Methods used in the development of computer programs capable of boolean operators on polyhedrons

This paper discusses a method which can be employed on a computer to allow the computer to perform Boolean operations on polygons and polyhedrons. Although current literature is full of algorithms which are vital in the construction of such a program, not many complete algorithms are available. The method described here employs several of the current algorithms and joins them together with other information to produce a complete package. The objects are stored using a boundary representation in linked lists. The polyhedrons are represented by the polygons that compose their faces . The polygons are processed by intersecting each line segment of a given polygon with all of the line segments the other polygon. The new line segments, induced by these intersections, are introduced and the fundamental cycles of the graph evaluated as to the region they bound and selected accordingly

Geology of the Cypress, Hanson and South Arm of Knife Lake Area, Boundary Waters Canoe Area: Eastern Vermilion District, Northeastern Minnesota

A Thesis submitted to the faculty of the Graduate School of the University of Minnesota by Timothy P. Flood in partial fulfillment of the requirements for the degree of Master of Science, June 1981. Plates 1-2 referenced in the thesis are also attached to this record.Archean volcanic and volcanogenic sedimentary rocks of the Cypress, Hanson and South Arm of Knife Lake Area are located within the eastern Vermilion district and lie in three of Gruner's (1941) structural segments. The dominant lithology within the Spoon Lake segment is dacite porphyry conglomerate, derived from a small lens of dacite porphyry. The dacite porphyry conglomerate is composed of dacite porphyry detritus and is interbedded with sequences of greywacke-argillite. The graywacke is of both the feldspathic and lithic type. Two small outcrops of greenstone, one of which is pillowed, occur within the segment and may be fault slices. Keweenawan diabasic dikes intrude both the igneous and the sedimentary rocks. Bedding within the sedimentary rocks indicates that the rocks within the Spoon Lake segment strike N 45°E and dip steeply to the southeast and northwest. The dominant lithology within the Knife Lake Greenstone segment is greenstone which is texturally and compositionally similar to the Ely Greenstone. Overlying the greenstone and containing abundant clasts of greenstone, is a greenstone pebble conglomerate. This is a thin unit and grades laterally into graywacke-argillite. Bedding within the graywacke-argillite sequences indicates the rocks within the Knife Lake Greenstone segment strike N 45°E and dip steeply to the southeast and northwest. The rocks within the Knife Lake Synclinorium segment are divided into two units; a tuff-mafic conglomerate-mixed conglomerate unit, and a younger graywacke unit. These two units are interbedded and gradational into one another. The graywacke of the Knife Lake Synclinorium segment is similar to the graywacke of the Spoon Lake segment and the Knife Lake Greenstone segment, but can be distinguished from them by a greater diversity of volcanic rock fragments. One Keweenawan diabasic dike is present in the segment. The rocks within this segment strike predominantly northeast and dip steeply to the northwest. The northern part of the segment is part of a large overturned syncline, the axis of which trends N 45°E and plunges 30° to the northeast. The southern part of the segment lies on the limbs of folds whose axes trend N 25°E and plunges 75° to the northeast. Longitudinal faulting has removed the axes of the folds from this part of the segment. Turbidite sequences within the Spoon Lake segment and the Knife Lake Greenstone segment are characteristic turbidites corresponding to the depositional lobe of the inner to middle portion of a submarine fan. Turbidite sequences within the Knife Lake Synclinorium segment are characteristic of proximal turbidites, and correspond to facies associated with the inner fan of the slope-fan-basin system of a turbidite basin. The structural information obtained from the Knife Lake Greens tone segment and the Spoon Lake segment is minimal, and few interpretations could be made. The structure of the Knife Lake Synclinorium segment however, can be accounted for in terms of three tectonic deformations. The first period of deformation produced isoclinal folds, which trend N 40° to 50°E and plunge 30° to the northeast. The second period of deformation produced a N 54° to 62° W cleavage throughout the segment. The third period of deformation occurred on a regional scale and produced major longitudinal faults which has divided the present area of study into discrete structural blocks. Transverse faulting of smaller dimensions transect the trend of the longitudinal faults and may have formed as a consequence of movements on the longitudinal faults. The volcanic and sedimentary rocks of the Cypress, Hanson and South Arm of Knife Lake Area belong to the basalt-andesiterhyolite association found in all of the greenstone belts of the Canadian Shield, which is also typical of continental orogenic belts or island arc systems

Hot gas ingestion characteristics and flow visualization of a vectored thrust STOVL concept

