Denna rapport omfattar ett examensarbete på 22,5 poäng. Examensarbetet har utförts inom ämnet integrerad produktutveckling vid Högskolan i Skövde tillsammans med Jai Designpartner AB. Målet med arbetet var att utveckla ett fällbord som enkelt kan fällas ihop, ha en längre livslängd och lägre vikt än företagets tidigare fällbord. Samarbetet genererade ett fällbord som inte följer de generella principerna av infällning av bordsben. Resultatet blev ett fällbord med minimal klämrisk, med en längre livslängd då infällning av bordsbenet sker med en vridning och med en mindre vikt då ramverk kan elimineras. / This report comprises a 22,5 points degree project. This project has been executed within the area of integrated product development at the University of Skövde in cooperation with Jai Designpartner AB. The objective of the project was to develop a collapsible table that is easy to collapse, has a lower weight and higher feeling of quality, compared to the company´s earlier versions of collapsible tables. The result of the cooperation became a collapsible table with a minimal risk of injury, with a greater endurance since the legs are folded with a turning motion and with a lesser weight since the table lacks framework.

Numerous cryptographic applications require a trusted authority to hold a secret. With a plethora of malicious attacks over the Internet, however, it is difficult to establish and maintain such an authority in online systems. Secret-sharing schemes attempt to solve this problem by distributing the required trust to hold and use the secret over multiple servers; however, they still require a trusted {\em dealer} to choose and share the secret, and have problems related to single points of failure and key escrow. A distributed key generation (DKG) scheme overcomes these hurdles by removing the requirement of a dealer in secret sharing. A (threshold) DKG scheme achieves this using a complete distribution of the trust among a number of servers such that any subset of servers of size greater than a given threshold can reveal or use the shared secret, while any smaller subset cannot. In this thesis, we make contributions to DKG in the computational security setting and describe three applications of it. We first define a constant-size commitment scheme for univariate polynomials over finite fields and use it to reduce the size of broadcasts required for DKG protocols in the synchronous communication model by a linear factor. Further, we observe that the existing (synchronous) DKG protocols do not provide a liveness guarantee over the Internet and design the first DKG protocol for use over the Internet. Observing the necessity of long-term stability, we then present proactive security and group modification protocols for our DKG system. We also demonstrate the practicality of our DKG protocol over the Internet by testing our implementation over PlanetLab. For the applications, we use our DKG protocol to define IND-ID-CCA secure distributed private-key generators (PKGs) for three important identity-based encryption (IBE) schemes: Boneh and Franklin's BF-IBE, Sakai and Kasahara's SK-IBE, and Boneh and Boyen's BB1-IBE. These IBE schemes cover all three important IBE frameworks: full-domain-hash IBEs, exponent-inversion IBEs and commutative-blinding IBEs respectively, and our distributed PKG constructions can easily be modified for other IBE schemes in these frameworks. As the second application, we use our distributed PKG for BF-IBE to define an onion routing circuit construction mechanism in the identity-based setting, which solves the scalability problem in single-pass onion routing circuit construction without hampering forward secrecy. As the final application, we use our DKG implementation to design a threshold signature architecture for quorum-based distributed hash tables and use it to define two robust communication protocols in these peer-to-peer systems.

This thesis is composed of two parts. The first part pertains to tree-based models. The second part deals with multiple testing in large-scale contingency tables. Tree-based models have gained enormous popularity in statistical modeling and data mining. We propose a novel tree-pruning algorithm called frontier-based tree-pruning algorithm (FBP). The new method has an order of computational complexity comparable to cost-complexity pruning (CCP). Regarding tree pruning, it provides a full spectrum of information. Numerical study on real data sets reveals a surprise: in the complexity-penalization approach, most of the tree sizes are inadmissible. FBP facilitates a more faithful implementation of cross validation, which is favored by simulations. One of the most common test procedures using two-way contingency tables is the test of independence between two categorizations. Current test procedures such as chi-square or likelihood ratio tests provide overall independency but bring limited information about the nature of the association in contingency tables. We propose an approach of testing independence of categories in individual cells of contingency tables based on a multiple testing framework. We then employ the proposed method to identify the patterns of pair-wise associations between amino acids involved in beta-sheet bridges of proteins. We identify a number of amino acid pairs that exhibit either strong or weak association. These patterns provide useful information for algorithms that predict secondary and tertiary structures of proteins.

