The effect of erbium and oxygen on the photoluminescence intensity of erbium and the composition of <Emphasis Type="Italic">a</Emphasis>-SiO<Subscript>x</Subscript>:(H,Er, O) films deposited by DC magnetron sputtering

The effect of the oxygen content (\(C_{O_2 } \)) in the gas mixture (20% of SiH₄ + 80% of Ar) + O₂ and the surface area of an erbium target (S_Er) on the composition and Er³⁺ photoluminescence of amorphous a-SiO_x:(H, Er, O) films prepared by dc magnetron sputtering has been investigated. Analysis of the experimental data shows that [Er-O] and [Er-O-Si-O] clusters are formed in the gas plasma due to the competing processes of oxidation and sputtering of Si and Er targets and to the interaction of [Si-O] and [Er-O] clusters with each other and with the oxygen in the gas phase. The discontinuities in the dependences of the contents of erbium-bound oxygen and erbium in a film, and N _O ^Er-O and N_Er = f(\(C_{O_2 } \), S_Er), at \(C_{O_2 } \) ≈ (5–6.5) mol % supports the hypothesis on the existence of different erbium clusters. The necessary conditions for preparing a-SiO_x:(H, Er, O) films with the highest photoluminescence intensity of erbium ions at a wavelength of 1.54 μm are determined.     

A study of the effect of oxygen on the intensity of erbium photoluminescence in amorphous SiO<Subscript>x</Subscript>:(H,Er) films formed by DC magnetron sputtering

The effect of oxygen on the intensity of erbium photoluminescence at λ=1.54 μm in amorphous a-SiO_x:H(Er) films formed by dc magnetron sputtering was studied. The oxygen content in the gaseous phase ranged from 0.1 to 12 mol %, with other parameters of deposition remaining constant. Analysis of an a-Si:(H, Er, O) system showed that the range of homogeneity of amorphous a-SiO_x:H(Er) is retrograde (T=const). The range of homogeneity can be conventionally divided into two portions, each of which should contain either of two differently charged [Er-O] ⁿ⁻ and [Er-O-Si-O] ^m− clusters (m>n). This inference is confirmed experimentally: in the range of oxygen concentrations amounting to 5.5–8 mol % in the plasma, unusual associative processes take place probably directly above the growing film surface; these processes are caused by the appearance of [Er-O-Si-O] ^m− clusters in the plasma and at the surface. It is these processes that account for the intensification of erbium photoluminescence as the oxygen content increases above 5.5 mol %. __________ Translated from Fizika i Tekhnika Poluprovodnikov, Vol. 37, No. 7, 2003, pp. 853–859. Original Russian Text Copyright ? 2003 by Undalov, Terukov, Gusev, Kudoyarova.     

Methods of rotating stall and surge detection in centrifugal compressors

Systems for prevention of surging of centrifugal compressors and methods of rotating stall detection and early surge diagnosis using statistical processing of sensor signals of various parameters, i.e., the method of calculation of the correlation function of the signal and the method of calculation of signal dispersion, are discussed. The results of routine tests of air and high-speed air centrifugal compressors and their detachable flow parts are adduced. __________ Translated from Khimicheskoe i Neftegazovoe Mashinostroenie, No. 6, pp. 30–33, June, 2006.     

Determining the mechanical properties of epoxy resin (DGEBA) composites by ultrasonic velocity measurement

In this study, the composites of diglycidyl ether of bisphenol A (DGEBA) epoxy resin that have been formed by mixing epoxy resin with allyl glycidyl ether (AGE) and 2,3‐epoxypropyl methacrylate [glycidyl methacrylate (GMA)] were prepared in weight % ratios of 90 : 10, 80 : 20, and 70 : 30. A computer controlled analyzer with 35 MHz and a digital oscilloscope with 60 MHz were used for measuring the velocities of ultrasonic wave. The measurement of ultrasonic velocity carried out by pulse echo method at frequencies of 2.25 and 3.5 MHz at room temperature. The values of acoustic impedance (Z), Poisson ratio (μ), and coefficients of elasticity (L, G, K, E) of composites were calculated by values of densities and velocities that obtained. Thus, the effect of modificating epoxy resin (DGEBA) by AGE and GMA on mechanical properties of DGEBA was investigated using the ultrasonic method. Atomic force microscopy has been used for determining the microstructure of composites. By the results obtained from the investigation, it have been established that the longitudinal and shear ultrasonic wave velocities, and the values of all the elasticity constants of DGEBA were increased by modification with AGE and GMA. Also the most suitable combination ratio for the compound of DGEBA : AGE and DGEBA : GMA has been found as 80 : 20. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Increasing productivity in sculpture surface machining via off-line piecewise variable feedrate scheduling based on the force system model

