Η ψηφιακή τεχνολογία έχει διεισδύσει πλήρως στην περιοχή της Ακουστικής και της Τεχνολογίας Ήχου, όπως επίσης και σε όλους σχεδόν τους κλάδους της σύγχρονης επιστήμης και της τεχνολογίας. Στον τομέα των ηλεκτρονικών για ηχητικές εφαρμογές, ιδιαίτερα καθοριστικό ρόλο κατέχουν οι ενι- σχυτές. Σκοπός της εργασίας αυτής, είναι να παρουσιάσει το λειτουργικό μοντέλο ενός ψηφιακού ενι- σχυτή Class-D για ηχητικά σήματα, το οποίο προσομοιώθηκε και λειτούργησε σε περιβάλλον Matlab & Simulink. Στο τέλος παρουσιάζονται τα αποτελέσματα χρήσιμων μετρήσεων για σημαντικούς δεί- κτες της ηλεκτροακουστικής όπως η Απόκριση Συχνότητας, Total Harmonic Distortion(THD), Total Harmonic Distortion plus Noise (THD+N) ως προς τη συχνότητα και ως προς την ισχύ, από όπου βγαίνουν συμπεράσματα σχετικά με την ποιότητα και την απόδοση της συγκεκριμένης τεχνολογίας υλοποίησης. / DigitalTechnology has been fully into Acousctics and Audio Technology,as in virtually all branches of modern science and technology.In audio electronics applications, amplifiers have a significant role. The purpose of this thesis is to present the functional model of a digital Class-D amplifier for audio signals, which has been simulated and run in Matlab & Simulink environment. Finally the results of measurements relating to some important electroacoustics indexes like Frequency Response, Total Harmonic Distortion (THD), Total Harmonic Distortion plus Noise (THD+N), relative to the audio signal’s frequency and power, are presented and lead to some conclusions concerning the quality and efficiency of this implementation technology.

