Implantable medical devices (IMDs) are medically necessary devices embedded in a human body that monitor chronic disorders or automatically deliver therapies, such as insulin pumps or pacemakers. Typically, they are small form-factor devices with limited battery and processing power. Most IMDs have wireless capabilities that allow them to share data with an offboard programming device, such as a smartphone application, that has more storage and processing power than the IMD itself. Additionally, the programming device can send commands back to the IMD to change its settings according to the treatment plan. As such, wirelessly sharing information between an IMD and offboard device can help medical providers monitor the patient's health remotely while giving the patient more insight into their condition, more autonomy, and fewer in-person appointments. However, serious security concerns have arisen as researchers have demonstrated it is possible to hack these devices to obtain sensitive information or potentially harm the patient. This is particularly easy to do as most IMDs transmit their data in the clear to avoid allocating their limited resources to encrypting their packets. As these concerns and the percentage of the American population with IMDs grows, there is another fear that bad actors could exploit the link between the programming device and IMD. Theoretically, a hacker could launch a man in the middle attack to send the IMD unauthorized commands, reprogramming it to act as a radio, sniffing signals of interest in the environment. As such, the hacker could use the IMD as a software defined radio (SDR) that captures sensitive or even classified information without the patient's knowledge. If this were to happen, it is possible an unwitting person with an IMD who has access to classified or sensitive information could be used to exfiltrate data that, in the wrong hands, could be used for corporate espionage or to the detriment of national security. While governing bodies agree that cybersecurity risks are present in IMD systems, there are no requirements for IMD manufacturers to create their devices with security measures that mitigate these risks. Researchers have proposed physical, technical, and administrative security measures for IMDs, but other existing wireless security techniques may apply to the healthcare space and need to be explored. Beamforming is an array signal processing technique that relies on individual elements of antenna arrays adjusting their phase and amplitude to create an overall effect of directing RF energy in a particular direction. Similarly, cooperative beamforming uses several physically separate "friendly" beamforming-capable devices to collectively send artificial noise to eavesdroppers while ensuring the signal is successfully received by the intended receiver. Although there are several cooperative jamming algorithms, they share the underlying principles of minimizing SINR at potential eavesdroppers while maximizing the SINR at the intended receiver. Researchers exploring cooperative jamming have largely used models to estimate its impact on channel secrecy. While RF propagation and communication system modeling provides valuable insight into system performance, many theoretical and empirical models are limited by the extent to which the operational environment matches that of the model itself. Ray tracing, alternatively, is more widely applicable as it accounts for a 3D environment and the objects a signal interacts with in that space. A ray is defined as an individual RF signal that travels in a straight line through a uniform medium; obeys the laws of reflection, refraction, and diffraction; and carries energy. As the ray interacts with objects in the environment, its energy will decrease by some amount that depends on the materials and geometry of the object. While research has predominantly focused on applications like cellular communications, the same principles of minimizing SINR at potential eavesdroppers while maximizing the SINR at the intended receiver can be applied to IMDs. As IMD use cases assume the programmer is nearby, the friendly nodes will not need to act as relays and can instead focus all their power on jamming. The number of cooperative jammers will be low to simulate the number of devices an individual might have in a workspace or office setting, like a personal phone, smart watch, or laptop, and realistic power constraints will be observed. Further, ray tracing software will provide additional visual insights into how various building materials like drywall, concrete, brick, and glass impact cooperative jamming. Through these simulations, the trade-off between secrecy rate and physical separation and layout of friendly nodes can be determined, which in turn may inform how companies or individuals can protect their proprietary and personal information. / Master of Science / Implantable medical devices (IMDs) are medically necessary devices embedded in a human body that monitor chronic disorders or automatically deliver therapies, such as insulin pumps or pacemakers. The data on IMDs need to be processed and their settings might need to be adjusted, but IMDs themselves usually cannot support direct user input, such as through screens or buttons, as they are inaccessible without surgery or generally too small to have space for displays. Further, they lack processing power and battery life due to their small form-factors, so relatively little data remains onboard. Instead, it is more convenient for the IMDs to wirelessly send their data to a more powerful external device like a smartphone. Since smartphones have more battery and processing resources available, and are easily recharged, they can store more data, monitor trends in the patient's health records, and upload the data to a server which the doctors can access. Additionally, these devices can send commands back to the IMD to change its settings according to the treatment plan. As such, wirelessly sharing information between an IMD and offboard programming device can help medical providers monitor the patient's health remotely while giving the patient more insight into their condition, more autonomy, and fewer in-person appointments. However, serious security concerns have arisen as researchers have demonstrated it is possible to hack these devices to obtain sensitive information or potentially harm the patient. As these concerns and the percentage of the American population with IMDs grows, there is another fear that bad actors could exploit the link between the programming device and IMD. Theoretically, a hacker could send the IMD unauthorized commands that change the IMD's behavior so that they are reprogrammed to act as radios listening for signals in the environment in order to steal sensitive or even classified information. While governing bodies agree that cybersecurity risks are present in IMD systems, there are no requirements for IMD manufacturers to create their devices with security measures that mitigate these risks. Researchers have proposed physical, technical, and administrative security measures for IMDs, but other existing wireless security techniques may apply to the healthcare space and need to be explored. Cooperative jamming is an existing defensive wireless technique that reduces the likelihood of an eavesdropper gaining access to unauthorized information. A known set of "friendly" transmitters each transmit noise to eavesdroppers while ensuring the signal is successfully received by the intended receiver. Researchers exploring cooperative jamming have largely used models to estimate its impact on channel secrecy. While RF propagation and communication system modeling provides valuable insight into system performance, many theoretical and empirical models are limited by the extent to which the operational environment matches that of the model itself. Ray tracing, alternatively, is more widely applicable as it accounts for a 3D environment and the objects a signal interacts with in that space. A ray is defined as an individual RF signal that travels in a straight line through a uniform medium; obeys the laws of reflection, refraction, and diffraction; and carries energy. As the ray interacts with objects in the environment, its energy will decrease by some amount that depends on the materials and geometry of the object. Thus, using ray tracing to model cooperative jamming will provide new insights into the degree to which cooperative jamming could be used to protect an IMD from eavesdroppers, and how companies or individuals can protect their proprietary and personal information.

