A Study of the Spatial-Emission Characteristics of Quantum-Cascade Lasers for the 8-μm Spectral Range

Technical Physics Letters - Near- and far-fields of quantum-cascade lasers emitting in the spectral range near 8 μm have been studied. For all laser samples with a ridge width of 20 and 50...     

Behavior of Hydroxyl Groups in Quartz Glass during Heat Treatment in the Range 750–950°C

The concentration of hydroxyl groups in different types of quartz glass tubes, the OH concentration profile across the tube wall, and the kinetics of OH removal during heat treatment in the temperature range 750–950°C have been studied by Fourier transform IR spectroscopy. For TK-I tubes, produced by vacuum electromelting of quartz, followed by annealing in a hydrogen atmosphere, we have calculated the diffusion coefficient of OH groups in this temperature range and the activation energy for diffusion: 215 ± 10 kJ/mol. We have found heat treatment conditions that ensure a considerable decrease in the concentration of OH groups in quartz tubes that are used in the fabrication of reactors for the preparation of extrapure chalcogenide glasses.     

Modeling of Gas Solubility Data for HFCs–Lubricant Oil Binary Systems by Means of the SRK Equation of State

The Soave–Redlich–Kwong (SRK) equation of state (EOS) is used to describe vapor-liquid (VLE) and vapor-liquid-liquid (VLLE) equilibria of mixtures containing environmentally friendly refrigerants (hydrofluorocarbons, HFCs) and lubricant oils (polyalkylene glycols, PAGs and polyol esters, POEs) at high pressures. For refrigerants, pure component parameters are used as they were found in refrigerant properties computer program Version 6.0 of REFPROP. For the PAG and POE oils, they are either predicted by group contribution methods or obtained from thermodynamic data. Extension to mixtures is performed by using the conventional quadratic mixing rule with only one parameter for each binary pair. The binary parameters are regressed from VLE experimental data available in the literature and subsequently used for prediction of VLLE. All results of the calculations are discussed, and the necessary parameters for prediction of thermodynamic properties of these types of mixtures for the SRK EOS are presented. The computations were performed using phase equilibria software (PE2000).     

Choice of Materials for Sorption Treatment of Pb–Bi Coolant to Remove the Accumulated Radionuclides

Sorption and phase distribution of activation products (⁶⁵Zn, ⁵⁴Mn, ⁵⁹Fe, ⁶⁰Со) in systems consisting of Pb–Bi melt and a porous material were studied under laboratory conditions. Radionuclides of elements with minimal oxygen affinity (Ru, Te, and Sb) remain predominantly in the coolant melt and are weakly sorbed by the solid phase. Radionuclides with higher oxygen affinity are well sorbed by structural solid sorbents. The maximum of the ⁶⁰Со sorption onto porous steel is reached at 853 K.     

A model for the prediction of liquid–liquid interfacial energies

A model for the calculation of liquid–liquid interfacial energies is presented. It is based on the assumption that the interface can be treated as a separate thermodynamic phase. Its derivation has been performed in an analogous way as the derivation of the Butler equation for the surface tension of liquid alloys. It requires as input parameters the excess free energy and the compositions of the bulk phases as functions of temperature. In addition, it also requires the partial molar volumes of the components. Comparison with existing experimental data for Al–Pb, Al–In, and Cu–Co in a non-equilibrium state shows very good agreements. For Al–Bi, the experimental data are either over or underestimated by a factor of ≈1.7, depending on which of the two thermodynamic assessments is used. For the Al-based systems, the calculated Al-mole fraction in the interface layer is close to the arithmetic average of the Al-mole fractions of the bulk phases.     

A Graphical Processing Unit–Based Parallel Implementation of Multiplicative Algebraic Reconstruction Technique Algorithm for Limited View Tomography

This article proposes an efficient two-dimensional (2D) pixel-driven multiplicative algebraic reconstruction technique (PdMART) on a general purpose graphical processing unit (GPU), Nvidia graphics card GTX-275. It has been tested on numerical data and also on real data that have been obtained from the micro–computed tomography scanner installed at University of Manchester. We have used real data having 90 projections and 256 rays in each projection to test the algorithm. The real data has been obtained by scanning the graphite core object of size 30 mm × 30 mm. It has been found that GPU can help PdMART to generate the weight matrix for the 256 × 256 pixel grid within a second which is very fast compared to any sequential machine. Experimental results reveal that PdMART on GPU is computationally inexpensive. Preliminary results also indicate much better performance (as compared to popular Fourier methods) for cases of limited-view projection data as is the case for the upcoming laminographic tomography machines.     

Behavior of Decomposition of Rifampicin in the Presence of Isoniazid in the pH Range 1–3

Abstract

The extent of decomposition of rifampicin in the presence of isoniazid was determined in the pH range 1–3 at 37°C in 50 min, the mean stomach residence time. With increase in pH, the degradation initially increased from pH 1 to 2 and then decreased, resulting in a bell-shaped pH-decomposition profile. This showed that rifampicin degraded in the presence of isoniazid to a higher extent at pH 2, the maximum pH in the fasting condition, under which antituberculosis fixed-dose combination (FDC) products are administered. At this pH and in 50 min, rifampicin decomposed by ? 34%, while the fall of isoniazid was 10%. The extent of decomposition for the two drugs was also determined in marketed formulations, and the values ranged between 13–35% and 4–11%, respectively. The extents of decomposition at stomach residence times of 15 min and 3 h were 11.94% and 62.57%, respectively, for rifampicin and 4.78% and 11.12%, respectively, for isoniazid. The results show that quite an extensive loss of rifampicin and isoniazid can occur as a result of interaction between them in fasting pH conditions. This emphasizes that antituberculosis FDC formulations, which contain both drugs, should be designed in a manner that the interaction of the two drugs is prevented when the formulations are administered on an empty stomach.     

Comparison of the Luus–Jaakola optimization procedure and the genetic algorithm

The success of both genetic algorithms (GA) and the Luus–Jaakola (LJ) optimization procedure in engineering optimization and the desire for efficient optimization methods arising from practical experience make the comparison of these two methods necessary. The GA and the LJ optimization procedure are compared in terms of convergence speed and reliability in obtaining the global optimum. Instead of using the number of function evaluations, this study uses computation time for comparison of convergence speed, which is more precise. Although for some problems, such as parameter estimation for the catalytic cracking process of gas oil, both GA and LJ converge to the optimum rapidly and show high reliability; in most cases, the LJ optimization procedure was found to be faster than GA and exhibited higher reliability in obtaining the global optimum. Furthermore, the LJ optimization procedure is easier to program.     

Semiconductor Type Dependent Comparison of Electrical Characteristics of Pt/InP Structures Fabricated by Magnetron Sputtering Technique in the Range of 20–400 K

Nano-Micro Letters - The paper describes how electrical properties of Pt/InP Schottky diode were affected by semiconductor type. We fabricated Pt/p-InP and Pt/n-InP Schottky diodes and measured...     

Working Standard of the Unit of Power of Electromagnetic Waves in the Frequency Range of 37.5–220 GHz

Measurement Techniques - We show the possibility of application of the bolometric converters of microwave power, included in the State Primary Standard of the unit of power of electromagnetic waves...     

Evaluation of the Temperature Range Suitable for the Synthesis of B4C–TiB2 and B4C–ZrB2 Powder Composite Materials

Inorganic Materials - Based on analysis of phase diagram data and thermodynamic modeling, we have evaluated the optimal temperature ranges of the processes underlying the preparation of...