Effects of error variation in means of measurement on reliability parameters in engineering-system monitoring

A method is given for calculating the monitoring reliability parameters (MRP) for an engineering system with allowance for the drift in the measurement error of the means of measurement (MM). The approach is based on introducing a biased MM error distribution into the traditional formulas for the conditional probabilities of spurious and unobserved failure. The bias at the center of the distribution is determined by the systematic error at the given instant. An example is given to illustrate the performance in MRP calculation.Translated from Izmeritel'naya Tekhnika, No. 1, pp. 12–13, January, 1994.     

Erbium ion electroluminescence in p ++/n +/n-Si:Er/n ++ silicon diode structures

Results of experimental studies of erbium ion electroluminescence in p ⁺⁺/n ⁺/n-Si:Er/n ⁺⁺ silicon diode structures grown by sublimation molecular-beam epitaxy are discussed. The distinctive feature of these structures is that the regions of electron flux formation of (n ⁺-Si) and impact excitation of erbium ions (n-Si:Er) are spaced. The influence of the n ⁺-Si layer thickness on electrical and electroluminescent properties of diodes was studied. It was shown that n ⁺-Si layer thinning causes the transformation of the structure breakdown mechanism from tunneling to avalanche. The dependence of the Er³⁺ ion electroluminescence on the thickness of the heavily doped n ⁺-Si region is bell-shaped. At the n ⁺-Si-layer doping level n ≈ 2 × 10¹⁸ cm^?3, the maximum electroluminescence intensity is attained at an n ⁺-Si layer thickness of ～23 nm.     

Generating vegetation leaf area index Earth system data record from multiple sensors. Part 2: Implementation,analysis and validation

The evaluation of a new global monthly leaf area index (LAI) data set for the period July 1981 to December 2006 derived from AVHRR Normalized Difference Vegetation Index (NDVI) data is described. The physically based algorithm is detailed in the first of the two part series. Here, the implementation, production and evaluation of the data set are described. The data set is evaluated both by direct comparisons to ground data and indirectly through inter-comparisons with similar data sets. This indirect validation showed satisfactory agreement with existing LAI products, importantly MODIS, at a range of spatial scales, and significant correlations with key climate variables in areas where temperature and precipitation limit plant growth. The data set successfully reproduced well-documented spatio-temporal trends and inter-annual variations in vegetation activity in the northern latitudes and semi-arid tropics. Comparison with plot scale field measurements over homogeneous vegetation patches indicated a 7% underestimation when all major vegetation types are taken into account. The error in mean values obtained from distributions of AVHRR LAI and high-resolution field LAI maps for different biomes is within 0.5 LAI for six out of the ten selected sites. These validation exercises though limited by the amount of field data, and thus less than comprehensive, indicated satisfactory agreement between the LAI product and field measurements. Overall, the inter-comparison with short-term LAI data sets, evaluation of long term trends with known variations in climate variables, and validation with field measurements together build confidence in the utility of this new 26 year LAI record for long term vegetation monitoring and modeling studies.     

Thermal conductivity of high-T c crystals: Dependence on magnitude and orientation of magnetic field,and effect of Zn doping

We present precise measurements of in-plane thermal conductivity for superconducting single crystals of YBa₂Cu₃O_7?x (YBCO) withT _c =92 and 60 K, Bi₂Sr₂CaCu₂O₈ (BSCCO), and of Zn-doped YBCO. Magnetization and thermal conductivity data obtained with the same 90-K YBCO crystal demonstrate a close relationship between the magnetic thermal resistivity and the internal magnetic fieldB in a superconductor in the mixed state. For all superconductors studied here, the magnetic thermal resistivity is a sublinear function of magnetic field. The origins of the nonlinearity are discussed. Angular dependences of the magnetic thermal resistivity have been shown to depart from the anisotropic 3D superconductor model and are in quantitative agreement with a quasi-2D model. Implications for spatial modulation of the order parameter are made.     

Fabrication of a complex aluminosilicochrome alloy by a slag-free method

The results of experimental studies of obtaining a complex alloy of aluminosilicochrome from high-ash coals of the Karaganda basin are presented. As a result of carrying out large-scale laboratory studies, a high-quality alloy not subjected to disintegration is formed. A method for melting of refined grades of ferrochrome using aluminosilicochrome as a reducer is suggested.     

Boson peak in low-frequency Raman spectra of polymethylmethacrylate

The role of the local field, anharmonicity, and degree of disorder in the formation of the boson peak has been studied. The low-frequency Raman spectrum of a model polymethylmethacrylate crystal with disorder elements was calculated using the method of atom-atom potentials taking into account the effect of local fields on the spectrum. The calculations were carried out for a crystal containing rigid molecules of an isotactic polymethylmethacrylate oligomer and for a structure with flexible molecules.     

Formation and Properties of Electron- and Ion-Conducting Layers of N-Substituted PVC Derivatives Grafted onto Active Carbon

Protection of Metals and Physical Chemistry of Surfaces - A systematization is presented of studies of carbon sorbent functionalization based on chemical modification of the active carbon surface...     

Structuring of the Surface Layer of Polycarbonate Film upon Interaction with Nematic Liquid Crystal

The structure formation observed in the surface layer of polycarbonate which proceeds when nematic liquid crystal is deposited on a film is studied. Films prepared from polycarbonate solutions in dichloromethane, chloroform, or pyridine and dried in thermobalance at different temperatures and different drying times are studied. Textures are prepared in the process of domain growth. The effect of the orientation of the disclination lines in a magnetic field and the memory effect of molecular ordering after removal and redeposition of the liquid crystal layer are observed. The process of structure formation is analyzed on the basis of the model of cooperative interaction of liquid crystal molecules with polymer chains taking into account the adsorption mechanism.