Experimental investigation of nanofluid stability on thermal performance and flow regimes in pulsating heat pipe

Pulsating heat pipe (PHP) is a type of wickless heat pipe that has a simple structure and an outstanding thermal performance. Nanofluid is a type of fluid in which nanoparticles are dispersed in a base fluid and have generally a better thermal conductivity in comparison with its base fluid. In this article, the performance of a nanofluid PHP is investigated. Graphene/water nanofluid with a concentration of 1 mg mL^?1 and TiO₂ (titania)/water nanofluid with a concentration of 10 mg mL^?1 are used as the working fluids. To simultaneously investigate the thermal performance and flow regimes in the PHP, a one-turn copper PHP with a Pyrex glass attached to its adiabatic section is used. A one-turn Pyrex PHP is also used to fully visualize flow patterns in the PHP. Our results show that the material for the fabrication of a PHP and temperature of the working fluid are the most important parameters that affect the stability of a nanofluid in the PHP. The more stable nanofluid keeps its stability in the cupper PHP, while the less stable nanofluid starts to aggregate right after the injection to the cupper PHP. The more stable nanofluid has a better thermal performance than water, while the less stable nanofluid has a worse thermal performance than water. In the case of flow regimes, no significant differences are observed between the nanofluid PHP and the water PHP which is different from the previous observations. These results can help researchers to choose the best working fluid for PHPs.

     

Quasi solid-state dye-sensitized solar cell with P(MMA-co-MAA)-based polymer electrolytes

Journal of Solid State Electrochemistry - A series of poly (methylacrylate-co-methylacrylic acid) (P(MMA-co-MAA)) gel polymer electrolytes containing iodide/triiodide (I−/I3−) redox...     

Ab initio calculation of Zn0.8Mn0.2O1−yNy

Based on first-principles spin-density functional calculations, using the Korringa–Kohn–Rostoker method (KKR) combined with the coherent potential approximation (CPA), we investigated the magnetic and half-metallic properties of Mn-doped p-type ZnO and the mechanism which control these properties. Mn-doped ZnO is anti-ferromagnetic spin-glass state, but it becomes half-metallic ferromagnetic upon holes doping. The electronic structure, total magnetic moment of Zn_0.8Mn_0.2O_1−yN_y and magnetic moments of Mn and N in Zn_0.8Mn_0.2O_1−yN_y are calculated for different holes (y) concentrations. In this paper we address the origin of half-metallic and ferromagnetic properties as controlled and oriented by the nature of hybridization of the Mn (3d) state and host p(N) states. The band structure has been used to explain the strong ferromagnetism observed in Zn_0.8Mn_0.2O_0.1N_0.9.     

Axisymmetric bending analysis of thick functionally graded circular plates using fourth-order shear deformation theory

In the present article, axisymmetric bending and stretching of functionally graded (FG) circular plates subjected to uniform transverse loading based on fourth-order shear deformation plate theory (FOST) have been studied. Using a fourth-order shear deformation theory, the solutions for deflection and rotation functions of FG plates are presented in terms of the corresponding quantities for a homogeneous plate using the classical plate theory (CPT), from which solutions one can easily obtain the FOST solutions for axisymmetric bending of FG circular plates. It is assumed that the effective mechanical properties of the functionally graded plates through the thickness are continuous functions of the volume fractions of the constituent parts which are themselves defined by a power-law function. Numerical results for maximum deflection and shear stress are presented for various percentages of ceramic–metal volume fractions. These results are also compared with those obtained from the first-order shear deformation plate theory of Mindlin (FST), the third-order shear deformation plate theory of Reddy (TST) as well as the exact three-dimensional elasticity solution. It is found that although the maximum deflections obtained using FOST and TST are close to each other, the through-thickness shear stress is predicted more accurately by the FOST formulation than by the TST.     

Fabrication of nitrogen-enriched graphene oxide/Cu NPs as a highly efficient and recyclable heterogeneous nanocatalyst for the Chan–Lam cross-coupling reaction

Herein, we demonstrate the direct polymerization of melamine and cyanuric chloride in the surface of graphene oxide (GO) (N-enriched GO) in order to develop a new nanocatalyst. The supramolecular polymerized GO acts not only as a spacer to prevent the restacking of graphene sheets but also as a nitrogen source to generate active centers for Cu NP attachments. Subsequently, the nitrogen on the surface of the GO sheets coordinates with copper ions to generate copper nanoparticles. The prepared nanocatalyst was characterized by Fourier transform infrared spectroscopy, X-ray powder diffraction, scanning electron microscopy, energy-dispersive X-ray spectroscopy and thermogravimetric analysis. This catalyst showed high efficiency and good activity in the Chan–Lam cross-coupling reaction of N-heterocycles and aniline derivatives with high yields in short reaction times. In addition, the nanocatalyst was easily recovered and reused for five consecutive runs without any noticeable loss of performance.     

