Converter-flux-based current control of voltage source PWM rectifiers - analysis and implementation

Pulsewidth-modulated (PWM) rectifier technology is increasingly used in industrial applications like variable-speed motor drives, since it offers several desired features such as sinusoidal input currents, controllable power factor, bidirectional power flow and high quality DC output voltage. To achieve these features,however, an effective control system with fast and accurate current and DC voltage responses is required. From various control strategies proposed to meet these control objectives, in most cases the commonly known principle of the synchronous-frame current vector control along with some space-vector PWM scheme have been applied. Recently, however, new control approaches analogous to the well-established direct torque control (DTC) method for electrical machines have also emerged to implement a high-performance PWM rectifier. In this thesis the concepts of classical synchronous-frame current control and DTC-based PWM rectifier control are combined and a new converter-flux-based current control (CFCC) scheme is introduced. To achieve sufficient dynamic performance and to ensure a stable operation, the proposed control system is thoroughly analysed and simple rules for the controller design are suggested. Special attention is paid to the estimationof the converter flux, which is the key element of converter-flux-based control. Discrete-time implementation is also discussed. Line-voltage-sensorless reactive reactive power control methods for the L- and LCL-type line filters are presented. For the L-filter an open-loop control law for the d-axis current referenceis proposed. In the case of the LCL-filter the combined open-loop control and feedback control is proposed. The influence of the erroneous filter parameter estimates on the accuracy of the developed control schemes is also discussed. A newzero vector selection rule for suppressing the zero-sequence current in parallel-connected PWM rectifiers is proposed. With this method a truly standalone and independent control of the converter units is allowed and traditional transformer isolation and synchronised-control-based solutions are avoided. The implementation requires only one additional current sensor. The proposed schemes are evaluated by the simulations and laboratory experiments. A satisfactory performance and good agreement between the theory and practice are demonstrated.

Measuring oscillating walking paths with a LIDAR

This work describes the analysis of different walking paths registered using a Light Detection And Ranging (LIDAR) laser range sensor in order to measure oscillating trajectories during unsupervised walking. The estimate of the gait and trajectory parameters were obtained with a terrestrial LIDAR placed 100 mm above the ground with the scanning plane parallel to the floor to measure the trajectory of the legs without attaching any markers or modifying the floor. Three different large walking experiments were performed to test the proposed measurement system with straight and oscillating trajectories. The main advantages of the proposed system are the possibility to measure several steps and obtain average gait parameters and the minimum infrastructure required. This measurement system enables the development of new ambulatory applications based on the analysis of the gait and the trajectory during a walk.

Bond strength tests of dental adhesive systems and their correlation with clinical results : a meta-analysis

OBJECTIVE: To evaluate the variability of bond strength test results of adhesive systems (AS) and to correlate the results with clinical parameters of clinical studies investigating cervical restorations. MATERIALS AND METHODS: Regarding the clinical studies, the internal database which had previously been used for a meta-analysis on cervical restorations was updated with clinical studies published between 2008 and 2012 by searching the PubMed and SCOPUS databases. PubMed and the International Association for Dental Research abstracts online were searched for laboratory studies on microtensile, macrotensile and macroshear bond strength tests. The inclusion criteria were (1) dentin, (2) testing of at least four adhesive systems, (3) same diameter of composite and (4) 24h of water storage prior to testing. The clinical outcome variables were retention loss, marginal discoloration, detectable margins, and a clinical index comprising the three parameters by weighing them. Linear mixed models which included a random study effect were calculated for both, the laboratory and the clinical studies. The variability was assessed by calculating a ratio of variances, dividing the variance among the estimated bonding effects obtained in the linear mixed models by the sum of all variance components estimated in these models. RESULTS: Thirty-two laboratory studies fulfilled the inclusion criteria comprising 183 experiments. Of those, 86 used the microtensile test evaluating 22 adhesive systems (AS). Twenty-seven used the macrotensile test with 17 AS, and 70 used the macroshear test with 24 AS. For 28 AS the results from clinical studies were available. Microtensile and macrotensile (Spearman rho=0.66, p=0.007) were moderately correlated and also microtensile and macroshear (Spearman rho=0.51, p=0.03) but not macroshear and macrotensile (Spearman rho=0.34, p=0.22). The effect of the adhesive system was significant for microtensile and macroshear (p<0.001) but not for macrotensile. The effect of the adhesive system could explain 36% of the variability of the microtensile test, 27% of the macrotensile and 33% of the macroshear test. For the clinical trials, about 49% of the variability of retained restorations could be explained by the adhesive system. With respect to the correlation between bond strength tests and clinical parameters, only a moderate correlation between micro- and macrotensile test results and marginal discoloration was demonstrated. However, no correlation between these tests and a retention loss or marginal integrity was shown. The correlation improved when more studies were included compared to assessing only one study. SIGNIFICANCE: The high variability of bond strength test results highlights the need to establish individual acceptance levels for a given test institute. The weak correlation of bond-strength test results with clinical parameters leads to the conclusion that one should not rely solely on bond strength tests to predict the clinical performance of an adhesive system but one should conduct other laboratory tests like tests on the marginal adaptation of fillings in extracted teeth and the retention loss of restorations in non-retentive cavities after artificial aging.

