Página 1 dos resultados de 380 itens digitais encontrados em 0.002 segundos

Avaliação numérica do comportamento de reforços de pavimento à reflexão de fendas

Freitas, Márcia Rubina Ascensão
Fonte: Instituto Politécnico de Bragança, Escola Superior de Tecnologia e Gestão Publicador: Instituto Politécnico de Bragança, Escola Superior de Tecnologia e Gestão
Tipo: Dissertação de Mestrado
Português
Relevância na Pesquisa
16.958606%
Os pavimentos rodoviários estão normalmente sujeitos à ação das cargas do tráfego e das variações climáticas. Estas provocam no pavimento diversos tipos de degradações, destacando-se o fendilhamento. O fendilhamento constitui a maior causa de degradação estrutural e funcional dos pavimentos a qual se reflete na segurança de circulação dos veículos. Além disso, permite a entrada de água pelas camadas do pavimento originando redução das capacidades de suporte e promovendo a origem de outras degradações. A aplicação de camadas de reforço de pavimento, em mistura betuminosa, constitui uma das principais estratégias de reabilitação orientada para a reposição da capacidade estrutural dos pavimentos rodoviários. Na maioria dos casos, constata-se que a aplicação de reforços de pavimento sobre camadas de pavimentos fendilhados propicia a ocorrência do fenómeno de reflexão de fendas. Este fenómeno consiste na propagação das fendas existentes no pavimento fendilhado através da camada de reforço até à sua superfície. Como tal, é fundamental para o estudo deste tipo de camadas a consideração deste fenómeno, de modo a que a vida à reflexão de fendas da camada de reforço seja determinada da forma adequada. No entanto...

Efeitos do beta hidroxi beta metilbutirato sobre a expressão de ubiquitina-ligases e vias de síntese protéica na musculatura esquelética de ratos alimentados e jejuados e suas repercussões funcionais.; Effects of beta hydroxy beta methylbutyrate on expression of ubiquitin ligases and the pathway of protein synthesis in skeletal muscle of fed and fasted rats and their functional consequences.

Romero, Frederico Gerlinger
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 20/08/2013 Português
Relevância na Pesquisa
16.958606%
Um metabólito do aminoácido leucina, o HMB, vem sendo utilizado por promover aumento da síntese e/ou redução da degradação protéica. O objetivo do presente estudo avaliou os mecanismos moleculares envolvidos no efeito do HMB sobre o metabolismo proteico na musculatura esquelética frente a um modelo de proteólise, bem como suas consequências funcionais. Ratos Wistar (~250 g) foram tratados com HMB (320 mg/Kg de peso corporal), ou salina (controle), por gavagem, durante 28 dias. Após esse período, uma parcela de ambos os grupos sofreu jejum de 24 horas. Após os tratamentos, parte dos animais foi submetida a ensaios funcionais in vivo. A outra parcela foi sacrificada, os músculos gastrocnêmio (GASTRO) removidos e pesados; sóleo (SOL) e extensor digital longo (EDL), bem como parte do fígado, retirados para avaliação da expressão gênica (real-time PCR) e protéica (Western Blotting) de diversas proteínas envolvidas na síntese e degradação protéica na musculatura esquelética (IGF-I/Akt/mTOR/4E-BP1 e Ub-ligases). Não detectamos alterações na expressão dos atrogenes em ambos os músculos (SOL/EDL) com o tratamento; no entanto observamos um indicativo de atenuação dos animais jejuados com o tratamento no jejum no EDL. Com relação à fosforilação da Akt não houve alteração da mesma com o jejum e nem com o tratamento com HMB no músculo SOL. Já no EDL...

Comparação entre diferentes processos de degradação do antibiótico sulfametoxazol; Comparison between different processes for degradation of antibiotic sulfamethoxazole

