Toward a numerical deshaker for PFS

The Planetary Fourier Spectrometer (PFS) onboard Mars Express (MEx) is the instrument with the highest spectral resolution observing Mars from orbit since January 2004. It permits studying the atmospheric structure, major and minor compounds. The present time version of the calibration is limited by the effects of mechanical vibration, currently not corrected. We proposed here a new approach to correct for the vibrations based on semi-blind deconvolution of the measurements. This new approach shows that a correction can be done efficiently with 85% reduction of the artefacts, in a equivalent manner to the stacking of 10 spectra. Our strategy is not fully automatic due to the dependence on some regularisation parameters. It may be applied on the complete PFS dataset, correcting the large-scale perturbation due to microvibrations for each spectrum independently. This approach is validated on actual PFS data of Short Wavelength Channel (SWC), perturbed by microvibrations. A coherence check can be performed and also validate our approach. Unfortunately, the coherence check can be done only on the first 310 orbits of MEx only, until the laser line has been switch off. More generally, this work may apply to numerically "deshake" Fourier Transform Spectrometer (FTS), widely used in space experiments or in the laboratory.Comment: 18 pages, 8 figures, submitted to Planetary and Space Scienc

Characterization of dust activity on Mars from MY27 to MY32 by PFS-MEX observations

We present spatial and temporal distributions of dust on Mars from Ls = 331 in MY26 until Ls = 80 in MY33 retrieved from the measurements taken by the Planetary Fourier Spectrometer (PFS) aboard Mars Express. In agreement with previous observations, large dust opacity is observed mostly in the southern hemisphere spring/summer and particularly over regions of higher terrain and large topographic variation. We present a comparison with dust opacities obtained from Thermal Emission Spectrometer (TES) - Mars Global Surveyor (MGS) measurements. We found good consistency between observations of two instruments during overlapping interval (Ls = 331 in MY26 until Ls = 77 in MY27). We found a different behavior of the dust opacity with latitude in the various Martian years (inter-annual variations). A global dust storm occurred in MY28. We observe a different spatial distribution, a later occurrence and dissipation of the dust maximum activity in MY28 than in other Martian years. A possible precursor signal to the global dust storm in MY 28 is observed at Ls = 200 - 235 especially over west Hellas. Heavy dust loads alter atmospheric temperatures. Due to the absorption of solar radiation and emission of infrared radiation to space by dust vertically non-uniformly distributed, a strong heating of high atmospheric levels (40 - 50 km) and cooling below around 30 km are observed.Comment: in press in Icarus. 47 pages, 15 figure

On Phasor Control for Linear Time Invariant systems

In some control applications, where the reference is sinusoidal, phasor-based strategies can be considered. The main advantage of these approaches is that instead of dealing with oscillating signals, one deals with constant or low-frequency signals. However, to implement this solution, several nonlinearities are included into the control loop. Then, linearization are performed around operating points to design a controller, but with no guaranties of performance. In this work, we present a "large-signal" model for the system. Then, considering ideal measurement of instantaneous amplitude and phase, we establish the correspondence between classical control architecture and a phasor-based one. Hence, we show that a controller can be designed as in a classical architecture and implemented in a phasor-based one with a simple transformation, ensuring the same performance level. However, in practical applications, the measurements of amplitude and phase are not ideal and may quickly degrade the behavior of the system. Thus, we propose a second design approach that takes these nonlinearities into account, ensuring nominal stability and performance. Examples illustrate the effectiveness of these methods

Compensation of Thermal Gradients Effects on a Quartz Crystal Microbalance

Quartz Crystal Microbalances (QCM) are widely used instruments thanks to their stability, low mass, and low cost. Nevertheless, the sensitivity to temperature is their main drawback and is often a driver for their design. Though the crystal average temperature is mostly considered as the only disturbance, temperature affects the QCM measurements also through the in-plane temperature gradients, an effect identified in the past but mostly neglected. Recently, it has been shown that this effect can prevail over that of the average temperature in implementations where the heat for thermal control is released directly on the crystal through deposited film heaters. In this study, the effect of temperature gradients for this kind of crystal is analyzed, the sensitivity of frequency to the average temperature gradient on the electrode border is determined, and a correction is proposed and verified. A numerical thermal model of the QCM has been created to determine the temperature gradients on the electrode borders. The frequency versus temperature-gradient function has been experimentally determined in different thermal conditions. The correction function has been eventually applied to a QCM implementing a crystal of the same manufacturing lot as the one used for the characterization. The residual errors after the implementation of the correction of both average temperature and temperature gradients were always lower than 5% of the initial temperature disturbance. Moreover, using the correlation between the heater power dissipation and the generated temperature gradients, it has been shown that an effective correction strategy can be based on the measurement of the power delivered to the crystal without the determination of the temperature gradient