Conventionally streamlines are traced using total flux across the grid cell faces. The visualization of total flux streamlines shows the movement of flood, injector-producer relationship, swept area and movement of tracer. But they fail to capture some important signatures of reservoir dynamics, such as dominant phase in flow, appearance and disappearance of phases (e.g. gas), and flow of components like CO2. In the work being presented, we demonstrate the benefits of visualizing phase and component streamlines which are traced using phase and component fluxes respectively. Although the phase and component streamlines are not appropriate for simulation, as they might be discontinuous, they definitely have a lot of useful information about the reservoir processes and recovery mechanisms. In this research, phase and component streamline tracing has been successfully implemented in three-phase and compositional simulation and the additional information obtained using these streamlines have been explored. The power and utility of the phase and component streamlines have been demonstrated using synthetic examples and two field cases. The new formulation of streamline tracing provides additional information about the reservoir drive mechanisms. The phase streamlines capture the dominant phase in flow in different parts of the reservoir and the area swept corresponding to different phases can be identified. Based on these streamlines the appearance and disappearance of phases can be identified. Also these streamlines can be used for optimizing the field recovery processes like water injection and location of infill wells. Using component streamlines the movement of components like CO2 can be traced, so they can be used for optimizing tertiary recovery mechanisms and tracking of tracers. They can also be used to trace CO2 in CO2 sequestration project where the CO2 injection is for long term storage in aquifers or reservoirs. They have also other potential uses towards study of reservoir processes and behavior such as drainage area mapping for different phases, phase rate allocations to reservoir layers, etc.

Advances in hardware acceleration has resulted in development of a variety of hardware accelerated ray tracing libraries. The purpose of this bachelor thesis is to investigate if a simple ray tracer, based on a hardware accelerated ray tracing library, can achieve acceptable frame rates in rendering simple 3D game-related environments. Games are often associated with fast rasterization-based rendering techniques, but rasterization is limited where instead ray tracing holds many advantages. Background research was done to gain knowledge about related work, state-of-the-art in ray tracing and available hardware accelerated libraries. By using a method similar to Kanban and Scrum [36], the implementation was split up into different tasks, prioritizing the tasks of implementing basic functionalities of a ray tracer. A simple ray tracer was implemented based on the chosen library Embree, a framework developed at Intel Corporation. Results show that the scenes rendered in lower resolutions (800 x 600) are good candidates for having a stable frame rate of 30 FPS, which is not enough in order to render a real game. The standard of games today require high resolution (full HD 1920 x 1080) and complex scenes. Earlier studies show that Embree has potential of higher performance and looking back the performance of real-time ray tracing has improved, but is still limited to low resolutions and simple lighting and shading models. / Framsteg inom hårdvaruacceleration har resulterat i att en rad olika hårdvaruaccelererade bibliotek för strålföljning utvecklats. Syftet med denna kandidat-uppsats är att undersöka om en enkel strålföljare, baserad på ett hårdvaruaccelererat bibliotek för strålföljning, kan uppnå acceptabla bildfrekvenser vid rendering av enkla spel-relaterade miljöer i 3D. Datorspel förknippas ofta med snabba renderingstekniker. Rasteriseringsalgoritmen är dock begränsad där istället strålföljning har många fördelar. En litteraturstudie gjordes för att få kunskap om relaterade arbeten, state-of-the-art i strålföljning och tillgängliga hårdvaruaccelererade bibliotek. Genom att använda en metod som kan liknas vid Kanban och Scrum [36], blev implementationen uppdelad i olika uppgifter (eng. tasks), där implementationen av grundläggande funktioner av en strålföljare hade högsta prioritet. En enkel strålföljare implementerades med det valda biblioteket Embree, ett ramverk som utvecklas hos Intel Corporation. Resultaten visar att scenerna som renderas med lägre upplösningar (800 x 600) är goda kandidater för att uppnå en stabil bildfrekvens med 30 bilder per sekund (eng. frames per second), vilket inte är tillräckligt för att rendera ett riktigt spel. Standarden hos spel idag kräver hög upplösning (full HD 1920 x 1080) och komplexa scener. Tidigare studier visar att Embree har potential för högre prestanda och tidigare resultat visar att prestandan av interaktiv strålföljning har förbättrats, men att den fortfarande är begränsad till låga upplösningar och enklare belysningsmodeller.

