Fuel containment, lightning protection and damage tolerance in large composite primary aircraft structures

The damage-tolerance characteristics of high strain-to-failure graphite fibers and toughened resins were evaluated. Test results show that conventional fuel tank sealing techniques are applicable to composite structures. Techniques were developed to prevent fuel leaks due to low-energy impact damage. For wing panels subjected to swept stroke lightning strikes, a surface protection of graphite/aluminum wire fabric and a fastener treatment proved effective in eliminating internal sparking and reducing structural damage. The technology features developed were incorporated and demonstrated in a test panel designed to meet the strength, stiffness, and damage tolerance requirements of a large commercial transport aircraft. The panel test results exceeded design requirements for all test conditions. Wing surfaces constructed with composites offer large weight savings if design allowable strains for compression can be increased from current levels

Effect of Flame Stabilizer Design on Performance and Exhaust Pollutants of a Two-Row Swirl-Can Combustor Operated to Near-Stoichiometric Conditions

Emissions and performance characteristics were determined for two full annulus modular combustors operated to near stoichiometric fuel air ratios. The tests were conducted to obtain stoichiometric data at inlet air temperatures from 756 to 894 K and to determine the effects of a flat plate circular flame stabilizer with upstream fuel injection and a contraswirl flame stabilizer with downstream fuel injection. Levels of unburned hydrocarbons were below 0.50 gram per kilogram of fuel for both combustors and thus there was no detectable difference in the two methods of fuel injection. The contraswirl flame stabilizer did not produce the level of mixing obtained with a flat plate circular flame stabilizer. It did produce higher levels of oxides of nitrogen, which peaked at a fuel air ratio of 0.037. For the flat plate circular flame stabilizer, oxides of nitrogen emission levels were still increasing with fuel air ratio to the maximum tested value of 0.045

Performance and Pollution Measurements of Two-Row Swirl-Can Combustor Having 72 Modules

A test program was conducted to evaluate the performance and gaseous-pollutant levels of an experimental full-annulus 72-module swirl-can combustor. A comparison of data with those for a 120-module swirl-can combustor showed no significant difference in performance or levels of gaseous pollutants. Oxides of nitrogen were correlated for the 72- and 120-swirl-can combustors by using a previously developed parameter

A complete record from colonization to extinction reveals density dependence and the importance of winter conditions for a population of the silvery blue, Glaucopsyche lygdamus.

Butterflies in the family Lycaenidac are often the focus of conservation efforts. However, our understanding of lycaenid population dynamics has been limited to relatively few examples of long-term monitoring data that have been reported. Here, factors associated with population regulation are investigated using a complete record of a single population of the silvery blue, Glaucopsyche lygdamus Doubleday (Lepidoptera: Lycaenidae). Adults of G. lygdamus were first observed in an annual grassland near Davis, California, in 1982 and were last seen in 2003. Relationships between inter-annual variation in abundance and climatic variables were examined, accounting for density dependent effects. Significant effects of both negative density dependence and climatic variation were detected, particularly precipitation and temperature during winter months. Variation in precipitation, the strongest predictor of abundance, was associated directly and positively with butterfly abundance in the same year. Winter temperatures had a negative effect in the same year, but had a lagged, positive effect on abundance in the subsequent year. Mechanistic hypotheses are posed that include climatic effects mediated through both larval and adult plant resources

A History of Sea Ice in the Canadian Arctic Archipelago Based on Postglacial Remains of the Bowhead Whale (Balaena Mysticetus)

