Force Scaling Research Articles

Size-dependent behavior of a MEMS microbeam under electrostatic actuation

The size-dependent behavior of a silicon microbeam with an axial force in MEMS is studied using a nonlinear finite element procedure. Based on a refined third-order shear deformation theory and the modified couple stress theory (MCST), nonlinear differential equations of motion for the beam are derived from Hamilton’s principle, and they are transferred to a discretized form using a two-node beam element. Newton-Raphson based iterative procedure is used in conjunction with Newmark method to obtain the pull-in voltages and deflections of a clamped-clamped microbeam under electrostatic actuation. The influence of the axial force, applied voltage and material length scale parameter on the behavior of the beam is studied in detail and highlighted.

The effects of TMS over the anterior intraparietal area on anticipatory fingertip force scaling and the size-weight illusion.

When lifting an object skillfully, fingertip forces need to be carefully scaled to the object's weight, which can be inferred from its apparent size and material. This anticipatory force scaling ensures smooth and efficient lifting movements. However, even with accurate motor plans, weight perception can still be biased. In the size-weight illusion, objects of different size but equal weight are perceived to differ in heaviness, with the small object perceived to be heavier than the large object. The neural underpinnings of anticipatory force scaling to object size and the size-weight illusion are largely unknown. In this study, we tested the role of anterior intraparietal cortex (aIPS) in predictive force scaling and the size-weight illusion, by applying continuous theta burst stimulation (cTBS) prior to participants lifting objects of different sizes. Participants received cTBS over aIPS, the primary motor cortex (control area), or Sham stimulation. We found no evidence that aIPS stimulation affected the size-weight illusion. Effects were, however, found on anticipatory force scaling, where grip force was less tuned to object size during initial lifts. These findings suggest that aIPS is not involved in the perception of object weight but plays a transient role in the sensorimotor predictions related to object size. NEW & NOTEWORTHY Skilled object manipulation requires forming anticipatory motor plans according to the object's properties. Here, we demonstrate the role of anterior intraparietal sulcus (aIPS) in anticipatory grip force scaling to object size, particularly during initial lifting experience. Interestingly, this role was not maintained after continued practice and was not related to perceptual judgments measured with the size-weight illusion.

Bubble wall velocities in local equilibrium

It is commonly expected that a friction force on the bubble wall in a first-order phase transition can only arise from a departure from thermal equilibrium in the plasma. Recently however, it was argued that an effective friction, scaling as γ2 w (with γ w being the Lorentz factor for the bubble wall velocity), persists in local equilibrium. This was derived assuming constant plasma temperature and velocity throughout the wall. On the other hand, it is known that, at the leading order in derivatives, the plasma in local equilibrium only contributes a correction to the zero-temperature potential in the equation of motion of the background scalar field. For a constant plasma temperature, the equation of motion is then completely analogous to the vacuum case, the only change being a modified potential, and thus no friction should appear. We resolve these apparent contradictions in the calculations and their interpretation and show that the recently proposed effective friction in local equilibrium originates from inhomogeneous temperature distributions, such that the γ2 w -scaling of the effective force is violated. Further, we propose a new matching condition for the hydrodynamic quantities in the plasma valid in local equilibrium and tied to local entropy conservation. With this added constraint, bubble velocities in local equilibrium can be determined once the parameters in the equation of state are fixed, where we use the bag equation in order to illustrate this point. We find that there is a critical value of the transition strength αcrit such that bubble walls run away for α>αcrit.

