Sustentabilidade e responsabilidade socioambiental: crenças provendo a formação de graduandos em administração

This research aims to focus on the education problem, since its source of development is the Research Base: Teachers Training and Qualification of UFRN. Therefore, we seek guidance in the beliefs in sustainability to propose plausible alternatives to promote the education process of UFRN administration undergraduates in order to meet the demands of a market-oriented society, since the market trend is to evolve from environmental guided activities, and future administrators should be trained to meet those conditions. The need to develop an instrument capable of understanding the beliefs of undergraduates on the sustainability problem becomes the object of analysis. This research aims to develop a normative questionnaire to study administration students beliefs in sustainability. The complexity and sensitivity of this research required the integration of various methodological procedures. These proposals were made as follows: analysis and selection of literature, expert validation procedures and psychometric methods and statistics. As for the literature, types of sustainability were identified and categorized, such as: political, social, economic and environmental sustainability. However, it is understood that the educational type, although included in all of those, needed to be converted into another type to fit the theme, since education is believed to be the best way to raise awareness about sustainability. Thus, it was required the categorization of the types, which was defined using criteria such as: contexts, objectives, goals, pathways and hypotheses. The normative questionnaire was the guiding instrument to investigate the role of administration students, regarding the level of knowledge established and regulated by social educational context, especially by becoming a basic condition for carrying out research on beliefs. The study confirmed that the types of sustainability - political, social, economic, environmental and educational - for having institutionalized literatures as sources, in international and national levels, are representative in the identification of future administrators. Therefore, it is believed that the types of sustainability categorized to provide a characterization of sustainability include the structuring of knowledge for undergraduates. The economic and political types, however, were not as representative with respect to their typicality and polarity indices as the educational, environmental and social ones. Although the beliefs of the undergraduates show how much they share ideas on all types, they present more identification with the educational and environmental types. Finally, it is expected that this instrument be subject to application in similar contexts so that it can ascertain whether such statements are part of the knowledge structure of future administrators from other institutions. Therefore, it is expected this strategy to strengthen the validation of the normative questionnaire

Contribuições para a detecção e identificação de faltas em inversores Multiníveis

This work presents contributions in the detection and identication of faults in multilevel inverters through the study of the converters behavior under these operation conditions. Basically, the approached fault consists of an open-circuit in any switch of a three-level clamped diode inverter. The converter operation is characterized in the pre and post-fault states. A wave form behavior analysis of the pole voltage, phase current and dc-bus current is also done, which highlights characteristics that allow the detection of failure and, even, under favorable conditions, the identication of the faulty device. A compensation strategy of the approached fault (open-switch) is also investigated with the purpose of maintaining the driving system operational when a failure occurs. The proposed topology uses SCRs in parallel with the internal switches of the inverter, which allows, in some occasions, the full utilization of the dc-bus

Extensive Comparisons of Optical Fast-OFDM and Conventional Optical OFDM for Local and Access Networks

A performance comparison between a recently proposed novel technique known as fast orthogonal frequency-division multiplexing (FOFDM) and conventional orthogonal frequency-division multiplexing (OFDM) is undertaken over unamplified, intensity-modulated, and direct-detected directly modulated laser-based optical signals. Key transceiver parameters, such as the maximum achievable transmission capacity and the digital-to-analog/analog-to-digital converter (DAC/ADC) effects are explored thoroughly. It is shown that, similarly to conventional OFDM, the least complex and bandwidth efficient FOFDM can support up to similar to 20 Gb/s over 500 m worst-case multimode fiber (MMF) links having 3 dB effective bandwidths of similar to 200 MHz X km. For compensation of the DAC/ADC roll-off, a power-loading (PL) algorithm is adopted, leading to an FOFDM system improvement of similar to 4 dB. FOFDM and conventional OFDM give similar optimum DAC/ADC parameters over 500 m worst-case MMF, while over 50 km single-mode fiber a maximum deviation of only similar to 1 dB in clipping ratio is observed due to the imperfect chromatic dispersion compensation caused by one-tap equalizers.

