O eggbeater (EB) é uma habilidade fundamental utilizada no polo aquático e no nado sincronizado com a finalidade de sustentação e deslocamentos. Sabe-se como o EB deve ser executado para ser mais eficiente, mas não é encontrada metodologia de ensino para o mesmo. O objetivo deste estudo foi verificar os efeitos de uma intervenção de ensino sobre parâmetros de desempenho de EB. Participaram 15 crianças de ambos os sexos (idade: 8,13 ± 1,68 anos) adaptadas ao meio aquático. O período de intervenção foi composto por 12 aulas com sequências de exercícios específicos para o ensino do EB. Na avaliação pré-intervenção foi realizada antropometria e um teste de impulsão vertical em terra para estimar a potência dos membros inferiores (PotMI). Os testes na água foram aplicados antes e após o período de intervenção. Foram realizados dois testes na água: o teste de EB de suporte, sob máxima intensidade, com duração de 10 s, para obter as variáveis distância média mantida entre os joelhos (DJs), variação vertical do quadril (Vvq) e sobreposição das fases de in-kick (SEB); e o teste de alçada (impulsão vertical na água), em três tentativas, para obter as variáveis altura absoluta da alçada (Hegg) e altura relativa da alçada (HRegg). Em ambos os testes, foram obtidas e posteriormente analisadas imagens de vídeo gravadas no plano frontal em relação ao executante. Adotou-se para a análise do teste de EB de suporte os seis primeiros ciclos completos de EB. Resultados: DJs e Vvq não apresentaram diferença entre os momentos pré e pós-período de intervenção. Foi encontrada diferença estatisticamente significativa para SEB, sendo, respectivamente, as médias pré e pós de 43,5 ± 29% e 20,1 ± 9%. Hegg e HRegg não apresentaram diferenças entre os momentos pré e pós-período de intervenção. De maneira geral, os resultados indicaram que as crianças que participaram do presente estudo melhoraram a técnica de execução do eggbeater a partir da análise da sobreposição. / The eggbeater kick (EB) is a fundamental skill used in water polo and synchronized swimming in order to support and to displace. It is known how the EB must be performed to be more efficient, but non teaching methodology is found for the same. The aim of this study was to investigate the effects of a teaching intervention on EB performance parameters. Fifteen children of both genders (age: 8.13 ± 1.68 years) adapted to the aquatic environment, participated in this study. The intervention period was composed by 12 lessons with specific sequences of exercise for EB teaching. In the pre-intervention period, anthropometric data were obtained and vertical jump test was carried out on land to estimate the power of the lower limbs (PotMI). Two tests in water were performed on the water, both applied before and after the intervention period: the EB support test under maximum intensity, lasting 10 s, for the variables mean distance maintained between the knees (DJs), vertical variation of the hip (Vvq) and overlapping in-kick phases (SEB); and the vertical jump test in water to get the variables absolute height (Hegg) and the relative height (HRegg). In both tests video images were obtained and analyzed from the frontal plane in relation to the performer. Six complete cycles of EB were analyzed in the EB support test. Results: DJs and Vvq showed no difference between pre-and post-intervention period. Statistically significant difference was found for SEB, being, respectively, pre-and post, 29% ± 43.5 and 20.1 ± 9%. Hegg and HRegg showed no differences between pre-and post-intervention period. Overall, the results indicated that children who participated in this study improved the technical execution of the eggbeater from the analysis of overlapping.

No description available.

Synchronized phasor measurements during dynamics tend to be affected by prevailing system frequency. Some major blackouts in power systems are indeed featured with very large frequency disturbance. Quantitative study done in this dissertation shows that small frequency disturbance may lead to measurement errors, and large frequency disturbance may lead to wrong measurements as well as catastrophic results if applied in system protection and control. The purpose of this dissertation is to bring up this issue, point to some possible solutions and application examples. A synchronized frequency measurement method, which has better dynamic performance, is proposed in this dissertation. Based on this accurate synchronized frequency, a phasor compensation algorithm is proposed to correct the errors due to frequency disturbance in legacy PMUs or as alternative frequency tracking algorithm in new PMUs. Phasor positioning and unbalance issues are also investigated in this dissertation. With these improved synchronized measurements, wide area protection and control can be achieved with higher reliability. As an application example, traditional preset out-of-step protection could be replaced by the adaptive out-of-step protection using wide area measurements. Real-time swing curve and real-time EEAC based adaptive out-of-step protection schemes are developed respectively in this dissertation. Numerical Simulations are performed for validation of the proposed concepts. / Ph. D.

