Art Nouveau in the context of realism: Ilya Repin at the turn of two centuries

The main subject of this research is the specificity of I. E. Repin's perception of the dynamics of artistic-aesthetic tasks formed under the influence of changing modernity. In view of this, one of the compositional centers of the research is the history of relationship that developed between I. E. Repin and the artists of the “first wave of symbolism” – members of the association “The World of Art” (primarily, the editor-in-chief of the eponymous journal S. P. Diaghilev, A. N. Benois, K. A. Somov, Y. Y. Lanceray). Special attention is given to the question of perception of I. E. Repin by certain representatives of the avant-garde in 1910s. Developing in the range “attraction – negation”, full of dramatic and comic moments, the dialogue between Repin and younger generation indicates the hastiness of univocal view of realism and Art Nouveau as opposing imagery systems. For the first time, on the current level of scientific comprehension of the aesthetics of symbolism and neo-romanticism, the article analyzes the attitude of I. E. Repin towards the innovative imagery pursuits of the Art Nouveau artists. At the same time, the very concept of Art Nouveau is interpreted in two dimensions: as a certain milestone in the context of the development of the history of art of the late XIX – early XX century; and as an inner dynamic potential embedded by I. E. Repin in his works since the beginning of his creative path. Based on systematization of the artistic and documentary sources and  the method of complex reconstruction of the views of Peredvizhniki and symbolist artists upon the objectives and nature of art, the author concludes that the poetics of art of Ilya Repin, synthesizing the ideas of time, tends to reflect a complicated and distinctive artistic image formed by realistic and idealistic principles.

Policy invariant explicit shaping: an efficient alternative to reward shaping

Reinforcement learning (RL) is a powerful learning paradigm in which agents can learn to maximize sparse and delayed reward signals. Although RL has had many impressive successes in complex domains, learning can take hours, days, or even years of training data. A major challenge of contemporary RL research is to discover how to learn with less data. Previous work has shown that domain information can be successfully used to shape the reward; by adding additional reward information, the agent can learn with much less data. Furthermore, if the reward is constructed from a potential function, the optimal policy is guaranteed to be unaltered. While such potential-based reward shaping (PBRS) holds promise, it is limited by the need for a well-defined potential function. Ideally, we would like to be able to take arbitrary advice from a human or other agent and improve performance without affecting the optimal policy. The recently introduced dynamic potential-based advice (DPBA) was proposed to tackle this challenge by predicting the potential function values as part of the learning process. However, this article demonstrates theoretically and empirically that, while DPBA can facilitate learning with good advice, it does in fact alter the optimal policy. We further show that when adding the correction term to “fix” DPBA it no longer shows effective shaping with good advice. We then present a simple method called policy invariant explicit shaping (PIES) and show theoretically and empirically that PIES can use arbitrary advice, speed-up learning, and leave the optimal policy unchanged.

The Derma of Crisis: Imagining Athens in Crisis as an Urban Collage

A close look at the urban surfaces of Athens during the years of the economic crisis reveals the extensive phenomenon of the people’s interaction with the surface of the cityscape, the skin of Athens. A derma of crises that reflects Greece’s socio-political conditions over this period, and the austerity measures enforced by the official state. This rapidly transformed and ever-changing surface imagery can be recorded and used for reading and further understanding of how the public sphere responds to this period of decline, and reacts to the recession’s strategies of sovereignty. The urgency to document, give prominence to this urban field and examine it as a whole is of pivotal importance, considering the fact that the official authorities (such as the mayor of Athens) have recently taken action to eliminate the urban traces. However, these inscriptions bear witness to the continuous crisis mirrored on the Athenian walls and architectural volumes. Over the last years, there have been numerous scholars and researchers that have engaged with the study of the Athenian cityscape. Nonetheless, they particularly focus on graffiti, street art and slogans, and this engagement sometimes facilitates the emerging artistry or the discussion of socio-political connotations. In contrast to this, this article moves towards the identification of the phenomenon as a dynamic potential of a derma–city skin and does not specifically focus on them as mere details (often intentionally made, e.g. a graffiti). It examines the wholeness, the anonymity, the unintentional activity; how they contribute to the formulation of an urban collage, an assemblage of visual elements that co-exist making Athens a unique case of an over-marked city. The study of various dimensions of this skin and of the virtual preservation means aims to add a further layer of understanding to the urban space as a main field of socio-political connotations during the crisis.