Flow-topography interactions in the western tropical Atlantic boundary off Northeast Brazil

Flow-Topography Interaction can be considered as a particular set of processes resulting of the currents interaction with a topographic gradient, specially associated with submarine canyon areas, which are important morphological features with potential to upwelling and cross-isobath transport on the continental margins. The South Pernambuco Continental Shelf (SPCS) and Pernambuco Plateau located on the Southwestern Tropical Atlantic (SWTA), present incised morphological features, highlighting the shelf valleys and blind canyons, which do not have a connection to the shelf or an onshore river system. They are likely features for interactions between the dominant along-shelf flow represented by the strong western boundary North Brazil Undercurrent. We investigated potential canyon induced upwelling and the respective mechanisms at the late spring/early fall context. CTD and reanalysis data from GLORYS12V1, and in situ bathymetric measurements were used to characterise the hydrodynamics and canyon morphology, respectively. Then, we combined both to obtain dimensionless numbers from dynamical scale analysis to infer possible imbalances of the acting forces. Reanalysis data evidenced uplift at the slope not related to the blind canyons. CTD data indicated a seasonal variation of the intrusion of water masses, especially at the shelf-break for the Middle shelf valley and Campas shelf valley. A temperature difference of 2.5 °C (2.0 °C) between surface and deep waters was observed during the late spring. A stepwise temperature structure was present in both seasons, indicating instability below the mixed layer depth, the uplifting of isotherms, and the corrosion of the lower portion of the surface mixed layer. The dimensionless parameters analysis reveals highest Rossby values during the fall, mainly in Zieta shelf valley (R0=130.87) and Csv (R0=111.71), and lower values for the canyons of the Pernambuco Plateau. Our hypothesis is that the shelf valleys might play a role in conducting the uplifted slope water coast-ward. For the blind canyons, although no related upwelling was observed, reanalysis revealed the presence of a deep anti-cyclonic eddy at one of the blind canyon's mouth. Rossby and Burger numbers indicate a weak geostrophic balance at the canyon rim, and instability of the horizontal length scale of the pressure gradient force, with tendency to vorticity control. While the paradigm that shelf and coastal waters off north-eastern Brazil are mostly oligotrophic in the surface is true, our observation of shallow (<60 m) subsurface uplift should be considered in future works in the SWTA.

Magnetic Entropic Forces Emerging in the System of Elementary Magnets Exposed to the Magnetic Field.

A temperature dependent entropic force acting between the straight direct current I and the linear system (string with length of L) of N elementary non-interacting magnets/spins is reported. The system of elementary magnets is supposed to be in the thermal equilibrium with the infinite thermal bath T. The entropic force at large distance from the current scales as , where r is the distance between the edge of the string and the current I, and is the Boltzmann constant; ( is adopted). The entropic magnetic force is the repulsion force. The entropic magnetic force scales as , which is unusual for entropic forces. The effect of “entropic pressure” is predicted for the situation when the source of the magnetic field is embedded into the continuous media, comprising elementary magnets/spins. Interrelation between bulk and entropy magnetic forces is analyzed. Entropy forces acting on the 1D string of elementary magnets that exposed the magnetic field produced by the magnetic dipole are addressed.

Seismicity modulation by external stress perturbations in plate boundary vs. stable plate interior

Characterization of critically stressed seismogenic fault systems in diverse tectonic settings can be used to explore the stress/frictional condition of faults, along with its sensitivity for seismicity modulation by periodic stress perturbation. However, the process of seismicity modulation in response to external stress perturbation remains debated. In this paper, the characteristic difference in the seismicity modulation due to resonance destabilization phenomenon governed by rate-and-state friction is presented and validated with the globally reported cases of seismicity modulation in diverse tectonic settings. The relatively faster-moving plate boundary regions are equally susceptible for both shorter-period (e.g., semi-diurnal, diurnal, and other small tidal constituents) and long-period (e.g., semi-annual, annual, pole tide and pole wobble) seismicity modulation processes in response to stress perturbations from natural harmonic forcing, including tidal, semi-annual, annual, or multi-annual time scales. In contrast, slowly deforming stable plate interior regions and diffuse deformation zones appear to be more sensitive for long-period seismicity modulation of semi-annual, annual, or even multi-annual time scales but less sensitive for short-period seismicity modulation. This finding is also supported by the theoretical model predictions from the resonance destabilization process and worldwide documented natural observations of seismicity modulation in diverse types of tectonic settings.

Space-warp coordinate transformation for efficient ionic force calculations in quantum Monte Carlo.

