ALBERT

All Library Books, journals and Electronic Records Telegrafenberg

feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
  • 1
    Series available for loan
    Series available for loan
    Hanover, NH : U.S. Army Cold Regions Research and Engineering Laboratory
    Associated volumes
    Call number: ZSP-201-82/43
    In: CRREL Report, 82-43
    Description / Table of Contents: The radar signatures of ice wedges and wedge-like structures have been investigated for a variety of soil conditions. The radar used for this study emitted short sinusoidal pulses of about 10-ns duration with an approximate center frequency of 150 MHz. Most of the ice wedges existed at depths of about 1 m in a variety of silty and sandy soils with both frozen and thawed active layers. The position of the wedges was usually identified from corresponding surface features. An artificial ice wedge in coarse-grained alluvium was also profiled as well as wedge-like structures of fine silt in a coarse-grained glacial outwash. All wedges and wedge-like structures produced a hyperbolic reflection profile except when an active layer of thawed, saturated silt was present which eliminated returns from the wedges. The peaks of the hyper-bolas were sometimes masked by reflections from the permafrost table or other material interfaces, and multiple hyperbolas occurred at some sites. The dielectric constant of the host medium was often calculated from the linear portions of the hyperbolas and the results were verified by laboratory time domain reflectometry measurements per-formed on field samples. In some cases, hyperbolic profiles originated at several meters depth suggesting that deep ice wedges could be detected in areas of cold permafrost.
    Type of Medium: Series available for loan
    Pages: iv, 19 Seiten , Illustrationen
    Series Statement: CRREL Report 82-43
    Language: English
    Note: CONTENTS Abstract Preface Introduction Background Objectives and procedures Equipment used Radar TDR Definitions Massive ice Results Artificial wedge: Norwich, Vermont Ice wedges in sand: Fish Creek, Alaska Ice wedges: Prudhoe Bay, Alaska Ice wedges under thawed fine-grained soils: North Slope, Alaska Wedge-like soil structures: Ft. Greely, Alaska TDR measurements Summary and concluding remarks Literature cited Appendix A: Brief discussion of dispersion
    Location: AWI Archive
    Branch Library: AWI Library
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 2
    Call number: ZSP-201-86/6
    In: CRREL Report, 86-6
    Description / Table of Contents: Short-pulse radar profiles and waveform traces were recorded over natural, freshwater ice sheets and an artificially made, 1.6-m-diameter column of brash ice. The purpose was to study the feasibility of this type of radar to detect ice thickness, determine ice properties and distinguish ice forms. The radar utilized two antennas: one with a spectrum centered near 900 MHz and a second more powerful one near 700 MHz. Distinct top and bottom reflections from several ice sheets were produced by both antennas, but the value of dielectric permittivity calculated from the time of delay of the reflections varied between sheets as one ice sheet was ready to candle and contained free water. The brash ice distorted signals and allowed no discernible bottom return. The lower frequency antenna also gave returns from the lake bottom (separated from the ice bottom by about 1 m of water), which could allow ice thickness to be determined indirectly. The report concludes that these antennas can be used to determine sheet ice thickness and to supply information to help in the detection of brash ice. The water content of an ice sheet may also be estimated if independent studies show a correlation between dielectric permittivity and free water content.
    Type of Medium: Series available for loan
    Pages: iv, 15 Seiten , Illustrationen
    Series Statement: CRREL Report 86-6
    Language: English
    Note: CONTENTS Abstract Preface Introduction Materials and methods Sites and site preparation Results and discussion Lake Morey Post Pond Conclusions and recommendations Literature cited
    Location: AWI Archive
    Branch Library: AWI Library
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 3
    Series available for loan
    Series available for loan
    Hanover, NH : U.S. Army Cold Regions Research and Engineering Laboratory
    Associated volumes
    Call number: ZSP-201-84/17
    In: CRREL Report, 84-17
    Description / Table of Contents: VHF-band radiowave short pulses were transmitted within the permafrost tunnel at Fox, Alaska, over distances between 2.2 and 10.5 m. The propagation medium was a frozen silt containing both disseminated and massive ice with temperatures varying from -7°C near the transmitter to probably -2 C near the center of the tunnel overburden. The short pulses underwent practically no dispersion in the coldest zones but did disperse and refract through the warmer overburden, as suggested by calculations of the effective dielectric constant. Most significantly the measured frequency content decreased as the effective dielectric constant increased. The results indicate that deep, cross-borehole pulse transmissions over distances greater than 10 m might be possible, especially when the ground is no warmer than -4°C. The information thus pined could be used for identifying major subsurface variations, including ground ice features.