Hussain, Sajjad
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 28/02/2014 Português
Relevância na Pesquisa
16.958606%
A ocorrência de produtos farmacêuticos e de cuidados pessoais no meio ambiente tem levado a preocupações sobre seu impacto ambiental e à saúde pública. O sulfametoxazol (SMX) é um fármaco que tem sido encontrado amplamente no ambiente. Neste estudo foi verificada a eficácia de vários processos, a saber eletroquímico, eletroquímico foto assistido, fotoquímico, Fenton e foto-Fenton, para a degradação de SMX em solução aquosa. A degradação eletroquímica e eletroquímica foto assistida foram realizadas em uma célula de fluxo do tipo filtro-prensa, usando um ânodo dimensionalmente estável comercial com composição nominal Ti/Ru0,3Ti0,7O2. Durante ambos os processos, efeitos de diferentes parâmetros foram analisados, como a natureza do eletrólito, a concentração de eletrólito suporte (NaCl) e a densidade de corrente aplicada. Os experimentos fotoquímicos, Fenton e foto-Fenton foram realizados em um reator de vidro cilíndrico de compartimento único. O efeito das concentrações inicias de Fe2+ e de H2O2 foram estudados para os processos Fenton e foto-Fenton. Similarmente, o efeito do pH inicial, a concentração inicial do SMX e a temperatura foram investigados para todos os processos. A variação da concentração de SMX foi determinada por cromatografia líquida de alta eficiência (CLAE) e a quantidade de matéria orgânica foi monitorada por análise de carbono orgânico total (COT). Os resultados obtidos indicaram que o SMX foi completamente degradado...

Diagnóstico ambiental da sub-bacia do Arroio Moinho - Porto Alegre / RS : evolução urbana, dinâmica da paisagem e degradação ambiental

Lopez, Rafael Sehn y
Fonte: Universidade Federal do Rio Grande do Sul Publicador: Universidade Federal do Rio Grande do Sul
Tipo: Dissertação Formato: application/pdf
Português
Relevância na Pesquisa
16.958606%
Este trabalho de pesquisa almeja diagnosticar uma área do município de Porto Alegre, que apresenta uma grande problemática de uso e ocupação do solo. Uma área que apresenta grandes declividades e degradações ambientais que acarretam riscos a população residente, e também concentra um grande contingente da população do município em condições precárias de habitação e sanidade. Estes problemas ambientais estão relacionados principalmente com a contaminação de mananciais superficiais e subterrâneos em razão do inadequado saneamento, inundações urbanas devido à ocupação de áreas de várzea e desenvolvimento da drenagem urbana totalmente imprópria, ampliando os problemas. Além disso, verifica-se a inapropriada disposição de material sólido e a ocorrência de acidentes geológicos, comumente associados a movimentos de massa, como escorregamentos e rolamentos de blocos, que são os efeitos resultantes em áreas de elevada declividade e ocupação irregular, características marcantes da área de interesse desta pesquisa. A sub-bacia hidrográfica em estudo está localizada na porção central do município de Porto Alegre, constituindo uma sub-bacia do arroio Dilúvio pela sua margem, apresentando ocupação urbana de jusante para montante...

Personal identification from degraded and incomplete high resolution palmprints

Carreira, L.; Singh, S.; Correia, P. L.; Soares, L.
Fonte: IET Publicador: IET
Tipo: Artigo de Revista Científica
Publicado em //2015 Português
Relevância na Pesquisa
16.958606%
WOS:000355256000003 (Nº de Acesso Web of Science); A high resolution palmprint recognition system using full or partial, eventually degraded, palmprints is presented. Previous work on palmprint matching addressed mostly commercial applications, using low resolution images. However, in forensic scenarios, high resolution palmprints, although incomplete and/or degraded, are often used. Degradations may result from surface irregularities or impurities, which are often modelled as Gaussian or salt and pepper noise, as well as smearing of the palmprint because of hand sliding, which in this work is modelled as motion blur. The proposed system matches palmprints, full or partial, undegraded or subjected to one of the above degradations, against palmprints registered in a database. The proposed system extends previous work of the authors by adaptively selecting between two palmprint matching approaches, achieving better recognition results than either of the two individual strategies. The first approach relies on a motion blur compensation technique, while the second is based on a combination of the Fourier–Mellin transform with a modified phase-only correlation matching strategy. The presented results show that for sufficiently large palmprint areas the blur compensation technique works better...

