ESCA characterization of polyacrylonitrile-based carbon fiber precursors during its stabilization process

Oxidation process control plays a key role in influencing the development of carbon fiber properties. The characterization of oxidized fibers is difficult because of their poor solubility in organic solvents and strong absorbance. X-ray photoelectron spectroscopy (XPS) has been used in the surface characterization of carbon fiber precursors during the oxidation or stabilization process. The changes in surface elemental composition and functionalities of carbon and oxygen have been identified. Quantitative changes have been noticed in surface functional groups as the oxidation process proceeds. © 1994 John Wiley & Sons, Inc.     

Destruction of bacterial spores by phenomenally high efficiency non-contact ultrasonic transducers

Conventional wisdom stipulates that high power ultrasound without direct or indirect transducer contact with the medium to be treated is not possible. This seemingly correct notion is based upon two major hurdles: inefficient transmission of ultrasound from the piezoelectric material into air/gases and exorbitant attenuation of ultrasound by gases. The latter is a natural phenomenon about which nothing can be done, and the former requires an un-conventional approach to transducer design. After many years of R& D in this area, we have finally succeeded in producing transducers that generate immense acoustic pressure in air in the frequency range of ∼50 kHz→10 MHz. By using these transducers without any contact with the material, we demonstrate destruction of 99.9% of dried bacterial spore samples of a close relative of anthrax, Bacillus thuringiensis. Following further refinement of the transducers and the mechanism of their excitation, we anticipate that non-contact ultrasound will have numerous applications including inactivation of agents of bioterrorism and sterilization of medical and surgical equipment, food materials, and air-duct systems of buildings, airplanes, space stations, and others. Electronic Publication     

Nickel based CdSe,CdS, and CdSe1−x semiconductor separator in two-compartment electrochemical photocells

A two-compartment electrochemical photocell using nickel-based polycrystalline CdSe, CdS, and mixed chalcogenides showed promising potential for constructing regenerative and/or storage batteries. The cell was able to generate photovoltages of up to 700 mV and photocurrent of 2–6 mA/cm² when different aqueous electrolytes were used in the dark compartment. The illuminated compartment was filled with polysulphide electrolyte and light intensity used was 70 mW/cm². Properties such as the open-circuit voltage, the short-circuit current, the efficiency, and the effect of applied voltages in different redox couples are reported.     

Comparative study of oral clonidine and diazepam as premedicants in children

In a prospective, double-blind, controlled study the efficacy of clonidine was assessed in children, with respect to sedation, intubation response, and recovery. Fifty children, aged 4-12 years, undergoing general anesthesia were studied. Twenty-five children (group I) received oral diazepam) 0.2 mg/kg and another 25 children (group II) received oral clonidine 3 micrograms/kg, 90-120 minutes before induction of anesthesia. The level of sedation, hemodynamic changes to laryngoscopy and intubation, the recovery from anesthesia were noted and compared between the groups. Clonidine 3 micrograms/kg produced sedation comparable to diazepam 0.2 mg/kg (p > 0.1). There was significant (p > 0.01) attenuation of hemodynamic intubation response with clonidine. The recovery with clonidine was not delayed (p < 0.01). Clinically significant hypotension and bradycardia were not observed in any of the patients. We conclude that clonidine 3 micrograms/kg produces sedation comparable to diazepam 0.2 mg/kg and also attenuates the intubation response without increasing the incidence of complications.     

Robust design using Bayesian Monte Carlo

In this paper, we propose an efficient strategy for robust design based on Bayesian Monte Carlo simulation. Robust design is formulated as a multiobjective problem to allow explicit trade‐off between the mean performance and variability. The proposed method is applied to a compressor blade design in the presence of manufacturing uncertainty. Process capability data are utilized in conjunction with a parametric geometry model for manufacturing uncertainty quantification. High‐fidelity computational fluid dynamics simulations are used to evaluate the aerodynamic performance of the compressor blade. A probabilistic analysis for estimating the effect of manufacturing variations on the aerodynamic performance of the blade is performed and a case for the application of robust design is established. The proposed approach is applied to robust design of compressor blades and a selected design from the final Pareto set is compared with an optimal design obtained by minimizing the nominal performance. The selected robust blade has substantial improvement in robustness against manufacturing variations in comparison with the deterministic optimal blade. Significant savings in computational effort using the proposed method are also illustrated. Copyright © 2007 John Wiley & Sons, Ltd.     

Scalable model for predicting the effect of negative bias temperature instability for reliable design

The authors present a predictive model for the negative bias temperature instability (NBTI) of PMOS under both short term and long term operation. On the basis of the reaction-diffusion mechanism, this model accurately captures the dependence of NBTI on the oxide thickness (t _ox), the diffusing species (H or H ₂) and other key transistor and design parameters. In addition, a closed form expression for the threshold voltage change (DeltaV_th) under multiple cycle dynamic operation is derived. Model accuracy and efficiency were verified with 180, 130 and 90 nm silicon data. The impact of NBTI on the delay degradation of a ring oscillator and the various metrics of the SRAM such as its data retention voltage, read and hold margins, as well as read and write delay, is also investigated.     

Host country cultural influences on foreign direct investment

Abstract and Key Results

Effects of the inclination angle on natural convection heat transfer and entropy generation in a square porous enclosure

ABSTRACT

In this paper, we analyze numerically the effects of the inclination angle on natural convection heat transfer and entropy generation characteristics in a two-dimensional square enclosure saturated with a porous medium. There is a significant alteration in Nusselt number with the orientation of the enclosure at higher values of Rayleigh number. It reveals that the variation of entropy generation rate with the inclination angle is significant for higher values of Darcy number. The dominant source of irreversibility is due to heat transfer at low values of Darcy number, whereas entropy generation due to fluid flow dominates over that due to heat transfer for larger values of Darcy number.     

Synergetic effects of radiolytically degraded PTFE microparticles and organoclay in PTFE-reinforced ethylene vinyl acetate composites

This article reports exceptional synergistic effects observed in organic–inorganic dual filler containing ethylene vinyl acetate (EVA) composites. Polytetrafluoroethylene microparticles (PTFEMP) were produced by mechanically grinding radiolytically degraded PTFE; composites of EVA containing PTFEMP and organoclay were prepared in different proportions by melt compounding and their mechanical, melt flow, morphological and crystallographic characteristics were examined. Mechanical properties of ternary composites demonstrated high synergy between fillers, leading to manifold increase in the modulus of dual filler filled composites in comparison to single filler systems. Nielsen model fitted well with EVA/PTFEMP system; however it predicted remarkably low values for EVA/PTFEMP/organoclay system, confirming exceptional synergy between two fillers. Melt viscosity of EVA increased substantially on the addition of either of the fillers. X-ray diffraction studies revealed around 10% intergallery expansion in organoclay, in the composites having high loading of PTFEMP; though the crystallinity of EVA did not change.     

Periodic heat transfer in sunlit moist ground: Evaluation of rates of moisture evaporation

This paper present an analysis of the periodic heat transfer in moist ground exposed to periodic solar radiation and atmospheric temperature. This analysis yields a novel method for the evaluation of daily/hourly moisture evaporation from the ground. It is found that in harsh climates a significant amount of moisture ( 4 lb/ft²/day) is evaporated from sunlit ground near the sea and in windy regions. The rate of moisture evaporation decreases with relative humidity and increases with wind speed.