8,893 research outputs found
A weather related causal analysis on consolidated delay at Newark Liberty International Airport
No full textThe closure of the European airspace due to the eruption of the Icelandic volcano Eyjafjallajokull in 2010 proved a major challenge for airlines and aviation authorities on a global scale. In contrast, more seasonal adverse meteorological conditions afflict many airports in the northern eastern seaboard of the United States. Newark Liberty International Airport (KEWR) is a representative airport that endures severe weather based delays. This dissertation explores the utilisation of Bayesian Networks (BN) and heuristic analyses to investigate weather based delays at Newark Liberty International airport (KEWR). In particular, it aims to understand which weather variables (namely, precipitation, visibility and wind) have the most impact on weather based delays at KEWR in contrast to past studies that have studied more generic weather phenomena (e.g. thunderstorms) at the same airport. An analysis using temporal functionality with Bayesian Networks (BN) software and heuristic analyses was conducted. Data extracted from weather and aviation based websites was extracted using software. The quality of the information was cross referenced with official data sources and validated using BN tools. The results revealed a causal correlation chain between crosswinds above a certain threshold and high delays at KEWR at various points in the experimentation. Though other meteorological elements examined had an impact on delays, airport authorities and airlines can mitigate these factors to a certain scale using Federal Aviation Authority (FAA) approved technology and training. Consequently, the implications could be significant on existing FAA and regional policy with Ground Delay Program (GDP) and Noise Abatement Procedures (NAP). These policies can be profound and far reaching for airlines, in terms of operating procedures and fuel cost implications. These findings can further alter the balance between efficiency, public safety and airline costing affecting all major stakeholders as this dissertation will investigate
High thermal conductance across c-BN/diamond interface
No full textHigh thermal conductivity electronic components with low interfacial thermal resistance are of technological importance and fundamental interest of research. Diamond, a superhard material with ultrahigh thermal conductivity at room temperature, is desirable for microelectronics thermal management. Cubic polymorph of boron nitride (c-BN) is a promising material due to wide bandgap and diamond like structure and properties. To understand the nature in thermal transport of diamond, c-BN and the most commonly used silicon (Si) semiconductor, ab initio phonon Boltzmann transport equations are employed to investigate lattice vibrational properties of these three materials. At 300 K, the predicted thermal conductivity of Si, diamond and c-BN reached 142, 2112, and 736 W/(m·K), respectively. What's more, heat transport phenomena across the interfaces of Si/diamond, c-BN/diamond and Si/c-BN are unfolded. In comparison, the interfacial thermal conductance of c-BN/diamond is ten-fold of Si/diamond; besides, the thermal conductance across Si/c-BN interface is 20.2% larger than that of Si/diamond at 300 K and 18.9% larger at 340 K. These findings provide us new vision and potential solution to heat dissipation of high-local-power density devices, shedding light on future thermal management of c-BN and diamond related electronics.Peer reviewe
A data-based comparison of BN-HRA models in assessing human error probability: An offshore evacuation case study
No full textBayesian Network (BN) has been increasingly exploited to improve different aspects of Human Reliability Analysis (HRA), resulting in a new generation of HRA techniques, known as BN-HRA models. However, validating and evaluating the accuracy of BN-HRA models is still a challenging task. In this study, we have assessed and compared the performance of some of well-known BN-HRA techniques using human performance data obtained from an offshore evacuation simulation. Based on the role of data in quantifying the BN-HRA models, three categories of BN-HRA models have been considered: (i) BN-CREAM and BN-SPARH, which are based on predefined rules (rule-based methods), (ii) Bayesian Parameter Learning (BPL), which is entirely based on the available data (data-based method), and (iii) BN-SLIM model which is based on both the available data and the predefined rules (hybrid method). The results of the present study show that the data-based methods, i.e., BN-SLIM and BPL, in general outperform the rule-based methods. Cross-validation analysis further demonstrates the superiority of BN-SLIM over BPL, particularly in case of data scarcity.Safety and Security Scienc
Towards Standardization for Through-Thickness Reinforcement of Laminates