Adaptive error-prediction aging sensor for synchronous digital circuits

Martins, Celestino Virtudes Dias
Fonte: Universidade do Algarve Publicador: Universidade do Algarve
Tipo: Dissertação de Mestrado
Publicado em //2012 Português
Relevância na Pesquisa
16.958606%
Dissertação de mest., Engenharia Eléctrica e Electrónica (Tecnologias da Informação e Telecomunicações), Instituto Superior de Engenharia, Univ. do Algarve, 2012; This paper presents a new approach on aging sensors for synchronous digital circuits. An Adaptive Error-Prediction Flip-Flop (AEP-FF) architecture with built-in aging sensor is proposed, to perform on-line monitoring of long-term performance degradation of CMOS digital systems, regardless of their origin. The main advantage is that the sensor’s performance degradation works in favor of the predictive error detection. Moreover, the sensor is out of the signal path, which allows sensor insertion with negligible performance penalty to the circuit. Performance error prediction is implemented by the detection of late transitions at flip-flop data input, caused by aging (namely, due to NBTI), by physical defects activated by long lifetime operation, or by other low drift operation dependent performance degradations. Performance errors must not occur in safety-critical systems (automotive, health, space), which highlights the importance of the Performance Failure Prediction (PFP) methodology. Sensors can be always active, to enhanced Predictive Fault-Detection (PFD)...

Viability of use of PVC tubes in solar collectors: an analysis of materials

Souza,Luiz Guillherme Meira de; Gomes,Uílame Umbelino
Fonte: ABM, ABC, ABPol Publicador: ABM, ABC, ABPol
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/06/2003 Português
Relevância na Pesquisa
16.958606%
This paper presents a study of the inherent degradations of PVC tubes due to the thermal effect and ultraviolet solar radiation. The approach relates its causes and its effect of use of the PVC tubes as elements to absorption, forming a coil, in solar collectors for water heating. It is demonstrated that such degradations can be burst through the use of an outflow and an appropriate regimen of work, as well as of a protective layer for the tubes, in this case black ink used to magnify its absorption. The results of the properties of tubes that had been exposed to the degradation effect for up to five years are presented. The viability of use of this type of collector is demonstrated through comparative analysis of tubes exposed and not exposed to the sun, concluding for the low cost, easy assembly and maintenance of the system.

Structural studies on heparan sulphate from human lung fibroblasts. Characterization of oligosaccharides obtained by selective periodate oxidation of d-glucuronic acid residues followed by scission in alkali

Sjöberg, Ingrid; Fransson, Lars-Ȧke
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em 01/10/1980 Português
Relevância na Pesquisa
16.958606%
1. 3H- and 35S-labelled heparan sulphate was isolated from monolayers of human lung fibroblasts and subjected to degradations by (a) deaminative cleavage and (b) periodate oxidation/alkaline elimination. Fragments were resolved by gel- and ion-exchange-chromatography. 2. Deaminative cleavage of the radioactive glycan afforded mainly disaccharides with a low content of ester-sulphate and free sulphate, indicating that a large part (approx. 80%) of the repeating units consisted of uronosyl-glucosamine-N-sulphate. Blocks of non-sulphated [glucuronosyl-N-acetyl glucosamine] repeats (3–4 consecutive units) accounted for the remainder of the chains. 3. By selective oxidation of glucuronic acid residues associated with N-acetylglucosamine, followed by scission in alkali, the radioactive glycan was degraded into a series of fragments. The glucuronosyl-N-acetylglucosamine-containing block regions yielded a compound N-acetylglucosamine–R, where R is the remnant of an oxidized and degraded glucuronic acid. Periodate-insensitive uronic acid residues were recovered in saccharides of the general structure glucosamine–(uronic acid–glucosamine)n–R. 4. Further degradations of these saccharides via deaminative cleavage and re-oxidations with periodate revealed that iduronic acid may be located in sequences such as glucosamine-N-sulphate→iduronic acid→N-acetylglucosamine. Occasionally the iduronic acid was sulphated. Blocks of iduronic acid-containing repeats may contain up to five consecutive units. Alternating arrangements of iduronic acid- and glucuronic acid-containing repeats were also observed. 5. 3H- and 35S-labelled heparan sulphates from sequential extracts of fibroblasts (medium...

