Video traffic is growing rapidly in wireless networks. Different from ordinary data traffic, video streams have higher data rates and tighter delay constraints. The ever-varying throughput of wireless links, however, cannot support continuous video playback if the video data rate is kept at a high level. To this end, adaptive video transmission techniques are employed to reduce the risk of playback interruptions by dynamically matching the video data rate to the varying channel throughput. In this dissertation, I develop new models to capture viewers' quality of experience (QoE) and design adaptive transmission algorithms to optimize the QoE. The contributions of this dissertation are threefold. First, I develop a new model for the viewers' QoE in rate-switching systems in which the video source rate is adapted every several seconds. The model is developed to predict an important aspect of QoE, the time-varying subjective quality (TVSQ), i.e., the up-to-the-moment subjective quality of a video as it is played. I first build a video database of rate-switching videos and measure TVSQs via a subjective study. Then, I parameterize and validate the TVSQ model using the measured TVSQs. Finally, based on the TVSQ model, I design an adaptive rate-switching algorithm that optimizes the time-averaged TVSQs of wireless video users. Second, I propose an adaptive video transmission algorithm to optimize the Overall Quality (OQ) of rate-switching videos, i.e., the viewers' judgement on the quality of the whole video. Through the subjective study, I find that the OQ is strongly correlated with the empirical cumulative distribution function (eCDF) of the video quality perceived by viewers. Based on this observation, I develop an adaptive video transmission algorithm that maximizes the number of video users who satisfy given constraints on the eCDF of perceived video qualities. Third, I propose an adaptive transmission algorithm for scalable videos. Different from the rate-switching systems, scalable videos support rate adaptation for each video frame. The proposed adaptive transmission algorithm maximizes the time-averaged video quality while maintaining continuous video playback. When the channel throughput is high, the algorithm increases the video data rate to improve video quality. Otherwise, the algorithm decreases the video data rate to buffer more videos and to reduce the risk of playback interruption. Simulation results show that the performance of the proposed algorithm is close to a performance upper bound. / text

Natural scene statistics (NSS) have played an increasingly important role in both our understanding of the function and evolution of the human vision system, and in the development of modern image processing applications. Because depth/range, i.e., egocentric distance, is arguably the most important thing a visual system must compute (from an evolutionary perspective), the joint statistics between natural image and depth/range information are of particular interest. However, while there exist regular and reliable statistical models of two-dimensional (2D) natural images, there has been little work done on statistical modeling of natural luminance/chrominance and depth/disparity, and of their mutual relationships. One major reason is the dearth of high-quality three-dimensional (3D) image and depth/range database. To facilitate research progress on 3D natural scene statistics, this dissertation first presents a high-quality database of color images and accurately co-registered depth/range maps using an advanced laser range scanner mounted with a high-end digital single-lens reflex camera. By utilizing this high-resolution, high-quality database, this dissertation performs reliable and robust statistical modeling of natural image and depth/disparity information, including new bivariate and spatial oriented correlation models. In particular, these new statistical models capture higher-order dependencies embedded in spatially adjacent bandpass responses projected from natural environments, which have not yet been well understood or explored in literature. To demonstrate the efficacy and effectiveness of the advanced NSS models, this dissertation addresses two challenging, yet very important problems, depth estimation from monocular images and no-reference stereoscopic/3D (S3D) image quality assessment. A Bayesian depth estimation framework is proposed to consider the canonical depth/range patterns in natural scenes, and it forms priors and likelihoods using both univariate and bivariate NSS features. The no-reference S3D image quality index proposed in this dissertation exploits new bivariate and correlation NSS features to quantify different types of stereoscopic distortions. Experimental results show that the proposed framework and index achieve superior performance to state-of-the-art algorithms in both disciplines. / text

