Epoxy Composites Filled with Micro-Sized AlN Particles for Microelectronic Applications

With the rapid development of the electronic information industry, better properties are required for substrate and packaging materials such as high thermal conductivity, low coefficient of thermal expansion, and low dielectric constant. Polymers are ordinarily being used for this purpose due to their high electrical resistivity and low density, but unfortunately they suffer from a disadvantage like low thermal conductivity. To offset this deficiency, adding inorganic conductive particles to polymer is a versatile method. In view of this, the present work aims at developing a class of particulate filled polymer composites with micro-sized aluminum nitride (AlN) particles having an average particle size of 60–80 µm reinforced in epoxy matrix. A set of composites, with filler content ranging from 0 to 25 vol%, have been prepared by the hand-layup technique. Effects of filler percentage on various properties like effective thermal conductivity (k_eff), coefficient of thermal expansion (CTE), glass transition temperature (T_g), and dielectric constant (ε_c) are studied. It is found that the incorporation of AlN in resin increases the k_eff and T_g, whereas CTE of the composite decreases favorably. Though dielectric constant of the matrix increases with filler content yet it remains well within the desirable limit. With modified thermal and dielectric characteristics, these composites can possibly be used for microelectronics applications.     

Calculation of penetration resistance of brittle materials using spherical cavity expansion analysis

In this paper, we show that the ‘target resistance’ of brittle materials can be calculated accurately using spherical cavity expansion analysis and a conventional brittle material model. The stress field ahead of the tip of the penetrator is assumed to have spherical symmetry. The brittle material is modeled as an elastic material which cracks under tension. The cracked material is considered to be pulverized when it fails in compression, which is then characterized as a Mohr-Coulomb material with pressure dependent shear strength. The target resistance value found from this analysis compares well with the reported experimental values for AD995 alumina (Al₂O₃) and aluminum nitride (A1N).     

‘Liking’, ‘Buying’, ‘Choosing’ and ‘Take Away’ preference tests for varying degrees of hedonic disparity

Paired preference tests of liking require consumers to specify which of two foods are preferred or whether there is no preference. For ‘Buying’ preference tests, consumers specify which of two foods they are more likely to buy or whether they might buy either or neither. For ‘Choosing’ preference tests, consumers specify which of two foods they are more likely to choose when offered both, or whether they might choose both or neither. The first test is designed to predict greater degrees of liking, the second to predict buying behavior and the third to predict choice behavior. Yet, test results may not necessarily predict ‘real life’ behavior once consumers have left the testing situation; the ‘test’ preferences may not be ‘operational’. To validate the predictive ability of such tests, consumer behavior should be monitored for several months. Another approach is to allow consumers to take away some of the foods used in the test and observe what they take away. Consumers of potato chips were required to taste chips whose flavor and appearance were obviously different. A first group (N = 107) were given ‘Liking’, ‘Buying’ and ‘Choosing’ preference tests for two palatable types of chip. After the test, out of sight of the experimenter, consumers were presented with two rows of plain plastic ‘snack’ bags, filled with the chips used in the test. They could take away either two bags of the same type of chip (a ‘Take Away’ preference) or one of each type (no ‘Take Away’ preference) or take neither (rejection). They were also subtly questioned regarding whether they were going to consume the chips themselves or were going to share them with friends. A second group (N = 103) repeated the experiment. However, for these consumers, one type of chip was unpalatable. In general, ‘Buying’ preferences corresponded more to ‘Take Away’ preferences while ‘Liking’ and ‘Choosing’ preferences showed little correspondence. For the palatable chips, the preferences were spread more evenly than for the case where one type of chip was undesirable. In this latter case, approximately 50% of consumers were consistent over all tests in choosing the palatable chip. This might suggest operational preferences. ‘Take Away’ preferences suggested low predictability for paired preference tests of liking, choosing and buying. ‘Take Away’ preferences are not a substitute for monitoring consumer behavior for several months but they are a step in the right direction.     

Brain Tumour Segmentation with a Muti-Pathway ResNet Based UNet

Journal of Grid Computing - One of the most important parameters that hackers have always considered is obtaining information about the status of computer networks, such as hacking into databases...     

