16,632 research outputs found

    Programmable multiport optical circuits in opaque scattering materials

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    We propose and experimentally verify a method to program the effective transmission matrix of general multiport linear optical circuits in random multiple-scattering materials by phase modulation of incident wavefronts. We demonstrate the power of our method by programming linear optical circuits in white paint layers with 2 inputs and 2 outputs, and 2 inputs and 3 outputs. Using interferometric techniques we verify our ability to program any desired phase relation between the outputs. The method works in a deterministic manner and can be directly applied to existing wavefront-shaping setups without the need of measuring a transmission matrix or to rely on sensitive interference measurements.Comment: 14 pages, 7 figure

    Programming balanced optical beam splitters in white paint

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    Wavefront shaping allows for ultimate control of light propagation in multiple-scattering media by adaptive manipulation of incident waves. We shine two separate wavefront-shaped beams on a layer of dry white paint to create two enhanced output speckle spots of equal intensity. We experimentally confirm by interference measurements that the output speckle spots are almost correlated like the two outputs of an ideal balanced beam splitter. The observed deviations from the phase behavior of an ideal beam splitter are analyzed with a transmission matrix model. Our experiments demonstrate that wavefront shaping in multiple-scattering media can be used to approximate the functionality of linear optical devices with multiple inputs and outputs

    The Influence of Temperature on Spike Probability in Day-Ahead Power Prices

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    It is well known that day-ahead prices in power markets exhibit spikes. These spikes are sudden increases in the day-ahead price that occur because power production is not flexible enough to respond to demand and/or supply shocks in the short term. This paper focuses on how temperature influences the probability on a spike. The paper shows that the difference between the actual and expected temperature significantly influences the probability on a spike and that the impact of temperature on spike probability depends on the season.Temperature;Day-ahead power price;Power production;Spike probability

    Branding of UK higher education institutions: an integrated perspective on the content and style of welcome adresses

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    The transformation to a more market-oriented steering approach in European higher education challenges universities and other higher education institutions to consider developing branding or image management activities. The existing literature focuses either on the content or the style, but we argue that an integrated perspective is needed to fully grasp the processes underlying branding. In a comparative case study of ten UK higher education institutions with varying reputations – five highly reputed versus five low(er) reputed institutions – we demonstrate how and why branding is deployed in welcome addresses of institutional leaders. Our findings indicate that isomorphic tendencies are visible, although brand differentiation could also be identified between highly and lowly reputed institutions. Our findings provide support for the competitive group perspective on branding activities

    Every connected sum of lens spaces is a real component of a uniruled algebraic variety

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    Let M be a connected sum of finitely many lens spaces, and let N be a connected sum of finitely many copies of S^1xS^2. We show that there is a uniruled algebraic variety X such that the connected sum M#N of M and N is diffeomorphic to a connected component of the set of real points X(R) of X. In particular, any finite connected sum of lens spaces is diffeomorphic to a real component of a uniruled algebraic variety.Comment: Nouvelle version avec deux figure

    A column generation approach to solve the crew re-scheduling problem

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    When tracks are out of service for maintenance during a certainperiod, trains cannot be operated on those tracks. This leads to amodified timetable, and results in infeasible rolling stock andcrew schedules. Therefore, these schedules need to be repaired.The topic of this paper is the rescheduling of crew.In this paper, we define the Crew Re-Scheduling Problem (CRSP).Furthermore, we show that it can be formulated as a large-scaleset covering problem. The problem is solved with a columngeneration based algorithm. The performance of the algorithm istested on real-world instances of NS, the largest passengerrailway operator in the Netherlands. Finally, we discuss somebenefits of the proposed methodology for the company.column generation;transportation;railways;crew re-scheduling;large-scale optimization
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