Multiphonon Relaxation in Lacl sub 3 -Nd super 3 super plus
Multiphonon relaxation in neodymium doped lanthanum chloride, determining transition rates between stark levels with lifetime and quantum efficiency measurements
EMISSION SPECTRUM↗
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Results for “Stark effect”
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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Birefringing arising from the reorientation of the polarizability anisotropy of molecules in collisionless gases
The refractive index change in a collisionless gas is evaluated from the Stark shifts of the rotational energy levels that arise from the polarizability anisotropy. For the limit of an extremely short-duration excitation, a multilevel coherent effect resulted in delayed refractive index bursts. Both stationary and transient responses of this birefringence to an optical field were considered for symmetric top molecules, with particular emphasis on the special case of linear molecules.
Lin, C. H.↗
Birefringence arising from the reorientation of the polarizability anisotropy of molecules in collisionless gases
The refractive-index change in a collisionless gas is evaluated from the Stark shifts of the rotational energy levels that arise from the polarizability anisotropy. In the limit of an extremely-short-duration excitation, a multilevel coherent effect results in delayed refractive-index bursts. Both stationary and transient responses of this birefringence to an optical field are considered for symmetric-top molecules, with particular emphasis on the special case of linear molecules.
Lin, C. H.↗
A Parametric Battery Model for the Conceptual Design of Electric Aircraft
Electric aircraft conceptual designs usually have an assumed specific power and specific energy for the aircraft’s energy storage system that dictates the total capacity and the peak power available. The specific energy and power are inherently linked to the state-of-charge and discharge rate from which they were derived; therefore, they will not directly correspond to the diverse circumstances encountered in various aircraft missions and flight segments. These parameters turn the battery system into a black box, disregard potential electrical restrictions, and disallow the aircraft and battery to be optimized as a system. Peering into this box, this study highlights the importance of incorporating a parametric battery model into the conceptual design workflow by splitting high-level terms such as power into voltage and current and investigating their variability during the discharge process. Through the modeling of these more detailed parameters, this methodology shows the feasibility of using low states-of-charge for contingency operations, including the end of the reserve mission, expanding the amount of usable capacity for electric aircraft. Stark differences in aircraft capabilities can arise between varying fidelity battery models due to late-mission, high-power flight operations. This parametric battery model effectively captures these differences by evaluating the limitations that arise within the individual battery cells and the aircraft powertrain. This paper shows that the unusable charge of a battery is set by the balked landing power requirement and can realistically range from 5% to 44% based on assumptions. This sets the analog to unusable fuel capacity in aircraft with liquid fuel systems. Needing only aircraft- and mission-level inputs and only seconds of run time, this model is a prime fit for the fast, accurate exploration of the electric aircraft conceptual design space.
Battery↗
Stark broadening tables for He I 4922 A
The Stark broadening of the He I 4922-A line and its forbidden components by both ions and electrons is calculated using a theory that includes ion dynamic effects. Tables are presented for temperatures from 5000 K to 40,000 K covering the density range 10 trillion to 10 quadrillion per cu cm for both helium and hydrogen ionic perturbers.-
Barnard, A. J.↗
Performance Analysis of Direct-Sequence Code-Division Multiple-Access Communications with Asymmetric Quadrature Phase-Shift-Keying Modulation
This article considers a quaternary direct-sequence code-division multiple-access (DS-CDMA) communication system with asymmetric quadrature phase-shift-keying (AQPSK) modulation for unequal error protection (UEP) capability. Both time synchronous and asynchronous cases are investigated. An expression for the probability distribution of the multiple-access interference is derived. The exact bit-error performance and the approximate performance using a Gaussian approximation and random signature sequences are evaluated by extending the techniques used for uniform quadrature phase-shift-keying (QPSK) and binary phase-shift-keying (BPSK) DS-CDMA systems. Finally, a general system model with unequal user power and the near-far problem is considered and analyzed. The results show that, for a system with UEP capability, the less protected data bits are more sensitive to the near-far effect that occurs in a multiple-access environment than are the more protected bits.
Wang, C.-W.↗
Pupillary escape intensified by large pupillary size
Pupil responses to light are greatly influenced by initial pupil size. Small pupils, operating under photopic conditions, show tonic responses to step increases of light and high gains; thus the pupil is a good regulator of light. Large pupils, operating under mesopic or scotopic conditions show phasic responses, 'pupillary escape', and smaller gains: the pupil only transiently influences retinal flux. By using accommodation level to set the size of the pupil, the mechanism of the 'pupil size effect' is shown to be dependent on retinal light level only so far as retinal activity sets pupil size.
