A Thermal Energy Storage (TES) system is meant for holding thermal energy in the form of hot or cold materials for later utilization. A TES system is an important technological system in providing energy savings as well as efficient and optimum energy use. The main types of a TES system are sensible heat and latent heat. A latent heat storage is a very efficient method for storing or releasing thermal energy due to its high energy storage density at constant temperatures, and a latent heat storage material can store 5-14 times more heat per unit volume than a sensible heat storage material can. Phase Change Materials (PCMs) are called latent heat storage materials. PCMs can save thermal energy, and use energy efficiently because PCMs can absorb thermal energy in the solid state, and the thermal energy can be released in the liquid state. Therefore, PCMs as new materials for saving energy can be applied into building applications. PCMs have been widely researched, but the current issues are lack of accurate and detailed information about thermophysical properties of PCMs to apply to buildings and inaccurate materials properties measured by existing methodology. The objective of this study is to develop a methodology and procedure to accurately determine the thermophysical properties of PCMs based on salt hydrates. TES systems of PCMs are measured and analyzed by various methods, such as DSC method and heat flow method. In addition, this study demonstrates to design a building roof with PCMs to save energy using Finite Element Analysis (FEA). The developed methodology is designed based on ASTM C1784-14, Standard Test Method for Using a Heat Flow Meter Apparatus for Measuring Thermal Storage Properties of Phase Change Materials and Products, for measuring the thermal energy storage properties of PCMs. The thermophysical properties and thermal stabilities are evaluated by using a Differential Scanning Calorimetry (DSC), which is made with DSC Q 200 equipment from TA Instruments and DSC STA 8000 equipment from Perkin Elmer Company. The thermal conductivities are assessed by heat flow meter, which is FOX 314 equipment from TA Instruments, and the enthalpy changes of the PCMs are determined by DSC method and heat flow method. Numerical FEA to evaluate potential energy savings is conducted using ABAQUS software. Four types of Phase Change Materials (PCMs), which have phase changes at 21ºC, 23ºC, 26ºC, and 30ºC, respectively, are used for measuring the thermophysical properties. The onset/peak temperature, the enthalpy, the heat flow, and the heat capacity of the PCMs are measured to assess the thermal energy storage system under the dynamic DSC mode. The results obtained using DSC equipment have a higher melting temperature than their own temperatures, which are known theoretically. The freezing temperatures of the PCMs are decreased by about 30ºC ~ 40ºC compare to their theoretical freezing temperatures. It is speculated that supercooling happens during the solidification. The enthalpy change curves as a function of temperature, which are determined by DSC method and heat flow method, are indicated to assess thermal energy storage system of the PCMs. During the phase change, the energy is increased. This is the reason why the energy is utilized to loosen or break apart the molecular or atomic bond structures of the PCMs by the latent heat. Moreover, the enthalpy change curves determined by heat flow method show more precise results than the curves by DSC method, because various factors lead to a temperature gradient in the PCM and the heat flux signal peak being shifted toward high temperatures. Regarding the thermal conductivities results of the PCMs, the thermal conductivities of the PCMs in the solid state are higher than those of the PCMs in the liquid state. This phenomenon happens due to the effect of the microstructure changing from the orderly solid structure in the solid state to the disorderly liquid structure in the liquid state. The numerical Finite Element Analysis (FEA) is conducted to evaluate potential energy savings of a roof. The results, such as the temperature variations from the outdoor to indoor measured under step 1 (the daytime) condition, show that the outdoor temperatures are higher than the indoor temperatures. This is due to the low thermal conductivity of the PCM in the liquid state. The low thermal conductivity of the PCM reduces the heat transmission to the indoor that in turn increases the outdoor temperature. This study shows the developed methodology and procedure, the accurate material information for the newly developed PCM, and the numerical FEA to analyze the TES systems with much more precision in the area of the PCMs.

