602 research outputs found
On high performance computing in geodesy : applications in global gravity field determination
Autonomously working sensor platforms deliver an increasing amount of precise data sets, which are often usable in geodetic applications. Due to the volume and quality, models determined from the data can be parameterized more complex and in more detail. To derive model parameters from these observations, the solution of a high dimensional inverse data fitting problem is often required. To solve such high dimensional adjustment problems, this thesis proposes a systematical, end-to-end use of a massive parallel implementation of the geodetic data analysis, using standard concepts of massive parallel high performance computing. It is shown how these concepts can be integrated into a typical geodetic problem, which requires the solution of a high dimensional adjustment problem. Due to the proposed parallel use of the computing and memory resources of a compute cluster it is shown, how general Gauss-Markoff models become solvable, which were only solvable by means of computationally motivated simplifications and approximations before. A basic, easy-to-use framework is developed, which is able to perform all relevant operations needed to solve a typical geodetic least squares adjustment problem. It provides the interface to the standard concepts and libraries used. Examples, including different characteristics of the adjustment problem, show how the framework is used and can be adapted for specific applications. In a computational sense rigorous solutions become possible for hundreds of thousands to millions of unknown parameters, which have to be estimated from a huge number of observations.
Three special problems with different characteristics, as they arise in global gravity field recovery, are chosen and massive parallel implementations of the solution processes are derived. The first application covers global gravity field determination from real data as collected by the GOCE satellite mission (comprising 440 million highly correlated observations, 80,000 parameters). Within the second application high dimensional global gravity field models are estimated from the combination of complementary data sets via the assembly and solution of full normal equations (scenarios with 520,000 parameters, 2 TB normal equations). The third application solves a comparable problem, but uses an iterative least squares solver, allowing for a parameter space of even higher dimension (now considering scenarios with two million parameters). This thesis forms the basis for a flexible massive parallel software package, which is extendable according to further current and future research topics studied in the department. Within this thesis, the main focus lies on the computational aspects.Autonom arbeitende Sensorplattformen liefern prĂ€zise geodĂ€tisch nutzbare DatensĂ€tze in gröĂer werdendem Umfang. Deren Menge und QualitĂ€t fĂŒhrt dazu, dass Modelle die aus den Beobachtungen abgeleitet werden, immer komplexer und detailreicher angesetzt werden können. Zur Bestimmung von Modellparametern aus den Beobachtungen gilt es oftmals, ein hochdimensionales inverses Problem im Sinne der Ausgleichungsrechnung zu lösen. Innerhalb dieser Arbeit soll ein Beitrag dazu geleistet werden, Methoden und Konzepte aus dem Hochleistungsrechnen in der geodĂ€tischen Datenanalyse strukturiert, durchgĂ€ngig und konsequent zu verwenden. Diese Arbeit zeigt, wie sich diese nutzen lassen, um geodĂ€tische Fragestellungen, die ein hochdimensionales Ausgleichungsproblem beinhalten, zu lösen. Durch die gemeinsame Nutzung der Rechen- und Speicherressourcen eines massiv parallelen Rechenclusters werden Gauss-Markoff Modelle lösbar, die ohne den Einsatz solcher Techniken vorher höchstens mit massiven Approximationen und Vereinfachungen lösbar waren. Ein entwickeltes GrundgerĂŒst stellt die Schnittstelle zu den massiv parallelen Standards dar, die im Rahmen einer numerischen Lösung von typischen Ausgleichungsaufgaben benötigt werden.