Recent image quality assessment (IQA) metrics achieve high correlation with human perception of image quality. Naturally, it is of interest to produce even better results. One promising method is to weight image quality measurements by visual importance. To this end, we describe three strategies - visual fixation-based weighting, quality-based weighting and weighting based on distribution of local quality scores about the mean. By contrast with some prior studies we find that these strategies can improve the correlations with subjective judgment significantly. We demonstrate improvements on the SSIM index in both its multi-scale and single-scale versions, using the LIVE database as a test-bed. / text

Bakalauro baigiamajame darbe nagrinėjama paslaugų kokybė Lietuvos kariuomenės atstovų, dalyvavusių renginyje „Gyvybės ir mirties keliu“, požiūriu. Teorinėje dalyje analizuojami sporto reikšmė, sporto renginio samprata, paslaugos ir paslaugos kokybės samprata. Buvo atlikta kokybės vertinimo modelių lyginamoji analizė ir pasirinktas tinkamiausias modelis šiam tyrimui – SERVQUAL. Remiantis šiuo modeliu parengta anketinė apklausa. Atlikus apklausa buvo surinkti ir išanalizuoti duomenis, bei pateiktos išvados. Raktiniai žodžiai: sporto renginys, paslauga, paslaugos kokybės vertinimas. Tyrimo objektas: sporto renginio paslaugų kokybės vertinimas. Tyrimo problema: koks egzistuoja Lietuvos kariuomenėje sporto renginių kokybės lygis ir kaip patenkinti, geriausiu atveju pranokti, vartotoju lūkesčius? Darbo tikslas: įvertinti sporto renginio „Gyvybės ir mirties keliu“, kaip paslaugos, kokybę. Darbo uždaviniai: 1. Apibrėžti sporto renginio sampratą; 2. Atskleisti paslaugų kokybės sampratą; 3. Išanalizuoti paslaugų kokybės vertinimo modelius bei metodus; 4. Ištirti ir įvertinti sporto renginio „Gyvybės ir mirties keliu“ , kaip paslaugos, kokybę. Tyrimo metodai: • Mokslinės literatūros analizė. • Anketinė apklausa. • Statistinė aprašomoji analizė. Darbe pateiktos 6 formulės, 12 paveikslų, 1 priedas. Darbo apimtis – 40 puslapiai. Panaudoti 39 literatūros šaltiniai. / Bachelor's thesis examined the quality of service of the sporting event "The way of life and death" through Lithuanian army representatives’, as a participants’, approach. The theoretical part analyzes the significance of sport, sporting event, the concepts of service and service quality. Comparative analysis of quality assessment models was carried out and the most appropriate model for this study – SERVQUAL – was selected. Based on this model questionnaire was developed. After the survey was conducted, data was collected and analyzed, and conclusions was formulated. Key words: sporting event, service, service quality assessment. The object of the work: sporting event quality assessment. Problem (research) question: what is the level of service quality of sporting events in Lithanian army, and how expectations of consumers can satisfied or even exceded? The porpose of work: to make an assessment of quality of sporting event “The way of life and death” as a service. Tasks of the work: 1. To define the concept of a sports event; 2. To reveal the concept of service quality ; 3. To analyze the service quality assessment models and methods; 4. To research and evaluate the service quality of “The way of life and death” sporting event. Methods of research: • The analysis of literature; • The quiz; • Statitical reviewing analysis. The work includes: 6 formulas, 12 pictures, 1 annex. Total: 40 pages. 39 references used.

Large Central European flood events of the past have demonstrated that flooding can affect several river basins at the same time leading to catastrophic economic and humanitarian losses that can stretch emergency resources beyond planned levels of service. For Germany, the spatial coherence of flooding, the contributing processes and the role of trans-basin floods for a national risk assessment is largely unknown and analysis is limited by a lack of systematic data, information and knowledge on past events. This study investigates the frequency and intensity of trans-basin flood events in Germany. It evaluates the data and information basis on which knowledge about trans-basin floods can be generated in order to improve any future flood risk assessment. In particu-lar, the study assesses whether flood documentations and related reports can provide a valuable data source for understanding trans-basin floods. An adaptive algorithm was developed that systematically captures trans-basin floods using series of mean daily discharge at a large number of sites of even time series length (1952-2002). It identifies the simultaneous occurrence of flood peaks based on the exceedance of an initial threshold of a 10 year flood at one location and consecutively pools all causally related, spatially and temporally lagged peak recordings at the other locations. A weighted cumulative index was developed that accounts for the spatial extent and the individual flood magnitudes within an event and allows quantifying the overall event severity. The parameters of the method were tested in a sensitivity analysis. An intensive study on sources and ways of information dissemination of flood-relevant publications in Germany was conducted. Based on the method of systematic reviews a strategic search approach was