• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 160
  • 71
  • 38
  • 23
  • 17
  • 16
  • 8
  • 4
  • 4
  • 3
  • 2
  • 2
  • 1
  • 1
  • 1
  • Tagged with
  • 387
  • 52
  • 52
  • 47
  • 39
  • 35
  • 34
  • 33
  • 26
  • 24
  • 23
  • 22
  • 22
  • 21
  • 21
  • 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.
231

The construction of optimal drape surfaces with constrained first and second derivatives

Fossati, Reiner Justin 31 January 2003 (has links)
The need to construct optimal drape surfaces arises in airborne geophysical surveys where it is necessary to fly a safe distance above the ground and within the performance limits of the aircraft used, but as close as possible to the surface. The problem is formulated as an LP with constraints at every point of a grid covering the area concerned, yielding a very large problem. The objective of the LP is to create as "good" a surface as possible. This formulation is new, as previous methods did not aim to minimise an objective function. If the desired surface has only slope limitations, the resulting drape surface must be constrained in the first derivative. Such a drape surface is readily constructed using the Lifting Algoritlun. It is shown that the Litling Algorithm is both exact and has great speed advantages. Some numerical results confinning exacmcss and speed are presented, as is the algorithm's analogy to a flow network method. An enhanced lifting method with a better order of complexity is also proposed and tested numerically. In most practical situations a drape surface is required which has both first and second derivatives constrained. If only a cut through such a surface is considered, the problem can be solved with relative ease by exploiting its nctwork~Jike structure. This method fonns the basis of one of the preferred heuristics developed later. It was not possible to generalise this method to a full two~dimensional drape surface. A commercially available LP package fares better in finding the optimal solution. Several heuristic methods were examined. first a general heuristic method based on a lifting approach was developed. This was followed by a method using repeated application of the method used for sections (the Alternating One-dimensional Dual Algorithm ["AODA"]). Three heuristics based on thimbles were also designed. Thimbles are caps whose first and second derivatives are acceptable and which are placed over local infeasibilities in the topography The work ends with a chapter comparing the efficiency of various heuristics and comparing the results obtained using a number of test datasets. It was fOLmd that heuristic methods provide acceptable drape surfaces and that the choice lies between speed and accuracy, with a previously designed smoothing method being the fastesl and the AODA the most accurate and quick enough. / Operations Research / D.Phil.
232

Videografia digital aérea: proposta de um sistema e aplicação no estudo de uso do solo, cobertura vegetal e silvicultura urbana na Amazônia Central, município de Manaus, AM

Bittencourt, Francisco Fernando Bessa 22 December 2010 (has links)
Made available in DSpace on 2015-04-13T12:17:49Z (GMT). No. of bitstreams: 1 Francisco Bessa (1).pdf: 5812910 bytes, checksum: 1772b9ac6e647ea7177d27ac7a88b59f (MD5) Previous issue date: 2010-12-22 / FAPEAM - Fundação de Amparo à Pesquisa do Estado do Amazonas / Tendo em vista a necessidade de planejamento, controle e monitoramento do espaço urbano e de áreas verdes, a área de geotecnologias tem desenvolvido métodos e técnicas, bem como softwares especializados que auxiliam na realização destas atividades, buscando solucionar problemas de uso e ocupação desordenada da terra. Dentre os métodos e técnicas destaca-se a Videografia Digital Aérea Multiespectral de Alta Resolução. Admitindo-se como premissa a possibilidade do uso de imagens aéreas na identificação de uso do solo e em silvicultura urbana, objetivou-se testar esta tecnologia como uma ferramenta na identificação, classificação e quantificação da silvicultura urbana e no mapeamento de classes de uso do solo e cobertura vegetal. A área de estudo foi o município de Manaus-AM, dentro da qual foram escolhidas três áreas localizadas na zona urbana e identificadas como áreas com cobertura vegetal. O trabalho teve início com o levantamento bibliográfico, sendo desenvolvido um sistema de videografia digital aérea, iniciando-se no sobrevôo das áreas, aquisição de frames (imagens), tratamento dos frames, identificação visual das classes de cada área por meio dos frames, definição das classes de acordo com suas características visuais, as mesmas receberam atributos, cada classe foi quantificada e foram gerados mapas de cada área. O estudo resultou em um sistema que utiliza tecnologias de alta resolução de imagem, proporcionando uma qualidade comparável ou superior a de imagens obtidas de forma tradicional, com tempo e custo reduzido, permitindo avaliar as condições urbanas e a cobertura de vegetação das cidades, separando-as em classes. A pesquisa comprovou a eficiência do uso de imagens obtidas por videografia digital aérea, quando utilizadas na identificação e quantificação dos diferentes tipos de cobertura do solo em superfície urbana, sendo portanto, útil em estudos de uso e cobertura do solo. Os resultados apresentados não são conclusivos, sendo que existem observações e limitações nesta técnica. Contudo, apresentou-se uma contribuição para o estudo de uso e cobertura vegetal e silvicultura da cidade de Manaus, buscando subsidiar o manejo do ecossistema urbano.
233

