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At least 343 records · Page 19

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DOE OSTI2025

Selection of high-redshift Lyman-Break Galaxies from broadband and wide photometric surveys

In this paper, we investigate the possibility of selecting high-redshift Lyman-Break Galaxies (LBG) using current and future broadband wide photometric surveys, such as the Ultraviolet Near Infrared Optical Northern Survey (UNIONS) or the Vera C. Rubin Legacy Survey of Space and Time (LSST), using a Random Forest algorithm. This work is conducted in the context of future large-scale structure spectroscopic surveys like DESI-II, the next phase of the Dark Energy Spectroscopic Instrument (DESI), which will start around 2029.We use deep imaging data from the Hyper Suprime Camera (HSC) and the Canada-France-Hawaii Telescope Large Area U-band Deep Survey (CLAUDS) on the COSMOS and XMM-LSS fields. To predict the selection performance of LBGs with image quality similar to UNIONS, we degrade the u,g,r,i and z bands to UNIONS depth.The Random Forest algorithm is trained with the u,g,r,i and z bands to classify LBGs in the 2.5 < z < 3.5 range.We find that fixing a target density budget of 1,100 deg$^{-2}$, the Random Forest approach gives a density of z > 2 targets of 873 deg$^{-2}$, and a density of 493 deg$^{-2}$ of confirmed LBGs after spectroscopic confirmation with DESI. This UNIONS-like selection was tested in a dedicated spectroscopic observation campaign of 1,000 targets with DESI on the COSMOS field, providing a safe spectroscopic sample with a mean redshift of 3. This sample is used to derive forecasts for DESI-II, assuming a sky coverage of 5,000 deg$^{2}$. We predict uncertainties on Alcock-Paczynski parameters α$_{⊥}$ and α$_{∥}$ to be 0.7% and 1% for 2.6 < z < 3.2, resulting in a potential 2% measurement of the dark energy fraction at high redshift. Additionally, we estimate the uncertainty in local non-Gaussianity and predict σ$_{fNL}$ ≈ 7, which would be comparable to the current best precision achieved by Planck. The latter forecast suggests that achieving the precision required to place stringent constraints on inflationary models (σ$_{fNL}$ ≈ 1) using spectroscopic galaxy surveys necessitates the development of a next-generation (Stage V) spectroscopic survey.

79 ASTRONOMY AND ASTROPHYSICS↗

NASA NTRS1972

Automatic computer subprogram selection from application program libraries

The program ALTLIB (ALTernate LIBrary) which allows a user access to an alternate subprogram library with a minimum effort is discussed. The ALTLIB program selects subprograms from an alternate library file and merges them with the user's program load file. Only subprograms that are called for (directly or indirectly) by the user's programs and that are available on the alternate library file will be selected. ALTLIB eliminates the need for elaborate control-card manipulations to add subprograms from a subprogram file. ALTLIB returns to the user his binary file and the selected subprograms in correct order for a call to the loader. The user supplies the alternate library file. Subprogram requests which are not satisfied from the alternate library file will be satisfied at load time from the system library.

Drozdowski, J. M.↗

NASA NTRS1971

Solid propellant selection and characterization

The techniques of propellant selection and characterization and the compromises that may be forced on the designer by the change of a propellant parameter are discussed. Rules for the selection of a general propellant type are presented. The characterization of various propellant properties is then approached parameter by parameter. Tailoring pitfalls and compromises are identified whenever possible, and appropriate cross references are used. Related design criteria monographs frequently are cited for a more detailed treatment of the topic under discussion. A list of source references is provided. These references, coupled with established texts in the field, should give the depth of knowledge necessary to the designer to aid in the selection of the most nearly optimum propellant for the design application.

Source record↗

NASA NTRS1972

Engine selection for transport and combat aircraft

The procedures that are used to select engines for transport and combat aircraft are discussed. In general, the problem is to select the engine parameters including engine size in such a way that all constraints are satisfied and airplane performance is maximized. This is done for four different classes of aircraft: (1) a long haul conventional takeoff and landing (CTOL) transport, (2) a short haul vertical takeoff and landing (VTOL) transport, (3) a long range supersonic transport (SST), and (4) a fighter aircraft. For the commercial airplanes the critical constraints have to do with noise while for the fighter, maneuverability requirements define the engine. Generally, the resultant airplane performance (range or payload) is far less than that achievable without these constraints and would suffer more if nonoptimum engines were selected.

