Search Results (109)

This study examines how farm workers working with cattle talk to and interact with these non-human animals. This study presents linguistic animal studies and multi-species pragmatics, and it is based on fieldwork, interviews, and video recordings from several types of Finnish dairy farms. This study concentrates especially on one facet of human–cattle interaction: how humans use dung pushers and other sticks when communicating with cows. Thus, it draws on the materiality of language. It is shown how objects, bodies, and spaces, as well as words and linguistic constructions, are meaningful in human–animal interaction. Videoed recordings are analysed with multimodal conversation analysis. It is shown how dung pushers and snow stakes are used when steering cows, making them stand up, and pointing at things. It is then shown how these objects become ‘meaning-carriers’ for humans and for cows. For example, the dung pusher acquires four different meaning qualities for the human participants in the cattle barns: floor-cleaner quality, shepherd’s-crook quality, pointer quality, and weapon quality. The study examines how the cows’ and humans’ Umwelts, the subjective meaning universes of these species and their constituent individuals, influence interaction on farms and how and why the dung pusher becomes a semiotic resource. Full article

Due to the non-smooth characteristics of stick-slip friction, analytical solutions for the Dry Friction Constrained System (DFCS) are generally unavailable. Consequently, numerical simulation has become the most widely used approach for analyzing the DFCS. However, the accuracy and efficiency of the numerical algorithm considering the Coulomb stick-slip motion and determining whether stick-slip motion is considered in engineering design to further improve the computational efficiency remain a critical area of study. In this paper, a single-degree-of-freedom DFCS is introduced to address these issues. The Runge-Kutta method, combined with the dichotomy, is employed to accurately capture the stick-slip transition point. The normal load and dry friction are both symmetrically and evenly distributed at contact surfaces. Firstly, stick-slip motion analyses are performed, and response characteristics of the DFCS are discussed. Then, the convergence characteristics of the numerical algorithm are analyzed, and the optimal iteration step size and the zero-velocity interval are determined. Finally, whether stick-slip motion is considered in numerical simulation in the design of the DFCS in engineering practice is analyzed based on the dimensionless external force and frequency ratio. The criteria for determining whether stick-slip motion is considered in engineering design are established, which can improve both computational accuracy and efficiency. Full article

Plasma separation is an essential step in blood-based diagnostics. While traditional centrifugation is effective, it is costly and usually restricted to centralized laboratories because it requires relatively expensive equipment, a supply of consumables, and trained personnel. In an effort to alleviate these shortcomings, microfluidic and point-of-care devices offering rapid and low-cost plasma separation from small sample volumes, such as finger-stick samples, are quickly emerging as an alternative. Such microscale plasma separation systems enable reduced costs, rapid test results, self-testing, and broader accessibility, particularly in resource-limited or remote settings and facilitate the integration of separation, fluid handling, and downstream analysis into portable, automated lab-on-a-chip platforms. This review highlights advances in microfluidic systems and lab-on-a-chip devices for plasma separation categorized in design strategies, separation principles and characteristics, application purposes, and future directions for the decentralization of healthcare and personalized medicine. Full article

Asymmetric friction, that is, different friction forces resisting sliding in opposing directions, works as a rectifier, transferring the applied oscillations into unidirectional motion. Locomotion of devices based on asymmetric friction is investigated by considering a model system consisting of an asymmetric friction block connected to a symmetric friction block by a spring. The symmetric friction block models the resistance to the movement by the environment. It is found that under harmonic oscillation, the system displays two distinct types of motion: Recurrent Movement (stick-slip-type movement) and Sub-Frictional Movement. The Recurrent Movement occurs when the inertia force is sufficient to overcome the frictional force. In this case, the system with asymmetric friction exhibits unidirectional locomotion, while the system with only symmetric friction oscillates about a fixed point. The Sub-Frictional Movement occurs when the inertia is insufficient to overcome the frictional force. Then the symmetric friction block moves against the asymmetric friction block and sufficiently loads the spring to enable some movement of the system. Thus, motion is generated even when the external forces are below the static friction threshold. These types of motion have been found to exhibit different types of spectral fallout: while the Recurrent Movement produces a typically observed frictional fallout 1/ω, where ω is the frequency, the Sub-Frictional Movement produces a stronger 1/ω² fallout, only observed in the development of an oblique fracture in rocks under compression. This discovery can shed light on mechanisms of rock failure in compression. Understanding of the unidirectional movement induced by asymmetric friction can be instrumental in designing novel locomotion devices that can move in narrow channels or fractures in the Earth’s crust or in extraterrestrial bodies utilising the (renewable) energy of external vibrations. Full article

