Effect of Al on High-Temperature Oxidation of Cr–W Alloys

The effect of Al on the high temperature oxidation behavior of Cr–10 wt.%W alloy was investigated using a cyclical oxidation test at 1,000 °C in dry air. First, Al was added into the Cr–W alloy as an alloying element up to 8 weight percent. Although alloying with Al reduced the spalling, it did not eliminate it. Secondly, Al was applied to the surface using an aluminizing process. Forming an Al–Cr layer on the Cr–W alloy reduced oxidation rate significantly and eliminated spalling completely.     

Effect of spherical pores on the strength of a polycrystalline ceramic

Bending tests on a ceramic material, lead zirconate-titanate, with varying amounts of porosity, show that the decrease in strength due to spherical pores is much less than would be expected from the stress concentration factor. Using the Weibull probabilistic approach to brittle strength, it is shown that reasonable predictions may be made for the median strength for porosity up to about ten percent.

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Résumé Les essais de flexion sur un matériau céramique: zirconate-titanate de plomb, avec des quantités variables de porosités, montrent que la diminution de la résistance due à la porosité est plus faible que celle donnée par le facteur de concentration de contraintes. En utilisant la méthode statistique de Weibull pour la résistance fragile, il est montré que des prévisions raisonables peuvent être faites pour déterminer la résistance médiane pour une porosité jusqu'aux environs de dix pourcents.

     

Evaluation of the acceptance of glass in bone

Six glasses in the SiO₂-Na₂O-CaO-P₂O₅-Al₂O₃-B₂O₃-system were implanted in rabbit tibia. The bone-implant interfaces were studied by scanning electron microscopy (SEM) and in a push-out test. In SEM it seems possible to distinguish between physical contact and chemical bonding between glass and bone. The measured push-out strength is about 0.5 MPa if no bone contact exists. If physical contact exists the push-out strength is 2–3 MPa. The push-out strength of titanium falls within these limits. Glasses, which on basis of the SEM study are concluded to chemically bond to bone, show push-out strengths of 16–23 MPa. Two non-bonding glasses are compared. One possesses only a silica-rich surface, whereas the other possesses a calcium phosphate-rich surface. Both develop a close contact with bone, but neither bonds chemically. There is no significant difference in their push-out strengths, which are comparable to that of titanium. Even if a calcium phosphate-rich layer forms at the glass surface, bonding may be reduced if Al₂O₃ is included in the glass composition. Further, a phosphate-free bioactive glass is compared with two phosphate-containing bioactive glasses. The phosphate-free glass bonds by incorporating phosphate from the body fluid into its surface. Push-out data indicate that this glass is not as firmly attached to bone as the phosphate-containing ones. The calcium phosphate layer formed is non-uniform, which might explain the lower bonding strength.     

Symmetric and antisymmetric outer plethysms of schur functions

Complete tables are given for the calculations of the outer plethysms of S functions for the symmetric and/or antisymmetric cases {n} ? {m}, {1ⁿ} ? {m}, {n} ? {1^m}, and {1ⁿ} ? {1^m} for all values of m and n with m·n < 30 as well as for m = 3 and n = 10–14, m = 4 and n = 8–10, and m = 5 and n = 6.     

Speed Sensorless Direct Torque Control of Induction Motor Drives

Abstract

In this paper, a sliding mode speed observer for direct torque controlled (DTC) induction motor drives is developed. The speed observer accuracy is guaranteed through the current observer. The rotor speed is estimated by the observer based on the measured and estimated stator currents. The system is firstly simulated by MATLAB and then tested by hardware in the loop. Then, the application is implemented on a TMS320C6711, 32-bit fixed point digital signal processor (DSP). The experimental results show the robustness, feasibility, and performance of the proposed observer structure.     

Superporous cryogel/conductive composite systems for potential sensor applications

