Contact Process Research Articles

Numerical Simulation of the Basal Scraping Effect of Debris Flows Based on the Distance-Potential Discrete-Element Method

High-speed and long-runout landslides constitute one of the most devastating natural disasters. The scraping and erosion of the foundation by these landslides significantly alter the dynamic and catastrophic properties of the landslide mass. This study centered on the movement process of the landslide mass, utilizing numerical simulations to delve into the interactions and dynamic mechanisms between the landslide mass and the foundation. It examined how the erosion of the foundation by the landslide mass impacts its movement distance and accumulation pattern. By employing the distance-potential discrete-element method, which was proposed by the authors, this research simulated the movement process of the landslide mass from a mesoscopic viewpoint. Through precise characterization of the contact forces between blocks, the study sheds light on the interactions among blocks and the energy transfer process during the landslide movement. Furthermore, a comparative analysis was performed to assess the movement distance and accumulation pattern of the landslide mass under varying foundation conditions. The findings revealed that the distance-potential discrete-element method effectively captures the impact and scraping action of the landslide mass on the foundation. The block units within the scraping zone, stimulated by the landslide’s impact and scraping, transition from a stable to a dynamic state. Under the influence of unbalanced forces, these units exhibit rotational and forward-moving motions. The kinetic energy among the blocks is progressively transferred from the rear of the scraping zone to the front through contact interactions and is continuously dissipated through contact, friction, and other mechanical processes, ultimately resulting in a stable accumulation. Due to the scraping zone’s influence, the movement distance of the landslide mass decreases compared to rigid foundations, but the volume of the accumulation increases.

Study on the Influence Mechanism of Soil Covering and Compaction Process on Maize Sowing Uniformity Based on DEM–MBD Coupling

In the production process of maize, the uniformity of maize sowing is one of the main factors affecting maize yield. The effect of soil coverage and the compaction process on sowing uniformity, as the final link in determining the seed bed position, needs to be further investigated. In this paper, the parameters between soil particles and boundaries are calibrated using the Plackett–Burman test and the central composite design. Furthermore, based on the DEM–MBD coupling, the influence of soil coverage and the compaction process on the seed position of the seeding monomer at different forward speeds are analysed. It was found that the adhesion between the soil and the soil-touching component can have a significant effect on the contact process between the component and the soil. Therefore, the EEPA model was used to analyse the soil–component interaction process and the contact parameters between the soil and components were obtained for the calibration. Further, based on the above work, it was found that before and after mulching, the displacement of seed particles of all shapes in the longitudinal direction increased significantly with the increase in the advancement speed of the sowing unit, while the displacement of seed particles in the transverse and sowing depth directions decreased with the increase in the advancement speed of the unit. In addition, before and after suppression, as the forward speed of the sowing unit increased, the displacement of seed particles of all shapes in the longitudinal and transverse directions gradually increased, and the displacement of seed particles of all shapes in the direction of the sowing depth decreased; the disturbance of seed displacement by the mulch suppression process was not related to seed shape. As the operating speed of the seeding unit increased, the mulching compaction process significantly reduced the sowing uniformity of maize seeds. This paper provides a theoretical basis for the next step in optimising the structure and working process of the soil coverage and the compaction.

Revised safety evaluation of the food enzyme glucose oxidase from the genetically modified Trichoderma reesei strain AR-352.

The food enzyme glucose oxidase (β-d-glucose: oxygen 1-oxidoreductase; EC 1.1.3.4) is produced with the genetically modified Trichoderma reesei strain AR-352 by AB Enzymes GmbH. In a previous opinion, the Panel on Food Contact Materials, Enzymes and Processing Aids of the European Food Safety Authority could not conclude on the absence of recombinant DNA from the production strain in the food enzyme due to uncertainties about the limit of detection of the applied methodology. New data provided by the applicant showed that no DNA from the production strain was found in the food enzyme with a limit of detection meeting the requirements of the applicable guidance. Based on the new data provided, the Panel concludes that this food enzyme is free from recombinant DNA from the production strain.

