Turbulence characteristics from minisodar data

Vertical profiles of atmospheric turbulence characteristics, including spatial and temporal longitudinal and transverse velocity structure functions, velocity structure characteristics, and turbulent kinetic energy dissipation rates retrieved from time series of vertical profiles of the wind velocity vector measured with a minisodar operating at a frequency of 4900 Hz are presented. It is established that the structure functions first increase with the separation distance between the observation points and then are saturated; moreover, the longitudinal structure function is much greater than the transverse one, which is in agreement with the data available from the literature. The velocity structure characteristic is well described by the z^−2/3 altitude dependence predicted theoretically. Calculated values of the turbulent energy dissipation rate are in agreement with the data available from the literature.     

High resolution prompt (n,γ) spectroscopy using a down hole logging tool

A down-hole logging tool is described utilising a 5 Ci²⁴¹Am–Be neutron source and intrinsic germanium gamma-ray detector. The tool was used to measure the prompt gamma-ray response from the irradiation of 4 well characterised coal samples. The correlation between the count-rate into the 2380 keV line arising from sulphur and the sulphur concentration as determined by chemical analysis is described. A depression in the count rate into the sulphur peak of interest is modelled using the neutron transport code ANISN and compares well with measurement. The influence of borehole diameter and the presence of borehole fluid upon logging performance is assessed.     

A gradient projection method for solving continuous games

This paper develops a procedure for numerically solving continuous games (and also matrix games) using a gradient projection method in a general Hilbert space setting. First, we analyze the symmetric case. Our approach is to introduce a functional which measures how far a strategy deviates from giving zero value (i.e., how near the strategy is to being optimal). We then incorporate this functional into a nonlinear optimization problem with constraints and solve this problem using the gradient projection algorithm. The convergence is studied via the corresponding steepest-descent differential equation. The differential equation is a nonlinear initial-value problem in a Hilbert space; thus, we include a proof of existence and uniqueness of its solution. Finally, nonsymmetric games are handled using the symmetrization techniques of Ref. 1.     

Synthesis of 1,2-disubstituted-3-alkylidenylpyrrolidines via a one-pot three-component reaction

Olsson’s three-component reaction of cyclopropylketones, aldehydes, and primary amines was investigated for application to parallel synthesis. Using an excess of Et₂AlI at elevated temperatures, pyrrolidines 4, the initial products reported by Olsson and co-workers, could be completely converted to pyrrolium salts 5, by a reaction sequence involving a retro-aza-Michael addition followed by iminium salt formation. The pyrrolium salts 5 were then cleanly reduced in situ by NaBH(OAc)₃ to give 3-alkylidenylpyrrolidines 6. In summary, this one-pot three-component reaction provided an efficient synthetic route to 3-alkylidenylpyrrolidines.     

Observation of a hybrid spin resonance

A new type of spin depolarization resonance has been observed at the Brookhaven Alternating Gradient Synchrotron (AGS). This spin resonance is identified as a strong closed-orbit sideband around the dominant intrinsic spin resonance. The strength of the resonance was proportional to the 9th harmonic component of the horizontal closed orbit and proportional to the vertical betatron oscillation amplitude. This "hybrid" spin resonance cannot be overcome by the partial snake at the AGS, but it can be corrected by the harmonic orbit correctors.     

Wide range stress-intensity-factor expression for an edge-cracked round bar bend specimen

An edge-cracked round bar was analyzed for use as a fracture-mechanics test specimen. Shallow and deep crack limit solutions were developed and combined with experimental and numerical results to obtain aK expression which applies for all crack depths. Specimen and loading geometries were suggested for standardized fracturemechanics tests using a round bar. was Visiting Scientist     

Fracture analysis of thick-wall cylinder pressure vessels

Fracture mechanics analysis of cylindrical pressure vessels is described in a brief fracture case study. Also included are additional examples of crack growth in pressure vessels and cannons. The case study is of an early brittle failure and subsequent redesign of a cannon tube. Fracture mechanics test methods are described which were developed specifically for testing of cylindrical geometries. Three examples of current fracture analysis of cylindrical pressure vessels are presented. Fast fracture of a vessel is described, including effects of tension residual stress and crack shape. Evidence of environmentally assisted fracture of a cannon tube is presented. Fatigue crack growth and life calculation methods for cylindrical pressure vessels are discussed including effects of compressive residual stress due to overstrain.     

Observing the geometry of warped compactification via cosmic inflation

Using Dirac-Born-Infeld inflation as an example, we demonstrate that the detailed geometry of warped compactification can leave an imprint on the cosmic microwave background. We compute cosmic microwave background observables for Dirac-Born-Infeld inflation in a generic class of warped throats and find that the results (such as the sign of the tilt of the scalar perturbations and its running) depend sensitively on the precise shape of the warp factor. In particular, we analyze the warped deformed conifold and find that the results can differ from those of other warped geometries, even when these geometries approximate well the exact metric of the warped deformed conifold.