Surface Contact Point Research Articles

Hybrid nanofluids flow over a Riga plate surrounded by a variable porous medium for heat transfer optimization

Enhancing the heat transfer rate in hybrid nanofluids is significantly aided by a porous medium. The nanofluid’s heat transfer to the surrounding medium is more efficient due to the presence of a porous medium. The porous space also provides additional surface contact points for heat exchange and an intricate network of interconnected pores. This article elaborates on the incorporation of single-walled carbon nanotubes (SWCNTs) and multi-walled carbon nanotubes (MWCNTs) into water to perform hybrid nanofluids. The flow is considered over a Riga plate surrounded by a variable porous space. Various applications, including thermal management systems, microelectronics cooling, and energy conversion devices, benefit greatly from the study of hybrid nanofluid flow on a Riga plate. The similarity equations of the flow problem are easily tackled with the homotopy analysis method (HAM) built on fundamental homotopy mapping. Furthermore, with the increments in paramount parameters, the skin friction coefficient and heat transfer rate are remarkably meliorated under a higher modified Hartmann number. All reverberations are illustrated in graphs and Tables. From the obtained results it is observed that flow control capabilities are enabled by the variations in permeability in the case of hybrid nanofluids. It is also observed that hybrid nanofluids are more capable to enhance the thermal capabilities of the traditional fluids as compared to the mano nanofluids.

Ellipsoid contact analysis and application in the surface conjugate theory of face gears

Abstract. The face gear tooth surface is a high-order variable curvature surface, and the curvature of the surface is complicated, so it is difficult to describe the characteristics of the face gear tooth surface by a specific equation. In this paper, the discrete curvature relation of the surface is used instead of an analytical equation to describe a spatial meshing surface, and the traditional meshing theory is neutralized to analyze the characteristics of the face gear tooth surface. Firstly, according to the structural characteristics of the face gear, the sampling method of the face gear tooth surface is analyzed, and the mathematical model of fitting the tooth surface contact point is established. Then, the discrete asymptotic surface development analysis method is studied, and the ellipsoid contact analysis method of the face gear pair is established by simplifying the conjugate surface and its region. Finally, the contact analysis method of the discrete tooth surface is studied, and the instantaneous contact ellipse of the face gear tooth surface is calculated, which formed a new numerical meshing method of space curved surface.

Overcoming Obstacles Using Tail STAR: A Novel Sprawling Robot With a Two-Joint Tail

This paper presents Tail STAR (TSTAR), a novel reconfigurable robot with an active two-link tail. TSTAR is also fitted with a sprawling mechanism that lets it run either upright or inverted and change its height. The tail enables the robot to move its center of mass (COM) forwards or backwards and extend its length, provides it with more surface contact points, and increases its climbing capabilities. After presenting a kinematic model of the robot, a quasi-static analysis is presented that aims at optimizing the design of the robot and evaluating its motor requirements, climbing conditions and limitations. Experiments then show that the combination of the sprawling and tail mechanisms enables the TSTAR to overcome extremely challenging obstacles, climb high steps (6 times its wheel radius), bridge gaps equal to its own body length, and flip over to switch between its whegs and wheels to operate on very different terrains such as dirt, stones and grass (see attached video).

An intelligent knee joint force tracking and balancing system using ANN

The knee joint is a complex joint in the body. It is one of the most active joints in the body. It also experiences some of the most extreme loads encountered during walking, running, jumping, etc. Damage due to arthritis or trauma or sports injuries can often result in Total Knee Replacement (TKR) surgery where implants are manufactured by a variety of implant manufacturers. Lima, Zimmer, Johnson & Johnson, Stryker, etc areamong many of the companies supplying these implants. The initial tension in the joint is set by the surgeon using feel and touch which has always been controversial and subjective. It is heavily dependent on the skill and experience of the surgeons and is performed in an artisan fashion. In such cases, surgeons rely upon their natural haptic feedback to decide if the initial tension is adequate. Depending on the size of the patient’s limbs or the doctor, these settings can vary substantially. Currently, there is no unique tool that can tell surgeons what the actual tension in the tendons or contact force in the joint is in terms of Newton's force and if the compartmental forces are balanced or not. The intensity of this load plus the additional force during walking or running will dictate the ultimate load the new knee joint had to handle. Poor load balance during surgery can result in premature failure of the knee due to excess wear or fracture of the bones or dislocation. Surgeons are longing for a load transducer that can measure and track the joint surface contact point during the surgery and give real-time information about contact forces and their location at any position or orientation of the knee joint. This paper examines two of the existing sensors through publications and proposed one that appears to be the most suitable.