Friction conditions, along with the flow behaviors of materials, significantly impact plastic deformation during metal forming. Extensive practical research on friction has thus been conducted, and industrial development has been remarkable. However, it has been continuously pointed out in academia that an in-depth analysis of friction laws and phenomena linked to the metal forming simulation (MFS) has not yet reached a sufficient state from an engineering perspective. Despite the significant impact of friction on the MFSs, its importance has been underestimated, and the related studies have been relatively limited. A few researchers on metal forming emphasized the inadequacy of the constant shear friction law (CSFL) and the constant friction coefficient for the Coulomb friction law (CFL). Yet, most researchers still use the CFL with a constant friction coefficient or the CSFL. Many researchers have related the friction coefficient to the yield criterion, and they believe that the friction coefficient cannot exceed a certain value (for example, 0.577). It has also been believed that the sticking condition is the same as the friction factor of unity, even though displacement and traction cannot be prescribed simultaneously in natural phenomena. Despite many researchers’ innovative academic and industrial contributions, friction phenomena in metal forming remain in an incomplete state of confusion. This study reviewed and synthesized research on friction phenomena during metal forming. The main review topics include friction phenomena, friction modeling and friction laws, friction-related issues, lubrication regime change (LRC), lubricants, and tribometers, with their application spaces limited to metal forming. This review synthesizes existing research related to friction in metal forming, proceeding in a problem-identifying and solution-oriented manner. Full article

The swinging sticks pendulum is an intriguing physical system that exemplifies the intersection of Lagrangian mechanics and chaos theory. It consists of a series of slender, interconnected metal rods, each with a counterweighted end that introduces an asymmetrical mass distribution. The rods are arranged to pivot freely about their attachment points, enabling both rotational and translational motion. Unlike a simple pendulum, this system exhibits complex and chaotic behavior due to the interplay between its degrees of freedom. The Lagrangian formalism provides a robust framework for modeling the system’s dynamics, incorporating both rotational and translational components. The equations of motion are derived from the Euler–Lagrange equations and lack closed-form analytical solutions, necessitating the use of numerical methods. In this work, we employ the Bulirsch–Stoer method, a high-accuracy extrapolation technique based on the modified midpoint method, to solve the equations numerically. The system possesses four fixed points, each one associated with a different level of energy. The fixed point with the lowest energy level is a center, around which small perturbations are studied. The other three fixed points are unstable. The maximum energy used for the perturbations is $0.001\%$ larger than the lowest equilibrium energy. When the system’s total energy is low, nonlinear terms in the equations can be neglected, allowing for a linearized treatment based on small-angle approximations. Under these conditions, the pendulum oscillates with small amplitudes around a stable equilibrium point. The resulting motion is analyzed using tools from nonlinear dynamics and Fourier analysis. Several trajectories are generated and examined to reveal frequency interactions and the emergence of complex dynamical behavior. When a small initial perturbation is applied to one rod, its motion is characterized by a single frequency with significantly greater amplitude and angular velocity compared to the second rod. In contrast, the second rod displayed dynamics that involved two frequencies. The present study, to the best of our knowledge, is the first attempt to describe the dynamical behavior of this pendulum. Full article

