6,516 research outputs found
Improving Orbit Estimates for Incomplete Orbits with a New Approach to Priors -- with Applications from Black Holes to Planets
We propose a new approach to Bayesian prior probability distributions
(priors) that can improve orbital solutions for low-phase-coverage orbits,
where data cover less than approximately 40% of an orbit. In instances of low
phase coverage such as with stellar orbits in the Galactic center or with
directly-imaged exoplanets, data have low constraining power and thus priors
can bias parameter estimates and produce under-estimated confidence intervals.
Uniform priors, which are commonly assumed in orbit fitting, are notorious for
this. We propose a new observable-based prior paradigm that is based on
uniformity in observables. We compare performance of this observable-based
prior and of commonly assumed uniform priors using Galactic center and
directly-imaged exoplanet (HR 8799) data. The observable-based prior can reduce
biases in model parameters by a factor of two and helps avoid under-estimation
of confidence intervals for simulations with less than about 40% phase
coverage. Above this threshold, orbital solutions for objects with sufficient
phase coverage such as S0-2, a short-period star at the Galactic center with
full phase coverage, are consistent with previously published results. Below
this threshold, the observable-based prior limits prior influence in regions of
prior dominance and increases data influence. Using the observable-based prior,
HR 8799 orbital analyses favor lower eccentricity orbits and provide stronger
evidence that the four planets have a consistent inclination around 30 degrees
to within 1-sigma. This analysis also allows for the possibility of
coplanarity. We present metrics to quantify improvements in orbital estimates
with different priors so that observable-based prior frameworks can be tested
and implemented for other low-phase-coverage orbits.Comment: Published in AJ. 23 pages, 14 figures. Monte Carlo chains are
available in the published article, or are available upon reques
Numerical Simulation of Porosity in Cements
The pores in cementitious materials, their sizes and connectivity have an important influence on the durability of concrete. Several microstructural models have been developed to simulate the three-dimensional pore network in cement pastes. In this article, microstructures with the \upmu ÎĽ ic model are compared with experimental results. It is seen that despite having a resolution for the capillary pores very close to reality, the experimentally observed breakthrough diameter from mercury intrusion is much lower than the values obtained by applying an algorithm of mercury intrusion to the simulated microstructure. The effect of some of the most important input parameters on the pore sizes in the simulated microstructure explored. The phenomenon which seems best able to explain this discrepancy is that C-S-H is not in fact a phase with a smooth surface as represented in microstructural models, but a phase which grows as needles into the pore space, leading to very small water-filled capillary pores from quite young ages. The results demonstrate it will be extremely challenging to represent the porosity of real microstructures in microstructural models on the scale of hundreds of microns necessary to study macroscopic transpor
Numerical Simulation of Porosity in Cements
The pores in cementitious materials, their sizes and connectivity have an important influence on the durability of concrete. Several microstructural models have been developed to simulate the three-dimensional pore network in cement pastes. In this article, microstructures with the ic model are compared with experimental results. It is seen that despite having a resolution for the capillary pores very close to reality, the experimentally observed breakthrough diameter from mercury intrusion is much lower than the values obtained by applying an algorithm of mercury intrusion to the simulated microstructure. The effect of some of the most important input parameters on the pore sizes in the simulated microstructure explored. The phenomenon which seems best able to explain this discrepancy is that C-S-H is not in fact a phase with a smooth surface as represented in microstructural models, but a phase which grows as needles into the pore space, leading to very small water-filled capillary pores from quite young ages. The results demonstrate it will be extremely challenging to represent the porosity of real microstructures in microstructural models on the scale of hundreds of microns necessary to study macroscopic transport
MediaEval 2016 Predicting Media Interestingness Task
Volume: 1739 Host publication title: MediaEval 2016 Multimedia Benchmark Workshop Host publication sub-title: Working Notes Proceedings of the MediaEval 2016 WorkshopNon peer reviewe
Enhancing Transport Efficiency by Hybrid Routing Strategy
Traffic is essential for many dynamic processes on real networks, such as
internet and urban traffic systems. The transport efficiency of the traffic
system can be improved by taking full advantage of the resources in the system.
In this paper, we propose a dual-strategy routing model for network traffic
system, to realize the plenary utility of the whole network. The packets are
delivered according to different "efficient routing strategies" [Yan, et al,
Phys. Rev. E 73, 046108 (2006)]. We introduce the accumulate rate of packets,
{\eta} to measure the performance of traffic system in the congested phase, and
propose the so-called equivalent generation rate of packet to analyze the
jamming processes. From analytical and numerical results, we find that, for
suitable selection of strategies, the dual- strategy system performs better
than the single-strategy system in a broad region of strategy mixing ratio. The
analytical solution to the jamming processes is verified by estimating the
number of jammed nodes, which coincides well with the result from simulation.Comment: 6 pages, 3 figure
Produção, melhoramento genético e potencialidades do feijão-caupi no Brasil.
