Diversely Regularized Matrix Factorization for Accurate and Aggregately Diversified Recommendation

When recommending personalized top-$k$ items to users, how can we recommend the items diversely to them while satisfying their needs? Aggregately diversified recommender systems aim to recommend a variety of items across whole users without sacrificing the recommendation accuracy. They increase the exposure opportunities of various items, which in turn increase potential revenue of sellers as well as user satisfaction. However, it is challenging to tackle aggregate-level diversity with a matrix factorization (MF), one of the most common recommendation model, since skewed real world data lead to skewed recommendation results of MF. In this work, we propose DivMF (Diversely Regularized Matrix Factorization), a novel matrix factorization method for aggregately diversified recommendation. DivMF regularizes a score matrix of an MF model to maximize coverage and entropy of top-$k$ recommendation lists to aggregately diversify the recommendation results. We also propose an unmasking mechanism and carefully designed mi i-batch learning technique for accurate and efficient training. Extensive experiments on real-world datasets show that DivMF achieves the state-of-the-art performance in aggregately diversified recommendation.Comment: 9 pages, 7 figures, 2 table

First aqueous chemistry with Seaborgium (element 106)

For the first time, chemical separations of element 106 (Seaborgium, Sg) were performed in aqueous solutions. The isotopes "2"6"5Sg and "2"6"6Sg were produced in the "2"4"8Cm+"2"2Ne reaction at a beam energy of 121 MeV. The reaction products were continuously transported by a He(KCl)-jet to the computer-controlled liquid chromatography system ARCA. In 0.1 M HNO_3/5 x 10"-"4 M HF, Sg was found to be eluted within 10 s from 1.6 x 8 mm cation-exchange columns (Aminex A6, 17.5#+-#2 #mu#m) together with the hexavalent Mo- and W-ions, while hexavalent U-ions and tetravalent Zr-, Hf-, and element 104 ions were strongly retained on the column. Element 106 was detected by measuring correlated #alpha#-decays of the daughter isotopes 78-s "2"6"1104 and 26-s"2"5"7102. For the isotope "2"6"6Sg, we have evidence for a spontaneous fission branch. It yields a partial spontaneous-fission half-life which is in agreement with recent theoretical predictions. The chemical results show that the most stable oxidation state of Sg in aqueous solution is +6, and that like its homologs Mo and W, Sg forms neutral or anionic oxo- or oxohalide-compounds under the present condition. In these first experiments, Sg exhibits properties very characteristic of group 6 elements, and does not show U-like properties. (orig.)Available from TIB Hannover: RO 801(96-56) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman