Unidirectional Force Research Articles

Stochastic force generation in an isometric binary mechanical system.

Accurate models of muscle contraction are necessary for understanding muscle performance and the molecular modifications that enhance it (e.g., therapeutics, posttranslational modifications, etc.). As a thermal system containing millions of randomly fluctuating atoms that on the thermal scale of a muscle fiber generate unidirectional force and power output, muscle mechanics are constrained by the laws of thermodynamics. According to a thermodynamic muscle model, muscle's power stroke occurs with the shortening of an entropic spring consisting of an ensemble of force-generating myosin motor switches, each induced by actin binding and gated by inorganic phosphate release. This model differs fundamentally from conventional molecular power stroke models that assign springs to myosin motors in that it is physically impossible to describe an entropic spring in terms of the springs of its molecular constituents. A simple two-state thermodynamic model (a binary mechanical system) accurately accounts for muscle force-velocity relationships, force transients following rapid mechanical and chemical perturbations, and a thermodynamic work loop. Because this model transforms our understanding of muscle contraction, it must continue to be tested. Here, we show that a simple stochastic kinetic simulation of isometric muscle force predicts four phases of a force-generating loop that bifurcates between periodic and stochastic beating through mechanisms framed by two thermodynamic equations. We compare these model predictions with experimental data including observations of spontaneous oscillatory contractions (SPOCs) in muscles and periodic force generation in small myosin ensembles.

Event-triggered adaptive dynamic programming for cable-driven parallel rehabilitation system with uncertainties

An event triggered adaptive dynamic programming (ET-ADP) controller is proposed for the cable-driven parallel rehabilitation system (CDPRS). Firstly, an error dynamics of CDPRS considering composite uncertainty is established. Secondly, to reduce the computational burden, a single critic network ADP method is proposed to obtain the approximate optimal cost function, and an event-triggered mechanism is introduced to save the communication resources simultaneously. Thirdly, considering the unidirectional force characteristics of the cables, the null-space reallocation method is adopted to optimise the tension of the cables. Then, based on Lyapunov stability theory, the uniformly ultimately boundedness (UUB) of the closed-loop system is proved. Finally, effectiveness of the proposed optimal tracking control strategy is verified based on the Matlab/simulink platform.

Mechanism and regulation of kinesin motors.

Kinesins are a diverse superfamily of microtubule-based motors that perform fundamental roles in intracellular transport, cytoskeletal dynamics and cell division. These motors share a characteristic motor domain that powers unidirectional motility and force generation along microtubules, and they possess unique tail domains that recruit accessory proteins and facilitate oligomerization, regulation and cargo recognition. The location, direction and timing of kinesin-driven processes are tightly regulated by various cofactors, adaptors, microtubule tracks and microtubule-associated proteins. This Review focuses on recent structural and functional studies that reveal how members of the kinesin superfamily use the energy of ATP hydrolysis to transport cargoes, depolymerize microtubules and regulate microtubule dynamics. I also survey how accessory proteins and post-translational modifications regulate the autoinhibition, cargo binding and motility of some of the best-studied kinesins. Despite much progress, the mechanism and regulation of kinesins are still emerging, and unresolved questions can now be tackled using newly developed approaches in biophysics and structural biology.

Experimental study on mechanical properties of pin-trunnion connection nodes of temporary steel brackets for elevated bridges

Currently, the pin connection test exists mainly for unidirectional force loading, while the pin connection of a temporary steel bracket applied to elevated bridges is for bi-directional force. The damage mechanism of the pin connection with bi-directional force is not yet fully understood in research. The effect of the loading direction, single-hole plate end distance and unilateral width ratio a/b, ear plate thickness ratio t1/2 t2, and ear plate shape on the mechanical properties of the pin connection need to be considered. In this study, destructive static loading tests were conducted on eight groups of double-hole pin connections, and the damage mode, bearing capacity, deformation, and strain of the pin connections were determined. The results show that the thickness of the trunnion plate primarily controls the damage mode of the pinned connection and the ratio is smaller for single-trunnion plate damage, which can achieve larger bearing capacity and deformation. The ratio of the end distance of the monocore plate to the width of the single side primarily controls the damage location of the monocore plate, and the ratio varies from large to small, gradually causing tensile damage to the side section, end cleavage damage, and end shear damage. The loading direction has a minor effect on the mechanical properties of the pin connection; however, the tensile deformation is significantly larger than the compressive deformation. By chamfering, the M shape is properly adjusted to optimize the shape of the double trunnion plate, which does not reduce the load-carrying capacity and deformation of the pin connection and can reduce the amount of steel used by 10 %. A comparative analysis of the change in the ear-plate shape before and after the open ear-plate test, determination of the cross-sectional damage location and effective calculation distance b1, and improvement and derivation of a practical method for calculating the load-carrying capacity for engineering are performed, at the same time, it can be applied to projects of different spans, which can greatly improve construction efficiency and reduce labor costs.