Konkrete Anwendungen mit unterschiedlichen Charakteristiken zeigen das detaillierte Vorgehen um das GrundgerĂŒst zu verwenden und zu spezifizieren. Rechentechnisch strenge Lösungen sind so fĂŒr Hunderttausende bis Millionen von unbekannten Parametern möglich, die aus einer Vielzahl von Beobachtungen geschĂ€tzt werden. Drei spezielle Anwendungen aus dem Bereich der globalen Bestimmung des Erdschwerefeldes werden vorgestellt und die Implementierungen fĂŒr einen massiv parallelen Hochleistungsrechner abgeleitet. Die erste Anwendung beinhaltet die Bestimmung von Schwerefeldmodellen aus realen Beobachtungen der Satellitenmission GOCE (welche 440 Millionen korrelierte Beobachtungen umfasst, 80,000 Parameter). In der zweite Anwendung werden globale hochdimensionale Schwerefelder aus komplementĂ€ren Daten ĂŒber das Aufstellen und Lösen von vollen Normalgleichungen geschĂ€tzt (basierend auf Szenarien mit 520,000 Parametern, 2 TB Normalgleichungen). Die dritte Anwendung löst dasselbe Problem, jedoch ĂŒber einen iterativen Löser, wodurch der Parameterraum noch einmal deutlich höher dimensional sein kann (betrachtet werden nun Szenarien mit 2 Millionen Parametern). Die Arbeit bildet die Grundlage fĂŒr ein massiv paralleles Softwarepaket, welches schrittweise um Spezialisierungen, abhĂ€ngig von aktuellen Forschungsprojekten in der Arbeitsgruppe, erweitert werden wird. Innerhalb dieser Arbeit liegt der Fokus rein auf den rechentechnischen Aspekten
On High Performance Computing in Geodesy : Applications in Global Gravity Field Determination
Autonomously working sensor platforms deliver an increasing amount of precise data sets, which are often usable in geodetic applications. Due to the volume and quality, models determined from the data can be parameterized more complex and in more detail. To derive model parameters from these observations, the solution of a high dimensional inverse data fitting problem is often required. To solve such high dimensional adjustment problems, this thesis proposes a systematical, end-to-end use of a massive parallel implementation of the geodetic data analysis, using standard concepts of massive parallel high performance computing. It is shown how these concepts can be integrated into a typical geodetic problem, which requires the solution of a high dimensional adjustment problem. Due to the proposed parallel use of the computing and memory resources of a compute cluster it is shown, how general Gauss-Markoff models become solvable, which were only solvable by means of computationally motivated simplifications and approximations before. A basic, easy-to-use framework is developed, which is able to perform all relevant operations needed to solve a typical geodetic least squares adjustment problem. It provides the interface to the standard concepts and libraries used. Examples, including different characteristics of the adjustment problem, show how the framework is used and can be adapted for specific applications. In a computational sense rigorous solutions become possible for hundreds of thousands to millions of unknown parameters, which have to be estimated from a huge number of observations. Three special problems with different characteristics, as they arise in global gravity field recovery, are chosen and massive parallel implementations of the solution processes are derived. The first application covers global gravity field determination from real data as collected by the GOCE satellite mission (comprising 440 million highly correlated observations, 80,000 parameters). Within the second application high dimensional global gravity field models are estimated from the combination of complementary data sets via the assembly and solution of full normal equations (scenarios with 520,000 parameters, 2 TB normal equations). The third application solves a comparable problem, but uses an iterative least squares solver, allowing for a parameter space of even higher dimension (now considering scenarios with two million parameters). This thesis forms the basis for a flexible massive parallel software package, which is extendable according to further current and future research topics studied in the department. Within this thesis, the main focus lies on the computational