Perusterveydenhuollon ja erikoissairaanhoidon käytön seuranta ja ennakointi kuntanäkökulmasta

Follow-up of utilisation and prediction of primary health care and hospital care from the municipality point of view. Planning, follow-up, and evaluation of primary health care within municipality entail comprehensive information about factors that influence health. In addition to populationbased research, various statistical data and registries serve as sources of information. The present study examined utilisation of primary health care and hospital care with the existing databases, registries, and categorization of Diagnosis Related Groups (DRGs) from the municipality (purchaser) point of view. Research involving the cases of Paimio, Sauvo, and Turku as examples of municipalities pointed out that, even in the small municipalities, it is possible to assess and predict health services to be offered to the inhabitants by following databases and registries. Health-related databases and registries include a plenty of possible uses that have not adequately been employed at the level of municipality. Descriptive futures research and community analysis formed the framework of the study. Descriptive futures research may be used to establish predictions based on past developmental traditions, and quantitative time trend analyses may be employed to make estimations about future events. Community analysis will assist in making conclusions about population- based health care needs, in assessing the functionality or effectiveness of the health care system, and in appropriately targeting limited resources. The aim of the present study was to describe the health service profile so that the arrangements and planning of health services as well as the contract negotiations of hospital care become easier within municipalities. Another aim was to assess the application of Hilmo (registry for posting hospital care periods), Aitta and Sotka (statistical databases) for the purposes of resource planning in the procurement of hospital care. A third aim was to evaluate how the system of the DRGs adapts in the prediction of retaining health services within short (1-year), intermediate (5-year) and long range (10-15-year) intervals. The findings indicated that the follow-up of primary health care utilisation combined with follow-up of hospital care utilisation allows municipalities to plan and predict health services when databases are applied. Information about the past contacts with the databases has indicated that the health care culture and incidence of disease change rather slowly in the area of investigation. For the purposes of health care research, it is recommended that methods of application used in making predictions about health care utilisation need to be further developed

Performance Measurement as Part of Management

To achieve success in a constantly changing environment and with ever-increasing competition, companies must develop their operations continuously. To do this, they must have a clear vision of what they want to be in the future. This vision can be attained through careful planning and strategising. One method of transforming a strategy and vision into an everyday tool used by employees is the use of a balanced performance measurement system. The importance of performance measurement in the implementation of companies' visions and strategies has grown substantially in the last ten years. Measures are derived from the company's critical success factors and from many different perspectives. There are three time dimensions: past, present and future. Many such performance measurement systems have been created since the 1990s. This is a case study whose main objective is to provide a recommendation for how the case company could make use of performance measurement to support strategic management. To answer this question, the study uses literature-based research and empirical research at the case company's premises. The theoretical part of the study consists of two sections: introducing the Balanced Scorecard and discussing how it supports strategic management and change management. The empirical part of this study determines the company's present performance measurement situation through interviews in the company. The study resulted in a recommendation to the company to start developing the Balanced Scorecard system. By setting up this kind process, the company would be able to change its focus more towards the future, beginning to implement a more process-based organisation and getting its employees to work together towards common goals.

