Structure Theory Research Articles

Demystifying the Link between Social Media Addiction and Sharing without Verification: The Role of Absentmindedness and Wellbeing

In this paper, we argue that one can understand the adoption and routine use of enterprise systems by examining the fit between the system and the social structures of the organization. We develop a model of the adoption and long- term use of enterprise systems based on sociological concepts (Lord Anthony Giddens’ structuration theory) rather than the usual cognitive psychology concepts. We focus on the adoption and use of three versions of an enterprise KMS to support sales representatives at a multinational pharmaceutical firm. Our first study (a five-year case study of the KMS that went through one failed deployment and two successful ones) shows that the structures of signification, legitimation, and domination all influence loyal use, although domination may be less important. Our second study (a survey of 893 users at the firm) shows that the structures of signification, legitimation, and domination explain about 50 percent of the variance in ongoing loyal use but that their relative importance depends on the job experience of the users: signification and legitimation influence novices more, and signification and domination influence experts more. We believe that this parsimonious three-factor model offers a useful approach for future research and practice.

STT Candra Metu Organization Communication In Building Menyama Braya Ties at Banjar Budamanis Sidemen Karangasem

STT Candra Metu is a youth organization in Budamanis Banjar, Tabola Traditional Village, Sidemen Village, Sidemen District, Karangasem Regency which is engaged in social activities, one of which is building bonds of mutual help between people, namely manyama braya. An organizational communication strategy is urgently needed in building manyama braya ties in Banjar Budamanis so that an active organization is created. This study raises three main issues, namely : What are the forms of manyama braya activities, Organizational Communication Strategies used and what are the implications of STT Candra Metu's Activities in building the manyama braya bond in Banjar Budamanis, Tabola Traditional Village, Sidemen Karangasem? This study uses a qualitative descriptive approach and uses three theories, namely fusion theory, attribution and structural functional theory. Data collection methods used include observation, interviews, documentation and literature. All data is processed using qualitative descriptive techniques. The results of this study indicate that the activities carried out by STT Candra Metu in building the manyama braya bond consist of activities in supporting the implementation of the yadnya ceremony, as a forum for strengthening intimate relationships and channeling creativity, interests and talents. While the communication strategy includes: Vertical communication consisting of bottom-up, top-down and horizontal communication. And the implications of STT Candra Metu in building manyama braya bonds include: Sociol cultural and economic implications for society. Based on this research, it can be concluded that an organizational communication strategy is needed to establish and move the wheels of the organization in building manyama braya ties between fellow STT Candra Metu.

Measuring Indonesian young consumers’ halal purchase intention of foreign-branded food products

This article is among the few focusing on halal young consumer behavior in Indonesia. The focus is to examine the topic of halal food product purchase intention. Here, we focus specifically on Muslim teenagers in Indonesia to explore whether they still hold on to the halal principle that most Muslims adhere to when consuming food. This research examine their halal awareness based on theory of planned behavior (TPB) theory and compare it to the previous publications so far. To reach this objective, we used quantitative methodology. Our data was acquired from 161 Indonesian young Muslim consumers. Furthermore, the variance-based structural equation modeling and Theory of Planned Behavior (TPB) research model were utilized. Our findings demonstrate that subjective norm and attitude are significant determinants of halal food buying intent. However, perceived behavioral control has not been established as a purchase intention component. Finally, this study provides additional research on halal consumer behavior, focusing on the empirical findings of young Indonesian consumers, especially seen from TPB perspective.

Optimal Vibration Fields in Problems of Modeling Dynamic States of Technical Objects