No description available.

Zugl.: Erlangen-Nürnberg, University, Diss., 2009.

The main focus of this research was to gain an understanding as to how waves propagate through structures. Lamb's Problem was studied on an isometric half plane, where numerical results were obtained. The calculated wavefronts for this problem were in agreement to the numerical results. When a distributed pressure is applied on an isometric half plane, after a long period of time, the wavefronts look as if a point force was applied on the half plane. Waves propagating through an orthotropic material were obtained numerically; it was found that Huygens' Principle cannot be used to calculate the wavefronts. The impact of spherical and cylindrical projectiles on glass plates was studied next. The waves introduced into the material were calculated using Finite Element Analysis, and compared to calculated wavefronts using Snell's Law, where they were found to be in agreement with one another. The effects of circular and square discontinuities were also studied, where a creeping wave that is produced after a wave propagates past a circular hole is explained. A sandwich beam was also modeled using FEA, where the wavefronts were obtained, and were found to be in agreement with calculated wavefronts. The displacement of the bottom layer of the sandwich beam was obtained numerically; it was found that the bending of the beam occurs at the same time as whether the middle layer is present or not.

High speed ray tracing for a headlamp lens and advanced algorithms for ray analysis are investigated. First, the basics of ray tracing, Algorithm to search intersection points between a ray and surfaces and refraction are reviewed, including intersection search for a ray with aspheric surfaces. A spherical surface, a plane surface, and a point cloud are reviewed as objects. Snell’s law is introduced from Fermat’s principle in 2D. Then, it extended to three dimensional spaces. Second, photometry is reviewed for the post processing of ray tracing, due to the convolution effect of its area. To accelerate ray tracing, the Nvidia GPU and CUDA platform of general purpose computing is evaluated in this study. Its architecture and memory architecture is unique. In addition, Mathematica is used in this study for file IO and graphic output with unique CUDA interface. Then, the each ray tracing method is validated using a spherical lens, aspherical lens, and a headlamp lens. From the comparison, the double precision floating Nagata triangular patch method is best in accuracy. Acceleration of ray tracing using CUDA was successful having 2 times implement in 362 million rays traced, compared to commercially available ray trace packages under the same computing resources.

