Η παρούσα εργασία αποτελεί μια μελέτη που πραγματοποιήθηκε στο πεδίο κρατήρων διαφυγής αερίων στην περιοχή Αιγίου στον Δυτικό Κορινθιακό Κόλπο. Για την μελέτη συλλέχθηκαν δεδομένα από ηχοβολιστικά συστήματα και συγκεκριμένα από τομογράφο υποδομής πυθμένα. Τα δεδομένα επεξεργάστηκαν για να μετατραπούν σε ψηφιακή μορφή έτσι ώστε, στη συνέχεια, να χρησιμοποιηθούν στα γεωφυσικά συστήματα επεξεργασίας δεδομένων, να γίνει η ψηφιοποίηση χαρτών και τομογραφιών. Ο σκοπός της εργασίας ήταν η δημιουργία αποτελεσμάτων σχετικά με τις αιτίες που προκαλούν τη διαφυγή αερίων και γλυκού νερού, δημιουργια βυθομετρικού χάρτη της περιοχής στον οποίο θα εμφανίζονται οι θέσεις των κρατήρων. Στην παρούσα εργασία περιλαμβάνεται η γεωλογία της περιοχής καθώς και τα βήματα που πραγματοποιήθηκαν για την διεξαγωγή των αποτελεσμάτων. / --

Αντικείμενο της έρευνας είναι η γεωφυσική διασκόπηση του πυθμένα με τη χρήση τομογράφου υποδομής πυθμένα (sub-bottom profiler) και ηχοβολιστή πλευρικής σάρωσης (side scan sonar) στη Λίμνη Παμβώτιδα με σκοπό: (α) τον προσδιορισμό της στρωματογραφικής υποδομής του πυθμένα της λίμνης Παμβώτιδας έτσι ώστε να είναι δυνατός ο εντοπισμός και η εκτίμηση του πάχους του επιφανειακού στρώματος υδαρούς λάσπης (ιλύος) που καλύπτει τον πυθμένα (β) τον καθορισμό της επιφανειακής εξάπλωσης του στρώματος υδαρούς λάσπης (ιλύος) στον πυθμένα της λίμνης. Επιπρόσθετα, πραγματοποιήθηκε δειγματοληψία επιφανειακών ιζημάτων με στόχο την καλύτερη εκτίμηση του επιφανειακού στρώματος υδαρούς ιλύος. / The object of this project is to have a full bottom and sub-bottom analysis for lake Pamvotida, using sub-bottom profiler and side scan sonar.

Most operating systems provide protection and isolation to user processes, but not to critical system components such as device drivers or other systems code. Consequently, failures in these components often lead to system failures. VirtuOS is an operating system that exploits a new method of decomposition to protect against such failures. VirtuOS exploits virtualization to isolate and protect vertical slices of existing OS kernels in separate service domains. Each service domain represents a partition of an existing kernel, which implements a subset of that kernel's functionality. Service domains directly service system calls from user processes. VirtuOS exploits an exceptionless model, avoiding the cost of a system call trap in many cases. We illustrate how to apply exceptionless system calls across virtualized domains. To demonstrate the viability of VirtuOS's approach, we implemented a prototype based on the Linux kernel and Xen hypervisor. We created and evaluated a network and a storage service domain. Our prototype retains compatibility with existing applications, can survive the failure of individual service domains while outperforming alternative approaches such as isolated driver domains and even exceeding the performance of native Linux for some multithreaded workloads. The evaluation of VirtuOS revealed costs due to decomposition, memory management, and communication, which necessitated a fine-grained analysis to understand their impact on the system's performance. The interaction of virtual machines with multiple underlying software and hardware layers in virtualized environment makes this task difficult. Moreover, performance analysis tools commonly used in native environments were not available in virtualized environments. Our work addresses this problem to enable an in-depth performance analysis of VirtuOS. Our Perfctr-Xen framework provides capabilities for per-thread analysis with both accumulative event counts and interrupt-driven event sampling. Perfctr-Xen is a flexible and generic tool, supports different modes of virtualization, and can be used for many applications outside of VirtuOS. / Ph. D.

