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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.
71

A Mathematical Model for Optimizing Mini-Hub Locations of Distribution Centers in Urban Areas

Unknown Date (has links)
Logistics play a vital role in the prosperity of today’s cities, but current urban logistics delivery practices have proven problematic and to be causing various negative effects in cities. This study proposes an alternative method for delivering cargo with the leasing of a network of logistics hubs within urban areas for designated daily time intervals and handcart last-mile deliveries. The objective of the study is the development of a mathematical programming model for identifying the optimal number and locations of hubs for serving demand with the minimum cost, as well as the optimal times during the day for leasing the facilities, while also allocating hubs to customers. The problem is effectively solved by applying a Lagrangian relaxation and subgradient optimization approach. Numerical examples and a sensitivity analysis provide evidence of the robustness of the model and its ability to be effectively applied to address real problems. / Includes bibliography. / Thesis (M.S.)--Florida Atlantic University, 2018. / FAU Electronic Theses and Dissertations Collection
72

Mixing and dispersion of a small estuarine plume

Sheridan, Megan January 2018 (has links)
Entrainment velocity, salt flux and the turbulent diffusivity of salt are estimated in the outflow of a small, radially spreading buoyant outflow, just outside of the Teign Estuary mouth, as a means to compare mixing dynamics between very small and larger-scale estuarine and river plumes, and build on a scant knowledge base regarding the former. The analysis was made using a control volume approach, based on the conservation of momentum, volume and salt, from a Lagrangian perspective. Drifting buoys were used to accomplish this. The analysis was based on that employed by McCabe et al. (2008), with some modifications to fit a small-scale outflow, namely: repeat deployments, shorter drifter tracks, and deployment-specific criteria used for choosing the plume base, a step in the analysis used to calculate vertical entrainment, flux and diffusivity. In addition, temperature was used as a proxy for salinity, and this is evaluated in the results. Overall results were compared to a similar study, which was conducted in the Columbia River plume, a system much larger in scale to the Teign. Drifter experiments were conducted on multiple days, under different conditions (i.e. wind, tides, river flow), and those results are discussed briefly, but the focus is on one specific day, April 3, 2014, where conditions most closely matched those of the comparison study, and those results are compared between the two systems. Entrainment velocity was measured along the drifter tracks, in the near-field plume, where shear-induced mixing dominates. Drifter track subsections were chosen so as to avoid source or frontal dynamics, the plume base was chosen for individual deployments as the plume dynamics could change relatively quickly, and repeat deployments were conducted as a way to look at near-field plume evolution over the course of the ebb (and with a smaller plume, time allowed for this) . On April 3, the mean value for entrainment velocity for the four deployments chosen in the Teign outflow was 4.3 x 10-4 ms-1. The mean cast value was slightly higher at 7.6 x 10-4 ms-1, as casts values were typically measured at the beginning of the drifter tracks. Entrainment values at the cast sites were calculated in the same way as the track values, taking plume thickness from hydrographic casts, as a means to evaluate accuracy of track values, which are based on a modelled plume thickness. A rough estimate for the mean entrainment velocity for one pair of drifters used in the Columbia River was 9 x 10-4 ms-1, approximately double that of the Teign, but within the same order of magnitude. Salt flux values ranged from 0-5 x 10-2 psu ms-1 and from 0-3 x 10-2 psu ms-1 for the Teign and the Columbia, respectively, and diffusivities ranged from 0.5-5.8 x 10-2 m2s-1 and from 0.2-9.6 x 10-3 m2s-1. With a similar range of entrainment and salt flux values, and almost an order of magnitude difference between diffusivity values, it was determined that weaker density gradients in the Teign are responsible for the latter, and that this increased level of mixing results in a larger horizontal horizontal salinity gradient, which balances out the terms in the entrainment equation that are related solely to the physical size of the system (i.e. plume thickness, velocity and the vertical salinity gradient). This higher level of mixing of a smaller physical entity, supports the view that smaller plumes mix more thoroughly over a shorter timescale, resulting in a larger impact to the local environment into which they flow.
73

Adaptive mesh methods for numerical weather prediction

Cook, Stephen January 2016 (has links)
This thesis considers one-dimensional moving mesh (MM) methods coupled with semi-Lagrangian (SL) discretisations of partial differential equations (PDEs) for meteorological applications. We analyse a semi-Lagrangian numerical solution to the viscous Burgers’ equation when using linear interpolation. This gives expressions for the phase and shape errors of travelling wave solutions which decay slowly with increasing spatial and temporal resolution. These results are verified numerically and demonstrate qualitative agreement for high order interpolants. The semi-Lagrangian discretisation is coupled with a 1D moving mesh, resulting in a moving mesh semi-Lagrangian (MMSL) method. This is compared against two moving mesh Eulerian methods, a two-step remeshing approach, solved with the theta-method, and a coupled moving mesh PDE approach, which is solved using the MATLAB solver ODE45. At each time step of the SL method, the mesh is updated using a curvature based monitor function in order to reduce the interpolation error, and hence numerical viscosity. This MMSL method exhibits good stability properties, and captures the shape and speed of the travelling wave well. A meteorologically based 1D vertical column model is described with its SL solution procedure. Some potential benefits of adaptivity are demonstrated, with static meshes adapted to initial conditions. A moisture species is introduced into the model, although the effects are limited.
74

