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.     

Theoretical and computational properties of transpositions

Transposable genetic elements are prevalent across many living organisms from bacteria to large mammals. Given the linear primary structure of genetic material, this process is natural to study from a theoretical perspective using formal language theory. We abstract the process of genetic transposition to operations on languages and study it combinatorially and computationally. It is shown that the power of such systems is large relative to the classic Chomsky Hierarchy. However, we are still able to algorithmically determine whether or not a string is a possible product of the iterated application of the operations.     

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     

An improved vertical-axis water-current turbine incorporating a channelling device

Water-Current Turbines (WCTs) are non-polluting electricity generation plants that harness the kinetic energy of natural water courses, using several kinds of rotors. At the School of Engineering of the University of Buenos Aires, researchers are developing a WCT whose particular characteristics improve technical and economic performance. A channelling device, integrated into the flotation system, is used to modify flow conditions in the neighbourhood of the rotor. This system was developed from theoretical modelling and small-scale model testing in a hydrodynamic test canal. The principal advantages of this kind of machine include reduced need for fixed civil works, ease of transport and relocation and autonomous, self-regulated operation, and it is expected to be a low-cost and long-lifetime system.     

Characterization of electrosynthesized iron diselenide thin films

Iron diselenide (FeSe₂) is an interesting p-type semiconductor with a band gap of 1 eV suitable for solar cell applications. Deposition of FeSe₂ thin films by electrodeposition from aqueous solutions is a low temperature and inexpensive technique. In the present work, FeSe₂ thin films were deposited onto tin oxide coated conducting glass substrates by cathodic electrodeposition technique. The deposited films were characterized by X-ray diffraction, Energy dispersive X-ray analysis, Scanning electron microscope and optical absorption techniques. The effects of electrolyte concentration and deposition potential on the structural, compositional, morphological and optical properties of FeSe₂ thin films are studied. The experimental observations are discussed in detail.     

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.     

Synthesis of Mixed Refrigerant Cascade Cycles

This paper considers the synthesis of refrigeration systems with refrigerant mixtures as working fluids. The employed refrigeration topology encompasses features from industrial liquefaction of natural gas (LNG) systems. This configuration consists of a combination of horizontal and vertical cascades generalizing the vertical cascade of pure refrigerant systems. The key features of mixtures exploited here are their ability to evaporate/condense over a temperature range and their potential to generate streams with different compositions through partial condensation. The synthesis problem is formulated and solved as a nonlinear program. The proposed methodology is illustrated using an example of cooling a methane-rich stream.