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51.
Bouquet S Stéhlé C Koenig M Chièze JP Benuzzi-Mounaix A Batani D Leygnac S Fleury X Merdji H Michaut C Thais F Grandjouan N Hall T Henry E Malka V Lafon JP 《Physical review letters》2004,92(22):225001
We present a supercritical radiative shock experiment performed with the LULI nanosecond laser facility. Using targets filled with xenon gas at low pressure, the propagation of a strong shock with a radiative precursor is evidenced. The main measured shock quantities (electronic density and propagation velocity) are shown to be in good agreement with theory and numerical simulations. 相似文献
52.
The pattern of freezing of two varieties of grapevine during spring bud burst was characterised using infrared thermography. All plants studied showed endogenous freezing of the stems and subsequent rapid ice spread (0.47 cm/s) analogous to ice spread in bulk water suggesting ice travel in the xylem. Barriers to ice spread were observed between stembranches and more importantly between the stem and buds. Buds froze after the stem and freezing appeared to be initiated from the stem. The lack of a fully functional xylem system is proposed as the barrier to ice spread. All buds which froze suffered complete frost kill whilst frozen stem recovered unharmed. Only 58% of the buds froze and those that did not freeze survived completely. 相似文献
53.
R. H. Abu-Eittah M. M. Hamed M. M. Abdou 《International journal of quantum chemistry》1987,31(6):855-869
The electronic absorption spectra of some phenylethylamine drugs, namely, d-pseudoepherine, l-pseudoephedrine, l-ephedrine, dl-ephedrine dl-norephedrine, phenylethylamine, methoxyphenamine, and l-noradrenaline were investigated in polar and nonpolar solvents. The observed transitions were interpreted, and the role of σ-π interaction was explored. Molecular orbital calculations were performed on representatives of the above group of compounds, namely, d-pseudoephedrine, l-ephedrine, and l-noradrenaline using the INDO procedures and adopting the best conformer of the molecule. The transition energy, band intensity, and dipole moments were calculated and corresponded satisfactorily with the experimental values. 相似文献
54.
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
55.
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
56.
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
57.
58.
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
59.
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
60.