Boundary layer model for char combustion and gasification

A non-steady boundary layer model is developed for numerical simulation of combustion and gasification of a single shrinking char particle. The model considers mass and energy conservation coupled with heterogeneous char reactions producing CO and homogeneous oxidation of CO to CO₂ in the boundary layer surrounding the char particle. Mass conservation includes accumulation, molecular diffusion, Stefan flow and generation by chemical reaction. Energy conservation includes radiation transfer at the particle surface and heat accumulation within the particle. Simulation results predict experimentally measured conversion and temperature profiles of a burning Spherocarb particle in a laminar flow reactor. Effects of bulk oxygen concentration and particle size on the combustion process are addressed. Predicted particle temperature is significantly affected by boundary layer combustion of CO to CO₂. With increasing particle size, char gasification to char combustion ratio increases, resulting in decreasing particle temperature and increasing peak boundary layer temperature.     

Optimization of coal liquefaction reactors

The method of Lagrangian multipliers of classical calculus is applied to obtain the optimum operating conditions of three continuous stirred tank reactors (CSTR) in series, to liquefy coal with minimum gas yield. In the formulation of the problem, the gas conversion was assumed to be the cost function. Results obtained were supported by the experimental findings in terms of liquefaction temperatures, reaction times, and conversion of coal into various liquefaction products.     

Optimal control of a continuous two valves in series letdown flow system

In the present work, the dynamics of two interacting valves-in-series letdown flow system subjected to the optimal control of the liquid levels in two vessels and of simultaneous distribution of the total pressure drop amongst the valves has been studied. The controllers of the process (the valve constants) have been obtained as functions of the input and output liquid volumetric flow rates and process characteristics, assuming no time-lags in the measurement of the state variables and of the controllers' actions.     

Seasonal effects in the nutritional quality of the body structural tissue of cephalopods

The most commonly-consumed cephalopods around the world (the common cuttlefish, Sepia officinalis, European squid, Loligo vulgaris, common octopus, Octopus vulgaris and musky octopus, Eledone moschata) were evaluated in terms of seasonal variations in proximate and fatty acid compositions. The arms of the octopuses were used for this study, whereas the mantle of the other species (squids and cuttlefish) were used for the analyses. The lipid contents of species were found to be very low and considered as lean. The lowest lipid content was obtained from E. moschata (0.60–0.68%), whereas L. vulgaris gave the highest level of lipid (1.34–1.92%) throughout all seasons. Unlike lipid content, protein contents of cephalopods did not change across the seasons. The fatty acid compositions of each species ranged from 28.18% to 35.28% saturated (SFA), 4.36–9.47% monounsaturated (MUFAs) and 43.58–56.55% polyunsaturated acids (PUFAs). The highest proportions of fatty acids in cephalopods were myristic acid (C14:0, 0.96–2.96%), palmitic acid (C16:0, 15.53–25.20%), heptadecanoic acid (C17:0, 1.05–2.56%), stearic acid (C18:0, 4.32–9.96%), oleic acid (cis18:1 n−9, 1.80–4.29%), cis-11-eicosenoic acid (C20:1, 2.07–4.69%), linoleic acid (C18:2 n−6, 0.17–1.95%), arachidonic acid (C20:4 n−6, 1.48–11.65%), cis-5,8,11,14,17-eicosapentaenoic acid (EPA, C20:5 n−3, 7.86–16.97%) and cis-4,7,10,13,16,19-docosahexaenoic acid (DHA, C22:6 n−3, 20.99–39.00%). The results indicated that these cephalopod species are excellent protein sources and very rich in n−3 fatty acids.     

