7 results on '"Cacheffo, Alexandre"'
Search Results
2. Analyzing the Influence of Vehicular Traffic on the Concentration of Pollutants in the City of São Paulo: An Approach Based on Pandemic SARS-CoV-2 Data and Deep Learning.
- Author
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Moreira, Gregori de Arruda, Cacheffo, Alexandre, Andrade, Izabel da Silva, Lopes, Fábio Juliano da Silva, Gomes, Antonio Arleques, and Landulfo, Eduardo
- Subjects
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DEEP learning , *COVID-19 pandemic , *ATMOSPHERIC boundary layer , *POLLUTANTS , *TRAFFIC patterns , *SOCIAL distancing - Abstract
This study employs surface and remote sensing data jointly with deep learning techniques to examine the influence of vehicular traffic in the seasonal patterns of CO, NO2, PM2.5, and PM10 concentrations in the São Paulo municipality, as the period of physical distancing (March 2020 to December 2021), due to SARS-CoV-2 pandemic and the resumption of activities, made it possible to observe significant variations in the flow of vehicles in the city of São Paulo. Firstly, an analysis of the planetary boundary layer height and ventilation coefficient was performed to identify the seasons' patterns of pollution dispersion. Then, the variations (from 2018 to 2021) of the seasonal average values of air temperature, relative humidity, precipitation, and thermal inversion occurrence/position were compared to identify possible variations in the patterns of such variables that would justify (or deny) the occurrence of more favorable conditions for pollutants dispersion. However, no significant variations were found. Finally, the seasonal average concentrations of the previously mentioned pollutants were compared from 2018 to 2021, and the daily concentrations observed during the pandemic period were compared with a model based on an artificial neural network. Regarding the concentration of pollutants, the primarily sourced from vehicular traffic (CO and NO2) exhibited substantial variations, demonstrating an inverse relationship with the rate of social distancing. In addition, the measured concentrations deviated from the predictive model during periods of significant social isolation. Conversely, pollutants that were not primarily linked to vehicular sources (PM2.5 and PM10) exhibited minimal variation from 2018 to 2021; thus, their measured concentration remained consistent with the prediction model. [ABSTRACT FROM AUTHOR]
- Published
- 2023
- Full Text
- View/download PDF
3. Collaborative development of the Lidar Processing Pipeline (LPP).
- Author
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Pallotta, Juan, Carvalho, Silvania A., Lopes, Fabio, Cacheffo, Alexandre, Landulfo, Eduardo, and Barbosa, Henrique M. J.
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LIDAR ,SPATIAL resolution ,OPTICAL properties ,COMMUNITIES ,AEROSOLS - Abstract
Lidars can simultaneously measure clouds and aerosols with high temporal and spatial resolution and hence help understand their interactions, which are the source of the largest uncertainties in current climate projections. However, lidars are typically custom-built, so there are significant differences between them. In this sense, lidar networks play a crucial role as they coordinate the efforts of different groups, providing the guidelines for quality-assured routine measurements aiming to homogenize the physical retrievals. With that in mind, this work describes an ongoing effort to develop a lidar processing pipeline (LPP) collaboratively. The LPP is a collection of tools developed in C/C++, python, and Linux script that handle all the steps of a typical lidar analysis. The first publicly released version of LPP produces data files at levels 0 (raw and metadata), 1 (averaging and layer-mask), and 2 (aerosol optical properties). We discussed the application of LPP for two case studies for Sao Paulo and Amazon, which shows the capabilities of the current release but also highlights the need for new features. From this exercise, we developed and presented a roadmap to guide future development, accommodating the needs of our community. [ABSTRACT FROM AUTHOR]
- Published
- 2022
- Full Text
- View/download PDF
4. Influence of a Biomass-Burning Event in PM2.5 Concentration and Air Quality: A Case Study in the Metropolitan Area of São Paulo
- Author
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de Arruda Moreira, Gregori, primary, da Silva Andrade, Izabel, additional, Cacheffo, Alexandre, additional, da Silva Lopes, Fábio Juliano, additional, Calzavara Yoshida, Alexandre, additional, Gomes, Antonio Arleques, additional, da Silva, Jonatan João, additional, and Landulfo, Eduardo, additional
- Published
- 2021
- Full Text
- View/download PDF
5. Redes de osciladores dissipativos: o modelo duplicado de Caldeira-Leggett, transferência quase-perfeita de estados e recoerência
- Author
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Cacheffo, Alexandre and Moussa, Miled Hassan Youssef
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Redes de osciladores quânticos ,Mecânica quântica ,Decoerência (Decoherence) ,Integrais de trajetórias ,FISICA [CIENCIAS EXATAS E DA TERRA] ,Transferência e recorrência de estados quânticos ,Recoerência - Abstract
