329 research outputs found
Experimental analysis and model validation of an opaque ventilated facade
Natural ventilation is a convenient way of reducing energy consumption in buildings. In this study an experimental module of an opaque ventilated façade (OVF) was built and tested for assessing its potential of supplying free ventilation and air preheating for the building. A numerical model was created and validated against the experimental data. The experimental results showed that the flow rates induced in the façade cavity were due to mixed driving forces: wind and buoyancy. Depending on the weather conditions one of them was the main driving force, or both were of the same order. When the wind force was the main driving force, higher flow rates were found. In these cases buoyancy acted as supporting driving force. When the wind speed was low and buoyancy prevailed lower flow rates were found. Air and surface temperatures were predicted by the numerical model with a better accuracy than flow and energy rates. The model predicts correctly the influence of the wind and buoyancy driving forces. The experimental OVF module showed potential for free ventilation and air preheating, although it depends on weather and geometrical variables. The use of the numerical model using the right parameters was found viable for analyzing the performance of an OVF
Late-Variscan multistage hydrothermal processes unveiled by chemical ages coupled with compositional and textural uraninite variations in W-Au deposits in the western Spanish Central System Batholith
The scheelite skarn from Los Santos and the W-Au veins from El Cabaco district, located in the Spanish Central System Batholith (SCSB), are some of the best-known tungsten ore deposits in Spain. Uraninite is an accessory mineral in both deposits, which underwent several hydrothermal flow events. Chemical and textural characteristics, as well as electron microprobe U-Th-Pb uraninite chemical data from the different stages of the skarn and the vein-type mineralizations, are presented here. Based on these data the uraninite was able to be classified into two groups. Group I uraninite has an octahedral habit and occurs as inclusions in K-feldspar relicts of the leucogranite related to Los Santos skarn formation. It shows high Th (6.95 to 8.51wt.% ThO2) and high Rare Earth Elements (REEs) contents (0.55 to 1.38wt.% âREE2O3). Group II uraninite occurs i) associated to El Cabaco granite, in a greenish selvage-style greisen and its reddish envelope and in the mineralized rimming quartz veins and ii) in Los Santos high-temperature endoskarn and anorthite skarn, where it is associated with U-rich mica. This uraninite type has lower Th and âREE2O3contents than Group-I uraninite. The mineral chemistry and the assemblage and textural relationships suggest that Group-I uraninite is magmatic and the attained U-Th-Pb chemical age of 300±4Ma is interpreted as the magmatic age of the skarn-forming aplite granites in the western part of the SCSB. Group-II uraninite includes two events: i) hydrothermal uraninite, which yields an age of 295±2Ma, dates a strong alkali mobilization and early tungsten deposition and ii) a later hydrothermal process, around 287±4Ma, that resulted in sulfides and late scheelite precipitation and widespread silicification. Finally, the gold deposition is younger than this silicification according to textural criteria. Therefore, W-Au deposits in the western part of the SCSB were formed by superposition of several processes that took place some 15Ma after the skarn-forming granite crystallized. Comparable W, W-Au and U deposits in the Variscan orogenic belt show a similar timing of hydrothermal events, suggesting that the hydrothermal history was controlled by large-scale Late-Variscan tectonic processes
TRIZ: creativity as exact science?
TRIZ is the acronym for the Russian phrase Theory of Inventive Problem Solving. Over two million patents have been examined, classified by level of inventiveness, and analyzed to look for principles of innovation. If these principles could be identified and codified, they could be taught to people to make the process of invention more predictable. In this paper we discuss some ideas to use this method in the preparation of Physics students.TRIZ Ă© a sigla para as palavras russas que, em portuguĂȘs, significam Teoria para a Resolução de Problemas Criativos. O estudo de mais de dois milhĂ”es de patentes no mundo tem permitido identificar princĂpios universais de invenção. Ensinando estes princĂpios e com a ajuda de tĂ©cnicas psicolĂłgicas de geração de idĂ©ias, a metodologia TRIZ pretende aprofundar e dinamizar o processo criativo. Neste artigo apresentamos algumas sugestĂ”es de como utilizar o mĂ©todo TRIZ na formação de estudantes de FĂsica.205209Fundação de Amparo Ă Pesquisa do Estado de SĂŁo Paulo (FAPESP)Conselho Nacional de Desenvolvimento CientĂfico e TecnolĂłgico (CNPq
Hadronic B Decays Involving Even Parity Charmed Mesons
Hadronic B decays containing an parity-even charmed meson in the final state
are studied. Specifically we focus on the Cabibbo-allowed decays and , where denotes generically a p-wave charmed meson.
