946 resultados para Mixed Collocation Methods


Relevância:

20.00% 20.00%

Publicador:

Resumo:

LUDA is a research project of Key Action 4 "City of Tomorrow & Cultural Heritage" of the programme "Energy, Environment and Sustainable Development" within the Fifth Framework Programme of the European Commission

Relevância:

20.00% 20.00%

Publicador:

Resumo:

Storm- and tsunami-deposits are generated by similar depositional mechanisms making their discrimination hard to establish using classic sedimentologic methods. Here we propose an original approach to identify tsunami-induced deposits by combining numerical simulation and rock magnetism. To test our method, we investigate the tsunami deposit of the Boca do Rio estuary generated by the 1755 earthquake in Lisbon which is well described in the literature. We first test the 1755 tsunami scenario using a numerical inundation model to provide physical parameters for the tsunami wave. Then we use concentration (MS. SIRM) and grain size (chi(ARM), ARM, B1/2, ARM/SIRM) sensitive magnetic proxies coupled with SEM microscopy to unravel the magnetic mineralogy of the tsunami-induced deposit and its associated depositional mechanisms. In order to study the connection between the tsunami deposit and the different sedimentologic units present in the estuary, magnetic data were processed by multivariate statistical analyses. Our numerical simulation show a large inundation of the estuary with flow depths varying from 0.5 to 6 m and run up of similar to 7 m. Magnetic data show a dominance of paramagnetic minerals (quartz) mixed with lesser amount of ferromagnetic minerals, namely titanomagnetite and titanohematite both of a detrital origin and reworked from the underlying units. Multivariate statistical analyses indicate a better connection between the tsunami-induced deposit and a mixture of Units C and D. All these results point to a scenario where the energy released by the tsunami wave was strong enough to overtop and erode important amount of sand from the littoral dune and mixed it with reworked materials from underlying layers at least 1 m in depth. The method tested here represents an original and promising tool to identify tsunami-induced deposits in similar embayed beach environments.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

In this paper, a mixed-integer nonlinear approach is proposed to support decision-making for a hydro power producer, considering a head-dependent hydro chain. The aim is to maximize the profit of the hydro power producer from selling energy into the electric market. As a new contribution to earlier studies, a risk aversion criterion is taken into account, as well as head-dependency. The volatility of the expected profit is limited through the conditional value-at-risk (CVaR). The proposed approach has been applied successfully to solve a case study based on one of the main Portuguese cascaded hydro systems.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

This paper is on the problem of short-term hydro scheduling (STHS), particularly concerning head-dependent reservoirs under competitive environment. We propose a novel method, based on mixed-integer nonlinear programming (MINLP), for optimising power generation efficiency. This method considers hydroelectric power generation as a nonlinear function of water discharge and of the head. The main contribution of this paper is that discharge ramping constraints and start/stop of units are also considered, in order to obtain more realistic and feasible results. The proposed method has been applied successfully to solve two case studies based on Portuguese cascaded hydro systems, providing a higher profit at an acceptable computation time in comparison with classical optimisation methods based on mixed-integer linear programming (MILP).

Relevância:

20.00% 20.00%

Publicador:

Resumo:

This paper is on the problem of short-term hydro scheduling (STHS), particularly concerning a head-dependent hydro chain We propose a novel mixed-integer nonlinear programming (MINLP) approach, considering hydroelectric power generation as a nonlinear function of water discharge and of the head. As a new contribution to eat her studies, we model the on-off behavior of the hydro plants using integer variables, in order to avoid water discharges at forbidden areas Thus, an enhanced STHS is provided due to the more realistic modeling presented in this paper Our approach has been applied successfully to solve a test case based on one of the Portuguese cascaded hydro systems with a negligible computational time requirement.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

