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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
601

A manual alphabet for touchless gesture-controlled writing input with a myoelectric device : Design, evaluation and user experience

Bieber Bardt, Raphaela January 2015 (has links)
The research community around gesture-based interaction has so far not paid attention to the possibility of replacing the keyboard with natural gestures for writing purposes. Additionally, insight into the actual user experience of such an interaction style is only insufficiently provided. This work presents a novel approach for text input that is based on a manual alphabet, MATImyo. The hand alphabet was developed in a user-centered design process involving potential users in pre-studies, design process and evaluation procedure. In a Wizard-of-Oz style experiment with accompanying interviews, the alphabet’s quality as input language for composing electronic texts was evaluated and the user experience of such an interaction style assessed. MATImyo was found to be very suitable as gestural input language with a positive user experience. The whole process of designing MATImyo and evaluating its suitability and user experience was based on the principles of Embodied Interaction, which was chosen as theoretical framework. This work contributes to understanding the bigger picture of the user experience of gesture-based interaction and presents a novel, more natural text input method.
602

Development of Short Term Storage Techniques for Grafted Vegetable Seedlings

Spalholz, Hans January 2013 (has links)
Vegetable grafting confers soil-borne disease resistance through the use of selected rootstocks. Additional costs associated with grafted vegetable seedling propagation limit grower access to this technology. The use of low temperature storage in grafted seedling production reduces labor costs and allows propagators to meet the seasonal and narrow-window demand of growers. For the first part of the experiment 22 genotypes of Solanaceae or Cucurbitaceae seedlings were evaluated in low temperature storage conditions (5 or 12°C). Seedling performance was better in 12°C storage than in 5°C storage. For the second part of the experiment watermelon, the most low-temperature sensitive species found in our first study, was grafted onto two different commercial rootstocks or on to other watermelon seedlings and stored at 12°C for two and four weeks. Both 'Strong Tosa' and 'Emphasis' rootstocks conferred chilling tolerance during storage to watermelon scions, allowing storage of grafted plants for two weeks.
603

Διερεύνηση της μετανάστευσης και της αποδέσμευσης αντιμικροβιακών ουσιών από πολυμερικές ίνες πολυλειτουργικών υφασμάτων

