By partly replacing the use of primary energy sources with waste heat recovery, climate and environmental goals for the future will be closer at hand. This thesis investigates the waste heat potential of Alfa Laval’s vacuum brazing furnaces in Ronneby and alternative ways of integrating the furnace’s waste heat into the building’s HVAC system. The main challenge was the low-temperature qualities associated with the cooling water, which constituted an obstacle to recovering waste heat without any additional equipment, such as a heat pump. Tests and analyses performed in this thesis are, therefore, mainly aimed at raising the temperature quality of the cooling water. A test was conducted on the cooling system to calculate the energy losses with regards to the cooling water. In one 11-hour cycle, 1546 kWh of electricity was used to heat the furnace. Out of that, 1360 kWh was cooled off to the atmosphere. Additionally, a test on the furnace’s clean-up cycle was performed. The maximum cooling water temperature reached during this test was 44 C. This shows excellent potential in the possibility of recovering the waste heat without any additional equipment. Further, this thesis aims to broaden the knowledge around areas concerning increased cooling water temperatures, which, during the writing, seemed to have a gap in documented sources. The results of this thesis indicate that a temperature quality increase of the furnaces’ cooling water is possible. Cooling system changes have also been suggested, which is necessary for an efficient and safe heat recovery.

This work discusses the modification and analysis of the Blue Thermal Vacuum Chamber (TVAC) located at the Space Environments Lab at California Polytechnic State University, San Luis Obispo. The modified design has a cylindrical test section and can accommodate 6U Cubesats or larger for educational or research purposes. The sizing process for the modified shroud cooling system and modular heating plates is discussed. The modified cooling system uses existing nitrogen plumbing into the chamber and control systems with a new copper shroud. The modified heating system uses modular heater plates, which utilize the existing three heater strips. The modified system includes high emissivity coatings for improved heat transfer performance, lower thermal mass materials to minimize thermal mass and liquid nitrogen consumption, and modular components for flexibility in operation. Analysis presented shows correlation between experimental results and a steady state thermal model using SolidWorks and SolidWorks Flow Simulation. The results demonstrate a maximum absolute difference in modeled vs experimental temperatures at measured locations of 11C in all cases, and 3C for test article temperatures only. Chamber performance is compared and characterized through a series of thermal vacuum tests and demonstrates capability exceeding ISO 19683 requirements for all thermal vacuum chamber testing categories except tolerance, with a tested temperature range of -145C at the shroud to 95C at the heater plates, >10 cycles between -15C and 55C, dwells in excess of 3 hours, ramp rates of 1-2C/min, and chamber pressures under

A novel strategy for site-specific DNA transformation of plants has been proposed and the first component of the system developed. The proposed method overcomes the limitations of current techniques by providing a specific integration site for the insertion of transgenes using features of the adeno-associated virus (AAV) life cycle. In the absence of helper virus, AAV integrates into a specific location on human chromosome 19, the AAVS1 locus. The sequence for AAV integration was introduced into the model plant Arabidopsis thaliana using Agrobacterium tumefaciens-mediated transformation. A portion of the human AAVS1 sequence, including the Rep binding site (RBS) and terminal resolution site (TRS), was cloned between T-DNA borders of the Agrobacterium Ti plasmid. The reporter gene, b-glucuronidase (GUS) was inserted proximal to AAVS1 in the plasmid for use in screening for the presence of T-DNA. In addition, it will serve as an indicator of the expression level expected for transgene inserted into AAVS1 by recombinant AAV. PCR amplification, dideoxy sequencing, GUS expression assays and genomic Southern blots were performed to examine putative transgenic plants for the presence of the AAVS1 sequence. / Master of Science

