We report a search for time variations of the solar 8 B neutrino flux using 5,804 live days of Super-Kamiokande data collected between May 31, 1996, and May 30, 2018. Super-Kamiokande measured the precise time of each solar neutrino interaction over 22 calendar years to search for solar neutrino flux modulations with unprecedented precision. Periodic modulations are searched for in a data set comprised of five-day interval solar neutrino flux measurements with a maximum likelihood method. We also applied the Lomb-Scargle method to this data set to compare it with previous reports. The only significant modulation found is due to the elliptic orbit of the Earth around the Sun. The observed modulation is consistent with astronomical data: we measured an eccentricity of (1.53±0.35) %, and a perihelion shift is (−1.5±13.5) days.

A search for Supernova Relic Neutrinosν e 's is first conducted via inverse-beta-decay by tagging neutron capture on hydrogen at Super-Kamiokande-IV. The neutron tagging efficiency is determined to be (17.74 ± 0.04 stat. ± 1.05 sys. )%, while the corresponding accidental background probability is (1.06 ± 0.01 stat. ± 0.18 sys. )%. Using 960 days of data, we obtain 13 inverse-beta-decay candidates in the range of Eν e between 13.3 MeV and 31.3 MeV. All of the observed candidates are attributed to background. Upper limits at 90% C.L. are calculated in the absence of a signal.

The optimal components design for grid-connected photovoltaic-battery systems should be determined with consideration of system operation. This study proposes a method to simultaneously optimize the battery capacity and rule-based operation strategy. The investigated photovoltaic-battery system is modeled using single diode photovoltaic model and Improved Shepherd battery model. Three rule-based operation strategiesincluding the conventional operation strategy, the dynamic price load shifting strategy, and the hybrid operation strategyare designed and evaluated. The rule-based operation strategies introduce different operation parameters to run the system operation. multi-objective Genetic Algorithm is employed to optimize the decisional variables, including battery capacity and operation parameters, towards maximizing the system's Self Sufficiency Ratio and Net Present Value. The results indicate that employing battery with the conventional operation strategy is not profitable, although it increases Self Sufficiency Ratio. The dynamic price load shifting strategy has similar performance with the conventional operation strategy because the electricity price variation is not large enough. The proposed hybrid operation strategy outperforms other investigated strategies. When the battery capacity is lower than 72 kWh, Self Sufficiency Ratio and Net Present Value increase simultaneously with the battery capacity.

2Cosmic-ray-muon spallation-induced radioactive isotopes with β decays are one of the major backgrounds for solar, reactor, and supernova relic neutrino experiments. Unlike in scintillator, production yields for cosmogenic backgrounds in water have not been exclusively measured before, yet they are becoming more and more important in next generation neutrino experiments designed to search for rare signals. We have analyzed the low-energy trigger data collected at Super-Kamiokande-IV in order to determine the production rates of 12 B, 12 N, 16 N, 11 Be, 9 Li, 8 He, 9 C, 8 Li, 8 B and 15 C. These rates were extracted from fits to time differences between parent muons and subsequent daughter β's by fixing the known isotope lifetimes. Since 9 Li can fake an inverse-beta-decay reaction chain via a β + n cascade decay, producing an irreducible background with detected energy up to a dozen MeV, a dedicated study is needed for evaluating its impact on future measurements; the application of a neutron tagging technique using correlated triggers was found to improve this 9 Li measurement. The measured yields were generally found to be comparable with theoretical calculations, except the cases of the isotopes 8 Li/ 8 B and 9 Li.

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