Στην παρούσα διπλωματική εργασία μοντελοποιήθηκε και αναλύθηκε η λειτουργία και η συμπεριφορά ενός τριφασικού ασύγχρονου κινητήρα τροφοδοτούμενου μέσω ηλεκτρονικού μετατροπέα τόσο στην περίπτωση της «υγιούς» μηχανής, όσο και στην περίπτωση μηχανής η οποία παρουσίαζε σφάλματα στον κλωβό. Πιο συγκεκριμένα, με την βοήθεια προγράμματος πεπερασμένων στοιχείων και ειδικότερα πραγματοποιώντας ανάλυση στις δύο διαστάσεις, προσομοιώσαμε την τάση εξόδου ενός αντιστροφέα πηγής τάσης με λειτουργία διαμόρφωσης εύρους παλμών μέσω κώδικα που σχεδιάσαμε, και στην συνέχεια τροφοδοτήσαμε με τους παλμούς που παρήχθησαν τα τυλίγματα του στάτη της ασύγχρονης υπό μελέτη μηχανής. Ακολούθως με την χρήση του προαναφερθέντος προγράμματος έγινε ηλεκτρομαγνητική ανάλυση, της μηχανής. Παρήχθησαν οι κυματομορφές των βασικότερων μεγεθών της μηχανής και πραγματοποιήσαμε με την βοήθεια του προγράμματος MATLAB/SIMULINK(R2008A) , αναλύσεις fourier στα φασικά ρεύματα και στις φασικές τάσεις του στάτη, τόσο για το μοντέλο της ασύγχρονης μηχανής χωρίς σφάλματα του δρομέα όσο και για το μοντέλο με σφάλματα. Για την διάγνωση του σφάλματος χρησιμοποιήθηκε η μέθοδος MCSA(motor current signature analysis) καθώς και η ανάλυση των αρμονικών στο φάσμα της ροπής. Αναλυτικότερα, στο πρώτο κεφάλαιο γίνεται μια εισαγωγή στα κατασκευαστικά χαρακτηριστικά καθώς και στις βασικές μεθόδους λειτουργίας της ασύγχρονής μηχανής, ενώ γίνεται ιδιαίτερη αναφορά στον έλεγχο κινητήρων γενικότερα όπως επίσης και στην λειτουργία αυτών σε περίπτωση σφαλμάτων. Στο δεύτερο κεφάλαιο περιγράφονται οι ηλεκτρονικοί μετατροπείς ισχύος για συστήματα οδήγησης ασύγχρονων κινητήρων. Ειδικότερα, παρουσιάζεται συνοπτικά η λειτουργία του τριφασικού ανορθωτή, ενώ ιδιαίτερη αναφορά γίνεται στον τριφασικό αντιστροφέα. Πιο συγκεκριμένα, παρουσιάζονται τα κατασκευαστικά και τα λειτουργικά χαρακτηριστικά του αντιστροφέα πηγής τάσης, γίνεται εκτενής αναφορά στην λειτουργία του με διαμόρφωση εύρους παλμών (PWM mode of operation) ενώ κυρίως αναλύεται η συμπεριφορά του στην γραμμική περιοχή λειτουργίας του(0<modulation index<0.907), όπου και μας ενδιαφέρει. Στο τρίτο κεφάλαιο παρουσιάζονται τα αποτελέσματα της εξομοίωσης του ασύγχρονου τριφασικού κινητήρα, με και χωρίς σφάλμα στον δρομέα όπως αυτά προέκυψαν από την ανάλυση που πραγματοποιήθηκε με χρήση του προγράμματος πεπερασμένων στοιχείων. Παράλληλα δίνεται ανάλυση του κώδικα που σχεδιάστηκε για την προσομοίωση της τάσης εξόδου ενός τριφασικού αντιστροφέα με λειτουργία PWM για την τροφοδοσία των τυλιγμάτων της μηχανής μας, γεγονός το οποίο και αποτελεί κυρίαρχο περιεχόμενο της παρούσας διπλωματικής εργασίας. Στο τέταρτο κεφάλαιο γίνεται αναφορά στο πειραματικό σκέλος της διπλωματικής εργασίας. Περιγράφεται δηλαδή η πειραματική διάταξη που υλοποιήθηκε στο εργαστήριο χρησιμοποιώντας δύο όμοιους τριφασικούς ασύγχρονους κινητήρες κλωβού, ένα με σφάλμα στο δακτύλιο βραχυκύκλωσης και ένα χωρίς σφάλμα, ενώ ταυτόχρονα παρατίθενται οι κυματομορφές του ρεύματος στάτη στις οποίες έγινε ανάλυση FFΤ έτσι ώστε να εντοπιστούν οι συχνότητες στις οποίες εισάγονται αρμονικές λόγω του σφάλματος στο δακτύλιο βραχυκύκλωσης και να γίνει έτσι η διάγνωση του σφάλματος. Στο πέμπτο κεφάλαιο πραγματοποιούμε επεξεργασία των πειραματικών αποτελεσμάτων καθώς και των αποτελεσμάτων τα οποία προκύπτουν από την εξομοίωση των δύο κινητήρων από το πρόγραμμα πεπερασμένων στοιχείων OPERA- 2D. Συγκεκριμένα πραγματοποιούμε ανάλυση FFT μέσω του προγράμματος MATLAB/SIMULINK(R2008A) στις κυματομορφές του ρεύματος στάτη και των τάσεων αυτού καθώς και της ροπής για τους δύο κινητήρες τόσο στην περίπτωση ημιτονοειδούς τροφοδοσίας τους, όσο και στην περίπτωση που τροφοδοτούνται με την τάση εξόδου ενός inverter με pwm διαμόρφωση. Από τα αποτελέσματα που προκύπτουν εξάγουμε σημαντικά συμπεράσματα όσο αφορά τη λειτουργία των δύο κινητήρων ενώ ταυτόχρονα επιτυγχάνεται και μια σύγκριση των πειραματικών αποτελεσμάτων με τα αποτελέσματα της εξομοίωσης. Τέλος, στο έκτο κεφάλαιο, το οποίο αποτελεί και το παράρτημα της παρούσας διπλωματικής εργασίας, δίνεται η μοντελοποίηση μέσω του SIMULINK του αντιστροφέα πηγής τάσης με λειτουργία PWM, ενώ παράλληλα γίνεται αναφορά στις διακοπτικές απώλειες των ασύγχρονων κινητήρων όταν αυτοί τροφοδοτούνται με την τάση εξόδου ενός inverter με pwm διαμόρφωση, αλλά και των αντιστροφέων πηγής τάσης, οι οποίοι αποτέλεσαν και κυρίαρχο αντικείμενο μελέτης . / This diploma thesis forms a study on modeling an analyzing an induction motor by using a faulty detection. These motors are often used in industrial applications thanks to their usability and their robustness. However, nowadays optimisation of production becomes so critical that the conceptual reliability of the motor is not suffcient anymore. In this thesis different implementations of control algorithm were examined along with the most important PWM modulation techniques. The cage induction motor is modeled with the space and time discretized finite element analysis using the program OPERA and developing an appropriate model for the motor in 2 dimensions. The fft analysis was performed by developing an appropriate algorithm for the system at the Matlab Tests have been conducted on an experimental construction in order to confirm the theoretically expected operational characteristics of the system.

