Rio de Janeiro, Brazil
Rio de Janeiro, Brazil

Time filter

Source Type

This paper investigated the effects of modified atmosphere packing (60% N2 and 40% CO2) and irradiation (with a 1.5kGy dose) either used alone or combined on the shelf life of fillets of refrigerated Nile Tilapia. A total of 120 fillets were used in the experiments in order to test four different treatments and included samples: packed in air (control), packed in modified atmosphere, packed in air and irradiated, and finally, packed in modified atmosphere and irradiated. Regular monitoring of physicochemical parameters (TVB, pH, ammonia and TBARS), bacteriological conditions (heterotrophic aerobic mesophilic and psychrotrophic bacteria) and sensory acceptance were performed. The results consistently indicated an increasing deterioration of the fillets with time, however those treated with irradiation, modified atmosphere or both combined had longer shelf lives (around two weeks) in comparison with the control (4 days only).

de Assis L.P.G.,Federal Rural University of Rio de Janeiro | de Assis L.P.G.,Brazilian Center for Research in Physics (CBPF) | Gaete P.,Federico Santa María Technical University | Helayel-Neto J.A.,Brazilian Center for Research in Physics (CBPF) | And 2 more authors.
International Journal of Theoretical Physics | Year: 2012

In the framework of three-dimensional Born-Infeld Electrodynamics, we pursue an investigation of the consequences of the space-time dimensionality on the existence of magnetostatic fields generated by electric charges at rest in an inertial frame, which are present in its four-dimensional version. Our analysis reveals interesting features of the model. In fact, a magnetostatic field associated with an electric charge at rest does not appear in this case. Interestingly, the addition of the topological term (Chern-Simons) to Born-Infeld Electrodynamics yields the appearance of the magnetostatic field. We also contemplate the fields associated to the would-be-magnetic monopole in three dimensions. © 2011 Springer Science+Business Media, LLC.

Pereira M.H.,Centro Tecnologico do Exercito CTEX | De Castro L.D.,Centro Tecnologico do Exercito CTEX | Michel R.,Federal University of Rio de Janeiro
Chemistry and Chemical Technology | Year: 2013

Mass spectrometry was used to characterize isotropic and anisotropic pitches as well as the parent heavy petroleum oil in order to investigate the molecular mass distributions (MMD) and changes during the heat treatment process. Sample preparation and matrix choice have a strong influence on MMD and results confirmed the oligomeric nature and the increasing molecular sizes as heat treatment proceeds. © Pereira M.-H., de Castro L., Michel R., 2013.

Teixeira Dornelles L.,Military Institute of Engineering of Rio de Janeiro | Bruno De Sa L.,Centro Tecnologico Do Exercito CTEx | Carneiro De Mesquita Filho A.,Federal University of Rio de Janeiro
IEEE Latin America Transactions | Year: 2016

This paper presents a new methodology for synthesis of broadband matching networks based on Clonal Selection Algorithms (CSA). This metaheuristic uses the hypermutation as only variation operator resulting in a gradual evolving of the network topology. A closed form expression for the transducer power gain (TPG) sensitivity with respect to the component values is employed, in such a way that the effects of the components tolerance on the matching network performance can easily be quantified. The evolvable function proposed is single-objective and eliminates the difficult task of assigning appropriate weights to parameters. The evaluation of the TPG sensitivity enables the designer to identify and remove irrelevant components of the circuit, simplifying it. The efficiency of the methodology is tested in two cases found in the literature: the traditional project of impedance matching for a simple RLC load proposed by Fano [1]; and a real synthesis of impedance matching network for a monopole whip antenna, proposed in [2]. The results are compared with other existing methods. © 2016 IEEE.

Furtado Filho A.A.M.,Centro Tecnologico Do Exercito CTEx | Gomes A.S.,Federal University of Rio de Janeiro
International Journal of Hydrogen Energy | Year: 2012

Composite sulfonated bisphenol-A-polysulfone (SPSF) based PEMs, containing tungstophosphoric acid (TPA) and modified by electron beam (EB) irradiation with doses of 50 and 100 kGy, were prepared and characterized by a number of physico-chemical methods. The probability of the cross-linking was increased by post treatment of the irradiated membranes at 180 °C for 8 h into a vacuum oven. The cross-linking strongly affected membrane properties, reducing their swelling, but at the same time decreasing their proton conductivity. The proton conductivity of the membranes was measured by a two electrode ac impedance technique using a frequency response analyzer. The PEMs performance was tested in H 2/O 2 fuel cell (FC) and found to approach that of Nafion ® 117 commercial PEM at the same conditions. The PEMs composite stability was adequate at least for 2 days, during which no degradation of the performance was observed. © 2011, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights.