De- and repeasantisation through wolves: a political ecology of predator-friendly farming

While wolves are often described as 'ecological engineers', this article reframes the image of this predator as a socioecological engineer. Adopting a more-than-human political ecology perspective, I highlight the imbrication of wolf agency with the political economy of farming in co-shaping processes of agrarian change in Tuscany, Italy. A multispecies ethnography elucidates how wolves are simultaneously contributing to and undermining a modernization of sheep husbandry practices in the region. This entanglement of wolf agency in processes of de- and re-peasantization is politically relevant, affecting human-wolf relations and local levels of conflict. Through their return, wolves are necessitating shifts in farming practices and affecting the topology of agricultural landscapes, favoring either an intensification of husbandry regimes (i.e., more sheep raised indoors) or a greater competitiveness of family-led free-ranging farms with a high availability of family labor. Emphasizing this aspect is important to politicize current discussions surrounding coexistence, and supports the rise of practices that are considered to be most socially, culturally, and ecologically valuable. A focus on wolf agency in this case entails 'thinking with' wolves in co-designing alternative (co)existences, providing a more nuanced understanding of socioecological change and human-wolf relations. This article informs critical scholarship on the value of moving beyond dualist lenses while still maintaining a focus on structural processes. These are an important though not unidirectional force of change. Reframing wolves as socioecological engineers calls for further research exploring such entanglements of human and non-human agencies in the coproduction of agrarian change and human-wildlife relations.

A Multiscale Modeling and Experimental Study on the Tensile Strength of Plain-Woven Composites with Hybrid Bonded-Bolted Joints.

CFRP hybrid bonded-bolted (HBB) joints combine the advantages of traditional joining methods, namely adhesive bonding, and bolting, to achieve optimal connection performance, making them the most favored connection method. The structural parameters of CFRP HBB joints, including overlap length, bolt-hole spacing, and fit clearance relationships, have a complex impact on connection performance. To enhance the connectivity performance of joint structures, this paper develops a multiscale finite element analysis model to investigate the impact of structural parameters on the strength of CFRP HBB joint structures. Coupled with experimental validation, the study reveals how changes in structural parameters affect the unidirectional tensile failure force of the joints. Building on this, an analytical approach and inverse design methodology for the mechanical properties of CFRP HBB joints based on deep supervised learning algorithms are developed. Neural networks accurately and efficiently predict the performance of joints with unprecedented combinations of parameters, thus expediting the inverse design process. This research combines experimentation and multiscale finite element analysis to explore the unknown relationships between the mechanical properties of CFRP HBB joints and their structural parameters. Furthermore, leveraging DNN neural networks, a rapid calculation method for the mechanical properties of hybrid joints is proposed. The findings lay the groundwork for the broader application and more intricate design of composite materials and their connection structures.

Theoretical study of a novel resettable‐inertia damper: Dynamic modeling, equivalent linearization, and performance assessment

AbstractTo passively achieve an inertial device with unidirectional force transmission similar to Bang Bang control, this study introduces a novel energy dissipation device known as the resettable‐inertia damper (RID). The ingenious motion principles of the RID, encompassing a rack‐and‐pinion, bevel gear commutation system, speed transmission, and eddy current damping, are elucidated in detail. In particular, a unidirectional rotational flywheel within the device selectively engages when the primary structure reciprocates. The physical mass of the flywheel undergoes conversion into an amplified inertia through the rack‐and‐pinion mechanism, which enables the enhancement of damping effects coupling the flywheel rotation and eddy current configuration. A coupled multibody dynamic model, combining the clutching effect, the flywheel inertia, and the rotational damping, is formulated to analyze the system with RID (RIDS). Currently, an analysis of the hysteretic behaviors of RID is carried out. To facilitate the design and evaluation of the performance of RIDS, an equivalent linearization method is proposed for RIDS. The feasibility of this simplified method is validated under harmonic excitation. Additionally, the study examines the performance of equivalent linear systems (ELSs) and RIDS under natural ground motions and stochastic stationary excitation in peak and variance responses levels, respectively. Comparison of RID with traditional inerter shows that RID can achieve a more pronounced control with less force transferred to the structure and with the potential to recover vibration energy, highlighting its unique advantages.

