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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.

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At least 37 records · Page 2
All sourcesNASA NTRSDOE OSTI
NASA NTRS1994

(abstract) Modeling Protein Families and Human Genes: Hidden Markov Models and a Little Beyond

We will first give a brief overview of Hidden Markov Models (HMMs) and their use in Computational Molecular Biology. In particular, we will describe a detailed application of HMMs to the G-Protein-Coupled-Receptor Superfamily. We will also describe a number of analytical results on HMMs that can be used in discrimination tests and database mining. We will then discuss the limitations of HMMs and some new directions of research. We will conclude with some recent results on the application of HMMs to human gene modeling and parsing.

Hidden Markov Models HMMs proteins computational m↗
NASA NTRS1967

Hidden Variables and Magnetic Relaxation

Nonlinear generalization of Schroedinger equation describing hidden variables effect solved for spin-1/2 magnetic moment relaxing in constant magnetic field

MAGNETIC RELAXATION↗
NASA NTRS1973

Hidden-line removal at 20 pictures/second through hybrid techniques.

A real-time computer image generation method is presented that is designed to operate in a parallel-computing environment. It can provide good quality pictures of limited complexity if implemented on a general purpose hybrid computing system. Such a hybrid approach can generate a new image every 50 milliseconds. These results have been demonstrated by a feasibility test program which impelements the hybrid concepts described. This hybrid-picture generation capability is shown to represent a significant contribution to the area of real-time hidden-line removal.

Brown, R. M.↗
NASA NTRS1974

Current constraints on hidden mass in the Coma Cluster

Various possible means of accounting for the dynamical mass of the Coma Cluster are reviewed. We intentionally choose to emphasize conventional forms of hidden mass, specifically gas and low-luminosity stars, while adopting conventional mass-to-luminosity ratios for the observed luminous material in galaxies. We have attempted to combine all previous work relating to assumed gas parameters in order to examine precisely what constraints current observations, together with theoretical and observational upper limits, place on any gas in the Coma Cluster. In particular, we make use of a density distribution function that is consistent with the dynamical data and express all constraints in a manner which explicitly displays their dependence on Hubble constant, current observational flux levels, distance from the dynamical center of the cluster, and the mass of gas postulated.

Tarter, J.↗
NASA NTRS1983

Tool Severs Hidden Adhesive Bonds

New tool enters narrow gap between fragile materials and removes adhesively bonded filler without damage to adjacent surfaces. Reaches deep into narrow crevices to reach hidden bond lines. Tool originally developed to remove ceramic filler from between Space Shuttle surface-insulation tiles.

Keir, A. R.↗
NASA NTRS1981

Solution to the hidden-line problem

It is pointed out that realistic three-dimensional renderings of solid objects or surfaces by computers have long been needed. The NASA Dryden Flight Research Center will soon publish a report and the computer program on an algorithm that solves for hidden lines. The computer program is written in FORTRAN IV and its size is approximately 35N + 9500 words, where N is the number of elements. A number of pictures are presented which were drawn by a computer using the algorithm.

Hedgley, D. R.↗
NASA NTRS1984

The triangle compare method of hidden-line elimination

An original algorithm which solves the classical computer graphics problem of eliminating those lines that should not be visible in a wire-frame model representation of a solid figure is presented. The basis of this Triangle Compare algorithm is that any polygon, regardless of its complexity, can be constructed from a set of triangles. In the Triangle Compare algorithm, once the triangles defining the figure are defined, they are ordered based on the nearness of each triangle to the viewer and stored in a linked list. The nearest triangle are compared to all succeeding triangles. The remaining parts of triangles are synthesized into other triangles and are added in order to the linked list. Subsequent reference triangles are provided by a traversal of the linked list. After the entire list is traversed and each triangle used as a reference, the resulting list is used for a final rendering with hidden lines removed via calligraphic MOVE and DRAW commands.