Introduction. Vibration interaction control is timely in production processes related to liquid and bulk media, systems of solids experiencing kinematic or force disturbances. At the same time, there is no single methodological basis for the formation of vibrational interactions. The issues of constructing optimal vibration fields of technical objects have not been addressed. The objective of the study is to develop a structural approach to the development of mathematical models in the problems of formation, evaluation, and correction of vibration fields of technical objects under conditions of intense force and kinematic loads. The task is to build vibration fields that are optimal in terms of the set of requirements, with the possibility of selecting the criterion of optimality of the vibration field of a technical object.Materials and Methods. A structural approach was used as the basic methodology. It was based on a comparison of mechanical vibratory systems used as computational schemes of technical objects, and structural schemes of automatic control systems, which are equivalent in dynamic terms. Lagrange formalism, elements of operational calculus based on Laplace integral transformations, sections of vibration theories, algebraic methods, and the theory of spline functions were used for structural mathematical modeling.Results. An approach to the selection of criteria for the optimality of vibration fields based on minimizing the residual of vibration fields for various required conditions was proposed. The problem was considered within the framework of a mechanical vibratory system formed by solids. It was shown that the optimal vibration field was determined by an external disturbance and was to satisfy condition Ay̅ = b. There, A — matrix mapping the operator of conditions to the shape of the vibration field at control points; b — vector of values of vibration field characteristics; “–” above y meant the vibration amplitude of the steady-state component of the coordinate. To evaluate the field with account for noisy or unreliable requirements for dynamic characteristics, the smoothing parameter was used, indicating the priority of the criterion of optimality of the vibration field shape. The construction of a field for a mechanical vibratory system showed that the value of the vibration amplitudes of generalized coordinates remained constant when the frequency of external kinematic disturbances changed. Two approaches to the correction of the field optimality criteria were considered: equalization of the vibration amplitudes of the coordinates of a technical object and the selection of an energy operator.Discussion and Conclusion. The development of the applied theory of optimal vibration fields involved, firstly, the correlation of the energy operator and the operator of the requirements for the shape of the vibration field in the theory of abstract splines. The second pair of comparable elements was the criterion of optimality of the vibration field and a system of requirements for the characteristics of the field at control points. The structural theory of optimal vibration fields improved in this way will find application in various industries. Accurate calculations in the formation, assessment, and correction of the states of systems under vibration loading are required in the tasks of increasing the durability of structures, improving measurements in complex vibratory systems, and developing new technologies and materials.

Preprocessing to reduce the search space: Antler structures for feedback vertex set

The goal of this paper is to open up a new research direction aimed at understanding the power of preprocessing in speeding up algorithms that solve NP-hard problems exactly. We explore this direction for the classic Feedback Vertex Set problem on undirected graphs, leading to a new type of graph structure called antler decomposition, which identifies vertices that belong to an optimal solution. It is an analogue of the celebrated crown decomposition which has been used for Vertex Cover. We develop the graph structure theory around such decompositions and develop fixed-parameter tractable algorithms to find them, parameterized by the number of vertices for which they witness presence in an optimal solution. This reduces the search space of fixed-parameter tractable algorithms parameterized by the solution size that solve Feedback Vertex Set.

THE DYNAMICS OF AGENT-STRUCTURE IN RITUAL COMMUNICATION OF THE SACRED GRAVE PILGRIMAGE

This study aims to reveal the agent-structure relationship that occurs from the phenomenon of sacred grave pilgrimage in Dewi Sekardadu, Sidoarjo through the structuration theory by Anthony Giddens’s perspective as well as ritual communication studies. The type of this research is qualitative with ethnographic methods. This research uses a multi-site ethnographic method, namely by comparing historical facts at all Dewi Sekardadu’s sacred graves spread across four cities involving Sidoarjo, Gresik, Lamongan and Banyuwangi. The key informants were door-keepers, grave caretakers, community leaders, pilgrims and businessmen. The research data was collected by direct observation and participant observation, in-depth interviews and documentations. Then obtained data was analyzed using structuration theory and ritual communication studies. The result of this research had theoretical implications that support and reject Gidden’s sight. First, the proficient agents in Kepetingan have succeeded in changing the stigma of Kepetingan from a criminal area to a religious area through the development of folklore and ritual communication practices. Second, Giddens does not assume any clustering of agents of society for instance the caretaker cluster which has dominance on national scale but not in society, because the appointment process is considered less sacred. Third, Nyadran community structure occurred among indigenous fisherman from Bluru Kidul and Balongdowo which created to the grave pilgrims community structure in Kepetingan which was inhabited by urban fisherman from Gresik dan Lamongan regency.

Strong Coupling of Two-Dimensional Excitons and Plasmonic Photonic Crystals: Microscopic Theory Reveals Triplet Spectra.

