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排序方式: 共有719条查询结果,搜索用时 31 毫秒
81.
Mohammad Reza Karafi Ramin Narimani Yousef Hojjat Mojtaba Gheybi 《The International Journal of Advanced Manufacturing Technology》2010,50(9-12):953-960
This paper presents a method for automatic control of arc length in tungsten inert gas (TIG) welding process using the arc voltage. By using this method, the role of operator in arc length control is played by an automatic control system based on a predefined arc voltage value for any special welding operation. A dynamic model for feed-rate mechanism and the relation between variations of arc length and voltage are described in details. Using a proportional-integral controller, variations of arc length in welding path is compensated with an automatic feed-rate mechanism in a normal direction to the welding path. By keeping the voltage constant during the process, a stable weld with higher quality and better appearance is obtained specially in welding of uneven surfaces. Theoretical and practical investigations show that the suggested method is able to control the TIG welding process successfully. Test results show that an accurate weld is obtained without the interference of the operator, and by comparing the predefined values of arc voltage with what is practically obtained, the welding gap is automatically adjusted. 相似文献
82.
Hassan Hassanzadeh Mehran Pooladi‐Darvish David W. Keith 《American Institute of Chemical Engineers》2009,55(2):475-485
Carbon dioxide injection into deep saline aquifers is an important option for managing CO2 emissions. Injected CO2 dissolves into formation brines from above, increasing brine density and creating an unstable hydrodynamic state favorable for natural convection. Long‐term buoyancy‐driven flow of high‐density CO2‐saturated brine leads to faster trapping through improved dissolution and can reduce the risk of CO2 leakage from storage sites. We investigate the role of natural flow of aquifers and associated dispersion on the onset of convection. A linear stability analysis of a transient concentration field in a laterally infinite, horizontal, and saturated porous layer with steady horizontal flow is presented. The layer is subjected to a sudden rise in CO2 concentration from the top and is closed from the bottom. Solution of the stability equations is obtained using a Galerkin technique and the resulting equations are integrated numerically. We found simple scaling relationships that follow tDc~60(1 + PeT)Ra‐2 for the onset time of convection and a~0.05Ra/(1 + PeT) for the wavenumber of the initial instabilities. Results reveal that transverse dispersion increases the time to onset of convection for the entire range of Ra. Furthermore, transverse dispersion decreases the critical wavenumber of the instabilities. These results facilitate screening candidate sites for geological CO2 storage. © 2008 American Institute of Chemical Engineers AIChE J, 2009 相似文献
83.
Yousef Kazemzadeh Behnam Dehdari Zahra Etemadan Masoud Riazi Mohammad Sharifi 《石油科学(英文版)》2019,(3):578-590
Nanofluids because of their surface characteristics improve the oil production from reservoirs by enabling different enhanced recovery mechanisms such as wettability alteration, interfacial tension (IFT) reduction, oil viscosity reduction, formation and stabilization of colloidal systems and the decrease in the asphaltene precipitation. To the best of the authors’ knowledge, the synthesis of a new nanocomposite has been studied in this paper for the first time. It consists of nanoparticles of both SiO2 and Fe3O4. Each nanoparticle has its individual surface property and has its distinct effect on the oil production of reservoirs. According to the previous studies, Fe3O4 has been used in the prevention or reduction of asphaltene precipitation and SiO2 has been considered for wettability alteration and/or reducing IFTs in enhanced oil recovery. According to the experimental results, the novel synthesized nanoparticles have increased the oil recovery by the synergistic effects of the formed particles markedly by activating the various mechanisms relative to the use of each of the nanoparticles in the micromodel individually. According to the results obtained for the use of this nanocomposite, understanding reservoir conditions plays an important role in the ultimate goal of enhancing oil recovery and the formation of stable emulsions plays an important role in oil recovery using this method. 相似文献
84.
85.
The purpose of this study was the production of copolymers and terpolymers with highly hydrophilic–hydrophobic properties, using inexpensive and available monomers as potential enhancing oil recovery (EOR) and water production control agents for high-temperature and high-salinity (HTHS) oil reservoirs. For this purpose, several copolymers and terpolymers with different molar percentage of acrylamide/styrene, acrylamide/maleic anhydride, and acrylamide/styrene/maleic anhydride were synthesized by the inverse emulsion polymerization technique. The presence of hydrophobic styrene and hydrophilic maleic anhydride monomers in the copolymer and terpolymer structure, provided some unique properties compared to polyacrylamide, was confirmed by several analyses including HNMR, elemental analysis, FTIR, SEM, TGA, and DSC. Simulating HTHS oil reservoir condition under high salinity, temperature, and shear rate, the rheological studies suggested unlike traditional EOR agents such as polyacrylamide, the viscosity of the copolymer, and terpolymer aqueous solutions showed a considerable increase after a critical polymer concentration and less reduction with the salt increment at both ambient and elevated temperatures. Furthermore, the swelling ratio of the insoluble terpolymers measured versus the time and temperature in salt water increased with the maleic anhydride mole fraction, decreased with the salt concentration, and showed a maximum value at around 57 °C. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47753. 相似文献
86.