This dissertation presents a novel modeling framework for understanding the dynamics of peer-to-peer (P2P) networks under churn (i.e., random user arrival/departure) and designing systems more resilient against node failure. The proposed models are applicable to general distributed systems under a variety of conditions on graph construction and user lifetimes. The foundation of this work is a new churn model that describes user arrival and departure as a superposition of many periodic (renewal) processes. It not only allows general (non-exponential) user lifetime distributions, but also captures heterogeneous behavior of peers. We utilize this model to analyze link dynamics and the ability of the system to stay connected under churn. Our results offers exact computation of user-isolation and graph-partitioning probabilities for any monotone lifetime distribution, including heavy-tailed cases found in real systems. We also propose an age-proportional random-walk algorithm for creating links in unstructured P2P networks that achieves zero isolation probability as system size becomes infinite. We additionally obtain many insightful results on the transient distribution of in-degree, edge arrival process, system size, and lifetimes of live users as simple functions of the aggregate lifetime distribution. The second half of this work studies churn in structured P2P networks that are usually built upon distributed hash tables (DHTs). Users in DHTs maintain two types of neighbor sets: routing tables and successor/leaf sets. The former tables determine link lifetimes and routing performance of the system, while the latter are built for ensuring DHT consistency and connectivity. Our first result in this area proves that robustness of DHTs is mainly determined by zone size of selected neighbors, which leads us to propose a min-zone algorithm that significantly reduces link churn in DHTs. Our second result uses the Chen-Stein method to understand concurrent failures among strongly dependent successor sets of many DHTs and finds an optimal stabilization strategy for keeping Chord connected under churn.

Interactions between macroeconomic fundamentals and term structure of interest rates be stronger according to the way of changes in structure of worldwide economy. Combined macro-finance analysis determines the joint dynamics of term structure of interest rates and macroeconomic fundamentals. This thesis provides analysis of two existing macro-finance models and an original one. Parameter estimations for these three macro-finance term structure models are done for monthly Turkish data by use of an efficient recursive estimator Kalman filter. In spite of the small scale application the results are satisfactory except first model but with longer sets of macroeconomic variables and interest rate data models provide more encouraging results.

<p>Denna rapport omfattar ett examensarbete på 22,5 poäng. Examensarbetet har utförts inom ämnet integrerad produktutveckling vid Högskolan i Skövde tillsammans med Jai Designpartner AB. Målet med arbetet var att utveckla ett fällbord som enkelt kan fällas ihop, ha en längre livslängd och lägre vikt än företagets tidigare fällbord. Samarbetet genererade ett fällbord som inte följer de generella principerna av infällning av bordsben. Resultatet blev ett fällbord med minimal klämrisk, med en längre livslängd då infällning av bordsbenet sker med en vridning och med en mindre vikt då ramverk kan elimineras.</p> / <p>This report comprises a 22,5 points degree project. This project has been executed within the area of integrated product development at the University of Skövde in cooperation with Jai Designpartner AB. The objective of the project was to develop a collapsible table that is easy to collapse, has a lower weight and higher feeling of quality, compared to the company´s earlier versions of collapsible tables. The result of the cooperation became a collapsible table with a minimal risk of injury, with a greater endurance since the legs are folded with a turning motion and with a lesser weight since the table lacks framework.</p>

