FITTING A PARAMETRIC MODEL TO A CLOUD OF POINTS VIA OPTIMIZATION METHODS

Computer Aided Design (CAD) is a powerful tool for designing parametric geometry. However, many CAD models of current configurations are constructed in previous generations of CAD systems, which represent the configuration simply as a collection of surfaces instead of as a parametrized solid model. But since many modern analysis techniques take advantage of a parametrization, one often has to re-engineer the configuration into a parametric model. The objective here is to generate an efficient, robust, and accurate method for fitting parametric models to a cloud of points. The process uses a gradient-based optimization technique, which is applied to the whole cloud, without the need to segment or classify the points in the cloud a priori. First, for the points associated with any component, a variant of the Levenberg-Marquardt gradient-based optimization method (ILM) is used to find the set of model parameters that minimizes the least-square errors between the model and the points. The efficiency of the ILM algorithm is greatly improved through the use of analytic geometric sensitivities and sparse matrix techniques. Second, for cases in which one does not know a priori the correspondences between points in the cloud and the geometry model\u27s components, an efficient initialization and classification algorithm is introduced. While this technique works well once the configuration is close enough, it occasionally fails when the initial parametrized configuration is too far from the cloud of points. To circumvent this problem, the objective function is modified, which has yielded good results for all cases tested. This technique is applied to a series of increasingly complex configurations. The final configuration represents a full transport aircraft configuration, with a wing, fuselage, empennage, and engines. Although only applied to aerospace applications, the technique is general enough to be applicable in any domain for which basic parametrized models are available

PotteryVR: virtual reality pottery

Handcrafting ceramic pottery in the traditional method or virtual reality (VR) with intricate surface details is still challenging for the ceramic and graphic artist. Free-form pottery modeling can be efficiently geometrically modeled with the right tools with detailed 3D print outputs, yet challenging to be manufactured using traditional art. The new advanced pottery VR simulation is a promising method to recreate the traditional pottery simulation for a better experience with some barriers. The challenges that arise from surface detail in pottery are a tedious task accomplished by mesh blending and retopology. This paper focuses on refining the VP application’s performance by adding unique sound resonance as a more likely infinite geometric phenomenon textures, blending it into the basic shapes. This paper combines creativity and visual computing technologies such as VR, mesh blending, fixing errors, and 3D printing to bring the ceramic artist’s imagination to life. We have used sound resonance with virtual pottery (VP) systems refinements to demonstrate several standard pottery methods from free form deformed pottery, retopology, mesh blended for surface details, and 3D printed pottery with materials including polymer and ceramic resins

Supercomputing in Aerospace

Topics addressed include: numerical aerodynamic simulation; computational mechanics; supercomputers; aerospace propulsion systems; computational modeling in ballistics; turbulence modeling; computational chemistry; computational fluid dynamics; and computational astrophysics

The Early Neolithic 'Broken World': The role of pottery breakage in south-eastern and central Europe

One of the most materially evident yet socially obscured aspects of modern consumer society has been the increasing accumulation of broken objects considered as ‘waste’ or ‘rubbish’. During the Neolithic period, central and south-eastern Europe were also to witness an unprecedented explosion of material remains, mostly pottery fragments, that would affect the social lives of local inhabitants, referred to as the Linearbandkeramik (LBK) and Starčevo-Körös-Criş (SKC) groups respectively. However, because of our modern tendency to write (pre)history in stages of technological development, the Neolithic is conventionally characterized as the moment where humans became masters over nature. Thus, it is emphasised that sedentism, agricultural production, and economic innovations like pottery were introduced. In contrast, the redefinition of the Neolithic as a 'thing-heavy world' (Robb 2013) allows envisioning the Neolithic as a world charged with broken objects. As such, this period can inform us of a unique form of knowledge on what people do when objects break. Determining how they were broken and deposited represent a fundamental way to understand this social knowledge. Through the study of the breakage and alteration of pottery fragments by a combination of wear, morphometric and failure analysis I show how breakage actions and broken objects shaped social practices in SKC sites from the Upper Tisza/Tisa Basin (NW Romania, NE Hungary and SW Ukraine), and LBK sites from the Northern Harz Foreland (northern Germany). Results indicate there was a significant variation in social responses to breakage in both regions resulting from the ubiquitous presence, continued exposure and movement of fragments through daily life, as well as from the paradoxical resilience and extensive cracking behaviour of their organic-tempered ceramics. This knowledge brought by living with broken objects marks a stark contrast to present lifestyles, and it becomes clear then that the modern waste crisis signals an epistemological crisis

