Wavelength assignment in optical burst switching networks using neuro-dynamic programming

Cataloged from PDF version of article.All-optical networks are the most promising architecture for building large-size, hugebandwidth transport networks that are required for carrying the exponentially increasing Internet traffic. Among the existing switching paradigms in the literature, the optical burst switching is intended to leverage the attractive properties of optical communications, and at the same time, take into account its limitations. One of the major problems in optical burst switching is high blocking probability that results from one-way reservation protocol used. In this thesis, this problem is solved in wavelength domain by using smart wavelength assignment algorithms. Two heuristic wavelength assignment algorithms prioritizing available wavelengths according to reservation tables at the network nodes are proposed. The major contribution of the thesis is the formulation of the wavelength assignment problem as a continuous-time, average cost dynamic programming problem and its solution based on neuro-dynamic programming. Experiments are done over various traffic loads, burst lengths, and number of wavelength converters with a pool structure. The simulation results show that the wavelength assignment algorithms proposed for optical burst switching networks in the thesis perform better than the wavelength assignment algorithms in the literature that are developed for circuit-switched optical networks.Keçeli, FeyzaM.S

SPICA:revealing the hearts of galaxies and forming planetary systems : approach and US contributions

How did the diversity of galaxies we see in the modern Universe come to be? When and where did stars within them forge the heavy elements that give rise to the complex chemistry of life? How do planetary systems, the Universe's home for life, emerge from interstellar material? Answering these questions requires techniques that penetrate dust to reveal the detailed contents and processes in obscured regions. The ESA-JAXA Space Infrared Telescope for Cosmology and Astrophysics (SPICA) mission is designed for this, with a focus on sensitive spectroscopy in the 12 to 230 micron range. SPICA offers massive sensitivity improvements with its 2.5-meter primary mirror actively cooled to below 8 K. SPICA one of 3 candidates for the ESA's Cosmic Visions M5 mission, and JAXA has is committed to their portion of the collaboration. ESA will provide the silicon-carbide telescope, science instrument assembly, satellite integration and testing, and the spacecraft bus. JAXA will provide the passive and active cooling system (supporting the

The Apertif Surveys:The First Six Months

Apertif is a new phased-array feed for the Westerbork Synthesis Radio Telescope (WSRT), greatly increasing its field of view and turning it into a natural survey instrument. In July 2019, the Apertif legacy surveys commenced; these are a time-domain survey and a two-tiered imaging survey, with a shallow and medium-deep component. The time-domain survey searches for new (millisecond) pulsars and fast radio bursts (FRBs). The imaging surveys provide neutral hydrogen (HI), radio continuum and polarization data products. With a bandwidth of 300 MHz, Apertif can detect HI out to a redshift of 0.26. The key science goals to be accomplished by Apertif include localization of FRBs (including real-time public alerts), the role of environment and interaction on galaxy properties and gas removal, finding the smallest galaxies, connecting cold gas to AGN, understanding the faint radio population, and studying magnetic fields in galaxies. After a proprietary period, survey data products will be publicly available through the Apertif Long Term Archive (ALTA, https://alta.astron.nl). I will review the progress of the surveys and present the first results from the Apertif surveys, including highlighting the currently available public data