A rapid heating and high magnetic field thermal analysis technique

Journal of Thermal Analysis and Calorimetry - A new thermal analysis technique is described that allows measurements to be performed on bulk samples at extreme heating and cooling rates and in high...     

An unsteady thermal investigation of a wetted longitudinal porous fin of different profiles

Journal of Thermal Analysis and Calorimetry - The unsteady thermal behavior of a porous longitudinal fin in a fully wet circumstance in the existence of convection as well as radiation effect is...     

Differential thermal analysis of porous silicon

Porous silicon materials, macro- and mesoporous silicon, obtained by electrochemical anodic etching of n- and p-Si were studied by differential thermal analysis at a steady temperature rise and under isothermal conditions in nitrogen atmosphere and in air. The method was used to estimate the presence and amount of phases of surface volatile compounds. The possibility was studied to perform a comparative estimate of the specific surface area of different types of porous silicon from data on the surface oxidation kinetics determined by the dynamic differential thermal analysis in air.     

Electron transport through an extended nano-ring in presence of magnetic field: An analytical approach

We analytically describe the influence of magnetic field on the electronic transport properties of an extended nano-ring by using Green's function technique in the nearest neighbor tight-binding approximation. We obtain exact analytic formulas for the electronic transmission coefficient, the total and local contact density of states as functions of incident electron energy, magnetic flux crossing over the ring and all the system parameters. Our formalism gives the ability to study the extended nano-rings of any size under certain conditions which provides useful tools to analyze electronic transport of these systems, much faster and more easily. The results show that the electronic transport quantities of a system consisting of a nano-ring are strongly sensitive to incoming electron energy, magnetic flux and contact hopping energies. The present approach may be useful to design nano-devices measuring magnetic field and magnetic based nano-switches.     

Destabilizing effect of time-dependent oblique magnetic field on magnetic fluids streaming in porous media

The present work studies Kelvin-Helmholtz waves propagating between two magnetic fluids. The system is composed of two semi-infinite magnetic fluids streaming throughout porous media. The system is influenced by an oblique magnetic field. The solution of the linearized equations of motion under the boundary conditions leads to deriving the Mathieu equation governing the interfacial displacement and having complex coefficients. The stability criteria are discussed theoretically and numerically, from which stability diagrams are obtained. Regions of stability and instability are identified for the magnetic fields versus the wavenumber. It is found that the increase of the fluid density ratio, the fluid velocity ratio, the upper viscosity, and the lower porous permeability play a stabilizing role in the stability behavior in the presence of an oscillating vertical magnetic field or in the presence of an oscillating tangential magnetic field. The increase of the fluid viscosity plays a stabilizing role and can be used to retard the destabilizing influence for the vertical magnetic field. Dual roles are observed for the fluid velocity in the stability criteria. It is found that the field frequency plays against the constant part for the magnetic field.     

Modeling of nanomaterial treatment through a porous space including magnetic forces

Journal of Thermal Analysis and Calorimetry - In present article, influence of magnetic forces on migration of nanomaterial through a permeable zone via an innovative method is investigated. The...     

A theoretical analysis of micelle-mediated transport through porous membranes

A novel method is proposed for the purpose of controlled release of a sparingly water soluble compound. The solubility of a sparingly water soluble compound can be increased by addition of a sufficient amount of surfactant to form micelles. The flux of the compound across a porous membrane can be enhanced if the membrane has pores larger than the micelle size so that the compound-loaded micelles can diffuse simultaneously, and micelle-mediated transport occurs. The membrane permeability of the micelle is a monotonically decreasing function of the ratio of the size of the micelle to the membrane pore size (R_m/R_p). However, the solubilizing capacity of the micelle increases with increasing size of the micelle. These opposing effects influence the transport and may result in an optimum flux of the solubilizate at a particular size of the micelle. In the determination of the optimum surfactant molecule, the concept of the hydrophilic-lipophilic balance (HLB) is employed in order to have stable aqueous solutions of the surfactants. For a family of nonionic surfactants solubilizing the hydrophobic and hydrocarbon substance n-heptane, it is shown that there exists a maximum flux of the solubilizate at a value of R_m/R_p within the limitation of the HLB. The release rates over a long period of time are nearly constant for micelles close to the optimum size for a given pore size.     

Efficient incorporation of quantum dots into porous microspheres through a solvent-evaporation approach

Quantum dot (QD)-encoded microspheres play an important role in suspension arrays by acting as supports for various reactions between biomolecules. With regard to QD-encoded microspheres utilized in suspension arrays, three key requirements are controllable size, abundant surface functional groups, and especially excellent fluorescence properties. In this paper, narrowly dispersed poly(styrene-co-divinylbenzene-co-methylacrylic acid) (PSDM) microspheres with specific size, surface carboxyl groups, and porous structures were synthesized by seeded copolymerization. In order to improve the incorporation efficiency of QDs within microspheres, we developed a swelling-evaporation approach in which the swelling process was combined with gradual evaporation of the solvent and thus gradual concentration of QDs in the dispersion solution. This approach was demonstrated to be an efficient method for improving the fluorescence intensity of resultant microspheres compared with the use of swelling alone. Moreover, the porous structure was shown to aid the penetration of QDs into the interiors of the microspheres. Through this approach, microspheres encoded with either single or multiple wavelength-emitting QDs were fabricated effectively. The suspension immunoassays were then founded based on the QD-encoded microspheres, by coating mouse antihuman chorionic gonadotropin as the probe for goat antimouse IgG detection. The positive results determined by Luminex 100 and the low cytotoxicity of the QD-encoded microspheres demonstrated their great potential in suspension arrays.     

