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排序方式: 共有792条查询结果,搜索用时 15 毫秒
71.
Denis Prodius Fliur Macaev Valeriu Mereacre Sergiu Shova Yurii Lutsenco Eugenia Styngach Patricia Ruiz Dmitry Muraviev Janusz Lipkowski Yurii A. Simonov Constantin Turta 《Inorganic chemistry communications》2009,12(7):642-645
The novel μ3-oxo-bridged heterotrinuclear iron(III)-copper(II) trichloroacetates of the composition [Fe2CuO(CCl3COO)6(THF)3] (1a) and [Fe2CuO(CCl3COO)6(4-DMAP)3] (1b) have been synthesized and characterized by X-ray crystallography, IR and Mossbauer spectroscopy. These clusters were used as precursors for the synthesis of the nanosized catalytic system (~5–6 nm of γ-Fe2O3/CuO), which works as an efficient organic phase catalyst (~0.02 mol%) in a one-pot three component Biginelli synthesis. 相似文献
72.
Dubis Eligiusz Poplawski Janusz Wróbel Jerzy T. Kúsmierz Józef Maliński Edmund Szafranek Janusz 《Lipids》1986,21(7):434-439
The exoskeleton triglyceride fraction isolated from the Colorado beetle,Leptinotarsa decemlineata Say, was studied. Analysis of the hydrolysis products and direct capillary column gas chromatography showed that, apart from
triglycerides, the fraction contained no diol lipids. The composition of the natural triacylglccerol mixture was assessed
by gas chromatography and by field desorption and electron impact mass spectrometry. Triglycerides isolated from the Colorado
beetle are typical glycerol triesters, with long chain (mainly oleic or palmitic) fatty acids. The structures of two major
components (91%), i.e., trioleoyl glycerol and 1,2-dioleoyl-3-palmitoyl glycerol, were determined. 相似文献
73.
The present paper describes numerical modelling of the radiative heat transfer process in the module chamber of an internal indirect reforming-type SOFC. The ability to do internal reforming is one of the characteristics of high-temperature fuel cells, SOFC. As in any high-temperature system, radiative heat transfer is important. In this article, heat transfer between the fuel reformer surface and all other surfaces facing the reformer surfaces is modelled. Governing equations for radiative heat transfer are described using Hottel's zone method. The resulting radiation–conduction conjugate heat transfer problems are numerically solved with a combination of Gauss–Seidel and Newton–Raphson methods. The steam reforming reaction occurring inside the fuel reformer is described using Achenbach model. The obtained results indicate that, for the development of effective indirect internal reforming, the position of the reformer in the module chamber and emissivity of the surfaces of the reformer, cell and other elements in the SOFC module all play a key role. 相似文献
74.
Room-temperature ultrasonic compressional wave velocity and attenuation measurements have been carried out on commercial poly-methyl methacrylate (PMMA) and fully deuterated PMMA. Deuteration was found to reduce the velocity by 4.4 ± 1.2% which can be completely accounted for by the density change of 8.0%, assuming no changes in atomic force constants or molar volume. The attenuation was 17% higher in the deuterated sample. Making reasonable assumptions about the distribution function for the relaxation times of molecular groupings moving in two-well potentials, the attenuation increase is attributed to a reduction in the attempt frequency for barrier hopping of main chain and/or ester methyl groups. 相似文献
75.
Riedel Silvia Gabrys Bogdan 《Knowledge and Data Engineering, IEEE Transactions on》2009,21(12):1753-1766
In this paper, we provide a theoretical analysis of effects of applying different forecast diversification methods on the structure of the forecast error covariance matrices and decomposed forecast error components based on the bias-variance-Bayes error decomposition of James and Hastie. We express the "diversity” of different forecasts in relation to different error components and propose a measure in order to quantify it. We illustrate and discuss typical inhomogeneities frequently occurring in the forecast error covariance matrices and show that previously proposed pooling based only on error variances cannot fully exploit the complementary information present in a set of diverse forecasts to be combined. If covariance values could be reliably calculated, they could be taken into account during the pooling process. We study the difficult case in which covariance information cannot be measured properly and propose a novel simplified representation of the covariance matrix, which is only based on knowledge about the forecast generation process. Finally, we propose a new pooling approach that avoids inhomogeneities in the forecast error covariance matrix by considering the information contained in the simplified covariance representation and compare it with the error-variance-based pooling approach introduced by Aiolfi and Timmermann. Applying our approach more than once leads to the generation of multistep and multilevel forecast combination structures, which have generated significantly improved forecasts in our previous extensive experimental work; the summary of which is also provided. 相似文献
76.
