Temperature Effects in Optical Fiber Dispersion Compensation Modules

This thesis presents the results for the temperature variation of the Differential Group Delay (DGD) measurements of a Dispersion Compensation Module (DCM) and interprets the results with a theoretical DGD model based on glass viscoelastic properties and estimated values of some of glass parameters. The results of our analysis demonstrate the existence of long birefringence relaxation times on the order of many hours in response to temperature changes. These results could be of significance in interpreting the behavior of optical fiber systems

Core Structures in Random Graphs and Hypergraphs

The k-core of a graph is its maximal subgraph with minimum degree at least k. The study of k-cores in random graphs was initiated by Bollobás in 1984 in connection to k-connected subgraphs of random graphs. Subsequently, k-cores and their properties have been extensively investigated in random graphs and hypergraphs, with the determination of the threshold for the emergence of a giant k-core, due to Pittel, Spencer and Wormald, as one of the most prominent results. In this thesis, we obtain an asymptotic formula for the number of 2-connected graphs, as well as 2-edge-connected graphs, with given number of vertices and edges in the sparse range by exploiting properties of random 2-cores. Our results essentially cover the whole range for which asymptotic formulae were not described before. This is joint work with G. Kemkes and N. Wormald. By defining and analysing a core-type structure for uniform hypergraphs, we obtain an asymptotic formula for the number of connected 3-uniform hypergraphs with given number of vertices and edges in a sparse range. This is joint work with N. Wormald. We also examine robustness aspects of k-cores of random graphs. More specifically, we investigate the effect that the deletion of a random edge has in the k-core as follows: we delete a random edge from the k-core, obtain the k-core of the resulting graph, and compare its order with the original k-core. For this investigation we obtain results for the giant k-core for Erdős-Rényi random graphs as well as for random graphs with minimum degree at least k and given number of vertices and edges

Numerical relativity on cosmological past null cones

The observational approach to cosmology is the endeavour to reconstruct the geometry of the Universe using only data that is theoretically verifiable within the causal boundaries of a cosmological observer. Using this approach, it was shown in [36] that given ideal cosmological observations, the only essential assumption necessary to determine the geometry of the Universe is a theory of gravity. Assuming General Relativity, the full set of Einstein field equations (EFEs) can be used to reconstruct the geometry of the Universe using direct observations on the past null cone (PNC) as initial conditions. Observationally and theoretically this is a very ambitious task and therefore, current developments have been restricted to spherically symmetric dust models while only relaxing the usual assumption of homogeneity in the radial direction. These restricted models are important for the development of theoretical foundations and also useful as verification models since they avoid the circularity of verifying what has already been assumed. The work presented in this thesis is the development of such a model where numerical relativity (NR) is used to simulate the observable universe. Similar to the work of Ellis and co-workers [36], a reference frame based on the PNC is used. The reference frame used here, however, is based on that of the characteristic formalism of NR, which has developed for calculating the propagation of gravitational waves. This provides a formalism that is well established in NR, making the use of existing algorithms possible. The Bondi-Sachs coordinates of the characteristic formalism is, however, not suitable for calculations beyond the observer apparent horizon (AH) since the diameter distance used as a radial coordinate becomes multi-valued when the cosmological PNC reconverges in the history of a universe, smaller in the past. With this taken into consideration, the Bondi-Sachs characteristic formalism is implemented for cosmology and the problem approaching the AH is investigated. Further developments address the limitations approaching the AH by introducing a metric based on the Bondi-Sachs metric where the radial coordinate is replaced with an affine parameter. The model is derived with a cosmological constant Λ incorporated into the EFEs where Λ is taken as a parameter of the theory of gravity rather than as a matter source term. Similar to the conventional characteristic formalism, this model consists of a system of differential equations for numerically evolving the EFEs as a characteristic initial value problem (CIVP). A numerical code implemented for the method has been found to be second order convergent. This code enables simulations of different models given identical data on the initial null cone and provides a method to investigate their physical consistency within the causally connected region of our current PNC. These developments closely follow existing 3D schemes developed for gravitational wave simulations, which should make it natural to extend the affine CIVP beyond spherical symmetric simulations. The developments presented in this thesis is an extended version of two papers published earlier

