Technical University of Berlin

About: Technical University of Berlin is a education organization based out in Berlin, Germany. It is known for research contribution in the topics: Laser & Catalysis. The organization has 27292 authors who have published 59342 publications receiving 1414623 citations. The organization is also known as: Technische Universität Berlin & TU Berlin.

Adaptation algorithm for adaptive streaming over HTTP

Abstract: Internet video makes up a significant part of the Internet traffic and its fraction is constantly growing. In order to guarantee best user experience throughout different network access technologies with dynamically varying network conditions, it is fundamental to adopt technologies enabling a proper delivery of the media content. One of such technologies is adaptive streaming. It allows to dynamically adapt the bit-rate of the stream to varying network conditions. There are various approaches to adaptive streaming. In our work, we focus on the receiver-driven approach where the media file is subdivided into segments, each of the segments is provided at multiple bit-rates, and the task of the client is to select the appropriate bit-rate for each of the segments. With this approach, the challenges are (i) to properly estimate the dynamics of the available network throughput, (ii) to control the filling level of the client buffer in order to avoid underflows resulting in playback interruptions, (iii) to maximize the quality of the stream, while avoiding unnecessary quality fluctuations, and, finally, (iv) to minimize the delay between the user's request and the start of the playback. During our work, we designed and implemented a receiver-driven adaptation algorithm for adaptive streaming that does not rely on cross-layer information or server assistance. We integrated the algorithm with a prototype implementation of a streaming client based on the MPEG DASH (Dynamic Adaptive Streaming over HTTP) standard. We evaluated the implemented prototype in real-world scenarios and found that it performes remarkably well even under challenging network conditions. Further, it exhibits stable and fair operation if a common link is shared among multiple clients.

Advances in neutron radiography and tomography

Abstract: Neutron imaging can provide two- or three-dimensional, spatially resolved images of the internal structure of bulk samples that are not accessible by other techniques, making it a unique tool with many potential applications. The method is now well established and is available at neutron sources worldwide. This review will give a survey of the technique of neutron imaging with a special focus on neutron tomography; the basics of the method as well as the technology of instrumentation will be outlined, and the techniques will be illustrated by representative applications. While the first part of the paper focuses on conventional attenuation contrast imaging, the second part reviews and critically assesses recent methodical developments.

Simulation of city-wide replacement of private cars with autonomous taxis in Berlin

Abstract: Autonomous taxi (AT) fleets have the potential to take over a significant amount of traffic handled nowadays by conventionally driven vehicles (CDV). In this paper, we simulate a city-wide replacement of private cars with AT fleets of various sizes. The simulation model comprises microscopic demand for all private car trips in Berlin (including incoming and outgoing traffic), out of which the internal ones are exclusively served by ATs. The proposed real-time AT dispatching algorithm was optimized to handle hundreds of thousands of vehicles and millions of requests at low computing times. Simulation results suggest, that a fleet of 100 000 vehicles will be enough to replace the car fleet in Berlin at a high service quality for customers. Based on this, one AT could replace the demand served by ten CDVs in Berlin.

An Introduction to Network Flows over Time

Abstract: We give an introduction into the fascinating area of flows over time—also called “dynamic flows” in the literature. Starting from the early work of Ford and Fulkerson on maximum flows over time, we cover many exciting results that have been obtained over the last fifty years. One purpose of this chapter is to serve as a possible basis for teaching network flows over time in an advanced course on combinatorial optimization.

Freezing and Melting of Water Confined in Silica Nanopores

Abstract: In nanosized pores, liquid water can be thermodynamically stable down to temperatures well below the limit of homogeneous nucleation of bulk water ( approximately 235 K). Studies of water in such pores therefore offer an opportunity to reveal the anomalous behavior of deeply supercooled water. Herein we focus on recent studies of the limits of freezing and melting of water in the cylindrical pores of ordered mesoporous silicas with pore diameters in the range of 2-10 nm, based on vapor sorption measurements, calorimetric studies, NMR spectroscopy and cryoporometry, and neutron diffraction studies.