The pyridoxal- and pyridoxal 5′-phosphate-catalysed non-enzymic degradations of l-serine O-sulphate and related compounds

Thomas, J. H.; Dodgson, K. S.; Tudball, N.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /12/1968 Português
Relevância na Pesquisa
26.958606%
1. l-Serine O-sulphate and l-threonine O-sulphate are degraded in the presence of pyridoxal 5′-phosphate to yield equimolar amounts of the corresponding keto acid, ammonia and sulphate. 2. Pyridoxal catalyses the same reactions at a faster rate. 3. One of a number of bi- or ter-valent metal ions must be present for these degradations to proceed. The reaction rates are dependent on a number of factors including pH and the nature of the metal ion used. 4. Studies with related sulphate esters indicate that the α-hydrogen atom and the amino group are essential for activity. 5. Spectral changes during the pyridoxal and pyridoxal 5′-phosphate catalysis of l-serine O-sulphate breakdown suggest the formation of a Schiff base. 6. The mechanism for these reactions appears to be in accordance with the general mechanism proposed for pyridoxal-catalysed αβ-elimination reactions.

An Evaluation of Iterative Reconstruction Strategies on Mediastinal Lesion Detection Using Hybrid Ga-67 SPECT Images

Pereira, N. F.; Gifford, H. C.; Pretorius, P. H.; Farncombe, T.; Smyczynski, M.; Licho, R.; Schneider, P.; King, M. A.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em //2007 Português
Relevância na Pesquisa
16.958606%
Hybrid LROC studies can be used to more realistically assess the impact of reconstruction strategies, compared to those constructed with digital phantoms. This is because hybrid data provides the background variability that is present in clinical imaging, as well as, control over critical imaging parameters, required to conduct meaningful tests. Hybrid data is obtained by adding Monte Carlo simulated lesions to disease free clinical projection data. Due to Ga-67 being a particularly challenging radionuclide for imaging, we use Ga-67 hybrid SPECT data to study the effectiveness of the various correction strategies developed to account for degradations in SPECT imaging. Our data was obtained using GE-VG dual detector SPECT-CT camera. After determining a target lesion contrast we conduct pilot LROC studies to obtain a near-optimal set of reconstruction parameters for the different strategies individually. These near-optimal parameters are then used to reconstruct the final evaluation study sets. All LROC study results reported here were obtained employing human observers only. We use final LROC study results to assess the impact of attenuation compensation, scatter compensation and detector resolution compensation on data reconstructed with the RBI-EM algorithm. We also compare these with FBP reconstructions of the same dataset. Our experiment indicates an improvement in detection accuracy...

The Modulation Transfer Function for Speech Intelligibility

Elliott, Taffeta M.; Theunissen, Frédéric E.
Fonte: Public Library of Science Publicador: Public Library of Science
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
16.958606%
We systematically determined which spectrotemporal modulations in speech are necessary for comprehension by human listeners. Speech comprehension has been shown to be robust to spectral and temporal degradations, but the specific relevance of particular degradations is arguable due to the complexity of the joint spectral and temporal information in the speech signal. We applied a novel modulation filtering technique to recorded sentences to restrict acoustic information quantitatively and to obtain a joint spectrotemporal modulation transfer function for speech comprehension, the speech MTF. For American English, the speech MTF showed the criticality of low modulation frequencies in both time and frequency. Comprehension was significantly impaired when temporal modulations <12 Hz or spectral modulations <4 cycles/kHz were removed. More specifically, the MTF was bandpass in temporal modulations and low-pass in spectral modulations: temporal modulations from 1 to 7 Hz and spectral modulations <1 cycles/kHz were the most important. We evaluated the importance of spectrotemporal modulations for vocal gender identification and found a different region of interest: removing spectral modulations between 3 and 7 cycles/kHz significantly increases gender misidentifications of female speakers. The determination of the speech MTF furnishes an additional method for producing speech signals with reduced bandwidth but high intelligibility. Such compression could be used for audio applications such as file compression or noise removal and for clinical applications such as signal processing for cochlear implants.

Cholesterol Sulfate Alters Substrate Preference of Matrix Metalloproteinase-7 and Promotes Degradations of Pericellular Laminin-332 and Fibronectin*

