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311.
Hydrodesulfurization catalysts Ni-Mo/C were prepared using active carbon extracted by various solvents. A special feature of the comparison with conventional alumina-supported catalyst was the use of increased hydrogen pressure of 1.6 MPa and the utilization of a commercial Ni-Mo/Al2O3 sample. The best Ni-Mo/C catalyst was 3.6 times more active than the Ni-Mo/Al2O3 reference catalyst. Therefore, better performance of carbon-supported sulfides is not limited to the region of low pressure as suggested by some previous authors. 相似文献
312.
The gas-phase epoxidation of propylene using N2O, air and air-ammonia mixture as an oxidants was studied. Propylene can be epoxidized by nitrous oxide with a yield as high
as 13.3% over silica supported iron oxide catalysts modified by amines. The iron oxide dispersion, the acidity of the support
and the nitrogen-containing modifiers are the key factors determining the catalytic performance. We suggest a reaction pathway
involving two concurrent mechanisms: the radical oxidation of propylene to acroleine, hexanediene, etc., and a non-radical
oxidation leading to epoxide. Propylene is epoxidized with air over silica-supported iron oxide catalysts at a conversion
of about 0.2%. Using air as an oxidizing agent, the presence of gaseous ammonia improves the propylene conversion by 10-fold
preserving the considerable selectivity (up to 60%). This observation suggests a reaction mechanism involving the oxidation
of ammonia to nitrous oxide in the first step, which subsequently produces active oxygen species, which selectively oxidize
propylene to propylene oxide (PO). 相似文献
313.
Radko Kíz 《国际自动化与计算杂志》2014,11(3):231-240
The goal of this paper is to analyze the Finnish gross domestic product(GDP) and to find chaos in the Finnish GDP. We chose Finland where data has been available since 1975, because we needed the longest time series possible. At first we estimated the time delay and the embedding dimension, which is needed for the Lyapunov exponent estimation and for the phase space reconstruction.Subsequently, we computed the largest Lyapunov exponent, which is one of the important indicators of chaos. Then we calculated the 0-1 test for chaos. Finally we computed the Hurst exponent by rescaled range analysis and by dispersional analysis. The Hurst exponent is a numerical estimate of the predictability of a time series. In the end, we executed a recurrent analysis and displayed recurrence plots of detrended GDP time series. The results indicated that chaotic behaviors obviously exist in GDP. 相似文献
314.
The paper investigates the impact of text and background color combinations on the legibility of text presented on LCDs. The legibility of 56 elementary color combinations was tested by 308 participants. The first task required the participants to identify 21 uppercase alphabetic characters selected and presented in conformance with a Snellen chart in various color combinations. For each color combination, the number of correctly identified characters was recorded as a visual performance measure. In the second task, participants subjectively rated the legibility of color combinations on a ten-point Likert scale. The results show that neither the Le Courier legibility table nor the CRT legibility table is appropriate for LCDs. A new legibility table is proposed for LCDs where the highest ranked are contrastive color combinations with positive polarity whereas for CRT displays, the highest ranked are contrastive color combinations with negative polarity. The findings of this study can be used to determine the best possible color combinations when developing content displayed on LCDs. 相似文献
315.
FPGA-based module for SURF extraction 总被引:1,自引:0,他引:1
Tomáš Krajník Jan Šváb Sol Pedre Petr Čížek Libor Přeučil 《Machine Vision and Applications》2014,25(3):787-800
We present a complete hardware and software solution of an FPGA-based computer vision embedded module capable of carrying out SURF image features extraction algorithm. Aside from image analysis, the module embeds a Linux distribution that allows to run programs specifically tailored for particular applications. The module is based on a Virtex-5 FXT FPGA which features powerful configurable logic and an embedded PowerPC processor. We describe the module hardware as well as the custom FPGA image processing cores that implement the algorithm’s most computationally expensive process, the interest point detection. The module’s overall performance is evaluated and compared to CPU and GPU-based solutions. Results show that the embedded module achieves comparable distinctiveness to the SURF software implementation running in a standard CPU while being faster and consuming significantly less power and space. Thus, it allows to use the SURF algorithm in applications with power and spatial constraints, such as autonomous navigation of small mobile robots. 相似文献
316.
317.
