Chemical Vapor Deposition (CVD) Diamond is a promising technology for the passive cooling of high power Gallium Nitride (GaN) semiconductor devices. The high thermal conductivity diamond can be placed near the junction of the GaN transistor either by direct growth on the backside of the GaN or by bonding it to the GaN. In both cases, the thermal resistance near the interface with the diamond and any semiconductor it is attached to has the potential for large thermal resistance that limits the effectiveness of the diamond layer. In this work, several techniques are developed to understand the thermal conductivity of thin diamond films and the thermal boundary resistance with Si and GaN substrates. Anisotropic thermal conductivity measurements are made using Raman spectroscopy temperature mapping along with electric resistance heating. For devices, the thermal boundary resistance is measured using transistors as the heat source and thermal mapping using Raman spectroscopy. Quick screening methods based on Raman, Fourier Transform Infrared Spectroscopy (FTIR) and X-Ray Photoelectron Spectroscopy (XPS) are also correlated with the thermal properties of the films. Based on this work, the properties of CVD diamond films near the interface of semiconductor substrates is revealed for layers less than 5 µm in thickness and their impact or limitations on thermal management shown through simulations.

Buildings consume more than 30 percent of the primary energy worldwide with 65 percent of this attributed to heating ventilation and cooling. To help address this, stratified concrete panels (SCP) have been developed to provide insulation without compromising the thermal mass of concrete. SCP is created by vibrating a single concrete mix containing heavy and lightweight aggregates. Vibration causes the heavy aggregates drop to the bottom so that two distinct strata are formed; an internal structural/heavyweight layer providing thermal mass and an external lightweight layer for insulation. SCP incorporates waste products, for both financial and environmental gains, from which technical benefits also result. Stratified concrete panels have been made and tested during past research projects with results suggesting that SCP could be a competitive product in the residential construction industry, an area in which precast concrete systems have not been favoured in New Zealand. Consideration has been given to the specific rheological requirements of the concrete mix design and the hardened properties of the finished panels. This research considers the commercial viability of SCP using an industrial setting. For practicality of the setting, some materials were altered from past laboratory work to materials that are more easily sourced and better understood but with similar properties as those used previously. Several panels were cast at Stahlton precast yard in an effort to optimise the production process. Consistent results were not achieved and a range of stratification levels were produced. This showed that some capital investment is required to commercialise SCP to provide more energy for vibration such that sufficient stratification can be reliably attained. Two panels were then stood up in an exposed area with the exterior facing north to test for warping effects in a practical setting. No measurable warping occurred over this time which concurred with past work and long term readings that were taken of four year old panels. Structural, thermal and durability tests were carried out on panels with a range of stratification levels to assess the sensitivity of these properties to the level of stratification. From this it was found that the panels with better stratification had significantly better thermal properties than those with moderate to poor stratification. Generally the thermal targets for this project were not met with the total thermal resistance (R-values) not meeting current code requirements. In some cases structural properties were improved with better stratification as the structural layer was stronger through better consolidation. Delamination potential increased with stratification and with age. This requires further research to minimise this effect using fibres across the layer boundary. Porosity was increased in the structural layer in the poorly to moderately stratified panels as the structural layer was not consolidated enough due to lightweight aggregate contamination. As with any new innovation, market acceptance is largely governed by public perception. With appropriate marketing as a sustainable energy saving product, SCP has the potential to be competitive in the residential construction market with some capital investment.

No description available.