No full textThrough-thickness reinforcement in the form of stitching, short fibrous or metallic rods (z-pins), or woven or braided tows suppresses delamination and may well offer a cost-effective approach to durable laminated structures. The through-thickness reinforcement acts as a crack bridging mechanism, with benefits of crack arrest or total suppression. However, certifying through-thickness reinforcement for delamination resistance has been impeded because delamination cracks do not behave according to Linear Elastic Fracture Mechanics (LEFM) in these composites. The bridging mechanism may act over quite long crack lengths, leading to so-called large scale bridging problems. Structural optimisation and the correct prediction of delamination, stiffness loss, and ultimate failure can therefore emerge only from correct fracture mechanics, which is not traditional LEFM, but involves fracture concepts that are new to most of the design community. Progress towards standardised design methods for these systems will be reviewed, including advances in modeling, the design of standard experiments, and the challenge of educating a generation of designers in simple but sound design practices
BN nanospheres as CpG ODN carriers for activation of toll-like receptor 9
No full textFor the first time, we demonstrated BN nanospheres (BNNSs) can interact with biomolecules and deliver unmethylated cytosine-phosphate-guanine oligodeoxynucleotides (CpG ODNs) into cells to activate toll-like receptor 9 (TLR9), which is a very important process for therapy of cancers and allergy diseases
Entre a tradição e a modernidade: o café e a imagem do Brasil na Exposição do Mundo Português
No full textTese (doutorado) - Universidade Federal de Santa Catarina, Centro de Filosofia e Ciências Humanas. Programa de Pós-Graduação em História.Esta tese trata da construção da nacionalidade brasileira durante o Estado Novo, discutida através da representação do Brasil levada a Lisboa durante a Exposição do Mundo Português, em 1940, que comemorou os Centenários da fundação (1140) e da restauração (1640) de Portugal e pretendeu ser um documento da consciência nacional, no qual ao Brasil foi destinado o papel de exemplo bem-sucedido do empreendimento colonizador português. A tese analisa o campo artístico brasileiro nos anos 30, discutindo as relações entre arte e política, dando visibilidade às obras e aos artistas que compuseram o conjunto exposto no Stand de Arte do Pavilhão do Brasil, em 1940, entre as quais o Café, de Portinari, encontra posição de destaque demonstrando que as políticas culturais brasileiras deste período se situam coetaneamente àquelas empreendidas pelos demais Estados Nacionais, entre a tradição e a modernidade
Estudo das propriedades eletrônicas, magnética e óptica do Penta-BN
No full textDesde a síntese do grafeno, os nanomateriais bidimensionais (2D) ganharam força no número de pesquisas realizadas. As já conhecidas propriedades do grafeno e do nitreto de boro (h-BN) levaram a recentes pesquisas sobre heteroestruturas laterais compostas pelos dois materiais, onde se analisaram as diferentes configurações de interfaces e os efeitos por elas provocadas. Outras pesquisas inspiradas no Pentagrafeno levaram a um trabalho teórico envolvendo um estudo com nanofitas de Pentagrafeno, na qual realizaram diferentes combinações de bordas e analisaram os efeitos que causariam no material. Nesta dissertação, utilizamos cálculos de primeiros princípios, baseados na Teoria do Funcional da Densidade (DFT), utilizando a Aproximação de Gradiente Generalizado (GGA) e o funcional Perdew-Burke-Ernzerhof (PBE), utilizados nas otimizações e nas descrições de propriedades estruturais, eletrônicas e ópticas. A presente dissertação é composta pelo estudo de dois materiais. O primeiro trabalho trata de um estudo realizado com nanofitas de Penta-BN com terminações hidrogenadas e comprimento infinito. Com o objetivo de calcular os efeitos provocados pelas diferentes combinações de bordas, investigamos as propriedades estruturais, eletrônicas e ópticas das nanofitas. Dentre os resultados obtidos, destacamos as propriedades magnéticas calculadas para as nanofitas de Penta-BN, por apresentarem estados eletrônicos polarizados por spin. Devido à natureza magnética intrínseca do material, essas nanofitas se tornam valiosas para desenvolvimento de novos dispositivos tecnológicos. Para o segundo trabalho realizamos um estudo dos efeitos de interface provocados na heteroestruturas laterais composta por Penta-BN/Penta-Graphane. Através de nossos cálculos, consideramos sistematicamente possíveis configurações de interface, por causarem impacto significativo nas
propriedades eletrônicas dessas estruturas híbridas. Para um melhor entendimento, mostramos resultados gráficos da estrutura de bandas, densidade de estados e das propriedades ópticas para as heteroestruturas trabalhadas.Since the synthesis of graphene, two-dimensional nanomaterials (2D), gain strength in
the number of researches conducted. We know that the properties of graphene and boron
nitrate (h-BN) led to a process of investigation of lateral heterostructures composed of two
materials, where the diferent configurations of interfaces and the efects caused by them
were analyzed. Other research inspired by Pentagrafene led to a theoretical work involving
a study of Pentagrafeno nanoribbons, in which they performed diferent combinations of
edges and analyzed the efects they would cause in the material. In this dissertation, we
use calculations of first principles, based on the Density Functional Theory (DFT), using
the Generalized Gradient Approximation (GGA) and the Perdew-Burke-Ernzerhof functional
(PBE), used in optimizations and descriptions of structural, electronic and optical properties.