Oliorelaatiotietokannan käyttö energianhallintajärjestelmässä

Empower Oy on energia-alan palveluja tarjoava yritys. Energianhallintajärjestelmää käytetään energiatietojen hallintaan ja ylläpitoon sekä tietojen esittämiseen loppukäyttäjille. Palvelun näytöt ja raportit on toteutettu web-pohjaisen käyttöliittymän kautta. Yhtiössä käynnistyi suurprojekti vanhan energianhallintajärjestelmän korvaamiseksi. Vanha järjestelmä otettiin käyttöön vuonna 1995 ja EMS-projekti käynnistettiin vuonna 2001. Diplomityö tehtiin osana EMS-projektia ja työn tavoitteina oli selvittää perusjärjestelmän käyttämän tietokantaratkaisun toimivuutta ja soveltuvuutta tehtävään sekä tutkailla eri tietokantamalleja teoreettisesti. Lisäksi työhön kuului erillisten haku- ja muutoskomponenttien ja rajapintojen toteuttaminen. Näiden avulla voidaan hakea ja muuttaa tietoa perusjärjestelmän pohjalla toimivasta oliorelaatiotietokannasta. Perusjärjestelmän DOR-tietokannaksi (Domain Object Repository) kutsuttu kokonaisuus on olioläheinen tietovarasto, josta tietoa haetaan ilmoittamalla haettavan olion tyyppi ja siihen liitoksissa olevat tyypit. Hakutulokseen mukaan haluttavat ominaisuudet ilmoitetaan kultakin tyypiltä erikseen. Haettaessa ja muutettaessa oliopohjaista DOR-tietoa, tulee noudattaa järjestelmän käyttämiä tietomalleja. Haku- ja muutoskomponentit toteutettiin Microsoftin kehittämällä .NET-teknologialla. Tietokantamallien teoreettinen tarkastelu auttoi ymmärtämään järjestelmän pohjalla toimivaa tietokantaratkaisua. Työssä selvisi, että perusjärjestelmän hyödyntämä oliorelaatiotietokanta soveltuu varsin hyvin tarkoitukseensa. Haku- ja muutoskomponenttien toteutus onnistui ja ne toimivat helppokäyttöisenä rajapintana energianhallintajärjestelmän tietokantaan.

Kiinteistön palautetiedon analysointi

Diplomityö käsittelee kiinteistön palautetiedon analysointia. Tässä diplomityössä palautetiedolla tarkoitetaan kiinteistön talotekniikkaan liittyviä teknisiä ja inhimillisiä tietoja, joiden perusteella rakennuksen ja sen tekniikan toimivuudesta voidaan tehdä päätelmiä. Tiedot kerätään järjestelmistä mittauspisteiden kautta etävalvomoon, josta niitä voidaan tarkastella ja edelleen analysoida. Valvomosta saatavan tiedon rinnalle pyritään suunnitteluvaiheessa kokoamaan valvottavasta kohteesta laskennallisia energiankulutusmalleja. Myös kiinteistön asukkaat, rakennuksen ominaisuudet ja ympäristö muodostavat osan palautetiedosta. Kiinteistön palautetieto voidaankin jakaa tekniseen ja inhimilliseen tietoon, ja edelleen analysoinnin kannalta staattiseen tai dynaamiseen tietoon. Tässä diplomityössä selvitettiin palautetiedon keruuta etävalvomolla yhdistämällä tähän rakentamisen laadunvalvonnan työkaluja ja sumeaa logiikkaa. Työn käytännön osio koostuu kiinteistön ja siihen yhdistetyn etävalvomon välillä kulkevan tiedon käsittelystä, mittauspisteiden määrittämisestä ja tietojen analysoinnista. Työssä esitellään kolme esimerkkikohdetta Helsingin seudulta. Työssä laadittiin arviointimalli, joka sisältää kaiken kiinteistön palautetietoon liittyvän aineiston ja sen analysointitavat, sekä erityisesti uutena asiana myös sumeaa logiikkaa. Tiedon analysointi etenee oletusarvojen muodostamisesta, simuloinnin laatimisesta ja sen vertaamisesta todellisiin tietoihin ja edelleen näistä tehtäviin päätelmiin. Tavanomaisten teknisten tietojen lisäksi sumean logiikan avulla tuotiin esille poikkeamia selittäviä tekijöitä mm. kiinteistön asukkaiden ominaisuuksista.

