bluuebunny/crossref_metadata_2025_split huggingface dataset:
Crystallographic Structure of Polycrystalline Ice
Authors: Matsuda M. , Wakahama G. 
Published: September 2017

AbstractFor several types of polycrystalline ice of different origins, the spatial lattice orientation of each crystal was determined by measurements of both the a- and c-axis orientations. Analyses of the orientations of adjoining crystals showed that a great majority of adjoining crystals may be in a twinning relation. With special reference to the multi-maximum c-axis preferred-orientation fabric (the so-called “diamond pattern”), which is expected to occupy the largest part of a glacier ice mass, the crystal boundary structure was estimated. The preferred c-axis orientations of this fabric were explained as being the result of coincident oxygen-oxygen lines (hydrogen-bond lines) between adjoining crystals being concentrated in the orientations where seven oxygen-oxygen lines of one single crystal of ice are distributed. From the above result, it was concluded that the multi-maximum fabric is of the polycrystalline structure closest to the structure of a single crystal of ice among all the fabrics found in large ice masses.It is found that the occurrence, in glaciers and ice sheets, of a multi-maximum fabric has a bias to the parts which have undergone a strong shear deformation for a long time. It is thus suggested that plastic deformation of ice with this fabric may be attributed to mechanical twinning due to a strong shear stress.
On the Heat Capacity, Entropy, and “Glass Transition” of Vitreous Ice
Authors: Johari G. P. 
Published: September 2017

AbstractAn analysis of the thermal properties of vitreous ice shows that both its heat capacity Cp and its entropy above 100 K are partly configurational in origin. The configurational contribution increases with temperature, and the excess Cp and entropy near the solid-liquid transformation temperature are 36.7 and 2.1 J K-1 mo1-1, respectively. The increase is interpreted as indicating the onset of molecular mobility in vitreous ice. The configurational Cp, of the melt of vitreous ice at 133.6 K, of ≈ 36.7 J K-1 mo1-1, is the same as the configurational Cp, of water at 273 K. Thus, the short-range order in the melt differs little from that in water at 273 K. The maximum calorimetric residual entropy of vitreous ice is 13.4 J K-1 mol-1, which is in fair agreement with the maximum value of 9.2 J K-1 mol-1 anticipated for a tetrahedral random-network model with fully disordered positions of H atoms. Thermodynamic consideration of a glass transition in supercooled liquid water indicates that there is no continuity of state between supercooled water and vitreous ice and, therefore, the structure and thermodynamic properties of a possible glassy state of water should be different from that of vapour-deposited vitreous ice. This paper is published in full in Philosophical Magazine, Eighth Ser., Vol. 35, No. 4, 1977, p. 1077-90.
The Dipolar Correlation Factor of Ice VI
Authors: Johari G. P. , Whalley E. 
Published: September 2017

AbstractThe dipole moment μ of an H2O molecule in the orientationally disordered ices is greater than the moment of an isolated molecule, 1.84 D, due to two factors: (i) the mutual polarization of molecules, and (ii) the short-range average correlation of the dipole vectors, if the molecules are able to reorient. The magnitude of the average enhancement is given by Kirkwood's equation,1where ϵ0 and ϵ∞ are respectively the limiting low- and high-frequency relative permittivity of orientational polarization, N is the number density of dipoles, k is the Boltzmann constant and T is the temperature. The dipolar correlation factor g is defined by,2where μi and μj are the dipole moments of molecules i and j in a spherical region of radius r immersed in a larger spherical region of radius R and the angular brackets indicate average over all molecules i and all their orientations. In view of the defects, vacancies, imperfections, etc., in ice, it is not certain if the limits in Equation (2) have any experimental significance. However, an approximate value of g can be calculated by taking molecules up to the second co-ordination shell.The theoretical value of g for polycrystalline ice VI which is fully disordered (within the restrictions of ice rules) has been calculated by taking molecules up to the second nearest neighbours, in both the dendritic and non-dendritic models. The calculations were done for two kinds of molecules, I and II, having multiplicities 2 and 8 respectively, in the tetragonal unit cell in space group P42/nmc, and, through the use of symmetry, keeping to a minimum the number of scalar products.In both the dendritic and non-dendritic, models, gI is 10%, or more, greater than gII and the appropriately weighted values of g are 2.342 in the former and 2.065 in the latter model. The effect of ring closure is, therefore, to reduce the value of g by 13%. The limiting high temperature experimental value of g from Equation (1), using Onsager's theory for the enhancement of the dipole moment by its own reaction field, is 2.42 (Johari and Whalley, 1976). By analogy with the 10% discrepancy between the theoretical and experimental values of g of ice I, a better estimate of the experimental g of ice VI (using a reaction field other than that given by the Onsager theory) would be about 10% less than this value. Thus the suggested experimental g of ice VI (2.18) is close to the theoretical values obtained from either of the two models and there is little contribution to g from neighbours beyond the second co-ordination shell.
Effect of Hydrostatic Pressure on the Creep of Ice
Authors: Jone Stephen J. 
Published: September 2017

