1.
Ahlström, Per
(författare)
Signalprediktering i vitt gaussiskt brus med hjälp av ett adaptivt signalanpassat filter
1976
Rapport (övrigt vetenskapligt/konstnärligt) abstract
Ett signalanpassat filter har ett impulssvar som är den exiterandesignalens spegelbild . Ett dylikt filter maximerar vid en viss tidpunkt signalbrusförhållandet på utgången.Ett adaptivt transversalfilter styrt av en gradientkännande algoritm, vilken maximerar signalbrusförhållandet på filterutgången, har studerats. Det spegelvända impulssvaret har använts som prediktion av signalen. Denna prediktion har, vid simulering gjord på dator, ej visat sig vara bättre än en klassisk prediktion med en ren summering av brusstörda upplagor av signalen. Inte ens då dylika summerade upplagor av den brusstörda signalenanvänts som insignal till filtret har signalprediktionen via filtrets impulssvar uppvisat ett lägre kvadratiskt medelfel än d en klassiska.
2.
Granlund, Gösta H.
(författare)
A Nonlinear, Image-content Dependent Measure of Image Quality
1977
Rapport (övrigt vetenskapligt/konstnärligt) abstract
In recent years, considerable research effort has been devoted to the development of useful descriptors for image quality. The attempts have been hampered by i n complete understanding of the operation of the human visual system. This has made it difficult to relate physical measures and perceptual traits.A new model for determination of image quality is proposed. Its main feature is that it tries to invoke image content into consideration. The model builds upon a theory of image linearization, which means that the information in an image can well enough be represented using linear segments or structures within local spatial regions and frequency ranges. This implies a l so a suggestion that information in an image has to do with one- dimensional correlations. This gives a possibility to separate image content from noise in images, and measure them both.Also a hypothesis is proposed that the visual system of humans does in fact perform such a linearization.
3.
Rowa, Per, et al.
(författare)
Automated Malaria Parasite Detection
1977
Rapport (övrigt vetenskapligt/konstnärligt) abstract
A system for malaria parasite detection in thin blood-smears is presented. Sample slides prepared with standard methods are accepted. A low-cost TV-camera mounted on an ordinary microscope with a computer controlled stage is used as a picture sensor. Frames, digitized in windows of 64 x 64 pixels are fed into a special purpose picture processor at normal frame rate (25 frames/sec). In the picture processor measurements are made on the images at high speed. The classification problem is split into different levels each having different characteristics such as different sampling density. Four classes, three of which are different types of malaria parasites, are recognized. As a whole the classification is best labelled as a sequential pattern recognition procedure.In its preliminary version the system has been run at a speed comparable to that of a human operator, that is l 500 cells per minute. A test on 80 000 cells gave 25 false negatives out of 283 parasites (9%) and 41 false positives (0.05%).
4.
Kailath, Thomas, et al.
(författare)
A Scattering Theory Framework for Fast Least-Squares Algorithms
1976
Ingår i: Proceedings of the 4th International Symposium on Mulitvariate Analysis. - 9780720405200
Konferensbidrag (refereegranskat) abstract
In scattering theory the Riccati equation arises in a natural family of equations evolving forwards as well as backwards in time. The authors show how this framework allows an interesting derivation of the fast Chandrasekhar-type equations for linear least-squares filtering of processes generated by a time-invariant, finite-dimensional linear system driven by white noise. The processes are not required to be stationary. The same ideas can be used to obtain Levinson- and Cholesky-type differential equations for the impulse responses of the whitening filter and the innovations representation of such processes. The scattering framework brings out clearly both the significance of the time-invariance of the parameters of the underlying finite-dimensional system and of the associated family of nonstationary processes. For stationary processes, it also becomes clear that the assumption of finite-dimensionality is unnecessary, but the proper extension of the nonstationary class of processes raises some interesting questions.
5.
Johansen, H. K., et al.
(författare)
Fast Hankel-Transforms
1979
Ingår i: Geophysical Prospecting. - : Wiley. - 0016-8025 .- 1365-2478. ; 27:4, s. 876-901
Tidskriftsartikel (refereegranskat)
6.
Kornfeldt, Eva, et al.
(författare)
Studium av två endimensionella koder för faksimil överföring
1978
Rapport (övrigt vetenskapligt/konstnärligt) abstract
Två endimensionella koder för faksimil överföring av dokument har studerats, Modified Huffman Code (MHC} och Intermediate Ternary Code (ITC}. Båda koderna är föreslagna till CCITT för standardisering. Vi har beräknat hur bra kompression man får med de båda koderna på CCITT:s 8 testdokument. skillnaderna är inte så stora men MHC har en något bättre kompressionsförmåga.
