Heat treatment of exteuded corrosion- and oxidation-resistant alloy fibers and their strength properties

Conclusions It is shown that fibers of corrosion- and oxidation-resistant nickel-base alloys can be obtained by subjecting viscose fibers filled with nickel, chromium, and molybdenum powders to heat treatment. It has been established that alloy formation in such fibers and the mechanical properties attained in them as a result of this operation depend on heat-treatment parameters controlling the amount of residual carbon in the fibers after the thermal destruction of the polymer binder (cellulose) and also on the final sintering temperature. After two-stage heat treatment — preoxidation in air at 400–450°C and final sintering in hydrogen at 1200°C — extruded Ni-20 Cr, Ni-30 Mo, and M-15 Cr-15 Mo alloy fibers (of 12- to 24-m diameters) were found to have ultimate tensile strengths of 40–52 kgf/mm².Translated from Poroshkovaya Metallurgiya, No. 2(218), pp. 1–5, February, 1981.     

Study of the thermodiffusion constant of an Ar-Kr mixture at low temperatures

Reasons for divergence between theoretical and experimental values of the thermodiffusion constant of an Ar-Kr mixture at temperatures below 273K are studied.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 37, No. 1, pp. 83–90, July, 1979.     

Multivariate autoregressive feature extraction and the recognition of multichannel waveforms

It is proposed that the autoregressive coefficient matrices appearing in a multivariate autoregressive model fitting may be used for feature extraction purposes in problems concerning recognition of multichannel waveforms. It is demonstrated how the information contained in the autoregressive parameters may be further compressed by applying the ordinary or a modified Karhunen-Loeve expansion. The feature extraction procedures are illustrated on a large data base of seismic wave traces originating from shallow earthquakes and underground nuclear explosions. The results obtained (using a multivariate Gaussian classification algorithm) suggest that the combined autore-gressive/Karhunen-Loeve method has a considerably larger discrimination potential than the more conventional seismic discriminants.     

Investigation into the formation of phases with a Ba<Subscript>2</Subscript>Ti<Subscript>9</Subscript>O<Subscript>20</Subscript>-type structure in the BaO-TiO<Subscript>2</Subscript> and BaO-SrO-TiO<Subscript>2</Subscript> systems

The mechanism of formation of barium titanate Ba₂Ti₉O₂₀ in the BaO-TiO₂ and BaO-SrO-TiO₂ systems is investigated using initial mixtures prepared by three methods, namely, mechanical grinding of the initial reactants, coprecipitation from aqueous solutions of salts, and the sol-gel technique. It is established that, irrespective of the preparation procedure, the formation of Ba₂Ti₉O₂₀ proceeds through the formation of the intermediate phases BaTi₄O₉ and BaTi₅O₁₁. The nature of the intermediate phases is determined by the homogeneity and dispersion of the initial mixture, as well as by the stability of the intermediate phase. The most optimum conditions for the synthesis of Ba₂Ti₉O₂₀ are provided by the formation of BaTi₅O₁₁ as an intermediate phase upon heat treatment of the coprecipitation products in the nanocrystalline state. The metastability and structural defects in the BaTi₅O₁₁ intermediate phase encourage a decrease in the temperature of the final heat treatment by 100–150°C in the course of the preparation of Ba₂Ti₉O₂₀ single-phase ceramics.     

Influence of diameter in the Raman spectra of aligned multi-walled carbon nanotubes

Aligned multi-walled carbon nanotubes (MWCNTs) were produced with different diameters, according to the thickness of Ni catalyst layer, by microwave plasmas enhanced chemical vapor deposition, in N₂/H₂/CH₄ environment. Raman spectroscopy, performed both on top and lateral surfaces, revealed that the relative intensity of the G′ band and the G and G′ bandwidths have high sensitivity to tube diameter distribution and also to structural variations along the tube axis. The D band present a distinct behavior: I_D/I_G is sensitive to structural organization, particularly along tube axis, while D bandwidth is sensitive to tube diameter distribution. This result may indicate D bandwidth as a parameter to correlate to the diameter of the aligned MWCNTs.     

Quantitative analysis of triglyceride species of vegetable oils by high performance liquid chromatography via a flame lonization detector

A method for the quantitative analysis of triglyceride species composition of vegetable oils by reversed-phase high performance liquid chromatography (RP-HPLC) via a flame ionization detector (FID) is described. Triglycerides are separated into molecular species via Zorbax chemically bonded octadecylsilane (ODS) columns using gradient elution with methylene chloride in acetonitrile. Identification of species is made by matching the retention times of the peaks in the chromatogram with the order of elution of all of the species that could be present in the sample on the basis of a random distribution of the fatty acids and comparision of experimental and calculated theoretical carbon numbers (TCN). Quantitative analysis is based on a direct proportionality of peak areas. Differences in the response of individual species were small and did not dictate the use of response factors. The method is applied to cocoa butter before and after randomization, soybean oil and pure olive oil.     

Light and electron microscope studies on cysts of sarcocystis fusiformis in the muscles of calves infected experimentally with oocysts and sporocysts of isospora hominis Railliet et Lucet, 1891. 1. The development of cyst and cyst wall (author's transl)

In several experiments young calves were infected with isospora hominis sporocysts excreted by human males who had ingested raw beef containing Sarcocystis fusiformis cysts. On the 29th, 48th, 62nd and 98 day p.i. the calves were killed and the development of S. fusiformis cysts in muscle cells was studied by light and electron microscopy. Beginning with the 48th day p.i. numerous cysts containing small numbers of metrocytes only were observed. The cysts developed from a parasitophorous vacuole within the host cells. At first this parasitophorous vacuole was limited by a single unit membrane, which soon became thickened at numberous places inside of the vacuole by osmiophilic material. This complex is called primary wall (equal to Prim?rhülle), reaching a thickness of up to 32 nm in old cysts. This primary wall became regularly folded. forming palisade-like protrusions. On the 62nd day after inoculation these protrusions measured about 2-3 mum in length and 0.5-0.7 mum in diameter. In light microscopy the combined protrusions had the appearance of a radially striated "thick wall", because of their close proximity to each other.     

Frequency and Orientation Effects on Whole Animal Absorption of Electromagnetic Waves

Experiments using a parallel plate waveguide as the measurement medium have revealed a strong dependence of RF absorption in rats and biological-phantom prolate spheroidal bodies upon the frequency and polarization of electromagnetic fields. The results correlate well to those of free space irradiation. Strongest power deposition is observed for fields polarized along the long dimension of the bodies for frequencies such that the major length is about one-quarter wavelength of radiation. At resonance, an effective absorption area of 2.5 to 3.5 times the shadow cross section is measured.