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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.
51

Světelný zdroj s nastavitelnou intenzitou osvětlení / A light source with variable intensity

Koždoň, Jakub January 2014 (has links)
This work is focused on description how the light impact human live, description of light sources and finally design and construction of light source with adjustable colour temperature and luminous flux. In introduction is mentioned the process of vision and how the light impact humans. In next part is characterization of currently used light sources, their construction, properties, benefits and drawback with their main parameters. Important part of this chapter is more extensive description of light emitting diodes with their operational parameters. The last two parts is focused on design and measuring the parameters of created light source with adjustable colour temperature and luminous flux and evaluating the results.
52

Možnosti osvětlení vozidel pro zvýšení bezpečnosti silničního provozu / Possibilities of Vehicle Lighting to Increase Road Transport Safety

Balharová, Gabriela January 2012 (has links)
This master’s thesis deals with the possibilities of illumination of motor vehicles. Thesis is divided into two sections, from which the first discusses precisely the possibilities of lighting of motor vehicles at the present time. What are the modern lighting techniques, that can be found on the market and what is their impact on safety enhancement in road traffic. Second section is about the practical measurement of low and high beam afterglow. This measurement is being compared between two types of headlamps, namely halogen headlights and xenon headlights. Part of the measurement is as well measurement of illumination intensity precisely for these headlights. The output of measurement is the creation of own illumination intensity diagrams and afterglow diagrams of particular headlights, in comparison to isolux diagrams provided by the headlights manufacturer. Consequently are solved the issues about utilization of the isolux diagrams in expert praxis.
53

ATRP with a light switch: photoinduced ATRP using a household fluorescent lamp

Zhang, Tao, Chen, Tao, Amin, Ihsan, Jordan, Rainer 06 December 2019 (has links)
Photoinduced atom transfer radical polymerization (ATRP) was achieved using a simple household fluorescent lamp as the light source. In solution, methyl methacrylate could be polymerized to welldefined polymers; the photoinduced ATRP system did only convert monomers during irradiation and was inactive in the dark. In situ monitoring by UV-vis spectroscopy revealed the photoredox cycle between Cuᶦᶦ and Cuᶦ species. The linear development of the polymer number average molar mass with monomer conversion, the low dispersity as well as chain extension experiments showed the controlled nature of the polymerization. Photoinduced ATRP was also used to prepare homo- and block copolymer brushes and patterned brushes on surfaces by photoinduced surface-initiated ATRP (PSI-ATRP).
54

Experimental study of supercontinuum generation in an amplifier based on an Yb3+ doped nonlinear photonic crystal fiber

Baselt, Tobias, Taudt, Christopher, Nelsen, Bryan, Lasagni, Andrés Fabián, Hartmann, Peter 29 August 2019 (has links)
The use of supercontinuum light sources in different optical measurement methods, like microscopy or optical coherence tomography, has increased significantly compared to classical wideband light sources. The development of various optical measurement techniques benefits from the high brightness and bandwidth, as well as the spatial coherence of these sources. For some applications, only a portion of the broad spectral range can be used. Therefore, an increase of the spectral power density in limited spectral regions would provide a clear advantage over spectral filtering. This study describes a method to increase the spectral power density of supercontinuum sources by amplifying the excitation wavelength inside a nonlinear photonic crystal fiber (PCF). An ytterbium doped photonic crystal fiber was manufactured by a nanopowder process (drawn by the company fiberware) and used in a fiber amplifier setup as the nonlinear fiber medium. In order to characterize the fiber’s optimum operational characteristics, group-velocity dispersion (GVD) measurements were performed on the fiber during the amplification process. For this purpose, a notch-pass mirror was used to launch the radiation of a stabilized laser diode at 976 nm into the fiber sample for pumping. The performance of the fiber was compared with a conventional PCF. Finally, the system as a whole was characterized in reference to common solid state-laser-based photonic supercontinuum light sources. An improvement of the power density up to 7.2 times was observed between 1100 nm to 1380 nm wavelengths.
55

