Effect of the NACA Injection Impeller on the Mixture Distribution of a Double-Row Radial Aircraft Engine

The NACA injection impeller was developed to improve the mixture distribution of aircraft engines by discharging the fuel from a centrifugal supercharger impeller, thus promoting a thorough mixing of fuel and charge air. Tests with a double-row radial aircraft engine indicated that for the normal range of engine power the NACA injection impeller provided marked improvement in mixture distribution over the standard spray-bar injection system used in the same engine. The mixture distribution at cruising conditions was excellent; at 1200, 15OO, and 1700 brake horsepower, the differences between the fuel-air ratios of the richest and the leanest cylinders were reduced to approximately one-third their former values. The maximum cylinder temperatures were reduced about 30 [degrees] F and the temperature distribution was improved by approximately the degree expected from the improvement in mixture distribution. Because the mixture distribution of the engine tested improves slightly at engine powers exceeding 1500 brake horsepower and because the effectiveness of the particular impeller diminished slightly at high rates of fuel flow, the improvement in mixture distribution at rated power and rich mixtures was less than that for other conditions. The difference between the fuel-air ratios of the richest and the leanest cylinders of the engine using the standard spray bar was so great that the fuel-air ratios of several cylinders were well below the chemically correct mixture, whereas other cylinders were operating at rich mixtures. Consequently, enrichment to improve engine cooling actually increascd some of the critical temperatures. The uniform mixture distribution providod by the injection impeller restored the normal response of cylinder temperatures to mixture enrichnent

Producing the 'problem of drugs': a cross national-comparison of ‘recovery' discourse in two Australian and British reports

The notion of ‘recovery’ as an overarching approach to drug policy remains controversial. This cross-national analysis considers how the problem of drugs was constructed and represented in two key reports on the place of ‘recovery’ in drug policy, critically examining how the problem of drugs (and the people who use them) are constituted in recovery discourse, and how these problematisations are shaped and disseminated. Bacchi's poststructuralist approach is applied to two documents (one in Britain and one in Australia) to analyse how the ‘problem of drugs’ and the people who use them are constituted: as problematic users, constraining alternative understandings of the shifting nature of drug use; as responsibilised individuals (in Britain) and as patients (in Australia); as worthy of citizenship in the context of treatment and recovery, silencing the assumption of unworthiness and the loss of rights for those who continue to use drugs in ‘problematic’ ways. The position of the organisations which produced the reports is considered, with the authority of both organisations resting on their status as independent, apolitical bodies providing ‘evidence-based’ advice. There is a need to carefully weigh up the desirable and undesirable political effects of these constructions. The meaning of ‘recovery’ and how it could be realised in policy and practice is still being negotiated. By comparatively analysing how the problem of drugs was produced in ‘recovery’ discourse in two jurisdictions, at two specific points in the policy debate, we are reminded that ways of thinking about ‘problems’ reflect specific contexts, and how we are invoked to think about policy responses will be dependent upon these conditions. As ‘recovery’ continues to evolve, opening up spaces to discuss its contested meanings and effects will be an ongoing endeavour

An annular lithium-drifted germanium detector for studying nuclear reaction gamma-rays

Fabrication and development of annular lithium drifted germanium detector for studying nuclear reaction gamma ray

Observation of long range magnetic ordering in pyrohafnate Nd2Hf2O7: A neutron diffraction study