Déposition et réenvol de spores fongiques : contribution à la compréhension du risque nosocomial aérotransmis / Fungal spore deposition and removal : Understanding the airborne nosocomial risk

Metahni, Amine 21 December 2012 (has links)
Les spores fongiques sont à l'origine d'infections nosocomiales affectant le pronostic vital de patients immunodéprimés, et peuvent se transmettre par l'air. C'est pourquoi nous nous sommes intéressé à la déposition et au réenvol de spores d'"Aspergillus", responsables de pathologies gravissimes comme l'aspergillose pulmonaire invasive. Nous avons lors de nos expérimentations utilisé deux méthodes d'aérosolisation : le nébuliseur Collison standard, nécessitant la mise en solution des spores, ainsi qu'un prototype permettant de souffler directement sur les cultures fongiques Ceci nous a permis de mesurer la vitesse de sédimentation des spores, et d'évaluer l'efficacité et la rémanence de traitements fongicides en utilisant un protocole original mettant en œuvre des conditions réalistes.Un dispositif expérimental a été mis au point afin de soumettre des spores déposées sur une surface à un flux d'air tangentiel, et de filmer leur réenvol ( http://tinyurl.com/bla9ynz ), et un critère prédictif théorique de détachement a été exhibé. Des simulations numériques de l'écoulement autour de sphères idéales ont complété cette étude en nous donnant accès à des paramètres critiques inaccessibles expérimentalement.Nous avons finalement appliqué les résultats de nos investigations à la problématique des infections nosocomiales aérotransmises, et découvert que les ventilateurs de refroidissement d'appareils électroniques sont un réservoir de pathogènes et une source de contamination croisée potentielle. Des expériences en milieu contrôlé associées à une campagne de prélèvements en milieu hospitalier ont mis à jour ce nouveau et important risque de contamination. / Fungal spores are a leading cause of lethal nosocomial infections affecting immunocompromised patients, and can be transmitted through the air. As such, we have studied the deposition and re-entrainment of "Aspergillus" fungal spores, which are responsible for invasive pulmonary aspergillosis, a severe disease with a high mortality rate among immunocompromised populations.In our studies two methods of fungal spore aerosolization are used; standard nebulization, and dry blowing using a homemade device. This enabled us to measure the spore settling velocity and to assess the efficiency of fungicide surface treatments using a newly developed test under realistic conditions. These tests have allowed us to quantify different surface treatment efficiencies and established their persistence.An experimental set-up has also been developed to expose spores deposited on a surface to a tangential flow, and to observe and record their removal ( http://tinyurl.com/bla9ynz ). These studies have lead to theoretical criteria for spore detachment. Furthermore, computational fluid dynamic simulations around ideal spherical particles exposed to a tangential flow were used to determine critical parameters needed to estimate particle detachment.Lastly, we have applied our findings to nosocomial infection concerns in the hospital environment and discovered that electronic fans are a pathogen reservoir and potential cross-contamination source. Systematic testing together with random sampling in hospital wards has revealed a new and important contamination risk.
234

DETERMINAÇÃO EXPERIMENTAL E NUMÉRICA DA REDUÇÃO SONORA AÉREA EM PAREDES DE ALVENARIA UTILIZADAS EM HABITAÇÕES / EXPERIMENTAL AND NUMERICAL DETERMINATION OF THE AIRBORNE SOUND REDUCTION USED IN MASONRY WALLS OF DWELLINGS