Shanju Zhang Lingbo Zhu Marilyn L. Minus Han Gi Chae Sudhakar Jagannathan Ching-Ping Wong Janusz Kowalik Luke B. Roberson Satish Kumar 《Journal of Materials Science》2008,43(13):4356-4362
We report continuous carbon nanotube (CNT) fibers and yarns dry-drawn directly from water-assisted chemical vapor deposition
(CVD) grown forests with about 1-mm height. As-drawn CNT fibers exist as aerogel and can be transformed into more compact
fibers through twisting or densification with a volatile organic liquid. CNT fibers are characterized by scanning electron
microscopy, X-ray photoelectron spectroscopy, Raman microscopy, and wide-angle X-ray diffraction. Mechanical properties and
electrical conductivity of the post-treated CNT fibers are investigated. The resulting fibers show the work of rupture of
30 J/g and DC electrical conductivity of 5.0 × 104 S/m. 相似文献
77.
Maria Lezanska Jerzy Wloch Janusz Niedojadlo Jan Kornatowski 《Microporous and mesoporous materials》2008,111(1-3):463-469
Synthesis of novel, carbon porous replicas of vesicular siliceous materials has been described. The original siliceous materials consist of small, spherical structures resembling onions, known in the literature as multilamellar vesicles (MLVs). They have been characterized with a number of analytical methods that allow one to determine its 3-D structure and basic parameters of the pore system. Carbonaceous materials, made similarly of onion-like porous structures, have been obtained using a standard procedure to form replicas. They have been characterized by the same methods as those applied to the parent materials. 相似文献
78.
The main goal of this paper is to model a multiphase flow of a monodispersed suspensions in various types of crystallizers: Draft Tube Magma (DTM), Double Draft Tube (DDT) and Fluidized bed (FL). To do this, the CFD (Computational Fluid Dynamics) methods were used. The geometry of model apparatus was similar to those applied in industry. The composition of suspensions and their physical properties were the same as in practical cases. 相似文献
79.
Janusz Nowicki 《Journal of surfactants and detergents》2010,13(2):195-199
The emulsion and phase properties of water-surfactant systems are reported for nonionic surface active compounds of the asymmetrical
gemini type resulting from the esterification of a polyethoxylated alcohol and a fatty acid. These products exhibit typical
gemini surfactant properties, in particular, low critical micelle concentration (CMC) and good emulsifying properties, and
they often form a gel depending on the temperature and concentration. 相似文献
80.
Direct determination of benzodiazepines in biological fluids by restricted-access solid-phase microextraction 总被引:6,自引:0,他引:6
A biocompatible solid-phase microextraction (SPME) fiber was prepared using an alkyl-diol-silica (ADS) restricted-access material as the SPME coating. The ADS-SPME fiber was able to simultaneously fractionate the protein component from a biological sample, while directly extracting several benzodiazepines, overcoming the present disadvantages of direct sampling in biological matrixes by SPME. The fiber was interfaced with an HPLC-UV system, and an isocratic mobile phase was used to desorb, separate, and quantify the extracted compounds. The calculated clonazepam, oxazepam, temazepam, nordazepam, and diazepam detection limits were 600, 750, 333, 100, and 46 ng/mL in urine, respectively. The method was confirmed to be linear over the range of 500-50000 ng/mL with an average linear coefficient (R2) value of 0.9918. The injection repeatability and intraassay precision of the method were evaluated over 10 injections, resulting in a RSD of approximately 6%. The ADS-SPME fiber was robust and simple to use, providing many direct extractions and subsequent determination of benzodiazepines in biological fluids. 相似文献