    Type of Medium: Series available for loan
    Pages: ii, 14 Seiten , Illustrationen
    Series Statement: CRREL Report 84-17
    Language: English
    Location: AWI Archive
    Branch Library: AWI Library
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 4
    Series available for loan
    Series available for loan
    Hanover, NH : U.S. Army Cold Regions Research and Engineering Laboratory
    Associated volumes
    Call number: ZSP-201-85/19
    In: CRREL Report, 85-19
    Description / Table of Contents: Ground-probing radar can be an effective tool for exploring the top 10 to 20 m of ground, especially in cold regions where the freezing of water decreases signal absorption. However, the large electrical variability of the surface, combined with the short wavelengths used, can often cause severe ground clutter that can mask a desired, deeper return. In this study a model facility was constructed consisting of a metallic reflector covered by sand. Troughs of saturated sand were emplaced at the surface to vary surface electrical properties and to act as a noise source to interfere with the bottom reflections. Antenna polarization and height, and signal stacking in both static (antennas stationary) and dynamic (antennas moving) modes were then investigated as methods for reducing the surface clutter. Polarization parallel to the profile direction (perpendicular to the troughs' axes) gave profiles superior to the perpendicular case because of the directional sensitivity of the antenna radiation. Dynamic stacking greatly improved the signal-to-noise ratio because noise sources were averaged as the antennas moved, while the desired reflector, buried at constant depth, was enhanced. Raising the antennas above the surface also reduced noise because the surface area over which reflections were integrated increased. All three noise reduction techniques could be effective in surveys for reflectors at nearly constant depth such as groundwater tables or ice/water interfaces if the lateral variation in undesired ground propertiesis sufficiently random.
    Type of Medium: Series available for loan
    Pages: iv, 23 Seiten , Illustrationen
    Series Statement: CRREL Report 85-19
    Language: English
    Note: CONTENTS Abstract Preface Introduction Objective and procedures Materials and methods Subsurface radar Model facility Results Isolated disturbances-surface and raised analog profiles Multiple disturbances Discussion and conclusions Literature cited
    Location: AWI Archive
    Branch Library: AWI Library
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 5
    Series available for loan
    Series available for loan
    Hanover, NH : U.S. Army Cold Regions Research and Engineering Laboratory
    Associated volumes
    Call number: ZSP-201-82/10
    In: CRREL Report, 82-10
    Description / Table of Contents: Dielectric measurements have been performed on silt and sand samples from permafrost areas using Time Domain Reflectometry. The sample temperatures were varied from +25 °C to -25 °C, and volumetric water content was varied between oven-dry and 0.55 gH2O/cm3. The data were processed for frequencies between 0.1 and 5.0 GHz. The results show a constant K' and a low K' for frequencies up to 1 GHz. A frequency dependence seen on the data above 2 GHz is probably the result of unfrozen, adsorbed water. At moisture levels near saturation at all temperatures, these soils have excellent propagation characteristics for ground-probing radar operating below 0.3 GHz. Massive ice should be easily detectable in permafrost within a few degrees of 0 °C.
