Processing optimization: A way to improve the ionic conductivity and dielectric loss of electroactive polymers

Electro‐active polymers (EAPs) such as P(VDF‐TrFE‐CTFE) are greatly promising in the field of flexible sensors and actuators, but their low dielectric strength driven by ionic conductivity is a main concern for achieving high electrostrictive performance. It is well known that there is a quadratic dependence of the strain response and mechanical energy density on the applied electric field. This dependence highlights the importance of improving the electrical breakdown EAPs while reducing the dielectric losses. This article demonstrates that it is possible to dramatically increase the electrical breakdown and decrease the dielectric losses by controlling processing parameters of the polymer synthesis and fabrication procedure. As a result, an enhancement of around 70% is achieved in both the strain and blocking force. The effects on the dielectric losses of the polymer crystallinity, molecular weight, solvent purity, and crystallization temperature are also investigated. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2018 , 56, 1164–1173     

A comparison of algainas and InGaAsP-based 1.3 μm semiconductor lasers using high pressure

Abstract

We have compared the effect of hydrostatic pressure on the threshold current, I_th, and lasing energy, E_lase, of 1.3 pm quantum-well devices based upon AlGaInAs and InGaAsP. Whilst we observe a very similar dependence of E_lase on pressure for the two materials, we measure strikingly different variations of I_th. By applying pressure to 1.3 μm InGaAsP lasers, I_th typically decreases by ～ 10% over 1 GPa consistent with the reduction of Auger recombination, which forms ～ 50% of I_th at room temperature. However, for the 1.3 μm AlGaInAs-based lasers, we observe an increase in I_th by ～ 8% over the same pressure range. From these results we conclude that non-radiative recombination accounts for only ～ 20% of I_th in AlGaInAs-based devices. This is in good agreement with previous temperature dependence measurements and shows why AlGaInAs-based devices exhibit a reduced temperature sensitivity of I_th which is very important for telecommunications applications.     

Superconductivity in the alkali metals

At ambient pressure there are 29 elemental superconductors in the periodic table, none of which is an alkali metal. The first alkali metal to become superconducting under high pressure is Cs followed years later by Li. Alkali metals are believed to be exemplary free-electron systems. The fact that an alkali metal becomes superconducting at all is surprising and is a result of the fact that under pressure it shows marked deviations from free-electron behaviour where, counterintuitively, bands narrow and gaps widen. For this reason the alkali metals are among the most interesting systems known to study in high-pressure experiments and superconductivity is one of their most fascinating properties.     

Azo benzene derivatives

Pressure-volume isotherms for 4-(trans-4-butylcylohexyl)benzonitrile were measured by means of piston-cylinder method. This substance has a monotropic nematic phase at atmospheric pressure. But over a pressure, the nature of isotropic to nematic phase transition changed from monotropic to enantiotropic phase transition. It is the first observation in P-V-T experiments that the monotropic isotropic-nematic transition changes enantiotropic under pressure.     

微米BCN棒的制备及相关材料的物理性质

轻元素共价键硼碳氮（ＢＣＮ）化合物随组分和原子环境的变化，表现了由半金属到宽湿润地导体之间可调的物理性质，利用偏压辅助的热丝化学气相沉积方法，成功地制备了直径为２０μｍ、长度为１００μｍ的微米量级ＢＣＮ棒，并进一步研究了它的化学成分和原子键态。     

Ostrowski type inequalities on H-type groups

The main aim of this paper is to establish an Ostrowski type inequality on H-type groups using the L^∞ norm of the horizontal gradient. The work has been motivated by the work of Anastassiou and Goldstein in [G.A. Anastassiou, J.A. Goldstein, Higher order Ostrowski type inequalities over Euclidean domains, J. Math. Anal. Appl. 337 (2008) 962-968].     

Experimental vapor pressures of 1,2-bis(dimethylamino)ethane, 1-methylmorpholine, 1,2-bis(2-aminoethoxy)ethane and N-benzylethanolamine between 273.18 and 364.97 K

In this work, the experimental vapor pressures of four amines 1,2-bis(dimethylamino)ethane, 1-methylmorpholine, 1,2-bis(2-aminoethoxy)ethane and N-benzylethanolamine using a static apparatus are reported. The temperature range is comprised between 273.18 and 364.97 K and the pressure range between 0.782 Pa and 333 kPa. The molar enthalpies of vaporization at 298.15 K were calculated from Clausius–Clapeyron equation fitted on the experimental results.     

Numerical investigation of the effects of sluice spillway roof profiles on the hydraulic characteristics

There is a need for evolving hydraulically efficient roof profile of bellmouth for high head sluice spillways, as sluice roof is susceptible to cavitation damage. In this paper, formulation and development of a numerical model for simulating the spillway flow and its application to a sluice spillway are presented. The main focus of the simulation study is to apply the developed model to investigate the effects of sluice roof profile geometry on the pressure distribution, the discharge coefficient and the nature of flow regime within the sluice bellmouth. From the analysis of results for eight different roof profiles by varying the entry and exit angles of elliptic bellmouth transition, some important observations have been suggested, which are of practical relevance to hydraulic design engineers. The numerical model results are compared for one profile with physical model study. The simulated results are in close agreement with the measured values. Copyright © 2007 John Wiley & Sons, Ltd.     

Conceptual linearization of Euler governing equations to solve high speed compressible flow using a pressure‐based method

The main objective of the current work is to introduce a new conceptual linearization strategy to improve the performance of a primitive shock‐capturing pressure‐based finite‐volume method. To avoid a spurious oscillatory solution in the chosen collocated grids, both the primitive and extended methods utilize two convecting and convected momentum expressions at each cell face. The expressions are obtained via a physical‐based discretization of two inclusive statements, which are constructed via a novel incorporation of the continuity and momentum governing equations. These two expressions in turn provide a strong coupling among the Euler conservative statements. Contrary to the primitive work, the linearization in the current work respects the definitions and essence of physics behind deriving the Euler governing equations. The accuracy and efficiency of the new formulation are then investigated by solving the shock tube as a problem with moving normal and expansion waves and the converging‐diverging nozzle as a problem with strong stationary normal shock. The results show that there is good improvement in performance of the primitive pressure‐based shock‐capturing method while its superior accuracy is not deteriorated at all. © 2007 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq, 2008