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Thesis (M.S.)--Ohio State University. / Includes bibliographical references (leaves 79-81). Available online via OhioLINK's ETD Center

The reliability of electronic component plays an important role in proper functioning of the electronic devices. The manufacturer tests electronic components before they are used by end users. Still at times electronic devices fail due to undue stresses existing inside the microelectronic components such as memory chips, microcontrollers, resistors etc. The stresses can be caused by variation in the operating voltage, variation in the usage frequency of the particular chip and other factors. This variation leads to variation in chip temperature, which can be made evident from thermal profiles of these chips. In this thesis, effort was made to study two different kind of stress existing in the electronic board, namely signal stress based on variation in duty cycle/frequency of chip usage and the voltage stress. Memory chips were stressed using these stresses causing change in heating rates, which were captured by infrared camera. This data was then extracted and plotted to obtain different curves for the heating rate. The same experiment was done time and again for a large number of chips to get heating rate data. This data consisting of average heating rate for large number of chips was used to build Neural Network model (NN). Back Propagation algorithm was used for modeling because of its advantage of converging to solution faster compared to other algorithms. To develop a prediction model, data sets were divided into two-third and one-third parts. This two-thirds of the data was used to build the prediction model and remaining one third was used to evaluate the model. The designed model would predict the stress levels existing in the chips based on the heating rates of the chips. Results obtained suggested 1. There is difference in heating rate for chips stressed at different stress levels. 2. Accuracy of the model to predict the stress is high (greater than 90 %). 3. Model is robust enough that is it can yield efficient results even if there is presence of noise in the data. 4. Generic methodology can be proposed based on the experiments. This work is a progress in direction of making predictive model, for a complete electronic device, which can predict the stress level existing on any component in the device and will provide an opportunity to either protect the data or removal of the defected components timely before it even fails.

Acrylamide is considered a carcinogen in animals and a possible carcinogen in humans. It has been found in starch rich foods cooked at high temperatures. Vacuum frying (10 Torr) was studied as a possible alternative to reduce acrylamide formation in potato chips. Seven potato cultivars were analyzed to determine their influence on acrylamide formation during traditional and vacuum frying. The White Rose cultivar produced the highest level of acrylamide during both traditional and vacuum frying. Vacuum frying (10 Torr, 118oC, 8 min) produced chips with lower acrylamide content than those produced under traditional frying (165oC, 4 min) for all cultivars. The cultivar Atlantic was used to determine the kinetics of acrylamide formation during traditional and vacuum frying at different temperatures because it is a good chipping cultivar and it was the most abundant in the lab. Acrylamide accumulation under vacuum frying was modeled using first-order kinetics, and during traditional frying it was modeled using the logistic kinetic model. The behavior of the kinetics of acrylamide content in potato chips fried under the two processes was different mainly due to the different temperatures used. During traditional frying, higher temperatures areused (150oC to 180oC) and acrylamide after some time is produced but also starts degrading, producing a constant level of acrylamide content at longer times. During vacuum frying (10 Torr), acrylamide increased exponentially (but at lower levels) for all frying times. The effect of potato components was studied by infusing leached potato slices with predetermined amounts of glucose and asparagine. Increasing glucose and asparagine content in the slices increased the acrylamide content in the potato chips. Color could not be used as an indication of acrylamide content, since potato chips with similar color had very different acrylamide concentrations.

The reliability of electronic component plays an important role in proper functioning of the electronic devices. The manufacturer tests electronic components before they are used by end users. Still at times electronic devices fail due to undue stresses existing inside the microelectronic components such as memory chips, microcontrollers, resistors etc. The stresses can be caused by variation in the operating voltage, variation in the usage frequency of the particular chip and other factors. This variation leads to variation in chip temperature, which can be made evident from thermal profiles of these chips. In this thesis, effort was made to study two different kind of stress existing in the electronic board, namely signal stress based on variation in duty cycle/frequency of chip usage and the voltage stress. Memory chips were stressed using these stresses causing change in heating rates, which were captured by infrared camera. This data was then extracted and plotted to obtain different curves for the heating rate. The same experiment was done time and again for a large number of chips to get heating rate data. This data consisting of average heating rate for large number of chips was used to build Neural Network model (NN). Back Propagation algorithm was used for modeling because of its advantage of converging to solution faster compared to other algorithms. To develop a prediction model, data sets were divided into two-third and one-third parts. This two-thirds of the data was used to build the prediction model and remaining one third was used to evaluate the model. The designed model would predict the stress levels existing in the chips based on the heating rates of the chips. Results obtained suggested 1. There is difference in heating rate for chips stressed at different stress levels. 2. Accuracy of the model to predict the stress is high (greater than 90 %). 3. Model is robust enough that is it can yield efficient results even if there is presence of noise in the data. 4. Generic methodology can be proposed based on the experiments. This work is a progress in direction of making predictive model, for a complete electronic device, which can predict the stress level existing on any component in the device and will provide an opportunity to either protect the data or removal of the defected components timely before it even fails.

