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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
81

Studium CP narušení na experimentu Belle / Study of CP-violation at the Belle experiment

Červenkov, Daniel January 2020 (has links)
We present a first measurement of time-dependent CP-violation in B0 → D∗∓ ρ± , where D∗∓ → D0 π. The analysis was performed using the final Belle dataset containing 772 × 106 B ¯B pairs collected at the KEKB e+ e− collider. Three D0 decay modes are analyzed, K∓ π± , K∓ π± π0 , and K∓ π± π∓ π± . Since the studied decay is a scalar → vector vector decay, three helicity configurations are present. Exploiting the helicity configura- tions via angular analysis, the time-dependent CP-violation parameters encoding 2ϕ1 +ϕ3 are obtained from the fit. 1
82

Robust Vehicle Routing in an Urban Setting / Robust fordonsruttning i en urban miljö

Lundkvist, Henrik January 2016 (has links)
In this thesis, the vehicle routing problem with stochastic, and time dependent, travel times is studied. The stochastic travel times are estimated from historical drive data. The variation of the drive times, as well as that of the variance, during the day was modeled.   The purpose of the thesis was to propose a method of handling the congestion related traffic impediments in an urban setting. Since the majority of times of delivery in the empirical test cases studied correlate with the time period of high traffic load, an efficient and robust handling of such traffic scenarios is of high importance.  It is shown that the stochastic models will shift the estimated arrivals to customers from the more volatile early and late extremes to more central regions of the time window. Previously delivered routes were evaluated both with the standard algorithm and the proposed stochastic algorithm. The difference between the actual drive times and the calculated drive times were analyzed by studying the correlation of the drive times between each customer in the route. It was shown that the routes of the proposed stochastic method increased this correlation. The drive times between nodes where also perturbed with a Gamma distributed noise. The results from the stochastic algorithm showed higher resilience to this disturbance than did the deterministic models. / I detta examensarbete har fordonsruttningsproblemet, VRP, med stokastiska och tidsberonds körtider behandlöats. De stokastiska körtiderna har estimerats från tidigare insamlad hasighetsdata. Modeller för körtidernas och variansernas förändring under dagen har tagits fram.   Syftet med examensarbetet var att föreslå en metod för hur påverkan på körtider av förutsägbar trafikträngsel i en urban trafikmiljö kan hanteras. Eftersom huvuddelen av alla leveranser sammanfaller med de tider på dygnet då trafikbelastning är som högst, ar är en effektiv och robust metod för att hantera sådana störningar av stor vikt. Det visas att den stokastiska modellen kommer att förflyttar ankomster från början och slutet av tidsfönstret till den mer okänsliga mittregionen. Tidigare, utförda leveranser studerades både med den ursprungliga deterministiska modellen och här framtagna stokastiska modellen. Skillnaden mellan de två analyserades genom att studera korrelationen mellan körtiderna som de beräknats av de två modellerna och de upmätta tiderna som de loggats av leveransfordonen. Det visas att korrelationen mellan körtiderna mellan de stokastiska körtiderna och de verkliga körtiderna är högre än korrelationen mellan de deterministiska körtiderna och de verkliga. Rutterna som föreslagits av den stokastiska modellen var också mer tlig mot störningar.
83

Studium časově závislého narušení CP invariance v experimentu Belle II / Study of the time-dependent CP violation at the Belle II experiment

Kapitánová, Lucia January 2021 (has links)
This thesis is devoted to studies of the proper decay-time resolution function and particle decay vertex reconstruction tools, their applicability and role in the studies of time-dependent CP violation at the Belle II experiment. A positive effect of beam spot constraints and new beam spot calibration on the vertex reconstruction precision is seen via MC/data comparison. The core part of the work focuses on studying universality of the time resolution function across nine different neutral and charged B-meson decay channels. The possibility to use a single form of this function for all studied channels is demon- strated and supported by the consistency between the lifetime values used for simulation and obtained as results of the decay time difference fit. 1
84

Inverse Atmospheric Dispersion Modeling in Complex Geometries / Invers atmosfärisk spridningsmodellering i komplexa geometrier