Discreteness of cell–surface contacts affects spatio-temporal dynamics, adhesion, and proliferation of mouse embryonic stem cells

The self-renewal and lineage-specific differentiation of stem cells are regulated by interactions with their microenvironments, called stem cell niche. Stem cells receive both biochemical and biophysical cues from their niche, which leads to the activation of signaling pathways, resulting in the modulation of gene expressions to guide their fate. Most of previous studies are focused on the effect of substrate stiffness using hydrogels with different Young’s moduli, and information is lacking on the effect of the discreteness of cell–substrate contacts on stem cells. Using mouse pluripotent, embryonic stem cells (mESCs) as the model system for early development, we quantitatively investigated the migration, dynamic deformation, and adhesion of mESCs on sparse and dense gelatin nanofibers deposited on glass surfaces, with a continuous layer of gelatin coated on glass substrates as the control. After confirming the maintenance of pluripotency on all the surfaces throughout the experiments, the centroid trajectories were monitored using timelapse imaging. The mean square displacement analysis indicated that both the diffusion coefficient and exponent were largest on sparse nanofibers, while the diffusion coefficient of mESCs on dense nanofibers was comparable to that on the control. Moreover, power spectral analysis of the shape deformation in the Fourier mode indicated that mESCs predominantly underwent elliptic deformation (mode 2), with the largest energy dissipation on sparse nanofibers. These data suggest that mESCs can deform and move on sparse nanofibers owing to the discrete cell–surface contact points. Intriguingly, using a self-developed technique based on laser-induced shock waves, a distinctly larger critical pressure was required to detach cells from nanofibers than from continuous gelatin. This finding suggests that the continuous but weak cell-substrate contacts suppress the deformation-driven mESC migration. As one of the key biological functions of stem cells, the proliferation rate of mESCs on these surfaces was determined. Although the observed difference was not statistically significant, the highest proliferation rate was observed on nanofibers, suggesting that the discreteness of cell–surface contacts can be used to regulate not only spatio-temporal dynamics but also the biological function of pluripotent stem cells.

Structural variations on the surface of metallic products at laser marking

Laser marking of products and details is used more and more wide in different production areas, because it has undisputable advantages in comparison with other marking methods. Action of laser beam on the surface of marking product is the principal feature of laser marking. It is accompanied with local heating of this surface and its partial melting together with material evaporation from the surface contact point. Influence of laser impulse action on efficiency of marking on the surface of machine-building details is examined in this work. The samples of 08Kh18N10 steel were used as material. Marking was conducted by the system “MiniMarker 2-20A4”, QR code was used as a marker. The marking parameters were optimized via the method of experimental design. The optimal marking procedure for getting maximal contrast of QR code was calculated and experimentally confirmed. Steel surface roughness was analyzed using profilograms. Contrasting effect and roughness of code were determined and relationship between these parameters was revealed. Contrast effect of marking increases with elevation of roughness. However, roughness has less input in increase of contrast effect comparing with colour hue of the surface of an information block and substrate. The link between surface roughness and contrast effect of marking is shown. Possibility of contrast effect assessment of QR code using profilometer is suggested. The reported study was financially supported by the Ministry of Science and Higher Education of the Russian Federation, research agreement No. 075-11-2019-066 of 22.11.2019, project title “Development of high-tech production of equipment and technologies for laser coding of transported goods and their optical identification for the implementation in modern material flow management systems” (within the framework of decree of the Government of the Russian Federation, No. 218 of 09.04.2010).

Topological barriers to defect nucleation generate large mechanical forces in an ordered fluid

Common fluids cannot sustain static mechanical stresses at the macroscopic scale because they lack molecular order. Conversely, crystalline solids exhibit long-range order and mechanical strength at the macroscopic scale. Combining the properties of fluids and solids, liquid crystal films respond to mechanical confinement by both flowing and generating static forces. The elastic response, however, is very weak for film thicknesses exceeding 10 nm. In this study, the mechanical strength of a fluid film was enhanced by introducing topological defects in a cholesteric liquid crystal, producing unique viscoelastic and optomechanical properties. The cholesteric was confined under strong planar anchoring conditions between two curved surfaces with sphere-sphere contact geometry similar to that of large colloidal particles, creating concentric dislocation loops. During surface retraction, the loops shrank and periodically disappeared at the surface contact point, where the cholesteric helix underwent discontinuous twist transitions, producing weak oscillatory surface forces. On the other hand, new loop nucleation was frustrated by a topological barrier during fluid compression, creating a metastable state. This generated exceptionally large forces with a range exceeding 100 nm as well as extended blueshifts of the photonic bandgap. The metastable cholesteric helix eventually collapsed under a high compressive load, triggering a stick-slip-like cascade of defect nucleation and twist reconstruction events. These findings were explained using a simple theoretical model and suggest a general approach to enhance the mechanical strength of one-dimensional periodic materials, particularly cholesteric colloid mixtures.

