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A Maintenance Optimzation Policy for an electric Power Distribution System: Case of the HV/MV Substations

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Engineering（科研） 2014年第5期6卷 236-253页

作者： Morad Mahmoudi Abdellah el Barkany ahmed el khalfi Department of Mechanical Engineering Faculty of Science and Technology Sidi Mohamed Ben Abdellah University Fez Morocco National Office of electricity and Water Supply (ONEE) Casablanca Morocco

Today, in the modern era, and under the pressure of rapid development around the kingdom regions, electric utilities are confronted with a myriad of challenges that include aging infrastructure, enhanced expectation of reliability, reduced cost, and coping effectively with uncertainties and changing regulation requirements. Indeed, for distribution systems, HV/MV substations represent a complex and critical physical asset that requires a careful evaluation of their maintenance practices aiming at more cost-effective tasks. The first concern of the electric power distribution company in Morocco is the optimization of the distribution network maintenance scheduling, to minimize system operating costs and ensure that the system is running most economically. There is significant pressure on power providers for greater system reliability and improvement of customer satisfaction, while similar emphasis is placed on cost reduction. These cost reductions focus on reducing operating and maintenance expenses, and minimizing investments in new plants and equipment. However, the present of the electricity distribution, influenced by a number of technical restrictions and strict regulatory requirements to meet, leads distribution utilities to search new ways of optimizing the maintenance management, make an effort to maximize profit by reducing their electricity supply and operation costs while maintaining their reliability, developing more effective activities, with lower costs. Furthermore, maximal HV/MV substation asset value and minimal maintenance cost are typical economic objectives of the electric utilities. The optimization of maintenance is one possible technique to reduce maintenance costs while improving reliability and utilities need to implement new strategies for more effective maintenance techniques and Asset Management (AM) methods programs to manage inspections and maintenance activities in order to control HV/MV substation equipment conditions. However, develop

关键词： HV/MV Distribution Substations Maintenance Strategy RCM Optimization Asset Management

Three-dimensional printing of biomaterials for bonetissue engineering: a review

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Frontiers of Materials Science 2023年第2期17卷 1-43页

作者： ahmed el-Fiqi Glass Research Department Advanced Materials Technology and Mineral Resources Research InstituteNational Research CentreCairo 12622Egypt

Processing biomaterials into porous scaffolds for bone tissueengineering is a critical and a key step in defining and controlling their physicochemical,mechanical,and biological *** such as polymers are commonlyprocessed into porous scaffolds using conventional processing techniques,e.g.,***,these traditional techniques have shown unavoidable limitations andseveral *** instance,tissue-engineered porous scaffolds with a complexthree-dimensional(3D)geometric architecture mimicking the complexity of theextracellular matrix of native tissues and with the ability to fit into irregular tissue defectscannot be produced using the conventional processing techniques.3D printing hasrecently emerged as an advanced processing technology that enables the processing ofbiomaterials into 3D porous scaffolds with highly complex architectures and tunableshapes to precisely fit into irregular and complex tissue defects.3D printing providescomputer-based layer-by-layer additive manufacturing processes of highly precise andcomplex 3D structures with well-defined porosity and controlled mechanical propertiesin a highly reproducible ***,3D printing technology provides anaccurate patient-specific tissue defect model and enables the fabrication of a patientspecifictissue-engineered porous scaffold with pre-customized properties.

关键词： 3D printing biomaterial ink printability 3D printing technique 3D printed scaffold bone tissue engineering

Sol-gel synthesis,properties and protein loading/delivery capacity of hollow bioactive glass nanospheres with large hollow cavity and mesoporous shell

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Frontiers of Materials Science 2022年第3期16卷 145-157页

作者： ahmed el-FIQI Glass Research Department National Research CentreCairo 12622Egypt

Hollow nanospheres exhibit unique properties and find a wide interest in several potential applications such as drug ***,novel hollow bioactive glass nanospheres(HBGn)with large hollow cavity and large mesopores in their outer shells were synthesized by a simple and facile one-pot ultrasound assisted sol-gel method using PEG as the core ***,the produced HBGn exhibited large hollow cavity with ~43 nm in diameter and mesoporous shell of ~37 nm in thickness and 7 nm pore size along with nanosphere size around 117 *** confirmed the presence of Si and Ca elements at the surface of the HBGn outer ***,HBGn showed high protein loading capacity(~570 mg of Cyto c per 1 g of HBGn)in addition to controlled protein release over 5 *** also demonstrated a good in vitro capability of releasing calcium(Ca^(2+):170 ppm)and silicate(SiO_(4)^(4-):78 ppm)ions in an aqueous medium over 2 weeks under physiological-like *** in vitro growth of bone-like hydroxyapatite nanocrystals was exhibited by HBGn during the soaking in SBF.A possible underlying mechanism involving the formation of spherical aggregates(coils)of PEG was proposed for the formation process of HBGn.