    Type of Medium: Series available for loan
    Pages: 7 Seiten , Illustrationen
    Series Statement: CRREL Report 82-10
    Language: English
    Location: AWI Archive
    Branch Library: AWI Library
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 6
    Call number: ZSP-201-79/23
    In: CRREL Report, 79-23
    Description / Table of Contents: The performance of surface impedance and magnetic induction electromagnetic subsurface exploration techniques was studied seasonally at various sites in Alaska where permafrost and massive ground ice occurred. The surface impedance method, which uses radiowaves in the LF and VLF bands, and the magnetic induction method, which uses low-frequency magnetic induction fields, distinguish subsurface materials by the electrical resistivity of the materials. The methods used have greatest sensitivity within about 20 m of the surface and are, therefore, most applicable for shallow subsurface investigations. The selection of study sites was based on anticipated contrasts in electrical resistivity between ground ice and adjacent earth materials. A magnetic induction instrument, using a separation of 3.66-m between the transmitter and receiver antennas, in general was able to detect near-surface zones of massive ice and to provide data regarding permafrost distribution in both the Fairbanks and Prudhoe Bay areas. At this antenna separation, the depth of magnetic field penetration was sufficient to include mainly the zone containing maximum contrasts in resistivity between ground ice and other earth materials. In the Fairbanks area, contrasts, in this zone were greatest in late winter when the seasonally thawed surface layer was completely frozen. When thawed, this layer usually becomes more conductive and often masks the deeper resistivity contrasts. In the Prudhoe Bay area, maximum ground resistivity contrasts were detected in late summer when shallow subsurface temperatures had risen sufficiently to permit resistivity contrasts between the massive ice and the ice-rich ground to appear.
    Type of Medium: Series available for loan
    Pages: v, 24 Seiten , Illustrationen
    Series Statement: CRREL Report 79-23
    Language: English
    Note: CONTENTS Abstract Preface Introduction Background Obiectives and procedures Ground electrical resistivity in permafrost regions Electromagnetic techniques General Magnetic induction method Surface impedance fradiowave method Direct current method General description of field sites Results Site 1 CRREL permafrost station, Fairbanks, Alaska Site 2 Planned road cut for Steese Highway near Fox, Alaska Site 3 Relic floodplain near Fairbanks, Alaska Site 4 Pingos, Prudhoe Bay, Alaska Site 5 Ice wedges, Prudhoe Bay, Alaska Comparisons between the surface impedance and magnetic induction methods Conclusions and recommendations Literature cited Appendix A. Discussion of the depth of sensitivity of the magnetic induction method using two- and three-layer apparent resistivity curves
    Location: AWI Archive
    Branch Library: AWI Library
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 7
    Series available for loan
    Series available for loan
    Hanover, NH : U.S. Army Cold Regions Research and Engineering Laboratory
    Associated volumes
    Call number: ZSP-201-82/6
    In: CRREL Report, 82-6
    Description / Table of Contents: The interpretation of continuous radar profiles requires an alternative geophysical means of obtaining ground dielectric information. Ground dielectric properties were measured using wide-angle reflection and refraction (WARR) soundings with a ground-probing radar set that transmits pulses f a few nanoseconds duration. The investigations, carried out over sandy gravel in interior Alaska, provided dielectric data to about a 5-m depth. The WARR soundings were displayed as individual traces allowing interference between separate events and dispersion to be observed, and the soundings were compared with continuous radar and resistivity profiles conducted concurrently to extract the maximum amount of dielectric information. The dielectric constants, derived mainly from the direct ground waves propagating along the surface, ranged from 2.9 to 7.4. Dielectric values interpreted for one site predicted the possibility of a refracted event which may have occurred during one of the soundings.