A key input parameter to governor feedback control and stability protection of generators is the angle of the induced voltage internal to the generator. Current practice is to estimate this value using measurements from the terminals of the generator and mathematical models. This project aims to develop a system that would directly measure the internal angle of the generator using a rotary encoder on the shaft of the machine. This document describes the theory and experimental setup of this proposed system and outlines the test procedure of experimentation. / Master of Science

Master of Science / Department of Industrial & Manufacturing Systems Engineering / Todd W. Easton / Integer programs (IPs) are mathematical models that can provide an optimal solution to a variety of different problems. They have been used to reduce costs and optimize organizations. Additionally, IPs are NP-complete resulting in many IPs that cannot be solved. Cutting planes or valid inequalities have been used to decrease the time required to solve IPs. Lifting is a technique that strengthens existing valid inequalities. Lifting inequalities can result in facet defining inequalities, which are the theoretically strongest valid inequalities. Because of these properties, lifting procedures are used in software to reduce the time required to solve an IP. The thesis introduces a new algorithm for exact synchronized simultaneous uplifting over an arbitrary initial inequality for knapsack problems. Synchronized Simultaneous Lifting (SSL) is a pseudopolynomial time algorithm requiring O(nb+n[superscript]3) effort to solve. It exactly uplifts two sets simultaneously into an initial arbitrary valid inequality and creates multiple inequalities of a particular form. This previously undiscovered class of inequalities generated by SSL can be facet defining. A small computational study shows that SSL is quick to execute, requiring on average less than a quarter of a second. Additionally, applying SSL inequalities to a knapsack problem enabled commercial software to solve problems that it could not solve without them.

La réplication de l'ADN chez les eucaryotes commence lorsque le complexe de reconnaissance de l'origine (ORC) se lie à l'ADN puis recrute les facteurs nécessaires à la duplication du génome. Bien que les mécanismes biochimiques et les facteurs impliqués dans l'initiation de la réplication semblent être conservés, les séquences d'ADN (les origines de réplication) sur lesquelles ces événements ont lieu ne le sont pas. L'ensemble des données connues suggèrent fortement un rôle prépondérant de la mise en place des origines de réplication dans la structuration du génome et l'organisation des autres processus cellulaires lors de la différenciation. Comprendre la coordination de ces processus in vivo et au cours du développement est primordial pour déchiffrer la régulation cellulaire dans son contexte réel. Le modèle du développement embryonnaire du nématode C.elegans constitue un outil génétique de premier choix pour l'étude de la mise en place des origines de réplication au cours du développement. Au cours de ma thèse, j'ai dû premièrement développer une technique de culture de C.elegans synchronisée en grosse échelle, afin d'obtenir le matériel nécessaire pour identifier les origines de réplication. Cette technique nous a aussi permis de caractériser, pour la première fois, la croissance synchronisée en bioréacteur d'un métazoaire. D'autre part, l'étude des origines de réplication a révélé une distribution hétérogène des origines de réplication dans les chromosomes qui corrèle avec des domaines de certaines marques épigénétiques, une corrélation avec des séquences d'ADN capables de former des structures cruciformes de l'ADN, ainsi comme une confirmation de la corrélation avec la transcription. Nous avons aussi vu que la corrélation de origines de réplication avec des CpG, est fortement établie après le début de la gastrulation, et que l'association avec des éléments fonctionnels spécifiques du génome, comme les operons, est perdu une fois la transcription embryonnaire deviens nécessaire après la gastrulation. L'ensemble de résultats suggèrent fortement un changement dans l'organisation des origines