One-dimensional Force Research Articles

Microfilm-Formation of High-Viscosity Liquids by Blade Shear Coating.

The distribution of high-viscosity microfilms in designated regions is crucial for the performance and durability of MEMS devices. This paper presents a novel method for controllable film formation in the milli/micron region by blade coating. A microfilm can be formed without viscosity limitation, and the formation process can be monitored only via a one-dimensional force sensor. The dynamics of the blade-coating process are analyzed in detail. The experimental results indicate that the initial height of the blade gap is the determining factor of film thickness, whereas the film length can be adjusted individually by the scratching speed without influence on film thickness. Moreover, the tangential force varies obviously in different coating parameters while exhibiting a similar trend.

Does the short-term learning effect impact vertical jump performance assessment on a portable force plate system?

One of the reoccurring questions that arises during the countermovement vertical jump (CVJ) assessment is whether the learning effect has an impact on the accuracy of the results obtained. Thus, the purpose of the present investigation was to examine the impact of the short-term learning effect on the assessment of lower-body neuromuscular performance characteristics when performed on a portable one-dimensional force plate system. Sixteen recreationally active college-age males volunteered to participate in the present study. Each participant completed four sets of three non-consecutive CVJs with no arm swing throughout a single day. Besides strong verbal encouragement, participants were constantly instructed to focus on pushing the ground as explosively as possible. Fourteen force-time metrics were selected for CVJ performance analysis purposes: eccentric and concentric peak and mean force and power, eccentric and concentric duration, contraction time, jump height, reactive strength index-modified, and countermovement depth. Repeated measures multivariate analysis of variance was used to examine statistically significant differences across four testing time points (p < 0.05). The results indicate an absence of any meaningful differences across four testing time points in force-time metrics of interest during both eccentric and concentric phases of the CVJ. Moreover, no differences were observed in CVJ outcome metrics such as countermovement depth, suggesting that the movement strategy tends to remain consistent. Overall, these findings reveal that CVJ test repeatability is not affected by the short-term learning effect and that data are stable at least within the scope of this study and within this population.

Theoretical analysis of cargo transport by catch bonded motors in optical trapping assays.

Dynein motors exhibit catch bonding, where the unbinding rate of the motors from microtubule filaments decreases with increasing opposing load. The implications of this catch bond on the transport properties of dynein-driven cargo are yet to be fully understood. In this context, optical trapping assays constitute an important means of accurately measuring the forces generated by molecular motor proteins. We investigate, using theory and stochastic simulations, the transport properties of cargo transported by catch bonded dynein molecular motors - both singly and in teams - in a harmonic potential, which mimics the variable force experienced by cargo in an optical trap. We estimate the biologically relevant measures of first passage time - the time during which the cargo remains bound to the microtubule and detachment force - the force at which the cargo unbinds from the microtubule, using both two-dimensional and one-dimensional force balance frameworks. Our results suggest that even for cargo transported by a single motor, catch bonding may play a role depending on the force scale which marks the onset of the catch bond. By comparing with experimental measurements on single dynein-driven transport, we estimate realistic bounds of this catch bond force scale. Generically, catch bonding results in increased persistent motion, and can also generate non-monotonic behaviour of first passage times. For cargo transported by multiple motors, emergent collective effects due to catch bonding can result in non-trivial re-entrant phenomena wherein average first passage times and detachment forces exhibit non-monotonic behaviour as a function of the stall force and the motor velocity.

Direct dielectrophoretic characterization of particles in the high-density microwell array using optical tweezers

In this work, a quantitative and intuitive measurement of dielectrophoresis (DEP) behavior in a high-density dielectrophoretic microwell array chip was accomplished in assistance with the holographic optical tweezers. A one-dimensional force balance system with high reliability was achieved between the transverse optical trapping (TOT) force and the DEP force. The value of the DEP force was inferred by accurately calculating the TOT force, and the direction of the DEP force was observed with high-magnification microscopy. In order to estimate the availability and operability of the DEP force measurement system, we systematically investigated the influences of various external factors on the DEP behaviors of microspheres and live cells. All the quantitative measurement results, which agree well with the theory, showed that this system could serve as an accurate research tool for DEP behavior characterizations to optimize and improve the DEP-based manipulations of microparticles and live cells for a broad range of applications. The system also provides an approach to quantitatively obtain important parameters such as Clausius-Mossotti factors for cells in mediums, which could potentially be used to understand the dielectric properties of different types of cells for cell differentiation and diagnosis at the single-cell level.

