A Probabilistic Model for the Cold-Start Problem in Rating Prediction using Click Data

One of the most efficient methods in collaborative filtering is matrix factorization, which finds the latent vector representations of users and items based on the ratings of users to items. However, a matrix factorization based algorithm suffers from the cold-start problem: it cannot find latent vectors for items to which previous ratings are not available. This paper utilizes click data, which can be collected in abundance, to address the cold-start problem. We propose a probabilistic item embedding model that learns item representations from click data, and a model named EMB-MF, that connects it with a probabilistic matrix factorization for rating prediction. The experiments on three real-world datasets demonstrate that the proposed model is not only effective in recommending items with no previous ratings, but also outperforms competing methods, especially when the data is very sparse.Comment: ICONIP 201

Degenerate Fermi Gases of Ytterbium

An evaporative cooling was performed to cool the fermionic 173Yb atoms in a crossed optical dipole trap. The elastic collision rate, which is important for the evaporation, turns out to be large enough from our study. This large collision rate leads to efficient evaporation and we have successfully cooled the atoms below 0.6 of the Fermi temperature, that is to say, to a quantum degenerate regime. In this regime, a plunge of evaporation efficiency is observed as the result of the Fermi degeneracy.Comment: 4 pages, 3figure

All-Optical Formation of Quantum Degenerate Mixtures

We report the realization of quantum degenerate mixed gases of ytterbium (Yb) isotopes using all-optical methods. We have succeeded in cooling attractively interacting 176Yb atoms via sympathetic cooling down to below the Bose-Einstein transition temperature, coexisting with a stable condensate of 174Yb atoms with a repulsive interaction. We have observed a rapid atom loss in 176Yb atoms after cooling down below the transition temperature, which indicates the collapse of a 176Yb condensate. The sympathetic cooling technique has been applied to cool a 173Yb-174Yb Fermi-Bose mixture to the quantum degenerate regime.Comment: 4 pages, 3 figure