Phase Change Materials (PCM) absorb and release heat at preset temperatures. Due to their relatively high values of latent heat, they are capable of storing and releasing large amounts of energy during phase change. When a PCM is in its solid phase, it will absorb heat as the external temperature rises. The temperature of the PCM will mirror the external temperature until the melting point of PCM is reached. At this stage, the PCM will begin to melt with almost no change in its temperature. PCM plays an opposite role when the external temperature drops. It releases the stored energy back while going through phase change from liquid phase to solid phase. The present work is a numerical study towards fundamental understanding of the impact of using PCM on enhancement of heat and mass transfer in several scenarios. A numerical analysis has been carried out to determine the impact of presence of PCM on the insulating characteristics of paper board packaging. Two different cases of a layered PCM and uniformly dispersed PCM within the packaging wall are considered. The numerical results illustrate significant reduction in exchange of heat between the exterior and the interior of the packaging. Specifically, the unique concept of utilizing PCM in drying of paper is proposed and a numerical investigation is performed to determine the corresponding transport characteristics. The results indicate that the PCM acts as a heat source and a heat sink alternatingly throughout the conventional paper drying process, enhancing the drying energy efficiency. This study also included presence of gas-fired infrared emitters in the drying process as well for which the spectral absorption coefficient of PCM was measured and incorporated into the theoretical model. Finally, the impact of the presence of PCM in convective air-drying of moist paper is numerically investigated. The hot air ow is generated by an in-line jet nozzle. The air impinges on the exposed surface of the moist paper while the other side is considered to be perfectly insulated. The results provide the corresponding air flow field as well as air temperature distribution in between the nozzle exit and the surface of the moist paper. The results also reveal the enhancement of drying rates with PCM, fundamentally confirming the role of PCM on enhancing the energy efficiency of convective drying of moist paper.

No / The heat balance integral method is a familiar technique for treating transport problems, particularly phase-change scenarios. Here a number of differences arising in the method's implementation are investigated that result in quantitatively distinct solutions. As a consequence some guidance is provided for selecting the appropriate implementation of the method.

Neutron radiography is well suited to non-invasive imaging of water within metal containers. The goal of this work is to determine if neutron radiography can be used to image water freezing within a 1.6mm diameter capillary tube with the ultimate goal of observing this phenomena within fuel cells. In this work, radiography was completed at the Thermal Neutron Imaging Facility in the Nuclear Engineering Teaching Lab at The University of Texas at Austin. The source of neutrons was a TRIGA Mark II nuclear research reactor capable of 1.1 MW steady state power, which creates a neutron flux at the neutron imaging plane in beam port 5 of 5×10^6 neutrons/cm^2s. A scintillation screen and CCD camera are utilized to obtain digital radiographs, in which differences in pixel intensity are related to differences in neutron attenuation. An image processing algorithm was developed in Matlab to extract necessary data from each image, analyze water column images, and compare one to another. Also, a neutron flux model was implemented in Matlab in order to understand how a non-unidirectional neutron flux will affect final results. Raw image intensities of the water column in liquid and solid form were found to differ from expectations by at most 12.0% and 13.3%, respectively from the predictions of the Matlab flux model. A difference in pixel intensity comparing liquid water to solid water data is apparent and quantified. A ratio of pixel intensity for the ice image to the water image at full thickness of the water column is expected to be 1.038. Experimental results find a maximum ratio of 1.027, 1.1% off from expectations. / text

In this thesis, some fundamentals and possible applications of high-pressure microfluidics have been explored. Furthermore, handling fluids at high pressures has been addressed, specifically by creating and characterizing strong microvalves and pumps. A variety of microstructuring techniques was used to realize these microfluidic devices, e.g., etching, lithography, and bonding. To be able to handle high pressures, the valves and pumps need to be strong. This necessitates a strong actuator material. In this thesis, the material of choice is paraffin wax. A new way of latching paraffin-actuated microvalves into either closed or open position has been developed, using the low thermal conductivity of paraffin to create large thermal gradients within a microactuator. This allows for long open and closed times without power consumption. In addition, three types of paraffin-actuated pumps are presented: A peristaltic high-pressure pump with integrated temperature control, a microdispensing pump with high repeatability, and a pump system with two pumps working with an offset to reduce flow irregularities. Furthermore, the fundamental behavior of paraffin as a microactuator material has been explored by finite element modeling. One possibility that arises with high-pressure microfluidics, is the utilization of supercritical fluids for different applications. The unique combination of material properties found in supercritical fluids yields them interesting applications in, e.g., extraction and cleaning. In an attempt to understand the microfluidic behavior of supercritical carbon dioxide, the two-phase flow, with liquid water as the second phase, in a microchannel has been studied and mapped with respect to both flow regime and droplet behavior at a bi-furcating outlet.

