The investigation of the effect of thermal barrier coating on the performance of Stirling engine

The shuttle heat transfer is one of the reasons reducing the performance of Stirling engines. This study is concerned with the reduction in shuttle heat transfer by coating the displacer. The displacer of a gamma type Stirling engine was coated with a layer of yttria‐stabilized zirconia (YSZ), and the effect of the coating on the engine performance was evaluated by comparing speed‐power and speed‐torque characteristics of the engine with coated and uncoated displacers. Characteristics were obtained for 700, 800 and 900°C heater temperatures. At each stage of the heater temperature, the charge pressure ranged from 1 to 3.5 bars with 0.5 bar increments. At 900°C heater temperature and 3 bars charge pressure, the shaft power before coating was 34.9 W, after coating the power increased to 43.8 W, which corresponds to a 25% increment. The temperature applied to the engine did not cause any damage on the coating layer. Copyright © 2008 John Wiley & Sons, Ltd.     

Automatic prostate cancer detection model based on ensemble VGGNet feature generation and NCA feature selection using magnetic resonance images

Multimedia Tools and Applications - Prostate cancer is one of the most common types of cancer in men and its frequency is 28 per hundred thousand in the world. This cancer is detected using...     

Investigation of Co-Substituted Nanosized Mn2Y-Hexaferrites Synthesized by Sol-Gel Autocombustion Method

The structural and electrical properties of Co-substituted and nano-sized Y-type hexagonal ferrites have been investigated in the present work. The samples with chemical composition Ba₂Co _x Mn_2?x Fe₁₂O₂₂ (x = 0.0, 0.5, 1.0, 1.5, 2.0) were prepared by sol-gel autocombustion method. The powdered samples and pellets were sintered simultaneously at 1000 °C for 5 h and characterized by means of DTA/TGA, FTIR spectroscopy, x-ray diffraction (XRD), field emission gun scanning electron microscopy, and energy dispersive x-ray spectroscopy. The XRD analysis confirms that the investigated ferrites have single phased Y-type hexagonal structure without showing any impurity phase. Lattice constants (a and c), cell volume (V), crystallite size (D), and x-ray density (ρ _x ) have also been calculated from the XRD data. DC electrical resistivity is measured within the temperature range of 30-100 °C for each sample and is observed to increase with increasing Co-substitution. The dielectric constant (∈) has also been measured which is observed to decrease with Co-substitution. Thus, high electrical resistivity and low dielectric constant make these materials suitable for multi-layer chip inductors and also for RF components and circuits.     

The effect of nitrogen flow rate on TiBN coatings deposited on cold work tool steel

TiBN coatings have high hardness and high adhesion. Due to these excellent properties there has been increasing interest in TiBN coatings. In this study, TiBN coatings were deposited on AISI D2 cold work tool steel and silicon wafers by closed field unbalanced magnetron sputtering (CFUBMS). The structural, mechanical and adhesion properties of these coatings were analysed by X-ray diffraction, scanning electron microscopy, microhardness test, indentation test and scratch tests. TiBN coatings produced by magnetron sputtering exhibited a dense and columnar structure. These results indicate that TiB₂, TiN and h-BN exist in crystalline forms at all coatings. The highest hardness was obtained at the lowest nitrogen flow rate. Very few cracks were observed at the edge of the indentation marks at the highest nitrogen flow rate. The highest critical load obtained with scratch test was identified as 102?N.     