Impact of proximal cavities and primary molar absence on space in the dental arches.

BackgroundA recently proposed treatment protocol for dental caries in primary teeth, called Ultra Conservative Treatment (UCT), keeps medium to large cavities open so that children can keep them clean with tooth brushing and fluoride toothpaste. However, carious lesions have been related to malocclusion and decrease of space for the eruption of the permanent successor.MethodsThis cross-sectional study evaluated dental casts of 235 schoolchildren, aged 6–7 years old of six public schools in deprived suburban areas, and with at least two cavitated dentin carious lesions. The casts were grouped according to the location of cavitated dentin lesions into non-proximal cavity (NPC), proximal cavity with buccal or lingual surface contact point to adjacent tooth (PCCP) and proximal cavity without contact to adjacent tooth (PCWC), as well as the absence of primary molars due carious lesions (PMA). The relationship between location of cavitated dentin lesions or absence of primary molars with C+D+E and D+E space was analyzed.ResultsChildren with absence of primary molars exhibited the smallest C+D+E and D+E space in the maxilla (P < 0.001) and mandible (P < 0.001), followed by proximal cavity without buccal or lingual surface contact. No significant difference was observed between NPC and PCCP groups in upper and lower arches.DiscussionPCWC are associated with minor (less than the leeway space) C+D+E and D+E space loss in both arches, and additional space loss is noted when primary molars are prematurely lost. These results may have implications for orthodontic and restorative dental care decisions in children.

Novel Aerial Manipulator for Accurate and Robust Industrial NDT Contact Inspection: A New Tool for the Oil and Gas Inspection Industry.

There is a strong demand in the oil and gas industry to develop alternatives to manual inspection. This paper presents AeroX, a novel aerial robotic manipulator that provides physical contact inspection with unprecedented capabilities. AeroX has a semi-autonomous operation, which provides interesting advantages in contact inspection. In the free-flight mode, the pilot guides the robot until performing contact with its end-effector on the surface to be inspected. During contact, AeroX is in its fully-autonomous global navigation satellite system (GNSS)-free contact–flight mode, in which the robot keeps its relative position w.r.t. the surface contact point using only its internal sensors. During autonomous flight, the inspector can move—with uninterrupted contact—the end-effector on the surface for accurately selecting the points where to perform A-scan measurements or continuous B-scan or C-scan inspections. AeroX adopts an eight-tilted rotor configuration and a simple and efficient design, which provides high stability, maneuverability, and robustness to rotor failure. It can perform contact inspection on surfaces at any orientation, including vertical, inclined, horizontal-top or horizontal-bottom, and its operation can be easily integrated into current maintenance operations in many industries. It has been extensively validated in outdoor experiments including a refinery and has been awarded the EU Innovation Radar Prize 2017.

Gait control in a soft robot by sensing interactions with the environment using self-deformation.

All animals use mechanosensors to help them move in complex and changing environments. With few exceptions, these sensors are embedded in soft tissues that deform in normal use such that sensory feedback results from the interaction of an animal with its environment. Useful information about the environment is expected to be embedded in the mechanical responses of the tissues during movements. To explore how such sensory information can be used to control movements, we have developed a soft-bodied crawling robot inspired by a highly tractable animal model, the tobacco hornworm Manduca sexta. This robot uses deformations of its body to detect changes in friction force on a substrate. This information is used to provide local sensory feedback for coupled oscillators that control the robot's locomotion. The validity of the control strategy is demonstrated with both simulation and a highly deformable three-dimensionally printed soft robot. The results show that very simple oscillators are able to generate propagating waves and crawling/inching locomotion through the interplay of deformation in different body parts in a fully decentralized manner. Additionally, we confirmed numerically and experimentally that the gait pattern can switch depending on the surface contact points. These results are expected to help in the design of adaptable, robust locomotion control systems for soft robots and also suggest testable hypotheses about how soft animals use sensory feedback.

3A1-J01 スライダリンク機構を用いた曲面に適応可能なヘビ型ロボットのユニット開発(バイオミメティクス・バイオメカトロニクス)

In this study, we develop a curved surface adaptive unit to realize snake robots' undulatory progression on a curved surface such as cylindrical surface. The unit is composed of unit-compliance mechanism using springs between unit and robot, and wheels-stretching mechanism using slider link between wheels. The unit can adapt to changes in relative position of a curved surface and the robot, and changes in distance between surface contact point and the unit center. Experiment with snake robot on cylinder surface is carried out in order to demonstrate the effectiveness of the adaptive function to curved surface of the developed unit.

