Euler Force Research Articles

Euler Force-Driven Siphon Valve Control for Precise Sequential Release in Centrifugal Microfluidic Chips

Controlling the fluids in centrifugal microfluidic chips for precise sequential release is critical for multi-step reactions and immunoassays. Currently, the traditional methods of liquid sequential release mainly rely on various types of microvalves, which face the problems of complex operation and high costs. Here, this work presents a method for driving liquid release using the Euler force. Under continuous acceleration and deceleration, the centrifugal and Euler forces can transfer the liquid from the sample chamber to the collection chamber. The liquid sequential release mechanism based on the Euler force was analyzed, which showed that the angular acceleration is key to the liquid release. Then, the geometrical parameters affecting the angular acceleration of complete release were investigated and simulated. Finally, based on the relationship between the geometrical parameters of the connecting channels and the angular acceleration of complete release, a simple and precise sequential release structure was designed, which allowed for a sequential and stable transfer of the liquid into the reaction chamber. The results showed that the proposed method is capable of transferring liquid, and its simple structure, low manufacturing cost, and ease of operation enable precise sequential liquid release in centrifugal microfluidic platforms.

The Dzhanibekov Effect as a Possible Source of Magnetar Activity

Magnetars, which are neutron stars with strong magnetic fields, exhibit occasional bursting activities. The shape of a magnetar is not perfectly spherical due to the Lorentz force exerted by its strong magnetic fields and is described as a triaxial body. We study the unstable free precession in a triaxial magnetar; one of the principal axes undergoes an upside-down flip. This flip is known as the Dzhanibekov effect. We find that during the flip, the Euler force can suddenly disturb the force balance on the surface layer of the magnetar, potentially leading to plastic flow of the layer. This, in turn, may trigger different forms of magnetar activity, such as the emission of the bursts and/or of gravitational waves.

Biofusion design and parameter optimization for a novel passive assisted knee exoskeleton robot based on eight-bar mechanism

Abstract In an effort to alleviate the issue of knee joint fatigue and injury during lower limb ambulation, a novel passive assisted exoskeleton robot with human–machine interaction is investigated to assist the movement of the human knee joint. The design of the exoskeleton configuration takes into consideration the physiological structure and gait function of the knee joint, ensuring that it satisfies the requirements for motion, force, and gait function of the knee joint. To explore the interaction between the wearer and the exoskeleton, a human–machine kinematic model after wearing exoskeleton is established, which is instrumental in analyzing the integration motion of the wearer and exoskeleton. In addition, the dynamic and static models of the knee joint after wearing the exoskeleton are established, utilizing the Newton–Euler method and force polygon method, respectively, to evaluate the effectiveness of the exoskeleton. Moreover, the size parameters and spring stiffness of the exoskeleton are optimized, using both human body kinematic model and mechanic model. Furthermore, the effectiveness of the exoskeleton in proving assistance is evaluated through human body simulation, using OpenSim. The results indicate that the exoskeleton significantly reduces the knee joint torque by 48.42%.

Lab on a bead with oscillatory centrifugal microfluidics for fast and complete mixing enables fast and accurate biomedical assays

Rapid mixing and precise timing are key for accurate biomedical assay measurement, particularly when the result is determined as the rate of a reaction: for example rapid immunoassay in which the amount of captured target is kinetically determined; determination of the concentration of an enzyme or enzyme substrate; or as the final stage in any procedure that involves a capture reagent when an enzyme reaction is used as the indicator. Rapid mixing and precise timing are however difficult to achieve in point-of-care devices designed for small sample volumes and fast time to result. By using centrifugal microfluidics and transposing the reaction surface from a chamber to a single mm-scale bead we demonstrate an elegant and easily manufacturable solution. Reagents (which may be, for example, an enzyme, enzyme substrate, antibody or antigen) are immobilised on the surface of a single small bead (typically 1–2 mm in diameter) contained in a cylindrical reaction chamber subjected to periodically changing rotational accelerations which promote both mixing and uniform mass-transfer to the bead surface. The gradient of Euler force across the chamber resulting from rotational acceleration of the disc, dΩdisc/dt, drives circulation of fluid in the chamber. Oscillation of Euler force by oscillation of rotational acceleration with period, T, less than that of the hydrodynamic relaxation time of the fluid, folds the fluid streamlines. Movement of the bead in response to the fluid and the changing rotational acceleration provides a dynamically changing chamber shape, further folding and expanding the fluid. Bead rotation and translation driven by fluid flow and disc motion give uniformity of reaction over the surface. Critical parameters for mixing and reaction uniformity are the ratio of chamber radius to bead radius, rchamber/rbead, and the product Trchamber(dΩdisc/dt), of oscillation period and Euler force gradient across the fluid. We illustrate application of the concept using the reaction of horse radish peroxidase (HRP) immobilised on the bead surface with its substrate tetramethylbenzidine (TMB) in solution. Acceleration from rest to break a hydrophobic valve provided precise timing for TMB contact with the bead. Solution uniformity from reaction on the surface of the bead in volumes 20–50 uL was obtained in times of 2.5 s or less. Accurate measurement of the amount of surface-bound HRP by model fitting to the measured kinetics of colour development at 10 s intervals is demonstrated.

