Evaporation from porous building materials and its cooling potential

Portuguese Foundation for Science and Technology (FCT) under the research project DRYMASS (PTDC/ECM/100553/2008)Evaporative cooling is a traditional strategy to improve summer comfort, which has gained renewed relevance in the context of the 6 transition to a greener economy. Here, the potential for evaporative cooling of two common porous building materials, natural stone and 7 ceramic brick, was evaluated. The work has relevance also to the protection of built heritage becauseevaporation underlies the problems of 8 dampness and salt crystallization, which are so harmful and frequent in this heritage. It was observed that the drying rate of the materials is, in 9 some cases, higher than the evaporation rate of a free water surface. Surface area measurements by a three-dimensional optical technique 10 suggested, as probable cause of this behavior, that surface irregularity gives rise to a large effective surface of evaporation in the material. 11 Surface temperature measurements by infrared were performed afterward during evaporation experiments outside during a hot summer day in 12 Lisbon. Their results indicate that ordinary building materials can be very efficient evaporative media and, thus, may help in achieving higher 13 energy efficiency while maintaining a simultaneous constructive or architectural function.proofpublishe

Seismic wave propagation in heterogeneous limestone samples

International audienceMimic near-surface seismic field measurements at a small scale, in the laboratory, under a well-controlled environment, may lead to a better understanding of wave propagation in complex media such as in geological materials. Laboratory experiments can help in particular to constrain and refine theoretical and numerical modelling of physical phenomena occurring during seismic propagation, in order to make a better use of the complete set of measurements recorded in the field. We have developed a laser Doppler vibrometer (laser interferometry) platform designed to measure non-contact seismic displacements (or velocities) of a surface. This technology enables to measure displacements as small as a tenth of a nanometer on a wide range of frequencies, from a few tenths to a few megahertz. Our experimental setup is particularly suited to provide high-density spatial and temporal records of displacements on the edge of any vibrating material (aluminum, limestone, ...). We will firstly present experiments in cuboid and cylinders of aluminum (homogeneous) in order to calibrate the seismic sources (radiation diagram, frequency content) and identify the wave arrivals (P, S, converted, surface waves). The measurements will be compared quantitatively to a direct 2D numerical elastodynamic simulation (finite elements, Interior Penalty Discontinuous Galerkin). We will then show wave measurements performed in cylindrical heterogeneous limestone cores of typical diameter size around 10 cm. Tomographic images of velocity (figure 2a) in 2D slices of the limestone cores will be derived based upon the time of first arrivals and implemented in the numerical model. By quantifying the difference between numerical and experimental results, the tomographic velocity model will be reciprocally improved and finally compared to a X − ray tomographic image of that slice. A brief overview of the studies Seismic sources We will explore piezo-electric sources of different frequencies (100 kHZ ∼ 5 M Hz) and test the new laser ablation source whose dominant frequency can reach 2 M Hz in aluminium. Avantages and drawbacks of each technology will be discussed in terms of source and wave propagation characterisation. Wave identification in an aluminium cube of side length 280 mm and seismic source at the center of one face We have identified experimentally P, S, head wave, PS, SP and surface waves measured on the cube surfaces. Meanwhile, direct numerical simulations have helped to quantitatively analyze the kinematics of wave fronts. For example, on the surface where the seismic source is excited, a P front, an S front and a PS head wave front are measured by the laser vibrometer right after the initial seismic impulse. These wavefronts can be understood by both the Huygens' Principle and the Snell-Descartes Law. In Figure 1, the seismic source excits simultaneously at time t = 0 a P wave and an S wave. As time evolves, waves propagate inside the volume and a P-wave propagates along the boundary as well: the latter one acts on the boundary as secondary sources which will emit both P and S waves, creating finally a new PS head wave front nicely measured in the experiments. The colours of magenta and green correspond to null amplitudes

