Ice resistance measurements in ridges with IB APU in the Baltic sea

Ice ridges form a difficult obstacle for ice navigation. Despite this fact, the resistance of ships in ridges has been investigated very little.A trial was performed with the Finnish icebreaker APU (propulsion machinery power of 8·8 MW) in April 1974 in the Baltic, in order to measure its resistance in ridges.Most of the 11 ridges were so massive that the ship could not penetrate through them by a continuous mode, the ramming mode had to be used.When the ship was penetrating a ridge, its speed and the propeller revolutions were registered for determining the resistance. A doppler radar was used for measuring ship spped.In case the ship was stopped in the ridge it was extracted, reversed and accelerated for the next ram. The time history was registered for determining the ship's speed of advance.Before starting a test, the ridge profile above the water level was measured. This was simply done by using a levelling instrument.The main object of the test was to determine the ship's speed of advance. The results, i.e. ice resistance, ship speed and ridge characteristics were analysed on three levels: momentary values average values for rams and average values for a series of rams in one ridge.The test series presented in the article was the first one in full scale in which the speed of the advance of a ship moving by ramming was determined and the ridge profiles were mapped. The measuring system developed worked well. As results the tests gave data of the ship's resistance and of the ship's speed of advance in ridges.     

New evidence from beneath the western North Atlantic for the depth of glacial erosion in Greenland and North America

Interpretation of Deep Sea Drilling Project results and air-gun seismic profiles suggests that about 10⁶ km³ of sediment have been eroded from eastern North America and southern Greenland and deposited in the adjacent North Atlantic since the beginning of continental glaciation. This volume is a minimum estimate which does not account for sediment beneath the continental shelf nor that portion carried south of the Blake-Bahama Outer Ridge by the Western Boundary Undercurrent. It represents erosion of about 100 m of solid rock and indicates that more than 90% of the sediment eroded from these areas was deposited as sands, silts, and clays in the adjacent western North Atlantic. Glaciation accounts for between 55 and 95 m of this average 100 m, and fluvial processes account for the remainder. The documented erosion in part substantiates W. A. White's (1972, Geological Society of America Bulletin83, 1037–1056) hypothesis of deep erosion and exhumation of shield regions, but is not in agreement with the entire volume of erosion implied by his model.     

NGC 7479: A Case Study

The most salient features of the barred spiral galaxy NGC 7479 include the unusually strong and long bar, asymmetric spiral structure and peculiar dust lanes. The central, bar-dominated region has been robbed of neutral atomic gas. The neutral hydrogen kinematics of the strong western spiral arm are consistent with substantial non-circular motions. In contrast, the molecular gas is strongly concentrated in the nucleus and along the bar dust lanes. A molecular disc with near-circular motion is found in the nuclear area. Outside this component, the molecular gas has a strong radial velocity component consistent with inflow. The velocity gradients across the bar dust lanes show jumps of a few hundred km s^-1. A comparison of the dust/gas lane morphology between the observations and numerical simulations suggests that the corotation radius is at 1.1 times the bar length. I have modelled many of the peculiar morphological and kinematic features in numerical simulations of a minor merger. The predicted position of the merging companion matches the position of a bright clump in the bar with perturbed kinematics. This revised version was published online in July 2006 with corrections to the Cover Date.     

Radio-continuum study of the Nearby sculptor group galaxies. Part 1: NGC 300 at λ=20 cm

A series of new radio-continuum (λ=20 cm) mosaic images focused on the NGC?300 galactic system were produced using archived observational data from the VLA and/or ATCA. These new images are both very sensitive (rms?=60 μJy) and feature high angular resolution (<10?″). The most prominent new feature is the galaxy’s extended radio-continuum emission, which does not match its optical appearance. Using these newly created images a number of previously unidentified discrete sources have been discovered. Furthermore, we demonstrate that a joint deconvolution approach to imaging this complete data-set is inferior when compared to an immerge approach.     

Deriving the unitgraph without using rainfall data

The characteristic of a linear time invariant system can be found uniquely from any two outputs that have no error: it is not necessary to know the inputs or the time duration of the system response. In hydrologic terms, the unitgraph of a catchment with linear characteristics may be found from records of runoff vs time.     

Quality mapping of the Ryytimaa dolomite in western Finland

The Ryytimaa dolomite formation in western Finland is mined for fertilizing purposes in agriculture. Ordinary kriging, indicator kriging, and indicator principal components simulation were used to map the dolomite quality. The fertilizing properties depend on the relative amounts of MgO and neutralizing CaO in dolomite. Based on the chemical composition the dolomite is divided into six quality classes according to the Finnish legislation. This quality classification is only partially in accordance with the three populations inferred from the distributions of the MgO, CaO, and neutralizing CaO contents. These populations probably represent compositionally different dolomite layers, now forming complicated fold interference structures that are visible on the kriged maps. The mapping of the quality, and thus, selective mining of the dolomite deposit is possible using the quality classification based on the three populations. In contrast, selective mining of the dolomite based on the legislation is difficult—at least with techniques used in this study.     

Neutral hydrogen gas distribution and kinematics in NGC 7479

We have investigated the effects of a bar and an asymmetric spiral structure on the neutral hydrogen distribution and kinematics in the strongly barred spiral galaxy NGC 7479. The strongest 21-cm line emission at 1-kpc resolution comes from the western spiral arm which appears to be slightly inclined to the plane of the main disc. In contrast, the area within the radius of the bar is devoid of 21-cm line emission. The radio continuum emission at 21 cm follows the bar dust lanes, but beyond 3 kpc from the nucleus the radio continuum emission has a peculiar morphology, unlike that of optical and near-infrared images. We did not detect any low surface brightness gas-rich companions in the near neighbourhood of NGC 7479. This leads us to propose that the strong western spiral arm was created in a recent minor merger.