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排序方式: 共有561条查询结果,搜索用时 0 毫秒
121.
Hamid Hamida H. Harb Mohamed E. Elshaer A. M. Erahim Sh. Soliman Moataz M. 《Microsystem Technologies》2018,24(4):1775-1781
Microsystem Technologies - Electrochemical biosensor has been developed for detection of danazol (Dz) based on electrochemical polyaniline (PANI) electrode. Electrochemical PANI films were prepared... 相似文献
122.
Mohamed Ahmed Ebrahim Haitham Saad Ramadan Mahmoud Soliman 《Asian journal of control》2019,21(4):1952-1965
The design of a blade pitch controller (BPC) for wind energy conversion system (WECS) applications is load‐dependent and has to be adjusted for each operating condition. Thus, BPC robustness is important for coping with the endless variations in operating conditions. The boundaries of a robust stability region are determined in regards to the controller parameters plane using their relevant set of polynomial inequalities via Referential Integrity between Routh‐Hurwitz criterion and Root‐Locus (RI‐RH/RL) approach. Constrained and unconstrained stability regions respectively are defined through a novel hybrid control technique based on the combination of both RI‐RH/RL and Kharitonov (Kh) theorem. The hybrid RI‐Kh method is used for globally analyzing all vertex plants to ensure the proposed controller robustness, non‐fragility, and resilience by selecting its parameters at the center of the robust stability region. The optimal BPC‐PID parameters estimated using different optimization techniques are always located within the specified stability region. Thus, the capability of the RI‐Kh approach in determining the most robust, non‐fragile and resilient controller is verified. Through simulation results, the effectiveness of the proposed approach and its applicability to WECS' global stabilization are validated. 相似文献
123.
M. Soliman A. El-Sabbagh M. Taha H. Palkowski 《Journal of Materials Engineering and Performance》2013,22(5):1331-1340
Hot deformation behavior of Al 6061- and Al 7108-SiC particulated composites (Al-PMMCs), prepared by stir casting with SiC particulates (SiCp) size of 8 and 15 μm and volume fraction from 0 to 20% is studied by uniaxial compression test carried out at temperature range from room temperature to 500 °C. The flow stress, work hardening behavior, and Young’s modulus are determined. Dynamic recrystallization is also studied. Work hardening and Young’s modulus are directly correlated with composite constituents, whereas the flow stress is greatly influenced by the porosity and SiCp agglomeration. The role of the SiCp in increasing the flow stress decreases by increasing the deformation temperature. The dynamic recrystallization process is stimulated by refining the SiCp and increasing their fraction in soft Al matrix. On the other hand, the PMMCs with Al6061 matrix has more potential for strain hardening than that with Al 7108 matrix. The strain hardening rate is influenced by the matrix type more than the SiCp volume fraction and size. 相似文献
124.
Nanocrystalline zirconia powder with high surface area and high tetragonal phase percentage is prepared by the precipitation method using ammonium hydroxide as a precipitating agent.The pH of precipitation,preparation temperature and calcinations’ temperature are optimized.Crystallite size,specific surface area,tetragonal phase percentage and the thermal stability of the prepared samples are identified by diferent characterization tools such as X-ray difraction(XRD),thermo gravimetric analysis(TGA),diferential scanning calorimetry(DSC),BET surface area,scanning electron microscopy(SEM)and transmission electron microscopy(TEM).The optimum preparation parameters for obtaining nanocrystalline zirconia with high percentage of tetragonal phase and high surface area are pH 9,preparation temperature of 80℃ and calcinations’ temperature of400℃.The sample prepared under optimized conditions showed a high specific surface area of 179.2 m2/g,high tetragonal phase percentage of 81%and high catalytic activity(60%)for synthesis of butyl acetate ester. 相似文献
125.