Development of a visuo-tactile sensor for non-destructive peach firmness and contact force measurement suitable for robotic arm applications

Precise measurement of firmness was crucial for determining optimal harvesting times, implementing rational storage strategies and minimizing avoidable waste. Current technologies for assessing peach firmness struggled to balance high precision and non-destructive methods, while demonstrating high sensitivity to environmental disturbances, thereby limiting their application to production line. Future various scenarios in agriculture would increasingly rely on robotic arms, yet existing firmness assessment technologies were not compatible with these automated systems. Additionally, monitoring contact force was essential for flexible operation of the robotic arms. This work introduced a visuo-tactile sensor equipped with markers to capable of measuring peach firmness and monitoring contact force simultaneously during a single contact process, making it suitable for robotic arm applications. The contact was operated by the texture analyzer to simulate the fruit grasping process by a robotic arm. Utilizing deep neural networks and machine learning-based techniques to process high-precision geometric images collected by an internal camera, the visuo-tactile sensor achieved non-destructive measurements of peach firmness and contact force. For firmness measurement in the test set, the sensor achieved coefficient of determination (R2) of 0.878 and a root mean square error (RMSE) of 0.732. For contact force detection, the R2 was 0.942, and RMSE was 1.115 in the test set. The results showed visuo-tactile sensor was feasible for non-destructive detection of peach firmness and contact force, and has a broad application prospect in the field of agricultural robotics.

(Invited) Reduction of Contact Resistance through the Application of Cylindrical Contacts to WSe2

Two-dimensional (2D) transition-metal dichalcogenides (TMDs) are gaining attention as the next-generation semiconductor materials instead of silicon, owing to their atomic thickness and thickness-dependent energy bandgap. Moreover, because of their atomic thickness, TMDs show effective electrostatic gate modulation, thereby short channel effects can be suppressed. Among various TMDs, tungsten diselenide(WSe2) has an ambipolar conductivity which can be tuned to n- or p-type via various processing and shows excellent electrical properties and mechanical stability. However, achieving Ohmic contact in 2D material-metal junction is challenging due to high Schottky barrier and Fermi-level pinning. Therefore, research on the improvement of contact resistance is crucial to maximizing the full potential of 2D materials and utilizing their superior electrical properties. Edge contact, where the junction is formed on the edge of the 2D material layers, has been researched as an effective method to minimize the contact resistance in 2D materials. Unlike the traditional surface contact method, which results in high tunnel barrier and out-of-plane current flow, the edge contact method provides strong orbital overlap and allows in-plane current flow through a narrower tunnel barrier, offering advantages in terms of carrier transport at the contact interface [1]. Yang et al. demonstrated conventional edge contacts to MoS2 using hexagonal boron nitride (h-BN) to encapsulate the surface of the MoS2. This method ensures that current flows only between the edge of the MoS2 and metal [2]. However, this approach necessitates additional process that requires h-BN to completely cover the entire upper part of the contact area and cannot control the area of the edge contact.In this work, edge contact using cylindrical contacts of WSe2 transistors is demonstrated. WSe2 flakes were fabricated through mechanical exfoliation and were dry-transferred on Si/SiO2 substrates. Spin-coating of electron-beam resist and electron-beam lithography (EBL) was performed to prepare the etch mask for cylindrical etching at the contact areas of WSe2. Reactive ion etching was conducted using 15 sccm of Ar, 15 sccm of SF6 with 20 W for 20 s. Spin-coating and EBL process was performed again to define the area for ultraviolet (UV)-ozone treatment and deposition of Pt/Au electrodes. UV-ozone treatment oxidizes the top few layers of WSe2 into WOx, resulting in the p-doping of the underlying WSe2 layer of the contact area. Pt/Au contact metal was deposited by electron-beam evaporation.The fabricated WSe2 FETs shows p-type dominant characteristic and Ohmic behavior, as shown in Fig. 1. Cylindrical contact and UV-ozone treatment process for WSe2 FETs enabled low contact resistance (4 kΩ·μm), high field-effect mobility (149 cm2/V·s) and high on-off ratio (>107). As the perimeter of the cross-sectional circle of the etched cylinder increases, the area of the edge contact becomes larger. The WSe2 FETs with cylindrical contacts exhibited decrease in the contact resistance and increase in the field-effect mobility as the ratio of the etched perimeter to the top contact area increased (Table 1). P-type WSe2 FETs with low contact resistance and high field-effect mobility were demonstrated using cylindrical contacts. With this fabrication, edge contact area can be controlled with the variation of the etched perimeter and electron transport can be improved using both top contact and edge contact.Reference:[1] J. Kang, W. Liu, D. Sarkar, D. Jena, K. Banerjee, Phys. Rev. X 2014,4, 1.[2] Z. Yang, C. Kim, K. Y. Lee, M. Lee, S. Appalakondaiah, C.-H. Ra, K.Watanabe, T. Taniguchi, K. Cho, E. Hwang, J. Hone, W. J. Yoo,Adv.Mater.2019,31, 1808231 Figure 1

