Improved Operating Characteristics Research Articles

SnO 2–Au nanocomposite synthesized by successive ionic layer deposition method: Characterization and application in gas sensors

A possibility of synthesizing the SnO 2–Au nanocomposite by the successive ionic layer deposition (SILD) method is demonstrated in this article. It is shown that as a result of successive treatments in solutions of Sn(OH) x F y Cl z and HAuCl 4 the SnO 2–Au nanocomposite with a Sn/Au ratio varying from 1:1 to 6:1 can be formed on the surface of substrates. It is found that the value of this ratio depends on the concentration of F ions in solution. The gold in the indicated composite is in the metallic state. The growth of the SnO 2–Au composite takes place through the formation of 3-D precipitates, which form a continuous film after 13 deposition cycles. As a result, a layer with averaged thickness of up to 20 nm is formed on the surface. Nanocomposite films, even after treatment at an annealing temperature T an ∼ 600 ° C, have finely dispersed structure. The size of the Au clusters incorporated in the SnO 2 matrix is in the range from 3 to 15 nm. Gas sensing characteristics of SnO 2 films modified by SnO 2–Au nanocomposites are discussed as well. It is shown that surface modification by SnO 2–Au nanocomposites can be used for improving operating characteristics of conductometric SnO 2-based gas sensors.

The effect of technological parameters of intensive electric sintering on the efficiency of inserts produced from diamond-containing composite materials in a cobalt binder

A device and express methods to analyze operating characteristics of diamond-containing composite materials in a cobalt binder have been developed. The experimental studies of the dependence of the diamond-containing composite material tools efficiency on intensive electric sintering have been conducted under the close-to-real operation conditions. Correlation dependences between technological parameters of sintering, microstructure, physico-mechanical properties, and operating characteristics of diamond-containing composite tool materials have been established. The ranges of variations and combinations of technological parameters of sintering, which are most promising in terms of the quality of the resultant materials, have been defined. On the strength of the data obtained an improved technology has been developed of producing segments from diamond-containing composite materials to equip tools with improved operating characteristics to be used in stone working.

A method of measuring the mass concentration of arsenic in water with the development of a promising sampler

A method of measuring the mass concentration of arsenic in water is considered. New samplers with improved operating characteristics for ecological monitoring of aqueous media are proposed.

Method for measuring the weight concentration of O-isobutyl methyl phosphonate with development of advanced sampling devices

A method is considered for measuring the weight concentration of O-isobutyl methyl phosphonate in air, and new engineering solutions are proposed for a sampling device with improved operating characteristics for ecological monitoring of the atmosphere.

Effect of Ionic Head Group on Admicelle Formation by Polymerizable Surfactants

AbstractOne of the problems of using surfactant‐modified adsorbents in a surfactant‐based adsorption process is loss of surfactant because of desorption. Recently, polymerizable surfactants have been used to minimize surfactant losses by polymerization of the surfactant admicellar structure to help secure it to the solid oxide surface. In this study, adsorption of polymerizable cationic gemini surfactant was used to form polymerized bilayers on silica. UV light was used to irradiate and initiate the polymerization process. Surfactant adsorption and desorption were evaluated to compare the efficiency of polymerized and non‐polymerized surfactants using gemini and conventional surfactants, respectively. Results demonstrate that the increased stability of the polymerized surfactant‐modified surface can reduce the desorption of surfactant from the surface, thereby improving operating characteristics of the surfactant‐modified media (e.g., maintaining adsolubilization potential, dispersion stability, etc.).

Method for measuring the weight concentration of O-pinacolyl methyl phosphonate in soil, snow, and loose materials using advanced sampling devices

New technical solutions are proposed for sampling soil, snow, and loose materials with improved operating characteristics that may be used in measuring the weight concentration of O-pinacolyl methyl phosphonate in ecological, geological, geochemical, and microbiological research.

Journal bearing design using multiobjective genetic algorithm and axiomatic design approaches

This paper describes the optimum design methodology for improving operating characteristics of fluid-film steadily loaded journal bearings. This methodology consists of (1) a simplified closed form solution to accelerate the computation, (2) finite difference mass conserving algorithm for accurate prediction of lubricant flow and power loss, (3) Pareto optimal concept to avoid subjective decision on priority of objective functions, (4) a genetic algorithm to deal with multimodal nature of hydrodynamic-bearing and develop a Pareto optimal front, (5) fitness sharing to maintain genetic diversity of the population used in genetic algorithm, and (6) axiomatic design to provide inside of objective functions and design variables. In the optimum design of journal bearings, the design variables such as radial clearance, length to diameter ratio, groove geometry, oil viscosity and supply pressure are used to simultaneously minimize oil flow and power loss. A step-by-step procedure, graphs and tables are presented to demonstrate the concept and effectiveness of suggested design methodology.