DTC-OHJATUN TAHTIKONEKÄYTÖN PYÖRIMISNOPEUSSÄÄDÖN ANALYYSI INTEGROIDUN SIMULOINTIMALLIN AVULLA

Työssä rakennettiin integroitu simulointimalli sähkökäytölle, jonka mekaniikka koostuu joustava-akselisesta kaksimassa systeemistä. Lisäksi tarkasteltiin kyseiselle sähkökäytölle ominaisia piirteitä ja niiden aiheuttamia ongelmia eri sovelluksissa, sekä tutkittiin teollisuudessa yleisesti esiintyvän pyörimisnopeussäädön, PI-säädön, parametrien vaikutusta kyseisen mekaniikan omaaviin sähkökäyttöihin. Taajuusmuuttajalle kehiteltiin yksinkertaistettu simulointimalli, jolla pystytään pienentämään merkittävästi simuloinnin laskenta-aikaa. Vääntövärähtelyiden kompensointiin tutkittiin optimaalista tilasäätöä, jossa Kalman suotimella estimoidaan systeemin tilojen lisäksi myös kuormamomentti ja jossa nopeussäätö suunnitellaan lineaarisella neliöllisellä menetelmällä (Linear Quadratic).

Paineilmajärjestelmän optimoinnin hyödyt tehtaan tuotantoprosessissa

Paineilmaa käytetään teollisuudessa hyvin yleisesti. Teollistuneissa maissa teollisuuden käyttämästä energiasta 8-10 % kuluu paineilman tuottamiseen. Paineilmakompressoreiden nykyaikaisen ohjausjärjestelmän avulla voidaan säästää paineilmajärjestelmän energiakustannuksia jopa 30 %. Ohjauksen optimoinnin yhteydessä on havaittu epäkohtia joiden poistaminen on parantanut tuotantolaitosten toimintaan niin, että saadut säästöt ovat olleet jopa energiasäästöjä suuremmat. Näitä optimoinnin välillisiä hyötyjä haluttiin selvittää tarkemmin. Tutkimuksessa perehdyttiin paineilman käytön ongelmiin eri tuotantolaitoksissa ja arvioitiin paineilmajärjestelmän optimoinnin vaikutuksia tehtaiden tuotantoon. Koska paineilmaa käytetään monissa tehtaiden kriittisissä kohteissa, on tutkimuskohteiden paineilmajärjestelmän ongelmista aiheutunut merkittäviä tuotannonmenetyksiä ja lisäkustannuksia. Merkittävimmät paperitehtaiden tuotantoa vaikeuttavat paineilmajärjestelmän tekniset ongelmat liittyvät paineilman puhtausvaatimuksiin ja riittävän verkkopaineen ylläpidon vaikeuteen. Organisatorisia ongelmia ovat paineilmajärjestelmän käyttöhenkilöstön asiantuntemuksen puutteellisuudet. Näistä aiheutuvaa tuotannon epäluotettavuutta voidaan merkittävästi pienentää kehittämällä paineilmakompressoreita, jälkikäsittelyä, ohjausta ja valvontaa alan asiantuntijoiden avustuksella.

Local thermodynamics and the generalized Gibbs-Duhem equation in systems with long-range interactions

The local thermodynamics of a system with long-range interactions in d dimensions is studied using the mean-field approximation. Long-range interactions are introduced through pair interaction potentials that decay as a power law in the interparticle distance. We compute the local entropy, Helmholtz free energy, and grand potential per particle in the microcanonical, canonical, and grand canonical ensembles, respectively. From the local entropy per particle we obtain the local equation of state of the system by using the condition of local thermodynamic equilibrium. This local equation of state has the form of the ideal gas equation of state, but with the density depending on the potential characterizing long-range interactions. By volume integration of the relation between the different thermodynamic potentials at the local level, we find the corresponding equation satisfied by the potentials at the global level. It is shown that the potential energy enters as a thermodynamic variable that modifies the global thermodynamic potentials. As a result, we find a generalized Gibbs-Duhem equation that relates the potential energy to the temperature, pressure, and chemical potential. For the marginal case where the power of the decaying interaction potential is equal to the dimension of the space, the usual Gibbs-Duhem equation is recovered. As examples of the application of this equation, we consider spatially uniform interaction potentials and the self-gravitating gas. We also point out a close relationship with the thermodynamics of small systems.