The effect of a magnetic field on the thermal destruction of cobalt formate

The thermal decomposition of cobalt formate in a flow of an inert gas led to the formation of cobalt nanoparticles in pores of various substrates (silica gel, alumina, activated carbon, and montmorillonite). Electron microscopic studies showed that the particle-size distribution of cobalt depended on the external magnetic field strength; the average particle size and distribution variance decreased as the field strength increased. It was assumed that the external magnetic field affected the nucleation constant of cobalt nanoparticles. Original Russian Text ? P.A. Chernavskii, V.I. Zaikovskii, G.V. Pankina, N.S. Perov, A.O. Turakulova, 2009, published in Zhurnal Fizicheskoi Khimii, 2009, Vol. 83, No. 3, pp. 586–589.     

A hierarchical approach to force field calculations through spline approximations

The objective of this paper is to outline a new approach to analyzing the geometry of macro-molecules and investigating important physical properties by means of simulations. The classical method of force field calculations requires minimizing the energy as a function of the Cartesian coordinates of all atoms. Due to the large number of variables this method is limited to relatively small molecules. We describe an approach to overcome this difficulty. On the one hand, the number of free variables is effectively reduced by assembling certain groups of atoms into configurational structures with considerably less degrees of freedom. In this way we build up a whole hierarchy of coordinate spaces with decreasing dimensions. On the other hand, approximations to the energy function with respect to these variables are constructed using methods from the theory of splines and radial basis functions. The hierarchical features of wavelet decompositions are utilized to exploit the physical importance of the different force field constants on the biological function of the macro-molecule.     

The analysis of emulsion structure changes during flow through porous structure

The aspects of emulsion flow through porous media are crucial for many industrial processes, especially in the development of Enhanced Oil Recovery (EOR) techniques and also during oily wastewater purification. In this paper we investigated the hydrodynamics of gravitational flow of emulsions with inner phase of different concentrations. We also tried to determine the quantitative changes in the droplet diameter distribution and concentration of emulsion flowing out of the bed. On the basis of experimental data, it was possible to describe the influence of emulsion concentration on the hydrodynamics process and to characterize the changes of the structure of emulsion.     

A numerical study on the effect of static magnetic field on the hemodynamics of magnetic fluid in biological porous media

Journal of Thermal Analysis and Calorimetry - High interstitial fluid pressure in the tumor is among the most important barriers to drug delivery. The use of the static magnetic field is one of the...     

Optimization of hybrid nanoparticles with mixture fluid flow in an octagonal porous medium by effect of radiation and magnetic field

Investigation of fluid behavior in a cavity enclosure has been a significant issue from the past in the field of fluid mechanics. In the present study, hydrothermal evaluation of hybrid nanofluid with a water–ethylene glycol (50–50%) as the base fluid which contains MoS₂–TiO₂ hybrid nanoparticles, in an octagon with an elliptical cavity in the middle of it, has been performed. In this problem, the effects of the radiation parameter, porosity, and the magnetic parameter have been analyzed on temperature distribution and fluid flow streamlines and also, on the local and average Nusselt numbers. The governing equations have been solved by the finite element method (FEM). As a novelty, the Taguchi method has been utilized for test design. Further, the response surface method (RSM) has been applied to achieving the optimum value of the involved parameters. The obtained results illustrate that with an augment in the Rayleigh number from 10 to 100, the average Nusselt number will improve by about 61.82%. Additionally, regarding the correlation, it is indeed transparent that the Rayleigh number has the most colossal contribution comparing other factors on the achieved equation, by about 61.88%.

     

A magnetic field strategy to porous Pt-Ni nanoparticles with predominant (111) facets for enhanced electrocatalytic oxygen reduction

For the first time, we developed porous Pt-Ni alloying nanoparticles with predominant(111) facets under intense magnetic fields. Electrochemical analysis revealed that the Pt-Ni alloying nanoparticles obtained at 2 Tesla exhibited a superior catalytic activity and durability for oxygen reduction reaction. This work demonstrated that the imposition of intense magnetic field could be considered as a new approach for developing efficient alloying electrocatalysts with preferential facets.     

Synthesis of a highly porous carbon material with magnetic properties

Russian Journal of Applied Chemistry - Double modification of birch wood sawdust was performed with the aim to prepare porous carbon materials with magnetic properties.     

Simulation of thermal radiation in a micropolar fluid flow through a porous medium between channel walls

Journal of Thermal Analysis and Calorimetry - Among numerous methods which have been employed to reinforce the thermal efficiency in many systems, one is the thermal radiation which is a mode of...     

Second law analysis of a porous structured enclosure with nano-enhanced phase change material and under magnetic force

Journal of Thermal Analysis and Calorimetry - The investigations show that an undeniable part of future smart energy system, which is to be based on 100% clean energies, is energy storage units....     

Surfactant induced one dimensional unsaturated flow through porous media: a classical mathematical approach

Surfactants reduce the interfacial tension, amend the solid–liquid contact angle and greatly influence the capillarity action in unsaturated porous media. Solubility studies of surfactants in inducing similar flow through such medium has been described to be of great importance to hydrologists, agriculturists and for the people related with water sciences to confine the flow problems in water infiltration system, seepage delinquent and the underground disposal of wastewater. Present article reviews the current state of knowledge to understand such one dimensional, unsteady surfactant flow phenomenon due to the capillary pressure gradients and is represented mathematically using one parameter group theory of similarity analysis. For the sake of definiteness in the analysis, we assumed certain specific relationships viz. the permeability of the medium as a specific linear function of moisture content and time which are consistent with the physical problem. We have not included any graphical or numerical illustrations due to our particular interest in deriving the classical solution to our problem.