Embedded environment imposes severe constraints of system resources on embedded applications. Performance, memory footprint, and power consumption are critical factors for embedded applications. Meanwhile, the data in embedded applications demonstrate unique properties. More specifically, narrow width data are data representable in considerably fewer bits than in one word, which nevertheless occupy an entire register or memory word and streaming data are the input data processed by an application sequentially, which stay in the system for a short duration and thus exhibit little data locality. Narrow width and streaming data affect the efficiency of register, cache, and memory and must be taken into account when optimizing for performance, memory footprint, and power consumption.This dissertation proposes methods to efficiently handle narrow width and streaming data in embedded applications. Quantitative measurements of narrow width and streaming data are performed to provide guidance for optimizations. Novel architectural features and associated compiler algorithms are developed. To efficiently handle narrow width data in registers, two register allocation schemes are proposed for the ARM processor to allocate two narrow width variables to one register. A static scheme exploits maximum bitwidth. A speculative scheme further exploits dynamic bitwidth. Both result in reduced spill cost and performance improvement. To efficiently handle narrow width data in memory, a memory layout method is proposed to coalesce multiple narrow width data in one memory location in a DSP processor, leading to fewer explicit address calculations. This method improves performance and shrinks memory footprint. To efficiently handle streaming data in network processor, two cache mechanisms are proposed to enable the reuse of data and computation. The slack created is further transformed into reduction in energy consumption through a fetch gating mechanism.

Slices are digraphs that can be composed together to form larger digraphs.In this thesis we introduce the foundations of a theory whose aim is to provide ways of defining and manipulating infinite families of combinatorial objects such as graphs, partial orders, logical equations etc. We give special attentionto objects that can be represented as sequences of slices. We have successfully applied our theory to obtain novel results in three fields: concurrency theory,combinatorics and logic. Some notable results are: Concurrency Theory: We prove that inclusion and emptiness of intersection of the causalbehavior of bounded Petri nets are decidable. These problems had been open for almost two decades. We introduce an algorithm to transitively reduce infinite familiesof DAGs. This algorithm allows us to operate with partial order languages defined via distinct formalisms, such as, Mazurkiewicztrace languages and message sequence chart languages. Combinatorics: For each constant z ∈ N, we define the notion of z-topological or-der for digraphs, and use it as a point of connection between the monadic second order logic of graphs and directed width measures, such as directed path-width and cycle-rank. Through this connection we establish the polynomial time solvability of a large numberof natural counting problems on digraphs admitting z-topological orderings. Logic: We introduce an ordered version of equational logic. We show thatthe validity problem for this logic is fixed parameter tractable withrespect to the depth of the proof DAG, and solvable in polynomial time with respect to several notions of width of the equations being proved. In this way we establish the polynomial time provability of equations that can be out of reach of techniques based on completion and heuristic search. / <p>QC 20131120</p>

A number of parameters have been identified as characteristic of the walking pattern in patients with INPH. Most of these have been identified through qualitative surveys and manually conducted test batteries. In order to obtain quantitative, standardized and objective measures, which enable studies based on larger patient populations and comparable results, there is a need for a user-friendly system that can measure specific key parameters over time in a reliable manner in everyday clinical work. Step height, width and the variability in the gait cycle are such parameters which are interesting research areas for this group of patient. Problems with balance and gait are very common in other patient groups as well, particularly in neurological diseases such as Parkinson's disease, multiple sclerosis and stroke. This is the reason that the development of this gait analyzer is performed. Giving access to a simple and objective method for estimating gait and balance ability in clinical routine investigations would increase the ability to provide the right kind of treatment, confirm treatment results, and conducting larger research studies. Therefore, this equipment can contribute to the assessment of diseases which contain impaired gait. As a first test of the usability and for the validation of accuracy and repeatability of the equipment a group of healthy volunteers was used. Results from tests on healthy subjects show god repeatability between measurements, for step width at normal gait the difference was -0,2 ±0,34 cm (mean, ±SD) and step height 0,69 ±3,34 cm. The stride time variability in the healthy group where very small 0,00048 ±0,00028 s2 with a difference between test of 0,000019 ±0,00038 s2. Three pilot patients have been tested where we have clearly seen indications of increased stride time variability and reduced step height.

