Quantitative NMR spectroscopy by matrix pencil methods

The matrix pencil (MP) method, based on the singular value decomposition (SVD), is applied to quantitative NMR spectroscopy. Its relationship to other SVD-based methods is also presented. Simulations and applications are given to demonstrate the capability of superior performance.©1993 John Wiley & Sons Inc     

SiO2 degradation with charge injection polarity

We have investigated gate oxide degradation in metal-oxide-semiconductor (MOS) devices as a function of high-field constant-current stress for charge injection from both gate and substrate. The two polarities are asymmetric: gate injection, where the substrate Si-SiO₂ interface is the collecting electrode for the energetic electrons, shows a higher rate of interface-state generation (ΔD_it) and lower charge-to-breakdown Q_bd. Thus the collecting electrode interface, which suffers primary damage, emerges as a critical degradation site in addition to the injecting electrode interface, which has been the traditional focus. Consistent with a physical-damage model of breakdown, we demonstrate that interfacial degradation is an important precursor of breakdown, and that the nature of breakdown-related damage is physical, such as trap-generation by broken bonds     

Transistors made in laser recrystallized polysilicon on insulator films

lpcvd polycrystalline silicon films were deposited on thermally oxidized silicon as well as onlpcvd silicon nitride deposited on silicon. Acw argon ion laser was used to recrystallize the polysilicon film into large grains (grain size from 5μm to 40μm). Boron was then implanted and standard N-channel silicon gate process and N-channel metal gate process were carried out to realisemosfets on this material. Channel mobilities upto 450 cm²/V-sec for electrons have been measured. This thin filmmosfet has a four-terminal structure with a top and a bottom gate and the influence of one gate on the drain current due to the other gate has been investigated. Comparison of theI _D v-V _D curves of the devices with physical models was found in good agreement.     

An overhead and resource contention aware analytical model for overloaded Web servers

A Web server, when overloaded, shows a severe degradation of goodput initially, with the eventual settling of goodput as load increases further. Traditional performance models have failed to capture this behavior. In this paper, we propose an analytical model, which is a two-stage and layered queuing model of the Web server, which is able to reproduce this behavior. We do this by explicitly modelling the overhead processing, the user abandonment and retry behavior, and the contention for resources, for the FIFO and LIFO queuing disciplines. We show that LIFO provides better goodput in most overload situations. We compare our model predictions with experimental results from a test bed and find that our results match well with measurements.     

Collusion set detection using graph clustering

Many mal-practices in stock market trading—e.g., circular trading and price manipulation—use the modus operandi of collusion. Informally, a set of traders is a candidate collusion set when they have “heavy trading” among themselves, as compared to their trading with others. We formalize the problem of detection of collusion sets, if any, in the given trading database. We show that naïve approaches are inefficient for real-life situations. We adapt and apply two well-known graph clustering algorithms for this problem. We also propose a new graph clustering algorithm, specifically tailored for detecting collusion sets. A novel feature of our approach is the use of Dempster–Schafer theory of evidence to combine the candidate collusion sets detected by individual algorithms. Treating individual experiments as evidence, this approach allows us to quantify the confidence (or belief) in the candidate collusion sets. We present detailed simulation experiments to demonstrate effectiveness of the proposed algorithms.     

Progress in application of high temperature superconductor in tokamak magnets

It has long been known that high temperature superconductors (HTS) could have an important role to play in the future of tokamak fusion research. Here we report on first results of the use of HTS in a tokamak magnet and on the progress in design and construction of the first fully-HTS tokamak.     