developed to identify relevant documentations for each of the 40 strongest trans-basin flood events. A novel framework for assessing the quality of event specific flood reports from a user’s perspective was developed and validated by independent peers. The framework was designed to be generally applicable for any natural hazard type and assesses the quality of a document addressing accessibility as well as representational, contextual, and intrinsic dimensions of quality. The analysis of time-series of mean daily discharge resulted in the identification of 80 trans-basin flood events within the period 1952-2002 in Germany. The set is dominated by events that were recorded in the hydrological winter (64%); 36% occurred during the summer months. The occurrence of floods is characterised by a distinct clustering in time. Dividing the study period into two sub-periods, we find an increase in the percentage of winter events from 58% in the first to 70.5% in the second sub-period. Accordingly, we find a significant increase in the number of extreme trans-basin floods in the second sub-period. A large body of 186 flood relevant documentations was identified. For 87.5% of the 40 strongest trans-basin floods in Germany at least one report has been found and for the most severe floods a substantial amount of documentation could be obtained. 80% of the material can be considered grey literature (i.e. literature not controlled by commercial publishers). The results of the quality assessment show that the majority of flood event specific reports are of a good quality, i.e. they are well enough drafted, largely accurate and objective, and contain a substantial amount of information on the sources, pathways and receptors/consequences of the floods. The inclusion of this information in the process of knowledge building for flood risk assessment is recommended. Both the results as well as the data produced in this study are openly accessible and can be used for further research. The results of this study contribute to an improved spatial risk assessment in Germany. The identified set of trans-basin floods provides the basis for an assessment of the chance that flooding occurs simultaneously at a number of sites. The information obtained from flood event documentation can usefully supplement the analysis of the processes that govern flood risk. / Abschätzungen zum Hochwasserrisiko beschränken sich zumeist auf die Analyse innerhalb eines Einzugsgebietes bzw. eines bestimmten Ortes. Die Zusammenhänge in größeren Regionen und vor allem Korrelationen zwischen verschiedenen Einzugsgebieten werden nur selten betrachtet. Solche einzugsgebietsübergreifenden Analysen sind jedoch sowohl für die Versicherungswirtschaft, den Katastrophenschutz sowie für großräumige strategische Hochwasserplanungen notwendig. Allerdings stehen nur für eine geringe Auswahl historischer Ereignisse Daten zur Verfügung und systematische Ansätze zu ihrer Erfassung wurden für Deutschland bisher nicht entwickelt. Die vorliegende Studie untersucht zum ersten die Häufigkeit und Intensität von flussgebietsübergreifenden Hochwasserereignissen in Deutschland anhand von gemessenen Abflüssen an einer Vielzahl von Stationen. Es können insgesamt 80 Hochwasserereignisse in Deutschland im Zeitraum von 1952-2002 nachgewiesen werden. Davon treten die meisten Ereignissen im hydrologischen Winterhalbjahr auf (64%). Wir können nachweisen, dass die Häufigkeit des Auftretens in verschiedenen Perioden unterschiedlich ist, und dass im Untersuchungszeitraum eine signifikante Zunahme von Winterereignissen und damit vor allem von sehr schweren flussgebietsübergreifenden Hochwasserereignissen zu verzeichnen ist. Die Studie hatte des Weiteren zum Ziel, die verfügbare Daten- und Informationsgrundlage zur Hochwasseranalyse zu erkunden. Im speziellen wird untersucht, inwieweit Hochwasserereignisdokumentationen und verwandte Berichte als eine weitere Datenquelle für ein verbessertes Prozessverständnis genutzt werden können. Im Rahmen einer systematischen Suche konnten für die 40 größten Hochwasserereignisse in Deutschland 186 relevante Berichte identifiziert werden. 80% des Materials kann als Grauliteratur eingestuft werden, d.h. als Veröffentlichungen welche nicht durch kommerzielle Verleger publiziert wird. Die sich daraus ergebende Frage nach der Qualität der Dokumente und ihres Informationsgehaltes wurde durch die Entwicklung und Anwendung eines Qualitätsbewertungsschemas beantwortet. Die Ergebnisse der Qualitätsbewertung zeigen, dass die Mehrheit der ereignisspezifischen Hochwasserberichte von guter Qualität ist, d.h. die Berichte sind in ausreichender Qualität verfasst, größtenteils korrekt und objektiv und beinhalten eine substantielle Menge an Informationen zu den Ursachen, Verläufen, betroffenen Objekten und Schäden eines Ereignisses. Es wird empfohlen diese Informationen in die Wissenssynthese für die Hochwasserrisikobewertung einfließen zu lassen. Sowohl Ergebnisse als auch Daten dieser Studie sind so publiziert, dass sie öffentlich zugänglich sind und für weitere Forschungsfragen genutzt werden können.

