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  • Hanover, NH : U.S. Army Cold Regions Research and Engineering Laboratory  (7)
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  • 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-201-82/7
    In: CRREL Report, 82-7
    In: Charged dislocation in ice, II.
    Description / Table of Contents: The contribution of electrically charged dislocation motion to dielectric relaxation was studied theoretically. Experimentally obtained data on charge density, dislocation density, and segment length and distribution described in Part I of this series were used to calculate dielectric relaxation spectra. The results indicate that the charged dislocation process can produce the observed audio frequency dielectric relaxation as well as the distribution of spectra.
    Type of Medium: Series available for loan
    Pages: iii, 15 Seiten , Illustrationen
    Series Statement: CRREL Report 82-7
    Language: English
    Note: CONTENTS Abstract Preface Introduction Theoretical development of dielectric relaxation due to charged dislocations Numerical calculations for distributed segment length Discussion Conclusions Literature cited Appendix A. Mosotti type catastrophe by charged dislocation processes
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  • 2
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    Series available for loan
    Hanover, NH : U.S. Army Cold Regions Research and Engineering Laboratory
    Associated volumes
    Call number: ZSP-201-79/25
    In: CRREL Report, 79-25
    In: Charged dislocation in ice, I.
    Description / Table of Contents: The motion of dislocations in single crystal ice under an electric field was observed by using X-ray topographic methods. Electric charge density on these dislocations was deduced from the amplitude and length of the dislocation segment under the known AC electrical field. The most likely linear charge density was about +5x10^-11 c/m, although considerable variation is possible depending on the effective field acting on the dislocation lines.
    Type of Medium: Series available for loan
    Pages: iii, 12 Seiten , Illustrationen
    Series Statement: CRREL Report 79-25
    Language: English
    Note: CONTENTS Abstract Preface Introduction Theory Experimental apparatus and procedure Results Discussion Concluding remarks Selected bibliography Appendix A. Mosotti type field on core of cylindrical cavity
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  • 3
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    Series available for loan
    Hanover, NH : U.S. Army Cold Regions Research and Engineering Laboratory
    Associated volumes
    Call number: ZSP-201-84/12
    In: CRREL Report, 84-12
    Description / Table of Contents: Icing on stationary structures such as oil rigs is becoming an increasingly serious problem as offshore drilling operations in the subpolar regions become more common. Little information exists on this subject. Extensive observations have been made of icing on the upper structures of moving ships, but the complexity of this problem makes analysis of the results very difficult. Even the generation of water drops in this case involves many factors, such as windspeed, wave direction relative to the bearing of the ship, and size and free-board of the ship. On stationary structures, however, the problem is much simpler, since the major factor in drop generation is whitecaps produced by wind, and no motion of the structure is involved. In the present study, a theoretical calculation was made by combining the data available on the generation of drops by wind with data on the proportion of ice frozen from the collected water. The rate of ice accumulation on stationary structures was calculated using published data. The results were compared with icing measured on board ships. Although the general trend of this calculation indicated parallelism with the onboard measurements, the measured ice accumulation rate on ships needed a 5 to 8 m/s higher windspeed to correspond with the calculated rate for stationary structures.
    Type of Medium: Series available for loan
    Pages: ii, 13 Seiten , Illustrationen
    Series Statement: CRREL Report 84-12
    Language: English
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  • 4
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    Series available for loan
    Hanover, NH : U.S. Army Cold Regions Research and Engineering Laboratory
    Associated volumes
    Call number: ZSP-201-86/10
    In: CRREL Report, 86-10
    Description / Table of Contents: Icing of a four-bladed rotor was studied under natural conditions at the top of Mt. Washington, N.H. The rotor had two cylindrical blades and two airfoil blades. The results were compared with studies conducted in icing wind tunnels. Considerable differences in icing regimes were observed. For instance, with comparable liquid water content and wind speed the wet-to-dry growth regime transition temperature was up to 10 C higher under natural conditions than in the wind tunnel studies. Results of other studies made under natural conditions were close to those of the present study, indicating that wind tunnel conditions are significantly different from natural conditions. Close examination of the conditions indicated that supersaturation of water vapor existing in most of the wind tunnel studies is the most probable cause of the differences.
