Distribución de polvo interestelar a pequeña escala de distancias

Se presenta un modelo estático, compuesto por nubes de simetría esférica, que permite ajustar el exceso de color medio y la dispersión de excesos de color observados para el cúmulo abierto NGC 2516 (CO 757-607). Las nubes poseed un perfil de densidad alto dado por: ρ(r)=ρ₀ exp(-r/r₀)² en la cual r es la distancia desde el centro de la nube, r₀ el radio típico y ρ₀ la densidad central de la misma.Asociación Argentina de Astronomí

Achievable Rate-Power Tradeoff in THz SWIPT Systems with Resonant Tunnelling Diodes

In this paper, we study terahertz (THz) simultaneous wireless information and power transfer (SWIPT) systems. Since coherent information detection is challenging at THz frequencies and Schottky diodes are not usable for THz energy harvesting (EH), we employ unipolar amplitude shift keying (ASK) modulation at the transmitter (TX) and a resonant tunnelling diode (RTD)- based EH circuit at the receiver (RX) to extract both information and power from the received signal. However, the electrical properties of Schottky diodes and RTDs are different, and unlike EH receivers based on a single Schottky diode, an accurate closed-form EH model for RTD-based RXs is not available, yet. In this paper, we model the dependency of the instantaneous RX output power on the instantaneous received power by a non-linear piecewise function, whose parameters are adjusted to fit circuit simulation results. We formulate an optimization problem to maximize the mutual information between the TX and RX signals subject to constraints on the peak amplitude of the transmitted signal and the required average harvested power at the RX. Furthermore, we determine a feasibility condition for the formulated problem, and for high and low required average harvested powers, we derive the achievable information rate numerically and in closed form, respectively. Our simulation results highlight a tradeoff between the information rate and the average harvested power. Finally, we show that this tradeoff is determined by the peak amplitude of the transmitted signal and the maximum instantaneous harvested power for low and high received signal powers, respectively.Comment: 6 pages, 5 figures, submitted for possible conference publicatio

Optical followup of galaxy clusters detected by the South Pole Telescope

The South Pole Telescope (SPT) is a 10 meter telescope operating at mm wavelengths. It has recently completed a three-band survey covering 2500 sq. degrees. One of the survey's main goals is to detect galaxy clusters using Sunyaev-Zeldovich effect and use these clusters for a variety of cosmological and astrophysical studies such as the dark energy equation of state, the primordial non-gaussianity and the evolution of galaxy populations. Since 2005, we have been engaged in a comprehensive optical and near-infrared followup program (at wavelengths between 0.4 and 5 {\mu}m) to image high-significance SPT clusters, to measure their photometric redshifts, and to estimate the contamination rate of the candidate lists. These clusters are then used for various cosmological and astrophysical studies.Comment: For TAUP 2011 proceeding

A Framework for Improving the Energy Efficiency and Sustainability of Collaborative Robots

On a worldwide scale, industry is responsible for a large part for the overall use of energy and resources: reducing this use is included in the targets of SDG9, one of the Sustainable Development Goals drawn by the United Nations. This work aims to create a framework for better understanding, modelling, and optimizing the energy consumption of industrial robots, with specific reference to the collaborative robot UR5e. The framework comprises a real robot and its electro-dynamic model, the latter being developed on the basis of experimental tests and of data supplied by the manufacturer. The paper presents the main features of the framework, and the future work aimed at improving the accuracy of the proposed energy model

Adesione di bracket precoated a un composito ibrido lucidato con gommini

Bonding of precoated bracket on a composite restoration needs adhesion between two exisiting polimerized materials. Composite restorations are usually polished by using rubber cups before bonding. The aim of this study was to evaluate the influence of a composite resin surface polishing on the adhesion to precoated brackets. Specimens of Filtek Z250 and enamel were polished with rubber cups according to different protocols; precoated brackets were bonded with Transbond XT to the specimens. The shear bond strength of brackets was evaluated and measured data were statistically analysed. The results highlight low adhesion forces between composite resin and brackets used, demonstrating an unsatisfactory bonding from a clinical point of view. Therefore, different surface polishing techniques have to be chosen before bonding precoated brackets on composite restorations

Influenza dei restauri estetici sulla cementazione adesiva dei bracket

Direct or indirect bonding of orthodontic brackets on previously restored anterior teeth must ensure clinically satisfactory adhesion forces to a surface that is often composed of a micro-filled composite resin. Being chemically passive because of its permanence in the oral cavity, this surface must be prepared to restore ideal conditions for bracket bonding. This study examines the effectiveness of polishing with rubber cup and abrasive paste in surface preparation before orthodontic bonding. Specimens of microfilled composite resin (Gradia Direct) and human enamel have been polished with fine silicon cups and Prisma-gloss extrafine paste; a standard bracket for upper central incisor has been bonded to these specimens by direct (Transbond XT system) or indirect (Transbond XT, Sondhi Rapid-set) technique. Adhesion forces have been evaluated with shear bond test. The values measured were lower than the clinically acceptable interval of 6-8 MPa for indirect technique on polished composite. Statistical analysis with ANOVA, Tukey and Student\u2019s T tests showed significant differences between enamel and composite as well as between direct and indirect techniques: the most effective adhesion has been found on enamel with direct technique