The objective of this research was to investigate the effects of twisted steel micro rebar (TSMR) fibers on 1) the mechanical properties of concrete used in bridge deck construction and 2) the early cracking behavior of concrete bridge decks. This research involved the evaluation of four newly constructed bridge decks through a series of laboratory and field tests. At each location, one deck was constructed using a conventional concrete mixture without TSMR, and one was constructed using the same conventional concrete mixture with an addition of 40 lb of TSMR per cubic yard of concrete. Regarding laboratory testing, the conventional and TSMR beam specimens exhibited similar average changes in height after 4 months of shrinkage testing. The electrical impedance measurements did not indicate a notable difference between specimens comprising concrete with TSMR and those comprising conventional concrete. Although no notable difference in behavior between conventional and TSMR specimens was apparent before initial cracking, the toughness of the TSMR specimens was substantially greater than that of the conventional concrete specimens. Regarding field testing, sensors installed in the bridge decks indicated that the addition of TSMR does not affect internal concrete temperature, moisture content, or electrical conductivity. The average Schmidt rebound number varied little between the TSMR decks and conventional decks; therefore, the stiffness of the TSMR concrete was very similar to that of conventional concrete. Distress surveys showed that the conventional decks exhibited notably more cracking than the TSMR decks. The TSMR fibers exhibited the ability to limit both crack density and crack width. For all of the decks, chloride concentrations increased every year as a result of the use of deicing salts on the bridge decks during winter. However, the chloride concentrations for samples collected over cracked concrete increased more rapidly than those for samples collected over non-cracked concrete. Although TSMR fibers themselves do not directly affect the rate at which chloride ions penetrated cracked or non-cracked concrete, the fibers do prevent cracking, which, in turn, limits the penetration of chloride ions into the decks. Therefore, the use of TSMR would be expected to decrease the area of a bridge deck affected by cracking and subsequent chloride-induced corrosion damage and thereby increase the service life of the bridge deck.

Spin-orbit coupling (SOC) is a relativistic effect whose origin lies in the Dirac’s equation – a relativistic analogue of Schrödinger’s equation. SOC corrects the electronic states of a quantum mechanical system up to ~1 eV in case of semiconductors and ~ 2 – 3.6 eV in case of actinides and heavy elements by considering not only the coordinates but also the spin of the electrons in the system. Most of the applications of the present day technology are based on manipulating the electronic structure of a system with very high accuracy and precision. This demands availability of correct electronic structure of a material or molecule within a feasible computational time. Some direct consequences of SOC in materials can be noticed in analyzing the charge-transport properties of a semiconductor, evaluating the candidature of transition metal dichalcogenides (TMDCs) for spintronic, twistronic and valleytronic applications, and in the origin of topological properties of a material. Not only in materials but also in molecules the SOC effects can be observed. Fine-structure of atomic spectra was explained on the account of SOC. Several additional peaks and wavelength shift in UV-vis spectroscopy of Gold Superatoms can only be explained by correctly considering the energy