Effect of magnesia rich spinel on densification and stabilization behavior of monoclinic zirconia

Abdelgawad Mahmoud,El-Gamal S. M. A.,Ewais Emad M. M.,Li Shufeng 한국세라믹학회 2021 한국세라믹학회지 Vol.58 No.3

Fully cubic-stabilized zirconia ceramic composites have been successfully fabricated by conventional sintering technique using commercial monoclinic zirconia, Yttrium oxide and waste-derived magnesia-rich spinel (MMA) powder mixtures. In this study, eff ect of MMA content and sintering temperature on stabilization and densifi cation properties of zirconia has been duly considered. The obtained results showed that m-ZrO 2 in MMA-free Z0 reference specimen is partially stabilized upon temperature rising into tetragonal phase by Y 3+ ions diff usion inside zirconia structure. MMA-free Z0 reference specimen sintered at 1600 ºC showed m- and t-ZrO 2 dual-phase structure with a relative density of 80.2%. Unlike, upon rising the sintering temperature, Z10–Z50 composites containing 10–50 wt% MMA demonstrated higher relative density of more than 99% and showed variant behavior, where their m-ZrO 2 is transformed and stabilized into cubic form by diff usion of Y 3+ , Mg 2+ and Al 3+ ions inside zirconia lattice structure. The outcomes indicate that MMA has significantly improved both the densification and stabilization behavior of m-ZrO 2 through facilitating Y 3+ diff usion inside zirconia lattice structure.

MgAl2O4-reinforced c-ZrO2 ceramics prepared by spark plasma sintering

El-Amir Ahmed A. M.,Li Shufeng,Abdelgawad Mahmoud,Ewais Emad M. M. 한국세라믹학회 2021 한국세라믹학회지 Vol.58 No.5

c-zirconia ceramic composites have been synthesized by spark plasma sintering (SPS) technique from commercial m-ZrO 2 , Y 2 O 3 and waste-derived magnesium aluminate spinel (MA) powders. In this study, eff ect of MA addition on stabilization and reinforcement of 5 mol% yttria-stabilized zirconia (YSZ) was carefully investigated. Spark plasma sintering of designed powder mixtures at 1400 °C for 30 min and 40 MPa produce fully dense compacts with an average grain size of 0.5–10 μm. The pressure was gradually increased up to 40 MPa using argon gas and was kept until the end of the sintering process. The refi ned microstructure (0.5–10 μm) obtained in this study has achieved superior compaction resistance values that are ten times more than strength values of conventionally sintered specimens. Such improvement in compaction resistance of the sintered specimens was attributed to particle size refi nement and grain boundary enhancement. What’s more, spark-plasma sintered composites containing 10–50 wt% MA revealed higher resistance to low temperature degradation (LTD) than the reference composite that doesn’t contain MA spinel; where about ~ 2.8% of t-ZrO 2 was converted into m-ZrO 2 in case of the latter composite while aging test didn’t infl uence at all on the structure of the former composites. The outcomes indicated that MA has a signifi cant eff ect on m-ZrO 2 stabilization into a cubic phase structure that concurrently owned an enhanced and comparable compression resistance to Yttrium-doped t-ZrO 2 (Y-TZP). In this respect, the ternary oxide ceramic composite systems prepared in this study present huge potential for development c-ZrO 2 -based industrial ceramics with a wide spectrum of mechanical characteristics for high-tech engineering applications of harsh-stress and humid environments.

Theoretical rotational stiffness of the flexible base connection based on parametric study via the whale optimization algorithm

Mahmoud T. Nawar,Ehab B. Matar,Hassan M. Maaly,Ahmed G. Alaaser,Osman Hamdy 국제구조공학회 2023 Structural Engineering and Mechanics, An Int'l Jou Vol.88 No.1

This paper handles the results of an extensive parametric study on the rotational stiffness of the flexible base connection using ABAQUS program. The results of the parametric study show the relation between the applied moment and the relative rotation for 96 different base connections. The configurations of the studied connections considered different numbers, diameters, and spacing of the anchor bolts along with different thicknesses of the base plate to investigate the effect of these parameters on the rotational stiffness behavior. The results of the previous parametric research used through the whale optimization algorithm (WOA) to detect different equation formulation of the moment-rotation (M-Ɵr) equation to detect optimum equation simulates the general nonlinear rotational behavior of the flexible base connection considering all variables used in the parametric study. WOA is a relatively new promising algorithm, which is used in different types of optimization problems. For more verification, the classical genetic algorithm (GA) is used to make a comparison with WOA results. The results show that WOA is capable of getting an optimum equation of the M-Ɵr relation, which can be used to simulate the actual rotational stiffness of the flexible base connections. The rotational stiffness at H/150 can be calculated using WOA (1) method and be used as a design aid for engineering design.

