Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “normalization method”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 433 records · Page 24
All sourcesNASA NTRSDOE OSTI
NASA NTRS2009

Processing Electromyographic Signals to Recognize Words

A recently invented speech-recognition method applies to words that are articulated by means of the tongue and throat muscles but are otherwise not voiced or, at most, are spoken sotto voce. This method could satisfy a need for speech recognition under circumstances in which normal audible speech is difficult, poses a hazard, is disturbing to listeners, or compromises privacy. The method could also be used to augment traditional speech recognition by providing an additional source of information about articulator activity. The method can be characterized as intermediate between (1) conventional speech recognition through processing of voice sounds and (2) a method, not yet developed, of processing electroencephalographic signals to extract unspoken words directly from thoughts. This method involves computational processing of digitized electromyographic (EMG) signals from muscle innervation acquired by surface electrodes under a subject's chin near the tongue and on the side of the subject s throat near the larynx. After preprocessing, digitization, and feature extraction, EMG signals are processed by a neural-network pattern classifier, implemented in software, that performs the bulk of the recognition task as described.

Jorgensen, C. C.↗
NASA NTRS1987

An L-U implicit multigrid algorithm for the three-dimensional Euler equations

An LU implicit multigrid scheme is developed for the calculation of three-dimensional transonic flow through rotating cascades. This numerical method solves the unsteady Euler equations of gas dynamics in a finite-volume form. The implicit scheme makes it possible to take a much larger time step than is normally permitted in most explicit schemes, while the multigrid method is incorporated to accelerate the convergence rate for steady state calculations. Using this method, computational storage requirements are comparable to those of explicit schemes, while operation counts are considerably less than those found in the more widely-used ADI schemes.

Yokota, Jeffrey W.↗
NASA NTRS1994

Efficient Updating of Model Parameters Using Modal Coordinates

Model correlation methods based on iterative modification of physical model parameters have been used with frequent success. The cost and time to perform these methods is driven mostly by the need to recompute normal modes and parameter sensitivities from the full finite element model after each adjustment.

modal↗
NASA NTRS1972

Compressible boundary layer with normal pressure gradients: Quasi-similarity equations - Their properties at the wall and at sharp and blunt leading edges.

The failure of most viscous-inviscid interaction methods at strong interactions is attributed to the presence of a normal pressure gradient. A new theory is proposed for supersonic laminar boundary layers that can generate normal pressure gradients. The Navier-Stokes equations are reexamined by an order of magnitude analysis and all first and second order terms are retained. The approximation is found to be dependent not only on the boundary layer thickness but also on the ratio of the dimensionless viscosity and density. The equations are transformed into two quasi-similar, nonlinear, third order, ordinary integro-differential equations for the velocity and pressure as functions of a single transverse variable. The properties of the equations at the boundaries are discussed.

Seginer, A.↗
NASA NTRS1954

Analytical Study of Losses at Off-design Conditions for a Fixed Geometry Turbine

An analytical investigation was made to determine the off-design loss characteristics of a fixed-geometry turbine of which the experimental performance was known. The method of analysis utilized an effective loss parameter and assumed that the velocity normal to the blade entrance angle was lost as a total-pressure loss. The method also assumed constant tangential component of velocity between the station just upstream and just downstream of the stator and rotor trailing edge. Good correlation between the analytically and experimentally obtained performance was found over the entire map until limiting loading was approached. The large decrease in efficiency at low-speed high pressure ratios and at high-speed low pressure ratios was found in the analysis to be almost entirely due to the rotor incidence and turbine exit whirl losses. From the results of the investigation it was concluded that for turbines designed to operate efficiently at more than one point, the design must compromise rotor incidence angle and exit whirl losses.

Stewart, Warner L↗
NASA NTRS1974

Analysis of complex elastic structures by a Rayleigh-Ritz component modes method using Lagrange multipliers

The free vibrations of elastic structures of arbitrary complexity were analyzed in terms of their component modes. The method was based upon the use of the normal unconstrained modes of the components in a Rayleigh-Ritz analysis. The continuity conditions were enforced by means of Lagrange Multipliers. Examples of the structures considered are: (1) beams with nonuniform properties; (2) airplane structures with high or low aspect ratio lifting surface components; (3) the oblique wing airplane; and (4) plate structures. The method was also applied to the analysis of modal damping of linear elastic structures. Convergence of the method versus the number of modes per component and/or the number of components is discussed and compared to more conventional approaches, ad-hoc methods, and experimental results.

