Experimental assessment of the acoustic performance of nozzles designed for clean agent fire suppression

Discharge through nozzles used in gas-based fire protection of data centers may generate noise that causes the performance of hard drives to decay considerably; silent nozzles are employed to limit this harmful effect. This work focuses on proposing an experimental methodology to assess the impact of sound emitted by gaseous jets by comparing various nozzles under several operating conditions, together with relating that impact to design parameters. A setup was developed and repeatability of the experiments was evaluated; standard and silent nozzles were tested regarding the discharge of inert gases and halocarbon compounds. The ability of silent nozzles to contain the emitted noise—generally below the 110 dB reference threshold—was proven effective; a relationship between Reynolds number and peak noise level is suggested to support the reported increase in noise maxima as released flow rate increases. Hard drives with lower speed were the most affected. Spectral analysis was conducted, with sound at the higher frequency range causing performance decay even if lower than the acknowledged threshold. Independence of emitted noise from the selected clean agent was also observed in terms of released volumetric flow rate, yet the denser the fluid, the lower the generated noise under the same released mass flow rate

Variation of DNA Fragmentation Levels During Density Gradient Sperm Selection for Assisted Reproduction Techniques: A Possible New Male Predictive Parameter of Pregnancy?

Predicting the outcome of in vitro fertilization (IVF)/intracytoplasmic sperm injection (ICSI) is one main goal of the present research on assisted reproduction. To understand whether density gradient centrifugation (DGC), used to select sperm, can affect sperm DNA integrity and impact pregnancy rate (PR), we prospectively evaluated sperm DNA fragmentation (sDF) by TUNEL/PI, before and after DGC. sDF was studied in a cohort of 90 infertile couples the same day of IVF/ICSI treatment. After DGC, sDF increased in 41 samples (Group A, median sDF value: 29.25% [interquartile range, IQR: 16.01–41.63] in pre- and 60.40% [IQR: 32.92–93.53] in post-DGC) and decreased in 49 (Group B, median sDF value: 18.84% [IQR: 13.70–35.47] in pre- and 8.98% [IQR: 6.24–15.58] in post-DGC). PR was 17.1% and 34.4% in Group A and B, respectively (odds ratio [OR]: 2.58, 95% confidence interval [CI]: 0.95–7.04, P = 0.056). After adjustment for female factor, female and male age and female BMI, the estimated OR increased to 3.12 (95% CI: 1.05–9.27, P = 0.041). According to the subgroup analysis for presence/absence of female factor, heterogeneity in the association between the Group A and B and PR emerged (OR: 4.22, 95% CI: 1.16–15.30 and OR: 1.53, 95% CI: 0.23–10.40, respectively, for couples without, n = 59, and with, n = 31, female factor). This study provides the first evidence that the DGC procedure produces an increase in sDF in about half of the subjects undergoing IVF/ICSI, who then show a much lower probability of pregnancy, raising concerns about the safety of this selection procedure. Evaluation of sDF before and after DGC configures as a possible new prognostic parameter of pregnancy outcome in IVF/ICSI. Alternative sperm selection strategies are recommended for those subjects who undergo the damage after DGC

Introduzione alla ricerca qualitativa. Domande e metodi

\u2013Essere in e fare ricerca, soprattutto empirica, \ue8 una postura esistenziale e professionale sempre pi\uf9 richiesta in contesti lavorativi condizionati da grandi complessit\ue0. Il punto di partenza della ricerca \ue8 sempre la dimensione della domanda: domande di senso sulle questioni che emergono dalla pratica, domande che richiedono risposte contestuali e non una mera rielaborazione di risposte pre-confezionate. Alle domande sul senso che gli individui vivono e sperimentano, sui processi psicologici e sociali, sui valori che informano la postura professionale degli educatori, \ue8 possibile rispondere grazie alla ricerca qualitativa: un modo di fare ricerca empirica che deve essere dotato di rigore, chiarezza e coerenza. Dopo aver discusso i criteri di scientificit\ue0 della ricerca empirica qualitativa, in questo capitolo davvero molto introduttivo, si affrontano i tre principali metodi: la Grounded Theory, la ricerca fenomenologica e l\u2019etnografia. Infine, si definiscono le implicazioni formative e auto-formative per l\u2019educatore professionale del fare questo tipo di ricerca

PEDAGOGIA GENERALE. EDUCAZIONE COMPARATA

Il contributo monografico introduce i principi teorici e metodologici dell'Educazione comparat