The Effect of Position on the Percentage of Body Mass Supported During Traditional and Modified Push-up Variants

The push-up is a popular upper-extremity weight-bearing exercise. However, limited information is available regarding its effectiveness. Much of the past research has focused on muscle activation levels, whereas very little has examined the forces encountered during push-up variants. The purpose of the present study was to examine the effect of position within the range of motion on the percentage of body mass (BM) supported by the upper extremities during the traditional and modified (knees-down) push-up. Twenty-eight highly strength-trained male subjects were positioned with their hands on a force platform in 4 static positions, consisting of the up and down position in both the traditional and modified push-up exercise. The performance measures included the average vertical ground reaction force (GRF), expressed as a percentage of BM, supported in each of the 4 static positions and the percentage of change between the up and down positions in each push-up exercise. In both the traditional and modified push-ups, subjects supported less weight in the up vs. the down position. The percentage change in % BM from the up to the down position was greater in the modified push-up variant. The pattern of resistances to the push-up exercises observed in this study may be a result of differing moment arms between the support surface contact point (knees or feet) and the hands. These results may be useful in prescribing programs for strengthening and/or rehabilitation for both the prime movers and stabilizers of the upper extremity. Further, range of motion may need to be altered to accommodate strength differences in beginners and clients rehabilitating from injury.

A Modified Version of the Rolling Sphere Method

The calculation of the striking distance can estimate the probability of lightning strike on a structure and thereby evaluate the effectiveness of a lightning protection system (LPS). The dimensioning and the positioning of air-termination on structures is often performed with the Rolling Sphere Method (RSM). RSM originated from the electric power transmission industry and is based on the well-known Electrogeometric Model (EGM). The EGM relates striking distance to the prospective peak stroke current. To apply this technique, an imaginary sphere is rolled over the structure. All surface contact points are deemed to require protection, whilst the unaffected volumes are deemed to be protected. The main drawback of this method is that it disregards the upward leadersiquest development and assumes the same probability for attachment to the ground, to a structure, and to a LPS. The proposed model is based on physical phenomena leading to the formation and the development of positive upward leader in the field produced by the negative downward leader charge distribution and by some other competing upward leaders. Its purpose is to develop a 3-D numerical model in order to improve the interception efficiency of the Lightning Protection System.

Single-molecule force spectroscopy of DNA-based reversible polymer bridges: Surface robustness and homogeneity

Single-molecule force spectroscopy, as implemented in an atomic force microscope, provides a rarely used method by which to monitor dynamic processes that occur near surfaces. Here, a methodology is presented and characterized that facilitates the study of polymer bridging across nanometer-sized gaps. The model system employed is that of DNA-based reversible polymers, and an automated procedure is introduced that allows the AFM tip–surface contact point to be automatically determined, and the distance d between opposing surfaces to be actively controlled. Using this methodology, the importance of several experimental parameters was systematically studied, e.g. the frequency of repeated tip/surface contacts, the area of the substrate surface sampled by the AFM, and the use of multiple AFM tips and substrates. Experiments revealed the surfaces to be robust throughout pulling experiments, so that multiple touches and pulls could be carried out on a single spot with no measurable affect on the results. Differences in observed bridging probabilities were observed, both on different spots on the same surface and, more dramatically, from one day to another. Data normalization via a reference measurement allows data from multiple days to be directly compared.

Haptic rendering for dental training system

Immersion and interaction are two key features of virtual reality systems, which are especially important for medical applications. Based on the requirement of motor skill training in dental surgery, haptic rendering method based on triangle model is investigated in this paper. Multi-rate haptic rendering architecture is proposed to solve the contradiction between fidelity and efficiency requirements. Realtime collision detection algorithm based on spatial partition and time coherence is utilized to enable fast contact determination. Proxy-based collision response algorithm is proposed to compute surface contact point. Cutting force model based on piecewise contact transition model is proposed for dental drilling simulation during tooth preparation. Velocity-driven levels of detail haptic rendering algorithm is proposed to maintain high update rate for complex scenes with a large number of triangles. Hapticvisual collocated dental training prototype is established using half-mirror solution. Typical dental operations have been realized including dental caries exploration, detection of boundary within dental cross-section plane, and dental drilling during tooth preparation. The haptic rendering method is a fundamental technology to improve immersion and interaction of virtual reality training systems, which is useful not only in dental training, but also in other surgical training systems.