Unveiling the essence of trash-talking: A phenomenological study of teenagers’ behavior in online games

ABSTRACT This study focuses on teens’ trash-talking behavior while playing internet games. Phenomenology is the method used, and it seeks to reduce individual perceptions of phenomena into descriptions of universal essences or essences. This research aims to discover and examine the trash-talking behavior that has become common among teenagers while playing online games (OG). The findings of this study suggest that markers of trash-talking conduct include insults to intelligence, swearing at prohibited items, and calling animal and dirt names. The symbol of trash-talking conduct represents a release of emotions such as anger and disappointment, sarcasm or criticism, admiration for a good game, and an outpouring of joy. This study’s findings indicate a process of symbolic contact amongst the five informants while playing the Mobile Legends game. On the mental side, three categories are distinguished: being conscious of the situation and conditions in trash-talking conduct, feeling strange if you don’t have trash-talking behavior, and being accustomed to trash-talking behavior. Trash-talking conduct can be classified into two types: showing team closeness and cohesion and disrupting the opposing team’s concentration. Trash-talking conduct is classified as either helping to break down the mood in a freshly established group or producing conflict in the actual world due to feelings of offense.

A high-precision GSG probe planarization method based on direct current signal

Since the GSG (ground-signal-ground) probe has three pins, it needs planarization before the wafer test. To ensure the reliability of the RF wafer test, a new high-precision GSG probe planarization method is first proposed based on DC (Direct Current) analysis. The angle-force model of the GSG probe contact and separation process is derived, which is based on the analysis of the collected real-time force and electrical data using a designed force sensing system, and voltage measuring circuit. The results show that when the GSG probe is in contact with the substrate and away from the substrate, the relationship between the angle and force model is a primary function and a quadratic function respectively. The angle of the GSG probe can be obtained by substituting the force of the change points of voltage and resistance into the angle and force model. In addition, the smaller the difference between the minimum force at two-pin contact and three-pin contact of the GSG probe, the smaller the angle of the GSG probe. This method can provide a method and idea for the automatic planarization of GSG probes.

Three dimensional thermally frictional adhesive contact problem of quasicrystals materials

It is difficult to analytically solve the contact problem of one-dimensional hexagonal quasicrystal (1DHQ) coating considering the coupling effects of adhesion, friction force and frictional heat in the contact region, especially considering both the frictional heat and adhesion simultaneously. The thermally frictional adhesive contact problem of 1DHQ coating is investigated using a discrete convolution-fast Fourier transform-based (DC-FFT-based) semi-analytical method. The adhesive behavior is described based on the Maugis-Dugdale model, which was used to investigate the influence of adhesive force on the thermoelastic field. It is a continuum-mechanics model with all microscopic features subsumed in the elastic constants, covers only elastic behavior, omitting all other physical characteristics of quasicrystals. By developing an adhesion-driven conjugate gradient method (AD-CGM), the contact process is numerically implemented, and the DC-FFT method is applied to solve the contact displacement. The numerical results indicate that the contact area under the consideration of adhesive force is much larger than that without. For a given external force, the contact radius and adhesive radius increase with increasing parameters. And each physical quantity exhibits different changing trends with the variation of adhesive parameters, with 0.5 as the dividing line. The research results may provide theoretical guidance for the practical application of quasicrystals as thermal barrier coating materials, nanodevice materials, and intelligent robot coating materials.