Pressure effect on the space charge in low density polyethylene (LDPE)

Abstract

Electrical conductivity of LDPE films was studied with pressure P (1 to 1500 bar). An anomalous discharge current (ADC) was observed in the transient state following a d.c field application. This anomalous current, depending on these parameters, and the steady state current were attributed to the existence of a space charge in polymer. The space charge phenomena and the conduction mechanisms could be given from experimental results and theoretical calculations.     

An analytical solution for buckling of moderately thick functionally graded sector and annular sector plates

In this article, an analytical solution for buckling of moderately thick functionally graded (FG) sectorial plates is presented. It is assumed that the material properties of the FG plate vary through the thickness of the plate as a power function. The stability equations are derived according to the Mindlin plate theory. By introducing four new functions, the stability equations are decoupled. The decoupled stability equations are solved analytically for both sector and annular sector plates with two simply supported radial edges. Satisfying the edges conditions along the circular edges of the plate, an eigenvalue problem for finding the critical buckling load is obtained. Solving the eigenvalue problem, the numerical results for the critical buckling load and mode shapes are obtained for both sector and annular sector plates. Finally, the effects of boundary conditions, volume fraction, inner to outer radius ratio (annularity) and plate thickness are studied. The results for critical buckling load of functionally graded sectorial plates are reported for the first time and can be used as benchmark.     

Radiation grafted poly(vinylidene fluoride)-graft-polystyrene sulfonic acid membranes for fuel cells: Structure-property relationships

<正>Structure-property relationships for poly(vinylidene fluoride)-graft-polystyrene sulfonic acid(PVDF-g-PSSA) fuel cell membranes prepared by a single step method involving radiation-induced grafting of sodium styrene sulfonate(SSS) onto electron beam(EB) irradiated poly(vinylidene fluoride)(PVDF) films were established.The physico-chemical properties of the membranes such as ion exchange capacity,water swelling and proton conductivity were correlated with the degree of grafting(G,%) and the structural changes taking place in the membrane matrix during the preparation procedure. The variation in the crystallinity and the thermal stability of membranes was studied by differential scanning calorimetry (DSC) and thermogravimetric analysis(TGA),respectively.The membranes were found to undergo substantial structural changes in forms of ionic sites increase,hydrophilicity enhancement,hydrophobicity reduction and crystallinity decrease with the variation in G(%) and the preparation method.The structural and thermal properties of the obtained membranes were also compared with their counterparts prepared by a conventional two-steps method i.e.radiation induced grafting of styrene onto EB irradiated PVDF films followed by sulfonation.The PVDF-g-PSSA membranes obtained by a single-step method were found to have superior properties compared to those obtained by the conventional two-steps method.     

Synthesis and antiproliferative activity of (Z + E)‐1‐[4‐(2‐(cyclopentadienyltricarbonylmanganese)‐2‐oxo‐ethoxy)phenyl]‐1,2‐di(p‐hydroxyphenyl)‐but‐1‐ene against breast cancer cells

This paper describes the synthesis of (Z + E)‐1‐[4‐(2‐(cyclopentadienyltricarbonylmanganese)‐2‐oxo‐ethoxy)phenyl]‐1,2‐di(p‐hydroxyphenyl)‐but‐1‐ene. Two synthetic pathways were explored. The best pathway consisted of the alkylation of 1,2‐bis‐[4‐(tert‐butyl‐dimethylsilyloxy)phenyl]‐1‐(4‐hydroxyphenyl)but‐1‐ene with BrCH₂COOEt. The ester obtained was transformed into the Weinreb amide by reaction with HN(OMe)Me–HCl. The reaction of lithium manganese tricarbonylcyclopentadienide with the Weinreb amide produced 1‐[4‐(2‐(cyclopentadienyltricarbonylmanganese)‐2‐oxo‐ethoxy)phenyl]‐1,2‐di(p‐tert‐butyldimethylsiloxyphenyl)‐but‐1‐ene. The deprotection of phenolic functions of the latter compound led to the formation of the final compound. The Z and E isomers could be separated but the isomerization of these isomers from one to another is an easy process. The Z + E compound 2 was tested against the hormone‐dependent MCF‐7 and hormone‐independent MDA‐MB‐231 breast cancer cell lines. The IC₅₀ values of compound 2 were 4.80 ± 2.00 µm and 4.79 ± 0.70 µm for MCF‐7 cells and MDA‐MB‐231 cells, respectively, which was three times better than the ferrocenyl analogue. Copyright © 2012 John Wiley & Sons, Ltd.