The possibility of determining open-cluster parameters from BVRI photometry

In the last decades we witnessed an increase in studies of open clusters of the Galaxy, especially because of the good determination for a wide range of values of parameters such as age, distance, reddening, and proper motion. The reliable determination of the parameters strongly depends on the photometry available and especially on the U filter, which is used to obtain the color excess E(B-V) through the color-color diagram (U-B) by (B-V) by fitting a zero age main-sequence. Owing to the difficulty of performing photometry in the U band, many authors have tried to obtain E(B-V) without the filter. But because of the near linearity of the color-color diagrams that use the other bands, combined with the fact that most fitting procedures are highly subjective (many done "by eye") the reliability of those results has always been questioned. Our group has recently developed, a tool that performs isochrone fitting in open-cluster photometric data with a global optimization algorithm, which removes the need to visually perform the fits and thus removes most of the related subjectivity. Here we apply our method to a set of synthetic clusters and two observed open clusters (Trumpler 1 and Melotte 105) using only photometry for the BVRI bands. Our results show that, considering the cluster structural variance caused only by photometric and Poisson sampling errors, our method is able to recover the synthetic cluster parameters with errors of less than 10% for a wide range of ages, distances, and reddening, which clearly demonstrates its potential. The results obtained for Trumpler 1 and Melotte 105 also agree well with previous literature values.Comment: 5 pages, 5 figures, accepted for publication in Astronomy&Astrophysic

Analysis of water absorbency into knitted spacer structures

The absorbency properties of knitted structures are very important in designing garments that both remove liquid sweat from the skin and provide tactile and sensorial comfort to the wearer. Water absorbency by knitted spacer structures was experimentally investigated using a gravimetric absorbency tester to record absorbency rate, total absorbency, and time taken to saturate the structure. The geometry of spacer structures was analyzed and a model created to define the capillary characteristic in the spacer yarn. Absorbency into the spacer structures was modeled using the fabric parameters, the capillary radius, and the properties of water. Experimental and theoretical results were compared to validate the models

Experimental knitted, textile frequency selective surfaces

A new approach to the manufacture of conducting textiles for operation at microwave frequencies is reported. The technique investigated utilises a commercial flat-bed knitting process which is configured to use conducting yarns to produce large area, patterned, conducting textiles in an efficient manner which is amenable to mass production. The computerised flat-bed knitting system is used to manufacture example frequency selective surfaces (FSSs) using silver coated nylon yarn combined with a polyester base yarn. Reflectivity measurements are presented to confirm the basic operation of both a lowpass and a highpass knitted, textile FSS

Models for the 3-D axisymmetric gravitational potential of the Milky Way Galaxy - A detailed modelling of the Galactic disk

Aims. Galaxy mass models based on simple and analytical functions for the density and potential pairs have been widely proposed in the literature. Disk models constrained by kinematic data alone give information on the global disk structure only very near the Galactic plane. We attempt to circumvent this issue by constructing disk mass models whose three-dimensional structures are constrained by a recent Galactic star counts model in the near-infrared and also by observations of the hydrogen distribution in the disk. Our main aim is to provide models for the gravitational potential of the Galaxy that are fully analytical but also with a more realistic description of the density distribution in the disk component. Methods. From the disk model directly based on the observations (here divided into the thin and thick stellar disks and the HI and H$_2$ disks subcomponents), we produce fitted mass models by combining three Miyamoto-Nagai disk profiles of any "model order" (1, 2, or 3) for each disk subcomponent. The Miyamoto-Nagai disks are combined with models for the bulge and "dark halo" components and the total set of parameters is adjusted by observational kinematic constraints. A model which includes a ring density structure in the disk, beyond the solar Galactic radius, is also investigated. Results. The Galactic mass models return very good matches to the imposed observational constraints. In particular, the model with the ring density structure provides a greater contribution of the disk to the rotational support inside the solar circle. The gravitational potential models and their associated force-fields are described in analytically closed forms, and in addition, they are also compatible with our best knowledge of the stellar and gas distributions in the disk component. The gravitational potential models are suited for investigations of orbits in the Galactic disk.Comment: 22 pages, 13 figures, 11 tables, accepted for publication in A&

Fitting isochrones to open cluster photometric data III. Estimating metallicities from UBV photometry

The metallicity is a critical parameter that affects the correct determination fundamental characteristics stellar cluster and has important implications in Galactic and Stellar evolution research. Fewer than 10 % of the 2174 currently catalog open clusters have their metallicity determined in the literature. In this work we present a method for estimating the metallicity of open clusters via non-subjective isochrone fitting using the cross-entropy global optimization algorithm applied to UBV photometric data. The free parameters distance, reddening, age, and metallicity simultaneously determined by the fitting method. The fitting procedure uses weights for the observational data based on the estimation of membership likelihood for each star, which considers the observational magnitude limit, the density profile of stars as a function of radius from the center of the cluster, and the density of stars in multi-dimensional magnitude space. We present results of [Fe/H] for nine well-studied open clusters based on 15 distinct UBV data sets. The [Fe/H] values obtained in the ten cases for which spectroscopic determinations were available in the literature agree, indicating that our method provides a good alternative to determining [Fe/H] by using an objective isochrone fitting. Our results show that the typical precision is about 0.1 dex

Knitted, textile, high impedance surface with integrated conducting vias

An experimental, microwave high impedance surface (HIS) manufactured from a combination of both conducting and insulating yarns using commercial, computerised flat-bed knitting machines is presented. The HIS consists of a knitted, conducting ground plane, a polyester spacer layer and a knitted, conducting patterned top surface. The structure also contains vias that link the conducting elements of the top layer to the ground plane. The entire structure (including the vias) is knitted in one continuous process that is both low cost and highly efficient in terms of manufacturing time. Measurements of the surface wave transmission properties of the knitted, textile HIS are made and data are presented that show that the HIS prevents surface wave transmission over a band of frequencies between 4 and 5GHz

Stabilization of the Electroweak Scale in 3-3-1 Models

One way of avoiding the destabilization of the electroweak scale through a strong coupled regime naturally occurs in models with a Landau-like pole at the TeV scale. Hence, the quadratic divergence contributions to the scalar masses are not considered as a problem anymore since a new nonperturbative dynamic emerges at the TeV scale. This scale should be an intrinsic feature of the models and there is no need to invoke any other sort of protection for the electroweak scale. In some models based on the $SU(3)_C\otimes SU(3)_W\otimes U(1)_{X}$ gauge symmetry, a nonperturbative dynamics arise and it stabilizes the electroweak scale.Comment: 10 pages. Version with some improvements and corrections in the tex