Νοχός, Αργύριος 12 February 2009 (has links)
Η παρούσα εργασία μελετά την ανάπτυξη ενός ευέλικτου συστήματος αντιμικροβιακής προστασίας για εφαρμογή σε είδη ρουχισμού και υφάσματα οικιακής χρήσης. Πιο συγκεκριμένα αναπτύχθηκαν διασυνδεδεμένα πολυμερικά νανοσφαιρίδια πολυστυρολίου-διβινυλοβενζολίου στα οποία ενσωματώθηκε Triclosan, μία ευρέος φάσματος εμπορική αντιμικροβιακή ουσία. Σημειώνεται ότι στο πλαίσιο ανάσχεσης των ενδονοσοκομειακών λοιμώξεων η ανάπτυξη αντιμικροβιακών νοσοκομειακών στολών, σεντονιών και άλλων σχετικών κλωστοϋφαντουργικών προϊόντων αποτελούν τις τελευταίες δεκαετίες αντικείμενο έντονου επιστημονικού ενδιαφέροντος. Το μέγεθος των νανοσωματιδίων βρέθηκε μετά από εξέταση με ηλεκτρονική μικροσκοπία σάρωσης (SEM) και δυναμική σκέδαση φωτός (DLS) να κυμαίνεται μεταξύ 35-350 nm ανάλογα την σύσταση. H θερμική συμπεριφορά τους μελετήθηκε μέσω διαφορικής θερμιδομετρίας σάρωσης (DSC) και διαπιστώθηκε σημείο τήξεως στους ~425 οC. Χρησιμοποιώντας την φασματοσκοπία UVVis προσδιορίστηκε ο πραγματικός εγκλωβισμός του αντιμικροβιακού στο σύστημα κατά μέσο όρο σε ποσοστό ~72% του ονομαστικού και παρακολουθήθηκε ο ρυθμός αποδέσμευσης του σε διαλύματα αιθανόλης-νερού. Επιπλέον, τα σφαιρίδια που όπως διαπιστώθηκε παρουσιάζουν χαρακτηριστικά ελεγχόμενης αποδέσμευσης ενσωματώθηκαν σε μήτρες πολυπροπυλενίου οι οποίες υπό την μορφή φιλμ εφελκύστηκαν μονοαξονικά. Τέλος κάνοντας χρήση της δονητικής φασματοσκοπίας Raman εκτιμήθηκε ο μοριακός προσανατολισμός που επιβλήθηκε στα εφελκυσμένα φιλμ και συσχετίσθηκε με την παρατηρούμενη μείωση που επιτεύχθηκε στην κινητική αποδέσμευσης της εγκλωβισμένης δραστικής ουσίας. Το πρώτο κεφάλαιο της παρούσας εργασίας ασχολείται με το πρόβλημα της μικροβιακής επιμόλυνσης υφασμάτων, τις διάφορες λύσεις που έχουν προταθεί κατά καιρούς και τέλος αναλύει τον στόχο της παρούσας εργασίας. Στο δεύτερο κεφάλαιο επεξηγείται η έννοια της ελεγχόμενης αποδέσμευσης και περιγράφονται οι διάφορες κατηγορίες συστημάτων ελεγχόμενης χορήγησης μαζί με χαρακτηριστικά παραδείγματα. Τα νανοσωματίδια, η σύστασή, οι μοναδικές ιδιότητες, οι εφαρμογές και οι διάφοροι τρόποι σύνθεσης και χαρακτηρισμού τους συζητούνται στο τρίτο κεφάλαιο. Το τέταρτο κεφάλαιο αναφέρει πληροφορίες για τα υλικά και επεξηγεί τις τεχνικές που χρησιμοποιήθηκαν στην σύνθεση, την επεξεργασία και τον χαρακτηρισμό των νανοσωματιδίων και των μιγμάτων τους. Τέλος στο πέμπτο κεφάλαιο παρουσιάζονται τα αποτελέσματα των πειραμάτων που πραγματοποιήθηκαν και ακολουθεί ο σχολιασμός τους. / The present thesis studies the development of a versatile system of antimicrobial protection for use in clothing and household products. In particular Triclosan incorporated crosslinked polystyrenedinylbenzene nanobeads were developed; triclosan is a widely used antimicrobial agent. It is noted that the health hazards arising during nosocomial treatment due to infections caused by microbial pathogens and the means to protect oneself against such threats have become the subject of many research activities during the last few decades. The size of the nanoparticles after examination with scanning electron microcopy (SEM) and dynamic light scattering (DLS) was found to vary between 35-350 nm depending on the system formulation. Their thermal behavior was studied with differential scanning calorimetry (DSC) and their melting point was measured at ~425 oC. Using UV-Vis spectroscopy the real encapsulation efficiency of the antimicrobial in the system was determined at ~72% and its release kinetics were studied in a water-ethanol solution. The nanobeads possess controlled release properties; they were furthermore incorporated into polypropylene matrixes which were uniaxially drawn in film form. Finally utilizing polarized Raman spectra, the draw induced molecular orientation of the films was correlated to the relevant variation of the related antimicrobial release kinetics. The first chapter of the present thesis reviews the textile microbial infections and the various solutions that have been proposed showing up the specific research goal targeted. In the second chapter the meaning of controlled release is explained and the basic system categories involved are presented along with characteristic examples. The nanoparticles, their composition, special attributes, applications, synthesis and characterization techniques are the subject of the third chapter. The fourth chapter reports information about the materials and the methods used in the synthesis, postprocessing and characterization of the nanoparticles and their blends. Finally the last chapter presents the experimental results and relevant comments.
604

Estimation of Jitter Effects in Oscillators and Frequency Synthesizers Due to Prototypical Perturbation Sources

