Switching graphitic polytypes in elastically coupled cavities.

2D compounds with nonzero Berry curvature are ideal systems to study exotic and technologically favorable thermoelectric and magnetoelectric properties. Within this class of materials, the topological trivial and nontrivial regimes have to present very different behaviors, which are encoded for the orbital susceptibility and magnetization. To try to reveal them, it is found that it was necessary to introduce a k‐dependent mass term in the relativistic formalism of these materials. Thus, while a topologically trivial insulator is predicted to have a very limited response, in the nontrivial regime, a singular contribution to the orbital magnetic susceptibility, which is inversely proportional to the square of the quantum magnetic flux is unveiled. In this scenario, besides determining the measurement conditions a new route for enhancing the intrinsic orbital magnetism of topological materials widening the range of temperatures and magnetic fields without involving tiny bandgaps is found.

Ultra-low friction is crucial for the anti-friction, anti-wear, and long-life operation of nanodevices. However, very few two-dimensional materials can achieve ultra-low friction, and they have some limitations in their applications. Therefore, exploring novel materials with ultra-low friction properties is greatly significant. The emergence of ternary two-dimensional materials has opened new opportunities for nanoscale ultra-low friction. This study introduced nickel phosphorous trisulfide (NiPS3, referred to as NPS), a novel two-dimensional ternary material capable of achieving ultralow friction in a vacuum, into the large nanotribology family. Large-size and high-quality NPS crystals with up to 14 mm × 6 mm × 0.3 mm dimensions were grown using the chemical vapor transport method. The NPS nanosheets were obtained using mechanical exfoliation. The dependence of the NPS nanotribology on layer, velocity, and angle was systematically investigated using lateral force microscopy. Interestingly, the coefficient of friction (COF) of NPS with multilayers was decreased to about 0.0045 under 0.005 Pa vacuum condition (with load up to 767.8 nN), achieving the ultra-low friction state. The analysis of the frictional dissipation energy and adhesive forces showed that NPS with multilayers had minimum frictional dissipation energy and adhesive forces since the interlayer interactions were weak and the meniscus force was excluded under vacuum conditions. This study on the nanoscale friction of a ternary two-dimensional material lays a foundation for exploring the nanoscale friction and friction origin of other two-dimensional materials in the future.

Structural superlubricity with a contaminant-rich interface

ABSTRACTThe purpose of this study was to investigate the effect of variations in the alignment of the feet on scrum kinetics during machine scrummaging. Twenty nine rugby forwards from amateur-level teams completed maximal scrum efforts against an instrumented scrum machine, with the feet in parallel and non-parallel positions. Three-dimensional forces, the moment about the vertical axis and sagittal plane joint angles were measured during the sustained pushing phase. There was a decrease in the magnitude of the resultant force and compression force in both of the non-parallel conditions compared to parallel and larger compression forces were associated with more extended hip and knee angles. Scrummaging with the left foot forward resulted in the lateral force being directed more towards the left and the turning moment becoming more clockwise. These directional changes were reversed when scrummaging with the right foot forward. Scrummaging with the right foot positioned ahead of the left may serve to counteract the natural clockwise wheel of the live scrum and could be used to achieve an anti-clockwise rotation of the scrum for tactical reasons. However, this would be associated with lower resultant forces and a greater lateral shear force component directed towards the right.

The rectangular concrete‐filled steel tube (RCFST) has been widely applied into many engineering fields like buildings and bridges. However, the shear mechanisms and the universal design methods under lateral shear forces still remain to be fully understood. In this paper, the composite action of RCFST columns under lateral shear forces was systematically investigated with improved 3‐dimensional finite element simulations. The models adopted the improved material constitutive models and detailed contact interactions between the encased steel tube and core concrete. On the basis of available test data and numerical results of parametric studies, the critical shear span ratio and its variation range were determined. The composite effect and interactions between the encased steel tube and core concrete under different configurational dimensions and loading conditions were investigated. Calculation formulas of the shear stiffness and capacity were proposed based on identified features. The cooperative working mechanism and the constraining effect of steel tube were considered. The proposed calculations were then compared to available design regulations in different countries, and yielded more accurate predictions than the others.