Irreducible holomorphic symplectic manifolds and monodromy operators

Onorati, Claudio January 2018 (has links)
One of the most important tools to study the geometry of irreducible holomorphic symplectic manifolds is the monodromy group. The first part of this dissertation concerns the construction and studyof monodromy operators on irreducible holomorphic symplectic manifolds which are deformation equivalent to the 10-dimensional example constructed by O'Grady. The second part uses the knowledge of the monodromy group to compute the number of connected components of moduli spaces of bothmarked and polarised irreducible holomorphic symplectic manifolds which are deformationequivalent to generalised Kummer varieties.
75

Symmetry in monotone Lagrangian Floer theory

Smith, Jack Edward January 2017 (has links)
In this thesis we study the self-Floer theory of a monotone Lagrangian submanifold $L$ of a closed symplectic manifold $X$ in the presence of various kinds of symmetry. First we consider the group $\mathrm{Symp}(X, L)$ of symplectomorphisms of $X$ preserving $L$ setwise, and extend its action on the Oh spectral sequence to coefficients of arbitrary characteristic, working over an enriched Novikov ring. This imposes constraints on the differentials in the spectral sequence which force them to vanish in certain situations. We then specialise to the case where $L$ is $K$-homogeneous for a compact Lie group $K$, meaning roughly that $X$ is Kaehler, $K$ acts on $X$ by holomorphic automorphisms, and $L$ is a Lagrangian orbit. By studying holomorphic discs with boundary on $L$ we compute the image of low codimension $K$-invariant subvarieties of $X$ under the length zero closed-open string map. This places restrictions on the self-Floer cohomology of $L$ which generalise and refine the Auroux-Kontsevich-Seidel criterion. These often result in the need to work over fields of specific positive characteristics in order to obtain non-zero cohomology. The disc analysis is then developed further, with the introduction of the notion of poles and a reflection mechanism for completing holomorphic discs into spheres. This theory is applied to two main families of examples. The first is the collection of four Platonic Lagrangians in quasihomogeneous threefolds of $\mathrm{SL}(2, \mathbb{C})$, starting with the Chiang Lagrangian in $\mathbb{CP}^3$. These were previously studied by Evans and Lekili, who computed the self-Floer cohomology of the latter. We simplify their argument, which is based on an explicit construction of the Biran-Cornea pearl complex, and deal with the remaining three cases. The second is a family of $\mathrm{PSU}(n)$-homogeneous Lagrangians in products of projective spaces. Here the presence of both discrete and continuous symmetries leads to some unusual properties: in particular we obtain non-displaceable monotone Lagrangians which are narrow in a strong sense. We also discuss related examples including applications of Perutz's symplectic Gysin sequence and quilt functors. The thesis concludes with a discussion of directions for further research and a collection of technical appendices.
76

Lagrangian angles of foliation in R² under curve shortening flow.

January 2011 (has links)
Ma, Man Shun. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2011. / Includes bibliographical references (leaves 75-76). / Abstracts in English and Chinese. / Chapter 1 --- Introduction --- p.6 / Chapter 2 --- Basic notions in Riemannian geometry --- p.10 / Chapter 2.1 --- Basic manifold theory --- p.11 / Chapter 2.2 --- "Connection, curvature" --- p.19 / Chapter 2.3 --- Submanifold theory --- p.29 / Chapter 3 --- Basic facts in symplectic and complex geometry --- p.33 / Chapter 3.1 --- "Symplectic manifolds, Lagrangian submanifolds" --- p.34 / Chapter 3.2 --- Kahler and Calabi-Yau manifolds --- p.39 / Chapter 3.3 --- Calibration --- p.49 / Chapter 4 --- Mean curvature flow --- p.52 / Chapter 4.1 --- Basic equations in Lagrangian immersions --- p.53 / Chapter 4.2 --- Evolution equation for --- p.57 / Chapter 4.3 --- Evolution equations for H and θ --- p.62 / Chapter 5 --- Lagrangian angle of a foliation --- p.67 / Chapter 5.1 --- "Proof of equation (5.1), (5.2)" --- p.68 / Chapter 5.2 --- Main theorem --- p.70 / Chapter 5.3 --- Examples of invariant solution --- p.73 / Bibliography --- p.75
77

Lagrangian duality in convex optimization.

