Harby K.,Minia University
Renewable and Sustainable Energy Reviews | Year: 2017
Vapor compression refrigeration systems consume high-grade energy and contribute to global warming and ozone layer depletion due to the environmentally unfriendly refrigerants. The use of hydrocarbons offer good drop-in replacements for the existing halogenated refrigerants in terms of environmental impacts and energy consumption. In this study, a review of the previous studies carried out with hydrocarbons as alternative refrigerants in refrigeration, air conditioning and heat pump, and automobile air conditioning systems is presented. An attempt has been made to cover the current status, possibilities, and problems related to the use of hydrocarbons as alternative refrigerants. Hydrocarbon characteristics, allowable refrigerant charge, flammable properties, and safety considerations are also presented. In addition, the study contains also a useful amount of information about the refrigerant properties, environmental impacts, and replacement strategy of conventional refrigerants. Results showed that in spite of highly flammable characteristics, hydrocarbons can offer proper alternatives to the halogenated refrigerants from the standpoint of environment impact, energy efficiency, COP, refrigerant mass, and compressor discharge temperatures. Roadmap on the future work needs in this field is presented. Finally, a summary of previous studies and strategies on pure HC, HC mixtures, and HC/HFC blends used for different applications has been presented and discussed in detail. © 2017 Elsevier Ltd
Farahat E.S.,Minia University
Lithos | Year: 2010
Ophiolites are widely distributed in the Central Eastern Desert (CED) of Egypt, occurring as clusters in the northern (NCEDO) and southern (SCEDO) segments. Mineralogical and geochemical data on the volcanic sections of Wizer (WZO) and Abu Meriewa (AMO) ophiolites as representatives of the NCEDO and SCEDO, respectively, are presented.The WZO volcanic sequence comprises massive metavolcanics of MORB-like compositions intruded by minor boninitic dykes and thrust over island-arc metavolcanic blocks in the mélange matrix. Such transitional MORB-IAT-boninitic magmatic affinities for the WZO metavolcanics suggest that they most likely formed in a protoarc-forearc setting. Chemical compositions of primary clinopyroxene and Cr-spinel relicts from the WZO volcanic section further confirm this interpretation. The compositional variability in the WZO volcanic sequence is comparable with the associated mantle rocks that vary from slightly depleted harzburgites to highly depleted harzburgites containing small dunite bodies, which are residues after MORB, IAT and boninite melt formation, respectively. Source characteristics of the different lava groups from the WZO indicate generation via partial melting of a MORB source which was progressively depleted by melt extraction and variably enriched by subduction zone fluids. MORB-like magma may have been derived from ~ 20% partial melting of an undepleted lherzolite source, leaving slightly depleted harzburgite as a residuum. The generation of island-arc magma can be accounted for by partial melting (~ 15%) of the latter harzburgitic mantle source, whereas boninites may have been derived from partial melting (~ 20%) of a more refractory mantle source previously depleted by melt extraction of MORB and IAT melts, leaving ultra-refractory dunite bodies as residuum.The AMO volcanic unit occurs as highly deformed pillowed metavolcanic rocks in a mélange matrix. They can be categorized geochemically into LREE-depleted (La/YbCN=0.41-0.50) and LREE-enriched (La/YbCN=4.7-4.9) lava types that show an island arc to MORB geochemical signature, respectively, signifying a back-arc basin setting. This is consistent, as well, with their mantle section. Source characteristics indicate depleted to slightly enriched mantle sources with overall slight subduction zone geochemical affinities as compared to the WZO.Generally, CED ophiolites show supra-subduction zone geochemical signature with prevalent island arc tholeiitic and minor boninitic affinities in the NCEDO and MORB/island-arc association in the SCEDO. Such differences in geochemical characteristics of the NCEDO and SCEDO, along with the abundance of mature island arc metavolcanics which are close in age (~ 750. Ma) to the ophiolitic rocks, general enrichment in HFSE of ophiolites from north to south, and lack of a crustal break and major shear zones, is best explained by a geotectonic model whereby the CED represents an arc-back-arc system above a southeast-dipping subduction zone. © 2010 Elsevier B.V.
Hassan A.S.,Minia University
Physics Letters, Section A: General, Atomic and Solid State Physics | Year: 2010
In this Letter a conventional method of statistical physics and quantum mechanics is used to calculate the effective area and the expansion energy for trapped Bose gas in a combined optical-magnetic potential. Correction due to the finite number of particles, interatomic interaction and the deepness of the lattice potential are given simultaneously. It is found that the system possess two different phases which are superfluid phase and Mott insulator phase. The critical temperature which separate these two phases is calculated. In the superfluid phase both the effective area and expansion energy is sensitive to the variation of temperature and lattice depth. Mott insulator phase is characterized by vanishing of the condensed fraction and freezing of the effective area at the value which corresponding to BEC transition temperature. So these parameters can serve as a practical thermometer for such system. The expansion energy shows that the lack of expansion in any direction is due to the strong anisotropy of the trapping potential in this direction. The obtained results provide a solid theoretical foundation for the current experiments. © 2010 Elsevier B.V. All rights reserved.