Four phases of a force transient emerge from a binary mechanical system

Accurate models of muscle contraction are important for understanding both muscle performance and the therapeutics that enhance physiological function. However, models are only accurate and meaningful if they are consistent with physical laws. A single muscle fiber contains billions of randomly fluctuating atoms that on the spatial scale of a muscle fiber generate unidirectional force and power output. This thermal system is formally constrained by the laws of thermodynamics, and a recently developed thermodynamic model of muscle force generation provides qualitative descriptions of the muscle force-velocity relationship, muscle force generation, muscle force transients, and the thermodynamic work loop of muscle with a thermodynamic (not molecular) power stroke mechanism. To demonstrate the accuracy of this model requires that its outputs be quantitatively compared with experimentally observed muscle function. Here I show that a two-state thermodynamic model accurately describes the experimentally observed four-phase force transient response to both mechanical and chemical perturbations. This is the simplest possible model of one of the most complex characteristic signatures of muscle mechanics.

Flexible wide-range multidimensional force sensors inspired by bones embedded in muscle

AbstractFlexible sensors have been widely studied for use in motion monitoring, human‒machine interactions (HMIs), personalized medicine, and soft intelligent robots. However, their practical application is limited by their low output performance, narrow measuring range, and unidirectional force detection. Here, to achieve flexibility and high performance simultaneously, we developed a flexible wide-range multidimensional force sensor (FWMFS) similar to bones embedded in muscle structures. The adjustable magnetic field endows the FWMFS with multidimensional perception for detecting forces in different directions. The multilayer stacked coils significantly improved the output from the μV to the mV level while ensuring FWMFS miniaturization. The optimized FWMFS exhibited a high voltage sensitivity of 0.227 mV/N (0.5–8.4 N) and 0.047 mV/N (8.4–60 N) in response to normal forces ranging from 0.5 N to 60 N and could detect lateral forces ranging from 0.2–1.1 N and voltage sensitivities of 1.039 mV/N (0.2–0.5 N) and 0.194 mV/N (0.5–1.1 N). In terms of normal force measurements, the FWMFS can monitor finger pressure and sliding trajectories in response to finger taps, as well as measure plantar pressure for assessing human movement. The plantar pressure signals of five human movements collected by the FWMFS were analyzed using the k-nearest neighbors classification algorithm, which achieved a recognition accuracy of 92%. Additionally, an artificial intelligence biometric authentication system is being developed that classifies and recognizes user passwords. Based on the lateral force measurement ability of the FWMFS, the direction of ball movement can be distinguished, and communication systems such as Morse Code can be expanded. This research has significant potential in intelligent sensing and personalized spatial recognition.

Suppression of the vortex-induced vibration of the cylinder by the baffle plates at different submerged depths

In this paper, the suppression effect of baffle on VIV of cylinder at different depths is studied. According to two-dimensional transient model and RANS equation, VIV responses of a cylinder with two baffle plates at a fixed distance and a fixed Angle at different depths are numerically simulated. The submersion depth radio h* is mainly 1.2, 1.5, 2.5 and 5. The experimental data and predicting results are compared to display the accuracy of numerical method. When h* is 2.5, the baffle plates have the best suppression effect on VIV. Compared to the bare cylinder, the amplitude is decreased by 69%. Meanwhile, the vibration of the cylinder at different depths shows instability, and the motion response has great jitter. The lower baffle plate is subject to a unidirectional force when h* = 1.5 and 1.2.

Grout sleeve splicing of steel-fiber reinforced polymer composite bars: Tensile behavior and bond mechanism

In reinforced concrete structures exposed to harsh environments, steel corrosion poses a significant problem. Ductile and durable steel-fiber reinforced polymer composite bars (SFCBs), which can effectively address this issue, are a perfect alternative to conventional steel bars. However, the lack of suitable connection methods for SFCB has hindered their widespread adoption in civil engineering. To address this limitation, this paper proposes the use of grout-filled steel sleeves as a solution for connecting SFCB. The study designed 120 specimens of grout sleeve splices for SFCB to investigate their performance under unidirectional tensile forces. The experimental variables included the ratio of grout thickness to SFCB diameter, SFCB diameter, anchorage length, and grout strength. The results revealed various failure modes and found that specimens with a smaller ratio of grout thickness to SFCB diameter and greater grout strength demonstrated higher peak stress. The peak stress first increases and then slowly declines with an increase in anchorage length. Additionally, the peak stress decreased with increasing SFCB diameter, and the peak slip remained constant. Meanwhile, the bond mechanism between SFCB and grout was revealed. Finally, the study derived a theoretical bond-slip curve between SFCB and grout, as well as the development anchorage length.

