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Visar resultat 1 - 5 av 119 avhandlingar som matchar ovanstående sökkriterier.

1. 1. Hybrid fiber preform fabrication using CO laser heating

   Författare :Taras Oriekhov; Michael Fokine; Cruz José; KTH; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; Preform; CO laser; silicon-core fiber; semiconductor-core fiber; specialty fiber; optical fiber.; Optik och fotonik; Optics and Photonics;

   Sammanfattning : This thesis describes the development of a new prototyping technique for specialty optical fibers and covers all the fabrication steps from preform to fiber. The technique allows to produce fibers of a custom core structure and material composition, mainly focusing on semiconductor core fibers. LÄS MER

3. 2. Nonlinear optical techniques for ultrafast laser diagnostics : Development of femtosecond LIF, LIGS, CARS and backward lasing

   Författare :Maria Ruchkina; Förbränningsfysik; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; laser diagnostics; femtosecond laser; nonlinear interactions; ultrafast spectroscopy; multi-photon excitation; laser-induced fluorescence; rotational coherent anti-Stokes Raman spectroscopy; laser-induced grating spectroscopy; lasing; backward lasing technique; Fysicumarkivet A:2021:Ruchkina;

   Sammanfattning : The thesis work concerns development and application of four versatile nonlinear optical techniques, based on exploiting ultrashort laser pulses, for diagnostic purposes in gases and flames. The four techniques, all laser-based, are two-photon laser-induced fluorescence (TPLIF), hybrid femtosecond/nanosecond (fs/ns) rotational coherent anti-Stokes Raman scattering (fs/ns RCARS), fs-laser-induced grating spectroscopy (fs-LIGS), and backward lasing. LÄS MER

4. 3. Ultrafast Probing of CO Reactions on Metal Surfaces : Changes in the molecular orbitals during the catalysis process

   Författare :Jörgen Gladh; Henrik Öström; Nils Mårtensson; Stockholms universitet; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; Hetrogenous catalysis; CO; transition metals; Ultrafast probing; oxidation; desorption; dissociation; kemisk fysik; Chemical Physics;

   Sammanfattning : This thesis presents experimental studies of three different chemical reaction steps relevant for heterogeneous catalysis: dissociation, desorption, and oxidation. CO on single-crystal metal surfaces was chosen as the model systems. LÄS MER

5. 4. Analysis and Monitoring of Laser Welding and Surface Texturing

   Författare :Rickard Olsson; Alexander Kaplan; John Powell; Jan Frostevarg; Michael Zäh; Luleå tekniska universitet; []
   Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; Laser welding; monitoring; Signal processing; laser texturing; texture analysis; Produktionsutveckling; Manufacturing Systems Engineering;

   Sammanfattning : This thesis can be conveniently divided into three sections as follows;Part I. Monitoring of laser welding In laser materials processing there has always been a need for suitable methods to supervise and monitor the processes on-line, to ensure correct production quality or to trigger alarms when failures are detected. LÄS MER

7. 5. Reactivity of Metal Clusters with Diatomic Molecules

   Författare :Lotta Holmgren; Chalmers tekniska högskola; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; Nbn; cluster; reactivity; Rhn; NO; D2; CO; N2; laser vaporization; Wn; Nin; photoionization; time-of-flight mass spectrometer; ionization potential; Cun; O2; Vn;

   Sammanfattning : The reactivity of transition-metal clusters, in the approximate size range 10-60 atoms, with diatomic molecules has been investigated. A pulsed beam of neutral clusters is produced by a laser-vaporization source and passed through a low-pressure reaction cell containing the reactive gas. LÄS MER