Hussein A.,Minia University
Fertility and Sterility | Year: 2013
Objective: To evaluate the use of a diagnostic testis biopsy and a repetition of testicular sperm extraction (TESE) surgeries in azoospermic patients and its impact on the outcome of TESE. Design: Retrospective, case-control study. Setting: University IVF center and hospital. Patient(s): A total of 552 azoospermic patients undergoing TESE for intracytoplasmic injection. Intervention(s): At the time of the TESE, a piece of testicular tissue was prepared for histopathologic evaluation. Main Outcome Measure(s): Sperm retrieval rate. Result(s): Testicular sperm retrieval was successful in 100% of patients with obstructive azoospermia, 95.6% of patients with hypospermatogenesis, 47.9% of patients with maturation arrest, and 28.6% of patients with Sertoli cell-only syndrome in cases with no previous testicular surgery; in 100%, 91.4%, 32%, and 13.3%, respectively, in cases with a history of one testicular surgery; and in 100%, 10%, 0, and 0, respectively, in cases with a history of two testicular surgeries. Conclusion(s): Testicular sperm retrieval may be successful for some patients in each histopathologic category of azoospermia, with variable degrees of success for different histopathologic categories. The repetition of testicular surgeries decreases the chance of finding sperm in subsequent testicular sperm retrieval procedures. Copyright © 2013 Published by Elsevier Inc.
Ahmed S.A.,Minia University
Carbohydrate Polymers | Year: 2011
Wood sawdust, a by-product of the world industry, is a low cost and promising industrial waste with cellulose-lignin polymeric structure. Its sorption properties after physical loading with Alizarin Red S (phase I) and Eriochrome Black T (phase II) for the removal of Fe(III) and Cu(II) under variable conditions of solution pH, contact times, weight of phase and concentration of the metal ion were investigated. Scanning electron microscope and Fourier transfer infrared spectra of phases before and after uptake of Fe(III) and Cu(II) were recorded to characterize the nature of the functional groups responsible for binding of these metal ions onto the studied modified polymers. Their equilibrium data were fitted with a Langmuir model. The adsorption kinetics data were best fitted with the pseudo-second-order. As a view to find a suitable application of phase I it was found that, Fe(III) in natural water samples were quantitatively recovered using column experiments. © 2010 Elsevier Ltd. All rights reserved.
Othman A.M.A.,Minia University
Archives of Orthopaedic and Trauma Surgery | Year: 2011
Background: Lateral epicondylitis is a common orthopedic problem. Rest, activity modification, and conservative therapies are generally efficacious in relieving symptoms in the majority of patients; however, a small percentage of people will experience refractory pain and require surgical intervention to alleviate their discomfort. Surgical release of the common extensor origin can be done through an open, percutaneous, or arthroscopic approach. Patients and methods: This prospective study includes 33 patients with chronic resistant lateral epicondylitis who had received conservative treatment including modification of activity and 2 injections of 80 mg of hydrocortisone, for more than 6 months, aiming to compare two different techniques of treatment. The first group included 14 patients with a mean age of 42 years treated by arthroscopic release of common extensor origin. The second group included 19 patients with a mean age of 48 years treated by percutaneous tenotomy. The mean follow up was 12 months for the arthroscopic group and 10 months for the percutaneous tenotomy group. Results: The results were evaluated according to the Disabilities of the Arm, Shoulder and Hand (DASH) score and the visual analogue scale (VAS). In the first group (treated by arthroscopy), the average DASH score improved from 72 to 48 and the average VAS improved from 9.1 to 2. In the second group (treated by percutaneous tenotomy), the average DASH score improved from 70 to 50 and the average VAS improved from 9 to 2.1. Concerning patient satisfaction after surgery, in the first group 7 patients (50%) were pleased, 6 (42.85%) were satisfied and 1 case (7.14%) was not satisfied. In the second group, 7 patients (36.84%) were pleased, 10(52.63%) were satisfied and 2 cases (10.52%) were not satisfied. Conclusion: Both arthroscopic and percutaneous release of the common extensor origin can be effective in treatment of lateral epicondylitis. Arthroscopic treatment of lateral epicondylitis gives more favorable results than percutaneous tenotomy. Although technically more difficult than percutaneous tenotomy, arthroscopy has the advantage of visualization of the pathology and much better improvement of elbow functions. © Springer-Verlag 2010.
