基于循环码的常重复合码的构造

研究给出了一类基于循环码的常重复合码的构造,并利用指数和计算其参数.与相关的常重复合码相比,该码具有更多的码字,且渐近性较好.     

Estimation of the solubility product of hydrocalumite–hydroxide,a layered double hydroxide with the formula of [Ca2Al(OH)6]OH·nH2O

From aqueous NaOH/Ca(OH)₂/NaAl(OH)₄ mixtures, after allowing short reaction times we observed the precipitation of Ca(OH)₂(s) at lower, and a mixture of Ca(OH)₂(s) and a layered double hydroxide, hydrocalumite (HC) at higher aluminate concentrations. From the maximum aluminate concentration, at which the equilibrium solid phase is still portlandite (i.e., further increase in the aluminate concentration results in HC appearing in the precipitate beside the portlandite), the concentration based solubility products of two polymorphs of HC with the formula of [Ca₂Al(OH)₆]OH·nH₂O (differing in n) has been estimated and was found to be log L_HC=−11.4 at 25 °C and −12.1 at 75 °C, respectively (where L_HC=[Ca²⁺]²[Al(OH)₄⁻][OH⁻]³) and at constant ionic strength (I=1 M NaCl). To the best of our knowledge, this is the first published estimate for the solubility product of hydrocalumite. Additionally, from the composition obtained for NaOH/Ca(OH)₂/NaAl(OH)₄ mother liquors in equilibrium with Ca(OH)₂(s), attempts were made to extract the formation constant of the ion pair CaAl(OH)₄⁺. It was found, that the effects caused by the supposed formation of this solution species are too small to be reliably determined, which allowed an upper estimate for its formation constant, K, to be suggested in the temperature range of 25–75 °C (K<200 and 40 M⁻¹ at 25 and 75 °C, respectively).     

Electrical Impedance Spectroscopic Study of CNT/Ethylene-alt-CO/Propylene-alt-CO Polyketones Nanocomposite

Impedance spectroscopy was utilized to investigate the dielectric properties, ac conductivity and charge transport mechanisms in propylene-alt-CO/ethylene-alt-CO (EPEC) random terpolymer filled with multi-walled carbon nanotubes (MWCNT) as a function of nanofiller content, frequency, and temperature. Equivalent resistor-capacitor (RC) circuit models were proposed to describe the impedance characteristics of the unfilled terpolymer and the nanocomposite at different temperatures. For the nanocomposites, the ac conductivity tended to be frequency independent at low frequencies. At high frequencies, the ac conductivity increased with frequency. The dc conductivity (i.e., plateau of the ac conductivity at low frequencies) at room temperature increased from 10^?9 (Ω·m)^?1 for the unfilled polymer to l0^?3 (Ω·m)^?1 for the 6 wt% MWCNT/EPEC nanocomposite. At low temperatures, the equivalent RC model for EPEC-0 and EPEC-2 was found to consist of a parallel RC circuit. However, for 6 wt% MWCNT/EPEC nanocomposite, an RC model consisting of an R/constant phase element (CPE) circuit and a resistor in series was required to describe the impedance behavior of the nanocomposite.     

Spectral,Optical and Mechanical studies on pure and thiourea doped ammonium di-hydrogen phosphate NLO single crystals

Pure and thiourea substituted single crystals of ammonium di-hydrogen phosphate have been grown from aqueous solution by isothermal solvent evaporation technique. Doped crystal exhibits prominent changes in physical and chemical properties. Single crystal XRD analyses of the samples are carried out and the results are compared. FTIR and UV–vis–NIR spectral analyses have been employed to identify the presence of various functional groups and the UV cut-off range in the grown crystals. Density measurements have been made and Photoconductivity studies revealed the negative photo conducting nature. Hardness measurement shows that the mechanical strength of the doped crystal is high when compared to pure ammonium di-hydrogen phosphate. The dielectric response of the samples has been studied in the frequency range 100 Hz–5 MHz at room temperature and the results are discussed.     

Variations of the elastic constants of InSb near the covalent-metallic transition

Abstract

The pulse-echo-overlap method was used to measure the longitudinal and transverse wave velocities in single-crystal (100) and (111) samples of InSb up to 3 GPa at room temperature. The peculiar variations of the elastic constants were observed near the covalent-metallic transition.     

TSC defect level in silicon produced by irradiation with muons of GeV-energy

Deep level transient spectroscopy has been used to observe the reduced concentrations of vacancy-related defects in γ-irradiated n-type Si containing hydrogen atoms. Data are presented on the efficiency and depth of this damage reduction as a function of the duration and temperature of the exposure to the plasma used to introduce the atomic hydrogen. A 3-hour exposure in an H plasma at 300°C prior to irradiation reduced the concentrations of the O-V, V-V and P-V centres by half or more to a depth of ～20 μm, compared to the control samples.     

Full rate constant matrix contraction method for obtaining branching ratio of unimolecular decomposition

The branching ratio of unimolecular decomposition can be evaluated by solving the rate equations. Recent advances in automated reaction path search methods have enabled efficient construction of the rate equations based on quantum chemical calculations. However, it is still difficult to solve the rate equations composed of hundreds or more elementary steps. This problem is especially serious when elementary steps that occur in highly different timescales coexist. In this article, we introduce an efficient approach to obtain the branching ratio from a given set of rate equations. It has been derived from a recently proposed rate constant matrix contraction (RCMC) method, and termed full‐RCMC (f‐RCMC). The f‐RCMC gives the branching ratio without solving the rate equations. Its performance was tested numerically for unimolecular decomposition of C₃H₅ and C₄H₅. Branching ratios obtained by the f‐RCMC precisely reproduced the values obtained by numerically solving the rate equations. It took about 95 h to solve the rate equations of C₄H₅ consisting of 234 elementary steps. In contrast, the f‐RCMC gave the branching ratio in less than 1 s. The f‐RCMC would thus be an efficient alternative of the conventional kinetic simulation approach. © 2016 Wiley Periodicals, Inc.     

A new approach in modeling of constant temperature boundary condition in thermal lattice‐Boltzmann method

The lattice‐Boltzmann method is being applied to a diversity of fluid flow and heat transfer problems nowadays. Because of its microscale nature, strict attention should be paid when introducing macroscopic inputs to the model. One of the challenging issues dealing with macroscale and microscale treatment is the implementation of boundary conditions. In this regard constant‐temperature boundaries are frequently used in energy transfer problems. Such boundaries are simply modeled in Navier–Stokes based solvers, but they are not so harnessed in lattice‐Boltzmann models. One of the problems is that the calculated tangential heat flux is not zero along such boundaries in most of the previous models. In the present paper, a model has been developed, which has the capability of controlling tangential heat flux along the constant‐temperature boundaries. It aims to set the heat flux nearly zero along the boundary in midplane grid schemes. Copyright © 2012 John Wiley & Sons, Ltd.     

Dihedral angle study in Hesperidin using NMR Spectroscopy

Hesperidin is flavonoid molecule found in citrus fruits (Citrus reticulata), especially difficult to extract, classify and characterize. Present work is to study the unresolved relative configuration of Hesperidin through the dihedral angle, coupling constant and different NMR techniques. The Karplus equation and its modifications have been originated from the valence bond theory and associated with dihedral angle and coupling constant. The result data set of calculated dihedral angle can probe significant method to assign the virtual configuration of natural products and also resolved stereochemistry of Hesperidin at C‐2 position in. Copyright © 2016 John Wiley & Sons, Ltd.