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Time domain ptychographySpangenberg, Dirk-Mathys 04 1900 (has links)
Thesis (PhD)--Stellenbosch University, 2015. / ENGLISH ABSTRACT: In this work we investigate a new method to measure the electric field of ultrafast laser
pulses by extending a known measurement technique, ptychography, in the spatial domain
to the time domain which we call time domain ptychography. The technique requires
the measurement of intensity spectra at different time delays of an unknown temporal
object and a known probe pulse. We show for the first time by measurement and
calculation that this technique can be applied with excellent results to recover both the
amplitude and phase of a temporal object. This technique has several advantages, such
as fast convergence, the resolution is limited by the usable measured spectral bandwidth
and the recovered phase has no sign ambiguity. We then extend the technique to pulse
characterization where the probe is derived form the temporal object by filtering meaning
the probe pulse is also unknown, but the spectrum of the probe pulse must be the same
as the spectrum of the temporal object before filtering. We modify the reconstruction
algorithm, now called ptychographic iterative reconstruction algorithm for time domain
pulses (PIRANA), in order to also reconstruct the probe and we show for the first time
that temporal objects, a.k.a laser pulses, can be reconstructed with this new modality. / AFRIKAANSE OPSOMMING: In hierdie werk het ons ’n nuwe metode ondersoek om die elektriese veld van ’n
ultravinnige laser puls te meet deur ’n bekende meettegniek wat gebruik word in die
ruimtelike gebied, tigografie, aan te pas vir gebruik in die tyd gebied genaamd tyd gebied
tigografie. Die tegniek vereis die meting van ’n reeks intensiteit spektra by verskillende
tyd intervalle van ’n onbekende ‘tyd voorwerp’ en ’n bekende monster puls. Ons wys vir
die eerste keer deur meting en numeriese berekening dat hierdie tegniek toegepas kan
word met uitstekende resultate, om die amplitude en fase van ’n ‘tyd voorwerp’ te meet.
Hierdie tegniek het verskeie voordele, die iteratiewe proses is vinnig, die resolusie van
die tegniek word bepaal deur die spektrale bandwydte gemeet en die fase van die ‘tyd
voorwerp’ word met die korrekte teken gerekonstrueer. Ons het hierdie tegniek uitgebrei
na puls karakterisering waar die monster pulse afgelei word, deur ’n bekende filter te
gebruik, van die onbekende ‘tyd voorwerp’ nl. die inset puls. Ons het die iteratiewe
algoritme wat die ‘tyd voorwerp’ rekonstrueer aangepas om ook die monster puls te vind
en ons wys dat ons hierdie metode suksesvol kan gebruik om laser pulse te karakteriseer
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An electro-optic measurement system for electric fields near RF and microwave radiators and scatterersTait, Jan 12 1900 (has links)
Thesis (MScEng)--University of Stellenbosch, 2000. / ENGLISH ABSTRACT: An electro-optic sensor system was developed which uses the modulated scatterer
technique [1] to measure the fine structure-amplitude and phase-of
electric fields with the minimum of perturbation. The theory for the technique
is discussed in detail, with the Lorentz Reciprocity theorem as foundation.
The system is also treated as a general two port and solved in
terms of the impedances present. This comprises self impedances and mutual
impedances.
The signals scattered by the dipole scatterer are modeled as amplitude modulated
signals and a detailed detection scheme is presented. The detection
of the signals is done by a digital correlation process. This is quite similar to
synchronous detection.
A detailed sensitivity analysis is presented that was used to determine the
quality of the system. This analysis is backed by a practical sensitivity
measurement. A few antennas and scatterers are measured in the X-band
using the system, and results are compared with theory. These systems
include a pyramidal horn, an E-plane sectoral horn and a simple waveguide.
Half plane diffraction by a metal sheet is also presented.