Universidade Federal de Minas Gerais In this work we treat firstly what we call the double Caldeira-Leggett model, which consists on the approach to the dynamics of two dissipative harmonic oscillators via Feynman-Vernon theory. We derived and solved the associated master equations in two different situations where i) each oscillator is coupled to its own reservoir and ii) both oscillators are coupled to the same reservoir. Finally we analyzed the decoherence process of entangled states prepared in both oscillators. Next, we treat the problem of quasi-perfect state transfer (QPST) in networks of dissipative harmonic oscillators. In this context, we have presented two different protocols for QPST: the first based in the detuning between the frequencies of the emitter and receiver oscillators regarding that of the transmitter oscillators and the second consisting in the use of what we call a decoherence quasi-free subspace (DQFS). To this end, we derived the regime of parameters enabling the emergence of DQFS. In both protocols we verified that QPST processes occur by means of a mechanism, similar to the tunneling effect, i. e., the excitations of the state to be transferred populate only virtually the transmission channel. Finally, regarding quantum open systems, we present the phenomenon that we call spontaneous recoherence of states. Through this phenomenon, we verified that the reservoir only shuffle the information of the system, instead of erasing it. The password to retrieve the original information consists of the knowledge of the initial state itself and its associated pure basis Neste trabalho tratamos primeiramente o que denominamos modelo duplicado de Caldeira-Leggett, que consiste no tratamento da dinâmica de dois osciladores harmônicos quânticos dissipativos acoplados, via teoria de Feynman-Vernon. Obtivemos e resolvemos as equações mestras associadas em duas diferentes situações, nas quais i) cada oscilador encontra-se acoplado a seu próprio reservatório ou ii) ambos os osciladores acoplam-se ao mesmo reservatório. Por fim, analisamos o processo de decoerência de estados emaranhados preparados nos osciladores. Tratamos, em seguida, do problema da transferência quase-perfeita de estados (TQPE) em redes de osciladores quânticos dissipativos. Apresentamos, neste contexto, dois diferentes protocolos para a TQPE: o primeiro baseado na dessintonia entre as freqüências dos osciladores emissor e receptor com relação àquelas dos osciladores transmissores; o segundo baseado na utilização do que denominamos subespaços quase-livres de decoerência (SQLD). Verificamos que em ambos os protocolos apresentados, o processo de transferência de estados se dá por um mecanismo similar ao efeito túnel, de forma que a excitação do estado a ser transferido ocupa apenas virtualmente o canal de transmissão. Por fim, apresentamos o fenômeno que denominamos recoerência espontânea de estados. Através deste fenômeno, verificamos que o reservatório térmico não apaga a informação do sistema, isto é, seu estado inicial; ele apenas embaralha esta informação. A senha para a recuperação da informação original consiste no conhecimento do estado inicial do sistema e da base pura a ele associada.
- Published
- 2010
6. Abordagem via integrais de trajetória do processo de troca e dissipação de energia num sistema composto por dois osciladores harmônicos dissipativos acoplados - o modelo duplicado de Caldeira & Leggett
- Author
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Cacheffo, Alexandre and Moussa, Miled Hassan Youssef
- Subjects
Óptica quântica ,Mecânica quântica ,FISICA [CIENCIAS EXATAS E DA TERRA] ,Integrais de trajetória ,Decoerência (decoherence) ,Dissipação de energia - Abstract
Universidade Federal de Minas Gerais In this work, we analyse the dissipation and interchange of energy in a system composed by two harmonic oscillators, each one associated with a thermal reservoir. To this end, we employ the Caldeira & Leggett approach, based on path integral formulation, to obtain the time evolution of the reduced density operator of the system composed by both oscillators. Tratamos, neste trabalho, os processos de troca e dissipação de energia num sistema composto por dois osciladores harmônicos cada qual associado a um reservatório térmico. Para isso, empregamos a abordagem de Caldeira & Leggett, baseada na formulação de integrais de trajetória, para a obtenção da evolução temporal do operador densidade reduzido do sistema composto por ambos os osciladores.
- Published
- 2005
7. Influence of a Biomass-Burning Event in PM 2.5 Concentration and Air Quality: A Case Study in the Metropolitan Area of São Paulo.
- Author
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de Arruda Moreira, Gregori, da Silva Andrade, Izabel, Cacheffo, Alexandre, da Silva Lopes, Fábio Juliano, Calzavara Yoshida, Alexandre, Gomes, Antonio Arleques, da Silva, Jonatan João, and Landulfo, Eduardo
- Subjects
METROPOLITAN areas ,OPTICAL radar ,PARTICULATE matter ,LIDAR ,AIR quality indexes ,AIR quality - Abstract
Severe biomass burning (BB) events have become increasingly common in South America in the last few years, mainly due to the high number of wildfires observed recently. Such incidents can negatively influence the air quality index associated with PM
2.5 (particulate matter, which is harmful to human health). A study performed in the Metropolitan Area of São Paulo (MASP) took place on selected days of July 2019, evaluated the influence of a BB event on air quality. Use of combined remote sensing, a surface monitoring system and data modeling and enabled detection of the BB plume arrival (light detection and ranging (lidar) ratio of (50 ± 34) sr at 532 nm, and (72 ± 45) sr at 355 nm) and how it affected the Ångström exponent (>1.3), atmospheric optical depth (>0.7), PM2.5 concentrations (>25 µg.m−3 ), and air quality classification. The utilization of high-order statistical moments, obtained from elastic lidar, provided a new way to observe the entrainment process, allowing understanding of how a decoupled aerosol layer influences the local urban area. This new novel approach enables a lidar system to obtain the same results as a more complex set of instruments and verify how BB events contribute from air masses aloft towards near ground ones. [ABSTRACT FROM AUTHOR]- Published
- 2021
- Full Text
- View/download PDF
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