All-fiber supercontinuum source with flat, high power spectral density in the range between 1.1 μm to 1.4 μm based on an Yb3+ doped nonlinear photonic crystal fiber

Baselt, Tobias, Taudt, Christopher, Nelsen, Bryan, Lasagni, Andrés Fabián, Hartmann, Peter 30 August 2019 (has links)
Supercontinuum light sources provide a high power spectral density with a high spatial coherence. Coherent octavespanning supercontinuum can be generated in photonic crystal fibers (PCFs) by launching short pulses into the fiber. In the field of optical metrology, these light sources are very interesting. For most applications, only a small part of the entire spectrum can be utilized. In biological tissue scattering, absorption and fluorescence limits the usable spectral range. Therefore, an increase of the spectral power density in limited spectral regions would provide a clear advantage over spectral filtering. This study describes a method to increase the spectral power density of supercontinuum sources by amplifying the excitation wavelength inside a nonlinear photonic crystal fiber (PCF). An all-fiber-based setup enables higher output power and power stability. An ytterbium-doped photonic crystal fiber was manufactured by a nanopowder process (drawn by the fiberware GmbH, Germany) and used in a fiber amplifier setup as the nonlinear fiber medium. In order to characterize the fiber’s optimum operational characteristics, group-velocity dispersion (GVD) measurements were performed. The performance of the fiber-based setup was compared with a free space setup. Finally, the system as a whole was characterized in reference to common solid state-laser-based supercontinuum light sources. An improvement of the power density was observed in the spectral range between 1100 nm to 1400 nm.
56

Light It Up - Designproces af en spisebordslampe

Stigborg, Christina January 2018 (has links)
This thesis studies how to design a light to a target group based on different theories and methods. The aim has been to investigate what factors are needed to design a good lamp based on theories developed by Poul Henningsen. The problem definition for this study is as follows: How can you use the ACD methods and design process to design a dining table lamp based on Poul Henningsen's theories about light?In order to answer the problem definition, a choice was made to work with the theoretical field of User Centered Design. The study is based on empirical evidence of light and methods that will investigate and analyze the specific needs of a target group in regard to a dining table lamp. Using a design process consisting of idea generation, conceptualizing and prototyping, a lamp that meets both the needs of the target group and the requirements of Poul Henningsen has been designed. The result of this was the development of a dining table lamp that has several different adjustment options physically and technically and casts theoretically correct shadows.This study shows how little empiric evidence that currently exist about light and its use. Therefore, there is ample opportunity to do more research on this topic. Additionally, this task opens up the possibility of designing new lamps based on clarified guidelines.
57

Mechanoluminescent and Phosphorescent Paint Systems for Automotive and Naval Applications

Krishnan, Srivatsava 02 September 2015 (has links)
No description available.
58

Inte en glödlampa LED-armatur 35000 timmar till, Not a lightbulb LED luminaire 35000 hours more

Tell, Erik January 2014 (has links)
Uppsatsen behandlar belysningsarmaturer inom LED-segmentet. Uppsatsen behandlar isynnerhet varför ljuskällan i LED-belysningsarmaturer oftast konstrueras så att ljuskällorna inteär utbytbara.Metoder som har använts i förstudien har varit; informationssökning, kvalitativa intervjuer,teknisk LED-modulsinventering samt konstruktionsundersökningar. Metoder som använts iproduktutvecklingsfasen har varit; tekniska informationsstudier, Idéinventering genom visuellidégenerering, imageboards och skissprocess (att tänka med en penna).Syftet med projektet har varit att utveckla en LED-armatur med utbytbar ljuskälla. Projektetsresultat blev en LED-golvarmatur med utbytbar ljuskälla. Ljuskällan som används i armaturenär enligt den unga branschfrivilliga standarden för LED-moduler, Zhaga. / The essay deals with luminaries in the LED segment. The essay deals in particular with why thelight sources in LED lighting fixtures usually is designed so that the light sources are notreplaceble.Methods used in this work has been; information searching, qualitative interviews, technicalLED module inventory and construction surveys. Methods used in the product developmentphase have been; technical information studies, Idea inventory by visual idea generation, imageboards and sketching process (thinking with a pen).The aim of the project was to develop an LED fixture with a replaceable light source. The resultof the project became an LED floor fixture with replaceable light source. The light source usedin the luminarie is of the young voluntary industry standard for LED modules, Zhaga.
59