    Type of Medium: Series available for loan
    Pages: v, 68 Seiten , Illustrationen
    Series Statement: CRREL Report 86-10
    Language: English
    Note: CONTENTS Abstract Preface Introduction Site weather Site selection Equipment Rotor Data logger Rotoscope Laser profile camera Thin section preparation Run procedure Sample collection and shutdown Dry runs and static runs Results and discussion Wet-to-dry growth regime transition Stagnation line icing rate Icing rate on cylindrical and airfoil blades Liquid water content vs stagnation line icing rate Droplet capture efficiency index Temperature rise Morphological and crystallographic aspects Summary and conclusion Literature cited Appendix A: Chronology of events .. Appendix B: Narrative description of icing runs Appendix C: Weather summary sheets for test days Appendix D: Signal conditioner circuit diagram and sample printout
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  • 5
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    Series available for loan
    Hanover, NH : U.S. Army Cold Regions Research and Engineering Laboratory
    Associated volumes
    Call number: ZSP-201-80/13
    In: CRREL Report, 80-13
    Description / Table of Contents: Specimens prepared from various types of ice without introducing excessive defects were tested at temperatures ranging from -2° to -190°C. These tests indicated slightly higher Charpy values at lower temperatures and in more highly dispersed material concentrations. Three modes of fracture occurred during testing. Depending on the temperature and the material composition, either of the first two modes, normal fracture or multiple fracture, will appear and will show a normal frequency distribution of Charpy values in each type of ice. The third mode, fracture from both ends,which frequently occurred in the NH4F doped ice, gave Charpy values two to five times higher than the mean value for normal fracture. It can, therefore, be concluded that certain types of doping can alter the mode of fracture, through which drastic modifications of impact resistance my be possible.
    Type of Medium: Series available for loan
    Pages: iii, 13 Seiten , Illustrationen
    Series Statement: CRREL Report 80-13
    Language: English
    Note: Contents Abstract Preface lntroduction Experimental Sample preparation Testing procedure Results General features Commercial Ice Notched commercial ice Sanded commercial ice Pure ice Single crystal ice Snow-ice Colloidal alumina-dispersed ice Colloidal silica.dispersed ice NH4F doped ice HF doped ice Discussion Literature cited
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  • 6
    Series available for loan
    Series available for loan
    Hanover, NH : U.S. Army Cold Regions Research and Engineering Laboratory
    Associated volumes
    Call number: ZSP-201-89/14
    In: CRREL Report, 89-14
    Description / Table of Contents: The effects of runner material and surface conditions on the friction between runners and ice were studied. A model sled was pushed over a 6-m-long ice sheet and the reduction of speed of the sliding sled was measured. The friction calculated by the reduction of speed between two gates indicated that smooth runners showed lower friction at around -1°C than at around -10°C, as expected, but the friction of rough runners showed little temperature dependence. The lower thermally conductive runners showed lower friction than higher thermally conductive smooth runners as the theory predicted, but such effects were obscured on rougher runners.
    Type of Medium: Series available for loan
    Pages: iii, 23 Seiten , Illustrationen
    Series Statement: CRREL Report 89-14
    Language: English
    Note: CONTENTS Preface Introduction Apparatus and procedures General approach Sled design Sled propulsion Ice sheet preparation Experimental procedure Results General remarks Effect of runner temperature Effect of runner surface Effect of ice surface conditions Effect of velocity Effect of runner materials Observations of replicate surfaces Statistical analysis Discussion Molecular interactions Mechanical deformations Thermal energy dissipation Hydrodynamidc processes Comparison of energy loss mechanisms Summary and conclusions Literature cited
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  • 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-201-83/26
    In: CRREL Report, 83-26
    Description / Table of Contents: Ice accreted on high-speed rotors operating in supercooled fog can be thrown off by centrifugal force, creating severe unbalance and dangerous projectiles. A simple force balance analysis indicates that the strength of accreted ice and its adhesive strength can be obtained by measuring the thickness of the accretion, the location of the separation, the rotor speed, and the density. Such an analysis was applied to field and laboratory observations of self-shedding events. The results agree reasonably well with other observations.
    Type of Medium: Series available for loan
    Pages: 13 Seiten , Illustrationen
    Series Statement: CRREL Report 83-26
    Language: English
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