615 research outputs found
Optimal Carbon Taxes for Emissions Targets in the Electricity Sector
The most dangerous effects of anthropogenic climate change can be mitigated
by using emissions taxes or other regulatory interventions to reduce greenhouse
gas (GHG) emissions. This paper takes a regulatory viewpoint and describes the
Weighted Sum Bisection method to determine the lowest emission tax rate that
can reduce the anticipated emissions of the power sector below a prescribed,
regulatorily-defined target. This bi-level method accounts for a variety of
operating conditions via stochastic programming and remains computationally
tractable for realistically large planning test systems, even when binary
commitment decisions and multi-period constraints on conventional generators
are considered.
Case studies on a modified ISO New England test system demonstrate that this
method reliably finds the minimum tax rate that meets emissions targets. In
addition, it investigates the relationship between system investments and the
tax-setting process. Introducing GHG emissions taxes increases the value
proposition for investment in new cleaner generation, transmission, and energy
efficiency; conversely, investing in these technologies reduces the tax rate
required to reach a given emissions target
Testable polarization predictions for models of CMB isotropy anomalies
Anomalies in the large-scale CMB temperature sky measured by WMAP have been
suggested as possible evidence for a violation of statistical isotropy on large
scales. In any physical model for broken isotropy, there are testable
consequences for the CMB polarization field. We develop simulation tools for
predicting the polarization field in models that break statistical isotropy
locally through a modulation field. We study two different models: dipolar
modulation, invoked to explain the asymmetry in power between northern and
southern ecliptic hemispheres, and quadrupolar modulation, posited to explain
the alignments between the quadrupole and octopole. For the dipolar case, we
show that predictions for the correlation between the first 10 multipoles of
the temperature and polarization fields can typically be tested at better than
the 98% CL. For the quadrupolar case, we show that the polarization quadrupole
and octopole should be moderately aligned. Such an alignment is a generic
prediction of explanations which involve the temperature field at recombination
and thus discriminate against explanations involving foregrounds or local
secondary anisotropy. Predicted correlations between temperature and
polarization multipoles out to l = 5 provide tests at the ~ 99% CL or stronger
for quadrupolar models that make the temperature alignment more than a few
percent likely. As predictions of anomaly models, polarization statistics move
beyond the a posteriori inferences that currently dominate the field.Comment: 17 pages, 15 figures; published in PRD; references adde
Teaching Tip: developing an intercollegiate Twitter forum to aid student exam study and the development of digital professionalism
#VetFinals has been developed as a novel online Twitter teaching event designed to support intercollegiate veterinary teaching using social media. Previous studies in other fields have suggested that Twitter use within universities may have benefits for undergraduate education. This āteaching tipā paper describes a project using Twitter to host online exam study sessions. The project has been a highly successful collaborative effort between the Royal Veterinary College and Nottingham Veterinary School in the UK. Over 4 years, the #VetFinals project has developed into a long-term, self-sustaining enterprise. This initiative provides a semi-structured means for student exam preparation with direct real-time input from a faculty member. It also creates a network of peers both horizontally across institutions and vertically throughout year groups. Based on similar initiatives in other disciplines, an anticipated outcome of this project was to contribute to student online professionalism. This could help address the veterinary community's recently highlighted problems with professional conduct and appropriate use of social media. Analysis of the success of this endeavor will be available in a future publication
Tris(ethane-1,2-diamine-Īŗ2 N,Nā²)nickel(II) diiodide
The title compound, [Ni(C2H8N2)3]I2, crystallizes with an [Ni(en)3
2+] cation (en is ethane-1,2-diamine) and two iodide ions in the asymmetric unit. Two of the en ligands surrrounding the Ni2+ ion have disordered C atoms, while the third exhibits extensive weak NāHāÆI interĀactions with the two iodide ions that extend throughout the crystalline lattice, producing an infinite network along (011)