The practical implementation of the theory is emphasized. / AFRIKAANSE OPSOMMING: 'n Elektro-optiese meetsisteem is ontwikkel wat die gemoduleerde strooier
tegniek [11 gebruik om die fyn struktuur-amplitude en fase-van elektriese
velde te meet. Hierdie tegniek versteur die velde minimaal. 'n Volledige
ondersoek word gedoen na die teorie van die stelsel. Die basis van die metode
Ie in die Lorentz Resiprook teorie. Alhoewcl daar gekonsentreer word op
hierdie teorie, is die stelsel ook beskou as 'n tweepoort. Die wedersydse en
ei impedansies van die verskillende komponente word gebruik om die velde
op te los.
Die gestrooide seine, as gevolg van die dipool strooier, word gemodelleer met
b hulp van amplitude modulasie. Die deteksie van hierdie seine word deeglik
bespreek. In plaas van 'n analoogstelsel, word 'n digitale korrellasie proses
gebruik om die velde te meet.
Di sensitiwiteit van die stelsel word geanaliseer. Verder word metings met
di stelsel gen em om die teoretiese analise te staaf. 'n Paar X-band sisteme
word gebruik om metings te neem. Hicrdi metings word ook vergelyk met
teor ti se resultate. Stelsels wat gemeet is sluit die volgencle in: 'n piramidale
horing antenna, 'n E-vlak sektorale horing antenna, 'n X-band golfgeleier en
die diffraksi op die rand van 'n plaat.
Die praktiese implemcntering van die teorie word beklemtoon.
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Intensidades de campos elétricos em centros cirúrgicos: um estudo in situMoura, Marcos Antonio Muniz de 11 December 2007 (has links)
Este trabalho apresenta um estudo de medições de intensidades de campos elétrico em um centro cirúrgico, oriundos de fontes de radiofreqüência comerciais operando na cidade de Curitiba, no Paraná. Com o aumento da telefonia celular e, por conseguinte, de suas torres somando-se às antenas de televisões, rádios, rádios chamadas, redes de dados sem fio, internet por ondas de rádio, microondas, serviço de rádio da polícia, dos bombeiros, de rádio táxi, rádio amador, GPS, etc., o que acaba provocando um tipo de poluição eletromagnética “no ar”. Tal poluição pode trazer problemas tanto para o meio ambiente como para a saúde e, entre as tecnologias, possíveis interferências entre as mesmas podendo, por vezes, levar equipamentos a executarem funções imprevisíveis. Conhecer os valores de intensidade desses campos torna-se relevante, principalmente em um hospital onde vidas humanas podem estar a perigo quando conectadas a equipamentos susceptíveis a falhar em suas funções devido à presença desses campos. Os resultados obtidos neste trabalho são comparados com os recomendados pelas principais agências regulamentadoras. Após definido um hospital com o maior número de antenas em seu contorno, montou-se um setup de ensaios em seu centro cirúrgico, observando as distâncias mínimas possíveis entre paredes, teto, chão, luminária e entre as antenas. O setup encontra-se a 1920 cm na direção frontal e a 900 cm na direção lateral direita, posição essas que serviram como referência para o posicionamento do GPS no terraço para a obtenção das coordenadas geográficas. Os equipamentos utilizados foram: um receptor de sinais seletivos, um notebook com um software utilizado na operação do receptor e na aquisição dos dados, uma antena seletiva e um medidor de campo elétrico isotrópico. Foram selecionados 11 canais de televisões, 16 de rádios FM e 13 estações de rádio base (telefonia celular). Nos resultados das medições seletivas, os valores encontrados de 0,005 V/m comparados com as recomendações mais rigorosas (ONIR/Suíça) que é de 4,0 V/m ficando então os valores medidos 0,13% desse valor. Na faixa especifica da ONIR (900 & 1900), ou seja, GSM, este trabalho encontrou 0,0068 V/m ou 0,14% em relação aos valores preconizados por ela para as exposições ocupacionais e de 0,17% para o público em geral.Em questão dos equipamentos médicos obteve-se 1,75 V/m medido contra 3 V/m da norma NBR/IEC60601-1-2, ou seja, um campo medido de 58,33% menor do valor aconselhado. Este trabalho recomenda principalmente: adotar o Princípio da Precaução, que prevê medidas protetoras antecipadas perante as incertezas e/ou riscos desconhecidos, na operação dos transmissores; exigir que todas as instalações de transmissores tenham EIA/RIMA-EIV e; realizar periodicamente medições no contorno desses transmissores para verificar o incremento dos campos elétricos de outras fontes, que se somaram aos dos mesmos. / The aim of this paper is to present a study of measurement of the intensity of electric fields in a surgery room coming from radio frequency broadcasting sources