35 research outputs found
Preparation of Mesoporous V2O5@TiO2 Composites with Enhanced Photoactivity for Gaseous Benzene Degradation
AbstractMesoporous V2O5@TiO2 composites were fabricated by an ultrasonic method with V2O5 sol as the guest precursor. The prepared materials were characterized by powder X-ray diffraction, field emission-scanning electron microscopy, transmission electron microscope, X-ray photoelectron spectroscopy, UV-Vis spectroscopy and nitrogen sorption analysis. The results indicated that V2O5 nanoparticles dispersed well on/into the porous structure of TiO2 matrix. The composites presented typical IUPAC IV isotherms with type H2 hysteresis loops, revealing the mesoporous structure. It was observed that V2O5 loading led to red shift of the absorption edge to 540nm and reduced the band gap < 3.0eV. The V2O5@TiO2 composites with V/Ti molar ratio of 0.1 exhibited outstanding degradation efficiency of gaseous benzene
A Planetary Microlensing Event with an Unusually Red Source Star: MOA-2011-BLG-291
We present the analysis of planetary microlensing event MOA-2011-BLG-291,
which has a mass ratio of and a source star that
is redder (or brighter) than the bulge main sequence. This event is located at
a low Galactic latitude in the survey area that is currently planned for NASA's
WFIRST exoplanet microlensing survey. This unusual color for a microlensed
source star implies that we cannot assume that the source star is in the
Galactic bulge. The favored interpretation is that the source star is a lower
main sequence star at a distance of kpc in the Galactic disk.
However, the source could also be a turn-off star on the far side of the bulge
or a sub-giant in the far side of the Galactic disk if it experiences
significantly more reddening than the bulge red clump stars. However, these
possibilities have only a small effect on our mass estimates for the host star
and planet. We find host star and planet masses of and from a Bayesian
analysis with a standard Galactic model under the assumption that the planet
hosting probability does not depend on the host mass or distance. However, if
we attempt to measure the host and planet masses with host star brightness
measurements from high angular resolution follow-up imaging, the implied masses
will be sensitive to the host star distance. The WFIRST exoplanet microlensing
survey is expected to use this method to determine the masses for many of the
planetary systems that it discovers, so this issue has important design
implications for the WFIRST exoplanet microlensing survey
Spectroscopic Mass and Host-star Metallicity Measurements for Newly Discovered Microlensing Planet OGLE-2018-BLG-0740Lb
We report the discovery of the microlensing planet OGLE-2018-BLG-0740Lb. The
planet is detected with a very strong signal of , but
the interpretation of the signal suffers from two types of degeneracies. One
type is caused by the previously known close/wide degeneracy, and the other is
caused by an ambiguity between two solutions, in which one solution requires to
incorporate finite-source effects, while the other solution is consistent with
a point-source interpretation. Although difficult to be firmly resolved based
on only the photometric data, the degeneracy is resolved in strong favor of the
point-source solution with the additional external information obtained from
astrometric and spectroscopic observations. The small astrometric offset
between the source and baseline object supports that the blend is the lens and
this interpretation is further secured by the consistency of the spectroscopic
distance estimate of the blend with the lensing parameters of the point-source
solution. The estimated mass of the host is and the mass
of the planet is (close solution) or (wide solution) and the lens is located at a distance of ~kpc.
The bright nature of the lens, with (), combined with
its dominance of the observed flux suggest that radial-velocity (RV) follow-up
observations of the lens can be done using high-resolution spectrometers
mounted on large telescopes, e.g., VLT/ESPRESSO, and this can potentially not
only measure the period and eccentricity of the planet but also probe for
close-in planets. We estimate that the expected RV amplitude would be .Comment: 12 pages, 11 figures, 4 table
Spitzer + VLTI-GRAVITY Measure the Lens Mass of a Nearby Microlensing Event
We report the lens mass and distance measurements of the nearby microlensing event TCP J05074264+2447555 (Kojima-1). We measure the microlens parallax vector π_E using Spitzer and ground-based light curves with constraints on the direction of lens-source relative proper motion derived from Very Large Telescope Interferometer (VLTI) GRAVITY observations. Combining this π_E determination with the angular Einstein radius θ_E measured by VLTI-GRAVITY observations, we find that the lens is a star with mass M_L = 0.495±0.063 M⊙ at a distance D_L = 429 ± 21 pc. We find that the blended light basically all comes from the lens. The lens-source proper motion is Μ_(rel,hel) = 26.55±0.36 mas yr⁻¹, so with currently available adaptive-optics instruments, the lens and source can be resolved in 2021. This is the first microlensing event whose lens mass is unambiguously measured by interferometry + satellite-parallax observations, which opens a new window for mass measurements of isolated objects such as stellar-mass black holes
Spitzer + VLTI-GRAVITY Measure the Lens Mass of a Nearby Microlensing Event
We report the lens mass and distance measurements of the nearby microlensing
event TCP J05074264+2447555. We measure the microlens parallax vector
using Spitzer and ground-based light curves with constraints on
the direction of lens-source relative proper motion derived from Very Large
Telescope Interferometer (VLTI) GRAVITY observations. Combining this
determination with the angular Einstein radius
measured by VLTI GRAVITY observations, we find that the lens is a star with
mass at a distance . We find that the blended light basically all comes from the lens.
The lens-source proper motion is , so with currently available adaptive-optics (AO) instruments,
the lens and source can be resolved in 2021. This is the first microlensing
event whose lens mass is unambiguously measured by interferometry + satellite
parallax observations, which opens a new window for mass measurements of
isolated objects such as stellar-mass black holes.Comment: 3 Figures and 6 Tables Submitted to AAS Journa
Spitzer Parallax Of Ogle-2015-blg-0966: A Cold Neptune In The Galactic Disk
We report the detection of a cold Neptune mplanet = 21 ± 2 M? orbiting a 0.38 M? M dwarf lying 2.5–3.3 kpc toward the Galactic center as part of a campaign combining ground-based and Spitzer observations to measure the Galactic distribution of planets. This is the first time that the complex real-time protocols described by Yee et al., which aim to maximize planet sensitivity while maintaining sample integrity, have been carried out in practice. Multiple survey and follow up teams successfully combined their efforts within the framework of these protocols to detect this planet. This is the second planet in the Spitzer Galactic distribution sample. Both are in the near to mid-disk and are clearly not in the Galactic bulge
Effect of internal surface structure of the north wall on Chinese solar greenhouse thermal microclimate based on computational fluid dynamics.
Chinese solar greenhouses are unique facility agriculture buildings and widely used in northeastern China, providing a favorable requirement for crop growth. The north wall configurations play an essential role in heat storage and thermal insulation and directly affect the management of the internal environment. This research is devoted to further improve the thermal performance of the greenhouse and explore the potential of the north wall. A mathematical model was designed to investigate the concave-convex wall configurations based on computational fluid dynamics. Four passive heat-storage north walls were analyzed by using the same constituent materials, including a plane wall, a vertical wall, a horizontal wall and an alveolate wall. The numerical model was validated by experimental measurements. The temperature distributions of the north walls were examined and a comparative analysis of the heat storage-release capabilities was carried out. The results showed that the heat-storage capacity of the north wall is affected by the surface structure. Moreover, the critical factor influencing the air temperature is the sum of the heat load released by the wall and the energy increment of greenhouse air. The results suggested that the alveolate wall has preferable thermal accumulation capacity. The concave-convex wall configurations have a wider range of heat transfer performance along the thickness direction, while the plane wall has a superior thermal environment. This study provides a basic theoretical reference to rationally design the internal surface structures of the north wall