de réplication après gastrulation, qui corrèle avec des éléments fonctionnels du génome. / Eukaryotic DNA replication begins when the origin recognition complexes (ORC) binds to DNA and recruits the necessary factors for genome duplication. Even though, biochemical mechanisms as well as the factors involved seem to be well conserved, the DNA sequences (replication origins) where these events take place are not. The known data strongly suggest that replication origins establishment may play an important role in genome structuring as well as in the organization of other cellular processes during cell differentiation. To understand how these processes are coordinated in vivo and during development, is essential for deciphering cellular regulation in its real context. C.elegans embryonic development is a genetic tool of first choice for studying replication origins in vivo and their correlation with other genome features and processes during development.During my thesis and with the aim of obtaining enough material for the replication origins identification method, I've had to develop a new technique of synchronized high-scale liquid culture of the nematode C.elegans. This technique has allowed the characterization for the first time of the synchronize growth of a metazoan in bioreactor. Furthermore, the study of replication origins has revealed a heterogenic distribution of replication origins along chromosomes that correlates with specific epigenetic marks. Moreover, replication origins are strongly associated with specific DNA structures able to form cruciforms, and we have confirmed the correlation of replication origins and transcription. This study also show that the association of replication origins with CpGs is greatly increased after gastrulation, and that the association with some genetic elements, such as operons, is reduced after gastrulation begins. Taken together these results show a change of replication origins before and after cell differentiation during embryonic development that correlate with functional genome elements.

Preterm birth (&lt; 37 complete gestation weeks, GWs) is the single most prominent risk factor for the development of cerebral palsy (CP). This is due to the immature physiological state of the preterm born infant which increases the risk of brain lesions. In CP, prominent sensorimotor, cognitive, and perceptual deviations are manifested with varying degrees of functional impairment. Although most children born preterm (PT) do not develop CP, sensorimotor and cognitive deficits are frequently reported in the absence of major disability. To date, few studies have focused on detailed kinematic analysis of upper-body goal-directed movements and how aspects of movement organization and control are related to hand preference, intellectual function, gestational age, and sex within groups of prematurely born children. Further, studies evaluating effects of sensorimotor training in persons with CP is needed and of importance as positive effects on movement performance may increase individual autonomy as a consequence.To investigate the prevalence of non-right hand preference within children born preterm (PT) in comparison to children born fullterm (FT), a meta-analysis and literature review were performed (study I). It was shown that children born PT had increased rates of non-right handedness (NRH) corresponding to 22% compared to 12% in the FT group (odds ratio 2.12). In study II, hand preference and side specific movement performance in children born PT (. 35 GWs) compared to an age matched group of children born FT were investigated. All included participants were 4-8 years of age without major disability. Movement performance was studied through detailed kinematic registrations of the head, arm, and hand during a goal-directed task and hand preference through observations of the hand used when manipulating different objects. On a group level, the children born PT, specifically those born &lt; 33 GWs, showed an increased rate of NRH, weaker strength of hand preference, and a lack of side specificity in terms of movement kinematics. In general, the children born &lt; 33 GWs also displayed poorer movement organization and control as expressed