The aggressive scaling of CMOS technology, to reduce device size while also increasing device performance, has reached a point where continuing improvement is becoming increasingly problematic and alternative routes for the development of future memory and processing devices may be necessary; in this thesis the use of phase-change and carbon based materials as one such alternative route is investigated. As pointed out by Ovshinsky [1, 2] some phase-change material should be capable of non-binary arithmetic processing, multi-value logic and biological (neuromorphic) type processing. In this thesis, generic, nanometre-sized, phase-change pseudodevices were fabricated and utilised to perform various types of computational operations for the first time, including addition, subtraction, division, parallel factorization and logic using a novel resistive switching accumulator-type regime in the electrical domain. The same accumulator response is also shown to provide an electronic mimic of an integrate-and-fire type neuron. The accumulator-type regime uses fast electrical pulses to gradually crystallize a phase-change device in a finite number of steps and does not require a multilevel detection scheme. The phase-change materials used in this study were protected by a capping layer of sputtered amorphous carbon. It was found that this amorphous carbon layer also underwent a form of resistive switching when subjected to electrical pulses. In particular, sputtered amorphous carbon layers were found to switch from an initially high resistivity state to a low resistivity state when a voltage pulse was locally applied using a Conductive Atomic Force Microscope (CAFM) tip. Further experiments on amorphous carbon vertical pseudo-devices and lithographically defined planar devices showed that it has potential as a new material for Resistive Random Access Memory (ReRam) applications. The switching mechanism was identified as clustering of the sp2 hybridized carbon sites induced by Joule heating. It was not possible to reset the devices back to their initial high resistivity state presumably due to the highly conductive nature of sputtered amorphous carbon.

A mathematical model is developed to describe the micro/nano-scale fluid flow and heat/mass transfer phenomena in an evaporating extended meniscus, focusing on the transition film region under nonisothermal interfacial conditions. The model incorporates thermocapillary stresses at the liquid-vapor interface, a slip boundary condition on the solid wall, polarity contributions to the working fluid field, and binary mixture evaporation. The analytical results show that the adsorbed film thickness and the thin film length decrease with increasing superheat by the thermocapillary stresses, which influences detrimentally the evaporation process by degrading the wettability of the evaporating liquid film. In contrast, the slip effect and the binary mixture enhance the stability of thin film evaporation. The slip effect at the wall makes the liquid in the transition region flow with smaller flow resistance and thus the length of the transition region increases. In addition, the total evaporative heat flow rate increases due to the slip boundary condition. The mixture of pentane and decane increases the length of the thin film by counteracting the thermocapillary stress, which enhances the stability of the thin film evaporation. The polarity effect of water significantly elongates the thin film length due to the strong adhesion force of intermolecular interaction. The strong interaction force restrains the liquid from evaporation for a polar liquid compared to a non-polar liquid. In the experimental part, laser induced fluorescence (LIF) thermometry has been used to measure the microscale temperature field of a heated capillary tube with a 1 mm by 1 mm square cross section. For the temperature measurement, the calibration curve between the temperature and the fluorescent intensity ratio of Rhodamine-B and Rhodamine-110 has been successfully obtained. The fluorescent intensity ratio provides microscale spatial resolution and good temperature dependency without any possible bias error caused by illuminating light and background noise usually encountered in conventional LIF techniques. For the validation of the calibration curve obtained, thermally stratified fields established inside a glass cuvette of 10 mm width were measured. The measurement result showed a good agreement with the linear prediction. The temperature measurement in a 1 mm capillary tube could provide the feasible method of temperature measurement for the thin film region in the future.

The cost of new cultivar development is high due to long juvenile periods and large tree size in tree fruit breeding programs. For apples, sour cherries, and saskatoon berries, grafting seedling scions onto the tips of branches of mature plants was hypothesized to shorten the juvenile period and reduce land use under the Canadian prairie conditions. For apples, a tip grafting system (tip grafting onto mature crabapple rootstocks) was compared with the traditional grafting system (grafting onto young Ottawa 3 rootstocks). Apple scions of Golden Delicious, McIntosh, and SK Prairie Sun which exhibit a range of inherent cold hardiness, were grafted in the spring of 2001. Over a two year period, winter survival of the scions was improved by 37% by the tip grafting system as compared to the traditional grafting system making it not feasible for evaluation of cold hardiness of scions. Vegetative growth of scions approximated the rootstocks on which the scions were grafted. Winter survival was highly correlated with shoot growth cessation (r = +0.83) and terminal bud stage (r = +0.85) observed around the time of first frost. Juvenile seedlings of saskatoon berry and sour cherry hybrids were tip grafted onto mature plants of their own species in the spring of 2000. After two growing seasons, the tip grafting system in sour cherries had reduced flowering by 69.7%, shoot length by 84%, and shoot diameter by 76% compared with the juvenile seedlings on their own roots (scion donors). Tip grafting saskatoon berry seedlings increased flowering by 68%, shoot length by 257%, and shoot diameter by 42% compared with scion donors. For sour cherries, the tip grafting system reduced winter dieback by 99.6%, hastened terminal bud development and leaf drop compared with the scion donors. Tip grafting of saskatoon berry seedlings had little effect on terminal bud development and cold hardiness of scions perhaps due to the cold hardy character of this species. For apples and sour cherries, the tip grafting system tested in this study enhanced cold hardiness of scions when combined with the appropriated rootstocks and may be useful for maintaining germplasm that otherwise would not be hardy in northern locations.

