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Kinematic analysis of flexible bipedal robotic systems

Applied mathematics and mechanics(English Edition) 2024年第5期45卷 795-818页

作者： R.FAZEL a.m.shafei S.R.NEKOO Department of mechanical Engineering Shahid Bahonar University of KermanKerman ***Iran Departamento de Ingenieria de Sistemas y Automatica Escuela Técnica Superior de IngenieriaUniversidad de SevillaSeville 41092Spain

In spite of its intrinsic complexities,the passive gait of bipedal robots on a sloping ramp is a subject of interest for numerous *** distinguishes the present research from similar works is the consideration of flexibility in the constituent links of this type of robotic *** is not a far-fetched assumption because in the transient(impact)phase,due to the impulsive forces which are applied to the system,the likelihood of exciting the vibration modes increases ***,the human leg bones that are involved in walking are supported by viscoelastic muscles and ***,for achieving more exact results,it is essential to model the robot links with viscoelastic *** this end,the Gibbs-Appell formulation and Newton's kinematic impact law are used to derive the most general form of the system's dynamic equations in the swing and transient phases of *** most important issue in the passive walking motion of bipedal robots is the determination of the initial robot configuration with which the system could accomplish a periodic and stable gait solely under the effect of gravitational *** extremely unstable nature of the system studied in this paper and the vibrations caused by the impulsive forces induced by the impact of robot feet with the inclined surface are some of the very serious challenges encountered for achieving the above-mentioned *** overcome such challenges,an innovative method that uses a combination of the linearized equations of motion in the swing phase and the algebraic motion equations in the transition phase is presented in this paper to obtain an eigenvalue *** solving this problem,the suitable initial conditions that are necessary for the passive gait of this bipedal robot on a sloping surface are *** effects of the characteristic parameters of elastic links including the modulus of elasticity and the Kelvin-Voigt coefficient on the walking stability of this type of

关键词： bipedal robot flexible link swing phase transient phase eigenvalue problem Kelvin-Voigt coefficient

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Tribological Characterization of Hybrid metal matrix Composites Processed by Powder metallurgy

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Acta metallurgica Sinica(English Letters) 2017年第8期30卷 781-790页

作者： m. megahed m. A. Attia m. Abdelhameed A. G. El-shafei Department of mechanical Design and Production Engineering Faculty of EngineeringZagazig UniversityP.O.Box 44519ZagazigEgypt

Aluminum （Al）-based aluminum oxide （Al2O3） and silicon carbide （SIC） particles hybrid metal matrix com- posites were processed by powder metallurgy technique, followed by sintering at 500 ℃ and then hot extrusion. The tribological properties of these composites with different weight fractions of Al2O3 and SiC were investigated; extrusion process significantly reduces the extent of porosity after cold compaction and sintering processes. Hybridization of the two reinforcements improved hardness and wear resistance of the composites. With an increase in SiC content, hardness was increased and consequently the wear resistance was enhanced also. Scanning electron microscopy observations show a better interfacial bond between matrix and reinforcements and a better distribution of the reinforcements.

关键词： Hybrid metal matrix composite Powder metallurgy Abrasive wear Hardness Porosity

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Petrology and Geochemistry of Some Ophiolitic metaperidotites from the Eastern Desert of Egypt:Insights into Geodynamic Evolution and metasomatic Processes

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Acta Geologica Sinica(English Edition) 2021年第4期95卷 1139-1157页

作者： Abdel-Aal m.ABDEL-KARIm mokhles K.AZER Shaimaa A.EL-shafei Geology Department Faculty of ScienceZagazig UniversityZagazig 44519Egypt Geological Sciences Department National Research Centre12622-DokkiCairoEgypt

Ophiolitic peridotites exposed in the Eastern Desert(ED)of Egypt record multiple stages of evolution,including different degrees of partial melting and melt extraction,serpentinization,carbonatization and *** present study deals with metaperidotites at two selected localities in the central and southern ED,namely Wadi El-Nabáand Wadi Ghadir,*** represent residual mantle sections of a Neoproterozoic dismembered ophiolite that tectonically emplaced over a volcano-sedimentary succession that represents island–arc *** studied metaperidotites are serpentinized,with the development of talc-carbonate and quartz-carbonate rocks,especially along shear and fault *** relics of primary minerals(olivine,orthopyroxene and Cr-spinel)are preserved in a few samples of partiallyserpentinized *** of the Cr-spinel crystals have fresh cores followed by outer zones of ferritchromite and Crmagnetite,which indicates that melt extraction from the mantle protolith took place under oxidizing *** protoliths of the studied metaperidotites were dominated by harzburgites,which is supported by the abundance of mesh and bastite textures in addition to some evidence from mineral and whole-rock chemical *** high Cr#(0.62–0.69;Av.0.66)and low TiO_(2)(mary olivine relics,together with the high mg#(0.91–0.93;Av.91)and low CaO,Al2 O3 and TiO_(2)of the orthopyroxene relics,are all comparable with depleted to highly depleted forearc harzburgite from a suprasubduction zone *** investigated peridotites have suffered subsequent phases of metasomatism,from oceanfloor hydrothermal alteration(serpentinization)to magmatic hydrothermal *** enrichment of the studied samples in light rare earth elements(LREEs)relative to the heavy ones(HREEs)is attributed to most probably be due to the contamination

