435 research outputs found
HSCT high lift system aerodynamic requirements
The viewgraphs and discussion of high lift system aerodynamic requirements are provided. Low speed aerodynamics has been identified as critical to the successful development of a High Speed Civil Transport (HSCT). The airplane must takeoff and land at a sufficient number of existing or projected airports to be economically viable. At the same time, community noise must be acceptable. Improvements in cruise drag, engine fuel consumption, and structural weight tend to decrease the wing size and thrust required of engines. Decreasing wing size increases the requirements for effective and efficient low speed characteristics. Current design concepts have already been compromised away from better cruise wings for low speed performance. Flap systems have been added to achieve better lift-to-drag ratios for climb and approach and for lower pitch attitudes for liftoff and touchdown. Research to achieve improvements in low speed aerodynamics needs to be focused on areas most likely to have the largest effect on the wing and engine sizing process. It would be desirable to provide enough lift to avoid sizing the airplane for field performance and to still meet the noise requirements. The airworthiness standards developed in 1971 will be the basis for performance requirements for an airplane that will not be critical to the airplane wing and engine size. The lift and drag levels that were required to meet the performance requirements of tentative airworthiness standards established in 1971 and that were important to community noise are identified. Research to improve the low speed aerodynamic characteristics of the HSCT needs to be focused in the areas of performance deficiency and where noise can be reduced. Otherwise, the wing planform, engine cycle, or other parameters for a superior cruising airplane would have to be changed
Mindful Awareness Training: A Pilot Study Integrating Mindfulness Practices into a Rural Jail-Based Substance Abuse Program
Mindfulness practices are now utilized in a variety of behavioral healthcare settings, including the criminal justice system. This article summarizes the findings of a pilot project incorporating mindfulness practices into a jail-based substance abuse program in a rural county jail. Participants that engaged in a psychoeducational mindfulness group that utilized practices adapted from the Mindfulness-Based Relapse Prevention (MBRP) curriculum had improved scores on measures of mindfulness, self-compassion, and quality of life. A mediated path model suggested that the length of time participants were involved in the group and their estimated amount of mindfulness practice outside the group was related to increases in mindfulness, which appeared to support subsequent increases in self-compassion and quality of life. Implications for incorporating these practices into jail-based programs and limitations are discussed
Ellipsometric determination of optical constants for silicon and thermally grown silicon dioxide via a multi-sample, multi-wavelength, multi-angle investigation
Optical constant spectra for silicon and thermally grown silicon dioxide have been simultaneously determined using variable angle of incidence spectroscopic ellipsometry from 0.75 to 6.5 eV. Spectroscopic ellipsometric data sets acquired at multiple angles of incidence from seven samples with oxide thicknesses from 2 to 350 nm were analyzed using a self-contained multi-sample technique to obtain Kramers–Kronig consistent optical constant spectra. The investigation used a systematic approach utilizing optical models of increasing complexity in order to investigate the need for fitting the thermal SiO2 optical constants and including an interface layer between the silicon and SiO2 in modeling the data. A detailed study was made of parameter correlation effects involving the optical constants used for the interface layer. The resulting thermal silicon dioxide optical constants were shown to be independent of the precise substrate model used, and were found to be approximately 0.4% higher in index than published values for bulk glasseous SiO2. The resulting silicon optical constants are comparable to previous ellipsometric measurements in the regions of overlap, and are in agreement with long wavelength prism measurements and transmission measurements near the band gap
Space Launch System Liftoff and Transition Aerodynamic Characterization in the NASA Langley 14- by 22-Foot Subsonic Wind Tunnel
A 1.75% scale force and moment model of the Space Launch System was tested in the NASA Langley Research Center 14- by 22-Foot Subsonic Wind Tunnel to quantify the aerodynamic forces that will be experienced by the launch vehicle during its liftoff and transition to ascent flight. The test consisted of two parts: the first was dedicated to measuring forces and moments for the entire range of angles of attack (0deg to 90deg) and roll angles (0 deg. to 360 deg.). The second was designed to measure the aerodynamic effects of the liftoff tower on the launch vehicle for ground winds from all azimuthal directions (0 deg. to 360 deg.), and vehicle liftoff height ratios from 0 to 0.94. This wind tunnel model also included a set of 154 surface static pressure ports. Details on the experimental setup, and results from both parts of testing are presented, along with a description of how the wind tunnel data was analyzed and post-processed in order to develop an aerodynamic database. Finally, lessons learned from experiencing significant dynamics in the mid-range angles of attack due to steady asymmetric vortex shedding are presented
Two Exoplanets Discovered at Keck Observatory
We present two exoplanets detected at Keck Observatory. HD 179079 is a G5
subgiant that hosts a hot Neptune planet with Msini = 27.5 M_earth in a 14.48
d, low-eccentricity orbit. The stellar reflex velocity induced by this planet
has a semiamplitude of K = 6.6 m/s. HD 73534 is a G5 subgiant with a
Jupiter-like planet of Msini = 1.1 M_jup and K = 16 m/s in a nearly circular
4.85 yr orbit. Both stars are chromospherically inactive and metal-rich. We
discuss a known, classical bias in measuring eccentricities for orbits with
velocity semiamplitudes, K, comparable to the radial velocity uncertainties.