Physical properties of CdS:Ga thin films synthesized by spray pyrolysis technique

This paper reports the investigation of physical properties of CdS:Ga thin films grown for the first time by a simple spray pyrolysis method as a function of Ga-doping level from 0 to 8 at.%. X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive photoelectron spectroscopy, transmittance, photoluminescence, Hall effect and resistivity measurements are utilized to search for the structural, morphological, chemical, optical and electrical properties of as-prepared samples. XRD data confirm the presence of hexagonal structure with a strong (101) preferred orientation. SEM results show that the surface morphology varies significantly via Ga-doping, particularly 6 at.% doping level. Optical transparency is improved by the lower Ga-doping (2 and 4 at.%) whereas higher doping concentration (6 and 8 at.%) causes a poor transmission in the visible region. With respect to CdS (2.42 eV), the calculated band gap values at first enhances for 2 at.% Ga-doping and reaches to 2.43 eV. But, further increase in Ga-doping amount leads to a drop in the band gap value (2.39 eV) for 8 at.% Ga-doping. Electrical analyses display that 2 at.% Ga-doped CdS thin films exhibit a maximum carrier density and a minimum resistivity that are related to the substitutional incorporation of Ga³⁺ ions at Cd²⁺ ions. However, higher doping of Ga atoms into CdS gives rise to a gradual diminish in the carrier concentration and a rise in the resistivity. Based on all the data, it should be concluded that 2 at.% Ga-doped CdS thin films exhibit the best optical and electrical properties that can be used in the optoelectronic applications.     

The Ball-Box Theorem for a Class of Corank 1 Non-differentiable Tangent Subbundles

We show that an analogue of the ball-box theorem holds true for a class of corank 1, non-differentiable tangent subbundles that satisfy a geometric condition. We also we give examples of such bundles and give an application to dynamical systems.     

A probabilistic model for breast cancer survival data

The aim of the present study is the development of a probabilistic model to analyze breast cancer survival data. A finite-state discrete-time Markov chain model has been formulated for the analysis of follow-up probability and mortality data for 780 breast cancer patients.

The proposed stochastic model can also be used in comparing the transition in order to estimate treatment effects.     

MASS TRANSFER LIMITATIONS IN COAL LIQUEFACTION

ABSTRACT

In a number of contributions to coal liquefaction, gas–liquid mass transfer limitation has been referred by neglecting mass transfer limitation of solvent Into solid coal. Reported apparent activation energies of coal liquefaction reactions are In the range of 10–20 kCal/g–mole, which are too low for thermal reactions, Imply that diffusion Is the rate controlling step. In this study, the solvent diffusion effect on solvolysis of vitrinitic macerals In Alberta subbituminous coal has been studied, by performing petrographlc analyses of original coal and liquefaction residues. Quasi–steady state and transient coal–solvent diffusion-chemical reaction models are developed to Interpret the experimental data. Results indicate that solvent diffusion into the reactive maceral most likely be a rate limiting step In coal liquefaction.     

MASS TRANSFER LIMITATIONS IN COAL LIQUEFACTION

In a number of contributions to coal liquefaction, gas-liquid mass transfer limitation has been referred by neglecting mass transfer limitation of solvent Into solid coal. Reported apparent activation energies of coal liquefaction reactions are In the range of 10-20 kCal/g-mole, which are too low for thermal reactions, Imply that diffusion Is the rate controlling step. In this study, the solvent diffusion effect on solvolysis of vitrinitic macerals In Alberta subbituminous coal has been studied, by performing petrographlc analyses of original coal and liquefaction residues. Quasi-steady state and transient coal-solvent diffusion-chemical reaction models are developed to Interpret the experimental data. Results indicate that solvent diffusion into the reactive maceral most likely be a rate limiting step In coal liquefaction.     

Modelling and simulation of vertebrate retina: extended network

Dissections reveal that each lymphatic organ characteristic of species is supplied with lymph hearts, smooth muscles, or striated muscles whose contractions (along with tranmitted arterial pulsations and changing gravitational forces) coordinately propel lymph centrally during breathing, swallowing, food absorption and joint flexion. In aquatic vertebrates and amphibians lymph hearts, closely related to the gills, propel central lymph into the jugular veins. In aerial vertebrates with well-developed lungs, the striated muscles which enable ventilation, propel central lymph into large veins coursing through the thoracic inlet at rates commensurate with oxygen consumption under normal conditions.