aspects.Autonom arbeitende Sensorplattformen liefern prĂ€zise geodĂ€tisch nutzbare DatensĂ€tze in gröĂer werdendem Umfang. Deren Menge und QualitĂ€t fĂŒhrt dazu, dass Modelle die aus den Beobachtungen abgeleitet werden, immer komplexer und detailreicher angesetzt werden können. Zur Bestimmung von Modellparametern aus den Beobachtungen gilt es oftmals, ein hochdimensionales inverses Problem im Sinne der Ausgleichungsrechnung zu lösen. Innerhalb dieser Arbeit soll ein Beitrag dazu geleistet werden, Methoden und Konzepte aus dem Hochleistungsrechnen in der geodĂ€tischen Datenanalyse strukturiert, durchgĂ€ngig und konsequent zu verwenden. Diese Arbeit zeigt, wie sich diese nutzen lassen, um geodĂ€tische Fragestellungen, die ein hochdimensionales Ausgleichungsproblem beinhalten, zu lösen. Durch die gemeinsame Nutzung der Rechen- und Speicherressourcen eines massiv parallelen Rechenclusters werden Gauss-Markoff Modelle lösbar, die ohne den Einsatz solcher Techniken vorher höchstens mit massiven Approximationen und Vereinfachungen lösbar waren. Ein entwickeltes GrundgerĂŒst stellt die Schnittstelle zu den massiv parallelen Standards dar, die im Rahmen einer numerischen Lösung von typischen Ausgleichungsaufgaben benötigt werden. Konkrete Anwendungen mit unterschiedlichen Charakteristiken zeigen das detaillierte Vorgehen um das GrundgerĂŒst zu verwenden und zu spezifizieren. Rechentechnisch strenge Lösungen sind so fĂŒr Hunderttausende bis Millionen von unbekannten Parametern möglich, die aus einer Vielzahl von Beobachtungen geschĂ€tzt werden. Drei spezielle Anwendungen aus dem Bereich der globalen Bestimmung des Erdschwerefeldes werden vorgestellt und die Implementierungen fĂŒr einen massiv parallelen Hochleistungsrechner abgeleitet. Die erste Anwendung beinhaltet die Bestimmung von Schwerefeldmodellen aus realen Beobachtungen der Satellitenmission GOCE (welche 440 Millionen korrelierte Beobachtungen umfasst, 80,000 Parameter). In der zweite Anwendung werden globale hochdimensionale Schwerefelder aus komplementĂ€ren Daten ĂŒber das Aufstellen und Lösen von vollen Normalgleichungen geschĂ€tzt (basierend auf Szenarien mit 520,000 Parametern, 2 TB Normalgleichungen). Die dritte Anwendung löst dasselbe Problem, jedoch ĂŒber einen iterativen Löser, wodurch der Parameterraum noch einmal deutlich höher dimensional sein kann (betrachtet werden nun Szenarien mit 2 Millionen Parametern). Die Arbeit bildet die Grundlage fĂŒr ein massiv paralleles Softwarepaket, welches schrittweise um Spezialisierungen, abhĂ€ngig von aktuellen Forschungsprojekten in der Arbeitsgruppe, erweitert werden wird. Innerhalb dieser Arbeit liegt der Fokus rein auf den rechentechnischen Aspekten
Is the air change efficiency sufficient to assess the removal of airborne contamination in mixing ventilation?
This investigation analyze the correlation between two common methods to assess the ventilation effectiveness: An averaged contamination removal effectiveness (CRE) value based on the residual lifetime and the air change efficiency (ACE) to better understand their relationship to then give a recommendation for the IAQ-assessment of ventilation designs. The present numerical investigation puts focus on a simple mixing ventilation scenario with different conditions: air change rate, specific heat flux, supply air diffuser and exhaust position. Statistically, the results show a significant correlation. A detailed consideration, especially for the partial load range, will be necessary to for a valide determination of removing airborne contaminationpublishedVersio
Quasi-soliton scattering in quantum spin chains
The quantum scattering of magnon bound states in the anisotropic Heisenberg
spin chain is shown to display features similar to the scattering of solitons
in classical exactly solvable models. Localized colliding Gaussian wave packets
of bound magnons are constructed from string solutions of the Bethe equations
and subsequently evolved in time, relying on an algebraic Bethe ansatz based
framework for the computation of local expectation values in real space-time.
The local magnetization profile shows the trajectories of colliding wave
packets of bound magnons, which obtain a spatial displacement upon scattering.
