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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Vibration sensors utilizing fiber fabry-perot interferometers and permanent magnets

Conkey, Andrew P. 15 May 2009 (has links)
A unique set of vibration sensors was designed that incorporate the fiber Fabry-Perot interferometer (FFPI) and permanent magnets. Feasibility of the design and its advantages over traditional sensors were verified by experiments. The new sensors consist of one that monitors the motion of a body across an air gap with the other designed to respond to the motion while in contact with the vibrating body. The FFPI is the device used to transmit the vibrational response while permanent magnets are used to transfer the vibratory motion to the FFPI. In the non-contacting sensor, a permanent magnet was used as the motive to transfer the vibratory motion to be registered at the FFPI. Although the magnet resulted in a non-linear response, the effect of the non-linearity can be removed by signal processing. The fiber optic gap sensor (FOGS) developed has a sensitivity of 250 mV/mil for a 30 mil gap to 50 mV/mil for a 65 mil gap and a dynamic range up to 820 Hz. An advantage of the FOGS over traditional eddy current based gap sensors (ECP), for measuring rotor vibration, was demonstrated with a test rotor face that had brass strips attached to it. The FOGS response was not affected by the strips whereas the response of the traditional ECP was greatly affected by the strips. This demonstrated the potential of the FOGS for measuring the motion of a coated shaft. The fiber optic vibration sensor (FOVS) had a marginal response as its construction led to spurious signals. The feasibility of it to act as a vibration sensor, however, was demonstrated. Due to problems in maintaining the proper gap between the proof mass and sensor head during assembly the natural frequency of the FOVS was around 31 Hz and not the targeted 10 Hz. The sensors presented were meant to be a first generation. However, access to additional FFPI elements was restricted limiting further development. Improvements to the sensors would be to modify the sensing head, magnet size, and the embedment of the FFPI as well as to employ tighter machining precision and assembly practices.
2

Vibration sensors utilizing fiber fabry-perot interferometers and permanent magnets

Conkey, Andrew P. 15 May 2009 (has links)
A unique set of vibration sensors was designed that incorporate the fiber Fabry-Perot interferometer (FFPI) and permanent magnets. Feasibility of the design and its advantages over traditional sensors were verified by experiments. The new sensors consist of one that monitors the motion of a body across an air gap with the other designed to respond to the motion while in contact with the vibrating body. The FFPI is the device used to transmit the vibrational response while permanent magnets are used to transfer the vibratory motion to the FFPI. In the non-contacting sensor, a permanent magnet was used as the motive to transfer the vibratory motion to be registered at the FFPI. Although the magnet resulted in a non-linear response, the effect of the non-linearity can be removed by signal processing. The fiber optic gap sensor (FOGS) developed has a sensitivity of 250 mV/mil for a 30 mil gap to 50 mV/mil for a 65 mil gap and a dynamic range up to 820 Hz. An advantage of the FOGS over traditional eddy current based gap sensors (ECP), for measuring rotor vibration, was demonstrated with a test rotor face that had brass strips attached to it. The FOGS response was not affected by the strips whereas the response of the traditional ECP was greatly affected by the strips. This demonstrated the potential of the FOGS for measuring the motion of a coated shaft. The fiber optic vibration sensor (FOVS) had a marginal response as its construction led to spurious signals. The feasibility of it to act as a vibration sensor, however, was demonstrated. Due to problems in maintaining the proper gap between the proof mass and sensor head during assembly the natural frequency of the FOVS was around 31 Hz and not the targeted 10 Hz. The sensors presented were meant to be a first generation. However, access to additional FFPI elements was restricted limiting further development. Improvements to the sensors would be to modify the sensing head, magnet size, and the embedment of the FFPI as well as to employ tighter machining precision and assembly practices.
3

Personlighetsdrag som prediktorer för högkänslighet : En enkätundersökning avseende högkänslighet i relation till personlighetsdragen enligt femfaktormodellen / Personality traits as predictors for sensory processing sensitivity : A questionnaire study regarding sensory processing sensitivity and its relation to the personality traits according to the five-factor model