Over recent years, organizations such as the Federal Highway Administration and Departments of Transportation across the United States have showed interest in automating highway construction processes. The addition of e-Construction and other advanced technologies can significantly improve the efficiency and safety of highway paving operations, specifically paving inspections. Activities such as collecting load tickets, tracking pavement lay-down temperatures, and monitoring roller movement are antiquated practices that DOT inspectors perform during paving operations. E-Ticketing, Paver Mounted Thermal Profiling, and Intelligent Compaction were proposed to automate paving inspections and were recently tested in two resurfacing pilot projects in the state of Kentucky. Findings from the projects indicate that the three technologies display great potential in improving safety and efficiency of paving inspections. The contribution of this thesis is to document the research effort, evaluate the effectiveness of the technologies compared to the traditional practices, and discuss the lessons learned for industry practitioners.

Transport and mixing of momentum and salt in an estuary varies in time and space due to river discharge, changes in tidal amplitude and phase, wind stress, and lateral mixing processes, such as secondary circulation. This dissertation focuses on observing, describing, parameterizing, and quantifying secondary circulation in a sinuous coastal plain estuary using acoustic Doppler current meters. This endeavor is made to improve our general understanding of secondary circulation, to identify its primary driving forces, and to better parameterize key physical processes necessary for further study in current numerical models. Secondary circulation is used to describe several mechanisms whose result is to vertically overturn the water column along the transverse axis of a channel. Secondary circulation is commonly generated by one or more of the following mechanisms: channel curvature, unusual bottom topography or channel geometry, planetary rotation, and/or the differential advection of density. Data for this dissertation was collected in the naturally sinuous Satilla River in southeast Georgia. A shallow coastal plain estuary, the Satilla is a partially-mixed estuary characterized by 2 meter range semidiurnal tides. It has a strong neap-to-spring axial current inequality and strong neap-to-spring vertical salinity differences. The balance of mechanisms responsible for the strength and location of secondary flow in the Satilla River varies with spatial location, phase of the tide, and lateral cross-channel position. A simple steady-state momentum balance between the Coriolis acceleration, centrifugal acceleration, the lateral baroclinic gradient, and bottom stress is sufficient to explain secondary circulation in the Satilla River under a wide variety of conditions. The primary momentum balance for this river is a three-way balance between the centrifugal acceleration, bottom stress, and the lateral baroclinic gradient. The dominant mechanism that drives the local secondary circulation depends on the phase of the tide and the lateral placement of the acoustic current profiler.

A Confluência Brasil-Malvinas (CBM) é formada pelo encontro da Corrente do Brasil (CB) com a Corrente das Malvinas (CM) no Atlântico Sul e, por constituir o encontro de correntes de contorno oeste (CCO), é demarcada por um intenso gradiente horizontal de temperatura. A inclinação das isopicnais na porção mais quente de regiões de encontro de duas CCO favorece a formação de águas modais ao final do inverno. O estudo de águas modais subtropicais ainda é incipiente no Atlântico Sul, quando comparado com os diversos trabalhos versando sobre o fenômeno em outras regiões do mundo. A realização do primeiro cruzeiro oceanográfico especificamente planejado para o estudo de águas modais na região da CBM e de retroflexão da CB permitiu verificar a anisotropia desse extenso corpo d\'água, cuja espessura e profundidades máxima e mínima variam mormente com a latitude em que o fenômeno ocorre. Os dados fornecidos pelos perfiladores Argo lançados durante o cruzeiro, e ainda em operação na região da CBM, corroboraram tal observação e revelaram o limite norte da região de formação da água modal subtropical do sudoeste do Atlântico Sul (AMSTAS) em torno da latitude de 34°S. A comparação dos resultados obtidos in situ com os dados do modelo oceânico HYCOM, numa simulação de 4 anos, permitiu observar a mesma anisotropia e limite norte da área de formação. Embora relativamente curta, a série temporal viabilizou a primeira estimativa de volume da AMSTAS e uma avaliação preliminar dos processos envolvidos na dissipação da AMSTAS recém formada. O emprego de dados de satélites altímetros para o cálculo do calor armazenado (CA) na região de estudo permitiu verificar que a instabilidade apresentada na série temporal de dados do modelo HYCOM se deve sobretudo à dinâmica de mesoescala na região mais próxima do encontro das duas CCO. A análise do CA na região onde foi realizado o cruzeiro oceanográfico do estudo, permitiu identificar mais claramente a existência de diferentes padrões de calor armazenado coincidentes com áreas típicas de formação, os quais não ocorreram em áreas que continham AMSTAS apenas afundada. / The Brazil-Malvinas confluence zone (BMCZ) is an energetic region of the South Atlantic Ocean where the Brazilian Current (BC) and the Malvinas Current (MC) meet. As a convergence area of Western Boundary Currents (WBC), it is marked by intense horizontal temperature gradients. The inclination of isopycnals in the warm side of WBC convergence zone enables the formation of mode water at the end of winter. The study of subtropical mode waters in the South Atlantic is still incipient compared to similar investigations conducted in other regions of the world. The first oceanographic cruise specifically dedicated to the study of mode waters in the BMCZ and the BC retroflection helped verify the anisotropy of such extensive water masses, whose maximum and minimum thickness and depth vary mainly with the latitude where these phenomenon occur. Data derived from Argo profilers released during the cruise and currently still operating in the BMCZ, support this observation and indicate the northern limit of the formation region of the Southwestern Atlantic subtropical mode water (SASTMW) near latitude 34°S. Comparison of in situ results with those obtained from a 4-years simulation with the HYCOM ocean model, indicates similar anisotropy and northern limit of the formation area. Despite its relatively small length, this time series enabled the first estimation of the SASTMW volume, and a preliminary validation of the processes involved in the dissipation of newly formed SASTMW. The use of satellite altimetry data for the computation of heat content in the study area helped conclude that the instability observed in the time series of the HYCOM model output is due to mesoscale dynamics near the convergence zone of the BC and the MC. Analysis of heat content in the region where the oceanographic cruise was conducted helped identify the existence of different patterns in heat content, that coincide with typical formation areas but not with areas where SASTMW is already submerged.

