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991.
Maryam Yaldagard Seyed Ali Mortazavi Farideh Tabatabaie 《Journal of the Institute of Brewing》2008,114(1):14-21
In this study the effects of different intensities and exposure time of ultrasound on barley seed have been investigated to determine the optimal conditions for accelerating germination. For optimization, the Taguchi approach was used. The germination rates and/or yield of the treated sample seed were compared with those of the untreated seed germinated under normal conditions. The seeds were treated with ultrasonic energy (input power 20–90% of 460W) and were exposed to three time periods ranging from 5 to 15 min. It was found that germination of the treated barley seed was increased about 1.042‐1.065 times compared with that of the untreated seed. The ultrasonic treatment proved to be efficient in reducing the germination period by 30–45%. It was concluded that priming of seeds with ultrasound was effective in improving water uptake and germination. The data presented in this paper suggest that the increase in final germination percentage, together with the reduced germination period in treated seeds, may be due to the action of ultrasound and that it led to an improved hydration process with concurrent shell fragmentation. 相似文献
992.
993.
This study was undertaken to investigate the influence of Al–5Ti–1B and Al–5Zr master alloys on the structural characteristics and tensile properties of Al–12Zn–3 Mg–2.5Cu aluminum alloy. The optimum amount for Ti and Zr containing master alloys was selected as 1 wt.% and 6 wt.%, respectively. The results also showed that Ti containing master alloy is more effective in reducing average grain size of the alloy. T6 heat treatment was applied for all specimens before tensile testing. In heat treated condition, the average tensile strength of 505 MPa was found to be increased to 621 MPa for sample refined with 1 wt.% Al–5Ti–1B (0.05 wt.% Ti). SEM fractography of the fractured faces of several castings showed an overall macroscopically brittle appearance at low magnifications. At higher magnifications, unrefined specimens showed cracking along the grains, whereas Ti-refined specimens showed cracks in individual intermetallic compounds. 相似文献
994.
A novel CMOS atto-ampere current mirror (AACM) is proposed which reaches the minimum yet reported current range of 0.4 aA. Operation of this circuit is based on the source voltage modulation instead of the conventionally used gate voltage modulation which interestingly prevents usage of commonly required voltage shifting in those circuits. The proposed circuit has a simple structure prohibiting large chip area consumption which consumes extremely low power of 1.5 μW. It is thus the best choice for ultra low power low voltage (ULPLV) applications. By using a very simple frequency compensation technique, its bandwidth is widened to 15.8 kHz. Simulation results in SMIC (Semiconductor Manufacturing International Corporation) 0.18 μm CMOS technology with Hspice are presented to demonstrate the validation of the proposed current mirror. 相似文献
995.
Fereydoon Jariri Seyed Hesameddin Zegordi 《The International Journal of Advanced Manufacturing Technology》2008,36(5-6):419-430
Platform design is an important design activity in the automotive industry. This task is usually performed by highly qualified
engineers. In this paper we introduce the mathematical programming model which uses QFD data and provide the starting solution
for the design team. The model essentially optimizes customer satisfaction subject to target cost. The empirical results for
one of the biggest automakers in the Middle East are provided. The comparison has been made between company solution and mathematical
model solution and shows the quality of the mathematical model solution. The second mathematical programming went through
the design process and provided more insight for the design team. Introducing an index for customer satisfaction is the secondary
result of our solution. 相似文献
996.
Seyed Habib A. Rahmati Vahid Hajipour Seyed Taghi Akhavan Niaki 《Applied Soft Computing》2013,13(4):1728-1740
In this paper, a novel multi-objective location model within multi-server queuing framework is proposed, in which facilities behave as M/M/m queues. In the developed model of the problem, the constraints of selecting the nearest-facility along with the service level restriction are considered to bring the model closer to reality. Three objective functions are also considered including minimizing (I) sum of the aggregate travel and waiting times, (II) maximum idle time of all facilities, and (III) the budget required to cover the costs of establishing the selected facilities plus server staffing costs. Since the developed model of the problem is of an NP-hard type and inexact solutions are more probable to be obtained, soft computing techniques, specifically evolutionary computations, are generally used to cope with the lack of precision. From different terms of evolutionary computations, this paper proposes a Pareto-based meta-heuristic algorithm called multi-objective harmony search (MOHS) to solve the problem. To validate the results obtained, two popular algorithms including non-dominated sorting genetic algorithm (NSGA-II) and non-dominated ranking genetic algorithm (NRGA) are utilized as well. In order to demonstrate the proposed methodology and to compare the performances in terms of Pareto-based solution measures, the Taguchi approach is first utilized to tune the parameters of the proposed algorithms, where a new response metric named multi-objective coefficient of variation (MOCV) is introduced. Then, the results of implementing the algorithms on some test problems show that the proposed MOHS outperforms the other two algorithms in terms of computational time. 相似文献
997.
