The global energy system is dominated by the use of fossil fuels. This system suffers from several problems, such as different environmental issues, while the long-term energy security is sometimes questioned. As an alternative to this situation, a transition to a global energy system based on renewable energy technologies, to a large extent solar and wind energy, is commonly proposed. Constructing the technology needed for such a transition requires resources and how fast this could happen is somewhat disputed. This thesis explores methods to assess the potential constraints for realizing such a transition by looking at potential technology growth rates and outlooks of production of the required natural resources. The thesis is based on three papers presenting case studies that look at growth rates of wind energy as well as future production outlooks of lithium and phosphate rock. Using different types of growth patterns reaching proposed installed capacities of wind power, annual commissioning requirements are investigated, taking account for the limited life expectancy oftechnology. Potential outlooks of mineral production are explored using resource constrained curve-fitting models on global lithium production. A more disaggregated model looking at individual countries are used on phosphate rock production to investigate new perspectives on production outlooks. It is concluded that the growth rates of individual energy technologies affect the resource requirements and prospective constraints on energy transitions. Resource constrained modelling of resource production can provide spans of potential outlooks for future production of resources required for anenergy transition. A higher disaggregation of the modelling can provide new perspectives of potential constraints on future production. These aspects should be further investigated when proposing alternative future energy systems.

The Boxall Profile (BP) aims at assessing the quality of adaptation of primary school pupils along with their particular difficulties of adaptation, in order to guide teacher interventions in classroom. At this time, the BP's psychometric proprieties have not been studied much. 169 boys and 23 girls ( N = 192) ranging from 6 to 13 years old (M = 9.24 years old, SD = 1.83) were assessed by their teacher using the French versions of the Boxall Profile, the Strenghts and Difficulties Questionnaire (SDQ) and the Teacher Report Form (TRF). Confirmatory and exploratory factor analysis (CFA/EFA) and area under receiver operating characteristic curve (ROC) were all performed. The results support the fit of the first level of factorial structure and a good concurrent validity. These results suggest the effectiveness of BP in properly identifying pupils in a problematic situation. However, one has to be cautious when it comes to interpreting given scale's scores to guide the intervention.

International Telemetering Conference Proceedings / October 26-29, 1998 / Town & Country Resort Hotel and Convention Center, San Diego, California / This paper analyzes the performance of a modified correlation, or delay-locked loop (DLL). These devices typically cross-correlate the received signal with a differentiated version of the originally transmitted signal. This paper describes some interesting properties the loop assumes when the differentiator is replaced by a Hilbert transform. The loop will still track the timing offset of the code, but it will also be able to acquire the signal when the initial offset is greater than one chip time. The new loop may also be superior to traditional DLL in low SNR environments, since it is much less likely to lose lock. Since the new loop is highly non-linear, it is studied through the use of computer simulations.

Sustainable energy systems require deployment of new technologies to help tackle the challenges of climate change and ensuring energy supplies. Future sources of energy are less economically competitive than conventional technologies, but there is the potential for cost reduction. Tools for modelling technological change are important for assessing the deployment potential of early-stage technologies. Learning curves are a tool for assessing and forecasting cost reduction of a product achieved through experience from cumulative production. They are often used to assess technological improvements, but have a number of limitations for emerging energy technologies. Learning curves are aggregate in nature, representing overall cost reduction gained from learning-by-doing. However, they do not identify the actual factors behind the cost reduction. Using the case study of onshore wind energy, this PhD study focuses on combining learning curves with engineering assessment methods for improved methods of assessing and managing technical change for emerging energy technologies. A third approach, parametric modelling, provides a potential means to integrate the two methods.

