User Response Based Recommendations: A Local Angle Approach

International audienceWhen a user interested in a service/item, visits an online web-portal, it provides description of its interest through initial search keywords. The system recommends items based on these keywords. The user is satisfied if it finds the item of its choice and the system benefits, otherwise the user explores an item from the list. Usually when the user explores an item, it picks an item that is nearest to its interest from the list. While the user explores an item, the system recommends new list of items. This continues till either the user finds its interest or quits. In all, the user provides ample chances and feedback for the system to learn its interest. The aim of this paper is to exploit the user-generated responses in the same session. One can further utilize the history (e.g., previous user ratings) to design good recommendation policies. We develop algorithms that efficiently utilize user responses to recommended items and find the item of user's interest quickly. We first derive optimal policies in the continuous Euclidean space and adapt the same to the space of discrete items. In the continuous Euclidean space, the optimal recommendations (e.g., with two recommendations) at the same time step are at 180 degrees from each other, while are at 90 degrees with respect to the ones at the previous time step. We propose the notion of local angle in the space of discrete items and develop user response-local angle (UR-LA) based recommendation policies. We compared the performance of UR-LA with widely used collaborative filtering (CF) based policies on two real datasets and showed that UR-LA performs better in majority of the test cases. We also proposed a hybrid scheme that combines the best features of both UR-LA and CF (and history) based policies, which outperforms them in most of the cases

Cyclotron instabilities of low frequency, parallel propagating electromagnetic waves in the magnetosphere

118-126Electromagnetic electron- and ion-cyclotron instabilities incorporating the details of wave-particle interactions have been studies with reference to low frequency waves in the magnetosphere. The general dispersion relation for transverse electromagnetic waves propagating along the ambient magnetic field in an anisotropic bi-Maxwellian plasma with a mirror loss-cone configuration has been considered. The growth/damping rates for electron-cyclotron waves (whistler) and ion-cyclotron waves have been derived. The electron- and ion-cyclotron wave growths have been computed from the magnetospheric VLF data from ISIS-2 satellite for equatorial and midlatitude auroral regions of the magnetosphere. The dependence of the growth rate of these waves on the temperature anisotropy and mirror loss-cone has been discussed. Loss-cone and electron-cyclotron instabilities are interpreted as the generation mechanism for the low frequency waves in the magnetosphere

Generation mechanism and interpretation of attenuation band of VLF-saucers

130-133An analysis of the ISIS-VLF data detected by magnetometer in the auroral region of the magnetosphere has been carried out for VLF-saucers. The generation mechanism of VLF-saucers has been studied in terms of excitation of electrostatic cyclotron harmonic emission due to energetic ions and electrons in the magnetospheric plasma. The attenuation bands of VLF-saucers, as observed by ISIS-2 satellite, have been discussed and it is interpreted that the cyclotron absorption of low energy protons at harmonics of local proton-cyclotron frequencies may be the cause for attenuation bands in VLF-saucers

3rd National Conference on Image Processing, Computing, Communication, Networking and Data Analytics

This volume contains contributed articles presented in the conference NCICCNDA 2018, organized by the Department of Computer Science and Engineering, GSSS Institute of Engineering and Technology for Women, Mysore, Karnataka (India) on 28th April 2018