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- Fakultät Medien und Informationswesen (M+I) (bis 21.04.2021) (8) (remove)
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Die wesentlichen Prinzipien und die Zukunft des Internet werden vorgestellt. Neben reinem Faktenwissen werden die Einschätzungen des Autors wiedergeben. An der Wertschöpfungskette wird unter Berücksichtigung der technischen Randbedingungen und der neu geschaffenen Möglichkeiten gezeigt, wie gewinnbringende Anwendungen des Internet entworfen werden können. Die Internet-Technik, die Internet-Organisation, die Internet-Protokollfamilie, die Internet-Dienste und das World Wide Web (WWW) werden ausführlich erörtert. Durch die Einbettung der Dienste in Internet-Anwendungen wie Just-in-time-Informationsbeschaffung, Electronic Commerce oder weltweite Unternehmenskommunikation wird der eigentliche Mehrwert zum Benutzer gebracht. Die Internet-Anwendungen werden unter den drei Aspekten Information, Kommunikation und Transaktion betrachtet. Mit der Anbindung existierender Software-Systeme an das WWW werden neue Möglichkeiten für Internet-Anwendungen aufgezeigt.
Monitoring of the molecular structure of lubricant oil using a FT-Raman spectrometer prototype
(2014)
The determination of the physical state of the lubricant materials in complex mechanical systems is highly critical from different points of view: operative, economical, environmental, etc. Furthermore, there are several parameters that a lubricant oil must meet for a proper performance inside a machine. The monitoring of these lubricants can represent a serious issue depending on the analytical approach applied. The molecular change of aging lubricant oils have been analyzed using an all-standard-components and self-designed FT-Raman spectrometer. This analytical tool allows the direct and clean study of the vibrational changes in the molecular structure of the oils without having direct contact with the samples and without extracting the sample from the machine in operation. The FT-Raman spectrometer prototype used in the analysis of the oil samples consist of a Michelson interferometer and a self-designed photon counter cooled down on a Peltier element arrangement. The light coupling has been accomplished by using a conventional 62.5/125μm multi-mode fiber coupler. The FT-Raman arrangement has been able to extract high resolution and frequency precise Raman spectra, comparable to those obtained with commercial FT-Raman systems, from the lubricant oil samples analyzed. The spectral information has helped to determine certain molecular changes in the initial phases of wearing of the oil samples. The proposed instrument prototype has no additional complex hardware components or costly software modules. The mechanical and thermal irregularities influencing the FT-Raman spectrometer have been removed mathematically by accurately evaluating the optical path difference of the Michelson interferometer. This has been achieved by producing an additional interference pattern signal with a λ= 632.8 nm helium-neon laser, which differs from the conventional zero-crossing sampling (also known as Connes advantage) commonly used by FT-devices. It enables the FT-Raman system to perform reliable and clean spectral measurements from the analyzed oil samples.
The bandwidth behavior of graded-index multimode fibers (GI-MMFs) for different launching conditions is investigated to understand and characterize the effect of differential mode delay. In order to reduce the launch-power distribution the near field of a single-mode fiber is used to produce a controlled restricted launch. The baseband response is measured by observing the broadening of a narrow input pulse (time-domain measurement). The paper verifies the degradation in bandwidth due to profile distortion by scanning the spot of the single-mode fiber with a transversal offset from the center of the test sample. In addition, the impact of the launch-power distribution tuned by different spot-size diameters is demonstrated. Measurements were taken on ‘older’ 50-μm and 62.5-μm GI-MMFs as well as on laser-performance-optimized fibers more recently developed.