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Ef.ects of.Plasticizers,Antioxidants and Burning Rate Modif.ers on Aging Perf.rmance of.the HTPB/HMDI Composite Solid Propellant

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含能材料 2019年第1期27卷 21-27,90页

作者： Ahmed M Enew ehab abadir Sahar Elmarsaf. Karim K Elsharkawy Chemical Department Faculty of EngineeringCairo University School of.Chemistry and Environment Beijing University of Aeronautics and Astronautics

The ef.ects of.plasticizers,antioxidants and burning rate modif.ers on the aging perf.rmance of.the composite solid propellant based on hydroxyl-terminated polybutadiene(HTPB)/hexamethylene diisocyanate(HMDI)were explored by apply-ing an accelerated aging program f.r 90 day at 70 ℃. The HTPB propellant matrix with the diisooctyl sebacate(DOS)as plasti-cizers and diisooctyl azelate(DOZ), antioxidants as N,N ′-Diphenyl-p-phenylenediamine(AO) and 2,2′-methylenebis(4-methyl-6-tert-butylphenol)(cyanox 2246)and burning rate modif.ers as barium f.rrite(Bf.,copper chromites(CC)and f.r-ric oxide(f.)were varied. Results show that sample(S1)which based on DOS decreases the stress value and increases the strain value which considered to be an excellent start f.r aging program. Sample(S3)containing AO presents the higher resis-tance to oxidation showing the better perf.rmance that ref.ects on increasing the shelf.lif. of.the composite solid propellant mo-tor. Sample(S5)which based on Bf.enhances the ballistic perf.rmance among over the other tested two samples. The accelerat-ed aging program allowed us to estimate the motor in-service lif.time.

关键词： polybutadiene(HTPB)/hexamethylene diisocyanate(HMDI)composite solid propellant plasticizers antioxidants burning rate modif.ers aging program

Adsorptive removal of.iron and manganese ions f.om aqueous solutions with microporous chitosan/polyethylene glycol blend membrane

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Journal of.Environmental Sciences 2012年第8期24卷 1425-1432页

作者： Neama A.Reiad Omar E.Abdel Salam ehab f.abadir f.rid A.Harraz Sanitary&Environmental Department Housing&Building National Research Center87 el Tahrir st.DokkiEgypt Department of.Chemical Engineering Faculty of EngineeringCairo UniversityGizaEgypt Advanced Materials Technology Department Central Metallurgical R&D InstituteHelwanEgypt

Microporous chitosan （CS） membranes were directly prepared by extraction of.poly（ethylene glycol）（PEG） f.om CS/PEG blend membrane and were examined f.r iron and manganese ions removal f.om aqueous solutions. The dif.erent variables af.ecting the adsorption capacity of.the membranes such as contact time, pH of.the sorption medium, and initial metal ion concentration in the f.ed solution were investigated on a batch adsorption basis. The af.inity of.CS/PEG blend membrane to adsorb f.（II） ions is higher than that of.Mn（II） ions, with adsorption equilibrium achieved af.er 60 min f.r f.（II） and Mn（II） ions. By increasing CS]PEG ratio in the blend membrane the adsorption capacity of.metal ions increased. Among all parameters, pH has the most signif.cant ef.ect on the adsorption capacity, particularly in the range of.2.9-5.9. The increase in CS/PEG ratio was f.und to enhance the adsorption capacity of.the membranes. The ef.ects of.initial concentration of.metal ions on the extent of.metal ions removal were investigated in detail. The experimental data were better f.tted to f.eundlich equation than Langmuir. In addition, it was f.und that the iron and manganese ions adsorbed on the membranes can be ef.ectively desorbed in 0.1 mol/L HCl solution （up to 98% desorption ef.iciency） and the blend membranes can be reused almost without loss of.the adsorption capacity f.r iron and manganese ions.

关键词： chitosan blend membrane iron and manganese ions adsorption

Metaheuristic Lightweight Cryptography f.r Security Enhancement in Internet of.Things

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Computers, Materials & Continua 2022年第8期72卷 3009-3023页

作者： Mahmoud Ragab ehab Bahaudien Ashary Inf.rmation Technology Department Faculty of Computing and Information TechnologyKing Abdulaziz UniversityJeddah21589Saudi Arabia Centre of.Artif.cial Intelligence f.r Precision Medicines King Abdulaziz UniversityJeddah21589Saudi Arabia Mathematics Department Faculty of ScienceAl-Azhar UniversityNaser City11884CairoEgypt Electrical and Computer Engineering Department Faculty of EngineeringKing Abdulaziz UniversityJeddah21589Saudi Arabia

The advancements made in Internet of.Things(IoT)is projected to alter the f.nctioning of.healthcare industry in addition to increased penetration of.dif.erent ***,data security and private are challenging tasks to accomplish in IoT and necessary measures to be taken to ensure secure *** this background,the current paper proposes a novel lightweight cryptography method f.r enhance the security in *** proposed encryption algorithm is a blend of.Cross Correlation Coef.icient(CCC)and Black Widow Optimization(BWO)*** the presented encryption technique,CCC operation is utilized to optimize the encryption process of.cryptography *** projected encryption algorithm works in line with encryption and decryption *** key selection is perf.rmed with the help of.Artif.cial Intelligence(AI)tool named BWO *** the combination of.AI technique and CCC operation,optimal security operation is improved in *** dif.erent sets of.images collected f.om databases,the projected technique was validated in MATLAB on the basis of.f.w perf.rmance metrics such as encryption time,decryption time,Peak Signal to Noise Ratio(PSNR),CC,Error,encryption time and decryption *** results were compared with existing methods such as Elliptical Curve cryptography(ECC)and Rivest-Shamir-Adleman(RSA)and the supremacy of.the projected method is established.