Monolayers of transition metal dichalcogenides (TMDCs) are direct-gap semiconductors with strong light-matter interactions featuring tightly bound excitons, while plasmonic crystals (PCs), consisting of metal nanoparticles that act as meta-atoms, exhibit collective plasmon modes and allow one to tailor electric fields on the nanoscale. Recent experiments show that TMDC-PC hybrids can reach the strong-coupling limit between excitons and plasmons, forming new quasiparticles, so-called plexcitons. To describe this coupling theoretically, we develop a self-consistent Maxwell-Bloch theory for TMDC-PC hybrid structures, which allows us to compute the scattered light in the near- and far-fields explicitly and provide guidance for experimental studies. One of the key findings of the developed theory is the necessity to differentiate between bright and originally momentum-dark excitons. Our calculations reveal a spectral splitting signature of strong coupling of more than 100 meV in gold-MoSe2 structures with 30 nm nanoparticles, manifesting in a hybridization of the plasmon mode with momentum-dark excitons into two effective plexcitonic bands. The semianalytical theory allows us to directly infer the characteristic asymmetric line shape of the hybrid spectra in the strong coupling regime from the energy distribution of the momentum-dark excitons. In addition to the hybridized states, we find a remaining excitonic mode with significantly smaller coupling to the plasmonic near-field, emitting directly into the far-field. Thus, hybrid spectra in the strong coupling regime can contain three emission peaks.

Manipulating electrochemical CO2 reduction pathway by engineering energy level of Cu/Zn dual-metal single atom catalysts

Dual-metal single atom catalysts (DSACs) demonstrate outstanding catalytic performance in the CO2 reduction reaction. However, the complexity of catalyst structures and interface environments has led to an unclear understanding of the synergistic catalysis mechanism involved. Here, we developed a series of catalysts with atomically dispersed Cu–N4 and Zn–N4 sites on N-doped carbon supports (Cu1-xZnx-NC), which can efficiently reduce CO2 to C2 products by optimizing the Zn loading. Specifically, a remarkable faradaic efficiency of 65 % at −1.1 VRHE for the C2 products on the Cu0.75Zn0.25-NC catalyst has been obtained. Structural characterizations and density functional theory calculations demonstrate that Cu/Zn DSACs synergistically lower the energy barrier of the rate-determining step and facilitate proton transfer kinetics. Among them, Zn atoms activate CO2, while Cu atoms aid in the adsorption and dissociation of intermediates. The electron energy redistribution induced by adjacent Cu–N4 and Zn–N4 site optimizes the 3d orbitals of Cu centers, thereby accelerating and promoting C–C coupling. The energy level optimization of Cu/Zn DSACs results in Cu0.75Zn0.25-NC with a high C2 selectivity and activity, improved kinetics. In summary, these findings provide new insights into the development of highly efficient DSACs and its synergistic catalysis mechanism in CO2 reduction.

High-order effects on the vibration of membrane structures

This study analyzed pretension membranes, focusing on high-order effects. Using a combination of the Carrera Unified Formulation (CUF) and the finite element method, the research employs the unique framework of CUF to integrate innovative structural theories in a seamlessly scalable way. The analysis methodically explores the complex effects of shear and bending stiffness on crucial factors such as thickness, geometry, and materials. A comprehensive numerical examination of the subject is undertaken on numerous cases, and the assessment includes established analytical solutions as well as findings provided by commercial software tools. Particular emphasis is placed on mode aberration, underscoring the critical need for more refined structural models. Furthermore, the results show the crucial role of adopting high-order theory in the dynamic analysis of membrane structure, especially for application in space.

Practical phase-space electronic Hamiltonians for abinitio dynamics.

Modern electronic structure theory is built around the Born-Oppenheimer approximation and the construction of an electronic Hamiltonian Ĥel(X) that depends on the nuclear position X (and not the nuclear momentum P). In this article, using the well-known theory of electron translation (Γ') and rotational (Γ″) factors to couple electronic transitions to nuclear motion, we construct a practical phase-space electronic Hamiltonian that depends on both nuclear position and momentum, ĤPS(X,P). While classical Born-Oppenheimer dynamics that run along the eigensurfaces of the operator Ĥel(X) can recover many nuclear properties correctly, we present some evidence that motion along the eigensurfaces of ĤPS(X,P) can better capture both nuclear and electronic properties (including the elusive electronic momentum studied by Nafie). Moreover, only the latter (as opposed to the former) conserves the total linear and angular momentum in general.