by longer durations, less smooth and longer distances of the movement trajectories. These findings imply that preterm birth has long term effects on sensorimoror organization and function, possibly reflecting a developmental delay and/or a persistent effect that may be associated with the increased risk of deviations in brain development.In study III, associations between movement performance, assessed with the same task as in study II, and intellectual function (Wechsler Intelligence Scale for Children, 4th ed; WISC-IV) were studied. This study included a subsample of the children from study II at 6-8 years of age. The results showed a link between movement organization and general intellectual functioning (IQ), when controlling for effects of GA and sex, for the PT born but not the FT born children. These findings suggest shared neural underpinnings and interrelated development of motor and intellectual functions.In study IV, kinematic analysis of upper-body movements and subjective experience of change in upper-body function were applied before and after a period of synchronized metronome training (SMT) in adolescents with varying degree of CP to study the effects of this type of training. The SMT method applied entailed elements of movement timing and rhythmic activation coupled with feedback and was hypothesized to train sensorimotor integration. It was found that SMT did improve, to varying degrees, the organization and control of movements in adolescents with CP. The participants with more severe forms of CP reported substantial effects in daily living activities. The observed effects of SMT warrant further study of specific effects on movement planning, biomechanical constraints, and attention.The relation between hand preference and movement performance, movement performance and intellectual function, and aspects related to the SMT method applied in study IV are discussed. Specifically, the lack of side specific movement organization within the group of children born PT is discussed from perspectives of motor learning, plasticity, and genetics. The relations between movement performance and intellectual functions are considered and ideas for how this association could be tested are given. With relation to study IV, the functions trained by the specific SMT method applied and the accessibility of individuals with different degree of CP is discussed. Methodological considerations and ideas for future research approaches within these areas are presented. / Varje år föds det drygt 100 000 barn i Sverige. Cirka 5% av dessa barn föds för tidigt, det vill säga före 37 kompletta graviditetsveckor. Av de barn som föds för tidigt har majoriteten en gestationsålder (antalet graviditetsveckor) över 33 veckor (Medicinska födelseregistret, 2009). Omkring 8% av barn som föds för tidigt diagnosticeras senare med cerebral pares (CP) (Ancel, et al., 2006) och omkring hälften av personer med diagnosen CP har en för tidig födelsehistorik (Beaino et al., 2010). CP är ett paraplybegrepp som innefattar ett flertal icke-progressiva motoriska utvecklingsavvikelser av olika karaktär och funktionsnedsättningsgrad, orsakade av hjärnskador som inträffar under fosterlivet eller vid förlossningen. Vanligtvis så påverkas även sensorik, perception, kognition, och beteende negativt (Rosenbaum, Paneth, Leviton, Goldstein, &amp; Bax, 2008). En prematur födsel utgör den största riskfaktorn för utvecklingen av CP där risken är störst för de barn som föds allra tidigast (Murphy, Sellers, MacKenzie, Yudkin, &amp; Johnson, 1995). De allra flesta barn som föds för tidigt drabbas dock inte av grav sensomotorisk funktionsnedsättning som till exempel CP trots att det finns en ökad risk för hjärnskador hos denna grupp. Ett flertal studier har ändå visat att barn som fötts för tidigt och ej diagnosticerats med CP i högre grad än fullgångna barn generellt har både motoriska (e.g., Williams et al., 2010) och kognitiva (e.g., Bhutta, 2002) funktionsnedsättningar.I dagsläget så har endast ett fåtal studier fokuserat på att i detalj studera organiseringen av målinriktade hand-armrörelser hos barn som fötts för tidigt. Av dessa har merparten fokuserat på spädbarn i syfte att finna tidiga markörer för