| 1. |
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| 2. |
- Adolfsson, Stefan, et al.
(author)
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On-line quality monitoring in short : circuit gas metal arc welding
- 1999
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In: Welding Journal. - New York,N.Y. : American welding society. - 0043-2296. ; 78:2, s. 59S-73S
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Journal article (peer-reviewed)abstract
- This paper addresses the problems involved in the automatic monitoring of the weld quality produced by robotized short-arc welding. A simple statistical change detection algorithm for the weld quality, the repeated Sequential Probability Ratio Test (SPRT), was used. The algorithm may similarly be viewed as a cumulative sum (CUSUM) type test, and is well-suited to detecting sudden minor changes in the monitored test statistic. The test statistic is based on the variance of the weld voltage, wherein it will be shown that the variance decreases when the welding process is not operating under optimal conditions. The performance of the algorithm is assessed through the use of experimental data. The results obtained from the algorithm show that it is possible to detect changes in weld quality automatically and on-line.
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| 3. |
- Andrén, Linus, et al.
(author)
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Active Control of Machine Tool Vibrations in External Turning Operations
- 2003
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In: Proceedings of the Institution of mechanical engineers. Part B, journal of engineering manufacture. - 0954-4054 .- 2041-2975. ; 217:6, s. 869-872
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Journal article (peer-reviewed)abstract
- Vibration and noise in metal cutting are ubiquitous problems in the workshop. The external turning operation is one kind of metal cutting that exhibits vibration related problems. Severe noise is also a problem growing in proportion due to regulations in preventing hearing loss. Active vibration control is a potential solution to such problems. With the piezo ceramic actuator technology of today, the size of the actuator can be kept small and still be able to produce a sufficient amount of force for the anti vibrations. Results from several continuous cutting experiments show a 40 dB reduction of the cutting tool vibration level. The design of the active technique enables this technology to be applicable to a general lathe provided the mounting arrangement is fairly similar.
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| 4. |
- Andrén, Linus, et al.
(author)
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Identification of Dynamic Properties of Boring Bar Vibrations in a Continuous Boring Operation
- 2004
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In: Mechanical systems and signal processing. - : Academic Press. - 0888-3270 .- 1096-1216. ; 18:4, s. 869-901
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Journal article (peer-reviewed)abstract
- Vibrations in internal turning operations are usually a cumbersome part of the manufacturing process. This article focuses on the boring bar vibrations. Boring bar vibrations in alloyed steel, stainless steel and cast iron have been measured in both the cutting speed direction and the cutting depth direction with the aid of accelerometers. The dynamic response of a boring bar seem to be a time varying process that exhibits non-linear behaviour. The process is influenced by non-stationary parameters that are not under the control of the operator or experimenter. The vibrations are clearly dominated by the first resonance frequency in one of the two directions of the boring bar. The problem with force modulation in rotary machinery, which appears as side band terms in the spectrum, is also addressed. Furthermore, the resonance frequencies of the boring bar are correlated to an Euler-Bernoulli beam model.
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| 5. |
- Andrén, Linus, et al.
(author)
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Identification of Motion of Cutting Tool Vibration in a Continuous Boring Operation : Correlation to structural Properties
- 2004
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In: Mechanical systems and signal processing. - : Academic Press, UK. - 0888-3270 .- 1096-1216. ; 18:4, s. 903-27
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Journal article (peer-reviewed)abstract
- The internal turning operation has a history of being a cumbersome metal working process as vibration in boring operations is usually inevitable. In this article, the deflection shapes and/or mode shapes as well as the resonance frequencies of a boring bar have been put under scrutiny. Three methods have been used in order to investigate dynamic properties of a clamped boring bar: a theoretical Euler-Bernoulli beam model, an experimental modal analysis and an operating deflection shape analysis. \\ The results indicate a correlation between the shapes of the deflection shapes and/or mode shapes produced by the three different analysis methods. On the other hand, the orientation of the forced deflection shapes and/or mode shapes and the resonance frequencies demonstrates differences between the three methods. During continuous cutting, it is demonstrated that the bending motion of the first two resonance frequencies is to a large extent in the cutting speed direction.
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| 6. |
- Bartunek, Josef Strom, et al.
