In situ deposition behavior of silica-based layers and its effect on thermal degradation of IN713 turbine blades during operation of a micro-gas turbine

This study examined the in situ deposition behavior of silica-based layers on IN713 turbine blades during the operation of a 13 kgf-class gas turbine at a rotation speed of 20,000/min as well as its effect on the degradation of the metallic substrate. Tetraethylorthosilicate (TEOS) was mixed with the fuel (liquid petroleum gas, LPG) and burned to generate silica-based coating precursors for deposition from the flame. Two deposition conditions were adopted. For condition 1 (C1), the silicon-to-carbon ratio in the mixed fuel was set at 0.1 mol% for the first 5 min and at zero mol% for the final 95 min in a 100-min operation. For condition 2 (C2), the ratio was set at 0.005 mol% during the entire 100 min operation. The total TEOS feed was the same under both conditions. C1 resulted in a rather uniform and thicker (5-10 μm on the pressure side) porous silica-based coating on the blade than C2. The in situ deposited layer of C1 was well preserved on the blade and protected the underlying metallic substrate from oxidation during the entire 100 min operation. The layer on the C2 blades was ∼5 μm thick at the region near to root, but was too thin in the other areas on the blade to be protective. The early build-up of a porous layer to an effective thickness on the blades produced a thermal barrier toward the substrate as well as a diffusion barrier toward the oxidizing elements during operation.     

Memory effects in an interacting magnetic nanoparticle system

We have performed a series of measurements to study the low temperature dynamics of an interacting magnetic nanoparticle system. The results obtained demonstrate striking memory effects in the dc magnetization and magnetic relaxation that support the existence of a spin-glass-like phase in interacting magnetic nanoparticles. Moreover, we observe an asymmetric response with respect to temperature change that supports a hierarchical picture, rather than the droplet model discussed in other works on nanoparticle systems.     

Single spin and chiral glass transition in vector spin glasses in three dimensions

Results of Monte Carlo simulations of XY and Heisenberg spin glass models in three dimensions are presented. A finite-size scaling analysis of the correlation length of the spins and chiralities of both models shows that there is a single, finite-temperature transition at which both spins and chiralities order.     

Investigation of the onset and development of forward scattering in an underdense plasma

We investigate the distortion of a spatial intensity modulation imposed on a 527 nm f/10 probe beam as it transmits through an underdense plasma characterized with Thomson scattering. Combining the measurements with full wave simulations of beam propagation through the entire plasma show that the key features of the data can be reproduced using the Kaiser thermal transport model.     

Submanifolds of complex space forms admitting an almost contact metric compound structure

Summary Real hypersurfaces of an almost Hermitian manifold naturally admit an almost contact metric structure and the (f, g, u, v, w, , , )-structure is defined on submanifolds of codimension 3 of an almost Hermitian manifold. We study the so-called semi-invariant submanifolds of a complex space form with almost contact metric compound structure which is a general notion of (f, g, u, v, w, , , )-structure.Dedicated to professor Eulyong Pak on his 60th birthdayThis research was partially supported by Korean Science and Engineering Foundation Grant.     

Determination of cadmium by atomic-fluorescence and atomic-absorption spectrophotometry

The adaptation of a conventional atomic-absorption/flameemission spectrophotometer to the measurement of atomic-fluorescence in an air-acetylene flame is described. The determination of cadmium on the same instrument by both atomic-fluorescence and absorption shows that, even with a rather simple and inefficient means of exciting and measuring fluorescence, results can be obtained which indicate that the fluorescence technique is considerably more sensitive than atomic-absorbance and is equally free from inter-element interference.     

Synthese de diterpenes tetracycliques du type hibane

Hibaone has been synthesized from manool through a photochemical cycloaddition of Δ⁸⁽¹⁴⁾ podocarpene-13-one to ethylene or 1,2 dichloroethylene.     

On the molecular structure and nmr spectrum of cis-[PtPh2(Ph2PCH2PPh2)]

The X-ray crystal structure analysis of cis-[PtPh₂(Ph₂PCH₂PPh₂)] suggests that the unusually low PtP coupling constant is a consequence of distortion of the valency angles at the platinum and phosphorus atoms; the restrictive geometry of the chelate ring does not effect the lengths of the metal—ligand bonds.     

Nitrato- and fluoroboracites M3B7O13NO3 and M3B7O13F

New boracites containing nitrato- or fluoroanions that appear to be true low-pressure phases have been synthesized at superatmospheric pressures. The M₃B₇O₁₃NO₃ compounds (M = Co, Ni, Cu, Zn, Cd) transform rapidly and reversibly in the temperature region 300–500°C between probable orthorhombic and face centered cubic symmetry, while the M₃B₇O₁₃F compounds (M = Mg, Mn, Fe, Co, Zn) appear to maintain rhombohedral symmetry up to their decomposition temperatures of 800–900°C. True high-pressure boracite-like phases containing F and Cr, Mn, Fe, or Co that decompose upon heating to M₃B₇O₁₃F have also been isolated.     

The synthesis of 1,4-diazacycl[3,2,2]azine

The diazaanalog of “cycl[3,2,2]azine”, “1,4-diazacycl[3,2,2]azine” (1,4,7b-triazacyclopent-[cd]indene) and its 2-methyl derivative were prepared. These compounds are subject to facile acid-catalyzed hydrolysis affording substituted imidazo[1,2-a]pyridines.