located in Curitiba, Paraná. This is a result of an increase in cellular telephony and, consequently, of its transmission towers which, along with radio and TV antennas, radio service calls, wireless networks, internet connections by means of radio waves, microwave ovens, police and firefighters radio calls, radio taxi service calls, amateur radio service, GPS, and so on, produce a kind of electromagnetic pollution “in the air”. Such pollution might cause problems for the environment as well as for people’s health and there might even be some interference concerning the technologies themselves, which might cause equipment to perform unpredictable functions. Thus, it is important to become aware of the level of the intensity of these fields, especially concerning hospitals where human lives might be in danger when they depend on equipment that is likely to fail due to the presence of these magnetic fields. The results obtained in our study are compared to those recommended by the main regulating agencies. After selecting a hospital with the greatest number of antennas around, we built an experimental setup inside a surgery room, observing the minimum distance required between the walls, between the ceiling and the floor, light equipment, and among the antennas. The set up was located 1920 cm to the front and 900 cm to the right lateral position, which served as reference for placing the GPS equipment in order to obtain geographical coordinates. The equipment used involved a selective signal receiver, a notebook with a software used to receive signals and collect data, a selective antenna and isotropic electric field measurement equipment. Eleven TV channels, 16 FM radio stations and 13 radio-based stations (cellular telephony stations) have been selected. Concerning selective measurement, the result obtained was 0,005 V/m and, when compared to the most rigorous recommendation (ONIR/Switzerland) which is 4,0 V/m, the result was 0,13% distant from the one suggested. Concerning ONIR specific band (900 & 1900), that is, GSM, our study has found 0,0068 V/m or 0,14% when compared to the results recommended by ONIR for occupational exposure and 0,17% for people’s exposure in general. Concerning medical equipment, our study has found 1,75 V/m, compared to 3 V/m, expected according to NBR/IEC60601-1-2, that is, the measured field was 58,33% lower than the one recommended. Therefore, we recommend that some actions be taken such as: adopting the Precautionary Principle, which proposes anticipated protective measures in relation to uncertainties and/or unknown risks, for using broadcasting equipment; demanding that all broadcasting facilities observe Environmental Impact Assessment Studies/EIRs – Neighboring Community Environmental Impact Studies; and, finally, performing periodical measurement of the surroundings in order to check the increase in magnetic fields from other sources which produce magnetic field pollution.
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Intensidades de campos elétricos em centros cirúrgicos: um estudo in situMoura, Marcos Antonio Muniz de 11 December 2007 (has links)
Este trabalho apresenta um estudo de medições de intensidades de campos elétrico em um centro cirúrgico, oriundos de fontes de radiofreqüência comerciais operando na cidade de Curitiba, no Paraná. Com o aumento da telefonia celular e, por conseguinte, de suas torres somando-se às antenas de televisões, rádios, rádios chamadas, redes de dados sem fio, internet por ondas de rádio, microondas, serviço de rádio da polícia, dos bombeiros, de rádio táxi, rádio amador, GPS, etc., o que acaba provocando um tipo de poluição eletromagnética “no ar”. Tal poluição pode trazer problemas tanto para o meio ambiente como para a saúde e, entre as tecnologias, possíveis interferências entre as mesmas podendo, por vezes, levar equipamentos a executarem funções imprevisíveis. Conhecer os valores de intensidade desses campos torna-se relevante, principalmente em um hospital onde vidas humanas podem estar a perigo quando conectadas a equipamentos susceptíveis a falhar em suas funções devido à presença desses campos. Os resultados obtidos neste trabalho são comparados com os recomendados pelas principais agências regulamentadoras. Após definido um hospital com o maior número de antenas em seu contorno, montou-se um setup de ensaios em seu centro cirúrgico, observando as distâncias mínimas possíveis entre paredes, teto, chão, luminária e entre as antenas. O setup encontra-se a 1920 cm na direção frontal e a 900 cm na direção lateral direita, posição essas que serviram