Dugan, J. F., Jr.↗

NASA NTRS1972

Program management aid for redundancy selection and operational guidelines

Although this criterion was developed specifically for use on the shuttle program, it has application to many other multi-missions programs (i.e. aircraft or mechanisms). The methodology employed is directly applicable even if the tools (nomographs and equations) are for mission peculiar cases. The redundancy selection criterion was developed to insure that both the design and operational cost impacts (life cycle costs) were considered in the selection of the quantity of operational redundancy. These tools were developed as aids in expediting the decision process and not intended as the automatic decision maker. This approach to redundancy selection is unique in that it enables a pseudo systems analysis to be performed on an equipment basis without waiting for all designs to be hardened.

Hodge, P. W.↗

NASA NTRS1971

Reflectance and transmittance characteristics of several selected green and blue-green unialgae.

Obtained reflectance properties of green and blue-green unialgae are evaluated for determining the feasibility of using selected wavelengths in differentiating between green and blue-green algae. The attempt is made to establish selected wavelengths and ratios that would delineate relative concentrations of the algal suspensions. The results should prove helpful in the selection of spectral bands usable in conjunction with multispectrum scanners for qualitative and quantitative studies of algae in bodies of water.

Gramms, L. C.↗

NASA NTRS1972

Path selection system simulation and evaluation for a Martian roving vehicle

The simulation and evaluation of proposed path selection systems for an autonomous Martian roving vehicle was developed. The package incorporates a number of realistic features, such as the simulation of random effects due to vehicle bounce and sensor-reading uncertainty, to increase the reliability of the results. Qualitative and quantitative evaluation criteria were established. The performance of three different path selection systems was evaluated to determine the effectiveness of the simulation package, and to form some preliminary conclusions regarding the tradeoffs involved in a path selection system design.

Boheim, S. L.↗

NASA NTRS1973

The luminosity function of quasars and its evolution: A comparison of optically selected quasars and quasars found in radio catalogs

The luminosity function of quasars and its evolution are discussed, based on comparison of available data on optically selected quasars and quasars found in radio catalogs. It is assumed that the red shift of quasars is cosmological and the results are expressed in the framework of the Lambda = 0, Q sub Q = 1 cosmological model. The predictions of various density evolution laws are compared with observations of an optically selected sample of quasars and quasar samples from radio catalogs. The differences between the optical luminosity functions, the red shift distributions and the radio to optical luminosity ratios of optically selected quasars and radio quasars rule out luminosity functions where there is complete absence of correlation between radio and optical luminosities. These differences also imply that Schmidt's (1970) luminosity function, where there exists a statistical correlation between radio and optical luminosities, although may be correct for high red shift objects, disagrees with observation at low red shifts. These differences can be accounted for by postulating existence of two classes (1 and 2) of objects.

Petrosian, V.↗

NASA NTRS1972

Apollo 16 Site Selection

The selection is discussed of the Descartes landing site for the Apollo 16 flight for direct sampling of highland materials that would be compositionally different from previous samples. The lessons learned in this site selection that should be considered in future site selection are listed.

Hinners, N. W.↗

NASA NTRS1973

Engine selection for transport and combat aircraft

The procedures for selecting engines for transport and combat aircraft during the design process are presented. The types of aircraft considered are: (1) a long haul conventional takeoff and landing transport, (2) a short haul vertical takeoff and landing transport, (3) a long range supersonic transport, and (4) a fighter aircraft. The influence of aircraft noise considerations on engine selection is examined. The aerodynamic characteristics of supercritical wings and their effect on engine selection are reported.

Dugan, J. F., Jr.↗

NASA NTRS1973

Choice: 36 band feature selection software with applications to multispectral pattern recognition

Feature selection software was developed at the Earth Resources Laboratory that is capable of inputting up to 36 channels and selecting channel subsets according to several criteria based on divergence. One of the criterion used is compatible with the table look-up classifier requirements. The software indicates which channel subset best separates (based on average divergence) each class from all other classes. The software employs an exhaustive search technique, and computer time is not prohibitive. A typical task to select the best 4 of 22 channels for 12 classes takes 9 minutes on a Univac 1108 computer.

Jones, W. C.↗

NASA NTRS1973

Apollo 17 site selection

The scientific arguments and recommendations concerning the selection of the Apollo 17 landing site are presented. The final selection was influenced by the accomplishments and circumstances of previous Apollo flights and by the proposed experiments for Apollo 17. The decisive factors in selecting the Taurus-Littrow landing area were: (1) certainty of acquiring highlands lunar samples, (2) superior orbital coverage, and (3) better use of the lunar roving vehicle capabilities.

Hinners, N. W.↗

NASA NTRS1974

Selection of sampling rate for digital control of aircrafts

The considerations in selecting the sample rates for digital control of aircrafts are identified and evaluated using the optimal discrete method. A high performance aircraft model which includes a bending mode and wind gusts was studied. The following factors which influence the selection of the sampling rates were identified: (1) the time and roughness response to control inputs; (2) the response to external disturbances; and (3) the sensitivity to variations of parameters. It was found that the time response to a control input and the response to external disturbances limit the selection of the sampling rate. The optimal discrete regulator, the steady state Kalman filter, and the mean response to external disturbances are calculated.