The bowhead whale (Balaena mysticetus) is a planktivore of the baleen group of whales adapted to live in the loose edges of the north polar sea ice. Its annual migrations roughly track the advance and retreat of the floe edge. The distribution and radiocarbon ages of bowhead subfossils in the Canadian Arctic Archipelago show that the range of the whale has expanded and contracted abruptly several times over the last 10.5 thousand years (ka). Each expansion or contraction was followed by nearly stable conditions that persisted for millennia. These changes in the geographic range of the bowhead are defined by >400 radiocarbon dates. The paleo-ranges are the basis for reconstructing summer sea-ice minima. Using this criterion, postglacial time is divided into four intervals: (1) 10.5-8.5 ka B.P. - A large bowhead population extended in the summer all the way to retreating glacier margins and ultimately from the Beaufort Sea to Baffin Bay; meltwater-driven outflows probably cleared the inter-island channels of sea ice; this interval terminated when the present interglacial circulation pattern was established; (2) 8.5-5 ka B.P. - Bowheads were excluded from most of the archipelago because the channels failed to clear of sea ice; summer sea-ice conditions for most of this time were more severe than during historical times; (3) 5-3 ka B.P. - Bowheads reoccupied the central channels of the Arctic Islands, and their range extended beyond historical limits; and (4) 3-0 ka B.P. - Sea ice excluded whales from the central channels, as it does today. This paleoenvironmental record based on bowhead whale distributions is more complex than that revealed in the delta 18O, conductivity or the percent-melt records of the Devon and Agassiz ice cores. A reconciliation of the two data sets may indicate the following general summer climatic conditions: 10-8 ka B.P. - warm summers with maximum postglacial warmth; 8-5 ka B.P. - cool, dry summers; 5-3 ka B.P. - cool, wet summers; 3-0 ka B.P. - cold, dry summers.La baleine boréale (Balaena mysticetus) est un planctivore du groupe des baleines à fanons adapté à la vie dans les écotones fluctuants de la banquise polaire septentrionale. Ses migrations annuelles suivent approximativement l'avance et le retrait de la zone de dislocation. La distribution et la datation au radiocarbone de subfossiles de la baleine boréale dans l'archipel canadien Arctique montrent que l'aire de la baleine s'est plusieurs fois étendue et rétrécie soudainement au cours des derniers 10,5 milliers d'années (Ka). Chaque extension ou rétrécissement a été suivi de conditions relativement stables qui ont duré plusieurs millénaires. Ces variations de l'aire géographique de la baleine boréale sont définies par la datation au radiocarbone > 400. Les paléo-aires constituent la base à partir de laquelle on reconstruit les minima de banquise estivale. En se servant de ce critère, on divise le temps postglaciaire en quatre intervalles: 1) de 10,5 à 8,5 Ka BP - En été, une vaste population de baleine boréale peuplait la mer jusqu'aux marges des glaciers en recul, et finalement de la mer de Beaufort à la baie de Baffin; des courants de décharge créés par les eaux de fonte dégageaient probablement la glace de mer des chenaux séparant les îles; cet intervalle s'est terminé quand le schéma actuel de circulation interglaciaire a pris place; 2) de 8,5 à 5 Ka BP - La baleine boréale était exclue de la plupart de l'archipel parce que les chenaux restaient bloqués par la glace de mer; durant presque tout ce temps-là, les conditions estivales en ce qui concerne la glace de mer étaient beaucoup plus extrêmes que durant la période historique; 3) de 5 à 3 Ka BP - La baleine boréale occupait de nouveau les chenaux centraux de l'archipel Arctique, et son aire s'étendait au-delà des limites historiques; et 4) de 3 à 0 Ka BP - La banquise excluait la baleine des chenaux centraux, comme c'est le cas de nos jours. Ce relevé paléoenvironnemental fondé sur la distribution de la baleine boréale est plus complexe que celui révélé par delta18O, par la conductivité ou par les relevés de pourcentage de fonte des carottes de glace de Devon et d'Agassiz. Une réconciliation des deux ensembles de données pourrait indiquer les conditions climatiques estivales générales suivantes: de 10 à 8 Ka BP - étés chauds avec chaleur postglaciaire maximale; de 8 à 5 Ka BP - étés frais et secs; de 5 à 3 Ka BP - étés frais et humides; de 3 à 0 Ka BP - étés froids et secs

Digital demodulator-correlator

An apparatus for demodulation and correlation of a code modulated 10 MHz signal is presented. The apparatus is comprised of a sample and hold analog-to-digital converter synchronized by a frequency coherent 40 MHz pulse to obtain four evenly spaced samples of each of the signal. Each sample is added or subtracted to or from one of four accumulators to or from the separate sums. The correlation functions are then computed. As a further feature of the invention, multipliers are each multiplied by a squarewave chopper signal having a period that is long relative to the period of the received signal to foreclose contamination of the received signal by leakage from either of the other two terms of the multipliers

Prehistoric Neoeskimo Komatiks, Victoria Island, Arctic Canada

The remains of five prehistoric Neoeskimo sleds—komatiks—were located during extensive ground surveys over several hundred square kilometres on the Wollaston Peninsula, western Victoria Island, Arctic Canada. The radiocarbon dates obtained on the remains range from 790 to 300 BP (cal. 736 – 300), which places the sleds within the Thule and Intermediate Copper Eskimo Period. Structurally, these sleds are similar to historic Copper Inuit and Netsilik Inuit sleds: they have wooden runners with lashing and front trace holes, wooden slats tapered at each end with lashing notches on each side, and antler sled shoes with drilled holes to receive pegs for attaching to the runners. However, the sleds range in length from 1.38 to 1.81 m, and thus are at the smaller end of the size range of historic Inuit sleds. The size suggests either that they represent special function sleds used in addition to larger sleds, or that larger sleds may have been a late historic development, perhaps influenced by contact. The fact that no sleds attributable to Paleoeskimo culture were recorded is consistent with the generally held belief that dogs and sleds were not an important part of Paleoeskimo transportation systems.Les vestiges matériels de cinq traîneaux néo-esquimaux – komatiks – ont été localisés lors de travaux de sondages effectués sur plusieurs centaines de kilomètres carrés sur la péninsule Wollaston, île Victoria de l›Ouest, dans l’Arctique canadien. Des dates au carbone 14 ont été obtenues et se situent dans l’intervalle de 790 – 300 BP (cal. 736 – 300), les associant aux périodes thuléenne et intermédiaire des Inuit du cuivre. Architecturalement, ces traîneaux sont similaires aux traîneaux historiques des Inuits du cuivre et Netsilik : ils ont des patins en bois munis de perforations pour y fixer les traverses et les laisses de chiens. Les traverses, également de bois, sont bordées d’encoches latérales. Leurs patins sont chaussés d’andouillers de caribou fixés à l’aide de chevilles et de perforations forées. Toutefois, la longueur des traîneaux oscille entre 1,38 et 1,81 mètre, les plaçant dans la limite dimensionnelle inférieure des traîneaux inuits historiques. Ceci suggère une fonction particulière pour ces petits traîneaux, éventuellement complémentaire à des modèles plus longs. Autrement, les grands traîneaux sont peut-être le fruit d’un développement historique tardif, notamment lié à des contacts extérieurs. Aucun traîneau attribuable aux cultures paléo-esquimaudes n’a été trouvé, ce qui est en accord avec la croyance générale que de tels objets et les chiens qui y sont associés n’occupaient pas une place importante dans les systèmes de transport de ces groupes

A study of participation in the Eastern Massachusetts Chapter of National Association of Social Workers

Thesis (M.S.)--Boston Universit