A Confluência Brasil-Malvinas (CBM) é formada pelo encontro da Corrente do Brasil (CB) com a Corrente das Malvinas (CM) no Atlântico Sul e, por constituir o encontro de correntes de contorno oeste (CCO), é demarcada por um intenso gradiente horizontal de temperatura. A inclinação das isopicnais na porção mais quente de regiões de encontro de duas CCO favorece a formação de águas modais ao final do inverno. O estudo de águas modais subtropicais ainda é incipiente no Atlântico Sul, quando comparado com os diversos trabalhos versando sobre o fenômeno em outras regiões do mundo. A realização do primeiro cruzeiro oceanográfico especificamente planejado para o estudo de águas modais na região da CBM e de retroflexão da CB permitiu verificar a anisotropia desse extenso corpo d\'água, cuja espessura e profundidades máxima e mínima variam mormente com a latitude em que o fenômeno ocorre. Os dados fornecidos pelos perfiladores Argo lançados durante o cruzeiro, e ainda em operação na região da CBM, corroboraram tal observação e revelaram o limite norte da região de formação da água modal subtropical do sudoeste do Atlântico Sul (AMSTAS) em torno da latitude de 34°S. A comparação dos resultados obtidos in situ com os dados do modelo oceânico HYCOM, numa simulação de 4 anos, permitiu observar a mesma anisotropia e limite norte da área de formação. Embora relativamente curta, a série temporal viabilizou a primeira estimativa de volume da AMSTAS e uma avaliação preliminar dos processos envolvidos na dissipação da AMSTAS recém formada. O emprego de dados de satélites altímetros para o cálculo do calor armazenado (CA) na região de estudo permitiu verificar que a instabilidade apresentada na série temporal de dados do modelo HYCOM se deve sobretudo à dinâmica de mesoescala na região mais próxima do encontro das duas CCO. A análise do CA na região onde foi realizado o cruzeiro oceanográfico do estudo, permitiu identificar mais claramente a existência de diferentes padrões de calor armazenado coincidentes com áreas típicas de formação, os quais não ocorreram em áreas que continham AMSTAS apenas afundada. / The Brazil-Malvinas confluence zone (BMCZ) is an energetic region of the South Atlantic Ocean where the Brazilian Current (BC) and the Malvinas Current (MC) meet. As a convergence area of Western Boundary Currents (WBC), it is marked by intense horizontal temperature gradients. The inclination of isopycnals in the warm side of WBC convergence zone enables the formation of mode water at the end of winter. The study of subtropical mode waters in the South Atlantic is still incipient compared to similar investigations conducted in other regions of the world. The first oceanographic cruise specifically dedicated to the study of mode waters in the BMCZ and the BC retroflection helped verify the anisotropy of such extensive water masses, whose maximum and minimum thickness and depth vary mainly with the latitude where these phenomenon occur. Data derived from Argo profilers released during the cruise and currently still operating in the BMCZ, support this observation and indicate the northern limit of the formation region of the Southwestern Atlantic subtropical mode water (SASTMW) near latitude 34°S. Comparison of in situ results with those obtained from a 4-years simulation with the HYCOM ocean model, indicates similar anisotropy and northern limit of the formation area. Despite its relatively small length, this time series enabled the first estimation of the SASTMW volume, and a preliminary validation of the processes involved in the dissipation of newly formed SASTMW. The use of satellite altimetry data for the computation of heat content in the study area helped conclude that the instability observed in the time series of the HYCOM model output is due to mesoscale dynamics near the convergence zone of the BC and the MC. Analysis of heat content in the region where the oceanographic cruise was conducted helped identify the existence of different patterns in heat content, that coincide with typical formation areas but not with areas where SASTMW is already submerged.