Mit dem Architekturkonzept von Microservices und der steigenden Anzahl an heterogenen Services, ergeben sich neue Herausforderungen hinsichtlich des Debuggings, Monitorings und Testens solcher Anwendungen. Verteiltes Tracing bietet einen Ansatz zur Lösung dieser Herausforderungen. Das Ziel in der vorliegenden Arbeit ist es zu untersuchen, wie verteiltes Tracing für eine automatisierte Fehleranalyse von Microservices genutzt werden kann. Dazu wird die folgende Forschungsfrage gestellt: Wie können Traces ausgewertet werden, um die Fehlerursachen beim Testen von Microservices zu identifizieren? Um die Forschungsfrage zu beantworten, wurde ein Datenformat zur automatisierten Auswertung von Tracing-Daten definiert. Zur Auswertung wurden Algorithmen konzipiert, welche die Fehlerpropagierung zwischen Services anhand kausaler Beziehungen auflösen. Dieses Vorgehen wurde in Form einer prototypischen Implementierung in Python umgesetzt und dessen Funktionalität evaluiert. Die Ergebnisse zeigen, dass in rund 77 % der durchgeführten Testszenarien, die Fehlerursache mithilfe des Prototyps korrekt aus den Tracing-Daten abgeleitet werden konnte. Ohne Einsatz des Prototyps und ohne weiteres Debugging konnte lediglich in circa 5 % der Testszenarien die Fehlerursache anhand der Fehlerausgabe der Anwendung selbst erkannt werden. Damit bietet das Konzept sowie der Prototyp eine Erleichterung des Debuggings von Pythonbasierten Microservice-Anwendungen.:1. Einleitung 1.1. Motivation 1.2. Abgrenzung 1.3. Methodik 2. Grundlagen 2.1. Verwandte Arbeiten 2.1.1. Automatisierte Analyse von Tracing-Informationen 2.1.2. Automatisierte Fehlerursachenanalyse 2.1.3. Fehlerursachenanalyse in Microservices 2.1.4. Ursachenanalyse von Laufzeitfehlern in verteilten Systemen 2.1.5. Tracing-Tool zur Fehlererkennung 2.2. Theoretische Grundlagen 2.2.1. Microservices 2.2.2. Verteiltes Tracing 2.2.3. OpenTracing 2.2.4. Jaeger 2.2.5. Exemplarische Anwendung für Untersuchungen 2.2.6. Continuous Integration/ Continuous Delivery/ Continuous Deployment 3. Konzeption 3.1. Definition des Datenformats 3.1.1. Analyse des Datenformats der OpenTracing Spezifikation 3.1.2. Erweiterungen 3.1.3. Resultierendes Datenformat für eine automatisierte Auswertung 3.1.4. Zeitversatz verteilter Systeme 3.2. Algorithmen zur Fehlerursachenanalyse 3.2.1. Erstellung eines Abhängigkeitsgraphen 3.2.2. Pfad-basierte Untersuchung von Fehlerursachen 3.2.3. Auswertung nach zeitlicher Abfolge und kausaler Beziehung 3.2.4. Bewertung potenzieller Fehlerursachen 3.3. Konzeption des Prototyps 3.3.1. Integration in den Entwicklungszyklus 3.3.2. Funktionale Anforderungen 3.3.3. Architektur des Prototyps 4. Durchführung/ Implementation 4.1. Implementation des Prototyps zur Fehlerursachenanalyse 4.2. Einbindung des Prototyps in Testszenarien und Continuous Integration 4.3. Tests zur Evaluation des Prototyps 5. Ergebnisse 51 5.1. Evaluation des Konzepts/ Prototyps 5.2. Evaluation der Methoden zur Fehlerursachen-Bewertung 5.3. Wirtschaftliche Betrachtung 6. Fazit/ Ausblick 6.1. Fazit 6.2. Ausblick Literatur Selbstständigkeitserklärung A. Abbildungen A.1. Mockups der Auswertungsberichte des Prototyps B. Tabellen B.1. Felder der Tags nach OpenTracing B.2. Felder der Logs nach OpenTracing B.3. Auswertung der Testergebnisse C. Listings C.1. Datenformat zur automatisierten Auswertung C.2. Definition von Regeln zur Auswertung D. Anleitung für den Prototyp

The goal of this thesis is to evaluate the usability of hardware accelerated ray tracing in near-future rendering engines. Specifically, DirectX Ray Tracing API and Nvidia Turing architecture are being examined. Design and implementation of a hybrid rendering engine with support for hardware accelerated ray tracing is included and used in implementation of frequently used graphical effects -- hard and soft shadows, reflections, and Ambient Occlusion. The assessment is made in terms of difficulty of integration into a rendering engine, performance of the resulting system and suitability of implementation of chosen graphical effects. Performance parameters -- including number of rays cast per second, time to build acceleration structures and computation time on the GPU -- are tested and discussed.

Understanding user and system behavior is most vital for designing efficient systems. Most systems are designed with certain user workload in mind. However, such workloads evolve over time, or the underlying hardware assumptions change. Further, most modern systems are not built or deployed in isolation, they interact with other systems whose behavior might not be exactly understood. Thus in order to understand the performance of a system, it must be inspected closely while user workloads are running. Such close inspection must be done with minimum disturbance to the user workload. Thus tracing or collection of all the user and system generated events becomes an important approach in gaining comprehensive insight in user behavior. As part of this work, we have three major contributions. We designed and implemented an in-depth block level I/O tracer, which would collect block level information like sector number, size of the I/O, actual contents of the I/O, along with certain file system information like filename, and offset in the file, for every I/O request. Next, to minimize the impact of the tracing to the running workload, we introduce and implement a sampling mechanism which traces fewer I/O requests. We validate that this sampling preserves certain I/O access patterns. Finally, as one of the application of our tracer, we use it as a crucial component of a system designed to do VM placements according to user workload. / Master of Science