Seismic imaging in laboratory trough laser Doppler vibrometry

International audienceMimic near-surface seismic field measurements at a small scale, in the laboratory, under a well-controlled environment , may lead to a better understanding of wave propagation in complex media such as in geological materials. Laboratory experiments can help in particular to constrain and refine theoretical and numerical modelling of physical phenomena occurring during seismic propagation, in order to make a better use of the complete set of measurements recorded in the field. We have developed a laser Doppler vibrometer (laser interferometry) platform designed to measure non-contact seismic displacements (or velocities) of a surface. This technology enables to measure displacements as small as a tenth of a nanometer on a wide range of frequencies, from a few tenths to a few megahertz. Our experimental setup is particularly suited to provide high-density spatial and temporal records of displacements on the edge of any vibrating material. We will show in particular a study of MHz wave propagation (excited by piezoelectric transducers) in cylindrical cores of typical diameter size around 10 cm. The laser vibrometer measurements will be first validated in homogeneous materials cylinders by comparing the measurements to a direct numerical simulation. Special attention will be given to the comparison of experimental versus numerical amplitudes of displacements. In a second step, we will conduct the same type of study through heterogeneous carbonate cores, possibly fractured. Tomographic images of velocity in 2D slices of the carbonate core will be derived based upon on the time of first arrival. Preliminary attempts of tomographic attenuation maps will also be presented based on the amplitudes of first arrivals. Experimental records will be confronted to direct numerical simulations and tomographic images will be compared to x-ray scanner imaging of the cylindrical cores

Seismic imaging in laboratory trough laser Doppler vibrometry

International audienceMimic near-surface seismic field measurements at a small scale, in the laboratory, under a well-controlled environment , may lead to a better understanding of wave propagation in complex media such as in geological materials. Laboratory experiments can help in particular to constrain and refine theoretical and numerical modelling of physical phenomena occurring during seismic propagation, in order to make a better use of the complete set of measurements recorded in the field. We have developed a laser Doppler vibrometer (laser interferometry) platform designed to measure non-contact seismic displacements (or velocities) of a surface. This technology enables to measure displacements as small as a tenth of a nanometer on a wide range of frequencies, from a few tenths to a few megahertz. Our experimental setup is particularly suited to provide high-density spatial and temporal records of displacements on the edge of any vibrating material. We will show in particular a study of MHz wave propagation (excited by piezoelectric transducers) in cylindrical cores of typical diameter size around 10 cm. The laser vibrometer measurements will be first validated in homogeneous materials cylinders by comparing the measurements to a direct numerical simulation. Special attention will be given to the comparison of experimental versus numerical amplitudes of displacements. In a second step, we will conduct the same type of study through heterogeneous carbonate cores, possibly fractured. Tomographic images of velocity in 2D slices of the carbonate core will be derived based upon on the time of first arrival. Preliminary attempts of tomographic attenuation maps will also be presented based on the amplitudes of first arrivals. Experimental records will be confronted to direct numerical simulations and tomographic images will be compared to x-ray scanner imaging of the cylindrical cores

Diagnóstico del plan estratégico que emplea Empresar Ltda

La época actual, todas las empresas se ven obligadas a realizar constantes estudios para enfrentarse a un mercado cada vez más competitivo, con la elaboración de planes que le permitan proyectarse hacia el futuro, para disminuir riesgos y mantenerse en el medio. Luego de recopilar información a través de visitas, observación, encuestas y entrevistas al Gerente, personal, proveedores y clientes de Empresar Ltda., se identificaron las fortalezas, debilidades, oportunidades y amenazas de la empresa, para el Análisis DOFA, que condujo al diseño de un Modelo Gerencial de Delegación para que la empresa aproveche su recurso humano. Los resultados obtenidos admitieron proponer un Modelo Gerencial de Delegación, dando oportunidad a investigaciones futuras que dejen la posibilidad de ingresar en aspectos de detalle o especialización, llegando a ser parte de este modelo, como un aporte al desarrollo de la empresa