Anàlisi de la incidència del sistema de joc en la creació de situacions de superioritat numèrica en el futbol amb el juvenil “A” del Futbol Club Barcelona

El present treball es centra en l’estudi de les situacions de superioritat numèrica generades al llarg de la temporada 2013-2014 de l’equip Juvenil A del Futbol Club Barcelona. L’objectiu principal d’aquest treball és esbrinar quina incidència té el sistema de joc 1-4-3-3 en la creació d’aquestes situacions ofensives en el joc de l’equip. Per tal d’enregistrar múltiples situacions de joc i diferenciar la seva complexitat, s’han establert tres variables d’estudi: la zona del camp on es crea la superioritat numèrica (dividint el camp en 12 zones), el tipus de superioritat produïda (2 contra 1, 3 contra 1, 3 contra 2, 4 contra 2 i 4 contra 3), i la freqüència d’interacció dels jugadors en les situacions de superioritat en relació al networking (jugadors que intervenen en les situacions de superioritat per tal de poder establir relacions entre posicions del sistema de joc 1-4-3-3). El mètode utilitzat és notacional (ja que s’enregistra la freqüència en què succeeix un fenomen a partir d’unes taules creades especialment per l’enregistrament de dades), on fent ús de la proposta de Gréhaigne (2001) s’analitzen 8 partits al llarg de la temporada 2013-2014. Els resultats obtinguts mostren que es produeixen més superioritats a les zones 4 i 6 (20,37% respectivament), seguides de les zones 7 (14,81%) i 5 (13,89%). El major tipus de superioritat ha estat el 2 contra 1 (48,15%) seguit del 3 contra 2 (39,81%). La interacció més freqüent entre jugadors en les situacions de 2 contra 1 ha estat: lateral dret i central dret (26,92%) i lateral esquerre i central esquerre (21,15%). En les situacions de tres jugadors (3 contra 1) ha estat: entre el central dret, central esquerre i el pivot (28,57%) i entre el central dret, el lateral dret i el pivot (28,75%). En les situacions de 3 contra 2: lateral dret, l’interior dret i l’extrem dret (18,60%) i entre el central esquerre, el lateral esquerre i l’interior esquerre (18,60%). Pel que fa a les situacions de 4 contra 2 no se n’ha produït cap, i les de 4 contra 3 hi ha una igualtat entre diverses posicions(16,67%), però no s’observen dades molt significatives en quan a la intervenció, excepte la posició del pivot que intervé en gairebé totes. Aquestes dades, s’assimilen al que diuen Sans i Frattarola (2009) sobre el fet que en la zona d’inici es creen més situacions de superioritat que en la zona de progressió i finalització. També Castelo (1999) aporta un estudi sobre els percentatges d’aportacions ofensives dels jugadors en funció de l’espai i la demarcació, però tot i que en aquest cas no ho compara amb situacions de superioritat numèrica, les dades extretes son interessants per la comparativa amb l’estudi que es presenta.

Iterative reconstruction in CT : using mathematical model observers to determine low dose images' trustworthiness