To ensure the safe operation of high-voltage direct current grids, circuit breakers are used to disconnect a faulty link from the rest of the grid. Incorporating vacuum interrupters as a part of these circuit breakers constitutes an outstanding technology for such DC interruptions. However, testing the interrupters take a long time and can be very expensive. Hence, to reduce the time and cost of testing the interrupters, the purpose of this project was to find the most important parameters to test in a vacuum interrupter to evaluate it for use in a DC circuit breaker. This was done by modeling the particle density, before and after current-zero, and the post-arc current using a new model along with existing ones. Review of existing research was also included to support the models in order to draw conclusions regarding reignitions and restrikes. dI/dt before current-zero, dV /dt after current-zero, and contact gap length were found to be the key contributors for reignition, while temperature, contact surface condition and contact gap length were of great importance for restrikes. These breakdowns should occur around the center of the contact surface, or at surface protrusions. The following parameters should be varied when testing vacuum interrupters: dI/dt before current-zero, ranging from 10 A µs−1 to 800 A µs−1; arcing current, from 1 kA to 20 kA; arcing time, from 1 ms to 4 ms before current-injection; dV /dt after current-zero, from 0.5 kV µs−1 to 20 kV µs−1; maximum TRV from 5 kV to 25 kV, to find the threshold voltage for failed interruption; and gap length, from 1 mm to 10 mm, to find the critical gap length. Furthermore, temperature should also be measured, though measuring postarc current seems to be of lesser importance. To minimize damage to the interrupter, it was recommended to start with higher gap lengths with low values on everything else. / För att säkerställa ett stabilt kraftflöde för högspända likströmsnät används brytare för att isolera defekta delar från resten av nätet. Vakuumbrytare kan utgöra en viktig komponent i sådana likströmsbrytare. Att testa brytarna tar dock lång tid och kan bli mycket dyrt. För att minska på tiden och kostnaderna för att testa brytarna, var syftet med detta projekt att hitta de viktigaste parametrarna att testa i en vakuumbrytare för att utvärdera den för användning i en likströmsbrytare. Detta gjordes genom att modellera partikeldensiteten före och efter nollgenomgången i strömmen, och strömmen som uppstår efter den nollgenomgången genom att använda en ny modell med hjälp av äldre modeller. Granskning av befintlig forskning inkluderades också för att stödja modellerna och dra slutsatser om nytändning och återtändning. dI/dt före strömnollgenomgången, dV /dt efter strömnollgenomgången, bågströmmen och kontaktseparationen visade sig vara nyckelparametrar för nytändning. Temperaturen, kontaktytstillståndet och kontaktseparationen var av stor betydelse för återtändning. Dessa elektriska urladdningar hade en högre sannolikhet att ske närmare mitten av kontaktytan eller vid små spetsiga ojämlikheter. Följande parametrar bör varieras vid testning av vakuumbrytare: dI/dt före strömnollgenomgången, från 10 A µs−1 till 800 A µs−1 ; strömmen före strömnollgenomgången, från 1 kA till 20 kA; ljusbågstiden, från 1 ms till 4 ms; dV /dt efter strömnollgenomgången, från 0.5 kV µs−1 till 20 kV µs−1 ; maximala TRV, från 5 kV till 25 kV, för att hitta tröskelspänningen för misslyckat brytning; och kontaktseparationen, från 1 mm till 10 mm. Att mäta strömmen efter strömnollgenomgången verkade vara av mindre betydelse. Dock föreslogs det att mäta temperaturen på vakuumbrytaren. För att minimera skador på brytaren rekommenderades det att börja testandet med högre kontaktseparationer med låga värden på allt annat.

No abstract provided. / Thesis / Doctor of Philosophy (PhD) / Scope and contents: The principal aim of the present investigation is to extend our knowledge of the merits and demerits of the mass spectroscopic method of solid analysis. This dissertation provides information concerning relative ionization efficiencies for several elements and factors which effect these efficiencies. Secondary purposes of this work are 1) to make an independent determination of the temperature of the vacuum spark, 2) to resolve the current discrepancy concerning the value of the C3+/C2+ ratio from graphite electrodes in a spark and, finally, 3) to provide an accurate value for the Ni58/Ni60 abundance ratio.

<p> The properties and device applications of silicon thin films vacuum evaporated both onto single crystal silicon and onto silicon dioxide substrates have been investigated. </p> <p> The feasibility of obtaining device quality homoepitaxial silicon thin films by vacuum evaporation onto non heat-treated substrates having temperatures of 700°C has been demonstrated. A new technique, that of gas-doping, has been developed and has been shown to be capable of reproducibly introducing controlled concentrations of doping impurities in the range applicable to device fabrication into the deposited layers. The combined deposition-doping technique has been employed in the production of silicon layers containing impurity steps more abrupt than may be obtained by conventional fabrication techniques. </p> <p> The electrical properties of the vacuum evaporated homoepitaxial silicon layers have been shown to be comparable in most respects to those of bulk high purity single crystal silicon. The characteristics of rectifying and of varactor diodes prepared by the technique of vacuum evaporation combined with gas doping have been considered. </p> <p> Silicon films evaporated onto Si02 substrates have been shown to possess structures ranging from amorphous through randomly oriented polycrystalline to oriented polycrystalline as the substrate temperature is increased from 25°C to 850°C. The electrical characteristics of doped polycrystalline films obtained both by vacuum evaporation combined with gas doping and by the diffusion-annealing of amorphous films have been shown to be comparable with those reported for similar material deposited by chemical techniques. The experimentally observed properties of the disordered material have been qualitatively explained employing an inhomogeneous film model. The suitability of thin films of doped polycrystalline silicon on sio2 substrates for the production of high value resistors for monolithic integrated circuits has been considered. </p> / Thesis / Doctor of Philosophy (PhD)