A agricultura brasileira vem passando por grandes mudanças tecnolĂłgicas e, alĂ©m disso, a globalização do agronegĂłcio tem provocado reflexos na cadeia produtiva de várias culturas, principalmente daquelas que dependem do uso de um grande volume de insumos, notadamente fertilizantes e defensivos agrĂcolas. Essas culturas vĂŞm tendo um custo de produção mais elevado a cada ano, em consequĂŞncia disso, os produtores tem buscado novas opções para seus arranjos produtivos. Constata-se que o cultivo do feijĂŁo-caupi está se expandindo para a regiĂŁo dos cerrados, das regiões Norte, Nordeste e Centro-Oeste, onde Ă© incorporado aos arranjos produtivos como safrinha apĂłs as culturas da soja e do arroz, e, em alguns locais, como cultura principal. Na regiĂŁo dos cerrados, principalmente quando Ă© cultivado em forma de safrinha, o feijĂŁo-caupi tem um custo muito competitivo, fator que tem feito aumentar o interesse dos produtores pela cultura. A oferta de um produto padronizado, de alta qualidade, em quantidade e com regularidade, vem despertando o interesse de agroindustriais de outras regiões e está contribuindo para a abertura de novos mercados para a cultura. O melhoramento genĂ©tico do feijĂŁo-caupi no Sistema Nacional de Pesquisa Agropecuária (SNPA) tem sido feito considerando os interesses de agricultores familiares e empresariais e com o foco voltado para o complexo produtor, comerciante, agroindustrial, distribuidor e consumidor, e recentemente, exportador. Neste trabalho sĂŁo apresentados dados de produção, informações sĂłcioeconĂ´micas, resultados do melhoramento genĂ©tico e considerações sobre a perspectiva da cultura do feijĂŁo-caupi no Brasil
Avaliação preliminar de famĂlias de F2:3 de feijĂŁo-caupi com de inflorescĂŞncia composta.
O feijĂŁo-caupi (Vigna unguiculata (L.) Walp.) Ă© uma leguminosa com destaque comercial devido ao seu curto ciclo para maturidade e por ser uma importante fonte de carboidratos e proteĂnas. Atualmente, devido a utilização da cultura em lavouras que empregam alta tecnologia tem sido dada maior atenção Ă arquitetura da planta, visando a facilidade do cultivo mecanizado e a obtenção de um maior potencial genĂ©tico produtivo. A inflorescĂŞncia composta mostra-se bastante promissora para o melhoramento do feijĂŁo-caupi, uma vez que aumenta o nĂşmero de vagens por pedĂşnculo e por planta, caracterĂstica que constitui importante componente de produção. Desse modo, este trabalho teve como objetivo a avaliação preliminar de famĂlias F2:3 de feijĂŁo-caupi portadoras de inflorescĂŞncia composta quanto a maturidade e a produção. Foram avaliados o ciclo e a produtividade de 460 famĂlias F2:3 em um experimento em delineamento de blocos aumentados. As famĂlias foram distribuĂdas em 10 blocos, sendo cada conjunto constituĂdo de 46 famĂlias e duas testemunhas. Das 460 famĂlias F2:3 somente 343 foram incluĂdas na análise de variância. NĂŁo houve diferença entre famĂlias para nenhum dos caracteres avaliados. Entretanto, houve diferença entre famĂlias e testemunhas. Do total de famĂlias, 4,0% e 7,8% apresentaram-se, para floração e maturidade, respectivamente, mais precoces que a testemunha mais precoce e 25,6% das famĂlias apresentaram produtividade por parcela superior a testemunha mais produtiva.CONAC 2012. DisponĂvel em: http://www.conac2012.org/resumos/pdf/182a.pdf. Acesso em: 02 ago. 2013
The impact of cataract surgey on vision-related quality of life for bilateral cataract patients in Ho Chi Minh City, Vietnam: a prospective study
BACKGROUND: To determine the impact of cataract surgery on vision-related quality of life (VRQOL) and examine the association between objective visual measures and change in VRQOL after surgery among bilateral cataract patients in Ho Chi Minh City, Vietnam. METHODS: A cohort of older patients with bilateral cataract was assessed one week before and one to three months after first eye or both eye cataract surgery. Visual measures including visual acuity, contrast sensitivity and stereopsis were obtained. Vision-related quality of life was assessed using the NEI VFQ-25. Descriptive analyses and a generalized linear estimating equation (GEE) analysis were undertaken to measure change in VRQOL after surgery. RESULTS: Four hundred and thirteen patients were assessed before cataract surgery and 247 completed the follow-up assessment one to three months after first or both eye cataract surgery. Overall, VRQOL significantly improved after cataract surgery (p < 0.001) particularly after both eye surgeries. Binocular contrast sensitivity (p < 0.001) and stereopsis (p < 0.001) were also associated with change in VRQOL after cataract surgery. Visual acuity was not associated with VRQOL. CONCLUSIONS: Cataract surgery significantly improved VRQOL among bilateral cataract patients in Vietnam. Contrast sensitivity as well as stereopsis, rather than visual acuity significantly affected VRQOL after cataract surgery
- …