This thesis documents the work and research effort on the design, fabrication and testing of a magnetocaloric MEMS microcooler, focusing on the testing of the microcooler at low magnetic fields. The phenomenon of magnetocaloric effect (MCE), or adiabatic temperature change, which is obtained by heating or cooling magnetic materials due to a varying magnetic field, can be exploited in the area of magnetic refrigeration as a reliable, energy-efficient cooling system. In particular, its applications are being explored primarily in cryogenic technologies as a viable process for the liquefaction of hydrogen. The challenge for magnetic refrigeration is that the necessary MCE is most easily achieved with high magnetic fields (5-6 Tesla) provided by superconducting magnets. However, a significant magnetocaloric effect can be exhibited at lower magnetic fields (1-2 Tesla) by carefully controlling initial temperature conditions as well as by selecting, preparing and synthesizing the optimal fabrication process of Silicon (Si) wafers. A microcooler was integrated based on previous works of others and tested. Finally, testing of the magnetocaloric effect was conducted and results analyzed. Experimental results in these domains demonstrate that magnetic refrigeration can be part of the best current cooling technology, without having to use volatile, environmentally hazardous fluids. The MEMS magnetocaloric refrigerator demonstrated a ~ -12°C change in the temperature of cooling fluid at a magnetic field of 1.2 T.

The evolution of human beings is marked by adaptation. The ability to adapt to and manipulate our environment is one definer of intelligence, and ours is unique among life on Earth. Since moving off of the African Continent, humans have migrated to inhabit every part of the Earth. Human existence and perpetuity in the universe depends upon the success of this adaptation, and inevitably, migrating off of this planet. The technological advances being developed today will change our way of life, and enable people to travel to and live permanently on the Moon and Mars. This study involves the architectural design and construction of a completely programmable permanent Martian settlement in the year 2050. Previous studies and proposals for Martian architecture rely mostly on existing technology. The first people are not expected to reach Mars until 2030, and new and emerging technologies will radically affect the designs being considered today. Technical challenges constrain designers of space architecture today, and scientific developments will solve many of these. This study seeks to explore how new technology can positively affect the architecture of the future, affording more comfortable and livable space on Mars. With a construction date of 2050, this project differs from others by benefitting from the next four decades of profound technological advancement. Leading Futurist Raymond Kurzweil predicts that the technological singularity is within this time frame, and that the 21st Century will, “Witness on the order of 20,000 years of progress (at today’s rate of progress) (Kurzweil, Law of Accelerating Change).” This thesis theorizes that nanotechnology will enable the deployment of a completely self-constructing and programmable permanent Martian settlement designed from a series of spatial modules. The anticipated results include a modular system of architectural spaces, and an increased awareness of the architectural benefits of emerging technologies as they relate to future space architecture.

published_or_final_version / Electrical and Electronic Engineering / Doctoral / Doctor of Philosophy

This dissertation consists of three essays in applied econometrics that analyze the strategic interactions between individuals and institutions. The first chapter examines the relationship between employee benefits and the performance of startups. Using national longitudinal data on startups, I find that an increase in the share of employee benefits in total compensation packages leads to increased productivity of startups. Results indicate that a 10 percent increase in the share of employee benefits leads to an increase ranging from 1.5 to 3.9 percent in productivity even if the returns to the employee benefits are heterogeneous across startups. I also find that an increase in the share of employee benefits increases the chance of survival of startups. The second chapter investigates the dynamics of employee screening and transitions from temporary to permanent employment. I analyze unique German data that contains specific information about the dynamics of the transition from temporary to permanent employment, I find that employers screen the abilities of employees only before they hire them. I find no evidence that employers screen the cognitive ability of employees during temporary employment. The third chapter examines the relationship between housing prices and the availability of curbside parking. Using a policy change in Istanbul as a quasi-experiment, this chapter explores the effect of Istanbul’s switch from informal and free curbside parking to formal and paid curbside parking on housing prices. In a differences-in-differences model coupled with a propensity score matching, we find that an exogenous change in the availability of parking leads to a statistically significant decrease in house prices. We estimate that house prices per square meter decrease by 13 percent in the neighborhoods where the city starts charging curbside parking spaces. However, rents stay the same compared to the other neighborhoods. / text