sensomotoriska avvikelser. Då de sensomotoriska problemen hos för tidigt födda barn kvarstår i skolåldern och i vissa fall är så diskreta att de upptäcks först när barnet börjar skolan så kan rörelseanalys vara en metod som kan bidra till ökad förståelse och kunskap om hur den sensomotoriska påverkan uttrycks hos äldre barn. Ett av syftena med denna avhandling var således att noggrant studera organiseringen av huvud-, arm-, och handrörelser under en målinriktad handling hos barn som fötts för tidigt jämfört med en grupp barn i samma åldrar (4-8 år) som fötts efter fullgången graviditet. Av intresse är att studera relationen mellan aspekter associerade med rörelseorganisation och handpreferens, intellektuell förmåga, gestationsålder, samt kön. Då barn och ungdomar med CP utgör den största diagnosgruppen som behandlas inom barn- och ungdomshabiliteringar (Odding, Roebroeck, &amp; Stam, 2006) finns det ett stort behov av att utvärdera effekten av redan existerande träningsmetoder. Ett ytterligare syfte med detta avhandlingsarbete var att utvärdera både kort- och långtidseffekter av en etablerad träningsmetod (synchronized metronome training; SMT) som antas främja den sensomotoriska integreringen hos ungdomar (12-17 år) med diagnosen CP. Effekterna av denna träningsmetod utvärderades med hjälp av detaljerad rörelseanalys samt ett frågeformulär gällande individens upplevelse av förändring.Då barn som fötts för tidigt i vissa studier har visat sig ha en ökad prevalens av icke-högerhänthet, det vill säga fler som är vänsterhänta eller tvåhänta (ambidextra), så utfördes en systematisk litteraturgenomgång och en metaanalys för att undersöka detta fenomen närmare (studie I). I denna studie visade det sig att barn som fötts för tidigt i större utsträckning var icke-högerhänta jämfört med barn som fötts efter en fullgången graviditet (odds ratio 2.12). Hos de för tidigt födda barnen var 22% icke högerhänta jämfört med 12% av de som fötts efter fullgången graviditet. Dock säger handpreferensstudier inget om hur kvaliteten på rörelser utförda med den föredragna eller icke-föredragna handen ser ut. För att undersöka sambandet mellan handpreferens och kvalitet på rörelser kopplade till den föredragna och icke-föredragna handen hos barn som fötts för tidigt, jämfört med fullgångna åldersmatchade kontroller, utfördes kinematiska rörelseanalyser samt ett testbatteri som undersöker handpreferens (studie II). Barnen utförde målinriktade rörelser, med en hand i taget, i en uppgift som ställer höga krav på öga-hand-koordination och precision. Uppgiften bestod i att plocka upp och trä så många pärlor som möjligt på en smal pinne under 30 sekunder. Denna studie visade att barnen med en för tidig födelsehistorik, speciellt de mycket för tidigt födda (före graviditetsvecka 33), i större utsträckning var klassificerade som icke-högerhänta och hade en svagare handpreferens i jämförelse med barnen som inte fötts för tidigt. De mycket för tidigt födda barnen visade även, som grupp, en sämre organisering av huvud-, arm-, och handrörelser vilket manifesterades i en ökad längd, tidsåtgång och ojämnhet av rörelsebanorna. Oavsett gestationsålder så visade den för tidigt födda gruppen barn inga sidoskillnader i kvaliteten på rörelserna vilket däremot var tydligt hos gruppen barn som fötts vid fullgången graviditet. Dock så skiljde sig gruppen barn som fötts moderat för tidigt (mellan graviditetsvecka 33 och 35) inte statistiskt signifikant åt från barnen i den fullgånget födda gruppen. Dessa resultat indikerar en långvarig effekt av för tidig födsel på sensomotorisk funktion. Den markanta påverkan som barnen som fötts före graviditetsvecka 33 uppvisade, kan tolkas som en effekt av den ökade risken för avvikelser i hjärnans utveckling.I studie III undersöktes sambanden mellan intellektuell förmåga och organiseringen av rörelser hos barn som fötts för tidigt samt hos barn som fötts efter en fullgången graviditet i 6-8 års ålder (en subgrupp ur studie II). Den intellektuella förmågan undersöktes med hjälp av Wechsler Intelligence Scale for Children, 4:e upplagan, och den kinematiska uppgiften var den samma som beskrivits ovan. Denna studie visade på skillnader i intellektuell förmåga, specifikt gällande generell