Shrinkage estimators for covariance matrices.

Estimation of covariance matrices in small samples has been studied by many authors. Standard estimators, like the unstructured maximum likelihood estimator (ML) or restricted maximum likelihood (REML) estimator, can be very unstable with the smallest estimated eigenvalues being too small and the largest too big. A standard approach to more stably estimating the matrix in small samples is to compute the ML or REML estimator under some simple structure that involves estimation of fewer parameters, such as compound symmetry or independence. However, these estimators will not be consistent unless the hypothesized structure is correct. If interest focuses on estimation of regression coefficients with correlated (or longitudinal) data, a sandwich estimator of the covariance matrix may be used to provide standard errors for the estimated coefficients that are robust in the sense that they remain consistent under misspecification of the covariance structure. With large matrices, however, the inefficiency of the sandwich estimator becomes worrisome. We consider here two general shrinkage approaches to estimating the covariance matrix and regression coefficients. The first involves shrinking the eigenvalues of the unstructured ML or REML estimator. The second involves shrinking an unstructured estimator toward a structured estimator. For both cases, the data determine the amount of shrinkage. These estimators are consistent and give consistent and asymptotically efficient estimates for regression coefficients. Simulations show the improved operating characteristics of the shrinkage estimators of the covariance matrix and the regression coefficients in finite samples. The final estimator chosen includes a combination of both shrinkage approaches, i.e., shrinking the eigenvalues and then shrinking toward structure. We illustrate our approach on a sleep EEG study that requires estimation of a 24 x 24 covariance matrix and for which inferences on mean parameters critically depend on the covariance estimator chosen. We recommend making inference using a particular shrinkage estimator that provides a reasonable compromise between structured and unstructured estimators.

Improvement of Operating Characteristics of High-Speed Hydrodynamic Journal Bearings by Optimum Design: Part I— Formulation of Methodology and Its Application to Elliptical Bearing Design

This paper describes the optimum design methodology for improving operating characteristics of hydrodynamic journal bearings and its application to elliptical journal bearing design used in high-speed rotating machinery. The hybrid optimization technique combining the direct search method and the successive quadratic programming is applied effectively to find the optimum solutions. In the optimum design of elliptical journal bearings, the design variables such as vertical and horizontal radial clearances, bearing length-to-diameter ratio and bearing orientation angle are determined to minimize the objective function defined by the weighted sum of maximum averaged oil film temperature rise, leakage flow rate, and the inversion of whirl onset speed of the journal under many constraints. The results obtained are shown in graphical form for a wide range of journal rotational speed. Comparing the optimized operating characteristics with the characteristics calculated from the random selected design variables, the effectiveness of optimum design is clarified.

OEIC-enabling LCI lasers with current guides: combined theoretical-experimental investigation of internal operating mechanisms

Lateral current injection (LCI) lasers are promising candidates for optoelectronic integration and novel functional devices. We investigate experimentally the performance of a new class of LCI lasers with improved operating characteristics, focusing in particular on regions of agreement and disagreement with our physical model. We then employ fully self-consistent two-dimensional modeling in order to study the impact on performance of current guides-vertical structures intended to lower the series resistance of the active region-and find that these structures were central to achieving improved performance. We find that with additional refinements in the design of LCI lasers with current guides, further improvements in CW room-temperature performance may be achieved.

Control of induction motor drive for improving operating characteristics and dynamic response

The control strategies of an indirect field-oriented induction motor drive for both good operating characteristics and dynamic rotor speed response are presented. The small-signal model representing detuning behavior around the steady-state of an ideal field-oriented induction motor is first developed and, according to it, the rotor resistance set in the indirect field-oriented mechanism (IFOM) is adjusted by a proposed adaptive inverse model controller (IMC) to improve the decoupling characteristic. Furthermore, a stator current minimization controller is designed for fine tuning of the field-orientation characteristic. In addition, a model following speed controller is proposed. In the proposed speed controller, the model following gain is tuned according to the control effort and the model following error. The effect of control force saturation is much reduced, and good model following and load regulation speed responses are obtained. The good operating characteristics and dynamic speed responses of the motor drive obtained using the developed controllers are demonstrated by simulated and experimental results.

