Saint Petersburg State University
  • Saint Petersburg, Russia
Recent publications
This paper investigates the role of lexical ambiguity in the processing and recognition of multimodal advertisements. First, we combined 28 Russian advertising posters: 14 ads with an ambiguous headline that leads to the conflict between text and pictural parts of a poster and 14 explicit ads of the same structure and advertising product as their ambiguous pairs. In Exp.1, 104 Russian participants looked at the stimuli and rated the stimuli by 6 parameters: how eye-catching, original, impelling to buy the advertised product, understandable, evoking positive emotions and matching the product the posters are. We used scales from 1 to 5. The experiment was conducted via Google Forms. 3–4 weeks later, in Exp. 2, the same participants were invited to recognize verbal and non-verbal “halves” of the posters from Exp. 1. The results of the scaling experiment showed that ambiguous advertising posters were ranked significantly higher than unambiguous ads by four of six parameters. Furthermore, ambiguous posters were rated as slightly more understandable than unambiguous posters, despite the expectation that word-play would complicate the understanding of the ambiguous posters. In the recognition task, we revealed that both verbal and non-verbal components of a poster are recognized better if they were a part of an ambiguous poster. These findings are discussed in relation to the multimodal text literature, and research perspectives are provided to explore ambiguous text processing empirically.
In this paper, the concept of divide and federate is evaluated to find the clusters that are different in densities and shapes and are contaminated with noise. The proposed divide-and-federate clustering method is based on the density and distance evaluation of the data. Wherein, the first phase of the algorithm divides the data into different sub-clusters based on the density evaluation with respect to all the data dimensions and, in the second phase, the small sub-clusters are federated with large sub-clusters to create the actual data clusters. The federation phase of the proposed clustering method is based on the distance evaluation of clusters and is merged based on the close proximity of neighbors. The proposed clustering algorithm is capable of handling noisy data through the integration of an outlier detection preprocessing method. The usefulness of the proposed algorithm is demonstrated with some examples of complex synthetic benchmark functions.KeywordsClusteringSubspace learningUnsupervised learning
Indole has been proposed as a Liquid Organic Hydrogen Carrier (LOHC) component. Its hydrogenation leads to octahydro indole, which can subsequently release hydrogen again in an endothermic, catalytic dehydrogenation reaction. This reaction requires high temperatures due to limitations by the reaction equilibrium. It is therefore interesting to find derivatives of the carrier molecules with lower enthalpies of reaction, which corresponds to a higher equilibrium constant. In this study, methyl and phenyl substituted derivatives of indole have been examined. Vapor pressures and enthalpies of vaporisation/sublimation have been measured. The standard molar enthalpies of formation in the gas phase have been calculated using quantum chemistry. The liquid phase standard molar enthalpies of formation were derived and used for calculating reaction enthalpies. The results show that methylation lowers the enthalpy of reaction for dehydrogenation. The reduction is not very pronounced in case of single methylation (up to 3.1 kJ mol⁻¹/H2), but can be increased by manifold methylation (e.g. 4.6 kJ mol⁻¹/H2 in case of 2,3-dimethyl-H8-indole). Substitution of indole with a phenyl group leads to a corresponding hydrogenated counterpart, that can only be dehydrogenated partially under mild conditions. This is due to the fact that the reducing effect of the nitrogen atom on enthalpy of reaction is only effective in the indole system itself, while the cyclohexyl ring has similar dehydrogenation properties to homocyclic LOHCs.
In this paper we introduce a new notion of a sequence of symmetry groups of an infinite word. Given a subgroup Gn of the symmetric group Sn, it acts on the set of finite words of length n by permutation. We associate to an infinite word w a sequence (Gn(w))n≥1 of its symmetry groups: For each n, a symmetry group of w is a subgroup Gn(w) of the symmetric group Sn such that g(v) is a factor of w for each permutation g∈Gn(w) and each factor v of length n of w. We study general properties of the symmetry groups of infinite words and characterize the sequences of symmetry groups of several families of infinite words. We show that for each subgroup G of Sn there exists an infinite word w with Gn(w)=G. On the other hand, the structure of possible sequences (Gn(w))n≥1 is quite restrictive: we show that they cannot contain for each order n certain cycles, transpositions and some other permutations. The sequences of symmetry groups can also characterize a generalized periodicity property. We prove that symmetry groups of Sturmian words and more generally Arnoux-Rauzy words are of order two for large enough n; on the other hand, symmetry groups of certain Toeplitz words have exponential growth.