La tomodensitométrie (TDM) est une technique d'imagerie pour laquelle l'intérêt n'a cessé de croitre depuis son apparition au début des années 70. De nos jours, l'utilisation de cette technique est devenue incontournable, grâce entre autres à sa capacité à produire des images diagnostiques de haute qualité. Toutefois, et en dépit d'un bénéfice indiscutable sur la prise en charge des patients, l'augmentation importante du nombre d'examens TDM pratiqués soulève des questions sur l'effet potentiellement dangereux des rayonnements ionisants sur la population. Parmi ces effets néfastes, l'induction de cancers liés à l'exposition aux rayonnements ionisants reste l'un des risques majeurs. Afin que le rapport bénéfice-risques reste favorable au patient il est donc nécessaire de s'assurer que la dose délivrée permette de formuler le bon diagnostic tout en évitant d'avoir recours à des images dont la qualité est inutilement élevée. Ce processus d'optimisation, qui est une préoccupation importante pour les patients adultes, doit même devenir une priorité lorsque l'on examine des enfants ou des adolescents, en particulier lors d'études de suivi requérant plusieurs examens tout au long de leur vie. Enfants et jeunes adultes sont en effet beaucoup plus sensibles aux radiations du fait de leur métabolisme plus rapide que celui des adultes. De plus, les probabilités des évènements auxquels ils s'exposent sont également plus grandes du fait de leur plus longue espérance de vie. L'introduction des algorithmes de reconstruction itératifs, conçus pour réduire l'exposition des patients, est certainement l'une des plus grandes avancées en TDM, mais elle s'accompagne de certaines difficultés en ce qui concerne l'évaluation de la qualité des images produites. Le but de ce travail est de mettre en place une stratégie pour investiguer le potentiel des algorithmes itératifs vis-à-vis de la réduction de dose sans pour autant compromettre la qualité du diagnostic. La difficulté de cette tâche réside principalement dans le fait de disposer d'une méthode visant à évaluer la qualité d'image de façon pertinente d'un point de vue clinique. La première étape a consisté à caractériser la qualité d'image lors d'examen musculo-squelettique. Ce travail a été réalisé en étroite collaboration avec des radiologues pour s'assurer un choix pertinent de critères de qualité d'image. Une attention particulière a été portée au bruit et à la résolution des images reconstruites à l'aide d'algorithmes itératifs. L'analyse de ces paramètres a permis aux radiologues d'adapter leurs protocoles grâce à une possible estimation de la perte de qualité d'image liée à la réduction de dose. Notre travail nous a également permis d'investiguer la diminution de la détectabilité à bas contraste associée à une diminution de la dose ; difficulté majeure lorsque l'on pratique un examen dans la région abdominale. Sachant que des alternatives à la façon standard de caractériser la qualité d'image (métriques de l'espace Fourier) devaient être utilisées, nous nous sommes appuyés sur l'utilisation de modèles d'observateurs mathématiques. Nos paramètres expérimentaux ont ensuite permis de déterminer le type de modèle à utiliser. Les modèles idéaux ont été utilisés pour caractériser la qualité d'image lorsque des paramètres purement physiques concernant la détectabilité du signal devaient être estimés alors que les modèles anthropomorphes ont été utilisés dans des contextes cliniques où les résultats devaient être comparés à ceux d'observateurs humain, tirant profit des propriétés de ce type de modèles. Cette étude a confirmé que l'utilisation de modèles d'observateurs permettait d'évaluer la qualité d'image en utilisant une approche basée sur la tâche à effectuer, permettant ainsi d'établir un lien entre les physiciens médicaux et les radiologues. Nous avons également montré que les reconstructions itératives ont le potentiel de réduire la dose sans altérer la qualité du diagnostic. Parmi les différentes reconstructions itératives, celles de type « model-based » sont celles qui offrent le plus grand potentiel d'optimisation, puisque les images produites grâce à cette modalité conduisent à un diagnostic exact même lors d'acquisitions à très basse dose. Ce travail a également permis de clarifier le rôle du physicien médical en TDM: Les métriques standards restent utiles pour évaluer la conformité d'un appareil aux requis légaux, mais l'utilisation de modèles d'observateurs est inévitable pour optimiser les protocoles d'imagerie. -- Computed tomography (CT) is an imaging technique in which interest has been quickly growing since it began to be used in the 1970s. Today, it has become an extensively used modality because of its ability to produce accurate diagnostic images. However, even if a direct benefit to patient healthcare is attributed to CT, the dramatic increase in the number of CT examinations performed has raised concerns about the potential negative effects of ionising radiation on the population. Among those negative effects, one of the major risks remaining is the development of cancers associated with exposure to diagnostic X-ray procedures. In order to ensure that the benefits-risk ratio still remains in favour of the patient, it is necessary to make sure that the delivered dose leads to the proper diagnosis without producing unnecessarily high-quality images. This optimisation scheme is already an important concern for adult patients, but it must become an even greater priority when examinations are performed on children or young adults, in particular with follow-up studies which require several CT procedures over the patient's life. Indeed, children and young adults are more sensitive to radiation due to their faster metabolism. In addition, harmful consequences have a higher probability to occur because of a younger patient's longer life expectancy. The recent introduction of iterative reconstruction algorithms, which were designed to substantially reduce dose, is certainly a major achievement in CT evolution, but it has also created difficulties in the quality assessment of the images produced using those algorithms. The goal of the present work was to propose a strategy to investigate the potential of iterative reconstructions to reduce dose without compromising the ability to answer the diagnostic questions. The major difficulty entails disposing a clinically relevant way to estimate image quality. To ensure the choice of pertinent image quality criteria this work was continuously performed in close collaboration with radiologists. The work began by tackling the way to characterise image quality when dealing with musculo-skeletal examinations. We focused, in particular, on image noise and spatial resolution behaviours when iterative image reconstruction was used. The analyses of the physical parameters allowed radiologists to adapt their image acquisition and reconstruction protocols while knowing what loss of image quality to expect. This work also dealt with the loss of low-contrast detectability associated with dose reduction, something which is a major concern when dealing with patient dose reduction in abdominal investigations. Knowing that alternative ways had to be used to assess image quality rather than classical Fourier-space metrics, we focused on the use of mathematical model observers. Our experimental parameters determined the type of model to use. Ideal model observers were applied to characterise image quality when purely objective results about the signal detectability were researched, whereas anthropomorphic model observers were used in a more clinical context, when the results had to be compared with the eye of a radiologist thus taking advantage of their incorporation of human visual system elements. This work confirmed that the use of model observers makes it possible to assess image quality using a task-based approach, which, in turn, establishes a bridge between medical physicists and radiologists. It also demonstrated that statistical iterative reconstructions have the potential to reduce the delivered dose without impairing the quality of the diagnosis. Among the different types of iterative reconstructions, model-based ones offer the greatest potential, since images produced using this modality can still lead to an accurate diagnosis even when acquired at very low dose. This work has clarified the role of medical physicists when dealing with CT imaging. The use of the standard metrics used in the field of CT imaging remains quite important when dealing with the assessment of unit compliance to legal requirements, but the use of a model observer is the way to go when dealing with the optimisation of the imaging protocols.

