Proceedings of the Second International Mobile Satellite Conference (IMSC 1990)

Presented here are the proceedings of the Second International Mobile Satellite Conference (IMSC), held June 17-20, 1990 in Ottawa, Canada. Topics covered include future mobile satellite communications concepts, aeronautical applications, modulation and coding, propagation and experimental systems, mobile terminal equipment, network architecture and control, regulatory and policy considerations, vehicle antennas, and speech compression

Fortgeschrittene Methoden und Algorithmen für die computergestützte geodätische Datenanalyse

Die fortschreitende Digitalisierung mit ihren innovativen Technologien stellt zunehmende Anforderungen an Wirtschaft, Gesellschaft und Verwaltungen. Digitale Daten gelten als Schlüsselressource, die hohe Ansprüche u.a. an die Datenverarbeitung stellt, wie z. B. hohe Geschwindigkeit und Zuverlässigkeit. Besondere Bedeutung sind digitalen Daten mit Raumbezug beizumessen. Digitale Daten stammen im Bereich der Geodäsie und Geoinformatik von Multi-Sensor-Systemen, Satellitenmissionen, Smartphones, technischen Geräten, Computern oder von Datenbanken unterschiedlichster Institutionen und Behörden. „Big Data“ heißt der Trend und es gilt die enormen Datenmengen so breit und so effektiv wie möglich zu nutzen und mit Hilfe von computergestützten Tools, beispielsweise basierend auf künstlicher Intelligenz, auszuwerten. Um diese großen Datenmengen statistisch auszuwerten und zu analysieren, müssen laufend neue Modelle und Algorithmen entwickelt, getestet und validiert werden. Algorithmen erleichtern Geodätinnen und Geodäten seit Jahrzehnten das Leben - sie schätzen, entscheiden, wählen aus und bewerten die durchgeführten Analysen. Bei der geodätisch-statistischen Datenanalyse werden Beobachtungen zusammen mit Fachkenntnissen verwendet, um ein Modell zur Untersuchung und zum besseren Verständnis eines datengenerierenden Prozesses zu entwickeln. Die Datenanalyse wird verwendet, um das Modell zu verfeinern oder möglicherweise ein anderes Modell auszuwählen, um geeignete Werte für Modellterme zu bestimmen und um das Modell zu verwenden, oder um Aussagen über den Prozess zu treffen. Die Fortschritte in der Statistik in den vergangenen Jahren beschränken sich nicht nur auf die Theorie, sondern umfassen auch die Entwicklung von neuartigen computergestützten Methoden. Die Fortschritte in der Rechenleistung haben neuere und aufwendigere statistische Methoden ermöglicht. Eine Vielzahl von alternativen Darstellungen der Daten und von Modellen können untersucht werden. Wenn bestimmte statistische Modelle mathematisch nicht realisierbar sind, müssen Approximationsmethoden angewendet werden, die oft auf asymptotischer Inferenz basieren. Fortschritte in der Rechenleistung und Entwicklungen in der Theorie haben die computergestützte Inferenz zu einer praktikablen und nützlichen Alternative zu den Standardmethoden der asymptotischen Inferenz in der traditionellen Statistik werden lassen. Die computergestützte Inferenz basiert auf der Simulation statistischer Modelle. Die vorliegende Habilitationsschrift stellt die Ergebnisse der Forschungsaktivitäten des Autors im Bereich der statistischen und simulationsbasierten Inferenz für die geodätische Datenanalyse vor, die am Geodätischen Institut der Gottfried Wilhelm Leibniz Universität Hannover während der Zeit des Autors als Postdoktorand von 2009 bis 2019 publiziert wurden. Die Forschungsschwerpunkte in dieser Arbeit befassen sich mit der Entwicklung von mathematisch-statistischen Modellen, Schätzverfahren und computergestützten Algorithmen, um raum-zeitliche und möglicherweise unvollständige Daten, welche durch zufällige, systematische, ausreißerbehaftete und korrelierte Messabweichungen charakterisiert sind, rekursiv sowie nicht-rekursiv auszugleichen. Herausforderungen bestehen hierbei in der genauen, zuverlässigen und effizienten Schätzung der unbekannten Modellparameter, in der Ableitung von Qualitätsmaßen der Schätzung sowie in der statistisch-simulationsbasierten Beurteilung der Schätzergebnisse. Die Forschungsschwerpunkte haben verschiedene Anwendungsmöglichkeiten in den Bereichen der Ingenieurgeodäsie und der Immobilienbewertung gefunden

