Sul controllo termico di dispositivi miniaturizzati mediante circuiti bifase a circolazione naturale

Nonostante il notevole interesse, rivolto dalla ricerca internazionale verso i circuiti bifase a circolazione naturale, alcune problematiche legate al loro impiego in applicazioni di piccola scala risultano ancora irrisolte. Ciò vale particolarmente per i termosifoni bifase a funzionamento periodico, indicati con l’acronimo PTPT, per i quali gli studi effettuati e presenti in letteratura risultano quasi esclusivamente relativi ad apparati di grandi dimensioni. Questa attività di ricerca si caratterizza dunque come uno sforzo di approfondimento nella conoscenza di uno specifico circuito bifase a circolazione naturale: il PTPT. In particolare sono stati analizzati il comportamento termico e le potenzialità di raffreddamento di un PTPT, nel caso di applicazione a componenti miniaturizzati. L’approccio seguito nell’attività è stato sia numerico che sperimentale, con la realizzazione di un modello di calcolo per l’interpretazione e la previsione delle prestazioni di un PTPT, e con la realizzazione di un prototipo di PTPT di piccola scala. Il modello matematico realizzato è stato validato, per confronto con una serie di dati sperimentali ottenuti in precedenti attività di ricerca. L’accordo mostrato, tra i dati sperimentali e quelli calcolati, risulta buono sia dal punto di vista qualitativo che da quello quantitativo. Con il modello di calcolo è stata effettuata un’analisi numerica delle prestazioni di un dissipatore bifase a PTPT, in scambio termico con tre differenti sorgenti. L’analisi ha permesso la caratterizzazione del comportamento del dispositivo al variare dei principali parametri operativi. In particolare sono stati considerati gli effetti prodotti da variazioni sistematiche delle temperature della sorgente fredda (275, 285, 295 K), della temperatura della sorgente intermedia (295, 305, 315 K) e della potenza termica dissipata (100÷1000 W) sulle temperature operative del PTPT. Il prototipo di PTPT, realizzato nel presente lavoro, possiede ingombro massimo circa 10 volte inferiore a quello degli analoghi dispositivi presenti al Dipartimento di Energetica dell’Università di Pisa. Le sue dimensioni risultano tali da consentire l’inserimento in un case middle tower (dimensioni 340x180x320 mm) di un comune personal computer. L’attività sperimentale condotta sul prototipo ha permesso di caratterizzare il comportamento del dispositivo, sottoposto a variazioni sistematiche dei principali parametri operativi. In particolare sono state esaminate variazioni di: flusso termico specifico dissipato (5.42÷16.25 W/cm2), quota relativa tra evaporatore ed accumulatore (-30÷30 cm), volume di fluido vettore circolante (64÷3 ml). Inoltre un accurato studio, delle condizioni di scambio termico nell’evaporatore, ha permesso di fornire criteri per il dimensionamento di evaporatori compatti operanti in condizioni transitorie

Analysis and Measurements of Artificial Optical Radiation (AOR) Emitted by Lighting Sources Found in Offices

In this paper the authors describe in detail the exposure limit values concerning artificial optical radiation due to the main incoherent light sources found in offices. In particular, for some examples of significant sources chosen as case studies, we discuss the results of in situ measurements of the exposure values using a broadband photoradiometer. By comparing the measurement results with the exposure limit values specified in the European legislation, the maximum exposure times for workers have been evaluated. From the analysis of the results it can be concluded that the lighting sources typically present in indoor workplaces under usual conditions of use, do not pose a health risks for workers. However, in the case of accidental exposure during work activities or exposure linked to maintenance activities (short exposure distance), values in excess of the limit values have been observed, with decidedly short maximum exposure times

Towards a holistic approach to indoor environmental quality assessment: Weighting schemes to combine effects of multiple environmental factors