The accurate simulation of additional interactions at the ATLAS experiment for the analysis of proton–proton collisions delivered by the Large Hadron Collider presents a significant challenge to the computing resources. During the LHC Run 2 (2015–2018), there were up to 70 inelastic interactions per bunch crossing, which need to be accounted for in Monte Carlo (MC) production. In this document, a new method to account for these additional interactions in the simulation chain is described. Instead of sampling the inelastic interactions and adding their energy deposits to a hard-scatter interaction one-by-one, the inelastic interactions are presampled, independent of the hard scatter, and stored as combined events. Consequently, for each hard-scatter interaction, only one such presampled event needs to be added as part of the simulation chain. For the Run 2 simulation chain, with an average of 35 interactions per bunch crossing, this new method provides a substantial reduction in MC production CPU needs of around 20%, while reproducing the properties of the reconstructed quantities relevant for physics analyses with good accuracy.
The article discusses the features of migration and the concentration of chemical elements in the earth’s crust during the formation of modern basins by evaporite sedimentation, on the example of “dry” salt Lake Baskunchak located in the Astrakhan region of the Russian Federation. The formation of the salt composition of the brines entering it is determined by the leaching activity of the ancient salt formations located in the immediate vicinity (salt rods, domes, etc.), followed by redeposition of salts in the basin in the course of evaporite sedimentation. In addition, the article, on the example of Lake Baskunchak, discusses the features of the evolutionary development of modern salt ponds from their inception to regression. In accordance with this, the main stages of the evolutionary development of saltwater reservoirs are pre-sedimentation, sedimentation including the phase of “brine” and “dry” salt lake, and post-sedimentation ones. It is emphasized that by the time of reaching the “dry” lake stage its hydrological period of development is completed, and the surface brine is transformed into an underground one, due to which a period comes when the further development of the basin begins to be determined by hydrogeological features. Among the main objectives of this study, it is also worth highlighting the features of the development and operation of modern solid salt deposits and their brines at Lake Baskunchak, and the possibility of regenerating its reserves based on thermodynamic and kinetic methods for calculating salt formation processes.
In a digitally empowered business world, a growing number of family businesses are leveraging the use of chatbots in an attempt to improve customer experience. This research investigates the antecedents of chatbots’ successful use in small family businesses. Subsequently, we determine the effect of two distinctive sets of human–machine communication factors—functional and humanoid—on customer experience. We assess the latter with respect to its effect on customer satisfaction. While a form of intimate attachment can occur between customers and small businesses, affective commitment is prevalent in customers’ attitudes and could be conflicting with the distant and impersonal nature of chatbot services. Therefore, we also test the moderating role of customers’ affective commitment in the relationship between customer experience and customer satisfaction. Data come from 408 respondents, and the results offer an explicit course of action for family businesses to effectively embed chatbot services in their customer communication. The study provides practical and theoretical insights that stipulate the dimensions of chatbots’ effective use in the context of small family businesses.
We study the validity of an extension of Frobenius theorem on integral manifolds for some classes of Pfaff-type systems of partial differential equations involving multidimensional “rough” signals, i.e. “differentials” of given Hölder continuous functions interpreted in a suitable way, similarly to Young Differential Equations in Rough Paths theory. This can be seen as a tool to study solvability of exterior differential systems involving rough differential forms, i.e. the forms involving weak (distributional) derivatives of highly irregular (e.g. Hölder continuous) functions; the solutions (integral manifolds) being also some very weakly regular geometric structures.
The electronic structure of the promising Li-ion battery anode material Li7MnN4 synthesized by a solid-state reaction is studied using ab initio calculations completed by Raman spectroscopy experiments. The structural optimization reliably reproduces the experimental one, hence validating the accuracy of the chosen Density Functional Theory method. The theoretical analysis of the electronic structure reveals the nature of the valence band as composed from band filled by electrons with spin-up states only, which allows refuting literature data about the claimed electronic character of Li7MnN4. Actually, the calculated electronic band gap Eg = 0.95 eV is found to be in good agreement with available experimental data. A careful experimental approach provides the first experimental Raman spectra of hygroscopic Li7MnN4 at 293 K and 130 K. The analysis of the phonon states in the Γ-point of the Brillouin zone, completed by the computation of the Raman scattering intensities of the vibrational modes of the Li7MnN4 structure give a remarkable agreement between simulated and experimental Raman spectra. With such a good matching, a reliable assignment of all the observed Raman peaks to the vibrations of specific structural units in the Li7MnN4 lattices is proposed. In particular, the most intense band in the Raman spectrum is ascribed to a totally symmetric MnN4 breathing mode. We also show that, using different wavelengths of exciting radiation, the transition from off-resonance to resonance Raman scattering process can be observed. Furthermore, Raman spectroscopy is revealed as an efficient in situ diagnostic tool to control the degradation of the Li7MnN4 powder in open air through the observation of extra bands in the Raman spectra. Results of this study shed a light on the understanding of the fundamental properties of Li7MnN4 and pave a way for the upcoming operando Raman spectroscopy investigation of the atomic-scale induced structural changes of this negative electrode material for Li-ion battery.