Ab initio quantum Monte Carlo (QMC) methods are a state-of-the-art computational approach to obtaining highly accurate many-body wave functions. Although QMC methods are widely used in physics and chemistry to compute ground-state energies, calculation of atomic forces is still under technical/algorithmic development. Very recently, force evaluation has started to become of paramount importance for the generation of machine-learning force-field potentials. Nevertheless, there is no consensus regarding whether an efficient algorithm is available for the QMC force evaluation, namely, one that scales well with the number of electrons and the atomic numbers. In this study, we benchmark the accuracy of all-electron variational Monte Carlo (VMC) and lattice-regularized diffusion Monte Carlo (LRDMC) forces for various mono- and heteronuclear dimers (1 ≤ Z ≤ 35, where Z is the atomic number). The VMC and LRDMC forces were calculated with and without the so-called space-warp coordinate transformation (SWCT) and appropriate regularization techniques to remove the infinite variance problem. The LRDMC forces were computed with the Reynolds (RE) and variational-drift (VD) approximations. The potential energy surfaces obtained from the LRDMC energies give equilibrium bond lengths (req) and harmonic frequencies (ω) very close to the experimental values for all dimers, improving the corresponding VMC results. The LRDMC forces with the RE approximation improve the VMC forces, implying that it is worth computing the DMC forces beyond VMC despite the higher computational cost. The LRDMC forces with the VD approximations also show improvement, which unfortunately comes at a much higher computational cost in all-electron calculations. We find that the ratio of computational costs between QMC energy and forces scales as Z∼2.5 without the SWCT. In contrast, the application of the SWCT makes the ratio independent of Z. As such, the accessible QMC system size is not affected by the evaluation of ionic forces but governed by the same scaling as the total energy one.

Evaluation on e-marketing exposure practice to minimize the customers’ online shopping purchase regret

As many of recent study showed that e-marketing activities lead into higher marketing performance such as sales, we believe that e-marketing should be evaluated in terms of its negative impact on marketing practices. This study aimed to evaluate e-marketing exposure and its impact on consumer behavior. Although we believed that marketing could lead a better purchase experience and sales, this study proposed that marketing could also lead into regretful experience to customers. In order to evaluate the regret model in online shopping activities, we proposed a behavioral model based on e-marketing exposure. In total, 400 participants were used in this study. Totally, 363 had regretful experience on online market and used in this study indicating 90.75% data used in this study. Data were collected through questionnaires given to online consumer. Data were analyzed through SEM-PLS as we employ 4-point forced likert scale, which lead to non-parametric analysis. As a result, we found that the excessive marketing exposure ultimately led to higher regret level to the customers. It is true that e-marketing exposure led to desirable behavior such as more rational at evaluating price and shaping a good image and perception toward the products; however, it also led to higher chance for impulsive buying behavior. This behavior led to purchasing regret. As we want to avoid regret as many as possible due to sustainable purchase and growth in the future, we must control e-marketing exposure so that it will not lead to regret on customers.

Analysis of direct force measurements during capillary pinching of visco-elastic fluids in CaBER type experiments

A novel device is presented for direct measurement of the axial force evolution during the pinching of fluid filaments following an extensional step stretch, based on the “tilted-CaBER.” The bending curve of a horizontally orientation fluid filament is fitted with the full expression of a catenary function, to directly and unambiguously extract the axial force from a single fitting parameter. The general limits of axial force determination from such devices are introduced in terms of a Bond number that accounts for the axial length scale. The new set-up is validated using a Newtonian PDMS oil, for which the axial force scaling and the related prefactors X of the similarity solution are known. For dilute polymer solutions in form of a Boger fluid, the so far theoretical factor X = 1.5 for an Oldroyd-B model fluid could be experimentally approached for the first time with the new setup.

