Influence of Ceramic Supports on Efficient Microwave Heating of Porous Dielectrics

2005 ◽  
Author(s):  
Tanmay Basak ◽  
K. Aparna ◽  
A. Meenakshi ◽  
A. R. Balakrishnan
Keyword(s):  
Average Power ◽  
Thermal Runaway ◽  
Test Cases ◽  
Uniform Heating ◽  
Heating Rates ◽  
Resonance Modes ◽  
Heating Effects ◽  
Al2o3 Support ◽  
The Face ◽  
Time Plot

A detailed theoretical analysis has been carried out to study efficient heating of 1D porous dielectric samples due to microwaves. The heating effects are analyzed for two types of porous material: beef-air (b/a) and beef-oil (b/o) with and without ceramic supports (Al2O3 and SiC). Three test cases for porosity (φ) 0.3, 0.45 and 0.6, are considered. The effective dielectric properties are obtained using Fricke’s complex conductivity model with air and oil being the discontinuous media. The maxima in average power corresponding to resonances occur at various sample thicknesses for all porous materials with and without supports and two dominant resonance modes R1 and R2 are considered where the average power at R1 is larger than that at R2. It is observed that the maxima at R1 mode decreases significantly with porosity for samples with and without supports. It is interesting to observe that average power absorption is enhanced for samples (b/a and b/o) in presence of Al2O3 support whereas the average power is smaller with SiC support. The detailed analysis on spatial distribution of electric field, power and temperature illustrate that runaway heating is observed at the face which is not attached with support for b/a samples, and the intensity of thermal runaway is increased with porosity whereas the less thermal runaway is observed for b/o samples with all porosity regimes. The thermal runaway is less pronounced for SiC supports. The thermal runaway is also represented by ΔTb (temperature difference) vs time plot which illustrates that greater magnitudes of ΔTb occur with φ = 0.6 for b/a samples. In contrast, ΔTb vs time distribution is almost identical with porosity for b/o samples. Based on the analysis, it may be recommended that b/o samples with all porosity regimes would exhibit uniform heating rates with Al2O3 and SiC supports, whereas b/a samples may be heated with minimal thermal runaway heating corresponding to Al2O3 support at the left face.

Analysis of Microwave Heating for Composite Dielectric Food Substances Supported on Ceramic Materials

2005 ◽  
Author(s):  
Tanmay Basak ◽  
A. Meenakshi
Keyword(s):  
Heating Rate ◽  
Thermal Processing ◽  
Preliminary Analysis ◽  
Average Power ◽  
Ceramic Materials ◽  
Uniform Heating ◽  
Small Thickness ◽  
Resonance Modes ◽  
Time Plot ◽  
Oil Thickness

A detailed theoretical analysis has been carried out to study efficient heating of 1D composite dielectric samples due to microwaves. Current study involves processing of beef with oil layers with/without support and three cases are considered where oil layer is followed by beef layer (case 1), beef layer is followed by oil layer (case 2) and oil-beef layers are exposed to microwaves at both the sides (case 3). For cases 1 and 2, microwaves are incident at the left face only and the support is generally attached with the oil layer. A preliminary analysis has been carried out for beef-oil composite without any support for all cases and it is observed that identical average power in beef sample occurs for small thickness of oil layer irrespective of either oil or beef directly exposed to microwaves (case 1 or 2) and for greater thicknesses of oil layer, the food composite would exhibit greater average power for case 1. The maxima in average power corresponding to resonances occur at various sample thicknesses for all cases with and without supports and two dominant resonance modes R1 and R2 are considered where the average power at R1 mode is greater than that at R2 mode for all cases. The detailed spatial distribution for various cases illustrates that for small oil thicknesses, heating rate is less and greater heating rate would correspond to larger oil thicknesses. However, the excessive heating in beef sample may correspond to thermal runaway which are also illustrated by ΔTb (difference between the maximum and minimum values of temperature) in beef samples vs time plot. The similar analysis has been extended for all cases with oil layer directly attached with ceramic supports (Al2O3 and SiC). Based on the detailed analysis, the suitability of the support would be guided by factors such as optimal oil thickness, uniform heating and enhanced thermal processing within the beef sample.