关键词： bioactive glass hollow nanosphere hollow cavity mesoporous shell soft-template ultrasound assisted sol-gel synthesis therapeutic protein delivery

LEO satellite clock analysis and prediction for positioning applications

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Geo-Spatial Information Science 2022年第1期25卷 14-33页

作者： Kan Wang ahmed el-Mowafy School of Earth and Planetary Sciences Curtin UniversityPerthAustralia

The positioning service aided by low Earth orbit(LEO)mega-constellations has become a hot topic in recent *** achieve precise positioning,accuracy of the LEO clocks is important for single-receiver *** bridge the gap between the applicable time of the clock products and the time of positioning,the precise LEO clocks need to be predicted over a certain period depending on the sampling interval of the clock *** study discusses the prediction errors for periods from 10 s to 1 h for two typical LEO clock types,*** ultra-stable oscillator(USO)and the oven-controlled crystal oscillator(OCXO).The prediction is based on GNSS-determined precise clock estimates,where the clock stability is related to the GNSS estimation errors,the behaviors of the oscillators themselves,the systematic effects related to the environment and the relativistic effects,and the stability of the time *** on real data analysis,LEO clocks of the two different types are simulated under different conditions,and a prediction model considering the systematic effects is *** to a simple polynomial fitting model usually applied,the proposed model can significantly reduce the prediction errors,*** about 40%-70%in simulations and about 5%-30%for real data containing different miss-modeled *** both clock types,short-term prediction of 1 min would result in a root mean square error(RMSE)of a few centimeters when using a very stable time *** RMSE amounts to about 0.1 m,when a typical real-time time reference of the national center for space studies(CNES)real-time clocks was *** long-term prediction of 1 h,the RMSE could range from below 1 m to a few meters for the USOs,depending on the complexity of the miss-modeled *** OCXOs,the 1 h prediction could lead to larger errors with an RMSE of about 10 m.

关键词： LEO clock prediction USO OCXO relativistic effects

Magnetoresistive properties of Ni-doped La_(0.7)Sr_(0.3)MnO_3 manganites

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Rare Metals 2016年第7期35卷 551-558页

作者： ahmed Mohamed ahmed Abd el-Moez ahmed Mohamed Medhat Abdelrady Abdellateef Hassan ahmed Abd el-Ghanny Physics Department Faculty of ScienceSohag University

Lao.7Sr0.3Mnl_xNixO3 （x = 0, 0.025, 0.050 and 0.075） ceramics were prepared by the conventional solid-state reaction method. The partial substitution of Mn by Ni2＋ leads to a decrease in cell volume as well as a structural transition from the rhombohedral to the orthorhombic structure. Ni2＋ doping increases the electrical resistivity, decreases the semiconductor-metal transition temperature （Tms） and relatively enhances the room temperature magnetoresistance （MR）, especially in x = 0.025 and around Tins. With respect to conduction mechanism, the small polaron hopping （SPH） and the variable range hopping （VRH） models were used to ex- amine conduction in the semiconducting region.

关键词： Manganites X-ray diffraction Structure electrical resistivity Magnetoresistance

Hepatoprotective Effect of Camel Thorn Polyphenols in Concanavalin A-Induced Hepatitis in Mice

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Chinese Journal of Integrative Medicine 2024年第12期30卷 1090-1100页

作者： Nageh ahmed el-Mahdy Thanaa ahmed el-Masry ahmed Mahmoud el-Tarahony .Fatemah AAlherz Enass Youssef Osman Department of Pharmacology and Toxicology Faculty of PharmacyTanta UniversityTanta 31527Egypt Department of Pharmaceutical Sciences College of PharmacyPrincess Nourah Bint Abdulrahman UniversityP.O.Box 84428Riyadh 11671Saudi Arabia

Objective:To explore the prophylactic and therapeutic effects of Alhagi maurorum ethanolic extract(AME)in concanavalin A(Con A)-induced hepatitis(CIH)as well as possible underlying ***:Polyphenols in AME were characterized using high performance liquid chromatography(HPLC).Swiss albino mice were divided into 4 *** group received intravenous phosphate-buffered saline(PBS);Con A group received 40 mg/kg intravenous Con *** group administered 300 mg/(kg·d)AME orally for 5 days before Con A *** group received intravenous Con A then administered300 mg/kg AME at 30 min and 3 h after Con A *** 24 h of Con A injection,hepatic injury,oxidative stress,and inflammatory mediators were *** examination and markers of apoptosis,inflammation,and CD4^(+)cell infiltration were also ***:HPLC analysis revealed that AME contains abundant polyphenols with pharmacological constituents,such as ellagic acid,gallic acid,ferulic acid,methylgallate,and *** alleviated Con A-induced hepatic injury,as manifested by a significant reduction in alanine aminotransferase,aspartate aminotransferase and alkaline phosphatase(Pels of proinflammatory cytokines(tumor necrosis factor-α,interferon-γ,and interleukin-6)and c-Jun N-terminal kinase(JNK)activity were reduced(Peliorated necrotic and inflammatory lesions induced by Con A(Pell hepatic infiltration(Peliorative effects in CIH mice

