A CFD-based virtual test-rig for rotating heat exchangers

Rotating heat exchangers are used in steel industry, air conditioning and thermal power plants to pre-heat air used in steam generators or for waste heat recovery. Here we focus on a rotating heat exchanger on a so-called Ljungström arrangement operated in thermal power plants to pre-heat the air fed to the steam generators. In these devices the heat exchange between two fluids is achieved through a rotating matrix that gets in contact alternatively with the two fluid streams and acts as a thermal accumulator. To increase the heat capacity and the overall exchange surface, the rotating matrix is filled by a series of folded metal sheets. In the paper we de-scribe a methodology to account for the effects of the Ljungström in a virtual test-rig implemented in a Computational Fluid Dynamics environment. To this aim, a numerical model based on the work of Molinari and Cantiano was derived and implemented in the OpenFOAM library. RANS numerical results were compared with those of a mono-dimensional tool used by ENEL to design Ljungström heat exchangers and validated against available measurements in a real configuration of a thermal power plant

Progetto di un sistema di Cruise Control in ambiente MatLab e Simulink

In questa tesi si realizza lo studio di un dispositivo di Cruise Control in ambiente Matlab e Simulink. Si effettua una modellizzazione del sistema e se ne simula il comportamento in modo che soddisfi alcune specifiche di progetto. Si procede con l'analisi in catena aperta, al progetto di controllori e alle rispettive analisi in catena chiusa, volte al soddisfacimento delle specifiche. Vengono infine tratte le conclusioni, volte a stabilire quale strategia di progetto sia preferibileope

Preparazione di film di poli(stirene) contenenti rotori molecolari fluorescenti sensibili a vapori di solventi organici

Il presente lavoro di tesi ha come oggetto la caratterizzazione di rotori molecolari fluorescenti, una classe di luminofori organici in grado di modulare l’intensità della propria emissione di fluorescenza caratteristica in base alle interazioni con il mezzo in cui sono dispersi. In particolare risultano poco emissivi in solventi a bassa viscosità dove la radiazione luminosa assorbita viene dissipata mediante transizioni non radiative, in particolare grazie alla rotazione attorno ad un legame. Questa risulta più impedita in solventi viscosi o allo stato solido così da consentire un’emissione per fluorescenza. Sono stati caratterizzati in soluzione e in matrici polimeriche termoplastiche rotori molecolari reperibili in commercio, 9-(2,2-dicianovinil)julolidina (DCVJ) e 9-(2-carbossi-2-cianovinil)julolidina (CCVJ), e uno sintetizzato opportunamente in questo lavoro. Quest’ultimo, 9-(2-(1H,1H,2H,2H-perfluorodecancarbalcossi)-2-cianovinil)julolidina (F8CVJ) è caratterizzato da una struttura simile a DCVJ e CCVJ ma è stato funzionalizzato inserendo un gruppo estereo preparato impiegando un alcol lineare perfluorurato. In particolare si è voluto valutare come varia il segnale di fluorescenza di un film di poli(stirene) contenente rotori molecolari ed esposto ad un ambiente saturo di vapori di composti organici volatili (VOCs). I vapori di solvente che diffondono attraverso il film polimerico, se affini per la matrice, causano un rilassamento delle catene macromolecolari con un conseguente aumento del volume libero che porta a maggior libertà di movimento per i rotori molecolari e favorendo quindi un rilassamento non radiativi. Questo si traduce in una diminuzione progressiva dell’intensità di fluorescenza in funzione del tempo di esposizione. Tale fenomeno è stato osservato per tutti i rotori molecolari ma in particolare impiegando il rotore F8CVJ che ha manifestato una risposta migliore nel rilevare la presenza di vapori di solventi volatili. Infatti la sua particolare struttura gli conferisce minor affinità per il poli(stirene) favorendo segregazione superficiale del colorante che si traduce in una migliore sensibilità verso i vapori. Si può concludere quindi che i rotori molecolari fluorescenti si prestano bene ad essere impiegati come additivi fluorescenti nella realizzazione di indicatori ottici di tipo on/off reversibili sensibili ai vapori di quei solventi che sono affini per la matrice plastica che costituisce il dispositivo

Julolidine fluorescent molecular rotors as vapour sensing probes in polystyrene films

We introduce a new sensing polymer system for detection of volatile organic compounds (VOCs) based on the optical response of polystyrene (PS) films doped with julolidine fluorescent molecular rotors (FMRs). The julolidine FMRs exhibited viscosity-dependent changes in the fluorescence intensity, that was enhanced when glycerol was added to ethanol solutions and when they were dispersed in PS films. Thus, reduction in medium mobility slowed down internal motions and allowed for a major radiative decay pathway. The FMR/PS films were exposed to several VOCs, and showed a significant decrease in fluorescence emission when exposed to chloroform, whereas a negligible variation in their emission occurred when methanol was utilized. This vapour sensing behaviour was much more evident when a perfluorodecyl chain was linked to the julolidine core being the molecule segregated at the film surface. This responsive behaviour was affected by solvent composition and its reproducible response was easily determined by luminescence experiments

Clinical Evidence: a useful tool for promoting evidence-based practice?