Jiří Čmolík Jan Pokorný Marek Doležal Zdeněk Svoboda 《European Journal of Lipid Science and Technology》2007,109(7):656-662
The effect of the operating temperature (between 220 and 270 °C) on the formation of trans isomers of linoleic and linolenic acids in physically refined rapeseed oil during deodorization in a plant‐scale semicontinuous tray‐type deodorizer (capacity 10 t/h) was investigated. The industrial procedures of physical refining consisted of a two‐step bleaching and deodorization process. The degree of isomerization of linoleic acid ranged from 0.33 to 4.77% and that of linolenic acid from 4.43 to 45.22% between 220 and 270 °C, respectively. A relation between the logarithm of the degree of isomerization and the deodorization temperature can be approximated by statistically highly significant linear functions for both linoleic and linolenic acids. Oleic acid was resistant to the heat‐induced geometrical isomerization. The values found for the ratio between the degrees of isomerization of linolenic and linoleic acids, slightly decreasing with increasing temperature, were equal to 13.6 and 12.9 at 230 and 240 °C, respectively. Two trans isomers of linoleic acid, exclusively with one double bond isomerized into trans configuration, and four trans isomers of linolenic acid, mostly with one double bond isomerized into trans configuration, were determined in deodorized rapeseed oils. Linolenic acid was observed to be the main source responsible for the formation of nearly all trans fatty acids in physically refined rapeseed oil. At 235 °C, a deodorization temperature considered as a reasonable technological compromise, the content of trans fatty acids in plant‐scale physically refined rapeseed oil was less than 1% of total fatty acids, which would be acceptable for further application. 相似文献
318.
The behaviour of perovskites La1?xSrxCoO3 (x = 0.02?0.04) was studied at pH = 5. The oxygen evolution is controlled by the chemical reaction of adsorbed Oads. The simultaneous presence of strong oxidants increases the concentration of active intermediates and accelerates the evolution of oxygen. La1?xSrxCoO3 is a P-type semiconductor with a narrow gap (0.27–0.07 eV) and high acceptor concentration. Neither photoelectrochemical effect nor Mott-Schottky barrier were observed in electrolytes; however, rectifying effect was observed on contact of metals with low-substituted cobaltate perovskites. 相似文献
319.
The influence of freezing rate on location, shape and size of ice crystals formed during freezing of beef M. longissimus dorsi, as well as its influence on ultrastructure, were investigated. Muscle samples were frozen at different rates: 0·22 cm/h and 0·39 cm/h (cooling agent was chilled air), and 3·33 cm/h, 3.95 cm/h, 4·92 cm/h and 5·66 cm/h (cooling agent was liquid carbon dioxide which expanded in the sucking-pipe of the tunnel freezer).
It was found that by slow freezing (freezing rates 0·22 cm/h and 0·39 cm/h) 30·00 μm). An increase in the freezing rate was followed by a change in ice crystal location. In this case they had also been formed intracellularly. The number of crystals increased while their size decreased.
The most intensive fibre damage was found in samples frozen at a rate of 0·22 cm/h, and the least in samples frozen at a rate of 3·95 cm/h with a freezing temperature of −50°C. 相似文献
320.
A liquid–liquid phase transfer catalyzed (PTC) esterification reaction of 4-t-butylphenol in aqueous phase (1 M sodium hydroxide solution) and 4-methoxybenzoyl chloride in organic phase (dichloromethane) in a microchannel under parallel laminar flow conditions was studied in this work. Tetrabutylammonium bromide was used as the PTC. Stable liquid–liquid hydrodynamic flow and a defined specific interfacial area in a microreactor offer considerable benefits over conventional batch reactors and are crucial to study interactions between kinetics and mass transfer effects. Mentioned features were used to develop a 3D mathematical model considering convection in the flow direction, diffusion in all spatial directions, and reactions in organic and aqueous phases. Results have shown a much higher mass transfer rate of the PTC between both phases as the one predicted by the 3D mathematical model. It may be assumed that the instability of parallel flow, along with the mass transfer of catalyst between both phases, causes rippling and erratic pulsation at the interface which then leads to interfacial convection and increased mass transfer rates. With a proposed correlation for mass transfer enhancement due to interfacial convection, all the experimental data were successfully predicted by the model. 相似文献