An analysis of the dense packing of disks : a computer simulated approach

This thesis is concerned with the analysis of dense packing of hard disks. The Voronoi diagram and the geometric neighbours were first computed. The average number of geometric neighbours of a disk is six. It is thus more efficient to choose structural neighbours from among the geometric neighbours than from among all other disks. Through the Monte Carlo simulation by Rosato et. al., disk configurations after pouring and subsequent shaking were provided for analysis. The mean number of geometric neighbours and the average coordination number were computed. The angular distribution of the structural neighbours was discussed. The packing fraction increases with number of shakes in a linear relationship. It seems to be packing into an ordered close packing after continued shaking. A configuration constrained by two rigid vertical walls was analyzed. It was found the packing fraction is smallest in the vicinity of the wall and increased asymptotically to the mean packing fraction when moving away from the wall

Enabling the Development and Implementation of Digital Twins : Proceedings of the 20th International Conference on Construction Applications of Virtual Reality

Welcome to the 20th International Conference on Construction Applications of Virtual Reality (CONVR 2020). This year we are meeting on-line due to the current Coronavirus pandemic. The overarching theme for CONVR2020 is "Enabling the development and implementation of Digital Twins". CONVR is one of the world-leading conferences in the areas of virtual reality, augmented reality and building information modelling. Each year, more than 100 participants from all around the globe meet to discuss and exchange the latest developments and applications of virtual technologies in the architectural, engineering, construction and operation industry (AECO). The conference is also known for having a unique blend of participants from both academia and industry. This year, with all the difficulties of replicating a real face to face meetings, we are carefully planning the conference to ensure that all participants have a perfect experience. We have a group of leading keynote speakers from industry and academia who are covering up to date hot topics and are enthusiastic and keen to share their knowledge with you. CONVR participants are very loyal to the conference and have attended most of the editions over the last eighteen editions. This year we are welcoming numerous first timers and we aim to help them make the most of the conference by introducing them to other participants

Aeronautical engineering: A continuing bibliography with indexes (supplement 253)

This bibliography lists 637 reports, articles, and other documents introduced into the NASA scientific and technical information system in May, 1990. Subject coverage includes: design, construction and testing of aircraft and aircraft engines; aircraft components, equipment and systems; ground support systems; and theoretical and applied aspects of aerodynamics and general fluid dynamics

Relationship between hailfall intensity and hail damage on ground, determined by radar and lightning observations