关键词： ophiolitic metaperidotites partial melting melt extraction geodynamic evolution Eastern Desert Egypt

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Sequence stratigraphic evaluation for the Abu madi Formation,Abu madi/El Qar'a/Khilala gas fields,onshore Nile Delta,Egypt

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Petroleum Research 2023年第4期8卷 514-523页

作者： Farouk I.metwalli Amir Ismail m.S.metwally Ibrahim m.El shafei Geology Department Faculty of ScienceHelwan UniversityCairoEgypt Desert Research Center CairoEgypt Petrobel Oil Company CairoEgypt

The present study aims to integrate a large set of geological and geophysical data into a comprehensive model describing the depositional features of the Abu madi/El Qar'a/Khilala gas *** model is based on the sequence stratigraphic framework of the Abu madi Formation defined using cores,well logs,and time-migrated seismic *** trace attribute sections and relative acoustic impedance sections are also used.A possible depositional pattern for the main Level Ill is established,based on the lithological and petrophysical information derived from the seismic data *** Abu madi For-mation can be regarded as a depositional sequence recording the progressive drowning of the incised *** sequence is bounded at the base by an erosional unconformity,created by a drop in the level of the Late messinian Sea,and at the top by a drowning unconformity related to the Early Pliocene *** bottom of Level II divides the Abu madi sequence into two smaller *** both sequences,gas-bearing traps can be found in the Lowstand Systems Tracts,represented by the fluvial Level Ill and fluvial-deltaic Level Il,respectively.

关键词： Abu madi gas field El Qar'a area Khilala area Sequence stratigraphy analysis Onshore Nile Delta Abu madi Formation

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Chitosan/Nanocrystalline Cellulose Biocomposites Based on Date Palm (Phoenix Dactylifera L.) Sheath Fibers

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Journal of Renewable materials 2019年第6期7卷 567-582页

作者： Abeer m.Adel Amira m.El-shafei Atef A.Ibrahim mona T.Al-Shemy Cellulose and Paper Department National Research Center33El-Bohouth St.(Former El-Tahrir St.)DokkiP.O.12622GizaEgypt Textile Research Division National Research Center33El-Bohouth St.(Former El-Tahrir St.)DokkiP.O.12622GizaEgypt

In this study,nanocrystalline celluloses were used to enhance physical,mechanical and water vapor barrier properties of chitosan films for potential food packaging *** different mineral acids(sulfuric and phosphoric)were used to extract nanocrystalline cellulose from date palm sheath *** influence of cellulose I and cellulose II on the properties of the isolated nanocrystalline celluloses(e.g.,yield,energy and length of intra-and intermolecular hydrogen bonds,and degree of substitution)were studied *** characteristics of chitosan biocomposite film with phosphorylated nanocrystalline cellulose were compared to those with sulfated nanocrystalline *** showed that besides cellulose polymorphism,the ionic ester groups on the surface of nanocrystalline cellulose is one of the factors influencing the physical,chemical,mechanical,and water vapor barrier properties in chitosan/nanocrystalline cellulose biocomposites.

关键词： Biocomposite Cellulose I Cellulose II Nanocrystalline cellulose(NCC) physico-mechanical properties Thermal stability

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modification of Serum Galectin-3 and Reversal of Cardiac Remodeling Following Pediatric Transcatheter Atrial Septal Defect Closure

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Congenital Heart Disease 2022年第2期17卷 173-185页

作者： Omnia shafei Alyaa A.Kotby mona mEl Ganzoury Nevin m.Habeeb Eman Elsayed Department of Pediatrics Faculty of MedicineAin Shams UniversityCairoEgypt Children’s Hospital Cardiology UnitAin Shams University HospitalsCairoEgypt

