5,355 research outputs found
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
Ultra-low feedback fibre end termination geometry for high power fibre source applications
No full textOptical fibre end termination techniques are very important in the development of fibre-based optical communication systems and high-power fibre sources in laser, amplifier and superfluorescent configurations. There are many situations where unwanted optical feedback from a fibre end-facet can be very detrimental to the performance of the fibre source. For example, in laser configurations in which an external cavity is employed to extend the functionality (e.g. for Q-switching, mode-locking or wavelength tuning), then feedback from the fibre end-facet adjacent to the external cavity will compete with the feedback provided by the external cavity itself and hence may impact adversely on the laser output characteristics
Jan Brancewicz : Landscape Constructions
No full textThe author traces the influences on the artist's abstract landscape paintings. Includes biographical notes and an artist's statement
Power scaling of novel fibre sources
No full textThis thesis explores novel fibre-based coherent light source architectures and strategies for scaling output power. The research focuses on fibre-based amplified spontaneous emission (ASE) sources with broadband output in the ~1 µm spectral region and on internally-frequency-doubled fibre lasers emitting in the visible (green) wavelength range. In Part I: Spectrum-controllable fibre-based amplified spontaneous emission sources modelling, development and characterisation of a versatile ASE source based on Yb-doped fibre gain stages, using power-efficient means for spectrum control is presented. Experiments have culminated in a versatile seed source with polarized output and a reasonable degree of spectral control. In its final configuration, the ASE source was capable of producing either a broad spectrum in the 1-1.1 μm band with a full-width at half-maximum of 15-40 nm and output power > 1 W. Alternatively, single/multiple narrow lines with a full-width at half-maximum ranging from several nanometres to < 0.05 nm and output power spectral densities of up to 100 mW/nm could be generated. The output power was temporally stable with fluctuations at the level < 0.3-0.8% of the total output power. Very high spectral stability was obtained, which was limited mostly by the mechanical stability of the external cavity. The output beam was nearly diffraction limited with M2 ~ 1.1. Part II: Efficient intracavity frequency doubling schemes for continuous-wave fibre lasers introduces a novel concept for resonant enhancement of the intracavity power in high power continuous-wave fibre lasers that is suitable for a wide range of applications. Using this concept, efficient frequency doubling in continuous-wave Yb-doped fibre lasers has been demonstrated and techniques for using it in devices based on both robustly single-mode and multi-mode fibres have been developed. Finally, this thesis presents wavelength tuning of continuous-wave Yb-doped fibre lasers over ~19 nm in the green spectral region and scaling the generated second harmonic power up to ~19 W with more than 21% pump to second harmonic conversion efficiency
Author Co-Citation Analysis (ACA): a powerful tool for representing implicit knowledge of scholar knowledge workers
Get PDFIn the last decade, knowledge has emerged as one of the most important and valuable organizational assets. Gradually this importance caused to emergence of new discipline entitled ―knowledge management‖. However one of the major challenges of knowledge management is conversion implicit or tacit knowledge to explicit knowledge. Thus Making knowledge visible so that it can be better accessed, discussed, valued or generally managed is a long-standing objective in knowledge management. Accordingly in this paper author co- citation analysis (ACA) will be proposed as an efficient technique of knowledge visualization in academia (Scholar knowledge workers)
Challenges of temperature-dependent emission spectra measurement of thulium-doped fibers around 2 µm
No full textUnderstanding temperature’s impact on spectroscopic properties in high-power thulium-doped fiber lasers is crucial for accurate numerical modeling. Our study discusses influence of thulium concentration and temperature-induced bend losses on emission spectra measurement
The design and synthesis of selective copper(II) chelators
No full textTitle: Design and synthesis of selective copper(II) chelators Author: Jan Havlík Department: Department of Inorganic Chemistry, Faculty of Science Supervisor: assoc. prof. RNDr. Jan Kotek, Ph.D. Supervisor's e-mail address: [email protected] The aim of this work was to prepare selective copper(II) chelators. Within the frame of this thesis were synthesized 13 compounds, from which 7 are new. All compounds were fully characterized by NMR spectroscopy and mass spectrometry. Copper(II) complex of synthesized ligand 1,11-bis(methylphosphinic acid)cyclam, (1,11-dipin), was studied in thermodynamic and formation/decomplexation studies. For 1,11-dipin-copper(II) complex were determined values of rate constants and activation parameters. Keywords: selective chelator, copper, cyclam derivatives, macrocyclic ligands, methylphosphonate, methylphosphinat
Simulation of tools coating
No full textAutor: Jan Ji'lek Katcdra: Katcdra aplikovanc matemaliky Vedouci bakalafske prace: RNDr. Jan Kara, Ph.D. e-mail vedouciho: Jan.KaratVnn ff.cuni.cz Abstrakl: Je dana povlakovaci komora, ve ktere je rolujiei system rotujicich drzaku, ktcrc drzi rotujici nastroje. Dale jsou v koinofe umisteny clcktrody (z ruznyeh matcrialu), zc kterych se odpafuje material a nanasi sc na nastroje. C'ilem prace je simulovat proccs nanaseni a co ncjvcrohodneji graficky zobrazit nanesenou vrstvu na danych mistceh povlakovanych nastroju v zavislosti na jejich umistcni, umisteni a poctu elektrod, rychlosti otaccni soustavy a umisteni ruznych stinidel. Title: Simulation of tools coating Author: Jan Jilek Department: Department of Applied Mathematics Supervisor: RNDr. Jan Kara, Ph.D. Abstract: In the given coating chamber is a system of rotating holders, which hold rotating tools. The chamber also contains electrode (of various materials), from which the material evaporates and is coating the tools. The goal of the thesis is lo simulate the process of coating and visualize the resulting layer in given places of coated tools depending on their placement, number of electrodes, speed of rotation and placement of various shades. - 4
Simulation of tools coating
Get PDFAutor: Jan Ji'lek Katcdra: Katcdra aplikovanc matemaliky Vedouci bakalafske prace: RNDr. Jan Kara, Ph.D. e-mail vedouciho: Jan.KaratVnn ff.cuni.cz Abstrakl: Je dana povlakovaci komora, ve ktere je rolujiei system rotujicich drzaku, ktcrc drzi rotujici nastroje. Dale jsou v koinofe umisteny clcktrody (z ruznyeh matcrialu), zc kterych se odpafuje material a nanasi sc na nastroje. C'ilem prace je simulovat proccs nanaseni a co ncjvcrohodneji graficky zobrazit nanesenou vrstvu na danych mistceh povlakovanych nastroju v zavislosti na jejich umistcni, umisteni a poctu elektrod, rychlosti otaccni soustavy a umisteni ruznych stinidel. Title: Simulation of tools coating Author: Jan Jilek Department: Department of Applied Mathematics Supervisor: RNDr. Jan Kara, Ph.D. Abstract: In the given coating chamber is a system of rotating holders, which hold rotating tools. The chamber also contains electrode (of various materials), from which the material evaporates and is coating the tools. The goal of the thesis is lo simulate the process of coating and visualize the resulting layer in given places of coated tools depending on their placement, number of electrodes, speed of rotation and placement of various shades. - 4
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