Air Force Institute of Technology Research Report 2019

This Research Report presents the FY19 research statistics and contributions of the Graduate School of Engineering and Management (EN) at AFIT. AFIT research interests and faculty expertise cover a broad spectrum of technical areas related to USAF needs, as reflected by the range of topics addressed in the faculty and student publications listed in this report. In most cases, the research work reported herein is directly sponsored by one or more USAF or DOD agencies. AFIT welcomes the opportunity to conduct research on additional topics of interest to the USAF, DOD, and other federal organizations when adequate manpower and financial resources are available and/or provided by a sponsor. In addition, AFIT provides research collaboration and technology transfer benefits to the public through Cooperative Research and Development Agreements (CRADAs). Interested individuals may discuss ideas for new research collaborations, potential CRADAs, or research proposals with individual faculty using the contact information in this document

Expanding the Horizons of Manufacturing: Towards Wide Integration, Smart Systems and Tools

This research topic aims at enterprise-wide modeling and optimization (EWMO) through the development and application of integrated modeling, simulation and optimization methodologies, and computer-aided tools for reliable and sustainable improvement opportunities within the entire manufacturing network (raw materials, production plants, distribution, retailers, and customers) and its components. This integrated approach incorporates information from the local primary control and supervisory modules into the scheduling/planning formulation. That makes it possible to dynamically react to incidents that occur in the network components at the appropriate decision-making level, requiring fewer resources, emitting less waste, and allowing for better responsiveness in changing market requirements and operational variations, reducing cost, waste, energy consumption and environmental impact, and increasing the benefits. More recently, the exploitation of new technology integration, such as through semantic models in formal knowledge models, allows for the capture and utilization of domain knowledge, human knowledge, and expert knowledge toward comprehensive intelligent management. Otherwise, the development of advanced technologies and tools, such as cyber-physical systems, the Internet of Things, the Industrial Internet of Things, Artificial Intelligence, Big Data, Cloud Computing, Blockchain, etc., have captured the attention of manufacturing enterprises toward intelligent manufacturing systems

Proceedings of the Third International Mobile Satellite Conference (IMSC 1993)

Satellite-based mobile communications systems provide voice and data communications to users over a vast geographic area. The users may communicate via mobile or hand-held terminals, which may also provide access to terrestrial cellular communications services. While the first and second International Mobile Satellite Conferences (IMSC) mostly concentrated on technical advances, this Third IMSC also focuses on the increasing worldwide commercial activities in Mobile Satellite Services. Because of the large service areas provided by such systems, it is important to consider political and regulatory issues in addition to technical and user requirements issues. Topics covered include: the direct broadcast of audio programming from satellites; spacecraft technology; regulatory and policy considerations; advanced system concepts and analysis; propagation; and user requirements and applications

Proceedings of the Mobile Satellite Conference

A satellite-based mobile communications system provides voice and data communications to mobile users over a vast geographic area. The technical and service characteristics of mobile satellite systems (MSSs) are presented and form an in-depth view of the current MSS status at the system and subsystem levels. Major emphasis is placed on developments, current and future, in the following critical MSS technology areas: vehicle antennas, networking, modulation and coding, speech compression, channel characterization, space segment technology and MSS experiments. Also, the mobile satellite communications needs of government agencies are addressed, as is the MSS potential to fulfill them

Investigation of flow-flow, flow-surface, and multiphase interaction problems in rarefied gas dynamics

