Utilization of Aerial Heterogeneous Cellular Networks: Signal-to-Interference Ratio Analysis

Mostafa Helmy,Hüseyin Arslan 한국통신학회 2018 Journal of communications and networks Vol.20 No.5

As a component of future communication networks,aerial telecommunication platforms are a promising solution tomeet surging traffic demands. These platforms can be used asaerial base stations (ABSs) to build an aerial heterogeneous networkarchitecture. In this study, we explore the promising utilizationof high- and low- altitude platforms (HAPs and LAPs) workingon the same network as macrocells and femtocells, respectively. First, using stochastic geometry, we determine the probability ofeach user being associated with either a HAP or a LAP. The associationprobability is used for deriving the cell load of ABSs. Next, wederive the outage probability of a typical user in a certain tier thatis equivalent to the downlink signal-to-interference ratio cumulativedistribution function in aerial heterogeneous cellular networks. Moreover, we propose a dynamic placement and sizing algorithmfor cells established by LAPs to achieve load balancing and enhancethe overall quality of service for users inside the coverage of a HAP. Our simulation results show that the algorithm provides considerablegains over static aerial cellular networks. Furthermore, wederive the coverage probability of a target receiver when the downlinkpaths are correlated or uncorrelated. The results demonstratethe impact of the difference in elevation angles between HAPs andLAPs on the coverage probability of the target receiver.

Enhanced oxygen evolution reaction over glassy carbon electrode modified with NiOx and Fe3O4

Reham Helmy Tammam,Amany Mohamed Fekry,Mahmoud Mohamed Saleh 한국화학공학회 2019 Korean Journal of Chemical Engineering Vol.36 No.11

Magnetite iron oxide (Fe3O4)/nickel oxide (NiOx) modified glassy carbon (GC) electrode shows enhancement of oxygen evolution reaction (OER) compared to GC electrode modified with single NiOx or Fe3O4 nanoparticles. Many techniques such as linear and cyclic sweep voltammetry, electrochemical impedance spectroscopy (EIS) have been employed. Field-emission scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX) are both used for characterization of the electrocatalysts. Effect of loading amount of both NiOx and Fe3O4 and the order of deposition on the OER was studied. A significant improvement of the electrocatalytic properties of the Fe3O4/NiOx binary catalyst modified GC is obtained when NiOx is electrodeposited on GC/Fe3O4 (i.e. GC/Fe3O4/NiOx) compared to GC/NiOx/Fe3O4 (where NiOx is deposited first on the GC then Fe3O4). The use of GC/Fe3O4/NiOx (where Fe3O4 is deposited first on the GC then NiOx) for OER in alkaline solution support higher currents and consequently negative shifts of the onset potential of OER compared to that of GC/NiOx or GC/Fe3O4. The obtained electrochemical impedance parameters confirmed the above conclusions. Tafel parameters confirm the superior activity of GC/Fe3O4/ NiOx and give insight into the mechanism of the OER on the above electrodes.

A comparative evaluation of CO2 and erbium-doped yttrium aluminium garnet laser therapy in the management of dentin hypersensitivity and assessment of mineral content

Mahmoud Helmy Belal,Abdulaziz Yassin 대한치주과학회 2014 Journal of Periodontal & Implant Science Vol.44 No.5

Purpose: Dentin hypersensitivity is a potential threat to oral health. Laser irradiation mayprovide reliable and reproducible treatment but remains controversial. The present studyaimed to evaluate the effects of CO2 or erbium-doped yttrium aluminium garnet (Er:YAG)laser therapy, and to assess mineral content. Methods: Eighteen human single-rooted teeth affected with advanced periodontitis wereobtained. Buccal and lingual surfaces were planed to form 36 specimens. Ethylenediaminetetraaceticacid gel (24%) was applied to remove the smear layer and simulate hypersensitiveteeth. The experimental groups were: group 1, control (no irradiation); group 2, CO2 laser(repetitive pulsed mode, 2 W, 2.7 J/cm²); and group 3, Er:YAG laser (slight contact mode,40 mJ/pulse and 10 Hz). To evaluate dentinal tubule occlusion, six specimens per group (2-mm thickness) were prepared and observed using scanning electron microscopy (SEM) forcalculation of the occlusion percentage. To evaluate the mineral content, six specimens pergroup (0.6-mm thickness) were used, and then the levels of Ca, K, Mg, Na, and P were measuredby inductively coupled plasma-atomic emission spectrometry. In addition, the surfacetemperature of the specimens during laser irradiation was analyzed by a thermograph. Results: The SEM photomicrographs indicated melted areas around exposed dentinal tubulesand a significantly greater percentage of tubular occlusion in the CO2 and Er:YAG lasergroups than the control, and in the Er:YAG group than the CO2 laser group. In addition,no significant differences were noted among the experimental groups for the mineral elementsanalyzed. The CO2 laser group showed an evident thermal effect compared to theEr:YAG group. Conclusions: CO2 and Er:YAG laser are effective in treating dentin hypersensitivity and reducingits symptoms. However, the Er:YAG laser has a more significant effect; thus, it mayconstitute a useful conditioning item. Furthermore, neither CO2 nor Er:YAG lasers affectedthe compositional structure of the mineral content.