Avaliação da viabilidade econômica do uso de líquidos iônicos imidazólios como catalisadores na produção de compostos deuterados

Os líquidos iônicos prolinato de 1-nbutil-2,3-dimetilimidazólio (BMMI.Pro) e imidazolato de 1-nbutil-2,3-dimetilimidazólio (BMMI.Im) foram empregados como catalisadores em reações de troca isotópica H/D de substratos com funcionalidade cetona e alcino, e os seguintes solventes: dimetilsulfóxido (DMSO), acetona e acetonitrila. O clorofórmio deuterado foi utilizado como fonte de deutério e as reações foram realizadas a temperatura ambiente. Os produtos foram quantificados através da técnica de Ressonância Magnética Nuclear de Hidrogênio (RMN 1H) e os resultados demonstraram graus de incorporação de deutério entre 40 e 84%. Teste de reciclagem do catalisador também foi realizado, confirmando a possibilidade de reciclo. A viabilidade econômica da metodologia proposta foi avaliada em comparação com os custos comerciais dos produtos deuterados e de catalisadores metálicos tradicionais disponíveis no mercado. Deste estudo se concluiu que a rota sintética é viável e apresenta bons rendimentos, com redução de custo de até 15 vezes para deuterados e superior a 319 vezes para o catalisador. Outra vantagem observada é o menor impacto ambiental gerado pelo processo proposto, uma vez que não são gerados subprodutos e que os produtos são obtidos sem qualquer purificação adicional.1-nbutyl-2,3-dimethylimidazolium prolinate (BMMI.Pro) and 1-nbutyl-2,3-dimethylimidazolium imidazolate (BMMI.Im) were used as catalysts in H/D isotopic exchange reactions of substrates with ketone and alkyne functionality, and the following solvents: dimethyl sulfoxide (DMSO), acetone and acetonitrile. The deuterated chloroform was used as a source of deuterium and the reactions were performed at room temperature. The products were quantified using the Nuclear Magnetic Resonance of Hydrogen (1H NMR) technique and the results showed degrees of incorporation of deuterium between 40% and 84%. Recycling test of the catalyst was also performed, confirming the possibility of recycling. The economic viability of the proposed methodology was evaluated in comparison with the commercial costs of the deuterated products and traditional metallic catalysts available in the market. From this study, it was concluded that the synthetic route is feasible and presents good yields, with cost reduction of up to 15 times for deuterates and more than 319 times for the catalyst. Another advantage observed was the lower environmental impact generated by the proposed process, since no by-products are generated and the products are obtained without any additional purification

Modelagem e controle para operação de inversores monofásicos em paralelo: uma abordagem via fasores dinâmicos e LMIS

Dissertação (mestrado) - Universidade Federal de Santa Catarina, Centro Tecnológico, Programa de Pós-Graduação em Engenharia de Automação e Sistemas, Florianópolis, 2016.A operação de inversores em paralelo tem se tornado cada vez mais atrativa, já que permite, por exemplo, a formação de micro redes de energia elétrica através de fontes de energia renováveis. No entanto, esse tipo de operação é bastante sensível e exige controladores que garantam o adequado funcionamento do sistema. Diversas técnicas são propostas na literatura, entre elas, as baseadas no droop control. A grande maioria desses trabalhos utiliza modelos de pequenos sinais para análise de estabilidade e projeto do controlador. No entanto, esses modelos possuem limitações. Assim, nos últimos anos começaram a surgir modelos mais precisos, permitindo um estudo mais detalhado de sistemas cujos controladores são baseados no droop control. Uma das técnicas utilizadas são os fasores dinâmicos, que permite a descrição do sistema da perspectiva de grandes sinais. Dessa forma, um modelo baseado em fasores dinâmicos é proposto nesse trabalho, incluindo as principais dinâmicas do sistema. A partir desse modelo, também se projeta um controlador multivariável através de desigualdades matriciais lineares (LMIs), garantindo estabilidade e desempenho do sistema, considerando as incertezas paramétricas no modelo. Simulações emulam um cenário realista, onde os controladores propostos são digitalizados e implementados em dois inversores, os quais estão conectados em paralelo e alimentam uma carga variável. Os resultados de simulação demonstram a precisão do modelo e a eficiência do controlador proposto.Abstract: The parallel operation of voltage source inverters has become increasingly attractive, as it allows, for instance, microgrids formation through renewable energy sources. Nonetheless, the parallelism of inverters is a quite sensible operation and requires controllers capable of making the system works correctly. Several techniques are found in the specialized literature, among them, the droop control-based ones. Most of these works consider small-signal models to assess stability analysis and control design. However, these models have limitations. Thus, during the last years, more accurate models have been presented, allowing a more detailed study of droop controlled systems. Dynamic phasors are a powerful tool that permits the description of the system behavior from a large-signal perspective. Hence, a dynamic phasor model is proposed in this work, including the system most relevant dynamics. From this model, a controller design methodology based on linear matrix inequality (LMI) constraints is also proposed, and ensures the system stability and performance, taking parametric uncertainties into account. Simulations emulate a realistic scenario, where the controllers are discretized and implemented into two parallel-connected inverters, feeding a variable load. The simulation results show the model accuracy and the controller effectiveness