Mecanismos da intoxicação do fígado de rato causada pelo gossipol

O fígado desempenha uma função central no metabolismo devido à sua interposição entre o trato digestivo e a circulação geral do organismo. Ele é também o principal órgão envolvido na biotransformação de substâncias exógenas (xenobióticos), com capacidade de converter compostos hidrofóbicos em hidrossolúveis, mais facilmente eliminados pelo organismo. O gossipol é uma substância fenólica tóxica presente na semente de algodão (Gossypium sp). Com o objetivo de estudar os mecanismos envolvidos na hepatotoxicidade do gossipol avaliou-se os seus efeitos no sistema antioxidante do fígado de ratos no que diz respeito ao estresse oxidativo e aspectos histopatológicos. Foram utilizados ratos machos da linhagem Wistar, separados em dois grupos, sendo que um recebeu óleo de canola (veículo, grupo Controle) e o outro recebeu gossipol na dosagem de 40 mg/kg de peso vivo do animal por 15 dias (grupo Tratado). O tratamento com gossipol promoveu alterações na atividade sérica das enzimas marcadoras de dano hepático e um significativo estresse oxidativo caracterizado pela diminuição nos níveis da glutationa reduzida (GSH) e consequente aumento da glutationa oxidada (GSSG), incluindo, ainda, danos à membrana plasmática e de organelas demonstrados pela peroxidação lipídica. O resultado da avaliação histopatológica demonstrou degeneração dos hepatócitos.

Alternative methodologies for the determination of aldehydes by capillary electrophoresis

This paper describes 2 alternative methodologies for the determination of selected aldehydes (formaldehyde, acetaldehyde, propionaldehyde, acrolein, and benzaldehyde) by capillary electrophoresis (CE), the first approach is based on the formation of aldehyde-bisulfite adducts and employs free solution CE with reversed electroosmotic flow and indirect detection, using 10 mmol/L 3,5-dinitrobenzoic acid (pH 4.5) containing 0.2 mmol/L cetyltrimethylammonium bromide as the electrolyte. This novel methodology showed a fairly good sensitivity to concentration, with detection limits with respect to a single aldehyde on the order of 10-40 mu g/L, a reasonable analysis time (separation was achieved in <8 min), and no need for sample manipulation. A second approach was proposed in which 2,4-dinitrophenylhydrazine derivatives of the aldehydes were detected in a micellar electrolyte medium (20 mmol/L berate buffer containing 50 mmol/L sodium dodecyl sulfate and 15 mmol/L beta-cyclodextrin). This latter methodology included a laborious sample preconcentration step and showed much poorer sensitivity (0.5-2 mg/L detection limit, with respect to a single aldehyde), despite the use of sodium chloride to promote sample stacking. Both methodologies proved adequate to evaluate aldehyde levels in vehicular emissions. Samples from the tailpipe exhaust of a passenger car vehicle without a catalytic converter and operated with an ethanol-based fuel were collected and analyzed; the results showed high levels of formaldehyde and acetaldehyde (0.41-6.1 ppm, v/v). The concentrations estimated by the 2 methodologies, which were not in good agreement, suggest the possibility of striking differences in sample collection efficiency, which was not the concern of this work.

Settling analysis of MOS regulated current mirrors applied to micropower D/A converters

This paper provides an insight to the trade-off between settling time and power consumption in regulated current mirrors as building parts in micropower current-switching D/A converters. The regulation-loop frequency characteristic is obtained and difficulties to impose a dominant-pole condition to the resulting 2nd-order system are evaluated. Raising pole frequencies in micropower circuits, while meeting consumption requirements, is basically limited by parasitic capacitances. For such cases, an alternative is to impose a twin-pole condition in which design constraints are somewhat relieved and settling slightly improved. Relationships between pole frequencies, transistor geometry and bias are established and design guidelines for regulated current mirrors founded. By placing loop-transistors in either weak or strong inversion, small (W/L) ratios are allowed and stray capacitances reduced. Simulated waveforms suggest a good agreement with theory. The proposed approach applied to the design of a micropower current-mode D/A converter improves both simulated and experimental settling performance.

Yttrium oxysulfide nanosized spherical particles doped with Yb and Er or Yb and Tm: efficient materials for up-converting phosphor technology field

This work reports on the preparation, structural and luminescent studies of nanosized up-converter phosphors Y2O2S:Yb(4%), Er(0.1%) and Y2O2S:Yb(4%), Tm(0.1%),both from polymeric and basic carbonate precursors. The precursors were submitted to a sulphuration process that was previously developed for oxysulfide preparation from basic carbonate. From XRD data, all phosphors presented the oxysulfide phase and the mean crystallite size estimated from the Scherrer formula in the range of 15-20 nm. Polymeric precursor leads to the smallest crystallite size independent on the doping ion. SEM and TEM results confirmed that basic carbonate leads to spherical particles with narrow size distribution and mean diameter of 150 nm, and polymeric precursor smaller spherical particles with diameter between 20 and 40 nm. Up-conversion studies under 980 nm laser excitation showed that Er-doped phosphors present strong green emission related to H-2(11/2), S-4(3/2) --> I-4(15/2) Er transitions as well as the red ones, F-4(9/2) --> I-4(15/2). Tm-doped samples show strong blue emission assigned to (1)G(4) --> H-3(6) and also the red ones, related to (1)G(4) --> F-3(4). Therefore, the sulphuration method was successfully applied to prepare nanosized and nanostructured blue and green up-converter oxysulfide phosphors starting from basic carbonate and polymeric precursors. (C) 2003 Elsevier B.V. All rights reserved.

