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| 24. |
- Brandt, Anders, et al.
(författare)
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Cyclostationary Analysis of Boring Bar Vibrations
- 2004
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Konferensbidrag (refereegranskat)abstract
- Internal turning or boring operation is a common metal working process that is usually associated with vibration problems. The vibration problems in internal turning considerably influence important factors such as surface quality, productivity, production costs, etc. In order to gain further understanding of the dynamic metal cutting process, an important early step is to thoroughly classify the vibrations. Boring bar vibrations have previously been proven to be nonstationary when analyzed with traditional methods. For vibrations originating in a combination of a rotating workpiece and random material inhomogeneities, it can be anticipated that the vibrations have cyclostationary properties. Methods for analysis of cyclostationary signals have rendered an increasing interest in the past decade, especially in the telecommunications field. However, very little has been published on the use of these methods in vibration applications. In this paper we show there is strong statistical evidence of cyclostationary behavior in vibrations on an operating boring bar. Methods for estimating the cyclic autocorrelation function and cyclic spectrum for sampled data are developed and results are compared. Some preliminary results from implementing these methods on operating boring bar vibrations are also presented.
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| 25. |
- Brandt, Christine Lycke, et al.
(författare)
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Cognitive effort and schizophrenia modulate large-scale functional brain connectivity
- 2015
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Ingår i: Schizophrenia Bulletin. - : Oxford University Press. - 0586-7614 .- 1745-1701. ; 41:6, s. 1360-1369
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Tidskriftsartikel (refereegranskat)abstract
- Schizophrenia (SZ) is characterized by cognitive dysfunction and disorganized thought, in addition to hallucinations and delusions, and is regarded a disorder of brain connectivity. Recent efforts have been made to characterize the underlying brain network organization and interactions. However, to which degree connectivity alterations in SZ vary across different levels of cognitive effort is unknown. Utilizing independent component analysis (ICA) and methods for delineating functional connectivity measures from functional magnetic resonance imaging (fMRI) data, we investigated the effects of cognitive effort, SZ and their interactions on between-network functional connectivity during 2 levels of cognitive load in a large and well-characterized sample of SZ patients (n = 99) and healthy individuals (n = 143). Cognitive load influenced a majority of the functional connections, including but not limited to fronto-parietal and default-mode networks, reflecting both decreases and increases in between-network synchronization. Reduced connectivity in SZ was identified in 2 large-scale functional connections across load conditions, with a particular involvement of an insular network. The results document an important role of interactions between insular, default-mode, and visual networks in SZ pathophysiology. The interplay between brain networks was robustly modulated by cognitive effort, but the reduced functional connectivity in SZ, primarily related to an insular network, was independent of cognitive load, indicating a relatively general brain network-level dysfunction.
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| 26. |
- Brandt, Christian, et al.
(författare)
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Role of Chromium and Vanadium in the Atmospheric Oxidation of Sulfur(IV)
- 1998
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Ingår i: Atmospheric Environment. - 1352-2310. ; 32:4, s. 797-800
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Tidskriftsartikel (refereegranskat)abstract
- Oxidation of HSO3- in aqueous solution has been studied in the presence of vanadium(V), chromium(III) and chromium(VI). Based on spectrophotometric kinetics data and product analysis it is concluded that the autoxidation rate of sulfur(IV) in slightly acidic solution is unaffected by the presence of vanadium(V) and chromium(III). Chromate(VI), on the other hand, oxidizes sulfur(IV) in a direct redox process in acidic solution. The overall rate of this reaction decreases with increasing pH and it becomes relatively slow in the atmospherically relevant pH range 4-6. Moreover, chromium(III) dominates strongly over chromium(VI) in the atmospheric aqueous phase. Hence, it is concluded that cations of vanadium vanadium and chromium have no significant influence on the atmospheric aqueous-phase oxidation of sulfur(IV) under most ambient atmospheric conditions. Only in very acidic droplets, direct redox between chromium(VI) and sulfite might be of some importance.
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| 27. |
- Brandt, Christian, et al.
(författare)
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The oxidation of sulfur(IV)-oxo compounds in the presence of transition metal ions
- 1997
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Ingår i: Proc. of the EUROTRAC Symposium 96 - Transport and transformation of pollutants in the troposphere, March 25-26, 1996, Garmisch-Partenkirchen : Volume 1: Clouds, Aerosols, Modelling and Photooxidants, Borrell, P.M., Borrell, P., Kelly, K., Cvitas, T., and Seiler, W., Eds. - Volume 1: Clouds, Aerosols, Modelling and Photooxidants, Borrell, P.M., Borrell, P., Kelly, K., Cvitas, T., and Seiler, W., Eds.. - 1853124958 ; , s. 423-426
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Konferensbidrag (refereegranskat)
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| 28. |
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| 29. |
- Brandt, Einar, et al.
(författare)
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Segmentation of echo cardiographic image sequences using spatio-temporal information
- 1999
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Ingår i: Medical Image Computing and Computer-Assisted Intervention – MICCAI’99. - Berlin : Springer. - 354066503X ; , s. 410-419
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Bokkapitel (refereegranskat)abstract
- This paper describes a new method for improving border detection in image sequences by including both spatial and temporal information. The method is based on three dimensional quadrature filters for estimating local orientation. A simplification that gives a significant reduction in computational demand is also presented. The border detection framework is combined with a segmentation algorithm based on active contours or ’snakes’, implemented using a new optimization relaxation that can be solved to optimality using dynamical programming. The aim of the study was to compare segmentation performance using gradient based border detection and the proposed border detection algorithm using spatio-temporal information. Evaluation is performed both on a phantom and in-vivo data from five echocardiographic short axis image sequences. It could be concluded that when temporal information was included weak and incomplete boundaries could be found where gradient based border detection failed. Otherwise there was no significant difference in performance between the new proposed method and gradient based border detection.
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