This paper is an elaboration of the DECA algorithm [1] to blindly unmix hyperspectral data. The underlying mixing model is linear, meaning that each pixel is a linear mixture of the endmembers signatures weighted by the correspondent abundance fractions. The proposed method, as DECA, is tailored to highly mixed mixtures in which the geometric based approaches fail to identify the simplex of minimum volume enclosing the observed spectral vectors. We resort then to a statitistical framework, where the abundance fractions are modeled as mixtures of Dirichlet densities, thus enforcing the constraints on abundance fractions imposed by the acquisition process, namely non-negativity and constant sum. With respect to DECA, we introduce two improvements: 1) the number of Dirichlet modes are inferred based on the minimum description length (MDL) principle; 2) The generalized expectation maximization (GEM) algorithm we adopt to infer the model parameters is improved by using alternating minimization and augmented Lagrangian methods to compute the mixing matrix. The effectiveness of the proposed algorithm is illustrated with simulated and read data.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

In this work, 14 primary schools of Lisbon city, Portugal, followed a questionnaire of the ISAAC - International Study of Asthma and Allergies in Childhood Program, in 2009/2010. The questionnaire contained questions to identify children with respiratory diseases (wheeze, asthma and rhinitis). Total particulate matter (TPM) was passively collected inside two classrooms of each of 14 primary schools. Two types of filter matrices were used to collect TPM: Millipore (IsoporeTM) polycarbonate and quartz. Three campaigns were selected for the measurement of TPM: Spring, Autumn and Winter. The highest difference between the two types of filters is that the mass of collected particles was higher in quartz filters than in polycarbonate filters, even if their correlation is excellent. The highest TPM depositions occurred between October 2009 and March 2010, when related with rhinitis proportion. Rhinitis was found to be related to TPM when the data were grouped seasonally and averaged for all the schools. For the data of 2006/2007, the seasonal variation was found to be related to outdoor particle deposition (below 10 μm).

Relevância:

20.00% 20.00%

Publicador:

Resumo:

This paper is on the problem of short-term hydro, scheduling, particularly concerning head-dependent cascaded hydro systems. We propose a novel mixed-integer quadratic programming approach, considering not only head-dependency, but also discontinuous operating regions and discharge ramping constraints. Thus, an enhanced short-term hydro scheduling is provided due to the more realistic modeling presented in this paper. Numerical results from two case studies, based on Portuguese cascaded hydro systems, illustrate the proficiency of the proposed approach.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

Storm- and tsunami-deposits are generated by similar depositional mechanisms making their discrimination hard to establish using classic sedimentologic methods. Here we propose an original approach to identify tsunami-induced deposits by combining numerical simulation and rock magnetism. To test our method, we investigate the tsunami deposit of the Boca do Rio estuary generated by the 1755 earthquake in Lisbon which is well described in the literature. We first test the 1755 tsunami scenario using a numerical inundation model to provide physical parameters for the tsunami wave. Then we use concentration (MS. SIRM) and grain size (chi(ARM), ARM, B1/2, ARM/SIRM) sensitive magnetic proxies coupled with SEM microscopy to unravel the magnetic mineralogy of the tsunami-induced deposit and its associated depositional mechanisms. In order to study the connection between the tsunami deposit and the different sedimentologic units present in the estuary, magnetic data were processed by multivariate statistical analyses. Our numerical simulation show a large inundation of the estuary with flow depths varying from 0.5 to 6 m and run up of similar to 7 m. Magnetic data show a dominance of paramagnetic minerals (quartz) mixed with lesser amount of ferromagnetic minerals, namely titanomagnetite and titanohematite both of a detrital origin and reworked from the underlying units. Multivariate statistical analyses indicate a better connection between the tsunami-induced deposit and a mixture of Units C and D. All these results point to a scenario where the energy released by the tsunami wave was strong enough to overtop and erode important amount of sand from the littoral dune and mixed it with reworked materials from underlying layers at least 1 m in depth. The method tested here represents an original and promising tool to identify tsunami-induced deposits in similar embayed beach environments.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