Paslauga - neapčiuopiama veikla, pasireiškianti vartotojui kontaktuojant su paslaugą teikiančiais asmenimis. Kokybė – tai tam tikri reikalavimai, kurių turi būti laikomasi teikiant paslaugas. Grӧnroos (1990) suvokiamos paslaugos kokybės modelis parodo, kad suvoktą kokybę lemia laukiama ir patirta kokybė. Parasuraman ir kt. (1985) pateikė kokybės spragų modelį, kuris atskleidžia, kad kokybę formuoja vartotojas ir paslaugos teikėjas. Taip pat pasiūlytas SERVQUAL metodas ir jo penkios vertinimo dimensijos: apčiuopiamumas, patikimumas, reagavimas, tikrumas, empatija. Nuotykių parkuose gausu įvairių trasų, aikštelių, ekstremalių pramogų. Taip pat teikiamos papildomos paslaugos kaip pirčių kompleksas, žiemą slidžių nuoma, vaikų gimtadienių šventės, žvejyba. Lietuvos nuotykių parkų lankytojų lūkesčiai visais klausimyno teiginiais nepatenkinti. Pagal patirtą paslaugų kokybės lygį žemiausiai įvertintos apčiuopiamumo ir reagavimo dimensijos. Didžiausios spragos atsivėrė taip pat šiose dimensijose. Daroma išvada, kad Lietuvos nuotykių parkų atstovų, bei darbuotojų didžiausias dėmesys turėtų būti skirtas apčiuopiamumo ir reagavimo dimensijų spragų dydžių tarp patirtos ir lauktos paslaugų kokybės mažinimui. / Service - intangible activities occurring user contact with the person providing the service. Quality - it is a number of requirements which must be met for the service. Grӧnroos (1990) perceived service quality model shows that perceived quality is determined by the expected and the quality of the experience. Parasuraman et al. (1985) provided a quality gap model, which reveals that the quality of the form user and the service provider. Also, the proposed method and its SERVQUAL five assessment dimensions: tangibles, reliability, responsiveness, authenticity, empathy. Adventure Park is full of different trails, parks, extreme entertainment. It also provides additional services such as saunas, winter ski rental, children's birthdays, fishing. Lithuania adventure parks visitor expectations all of the statements unsatisfied. According to the loss of quality of service equal to the lowest evaluated more tangible and response dimensions. The largest gaps opened up as well in these dimensions. In conclusion, the Lithuanian adventure parks representatives and staff focus should be given more tangible dimensions and response gaps in sizes between the damage and the expected quality of service reduction.

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This thesis describes an automatic evaluation approach for estimating the quality of stereo displays and vision systems using image features. The method is inspired by the human visual system. Display of stereo images is widely used to enhance the viewing experience of three-dimensional (3D) visual displays and communication systems. Applications are numerous and range from entertainment to more specialized applications such as: 3D visualization and broadcasting, robot tele-operation, object recognition, body exploration, 3D teleconferencing, and therapeutic purposes. Consequently, perceived image quality is important for assessing the performance of 3D imaging applications. There is no doubt that subjective testing (i.e., asking human viewers to rank the quality of stereo images) is the most accurate method for quality evaluation. It reflects true human perception. However, these assessments are time consuming and expensive. Furthermore, they cannot be done in real time. Therefore, the goal of this research is to develop an objective quality evaluation methods computational models that can automatically predict perceived image quality) correlating well with subjective predictions that are required in the field of quality assessment. I believe that the perceived distortion and disparity of any stereoscopic display are strongly dependent on local features, such as edge (non-uniform) and non-edge (uniform) areas. Therefore, in this research, I propose a No-Reference (NR) objective quality assessment for coded stereoscopic images based on segmented local features of artifacts and disparity. Local feature information such as edge and non-edge area based relative disparity estimation, as well as the blockiness, blur, and the zero-crossing within the block of images, are evaluated in this method. A block-based edge dissimilarity approach is used for disparity estimation. I use the Toyama stereo images database to evaluate the performance and to compare it with other approaches both qualitatively and quantitatively.