Research on Climbing Robot for Transmission Tower Based on Foot-End Force Balancing Algorithm

This paper aims to introduce robot technology to carry out the safety inspection of transmission towers in long-distance power transmission, so as to improve the safety and efficiency of inspection. However, aiming at the problem that the existing climbing robots are mainly used for large load applications, which leads to the large size and lack of flexibility of the robot, we propose an innovative solution. Firstly, a lightweight quadruped climbing robot is designed to improve portability and operational flexibility. Then, a one-dimensional force sensor is added at the end of each leg of the robot, and a special swing phase trajectory is designed. The robot can judge whether the electromagnetic adsorption is effective and avoid potential safety hazards. Finally, based on the principle of virtual model control (VMC), a foot-end force balancing algorithm is proposed to achieve uniform distribution and continuous change in force, and improve safety and load capacity. The experiments show that the scheme has a stable climbing ability in the environments of angle steel, vertical ferromagnetic plane and transmission tower.

The effects of a 12-week yoga program on the CoP of military pilots before and after a flight emergency simulation using Biosignals Plux force platform

This study examined the effects of Ashtanga Vinyasa Yoga Supta on Center of Pressure (CoP) displacement in healthy student pilots, using the Biosignals Plux force platform, under the premise that yoga would lead to improvements in postural control responses. CoP response was analyzed by the Plux (Portugal) one-dimensional force platform. A total of 18 military pilots participated in this study. The pilots were in their Portuguese Air Force Academy course “Masters in Military Aeronautics: Aviator Pilot Specialist,” also called Tirocinium. Participants were randomly assigned to yoga classes (intervention group) or a waiting list (control group) and completed a flight emergency protocol in a flight simulator. CoP displacement was collected before and after all these maneuvers had been completed and both measures occurred before (baseline values) and after a 12-week yoga program. Although the differences observed between groups are not significant, after calculating the effect size, we can theorize that the intervention group maintains CoP displacement before and after flight and the control group has a higher CoP displacement after flight simulation. CoP information collected through noninvasive portable devices such as the Biosignals Plux force platform can relay important information quickly and easily. Knowing under what circumstances pilots are affected can then lead to development or enhancement of training strategies to improve those psychophysiological responses. In this study the effects, while not significant, are present, so it may be necessary to add more weeks of training to make the yoga program effective.

Experimental Test of Sinai's Model in DNA Unzipping.

The experimental measurement of correlation functions and critical exponents in disordered systems is key to testing renormalization group (RG) predictions. We mechanically unzip single DNA hairpins with optical tweezers, an experimental realization of the diffusive motion of a particle in a one-dimensional random force field, known as the Sinai model. We measure the unzipping forces F_{w} as a function of the trap position w in equilibrium and calculate the force-force correlator Δ_{m}(w), its amplitude, and correlation length, finding agreement with theoretical predictions. We study the universal scaling properties since the effective trap stiffness m^{2} decreases upon unzipping. Fluctuations of the position of the base pair at the unzipping junction u scales as u∼m^{-ζ}, with a roughness exponent ζ=1.34±0.06, in agreement with the analytical prediction ζ=4/3. Our study provides a single-molecule test of the functional RG approach for disordered elastic systems in equilibrium.

Development of a Fiber Bragg Grating-Based Force Sensor for Minimally Invasive Surgery–Case Study of Ex-Vivo Tissue Palpation

In this paper, a one-dimensional distal force sensor design is proposed for minimally invasive surgery based on fiber Bragg grating (FBG) sensing principle. The sensor is made with a miniaturized force-sensitive flexure within which an optical fiber is embedded. The former includes a spiral elastomer utilized for high axial force sensitivity, while the fiber includes dual FBGs that are tightly suspended around the distal parts of the flexure and along elastomer’s centerline, respectively. Theoretical model of the flexure was derived based on its components and a design approach for decoupling strain and temperature cross-effects during sensor usage. In addition, design parameters of the flexure were analyzed on physics-based model optimization using fmincon function, while the static and dynamic properties were analyzed in-silico using finite element method. Further experiments were also carried out to analyze the sensor’s performance, and the data obtained was used for calibration study. The latter was done by training a feed-forward neural network designed for predicting the force vs. wavelength-shift relationship. The experimental results show the designed force sensor design can sense force values in a range of 1N with an average relative error less than 2% of full scale. Ex-vivo tissue palpation experiments were further done on pig liver organs to verify the effectiveness and applicability of the proposed sensor design in minimally invasive surgery.