Mode of Heavy Meromyosin Adsorption and Motor Function Correlated with Surface Hydrophobicity and Charge

The in vitro motility assay is valuable for fundamental studies of actomyosin function and has recently been combined with nanostructuring techniques for the development of nanotechnological applications. However, the limited understanding of the interaction mechanisms between myosin motor fragments (heavy meromyosin, HMM) and artificial surfaces hampers the development as well as the interpretation of fundamental studies. Here we elucidate the HMM-surface interaction mechanisms for a range of negatively charged surfaces (silanized glass and SiO2), which is relevant both to nanotechnology and fundamental studies. The results show that the HMM-propelled actin filament sliding speed (after a single injection of HMM, 120 microg/mL) increased with the contact angle of the surfaces (in the range of 20-80 degrees). However, quartz crystal microbalance (QCM) studies suggested a reduction in the adsorption of HMM (with coupled water) under these conditions. This result and actin filament binding data, together with previous measurements of the HMM density (Sundberg, M.; Balaz, M.; Bunk, R.; Rosengren-Holmberg, J. P.; Montelius, L.; Nicholls, I. A.; Omling, P.; Tågerud, S.; Månsson, A. Langmuir 2006, 22, 7302-7312. Balaz, M.; Sundberg, M.; Persson, M.; Kvassman, J.; Månsson, A. Biochemistry 2007, 46, 7233-7251), are consistent with (1) an HMM monolayer and (2) different HMM configurations at different contact angles of the surface. More specifically, the QCM and in vitro motility assay data are consistent with a model where the molecules are adsorbed either via their flexible C-terminal tail part (HMMC) or via their positively charged N-terminal motor domain (HMMN) without other surface contact points. Measurements of zeta potentials suggest that an increased contact angle is correlated with a reduced negative charge of the surfaces. As a consequence, the HMMC configuration would be the dominant configuration at high contact angles but would be supplemented with electrostatically adsorbed HMM molecules (HMMN configuration) at low contact angles. This would explain the higher initial HMM adsorption (from probability arguments) under the latter conditions. Furthermore, because the HMMN mode would have no actin binding it would also account for the lower sliding velocity at low contact angles. The results are compared to previous studies of the microtubule-kinesin system and are also discussed in relation to fundamental studies of actomyosin and nanotechnological developments and applications.

Analytical study on the kinematic and dynamic behaviors of a knee joint

A knee model in the sagittal plane is established in this study. Specifically, the model is used to study the effects of inertia, articular surfaces of the knee joint, and patella on the behaviors of a knee joint. These behaviors include the joint surface contact point, ligament forces, instantaneous center and slide/roll ratio between the femur and tibia. Model results are compared to experimental cadaver studies available in the literature, as well as between the quasistatic and dynamic models. We found that inertia increases the sliding tendency in the latter part of flexion, and lengthens the cruciate ligaments. Decreasing the curvature of the femur surface geometry tends to reduce the ligament forces and moves the contact points towards the anterior positions. The introduction of the patellar ligament in the model seems to stabilize the behaviors of the knee joint as reflected by the behavior of the instant centers and the contact point pattern on the tibia surface. Furthermore, we found that different magnitudes of the external load applied to the tibia do not alter the qualitative behaviors of the knee joint.

Hygroscopic Effects on Magnetic Tape Friction

The frictional behavior of magnetic tape at metal surface contact points was experimentally determined under environmentally controlled conditions approximating start/stop and slow tape speed. The main goal of this work is to use tape friction results at isolated contact points to predict the handling performance of the tape. The binder composition, acid lubricant level, tape smoothness, and humidity were identified as major contributors to tape frictional behavior at the three contact points studied. The importance of a hydrophobic binder in environmental stiction was demonstrated. A discovery of acid lubricant level effects on high humidity friction was made. The effect of tape surface topography on friction shows the expected roughness vs. friction and lubrication dependance. Presented as a Society of Tribologlsts and Lubrication Engineers paper at the ASME/STLE Trlbology Conference in Toronto, Ontario, Canada, October 8–10, 1990

Analytical Study On The Kinematic AndDynamic Behaviours Of Tibiofemoral Joint

The focus of this study is to simulate the kinematic and dynamic behaviors of a two dimensional tibiofemoral joint with a quasi-static and a dynamic model. Parameters of interest include the joint surface contact point, ligament forces, and slide/roll ratio between the femur and tibia. Model results are compared to experimental cadaver studies available in literature. Furthermore, the effect of femur surface geometry on the above mentioned characteristics is also determined. The pattern of ligament forces from the analytical study matches well qualitatively with the experimental study. Change of femur surface geometry has little effect on the pattern of slide/roll ratio.