AbstractUniaxial compressive creep tests on single crystals and polycrystals of ice at about -10°C under different hydrostatic pressures are described . After creeping under a constant load at atmospheric pressure for some hours, a hydrostatic pressure of the order of 35 MN m-2 was applied and the change in strain-rate was noted. Some hours later the hydrostatic pressure was removed and the test continued at atmospheric pressure. From these changes in strain-rate , an activation volume V was determined from the equationwhere R is the gas constant, T is the absolute temperature, P is the hydrostatic pressure and τ is the superimposed uniaxial creep stress. V is negative if E increases with P.For single crystals, which show an accelerating creep curve, that is the strain-rate increases continuously with time, no sensible activation volume was determined because the strain-rate increased both on the application of the hydrostatic pressure, and on its removal. For polycrystals, application of a hydrostatic pressure caused an increase in strain-rate which gave an activation volume of about - 10 cm3 mol-1. However, on removal of the pressure the strain-rate did not return to its original atmospheric-pressure value implying that steady-state creep had not been reached.This value of activation volume is in general agreement with two previously published values for creep deformation, but is of opposite sign to the activation volume for dielectric relaxation. Further tests are in progress.
Breaking Strength and Creep Expansion of Deposited Snow
Authors: Watanabe Z. 
Published: September 2017

AbstractThe breaking strengths of snow were measured by a new tester which had been made by the author, and were expressed as functions of density or hardness. One special merit of the apparatus is that they are useable even for new snow, and the strengths were easily measured to several grammes per cm2. The creep expansion of snow was measured by using an optical level, and was expressed as a function of snow density, temperature, internal stress, and lapsed time. One point of the measurement is that the creep expansion rate did not become constant, hut was decreasing with time even several hours from the beginning of the test.
Application of Nucleation Theory to the Process of Droplet Freezing on an Ice Substrate
Authors: Levi L. 
Published: September 2017

AbstractThe probability P that ice embryos, nucleated inside droplets colliding with an ice surface, have crystallographic orientations different from that of the substrate, is correlated with the mean number of droplets which form each crystal in accretions grown in dry regime (substrate temperature Ts < 0°C). The theory of heterogeneous nucleation is applied to represent the ice embryo nucleation rate and the approximate expression is obtained, where ΔGy* is the nucleation energy for randomly oriented critical embryos. Assuming cap-shaped embryos and taking into account the crystal size in accretions grown at Ts = —15°C and air temperatures , it is found that ergThe relationship between the value of ΔGy* and those of the crystal-embryo and crystal-melt interfacial free energies is discussed. Finally the dependence of P0 on the growth conditions and on the ice substrate orientation is analysed, considering the effect of embryo breeding by collision and that of orientation selection, which is responsible for the establishment of preferential orientations in the accretions.
The Morphological Stability of Internal Melting Figures in Ice
Authors: Mae Shinji 
Published: September 2017