Uncertainty-Informed Renewable Energy Scheduling: A Scalable Bilevel Framework
Accommodating the uncertainty of variable renewable energy sources (VRES) in
electricity markets requires sophisticated and scalable tools to achieve market
efficiency. To account for the uncertain imbalance costs in the real-time
market while remaining compatible with the existing sequential market-clearing
structure, our work adopts an uncertainty-informed adjustment toward the VRES
contract quantity scheduled in the day-ahead market. This mechanism requires
solving a bilevel problem, which is computationally challenging for practical
large-scale systems. To improve the scalability, we propose a technique based
on strong duality and McCormick envelopes, which relaxes the original problem
to linear programming. We conduct numerical studies on both IEEE 118-bus and
1814-bus NYISO systems. Results show that the proposed relaxation can achieve
good performance in accuracy (0.7%-gap in the system cost wrt. the least-cost
stochastic clearing benchmark) and scalability (solving the NYISO system in
minutes). Furthermore, the benefit of the uncertainty-informed VRES-quantity
adjustment is more significant under higher levels of VRES (e.g., 70%), under
which the system cost can be reduced substantially compared to a myopic
day-ahead offer strategy of VRES.Comment: Submitted to IEEE PES general meeting 202
Seismic-scale petrophysical interpretation and gas-volume estimation from simultaneous impedance inversion
Ā© 2017 by The Society of Exploration Geophysicists. Simultaneous impedance inversion was performed to obtain the seismic-scale P-and S-wave impedances as well as the bulk density volumes from seismic angle stacks at a siliciclastic turbidite offshore gas reservoir. To translate these variables into seismic-scale total porosity (Ļ), clay content, and water saturation (S w ), we used a deterministic rock-physics model established at the well. A crucial input into this model is the bulk modulus (K f ) of the brine/gas system. We need to link it to S w at the seismic scale. This link can be one of simple mixing laws, such as harmonic and arithmetic. Alternately, it can be derived at the well by using upscaled variables and ensuring that they obey the well-data-driven rock-physics model. These different K f -S w relations produce different interpretations for Ļ and S w thus allowing one to assess the variability in the estimates of the gas volume in place that is proportional to the product of Ļ and (1 - S w )
Tris(ethane-1,2-diamine-Īŗ2 N,Nā²)cobalt(III) carbonate iodide tetraĀhydrate
The title compound, [Co(C2H8N2)3](CO3)IĀ·4H2O, crystallizes with a [Co(en)3]3+ cation (en is ethane-1,2-diamine), CO3
2ā and Iā anions and four water molĀecules in the asymmetric unit. In the cation, the three rings formed by the ethylĀenediamine units and the CoIII metal ion are in slightly distorted twist conformations. Numerous OāHāÆO, NāHāÆO, NāHāÆI and OāHāÆI interĀmolecular hydrogen bonds between the cation and two anions in concert with the four water molĀecules dominate the crystal packing and create a supraĀmolecular infinite three-dimensional framework
BICEP2 / Keck Array VIII: Measurement of gravitational lensing from large-scale B-mode polarization
We present measurements of polarization lensing using the 150 GHz maps which
include all data taken by the BICEP2 & Keck Array CMB polarization experiments
up to and including the 2014 observing season (BK14). Despite their modest
angular resolution (), the excellent sensitivity (K-arcmin) of these maps makes it possible to directly reconstruct the
lensing potential using only information at larger angular scales (). From the auto-spectrum of the reconstructed potential we measure an
amplitude of the spectrum to be (Planck
CDM prediction corresponds to ), and reject
the no-lensing hypothesis at 5.8, which is the highest significance
achieved to date using an EB lensing estimator. Taking the cross-spectrum of
the reconstructed potential with the Planck 2015 lensing map yields
. These direct measurements of
are consistent with the CDM cosmology, and with
that derived from the previously reported BK14 B-mode auto-spectrum (). We perform a series of null tests and consistency
checks to show that these results are robust against systematics and are
insensitive to analysis choices. These results unambiguously demonstrate that
the B-modes previously reported by BICEP / Keck at intermediate angular scales
() are dominated by gravitational lensing. The
good agreement between the lensing amplitudes obtained from the lensing
reconstruction and B-mode spectrum starts to place constraints on any
alternative cosmological sources of B-modes at these angular scales.Comment: 12 pages, 8 figure
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