Local twinning behavior of ZK61m magnesium alloy sheet under multiaxial stress during drawing-pressing with Erichsen test machine

In order to find a more effective method to preset twins and to explore the microstructure and twin evolution of magnesium alloy sheet under multi-axial stress state deformation, drawing-pressing deformation with Erichsen test machine is used as a sheet processing method to process ZK61m magnesium alloy sheet in this experiment. During repeated drawing-pressing deformation, the central area of the plate was subjected to annular tensile and compressive stress. In the process of deformation under unidirectional force, the slip direction of some grains is in hard orientation and it is difficult for the slip to operate, while the annular tensile and compressive stress state will provide the grains with multidirectional slipping options. Electron back-scattered diffraction (EBSD) technique was used to analyze the microstructure of magnesium alloy plates with different drawing-pressing times and different positions from local deformation center to edge. In this study, the complex circumferential force environment will weaken the anisotropy of deformation structure during repeated drawing-pressing, and the effect of prefabricated twins is more obvious. Based on the modified generalized Schmid factor (GSF) analysis, it is easier to show a variety of twin variation behaviors within a grain during Erichsen deformation. After the plate is deformed by Erichsen processing, the mechanical properties of magnesium alloy sheet have also been effectively improved.

Controlling the Influence of an Asymmetric Air Gap in a Synchronous Electrical Machine on the Unidirectional Attractive Force

Controlling the Influence of an Asymmetric Air Gap in a Synchronous Electrical Machine on the Unidirectional Attractive Force

Congruent visual cues speed dynamic motor adaptation

We demonstrate that adaptation to novel dynamics is stronger when additional online visual cues that are congruent with the dynamics are presented during adaptation, compared with either a constant or incongruent visual cue. This effect was found regardless of whether a bidirectional or unidirectional velocity-dependent force field was presented to the participants. We propose that this effect might arise through the inclusion of this additional visual cue information within the state estimation process.

Application And Improvement of Composite Materials in Truss Bridge Structure

Composite materials are new materials with the features of light weight, high strength, high specific modulus, strong corrosion resistance, and aging resistance. The truss structure is subject to unidirectional force, which gives full play to the advantages of high strength of composite materials along the fiber direction. Therefore, composite truss structure is gradually attracted attention in engineering fields, i.e., aerospace, bridges, and construction. By analyzing the application status of composite truss bridge at home and abroad, it can be concluded that compared with traditional steel truss, composite truss bridge has advantages in flexural performance, tensile performance, stability and other mechanical properties. However, due to the stiffness control design, the strength of composite material is not fully utilized, and the structural reliability of composite truss bridge is low due to the low efficiency of structural joints. The improvement methods of these two problems are reducing the allowable deflection-span ratio of composite truss bridge design and using composite materials with greater stiffness and changing the laying Angle and laying proportion of composite materials, respectively.

Research on a rotary piezoelectric wind energy harvester with bilateral excitation.

This paper describes a rotary piezoelectric wind energy harvester with bilateral excitation (B-RPWEH) that improves power generation performance. The power generating unit in the current piezoelectric cantilever wind energy harvester was primarily subjected to a periodic force in a single direction. The B-RPWEH adopted a reasonable bilateral magnet arrangement, thus avoiding the drawbacks of limited piezoelectric cantilever beam deformation and unstable power generation due to unidirectional excitation force. The factors affecting the power generation were theoretically analyzed, and the natural frequency and excitation force of the piezoelectric cantilever have been simulated and analyzed. A comprehensive experimental research method was used to investigate the output performance. The B-RPWEH reaches a maximum output voltage of 20.48Vpp when the piezoelectric sheet is fixed at an angle of 30°, the Savonius turbine number is 3, and the magnet diameter is 8mm. By adjusting the fixed angle of the piezoelectric sheet, the number of Savonius wind turbine blades, and the magnet diameter, the maximum voltage is increased by 52.38%, 4.49%, and 245.95%, respectively. The output power is 24.5 mW with an external resistor of 8 kΩ, and the normalized power density is 153.14 × 10-3 mW/mm3, capable of powering light-emitting diodes (LEDs). This structure can drive wireless networks or low-power electronics.

