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排序方式: 共有61条查询结果,搜索用时 200 毫秒
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M. Saeed Abaee Soodabeh Forghani Mohammad M. Mojtahedi Klaus Harms 《Journal of Sulfur Chemistry》2016,37(6):683-691
A facile procedure is developed for one-pot synthesis of a new group of dicyanoanilines. Tetrahydro-4H-thiopyran-4-one, 1, undergoes a pseudo four-component reaction with various aldehydes bearing different groups and two equivalents of malononitrile in aqueous media in the presence of triethylamine (Et3N). As a result, novel thiopyran-fused dicyanoanilines 4 are formed efficiently in the reaction mixtures in 90–97% yield within 9–12?h mixing at 40°C. Due to the polarity of the medium, products precipitate in the mixture spontaneously allowing for easy purification by recrystallization avoiding cumbersome chromatographic separations. Characterization of the products was performed by spectroscopic methods and, in one case, was further supported by X-ray crystallographic experiments. 相似文献
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Bacillus cereus comprises the largest group of endospore‐forming bacteria and can cause emetic and diarrheal food poisoning. A total of 496 B. cereus strains isolated from various sources (food, environmental, clinical) were assessed by a multiplex PCR for the presence of enterotoxin genes. The detection rate of nheA, entFM, hblC, and cytK enterotoxin genes among all B. cereus strains was 92.33%, 77.21%, 59.47%, and 47.58%, respectively. Enterotoxigenic profiles were determined in emetic toxin‐ (8 patterns) and enterotoxin‐producing strains (12 patterns). The results provide important information on toxin prevalence and toxigenic profiles of B. cereus from various sources. Our findings revealed that B. cereus must be considered a serious health hazard and Bacillus thuringiensis should be considered of a greater potential concern to food safety among all B. cereus group members. Also, there is need for intensive and continuous monitoring of products embracing both emetic toxin and enterotoxin genes. 相似文献
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Fereidoun Amini N. Khanmohammadi Hazaveh A. Abdolahi Rad 《Computer-Aided Civil and Infrastructure Engineering》2013,28(7):542-557
This study presents a new method to find the optimal control forces for active tuned mass damper. The method uses three algorithms: discrete wavelet transform (DWT), particle swarm optimization (PSO), and linear quadratic regulator (LQR). DWT is used to obtain the local energy distribution of the motivation over the frequency bands. PSO is used to determine the gain matrices through the online update of the weighting matrices used in the LQR controller while eliminating the trial and error. The method is tested on a 10‐story structure subject to several historical pulse‐like near‐fault ground motions. The results indicate that the proposed method is more effective at reducing the displacement response of the structure in real time than conventional LQR controllers. 相似文献
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Mathematical modelling of a hydrocracking reactor for triglyceride conversion to biofuel: model establishment and validation 下载免费PDF全文
In the study, a 2D, non‐isothermal, heterogeneous model of a triglyceride hydrocracking reactor is investigated. The internal heat and mass transfer within the phases in the reactor were considered using the film theory. The conservation equations for energy and mass were solved simultaneously using appropriate numerical techniques whose reliability was assessed by comparison of the results with previously reported experimental data. The modelling was performed with consideration of two proposed hydrocracking kinetic models. The model predictions showed reasonable correlation with published experimental data and conversion rates. The calculations indicated that at feed temperature of 380 °C, liquid hourly space velocity of 8 h?1 and hydrogen : feed ratio of 1500:1, the total triglyceride conversion was 82.54% for four major classes of hydrocarbons (light, middle, heavy and oligomerised). In addition, the concentration distribution and temperature profile along the reactor were investigated. The product concentrations along the reactor show that higher rates of production at the beginning of the reactor were achieved because of high concentration of triglyceride due to the exothermic hydrocracking reactions and counter‐current flow modes of triglyceride and hydrogen; a jump of 90 °C was shown at the beginning of the reactor temperature profile. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
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M.R. Rahimpour A.A. Forghani A. Khosravanipour Mostafazadeh A. Shariati 《Fuel Processing Technology》2010,91(1):33-44
