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1.
CV Tomy D Pal SS Banerjee S Ramakrishnan AK Grover S Bhattacharya MJ Higgins G Balakrishnan McK Paul 《Pramana》2002,58(5-6):925-935
The weakly pinned single crystals of the hexagonal 2H-NbSe2 compound have emerged as prototypes for determining and characterizing the phase boundaries of the possible order-disorder
transformations in the vortex matter. We present here a status report based on the ac and dc magnetization measurements of
the peak effect phenomenon in three crystals of 2H-NbSe2, in which the critical current densities vary over two orders of magnitude. We sketch the generic vortex phase diagram of
a weakly pinned superconductor, which also utilizes theoretical proposals. We also establish the connection between the metastability
effects and pinning. 相似文献
2.
Simultaneous determination of dextromethorphan hydrobromide (DEX), phenylephrine hydrochloride (PHEN), and carbinoxamine maleate (CAR) in pharmaceutical preparations was performed by using liquid chromatograpy (LC) and spectrophotometry. In LC, the separation
was achieved on a C18 column and the optimal mobile phase for satisfactory separation in a gradient elution program was found
to be acetonitrile-sodium perchlorate solution (5: 95, v/v) initially, then a linear gradient up to 60% acetonitrile in 8
min. In spectrophotometric method, a chemometric technique, principal component regression (PCR), was used. In the method,
the absorbance data matrix corresponding to the concentration data matrix was obtained by the measurement of absorbances in
their zero order spectra by Δλ = 1 nm in the 210–300 nm range. Then, the calibration was obtained by using this data matrix
for the prediction of unknown concentrations of DEX, PHEN, and CAR in their ternary mixture. The methods proposed were validated
and successfully applied to a pharmaceutical preparation, capsule, and the results were compared. 相似文献
3.
Ibrahim Palabiyik Zenfira Musina Sanjeeva Witharana Yulong Ding 《Journal of nanoparticle research》2011,13(10):5049-5055
The dispersion stability and thermal conductivity of propylene glycol-based nanofluids containing Al2O3 and TiO2 nanoparticles were studied in the temperature range of 20–80 °C. Nanofluids with different concentrations of nanoparticles
were formulated by the two-step method and no dispersant was used. In contrast to the common belief, the average particle
size of nanofluids was observed to decrease with increasing temperature, and nanofluids showed an excellent stability over
the temperature range of interest. Thermal conductivity enhancement for both studied nanofluids was a nonlinear function of
concentration and was temperature independent. Theoretical analyses were also performed using existing models compared with
experimental results. The model based on the aggregation theory appears to be the best. 相似文献
4.
In subnormal glow discharge under d.c. excitation at different pressure in a varying transverse magnetic field (0 to 30 G)
some measurements have been carried out for various initial average tube currents. The voltage across the discharge increases
and average tube current and residual current decreases in the magnetic field. With the help of Beckman’s expression [4] for
the axial field and the electron density distribution in a transverse magnetic field the observed variation of current and
voltage can be satisfactorily explained. The variation of axial electric field with transverse magnetic field can be represented
to a fair degree of accuracy by the derived equation. The behaviour of residual current with magnetic field has been observed
in these oscillations. 相似文献
5.
An integral equation formulation for buoyancy-driven convection problems is developed and illustrated. Buoyancy-driven convection in a bounded cylindrical geometry with a free surface is studied for a range of aspect ratios and Nusselt numbers. The critical Rayleigh number, the nature of the cellular motion, and the heat transfer enhancement are computed using linear theory. Green's functions are used to convert the linear problem into linear Fredholm integral equations. Theorems are proved which establish the properties of the eigenvalues and eigenfunctions of the linear integral operator which appears in these equations. 相似文献
6.