The cost of new cultivar development is high due to long juvenile periods and large tree size in tree fruit breeding programs. For apples, sour cherries, and saskatoon berries, grafting seedling scions onto the tips of branches of mature plants was hypothesized to shorten the juvenile period and reduce land use under the Canadian prairie conditions. For apples, a tip grafting system (tip grafting onto mature crabapple rootstocks) was compared with the traditional grafting system (grafting onto young Ottawa 3 rootstocks). Apple scions of Golden Delicious, McIntosh, and SK Prairie Sun which exhibit a range of inherent cold hardiness, were grafted in the spring of 2001. Over a two year period, winter survival of the scions was improved by 37% by the tip grafting system as compared to the traditional grafting system making it not feasible for evaluation of cold hardiness of scions. Vegetative growth of scions approximated the rootstocks on which the scions were grafted. Winter survival was highly correlated with shoot growth cessation (r = +0.83) and terminal bud stage (r = +0.85) observed around the time of first frost. Juvenile seedlings of saskatoon berry and sour cherry hybrids were tip grafted onto mature plants of their own species in the spring of 2000. After two growing seasons, the tip grafting system in sour cherries had reduced flowering by 69.7%, shoot length by 84%, and shoot diameter by 76% compared with the juvenile seedlings on their own roots (scion donors). Tip grafting saskatoon berry seedlings increased flowering by 68%, shoot length by 257%, and shoot diameter by 42% compared with scion donors. For sour cherries, the tip grafting system reduced winter dieback by 99.6%, hastened terminal bud development and leaf drop compared with the scion donors. Tip grafting of saskatoon berry seedlings had little effect on terminal bud development and cold hardiness of scions perhaps due to the cold hardy character of this species. For apples and sour cherries, the tip grafting system tested in this study enhanced cold hardiness of scions when combined with the appropriated rootstocks and may be useful for maintaining germplasm that otherwise would not be hardy in northern locations.

Over the past several decades, memory technologies have exploited continual scaling of CMOS to drastically improve performance and cost. Unfortunately, charge-based memories become unreliable beyond 20 nm feature sizes. A promising alternative is Phase-Change-Memory (PCM) which leverages scalable resistive thermal mechanisms. To realize PCM's potential, a number of challenges, including the limited wear-endurance and costly writes, need to be addressed. This thesis introduces novel methodologies for encoding data on PCM which exploit asymmetries in read/write performance to minimize memory's wear/energy consumption. First, we map the problem to a distance-based graph clustering problem and prove it is NP-hard. Next, we propose two different approaches: an optimal solution based on Integer-Linear-Programming, and an approximately-optimal solution based on Dynamic-Programming. Our methods target both single-level and multi-level cell PCM and provide further optimizations for stochastically-distributed data. We devise a low overhead hardware architecture for the encoder. Evaluations demonstrate significant performance gains of our framework.

Non-volatile memories are an emerging storage technology with wide applica- tions in many important areas. This study focuses on new storage techniques for flash memories and phase-change memories. Flash memories are currently the most widely used type of non-volatile memory, and phase-change memories (PCMs) are the most promising candidate for the next-generation non-volatile memories. Like magnetic recording and optical recording, flash memories and PCMs have their own distinct properties, which introduce very interesting data storage problems. They include error correction, cell programming and other coding problems that affect the reliability and efficiency of data storage. Solutions to these problems can signifi- cantly improve the longevity and performance of the storage systems based on flash memories and PCMs. In this work, we study several new techniques for data storage in flash memories and PCMs. First, we study new types of error-correcting codes for flash memories – called error scrubbing codes –that correct errors by only increasing cell levels. Error scrubbing codes can correct errors without the costly block erasure operations, and we show how they can outperform conventional error-correcting codes. Next, we study the programming strategies for flash memory cells, and present an adaptive algorithm that optimizes the expected precision of cell programming. We then study data storage in PCMs, where thermal interference is a major challenge for data reliability. We present two new coding techniques that reduce thermal interference, and study their storage capacities and code constructions.