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Volume 42 (1980)
- Issue 4 Pages 203-
- Issue 3 Pages 119-
- Issue 2 Pages 61-
- Issue 1 Pages 1-
Volume 42, Issue 2
Displaying 1-6 of 6 articles from this issue
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Nobuyuki YAMAMI1980 Volume 42 Issue 2 Pages 61-66
Published: June 30, 1980
Released on J-STAGE: July 23, 2009
JOURNAL FREE ACCESSThe growth mechanism of ice crystals abnormally extended to the b-axis in the temperature range where singular surface appears is discussed.
A screw dislocation introduced to one of six prism faces growing under the two-dimansional nucleation in the low supersaturation range causes more rapid growth rate of the prism face than that of the others, which results in the change of the ice crystal form from hexagon to pentagon.View full abstractDownload PDF (10595K) -
in colder temperature regionsNobuyuki YAMAMI1980 Volume 42 Issue 2 Pages 67-70
Published: June 30, 1980
Released on J-STAGE: July 23, 2009
JOURNAL FREE ACCESSThe growth rate of basal faces and prism faces was calculated on the case of two-dimensional nucleation and the case of Frank mechanism. The following results were obtained.
A screw dislocation introduced to only a basal face in the low supersaturation range causes more rapid growth rate of the basal face than that of the others, which results in the change of the ice crystals form to long solid column. When the same accident happened on only a prism face in the low supersaturation, the ice crystal abnormally extended to the b-axis.View full abstractDownload PDF (460K) -
Masami FUKUDA, Takeshi ISHIZAKI1980 Volume 42 Issue 2 Pages 71-80
Published: June 30, 1980
Released on J-STAGE: July 23, 2009
JOURNAL FREE ACCESSIt is often required to predict frost penetration beneath the ground using limited weather records. Previously, estimations of frost penetration beneath the ground were based mainly upon accumulated degree days of frost. These methods, however, caused non-negligible errors in estimation because of an unrealistic assumption that the air temperature is equal to the surface temperature of the ground.
For the improvement of simulation models for estimating frost penetration beneath the ground, the authors used the equilibrium surface temperature which is associated with the thermal regime of the energy balance at the ground surface. In the model, time-variable surface boundary conditions were used and the quilibrium surface temperature was calculated in each time interval. Records of total solar radiation, wind velocity, air temperature, cloud cover and atmospheric pressure were used for the simulations.
In addition to the equilibrium surface temperature, the present computer simulation model employs a finite difference solution to a heat conduction equation with phase changes of soil moisture. The results of simulations are compared with the results of on-the-spot investigations at various places. The model is also applied to the palaeoclimate in Hokkaido during the last glaciation. The results show good agreement with the presence of permafrost.View full abstractDownload PDF (1217K) -
Yoshiyuki FUJII1980 Volume 42 Issue 2 Pages 81-92
Published: June 30, 1980
Released on J-STAGE: July 23, 2009
JOURNAL FREE ACCESSStudies on permafrost and its related environments were carried out in Khumbu Himal in 1973 and in Hidden Valley, Mukut Himal in 1974. There appears to be a zone of permafrost above 4900-5000 m and a zone of seasonal frost below 4900-5000 m in Khumbu Himal and Mukut Himal. The lapse rate of the ground temperature at 50 cm depth of 0.9-1.0 cm/100 m in the zone of permafrost is larger than that of 0.4- 0.5°C/100 m in the zone of seasonal frost. The temperature gradient at a depth of 50-100 cm shows the tendency of decrease with altitude in the zone of permafrost but almost uniform in the zone of seasonal frost. The mean annual air temperature at the lower limit of permafrost in Khumbu Himal is -2.4-3.0°C. This value is lower than that at the southern limit of discontinuous permafrost zone in the high latitudes of the northern hemisphere because of stronger solar radiation in the Himalayas. The lower limit of permafrost is higher than the forest limit of 4200 m in Khumbu Himal and 3800 m in Mukut Himal and is lower than the snow line of 5600-5700 m in Khumbu Himal and 5800 m in Mukut Himal. Almost of the summer ponds exists in the zone of permafrost in relation to the existence of permafrost. Glaciers existing in both regions are found in the zone of permafrost. These glaciers are classified into polar type by the ice temperature measurements in summer. These seem to be climatologically synonymous.View full abstractDownload PDF (1841K) -
Energy analysis for track motion on snow covered terrainTatsuro MURO, Raymond N. YONG1980 Volume 42 Issue 2 Pages 93-100
Published: June 30, 1980
Released on J-STAGE: July 23, 2009
JOURNAL FREE ACCESSAs in snow trafficability the first pass is the worst pass, the study on vehicle-snow interaction problem should be started on the basis of technology for vehicle mobility but from evaluating some of the various characteristics of compressibility and shear in snow with reference to the requirements for prediction of trafficability. After presenting energy equilibrium equation for track motion on snow covered terrain, the relation between tractive force of over snow vehicle T4 per one traok and slip ratio s has been given as follows;
T4=1/1-ST1-S/1-S (T3+T6) - (T2+T5)
Here, T1 is traction force of track belt driven by sprocket, T2 is compaction resistance, T3 is tractive resistance of snow terrain, T5 is side friction resistance between mounted snow and natural snow terrain and T6 is side friction resistance between compacted snow among shoe grousers and natural snow terrain.
T1 is determined to be effective traction force of track belt from engine power, and T2 and the sinkage of vehicular footing is calculated from rectangular plate loading test on snow from finite shallow snow depth to infinite snow depth. T3, T5 and T6 are calculated from vane cone test on snow, and the tractive resistance of snow terrain T3 can be calculated from the maximum shearing strength for compacted pressure of maximum contact pressure which is approximately equal to 4 times average contact pressure of tractor.View full abstractDownload PDF (1112K) -
Tatsuro MURO, Raymond N. YONG1980 Volume 42 Issue 2 Pages 101-108
Published: June 30, 1980
Released on J-STAGE: July 23, 2009
JOURNAL FREE ACCESSTo predict drawbar pull property of flexible tractor on snow covered terrain for fresh or newly fallen fresh snow and sintered snow in low temperature -13°C, some energy equilibrium equation of track motion for various snow depths has been analysed. It has been cleared that the drawbar pull decreases gradually with slippage of tractor and gets a peak value at no slip ratio, and the drawbar pull D.B.P. can be calculated approximately by effective maximum traction force of track belt T drove from engine power, track width B and deformation energy loss per unit area En of snow terrain under track belt due to compaction as
D.B.P.=T-2BEn.
And to predict the drawbar pull from field measurements, some circular plate penetration test and vane cone shear test results are cleared to be usefull.View full abstractDownload PDF (1138K)
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