Janczak, Teresa Krystyna January 2005 (has links)
The Phase Locked Loops (PLLs) are widely used in contemporary electronic systems for frequency synthesis, clock recovery, frequency multiplication and other purposes. Because of continuous increase in operating frequency of clocking systems the requirements on the clock spectral purity and low jitter became very demanding and are one of major designers' concerns.Frequency synthesizers used in microprocessors are integrated on the same substrate as the rest of the circuit and thus suffer from a substantial switching noise injected into global supply and ground busses. Usually when the reference signal comes from a crystal oscillator, VCO becomes a main source of phase noise. A designer of VCO needs to determine the best circuit structure by considering different prototypical perturbations scenarios and predicting the worst case and jitter response when the perturbation signals are switched on and off. Therefore the time efficient estimation of the jitter effects resulting from many shapes, frequencies and phases of perturbation is critical.The presented dissertation demonstrates simulation methodology for rapid estimation of jitter in oscillators, particularly in VCOs, caused by perturbation sources such as power supply and substrate couplings. The methodology is also extended to these types of PLLs in which the VCO instability is a main contributor to the output timing jitter.Simulation of oscillatory circuits is strongly effected by the round-off errors. Special technique was developed to eliminate these effects.The technique is applicable for predicting timing non-idealities for arbitrary perturbation shapes, frequencies and phases. Different jitter metrics can be easily extracted for all important perturbation scenarios.The methodology utilizes the new concept of the transient multi-cycle Voltage Impulse Sensitivity Function (VISF), which has been developed in the dissertation. It contains information about sensitivity of oscillator to noise injection and also allows for efficient prediction of the transient effects caused by switching on and off the perturbation sources. The methodology offers efficiency and great simplicity of use, which frees designers from complicated, time consuming analysis of data generated by a simulator. The very involved postprocessing of simulation data can be fully automated.
605

Next Generation Computer Controlled Optical Surfacing

Kim, Dae Wook January 2009 (has links)
Precision optics can be accurately fabricated by computer controlled optical surfacing (CCOS) that uses well characterized polishing tools driven by numerically controlled machines. The CCOS process is optimized to vary the dwell time of the tool on the workpiece according to the desired removal and the calibrated tool influence function (TIF), which is the shape of the wear function by the tool. This study investigates four major topics to improve current CCOS processes, and provides new solutions and approaches for the next generation CCOS processes.The first topic is to develop a tool for highly aspheric optics fabrication. Both the TIF stability and surface finish rely on the tool maintaining intimate contact with the workpiece. Rigid tools smooth the surface, but do not maintain intimate contacts for aspheric surfaces. Flexible tools conform to the surface, but lack smoothing. A rigid conformal (RC) lap using a visco-elastic non-Newtonian medium was developed. It conforms to the aspheric shape, yet maintains stability to provide natural smoothing.The second topic is a smoothing model for the RC lap. The smoothing naturally removes mid-to-high frequency errors while a large tool runs over the workpiece to remove low frequency errors efficiently. The CCOS process convergence rate can be significantly improved by predicting the smoothing effects. A parametric smoothing model was introduced and verified.The third topic is establishing a TIF model to represent measured TIFs. While the linear Preston's model works for most cases, non-linear removal behavior as the tool overhangs the workpiece edge introduces a difficulty in modeling. A parametric model for the edge TIFs was introduced and demonstrated. Various TIFs based on the model are provided as a library.The last topic is an enhanced process optimization technique. A non-sequential optimization technique using multiple TIFs was developed. Operating a CCOS with a small and well characterized TIF achieves excellent performance, but takes a long time. Sequential polishing runs using large and small tools can reduce this polishing time. The non-sequential approach performs multiple dwell time optimizations for the entire CCOS runs simultaneously. The actual runs will be sequential, but the optimization is comprehensive.
606

Understanding the mechanisms behind atom transfer radical polymerization : exploring the limit of control