Stark, L.↗
Effects of loads on time optimal head movements: EMS, oblique, and main sequence relationships
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Hannaford, Blake↗
Promethazine and its use as a treatment for space motion sickness
Until Mar. 1989, no effective treatment--either prophylactic or symptomatic--for space motion sickness (SMS) had been discovered. Since Mar. 1989, intramuscular (IM) promethazine (PMZ) has been used in the treatment of SMS with extremely favorably results reported by the crew. A retrospective study was undertaken to quantify the efficacy of IM PMZ since its institution and the incidence of its major anticipated side-effect drowsiness and sedation. The results from a standardized crew medical debriefing conducted immediately after landing and follow-up interviews with the crews were used in establishing the efficacy and incidence of side effects from treatment. Only crews from the first 44 Shuttle flights on their first mission were considered. For a total of 132 crewmembers, 96 exhibited symptoms of SMS; and, of these, 20 were treated with IM PMZ. Ninety percent of those receiving IM PMZ 25-50mg received nearly immediate (less than 2 hours) relief of symptoms and 75 percent required no further treatment through the first 2 days of spaceflight. Those not receiving this treatment did not have any near-term resolution of their symptoms, and 50 percent were still ill through the second day of flight. This represents a significant difference at the p = 0.46 level. In stark contrast to the 60 percent to 73 percent incidence of sedation or drowsiness reported in individuals treated with PMZ in terrestrial environment at the doses used here, less than 5 percent reported these symptoms during spaceflight. IM PMZ is an effective therapy for SMS and is associated with minimal incidence of sedation or drowsiness. This combination of efficacy that is absent of significant side effects represents a substantial improvement in the operational situation of crewmembers afflicted with SMS. Studies to understand the mechanisms underlying these observations will be undertaken in the future.
Bagian, James P.↗
The physical basis for absorption of light
The effects of light absorption on the wave functions of gas-phase molecules and atoms are investigated by high resolution spectral measurements of radiation emerging from a sample. A Stark-modulated sample of methyl fluoride was irradiated at the 102 GHz rotational transition and the emergent radiation was resolved by means of a spectrum analyzer. For signal oscillator frequencies below or above the molecular resonance by one modulation frequency, the amplitudes of the upper and lower modulation sidebands are found to be of nonuniform intensity, which is inconsistent with amplitude modulation. Emission due to polarization is, however, calculated to be consistent with the results observed, indicating that light absorption should be considered as a subtractive stimulated emission.
Pickett, H. M.↗
The Effect of Bluntness on the Drag of Spherical-tipped Truncated Cones of Fineness Ratio 3 at Mach Numbers 1.2 to 7.4
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Sommer, Simon C↗
MEMS Reliability Assurance Activities at JPL
An overview of Microelectromechanical Systems (MEMS) reliability assurance and qualification activities at JPL is presented along with the a discussion of characterization of MEMS structures implemented on single crystal silicon, polycrystalline silicon, CMOS, and LIGA processes. Additionally, common failure modes and mechanisms affecting MEMS structures, including radiation effects, are discussed. Common reliability and qualification practices contained in the MEMS Reliability Assurance Guideline are also presented.
Kayali, S.↗
Chandra Grating Spectroscopy of Three Hot White Dwarfs
High-resolution soft X-ray spectroscopic observations of single hot white dwarfs are scarce. With the Chandra Low-Energy Transmission Grating, we have observed two white dwarfs, one is of spectral type DA (LB1919) and the other is a non-DA of spectral type PG1159 (PG1520+525). The spectra of both stars are analyzed, together with an archival Chandra spectrum of another DA white dwarf (GD246). Aims. The soft X-ray spectra of the two DA white dwarfs are investigated in order to study the effect of gravitational settling and radiative levitation of metals in their photospheres. LB1919 is of interest because it has a significantly lower metallicity than DAs with otherwise similar atmospheric parameters. GD246 is the only white dwarf known that shows identifiable individual iron lines in the soft X-ray range. For the PG1159 star, a precise effective temperature determination is performed in order to confine the position of the blue edge of the GW Vir instability region in the HRD. Methods. The Chandra spectra are analyzed with chemically homogeneous as well as stratified NLTE model atmospheres that assume equilibrium between gravitational settling and radiative acceleration of chemical elements. Archival EUV and UV spectra obtained with EUVE, FUSE, and HST are utilized to support the analysis. Results. No metals could be identified in LB1919. All observations are compatible with a pure hydrogen atmosphere. This is in stark contrast to the vast majority of hot DA white dwarfs that exhibit light and heavy metals and to the stratified models that predict significant metal abundances in the atmosphere. For GD246 we find that neither stratified nor homogeneous models can fit the Chandra spectrum. The Chandra spectrum of PG1520+525 constrains the effective temperature to T(sub eff) = 150 000 +/- 10 000 K. Therefore, this nonpulsating star together with the pulsating prototype of the GWVir class (PG1159-035) defines the location of the blue edge of the GWVir instability region. The result is in accordance with predictions from nonadiabatic stellar pulsation models. Such models are therefore reliable tools to investigate the interior structure of GW Vir variables. Conclusions. Our soft X-ray study reveals that the understanding of metal abundances in hot DA white dwarf atmospheres is still incomplete. On the other hand, model atmospheres of hydrogen-deficient PG1159-type stars are reliable and reproduce well the observed spectra from soft X-ray to optical wavelengths.