    Type of Medium: Series available for loan
    Pages: iii, 11 Seiten , Illustrationen
    Series Statement: CRREL Report 82-6
    Language: English
    Note: CONTENTS Abstract Preface Introduction Theory of ground wave propagation from a horizontal electric dipole Equipment and methods Results Site 1 Site 2 Site 3 Summary and concluding remarks Literature cited
    Location: AWI Archive
    Branch Library: AWI Library
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 8
    Series available for loan
    Series available for loan
    Hanover, NH : U.S. Army Cold Regions Research and Engineering Laboratory
    Associated volumes
    Call number: ZSP-201-79/15
    In: CRREL Report, 79-15
    Description / Table of Contents: This report discusses the application of several modern geophysical techniques to groundwater exploration in areas in permafrost. These methods utilize the principles of magnetic induction and radiowave surface impedance in the 10- to 400-kHz band, the techniques of impulse and side-looking radar in the 50- to 10,000-MHz band, and also some optical techniques using imagery obtained from a satellite. Low frequency case studies demonstrate the use of the techniques for detecting free water under an ice cover in shallow, almost completely frozen lake basins, and thaw zones within lake beds, stream channels, and in permafrost in general. The radar studies demonstrate the use of these techniques for determining depth of free water and ice cover thickness on lakes and rivers
    Type of Medium: Series available for loan
    Pages: iv, 30 Seiten , Illustrationen
    Series Statement: CRREL Report 79-15
    Language: English
    Note: CONTENTS Abstract Preface Introduction Part I. Low frequency resistivity methods Resistivity of earth materials Theory and description of techniques Surface impedance technique Airborne radiowave technique Magnetic induction technique Case studies Location of thaw zones beneath lakes and rivers Location of permeable materials in unfrozen ground Delineating permafrost boundaries Part II. High frequency dielectric methods Dielectric properties of earth materials Theory and description of equIpment Profiling radar Imaging radar Case studies Radar profile of a river channel Impulse radar profile of a freshwater lake SLAR imagery of Arctic lakes Literature cited Appendix A: Satellite imagery for subsurface water exploration
    Location: AWI Archive
    Branch Library: AWI Library
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 9
    Series available for loan
    Series available for loan
    Hanover, NH : U.S. Army Cold Regions Research and Engineering Laboratory
    Associated volumes
    Call number: ZSP-201-77/2
    In: CRREL Report, 77-2
    Description / Table of Contents: A computer program was developed for finding the d-c resistance to ground of two simple electrodes, a straight horizontal wire and a vertically driven rod. The objective of this study was to develop a rapid means of finding the resistance to ground of simple electrode types in arctic environments where a two-layer earth model, frozen and unfrozen ground, is applicable. The program can consider homogeneous as well as two-layer earth, and the length, diameter and position of the electrodes. The computations were performed first by dividing an electrode into several smaller segments. Next the electrostatic potential of each segment was computed at the center of the electrode for unit-applied current. The segment potentials were then summed to find the total resistance to ground. Some specific computations are presented in comparison with previous theoretical work of other authors. The following conclusions were made: 1) A maximum run time of 165 seconds is needed for all two-layer arctic models where (a) the depth of the upper layer does not exceed 10 m, (b) the vertical rod length is less than 30 m, or (c) the horizontal wire length is less than 100 m; 2) Best accuracy is obtained when rod and wire radii are less than 0.01 m; and 3) Coincidence of the center of the vertical electrode with the two-layer interface must be avoided.
    Type of Medium: Series available for loan
    Pages: iv, 16 Seiten , Illustrationen
    Series Statement: CRREL Report 77-2
    Language: English
    Location: AWI Archive
    Branch Library: AWI Library
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 10
    Call number: ZSP-201-87/17
    In: CRREL Report, 87-17
    Description / Table of Contents: The ability to map frazil ice deposits and water channels beneath an ice-covered river in central Alaska using the magnetic induction conductivity (MI) technique has been assessed. The study was performed during the first week of March of 1986 on the Tanana River near Fairbanks and employed a commercially available instrument operating at a fixed frequency with a fixed antenna (coil) spacing and orientation. Comparisons of the MI data with theoretical models based upon physical data measured along three cross sections of the river demonstrate the sensitivity of the MI technique to frazil ice deposits. The conductivity generally derived for the frazil ice deposits encountered is very low (approx. .00063 s/m) when compared with the measured value for water (approx. 0.011 S/m), and is similar to the calculated values for gravel and sandy gravel bed sediments. In all three cross sections, maxima in the apparent conductivity profiles correlated with frazil ice deposits. Difficulties, possibly due to adverse effects of cold weather upon instrument calibration, affected the quantitative performance of the instrument on one cross section, although the interpretation of the data (locations of open channels vs frazil deposits) was qualitatively unaffected.
    Type of Medium: Series available for loan
    Pages: iii, 17 Seiten , Illustrationen
    Series Statement: CRREL Report 87-17
    Language: English
    Note: CONTENTS Abstract Preface Introduction Magnetic induction conductivity method Site description and survey methods Cross section field data and modeling results X6 X3A X4 Conclusions and recommendations Literature cited Appendix A: Discussion of errors Appendix B: Modeling data
    Location: AWI Archive
    Branch Library: AWI Library
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...