Wetterradargeräte werden mittlerweile in vielen Ländern zur Beobachtung und Messung von Hagelstürmen verwendet und liefern einen detaillierten Überblick über die Entwicklung und die Struktur von starken Gewittern. Viel Aufwand wurde in die quantitative Messung von Hagelschlägen und Kurzfristprognosen (Nowcasting) von hagelträchtigen Gewittern investiert, was für nationale Wetterdienste und Flughäfen (Warnungen), die Landwirtschaft (Hagelschutz) und Versicherungen (Schadenabschätzung und Prävention) von grossem Interesse ist. Obwohl Dual-Polarisation Techniken in letzter Zeit entscheidend verbessert wurden, basieren Methoden zur Hagelerkennung und –messung immer noch auf Single-Polarisations Radargeräten. Eine der besten Methoden zur Bestimmung der Hagelintensität mit Single-Polarisation Radargeräten ist die kinetische Hagelenergie, die aus der Radarreflektivität berechnet wird und das gesamte Hagelvolumen pro Fläche repräsentiert. Es hat sich gezeigt, dass die radarvermessene kinetische Hagelenergie (EKINPIX) gut mit Bodenmessungen von Hagel (Hailpads) und Hagelschäden an landwirtschaftlichen Kulturen korreliert. Aufgrund der guten Beziehung zwischen radar- und bodenvermessener Hagelintensität, wird EKINPIX in dieser Dissertation in Beziehung zu Hagelschäden an Autos, an Gebäuden und zur Häufigkeit von Wolken-Boden Blitzen (WB) gesetzt und anhand einer grossen Anzahl Hagelzellen analysiert. Die Dissertation besteht aus den folgenden drei Teilen: einer Einführung, drei wissenschaftlichen Publikationen (eingereicht oder publiziert in (Athmospheric Research) die in einzelnen Kapiteln wiedergegeben sind, und einem abschliessenden Kapitel, in dem zwei methodische Ansätze wie aus räumlichen Verteilungen von WB Blitzen gesamte Hagelflächen abgeleitet werden könnten. Artikel 1 zeigt die Beziehung zwischen Hagelintensitäten und Hagelschäden an Autos, während in Artikel 2 der Zusammenhang mit Schäden an Wohn- und Landwirtschaftsgebäuden untersucht wird. Die Radardaten stammen vom C-Band Doppler-Radar, der von der Eidgenössischen Technischen Hochschule (ETH) in der Nähe von Zürich (Schweiz) betrieben wird. Hagelschäden an Autos waren durch die Winterthur Versicherungen (1992-1998) und Hagelschäden an Gebäuden durch verschiedene Kantonale Gebäudeversicherungen (1992-1999) erhältlich. Die Beziehung zwischen Hagelintensitäten (EKINPIX) und Schäden an Autos (Gebäuden) wurden für 12 (neun) Hagelzellen analysiert, mit den folgenden Resultaten: Da das Ausmass eines Hagelschadens sehr stark vom Exposure und den physikalischen Eigenschaften der versicherten Objekte abhängt, wurden verschiedene Annahmen getroffen und Vereinfachungen eingeführt. Die Beziehung zwischen den mittleren Schäden und EKINPIX hängt von der Hagelsaison ab: Hagelzellen der Hauptsaison (15. Juni-15. August) produzierten generell höhere Schäden als Gewitter der Nebensaison (vorher und nachher). Ein saisonaler Unterschied in der Hagelintensität zeigt sich auch aus der Anzahl und der maximalen Hagelkorngrösse von Hailpad Daten, die aus dem Grossversuch IV stammen, welcher in der Zentralschweiz durchgeführt wurde (1976-1983). Die nicht-linearen Beziehungen zwischen EKINPIX und den Schadenvariablen lassen sich am besten mit logistischen Funktionen beschreiben, wobei Korrelationskoeffizienten von 0.80 resultieren. Nach entsprechender Verifikation und Kalibrierung generierten die logistischen Funktionen für die Schadenrate (Verhältnis zwischen Schäden und Gesamtversicherungssumme) Schäden an Wohn- und Landwirtschaftsgebäuden, die in der Grössenordnung der tatsächlich vorgekommenen Schäden liegen. Der relative Fehler zwischen realen und mit den Schadenfunktionen geschätzten Schäden liegt für die stärksten Stürme unter 30%. Die erarbeiteten logistischen Schadenfunktionen zwischen radarvermessener kinetischen Hagelenergie und Hagelschäden könnten von Versicherungen zur Bestimmung von maximal möglichen Schäden (PMLs) gebraucht werden, indem eine radarvermessene Hagelzelle über ein Auto- und/oder Gebäudeportefeuille eines bestimmten Gebietes (z.B. einer grösseren Stadt) verschoben werden kann. In Artikel 3 werden WB Blitze, die von den Blitzmessnetzen der Schweiz und Süddeutschland geortet wurden, miteinander verglichen, um eine Angabe über die relative Erfassungseffizienz zu erhalten. WB Blitzmessungen des Schweizer Ortungssystems werden einzelnen Hagelzellen (5 min. Auflösung) zugeordnet, so dass der gesamte Lebenszyklus einer Zelle erfasst und in Beziehung zur radarvermessenen kinetischen Hagelenergie (ETH C-Band Doppler-Radar) gesetzt werden kann. Die Auswertung von 41 Hagelzellen die über das Schweizer Mittelland gezogen sind (1992-1995), zeigt die folgenden Resultate: Die totale kinetische Hagelenergie steht in einer linearen Beziehung (Korrelationskoeffizient von 0.95) mit der totalen Anzahl negativer WB Blitzen (–WB). Kein direkter Zusammenhang wurde dagegen mit der Anzahl positive geladener WB Blitzen (+WB) gefunden, obwohl zwischen verschiedenen Gewittertypen unterschieden wurde. Positionen von maximaler Hagelintensität korrelieren mit zeitlichen (0.88) und räumlichen (0.84) Höchstwerten in der Häufigkeit von –WB Blitzen. Die meisten Hagelzellen (66%) zeigen, dass –WB Blitze im Mittel 22 min. (0-65 min.) und 19 km (3-58 km) vor der höchsten Hagelintensität vorkommen. Im Bezug zur maximalen Hagelenergie zeigt sich eine grosse Varianz in Positionen von Höchstwerten in der Anzahl von +WB Blitzen. In schwachen Hagelzellen befindet sich der Höchstwert von +WB Blitzen im Mittel 10 min. vor und 3.5 km nach der höchsten Hagelintensität. In grossen isolierten Zellen liegt hingegen die Position der meisten +WB Blitze 30 min. und 45 km nach der höchsten Hagelintensität. Die Resultate der relativ grossen Anzahl untersuchter Gewitter bestätigen den Einfluss des nicht-induktiven Graupel-Eis Ladungsmechanismus. Dieser erklärt die Tatsache, dass die Mehrheit der –WB Blitze zu Beginn der Gewitterentwicklung vorkommen, während die meisten +WB Blitze eher am Ende der Gewittertätigkeit, während einer Umkehrung der Ladungsteilung beim Ausfall des Niederschlags, auftreten. Die zeitliche und räumliche Beziehung zwischen Höchstwerten von WB Blitzen und maximaler Hagelintensität könnte in der Zukunft für die Verbesserung der Kurzvorhersagen (Nowcasting) von starken Gewittern verwendet werden, speziell durch eine frühere Erkennung eines Hagelschlags anhand von WB-Blitz Informationen. Im letzten Kapitel wird die räumliche Beziehung zwischen Mustern von –WB Blitzen und radarvermessener kinetischer Hagelenergie für 18 ausgewählte Hagelzellen untersucht. Kreuzkorrelationen zwischen den Blitz- und Energiemuster ergeben Koeffizienten zwischen 0.33 und 0.66, was ein vielversprechender Ansatz für eine direkte Bestimmung von Hagelflächen mittels Blitzdaten ist. Zwei methodische Ansätze zur räumlichen Verteilung der Hagelenergie