Improved operation characteristics of long-wavelength lasers using strained MQW active layers

Long-wavelength semiconductor lasers and amplifiers with strained MQW structures as active layer materials in the region of 1.48-1.55 /spl mu/m are reported. Various improvements in device performance by employing the strained MQW structures were experimentally demonstrated in high-power operation at 1.48 /spl mu/m, high-speed operation with narrow linewidth at 1.55 /spl mu/m, and polarization-insensitive optical amplification in the 1.5 /spl mu/m band. A compressively strained InGaAsP/InGaAsP MQW structure was used for high-power operation. The maximum power could be increased by introducing a compressive strain into the well layers, as theoretically predicted. This increase can be attributed to the suppression of Auger nonradiative recombination and intravalence band absorption. High-speed characteristics were tested on two different active layer materials. The compressively strained InGaAsP/InGaAsP MQW structure proved to be better than the strained InGaAs/InGaAsP MQW structure as an active layer material because of its high differential gain at low threshold current due to a smaller valence band density of states and small carrier life time. Compressively strained InGaAs/AlGaInAs MQW structure, having larger quantum confinements due to larger band offsets than the InGaAsP-based structures, were employed for the high-speed laser. The relaxation frequency was estimated to be 26 GHz, and a small linewidth enhancement factor of 1.5 was obtained. Polarization insensitive optical amplification in the semiconductor laser amplifiers (SLAs) was demonstrated by using the tensile strained MQW structure. The device length and strain were optimized for polarization insensitive amplification.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Changed structure and improved operation characteristics of metals and alloys exposed to high power ion beams

The effect of high power ions beams (HPIB) on the structure of Al and Cu metals and P6M5 steel (8.5 × 10 −4% C, 5% Mo, 6% W, 4% Cr, 2% V, 72% Fe) is presented. The thickness of the modified layer in Al and Cu was 150 to 180 μm. Defects observed in the bulk of the sample were shown to increase the microhardness and abrasive wear resistance of the samples. These defects are dislocation loops and prisms of vacancy or may be of interstitial type. The current density (or total deposited energy) was found to be the parameter most strongly influencing the target modification. To investigate the near surface layers, we used positron annihilation and Auger spectroscopy. Further, we measured microhardness and abrasive wear resistance.

Testing goodness of fit to the increasing failure rate family

AbstractOne branch of the reliability literature is concerned with devising statistical procedures with various nonparametric “restricted family” model assumptions because of the potential improved operating characteristics of such procedures over totally nonparametric ones. In the single‐sample problem with unknown increasing failure rate (IFR) distribution F, (1) maximum‐likelihood estimators of F have been calculated, (2) upper or lower tolerance limits for F have been determined, and (3) tests of the null hypothesis that F is exponential have been constructed. Barlow and Campo proposed graphical methods for assessing goodness of fit to the IFR model when the validity of this assumption is unknown. This article proposes several analytic tests of the IFR null hypothesis based on the maximum distance and area between the cumulative hazard function and its greatest convex minorant (GCM), and the maximum distance and area between the total time on test statistic and its GCM. A table of critical points is provided to implement a specific test having good overall power properties.

Some technological laws and properties for highly porous ceramic concretes

Using ceramic concrete made from zirconia as an example we formulated conditions and established the main technological laws for obtaining highly porous ceramic concretes. We analyzed the composition and microstructure of the ceramic concrete from the point of view of the existence in the system of noncompensated shrinkage. It is shown that for ceramic concrete with a high bond shrinkage during drying and heat treatment, with the purpose of reducing the shrinkage stresses in the system, it is necessary to use multifraction (coarse, medium, and fine) fillers. We show the effectiveness of using, as one of the filler components, removable poreforming additive, based on foamed polystyrol. The optimum region of the grain-size distribution of the components was established; this comes within the true specific volumes in the structure of the shaped ceramic concrete and amounts to 20–30% bond, 20–25% fine (0.1–0.4 mm) and 25–40% coarse (5–10 mm) filler made from waste zirconia foamed ceramics, and 20–25% foamed polystrol (0.63–1.6 mm). We studied certain properties of the resulting materials with a porosity of 60–75% and a compressive strength of 5–20 MPa. Compared with other highly porous materials, for example, foamed ceramics, the highly porous ceramic concretes have technological advantages (much lower water capacity of the shaping system, reduced shrinkage in drying and firing) and also improved operating characteristics, for instance, thermal conductivity, thermal-shock resistance and volume constancy.

Improving operating characteristics of x-ray flourescence gamma coating-thickness meters based on scintillation counters using NaI(T1) crystals

Improving operating characteristics of x-ray flourescence gamma coating-thickness meters based on scintillation counters using NaI(T1) crystals