1. |
Effect of Fast Neutron Bombardment on Physical Properties of Graphite: A Review of Early Work at the Metallurgical Laboratory |
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Journal of Applied Physics,
Volume 27,
Issue 6,
1956,
Page 557-567
M. Burton,
T. J. Neubert,
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摘要:
Fast neutron bombardment of artificial graphite increases the longitudinal elastic modulus and electrical resistivity and decreases the thermal conductivity. Annealing at temperatures higher than the bombardment temperature reverses the neutron‐induced property changes, but complete recovery does not occur until annealing temperatures approach 2000°C. These effects are considered to be the results of the displacement of carbon atoms from normal positions in graphite crystallites to interstitial positions and the production of lattice vacancies. The displaced atoms are trapped in a variety of metastable interstitial trapping centers and, as a result, increase the internal energy of the graphite. Annealing causes interstitial atoms to move to more stable positions, thus releasing stored energy and causing recovery of other neutron‐induced changes. Hall effect studies indicate that the neutron‐induced disturbances (interstitial atoms and clusters of atoms, and lattice vacancies) are electron traps. Data are presented and the implications of various observations are discussed.
ISSN:0021-8979
DOI:10.1063/1.1722423
出版商:AIP
年代:1956
数据来源: AIP
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2. |
Neutron‐Induced Discomposition in Graphite. II. Preliminary Studies of Elastic Modulus |
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Journal of Applied Physics,
Volume 27,
Issue 6,
1956,
Page 568-568
T. J. Neubert,
R. C. Hirt,
A. R. Van Dyken,
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ISSN:0021-8979
DOI:10.1063/1.1722425
出版商:AIP
年代:1956
数据来源: AIP
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3. |
Neutron‐Induced Discomposition in Graphite. IV. Further Studies of Elastic Modulus and Electrical Resistivity |
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Journal of Applied Physics,
Volume 27,
Issue 6,
1956,
Page 569-569
M. G. Bowman,
W. R. Burns,
R. C. Hirt,
T. J. Neubert,
A. Novick,
J. Royal,
A. R. Van Dyken,
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ISSN:0021-8979
DOI:10.1063/1.1722427
出版商:AIP
年代:1956
数据来源: AIP
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4. |
Neutron‐Induced Discomposition in Graphite. VI. Rate of Healing Experiments |
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Journal of Applied Physics,
Volume 27,
Issue 6,
1956,
Page 570-570
T. J. Neubert,
A. Novick,
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ISSN:0021-8979
DOI:10.1063/1.1722429
出版商:AIP
年代:1956
数据来源: AIP
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5. |
Neutron‐Induced Discomposition in Graphite. VIII. Increase in Internal Energy |
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Journal of Applied Physics,
Volume 27,
Issue 6,
1956,
Page 571-571
Robert Maurer,
Richard Ruder,
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ISSN:0021-8979
DOI:10.1063/1.1722431
出版商:AIP
年代:1956
数据来源: AIP
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6. |
Neutron‐Induced Discomposition in Graphite. X. Rate of Bromine Absorption |
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Journal of Applied Physics,
Volume 27,
Issue 6,
1956,
Page 572-572
A. Novick,
T. J. Neubert,
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ISSN:0021-8979
DOI:10.1063/1.1722433
出版商:AIP
年代:1956
数据来源: AIP
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7. |
Flicker Noise in Secondary Emission Tubes and Multiplier Phototubes |
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Journal of Applied Physics,
Volume 27,
Issue 6,
1956,
Page 573-577
R. C. Schwantes,
H. J. Hannam,
A. Van Der Ziel,
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摘要:
Flicker noise with a 1/ffrequency dependence has been observed in the secondary emission process. No flicker noise was observed in multiplier phototubes which means that a possible flicker noise component caused by the photoemission or secondary emission process is small in comparison with the shot noise of the tube. The secondary emission flicker noise resistance, measured for Philips EFP60 tubes, increases with increasing primary current and also increases with increasing primary energy. The results are interpreted in terms of a fluctuating work function.
ISSN:0021-8979
DOI:10.1063/1.1722434
出版商:AIP
年代:1956
数据来源: AIP
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8. |
Velocity Discontinuity Instability of a Liquid Jet |
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Journal of Applied Physics,
Volume 27,
Issue 6,
1956,
Page 577-582
B. Dunne,
B. Cassen,
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摘要:
The instability of a high‐speed liquid jet with a velocity which has a transient rise followed by a linear decay with time is studied experimentally and theoretically. The jet is produced experimentally by subjecting a liquid reservoir to a shock‐wave pressure. Using a shadowgraph technique, in an interval of thirty microseconds four successive quarter‐microsecond exposures were taken using jets of water and ethanol in external atmospheres of air and helium. It is found theoretically that a velocity discontinuity is advanced through the jet at a velocity which is the mean of the instantaneous particle velocities immediately in front of and behind the discontinuity. The discontinuity consists of a thin disk of liquid normal to the jet axis. Nodules previously observed on high‐speed liquid jets [J. Appl. Phys.25, 569 (1954)] can be explained by this mechanism.
ISSN:0021-8979
DOI:10.1063/1.1722435
出版商:AIP
年代:1956
数据来源: AIP
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9. |
Theory of Mechanical Damping Due to Dislocations |
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Journal of Applied Physics,
Volume 27,
Issue 6,
1956,
Page 583-593
A. Granato,
K. Lu¨cke,
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摘要:
A quantitative theory of damping and modulus changes due to dislocations is developed. It is found that the model used by Koehler of a pinned dislocation loop oscillating under the influence of an applied stress leads to two kinds of loss, one frequency dependent and the other not. The frequency dependent loss is found to have a maximum in the high megacycle range. The second type of loss is a hysteresis loss which proves to be independent of frequency over a wide frequency range which includes the kilocycle range. This loss has a strain‐amplitude dependence of the type observed in the kilocycle range. The theory provides a quantitative interpretation of this loss.
ISSN:0021-8979
DOI:10.1063/1.1722436
出版商:AIP
年代:1956
数据来源: AIP
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10. |
Effect of Strain on the Work Function of Polycrystalline Silver |
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Journal of Applied Physics,
Volume 27,
Issue 6,
1956,
Page 594-598
George Wallis,
H. E. Farnsworth,
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摘要:
Contact potential difference measurements in a pressure range from one atmosphere to about 10−8mm Hg have indicated that mechanically induced strain of the order of 1% (beyond elastic limit) in polycrystalline strips of silver produces an increase in work function of between 0.01 and 0.03 ev. Annealing at about 400°C for a period of ten minutes approximately restores the original value of work function. Possible explanations of the effect are discussed.
ISSN:0021-8979
DOI:10.1063/1.1722437
出版商:AIP
年代:1956
数据来源: AIP
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