All at Once

Senior Project submitted to the Division of Arts of Bard Colleg

Performance of constrained wireless devices in the Internet of Things

The Internet of Things is an emerging concept where every device, regardless of size, have their own connection to the Internet. This thesis examines what possible limitations are imposed on the functionality of resource constrained, wireless devices. Several different technologies are evaluated and compared, before a set of them is chosen for inclusion in an implementation, for example: IEEE 802.15.4, 6LoWPAN and CoAP. The implementation uses the Contiki operating system, and runs on a Texas Instruments CC2530 SoC. We then examine several different performance aspects of our implementation: the amount of data sent, memory usage and energy consumption. The results are discussed together with security aspects applicable to the Internet of things. The memory usage and power consumption were found to be severe issues. Due to the small amount of memory on the chip, all features could not be used at the same time. In addition, the power consumption was found to be too high for battery-powered usage, giving a lifetime of only 27 hours using a button cell battery. The conclusion is that hardware with more memory, and lower power consumption is required. New protocols for radio power-saving should also be developed and implemented in software.Internet of Things – sakernas internet – är ett framväxande koncept där varje enhet, oavsett storlek, har en anslutning till Internet. Detta examensarbete undersöker vilka möjliga begränsningar i funktionalitet detta får på trådlösa enheter med begränsade resurser. Flera olika teknologier undersöks och jämförs, innan ett antal väljs ut för att ingå i en implementation, till exempel: IEEE 802.15.4, 6LoWPAN och CoAP. Implementationen använder operativsystemet Contiki och körs på ett Texas Instruments CC2530 SoC. Flera prestandaaspekter undersöks: mängden skickad data, minnesanvändning och energiförbrukning. Resultaten diskuteras tillsammans med säkerhetsaspekter att ta hänsyn till i Internet of Things. Minnesanvändningen och energiförbrukningen är de mest problematiska områdena. På grund av chippets begränsade mängd minne kan inte all funktionalitet användas samtidigt. Dessutom är energiförbrukningen för hög för längre tids strömförsörjning med batteri, vilket ger en livslängd på enbart 27 timmar med ett knappcellsbatteri. Slutsatsen är att hårdvara med mer minne och lägre energiförbrukning behövs. Nya protokoll för energibesparande radioanvändning behöver också utvecklas och implementeras i mjukvara

Le métier de modélisateur multinational

Cet article présente les principaux problèmes que posent la construction et l'utilisation des modèles macro-économétriques multinationaux. Il montre les disparités qui existent entre les différents modèles multinationaux. Il met l'accent sur la difficulté de mettre en évidence et d'expliquer les différences de comportement entre les différents pays. L'analyse de l'évolution du taux de change est également un point délicat. Les modèles multinationaux permettent de comparer les équilibres non coopératifs où chaque pays choisit isolément sa politique économique aux équilibres coopératifs où les politiques sont coordonnées.This article presents the main problems that economists face when they build or when they use multinational macroeconometric models. It shows the disparities between the existing multinational models. It insists on the difficulties to estimate and to explain behaviour disparities between countries. Analysis of the exchange rate evolution is also a delicate art. Multinational models allow to compare non-cooperative equilibria where each country fixes individually its policy instruments to cooperative equilibria where economie policies are coordinate

Investment in Swedish Manufacturing: Analysis and Forecasts

This paper uses a neoclassical investment model extended with installation costs for capital, agency costs for investment financing, and the possibility of the firm being output constrained as a framework for an empirical analysis of investment behaviour in the Swedish manufacturing industry. The theory is implemented within a multivariate error-correction approach on data covering the time period 1951 to 1995, and we gain the following main results: (1) Tobins average Q is not the sole determinant of investment, neither in the short nor in the long run, and other variables like real output and capital gearing also affect investment activity; (2) the out-of-sample forecasts of the model track the evolution of actual investment growth quite impressively, especially at short- and medium-term horizons (1-2 years); (3) a relative equity-price variable is shown to constitute a good approximation of average Q, both for empirical modelling in general and forecasting in particular

PERF: Performant, Explicit Radiance Fields

We present a novel way of approaching image-based 3D reconstruction based on radiance fields. The problem of volumetric reconstruction is formulated as a non-linear least-squares problem and solved explicitly without the use of neural networks. This enables the use of solvers with a higher rate of convergence than what is typically used for neural networks, and fewer iterations are required until convergence. The volume is represented using a grid of voxels, with the scene surrounded by a hierarchy of environment maps. This makes it possible to get clean reconstructions of 360\ub0 scenes where the foreground and background is separated. A number of synthetic and real scenes from well-known benchmark-suites are successfully reconstructed with quality on par with state-of-the-art methods, but at significantly reduced reconstruction times

PERF: Performant, Explicit Radiance Fields

We present a novel way of approaching image-based 3D reconstruction based on radiance fields. The problem of volumetric reconstruction is formulated as a non-linear least-squares problem and solved explicitly without the use of neural networks. This enables the use of solvers with a higher rate of convergence than what is typically used for neural networks, and fewer iterations are required until convergence. The volume is represented using a grid of voxels, with the scene surrounded by a hierarchy of environment maps. This makes it possible to get clean reconstructions of 360\ub0 scenes where the foreground and background is separated. A number of synthetic and real scenes from well-known benchmark-suites are successfully reconstructed with quality on par with state-of-the-art methods, but at significantly reduced reconstruction times

A low-cost, practical acquisition and rendering pipeline for real-time free-viewpoint video communication

We present a semiautomatic real-time pipeline for capturing and rendering free-viewpoint video using passive stereo matching. The pipeline is simple and achieves agreeable quality in real time on a system of commodity web cameras and a single desktop computer. We suggest an automatic algorithm to compute a constrained search space for an efficient and robust hierarchical stereo reconstruction algorithm. Due to our fast reconstruction times, we can eliminate the need for an expensive global surface reconstruction with a combination of high coverage and aggressive filtering. Finally, we employ a novel color weighting scheme that generates credible new viewpoints without noticeable seams, while keeping the computational complexity low. The simplicity and low cost of the system make it an accessible and more practical alternative for many applications compared to previous methods