(author)
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Adaptive Fingerprint Image Enhancement with Emphasis on Preprocessing of Data
- 2013
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In: IEEE Transactions on Image Processing. - : IEEE. - 1941-0042 .- 1057-7149. ; 22:2, s. 644-656
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Journal article (peer-reviewed)abstract
- This article proposes several improvements to an adaptive fingerprint enhancement method that is based on contextual filtering. The term adaptive implies that parameters of the method are automatically adjusted based on the input fingerprint image. Five processing blocks comprise the adaptive fingerprint enhancement method, where four of these blocks are updated in our proposed system. Hence, the proposed overall system is novel. The four updated processing blocks are; preprocessing, global analysis, local analysis and matched filtering. In the pre-processing and local analysis blocks, a nonlinear dynamic range adjustment method is used. In the global analysis and matched filtering blocks, different forms of order statistical filters are applied. These processing blocks yield an improved and new adaptive fingerprint image processing method. The performance of the updated processing blocks is presented in the evaluation part of this paper. The algorithm is evaluated towards the NIST developed NBIS software for fingerprint recognition on FVC databases.
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| 7. |
- Berggren, Magnus, et al.
(author)
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Low-complexity network echo cancellation approach for systems equipped with external memory
- 2011
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In: IEEE Transactions on Audio, Speech, and Language Processing. - : IEEE. - 1558-7916 .- 1558-7924. ; 19:8, s. 2506-2515
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Journal article (peer-reviewed)abstract
- Long delays and sparseness characterize impulse responses in telecommunication networks and a vast number of solutions for network echo cancellation have been proposed over the years. In this paper, an approach for detecting dispersive regions of a sparse impulse response and a proportionate normalized least mean square (PNLMS)-based selective updating approach are combined with an adaptive double-talk detector to form a complete solution for echo cancellation. The proposed solution has low computational complexity and is targeted for systems equipped with external memory.
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| 8. |
- Borgh, Markus, 1983-, et al.
(author)
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An improved adaptive gain equalizer for noise reduction with low speech distortion
- 2011
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In: EURASIP Journal on Audio, Speech, and Music Processing. - : Springer. - 1687-4714 .- 1687-4722. ; 7
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Journal article (peer-reviewed)abstract
- In high-quality conferencing systems, it is desired to perform noise reduction with as limited speech distortion as possible. Previous work, based on time varying amplification controlled by signal-to-noise ratio estimation in different frequency subbands, has shown promising results in this regard but can suffer from problems in situations with intense continuous speech. Further, the amount of noise reduction cannot exceed a certain level in order to avoid artifacts. This paper establishes the problems and proposes several improvements. The improved algorithm is evaluated with several different noise characteristics, and the results show that the algorithm provides even less speech distortion, better performance in a multi-speaker environment and improved noise suppression when speech is absent compared with previous work.
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| 9. |
- Claesson, Ingvar, et al.
(author)
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A Multi-DSP implementation of a Broadband Adaptive Beamformer for use in a Hands-free Mobile Radio Telephone
- 1991
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In: IEEE Transactions on Vehicular Technology. - New York : Institute of electrical and electronics engineers. - 0018-9545. ; 40:1, s. 194-202
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Journal article (peer-reviewed)abstract
- An implementation of a broadband adaptive array on a multiprocessor digital signal processing (DSP) system for use in a hands-free mobile radio telephone is described. This implementation of a five-microphone adaptive Griffiths-Jim array can handle FIR filters with up to 128 taps behind each microphone at a sampling rate of 8 kHz. The filter structure makes it possible to combine an adaptive array with a noise canceler. The near-field problem has been solved by using focusing, a speech-controlled adaptive algorithm, and a short hourglass. Preliminary measurements indicate a considerable potential for this technique in hands-free mobile telephony. The array gives a 20-30-dB suppression of a broadband jammer covering 300-1100 Hz, even with three reflecting walls surrounding the microphone.
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| 10. |
- Claesson, Ingvar, et al.
(author)
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A Spatial Filtering Approach to Robust Adaptive Beamforming
- 1992
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In: IEEE Transactions on Antennas and Propagation. - New York : Institute of electrical and electronics engineers. - 0018-926X. ; 40:9, s. 1093-1096
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Journal article (peer-reviewed)abstract
- This communication treats the problem of controlling the superresolution in adaptive beamformers. A straightforward method is presented that works for both narrow-band and broad-band arrays. The method is based on forming the blocking matrix in a general sidelobe canceller (GSC) structure using a spatial FIR filter. The suppression of this spatial filter and the implicit noise of the leaky (LMS) algorithm together determine the beamformer.
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