level splittings caused by SOC. SOC allows intersystem and reverse intersystem crossing by mixing the spin states, ultimately opening various chemical reaction pathways which were spin forbidden before. Current advancements in computational power enrich us to work shoulder to shoulder with experiments where one can simulate the synthesized structures containing thousands of atoms using semi-empirical methods as in DFTB, GFN-XTB. These methods so far considered SOC effects but only as case studies in testing the implementation of SOC Hamiltonian rather than a systemic extension of SOC parameters to most part of the periodic table and studying SOC effects for different categories of materials and molecules. This motivated us to implement the SOC either in the form of highly accurate parameters throughout the periodic table or as addition in hamiltonian in such methods. Twisted van der Waals 2D materials as in twisted TMDC bilayers shows exciting electronic and optoelectronic properties and depending on the twist angle and chemical composition they can have thousands of atoms in their superlattices. A correct electronic analysis of such structures with SOC corrected DFT is computationally very expensive but is feasible at semi-empirical level. Here, we have applied our implementation on TMDC homo and heterobilayer twisted superlattices and studied the effect of SOC on the excitonic properties of the system. Therefore, this work opens the way for realizing various exotic applications of present day materials as well as molecules.:Table of Contents Abstract 4 1 Introduction 8 1.1 Quantum Chemistry: 8 1.2 HF based Semi-Empirical Methods 9 1.3 DFT based Semi-Empirical Methods 11 1.3.1 Density Functional based Tight-Binding Method (DFTB) 11 1.3.2 Geometry, Frequency, Non-Covalent, extended Tight Binding (GFN-xTB) 12 1.4 Spin-Orbit Coupling (SOC) 14 1.4.1 SOC in Materials 18 1.4.2 SOC in Molecular Structures 22 1.5 Theoretical Models for Accounting SOC 24 1.6 Motivation, Objective and Outline of thesis 26 2 Methodology 29 2.1 Quantum Chemistry 30 2.1.1 Schrödinger equation 30 2.2 Density Functional Theory 33 2.2.1 Generalized Gradient Approximations 39 2.3 Spin-orbit Coupling (SOC) 41 2.3.1 Classical Picture of SOC in LS model 42 2.3.2 Quantum Picture of SOC in LS model: 43 2.3.3 Calculation of SOC Paramentes 45 2.4 Density Functional Based Semi-empirical Quantum Mechanical Methods 48 2.4.1 Self-Consistent Charge Density Functional Based Tight Binding Method (SCC-DFTB) 48 2.4.2 Extended Tight-Binding (GFN1-xTB) 51 2.4.3 Addition of Spin-Orbit Coupling Hamiltonian in DFTB and GFN-xTB 54 3 Benchmarking Spin-Orbit Coupling Parameters for DFTB 56 3.1 Introduction 58 3.2 Computational Details of the DFT benchmark calculations 60 3.3 Benchmarking Spin-Orbit Coupling Parameters 60 3.3.1 III-V Bulk Semiconductor 61 3.3.2 Transition Metal Dichalcogenide 2D Crystals 65 3.3.3 Topological Insulators 68 3.4 Conclusions 70 4 Spin-Orbit Coupling Corrections for the GFN-xTB method 71 4.1.1 Introduction 73 4.2 Computational Details of The Benchmark Calculations 75 4.3 Results & Discussion 76 4.3.1 Geometries 76 4.3.2 Effect of SOC on Charge Transport Properties of Chromophores in MOFs 77 4.3.3 Superatoms 82 4.3.4 Effect of SOC on Binding of O2 on Ferrous Deoxyheme 85 4.4 Conclusions 86 5 Spin Orbit Coupling Effects on The Excitonic Properties of Twisted Moiré Transition Metal Dichalcogenides 88 5.1 Introduction 90 5.2 Computational Details 92 5.3 Results & Discussions 93 5.4 Excitons in Twisted Moiré Homobilayers 93 5.5 Excitons in Twisted Moiré Heterobilayers 102 5.6 Conclusions 109 6 Summary 112 A. Acronym 116 B. Appendices 120 SOC Parameters 120 7 References 147 C. Acknowledgement 173

No description available.

