| 1. |
- Ahlström, Per
(författare)
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Signalprediktering i vitt gaussiskt brus med hjälp av ett adaptivt signalanpassat filter
- 1976
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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.
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| 2. |
- Ingemarsson, Ingemar
(författare)
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Encryption in Telefax
- 1978
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Our standpoint is that the basic need for information security in TELETEX is provided by the data network used together with the possibility to encrypt the messages in the terminals, thereby protecting the messages from information loss. Means for detection of information destruction or change and f or verification at unencrypted data may then be provided for by the user of the TELETEX system.
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| 3. |
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| 4. |
- Blom, Rolf, et al.
(författare)
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Data Network Security : Part I Problem Survey and Model
- 1977
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Data encryption and related methods may be used to preserve information security i n a data network. Here information security is defined as the degree to which the destruction, change or loss of information is presented. Information is defined as the content of the message represented by the data. The information in a block of data is unchanged if the intended result of the transmission of the block is obtained. This means for example that the original message reaches the correct destination where it is interpreted as intended. Undisturbed information does not, in general, require un disturbed data.The network is supposed to be a public network, accessed by many different users. We are interested in a well defined group of users who are communicating mainly among themselves. Different groups, however, are also allowed to communicate in a well defined manner. The logical structure of the communication within a group is star-shaped. The information communicated within the groups hall be protected against threats from other users of the network, from illegitimate users (wiretappers etc) and from members in the group. The structure of the threats is described in section 3 of this paper.The network itself and the requirement it imposes are supposed to be unchanged. Encryption and decryption are taking place outside the network. The encrypted data shall comply with the requirements of the network. The communication process in the group consists of time-limited messages which are essentially transmitted from one point to another in the network. This is the basis for the model of the communication which is described in section 4. The model, although simple, enables us to structure the problems in connection with encryption/decryption. This is done in section 5 and 6. The purpose of the paper is to form a basis for synthesis of security measures by means on cryptological methods. The analysis is general enough to be applied to any data network and any type of user group.
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| 5. |
- Ask, Per, et al.
(författare)
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Frequency content of esophageal peristaltic pressure.
- 1979
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Ingår i: American Journal of Physiology. - 0002-9513 .- 2163-5773. ; 236:3, s. E296-300
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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.
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| 6. |
- Ask, Per, et al.
(författare)
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Pressure integrating transducer for oesophageal manometry.
- 1979
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Ingår i: Medical and Biological Engineering and Computing. - 0140-0118 .- 1741-0444. ; 17:3, s. 360-364
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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.
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| 7. |
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| 8. |
- Hyyppä, Kalevi
(författare)
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Dielectric absorption in memory capacitors
- 1972
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Ingår i: IEEE Transactions on Instrumentation and Measurement. - 0018-9456 .- 1557-9662. ; IM-21:1, s. 53-56
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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.
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| 9. |
- Wannberg, B., et al.
(författare)
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Imaging properties of electrostatic energy analyzers with toroidal fields
- 1976
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Ingår i: Journal of Electron Spectroscopy and Related Phenomena. - 0368-2048 .- 1873-2526. ; 9, s. 111-27
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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
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| 10. |
- Börjesson, Per Ola, et al.
(författare)
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Simple approximations of the error function Q(x) for cummunications applications
- 1979
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Ingår i: IEEE Transactions on Communications. - 0090-6778. ; 27:3, s. 639-643
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Tidskriftsartikel (refereegranskat)abstract
- Simple analytical upper bounds, approximations and lower bounds on the error functionQ(x)are presented and analyzed. A class of functions are given, where the choice of two parameters result in good upper bounds, lower bounds and approximations onQ(x). The results are given in formulas, parameter tables and graphs. The approximations are suitable for programmable pocket calculators.
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