Numerical Studies on Microwave Heating of Thermoplastic-Ceramic Composites Supported on Ceramic Plates

2010 ◽  
Vol 132 (7) ◽  
Author(s):  
Tanmay Basak ◽  
Sankaran Durairaj
Keyword(s):  
Ceramic Composite ◽  
Ceramic Composites ◽  
Thermal Runaway ◽  
Ceramic Plate ◽  
Uniform Heating ◽  
Processing Rate ◽  
Numerical Studies ◽  
Element Simulation ◽  
Al2o3 Composite ◽  
Alumina Composite

A detailed theoretical analysis has been carried out to study efficient microwave assisted heating of thermoplastic (Nylon 66) slabs via polymer-ceramic-polymer composite attached with ceramic plate at one side. The ceramic layer or plate is chosen as Al2O3 or SiC. The detailed spatial distributions of power and temperature are obtained via finite element simulation. It is found that uniform heating with enhanced processing rate may occur with specific thickness of Al2O3 composite, whereas SiC composite leads to enhanced processing rate with higher thermal runaway for thick Nylon samples attached with Al2O3 plate. SiC composite is effective due to enhanced processing rate, whereas Al2O3 is not effective due to reduced processing rate for thin samples attached with Al2O3 plate. For samples attached with SiC plate, thermal runaway is reduced by SiC composite, whereas that is not reduced by Alumina composite. Current study recommends efficient heating methodologies for thermoplastic substances with ceramic composite to achieve a higher processing rate with uniform temperature distribution.

Finite Elements for Curved Sandwich Beams

1977 ◽  
Vol 28 (2) ◽  
pp. 123-141 ◽  
Author(s):  
P J Holt ◽  
J P H Webber
Keyword(s):  
Finite Elements ◽  
Stiffness Matrix ◽  
Test Cases ◽  
Sandwich Beams ◽  
Honeycomb Core ◽  
The Core ◽  
The Face ◽  
Core Thickness ◽  
Displacement Approach ◽  
Circular Sandwich Ring

SummaryThe formulation of curved finite elements to represent a two-dimensional circular sandwich ring with honeycomb core and laminated faces is investigated. Assumed stress hybrid and equilibrium methods are found to be easier to employ in this case than the displacement approach. Using these methods, an element stiffness matrix is developed. The approximations of membrane faces and an infinite core normal stiffness are then used to develop simpler elements. Test cases show that these assumptions may become invalid, but that they are adequate for most practical cases where the core thickness to radius ratio and the face thickness to core thickness ratio are both low.

COLOR FACE SEGMENTATION USING A FUZZY MIN-MAX NEURAL NETWORK

2002 ◽  
Vol 02 (04) ◽  
pp. 587-601
Author(s):  
JUAN WACHS ◽  
HELMAN STERN ◽  
MARK LAST
Keyword(s):  
Neural Network ◽  
Color Model ◽  
Test Cases ◽  
Difficult Case ◽  
Automated Method ◽  
Hsv Color Model ◽  
Face Segmentation ◽  
The Face ◽  
Feature Information ◽  
Large Background

This work presents an automated method of segmentation of faces in color images with complex backgrounds. Segmentation of the face from the background in an image is performed by using face color feature information. Skin regions are determined by sampling the skin colors of the face in a Hue Saturation Value (HSV) color model, and then training a fuzzy min-max neural network (FMMNN) to automatically segment these skin colors. This work appears to be the first application of Simpson's FMMNN algorithm to the problem of face segmentation. Results on several test cases showed recognition rates of both face and background pixels to be above 93%, except for the case of a small face embedded in a large background. Suggestions for dealing with this difficult case are proffered. The image pixel classifier is linear of order O(Nh) where N is the number of pixels in the image and h is the number of fuzzy hyperbox sets determined by training the FMMNN.

Conduction Heating in RTP Fast, and Pattern-Independent

2008 ◽  
Vol 573-574 ◽  
pp. 375-386 ◽  
Author(s):  
Ernst Granneman
Keyword(s):  
Small Distance ◽  
Uniform Heating ◽  
Hot Plate ◽  
Pattern Density ◽  
Heating Effects ◽  
Lamp System ◽  
Gas Bearing ◽  
Very High ◽  
Conduction Heating

