A feasibility study of steam-jet refrigeration

In this paper a feasibility study of steam-jet refrigeration is conducted. First and second law analyses as well as the economics of a steam-jet refrigeration system are presented. Thermodynamic parameters investigated include the coefficient of performance (COP), refrigerating effect, condenser heat rejection, motive steam requirements, second law efficiency, and system irreversibility. Economic parameters investigated include equipment costs, space needs, power requirements, and installed and operational costs. © 1998 John Wiley & Sons, Ltd.     

Pulse oximetry theory and calibration for low saturations

Pulse oximetry is a widely used technique in biomedical optics, but currently available pulse oximeters rely on empirical calibration approaches, which perform poorly at low saturations. We present an exact solution for pulse oximetry and show how this can be used as the basis for the development of a semiempirical calibration approach that may be useful, especially at low saturations and variable probe geometries. This new approach was experimentally tested against traditional empirical calibration techniques on transmission pulse oximetry for monitoring of fetal sheep using a minimally invasive spiral probe. The results open the way for the development of more accurate pulse oximetry.     

Components of variation in normal personality.

Applied a random effects linear model to personality data (e.g., the Eysenck Personality Questionnaire and the Comrey Personality Scales) gathered from 138 adult Swedish twins and their families. The multiple relationships surrounding the twins allowed for the estimation of variance fractions due to several genetic and environmental factors. A striking pattern of similarity among personality traits emerged. All variables were characterized by having near-zero additive genetic, small–moderate nonadditive genetic, negligible prenatal, small postnatal familial, and quite large postnatal extrafamilial effects. Personality traits were influenced primarily by the environment, especially those outside the home. Genetic influences were confounded by cultural factors. It is suggested that temporal instability, genetic epistasis, or both could be underlying factors that unify the results for personality variables. (22 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The rate of formation of intermetallic layers between aluminum and steel below 660°C

The rate of formation of intermetallic compounds between aluminum and three ferritic steels, one austenitic steel, and Inconel has been determined by an electrolytic method. The steel was held at zero potential with respect to aluminum in a NaCl-AlCl₃ melt, and the current measured. Comparison of measured thicknesses of intermetallic layers with those calculated from the integrated current gives an average deposition efficiency of 95 pct. For the Type 304 austenitic steel thickness (min), andk is given by logk= −6400/T(⁰K) +4.469. The ferritic steels show a linear rate of growth of Al₅Fe₂, with an initial higher rate such that extrapolation of the linear curve back to zero time gives an intercept of 16±7 μm. The rate constants (mm min⁻¹) may be represented by log (rate)=α/T+β, and the values of α and β are respectively −2650 and−0.788 for a plain carbon steel,−6580 and + 3.469 for a 1.3 pct Cr, 0.4 pct Mo steel, and−5950 and +2.466 for a 2.2 pct Cr, 0.9 pct Mo steel. The more highly alloyed steels are thus attacked, more slowly. Results for Inconel could not be fitted to any simple equation. With the ferritic steels growth is by aluminum diffusing inwards; with Inconel it is by nickel diffusing outward.     

Apportioning: a technique for efficient reachability analysis ofconcurrent object-oriented programs

The object-oriented paradigm in software engineering provides support for the construction of modular and reusable program components and is attractive for the design of large and complex distributed systems. Reachability analysis is an important and well-known tool for static analysis of critical properties in concurrent programs, such as deadlock freedom. It involves the systematic enumeration of all possible global states of program execution and provides the same level of assurance for properties of the synchronization structure in concurrent programs, such as formal verification. However, direct application of traditional reachability analysis to concurrent object-oriented programs has many problems, such as incomplete analysis for reusable classes (not safe) and increased computational complexity (not efficient). We propose a novel technique called apportioning, for safe and efficient reachability analysis of concurrent object-oriented programs, that is based upon a simple but powerful idea of classification of program analysis points as local (having influence within a class) and global (having possible influence outside a class). We have developed a number of apportioning-based algorithms, having different degrees of safety and efficiency. We present the details of one of these algorithms, formally show its safety for an appropriate class of programs, and present experimental results to demonstrate its efficiency for various examples     

Micropatterning of Electrospun Polyurethane Fibers Through Control of Surface Topography

A novel technique was developed to control the deposition of electrospun polyurethane fibers using a silicone collector substrate patterned with soft lithography. This method can be used to control selective fiber deposition with broad pattern dimensions (50–500 µm) over a large area. The combination of ease of use, low cost, tunability, and generation of relatively large fiber mats available with this technique is expected to advance our ability to mimic the orientation and anisotropic properties of native tissues to generate improved tissue engineering scaffolds.

