Comparison of different approaches for thermal performance improvement of a phase change energy storage system

Journal of Thermal Analysis and Calorimetry - Performance improvement of a phase change material (PCM) thermal storage system is numerically investigated. A finite volume solver is employed to...     

Interactions of ion acoustic multi-soliton and rogue wave with Bohm quantum potential in degenerate plasma

This work investigates the interactions among solitons and their consequences in the production of rogue waves in an unmagnetized plasmas composing non-relativistic as well as relativistic degenerate electrons and positrons, and inertial non-relativistic helium ions. The extended Poincare′–Lighthill–Kuo(PLK) method is employed to derive the two-sided Korteweg–de Vries(Kd V) equations with their corresponding phase shifts. The nonlinear Schr o¨dinger equation(NLSE) is obtained from the modified Kd V(m Kd V) equation, which allows one to study the properties of the rogue waves. It is found that the Fermi temperature and quantum mechanical effects become pronounced due to the quantum diffraction of electrons and positrons in the plasmas. The densities and temperatures of the helium ions, degenerate electrons and positrons, and quantum parameters strongly modify the electrostatic ion acoustic resonances and their corresponding phase shifts due to the interactions among solitons and produce rogue waves in the plasma.     

Design,Synthesis, and Structural Elucidation of New Pyridine and Thienopyridine Derivatives

New series of 3‐cyanopyridine scaffolds were prepared from the reaction of 3‐(4‐bromophenyl)‐1‐(3,4‐dimethoxyphenyl)prop‐2‐en‐1‐one with active nitriles, including malononitrile and 2‐cyanothioacetamide. The newly prepared 6‐(4‐bromophenyl)‐4‐(3,4‐dimethoxyphenyl)‐2‐thioxo‐1,2‐dihydropyridine‐3‐carbonitrile was used as a scaffold for the preparation of new series of condensed thienopyridines by its reactions with active halo compounds, namely, ethyl chloroacetate, chloroacetonitrile, phenacyl bromide, chloroacetone, and 2‐chloro‐N‐arylacetamide. The structures of the synthesized compounds were elucidated by the elemental analysis, spectral data and chemically by their preparations with other pathways.     

Flow equations for the ionic Hubbard model

Taking the site-diagonal terms of the ionic Hubbard model (IHM) in one and two spatial dimensions, as H₀, we employ Continuous Unitary Transformations (CUT) to obtain a “classical” effective Hamiltonian in which hopping term has been renormalized to zero. For this Hamiltonian spin gap and charge gap are calculated at half-filling and subject to periodic boundary conditions. Our calculations indicate two transition points. In fixed Δ, as U increases from zero, there is a region in which both spin gap and charge gap are positive and identical; characteristic of band insulators. Upon further increasing U, first transition occurs at U=Uc₁, where spin and charge gaps both vanish and remain zero up to U=Uc₂. A gap-less state in charge and spin sectors characterizes a metal. For U>Uc₂ spin gap remains zero and charge gap becomes positive. This third region corresponds to a Mott insulator in which charge excitations are gaped, while spin excitations remain gap-less.     

Finite element solution of the Navier–Stokes equations by a velocity–vorticity method

A velocity–vorticity formulation of the Navier–Stokes equations is presented as an alternative to the primitive variables approach. The velocity components and the vorticity are solved for in a fully coupled manner using a Newton method. No artificial viscosity is required in this formulation. The pressure is updated by a method allowing natural imposition of boundary conditions. Incompressible and subsonic results are presented for two-dimensional laminar internal flows up to high Reynolds numbers.     

An EPR study of γ-irradiated single crystals of cholesta-4, 6-diene-3-one

Cholesta-4, 6-diene-3-one single crystals irradiated with γ-rays at room temperature have been investigated by electron spin resonance. EPR spectra at room temperature exhibit a characteristics triplet which splits into two doublets. The main triplet has been interpreted as being caused by the addition of a hydrogen atom to the 7-position of the molecule, leaving an unpaired electron in the 2p₂ orbital of the carbon atoms in position 6 and 4. The hyperfine spectrum is generated by interaction of the unpaired electron with two equivalent -protons in position 4 and 6 and with tow non-equivalent β-protons in position 7. The principal values of the hydrogen hyperfine tensors are determined together with the g tensor of this radical.     

Reactions with heterocyclic diazonium salts. Synthesis of several new azolylhydrazones

Several new stable azolylhydrazones could be synthesized via coupling of diazotised cycliuc amidines with active methylene reagents. The obtained compounds were utilised for synthesis of several, otherwise not readily accessible fused azoles.     

Thermal studies on anisaldehyde carbohydrazone methyl trimethylammonium chloride complexes of zinc,cadmium and mercury

The kinetic parameters of the thermal decomposition of Zn, Cd and Hg(II) hydrazone complexes of the general formula [MCl₂(AGT)₂]Cl₂, where AGT=anisaldehyde carbohydrazone methyl trimethylammonium cation, $$CH_3 O - C_6 H_4 - CH = N - NH - CO - CH_2 - \mathop N\limits^ + (CH_3 )_3 ,$$ and M=Zn, Cd and Hg(II), have been determined from the corresponding thermal curves. The order of the reaction (n) and the activation energy (E _a) have been derived. The kinetic data are discussed in terms of the effect of the metal ion on the activation energy. A thermal decomposition mechanism is suggested.