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Williams, D.

Publications and source records attributed to Williams, D..

At least 37 records · Page 2
All sourcesNASA NTRSDOE OSTI
NASA NTRS1984

The evaluation of display symbology - A chronometric study of visual search

Three single-target visual search tasks were used to evaluate a set of CRT symbols for a helicopter traffic display. The search tasks were representative of the kinds of information extraction required in practice, and reaction time was used to measure the efficiency with which symbols could be located and identified. The results show that familiar numeric symbols were responded to more quickly than graphic symbols. The addition of modifier symbols such as a nearby flashing dot or surrounding square had a greater disruptive effect on the graphic symbols than the alphanumeric characters. The results suggest that a symbol set is like a list that must be learned. Factors that affect the time to respond to items in a list, such as familiarity and visual discriminability, and the division of list items into categories, also affect the time to identify symbols.

Remington, R.↗
NASA NTRS1983

LANDSAT-4 hightlights

The LANDSAT 4 thematic mapper sensor possesses approximately twice the spectral resolution, three times the spatial resolution, and four times the spectral sensitivity of the MSS sensor on earlier LANDSAT satellites. Spectral bands on the TM, particularly those at wavelengths of 1.6 and 2.2 micrometers are useful for: (1) distinguishing crops such as rice and soybeans; (2) surveying areas that are cultivated in strip crop fashion; (3) determining clay variations and abundances and rock classifications; and (4) differentiating nutrients and sediments found in coastal waters. The sensor can identify surface features 30 meters on a side, which roughly corresponds to a standard city block. Highway construction, land excavation, urban growth, and the health and extent of vegetation can be detected.

Williams, D.↗
NASA NTRS1980

Data base systems in electronic design engineering

The concepts of an integrated design data base system (DBMS) as it might apply to an electronic design company are discussed. Data elements of documentation, project specifications, project tracking, firmware, software, electronic and mechanical design can be integrated and managed through a single DBMS. Combining the attributes of a DBMS data handler with specialized systems and functional data can provide users with maximum flexibility, reduced redundancy, and increased overall systems performance. Although some system overhead is lost due to redundancy in transitory data, it is believed the combination of the two data types is advisable rather than trying to do all data handling through a single DBMS.

Williams, D.↗
NASA NTRS1979

Optical constants of alcohols in the infrared

The spectral reflectances at near-normal incidence for methanol, ethanol, 1-propanol, 1-butanol, and 1-pentanol are reported for the spectral range 6700-350 kaysers. The real and imaginary parts of the complex index of refraction of these liquids are obtained in the range 4000-400 kaysers by use of Kramers-Kronig phase-shift analysis. For all of the alcohols studied, the strength for the OH-stretch bands is directly proportional to the number of OH groups per unit volume; similar relations are established for CH- and CO-stretch bands. Absorption cross sections for stretch vibrations of the three groups are considered, and the role of characteristic group intensities in intensity spectroscopy is discussed.

Sethna, P. P.↗
NASA NTRS1978

Infrared band intensities of saturated hydrocarbons

Kramers-Kronig analysis is applied to measured values of spectral reflectance at near-normal incidence to determine the real and the imaginary parts of the complex index of refraction for methane, ethane, propane, n-butane, n-hexane, n-heptane, and n-decane in the liquid state. The results indicate that the strengths of the characteristic bands as measured by the integral of the imaginary part are roughly constant for all the liquid alkanes except for methane. The intensity of the CH valence vibration bands in the spectra of the alkanes except methane is directly proportional to the number of CH groups per unit volume. The relations for the intensity of the bands due to CH2 and CH3 deformations are examined. Characteristic band intensities of the type established for NH4(+) and SO4(2-) groups in solutions and crystals cannot be extended to the more closely coupled CH2 and CH3 groups in alkane molecules.

Pinkley, L. W.↗
NASA NTRS1978

Dielectric constants of soils at microwave frequencies-2

The dielectric constants of several soil samples were measured at frequencies of 5 and 19 GHz using the infinite transmission line method. The results of these measurements are presented and discussed with respect to soil types and texture structures. A comparison is made with other measurements at 1.4 GHz. At all three frequencies, the dependence of dielectric constant on soil moisture can be approximated by two straight lines. At low moisture, the slope is less than at high moisture level. The intersection of the two lines is believed to be a function of soil texture.

Wang, J.↗
NASA NTRS1978

Infrared band intensities in ammonium hydroxide and ammonium salts

We have applied Kramers-Kronig analysis to reflection spectra to determine the optical constants of ammonium hydroxide and of aqueous solutions of ammonium chloride and bromide. From considerations of the absorption indices k(nu) we conclude that ammonium hydroxide consists of a solution of NH3 in water, in which NH3 molecules are hydrogen bonded to neighboring water molecules. The spectrum of ammonium hydroxide differs from the spectra of ammonium salts, in which bands characteristic of NH4(+) ions are prominent. The existence of ammonium hydroxide as an aerosol in planetary atmospheres is briefly discussed

Sethna, P. P.↗
NASA NTRS1977

Infrared laboratory studies of synthetic planetary atmospheres

Topics covered include: the broadening of individual lines in the CO fundamental by various gases; total band absorptance as a function of absorber thickness and total effect pressure at various temperatures for bands of CO and N2O; nitric acid vapor content in the region of the ozone layer; optical properties of solid NH3; HSO4 concentration in Venus clouds; Burch's law of multiplicative transmittance for mixing absorbing gases when their lines are broadened by helium and hydrogen; ling strength and self-broadening parameters in the v3 fundamental of CO2 and N2O; optical constants of liquid ammonia, liquid methane, saturated hydrocarbons, ammonium hydride and ammonium salts.

