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Experimental and parametrical investigation of pre-stressed ultrahigh-performance fiberreinforced concrete railway sleepers

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Frontiers of Structural and Civil Engineering 2023年第3期17卷 411-428页

作者： Sayed ahmed Hossam atef Mohamed HUSAIN Department of Structural Engineering Faculty of EngineeringZagazig UniversityZagazig 44519Egypt Track Work Department National Authority for TunnelsCairo 11522Egypt

In this study,ultrahigh-performance fiber-reinforced concrete(UHPFRC)used in a type B70 concrete sleeper is investigated experimentally and *** main parameters investigated are the steel fiber volume fractions(0%,0.5%,1%,and 1.5%).Under European standards,35 UHPFRC sleepers are subjected to static bending tests at the center and rail seat sections,and the screw on the fastening system is pulled *** first cracking load,failure load,failure mode,crack propagation,load–deflection curve,load–crack width,and failure load from these tests are measured and compared with those of a control sleeper manufactured using normal concrete *** accuracy of the parametric study is verified ***,the results of the study are applied to UHPFRC sleepers with different concrete volumes to investigate the effects of the properties of UHPFRC on their *** and parametric study results show that the behavior of UHPFRC sleepers improves significantly when the amount of steel fiber in the mix is *** manufactured using UHPFRC with a steel fiber volume fraction of 1%and a concrete volume less than 25%that of standard sleeper B70 can be used under the same loads and requirements,which contributes positively to the cost and surrounding environment.

关键词： pre-stressed concrete sleeper ultrahigh performance fiber-reinforced concrete pull-out test static bending test steel fiber aspect ratio volume fraction

Modular Multilevel Converter with Wireless Magnetic Power Decoupling for Three-phase MV Adjustable-speed Drives

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CSEE Journal of Power and Energy Systems 2022年第5期8卷 1497-1507页

作者： Mohamed atef Tawfik Mohammad Sameer Irfan Ashraf ahmed Joung-Hu Park Department of Electrical Engineering Soongsil UniversitySeoul 156-743South Korea

In this paper,we propose a modular multilevel converter(MMC)with a wireless magnetic power decoupling approach suitable for medium-voltage high-power variable-speed machine *** proposed power decoupling approach is independent of the operating frequency,which solves the issue of wide fluctuations of low-frequency voltage ripple components in submodule(SM)capacitors,especially at low-speed operations without using any ripple power *** wireless magnetic elements reduces the amount of high-voltage insulation between the transformer windings,resulting in a significant reduction in the overall size of the *** basic idea of our proposed approach is to magnetically couple the instantaneous three-phase ripple power of each of the three adjacent-arm *** proposed MMC is free from low-frequency capacitors,resulting in enhanced system reliability,volume,and *** operation principles of the proposed MMC are explained,and a control design is *** performance of the proposed scheme was verified via simulation and experimental tests.

关键词： Modular multilevel converter power decoupling submodule capacitor voltage ripple variable-speed drives wireless high-frequency transformer

Scheduling Multi-Mode Resource-Constrained Projects Using Heuristic Rules Under Uncertainty Environment

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Computers, Materials & Continua 2022年第1期70卷 847-874页

作者： Mohamed Abdel-Basset ahmed Sleem Asmaa atef Yunyoung Nam Mohamed Abouhawwash Faculty of Computers and Informatics Zagazig UniversityZagazig44519Egypt Department of Computer Science and Engineering Soonchunhyang UniversityAsan31538Korea Department of Mathematics Faculty of ScienceMansoura UniversityMansoura35516Egypt Department of Computational Mathematics Scienceand Engineering(CMSE)Michigan State UniversityEast Lansing48824MIUSA