Henrique Costa Dias M.,Military Institute of Engineering of Rio de Janeiro | Carlos Araujo Dos Santos J.,Military Institute of Engineering of Rio de Janeiro | De Magalhaes Ottoni Da Silva G.,Centro Tecnologico Do Exercito CTEx
IEEE Latin America Transactions | Year: 2011

This work addresses the main features of a coverage planning algorithm for VHF/UHF low power radio communications systems operating at urban sites, in which special attention was given to mixed terrain clutter transitions. Most of the available commercial prediction tools adopt rough solutions to some problems derived from the use of semi-empirical models with geographical databases. The influence of mixed-path terrains and the path loss due to dense vegetation are typical related examples of usually overlooked aspects. The developed code is based on Hatas semi-empirical approach with additional point-to-point adjusts, and includes specific procedures for those two aspects. It has been developed as Matlab routines, which were evaluated comparing its outputs to the ones obtained from the use of a commercial planning tool. Results were coherent with the specific features of the site chosen for the analysis. © 2011 IEEE.

Cardoso M.H.W.M.,Instituto Nacional Of Controle Of Qualidade Em Saude | de Nobrega A.W.,Instituto Nacional Of Controle Of Qualidade Em Saude | Vital H.C.,Centro Tecnologico do Exercito CTEx | Abrantes S.M.P.,Instituto Nacional Of Controle Of Qualidade Em Saude
Ciencia e Tecnologia de Alimentos | Year: 2010

This research presents the results of stability studies regarding the production of certified reference materials. The residual concentration levels of four pesticides, namely γ-HCH, fenitrothion, chlorpyrifos, and procymidone were investigated. Pasteurization combined with gamma irradiation was used to maintain the integrity of the mixture tested as a reference material candidate. The pulp was prepared and split into two parts. Each part was then spiked with those pesticides in the concentration range of 0.1 to 0.2 in tomato pulp. One of them was submitted to pasteurization at 90 °C for 4 minutes after being homogenized, and the other was irradiated with a gamma dose of 2.0 kGy. The material stability and the corresponding uncertainty during the period of time evaluated were determined using regression analysis and ANOVA. The results indicated that the dose of 2.0 kGy was appropriated for the conservation of tomato pulp spiked with the four aforementioned pesticides.

Vieira F.R.,Centro Tecnologico Do Exercito CTEx | De Castro Dutra C.H.M.,Centro Tecnologico Do Exercito CTEx | De Castro L.D.,Centro Tecnologico Do Exercito CTEx
Fuel | Year: 2011

The anisotropic content of a pitch is one of the most important parameters for characterizing such materials. Polarized light optical microscopy is the technique most commonly employed (ASTM D 4616 standard procedure) to measure this pitch parameter. However, this standard procedure is limited to pitches with mesophase contents only up to 20%. An alternative technique for determining the anisotropic content of a pitch is high-temperature centrifugation, which can be used without limitation for pitches with up to 100% anisotropic content. In this work, the two techniques have been compared; samples of four pitches with mesophase contents lower than 20% have been analyzed by both techniques and the results have been compared. The high-temperature centrifugation technique showed good repeatability, and the results that it yielded matched those obtained from optical microscopy when the anisotropic content of the pitch was higher than around 5%. The centrifugation technique is always faster, simpler, and possibly more accurate than optical microscopy for pitches with mesophase contents higher than 20%. © 2010 Elsevier Ltd. All rights reserved.

Camilo M.,Secao Of Engineering Of Computacao Institute | Moura D.,Centro Tecnologico Do Exercito CTEx | Galdino J.,Centro Tecnologico Do Exercito CTEx | Salles R.M.,Secao Of Engineering Of Computacao Institute
Proceedings - IEEE Military Communications Conference MILCOM | Year: 2012

Cognitive Radio is a technology that enables the spectrum sharing in an opportunistic fashion. However, as the development of cognitive radio technology occurs, its security problems like jamming arise. In this paper, we studied the jamming attack in cognitive radio networks. We sketched a scenario comprised by a primary user, a secondary user, and a spectrum jammer (namely attacker). Since the legitimate secondary user needs to transmit control messages and data in the available channels, we derived the best combinations of the number of control and data channels to the legitimate secondary user in face of different data applications considering the quality of service requirements reliability and throughput. We also considered the device with and without power constraints. © 2012 IEEE.

Aguiar L.A.,NASA | Damaso V.C.,Centro Tecnologico Do Exercito CTEx
WIT Transactions on Ecology and the Environment | Year: 2010

Infiltration of water into a waste disposal facility and into the waste region is the main factor inducing the release of radionuclides from a disposal facility. Since infiltrating water flow is dependent on the natural percolation at the site and the performance of engineered barriers, its prediction requires modelling of unsaturated water flow through intact or partially/completely failed components of engineered barriers. These include the cover systems, concrete vault, backfill, waste forms, and overpacks. This paper aims to carry out a performance study regarding a near surface repository in terms of reliability engineering. It is assumed that surface water infiltrates through the barriers reaching the matrix where radionuclides are contained, thus releasing them into the environment. The repository consists of a set of barriers which are considered saturated porous medium, except geosphere. A genetic algorithm is employed to establish an optimized configuration to the structure of the repository, by determining the thicknesses of barriers and waste packages arrangement, taking into account the engineering and radiological constraints. Such restrictions aim to keep the risks associated with the migration of radionuclides at a low level. © 2010 WIT Press.

Loading Centro Tecnologico Do Exercito CTEx collaborators
Loading Centro Tecnologico Do Exercito CTEx collaborators