• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 50
  • 6
  • 5
  • 4
  • 3
  • 2
  • 1
  • 1
  • Tagged with
  • 90
  • 90
  • 11
  • 10
  • 8
  • 7
  • 7
  • 7
  • 7
  • 7
  • 6
  • 6
  • 5
  • 5
  • 5
  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
51

RESPONSE OF HEART RATE VARIABILITY TO PHYSIOLOGICAL STRESS IN HEALTHY COLLEGE STUDENTS

Claiborne, Stephen Alexander 27 April 2018 (has links)
No description available.
52

STRUCTURAL ANALYSIS OF REINFORCED SHELL WING MODEL FOR JOINED-WING CONFIGURATION

NARAYANAN, VIJAY 13 July 2005 (has links)
No description available.
53

Experimental Study - High Altitude Forced Convective Cooling of Electromechanical Actuation Systems

Racine, Evan Michael January 2015 (has links)
No description available.
54

An Adaptive Dual-Optimal Path-Planning Technique for Unmanned Air Vehicles with Application to Solar-Regenerative High Altitude Long Endurance Flight

Whitfield, Clifford A. 22 July 2009 (has links)
No description available.
55

Adrenal chromaffin cell function in high-altitude deer mice (Peromyscus maniculatus)

Pranckevicius, Nicole 11 1900 (has links)
The deer mouse (Peromyscus maniculatus) inhabits a broad altitudinal range from sea level to over 4300m, where they experience continuous hypoxia. Typically hypoxia activates the sympathetic nervous system; however this could become maladaptive in high-altitude residents if it is maintained over chronic periods. We hypothesized that high-altitude deer mice might have altered the physiology of adrenaomedullary chromaffin cells (AMC) in the adrenal gland to avoid chronic activation of the sympathetic response. Highland mice had lower plasma adrenaline levels compared to lowland populations of Peromyscus mice, both before and after acclimation to hypobaric hypoxia. This did not correspond to any apparent changes in AMC Ca2+-signalling dynamics. Instead a profound blunting of catecholamine storage was found in highland AMCs that appeared to underlie the reduction in adrenaline release / Thesis / Master of Science (MSc)
56

THE EFFECT OF ALTITUDE ON DECOMPOSITION: TOWARD AN UNDERSTANDING OF THE POSTMORTEM INTERVAL IN THE ROCKY MOUNTAIN REGION OF COLORADO.

Baigent, Christiane Irene 01 May 2024 (has links) (PDF)
The estimation of postmortem interval (PMI) is a critical component of medicolegal death investigation. An accurate PMI estimate has the potential to influence the allocation of investigative resources, establish the probative value of associated biological and material evidence, shape the analytical framework applied to skeletal analysis, and inform cause and manner of death. Forensic anthropologists are often tasked with PMI estimation throughout all stages of decomposition and typically rely on categorical phases of soft tissue and skeletal change purported to correspond to broad estimates of elapsed time. In an attempt to improve precision, Megyesi et al. (2005) developed the Total Body Score model (TBS). This quantitative method relies on qualitative assessment of value-assigned categories of tissue change within three anatomical regions to estimate accumulated degree days (ADD), and subsequently, PMI. However, the TBS model has failed to prove reliable in a diversity of region-specific validation studies, emphasizing the need for environment-specific research in taphonomy study. Toward that end, the rate, pattern, and trajectory of decomposition was assessed among a cohort of 12 human donors in the high-altitude Rocky Mountain region of Colorado. This research was performed at Colorado Mesa University’s Forensic Investigation Research Station high-altitude satellite facility, FIRS-TB40. The site lies at an elevation of 3000 meters/9840 feet above mean sea level (AMSL), in the Dfc (snow, fully humid, cool summer) climate region. With both significantly higher elevation and an unrepresented climate classification, FIRS-TB40 introduces a novel environment for the controlled study of human decomposition. This quadripartite study sought to (1) test the qualitative and quantitative aspects of the TBS model in a high-altitude environment to assess suitability of application in the estimation of local PMI; (2) test seven atmospheric variables to assess the utility of integrating atmospheric data beyond ADD into PMI estimation; (3) establish the rate and pattern of human decomposition, isolate and describe phasic patterns of soft tissue change throughout the trajectory of decomposition, and (4) develop a region specific bioecological profile with an emphasis on the integration of human behavior.Results: (1) Neither the qualitative or quantitative aspects of the TBS model tested well at high-altitude and are therefore not recommended for application within the study environment. The qualitative changes presented in the TBS model were not observed among the high-altitude cohort. While Megyesi et al. report that time and temperature - as measured by ADD - accounts for 84% of the variance observed throughout decomposition, ADD accounted for only 42% of the variance observed in decomposition within the high-altitude cohort. (2) Seven atmospheric variables were assessed using locally estimated scatterplot smoothing (LOESS) and multivariate regression. Two of these variables - accumulated solar radiation days (r2 = 0.67) and accumulated windspeed days (r2 = 0.65) – explained more variance in decomposition than ADD (r2 = 64). (3) Five categories of phasic, macroscopic soft tissue change, the suite of which is inferred unique to high-altitude, were identified. These include adipocere formation, trajectory of soft tissue color change, fluid bloat, tissue island formation, and skin sloughing. Patterns of slope roll and slope wash were also described to inform the local taphonomic profile. (4) A forensic bioecological profile was developed using empirically derived patterns of scavenger behavior, census and land use data, extant ethnographic data, and forensic case study. Analysis demonstrated that the data sources were cyclically informative and sufficient to develop an early phase foundational model that will benefit from future interdisciplinary research.Summarily, the high-altitude region of Colorado is culturally and environmentally distinct. The observed disparity in rate and pattern of human decomposition between the high-altitude cohort and the TBS model, and the inadequacy of ADD alone to predict PMI are demonstrative of the need for environment-specific model building in human taphonomy research.
57