Aeronautical engineering: A continuing bibliography with indexes (supplement 270)

This bibliography lists 600 reports, articles, and other documents introduced into the NASA scientific and technical information system in September, 1991. 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

Biconic subdivision of surfaces of revolution and its applications in intersection problems

This paper presents a novel method for the subdivision of surfaces of revolution. We develop a new technique for approximating the genertrix by a series of pairs of conic sections. By using an error estimate based on convex combination, an efficient least-squares approach is proposed that yields near-optimal fitting. The resulting surface approximation is shown to be more efficient than other tessellation methods in terms of the number of fitting segments. This in turn allows us to implement efficient and robust algorithms for such surfaces. In particular, novel intersection techniques based on the proposed subdivision method are introduced for the two most fundamental types of intersections - line/surface and surface/surface intersections. The experimental results show that our method outperforms conventional methods significantly in both computing time and memory cost

Social Logics Under Empire: The Armenian 'Highland Satrapy' and Achaemenid Rule, CA. 600-300 BC.

This dissertation is a multi-scalar archaeological inquiry into the re-making of social order in a single province, or satrapy, of the Achaemenid Persian Empire (ca. 550-330 BC). The work forwards a perspective on the study of imperial provinces that focuses on social logics, the practical understandings that articulate structures, social roles, and temporal rhythms within historical contexts, as mediated by places and things. The geographic focus of this research is the mountainous region extending from the northern Euphrates eastward to the Lesser Caucasus, a “highland satrapy” which the Achaemenid kings appear to have called Armenia. Through investigations in this little-explored province, the work advances a new direction in the archaeology of early empires generally, and the study of the Achaemenid empire in particular, that examines the workings of political and social life within incorporated territories. This research departs from approaches to imperial provinces framed around macro-structural and centrifugal phenomena such as strategies of control and the influence of imperial institutions on provinces. I focus instead on how imperial formations are made through practices and relations of power in routine human associations that are significantly shaped by pre-conquest sociopolitical traditions. During the late second and first millennia BC, across the rugged landscapes of the highlands, stone fortresses set atop craggy hilltops were the pivot around which society was ordered and transformed. This social archaeology examines the ways in which the changing position of the fortress was a part of changing social logics following the emergence of Achaemenid imperial power. Local leaders pursued new practices in new kinds of spaces that reproduced their authority and connected them to one other, to their antecedents, and to the wider empire. The study explores three scales of analysis, beginning with a single site in modern central Armenia named Tsaghkahovit, where I conducted original fieldwork. From this intimate view on a single town, the work expands to a regional scale, comparing survey data from across the highlands to examine broad-scale change. The work then culminates in the examination of the highest echelons of satrapal authority in the revitalized former Urartian fortresses of Erebuni and Altıntepe.Ph.D.Classical Art & ArchaeologyUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/61647/1/lkhatcha_1.pd

A Living Landscape

Today, half of the Netherlands is situated below sea level. Because of this, water-management is of key importance when it comes to maintaining present-day habitation of the Dutch low-lands. In prehistory, however, large parts of the Dutch landscape were highly dynamic due to ongoing fluvial sedimentation. Vast deltaic areas with ceaseless river activity formed the backdrop against which prehistoric occupation took place. Although such landscapes may seem inhospitable, the often excellently preserved archaeological evidence indicates that people lived in these lowlands throughout prehistory. This book describes why Bronze Age farmers were keen to settle here and how these prehistoric communities structured the landscape around their house-sites at various scales. Using a vast body of evidence from several large-scale excavations in the Dutch river area, the author, reconstructs the changes in the cultural landscape over time. Starting from the Middle Neolithic, changing preferences for settlement site locations and changes in domestic architecture are traced in detail to the Iron Age. However, for proper understanding of the cultural landscape, not only settlements but also graves and patterns of object deposition - and their landscape characteristics - are discussed. By using evidence of over 50 major excavations, yielding over 300 house plans, this book contains by far the richest data-set on Dutch Bronze Age settlements. Most of these results were not before published in English, making this book of over 500 pages a true academic treasure for an international audience. The in-depth presentation of Bronze Age settlement sites, as well as the critical discussion of models and premises current in later prehistoric settlement archaeology, have an important relevance stretching beyond the Dutch lowland areas on which it is based. The wealth of high-quality Dutch data is presented as a synthesized (yet well-annotated) narrative, that rises above mere site interpretation, even more so due to its landscape-scale focus. Therefore this book is a must-have for those interested in later prehistoric cultural landscapes and settlement archaeology