During the operation of phase-change ink-jet printers a bubble formation phenomenon often occurs. These bubbles are detrimental to the operation of the printer and substantial efforts are made to remove them. The objective of this research was 1: to develop a fundamental understanding of how bubble or void formation occurs during the phase-change process, and, 2: to develop a simple computer model to simulate this behavior which can then be used as a tool for better design of print-head geometries. Preliminary experimental work indicated the void formation to be a result of the density change accompanying the phase-change process. The commercial numerical code, Flow 3-D, was used to model the phase-change process in print-head geometries and substantiate certain simplifying assumptions. These assumptions included the effect of convection on the process and the effect of the varying material properties. For channel sizes less than 0.5 cm the phase-change process was found to be a pure conduction process. Convection effects are thus negligible and can be eliminated from the model. The variability of density, specific heat and thermal conductivity must be included in the model, as they affect the phase-change process dramatically. Specific heat is the most influential of the properties and determines, along with the conductivity, the rate at which the phase change takes place. The density must be included since it is directly linked to the void formation. / Graduation date: 1994

In the living cell, the organization of the complex internal structure relies to a large extent on molecular motors. Molecular motors are proteins that are able to convert chemical energy from the hydrolysis of adenosine triphosphate (ATP) into mechanical work. Being about 10 to 100 nanometers in size, the molecules act on a length scale, for which thermal collisions have a considerable impact onto their motion. In this way, they constitute paradigmatic examples of thermodynamic machines out of equilibrium. This study develops a theoretical description for the energy conversion by the molecular motor myosin V, using many different aspects of theoretical physics. Myosin V has been studied extensively in both bulk and single molecule experiments. Its stepping velocity has been characterized as a function of external control parameters such as nucleotide concentration and applied forces. In addition, numerous kinetic rates involved in the enzymatic reaction of the molecule have been determined. For forces that exceed the stall force of the motor, myosin V exhibits a 'ratcheting' behaviour: For loads in the direction of forward stepping, the velocity depends on the concentration of ATP, while for backward loads there is no such influence. Based on the chemical states of the motor, we construct a general network theory that incorporates experimental observations about the stepping behaviour of myosin V. The motor's motion is captured through the network description supplemented by a Markov process to describe the motor dynamics. This approach has the advantage of directly addressing the chemical kinetics of the molecule, and treating the mechanical and chemical processes on equal grounds. We utilize constraints arising from nonequilibrium thermodynamics to determine motor parameters and demonstrate that the motor behaviour is governed by several chemomechanical motor cycles. In addition, we investigate the functional dependence of stepping rates on force by deducing the motor's response to external loads via an appropriate Fokker-Planck equation. For substall forces, the dominant pathway of the motor network is profoundly different from the one for superstall forces, which leads to a stepping behaviour that is in agreement with the experimental observations. The extension of our analysis to Markov processes with