In this work, a comparison of co-current and counter-current modes of operation for a novel hydrogen-permselective membrane reactor for Fischer-Tropsch Synthesis (FTS) has been carried out. In both modes of operations, a system with two-catalyst bed instead of one single catalyst bed is developed for FTS reactions. In the first catalytic reactor, the synthesis gas is partly converted to products in a conventional water-cooled fixed-bed reactor, while in the second reactor which is a membrane fixed-bed reactor, the FTS reactions are completed and heat of reaction is used to preheat the feed synthesis gas to the first reactor. In the co-current mode, feed gas is entered into the tubes of the second reactor in the same direction with the reacting gas stream in shell side while in the counter-current mode the gas streams are in the opposite direction. Simulation results for both co-current and counter-current modes have been compared in terms of temperature, gasoline and CO2 yields, H2 and CO conversion, selectivity of components as well as permeation rate of hydrogen through the membrane. The results showed that the reactor in the co-current configuration operates with lower conversion and lower permeation rate of hydrogen, but it has more favorable profile of temperature. The counter-current mode of operation decreases undesired products such as CO2 and CH4 and also produces more gasoline. 相似文献
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Active control is one of the modern approaches in seismic design of steel structures. Recently, induced by economic considerations, especially high expenses of control systems, optimality has become an important issue. In this paper an active system is used to control a steel structure’s displacements by a simplified pole assignment method. To optimize the number, the locations, and the total driving force of the required actuators, an improved particle swarm algorithm is presented focusing on the parameters of the velocity equation. A Geographical neighborhood topology and an adaptive inertia weight are used to improve the standard PSO algorithm. In addition to the local and global best solutions, the positions of the best particles in the geographical neighborhood are mathematically represented in an additional term. The performance of the proposed algorithm is compared with the traditional Genetic Algorithm (GA) and the standard particle swarm considering the optimal control of a 12-story steel structure as a numerical example. High capabilities of the proposed method in terms of the control target, convergence rate, and accuracy are simultaneously clarified by the results. 相似文献
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Fatemeh Bandarian Mehdi Hedayati Maryam Sadat Daneshpour Mohsen Naseri Fereidoun Azizi 《Lipids》2013,48(12):1207-1216
Low high density lipoprotein cholesterol (HDL-C) is a known risk factor of coronary artery disease. Apolipoprotein A1 (APOA1) is the most abundant component of HDL-C. This study aimed at identifying sequence variations (rare and common) in the APOA1 gene and its association with serum HDL-C levels. This study was conducted from April 2012 to February 2013 on 79 Tehranians (participants of Tehran Lipid and Glucose Study) with extremely low HDL-C (within the 5th percentile) and 63 individuals with extremely high HDL-C (within the 95th percentile) levels. After DNA amplification by PCR, DNA sequencing of all three exons and 700 bps of promoter region of the APOA1 gene was performed. Sequence results were analyzed and interpreted using the appropriate software and variants were identified. After sequencing 42 common and rare variants were identified, 11 of which were known variants and the others had been unreported so far. Of the exonic variants, 11 were missense, 6 were synonymous and 1 was nonsense. There was a significant association between serum HDL-C and variant of rs2070665 as well as variants Chr.11:116707788, Chr.11:116708059, Chr.11:116708036, Chr.11:116707729, rs201148448, Chr.11:116707018, Chr.11:116707801, Chr.11:116708530, Chr.11:116708088, rs121912724 and Chr.11:116706966 (p < 0.001). Variants Chr.11:116707018, rs121912724 and 2070665 were independent predictors of the HDL-C level (p < 0.001). SNP Chr.11:116707018 was the strongest predictor of the HDL-C level (OR 7.527, p < 0.001). This study identified 42 variants in APOA1 gene, 31 of which were new variants. Three variants of rs2070665, rs121912724 and Chr.11:116707018 could predict the HDL-C level independently. Variant rs2070665 was protective against low-HDL-C levels while variants rs121912724 and Chr.11:116707018 were risk factors for that in our population. 相似文献