Abstract In the recent past, great attention has been posed on the assessment of the energy performance and of the operating and maintenance costs of the building stock. Currently, new approaches of analysis are considered by the scientific community, which put the occupant's well–being at the centre of the evaluation process. In this context, the IEQ assessment acquires an ever increasing importance, especially if the combined effects of multiple environmental factors are considered. With this purpose, to date, different weighting schemes can be found in the literature, obtained through subjective investigations and mathematical methods. In this paper, the weighting schemes proposed in the literature in the period 2002–2018 were examined, considering the survey methodologies used. The more relevant studies found in the literature were compared and the related weighting schemes were discussed, based on the intended use of the buildings. In particular, 122,000 questionnaires in 18 different countries all over the world were examined and the most relevant environmental factors were selected: Thermal Environment (TH), Air Quality (AQ), Acoustics (AC), and Lighting (LT). Three different average weighting schemes were obtained for each of the following uses: offices, schools, dwellings; a final additional weighting scheme was obtained considering the average values of the normalized weights for all the building uses, a possible solution for buildings with an unspecified or not unique intended use. Moreover, an original weighting scheme was obtained and proposed on the basis of the results of three different subjective surveys, involving about 1400 participants, carried out in some university classrooms at the School of Engineering of the University of Pisa: it was compared with the one obtained by the literature for school buildings. It was observed an overestimation of the importance of TH (0.42 instead of 0.33) and an underestimation of AC (0.19 instead of 0.26), whereas AQ and LT are in accordance (0.17 instead of 0.19 and 0.22, respectively). The results of the present study can be useful to those who intend to deal with holistic approaches to building design, for which accurate assessments of occupants' well-being are taken into consideration as well as aspects related to energy performance and building management costs

General lighting in offices building: Techno-economic considerations on the fluorescent tubes replacement with LED tubes

The use of LED light sources is nowadays an attractive solution because it can easily lead to lower operating costs of artificial lighting. In the last years, the replacement of fluorescent lamps with LED tubes for lighting of workplaces have been frequently proposed. The aim of the Authors is to analyze, from techno-economic's point of view, the fluorescent tubes replacement of a typical office building with LED tubes. Using the evaluation of the Lighting Energy Numeric Indicator has been possible to point out that the replacement of the fluorescent tubes allows a reduction in energy consumption for lighting higher than 50% with an obvious reduction in the annual operating cost. For the lamps replacement, in the case study have been estimated a simple payback time of less than 5 years. The methodological approach used by the Authors, although based on a case study, can be extended to numerous office buildings because the analyzed configurations (use and dimension of the rooms, type and features of the luminaires) can be considered significantly representative of this type of buildings. The choice of the LED sources that are suitable for the fluorescent lamps replacement must be preceded by a careful lighting analysis in order to ensure the compliance with the standards requirements

Valutazione numerica del cocktail party effect nell’acustica degli ambienti chiusi

Il problema di riconoscere selettivamente un segnale proveniente da una sorgente ed ignorare i segnali emessi da tutte le altre sorgenti presenti nello stesso ambiente, ha assunto attualmente un notevole interesse in vari contesti applicativi. Nel presente lavoro è analizzato il cocktail party effect ai fini di ottenere un adeguato comfort acustico negli ambienti interni, per questo viene proposto un modello di calcolo analitico atto a valutare il numero massimo di parlatori che possono essere presenti in un ambiente per assicurare una buona intelligibilità delle conversazioni che vi si svolgono

Building Energy Models with Morphological Urban-Scale Parameters: A Case Study in Turin

With a growing awareness around the importance of the optimization of building efficiency, being able to make accurate predictions of building energy demand is an invalu¬able asset for practitioners and designers. For this reason, it is important to continually improve existing models as well as introduce new methods that can help reduce the so-called energy performance gap, which separates pre¬dicted from actual consumption values. This is particularly true for urban scale simulations, where even small scenes can be very complex and carry the necessity of finding a reasonable balance between precision and computational efforts. The scope of this work is to present two different models that make use of morphological urban-scale pa¬rameters to improve their performances, taking into account the interactions between buildings and their surroundings. In order to do this, two neigh¬bourhoods in the city of Turin (IT) were taken as case stud¬ies. The buildings studied present similar characteristics but are inserted in a different urban context. Several urban pa-rameters were extracted using a GIS tool and used as input, alongside the building-scale features, for two different mod-els: i) a bottom-up engineering approach that evaluates the energy balance of residential buildings and introduc¬es some variables at block-of-buildings scale, ii) a ma¬chine learning approach based on the bootstrap aggregat¬ing (bagging) algorithm, which takes the same parameters used by the previous model as inputs and makes an es¬timation of the hourly energy consumption of each build¬ing. The main results obtained confirm that the urban context strongly influences the energy performance of buildings located in high built-up areas, and that intro¬ducing simple morphological urban-scale parameters in the models to take these effects into account can improve their performance while having a very low impact on the computational efforts