Ένα από τα βασικά προβλήματα κρυπτογραφίας είναι η δημιουργία και διαχείριση κλειδιών.Αν δύο ή περισσότερες οντότητες θέλουν να επικοινωνήσουν ασφαλώς, τότε πρέπει να διασφαλίσουν το απόρρητο της επικοινωνίας τους μέσω κρυπτογράφησης δεδομένων. Για να γίνει, όμως, αυτό πρέπει να γεννηθεί ένα κοινό κλειδί(κλειδί συνεδρίας) στο οποίο πρέπει να συμφωνήσουν όλοι οι εμπλεκόμενοι και το οποίο θα μπορεί να πιστοποιηθεί και να διανεμηθεί ασφαλώς. Ένα πρωτόκολλο συμφωνίας κλειδιών είναι μια τεχνική δημιουργίας κλειδιών στην οποία ένα μοιραζόμενο μυστικό προκύπτει από δύο ή περισσότερους εμπλεκόμενους ως συνάρτηση πληροφοριών που συνεισφέρονται ή σχετίζονται με κάθε έναν εμπλεκόμενο έτσι, ώστε(ιδανικά), κανένας εμπλεκόμενος από μόνος του να μην μπορεί να προϋπολογίσει,προαποφασίσει το προκύπτoν μυστικό. Με άλλα λόγια ,όλες οι οντότητες που εμπλέκονται στο πρωτόκολλο πρέπει να συνεισφέρουν μια δικιά τους πληροφορία(την ψηφιακή τους ταυτότητα, το προσωπικό τους δημόσιο κλειδί, ένα password κ.τ.λ.) έτσι, ώστε να προκύψει το συνολικό κλειδί ασφάλισης του καναλιού επικοινωνίας τους. Τέτοια πρωτόκολλα είναι τα πρωτόκολλα Diffie-Hellman τα οποία εμφανίζονται σε πολλές παραλλαγές (και επίπεδα ασφαλείας). Η υλοποιησή τους, όμως, για πολλούς εμπλεκόμενους φορείς παραμένει δύσκολη, επειδή απαιτεί κόστος σε πόρους υλικού και δεν διασφαλίζει πλήρως ένα υψηλό επίπεδο ασφαλείας. Βασίζονται στις αρχές της κρυπτογραφίας Δημοσίου κλειδιού και η λειτουργικότητά τους για παραπάνω από έναν χρήστη αποτελεί ένα ανοικτό κεφάλαιο έρευνας. Στα πλαίσια αυτής της διπλωματικής θα μελετηθεί η λειτουργία αυτών των πρωτοκόλλων και θα επικεντρωθούμε σε σύγχρονες τεχνικές τους με την χρήση ελλειπτικών καμπυλών (Πρωτόκολλα Diffie Hellman ελλειπτικών καμπυλών).Θα αναλυθεί η ασφάλεια των πρωτοκόλλων αυτών και θα σχεδιαστεί ένα μοντέλο επίθεσης. Στόχος είναι να προταθεί μια λύση πάνω σε αυτά τα πρωτόκολλα που θα διασφαλίζει το υψηλό επίπεδο ασφάλειας των εμπλεκόμενων φορέων και θα έχει υψηλή απόδοση και χαμηλές απαιτήσεις υλικού. Για να γίνει αυτό το προτεινόμενο πρωτόκολλο θα αναλυθεί και μια αρχιτεκτονική υλικού θα σχεδιαστεί. Η αρχιτεκτονική αυτή θα υλοποιηθεί μέσω της γλώσσας VHDL σε τεχνολογία FPGA με στόχο να μετρηθεί το επίπεδο απόδοσης της αρχιτεκτονικής και του πρωτοκόλλου γενικότερα. / One of the basic problems in cryptography is the creation and management of keys. If two or more entities want to communicate securely then they must ensure the confidentiality of communication through data encryption. In order to do this must be born a public key (session key) in which they have to agree all the participants and which will be certified and distributed securely. A protocol of key agreement is a technique of creation keys in which a shared secret results from two or more participants as interelation of informations that contributed or is related with each one involved, so (ideally) nobody from himself cannot budget or predetermine the resulting secret. In other words all entities that are involved in the protocol should contribute their own information (their digital identity, their personal public key, password etc.) so as to result the total key of insurance of their channel of communication. Such protocols are the protocols Diffie-Hellman which are presented in a lot of variants (and levels of safety). Their implementation however for a lot of involved entities remains difficult and requires cost in resources of hardware and does not ensure completely a high level of safety. They are based on the principles of cryptography of Public key and their functionalism for more than one user constitutes an open chapter of research. Within this thesis, we study the function of these protocols and focus on modern techniques using Elliptic Curves (Diffie Hellman Elliptic Curves Protocols). We analyze the security of these protocols and design a model attack. The aim is to propose a solution on these protocols to ensure the highest level of security among the involved entities and have high efficiency and low hardware requirements. To do that the proposed protocol will be analyzed and a hardware architecture will be designed. This architecture will be implemented by the language VHDL on FPGA technology in order to measure the performance level of the architecture and the protocol in general.

