性提高,结晶度增大;非晶共聚组分MA含量的增加,限制了介晶基团的有序排列,当MA含量超过83%后,只得到非晶共聚物.
Resumo:
乙二醇-双-(α-氨基乙基醚)四乙酸(EGTA)是一种Ca~(2+)高选择性螯合剂,结合Ca~(2+)能力比Mg~(2+)强10~6倍,被认为是钙结合蛋白钙结合位的理想配位模型。Ca(EGTA)的晶体结构虽已确定,但其溶液结构仍不清楚。考虑Ca~(2+)离子半径(0.99
Resumo:
The origin and pathway of the thermostad water in the eastern equatorial Pacific Ocean, often referred to as the equatorial 13 degrees C Water, are investigated using a simulated passive tracer and its adjoint, based on circulation estimates of a global general circulation model. Results demonstrate that the source region of the 13 degrees C Water lies well outside the tropics. In the South Pacific, some 13 degrees C Water is formed northeast of New Zealand, confirming an earlier hypothesis on the water's origin. The South Pacific origin of the 13 degrees C Water is also related to the formation of the Eastern Subtropical Mode Water (ESTMW) and the Sub-Antarctic Mode Water (SAMW). The portion of the ESTMW and SAMW that eventually enters the density range of the 13 degrees C Water (25.8 < sigma(theta) < 26.6 kg m(-3)) does so largely by mixing. Water formed in the subtropics enters the equatorial region predominantly through the western boundary, while its interior transport is relatively small. The fresher North Pacific ESTMW and Central Mode Water (CMW) are also important sources of the 13 degrees C Water. The ratio of the southern versus the northern origins of the water mass is about 2 to 1 and tends to increase with time elapsed from its origin. Of the total volume of initially tracer-tagged water in the eastern equatorial Pacific, approximately 47.5% originates from depths above sigma(theta) = 25.8 kg m(-3) and 34.6% from depths below sigma(theta) = 26.6 kg m(-3), indicative of a dramatic impact of mixing on the route of subtropical water to becoming the 13 degrees C Water. Still only a small portion of the water formed in the subtropics reaches the equatorial region, because most of the water is trapped and recirculates in the subtropical gyre.
Resumo:
本文描述了基于集散控制原理,采用分层递阶结构建立的一个3级结构双机器人协调控制系统.该系统共分3层,最高层为任务规划级.它对双机器人作业进行离线编程及仿真,并负责对整个系统的监控和管理.第2层为协调级,它实现机器人作业的协调控制.并通过传感器信息对机器人轨迹进行实时修正.该层既可接收来自上层的命令或指令.对机器人进行控制,亦可在该层上独立编程.实现对机器人的控制.第3层为执行级,它实现高精度伺服控制.此外,该系统还提供了灵活的编程环境及良好的人机界面.用户可根据需要选择离线编程环境或实时编程环境,并且可在其相应的界面下工作,运行结果表明,系统性能稳定可靠,结构合理,编程环境灵活.我们在该系统上,成功地进行了PUMA562机器人和PUMA760机器人的点位协调和轨迹协调以及复杂的联合作业.
Resumo:
Rock heterogeneity plays an important role in rock fracturing processes. However, because fracturing is a dynamic process and it is very difficult to quantify materials' heterogeneity, most of the theories dealing with local failure were based on the homogeneity assumption, very few involving stress distribution heterogeneity and successive local failure due to rock heterogeneity. Therefore, based on various references, the author studied the laws and mechanism of influences of heterogeneity on rock fracturing processes, under the frame of the project "Study on Associate Mechanism between Rock Mass Fracture and Strength Failure", funded by Nation Natural Science Fund. the research consists of such aspects as size effect correction to rock fracture parameters, SEM (Scanning Electron Microscope) real-time observation on rock samples under different loads, micro-hardness testing, and numerical simulating based on microstructure. There are some important research results as followed: 1. Unifying formula for nonlinear and non-singularity correction, simplifying the complex process of correcting size effect on rock fracture toughness. 2. Using the methods of micro-hardness testing mineral grain and random jointing micrograph digitizing mineral slice, preliminarily solving the problems of numerical simulating and quantitatively describing the heterogeneous strength and its distribution rules, which has certain innovation and better practicability. 3. Based on SEM real-time observation, studying the micro-process of fracturing in marble, sandstone, granite, and mushroom stone samples with premanufactured cracks under tension, pure-shear and compression-shear conditions. Strength Failure was observed: there was some kind failure occurred before Fracture Failure in marble and sandstone samples with double cracks under pure-shearing. It is believed that the reason of strength failure developing is that stress concentrations is some locations are larger than that near the end of pre-manufactured cracks. 4. Based on the idea that rock macro-constitute is composed of complex microstructure, the promising method used to handle heterogeneity considers not only the heterogeneity of the rock medium, but also the heterogeneity of the rock structure. 5. Putting forward two types of rock strength failure: medium strength failure induced by heterogeneity of rock medium and structure strength failure induced by heterogeneity rock structure. 6. By evaluating potential fracture cell with proper failure priority, the numerical simulating method solved the problem of simulating the coextensive strength failure and fracture failure with convention strength failure rules. The result of numerical analysis shows that the influence of heterogeneity on rock fracturing processes is evident. The sinuosity of the rock fracture-propagation path, and the irregular fluctuation of loading displacement curve, is mainly controlled by the heterogeneity of rock medium.
Resumo:
喀斯特石漠化是近年来所认识到的一种地质生态灾害,所造成的经济、环境乃至社会影响越来越大,受到国家的广泛关注,但却存在生态建设超前、基础研究落后的严峻现实。本文总结了当前石漠化的类型划分和存在问题,从喀斯特生态系统运行的地学过程、生物学过程和人为过程出发,提出石漠化过程存在地质石漠化过程、生态系统石漠化过程和人为加速石漠化过程,对不同类型的石漠化宜分别采取保护、恢复、重建、维持措施。石漠和石漠化表达的时空范畴不同,是石漠化这一土地退化过程的最后或顶极结果,自然条件下其形成多与地表坡度较大有关,而人为加速石漠化过程中石漠化土地空间分布与地形坡度、地貌部位并无直接联系。建议以“干扰方式+植被+土壤+地貌”对人为加速石漠化过程导致的石漠化土地进行类型划分,评价的土地应分为非石漠化土地、行漠化土地和逆转优化的“基准化”土地.