Ultimate section capacity of steel thin-walled I-section beam-columns

Adel Helmy Salem,Ezzeldin Yazeed Sayed-Ahmed,Ahmed Abdelsalam El-Serwi,Mohamed Mostafa Korashy 국제구조공학회 2004 Steel and Composite Structures, An International J Vol.4 No.5

A numerical model based on the finite element technique is adopted to investigate the behavior and strength of thin-walled I-section beam-columns. The model considers both the material and geometric nonlinearities. The model results were first verified against some of the currently available experimental results. A parametric study was then performed using the numerical model and interaction diagrams for the investigated beam-columns have been presented. The effects of the web depth-to-thickness ratio, flange outstand-to-thickness ratio and bending moment-to-normal force ratio on the ultimate strength of thin-walled I-section beam-columns were scrutinized. The interaction equations adopted for beam columns design by the NAS (North American Specifications for the design of cold formed steel structural members) have been critically reviewed. An equation for the buckling coefficient which considers the interaction between local buckling of the flange and the web of a thin-walled I-section beam-column has been proposed.

Hypolipidemic Effect of Moringa oleifera Lam Leaf Powder and its Extract in Diet-Induced Hypercholesterolemic Rats

Shahinaz A. Helmy,Nashwa F.S. Morsy,Shahenda M. Elaby,Mohammed A.A. Ghaly 한국식품영양과학회 2017 Journal of medicinal food Vol.20 No.8

The leaves of Moringa oleifera Lam possess some potential medicinal value. The aim of this study was to evaluate the protective effect of M. oleifera leaf powder and its extract against hyperlipidemia in rats. Adult male albino rats were divided into six groups. The first group was fed on a basal diet that served as a negative control, whereas the others were fed on a high-fat diet (HFD) containing moringa leaf powder at 0.737% or 1.475% or administered daily with 200 or 400 mg dry moringa leaf extract/kg bw for 60 days. A positive control group was fed on the HFD. Serum indices related to lipid profile, oxidative status, and liver function were analyzed. Feeding rats on an HFD containing moringa leaf powder at 0.737% or an oral dose of its dry extract at 400 mg/kg bw alleviated the harmful elevation of cholesterol, triglycerides, low-density lipoprotein cholesterol, malondialdehyde, and the activities of alanine aminotransferase and aspartate aminotransferase in serum that were induced by the HFD. This is the first study demonstrating the hypocholesterolemic effect of M. oleifera leaf powder.

A comparative evaluation of $CO_2$ and erbium-doped yttrium aluminium garnet laser therapy in the management of dentin hypersensitivity and assessment of mineral content

Belal, Mahmoud Helmy,Yassin, Abdulaziz Korean Academy of Periodontology 2014 Journal of Periodontal & Implant Science Vol.44 No.5