Yamamoto, Kazuhiro; Miyazaki, Kaoru; Higashi, Shouichi
Fonte: American Society for Biochemistry and Molecular Biology Publicador: American Society for Biochemistry and Molecular Biology
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
26.958606%
Localization of secreted matrix metalloproteinases (MMPs) on the cell surface is required not only for processing of cell surface proteins, but also for controlled degradation of the extracellular matrix (ECM). Our previous study demonstrated that binding of MMP-7 (matrilysin) to cell surface cholesterol sulfate (CS) is essential for the cell membrane-associated proteolytic action of this MMP. In this study, we investigated the role of CS in the MMP-7-catalyzed degradation of protein components of ECM. We found that the degradation of laminin-332 (laminin-5) catalyzed by MMP-7 was accelerated dramatically in the presence of CS, whereas the sulfated lipid inhibited the degradation of casein catalyzed by the protease. The MMP-7-catalyzed degradation of fibronectin was partially inhibited in the presence of low concentrations of CS, whereas it was accelerated significantly at high concentrations of the lipid. Therefore, it is likely that CS alters the substrate preference of MMP-7. We also found that the proteins of which MMP-7-catalyzed degradation were accelerated by CS also had affinities for CS, suggesting that CS facilitates the proteolyses by cross-linking MMP-7 to its substrates. Moreover, MMP-7 tethered to cancer cell surface via CS degraded fibronectin and laminin-332 coated on a culture plate. The degradations of the adhesive proteins led to significant detachment of the cells from the plate. Taken together...

Effect of Speech Degradation on Top-Down Repair: Phonemic Restoration with Simulations of Cochlear Implants and Combined Electric–Acoustic Stimulation

Başkent, Deniz
Fonte: Springer-Verlag Publicador: Springer-Verlag
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
16.958606%
The brain, using expectations, linguistic knowledge, and context, can perceptually restore inaudible portions of speech. Such top-down repair is thought to enhance speech intelligibility in noisy environments. Hearing-impaired listeners with cochlear implants commonly complain about not understanding speech in noise. We hypothesized that the degradations in the bottom-up speech signals due to the implant signal processing may have a negative effect on the top-down repair mechanisms, which could partially be responsible for this complaint. To test the hypothesis, phonemic restoration of interrupted sentences was measured with young normal-hearing listeners using a noise-band vocoder simulation of implant processing. Decreasing the spectral resolution (by reducing the number of vocoder processing channels from 32 to 4) systematically degraded the speech stimuli. Supporting the hypothesis, the size of the restoration benefit varied as a function of spectral resolution. A significant benefit was observed only at the highest spectral resolution of 32 channels. With eight channels, which resembles the resolution available to most implant users, there was no significant restoration effect. Combined electric–acoustic hearing has been previously shown to provide better intelligibility of speech in adverse listening environments. In a second configuration...

FocusDET, A New Toolbox for SISCOM Analysis. Evaluation of the Registration Accuracy Using Monte Carlo Simulation

Martí Fuster, Berta; Esteban, Oscar; Planes, Xavier; Aguiar, Pablo; Crespo, Cristina; Falcon, Carles; Wollny, Gert; Rubí Sureda, Sebastià; Setoain, Xavier; Frangi, Alejandro F.; Ledesma, Maria J.; Santos, Andrés; Pavía, Javier; Ros, Domènec
Fonte: Springer-Verlag Publicador: Springer-Verlag
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
17.238408%
Subtraction of Ictal SPECT Co-registered to MRI (SISCOM) is an imaging technique used to localize the epileptogenic focus in patients with intractable partial epilepsy. The aim of this study was to determine the accuracy of registration algorithms involved in SISCOM analysis using FocusDET, a new user-friendly application. To this end, Monte Carlo simulation was employed to generate realistic SPECT studies. Simulated sinograms were reconstructed by using the Filtered BackProjection (FBP) algorithm and an Ordered Subsets Expectation Maximization (OSEM) reconstruction method that included compensation for all degradations. Registration errors in SPECT-SPECT and SPECT-MRI registration were evaluated by comparing the theoretical and actual transforms. Patient studies with well-localized epilepsy were also included in the registration assessment. Global registration errors including SPECT-SPECT and SPECT-MRI registration errors were less than 1.2 mm on average, exceeding the voxel size (3.32 mm) of SPECT studies in no case. Although images reconstructed using OSEM led to lower registration errors than images reconstructed with FBP, differences after using OSEM or FBP in reconstruction were less than 0.2 mm on average. This indicates that correction for degradations does not play a major role in the SISCOM process...

