4,654 research outputs found
A possible sequential star formation in the giant molecular cloud G174+2.5
We investigate the nature of 14 embedded clusters (ECs) related to a group of
four H II regions Sh2-235, Sh2-233, Sh2-232, and Sh2-231 in the giant molecular
cloud G174 + 2.5. Projected towards the Galactic anticentre, these objects are
a possible example of the collect and collapse scenario. We derive
astrophysical parameters (age, reddening, distance, core and cluster radii) for
the ECs and investigate the relationship among their parameters. Parameters are
derived with field decontaminated 2MASS colour-magnitude diagrams (CMDs) and
stellar radial density profiles (RDPs). The CMDs of these young clusters are
characterised by a poorly-populated main sequence and a significant number of
pre-main sequence stars, affected by differential reddening. The ECs are KKC
11, FSR 784, Sh2-235 E2, Sh2-235 Cluster, Sh2-233SE Cluster, BDSB 73, Sh2-235B
Cluster, BDSB 72, BDSB 71, Sh2-232 IR, PCS 2, and the newly found clusters CBB
1 and CBB 2. We were able to derive fundamental parameters for all ECs in the
sample. Structural parameters are derived for FSR 784, Sh2-235 Cluster and
Sh2-235E2.Comment: 14 pages and 15 figures; MNRAS 201
THREE METHODS TO EVALUATE THE USE OF EVAPORATIVE COOLING FOR HUMAN THERMAL COMFORT
This paper presents three methods that can be used as reference for efficientuse of evaporative cooling systems, applying it, latter, to several Braziliancities, characterized by different climates. Initially it presents the basicprinciples of direct and indirect evaporative cooling and defines theeffectiveness of the systems. Afterwards, it presents three methods thatallows to determinate where the systems are more efficient. It concludesthat evaporative cooling systems have a very large potential to propitiatethermal comfort and can still be used as an alternative to conventionalsystems in regions where the design wet bulb temperature is under 24ºC
A MATHEMATICAL MODEL FOR DIRECT EVAPORATIVE COOLING AIR CONDITIONING SYSTEM
Air conditioning systems are responsible for increasing men's work
efficiency as well for his comfort, mainly in the warm periods of the year.
Currently, the most used system is the mechanical vapor compression
system. However, in many cases, evaporative cooling system can be an
economical alternative to replace the conventional system, under several
conditions, or as a pre-cooler in the conventional systems. It leads to a
reduction in the operational cost, comparing with systems using only
mechanical refrigeration. Evaporative cooling operates using induced
processes of heat and mass transfer, where water and air are the working
fluids. It consists in water evaporation, induced by the passage of an air
flow, thus decreasing the air temperature. This paper presents the basic
principles of the evaporative cooling process for human thermal comfort,
the principles of operation for the direct evaporative cooling system and
the mathematical development of the equations of thermal exchanges,
allowing the determination of the effectiveness of saturation. It also
presents some results of experimental tests in a direct evaporative cooler
that take place in the Air Conditioning Laboratory at the University of
Taubaté Mechanical Engineering Department, and the experimental results
are used to determinate the convective heat transfer coefficient and to
compare with the mathematical model
Lifetimes of ultralong-range strontium Rydberg molecules in a dense BEC
The lifetimes and decay channels of ultralong-range Rydberg molecules created
in a dense BEC are examined by monitoring the time evolution of the Rydberg
population using field ionization. Studies of molecules with values of
principal quantum number, , in the range to that contain tens
to hundreds of ground state atoms within the Rydberg electron orbit show that
their presence leads to marked changes in the field ionization characteristics.
The Rydberg molecules have lifetimes of s, their destruction
being attributed to two main processes: formation of Sr ions through
associative ionization, and dissociation induced through -changing
collisions. The observed loss rates are consistent with a reaction model that
emphasizes the interaction between the Rydberg core ion and its nearest
neighbor ground-state atom. The measured lifetimes place strict limits on the
time scales over which studies involving Rydberg species in cold, dense atomic
gases can be undertaken and limit the coherence times for such measurements.Comment: 9 pages, 8 figure
Cuadrado del binomio
En este capÃtulo, presentamos el proceso de diseño e implementación de la unidad didáctica del cuadrado de un binomio para grado octavo. Iniciamos con la descripción de los análisis previos (análisis de contenido, análisis cognitivo y análisis de instrucción) a la implementación que permitieron producir el primer diseño de la unidad didáctica del tema. Seguidamente, detallamos el trabajo realizado en el análisis de actuación, con el cual empezamos a analizar y a revaluar aspectos del diseño implementado de acuerdo con los resultados obtenidos por los estudiantes. Justi camos el nuevo diseño de la unidad didáctica con base en los resultados de esos análisis. Por último, concluimos con algunas re exiones sobre la experiencia vivida a lo largo del proceso
Collider and Dark Matter Searches in the Inert Doublet Model from Peccei-Quinn Symmetry
Weakly Interacting Massive Particles (WIMPs) and axions are arguably the most compelling dark matter candidates in the literature. Could they coexist as dark matter particles? More importantly, can they be incorporated in a well motivated framework in agreement with experimental data? In this work, we show that this two component dark matter can be realized in the Inert Doublet Model in an elegant and natural manner by virtue of the spontaneous breaking of a Peccei-Quinn symmetry into a residual symmetry. The WIMP stability is guaranteed by the symmetry and a new dark matter component, the axion, arises. There are two interesting outcomes: (i) vector-like quarks needed to implement the Peccei-Quinn symmetry in the model act as a portal between the dark sector and the SM fields with a supersymmetry-type phenomenology at colliders; (ii) two-component Inert Doublet Model re-opens the phenomenologically interesting 100-500 GeV mass region. We show that the model can plausibly have two component dark matter and at the same time avoid low and high energy physics constraints such as monojet and dijet plus missing energy, as well as indirect and direct dark matter detection bounds
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