<p>The aim of the research work presented here, is to contribute to the adaptation of electronic packaging towards the needs of high frequency applications. As the field of electronic packaging stretches over several very different professional areas, it takes an interdisciplinary approach to optimize the technology of electronic packaging. Besides this, an extensive knowledge of industrial engineering should be an essential part of this undertaking to improve electronic packaging. Customary advances in technology are driven by new findings and a continuous development of processes in clearly defined fields. However, in the field of the higher levels of the interconnection hierarchy, that is external to the chip level interconnections and chip packaging, it is supposed that a wide combination of disciplines and technical creativity, instead of advanced technology in a special area should produce most added value.</p><p>The thesis is divided into five areas, interlinked by the overall aim of there advantages to the common goal. These areas are the Printed Wiring Board (PWB) technology, PWB connections using flexible printed circuit boards, multiconductor cable connections, shielded enclosures and the related EMC issues, and finally the cooling of electronics. A central issue was to improve the shielded enclosures to be effective also at very high frequencies; it will be shown that shielded enclosures without apertures can cope with frequencies up to and above 15 GHz. Due to this enclosure without apertures, it was necessary to develop a novel cooling structure. This cooling structure consists of a heat sink where the PCB’s are inserted in close contact to the cooling fins on one side, whereas the other side of the heat sink is cooled by forced ventilation. The heat transfer between these parts is completely inside the same body. Tests carried out on a prototype have shown that the performance of the cooling structure is satisfactory for electronic cooling.</p><p>Another problem area that is addressed are the interconnect problems in high frequency applications. Interconnections between parts of a local electronic system, or as within the telecom and datacom field between subscribers, are commonly accomplished by cable connections. In this research work multiconductor cables are examined and a patented novel cable-connector for high frequency use is presented. Further, an experimental complex soldering method between flexible printed circuits boards and rigid printed circuits boards, as part of connections between PCBs, is shown. Finally, different sectors of the PCB technology for high frequency applications are scrutinized and measurements on microstrip structures are presented.</p>

This research comprises an experimental and theoretical study on convective boiling inside tubes containing twisted-tape inserts. The demand for more compact and efficient thermal systems, in which the heat exchangers plays an important role, has led to the development and use of various heat transfer enhancement techniques. Among them twisted-tape insert as a swirl flow device is one of the most used. Twisted-tape inserts have been used for over more than one century ago as a technique of heat transfer enhancement applied to heat exchangers. However, the heat transfer augmentation comes together with pressure drop increment, impacting the pumping power and, consequently, the system efficiency. Moreover, until now it is not clear, the operational conditions under which the heat transfer coefficient augmentation by the use of twisted-tape inserts overcomes pressure drop penalty. In the present study, initially, extensive investigations of the literature concerning convective boiling inside plain tubes with and without twisted-tape inserts were performed. This literature review covers pressure drop, heat transfer coefficient and the leading frictional pressure drop gradient and heat transfer coefficient predictive methods during convective boiling inside tubes with and without twisted-tape inserts. Then, pressure drop and heat transfer coefficient results acquired in the present study were obtained in an experimental apparatus of 12.7 and 15.9 mm ID tubes during flow boiling of R134a for twisted-tape ratios of 3, 4, 9, 14 and tubes without inserts, mass velocities ranging from 75 to 200 kg/m2 s, saturation temperatures of 5 and 15°C and heat fluxes of 5 and 10 kW/m2. The experimental results were parametrically analyzed and compared against the predictive methods from literature. An analysis of the enhancement of the heat transfer coefficient and the pressure drop penalty is presented. Heat transfer coefficient increments up to 45% keeping the same pumping power and pressure drop penalty of about 35% were obtained by using twisted-tape relative to tubes without inserts. Additionally, through comparison of the present study experimental results with the predictive methods from the literature for heat transfer coefficient during two-phase flow inside tube containing twisted-tape inserts, it was verified that non of these methods predict satisfactory well the experimental results. However, a new method was develop for predicting the heat transfer coefficient during flow boiling inside tubes containing twisted-tape inserts based on the experimental results obtained in the present study. The predictive method takes into account the physical picture of the swirl flow phenomenon by including swirl flow effects promoted by the twisted-tape inserts. The proposed method predicts satisfactorily well the data obtained in the present study, predicting 