A Study of Russian-Belarusian Border Dialects: The Use of the Genitive Case Ending -u in the Khislavichi Dialect

Summary This article explores the features of noun declension in the Khislavichi dialect, focusing on the use of the genitive case ending -u. The study is based on data from the Khislavichi Corpus, which consists of texts recorded from native speakers in the western part of the Khislavichi district of the Smolensk Region during field trips in 2018–2019. The linguistic situation in this area is characterized by the Russification of genetically Belarusian dialects. The analysis examines the preservation of dialect features, the historical and contemporary usage of the genitive case in Russian and Belarusian, and the specificities of the genitive ending -u in the Khislavichi dialect. The findings indicate that the Khislavichi dialect employs the -u ending in the genitive case for a larger number of lexemes compared to standard Russian. This raises the question of whether these "extra" -u forms can be linked to the previous Belarusian system. The study explores the variability found in the usage of both the -u and -a endings, suggesting that their selection may be contingent upon the intended meaning and the age of the speaker. Additionally, the article contributes to the development of a broader theoretical problem: the transition from one idiom to another, and ultimately the theory of language change. This research adds to our understanding of dialectal variation and the mechanisms of language change, particularly in regions experiencing language contact and assimilation processes.

Anthropomorphic modular gripper finger actuated by antagonistic wire and shape-memory alloy (SMA) springs

Abstract. The traditional underactuated grippers can only passively adapt to the contour of the object, and the passive contact process may lead to the object slipping, affecting the stability of the grasping process. In this paper, an anthropomorphic modular gripper finger actuated by antagonistic wire and shape-memory alloy (SMA) springs, which can actively control the grasping morphology according to the characteristics of the objects to be grasped, is proposed. The wire drive simulates the flexor muscle, and the SMA and reset springs simulate the extensor muscles of the finger, which antagonistically control the grasping morphology of the finger. It is more in line with the grasping characteristics of the human hand. According to the moment equilibrium principle of the finger joints, the deformation model of the gripper is established, the influence of the wire tension and the equivalent stiffness of the finger joints on the grasping morphology is analyzed, and the theoretical joint angle results are verified by the Adams simulation; finally, the experimental system of the gripper is constructed, and the verification of the deformation morphology of the single finger and the gripper's enveloping–grasping experiments is completed. The results show that according to the contour size of the object, by actively controlling the wire force of the gripper and the equivalent stiffness of the interphalangeal joints, the enveloping–grasping action of different objects can be completed and the stable grasping of objects of different shapes and sizes can be realized.

The contact process over a dynamical d-regular graph

The contact process over a dynamical d-regular graph

An In Vitro Study of 355‐nm Laser Ablation of Atherosclerotic Lesions Model

ABSTRACTA study of 355 nm laser with high pulse energy across various types of atherosclerotic lesion models is presented. The 355 nm laser pulses (10 ns) are delivered via a single fiber (600 μm diameter), and the ablation of calcified tissue, lipid tissue, and thrombus‐like tissue are studied under varied laser fluence (40–70 mJ/mm2) and repetition rate (5–30 Hz). The contact and noncontact ablation processes of chicken tibia samples (calcified tissue) are compared at 60 mJ/mm2 and 30 Hz, and the size of ablation particles is in the range of 0.1–1 μm. At the same repetition rate, the advancement rate of tricalcium phosphate samples reaches 150 μm/s at 70 mJ/mm2. Calcified and lipid models demonstrate predictable increases in ablation with higher laser fluence and repetition rate. The fresh porcine blood clot samples exhibit high‐quality ablation with good channel effect at 50 mJ/mm2 and 30 Hz.

An electro-elastic contact problem with an internal state variable

We consider a mathematical model which describes the quasistatic process of contact between a piezoelectric body and an electrically conductive foundation. General models for elastic materials with piezoelectirec effect, called electro-elastic materials. This paper is devoted to the study of the model involving a frictionless contact between an electro-elastic body characterized by long memory and a conductive adhesive foundation. The process is mechanically quasistatic and electrically static. We model the material with a general nonlinear electro-elastic constitutive law with internal state variable and the contact with normal compliance and unilateral constraint, where the adhesion is taken into account and a regularized electrical conductivity condition. The main feature of these models consists of the fact that their variational formulation is given by a history-dependent quasivariational inequality for the displacement field and a linear variational equation for the electric potential. A weak formulation for the model is given in the form of a coupled system for the displacement, the stress, the electric displacement, the electric potential, the bonding and the variable state internal fields. We derive a variational formulation for the problem and then, under a smallness assumption on the data, we prove the existence of a unique weak solution to the model. We also investigate the behavior of the solution with respect the electric data on the contact surface and prove its unique weak solution. The proof is based on nonlinear evolution equations with monotone operators, differential equations and Banach fixed point arguments.

