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Considerazioni sulla sostenibilità dello sviluppo del condizionamento dell’aria e della refrigerazione
No full textAirborne particle and microbiological human emission rate investigation for cleanroom clothing combinations
Full text linkThe control of airborne particles and bio contaminants is a key factor in several industries in order to avoid product defects, to assure process quality and to protect personnel and outdoor environment. Cleanrooms and controlled environments are spaces with strict control of airborne contaminants and thermo-hygrometric parameters. Humans are one of the main sources of contamination in clean environments. A correct technical clothing system reduces the contamination released by humans. Despite substantial work done in this field, it is difficult to compare previous results due to differences in test rig, procedures, gowning systems and sampling locations. This study implements a dispersal chamber test methodology and an experimental campaign on 7 combinations of technical clothing and undergarments. It presents comparative experimental results of total particle and microbiological contaminants released by humans in terms of emission rate (ER). It is found that ageing factor, sterilization, physical movements, donning and warping type, and materials influence the human ER in clean environments. Sterile garment systems entirely composed of synthetic materials decrease the particle release compared to the non-sterile mixed ones. Sterile garment systems show a better performance, achieving 10 to 30 times fewer particle emission rates in wider movements and almost zero microbiological release. A low human contamination ER benefits the cleanroom design and operation, either reducing the energy consumption or increasing the number of personnel in clean environments
Surgical smoke and airborne microbial contamination in operating theatres: Influence of ventilation and surgical phases
Full text linkAir cleanliness is a crucial factor in operating theatres (OTs), where the health of patients and staff must be preserved by controlling air contamination. Particular attention must be paid to ultrafine particles (UFPs) size range, generated for instance by electrosurgical instruments (ESTs). OT contamination is also affected by ventilation systems, medical staff and their gowning system, staff routines, instruments, etc. This comparative study is based on experimental measurements of airborne microbial contamination and UFPs carried out during real ongoing surgeries in two OTs equipped with upward displacement ventilation (UWD) and hybrid ventilation, with unidirectional airflow on the operating table and peripheral mixing (UDAF+Mixing) ventilation systems. Airborne contamination concentration at the exit grilles has been analyzed as function of four different surgical phases normally performed during an operation. Results highlight that airborne contamination is influenced by the activities carried out during the surgical phases. EST usage affects the contamination level more than staff size during operation observed. Colony forming unit (CFU) values in the protected area close to the patient’s wound are influenced more by the type of ventilation system than by surgical phases. CFU values decrease by 18 to 50 times from the UWD system to the hybrid one. The large airflow volumes supply together with high air velocities in OTs equipped with UDAF+Mixing systems guarantee a better and a safer airborne contamination control for patients and medical team in comparison with UWD systems
Simulazione termofluidodinamica di un impianto di riscaldamento a pavimento radiante a servizio di un locale di rilevante altezza
No full textSono illustrati dapprima per l'impianto ed il locale inesame: le schematizzazioni matematiche e le ipotesi semplificative per la modellizzazione del fabbricato e dell'impianto con le relative condizioni al contorno, l'algoritmo utilizzato per la simulazione e le relative equazioni di conservazione, i risultati della simulazione in termini di distribuzione spaziale di temperatura e velocità dell'aria. Sono di seguito descritti i risultati della simulazione relativamente ad un impianto di riscaldamento "tradizionale" con generatori d'aria calda a scambio diretto a servizio del locale sopra citato. E' infine effettuato il confronto tra i risultati ottenuti dalle n. 2 sopra citate simulazioni in termini di: comfort, consumo energetico
Preserving Leonardo's Last Supper: A CFD case study
No full textComputational Fluid Dynamics was used to assess the effectiveness of heating the surface of the Last Supper to preserve the masterpiece from PM10 deposition as well as to investigate the consequences of increasing the number of visitors simultaneously admitted in the room. For this purpose, the flow of moist air in the Refectory of “Santa Maria delle Grazie” in Milan was numerically simulated. In addition, the trajectories of the PM10 particles emitted by visitors were traced and their concentration monitored, the latter considered one of the main parameters possibly harmful to the painting. Moreover a velocity deposition model was applied to evaluate the soiling hazard through a dose-response function. It was found that, even doubling the number of visitors, no perceptible blackening of the surface of the Last Supper can be foreseen also in the far future
Operating theatre ventilation systems and their performance in contamination control: “at rest” and “in operation” particle and microbial measurements made in an Italian large and multi-year inspection campaign
Full text linkIn Operating Theatres (OT), the ventilation system plays an important role in controlling airborne contamination and reducing the risks of Surgical Site Infections (SSIs). The air cleanliness is really crucial in this field and different measurements are used in order to characterize the situation in terms of both airborne microbiological pollutants and particle size and concentration. Although the ventilation systems and airborne contamination are strictly linked, different air diffusion schemes (in particular, the Partial Unidirectional Airflow, P-UDAF, and the Mixing Airflow, MAF) and various design parameters are used, and there is still no consensus on real performance and optimum solutions. This study presents measurements procedures and results obtained during Inspection and Periodic Performance Testing (1228 observations) in a large sample of Italian OTs (175 OTs in 31 Italian hospitals) in their operative life (period from 2010 to 2018). The inspections were made after a cleaning procedure, both in “at-rest” conditions and “in operation” state. Inert and microbial contamination data (in air and on surfaces) are analyzed and commented according to four relevant air diffusion schemes and design classes. Related data on Recovery Time (RT) and personnel presence were picked up and are commented. The results confirm that the ventilation systems are able to maintain the targeted performance levels in the OT operative life. However, they attest that significant differences in real OT contamination control capabilities do exist and could be ascribed to various design choices and to different operation and maintenance practices. The study shows and confirms that the air diffusion scheme and the design airflow rate are critical factors. Beside large variations in measurements, the performance values, in terms of control of airborne particle and microbial contamination (in air and on surfaces), for P-UDAF systems are better than those that were assessed for the MAF air diffusion solution. The average performances do increase with increasing airflows, and the results offer a better insight on this relationship leading to some possible optimization
Performance measurement of a cross-flow indirect evaporative cooler: Effect of water nozzles and airflows arrangement
No full textThe indirect evaporative cooler (IEC) can be effectiVely used to increase energy efficiency and reduce energy consumption of HVAC systems. In particular, such system can be suitably adopted in data center applications, where the design indoor temperature can reach 45 degrees C, according to recent ASHRAE standards.It is well known that IEC performance can be significantly increased by an effective secondary air humidification process. In particular, the system should be designed in order to obtain an optimal water distribution on heat exchanger plates. In this paper, five different water nozzles and airflows arrangements of a IEC system based on a cross flow heat exchanger are experimentally investigated. The system is designed to have a limited water consumption (water to secondary air mass flow ratio between 1.4%-4%) and performance are measured in different operating conditions.Results show the highest wet bulb effectiveness (up to 82%-84% in the investigated conditions) is obtained in two configurations: (i) Horizontal orientation of heat exchanger plates; (ii) Vertical orientation of heat exchanger plates and water/secondary air supplied from the top. (C) 2018 Elsevier B.V. All rights reserved
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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