Reinforcement of concrete flexural components has been traditionally provided by steel rebar; however, durability concerns and life maintenance costs of this product have powered the emergence of fibre reinforced polymers (FRP) as reinforcement in concrete. FRP products hold tremendous promise but their application can be constrained due to design challenges resulting from a reduced modulus of elasticity. The ability to meet serviceability behavior, such as crack width and deflection, is commonly the limiting factor for design. Therefore, the area of FRP reinforcement provided is often greater than the amount required for strength alone and this has significant impacts on the project economics. The bond dependent coefficient (kb) of FRP is required for serviceability design purposes in order to account for the bonding capability of FRP to concrete. The values of this coefficient reported in experimental studies are highly variable, resulting in unreliable crack response predictions. Therefore, a more consistent interpretation and calculation must be found for the bond dependent coefficient due to its critical importance in design. The bond dependent coefficient, as well as physical parameters which influence crack width in GFRP reinforced concrete, were investigated experimentally in this study using a total of 33 specimens. The test procedure was taken from a procedure being developed by the American Concrete Institute (ACI) Committee 440 and was evaluated and modified as required during testing. Phase I testing was used to investigate and determine the physical parameters which had the most significant influence on cracking behaviour and bonding capability. Using significant findings from Phase I, Phase II testing was structured to focus on the interpretation of the bond dependent coefficient and the statistical variation in a set of 5 identical test specimens. Current design equations, as recommended by ACI 440.1R-06 and CHBDC CAN/CSA-S6-06, were used for the calculation of the bond dependent coefficient for all specimens. Interpretation of the bond dependent coefficient was considered using the stress-level approach and newly developed slope approach. Results of the study indicated that the high variability of kb was likely due to its interpretation. Current design equations force a zero intercept, neglecting the fact that concrete does not crack immediately upon loading. In addition, clear definitions of service stress and maximum crack width are ambiguous, further complicating the calculation of the bond dependent coefficient. This resulted in a range of kb values for a given beam despite the fact that kb is inherently a material property of the bar. The behaviour of specimens following load cycling was also very different than the initial loading cycle and consequently, kb was also significantly different. As structures in the field will be subjected to continual loading and unloading, the effect of cyclic loading becomes a consideration in the calculation of kb.

No description available.

No description available.

Low-energy trauma and fragility fractures represent a major public health problem. The societal cost of the fragility fractures that occurred in Sweden 2010 has been estimated at €4 billion. In rheumatoid arthritis (RA), patient outcomes have improved greatly in recent years. However, the therapeutic decision making is still hampered by a lack of effective validated biomarkers. The cost of RA in Sweden 2010 has been estimated at €600 million, of which biologic drugs was €180 million. Digital X-ray radiogrammetry (DXR) is a method to measure bone mineral density (BMD) in the metacarpals of the hand. It can be applied opportunistically in several workflows where a person is already at an X-ray machine, including fracture repositioning follow up, mammography screening and hand imaging in RA. This thesis explored DXR-BMD as a marker to identify individuals who would benefit from anti-osteoporotic treatment, change rate of DXR-BMD as a biomarker in RA and under what conditions historical X-ray images can be used to estimate DXR-BMD. An automated method for measurement of joint space width in metacarpophalangeal and interphalangeal joints was also developed and evaluated as a biomarker in RA. Low DXR-BMD was predictive for hip fractures and predicted fragility fractures to a comparable degree as other BMD measurement sites. Rapid decrease of DXR-BMD was a strong and independent predictor for progression of radiographic damage in RA when manual radiographic progression scores were not available. Change of metacarpal joint space width was a statistically significant but weak predictor of joint space narrowing score progression. Guidelines and considerations for use of historical X-ray radiographs for DXR-BMD measurements in clinical trials have been developed and published.

Studies were conducted in 2011 and 2012 to determine if narrow row corn (Zea mays L.) and/or greater plant populations could affect yield, time to silking, and other physiological characteristics. Main plots of six hybrids were arranged as a randomized complete bock design with three replications. Split plots were row widths of 76-cm (wide rows) and 20-cm rows on 76-cm spacing (twin rows). Split-split plots were target plant populations of 75 000 and 111 000 plants ha-1. Corn was no-till seeded into soybean stubble near Lexington, KY in 2011 and 2012. Year interacted with most factors analyzed in the study. This was expected, given the extreme differences in weather. 2011 ASI (days) approached zero as plant population increased in wide rows in two out of four hybrids. ASI response to plant population in twin rows was not significant for any hybrid. In 2011, yield was greater in twin rows than wide rows. For significant equations, in 2011 grain yield increased as plant population increased, but in 2012 grain yield decreased as plant population increased, across both row widths. Kernel number per ear decreased as plant population increased in 2011 and 2012, but at different rates for wide and twin rows.