This paper provides a solution for the preservation of consensus in a network of several agents, described by discrete-time nonlinear dynamical systems. Consensus preservation is the problem of maintaining a certain distance between the states of several systems, given that the systems’ initial states are close to each other. The agents are equipped with both a smart sensor, capable of measuring the state of the system and performing some computations, and a controller. The sensors and controllers are placed at locations that are remote from one another. A network of communication channels with limited transmission capacity connects the agents by allowing the sensors to send messages to the controllers of their system as well as to the controllers of other systems. The controllers use the messages that they receive to steer the agents such that the consensus is preserved. Sensors and controllers that achieve this feature are called consensus-preserving protocols. In this paper, three distinct consensus-preserving protocols are presented, each with an increasing degree of interaction between the systems. For each of these protocols, a theorem providing conditions on the minimum communication capacity sufficient to implement them is presented. The protocols are tested by simulations for a network of logistic maps and a network of Hénon maps. For both of these networks, analytical bounds on the sufficient transmission capacities in the communication channels to implement the protocols are provided. These bounds are compared to rates observed in simulations of the consensus-preserving protocols.
Solution-processable polyelectrolyte complex (PEC) modified with various water-soluble fullerene derivatives (fullerenol, carboxyfullerene, fullerene derivative with L-arginine) were synthesized by using sodium carboxymethyl cellulose (CMC) and poly(diallyldimethylammonium chloride) (PDADMAC) for the creation of novel supported mixed matrix membranes for enhanced pervaporation and nanofiltration. The optimal preparation conditions and membrane composition were found. The structural characteristics and physicochemical properties of PEC-based membranes were analysed by Fourier-transform infrared (FTIR) spectroscopy, X-ray photoelectron spectroscopy (XPS), scanning electron (SEM) and atomic force (AFM) microscopies, thermogravimetric analysis (TGA), contact angle measurements and swelling experiments. The developed membranes were tested in pervaporation dehydration of isopropanol (12–50 wt% water) and, for the first time, in nanofiltration of heavy metals (model solutions and wastewater from galvanic production). Optimal transport characteristics were possessed by a supported membrane with a selective layer based on PEC-fullerenol (4%) composite: improved permeation flux of 0.28–1.62 kg/(m²h) and 99.99–79.30 wt% water in permeate in pervaporation dehydration of isopropanol (12–50 wt% water) at 22 °C, and 2.5 times improved permeability at a high rejection coefficients in nanofiltration of heavy metals compared to the pristine CMC membrane, which indicated its promise industrial application for water purification.
We introduce a class of subshifts governed by finitely many two-sided infinite words. We call these words leading sequences. We show that any locally constant cocycle over such a subshift is uniform. From this we obtain Cantor spectrum of Lebesgue measure zero for associated Jacobi operators if the subshift is aperiodic. Our class covers all simple Toeplitz subshifts as well as all Sturmian subshifts. We apply our results to the spectral theory of Schreier graphs for uncountable families of groups acting on rooted trees.
Synthesized cement systems made with variable C3A/C4AF ratios, containing C3S, gypsum and, optionally, calcite, were stored long-term at humid conditions at 5 or 20 °C, without any protection against atmospheric carbonation. Analytical techniques able to assess both the crystalline and amorphous phases were used. Experimental results were compared with thermodynamic simulations. The systems with C3A/C4AF < 1 better preserved the soundness of the CSH phase, which hosted iron, and prevented thaumasite formation. The addition of calcite in these systems inhibited carbonation. When occurred (mixtures without calcite), the carbonation was significantly more intense at ambient temperature. In the systems that underwent extensive deterioration, cross-linking of silicate structures, AFt decomposition, and iron release from the deteriorating CSH, occurred, while Al-incorporating amorphous silica, calcium carbonate polymorphs and hydrous iron oxide formed. The presence of unreacted C3A in the systems with C3A/C4AF = 1, suggested that CSH decomposition was contributed by available sulfates.