Limpet Shells from the Aterian Level 8 of El Harhoura 2 Cave (Témara, Morocco): Preservation State of Crossed-Foliated Layers

Nouet, Julius; Chevallard, Corinne; Farre, Bastien; Nehrke, Gernot; Campmas, Emilie; Stoetzel, Emmanuelle; El Hajraoui, Mohamed Abdeljalil; Nespoulet, Roland
Fonte: Public Library of Science Publicador: Public Library of Science
Tipo: Artigo de Revista Científica
Publicado em 16/09/2015 Português
Relevância na Pesquisa
16.958606%
The exploitation of mollusks by the first anatomically modern humans is a central question for archaeologists. This paper focuses on level 8 (dated around ∼ 100 ka BP) of El Harhoura 2 Cave, located along the coastline in the Rabat-Témara region (Morocco). The large quantity of Patella sp. shells found in this level highlights questions regarding their origin and preservation. This study presents an estimation of the preservation status of these shells. We focus here on the diagenetic evolution of both the microstructural patterns and organic components of crossed-foliated shell layers, in order to assess the viability of further investigations based on shell layer minor elements, isotopic or biochemical compositions. The results show that the shells seem to be well conserved, with microstructural patterns preserved down to sub-micrometric scales, and that some organic components are still present in situ. But faint taphonomic degradations affecting both mineral and organic components are nonetheless evidenced, such as the disappearance of organic envelopes surrounding crossed-foliated lamellae, combined with a partial recrystallization of the lamellae. Our results provide a solid case-study of the early stages of the diagenetic evolution of crossed-foliated shell layers. Moreover...

Water erosion prediction by stochastic and empirical models in the Mediterranean: A case study in Northern Sicily (Italy); Prognose der Bodenerosion im Mittelmeerraum anhand statistischer und empirischer Modelle: Eine Fallstudie in Nordsizilien (Italien)

Angileri, Silvia Eleonora
Fonte: Universidade de Tubinga Publicador: Universidade de Tubinga
Tipo: Dissertação
Português
Relevância na Pesquisa
16.958606%
The present thesis aimed to explore the methodological advantages as well as limitations in applying different modelling approaches to predict water soil erosion in Mediterranean environments. The research was accomplished in the central northern part of Sicily (Italy), considering this region to be representative of Mediterranean environmental conditions. In this region soil degradation problems, due to water erosion are becoming more and more serious. Consequently, defining models being able to predict erosion susceptibility and to discriminate environmental factors causing erosion is important to protect soil resources. The prediction of the spatial distribution of soil erosion processes was carried out by means of GIS tools and multivariate statistical analysis. A stochastic gradient boosting model (TreeNet) was proposed to classify erosion and mass wasting processes and to define the functional relationship between spatial data sets of driving factors and response variables. The TreeNet method allowed identifying a susceptibility model that accurately fits the relationship between a set of several attributes and the activity of different erosion processes with a high resistance to over-training. Moreover, a better understanding of the prediction model was provided by the evaluation of the relative overall importance of the predictive variables in the tree construction. In order to estimate the overall prediction skill of the model...

European Clearinghouse: Report on ageing related events

DUCHAC Alexander
Fonte: Publications Office of the European Union Publicador: Publications Office of the European Union
Tipo: EUR - Scientific and Technical Research Reports Formato: Printed
Português
Relevância na Pesquisa
17.238408%
Ageing management at nuclear power plants should be proactive so that to timely detect the ageing degradations, and propose corrective actions to prevent structures, systems and components important to safety from ageing related faults. In order to mange the effect of ageing effectively, there are various plant programmes available which provide guidance on ageing management of active and passive components. Passive components are subject to ageing management review in order to identify ageing related degradations for given material, environment, stressors and operating loads. A comprehensive ageing management re-view is also required either for license renewal [1] or periodic safety review [2] of nuclear power plants. Active components which perform their intended functions with moving parts or with a change in con-figuration are subject to preventive maintenance and replacement based on qualified life or specified time period; therefore the ageing management review is typically not performed. Instead, the plant maintenance programmes are established that should be able to detect timely the component degradation before it fails. The plant maintenance and ageing management programmes aim at early detection of component ageing degradations; in an ideal case...