Klein, L. R.↗
NASA NTRS1975

Discrete model reference adaptive control with an augmented error signal

A method for designing discrete model reference adaptive control systems when one has access to only the plant's input and output signals is given. Controllers for single-input, single-output, nonlinear, nonautonomous plants are developed via Liapunov's second method. Anticipative values of the plant output are not required, but are replaced by signals easily obtained from a low-pass filter operating on the plant's output. The augmented error signal method is employed, ensuring finally that the normally used error signal also approaches zero asymptotically.

Ionescu, T.↗
NASA NTRS1975

Clinical applications of a quantitative analysis of regional lift ventricular wall motion

Observations were summarized which may have clinical application. These were obtained from a quantitative analysis of wall motion that was used to detect both hypokinesis and tardokinesis in left ventricular cineangiograms. The method was based on statistical comparisons with normal values for regional wall motion derived from the cineangiograms of patients who were found not to have heart disease.

Leighton, R. F.↗
NASA NTRS1976

Table and Charts of Equilibrium Normal-shock Properties for Pure Hydrogen with Velocities to 70 km/sec. Revised.

Errors found in the original edition are corrected. Refinement was made in procedures for solving the conservation relations for an incident (moving), standing, and reflected normal shock, as well as in computational methods for determining thermochemical-equilibrium hydrogen properties. A six-species hydrogen model replaces the original four-species model, and the heat of formation and spectroscopic constants used in this six-species model are listed in appendix A. In appendix B, comparisons are made between a number of methods for determining equilibrium thermodynamic properties for hydrogen for several values of pressure and temperatures to 50000 K. A comparison is also performed between the present method and a second method for determining thermodynamic properties and flow velocity behind an incident shock into pure hydrogen and behind a reflected shock.

Miller, C. G., III↗
NASA NTRS1976

The control of calcium metabolism by parathyroid hormone, calcitonin and vitamin D

Advances in analysis of chemistry and physiology of parathyroid hormone, calcitonin, and Vitamin D are described along with development of techniques in radioassay methods. Emphasis is placed on assessment of normal and abnormal patterns of secretion of these hormones in specific relation to the physiological adaptations of weightlessness and space flight. Related diseases that involve perturbations in normal skeletal and calcium homeostasis are also considered.

Potts, J. T., Jr.↗
NASA NTRS1978

Estimation of payload loads using rigid body interface accelerations

In the design/analysis process of a payload structural system, the accelerations at the payload/launch vehicle interface obtained from a system analysis using a rigid payload are often used as the input forcing function to the elastic payload to obtain structural design loads. Such an analysis is at best an approximation since the elastic coupling effects are neglected. This paper develops a method wherein the launch vehicle/rigid payload interface accelerations are modified to account for the payload elasticity. The advantage of the proposed method, which is exact to the extent that the physical system can be described by a truncated set of generalized coordinates, is that the complete design/analysis process can be performed within the organization responsible for the payload design. The method requires the updating of the system normal modes to account for payload changes, but does not require a complete transient solution using the composite system model. An application to a real complex structure, the Viking Spacecraft System, is given.

Chen, J. C.↗
NASA NTRS1982

Application of an airfoil stall flutter computer prediction program to a three-dimensional wing: Prediction versus experiment

An aerodynamic computer code, capable of predicting unsteady and C sub m values for an airfoil undergoing dynamic stall, is used to predict the amplitudes and frequencies of a wing undergoing torsional stall flutter. The code, developed at United Technologies Research Corporation (UTRC), is an empirical prediction method designed to yield unsteady values of normal force and moment, given the airfoil's static coefficient characteristics and the unsteady aerodynamic values, alpha, A and B. In this experiment, conducted in the PSU 4' x 5' subsonic wind tunnel, the wing's elastic axis, torsional spring constant and initial angle of attack are varied, and the oscillation amplitudes and frequencies of the wing, while undergoing torsional stall flutter, are recorded. These experimental values show only fair comparisons with the predicted responses. Predictions tend to be good at low velocities and rather poor at higher velocities.