XAFS Investigation of Platinum Impurities in Phosphate Glasses

The coordination environments of Pt impurities in a ternary K-aluminophosphate (KAP) glass and commercial K,Mg-aluminophosphate (KMAP) laser glasses have been investigated by Pt L _III-edge X-ray absorption fine structure (XAFS) spectroscopy. Pt valence in the KAP glass depends on the melt preparation atmosphere. Pt⁴⁺ ions form in melts that are bubbled with oxygen, whereas metallic Pt particles form when these same samples are remelted in air. Residual chlorine in KMAP glasses has an effect on Pt bonding. In chlorine-free samples, Pt⁴⁺ ions are coordinated with ∼5.4 (8) oxygen atoms with an average distance of 2.02 (1) Å. For glasses with low chlorine contents (<200 ppm Cl), the Pt⁴⁺ ions have both O and Cl atoms in the first coordination shell. As the Cl concentration increases, the number of O nearest neighbors decreases and for Cl:Pt > 5, only Cl nearest neighbors are observed. Pt⁴⁺ ions in these latter glasses are coordinated by ∼5.5 (8) Cl atoms at an average distance of 2.27 (2) Å.     

A fractal approach for interpretation of local instantaneous temperature signals around a horizontal heat transfer tube in a bubbling fluidized bed

Temperature signals measured around a horizontal heat transfer tube in a bubbling fluidized bed have been analyzed using Hurst's rescaled range (R/S) analysis. This analysis estimates and identifies long-term persistence or correlation in measured time series. The Hurst exponent H, which is evaluated from R/S analysis, also provides the local fractal dimension of the time series. A new approach to analyze an air fluidized particle system is proposed based on the evaluation of the Hurst exponent. Two Hurst exponents can be evaluated from a single time series, one from the discrete time fractional noise (where the linearity of the signal is subtracted and short-term fluctuations are emphasized) and the other from the signal itself (without subtracting the linearity of the signal). The authors argue that the Hurst exponent obtained from discrete time fractional noise characterizes the particle motion, whereas the Hurst exponent obtained from the signal itself characterizes the bubble motion. Moreover, a comparison between these two Hurst components identifies the zones where an alternating type of contact between the tube surface and the bubble-emulsion phase occur. The results were interpreted in conjunction with the mutual information function. The mutual information function provides the relationship between the data points separated in time and uses only the statistical relationship between the data points. The mutual information functions and the Hurst exponents exhibited similar trends around the heat transfer tube.     

Experimental study on shear resistance of reactive powder concrete beams without stirrups

Abstract

The tests results of 18 longitudinally reinforced reactive powder concrete (RPC) beams without stirrups and subjected to combined flexural and shear are presented in this paper. The main test variables were the ratio of the shear span-to-effective depth (a/d), the ratio of the longitudinal reinforcement (ρ_w), the percentage of steel fibers volume fractions (V_f) and the percentage of silica fume (SF) powder. The findings of this paper reveal that addition of steel fibers into the RPC mixture does not considerably affect the initial diagonal cracking load but it influences the ultimate load capacity. For all tested fibrous RPC beams, the ratio of the ultimate shear force to diagonal cracking force (V_u∕V_cr) have an average ratio of about 2.5. The shear design equations recommended by the (ACI 318-14) code, (CSA A23.3-04) code, (NZS 3101-06) code and (BS 8110-97) code have been modified to predict the ultimate shear strength of RPC beams without stirrups. The suggested equations gave satisfied predictions for the shear strength of the tested RPC beams with coefficients of variation (COV) ranging from 0.09049 to 0.1817.     

An Efficient Algorithm for the Single Machine Total Tardiness Problem

This paper presents an exact algorithm for the single machine total tardiness problem (1// Σ T_i). We present a new synthesis of various results from the literature which leads to a compact and concise representation of job precedences, a simple optimality check, new decomposition theory, a new lower bound, and a check for presolved subproblems. These are integrated through the use of an equivalence concept that permits a continuous reformation of the data to permit early detection of optimality at the nodes of an enumeration tree. The overall effect is a significant reduction in the size of the search tree, CPU times, and storage requirements. The algorithm is capable of handling much larger problems (e.g., 500 jobs) than its predecessors in the literature (≤ 150). In addition, a simple modification of the algorithm gives a new heuristic which significantly outperforms the best known heuristics in the literature.