Disorder-induced double resonant Raman process in graphene

An analytical study is presented of the double resonant Raman scattering process in graphene, responsible for the D and D$^{\prime}$ features in the Raman spectra. This work yields analytical expressions for the D and D$^{\prime}$ integrated Raman intensities that explicitly show the dependencies on laser energy, defect concentration, and electronic lifetime. Good agreement is obtained between the analytical results and experimental measurements on samples with increasing defect concentrations and at various laser excitation energies. The use of Raman spectroscopy to identify the nature of defects is discussed. Comparison between the models for the edge-induced and the disorder-induced D band intensity suggests that edges or grain boundaries can be distinguished from disorder by the different dependence of their Raman intensity on laser excitation energy. Similarly, the type of disorder can potentially be identified not only by the intensity ratio $I_{\mathrm{D}}/I_{\mathrm{D}^{\prime}}$, but also by its laser energy dependence. Also discussed is a quantitative analysis of quantum interference effects of the graphene wavefunctions, which determine the most important phonon wavevectors and scattering processes responsible for the D and D$^{\prime}$ bands.Comment: 10 pages, 4 figure

Time-Reversal Symmetry Breaking and Decoherence in Chaotic Dirac Billiards

In this work, we perform a statistical study on Dirac Billiards in the extreme quantum limit (a single open channel on the leads). Our numerical analysis uses a large ensemble of random matrices and demonstrates the preponderant role of dephasing mechanisms in such chaotic billiards. Physical implementations of these billiards range from quantum dots of graphene to topological insulators structures. We show, in particular, that the role of finite crossover fields between the universal symmetries quickly leaves the conductance to the asymptotic limit of unitary ensembles. Furthermore, we show that the dephasing mechanisms strikingly lead Dirac billiards from the extreme quantum regime to the semiclassical Gaussian regime

Classification of areas using pixel-by-pixel and sample classifiers

There are no author-identified significant results in this report

Time-Driven Activity-Based Costing: designing a model in a Portuguese production environment

Purpose: By designing a pilot Time-Driven Activity-Based Costing (TDABC) model, this study seeks to examine in depth the suitability and the complexity of TDABC in a manufacturing company. Design/Methodology/Approach: To obtain a deeper understanding on the matters to analyse, this research adopts an interventionist approach. The host organisation is GP, a Portuguese company in the frozen food sector. Findings: Our experience allows us to assert that TDABC is suitable for a manufacturing company and it is able to deal with the variability of the industrial processes. Nonetheless, through a comparison with the models presented in the literature, TDABC appears to be more complex for manufacturing. We argue that this happens for two reasons: First, the two types of resources (human labour and machinery) used in production areas create a need to split tasks and to create two equations for each process, something that does not happen in service companies. Second, times are difficult to individualise for certain highly automated procedures, which could also give rise to some errors. Research limitations/implications: The designed model is compared to other models presented in the literature. Practical implications: This study shows a real example of TDABC in manufacturing and the procedural innovation of the time equations. Originality/Value: Since the TDABC literature has been mostly focused on examples of service companies, we examine the technical suitability and the complexity of TDABC in manufacturing companies.info:eu-repo/semantics/acceptedVersio

Inferência de impacto causal de um sistema de recomendação na taxa de rejeição de páginas da Agência Embrapa.

A Agência de Informação Embrapa é um sistema web com o objetivo de organizar, tratar, armazenar e divulgar informações técnicas e conhecimentos gerados pela Empresa Brasileira de Pesquisa Agropecuária (Embrapa). Diariamente o site recebe milhares de acessos que são registrados em uma base de dados

The GREATS Hβ\beta+[OIII] Luminosity Function and Galaxy Properties at z∼8\mathbf{z\sim8}: Walking the Way of JWST

The James Webb Space Telescope will allow to spectroscopically study an unprecedented number of galaxies deep into the reionization era, notably by detecting [OIII] and H$\beta$ nebular emission lines. To efficiently prepare such observations, we photometrically select a large sample of galaxies at $z\sim8$ and study their rest-frame optical emission lines. Combining data from the GOODS Re-ionization Era wide-Area Treasury from Spitzer (GREATS) survey and from HST, we perform spectral energy distribution (SED) fitting, using synthetic SEDs from a large grid of photoionization models. The deep Spitzer/IRAC data combined with our models exploring a large parameter space enables to constrain the [OIII]+H$\beta$ fluxes and equivalent widths for our sample, as well as the average physical properties of $z\sim8$ galaxies, such as the ionizing photon production efficiency with $\log(\xi_\mathrm{ion}/\mathrm{erg}^{-1}\hspace{1mm}\mathrm{Hz})\geq25.77$. We find a relatively tight correlation between the [OIII]+H$\beta$ and UV luminosity, which we use to derive for the first time the [OIII]+H$\beta$ luminosity function (LF) at $z\sim8$. The $z\sim8$ [OIII]+H$\beta$ LF is higher at all luminosities compared to lower redshift, as opposed to the UV LF, due to an increase of the [OIII]+H$\beta$ luminosity at a given UV luminosity from $z\sim3$ to $z\sim8$. Finally, using the [OIII]+H$\beta$ LF, we make predictions for JWST/NIRSpec number counts of $z\sim8$ galaxies. We find that the current wide-area extragalactic legacy fields are too shallow to use JWST at maximal efficiency for $z\sim8$ spectroscopy even at 1hr depth and JWST pre-imaging to $\gtrsim30$ mag will be required.Comment: 13 pages, 9 figures, accepted for publication in MNRA