Muffoletto, A. J.↗
NASA NTRS1982

The AVE/VAS 2: The 25 mb sounding data

The rawinsonde sounding program for the AVE/VAS II experiment is described and tabulated data at 25 mb intervals are presented. Soundings were taken at 3 hr intervals, was an 18 hour period. An additional sounding was taken at the normal synoptic observation time. The processing soundings method is discussed, estimates of the RMS errors in the data are presented, and an example of contact data is given. Termination pressures of soundings taken in the meso-beta-scale network are tabulated, as are observations of ground temperature at a depth of 2 cm.

Sienkiewicz, M. E.↗
NASA NTRS1983

The theory of an active magnetic regenerative refrigerator

The adiabatic temperature change with field which is limited to about 2 K/Tesla for ferromagnets near their Curie temperatures by the change of magnetization with temperature and the lattice heat capacity is discussed. Practical magnetic refrigerators operate on a regenerative cycle such as the Brayton cycle. This cycle can be executed through the use of an active magnetic regenerator, i.e., a regenerator composed of magnetic material that is cycled in an out of a magnetic field with appropriate fluid flows. The theory of these devices is predicted by solving the partial differential equations that describe fluid and the magnetic solid. The active magnetic regenerator is described along with the method of calculation. Temperature profiles for a normal regenerator and a magnetic regenerative refrigerator are shown.

Barclay, J. A.↗
NASA NTRS1984

Modification to shock fitting program

A modified form of the Lepping - Argentiero single spacecraft, shock normal determination procedure is presented. The modified method incorporates a simple predictor-corrector algorithm which allows a faster convergence rate and the use of average values of the parameters for the starting vector.

Acuna, M. H.↗
NASA NTRS1985

Recent Developments in Nonlinear Normal Mode Initialization

The importance of a balanced initial condition upon GLAS GCM forecasts and assimilation cycles was assessed. An effort to combine previous work on normal mode initialization at GLA is underway to develop an initialization process for the production version of the GLAS 4th order GCM. The major aspects of this work fall into two parts: vectorization of the linear projector code and the insertion of the mode projector and Machenhauer iteration algorithm into the full GLAS GCM. Memory and paging constraints place restrictions on the number of horizontal modes stored for initialization purposes, and on the manner in which they are stored. Only the first five vertical structures of the gravity modes are used. Differing phase and normalization conventions provided many elusive coding errors. A Machenhauer nonlinear normal mode initialization technique is used. This method entails the insertion of a modified version of the mode projector into the full GCM, and the modification of the GCM to allow for iterative calls to the projector.

Bloom, S. C.↗
NASA NTRS1984

Modification to shock fitting program

A modified form of the Lepping-Argentiero single spacecraft, shock normal determination procedure is presented. The modified method incorporates a simple predictor-corrector algorithm which allows a faster convergence rate and the use of average values of the parameters for the starting vector.

Acuna, M. H.↗
NASA NTRS1985

Acceleration of greater than 47 keV ions and greater than 2 keV electrons by interplanetary shocks at 1 AU

It is pointed out that collisionless shocks may be responsible for much of the particle acceleration which occurs in the interplanetary medium. The present investigation is concerned with the conditions for acceleration of particles by interplanetary shocks near 1 AU. Interplanetary shocks near 1 AU have large scale sizes, radii of curvature on the order of 1 AU, or about 1000 times the size of the earth's bow shock. At the considered heliocentric distance the shocks are primarily associated with solar flares and/or solar coronal transients. Observations of magnetic fields, solar wind plasma, and energetic ions and electrons from the ISEE 3 spacecraft are used to study the interplanetary shocks occurring in the period from launch in August 1978 through November 1979. Attention is given to the method of analysis, the determination of the normal to the shock, and energetic particle results.

Tsurutani, B. T.↗