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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.
Large sheet asymmetric polyethersulfone (PES) ultrafiltration membranes were prepared via phase inversion process in a continuous conveyor system with addition of PVP to the casting solution. Dimethylacetamide (DMAc) and mixture of water and isopropyl alcohol (70/30 v%) were used as solvent and non‐solvent respectively. The prepared membrane was 0.96 m wide and 3 m long. The pieces of the membrane were selected randomly for characterization in terms of performance using cross flow filtration for milk concentration, image analysis, scanning electron microscopy (SEM), and cleaning procedures. It was found that the prepared membrane has high porosity and high water flux during milk filtration. In addition, cleaning experiments indicated that NaOH/HCl/NaOH sequence is an effective procedure for cleaning the fouled membrane during milk concentration. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
3.
The complexes of murexide with alkali-metal cations have been studied spectrophotometrically in methanol, dimethylformamide and dimethylsulphoxide media at 25 degrees . The stoichiometry of the complexes was found to be 1:1. The formation constants of the complexes were determined, and found to decrease in the order Na(+) > K(+) > Rb(+) approximately Li(+) for all solvents studied. The complex formation constants varied inversely with the Gutmann donicity of the solvents. 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.
A kinetic study of Hg(II) ions transport through a bulk liquid membrane (BLM) was investigated. The commercially available liquid bis(2,4,4‐trimethyl(pentyl) dithiophosphinic acid) (Cyanex 301) was employed as mobile carrier. The influences of the carrier concentration in the liquid membrane, HNO3 concentration in the feed phase, type of organic solvent, composition of the receiving phase, and stirring speed on mass transfer were studied. Various solvents including CH2Cl2, CHCl3, C2H4Cl2 and CCl4 were used as organic membrane. Among the solvents, CHCl3 provided the superior results. The kinetic parameters (k1, k2, Rmmax, tmax, Jdmax, and Jamax) were calculated for the interface reaction assuming two consecutive, irreversible first‐order reactions. The analysis of Hg(II) accumulation in liquid membrane and the rate‐controlling step under different experimental conditions were elucidated. The experiments demonstrated that Cyanex 301 is an appropriate carrier for Hg(II) transport through liquid membrane. 相似文献
7.
S.S. Madaeni A. Rahimpour 《高分子科学》2005,(5):539-548
Polyethersulfone membranes were prepared from quaternary systems containing N,N-dimethylacetamide (DMAc) as solvent, polyvinylpyrrolidone (PVP) as constant additive and acetic acid, acetone and water as variable additives. Phase inversion via immersion precipitation was employed for manufacturing of membranes. The prepared films were immersed in the mixture of pure water and 2-propanol (30/70 vol%) as the non-solvent. Acetic acid caused an increment in the flux at high polymer concentration (16 wt%) and a decline in the flux at low polymer concentrations (10 wt% and 13 wt%). Acetone and water as the solvent in the casting solution declined the flux at any polymer concentration tested. The morphology and performance of the prepared membranes were investigated by scanning electron microscopy and separation experiments using milk as the feed. 相似文献
8.
In this paper factors affecting the ultrafiltration of mixtures of HA and BSA including concentration, pH, ionic strength,
ionic charge and size of hydrated ion were elucidated. In the presence of BSA, higher HA rejection and lower flux were obtained
during ultrafiltration. This is due to interactions between HA and BSA. A bond may be established between humic acid and protein
molecules. Flux was decreased and HA rejection was increased with increasing the humic acid concentration in constant concentration
of BSA. At low concentration, the humic macromolecules pass more easily through the membrane pores due to their structure.
The HA rejection depends on the molecular weight cut off (MWCO) of the membrane. Higher rejection is anticipated for membranes
with lower MWCO. However cake deposition is the dominant mechanism during ultrafiltration of solutions containing mixtures
of HA and BSA using XM50, YM100 and XM300 ultrafiltration membranes. By increasing the pH of solutions containing mixture
of HA and BSA, higher flux and lower HA rejection were achieved. At the protein isoelectric point, flux showed a minimum and
increased for higher pH values. A higher flux was obtained for solutions with lower ionic strength. At the beginning of the
filtration, HA rejection was low for solution with higher ionic strength. However during filtration the trend was conversely
changed. In the presence of Ba2+ cation the HA rejection for solutions containing HA and BSA was higher compare to the solutions containing Na+ cation. 相似文献
9.
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
10.
Metallic membranes can be prepared by various techniques. This work introduces a novel method for the preparation of metallic membranes using wire arc spraying. The formed metallic membranes were characterized by metallographic techniques such as microscopy image analysis. The distance between gun and the substrate surface, which is called spray distance or gun distance, was selected as the variable of metal spraying. The effects of gun distance on coating properties and membrane performance were investigated. The metallographic and performance data showed that the range of 35–40 cm is the optimum gun distance for spraying. Ion rejection capability of the prepared membrane was tested using saline water as the feed. Moreover the filtration capability of the prepared membranes for blue indigo dye particles was investigated. Energy dispersive X-ray (EDX) analysis and SEM technique were used for the investigation of filtration mechanism. The results indicate that the prepared stainless steel membrane is able to efficiently remove particles from water. 相似文献