An Innovative System for Monitoring Radon and Indoor Air Quality

Nowadays, a global trend towards increasing the performance of a building is the reduction in energy consumption. In this respect, for existing residential buildings the most common techniques are the application of a thermal insulation layer to the exterior wall of the building and / or window replacements. Unfortunately, their application without proper education of those involved may have a negative effect on the indoor air quality. The use of a continuous monitoring device can give the owner the ability to understand the impact of his behaviour on indoor air quality and, as such, to adjust his routine in order to maintain the indoor air quality at the desired level. This paper introduces a prototype, called ICA system, for continuous, real-time indoor air quality monitoring. The ICA system presents sensors for monitoring the concentration of radon, CO2, CO, VOCs, as well as meteorological parameters, such as temperature, pressure, and relative humidity. Experiments were performed both in laboratory and in situ conditions for testing and validating the proposed system.This work was supported by the project ID P_37_229, Contract No. 22/01.09.2016, with the title “Smart Systems for Public Safety through Control and Mitigation of Residential Radon linked with Energy Efficiency Optimization of Buildings in Romanian Major Urban Agglomerations SMART-RAD-EN” of the POC Programme

Collective behavior of "electronic fireflies"

A simple system composed of electronic oscillators capable of emitting and detecting light-pulses is studied. The oscillators are biologically inspired, their behavior is designed for keeping a desired light intensity, W, in the system. From another perspective, the system behaves like modified integrate and fire type neurons that are pulse-coupled with inhibitory type interactions: the firing of one oscillator delays the firing of all the others. Experimental and computational studies reveal that although no driving force favoring synchronization is considered, for a given interval of W phase-locking appears. This weak synchronization is sometimes accompanied by complex dynamical patterns in the flashing sequence of the oscillators.Comment: 4 pages, 4 figures include

Low Temperature Magnetic Properties of Pr0.7(Ca,Sr)0.3CoO3Pr_{0.7}(Ca,Sr)_{0.3}CoO_{3} Oxides

We have investigated magnetic and magnetocaloric properties of $Pr_{0.7}(Ca_{1-x}Sr_{x})_{0.3}CoO_{3},$ when the average size of the interpolated cation was changed. $Pr_{0.7}Ca_{0.3}CoO_{3}$ has an orthorhombic Pnma symmetry and it shows a magnetic cluster-glass behavior below 70 K. When Sr partially replaces Ca in this compound, its magnetic properties are improved, and it begins to have ferromagnetic-like behavior. The magnetic transition temperature, gradually, increases with increasing Sr content, up to 170 K, for x=1. The electrical conduction also improved when Sr content increased. All the samples show negative magnetoresitance. Magnetic entropy change $\Delta S_{M}$ was estimated from isothermal magnetization data. We have found that it had higher values for the samples with x>0.5, around 1 J/kg K for Δ B=4 T, with reasonable good relative cooling power

The Boltzmann constant from a snifter The Boltzmann constant from a snifter

Abstract Evaporation of a small glass of ethylic alcohol is studied both experimentally and through an elementary thermal physics approach. For a cylindrical beaker and no air flow in the room, a simple quadratic relation is found between the evaporation time and the mass of evaporated liquid. This problem and the obtained results offer excellent possibilities for simple student experiments and for testing basic principles of thermal physics. As an example, we use the obtained results for estimating the value of the Boltzmann constant from evaporation experiments

Magnetic and structural behaviour of (Nd,Dy)(2)Fe14B/alpha-Fe nanocomposites obtained by mechanical milling and annealing

International audience(Nd0.92Dy0.08)2Fe14B/alfa-Fe hard/soft magnetic nanocomposite have been obtained by mechanical milling in a high-energy planetary mill and subsequent annealing under vacuum. The influence of the milling and annealing conditions (temperature and time) on the structural and magnetic properties of (Nd0.92Dy0.08)2Fe14B/alfa -Fe nanocomposite have been investigated. Annealing at 550°C restores the magnetic features of the Nd2Fe14B – type phase. The coercive field, remanent magnetization and the degree of the exchange coupling between the hard magnetic grains and the soft grains are strongly dependent on the milling time and the annealing conditions

Optimization induced collective behavior in a system of flashing oscillators

An array of pulse-emitting oscillators capable of emerging collective behavior is investigated by computer simulations and through a simple experimental setup. The oscillators emit pulse-like signals and detect the signal emitted by the others. They have stochastically fluctuating periods and can operate in two different modes, one with a short output pulse and one with a longer one. The switching between modes is governed by a simple optimization rule: whenever the total output in the system is lower than a desired f* threshold level they emit long pulses and when the output is higher than f* they emit short-length pulses. This simple dynamical rule optimizes the average output level in the system around the f* value and acts as a coupling between the units. As a side-effect of this simple dynamics complex collective behavior appears. In spite of the fact that there is no direct phase-minimizing interaction between the units, for a certain f* interval the pulses of the oscillators synchronize. Synchronization appears and disappears abruptly as a function of the f* threshold parameter, suggesting a dynamic phase-transition. In the synchronized phase the collective output of the system has a better periodicity than the oscillators individually. A simple experimental setup with flashing multimode oscillators is built. For a given range of the threshold parameter the experimental setup reproduces the theoretically predicted synchronization. </jats:p