Thermal Transport in BPSCCO System Between 20 and 170 K

Thermal conductivity of superconducting (Bi,Pb)2223 pellet in the temperature range 20–170 K is reported. Electronic contribution to thermal conductivity in the normal state is estimated to be 25%. Considering both phonon and phonon + electron approach, we attempted to examine the observed nature of the temperature dependence of thermal conductivity. Our analysis strongly supports the role of phonons as well as electrons in the origin of the thermal conductivity peak in the superconducting state. Some of the microscopic quantities evaluated from the best-fit parameters obtained from phonon + electron approach give reasonable values.     

Thermoelectric Power Studies on YBa2?xCaxCu3O7?δ System

The temperature dependence of the thermoelectric power of calcium substituted YBa_2–x Ca _x Cu₃O_7– pellets with 0x1.5 is presented between 60 K and 300 K. A metal–insulator transition was reported earlier by us in this system and was attributed to the ionic size-dependent localization effect. While the sign of thermoelectric power of all the calcium substituted samples was found to be positive, its magnitude increases significantly with calcium content in YBCO. The normal state thermoelectric power data of substituted YBa_2–x Ca _x Cu₃O_7– (0x1.5) are discussed in light of a two-band model originally proposed by Gottwick et al. for heavy fermion systems and later modified by Forro et al.     

A note on the linear instability of the Blasius flow

Summary It is found that in a ribbon-excited Blasius boundary layer, a wave Reynolds number defined here on the basis of phase speed and wave number of the disturbance remains nearly independent of the local mean flow Reynolds number, and so also of the streamwise distance, under the parallel flow approximation. Consequently, a limited similarity feature of the Orr-Sommerfeld equation has been found to exist for the streamfunction in the outer region of the boundary layer.     

Design of testable sequential circuits by repositioning flip-flops

This paper presents a technique to enhance the testability of sequential circuits by repositioning flip-flops. A novel retiming for testability technique is proposed that reduces cycle lengths in the dependency graph, converts sequential redundancies into combinational redundancies, and yields retimed circuits that usually require fewer scan flip-flops to break all cycles (except self-loops) as compared to the original circuit. Our technique is based on a new minimum cost flow formulation that simultaneously considers the interactions among all strongly connected components (SCCs) of the circuit graph to minimize the number of flip-flops in the SCCs. A circuit graph has a vertex for every gate, primary input and primary output. If gatea has a fanout to gateb, then the circuit graph has an arc from vertexa to vertexb. Experimental results on several large sequential circuits demonstrate the effectiveness of the proposed retiming for testability technique in reducing the number of partial scan flip-flops.     

Double stripe reconstruction of the Pt(111) surface

We have studied the reconstruction of the Pt(111) surface theoretically, using a 2D generalization of the Frenkel-Kontorova model. The parameters in the model are obtained by performingab initio density functional theory calculations. The Pt(111) surface does not reconstruct under normal conditions but experiments have shown that there are two ways to induce the reconstruction: by increasing the temperature, or by depositing adatoms on the surface. The basic motif of this reconstruction is a ‘double stripers with an increased surface density and alternatinghcp andfcc domains, arranged to form a honeycomb pattern with a very large repeat distance of 100–300 Å. In this paper, we have studied the ‘double stripe’ reconstruction of the Pt(111) surface. In agreement with experiment, we find that it is favourable for the surface to reconstruct in the presence of adatoms, but not otherwise.     

Scour below a High Vertical Drop

Experimental results on scour below a high vertical drop (drop height/critical depth >1) in uniform sands and gravels are presented. The experimental results are used to describe the effects of important parameters, identified from the dimensional analysis, on equilibrium scour depth. The important observations are that the equilibrium scour depth increases with increase in densimetric Froude number, whereas the scour depth decreases with increase in sediment size and tailwater depth. The time scale of scour depth that follows an exponential law is determined. The nondimensional time scale decreases with increase in densimetric Froude number.     

Diamond like carbon coatings deposited by microwave plasma CVD: XPS and ellipsometric studies

Diamond-like carbon (DLC) films were deposited by microwave assisted chemical vapour deposition system using d.c. bias voltage ranging from −100 V to −300 V. These films were characterized by X-ray photoelectron spectroscopy (XPS) and spectroscopic ellipsometry techniques for estimating sp ³/sp ² ratio. The sp ³/sp ² ratio obtained by XPS is found to have an opposite trend to that obtained by spectroscopic ellipsometry. These results are explained using sub-plantation picture of DLC growth. Our results clearly indicate that the film is composed of two different layers, having entirely different properties in terms of void percentage and sp ³/sp ² ratio. The upper layer is relatively thinner as compared to the bottom layer.     

Transactions Letters - Outage Capacity and Optimal Power Allocation for Multiple Time-Scale Parallel Fading Channels

In this paper, we address the optimal power allocation problem for minimizing capacity outage probability in multiple time-scale parallel fading channels. Extending ideas from the work of Dey and Evans (2005), we derive the optimal power allocation scheme for parallel fading channels with fast Rayleigh fading, as a function of the slow fading gains. Numerical results are presented to demonstrate the outage performance of this scheme for lognormal slow fading on two parallel channels.     

Ultra-Thin Si<Subscript>1−<Emphasis Type="Italic">x</Emphasis></Subscript>Ge<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript> Dislocation Blocking Layers for Ge/Strained Si CMOS Devices

We demonstrate ultra-thin (<150 nm) Si_1−x Ge _x dislocation blocking layers on Si substrates used for the fabrication of tensile-strained Si N channel metal oxide semiconductor (NMOS) and Ge P channel metal oxide semiconductor (PMOS) devices. These layers were grown using ultra high vacuum chemical vapor deposition (UHVCVD). The Ge mole fraction was varied in rapid, but distinct steps during the epitaxial layer growth. This results in several Si_1−x Ge _x interfaces in the epitaxially grown material with significant strain fields at these interfaces. The strain fields enable a dislocation blocking mechanism at the Si_1−x Ge _x interfaces on which we were able to deposit very smooth, atomically flat, tensile-strained Si and relaxed Ge layers for the fabrication of high mobility N and P channel metal oxide semiconductor (MOS) devices, respectively. Both N and P channel metal oxide semiconductor field effect transister (MOSFETs) were successfully fabricated using high-k dielectric and metal gates on these layers, demonstrating that this technique of using ultra-thin dislocation blocking layers might be ideal for incorporating high mobility channel materials in a conventional CMOS process.     

A single period inventory model with a truncated normally distributed fuzzy random variable demand

In this article, a single period inventory model has been considered in the mixed fuzzy random environment by assuming the annual customer demand to be a fuzzy random variable. Since assuming demand to be normally distributed implies that some amount of demand information is being automatically taken to be negative, the model has been developed for two cases, using the non-truncated and the truncated normal distributions. The problem has been developed to represent scenarios where the aim of the decision-maker is to determine the optimal order quantity such that the expected profit is greater than or equal to a predetermined target. This ‘greater than or equal to’ inequality has been modelled as a fuzzy inequality and a methodology has been developed to this effect. This methodology has been illustrated through a numerical example.