Gamma ray shielding characteristics and exposure buildup factor for some natural rocks using MCNP-5 code

K.A. Mahmoud,M.I. Sayyed,O.L. Tashlykov 한국원자력학회 2019 Nuclear Engineering and Technology Vol.51 No.7

The mass attenuation coefficient for eight rock samples having different chemical composition was simulated using the MCNP 5 code in energy range . Moreover, the for the studied rock samples was computed theoretically using XCOM database. The comparison between simulated and computed data for all selected rock samples showed a good agreement with differences varied between 0.01 and 8%. The highest was found for basalt rocks M2 and M1 and the lowest one is reported for limestone rocks Dike. The simulated values of the then were used to calculate other important shielding parameters such as the mean free path, effective electron density and effective atomic number. The exposure buildup factor was also computed for the selected rocks with the contribution of G-P fitting parameters and the highest EBF attended by the basalt sample Sill and varied between 1.022 and 744 in the energy range between but the lowest EBF achieved by basalt sample M2 and varied between 1.017 and 491 in the same energy range.

Dental Panoramic Radiographic Indices as a Predictor of Osteoporosis in Postmenopausal Saudi Women

Ayman Zaky Elsamanoudy,Madiha Mahmoud Gomaa,Rabab Mohammed Feteih,Najlaa Mohammed AlAmoudi,Ayman Zaky Elsamanoudy,Mohammed Ahmed Hassanien,Mohammed-Salleh M. Ardawi 대한골대사학회 2018 대한골대사학회지 Vol.25 No.3

Background: Many oral presentations of osteoporosis-a bone metabolic disease-were recorded. Thus, we aimed to assess panoramic radiomorphometric indices with bone mineral density (BMD) values among Saudi postmenopausal women and its importance in the prediction of osteoporosis. Methods: A total of 431 Saudi women were enrolled in this study. Panoramic radiographs were obtained at the time of BMD measurement. Subjects were fatherly classified into; normal BMD, osteopenia, and osteoporosis groups. Serum follicle-stimulating hormone, luteinizing hormone (LH), estradiol (E2), 25-hydroxy-vitamin D (25[OH]D) and intact-parathyroid hormone were measured. Moreover, serum creatinine, calcium, and phosphate, together with serum osteocalcin (s-OC), procollagen type I N-terminal propeptide (s-PINP) and cross-linked C-terminal telopeptide of type 1 collagen (s-CTX) were measured. Receiver-operator curve (ROC) curve analysis for use of mandibular cortical width (MCW), panoramic mandibular index (PMI), and maxillary-mandibular ratio (M/M ratio) to differentiate women with osteoporosis or osteopenia from normal subjects was calculated. Cut off values of 4.6 at T score <-1 and 4.1 at T score ≤-2.5 were used. Results: Body mass index is significantly low in the osteoporotic group. There is no significant difference in serum levels of LH, E2, calcium, phosphate, and 25(OH)D between the studied groups. Moreover, s-OC, C-terminal propeptide of procollagen type I, s-PINP, s-CTX, and urinary-CTX are significantly higher in osteoporosis than normal and osteopenia groups. ROC curve analysis revealed that MCW and PMI showed significant data while M/M ratio is non-significant. Conclusions: It could be concluded that MCW as an important panoramic radiographic parameter can be used for prediction and diagnosis of osteoporosis in postmenopausal Saudi women with low BMD.