Introduzione alla ricerca qualitativa. Domande e metodi

Essere e fare ricerca, soprattutto empirica, \ue8 una postura esistenziale e professionale sempre pi\uf9 richiesta in contesti lavorativi condizionati da grandi complessit\ue0. Il punto di partenza della ricerca \ue8 sempre la dimensione della domanda: domande di senso sulle questioni che emergono dalla pratica, domande che richiedono risposte contestuali e non una mera rielaborazione di risposte pre-confezionate. Alle domande sul senso che gli individui vivono e sperimentano, sui processi psicologici e sociali, sui valori che informano la postura professionale degli educatori, \ue8 possibile rispondere grazie alla ricerca qualitativa: un modo di fare ricerca empirica che deve essere dotato di rigore, chiarezza e coerenza. Dopo aver discusso i criteri di scientificit\ue0 della ricerca empirica qualitativa, si affrontano i tre principali metodi: la Grounded Theory, la ricerca fenomenologica e l\u2019etnografia. Infine, si definiscono le implicazioni formative e auto-formative per l\u2019educatore professionale del fare questo tipo di ricerca

Full–scale experiments of water–mist systems for control and suppression of sauna fires

Sauna is a common fixture in many facilities; a specific fire–protection system is typically designed and installed for this application, as short circuits or direct contact with incandescent materials may result in a fire. Water mist has been recently considered as a promising option for this purpose; so, assessing its control and suppression capability in a sauna configuration has become of paramount importance for designers and engineers. To this end, an unprecedented real–scale test rig was built and instrumented with thermocouples and a hot–plate thermometer towards the evaluation of water–mist performance against various fire scenarios and, ultimately, to provide guidelines to designers. Timber benches were employed as target materials, while the fire was initiated in a wood crib. Design parameters, such as initial room temperature, location of the ignition source, nozzle–to–wall distance, and air gap between benches and wall, were varied, also including natural ventilation in a dedicated experiment. The system proved successful in controlling and containing the fire: bench damage ratio—selected as a quantitative parameter to assess water–mist performance—was consistently lower than 5%. However, extinction was not always achieved, especially under the most challenging configuration in terms of ventilation, initial room temperature, and nozzle–to–wall distance

Droplets wall interaction: Measurement of the interface temperature through infrared-transparent media

A new, non-intrusive method is proposed to measure the solid-liquid contact temperature during dropwise evaporative cooling. The droplets are deposited onto a material, BaF2, which is transparent in the infrared spectral band. The transparent tile is coated with a very thin layer of high-emissivity, opaque paint on its upper side, so that it can effectively respond to the infrared camera below. The interface temperature can thus be measured through the solid material by a thermographic camera. Tests are carried out on the black painted BaF2 disk after its optimization by mechanical machining. The experimental tests are conducted following two deposition procedures: a) multi-droplet arrays, b) sprays. The two different behaviors and the corresponding cooling results are finally compared

Full-scale experiments of fire control and suppression in enclosed car parks: A comparison between sprinkler and water-mist systems

Recent efforts to investigate car-park fires and understand the related mechanisms have fostered the need for analyses of suppression performance against this type of fire scenario. This work aims at providing an insight into the ability of sprinklers and water-mist systems to control and extinguish a fire within an enclosed car park through a series of real-scale experiments. Three cars were employed in each test: the central one was ignited by a heptane pool fire and the adjacent ones served as targets. Two configurations were explored: in the first one, a nozzle was placed directly at the vertical axis of the ignition source, whereas the ignition source was located between the area coverage of four nozzles in the second one. The sprinkler system mainly served as a reference; two values of discharge density were evaluated for water mist at high operative pressure and a biodegradable surfactant was also tested against the most challenging configuration. A quantitative analysis of free-burn and discharge phases by temperature measurements was coupled with radiant heat-flux measurements and an assessment of post-fire damage. Sprinkler and water-mist systems were capable of containing the fire spread and thermally controlling the fire, thus preventing structural damage. The water mist’s ability to overpower the plume and reach the burning surfaces proved more effective than that of sprinklers, especially as no nozzles were located right above the ignition surface. The higher discharge density showed better capability of preventing re-ignition phenomena and suppression was attained in both the investigated configurations, which suggests that a certain amount of flux is also needed to achieve flame cooling. The additive had promising impact on suppression performance; however, more tests are required to specifically explore its ability to enhance thermal control