absorbing boundaries allows for the calculation of the motor's dwell time distributions. These reveal aspects of the coordination of the motor's heads and contain direct information about the backsteps of the motor. Our theory provides a unified description for the myosin V motor as studied in single motor experiments. / Die hier vorgelegte Arbeit entwickelt unter Verwendung vieler verschiedener Aspekte der statistischen Physik eine Theorie der chemomechanischen Kopplung für den Energieumsatz des molekularen Motors Myosin V. Das Myosin V ist sowohl in chemokinetischen wie in Einzelmolekülexperimenten grundlegend untersucht worden. Seine Schrittgeschwindigkeit ist in Abhängigkeit verschiedener externer Parameter, wie der Nukleotidkonzentration und einer äußeren Kraft, experimentell bestimmt. Darüber hinaus ist eine große Anzahl verschiedener chemokinetischer Raten, die an der enzymatischen Reaktion des Moleküls beteiligt sind, quantitativ erfasst. Unter der Wirkung externer Kräfte, die seine Anhaltekraft überschreiten, verhält sich der Motor wie eine Ratsche: Für Kräfte, die entlang der Schrittbewegung des Motors wirken, hängt seine Geschwindigkeit von der ATP-Konzentration ab, für rückwärts angreifende Kräfte jedoch ist die Bewegung des Motors unabhängig von ATP. Auf der Grundlage der chemischen Zustände des Motors wird eine Netzwerktheorie aufgebaut, die die experimentellen Beobachtungen des Schrittverhaltens für Myosin V einschließt. Diese Netzwerkbeschreibung dient als Grundlage für einen Markovprozess, der die Dynamik des Motors beschreibt. Die Verwendung diskreter Zustände bietet den Vorteil der direkten Erfassung der chemischen Kinetik des Moleküls. Darüber hinaus werden chemische und mechanische Eigenschaften des Motors in gleichem Maße im Modell berücksichtigt. Durch die Erfassung der Enzymkinetik mittels eines stochastischen Prozesses lässt sich die Motordynamik mit Hilfe des stationären Zustands der Netzwerkdarstellung beschreiben. Um diesen zu bestimmen, verwenden wir eine graphentheoretische Methode, die auf Kirchhoff zurückgreift. Wir zeigen in Einklang mit den Gesetzen der Thermodynamik für Nichtgleichgewichtssysteme, dass das Schrittverhalten des Motors von mehreren chemomechanischen Zyklen beeinflusst wird. Weiterhin untersuchen wir das funktionale Verhalten mechanischer Schrittraten in Abhängigkeit der äußeren Kraft unter Verwendung einer geeigneten Fokker-Planck-Gleichung. Hierfür wird auf die Theorie einer kontinuierlichen Beschreibung von molekularen Methoden zurückgegriffen. Wir berechnen Größen wie die mittlere Schrittgeschwindigkeit, das Verhältnis von Vorwärts- und Rückwärtsschritten, und die Lauflänge des Motors in Abhängigkeit einer äußeren angreifenden Kraft sowie der Nukleotidkonzentration, und vergleichen diese mit experimentellen Daten. Für Kräfte, die kleiner als die Anhaltekraft des Motors sind, unterscheidet sich der chemomechanische Zyklus grundlegend von demjenigen, der für große Kräfte dominiert. Diese Eigenschaft resultiert in einem Schrittverhalten, das mit den experimentellen Beobachtungen übereinstimmt. Es ermöglicht weiterhin die Zerlegung des Netzwerks in einzelne Zyklen, die die Bewegung des Motors für verschiedene Bereiche externer Kräfte erfassen. Durch die Erweiterung unseres Modells auf Markovprozesse mit absorbierenden Zuständen können so die Wartezeitenverteilungen für einzelne Zyklen des Motors analytisch berechnet werden. Sie erteilen Aufschluss über die Koordination des Motors und enthalten zudem direkte Informationen über seine Rückwärtsschritte, die experimentell nicht erfasst sind. Für das gesamte Netzwerk werden die Wartezeitenverteilungen mit Hilfe eines Gillespie-Algorithmus bestimmt. Unsere Theorie liefert eine einheitliche Beschreibung der Eigenschaften von Myosin V, die in Einzelmolekülexperimenten erfasst werden können.

