20,830 research outputs found
Direct measurements and analysis of skin friction and cooling downstream of multiple flush-slot injection into a turbulent Mach 6 boundary layer
Experiments were conducted to determine the reduction in surface skin friction and the effectiveness of surface cooling downstream of one to four successive flush slots injecting cold air at an angle of 10 deg into a turbulent Mach 6 boundary layer. Data were obtained by direct measurement of surface shear and equilibrium temperatures, respectively. Increasing the number of slots decreased the skin friction, but the incremental improvement in skin-friction reduction decreased as the number of slots was increased. Cooling effectiveness was found to improve, for a given total mass injection, as the number of slots was increased from one to four. Comparison with previously reported step-slot data, however, indicated that step slots with tangential injection are more effective for both reducing skin friction and cooling than the present flush-slot configuration. Finite-difference predictions are in reasonable agreement with skin-friction data and with boundary-layer profile data
Wind Tunnel Test of Low Boom Equivalent Body at Mach 4
A body of revolution, representing the equivalent area distribution of a low boom aircraft design cruising at 24,384 meters at a Mach number of 4, was tested to determine whether its theoretical sonic boom characteristics could be experimentally verified. Results indicate that the essential features of the ground signature are well predicted
Burrowing apparatus
A soil burrowing mole is described in which a housing has an auger blade wound around a front portion. This portion is rotatable about a housing longitudinal axis relative to an externally finned housing rear portion upon operation of driving means to cause an advance through soil and the like. The housing carries a sensor sensitive to deviation from a predetermined path and to which is coupled means for steering the housing to maintain the path
UK Soils: their phosphorus sorption capacity and potential for P removal from sewage effluents in emergent hydrophyte treatment systems
Stripping of Acacia koa Bark by Rats on Hawaii and Maui
Koa (Acacia koa) is the most valuable native timber species in
Hawaii. Bark stripping of young trees by rats, a common but unstudied phenomenon,
may affect survival, growth, and quality of koa. Up to 54% of the trees
sampled in 4- to 6-year-old stands in the Laupahoehoe and Waiakea areas on
Hawaii were wounded by rats; only 5% of trees sampled in a l-year-old stand on
Borge Ridge, Maui, were wounded. Wounds were generally long and narrow.
Complete girdling was not observed, and direct mortality seemed low. However,
indirect effects of damage-deformation of stems, infection by pathogens, and
premature death-require further study. Because only young trees seem susceptible
to bark stripping, rodent control may be desirable during the first 5 years
of koa stand growth
Conditions for CP-Violation in the General Two-Higgs-Doublet Model
The most general Higgs potential of the two-Higgs-doublet model (2HDM)
contains three squared-mass parameters and seven quartic self-coupling
parameters. Among these, one squared-mass parameter and three quartic coupling
parameters are potentially complex. The Higgs potential explicitly violates CP
symmetry if and only if no choice of basis exists in the two-dimensional Higgs
``flavor'' space in which all the Higgs potential parameters are real. We
exhibit four independent potentially complex invariant (basis-independent)
combinations of mass and coupling parameters and show that the reality of all
four invariants provides the necessary and sufficient conditions for an
explicitly CP-conserving 2HDM scalar potential. Additional potentially complex
invariants can be constructed that depend on the Higgs field vacuum expectation
values (vevs). We demonstrate how these can be used together with the
vev-independent invariants to distinguish between explicit and spontaneous
CP-violation in the Higgs sector.Comment: 46 pages, minor typographical errors corrected, accepted for
publication in Phys. Rev.
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