ПОТЕНЦИАЛЬНАЯ РАБОЧАЯ СИЛА СОВРЕМЕННОЙ РОССИИ: СОЦИАЛЬНО-ДЕМОГРАФИЧЕСКИЙ ПОРТРЕТ И УРОВЕНЬ ОБРАЗОВАНИЯ

The study aims to determine the scale and socio-demographic characteristics of the potential labor force in the Russian labor market. The object of the study is the unemployed persons who want to get a paid job, but due to circumstances are limited in their search or desire to start it. The paper is based on new approaches to the study of economic inactivity of the population, enshrined in the “Resolution on Statistics of labor activity, Employment and Labor Underutilization” (ILO, 2013). For the analysis of statistical data, the author applies the methods of logical analysis and mathematical statistics. The results of the study showed that the size of the potential labor force in Russia is comparable to the scale of general unemployment. In the course of the research, the main sociodemographic characteristics of this population group were identified, indicating a high level of its human potential and, accordingly, the feasibility of developing measures to involve this category of the population in economic activity, since its representatives are balanced across all working ages, have a relatively high level of professional education (more than half graduated from an academic institution), low gender and inter-settlement asymmetry. The empirical basis of the study was the data of the Sample Labor Force Survey (LFS) conducted by Rosstat in 2010-2021. The author concludes that Federal executive authorities can use the research materials in developing state employment policy and academic institutions to prepare students and postgraduates in the “Labor Economics” specialty.

ASTRE: Prototyping Technique for Modular Soft Robots With Variable Stiffness

Soft robots are advantageous for human interaction because of their adaptability and safe interactivity. However, soft robots research entry is challenging due to the complex fabrication process of elastomeric materials with multiple channels. In this paper, we introduce a prototyping technique for fabrication-friendly soft robots using pneumatic artificial muscle(PAMs) and modular 3D printed reinforcement. We present three primitive deformation structures including bending, twisting, and contracting. Moreover, we propose a novel variable stiffness technique, altering PAMs contraction and radial expansion behavior into locking, malleable, and rotational brake features. We explore both the parallel and series arrangement of the reinforcement module, and we propose new kinds of mixing configurations and scaling techniques. We quantitatively verify the force scaling technique on different types of features. We demonstrate the feasibility of this prototyping technique through six application examples and conclude with a discussion of our research limitations and possible future improvements.

Synthesis of Germanium Nanospheres as High-Precision Optical Tweezers Probes.

Force spectroscopy on single molecular machines generating piconewton forces is often performed using optical tweezers. Since trapping forces scale with the particle volume, piconewton-force measurements so far required micron-sized probes practically limiting the spatiotemporal resolution. Here, we have overcome this limit by developing high-refractive index germanium nanospheres as ultraresolution trapping probes. With a refractive index of 4.4, their trapping efficiency and maximum force per power is more than 10-fold higher compared to silica spheres of equal size. Therefore, the use ofgermanium allows piconewton-force measurements with nanometer sized probes. Using 70-nm-diameter germanium nanospheres as trappable optical probes (GeNTOPs), we could show that kinesin-1 walks with 4-nm-center-of-mass steps. In the long-term, the application of these novel high-precision GeNTOPs will provide new insight into the working mechanism of molecular machines and are promising candidates for other applications in microscopy, optoelectronics, and nanophotonics.

A comparison of models of linear collisions between spherical particles in the pendular regime

This study examines granular collisions between spherical particles coated with a thin layer of viscous liquid, such that the capillary number is high and viscous forces dominate. Measurements were performed using high-speed particle tracking velocimetry. The measurements were used to examine four theoretical models that describe the collisions. The viscous force scales with the inverse of the separation distance between particles. The models limit the viscous force by setting a minimum approach distance. A fair match between experiments and simulations was obtained for all models by fitting this minimum approach distance. However, in some cases, to achieve a good match to the experiments, the minimum approach distance had to be set to a non-physical value. The best, and most physically reasonable, agreement was obtained when the viscous force accounted for the curvature of the surface and the minimum approach distance was determined using an empirically-fitted glass transition pressure model.

Tissue hydraulics: Physics of lumen formation and interaction.