89.1% of the experimental data within an error band of ± 30% and absolute mean deviation of 15.7%. / A presente pesquisa trata-se de um estudo teórico e experimental sobre a ebulição convectiva no interior de tubos com fitas retorcidas. A crescente demanda por sistemas térmicos mais compactos e eficientes, nos quais os trocadores de calor apresentam elevada relevância, tem motivado o desenvolvimento de inúmeras técnicas de intensificação de troca de calor, sendo que a utilização de fitas retorcidas é uma das técnicas mais adotadas. Fitas retorcidas são utilizadas como técnicas de intensificação de troca de calor há mais de um século. Entretanto o incremento da transferência de calor é acompanhado do aumento da perda de pressão, que por sua vez implica em aumento da potência de bombeamento, e consequentemente afeta a eficiência global do sistema. Adicionalmente, até os dias de hoje não há consenso sobre as condições operacionais em que o ganho com o incremento do coeficiente de transferência de calor é superior à perda devido ao aumento da perda de pressão. Neste estudo, inicialmente foi realizada uma extensa revisão da literatura sobre a ebulição convectiva no interior de tubos com e sem fitas retorcidas. Esta revisão aborda aspectos relacionados à perda de pressão e ao coeficiente de transferência de calor, juntamente com os métodos de previsão destes parâmetros. Foram realizados experimentos para determinação experimental de perda de pressão e coeficiente de transferência de calor, em aparato experimental contando com tubos horizontais com diâmetros internos iguais a 12,7 e 15,9 mm, para escoamento bifásico de R134a, razões de retorcimento iguais a 3, 4, 9, 14 e tubo sem fita, velocidades mássicas entre 75 e 200 kg/m²s, temperaturas de saturação iguais a 5 e 15°C, e fluxo de calor iguais a 5 e 10 kW/m². Os resultados experimentais foram analisados e comparados com estimativas segundo métodos disponíveis na literatura. Uma análise do aumento do coeficiente de transferência de calor e da perda de pressão friccional é apresentada. Foram verificados incrementos do coeficiente de transferência de calor de até 45% para a mesma potência de bombeamento, e aumento de perda de pressão de aproximadamente 35% para tubos com fitas retorcidas em relação aos tubos sem fita. Adicionalmente, através da comparação dos resultados experimentais com os métodos de previsão para coeficiente de transferência de calor, foi verificado que nenhuma metodologia apresentava previsões satisfatórias dos resultados. Portanto um novo método para previsão do coeficiente de transferência de calor durante ebulição convectiva no interior de tubos com fitas retorcidas foi desenvolvido com base nos resultados experimentais obtidos durante o presente estudo. O método proposto é função de parâmetros geométricos e do escoamento, e também de parâmetros físicos do escoamento rotacional induzido pela fita. A metodologia desenvolvida apresenta previsões satisfatórias dos resultados experimentais, prevendo 89,1% dos resultados experimentais com erro inferior a ± 30% e erro médio absoluto igual a 15,7%.

No presente trabalho, estudamos alguns aspectos da teoria de estruturas complexas em espaços de Banach. Demonstramos que se um espaço de Banach real $X$ tem a propriedade $P$, então todas as estruturas complexas em $X$ também satisfazem $P$, quando $P$ é qualquer uma das seguintes propriedades: propriedade de aproximação limitada, \\emph{G.L-l.u.st}, ser injetivo e ser complementado num espaço dual. Abordamos o problema da unicidade de estruturas complexas em espaços de Banach com base subsimétrica, provando que um espaço de Banach real $E$ com base subsimétrica e isomorfo ao espaço de sequências $E[E]$ admite estrutura complexa única. Por outro lado, apresentamos um exemplo de espaço de Banach com exatamente $\\omega$ estruturas complexas distintas. Também usamos a teoria de estruturas complexas para estudar o clássico problema dos hiperplanos no espaço $Z_2$ de Kalton-Peck. Com o propósito de distinguir $Z_2$ de seus hiperplanos nos perguntamos se os hiperplanos admitem estrutura complexa. Nesse sentido, provamos que os hiperplanos de $Z_2$ contendo a cópia canônica de $\\ell_2$ não admitem estruturas complexas que sejam extensões de estruturas complexas em $\\ell_2$. Também construímos uma estrutura complexa em $\\ell_2$ que não pode-se estender a nenhum operador em $Z_2$. / In this work, we study some aspects of the theory of complex structures in Banach spaces. We show that if a real Banach space $X$ has the property $P$, then all its complex structures also satisfy $P$, where $P$ is any of the following properties: bounded approximation property, \\emph{G.L-l.u.st}, being injective and being complemented in a dual space. We address the problem of uniqueness of complex structures in Banach spaces with subsymmetric basis by proving that a real Banach space $E$ with subsymmetric basis and isomorphic to the space of sequences $E [E]$ admits a unique complex structure. On the other hand, we show an example of Banach space with exactly $\\omega$ different complex structures. We also use the theory of complex structures to study the classical problem of hyperplanes in the Kalton-Peck space $Z_2$. In order to distinguish between $Z_2$ and its hyperplanes we wonder whether the hyperplanes admit complex structures. In this sense we prove that no complex structure on $\\ell_2$ can be extended to a complex structure on the hyperplanes of $Z_2$ containing the canonical copy $l_2$. We also constructed a complex structure on $l_2$ that can not be extended to any operator in $Z_2$.