An evapotranspiration system was defined as six coupled, parallel subsystems defined by five rectangular and one radial, one-dimensional diffusion equations. A block diagram and system transfer function Were developed for each subsystem and the subsystems were coupled to obtain a block diagram of the evapotranspiration system. The soil heat transfer subsystem was assumed to be defined by the diffusion equation for a homogeneous soil of infinite depth with constant diffusivity and heat transfer by conduction only. The solution of the diffusion equation was obtained in the frequency domain as the frequency response function and in the time domain as the convolution integral. The frequency response function was used as an analytical model in the form of a gain and a phase function in conjunction with time series analysis to determine the system constant. A numerical solution of the convolution integral was used to determine soil heat diffusivity from arbitrary time distributions of temperature at two depths. The system response as the temperature at a depth was computed from an arbitrary time distribution of input temperature given the diffusivity. Results from time series analysis of analytically generated temperature data gave values for diffusivity from the gain and phase function of 16.24- and 16.21-cm²/hr, respectively. The value used to generate the data was 16.2 cm²/hr. The corresponding value of diffusivity obtained from a trial and error numerical convolution was 16.3 cm²/hr. Values of numerical convolution computed temperature, obtained after 72 hours to remove a starting transient, differed from the analytically correct temperatures by less than 0.1 ° C for an 8° amplitude or a 16° range. For 50 days of 6-hour interval temperatures the 95 percent confidence interval on diffusivity was within two percent of the analytically correct value. Soil temperature data for the 10- and 15-cm depth from an experiment where cold (4° C) irrigation water was applied, including the temperature data during the time of irrigation, was analyzed by time series analysis. The value of diffusivity obtained from time series analysis and the gain function was 14.7 cm²/hr compared to a range of 15.1 to 16.9 for amplitude and phase plots and 16.6 for a finite difference solution of the diffusion equation. The value from phase was 21.61 cm²/hr which is much higher due to the time-varying effects of diffusivity or improper alignment of the two time series. Confidence intervals for diffusivity were very wide because of the short period of record and because of heat transfer by moisture during the irrigation. Numerical convolution determined values of diffusivity of 15.1-and 14.9-cm²/hr for before and after irrigation indicated some change in soil heat diffusivity with time. Numerical convolution computed temperatures were within 0.17° C of the measured temperature except during and immediately after the application of the irrigation water. The maximum error between measured and computed temperature was 3.88° C. Time series analysis can be used to determine the soil heat diffusivity from arbitrary time distributions of temperatures at two depths. Confidence limits for diffusivity can be established by certain assumptions as a measure of the adequacy with which the diffusivity has been determined. Numerical convolution can also be used to determine soil heat diffusivity by trial and error from arbitrary time distributions of temperatures measured at two depths. Simulation of soil temperatures from arbitrary time distributions of measured input can be achieved by numerical convolution.

No description available.

Submitted in fulfillment of the academic requirements for the Masters of Applied Science (Chemistry), Durban University of Technology, Durban, South Africa, 2016. / In this work, the thermodynamic properties for the binary mixtures containing the ionic liquid (IL): 1-ethyl-3-methylimidazolium ethyl sulphate ([EMIM] [EtSO4]) were calculated. The binary systems studied were {pyridine (Py) or ethyl acetoacetate (EAA) or thiophene (TS) + [EMIM] [EtSO4]}. The results were interpreted in terms of the intermolecular interactions between the (pyridine + IL), (ethyl acetoacetate + IL), and (thiophene + IL) molecules. The physical properties: density, speed of sound, and refractive index were measured for the binary mixtures over the complete mole fraction range using an Anton Paar DSA 5000 M vibrating U- tube densimeter and an Anton Paar RXA 156 refractometer, respectively. The measurements were done at T = (298.15, 303.15, 308.15, 313.15, and 318.15) K and at p = 0.1 MPa. The experimental data was used to calculate the derived properties for the binary mixtures namely:- excess molar volume (V E ), isentropic compressibility (ks), molar refractions (R) and deviation in refractive index (Δn). For the binary mixtures, (Py or EAA or TS + IL), V E was negative throughout the whole composition range which indicates the existence of attractive intermolecular interaction between (pyridine + IL) and (ethyl acetoacetate + IL) for (thiophene + IL), V E was negative at low mole fraction of thiophene and became positive at high mole fraction of thiophene. For the binary mixtures (pyridine + IL), (ethyl acetoacetate + IL), ks was positive indicating that the binary mixtures were more compressible than the ideal mixture. For the binary mixture (thiophene + IL) ks was negative at low thiophene composition and positive at high composition indicating that the binary mixture was less compressible than the ideal mixture at low thiophene composition and more compressible at high composition of thiophene. The molar refraction, R, is positive for the (Py or EAA or TS + IL) binary systems at T = (298.15 – 318.15) K, molar refraction decreases as the organic solvent composition increases. For the binary mixture (pyridine + [EMIM] [EtSO4]), Δn is negative at mole fractions < 0.75 of pyridine and positive at mole fractions >0.75 at all temperatures and decreases with an increase in temperature. For the binary system (ethyl acetoacetate + [EMIM] [EtSO4]), Δn values are positive over the entire composition range and at all temperatures and increases with an increase in temperature. Δn values for the (thiophene + IL) system are negative for mole fractions of thiophene < 0.62 and becomes positive for mole fractions of thiophene > 0.62 and Δn increases with an increase in temperature. The Redlich-Kister smoothing equation was used successfully for the correlation of V E and Δn data. The Lorentz- Lorenz equation gave a poor prediction of V E , but a good prediction of density or refractive index. / M