Sculpture surface machining is a critical process commonly used in various industries such as the automobile, aerospace, die/mold industries. Since there is a lack of scientific tools in practical process planning stages, feedrates for CNC machining are selected based on the trial errors and previous experiences. In the selections of the process parameters, production-planning engineers are conservative in order to avoid undesirable results such as chipping, cutter breakage or over-cut due to excessive cutter deflection. Currently, commonly used CAD/CAM programs use only the geometric and volumetric analysis, but not the physics of the processes, and rely on experience based cutting tool database and users’ inputs for selection of the process parameters such as feed and speed. Usually, the feeds and cutting speeds are set individual constant values all along the roughing, semi-finishing, and finishing processes. Being too conservative and setting feedrate constant all along the tool path in machining of sculpture surfaces can be quite costly for the manufacturers. However, a force model based on the physics of the cutting process will be greatly beneficial for varying the feedrate piecewise along the tool path.The model presented here is the first stage in order to integrate the physics of the ball-end milling process into the selection of the feeds during the sculpture surface machining. Therefore, in this paper, an enhanced mathematical model is presented for the prediction of cutting force system in ball end milling of sculpture surfaces. This physical force model is used for selecting varying and ‘appropriate’ feed values along the tool path in order to decrease the cycle time in sculpture surface machining. The model is tested under various machining conditions, and some of the results are also presented in the paper.     

Methods of detecting rotating surge and stall based on group statistical treatment of centrifugal compressor regime parameters

It is noted that one of the most promising trends in the field of detecting turbocompressor stall and revelation of the signs that characterize different forms of the development of gas dynamic instability (stall and rotating surge) is the use of statistical processing methods and signals. A procedure is presented for using statistical functions for analyzing the nonstationary nature of compression in turbocompressors and revelation of signs of stall based on calculating covariation of signals of regime parameters. Results are provided for studies based on analyzing covariation of the signals of regime parameters for centrifugal compressors of different construction that demonstrate the suitability of this parameter for detecting the phenomenon of compression gas dynamic instability. The procedure proposed is used successfully in practice in the form of special software for stall signalers used in centrifugal compressor automation systems.     

Influence of the substrate temperature and annealing on the 1.54-µm erbium photoluminescence of a-Si:H films obtained using a glow discharge

Effective Er photoluminescence is observed at room temperature in a-Si:H films doped with Er atoms through a gas phase using powdered Er(TMND)₃ as a source of Er ions. It is shown that the conditions for deposition of the films and their subsequent annealing influence the photoluminescence intensity and its temperature dependence. The observed behavior is attributed to restructuring of the amorphous silicon matrix within an Auger excitation mechanism involving defects. Fiz. Tekh. Poluprovodn. 33, 208–210 (February 1999)     

Effect of Salinity on Stomatal Conductance,Leaf Hydraulic Conductance,HvPIP2 Aquaporin,and Abscisic Acid Abundance in Barley Leaf Cells

The stomatal closure of salt-stressed plants reduces transpiration bringing about the maintenance of plant tissue hydration. The aim of this work was to test for any involvement of aquaporins (AQPs) in stomatal closure under salinity. The changes in the level of aquaporins in the cells were detected with the help of an immunohistochemical technique using antibodies against HvPIP2;2. In parallel, leaf sections were stained for abscisic acid (ABA). The effects of salinity were compared to those of exogenously applied ABA on leaf HvPIP2;2 levels and the stomatal and leaf hydraulic conductance of barley plants. Salinity reduced the abundance of HvPIP2;2 in the cells of the mestome sheath due to it being the more likely hydraulic barrier due to the deposition of lignin, accompanied by a decline in the hydraulic conductivity, transpiration, and ABA accumulation. The effects of exogenous ABA differed from those of salinity. This hormone decreased transpiration but increased the shoot hydraulic conductivity and PIP2;2 abundance. The difference in the action of the exogenous hormone and salinity may be related to the difference in the ABA distribution between leaf cells, with the hormone accumulating mainly in the mesophyll of salt-stressed plants and in the cells of the bundle sheaths of ABA-treated plants. The obtained results suggest the following succession of events: salinity decreases water flow into the shoots due to the decreased abundance of PIP2;2 and hydraulic conductance, while the decline in leaf hydration leads to the production of ABA in the leaves and stomatal closure.