The effect of field-of-view on the manual control of visually simulated aircraft roll

Thesis (M.S.)--Massachusetts Institute of Technology. Dept. of Aeronautics and Astronautics, 1986.Microfiche copy available in Archives and Barker.Bibliography: leaves 219-220.by Edward William Kneller.M.S

Neutron scattering and microscopy studies of the structure and dynamics of water near a nanostructured hydrophilic copper oxide surface

Recently, it has been shown that superhydrophilic coatings of "grass-like" cupric oxide (CuO) nanostructures can significantly improve the thermal performance of heat transfer devices known as oscillating heat pipes (OHPs). The origin of this enhanced performance is currently unknown, but it is believed to be attributed to the thin film of interfacial water supported by the nanostructures that coat the OHP's interior surface. The aim of this work is to investigate the microscopic origin of enhanced heat transfer at the CuO surface by studying the structure, morphology, freezing/melting behavior, and dynamics of the water in proximity to the CuO coating over time and length scales that span picosecond-to-seconds and angstroms-to-millimeters, respectively . ... Our results demonstrate that water near superhydrophilic CuO nanostructures exhibits low-temperature anomalies in its structure and dynamics at the molecular level-a direction of research that has both applied and fundamental interest. The significantly altered structure and dynamics of the interfacial water could affect the boundary conditions for bulk water motion inside of an OHP during its operation. To test this hypothesis, we have proposed time-resolved neutron imaging experiments to characterize the kinetics of water oscillations in CuO-coated OHPs.Includes bibliographical reference

Cleaning principles in automatic dishwashers

Cleaning inside automatic dishwashers (ADWs) represents an example of a ‘black box’ problem. The description of the phenomena occurring during a typical wash cycle is not currently well known. This thesis aims to illustrate and expand the in-depth knowledge required to better understand the wash process by analysing the different mechanical and chemical factors involved as well as the interactions between them. Online measurements techniques (Positron Emission Particle Tracking, scanning Fluid Dynamic Gauge or Image Analysis) were combined with statistical and numerical modelling to investigate the evolution over time of the cleaning system

Analysis and Development of Instrument Software Paradigms: Conception and Implementation of a New Instrument Control and Data Acquisition System, Proven by Material Scientific Applications

During the last 50 years, the quality of analysis methods in many scientific disciplines has been enhanced by electronic applications, automation and data processing. While the features, performance and usability of these processes have been continually enhanced, it is conspicuous that the majority of institutes operate own proprietary software. This situation arises for both historical and financial reasons, plus a wish to retain autonomy fuelled by the requirement for a system that remains compatible with both new and legacy hardware. This thesis reviews the commonly used scientific software systems and their stakeholders and tries to identify generic problems. The demands on instrument systems are summarized by a requirement specification. Based on these requirements, a basic concept is developed that reflects the current state-of-the art in software design and which may provide a blueprint for instrument system architectures. The results are used to create a proof-of-concept implementation. Core to this approach is an application server that comes with a container, which makes use of the Inversion-of-Control pattern to loosely couple and execute components. These do not need to implement fixed interfaces and are thus decoupled from a specific use-case. Components can, for example, be proxies that control and acquire data from legacy hardware, perform calculations, provide a human-machine interface or act as storage. They are dynamically wired to experiments using XML-based Assembly files. Both Assemblies and Components can be published using a central store on a collaboration platform and shared by the community. This increases reusability and allows the use of existing Assemblies with new hardware by simply replacing the hardware proxy modules. Example components have been provided for the access to legacy and new instrument hardware, the storage of results in the NeXus format, data reduction, simulation with McStas, the execution of customizable scans and the visualization of data