Katz, P.↗

NASA NTRS1975

Optimal selection of passes

Preliminary numerical results obtained from the application of a linear feature selection technique to the determination of combinations of passes which best discriminate between a given set of crops in a given area of interest, are reported. The results obtained are not purported to hold in a general situation, but only for the given set of crops and the given, but unknown, levels of several factors-such as soil type, and fertilizer practice, holding in the area of interest. However, by identifying the various factors affecting the spectral signatures, and by formulating a regression model one could use the feature selection technique to determine the regression coefficients for predicting optimal passes for a given set of crops. Another use of the feature selection technique as applied to multiple pass registered data is the generation of enhanced grey scale displays by using a single linear combination of all channels of all designated passes as opposed to a single channel within a single pass.

Guseman, L. F., Jr.↗

NASA NTRS1975

Flat-Plate Solar-Collector Performance Evaluation with a Solar Simulator as a Basis for Collector Selection and Performance Prediction

The use of a solar simulator for performance determination permits collector testing under standard conditions of wind, ambient temperature, flow rate and sun. The performance results determined with the simulator have been found to be in good agreement with outdoor performance results. The measured thermal efficiency and evaluation of 23 collectors are reported which differ according to absorber material (copper, aluminum, steel), absorber coating (nonselective black paint, selective copper oxide, selective black nickel, selective black chrome), type of glazing material (glass, Tedlar, Lexan, antireflection glass), the use of honeycomb material and the use of vacuum to prevent thermal convection losses. The collectors were given performance rankings based on noon-hour solar conditions and all-day solar conditions. The determination with the simulator of an all-day collector performance was made possible by tests at different incident angles. The solar performance rankings were made based on whether the collector is to be used for pool heating, hot water, absorption air conditioning, heating, or for a solar Rankine machine.

Simon, F. F.↗

NASA NTRS1975

Flat-plate solar-collector performance evaluation with a solar simulator as a basis for collector selection and performance prediction

This paper reports the measured thermal efficiency and evaluation of 23 collectors which differ according to absorber material (copper, aluminum, steel), absorber coating (nonselective black paint, selective copper oxide, selective black nickel, selective black chrome), type of glazing material (glass, Tedlar, Lexan, anti-reflection glass), the use of honeycomb material and the use of vacuum to prevent thermal convection losses. The collectors are given performance rankings based on noon-hour solar conditions and all-day solar conditions. The determination with the simulator of an all-day collector performance is made possible by tests at different incident angles. The solar performance rankings are made based on whether the collector is to be used for pool heating, hot water, absorption air conditioning, heating, or for a solar Rankine machine.

Simon, F. F.↗

NASA NTRS1976

Selective attention and the auditory vertex potential. I - Effects of stimulus delivery rate. II - Effects of signal intensity and masking noise

The effects of varying the rate of delivery of dichotic tone pip stimuli on selective attention measured by evoked-potential amplitudes and signal detectability scores were studied. The subjects attended to one channel (ear) of tones, ignored the other, and pressed a button whenever occasional targets - tones of a slightly higher pitch were detected in the attended ear. Under separate conditions, randomized interstimulus intervals were short, medium, and long. Another study compared the effects of attention on the N1 component of the auditory evoked potential for tone pips presented alone and when white noise was added to make the tones barely above detectability threshold in a three-channel listening task. Major conclusions are that (1) N1 is enlarged to stimuli in an attended channel only in the short interstimulus interval condition (averaging 350 msec), (2) N1 and P3 are related to different modes of selective attention, and (3) attention selectivity in multichannel listening task is greater when tones are faint and/or difficult to detect.

Schwent, V. L.↗

NASA NTRS1977

Spacecraft flight control with the new phase space control law and optimal linear jet select

An autopilot designed for rotation and translation control of a rigid spacecraft is described. The autopilot uses reaction control jets as control effectors and incorporates a six-dimensional phase space control law as well as a linear programming algorithm for jet selection. The interaction of the control law and jet selection was investigated and a recommended configuration proposed. By means of a simulation procedure the new autopilot was compared with an existing system and was found to be superior in terms of core memory, central processing unit time, firings, and propellant consumption. But it is thought that the cycle time required to perform the jet selection computations might render the new autopilot unsuitable for existing flight computer applications, without modifications. The new autopilot is capable of maintaining attitude control in the presence of a large number of jet failures.

Bergmann, E. V.↗