Pinto, Rodrigo Barcelos 15 March 2011 (has links)
In this research some kinds of masonry walls have been used as internal divisions in three Brazilian dwelling buildings to determine the airborne sound reduction, by experimental tests in field and computer simulations. The masonry walls studied are composed by massive bricks, bored ceramic blocks (6 and 4 holes) and structural (7 and 10 MPa), with mortar lining in both sides. The acoustic evaluations, in field, were accomplished according to the international rules ISO 140 part 4, ISO 717 part 1 and ISO 354. The determination of the airborne sound reduction among places it was accomplished from a direct and indirect sound transmission of constructive elements of the edifications, according to the EN 12354 rule part 1 and using a commercial computer program. The mainly results of this research showed the weighted values of the level standard difference (DnT,w) vary from 37 to 44 decibels to the evaluated walls. It was also observed the difference of 2 dB among the weighted values of the level standard difference (DnT,w) and the apparently sound reduction (R w). Almost all the masonry walls evaluated reached the minimum recommended values by the NBR 15575. In general, it happened a relation between the experimental results and the computer simulations, mainly with the weighted values relation and the isolation curves of the structural masonry walls. The computer simulation of the airborne sound transmission can be a good project tool, besides the initial datas don t represent properly the masonry material components evaluated, due to the national datas more complete and precise. / Neste trabalho são avaliadas alguns tipos de paredes de alvenaria utilizadas como divisórias internas em três edifícios habitacionais brasileiros para determinar a redução sonora aérea, através de ensaios experimentais em campo e de simulações computacionais. As paredes de alvenaria estudadas são compostas por tijolos maciços, blocos cerâmicos furados (6 e 4 furos) e estruturais (7 e 10 MPa), com revestimento de argamassa em ambos os lados. As avaliações acústicas, em campo, foram realizadas de acordo com as normas internacionais ISO 140 parte 4, ISO 717 parte 1 e ISO 354. A determinação da redução sonora aérea entre ambientes foi realizada a partir da transmissão sonora direta e indireta dos elementos construtivos das edificações, conforme a norma EN 12354 parte 1 e utilizando um programa computacional comercial. Os resultados principais desta pesquisa mostram que os valores ponderados da diferença padronizada de nível (DnT,w) variaram de 37 a 44 decibéis para as paredes avaliadas. Também, foi observada uma diferença de 2 dB entre os valores ponderados da diferença padronizada de nível (DnT,w) e do índice de redução sonora aparente (R w). Praticamente, todas as amostras de paredes de alvenaria avaliadas atingiram os valores mínimos de desempenho recomendados pela NBR 15575. Em geral, ocorreu uma boa correlação entre os resultados experimentais e as simulações computacionais, principalmente com relação aos valores ponderados e as curvas de isolamento das paredes de alvenaria estrutural. A simulação computacional da transmissão sonora aérea pode ser uma boa ferramenta de projeto, apesar dos dados de entrada não representarem fielmente as propriedades dos materiais componentes das alvenarias avaliadas, devido à carência de dados nacionais mais completos e precisos.
235

Využití doplňkových informací o pulsu pro klasifikaci dat LLS v členitém terénu / Utilization of additional information on the pulse for ALS data classification in rugged terrain

Poláková, Tereza January 2016 (has links)
Utilization of additional information of the pulse for ALS data classification in ragged terrain Abstract The diploma thesis deals with airborne laser scanning filtering problem in sandstone landscape which is characterized by ragged terrain and in our country also by dense vegetation that makes difficult to transit laser pulse to terrain that can lead to lower accuracy of created DTM. In the first part the basic filtering algorithm that are systematic divided into several groups are described. The emphasis is also put on theoretic problems which we have to deal with during the filtering of laser scanner data acquired in sandstone landscape. The main goal of the thesis is to suggest changes in one of the existing algorithm to additional information of the pulse (mainly amplitude and width of the pulse) be used, and to test this method over the real data. At the end the results of the method and its implementation are critically evaluated. Keywords: airborne laser scanning, point cloud segmentation, point cloud classification, sandstone landscape, DTM
236

Assessing industrial pollution by means of environmental samples in the Kemi-Tornio region

