Colloquia and Seminars

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Upcoming Colloquia & Seminars

  • Pixel Club: Efficient Coding vs. Efficient Reconstruction in the Visual Cortex

    Speaker:
    Yacov Hel-Or ( School of CS, Interdisciplinary Center, Herzliya)
    Date:
    Tuesday, 21.4.2015, 11:30
    Place:
    EE Meyer Building 1061

    Several interesting observations about the Human Visual System have been investigated in recent years: 1. Sensory data is encoded in the visual cortex using color opponent space (luminance / chrominance space). 2. The distribution of RGB cones over the retina is non-uniform and highly biased towards the red/green cones. 3. The Human Visual System has high spatial sensitivity in the luminance band and low spatial sensitivity in the chrominance bands. These observations have been viewed as independent phenomena originating from different sources. In this talk we propose a novel view which unifies these phenomena and interpret them as a direct outcome of the statistical properties of color images. Unlike the current belief that the cortical representation stems from “efficient coding” that reduces data redundancies, this view proposes that the sensory setup as well as the cortical representation are outcome of “efficient reconstruction” where the goal is to maximize the information available from the limited amount of samples obtained by the retinoscopic sensors.

  • Theory Seminar: Cops, Robbers, and Threatening Skeletons (Padded Decomposition for Minor-Free Graphs)

    Speaker:
    Ofer Neiman (Ben-Gurion University)
    Date:
    Wednesday, 22.4.2015, 12:30
    Place:
    Taub 401

    We prove that any graph excluding $K_r$ as a minor can be partitioned into clusters of diameter at most $\Delta$ while removing at most $O(r/\Delta)$ fraction of the edges. This improves over the results of Fakcharoenphol and Talwar, who building on the work of Klein, Plotkin and Rao gave a partitioning that required to remove $O(r^2/\Delta)$ fraction of the edges.

    Our result is obtained by a new approach to relate the topological properties (excluding a minor) of a graph to its geometric properties (the induced shortest path metric). Specifically, we show that techniques used by Andreae in his investigation of the cops-and-robbers game on excluded-minor graphs can be used to construct padded decompositions of the metrics induced by such graphs. In particular, we get probabilistic partitions with padding parameter $O(r)$ and strong-diameter partitions with padding parameter $O(r^2)$ for $K_r$-free graphs, padding $O(k)$ for graphs with treewidth $k$, and padding $O(\log g)$ for graphs with genus $g$.

    Joint work with: Ittai Abraham, Cyril Gavoille, Anupam Gupta and Kunal Talwar.

  • Startup Fair and Recruitment at CS

    Startup Fair and Recruitment at CS

    Date:
    Wednesday, 29.4.2015, 12:30
    Place:
    CS Taub Lobby & Auditorium 2

    CS invites you to a STARTUP FAIR and recruitment by the presenting firms: Click-tale, Forter, Kamimnario, Ravello, Outbrain, Taxi, Wix.com and more. In addition, lectures will be given by the firms representatives.

    The event will take place on Wednesday, April 29, between 12:30-14:30 at the CS Taub Lobby. The lectures will be held in Auditorium 2.

    You are all welcome!

  • Coding for New Applications in Storage Media

    Speaker:
    Artyom Sharov, Ph.D. Thesis Seminar
    Date:
    Wednesday, 29.4.2015, 16:30
    Place:
    Taub 601
    Advisor:
    Prof. Ronny Roth

    Conventional magnetic recording media are composed of basic magnetizable two-dimensional units called grains, which might be random in size and shape. Recently, a new technological enhancement was proposed, which enables magnetizing areas as small as the size of grains. This novelty effectively created a different type of medium, in which one observes a new type of errors. Handling such errors is the main subject of this work. We first consider a combinatorial model of this medium, where so-called grain-correcting codes are used to handle worst-case error patterns. We also study a variant of this model where the errors are allowed to overlap (the supporting application of this variant can be found in shingled writing on bit-patterned media). For these two models, we present improved lower and upper bounds on the size and the growth rate of grain-correcting codes. In addition, we give explicit constructions of grain-correcting codes for correcting very small or very large number of errors. We then switch to the problem of detecting grain errors and provide lower and upper bounds on the minimum redundancy of codes that can detect any number of grain errors. Then, we turn to a probabilistic characterization of overlapping grain error patterns as a generalized Ising channel, for which we give almost-tight bounds on the capacity. We also consider a variant of this channel where feedback is added and compute lower bounds on its capacity. Moreover, for a certain range of values of the channel error probability, we establish a closed-form expression for that capacity.

  • Amdocs Best Project Contest - The Finals

    Amdocs Best Project Contest - The Finals

    Date:
    Wednesday, 29.4.2015, 16:30
    Place:
    CS Taub Auditorium 2

    You are invited to the final stage of the 2014 Amdocs Best Project Contest. The competing teams will present and talk about their projects.

    The event will take place on Thursday, April 29, 2015, 16:30-18:30, in Auditorium 2, CS Taub Building.

    You are all invited to cheer, support and be exposed to outstanding projects.