como referência para o posicionamento do GPS no terraço para a obtenção das coordenadas geográficas. Os equipamentos utilizados foram: um receptor de sinais seletivos, um notebook com um software utilizado na operação do receptor e na aquisição dos dados, uma antena seletiva e um medidor de campo elétrico isotrópico. Foram selecionados 11 canais de televisões, 16 de rádios FM e 13 estações de rádio base (telefonia celular). Nos resultados das medições seletivas, os valores encontrados de 0,005 V/m comparados com as recomendações mais rigorosas (ONIR/Suíça) que é de 4,0 V/m ficando então os valores medidos 0,13% desse valor. Na faixa especifica da ONIR (900 & 1900), ou seja, GSM, este trabalho encontrou 0,0068 V/m ou 0,14% em relação aos valores preconizados por ela para as exposições ocupacionais e de 0,17% para o público em geral.Em questão dos equipamentos médicos obteve-se 1,75 V/m medido contra 3 V/m da norma NBR/IEC60601-1-2, ou seja, um campo medido de 58,33% menor do valor aconselhado. Este trabalho recomenda principalmente: adotar o Princípio da Precaução, que prevê medidas protetoras antecipadas perante as incertezas e/ou riscos desconhecidos, na operação dos transmissores; exigir que todas as instalações de transmissores tenham EIA/RIMA-EIV e; realizar periodicamente medições no contorno desses transmissores para verificar o incremento dos campos elétricos de outras fontes, que se somaram aos dos mesmos. / The aim of this paper is to present a study of measurement of the intensity of electric fields in a surgery room coming from radio frequency broadcasting sources located in Curitiba, Paraná. This is a result of an increase in cellular telephony and, consequently, of its transmission towers which, along with radio and TV antennas, radio service calls, wireless networks, internet connections by means of radio waves, microwave ovens, police and firefighters radio calls, radio taxi service calls, amateur radio service, GPS, and so on, produce a kind of electromagnetic pollution “in the air”. Such pollution might cause problems for the environment as well as for people’s health and there might even be some interference concerning the technologies themselves, which might cause equipment to perform unpredictable functions. Thus, it is important to become aware of the level of the intensity of these fields, especially concerning hospitals where human lives might be in danger when they depend on equipment that is likely to fail due to the presence of these magnetic fields. The results obtained in our study are compared to those recommended by the main regulating agencies. After selecting a hospital with the greatest number of antennas around, we built an experimental setup inside a surgery room, observing the minimum distance required between the walls, between the ceiling and the floor, light equipment, and among the antennas. The set up was located 1920 cm to the front and 900 cm to the right lateral position, which served as reference for placing the GPS equipment in order to obtain geographical coordinates. The equipment used involved a selective signal receiver, a notebook with a software used to receive signals and collect data, a selective antenna and isotropic electric field measurement equipment. Eleven TV channels, 16 FM radio stations and 13 radio-based stations (cellular telephony stations) have been selected. Concerning selective measurement, the result obtained was 0,005 V/m and, when compared to the most rigorous recommendation (ONIR/Switzerland) which is 4,0 V/m, the result was 0,13% distant from the one suggested. Concerning ONIR specific band (900 & 1900), that is, GSM, our study has found 0,0068 V/m or 0,14% when compared to the results recommended by ONIR for occupational exposure and 0,17% for people’s exposure in general. Concerning medical equipment, our study has found 1,75 V/m, compared to 3 V/m, expected according to NBR/IEC60601-1-2, that is, the measured field was 58,33% lower than the one recommended. Therefore, we recommend that some actions be taken such as: adopting the Precautionary Principle, which proposes anticipated protective measures in relation to uncertainties and/or unknown risks, for using broadcasting equipment; demanding that all broadcasting facilities observe Environmental Impact Assessment Studies/EIRs – Neighboring Community Environmental Impact Studies; and, finally, performing periodical measurement of the surroundings in order to check the increase in magnetic fields from other sources which produce magnetic field pollution.
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