Nesar Merah Seyed Nizamuddin Zafarullah Khan Faleh Al-Sulaiman Moeid Mehdi 《Applied Composite Materials》2010,17(4):363-372
This paper presents a study of the effects of harsh outdoor weather and warm sea water on the tensile behavior of Glass-Fiber
Reinforced Vinylester (GFRV) pipe materials destined for sea water handling and transportation. The effect of Dhahran’s outdoor
weather for exposure periods ranging from 3 to 36 months revealed an improvement in tensile strength when compared with the
as received GFRV sample. A significant increasing trend of tensile strength from 3 to 12 months was noted. This is attributed
mainly to the post curing effects resulting in higher cross linking density. After 12 months of exposure the tensile strength
showed a decreasing trend, but remaining still higher than the average tensile strength of as received (baseline) GFRV sample.
Similar results of enhanced tensile strength were noted after immersion of GFRV pipes in warm Gulf sea water for 12 months.
Fractographic analysis was performed on the tensile tested GFRV samples using optical microscope followed by scanning electron
microscope (SEM). The characterization of the controlling failure mechanisms involved from fracture initiation to fracture
propagation through the gage section of the specimen were predicted and were justified by correlating the optical and SEM
pictures. 相似文献
998.
In this work, polyvinyl alcohol (PVA), poly(ε-caprolactone) (PCL), and their electrospun PVA/PCL (80/20) hybrid nanofibrous mats were used for the development of active wound dressings. The biocompatibility and therapeutic effects of the developed products were studied by in vitro cell culture and in vivo experimental rat wound model. The release rate measurements by HPLC showed that the PVA nanofibrous sample containing phenytoin sodium (PHT-Na) has a higher level of the drug release compared to the hybrid PVA/PCL (80/20) and PCL nanofibrous mats. A mesenchymal stem cell was seeded on neat as well as drug-loaded PVA nanofibrous mats. The results represented that the mats provide a suitable environment for cell growth and viability. PVA nanofibers containing PHT-Na have a unique performance for fibroblasts and myofibroblasts cells formation and consequently reaching to the remodeling phase and faster healing of the wounds. Also, PHT-Na-loaded electrospun PVA nanofibrous mats showed a remarkable efficiency in wound closure compared with the treatments results from gauze, commercial wound dressing Comfeel®Plus, and 2 % PHT-Na ointment. Histology analysis showed the formation of epidermis, the lack of necrosis, and accumulation of collagen fibers in dermis for PVA nanofibrous mats containing PHT-Na. 相似文献
999.
In this study a non-parametric method of data envelopment analysis (DEA) was applied to analyze the efficiency of farmers, discriminate efficient farmers from inefficient ones and to identify wasteful uses of energy in order to optimize the energy inputs for apple production in Tehran province, Iran. From this study the following results were obtained: from the total of 56 farmers, considered for the analysis, 34% and 54% were found to be technically and pure technically efficient, respectively. The technical, pure technical and scale efficiency scores of farmers were 0.7857, 0.8982 and 0.8666, respectively. Optimum energy requirement was found to be 37993.15 MJ ha−1; indicating that 11.29% of total energy input could be saved if the recommendations of this study are followed. From total energy saving, the contribution of electrical energy was the highest; it followed by chemicals energy inputs; implying that there was a great scope for saving energy inputs by improving the use pattern of these inputs. The results of economical analysis showed that the total costs of production could decreased from 8227.70 to 7570.01 $ ha−1; also the benefit to cost ratio and productivity improved from 1.24 to 1.34 and 2.52 to 2.74, respectively. 相似文献
1000.
Seyed Abbas Taher Ali Karimian Mohammad Hasani 《Simulation Modelling Practice and Theory》2011,19(2):662-672
This paper presents an optimization algorithm for simultaneous improvement of power quality (PQ), optimal placement and sizing of fixed capacitor banks in radial distribution networks in the presence of voltage and current harmonics. The algorithm is based on particle swarm optimization (PSO). The objective function includes the cost of power losses, energy losses and those of the capacitor banks. Constraints include voltage limits, number/size of installed capacitors at each bus, and PQ limits of standard IEEE-519. Using a newly proposed fitness function, a suitable combination of the objective function and relevant constraints is defined as a criterion to select a set of the most suitable buses for capacitor placement. This method is also capable of improving particles in several steps for both converging more readily to the near global solution as well as improving satisfaction of the power quality constraints. Simulation results for the 18-bus and 33-bus IEEE distorted networks using the proposed method are presented and compared with those of previous works. In the 18-bus IEEE distorted network, this indicated an improvement of 3.29% saving compared with other methods. Using the proposed optimization method and simulation performed on the 33-bus IEEE distorted network an annual cost reduction of 31.16% was obtained. 相似文献