Fresh and pasteurized orange juice analysis by TXRF

Orange is considered the main product of the Brazilian citrus agro-industrial complex. However, in the end of 2016, the ANVISA pointed out orange as a risky product due to contamination using pesticides in its cultivation. Therefore, in this context, an analysis of the chemical elements present in fresh and pasteurized orange juices becomes extremely relevant. Thus, this work aims to quantify the elements that are present in fresh and pasteurized orange juices, using the TXRF technique. Samples of fresh orange juice of Pêra variety were acquired in a store in the city of Londrina-PR, were analysed; three samples of oranges were purchased at a store in Itápolis, São Paulo and five more samples of Pêra orange were obtained in the rural area. Samples of pesticides used in orange cultivation were quantified, and three different trademarks of pasteurized juice were analysed. In some of the samples that were collected in Itápolis-SP market, lead (Pb) element was quantified, however its concentration was within the limit established by Brazilian legislation. The aluminium (Al) element was detected in all samples of pasteurized orange juice, showing the influence of the packaging on the elemental concentration of the juice. All pesticides quantified in this work showed a significant concentration of some micro-contaminants, but when the pesticide was diluted in deionized water, those micro-contaminants could not be quantified.

Linear detectors and precoding methods for massive MIMO

Detection in multiple-input-multiple-output (MIMO) wireless communication systems is a crucial procedure in receivers since the multiple access transmission schemes generate interference due to the simultaneous transmission along with the several antennas, unlike single-input-single-output (SISO) transmission schemes. Precoding is a technique in MIMO systems used to mitigate the effects of the channel over the received signal. Hence, it is possible to adjust continuously the transmitted information to reverse the effect of the wireless channel at the receiver side. In this work, linear sub-optimal detectors and precoders for massive MIMO (M-MIMO) systems are implemented, analyzed, and compared in terms of performance-complexity trade-off. It is also being considered numerical results in both channel scenarios: a) receiver and transmitter have perfect channel state information (CSI); b) complex channel coefficients are estimated with different levels of inaccuracy. Monte-Carlo simulations (MCS) reveal that linear zero-forcing (ZF) and minimum mean squared error (MMSE) massive MIMO detectors result in a certain robustness against multi-user interference when operating under low and medium system loading, L = K/M, thanks to the favourable propagation phenomenon arising in massive MIMO systems.

Damping techniques for grid-connected converters with LCL filter: an overview

Distributed generation systems, based on renewable energy sources, are typically connected to the main grid by a voltage-source inverter with a low-pass filter. The need for improved efficiency led to the use of third order low-pass filters, such as the LCL configuration, which has resonant behavior. In order to meet energy quality requirements and ensure the systems stability it is necessary to suppress the LCL filters resonance through damping techniques. Therefore, this paper presents an overview of some damping strategies found in literature and its design procedure, applied to a simulated single-phase grid-tied inverter. The comparison of each presented damping methodology characteristics is described, with analysis of advantages and drawbacks for each case.

Overview of the main powertrain architectures for hybrid and electric vehicles

The research for alternative solutions to assist the propulsion, fuel converters and energy storage systems (ESS) in vehicular applications has become the focus of many institutions and mainly in the automotive industry, aiming to reduce the impacts caused by the emission of gases in the exhaust pipe and to improve energy efficiency in the worldwide vehicle fleet. Hybrid Electric Vehicles (HEV) and Electric Vehicles (EV) are currently a reality and meet this requirement to build a greener and less polluting society. In this context, this paper describes the operational characteristics of the different powertrain architectures employed in hybrid electric vehicles, including series, parallel and series-parallel topologies, as well as battery-powered and fuel cell electric vehicles. Finally, some of the elementary issues facing these advanced vehicular technologies, including the challenges for market penetration are highlighted.