werden in diesem Kapitel diskutiert, wobei die vollständige Ausarbeitung der Methoden nicht mehr im Rahmen dieser Arbeit liegt. Falls dies jedoch gelingt, können Hagelflächen für grosse Gebiete bestimmt werden, ohne direkt auf Radardaten angewiesen zu sein.Weather radars are now available in many countries for operational observations and measurements of hailstorms and provide detailed information on the formation and structure of severe thunderstorms. Much research has been devoted to the quantitative measurement of hailfalls and the nowcasting of hail-bearing thunderstorms which is of interest for national weather services and airports (warning), the agricultural community (protection) and the insurance industry (damage estimation and mitigation). Although dual-polarization techniques have been improving in recent years, hail detection and measuring methods still have to rely on single-polarization radars. One of the most successful methods to derive hailfall intensities from single-polarization radars is hail kinetic energy that is calculated from radar reflectivity measurements and represents the total volume of hailfall per surface unit. Radar-derived hail kinetic energy (EKINPIX) showed valuable results in relation to ground-based measurements of hailfalls (hailpads) and amounts of hail damage to various crops. Based on the good agreement between radar- and ground-measured hailfall intensity, EKINPIX is related in this thesis to hail damage amounts on automobiles, buildings and cloud-to-ground (CG) lightning activity in analyzing a large number of radar-measured hail cells. The thesis consists of three parts: an introduction, three articles (submitted or published in Atmospheric Research) that are reproduced in individual chapters and a final chapter that presents two methodological approaches of how CG lightning location data could be used in the future to directly determine hailfall areas. Article 1 deals with the relationship between hailfall intensities and damages to automobiles, whereas Article 2 investigates a corresponding relationship for residential and agricultural buildings in Switzerland. Radar measurements were available from the C-band Doppler radar located at the Swiss Federal Institute of Technology (ETH) near Zurich, Switzerland. Damage claim data on automobiles were available from Winterthur Insurance (1992-1998) and several cantonal building insurance companies provided hail damage data of buildings (1992-1999). Relationships between hailfall intensity (EKINPIX) and damages to automobiles (buildings) have been analyzed for 12 (nine) hail cells with the following result: As the amount of hail damage depends strongly on the exposure and the physical characteristics of the units insured, some assumptions and simplifications were necessary. The relationship between mean damages and EKINPIX depends on the hailstorm season: high season storms (15 June-15 August) produced higher damages than low season storms vi (before and after). A seasonal difference in hailfall intensity between high and low season storm appears also from numbers and maximum hailstone diameters that were available from hailpad measurements conducted during Grossversuch IV in central Switzerland (1976-1983). The nonlinear relationships between EKINPIX and the damage variables are best described by logistic damage functions that yield correlation coefficients of 0.80. After suitable verification and calibration, logistic functions for total loss ratios (ratio between damage amounts and total sums insured) of both residential and agricultural buildings, predicted damages that are in the range of occurred losses from hailfall. Relative prediction errors for the most severe hailstorms are below 30%. The results suggest that the established logistic damage functions between radar-derived hail kinetic energy and hail damage amounts could be used by insurance companies to determine possible maximum losses (PMLs), shifting a radar-measured hail cell over a motor and/or a building portfolio of interest (e.g., over a major city). In Article 3, CG lightning measurements from Lightning Location and Tracking Systems (LPATS) of Switzerland and southern Germany are compared to determine relative detection efficiencies. CG lightning measurements of the Swiss LPATS are attributed to individual hail cells (5-min resolution), so that the entire lifecycle can be assessed and be related to radar-derived hail kinetic energy (ETH C-band Doppler radar). Analyzes of 41 hail cells that propagated over the Swiss Mittelland (1992-1995) show the following key results: Total hail kinetic energy (EKINTOT) shows good linear correspondence (correlation coefficient of 0.95) with totals of negative CG (–CG) stroke counts but reveals no direct relationship regarding positive CG (+CG) stroke totals, although hail cells were stratified according to the type of cell organization. Temporal and spatial locations of maximally expected hailfall correlate with temporal (0.88) and spatial (0.84) peaks of –CG strokes. Most hail cells (66%) show –CG stroke peaks on the average 22 min (0-65 min) and 19 km (3-58 km) prior to maximally expected hailfall. Locations of +CG stroke peaks reveal large variance relative to maximally expected hailfall. +CG strokes in weak cells tend to peak on the average 10 min before and 3.5 km after maxima in hail kinetic energy, whereas +CG stroke peaks in strong large isolated cells lag maximally expected hailfall up to 30 min and 45 km. The results of the relatively large data sample confirm the importance of the non-inductive graupel-ice charging mechanisms that explains the majority of –CG strokes at the beginning of thunderstorm development and the fact that most CG discharges are of positive polarity at mature storm phase, when an electrical charge reversal occurs in the thunderstorm with the fallout of precipitation. The spatial-temporal relationship between peaks in CG strokes and maximum hailfall intensity could be used to improve nowcasting systems of severe thunderstorms, particularly through an increase of the time of onset between CG lightning initiation and the fallout of hail. In the last chapter, the spatial relationship between patterns of –CG strokes and radar-derived hail kinetic energy is analyzed for 18 selected hail cells. Cross-correlations between lightning and energy patterns produced coefficients between 0.33 and 0.66, which are the basis for a promising approach to determine hailfall surfaces directly from lightning location data. This chapter shows two methodological approaches of how hail kinetic energy could be distributed in space, whereas the full implementation of these methods is not covered in the thesis. Once accurate methods are available, it would be possible to determine entire areas of hailfall without relying on radar data