Structural Entropy Based Graph Structure Learning for Node Classification

As one of the most common tasks in graph data analysis, node classification is frequently solved by using graph structure learning (GSL) techniques to optimize graph structures and learn suitable graph neural networks. Most of the existing GSL methods focus on fusing different structural features (basic views) extracted from the graph, but very little graph semantics, like hierarchical communities, has been incorporated. Thus, they might be insufficient when dealing with the graphs containing noises from real-world complex systems. To address this issue, we propose a novel and effective GSL framework for node classification based on the structural information theory. Specifically, we first prove that an encoding tree with the minimal structural entropy could contain sufficient information for node classification and eliminate redundant noise via the graph's hierarchical abstraction. Then, we provide an efficient algorithm for constructing the encoding tree to enhance the basic views. Combining the community influence deduced from the encoding tree and the prediction confidence of each view, we further fuse the enhanced views to generate the optimal structure. Finally, we conduct extensive experiments on a variety of datasets. The results demonstrate that our method outperforms the state-of-the-art competitors on effectiveness and robustness.

Generation of Visual Representations for Multi-Modal Mathematical Knowledge

In this paper we introduce MaRE, a tool designed to generate representations in multiple modalities for a given mathematical problem while ensuring the correctness and interpretability of the transformations between different representations. The theoretical foundation for this tool is Representational Systems Theory (RST), a mathematical framework for studying the structure and transformations of representations. In MaRE’s web front-end user interface, a set of probability equations in Bayesian Notation can be rigorously transformed into Area Diagrams, Contingency Tables, and Probability Trees with just one click, utilising a back-end engine based on RST. A table of cognitive costs, based on the cognitive Representational Interpretive Structure Theory (RIST), that a representation places on a particular profile of user is produced at the same time. MaRE is general and domain independent, applicable to other representations encoded in RST. It may enhance mathematical education and research, facilitating multi-modal knowledge representation and discovery.

An innovative method integrating run theory and DBSCAN for complete three-dimensional drought structures

Drought displays dynamic and uncertain spatiotemporal characteristics, thus it is typically not confined to fixed temporal-spatial boundaries. Existing drought clustering methods often involve spatially clustering drought points or grids into patches, subsequently connected over time to form three-dimensional structures. Despite this process being able to extract three-dimensional drought clusters, it is likely to overlook mild or relatively small, isolated drought patches. To overcome this limitation, this paper presented an effective method (named STD-CLUSTER) for identifying drought clusters with complete three-dimensional structures. The method initially employed run theory to extract drought events as “lines” and subsequently clustered these events using the Density-Based Spatial Clustering of Applications with Noise (DBSCAN) algorithm. A case study on the 2006 flash drought in the Yangtze River Basin demonstrated that STD-CLUSTER successfully clustered drought events and ensured the integrity of drought clusters by considering small, isolated, or disconnected patches. Additionally, an in-depth analysis using STD-CLUSTER examined seasonal drought events in China from 1991 to 2022, identifying a total of 35 drought clusters. These clusters began and ended with small-area patches, exhibiting features of expansion, contraction, spread, merging, and splitting over time. Furthermore, seasonal changes significantly influenced the evolution of drought clusters, with affected area and severity increasing in spring and summer and decreasing in autumn and winter. The applicability of the proposed method extends beyond various geographical regions and time scales, providing effective support for comprehensively investigating the spatiotemporal evolution of drought.

Tuning Electrocatalytic Water Oxidation Activity: Insights from the Active-Site Distance in LnCu6 Clusters.

Atomically precise metal clusters serve as a unique model for unraveling the intricate mechanism of the catalytic reaction and exploring the complex relationship between structure and activity. Herein, three series of water-soluble heterometallic clusters LnCu6, abbreviated as LnCu6-AC (Ln = La, Nd, Gd, Er, Yb; HAC = acetic acid), LnCu6-IM (Ln = La and Nd; IM = Imidazole), and LnCu6-IDA (Ln = Nd; H2IDA = Iminodiacetic acid) are presented, each featuring a uniform metallic core stabilized by distinct protected ligands. Crystal structure analysis reveals a triangular prism topology formed by six Cu2+ ions around one Ln3+ ion in LnCu6, with variations in Cu···Cu distances attributed to different ligands. Electrocatalytic oxygen evolution reaction (OER) shows that these different LnCu6 clusters exhibit different OER activities with remarkable turnover frequency of 135s-1 for NdCu6-AC, 79s-1 for NdCu6-IM and 32s-1 for NdCu6-IDA. Structural analysis and Density Functional Theory (DFT) calculations underscore the correlation between shorter Cu···Cu distances and improves OER catalytic activity, emphasizing the pivotal role of active-site distance in regulating electrocatalytic OER activities. These results provide valuable insights into the OER mechanism and contribute to the design of efficient homogeneous OER electrocatalysts.