We have investigated the physical properties of a pyrochlore hafnate Nd2Hf2O7 using ac magnetic susceptibility \chi_ac(T), dc magnetic susceptibility \chi(T), isothermal magnetization M(H) and heat capacity C_p(T) measurements, and determined the magnetic ground state by neutron powder diffraction study. An upturn is observed below 6 K in C_p(T)/T, however both C_p(T) and \chi(T) do not show any clear anomaly down to 2 K. The \chi_ac(T) shows a well pronounced anomaly indicating an antiferromagnetic transition at T_N = 0.55 K. The long range antiferromagnetic ordering is confirmed by neutron diffraction. The refinement of neutron diffraction pattern reveals an all-in/all-out antiferromagnetic structure, where for successive tetrahedra, the four Nd3+ magnetic moments point alternatively all-into or all-out-of the tetrahedron, with an ordering wavevector k = (0, 0, 0) and an ordered state magnetic moment of m = 0.62(1) \mu_B/Nd at 0.1 K. The ordered moment is strongly reduced reflecting strong quantum fluctuations in ordered state.Comment: 10 pages, 9 figures and 2 tables; to appear in Phys. Rev.

Principal manifolds and graphs in practice: from molecular biology to dynamical systems

We present several applications of non-linear data modeling, using principal manifolds and principal graphs constructed using the metaphor of elasticity (elastic principal graph approach). These approaches are generalizations of the Kohonen's self-organizing maps, a class of artificial neural networks. On several examples we show advantages of using non-linear objects for data approximation in comparison to the linear ones. We propose four numerical criteria for comparing linear and non-linear mappings of datasets into the spaces of lower dimension. The examples are taken from comparative political science, from analysis of high-throughput data in molecular biology, from analysis of dynamical systems.Comment: 12 pages, 9 figure

CRASHWORTHY RAILING FOR TIMBER BRIDGES

Bridge railing systems in the United States have historically beers designed based on static load criteria given in the American Association of State Highway and Transportation 0fficials (AASHTO) Standard Specifications for Highway Bridges. In the past decade, full-scale vehicle crash testing has been recognized as a more appropriate and reliable method of evaluating bridge railing acceptability. In 1993, the National Cooperative Highway Research Program published Report 350, Recommended Procedures for the Saftey Performance Evaluation of Highway Features, which provides new criteria for evaluating longitudinal barriers. Based on these specifications, a cooperative research program is continuing between the USDA Forest Service, Forest Products Laboratory, the Midwest Roadside Saftety Facility of the University of Nebraska- Lincoln; and the Federal Highway Administration to develop and crash test bridge railings for wood bridge decks. This paper describes research that resulted in the successful development and testing of several bridge railings for longitudinal and transverse wood decks in accordance with NCHRP Report 350 requirements

Crash-Tested Bridge Railings for Timber Bridges

Bridge railing systems in the United States historically have been designed on the basis of static load criteria given in the AASHTO Standard Specifications for Highway Bridges. In the past decade, full-scale vehicle crash testing has been recognized as a more appropriate and reliable method of evaluating bridge railing acceptability. In 1989 AASHTO published Guide Specifications for Bridge Railings, which gives the recommendations and procedures to evaluate bridge railings by full-scale vehicle crash testing. In 1993 NCHRP published Report 350: Recommended Procedures for the Safety Performance Evaluation of Highway Features, which provides criteria for evaluating longitudinal barriers. From these specifications, a cooperative research program was initiated to develop and crash test several bridge railings for longitudinal wood decks. The research resulted in the successful development and testing of five bridge railing systems for longitudinally laminated wood bridge decks in accordance with the AASHTO Performance Level 1 and Performance Level 2 requirements and the Test Level 4 requirements of NCHRP Report 350

Graphene on Si(111)7x7

We demonstrate that it is possible to mechanically exfoliate graphene under ultra high vacuum conditions on the atomically well defined surface of single crystalline silicon. The flakes are several hundred nanometers in lateral size and their optical contrast is very faint in agreement with calculated data. Single layer graphene is investigated by Raman mapping. The G and 2D peaks are shifted and narrowed compared to undoped graphene. With spatially resolved Kelvin probe measurements we show that this is due to p-type doping with hole densities of n_h \simeq 6x10^{12} cm^{-2}. The in vacuo preparation technique presented here should open up new possibilities to influence the properties of graphene by introducing adsorbates in a controlled way.Comment: 8 pages, 7 figure