3,168 research outputs found
Effect of Target Thickness on Cratering and Penetration of Projectiles Impacting at Velocities to 13,000 Feet Per Second
In order to determine the effects of target thickness on the penetration and cratering of a target resulting from impacts by high-velocity projectiles, a series of experimental tests have been run. The projectile-target material combinations investigated were aluminum projectiles impacting aluminum targets and steel projectiles impacting aluminum and copper targets. The velocity spectrum ranged from 4,000 ft/sec to 13,000 ft/sec. It has been found that the penetration is a function of target thickness provided that the penetration is greater than 20 percent of the target thickness. Targets of a thickness such that the penetration amounts to less than 20 percent of the thickness may be regarded as quasi-infinite. An empirical formula has been established relating the penetration to the target thickness and to the penetration of a projectile of the same mass, configuration, and velocity into a quasi- infinite target. In particular, it has been found that a projectile can completely penetrate a target whose thickness is approximately one and one-half times as great as the penetration of a similar projectile into a quasi-infinite target. The diameter of a crater has also been found to be a function of the target thickness provided that the target thickness is not greater than the projectile length in the case of cylindrical projectiles and not greater than two to three times the projectile diameter in the case of spherical projectiles
Suppression of Giant Magnetoresistance by a superconducting contact
We predict that current perpendicular to the plane (CPP) giant
magnetoresistance (GMR) in a phase-coherent magnetic multilayer is suppressed
when one of the contacts is superconducting. This is a consequence of a
superconductivity-induced magneto-resistive (SMR) effect, whereby the
conductance of the ferromagnetically aligned state is drastically reduced by
superconductivity. To demonstrate this effect, we compute the GMR ratio of
clean (Cu/Co)_nCu and (Cu/Co)_nPb multilayers, described by an ab-initio spd
tight binding Hamiltonian. By analyzing a simpler model with two orbitals per
site, we also show that the suppression survives in the presence of elastic
scattering by impurities.Comment: 5 pages, 4 figures. Submitted to PR
Effective range function below threshold
We demonstrate that the kernel of the Lippmann-Schwinger equation, associated
with interactions consisting of a sum of the Coulomb plus a short range nuclear
potential, below threshold becomes degenerate. Taking advantage of this fact,
we present a simple method of calculating the effective range function for
negative energies. This may be useful in practice since the effective range
expansion extrapolated to threshold allows to extract low-energy scattering
parameters: the Coulomb-modified scattering length and the effective range.Comment: 14 pages, 1 figur
Non-BPS D-brane Near NS5-branes
We use tachyon field theory effective action to study the dynamics of a
non-BPS Dp-brane propagating in the vicinity of k NS5-branes. For the time
dependent tachyon condensation we will concentrate on the case of the large
tachyon and the case when a non-BPS D-brane is close to NS5-branes. For spatial
dependent tachyon condensation we will argue that the problem reduces to the
study of the motion of an array of D(p-1)-branes and D(p-1)-antibranes in the
vicinity of k NS5-branes.Comment: 21 page
Recommended from our members
1966
Proper Watering by Earl P. Grey (page 1) Soil Structure and Plant Feeding for Trees and Shrubs on the Golf Course by William Teece (2) Power Golf Carts: A Blessing or a Curse by David Dunlavey (3) A Comparison by Paul White (3) Trees on a Golf Course by Oliver Leech (5) Turf Management Majors Want a Golf Team by Richard Rossiter (6) Class Will of \u2766 (7)Famous Last Words from 1966 (8) Turf Heating with Electric Cables by J.R. Barrett, Jr. and W.H. Daniel (A-1) Poa Annua Restriction by C. F. Kerr and W.H. Daniel (A-9) Phosphorus by Marvin H. Ferguson (A-14) Role of Potassium in Turf Grass management by R. E. Wagner (A-16) Role of Minor Elements in Turfgrass Management by Alexander Radko (A-22) Rhizoctonia Brown patch and Pythium Diseas by Malcolm C. Shurtleff (A-27) Sclerotinia Dollar Spot and Snow Mold by Noel Jackson (A-32) Fusarium Blight - Disease of Turf Grasses by George A. Bean (A-35) Observing the Weather - Old and New Techniques by Robert C. Copeland (A-39) Water Supply by Allan Grieve Jr. (A-41) Establishment and Maintenance of Campus Turf by William A. Lambert (A-51) Athletic Field Management by J. T. Williams (A-56
On the worldsheet theory of the type IIA AdS(4) x CP(3) superstring
We perform a detailed study of the type IIA superstring in AdS(4) x CP(3).
After introducing suitable bosonic light-cone and fermionic kappa worldsheet
gauges we derive the pure boson and fermion SU(2|2) x U(1) covariant light-cone
Hamiltonian up to quartic order in fields.