关键词： concanavalin A-induced hepatitis Alhagi maurorum ethanolic extract hepatoprotective effect

Efficacy of octreotide in the prevention of complications after pancreaticoduodenectomy in patients with soft pancreas and non-dilated pancreatic duct: A prospective randomized trial

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Hepatobiliary & Pancreatic Diseases International 2018年第1期17卷 59-63页

作者： Ayman el Nakeeb ahmed el Gawalby Mahmoud A.Ali ahmed Shehta Hosam Hamed Mohamed el Refea ahmed Moneer ahmed Abd el Rafee Gastroenterology Surgical Center Mansoura University

Background: The efficacy of octreotide to prevent postoperative pancreatic fistula(POPF) of pancreaticoduodenectomy(PD) is still controversial. This study aimed to evaluate the effect of postoperative use of octreotide on the outcomes after ***: This is a prospective randomized controlled trial for postoperative use of octreotide in patients undergoing PD. Patients with soft pancreas and pancreatic duct elayed gastric emptying(P = 0.472), and early postoperative mortality(P = 0.727).Conclusions: Octreotide did not reduce postoperative morbidities, reoperation and mortality rate. Also, it did not affect the incidence of POPF and its clinically relevant variants.

关键词： Pancreaticoduodenectomy Postoperative pancreatic fistula Octreotide Periampullary tumor

Experimental and numerical investigation of the abrasive waterjet machining of aluminum-7075-T6 for aerospace applications

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Advances in Manufacturing 2021年第2期9卷 286-303页

作者： Joseck Nyaboro Mahmoud ahmed Hassan el-Hofy Mohamed el-Hofy Department of Industrial and Manufacturing Engineering Egypt-Japan University of Science and Technology(E-JUST)Alexandria 21934Egypt Department of Energy Resources Engineering Egypt-Japan University of Science and Technology(E-JUST)Alexandria 21934Egypt Advanced Manufacturing Research Centre(AMRC)with Boeing The University of SheffieldRotherham S605TZUK

The machining of hard-to-cut materials with a high degree of precision and high surface quality is one of the most critical considerations when fabricating various state-of-the-art engineered *** this investigation,a comprehensive three-dimensional model was developed and numerically simulated to predict kerf profiles and material removal rates while drilling the aluminum-7075-T6 aerospace *** profile and material removal prediction involved three stages:jet dynamic flow modeling,abrasive particle tracking,and erosion rate *** investigations were conducted to validate the developed *** results indicate that the jet dynamic characteristics and flow of abrasive particles alter the kerf profiles,where the top kerf diameter increases with increasing jet pressure and standoff *** kerf depth and hole aspect ratio increase with jet pressure,but decrease with standoff distance and machining *** profiles were characterized by progressive edge rounding and parabolic *** can be minimized by utilizing high jet pressure and small standoff *** material removal rate increases with increasing jet pressure,abrasive particle size,and exposure time,but decreases with increasing standoff distance.

关键词： Non-traditional machining Abrasive waterjet machining Computational fluid dynamics(CFD) Erosion modeling Kerf characteristics

Atezolizumab and bevacizumab combination in advanced hepatocellular carcinoma patients:The imperative for safety assessment studies

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World Journal of Clinical Cases 2025年第9期13卷 56-59页

作者： Mina Tharwat ahmed Tawheed Mohamed el-Kassas Department of Tropical Medicine and Gastroenterology Faculty of MedicineAswan UniversityAswan 81528Egypt Department of Endemic Medicine Faculty of MedicineHelwan UniversityCairo 11795Egypt

Hepatocellular carcinoma(HCC)is the most prevalent cancer of the hepatobiliary tract and the third leading cause of cancer-related mortality *** and bevacizumab combination is currently considered among the frontline treatment modalities for advanced unresectable *** studies examining this combination were focused on evaluating its *** numerous case reports documenting some side effects,there is a limited number of large-scale studies assessing these side *** this article,we comment on the case report by Park et al published recently,reporting a fatal intra-tumoral hemorrhage in a patient with HCC who received systemic therapy in the form of the combination of atezolizumab and bevacizumab.

关键词： Hepatocellular carcinoma Atezolizumab Bevacizumab Hemorrhage Side effects