Volume 11, Issue 3 , September 2018, Pages 293-308
Abstract
This paper deals with the performance analysis of three phase Induction Motor (IM) with Direct Torque Control based Space Vector Modulation (DTC-SVM). The DTC-SVM scheme is a kind of high-performance control of IM drives to improve the ripples of torque and flux in steady state, which one drawback of ...
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This paper deals with the performance analysis of three phase Induction Motor (IM) with Direct Torque Control based Space Vector Modulation (DTC-SVM). The DTC-SVM scheme is a kind of high-performance control of IM drives to improve the ripples of torque and flux in steady state, which one drawback of conventional DTC. DTC-SVM has three Proportional-Integral (PI) controllers, one used as the PI speed controller and other PI flux controller and PI torque controller, which are utilized to produce the stator voltage references (
Volume 11, Issue 3 , September 2018, Pages 309-331
Abstract
Preliminary studies on Iraqi power system show a significant increase in the short circuit level at some of the grid substations and some power stations. This increasing results from the growth of the power generation and transmission systems in size and complexity. Islanding or splitting is dividing ...
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Preliminary studies on Iraqi power system show a significant increase in the short circuit level at some of the grid substations and some power stations. This increasing results from the growth of the power generation and transmission systems in size and complexity. Islanding or splitting is dividing the power system into several islands inorder to reduce short circuit levels and avoiding blackouts. The main islanding problem is determining the location of proper splitting points and load balance and satisfaction of transmission capacity constraints for each islands.
This paper mainly introduces new proposed splitting strategies of large-scale power systems by using (PSS™E version 30.3 PACKAGE PROGRAME), such that, make re-interconnection of 400KV super high voltage substation based on three-phase load flow to be minimum flow at splitting point and infeed fault current details method to control short circuit levels in Iraq power system without islanding the power system into isolated islands. Controlled islanding or splitting scheme is frequently considered as the final solution to avoid blackouts of power system.
Simulation IEEE-25 bus and Iraqi power system used as the test systems for this method. Furthermore, simulation results show significant effectiveness on reducing short circuit levels with same time give stable splitting islands with same frequency for preventing the system blackouts.
Volume 11, Issue 3 , September 2018, Pages 332-344
Abstract
In today's complex environment, a high responding ability represents a core for each organization to survive in a competitive environment. To grip your position in intense competition market, the organization must design high efficiency inventory system that has the ability to respond to changes in demand ...
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In today's complex environment, a high responding ability represents a core for each organization to survive in a competitive environment. To grip your position in intense competition market, the organization must design high efficiency inventory system that has the ability to respond to changes in demand and at the same time reduce holding cost of accommodation to the lowest possible value by controlling inventory drivers such as safety stock level (SS). The traditional approaches of safety stock are limited to deal with dynamic behavior of market. Advanced approaches based on soft computing allow the dynamic updating of SS level. In this paper, a highly advanced dynamic fuzzy logic (DFL) has been suggested as an innovation step to identify safety stock level in dairy industries with objective of minimizing total cost and meet with customer requirements. The proposed approach consists of three main steps firstly, identifying demand uncertainty conditions by applying fuzzy logic steps embedded by identifying dynamic (N) factor which represents the increasing level in demand in period time. Secondly, identifying of raw material availability conditions by applying fuzzy logic steps, and finally, identification of inventory on hand conditions by applying fuzzy logic steps. It is necessary to identify the level of SS dynamically in fuzzy logic as an output embedded with identifying of period specification concept which describes states of demand in a specific period in which the demand is high, medium, or low which leads to identify maximum values of universe of discourse of output (safety stock). Here Matlab program was used. The provided solution demonstrates the proposed model validity. There has been a significant reduction in safety stock level ranging from (7-98)% depending on product type and period specification with a reduction also in holding cost, while keeping the requirements fulfillment of customers demand
Volume 11, Issue 3 , September 2018, Pages 345-356
Abstract
In demand to the industrial needs to produce Cu-Al alloys with controlled chemical compositions. The present research focuses on the production of Cu-Al alloys with different aluminum additions of 1.9, 3.6, 5.8 and 7.7 wt. % by stir casting method in argon atmosphere. Then, homogenized treatment was ...
