Corrosion of type 316L stainless steel in molten LiCl–KCl salt

Pyrochemical reprocessing in molten chloride salt medium has been considered as one of the best options for the reprocessing of spent metallic fuels. The AISI 316L stainless steel (SS) is envisaged as a candidate material for the fabrication of components for various unit operations like salt preparation vessel, electro‐refiner and cathode processor, on which ceramic coatings with metallic bond coat will be applied by the thermal plasma spraying. The unit operation like electro‐refining is carried out in the molten lithium chloride–potassium chloride (LiCl–KCl) eutectic salt at 773 K in argon atmosphere. The corrosion behaviour of the container vessel in molten chloride salts is therefore important, hence corrosion tests were carried out in a molten salt test assembly under argon gas atmosphere. The present paper discusses the corrosion behaviour of 316L SS in the molten LiCl–KCl eutectic salt at 873 K. The 316L SS samples were immersed in the molten LiCl–KCl eutectic for 25, 100 and 250 h, while 316L SS with yttria stabilized zirconia coating was exposed for 1000 h. The exposed samples were examined by optical and scanning electron microscope for corrosion attack. The X‐ray mappings of the cross‐section of the degraded layer onto the 316L SS indicated that the mechanism of corrosion corresponds to the selective diffusion of Cr to the surface with the formation of voids below, and the formation of chromium compounds at the surface. The results of the present study indicated that the yttria stabilized zirconia coating onto the 316L SS exhibits a better corrosion resistance in molten chloride salt than with uncoated 316L SS.     

A new parallel algorithm for parsing arithmetic infix expressions

A new parallel algorithm for transforming an arithmetic infix expression into a par se tree is presented. The technique is based on a result due to Fischer (1980) which enables the construction of the parse tree, by appropriately scanning the vector of precedence values associated with the elements of the expression. The algorithm presented here is suitable for execution on a shared memory model of an SIMD machine with no read/write conflicts permitted. It uses O(n) processors and has a time complexity of O(log²n) where n is the expression length. Parallel algorithms for generating code for an SIMD machine are also presented.     

Superior Analog Performance due to Source-Gate Overlap in Vertical Line-Tunneling FETs and Their Circuits

Silicon - This paper presents a Vertical Line-Tunneling FET (VLTFET) optimized for superior performance in analog applications. The saturation mechanism, DC, and small-signal behaviors are...     

Heat transport in magnetohydrodynamic physiological blood flow through a constricted artery

In this paper, we study how the magnetohydrodynamic (MHD) pulsatile flow of blood and heat transfer works through a constricted artery with a flexible wall. The human circulatory network consists of veins and arteries that sometimes contain constrictions, allowing the impact of the applied magnetic field on flow fields to be observed. The walls of the flowing medium are considered to be a function of time. The flowing blood is hypothesized as shear-thinning fluid, emulating Yeleswarapu's viscosity replica. Additionally, we consider the energy equation to understand the impact of a magnetic field on heat transfer rates for such flows. The vorticity transport equation along with the stream function equation is obtained using the vorticity–stream function technique. Numerical solutions of the governing nonlinear MHD equations and energy equation in addition to physically pertinent flow conditions were achieved by adapting a finite difference scheme. Considerable attention has been paid to ensure an accurate comparison between the current and previous results. The two sets of numbers appear to match closely. For an even deeper understanding of the flow and heat transport process, the effects of height of stenosis and diverse physiological parameters on time-averaged wall shear stress (TAWSS), rate of heat transport, and so on are explored in depth through their graphical depiction. In the vicinity of the constriction, it is observed that the separation becomes longer with increasing constriction height. Higher magnetic force strength leads to a reduction in separation length. Newtonian fluids transfer heat more rapidly in their narrowing regions and downstream than fluids with non-Newtonian behavior.     

Experimental and Morphological Investigations Into Electrical Discharge Surface Grinding (EDSG) of 6061Al/Al2O3p 10% Composite by Composite Tool Electrode

In this study, a special experimental setup of EDSG using EDM and surface grinding machine has been developed in the laboratory to investigate the effect of seven input parameters namely tool polarity, peak current, pulse on-time, pulse off-time, rotational speed, abrasive particle size, and abrasive particle concentration on material removal rate (MRR) as performance measure of the process. The novelty of the present research work is that successful efforts have been made to machine the 6061Al/Al₂O_3p 10% metal matrix composites (MMC) by composite tool itself. The copper-based composite tool electrodes were fabricated by powder metallurgy route with different sizes of abrasives of silicon carbide, while 6061Al/Al₂O_3p 10% MMC were fabricated through stir-casting process. The research outcome will identify the important parameters and their effect on MRR of 6061Al/Al₂O_3p 10% composite in EDSG. The experimental results reveal that tool polarity, peak current, and rotational speed are the most influential parameters that affect MRR in EDSG process. The micro-structural and morphological analysis of machined surfaces has also been carried out to analyze the surface topography. It has been concluded that the abrasive particles substantially improves the MRR after removing the resolidified layer from the machined surface.     

