arXiv subjects

Keisuke Sugawara

Publications and source records attributed to Keisuke Sugawara.

3 recordsLinked to original sources

arXiv2026

Neural Architecture Search of Sample Reweighting Networks for Complex Distribution Shift

Sample reweighting is a major approach to addressing distribution shifts, such as label noise and class imbalance. Meta-Weight-Net (MW-Net) is a promising sample reweighting network that computes weights based on classification loss. Although MW-Net improves prediction performance under a single type of distribution shift using a simple neural network, its performance degrades when facing both label noise and class imbalance, where it is hard to determine appropriate weights solely from classification loss and using a simple network. In this study, we introduce neural architecture search to MW-Net to mitigate such performance degradation. Using the tree-structured Parzen estimator, we explore the optimal number of hidden layers and nodes and select the most suitable intermediate layer in the classification model to serve as the input for MW-Net. Experimental results on the CIFAR-10 and CIFAR-100 datasets that were modified to include both label noise and class imbalance demonstrate the effectiveness of neural architecture search for MW-Net.

cs.LG↗

arXiv2016

Effect of pressure on magneto-transport properties in the superconducting and normal phases of the metallic double chain compound Pr$_{2}$Ba$_{4}$Cu$_{7}$O$_{15-δ}$

To examine the electronic phase diagram of superconducting CuO double chains, we report the effect of external pressure on the magneto-transport properties in superconducting and non-superconducting polycrystalline samples of Pr$_{2}$Ba$_{4}$Cu$_{7}$O$_{15-δ}$ at low temperatures (1.8-40 K) under various magnetic fields (up to 14 T). In the as-sintered non-superconducting sample, the magneto-resistance (MR) follows a power law of $H^{3/2}$ at low temperatures, which is in no agreement with the $H^{2}$ dependence of MR in the PrBa$_{2}$Cu$_{4}$O$_{8}$ system. The negative pressure dependence of the superconducting phase is qualitatively consistent with a theoretical prediction on the basis of the Tomonaga-Luttinger Liquid theory. The 48-h-reduced superconducting sample at ambient pressure exhibits no clear increase in MR for $T > T_{c,on}=26.5$ K. In contrast, with the application of pressure to the superconducting sample, the MR effects reappear and are also well fitted by $H^{3/2}$. The model of slightly warped Fermi surfaces explains not only the MR effect of the non-superconducting sample, but is also related to the reasons for the pressure-induced MR phenomena of the superconducting sample.

cond-mat.supr-con↗

arXiv2015

Thermodynamic Properties of Superconducting and Non-Superconducting Pr$_{2}$Ba$_{4}$Cu$_{7}$O$_{15-δ}$ Compounds with Metallic Double Chains

To examine the thermodynamic properties of Pr$_{2}$Ba$_{4}$Cu$_{7}$O$_{15-δ}$ compounds with metallic CuO double chains, we measured the specific heats of superconducting and non-superconducting polycrystalline samples at low temperatures (1.8-40 K) under various magnetic fields (up to 9 T). In the as-sintered non-superconducting sample, a $λ-$like enhancement in the specific heat measurement appeared near the antiferromagnetic transition temperature $T_{N}=17$ K. In contrast, the reduced superconducting sample with $T_{c,on}=26.5$ K exhibited no obvious superconducting anomaly in its specific data, but a Schottky-like broad maximum appeared at low temperatures. The Schottky-like anomaly was attributed to low-lying quasi-triplet splitting of Pr$^{3+}$ ions under the crystal field effect.

cond-mat.supr-con↗