Breisha G.Z.,Minia University
Biomass and Bioenergy | Year: 2010
A strain of Saccharomyces cerevisiae, which showed marked fermentation activity, ethanol and temperature tolerance and good flocculation ability, was selected for ethanol production. A stuck fermentation occurred at sucrose concentration of 25%. Increasing the yeast inoculum volume from 3% to 6% showed positive effects on fermentation from 25% sucrose. The ratio of added nitrogen to sucrose, which gave the best results (for the selected yeast strain), was determined. It was concluded that this ratio (nitrogen as ammonium sulphate at a rate of 5mgg-1 of consumed sucrose) is constant at various sugar concentrations. Addition of nitrogen at this ratio produced 11.55% ethanol with complete consumption of 25% sucrose after 48h of fermentation. However fermentation of 30% sucrose at the above optimum conditions was not complete. Addition of yeast extract at a level of 6gl-1 together with thiamine at a level of 0.2gl-1 led to complete utilization of 30% sucrose with resultant 14% ethanol production. However the selected yeast strain was not able to ferment 35% sucrose at the same optimum conditions. Addition of air at a rate of 150dm3min-1m3 of reactor volume during the first 12h of fermentation led to complete consumption of 35% sucrose and 16% ethanol was produced. This was approximately the theoretical maximum for ethanol production. © 2010 Elsevier Ltd.
Abu El Makarem M.,Minia University
Hepatitis Monthly | Year: 2012
Context: Primary liver cancer is one of the most common and deadly malignant neo-plasms worldwide. The incidence and mortality rates for hepatocellular carcinoma (HCC) are virtually identical, reflecting the poor overall survival of patients with this kind of tumor. Effective therapies mostly achieved if the HCC diagnosis is made at early stages of the tumor. Surveillance tests include serologic and radiologic examinations. Evidence Acquisition: In this review, an overview of biomarkers for the diagnosis of HCC and future challenges in this popular field has been presented. Results: Serum tumor markers, such as alpha-fetoprotein (AFP) and des-gammacarboxy prothrombin (DCP) are commonly used for the surveillance, but their roles have been intensely debated despite the existence of sensitive radiologic tests. Most HCC-related cancer biomarkers are involved in chronic inflammation and cancer. These biomarkers, according to their biologic characteristics are primarily divided into three groups in-cluding onco-foetal protein, stress protein, and post-translational modification. Conclusions: Because of the limitations of traditional HCC biomarkers, exploration for novel biomarkers for the diagnosis of HCC is an evolving process. © 2012 Baqiyatallah Research Center for Gastroentrology and liver diseases; Published by Kowsar Corp.
Shehata E.G.,Minia University
Electric Power Components and Systems | Year: 2013
This article presents a direct power control design of a wind turbine driven doubly fed induction generators under unbalanced network voltage conditions. A coordinate control strategy for the rotor-side converter and grid-side converter is proposed. The rotor-side converter is controlled based on the direct power control principle to eliminate the electromagnetic torque oscillations at a double supply frequency under unbalanced grid voltage. The grid-side converter is controlled to regulate the DC-link voltage and to cancel the pulsations in the total output active or reactive powers. The proposed control scheme removes both rotor current regulators and decomposition processing of positive- and negative-sequence rotor or grid currents. Simulation works are carried out to confirm the validity of the proposed scheme during unbalanced voltage supply. The performance of the proposed direct power control scheme is analyzed and compared with an improved vector control during grid voltage transients. The results show that the proposed direct power control scheme reduces the double frequency oscillations in the total and grid-side converter active and reactive powers, electromagnetic torque, and DC-link voltage. © 2013 Copyright Taylor and Francis Group, LLC.
Shehata E.G.,Minia University
International Journal of Electrical Power and Energy Systems | Year: 2013
Speed sensorless control of an interior permanent magnet synchronous motor (IPMSM) based on direct torque control (DTC) is proposed in this paper. The rotor speed and position of the IPMSM are estimated based on an active flux concept, where, the active flux vector position is identical to the rotor position. The proposed algorithm does not require neither high frequency injection signal nor complicated schemes even at vary low speed operation. Torque/ flux sliding mode controller (SMC) combined with space vector modulation is proposed to improve the performance of the classical DTC. Stator resistance value is required for a stator flux and electromagnetic torque estimation. Its variation due to temperature or frequency degrades the scheme performance, especially, at low speed operation. To overcome this problem, a reduced order extended Kalman filter (EKF) is proposed to update online the stator resistance. The advantages of the direct torque control, sliding mode controller, and speed sensorless control are incorporated in the proposed scheme. Simulation works are carried out to show the ability of the proposed scheme at different operating conditions. The results demonstrate the activity of the scheme at wide range speed operation with load disturbance and parameters variation. © 2012 Elsevier Ltd. All rights reserved.