1,721,021 research outputs found
The Appraisal of Real Estate whit a Small and Noise Data Set: A Bayesan Neural Network Model
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Effect of non-condensable gas in steam condensation at sub-atmospheric pressure condition
No full textIn the International Thermonuclear Experimental Reactor (ITER), a postulated Loss Of Coolant Accident (LOCA) in the Vacuum Vessel (VV) has to be managed with a pressure suppression system working at sub-atmospheric pressure. The operating conditions considerably differ from those experienced in the fission nuclear power plants such as BWR, since the ITER Tokamak works at very low pressure conditions and can withstand a maximum pressure of 0.15 MPa. For this reason, the pressure value must not exceed 10 kPa for a water temperature of 30 °C inside the Vapour Suppression Tanks (VSTs) that are the fundamental components of the Vacuum Vessel Pressure Suppression System (VVPSS). During a LOCA some non-condensable gases (mainly hydrogen and oxygen gases due to the water radiolysis or thermolysis) may be mixed in the steam and this could impair the condensation efficiency. In order to investigate the effects of non-condensable gas on DCC, we conducted a research program funded by ITER Organization at the laboratory of the University of Pisa: we designed and built a small-scale experimental rig to study the steam Direct Contact Condensation (DCC) with the presence of non-condensable gas and simulate the behaviour of a VST. Since DCC can occur with different characteristics, we ran 12 closed mode tests exploring all condensation regimes injecting a certain mass of air with the steam discharged in the subcooled water. The tests started at the saturation pressures corresponding to water temperatures ranging from 40 °C to 80 °C and ended when the free space volume reached the atmospheric pressure. From the analysis of the data acquired during the tests we observed that the condensation efficiency remained higher than 95%. We observed that despite this, the presence of a certain quantity of non-condensable gas has negative aspects on condensation: the condensation regime never reaches stability (the regimes quickly shift towards instability). Furthermore, the presence of air triggers a turbulence of the flow which interferes with the transfer of heat from the steam to the water. Not only the introduction of air into the flow increases linearly the pressure above the water head but its high temperature further contributes to the pressure increase. The air mixed with the flow also forms eddies that can trap the steam and transport it out of the water, preventing it from condensing. Apart from condensation, the most noticeable problem is the rapid increase in pressure inside the condensation tank
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
Towards a haptic-based virtual cane to assist blind people in obstacle detection
No full textBlind persons rely on the traditional white cane to explore and avoid obstacles while moving independently in indoor and outdoor environments. Although numerous electronic aids have been proposed in the literature and on the market, orienting and moving are still a challenge for people who cannot see. Usually, electronic support devices are used in combination with the stick as blind people consider it a fundamental tool for exploring and getting information about the surrounding. In this paper, a virtual version of the traditional white cane based on the use of a laser sensor, actuators and haptic feedback for obstacle detection is proposed to move towards a single aid for mobility tasks. Although the proposed electronic aid is the first prototype tested in an indoor environment, it is a first step towards a discreet and lightweight virtual cane
Dust produced by plasma off normal event in the vacuum vessel: Experimental analyses of the deposition inside the pressure suppression tank during a LOCA
No full textThis paper deals with experimental tests simulating the dust deposition, produced in the Vacuum Vessel of the nuclear fusion reactor ITER, and carried by steam and gases inside the Pressure Suppression Tanks during a Loss of Coolant Accident (LOCA). The dust, mainly tungsten and beryllium, is produced by the erosion of the divertor or of the first wall due to plasma off-normal events, like plasma disruptions or vertical displacement events. The activity is performed in the frame of a research program performed at the University of Pisa, funded by the ITER Organization, for studying the behaviour of the Vacuum Vessel Pressure Suppression System (VVPSS). A reduced scale of VVPSS was built at the University of Pisa (1/32 geometrical scale). The experimental rig is composed by an electric steam generator and steam and air mass flow rate control lines. Steam with (or without) air is sent in a condensation container, partially filled with water. These fluids entrain a mass of dust measured by a dust mini-dosing system. The air and the non-condensed steam flow in the atmosphere through a demister and HEPA filters. A tests campaign was carried out injecting a simulant of the actual dust (aluminium oxide) in a flux of steam and air into the condensation tank. The tests were performed at different values of steam, air and dust mass flow rate. During the test, the dust concentration in the water was measured versus time, in order to determine the settling time. The dust deposition on the surfaces of the condensation tank was measured as well as the decontamination efficiency of the tank. The results demonstrated that about 99 % of dust is deposited on the tank surfaces and only a quantity less than 1 % is carried by the water during the tank discharge
Biocompatibility tests with fibroblasts of CaO rich calcium silicate glasses
No full textIn the present preliminary work a series of in vitro biocompatibility test on CaO rich calcium silicate glasses,was performed, to study the cell behavior when seeded on 1 cm2 material fragments, introduced inside
an in vitro culture system. A strain of physiologically adherent cells, like fibroblasts, was deliberately selected to facilitate cell attachment to the materials
Experimental Analysis of Steam Condensation Heat Transfer Coefficient in Water Pool at Sub-Atmospheric Pressure
No full textThe experimental analysis of steam direct contact condensation in a water pool at sub-atmospheric condition was carried out in relevant configurations for the International Thermonuclear Experimental Reactor (ITER) Vacuum Vessel Pressure Suppression System, during a postulated Ingress of Coolant Event category IV accidental scenario. This transient accident was experimentally simulated in a reduced scale (1:22) facility at University of Pisa, adopting a defined scaling law. The steam jet plumes were video recorded and image analysis was performed at stable and interfacial oscillation condensation regimes, providing steam plume average length and interfacial area. The average heat transfer coefficient was therefore computed and correlated to the condensation driving potential. Also, the steam jet length divided by orifice diameter (L/D) was characterised as function of driving potential. Empirical correlations available in literature at atmospheric conditions were modified for evaluating vacuum conditions peculiarities. The remarkable higher dependence of heat transfer coefficient (HTC) to driving potential parameter, at vacuum conditions, was highlighted by the driving potential exponent equal to 1.2 instead of 0.04 at ambient pressure. The obtained L/D and HTCcorrelations are able to predict with ± 15% and ± 30% of error the corresponding experimental data, respectively
Release kinetics of ampicillin, biocompatibility tests with a fibroblast strain of a Zirconia gel glass
No full textBiocompatibility remains the central theme for biomaterials applications in medicine. It is generally accepted that this term does not indicate only absence of a cytotoxic effect but also positive effects in the sense of biofunctionality, i.e. promotion of biological processes considering the intended aim of the application of a biomaterial.
Biocompatibility of zirconia gel glass was studied using in vitro testing methods, the incubation period was 7, 14, 21 days. The bioactivity of the synthesized material had been shown by the formation of a layer of hydroxyapatite on the surface of ZrO2-Y2O3(5wt%) samples soaked in a fluid simulating the composition of the human blood plasma (SBF), as observed by SEM and EDS microscopy.
Studies of drug delivery kinetics were also carried out. The amount of sodium ampicillin released has been detected by UV-VIS spectroscopy. The released kinetics seems to occur in more than one stage. HPLC analysis had also been carried out to ensure the integrity of ampicillin after the synthetic treatment
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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