Pathfinder algorithm optimized fractional order tilt-integral-derivative (FOTID) controller for automatic generation control of multi-source power system

Microsystem Technologies - This paper introduces a fractional order tilt-integral-derivative (FOTID) controller which is structurally analogous to fractional order proportional-integral-derivative...     

Improved prediction of daily pan evaporation using Deep-LSTM model

Neural Computing and Applications - Precise measurement or estimation of evaporation losses is extremely important for the development of water resource management strategies and its effective...     

Characteristics and catalytic properties of Pt–Sn/Al2O3 nanoparticles synthesized by one-step flame spray pyrolysis in the dehydrogenation of propane

The Pt–Sn/Al₂O₃ catalysts with 0.3 wt% Pt and 0.5–1.5 wt% Sn loading were prepared by one-step flame spray pyrolysis (FSP). Unlike the catalysts prepared by conventional impregnation method, the FSP-derived catalysts were composed of single-crystalline γ-alumina particles with the as-prepared primary particle size of 10–18 nm and contained only large pores. The FSP catalysts exhibited superior catalytic activity and better stability than the ones made by impregnation in the dehydrogenation of propane, while they did not alter the selectivity to propylene (in all cases, propylene selectivity ≥96%). The presence of large pores in the flame-made catalysts not only facilitated diffusion of the reactants and products but could also lessen the amount of carbon deposited during reactions. As revealed by CO chemisorption, transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS), the metal particles appeared to be partially covered by the alumina matrix (Al–O) due to the simultaneous formation of particles during FSP synthesis. Such phenomena, however, were shown to result in the formation of active Pt–Sn ensembles for propane dehydrogenation as shown by higher turnover frequencies (TOFs).     

A new approach to compensation of extra high voltage transmission lines

A computer-aided design procedure has been developed for the series compensation of an extra high voltage line with a compensating network connected at one or the other end or both ends. Higher degree polynomial equations are derived in terms of compensating elements to compute the network parameters for optimum received power with constrained capacitor terminal voltage, safe line current, Ferranti voltage and transient stability. It is shown that series capacitors located at both ends provide the most effective means from the viewpoint of power transmission capability in either direction, transmission efficiency and series capacitor rating in comparison with a capacitor located at one or the other end.     

A transversely isotropic composite with a penny-shaped crack

Summary We consider the problem of determining the stress intensity factor and the crack energy in a transversely isotropic composite medium, containing a penny-shaped crack. We assume that the crack surface is perpendicular to the bond face and the crack is opened by constant internal pressure. By use of integral transform, we reduce the problem to solving a Fredholm integral equation of the second kind. Numerical results are given for the combination of some practical materials such as magnesium and cadmium. The effect of transverse isotropy upon the stress intensity factor, the crack energy and the deformation on the crack surface is discussed.

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Ein transversal, isotropes, komposites Medium mit einem münzenförmigen Riß

Zusammenfassung Das Problem der Bestimmung des Spannungsintensitätsfaktors und der Rißenergie, in einem transversalen, isotropen, kompositen Medium mit einem münzenförmigen Riß, wird betrachtet. Es wird vorausgesetzt, daß die Rißoberfläche normal zur Verbundfläche liegt, und der Riß sich durch konstanten inneren Druck öffnet. Durch Anwendung einer Integraltransformation, wird das Problem auf die Lösung einer Fredholmschen Integralgleichung zweiter Art reduziert. Numerische Ergebnisse werden für die Kombination einiger Materialien, wie Magnesium und Cadmium angegeben. Der Einfluß der transversalen Isotropie auf den Spannungskonzentrationsfaktor, die Rißenergie und die Deformation an der Rißoberfläche werden diskutiert.

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With 3 Figures

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This work is supported by the Board of Scientific and Industrial Research, Orissa (India).     

Atmospheric Corrosion Resistance of Stainless Steel: Results of a Field Exposure Program in the Middle-East

Stainless steels have been widely used as architectural and construction materials because of their high degree of corrosion resistance, unique aesthetic quality, and stability in an unpolluted atmosphere. Although stainless steel is highly corrosion resistant, localized corrosion can occur in certain environments, especially in marine atmospheric conditions if the appropriate grade is not used. Exposure of stainless steel to an environment more aggressive than the limiting conditions may be harmful to its aesthetic appearance and ultimately even to its load-bearing capacity.