1,238 research outputs found
The dynamics of cryosorption pumping
Dynamics of cryosorption pumping of air, argon, and hydrogen by activated charcoa
Buyer and grower perceptions of liner quality and associated production costs of nursery liner stock
Liner production is a key segment in the nursery industry. Due to a lack of specific of quality standards by governing industry organizations as well as a lack of general consensus among growers of perceived liner quality, a conjoint analysis study was developed to determine buyer and grower preferences for nursery liner product features during point-of-purchase decisions. The study used a visual survey using six variables (first order lateral roots (FOLR), price, region of production, and height, canopy density and caliper uniformity) with varying levels yielding a 3 x 3 x 3 x 2 x 2 x 2 factorial design. Surveys were administered at tradeshows and events around the southeastern United States. Results indicated that a high FOLR, a uniform canopy density and height were most important to purchasing decisions of nursery liner buyers, while liner price and region of production were found not to be important. From the experimental model, utility values for each product feature were derived and can be inserted into an equation to determine a hypothetical quality rating. Growers can use this formula to determine hypothetical quality ratings for their products and serve as a marketing tool for growers.
To determine if the production of premium quality liners is economically feasible and help aid growers to take advantage of niche opportunities we investigated production costs of growing ornamental nursery liners in a USDA Plant Hardiness Zone 6b to 7a nursery. We used three contemporary nursery liner production systems: a fieldgroundbed system, a polyhouse-covered groundbed, and a polyhouse covered container system. We estimated capital requirements, fixed costs and variable costs for each system. We also compared production costs of a deciduous plant, a broadleaf evergreen, and a needle leaf evergreen to allow inferences about the widest variety of nursery liner crops
NASA JSC water monitor system: City of Houston field demonstration
A water quality monitoring system with on-line and real time operation similar to the function in a spacecraft was investigated. A system with the capability to determine conformance to future high effluent quality standards and to increase the potential for reclamation and reuse of water was designed. Although all system capabilities were not verified in the initial field trial, fully automated operation over a sustained period with only routine manual adjustments was accomplished. Two major points were demonstrated: (1) the water monitor system has great potential in water monitoring and/or process control applications; and (2) the water monitor system represents a vast improvement over conventional (grab sample) water monitoring techniques
Constraining the Circumbinary Envelope of Z CMa via imaging polarimetry
Z CMa is a complex binary system, composed of a Herbig Be and an FU Ori star.
The Herbig star is surrounded by a dust cocoon of variable geometry, and the
whole system is surrounded by an infalling envelope. Previous
spectropolarimetric observations have reported a preferred orientation of the
polarization angle, perpendicular to the direction of a large, parsec-sized jet
associated with the Herbig star. The variability in the amount of polarized
light has been associated to changes in the geometry of the dust cocoon that
surrounds the Herbig star. We aim to constrain the properties of Z CMa by means
of imaging polarimetry at optical wavelengths. Using ExPo, a dual-beam imaging
polarimeter which operates at optical wavelengths, we have obtained imaging
(linear) polarimetric data of Z CMa. Our observations were secured during the
return to quiescence after the 2008 outburst. We detect three polarized
features over Z CMa. Two of these features are related to the two jets reported
in this system: the large jet associated to the Herbig star, and the micro-jet
associated to the FU Ori star. Our results suggest that the micro-jet extends
to a distance ten times larger than reported in previous studies. The third
feature suggests the presence of a hole in the dust cocoon that surrounds the
Herbig star of this system. According to our simulations, this hole can produce
a pencil beam of light that we see scattered off the low-density envelope
surrounding the system.Comment: Accepted for publication in A\&
The color dependent morphology of the post-AGB star HD161796
Context. Many protoplanetary nebulae show strong asymmetries in their
surrounding shell, pointing to asymmetries during the mass loss phase.
Questions concerning the origin and the onset of deviations from spherical
symmetry are important for our understanding of the evolution of these objects.
Here we focus on the circumstellar shell of the post-AGB star HD 161796. Aims.