Phase transitions and their critical scaling properties, especially in systems with disorder, are important both for our theoretical understanding of our environment, but also for their practical use in applications and materials in our everyday life. This thesis presents results from finite size scaling analysis of critical phenomena in systems with disorder, using high-precision Monte Carlo simulations and state of the art numerical methods. Specifically, theoretical models suitable for simulations in the presence of uncorrelated or correlated disorder are studied. Uncorrelated strong disorder, as present in the two dimensional gauge glass model to study the vortex glass phase of high temperature superconductors in an applied magnetic field is shown to lack a finite temperature phase transition. Further, results from dynamic quantities, such as resistance and autocorrelation functions, indicate the existence of two distinct diverging correlation times, one associated with local relaxation and one associated with vortex phase slips. Correlated disorder is studied both in the superfluid transition of helium-4 and in the anisotropic critical scaling of a transverse Meissner-like transition in an experimental setup of a high temperature superconductor. For the superfluid helium transition, it is shown that the presence of fractally correlated disorder presumably alters the universality class of the pure model. Also, a comparison with experimental data suggests that the critical scaling theory describing the heat capacity of helium-4 may need to be modified in the presence of the disorder. In the case of superconductors, analyzing experimental data from resistance measurements in a system with columnar defects together with an anisotropy in the applied magnetic field, reveals a fully anisotropic scaling regime. Finally, a data analysis is presented from simulations of a charged particle gas system in three dimensions, where the normal Coulomb interaction between charges is changed into a logarithmic interaction. Previous work indicates the possibility of a transition similar to the Kosterlitz-Thouless transition in certain two dimensional systems. On the contrary, our simulations seem to favor a system whose critical scaling behavior is consistent with a transition occurring only at zero critical temperature. Overall, disorder in the model systems studied leads to important modifications of the critical scaling properties of pure systems, and thereby also to possible changes of the corresponding universality classes. This results in interesting predictions with experimentally relevant consequences. / QC 20100811

Complex systems are neither perfectly regular nor completely random. They consist of a multitude of players who, in many cases, playtogether in a way that makes their combined strength greater than the sum of their individual achievements. It is often very effective to represent these systems as networks where the actual connections between the players take on a crucial role.Networks exist all around us and are an important part of our world, from the protein machinery inside our cells to social interactions and man-madecommunication systems. Many of these systems have developed over a long period of time and are constantly undergoing changes driven by complicated microscopic events. These events are often too complicated for us to accurately resolve, making the world seem random and unpredictable. There are however ways of using this unpredictability in our favor by replacing the true events by much simpler stochastic rules giving effectively the same outcome. This allows us to capture the macroscopic behavior of the system, to extract important information about the dynamics of the system and learn about the reason for what we observe. Statistical mechanics gives the tools to deal with such large systems driven by underlying random processes under various external constraints, much like how intracellular networks are driven by random mutations under the constraint of natural selection.This similarity makes it interesting to combine the two and to apply some of the tools provided by statistical mechanics on biological systems.In this thesis, several null models are presented, with this view point in mind, to capture and explain different types of structural properties of real biological networks. The most recent major transition in evolution is the development of language, both spoken and written. This thesis also brings up the subject of quantitative linguistics from the eyes of a physicist, here called linguaphysics. Also in this case the data is analyzed with an assumption of an underlying randomness. It is shown that some statistical properties of books, previously thought to be universal, turn out to exhibit author specific size dependencies. A meta book theory is put forward which explains this dependency by describing the writing of a text as pulling a section out of a huge, individual, abstract mother book. / Komplexa system är varken perfekt ordnade eller helt slumpmässiga. De består av en mängd aktörer, som i många fall agerar tillsammans på ett sådant sätt att deras kombinerade styrka är större än deras individuella prestationer. Det är ofta effektivt att representera dessa system som nätverk där de faktiska kopplingarna mellan aktörerna spelar en avgörande roll. Nätverk finns överallt omkring oss och är en viktig del av vår värld , från proteinmaskineriet inne i våra celler till sociala samspel och människotillverkade kommunikationssystem.Många av dessa system har utvecklats under lång tid och genomgår hela tiden förändringar som drivs på av komplicerade småskaliga händelser.Dessa händelser är ofta för komplicerade för oss att noggrant kunna analysera, vilket får vår värld att verka slumpmässig och oförutsägbar. Det finns dock sätt att använda denna oförutsägbarhet till vår fördel genom att byta ut de verkliga händelserna mot mycket enklare regler baserade på sannolikheter, som ger effektivt sett samma utfall. Detta tillåter oss att fånga systemets övergripande uppförande, att utvinna viktig information om systemets dynamik och att få kunskap om anledningen till vad vi observerar. Statistisk mekanik hanterar stora system pådrivna av sådana underliggande slumpmässiga processer under olika restriktioner, på liknande sätt som nätverk inne i celler drivs av slumpmässiga mutationer under restriktionerna från naturligt urval. Denna likhet gör det intressant att kombinera de två och att applicera de verktyg som ges av statistisk mekanik på biologiska system. I denna avhandling presenteras flera nollmodeller som, baserat på detta synsätt, fångar och förklarar olika typer av strukturella egenskaper hos verkliga biologiska nätverk. Den senaste stora evolutionära övergången är utvecklandet av språk, både talat och skrivet. Denna avhandling tar också upp ämnet om kvantitativ linguistik genom en fysikers ögon, här kallat linguafysik. även i detta fall så analyseras data med ett antagande om en underliggande slumpmässighet. Det demonstreras att vissa statistiska egenskaper av böcker, som man tidigare trott vara universella, egentligen beror på bokens längd och på författaren. En metaboksteori ställs fram vilken förklarar detta beroende genom att beskriva författandet av en text som att rycka ut en sektion ur en stor, individuell, abstrakt moderbok.

