Bayesian shrinkage estimation of system reliability with Weibull distribution of components

This paper considers two different Bayesian shrinkage estimators of series system and parallel system reliabilities, based on type II censored samples, assuming that the lifetimes of the components follow independent Weibull distributions with known scale parameters. The mean squared errors and relative efficiencies of the estimators are investigated through Monte Carlo simulation studies.     

Application of U and g values for sizing passive heating concepts

The concept of solar gain factor and the overall heat loss coefficient, obtained for solar passive heating concepts, has been extended to size these as building elements for different climatic conditions. As an example, India's four climatic zones where winter heating is required have been selected and the required area of passive heating concepts calculated by a steady-state analysis applied to a single zone building. The size of various concepts expressed as percentages of the south wall area are independent of the building size as confirmed for the case of army shelters in cold and sunny conditions of Laddakh in northern India. For a building with capacity effects in walls and roof, the dynamic simulation confirms the values of room temperature at a comfortable level assumed to be 18.3°C in the steady-state analysis.     

Some asymmetric Stokes-flow problems

Solutions are given to a number of asymmetric Stokes-flow problems which involve the slow motion of a fluid in the presence of a rigid plane containing a circular hole. The particular instances of motion generated by a linear shear flow along the plane and by a Stokeslet, placed on the axis of symmetry of the hole and oriented perpendicular to this axis, are examined in detail. The paper concludes with a solution to the shear-flow problem when the circular hole is replaced by one of elliptical geometry.     

Cyclic charging and discharging of obliquely deposited FeTi thin films

The charging of FeTi thin films with hydrogen of 1000 Å thickness deposited at different angles (θ = 0°, 30°, 45°, 60° and 75°) was carried out at 1 atm hydrogen pressure and at room temperature. The discharging was carried out at 10⁻⁵ Torr pressure by heating. The resistance of FeTi films on charging with hydrogen increases and decreases on discharging. The change in resistance in subsequent charging cycles was found to decrease, indicating saturation stage.     

Rate of degradation of λ-cyhalothrin and methomyl in grapes (Vitis vinifera L.)

Rates of degradation of λ-cyhalothrin and methomyl residues in grape are reported. The dissipation behavior of both insecticides followed first-order rate kinetics with similar patterns at standard and double-dose applications. Residues of λ-cyhalothrin were lost with pre-harvest intervals (PHI) of 12.0-12.5 and 15.0-15.5 days, corresponding to the applications at 25 and 50 g a.i. ha^-1, respectively. In the case of methomyl, residues were lost with PHI of 55.0 and 61.0 days, following applications at 1 and 2 kg a.i. ha^-1, respectively. The PHI, recommended on the basis of the experimental results, was shown to be effective in minimizing residue load of these insecticides below their maximum residue limits (MRLs) in vineyard samples.     

Treatment of design fire uncertainty using Quadrature Method of Moments

The use of a single-design fire in a performance-based fire design code typically fails to account for the inherent uncertainty in knowledge of the future use of the space. Uncertainties in knowledge of intended use and the implications in terms of fuel loading and potential heat release rate can be bounded using probabilistic methods. Use of a cumulative distribution function (CDF) and the related probability density function (PDF) specify the best available estimate of the probability (likelihood) of a fire of given size to take place in a compartment. Monte Carlo simulation is a widely used computational method for treating uncertainty that might be described by a PDF. In this technique, one samples the uncertain variables from their underlying PDFs and runs a fire model for each sample. For complex fire models, this approach may be computationally intractable. In this work we present a computationally efficient technique called the Quadrature Method of Moments (QMOM) for propagating uncertainty bounds in distributions. In QMOM one solves for only the moments of a relevant uncertain parameter. The CDF of the uncertain parameter provides all the statistical information required for risk assessments. We consider a simplified propagation of uncertainty problem. Results using both the ASET and CFAST fire models indicate that computation of the moments of the PDF using QMOM and the reconstruction of the CDF by matching the moments with those of a four-parameter Generalized Lambda Distribution (GLD) give accurate results at a significantly smaller computational cost.     

