Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “Search”

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 163 records · Page 9
All sourcesNASA NTRSDOE OSTI
NASA NTRS2016

Earthdata Search: Scaling, Assessing and Improving Relevancy

NASA's Earthdata Search (https:search.earthdata.nasa.gov) application allows users to search, discover, visualize, and access NASA and international interagency data about the Earth. As a client to NASA's Common Metadata Repository (CMR), its catalog of data collections grew 700 in late 2015. This massive expansion brought improved search and discovery to the forefront of the client's usability needs. During this talk, we will give a brief overview of the application, the challenges that arose during this period of growth, the metrics-driven way we addressed them, and the latest outcomes.

CMR↗
NASA NTRS2017

Earthdata Search Summer ESIP Usability Workshop

The Earthdata Search Client has undergone multiple rounds of usability testing during 2017 and the user feedback received has resulted in an enhanced user interface. This session will showcase the new Earthdata Search Client user interface and provide hands-on experience for participants to learn how to search, visualize and download data in the desired format.

Discovery↗
NASA NTRS1971

Parameter identification using a creeping-random-search algorithm

A creeping-random-search algorithm is applied to different types of problems in the field of parameter identification. The studies are intended to demonstrate that a random-search algorithm can be applied successfully to these various problems, which often cannot be handled by conventional deterministic methods, and, also, to introduce methods that speed convergence to an extremal of the problem under investigation. Six two-parameter identification problems with analytic solutions are solved, and two application problems are discussed in some detail. Results of the study show that a modified version of the basic creeping-random-search algorithm chosen does speed convergence in comparison with the unmodified version. The results also show that the algorithm can successfully solve problems that contain limits on state or control variables, inequality constraints (both independent and dependent, and linear and nonlinear), or stochastic models.

Parrish, R. V.↗
NASA NTRS1973

The search for signals from extraterrestrial civilizations.

The probability that a star has a habitable planet with a communicative civilization is investigated. One approach to the search problem is to assume that the other civilization will do most of the work, which implies that the search is limited to 'supercivilizations' able to transmit detectable signals in all directions all the time. The development of an optimal search strategy is discussed together with questions of the probability of success.

Walker, J. C. G.↗
NASA NTRS1973

LP-search and its use in analysis of the accuracy of control systems with acoustical models

The LP-search is proposed as an analog of the Monte Carlo method for finding values in nonlinear statistical systems. It is concluded that: To attain the required accuracy in solution to the problem of control for a statistical system in the LP-search, a considerably smaller number of tests is required than in the Monte Carlo method. The LP-search allows the possibility of multiple repetitions of tests under identical conditions and observability of the output variables of the system.

Sergeyev, V. I.↗
NASA NTRS1973

The advanced OPLE for search and rescue

Recent technological advances have made it possible to develop an advanced OMEGA position location experiment for a global search and rescue application. This application generated some new problem areas such as the OMEGA lane ambiguity, random access, location accuracy, real time processing, and size and weight of the Search and Rescue Communication (SARCOM). This experiment will demonstrate the feasibility of instantaneous alarm and position location by using a relatively inexpensive, battery operated, three-pound package. This package can transmit the alarm and position through a synchronous satellite to a search and rescue station in less than three minutes.

Morakis, J. C.↗
NASA NTRS1976

An observational program to search for radio signals from extraterrestrial intelligence through the use of existing facilities

It is argued that a substantial portion of the capability for detecting microwave signals from extraterrestrial civilizations lies not in the application of ever larger antenna collecting areas but rather in the application of millions or billions of simultaneous frequency-channel observations combined with rapid and powerful data processing techniques. The application of these methods to existing facilities is discussed in terms of a program of modest expense and duration which will seek to discover certain classes of extraterrestrial signals of intelligent origin while defining boundaries to the search problem throughout the range of interest. This program will investigate radio-astronomical phenomena of interest and simultaneously define the background of environmental radiation in order to determine physical limitations on both the search strategies and the potential for deep-space communications. Signal parameters that must be determined are examined along with the potential of existing radio-astronomical facilities for detecting narrow-band signals. A seven-year program is described which will carry out a search for extraterrestrial intelligence over 80% of the sky and over the entire frequency range from 1 to 25 GHz with a sensitivity limit varying from 10 to the -21st power W/sq cm at the lowest frequencies to 10 to the -19th power W/sq cm at the higher frequencies.

Edelson, R. E.↗
NASA NTRS1976

Improvements in search and rescue distress alerting and locating using satellites

This paper describes a system concept for search and rescue which is capable of making a major contribution to saving lives and reducing the search time for downed aircraft. In addition, a beacon location experiment is described using the Amateur Radio Satellite Corporation Oscar-6 and Oscar-7 spacecraft. The purpose of this experiment was to demonstrate the system concept above by determining the geographical location of a low power 'distress beacon' via satellite based on a single pass of Doppler frequency measurements. Preliminary results are presented showing beacon location recovery on the order of 10 km with indications that an order of magnitude improvement is entirely possible. This experiment is in support of NASA's current exploration into the role satellites might play in providing much needed improvements in the reliability, coverage and accuracy of present search and rescue procedures.

Brandel, D. L.↗
NASA NTRS1977

Searching for extraterrestrial intelligence - The ultimate exploration

A survey highlighting the central issues of the SETI program (Search for Extraterrestrial Intelligence), including its rationale, scope, search problems, and goals is presented. Electromagnetic radiation is suggested as the most likely means via which knowledge of extraterrestrial intelligence will be obtained, and the variables governing these signals are discussed, including: signal frequency and polarization, state, possible coordinates, and signal duration. The modern history of SETI and NASA's involvement is briefly reviewed, and the search strategies used by the Jet Propulsion Laboratory and the Ames Research Center are discussed and compared. Some of the potential scientific and cultural impacts of the SETI program are mentioned, noting advancements in technological, biological, and chemical research.