Mechanical properties of steel-plastic grating and its application in fractured rock slope support project

Anchor network support is an effective method for rocky slope support, but the defects of metal mesh in anchor network support structure to lead to the decrease of support effect and increase of support cost, which cannot be ignored. In view of the disadvantages of the metal mesh support, the steel-plastic grid is introduced into the anchor mesh support structure. In order to study the mechanical properties of steel-plastic grating and its application effect in rocky slope support, the influence mechanism of mesh size and node form on the mechanical properties of steel-plastic grating was studied by indoor experiments, and the feasibility of applying steel-plastic grating to high slope support structure was investigated by field tests. The conclusion of the study shows that the strength is maximum when the mesh size is 1:1 and the force distribution is uniform, but for the unidirectional force situation, the steel-plastic geogrid with a transverse to longitudinal ratio of 1:1.5 mesh is more economical. The influence law of nodal protrusion on the reinforcing effect of steel-plastic grating. The friction coefficient of the interface of steel-plastic grating is related to the interface of tendon and soil, and the friction coefficient of the interface is proportional to the mesh size, and the degree of influence of the nodes on the friction resistance is larger, and the larger the nodes, the better the reinforcement effect. The feasibility of steel-plastic grating applied to high slope support structure provides experience for similar construction projects.

Dynamic Full‐Field Imaging of Rupture Radiation: Material Contrast Governs Source Mechanism

AbstractIn seismology, the rupture mechanisms of an earthquake, a glacier stick‐slip and a landslide are not directly observed, but inferred from surface measurements. In contrast, laboratory experiments can illuminate near field effects. The near field reflects the rupture mechanism but is highly attenuated in the case of real‐world surface data. We directly image the elastic wave‐field of a nucleating rupture non‐invasively in its near‐field with ultrasound speckle correlation. Our imaging yields the particle velocity of the full shear wave field at the source location and inside the 3D frictional body. We experimentally show that a strong bimaterial contrast, as encountered in environmental seismology, yields a unidirectional or linear force mechanism for pre‐rupture microslips and decelerating supershear ruptures. A weak contrast, characteristic for earthquakes, generates a double‐couple source mechanism for sub‐Rayleigh ruptures, sometimes preceded by slow deformation at the interface. This deformation is reproduced by the NF of a unidirectional force.

Characterization of the flow rate on lab-on-a-disc by a low-powered electrolysis pump for wireless-controlled automation of bioanalytical assays

Pumping mechanism in centrifugal microfluidic platforms enable liquid delivery against the unidirectional centrifugal force. Electrolysis pumping is a method that relies on pneumatic pressure generated by the accumulation of oxygen and hydrogen to propel liquids towards the CD center. Previously, we presented a wirelessly controlled electrolysis (EL) pump with 3D structure to optimize CD space for multiple pump integration. However, the performance of EL pump for low power ranges, and its usage in a real-life application have not been yet demonstrated. In this study, we present the analysis of the EL pump performance over a rotational speed range from 600 to 1500 RPM at low electrical power rates of up to 45 mW. The liquid pumping rate was studied theoretically and compared with the experimental data. The EL pump presented a consistent flow rate of 70–410 nL/s, showing a robust and predictable actuation for small volume delivery. As a first real-life application, we presented the isolation of a specific volume of supernatant liquid after sedimentation of yeast. A theoretical model predicted a period time of 135 s needed to pump 40 µL of supernatant. In our experimental set-up we observed a volume of 43 µL moved in the same amount of time which makes a very good match with the predicted value. As a second real-time application, we presented a centrifugal microfluidic design with multiple wirelessly controlled EL pumps to automate a peptide microarray-based immunoassay for the detection of influenza hemagglutinin antibody.

Friction and wear behavior of diamond film with adjustable grain size against silicon carbide in different tribological tests

Efficient processing of silicon carbide (SiC) is still challenging due to its high hardness. Microcrystalline diamond (MCD) and nanocrystalline diamond (NCD) films were deposited on SiC ceramics by controlling methane concentration and gas pressure. Two different tribological tests were executed on rotating ball-on-plates and linear reciprocating tribometers. The morphology and the elemental composition of abrasion marks and ball surface were evaluated to determine the main wear mechanism. We found that the MCD film had high grinding efficiency, leading to the roughness Ra of 68 nm on the surface of the SiC ceramic ball, while NCD film obtained the lower roughness although there was a lower grinding efficiency. Both diamond films had no damage, but a layer of SiC debris was covered on the NCD. The efficiency of MCD was 20 times that of NCD in terms of wear rate. The grinding efficiency of the reciprocating friction test was only half that of the rotary test due to the unidirectional axial force. Diamond films with different grain sizes are expected for different applications for SiC processing, such as thinning, coarse grinding, and fine grinding.