For exoplanets with periods longer than 10 days, the observed exoplanet
eccentricity distribution is nearly flat for large amplitude systems (K > 80
m/s), but rises linearly toward low eccentricity for lower amplitude systems (K
> 20 m/s).Comment: 8 figures, 6 tables, accepted, Ap
The NASA-UC Eta-Earth Program: I. A Super-Earth Orbiting HD 7924
We report the discovery of the first low-mass planet to emerge from the
NASA-UC Eta-Earth Program, a super-Earth orbiting the K0 dwarf HD 7924.
Keplerian modeling of precise Doppler radial velocities reveals a planet with
minimum mass M_P sin i = 9.26 M_Earth in a P = 5.398 d orbit. Based on
Keck-HIRES measurements from 2001 to 2008, the planet is robustly detected with
an estimated false alarm probability of less than 0.001. Photometric
observations using the Automated Photometric Telescopes at Fairborn Observatory
show that HD 7924 is photometrically constant over the radial velocity period
to 0.19 mmag, supporting the existence of the planetary companion. No transits
were detected down to a photometric limit of ~0.5 mmag, eliminating transiting
planets with a variety of compositions. HD 7924b is one of only eight planets
known with M_P sin i < 10 M_Earth and as such is a member of an emerging family
of low-mass planets that together constrain theories of planet formation.Comment: ApJ accepted, 10 pages, 10 figures, 4 table
The NASA-UC Eta-Earth Program: II. A Planet Orbiting HD 156668 with a Minimum Mass of Four Earth Masses
We report the discovery of HD 156668b, an extrasolar planet with a minimum
mass of M_P sin i = 4.15 M_Earth. This planet was discovered through Keplerian
modeling of precise radial velocities from Keck-HIRES and is the second
super-Earth to emerge from the NASA-UC Eta-Earth Survey. The best-fit orbit is
consistent with circular and has a period of P = 4.6455 d. The Doppler
semi-amplitude of this planet, K = 1.89 m/s, is among the lowest ever detected,
on par with the detection of GJ 581e using HARPS. A longer period (P ~ 2.3 yr),
low-amplitude signal of unknown origin was also detected in the radial
velocities and was filtered out of the data while fitting the short-period
planet. Additional data are required to determine if the long-period signal is
due to a second planet, stellar activity, or another source. Photometric
observations using the Automated Photometric Telescopes at Fairborn Observatory
show that HD 156668 (an old, quiet K3 dwarf) is photometrically constant over
the radial velocity period to 0.1 mmag, supporting the existence of the planet.