AbstractWavy perturbations formed on disc-shaped internal melting figures in ice were observed. It was found that a minimum wavelength of the perturbations was approximately 100 μm and a critical thickness of the figures for the formation of the perturbations was 10 μ.m. The critical thickness did not depend on the radius and growth rate of the figures. A minimum wave number of the perturbation was 6 and the axis of its sixfold symmetry was parallel to the <1120> direction, The perturbations with large wave number were formed on the inclined side faces of internal melting figures of which the shape was like a truncated cone. Therefore, it was concluded that the perturbations were nucleated at the sharp edge where the side face and the larger plane of the figures intersected. This conclusion was supported by the observation of internal melting figures at grain boundaries where their periphery was always sharp.
Radio-Echo Sounding: Glaciological Interpretations and Applications
Authors: Robin G. de Q. 
Published: September 2017

AbstractAfter a brief review of factors relevant to the propagation of radio waves in ice, problems of profiling the upper and bedrock surfaces of ice sheets are considered. These include deconvolution of echo traces and accurate navigation. Results already available not only provide knowledge of sub-ice geomorphology, but also confirm our general ideas on interaction of temperature and flow in large ice sheets. Difficulties encountered in the study of temperate glaciers appear to be due to irregular dielectric properties of the ice mass, which in turn suggest an irregular distribution of water. In the future, application of radio-echo methods should lead to more detailed knowledge of accumulation and ablation over ice masses, improve our understanding of temperatures at great depths in polar ice sheets, and give data on ice movement from central areas of ice sheets.
Investigation of Sub-Ice Bedrock Characteristics by Radio-Echo Sounding
Authors: Oswald G. K. A. 
Published: September 2017

AbstractQualitative inspection of the results of the 1971/72 S.P.R.I.-N.S.F. Antarctic radio-echo sounding programme shows that it is possible to infer some characteristics of the lower face of the ice from the form of received echoes. We confirm the existence of lakes of liquid water beneath the east Antarctic ice by inspection of the top and bottom surface gradients of the ice, and suggest that basal melting occurs over a wide area in this region.Quantitative studies in Devon Island indicate that small-scale irregularities in the bedrock are characterized by slopes of about 1: 40, with some higher gradients present, possibly indicating the presence of morainal boulders. We deduce that a geological boundary was crossed between 25 and 40 km west of the base camp, the rock to the west of the boundary having lower permittivity, and higher surface slopes than that to the east.The question of the usefulness of the spatial fading of the echo in deducing surface characteristics is briefly discussed. We conclude that measurements of the fading are indeed useful, especially in the case of echoes with short “tails”.
Advances in geophysical exploration of ice sheets and glaciers
Authors: Bentley Charles R. 
Published: September 2017

AbstractThe techniques of geophysical exploration can be used in a number of ways to investigate the internal characteristics of ice bodies. The application of radio-echo sounding is discussed elsewhere by Robin (1975[a]) so is not considered here except for a few special cases. Anisotropy resulting from non-random ordering of crystal axes produces effects on seismic wave propagation speeds measurable by both refraction and reflection techniques. The effects on shear waves are particularly strong, so the recent development of an effective shear-wave generator should prove very useful. Marked effects on radio-wave polarizations have also been noted, but are not readily interpretable because the anisotropic dielectric characteristics of single-crystal ice in the radio-echo frequency range are not yet known. Elastic internal friction can be determined by careful measurements of seismic-wave amplitudes. Dielectric properties of the ice can be found from VLF propagation experiments and electrical logging in drill holes as well as from the radio-echo sounding techniques discussed by Robin (1975[a]). An activation energy can be estimated from d.c. resistivity measurements where the temperature profile is known. Recent developments have led to much improved methods of determining density-depth variations and long-term mean annual snow accumulation rates from seismic refraction shooting. Internal discontinuities which can be studied include a probable morainal layer detected by seismic reflections, a brine-soaked zone in shelf ice observed from radio-echo. sounding and electrical resistivity surveying, and inverted crevasses penetrating upward from the base of shelf ice, detected by radio echoes. Secular changes in gravity offer a sensitive means of determining long-term changes in surface elevation.
Ultrasonic Properties of Plastically Deformed Ice
Authors: Tatibouet J. , Vassoille R. , Perez J. 
Published: September 2017