Project scheduling is a key objective of many models and is the proposed method for project planning and *** scheduling problems depend on precedence relationships and resource constraints,in addition to some other limitations for achieving a subset of *** scheduling problems are dependent on many limitations,including limitations of precedence relationships,resource constraints,and some other limitations for achieving a subset of *** project scheduling models consider all information about the scheduling problem such as activity durations and precedence relationships information resources available and required,which are known and stable during the implementation *** concept of deterministic project scheduling conflicts with real situations,in which in many cases,some data on the activity’s durations of the project and the degree of availability of resources change or may have different modes and strategies during the process of project implementation for dealing with multi-mode conditions surrounded by projects and their activity *** the multi-mode resource-constrained project problem is an optimization problem whose minimum project duration subject to the availability of resources is of particular interest to *** use the multi-mode resource allocation and schedulingmodel that takes into account the dynamicity features of all parameters,that is,the scheduling process must be flexible to dynamic environment *** this paper,we propose five priority heuristic rules for scheduling multi-mode resource-constrained projects under dynamicity features for more realistic situations,in which we apply the proposed heuristic rules(PHR)for scheduling multi-mode resource-constrained *** projects are considered test problems for the *** obtained results rendered by these priority rules for the test problems are compared by the results obtained from 10 well-known heuristics rules rendered for

关键词： Constrained resource scheduling multi-mode durations dynamic scheduling resource allocation heuristic rules

Impact of lipids and lipoproteins on hepatitis C virus infection and virus neutralization

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World Journal of Gastroenterology 2014年第43期20卷 15975-15991页

作者： Koen Vercauteren ahmed atef Mesalam Geert Leroux-Roels Philip Meuleman Center for Vaccinology Ghent University Hospital Ghent University

Hepatitis C virus(HCV)infections represent a major global health ***-stage liver disease caused by chronic HCV infection is a major indication for liver ***,after transplantation the engrafted liver inevitably becomes infected by the circulating *** acting antivirals are not yet approved for use in liver transplant patients,and limited efficacy and severe side effects hamper the use of pegylated interferon combined with ribavirin in a post-transplant ***,alternative therapeutic options need to be *** entry represents an attractive target for such therapeutic *** the mechanisms of viral entry is essential to define the viral and cellular factors *** HCV life cycle is dependent of and associated with lipoprotein physiology and the presence of lipoproteins has been correlated with altered antiviral efficacy of entry *** thisreview,we summarise the current knowledge on how lipoprotein physiology influences the HCV life *** focus especially on the influence of lipoproteins on antibodies that target HCV envelope proteins or antibodies that target the cellular receptors of the *** information can be particularly relevant for the prevention of HCV re-infection after liver transplantation.

关键词： Hepatitis Lipids Neutralisation Antiviral therapy Animal models

Outcomes of pancreaticoduodenectomy in elderly patients

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Hepatobiliary & Pancreatic Diseases International 2016年第4期15卷 419-427页

作者： Ayman El Nakeeb Ehab atef Ehab El Hanafy Ali Salem Waleed Askar Helmy Ezzat ahmed Shehta Mohamed Abdel Wahab Gastroenterology Surgical Center Mansoura University

BACKGROUND： Although the mortality and morbidity of pancreaticoduodenectomy（PD） have improved significantly over the past years, the concerns for elderly patients undergoing PD are still present. Furthermore, the frequency of PD is increasing because of the increasing proportion of elderly patients and the increasing incidence of periampullary tumors. This study aimed to analyze the outcomes of PD in elderly ***： We studied all patients who had undergone PD in our center between January 1995 and February 2015. The patients were divided into three groups based on age： group I（patients aged 〈60 years）, group II（those aged 60 to 69 years） and group III（those aged ≥70 years）. The primary outcome was the rate of total postoperative complications. Secondary endpoint included total operative time, hospital mortality, length of postoperative hospital stay, delayed gastric emptying, re-exploration, and survival ***： A total of 828 patients who had undergone PD for resection of periampullary tumor were included in this study. There were 579（69.9%） patients in group I, 201（24.3%） in group II, and 48（5.8%） in group III. The overall incidence of complications was higher in elderly patients（25.9% in group I, 36.8% in group II, and 37.5% in group III; P=0.006）. There were more patients complicated with delayed gastric emptying in group II compared with the other two groups. There was no significant difference in the incidence of postoperative pancreatic fistula, biliary leakage, pancreatitis, pulmonary complications and hospital ***： PD can be performed safely in selected elderly patients. Advanced age alone should not be a contraindication for PD. The outcome of elderly patients who have undergone PD is similar to that of younger patients, and the increased rate of complications is due to the presence of associated comorbidities.