No transits were detected down to a photometric limit of ~3 mmag, ruling out
transiting planets dominated by extremely bloated atmospheres, but not
precluding a transiting solid/liquid planet with a modest atmosphere.Comment: This planet was announced at the 2010 AAS meeting in Wash. DC; 12
pages, 8 figures, 3 tables, submitted to Ap
A High Eccentricity Component in the Double Planet System Around HD 163607 and a Planet Around HD 164509
We report the detection of three new exoplanets from Keck Observatory. HD
163607 is a metal-rich G5IV star with two planets. The inner planet has an
observed orbital period of 75.29 0.02 days, a semi-amplitude of 51.1
1.4 \ms, an eccentricity of 0.73 0.02 and a derived minimum mass of
\msini = 0.77 0.02 \mjup. This is the largest eccentricity of any known
planet in a multi-planet system. The argument of periastron passage is 78.7
2.0; consequently, the planet's closest approach to its parent
star is very near the line of sight, leading to a relatively high transit
probability of 8%. The outer planet has an orbital period of 3.60 0.02
years, an orbital eccentricity of 0.12 0.06 and a semi-amplitude of 40.4
1.3 \ms. The minimum mass is \msini = 2.29 0.16 \mjup. HD 164509 is
a metal-rich G5V star with a planet in an orbital period of 282.4 3.8
days and an eccentricity of 0.26 0.14. The semi-amplitude of 14.2
2.7 \ms\ implies a minimum mass of 0.48 0.09 \mjup. The radial velocities
of HD 164509 also exhibit a residual linear trend of -5.1 0.7 \ms\ per
year, indicating the presence of an additional longer period companion in the
system. Photometric observations demonstrate that HD 163607 and HD 164509 are
constant in brightness to sub-millimag levels on their radial velocity periods.
This provides strong support for planetary reflex motion as the cause of the
radial velocity variations.Comment: 10 pages, 8 figures, accepted to Ap
The NASA-UC Eta-Earth Program: III. A Super-Earth orbiting HD 97658 and a Neptune-mass planet orbiting Gl 785
We report the discovery of planets orbiting two bright, nearby early K dwarf
stars, HD 97658 and Gl 785. These planets were detected by Keplerian modelling
of radial velocities measured with Keck-HIRES for the NASA-UC Eta-Earth Survey.
HD 97658 b is a close-in super-Earth with minimum mass Msini = 8.2 +/- 1.2
M_Earth, orbital period P = 9.494 +/- 0.005 d, and an orbit that is consistent
with circular. Gl 785 b is a Neptune-mass planet with Msini = 21.6 +/- 2.0
M_Earth, P = 74.39 +/- 0.12 d, and orbital eccentricity 0.30 +/- 0.09.
Photometric observations with the T12 0.8 m automatic photometric telescope at
Fairborn Observatory show that HD 97658 is photometrically constant at the
radial velocity period to 0.09 mmag, supporting the existence of the planet.Comment: Submitted to ApJ, 7 pages, 6 figures, 5 table
Retired A Stars and Their Companions VI. A Pair of Interacting Exoplanet Pairs Around the Subgiants 24 Sextanis and HD200964
We report radial velocity measurements of the G-type subgiants 24 Sextanis
(=HD90043) and HD200964. Both are massive, evolved stars that exhibit periodic
variations due to the presence of a pair of Jovian planets. Photometric
monitoring with the T12 0.80m APT at Fairborn Observatory demonstrates both
stars to be constant in brightness to <= 0.002 mag, thus strengthening the
planetary interpretation of the radial velocity variations. 24 Sex b,c have
orbital periods of 453.8 days and 883~days, corresponding to semimajor axes
1.333 AU and 2.08 AU, and minimum masses (Msini) 1.99 Mjup and 0.86 Mjup,
assuming a stellar mass 1.54 Msun. HD200964 b,c have orbital periods of 613.8
days and 825 days, corresponding to semimajor axes 1.601 AU and 1.95 AU, and
minimum masses 1.85 Mjup and 0.90 Mjup, assuming M* = 1.44 Msun. We also carry
out dynamical simulations to properly account for gravitational interactions
between the planets. Most, if not all, of the dynamically stable solutions
include crossing orbits, suggesting that each system is locked in a mean motion
resonance that prevents close encounters and provides long-term stability. The
planets in the 24 Sex system likely have a period ratio near 2:1, while the
HD200964 system is even more tightly packed with a period ratio close to 4:3.
However, we caution that further radial velocity observations and more detailed
dynamical modelling will be required to provide definitive and unique orbital
solutions for both cases, and to determine whether the two systems are truly
resonant.Comment: AJ accepte
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