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21.
In this paper, a plasma sheath containing primary electrons, cold positive ions, and secondary electrons is studied using a one-dimensional fluid model in which the primary electrons are described by q-non-extensive distribution according to the Tsallis statistics. Based on the Sagdeev potential method and the current balance relation, a modified sheath criterion, and floating potential are established theoretically. The effect of secondary electron emission on q-non-extensive plasma sheath characteristics have been numerically examined. A significant change is observed in the quantities characterizing the non-extensive plasma sheath with the presence of the secondary electrons. It is found that the sheath properties with super-extensive distribution and sub-extensive distribution are different compared with plasma sheath with Maxwell distribution . 相似文献
22.
We consider a linear system of Timoshenko type in a bounded interval. No dissipative mechanism is added in the system or at
the edges of the beam. The damping occurs through a thermal effect by coupling the system with a heat equation suggested by
Green and Naghdi. We prove exponential decay of solutions of the augmented system. 相似文献
23.
Abdelhak Ayadi Sana Elgasri Abderrazek Mezghani Mickaël Castro Foued Elhaouani 《ournal of non Newtonian Fluid Mechanics》2011,166(12-13):661-666
The gross melt fracture defect is related to the flow instabilities developed in the contraction region. To mitigate these upstream instabilities, a convergent radial flow in the die entrance has been created. In fact, the ultimate objective of the present work is to examine the effect of the clearance width of radial flow on the appearance and development of gross melt fracture defect. So, capillary rheometer experiments were performed with linear polydimethylsiloxane (PDMS) oil.As for the influence of radial flow width on the morphology of gross melt fracture defect, extrudate photographs show that this imperfection can be mitigated since its frequency is higher and amplitude smaller when the gap of radial flow decreases. Such results may be related both to shear and elongational components of radial flow. Actually, when gap width is very small compared to the external diameter of radial flow, shear deformations become more enhanced with respect to the elongational deformations and thus the helical gross melt fracture becomes more like a surface defect than volume defect. 相似文献
24.
Alberto Santos Mohamed Ajbary Abdelhak Kherbeche Manuel Piñero N. De la Rosa-Fox Luis Esquivias 《Journal of Sol-Gel Science and Technology》2008,45(3):291-297
The increasingly evident impact of anthropogenic CO2 emissions on climate change and associated environmental effects is stimulating the search for viable methods to remove this
gas. One of the most promising strategies is the long-term storage of CO2 in inert, insoluble and thermodynamically-stable materials. This strategy mimics the natural reactions that transform silicates
into carbonates regulating the cycle of CO2 on the surface of the Earth, operating on a geological time-scale. Consequently, the aim is to accelerate these reactions
to be applicable on the timescale of human lives. We present the various technologies developed or proposed to date, based
on this particular approach. The principal limiting factor is that high pressures and temperatures are required to produce
appropriate materials capable of CO2 sequestration and storage. Nevertheless, the synthetic materials known as aerogels can be modified in shape, size and chemical
functionality so as to catalyse the process of CO2 elimination through silicates (of Ca or Mg), considerably reducing the reaction time and working at atmospheric pressure
and temperature. 相似文献
25.
Abdelhak Djouadi Grégory Moreau 《The European Physical Journal C - Particles and Fields》2013,73(9):1-12
Using the full set of the LHC Higgs data from the runs at 7 and 8 TeV center of mass energies that have been released by the ATLAS and CMS collaborations, we determine the couplings of the Higgs particle to fermions and gauge bosons as well as its parity or CP composition. We consider ratios of production cross sections times decay branching fractions in which the theoretical (and some experimental) uncertainties as well as some ambiguities from new physics cancel out. A fit of both the signal strengths in the various search channels that have been conducted, H→ZZ,WW,γγ,ττ and $b\bar{b}$ , and their ratios shows that the observed ~126 GeV particle has couplings to fermions and gauge bosons that are Standard Model-like already at the 68 % confidence level (CL). From the signal strengths in which the theoretical uncertainty is taken to be a bias, the particle is shown to be at most 68 % CP-odd at the 99 %CL and the possibility that it is a pure pseudoscalar state is excluded at the 4σ level when including both the experimental and theoretical uncertainties. The signal strengths also measure the invisible Higgs decay width which, with the same type of uncertainty analysis, is shown to be $\varGamma_{H}^{\mathrm{inv}}/ \varGamma_{H}^{\mathrm{SM}} \leq0.52$ at the 68 %CL. 相似文献
26.
27.
Jean-Louis Ripoll Yannick Valle Mohamed Khalid Abdelhak Hakiki 《Journal of heterocyclic chemistry》1992,29(7):1867-1868
4,5-Dihydro-1H,3H-thieno[3,4-c]thiophene and 4,5-dihydro-1H,3H-thieno[3,4-c]furan were synthesized by retro Diels-Alder reactions under flash vacuum thermolysis conditions. 相似文献
28.
Aïssa Keffous Abdelhak Cheriet Noureddine Gabouze Yacine Boukennous Rabah Cherfi Lakhdar Guerbous Hamid Menari 《Applied Surface Science》2010,256(14):4591-4595
Hydrogenated amorphous SiC films (a-Si1−xCx:H) were prepared by dc magnetron sputtering technique on p-type Si(1 0 0) and corning 9075 substrates at low temperature, by using 32 sprigs of silicon carbide (6H-SiC). The deposited a-Si1−xCx:H film was realized under a mixture of argon and hydrogen gases. The a-Si1−xCx:H films have been investigated by scanning electronic microscopy equipped with an EDS system (SEM-EDS), X-ray diffraction (XRD), secondary ions mass spectrometry (SIMS), Fourier transform infrared spectroscopy (FTIR), UV-vis-IR spectrophotometry, and photoluminescence (PL). XRD results showed that the deposited film was amorphous with a structure as a-Si0.80C0.20:H corresponding to 20 at.% carbon. The photoluminescence response of the samples was observed in the visible range at room temperature with two peaks centred at 463 nm (2.68 eV) and 542 nm (2.29 eV). In addition, the dependence of photoluminescence behaviour on film thickness for a certain carbon composition in hydrogenated amorphous SiC films (a-Si1−xCx:H) has been investigated. 相似文献
29.
Abdelhak Djouadi 《Pramana》2003,60(2):215-238
I briefly review the Higgs sector in the standard model (SM) and its minimal aupersymmetric extension, the MSSM. After summarizing
the properties of the Higgs bosons and the present experimental constraints, I will discuss the prospects for discovering
these particle at the upgraded Tevatron, the large hadron collider (LHC) and a high-energye
+
e
− linear collider. The possibility of studying the properties of the Higgs particles will be then summarized. 相似文献
30.
We report the synthesis and properties of a homologous series of asymmetrically substituted 4-(5-(4-benzyloxyphenyl)-1,3,4-oxadiazol-2-yl)phenyl 2-X-4-dodecyloxybenzoates, which have pronounced hockey-stick molecular architectures. The structure was varied through the lateral substitution with various groups, X (H, Me, MeO, Cl, F) in the outer benzene ring. The effect of the lateral group on liquid crystal phase behaviour was investigated by thermal optical microscopy and differential scanning calorimetry. Nematic and dark conclomerate phases were observed with both displaying macroscopically chiral domains. 相似文献