Relaxation dynamic and electrical mobility for poly(methyl methacrylate)‐polyaniline composites 下载免费PDF全文
Mohammed A. Moussa Ahmed M. Ghoneim Mona H. Abdel Rehim Sherif A. Khairy Mohamed A. Soliman Gamal M. Turky 《应用聚合物科学杂志》2017,134(42)
Composites of emeraldine form of polyaniline (PAni) and poly(methyl methacrylate) (PMMA) are prepared by emulsion polymerization method in definite ratios. The chemical structure of the samples and their morphologies have been investigated by different techniques including FTIR, UV–vis, XRD, SEM, and TGA. Enhancement in thermal stability of the obtained composites by PAni additions has been confirmed. Alpha analyzer, in frequency range 0.1 Hz to 20 MHz, was employed to investigate the molecular dynamics of the prepared samples and the accompanied electrical conductivity at temperatures ranging from 223 to 423 K. Conductivity investigations showed that mobility has the more dominant effect on the charge transportation. The dynamic peak at lower temperatures of the PMMA has high activation energy (83.8 kJ/mol). While, Maxwill‐Wagner‐Siller process due to the interfacial polarization in the composites has only 7.5 kJ/mol activation energy. This is a clear indication of the ease of the investigated dynamic. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45415. 相似文献
126.
Amal A. Hafiz A. M. Badawi F. I. El-Deeb E. A. Soliman M. Y. El-Awady D. E. Mohamed 《Journal of surfactants and detergents》2010,13(2):165-172
A novel series of ferrocenyl surfactants was synthesized by the reaction of ferrocene disulfonic acid with different primary
and tertiary fatty amines to produce the corresponding ammonium salts Fc[SO3
−
+NH3(CH2)
n
CH3]2, where n = 9, 11, or 15 and Fc[SO3− +NH(CH3)2(CH2)
n
CH3]2, where n = 7 or 11, respectively, and where Fc = ferrocene. Chemical structures were confirmed by microelemental analysis, FTIR, and
1H NMR spectroscopy. The critical micelle concentration of each prepared surfactant was determined using equilibrium surface
tension. Furthermore, air/water interface parameters including effectiveness (π
CMC), efficiency (Pc20), maximum surface excess (Гmax), and minimum surface area (A
min) were determined at 30, 40, and 50 °C. Thermodynamic parameters (ΔG°, ΔS°, and ΔH°) for both micellization and adsorption processes were recorded. The new synthesized surfactants were screened as antimicrobial
agents against different bacterial and fungal organisms. 相似文献
127.
Immobilized Cu2+ ions affinity cellophane–poly(glycidyl methacrylate) (PGMA)‐grafted membranes have been prepared through three steps. The first step was introducing of epoxy groups to its chemical structure through grafting process with PGMA. Factors affecting the grafting process have been studied and grafting percentage (GP) up to 233% has been obtained. The second step was converting the introduced epoxy groups to sulfonic ones. It was found that maximum amount of sulfonic groups (2.7 mmol/g) was obtained with minimum GP (46.08%). The third and last step was the immobilization of Cu2+ ions into sulfonated grafted membranes obtained from the previous step. Maximum amount of immobilized Cu2+ ions was found to be 60.9 ppm per gram of polymer. The verification of the grafting and sulfonation steps has been performed through characterization of the obtained membranes using FTIR, TGA, and EDAX analysis. Finally, Cu2+‐immobilized membranes have been evaluated in separation of β‐galactosidase (β‐Gal) enzyme from its mixture with bovine serum albumin (BSA) in different pH medium. Maximum protein adsorption, for both proteins, has been obtained at pH range 4–4.5; as 90 and 45% for β‐Gal and BSA, respectively. The results showed high affinity toward β‐Gal separation although BSA concentration (0.5%) is 20‐folds of β‐Gal (0.025%). © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009 相似文献
128.