In the specific case of curved cable-stayed bridges, the horizontal component of the load introduced by the stay cables on the deck is variable, concentric and dependent on the connection configuration between the tower and the cables, becoming a challenge in the design of these type of bridges. Hitherto, designers have dealt with this challenge in different ways, either by optimizing the position of the tower and its geometric characteristics, or by modifying the morphology of the stay cable system. This paper proposes the use of funicular and anti-funicular curves of the horizontal concentric load, introduced by the stay cables, to design the curved deck directrix, reducing lateral forces on the deck under the self-weight hypothesis. For the design of the deck directrix, two different formulations are considered: one discrete by means of summations and the other continuous by means of non-linear differential equations. Both formulations study the two possible signs of the axial force which will govern the design (funicular and anti-funicular curves). A least squares approximation is developed to facilitate the implementation of these formulations. The paper introduces a method to liberate the deck from its most important lateral loads, i.e., the concentric loads introduced by the stay cables. This way, it develops a deck dominated by axial forces instead of lateral ones (Bending moment with vertical axis, Mz, and lateral shear force, Vy), which can be critical for its design and decrease the stay-cable system efficiency. It explains, by different methods, how this directrices vary with different design decisions, so that the designer can develop the directrix that suits his design. Finally, two examples of directrices are given as a conclusion.

The human fingertip is extremely sensitive to lateral (shear) forces that arise in surface exploration. We and others have developed haptic displays that work by modulating surface friction via electrostatic attraction. Despite the demonstrated ability of these displays to render haptic environments, an understanding of the fingertip-surface interface is lacking. We have developed a tribometer for measuring the lateral frictional forces on a fingertip under well-controlled conditions. We show an expected square law dependence of frictional force (and inferred electrostatic normal force) on actuation voltage, although we observe a large person to person variability. We model an expected dependence of the frictional force on the frequency of the actuation voltage, predicting a first order cut off below about 500Hz. However, our measurements are unambiguously at odds with the model's predictions.

Atomically flat and clean metal surfaces exhibit a regime of ultra-low friction at low normal loads. Atomic force microscopy, performed in ultra-high vacuum on Cu(100) and Au(111) surfaces, reveals a clear stick-slip modulation in the lateral force but almost zero dissipation. Significant friction is observed only for higher loads (∼4–6 nN above the pull-off force) together with the onset of wear. We discuss the minor role of thermal activation in the low friction regime and suggest that a compliant metallic neck between tip and surface is formed which brings upon the low, load-independent shear stress.

Eighteen males and two females (mean age, 26.5 years) underwent biomechanical assessment and Cybex evaluation prior to ACL reconstruction. Clinically, all patients had at least a 1+ grade with the Lachman, anterior drawer, and pivot shift tests, the majority being graded as 2+. Footswitch, high speed photography, force plate, and indwelling wire electrode data were collected while each subject performed free and fast walking, running, cutting, and stair climbing activities. During walking, single limb support times did not differ between the subject's involved and uninvolved limbs. Knee joint angles were similar between limbs during walking, running, and stair climbing maneuvers. Dynamic EMG tracings during walking demonstrated similar quadriceps and calf activity between limbs, while greater variation in hamstring firing was evident among subjects. During running, the involved limb had a longer duration of medial hamstring activity compared to the lateral hamstring. No significant differences were seen in either vertical or sagittal shear forces during free walking. During fast walking, higher midstance vertical forces (F2) were present in the involved limb (P less than 0.05). During running, the involved limb experienced lower vertical forces (P less than 0.05), while both anterior and posterior sagittal shear differences were insignificant. Straight cut maneuvers demonstrated significantly lower lateral shear and vertical forces in the involved limb (P less than 0.05). Lower lateral and sagittal shear forces in the involved limb (P less than 0.01 and P less than 0.05, respectively), combined with a reduced angle of the cut during the cross-cut maneuver, may be the first means to assess the functional pivot shift phenomenon ever documented.(ABSTRACT TRUNCATED AT 250 WORDS)

