Comonotonic stochastic processes and generalized mean-square stochastic integral with applications

The concept of monotonic stochastic processes was introduced by Skowroński [Aequationes mathematicae 44 (1992) 249–258]. In this paper, we intro     

Poly(p-xylene disulfide) and poly(p-xylene tetrasulfide): synthesis,cure and investigation of mechanical and thermophysical properties

Abstract

In this work, two polysulfide polymers were synthesized using aromatic organic monomer (α,α′-dichloro-p-xylene) and sodium disulfide (Na₂S₂) and sodium tetrasulfide (Na₂S₄) aqueous monomers. Then, the curing process of the polymers was carried out at 170° C using a rheometer. The structural characteristics of synthesized and cured samples were identified by Raman and Fourier transform infrared (FT-IR) spectroscopies. Also, morphological and thermophysical properties of samples were studied by using the X-ray diffraction (XRD) and differential scanning calorimetry (DSC), respectively. Moreover, the molecular weight of the synthesized samples was determined by proton nuclear magnetic resonance (¹H NMR). Furthermore, the mechanical properties and hardness of the samples were investigated by tensile test and Shore A. The results showed that in the noncured samples during the increase of sulfur in the polymer structure, solubility was increased whereas it decreased the hardness, melting point (T_m ) and glass transition temperature (T_g ) of polymers. But in cured samples, hardness and T_g increase by increasing sulfur and the mechanical properties also improved. This is due to the increase in crosslinks. Also, Tm and solubility are not observed due to the formation of crosslinks.     

The response of selected isomers of B80 buckyball toward NH3 adsorption: a density functional theory investigation

Density functional theory calculations at the B3LYP/6-31G(d) and B3LYP/6-31+G(d) levels were carried out for the adsorption of NH₃ on three symmetric isomers of B₈₀ {C ₁, T _h, I _h}. To investigate the binding features of B₈₀ isomers with NH₃, different studies including the structural and electronic parameters, the ¹⁴N electric field gradient tensors and the atoms in molecules (AIM) properties were considered. The calculated parameters by these investigations can be used as powerful tools to find out some of the unknown aspects of electronic structures of the boron buckyball and its isomers. According to previous studies, boron buckyball as an amphoteric and a hard molecule has two distinct reactive sites defined as cap and frame which act as an acid and a base, respectively. Regarding the obtained results in this study, all the isomers had the same exposure when NH₃ molecule reacted with the external wall of B₈₀. For instance, the stability of N–B bond in the cap site was significantly more than the stability of N–B bond in the frame. Moreover, the adsorption of NH₃ on frame site showed a considerable reduction in HOMO–LUMO energy gap. According to AIM theory, an electrostatic nature was observed for N–B interaction. Concerning the selected isomers of buckyball, the capability of the NH₃–B₈₀ complexes to localize electron at the N–B bond critical points depend on the reaction sites significantly. In general, ¹⁴N nuclear quadruple coupling constants and asymmetry parameter reveal a remarkable effect of NH₃ adsorption on electronic structure of the B₈₀.     

A novel method for the cyclotron production no-carrier-added <Superscript>93m</Superscript>Mo for nuclear medicine

Amongst the various radioisotopes of molybdenum, ^93mMo in its no-carrier added form might be a potential candidate radionuclide in the field of nuclear medicine due to its suitable half-life (T _1/2 = 6.85 h) and for its intense gamma line at 263.14 keV. Aim of the presented study is to compare the calculated cross sections for the production of ^93mMo incident proton energy up to 30 MeV, theoretical calculation of production yield and calculation of target thickness requirement. Also, deposition of ⁹³NbO₂ on Cu substrate was carried out via two special sedimentation methods for the production of ^93mMo and a simple and selective extraction of molybdenum was described.     

A one‐pot green synthesis of 2‐amino‐4H‐benzo[h]chromenes catalyzed by a dioxomolybdenum Schiff base complex supported on magnetic nanoparticles as an efficient and recyclable nanocatalyst

In this work, catalytic performance of a molybdenum Schiff base complex‐supported magnetic support as a nanocatalyst was evaluated for the preparation of 2‐amino‐4H‐benzo[h]chromenes through one‐pot, three component reactions of 1‐naphthol, various aldehydes, and malononitrile under solvent‐free conditions. A promising greener and eco‐friendly method with a short reaction time, high yield of products, and simple work‐up procedure was achieved. The nanocatalyst could be easily separated and regenerated from reaction media by an external magnet and reused at least seven consecutive times with small drops in its catalytic performance.     

Heat transfer and Marangoni flow in a circular heat pipe using self-rewetting fluids

In this study, Marangoni flow and heat transfer enhancement in a heat pipe have been investigated. The experiments were carried out at different heat inputs. A constant temperature water bath was used at the condenser section at three temperature levels. Heat transfer coefficients and thermal resistances of the heat pipe were measured for pure water and water/butanol solutions. The experimental results confirmed that the heat pipe filled with butanol solutions showed better thermal performance than the water-filled heat pipe. At maximum heat flux, 25% heat transfer improvement was obtained when 7 wt% butanol solution was used instead of pure water.     

On the development of a nonlinear time-domain numerical method for describing vortex-induced vibration and wake interference of two cylinders using experimental results

Nonlinear Dynamics - A nonlinear mathematical model is developed in the time domain to simulate the behaviour of two identical flexibly mounted cylinders in tandem while undergoing vortex-induced...     

Analytical Nusselt number for forced convection inside a porous-filled tube with temperature-dependent thermal conductivity arising from high-temperature applications

Journal of Thermal Analysis and Calorimetry - The convection heat transfer inside a tube filled with a porous material under the constant heat flux thermal boundary condition which is widely used...