Experimental and numerical investigation of flow dynamics in an upward bubbly flow in a tube undergoing oscillating rolling motion

Offshore nuclear power plants are characterized by a potential oscillatory motion depending on ocean waves. Investigating the local flow behavior in a system undergoing oscillating motion is necessary. In particular, because the local void fraction near the heating element surface significantly affects the nucleating boiling heat transfer and critical heat flux, understanding the dynamic behavior of the local void fraction is very important. Therefore, in this study, as an essential first step in predicting boiling heat transfer and departure from nucleate boiling in offshore nuclear reactors, the dynamic behavior of air–water bubbly flows has been experimentally and numerically investigated in a tube under oscillatory rolling conditions. An optical fiber Doppler probe was used to measure the local bubble parameters. The effects of the rolling period on the void fraction distributions, bubble sizes, and bubble velocities were insignificant. However, the rolling amplitude effect was significant. The void fraction was the highest at the downward-facing wall when the tube was at its maximum tilt. Moreover, the local water velocity became the highest when the tube returned to near vertical because of the combined effect of gravity and Euler force. These findings provide insights into understanding the characteristics of bubbly flow in a rolling tube.

Numerical investigation of departure from nucleate boiling for subcooled flow boiling in a rolling tube

A crucial issue in floating nuclear plants is the critical heat flux (CHF) under oscillatory conditions by ocean waves. CHF must be predicted considering the dynamic motion of the floating platform. We present numerical simulations for predicting the DNB (departure-from-nucleate-boiling)-type CHF of subcooled R134a flow in a rolling tube and provide physical insight into the dynamic flow behavior regarding the DNB, considering rolling amplitudes of 15°, 30°, and 40° and a rolling period of 6 s. The local wall temperature and void fraction depended mainly on the dynamic changes in the gravitational direction. Gravity had the effect of lowering DNB. The Euler force created a secondary liquid flow that somewhat reduced the liquid temperature at the heating wall during the rolling period, thereby enhancing the convective and quenching heat fluxes. Furthermore, the secondary flow rapidly increased the liquid area fraction at the overheated wall and decreased the temporarily increased wall temperature before DNB occurred. The secondary flow had the effect of increasing DNB. In this study, the effect of increasing the DNB value is greater than the effect of reducing the DNB value. The occurrence of DNB depended on sufficient cooling of the downward-facing wall during the rolling period.

Sagnac effect and EMF in heavy-electron materials: Revisitation of Coriolis force and Euler force

The “inertial mass” mi in the equation of motion to describe a carrier is usually m∗≠m0 where m0=9.1×10-31kg is the rest mass of an electron in free space. The aim of this paper is to study its “gravitational mass” mG and test the weak equivalence principle (WEP) mi=mG in condensed matter physics. First, the inertial forces in rotating systems are not 2miv×Ω and -miΩ̇×r. They should be 2mGv×Ω and -mGΩ̇×r. Secondly, we use the Sagnac effect and electromotive force (EMF) to determine the coefficient and compare with mi. Finally, the quantum energy levels caused by rotation are presented. The energies rely on the “gravitational mass”-to-“inertial mass” ratio mGmi=m0m∗≠1.

Modular design of centrifugal microfluidic system and its application in nucleic acid screening

Modular integration of functional components on the chip and increasement in control accuracy through real-time alteration in the force direction of droplets is an effective way to optimize centrifugal microfluidic systems and realize passive components, compact modules, and high-throughput control. Conventional centrifugal microfluidic chips are mainly driven and controlled by centrifugal force and Euler force. The control valves are easily affected by machining precision, making the control unstable. In this study, a novel centrifugal microfluidic system is introduced to improve the freedom and accuracy of chip control while facilitating the design and addition of passive functional components. Furthermore, we modularize the centrifugal microfluidic chip to greatly shorten the period of design and optimization cycle and achieve chip reusability and multi-threaded control. Finally, to verify the feasibility of the modular centrifugal microfluidic chip applied to high-throughput nucleic acid screening, we test the nucleic acid purification and detection colorimetric reactions based on the modular centrifugal microfluidic chip. Among them, Chelex-100 is used to realize the purification of nucleic acid in cell lysate, and the purified solution can realize amplification in the PCR instrument, and the nucleic acid detection results are consistent with the off-chip kit by experimental testing. The system has great flexibility and stability under the acceptable purity of nucleic acid, which indicates that the platform has great potential for large-scale rapid screening applications.

