Streaming Video over HTTP with Consistent Quality

In conventional HTTP-based adaptive streaming (HAS), a video source is encoded at multiple levels of constant bitrate representations, and a client makes its representation selections according to the measured network bandwidth. While greatly simplifying adaptation to the varying network conditions, this strategy is not the best for optimizing the video quality experienced by end users. Quality fluctuation can be reduced if the natural variability of video content is taken into consideration. In this work, we study the design of a client rate adaptation algorithm to yield consistent video quality. We assume that clients have visibility into incoming video within a finite horizon. We also take advantage of the client-side video buffer, by using it as a breathing room for not only network bandwidth variability, but also video bitrate variability. The challenge, however, lies in how to balance these two variabilities to yield consistent video quality without risking a buffer underrun. We propose an optimization solution that uses an online algorithm to adapt the video bitrate step-by-step, while applying dynamic programming at each step. We incorporate our solution into PANDA -- a practical rate adaptation algorithm designed for HAS deployment at scale.Comment: Refined version submitted to ACM Multimedia Systems Conference (MMSys), 201

Numerical simulation of gas-phase detonation transmission

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/77137/1/AIAA-1991-579-313.pd

Identifying and Imposing Partial Equilibrium in Chemically Reacting Systems

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/76236/1/AIAA-2003-667-389.pd

Localisation of gamma-ray interaction points in thick monolithic CeBr3 and LaBr3:Ce scintillators

Localisation of gamma-ray interaction points in monolithic scintillator crystals can simplify the design and improve the performance of a future Compton telescope for gamma-ray astronomy. In this paper we compare the position resolution of three monolithic scintillators: a 28x28x20 mm3 (length x breadth x thickness) LaBr3:Ce crystal, a 25x25x20 mm3 CeBr3 crystal and a 25x25x10 mm3 CeBr3 crystal. Each crystal was encapsulated and coupled to an array of 4x4 silicon photomultipliers through an optical window. The measurements were conducted using 81 keV and 356 keV gamma-rays from a collimated 133Ba source. The 3D position reconstruction of interaction points was performed using artificial neural networks trained with experimental data. Although the position resolution was significantly better for the thinner crystal, the 20 mm thick CeBr3 crystal showed an acceptable resolution of about 5.4 mm FWHM for the x and y coordinates, and 7.8 mm FWHM for the z-coordinate (crystal depth) at 356 keV. These values were obtained from the full position scans of the crystal sides. The position resolution of the LaBr3:Ce crystal was found to be considerably worse, presumably due to the highly diffusive optical in- terface between the crystal and the optical window of the enclosure. The energy resolution (FWHM) measured for 662 keV gamma-rays was 4.0% for LaBr3:Ce and 5.5% for CeBr3. The same crystals equipped with a PMT (Hamamatsu R6322-100) gave an energy resolution of 3.0% and 4.7%, respectively

The Arctic in World Affairs: A North Pacific Dialogue on Will Great Power Politics Threaten Arctic Sustainability

The eight Arctic states (Canada, Denmark/Greenland, Finland, Iceland, Norway, Sweden, the Russian Federation, and the United States) wish to maintain a position of preeminence when it comes to dealing with matters of Arctic Ocean governance. However, major non-Arctic states, while recognizing the sovereign rights of the coastal states in their economic zones and on their continental shelves, have growing interests in the maritime Arctic relating to activities such as commercial shipping, oil and gas development, fishing and ship-based tourism. They are increasingly claiming to have a legitimate interest in being consulted when it comes to addressing matters relating to the governance of such activities. Many questions arise from these new formulations: What is the appropriate mechanism for introducing the concerns of the non-Arctic North Pacific countries in forums dealing with Arctic issues? Can they achieve a significant voice in the deliberations of the Arctic Council? Can they address these issues through other mechanisms

Overview: Will Great Power Politics Threaten Arctic Sustainability?

The eight Arctic states (Canada, Denmark/Greenland, Finland, Iceland, Norway, Sweden, the Russian Federation, and the United States) wish to maintain a position of preeminence when it comes to dealing with matters of Arctic Ocean governance. However, major non-Arctic states, while recognizing the sovereign rights of the coastal states in their economic zones and on their continental shelves, have growing interests in the maritime Arctic relating to activities such as commercial shipping, oil and gas development, fishing and ship-based tourism. They are increasingly claiming to have a legitimate interest in being consulted when it comes to addressing matters relating to the governance of such activities. Many questions arise from these new formulations: What is the appropriate mechanism for introducing the concerns of the non-Arctic North Pacific countries in forums dealing with Arctic issues? Can they achieve a significant voice in the deliberations of the Arctic Council? Can they address these issues through other mechanisms

Towards a Network Marketplace in a Cloud

Abstract Virtually all public clouds today are run by single providers, and this creates near-monopolies, inefficient markets, and hinders innovation at the infrastructure level. There are current proposals to change this, by creating open architectures that allow providers of computing and storage resources to compete for tenant services at multiple levels, all the way down to the bare metal. Networking, however, is not part of this, and is viewed as a commodity much like power or cooling. In this paper we borrow ideas from the Internet architecture, and propose to structure the cloud datacenter network as a marketplace where multiple service providers can offer connectivity services to tenants. Our marketplace, NetEx, divides the network into independently managed pods of resources, interconnected with multiple providers through special programmable switches that play a role analogous to that of an IXP. We demonstrate the feasibility of such an architecture by a prototype in Mininet, and argue that this can be a way to provide innovation, competition, and efficiency in future cloud datacenter networks