Phase Equilibria of the MnTe-Sb2Te3 System and Synthesis of Novel Ternary Layered Compound – MnSb4Te7

By using Differential Thermal Analysis (DTA) and Powder X-ray Diffraction (PXRD) techniques, the phase diagram of the MnTe-Sb2Te3 system has been constructed for the first time in the entire composition range. The system features two ternary layered van der Waals (vdW) compounds. Apart from known MnSb2Te4, novel MnSb4Te7 which a structural analogous of the known MnBi4Te7 was found in the system. Crystal structure parameters of both compounds were determined by Rietveld refinement using the fundamental parameter approach. Both compounds were found to decompose via peritectic reactions and possess significant homogeneity ranges. The title system is also characterized by the existence of the wide solid solution field based on the starting Sb2Te3. The present results would be useful for the bulk single crystal growth of both compounds from the liquid phase via the determination of primary crystallization areas.

Comparison of well-posedness criteria of two-fluid models for numerical simulation of gas-liquid two-phase flows in vertical pipes

The purpose of the present study is to compare the well-posedness criteria of the free-pressure two-fluid model, single-pressure two-fluid model, and two-pressure two-fluid model in a vertical pipe. Two-fluid models were solved using the Conservative Shock Capturing Method. A water faucet case is used to compare two-fluid models. The free pressure two-fluid model can accurately predict discontinuities in the solution field if the problem's initial condition satisfies the Kelvin Helmholtz instability conditions. The single-pressure two-fluid model can accurately predict the behavior of flows in which the two phases are poorly coupled. The two-pressure two-fluid model is an unconditionally well-posed one; if in the free-pressure two-fluid model and single-pressure two-fluid model, the range of velocity difference of two phases exceeds certain limits, the models will be ill-posed. The two-pressure two-fluid model produces more numerical diffusion than the free-pressure two-fluid and single-pressure two-fluid models in the solution field. High numerical diffusion of two-pressure two-fluid models leads to failure to better comply with the problem's analytical solution. Results show that a single-pressure model is a powerful model for numerical modeling of gas-liquid two-fluid flows in the vertical pipe due to a broader range of well-posed than free-pressure models and less numerical diffusion than the two-pressure model.

Effect of liquid phase compressibility on modeling of gas-liquid two-phase flows using two-fluid model

In this paper, a numerical study is performed in order to investigate the effect of the liquid phase compressibility two-fluid model. The two-fluid model is solved by using conservative shock capturing method. At the first, the two-fluid model is applied by assuming that the liquid phase is incompressible, then it is assumed that in three cases called water faucet case, large relative velocity shock pipe case, and Toumi?s shock pipe case, the liquid phase is compressible. Numerical results indicate that, if an intense pressure gradient is governed on the fluid-flow, single-pressure two-fluid model by assuming liquid phase incompressibility predicts the flow variables in the solution field more accurate than single-pressure two-fluid model by assuming liquid phase compressibility.

The impact of the order of numerical schemes on slug flows modeling

This paper aims to explore the impact of the order of numerical schemes on the simulation of two-phase slug flow with a two-fluid model initiation. The governing equations of the two-fluid model have been solved by a class of Riemann solver. The numerical schemes applied in this paper involve first-order (Lax-Friedrichs and Rusanov), second-order (Ritchmyer), and high-order (flux-corrected transport or FCT and total variance diminishing or TVD). The results suggest that the TVD and FCT are able to predict the slug initiation with high accuracy compared with experimental results. Lax-Friedrichs and Rusanov are both first-order schemes and have second-order truncation error. This second-order truncation error caused numerical diffusion in the solution field and could not predict the slug initiation with high accuracy in contrast to TVD and FCT schemes. Ritchmyer is a second-order scheme and has third-order truncation error. This third-order truncation error caused dispersive results in the solution field and was not a proper scheme.

Effect of Different Mediated Agents on Morphology and Crystallinity of Synthesized Silver Nanowires Prepared by Polyol Process

Synthesis and characterization of multiple crystalline silver nanowires (NWs) with uniform diameters were carried out by using 1,2-propandiol and ethylene glycol (EG) as comediated solvents and FeCl3as mediated agent in the presence of poly(vinyl pyrrolidone) (PVP). Experimental data and structural characterizations revealed that AgNWs have evolved from the multiple crystalline seeds initially generated by reduction of AgNO3with EG and 1,2-propandiol followed by reducing Fe(III) to Fe(II) which in turn reacts with and removes adsorbed atomic oxygen from the surfaces of silver seeds. In addition, uniform silver nanowires were obtained by using FeCl2and AlCl3as mediated agents in EG solution. Field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM) showed uniform nanowires in both diameter and length. UV-Vis spectra showed adsorption peaks confirming the formation of nanowires. X-ray diffraction (XRD) patterns displayed the final product with high crystallinity and purity. In this study, a growth mechanism for forming AgNWs was proposed and a comparison between different mediated agents was carried out.

A CASE STUDY IN SYSTEMATIC AND METHODICAL DESIGN ENGINEERING

At RMC, in Mechanical Engineering, the third-year course MEE 303 ‘Principles of Engineering Design’ consists of 12 lectures and two mini-projects, one for redesign, and one for novel design. The redesign alternates between a water valve and an automotive oil pump. This case study is now up-to-date according to the most recent developments in the theoretical framework that is the basis for the systematic and methodical process. The search for solutions in this process involves creativity supported by systematic working.An automotive oil pump is to be redesigned for revised conditions. The existing oil pump originated from the 1970’s, and was used in a V-8 engine. A reconstituted set of engineering drawing was prepared. Using the recommended systematic procedure, and other appropriate methods, students were asked to perform the redesign process: to develop a design specification, to analyze the existing pump to detect organs and functions, to explore the solution field with a morphology, and to suggested an improved embodiment. The case study as presented here serves as a sample solution.

Changes in excitation-contraction coupling in an isolated ventricular myocyte model of cardiac stunning

To investigate cardiac stunning, we recorded intracellular [Ca2+], contractions, and electrical activity in isolated guinea pig ventricular myocytes exposed to simulated ischemia and reperfusion. After equilibration, ischemia was simulated by exposing myocytes to hypoxia, acidosis, hyperkalemia, hypercapnia, lactate accumulation, and substrate deprivation for 30 min at 37°C. Reperfusion was simulated by exposure to Tyrode solution. Field-stimulated myocytes exhibited stunning upon reperfusion. By 10 min of reperfusion, contraction amplitude decreased to 43.0 ± 5.5% of preischemic values ( n = 15, P < 0.05), although action potential configuration and sarcoplasmic reticulum Ca2+stores, assessed with caffeine, were normal. Diastolic [Ca2+] and Ca2+ transients (fura 2) were also normal in stunned myocytes. In voltage-clamped cells, peak L-type Ca2+ current was reduced to 47.4 ± 4.5% of preischemic values at 10 min of reperfusion ( n= 21, P < 0.05). Contractions elicited by Ca2+-induced Ca2+ release and the voltage-sensitive release mechanism were both depressed in reperfusion. Our observations suggest that stunning is associated with reduced L-type Ca2+ current but that alterations in Ca2+ homeostasis and release are not directly responsible for stunning.