Various types of conduction-based RTP systems are discussed. It is shown that simple hot plate systems suffer from severe bow of the wafer, when placed directly on the susceptor. This results in non-uniform heating. A solution is to place the wafer on pins; however, this considerably reduces the heat-up rate. An effective way to heat wafers through conduction fast and wellcontrolled is by placing it in a so-called gas bearing, an arrangement in which the wafer floats in between two hot blocks, at a well-controlled, small distance from both blocks. The heat-up rate in this so-called Levitor system is very high (~900°C/s) and uniform. It is demonstrated that this conduction-based system does not suffer from non-uniformities caused by variations in emissivity and/or pattern density across-wafer or within-die. In a direct comparison on pattern-dependent heating effects, substrates with trenches with varying dimensions are spike-annealed in a state-ofthe- art lamp system and in the Levitor. It was shown that temperature non-uniformities in the lampbased and the conduction-based systems are > 40°C and < 1°C, respectively. The conclusion is that the Levitor provides emissivity and pattern-independent heating.

scholarly journals Pyrolysis and Combustion Kinetics of Disposable Surgical Face Mask Produced During Covid-19 Pandemic

2021 ◽  
Author(s):  
Arshad Adam Salema ◽  
Yasmin Mohd Zaifullizan ◽  
Wong Wai Hong
Keyword(s):  
Weight Loss ◽  
Face Mask ◽  
Chemical Processes ◽  
X Rays ◽  
Combustion Kinetics ◽  
Heating Rates ◽  
Safe Disposal ◽  
Model Free ◽  
The Face ◽  
Kinetics Of

Abstract In order to prevent the spread of Covid 19, most countries have made face masks compulsory. Millions of face mask are disposed of daily in the community. Therefore, the aim of the present paper is to study the thermo-chemical (pyrolysis and combustion) behavior of the face mask for its safe disposal. The kinetic parameter activation energy was calculated using both the model-based Coats–Redfern method and model-free methods (Flynn-Wall-Ozawa, Kissinger-Akihara-Sunose, and Starink) at four different heating rates (5, 10, 15, and 20 °C/min). Physical morphology with elemental analysis was performed using field-emission scanning electron microscopy and energy-dispersive X-rays. Results have shown that face masks decompose in the temperature range of 320–480 °C during pyrolysis with a maximum derivative weight loss of 2.5 %/°C. Combustion took place between 200 and 370 °C with a maximum derivative weight loss of 1.25 %/°C. The average activation energies calculated using model-free methods for pyrolysis and combustion were ~135 kJ/mol and ~65 kJ/mol, respectively. The leftover residue for both pyrolysis and combustion was in the range of 1.35 to 3.50 wt.%. In conclusion, thermo-chemical processes are a promising method for the safe disposal of face mask waste.

scholarly journals Mechanisms of structural-phase transformations during crystallization of a solder melt

2020 ◽  
Vol 6 (3-4) ◽  
pp. 27-34
Author(s):  
Anatoliy Kuzey ◽  
◽  
Vladimir Lebedev ◽  
Andrii Slipchuk ◽  
Pavel Tsykunov ◽  
...  
Keyword(s):  
Contact Interaction ◽  
High Frequency ◽  
Structural Phase ◽  
Iron Particles ◽  
Uniform Heating ◽  
Heating Rates ◽  
Problem Statement ◽  
Soldering Temperature ◽  
Copper Zinc ◽  
Structural Phase Transformations

Problem statement. An important requirement is quality assurance of joining materials with minimal overheating of materials, lowering the soldering temperature and suppressing the interaction of the solder with the materials to be soldered. The heating of the solder and the holder should be as uniform as possible and with a minimum temperature difference along the depth. One solution may be to develop more efficient solders and fluxes, adapted to the high heating rates that are typical when using high frequency currents Purpose. Thus, the problems of uniform heating of parts during brazing are relevant. This is necessary for optimal distribution of the electromagnetic field in the contact area Methodology. The effect of the heating rate was investigated. The composition of the flux and solders on the microstructure of the solders and the brazed seam was performed on the joints of HV510 (DIN), HS345 (DIN), HG30 (DIN) hardmetal plates with steel holders made of 5135 (USA) steel with a section of 25×20. Results. The research of the processes showed that during the contact interaction of low-melting and refractory components of the solders, when the tool was soldered, the solder is formed in the seam and proceeds through several stages. Practical value. Contact interaction of copper-zinc melts with iron particles does not lead to complete dissolution of iron particles. This is explained to the low values of the solubility of iron in copper-zinc melts despite the fact that resistive heat release occurs in the particles. Such iron particles (iron-based alloy) act as a dispersed phase in the structure of the composite material.