Stem cell-derived exosomes for dentin-pulp complex regeneration: a mini-review

Hammouda Dina A.,Mansour Alaa M,Saeed Mahmoud A.,Zaher Ahmed R.,Grawish Mohammed E. 대한치과보존학회 2023 Restorative Dentistry & Endodontics Vol.48 No.2

This mini-review was conducted to present an overview of the use of exosomes in regenerating the dentin-pulp complex (DPC). The PubMed and Scopus databases were searched for relevant articles published between January 1, 2013 and January 1, 2023. The findings of basic in vitro studies indicated that exosomes enhance the proliferation and migration of mesenchymal cells, as human dental pulp stem cells, via mitogen-activated protein kinases and Wingless-Int signaling pathways. In addition, they possess proangiogenic potential and contribute to neovascularization and capillary tube formation by promoting endothelial cell proliferation and migration of human umbilical vein endothelial cells. Likewise, they regulate the migration and differentiation of Schwann cells, facilitate the conversion of M1 pro-inflammatory macrophages to M2 anti-inflammatory phenotypes, and mediate immune suppression as they promote regulatory T cell conversion. Basic in vivo studies have indicated that exosomes triggered the regeneration of dentin-pulp–like tissue, and exosomes isolated under odontogenic circumstances are particularly strong inducers of tissue regeneration and stem cell differentiation. Exosomes are a promising regenerative tool for DPC in cases of small pulp exposure or for whole-pulp tissue regeneration.

Development, validation and implementation of multiple radioactive particle tracking technique

Vesvikar Mehul S.,Aljuwaya Thaar M.,Taha Mahmoud M.,Al-Dahhan Muthanna H. 한국원자력학회 2023 Nuclear Engineering and Technology Vol.55 No.11

Computer Automated Radioactive Particle Tracking (CARPT) technique has been successfully utilized to measure the velocity profiles and mixing parameters in different multiphase flow systems where a single radioactive tracer is used to track the tagged phase. However, many industrial processes use a wide range of particles with different physical properties where solid particles could vary in size, shape and density. For application in such systems, the capability of current single tracer CARPT can be advanced to track more than one particle simultaneously. Tracking multiple particles will thus enable to track the motion of particles of different size shape and density, determine segregation of particles and probing particle interactions. In this work, a newly developed Multiple Radioactive Particle Tracking technique (M-RPT) used to track two different radioactive tracers is demonstrated. The M-RPT electronics was developed that can differentiate between gamma counts obtained from the different radioactive tracers on the basis of their gamma energy peak. The M-RPT technique was validated by tracking two stationary and moving particles (Sc-46 and Co-60) simultaneously. Finally, M-RPT was successfully implemented to track two phases, solid and liquid, simultaneously in three phase slurry bubble column reactors.

Development of a Smart Aquaponic System based on IoT

M. M. M. Mahmoud,Rania Darwish,A. M. Bassiuny 제어로봇시스템학회 2023 제어로봇시스템학회 국제학술대회 논문집 Vol.2023 No.10

Electrooxidation of DL-norvaline at Glassy Carbon Electrode: Approaching the Modified Electrode for Voltammetric Studies of Hydroquinone and Catechol

Kamel, Mahmoud M. The Korean Electrochemical Society 2014 Journal of electrochemical science and technology Vol.5 No.1

The DL-norvaline was electrochemically oxidized and deposited on the glassy carbon electrode surface using cyclic voltammetry (CV). The modified electrode was examined for electrochemical oxidation of hydroquinone (HQ) and catechol (CC). It exhibited good electrocatalytic ability towards their oxidation and simultaneous determination in a binary mixture using differential pulse voltammetry (DPV). The peak currents were linear to the concentration of HQ and CC, in the range from $5{\mu}M$ to $100{\mu}M$, and $4{\mu}M$ to $140{\mu}M$, respectively. The determination limits(S/N = 3) for HQ and CC were $1{\mu}M$ and $0.8{\mu}M$, respectively. The obtained modified electrode was applied to simultaneous detection of HQ and CC in water sample.

Vehicles Communications Handover in 5G: A Survey

Mahmoud M. Elsayed,Khalid M. Hosny,Mostafa M. Fouda,Marwa M. Khashaba 한국통신학회 2023 ICT Express Vol.9 No.3

A communications system consists of interconnected telecommunications networks, transmission systems, relay stations, tributary stations, and terminal equipment. Increasing network limits to fulfill the developing needs of consumers has prompted the advancement of cell correspondence networks from 1G to 5G. Many heterogeneous connections request higher information rates, lesser postponements, improved framework limit, and predominant throughput. The accessible range of assets is restricted and should be deftly utilized by mobile network operators (MNOs) to cope with the rising demands. This paper presents a detailed survey on vehicular communications systems, their forms, and handover in each category in 5G networks.