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Dynamic Models for Insect Mortality Due to Exposure to InsecticidesJoyner, Sarah Lynn 15 April 2008 (has links)
Chemical pesticides have long been used to control insect populations on field crops, and their widespread availability and ease of manipulation present an ideal system for the exploration of the relationship between vital rates and population dynamics. Research has shown that models of population effects of insecticides are more accurate when timevarying parameters are used, but the scientific community has been slow to accept such models, which may involve complicated mathematics such as partial differential equations. Additionally, many of the pesticides now in use have both acute and sublethal effects, and these differing modes of action, along with concerns for the scientific community's understanding of the models, motivate a new approach to mathematical modeling of the effects of insecticides on population dynamics. We first consider an ordinary differential equation model, which, while simple, provides highly accurate fits to population data, though it accounts for only one generation at a time without explicitly considering reproductive effects. An evaluation of the effects of insecticides on insect fecundity is considered separately. We then develop, implement, and analyze a coupled timedelay differential equation model, which incorporates information for multiple generations and is an intermediate model in terms of ease of understanding for nonmathematicians. Sensitivity results for the time delay kernel are also presented.

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Fast Numerical Methods for Evolving InterfacesKuster, Christopher M. 10 July 2006 (has links)
Free and/or moving boundary problems occur in a wide range of applications. These boundaries can obey either local or global conditions. In this dissertation, new numerical techniques for solving some of these problems are developed, analyzed, implemented and tested. The new techniques for free and moving boundary problems are 1) a second order method for solving moving boundary problems and 2) a hybrid level set/boundary element method for solving some free boundary problems. The main tool used in both is the Fast Marching method, a fast algorithm for solving the eikonal equation. An application using Fast Marching to solve a model for sand pile formation in domains with obstacles is shown. A new, second order Fast Marching scheme for domains with obstacles is introduced. We look at the stability and accuracy of discretizations commonly used with Fast Marching. The performance of Fast Marching is compared that of Fast Sweeping, another eikonal solver. The second order method for solving moving boundary problems is applied to some simple examples. Finally, a globally defined free boundary problem inspired by fluid dynamics, the Bernoulli problem, is solved using the hybrid method.

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Molecularbased Models for Viscoelasticity of PolymersHood, Jeffrey Braidon 22 July 2005 (has links)
Various models are developed to describe several different aspects of the dynamics of polymers. First, a model is developed which describes the dynamics of a single polymer chain, residing in a viscous fluid, in response to various stimuli. Next, constitutive models leading to reptation are developed, which determine the stressstrain relations for a system of physically constrained (PC) molecules residing within a chemically crosslinked (CC) system of molecules acting as a constraining tube for the PC system. These reptation models treat relaxation within the context of both intramolecular and intermolecular variability. Finally, a model is developed which combines the Rouse model of relaxing polymers and the stickslip reptation model. This stickslip/Rouse hybrid model incorporates parameters which were ignored in models developed in the earlier parts of the dissertation.

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Domain theory in realizability toposesPhoa, Wesley January 1990 (has links)
No description available.

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Realizability semantics for intuitionistic formal systemsMcCarty, D. C. January 1984 (has links)
No description available.

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Families of Sets Without the Baire PropertyNyagahakwa, Venuste January 2017 (has links)
The family of sets with the Baire property of a topological space X, i.e., sets which differ from open sets by meager sets, has different nice properties, like being closed under countable unions and differences. On the other hand, the family of sets without the Baire property of X is, in general, not closed under finite unions and intersections. This thesis focuses on the algebraic settheoretic aspect of the families of sets without the Baire property which are not empty. It is composed of an introduction and five papers. In the first paper, we prove that the family of all subsets of ℝ of the form (C \ M) ∪ N, where C is a finite union of Vitali sets and M, N are meager, is closed under finite unions. It consists of sets without the Baire property and it is invariant under translations of ℝ. The results are extended to the space ℝn for n ≥ 2 and to products of ℝn with finite powers of the Sorgenfrey line. In the second paper, we suggest a way to build a countable decomposition <img src="http://www.divaportal.org/cgibin/mimetex.cgi?%5Ctiny%5Clbrace%5Ctext%20X_i%5Crbrace%20_%7Bi=1%7D%5E%5Cinfty" /> of a topological space X which has an open subset homeomorphic to (ℝn, τ), n ≥ 1, where τ is some admissible extension of the Euclidean topology, such that the union of each nonempty proper subfamily of <img src="http://www.divaportal.org/cgibin/mimetex.cgi?%5Ctiny%5Clbrace%5Ctext%20X_i%5Crbrace%20_%7Bi=1%7D%5E%5Cinfty" /> does not have the Baire property in X. In the case when X is a separable metrizable manifold of finite dimension, each element of <img src="http://www.divaportal.org/cgibin/mimetex.cgi?%5Ctiny%5Clbrace%5Ctext%20X_i%5Crbrace%20_%7Bi=1%7D%5E%5Cinfty" /> can be chosen dense and zerodimensional. In the third paper, we develop a theory of semigroups of sets with respect to the union of sets. The theory is applied to Vitali selectors of ℝ to construct diverse abelian semigroups of sets without the Baire property. It is shown that in the family of such semigroups there is no element which contains all others. This leads to a supersemigroup of sets without the Baire property which contains all these semigroups and which is invariant under translations of ℝ. All the considered semigroups are enlarged by the use of meager sets, and the construction is extended to Euclidean spaces ℝn for n ≥ 2. In the fourth paper, we consider the family V1(Q) of all finite unions of Vitali selectors of a topological group G having a countable dense subgroup Q. It is shown that the collection <img src="http://www.divaportal.org/cgibin/mimetex.cgi?%5Ctiny%5Clbrace%5Ctext%20G%20%5Csetminus%20%5Ctext%20U%20:%20%5Ctext%20U%20%5Cin%20%5C%20%5Cmathcal%7BV%7D_1(%5Ctext%7BQ%7D)%5Crbrace" /> is a base for a topology τ(Q) on G. The space (G, τ (Q)) is T1, not Hausdorff and hyperconnected. It is proved that if Q1 and Q2 are countable dense subgroups of G such that Q1 ⊆ Q2 and the factor group Q2/Q1 is infinite (resp. finite) then τ(Q1) <img src="http://www.divaportal.org/cgibin/mimetex.cgi?%5Ctiny%5Cnot%5Csubseteq" /> τ(Q2) (resp. τ (Q1) ⊆ τ (Q2)). Nevertheless, we prove that all spaces constructed in this manner are homeomorphic. In the fifth paper, we investigate the relationship (inclusion or equality) between the families of sets with the Baire property for different topologies on the same underlying set. We also present some applications of the local function defined by the Euclidean topology on R and the ideal of meager sets there.