Submitted in fulfillment of the academic requirements of the degree of Master of Technology, Durban University of Technology, Durban, South Africa, 2016. / The thermophysical properties of the binary mixtures containing biofuel components derived from biomass were determined. Experimental densities, speed of sound, and refractive indices for the binary mixtures (methanol or 1-ethyl-3-methylimidazolium acetate [EMIM][OAc] + furfural or furfuryl alcohol ) were measured at T = (298.15, 303.15, 308.15, 313.15 and 318.15) K. From the experimental data, excess molar volume, E m V , isentropic compressibility, s  , molar refractions, R, and deviation in refractive index, Δn, were calculated. The excess molar volumes were found to be negative for all systems studied. The isentropic compressibility were found to be both positive for the whole composition and temperature range and increases slightly with increasing temperature. The deviation in refractive index was positive over the whole composition range. The obtained values of excess molar volumes and changes of refractive index on mixing were satisfactorily correlated by the Redlich–Kister equation. The Lorentz–Lorenz equation was applied to predict the density and calculate the excess molar volume of the binary mixtures. / M

No description available.

by Chan Kwok Ming. / Chinese title in romanization: Yi wei xi tong re li xue xing zhi zhi Mengdikaluo yan jiu. / Thesis (M.Ph.)--Chinese University of Hong Kong, 1987. / Bibliography: leaf 69.

by Tong Kwok Wang. / Parallel title in Chinese characters. / Thesis (M.Phil.)--Chinese University of Hong Kong, 1990. / Bibliography: leaves 71-74. / Acknowledgement / Abstract / Chapter 1. --- Introduction / Chapter 1.1 --- General Introduction --- p.1 / Chapter 1.2 --- Properties --- p.5 / Chapter 1.3 --- Background of this research --- p.10 / Chapter 1.4 --- The Present Experiment --- p.11 / Chapter 2. --- Theory / Chapter 2.1 --- Conduction Mechanism --- p.15 / Chapter 2.2 --- Temperature Dependence of Thermal Conductivity --- p.16 / Chapter 2.3 --- Phonon Conductivity and phonon mean free path --- p.20 / Chapter 3. --- Experimental / Chapter 3.1 --- Thermal Diffusivity by Laser Photothermal Radiometry --- p.22 / Chapter 3.2 --- Resistivity Measurement --- p.30 / Chapter 3.3 --- Sample Preparation --- p.36 / Chapter 3.4 --- Data Analysis --- p.37 / Chapter 4. --- Results and Discussion / Chapter 4.1 --- Thermal Conductivity --- p.41 / Chapter 4.2 --- Electronic Thermal Conductivity --- p.47 / Chapter 4.3 --- Phonon Thermal Conductivity --- p.52 / Chapter 4.4 --- Phonon Mean Free Path --- p.58 / Chapter 5. --- Conclusion and Suggestions for Further Work --- p.68 / References --- p.71 / Appendixes --- p.75