We aim at detecting signatures of an aspherical outflow, as well as to derive
the properties of it. Methods. We use the imaging polarimeter ExPo (the extreme
polarimeter), a visitor instrument at the William Herschel Telescope, to
accurately image the dust shell surrounding HD 161796 in various wavelength
filters. Imaging polarimetry allows us to separate the faint, polarized, light
from circumstellar material from the bright, unpolarized, light from the
central star. Results. The shell around HD 161796 is highly aspherical. A clear
signature of an equatorial density enhancement can be seen. This structure is
optically thick at short wavelengths and changes its appearance to optically
thin at longer wavelengths. In the classification of the two different
appearances of planetary nebulae from HST images it changes from being
classified as DUPLEX at short wavelengths to SOLE at longer wavelengths. This
strengthens the interpretation that these two appearances are manifestations of
the same physical structure. Furthermore, we find that the central star is
hotter than often assumed and the relatively high observed reddening is due to
circumstellar rather than interstellar extinction.Comment: Accepted for publication in A&
The Extreme Polarimeter: Design, Performance, First Results & Upgrades
Well over 700 exoplanets have been detected to date. Only a handful of these
have been observed directly. Direct observation is extremely challenging due to
the small separation and very large contrast involved. Imaging polarimetry
offers a way to decrease the contrast between the unpolarized starlight and the
light that has become linearly polarized after scattering by circumstellar
material. This material can be the dust and debris found in circumstellar
disks, but also the atmosphere or surface of an exoplanet. We present the
design, calibration approach, polarimetric performance and sample observation
results of the Extreme Polarimeter, an imaging polarimeter for the study of
circumstellar environments in scattered light at visible wavelengths. The
polarimeter uses the beam-exchange technique, in which the two orthogonal
polarization states are imaged simultaneously and a polarization modulator
swaps the polarization states of the two beams before the next image is taken.
The instrument currently operates without the aid of Adaptive Optics. To reduce
the effects of atmospheric seeing on the polarimetry, the images are taken at a
frame rate of 35 fps, and large numbers of frames are combined to obtain the
polarization images. Four successful observing runs have been performed using
this instrument at the 4.2 m William Herschel Telescope on La Palma, targeting
young stars with protoplanetary disks as well as evolved stars surrounded by
dusty envelopes. In terms of fractional polarization, the instrument
sensitivity is better than 10^-4. The contrast achieved between the central
star and the circumstellar source is of the order 10^-6. We show that our
calibration approach yields absolute polarization errors below 1%
Automated water monitor system field demonstration test report. Volume 2: Technical summary
The NASA Automatic Water Monitor System was installed in a water reclamation facility to evaluate the technical and cost feasibility of producing high quality reclaimed water. Data gathered during this field demonstration test are reported
Automated water monitor system field demonstration test report. Volume 1: Executive summary
A system that performs water quality monitoring on-line and in real time much as it would be done in a spacecraft, was developed and demonstrated. The system has the capability to determine conformance to high effluent quality standards and to increase the potential for reclamation and reuse of water
Surprisingly different star-spot distributions on the near equal-mass equal-rotation-rate stars in the M dwarf binary GJ 65 AB
We aim to understand how stellar parameters such as mass and rotation impact the distribution of star-spots on the stellar surface. To this purpose, we have used Doppler imaging to reconstruct the surface brightness distributions of three fully convective M dwarfs with similar rotation rates. We secured high cadence spectral time series observations of the 5.5 au separation binary GJ 65, comprising GJ 65A (M5.5V, Prot = 0.24 d) and GJ 65B (M6V, Prot = 0.23 d). We also present new observations of GJ 791.2A (M4.5V, Prot = 0.31 d). Observations of each star were made on two nights with UVES, covering a wavelength range from 0.64 - 1.03μm. The time series spectra reveal multiple line distortions that we interpret as cool star-spots and which are persistent on both nights suggesting stability on the time-scale of 3 d. Spots are recovered with resolutions down to 8.3° at the equator. The global spot distributions for GJ 791.2A are similar to observations made a year earlier. Similar high latitude and circumpolar spot structure is seen on GJ 791.2A and GJ 65A. However, they are surprisingly absent on GJ 65B, which instead reveals more extensive, larger, spots concentrated at intermediate latitudes. All three stars show small amplitude latitude-dependent rotation that is consistent with solid body rotation. We compare our measurements of differential rotation with previous Doppler imaging studies and discuss the results in the wider context of other observational estimates and recent theoretical predictions
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