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Klumpade fotoner för kaotisk LiDAR
No full textThis thesis investigates thermal light sources for application in chaotic LiDAR, focusing on their optimization and the unexpected appearance of a structured interference or beating patternin the second-order coherence measurements. Chaotic LiDAR leverages the photon bunching characteristics of chaotic light to measure distances with high temporal resolution, enabling long-range and avoids ambiguity in range sensing. The first part of the work explores how spectral filtering and light source configuration affect photon correlations. Several filtration schemes at telecom wavelengths (1550 nm) were tested on various light sources, including a sub-threshold continuous-wave laser, halogen light and sunlight. Narrowband filtering using a notch filter combined with an etalon significantly improved the observed photon bunching for classical sources. In the second part, the unexpected beating pattern in g^(2) when using the sub-threshold laser was further studied. The pattern’s visibility and number of periods (oscillations) were found to strongly depend on the laser bias current and its spectral alignment with etalon transmission peaks. The phenomenon was linked to the ratio of spontaneous emission to stimulated emission near the lasing threshold. Attempts were made to model the behavior using a two-mode statistical mixture framework, though no conclusive fit was obtained. The findings suggest complex emission dynamics near the lasing threshold that are not captured by standard models. This work advances the understanding of photon statistics in threshold lasers and informs the design of improved bunched light sources for future chaotic LiDAR systems.Detta examensarbete undersöker termiska ljuskällor för användning i kaotisk LiDAR, med fokus på dess optimering samt det oväntade beteendet av ett strukturerat interferens eller svävningsmönster i andra ordningens koherensmätningar. Kaotisk LiDAR utnyttjar foton bunching (buntning, klumpar) egenskaperna hos kaotiskt ljus för att mäta avstånd med hög tidsupplösning, vilket möjliggör lång räckvidd och undviker tvetydigheter i avståndsbestämning. Den första delen av arbetet undersöker hur spektral filtrering och konfigurationen av ljuskällan påverkar fotonkorrelationer. Flera filtreringsscheman vid telekomvåglängder (1550 nm) testades på olika ljuskällor, inklusive en kontinuerlig laser under lasrandetröskeln samt halogenljus och solljus. Smalbandig filtrering av ett notch-filter kombinerad med en etalon förbättrade den observerade foton bunchingen signifikant för de klassiska ljuskällorna (halogen samt solljus). I den andra delen studerades det oväntade beating mönstret i g^(2) när under tröskelvärde lasern användes. Mönstrets synlighet och antal perioder (oscillationer) visade sig vara starkt beroende av laserns strömnivå och dess spektrala överlapp med etalonens transmissionstoppar. Fenomenet kopplades till förhållandet mellan spontan emission och stimulerad emission nära lasrandetröskeln. Försök gjordes att modellera beteendet med en två-moders statistisk mixmodell, men utan att nå en entydig anpassning. Resultaten tyder på komplexa emissionsdynamik nära lasrandetröskeln som inte fångas av standardmodeller. Arbetet bidrar till en ökad förståelse för fotonstatistiken runt tröskelvärdet av lasrar och vägleder utformningen av förbättrade bunched ljuskällor för framtida kaotiska LiDAR system
Klumpade fotoner för kaotisk LiDAR
No full textThis thesis investigates thermal light sources for application in chaotic LiDAR, focusing on their optimization and the unexpected appearance of a structured interference or beating patternin the second-order coherence measurements. Chaotic LiDAR leverages the photon bunching characteristics of chaotic light to measure distances with high temporal resolution, enabling long-range and avoids ambiguity in range sensing. The first part of the work explores how spectral filtering and light source configuration affect photon correlations. Several filtration schemes at telecom wavelengths (1550 nm) were tested on various light sources, including a sub-threshold continuous-wave laser, halogen light and sunlight. Narrowband filtering using a notch filter combined with an etalon significantly improved the observed photon bunching for classical sources. In the second part, the unexpected beating pattern in g^(2) when using the sub-threshold laser was further studied. The pattern’s visibility and number of periods (oscillations) were found to strongly depend on the laser bias current and its spectral alignment with etalon transmission peaks. The phenomenon was linked to the ratio of spontaneous emission to stimulated emission near the lasing threshold. Attempts were made to model the behavior using a two-mode statistical mixture framework, though no conclusive fit was obtained. The findings suggest complex emission dynamics near the lasing threshold that are not captured by standard models. This work advances the understanding of photon statistics in threshold lasers and informs the design of improved bunched light sources for future chaotic LiDAR systems.Detta examensarbete undersöker termiska ljuskällor för användning i kaotisk LiDAR, med fokus på dess optimering samt det oväntade beteendet av ett strukturerat interferens eller svävningsmönster i andra ordningens koherensmätningar. Kaotisk LiDAR utnyttjar foton bunching (buntning, klumpar) egenskaperna hos kaotiskt ljus för att mäta avstånd med hög tidsupplösning, vilket möjliggör lång räckvidd och undviker tvetydigheter i avståndsbestämning. Den första delen av arbetet undersöker hur spektral filtrering och konfigurationen av ljuskällan påverkar fotonkorrelationer. Flera filtreringsscheman vid telekomvåglängder (1550 nm) testades på olika ljuskällor, inklusive en kontinuerlig laser under lasrandetröskeln samt halogenljus och solljus. Smalbandig filtrering av ett notch-filter kombinerad med en etalon förbättrade den observerade foton bunchingen signifikant för de klassiska ljuskällorna (halogen samt solljus). I den andra delen studerades det oväntade beating mönstret i g^(2) när under tröskelvärde lasern användes. Mönstrets synlighet och antal perioder (oscillationer) visade sig vara starkt beroende av laserns strömnivå och dess spektrala överlapp med etalonens transmissionstoppar. Fenomenet kopplades till förhållandet mellan spontan emission och stimulerad emission nära lasrandetröskeln. Försök gjordes att modellera beteendet med en två-moders statistisk mixmodell, men utan att nå en entydig anpassning. Resultaten tyder på komplexa emissionsdynamik nära lasrandetröskeln som inte fångas av standardmodeller. Arbetet bidrar till en ökad förståelse för fotonstatistiken runt tröskelvärdet av lasrar och vägleder utformningen av förbättrade bunched ljuskällor för framtida kaotiska LiDAR system
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
Modellering av Krypning och Relaxation i Vitongummi
No full textSyftet med arbetet är att undersöka huruvida Vitongummi som tätning för värmepumpar påverkasav relaxation i långa tidslopp, och hur detta påverkar dess funktion. Problemet analyseras genomatt finna matematiska modeller som beskriver materialet och de fenomen som sker i materialet.Dessa modeller verifieras med hjälp av data erhållen från praktiska experiment, och en tidsprognos på gummits livslängd görs sedan med modellerna. Resultatet visar att gummit uppfyller sinfunktion som tätning längre desto mer komprimerat materialet är när det installeras i pumpen,dock krävs en betydande kompression för att få livslängden i årtionden så att tillämpningen äropraktisk i verkligheten
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
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