Spread-spectrum techniques for fiber-fed microcellular networks

It is well known that for a specified radio capacity, the peak performance [such as the minimum bit error rate (BER) or probability of outage] of subcarrier multiplexing (SCM)-based fiber-fed microcellular systems is limited by the nonlinearity of the optical source. Conversely, for a specified performance, the maximum radio capacity is restricted by the source nonlinearity. It is the goal of this paper to examine the robustness of a code-division multiple-access (CDMA)-based system in the presence of these nonlinearities. This is done by comparing the error and outage probabilities of a CDMA-based system to that of a conventional SCM system, which utilizes frequency-division multiple access (FDMA). It is shown that a CDMA system can relax the bounds on the performance or capacity. However, this improvement is obtained at the expense of large chunks of bandwidth. An alternative hybrid CDMA/FDMA approach is examined, wherein the inherent benefits of both CDMA and FDMA techniques are utilized. Performance evaluation shows that the hybrid system achieves the same system requirements in a more spectrally efficient manner     

Design and analysis of a flow control scheme over wireless networks

This paper studies the problem of congestion control on wireless networks. A dynamical model for the end‐to‐end network flow control that exploits the differentiation between congestion loss and physical channel error loss is proposed. The introduction of a specific wireless model is motivated by the distinctive presence of channel errors, which are often not known exactly. We assume that each wireless link is associated with an additional error function that depends on the current flow along the link and that accounts for the packet loss rate caused by the physical channel. This leads to a new dynamic flow control scheme that naturally extends a known mathematical model for the fluid‐flow approximation of the Transmission Control Protocol for wireline networks. The main objective of this work is to study the dynamical properties of the new model: we analyze its nonlinear dynamics, derive its stability properties, and study its robustness to delays. We also present and discuss some ns‐2 simulations of its dynamics. This work additionally looks at the actual implementation of the proposed scheme: by requiring only modifications to the application layer rather than the transport one, no alterations to the network infrastructure or transport protocols are needed. The article argues that the new scheme appears to be not only theoretically meaningful but also practically relevant for an application layer implementation. Copyright © 2011 John Wiley & Sons, Ltd.     

Favorable Environment for a Nondendritic Morphology in Controlled Diffusion Solidification

The novelty of the controlled diffusion solidification (CDS) process is the mixing of two precursor alloys with different thermal masses to obtain the resultant desired alloy, which is subsequently cast into a near-net-shaped product. The critical event in the CDS process is the ability to generate a favorable environment during the mixing of the two precursor alloys to enable a well-distributed and copious nucleation event of the primary Al phase leading to a nondendritic morphology in the cast part. The turbulence dissipation energy coupled with the undercooling of the precursor alloy with the higher temperature enables the copious nucleation events, which are well distributed in the resultant mixture.     

Low cycle fatigue and creep-fatigue interaction behavior of modified 9Cr-1Mo ferritic steel and its weld joint

The aim of the present paper is to study the low cycle fatigue and creep-fatigue interaction behavior of modified 9Cr-1Mo ferritic steel weld joint. Total axial strain controlled continuous cycling tests were conducted between 773 K and 873 K and at strain amplitudes ±0.25%, ±0.4%, ±0.6% and ±1%. Hold tests were also conducted at +0.6% and 823 K and 873 K temperatures to study the creep-fatigue interaction behavior of the weld joint. The alloy exhibited cyclic softening from first cycle onwards irrespective of the loading conditions. Failure location in the weld joint was correlated to the test parameters. Detailed replica study conducted on all the failed specimens revealed that most of the failures occurred in one side of the heat affected zone (HAZ) of the weld joint. Strain localization in the soft zone of the HAZ and subsurface creep cavity formation in this region and their linkage had caused enhanced crack propagation that translated into lower fatigue life of the weld joint at high temperatures. Type IV mode of failure was identified to be operative under tensile hold and high temperatures. The alloy was also found to be compressive dwell sensitive and it was ascertained that the lower life under compression hold compared to tension hold was due to the deleterious effect of oxidation.