Velander, Ida January 2017 (has links)
The aim of the present study was to investigate how sensory processing sensitivity is related to the personality traits extraversion, agreeableness, emotional stability, conscientiousness and autonomy of the five-factor model. The samples for the study were members of the Association for the Highly Sensitive in Sweden and a Facebook community for highly sensitive individuals. The participants in the present study responded on a web-based questionnaire to participate. To answer the purpose of the study The Highly Sensitive Person scale (HSPS) were used to measure the degree of a person’s sensitivity. The Five Factor Personality Inventory (FFPI) was used to measure the Big Five personality traits. The data were analyzed in the statistics program SPSS with Pearson’s correlations coefficient and a multiple regression analysis. The result of the multiple regression analysis showed that personality traits of neuroticism and agreeableness predicted sensory processing sensitivity. Further on results showed that the personality traits of extraversion, conscientiousness and autonomy not predicted sensory processing sensitivity. The results of the study conclude that participants of the study are much likely to have the personality traits neuroticism and introversion. Furthermore, results indicated that the participants of the study had the personality traits agreeableness, conscientiousness and autonomy. Continued studies with other methodological starting points are needed to achieve greater knowledge about the personality trait sensory processing sensitivity. / Studiens syfte var att undersöka om det fanns en relation mellan högkänslighet och personlighetsdragen extraversion, vänlighet, samvetsgrannhet, öppenhet samt emotionell stabilitet enligt femfaktormodellen. Urvalet bestod av medlemmar från Sveriges Förening för Högkänsliga och en Facebookgrupp som riktar sig till högkänsliga personer. För att besvara frågeställningen användes en webbaserad enkät som mailades ut till medlemmarna i Sveriges Förening för Högkänsliga samt publicerades i Facebookgruppen. Beroendevariabeln högkänslighet mättes med mätinstrumentet The Highly Sensitive Person Scale (HSPS). Oberoendevariablerna extraversion, vänlighet, samvetsgrannhet, emotionell stabilitet och öppenhet mättes med mätinstrumentet The Five Factor Personality Inventory (FFPI). Dataanalyserna som genomfördes i studien var Pearsons korrelationskoefficient och multipel regressionsanalys. Regressionsanalysen visade att personlighetsdragen emotionell stabilitet och vänlighet var prediktorer för högkänslighet. Personlighetsdragen extraversion, samvetsgrannhet och öppenhet var inte prediktorer för högkänslighet. Resultatet indikerade att studiens deltagare i högre grad hade personlighetsdragen neuroticism och introversion. Vidare visade resultatet att studiens deltagare hade grad av personlighetsdragen samvetsgrannhet, vänlighet och öppenhet. Studien gav en indikation på hur hög grad av högkänslighet var i relation till andra personlighetsdrag. Resultatet kan således öka kunskapen om högkänslighet och vad det medför. Fortsatta studier med andra metodologiska utgångspunkter krävs för att få ökad kunskap om personlighetsdraget högkänslighet.
4

Fiber Fabry-Perot interferometer (FFPI) sensor using vertical cavity surface emitting laser (VCSEL)

Lee, Kyung-Woo 30 October 2006 (has links)
This research represents the first effort to apply vertical cavity surface emitting lasers (VCSELs) to the monitoring of interferometric fiber optic sensors. Modulation of the drive current causes thermal tuning of the laser light frequency. Reflection of this frequency-modulated light from a fiber Fabry-Perot interferometer (FFPI) sensor produces fringe patterns which can be used to measure the optical path difference of the sensor. Spectral characteristics were measured for 850nm VCSELs to determine the combination of dc bias current, modulation current amplitude and modulation frequency for which single mode VCSEL operation and regular fringe patterns are achieved. The response characteristics of FFPI sensors were determined experimentally for square, triangular, saw-tooth waveforms at frequencies from 10kHz to 100kHz. The dependence of VCSEL frequency on the dc bias current was determined from spectral measurements to be ~165GHz/mA. An independent measurement of this quantity based on counting fringes from the FFPI sensor as the laser modulated was in good agreement with this value. The effect of optical feedback into the laser was also studied. By observing the fringe shift as the FFPI sensor was heated, a fractional change in optical length with temperature of 6.95 X 10-6/°C was determined in good agreement with previous measurements on a 1300nm single mode fiber. The performance of 850nm VCSEL/FFPI systems was compared with their counterparts using 1300nm distributed feedback (DFB) lasers. The results of these experiments show that the 850nm VCSEL/FFPI combination gives regular fringe patterns at much lower bias current and modulating current amplitudes than their 1300nm DFB/FFPI counterparts.
5

Fiber Fabry-Perot interferometer (FFPI) sensor using vertical cavity surface emitting laser (VCSEL)

Lee, Kyung-Woo 30 October 2006 (has links)
This research represents the first effort to apply vertical cavity surface emitting lasers (VCSELs) to the monitoring of interferometric fiber optic sensors. Modulation of the drive current causes thermal tuning of the laser light frequency. Reflection of this frequency-modulated light from a fiber Fabry-Perot interferometer (FFPI) sensor produces fringe patterns which can be used to measure the optical path difference of the sensor. Spectral characteristics were measured for 850nm VCSELs to determine the combination of dc bias current, modulation current amplitude and modulation frequency for which single mode VCSEL operation and regular fringe patterns are achieved. The response characteristics of FFPI sensors were determined experimentally for square, triangular, saw-tooth waveforms at frequencies from 10kHz to 100kHz. The dependence of VCSEL frequency on the dc bias current was determined from spectral measurements to be ~165GHz/mA. An independent measurement of this quantity based on counting fringes from the FFPI sensor as the laser modulated was in good agreement with this value. The effect of optical feedback into the laser was also studied. By observing the fringe shift as the FFPI sensor was heated, a fractional change in optical length with temperature of 6.95 X 10-6/°C was determined in good agreement with previous measurements on a 1300nm single mode fiber. The performance of 850nm VCSEL/FFPI systems was compared with their counterparts using 1300nm distributed feedback (DFB) lasers. The results of these experiments show that the 850nm VCSEL/FFPI combination gives regular fringe patterns at much lower bias current and modulating current amplitudes than their 1300nm DFB/FFPI counterparts.

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