8,715 research outputs found
Development of improved single crystal gallium phosphide solar cells final report, jun. 12, 1963 - aug. 12, 1964
Single crystal gallium phosphide solar cell
The Understanding of the Other in Orientalist and Primitivst Art
In 1978, Edward Said published Orientalism, a seminal book that shed light on one of the âleftoversâ of European colonialism. In it, he describes the Westâs attempts to exotify and romanticize the non-Western world. While the Near East, the Far East, and East/Southeast Asia are geographic terms that correspond to specific countries and cultures, the âOrientâ is a Euro-American fantasy that only exists to contradict the West. The term is intentionally vague in order to satisfy any and all exotic desires that a consumer may have.
A great deal of European and American artists found inspiration in the exotic during the late 19th century. The artworks they created, however, rarely celebrate or appreciate non-Western culture. They emphasize âotherness,â and turn dynamic societies into mere playgrounds for their own artistic expression. The beginning of the 20th century saw a rise in artistic Primitivism, or the influence of so-called âsavageâ cultures on modern art. Both of these movements represent a justification for ethnocentrism.
Since the publication of Saidâs book, art historians, anthropologists, and historians have been taking an inquisitive look at how (and why) cultures outside of Europe and America have been generalized and exoticized. In response, many artists, curators, designers, and art collectors have asked themselves if they are representing non-European cultures as a mysterious âotherâ, or as diverse histories hosting a myriad of different cultures, languages, and histories.
In my paper, I will be evaluating the scope of Orientalism in the 19th century and Primitivism in the 20th century. I will also discuss the value of authenticity and what causes âthe Westâ to crave exotic art
Characterizing spiral arm and interarm star formation
Interarm star formation contributes significantly to a galaxy's star
formation budget, and provides an opportunity to study stellar birthplaces
unperturbed by spiral arm dynamics. Using optical integral field spectroscopy
of the nearby galaxy NGC 628 with VLT/MUSE, we construct Halpha maps including
detailed corrections for dust extinction and stellar absorption to identify 391
HII regions at 35pc resolution over 12 kpc^2. Using tracers sensitive to the
underlying gravitational potential, we associate HII regions with either arm
(271) or interarm (120) environments. Using our full spectral coverage of each
region, we find that most HII region physical properties (luminosity, size,
metallicity, ionization parameter) are independent of environment. We calculate
the fraction of Halpha luminosity due to the diffuse ionized gas (DIG)
background contaminating each HII region, and find the DIG surface brightness
to be higher within HII regions compared to the surroundings, and slightly
higher within arm HII regions. Use of the temperature sensitive [SII]/Halpha
line ratio map instead of the Halpha surface brightness to identify HII region
boundaries does not change this result. Using the dust attenuation as a tracer
of the gas, we find depletion times consistent with previous work (2 x 10^9 yr)
with no differences between the arm and interarm, however this is very
sensitive to the DIG correction. Unlike molecular clouds, which can be
dynamically affected by the galactic environment, we see fairly consistent HII
region properties in both arm and interarm environments. This suggests either a
difference in arm star formation and feedback, or a decoupling of dense star
forming clumps from the more extended surrounding molecular gas.Comment: 10 pages, 4 figures, 1 table, accepted for publication in Ap
Robust Positioning in the Presence of Multipath and NLOS GNSS Signals
GNSS signals can be blocked and reflected by nearby objects, such as buildings, walls, and vehicles. They can also be reflected by the ground and by water. These effects are the dominant source of GNSS positioning errors in dense urban environments, though they can have an impact almost anywhere. Non- line-of-sight (NLOS) reception occurs when the direct path from the transmitter to the receiver is blocked and signals are received only via a reflected path. Multipath interference occurs, as the name suggests, when a signal is received via multiple paths. This can be via the direct path and one or more reflected paths, or it can be via multiple reflected paths. As their error characteristics are different, NLOS and multipath interference typically require different mitigation techniques, though some techniques are applicable to both. Antenna design and advanced receiver signal processing techniques can substantially reduce multipath errors. Unless an antenna array is used, NLOS reception has to be detected using the receiver's ranging and carrier-power-to-noise-density ratio (C/N0) measurements and mitigated within the positioning algorithm. Some NLOS mitigation techniques can also be used to combat severe multipath interference. Multipath interference, but not NLOS reception, can also be mitigated by comparing or combining code and carrier measurements, comparing ranging and C/N0 measurements from signals on different frequencies, and analyzing the time evolution of the ranging and C/N0 measurements