Caracterização do perfil de virulência de isolados de Staphylococcus pseudintermedius

O agente bacteriano Staphylococcus pseudintermedius é um patógeno oportunista, responsável por uma ampla gama de infecções, principalmente em cães, incluindo piodermatite, otite externa, bacteremia, infecções do trato urinário e infecções pós-cirúrgicas. Esta espécie é capaz de sintetizar uma série de toxinas. Essas, porém, ainda não foram caracterizadas detalhadamente e há divergência entre o perfil de toxinas presentes nos isolados. Para trazer mais informações a respeito do potencial patogênico dessa espécie, 33 isolados de S. pseudintermedius provindos de diferentes sítios de infecção foram investigados através de identificação molecular quanto à presença do gene de resistência à antimicrobianos mecA, e para 11 genes codificadores de toxinas: citotoxinas (lukS, lukF), toxina esfoliativa (siet), enterotoxinas (sea, seb, sec, seccanine, sel, sem e seq) e toxina da síndrome do choque tóxico (tst-1). Os mesmos isolados foram submetidos ao teste de formação de biofilme in vitro, e ao teste de susceptibilidade aos antimicrobianos. Os resultados mostraram que 81 % dos isolados foram positivos para lukS, 90 % foram positivos para lukF e 87 % positivos para siet. Já outros genes foram de detecção menos frequente, como seq (12 %), sel (9 %) e sem (3 %). Os genes, sea, seb, sec, seccanine e tst-1, não foram detectados em nenhum dos isolados do presente estudo. Os isolados fenotipicamente resistentes à oxacilina foram previamente descritos como positivos para mecA, e dentre os 14 isolados fenotipicamente suscetíveis à oxacilina, somente um deles foi positivo para o mesmo gene. Referente a resistência aos antimicrobianos, 57,5 % apresentaram o padrão fenotípico de cepas oxacilina resistentes, enquanto que 42,4 % foram descritas como sensíveis. Já o percentual de isolados multirresistentes foi de 84,8 %. Com exceção de um isolado, todos os demais foram classificados como fortes formadores de biofilme. Em conclusão, a alta prevalência de genes codificadores de toxinas, a forte capacidade de formação de biofilme e os diversos perfis de multirresistência aos antimicrobianos sugerem o grande potencial patogênico e virulento desta espécie, e também pôde-se observar que existe uma variação da presença de alguns desses fatores conforme o sítio de infecção do isolado.The bacterial agent Staphylococcus pseudintermedius is a timely pathogen, responsible for a range of infections, mainly in dogs, including pyodermatitis, external otitis, bacteremia, urinary tract infections and post-surgery infections. This species is capable of synthesizing a series of toxins and, besides these not being described in detail so far, there are divergences between the data published, where the presence of these toxins varies, bringing a greater need for studies on this topic. To provide more information about the pathogenic potential of this species, 33 isolates of S. pseudintermedius from different infection sites were screened by molecular identification for the mecA antimicrobial resistance gene, and for 11 toxin coding genes: cytotoxins (lukS), lukF), exfoliative toxin (siet), enterotoxins (sea, seb, sec, seccanine, sel, sem and seq) and toxic shock syndrome toxin (tst-1). The same isolates were submitted to the in vitro biofilm formation test and the antimicrobial susceptibility test. Results showed that 81 % of isolates were positive for lukS, 90 % were positive for lukF and 87 % positive for siet. Other genes were less frequent detection, such as seq (12 %), sel (9 %) and sem (3 %). The genes, sea, seb, sec, seccanine and tst-1 were not detected in any of the isolates of the present study. Phenotypically oxacycline-resistant isolates were previously described as positive for mecA, and of the 14 phenotypically oxacycline-susceptible isolates, only one was positive for the same gene. Regarding antimicrobial resistance, 57.5 % presented the phenotypic pattern of resistant oxacillin strains, while 42.4 % were described as sensitive. The percentage of Multidrug resistant isolates was 84.8 %. With the exception of one isolate, all others were classified as strong biofilm forming. In conclusion, the high prevalence of toxin-coding genes, the strong biofilm formation capacity and the diverse antimicrobial multidrug resistance profiles suggest the great pathogenic and virulent potential of this species, and it was also observed that there is a variation in the presence of some of these factors depending on the site of infection of the isolate