Results 1 - 10 of 1558
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[en] Two measurement techniques are investigated to characterize photodetector linearity. A model for the two-tone and three-tone photodetector systems is developed to thoroughly investigate the influences of setup components on the measurement results. We demonstrate that small bias shifts from the quadrature point of the modulator will induce deviation into measurement results of the two-tone system, and the simulation results correspond well to experimental and calculation results. (authors)
[en] In robust design, the mean and variance of design performance are frequently used to measure the design performance and its robustness under uncertainties. In this paper, we present the Gauss-type quadrature formula as a rigorous method for mean and variance estimation involving arbitrary input distributions and further extend its use to robust design optimization. One dimensional Gauss-type quadrature formula are constructed from the input probability distributions and utilized in the construction of multidimensional quadrature formula such as the tensor product quadrature (TPQ) formula and the univariate dimension reduction (UDR) method. To improve the efficiency of using it for robust design optimization, a semi-analytic design sensitivity analysis with respect to the statistical moments is proposed. The proposed approach is applied to a simple bench mark problems and robust topology optimization of structures considering various types of uncertainty
[en] This paper is devoted to describing properties of complete intersections of two real projective quadrics. For brevity we call such varieties biquadrics. One of the main sections is devoted to real projective spaces on real biquadrics. In another main section we study the topology of the real parts of biquadrics. The other sections are auxiliary. (paper)
[en] The boundary layer of a finite domain [ a, b ] covers mesoscopic lateral neighborhoods, inside [ a, b ], of the endpoints a and b. The correct diagnostic of the integrand behavior at a and b, based on its sampling inside the boundary layer, is the first from a set of hierarchically ordered criteria allowing a priori Bayesian inference on efficient mesh generation in automatic adaptive quadrature.
[en] Quantum discord is a measure of non-classical correlations, which are excess correlations inherent in quantum states that cannot be accessed by classical measurements. For multipartite states, the classically accessible correlations can be defined by the mutual information of the multipartite measurement outcomes. In general the quantum discord of an arbitrary quantum state involves an optimisation of over the classical measurements which is hard to compute. In this paper, we examine the quantum discord in the experimentally relevant case when the quantum states are Gaussian and the measurements are restricted to Gaussian measurements. We perform the optimisation over the measurements to find the Gaussian discord of the bipartite EPR state and tripartite GHZ state in the presence of different types of noise: uncorrelated noise, multiplicative noise and correlated noise. We find that by adding uncorrelated noise and multiplicative noise, the quantum discord always decreases. However, correlated noise can either increase or decrease the quantum discord. We also find that for low noise, the measurements that maximise the classically accessible correlations are single quadrature measurements. As the noise increases, a dual quadrature measurement becomes optimal. (paper)
[en] NMR spectroscopy is central to atomic resolution studies in biology and chemistry. Key to this approach are multidimensional experiments. Obtaining such experiments with sufficient resolution, however, is a slow process, in part since each time increment in every indirect dimension needs to be recorded twice, in quadrature. We introduce a modified compressed sensing (CS) algorithm enabling reconstruction of data acquired with random acquisition of quadrature components in gradient-selection NMR. We name this approach random quadrature detection (RQD). Gradient-selection experiments are essential to the success of modern NMR and with RQD, a 50 % reduction in the number of data points per indirect dimension is possible, by only acquiring one quadrature component per time point. Using our algorithm (CSRQD), high quality reconstructions are achieved. RQD is modular and combined with non-uniform sampling we show that this provides increased flexibility in designing sampling schedules leading to improved resolution with increasing benefits as dimensionality of experiments increases, with particular advantages for 4- and higher dimensional experiments.
[en] As with any discrete-ordinates code, ray-effects are an inherent problem, especially for shielding type problems with optically thin regions and localized (point) sources. Although ray-effects may be mitigated by increasing the quadrature order, this is often computationally prohibitive. To mitigate ray-effects, many discrete-ordinates codes use first collision source methods. Such methods are characterized by a decomposition of the flux into its uncollided and collided components. The uncollided flux is calculated analytically and the collided flux is calculated with the discrete-ordinates method. In this paper, the implementation of the first collision source method in the MUST (Multi-group Unstructured geometry SN Transport) code is presented and the results are compared with that of Attila