La consommation annuelle totale moyenne en France dans le secteur tertiaire varie entre 300 et 380 kWh/m². Cette consommation se rapporte à l'ensemble des usages énergétiques du bâtiment: chauffage, climatisation, ventilation, éclairage, bureautique, auxiliaires et ECS. Ce travail a donné une méthode pour déterminer les meilleures combinaisons de solutions techniques existantes ou émergentes permettant de réduire les consommations énergétiques dans les bâtiments climatisés du secteur tertiaire. La réduction obtenue est d'un facteur 4 à 5. Une typologie représentative a été mise en place pour chaque secteur et les scénarios nécessaires pour effectuer les simulations définis. Une matrice de sélection du type de système par type de bâtiment a été fixée. Un niveau simplifié de modélisation des systèmes compatible avec les outils de prévision d'énergie a été employé. Vu le très grand nombre de variables à étudier, le nombre de simulations à effectuer et le traitement des résultats nécessite un temps énorme. Ce problème a été résolu par l'emploi de plans d'expériences fractionnaires. Cette méthode est nouvelle dans le domaine du bâtiment et répond à la question fréquente de réduction du nombre de simulation. Un modèle paramétrique de consommation a ainsi été élaboré. Il permet d'évaluer l'effet de chaque paramètre étudié sur les différentes postes consommateurs et la consommation annuelle totale. Ce modèle pourra servir à déduire la rentabilité des solutions et contribuer à une optimisation économique. La thèse traite la question d'un effet contradictoire possible de l'isolation sur la minimisation des consommations de refroidissement et de chauffage. Deux secteurs principaux du tertiaire sont étudiés: bâtiments de bureaux et bâtiments de santé. Le premier secteur est présenté dans l'intégralité de ses aspects tandis que le deuxième est traité brièvement. Le travail a permis d'élaborer une méthodologie complète pour minimiser les consommations énergétiques annuelles et pour étudier l'effet de chaque paramètre sur cette consommation.

Thesis (M.S.) -- Mississippi State University. Department of Electrical and Computer Engineering. / Title from title screen. Includes bibliographical references.

Η προσασρμοστική μάθηση (adaptive learning) είναι μια εκπαιδευτική μέθοδος η οποία χρησιμοποιεί κάποιο υπολογιστικό σύστημα ως διαδραστική συσκευή διδασκαλίας αναλαμβάνοντας να προσαρμόσει την παρουσίαση του εκπαιδευτικού υλικού σύμφωνα με τις ανάγκες των μαθητών, όπως αυτές προκύπτουν από τις απαντήσεις τους στις ερωτήσεις και τις εργασίες αλλά και γενικότερα παρατηρώντας παραμέτρους της συμπεριφοράς τους στο σύστημα. Η τεχνολογία που υποστηρίζει τη συγκεκριμένη εκπαιδευτική μέθοδο περιλαμβάνει τις πτυχές που προέρχονται από διάφορους επιστημονικούς τομείς όπως η επιστήμη των υπολογιστών, η εκπαίδευση και η ψυχολογία. Η προσαρμοστικής μάθηση έχει οδηγηθεί εν μέρει από τη συνειδητοποίηση ότι προσωπική μάθηση δεν μπορεί να επιτευχθεί σε μια μεγάλη κλίμακα χρησιμοποιώντας παραδοσιακές, μη-προσαρμοστικές προσεγγίσεις. Τα συστήματα προσαρμοστικής μάθησης στοχεύουν στο να μετατρέψουν τον μαθητή από παθητικό δέκτη πληροφοριών σε συνεργαζόμενο και ενεργό μέλος στην εκπαιδευτική διαδικασία. Ενώ μπορεί να υπάρχουν εξαιρέσεις, τα συστήματα προσαρμοστικής μάθησης είναι γενικά χτισμένα με τρία βασικά στοιχεία: ένα μοντέλο εμπειρογνώμονα ή περιεχομένου, ένα μοντέλο μαθητή, και ένα εκπαιδευτικό ή διδασκαλικό μοντέλο. Στα πλαίσια της διπλωματικής αυτής εργασίας μεταπτυχιακής ειδίκευσης αναπτύχθηκε ένα ηλεκτρονικό εκπαιδευτικό παιχνίδι για φορητή συσκευή το οποίο απευθύνεται σε μαθητές επιπέδου δημοτικού σχολείου και υιοθετεί τις αρχές της προσαρμοστικής μάθησης. Στόχος του παιχνιδιού είναι η εξάσκηση και η σταδιακή βελτίωση εκμάθησης της προπαίδειας. Το εκπαιδευτικό παιχνίδι υλοποιήθηκε σε LUA (Corona SDK) και δοκιμάστηκε σε Android συσκευές. Για να καθοριστούν οι λειτουργικές προδιαγραφές διερευνήθηκαν και καταγράφηκαν ήδη υπάρχοντα αντίστοιχα εκπαιδευτικά παιχνίδια, πραγματοποιήθηκε συνέντευξη με έμπειρη εκπαιδευτικό ώστε να προσαρμοστεί ο σχεδιασμός του σεναρίου του παιχνιδιού στην εκπαιδευτική πρακτική που εφαρμόζεται στο σχολείο, ενώ αφού ολοκληρώθηκε η υλοποίηση πραγματοποιήθηκαν δοκιμές με μαθητές α’, β’, γ’ δημοτικού ώστε να διερευνηθεί η αποτελεσματικότητα του εκπαιδευτικού παιχνιδιού. / Adaptive learning is an educational method that uses a computer system as an interactive teaching apparatus undertaking to adjust the presentation of educational material according to the needs of students, as reflected by their answers to the questions and work well generally observing aspects of their behavior in the system. The technology that supports this educational method includes aspects from different disciplines such as computer science, education and psychology. Adaptive learning has been driven in part by the realization that personal learning can not be achieved on a large scale using traditional non-adaptive approaches. Adaptive learning systems aim to transform the student from passive recipient of information at a partner and active member in the educational process. While there may be exceptions, adaptive learning systems are generally built with three key elements: a model expert or content, a user model, and an educational teaching model. As part of this thesis postgraduate specialization developed an online educational game for mobile device which is aimed at primary school level students and adopts the principles of adaptive learning. The objective of the game is to practice and the gradual improvement of learning the multiplication tables. The educational game implemented in LUA (Corona SDK) and tested on Android devices. To determine the functional specifications were investigated and recorded existing respective educational games, interviewed by experienced teacher to fit the design of the scenario of the game in the educational practice at school, and after the completed implementation was tested with students a, b, c grade to investigate the effectiveness of educational game.

