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51.
Mostafa A. Hamed 《Experimental Mechanics》1987,27(3):250-254
A basic theory of acoustical speckle and cross-correlation is described which utilizes the ubiquitous wave characteristics
in ultrasonics. A computer-based pulse-echo system has been developed. It is interfaced to a VAX11/780 computer which operates
the system and performs the data analysis. Data from three tests using specimens of steel, aluminum and Plexiglas are discussed.
On each specimen, a pulse-echo scan of a scattering surface is made over some area which represents reference configuration.
After the surface is displaced, a pulse-echo scan is made over the same area. A small region of the displaced configuration
is correlated with the reference as a measure of object motion. 相似文献
52.
Mohamed Rafat Mahmoud Maher Mohamed Ahmed Hamed Ali Mohamed Shaker 《Journal of solution chemistry》1986,15(9):765-776
Kinetics of base hydrolysis of new heterocyclic azomethines derived from active methyl quaternary salts and aromatic nitroso compounds were investigated in the presence of 70% (wt/wt) water-methanol. The base hydrolysis of these compounds is strictly first-order with respect to OH– and azomethine. The rate determining step is suggested to be the attack of the hydroxide ion on the free base. Effects of water content and nature of organic hydroxylic solvent have been studied. It is concluded that specific solute-solvent interactions through dispersion forces play a major role in the base hydrolysis rate of the azomethines investigated. The effect of pH (2.98 – 12.24) on hydrolysis rates of compounds having a diethylamino substituent in the presence of 30% methanol has been studied. In acidic media, the rate determining step is probably the water attack on the protonated substrate. 相似文献
53.
Mahdi Rabbani Yongli Wang Reza Khoshkangini Hamed Jelodar Ruxin Zhao Sajjad Bagheri Baba Ahmadi Seyedvalyallah Ayobi 《Entropy (Basel, Switzerland)》2021,23(5)
Network anomaly detection systems (NADSs) play a significant role in every network defense system as they detect and prevent malicious activities. Therefore, this paper offers an exhaustive overview of different aspects of anomaly-based network intrusion detection systems (NIDSs). Additionally, contemporary malicious activities in network systems and the important properties of intrusion detection systems are discussed as well. The present survey explains important phases of NADSs, such as pre-processing, feature extraction and malicious behavior detection and recognition. In addition, with regard to the detection and recognition phase, recent machine learning approaches including supervised, unsupervised, new deep and ensemble learning techniques have been comprehensively discussed; moreover, some details about currently available benchmark datasets for training and evaluating machine learning techniques are provided by the researchers. In the end, potential challenges together with some future directions for machine learning-based NADSs are specified. 相似文献
54.
55.
Ali Sarafraz-Yazdi Soroosh Sepehr Zarrin Es’haghi Hamed Piri Moghadam 《Chromatographia》2010,72(9-10):923-931
In this research, the sol–gel technology was applied for the preparation of solid-phase microextraction fibers for extracting of methyl tert-butyl ether (MTBE) from environmental water samples. For this purpose, two different polymers such as poly(ethylene glycol) (PEG) and combination of PEG and multiwall carbon nanotubes (MWCNTs) were prepared using sol–gel technology as coating procedure for the fibers. The pre-concentration process followed by GC–FID determination was used and the results evidenced that pre-concentration factor for PEG/CNTs fiber was approximately five times higher than PEG. Parameters affecting the extraction efficiency such as temperature, extraction time, stirring speed and salt effect for each fiber were investigated and optimized. On the optimal conditions, the linear range for MTBE with PEG and PEG/CNT fibers were 10–3,000 and 1–1,000 ng mL?1 and the detection limits (S/N = 3) were 1.0 and 0.3 ng mL?1, respectively. The sol–gel PEG/CNTs fiber has good performance and therefore relatively better figures of merit and experimental results such as thermal stability (up to 320 °C), average of life time (over 150 times) and repeatability (RSD < 4) in comparison to conventional PDMS/Carboxen fiber, which was already reported for determination of MTBE. 相似文献
56.
Seyyed Hossein Asadpour Mostafa Sahrai Rasoul Sadighi-Bonabi Amir Soltani Hamed Mahrami 《Physica E: Low-dimensional Systems and Nanostructures》2011,43(10):1759-1762
The giant Kerr nonlinearity with reduced linear and nonlinear absorption in a four-level quantum dot by employing the tunnel coupling is investigated. It is shown that by enhancement of tunnel coupling value the Kerr nonlinearity increases and at the same time linear and nonlinear absorption reduces at the long wavelength which is very important for communicational applications. Enhanced of Kerr nonlinearity in a double quantum dots is investigated. It is found that the electron tunneling has an essential role to reducing the linear absorption and increasing the Kerr nonlinearity at long wavelength. 相似文献
57.
58.
Mostafa M. Hamed S. M. Yakout H. S. Hassan 《Journal of Radioanalytical and Nuclear Chemistry》2013,295(1):697-708
Radioactive waste contains nitrate and nitrite as well as radioactive fission products. Nitrate and nitrite anions are two of the major components of nuclear waste streams and contribute to environmental release hazards. The removal of nitrate and nitrite is a necessary step for the further treatment low-level radioactive wastes. The focus of the research is to evaluate the adsorption potential of solid phase derived from rice straw for nitrate and nitrite anions in single- and binary-component systems due to the fact that the rice straw is a very abundant and by-product material. The removal was accomplished under the optimize conditions of temperature, concentration, pH, contact time and quantity of adsorbent as these parameters are some of the main factors influencing the uptake of two solutes at the solid–solution interface. Batch-mode kinetic and equilibrium studies have been carried out. The experimental data was analyzed using equilibrium isotherm and kinetic models. The thermodynamic parameters (?G°, ?H°, and ?S°) were also determined using the equilibrium constant value obtained at different temperatures. Results show that this adsorbent is effective and much better or even superior than many sorbents for removal of nitrate and nitrite. The prepared sorbent as solid-phase extractant was successfully applied for the extraction of nitrate from actual water samples. 相似文献
59.
60.
Clobutinol (Cb) ion-selective plastic-membrane electrodes based on ion associates of clobutinolium phosphotungstate (Cb-PTA),
clobutinolium phosphomolybdate (Cb-PMA), or a mixture of both Cb-PTA and PMA were prepared. The electrodes were fully characterized
in terms of membrane composition, life span, pH, and temperature. The electrodes were applied to the potentiometric determination
of clobutinol in pure form and pharmaceutical preparations under batch and flow-injection conditions. Also, conductimetric
titrations were applied to the assay of clobutinol in its pure form and pharmaceutical preparations. The selectivity of the
electrodes towards a large number of inorganic cations, amino acids, and sugars was tested. The solubility product of ion-associates
and the formation constant of the precipitation reactions leading to the ion-associate formation were determined conductimetrically.
The text was submitted by the authors in English. 相似文献