Antenna Options for High Altitude IMT Base Stations (HIBS) in Cellular Networks

Magnusson, Harald January 2022 (has links)
This thesis is the result of a collaboration between Ericsson AB and Luleå University of Technology. A feasibility study has been conducted to investigate antenna options for the HIBS access link. The study contains two parts. Firstly, a link budget investigating the gain required from the antenna. The metric of concern in the link budget was SNR. Secondly, a wide area coverage investigation that explored coverage feasibility over an area with a radius of 100 km. The metrics of concern in this investigation were antenna gain and beamwidth. Two types of antennas have been included: parabolic reflector and phased array. Seven frequency bands have been studied: 0.7, 1.9, 2.7, 3.5, 6, 10, and 26 GHz. The first three bands shared a bandwidth of 20 MHz, the next three shared a bandwidth of 80 MHz, and the last band had a bandwidth of 100 MHz. This bandwidth difference was found to have a meaningful effect on SNR. The feasibility condition for the link budget was -6 dB SNR for uplink and 6 dB SNR for downlink. The link budget concluded that the first three bands (0.7, 1.9, and 2.7 GHz) are feasible with reasonably sized antennas. This meant a parabolic reflector dish diameter of 0.6 m for all three bands, or a phased array antenna with 4, 32, and 64 elements, respectively, that all resulted in a roughly equal physical size of the array. The 3.5 GHz frequency band was found to be feasible with a much larger antenna (512 element array). The bands above 3.5 GHz were not deemed feasible. The wide area investigation limited the antenna to a phased array antenna. Two cell layouts were considered for coverage: a 7 cell layout with one nadir cell surrounded by 6 cells and a 19 cell layout which encapsulates the former with another layer of 12 cells. The feasibility condition was that the half power beamwidth is equal to the angular size of a cell from the HIBS for each cell layer while maintaining gain. Beamwidth was controlled through array tapering and altering element configurations. This investigation concluded that coverage is feasible for two bands. In the 0.7 GHz band, the chosen option was a 7 cell layout using a single element antenna for the nadir cell and 3 by 1 arrays for the outer cells. In the 1.9 GHz band, the chosen option was a 19 cell layout with a single element antenna for the nadir cell, 5 by 1 arrays for the cells in the middle layer, and 8 by 5 arrays for the outer layer. Higher frequency bands required higher gain antennas which in turn did not provide adequate beamwidth for coverage.
58