This paper presents a comprehensive study of torsional stick–slip vibrations in rotary drilling systems through a comparison between two lumped parameter models with differing complexity: a simple two-degree-of-freedom (2-DOF) model and a complex high-degree-of-freedom (high-DOF) model. The two models are developed under identical boundary conditions and consider an identical nonlinear friction torque dynamic involving the Stribeck effect and dry friction phenomena. The high-DOF model is calculated with the Finite Element Method (FEM) to enable accurate simulation of the dynamic behavior of the drill string and accurate representation of wave propagation, energy build-up, and torque response. Field data obtained from an Algerian oil well with Measurement While Drilling (MWD) equipment are used to guide modeling and determine simulations. According to the findings, the FEM-based high-DOF model demonstrates better performance in simulating basic stick–slip dynamics, such as drill bit velocity oscillation, nonlinear friction torque formation, and transient bit-to-surface contacts. On the other hand, the 2-DOF model is not able to represent these effects accurately and can lead to inappropriate control actions and mitigation of vibration severity. This study highlights the importance of robust model fidelity in building reliable real-time rotary drilling control systems. From the performance difference measurement between low-resolution and high-resolution models, the findings offer valuable insights to optimize drilling efficiency further, minimize non-productive time (NPT), and improve the rate of penetration (ROP). This contribution points to the need for using high-fidelity models, such as FEM-based models, in facilitating smart and adaptive well control strategies in modern petroleum drilling engineering. Full article

During the operation of structures, the components and materials from which they are made are exposed to various environmental, technological, and operational impacts. In this context, the use of a modified water-dispersion composition containing finely dispersed fillers with enhanced protective and performance characteristics proves to be effective. This article examines the development of a paint-and-coating composition using hollow glass microspheres and modified diatomite as finely dispersed fillers. The influence of technological factors on the properties of coating materials based on a synthesized acrylic dispersion and fillers—such as modified diatomite and hollow glass microspheres ranging from 20 to 100 μm in size with a bulk density of 0.107–0.252 g/cm³—is analyzed. The optimal formulation of the coating materials was determined to ensure the required coating quality. Experimental results demonstrate the improved strength and hardness of the coating due to the use of acrylic dispersion obtained through an emulsifier-free method and modifiers in the form of finely dispersed fillers. It has been established that the resulting samples also exhibit high adhesion to mineral and metallic substrates, along with excellent corrosion resistance. Moreover, the incorporation of acrylic dispersion contributes to increased elasticity of the coating, resulting in improved resistance to washing and abrasion. The developed protective material can be applied to a variety of surfaces, including walls, ceilings, and roofs of buildings and structures, pipelines, and many other applications. Thus, modified water-dispersion compositions based on synthesized acrylic dispersion showed the following results: resistance to sticking—5, which is the best; chemical resistance and gloss level with standard single-phase acrylic dispersion—no destruction or change in gloss. The adhesion of coatings cured under natural conditions and under the influence of UV radiation was 1 point. The developed formulations for obtaining water-dispersion paint and varnish compositions based on synthesized polymer dispersions, activated diatomite, and hollow glass microspheres, meet all the regulatory requirements for paint and varnish materials in terms of performance, and in terms of economic indicators, the cost of 1 kg of paint is 30% lower than the standard. Full article

Authentic learning opportunities that simulate full-scale design and construction using real materials provide valuable experiential learning environments for construction and civil engineering students by challenging students to apply building concepts in practical settings. These activities challenge students to apply theoretical concepts in a realistic, hands-on context. However, the excessive cost of real building materials required for this mode of education limits access to the vast majority of students. As a result, educational researchers have explored potential alternatives to provide cost-effective experiential learning through activities using mock-up materials (e.g., plastic straws and popsicle sticks) and a simulation of experiences using immersive technologies (e.g., virtual reality or augmented reality). While some of these alternatives approximate the environment and others provide physical interaction with mock-up materials, the lack of authenticity in the building materials used introduces some apparent differences between the “authentic” learning environments and their cost-effective approximations. Therefore, this research aims to identify the learning processes reported by students and faculty who participated in authentic learning experiences to understand the ways in which this mode of education offers unique value to construction education. Their interview responses illustrated characteristics of authentic learning experiences that were believed to be critical to the learning process, some of which included working in groups; interdisciplinary participants; and the use of real construction materials. Although some of these characteristics are intrinsically linked to the use of real materials, others do not explicitly refer to interaction with real materials. This may point to specific aspects of authentic learning that educational researchers can replicate or enhance to provide cost-effective learning environments, such as virtual or augmented reality. The contribution of this paper is in identifying the characteristics of authentic learning experiences that may guide educational investment and research innovations that aim to replicate some of these learning experiences through more accessible learning environments. Full article