关键词： pancreaticoduodenectomy elderly pancreatic fistula delayed gastric emptying

Tailored pancreatic reconstruction after pancreaticoduodenectomy: a single-center experience of 892 cases

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Hepatobiliary & Pancreatic Diseases International 2017年第5期16卷 528-536页

作者： Ayman El Nakeeb Ahmad M Sultan Ehab atef Ali Salem Mostaffa Abu Zeid ahmed Abu El Eneen Gamal El Ebidy Mohamed Abdel Wahab Gastroenterology Surgical Center Mansoura UniversityMansoura 35516 Egypt

BACKGROUND: Pancreatic reconstruction following pancreaticoduodenectomy(PD) is still debatable even for pancreatic surgeons. Ideally, pancreatic reconstruction after PD should reduce the risk of postoperative pancreatic fistula(POPF) and its severity if developed with preservation of both exocrine and endocrine pancreatic functions. It must be tailored to control the morbidity linked to the type of *** study was to show the best type of pancreatic reconstruction according to the characters of pancreatic stump. METHODS: We studied all patients who underwent PD in our center from January 1993 to December 2015. Patients were categorized into three groups depending on the presence of risk factors of postoperative complications: low-risk group(absent risk factor), moderate-risk group(presence of one risk factor) and high-risk group(presence of two or more risk factors). RESULTS: A total of 892 patients underwent PD for resection of periampullary tumor. BMI >25 kg/m~2, cirrhotic liver, soft pancreas, pancreatic duct diameter <3 mm, and pancreatic duct location from posterior edge <3 mm are risk variables for development of postoperative complications. POPF developed in 128(14.3%) patients. Delayed gastric emptying occurred in 164(18.4%) patients, biliary leakage developed in 65(7.3%) and pancreatitis presented in 20(2.2%). POPF in low-, moderate-and high-risk groups were 26(8.3%), 65(15.7%) and 37(22.7%) patients, respectively. Postoperative morbidity and mortality were significantly lower with pancreaticogastrostomy(PG) in high-risk group, while pancreaticojejunostomy(PJ) decreases incidence of postoperative steatorrhea in all groups. CONCLUSIONS: Selection of proper pancreatic reconstruction according to the risk factors of patients may reduce POPF and postoperative complications and mortality. PG is superior to PJ as regards short-term outcomes in high-risk group but PJ provides better pancreatic function in all groups and therefore, PJ is superior in l

关键词： periampullary tumor pancreaticogastrostomy pancreaticojejunostomy pancreaticoduodenectomy postoperative pancreatic fistula

Maximizing the exploitation of phosphogypsum wastes using soaking technique with citric acid, recovering rare-earth and residual phosphate contents

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Journal of Central South University 2022年第12期29卷 3896-3911页

作者： ahmed atef ELIWA Amal Essam MUBARK Nasr Abelaziz ABDELFATTAH Ebrahim Abd El GAWAD Production Sector Nuclear Materials AuthorityP.O.Box 530 El-MaadiCairoEgypt

Phosphogypsum(PG), the main by-product of phosphoric acid production industries, is considered one of the most important secondary sources of rare earth elements(REEs). The current study focuses on the recovery of REEs content and the residual phosphate content existing in the PG with preserving on the CaSO_(4)skeleton to be used in other various applications. These attainments are carried out using citric acid leaching process via soaking technique. Several dissolution parameters for REEs using citric acid were studied, including soaking time, soaking temperature, citric acid concentration, solid-to-liquid ratio, and recycling of the citrate leaching solutions in the further REEs dissolution experiments. The best-operating conditions were 14 d of soaking time, 7.5% citric acid concentration, and the solid-toliquid ratio of 1/5 at ambient temperature. About 79.57% dissolution efficiency of REEs was achieved using the optimal conditions. Applying four soaking stages by mixing different fresh PG samples with the same citrate solution sequentially, cumulative dissolution efficiency for REEs was found to be 64.7% under optimal soaking conditions. REEs were recovered using Dowex 50X8 resin from citrate solutions with 96% extraction efficiency. Dissolution kinetics proved the pseudo-first-order nature, reversible reactions, and two activation energies for all REEs.