Epidemiological studies of drug misusers have until recently relied on two main forms of sampling: probability and convenience. The former has been used when the aim was simply to estimate the prevalence of the condition and the latter when in depth studies of the characteristics, profiles and behaviour of drug users were required, but each method has its limitations. Probability samples become impracticable when the prevalence of the condition is very low, less than 0.5% for example, or when the condition being studied is a clandestine activity such as illicit drug use. When stratified random samples are used, it may be difficult to obtain a truly representative sample, depending on the quality of the information used to develop the stratification strategy. The main limitation of studies using convenience samples is that the results cannot be generalised to the whole population of drug users due to selection bias and a lack of information concerning the sampling frame. New methods have been developed which aim to overcome some of these difficulties, for example, social network analysis, snowball sampling, capture-recapture techniques, privileged access interviewer method and contact tracing. All these methods have been applied to the study of drug misuse. The various methods are described and examples of their use given, drawn from both the Brazilian and international drug misuse literature.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

Lidar com as problemáticas da saúde, implica um domínio dos processos cognitivos (raciocínio, resolução de problemas e tomada de decisão) e de desempenhos práticos, o que obriga a afectação de um conjunto de atitudes e comportamentos específicos. Este estudo, implementou e avaliou o impacto de experiências pedagógicas desenvolvidas com os estudantes da unidade curricular Radiologia do Sistema Nervoso (RSN) da Escola Superior de Tecnologia da Saúde de Lisboa (ESTeSL). Aplicaram-se metodologias de ensino mistas (presenciais e virtuais) utilizadas na leccionação teórica e prática no ano curricular 2008/2009. Para a avaliação do perfil de aprendizagem dos estudantes foi aplicado o método de Honey & Munford e para a avaliação e monitorização dos conhecimentos aplicaram-se check list baseadas nos conteúdos programáticos. A monitorização das ferramentas da plataforma moodle complementaram a restante informação. Verificou-se uma progressão de aprendizagem positiva para um grupo de estudantes maioritariamente do estilo reflexivo (média=10,6 estudantes). As conclusões apontaram para um impacto positivo quanto à aplicação das metodologias híbridas com maior índice de sucesso para a metodologia assíncrona. Verificou-se também mais flexibilidade no acesso aos conteúdos porém com algumas limitações tais como residência inicial por parte dos estudantes, maior carga de trabalho para os docentes, falta de terminais para acesso à plataforma e pouca experiência de todos os envolvidos no domínio e manipulação da plataforma. ABSTRACT - This study focused on the role of cognitive processes (reasoning, problem solving and decision making) and performance practice in the formation of attitudes and behaviours relating to health issues. It was conducted to evaluate the effects of pedagogical experiences on students who participated in the course in radiography in the Nervous System Imaging Unit (RSN) of the Lisbon Health School of Technology. Mixed (face-to-face and virtual) teaching methodologies were used in theory and practice sessions. Honey and Munford’s method was used to evaluate the learning profile of students. To monitor and evaluate students’ knowledge acquisition, check lists based on program topics were applied. Other information was supplied through the learning platform of Moodle. The student group with mostly a reflective learning style increased their knowledge. The asynchronous method was shown to produce a higher success rate and more flexibility in accessing content but also registered some limitations such as resistance by students, increased workload for teachers, lack of access to the platform and inexperience of all involved in handling the platform.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

Chromium dioxide (CrO2) has been extensively used in the magnetic recording industry. However, it is its ferromagnetic half-metallic nature that has more recently attracted much attention, primarily for the development of spintronic devices. CrO2 is the only stoichiometric binary oxide theoretically predicted to be fully spin polarized at the Fermi level. It presents a Curie temperature of ∼ 396 K, i.e. well above room temperature, and a magnetic moment of 2 mB per formula unit. However an antiferromagnetic native insulating layer of Cr2O3 is always present on the CrO2 surface which enhances the CrO2 magnetoresistance and might be used as a barrier in magnetic tunnel junctions.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

