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- Axelsson, Jan, et al.
(author)
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Electron Capture Dissociation of Substance-P using a Commercially Available Fourier Transform Ion Cyclotron Resonance Mass Spectrometer
- 1999
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In: Rapid Communications in Mass Spectrometry. - 0951-4198 .- 1097-0231. ; 13:6, s. 474-477
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Journal article (peer-reviewed)abstract
- Electron capture dissociation of the peptide Substance P is reported for the first time, with an unmodified, commercially available Fourier transform ion cyclotron resonance (FTICR) mass spectrometer. The fragmentation pattern is compared with that obtained with collisionally induced dissociation of the ions in the electrospray ion source, and note that electron capture dissociation gives a more easily interpreted spectrum, showing mainly C-fragments. With the exception of the proline residues, which require cleavage of two chemical bonds, we observe all C-fragmental we find the bias voltage of the electron gun not to be very critical.
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- Håkansson, Lars, et al.
(author)
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Adaptiv reglering av verktygsvibrationer i svarvoperationen
- 1998
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Conference paper (peer-reviewed)abstract
- I svarvoperationen är relativ dynamisk rörelse mellan verktyg och arbetsstycke ett vanligt förekommande problem. Rörelsen påverkar bearbetningsresultatet, speciellt arbetsstyckets yta, men även verktygets livslängd påverkas. Arbetsmiljöproblem som buller förekommer också på grund av vibrationer i svarvoperationen. Problemet kan delvis lösas med lämplig konstruktion som ökar styvheten i maskinstrukturen, vilken dock begränsas av den dynamiska styvheten i strukturen hos verktygshållare samt arbetsstycke. Med aktiv reglering av verktygshållarens respons, dvs. aktiv reglering av verktygsvibrationer, kan en ytterligare ökning av den dynamiska styvheten i det skärtekniska systemet erhållas. Regleringen av verktygsvibrationer har utförts med en återkopplad regulator som är baserad på den så kallade "filtered-x LMS"-algoritmen samt aktuatorer baserade på magnetostriktiv teknik. Verktygshållarens respons, verktygsvibrationerna, detekteras med en givare (accelerometer) som är monterad på verktygshållaren. Genom att introducera motvibrationer i verktygshållaren med en sekundär vibrationskälla, aktuator, via regulatorn som matas med de uppmätta vibrationerna, modifieras verktygshållarens respons. Med aktiv reglering av verktygsvibrationer uppmättes en reduktion av vibrationerna med ca 30 dB vid 1.7 kHz. Vidare erhölls en signifikant förbättring av arbetsstyckets yta och en avsevärd reducering av bullernivån erhölls.
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- Håkansson, Lars, et al.
(author)
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Fix-Number Realization of Adaptive Control of Machine-Tool Vibration
- 1998
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Conference paper (peer-reviewed)abstract
- In the turning operation the relative dynamic motion between cutting tool and workpiece, or vibration, is a frequent problem, which affects the result of the machining, and, in particular, the surface finish. Tool life is also influenced by vibration. Severe acoustic noise in the working environment frequently occurs as a result of dynamic motion between the cutting tool and the workpiece. Dynamic motion between cutting tool and workpiece can be reduced substantially by active control of the machine-tool vibration based on the filtered-x LMS-algorithm. However, in the digital implementation of the filtered-x LMS-algorithm both the inputs and the internal algorithmic quantities are limited to a certain precision. The process of machining a workpiece is also likely to introduce large variations in the level of both input and output signals of the digital controller. The tool shank vibrations can generally be described as a superposition of narrow-band random processes at each modal frequency. Both the variation in signal level and the narrow-band character of the vibration are likely to be unfavorable a fix number realization of the filtered-x LMS-algorithm. The potential large dynamic range in the input signal may introduce coefficient bias and stalling of the convergence of the adaptive FIR filter. Furthermore, both the narrow-band character of the vibration and a large dynamic range in the input signal may result in overflow and thereby seriously degrade the performance of the control system. However, by the use of the leaky filtered-x LMS algorithm problems due to the limited numerical precision such as overflow will be reduced to a large extent.
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