Ideal Temperature Rise Due to Constant-pressure Combustion of a JP-4 Fuel

The ideal temperature rise due to the constant-pressure combustion of a methylene (CH sub 2) fuel was calculated. CH sub 2 fuel closely approximates MIL-F-5624 grade JP-4 fuel presently used in most turbojet and ram-jet engines. Charts are presented from which the ideal temperature rise or the ideal quantity of fuel required to obtain a specified combustion temperature may be obtained for any flight condition likely to be encountered with turbojet or ram-jet engines using this fuel. The charts are applicable only to a fuel having a hydrogen-carbon mass ratio of 0.168. They include a range of fuel-air ratios from 0 to 1.2 fraction of stoichiometric fuel-air ratio with dissociation taken into account, inlet-air temperatures from 400 degrees to 1600 degrees R, and combustion pressures from 1/16 to 64 atmospheres. The use of the charts is illustrated by several examples

Effect of variable-position inlet guide vanes and interstage bleed on compressor performance of a high-pressure-ratio turbojet engine

Increased guide-vane turning resulted in poorer overall performance, the decrease being greatest at the highest rotor speed. Rotating stall originating at the tips of the first stage correlated with the knee in the stall-limit line. Increasing guide-vane turning shifted the first-stage stall-free performance and the knee in the stall-limit line to a lower engine speed. Opening the interstage bleed reduced the minimum rotor speed at which stall-free performance of the first stage was possible and tended to eliminate the knee in the stall-limit line

A meta-analysis of randomised controlled trials of physical activity in people with Alzheimer's disease and mild cognitive impairment with a comparison to donepezil

OBJECTIVES: Physical exercise may benefit people with Alzheimer's disease (AD) and mild cognitive impairment (MCI). However, randomised controlled trials (RCTs) of exercise have shown conflicting findings and it is unclear if positive outcomes are comparable to a commonly used cholinesterase inhibitor, donepezil. METHODS: Embase, Medline, PsycINFO, PsycARTICLES, SCOPUS were searched for RCTs of physical activity compared to a control condition, and donepezil compared to placebo in people with AD and MCI. Effect sizes were calculated from pre- and post-MMSE and ADAS-Cog scores and pooled using a random effects meta-analysis. RESULTS: Ninteen RCTs were included in the exercise meta-analysis (AD, N = 524; MCI, N = 1269). Physical exercise improved MMSE scores in AD (Hedges' g = 0.46) and MCI groups (g = 0.63). For the MCI group, exercise appeared to have a stronger effect for those with lower MMSE scores at baseline (p = 0.022). 18 RCTs were included in the donepezil meta-analysis (AD, N = 2984, MCI, N = 1559). In people with AD, donepezil improved cognition (MMSE g = 0.23; ADAS-Cog, g = −0.17) but there was no evidence of improved cognition in MCI. CONCLUSIONS: Physical exercise improved cognition in both AD and MCI groups. Where comparisons were possible, the effect size for physical exercise was generally comparable to donepezil. These results strengthen the evidence base for exercise as an effective intervention in AD and MCI, and future clinical trials should examine exercise type, intensity and frequency, in addition to cholinesterase inhibitors to determine the most effective interventions for AD and MCI

Comparison of locked-rotor and windmilling drag characteristics of an axial-flow-compressor type turbojet engine

The internal drag of an axial-flow turbojet engine with the rotor locked in place to prevent windmilling and with the engine windmilling was obtained over a range of simulated Mach numbers. The corrected internal drag of the engine with the locked rotor was 210 pounds or only 46 percent of the windmilling drag at a flight Mach number of 0.8

Temperature scaling in a dense vibro-fluidised granular material

The leading order "temperature" of a dense two dimensional granular material fluidised by external vibrations is determined. An asymptotic solution is obtained where the particles are considered to be elastic in the leading approximation. The velocity distribution is a Maxwell-Boltzmann distribution in the leading approximation. The density profile is determined by solving the momentum balance equation in the vertical direction, where the relation between the pressure and density is provided by the virial equation of state. The predictions of the present analysis show good agreement with simulation results at higher densities where theories for a dilute vibrated granular material, with the pressure-density relation provided by the ideal gas law, are in error. The theory also predicts the scaling relations of the total dissipation in the bed reported by McNamara and Luding (PRE v 58, p 813).Comment: ReVTeX (psfrag), 5 pages, 5 figures, Submitted to PR