Purpose: Dentin hypersensitivity is a potential threat to oral health. Laser irradiation may provide reliable and reproducible treatment but remains controversial. The present study aimed to evaluate the effects of $CO_2$ or erbium-doped yttrium aluminium garnet (Er:YAG) laser therapy, and to assess mineral content. Methods: Eighteen human single-rooted teeth affected with advanced periodontitis were obtained. Buccal and lingual surfaces were planed to form 36 specimens. Ethylenediaminetetraacetic acid gel (24%) was applied to remove the smear layer and simulate hypersensitive teeth. The experimental groups were: group 1, control (no irradiation); group 2, $CO_2$ laser (repetitive pulsed mode, 2 W, $2.7J/cm^2$); and group 3, Er:YAG laser (slight contact mode, 40 mJ/pulse and 10 Hz). To evaluate dentinal tubule occlusion, six specimens per group (2-mm thickness) were prepared and observed using scanning electron microscopy (SEM) for calculation of the occlusion percentage. To evaluate the mineral content, six specimens per group (0.6-mm thickness) were used, and then the levels of Ca, K, Mg, Na, and P were measured by inductively coupled plasma-atomic emission spectrometry. In addition, the surface temperature of the specimens during laser irradiation was analyzed by a thermograph. Results: The SEM photomicrographs indicated melted areas around exposed dentinal tubules and a significantly greater percentage of tubular occlusion in the $CO_2$ and Er:YAG laser groups than the control, and in the Er:YAG group than the $CO_2$ laser group. In addition, no significant differences were noted among the experimental groups for the mineral elements analyzed. The $CO_2$ laser group showed an evident thermal effect compared to the Er:YAG group. Conclusions: $CO_2$ and Er:YAG laser are effective in treating dentin hypersensitivity and reducing its symptoms. However, the Er:YAG laser has a more significant effect; thus, it may constitute a useful conditioning item. Furthermore, neither $CO_2$ nor Er:YAG lasers affected the compositional structure of the mineral content.

Authentication Scheme Based on Principal Component Analysis for Satellite Images

Ashraf. K. Helmy,GH.S.El-Taweel 보안공학연구지원센터(IJSIP) 2009 International Journal of Signal Processing, Image Vol.2 No.3

DFT and experimental study on adsorption of dyes on activated carbon prepared from apple leaves

Abdel-Aziz Mohamed Helmy,El-Ashtoukhy Elsayed Zakaria,Bassyouni Mohamed,Al-Hossainy Ahmed Farouk,Fawzy Eman M.,Abdel-Hamid Shereen M. S.,Zoromba Mohamed Shafick 한국탄소학회 2021 Carbon Letters Vol.31 No.5

This work reports utilization of apple leaves as a source of activated carbon. Activated carbon from apple leaves is prepared by two diferent methods, thermal activation where AC1 is obtained and chemical activation using H3PO4 and ZnCl2 where AC2 and AC3 are obtained, respectively. XRD analysis revealed that all types of prepared ACs have a semi-crystalline nature with a mean crystallite size of 13, 21.02, and 39.47 nm for AC1, AC2, and AC3, respectively. To identify the most suitable desorption temperature, the exothermic behavior was discovered for the three types of ACs by DSC. The exothermic onset temperatures are 340 °C, 200 °C, 400 °C, or AC1, AC2, and AC3, respectively. The point of zero charge for the three types of ACs is 8.6, 7.3, and 2.5 for AC1, AC2, and AC3, respectively. The BET surface area analysis data demonstrated that mesoporous structure was developed in AC1 and AC2, while a microporous structure was developed in AC3. Quantum chemical calculations for ACs is carried out using Density Functional Theory (DFT). Application of the prepared ACs in adsorption of basic dye C.I. base blue 47 is studied. The maximum removal efciency was 65.1%, 96% and 99% for AC1, AC2, and AC3, respectively under the infuence of diferent operating aspects. Adsorption data are modeled by Langmuir, Freundlich, and Temkin isotherms. The data revealed that adsorption of basic dye C.I. base blue 47 on AC1 follows Langmuir isotherm and adsorption on AC2 and AC3 follows Freundlich isotherm.

Circulating Neutrophil Phagocytic Dysfunction Is Associated with Systemic Inflammation, Hyponatremia, and Renal Impairment in Patients with Cirrhosis

( Hayam El Aggan ),( Myriam Helmy ) 대한간학회 2021 춘·추계 학술대회 (KASL) Vol.2021 No.1

Optimal Maintenance Scheduling in a Two Identical Component Parallel Redundant System Subject to Exponential Power Hazards

El-Damcese, M.A.,Helmy, A.N. The Korean Reliability Society 2008 International Journal of Reliability and Applicati Vol.9 No.2

This paper presents equations, which can be used to evaluate the failure frequency and the failure rate of a two identical component parallel redundant system in which each component can operate in its wear out period, and the failure rate of each component is exponential power distribution. The optimum maintenance interval for a two identical component parallel redundant system can be obtained using these equations. The proposed approach is presented and illustrated using several numerical examples. The optimum maintenance interval for each component in a two identical parallel redundant system will depend on factors such as: failure rate, repair and maintenance times of each component in the parallel redundant systems.