2,471 research outputs found
UN APPROCCIO “OPEN-SOURCE” ALLA CARATTERIZZAZIONE ACUSTICA DEI SOLAI LATEROCEMENTIZI MEDIANTE MISURE IN OPERA
No full textDa alcuni anni, diversi gruppi di ricerca indipendenti stanno lavorando in Italia nel settore dell’acustica edilizia con lo scopo di migliorare l’accuratezza della stima del li-vello di rumore di calpestio per le tipologie di solai ampiamente diffuse, ma non ben rappresentate dai modelli di previsione standardizzati.
Partendo dal presupposto che la riduzione del livello di pressione sonora di calpestio ad opera di un sistema resiliente è indipendente dalla struttura di base che lo supporta, è stato messo a punto un vasto programma di misurazioni in opera su solai laterocementi-zi, in modo da confrontare i risultati ottenuti per mezzo di uno specifico protocollo di prova su solai al grezzo con quelli relativi alla medesime strutture dotate di pavimentazione galleggiante.
Dai risultati di questi studi è nata la proposta di un modello parametrico specifico per la valutazione del livello di calpestio in solai laterocementizi ed attualmente i ricer-catori coinvolti nel progetto stanno lavorando per migliorare la correlazione del modello con l’aumento dei dati raccolti in opera su solai al grezz
Il rumore degli impianti aeraulici. Tecniche di controllo attive e passive
No full textIl problema del comfort acustico nell'ambiente domestico e di lavoro assume oggi sempre maggiore importanza. All’interno di un ufficio si possono rilevare varie fonti di rumore, alcune esterne e altre interne. Tra tutte, i sistemi di condizionamento dell'aria sono una delle principali cause di disturbo uditivo e su tali impianti vanno concentrati gli sforzi e la ricerca per la riduzione e l'abbattimento delle emissioni sonore, essendo provato che l'esposizione prolungata a fonti di rumore è causa di stress e può avere effetti nocivi sulla salute dell'uomo. Inoltre, l’esposizione continua a fonti di rumore può influenzare pesantemente il rendimento dei lavoratori. Il miglioramento del comfort acustico non solo preserva la salute, ma migliora anche la qualità della vita e le condizioni dell’ambiente lavorativo.
In caso di impianti di condizionamento ad aria, il rumore generato dai ventilatori e dalle altre macchine dell’impianto si propaga lungo i condotti di aerazione e quindi sfocia all’interno degli ambienti di lavoro; altre componenti di rumore nascono dalla turbolenza causata dal passaggio dell’aria attraverso il condotto e dall'uscita dell'aria dalle bocchette d’aerazione.
Un'analisi in frequenza di tali rumori ha dimostrato la presenza di due tipi di componenti: una in bassa frequenza, difficilmente attenuabile con i metodi tradizionali di trattamento del rumore, derivante da componenti meccaniche in movimento (pompe o ventilatori) e un'altra a larga banda (ovvero distribuita su un ampio numero di frequenze), concentrata sulle alte frequenze, dovuta soprattutto a fenomeni aerodinamici.
Le componenti a larga banda e ad alta frequenza si possono abbattere in modo relativamente semplice e con buona efficacia mediante sistemi passivi, ad esempio l'impiego di silenziatori costituiti da materiale fonoassorbente posti all'interno del condotto aeraulico. Per ragioni fisiche però tali sistemi hanno la massima efficacia alle frequenze medio-alte, essendo la lunghezza dell'onda acustica da assorbire direttamente legata alla dimensione del dispositivo silenziatore. Quindi sarebbe, in linea teorica, possibile costruire un silenziatore passivo efficace anche sulle basse frequenze, ma avrebbe dimensioni e costi tali da non renderne pratico l'utilizzo
La civilta dell\u27umanesimo nell\u27Utopia del More
No full textLa civilta dell\u27umanesimo nell\u27Utopia del More / Giovanni Semprini. - Genova : Edizioni Italia, A. XVIII (1940)
Dedica manoscritta dell\u27autore: A S. E. Emilio Bodrero / luminare del pensiero italiano / con sincera ammirazione / G. Semprini
https://galileodiscovery.unipd.it/discovery/fulldisplay?context=L&vid=39UPD_INST:VU1&search_scope=MyInst_and_CI&tab=Everything&docid=alma99000535455020604
Numerical study on indoor environmental quality in a room equipped with a combined hrv and radiator system
No full textHeat recovery ventilation (HRV) systems can be integrated with an additional air heater in buildings with low energy demand in order to cover space heating demand. The employment of coupled HRV-heater systems is, therefore, gaining increasing interest for the improvement of the indoor environmental quality (IEQ), as well as the reduction of ventilation energy loss. The present paper analyses the efficacy of a HRV system, coupled with a low-temperature radiator, in satisfying the IEQ indices inside a retrofitted dormitory room. A computational fluid dynamic (CFD) model based on the finite volume method is established to investigate IEQ characteristics including indoor air quality and thermal comfort condition. The presented CFD code provides a practical tool for a comprehensive investigation of the IEQ indices in spaces employing a coupled HVAC system. In an analysis of indoor air quality, parameters such as age of the air, air change efficiency, and ventilation efficiency in removal of gaseous contaminants, namely VOCs and CO2, are evaluated. The results obtained by the numerical model allow addressing the interaction between HRV and radiator systems and its effects on airflow field. The results show the decrease of the indoor operative temperature with increment of the supply air flow rate, which is mainly due to the decreased thermal efficiency of the HRV system. The obtained results indicate that, while higher ventilation rates can significantly decrease the age of the air and gaseous contaminants level, at the same time, it would cause a local discomfort in some parts of the room