Prediction of milling force based on spindle current signal by neural networks

Milling force is an important physical indicator, which affects chatter stability, tool wear and life. Based on the theory that there is a non-linear mapping relationship between the spindle current and the milling force signal, this paper proposes a method for predicting the instantaneous milling force based on a neural network model of the current signal. The current signal is processed by a sliding window to establish the input signal for the model, and a multidimensional current signal is used to predict the one-dimensional milling force signal. The proposed neural network model is capable of the time lag relationship between the current signal and the instantaneous milling force and reconstructing the instantaneous milling force by combining multiple feature information according to the variation of the current. The experimental results show that the proposed method can achieve an accurate prediction of the instantaneous milling force under different milling parameters.

The symmetrical rate-equations of particle–wave mechanics

At various times in his life, Louis de Broglie firmly believed in the coexistence of both particle and an associated wave referring to “the theory of the double solution”, and an equation which he called “the guidance formula”. In an attempt to account for both particle and wave, the author has proposed a Lorentz invariant alternative to Newton’s second law which is developed in Hill (Zeitschrift fur angewandte Mathematik und Physik 69:133–145, 2018; Zeitschrift fur angewandte Mathematik und Physik 70:5–14, 2019; Zeitschrift fur angewandte Mathematik und Physik 70:131–153, 2019; Math Mech Solids 26:263–284, 2020; Math Mech Solids 25: 1763–1777, 2020; Zeitschrift fur angewandte Mathematik und Physik 72:1–14; Mathematics of particle–wave mechanical systems, Springer, Cham, 2022). Here, we summarise some of the major outcomes of this approach, including simple solutions of the proposed model exhibiting both sub-luminal and superluminal behaviour dependent upon the region of space-time, and two symmetrical sets of rate-differential relations for the two Lorentz invariants for a single spatial dimension x. One set follows the particle, while the other follows the wave, revealing a complete symmetry between the one-dimensional spatial physical force f and the force g in the “direction of time”. The existence of these symmetrical equations reinforces the parity and interchangeability of particles and waves.

Theoretical wind clumping predictions from 2D LDI models of O-star winds at different metallicities

Context.Hot, massive (OB) stars experience strong line-driven stellar winds and mass loss. As the majority of efficient driving lines are metallic, the amount of wind driving and mass loss is dependent on the stellar metallicityZ.In addition, line-driven winds are intrinsically inhomogeneous and clumpy. However, to date, neither theoretical nor empirical studies of line-driven winds have investigated how such wind clumping may also depend onZ.Aims.We theoretically investigated the degree of wind clumping due to the line-deshadowing instability (LDI) as a function ofZMethods.We performed two-dimensional hydrodynamic simulations of the LDI with an assumed one-dimensional radiation line force for a grid of O-star wind models with fixed luminosity, but with different metal contents by varying the accumulative line strengthQ̄describing the total ensemble of driving lines.Results.We find that, for this fixed luminosity, the amount of wind clumping decreases with metallicity. The decrease is clearly seen in the statistical properties of our simulations, but is nonetheless rather weak; a simple power-law fit for the dependence of the clumping factorfcl≡ 〈ρ2〉 / 〈ρ〉2on metallicity yieldsfcl∝Z0.15±0.01. This implies that empirically derived power-law dependencies of mass-loss rateṀon metallicity – which were previously inferred from spectral diagnostics effectively depending onṀ√fclbut without having any constraints onfcl(Z) – should be only modestly altered by clumping. We expect that this prediction can be directly tested using new data from theHubbleSpace Telescope Ultraviolet Legacy Library of Young Stars as Essential Standards (ULLYSES) project.

Diagnosis of inhomogeneous one-dimensional discrete chains by photon scattering

Among the ways to reduce radiation doses (increasing the distance from the source to the person, reducing the time spent in radiation fields, reducing the radiation dose rate of the source) an important role is played by shielding the source of ionizing radiation.Currently, the use of screens is limited by the small selection of materials and the inconvenience of their use, which complicates their operation, installation and replacement, or disassembly.The propagation of a plane wave in a one-dimensional force chain with Hertzian contacts is analyzed in a linear approximation for cases with the presence of incorporated single and double impurities (defects). The algorithm of analytical solution of control equations and finding of reflection and transmission coefficients of incident radiation is determined. In terms of phase shifts, the frequency criterion of multi-modes of generation of transparent modes for inhomogeneous chains (with double impurities) similar to the Ramsauer-Townsend effect in the scattering of electrons by inert gas atoms is established. The obtained theoretical results are consistent with the data obtained from alternative sources. Possibilities of application of terahertz spectroscopy of radiation transmission for structural diagnostics and detection of in homogeneities, impurities and defects in discrete micro-mechanical (granular) systems are discussed. In particular, preliminary experimental data on scattering of terahertz radiation on samples of granular materials with different degrees of packing, from low to densely packed, which clearly indicate the dependence of the transmittance on the degree of packing and the formation of the corresponding band structure of spectra. The obtained results are also discussed in terms of applications to the creation of the element base of photonic circuitry in the sub millimeter range using decorated with impurities and structured low-dimensional discrete power circuits.