Microsoft Research / Although runtime systems and the dynamic compilation model have revolutionized the process of application development and deployment, the associated performance overheads continue to be a cause for concern and much research. In the first part of this thesis, we describe the design and implementation of an adaptive recompilation framework for Rotor, a shared source implementation of the Common Language Infrastructure (CLI) that can increase program performance through intelligent recompilation decisions and optimizations based on the program's past behavior. Our extensions to Rotor include a low overhead runtime-stack based sampling profiler that identifies program hotspots. A recompilation controller oversees the recompilation process and generates recompilation requests. At the first-level of a multi-level optimizing compiler, code in the intermediate language is converted to an internal intermediate representation and optimized using a set of simple transformations. The compiler uses a fast yet effective linear scan algorithm for register allocation. Hot methods can be instrumented in order to collect basic-block, edge and call-graph profile information. Profile-guided optimizations driven by online profile information are used to further optimize heavily executed methods at the second level of recompilation. An evaluation of the framework using a set of test programs shows that performance can improve by a maximum of 42.3% and by 9% on average. Our results also show that the overheads of collecting accurate profile information through instrumentation to an extent outweigh the benefits of profile-guided optimizations in our implementation, suggesting the need for implementing techniques that can reduce such overheads. A flexible and extensible framework design implies that additional profiling and optimization techniques can be easily incorporated to further improve performance. As previously stated, fine-grained and accurate profile information must be available at low cost for advanced profile-guided optimizations to be effective in online environments. In this second part of this thesis, we propose a generic framework that makes it possible for instrumentation based profilers to collect profile data efficiently, a task that has traditionally been associated with high overheads. The essence of the scheme is to make the underlying hardware aware of instrumentation using a special set of profile instructions and tuned microarchitecture. This not only allows the hardware to provide the runtime with mechanisms to control the profiling activity, but also makes it possible for the hardware itself to optimize the process of profiling in a manner transparent to the runtime. We propose selective instruction dispatch as one possible controlling mechanism that can be used by the runtime to manage the execution of profile instructions and keep profiling overheads under check. We propose profile flag prediction, a hardware optimization that complements the selective dispatch mechanism by not fetching profile instructions when the runtime has turned profiling off. The framework is light-weight and flexible. It eliminates the need for expensive book-keeping, recompilation or code duplication. Our simulations with benchmarks from the SPEC CPU2000 suite show that overheads for call-graph and basic block profiling can be reduced by 72.7% and 52.4% respectively with a negligible loss in accuracy.

The problem that the researcher encountered was that forensic investigators were found not to be formally using offender profiling as an investigative technique during investigations into fraud. This research was conducted to ascertain how offender profiling may be useful in expediting the forensic investigation process. The purpose of this research was to establish what offender profiling is, and what aspects or ingredients constitute such an offender profile. As offender profiles will serve as an aid in future forensic investigations into fraud, this study attempted to create an understanding and awareness of the value of offender profiling. In order for forensic investigators to use offender profiling during routine fraud investigations, it is extremely important that they understand the concept and its practical implementation. The overall purpose of this study is to provide practical recommendations for the implementation and use of offender profiling to forensic investigators both in the public and private sectors. / Criminal and Procedural Law / (M.Tech. (Forensic Investigation))

The problem that the researcher encountered was that forensic investigators were found not to be formally using offender profiling as an investigative technique during investigations into fraud. This research was conducted to ascertain how offender profiling may be useful in expediting the forensic investigation process. The purpose of this research was to establish what offender profiling is, and what aspects or ingredients constitute such an offender profile. As offender profiles will serve as an aid in future forensic investigations into fraud, this study attempted to create an understanding and awareness of the value of offender profiling. In order for forensic investigators to use offender profiling during routine fraud investigations, it is extremely important that they understand the concept and its practical implementation. The overall purpose of this study is to provide practical recommendations for the implementation and use of offender profiling to forensic investigators both in the public and private sectors. / Criminal and Procedural Law / (M.Tech. (Forensic Investigation))