19 research outputs found
Brotini P., Carbone C., D'Auria F., DeSanti G., Mazzini M., Oriolo F., "LOBI test A2-55: electric power evaluation and preliminary analysis of results obtained by RELAP4/MOD6 code", University of Pisa Report, IIN - RP 472(81), Pisa (I)
No full textThe document deals with the application of a numerical model, called POTEL, to determine the electrical power to be supplied to hollow rods, available in the LOBI experimental simulator, in order to simulate the performance of the nuclear fuel. Hollow rods are easy to construct but have a thermal capacity much lower than the reference nuclear fuel rods. The difference becomes important in transient conditions. In those conditions electrical power must be controlled in order to reproduce the temperature transient expected on the surface of the nuclear fuel rods. A complex software was developed to determine the electrical power transient based on the inverse solution for transient conduction heat transfer, i.e. the Fourier equation. Reference conditions (surface temperature and heat flux) were calculated by the RELAP code for nuclear fuel in the expected experimental conditions and were transformed into electrical power to be supplied to LOBI heaters during the actual experimental conditions (obviously if the code prediction was wrong – to be demonstrated a posteriori – the calculated transient for electrical power resulted inconsistent with the occurring thermal-hydraulic conditions). The application of the software to the experiment A2-55 performed in LOBI is discussed in this report. LOBI was a Pressurized Water Reactor (PWR) simulator installed in the EC center of Ispra Italy supported by EURATOM
Post-test analysis of LOBI test SD-SL-03 performed by RELAP4/MOD6 code
No full textThe document deals with the post-test analysis of an experiment performed to characterize the LOBI system performance in the configuration Mode2. LOBI was a Pressurized Water Reactor (PWR) simulator installed in the EC center of Ispra Italy financially supported by EURATOM.
The configuration Mod2 of LOBI was designed as a consequence of the Three Mile accident in US and is the follow-up of the configuration Mod1. Mod2 was designed to simulate stratification phenomena and natural circulation which are important during Small Break Loss of Coolant Accidents (SBLOCA); as a difference Mod1 was designed to simulate phenomena expected during Large Break Loss of Coolant (LBLOCA) scenarios. Namely downcomer size in Mod2 was much smaller than in the case of Mod1 and a large number of Emergency Core Cooling Systems (ECCS) were installed in Mod2. The concerned SD-SL-03 experiment was performed to characterize the facility. The code application allowed the optimization of the nodalization by Relap 4 preparing for the campaign of experiments. Furthermore the comparison between experiment and calculation constituted the basis for developing accuracy quantification method. (relevant to code validation) .
The work was discussed in a specific meeting of the so-called SBATF research group where University of Pisa represented Italy
Impiego della sulpiride e L-Dopa per la valutazione della funzione ipofisaria nelle iperprolattinemie.
No full textRestless Legs Syndrome in end-stage renal disease.
No full textBackground and purpose: Patients undergoing dialysis therapy due to end-stage renal disease (ESRD) present a high prevalence of sleep disorders, including restless legs syndrome (RLS).However, the known data generally have been obtained from relatively small patient samples, coming from single or very few dialysis units. Moreover, some data were collected prior to the recent improvements in dialysis techniques, pharmacological therapies and to the establishment of internationally recognised diagnostic criteria for RLS. Patients and methods: In order to study the incidence of the different sleep disorders, and of RLS in particular, in a large population of dialysis patients, a questionnaire was administered to all the patients in dialysis units of the 'Triveneto' area (Italy) who agreed to participate. The first part of the questionnaire included questions about demographic data, general medical history, history of renal disease, dialytic treatment and pharmacological therapy. The second part, which was self-administered, explored the patient's complaints about sleep, the presence of the minimal International Restless Legs Syndrome Study Group (IRLSSG) criteria for the diagnosis of RLS, the Epworth Sleepiness Scale and questions particularly related to somnolence. Patients whose responses indicated a diagnosis of RLS according to the IRLSSG criteria were requested to answer the 10 questions of the IRLSSG Severity Scale. The same group of patients was compared to those who did not fulfil any of the four minimal criteria for RLS. Statistical analysis was performed by using ANOVA and non-parametric tests. Whenever possible, data were compared with the database of the Veneto Dialysis Register. The first 601 consecutive questionnaires that we were able to analyse are presented in this paper. Results: Applying the IRLSSG criteria for the diagnosis, the percentage of RLS patients in our sample was 21.5%, with a score of 20.5±8.7 on the IRLSSG Severity Scale. Comparing patients who are definitely affected by RLS (n=127) with unaffected patients (n=280), we found that the two groups did not differ as to age, sex, weight, body mass index (BMI), and intake of nicotine, alcohol and caffeine. Similarly, the two groups did not differ as to the etiology of ESRD, type of dialysis or percentage of previous transplantations; however, the period of dialysis dependence was significantly lower in the group negative for RLS. The use of drugs did not differ in the two groups, except for lower intake of phosphorus binders and antihypertensive drugs among RLS patients. No patient was receiving specific treatment for RLS.RLS patients reported more fragmented, less restful nightly sleep and more daytime somnolence, more often presented symptoms of other sleep disorders and were more affected by anxiety or depression. Conclusions: The high prevalence of RLS and other sleep disorders among uremics requires careful investigation of nocturnal sleep; although often underdiagnosed, correct identification of these disorders can lead to better therapy and improvement of clinical conditions and quality of life. Sleep fragmentation and sleep deprivation caused by RLS may contribute to the cardiovascular complications and infections, often with bad prognosis in dialysis patient
Automatic assessment of myocardial fibrosis by delayed enhanced magnetic resonance imaging
No full textCardiovascular magnetic resonance is able to detect myocardial fibrosis by delayed enhancement of a contrast media. However, detection and quantification of fibrosis is difficult due to the complex pattern of the fibrotic tissue signal. In this study a software model of the signal distribution in normal and fibrotic myocardium was inferred from MR images of healthy subjects and patients with hypertrophic cardiomyopathy. The developed model allowed to define a methodology for the discrimination of fibrotic areas. The method was based on the fitting of the signal histogram with a modified gamma function. The scale parameter characterizing the gamma function was used as discriminating factor in MR image analysis, reaching a sensitivity of 85% and a specificity of 86%. The proposed approach outperformed the standard approach used in the clinical practice
Development of High Speed Hybrid Bearings for Reusable Pump-Fed Liquid Rocket Engines
No full textFor truly reusable rocket propulsion systems, the next generation first-stage engines have to ensure reusability with a reduced maintenance effort to optimize turnover time and costs. This goal can be better achieved by developing long-life turbopumps with a lifetime requirement of several hours. Specifically, the replacement of rolling bearings with lubricated journal bearings is one of the most promising solution to increase bearing lifetime and reliability. In the framework of the European Space Agency project “Long Life Journal Bearings for Turbopumps,” the Department of Civil and Industrial Engineering of the University of Pisa has selected and designed two promising high-speed journal bearings geometries: a square-recessed journal bearing with 45° orifices and a radial-orifice compensated bearing. Both configurations will be manufactured and tested with a Inconel 718 material, whereas an innovative solution based on ceramic matrix composite, CMC, will be tested with the simpler configuration without recesses. With the goal of implementing such bearings in future pump-fed LOX-CH4 rocket engines, the configurations will be tested in a cryogenic test facility suitably developed to assess the performance with methane in a representative pump environment. In this paper the design bearing choices will be presented and justified, alongside the ongoing test facility development activities