<p> The deposition parameters of thin vacuum-evaporated films were studied in the development of thin-film devices. These devices, including resistors, diodes and transistors, were constructed by the use of vacuum deposition techniques and metal masks for pattern generation.</p> <p> Stable thin-film resistors were fabricated using nichrome as the resistance material. The variation of resistance value with both temperature and time was investigated.</p> <p> A metal-cadmium sulphide-metal structure was employed as a thin-film diode, the electrodes being of aluminium or gold. The electrical evaluation of such a device demonstrated the importance of the deposition of the semiconductor on the rectifying properties. Forward to reverse resistance ratios of 10^5 were observed for experimental units.</p> <p> The staggered-electrode structure was incorporated in the production of thin-film transistors. Cadmium sulphide was used as the semiconducting material while silicon monoxide and aluminium were used as the insulator and electrodes respectively. Operating devices exhibiting good saturation characteristics has transconductances of 450μ mhos. Simple circuits were constructed to demonstrate the performance of thin-film transistors. (</p> / Thesis / Master of Engineering (MEngr)

Within the high-performance composite manufacturing industry, there exists a need to improve the reliability of LCM (Liquid Composite Molding) manufacturing processes in producing composite parts that better approach the quality and consistency of pre-impregnated composite tapes that are cured in autoclaves with cost being a driving factor of this need. One obstacle to that end is the phenomenon of void formation during the LCM infusion processes. The formation of these voids through different mechanisms leads to composite parts with lower mechanical properties and consistency than their pre-impregnated autoclave cure counterparts. The objective of this research is to investigate the different mechanisms through which voids form during LCM processes as well as potential actions that can be taken to reduce the total percent volume of voids that form during the infusion. This research also aims to investigate the correlation of the void content observed at the tool-ply interface compared to the void content through the thickness of composite laminates. Finally, this research investigates the effect that chemical modification of the wettability of carbon fiber fabrics has on void formation during infusions.

Metastable states are classically stable at zero temperature but can decay due to quantum tunneling. The rate of this process is exponentially small and it may be computed in Euclidean space in the Coleman-de Luccia formalism. The exponential suppression is determined by the Euclidean action computed on a trajectory with definite boundary conditions, known as Coleman-de Luccia instanton, or bounce. In some theories, the bounce may not exist or its on-shell action may be ill-defined or infinite, thus hindering the vacuum decay process. The issue of vacuum stability is, in fact, not just speculation: the Standard Model vacuum state is itself metastable. The Higgs field may tunnel outside its potential well, with catastrophic consequences for all observers. Luckily, the typical lifetime of such a state is predicted to be very long. Still, unknown high energy physics can change it by several orders of magnitude, and particle physics theories as well as cosmological models that predict large decay rates are ruled out thanks to the anthropic principle. Moreover, gravitational effects play an important role in this process, especially in the early Universe. It is thus important to examine in detail vacuum decay phenomena in gravitational settings and to keep the underlying field theory as general as possible. This thesis aims at exploring existence conditions for the Coleman-de Luccia instanton in gravitational settings. The first two chapters are dedicated to outlining the basic formalism and describing preexisting results about vacuum decay in cosmology. The Euclidean path integral approach for decay rate calculations, which was first discussed by Callan and Coleman, is introduced in Chapter 1. A quantum mechanical description of the problem is formulated and then extended to field theory. A detailed analysis of bounce calculations and their physical interpretation as bubbles of true vacuum follows. The Higgs field stability within the Standard Model is also addressed. Gravitational effects on the vacuum decay process are considered in Chapter 2, by focusing on the decay from Minkowski and de Sitter space, as they have important cosmological consequences respectively in the current Universe (due to the smallness of the cosmological constant) and at early times. The implications on Higgs decay are discussed in both settings. The last two chapters are dedicated to new results. Vacuum decay in field theories with a scalar field and quadratic gravity is investigated. An Einstein-Hilbert term, a non-minimal coupling, and a quadratic Ricci scalar are considered while keeping the scalar field potential general. The focus is on decay from Minkowski and de Sitter space, due to their importance in cosmology. Scalar fields with Einstein-Hilbert gravity are discussed in Chapter 3, by showing that the bounce at large Euclidean radii has an analytical form that is almost entirely independent of the potential, which is called the "asymptotic bounce". Bounds on the Hubble parameter in the de Sitter case are also explored, by giving an analytical explanation to numerical evidence present in the literature. These properties are used, in Chapter 4, to test for stabilization of the false vacuum state in quadratic gravity. Conclusions follow.

No description available.