Velocity compensation in stepped frequency rada

Ma, Yu-Bin
Fonte: Monterey, California. Naval Postgraduate School Publicador: Monterey, California. Naval Postgraduate School
Tipo: Tese de Doutorado
Português
Relevância na Pesquisa
16.958606%
As compared to the commonly used constant frequency radar waveforms, the stepped-frequency waveform can achieve high range resolution while still retaining the advantages of lower instantaneous receiver bandwidth and lower analog-to-digital sampling rate. However, the relative radial motion between the target and the stepped-frequency radar will result in performance degradations, such as range error, loss in signal-to-noise ratio, and degraded range resolution. The solution to this problem is to apply velocity compensation to the received signal, which can eliminate the degradations due to Doppler effects. Three velocity compensation schemes for the detection of a moving target in clutter are designed, discussed, and compared in this thesis. Also, a simulation is presented to verify the concepts, and simulation results are compared and discussed.

Cartografia das atividades de extração de minerais utilizados na construção civil e qualificação do grau de degradação ambiental na região de Manaus-AM; Cartography of the activities of mineral extration used in the civil construction and qualification of the degree of environemental degradation in the region of Manaus-AM-Brazil; Cartographie des activités d'extraction de minéraux employés dans la construction civile et qualification du dégré de la dégradation environnementale dans la région de Manaus-AM-Brésil

Cardoso, Manoel Juares Simões
Fonte: Universidade de Brasília Publicador: Universidade de Brasília
Tipo: Dissertação
Português
Relevância na Pesquisa
17.410593%
Dissertação (mestrado)—Universidade de Brasília, Instituto de Ciências Humanas, Departamento de Geografia, 2008.; O presente estudo foi concluído a partir da análise do tamanho das áreas degradadas e da magnitude das degradações constatadas em cada área. Este estudo foi apoiado, principalmente, em dados de campo e análise visual de imagens de satélite. Os dados de campo foram obtidos por meio de consultas de processos de licenciamento mineral-ambiental no órgão do município e visitas nas respectivas áreas mineradas. O trabalho de campo permitiu mapear áreas com o uso de GPS, percorrendo-se todo o perímetro da área atingida pela degradação e descrever qualitativamente as degradações encontradas, totalizando 45 pontos visitados e incluindo 57 áreas de mineração em área rural. Já o mapeamento visual, nas imagens de satélite, permitiu a identificação de 151 áreas de extração mineral em área urbana e periurbana. Deste modo, o trabalho de campo e o mapeamento visual totalizaram 196 áreas de mineração, em áreas urbana e rural, de extração de areia, arenito, latossolo e argila, incluindo atividades ativas e inativas, antigas e recentes. Como resultado, o perfil do minerador da área de estudo é de um ator que descumpre a legislação ambiental...

Utilizing Knowledge from Prior Plans in the Evaluation of Quality Assurance and Physics Considerations for Single-Isocenter Volumetric Modulated Arc Radiosurgery for Treatment of Multiple Intracranial Targets

Stanhope, Carl
Fonte: Universidade Duke Publicador: Universidade Duke
Tipo: Tese de Doutorado
Publicado em //2015 Português
Relevância na Pesquisa
17.238408%

Purpose: (Project 1): Increased interest in the Radiation Oncology Physics community regarding sensitivity of pre-treatment IMRT/VMAT QA to delivery errors has led to the development of DVH based analysis for pre-treatment QA. This paradigm shift necessitates a change in the acceptance criteria and action tolerance for QA. Here we present a knowledge based technique to objectively compare degradations in the DVH to the range from prior clinically accepted plans after adapting to the new patient's anatomy. We apply this knowledge based method to low risk prostate radiotherapy.

(Project 2): To address many of the physics challenges associated with single isocenter radiosurgery for multiple intracranial metastases (SIRMIT). Because the Varian High Definition MLC has variable leaf width with thicker leaves located >4cm from the isocenter (0.5cm vs. 0.25cm), this raises the question of whether the dose falloff and plan quality is inferior for targets located distal from the isocenter (>4cm). We hypothesize that such an effect will be greater for smaller targets, and we test this hypothesis and evaluate various isocenter placement strategies including one that favors placement of smaller targets closer to the isocenter.

Methods and Materials: (Project 1): DVHs for relevant organs at risk from a population of prior patients' plans were adapted using a machine learning algorithm to establish the DVH range specific to the patient's anatomy. The population of prior plans consisted of 198 (for OARs) and 40 (for PTVs) prostate cancer patients that had previously been planned and treated using IMRT. We then applied this technique to evaluate for single arc VMAT plans the clinical effect of six types of delivery errors: systematic offsets in a single centrally located MLC leaf; systematic leaf bank offsets...