Darmstadt, Techn. Universiẗat, Diss., 2002.

Tierärztl. Hochsch., Diss., 2004--Hannover.

A typical "white" LED comprises a blue source and one or more phosphors, which down-convert the high energy blue light to longer wavelengths. The resultant "mixture" of wavelengths (predominantly residual blue light from the source and yellow and red from the phosphors) produces white light. Typically, phosphors are coated directly (proximally) onto the blue source. This work differs from the conventional approach by incorporating phosphors in a secondary optic, which is remote from the source. This has the advantages of being able to recover the source LED and to change the output wavelength by stacking optics that contain different levels of different phosphors, or by mixing different phosphors into a single optic. The work has created a range of secondary optics that contain one or more phosphors at relatively low levels of addition (1%-4% by weight) in thermoplastic and thermosetting matrices including polystyrene, poly(methylmethacrylate) and silicone. The phosphors are based on a range of YAGs and nitrides. The secondary optics were manufactured by injection moulding (thermoplastics) or casting (thermosets) and were used singly or in stacked layers to down-convert light from a royal blue (450 nm) LED source to produce a range of "white" light sources. Both injection moulding and casting are relatively inexpensive and commonly encountered processes. The optical performance of these optics was measured by Spectral Power Distribution (SPD), chromaticity, Colour Temperature (CCT) and Colour Rendering Index (CRI). CCT and CRI values ranged from 3000K to 6500K and (80-95) depending on the phosphor composition. Measurements were also carried out on the long-term performance of the secondary optics and these showed little or no change after 24 months continuous and intermittent exposure.

No description available.

No description available.

In this thesis , we used organic phosphors 10-(2-benzothiazolyl) -1,1,7,7-tetramethyl-2,3,6,7-tetrahydro-1H,5H,11Hbenzo[l]-pyrano[6,7,8-ij]inolizin-11- one (C545T) and 10-(2-benzothiazolyl)- 1,3,3,7,7-pentametquhyl-2, 3, 6,7-tetrahydro-1H,5H,11H-benzo[l]-pyrano[6,7,8-ij]-quinolizin-11-one(C-545P) , by mixed method to package for LED. First , we used C545T and C545P with different concentration of Silicone ,to find the best mixed ratios. Organic C545T and C545P were proposed to be the candidate of the green phosphor. The emitting peaks of C545P and C545T were 496 nm and 500 nm measured by photoluminescence, respectively. Organic green phosphors were mixed with silicone with different concentration.The optimal mixed weight ratio of phosphor to silicone were 1:500 and 1:300 for C545P and C545T,respectively. Second, we used InGaN/GaN multi-quantum well(MQW) Blue chip toexcite Organic phosphors were mixed with silicone with different concentration to fabricated device. With an injected current 20 mA ,we obtained the luminous efficiency was 79 lm/W , CIE coordinate at (0.33, 0.60) of packaged device C545T @ 1:500 ,and then the luminous efficiency was 68 lm/W , CIE coordinate at (0.33, 0.60) of package device C545P @1:300.Compared with commercial InGaN green LED , we find mixed organic phosphors packaged devices of luminous flux and luminous efficiency and have improved. The best mixed at 1:500 packaged device of C545T and silicone, and luminous efficiency increase 1/3.

Regensburg, Univ., Diss., 2007

Zugl.: München, Univ., Diss., 2007

Die 31P-MRS wird zur Diagnostik des Energiemetabolismus bei verschiedenen kardialen Erkrankungen eingesetzt. Die vorliegende Arbeit befasst sich mit einer Verbesserung und Vereinfachung der Quantifzierung kardialer Energiemetaboliten mittels der 31P-MRS. Durch Akquisitonsgewichtung kann eine genauere Beurteilung der Konzentrationen von PCr und ATP im gesunden Myokard durch Verbesserung der Effizienz und Sensitivität der 31P-MRS erreicht werden. Die Kontamination des MR-Signals durch die Brustwand wird mittels des CORRECT-SLIM-Algorithmus verringert. Eine Fallstudie am rechten Ventrikel zeigt die starke metabolische Aussagekraft der 31P-MRS vor, während und nach medikamentöser Therapie. Die 31P-MRS unter Verwendung räumlicher Sättigungspulse liefert einen unmittelbaren Einblick in den Energiemetabolismus des menschlichen Herzens mit einer deutlich kürzen Nachbearbeitungszeit. Durch diese Optimierungen ermöglicht die 31P-MRS des menschlichen Herzens eine exakte Beurteilung des Energiemetabolismus im gesunden wie erkrankten Myokard.

The powder phosphor of £]-LiGaO2¡GCe3+ ¡B£]-LiGaO2¡GEu3+ and £^-LiAlO2 were prepared by using the reagents of Ga2O3 (99.999%), Al2O3 (99.99¢H), Li2CO3 (99.999%), CeO2 (99.98%) and Eu2O3 (99.98%). Cerium and europium doped £]-LiGaO2 respectively and europium doped £^-LiAlO2 phosphors were synthesized by the method of high temperature solid-state reaction. The Ga, Al, Li, Ce and Eu reagents were mixed according to the requisite stoichiometric ratios. The mixture was mixed thoroughly and sintered at requisite temperature in a tube furnace in atmosphere for several hours. Then the products were cooled down to room temperature and ground into powder to get the final product. The phase purity and crystallinity of the as-synthesized, cerium and europium doped £]-LiGaO2 phosphors respectively and europium doped £^-LiAlO2 phosphors, were characterized using x-ray powder diffraction. The particle size and the morphology of the samples were analyzed by scanning electron microscopy. Luminescence properties of the £]-LiGaO2 and the £^-LiAlO2 phosphor samples with different cerium doping and europium doping concentrations were studied. The photoluminescence spectra of cerium doped £]-LiGaO2 showed a broad yellow-green light emission range from 450 to 640 nm with the peak at 519 nm. The strongest intensity peak of luminescence was found at 0.5 % cerium doping concentration synthesized at 1000¢J. The photoluminescence spectra of europium doped £]-LiGaO2 and £^-LiAlO2 showed the orange-red light emission range from 588 to 630 nm with the maximum peak at 612 nm. The strongest intensity peaks of luminescence were found respectively at 9 % and 7 % europium doping concentration synthesized at 1000¢J.