We calculate the strange quark content of the nucleon, <N|ss|N> − <0|ss|0> using a novel method with the MILC lattice QCD gauge ensembles. The strangeness of the nucleon is related to the interaction cross section between dark matter and ordinary nuclear matter (e.g. in detectors) in many models. Previous results for this quantity suffered from uncontrolled systematic errors and/or large statistical uncertainties. The first result using our methods was the first modern calculation of the strangeness of the nucleon[76] with good control of systematic errors and reasonably small statistical errors, greatly reducing the uncertainty in dark matter detection cross sections. A refinement of this method allows for further reduction of statistical error. On the MILC Asqtad data, we obtain <N|ss|N> = 0.637(55)(stat)(74)(sys). The results obtained from this method are consistent with those obtained from other commonly-used methods applied to the MILC data. We also calculate the disconnected part of the pion-nucleon sigma term and the intrinsic charm of the nucleon using this method. The intrinsic charm has large statistical errors but is consistent with a perturbative calculation.

Neste trabalho, uma combinação de cálculos de mecânica quântica, simualções computacionais e teoria de perturbação termodinâmica, foi usada para estudar a solvatação do carbono de etileno (EC) e do carbonato de propileno (PC) em água. As estruturas do líquido foram geradas usando simulações com o método Monte Carlo e amostragem de Metropólis. A função de autocorrelação em energia foi usada para analisar a correlação estatística entre estas configurações. Após uma analise detalhada das ligações de hidrogênio, configurações supermoleculares descorrelacionadas ( carbonato + ligações de hidrogênio cercadas por 350 moléculas de água tratadas como cargas pontuais) foram amostradas das simulações e cálculos do momento de dipolo, no nível de cálculo MP2/ aug-cc-pvDZ, foram realizados. Em média foram formadas 1,4 ligações de hidrogênio entre a água e os solutos (EC ou PC). Foi obtido um momento de dipolo médio 9,9 ± 0,2 D para o EC-água e de 10,6 ± 0,2 D para o PC-água. Finalmente, simulações com o método de Monte Carlo no ensemble NPT e a técnica de perturbação de energia livre foram usados para determinar as energias livres de solvação, e os resultados foram Gsolv = -15,1 ± 0,8 Kcal/ mol para o EC em água e Gsolv = -15,3 ± 1,2 Kcal/mol para o PC em água. A análise destes resultados leva a conclusão de que o EC e o PC são igualmente estáveis em solução aquosa, ou seja, a metilação não tem efeito significativo na solvatação do PC e nem influência a formação das ligações de hidrogênio. / In this work, a combination of quantum mechanics, Monte Carlo simulations and thermodynamic perturbation theory was used to study the solvation of ethylene carbonate (EC) and propylene carbonate (PC) in water. The liquid structures was generated by NVT Monte Carlo simulation using standard procedures for the Metropolis sampling technique. The auto-correlation function of the energy was used to analyse the statistical correlation between the configurations (carbonates + hydrogen bonds sorrounded by 350 water molcules treated as point charges) were smpled from the simulations and dipole moment calculations, at the MP2/ aug-cc-pvDZ, were performed. On average, 1,4 hydrogen bonds were formed between water and the solutes (EC or PC). An average dipole momento of 9,9 ± 0,2 D was obtained for EC-water and 10,6 ± 0,2 D for PC-water. Finally, Monte Carlo simulations in the NPT ensemble combined with free energy pertubation technique were used to determine solvation free energies, and the results were Gsolv = -15,1 ± 0,8 kcal/mol for EC in water and Gsolv = -15,3 ± 1,2 kcal/mol for PC in water. The analysis of these results leads to the conclusion that EC and PC are equally stable in aqueous solution, i.e, the methylation hás no effect on the solvation of PC and no influence on the hydrogen bond formation.

