Jožef Stefan Institute

About: Jožef Stefan Institute is a facility organization based out in Ljubljana, Slovenia. It is known for research contribution in the topics: Liquid crystal & Dielectric. The organization has 3828 authors who have published 12614 publications receiving 291025 citations.

VizRank: Data Visualization Guided by Machine Learning

Abstract: Data visualization plays a crucial role in identifying interesting patterns in exploratory data analysis. Its use is, however, made difficult by the large number of possible data projections showing different attribute subsets that must be evaluated by the data analyst. In this paper, we introduce a method called VizRank, which is applied on classified data to automatically select the most useful data projections. VizRank can be used with any visualization method that maps attribute values to points in a two-dimensional visualization space. It assesses possible data projections and ranks them by their ability to visually discriminate between classes. The quality of class separation is estimated by computing the predictive accuracy of k-nearest neighbor classifier on the data set consisting of x and y positions of the projected data points and their class information. The paper introduces the method and presents experimental results which show that VizRank's ranking of projections highly agrees with subjective rankings by data analysts. The practical use of VizRank is also demonstrated by an application in the field of functional genomics.

Titanium Incorporation in Zn2TiO4 Spinel Ceramics

Abstract: Compositions in the Zn2TiO4+xTiO2 system (x= 0–0.43) were synthesized via the solid-state reaction route, using high-purity (≥99.99%) metal-oxide powders. The incorporation of titanium, in the form of TiO2, in Zn2TiO4 spinel ceramics was investigated by analyzing the crystal structure and measuring the dielectric properties. The results of the crystal structure analyses suggested that TiO2 levels of x≤ 0.33 could be incorporated into the Zn2TiO4 spinel at temperatures of T > 945°C, whereas the solid solubility of titanium in Zn2TiO4 decreased for T < 945°C. When x≥ 0.28, the Zn2Ti3O8 phase formed in the Zn2TiO4 grain interior while cooling after heat treatment. Measurement of the microwave dielectric properties also supported the conclusion that the solubility limit of titanium in Zn2TiO4 was close to x= 0.33, as determined through analysis of the crystal structure.

Coherent phonon dynamics in semiconducting carbon nanotubes: a quantitative study of electron-phonon coupling.

Abstract: We excite and detect coherent phonons in semiconducting (6,5) carbon nanotubes via a sub-10-fs pump-probe technique. Simulation of the amplitude and phase profile via time-dependent wave packet theory yields excellent agreement with experimental results under the assumption of molecular excitonic states and allows determining the electron-phonon coupling strength for the two dominant vibrational modes.