Pelland, Charlie January 2022 (has links)
In the event of a radioactive release in an urban environment the consequent response mustbe swift and precise. As soon as first responders have correct information, they can make anaccurate risk assessment. However, if the position, release rate and time of the radioactiverelease is unknown it is hard to know how the pollutant will spread. This thesis aims to testa model which approximates these three unknowns using weather data (wind and rain) as wellas measurement data collected at sensors placed around an urban environment. An atmospheric dispersion model based on an existing Reynolds Averaged Navier-Stokes modelis set up in two geometries of different complexity to create forward mode synthetic depositiondata and adjoint mode concentration fields resulting from a fixed dry deposition velocity andscavenging effect for wet deposition. Variations of time- and space-dependent rainfall is simu-lated. The resulting data is used in an existing optimization model, where a parameter studyis conducted regarding regularization coefficients. This thesis shows that the optimization model accurately estimates position and its approximaterelease rate of a 2D geometry of radioactive releases using a logarithmic optimization approach,and fail to do so using a linear optimization approach. The logarithmic optimization model alsoapproximately estimates position and release rate in a 3D geometry. Regularization parametersshould be within the range of 0.1 and 1.2 depending on rain. More rain requires smallerparameters and will estimate a lower release rate. Time-dependent rainfall is shown to have amajor negative effect on simulation time.iii
85

A Study of the Gradient Drift Instability in the High-Latitude Ionosphere Using the Utah State University Time Dependent Ionospheric Model

Subramanium, Mahesh 01 May 1996 (has links)
Research over the years has established that the Gradient Drift Instability process causes small-scale irregularities, mostly along the edges of the high-latitude polar cap patches. Studying these irregularities will help in the development of a global Scale Ionospheric model, which is a central part of a global space weather forecast system. Much theoretical work has been done with varying degrees of complexity to study this instability in the high latitude patches. In this work we have used the Utah State University Time Dependent Ionospheric Model to model the high-latitude patches, calculate the growth rate of the instability, and perform a macro-scale study of the phenomenon. This is the first time that real ionospheric values have been used to calculate the growth rate and to provide two-dimensional maps identifying Gradient Drift Instability-caused irregularity regions in the polar cap. Our research shows that regions of intense instability occur along the edges of the tongue of ionization and its throat regions with strong rates along the borders of the cusp region.
86

An Optimal Adaptive Routing Algorithm for Large-scale Stochastic Time-Dependent Networks

Ding, Jing 01 January 2012 (has links) (PDF)
The objective of the research is to study optimal routing policy (ORP) problems and to develop an optimal adaptive routing algorithm practical for large-scale Stochastic Time-Dependent (STD) real-life networks, where a traveler could revise the route choice based upon en route information. The routing problems studied can be viewed as counterparts of shortest path problems in deterministic networks. A routing policy is defined as a decision rule that specifies what node to take next at each decision node based on realized link travel times and the current time. The existing routing policy algorithm is for explorative purpose and can only be applied to hypothetical simplified network. In this research, important changes have been made to make it practical in a large-scale real-life network. Important changes in the new algorithm include piece-wise linear travel time representation, turn-based, label-correcting, criterion of stochastic links, and dynamic blocked links. Complete dependency perfect online information (CDPI) variant is then studied in a real-life network (Pioneer Valley, Massachusetts). Link travel times are modeled as random variables with time-dependent distributions which are obtained by running Dynamic Traffic Assignment (DTA) using data provided by Pioneer Valley Planning Commission (PVPC). A comprehensive explanation of the changes by comparing the two algorithms and an in-depth discussion of the parameters that affects the runtime of the new algorithm is given. Computational tests on the runtime changing with different parameters are then carried out and the summary of its effectiveness are presented. To further and fully understand the applicability and efficiency, this algorithm is then tested in another large-scale network, Stockholm in Sweden, and in small random networks. This research is also a good starting point to investigate strategic route choice models and strategic route choice behavior in a real-life network. The major tasks are to acquire data, generate time-adaptive routing policies, and estimate the runtime of the algorithm by changing the parameters in two large-scale real-life networks, and to test the algorithm in small random networks. The research contributes to the knowledge base of ORP problems in stochastic time-dependent (STD) networks by developing an algorithm practical for large-scale networks that considers complete time-wise and link-wise stochastic dependency.
87

Investigation of Concrete Mixtures to Reduce Differential Shrinkage Cracking in Composite Bridges

