Incidence of the Ventilation Holes and the Mechanical Ventilation Systems of Façade on the Noise Insulation

This study will assess the influence on the acoustic insulation of façade of small elements such as ventilation holes or mechanical ventilation systems. These elements are present to ensure an appropriate air exchange, and they can be with or without heat recovery units. The noise insulation of façade, taking into account such ventilation holes, was evaluated starting from the calculations carried in accordance with the procedures laid down by the standard EN 12354 and performing measurements concerning specific case studies

Study of the Correlation among Luminous Properties of Smart Glazing for Adaptive Energy Saving Buildings

A smart window, such as electrochromic or thermochromic windows, may not be able to accomplish at the same time energy efficiency and visual comfort functions, since satisfying one criterium interferes with the other. This recalls to the important issue of establishing precise relationships among parameters affecting energy, glare control, and color rendering tasks and the influence on them of glazing material composition and preparation technique. With this aim, the luminous properties of a number of advanced glazings found in literature and of three home-made electrochromic devices differing by material composition and/or preparation technique are analyzed in this study. The investigation has involved the determination of the CIE (Commission International de l'Eclairage) Color Rendering Index (CIE CRI), the Correlated Color Temperature (CCT), and the luminous transmittance coefficient (tau(V)) of the devices which are discussed with regard to their potential in absolving to energy and visual comfort tasks. Results lead to the main conclusion that the CIE CRI, CCT, and tau(V) indexes are clearly linked by an exponential correlation. At low tau(V) values (tau(V) < 0.5), however, the correlation weakens and the variation of the CIE CRI and CCT indexes becomes entirely material dependent. The influence of preparation technique appears to be irrelevant since the color rendering indexes appear to be well correlated to tau(V) over all the investigated tau(V) range

an adaptive neural network model for thermal characterization of building components

Abstract Building materials are usually characterized in stationary or almost-stationary conditions and mono dimensional heat flow regime. The existing standards (such as ISO 9869 or EN ISO 6946, EN 12664, EN 12667, ISO 8302 etc), require experiments carried out in steady-state conditions, with a very fine control of the measuring parameters with the aim to apply a simple and reproducible procedure for the determination of thermal properties. However, the thermodynamic conditions that lead to a steady-state operating mode and mono dimensional flow are very difficult to obtain (in real conditions) or very expensive and time consuming (in climate chambers). In this paper the authors present the development of a method for thermal characterization of building components, inferring the steady-state conditions, when only measures in transient conditions are available. The method, based on an adaptive linear neural network (ALNN) model also could be have the potentialities to determine the thermal diffusivity from a significant transient behavior ad hoc imposed. The study targets multilayered walls homogeneous and the results are compared with the experimental data measured by a climate chamber that operate according to the standard EN 1266

Wide Band Gap Devices and Their Application in Power Electronics

Power electronic systems have a great impact on modern society. Their applications target a more sustainable future by minimizing the negative impacts of industrialization on the environment, such as global warming effects and greenhouse gas emission. Power devices based on wide band gap (WBG) material have the potential to deliver a paradigm shift in regard to energy efficiency and working with respect to the devices based on mature silicon (Si). Gallium nitride (GaN) and silicon carbide (SiC) have been treated as one of the most promising WBG materials that allow the performance limits of matured Si switching devices to be significantly exceeded. WBG-based power devices enable fast switching with lower power losses at higher switching frequency and hence, allow the development of high power density and high efficiency power converters. This paper reviews popular SiC and GaN power devices, discusses the associated merits and challenges, and finally their applications in power electronics

La valutazione ecocolor-Doppler degli assi vascolari mesenterici nell'addome acuto. Studio prospettico su 325 pazienti

La diagnosi di infarto intestinale in un paziente con acuzie addominale è difficile. La sua elevata mortalità è essenzialmente determinata da un ritardo diagnostico e terapeutico. Ciò è dovuto sia ad una scarsa specificità dei dati di laboratorio sia alla scarsità dei segni clinici nelle fasi iniziali della malattia. Obiettivo. Identificare il valore predittivo e negativo della metodica ecocolor-Doppler applicata ai vasi mesenterici nella diagnosi di ischemia acuta intestinale. Pazienti e metodi. 325 pazienti sono stati prospetticamente analizzati con un ecocolor-Dopper Aloka ssd 1700: 120 con addome acuto (gruppo A); 120 soggetti sani senza preparazione intestinale (gruppo B); 85 pazienti sani con preparazione intestinale (gruppo C). Abbiamo valutato la visualizzazione in B mode, l’estensione del vaso, la captazione del segnale colore ed i velocitogrammi. Risultati. In un campione selezionato di 32 pazienti con alto sospetto clinico di infarto mesenterico abbiamo rilevato 21 veri negativi,3 falsi positivi, 5 veri positivi e tre falsi negativi. Il valore predittivo positivo e negativo sono stati rispettivamente di 0,62 e 0,87. Conclusioni. La metodica ecocolor-Doppler si è dimostrata più efficace nell’escludere la presenza di una ischemia intestinale piuttosto che nel confermarla quando presente