Depensation (or an Allee effect) has recently been detected in stock–recruitment relationships (SRRs) in four Atlantic herring stocks and one Atlantic cod stock using a Bayesian statistical approach. In the present study, we define the Allee effect threshold (B_AET) for these five stocks and propose B_AET as a candidate limit reference point (LRP). We compare B_AET to traditional LRPs based on proportions of equilibrium unfished biomass (B₀) and biomass at maximum sustainable yield (B_MSY) assuming a Beverton–Holt or Ricker SRR with and without depensation, and to the change point from a hockey stick SRR (B_CP). The B_AET for the case studies exceeded 0.2 B₀ and 0.4 B_MSY for three of the case study stocks and exceedances of 0.2 B₀ were more common when the Ricker form of the SRR was assumed. The B_AET estimates for all case studies were less than B_CP. When there is depensation in the SRR, multiple equilibrium states can exist when fishing at a fixed fishing mortality rate (F) because the equilibrium recruits-per-spawner line at a given F can intersect the SRR more than once. The equilibrium biomass is determined by whether there is excess recruitment at the initial projected stock biomass. Estimates of equilibrium F_MSY in the case studies were generally higher for SRRs that included the depensation parameter; however, the long-term F that would lead the stock to crash (F_crash) in the depensation SRRs was often about half the F_crash for SRRs without depensation. When warranted, this study recommends exploration of candidate LRPs from depensatory SRRs, especially if Allee effect thresholds exceed commonly used limits, and simulation testing of management strategies for robustness to depensatory effects. Full article

This paper presents an intelligent navigation wearable device for visually impaired individuals. The system aims to improve their independent travel capabilities and reduce the negative emotional impacts associated with visible disability indicators in travel tools. It employs an RGB-D camera and an inertial measurement unit (IMU) sensor to facilitate real-time obstacle detection and recognition via advanced point cloud processing and YOLO-based target recognition techniques. An integrated intelligent interaction module identifies the core obstacle from the detected obstacles and translates this information into multidimensional auxiliary guidance. Users receive haptic feedback to navigate obstacles, indicating directional turns and distances, while auditory prompts convey the identity and distance of obstacles, enhancing spatial awareness. The intuitive vibrational guidance significantly enhances safety during obstacle avoidance, and the voice instructions promote a better understanding of the surrounding environment. The device adopts an arm-mounted design, departing from the traditional cane structure that reinforces disability labeling and social stigma. This lightweight mechanical design prioritizes user comfort and mobility, making it more user-friendly than traditional stick-type aids. Experimental results demonstrate that this system outperforms traditional white canes and ultrasonic devices in reducing collision rates, particularly for mid-air obstacles, thereby significantly improving safety in dynamic environments. Furthermore, the system’s ability to vocalize obstacle identities and distances in advance enhances spatial perception and interaction with the environment. By eliminating the cane structure, this innovative wearable design effectively minimizes social stigma, empowering visually impaired individuals to travel independently with increased confidence, ultimately contributing to an improved quality of life. Full article

Co-combustion of coal and biomass for power generation technology could not only realize the effective utilization of biomass energy, but also reduce the emission of greenhouse gases. In this study, a system of a settling furnace with high temperature is applied to study the ash deposition of the co-combustion of coal and salix. The effects of salix blending ratio, flue gas temperature, and wall temperature on ash deposition are studied. The micro-morphology, elemental content, and compound composition of the ash samples are characterized by scanning electron microscopy and energy-dispersive spectroscopy (SEM-EDS) and X-Ray Diffraction (XRD), respectively. The results show that with the biomass blending ratio increasing from 5% to 30%, the content of Ca in ash increases from 8.92% to 20.59%. In particular, when the salix blending ratio exceeds 20%, plenty of the low-melting-point compounds of Ca aggravate the melting adhesion of ash particles, causing serious ash accumulation. Therefore, the salix blending radio is recommended to be limited to no more than 20%. With the increase in flue gas temperature, ash particles melt and stick, forming ash accumulation. Under the condition of flue gas temperature ≥ 1200 °C, a serious ash particle melting flow occurs, and CaO covers the surface of the ash particles, making the ash particles adhere to each other, which makes them difficult to remove. Therefore, controlling the flue gas temperature below 1200 °C is necessary. When the temperature crosses the threshold range of 500–600 °C, the Ca and K contents increase by 35.6% and 41.9%, respectively, while the Si content decreases by 9.7%. The increase in K and Ca content leads to the thickening of the initial layer of the ash deposit, which facilitates the formation of the sintered layer of the deposited ash. Meanwhile, the reduction in Si content leads to the particles’ adhesion, which markedly increases the degree of ash slagging. Once the wall temperature exceeds 600 °C, severe ash slagging becomes a threat to the safe operation of the boiler. Therefore, the wall temperature should not exceed 600 °C. Full article

