| 1. |
- Bengtsson, Lars, 1958-, et al.
(författare)
-
A processor array module for distributed, massively parallel, embedded computing
- 1993
-
Ingår i: Microprocessing and Microprogramming. - Amsterdam : Elsevier. - 0165-6074. ; 38:1-5, s. 529-537
-
Tidskriftsartikel (refereegranskat)abstract
- With the increased degree of miniaturization resulting from the use of modem VLSI technology and the high communication bandwidth available through optical connections, it is now possible to build massively parallel computers based on distributed modules which can be embedded in advanced industrial products. Examples of such future possibilities are ''action-oriented systems'', in which a network of highly parallel modules perform a multitude of tasks related to perception, cognition, and action. The paper discusses questions of architecture on the level of modules and inter-module communication and gives concrete architectural solutions which meet the demands of typical, advanced industrial real-time applications. The interface between the processors arrays and the all-optical communication network is described in some detail. Implementation issues specifically related to the demand for miniaturization are discussed.
|
|
| 2. |
- Bjurwill, Christer, 1941-
(författare)
-
Read and react : The football formula
- 1993
-
Ingår i: Perceptual and Motor Skills. - Thousand Oaks, CA : Sage Publications. - 0031-5125 .- 1558-688X. ; 76:3_suppl, s. 1383-1386
-
Tidskriftsartikel (refereegranskat)abstract
- This essay is focused on the problem of vision and intelligence in football (soccer). One-touch play is the type of football that we are to see more often in the future. To prepare the players for such play, both managers and coaches must notice the importance of technical speed and tactical creativity. © Perceptual and Motor Skills 1993
|
|
| 3. |
- Borkowski, Kazimierz M., et al.
(författare)
-
Determination of the Toruń Antenna Position from VLBI Observations
- 1992
-
Ingår i: Acta Astronomica. - Warsaw : Fundacja Astronomii Polskiej im. Mikolaja Kopernika / Copernicus Foundation for Polish Astronomy. - 0001-5237. ; 42, s. 371-375
-
Tidskriftsartikel (refereegranskat)abstract
- Four strong radio sources were observed over a 12-hr session in March, 1990 between radio telescopes at Onsala and Torun at wavelength of 6 cm in the standard VLBI Mark II setup for the purpose of improving the coordinates of the Torun 15-meter antenna. The Cartesian coordinates of the antenna derived from the presented measurements are (in meters): 3638609.62 +/- 0.19, 1221773.23 +/- 0.54 and 5077024.50 +/- 1.66 in the x, y, and z directions, respectively.
|
|
| 4. |
- Brönmark, Christer, et al.
(författare)
-
Indirect effects of fish community structure on submerged vegetation in shallow, eutrophic lakes : an alternative mechanism
- 1992
-
Ingår i: Hydrobiologia. - Dordrecht : Springer Netherlands. - 0018-8158 .- 1573-5117. ; 243/244:1, s. 293-301
-
Tidskriftsartikel (refereegranskat)abstract
- The loss of submerged macrophytes during eutrophication of shallow takes is a commonly observed phenomenon. The proximate reason for this decline is a reduction of available light due to increasing phytoplankton and/or epiphyton biomass. Here we argue that the ultimate cause for the transition from a macrophyte-dominated state to a phytoplankton-dominated state is a change in fish community structure. A catastrophic disturbance event (e.g. winterkill) acting selectively on piscivores, cascades down food chains, eventually reducing macrophyte growth through shading by epiphyton, an effect that is reinforced by increasing phytoplankton biomass. The transition back from the phytoplankton to the macrophyte state depends on an increase in piscivore standing stock and a reduction of planktivores. A conceptual model of these mechanisms is presented and supported by literature data and preliminary observations from a field experiment. © 1992 Kluwer Academic Publishers.
|
|
| 5. |
- Bååth, L.B. 1948-, et al.
(författare)
-
0735+178 : The cosmic conspiracy
- 1991
-
Ingår i: Astronomy and Astrophysics. - Les Ulis : EDP Sciences. - 0004-6361 .- 1432-0746. ; 250:1, s. 50-56
-
Tidskriftsartikel (refereegranskat)abstract
- This paper discusses a radio outburst in the BL Lac-object 0735+178 which started in early 1988, ended during 1990 and was succeeded by a new outburst which is still in progress. Our image obtained with a global VLBI network shows the source to mainly consist of a core-jet like structure ending in diffuse emission region of low surface brightness located to the east of the core. We identify two new components as having been produced during the late 1980's. They are moving out with apparent superluminal motion in a viewing angle of greater-than-or-similar-to 10-degrees at a distance of less-than-or-similar-to 2 mas from the core. The core includes another new component, but our resolution is just sufficient to resolve out this component from the core at our epoch of observation. We suggest that the weak emission region is caused by an older component reaching the point at which the Doppler boosting is at its maximum and that the long time scale flux variation are due to successive events when evolved components reach that point.
|
|
| 6. |
- Bååth, L.B. 1948-
(författare)
-
A closer look at active galactic nuclei — the great engines of the universe
- 1992
-
Ingår i: Physica scripta. T. - Stockholm, Sweden : Kungliga Vetenskapsakademien. - 0281-1847. ; T43, s. 57-66
-
Tidskriftsartikel (refereegranskat)abstract
- The intensive radio emission from powerful radio galaxies and quasars Make these attractive candidates to become "standard candles" to probe the Universe. This paper discusses this possibility and the physics of the radio sources.
|
|
| 7. |
- Bååth, L.B. 1948-, et al.