Calculation of coupled bunch effects in the synchrotron light source BESSY VSR

Ruprecht, Martin 29 February 2016 (has links)
Im Rahmen dieser Dissertation wird die Stärke der Multibunch-Instabilität (MBI), die von longitudinalen Dipol-, transversalen Dipol- und Quadrupolschwingungsmoden höherer Ordnung getrieben werden mithilfe von analytischen Rechnungen und Trackingsimulationen in dem Ausbauprojekt BESSY Variable Pulse Length Storage Ring (BESSY VSR) des Helmholtz-Zentrum Berlin für Materialien und Energie GmbH (HZB) untersucht und mit dem vorhanden aktiven Dämpfungssystem verglichen. Algorithmen für Trackingsimulationen werden hergeleitet und eine halbempirische Formel zur Abschätzung der transversalen quadrupolaren MBI wird präsentiert. MBI Studien bilden einen wesentlichen Teil der Beurteilung der BESSY VSR Hohlraumresonatoren und begleiteten und beeinflussten ihren Entwicklungsprozess. Mit Berechnungen auf Grundlage des neusten BESSY VSR Hohlraumresonatormodels kann Strahlstabilität als wahrscheinlich und unabhängig vom Füllmuster angesehen werden. Des weiteren wurden Messungen der MBI an BESSY II und der Metrology Light Source (MLS) der Physikalisch-Technischen Bundesanstalt durchgeführt, bei welcher die longitudinale langreichende Impedanz charakterisiert wurde. Transiente Strahllast wird in dieser Arbeit mit analytischen Formeln und neuen, experimentell überprüften Trackingsimulationen berechnet. Für das Standardfüllmuster von BESSY VSR wurde gezeigt, dass die besondere Konfiguration der Hohlraumresonatorfrequenzen zu einer relativ starken Beeinflussung der langen Elektronenpakete führt. Diese verkürzt das Elektronenpaket und vergrößert die Touschekverluste. / In the scope of this thesis, the strength of coupled bunch instabilities (CBIs) driven by longitudinal monopole higher order modes (HOMs) and transverse dipole and quadrupole HOMs is evaluated for the upgrade project BESSY Variable Pulse Length Storage Ring (BESSY VSR) at Helmholtz-Zentrum Berlin für Materialien und Energie GmbH (HZB), based on analytic calculations and tracking simulations, and compared to the performance of an active bunch-by-bunch feedback (BBFB). Algorithms for tracking codes are derived, and a semi-empirical formula for the estimation of transverse quadrupole CBIs is presented. CBI studies are an integral part of the benchmarking of the cavity models for BESSY VSR and have been accompanying and influencing their entire design process. Based on the BESSY VSR cavity model with highly advanced HOM damping, beam stability is likely to be reached with a BBFB system, independent of the bunch fill pattern. Additionally, measurements of CBIs have been performed at BESSY II and the Metrology Light Source of the Physikalisch-Technische Bundesanstalt (MLS), where the longitudinal long range impedance was characterized. Transient beam loading is evaluated by means of analytic formulas and new experimentally verified tracking codes. For the baseline bunch fill pattern of BESSY VSR, it is shown that the particular setup of cavity frequencies amplifies the transient effect on the long bunch, limiting its elongation and potentially resulting in increased Touschek losses.
60