Pöykiö, R. (Risto) 29 November 2002 (has links)
Abstract The results of the comparison of various dissolution methods for sulphur showed, that HNO3 together with H2O2 gave more complete decomposition of organic components than HNO3 alone. The acid procedure with a mixture of HNO3+H2O2 slightly underestimated the S concentrations of plant material. The losses of sulphur were the highest in the dry ashing digestion procedure (HF(DAC)). The Leco combustion technique with infrared (IR) detection gave good precision and accuracy for sulphur. For the determination of heavy metals in plant materials, both the HNO3 and HNO3+H2O2 procedures were especially effective for determining Cr. However, the HNO3+HClO4 procedure gave lower results, and HF and HF(DAC) procedures greater values for Cr. Sulphur accumulation in pine needles around the pulp and paper mills was clearly higher than other points in the Kemi area. For example, within a radius of about 1-1.5 km around the mills of Oy Metsä-Botnia Ab Kemi Mills, the sulphur concentrations for (C) and (C+1) needles were 28 % and 26 % higher than those in the corresponding background samples collected in Kuivaniemi at a distance about 25 km from Kemi. Pine needles do not appeared to be appropriate a method for monitoring the accumulation of Fe, Zn, V and Pb emitted from pulp and paper mills. However, the Ca concentrations in (C+1) needles in the vicinity of the Oy Metsä-Botnia Ab Kemi Mills was 48 % higher than the average Ca concentration calculated from all (C+1) needles; thus it is likely that part of the Ca in the needles is derived from the mills. The regional distribution pattern of Cr and Ni in mosses in the Kemi-Tornio area in 2000 showed clearly that the most polluted area (Cr > 200 μg/g and Ni > 20 μg/g) appeared to lie within a few kilometres of the ferrochrome and stainless steel works of AvestaPolarit Stainless Oy. Within this area, the Cr concentrations in mosses were 4-13 times higher than those outside the urban area of Tornio. The area most polluted by the opencast chromium mining complex (Cr > 200 μg/g and Ni < 20 μg/g) appeared to be in the immediate vicinity of complex. All the 95th percentile values for TSP (total suspended particles) in the mine area of AvestaPolarit Chrome Oy Kemi Mine were below the current Finnish air quality limit value of 300 μg/m3. However, the 98th percentile value exceeded the Finnish air quality guideline value of 120 μg/m3 at one monitoring site. According to leaching studies, the sum of calculated annual airborne pollution impact of water-soluble fraction (H2O) and environmentally mobile (CH3COONH4) fraction from the AvestaPolarit Chrome Oy Kemi Mine was Cr 1.2 kg, Fe 29 kg, Cu 63 kg, Ni 2.5 kg and Cd < 100 mg. According to the homogeneity studies of heavy metal deposition on TSP filters, Cr, Ni, Cu and Fe were non-uniformly distributed over the glass fibre filters. The rsd values varied between 5.4-33.9 % for Cr, between 7.5-35.0 % for Ni, between 3.6-25.9 % for Cu, and between 6.6-19.9 % for Fe.
237

Tvorba kartograficky správných vrstevnic z dat LLS v rovinatém terénu / Production of cartographically correct countour lines from airborne laserscanning data in flat terrain

Picek, Jan January 2017 (has links)
Production of cartographically correct countour lines from airborne laserscanning data in flat terrain Abstract The thesis is dedicated to the creation of contour lines from the data of airborne laserscanning in flat areas. For creation of contour lines in these parts is necessary specific generalization, that smooths unwanted artifacts, but does not delete the shapes, which are characteristic for the relief. The first part of the thesis is to serve as a short insight into the areas on which it is built, this thesis: the principle of airborne laserscanning and basic information on the contour line model. On the basis of technical literature are defined the requirements for the correct representation of the contour and cartographicly presented the different types of the DEM and generalization of contours. The main aim of this work is to design an algorithm that will combine several methods of generalization of contour while maintaining altitude accuracy as well as other requirements on their cartographicly the right terms, and to test this approach in several territories. In conclusion, the results of the methods of work and its implementation critically evaluated and outlined other possible developments of this issue. Keywords hypsography, airborne laserscanning, digital cartography, contour lines,...
238

The use of dioxy MP 14 (stabilized aqueous chlorine dioxide) to control environmental airborne microorganisms

Mbamalu, Oluchi Nneka January 2009 (has links)
Magister Pharmaceuticae - MPharm / Dioxy MP 14 is a locally developed form of stabilized chlorine dioxide in an aqueous medium. It has all the sanitizing properties of chlorine dioxide gas, a neutral compound of chlorine in the +IV oxidation state, which has been used extensively as a non-toxic sterilizing agent with various applications. In this study, Dioxy MP14 was tested in a commercial chicken pen to determine its effectiveness as an environmental sanitizing agent. Control of environmental microbes in a chicken pen is important to ensure healthy birds and optimum egg production. The biocide was introduced via an overhead misting system with a variable dosing pump at various daily frequencies.The effectiveness of environmental microorganism control was determined with air settle plates. The health and performance of the chickens were evaluated and compared to chickens in a control pen.The results show a decrease in airborne microbial load in the treated pen. Better egg production and lower mortality of the chickens in the treated pen compared to the control pen, indicate effective environmental microbial control was achieved with a residual 7.46 ppm Dioxy MP 14 at a daily dose given for 5 minutes every 2 hours.This study was a pilot study, with encouraging results, for an extended study to investigate the feasibility of introducing Dioxy MP 14 through a misting system in a clinical environment (clinics and hospitals) to control airborne pathogens like Mycobacterium tuberculosis thereby reducing the infection risks for clinical workers and medical staff.
239