A novel methodology for direct esterification of olives optimized through design of experiments

A novel methodology was proposed, and optimized using the Design Expert software, aiming to enable characterization of the fatty acid profile of olives whilst abolishing the lipid extraction step. Furthermore, the proposed method was proven more efficient whereas requiring less time, and sample and solvent amounts, consequently improving process yield. Optimum conditions obtained after experimental design were as follows: sonication temperature and time of 60 ºC and 8 minutes, respectively, and concentrations for alkaline and acid reactions of 0.70 and 1.5 mol L-1, respectively. Total fatty acid content for olive sample was 172.0 mg g-1, the predicted value was and is in the coefficient of variation range of 11.52%

The real COVID-19 pandemic dynamics in Qatar in 2021: simulations, predictions and verifications of the SIR model

The third COVID-19 pandemic wave in Qatar was simulated with the use of the generalized SIR-model and the accumulated number of cases reported by Johns Hopkins University for the period: April 25 - May 8, 2021. The results were compared with the SIR simulations performed before for the second wave and the number of laboratory-confirmed cases in the first half of 2021. Despite the mass vaccination that began in December 2020, Qatar experienced a new epidemic wave in March-April 2021. As of the end of June 2021, the positive effects of vaccination were still unclear, although the number of fully vaccinated was already approaching half the population. Additional simulations have demonstrated that many COVID-19 cases are not detected. The real accumulated number of cases in Qatar can exceed the laboratory-confirmed one more than 5 times. This fact drastically increases the probability of meeting an infectious person and the epidemic duration.

COVID-19 em Londrina-PR: Modelo SEIR com Otimização de Parâmetros

The first cases of COVID-19 in Londrina-PR were manifested in March 2020 and the disease lasts until the present moment. We aim to inform citizens in a scientific way about how the disease spreads. The present work seeks to describe the behavior of the disease over time. We started from a compartmental model of ordinary differential equations like SEIR to find relevant information such as: transmission rates and prediction of the peak of infected people. We used the data released by city hall of Londrina to carry out simulations in periods of 14 days, applying a parameter optimization technique to obtain results with thegreatest possible credibility.

Assessing vaccination strategies for the COVID-19 epidemic in Minas Gerais (Brazil)

In this work we analyze the effectiveness of vaccination strategies for the COVID-19 epidemic in the Brazilian state of Minas Gerais. Firstly we study the effectiveness of general vaccination in the decreasing of the number of infected individuals using a traditional non structured SEIR model. Secondly we consider an age-structured SEIR model with three age classes (youngster, adult and elderly) and we analyze the current strategy in the Brazilian state of Minas Gerais, of focusing the vaccination on the elderly group. We conclude by showing this strategy to be mistaken and that a vaccination focusing on the age group of the adults would be much more efficient in decreasing the total number of infected individuals.

Review and comparison of works on heterogeneous data and semantic analysis in Big Data

In integration approaches, heterogeneity is one of the main challenging factors on the task of providing integration among different data sources, whose solution lies in the search for equality among them. This work describes the state of the art and theoretical foundation involved in the structural and semantic analysis of heterogeneous data and information. The work aims to review methods and techniques used in data integration in Big Data, considering data heterogeneity, reviewing techniques that use the concepts of Semantic Web, Cloud Computing, Data Analysis, Big Data, Data Warehouse and other technologies to solve the problem of data heterogeneity. The research was divided into three stages. In the first stage, articles were selected from digital libraries according to their titles and keywords. In the second stage, the papers went through a second filter based on their summary, and, besides that, duplicate articles were also removed. The works’ introduction and conclusion were analyzed in the third stage to select the articles belonging to this systematic review. Throughout the study, articles were analyzed, compared and categorized. At the end of each section, the interrelationships and possible areas for future work were shown.

Efficiency Study of PbTe/CdTe Core/Shell Quantum Dots Solar Cells

In this work we theoretically study how to optimize the efficiency of an intermediate band solar cell based on IV-VI PbTe/CdTe semiconductor materials. We focus our attention on how control structural parameters, such as the height and radius in cylindrical quantum dots and the radius in spherical quantum dots to obtain the inter and intraband transition energies that provide the highest efficiency values of the solar cell. The calculation of the energy levels, the selection rules for transitions energies were performed using the 4×4 k.p Kane-Dimmok Hamiltonian.