Civil engineering infrastructures are prone to natural disasters like earthquakes, floods, and hurricanes. Dissipation energy plays the main role in design of structures under Earthquake loads and controls the behavior of buildings when it bears the lateral loads and transfers them to the foundation. To resist the vibrations in the structure, it is important to use a high technology like Base isolation which reduces base frequency of building vibration and reaching it to a lower value. In other words, seismic isolation has the main objective to protect structure during earthquake events. Base isolation is a flexible layer between foundation and superstructure thus decoupling the structure from damaging effect of ground motion. This edits the dynamic characteristics of the structural system. A comparative study is conducted of seismic performance on three types of thickness (100mm,200mm, 300mm) in which M1T1, M2T1, M3T1, M1T2, M2T2, M3T2, M1T3, M2T3, M3T3, M1T4, M2T4, and M3T4 has been analyzed of isolators namely Lead Rubber Base Isolators (LRBI). For this evaluation, an 8-story structure has been analyzed by using (ETABS) finite element program where Models have ordinary RC moment- resisting frames with square column cross- sections. Parameters like drift, displacement, story acceleration, frequency, and story velocity have been analyzed and it has been found that due to the presence of Lead Rubber Isolators the story drift, story accelerations, base shear, lateral shear forces, and velocity are greatly reduced and story displacement is increased in both X and Y directions compared for various thickness of lead rubber base isolation systems under near and far-field earthquakes. Most importantly it has been established that the transmission of the high energy seismic waves to the superstructure is greatly reduced by introducing base isolators in between the top of the footing and the bottom of the superstructure. The base isolator with thickness 100mm for the concrete grade M20, M30, M40 performed more efficiently than other thicknesses. In conclusion, the deformation and transmissibility ratio must be minimized to introduce as a solution for absorbing the vibrations where the engineer should consider this effect for adequate design.

Thinned, small larch logs have small diameters and no value-added final use, except as wood chips, pallets, or fuel wood, which are products with very low economic value; however, their mechanical strength is suitable for structural applications. In this study, small larch logs were sawed, dried, and cut into square timbers (with a 90 mm × 90 mm cross section) that were laterally glued to form core panels used to manufacture cross-laminated timber (CLT) wall panels. The surface and back of these core panels were covered with 12-mm-thick structural plywood panels, used as cross bands to obtain three-ply CLT wall panels. This attachment procedure was conducted in two different ways: gluing and pressing (CGCLT) or gluing and nailing (NGCLT). The size of the as-manufactured CLT panels was 1,220 mm × 2,440 mm, the same as that of the plywood panels. The final wall panels were tested under lateral shear force in accordance with KS F 2154. As the lateral load resistance test required 2,440 mm × 2,440 mm specimens, two CLT wall panels had to be attached in parallel. In addition, the final CLT panels had tongued and grooved edges to allow parallel joints between adjacent pieces. For comparison, conventional light-frame timber shear walls and midply wall systems were also tested under the same conditions. Shear walls with edge nail spacing of 150 mm and 100 mm, the midply wall system, and the fabricated CGCLT and NGCLT wall panels exhibited maximum lateral resistances of 6.1 kN/m (100%), 9.7 kN/m (158%), 16.9 kN/m (274%), 29.6 kN/m (482%), and 35.8 kN/m (582%), respectively.

IN a recent unpublished lecture to the Cambridge Natural History Society on analogies between insects and aeroplanes, Mr. J. W. S. Pringle pointed out that many insects lack inherent stability ; equilibrium during flight being maintained by appropriate displacements of the wings. Their difficulties are greatest when only a single pair of wings is present. It is in such insects (Diptera, in which the forewings alone are functional, and Strepsiptera with functional hindwings only) that the reduced appendages are transformed into halteres. According to the hypothesis of Fraenkel and Pringle1, the knobbed haltere serves as an organ of equilibrium. Vibrating in one plane it acts as an alternating gyroscope. If the insect is rotated so that the plane of vibration is changed, lateral shearing forces will be set up in the cuticle of the base of the haltere and will be perceived by the campani-form sensilla.

The stability and geometrical characteristics of solid-liquid interfacial nanobubbles in complex aqueous solution environments

Simple empirical relationships are available in many design codes to relate the height of a building to its fundamental period of vibration. These relationships have been realised for force-based design and so produce conservative estimates of period such that the lateral shear force will be conservatively predicted from an acceleration spectrum. Where assessment of a structure is concerned, however, it is the displacement demand that gives an indication of the damage that can be expected; this displacement would be underestimated with the use of the aforementioned period-height formulae. Furthermore, the period of vibration of interest in assessment is the yield period, which is calculated using the yield stiffness, also often referred to as the cracked or elastic stiffness. The derivation of a yield period-height formula for use in displacement-based assessment of European buildings is thus the focus of this work. Analytical fibre element models of RC frames of varying height have been developed and the yield period has been sought using eigenvalue, pushover and dynamic analyses.

There are some interesting problems and pitfalls in plate analysis and design which are worth reviewing. The applications of boundary conditions, stress recovery, support stiffness, lateral shear force and design of shear are addressed in the paper. It is recommended that greater care must be paid if a proper analysis is to be performed, and cost saving may be possible in some situations.