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排序方式: 共有559条查询结果,搜索用时 609 毫秒
91.
Corneliu Sergiu Stan Ioan Rosca Daniel Sutiman Marius Sebastian Secula 《中国稀土学报(英文版)》2012,30(5):401-407
The preparation of two highly luminescent europium(III) and terbium(III) complexes with succinimide(SI) and N-hydroxysuccinimide(NHSI) were reported,which were further investigated through elemental chemical analysis,thermal analysis,FT-IR,powder X-ray diffraction,SEM and fluorescence spectroscopy.Data collected through these analysis revealed the formation of the Eu(III) and Tb(III) complexes with the above mentioned ligands at a metal to ligand(M:L) molar ratio of 1:3.Interesting conclusions regarding the efficient sensitization through the coordination site of the lanthanide luminescent centers were retained from the photoluminescent spectra investigation.Strong luminescence emission was observed in case of Eu(III)-SI and Tb(III)-NHSI complexes while the corresponding Eu(III)-NHSI and Tb(III)-SI complexes exhibited no photo luminescent properties.Newly obtained luminescent lanthanide complexes may be of particular interest for various applications in optoelectronics. 相似文献
92.
Biodiesel production using enzymatic transesterification - Current state and perspectives 总被引:1,自引:0,他引:1
Biodiesel has attracted considerable interest in recent years as an alternative, biodegradable and nonpolluting transportation fuel. Conventional alkaline process for biodiesel production are energy-consuming and generate undesirable by-products such as soaps, that make difficult the separation and purification of biodiesel.Particular attention has been dedicated to the use of lipases as biocatalysts for biodiesel production due to their favorable conversion rate obtained in gentle conditions and relatively simple downstream processing steps for the purification of biodiesel and by-products. However, comparatively to conventional chemical processes, the major obstacles for enzymatic production of biodiesel remain the cost of lipases, the relatively slower reaction rate and lipases inactivation caused by methanol and glycerol.This review evaluates the current status and perspectives for enzymatic biodiesel production and indicates the key operational variables that influence lipase activity and stability together with the technological solutions for industrial implementation of enzymatic process. 相似文献
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95.
Alemgena A. Araya Marius Huurman André A. A. Molenaar Lambert J. M. Houben 《Materials and Structures》2012,45(5):695-705
In many developing countries, where resources are at premium, thin asphalt layers or chip seals are widely used to provide
a durable all weather pavement surfacing. In such pavements the role of granular layers is very important in the general performance
of the structure. Pavement designs in these countries are empirical in nature and rely on simple input parameters like California
Bearing Ratio (CBR) values. Although widely applicable the traditional CBR test does not provide the mechanical properties
such as resilient and permanent deformation characteristics of granular road materials. This paper documents the characterization
technique developed to determine the mechanical behavior of granular (sub-) base materials based on CBR test using repeated
load cycles. The confining pressure developed in the complex CBR stress state is estimated using strain gauges. Finite Element
analysis has been attempted to model the repeated load CBR (RL-CBR) and derive an equivalent resilient modulus. Furthermore,
a large scale cyclic load triaxial test was carried out on coarse unbound granular materials (UGMs) to validate the result
of the RL-CBR. The RL-CBR test reasonably estimates the resilient modulus of UGMs which can be used as an input in mechanistic
pavement design analysis in the absence of triaxial testing facilities. 相似文献
96.
We have analyzed data published by others reporting the solubility of helium in liquid hydrogen, oxygen, and methane, and of nitrogen in liquid oxygen, to develop empirical correlations for the mole fraction of these pressurant gases in the liquid phase as a function of temperature and pressure. The data, compiled and provided by NIST, are from a variety of sources and covers a large range of liquid temperatures and pressures. The correlations were developed to yield accurate estimates of the mole fraction of the pressurant gas in the cryogenic liquid at temperature and pressures of interest to the propulsion community, yet the correlations developed are applicable over a much wider range. The mole fraction solubility of helium in all these liquids is less than 0.3% at the temperatures and pressures used in propulsion systems. When nitrogen is used as a pressurant for liquid oxygen, substantial contamination can result, though the diffusion into the liquid is slow. 相似文献
97.
Run-out distances and flow velocities of snow avalanches are mainly determined by frictional processes originating from the interaction with the ground. At the SLF snow chute at the Weissfluhjoch near Davos, a setup was developed which allowed us to record high-speed movies of the basal shear layer of small-scale avalanches with a frame rate of 1000 frames per second. Shear processes could be observed in high-resolution slow motion. Downstream velocity profiles were extracted by a pattern matching algorithm. The comparison of computed profiles with velocity profiles obtained from optical sensors showed good agreement. However, the temporal and spatial resolutions are much higher for the high-speed video data. Because the optical velocity sensors are one-dimensional, we found that they overestimate the velocities when a flow-normal velocity component exists as well. All measured velocity profiles exhibited very high shear rates near the ground. The maximum shear rates were up to 600/s for dry snow and 200/s for wet snow avalanches. The observations of the video images suggested a turbulent motion of the snow in the basal shear layer. 相似文献
98.
Prevalence and Characterization of Multi‐Resistant Staphylococcus SPP. Isolated from Poultry Liver 下载免费PDF全文
99.
Florin Tudorache Paul Dorin Popa Marius Dobromir Felicia Iacomi 《Materials Science and Engineering: B》2013,178(19):1334-1338
The influence of Co2+ ions content on structure and sensing properties of Ni1−xCoxFe2O4 (x = 0.25, 0.5, 0.75) thin films deposited on glass substrates by spin coating is presented. Structural characterization evidenced thin films with cubic spinel structures and morphologies dependent on cobalt content. Repartition of cations in spinel tetrahedral and octahedral sites was determined and was found that the presence of Co2+ ions in octahedral sites favor the formation of Fe2+ species. The sensitivity to some reducing vapor gases (acetone, liquefied petroleum gas LPG, ethyl alcohol and methyl alcohol) was investigated and was found that thin films with x = 0.75 exhibit high sensitivity to ethyl alcohol and thin films with x = 0.25 have high sensitivity to acetone. This sensitivity largely depends on the temperature and test gas concentration and was related to the Fe2+ species formed in octahedral sites. 相似文献
100.
Yao Koffi Jocelyne M. Bosson Marius Ipo Gnetto Edoe F. Mensah Jeremie T. Zoueu 《Journal of Modern Optics》2013,60(17):1763-1776
ABSTRACTWe describe in this work an approach that individually combines constant initialization, free-space backpropagation, transport of intensity equation (TIE) and multi-height phase recovery with Fast Iterative Shrinkage-Thresholding Algorithm (FISTA) to predict reconstruction of the phase microspheres from diffracted field measurements. We incorporate appropriate initialization and regularization to reconstruct unknown phase microspheres (transparent objects). 相似文献