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.
Hagander, Per, et al.
(författare)
Models for the Insulin Response to Intravenous Glucose
1978
Ingår i: Mathematical Biosciences. - : Elsevier BV. - 0025-5564. ; 42, s. 15-29
Tidskriftsartikel (refereegranskat) abstract
The Grodsky packet storage model describes many features of insulin release, but at present more or less arbitrary simplifications are necessary. The consequences of various simplifications are discussed, especially with regard to identification of parameters thought to be of importance for glucose tolerance. In particular, the insulin release dynamics of the ordinary intravenous glucose tolerance test is examined. The proposed model contains the following features: It considers arterial rather than venous blood glucose concentration as the stimulus, it takes the glucose injection time into account, and it contains a positive derivative term during the rise of the glucose concentration. When the insulin elimination-rate time constant is fixed to an a priori value, model fitting gives a clear quantification of the sensitivity of early and late insulin release to glucose.
5.
Wannberg, B., et al.
(författare)
Imaging properties of electrostatic energy analyzers with toroidal fields
1976
Ingår i: Journal of Electron Spectroscopy and Related Phenomena. - 0368-2048 .- 1873-2526. ; 9, s. 111-27
Tidskriftsartikel (refereegranskat) abstract
Numerical values of the second-order aberration coefficients are given for two classes of toroidal fields, namely (1) the ‘quasi-spherical’ field with c=1, c’≠-1, and (2) fields with c in the region 1.6-1.8. For the ‘quasi-spherical’ fields, the second-order coefficients are given as functions of the deflection angles ω for 90°⩽ω⩽180°. The third-order coefficient for the spherical field are given in the same region. For the devices in the second class, which have one intermediary axial image, the second-order coefficients are studied as functions of c and ω, subject to the conditions that double-focusing should be obtained. The conditions under which the radial and axial image planes coincide are considered. The influence of axially curved entrance and exit surfaces is investigated. One special case (ω=180°, c=1.691, c’=-1.11), which may be favourable for an electron monochromator is discussed
6.
Ask, Per, et al.
(författare)
Frequency content of esophageal peristaltic pressure.
1979
Ingår i: American Journal of Physiology. - 0002-9513 .- 2163-5773. ; 236:3, s. E296-300
Tidskriftsartikel (refereegranskat) abstract
Fourier analysis of esophageal peristaltic pressure waves was performed by computer fast Fourier transform. The highest power spectral density was obtained in the frequency range below 1 Hz. The Fourier analysis showed spectral components up to about 12 Hz in the upper esophageal sphincter (UES). The significance of different frequency components was investigated by low-pass filtering at different cut-off frequencies. A reduction in the amplitude of UES contractions was obtained at a cut-off frequency of 4 Hz, whereas the cut-off frequency of 8 Hz did not show any distortion. For perfused manometry systems, only a low-compliance perfusion pump will have sufficient bandwidth for accurate recording of esophageal peristaltic pressures.
7.
Ask, Per, et al.
(författare)
Pressure integrating transducer for oesophageal manometry.
1979
Ingår i: Medical and Biological Engineering and Computing. - 0140-0118 .- 1741-0444. ; 17:3, s. 360-364
Tidskriftsartikel (refereegranskat) abstract
A transducer has been designed that gives an integrated measure of the radial pressure profile at a specific level in the oesophagus. The oesophageal pressure is picked up by a semicylinder elastically connected to a transducer housing by means of a slotted semicylinder. The displacement of the semicylinder is sensed by a semiconductor transducer element. The transducer has a linear relation between static pressure and output voltage, flat frequency characteristic and low temperature drift.
8.
9.
Hyyppä, Kalevi
(författare)
Dielectric absorption in memory capacitors
1972
Ingår i: IEEE Transactions on Instrumentation and Measurement. - 0018-9456 .- 1557-9662. ; IM-21:1, s. 53-56
Tidskriftsartikel (refereegranskat) abstract
Experience from experiments with a sample and hold circuit showed that dielectric absorption constitutes a fundamental limitation of the accuracy in analog memories. To gain more insight into the problem several materials commonly used as dielectrics in capacitors have been investigated. The theory of dielectric absorption is discussed. Results from measurements on capacitors with paper, cellulose acetate, parylene, polyester, polycarbonate, and polystyrene dielectrics are reported. The components in Dow's model, which describes the dielectric absorption, are calculated for the polycarbonate dielectric. A compensation circuit is suggested, which considerably reduces the effect of dielectric absorption in analog memories and electronic integrators.