No presente trabalho, estudamos alguns aspectos da teoria de estruturas complexas em espaços de Banach. Demonstramos que se um espaço de Banach real $X$ tem a propriedade $P$, então todas as estruturas complexas em $X$ também satisfazem $P$, quando $P$ é qualquer uma das seguintes propriedades: propriedade de aproximação limitada, \\emph{G.L-l.u.st}, ser injetivo e ser complementado num espaço dual. Abordamos o problema da unicidade de estruturas complexas em espaços de Banach com base subsimétrica, provando que um espaço de Banach real $E$ com base subsimétrica e isomorfo ao espaço de sequências $E[E]$ admite estrutura complexa única. Por outro lado, apresentamos um exemplo de espaço de Banach com exatamente $\\omega$ estruturas complexas distintas. Também usamos a teoria de estruturas complexas para estudar o clássico problema dos hiperplanos no espaço $Z_2$ de Kalton-Peck. Com o propósito de distinguir $Z_2$ de seus hiperplanos nos perguntamos se os hiperplanos admitem estrutura complexa. Nesse sentido, provamos que os hiperplanos de $Z_2$ contendo a cópia canônica de $\\ell_2$ não admitem estruturas complexas que sejam extensões de estruturas complexas em $\\ell_2$. Também construímos uma estrutura complexa em $\\ell_2$ que não pode-se estender a nenhum operador em $Z_2$. / In this work, we study some aspects of the theory of complex structures in Banach spaces. We show that if a real Banach space $X$ has the property $P$, then all its complex structures also satisfy $P$, where $P$ is any of the following properties: bounded approximation property, \\emph{G.L-l.u.st}, being injective and being complemented in a dual space. We address the problem of uniqueness of complex structures in Banach spaces with subsymmetric basis by proving that a real Banach space $E$ with subsymmetric basis and isomorphic to the space of sequences $E [E]$ admits a unique complex structure. On the other hand, we show an example of Banach space with exactly $\\omega$ different complex structures. We also use the theory of complex structures to study the classical problem of hyperplanes in the Kalton-Peck space $Z_2$. In order to distinguish between $Z_2$ and its hyperplanes we wonder whether the hyperplanes admit complex structures. In this sense we prove that no complex structure on $\\ell_2$ can be extended to a complex structure on the hyperplanes of $Z_2$ containing the canonical copy $l_2$. We also constructed a complex structure on $l_2$ that can not be extended to any operator in $Z_2$.

Otto Scheeloch's U.S. Patent No. 134,442 of 1872 describes a unique firearm that uses triangular bullets. The current research effort evaluates the ballistic performance of Otto's disclosure for the very first time. To achieve this goal it was necessary to seek out surviving artifacts and scour the historical record in search of all the parameters needed to meticulously recreate the curious triangular cartridges and the corresponding gun barrel, with its matching twisted triangular bore. Every aspect of the resulting reproduction ammunition was made to be as authentic as possible, including the use of vintage civil war era bullet lead, bullet grease of period recipe, and the correct type of black powder propellant. 3D CAD (SolidWorksTM) was employed in designing the components, while advanced rapid prototyping (FDM & DMLS) techniques and investment casting were used in the physical construction of the ammunition and barrel. The ballistics testing was performed from a shooting rest over a range of 10-feet. Data was obtained for five rounds using a chronograph, paper targets and ballistic gel. The triangular bullets proved to be surprisingly accurate, consistent, and stable in flight. Data was recorded for sectional density, ballistic coefficient, muzzle velocity and energy, group size and penetration.