Licentiatavhandling Linköping : Linköpings universitet, 2009.

Diss. Linköping : Univ., 2005.

This work was carried out to determine and quantify the mechanism whereby oil was transferred into potato slices during frying. At the same time processing variables were identified and examined to determine the effect of each variable on oil uptake. Samples of potatoes of the variety Record UK were sliced, using a commercial slicer, and fried in "Sizzle", a 50:50 blend of hydrogenated soya and palm oils. The moisture loss / oil uptake was examined at 145°C, 165°C, 185°C by frying samples for 0–5 minutes at 30 second intervals. It was found that oil uptake, a temperature independent effect in the range examined, was related to moisture loss and that moisture loss was a diffusion controlled process. Mass transfer data were analysed to determine the diffusion coefficients at each of the three frying temperatures. Thermal changes in the frying medium and in the core of the slices were measured to examine the heat transfer process during frying and its relationship to mass transfer. Attempts were made to determine the process of thermal transfer and thermal diffusivities were calculated using the unsteady state heat transfer equations. The thermal changes occurring were not able to be characterised in any simplified form. The processing variables of frying time (0–5 minutes), temperature (145°C–185°C), slice thickness (40–70 thousandths of an inch) and initial solids content (20–24.4%) were used to examine the effect of each variable on the yield of product and its oil content. Use of equations included allow oil uptake to be modified by determined amounts by controlling initial solids content or slice thickness. Frying process modifications are suggested to exploit the determined effects of pre-fry drying and salt blanching to lower oil uptake. Pre-fry drying using hot air or microwave processing will reduce the final oil content by known amounts depending on the drying operation time. A freeze drying process will increase oil uptake also by a known amount. The effect of blanching on oil uptake was measured using time (1–4 minutes), temperature (60–80 °C) ionic component (sodium and calcium cations) and ionic concentration (0–2.0 M) as variables. Salt blanching in solutions of sodium or calcium chloride will reverse the trend in oil uptake increase identified in hot water blanching. Throughout the course of the work structural changes were examined by microscopic analysis of sections taken using a cryostatic ultramicrotome. Sections were differentiated using vapour stains such as iodine and osmic acid. To locate oil in the prepared slices a technique was developed in the laboratory involving frying in oil containing 0.5g litre-1 of the lipo-selective stain oil Red O. Photographs and photomicrographs are included in this report.

The commercial rotary dryers used to dry wood wafers (of approximate dimensions 0.63 mm thick, 50 mm wide and 76+ mm long) for the production of panelboard are modified versions of agricultural dryers and have not been designed for the optimal drying of wood wafers. The lack of available information on wafer drying necessitated that the first goal of this research was the characterization of wafer drying behaviour. After the important parameters of wafer drying were identified, the applicability of fluidized bed technology to wafer drying was assessed and an industrial size dryer was designed. The proposed fluidized bed wafer dryer was then compared to a commercial rotary dryer in terms of energy efficiency. Wafer drying behaviour was investigated in two factorial experiments. Three lengths of wafers (25 mm, 44 mm and 63 mm) were individually dried in a 0.15 m draft tube at temperatures of 90°C, 120°C and 150°C. The statistical analysis of the resultant drying rate curves showed that the drying behaviour of aspen wafers was influenced by the effect of wafer length on the external heat and mass transfer rates to the wafer surface, and on the length of internal pathways for bulk flow and diffusion of water. The external drying conditions had a decreasing effect on drying rate until about 10% moisture content at which time drying became limited by internal heat and mass transport. The initial assessment of fluidized bed technology for wafer drying used a 0.15 m semi-cylindrical column for the determination of wafer drying rate curves and wafer behaviour in a fluidized bed of inert particulate solids at excess superficial velocities of 0.25 to 1.0 m/s. Wafer drying times in a bed of 0.5 mm sand at 150°C were about 40% of the drying times for wafers dried by forced convection of air at the same temperature and twice the superficial velocity (~ 1 m/s). Wafer movement in the fluidized bed followed the circulation patterns of the emulsion phase and was thus dependent on the bubbling behaviour of the bed. A minimum excess superficial velocity of 0.25 m/s (depending on distributor design) was required to prevent permanent settling of the wafers to the distributor. Preliminary experimentation on a 2-compartment bed showed that wafers could be circulated through the two compartments in near plug flow. However, the application of this technique to a 4-compartment continuous fluidized bed wafer dryer was unsuccessful because of the separation of sand and wafers caused by slugging beds in two of the compartments. A preliminary design was prepared for an industrial size, 5-compartment fluidized bed wafer dryer to approximate plug flow of wafers by a series of well-mixed fluidized beds in series. The design calculations showed that this dryer was more efficient in terms of energy and plant space than a conventional triple pass rotary dryer. / Applied Science, Faculty of / Chemical and Biological Engineering, Department of / Graduate