关键词： Security images encryption time correlation coef.icient black widow optimization artif.cial intelligence decryption time

Mathematical analyses of.the GPS receiver interf.rence tolerance and mean time to loss lock

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Def.nce Technology（防务技术） 2019年第3期15卷 440-449页

作者： ehab M.Shaheen Sherif.A.Elgamel Electronic Warf.re Department Military Technical College

In this paper, novel mathematical expressions are derived f.r the Global Positioning System (GPS) receiver interf.rence tolerance in the presence of.dif.erent types of.interf.rence signals such as: continuous wave interf.rence, narrowband interf.rence, partial band interf.rence, broadband interf.rence, match spectrum interf.rence and pulse interf.rence. Also, in this paper the mean time to loss lock is determined in order to analyse the mentioned interf.rences ef.ect on the GPS receiver. These derived analytical expressions are validated with the aid of.extensive simulation experiments.

关键词： Mathematical analyses GPS receiver interf.rence tolerance

Ef.icient Channel Estimation Techniques f.r MIMO Systems with 1-Bit ADC

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China Communications 2020年第5期17卷 50-64页

作者： Hany SHussein Shaimaa Hussein ehab Mahmoud Mohamed Electrical Engineering Dept. College of EngineeringKing Khalid UniversityAbha 61411King of Saudi Arabia Electrical Engineering Dept. Faculty of EngineeringAswan UniversityAswan 81542Egypt Electrical Engineering Dept. College of EngineeringPrince Sattam Bin Abdulaziz UniversityWadi Addwasir 11991King of Saudi Arabia

With a low resolution 1-bit ADC on its receiver(RX) side, MIMO with 1-bit ADC took a considerable step in the f.lf.llment of.the hardware complexity constrains of.the internet of.things(IoT) PHY layer design. However, applying 1-bit ADC at MIMO RX results in severe nonlinear quantization error. By which, almost all received signal amplitude inf.rmation is completely distorted. Thus, MIMO channel estimation is considered as a major barrier towards practical realization of.1-bit ADC MIMO system. In this paper, two ef.icient sparsity-based channel estimation techniques are proposed f.r 1-bit ADC MIMO systems, namely the low complexity sparsity-based channel estimation(LCSCE), and the iterative adaptive sparsity channel estimation(IASCE). In these techniques, the sparsity of.the 1-bit ADC MIMO channel is exploited to propose a new adaptive and iterative compressive sensing(CS) recovery algorithm to handle the 1-bit ADC quantization ef.ect. The proposed algorithms are tested with the state-of.the-art 1-bit ADC MIMO constant envelope modulation(MIMO-CEM). The 1-bit ADC MIMO-CEM system is chosen as it f.lf.lls both energy and hardware complexity constraints of.the IoT PHY layer. Simulation results reveal the high ef.ectiveness of.the proposed algorithms in terms of.spectral ef.iciency(SE) and computational complexity. The proposed LCSCE reduces the computational complexity of.the 1-bit ADC MIMO-CEM channel estimation by 86%, while the IASCE reduces it by 96% compared to the recent techniques of.MIMO-CEM channel estimation. Moreover, the proposed LCSCE and IASCE improve the spectrum ef.iciency by 76 % and 73 %, respectively, compared to the recent techniques.

关键词： channel estimation 1-bit ADC MIMO sparsity recovery compressive sensing Internet of.things

Orthogonal Codes-Based Dynamic Spectrum Access in Cognitive Radio Networks

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China Communications 2019年第12期16卷 34-46页

作者： ehab f.Badran Amr A.Bashir Amira I.Zaki Waleed K.Badawi Department of.Electronics and Communications Engineering Arab Academy for Science Technology and Maritime Transport

Dynamic spectrum access(DSA) in cognitive radio(CR) networks became a challenging research area recently. In CR technology, the DSA between primary users(PUs) and secondary users(SUs) simultaneously can be achieved without degrading the perf.rmance of.the PUs by SUs interf.rence. This can be achieved by donating incentive power to the PUs in order to compensate the interf.rence caused by the SUs. Consequently, PUs allow SUs to share the spectrum. In this paper, orthogonal codes-based dynamic spectrum access(OC-DSA) technique is proposed. OC-DSA technique employs orthogonality between PUs and SUs transmitted data symbols in addition to the incentive power donation. Compared to other techniques, the proposed technique uses a simple encoder at the SU network f.r the same PU network inf.astructure. By applying orthogonal codes, the interf.rence caused by SUs is canceled and hence the donated power to incentivize the PUs is reduced. Also, the SU packet rate is increased signif.cantly. The simulation results show that the proposed technique provides ef.ective improvements over other existing techniques in the signal strength and the bit error rate perf.rmance of.both the PU network and the SU network at the receiver side. Moreover, the proposed technique requires less donated power to incentivize the PU and has higher packet rate.