<p>Real world modeling has become a very useful tool when new designs and applications are tested before they are introduced on the market. A field that recently has discovered the possible use of modeling is reliability prediction. The reliability and lifetime of a component has until recently been based on months and years of testing. In order to shorten the test time it is possible to simulate the environmental effect on the components. Another advantage of modeling is that changes of large systems where many different components work together can easily be studied. Without modeling the reliability has to be tested over and over again if the system is redesigned since it is impossible to know how the new change will affect the reliability.</p><p>Since electronic circuits are being made smaller and smaller with the increasing demand of faster technology the circuits are very vulnerable to corrosion. A trend in the automotive industry is also to move the electronic devices from the benign environment in the cab to the hash environment on the driveline or the chassi. The most common way to protect the electronics from the hash environment is to put it into a protective covering, also called Electronic Control Unit (ECU). Even though the ECU is sealed, water can still enter the ECU in several ways and cause serious damages by corrosion. The corrosion rate of a component is among others depending of the environmental humidity and temperature. Knowing the humidity and temperature are therefore very important to be able to eliminate corrosion problems. In order to achieve a better understanding of the physics behind the failure and to improve the reliability of the ECU a model of the temperature and humidity penetration is built in this thesis.</p><p>There are several components in the ECU which all responds differently to water vapour. By measuring the humidity penetration in the ECU while components were added one by one, the physical properties of the components could be determined. Some properties were also determined through additional solubility measurements. The humidity penetration of the ECU is then predicted by inserting these properties into mathematical models in Simulink^Ó.</p><p>The conclusion is that it is possible to model the humidity penetration and the temperature changes in the ECU. After the physical properties of the components were determined, the diffusion model agreed well with measurements. The numerical method used in this thesis has been found to be fast and stable. The length of the time-steps has been varied from a couple of minutes to more than an hour in the numerical model. A few physical properties has to be examined more in detailed and the model is then going to be a good foundation on which corrosion and other damaging processes can be modelled.</p>

Real world modeling has become a very useful tool when new designs and applications are tested before they are introduced on the market. A field that recently has discovered the possible use of modeling is reliability prediction. The reliability and lifetime of a component has until recently been based on months and years of testing. In order to shorten the test time it is possible to simulate the environmental effect on the components. Another advantage of modeling is that changes of large systems where many different components work together can easily be studied. Without modeling the reliability has to be tested over and over again if the system is redesigned since it is impossible to know how the new change will affect the reliability. Since electronic circuits are being made smaller and smaller with the increasing demand of faster technology the circuits are very vulnerable to corrosion. A trend in the automotive industry is also to move the electronic devices from the benign environment in the cab to the hash environment on the driveline or the chassi. The most common way to protect the electronics from the hash environment is to put it into a protective covering, also called Electronic Control Unit (ECU). Even though the ECU is sealed, water can still enter the ECU in several ways and cause serious damages by corrosion. The corrosion rate of a component is among others depending of the environmental humidity and temperature. Knowing the humidity and temperature are therefore very important to be able to eliminate corrosion problems. In order to achieve a better understanding of the physics behind the failure and to improve the reliability of the ECU a model of the temperature and humidity penetration is built in this thesis. There are several components in the ECU which all responds differently to water vapour. By measuring the humidity penetration in the ECU while components were added one by one, the physical properties of the components could be determined. Some properties were also determined through additional solubility measurements. The humidity penetration of the ECU is then predicted by inserting these properties into mathematical models in SimulinkÓ. The conclusion is that it is possible to model the humidity penetration and the temperature changes in the ECU. After the physical properties of the components were determined, the diffusion model agreed well with measurements. The numerical method used in this thesis has been found to be fast and stable. The length of the time-steps has been varied from a couple of minutes to more than an hour in the numerical model. A few physical properties has to be examined more in detailed and the model is then going to be a good foundation on which corrosion and other damaging processes can be modelled.