A Closure Contact Model of Self-Affine Rough Surfaces Considering Small-, Meso-, and Large-Scale Stage Without Adhesive

Contact interface is essential for the dynamic response of the bolted structures. To accurately predict the dynamic characteristics of bolted joint structures, a fractal extension of the segmented scale model, i.e., the JK model, is proposed in this paper to comprehensively analyze the dynamic contact performance of engineering surfaces and revisit the multi-scale model based on the concept of asperities. The influence of asperity geometry, dimensionless material properties, and the elastic, elastoplastic, and full plastic mechanical models of a single asperity is established considering the asperity–substrate interaction. Then, a segmented scale contact model of rough surfaces is proposed based on the island distribution function in a strict sense. The mechanical contact process of determining rough surfaces is divided into small-scale, medium-scale, and large-scale stages. Moreover, cross-scale boundary conditions, i.e., al1′, al2′, and al3′, are provided through strict mathematical deduction. The results show that the real contact area and contact stiffness are positively correlated with fractal dimension and negatively correlated with fractal roughness. On a small scale, the contact damping decreases with an increase in load. In meso-scale and large-scale stages, the contact damping increases with the load. Finally, the reliability of the proposed model is verified by setting up three groups of modal vibration experiments.

Machine learning stochastic differential equations for the evolution of order parameters of classical many-body systems in and out of equilibrium

Abstract We develop a machine learning algorithm to infer the emergent stochastic equation governing the evolution of an order parameter of a many-body system. We train our neural network to independently learn the directed force acting on the order parameter as well as an effective diffusive noise. We illustrate our approach using the classical Ising model endowed with Glauber dynamics, and the contact process as test cases. For both models, which represent paradigmatic equilibrium and nonequilibrium scenarios, the directed force and noise can be efficiently inferred. The directed force term of the Ising model allows us to reconstruct an effective potential for the order parameter which develops the characteristic double-well shape below the critical temperature. Despite its genuine nonequilibrium nature, such an effective potential can also be obtained for the contact process and its shape signals a phase transition into an absorbing state. Also, in contrast to the equilibrium Ising model, the presence of an absorbing state renders the noise term dependent on the value of the order parameter itself.

Mathematical modeling and optimal control of the dynamics of terrorist ideologies

We describe the dynamics of the spread of terrorist ideologies within a population, described as an epidemic. The equations of the model are obtained using a contact process, which gives us first-order autonomous non-linear differential equations. Next, the stability of the equilibrium point is established using the basic reproduction number technique; numerical simulations allow us to verify the mathematical results. Finally, optimal control analysis highlights the importance of synergy of action (numbers, equipment, strategy, and training) within the defence and security forces and the importance of patriotism in a nation. In addition, ongoing awareness-raising campaigns are helping to speed up the eradication process.

Green Synthesis of Sulphuric Acid Based on "Geber's Method": A Detailed Aspen Plus Simulation

Sulfuric acid (H2SO4) has a wide range of applications, but its current synthesis route via the contact process negatively impacts the atmospheric environment with harmful gaseous pollutants. Thus, based on the non-random two-liquids (NRTL) thermodynamic method, this study presents a detailed Aspen Plus V8.8 simulation of the green synthesis route of H2SO4 based on Geber's method developed already in the 18th century. The research investigates the efficiency and energy dynamics of the process through the analysis of key process parameters such as reactor's heat duty, vapor fraction, and molar extent of reaction in the selected configuration, using green vitriol (FeSO4∙7H2O) as a natural raw material. This study presented a novel manufacturing route that resulted in H2SO4 of 85.76% purity (33.71 kg/h), considering the chosen parameter space. The results highlight the impact of reactant component molar yield and fractional conversion of iron (II) sulfate (FeSO4) on heat duty and the optimal molar extent for maximizing H2SO4 production in a series of equilibrium reactors. In addition, appropriate operational parameters for the synthesis process were carefully specified, offering a pathway towards sustainable and eco-friendly H2SO4 production, which should emit zero greenhouse gases. Further optimization of the reactor conditions, can help maximize the yield of H2SO4, while minimizing energy consumption and byproduct formation. Developing advanced wastewater treatment units to purify the wastewater stream containing trace amounts of H2SO4 and dissolved sulfur trioxide (SO3) can mitigate environmental impact and ensure compliance with regulatory standards.