Effect of Backing Plate Thermal Property on Friction Stir Welding of 25-mm-Thick AA6061

By using backing plates made out of materials with widely varying thermal diffusivity this work seeks to elucidate the effects of the root side thermal boundary condition on weld process variables and resulting joint properties. Welds were made in 25.4-mm-thick AA6061 using ceramic, titanium, steel, and aluminum as backing plate (BP) material. Welds were also made using a “composite backing plate” consisting of longitudinal narrow strip of low diffusivity material at the center and two side plates of high diffusivity aluminum. Stir zone temperature during the welding was measured using two thermocouples spot welded at the core of the probe: one at the midplane height and another near the tip of the probe corresponding to the root of the weld. Steady state midplane probe temperatures for all the BPs used were found to be very similar. Near root peak temperature, however, varied significantly among weld made with different BPs all other things being equal. Whereas the near root and midplane temperature were the same in the case of ceramic backing plate, the root peak temperature was 318 K (45 °C) less than the midplane temperature in the case of aluminum BP. The trends of nugget hardness and grain size in through thickness direction were in agreement with the measured probe temperatures. Hardness and tensile test results show that the use of composite BP results in stronger joint compared to monolithic steel BP.     

Multifunctional Additive Performance of Liquid Crystal Blended Polydecylacrylate in Lubricating Oil

A comparative study of additive performance (viscosity modifier [VM], pour point depressant [PPD], and anti wear [AW]) of homo polydecylacrylate (D) and its blend with three different types of liquid crystals (each containing three samples) has been performed. Very low concentrations (100 ppm) of liquid crystals are used in this study and processes include synthesis of D, characterization (FT-IR, NMR) and evaluation. A comparison based on performances has been made among the three different series of liquid crystals (LC) blended homo polydecylacrylate (D). The study indicates the LC blended additives are far better in AW performance compare to only D and their VM and PPD properties are comparable with D and amongst all the three series of liquid crystals, AW performance is better for long alkyl chain length sample. Multifunctional additive performance of this kind of LC blended polyacrylate is reporting for the first time.     

Liquid Crystal Blended Polyacrylate as a Potential Multifunctional Additive for Lube Oil

Polydecylacrylate (PDA) is synthesized, characterized (FT-IR and NMR), and evaluated for its performance as anti wear (AW), pour point depressant (PPD), viscosity modifier (VM), and thickening agent in lube oil of different compositions. In addition physical blend of it with liquid crystal (LC) of cholesteryl benzoate (CB) is also made and evaluated, and the data is compared. Molecular weight of the prepared polymer and that of it blends was determined by viscometric analysis. The blends showed better efficiency to act as multifunctional (AW, PPD, VM) additives compare to the pure homopolymer in lubricating oil.     

Rigid-motion-invariant classification of 3-D textures

This paper studies the problem of 3-D rigid-motion-invariant texture discrimination for discrete 3-D textures that are spatially homogeneous by modeling them as stationary Gaussian random fields. The latter property and our formulation of a 3-D rigid motion of a texture reduce the problem to the study of 3-D rotations of discrete textures. We formally develop the concept of 3-D texture rotations in the 3-D digital domain. We use this novel concept to define a "distance" between 3-D textures that remains invariant under all 3-D rigid motions of the texture. This concept of "distance" can be used for a monoscale or a multiscale 3-D rigid-motion-invariant testing of the statistical similarity of the 3-D textures. To compute the "distance" between any two rotations R(1) and R(2) of two given 3-D textures, we use the Kullback-Leibler divergence between 3-D Gaussian Markov random fields fitted to the rotated texture data. Then, the 3-D rigid-motion-invariant texture distance is the integral average, with respect to the Haar measure of the group SO(3), of all of these divergences when rotations R(1) and R(2) vary throughout SO(3). We also present an algorithm enabling the computation of the proposed 3-D rigid-motion-invariant texture distance as well as rules for 3-D rigid-motion-invariant texture discrimination/classification and experimental results demonstrating the capabilities of the proposed 3-D rigid-motion texture discrimination rules when applied in a multiscale setting, even on very general 3-D texture models.