Microcontrolled pyro-electric instrument for measuring X-ray intensity in mammography

A novel instrument for measurement of X-ray intensity from mammography consists of a sensitive pyro-electric detector, a high-sensitivity, low-noise current-to-voltage converter, a microcontroller and a digital display. The heart of this device, and what makes it unique is the pyro-electric detector, which measures radiation by converting heat from absorbed incident X-rays into an electric current. This current is then converted to a voltage and digitised. The detector consists of a ferro-electric crystal; two types were tested; lithium tantalate and lithium niobate. X-ray measurement in mammography is challenging because of its relatively low photon energy range, from 11 keV to 15 keV equivalent mean energy, corresponding to a peak tube potential from 22 to 36 kV. Consequently, energy fluence rate or intensity is low compared with that of common diagnostic X-ray. The instrument is capable of measuring intensities as low as 0.25 mWm -2 with precision greater than 99%. Not only was the instrument capable of performing in the clinical environment, with high background electromagnetic interference and vibration, but its performance was not degraded after being subjected to 140 roentgen (3.6 × 10 -2 C kg -2 air) as measured by piezo-electric (d 33) or pyro-electric coefficients. © IFMBE 2005.

Measurement of orthovoltage X-ray intensity with a lithium niobate transducer

A microcontrolled instrument for measuring the energy fluence rate (or intensity) of X-ray pulses in the orthovoltage range of 120 to 300 kV is described. The prototype instrument consists of a pyroelectric sensor, a low-noise highsensitivity current-to-voltage converter, a microcontroller and a digital display. The response of the instrument is nonlinear with the intensity of the radiation. The precision is better than 3%. The equipment is inexpensive, rugged, simple to construct and has good long-term stability. © 2009 Springer-Verlag.

Practical comparisons among electronic energy meters, a precision energy meter and IEEE1459 for reactive energy measurements, under unbalanced and non-sinusoidal conditions

This paper presents a practical experimentation for comparing reactive/non-active energy measures, considering three-phase four-wire non-sinusoidal and unbalanced circuits, involving five different commercial electronic meters. The experimentation set provides separately voltage and current generation, each one with any waveform involving up to fifty-first harmonic components, identically compared with acquisitions obtained from utility. The experimental accuracy is guaranteed by a class A power analyzer, according to IEC61000-4-30 standard. Some current and voltage combination profiles are presented and confronted with two different references of reactive/non-active calculation methodologies; instantaneous power theory and IEEE 1459-2010. The first methodology considers the instantaneous power theory, present into the advanced mathematical internal algorithm from WT3000 power analyzer, and the second methodology, accomplish with IEEE 1459-2010 standard, uses waveform voltage and current acquisition from WT3000 as input data for a virtual meter developed on Mathlab/Simulink software. © 2012 IEEE.

Development of a simplified transmission line model directly in the phase domain

A transmission line digital model is developed direct in the phase and time domains. The successive modal transformations considered in the three-phase representation are simplified and then the proposed model can be easily applied to several operation condition based only on the previous knowing of the line parameters, without a thorough theoretical knowledge of modal analysis. The proposed model is also developed based on lumped elements, providing a complete current and voltage profile at any point of the transmission system. This model makes possible the modeling of non-linear power devices and electromagnetic phenomena along the transmission line using simple electric circuit components, representing a great advantage when compared to several models based on distributed parameters and inverse transforms. In addition, an efficient integration method is proposed to solve the system of differential equations resulted from the line modeling by lumped elements, thereby making possible simulations of transient and steady state using a wide and constant integration step. © 2012 IEEE.

Sistema de extração de potência (power harvesting) usando transdutores piezelétricos

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Metodologias de medição de energia elétrica reativa (varh) e erros de medição em equipamentos eletrônicos de (varh)

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Projeto de uma referência de tensão com baixa susceptibilidade a interferência eletromagnética (EMI)

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Efeitos das distorções harmônicas (tensões e correntes) e desequilíbrios (tensões) em medidores eletrônicos trifásicos de energia elétrica ativa

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Estimação dos parâmetros de linha de transmissão a partir de um segmento de linha discretizado

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Implementação de um sistema detector piroelétrico para medição de intensidade de radiação X na faixa de ortovoltagem

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Análise experimental de erros de medição de energia elétrica ativa em medidores eletromagnéticos tipo indução, sujeitos a distorções harmônicas de correntes e tensões, em sistemas equilibrados e desequilibrados

Pós-graduação em Engenharia Elétrica - FEIS

Análise de controladores eletrônicos em sistemas de distribuição de energia

Pós-graduação em Engenharia Elétrica - FEIS

Dinâmica não-linear de um sistema mono-pendular invertido, excitado por um vibrador eletrodinâmico de potência controlada

Pós-graduação em Engenharia Mecânica - FEB

Análise de viabilidade técnica-econômica para a aplicação de inversores de frequência em sistemas de bombeamento de baixa potência

Pós-graduação em Engenharia Mecânica - FEG

Formação de filmes finos de Al2O3 por anodização e seu uso em dispositivos com filmes de Poli(3-Hexiltiofeno)

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)