Electronic ballast for multiple fluorescent lamp systems

An electronic ballast for multiple tubular fluorescent lamp systems is presented. The proposed structure has a high value for the power factor, a dimming capability, and soft switching of the semiconductor devices operated at high frequencies. A zero-current switching pulse width modulated SEPIC converter is used as the rectifying stage and it is controlled using the instantaneous average input current technique. The inverting stage consists of classical resonant half-bridge converter with series-resonant parallel-loaded filters. The dimming control technique is based on varying the switching frequency and monitoring the phase shift of the current drained by the filters and lamps in order to establish a closed loop control. Experimental results are presented that validate the theoretical analysis.

A 12 kW three-phase low THD rectifier with high-frequency isolation and regulated DC output

A robust 12 kW rectifier with low THD in the line currents, based on an 18-pulse transformer arrangement with reduced kVA capacities followed by a high-frequency isolation stage is presented in this work. Three full-bridge (buck-based) converters are used to allow galvanic isolation and to balance the dc-link currents, without current sensing or current controller. The topology provides a regulated dc output with a very simple and well-known control strategy and natural three-phase power factor correction. The phase-shift PWM technique, with zero-voltage switching is used for the high-frequency dc-dc stage. Analytical results from Fourier analysis of winding currents and the vector diagram of winding voltages are presented. Experimental results from a 12 kW prototype are shown in the paper to verify the efficiency, robustness and simplicity of the command circuitry to the proposed concept.

Performance evaluation of a novel hybrid multipulse rectifier for utility interface of power electronic converters

This paper presents an improved analysis of a novel Programmable Power-factor-corrected-Based Hybrid Multipulse Power Rectifier (PFC-HMPR) for utility interface of power electronic converters. The proposed hybrid multipulse rectifier is composed of an ordinary three-phase six-pulse diode-bridge rectifier (Graetz bridge) with a parallel connection of single-phase switched converters in each three-phase rectifier leg. In this paper, the authors present a complete discussion about the controlled rectifiers' power contribution and also a complete analysis concerning the total harmonic distortion of current that can be achieved when the proposed converter operates as a conventional 12-pulse rectifier. The mathematical analysis presented in this paper corroborate, with detailed equations, the experimental results of two 6-kW prototypes implemented in a laboratory.

Red and blue emissions of europium doped gadolinium silicate from porous silica matrix and hydroxide carbonate with spherical shaped particles

In this work, Eu(III) and Eu(II) doped gadolinium silicates has been obtained as compact tubes starting from spherical gadolinium hydroxide carbonate using the pores of silica matrix as support and its surface as reagent. Eu(III) doped gadolinium silicate with hexagonal phase shows an interesting visible shifted charge transfer band when compared to disilicate with orthorhombic phase that was also obtained. Eu(II) gadolinium silicate has been prepared using CO atmosphere presenting an intense blue emission. The divalent europium system shows a potential application as an UV-blue converter. The samples were characterized by scanning electron microscopy (SEM), X-ray powder diffractometry (XRD) and photoluminescence spectroscopy. (C) 2002 Elsevier B.V. B.V. All rights reserved.

A Family of Autoconnected Transformers for 12-and 18-Pulse Converters-Generalization for Delta and Wye Topologies

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Single-phase high power factor hybrid rectifier suitable for high-power applications

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

MS2SV: Tradução de modelos em Simulink para VHDL-AMS

This paper presents a methodology and a tool for projects involving analogue and digital signals. A sub-systems group was developed to translation a Matlab/Simulink model in the correspondent structural model described in VHDL-AMS. The developed translation tool, named of MS(2)SV, can reads a file containing a Simulink model translating it in the correspondent VHDL-AMS structural code. The tool also creates the directories structure and necessary files to simulate the model translated in System Vision environment. Three models of D/A converters available commercially that use R-2R ladder network were studied. This work considers some of challenges set by the electronic industry for the further development of simulation methodologies and tools in the field of mixed-signal technology. Although the objective of the studies has been the D/A converter, the developed methodology has potentiality to be extended to consider control systems and mechatronic systems.

A unity power factor multiple isolated outputs switching mode power supply using a single switch

The authors present an offline switching power supply with multiple isolated outputs and unity power factor with the use of only one power processing stage, based on the DC-DC SEPIC (single ended primary inductance converter) modulated by variable hysteresis current control. The principle of operation, the theoretical analysis, the design procedure, an example, and simulation results are presented. A laboratory prototype, rated at 160 W, operating at a maximum switching frequency of 100 kHz, with isolated outputs rated at +5 V/15 A -5 V/1 A, +12 V/6 A and -12 V/1 A, has been built given an input power factor near unity.