Reflection high-energy electron diffraction experimental analysis of polycrystalline MgO films with grain size and orientation distributions
Analysis of biaxial texture of MgO films grown by ion-beam-assisted deposition (IBAD) has been performed using a quantitative reflection high-energy electron diffraction (RHEED) based method. MgO biaxial texture is determined by analysis of diffraction spot shapes from single RHEED images, and by measuring the width of RHEED in-plane rocking curves for MgO films grown on amorphous Si3N4 by IBAD using 750 eV Ar+ ions, at 45° incidence angle, and MgO e-beam evaporation. RHEED-based biaxial texture measurement accuracy is verified by comparison with in-plane and out-of-plane orientation distribution measurements made using transmission electron microscopy and x-ray rocking curves. In situ RHEED measurements also enable the analysis of the evolution of the biaxial texture which narrows with increasing film thickness. RHEED-based measurements of IBAD MgO biaxial texture show that the minimum in-plane orientation distribution depends on the out-of-plane orientation distribution, and indicates that the minimum obtainable in-plane orientation on distribution is 2°
IMPACTS OF PESTICIDE REGULATION ON THE CALIFORNIA STRAWBERRY INDUSTRY
Environmental regulation of agriculture is becoming increasingly important, and growers are increasingly concerned about the effects of regulations on their profitability. Regulations governing the use of a pesticide affect its economic value. Further, growers often face a choice among pesticide alternatives, each with its own set of regulatory restrictions. In this environment, the introduction of a new regulation can have complex effects on growers' profit-maximizing pesticide choices. Buffer zones and regional emissions caps mean that pesticide choices can have important spatial components. Our paper presents an optimization model that incorporates spatial considerations at the field and regional level. We apply our model to fumigant choice by California strawberry growers. The industry is facing an impending ban on the use of methyl bromide, which in conjunction with chloropicrin was the standard fumigant for over forty years. In addition to the forthcoming ban, the state government has imposed regulations governing methyl bromide application, including buffer zones, etc. These extreme use restrictions provide us with an interesting environment for modeling the effects of pesticide regulations. There are currently two legally available fumigants that may substitute for methyl bromide in strawberries: 1,3-D and chloropicrin. 1, 3-D is subject to township caps and other restrictions. Township caps limit total application in an area. The California Department of Pesticide Regulation is currently undertaking air monitoring and other activities to determine whether or not buffer zones and other restrictions should be applied to chloropicrin. We evaluate the effects of current and proposed regulations on field-level decisions and industry costs and returns. Methodology To the best of our knowledge, no study has examined the role of pesticide use regulations in determining growers' profit-maximizing pesticide choices at the field level. We do so by combining three datasets with a field-level spatial model of the profit-maximizing fumigation decision. The first dataset includes detailed field-level information regarding the costs and yields associated with alternative fumigants obtained from a multi-disciplinary research project. The second includes chemical-specific California use regulations regarding treatment rates, buffer zones, and other restrictions. The third includes information on the shapes and sizes of strawberry fields in California. Using these data, the optimization model computes the profit-maximizing treatment for each field including pattern of treatment and number of acres treated per day, etc. Field-level results are aggregated to evaluate the impact of regional pesticide regulations, and then to estimate the industry-level effects of current and proposed pesticide use regulations. We model the effects of the entire regulatory system on the fumigation decisions made by farmers. The restrictions on fumigants are integrated into a field-level programming model of a grower's fumigant decision choice. The program calculates the optimal fumigation plan for a field, given the field's size and shape, and use regulations, and per-acre costs and returns associated with each