In this thesis, we investigate the propagation of some coherent and partially coherent laser beams, including a dark hollow beam (DHB), an elliptical Gaussian beam (EGB), a flat-topped beam and a twisted anisotropic Gaussian Schell-model (TAGSM) beam, through a paraxial optical system or a turbulent atmosphere. Several theoretical models are proposed to describe a DHB of circular or non-circular symmetry. Approximate analytical formulas for a DHB and a partially coherent TAGSM beam propagating through an apertured paraxial optical system are derived based on the generalized Collins formula. Analytical formulas for a DHB, an EGB, a flat-topped beam and a partially coherent TAGSM beam propagating in a turbulent atmosphere are derived in a tensor form based on the extended Huygens-Fresnel integral formula. It is found that after a long propagation distance these beams become circular Gaussian beams in a turbulent atmosphere, and this is quite different from their propagation properties in free space. The conversion of any of these beams to a circular Gaussian beam becomes quicker and the beam spot in the far field spreads more rapidly for a larger structure constant of the turbulent atmosphere, a shorter wavelength and a smaller waist size of the initial beam. Lower coherence and larger twist have a stronger effect of anti-circularization of the beam spot. Our analytical formulas provide a convenient way for studying the propagation of various laser beams through a paraxial optical system or a turbulent atmosphere. The concept of coincidence fractional Fourier transform (FRT) with an incoherent or partially coherent beam is introduced, and the optical system for its implementation is designed. The coincidence FRT is demonstrated experimentally with a partially coherent beam, and the experimental results are consistent with the theoretical results. / QC 20100831

The aim of the research work presented here, is to contribute to the adaptation of electronic packaging towards the needs of high frequency applications. As the field of electronic packaging stretches over several very different professional areas, it takes an interdisciplinary approach to optimize the technology of electronic packaging. Besides this, an extensive knowledge of industrial engineering should be an essential part of this undertaking to improve electronic packaging. Customary advances in technology are driven by new findings and a continuous development of processes in clearly defined fields. However, in the field of the higher levels of the interconnection hierarchy, that is external to the chip level interconnections and chip packaging, it is supposed that a wide combination of disciplines and technical creativity, instead of advanced technology in a special area should produce most added value. The thesis is divided into five areas, interlinked by the overall aim of there advantages to the common goal. These areas are the Printed Wiring Board (PWB) technology, PWB connections using flexible printed circuit boards, multiconductor cable connections, shielded enclosures and the related EMC issues, and finally the cooling of electronics. A central issue was to improve the shielded enclosures to be effective also at very high frequencies; it will be shown that shielded enclosures without apertures can cope with frequencies up to and above 15 GHz. Due to this enclosure without apertures, it was necessary to develop a novel cooling structure. This cooling structure consists of a heat sink where the PCB’s are inserted in close contact to the cooling fins on one side, whereas the other side of the heat sink is cooled by forced ventilation. The heat transfer between these parts is completely inside the same body. Tests carried out on a prototype have shown that the performance of the cooling structure is satisfactory for electronic cooling. Another problem area that is addressed are the interconnect problems in high frequency applications. Interconnections between parts of a local electronic system, or as within the telecom and datacom field between subscribers, are commonly accomplished by cable connections. In this research work multiconductor cables are examined and a patented novel cable-connector for high frequency use is presented. Further, an experimental complex soldering method between flexible printed circuits boards and rigid printed circuits boards, as part of connections between PCBs, is shown. Finally, different sectors of the PCB technology for high frequency applications are scrutinized and measurements on microstrip structures are presented. / QC 20101006