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In demand to the industrial needs to produce Cu-Al alloys with controlled chemical compositions. The present research focuses on the production of Cu-Al alloys with different aluminum additions of 1.9, 3.6, 5.8 and 7.7 wt. % by stir casting method in argon atmosphere. Then, homogenized treatment was done for these alloys at 850 oC in different periods of soaking time of 2, 4, and 6 hrs to determine the best conditions for increasing the mechanical properties. This is carried out in the α phase region. The microstructure of the samples is analyzed by using Optical and Scanning Electron Microscopy (SEM) with (EDS). The results showed the mechanical properties of copper were increased with increasing in Aluminum content. The microstructure of the castings consist of the dendiritic structure, columinar grains and segregation. The results showed that after homogenization, the microstructure changed to fine grains, elimination of the columnar segregation and the clusters disappeared. The XRD results show that the phases are α (Cu-rich) phase as highest peaks and the small amount of CuAl2 phase. The best Aluminum content value was 7.7 wt % and the soaking time 4 hrs were given the high hardness 204 Hv and the highest ultimate tensile stress value of 383.8 Mpa
Volume 11, Issue 3 , September 2018, Pages 357-371
Abstract
Unsupported MoS2 catalysts were synthesized for the hydrodesulfurization (HDS) of real feed gas oil using different temperatures and pressures. Hydrothermal method was utilized to prepare by using molybdenum trioxide and sodium sulfide. The characterization of the catalyst was identified by XRD, SEM, ...
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Unsupported MoS2 catalysts were synthesized for the hydrodesulfurization (HDS) of real feed gas oil using different temperatures and pressures. Hydrothermal method was utilized to prepare by using molybdenum trioxide and sodium sulfide. The characterization of the catalyst was identified by XRD, SEM, and BET techniques. It was found that BET surface and pore volume were positively affected by pressure and temperature that could improve the activity of MoS2. Kinetic analysis showed that HDS reaction over MoS2 follow pseudo-first order kinetics. Experimental results revealed that the HDS activity of the unsupported MoS2 catalyst was better than supported CoMo/Al2O3 catalyst under the same operating conditions.
Volume 11, Issue 3 , September 2018, Pages 372-395
Abstract
Clathrate hydrates are complex molecules formed by the contact between water and gas at high pressure and low temperatures. One of the important aims of gas hydrate technology is to enhance the formation of hydrate and reduction the induction time for clathrate formation. Effect of the different promoters ...
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Clathrate hydrates are complex molecules formed by the contact between water and gas at high pressure and low temperatures. One of the important aims of gas hydrate technology is to enhance the formation of hydrate and reduction the induction time for clathrate formation. Effect of the different promoters (nonionic surfactant Tween80) on R-134a gas hydrate formation has been investigated in the isochoric system experiment. It is noted that the surfactants have a significant effect of increasing the speed of nucleation as well as improving the growth of hydrate. In the experiment, the effect of Tween80 surfactant was studied to determine its effect on the composition and cooling capacity of 134 hydrates. From kinetic models, many objective functions such as the amount of gas consumed (Δn), the growth rate (r (t)), the apparent rate constant (Kapp) and conversion of the water to hydrate were obtined. The improvement of hydrate growth is marked by the addition of surfactants, which in turn increase the solubility of hydrate gas and reduce the contact angle. In addition, surfactants positively the contact with the gas through the increase of the gas diffusion in the water and this increases the rate of formation of hydrate. Best value achieved at a surfactant concentration of 100 ppm with maximum gas consumed amount (0.16 mol) and less indction time 32 min.
Volume 11, Issue 3 , September 2018, Pages 396-409
Abstract
Adsorption and desorption kinetic curves for equimolar hydrogen – methane mixture on molecular sieve type 5A were experimentally obtained for pressure range 0.122 – 3.546 MPa.The linear driving force rate expression model was used to simulate the dynamic of adsorption and desorption in adiabatic ...
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Adsorption and desorption kinetic curves for equimolar hydrogen – methane mixture on molecular sieve type 5A were experimentally obtained for pressure range 0.122 – 3.546 MPa.The linear driving force rate expression model was used to simulate the dynamic of adsorption and desorption in adiabatic fixed bed adsorber. The model takes into account the interference effects for non-linear isotherms and non-isothermal system. The equations were solved by backward finite difference method with a fixed gridding technique. The individual mass transfer parameters were obtained by matching the theoretical with the experimental data and found to be equal to 8.510 s-1 and 0.783 s-1 for hydrogen and methane, respectively.The predicted effluent histories were shown to be in close agreement with the experimental data for the system. The lowest relative capacity of the bed for methane was almost approximately 95% of that predicted equilibrium capacity. The predicted temperature profiles tracked the experimental temperature data points, but with higher values. Furthermore, the maximum temperature increasing was observed for the adsorption of methane onto 5A molecular sieve at 35 atmospheres and was recorded as 44 K.