Node assembly for waste level measurement: embrace the smart city

Municipal Solid Waste Management Systems (MSWMS) worldwide are currently facing pressure due to the rapid growth of the population in cities. One of the biggest challenges in this system is the inefficient expenditure of time and fuel in waste collection. In this regard, cities/- municipalities in charge of MSWMS could take advantage of information and communication technologies to improve the overall quality of their infrastructure. One particular strategy that has been explored and is showing interesting results is using a Wireless Sensors Network (WSN) to monitor waste levels in real-time and help decision-making regarding the need for collection. The WSN is equipped with sensing devices that should be carefully chosen considering the real scenario in which they will work. Therefore, in this work, three sets of sensors were studied to evaluate which is the best to be used in the future WSN assembled in Bragança, Portugal. Sets tested were HC-SR04 (S1), HC-SR04 + DHT11 (S2), and US-100 (S3). Tests considered for this work were air temperature and several distances. In the first, the performance of each set to measure a fixed target (metal and plastic box) was evaluated under different temperatures (1.7 - 37 ℃). From these results, two best sets were further used to assess distance measurement at a fixed temperature. This test revealed low absolute errors measuring the distances of interest in this work, ranging from 0.18% to 1.27%.This work has been supported by FCT - Fundação para a Ciência e Tecnologia within the R&D Units Project Scope: UIDB/05757/2020, UIDB/00690/2020, LA/P/0045/2020, UIDB/50020/2020, and UIDP/50020/2020. Adriano Silva was supported by FCT-MIT Portugal PhD grant SFRH/BD/151346/2021, and Thadeu Brito was supported by FCT PhD grant SFRH/BD/08598 /2020. Jose L. Diaz de Tuesta acknowledges the finantial support through the program of Atraccion de Talento of Atraccion al Talento of the Comunidad de Madrid (Spain) for the individual research grant 2020-T2/AMB-19836.info:eu-repo/semantics/acceptedVersio

The fate of (phantom) dark energy universe with string curvature corrections

We study the evolution of (phantom) dark energy universe by taking into account the higher-order string corrections to Einstein-Hilbert action with a fixed dilaton. While the presence of a cosmological constant gives stable de-Sitter fixed points in the cases of heterotic and bosonic strings, no stable de-Sitter solutions exist when a phantom fluid is present. We find that the universe can exhibit a Big Crunch singularity with a finite time for type II string, whereas it reaches a Big Rip singularity for heterotic and bosonic strings. Thus the fate of dark energy universe crucially depends upon the type of string theory under consideration.Comment: 6 pages and 3 figures, discussion on dynamically evolving dilaton and modulus included, references added, version to appear in Physics Letters

Análisis y caracterización de aeropuertos emplazados en grandes urbes

Al momento del presente desarrollo existen aproximadamente 45.000 campos de vuelo en todo el mundo, una porción importante de ellos fueron emplazados próximos a ciudades que cuyo posterior desarrollo generó una situación limitante para con el crecimiento del propio aeródromo o aeropuerto. El presente trabajo tiene como objeto realizar un análisis comparativo de éstos, relacionando las características operacionales y de su entorno próximo. Se considera aeropuerto de ciudad a aquellos que presentan su desarrollo inmerso en la trama urbana de la metrópolis a la que sirven. Se analizarán los distintos aeropuertos respecto a su emplazamiento en las distintas regiones, cantidad de pasajeros, operaciones al año, configuraciones de pista y características urbanas de la ciudad entre otros parámetros de relevancia. Por último, se profundizará el análisis en Latinoamérica, destacando entre otras cosas, los países que poseen mayor número de aeropuertos de esta índole. De la comparación surgirán cuestiones relacionadas con las estrategias de desarrollo adoptadas por las diversas Autoridades de aplicación en función de la disponibilidad de recursos y criterios definidos.The aim of this publication is to carry out a basic description associated with the operational and environmental characteristics of airports developed within urban settings. To begin with, "city airports" are identified at a worldwide level. Summarizing characteristic information of each of these airports, they are classified with respect to their location, capacity, operating features and cities which they serve. A comparative analysis of this type of airports,accordingto their location in different regions, passengers handled per year, runway configurations, urban characteristics of the city they serve, among others, is performed. To finish with, an in depth analysis is carried out in Latin America, highlighting the countries where the larger numbers of “city airports” are found.Trabajo publicado en Actas del Cuarto Congreso de la Red Iberoamericana de Investigación en Transporte Aéreo. La Plata, Universidad Nacional de La Plata, 2013.Grupo de Transporte Aéreo - Grupo de Ingeniería Aplicada a la Industri