Adamczak, J.↗
A preliminary analysis of lunar extra-mare basalts - Distribution, compositions, ages, volumes, and eruption styles
Extra-mare basalts occupy 8.5% of the lunar basalt area and comprise 1% of the total mare basalt volume. They are preferentially located where the crust is thin and topographically low. In terms of age, eruption style, and composition they are as variable as the mare basalts. In some instances extrusion in extra-mare craters was preceded by floor-fracturing whereas in other cases it apparently was not. The volume of lava erupted may have been controlled more by the volume of magma produced than by hydrostatic effects. A minimum of nearly 1300 separate basalt eruptions is indicated; the true value could be nearer 30,000 separate eruptions.
Whitford-Stark, J. L.↗
Modification of the Simons model for calculation of nonradial expansion plumes
The Simons model is a simple model for calculating the expansion plumes of rockets and thrusters and is a widely used engineering tool for the determination of spacecraft impingement effects. The model assumes that the density of the plume decreases radially from the nozzle exit. Although a high degree of success has been achieved in modeling plumes with moderate Mach numbers, the accuracy obtained under certain conditions is unsatisfactory. A modification made to the model that allows effective description of nonradial behavior in plumes is presented, and the conditions under which its use is preferred are prescribed.
Boyd, I. D.↗
Effects of Mackenzie River Discharge and Bathymetry on Sea Ice in the Beaufort Sea
Mackenzie River discharge and bathymetry effects on sea ice in the Beaufort Sea are examined in 2012 when Arctic sea ice extent hit a record low. Satellite-derived sea surface temperature revealed warmer waters closer to river mouths. By 5 July 2012, Mackenzie warm waters occupied most of an open water area about 316,000 sq km. Surface temperature in a common open water area increased by 6.5 C between 14 June and 5 July 2012, before and after the river waters broke through a recurrent landfast ice barrier formed over the shallow seafloor offshore the Mackenzie Delta. In 2012, melting by warm river waters was especially effective when the strong Beaufort Gyre fragmented sea ice into unconsolidated floes. The Mackenzie and other large rivers can transport an enormous amount of heat across immense continental watersheds into the Arctic Ocean, constituting a stark contrast to the Antarctic that has no such rivers to affect sea ice.
Mackenzie↗
Enhancement of dielectronic recombination by plasma electric microfields
A description is presented of an application of techniques from Stark-broadening theory considered by Griem (1974) to the computation of dielectronic recombination rated for multiply charged Fe ions under the influence of plasma electric microfields. Attention is given to a dielectronic recombination process for which the effects of surrounding charged particles have been found to be important at surprisingly low densities.
Jacobs, V. L.↗
Preliminary plume characteristics of an arcjet thruster
An experimental investigation of a low power arcjet plume was conducted using emission spectroscopy. A laboratory model arcjet incorporating a segmented anode was run on simulated hydrazine at a flow rate of 5 x 10(exp -5) kg/s. The complete visible spectrum measured in the exit plane of the arcjet showed the presence of N2, N2(+), NH, and H. Radial intensity profiles for the H alpha, H sub beta, and the NH A(sup 3)Pi yields X(sup 3)Sigma(0,0) transitions at four different axial locations were measured. These line of sight intensity measurements, spaced 0.05 mm apart, were deconvoluted to give the radial intensity distribution using an inverse Abel transformation. The ratio between the intensities from the H sub alpha and H sub beta transitions indicated a non-Boltzmann energy distribution between excited states in the plume. Axial intensity profiles taken on center line indicated the decay rate of excited states in the plume. An electron number density of 2 x 10(exp 13)/cu cm at the exit plane was determined based on Stark broadening of the H sub beta line. Rotational temperatures of 750 K, 1750 K, and 2500 K were determined for N2, N2(+), and NH respectively. The results demonstrate that the location of the current attachment on the anode has a measurable effect on the electronically excited species in the plume and that dissociation is the dominant frozen flow loss mechanism in low power arcjets.
Manzella, David H.↗