5,039 research outputs found
Very short term irradiance forecasting using the lasso
We find an application of the lasso (least absolute shrinkage and selection operator) in sub-5-min solar irradiance forecasting using a monitoring network. Lasso is a variable shrinkage and selection method for linear regression. In addition to the sum of squares error minimization, it considers the sum of ℓ1-norms of the regression coefficients as penalty. This bias–variance trade-off very often leads to better predictions.<p></p>
One second irradiance time series data are collected using a dense monitoring network in Oahu, Hawaii. As clouds propagate over the network, highly correlated lagged time series can be observed among station pairs. Lasso is used to automatically shrink and select the most appropriate lagged time series for regression. Since only lagged time series are used as predictors, the regression provides true out-of-sample forecasts. It is found that the proposed model outperforms univariate time series models and ordinary least squares regression significantly, especially when training data are few and predictors are many. Very short-term irradiance forecasting is useful in managing the variability within a central PV power plant.<p></p>
Nuclear-nuclear interaction mediated by a mechanically controlled nitrogen-vacancy-center spin in diamond
We propose a scheme to achieve nuclear-nuclear indirect interactions mediated
by a mechanically driven nitrogen-vacancy (NV) center in diamond. Here we
demonstrate two-qubit entangling gates and quantum-state transfer between two
carbon nuclei in diamond. In such a system, the NV center interacts with a
nearby nuclear spin via a dipole-dipole interaction. Under the quantum Zeno
condition, the scheme is robust against decoherence caused by coupling between
the NV center (nuclear spins) and the environment. Conveniently, precise
control of dipole coupling is not required so this scheme is insensitive to
fluctuating positions of the nuclear spins and the NV center. Our scheme
provides a general blueprint for multi-nuclear-spin gates and for multi-party
communication in a polygon geometry with each vertex occupied by a nuclear
spin.Comment: 11 pages, 8 figure
Production of charged meson in bottom hadron charmed decays and the effect of the finite width correction of the meson
We calculate the branching ratio of a bottom hadron decaying into a charmed
hadron and a charged meson within the QCD factorization approach. We
consider the effect of the finite width correction of the meson. Our
numerical calculation shows an obvious correction because of this effect. We
find that the finite width effect of the meson reduces the branching
ratios by about 9% to 11% for bottom meson decay channels:
, , and , and
increases the branching ratio by about 10% for
.Comment: 12 page
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