Acoustic performance of two 1.83-meter-diameter fans designed for a wind-tunnel drive system

A parametric study was made of the noise generated by two 1.83-m (6-ft) diameter fans operating up to a maximum pressure ratio of 1.03. One fan had 15 rotor blades, 23 stator blades, and a maximum rotational speed of 1200 rpm. The other fan had 9 rotor blades, 13 stator blades, and a maximum speed of 2,000 rpm. The fans were approximately 1/7-scale models of the 12.2-m (40-ft) diameter fans proposed for repowering the NASA-Ames 40- by 80 foot wind tunnel. The fans were operated individually in a 23.8-m (78-ft) long duct. Sound pressure levels in the duct were used to determine radiated acoustic power as fan speed, blade angle, and mass flow were varied. Results show that the low speed fan was slightly quieter than the high speed fan and, when scaled to full scale, would be 16 db quieter than the present wind tunnel fans. The fan noise varied directly with thrust regardless of whether thrust was varied by rotational speed or blade setting for the ranges studied

The Kahler Structure of Supersymmetric Holographic RG Flows

We study the metrics on the families of moduli spaces arising from probing with a brane the ten and eleven dimensional supergravity solutions corresponding to renormalisation group flows of supersymmetric large n gauge theory. In comparing the geometry to the physics of the dual gauge theory, it is important to identify appropriate coordinates, and starting with the case of SU(n) gauge theories flowing from N=4 to N=1 via a mass term, we demonstrate that the metric is Kahler, and solve for the Kahler potential everywhere along the flow. We show that the asymptotic form of the Kahler potential, and hence the peculiar conical form of the metric, follows from special properties of the gauge theory. Furthermore, we find the analogous Kahler structure for the N=4 preserving Coulomb branch flows, and for an N=2 flow. In addition, we establish similar properties for two eleven dimensional flow geometries recently presented in the literature, one of which has a deformation of the conifold as its moduli space. In all of these cases, we notice that the Kahler potential appears to satisfy a simple universal differential equation. We prove that this equation arises for all purely Coulomb branch flows dual to both ten and eleven dimensional geometries, and conjecture that the equation holds much more generally.Comment: 26 pages. Late

Unexpected nucleophilic participation and rearrangement of DBU in reactions with saccharin derivatives

DBU attacks saccharin derivatives with subsequent rearrangement to give rise to 3-[3'-(1"-azepin-2"-onyl)propylamino]-1,2-benzisothiazole-1,1-dioxide 2 after work-up

Planar Two-Loop Five-Parton Amplitudes from Numerical Unitarity

We compute a complete set of independent leading-color two-loop five-parton amplitudes in QCD. These constitute a fundamental ingredient for the next-to-next-to-leading order QCD corrections to three-jet production at hadron colliders. We show how to consistently consider helicity amplitudes with external fermions in dimensional regularization, allowing the application of a numerical variant of the unitarity approach. Amplitudes are computed by exploiting a decomposition of the integrand into master and surface terms that is independent of the parton type. Master integral coefficients are numerically computed in either finite-field or floating-point arithmetic and combined with known analytic master integrals. We recompute two-loop leading-color four-parton amplitudes as a check of our implementation. Results are presented for all independent four- and five-parton processes including contributions with massless closed fermion loops.Comment: v3: corrected wrong signs for five-gluon $N_f^2$ amplitudes with vanishing tree

Definition of a resistojet control system for the Manned Orbital Research Laboratory. Volume 5 - Resistojet design and Development Final report

Resistojet design and development for Manned Orbital Research Laborator

Thermal Evolution and Light Curves of Young Bare Strange Stars

The cooling of a young bare strange star is studied numerically by solving the equations of energy conservation and heat transport for both normal and superconducting strange quark matter inside the star. We show that the thermal luminosity from the strange star surface, due to both photon emission and e+e- pair production, may be orders of magnitude higher than the Eddington limit, for about one day for normal quark matter but possibly for up to a hundred years for superconducting quark matter, while the maximum of the photon spectrum is in hard X-rays with a mean energy of ~ 100 keV or even more. This differs both qualitatively and quantitatively from the photon emission from young neutron stars and provides a definite observational signature for bare strange stars. It is shown that the energy gap of superconducting strange quark matter may be estimated from the light curves if it is in the range from ~ 0.5 MeV to a few MeV.Comment: Ref [10] added and abstract shortened. 4 pages, 3 figures, revtex4. To be published in Phys. Rev. Letter

Feasibility of Fused Deposition of Ceramics with Zirconia and Acrylic Binder

Processing of ceramics has always been difficult due to how hard and brittle the material is. Fused Deposition of Ceramics (FDC) is a method of additive manufacturing which allows ceramic parts to be built layer by layer, abetting more complex geometries and avoiding the potential to fracture seen with processes such as grinding and milling. In the process of FDC, a polymeric binder system is mixed with ceramic powder for the printing of the part and then burned out to leave a fully ceramic part. This experiment investigates a new combination of materials, zirconia and acrylic binder, optimizing the process of making the material into a filament conducive to the printer system and then performing trials with the filament in the printer to assess its feasibility. Statistical analysis was used to determine optimal parameter levels using response surface methodology to pinpoint the material composition and temperature yielding the highest quality filament. It was discovered that although the mixture had adequate melting characteristics to be liquefied and printed into a part, the binder system did not provide the stiffness required to act as a piston to be fed through the printer head. Further studies should be completed continuing the investigation of zirconia and acrylic binder, but with added components to increase strength and rigidity of the filament

Definition of a resistojet control system for the manned orbital research laboratory. Addendum to volume 5 - 720 hour resistojet life test Final report

Life test data for resistojet thrustors operating with ammonia or hydroge