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排序方式: 共有443条查询结果,搜索用时 906 毫秒
31.
32.
Asghar Alizadehdakhel Masoud Rahimi Jafar Sanjari Ammar Abdulaziz Alsairafi 《International Communications in Heat and Mass Transfer》2009,36(8):850-856
A large number of experiments in a 2 cm diameter and 6 m length tube were carried out in order to study the two-phase flow regimes and pressure drops in it. The two-phase flow in the experimental tube was modeled using commercial CFD code, Fluent 6.2. An Artificial Neural Network (ANN) with three inputs including gas and liquid velocities and tube slope was designed and trained to predict average pressure drop across the tube. The comparison between CFD and ANN predictions of pressure drops with experimental measurements shows that the CFD results are more accurate than the ANN evaluations for new conditions. 相似文献
33.
Effect of process variables on product yield distribution in thermal catalytic cracking of naphtha to light olefins over Fe/HZSM-5 总被引:1,自引:0,他引:1
Mina Alyani Jafar Towfighi Seyed Mojtaba Sadrameli 《Korean Journal of Chemical Engineering》2011,28(6):1351-1358
The effect of temperature, WHSV and Fe loading over HZSM-5 catalyst in thermal-catalytic cracking (TCC) of naphtha for the
production of light olefins has been studied. The response surface defined by three most significant parameters is obtained
from Box-Behnken design method and the optimal parameter set is found. The results show that ethylene increases with temperature,
while propylene shows an optimum at 650 °C. Moderate WHSV is favorable for maximum production of light olefins. Addition of
Fe to HZSM-5 has a favorable effect on the production of light olefins up to 6% of loading. Excess amount of loading decreases
the conversion of naphtha, which leads to a drop in light olefin yields. The yield of light olefins (ethylene and propylene)
at 670 °C, 44 hr−1 and 6 wt% Fe has been increased to 5.43 wt% compared to the unmodified HZSM-5 and reaches to 42.47 wt%. 相似文献
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Jafar Safarian Gabriella Tranell Merete Tangstad 《Metallurgical and Materials Transactions B》2013,44(3):571-583
Boron (B) is the most problematic impurity to be removed in the processes applied for the production of solar grade silicon. Boron removal from liquid silicon by sodium-silicate slags is experimentally studied and it is indicated that B can be rapidly removed within short reaction times. The B removal rate is higher at higher temperatures and higher Na2O concentrations in the slag. Based on the experimental results and thermodynamic calculations, it is proposed that B removal from silicon phase takes place through its oxidation at the slag/Si interfacial area by Na2O and that the oxidized B is further gasified from the slag through the formation of sodium metaborate (Na2B2O4) at the slag/gas interfacial area. The overall rate of B removal is mainly controlled by these two chemical reactions. However, it is further proposed that the B removal rate from silicon depends on the mass transport of Na in the system. Sodium is transferred from slag to the molten silicon through the silicothermic reduction of Na2O at the slag/Si interface and it simultaneously evaporates at the Si/gas interfacial area. This causes a Na concentration rise in silicon and its further decline after reaching a maximum. A major part of the Na loss from the slag is due to its carbothermic reduction and formation of Na gas. 相似文献
37.
Mohammad Rezanejad Abdolreza Sheikholeslami Jafar Adabi Mohammadreza Valinejad 《International Journal of Electronics》2016,103(5):868-877
This article proposes a new structure of voltage multiplier for portable pulsed power applications. In this configuration, which is based on capacitor-diode voltage multiplier, the capacitors are charged by low AC input voltage and discharge through the load in series during pulse generation mode. The proposed topology is achieved by integrating of solid-state switches with conventional voltage multiplier, which can increase the low input voltage step by step and generate high-voltage high-frequency pulsed power across the load. After some discussion, simulations and experimental results are provided to verify the effectiveness of the proposed topology. 相似文献
38.
Md. Irshad Irfan Ahmad Syed Jafar Mehdi Harish Chandra Goel 《International Journal of Food Properties》2013,16(1):179-186
The antioxidant capacity of commonly consumed cucurbits vegetable was determined by the DPPH, FRAP, Fe3+ reducing power, and hydrogen peroxide scavenging assay. The aqueous extract of Luffa cylindrica showed the highest value of phenolic content and antioxidant capacity based on FRAP, Fe3+ reducing power, and hydrogen peroxide scavenging assay. However, Laginaria siceraria extract showed the highest flavonoid and DPPH scavenging activities among all three cucurbits used in this study. Phenolic content in aqueous extracts of Luffa cylindrica and Laginaria siceraria was almost equal. Cucurbita maxima exhibited the lowest phenolic, flavonoid content, and exhibited the lowest power of antioxidant scavenging. The antioxidant capacity of cucurbits was significantly correlated (P < 0.05) with the phenolic content of their extracts. The antioxidant capacity of Luffa cylindrica and Laginaria siceraria have also shown a significant correlation (P < 0.05). 相似文献
39.
Soheila Kashanian Jafar Ezzati Nazhad Dolatabadi 《European Food Research and Technology》2010,230(6):821-825
The interaction of native calf thymus DNA (CT-DNA) with 2-tert-butyl-4-methylphenol (TBMP) at physiological pH has been investigated by spectrofluorometric and viscosimetric techniques.
TBMP molecules were found to intercalate between base pairs of DNA, demonstrated by an increase in the specific viscosity
of DNA and decrease in the fluorescence of TBMP solutions in the presence of increasing amounts of DNA and the calculated
binding constants (K
f) at different temperatures. Furthermore, the enthalpy and entropy of the reaction between TBMP and CT-DNA showed that the
reaction is exothermic and enthalpy favored (ΔH = −19.18 kJ mol−1; ΔS = −26.98 J mol−1 K−1) which are other evidences to indicate that TBMP is able to be intercalated in the DNA base pairs. 相似文献
40.