The scaling of specific cutting energy is studied when micro-cutting ductile metals. A unified framework for understanding the scaling in specific cutting energy is first presented by viewing the cutting force as a combination of constant, increasing, and decreasing force components, the independent variable being the uncut chip thickness. Then, an attempt is made to isolate the constant force component by performing high rake angle orthogonal cutting experiments on OFHC Copper. The data shows a trend towards a constant cutting force component as the rake angle is increased. In order to understand the source of this constant force component the chip-root is investigated. By quickly stopping the spindle at low cutting speeds, the chip is frozen and the chip-workpiece interface is examined in a scanning electron microscope. Evidence of ductile tearing ahead of the cutting tool is seen at low and high rake angles. At higher cutting speeds a quick-stop device is used to obtain chip-roots. These experiments also clearly indicate evidence of ductile fracture ahead of the cutting tool in both OFHC Copper and Al-2024 T3. To model the cutting process with ductile fracture leading to material separation the finite element method is used. The model is implemented in a commercial finite element software using the explicit formulation. Material separation is modeled via element failure. The model is then validated using the measured cutting and thrust forces and used to study the energy consumed in cutting. As the thickness of layer removed is reduced the energy consumed in material separation becomes important. Simulations also show that the stress state ahead of the tool is favorable for ductile fracture to occur. Ductile fracture in three locations in an interface zone at the chip root is seen while cutting with edge radius tool. A hypothesis is advanced wherein an element gets wrapped around the tool edge and is stretched in two directions leading to fracture. The numerical model is then used to study the difference in stress state and energy consumption between a sharp tool and a tool with a non-zero edge radius.

In this thesis the entanglement properties of atom-atom, atom-photon, and photon-photon are investigated. The recent developments of quantum computation as well as quantum information and communication have attracted much interest in the generation of these entanglements in the laboratory. To generate atom-photon entanglement, I discuss a model system in the cavity QED setup. By using a four-level atom and two resonant cavity modes, we can generate atom-photon entanglement almost deterministically. An extension of the above model to a six-level atom and again two resonant cavity modes can generate entangled photon pairs by appropriately adjusting system parameters. I then investigate the atom-atom entanglement in a 1D harmonic trap. I show the dependence of the pair entanglement on the scattering length and temperature, as well as the particle symmetry requirement (bosons or fermions). Among many peculiar properties in a 1D system, we briefly discuss the Fermi-Bose duality". While the entanglement properties of a single-channel model have recently been obtained for 1D and 3D systems, I thus study the entanglement of a multi-channel process in a cylindrical harmonic trap. I discuss the dependence of entanglement on the trap geometry. Finally I present detailed studies of the spin mixing between two Rb87 atoms in a single lattice site. The topic is emphasized on various motional state approximations and dipolar effect. Various motional state approximations can cause up to 20% error to experimental data. I also find that the dipolar interaction can lead to an experimentally observable frequency shift in a cylindrical harmonic trap with very large aspect ratio. The spin mixing of spin-2 manifold has also been discussed.

Thesis (M.S.)--University of Central Florida, 2009. / Adviser: Kuo-Chi Lin. Includes bibliographical references (p. 84-92).

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