Bergenudd, Helena January 2011 (has links)
Atom transfer radical polymerization (ATRP) is one of the most commonly employed techniques for controlled radical polymerization. ATRP has great potential for the development of new materials due to the ability to control molecular weight and polymer architecture. To fully utilize the potential of ATRP as polymerization technique, the mechanism and the dynamics of the ATRP equilibrium must be well understood. In this thesis, various aspects of the ATRP process are explored through both laboratory experiments and computer modeling. Solvent effects, the limit of control and the use of iron as the mediator have been investigated. It was shown for copper mediated ATRP that the redox properties of the mediator and the polymerization properties were significantly affected by the solvent. As expected, the apparent rate constant (kpapp) increased with increasing activity of the mediator, but an upper limit was reached, where after kpapp was practically independent of the mediator potential. The degree of control deteriorated as the limit was approached. In the simulations, which were based on the thermodynamic properties of the ATRP equilibrium, the same trend of increasing kpapp with increasing mediator activity was seen and a maximum was also reached. The simulation results could be used to describe the limit of control. The maximum equilibrium constant for controlled ATRP was correlated to the propagation rate constant, which enables the design of controlled ATRP systems. Using iron compounds instead of copper compounds as mediators in ATRP is attractive from environmental aspects. Two systems with iron were investigated. Firstly, iron/EDTA was investigated as mediator as its redox properties are within a suitable range for controlled ATRP. The polymerization of styrene was heterogeneous, where the rate limiting step is the adsorption of the dormant species to the mediator surface. The polymerizations were not controlled and it is possible that they had some cationic character. In the second iron system, the intention was to investigate how different ligands affect the properties of an ATRP system with iron. Due to competitive coordination of the solvent, DMF, the redox and polymeri­zation properties were not significantly affected by the ligands. The differences between normal and reverse ATRP of MMA, such as the degree of control, were the result of different FeIII speciation in the two systems. / QC 20110406
607

Family Controlled Firms on the Stock Market : Do family-controlled firms show a convergence in corporate governance systems?

Mártires, Miguel Ángel, Sawicki, Kamil January 2008 (has links)
Background: Family-business is considered to be the most frequent and complex form of business organization around the world. However, recently there has been a large number of corporate scandals in such firms especially at the board level (e.g. Parmalat). Within the framework of two corporate governance models characterized by the Continental European and the Anglo-Saxon model, boards of directors hold a central position. This position becomes of great importance when talking about public companies and more specifically in public family-controlled companies. The concentration of ownership is the main characteristic of the Continental European, which is the most workable form of corporate governance for family-controlled business. Nevertheless, family-controlled companies acting under the Anglo-Saxon model have also been able to operate successfully. Therefore, we will investigate if there is a convergence of corporate governance in family-controlled companies across frontiers focusing mainly on boards’ structures and composition as well as ownership, and the sub-committees. Purpose: The overall purpose of this thesis is to contribute to the understanding of Corporate Governance in public Family-controlled firms which are in the Swedish and United Kingdom stock market. More specifically, investigate whether the boards’ structures and composition, as well as ownership and the existence of sub-committees show similarities or not in Family-controlled firms acting within the framework of an Anglo-Saxon and Continental model of Corporate Governance Method: A quantitative approach was used to fulfill the purpose of this thesis. Furthermore, the top 10 family-controlled companies with highest market-capitalization have been selected from both countries to constitute our sample. The empirical material was gathered mainly from the annual reports of the companies but also by contacting the companies by email or from articles in online newspapers. Conclusion: This study found that in some aspects of corporate governance convergence exists while in others it does not. Regarding board structures and composition, there is a convergence to “one tier board” and the presence of family members and employee representation in boards. On the other hand, when it comes to the sizes of the boards and number of independent directors in the boards we argue that convergence is not present.
608

