Long-term effect of inducible silent ischaemia on left ventricular systolic function

A new method of thin section preparation of III-V semiconductors and multilayers for transmission electron microscopy (TEM) is presented that exhibits considerable advantages over conventional methods such as ion beam milling and jet thinning. GaAs thin films and multilayers of GaAs/In chi Ga1-chi As/GaAs are grown over an etch release layer of AlAs on GaAs substrates by molecular beam epitaxy (MBE). Planar TEM sections prepared by selective etching from these samples show improved ability to image film morphology and dislocation arrangements, and the resulting large thin electron transparent areas facilitate dislocation density measurements and detection of spatial variations. Avoidance of radiation effects and wedge shaping, both common to ion milled samples, allows this method to be used to prepare uniform thickness standards of single layer GaAs films for EDS analysis or lattice imaging.     

Inspecting the Lightweight Precast Concrete Panels in the Woodrow Wilson Bridge Deck of 1982

This paper presents the results of a detailed inspection of the deck panels of the Woodrow Wilson Bridge installed in 1982. The original cast-in-place concrete deck, constructed in 1962, was replaced with full-depth lightweight precast concrete deck panels that enabled rapid construction with minimal traffic disruption. The inspection of the Woodrow Wilson deck provides valuable information about the performance of the precast concrete panels, joints, and connections after 20 years of very harsh traffic loads and environmental stressors. The deck panels performed well overall, with the only serious problems at expansion and contraction joints. All of these joints exhibited cracking and rusting. The most prevalent type of cracking appeared to be due to restrained shrinkage between the new polymer concrete, the older precast panels, and the rigid steel joints. This location is more vulnerable to cracking and leaking because there is no prestress across the joint. The multilayered corrosion protection methods used for the transverse and longitudinal post-tensioning tendons were very successful.     

Mapping subalpine forest types using networks of nearest neighbour classifiers

Predictive vegetation mapping systems use a variety of remote sensing and other geospatial data in a mixture of empirical and biophysical models to predict vegetation characteristics. These systems are important tools for understanding and monitoring spatial patterns over the landscape. We have developed a system that partitions the geospatial data into resource gradients, indirect gradients and remotely sensed reflectance. These data are input to nearest neighbour classifiers and the resulting likelihoods are combined used Dempster's rule. We show that this system yields a more accurate classification than if the data were input to a single classifier.     

Transport properties of nonelectrolyte liquid mixtures—VII. Viscosity coefficients for isooctane and for equimolar mixtures of isooctane + n-octane and isooctane + n-dodecane from 25 to 100°C at pressures up to 500 MPa or to the freezing pressure

Changes in the high-pressure self-centering falling-body viscometer system, and the new automated data logging system, are described. Viscosity coefficient measurements made with an estimated accuracy of ± 2 % are reported for isooctane and for equimolar mixtures of isooctane + n-octane and isooctane + n-dodecane at 25, 50, 75, and 100°C at pressures up to 500 MPa or to the freezing pressure. The pressure dependence of the results is found to be represented equally well by the recent equation of Makita and by a free-volume form of equation. The Grunberg and Nissan equation gives a good fit to the mixture viscosity coefficient data.     

Corrections to the smooth hard-sphere theory of thermal conductivity for internal energy transport: Application to methane

Thermal conductivities have been calculated for dense fluid methane from the exact smooth hard-sphere expression valid for monoatomics with core sizes derived from fitting self-diffusion and viscosity data. The results are lower than experimental values by about 16% at all densities greater than the critical density. This difference is attributed to the effect of internal energy transport on this property.     

Comparison of techniques for measurement of shaft currents inrotating machines

Irregularities in the magnetic circuits of motors may result in spurious voltages that lead to shaft currents through the shaft, bearings, bearing supports and closing through the machine framework. The IEEE Standard Test Procedure for Polyphase Induction Motors and Generators discusses the shaft current and presents a measurement method for recording either the voltage across the ends of the shaft or the current. This paper discusses an alternative measurement approach and its application to the identification of shaft current in a large induction machine. Procedures were developed for measuring the shaft current. The procedures include the shunt current method and the measurement using the Rogowski coil. Only the Rogowski coil measurement yields accurate measurements of shaft currents whereas the other method either yields inaccurate measurement or may result in other problems for the machine's integrity. The theory and justification for the superiority of the Rogowski coil method is presented along with supporting test data     

Correlation and prediction of dense fluid transport coefficients. V. Aromatic hydrocarbons

A previously described method, based on consideration of hard-sphere theory, is used for the simultaneous correlation of the coefficients of self-diffusion, viscosity, and thermal conductivity for benzene, toluene, o-, m-, and p-xylene, mesitylene, and ethylbenzene in excellent agreement with experiment, over extended temperature and pressure ranges. Values are given for the roughness factors R _D , R , and R , and the characteristic volume, V ₀, is expressed as a function of both carbon number and temperature.     

Sparking, electrical discharge, and heating in synchronous andinduction machines: can it be controlled?

It is impossible to eliminate all occurrences of sparking and localized heating from the interior of electric machines during the 20-40 years that they are normally in service. One can minimize the probability of sparking and localized heating by exercising precautions which will eliminate or minimize the sources of these conditions in AC machines. Most new machines have a low probability of sparking, but some design steps can be taken which condition the machine as a sparking type or a nonsparking type. This paper discusses the aspects of arcing between rotor and stator in the air gap, sparking between rotor parts, sparking between frame components, sparking due to broken or open bars and endrings, and surface discharge on the stator winding. Also discussed is what action, if any, can be taken in design, application, and maintenance to eliminate or control these problems     

Prediction of the Viscosity of Liquid Mixtures: An Improved Approach1

A recently developed theoretically based scheme for the prediction of the viscosity of gas mixtures is modified by making use of the hard-sphere theory and applied to the prediction of the viscosity of liquid mixtures. Preliminary results are compared with viscosity measurements of mixtures of n-hexane with toluene and with cyclohexane, and demonstrate the predictive power of this scheme.     

Viscosity and thermal conductivity of binary n-heptane + n-alkane mixtures

New absolute measurements of the viscosity of binary mixtures of n-heptane with n-hexane and n-nonane are presented. The measurements, performed in a vibrating-wire instrument, cover a temperature range 290–335 K and pressures up to 75 MPa. The concentrations studied are 40 and 70% by weight of n-heptane. The accuracy of the reported viscosity data is estimated to be ±0.5%. The present measurements, together with other n-heptane + n-alkane viscosity and thermal-conductivity measurements, are used to develop a consistent semiempirical scheme for the correlation and prediction of these mixture properties from those of the pure components.