Trasporti e sviluppo territoriale negli spazi intermedi : l'esempio della regione transfrontaliera Insubrica

Avec cette thèse de doctorat nous proposons une réflexion transversale concernant les relations entre infrastructures de transport et développement territorial dans des espaces dits « intermédiaires ». Le concept d'espace intermédiaire, relativement nouveau en géographie, est conçu en fonction d'une double approche : celle des infrastructures où les espaces intermédiaires constituent des zones de transit obligées entre des pôles urbains hiérarchiquement supérieurs (par rapport une échelle horizontale) et celle des frontières où les espaces intermédiaires constituent des territoires de coopération entre différents niveaux politico-institutionnels (par rapport à une échelle verticale). Cette problématique de recherche est traitée aussi bien du point de vue théorique qu'avec des études de cas portant sur les effets des nouvelles infrastructures de transports dans la région transfrontalière insubrique (entre le Canton du Tessin et la Lombardie). L'objectif visé est de défendre un scénario d'organisation spatiale polycentrique à plusieurs niveaux comme solution pour le développement durable et cohérent de ces espaces intermédiaires. Ainsi, pour le « niveau macro », nous proposons une analyse des changements d'accessibilité spatiale et des potentiels de développement territorial pour les agglomérations concernées par la mise en service du nouveau tunnel ferroviaire de base du Monte Ceneri (TBC) et de la nouvelle ligne Lugano/Como-Mendrisio-Varese-Malpensa (FMV) à l'horizon 2020. Pour le « niveau meso », nous analysons les effets de la nouvelle ligne FMV en termes de potentiel de densification polycentrique autours des gares ferroviaires. Pour le « niveau micro », nous proposons une analyse sur les comportements de mobilité ainsi que des améliorations ciblées du système de transport pour la ville de Mendrisio visant à promouvoir le développement polycentrique de cette commune. De plus, un système d'analyse permettant de mettre en lien les divers facteurs explicatifs dans l'analyse des relations entre les nouvelles infrastructures de transport et les effets sur la mobilité et le développement territorial est également élaboré et testé dans notre recherche. -- With this Ph.D. thesis we investigate the relationship between transport infrastructures and territory development inside the so called "in-between spaces". The idea of "in-between space", relatively novel in geography, is the formal outcome of a double approach: the one of the infrastructures, saying that these spaces can be described as areas of constrained transit between urban centres of superior hierarchical level (on a horizontal scale), and the one of the borders, stating that in-between spaces are areas of cooperation between various political-institutional levels. The above mentioned research issues are deepened both at theoretical and empirical level, being the latter based on field studies of the cross-boundary Western-Lombard area (between the Swiss canton of Ticino and the Italian region of Lombardy). This research pursues the goal of defending the argument that a multi-level polycentric spatial scenario can be a possible solution fora sustainable development of the above described in- between areas. From a "macro" perspective, what we submit here is an analysis on the expected changes in spatial accessibility and on the potential territorial development for the built-up areas influenced by the construction of the new train tunnel of the Monte Ceneri (TBC) and of the new railway line Lugano/Como-Mendrisio-Varese-Malpensa (FMV). At a "meso" level we analyse the effects exerted by the new FMV line taking into account the potential densification of the areas surrounding the railway stations. Finally, at a "micro" level, we analyse the mobility behaviours in the town of Mendrisio and we propose some possible improvements to the local public transport system, with the scope to promote a polycentric development of this municipality. Moreover, we developed and tested an analytic system able to define the existing links between the various explaining factors characterizing the relationship between new transport infrastructures and effects on mobility. -- With this Ph.D. thesis we investigate the relationship between transport infrastructures and territory development inside the so called "in-between spaces". The idea of "in-between space", relatively novel in geography, is the formal outcome of a double approach: the one of the infrastructures, saying that these spaces can be described as areas of constrained transit between urban centres of superior hierarchical level (on a horizontal scale), and the one of the borders, stating that in-between spaces are areas of cooperation between various political-institutional levels. The above mentioned research issues are deepened both at theoretical and empirical level, being the latter based on field studies of the cross-boundary Western-Lombard area (between the Swiss canton of Ticino and the Italian region of Lombardy). This research pursues the goal of defending the argument that a multi-level polycentric spatial scenario can be a possible solution for a sustainable development of the above described in- between areas. From a "macro" perspective, what we submit here is an analysis on the expected changes in spatial accessibility and on the potential territorial development for the built-up areas influenced by the construction of the new train tunnel of the Monte Ceneri (TBC) and of the new railway line Lugano/Como-Mendrisio-Varese-Malpensa (FMV). At a "meso" level we analyse the effects exerted by the new FMV line taking into account the potential densification of the areas surrounding the railway stations. Finally, at a "micro" level, we analyse the mobility behaviours in the town of Mendrisio and we propose some possible improvements to the local public transport system, with the scope to promote a polycentric development of this municipality. Moreover, we developed and tested an analytic system able to define the existing links between the various explaining factors characterizing the relationship between new transport infrastructures and effects on mobility.