The transition form factors are studied in the improved version
of the Isgur-Scora-Grinstein-Wise quark model. We apply heavy quark effective
theory and chiral symmetry to study the strong decays of p-wave charmed mesons
and determine the magnitude of the mixing angle. Except
the decay to the predictions for agree
with experiment. The sign of mixing angle is found to be
positive in order to avoid a severe suppression on the production of
. The interference between color-allowed and color-suppressed
tree amplitudes is expected to be destructive in the decay . Hence, an observation of the ratio
can be used to test the relative signs of
various form factors as implied by heavy quark symmetry. Although the predicted
at the level of exceeds the
present upper limit, it leads to the ratio
as expected from the factorization
approach and from the ratio . Therefore, it is
crucial to have a measurement of this mode to test the factorization
hypothesis. For decays, it is expected that \bar
D_{s0}^*D\gsim \bar D_{s1}D as the decay constants of the multiplet
become the same in the heavy quark limit.Comment: 27 pages, Belle's new data on DD_s^{**} productions in B decays and
on the radiative decay D_{s1}-> D_s\gamma are updated and discussed. Add two
reference
Performance of Scheduling Policies in Adversarial Networks with Non-synchronized Clocks
In this paper we generalize the Continuous Adversarial Queuing Theory (CAQT) model (Blesa et al. in MFCS, Lecture Notes in Computer Science, vol. 3618, pp. 144â155, 2005) by considering the possibility that the router clocks in the network are not synchronized. We name the new model Non Synchronized CAQT (NSCAQT). Clearly, this new extension to the model only affects those scheduling policies that use some form of timing. In a first approach we consider the case in which although not synchronized, all clocks run at the same speed, maintaining constant differences. In this case we show that all universally stable policies in CAQT that use the injection time and the remaining path to schedule packets remain universally stable. These policies include, for instance, Shortest in System (SIS) and Longest in System (LIS). Then, we study the case in which clock differences can vary over time, but the maximum difference is bounded. In this model we show the universal stability of two families of policies related to SIS and LIS respectively (the priority of a packet in these policies depends on the arrival time and a function of the path traversed). The bounds we obtain in this case depend on the maximum difference between clocks. This is a necessary requirement, since we also show that LIS is not universally stable in systems without bounded clock difference. We then present a new policy that we call Longest in Queues (LIQ), which gives priority to the packet that has been waiting the longest in edge queues. This policy is universally stable and, if clocks maintain constant differences, the bounds we prove do not depend on them. To finish, we provide with simulation results that compare the behavior of some of these policies in a network with stochastic injection of packets
Role of post-translational modifications at the ÎČ-subunit ectodomain in complex association with a promiscuous plant P4-ATPase.
P-type ATPases of subfamily IV (P4-ATPases) constitute a major group of phospholipid flippases that form heteromeric complexes with members of the Cdc50 (cell division control 50) protein family. Some P4-ATPases interact specifically with only one ÎČ-subunit isoform, whereas others are promiscuous and can interact with several isoforms. In the present study, we used a site-directed mutagenesis approach to assess the role of post-translational modifications at the plant ALIS5 ÎČ-subunit ectodomain in the functionality of the promiscuous plant P4-ATPase ALA2. We identified two N-glycosylated residues, Asn(181) and Asn(231) Whereas mutation of Asn(231) seems to have a small effect on P4-ATPase complex formation, mutation of evolutionarily conserved Asn(181) disrupts interaction between the two subunits. Of the four cysteine residues located in the ALIS5 ectodomain, mutation of Cys(86) and Cys(107) compromises complex association, but the mutant ÎČ-subunits still promote complex trafficking and activity to some extent. In contrast, disruption of a conserved disulfide bond between Cys(158) and Cys(172) has no effect on the P4-ATPase complex. Our results demonstrate that post-translational modifications in the ÎČ-subunit have different functional roles in different organisms, which may be related to the promiscuity of the P4-ATPase
Evolution and Flare Activity of Delta-Sunspots in Cycle 23
The emergence and magnetic evolution of solar active regions (ARs) of
beta-gamma-delta type, which are known to be highly flare-productive, were
studied with the SOHO/MDI data in Cycle 23. We selected 31 ARs that can be
observed from their birth phase, as unbiased samples for our study. From the
analysis of the magnetic topology (twist and writhe), we obtained the following
results. i) Emerging beta-gamma-delta ARs can be classified into three
topological types as "quasi-beta", "writhed" and "top-to-top". ii) Among them,
the "writhed" and "top-to-top" types tend to show high flare activity. iii) As
the signs of twist and writhe agree with each other in most cases of the
"writhed" type (12 cases out of 13), we propose a magnetic model in which the
emerging flux regions in a beta-gamma-delta AR are not separated but united as
a single structure below the solar surface. iv) Almost all the "writhed"-type
ARs have downward knotted structures in the mid portion of the magnetic flux
tube. This, we believe, is the essential property of beta-gamma-delta ARs. v)
The flare activity of beta-gamma-delta ARs is highly correlated not only with
the sunspot area but also with the magnetic complexity. vi) We suggest that
there is a possible scaling-law between the flare index and the maximum umbral
area
Connecting the dots: social networks in the classroom and white matter connections in the brain: social networks in the classroom and white matter connections in the brain
Pathways through Adolescenc
The Imaging Magnetograph eXperiment (IMaX) for the Sunrise balloon-borne solar observatory
The Imaging Magnetograph eXperiment (IMaX) is a spectropolarimeter built by
four institutions in Spain that flew on board the Sunrise balloon-borne
telesocope in June 2009 for almost six days over the Arctic Circle. As a
polarimeter IMaX uses fast polarization modulation (based on the use of two
liquid crystal retarders), real-time image accumulation, and dual beam
polarimetry to reach polarization sensitivities of 0.1%. As a spectrograph, the
instrument uses a LiNbO3 etalon in double pass and a narrow band pre-filter to
achieve a spectral resolution of 85 mAA. IMaX uses the high Zeeman sensitive
line of Fe I at 5250.2 AA and observes all four Stokes parameters at various
points inside the spectral line. This allows vector magnetograms, Dopplergrams,
and intensity frames to be produced that, after reconstruction, reach spatial
resolutions in the 0.15-0.18 arcsec range over a 50x50 arcsec FOV. Time
cadences vary between ten and 33 seconds, although the shortest one only
includes longitudinal polarimetry. The spectral line is sampled in various ways
depending on the applied observing mode, from just two points inside the line
to 11 of them. All observing modes include one extra wavelength point in the
nearby continuum. Gauss equivalent sensitivities are four Gauss for
longitudinal fields and 80 Gauss for transverse fields per wavelength sample.
The LOS velocities are estimated with statistical errors of the order of 5-40
m/s. The design, calibration and integration phases of the instrument, together
with the implemented data reduction scheme are described in some detail.Comment: 17 figure
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