12,931 research outputs found

    A 3D pyramid network for short ranged high data rate communications at 60 GHz

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    An evaluation of the performance of IEEE 802.11a and 802.11g wireless local area networks in a corporate office environment

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    Effect of antenna element properties and array orientation on performance of MIMO systems

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    A spatio-temporal ray launching propagation model for UMTS pico and microcellular environments

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    Breakdown and recovery in traffic flow models

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    Most car-following models show a transition from laminar to ``congested'' flow and vice versa. Deterministic models often have a density range where a disturbance needs a sufficiently large critical amplitude to move the flow from the laminar into the congested phase. In stochastic models, it may be assumed that the size of this amplitude gets translated into a waiting time, i.e.\ until fluctuations sufficiently add up to trigger the transition. A recently introduced model of traffic flow however does not show this behavior: in the density regime where the jam solution co-exists with the high-flow state, the intrinsic stochasticity of the model is not sufficient to cause a transition into the jammed regime, at least not within relevant time scales. In addition, models can be differentiated by the stability of the outflow interface. We demonstrate that this additional criterion is not related to the stability of the flow. The combination of these criteria makes it possible to characterize commonalities and differences between many existing models for traffic in a new way

    Bounds on Dimension Reduction in the Nuclear Norm

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    \newcommand{\schs}{\scriptstyle{\mathsf{S}}_1} For all n≄1n \ge 1, we give an explicit construction of m×mm \times m matrices A1,
,AnA_1,\ldots,A_n with m=2⌊n/2⌋m = 2^{\lfloor n/2 \rfloor} such that for any dd and d×dd \times d matrices A1â€Č,
,Anâ€ČA'_1,\ldots,A'_n that satisfy \|A'_i-A'_j\|_{\schs} \,\leq\, \|A_i-A_j\|_{\schs}\,\leq\, (1+\delta) \|A'_i-A'_j\|_{\schs} for all i,j∈{1,
,n}i,j\in\{1,\ldots,n\} and small enough ÎŽ=O(n−c)\delta = O(n^{-c}), where c>0c> 0 is a universal constant, it must be the case that d≄2⌊n/2⌋−1d \ge 2^{\lfloor n/2\rfloor -1}. This stands in contrast to the metric theory of commutative ℓp\ell_p spaces, as it is known that for any p≄1p\geq 1, any nn points in ℓp\ell_p embed exactly in ℓpd\ell_p^d for d=n(n−1)/2d=n(n-1)/2. Our proof is based on matrices derived from a representation of the Clifford algebra generated by nn anti-commuting Hermitian matrices that square to identity, and borrows ideas from the analysis of nonlocal games in quantum information theory.Comment: 16 page

    Treatment of Intractable Neurogenic Cough with Cricopharyngeal Myotomy

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    Objectives: Neuropathic cough that is incompletely responsive to medical therapy may be due to cricopharyngeal hypertonicity. The objective was to describe the utility of cricopharyngeal myotomy in alleviating symptoms of intractable neuropathic cough. Study Design: Retrospective review. Methods: A retrospective chart review was performed for three patients who underwent cricopharyngeal myotomy for intractable cough. Trigger phenomena, previous evaluation and treatment, and outcomes after surgery, namely patient perception of improvement and medication use after surgery, were assessed and documented. Results: After cricopharyngeal myotomy, all three patients noted symptomatic improvement and were weaned off medication. Continued improvement was noted at follow up, with a mean length of 22 months (range: 7-36 months). Conclusions: Cricopharyngeal myotomy may be an alternative treatment for chronic cough in patients for whom workup is negative and medical management, dilation, and botulinum toxin have failed to provide long-term relief. Poster presented at CSOM: Combined Otolaryngology Spring Meeting in Orlando Florida, April 10-14, 2013

    Site specific prediction and measurement of indoor power delay and power azimuth spectra at 5 GHz

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