Platone
No full textPlatone / Giovanni Semprini. - Milano : Athena, 1926
Dedica manoscritta dell\u27autore: A S. E. On. Emilio Bodrero / con sincera stima e ammirazione / G. Semprini / Genova 29-4-29
https://galileodiscovery.unipd.it/discovery/fulldisplay?context=L&vid=39UPD_INST:VU1&search_scope=MyInst_and_CI&tab=Everything&docid=alma99001179773020604
Integrated effects of the heat recovery ventilation and heat source on decay rate of indoor airborne particles: A comparative study
No full textGiven the high concentration of indoor airborne particles during the winter and their harmful effects on human health, it is of great importance to examine combined effects of the ventilation and heat source on indoor particle dispersion. The present study aims to investigate transient dispersion and deposition of indoor particles under the heat recovery ventilation (HRV). Five groups of particles with different diameters ranging from 0.1 to 10 μm were taken into account, representing the inhalable indoor airborne particles. By considering three different heating systems, including the radiator, floor heating system and fan coil, the integrated ventilation-heating effects on particle dispersion were evaluated and compared. An Eulerian-Lagrangian CFD model was developed to predict turbulent characteristics of the airflow field and unsteady particle trajectories. The role of particle size, air change rate and outdoor temperature was addressed. In addition, influence of the heat source position on the particle decay rate and removal efficiency was investigated. The results indicated that the impact of heating system on the particle decay rate is weakened by increasing the ventilation rate. Among all heating systems, the radiator renders the highest dispersion rate and the slowest decay rate, even lower than a single HRV unit. It was revealed that, for an intermediate ventilation rate, the particle deposition rate in fan coil system is 3.6 and 2.4 times faster than the radiator and floor heating systems, respectively. It was also found that displacing the radiator to the opposite side of the ventilation unit quadruplicates the removal efficiency and leads to 146% enhancement of the decay rate coefficient
The role of near-wall downdraught and asymmetric temperature distribution in dispersion of respiratory aerosols in radiant floor heating systems
No full textIn radiant floor heating (RFH) systems, the downdraught due to the asymmetric temperature distribution causes descending airflows towards the floor surface, where the warm air adjacent to the RFH system tends to be driven upwards by the buoyancy force. Hence, this conflict creates a zone that prevents the warm air to ascend affecting the streamlines of the indoor air. The present study aims to investigate the integrated effects of this phenomenon at different levels of the RFH temperature and thermal transmittance on the behaviour of indoor airborne particles (PMs2.5). In this context, a Eulerian-Lagrangian computational fluid dynamic (CFD) code is established, validated against experimental data, to address the dispersion and deposition patterns of PMs2.5. To generate different levels of the downdraught and non-uniform temperature distribution, five scenarios are considered regarding different thermal transmittance (U-value) levels, assessed for four RFH temperatures. Firstly, by introducing the near-wall and zonal spaces, the dispersion of particles in each scenario is evaluated. Then, the role of RFH system temperature in conjunction with each scenario is investigated. Finally, simple correlations are proposed allowing for fast evaluation of the decay rate coefficient of PMs2.5. According to the obtained results, the asymmetric temperature distribution causes a striking disparity in the zonal concentration of suspended PMs2.5, i.e., up to 32 % difference in the number of particles between quarters. It is shown that a faster decay rate of PMs2.5 is associated with a larger value of the characteristic temperature difference and the Rayleigh number (Ra). For a given RFH temperature, thermal performance improvement of the envelope reduces the number of deposited particles on the ceiling surface, whereas it gives a boost to the number of particles adhering to the floor. A sensitivity analysis on the results revealed that a 1 °C increment in the RFH temperature leads to an 8.4 % reduction on average in the number of suspended PMs2.5 in the breathing zone, regardless of the level of thermal transmittance from surrounding walls
IAS/IFRS and "Capital Accounting System": a literature analysis
No full textThe purpose of this study is to analyse the “capital accounting system” and its evolution in the
National and International literature to point out which are the elements that mainly affect
International Accounting Standards.
This work, starting from the theorization of Besta (the most important author modelling the
“classic capital accounting system” at the beginning of ‘900) and following with De Dominicis
(the author of the “variante corrente” of the capital accounting system), analyses the theorizations
arising from the International literature, reaching to point out some specific characteristics of the
capital accounting system that specifically affect International Accounting Standards Ias/Ifrs
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