In situ synthesis of conductive polymers, poly(Aniline) (p(An)), poly(Pyrrole) (p(Py)), and poly(Thiophene) (p(Th)) within network of superporous cryogels with tunable functionalities as neutral poly(acrylamide) (p(AAm), anionic poly(acrylic acid) (p(AAc)), and cationic poly(4-vinylpyridine) (p(4-VP)) were carried out via oxidation polymerization technique. The highest conductivity values were measured for p(AAm)/p(An) semi-IPN cryogel with 1.4 × 10^?2 S.cm^?1 and for p(AAc)/p(Py) cryogel with 3.2 × 10^?4 S.cm^?1. In addition, to increase the amounts of conductive polymers within cryogel networks, reloading/polymerization cycle was carried out thrice, and found that there is no significant increase in the amounts of conductive polymers and the measured conductivity values. The prepared p(AAm), p(AAc), and p(4-VP) cryogels and their corresponding p(An), p(Py), and p(Th) composites were tested potential sensor materials against HCl and NH₃ vapor. The changes on conductivities for bare p(4-VP) cryogel were observed as 70 and 52-fold increase upon HCl and NH₃ gas treatment, respectively. The p(4-VP)/p(An) p(An) composites showed 7-fold conductivity decrease upon the treatments of HCl and NH₃ vapors. The p(AAm)/p(Py) composite responded 2-fold increase upon HCl vapor exposure and 50-fold decrease upon NH₃ vapor exposure. Furthermore, p(AAm)/p(Th) cryogel composite responded 7-fold decrease and 300-fold increase in their conductivities upon HCl and NH₃ vapor exposure, respectively.

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Macroscopic assembly of indefinitely long and parallel nanowires into large area photodetection circuitry

Integration of nanowires into functional devices with high yields and good reliability turned out to be a lot more challenging and proved to be a critical issue obstructing the wide application of nanowire-based devices and exploitation of their technical promises. Here we demonstrate a relatively easy macrofabrication of a nanowire-based imaging circuitry using a recently developed nanofabrication technique. Extremely long and polymer encapsulated semiconducting nanowire arrays, mass-produced using the iterative thermal drawing, facilitate the integration process; we manually aligned the fibers containing selenium nanowires over a lithographically defined circuitry. Controlled etching of the encapsulating polymer revealed a monolayer of nanowires aligned over an area of 1 cm(2) containing a 10 × 10 pixel array. Each light-sensitive pixel is formed by the contacting hundreds of parallel photoconductive nanowires between two electrodes. Using the pixel array, alphabetic characters were identified by the circuitry to demonstrate its imaging capacity. This new approach makes it possible to devise extremely large nanowire devices on planar, flexible, or curved substrates with diverse functionalities such as thermal sensors, phase change memory, and artificial skin.     

Architectural mimicry,spaces of modernity: the Island Casino,Izmir, Turkey

This article looks through the lense of an entertainment building in Izmir, Turkey, within the larger framework of modernity and identity in order to scrutinise ways in which cross-cultural influences are mediated. The programme of the building is conceptualised as a social structure and its aesthetics as a cultural form, which work to connect localities to the processes of modernisation and westernisation in the Turkish context of the 1950s' era. The analysis exposes how the edifice operates as a spatial structure that influences cultural norms and Western behaviour through practices of entertainment and architectural design, simultaneously serving as a medium through which people could perform and express their modernity.     

Development of Through-Thickness Reinforcement in Advanced Composites Incorporating Rigid Cellular Foams

This paper presents a method of joining carbon-fibre plies and rigid cellular foam core with stitching for producing light-weight composite structures. After resin infusion and consolidation, the stitched sandwich panel exhibits superior damage tolerance as well as improved transverse properties due to the presence of through-thickness fibre reinforcement. First part of the paper deals with the conceptual development of a multi-needle stitching machine for rigid foams. A needle penetration model for computing the penetration forces has been reported—there is a good agreement between the experimental and theoretical penetration force-displacement curves. A number of sandwich panels with orthogonal and bias stitch orientations have been developed and examined for stitch quality with the aid of X-ray tomography. The paper also presents results from quasi-static indentation, three-point bending and transverse compression tests, on both the stitched and unstitched sandwich panels.     

Glass Transition of Rainbow Trout and Its Oxidation Stability During Storage

Glass transition of rainbow trout muscle was measured by differential scanning calorimetry (DSC) as ?13°C. Sucrose and sorbitol (2, 2), sucrose and mannitol (2, 2), sucrose and gum arabic (2, 0.15), sucrose and carrageenan (2, 0.15), sorbitol and mannitol (2, 2), sorbitol and gum arabic (2, 0.15), sorbitol and carrageenan (2, 0.15), mannitol and gum arabic (2, 0.15) and mannitol and carrageenan (2, 0.15) were blended with ground rainbow trout as g/100 g fish and stored for 6 months separately at ?9°C, ?13°C and ?18°C. Total volatile basic nitrogen (TVB-N) and Thiobarbituric acid-reactive substances (TBARS) were determined at 1^st, 3^rd and 6^th months of storage periods. Biopolymers blends, storage temperature and storage period had a significant effect (p < 0.05) on the TVB-N and TBARS values.