Implementing autonomous crowds in a computer generated feature film

The implementation of autonomous, flocking crowds of background characters in the feature film ÂRobots is discussed. The techniques for obstacle avoidance and goal seeking are described. An overview of the implementation of the system as part of the production pipeline for the film is also provided

Aeronautical engineering: A continuing bibliography with indexes (supplement 291)

This bibliography lists 757 reports, articles, and other documents introduced into the NASA scientific and technical information system in May. 1993. Subject coverage includes: design, construction and testing of aircraft and aircraft engines; aircraft components, equipment, and systems; ground support systems; and theoretical and applied aspects of aerodynamics and general fluid dynamics

Proceedings, MSVSCC 2015

The Virginia Modeling, Analysis and Simulation Center (VMASC) of Old Dominion University hosted the 2015 Modeling, Simulation, & Visualization Student capstone Conference on April 16th. The Capstone Conference features students in Modeling and Simulation, undergraduates and graduate degree programs, and fields from many colleges and/or universities. Students present their research to an audience of fellow students, faculty, judges, and other distinguished guests. For the students, these presentations afford them the opportunity to impart their innovative research to members of the M&S community from academic, industry, and government backgrounds. Also participating in the conference are faculty and judges who have volunteered their time to impart direct support to their students’ research, facilitate the various conference tracks, serve as judges for each of the tracks, and provide overall assistance to this conference. 2015 marks the ninth year of the VMASC Capstone Conference for Modeling, Simulation and Visualization. This year our conference attracted a number of fine student written papers and presentations, resulting in a total of 51 research works that were presented. This year’s conference had record attendance thanks to the support from the various different departments at Old Dominion University, other local Universities, and the United States Military Academy, at West Point. We greatly appreciated all of the work and energy that has gone into this year’s conference, it truly was a highly collaborative effort that has resulted in a very successful symposium for the M&S community and all of those involved. Below you will find a brief summary of the best papers and best presentations with some simple statistics of the overall conference contribution. Followed by that is a table of contents that breaks down by conference track category with a copy of each included body of work. Thank you again for your time and your contribution as this conference is designed to continuously evolve and adapt to better suit the authors and M&S supporters. Dr.Yuzhong Shen Graduate Program Director, MSVE Capstone Conference Chair John ShullGraduate Student, MSVE Capstone Conference Student Chai