Improving imbalanced classification using near-miss instances

The class imbalance is a major issue in classification, i.e., the sample size of a rare class (positive) is often a performance bottleneck. In real-world situations, however, “near-miss” positive instances, i.e., negative but nearly-positive instances, are sometimes plentiful. For example, natural disasters such as floods are rare, while there are relatively plentiful near-miss cases where actual floods did not occur but the water level approached the bank height. We show that even when the true positive cases are quite limited, such as in disaster forecasting, the accuracy can be improved by obtaining refined label-like side-information “positivity” (e.g., the water level of the river) to distinguish near-miss cases from other negatives. Conventional cost-sensitive classification cannot utilize such side-information, and the small size of the positive sample causes high estimation variance. Our approach is in line with learning using privileged information (LUPI), which exploits side-information for training without predicting the side-information itself. We theoretically prove that our method reduces the estimation variance, provided that near-miss positive instances are plentiful, in exchange for additional bias. Results of extensive experiments demonstrate that our method tends to outperform or compares favorably to existing approaches

Neutrino masses and mixing from S4 flavor twisting

We discuss a neutrino mass model based on the S4 discrete symmetry where the symmetry breaking is triggered by the boundary conditions of the bulk right-handed neutrino in the fifth spacial dimension. While the symmetry restricts bare mass parameters to flavor-diagonal forms, the viable mixing angles emerge from the wave functions of the Kaluza-Klein modes which carry symmetry breaking effect. The magnitudes of the lepton mixing angles, especially the reactor angle is related to the neutrino mass patterns and the model will be tested in future neutrino experiments, e.g., an early (late) discovery of the reactor angle favors the normal (inverted) hierarchy. The size of extra dimension has a connection to the possible mass spectrum; a small (large) volume corresponds to the normal (inverted) mass hierarchy.Comment: 22 pages, 3 figures; added references for section

High-field magnetization and magnetic phase transition in CeOs2Al10

We have studied the magnetization of CeOs2Al10 in high magnetic fields up to 55 T for H // a and constructed the magnetic phase diagram for H // a. The magnetization curve shows a concave H dependence below T_max \sim40 K which is higher than the transition temperature T_0 \sim29 K. The magnetic susceptibility along the a-axis shows a smooth and continuous decrease down to \sim20 K below T_max \sim40 K without showing an anomaly at T_0. From these two results, a Kondo singlet is formed below T_max and coexists with the antiferro magnetic order below T_0. We also propose that the larger suppression of the spin degrees of freedom along the a-axis than along the c-axis below T_max is associated with the origin of the antiferro magnetic component.Comment: 4 pages, 4 figures, to appear in Phys. Rev. B, Rapid Commu

Evaluation of belowground seasonal dynamics of Typha angustifolia after cutting treatment

Typha angustifolia, an emergent macrophyte, shows different growth characteristics under the influence of external forces. In this study, the growth characteristics of T, angustifolia were investigated after cutting the shoots (treatment area: 3m×4m). The treatment is considered as an external force. Two stands, one in a sterile zone and the other in a fertile zone, were cut at the end of June 2001 and the subsequent re-growth characteristics were observed. The difference of response, after cutting their shoots in the fertile zone and sterile zone was prominent. Shoot re-growth model was developed to evaluate the belowground dynamics by calibrating the choot height and aboveground parameters. The belowground biomass of cut area after one year was simulated to be about 80% of that of uncut area. The results were verified using the belowground biomass observed in April 2002. The buds in the cut area are shorter than those of the uncut area. Morever, the cut area in the ferile zone generated thinner buds than that of the sterile zone. The belowground biomass and re-growth strategy after cutting were supposed to cause the differences of their buds the year after.Article信州大学山地水環境教育研究センター研究報告 2: 29-34(2004)departmental bulletin pape