Objectives:We aimed to evaluate the effect of percutaneous atrial septal defect(ASD)closure in children using right heart indices and serum galectin-3(Gal-3),as potential biomarkers of right heart ***:This case–control prospective study included 40 children with ASD and 25 control *** echocardiographic evaluation was performed before the procedure,as well as 24 h,1 month,and 6 months after *** Gal-3 was measured before,and 1 month after the ***:Serum Gal-3 concentration,right atrial(RA)dimensions,right ventricular(RV)dimensions,indexed RA area,and right index of myocardial performance(RImP)were significantly increased in children with ASD compared with control subjects while tricuspid annular plane systolic excursion(TAPSE)was significantly *** months after closure,RA,and RV dimensions significantly decreased and RVfunction improved(RImP decreased and TAPSE increased).Gal-3 oncentration significantly decreased 1 month after ASD closure,but it did not reach normal range compared with control subjects.A positive correlation between Gal-3 and age at closure,RA area,RV dimensions,and RImP was observed.A positive correlation was observed between the decrease in Gal-3 concentration and the decrease in RA area and RV dimensions 1 month after ASD closure.A significant negative correlation was observed between TAPSE and Gal-3 concentration before and after ***:Percutaneous ASD closure can improve right-sided indices and decrease serum Gal-3 ***-3 can be used as a sensitive biomarker of right heart remodeling,with a decrease in Gal-3 concentration suggesting reversal of maladaptive remodeling.

关键词： Percutaneous device closure Galectin-3 cardiac remodeling children atrial septal defect

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Synthesis and Photophysical Properties of Novel Highly Stable Zero/Bis-Zero methine Cyanine Dyes Based on N-Bridgehead Heterocycles

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International Journal of Organic Chemistry 2018年第3期8卷 282-297页

作者： Ahmed I. Koraiem Islam m. Abdellah Ahmed m. El-shafei Department of Chemistry Faculty of Science Aswan University Aswan Egypt Polymer and Color Chemistry Program North Carolina State University Raleigh USA

Cyanine dyes of zero/bis-zero methine incorporating imid-azo(1,2-a)Pyridine (quinoline) or pyrazino(1,2-a)pyridine (quinoline) with stable C-N bond were synthesized using keto-oxime methylene C-link heterocyclic quaternary salts [1-phenyl-3-methyl-pyrazolino-4-keto-oxime-α-methylene-bis-pyridin-(quinoin)-1(4)-di-ium-iodide(ethiodide) salts and 1-phenyl-3-methyl-pyrazolino- 4-ketooxime-α-methylene-N-2-methyl-bis pyridin (quinoin)-1(4)-di-ium-iodide(ethiodide) salts]. Such heterocyclic precursors and related dyes were identified by elemental and spectral analyses. The absorption spectra properties of such dyes were investigated in 95% Ethanol to attempt and throw some light on the influence of such new heterocyclic nuclei and to compare or evaluate spectral behaviors. The absorption spectra of dyes in different pure solvents were examined in the visible region showing solvatochromism and the colour changes of dyes with solvents having different polarities. This permits a selection of the optimal solvent (fractional solvent) when such dyes are applied as photosensitizers. The spectral behavior of some selected newly synthesized cyanine dyes is observed in mixed solvents of different polarities and progressively increasing quantities of one solvent over the other were studied and showed an increase in the absorbance of CT band with increasing proportion of that solvent. Evidence for hydrogen bond formation between the solute molecules and solvent molecules allows measurement of certain energies such as hydrogen bonding, orientation, and free energies.

关键词： N-Bridgehead Heterocycles Cyanine Dyes Zero/Bis-Zero methine Solvatochromic Behaviours

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Application of Solar Energy for Recovery of Water from Atmospheric Air in Climatic Zones of Saudi Arabia

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Natural Resources 2011年第1期2卷 8-17页

作者： Ahmed m. Hamed Ayman A. Aly El-shafei B. Zeidan 不详

In the present work, an investigation on the application of solar energy to heat a sandy bed impregnated with calcium chloride for recovery of water from atmospheric air is presented. The study also aimed at evaluating the effects of different parameters on the productivity of the system during regeneration. These parameters include system design characteristics and the climatic conditions. An experimental unit has been designed and installed for this purpose in climatic conditions of Taif area, Saudi Arabia. The experimental unit which has a surface area of 0.5 m2, comprises a solar/desiccant collector unit containing sandy bed impregnated with calcium chloride. The sandy layer impregnated with desiccant is subjected to ambient atmosphere to absorb water vapor in the night. During the sunshine period, the layer is covered with glass layer where desiccant is regenerated and water vapor is condensed on the glass surface. Ambient temperature, bed temperature and temperature of glass surface are recorded. Also, the productivity of the system has been evaluated. Desiccant concentration at start of regeneration is selected on the basis of the climatic data of Al-Hada region, which is located at Taif area, Saudi Arabia. Experimental measurements show that about 1.0 liter per m2 of pure water can be regenerated from the desiccant bed at the climatic conditions of Taif. Liquid desiccant with initial concentration of 30% can be regenerated to a final concentration of about 44%. Desiccant concentration at start of regeneration is selected on the basis of the climatic data of Al-Hada region. The climate of Taif city is dry compared with that for Al-Hada region. This method for extracting water from atmospheric air is more suitable for Al-Hada region especially in the fall and winter.

