Stimulated Raman scattering of a laser beam is investigated in the plasma with strong self generated magnetic field. The magnetized plasma supports various localized radial and azimuthal modes of lower hybrid frequencies. The density fluctuations due to lower hybrid modes couple with the oscillating velocity due to the pump, and drive the scattered wave. Equations describing the Raman process are derived and effects of various modes are studied on the growth rate analytically. Self generated magnetic field has a strong localization effect on the Raman process and growth rate is maximum for radial eigen mode number q = 0 and azimuthal eigen mode number l = 3. The frequency shift has signatures of self generated magnetic field and could serve as a diagnostic. 相似文献
We report the results of a theoretical study on the effects of substitutional and interstitial hydrogen atoms in niobium. We confirm that any contaminated hydrogen will occupy the interstitial site over the substitutional site in niobium. For interstitial hydrogens, the lattice deformation increases with the percentage content of hydrogen, though it is negligible at low concentrations. Substitutional hydrogens are found to prefer off-center sites in the host lattice. 相似文献
A low-pressure gas chromatography-ion trap mass spectrometry (LPGC-ITMS) method was investigated to shorten the analysis time for 18 US Environmental Protection Agency priority listed polycyclic aromatic hydrocarbons (PAHs). Their elution was optimised with a short, wide-bore column coupled to a deactivated capillary at the inlet end and with a long, conventional column to compare their analytical performance. The analytical figures of merit under optimal LPGC-ITMS conditions were determined with respect to chromatographic separation, S/N ratio, limit of detection and precision. The peak width at half height of 1.5s matched the ITMS duty cycle. Up to 16 PAHs in the molecular weight (MW) range of 128-278 Da could be separated in a very short time, i.e. less than 13 min using LPGC-ITMS, whereas with conventional GC-MS, it took approximately 40 min. However, LPGC-ITMS has a limited loss of separation power compared to that of conventional GC-MS due to the occurrence of three critical pairs for high-MW PAHs. For a practical evaluation, the LPGC-ITMS approach was applied to the determination of PAHs in gas and aerosol phase samples collected in the ambient air of Hasselt, Belgium. 相似文献
We report the results of a theoretical study of AlnNn (n=7-16) clusters that is based on density functional theory. We will focus on the evolution of structural and electronic properties with the cluster size in the stoichiometric AlN clusters considered. The results reveal that the structural and electronic properties tend to evolve toward their respective bulk limits. The rate of evolution is, however, slow due to the hollow globular shape exhibited by the clusters, which introduces large surface effects that dominate the properties studied. We will also discuss the changes induced upon addition of an extra electron to the respective neutral clusters. 相似文献
A straightforward process for synthesis of hybrid porous electrode material composed of reduced graphene oxide (rGO) and copper sulfide (CuS) with layered structure on the stainless steel substrate is developed. As-synthesized hybrid electrode shows hexagonal crystal structure of CuS with 77 m2 gm−1 specific surface area and 22 nm average pore size. The specific capacitance obtained with rGO-CuS5 hybrid electrode is 1201 F g−1 at the sweep rate of 5 mV s−1 in 1 M LiClO4 aqueous electrolyte. The majority of charge stored by diffusion-controlled process indicates benefits of layered structures for solid-state energy storage. The rGO-CuS5-based hybrid symmetric supercapacitor delivers a specific capacitance (Cs) as high as 109 F g−1 at a sweep rate of 5 mV s−1 with polyvinyl alcohol (PVA)-LiClO4 gel electrolyte. Also, the specific energy of 44 Wh kg−1 and specific power of 1.4 kW kg−1 with 87% stability after 6000 cycles at an applied current of 5 mA are obtained. The simple process of synthesis of layered hybrid electrode material for flexible supercapacitor promises its use in smart textile and wearable electronic devices.
Summary The fully developed heat transfer in laminar flow of Bingham material through a straight circular pipe has been analysed when the effect of dissipation is taken into consideration. The temperature distribution, the mixed-mean temperature and the Nusselt number are calculated and found to depend on the Modified Reynolds number, the Brinkman number and the rate of heat transfer at the wall. The effect of dissipation is to increase the temperature and the mixed-mean temperature of the material while the Nusselt number is found to decrease with increasing dissipation.Nomenclature
r, , z
space coordinates
-
u, v, w
velocity components
-
density of the fluid
-
modulus of rigidity (constant)
-
bulk modulus
-
ekk, the dilation
-
1
coefficient of viscosity (constant)
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eik
strain tensor
-
dik
rate of strain tensor
-
pik
stress tensor primes denote deviatoric components of tensors, e.g.
-
pikpikpik, p=–1/3pkk
-
yield value (constant)
- D/Dt
material derivative with regard to time following the particle
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R
radius of the pipe
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r0
radius of the yield surface (cylindrical)
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r=r0/R
non-dimensional radius of the yield surface
-
T0
temperature of the pipe
-
K
conductivity
-
Modified Reynolds number
-
Br
Brinkman number 相似文献
The decalin structure is found in bioactive molecules. We have developed catalytic enantioselective formal (4+2) cycloaddition reactions via aldol–aldol cascade reactions between pyruvate‐derived diketoester derivatives and cyclohexane‐1,3‐dione derivatives that afford highly functionalized decalin derivatives. The reactions were performed using a quinidine‐derived catalyst under mild conditions. Decalin derivatives bearing up to six chiral carbon centers including tetrasubstituted carbon centers were synthesized with high diastereo‐ and enantioselectivities. Five to six stereogenic centers were generated from achiral molecules with the formation of two C?C bonds in a single transformation resulting in the formation of the decalin system. 相似文献
A novel homologous series RO-C6H4-COO-C6H3-(NO2)-CO-CH?CH-C6H4OC18H37(n) para of chalconyl ester derivatives have been synthesized and studied with view to understanding the effect of an ortho substituted nitro group on thermotropic liquid crystal (LC) behavior. The novel homologous series consists of thirteen homologues (C1 to C18). The C1 to C4 homologues are nonliquid crystal (NLC) and the rest of the homologues (C5 to C18) homologues are enantiotropically nematogenic without exhibition of a smectic phase even in the monotropic condition. Transition temperatures were determined by an optical polarizing microscope (POM) equipped with a heating stage. Texture of nematic phase are threaded or Schlieren. Analytical, thermal and spectral data supported molecular structure of homologues. Thermal stability for nematic is 147.1°C whose mesophase lengths vary between 16.0 and 32.0°C the C7 and C18 homologues, respectively, and their mesogenic exhibition range between 96.0 and 166.0°C. Thus, the present novel series is middle ordered melting type, Group efficiency order is derived from comparative study of structurally similar series. The transition curves of a phase diagram behaved in normal manner except C10 and C16 homologues. Odd-even effect is observed for N-I transition curve. Group efficiency order derived is: -OC12H25 (n) > -OC18H37 (n) > -OC18H37 (n). 相似文献