Bereitung des Jodkalium;

n/

Thermomechanical force application

The present work conducted in Summer 1987 continues investigations on Thermal Components for 1.8 K Space Cryogenics (Grant NAG 1-412 of 1986). The topics addressed are plug characterization efforts in a small pore size regime of sintered metal plugs, characterization in the nonlinear regime, temperature profiles in a heat supply unit for a fountain effect pump and modeling efforts

SIRTF Telescope Instrument Changeout and Cryogen Replenishment (STICCR) Study

The Space Infrared Telescope Facility (SIRTF) is a long-life cryogenically cooled space-based telescope for infrared astronomy from 2 to 700 micrometers. SIRTF is currently under study by NASA-ARC (Reference AP) and planned for launch in approximately the mid 1990s. SIRTF will operate as a multiuser facility, initially carrying three instruments at the focal plane. It will be cooled to below 2 K by superfluid liquid helium to achieve radiometric sensitivity limited only by the statistical fluctuations in the natural infrared background radiation over most of its spectral range. The lifetime of the mission will be limited by the lifetime of the liquid helium supply, and baseline is currently to be 2 years. The telescope changes required to allow in-space replenishment of the 4,000-L superfluid helium tank was investigated. A preliminary design for the space services equipment was also developed. The impacts of basing the equipment and servicing on the space station were investigated. Space replenishment and changeout of instruments required changes to the telescope design. Preliminary concepts are presented

Utilization of FEP energetics

The research and development work on Fountain Effect Pump Systems (FEP systems) has been of interest in the competition between mechanical pumps for He II and FEP units. The latter do not have moving parts. In the course of the work, the energetics have been addressed using one part of a simple four-changes-of-state cycle. One option is the FEP ideal change of state at constant chemical potential (mu). The other option is the two-state sequence mu-P with a d mu=0 state change followed by an isobar. Questions of pump behavior, of flow rate response to temperature difference at the hot end, and related questions of thermodynamic cycle completion and heat transfer have been addressed. Porous media data obtained elucidate differences between vapor-liquid phase separation (VLPS) and Zero Net Mass Transfer (ZNMF)

Experience with the Canadian Standards Association Offshore Structures Code.

The Canadian Standards Association (CSA) developed a comprehensive Offshore Structures Standard in the early 1990s. The Code has had limited use in Canada, but S471 General Requirements, Design Criteria, the Environment, and Loads has seen international application. The Code is performance-based; setting overall targets for reliability and provides specific guidance on achieving these targets. The provisions in the CSA Standard for ice loads have been reconciled with the Russian codes such as SNiP and VSN. A comparison of the codes has shown that they predict similar ice loads.NRC publication: Ye

Influence of vibrations on indentation and compression strength of sea ice

Indentation and compression strengths of floating sea ice subjected to vibrations is discussed. The experiments were performed on the land fast ice of the Van-Mijen Fjord in March of 2018 and 2019. The ice thickness was around 70 cm, and the ice salinity was 4-5 ppt. Vibrations were introduced in the ice by the vibration plate with weight of 400 kg before the tests during 10-15 min. The vibration plate was standing and vibrating on the ice surface. The spectrum of vibrations was recorded with accelerometers. Analysis of thin sections of ice was performed on the place of the field works. Indentation tests were performed with the original hydraulic rig on natural ice and ice subjected to the action of vibrating plate. It was discovered that stroke rates tests were higher in the tests performed on the ice subjected to vibrations. Uniaxial compression tests were also performed on ice cores taken from the natural ice and from the ice subjected to the vibrations. Uniaxial compression strength of ice cores taken from the ice subjected to vibrations was higher than in the tests with natural ice

Elastic moduli of sea ice and lake ice calculated from in-situ and laboratory experiments

The effective elastic modulus of ice is an important physical parameter for the calculation of ice stresses in different situations when ice deformations are small. In the present paper the review of methods used for the calculation of the elastic modulus of ice is performed, new tests for the calculation of the elastic modulus are described, and their results are discussed. Field experiments with floating vibrating ice beams with fixed ends were performed in March and November 2019 on sea ice of the Van Mijen Fjord and fresh-water ice of a lake near Longyearbyen. Laboratory experiments with vibrating cantilever beams were performed in the cold laboratory of UNIS in November 2019. The results are compared with the values of the effective elastic modulus obtained in quasi-static tests with floating cantilever beams, and with in-situ dynamic tests where the effective elastic modulus was measured by the speed of sound waves

Review of flexural strength of multi-year ice

Flexural strength from dedicated beam tests and ramming of multi-year floes has been compared. Flexural strength of multi-year ice from beam tests indicates the strength decreases as the size of the beams increases and this is important in comparing flexural strength data from various sources. In terms of relative flexural strength; from strongest to weakest is fresh-water ice, multi-year ice and first-year sea ice. Ship ramming results provide comparative results for flexural strength, even if the absolute values are greater than would be expected given the thickness of the ice. Colder ice floes have greater flexural strength. The MV Arctic ramming tests indicate that multi-year floes in a small area can be quite variable in thickness, temperature and flexural strength. Copyright \ua9 2013 by the International Society of Offshore and Polar Engineers (ISOPE).Peer reviewed: YesNRC publication: Ye

Flux of multi-year ice past the Molikpaq in the Beaufort sea, 1985-86 season

As part of the environmental monitoring program that supported drilling operations from the Molikpaq at the Amauligak I-65 location during the winter of 1985-86, information about the ice conditions and movements round the structure were collected on an hourly basis. These observations included ice thickness, ice type, partial concentrations, floe sizes and drift rate and direction. In this paper the data were used to assess the flux of ice passing a fixed location. Of particular interest was the amount of multi-year ice present and the relative exposure of the Molikpaq to multi-year ice interactions. In addition to the hourly ice observations, which were representative of a zone within a several km radius of the Molikpaq, detailed observations and video records of ice interactions with the structure were also made. Monthly Canadian Ice Service regional ice charts and drift buoys provided regional data. The various sources of ice data are compared to put the 1985-86 data into a broader context. The total flux of ice through the 2 km radius zone of observation was about 1000 km over the 240 day observation period, of which 30 km was multi-year ice. The flux of multi-year ice that actually interacted with the 100 m wide Molikpaq was about 10 km, the majority of which was second-year ice in November.Peer reviewed: YesNRC publication: Ye

Local contact pressures in ship/ice and structure/ice interactions

Data on localicepressures and forces were compiled. The two primary sources were controlled indenter experiments in the field and ship trials. Loads and average localpressures on areas up to 7 m2 were examined. All the data were plotted on a basis of average pressure versus contact area. Similar trends of decreasing pressure with increasing contact area were observed for all data sets. In order to extrapolate these data to larger contact areas, measurements on structures with contact areas greater then 100 m2 were reviewed. The larger contact area data indicate that the trend of decreasing localicepressures levels off at larger areas. Based on all the data examined, design curves for localicepressures on structures were suggested.NRC publication: Ye