SOLVING THE PROBLEM OF LONGITUDINAL BENDING OF A ROD BY METHODS OF DISCRETE CALCULUS OF VARIATIONS

The question of the longitudinal bending of a rod consisting of rigid links connected by hinges is being studied. It is shown that, as in the classical version of a solid rod, the problem can be posed as a variational minimum energy problem, but given by a functional defined on a class of functions with a discrete domain of definition. The main provisions of the classical calculus of variations are transferred to functionals of this type: the formula of variation is found, a generalization of the main lemma of the calculus of variations is proved, an analogue of the Euler equation, which is a difference equation, is obtained. Applying the results obtained and the known properties of classical difference equations, we succeeded in solving an analogue of the Euler problem for two types of a hinge rod: for a rod consisting of links of the same length, and for an arbitrary choice of lengths of links. In both cases we find the critical Euler force, as well as the equation and the form of the deflection curve.

Enhancing Mixing Performance in a Rotating Disk Mixing Chamber: A Quantitative Investigation of the Effect of Euler and Coriolis Forces.

Lab-on-a-CD (LOCD) is gaining importance as a diagnostic platform due to being low-cost, easy-to-use, and portable. During LOCD usage, mixing and reaction are two processes that play an essential role in biochemical applications such as point-of-care diagnosis. In this paper, we numerically and experimentally investigate the effects of the Coriolis and Euler forces in the mixing chamber during the acceleration and deceleration of a rotating disk. The mixing performance is investigated under various conditions that have not been reported, such as rotational condition, chamber aspect ratio at a constant volume, and obstacle arrangement in the chamber. During disk acceleration and deceleration, the Euler force difference in the radial direction causes rotating flows, while the Coriolis force induces perpendicular vortices. Increasing the maximum rotational velocity improves the maximum rotational displacement, resulting in better mixing performance. A longer rotational period increases the interfacial area between solutions and enhances mixing. Mixing performance also improves when there is a substantial difference between Euler forces at the inner and outer radii. Furthermore, adding obstacles in the angular direction also passively promotes or inhibits mixing by configuration. This quantitative investigation provides valuable information for designing and developing high throughput and multiplexed point-of-care LOCDs.

Numerical Study of the Effect of the Rolling Motion on the Subcooled Flow Boiling in the Subchannel

The marine environment may change the force on the fluid and inevitably influence bubble behavior and the two-phase flow in the reactor core, which are vital to the safety margin of a nuclear reactor. To explore the effect of the marine motion on the flow and heat transfer features of subcooled flow boiling in the reactor core, the volume of fluid (VOF) method is employed to reveal the interaction between the interface structure and two-phase flow in the subchannel under rolling motion. The variations of several physical parameters are obtained, including the transverse flow, the vapor volume fraction, the vapor adhesion ratio, and the phase distribution of boiling two-phase flow with time. Sensitivity analyses of the amplitude and the period of the rolling motion were performed to demonstrate the mechanisms of the influence of the rolling motion. We found that the transverse flow in the subchannel was mainly affected by the Euler force under the rolling motion. In contrast to the two-phase flow in the static state, the vapor volume fraction and vapor adhesion ratio show different characteristics under rolling motion. Additionally, the onset of significant void (OSV) point changes periodically under rolling motion.

Euler force-assisted sequential liquid release on the centrifugal microfluidic platform

The sequential release of liquid is essential for the automation of multistage biochemical analyses, such as immunoassays and nucleic acid extraction. Current methods for sequential liquid release are either too complicated owing to the bulky external control component or lack of flexibility. The Euler force can be flexibly adjusted on centrifugal platforms; this characteristic has great potential for developing interior force-triggered valves, increasing the methods for liquid manipulation in centrifugal microfluidic devices. In this study, a Euler force-assisted method is proposed to realize sequential liquid release in a convenient and flexible manner. The Euler force-assisted siphon valve proposed in this study has an ascent part of the siphon channel for priming by Euler force and a descent part for priming by capillary forces so that this siphon can be actively actuated by acceleration. With a certain channel size and angle, siphons with different lengths of the ascent channel can be triggered by different Euler forces, making the controllable release of liquid with different accelerations possible. By the simple combination of this kind of siphon, multiple unit operations can be realized, including sequential release, selective distribution, interruptible priming, and multistep immunoassay. This suggests that Euler force-assisted siphon priming can be a simple but efficient solution for complex liquid manipulation on the centrifugal microfluidic platform.