Not available

The observation of a permanent electric dipole moment (EDM) in a non-degenerate system would indicate the violation of discrete symmetries of Time reversal (T) or combined application of Charge (C) and Parity (P) symmetry violation through the CPT theorem. The diamagnetic 225Ra atom with nuclear spin I=1/2 is a favorable candidate for an EDM search. Experimental sensitivity to its EDM is enhanced due to its high atomic mass and the increased Schiff moment of its octupole deformed nucleus. An experimental setup is developed where laser cooled neutral radium atoms are collected in a magneto-optical trap (MOT). The collected atoms are transported 1 meter with a far off-resonant optical dipole trap (ODT) and then the atoms are transferred to a second standing-wave ODT in an experimental chamber. The atoms are then optically polarized and allowed to Larmor precess in parallel and antiparallel electric and magnetic fields. The difference between the Larmor precession frequency for parallel and antiparallel fields is experimentally determined to measure the EDM. This thesis is about the first measurement of the EDM of the 225Ra atom where an upper limit of |d(225Ra)|<5.0*10-22 e cm (95\% confidence) is reached.

By September 2010, in its ongoing effort to clarify the subject of taxing a permanent establishment, the OECD launched a new article 7 in its model tax convention together with a revised version of the report on the attribution of profits to permanent establishments. The article and the report contain a new order of taxation, where a permanent establishment should, in almost all aspects, be treated as a separate entity. The question is if the new approaches, methods and solutions provided by the article and the report will prove effective against double taxation. The thesis has studied this by analysing and then comparing the OECD’s authorised approach with the relevant literature and the current practical situation. The result of the thesis presents that there are problems with the approaches and methods, which in some situations will cause double taxation, not the least regarding allocation of Free Capital. The thesis also concludes that the way in which article 7 of the model tax convention tries to solve double taxation without unnecessary use of the mutual agreement procedure is flawed in relation to differences in national legislation.

This dissertation presents the development of an anisotropic viscoplastic continuum damage model to describe the permanent deformation of asphalt pavements. The model is developed to account for several phenomena that influence the permanent deformation of Asphalt Concrete (AC) at high temperatures. These phenomena include strain rate dependency, confining pressure dependency, dilation, aggregate friction, anisotropy, and damage. The model is based on Perzyna's theory of viscoplasticity with Drucker-Prager yield function modified to account for the microstructure anisotropy and damage. A parametric study was conducted to study the effect of key factors such as inherent anisotropy and damage on the model response. A preliminary investigation was conducted to demonstrate the capabilities of the model and its sensitivity to changes in the microstructure distribution and loading conditions. The model was used to describe laboratory experimental measurements obtained from the Federal Highway Administration (FHWA) Accelerated Loading Facility (ALF). The model had a good match with these experimental measurements. In particular, using the damage parameter, the model was able to capture the point at which AC experienced tertiary creep in a static creep test. A comprehensive experiment was conducted to systematically determine the model parameters and the evolution laws that describe AC hardening, anisotropy, and damage. The experiment consisted of a set of compressive triaxial strength tests conducted at three confining pressures and five strain rates. Based on these experimental measurements, the model was modified to include a nonassociated flow rule. The model was shown to capture the experimental measurements very well. Furthermore, an experiment was conducted to capture and characterize damage evolution in AC due to permanent deformation. AC specimens were loaded using a triaxial compression setup to four predefined strain levels at three confining pressures. X-Ray computed tomography and image analysis techniques were used to capture and characterize the evolution of cracks and air voids in the deformed specimens. Damage was found to be a localized phenomenon in the sense that there exists a critical section in an AC specimen that is mainly responsible for failure. The results of the damage experiment supported the damage evolution function proposed in the viscoplastic model.