AbstractMany authors have used propagation of ultrasonic waves in ice for glaciological studies. This propagation is characterized by the velocity of sound and by the attenuation of stress waves. In crystalline materials, these two characteristics depend on structural slate. In particular plastic deformation gives velocity and attenuation variations.We have measured the sound velocity and attenuation of ultrasonic waves in strained specimens of ice (single crystals and polycrystals). These measurements done between 100 and 273 K at a frequency of 5 MHz show that plastic deformation leads to an increase of attenuation arid an increase of velocity. Annealing treatments at 271 K cause recovery of propagation characteristics. The variation in attenuation can be interpreted by the theory of dislocations and this interpretation is supported by our data on the influence of frequency on this increase of attenuation induced by plastic deformation, but the theory of dislocations implies a decrease of modulus, i.e. of velocity, hence we must postulate that an added phenomenon screens the effect of dislocations. That phenomenon could be connected with ageing effects observed on different physical properties of ire and may be due to modification of protonic arrangement or creation of interstitials during plastic deformation. Thus our experiments show that it is necessary to be careful in using results determined from the propagation of ultrasonic waves in ice.
Application of Radar Techniques to Ice and Snow Studies
Authors: Page D. F. , Ramseier R. O. 
Published: September 2017

AbstractThis paper presents an overview of the active microwave tools becoming available to the glaciologist with emphasis on recent radar developments as applied to floating ice. Sufficient theory is presented for the user to understand the techniques. Side-looking radar imagery is discussed using a number of examples resulting from the use of real and synthetic aperture, single and dual polarization. Recent studies of the microwave properties of ice and snow are reviewed, and are shown to be leading to significant advances in high-resolution radar techniques for accurate sounding of these materials. Remote sensing of fresh-water ice thickness is shown to be well established and operational, with similar techniques feasible in the near future for sea ice. It is pointed out that both imaging and probing radars applied to studies of sea ice and snow usually must be used in association with data from other sensors.
Interpretation of Slar Imagery of Sea Ice in Nares Strait and the Arctic Ocean
Authors: Dunbar Moira 
Published: September 2017

AbstractSLAR imagery of Nares Strait was obtained on three flights carried out in. January, March, and August of 1973 by Canadian Forces Maritime Proving and Evaluation Unit in an Argus aircraft equipped with a Motorola APS-94D SLAR; the March flight also covered two lines in the Arctic Ocean, from Alert 10 the North Pole and from the Pole down the long. 4ºE. meridian to the ice edge at about lat. 80º N. No observations on the ground were possible, but -some back-up was available on all flights from visual observations recorded in the air, and on the March flight from infrared line-scan and vertical photography.The interpretation of ice features from the SLAR imagery is discussed, and the conclusion reached that in spite of certain ambiguities the technique has great potential which will increase with improving resolution, Extent of coverage per distance flown and independence of light and cloud conditions make it unique among airborne sensors.
Sea-ice Reconnaissance by Radar
Authors: Tabata Tadashi 
Published: September 2017

AbstractTo observe the distribution of pack ice off the coast of the Okhotsk Sea coast of Hokkaido, a radar network consisting of three radar stations was constructed during 1967-69. It covers an area about 70 km wide and 250 km long. The stations are remote-controlled by radio from the Sea Ice Research Laboratory and the information obtained is transmitted back to the laboratory and observed there. Radar has the great advantage of being able to make continuous observations of ice. Usually several special features can be seen on the radar screen, and they are used as markers for the observation of movement. It is ascertained that the average pattern of drift in this area is from north to south-east along the coast line and the ice field undergoes internal deformation during its drift. To get some information on the surface topography of ice from A-scope radar, the intensity of echo signals is classified into 16 steps by computer. To obtain the movement of an ice field from the numerical radar information, a modified two-dimensional cross-correlation method was tested.
Seasonal Effects on Ground-Wave propagation in Cold Regions
Authors: Blomquist Ake 
Published: September 2017