(författare)
-
IMAGES OF THE BL LACERTAE OBJECT 1749+701 AT 5 GHZ
- 1992
-
Ingår i: Astronomy and Astrophysics. - Les Ulis, France : EDP Sciences. - 0004-6361 .- 1432-0746. ; 262:1, s. 1-7
-
Tidskriftsartikel (refereegranskat)abstract
- This paper presents images of 1749+701 from data obtained between 1980 and 1983 as a part of our VLBI programme to monitor a subsample of BL Lac objects at 5GHz. Our images show that this source has a complex structure with a jet pointing towards the north-west at a position angle of about -65-degrees. The brightest component is growing in extension along this position angle. We suggest this to be the core and that the growing extension was caused by a shock generated during an outburst and moving out along the jet. From the extension rate, we obtain an angular separation speed of 0.18 mas yr-1, which corresponds to an apparent transverse speed of 5c. The distances and position angles of two outer components seem remarkably constant. The phenomenon can be understood through a model in which a relativistic jet bends such that its axis is very close to the line of sight in two points. We also deduce that the Lorentz factor must be 4.5 less-than-or-equal-to gamma less-than-or-equal-to 6.5 and that the viewing angle must be 5-degrees less-than-or-equal-to theta less-than-or-equal-to 10-degrees. In this paper, we also present two images obtained from 5GHz MERLIN and combined MERLIN-VLBI data respectively. These maps show that there is a weak component located at a distance of 0.42 arcsec from the core at p.a -155-degrees.
|
|
| 8. |
- Bååth, L.B. 1948-, et al.
(författare)
-
The microarcsecond structure of 3C 273 at 3 MM
- 1991
-
Ingår i: Astronomy and Astrophysics. - Les Ulis : EDP Sciences. - 0004-6361 .- 1432-0746. ; 241:1, s. L1-L4
-
Tidskriftsartikel (refereegranskat)abstract
- Recent improvements in data analysis and receiver techniques have allowed us to produce a map of the 100GHz emission from the compact radio source 3C273 with the unsurpassed resolution of 50-mu-as (microarcseconds). Our map shows that the structure within 300-mu-as (approximately 1.5.10(18).h-1 cm) has a position angle significantly different from the position angle of the jet observed at lower frequencies. There are also indications in our map that the inner structure has a more pronounced wiggling structure than has been observed on larger scales. The observations were made about 60 days from the start of the outburst of 1988. Most of the flux from the outburst is concentrated in a component which is elongated approximately (56 x 5).10(16).h-1 cm perpendicular to the overall jet-axis. The distance between this component and the core is approximately 128-mu-as, which corresponds to the distance expected from an apparent velocity of approximately 800-mu-as year-1.
|
|
| 9. |
- Bååth, L.B. 1948-, et al.
(författare)
-
The radio fine structure of the BL Lacertae object 0735 + 178
- 1991
-
Ingår i: Astronomy and Astrophysics. - Les Ulis : EDP Sciences. - 0004-6361 .- 1432-0746. ; 243:2, s. 328-332
-
Tidskriftsartikel (refereegranskat)abstract
- The BL Lacertae object 0735 + 178 has been mapped with global VLBI arrays at four epochs from 1979 to 1983. The hybrid maps presented in this paper show a complex structure with a component separating from the core with an apparent transverse velocity of almost-equal-to 7.9 c. We suggest a model in which new components are born in the core during an outburst, initially move away towards northeast and then at a distance of almost-equal-to 4.2 mas turn towards the southeast. At this point, the component does not show any discernible motion away from the core. We suggest that the jet curls towards the south and towards the observer and at this point has its minimum viewing angle, with maximum boosting and minimum apparent velocity. We associate the outburst of 1989 with the event when a superluminally moving component reaches this point.
|
|
| 10. |
- Bååth, L.B. 1948-, et al.
(författare)
-
VLBI observations of active galactic nuclei at 3 MM
- 1992
-
Ingår i: Astronomy and Astrophysics. - Les Ulis : EDP Sciences. - 0004-6361 .- 1432-0746. ; 257:1, s. 31-46
-
Tidskriftsartikel (refereegranskat)abstract
- Recent improvements in data analysis and receiver techniques have allowed us to produce maps of the 100 GHz emission from the compact cores of active galactic nuclei with the unsurpassed resolution of 50-mu-as (microarcseconds). We present here hybrid maps of a set of compact radio sources observed at two epochs with a global VLBI array. The high resolution enables us to show details of active galactic nuclei on size scales of 10(16)-10(17) cm. Jets are shown to be more curved in these inner parts than further out in the areas mapped with VLBI at lower frequencies. Our maps of the quasar 3C345 show that the curvature seen with lower resolution instruments continues very close to the core. New components are seen separating from the cores of 3C84 and BL Lac. We observe a component in 3C84 separating from the core with an apparent speed approximately 21000 km sec-1. The radio source OJ287 is still unresolved with our array, having a core size of less-than-or-similar-to 10(17) cm. There is no indication of any compact component in 3C279 which would be associated with the outburst in integrated flux density which happened some months before our observation. The flux density of the most compact component we observe in 3C279 agrees well with that of the quiet core as extrapolated from its radio spectrum at lower frequencies. The inner part of the radio jet of the giant elliptical galaxy M87 also shows a continuation of the structure on a larger size scale, with a structure we interpret as parts of a helical pattern. No fringes were found for 4C39.25 or Sgr A.
|
|