Maximizing the Power Extraction From Train Suspension Energy Harvesting System

2019 ◽  
Author(s):  
Luigi Costanzo ◽  
Massimo Vitelli ◽  
Yu Pan ◽  
Lei Zuo
Keyword(s):  
Power Output ◽  
Average Power ◽  
Railway Vehicle ◽  
Test Cases ◽  
Resistive Load ◽  
Load Case ◽  
Power Extraction ◽  
Optimal Load ◽  
Power Maximization ◽  
Energy Harvesting System

Abstract In this paper, an equivalent electric model for railway vehicle suspension harvester is proposed. With reference to the maximization of the extracted power, the open issues for such kinds of systems are reviewed. In particular, it is evidenced that the use of passive diode bridge rectifiers unavoidably leads to a reduction of power with respect to both the resistive load case and the theoretical optimal load case. Therefore, suitable average power maximization techniques and power electronics architectures are needed. In this paper, two techniques are proposed. The first technique is based on the adoption of additional passive components and, in the considered test cases, it allows the increase of the power output up to 45%. The second technique is based on the adoption of a properly controlled active power electronic interface and it is much more efficient since, in the considered test cases, it allows the increase of the power output up to 135%.

A model for the conservation of interactive electroacoustic repertoire: analysis, reconstruction, and performance in the face of technological obsolescence

2006 ◽  
Vol 11 (3) ◽  
pp. 273-284 ◽  
Author(s):  
DAVID BROOKE WETZEL
Keyword(s):  
Test Case ◽  
Test Cases ◽  
Interactive Electronics ◽  
Second Stage ◽  
Third Stage ◽  
Specific Device ◽  
The Face ◽  
Available Technology ◽  
And Performance ◽  
Stage Analysis

This paper presents a three-stage model (analysis, reconstruction and performance) for the conservation of interactive electroacoustic works for which the original technology is now obsolete or otherwise unavailable. The first stage, analysis, is a detailed documentation of the electronic processes and effects required for each work in a format that is independent of any specific device or system. The analysis provides a blueprint for future realisations using available technology. The second stage, reconstruction, provides a working performance resource, as well as a test case for the validity of the analysis. Reconstructed systems are then tested and refined through the third stage, performance. With repeated performances, compositions gain wider exposure and may be evaluated by listeners on their musical merits. To date, the author has analysed, reconstructed and performed several works for clarinet and interactive electronics. Each performance has informed the continued development of the newly reconstructed system, and has in some cases led to corrections to the underlying analysis. As a classically trained clarinettist and computer musician, the author's approach to the conservation of electroacoustic repertoire comes from a desire to find performable works and to keep them viable and accessible for as long as possible. Four works for clarinet and interactive electronics (by Musgrave, Pennycook, Kramer, and Lippe) are presented as test cases for this model.

THE DIFFERENTIAL THERMAL ANALYSIS OF NATURAL AND SYNTHETIC HYDRATES OF CALCIUM SULPHATE

1960 ◽  
Vol 38 (6) ◽  
pp. 936-943 ◽  
Author(s):  
W. E. P. Fleck ◽  
M. H. Jones ◽  
R. A. Kuntze ◽  
H. G. McAdie
Keyword(s):  
Heating Rate ◽  
Calcium Sulphate ◽  
Endothermic Effect ◽  
Exothermic Effect ◽  
Uniform Heating ◽  
Heating Rates ◽  
Sample Concentration ◽  
Naturally Occurring ◽  
Lower Temperature ◽  
Dehydration Behavior

A variety of naturally occurring forms of calcium sulphate dihydrate produce substantially identical differential thermograms under conditions of uniform heating rate and particle size. These thermograms closely resemble those for synthetic dihydrate and β-hemihydrate, showing four endothermic effects and one exothermic effect below 500 °C. Two of these endothermic effects, at about 170° and 300 °C, respectively, which have not been reported previously, were found to be easily masked by changes in heating rate or sample concentration. Resolution of the several effects was improved by using different heating rates at different stages of the thermogram. Thermograms of the α-hemihydrate were similar, except that the endothermic effect at 300 °C was not evident and the exothermic effect occurred at a much lower temperature than for the dihydrate. No conspicuous differences were found in the temperatures corresponding to the various endothermic and exothermic effects which might be correlated with the general dehydration behavior of the particular material. The endothermic effect at about 170 °C appears to be associated with part of the hemihydrate to soluble anhydrite transition, possibly arising during the removal of the last traces of water.

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