Williams, D.↗
NASA NTRS1977

Optical constants of ammonium sulfate in the infrared

The infrared spectral reflectance at near normal incidence has been measured for 3.2 M, 2.4 M, and 1.6 M solutions of ammonium sulfate, an aerosol abundant in the stratosphere and also present in the troposphere. Kramers-Kronig analysis was used to determine values of the refractive and absorption indices from the measured spectral reflectance. A synthetic spectrum of crystalline ammonium sulfate was obtained by extrapolation of the absorption index obtained for the solution to the absorber number densities of the NH4 and SO4 ions characteristic of the crystal.

Downing, H. D.↗
NASA NTRS1976

Vibrational and rotational relaxation in mixtures of water vapor and oxygen

Experimental measurements of sound absorption in air, measurements of ultrasonic absorption in H2O/O2 mixtures at 500 K, and experimental measurements in mixtures of H2O with other impurities have been analyzed to determine the energy transfer rates in mixtures of O2 and H2O as a function of temperature. A set of energy transfer rate coefficients was found that give results consistent with all the experimental data examined and with vibrational energy transfer theory. The rotational relaxation time for H2O/O2 mixtures was determined from the 500 K ultrasonic measurements.

Bass, H. E.↗
NASA NTRS1976

The infrared optical constants of sulfuric acid at 250 K

Results are presented for measurements of the IR spectral reflectance at near-normal incidence of aqueous solutions of sulfuric acid with acid concentrations of 75% and 95.6% by weight. Kramers-Kronig analyses of the reflectance data are employed to obtain values of the optical constants n(nu) and k(nu) in the spectral range from 400 to 6000 cm to the -1 power. The optical constants of these solutions at 250 K and 300 K are compared. It is found that in spectral regions remote from strong absorption bands, the values of the n(nu) indices obtained at 250 K agree with the values given by Lorentz-Lorenz correction of the same indices at 300 K. All absorption bands observed at 300 K are found to be present at 250 K with slight shifts in frequency and with significant differences in the k(nu) indices at the band maxima. Based on these results, it is concluded that the clouds of Venus probably consist of droplets of aqueous solutions of sulfuric acid with acid concentrations of about 75% by weight.

Pinkley, L. W.↗
NASA NTRS1976

Comparison of numeric keyboard and CRT line-labeled buttons for information access

Test were conducted to determine whether differences in speed and accuracy are experienced when using either line-labeled index buttons or a numeric keyboard for page selection in airborne CRT-display area navigation systems. The experiment was conducted with six airline pilots, each flying the same two simulated RNAV routes. Three pilot subjects used line-labeled buttons adjacent to the CRT screen, while three used a numeric keyboard for page access. The hypothesis of no differences in response times between the two modes of access could not be rejected.

Williams, D.↗
NASA NTRS1975

Optical constants of solid ammonia in the infrared

No direct measurements of the refractive index for solid ammonia could be obtained because of failures in attempts to map the reflection spectrum. Kramers-Kronig techniques were, therefore, used in the investigation. The subtractive Kramers-Kronig techniques employed are similar to those discussed by Ahrenkiel (1971). The subtractive method provides a more-rapid convergence than the conventional techniques when data are available over a limited spectral range.

Robertson, C. W.↗
NASA NTRS1975

Optical constants of sulfuric acid - Application to the clouds of Venus

Young (1973) and Sill (1972) have independently suggested that the clouds of Venus may well consist of particles composed of sulfuric acid molecules with attached water molecules. For a further study of this hypothesis an investigation has been conducted with the objective to supply the needed laboratory data for a wide range of sulfuric acid concentrations. Optical constants have been determined for the visible, near infrared, and intermediate infrared wavelength regions.

Palmer, K. F.↗
NASA NTRS1974

Infrared laboratory studies of synthetic planetary atmospheres

Research involving a test of multiplicative transmittance for mixed absorbing gases when their lines are broadened by H2 and He, which are constituents of the atmospheres of the major planets was conducted. The results indicate that the multiplicative law as originally formulated can be applied with confidence. The broadening of individual lines in the CO fundamental by various gases has been investigated. The results indicate that the ratio of the self-broadening ability of CO to the line-broadening ability of foreign gases is greater for lines in the band wings than for lines near the band center when the molecular mass of the broadener is less than that of CO. The results have been interpreted in terms of a phenomenological theory. Studies of the relative line broadening abilities of foreign gases have provided information that can be used to provide optical collision cross sections for individual lines in the CO fundamental.

Williams, D.↗
NASA NTRS1974

Optical properties of particles in planetary atmospheres - Laboratory studies

The laboratory techniques employed for the determination of optical constants are discussed briefly. The values obtained for the real n and imaginary k parts of the refractive indices of water, ice, and liquid ammonia are presented graphically. Work currently in progress on solid ammonia and on sulphuric acid is discussed. Other approaches to studies of the properties of aerosols in planetary atmospheres are presented briefly.

Williams, D.↗