Contrasting the Harmonic Balance and Linearized Methods for Oscillating-Flap Simulations

In the framework of unsteady aerodynamics, forced-harmonic-motion simulations can be used to compute unsteady loads. In this context, the present paper assesses two alternatives to the unsteady Reynolds-averaged Navier–Stokes approach, the linearized unsteady Reynolds-averaged Navier–Stokes equations method, and the harmonic balance approach. The test case is a NACA 64A006 airfoil with an oscillating ␣ap mounted at 75% of the chord. Emphasis is put on examining the performances of the methods in terms of accuracy and computational cost over a range of physical conditions. It is found that, for a subsonic ␣ow, the linearized unsteady Reynolds-averaged Navier–Stokes method is the most ef␣cient one. In the transonic regime, the linearized unsteady Reynolds-averaged Navier–Stokes method remains the fastest approach, but with limited accuracy around shocks, whereas a one- harmonic harmonic balance solution is in closer agreement with the unsteady Reynolds-averaged Navier–Stokes solution. In the case of separation in the transonic regime, the linearized unsteady Reynolds-averaged Navier–Stokes method fails to converge, whereas the harmonic balance remains robust and accurate

Rickettsial Infections and Fever, Vientiane, Laos

Rickettsia spp. are an underrecognized cause of undifferentiated febrile illness

Partition coefficient of Ca among leucite, sanidine, silicic-sanidinic melt, and hydrothermal solution at 2Kb and high temperatures (920º and 1030ºC)

Results of synthesis experiments of leucite (Lc), sanidine (San) and fused sanidine, the latter with slightly excess SiO2 are reported. Starting materiais were amorphous oxide gels with the appropriate stoichiometric compositions in contact with KCl hydrothermal solutions (HS) containing variable amounts of tagged CaCl2(45Ca) at pressures of 2 kbars and temperatures of 930º and 1030ºC. The distribution coefficients ; were obtained from the Ca/K ratios measured in both ideal synthesized materiais and solutions. The results were as follows: ; and ;Foram realizadas séries de experimentos de síntese de leucita, sanidina e de sanidina fundida com pequeno excesso de sílica a partir de gels amorfos dos óxidos na estequiometria desejada, em contato com solução hidrotermal de KCl, contendo proporções variáveis de traços de cloreto de cálcio "marcado" (45Ca). As relações Ca/K determinadas nos matérias sintetizados e na solução hidrotermal após os experimentos permitiram a obtenção dos coeficientes de partição médios Kd = Ca/K do material sintetizado/Ca/K da solução hidrotermal, dentro de intervalo de comportamento ideal das soluções hidrotermais, das soluções sólidas (minerais) e da fusão sílico-sanidínica (sanidina fundida). Os valores de Kd obtidos foram: ; e

Constraints on F vs. OH incorporation in synthetic [6]Al-bearing monoclinic amphiboles

In this work we have systematically replaced OH with F in an amphibole composition intermediate between richterite and pargasite [60% richterite and 40% pargasite in molar proportion; nominal composition Na(Na0.6Ca1.4)(Mg4.6Al0.4)(Si7.2Al0.8)O-22(OH,F)(2)]. Syntheses have been done at 3 kbar P-H2O and 900 degreesC, and for all compositions an assemblage of amphibole plus minor Na-phlogopite has been obtained. Crystal-chemical variations in the amphibole as a function of F have been characterized by a combination of EMPA, X-ray powder diffraction, and infrared spectroscopy. EMPA analyses show that for increasing F in the system (i) the Al-[6] content decreases to 0.13 apfu for the nominal fluorine end-member whereas the Al-[4] content is virtually constant and close to the nominal value; (ii) the fluorine content is systematically lower than expected. The infrared OH-stretching spectra show that those OH-groups locally bonded to (MgMgMg)-Mg-M1-Mg-M1-Mg-M3 configurations are preferentially replaced by F whereas those OH-groups locally bonded to (MgMgAl)-Mg-M1-Mg-M1-Al-M3 configurations are not replaced by F