Hemant Tyagi

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Automatic identification of bird calls without manual intervention has been a challenging task for meaningful research on the taxonomy and monitoring of bird migrations in ornithology. In this paper we apply several techniques used in speech recognition to the automatic identification of bird calls. A new technique which computes the ensemble average on the(More)
We present a simple refractive index sensor based on a step-index fiber with a hollow micro-channel running parallel to its core. This channel becomes waveguiding when filled with a liquid of index greater than silica, causing sharp dips to appear in the transmission spectrum at wavelengths where the glass-core mode phase-matches to a mode of the(More)
We report the successful production of high-quality gold wires, with diameters down to 260nm, by direct fiber drawing from a gold-filled fused-silica cane. The stack-and-draw technique makes it straightforward to incorporate a conventional step-index core, adjacent to the gold wire, in the cane. In the drawn fiber, strong coupling of light from the glass(More)
Using a selective hole closure technique, individual hollow channels in silica-air photonic crystal fibers are filled with pure Ge by pumping in molten material at high pressure. The smallest channels filled so far are 600 nm in diameter, which is 10x smaller than in previous work. Electrical conductivity and micro-Raman measurements indicate that the(More)
We report a novel splicing-based pressure-assisted melt-filling technique for creating metallic nanowires in hollow channels in microstructured silica fibers. Wires with diameters as small as 120 nm (typical aspect ration 50:1) could be realized at a filling pressure of 300 bar. As an example we investigate a conventional single-mode step-index fiber with a(More)
We consider the problem of learning multi-ridge functions of the form f (x) = g(Ax) from point evaluations of f. We assume that the function f is defined on an 2-ball in R d , g is twice continuously differentiable almost everywhere, and A ∈ R k×d is a rank k matrix, where k d. We propose a randomized, polynomial-complexity sampling scheme for estimating(More)
We consider the stochastic and adversarial settings of continuum armed bandits where the arms are indexed by [0, 1] d. The reward functions r : [0, 1] d → R are assumed to intrinsically depend on at most k to be fixed across time, we propose a simple modification of the CAB1 algorithm where we construct the discrete set of sampling points to obtain a bound(More)
We study the problem of learning ridge functions of the form f(x) = g(a<sup>T</sup> x), x &#x2208; &#x211D;<sup>d</sup>, from random samples. Assuming g to be a twice continuously differentiable function, we leverage techniques from low rank matrix recovery literature to derive a uniform approximation guarantee for estimation of the ridge function f. Our(More)