94,873 research outputs found
Response-surface-model-based system sizing for nearly/net zero energy buildings under uncertainty
Properly treating uncertainty is critical for robust system sizing of nearly/net zero energy buildings (ZEBs). To treat uncertainty, the conventional method conducts Monte Carlo simulations for thousands of possible design options, which inevitably leads to computation load that is heavy or even impossible to handle. In order to reduce the number of Monte Carlo simulations, this study proposes a response-surface-model-based system sizing method. The response surface models of design criteria (i.e., the annual energy match ratio, self-consumption ratio and initial investment) are established based on Monte Carlo simulations for 29 specific design points which are determined by Box-Behnken design. With the response surface models, the overall performances (i.e., the weighted performance of the design criteria) of all design options (i.e., sizing combinations of photovoltaic, wind turbine and electric storage) are evaluated, and the design option with the maximal overall performance is finally selected. Cases studies with 1331 design options have validated the proposed method for 10,000 randomly produced decision scenarios (i.e., users’ preferences to the design criteria). The results show that the established response surface models reasonably predict the design criteria with errors no greater than 3.5% at a cumulative probability of 95%. The proposed method reduces the number of Monte Carlos simulations by 97.8%, and robustly sorts out top 1.1% design options in expectation. With the largely reduced Monte Carlo simulations and high overall performance of the selected design option, the proposed method provides a practical and efficient means for system sizing of nearly/net ZEBs under uncertainty
Isospin-symmetry breaking in superallowed Fermi beta-decay due to isospin-nonconserving forces
We investigate isospin-symmetry breaking effects in the sd-shell region with
large-scale shell-model calculations, aiming to understand the recent anomalies
observed in superallowed Fermi beta-decay. We begin with calculations of
Coulomb displacement energies (CDE's) and triplet displacement energies (TDE's)
by adding the T=1,J=0 isospin nonconserving (INC) interaction into the usual
isospin-invariant Hamiltonian. It is found that CDE's and TDE's can be
systematically described with high accuracy. A total number of 122 one- and
two-proton separation energies are predicted accordingly, and locations of the
proton drip-line and candidates for proton-emitters are thereby suggested.
However, attempt to explain the anomalies in the superallowed Fermi beta-decay
fails because these well-fitted T=1,J=0 INC interactions are found no effects
on the nuclear matrix elements. It is demonstrated that the observed large
isospin-breaking correction in the 32Cl beta-decay, the large isospin-mixing in
the 31Cl beta-decay, and the small isospin-mixing in the 23Al beta-decay can be
consistently understood by introducing additional T=1,J=2 INC interactions
related to the s1/2 orbit.Comment: 7 pages, 3 figures, accepted in Phys. Lett.
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