Border-ownership-dependent tilt aftereffect

Single-cell recordings from macaque visual cortex have shown orientation-selective neurons in area in V2 code for border ownership [J. Neurosci. 20, 6594 (2000)]: Each piece of contrast border is represented by two pools of neurons whose relative firing rate indicates the side of border ownership. Here we show that the human visual cortex uses a similar coding scheme by demonstrating a border-ownership-contingent tilt aftereffect. The aftereffect was specific for the adapted location, indicating that the adapted neurons have small receptive fields. We conclude that figure-ground organization is represented by border-ownership-selective neurons at early stages in the human visual cortex.     

Correlation of gamma-gamma prime mismatch and strengthening in Ni/Fe-Ni base alloys containing aluminum and titanium as hardeners

Various authors have invoked coherency strains and disregistry between the crystal lattices of the matrix and γ′ phase to account for considerable hardening in γ′-strengthened superalloys. Hagel and Beattie correlated the mode of precipitation with the degree of its lattice mismatch. Heydt and Whitney used this approach during the development of an Fe-Ni base high temperature alloy. To understand the role of such a relationship, an investigation of a few experimental Ni-base/Fe-Ni base alloys was carried out. These alloys were strengthened by variable titanium, aluminum, and molybdenum additions and contained chromium. Lattice parameters of the solution treated and aged samples were measured. The γ′ phase was electrolytically extracted for lattice parameter determinations, and γ?γ′ mismatch calculated. The γ?γ′ mismatch calculated. The γ?γ′ mismatch was correlated with room temperature hardness and stress rupture properties at 1200°F. The influence of alloying additions, matrix and γ′ lattice parameters were interrelated.     

Synchronous generator model identification and parameter estimation from operating data

A novel technique to estimate and model parameters of a 460-MVA large steam turbine generator from operating data is presented. First, data from small excitation disturbances are used to estimate linear model armature circuit and field winding parameters of the machine. Subsequently, for each set of steady state operating data, saturable inductances L/sub ds/ and L/sub qs/ are identified and modeled using nonlinear mapping functions-based estimators. Using the estimates of the armature circuit parameters, for each set of disturbance data collected at different operating conditions, the rotor body parameters of the generator are estimated using an output error method (OEM). The developed nonlinear models are validated with measurements not used in the estimation procedure.     

A Convenient Multivariate Gram-Charlier Type A Series

It is often necessary to approximate the probability density function of a random variable from given statistical moments. The Gram-Charlier Type A series is one well known method for such representations. In this note, the Gram-Charlier Type A series is generalized to the multidimensional case.     

Parameter Estimation Using An Orthogonal Series Expansion

This paper presents an innovative alternative to estimate parameters of a system for which a dynamic model is known. The focus of this paper is the estimation of the armature circuit parameters of large utility generators using real time operating data. Other applications are possible. The alternatives considered are the use of orthogonal series expansions, in general, and the Hartley series, in particular. The main idea considers the use of orthogonal series expansions for fitting operating data (e.g., voltage and currents measurements). This allows writing a set of linear algebraic equations that can be “ solved” in the least squares sense for the unknown parameters. The method shown utilizes the pseudoinverse in the solution. The essence of the approach is linear state estimation. Several alternative types of orthogonal expansions are briefly discussed. Although solutions are the same in all domains, one wishes to employ the expansion that gives the most efficient computation. The approach may be used for static as well as dynamic problems. The approach is tested for noise corruption likely to be found in measurements. The method is found to be suitable for the processing of digital fault recorder data to identify synchronous machine parameters.     

An assessment of ocean thermal energy conversion as an advancedelectric generation methodology

The history of ocean thermal energy conversion (OTEC), a process that employs the temperature difference between surface and deep ocean water to alternately evaporate and condense a working fluid, is reviewed. In the open-cycle OTEC configuration, the working fluid is seawater. In the closed-cycle configuration, a working fluid such as propane is used. OTEC is assessed for its practical merits for electric power generation. Because rather large amounts of seawater and working fluid are required, the energy requirements for pumping them may be greater than the energy recovered from the OTEC engine itself. The concept of net power production is discussed. The components of a typical OTEC plant are described with emphasis on the evaporator heat exchanger. Operation of an OTEC electric generating station is discussed, including transient operation. Recent experiments and efforts at the National Energy Laboratory-Hawaii (NELH) are summarized. Remarks are made on bottlenecks and the future of OTEC as an advanced electric generation methodology     

Transposition and Voltage Unbalance in High Phase Order Power Transmission Systems

—High phase order systems have been proposed at the early inception of power transmission engineering, but few direct applications have been made. High phase order transmission should be considered as an alternative in the case of high power density applications. In this article, an analysis of transposition of high phase order overhead transmission lines is presented and voltage unbalance in high phase order systems is considered. Definitions are presented for “fully transposed” and “roll transposed” along with advantages and disadvantages of each. A generalized voltage unbalance factor is introduced and utilized to determine the benefits of transposition. The generalized voltage unbalance factor is compared with three other possible unbalance factors to determine if the generalized voltage unbalance factor is an appropriate indication of unbalance. Exemplary results are presented for 6-phase and 12-phase designs. Conclusions show that the generalized voltage unbalance factor is a good indication of transmission line voltage unbalance and certain configurations may not need full rotation transposition to minimize the unbalance factor. The transposition analysis and voltage unbalance are considerations in the assessment of high phase order as a high power transmission alternative.     

Analysis of switching loads in networks using operational matrices

This letter presents an approach for rapid calculation of the steady state of time-varying electric networks based on the use of orthogonal series expansions. The method takes advantage of the operational properties available to most orthogonal series expansions, i.e., integration, differentiation, product, and coefficients matrices. An important feature of this approach is that an analytical expression for the steady state is provided. The approach may be seen as an extension of phasor analysis commonly used for the analysis of linear time invariant electric networks to periodic networks