Design and construction of an quasi-adiabatic dissolution calorimeter with a novel dosing apparatus and a low heat capacity

A quasi-adiabatic calorimeter for determining the molar solution enthalpies (Δ_sol H) of non-volatile solids was constructed. The design of the instrument was adjusted to allow the determination of solution enthalpies of small amounts of solids. For that purpose, the novel apparatus for sample dosage with virtually negligible “blank heat” was built. The rather low heat capacity of the calorimeter was achieved by reducing the volume of the reaction cell (20 mL), the dosing unit, and electric elements (the thermistor and the heater). Good thermal isolation of the reaction cell from the surroundings was accomplished by placing the cell into an evacuated polypropylene vessel. A computer program for processing the calorimetric data according to modified Regnault–Pfaundler method was written. The performance of the calorimeter was tested by determining the heats of the reactions serving as thermochemical standards at 25 °C (the dissolution of KCl and NaCl in water and the dissolution of tris(hydroxymethyl)-aminomethane in 0.1 mol dm^?3 HCl(aq)). The obtained data were in very good agreement with the literature values.     

Kinematics of layered reinforced-concrete planar beam finite elements with embedded transversal cracking

In this work crack formation and development is addressed and implemented in a planar layered reinforced-concrete beam element. The crack initiation and growth is described using the strength criterion in conjunction with exact kinematics of the interlayer connection. In this way a novel embedded-discontinuity beam finite element is derived in which the tensile stresses in concrete at the crack position reaching the tensile strength will trigger a crack to open. Since the element is multi-layered, in this way the crack is allowed to propagate through the depth of the beam. The cracked layer(s) will involve discontinuity in the cross-sectional rotation equal to the crack-profile angle, as well as a discontinuity in the position vector of the layer’s reference line. A bond–slip relationship is superimposed onto this model in a kinematically consistent manner with reinforcement being treated as an additional layer of zero thickness with its own material parameters and a constitutive law implemented in the multi-layered beam element.     

A highly accurate method to solve Fisher’s equation

In this study, we present a new and very accurate numerical method to approximate the Fisher’s-type equations. Firstly, the spatial derivative in the proposed equation is approximated by a sixth-order compact finite difference (CFD6) scheme. Secondly, we solve the obtained system of differential equations using a third-order total variation diminishing Runge–Kutta (TVD-RK3) scheme. Numerical examples are given to illustrate the efficiency of the proposed method.     

Pure and Disiline-doped (6,0) AIN Nanotube: A Computational DFT Study on the NMR Parameters

Nuclear Magnetic Resonance (NMR) parameters including isotropic and anisotropic chemical shielding parameters (CSI, CSA) and electronic structures were calculated using Density Functional Theory (DFT) for Disiline-doped Aluminum Nitride Nanotubes (Disiline-AlNNTs). The 27Al and 15N nuclear magnetic resonance (NMR) was calculated by means of the GIAO, CSGT, and IGAIM methods. Geometry optimizations were carried out at the B3LYP/6-311+G* level of theory using the Gaussian 98 program suite. The calculated parameters indicate that the Al and N atoms located at the mouths of nanotube have the smallest and largest chemical shielding isotropic (CSI) values among those of other identical ones, respectively. In the Disiline-doped model, the NMR parameters of those nuclei directly bonded to the C and Si atoms show significant changes, while other nuclei changes are inferior.     

On minimal representations of Chevalley groups of type D n , E n and G 2

Let G be a simply connected Chevalley group of type D _n , E _n or G₂. In this paper, we show that the minimal representation of G is unique for types D _n and E _n and it does not exist for the type G₂.     

Das Zerfallen der Curven in gerade Linien

Ohne Zusammenfassung     

Ueber einen Satz von Hilbert

Ohne Zusammenfassung     

Die simultanen Systeme binärer Formen

Ohne Zusammenfassung     

Die Discriminante der Form 7. Gradesf=a x 7

Ohne Zusammenfassung