Honarparvar B Makatini MM Pawar SA Petzold K Soliman ME Arvidsson PI Sayed Y Govender T Maguire GE Kruger HG 《ChemMedChem》2012,7(6):1009-1019
Novel compounds incorporating a pentacycloundecane (PCU) diol moiety were designed, synthesized, and evaluated as inhibitors of the wild-type C-South African (C-SA) HIV-1 protease. Seven compounds are reported herein, three of which displayed IC(50) values in the 0.5-0.6 μM range. The cytotoxicity of PCU cage peptides toward human MT-4 cells appears to be several orders of magnitude less toxic than the current antiviral medications ritonavir and lopinavir. NMR studies based on the observed through-space (1)H,(1)H distances/contacts in the EASY-ROESY spectra of three of the considered PCU peptide inhibitors enabled us to describe their secondary solution structure. Conserved hydrogen bonding interactions were observed between the hydroxy group of the PCU diol inhibitors and the catalytic triad (Asp25, Ile26, Gly27) of HIV protease in docking and molecular dynamics simulations. The biological significance and possible mode of inhibition by PCU-based HIV protease inhibitors discussed herein facilitates a deeper understanding of this family of inhibitors and their potential application to a vast number of alternative diseases related to proteases. 相似文献
129.
Observer‐based controller for constrained uncertain stochastic nonlinear discrete‐time systems 下载免费PDF全文
Mohamed F. Hassan Muthana T. Alrifai Hisham M. Soliman Mohammed A. Kourah 《国际强度与非线性控制杂志
》2016,26(10):2090-2115
》2016,26(10):2090-2115
In this paper, an observer‐based control approach is proposed for uncertain stochastic nonlinear discrete‐time systems with input constraints. The widely used extended Kalman filter (EKF) is well known to be inadequate for estimating the states of uncertain nonlinear dynamical systems with strong nonlinearities especially if the time horizon of the estimation process is relatively long. Instead, a modified version of the EKF with improved stability and robustness is proposed for estimating the states of such systems. A constrained observer‐based controller is then developed using the state‐dependent Riccati equation approach. Rigorous analysis of the stability of the developed stochastically controlled system is presented. The developed approach is applied to control the performance of a synchronous generator connected to an infinite bus and chaos in permanent magnet synchronous motor. Simulation results of the synchronous generator show that the estimated states resulting from the proposed estimator are stable, whereas those resulting from the EKF diverge. Moreover, satisfactory performance is achieved by applying the developed observer‐based control strategy on the two practical problems. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
130.
Chromogranin-A (CgA) and PTH are the two major secretory products of the parathyroid gland. In vitro, 1,25-dihydroxyvitamin D3 [1,25-(OH)2D3] increases CgA, but decreases PTH messenger RNA (mRNA) levels. We investigated the physiological significance of the induced changes in CgA expression by examining the effects of 1,25-(OH)2D3 on parathyroid CgA mRNA levels in vivo. Normal rats were injected with 1,25-(OH)2D3 at 48 and 24 h before blood sampling and isolation of both parathyroid glands. Parathyroid total RNA was extracted and CgA and PTH mRNA quantified by Northern blot analysis. CgA mRNA levels increased 1.6-, 3.2- and 5.6-fold, whereas PTH mRNA levels decreased by 37, 63 and 97%, respectively, with 1,25-(OH)2D3 doses of 10, 50, and 250 pmol/100 g BW. Parathyroid gland CgA expression also was examined in rats with mild chronic renal insufficiency, induced by a 5/6 nephrectomy 5 weeks earlier. Chronic renal insufficiency rats, fed normal chow, had elevated serum urea, creatinine, and PTH levels and reduced 1,25-(OH)2D3 but normal serum levels of calcium and phosphate. PTH mRNA levels were elevated 4-fold and CgA mRNA levels were 50% lower in the uremic animals. This indicates that the regulation of CgA expression in normocalcemic rats occurs at physiological 1,25-(OH)2D3 concentrations. In summary, increases and decreases in serum 1,25-(OH)2D3 levels are associated with corresponding increases and decreases in CgA mRNA levels in the parathyroid glands of rats. Therefore, this study is the first to demonstrate the physiological relevance of the earlier in vitro observations. 相似文献