Presently, with the development of technology, the need to study and understand high-speed rarefied gas flows has become an impending reality in terms of its potential assets to a wide spectrum of industries, ranging from interplanetary travel to coating technology. This study addresses the interactions of high-speed rariefied gas flows with one another, surfaces, and solid particles in order to ascertain high-speed rarefied gas behaviours in various applications. Three different interaction scenarios -two of which rely on numerical analysis and one which is based on the development of a novel solver- are investigated, where computations are conducted with a direct simulation Monte Carlo (DSMC) solver, dsmcFoam+, and a particle laden rarefied gas multiphase flow solver, rarefiedMultiphaseFoam, within the framework of an open-source tool, OpenFOAM. Rarefied shock-shock interactions have a crucial impact on aerodynamic performance and aero-heating characteristics in supersonic and hypersonic flight platforms. A shock-shock interaction problem can arise in high-speed vehicles, where an oblique shock on one part of the body impinges on a bow shock from a different part of the body and the nature of the interaction can change as the vehicle increases in altitude to a more rarefied environment. Part of this research examines the outcomes of a numerical study investigating the formation of Edney shock patterns from type-I to type-VI as a result of shock-shock interactions at different rarefaction levels. The free-stream flow is at a Mach number of 10. Both geometrical and rarefaction parameters in shock-shock interaction problems determine what type of Edney pattern is formed. As the flow becomes more rarefied, the regions of enhanced thermo mechanical loading spread further over the surface but their peak values decrease. It is known that these shock interactions can have unsteady behaviour in the continuum regime; current works show that although increasing rarefaction tends to move the flow towards steady behaviour, it still possible to have unsteady flow behaviour under more rarefied conditions. In another case, the interactions of high-speed rarefied flows with one another and a surface are analysed. The canting axis of thrusters on space platforms, which likely operate in a vacuum environment with a high degree of flow rarefaction, is significant in order to create the desired torque for manoeuvring, maintaining orbit, eliminating perturbation forces, docking, etc. Therefore, the interactions of expanding plumes with one another and with solid surfaces in multi-nozzle arrays are inevitable. In order to gain a better understanding of the effect of nozzle configurations and conditions on the plume-plume and plume-surface interactions, a simulation matrix is carried out for a sonic nozzle. As nozzle arrays are packed more tightly together, the plume-plume interactions become stronger, which has an influence on the stagnation line density and temperature profiles. For a given stagnation temperature, the spacing between nozzles in the array does not have a strong influence on the normalised surface pressure, but there is an increase in the maximum normalised shear stress as the distance between the nozzles increases. There is a significant difference in the results for double and quadruple nozzle arrays, with greater normalised stagnation pressures and shear stresses found as the number of nozzles in the array is increased. For a single nozzle, increasing the stagnation temperature does not have a significant effect on the normalised surface pressures, but does increase the maximum normalised shear stress and the measured heat flux on the surface. For arrays of double and quadruple nozzles, the number of nozzles has a much greater influence on the measured surface pressure, surface shear stress, and surface heat transfer than the stagnation temperature. In the last case, the effect of the impingement height on the plume and surface parameters is discussed while maintaining all the parameters of the 1000 K single plume case but with varying impingement heights. It is found that the smaller impingement height results in a denser plume, and a greater impact on the surface. However, higher impingement heights result in a wider distribution on the surface as the plume can expand more. With the awareness of a lack of a solver for rarefied gas flows-solid particle interactions, the final case in this thesis focuses on the development, benchmarking and testing of a multiphase open-source code, rarefiedMultiphaseFoam. Such a solver provides applicable benefits such as modelling of the transport of unburnt solid propellant in rocket a plume, and simulating of the impingement of two-phase plume on a surface in a vacuum environment, as well as providing numerical solutions in terms of surface coating technology, where multiphase gas and solid flows are employed, etc. This dsmcFoam+ based solver is capable of simulating one-way coupling interactions. This type of particle-laden rarefied gas flow has two components: the rarefied gas flow itself and the solid particles transported by the gas flow. The main restriction is that the solid phase surrounded by the gas phase is assumed to be in the free-molecular regime with respect to the solid particle diameters and that it is a one-way coupling, so that only the effect of gas particles on the solid particles is considered. rarefiedMultiphaseFoam can produce results for steady and transient one-way coupling problems in zero-dimensional (0D), one-dimesion (1D), two-dimensions (2D) (both planar and maxisymmetric), and three-dimensions (3D). Two benchmarking cases on momentum and energy transfer from gas molecules to solid particles, and free expansion of a two-phase jet flow are presented. The reliability of the solver is further demonstrated through a test case on surface coating using the Aerosol Deposition Method. The benchmarking cases yield results that are in good agreement with theoretical, experimental, and numerical data in the literature