HIGH ALTITUDE TRANSMITTER FLIGHT TESTING

Brown, K. D., Sorensen, Trevor 10 1900 (has links)
International Telemetering Conference Proceedings / October 18-21, 2004 / Town & Country Resort, San Diego, California / This paper describes a high altitude experimental flight test platform developed by the University of Kansas (KU) and the National Nuclear Security Administration’s Kansas City Plant (NNSA’s Kansas City Plant) for high altitude payload flight testing. This platform is called the Kansas University Balloon Experiment Satellite (KUBESat). The paper describes the flight test platform and experimental flight test results captured at Fort Riley, KS from characterization of the KCP developed Distributed Transmitter (DTX).
59

Estudos floristicos, fitossociologicos e fitogeograficos em formações vegetacionais altimontanas da Serra da Mantiqueira Meridional, sudeste do Brasil / Floristic, phytossociology and phytogeography of the high-altitude vegetation of Serra da Mantiqueira Meridional, southeastern Brazil

Meireles, Leonardo Dias 14 August 2018 (has links)
Orientador: George John Shepherd / Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Biologia / Made available in DSpace on 2018-08-14T22:19:27Z (GMT). No. of bitstreams: 1 Meireles_LeonardoDias_D.pdf: 52013493 bytes, checksum: d5034b3efafae60949067d81a6753f38 (MD5) Previous issue date: 2009 / Resumo: A Serra Fina é o nome de umas das áreas da Serra da Mantiqueira Meridional, uma cadeia montanhosa na divisa geográfica entre Minas Gerais, São Paulo e Rio de Janeiro, sudeste do Brasil. A Serra Fina compreende um dos maciços de rochas alcalinas que forma uma das áreas de maior altitude dessa região com mais de 2.500 metros de altitude em vários locais. Ela apresenta um destacado gradiente altitudinal que permite a ocorrência de diferentes formações vegetacionais altimontanas. Sua vegetação apresenta-se ainda relativamente conservada, mas pouquíssimo conhecida. Nós objetivamos analisar a composição florística de suas formações vegetacionais altimontanas, descrever a estrutura fitossociológica das florestas nebulares, verificar a similaridade dessa floresta com outras florestas montanas brasileiras e verificar como mudanças climáticas quaternárias influenciaram a distribuição geográfica das espécies que as compõem. Nos campos de altitude, matas de candeias e nas florestas nebulares foram coletadas 393 espécies das quais sete são provavelmente novas para a ciência. As famílias Asteraceae, Poaceae, Melastomataceae, Rubiaceae, Cyperaceae, Fabaceae, Myrtaceae, Orchidaceae e Ericaceae apresentaram as maiores riquezas específicas. Duas espécies novas da família Asteraceae restritas aos campos de altitude acima de 2.500 metros de altitude foram descritas e ilustradas e as demais necessitam de estudos detalhados por especialistas. A riqueza específica amostrada denota a importância das áreas de altitude na diversidade da Floresta Atlântica e denotam a importância fitogeográfica da Serra Fina por apresentar um grande número de espécies endêmicas ou com distribuição geográfica restrita e comportar espécies com fortes relações com a flora dos Andes, oeste da América do Sul. As florestas apresentaram características típicas de florestas nebulares como menor riqueza, elevada densidade e um dossel reduzido. Myrsinaceae, Myrtaceae, Symplocaceae e Cunoniaceae foram as famílias de maior valor de importância. As florestas alto-montanas da Serra da Mantiqueira apresentaram alta similaridade florística com florestas nebulares sulinas e em parte com as florestas alto-montanas do interior de Minas Gerais e do topo da Serra do Mar em São Paulo, que apresentam uma composição florística relativamente diferenciada. A similaridade dessas florestas com florestas em altitudes mais baixas é relativamente menor. Os modelos de distribuição potencial para espécies florestais montanas destacaram intensas modificações na área de ocupação dessas espécies em cenários climáticos para o Quaternário Tardio e sugerem que estas espécies possam ter ocorrido em altitudes e latitudes menores e longitudes maiores do que atualmente observado. Esses resultados sugerem que florestas com composição florística similar às atuais florestas alto-montanas possam ter ocupado uma área mais extensa no passado, formando em algumas regiões florestas mais extensas que foram posteriormente fragmentadas e confinadas ao topo de cadeias montanhosas na região leste ao sul do Brasil. / Abstract: The "Serra Fina" is the name given to a block of the Serra da Mantiqueira, a mountain chain that forms the boundary between the states of Minas Gerais, São Paulo, and Rio de Janeiro, southeastern Brazil. The Serra Fina largely corresponds to a massif of alkaline rocks and forms the highest part of the range, rising to more than 2500m at several points. It offers an exceptionally extensive altitudinal gradient, with the occurrence of several high-montane vegetation formations. These formations are still relatively well-conserved, but are very poorly known. The main objectives of the present study were to analyze the floristic composition of some of the high-montane vegetation types, describe and analyze the phytosociological structure of the cloud forests, determine the degree of similarity between these forests and other montane forests in Brazil and to investigate possible explanations of the patterns seen, especially with regard to climate changes in the quaternary. A total of 393 species, of which seven are probably new to science, were collected in the grasslands, "candeia" scrub and cloud forests. The greatest species-level richness was found in the families Asteraceae, Poaceae, Melastomataceae, Rubiaceae, Cyperaceae, Fabaceae, Myrtaceae, Orchidaceae and Ericaceae. Two new species of Asteraceae, confined to grasslands above 2500m have been described and illustrated, and the remainder await more detailed studies by specialists. The species richness encountered demonstrates the importance of the contribution of high altitude areas to the overall diversity of the Atlantic Forest of eastern Brazil, and the phytogeographic importance of the Serra Fina with a large number of endemic species or species with restricted distributions with strong links to the Andean flora of western South America. The forests showed a number of characteristics typical of cloud forests, such as low richness, high density and a reduced canopy, with Myrsinaceae, Myrtaceae, Symplocaceae and Cunoniaceae as the most important families. The Serra da Mantiqueira upper montane forests showed their greatest floristic similarity to be with the cloud forests of southern Brazil and to some extent with the upper montane forests of the interior of Minas Gerais and the crest of the coastal range ("Serra do Mar") in São Paulo, though with a somewhat differentiated floristic composition. Similarities with the surrounding forest matrix at lower altitudes were much less. Models of potential distribution for montane forest species using scenarios for Late Quaternary conditions suggest that extensive modifications of currently observed distributions are likely to have occurred, with many species occupying much lower altitudes and latitudes, together with much greater longitudes. These results suggest that forests similar in composition to current upper montane forests may have occupied much more extensive areas in the past, forming an almost continuous forest that has subsequently been fragmented and confined to high mountain areas in the east-south Brazil. / Doutorado / Doutor em Biologia Vegetal
60