Drilling long horizontal wells in naturally cracked/fractured unconventional shale gas/oil formations presents a huge challenge to the energy industry because of wellbore clogging complications that cause pipe sticking problems. This work proposes to use smooth catenary well trajectories to reduce drilling friction to mitigate these problems. A mathematical model was developed in this study for designing well trajectory profiles with a smooth transition from the kick-out point (KOP) to the catenary section. This model consists of closed-form equations for the radius of curvature and inclination angle in the catenary section. Using the radius of curvature at the top point of the catenary section to design the arc section below the KOP eliminates the trial-and-error procedure required for achieving the smooth transition between the two sections. The result of a field case study with Tuscaloosa Marine Shale (TMS) data shows that the drilling drag (hook load) can be reduced by 15% to 30% with the use of smooth catenary well trajectories to replace the conventional arc-type well trajectories. Model-calculated reduction in the hook load drops linearly with the horizontal borehole friction coefficient (clog indicator). The reduction increases non-linearly from 15% to 30% with drill collar weight increasing from 20 lb/ft to 92 lb/ft. Full article

Torsional vibrations pose a serious challenge in drilling operations and can lead to effects such as stick-slip phenomena, tool wear, and reduced drilling efficiency. While previous research has been conducted on torsional vibrations, there is a notable gap in comparative studies that assess the scalability of downscale models to real-world drilling conditions. This study fills this gap by systematically comparing torsional vibrations in downscale and upscale drill strings under different torque conditions at three different depths, shedding light on scaling effects in drilling vibrations. Numerical simulation was carried out taking into account non-linear interactions, damping effects, and torque variations. The laboratory set-up was for a well length of 15 m and was geometrically scaled to represent an upscale well of 450 m. Certain operational parameters such as rotation speed, torque, density, and friction coefficients were modified to keep realistic dynamic behavior, and all models were run at an identical speed of rotation to enforce consistency. The results show that both the upscale and downscale models exhibited stick-slip behavior, but differences in vibration intensity and stabilization trends point out how scaling affects torsional dynamics. Notably, the upscale bit first faced higher torsional oscillation than the set rotation speed after overcoming stick-slip before stabilizing, whereas the downscale bit went through prolonged stick-slip instability before synchronization. This study enhances the understanding of scaling effects in torsional drilling vibrations, offering a foundation for optimizing experimental setups and improving predictive modeling in drilling operations. Full article

The importance of using sophisticated interface models to obtain realistic numerical solutions of soil–structure interaction (SSI) problems has been recognised in recent decades. With this aim, various advanced interface models have been developed, which assume that the same advanced constitutive model can describe the soil behaviour inside and outside the shear zone. These models fail to adequately address the experimentally observed stick–slip transition, assuming permanent sticking between the soil and structure. Furthermore, the influence of interface roughness requires model parameter adjustments, e.g., in the critical state of the soil, which are questionable from a physical point of view. To overcome these shortcomings, we propose a general relationship to describe the evolution of the shear strain in the shear zone as a function of the surface roughness, the density, and the normal stress. This relationship, which assumes a stick–slip transition at the interface, can be combined with an advanced constitutive model to describe soil–structure interface behaviour using the same set of model parameters as for the surrounding soil. Depending on the surface roughness of the interface, this transition leads to a localisation within the soil in the shear zone (for rough surfaces) or at the contact surface (for smooth surfaces). The proposed model was validated using interface shear tests from the literature on dry granular soils. A hypoplastic constitutive model was used in the simulations. The comparison of experimental and calculated results demonstrates the ability of the proposed model to realistically reproduce shear stress and relative displacements, including the stick–slip transition observed in the experiments. This instils confidence in the model’s reliability and accuracy, thus providing a reliable numerical tool for SSI analyses. Full article