Temperature-Induced Structural Transformations in Undoped and Eu3+-Doped Ruddlesden–Popper Phases Sr2SnO4 and Sr3Sn2O7: Relation to the Impedance and Luminescence Behaviors

We report that luminescence of Eu3+ ion incorporated into Ruddlesden–Popper phases allows monitoring phase transition in powders (instead of single crystals), in a time-efficient manner (compared to neutron diffraction), and importantly, with greater sensitivity than previous methods. Crystal structure and dielectric response of undoped and 0.5%Eu3+-doped Sr3Sn2O7 ceramics were studied as a function of temperature over the temperature range of 300–800 K. The luminescence studies of 0.5%Eu3+-doped Sr2SnO4 and Sr3Sn2O7 samples were performed in the temperature range of 80–500 K. These results were compared with the respective dependences for the undoped compounds. The structural transformations in 0.5%Eu3+-doped Sr3Sn2O7 were found at 390 and 740 K. The former is associated with the isostructural atomic rearrangement that resulted in a negative thermal expansion along two of three orthorhombic crystallographic axes, while the latter corresponds to the structural transition from the orthorhombic Amam phase to the tetragonal I4/mmm one. A similar temperature behavior with the structural transformations in the same temperature ranges was observed in undoped Sr3Sn2O7, although the values of lattice parameters of the Eu3+-doped and undoped compounds were found to be slightly different indicating an incorporation of europium in the crystal lattice. A dielectric anomaly associated with a structural phase transition was observed in Sr3Sn2O7 at 390 K. Optical measurements performed over a wide temperature range demonstrated a clear correlation between structural transformations in Eu3+-doped Sr2SnO4 and Sr3Sn2O7 and the temperature anomalies of their luminescence spectra, suggesting the efficacy of this method for the determination of subtle phase transformations

Design and development of a low-cost mask-type eye tracker to collect quality fixation measurements in the sport domain

The aim of the study was to build a low-cost mask-type eye tracker with accuracy and precision levels similar to those reported for commercial eye tracking devices. To this end, head-mounted hardware was designed and developed, while open-source software was modified for digital image capture, manipulation, and fixation analysis. An image recognition application was also included with different lighting scenarios. Moreover, parallax and viewing perspective errors were controlled to ensure the quality of data collection. The device was wireless and lightweight (99 g) to allow for natural movement and avoid participant discomfort. After calibration of a 9-target monocular grid, spatial accuracy and precision of the eye tracker was evaluated by 30 participants, at four different lighting setups, both before and after a climbing task. Validity tests showed high levels of accuracy in all conditions as evidenced by a systematic error for a 13-target grid of <0.5°. The reliability tests also showed consistent measurements with no differences in accuracy recorded between participants, lighting conditions, and visual behaviors for the pre- versus post-climbing task. These results suggest that the present eye tracker reports spatial accuracy similar to other commercial systems with levels of high quality. Altogether, this innovative user interface is suitable for research purposes and/or performance analysis in physical activity and sport-related activities. Also, features of this mask-type eye tracking system make it a suitable perceptual user interface to investigate human–computer interactions in a large number of other research fields including psychology, education, marketing, transportation, and medicine

Exchange bias effect in bulk multiferroic BiFe0.5Sc0.5O3

Below the Néel temperature, TN ∼ 220 K, at least two nano-scale antiferromagnetic (AFM) phases coexist in the polar polymorph of the BiFe0.5Sc0.5O3 perovskite; one of these phases is a weak ferromagnetic. Non-uniform structure distortions induced by high-pressure synthesis lead to competing AFM orders and a nano-scale spontaneous magnetic phase separated state of the compound. Interface exchange coupling between the AFM domains and the weak ferromagnetic domains causes unidirectional anisotropy of magnetization, resulting in the exchange bias (EB) effect. The EB field, HEB, and the coercive field strongly depend on temperature and the strength of the cooling magnetic field. HEB increases with an increase in the cooling magnetic field and reaches a maximum value of about 1 kOe at 5 K. The exchange field vanishes above TN with the disappearance of long-range magnetic ordering. The effect is promising for applications in electronics as it is large enough and as it is tunable by temperature and the magnetic field applied during cooling.publishe

Insights from the NeurIPS 2021 NetHack Challenge

In this report, we summarize the takeaways from the first NeurIPS 2021 NetHack Challenge. Participants were tasked with developing a program or agent that can win (i.e., ‘ascend’ in) the popular dungeon-crawler game of NetHack by interacting with the NetHack Learning Environment (NLE), a scalable, procedurally generated, and challenging Gym environment for reinforcement learning (RL). The challenge showcased community-driven progress in AI with many diverse approaches significantly beating the previously best results on NetHack. Furthermore, it served as a direct comparison between neural (e.g., deep RL) and symbolic AI, as well as hybrid systems, demonstrating that on NetHack symbolic bots currently outperform deep RL by a large margin. Lastly, no agent got close to winning the game, illustrating NetHack’s suitability as a long-term benchmark for AI research

SERVITIZATION OF LITHUANIAN AGRICULTURAL COOPERATIVES

To survive and be competitive in the changing economic environment, agricultural cooperatives are innovating and creating more sophisticated, added-value products and broadening the range of provided services. Lithuanian cooperatives, facing the same challenges, are less flexible and adaptable to changes due to short operational history and sparse membership. Therefore, the following scientific problem is addressed: do Lithuanian agricultural cooperatives still represent a shift to servitizing? The aim of this paper is to investigate the current state of servitization among Lithuanian agricultural cooperatives, and to frame directions for further research in this novel research field. The research relies on structured interviews conducted with Lithuanian agricultural cooperatives. The results of statistical data analysis indicate a slow shift of agricultural cooperatives towards servitization, particularly related to the provision of knowledge-based and adding-value services. Identification of general and personal causes of slow servitization among cooperatives is suggested for further researches.Siekdami išlikti ir būti konkurencingi besikeičiant pasaulinėms ekonominėms sąlygoms, žemės ūkio kooperatyvai kuria sudėtingesnę, didesnę pridėtinę vertę turinčią produkciją bei plečia teikiamų paslaugų asortimentą. Lietuvos kooperatyvai susiduria su tais pačiais iššūkiais, tačiau dėl trumpos veiklos patirties ir mažo narių skaičiaus yra riboto lankstumo ir sunkiau prisitaiko prie pokyčių. Todėl straipsnyje formuluojama mokslinė problema: ar Lietuvos žemės ūkio kooperatyvai pereina prie veiklos servitizacijos? Tyrimo tikslas – ištirti kooperatyvų servitizacijos situaciją ir pasiūlyti tolimesnių tyrimų, susijusių su šia žemės ūkiui nauja tema, kryptis. Tyrimas remiasi struktūruotais interviu, atliktais su Lietuvos žemės ūkio kooperatyvais. Statistinės duomenų analizės metu gauti rezultatai rodo labai lėtą kooperatyvų servitizaciją, ypač kalbant apie žiniomis grįstų ir pridėtinę vertę kuriančių paslaugų teikimą. Ateityje siūloma nustatyti bendrąsias ir asmenines lėtos kooperatyvų servitizacijos priežastis