Numerous cryptographic applications require a trusted authority to hold a secret. With a plethora of malicious attacks over the Internet, however, it is difficult to establish and maintain such an authority in online systems. Secret-sharing schemes attempt to solve this problem by distributing the required trust to hold and use the secret over multiple servers; however, they still require a trusted {\em dealer} to choose and share the secret, and have problems related to single points of failure and key escrow. A distributed key generation (DKG) scheme overcomes these hurdles by removing the requirement of a dealer in secret sharing. A (threshold) DKG scheme achieves this using a complete distribution of the trust among a number of servers such that any subset of servers of size greater than a given threshold can reveal or use the shared secret, while any smaller subset cannot. In this thesis, we make contributions to DKG in the computational security setting and describe three applications of it. We first define a constant-size commitment scheme for univariate polynomials over finite fields and use it to reduce the size of broadcasts required for DKG protocols in the synchronous communication model by a linear factor. Further, we observe that the existing (synchronous) DKG protocols do not provide a liveness guarantee over the Internet and design the first DKG protocol for use over the Internet. Observing the necessity of long-term stability, we then present proactive security and group modification protocols for our DKG system. We also demonstrate the practicality of our DKG protocol over the Internet by testing our implementation over PlanetLab. For the applications, we use our DKG protocol to define IND-ID-CCA secure distributed private-key generators (PKGs) for three important identity-based encryption (IBE) schemes: Boneh and Franklin's BF-IBE, Sakai and Kasahara's SK-IBE, and Boneh and Boyen's BB1-IBE. These IBE schemes cover all three important IBE frameworks: full-domain-hash IBEs, exponent-inversion IBEs and commutative-blinding IBEs respectively, and our distributed PKG constructions can easily be modified for other IBE schemes in these frameworks. As the second application, we use our distributed PKG for BF-IBE to define an onion routing circuit construction mechanism in the identity-based setting, which solves the scalability problem in single-pass onion routing circuit construction without hampering forward secrecy. As the final application, we use our DKG implementation to design a threshold signature architecture for quorum-based distributed hash tables and use it to define two robust communication protocols in these peer-to-peer systems.