Modeling, simulation, hardware development, and testing of a lab-scale airborne wind energy system

Klein-Miloslavich, Andreas 24 January 2020 (has links)
Airborne Wind Energy Systems (AWES) harness the power of high-altitude winds using tethered planes or kites. Continuous and reliable operation requires that AWES become autonomous devices, but the wind intermittency forces the system to repeatedly take-off to start, and land to shut-off. Therefore, a common approach to facilitate the operation is implementing Vertical take-off and landing (VTOL) functionality. This thesis models and simulates AWES flights working towards the implementation of flight controller hardware and autonomous operation of an AWES demonstrator platform. The Ardupilot open-source autopilot platform provides a convenient tool for modeling, simulation, and hardware implementation of small-scale airplanes. An AWES lab-scale demonstrator was developed to obtain operational insight, get preliminary flight data, and real-world experience in this technology. A quadplane was developed by combining a structurally reinforced glider with VTOL and autopilot components. Its performance is obtained from static and aerodynamic studies and converted into the Ardupilot parameter format to define it in the simulation. An AWES flight model was developed from the ground up to evaluate the performance of a simple flight controller in trajectory tracking. The Ardupilot Software-in-Loop (SIL) tool expands the simulation capabilities by running the flight controller code without requiring any hardware. This allowed controller tuning and flight plan evaluation with a more advanced fight model. AWES crosswind flight simulation was only possible due to the incorporation of an elastic tether and an ideal winch into the physics model. As a result, different trajectories and configurations were tested to find the optimal parameters that were uploaded to the flight controller board. The operational capabilities of the AWES demonstrator were expanded with a flight testing campaign. By targeting individual objectives, each test gradually increased its complexity and ensured that the flight envelope was safely expanded. The results were validated with the simulation before moving on to the next flight test. The testing campaign is still underway due to challenges and limitations presented by the legal and logistical aspects of operating the quadplane. However, preliminary flight tests in VTOL mode have been completed and were consistent with the simulated results in terms of autonomous waypoint navigation and attitude control. / Graduate
240

THE EFFECT OF FACEMASK TYPES ON THE INHALED DEPOSITED DOSE RATE OF PATHOGENIC BIOAEROSOLS IN MEDICAL FACILITIES

Jun Ho Kim (11773106) 03 December 2021 (has links)
<p>Evidence exists for the airborne transmission of contagious pathogens such as SARS-CoV-2, influenza A virus and <i>Mycobacterium</i> <i>tuberculosis</i> in indoor environments. These pathogens are carried in the respiratory droplets and transmitted through airborne route to infect individuals. An important element in risk assessment for pathogenic bioaerosol exposure is a determination of the inhaled deposited dose rate – the number of deposited pathogenic particles per minute – received by each respiratory region and the fractional reduction of dose rate by different material facemasks. This paper presents an aerosol physics-based modeling framework to estimate the fractional reduction of regional dose rate in diverse indoor healthcare environments. The fractional reduction of dose rate is a useful metric to evaluate the facemask effectiveness in reducing the inhaled dose rate. Data extraction of pathogenic bioaerosol size distributions and size-dependent facemask filtration efficiency curve combined with deposition fraction model become the baseline to calculate the fractional reduction of dose rate by 10 different facemasks. Facemask leakage is also considered for the realistic representation of its impact on reduction fraction as current studies focus on mask material filtration efficiency. This analysis considers how the fractional reduction of dose rate is influenced by the pathogenic bioaerosol size distribution, age-dependent respiratory parameters, age-specific deposition fraction, facemask filtration efficiency and mask leakage. Different factors drove variations in the reduction fraction of various sized-pathogenic bioaerosols received by each respiratory region for each age group. This framework can be a useful tool for decision-makers in evaluating the mask’s effectiveness in reducing deposition of pathogenic bioaerosols.</p>

Page generated in 0.0447 seconds