AbstractThe ground-wave is the most important mode of propagation of radio waves in Connection with glaciology. In cold regions, special conditions are often prevalent, involving propagation over non-homogeneous earth, presence of stratified media, and low values of conductivity and dielectric constant in the upper strata.A radio wave which propagates along the Earth's surface is, however, also influenced by atmospheric refraction. As the frequency is increased, the roughness of the Earth's surface must also be taken into account. Thus seasonal variations are to be expected due to changes in the electrical and topographical properties of the ground as well as the propagation conditions in the atmosphere. It is, however, difficult to separate these various effects, a fact which reduces the possibility of using ground-wave propagation as a loot for obtaining information on the properties of the ground.Though the propagation of the ground-wave has been dealt with both theoretically and experimentally for almost a century, some of the most valuable information of major importance in cold regions has been obtained during the last ten years. New theoretical papers on propagation over stratified media offer an explanation of the amplitude and phase variations of the ground-wave field, which have been measured, as well as suggesting new methods to be tested as possible aids in solving glaciological problems.In many practical eases of ground-wave propagation in arctic regions, the formula for the ground-wave field strength can be written in a very simple way. Such a propagation model for frequencies above 30 MHz is presented in which account is taken of the Earth's curvature, the terrain irregularities, and the effect of the tropospheric refraction. This model also includes the recovery effect which occurs in propagation over mixed paths. At the higher frequencies the effect of depolarization becomes very important and sometimes overshadows field-strength variations due to the influence of the electrical properties. Finally some problems will be discussed which remain to be solved or have been given very little attention up to now.
A Submarine Sonar Study of Arctic Pack Ice
Authors: Elizabeth Williams , Charles Swithinbank , Robin G.DE Q. 
Published: September 2017

AbstractA continuous profile of the Arctic Ocean ice canopy from Spitsbergen to the North Pole was made with 48 kHz echo sounders mourned on a nuclear submarine. A semi-automatic digitizer was used to measure coordinates from the records at a frequency of about 1 000 points per linear kilometre of track. Methods derived for the reconstruction of subglacial relief from 35 MHz radio-echo sounding records were applied to eliminate part of the distortion due to the 20° beam width of the sounders. A corrected profile was used to obtain ice drafts at 2 m intervals. Data were analysed in 10 km sections and figures were summarized for each degree of latitude. The results include: mean ice draft, percentage of ice less than 0.3 m draft, and percentage of level ice. Histograms show the level ice drafts which occur most frequently, and these may indicate the ratio of first-year to older ice. The number of ice keels is listed together with their mean draft and draft distribution. Definitions are found to be of overriding importance in the comparison of data from different areas.
Optical Properties of Salt Ice
Authors: Lane J. W. 
Published: September 2017

AbstractThe dependence of the extinction coefficient on salinity was investigated for both NaCl-ice and salt-ice made from natural sea-water. Specimens were prepared under a variety of conditions and examined over the wavelength range 4 000 to 8 000 Â. The effects of scattering from air bubbles trapped in the ice were examined for ice made from distilled water. It was found that the method of preparing samples markedly affected their structure, but that, when prepared in the same manner, salt-ice made from natural sea-water and NaCl-ice did not show significantly different transmission properties. It was found that, for a wavelength of 6 328 Â, the data could be fit to the relation

within an uncertainty of 26%, where ke is the extinction coefficient, x is the salinity of the ice in g/kg. Within an uncertainty of 10%, there was no variation in transmission for ice at the same temperature and salinity over the wavelength range 4 000 to 8 000 Â. All measurements were made at a temperature of -20° C.