The role of surface vertical mixing in phytoplankton distribution in a stratified reservoir

We investigated convection caused by surface cooling and mixing attributable to wind shear stress and their roles as agents for the transport of phytoplankton cells in the water column by carrying out two daily surveys during the stratified period of the Sau reservoir. Green algae, diatoms, and cryptophyceae were the dominant phytoplankton communities during the surveys carried out in the middle (July) and end (September) of the stratified period. We show that a system with a linear stratification and that is subject to weak surface forcing, with weak winds , < 4 m S (-1) and low energy dissipation rate values of the order of 1028 m2 s23 or lower, enables the formation of thin phytoplankton layers. These layers quickly disappear when water parcels mix because there is a medium external forcing (convection) induced by the night surface cooling, which is characterized by energy dissipation rates on the order of , 5x10(-8)m2s(-3). During both surveys the wind generated internal waves during the entire diurnal cycle. During the day, and because of the weak winds, phytoplankton layers rise in the water column up to a depth determined by both solar heating and internal waves. In contrast, during the night phytoplankton mixes down to a depth determined by both convection and internal waves. These internal waves, together with the wind-driven current generated at the surface, seem to be the agents responsible for the horizontal transport of phytoplankton across the reservoir.

Efeito da adição de Na2O na viscosidade e devitrificação do vidro obtido a partir de cinzas volantes e Li2O

Glass-ceramic materials can be produced by the addition of LiO2 to fly ashes disposible in Southern Brazil. These glass-ceramics are based on the Al2O3-SiO2-Li 2O system. The high viscosity of the obtained glasses, however, makes forming useful articles with these materials difficult. In this study we investigate the effect of adding low cost Na2CO3 on the melt viscosity and on the nature of the developed crystalline phases. It was intended that the ultimate crystalline phase (LiAlSi3O8) should not be altered. With additions up to 3 wt. % Na2CO3, the viscosity was apparently lowered and no new crystalline phase were detected.