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.     

Complexity theory of parallel time and hardware

The parallel resources time and hardware and the complexity classes defined by them are studied using the aggregate model. The equivalence of complexity classes defined by sequential space and uniform aggregate hardware is established. Aggregate time is related to (bounded fanin) circuit depth and, similarly, aggregate hardware is related to circuit width. Interelationships between aggregate time and hardware follow as corollaries. Aggregate time is related to the sequential resource reversal. Simultaneous relationships from aggregate hardware and time to sequential space and reversal are shown (and conversely), and these are used as evidence for an “extended parallel computation thesis.” These simultaneous relationships provide new characterizations for the simultaneous parallel complexity class NC and for the complementary class SC. The evaluation of monotone planar circuits is shown to be in NC, in fact in LOGCFL.     

Correlation of high-pressure thermal conductivity,viscosity, and diffusion coefficients for n-alkanes

Thermal conductivity, viscosity, and self-diffusion coefficient data for liquid n-alkanes are satisfactorily correlated simultaneously by a method based on the hard-sphere theory of transport properties. Universal curves are developed for the reduced transport properties ^*, ^*, and D ^* as a function of the reduced volume. A consistent set of equations is derived for the characteristic volume and for the parameters R , R , and R _D, introduced to account for the nonsphericity and roughness of the molecules. The temperature range of the above scheme extends from 110 to 370 K, and the pressure range up to 650 MPa.     

Correlation and prediction of dense fluid transport coefficients. I. n-alkanes

Recent accurate measurements of the self-diffusion coefficient for n-hexadecane and n-octane and of the viscosity coefficient for n-heptane, n-nonane, and n-undecane over wide pressure ranges have been used to provide a critical test of a previously described method, based on consideration of hard-sphere theory, for the correlation of transport coefficient data. It is found that changes are required to the universal curve for the reduced viscosity coefficient as a function of reduced volume and, also, to the parameters R _D, R , and R which were introduced to account for effects of nonspherical molecular shape. The scheme now accounts most satisfactorily for the self-diffusion, viscosity, and thermal conductivity coefficient data for all n-alkanes from methane to hexadecane at densities greater than the critical density.     

Effect of energetic electron and proton bombardment on the reflectance of silicon-carbide mirrors in the extreme-ultraviolet region

Chemical-vapor-deposited silicon-carbide mirrors were exposed to bombardment by 95-keV electrons and 100-keV protons with accumulated fluxes comparable with those expected in low-altitude Earth orbit for simulated periods of as many as 5 years. The reflectances of four mirrors were measured at five wavelengths (58.4, 73.6, 104.8, 121.6, and 161 nm) and at 11 angles of incidence from 5° to 80°. The electron and proton exposure resulted in no significant change in the reflectances of the mirrors.     

Transport properties of nonelectrolyte liquid mixtures—IV. Viscosity coefficients for benzene,perdeuterobenzene, hexafluorobenzene,and an equimolar mixture of benzene + hexafluorobenzene from 25 to 100°c at pressures up to the freezing pressure

Viscosity coefficient measurements made with an estimated accuracy of ±2% using a self-centering falling body viscometer are reported for benzene, perdeuterobenzene, hexafluorobenzene and an equimolar mixture of benzene + hexafluorobenzene at 25, 50, 75 and 100°C at pressures up to the freezing pressure. The data for each liquid at different temperatures and pressures are correlated very satisfactorily by a graphical method based on plots of 9.118×10⁷ V ^2/3/(MRT)^1/2 versus logV, and are reproduced to within the experimental uncertainty by a free-volume form of equation. Application of the empirical Grunberg and Nissan equation to the mixture viscosity coefficient data shows that the characteristic constant G is practically temperature- and pressure-independent for this system.     

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.     

Instructional overview of IEEE 1349-2001-guide for the application of electric motors in class I, division 2 hazardous (classified) locations

This work presents an overview of IEEE 1349-2001, a Guide that assists individuals, organizations, and suppliers with the application of motors in Class I, Division 2 locations, where flammable gases and vapors may occasionally be present. Three-phase and single-phase ac synchronous and induction electric motors in sizes from fractional horsepower through 10 000 hp and beyond are covered in the Guide. Primary emphasis is on the use of general-purpose enclosures and precautions against excessive surface temperatures and sparking of rotor bars and enclosure joints. The Guide also provides guidance for maintaining the life-cycle integrity of motors in Division 2 locations. Existing codes and standards, such as the National Electrical Code, contain cautionary notes for general-purpose motor applications in Division 2 areas. This Guide documents industry experience and established practices for the application of general-purpose motors in Division 2 locations and provides guidance for applying motors in these locations. It is not a specification and is not intended to be used as a specification for purchasing motors installed in Division 2 locations. This paper does not replace the Guide, but should be used to supplement and understand the Guide. Significant motor temperature information is contained in the Guide including maximum recommended Division 2 exposed surface temperatures at full load. Manufacturers, users, and other industry experts worked about eight years to develop this consensus standard. It was approved by the IEEE-SA Standards Board in December 2001 and published in June 2002.     

Acceleration tests to determine salient pole synchronous motorinrush currents and torques

Determining torque and current at locked rotor and various slips during the acceleration test on a synchronous machine is very tedious and time consuming. Induction and synchronous machines behave similarly during acceleration except that synchronous machine acceleration can include a pulsation torque. Because of the salient poles, conditions exist where the synchronous motor has minimum torque at quadrature axis and maximum torque at direct axis during locked rotor or stall. Since synchronous machines do not have large numbers of rotor bars in the amortisseur winding, like the induction motor has in the squirrel cage, their stall times tend to be shorter. Due to the shorter stall time and large starting torque, locked-rotor torque and current are generally determined from acceleration tests conducted at reduced voltage rather than by tests at stand-still. Data showing that saturation effects impact both torque and current are presented in this paper. The data shows that the voltage index that has to be applied to the torque and current measured at reduced voltage varies with speed and can be obtained from a series of acceleration tests     

Estimation of timber volume in a coniferous plantation forest using Landsat TM

Optimisation of economic return from forests requires that comprehensive forest inventory data be available to support the design of harvesting strategies. Such inventory data can potentially be obtained by remote sensing. This study investigates the accuracy with which wood volume (m3 ha -1) in a plantation forest can be calculated from Landsat TM data at the pixel and foreststand spatial scales. Wood volumes were estimated from regression analysis, nonparametric line-fitting, and an N-dimensional K-nearest-neighbour classification scheme. At the pixel scale, relations between Landsat data and measured wood volume were found to be significant but weak, with r2 values of 0.3, and with correspondingly poor estimates of wood volume (root-mean-square errors rmses of 100 m3 ha -1). By averaging the pixel-scale estimates, wood volume estimates of acceptable accuracy were obtained for forest-stand areas of about 40 ha (rmses of 46 m3 ha -1). Parametric regression performed slightly better overall than non-parametric line fitting techniques for estimating wood volume. Estimates of similar accuracy to those obtained by regression were also given by NK-classification at the pixel-scale, provided K was large ( 15), although the classifier produced biased results at the forest-stand scale. It is concluded that Landsat TM only provides an acceptable data source for estimating wood volumes in plantation forests for areas of about 40 ha and larger. The very low dynamic range in the Landsat data is probably a significant factor limiting its use for inventory at more detailed scales.