Causes and Forms of Cyberbullying among Teenagers in Indonesian Urban Areas: Cases of Jakarta, Bandung and Surabaya

The development of digitalization has had an impact on the increasing cases of cyberbullying among Indonesian youth, especially in urban areas such as Jakarta, Surabaya, and Bandung. This article finds out why teenagers in urban areas are rampant in carrying out cyberbullying behavior. The existing studies were examined to map the causes and forms of cyberbullying experienced by teenagers in the three cities by applying inclusion and exclusion criteria. Employing Anthony Giddens structuration theory, this article reveals that cyberbullying among urban teenagers is the impact of the relationship between agents and structures that shape social reality. In Jakarta, cyberbullying has emerged as a result of the lack of social support from peers and the low emotional intelligence that teenagers have. In Surabaya, cyberbullying arose as a result of lack of self-control and parental evaluation mediation, low self-esteem, and a strong desire for self-recognition in order to show their power. In Bandung, cyberbullying arose as a result of the anonymity and authoritarian pattern of parental care.

UV-promoted NH3 sensor based on Ti3C2Tx/TiO2/ graphene sandwich structure with ultrasensitive RT sensing performances for human health detection

Gases produced by human respiration can effectively forewarn physiological health, and developing high-performance gas sensors for breath detection can help in the early diagnosis of many diseases. In this paper, Ti3C2Tx/TiO2/graphene composite with a unique sandwich structure was fabricated by hydrothermal method for resistive NH3 sensor, which is composed of the staggered interlayer of graphene, Ti3C2Tx, and in situ grown TiO2 nanosheets. The results indicate that the Ti3C2Tx/TiO2/graphene composite sensor has a response value of 35.8 at 50 ppm NH3 at room temperature and in a dark environment, which is 12.8 times higher than that of the single Ti3C2Tx and can detect dilute NH3 at ppb level with a calculated limit of 26 ppb. The sensor also possesses a fast response/recovery time of 19/29 s and excellent humidity resistance. Furthermore, with the assistance of UV illumination, the sensor response value for 50 ppm NH3 is increased to 45.18, the response/recovery time is accelerated to 18/25 s, and the calculated limit of detection is 22.23 ppb. Additionally, simulated breath detection demonstrates the potential application of the sensor for early respiratory warning in patients with renal failure. Finally, the NH3 gas sensing mechanism is discussed in terms of heterogeneous structure, morphology promotion, and energy band theory. It is believed that the sensing material with this structure has great potential for human health applications.

Observation of Renner-Teller and predissociation coupled vibronic intensity borrowing in dissociative electron attachment to OCS.

We use a time-of-flight-based velocity map imaging method to look into the dissociative electron attachment to a linear OCS molecule at electron beam energies ranging from 4.5 to 8.5eV. The conical time-gated wedge slice imaging method is utilized to extract fragments' slice images, kinetic energy (KE), and angular distributions, which provide a complete kinematic understanding of this experiment on the dissociative electron attachment process. We observe that the formation of S- is relatively higher than the O- product. Three distinct dissociative KE bands of S-/OCS have been observed for the 5.0 and 6.5eV resonance positions. We notice a prominent rovibrationally coupled bimodality for each KE band in the variation of the most probable KE values. When the electron energy is changed from 5.5 to 6.0eV, we observed vibronic intensity borrowing in the highest momentum band of S- via the Σ → Π symmetric dipole-forbidden transitions within the 1.5eV energy gap. Multiple peaks in the angular distributions of S- and their modeling indicate the presence of Renner-Teller vibronic splitting. Using Q-Chem's implemented complex absorbing potential-equation of motion-electron affinity coupled cluster singles and doubles aug-cc-pVDZ+4s3p level of multireference-based electronic structure theory, we confirm the presence of OCS temporary negative ion bending vibrations and Renner-Teller vibronic splittings for the Π symmetric states. Additionally, we notice the presence of a non-radiative predissociation continuum (bringing down the rotational spectrum) and speed-dependent angular anisotropy in the S- fragmentation. Our findings at the resonance of OCS at 6.5eV closely align with the prediction of vibronic intensity borrowing by Orlandi and Siebrand [J. Chem. Phys. 58, 4513 (1973)].