As a first application of our derivation we calculate energy shifts for
string configurations in a closed fermionic subsector and successfully match
these with a set of light-cone Bethe equations. We then turn to investigate the
mismatch between the degrees of freedom of scattering states and oscillatory
string modes. Since only light string modes appear as fundamental Bethe roots
in the scattering theory, the physical role of the remaining massive
oscillators is rather unclear. By continuing a line of research initiated by
Zarembo, we shed light on this question by calculating quantum corrections for
the propagators of the bosonic massive fields. We show that, once loop
corrections are incorporated, the massive coordinates dissolve in a continuum
state of two light particles.Comment: 40 pages, 2 figures. v3: Minor clarifications made and reference list
updated. Published version
Andreev Reflection in Ferromagnet/Superconductor/Ferromagnet Double Junction Systems
We present a theory of Andreev reflection in a
ferromagnet/superconductor/ferromagnet double junction system. The spin
polarized quasiparticles penetrate to the superconductor in the range of
penetration depth from the interface by the Andreev reflection. When the
thickness of the superconductor is comparable to or smaller than the
penetration depth, the spin polarized quasiparticles pass through the
superconductor and therefore the electric current depends on the relative
orientation of magnetizations of the ferromagnets. The dependences of the
magnetoresistance on the thickness of the superconductor, temperature, the
exchange field of the ferromagnets and the height of the interfacial barriers
are analyzed. Our theory explains recent experimental results well.Comment: 8 pages, 9 figures, submitted to Phys. Rev.
Geometrical Tachyon Kinks and NS5 Branes
We further investigate the 5 ring background using the tachyon map.
Mapping the radion fields to the rolling tachyon helps to explain the motion of
a probe -brane in this background. It turns out that the radion field
becomes tachyonic when the brane is confined to one dimensional motion inside
the ring. We find explicit solutions for the geometrical tachyon field that
describe stable kink solutions which are similar to those of the open string
tachyon. Interestingly in the case of the geometric tachyon, the dynamics is
controlled by a cosine potential. In addition, we couple a constant electric
field to the probe-brane, but find that the only stable kink solutions occur
when there is zero electric field or a critical field value. We also
investigate the behaviour of Non-BPS branes in this background, and find that
the end state of any probe brane is that of tachyonic matter 'trapped' around
the interior of the ring. We conclude by considering compactification of the
ring solution in one of the transverse directions.Comment: Latex, 24 pages, 1 eps fig; clarifying comments added to Section 2;
typos correcte
Blueberry Advisory Committee Research Report
The 1987 edition of the Blueberry Advisory Committee Research Reports was prepared for the Maine Wild Blueberry Commission and the University of Maine Wild Blueberry Advisory Committee by researchers with the Maine Agricultural Experiment Station and Maine Cooperative Extension Service at the University of Maine, Orono. Projects in this report include:
1. Effect of Pruning Practices on Blueberry Insect Abundance
2. Economic Thresholds and Control of Secondary Blueberry Pests
3. Control of Blueberry Maggot
4. Evaluation of Fungicides for Control of Botrytis Blight on Lowbush Blueberry, 1987
5. Evaluation of Fungicides for Control of Mummy Berry on Lowbush Blueberry, 1987
6. Miscellaneous Activity: a) Fungicide Residue Analysis b) Blueberry fact sheet c) Berry contamination
7. Effects of Pruning Methods on Mummy Berry Disease Incidence, 1987
8. Effects of Pruning Methods on Powdery Mildew and Red Leaf Disease Incidence, 1987
9. Nutrition Survey 1987
10. Nutritional Responses of Seedlings
11. The Effect of Several Mulches on Frost Heaving, Soil Moisture, Soil Temperature and Rhizome Development
12. Time-temperature Effects on Sugar Migration and Physical Characterization in Lowbush Blueberries
13. Fabricated Blueberry Raisins Prepared from Puree using Alginate as the Gelling Agent
14. Blueberry Gelatin
15. Effect of Hexazinone (VELPAR) on Species Distribution in Lowbush Blueberry Fields
16. Evaluation of Postemergence Herbicides for Grass Control
17. Evaluation of Sulfonyl urea and Imidazoline compounds for Bunchberry Control
18. Use of Mechanical wiper with glyphosate (ROUNDUP) or dicamba for control of dogbane
19. Integrated Weed Management
20. Evaluation of Five Preemergence Herbicides for Control of Oat grass and Bunchgrass
21. Wiper Application of Dicamba for Woody Weed control
22. Hexazinone (VELPAR) and terbacil (SINBAR) combinations for weed control
23. Evaluation of Clopyralid and Lactofen for Bunchberry Control
24. Evaluation of Postemergence Applications of chlorimuron for Bunchberry Control
25. Hexazinone seedling study
26. Seedling Pruning Study
27. Effect of bracken fern on blueberry yield
28. Evaluation of two mechanical harvesters vs hand raking of lowbush blueberrie
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