A novel one-dimensional force sensor calibration method to improve the contact force solution accuracy for legged robot

• This method can be carried out on LHDS without disassembling the force sensor. • This method can avoid the irregular variation of calibration coefficient. • This method can simply compensate for the influence of dynamics. Abstract In this paper, aiming at the phenomenon that the calibration coefficient deviation of the one-dimensional force sensor will lead to the deviation in measuring force, a novel method is proposed to recalibrate the one-dimensional force sensors of each joint directly on the leg hydraulic driving system (LHDS) of legged robot. This method has two main contributions. One is that it not only can be carried out directly on LHDS without disassembling the force sensor but also can avoid the irregular variation of calibration coefficient caused by the installation preloading force, friction, mechanical clearance, and other factors. The other is that the method can simply compensate for the influence of dynamics in the calibration process and avoid the complicated mathematical calculation. Under eight working conditions, the experimental results show that the proposed calibration method can decrease the foot end contact force deviation rate more than 20% in the whole cycle. The novel calibration method proposed in this paper can be extended to any leg structure equipped with the same kind of one-dimensional force sensor. It has practical value in engineering.

Simulations of the line-driven instability in magnetic hot star winds

Context. Line-driven winds of hot, luminous stars are intrinsically unstable due to the line-deshadowing instability (LDI). In non-magnetic hot stars, the LDI leads to the formation of an inhomogeneous wind consisting of small-scale, spatially separated clumps that can have great effects on observational diagnostics. However, for magnetic hot stars the LDI generated structures, wind dynamics, and effects on observational diagnostics have not been directly investigated so far. Aims. We investigated the non-linear development of LDI generated structures and dynamics in a magnetic line-driven wind of a typical O-supergiant. Methods. We employed two-dimensional axisymmetric magnetohydrodynamic simulations of the LDI using the Smooth Source Function approximation for evaluating the assumed one-dimensional line force. To facilitate the interpretation of these magnetic models, they were compared with a corresponding non-magnetic LDI simulation as well as a magnetic simulation neglecting the LDI. Results. A central result obtained is that the wind morphology and wind clumping properties change strongly with increasing wind-magnetic confinement. Most notably, in magnetically confined flows, the LDI leads to large-scale, shellular sheets (‘pancakes’) that are quite distinct from the spatially separate, small-scale clumps in non-magnetic line-driven winds. We discuss the impact of these findings for observational diagnostic studies and stellar evolution models of magnetic hot stars.

A single-layer based numerical method for the slender body boundary value problem

Fluid flows containing dilute or dense suspensions of thin fibers are widespread in biological and industrial processes. To describe the motion of a thin immersed fiber, or to describe the forces acting on it, it is convenient to work with one-dimensional fiber centerlines and force densities rather than two-dimensional surfaces and surface tractions. Slender body theories offer ways to model and simulate the motion of immersed fibers using only one-dimensional data. However, standard formulations can break down when the fiber surface comes close to intersecting itself or other fibers. In this paper we introduce a numerical method for a recently derived three-dimensional slender body boundary value problem that can be stated entirely in terms of a one-dimensional distribution of forces on the centerline. The method is based on a new completed single-layer potential formulation of fluid velocity which removes the nullspace associated with the unmodified single layer potential. We discretize the model and present numerical results demonstrating the good conditioning and improved performance of the method in the presence of near-intersections. To avoid the modeling and numerical choices involved with free ends, we consider closed fibers.

A collaborative robot for COVID-19 oropharyngeal swabbing

The coronavirus disease 2019 (COVID-19) outbreak has increased mortality and morbidity world-wide. Oropharyngeal swabbing is a well-known and commonly used sampling technique for COVID-19 diagnose around the world. We developed a robot to assist with COVID-19 oropharyngeal swabbing to prevent frontline clinical staff from being infected. The robot integrates a UR5 manipulator, rigid–flexible coupling (RFC) manipulator, force-sensing and control subsystem, visual subsystem and haptic device. The robot has strength in intrinsically safe and high repeat positioning accuracy. In addition, we also achieve one-dimensional constant force control in the automatic scheme (AS). Compared with the rigid sampling robot, the developed robot can perform the oropharyngeal swabbing procedure more safely and gently, reducing risk. Alternatively, a novel robot control schemes called collaborative manipulation scheme (CMS) which combines a automatic phase and teleoperation phase is proposed. At last, comparative experiments of three schemes were conducted, including CMS, AS, and teleoperation scheme (TS). The experimental results shows that CMS obtained the highest score according to the evaluation equation. CMS has the excellent performance in quality, experience and adaption. Therefore, the proposal of CMS is meaningful which is more suitable for robot-sampling.

