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- Domaschuk, L., et al.
(författare)
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Creep of frozen sand under isotropic and deviatoric components of stress
- 1985
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Ingår i: Journal of energy resources technology. - : ASME International. - 0195-0738 .- 1528-8994. ; 107:2, s. 199-203
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Tidskriftsartikel (refereegranskat)abstract
- The creep behavior of frozen soil is being studied by examining its response to changes in the mean normal stress and changes in the deviatoric components of stress, using separate tests.^The two response components will then be coupled to provide a model for a general stress state.^The paper contains the results of three triaxial compression creep tests on frozen sand (T=-3 C) in which the samples were subjected to changes in the deviatoric components of stress only. Stepwise stress increases were applied for periods up to 1700 hr during which volumetric and axial strains were measured. The samples underwent attenuating creep when subjected to low stress levels and accelerating creep when subjected to higher stress levels, with no indication of a significantly long period of steady-state creep.The samples underwent volume reduction when the axial strains were attenuating and dilated when the axial strain rates began to accelerate.
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- Granlund, Gösta H., et al.
(författare)
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GOP, A Paradigm in Hierarchical Image Processing
- 1982
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Ingår i: Proceedings of The First IEEE Computer Society International Symposium on Medical Imaging and Image Interpretation, ISMI II'82.
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Konferensbidrag (refereegranskat)
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- Granlund, Gösta H., et al.
(författare)
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Image Enhancement
- 1983
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Ingår i: Fundamentals in Computer Vision. - Cambridge : Cambridge University Press. - 0521250994 ; , s. 57-68
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Bokkapitel (refereegranskat)
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- Knutsson, Hans, et al.
(författare)
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Anisotropic Filtering Controlled by Image Content
- 1981
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Ingår i: Proceedings of the 2nd Scandinavian Conference on Image Analysis. ; , s. 146-151
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Konferensbidrag (refereegranskat)abstract
- The related problems of enhancing and restoring noisy images have received a considerable amount of attention in recent years. Restoration methods have generally been based on minimum mean-squared error operations, such as Wiener filtering or recursive filtering. The rather vague title of enhancement has been given to a wide variety of more or less ad-hoc methods, such as median filtering, which have nonetheless been found useful. In mast cases, however, the aim is the same: an improvement of the subjective quality of the image.
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- Knutsson, Hans, et al.
(författare)
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Anisotropic Non-Stationary Image Estimation and its Applications : Part I. Restoration of Noisy Images
- 1983
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Ingår i: IEEE Transactions on Communications. - 0090-6778 .- 1558-0857. ; COM--31:3, s. 388-397
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Tidskriftsartikel (refereegranskat)abstract
- A new form of image estimator, which takes account of linear features, is derived using a signal equivalent formulation. The estimator is shown to be a nonstationary linear combination of three stationary estimators. The relation of the estimator to human visual physiology is discussed. A method for estimating the nonstationary control information is described and shown to be effective when the estimation is made from noisy data. A suboptimal approach which is computationally less demanding is presented and used in the restoration of a variety of images corrupted by additive white noise. The results show that the method can improve the quality of noisy images even when the signal-to-noise ratio is very low.
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- Knutsson, Hans E., et al.
(författare)
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Ectomography. A New Radiographic Reconstruction Method : I. Theory and Error Estimates
- 1980
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Ingår i: IEEE Transactions on Biomedical Engineering. - 0018-9294 .- 1558-2531. ; BME--27:11, s. 640-645
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Tidskriftsartikel (refereegranskat)abstract
- Radiographic technology has advanced considerably during the last years with the advent of reconstruction techniques allowing visualization of slices through the body. In spite of the advantage of computed tomography compared to conventional radiographic methods, there are still some shortcomings with the method If a different section of the body is desired, another recording has to be made, the width of the dice reconstructed is fixed, and a full 1800 view angle is required.
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- Petersson, Christer U., et al.
(författare)
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Ectomography. A New Radiographic Reconstruction Method : II. Computer Simulated Experiments
- 1980
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Ingår i: IEEE Transactions on Biomedical Engineering. - 0018-9294 .- 1558-2531. ; BME--27:11, s. 649-655
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Tidskriftsartikel (refereegranskat)abstract
- In a special radiographic process, ectomography, an image of a slice is produced by simple summation of a set of specially filtered component images, of which each represents one of at least 60 different projections of the object. After being digitized, they are stored, filtered, and summed in a computer. Images representing any slice of any thickness in the object may be produced from the same set of component images. All details within the slice are pictured correctly while details outside are almost completely eliminated.
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| 29. |
- Stern, J. H., et al.
(författare)
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Divalent Cations Directly Affect the Conductance of Excised Patches of Rod Photoreceptor Membrane.
- 1987
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Ingår i: Science. - : American Association for the Advancement of Science (AAAS). - 0036-8075 .- 1095-9203. ; 236:4809, s. 1674-1678
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Tidskriftsartikel (refereegranskat)abstract
- Phototransduction in rod cells is likely to involve an intracellular messenger system that links the absorption of light by rhodopsin to a change in membrane conductance. The direct effect of guanosine 3',5'-monophosphate (cGMP) on excised patches of rod outer segment membrane strongly supports a role for cGMP as an intracellular messenger in phototransduction. It is reported here that magnesium and calcium directly affect the conductance of excised patches of rod membrane in the absence of cGMP and that magnesium, applied to intact rod cells, blocks a component of the cellular light response. The divalent cation-suppressed conductance in excised patches showed outward rectification and cation-selective permeability resembling those of the light-suppressed conductance measured from the intact rod cell. The divalent cation-suppressed conductance was partly blocked by a concentration of the pharmacological agent L-cis-diltiazem that blocked all of the cGMP-activated conductance. Divalent cations may act, together with cGMP, as an intracellular messenger system that mediates the light response of the rod photoreceptor cell.
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| 30. |
- Wiklund, Johan, et al.
(författare)
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Time Sequence Analysis Using Multi-Resolution Spatio-Temporal Filters
- 1989
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Ingår i: Time-Varying Image Processing and Moving Object Recognition, 2. - Amsterdam : Elsevier Science Publishers. - 0 444 88559 5 ; , s. 258-265
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Konferensbidrag (refereegranskat)abstract
- A methodology for spatio-temporal filtering of image sequences is under development at Computer Vision Laboratory, Linköping University. In later years scale analysis has been found to be a necessary tool in image analysis of stationary images. It is our belief that a combination of spatio-temporal filtering and scale analysis is required to get satisfactory results on image sequences. A growing need and the availability of more powerful computers are the most important reasons for this development. The objectives and proposed methods are discussed in relation to known properties of mammal vision.
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| 31. |
- Wilson, Roland, et al.
(författare)
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Anisotropic Non-Stationary Image Estimation and its Applications : Part II. Predictive Image Coding
- 1983
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Ingår i: IEEE Transactions on Communications. - 0090-6778 .- 1558-0857. ; 31:3, s. 398-406
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Tidskriftsartikel (refereegranskat)abstract
- A new predictive coder, based on an estimation method which adapts to line and edge features in images, is described. Quantization of the prediction error is performed by a two-level adaptive scheme: an adaptive transform coder, and a threshold coding in both transform and spatial domains. Control information, which determines the behavior of the predictor, is quantized using a simple variable rate technique. The results are improved by pre- and post-filtering using a related noncausal form of the estimator. Acceptable images have been produced in this way at bit rates of less than 0.5 bit/pixel.
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