The present dissertation is composed by the study of two materials. The first work deals
with a study with Penta-BN nanoribbons with hydrogenated endings and infinite length. In
order to calculate the e ects caused by the diferent combinations of edges, we investigated
the structural, electronic and optical properties of the nanoribbons. Among the obtained
results, we highlight the magnetic properties calculated for the nanoribbons of Penta-BN,
because they present electronic states polarized by spin. Due to the intrinsic magnetic nature
of the material, these nanoribbons become valuable for the development of new technological devices. In the second work, we performed a study of the efects of interface provoked in the lateral heterostructures composed by Penta-BN/Penta-Graphane. Through our calculations, we systematically consider possible interface configurations, since they have a significant impact on the electronic properties of these hybrid structures. For a better understanding, we show graphical results of the band structure, state density and optical properties for the worked heterostructures.Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPE
Os estudos africanos no desenvolvimento da biblioteca Norte/Sul (BN/S) do Centro de Estudos Sociais (CES) da Universidade de Coimbra
No full textEsta comunicação pretende constituir uma partilha das dinâmicas de apoio à pesquisa especializada e das interacções desenvolvidas pela Biblioteca Norte/Sul (BN/S) no contexto da criação de um espaço teórico alternativo não limitado às influências culturais ocidentais.
A BN/S apoia a missão do Centro de Estudos Sociais (CES) da Faculdade de Economia da Universidade de Coimbra acompanhando o seu planeamento estratégico, tendo também o compromisso de apoiar a investigação dos projectos, dos núcleos e dos programas de doutoramento da instituição, alguns ministrados em parceria com as Faculdades de Direito, de Economia e de Letras. A “clientela” é – na sua grande maioria – investigadores permanentes, investigadores juniores, doutorandos, pós-doutorandos e alunos integrados em parcerias com universidades brasileiras, em particular, e com as universidades angolanas, cabo-verdianas, goesas, guineenses, moçambicanas, entre outras.
A BN/S pretende criar um acervo – prioritariamente constituído por monografias e publicações periódicas – resultante da produção científica realizada nos países do hemisfério Sul – na área das ciências sociais e humanas, englobando um amplo espectro de temas.
Pretende-se, assim, com esta comunicação partilhar a experiência da BN/S, resultante da necessidade de melhorar sobretudo a qualidade das publicações sobre estudos africanos, adquiridas com o intuito de apoiar o Programa de Doutoramento “Pós-colonialismo e cidadania global” que abrange temas tão diversos como Justiça, Cidadania, Religião, Feitiçaria, Conhecimentos alternativos, Literatura, etc
Adsorption and Catalytic Activation of the Molecular Oxygen on the Metal Supported h-BN
No full textAdsorption and catalytic activation of the molecular oxygen on the hexagonal boron nitride (h-BN) monolayer supported on Ni(111) and Cu(111) surfaces have been studied theoretically using density functional theory. It is demonstrated that an inert h-BN monolayer can be functionalized and become catalytically active on the transition metal support as a result of mixing of the metal d and h-BN pi bands
BN-SLIM: A Bayesian network methodology for human reliability assessment based on Success Likelihood Index Method (SLIM)
No full textSuccess Likelihood Index Model (SLIM) is one of the widely-used deterministic techniques in human reliability assessment especially when data is insufficient. However, this method suffers from epistemic uncertainty as it extremely relies on expert judgment for determining the model parameters such as the rates and weights of the performance shaping factors (PSFs). Besides, given an operation consisting of several tasks, SLIM calculates the human error probability (HEP) by ignoring possible dependencies among the tasks.The present study is aimed at using Bayesian Network (BN) for improving the performance of SLIM in handling uncertainty arising from experts opinion and lack of data. To this end, SLIM is combined with BN to form the so-called BN-SLIM technique. We demonstrate how BN-SLIM can consider uncertainty associated with the rates of PSFs by using probability distributions. BN-SLIM is also able to provide a better estimation of human error probability by considering conditional dependencies resulting from common PSFs. The probability updating feature of BN-SLIM can be used to identify the PSFs contributing the most to human failure event. The outperformance of BN-SLIM over SLIM is demonstrated via an illustrative example.Safety and Security Scienc
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