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Search Results: 1 - 10 of 119997 matches for " T. T. Hansen "
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Integral equation analysis of complex (M)MIC-structures with optimized system matrix decomposition and novel quadrature techniques
T. Vaupel,V. Hansen
Advances in Radio Science : Kleinheubacher Berichte , 2004,
Abstract: Using integral equation methods for the analysis of complex (M)MIC structures, the computation and storage effort for the solution of the linear systems of equations with their fully populated matrices still forms the main bottleneck. In the last years, remarkable improvements could be achieved by means of diakoptic methods and related preconditiners. In this contribution, we present a method based on the optimized decomposition of the system matrix depending on the circuit topology. The system matrix is splitted in a densely populated matrix and a mainly blockdiagonal matrix with overlapping submatrices. The latter matrix is used for the generation of high performance preconditioners within Krylov subspace methods using sparsified matrix storage methods, adaptive Cholesky decompositions and optimized forward/backward substitutions. Furthermore, we present an integration technique using a complete analytical treatment for the strongly oscillating parts of the spectral domain integrands allowing the analysis of very large structures as compared to the wavelength.
L roplanen och f rest llningen om ett kosmopolitiskt arv
David T. Hansen
Utbildning & Demokrati : Tidsskrift f?r Didaktik och Utbildningspolitik , 2010,
Abstract: The ancient idea of cosmopolitanism is a topic of renewed interest today. Scholars and practitioners in many fields are examining what it means to conceive all human beings as linked by their membership in a shared cosmos. Some people focus on political cosmopolitanism, others on moral, cultural, or economic cosmopolitanism. This paper examines educational cosmopolitanism by elucidating the idea of curriculum as a cosmopolitan inheritance. It argues that curriculum can generate a cosmopolitan sensibility, by which one means an outlook that regards life experience as universally educational. It suggests that a cosmopolitan sensibility can assist people in working through some of the tensions that accompany global and local change in our time. It can position them to reconstruct creatively cultural and individual values rather than abandon them in the face of the ceaseless pressure of globalization. A cosmopolitan ensibilityedifies human beings by helping them perceive why all persons, in principle, can be creative guardians and practitioners of creativity itself.
Symbolic dynamics I. Finite dispersive billiards
Kai T. Hansen
Physics , 1993, DOI: 10.1088/0951-7715/6/5/005
Abstract: Orbits in different dispersive billiard systems, e.g. the 3 disk system, are mapped into a topological well ordered symbol plane and it is showed that forbidden and allowed orbits are separated by a monotone pruning front. The pruning front can be approximated by a sequence of finite symbolic dynamics grammars.
Symbolic dynamics III. Bifurcations in billiards and smooth potentials
Kai T. Hansen
Physics , 1993, DOI: 10.1088/0951-7715/6/5/006
Abstract: The singular bifurcations in a dispersive billiard are discussed in terms of symbolic dynamics and is compared to an example of a bifurcation tree in a smooth potential. Possible generalizations to other smooth potentials are discussed.
Symbolic dynamics II. The stadium billiard
Kai T. Hansen
Physics , 1993,
Abstract: We construct a well ordered symbolic dynamics plane for the stadium billiard. In this symbolic plane the forbidden and the allowed orbits are separated by a monotone pruning front, and allowed orbits can be systematically generated by sequences of approximate finite grammars.
Bifurcations and Complete Chaos for the Diamagnetic Kepler Problem
Kai T. Hansen
Physics , 1995, DOI: 10.1103/PhysRevE.51.1838
Abstract: We describe the structure of bifurcations in the unbounded classical Diamagnetic Kepler problem. We conjecture that this system does not have any stable orbits and that the non-wandering set is described by a complete trinary symbolic dynamics for scaled energies larger then $\epsilon_c=0.328782\ldots$.
Bifurcations of homoclinic orbits in bimodal maps
Kai T. Hansen
Physics , 1994, DOI: 10.1103/PhysRevE.50.1653
Abstract: We discuss the bifurcation structure of homoclinic orbits in bimodal one dimensional maps. The universal structure of these bifurcations with singular bifurcation points and the web of bifurcation lines through the parameter space are described. The bifurcations depend on two parameters (codimension 2 bifurcations). We find the bifurcation lines exactly in a symbolic dynamics parameter plane and numerically in the parameter planes of a polynomial map and a piecewise linear map.
Alternative method to find orbits in chaotic systems
Kai T. Hansen
Physics , 1995, DOI: 10.1103/PhysRevE.52.2388
Abstract: We present here a new method which applies well ordered symbolic dynamics to find unstable periodic and non-periodic orbits in a chaotic system. The method is simple and efficient and has been successfully applied to a number of different systems such as the H\'enon map, disk billiards, stadium billiard, wedge billiard, diamagnetic Kepler problem, colinear Helium atom and systems with attracting potentials. The method seems to be better than earlier applied methods.
Extracting three-body observables from finite-volume quantities
Maxwell T. Hansen
Physics , 2015,
Abstract: Scattering and transition amplitudes with three-hadron final states play an important role in nuclear and particle physics. However, predicting such quantities using numerical Lattice QCD is very difficult, in part because of the effects of Euclidean time and finite volume. In this review we highlight recent formal developments that work towards overcoming these issues. We organize the presentation into three parts: large volume expansions, non-relativistic nonperturbative analyses, and nonperturbative studies based in relativistic field theory. In the first part we discuss results for ground state energies and matrix elements given by expanding in inverse box length, $1/L$. We describe complications that arise at $\mathcal O(1/L^6)$ and include a table summarizing the results of different calculations. In the second part we summarize three recent non-relativistic non-perturbative studies and highlight the main conclusions of these works. This includes demonstrating that the three-particle finite-volume spectrum is determined, up to exponentially suppressed effects, by on-shell amplitudes, as well as recovering a finite-volume quantization condition for scattering a stable particle off a two-particle bound state. In this part we also highlight recent work concerning a three-particle bound state in a finite volume. In the third and final part, we review recent work based in non-perturbative relativistic field theory. Here the finite-volume spectrum has been related to an intermediate infinite-volume quantity which itself is related via a known integral equation to the relativistic, model-independent three-particle scattering amplitude. We motivate the appearance of the intermediate quantity, explain how it is related to the standard amplitude, and discuss prospects for using the result to constrain three-particle observables.
Isotope and REE Characterization of Groundwater Aquifers within the Aquifer Storage and Recovery Programme in Sukhothai (N.-Thailand)  [PDF]
Manussawee Hengsuwan, Monthon Yongprawat, Klaus Simon, Bent T. Hansen
Journal of Water Resource and Protection (JWARP) , 2016, DOI: 10.4236/jwarp.2016.86055
Abstract: Aquifer Storage and Recovery (ASR) was a pilot project for solving flood and drought problem in the northern part of Chao Phraya River basin, Thailand. This part of Thailand always faces flooding in rainy season and drought during dry season every year. The overexploitation of groundwater during dry season leads to continuously decline of water level in this area. In this project, the excessive surface water during rainy season was stored by injection of this treated surface water through recharge wells into the underground aquifers. This would serve to raise the water level, which can be extracted for use during the dry season. To assess the efficiency of the ASR process some tracers are required. The aim of this study is to prove the suitability of natural tracers to follow up the artificial recharge process; emphasis will be placed on Strontium (Sr) isotopic composition. The results showed that the change in 87Sr/86Sr ratios could be observed during an artificial recharge due to the different isotopic fingerprint of surface water and groundwater. However, the flow direction of the injected water cannot be clearly interpreted because of the limited number of monitoring wells, small distance between each monitoring well and the short duration of injection.
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