Background: With the decrease of DNA sequencing costs, sequence-based typing methods are rapidly becoming the gold standard for epidemiological surveillance. These methods provide reproducible and comparable results needed for a global scale bacterial population analysis, while retaining their usefulness for local epidemiological surveys. Online databases that collect the generated allelic profiles and associated epidemiological data are available but this wealth of data remains underused and are frequently poorly annotated since no user-friendly tool exists to analyze and explore it. Results: PHYLOViZ is platform independent Java software that allows the integrated analysis of sequence-based typing methods, including SNP data generated from whole genome sequence approaches, and associated epidemiological data. goeBURST and its Minimum Spanning Tree expansion are used for visualizing the possible evolutionary relationships between isolates. The results can be displayed as an annotated graph overlaying the query results of any other epidemiological data available. Conclusions: PHYLOViZ is a user-friendly software that allows the combined analysis of multiple data sources for microbial epidemiological and population studies. It is freely available at http://www.phyloviz.net.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

Objetivo – Comparar a técnica convencional, a técnica de energias mistas e a técnica field-in-field com energias mistas, verificando a dose recebida nos órgãos de risco e no volume alvo. Metodologia – Quinze doentes com carcinoma da mama esquerda classificadas de T1-T3N0M0 foram tratadas com cirurgia conservadora da mama, seguida de radioterapia pós-operatória. Para cada doente realizaram-se 3 planeamentos dosimétricos, sendo que cada um deles diz respeito a uma das diferentes técnicas em estudo. Através dos HDV gerados avaliaram-se a Dmáx, Dmed, Dmín, D95%, D3% e a homogeneidade da dose no volume alvo, bem como a dose nos órgãos de risco. Utilizou-se o teste de Friedman para verificar a significância do estudo, com um intervalo de confiança de 95%. Resultados – Relativamente ao pulmão esquerdo e ao coração obtiveram-se, com a técnica field-in-field com energias mistas, doses inferiores em comparação com as outras duas técnicas. Para a Dmáx e a homogeneidade de dose no PTV, a técnica field-in-field com energias mistas revelou-se mais eficaz, comparativamente às outras técnicas. No entanto, verificou-se uma melhor cobertura de dose no PTV com a técnica convencional. Considerações finais – A técnica field-in-field com energias mistas permite uma redução da dose nos órgãos de risco, uma redução significativa da Dmáx no PTV e melhora a homogeneidade da dose, comparativamente com as outras técnicas. Os resultados obtidos com a técnica field-in-field com energias mistas apontam para a redução dos efeitos secundários provocados pelo tratamento. ABSTRACT - Purpose – To compare the conventional technique, the technique of mixed energies and the technique field-in-field with mixed energies, checking the received dose in organs at risk and target volume. Methods – Fifteen patients with carcinoma of the left breast classified as T1-T3N0M0 were treated with breast-conserving surgery, followed by postoperative radiotherapy. For each patient were carried out three dosimetric plannings, each one of them concerns the different techniques under study. Through the DVH generated to evaluate Dmax, Dmed, Dmin, D95%, D3% and the homogeneity of the target volume dose, well as the dose in organs at risk. We used the Friedman test to assess the significance of the study, with a confidence interval of 95%. Results – For the left lung and heart were obtained with the technique field-in-field with mixed energies, lower doses compared with the other two techniques. For the Dmax and the homogeneity of the PTV dose, the technique field-in-field with mixed energies was more effective compared to other techniques. However, there was a better coverage of the PTV dose with conventional technique. Conclusions – The technique field-in-field with mixed energy allows a reduction in dose for organs at risk, a significant reduction Dmax in PTV and improves the homogeneity of the dose compared with other techniques. The results obtained with the technique field-in-field with mixed energy indicate to reduce the side effects caused by the treatment.