Nelson, Douglas A. 04 December 2013 (has links)
The objective of the research presented in this thesis was to develop a concrete bridge deck topping mixture that resists the effects of differential shrinkage by decreasing shrinkage and increasing creep. . In addition, the amount of tensile creep that concrete experiences under long-term tensile stresses were quantified and compared to compressive creep values in order to gain a better understanding of how concrete behaves under tension. Test results show that the amount of tensile creep exceeded compressive creep by a factor of 2-5. Various shrinkage and creep models were compared against test data in order to quantify results and determine the best model to use for the mixes examined during this research project. Data analysis revealed that the AASHTO time dependent effects (shrinkage and creep) models outperformed the other models used in this research project. Other material property data including compressive strength, splitting tensile strength, Young's modulus of elasticity, and unrestrained shrinkage was also collected to compare against a common bridge deck topping mix to ensure that the mixes used in this research project are suitable for use in the field. A parametric study utilizing the Age Adjusted Effective Modulus (AAEM) method was performed which showed that the most important factor in reducing tensile stresses was to decrease the amount of shrinkage experienced by the concrete bridge deck topping mixture. Three concrete mixtures, one included saturated lightweight aggregates (SLWA), one including ground granulated blast furnace slag (GGBFS), and one incorporating both were tested. Preliminary results show that the inclusions of SLWA into a concrete mixture reduced shrinkage by 25% and overall tensile stress by 38%. / Master of Science
88

On the Variability of the Fine Structure Constant

Evans, Jason Lott 13 July 2004 (has links) (PDF)
This thesis addresses the issue of the time variability of the fine structure constant, alpha. Recent claims of a varying alpha are set against the established standards of quantum electrodynamical theory and experiments. A study of the feasibility of extracting data on the time dependence of alpha using particles in Penning traps is compared to the results obtained by existing methods, including those using astrophysical data and those obtained in atomic clock experiments. Suggestions are made on the nature of trapped particles and the trapping fields.
89

Real-Space Approach to Time Dependent Current Density Functional Theory

Jensen, Daniel S. 09 July 2010 (has links) (PDF)
A real-space time-domain calculation of the frequency-dependent dielectric constant of nonmetallic crystals is outlined and the integrals required for this calculation are computed. The outline is based on time dependent current density functional theory and is partially implemented in the ab initio density functional theory FIREBALL program. The addition of a vector potential to the Hamiltonian of the system is discussed as well as the need to include the current density in addition to the particle density. The derivation of gradient integrals within a localized atomic-like orbital basis is presented for use in constructing the current density. Due to the generality of the derivation we also give the derivation of the kinetic energy, dipole, and overlap interactions.
90

Transient Multi-scale Computational Fluid Dynamics (cfd) Model For Thrombus Tracking In An Assit Device Vascular Bed

Osorio, Ruben 01 January 2013 (has links)
Heart failure occurs when the heart is not capable to pump blood at a sufficient rate to meet the demands of the body. Depending on the health of the heart, doctors may recommend a heart transplant, but finding a suitable donor is often a long duration process and the patient might be at an advance condition or the patient is not adequate for a heart transplant. In such cases Ventricular assist devices (VAD) are implemented. The purpose of a VAD is to aid the heart to pump the correct amount of blood, by doing so it relives the load that is put on the heart while giving the patient a chance for recovery. This study focuses on observing the hemodynamic effects of implementing a left ventricular assist device (LVAD) along the aortic arch and main arteries. Thrombi creation and transportation is other subject included in the study, due to the fact that thrombi can obstruct blood flow to critical arteries, manly carotid and vertebral. Occlusion of these can lead to a stroke with devastating effects on the neurocognitive functions and even death. A multi-scale CFD analysis a patient specific geometry model is used as well as a lumped system which provides the correct conditions in order to simulate the whole cardiovascular system. The main goal of the study is to understand the difference in flow behavior created by the unsteady pulsatile boundary conditions. The model described in this work has a total cardiac output of 7.0 Liters/ minute, this for a healthy heart. Two cardiac output splits are used to simulate heart failure conditions. The first split consists of 5 Liters/minute flowing through the LVAD cannula and 2 Liters/minute via the aortic root. The second scenario is when heart iv failure is critical, meaning that zero flow is being output by the left ventricle, thus a split of 7 Liter/minute trough the LVAD cannula and 0 Liters/minute traveling through the aortic root. A statistical analysis for the thrombi motion throughout the patient aortic arch was performed in order to quantify the influence that pulsatile flow has on the particles being track. Spherical particles of 2mm, 4mm and 5mm were released and accounted in the statistical analysis for each of the two split configurations. The study focuses on particles that escaped on the outlet boundaries of the upper arteries (Right Carotid, Left Carotid, and Vertebral). Results exhibit the statistical comparison of means for each particle diameter as well as for the overall probability for the steady and unsteady flow condition.

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