intelligens samt verbal och perceptuell förmåga, där de för tidigt födda barnen hade lägre poäng än de fullgångna barnen. Viktigt att poängtera är dock att medelvärdena för gruppen för tidigt födda barn låg inom det normala spannet. Vidare så visade sig gestationsålder och generell intellektuell förmåga ha betydelse för det motoriska utförandet hos de för tidigt födda barnen, speciellt på den föredragna sidan. Kön bidrog inte till att förklara skillnader i organiseringen av rörelser. Intellektuell förmåga hade ingen relation till den sensomotoriska funktionen hos gruppen barn som fötts efter en fullgången graviditet. Detta belyser vikten av att studera kognitiva aspekter av motorisk funktion för att bättre förstå de skillnader eller avvikelser som ofta påvisas hos barn med en för tidig födelsehistorik. Dessutom skulle en sådan ansats öka kunskapen om den interrelaterade utvecklingen av motorisk och intellektuell förmåga, både ur ett beteendeperspektiv och ur ett hjärnutvecklingsperspektiv.Kinematisk rörelseanalys användes även i studie IV för att beskriva eventuella förändringar i rörelseorganisation efter SMT-träning hos ungdomar med olika typer av CP och varierande grad av funktionsnedsättning (studie IV). Ungdomarna utförde en målinriktad uppgift som bestod i att tända små lampor i sekventiell ordning. Testerna genomfördes vid tre tillfällen, före, i anslutning till avslutad SMT-träning samt 6 månader efter avslutad SMT-träning. Träningsperioden varade i 4 veckor och innefattade 12 individanpassade SMT-sessioner. Den typ av SMT-träning som användes i denna studie antas främja sensomotorisk integrering genom rytmisk aktivering och timing av rörelser mot en auditiv och visuell signal. Feedback på avvikelsen i synkronisering, och en instruktion om hur deltagaren skall uppnå bättre rörelsetiming, ges direkt både auditivt och visuellt. Denna studie visade på förändringar i rörelseorganisation och motorisk kontroll hos flertalet av deltagarna. Dessa effekter kvarstod till viss del vid uppföljningen efter 6 månader. Deltagarna med gravare funktionsnedsättning rapporterade substantiella förändringar i förmågan att delta i dagliga aktiviteter både direkt efter avslutad träning samt 6 månader senare. De rapporterade effekterna gällde ökad snabbhet, minskad muskeltonus, bättre arm-, hand- och fingerkontroll, samt ökad motivation att använda armen och handen både i träning och vardagliga aktiviteter. Dessa subjektivt upplevda förändringar tillsammans med de vi observerat i de kinematiska parametrarna utgör en grund för fortsatta studier av effekter av SMT hos denna grupp ungdomar och även hos andra grupper barn och ungdomar med motoriska problem. En ansats där effekter av SMT-metoder studeras utifrån rörelseplanering, biomekaniska restriktioner, samt uppmärksamhet skulle vara av betydelse.I avhandlingen diskuteras relationen mellan handpreferens och kvalitet på rörelser i relation till den föredragna och icke-föredragna handen, samband mellan organisering av rörelser och intellektuell förmåga, samt aspekter relaterade till SMT-metoden som applicerats i studie IV. Specifikt diskuteras avsaknaden av en sidospecifik rörelseorganisering hos gruppen barn som fötts för tidigt i relation till motorisk inlärning, hjärnans förmåga att förändra sig, och genetik. Relationen mellan organisering av rörelser och intellektuell förmåga betänks och förslag på hur detta samband kan undersökas i kommande studier ges. Vidare så diskuteras vilka funktioner som SMT-metoden tränar samt dess tillgänglighet för barn och ungdomar med olika grad av funktionsnedsättning relaterad till typ av CP diagnos. Metodologiska överväganden och idéer för framtida forskningsansatser inom dessa områden presenteras. / <p>En viktig annan finansiär är Norrbacka-Eugenia Stiftelsen som bekostade hela min forskarutbildning.</p>