One-Dimensional Lateral Force Anisotropy at the Atomic Scale in Sliding Single Molecules on a Surface.

Using a q+ atomic force microscopy at low temperature, a sexiphenyl molecule is slid across an atomically flat Ag(111) surface along the direction parallel to its molecular axis and sideways to the axis. Despite identical contact area and underlying surface geometry, the lateral force required to move the molecule in the direction parallel to its molecular axis is found to be about half of that required to move it sideways. The origin of the lateral force anisotropy observed here is traced to the one-dimensional shape of the molecule, which is further confirmed by molecular dynamics simulations. We also demonstrate that scanning tunneling microscopy can be used to determine the comparative lateral force qualitatively. The observed one-dimensional lateral force anisotropy may have important implications in atomic scale frictional phenomena on materials surfaces.

Stress orientation dependence for the propagation of stacking faults and superlattice stacking faults in nickel-based superalloys

Superlattice stacking fault propagation dominates the creep deformation behaviour of nickel-based superalloys at intermediate temperatures. These planar defects may appear under many different configurations depending on the dislocation arrangements and their interactions with the precipitates. Whilst these have been spotted and described before, no systematic way to explain their configurations has been provided. The current study quantifies the types of faults in multiple grains within a tensile crept polycrystalline alloy via a combination of scanning transmission electron microscopy and electron backscatter diffraction. A new defect consisting of a superlattice intrinsic stacking fault in the precipitates and an extrinsic stacking fault in the matrix is observed and a mechanism for its formation is proposed. In combination with data from the literature on single crystals, the results are incorporated into a robust framework to discern the orientation dependencies of these faults. A comprehensive analytical model based on a series of one-dimensional force balances on different dislocation configurations is developed first for the case of athermal stacking fault propagation for the cases of cuboidal and spherical precipitates. The model is then extended to include six configurations of superlattice faults and microtwinning. This results in novel mechanistic maps that account for stress, orientation and microstructure, with excellent qualitative agreement with experiments.

Hybrid active/passive force control strategy for grinding marks suppression and profile accuracy enhancement in robotic belt grinding of turbine blade

Grinding marks and traces, as well as the over- and under-cutting phenomenon are the severe challenges in robotic abrasive belt grinding of turbine blades and it greatly limits the further application of robotic machining technology in the thin-walled blade fields. In the paper, an active force control method consisting of force/positon and PI/PD controller based on six-dimensional force/torque sensor is introduced to eliminate the grinding marks and traces, and a passive force control method including PID controller based on one-dimensional force sensor is proposed to reduce the over- and under-cutting phenomenon in robotic machining system. Then the Kalman filter information fusion methodology is adopted to combine the active and passive force control methods which could improve the controlled force accuracy and efficiency, as well as avoid the control interference. Finally both the test workpiece and turbine blade are employed to examine and verify the reliability and practicality of the proposed hybrid force control method by achieving the desired surface quality and higher profile precision.

Robot Grinding System Trajectory Compensation Based on Co-Kriging Method and Constant-Force Control Based on Adaptive Iterative Algorithm

To reduce the grinding trajectory deviation caused by the absolute positioning accuracy of robot, a trajectory compensation method based on Co-Kriging space interpolation method is proposed. Meanwhile, an adaptive iterative constant force control method based on one-dimensional force sensor is proposed to improve the processing quality and efficiency of robot belt grinding. Firstly, an error model based on 6 DOF robot is constructed. Then, considering the workspace of robot belt grinding and the similarity of robot position error, the Co-Kriging compensation algorithm is used to compensate the grinding trajectory, which makes the compensation process convenient and accurate. Then, a grinding dynamics model based on deformation is established, and an adaptive iterative constant force control is proposed for complex robot belt grinding process, which overcomes the instability of grinding force and shortens its convergence time. Finally, the grinding trajectory compensation experiment and the force control experiment of spherical workpiece are carried out. The results show that the space interpolation compensation algorithm based on Co-Kriging method can significantly improve both the space position error of grinding trajectory and the actual error of workpiece, which proves the feasibility of compensation algorithm. Through force control algorithm, the grinding force fluctuation is maintained within 2 N, the mean value, standard deviation and variance of absolute value of force error are significantly reduced, the convergence rate of grinding force and the roughness of workpiece are much better than before, which shows the effectiveness of the proposed force control algorithm.