Representation of thermodynamic properties of quaternary systems using interaction parameters

Integral excess free energy of a quaternary system has been expressed in terms of the MacLaurin infinite series. The series is subjected to appropriate boundary conditions and each of the derivatives correlated to the corresponding interaction coefficients. The derivation of the partial functions involves extensive summation of various infinite series pertaining to the first order and quaternary parameters to remove any truncational error. The thermodynamic consistency of the derived partials has been established based on the Gibbs-Duhem relations. The equations are used to interpret the thermodynamic properties of the Fe-Cr-Ni-N system.     

A model for calculation of pressure in the duct due to discharge of gas from a failed fuel pin

In this paper an anlytical model for the calculation of the pressure pulse in hexagonal ducts due to discharge of gas from a failed fuel pin is developed. The analysis yields the time history of the pressure pulse which can be used in the calculation of permanent deformation of the duct or in the assessment of the susceptibility of the duct to fracture. In this model the analysis is divided into two stages. In the first stage the gas expands as a spherical bubble, but the influence of duct wall is taken into account. At the end of the first stage the spherical shape of the bubble is assumed to be lost and the gas is assumed to expand axially as a column. The end conditions of stage 1 are the initial conditions for stage 2. The analysis involves solving the continuity and momentum equations for the liquid along with the energy balance equation for the gas. In the analysis the liquid is assumed to be incompressible.     

Intraparticle effects in char combustion ii steady state analysis

Based on the results of an earlier paper, a model is developed to include the homogeneous reaction in the external boundary layer. It is assumed, consistent with those results, that there is no homogeneous reaction within the particle. A feasibility region is constructed using limiting cases along the lines described there. Under some conditions, the model predicted up to five steady states for a given set of ambient conditions. For large particles, a flame develops in the boundary layer and the main product is CO₂. Under such conditions, the reaction locus coincides with the double film model. While for small particles, no flame develops and the major product is CO. The solution is sensitive to the type of radiative interaction which obtains. The combustion rate increases with increase in particle temperature until a certain point, then decreases with further increase in temperature, and eventually turns back and increases again. Such behavior has been observed in some rate measurement experiments.     

Influence of heat treatment on the strength and fracture behaviour of Fe-12Cr-6Al ferritic stainless steel

The changes in the tensile properties and fracture mode brought about by heat treatment of Fe-12Cr-6Al ferritic stainless steel have been studied. A favourable combination of high strength and good ductility is obtained by heating the material at 1370 K for 2 h followed by a water quench. The high-temperature treatment results in carbide dissolution as well as an increase in the grain size. The mechanism of strengthening has been evaluated from the apparent activation energy (28 kJ mol^–1) and is identified to be the unpinning of dislocations from the atmosphere of carbon atoms. As the heat-treatment temperature is increased, the fracture behaviour changes from ductile to brittle mode and this is related to the changes in grain size and friction stress.     

Estimating windblown PM-10 emissions from vacant urban land using GIS

This paper presents a Geographic Information Systems (GIS)-based methodology to estimate annual area-wide airborne particulate matter with an aerodynamic diameter of less than 10 microm (PM-10) emissions, and identify zones with high emissions in order to efficiently implement mitigation strategies. Application of the methodology is demonstrated using the land disposal boundary within Clark County, NV as the study area, which is currently classified as a non-attainment area by United States Environmental Protection Agency (US EPA). The estimated PM-10 emissions depend on the extent of disturbed vacant land area, undisturbed vacant land area, emission factors by soil group, and wind speeds. Portable wind tunnel field test data were used to estimate emission factors at 78 sites in the study area. Portable wind tunnel results were categorized by the wind speed range and the corresponding site soil group in order to estimate emission factors by soil group and the wind speed range. Wind speed data were obtained from the Clark County Health District's air quality monitoring stations. The proximal area over which the wind speeds are same is obtained by constructing "Thiessen" polygons around each wind speed monitoring station. PM-10 emissions were estimated as a function of the extent of disturbed vacant lands, the measured or estimated erodibility of the soil surfaces, and the intensity, duration and frequency of erosive wind events.     

A new configuration of two-level 48-pulse VSCs based STATCOM for voltage regulation

In this paper, a new configuration of STATCOM (Static Compensator) with constant DC link voltage is proposed for the voltage regulation. The proposed STATCOM consists of eight sets of two-level double-way Voltage Source Converters (VSCs). Each double-way VSC consists of two six-pulse VSCs connected through an open winding transformer unit. The phase-angle difference between these two VSCs is varied for the reactive power control. The proposed STATCOM model is developed using MATLAB/Simulink, SimPowerSystems (SPS) toolboxes and dynamic performance is studied for the change in the reference reactive power, the terminal voltage reference and voltage control under switching on an inductive and a capacitive loads. Simulation results are presented to demonstrate the voltage regulation capability of the STATCOM under these conditions.     

Gene dosage effect on starch structure studied using maize polygenic model containing ae and su1 mutant alleles

The aim of this work was to enhance our understanding on the gene dosage effect on starch structure. Two mutant alleles, ae and su1, were selected for this study. With regard to their genetic functions, ae and su1 mutations are at two opposite extremes; therefore ae and su1 constituted an ideal pair of mutant alleles for manipulating starch structures. A full set of dosage combinations of ae and su1 were constructed in the maize W64A inbred line, and matured kernels were subjected to starch structure analysis. Scanning electron microscopy showed that starch granule morphology was affected by high doses of ae and su1 alleles. X-ray powder diffraction showed that 3 doses of su1 were not able to change the crystalline pattern of starch, whereas 3 doses of ae transformed A-type pattern to B-type. Size-exclusion chromatography showed that homozygous ae, su1, and ae su1 led to drastic change of starch structure from that of non-mutant. In addition, starches from certain ae and su1 dosage combinations were different from those of homozygous genotypes. This study will lay further foundation towards genetic modification of starch for desirable functional properties in food.