A 9.2 percent scale short takeoff and vertical landing (STOVL) hot gas ingestion model was designed and built by McDonnell Douglas Corporation (MCAIR) and tested in the NASA Lewis Research Center 9- by 15-Foot Low Speed Wind Tunnel (LSWT). Hot gas ingestion, the entrainment of heated engine exhaust into the inlet flow field, is a key development issue for advanced short takeoff and vertical landing aircraft. The Phase 1 test program, conducted by NASA Lewis and McDonnell Douglas Corporation, evaluated the hot ingestion phenomena and control techniques and Phase 2 test program which was conducted by NASA Lewis are both reported. The Phase 2 program was conducted at exhaust nozzles temperatures up to 1460 R and utilized a sheet laser system for flow visualization of the model flow field in and out of ground effects. Hot gas ingestion levels were measured for the several forward nozzle splay configurations and with flow control/lift improvement devices which reduced the hot gas ingestion. The model support system had four degrees of freedom, heated high pressure air for nozzle flow, and a suction system exhaust for inlet flow. The headwind (freestream) velocity for Phase 1 was varied from 8 to 90 kn, with primary data taken in the 8 to 23 kn headwind velocity range. Phase 2 headwind velocity varied from 10 to 23 kn. Results of both Phase 1 and 2 are presented. A description of the model, facility, a new model support system, and a sheet laser illumination system are also provided. Results are presented over a range of main landing gear height (model height) above the ground plane at a 10 kn headwind velocity. The results contain the compressor face pressure and temperature distortions, total pressure recovery, compressor face temperature rise, and the environmental effects of the hot gas. The environmental effects include the ground plane temperature and pressure distributions, model airframe heating, and the location of the ground flow separation. Results from the sheet laser flow visualization test are also shown

Learning to Compare: Relation Network for Few-Shot Learning

We present a conceptually simple, flexible, and general framework for few-shot learning, where a classifier must learn to recognise new classes given only few examples from each. Our method, called the Relation Network (RN), is trained end-to-end from scratch. During meta-learning, it learns to learn a deep distance metric to compare a small number of images within episodes, each of which is designed to simulate the few-shot setting. Once trained, a RN is able to classify images of new classes by computing relation scores between query images and the few examples of each new class without further updating the network. Besides providing improved performance on few-shot learning, our framework is easily extended to zero-shot learning. Extensive experiments on five benchmarks demonstrate that our simple approach provides a unified and effective approach for both of these two tasks.Comment: To appear in CVPR201

Survival of children with trisomy 13 and trisomy 18: A multi-state population-based study

Trisomy 13 (T13) and trisomy 18 (T18) are among the most prevalent autosomal trisomies. Both are associated with a very high risk of mortality. Numerous instances, however, of long-term survival of children with T13 or T18 have prompted some clinicians to pursue aggressive treatment instead of the traditional approach of palliative care. The purpose of this study is to assess current mortality data for these conditions. This multi-state, population-based study examined data obtained from birth defect surveillance programs in nine states on live-born infants delivered during 1999–2007 with T13 or T18. Information on children’s vital status and selected maternal and infant risk factors were obtained using matched birth and death certificates and other data sources. The Kaplan–Meier method and Cox proportional hazards models were used to estimate age-specific survival probabilities and predictors of survival up to age five. There were 693 children with T13 and 1,113 children with T18 identified from the participating states. Among children with T13, 5-year survival was 9.7%; among children with T18, it was 12.3%. For both trisomies, gestational age was the strongest predictor of mortality. Females and children of non-Hispanic black mothers had the lowest mortality. Omphalocele and congenital heart defects were associated with an increased risk of death for children with T18 but not T13. This study found survival among children with T13 and T18 to be somewhat higher than those previously reported in the literature, consistent with recent studies reporting improved survival following more aggressive medical intervention for these children

Integrative Acoustic Mapping Reveals Hudson River Sediment Processes and Habitats

Rivers and estuaries around the world are the focus of human settlements and activities. Needs for clean water, ecosystem preservation, commercial navigation, industrial development, and recreational access compete for the use of estuaries, and management of these resources requires a detailed understanding of estuarine morphology and sediment dynamics. This article presents an overview of the first estuary-wide study of a heavily used estuary, the Hudson River, based on high-resolution acoustic mapping of the river bottom. The integration of three high-resolution acoustic methods with extensive sampling reveals an unexpected complexity of bottom features and allows detailed classification of the benthic environment in terms of riverbed morphology, sediment type, and sedimentary processes