Analysis of injection and recovery schemes for ERL based light source

Petenev, Yuriy 02 July 2014 (has links)
Helmholtz Zentrum Berlin (HZB) baut seit 2011 eine Testanlage Energy Recovery Linac (ERL) Project – BERLinPro. Das Ziel dieses Projektes ist den hohen Strom und hohe Brillanz von dem Elektronenstrahl in einem ERL zu demonstrieren. Die angestrebten Strahlparameter sind vergleichbar mit den Parametern von e.g. zukünftigen ERL-basierten Lichtquellen. Eine von solchen Anlagen ist Femto-Science Factory (FSF), die am HZB konzipiert wurde. FSF ist eine Lichtquelle in Röntgenbereich auf Basis von einem mehrumläufigen ERL mit zweistüfiger Injektion und Energie von einigen GeV. Die Quelle soll Diffraktionslimitiert sein und kurze (Femtosekundenbereich) Lichtpulse erzeugen. Die durchschnittliche und spitzen- Brillanz soll mindesten eine Größenordnung höher liegen als die Brillanz der modernen Speicherring-basierten Lichtquellen. Ein Überblick von BERLinPro und FSF ist gegeben. Eine potentielle Schwäche von ERL besteht in Strahlinstabilitäten, insbesondere regenerative Beam Break Up (BBU). Die Instabilität kann den erreichbaren durchschnittlichen Strom in einem ERL begrenzen. Der Grenzstrom von der BBU für BERLinPro ist berechnet in der Dissertation. Vergleich von zwei Linacs mit zwei verschiedenen supraleitenden Kavitätendesigns ist vorgestellt. Drei Methoden für Strahlstabilisierung (Einfluss von Strahlrotation mit einem Soleniod, Pseudoreflektor, und Tripleten von Quadrupolen in dem Linac auf den Grenzstrom) sind untersucht. Analytische Lösungen für die Twiss-Parameter wurden gefunden für die beste Linacoptik mit und ohne zusätzliche optische Elemente. Zukünftige große ERLs können unterschiedliche Beschleunigungsschemen benutzen. Diese Dissertation vergleicht drei Schemas: unmittelbare Injektion in einen 6 GeV Linac; zweistufige Injektion in einen 6 GeV Linac; und zweistufige Injektion in einen mehrumläufigen Beschleuniger mit geteiltem Hauptlinac in zwei 1 GeV Linacs. Der Basis für den Vergleich ist die Vollkostenanalyse sowie erreichbarer Grenzstrom von den Instabilitäten. / In January 2011 Helmholtz-Zentrum Berlin officially started the realization of the Berlin Energy Recovery Linac (ERL) Project – BERLinPro. The goal of this compact ERL is to develop the accelerator physics and technology required to accelerate a high-current (100 mA) low emittance beam. The parameters are desired for future large scale facilities based on ERLs, e.g. ERL-based synchrotron light sources. One of such large scale facilities is in the design phase at Helmholtz-Zentrum Berlin. This facility is called Femto-Science Factory (FSF). It is a GeV-scale multi-turn ERL-based light source. This light source will operate in the diffraction limited regime for X-rays and offer a short length of a light pulse in the femtosecond region. The average and peak brightness will be at least an order of magnitude higher than achievable from storage rings. In this work an overview of these two projects is given. One potential weakness of the Energy Recovery Linacs is a regenerative form of BBU – transverse beam break up instability. This instability can limit a beam current. In this work the threshold current of the BBU instability was calculated for BERLinPro. The comparison of two linacs based on different types of superconducting cavities is made. Different methods of BBU suppression are investigated (e.g. the influence of solenoid, pseudo-reflector and quadruple triplets in the linac structure on the BBU threshold). Analytic solutions of the Twiss parameters are used to find the best optic in the linac with and without external focusing are presented. Large scale ERL facilities can be realized on different schemes of beam acceleration. This dissertation compares a direct injection scheme with acceleration in a 6 GeV linac, a two-stage injection with acceleration in a 6 GeV linac and a multi-turn (3-turn) scheme with a two-stage injection and two main 1 GeV linacs. The key points of the comparison were total costs and BBU instability. Linac optic solutions are presented.

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