Design of Controlled Rocking Steel Frames to Limit Higher Mode Effects

Andree Wiebe, Lydell Deighton 14 January 2014 (has links)
Because conventional seismic force resisting systems rely on yielding of key structural members to limit seismic forces, structural damage is expected after a design-level earthquake. Repairing this damage can be very expensive, if it is possible at all. Researchers have been developing a new family of self-centring systems that avoid structural damage. One such system is a controlled rocking steel frame, which is the subject of this thesis. In a controlled rocking steel frame, the columns of a frame are permitted to uplift from the foundation, and the response is controlled by using a combination of post-tensioning and energy dissipation. Although previous studies have confirmed the viability of this system, they have also shown that rocking does not fully limit the peak seismic forces because of higher mode effects. If a structure is designed to account for these effects, it may be uneconomical, but if it is not designed to account for them, it may be unsafe. The purpose of this thesis is to develop recommendations for the design of controlled rocking steel frames, particularly with regard to higher mode effects. A theoretical framework for understanding higher mode effects is developed, and large-scale shake table testing is used to study the behaviour of a controlled rocking steel frame. Two mechanisms are proposed to mitigate the increase in structural forces due to higher mode effects, and these mechanisms are validated by shake table testing. Numerical modelling of controlled rocking steel frames is shown to become more reliable when higher mode mitigation mechanisms are used to limit the seismic response. In the final chapters, the thesis proposes and validates a new methodology for the limit states design of controlled rocking steel frames.
609

Design and Validation of a Comprehensive Simulation-enhanced Training Curriculum for a Complex Minimally Invasive Operation

Zevin, Boris 02 April 2014 (has links)
Laparoscopic bariatric procedures are complex minimally invasive operations with a potential for substantial morbidity and mortality along the early part of a surgeon’s learning curve. Simulation-enhanced training can improve a surgeon's technical and non-technical performance and lessen the learning curves in the operating room. Unfortunately, despite the convincing evidence supporting the use of simulation in surgical education, there is still a gap in translation of knowledge and technical skills from the research environment into clinically relevant training curricula. The objective of this thesis was to design and validate a comprehensive simulationenhanced training curriculum that addressed cognitive knowledge, technical and non-technical skill in laparoscopic bariatric surgery. This objective was achieved using three experimental studies. The first study employed a modified Delphi methodology and an international panel of experts in surgical and medical education to develop a consensus-based framework for design, validation and implementation of simulation-enahnced training curricula in surgery. The second study used a modified Delphi methodology and an international panel of experienced bariatric surgeons to develop an objective scale for assessment of operative skill in laparoscopic gastric bypass procedure. This scale was feasible to use and had high inter-rater and test-retest reliability, as well as evidence of construct and concurrent validity. The third study used the previously developed consensus-based framework to design a comprehensive simulation-enhanced training curriculum for laparoscopic bariatric surgery. A prospective, single-blinded randomized controlled trial was used to compare the effectiveness of this curriculum in comparison to conventional surgery training. Surgery residents who were trained in this curriculum demonstrated superior technical skills, superior non-technical skills and enhanced safety in the operating room.
610

Design and Validation of a Comprehensive Simulation-enhanced Training Curriculum for a Complex Minimally Invasive Operation

Zevin, Boris 02 April 2014 (has links)
Laparoscopic bariatric procedures are complex minimally invasive operations with a potential for substantial morbidity and mortality along the early part of a surgeon’s learning curve. Simulation-enhanced training can improve a surgeon's technical and non-technical performance and lessen the learning curves in the operating room. Unfortunately, despite the convincing evidence supporting the use of simulation in surgical education, there is still a gap in translation of knowledge and technical skills from the research environment into clinically relevant training curricula. The objective of this thesis was to design and validate a comprehensive simulationenhanced training curriculum that addressed cognitive knowledge, technical and non-technical skill in laparoscopic bariatric surgery. This objective was achieved using three experimental studies. The first study employed a modified Delphi methodology and an international panel of experts in surgical and medical education to develop a consensus-based framework for design, validation and implementation of simulation-enahnced training curricula in surgery. The second study used a modified Delphi methodology and an international panel of experienced bariatric surgeons to develop an objective scale for assessment of operative skill in laparoscopic gastric bypass procedure. This scale was feasible to use and had high inter-rater and test-retest reliability, as well as evidence of construct and concurrent validity. The third study used the previously developed consensus-based framework to design a comprehensive simulation-enhanced training curriculum for laparoscopic bariatric surgery. A prospective, single-blinded randomized controlled trial was used to compare the effectiveness of this curriculum in comparison to conventional surgery training. Surgery residents who were trained in this curriculum demonstrated superior technical skills, superior non-technical skills and enhanced safety in the operating room.

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