The current standard electrical downhole machine is the induction machine which is relatively inefficient. Permanent magnet (PM) machines, having higher efficiencies, higher torque densities and smaller volumes, have widely employed in industrial applications to replace conventional machines, but few have been developed for downhole applications due to the high ambient temperatures in deep wells and the low temperature stability of PM materials over time. Today, with the development of variable speed drives and the applications of high temperature magnet materials, it is increasingly interesting for oil and gas industries to develop PM machines for downhole applications. Recently, some PM machines applications have been presented for downhole applications, which are normally addressed on certain specific downhole case. In this thesis the focus has been put on the performance investigation of different PM machines for general downhole cases, in which the machine outer diameter is limited to be small by well size, while the machine axial length may be relatively long. The machine reliability is the most critical requirement while high torque density and high efficiency are also desirable. The purpose is to understand how the special constraints in downhole condition affect the performances of different machines.  First of all, three basic machine concepts, which are the radial, axial and transverse flux machines, are studied in details by analytical method. Their torque density, efficiency, power factor and power capability are investigated with respect to the machine axial length and pole number. The presented critical performance comparisons of the machines provide an indication of machines best suitable with respect to performance and size for downhole applications. Conventional radial flux permanent magnet (RFPM) machines with the PMs on the rotor can provide high torque density and high efficiency. This type of machine has been suggested for several different downhole applications. Flux-switching PM (FSPM) machines, which have the PMs located on the stator and are therefore more reliable, can theoretically also exhibit high torque density and relatively high efficiency. This thesis has put an emphasis on studying this type of machine. Two FSPM machines have been investigated in detail and compared by analytical method, FEM simulation and prototype measuremens. Their operating principle and important design parameters are also presented. A lumped parameter magnetic circuit model for designing a high-torque FSPM machine is newly introduced and the designed machine is verified by FEM simulations. A prototype machine with an outer diameter of 100 mm and an axial length of 200 mm is built in the laboratory and tested at room temperature. Based on that, the machine performance at an ambient temperature of 150°C is also predicted. The results show that the FSPM machine can provide a high torque density with slight compromise of efficiency and power factor. Choosing a proper machine type is significantly dependent on the application specifications. The presented results in this thesis can be used as a reference for selecting the best machine type for a specific downhole case.

Magistro baigiamajame darbe išanalizuota nuolatinės buveinės samprata fizinėje erdvėje ir ją nustatantys kriterijai, bei atskleistas minėtų kriterijų turinys. Vadovaujantis nustatytais kriterijais išanalizuota nuolatinės buveinės samprata elektroninėje komercijoje ir pateiktos priemonės, kuriomis remiantis nustatoma nuolatinė buveinė elektroninėje komercijoje, nurodytos galimos problemos ir esami problemų sprendimo būdai, bei identifikuotos, kai kurios naujos problemos, kurios reikalauja tolimesnio tyrimo. Pirmojoje darbo dalyje aptarta nuolatinės buveinės samprata fizinėje erdvėje ir išskirti pagrindiniai kriterijai, turintys įtakos nustatant nuolatinės buveinės buvimo faktą fizinėje erdvėje. Antroje dalyje atsižvelgiant į nustatytus kriterijus išanalizuota nuolatinė buveinė elektroninėje komercijoje ir nustatyti skirtumai ir panašumai su nuolatine buveine fizinėje erdvėje. Trečioje darbo dalyje ištirta užsienio valstybių ir Lietuvos praktika nuolatinės buveinės kontekste. / This master‘s degree thesis is about permanent establishment in physical space and it’s parameters. These parameters and definition of permanent establishment are analyzed in details. In accordance with the criteria laid down in the analysis, conception of permanent establishment in e-commerce was reviewed and remedies for identification of permanent establishment were proposed for e-commerce. Also in this thesis major problems related to permanent establishment and their existing resolutions are considered, including new problems identified that should be analyzed collaterally. In the first chapter of this thesis conception of permanent establishment in physical space is analyzed and main criteria that have direct or indirect impact to identification of permanent establishment in physical space are excluded. The second chapter is dedicated for analysis of permanent establishment in e-commerce and identification of principal discrepancies and similarities, while comparing it with physical space. In the third chapter of this thesis survey of Lithuania’s and other foreign countries’ practices related to permanent establishment is presented.