Black, D.↗
NASA NTRS1977

An experiment protocol for a search for radio signals of extraterrestrial intelligent origin in the presence of man-made radio frequency sources

Some aspects of signal extraction in a microwave search for evidence of extraterrestrial intelligence are examined. Parametric relations are summarized which are applicable to a microwave search of constrained duration that employs FFT spectrum-analyzer receivers, with sensitivity enhancement by spectrum accumulation and detection by a threshold criterion. Three types of natural and man-made false alarms are identified, the probability of false alarm in a single data channel is computed, and the implications of false alarms for a constant-beamwidth sky survey are considered. It is shown that the key to an efficient search is the prompt and unambiguous elimination of false alarms. An experimental protocol is suggested which eliminates spurious signals primarily through procedural techniques involving antenna repointing, delayed repeated observations, and storage of particular historical parameters for suspect signals.

Edelson, R. E.↗
NASA NTRS1977

Results of literature search on dielectric properties and electron interaction phenomena related to spacecraft charging

The objective of the literature search was to determine the required material properties and electron interaction parameters needed for modeling charge buildup and breakdown in insulators. A brief overview of the results of the literature search is given. A partial list of the references covered is included in a bibliography. Although inorganic insulators were also considered in the search, coverage is limited to the organics, primarily Kapton and Teflon.

Wall, J. A.↗
NASA NTRS1977

Space shuttle search and rescue experiment using synthetic aperture radar

The feasibility of a synthetic aperture radar for search and rescue applications was demonstrated with aircraft experiments. One experiment was conducted using the ERIM four-channel radar and several test sites in the Michigan area. In this test simple corner-reflector targets were successfully imaged. Results from this investigation were positive and indicate that the concept can be used to investigate new approaches focused on the development of a global search and rescue system. An orbital experiment to demonstrate the application of synthetic aperture radar to search and rescue is proposed using the space shuttle.

Sivertson, W. E., Jr.↗
NASA NTRS1977

The Search for Extraterrestrial Intelligence (SETI)

A bibliography of reports concerning the Search for Extraterrestrial Intelligence is presented. Cosmic evolution, space communication, and technological advances are discussed along with search strategies and search systems.

Morrison, Philip↗
NASA NTRS1978

Observational program options and system requirements for the search for extraterrestrial intelligence /SETI/

The possibility that intelligent life may be widespread in the universe is now being investigated. A formula for estimating the number of coexisting communicative civilizations has been developed by Drake. A good way of conducting a search for extraterrestrial intelligence (SETI) is to examine the microwave window of the electromagnetic spectrum for narrow-band signals which such civilizations may be transmitting. Two specific search strategies are described. Both employ existing antennas equipped with sophisticated multichannel spectrum analyzers and pattern recognition devices. The Ames Research Center proposal is a high sensitivity, high-resolution search of nearby promising stars and selected sky areas in the 'water hole' (1400-1727 MHz). The Jet Propulsion Laboratory proposal is for a survey of most of the sky over a significant portion of the free-space microwave window at lower sensitivities and resolutions. The approaches are complementary and both are being pursued. The consummation of these programs could achieve one of the most profound discoveries in the history of human civilization, or at least will show the way to future efforts.

Billingham, J.↗
NASA NTRS1980

A bimodal search strategy for SETI

The search strategy and resultant observational plan which was developed to carry out a comprehensive Search for Extraterrestrial Intelligence (SETI) over that portion of the electromagnetic spectrum known as the terrestrial microwave window is described. The limiting sensitivity achieved was parameterized and calculated for Deep Space Network antennas as well as several radio astronomy observatories. A brief description of the instrumentation to be employed in the search and the classes of signals to be looked for is given. One observational goal is to survey the entire sky over a wide range of frequency to a relatively constant flux level. This survey ensures that all potential life sites are observed to some limiting equivalent isotropic radiated power depending upon their distance. A second goal is to survey a set of potential transmission sites selected a priori to be especially promising, achieving very high sensitivity over a smaller range of frequency.

Gulkis, S.↗
NASA NTRS1980

Costs and benefits to industry of online literature searches

A description is given of a client survey conducted by the NASA Industrial Application Center, U.S.C., examining user-identified dollar costs and benefits of an online computerized literature search. Telephone interviews were conducted on a random sample of clients using a Denver Research Institute questionnaire. Of the total 159 clients surveyed, over 53% identified dollar benefits. A direct relationship between client dollars invested and benefits derived from the search was shown. The ratio of dollar benefit to investment dollar averaged 2.9 to 1. Precise data on the end user's evaluation of the dollar value of an information search are presented.

Jensen, R. J.↗
NASA NTRS1981

Effect of long-term intensity variations on pulsar searches and the pulsar luminosity function

Long-term intensity data for five pulsars are used to obtain the probability density distribution of intensities for each pulsar, and it is found that they are described satisfactorily by chi-squared distributions. Based on these distributions, the number of new pulsars expected to be found on repeatedly searching the same region of the sky with the same sensitivity is given. Nearly 25 percent more new pulsars are expected to be found on the first repeat search. It is also shown that the luminosity function deduced from either a single survey or surveys with very different sensitivities is not affected by the omission of flux density variations in the calculation of selection effects. Finally, a method is proposed for deriving the luminosity function by combining the different searches of a given area on the basis of a probabilistic approach to the evaluation of selection effects.

Krishnamohan, S.↗