BACKGROUND: Research has shown that many healthcare professionals have problems with guidelines as they would prefer to be given all relevent information relevent to decision-making rather than being told what they should do. This study assesses doctors' judgement of the validity, relevance, clarity and usability of the Italian translation of Clinical Evidence (CE) after its free distribution launched by the Italian Ministry of Health METHODS: Opinions elicited using a standardised questionnaire delivered either by mail or during educational or professional meetings RESULTS: Twenty percent (n = 1350) doctors participated the study. Most of them found CE's content valid, useful and relevant for their clinical practice, and said CE can foster communications among clinicians, particularly among GPs and specialists. Hospital doctors (63%) more often than GPs (48%) read the detailed presentation of individual chapters. Twenty-nine percent said CE brought changes in their clinical practice. Doctors appreciated CE's nature of an evidence-based information compendium and would have not preferred a collection of practice guidelines. CONCLUSIONS: Overall, the pilot initiative launched by the Italian Ministry of Health seems to have been well received and to support the subsequent decision to make the Italian edition of Clinical Evidence concise available to all doctors practising in the country. Local implementation initiatives should be warranted to favour doctor's use of CE

Imaging the structural style of an active normal fault through multidisciplinary geophysical investigation: a case study from the Mw 6.1, 2009 L'Aquila earthquake region (central Italy)

The normal fault-system responsible of the 2009 Mw 6.1 L'Aquila earthquake (Paganica-San Demetrio fault-system) comprises several narrow, fault-parallel valleys of controversial origin. We investigated a key section of the southeastern portion of this fault network along the small Verupola Valley. In order to characterize its nature and possible tectonic activity, we applied multiple-geosciences techniques able to image at depth the structure associated to this peculiar landform. We integrated magnetometry, 2-D P wave and resistivity tomography, surface waves and seismic noise analysis coupled with field mapping, shallow boreholes and trenching. According to our results, the Verupola Valley is a ∼30–40-m-deep graben controlled by a SW-dipping master fault and synthetic splays paired with an antithetic NE-dipping fault. The SW-dipping splays are active and cut very shallow (<2 m deep) Late Pleistocene sediments. The small amount of cumulated vertical offset (∼15 m) across the conjugated system may indicate a young fault inception or very low Quaternary slip-rates. Due to its structural continuity with the adjacent mapped strands of the Paganica–San Demetrio fault network, we relate the Verupola Valley to the recent activity of the southeastern segment of this fault system. We also suggest that other fault-parallel valleys can have the same tectonic origin and setting of the Verupola Valley. This latter represents a scale-independent analogue from metric scale (exposed in the palaeoseismological trenches) to the Middle Aterno Basin scale (seen from seismic profiles and fault mapping). Overall, the imaged structural style is coherent with the regional tectonic setting due to Quaternary crustal extension

Older people with hip fracture and IADL disability require earlier surgery

Background: Hip fractures represent a major challenge for physicians as well as society as a whole. Both poor functional status and delay to surgery are well known risk factors for negative outcomes. We hypothesized that the timing of the operation is more important for frail older people than older people without functional limitations before fracture. Methods: We performed a prospective multicenter cohort study on 806 consecutive patients, 75 years of age or older, admitted with a fragility hip fracture to three hospitals in the Emilia-Romagna Region (Italy). All three hospitals had a comanaged care model, and the patients were under the shared responsibility of an orthopedic surgeon and a geriatrician. Results: Functional status assessed as instrumental activities of daily living was an important predictor of survival after 1 year from fracture. After adjusting for confounders, the hazard ratios per 1 point score of increase from 0 to 8 was 1.30 (95% confidence interval 1.19-1.42, p =. 000). Time to surgery increased 1-year mortality in patients with a low instrumental activities of daily living score (hazard ratios per day of surgical delay 1.14, 95% confidence interval 1.06-1.22, p &lt;. 001) and intermediate instrumental activities of daily living score (hazard ratios 1.21, 95% confidence interval 1.09-1.34, p &lt;. 001) but was an insignificant risk factor in functionally independent patients (hazard ratios 1.05 95% confidence interval 0.79-1.41, p =. 706). Conclusions: Surgery delay is an independent factor for mortality in older patients after hip fracture but only for the frail older people with prefracture functional impairment. If our results are confirmed, a more intensive approach should be adopted for older people with hip fractures who have disabilities. © 2012 The Author

orthostatic hypotension does not increase cardiovascular risk in the elderly at a population level

n/

Design of a study to investigate the mechanisms of obstructive sleep apnoea by means of drug-induced sleep endoscopy

Background Obstructive sleep apnoea (OSA) is an independent risk factor of hypertension and cardiovascular diseases. Recurrent episodes of upper airways collapse during sleep causing blood oxygen desaturation, hypercapnia, and micro-arousals, are known to activate the sympathetic nervous system (SNS). However, whether changes in the renin-angiotensin-aldosterone system and endothelial activation also occur remains contentious. Methods Based on routine use of drug-induced sleep endoscopy (DISE) for the work-up of OSA patients in our centre, we designed a prospective study to investigate the haemodynamic and humoral changes occurring during the apnoeic episodes reproduced in vivo in the course of DISE. Specifically, plasma aldosterone concentration and renin activity, C-terminal fragment of proendothelin-1, as a marker of endothelial damage, and free plasma catecholamines, will be measured at fixed times during DISE. The activity of catechol-O-methyltransferase (COMT), a key catecholamine-inactivating enzyme that has been scantly investigated thus far owing to the lack of commercially available kits, will be also determined by a newly developed high performance liquid chromatography method, which is herein described. Results and conclusions The aim of this study is to provide novel information on the haemodynamic, hormonal, and SNS changes, and also on COMT activity modification concomitantly occurring during apnoea, thus contributing substantively to the understanding of the pathophysiology of OSA