关键词： cognitive radio dynamic spectrum access orthogonal codes

f.rmation and Microstructural Characterization of.Silicon-modif.ed Aluminide Coating on Nickel-based Superalloy IN738LC

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材料热处理学报 2004年第05B期25卷 657-660页

作者： f. Shahriari f. Ashraf.zadeh A. Monshi Materials engineering department Isfahan University of Technology Isfahan IranMaterials engineering department Isfahan University of Technology Isfahan IranMaterials engineering department Isfahan University of Technology Isfahan Iran

In this investigation, aluminide coatings used to protect industrial components at high temperature and corrosive environments were modif.ed with silicon addition and the microstructural f.atures and f.rmation mechanism were evaluated. The coating on the nickel-based superalloy IN738LC was carried out by a two stage process including siliconizing at f.rst and aluminizing thereaf.er. Pack cementation siliconizing perf.rmed at 950C f.r 2, 4 and 6 hours in several powder mixtures of.Si, A12O3 and NHiCl, then aluminum was dif.used into the surf.ce of.the specimens by an industrial aluminizing process. The modif.ed coatings were characterized by means of.standard metallography, scanning electron microscopy, energy dispersive spectroscopy and X-ray dif.raction methods. The results show that Si in the coatings mainly presents in the f.rm of.secondary phases including Cr3Si, Mo5Si3 and Nii6Ti6Si7, well distributed within the NiAl matrix. The advantages of.this two stage modif.ed coating is discussed.

关键词：显微结构 IN738LC 镍超级合金扩散渗碳处理生长机制

Closed-f.rm solutions f.r f.ee vibration of.rectangular f.M thin plates resting on elastic f.undation

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Acta Mechanica Sinica 2016年第6期32卷 1088-1103页

作者： T. f. Xu Y. f. Xing Institute of.Solid Mechanics Beihang UniversityBeijing 100191 China China Academy of.Launch Vehicle Technology R&D Center Beijing 100076 China

This article presents closed-f.rm solutions f.r the f.equency analysis of.rectangular f.nctionally graded material (f.M) thin plates subjected to initially in-plane loads and with an elastic f.undation. Based on classical thin plate theory, the governing dif.erential equations are derived using Hamilton's principle. A neutral surf.ce is used to eliminate stretching-bending coupling in f.M plates on the basis of.the assumption of.constant Poisson's ratio. The resulting governing equation of.f.M thin plates has the same f.rm as homogeneous thin plates. The separation-of.variables method is adopted to obtain solutions f.r the f.ee vibration problems of.rectangular f.M thin plates with separable boundary conditions, including, f.r example, clamped plates. The obtained normal modes and f.equencies are in elegant closed f.rms, and present f.rmulations and solutions are validated by comparing present results with those in the literature and f.nite element method results obtained by the authors. A parameter study reveals the ef.ects of.the power law index n and aspect ratio a/b on f.equencies.

关键词： f.nctionally graded material f.ee vibration Rectangular plate Close f.rm solutions Neutral surf.ce

Beamf.rming techniques f.r massive MIMO systems in 5G:overview,classif.cation,and trends f.r f.ture research

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f.ontiers of.Inf.rmation Technology & Electronic Engineering 2017年第6期18卷 753-772页

作者： ehab ALI Mahamod ISMAIL Rosdiadee NORDIN Nor f.dzilah ABDULAH Department of.Electrical Electronic and System EngineeringUniversiti Kebangsaan Malaysia(UKM)Bangi 43600Malaysia

Massive multiple-input multiple-output(MIMO) systems combined with beamf.rming antenna array technologies are expected to play a key role in next-generation wireless communication systems(5G), which will be deployed in 2020 and beyond. The main objective of.this review paper is to discuss the state-of.the-art research on the most f.vourable types of.beamf.rming techniques that can be deployed in massive MIMO systems and to clarif. the importance of.beamf.rming techniques in massive MIMO systems f.r eliminating and resolving the many technical hitches that massive MIMO system implementation f.ces. Classif.cations of.optimal beamf.rming techniques that are used in wireless communication systems are reviewed in detail to determine which techniques are more suitable f.r deployment in massive MIMO systems to improve system throughput and reduce intra-and inter-cell interf.rence. To overcome the limitations in the literature, we have suggested an optimal beamf.rming technique that can provide the highest perf.rmance in massive MIMO systems, satisf.ing the requirements of.next-generation wireless communication systems.

关键词： Beamf.rming classif.cations Massive MIMO Hybrid beamf.rming Millimetre-wave beamf.rming