Gaussian Fluctuations for the Stochastic Burgers Equation in Dimension d≥2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$d\\ge 2$$\\end{document}

The goal of the present paper is to establish a framework which allows to rigorously determine the large-scale Gaussian fluctuations for a class of singular SPDEs at and above criticality, and therefore beyond the range of applicability of pathwise techniques, such as the theory of Regularity Structures. To this purpose, we focus on a d-dimensional generalization of the Stochastic Burgers equation (SBE) introduced in van Beijeren et al. (Phys Rev Lett 54(18):2026–2029, 1985. https://doi.org/10.1103/PhysRevLett.54.2026). In both the critical d=2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$d=2$$\\end{document} and super-critical d≥3\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$d\\ge 3$$\\end{document} cases, we show that the scaling limit of (the regularised) SBE is given by a stochastic heat equation with non-trivially renormalised coefficient, introducing a set of tools that we expect to be applicable more widely. For d≥3\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$d\\ge 3$$\\end{document} the scaling adopted is the classical diffusive one, while in d=2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$d=2$$\\end{document} it is the so-called weak coupling scaling which corresponds to tuning down the strength of the interaction in a scale-dependent way.

Modeling surface structure of tribotechnical materials

Modern tribology makes it possible to correctly calculate, diagnose, predict and select appropriate materials for friction pairs, to determine the optimal mode of operation of the tribo-joint. The main parameter for solving friction problems and other problems of tribology is the topography of the surface. The main purpose of the models in these tasks is to display the tribological properties of engineering surfaces. In the framework of the classical approach, the topography of the surface is studied on the basis of its images from the point of view of functional and statistical characteristics: the evaluation of the functional characteristics is based on the maximum roughness along the height and the average roughness along the center line, and the statistical characteristics are estimated using the power spectrum or the autocorrelation function. However, these characteristics are not only surface properties. They depend on the resolution of the device for measuring the surface geometry and the length of the scan. However, the degree of complexity of a surface shape can be represented by a parameter called the fractal dimension: a higher degree of complexity has a larger value of this parameter. Fractal dimensionality is a characteristic of surface relief and makes it possible to explain tribological phenomena without the influence of resolution. This article provides an overview of mathematical approaches to the description of the relief of engineering surfaces, in particular statistical, stochastic and topological modeling, their limitations, advantages and disadvantages. The implementation of the principles of the theory of fractal structures is discussed, which makes it possible to introduce the degree of imbalance of the tribological system into the analysis of structure formation in the surface and near-surface layers of materials and to describe the development of friction and wear processes. This is the basis for controlling the structure of the surface layers of materials with given properties. The concept of fractals, used for the quantitative description of the dissipative structure of the tribojunction zone, makes it possible to establish a connection between its fractal dimension and mechanical properties, as well as critical states of deformation of metals and alloys. The course of research and stages of fractal modeling, the classification of methods of fractal analysis of the structure of engineering contact surfaces are considered. A critical analysis of modern models based on the energy-spectral density function, which are quite similar to fractal models, is presented. Readers are expected to gain an overview of research developments in existing modeling methods and directions for future research in the field of tribology

Big Ramsey degrees in ultraproducts of finite structures

We develop a transfer principle of structural Ramsey theory from finite structures to ultraproducts. We show that under certain mild conditions, when a class of finite structures has finite small Ramsey degrees, under the (Generalized) Continuum Hypothesis the ultraproduct has finite big Ramsey degrees for internal colorings. The necessity of restricting to internal colorings is demonstrated by the example of the ultraproduct of finite linear orders. Under CH, this ultraproduct L⁎ has, as a spine, η1, an uncountable analogue of the order type of rationals η. Finite big Ramsey degrees for η were exactly calculated by Devlin in [5]. It is immediate from [39] that η1 fails to have finite big Ramsey degrees. Moreover, we extend Devlin's coloring to η1 to show that it witnesses big Ramsey degrees of finite tuples in η on every copy of η in η1, and consequently in L⁎. This work gives additional confirmation that ultraproducts are a suitable environment for studying Ramsey properties of finite and infinite structures.