Metal Fusion and Granulation

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Real-Time Planning with Multi-Fidelity Models for Agile Flights in Unknown Environments

Autonomous navigation through unknown environments is a challenging task that entails real-time localization, perception, planning, and control. UAVs with this capability have begun to emerge in the literature with advances in lightweight sensing and computing. Although the planning methodologies vary from platform to platform, many algorithms adopt a hierarchical planning architecture where a slow, low-fidelity global planner guides a fast, high-fidelity local planner. However, in unknown environments, this approach can lead to erratic or unstable behavior due to the interaction between the global planner, whose solution is changing constantly, and the local planner; a consequence of not capturing higher-order dynamics in the global plan. This work proposes a planning framework in which multi-fidelity models are used to reduce the discrepancy between the local and global planner. Our approach uses high-, medium-, and low-fidelity models to compose a path that captures higher-order dynamics while remaining computationally tractable. In addition, we address the interaction between a fast planner and a slower mapper by considering the sensor data not yet fused into the map during the collision check. This novel mapping and planning framework for agile flights is validated in simulation and hardware experiments, showing replanning times of 5-40 ms in cluttered environments.Comment: ICRA 201

Factors Impacting Observation-Based Estimates of Urban Greenhouse Gas Emissions

Urban areas are responsible for a large and increasing fraction of anthropogenic greenhouse gas emissions. Accurate methods for quantifying and monitoring those emissions are needed to suggest and evaluate mitigation policies, as well as for fundamental carbon cycle science as anthropogenic carbon dioxide emissions become a dominant source of uncertainty in closing the global carbon budget. I present investigations into several factors that can impact our ability to characterize urban greenhouse gas emissions using observations in the atmosphere. An automated method is developed for estimating the mixing depth, a key meteorological variable affecting the sensitivity of mole fraction observations to emissions fluxes, using optical remote sensing instruments. In a long time series of mixing depth estimates in Pasadena, California, day-to-day variability is shown to be large in comparison to seasonal trends. Significant mixing depth biases are demonstrated in meteorological models, and the likely impacts on emissions estimation are discussed. Optimized estimates of methane emissions in the South Coast Air Basin, California, are made using several flux inversion or regularization methods, with four sources of meteorological information, and with all or some of the mole fraction observations taken at nine within-basin observing sites associated with the LA Megacities Carbon Project. Using the full observational dataset in a geostatistical inversion, the capability to detect seasonal and event-driven emissions changes is demonstrated with generic meteorology, opening the door to near-real-time monitoring. Differences in absolute methane emissions flux magnitude according to the source of driving meteorological information are shown to be largely removable by calibration to a trusted model. The choice of inversion or regularization method is shown to have substantial impacts both on the estimated emissions time series and on the capacity to detect emissions changes, especially when the observational constraint is reduced.PHDPhysicsUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttps://deepblue.lib.umich.edu/bitstream/2027.42/145986/1/johnware_1.pd

Adapting to a new role: a study designed to help senior managers adapt to new positions after organisation restructuring

The work on which this thesis is based, studies the implementation phase of the total organisation restructure of the National Health Service in 1974 as experienced by a large group of Senior Pharmaceutical Managers who found it difficult to establish themselves in their new positions. The study starts in 1976 and researches to identify the nature and cause of the difficulties facing the managers. It is concluded that the probable cause is rooted in the sudden destruction of mechanisms developed before 1974 to assist new managers establish themselves in their positions. A solution is designed and tested before being implemented with the Senior Pharmaceutical Managers, By 1977 it had become clear that a similar situation faced other large groups of Senior Managers belonging to the Nursing and Works professions of the Health Service. As a result the project and study is continued to help these two other professions and with apparent equal success until 1985.A number of objectives are met during this study. A system is developed for facilitating role identification and implementation during a period of organisation restructuring as a means to help new managers adapt and become established in equally new positions. In addition this project is an example of the use of collaboration as a method to assist large numbers of senior managers belonging to Health Service professions meet radically new demands of role

A View of Celi\u27s Journal of Surveys and Chart of 1757

The San Francisco de Asis was a xebec, one of a class of relatively small three-masted sailing vessels used around the Spanish and Portuguese coasts. Her fore and mizzenmasts were lateen rigged, and her mainmast was square rigged, having three sails - main, lower main, and upper mainsails. This type was frequently outfitted with oars for use in calm water, but there is no indication that this vessel was so equipped

Multi-scale data storage schemes for spatial information systems

This thesis documents a research project that has led to the design and prototype implementation of several data storage schemes suited to the efficient multi-scale representation of integrated spatial data. Spatial information systems will benefit from having data models which allow for data to be viewed and analysed at various levels of detail, while the integration of data from different sources will lead to a more accurate representation of reality. The work has addressed two specific problems. The first concerns the design of an integrated multi-scale data model suited for use within Geographical Information Systems. This has led to the development of two data models, each of which allow for the integration of terrain data and topographic data at multiple levels of detail. The models are based on a combination of adapted versions of three previous data structures, namely, the constrained Delaunay pyramid, the line generalisation tree and the fixed grid. The second specific problem addressed in this thesis has been the development of an integrated multi-scale 3-D geological data model, for use within a Geoscientific Information System. This has resulted in a data storage scheme which enables the integration of terrain data, geological outcrop data and borehole data at various levels of detail. The thesis also presents details of prototype database implementations of each of the new data storage schemes. These implementations have served to demonstrate the feasibility and benefits of an integrated multi-scale approach. The research has also brought to light some areas that will need further research before fully functional systems are produced. The final chapter contains, in addition to conclusions made as a result of the research to date, a summary of some of these areas that require future work