关键词： phosphogypsum rare earths citric acid dissolution soaking Dowex 50X8 pre-concentration

Neuronal Type Specific Fluorescence Labeling in ***

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作者： Arwa ahmed Awadh atef 华中科技大学

学位级别：硕士

Caenorhabditis elegans （C. elegans） are studied due to its useful systems. It offersvarious neurobiological processes at the molecular and cellular level cellular for studying.C. elegans has a very simple nervous system （302neurons）. It explores its environment byinterrupting its forward movement with occasional turns and reversals turns. Its reversalsturns occur at stable frequencies but in irregular intervals, producing probabilisticexploratory behaviors. In this thesis, we discuss how the neurons circuit controls are usedfor seeking food behaviors in C. elegans. By stimulating long reversals and omega turns upon removal from food, AWC andASK play a major role in the local search state. npr-9is responsible of search/pivoting. Itdisplays an increased local search/pivoting that impairs their ability to travel long distancesand roam on for food. Role head motor neurons were manipulated and tested. Thefrequency of short reversals increased when RIM was killed. On the other hand when bothRIM and AVA neurons were killed, the effect of eliminating RIM was suppressed. RIMmakes synapses and gap junctions onto the command interneurons, which mean that it mayinhibit short reversals through these connections. SMB motor neurons also make synapsesonto the command neurons, and it inhibits short reversals. Neither RMD nor SMD synapseonto the command neurons directly. Killing either cell increases the frequency of *** turns were stimulated by SMD and RIV motor neurons. Killing SMD and RIVneurons leads to a decrease in the frequency of omega turns. RMG inter/motor neuron is a hub of a gap-junction network connecting sevenclasses of neurons. RMG neurons stimulate aggregation-related behaviors in npr-1mutants,and indicate that NPR-1inhibits RMG activity in solitary strains. When RMG was killed,it resulted in the elimination of aggregation, bordering and rapid movement. AVECommand interneurons along with AVA, AVD and A-type motor neurons drive backwardmovement of the

关键词： C.elegans Neuropeptide RMG and AVE aggregation behaviors

Intraoperative endoscopic retrograde cholangiopancreatography: A useful tool in the hands of the hepatobiliary surgeon

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World Journal of Gastroenterology 2015年第2期21卷 609-615页

作者： Ayman El Nakeeb Ahmad M Sultan Emad Hamdy Ehab El Hanafy Ehab atef Tarek Salah ahmed A El Geidie Tharwat Kandil Mohamed El Shobari Gamal El Ebidy Gastroenterology surgical center Mansoura UniversityDaqahlia 35516Egypt

AIM: To evaluate the efficacy of intraoperative endoscopic retrograde cholangio-pancreatography(ERCP) combined with laparoscopic cholecystectomy(LC) forpatients with gall bladder stones(GS) and common bile duct stones(CBDS).METHODS: Patients treated for GS with CBDS were included. LC and intraoperative transcystic cholangiogram(TCC) were performed in most of the cases. Intraoperative ERCP was done for cases with proven ***: Eighty patients who had GS with CBDS were included. LC was successful in all cases. Intraoperative TCC revealed passed CBD stones in 4 cases so intraoperative ERCP was performed only in 76 patients. Intraoperative ERCP showed dilated CBD with stones in 64 cases(84.2%) where removal of stones were successful; passed stones in 6 cases(7.9%); short lower end stricture with small stones present in two cases(2.6%) which were treated by removal of stones with stent insertion; long stricture lower 1/3 CBD in one case(1.3%) which was treated by open hepaticojejunostomy; and one case(1.3%) was proved to be ampullary carcinoma and whipple's operation was scheduled. CONCLUSION: The hepatobiliary surgeon should be trained on ERCP as the third hand to expand his field of therapeutic options.

关键词： Obstructive jaundice Endoscopic retrograde cholang