Browsing by Author "Özel, T."

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    Dual-color emitting quantum-dot-quantum-well CdSe-ZnS heteronanocrystals hybridized on InGaN/GaN light emitting diodes for high-quality white light generation
    (AIP Publishing LLC, 2008-03) Nizamoglu, S.; Mutlugun, E.; Özel, T.; Demir, Hilmi Volkan
    We report white light generation by hybridizing green-red emitting (CdSeZnS/CdSe (core) shell/ shell quantum-dot-quantum-well heteronanocrystals on blue InGaN/GaN light emitting diodes with the photometric properties of tristimulus coordinates (x, y) =(0.36, 0.30), luminous efficacy of optical radiation LE= 278 lm/W, correlated color temperature CCT= 3929 K, and color-rendering index CRI= 75.1. We present the photometric analysis and the quantum mechanical design of these dual-color emitting heteronanocrystals synthesized to achieve high-quality white light when hybridized on light emitting diodes. Using such multicolor emitting heteronanocrystals facilitates simple device implementation while providing good photometric properties
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    Hard turning with variable micro-geometry PcBN tools
    (Elsevier, 2008) Özel, T.; Karpat, Y.; Srivastava, A.
    This paper presents investigations on hard turning with variable edge design PcBN inserts. Turning of hardened AISI 4340 steel with uniform and variable edge design PcBN inserts is conducted, forces and tool wear are measured. 3D finite element modelling is utilized to predict chip formation, forces, temperatures and tool wear on uniform and variable edge micro-geometry tools. Predicted forces and tool wear contours are compared with experiments. The temperature distributions and tool wear contours demonstrate the advantages of variable edge micro-geometry design.
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    ItemOpen Access
    Process simulations for 3D turning using uniform and variable microgeometry PCBN tools
    (Inderscience Publishers, 2008) Karpat, Y.; Özel, T.
    In this paper, uniform and variable edge microgeometry design inserts are utilised and tested for 3D turning process. In 3D tool engagement with workpiece, thickness of the chip varies from a maximum equal to the feed rate (at primary cutting edge) to a minimum on the tool's corner radius (at trailing cutting edge). The ideal tool edge preparation should posses a variable configuration which has larger edge radius at the primary cutting edge than at the trailing cutting edge. Here the key parameter is the ratio of uncut chip thickness to edge radius. If a proper ratio is chosen for given cutting conditions, a variable cutting edge along the corner radius can be designed or 'engineered'. In this study, Finite Element Modelling (FEM)-based 3D process simulations are utilised to predict forces and temperatures on various uniform and variable edge microgeometry tools. Predicted forces are compared with experiments. The temperature distributions on the tool demonstrate the advantages of variable edge microgeometry design.