WANG Er-Kang ZHOU Wei-HongLaboratory of Electroanalytical Chemistry Changchun Institute of Applied Chemistry Chinese Academy of Sciences Changchun Jilin SS China 《中国化学》1996,14(2):131-137
Capillary electrpphoresis (CE)/electrochemical detection (EC) for the simultane-ous determination of hydrazine and isoniazid has been developed.The electrochemical method uses a novel modified electrode dispersed with ultrafine platinum particles on the surface of a 30μm carbon fiber microelectrode.The unique characteristic of the Pt-particles modified carbon fiber microelectrode is its excellent stability.The current measurement for hydrazine is more sensitive than that of isoniazid.Selective determination of trace amount of free hydrazine in isoniazid and its formulation can be achieved at applied potential of 0.5V. 相似文献
7.
A Soibel SS Banerjee Y Myasoedov ML Rapparort E Zeldov S Ooi T Tamegai 《Pramana》2002,58(5-6):893-898
Using a novel differential magneto-optical imaging technique we investigate the phenomenon of vortex lattice melting in crystals
of Bi2Sr2CaCu2O8 (BSCCO). The images of melting reveal complex patterns in the formation and evolution of the vortex solid-liquid interface
with varying field (H)/temperature (T). We believe that the complex melting patterns are due to a random distribution of material disorder/inhomogeneities across
the sample, which create fluctuations in the local melting temperature or field value. To study the fluctuations in the local
melting temperature/field, we have constructed maps of the melting landscape T
m(H, r), viz., the melting temperature (T
m) at a given location (r) in the sample at a given field (H). A study of these melting landscapes reveals an unexpected feature: the melting landscape is not fixed, but changes rather
dramatically with varying field and temperature along the melting line. It is concluded that the changes in both the scale
and shape of the landscape result from the competing contributions of different types of quenched disorder which have opposite
effects on the local melting transition. 相似文献
8.
Senem Şanli İsmail M. Palabiyik Nurullah Şanli Zeynep B. Guzel-Seydim Güleren Alsancak 《Journal of Analytical Chemistry》2011,66(9):838-847
The simple, rapid and sensitive liquid chromatographic separation of five macrolides (tilmicosin, erythromycin, tylosin, roxithromycin
and josamycin) widely used in food producing animals was developed. Response surface methodology was used as an optimization
method of mobile phase, column temperature and pH to provide the best resolution of these analytes. The separation was performed
by using an end-capped X-Terra RP-18 column (250 × 4.6 mm I.D × 5 m) with an isocratic system of 15 mM hydrochloric acid (pH
2.5)-acetonitrile as the mobile phase at a temperature of 30°C and flow-rate of 1.0 mL/min. The suitability of the method
for multi-residue determination of the macrolides is demonstrated by the analysis of milk samples spiked with tylosin. Roxithromycin
was used as internal standard. The recovery of tylosin was quite good as 90.8%. The limit of quantification and detection
limit were 0.024 and 0.007 μg/mL, respectively. The method was successfully applied to determination of macrolides at levels
below the maximum concentration legally allowed in milk samples. 相似文献
9.
Rednikov AY; Zhao Hong; Sadhal SS; Trinh EH 《The Quarterly Journal of Mechanics and Applied Mathematics》2006,59(3):377-397
The steady (acoustic) streaming associated with a sphericaldrop displaced from the velocity antinode of a standing waveis studied. The ratio of the particle size to the acoustic wavelengthis treated as small but non-zero, and the solution is developedin the form of a two-term expansion in terms of the correspondingsmallness parameter. The drop viscosity is assumed to be muchhigher than that of the surrounding fluid, which is the casefor a drop in a gas medium. There are essentially three distinctregions where the steady streaming flow is analysed: insidethe drop (internal circulation), in the Stokes shear-wave layerat the surface on the gas side, and the gas outside the Stokeslayer (the outer streaming region). Solutions for the internalcirculation and the outer streaming are obtained in the limitof small Reynolds number. Despite the gas-to-liquid viscosity ratio being small, the outerstreaming may be dramatically affected by the fact that thesphere is liquid as opposed to solid. The parameter that measuresthe effect of liquidity is essentially the viscosity ratio dividedby the relative (to the particle size) thickness of the Stokeslayer. The case of a solid sphere is recovered by letting thisparameter go to zero. 相似文献
10.