We milled a sub-wavelength diffraction grating on the facet of a large mode area fiber. The diffraction grating had different reflectivities for TE and TM polarized light. It was tested in a thulium-doped fiber laser where it functioned as a low reflectivity output mirror integrated with an intracavity polarizer. Compared to the laser with a perpendicularly cleaved output fiber, the laser with diffraction grating had a slightly increased threshold power and the same slope efficiency. The beam quality factor M2 was not impaired. Polarization extinction ratios of about 20 dB that were observed at low laser powers dropped to 10 dB at high powers.
Numerical investigation shows that an optimised leaky-mode resonant diffraction gratings fabricated in Ta 2 O 5 layer deposited on the facet of an optical fibre can have a modal reflectance peak of more than 95%, 3 dB spectral bandwidth of about 50 nm and polarization extinction ratio of almost 18 dB. The grating is intended to be employed as a high-reflectance, wavelength-and polarization-dependent mirror in a fibre laser. We compare results of 2D and 3D modelling, investigate influence of grating parameters on spectral shape of modal reflectance and discuss fabrication tolerances.
There is a significant number of railway networks within many Middle-and East-European countries operated only by regional lines, usually with a great difference between travel demand and transportation offer. This difference is reflected in the whole economic balance of the lines of the service there, resulting as an essential input for the assessment of rail system efficiency. This paper is the conclusion of the Czech Technical University in Prague (CTU), Faculty of Transportation Sciences research and development project (further as the Project), which aims to analyse the current status and potential of the regional railway network in the country. The paper presents the characteristics of that segment of Czech railway network from the perspective of all scopes evaluated within the Project. A general multi-branch categorization of regional lines is proposed, arising from their technical and economical parameters, and potential for travelling. BEWERTUNG DES POTENZIALS DER EISENBAHNSTRECKEN VON REGIONALER BEDEUTUNG Annotation. Das Eisenbahnnetz der Länder vor allem im Mittel-und Osteuropa weist einen großen Anteil der Eisenbahnstrecken auf, die nur der Verkehrsbedienung von dem lokalen Charakter mit einem oft abgründigen Unterschied zwischen der Beförderungsnachfrage und dem Verkehrsangebot dienen. Dieser Unterschied beeinflusst das Wirtschaftsresultat dieser Strecken, resp. des auf ihnen betriebenen Verkehrs, und stellt somit eine wesentliche Eingabe für die Bewertung der Effektivität des ganzen Eisenbahnsystems dar. Der Artikel ist eine Zusammenfassung eines Forschungsvorhabens, das an der Verkehrsfakultät der CVUT in Prag ausgeführt wurde und das sich als Ziel setzte, den bestehenden Zustand und das Potenzial des Eisenbahnnetzes von regionaler Bedeutung auf dem Gebiet der Tschechischen Republik allseitig zu analysieren. Der Artikel beschreibt die für die Analyse der wirtschaftlichen Bilanz und für die Analyse des Beförderungspotenzials benutzten Methoden und die Multikriterienbewertung der technischen Parameter der besagten Strecken. Weiter legt der Artikel die Charakteristiken des erwähnten Segments des tschechischen Eisenbahnnetzes in allen geforschten Bereichen vor. In seinem Schlussteil schlägt der Artikel eine gesamte Kategorisierung eines Streckenabschnittes von regionaler Bedeutung in Gruppen laut seinen technisch-ökonomischen Parametern und seinem Potenzial der Beförderungsnachfrage vor.
Type A aortic dissection involves the separation of the wall of the ascending aorta into a true lumen and a false lumen. The finding of an aortic dissection in a patient experiencing mild to moderate symptoms for several weeks may be surprising for clinicians, given the severity of the underlying process. Here, we present an 88-year-old patient who was admitted to our hospital due to orthopnea and leg swelling for the past two to three weeks and was found to have a chronic dissection of the ascending aorta, complicated by hemopericardium and tamponade. The existing literature very rarely reports chronic type A aortic dissection with tamponade on presentation.
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