Reduction of fan noise: A concept

Acoustic materials strategically located within or near noise sources are effective for noise abatement on wing mounted lift fans, nozzles, engines and other noise sources. Panels are straightforward and easily adaptable to situations outside of aircraft technology

Analytical and experimental investigation of flow fields of annular jets with and without swirling flow

Analytical and experimental studies were performed to define the flowfield of annular jets, with and, without swirling flow. The analytical model treated configurations with variations of flow angularities, radius ratio, and swirl distributions. Swirl distributions characteristic of stator vanes and rotor blade rows, where the total pressure and swirl distributions are related were incorporated in the mathematical model. The experimental studies included tests of eleven nozzle models, both with and, without swirling exhaust flow. Flowfield surveys were obtained and used for comparison with the analytical model. This comparison of experimental and analytical studies served as the basis for evaluation of several empirical constants as required for application of the analysis to the general flow configuration. The analytical model developed during these studies is applicable to the evaluation of the flowfield and overall performance of the exhaust of statorless lift fan systems that contain various levels of exhaust swirl

Design of a miniature hydrogen fueled gas turbine engine

The design, development, and delivery of a miniature hydrogen-fueled gas turbine engine are discussed. The engine was to be sized to approximate a scaled-down lift engine such as the teledyne CAE model 376. As a result, the engine design emerged as a 445N(100 lb.)-thrust engine flowing 0.86 kg (1.9 lbs.) air/sec. A 4-stage compressor was designed at a 4.0 to 1 pressure ratio for the above conditions. The compressor tip diameter was 9.14 cm (3.60 in.). To improve overall engine performance, another compressor with a 4.75 to 1 pressure ratio at the same tip diameter was designed. A matching turbine for each compressor was also designed. The turbine tip diameter was 10.16 cm (4.0 in.). A combustion chamber was designed, built, and tested for this engine. A preliminary design of the mechanical rotating parts also was completed and is discussed. Three exhaust nozzle designs are presented

EVALUATION OF HEAT TRANSFER BOUNDARY CONDITIONS FOR CFD MODELING OF A 3D PLATE HEAT EXCHANGER GEOMETRY

In this paper fluid flow and heat transfer are modeled in a corrugated 3D plate heat exchanger geometry with a commercial computational fluid dynamics (CFD) program, Fluent 6.1.22 (Fluent Inc., Lebanon), in order to find out the most realistic heat transfer boundary conditions for a plate heat exchanger. The built-in boundary conditions of Fluent available for this case are Heat flux, Convection and Constant wall temperature. The CFD models are verified with correlations and experimental data obtained by a flat plate test equipment of which parameters can be calculated analytically. Deficiencies are found in all the built-in heat transfer boundary conditions. Heat transfer modeling with CFD in a corrugated plate heat exchanger is problematic because of the assumptions that have to be made when defining the boundary conditions in the complex geometry. The values of the computational parameters have spatial variations and can not be defined explicitly. However, when compared to the experimental correlations in the literature, the Convection boundary condition gives the most realistic results in the case of corrugated plate heat exchanger

Nanoelectromechanical Resonator Arrays for Ultrafast, Gas-Phase Chromatographic Chemical Analysis

Miniaturized gas chromatography (GC) systems can provide fast, quantitative analysis of chemical vapors in an ultrasmall package. We describe a chemical sensor technology based on resonant nanoelectromechanical systems (NEMS) mass detectors that provides the speed, sensitivity, specificity, and size required by the microscale GC paradigm. Such NEMS sensors have demonstrated detection of subparts per billion (ppb) concentrations of a phosphonate analyte. By combining two channels of NEMS detection with an ultrafast GC front-end, chromatographic analysis of 13 chemicals was performed within a 5 s time window

Système de surveillance du VIH et des IST de deuxième génération en Suisse : Rapport de synthèse 2012-2016