     

Diameter dependence of interwall separation and strain in multiwalled carbon nanotubes probed by X-ray diffraction and Raman scattering studies

We have made a systematic study on the diameter dependent spectral features in X-ray diffraction (XRD) and Raman scattering studies of multiwalled carbon nanotubes (MWCNTs) of various diameters in the range 5?100 nm. High resolution transmission electron microscopy (HRTEM) imaging reveals a systematic decrease in the interwall separation from 3.8 Å down to 3.2 Å as the diameter of nanotubes increases from 5.8 nm to 63.2 nm. Analysis of the XRD patterns shows an exponential decrease in d₀₀₂ interlayer spacing with increasing tube diameter, in close agreement with the HRTEM results. Further, XRD profile line width shows inverse diameter dependence and exponential increase in intensity as the diameter of the MWCNTs increases. Raman spectra of different diameter nanotubes show different evolutions of metallic and semiconducting components in the G-band, as found from spectral deconvolution. The frequency and full width at half maximum (FWHM) of the semiconducting component of the G^? band gradually decreases as the tube diameter increases. Ratio of intensities of G^? band to D-band first shows a sharp fall as the tube diameter increases from 7 nm to 15 nm and then slowly increases with increasing diameter. On the other hand, G′ mode frequency shows large up shift when average diameter is increased from 7 nm to 15 nm and then saturates for higher diameter tubes. Analysis of Raman and XRD data reveals that the lowest diameter (7 nm) MWCNTs have features similar to those of the single walled nanotubes, while the spectral features are distinctly different for higher diameter MWCNTs due to the interaction among tube walls that is very significant for large diameter MWCNTs. Observed diameter dependence of the spectral features is explained in terms of nanotube curvature and atomic vibrations involving interaction among the walls in MWCNTs. The present study demonstrates the power of XRD for nondestructive evaluation of diameter distribution and interwall separation in MWCNTs with wide range of diameters.     

Scuffing resistance of salt bath nitrocarburized medium carbon steel

The usefulness of the ferritic nitrocarburizing treatment for improving the tribological properties of ferrous components is well established. However, the thin compound layer of beneficial epsilon carbonitride that develops at the surface lacks the ability to bear high Hertzian stresses. Nitrocarburizing in the austenite phase field of the Fe---N---C system overcomes this disadvantage since the formation of a hard zone of martensite-bainite below the compound layer provides the back-up to withstand point loads. Results of the Falex scuffing test indicate that the failure load increases on account of the thicker compound layer at the surface. The results indicate further that the frictional heat generated during the test coupled with working by the jaws convert the retained austenite present in the sub-compound layer to harder microconstituents. The study suggests that the austenitic treatment could be useful for applications involving simultaneous heat and work such as hot working dies.     

Wear of steel in rolling contact with silicon nitride

Wear of steel (AISI M-50 and AISI 52100) bearing balls in lubricated rolling contact with ground and ground-and-lapped silicon nitride rods was studied using a ball-on-rod rolling-contact-fatigue (RCF) tester. The steel balls suffered significant wear in rolling contact with the as-ground (R_a = 0.18 μm) silicon nitride rods. The wear volume loss was approximately linear with the rolling distance. The wear rate increased linearly with the initial Hertzian contact stress in the range, 3–6.5 GPa. Examination of the wear tracks in a scanning electron microscope revealed surface features that suggested a wear mechanism that involved plastic deformation of the steel surface, squeezing of the metal symmetrically outward and rupture of the metal layers at the edges. The steel balls suffered negligible wear but failed by spalling in rolling contact with the ground-and-lapped silicon nitride rods (R_a = 0.08 μm) at an initial contact stress of 5.5 GPa. The as-ground silicon nitride rods exhibited neither wear nor spalling in the RCF tests, while the ground-and-lapped silicon nitride rods showed no wear but occasional spalling failure.