Bayesian Ranker Comparison Based on Historical User Interactions

ABSTRACT We address the problem of how to safely compare rankers for information retrieval. In particular, we consider how to control the risks associated with switching from an existing production ranker to a new candidate ranker. Whereas existing online comparison methods require showing potentially suboptimal result lists to users during the comparison process, which can lead to user frustration and abandonment, our approach only requires user interaction data generated through the natural use of the production ranker. Specifically, we propose a Bayesian approach for (1) comparing the production ranker to candidate rankers and (2) estimating the confidence of this comparison. The comparison of rankers is performed using click model-based information retrieval metrics, while the confidence of the comparison is derived from Bayesian estimates of uncertainty in the underlying click model. These confidence estimates are then used to determine whether a risk-averse decision criterion for switching to the candidate ranker has been satisfied. Experimental results on several learning to rank datasets and on a click log show that the proposed approach outperforms an existing ranker comparison method that does not take uncertainty into account

Coronavirus-like all-angle all-polarization broadband scatterer

This is the final version. Available on open access from Nature Research via the DOI in this recordData availability: All data generated or analyzed during this study are included in this published article. The modeling script is available online: https://zenodo.org/record/6962448#.ZA8jvS8w2LcCreeping waves traveling around a volumetric electromagnetic scatterer provide a significant contribution to its radar cross-section. While quite a few efforts were devoted to suppressing creeping waves as a part of radar countermeasures, here we utilize specially engineered creeping waves to our advantage to create broadband, all-angle, and polarization scatterers. Metalized spherical surfaces, patterned with corona virus-like spikes are designed to provide a broadband constructive interference between the specular reflection and creeping waves, elevating the scattering cross-section. The demonstrated miniature corona scatterers utilize both resonant cascading phenomena and traveling wave interference to tailor electromagnetic interactions, outperforming a resonant dipole in terms of amplitude and bandwidth quite significantly. Our experimental samples are fabricated with an additive manufacturing technique, where a 3D-printed plastic skeleton is subsequently metalized. Micron-thick layers allow governing electromagnetic interactions as if the entire object was made of solid metal. Lightweight, all-angle, all-polarization, and broadband compact scatterers such as these, reported here, have numerous applications, including radar deception, electromagnetic beckoning, and many others.Department of the Navy, Office of Naval Research GlobalRRF project Latvian Quantum Technologies InitiativeRoyal Academy of Engineerin

Optimizing web search engines with interactions

Web search engines are used by many people everyday, serving as one of the primary gateways to information stored online. Optimizing search engines is challenging because it requires large datasets annotated by human judges. Such datasets are expensive to create and are often not reliable because there can be a mismatch between what human judges and real users find relevant. This motivates using observed interactions between the user and the web search engine. These interactions are readily available in massive quantities and have been shown to correlate with user satisfaction with the search engine. In this thesis we study how to use these interactions to optimize web search engines

Mass, Heat and Salt Balances in the Eastern Barents Sea Obtained by Inversion of Hydrographic Section Data

Standard hydrological section data, collected in the eastern Barents Sea in September 1997, have been analyzed using a variational data assimilation technique. This method allows us to obtain temperature, salinity and velocity fields that are consistent with observations and dynamically balanced within the framework of a steady-state model describing large-scale nearly geostrophic circulation. Error bars of the optimized fields are computed by explicit inversion of the Hessian matrix. The optimized velocity field is in agreement with independent velocity observations derived from surface drifter trajectories in the southwestern part of the Barents Sea. Optimized fields provide the following estimates of integral characteristics of the circulation in the region: i) the North Cape current transport is 2.12 +/- 0.25 Sv; ii) the Karskie Vorota Strait throughtlow is 0.7 +/- 0.06 Sv; iii) heat flux with Atlantic water is 4.7 +/- 0.16- 10(11) W; iv) salt import from the Atlantic Ocean is 7.41 +/- 0.46.10(3) kg/s. The imbalance of the heat budget in the eastern part of the Barents Sea indicates the presence of statistically insignificant surface heat fluxes which are less than 1 W/m(2)

User Behavior in Location Search on Mobile Devices

Abstract. Location search engines are an important part of GPS-enabled de-vices such as mobile phones and tablet computers. In this paper, we study how users behave when they interact with a location search engine by analyzing logs from a popular GPS-navigation service to find out whether mobile users ’ location search characteristics differ from those of regular web search. In particular, we analyze query- and session-based characteristics and the temporal distribution of location searches performed on smart phones and tablet computers. Our findings may be used to improve the design of search interfaces in order to help users perform location search more effectively and improve the overall experience on GPS-enabled mobile devices.