3,430 research outputs found
Análisis de la transición de la física clásica a la relativista desde la perspectiva del "cambio conceptual"
Interviews about special relativity are realized with students of a Modern Physics course. The results of the interviews' analysis suggest that conceptual change doesn't mean a substitution of classic physics conceptions by the relativistic ones but that there is an interactive coexistence of both
Sustainability of non-residential buildings and relevance of main environmental impact contributors’ variability. A case study of food retail stores buildings
European tertiary sector represents about 13% of EU-28 final energy consumption. As an example, food retail stores sector amounts about 3% of EU members’ electricity consumption. Furthermore, currently, fluorinated gases, which are the most used refrigerants for space conditioning and refrigeration systems, involve 2% of EU emissions, having risen since 1990 by 60%. Specifically, commercial refrigeration is responsible for 35% of EU-27 CO2-eq emissions related to refrigerants. A methodology based on Life Cycle Assessment standards is presented in this study to assess the energy and environmental implications of non-residential buildings, adapted to particularities of food retail stores buildings, in terms of Primary Energy Demand, carbon footprint and water demand. Relying on a reference building, constructive improvements are tested and evaluated. Then a sensitivity analysis of several configurations of food retail stores are studied considering their building location, refrigerant typology and schedule. Results show that electricity and refrigerants are the main contributors and sensitive to potential improvements. In fact, static calculations reveal that a food retail store may involve, in terms of Global Warming Potential, about 800 kgCO2- eq/m2 year, more than 20 times higher than a regular building. Thus, future scenarios are estimated through a dynamic calculation methodology. Due to optimal dimensioning and configuration of the refrigeration system, together with refrigerant replacement, an 80% of Global Warming Potential minimization can be reached. Furthermore, temporal dynamic assessment can present a variability of environmental impacts estimation from static Life Cycle Assessment of more than 15%, by considering a wider approach towards sustainability assessment of non-residential buildings
Conductance Distributions in Random Resistor Networks: Self Averaging and Disorder Lengths
The self averaging properties of conductance are explored in random
resistor networks with a broad distribution of bond strengths
P(g)\simg^{\mu-1}. Distributions of equivalent conductances are estimated
numerically on hierarchical lattices as a function of size and distribution
tail parameter . For networks above the percolation threshold, convergence
to a Gaussian basin is always the case, except in the limit --> 0. A {\it
disorder length} is identified beyond which the system is effectively
homogeneous. This length diverges as ( is the
regular percolation correlation length exponent) as -->0. This suggest
that exactly the same critical behavior can be induced by geometrical disorder
and bu strong bond disorder with the bond occupation probability .
Only lattices at the percolation threshold have renormalized probability
distribution in a {\it Levy-like} basin. At the threshold the disorder length
diverges at a vritical tail strength as , with
, a new exponent. Critical path analysis is used in a generalized
form to give form to give the macroscopic conductance for lattice above .Comment: 16 pages plain TeX file, 6 figures available upon
request.IBC-1603-01
The RoPES project with HARPS and HARPS-N. I. A system of super-Earths orbiting the moderately active K-dwarf HD 176986
We report the discovery of a system of two super-Earths orbiting the
moderately active K-dwarf HD 176986. This work is part of the RoPES RV program
of G- and K-type stars, which combines radial velocities (RVs) from the HARPS
and HARPS-N spectrographs to search for short-period terrestrial planets. HD
176986 b and c are super-Earth planets with masses of 5.74 and 9.18
M, orbital periods of 6.49 and 16.82 days, and distances of 0.063
and 0.119 AU in orbits that are consistent with circular. The host star is a
K2.5 dwarf, and despite its modest level of chromospheric activity (log(R'hk) =
- 4.90 +- 0.04), it shows a complex activity pattern. Along with the discovery
of the planets, we study the magnetic cycle and rotation of the star. HD 176986
proves to be suitable for testing the available RV analysis technique and
further our understanding of stellar activity.Comment: 21 pages, 24 figures, 7 table
Shimura varieties in the Torelli locus via Galois coverings of elliptic curves
We study Shimura subvarieties of obtained from families of
Galois coverings where is a smooth complex
projective curve of genus and . We give the complete list
of all such families that satisfy a simple sufficient condition that ensures
that the closure of the image of the family via the Torelli map yields a
Shimura subvariety of for and for all and
for and . In a previous work of the first and second author
together with A. Ghigi [FGP] similar computations were done in the case .
Here we find 6 families of Galois coverings, all with and
and we show that these are the only families with satisfying this
sufficient condition. We show that among these examples two families yield new
Shimura subvarieties of , while the other examples arise from
certain Shimura subvarieties of already obtained as families of
Galois coverings of in [FGP]. Finally we prove that if a family
satisfies this sufficient condition with , then .Comment: 18 pages, to appear in Geometriae Dedicat
The HADES RV Programme with HARPS-N at TNG XI. GJ 685 b: a warm super-Earth around an active M dwarf
Small rocky planets seem to be very abundant around low-mass M-type stars.
Their actual planetary population is however not yet precisely understood.
Currently several surveys aim to expand the statistics with intensive detection
campaigns, both photometric and spectroscopic. We analyse 106 spectroscopic
HARPS-N observations of the active M0-type star GJ 685 taken over the past five
years. We combine these data with photometric measurements from different
observatories to accurately model the stellar rotation and disentangle its
signals from genuine Doppler planetary signals in the RV data. We run an MCMC
analysis on the RV and activity indexes time series to model the planetary and
stellar signals present in the data, applying Gaussian Process regression
technique to deal with the stellar activity signals. We identify three periodic
signals in the RV time series, with periods of 9, 24, and 18 d. Combining the
analyses of the photometry of the star with the activity indexes derived from
the HARPS-N spectra, we identify the 18 d and 9 d signals as activity-related,
corresponding to the stellar rotation period and its first harmonic
respectively. The 24 d signals shows no relations with any activity proxy, so
we identify it as a genuine planetary signal. We find the best-fit model
describing the Doppler signal of the newly-found planet, GJ 685\,b,
corresponding to an orbital period d and a
minimum mass M. We also study a
sample of 70 RV-detected M-dwarf planets, and present new statistical evidence
of a difference in mass distribution between the populations of single- and
multi-planet systems, which can shed new light on the formation mechanisms of
low-mass planets around late-type stars.Comment: 18 pages, 13 figures, accepted for publication in A&
- …