Machine Learning Model Generation With Copula-Based Synthetic Dataset for Local Differentially Private Numerical Data

With the development of IoT technology, personal data are being collected in many places. These data can be used to create new services, but consideration must be given to the individual’s privacy. We can safely collect personal data while adding noise by applying differential privacy. However, because such data are very noisy, the accuracy of machine learning trained by the data greatly decreased. In this study, our objective is to build a highly accurate machine learning model using these data. We focus on the decision tree machine learning algorithm, and, instead of applying it as is, we use a preprocessing technique wherein pseudodata are generated using a copula while removing the effect of noise added by differential privacy. In detail, the proposed novel protocol consists of three steps: generating a covariance matrix from the differentially private numerical data, generating a discrete cumulative distribution function from differentially private numerical data, and generating copula-based numerical samples. Simulation results using synthetic and real datasets verify the utility of the proposed method not only for the decision tree algorithm but also for other machine learning algorithms such as deep neural networks. This method will help create machine learning models, such as recommendation systems, using differential privacy data.journal articl

コーデイエライト/ジルコン焼結体の緻密化

Raw materials of talc, feldsper, kaolin, alumina, silica, and zircon were used for fabrication of dense cordierite / zircon sintered body by a reaction sintering method. Density of the fabricated sintered body decreased with increasing sintering temperature ranging from 1473 to 1573K. Scanning electron microscope (SEM) and X-ray diffractometry (XRD) revealed that decreasing of the density of tpe sintered body was caused by pore formation accompanied with crystallization of cordierite. It was considered that the pore formation was due to reaction of crystalline talc with matrix phase during sintering process.textapplication/pdfdepartmental bulletin pape

Search for matter-dependent atmospheric neutrino oscillations in Super-Kamiokande

We consider ν_μ→ν_τ oscillations in the context of the mass varying neutrino (MaVaN) model, where the neutrino mass can vary depending on the electron density along the flight path of the neutrino. Our analysis assumes a mechanism with dependence only upon the electron density, hence ordinary matter density, of the medium through which the neutrino travels. Fully-contained, partially-contained and upward-going muon atmospheric neutrino data from the Super-Kamiokande detector, taken from the entire SK-I period of 1489 live days, are compared to MaVaN model predictions.We find that, for the case of 2-flavor oscillations, and for the specific models tested, oscillation independent of electron density is favored over density dependence. Assuming maximal mixing, the best-fit case and the densityindependent case do not differ significantly.journal articl

Study of Time-Dependent CP Violation in B0→J/ψπ0 Decays

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教育学部 情報科学基礎 1コマコース (平成18年度)

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Temperature Dependence of Magnetically Active Charge Excitations in Magnetite across the Verwey Transition

We study the electronic structure of bulk single crystals and epitaxial films of Fe3O4. Fe 2p core level spectra show clear differences between hard x-ray (HAX) and soft x-ray photoemission spectroscopy (PES). The bulk-sensitive spectra exhibit temperature (T) dependence across the Verwey transition, which is missing in the surface-sensitive spectra. By using an extended impurity Anderson full-multiplet model-and in contrast to an earlier peak assignment-we show that the two distinct Fe species (A and B site) and the charge modulation at the B site are responsible for the newly found double peaks in the main peak above TV and its T-dependent evolution. The Fe 2p HAXPES spectra show a clear magnetic circular dichroism (MCD) in the metallic phase of magnetized 100-nm-thick films. The model calculations also reproduce the MCD and identify the contributions from magnetically distinct A and B sites. Valence band HAXPES shows a finite density of states at EF for the polaronic half metal with a remnant order above TV and a clear gap formation below TV. The results indicate that the Verwey transition is driven by changes in the strongly correlated and magnetically active B-site electronic states, consistent with resistivity and optical spectra.journal articl