Lumen formation plays an essential role in the morphogenesis of tissues during development. Here we review the physical principles that play a role in the growth and coarsening of lumens. Solute pumping by the cell, hydraulic flows driven by differences of osmotic and hydrostatic pressures, balance of forces between extracellular fluids and cell-generated cytoskeletal forces, and electro-osmotic effects have been implicated in determining the dynamics and steady-state of lumens. We use the framework of linear irreversible thermodynamics to discuss the relevant force, time and length scales involved in these processes. We focus on order of magnitude estimates of physical parameters controlling lumen formation and coarsening.

A Multiple-Output Hybrid Ship Trajectory Predictor With Consideration for Future Command Assumption

Onboard sensors contribute to data-driven understanding of complex and nonlinear ship dynamics in real time. By using sensors, precise ship trajectory prediction plays a key role in intelligent collision avoidance. A hybrid predictor makes prediction based on a mathematical model of which error is compensated by a black-box model. A Multiple-output Hybrid Predictor (MHP), which makes a long-horizon prediction at a time based on onboard sensor data, was developed in the previous study. However, it cannot handle a time series of future command assumption. This limitation hinders an MHP from being applied to the evaluation of future command assumption in the predictive decision making. A novel architecture of MHP presented in this study converts a long time series of future command assumption into a fixed-length model-based-predicted vessel state; then, it is included in inputs of a black-box error compensator. This idea is robust to multidimensionality of commands and long control horizon. Assuming a low-fidelity vessel model and a limited data are available, simulation experiments are conducted. The effect of environmental disturbances and maneuverings on the prediction performance is examined comprehensively for the first time. The present study successfully incorporates a long time series of future command assumption in an MHP. It reduces the mean error by 81.8% compared to a model-based predictor and by 45.6% compared to a data-driven predictor under Beaufort wind force scale 4 wave, wind, and ocean current. Present study expands the application of MHP to the predictive decision making of future autonomous ships.

Mechanisms for destabilisation of RNA viruses at air-water and liquid-liquid interfaces

Understanding the interactions between viruses and surfaces or interfaces is important, as they provide the principles underpinning the cleaning and disinfection of contaminated surfaces. Yet, the physics of such interactions is currently poorly understood. For instance, there are longstanding experimental observations suggesting that the presence of air-water interfaces can generically inactivate and kill viruses, yet the mechanism underlying this phenomenon remains unknown. Here we use theory and simulations to show that electrostatics may provide one such mechanism, and that this is very general. Thus, we predict that the electrostatic free energy of an RNA virus should increase by several thousands of kBT as the virion breaches an air-water interface. We also show that the fate of a virus approaching a generic liquid-liquid interface depends strongly on the detailed balance between interfacial and electrostatic forces, which can be tuned, for instance, by choosing different media to contact a virus-laden respiratory droplet. Tunability arises because both the electrostatic and interfacial forces scale similarly with viral size. We propose that these results can be used to design effective strategies for surface disinfection.

Nanoscale structural and mechanical characterization of thin bicontinuous cubic phase lipid films

The mechanical response of lipid membranes to nanoscale deformations is of fundamental importance for understanding how these interfaces behave in multiple biological processes; in particular, the nanoscale mechanics of non-lamellar membranes represents a largely unexplored research field. Among these mesophases, inverse bicontinuous cubic phase QII membranes have been found to spontaneously occur in stressed or virally infected cells and to play a role in fundamental processes, such as cell fusion and food digestion. We herein report on the fabrication of thin ( ̴150 nm) supported QII cubic phase lipid films (SQIIFs) and on their characterization via multiple techniques including Small Angle X-Ray Scattering (SAXS), Ellipsometry and Atomic Force Microscopy (AFM). Moreover, we present the first nanomechanical characterization of a cubic phase lipid membrane, through AFM-based Force Spectroscopy (AFM-FS). Our analysis reveals that the mechanical response of these architectures is strictly related to their topology and structure. The observed properties are strikingly similar to those of macroscopic 3D printed cubic structures when subjected to compression tests in material science; suggesting that this behaviour depends on the 3D organisation, rather than on the length-scale of the architecture. We also show for the first time that AFM-FS can be used for characterizing the structure of non-lamellar mesophases, obtaining lattice parameters in agreement with SAXS data. In contrast to classical rheological studies, which can only probe bulk cubic phase solutions, our AFM-FS analysis allows probing the response of cubic membranes to deformations occurring at length and force scales similar to those found in biological interactions.