Price, C. R.↗
NASA NTRS1986

Hydraulic-Leak Detector for Hidden Joints

Slow leakage of fluid made obvious. Indicator consists of wick wrapped at one end around joint to be monitored. Wick absorbs hydraulic fluid leaking from joint and transmits to opposite end, located outside cover plate and visible to inspector. Leakage manifested as discoloration of outside end of wick. Indicator reveals leaks in hidden fittings on hydraulic lines. Fast inspection of joints without disassembly. Used in aerospace, petroleum, chemical, nuclear, and other industries where removing covers for inspection impossible, difficult, or time-consuming.

Anderson, G. E.↗
NASA NTRS1987

Taking Impressions of Hidden Cavity Walls

Lightweight, portable internal-molding device makes it possible to measure radii of, or examine contours of, passageways in hidden or complicated cavities. With device, measurements made in field, without returning assemblies to shop or laboratory for inspection. Molding head expands when compressed air applied. Inflatable tubes around head perform dual sealing and aligning function.

Burley, D.↗
NASA NTRS1988

Output-sensitive hidden surface elimination for rectangles

An algorithm for the well-known hidden-surface elimination problem for rectangles, which is also known as the window rendering problem is presented. The time complexity of the algorithm is sensitive to the size of the output. Specifically, it runs in time that is O (n(1.5) + k), where k is the size of the output (which can be as large as theta (n(squared)). For values of k in the range between n(1.5)/log n and n squared, the algorithm is asymptotically faster than previous ones.

Atallah, Mikhail J.↗
NASA NTRS1991

Hidden-Markov-Model Analysis Of Telemanipulator Data

Mathematical model and procedure based on hidden-Markov-model concept undergoing development for use in analysis and prediction of outputs of force and torque sensors of telerobotic manipulators. In model, overall task broken down into subgoals, and transition probabilities encode ease with which operator completes each subgoal. Process portion of model encodes task-sequence/subgoal structure, and probability-density functions for forces and torques associated with each state of manipulation encode sensor signals that one expects to observe at subgoal. Parameters of model constructed from engineering knowledge of task.

Hannaford, Blake↗
NASA NTRS1990

IC5063: A merger with a hidden luminous active nucleus

IC5063 is a nearby galaxy classified as an SO and containing a system of dust lanes parallel to its major optical axis (Danziger, Goss and Wellington, 1981; Bergeron, Durret and Boksenberg, 1983). Extended emission line regions with high excitation properties have been detected over distances of up to 19 kpc from the nucleus. This galaxy has been classified as Seyfert 2 on the basis of its emission line spectrum. These characteristics make IC5063 one of the best candidates for a merger remnant and an excellent candidate for a hidden luminous active nucleus. Based on new broad and narrow band images and long-slit spectroscopy obtained at the ESO 3.6 m telescope, the authors present some preliminary results supporting this hypothesis.

Colina, L.↗
NASA NTRS1991

Hidden Markov model analysis of force/torque information in telemanipulation

A model for the prediction and analysis of sensor information recorded during robotic performance of telemanipulation tasks is presented. The model uses the hidden Markov model to describe the task structure, the operator's or intelligent controller's goal structure, and the sensor signals. A methodology for constructing the model parameters based on engineering knowledge of the task is described. It is concluded that the model and its optimal state estimation algorithm, the Viterbi algorithm, are very succesful at the task of segmenting the data record into phases corresponding to subgoals of the task. The model provides a rich modeling structure within a statistical framework, which enables it to represent complex systems and be robust to real-world sensory signals.

Hannaford, Blake↗
NASA NTRS1992

Laser Shearography Reveals Hidden "Unbonds"

Flaws identified faster than in ultrasonic inspection. Holographic technique detects hidden "unbonds", and does not require elaborate provisions for suppression of vibrations. Laser-shearographic apparatus used to observe object while stress being applied. Shearographic image indicative of deflection caused by stress. Also used to inspect complexly contoured surfaces.

Schaefer, Lloyd A.↗
NASA NTRS1992

Gamma rays from hidden millisecond pulsars

The properties were studied of a new class of gamma ray sources consisting of millisecond pulsars totally or partially surrounded by evaporating material from irradiated companion stars. Hidden millisecond pulsars offer a unique possibility to study gamma ray, optical and radio emission from vaporizing binaries. The relevance of this class of binaries for GRO observations and interpretation of COS-B data is emphasized.

Tavani, Marco↗