Doctor of Philosophy / Department of Civil Engineering / Sunanda Dissanayake / Malgorzata J. Rys / Driver workload increases on horizontal curves due to more complicated navigation compared to navigation on straight roadway sections. Although only a small portion of roadways are horizontal curve sections, approximately 25% of all fatal highway crashes occur at horizontal curve sections. According to the Fatality Analysis Reporting System (FARS) database, fatalities associated with horizontal curves were more than 25% during last years from 2008 to 2014, reinforcing that investigation of horizontal curve crashes and corresponding safety improvements are crucial study topics within the field of transportation safety. Improved safety of horizontal curve sections of rural transportation networks can contribute to reduced crash severities and frequencies. Statistical methods can be utilized to develop crash prediction models in order to estimate crashes at horizontal curves and identify contributing factors to crash occurrences, thereby correlating to the primary objectives of this research project. Primary data analysis for 221 randomly selected horizontal curves on undivided two-lane two-way highways with Poisson regression method revealed that annual average daily traffic (AADT), heavy vehicle percentage, degree of curvature, and difference between posted and advisory speeds affect crash occurrence at horizontal curves. The data, however, were relatively overdispersed, so the negative binomial (NB) regression method was utilized. Results indicated that AADT, heavy vehicle percentage, degree of curvature, and long tangent length significantly affect crash occurrence at horizontal curve sections. A new dataset consisted of geometric and traffic data of 5,334 horizontal curves on the entire state transportation network including undivided and divided highways provided by Kansas Department of Transportation (KDOT) Traffic Safety Section as well as crash data from the Kansas Crash and Analysis Reporting System (KCARS) database were used to analyze the single vehicle (SV) crashes. An R software package was used to write a code and combine required information from aforementioned databases and create the dataset for 5,334 horizontal curves on the entire state transportation network. Eighty percent of crashes including 4,267 horizontal curves were randomly selected for data analysis and remaining 20% horizontal curves (1,067 curves) were used for data validation. Since the results of the Poisson regression model showed overdispersion of crash data and many horizontal curves had zero crashes during the study period from 2010 to 2014, NB, zero-inflated Poisson (ZIP), and zero-inflated negative binomial (ZINB) methods were used for data analysis. Total number of crashes and severe crashes were analyzed with the selected methods. Results of data analysis revealed that AADT, heavy vehicle percentage, curve length, degree of curvature, posted speed, difference between posted and advisory speed, and international roughness index influenced single vehicle crashes at 4,267 randomly selected horizontal curves for data analysis. Also, AADT, degree of curvature, heavy vehicle percentage, posted speed, being a divided roadway, difference between posted and advisory speeds, and shoulder width significantly influenced severe crash occurrence at selected horizontal curves. The goodness-of-fit criteria showed that the ZINB model more accurately predicted crash numbers for all crash groups at the selected horizontal curve sections. A total of 1,067 horizontal curves were used for data validation, and the observed and predicted crashes were compared for all crash groups and data analysis methods. Results of data validation showed that ZINB models for total crashes and severe crashes more accurately predicted crashes at horizontal curves. This study also investigated the effect of speed limit change on horizontal curve crashes on K-5 highway in Leavenworth County, Kansas. A statistical t-test proved that crash data from years 2006 to 2012 showed only significant reduction in equivalent property damage only (EPDO) crash rate for adverse weather condition at 5% significance level due to speed limit reduction in June 2009. However, the changes in vehicles speeds after speed limit change and other information such as changes in surface pavement condition were not available. According to the results of data analysis for 221 selected horizontal curves on undivided two-lane highways, tangent section length significantly influenced total number of crashes. Therefore, providing more information about upcoming changes in horizontal alignment of the roadway via doubling up warning sings, using bigger sings, using materials with higher retroreflectivity, or flashing beacons were recommended for horizontal curves with long tangent section lengths and high number of crashes. Also, presence of rumble strips and wider shoulders significantly and negatively influenced severe SV crashes at horizontal curve sections; therefore, implementing rumble strips and widening shoulders for horizontal curves with high number of severe SV crashes were recommended.