The work in this thesis concerns mechanisms of excitability of neurons. Specifically, it deals with how neurons respond to input, and how their response is controlled by ion channels and other active components of the neuron. I have studied excitability in two systems of the nervous system, the hippocampus which is responsible for memory and spatial navigation, and the peripheral C–fibre which is responsible for sensing and conducting sensory information to the spinal cord. Within the work, I have studied the role of excitability mechanisms in normal function and in pathological conditions. For hippocampus the normal function includes changes in excitability linked to learning and memory. However, it also is intimately linked to pathological increases in excitability observed in epilepsy. In C–fibres, excitability controls sensitivity to responses to stimuli. When this response becomes enhanced, this can lead to pain. I have used computational modelling as a tool for studying hyperexcitability in neurons in the central nervous system in order to address mechanisms of epileptogenesis. Epilepsy is a brain disorder in which a subject has repeated seizures (convulsions) over time. Seizures are characterized by increased and highly synchronized neural activity. Therefore, mechanisms that regulate synchronized neural activity are crucial for the understanding of epileptogenesis. Such mechanisms must differentiate between synchronized and semi synchronized synaptic input. The candidate I propose for such a mechanism is the fast outward current generated by the A-type potassium channel (KA). Additionally, I have studied the propagation of action potentials in peripheral axons, denoted C–fibres. These C–fibres mediate information about harmful peripheral stimuli from limbs and organs to the central nervous system and are thereby linked to pathological pain. If a C–fibre is activated repeatedly, the excitability is altered and the mechanisms for this alteration are unknown. By computational modelling, I have proposed mechanisms which can explain this alteration in excitability. In summary, in my work I have studied roles of particular ion channels in excitability related to functions in the nervous system. Using computational modelling, I have been able to relate specific properties of ion channels to functions of the nervous system such as sensing and learning, and in particular studied the implications of mechanisms of excitability changes in diseases. / <p>QC 20102423</p>

Κατά τη διάρκεια των τελευταίων δεκαετιών, το διεθνές ενδιαφέρον για την φωτοβολταϊκή μετατροπή της ηλιακής ακτινοβολίας αυξάνει συνεχώς. Έχει δοθεί ιδιαίτερη σημασία στην ανάπτυξη φωτοβολταϊκών συστημάτων για την σύνδεσή τους με το δίκτυο, έτσι ώστε να αξιοποιείται η ηλιακή ακτινοβολία για παραγωγή ηλεκτρικής ενέργειας με τον καλύτερο δυνατό τρόπο. Στην παρούσα εργασία γίνεται μελέτη των φωτοβολταϊκών συστημάτων παραγωγής ηλεκτρικής ενέργειας και σκοπός αυτής είναι η κατασκευή ενός συστήματος μετατροπής συνεχούς τάσης σε εναλλασσόμενη για τη διασύνδεση μιας πηγής συνεχούς τάσης με το μονοφασικό δίκτυο. Το σύστημα αυτό αποτελείται από ένα ηλεκτρονικό μετατροπέα ισχύος διπλής βαθμίδας. Το πρώτο τμήμα είναι ένας μετατροπέας συνεχούς τάσης σε συνεχή τάση υψηλότερης τιμής. Συγκεκριμένα, ο μετατροπέας αυτός ανυψώνει την τάση του φωτοβολταϊκού συστήματος του Εργαστηρίου στα 400V. Στη συνέχεια υπάρχει το δεύτερο τμήμα, αποτελούμενο από το σύστημα μετατροπής συνεχούς τάσης σε εναλλασσόμενη, το οποίο μετατρέπει την εισερχόμενη συνεχή τάση των 400V σε εναλλασσόμενη τάση συχνότητας 50 Hz και ενεργού τιμής 220V. Η διπλωματική αυτή εργασία πραγματοποιήθηκε στο Εργαστήριο Ηλεκτρομηχανικής Μετατροπής Ενέργειας του Τμήματος Ηλεκτρολόγων Μηχανικών και Τεχνολογίας Υπολογιστών της Πολυτεχνικής Σχολής του Πανεπιστημίου Πατρών, υπό την επίβλεψη του Ομότιμου Καθηγητή Δρ.-Μηχ. Αθανασίου Σαφάκα. Αρχικά, αναλύεται η αρχή λειτουργίας των ηλιακών κυττάρων και περιγράφονται οι υπάρχουσες τεχνολογίες τους. Έπειτα γίνεται αναφορά στα φωτοβολταϊκά συστήματα και τους τρόπους που μπορεί να χρησιμοποιηθούν, δηλαδή συνδεδεμένα με το δίκτυο ή αυτόνομα. Στη συνέχεια, αναφέρονται και αναλύονται διάφορες τεχνικές συγχρονισμού μετατροπέων με το μονοφασικό δίκτυο και τρόποι ρύθμισης της ενεργού και αέργου ισχύoς που παρέχεται από τις πηγές ενέργειας στο δίκτυο. Παρατίθενται στοιχεία του μετατροπέα συνεχούς τάσης σε συνεχή και γίνεται η μελέτη του μονοφασικού αντιστροφέα που πρόκειται να κατασκευαστεί. Επιπρόσθετα γίνεται προσομοίωση του συστήματός στο λογισμικό MATLAB/Simulink. Συγκρίνεται η λειτουργία του αντιστροφέα με τη μέθοδο παλμοδότησης