Analytic predictions on the displacements for various values of anisotropy and
string lengths are derived from scattering theory and Bethe ansatz phase
shifts, matching time evolution fits on the displacements. The time evolved
block decimation (TEBD) algorithm allows for the study of scattering
displacements from spin-block states, showing similar scattering displacement
features.Comment: 15 pages, 7 figures. (v2: citations added
The Effects of Relative Humidity and Compound Interaction on the Adsorption of Mineral Oil Vapor by Activated Carbon
A bench-scale carbon adsorption system was constructed to examine the effects of relative humidity and compound interaction on the adsorption of specific components of mineral oil vapor by activated carbon. Small beds of activated carbon were challenged with single and binary component vapor at low and high relative humidities (less than 13 percent and greater than 87 percent). The components consisted of undecane and dodecane at nominal concentrations of 4 ppm each. High relative humidity and compound interaction substantially reduced the carbon's adsorption capacity for both compounds, however, the effect of the latter was more pronounced on the adsorption of undecane versus dodecane. The equilibrium adsorption capacity of the carbon for the single and binary component vapor at high relative humidity was approximately 0.20 grams of vapor per gram of carbon. This adsorption capacity was 24 to 28percent of the capacities quoted by the carbon vendor for similar compounds.Master of Science in Environmental Engineerin
Ultrastructure of the Membrana Limitans Interna after Dye-Assisted Membrane Peeling
The purpose of this study was to investigate the ultrastructure
of the membrana limitans interna (internal limiting
membrane, ILM) and to evaluate alterations to the retinal cell
layers after membrane peeling with vital dyes. Twenty-five
patients (25 eyes) who underwent macular hole surgery
were included, whereby 12 indocyanine green (ICG)- and 13
brilliant blue G (BBG)-stained ILM were analyzed using light,
transmission electron and scanning electron microscopy.
Retinal cell fragments on the ILM were identified in both
groups using immunohistochemistry. Comparing ICG- and
BBG-stained membranes, larger cellular fragments were observed
at a higher frequency in the BBG group. Thereby, the
findings indicate that ICG permits an enhanced separation
of the ILM from the underlying retina with less mechanical
destruction. A possible explanation might be seen in the
known photosensitivity of ICG, which induces a stiffening
and shrinkage of the ILM but also generates retinal toxic metabolite
Collective Excitations and Ground State Correlations
A generalized RPA formalism is presented which treats pp and ph correlations
on an equal footing. The effect of these correlations on the single-particle
Green function is discussed and it is demonstrated that a self-consistent
treatment of the single-particle Green function is required to obtain stable
solutions. A simple approximation scheme is presented which incorporates for
this self-consistency requirement and conserves the number of particles.
Results of numerical calculations are given for O using a G-matrix
interaction derived from a realistic One-Boson-Exchange potential.Comment: 16 Pages + 2 Figures (included at the end as uuencoded ps-files),
TU-18089
Photoproduction of the Lambda(1405) on the proton and nuclei
We study the gamma p ---> K^+ Lambda(1405) reaction at energies close to
threshold using a chiral unitary model where the resonance is generated
dynamically from K^-p interaction with other channels constructed from the
octets of baryons and mesons. Predictions are made for cross sections into
several channels and it is shown that the detection of the K^+ is sufficient to
determine the shape and strength of the Lambda(1405) resonance. The
determination of the resonance properties in nuclei requires instead the
detection of the resonance decay channels. Pauli blocking effects on the
resonance, which have been shown to be very important for the resonance at rest
in the nucleus, are irrelevant here where the resonance is produced with a
large momentum. The nuclear modifications here would thus offer information on
the resonance and K^- nucleus dynamics complementary to the one offered so far
by K^- atoms.Comment: 9 pages, 4 postscripts figure
The complete conformal spectrum of a invariant network model and logarithmic corrections
We investigate the low temperature asymptotics and the finite size spectrum
of a class of Temperley-Lieb models. As reference system we use the spin-1/2
Heisenberg chain with anisotropy parameter and twisted boundary
conditions. Special emphasis is placed on the study of logarithmic corrections
appearing in the case of in the bulk susceptibility data and in
the low-energy spectrum yielding the conformal dimensions. For the
invariant 3-state representation of the Temperley-Lieb algebra with
we give the complete set of scaling dimensions which show huge
degeneracies.Comment: 18 pages, 5 figure
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