fumigant. The resulting field-level choices are aggregated in order to check for consistency with township caps. If caps are exceeded, the model is rerun using a number of allocation rules. All choices for all fields are aggregated in order to obtain industry-level results. We perform this procedure for the current set of restrictions and for several alternative sets, assessing the profitability of each alternative. For example, we remove the existing township caps on 1,3-D and evaluate how much the results change. We include varying buffer zone restrictions on chloropicrin, and evaluate whether growers' fumigant choices are sensitive to the size of the buffer zone. Relevance Environmental regulation of agriculture is becoming increasingly important. By explicitly analyzing the effect of regulations affecting methyl bromide alternatives in a model that includes both the spatial dimensions of some regulations and the costs and yields associated with each alternative, we will obtain a more detailed and accurate assessment of the costs of these regulations than is currently available. Our results will provide a greater understanding of the effects of these regulations on industry profitability, and how these regulations interact. Our model can be applied to other cases of pesticide regulations. Given the increasing importance of environmental regulation in agriculture, it is important to aid policymakers in understanding how regulations interact with each other, possibly in unexpected ways.Environmental Economics and Policy,
A physically-based model of the ionizing radiation from active galaxies for photoionization modeling
We present a simplified model of Active Galactic Nucleus (AGN) continuum
emission designed for photoionization modeling. The new model {\sc oxaf}
reproduces the diversity of spectral shapes that arise in physically-based
models. We identify and explain degeneracies in the effects of AGN parameters
on model spectral shapes, with a focus on the complete degeneracy between the
black hole mass and AGN luminosity. Our re-parametrized model {\sc oxaf}
removes these degeneracies and accepts three parameters which directly describe
the output spectral shape: the energy of the peak of the accretion disk
emission , the photon power-law index of the non-thermal
emission , and the proportion of the total flux which is emitted in the
non-thermal component . The parameter is
presented as a function of the black hole mass, AGN luminosity, and `coronal
radius' of the {\sc optxagnf} model upon which {\sc oxaf} is based. We show
that the soft X-ray excess does not significantly affect photoionization
modeling predictions of strong emission lines in Seyfert narrow-line regions.
Despite its simplicity, {\sc oxaf} accounts for opacity effects where the
accretion disk is ionized because it inherits the `color correction' of {\sc
optxagnf}. We use a grid of {\sc mappings} photoionization models with {\sc
oxaf} ionizing spectra to demonstrate how predicted emission-line ratios on
standard optical diagnostic diagrams are sensitive to each of the three {\sc
oxaf} parameters. The {\sc oxaf} code is publicly available in the Astrophysics
Source Code Library.Comment: 14 pages, 9 figures, 1 table. Accepted for publication in Ap
The mass-metallicity relation of local active galaxies
We systematically measure the gas-phase metallicities and the
mass-metallicity relation of a large sample of local active galaxies for the
first time. Observed emission-line fluxes from the Sloan Digital Sky Survey
(SDSS) are compared to a four-dimensional grid of photoionization models using
the Bayesian parameter estimation code NebulaBayes. For the first time we take
into account arbitrary mixing between HII region and narrow-line region (NLR)
emission, and the models are also varied with metallicity, ionization parameter
in the NLR, and the gas pressure. The active galactic nucleus (AGN) oxygen
abundance is found to increase by dex as a function
of host galaxy stellar mass over the range .
We also measure the metallicity and ionization parameter of 231000 star-forming
galaxies for comparison with the sample of 7670 Seyfert 2 galaxies. A
systematic offset in oxygen abundance of 0.09 dex is observed between the
mass-metallicity relations of the star-forming and active galaxies. We
investigate potential causes of the offset, including sample selection and the
treatment in the models of diffuse ionized gas, pressure, and ionization
parameter. We cannot identify the major cause(s), but suspect contributions due
to deficiencies in modeling the ionizing spectra and the treatment of dust
physics. Optical diagnostic diagrams are presented with the star-forming and
Seyfert data colored by the inferred oxygen abundance, ionization parameter and
gas pressure, clearly illustrating the trends in these quantities.Comment: 12 pages, 4 figures and 1 table; accepted for publication in Ap
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