Combined Trajectory, Propulsion and Battery Mass Optimization for Solar-Regenerative High-Altitude Long-Endurance Aircraft

Gates, Nathaniel Spencer 09 April 2021 (has links)
This thesis presents the work of two significant projects. In the first project, a suite of benchmark problems for grid energy management are presented which demonstrate several issues characteristic to the dynamic optimization of these systems. These benchmark problems include load following, cogeneration, tri-generation, and energy storage, and each one assumes perfect foresight of the entire time horizon. The Gekko Python package for dynamic optimization is introduced and two different solution methods are discussed and applied to solving these benchmarks. The simultaneous solve mode out-performs the sequential solve mode in each benchmark problem across a wide range of time horizons with increasing resolution, demonstrating the ability of the simultaneous mode to handle many degrees of freedom across a range of problems of increasing difficulty. In the second project, combined optimization of propulsion system design, flight trajectory planning and battery mass optimization is applied to solar-regenerative high-altitude long-endurance (SR-HALE) aircraft through a sequential iterative approach. This combined optimization approach yields an increase of 20.2% in the end-of-day energy available on the winter solstice at 35°N latitude, resulting in an increase in flight time of 2.36 hours. The optimized flight path is obtained by using nonlinear model predictive control to solve flight and energy system dynamics over a 24 hour period with a 15 second time resolution. The optimization objective is to maximize the total energy in the system while flying a station-keeping mission, staying within a 3 km radius and above 60,000 ft. The propulsion system design optimization minimizes the total energy required to fly the optimal path. It uses a combination of blade element momentum theory, blade composite structures, empirical motor and motor controller mass data, as well as a first order motor performance model. The battery optimization seeks to optimally size the battery for a circular orbit. Fixed point iteration between these optimization frameworks yields a flight path and propulsion system that slightly decreases solar capture, but significantly decreases power expended. Fully coupling the trajectory and design optimizations with this level of accuracy is infeasible with current computing resources. These efforts show the benefits of combining design and trajectory optimization to enable the feasibility of SR-HALE flight.

Page generated in 0.0739 seconds