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Inverse factorization in electronic structure theory : Analysis and parallelizationArtemov, Anton G. January 2019 (has links)
This licentiate thesis is a part of an effort to run large electronic structure calculations in modern computational environments with distributed memory. The ultimate goal is to model materials consisting of millions of atoms at the level of quantum mechanics. In particular, the thesis focuses on different aspects of a computational problem of inverse factorization of Hermitian positive definite matrices. The considered aspects are numerical properties of the algorithms and parallelization. Not only is an efficient and scalable computation of inverse factors necessary in order to be able to run large scale electronic computations based on the Hartree–Fock or Kohn–Sham approaches with the selfconsistent field procedure, but it can be applied more generally for preconditioner construction. Parallelization of algorithms with unknown load and data distributions requires a paradigm shift in programming. In this thesis we also discuss a few parallel programming models with focus on taskbased models, and, more specifically, the Chunks and Tasks model. / eSSENCE

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Implementing and testing possible hedging strategies to minimise value fluctuations in a defaulted portfolioNilsson, Gabriel January 2019 (has links)
A Central Counterparty (CCP) handles clearing between its members and can mutualise and reduce the counterparty and credit risk in a network. In the case of a clearing member defaulting on its obligations, the defaulted portfolio will be taken over by the CCP, which will attempt to close out the positions as quickly as possible. It is vital that the CCP minimises the losses they may suffer during the period between default and close out, the so called holding period. This thesis investigates and tests several potential hedging strategies to minimise value fluctuations during the holding period. These include neutralising the exposure to different risk factors, as well as finding the ideal hedging position using principal component analysis. The defaulted portfolio can contain different instruments, such as options, interest rate swaps and bonds, which requires different approaches to neutralise exposure. To determine the performance of the different strategies, backtesting was performed on historical data from the years 2001 to 2013, and the results were analysed in order to determine the effectiveness and potential costs of the hedging. The results show that significant reduction in value fluctuations can be achieved by employing these strategies, while not exceeding an affordable level of cost. Based on the findings, a function was created in Java that can recommend optimal hedging positions given a defaulted portfolio of any composition.

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Linearscaling recursive expansion of the FermiDirac operatorAndersson, Linnéa January 2019 (has links)
No description available.

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Nonlinear inverse geothermal problemsWokiyi, Dennis January 2017 (has links)
The inverse geothermal problem consist of estimating the temperature distribution below the earth’s surface using temperature and heatflux measurements on the earth’s surface. The problem is important since temperature governs a variety of the geological processes including formation of magmas, minerals, fosil fuels and also deformation of rocks. Mathematical this problem is formulated as a Cauchy problem for an nonlinear elliptic equation and since the thermal properties of the rocks depend strongly on the temperature, the problem is nonlinear. This problem is illposed in the sense that it does not satisfy atleast one of Hadamard’s definition of wellposedness. We formulated the problem as an illposed nonlinear operator equation which is defined in terms of solving a wellposed boundary problem. We demonstrate existence of a unique solution to this wellposed problem and give stability estimates in appropriate function spaces. We show that the operator equation is welldefined in appropriate function spaces. Since the problem is illposed, regularization is needed to stabilize computations. We demostrate that Tikhonov regularization can be implemented efficiently for solving the operator equation. The algorithm is based on having a code for solving a well posed problem related to the operator equation. In this study we demostrate that the algorithm works efficiently for 2D calculations but can also be modified to work for 3D calculations.

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