January 2009 (has links)
Li, Xing. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2009. / Includes bibliographical references (leaves 76-80). / Abstract also in Chinese. / Introduction --- p.4 / Chapter 1 --- Preliminary --- p.6 / Chapter 1.1 --- Notations --- p.6 / Chapter 1.2 --- On Properties of Epigraphs --- p.10 / Chapter 1.3 --- Subdifferential Calculus --- p.14 / Chapter 1.4 --- Conical Approximations --- p.16 / Chapter 2 --- Duality in the Cone-convex System --- p.20 / Chapter 2.1 --- Introduction --- p.20 / Chapter 2.2 --- Various of Constraint Qualifications --- p.28 / Chapter 2.2.1 --- Slater´ةs Condition Revisited --- p.28 / Chapter 2.2.2 --- The Closed Cone Constrained Qualification --- p.31 / Chapter 2.2.3 --- The Basic Constraint Qualification --- p.38 / Chapter 2.3 --- Lagrange Multiplier and the Geometric Multiplier --- p.45 / Chapter 3 --- Stable Lagrangian Duality --- p.48 / Chapter 3.1 --- Introduction --- p.48 / Chapter 3.2 --- Stable Farkas Lemma --- p.48 / Chapter 3.3 --- Stable Duality --- p.57 / Chapter 4 --- Sequential Lagrange Multiplier Conditions --- p.63 / Chapter 4.1 --- Introduction --- p.63 / Chapter 4.2 --- The Sequential Lagrange Multiplier --- p.64 / Chapter 4.3 --- Application in Semi-Infinite Programs --- p.71 / Bibliography --- p.76 / List of Symbols --- p.80
78

Les anomalies fortes et électromagnétiques dans les désintégrations faibles des mésons

Trine, Stéphanie 06 December 2004 (has links)
Les effets des opérateurs liés aux anomalies axiale et de trace de QCD et de QED dans les désintégrations faibles des mésons sont analysés dans deux régimes extrêmes: tout d'abord lorsque les densités anomales de gluons et de photons sont générées à courte distance par une boucle de quark lourd, ensuite lorsqu'elles sont générées à longue distance par des corrections fortes associées aux quarks légers u, d et s. A courte distance, l'ensemble des corrections de type pingouin à une interaction effective à quatre quarks arbitraire est obtenu à partir de l'expansion en la masse inverse du propagateur d'un quark lourd plongé dans un champ de jauge classique. Une suppression des effets anomaux est ainsi mise en évidence dans le Modèle Standard. Un nouvel ensemble d'opérateurs de dimension huit décrivant les effets du quark charmé dans les désintégrations des kaons est également établi. A longue distance, les effets anomaux associés aux quarks légers dans les désintégrations faibles hadroniques et radiatives des kaons sont analysés dans le formalisme des Lagrangiens chiraux. Une contribution potentiellement importante de l'opérateur d'anomalie de trace est ainsi mise en évidence. Les implications d'une éventuelle dominance des anomalies sont également étudiées.
79

A Comparison of Mixed-Integer Programming Models for Non-Convex Piecewise Linear Cost Minimization Problems

Croxton, Keely L., Gendon, Bernard, Magnanti, Thomas L. 07 1900 (has links)
We study a generic minimization problem with separable non-convex piecewise linear costs, showing that the linear programming (LP) relaxation of three textbook mixed integer programming formulations each approximates the cost function by its lower convex envelope. We also show a relationship between this result and classical Lagrangian duality theory.
80

Using Lagrangian Coherent Structures to Study Coastal Water Quality

Fiorentino, Laura A 15 June 2011 (has links)
In order to understand water quality in the coastal ocean and its effects on human health, the necessity arises to locate the sources of contaminants and track their transport throughout the ocean. Dynamical systems methods are applied to the study of transport of enterococci as an indicator of microbial concentration in the vicinity of Hobie Beach, an urban, subtropical beach in Miami, FL that is used for recreation and bathing on a daily basis. Previous studies on water quality have shown that Hobie Beach has high microbial levels despite having no known point source. To investigate the cause of these high microbial levels, a combination of measured surface drifter trajectories and numerically simulated flows in the vicinity of Hobie Beach is used. The numerically simulated flows are used to identify Lagrangian Coherent Structures (LCSs), which provide a template for transport in the study area. Surface drifter trajectories are shown to be consistent with the simulated flows and the LCS structure. LCSs are then used to explain the persistent water contamination and unusually high concentrations of microbes in the water off of this beach as compared with its neighboring beaches. From the drifter simulations, as well as field experiments, one can see that passive tracers are trapped in the area along the coastline by LCS. The Lagrangian circulation of Hobie Beach, influenced primarily by tide and land geometry causes a high retention rate of water near the shore, and can be used to explain the elevated levels of enterococci in the water.

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