Tagging of pollack on the Norwegian west coast in 1979

In August 1979, 160 3-4-year-old pollack were tagged on the Norwegian west coast at about 60°N. Recaptures were mostly within 5 nautical miles and not more than 20 nautical miles from the tagging locality. The recapture rate of 23 per cent indicates considerable exploitation locally. The results give no indication of connection between the coastal pollack and the pollack in the North Sea. There may be local stocks of pollack along the Norwegian west coast

Tagging of pollack on the Norwegian west coast in 1979

In August 1979, 160 3-4-year-old pollack were tagged on the Norwegian west coast at about 60°N. Recaptures were mostly within 5 nautical miles and not more than 20 nautical miles from the tagging locality. The recapture rate of 23 per cent indicates considerable exploitation locally. The results give no indication of connection between the coastal pollack and the pollack in the North Sea. There may be local stocks of pollack along the Norwegian west coast

Friction Stir Welding using Mazak VCN-430a Milling Centre and Taguchi’s robust design method finding optimum parameters.

Master's thesis in Stuctural EngineeringFriction Stir welding has become an important method for welding of aluminium alloys. Excellent mechanical properties, economic benefits and environment friendly is just some of the advantages compared to ordinary fusion welding. However, large investments are needed as the workpiece need to be clamped properly against the worktable to resist any movement and the machine have to produce a large downforce. FSW can be performed using ordinary CNC- machines but force control or position control are suggested to make sound welds. This experiment used a Mazak VCN430a vertical milling centre and tools from Stirweld. The welding was conducted without any force control or force measuring system. To get a better control of the shoulder depth, the plates surface was measured using a measuring probe and the surface curvature was interpolated along the weld path. Friction stir welding was successfully performed on 300x150x3 mm plates of AA6082-T6 alloy using the Tagushi robust design approach. Optimal parameters for this particular machine and experiment was found to be 1200 rpm for the rotation speed, 150 mm/min for the welding speed, 2 seconds dwell time and a shoulder depth of 0.11 mm. The matrix experiment revealed almost the same value for the 0.07 mm shoulder depth which can be a prove of interaction among the parameters. Ultimate tensile strength test for the optimal weld parameters was 222.7 MPa. The predicted value was higher, but the measured value was inside the 2-standard confidence interval. Vickers hardness test showed that weakening of material had occurred throughout the specimen. The measured value 60 mm from the weld centre was approximately 75 Vickers HV. Developing the welding jig, clamping system and also simultaneously finding welding parameters without having any force control or position control proved itself to be very difficult. The clamping system seemed to be the most important factor to be able producing sound welds. For further friction welding experiment a welding jig and clamping system with the possibility of force control or position control need to be considered to eliminate defects

Loddeundersøkelser med F/F "G. O. Sars" i Barentshavet i februar-mars 1973

During the period 16 February-3 March 1973 R. V. «G. O. Sars» carried out a survey on spawning and prespawning capelin in the Barents Sea. The investigations were a continuation of those reported by Monstad and Midttun 1973. In the area north of the Skolpen Bank the distribution and maturity stage of the capelin were as reported by the mentioned authors. However, during the last week of February an influx towards the Norwegian coast of spawning capelin was observed off the Murman Coast. It is believed that these schools had been moving southwestward east of the area covered by the earlier investigations in the winter season

The spawning migration of Arctic cod in Lofoten in 1975

In the period 24 February to 14 March 1975 three echo surveys were made with R. V. "Peder Rønnestad" in the Lofoten area. The distribution of the spawning Arctic cod was charted by counting the number of fish recorded per nautical mile by the echo sounder. The spawning in 1975 occurred relatively late, probably because of low sea temperatures. Purse line catches indicate that the spawning population is still to a considerable extent composed of older fish

The spawning migration of Arctic cod in Lofoten in 1978

In the period 5 February to 2 March 1978 three echo surveys were made with R.V. "Johan Ruud" and R.V. "Peder Rønnestad" in Lofoten. The distribution of Arctic cod was charted by counting the number of fish recorded per nautical mile on the echo sounder. There seemed to be more fish present than in 1977, but in spite of seemingly favourable hydrographical conditions, fish migrating to the innermost eastern part of the spawning area were sparse. The 1970 year class dominated the cathces even more than in 1977