Magíster en Ciencias de la Ingeniería, Mención Eléctrica. Ingeniero Civil Eléctrico / Existe una creciente preocupación por la sostenibilidad, producto del ritmo de consumo de recursos naturales de la actividad económica humana y en un contexto de cambio climático a escala global. En este sentido, la descarbonización de la oferta de energía de los sistemas eléctricos constituye un elemento clave. De hecho, se ha logrado incrementar sostenidamente la penetración de fuentes renovables a nivel mundial. Estas fuentes (eólica y solar), en su mayoría, tienen la desventaja de presentar una alta variabilidad y baja predictibilidad. Lo anterior se debe compensar agregando soluciones que aporten flexibilidad a los sistemas eléctricos. Las tendencias de costos observadas permiten suponer que las tecnologías de almacenamiento energético jugarán un rol relevante en la provisión de flexibilidad, debido a las características técnicas que éstas poseen. Si bien se han realizado importantes esfuerzos para determinar el dimensionamiento óptimo de estas tecnologías, se identifica una falencia de metodologías simplificadas y suficientemente precisas que faciliten el entendimiento de los conceptos básicos asociados. Por otra parte, también es deseable que estas metodologías puedan, además, ser utilizadas en la toma de decisiones en el sector. El objetivo de esta tesis es desarrollar una metodología gráfica-analítica que permita determinar la combinación mix óptima de tecnologías de generación y almacenamiento en un sistema eléctrico de potencia. Una metodología clásica utilizada para planificar parques de generadores es la denominada screening curves , en la cual los consumos se representan a través de una curva de duración. La metodología propuesta consiste en integrar de manera sistemática las tecnologías de almacenamiento, lográndose desarrollar un procedimiento secuencial que permite realizar una planificación centralizada a mínimo costo de tecnologías de generación y almacenamiento. Las energías renovables de carácter variable son integradas a través de distintos escenarios de penetración y su generación es descontada en forma cronológica de la estimación de consumo horario en el año de análisis. Junto con entregar un respaldo teórico a la metodología propuesta, ésta se valida con dos casos de estudio: uno teórico que permite detallar la aplicación del algoritmo, y un sistema basado en la proyección del sistema eléctrico chileno al año 2050. Ambos casos son contrastados con los resultados obtenidos con una metodología de planificación convencional de simulación numérica. Asimismo, se presenta un estudio adicional del sistema eléctrico alemán al año 2050. Los resultados obtenidos permiten validar el algoritmo propuesto. Se constata que la metodología converge al óptimo cuando el mismo problema es resuelto con métodos numéricos. Además, se observan bajos porcentajes de error al comparar con el resultado obtenido al resolver la planificación utilizando la curva de duración de carga sin su aproximación por bloques. Por otro lado, las diferencias son mayores cuando se compara con un modelamiento cronológico, lo que demanda una calibración exógena de parámetros del modelo, tales como el número de ciclos esperados del sistema de almacenamiento. Se presenta un análisis de conceptos técnico-económicos claves que determinan la integración y mix de tecnologías de almacenamiento a un sistema eléctrico. Estos constituyen el aporte de la tesis a potenciar la toma de decisiones respecto de la integración de sistemas de almacenamiento en un sistema eléctrico de potencia. Asimismo, estos conceptos buscan ser un aporte a la docencia y formación en el área. Como trabajo futuro se propone optimizar la selección del número de bloques de la curva de carga y la estimación del número de ciclos esperados de los Sistemas de Almacenamiento de Energía. / Este trabajo ha sido financiado por CONICYT

Thesis advisor: John A. Baldwin / We study the relationship between knots in contact three-manifolds and complex curves in Stein surfaces. To do so, we extend the notion of quasipositivity from classical braids to links that are braided with respect to an open book decomposition of an arbitrary closed, oriented three-manifold. Our main results characterize the transverse links in Stein-fillable contact three-manifolds that bound smooth holomorphic curves in Stein fillings. This characterization is made possible by new techniques in the theory of characteristic and open book foliations on surfaces in three-manifolds. We also explore the Seifert genera of cross-sections of complex plane curves, minimal braid representatives of quasipositive links, and the relationship between Legendrian ribbons in contact three-manifolds and strongly quasipositive braids with respect to compatible open books. / Thesis (PhD) — Boston College, 2018. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Mathematics.

Thesis advisor: Robert Murphey / This paper demonstrates that a linear Phillips Curve has neither theoretical nor empirical justification. I first alter the traditional linear model specification to allow for non-linearity between inflation and unemployment. I show that these non-linear models produce greater R2’s than similar linear versions. I provide theoretical justification for the non-linear models and demonstrate why the theoretical reasoning for linear models is flawed. Finally, by introducing the natural rate of unemployment as a separate independent variable, I increase the explanatory power of the model. I allow the natural rate’s marginal effect on inflation to vary with time and suggest a theoretical framework that supports this final model. I conclude that non-linearity and therefore convexity between inflation and unemployment is the correct framework under any time period for Phillips Curve analysis and application. / Thesis (BA) — Boston College, 2017. / Submitted to: Boston College. College of Arts and Sciences. / Discipline: Departmental Honors. / Discipline: Economics.

In a projective plane (PG(2, K) defined over an algebraically closed field K of characteristic p = 0, we give a complete classification of 3-nets realizing a finite group. The known infinite family, due to Yuzvinsky, arised from plane cubics and comprises 3-nets realizing cyclic and direct products of two cyclic groups. Another known infinite family, due to Pereira and Yuzvinsky, comprises 3-nets realizing dihedral groups. We prove that there is no further infinite family and list all possible sporadic examples. If p is larger than the order of the group, the same classification holds true apart from three possible exceptions: Alt4, Sym4 and Alt5. / by Nicola Pace. / Thesis (Ph.D.)--Florida Atlantic University, 2012. / Includes bibliography. / System requirements: Adobe Reader. / Mode of access: World Wide Web.