A survey of physical methods for studying nuclear mechanics and mechanobiology.

It is increasingly appreciated that the cell nucleus is not only a home for DNA but also a complex material that resists physical deformations and dynamically responds to external mechanical cues. The molecules that confer mechanical properties to nuclei certainly contribute to laminopathies and possibly contribute to cellular mechanotransduction and physical processes in cancer such as metastasis. Studying nuclear mechanics and the downstream biochemical consequences or their modulation requires a suite of complex assays for applying, measuring, and visualizing mechanical forces across diverse length, time, and force scales. Here, we review the current methods in nuclear mechanics and mechanobiology, placing specific emphasis on each of their unique advantages and limitations. Furthermore, we explore important considerations in selecting a new methodology as are demonstrated by recent examples from the literature. We conclude by providing an outlook on the development of new methods and the judicious use of the current techniques for continued exploration into the role of nuclear mechanobiology.

TRADE DEFICIT IN NEPAL: A REVIEW ON CURRENT TRADE DEFICIT, CAUSES AND SOLUTIONS

With globalization, world trade has been growing at a rapid pace. In most developing countries like Nepal, the problem of trade deficit has always been a part of the concern. The objective of this paper is to articulate the historical trend of the trade deficit in Nepal, the major imports and exports, the causes of the trade deficit, and some recommendations to solve the trade deficit. Nepal expanded its trade relationship after becoming a member of WTO on 23rd April 2004. Nepal mainly exports readymade garments, pashmina products, leather products, pulses, handicrafts, spices, medicinal herbs. The main imports are cereals, vehicles, pharmaceuticals, Mineral fuels, oils, iron &amp; steel, plastics, gems, machinery. Major trading partners of Nepal are India, China, the USA, UAE, Canada, Indonesia, Argentina, France, Malaysia, and Ukraine. In the fiscal year 2019/20, imports decreased by 15.63%, and export increased by 0.62%. As a result, the total trade deficit decreased by 16.83%. Landlockedness, higher production cost, political instability, devaluation of currency are the factors impeding Nepal from coming out from the labyrinth of trade deficit. Fortification of the agricultural sector, focus on hydropower, improvement of infrastructures, modified trade policy, prioritization on export potential goods can solve the trade deficit. The country should strive towards specialization, strengthening the rural economy, gaining economies of scale, exploiting entrepreneurial and management skills of the labor force.

Kinematics of sea star legged locomotion.

Sea stars have slower crawling and faster bouncing gaits. Both speed and oscillation amplitude increase during the transition from crawling to oscillating. In the bouncy gait, oscillating vertical velocities precede oscillating horizontal velocities by 90 deg, as reflected by clockwise circular hodographs. Potential energy precedes horizontal kinetic energy by 9.6 deg and so they are nearly in phase. These phase relationships resemble terrestrial running gaits, except that podia are always on the ground. Kinetic and potential energy scale with body mass as Mb 1.1, with the change in kinetic energy consistently two orders of magnitude less, indicating that efficient exchange is not feasible. Frequency of the bouncy gait scales with Mb-0.14, which is similar to continuously running vertebrates and indicates that gravitational forces are important. This scaling differs from the Hill model, in which scaling of muscle forces determine frequency. We propose a simple torque-stabilized inverted pendulum (TS-IP) model to conceptualize the dynamics of this gait. The TS-IP model incorporates mathematics equivalent to an angular spring, but implemented by a nearly constant upward force generated by the podia in each step. That upward force is just larger than the force required to sustain the underwater weight of the sea star. Even though the bouncy gait is the rapid gait for these sea stars, the pace of movement is still very slow. In fact, the observed Froude numbers (10-2 to 10-3) are much lower than those typical of vertebrate locomotion and are as low or lower than those reported for slow-walking fruit flies, which are the lowest values for pedestrian Froude numbers of which we are aware.