关键词： Extraction Atmospheric Air Absorption Liquid Desiccant Solar Energy Dew Collection Regeneration

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Production of High Quality Functional Labneh Cheese Using Exopolysaccharides Producing Encapsulated Lactobacillus Bulgaricus

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Journal of Life Sciences 2011年第2期5卷 120-128页

作者： Kawther EI-shafei Fayza m. Assem Azzat B. Abd-EI-Khalek Osama m. Sharaf Food Industries ＆ Nutrition Division Dairy Department National Research Center Dokki Giza Egypt

Production of polysaccharides by lactic acid bacteria is vital and its technology is very important, too in dairy study. The selection ofexpolysaccharides producing encapsulated Lactobacillus bulgaricus in alginate gel and the factors affecting the production of polysaccharides such as time, temperature, pH and the growth with Streptococcus thermophilus were studied, pH 5.5 and temperature 35℃/18hr were found to be optimal for exopolysaccharides production by encapsulated L. bulgaricus and free culture yielding 600 mg/L and 380 mg/L respectively. Co-culturing L. bulgaricus with S. thermophilus increased exopolysaccharides production at 35 ℃/18hr to 660 mg/L by encapsulated cells and 400 mg/L by free culture. Results of this study were applied in the manufacture of Labneh cheese vitally containing probiotic species ofL. acidophilus, L. gasseri, L. johnsonii and protection of these bacteria by polysaeeharide produced encapsulated L. bulgaricus. The use of exopolysaccharides producing encapsulated L. bulgaricus and probiotic bacteria can provide acceptable quality to functional Labneh. This product can be used as therapeutic and diabetic milk product with highly acceptable qualities. It is noted that all of the results are the means of triplicate experiments.

关键词： Lactobacillus bulgaricus encapsulation Labneh Sterptococcus thermophilus polysaccharides probiotic bacteria.

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Therapeutic mammoplasty in management of Breast Cancer: A Prospective Clinical Study

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Advances in Breast Cancer Research 2017年第4期6卷 107-116页

作者： Ahmed mohamed Farahat Amr Abdel meguid Attia mohamed Aly m. El shafei El Zawahry mohamed H. Zedan Hussein Osama Soliman National Cancer Institute Cairo University Giza Egypt

Background: The introduction of oncoplasticbreast surgery, with a concomitant contralateral symmetrization procedure, allows the surgical oncologist the freedom to perform wider excisions, with more favorable cosmetic outcomes. Objective: To assess the feasibility of bilateral breast reduction for the management of breast cancer, and to determine the most suitable surgical technique of therapeutic mammoplasty for each patient. And to evaluate the cosmetic outcome during the postoperative period. methods: This study was from June 2014 until June 2016, and included 86 female patients with breast cancer;divided in 3 groups;group A;had bilateral superior pedicle reduction mammoplasty, group B;had bilateral inferior pedicle reduction mammoplasty, group C;had bilateral batwing mastopexy. 1 month postoperative, patients were asked to answer a 5-scale questionnaire evaluating their own cosmetic outcome. Criteria they were asked to evaluate were: symmetry, shape and volume, projection, correction of ptosis, visibility of the scars and overall satisfaction. A similar questionnaire was answered by a panel made up of a surgeon and breast-care nurse after seeing the pre- and post-operative photos of the patients in question. Results: Group A had a mean tumor size of 2.7 ± 0.69 cm, least resected margins 1.2 - 4.3 cm, Group B had a mean tumor size of 3.2 ± 1.19 cm, least resected margins 0.7 - 3.8 cm, Group C had a mean tumor size of 3.4 ± 1.12 cm, least resected margins 1.7 - 5.2 cm. Cosmetic results fared high above average. Group C fared better in overall satisfaction but Group B fared better in ptosis correction, projection and symmetry. The panel answers showed difference regarding shape and volume;the only two criteria to be almost of the same result among the three groups. Conclusion: Bilateral Tm has some advantages when compared to standard conventional BCS techniques without having any unfavorable effects on surgical margin confidence, local recurrence, and survival rat

关键词： Breast Oncoplasty Therapeutic mammoplasty Surgery Oncology Plastic Symmetry

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