3,464 research outputs found
Modeling of a Building Scale Liquid Air Energy Storage and Expansion System with ASPEN HYSYS
Liquid Air Energy Storage (LAES) is a potential solution to mitigate renewable energy intermittency on islanded microgrids. Renewable microgrid generation in excess of the immediate load runs a cryogenic cycle to create and store liquid air. LAES systems can be combined with an expansion turbine to recover the stored energy. Using analytic methods to design a LAES and expansion system is complex and time consuming, suggesting modeling and simulation as a more efficient approach. Aspen HYSYS, an industrial process modeling software package, was used to model a combined Linde- Hampson cryogenic cycle (for liquefaction of air) and an expansion cycle (to convert the energy from liquid air vaporization to mechanical energy). The model was validated against previous analytic work. The validated model will be used to implement a model-based systems engineering (MBSE) approach to design an LAES and expansion system to reduce intermittency on an experimental microgrid at the Naval Postgraduate School in Monterey, CA, USA. Data from this facility will be used to further modify and validate the HYSYS model
Science with an ngVLA: Observing the Effects of Chemistry on Exoplanets and Planet Formation
One of the primary mechanisms for inferring the dynamical history of planets
in our Solar System and in exoplanetary systems is through observation of
elemental ratios (i.e. C/O). The ability to effectively use these observations
relies critically on a robust understanding of the chemistry and evolutionary
history of the observed abundances. Significant efforts have been devoted to
this area from within astrochemistry circles, and these efforts should be
supported going forward by the larger exoplanetary science community. In
addition, the construction of a next-generation radio interferometer will be
required to test many of these predictive models in situ, while simultaneously
providing the resolution necessary to pinpoint the location of planets in
formation.Comment: To be published in the ASP Monograph Series, "Science with a
Next-Generation VLA", ed. E. J. Murphy (ASP, San Francisco, CA
Deep Sea Underwater Robotic Exploration in the Ice-Covered Arctic Ocean with AUVs
The Arctic seafloor remains one of the last unexplored areas on Earth. Exploration of this unique environment using standard remotely operated oceanographic tools has been obstructed by the dense Arctic ice cover. In the summer of 2007 the Arctic Gakkel Vents Expedition (AGAVE) was conducted with the express intention of understanding aspects of the marine biology, chemistry and geology associated with hydrothermal venting on the section of the mid-ocean ridge known as the Gakkel Ridge. Unlike previous research expeditions to the Arctic the focus was on high resolution imaging and sampling of the deep seafloor. To accomplish our goals we designed two new Autonomous Underwater Vehicles (AUVs) named Jaguar and Puma, which performed a total of nine dives at depths of up to 4062m. These AUVs were used in combination with a towed vehicle and a conventional CTD (conductivity, temperature and depth) program to characterize the seafloor. This paper describes the design decisions and operational changes required to ensure useful service, and facilitate deployment, operation, and recovery in the unique Arctic environment.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/86060/1/ckunz-17.pd
The Multiwavelength Survey by Yale-Chile (MUSYC): Deep Near-Infrared Imaging and the Selection of Distant Galaxies
We present deep near-infrared JHK imaging of four 10'x10' fields. The
observations were carried out as part of the Multiwavelength Survey by
Yale-Chile (MUSYC) with ISPI on the CTIO 4m telescope. The typical point source
limiting depths are J~22.5, H~21.5, and K~21 (5sigma; Vega). The effective
seeing in the final images is ~1.0". We combine these data with MUSYC UBVRIz
imaging to create K-selected catalogs that are unique for their uniform size,
depth, filter coverage, and image quality. We investigate the rest-frame
optical colors and photometric redshifts of galaxies that are selected using
common color selection techniques, including distant red galaxies (DRGs),
star-forming and passive BzKs, and the rest-frame UV-selected BM, BX, and Lyman
break galaxies (LBGs). These techniques are effective at isolating large
samples of high redshift galaxies, but none provide complete or uniform samples
across the targeted redshift ranges. The DRG and BM/BX/LBG criteria identify
populations of red and blue galaxies, respectively, as they were designed to
do. The star-forming BzKs have a very wide redshift distribution, a wide range
of colors, and may include galaxies with very low specific star formation
rates. In comparison, the passive BzKs are fewer in number, have a different
distribution of K magnitudes, and have a somewhat different redshift
distribution. By combining these color selection criteria, it appears possible
to define a reasonably complete sample of galaxies to our flux limit over
specific redshift ranges. However, the redshift dependence of both the
completeness and sampled range of rest-frame colors poses an ultimate limit to
the usefulness of these techniques.Comment: 17 pages in emulateapj style, 13 figures. Submitted to the
Astronomical Journal. Data will be made available upon publicatio
Detection of Interstellar HCNC and an Investigation of Isocyanopolyyne Chemistry under TMC-1 Conditions
We report an astronomical detection of HCNC for the first time in the
interstellar medium with the Green Bank Telescope toward the TMC-1 molecular
cloud with a minimum significance of . The total column density
and excitation temperature of HCNC are determined to be
cm and K,
respectively, using the MCMC analysis. In addition to HCNC, HCCNC is
distinctly detected whereas no clear detection of HCNC is made. We propose
that the dissociative recombination of the protonated cyanopolyyne,
HCNH, and the protonated isocyanopolyyne, HCNCH, are the main
formation mechanisms for HCNC while its destruction is dominated by
reactions with simple ions and atomic carbon. With the proposed chemical
networks, the observed abundances of HCNC and HCCNC are reproduced
satisfactorily.Comment: Accepted in the Astrophysical Journal Letter
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