This research project has developed a computer-assisted methodology whereby the temporal and spatial distribution of temperature in thick film circuits fabricated on ceramic substrates may be predicted. The analogy between thermal and electrical systems is used to define a thermal structure in electrical format which is then simulated using ASTEC3 electronic analysis package. Procedures have been developed whereby the three heat transfer mechanisms namely conduction, convection and radiation may be modelled. Models have also been proposed which allow the more important sections of a thermal structure to be analysed in finer detail. These procedures have been used hi the solution of some standard heat flow problems whose solutions have also been obtained by other more conventional techniques for comparison. Programs have been developed which facilitate the presentation of the results in the form of contour-maps or 3-D temperature distribution plots. Software has also been developed which can generate the electrical equivalent description of a device in ASTEC3 syntax. Estimates of the computing times required to carry out electro-thermal simulations of hybrid and VLSI devices have been made. The predicted computation times are feasible. Confirmatory experiments have been carried out in large scale using partially heated samples prepared from printed circuit boards. These were heated electrically and temperature measurements were made using an infrared thermometer. These structures were modelled and simulated using ASTEC3 for comparison. It was found that for an accurate thermal analysis there was a need for reliable data for the thermal conductivity of the glass-fibre laminate and the heat transfer coefficients of convection. Experiments were designed to measure the thermal conductivity of the laminates tangential to the plane of the boards. A standard Lees' disc apparatus was also used to measure this parameter in a direction normal to the boards. A Schlieren optics apparatus was used to study the convection plumes over the surface of the plates in a horizontal position with the heated side facing upwards which provided a significant insight into the flow regime over such surfaces. Values were subsequently determined for the convection coefficients from the boards. Using the measured thermal conductivities of FR4 boards and the estimated convection coefficients, excellent agreement was achieved between the measured and simulated results. Temperature measurements were also conducted at reduced dimensional scale on especially designed thick film resistor samples. The samples were fabricated by R.S.R.E and temperature measurements were carried out using a thermal imaging equipment manufactured by AGEMA. Again the Schlieren apparatus was used to observe the convection plumes forming over the devices which led to a better understanding of the heat transfer mechanism from such devices. These observations were then used to estimate the natural convection coefficients from the surface of horizontally positioned resistor samples which were then included in the ASTEC3 model of the devices. The subsequent ASTEC3 thermal simulation showed an excellent agreement with the measured temperature profile.

Thesis (MTech (Chemistry))--Cape Peninsula University of Technology, 2012. / Crystal engineering is the synthesis of new crystalline materials with specific chemical and physical properties which allows the comprehensive understanding of the non covalent interactions that occur between molecules in the crystalline state. This has lead to extensive work being done in terms of host design. The study of non-covalent interactions formed by - these materials is crucial to understanding many biological processes. This study focuses on the inclusion compounds of 1, 4-bis (diphenylhydroxymethyl) benzene H, a host compound engineered by EWeber, that conforms to Weber's rules for host design as it is bulky, rigid, and has hydroxyl moieties that act as hydrogen-bonding donors. A Cambridge Structural Database (CSDversion 5.33) search has revealed that no research has been conducted on this host compound. Characterization of the compounds were conducted using thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), hot stage microscopy (HS), gas chromatography (GC), powder X-ray diffraction(PXRD) and single X -ray diffraction. Host: guest ratios determined from TG analysis were correlated with structural analysis results. We have successfully prepared inclusion compounds with N, N- dimethylformamide(DMF) N, N- dimethylacetamide (DMA), N-methylformamide (NMF) and N-methylacetamide (NMA), 2-picoline, 3-picoline, 4-picoline, pyridine and morpholine. Following which a series of competition experiments were conducted to establish the selectivity profile of the host by dissolving the host in an excess of two guests pairs, between DMF: DMA, DMF: NMF, DMF: NMA, DMA: NMF, DMA: NMA and NMF: NMA. The results of the competition experiment showed that the host had high selectivity for DMF and the selectivity profile follows a trend as follows DMF>NMA>NMF>DMA. The results for the competition experiments between the picolines, pyridine and morpholine were inconclusive.