Antifungal activity of Lactobacillus paracasei ssp. tolerans isolated from a sourdough bread culture 总被引:2,自引:0,他引:2
Lactic acid bacteria were isolated from four different sourdough bread cultures previously investigated for antifungal activity. A total of 116 isolates were obtained and screened for antifungal activity against a battery of molds. The most inhibitory isolate obtained was identified by API 50 CHL and 16s ribosomal RNA genotyping and found to be Lactobacillus paracasei ssp. tolerans. This isolate completely inhibited the growth of Fusarium proliferatum M 5689, M 5991 and Fusarium graminearum R 4053 compared to controls in a dual agar plate assay. 相似文献
87.
Prediction of Egg Freshness and Albumen Quality Using Visible/Near Infrared Spectroscopy 总被引:1,自引:0,他引:1
Nicolas Abdel-Nour Michael Ngadi Shiv Prasher Yousef Karimi 《Food and Bioprocess Technology》2011,4(5):731-736
Important changes occur in egg during storage leading to loss of quality. Prediction of these changes is critical in order
to monitor egg quality and freshness. The aim of this research was to evaluate application of visible (VIS) and near infrared
(NIR) spectroscopy as a rapid and non-destructive technique for egg quality assessment. Three hundred and sixty intact white-shelled
eggs freshly laid by the same flock of hens fed with a standard feed were obtained. They were put under controlled conditions
of temperature and humidity (T = 18 °C and RH = 55%) for 16 days of storage. Forty eggs were analyzed at day 0, 2, 4, 6, 8, 10, 12, 14, and 16. Transmission
spectral data was obtained in the range from 350 to 2,500 nm. The non-destructive spectral data was compared to egg sample’s
Haugh unit (HU) and albumen pH in terms of quality and to the number of storage days in terms of freshness. A partial least
squares predictive model was developed and used to link the destructive assessment methods and the number of storage days
with the spectral data. The correlation coefficient between the measured and predicted values of HU, albumen pH, and number
of storage days were up to 0.94, R
2 was up to 0.90 and the root mean square error values for the validation were 5.05, 0.06, and 1.65, respectively. These results
showed that VIS/NIR transmission spectroscopy is a good tool for assessment of egg freshness and albumen pH and can be used
as a non-destructive method for the prediction of HU, albumen pH, and number of storage days. In addition, the relevant information
about these parameters was in the VIS and NIR ranging from 411 to 1,729 nm. 相似文献
88.
In the work, synthesis and application of the ternary nanocomposite of SiO2/Fe3O4/multi-walled carbon nanotubes (SFCNT) for adsorptive removal of malachite 相似文献
89.
This study proposes a multiperiod mixed integer linear programming model for the management of a single municipal solid waste (MSW) treatment plant with sustainability as the objective. Discrete and continuous variables define the capacity selections for diverse MSW technologies, and the operation of the MSW network, respectively. The economic target is considered to maximize the net present value. The environmental impact is the minimization of a normalized environmental objective function (NEOF). The social target is the maximization of jobs. An interesting feature about the research work is the requirement of biodrying technologies for MSW moisture content control. Due to the conflicted nature among the sustainability components, a multiobjective optimization (MO) is carried out to find the Pareto optimal solutions. The MO results show that the Pareto optimal solutions vary around profit range of $4.9–8.5 billion, NEOF impact range of 3.2–3.6 units, and social benefit range of 2700–4828 jobs. 相似文献
90.
Effects of yoghurt butter oils on rat plasma lipids,haematology and liver histology parameters in a 150‐day study
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Mohammadmehdi Hassanzadeh‐Taheri Mahsa Hassanzadeh‐Taheri Farnaz Jahani Mehran Hosseini 《International Journal of Dairy Technology》2018,71(1):140-148
Although yoghurt butter oil as a fermented dairy product is widely consumed in several countries, its metabolic effects have not been fully elucidated. In this study, male Wistar rats were treated with standard diet, standard diet enriched with 10% or 20% (W/W) of either cow yoghurt butter oil (CYBO), sheep yoghurt butter oil (SYBO) or cottonseed oil (COT) for 20 weeks. Treatment of rats with CYBO or SYBO (at both concentrations) did not significantly influence haematological parameters, plasma lipids and liver histological structure. However, in contrast to popular belief, COT treatment at the higher dose induced leukocytosis, dyslipidaemia and liver steatosis. 相似文献