2,835 research outputs found
Labor Law — Effect of Negotiating Impasse on an Employer\u27s Right to Withdraw from a Multi-Employer Bargaining Association —NLRB v. Beck Engraving
The primordial deuterium abundance at z = 2.504 from a high signal-to-noise spectrum of Q1009+2956
The spectrum of the quasar Q1009+2956 has been observed
extensively on the Keck telescope. The Lyman limit absorption system was previously used to measure D/H by Burles & Tytler using a
spectrum with signal to noise approximately 60 per pixel in the continuum near
Ly {\alpha} at . The larger dataset now available combines
to form an exceptionally high signal to noise spectrum, around 147 per pixel.
Several heavy element absorption lines are detected in this LLS, providing
strong constraints on the kinematic structure. We explore a suite of absorption
system models and find that the deuterium feature is likely to be contaminated
by weak interloping Ly {\alpha} absorption from a low column density H I cloud,
reducing the expected D/H precision. We find D/H =
for this system. Combining this new
measurement with others from the literature and applying the method of Least
Trimmed Squares to a statistical sample of 15 D/H measurements results in a
"reliable" sample of 13 values. This sample yields a primordial deuterium
abundance of (D/H). The
corresponding mean baryonic density of the Universe is . The quasar absorption data is of the same precision as, and
marginally inconsistent with, the 2015 CMB Planck (TT+lowP+lensing)
measurement, . Further quasar and more
precise nuclear data are required to establish whether this is a random
fluctuation.Comment: accepted by MNRAS, 18 pages, 12 figures, 6 table
X-ray He-like ions diagnostics: New Computations for Photoionized Plasmas: I. preliminary considerations
Using the new version of the photoionization code Titan designed for
plane-parallel photoionized thick hot media, which is unprecedented from the
point of view of line transfer, we have undertaken a study of the influence of
different parameters on the He-like and H-like emission of a medium
photoionized by an X-ray source. We explain why in modelling the emitting
medium it is important to solve in a self-consistent way the thermal and
ionization equilibria and to take into account the interconnection between the
different ions. We give the equivalent widths of the sum of the He-like
triplets and the triplet intensity ratios and , for the most important
He-like ions, for a range of density, column density, and ionization parameter,
in the case of constant density media. We show that the line intensities from a
given ion can be accounted for, either by small values of both the column
density and of the ionization parameter, or by large values of both quantities,
and it is necessary to take into account several ions to disentangle these
possibilities. We show also that a "pure recombination spectrum" almost never
exists in a photoionized medium: either it is thin, and resonance lines are
formed by radiative excitation, or it is thick, and free-bound absorption
destroys the resonance photons as they undergo resonant diffusion.Comment: 19 pages, 14 figures, accepted in A &
Energy Performance and Economic Evaluation of Heat Pump/Organic Rankine Cycle System with Sensible Thermal Storage
ASO Author Reflections: Is There Still a Role for Intraperitoneal Oxaliplatin for Colorectal Peritoneal Metastases?
International audienc
The creation of an in vitro germplasm collection of yam (Dioscorea spp.) for genetic resources preservation
Control strategy and performance of a small-size thermally integrated Carnot battery based on a Rankine cycle and combined with district heating
To encourage decarbonization and promote a widespread penetration of renewable energy sources in all energy sectors, the development of efficient energy storage systems is essential. Interesting grid-scale electricity storage technologies are the Carnot batteries, whose working principle is based on storing electricity in the form of thermal energy. The charging phase is performed through a heat pump cycle, and the discharging phase is conducted through a heat engine. Since both thermal and electric energy flows are involved, Carnot batteries can be adopted to provide more flexibility in heat and power energy systems. To this aim, efficient scheduling strategies are necessary to manage different energy flows. In this context, this work presents a detailed rule-based control strategy to schedule the synergetic work of a 10-kWe reversible heat pump/organic Rankine cycle Carnot battery integrated to a district heating substation and a photovoltaic power plant, to satisfy a local user's thermal and electric demand. The coupling of a Carnot battery with a district heating substation allows for shaving the thermal demand peaks through the thermal energy stored in the Carnot battery storage, allowing for a downsizing of the district heating substation, with a considerable reduction of the investment costs. Due to the multiplicity of the involved energy flows and the numerous modes of operation, a scheduling logic for the Carnot battery has been developed, to minimize the system operating costs, depending on the boundary conditions. To investigate the influence of the main system design parameters, a detailed and accurate model of the Carnot battery is adopted. Two variants of the reference system, with different heat pump cold source arrangements, are investigated. In the first case, the heat pump absorbs thermal energy from free waste heat. In the second case, the heat pump cold source is the return branch of the district heating substation. The simulation results show that, in the first case, the Carnot battery allows the downsizing of the district heating substation by 47 %, resulting in an annual gain of more than 5000 €. About 70 % of the economic benefit is due to the possibility of reducing the power size of the district heating substation, which can be from 300 to more than 500 kW. The payback period is estimated to be lower than 9 years, while in the second case, the Carnot battery is not able to provide a gain. Eventually, the influence of some parameters, such as the photovoltaic power plant surface, the storage volume, the electricity price profile and the reversible heat pump/organic Rankine cycle specific investment cost, on the techno-economic performance of the system, is investigated through a wide sensitivity analysis. According to the results, the photovoltaic panels surface does not significantly affect the economic gain, while the storage capacity strongly affects the system scheduling and the operating costs. Indeed, it is possible to identify that 13 m3 is the size of the storage volume that minimizes the payback period to 8.22 years, for the considered application. An increase in the electricity price without an increase in the thermal energy price leads to a decrease in economic gain because the benefit brought by the downsizing of district heating is less significant on the economic balance. The specific investment cost of the reversible heat pump/organic Rankine cycle does not influence the operating cost; thus, it does not change the Carnot battery management, nor the economic gain. The specific investment cost affects the payback period, which increases from 8.6 years for a specific cost of 2000 €/kWe to 15.7 years for a specific cost of 5000 €/kWe
Primordial deuterium abundance at z=2.504 towards Q1009+2956
The z_abs = 2.504 Lyman Limit absorption system (LLS) towards Q1009+2956 has
previously been used to estimate the primordial deuterium abundance. Since the
initial measurement by Burles & Tytler, this quasar has been observed
extensively with the Keck telescope, providing a substantial increase in
signal-to-noise (from 60 to 147 at continuum level of Ly-alpha at z_abs=2.504).
We explore a set of different models for the absorption system and find that
the deuterium feature is contaminated by Ly-alpha absorption from a low column
density H I cloud. This significantly limits precision to which one can
estimate the D/H ratio in this LLS. Our final result for this system D/H
=2.48^{+0.41}_{-0.35}*10^{-5} has the same relative uncertainty of 17% as the
previous estimate by Burles & Tytler despite the far higher signal-to-noise of
our dataset. A weighted mean of 13 D/H measurements available in the literature
(including our result) gives the primordial deuterium abundance of (D/H)_p =
(2.545 +/- 0.025)*10^{-5} and the corresponding baryon density of the Universe
of Omega_b h^2 = 0.02174 +/- 0.00025 marginally inconsistent with the 2015
Planck CMB data.Comment: 7 pages, 3 figures, conference proceedings from PhysicA.SPb 201
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