Objective: Access to, and reliance upon, high quality data is an enabling cornerstone of modern health delivery systems. Sadly, health systems are often awash with poor quality data which contributes both to adverse outcomes and can compromise the search for new knowledge. Traditional approaches to purging poor data from health information systems often require manual, laborious and time-consuming procedures at the collection, sanitizing and processing stages of the information life cycle with results that often remain sub-optimal. A promising solution may lie with semantic technologies - a family of computational standards and algorithms capable of expressing and deriving the meaning of data elements. Semantic approaches purport to offer the ability to represent clinical knowledge in ways that can support complex searching and reasoning tasks. It is argued that this ability offers exciting promise as a novel approach to assessing and improving data quality. This study examines the effectiveness of semantic web technologies as a mechanism by which high quality data can be collected and assessed in health settings. To make this assessment, key study objectives include determining the ability to construct of valid semantic data model that sufficiently expresses the complexity present in the data as well as the development of a comprehensive set of validation rules that can be applied semantically to test the effectiveness of the proposed semantic framework. Methods: The Semantic Framework for Data Quality Assessment (SemDQ) was designed. A core component of the framework is an ontology representing data elements and their relationships in a given domain. In this study, the ontology was developed using openEHR standards with extensions to capture data elements used in for patient care and research purposes in a large organ transplant program. Data quality dimensions were defined and corresponding criteria for assessing data quality were developed for each dimension. These criteria were then applied using semantic technology to an anonymized research dataset containing medical data on transplant patients. Results were validated by clinical researchers. Another test was performed on a simulated dataset with the same attributes as the research dataset to confirm the computational accuracy and effectiveness of the framework. Results: A prototype of SemDQ was successfully implemented, consisting of an ontological model integrating the openEHR reference model, a vocabulary of transplant variables and a set of data quality dimensions. Thirteen criteria in three data quality dimensions were transformed into computational constructs using semantic web standards. Reasoning and logic inconsistency checking were first performed on the simulated dataset, which contains carefully constructed test cases to ensure the correctness and completeness of logical computation. The same quality checking algorithms were applied to an established research database. Data quality defects were successfully identified in the dataset which was manually cleansed and validated periodically. Among the 103,505 data entries, application of two criteria did not return any error, while eleven of the criteria detected erroneous or missing data, with the error rates ranging from 0.05% to 79.9%. Multiple review sessions were held with clinical researchers to verify the results. The SemDQ framework was refined to reflect the intricate clinical knowledge. Data corrections were implemented in the source dataset as well as in the clinical system used in the transplant program resulting in improved quality of data for both clinical and research purposes. Implications: This study demonstrates the feasibility and benefits of using semantic technologies in data quality assessment processes. SemDQ is based on semantic web standards which allows easy reuse of rules and leverages generic reasoning engines for computation purposes. This mechanism avoids the shortcomings that come with proprietary rule engines which often make ruleset and knowledge developed for one dataset difficult to reuse in different datasets, even in a similar clinical domain. SemDQ can implement rules that have shown to have a greater capacity of detect complex cross-reference logic inconsistencies. In addition, the framework allows easy extension of knowledge base to cooperate more data types and validation criteria. It has the potential to be incorporated into current workflow in clinical care setting to reduce data errors during the process of data capture.

This thesis describes an automatic evaluation approach for estimating the quality of stereo displays and vision systems using image features. The method is inspired by the human visual system. Display of stereo images is widely used to enhance the viewing experience of three-dimensional (3D) visual displays and communication systems. Applications are numerous and range from entertainment to more specialized applications such as: 3D visualization and broadcasting, robot tele-operation, object recognition, body exploration, 3D teleconferencing, and therapeutic purposes. Consequently, perceived image quality is important for assessing the performance of 3D imaging applications. There is no doubt that subjective testing (i.e., asking human viewers to rank the quality of stereo images) is the most accurate method for quality evaluation. It reflects true human perception. However, these assessments are time consuming and expensive. Furthermore, they cannot be done in real time. Therefore, the goal of this research is to develop an objective quality evaluation methods computational models that can automatically predict perceived image quality) correlating well with subjective predictions that are required in the field of quality assessment. I believe that the perceived distortion and disparity of any stereoscopic display are strongly dependent on local features, such as edge (non-uniform) and non-edge (uniform) areas. Therefore, in this research, I propose a No-Reference (NR) objective quality assessment for coded stereoscopic images based on segmented local features of artifacts and disparity. Local feature information such as edge and non-edge area based relative disparity estimation, as well as the blockiness, blur, and the zero-crossing within the block of images, are evaluated in this method. A block-based edge dissimilarity approach is used for disparity estimation. I use the Toyama stereo images database to evaluate the performance and to compare it with other approaches both qualitatively and quantitatively.