Thermal analysis of the building envelope of lightweight temporary housing

In the last few years, to meet the need of build efficient homes in a short time and with maximum constructive simplification, lightweight prefabricated building systems have proved to be particularly suitable, especially in geographical areas which must deal with emergency situations (i.e., temporary housing). In this paper the winter and summer thermal performance of a building prototype, realised with modular steel framed elements, have been studied, in both winter and summer conditions. Special attention has been paid to the optimisation of the dynamic thermal performance of the multi-layered envelope structures. The dynamic thermal behaviour of the outer wall, analysed and discussed in details in the paper, shows that it is possible to improve the performance of lightweight walls by using an optimised stratigraphy characterised by an opportune sequence of resistive and capacitive layers. The influence of inner structures (partitions, floor and roof) on the building thermal behaviour has also analyzed trough the introduction of room performance indices appropriately defined. The results of the study have been discussed with special reference to the requirements fixed by the Energy Performance Buildings European Directive (EPBDs) and the resulting implementation in Italian Legislation

Morphology and Light‐Dependent Spatial Distribution of Spin Defects in Carbon Nitride

Carbon nitride (CN) is a heterogeneous photocatalyst that combines good structural properties and a broad scope. The photocatalytic efficiency of CN is associated with the presence of defective and radical species. An accurate description of defective states—both at a local and extended level—is key to develop a thorough mechanistic understanding of the photophysics of CN. In turn, this will maximise the generation and usage of photogenerated charge carriers and minimise wasteful charge recombination. Here the influence of morphology and light-excitation on the number and chemical nature of radical defects is assessed. By exploiting the magnetic dipole-dipole coupling, the spatial distribution of native radicals in CN is derived with high precision. From the analysis an average distance in the range 1.99–2.34 nm is determined, which corresponds to pairs of radicals located approximately four tri-s-triazine units apart

Investigations on male traits, female mate choice, and the role of parasites in the three-spined stickleback (Gasterosteus aculeatus)

Ich habe den Einfluss von Parasitierung und Resistenzgenen (MHC, Haupt Gewebekompatibilitäts Komplex), auf von Weibchen gewählte Männchenmerkmale am Dreistachligen Stichling (Gasterosteus aculeatus) untersucht. Ein Infektionsexperiment zeigte, dass zwei parasitische Nematoden, C. lacustris und A. crassus, sich in ihrer Prävalenz und der ausgelösten Immunantwort im Stichlingswirt unterschieden. Eine korrelative Analyse zeigte, dass sowohl die rote Balzfärbung der Männchen als auch bestimmte Qualitätsmerkmale ihrer Nester im Zusammenhang mit der Anzahl von MHC der Klasse I und II stehen. Wahlexperimente an weiblichen Stichlingen zeigten, dass visuelle und olfaktorische Männchenmerkmale für ihre Wahl kombiniert werden. Um zu überprüfen, ob sich die im Labor gewonnenen Ergebnisse auf die natürliche Lebenssituation der Fische im See übertragen lassen, wurde ein Enclosure Experiment im Freiland durchgeführt. Analysen von Elternschaften, Männchenmerkmalen und Parasitenbelastung sollten Aufschluss über den Fortpflanzungserfolg der Männchen geben

Non-pegylated liposomal doxorubicin in older adjuvant early breast cancer patients: cardiac safety analysis and final results of the COLTONE study

Aims: To explore the cardiac safety of adjuvant Non-Pegylated Liposomal Doxorubicin (NPL-DOX) plus Cyclophosphamide (CTX) followed by weekly Paclitaxel, in elderly women (≥ 65 years) with high-risk breast cancer. Previously, we described no symptomatic cardiac events within the first 12 months from starting treatment. We now reported the updated results after a median follow-up 76 months. Methods: The cardiac activity was evaluated with left ventricular ejection fraction (LVEF) echocardiograms assessments, before starting chemotherapy and every 6 months, until 30 months from baseline, then yearly for at least 5 years. Results: Forty-seven women were recruited by two Units of Medical Oncology (Ethics Committee authorization CESM-AOUP, 3203/2011; EudraCT identification number: 2010-024067-41, for Pisa and Pontedera Hospitals). An episode of grade 3 CHF (NCI-CTCAE, version 3.0) occurred after 18 months the beginning of chemotherapy. The echocardiograms assessments were performed comparing the LVEF values of each patient evaluated at fixed period of time, compared to baseline. We observed a slight changed in terms of mean values at 48, 60, 72 and 84 months. At these time points, a statistically significant reduction of - 3.2%, - 4.6%, - 6.4% and - 7.1%, respectively, was observed. However, LVEF remained above 50% without translation in any relevant clinical signs. No other cardiac significant episodes were reported. To this analysis, in 13 patients (28%) occurred disease relapse and,  of them, 11 (23%) died due to metastatic disease. Eight patients died of cancer-unrelated causes. Conclusions: The combination including NPL-DOX in elderly patients revealed low rate of cardiac toxic effects. Comparative trials are encouraged