The evolution of 6TiSCH networks is greatly increasing in the field of IIoT which supports reliable communication in IIoT environments. However, there is a lot of research gaps in the field of IIoT using 6TiSCH networks in terms of high latency, more energy consumption which degrades the overall performance of the IIoT environment. To address the above limitation in existing IIoT 6TiSCH approaches, an Edge-assisted 6TiSCH network for IIoT is proposed to overcome the above challenges such as Low latency and more energy consumption by efficient task scheduling and edge offloading considering risk in IIoT environment. The proposed work consists of three layers namely the 6TiSCH layer, Edge layer, and Cloud layer. In the 6TiSCH layer, initially, devices are registered by their credentials and authenticated by TA using Enhanced Advanced Encryption Standard (EAES) which reduces the unwanted energy consumption and latency by dropping the malicious devices. After authentication, only the verified devices are allowed for network construction using CORONA-based DODAG construction for selecting optimal parent which reduces the energy consumption. The optimal parent is selected by using Red Colobuses Monkey (RCM) optimization algorithm. Then two-level task scheduling is done namely Slot frame length optimization using Stochastic Gradient Descent (SGD) algorithm and adaptive partitioning using XG boost algorithm. In the Edge layer, effective offloading is done by using the Soft Actor-Critic (SAC) algorithm for reducing the energy consumption during offloading. Finally, all the processed data are sent to the cloud layer for access. The proposed work is experimented with using the Cooja simulation tool with Contiki 3 OS. The performance of the proposed work is compared to the existing works in terms of Latency (42 ms-20.4 ms) low, energy consumption (28.8 J-12 J) low in 6TiSCH layer, Latency (40 ms-20.4 ms) low, energy consumption (24.8 J-13.6 J) low in Edge layer, and overall comparison achieves throughput (508.8Kbps-322Kbps) high, packet delay ratio (8 %-4.6 %) high, end-to-end delay (6 s-9 s) low and efficiency (14.6 %-7.8 %) high. The experimental results show that our proposed work performs well than existing works.
Starch-based electrolytes are used here to achieve safe, efficient, inexpensive, and eco-friendly lithium ion batteries (LIBs). Carboxymethyl starch (CMS) and starch acetate (SA) are synthesized as starch amorphous derivatives from corn starch, and then crosslinked by poly(vinyl alcohol) (PVA) to form a polymer network. In the following, the electrochemical properties of the obtained electrolytes in both solid and gel states are investigated. At room temperature, the ionic conductivity for solid CMS and gel SA electrolytes are 9.2*10⁻³ S cm⁻¹ and 1.13*10⁻² S cm⁻¹, respectively. Other remarkable results of these electrolytes are the wide electrochemical stability window, stable cyclic performance, charge capacity higher than 210 mAh/g, CE = 100 % before 10 cycles charge–discharge for both CMS and SA, and good electrode/electrolyte compatibility. The unparalleled electrochemical performance of CMS and SA, along with their unique properties, make them a unique alternative to liquid electrolytes in LIB.
Concrete building structures often suffer serious damage after fire, which poses a great threat to the durability of structures. Due to the high thermal stability and pressure relief mechanism of glazed hollow beads (GHBs), GHBs are of positive significance in improving the concrete’s resistance against high temperature. In this paper, the electric flux test was utilized to investigate the chloride ion transport behaviors of concrete containing insulating GHBs (GIC) after high temperature exposure. The electron probe micro-analysis (EPMA) combined with chemical titration method was adopted as a supplement to carry out a more in-depth analysis on concrete’s permeability. The results show that the anti-chloride ion transport performance of GIC was significantly improved compared to normal concrete. Experimental permeation data were further used to prepare a thermal damage permeability model. That is then used to discuss the impact of including glazed hollow beads on concrete’s residual service life after a fire. These data provide technical guidance for the engineering design and safe operation of undersea tunnels and other structures at risk of fire and subsequent saline water intrusion.
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10,859 members
Л. П. Чурилов
  • School of Medicine
Yuri Kuprin
  • Faculty of Physics
Semyon Grigorev
  • Faculty of Mathematics and Mechanics
Ivan Nekhaev
  • Department of Applied Ecology
Maxim Vinarski
  • Laboratory of Macroecology and Biogeography of Invertebrates
7-9, Universitetskaya emb., 199034, Saint Petersburg, Russia
Head of institution
Rector Nikolay Kropachev
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