In this thesis, I present an excitonic approach to treating the coherent dynamics of optically generated charge carriers in semiconductor nanostructures. The main feature of this approach is that it includes exchange interactions and phase space filling effects, which have generally been omitted in previous excitonic treatments of coherent dynamics, so that it can go beyond the low excitation limit. In contrast to the well-known semiconductor Bloch equations, this approach treats intraband correlations without factorization. The excitonic formalism and the obtained excitonic equations are shown to be particularly advantageous in systems where bound excitons dominate the optical response and where intraband correlations play a central role. To demonstrate the application of the excitonic approach, we simulate the coherent carrier dynamics of an optically-excited, updoped AlGaAs superlattice in the presence of a terahertz pulse, where 1s excitonic states as well as higher in-plane excited states are included. We find that gain coefficients greater than 20/cm can be achieved over a tuning range of 3-11THz and that due to the coherent cascading of the carriers down the excitonic Wannier-Stark ladder, the gain coefficients have much higher gain saturation fields than comparable two-level systems. To investigate the effects of phase space filling and exchange interaction on exciton dynamics, we then apply the excitonic formalism to a simple model of a quantum ring as well as a realistic model of a quantum well. For the quantum ring, we have obtained numerical results regarding exciton population and interband polarization. We also compared our excitonic approach to the semiconductor Bloch equations in detail using this simple model. For the quantum well, in addition to the investigation of exciton dynamics, we propose and examine several approximations that can make our excitonic dynamic equations very efficient. The excitonic formalism presented in this thesis is an efficient approach that can be applied in a wide range of systems, which makes it a potential alternative to the standard miconductor Bloch equations for many systems where the intraband correlations are crucial. / Thesis (Ph.D, Physics, Engineering Physics and Astronomy) -- Queen's University, 2008-12-01 18:21:17.181

<p> The fractional quantum Hall effect (FQHE) in the half-filled second Landau level (filling factor &nu; = 5/2) offers new insights into the physics of exotic emergent quasi-particles. The FQHE is due to the collective interactions of electrons confined to two-dimensions, cooled to sub-Kelvin temperatures, and subjected to a strong perpendicular magnetic field. Under these conditions a quantum liquid forms displaying quantized plateaus in the Hall resistance and chiral edge flow. The leading candidate description for the FQHE at 5/2 is provided by the Moore-Read Pfaffian state which supports non-Abelian anyonic low-energy excitations with potential applications in fault-tolerant quantum computation schemes. The Moore-Read Pfaffian is the exact zero-energy ground state of a particular three-body Hamiltonian and explicitly breaks particle-hole symmetry. In this thesis we investigate the role of two and three body interaction terms in the Hamiltonian and the role of particle hole symmetry (PHS) breaking at &nu; = 5/2. We start with a PHS two body Hamiltonian (<i>H</i>₂) that produces an exact ground state that is nearly identical with the Moore-Read Pfaffian and construct a Hamiltonian H(&alpha;) = (1 &ndash; &alpha;)<i>H</i>₃ + &alpha; <i>H</i>₂ that tunes continuously between <i>H</i>₃ and <i> H</i>₂. We find that the ground states, and low-energy excitations, of <i>H</i>₂ and <i>H</i>₃ are in one-to-one correspondence and remain adiabatically connected indicating they are part of the same universality class and describe the same physics in the thermodynamic limit. In addition, evidently three body PHS breaking interactions are not a crucial ingredient to realize the FQHE at 5/2 and the non-Abelian quasiparticle excitations.</p><p>

Neste trabalho, uma combinação de cálculos de mecânica quântica, simualções computacionais e teoria de perturbação termodinâmica, foi usada para estudar a solvatação do carbono de etileno (EC) e do carbonato de propileno (PC) em água. As estruturas do líquido foram geradas usando simulações com o método Monte Carlo e amostragem de Metropólis. A função de autocorrelação em energia foi usada para analisar a correlação estatística entre estas configurações. Após uma analise detalhada das ligações de hidrogênio, configurações supermoleculares descorrelacionadas ( carbonato + ligações de hidrogênio cercadas por 350 moléculas de água tratadas como cargas pontuais) foram amostradas das simulações e cálculos do momento de dipolo, no nível de cálculo MP2/ aug-cc-pvDZ, foram realizados. Em média foram formadas 1,4 ligações de hidrogênio entre a água e os solutos (EC ou PC). Foi obtido um momento de dipolo médio 9,9 ± 0,2 D para o EC-água e de 10,6 ± 0,2 D para o PC-água. Finalmente, simulações com o método de Monte Carlo no ensemble NPT e a técnica de perturbação de energia livre foram usados para determinar as energias livres de solvação, e os resultados foram Gsolv = -15,1 ± 0,8 Kcal/ mol para o EC em água e Gsolv = -15,3 ± 1,2 Kcal/mol para o PC em água. A análise destes resultados leva a conclusão de que o EC e o PC são igualmente estáveis em solução aquosa, ou seja, a metilação não tem efeito significativo na solvatação do PC e nem influência a formação das ligações de hidrogênio. / In this work, a combination of quantum mechanics, Monte Carlo simulations and thermodynamic perturbation theory was used to study the solvation of ethylene carbonate (EC) and propylene carbonate (PC) in water. The liquid structures was generated by NVT Monte Carlo simulation using standard procedures for the Metropolis sampling technique. The auto-correlation function of the energy was used to analyse the statistical correlation between the configurations (carbonates + hydrogen bonds sorrounded by 350 water molcules treated as point charges) were smpled from the simulations and dipole moment calculations, at the MP2/ aug-cc-pvDZ, were performed. On average, 1,4 hydrogen bonds were formed between water and the solutes (EC or PC). An average dipole momento of 9,9 ± 0,2 D was obtained for EC-water and 10,6 ± 0,2 D for PC-water. Finally, Monte Carlo simulations in the NPT ensemble combined with free energy pertubation technique were used to determine solvation free energies, and the results were Gsolv = -15,1 ± 0,8 kcal/mol for EC in water and Gsolv = -15,3 ± 1,2 kcal/mol for PC in water. The analysis of these results leads to the conclusion that EC and PC are equally stable in aqueous solution, i.e, the methylation hás no effect on the solvation of PC and no influence on the hydrogen bond formation.