Studies on melt spinning. VIII. The effects of molecular structure and cooling conditions on the severity of draw resonance

The effects of molecular structure and cooling conditions on the severity of draw resonance was investigated by carrying out carefully controlled melt spinning experiments. For the study, two types of polymeric materials were used: one which exhibits viscoelastic behavior (high-density polyethylene, polypropylene, and polystyrene), and the other which exhibits almost Newtonian behavior [nylon-6 and poly(ethylene terephthalate)]. In order to investigate the effect of cooling on the severity of draw resonance, different methods of cooling the molten threadline were employed. In one set of experiments, isothermal chambers of various lengths (3, 6, and 12 in.) were attached to the spinnerette face, so that the molten threadline, upon exiting from the spinnerette, began to cool in the ambient air only after it had passed through the isothermal chamber. This method of cooling is called “delayed cooling,” providing both an isothermal region (inside the isothermal chamber) where only stretching occurs, and a nonisothermal region (outside the isothermal chamber) where both stretching and cooling occur simultaneously. In other experiments, the temperature profile of the molten threadline was controlled by adjusting the temperature of the heated chamber. This method of cooling provides a gradual drop of the threadline temperature, compared to the more sudden drop when spinning into a cold environment provided at the spinnerette exit. The severity of draw resonance was recorded on movie film, and the thread tension was measured with a low-force load cell transducer and recorded on a chart recorder. The temperature of the threadline along the spin direction was measured using a fiber optical probe attached to a Vanzetti Infrared Thermal Monitoring System (Model TM-1). It was found that the severity of draw resonance depended on the molecular structure and the way the molten threadline was cooled. Of particular interest is the observation that, for the viscoelastic materials investigated, cooling destabilized the molten threadline outside the isothermal chamber. This gave rise to more severe resonant behavior, at and above the critical draw-down ratio, in contradiction to the theoretical prediction by Fisher and Denn. It was observed, also, that the elasticity of the materials tended to destabilize the molten threadline (i.e., it increased the severity of draw resonance), again in contradiction to the theoretical prediction of Fisher and Denn. It is believed that morphological changes of polymers may play an important role in the occurrence of draw resonance when a melt threadline is stretched under cooling. Our study indicated that a good understanding of draw resonance of viscoelastic fluids requires more careful study than the classical hydrodynamic stability analysis reported by Fisher and Denn. They based their analysis on several convenient and yet unjustified assumptions, and solely on phenomenological considerations. We suggest that future theoretical analysis of draw resonance be carried out by considering a fluid model with a nonlinear memory function in order to properly account for the deformation history of the fluid, and the relaxation and cooling processes in the die swell region and the region below it.     

Removal of p-nitrophenol using hydrodynamic cavitation and Fenton chemistry at pilot scale operation

In the current work removal of p-nitrophenol has been investigated using hydrodynamic cavitation, either operated individually or in combination with H₂O₂ and conventional Fenton process. In hydrodynamic cavitation, two different cavitating devices viz. orifice plate and venturi have been used. Effect of different operating parameters such as initial concentration (5 g/l and 10 g/l), inlet pressure (over a range 5.7–42.6 psi) and pH (over a range 2–8) on the extent of removal has been investigated. In conventional Fenton process two loadings of FeSO₄, 0.5 g/l and 1 g/l were investigated and three ratios of FeSO₄:H₂O₂ viz. 1:5, 1:7.5 and 1:10 were used. Removal observed with venturi was higher than with orifice plate in combination with Fenton chemistry. For 5 g/l initial concentration of p-nitrophenol, maximum removal of 63.2% was observed whereas for 10 g/l solution it was 56.2%.     

Use of a TiN cap to attain low sheet resistance for scaledTiSi2 on sub-half-micrometer polysilicon lines

A new process technology has been demonstrated that successfully addresses an urgent challenge in silicide technology scaling: the formation of low-resistivity TiSi₂ on sub-half-micrometer polysilicon lines. The key idea is the use of a TiN cap during the silicide process to minimize contaminants and stress in the film. No complex process steps have been added, and the thermal budget actually has been reduced, allowing for easy integration into standard CMOS technology. The new technology enables low sheet resistance values to be attained for scaled-down TiSi₂ thicknesses on sub-half-micrometer geometries, and thus, is eminently suited for scaling TiSi₂ technology