The capabilities of remote sensing can be utilized to map the thermal inertia of a surface. Thermal inertia is a property governing the temperature response of a medium to a heat flux at its surface and is beneficial to geologic mapping and soils stud ies. It is hypothesized that a method using only nighttime cooling will give a simple thermal inertia model requiring a minimum of input. Albedo and topographic slope and aspect data are not required. Since latent heat flux is commonly small at night the model should be applicable over surfaces of varying moisture content. The objective of this thesis is to develop a nighttime cooling model for remote sensing thermal inertia mapping. Three models (I, II, and III) are presented. They are based on solutions to the one-dimensional heat conduction equation for a semi-infinite homogeneous solid with isothermal initial temperature and time dependent boundary conditions of heat flux at the surface. Tests of the models on several soil types using ground based data indicate that all three models give meaningful relative relationships between thermal inertias and that model III often yields accurate quantitative results. For the remote sensing implementation of the model ground heat flux is determined as the residual of the energy balance of the surface. Thus, a procedure for determining net radiation using remotely sensed temperature is discussed. Also, aerodynamic heat transfer theory is used to develop a remote sensing method of estimating sensible heat flux. Corrections for the surface sublayer are necessary. Results for vegetated surfaces are expected to be unreliable. Latent heat flux is assumed to be zero or the average of several sites. Tests of these methods using ground based data give good results. An error analysis approach is used to estimate the errors resulting from a remote sensing implementation of Model III. Airborne thermal line-scan data and ground based micrometeorological observations are used to determine typical errors in the input parameters of the model. Errors in determining the energy balance components are also analyzed in detail. With good input, model III gives reasonable results (generally less than 50 percent probable error) at low thermal inertias (< 2000 J m⁻² C⁻¹ s⁻[sub ½] ). For surfaces of high thermal inertia, errors are large. The limitation of the model is not in the model itself, but in the accuracy of remotely sensed surface temperature as determined from thermal infrared line-scan surveys. For surfaces of low thermal inertia model III provides a simple thermal inertia mapping method which requires a minimum of input and is applicable over a wide variety of terrain and ground moisture conditions. The model is most suitable for the investigation of soils and may provide a useful model for planetary studies. / Land and Food Systems, Faculty of / Graduate

Thesis (Ph. D.)--Missouri University of Science and Technology, 2010. / Vita. The entire thesis text is included in file. Title from title screen of thesis/dissertation PDF file (viewed June 30, 2010) Includes bibliographical references (p. 129-135).

This thesis investigates the use of CO2 laser radiation to treat concrete surfaces. Specimens were treated with varying laser parameters, and the resultant surfaces were analysed mechanically and chemically. A glass was formed by laser interaction, with underlying decomposition of both the cement paste and aggregate. The application of a cement-based coating prior to processing protects the concrete from excessive temperature rises during treatment. Processing of the coated material resulted in a glazed surface with no decomposition of the concrete substrate. With low energy density, OPC concrete exhibits only surface dehydration. However, when the energy density is increased, a glassy layer, with surrounding and underlying dehydration, is formed. Increasing the spot size results in a change in behaviour when the material is laser treated: several mm of concrete are removed, leaving either rough, bare concrete or a glazed trench. The resulting surface condition is dependent on the laser power. Thermal analysis techniques were used to identify the degradation reactions and the temperatures at which they occur during laser treatment. These are dehydration of the ettringite and ferrite phases at 1149C, dehydration of Ca(OH)2 at 462C, decarbonation of CaCO3 and ejection of material from 8129C onwards and the formation of a fiised glass layer at 1283 `C. The strength of attachment of the glass to the concrete decreases with increasing power or decreasing traverse speed due to the dehydration of the underlying material. The strength also decreases with time after treatment, due to rehydration of CaO. Mechanical failure occurs several mm below the glassy area into the dehydrated substrate, where dehydration of Ca(OH)2 has caused disruption to the structure of the material. The temperature rise in the material was monitored using embedded thermocouples at various depths. A one dimensional theoretical model agrees well with the experimental results over only a limited range of depth and time. A three dimensional finite difference model shows close agreement with experimental results over a range of operating parameters equivalent to those determined experimentally. Operating maps were generated which predict the depths to which the identified reactions occur. II A combination of pozzolanic Portland cement, chamotte, sand and waterglass can be successfully applied to the concrete surface. It acts both as a thermal insulator and provides vitrifiable material for laser treatment. Low power levels drive water out of the coating resulting in dehydration and colour changes, whilst higher power levels result in the formation of a glass on the coating surface. The attachment of the glass shows an area of maximum strength when power levels are below 150 Watts and traverse speeds below 2mm/s. Beyond these parameters the attachment becomes progressively weaker. Thermal analysis of the coating material shows no evidence of Ca(OH)2 dehydration and no decarbonation, resulting in no ejection of material. The underlying concrete is unheated, and therefore undergoes no decomposition reactions. Mechanical failure occurs at the limit of the glassy region rather than several mm below it as with bare concrete. Thus, the weakest point is the interface of the glazed-unglazed regions now that no significant Ca(OH)2 dehydration occurs.

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Thesis (Ph. D.)--University of Washington, 1989. / Vita. Includes bibliographical references (leaves [261]-269).

Thesis (M. App. Sc.)--Carleton University, 2001. / Includes bibliographical references (p. 133-137). Also available in electronic format on the Internet.