A Novel Fractal Model for Contact Resistance Based on Axisymmetric Sinusoidal Asperity

In this paper, a novel fractal model for the contact resistance based on axisymmetric sinusoidal asperity is proposed, which focuses on the resistance characteristics of the rough interface at a microscopic scale. By introducing the unique geometric shape of axisymmetric sinusoidal asperity, and combining it with a three-dimensional fractal theory, the micro-morphology characteristics of the rough interface can be characterized more precisely. Subsequently, by conducting a theoretical analysis and numerically solving the deformation mechanisms of asperities on the rough interface, a refined model for contact resistance is constructed. This research comprehensively employs theoretical analysis, numerical simulation, and experimental testing methods to deeply explore the current transmission mechanisms during the contact process of the rough interface. The findings suggest that the proposed model is capable of precisely capturing the intricate interplay of various factors, including contact area, contact load, and material properties, with the contact resistance. Compared to the existing models, the presented model demonstrates significant advantages in terms of prediction accuracy and practicality. This research provides an important theoretical basis and design guidance for optimizing the electrical performance of the rough interface, which has great significance for engineering applications.

Research on Discrete Clamp Motion Path Control-Based Stretch-Forming Method for Large Surfaces

In this paper, a near-net discrete clamp motion path control (SF-CMPC)-based stretch-forming method is proposed as a solution for the low-cost high-quality machining of highly curved surfaces. In this approach, the clamps are discretized, the motion paths are designed to control deformation distribution and avoid forming defects, the stretch-forming transition zone can be effectively reduced, the material utilization rate can be increased, and the near-net formation of large surfaces can be achieved. To investigate this method’s feasibility, the conventional stretch-forming (SF-C) and SF-CMPC processes are numerically analyzed. The results indicate that, upon increasing the transition zone length via SF-CMPC, the maximum thickness reduction and strain value are reduced by 0.010 mm and 0.0249, respectively, with the dependence of the forming quality on the transition zone length being significantly reduced compared to SF-C. In the formation of surfaces with large curvatures, SF-CMPC’s crack risk is lower than SF-C’s crack risk, with better adaptability. Through controlling the contact process with a die, the sheet metals’ constraint state is improved, the transverse compressive strain can be effectively reduced via friction, and the wrinkling defects can be suppressed. A stretch-forming experiment was carried out on a spherical surface, using self-developed equipment. The feasibility of achieving surfaces’ near-net stretch forming by controlling the clamps’ motion paths was hereby proven.

The evaluation of wear processes of the rolling-sliding contact by means of flake wear debris in dry and wet contact

One of the tasks of this paper is to explain the cause-and-effect relationship of the influence of operating parameters on the wear of the wheel-rail system where fatigue processes are initiated. In this way, learning about and defining the nature of the phenomenon, makes it possible to determine the reliability of component operation. The aim of this study was to determine the influence of operational parameters on tribological properties of the rolling-rail contact representing the wheel-rail association in real operating conditions. Determining the form of wear on the basis of laboratory tests carried out on an Amsler-type wear testing machine in the wheel-roller system makes it possible to determine the nature of changes occurring as a result of cyclic interaction of normal and tangential forces on the surface of the tested material, without the need for long-term and costly observation of the tested object in normal operation. Quantitative metallographic analysis of the morphology of wear debris was used to determine the intensity of surface wear. Determination of the influence of operational parameters on the stereological characteristics of wear debris makes it possible to predict the regenerative grinding of rails in service in the track and allows practical application by the sections of operation and diagnosis of the railway system.