Les résultats présentés dans ce rapport s’appuient sur plusieurs sources de données. Nous avons conduit des enquêtes nationales auprès des hommes qui ont des rapports sexuels avec des hommes (HSH, études Gaysurvey 2012 et 2014), auprès des migrant-e-s originaires d’Afrique subsaharienne (migrant-e-s ASS, étude ANSWER 2014), auprès des travailleuses et des travailleurs du sexe (TS, étude SWAN 2016), ainsi qu’auprès des consommatrices et des consommateurs de drogue fréquentant les structures à bas seuil (UD, étude SBS 2011). A cela s’ajoute une analyse secondaire des données sur les comportements sexuels de l’enquête suisse sur la santé (ESS 2012). Nous avons également collecté des données de monitoring sur le nombre de seringues remises aux UDI dans différents settings (structures à bas seuil, programmes de prescription d’héroïne et pharmacies), ainsi que des données relatives à la mise sur le marché de préservatifs en Suisse. Nous avons conduit ou participé à la réalisation de cinq études additionnelles qui apportent un éclairage complémentaire aux résultats présentés dans ce rapport : évaluation de la campagne « Break the chains » 2015 ; analyse des données disponibles pour estimer le nombre de préservatifs écoulés sur le marché suisse ; entretiens avec des experts concernant l’évolution des comportements préventifs chez les UDI ; inventaire des dispositifs de remise de matériel d’injection stérile en milieu carcéral ; rapid assessment de la situation des personnes transgenres par rapport au risque d’infection par le VIH et les autres IST. Nous nous sommes enfin appuyés sur des résultats publiés sous l’égide de la Swiss HIV cohort study et de l’étude Health behaviour in school-aged children

Developing improved MD codes for understanding processive cellulases

"The mechanism of action of cellulose-degrading enzymes is illuminated through a multidisciplinary collaboration that uses molecular dynamics (MD) simulations and expands the capabilities of MD codes to allow simulations of enzymes and substrates on petascale computational facilities. There is a class of glycoside hydrolase enzymes called cellulases that are thought to decrystallize and processively depolymerize cellulose using biochemical processes that are largely not understood. Understanding the mechanisms involved and improving the efficiency of this hydrolysis process through computational models and protein engineering presents a compelling grand challenge. A detailed understanding of cellulose structure, dynamics and enzyme function at the molecular level is required to direct protein engineers to the right modifications or to understand if natural thermodynamic or kinetic limits are in play. Much can be learned about processivity by conducting carefully designed molecular dynamics (MD) simulations of the binding and catalytic domains of cellulases with various substrate configurations, solvation models and thermodynamic protocols. Most of these numerical experiments, however, will require significant modification of existing code and algorithms in order to efficiently use current (terascale) and future (petascale) hardware to the degree of parallelism necessary to simulate a system of the size proposed here. This work will develop MD codes that can efficiently use terascale and petascale systems, not just for simple classical MD simulations, but also for more advanced methods, including umbrella sampling with complex restraints and reaction coordinates, transition path sampling, steered molecular dynamics, and quantum mechanical/molecular mechanical simulations of systems the size of cellulose degrading enzymes acting on cellulose."http://deepblue.lib.umich.edu/bitstream/2027.42/64203/1/jpconf8_125_012049.pd

Magnetic structure of Yb2Pt2Pb: Ising moments on the Shastry-Sutherland lattice.

Neutron diffraction measurements were carried out on single crystals and powders of Yb2Pt2Pb, where Yb moments form two interpenetrating planar sublattices of orthogonal dimers, a geometry known as Shastry-Sutherland lattice, and are stacked along the c axis in a ladder geometry. Yb2Pt2Pb orders antiferromagnetically at TN=2.07K, and the magnetic structure determined from these measurements features the interleaving of two orthogonal sublattices into a 5×5×1 magnetic supercell that is based on stripes with moments perpendicular to the dimer bonds, which are along (110) and (−110). Magnetic fields applied along (110) or (−110) suppress the antiferromagnetic peaks from an individual sublattice, but leave the orthogonal sublattice unaffected, evidence for the Ising character of the Yb moments in Yb2Pt2Pb that is supported by point charge calculations. Specific heat, magnetic susceptibility, and electrical resistivity measurements concur with neutron elastic scattering results that the longitudinal critical fluctuations are gapped with ΔE≃0.07meV