Long-range transport of 2D excitons in dynamic acoustic lattice

Excitons are elementary optical excitation in semiconductors. The ability to manipulate and transport these quasiparticles would enable excitonic circuits and devices for quantum photonic technologies. Recently, interlayer excitons in 2D semiconductors have emerged as a promising candidate for engineering excitonic devices due to long lifetime, large exciton binding energy, and gate tunability. However, the charge-neutral nature of the excitons leads to a weak response to the in-plane electric field and thus inhibits transport beyond the diffusion length. Here, we demonstrate the directional transport of interlayer excitons in bilayer WSe2 driven by the dynamic potential lattice induced by surface acoustic waves (SAW). We show that at 100 K, the SAW-driven excitonic transport is activated above a threshold acoustic power and reaches a distance at least ten times longer than the diffusion length, only limited by the device size. Temperature-dependent measurement reveals the transition from the diffusion-limited regime at low temperature to an acoustic field-driven regime at elevated temperature. Our work shows that acoustic waves are an effective, contact-free means to control exciton dynamics and transport, promising for realizing 2D materials-based excitonic devices such as exciton transistors, switches, and transducers.

Electrochemical corrosion resistance of thermal oxide formed on anodized stainless steel

Purpose The purpose of this paper is to investigate and explain thermal oxide effect on electrochemical corrosion resistance anodized stainless steel (SS). Design/methodology/approach Electrochemical corrosion resistance of thermal oxides produced on anodized 304 SS in air at 350°C, 550°C, 750°C and 950°C in 3.5 wt.% NaCl solution have been investigated by dynamic potential polarization, EIS and double-loop dynamic polarization. Anodized 304 SS were obtained by anodization at the constant density of 1.4 mA.cm-2 in the solution containing 28.0 g.L-1H3PO4, 20.0 g.L-1C6H8O7, 200.0 g.L-1H2O2 at 70°C for 50 min. SEM and EDS had been also used to characterize the thermal oxides and passive oxide. Findings Interestingly, anodized 304SS with thermal oxide produced at 350°C displayed more electrochemical corrosion and pitting resistance than anodized 304 SS only with passive oxide, as related to the formation of oxide film with higher chromium to iron ratio. Whereas, anodized 304SS with thermal oxide formed at 950°C shows the worse electrochemical corrosion and pitting resistance among those formed at the high temperatures due to thermal oxide with least compact. Originality/value When thermally oxidized in the range of 350°C–950°C, electrochemical corrosion and pitting corrosion resistance of anodized 304 SS decrease with the increase of temperature due to less compactness, more defects of thermal oxide.

Dynamic Movement Primitives: Volumetric Obstacle Avoidance Using Dynamic Potential Functions

Obstacle avoidance for Dynamic Movement Primitives (DMPs) is still a challenging problem. In our previous work, we proposed a framework for obstacle avoidance based on superquadric potential functions to represent volumes. In this work, we extend our previous work to include the velocity of the system in the definition of the potential. Our formulations guarantee smoother behavior with respect to state-of-the-art point-like methods. Moreover, our new formulation allows obtaining a smoother behavior in proximity of the obstacle than when using a static (i.e. velocity independent) potential. We validate our framework for obstacle avoidance in a simulated multi-robot scenario and with different real robots: a pick-and-place task for an industrial manipulator and a surgical robot to show scalability; and navigation with a mobile robot in a dynamic environment.