11,480 research outputs found
Flight measurements of hinged-plate wing-spoiler hinge moments
Hinge moment of hinged-plate wing spoilers were measured during flight of a twin turboprop airplane modified by the addition of upper and lower wing-surface spoilers. The spoiler-actuating hydraulic cylinders were instrumented to measure the forces required to extend the spoiler panels. Those measurements were converted to moment coefficient form, and are presented as a function of spoiler deployment angle. The hinge-moment data were collected at three flight conditions: with flaps extended at approach speed; with flaps retracted at a low speed; and with flaps retracted at a high speed (C sub L = 1.4, 1.0, and 0.5). In general, the magnitude of measured spoiler hinge moments were lower than predicted. Furthermore, for upper surface spoilers with flaps extended, the hinge moments increased in a discontinuous manner between spoiler deflection 10 and 10
Nonperturbative results for the mass dependence of the QED fermion determinant
The fermion determinant in four-dimensional quantum electrodynamics in the
presence of O(2)XO(3) symmetric background gauge fields with a nonvanishing
global chiral anomaly is considered. It is shown that the leading mass
singularity of the determinant's nonperturbative part is fixed by the anomaly.
It is also shown that for a large class of such fields there is at least one
value of the fermion mass at which the determinant's nonperturbative part
reduces to its noninteracting value.Comment: This is an extended version of the author's paper in
Phys.Rev.D81(2010)10770
Feasibility of V/STOL concepts for short-haul transport aircraft
Feasibility of V/STOL concepts for short-haul transport aircraf
Low-order modeling of micro-flier impact with thin stationary energetic targets
The impact of high-speed (500-1500 m/s), laser driven micro-fliers with thin energetic targets (10-100 &# 956;m) is being examined to characterize impact-induced heating and combustion of these materials. Aluminum fliers are propelled by a laser into a thin metallic target plate having a layer of energetic material deposited on its backside. Mass spectrometry is performed in vacuo on the energetic side to interrogate the shock-induced chemistry of the energetic material. It is important to ignite and possibly detonate the energetic material without perforation of the target plate avoiding contamination of the vacuum chamber. To guide development of these experiments, a low-order (zero-dimensional) model is formulated to estimate ballistic performance for large dimensional parameter spaces in a computationally inexpensive manner. The imaging of post-impact target coupons gives insight into deformation and failure modes of the target plate. The model accounts for both the early-time system response with 1-D shock relations and the late-time response with quasi-static strength of flat plates. The model is validated against impact data for larger scale flier-target configurations, and gives predictions for micro-scale configurations. The post-impact target plates show that the system behavior is stochastic in nature. Thus, a method for propagating input uncertainty is presented to estimate the uncertainty in model output variables, and a sensitivity study is performed to highlight dependence of the system response on input parameters. Model output is most sensitive to the ratio of flier width to diameter. Predictions are performed for energetic materials including HMX (C4H8N8O8), TNT (C7H5N3O6), and PETN (C5H8N4O12) over the initial flier velocity - flier thickness parametric plane for given target thicknesses to produce ballistic initiation maps to identify configurations for which initiation of energetic material may occur without perforation of the target plate. Because of the high critical shock initiation energy of HMX (150 J/cm2) and TNT (77 J/cm2), it is difficult to identify micro configurations that result in initiation. However, such configurations were found for PETN which has a lower critical shock energy (5.03 J/cm2). The area of the region for initiation increases with increasing target thickness for these configurations
You Can\u27t Have Your Cake and Eat It Too: Accord and Satisfaction Survives the Uniform Commercial Code
Flight investigation of methods for implementing noise-abatement landing approaches
Flight tests and simulation of steep noise reducing landing approaches with jet transpor
QED in strong, finite-flux magnetic fields
Lower bounds are placed on the fermionic determinants of Euclidean quantum
electrodynamics in two and four dimensions in the presence of a smooth,
finite-flux, static, unidirectional magnetic field , where
or , and is a point in the xy-plane.Comment: 10 pages, postscript (in uuencoded compressed tar file
Chern-Simons action for zero-mode supporting gauge fields in three dimensions
Recent results on zero modes of the Abelian Dirac operator in three
dimensions support to some degree the conjecture that the Chern-Simons action
admits only certain quantized values for gauge fields that lead to zero modes
of the corresponding Dirac operator. Here we show that this conjecture is wrong
by constructing an explicit counter-example.Comment: version as published in PRD, minor change
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