SPWM (Ημιτονοειδής Διαμόρφωση του Εύρους Παλμών) με διπολική και μονοπολική τάση εξόδου και παρουσιάζονται αποτελέσματα της προσομοίωσης για παραλληλισμό του συστήματος με το δίκτυο και προσφορά ισχύος από πηγή συνεχούς τάσης προς το δίκτυο. Αναλύονται τα τεχνικά χαρακτηριστικά του αντιστροφέα που κατασκευάστηκε, καθώς και ο τρόπος κατασκευής των απαραίτητων κυκλωμάτων για την οδήγηση του. Τέλος, παρατίθενται πειραματικά αποτελέσματα από τη λειτουργία του συστήματος. / During the last decades, the international interest in the photovoltaic conversion of solar radiation is increasing. Special attention has been given to the development of photovoltaic systems for their connection to the utility grid, in order to use solar radiation for electricity generation in the best possible way. In this diploma thesis, the photovoltaic power generation is studied and the purpose of this work is to construct a single phase grid connected dc/ac converter system in order to connect a dc voltage source to the grid. This system consists of a dual-stage electronic power converter. The first part is a dc-dc converter, which converts a source of direct current (dc) from one voltage level to another, with an output voltage greater than its input voltage. Specifically, the dc/dc converter increases the voltage of the photovoltaic system, which is installed on the laboratory, to 400V DC. The second part consists of a dc/ac inverter, which converts the incoming voltage of 400V DC to 220V AC at 50Hz. The work presented on this diploma thesis was carried out at the Laboratory of Electromechanical Energy Conversion, Department of Electrical and Computer Engineering, University of Patras, under the supervision of Emeritus Professor Dr.-Ing. Athanasios Safacas. Initially, the working principle of solar cells is analysed and its current technologies are described. Then, reference is given to the photovoltaic systems and their applications, i.e. stand-alone PV systems and grid-connected PV systems. Next, reference and analysis are given to the various grid synchronization techniques for single phase inverter systems and control methods to regulate the active and reactive power supplied from sources of energy into the grid. Data are presented about the dc/dc converter and the study of the single-phase inverter to be constructed. Additionally, the system is simulated with MATLAB/Simulink software and the simulation results of the specific system are presented. A comparison of the operation of the inverter is made using sinusoidal pulse width modulation technique (“SPWM”) with bipolar and unipolar output voltage and simulation results of the grid connected converter system are presented. The technical characteristics of the constructed inverter and the design of its necessary integrated circuits are analysed. Finally, experimental results from the operation of the grid connected dc/ac inverter are presented.

Title: Compensatory exercise in synchronized swimming Aims: The aim of this diploma thesis is to find out the effect of movement intervention on compensating the deviations in the posture related to muscle imbalance and to influence the feeling of muscular tension of the back muscles in the girls of synchronized swimming TJ Tábor. Methods: The diploma thesis is elaborated by the form of qualitative research with elements of quantitative research. The experiment was attended by eight probes with deviations in the posture. A physical intervention in the form of compensatory exercise was introduced to influence the muscular dysbalance in the fuselage region. The research was conducted from October 2016 to May 2017. The research methods consisted of the examination of aspects using a plumb line in the sagittal and frontal plane. Depending on the subjective sensation, probands marked the muscular tension of the back muscles on the modified VAS. Results: The obtained data were processed by the statistical method (relative analysis). The results showed a positive effect on the body's position in the sagittal and frontal plane. Interventions also positively influenced subjective feelings of muscle tension. Keywords: synchronized swimming, posture, compensatory exercise, muscle tension, VAS modification