No description available.

abstract: Computability of spray flows is an important issue, from both fundamental and practical perspectives. Spray flows have important applications in fuel injection, agriculture, medical devices, and industrial processes such as spray cooling. For this reason, many efforts have been devoted to experimental, computational and some theoretical aspects of spray flows. In particular, primary atomization, the process of bulk liquid transitioning to small droplets, is a central and probably the most difficult aspect of spray flows. This thesis discusses developed methods, results, and needed improvements in the modeling of primary atomization using a predictive Sauter Mean Diameter (SMD) formula. Primary atomization for round injectors and simplex atomizers is modeled using a three-step procedure. For each spray geometry, a volume-of-fluid simulation is run to resolve the trajectory of the intact liquid core. Atomization criterion is applied to the volume-of-fluid velocity field to determine atomization sites. Local droplet size is predicted at the atomization sites using the quadratic formula for Sauter Mean Diameter. Droplets with the computed drop size are injected from the atomization sites and are tracked as point-particles. A User Defined Memory (UDM) code is employed to compute steady-state Sauter Mean Diameter statistics at locations corresponding to experimental interrogation locations. The resulting Sauter Mean Diameter, droplet trajectory, and droplet velocity are compared against experimental data to validate the computational protocol. This protocol can be implemented on coarse-grid, time-averaged simulations of spray flows, and produces convincing results when compared with experimental data for pressure-atomized sprays with and without swirl. This approach is general and can be adapted in any spray geometry for complete and efficient computations of spray flows. / Dissertation/Thesis / Masters Thesis Mechanical Engineering 2020

Water is one of the most important materials and has enormous impacts on life. Due to its delicate Hydrogen bond (H-bond) network, water shows various anomalous properties which has not been fully illuminated. Advanced experimental methods, such as scattering experiments and various spectroscopy techniques, have been developed and applied to study the nature of H-bond in liquid water. On the other hand, ab initio molecular dynamics (AIMD) have been widely adopted as an important theoretical tool to provide microscopic information of water on a sub-picosecond timescale. Recent AIMD studies based on the strongly constrained and appropriately normed (SCAN) exchange correlation functional yield an excellent description of the structural, electronic, and dynamic properties of liquid water. In this dissertation, we will focus on studying the structural, electronic and dynamic properties of liquid water as well as the modeling of the hydration structures of ions in aqueous solutions, using AIMD with potential energy surface provided by the novel SCAN functional. In the first work we represent an accurately predicted infrared spectrum of liquid water and show how the improvements are connected to the description of the underlying H-bond network. The second work mainly focusing on modeling the nuclear quantum effects (NQEs) and isotope effect of liquid water with a force field model based on artificial neural network, where qualitative agreements with experimental observations are achieved. In the third work, we study the isotope effect on the x-ray absorption spectra of liquid and attribute observed differences to the structural distinctions between light and heavy water as mentioned in the previous work. And in the last two projects, we systematically show the necessity of including NQEs of the hydrogen atom when modeling chloride ionic solution. Prominent changes in the hydration structure as well as electronic structure can be identified when NQEs are taken into consideration. / Physics