STRENGTH OF SHIPS’ GRILLAGES UNDER LATERAL LOAD AND IN-PLANE COMPRESSION

The paper deals with strength of a grillage loaded by lateral load and in-plane compression load (in one direction). It consists of a system of prismatic girders crossing under 90°. The compression load is taken by the longitudinal girders that are elastically fixed on rigid supports. The system of aggregated differential equations is derived for solution of the problem using the Lagrange method. It allows for replacement of the system of aggregated differential equations by a system of independent differential equations. These equations for the case of simultaneous action of lateral and longitudinal compression load have the form of differential equations for bending of prismatic girders laying on elastic foundation and loaded with lateral and longitudinal compression forces. When only lateral load exists, the form of these equations coincides with the form of differential equations for bending of girders laying on elastic foundation and loaded with lateral load alone. When only longitudinal compression load exists, the form of these equations coincides with the form of differential equations for buckling of girders laying on elastic foundation.
 Solutions are given for bending of a grillage (the first two problems). Formulas are derived for calculation of the parameters of longitudinal girders’ bending when girders’ end sections are elastically fixed. Also, formulas are derived for calculation of the reaction forces at cross-points of transverse and longitudinal girders. When only longitudinal compression load exists (third problem), a solution is given for the connection between the coefficient of elastic foundation’s rigidity and the Euler force. Results obtained by using the proposed method are compared with FEA simulations.

Migration Behavior of Low-Density Particles in Lab-on-a-Disc Devices: Effect of Walls.

The effect of the lateral walls of a Lab-On-a-Disc device on the dynamics of a model system of particles with a density lower than that of the solvent (modelling parasites eggs) is analyzed theoretically and experimentally. In the absence of lateral walls, a particle always moves in the direction of the centrifugal force, while its trajectory is deflected in the tangential direction by the inertial Coriolis and Euler forces. Lateral walls, depending on the angle forming with the radial direction, can guide the particle either in the same or in the opposite direction to the centrifugal force, thus resulting in unusual particle trajectories including zig-zag or backwards particle motion. The effect is pronounced in the case of short operation times when the acceleration of the angular rotation, and thus the Euler force, is considerable. The predicted unusual motion is demonstrated by numerically solving the equation of motion in the presence of lateral walls and verified in the experiment with particles of density lower than that of the solvent. Our analysis is useful for design and operational considerations of Lab-On-a-Disc devices aiming for or involving (bio)particle handling.

Bearing Capability for Mirco-Pile with Concrete-Filled Steel Tubular Reinforced Building Foundation

In general, the bearing capability is strength capability for mirco-pile. The stability bearing capability for mirco-pile with concrete-filled steel tubular becomes important in reinforced building foundation. The theory of buckling stability is applied to study the bearing capability of mirco-pile. According to the character of concrete filled steel tubular, the Euler force and the friction between pile and soil are combined for the buckling bearing capability of mirco-pile with concrete-filled steel tubular. The equation of mirco-pile with concrete-filled steel tubular is confirmed by some test data and numerical simulation. The slenderness ratio and material strength took great effects on the bearing capability of mirco-pile with concrete filled steel tubular. The equation on bearing capability mirco-pile with concrete filled steel tubular is applied for reinforce building foundation and referred to other application of concrete filled steel tubular.

Fatigue predictions for flexible marine propellers using FSI analysis considering Euler force in the rotating frame

Analysis of flexible marine propellers in terms of their structural response and stress is the key to accurate fatigue prediction. At present, finite element method (FEM) analyses of flexible propellers have been performed as a part of the fluid–structure interaction (FSI) analysis using a numerical method for the flexible structures, which is identical to that used for their rigid counterparts. In this study, the Euler force in a rotating frame is employed as an additional external force on the blades of the marine propeller during the FSI analysis. The Euler force is an inertial force component in the rotating frame due to angular acceleration. Acceleration of the rotating frame arises from large deformations of the propeller due to its flexible characteristics. The angular acceleration of the propeller is obtained for each time step, and the resulting Euler force is accounted for as a body force. The FSI analysis results are compared to experimental results in terms of the structural response, stress, and fatigue. It is clear that the Euler force has a major effect on the fatigue characteristics of the propeller because it amplifies the main response components. In conclusion, incorporating the Euler force in FSI analyses of flexible marine propellers is necessary for adequate prediction of the propeller fatigue.

Modelling shows that stimulation of the semicircular canals depends on the rotation centre

The vestibular system in the inner ear senses head movements, which is indispensable for balance during locomotion. The semicircular canals of the vestibular system are stimulated during head rotations, due to the interplay between its endolymph fluid and its cupula membrane. Until now, it has been assumed that the stimulation of the canals is independent of the rotation centre. However, Fluid-Structure Interaction investigation now shows that the horizontal canal is more strongly stimulated when the rotation centre lies further from the canal. Such eccentric rotations result in a different stimulation of the left and the right canal, because the distance to the rotation centre differs between both ears. The dissimilar stimulation enables localization of the rotation centre based on information from the canals alone, similar to sound localization based on the interaural time difference for hearing. Additionally, a rotation centre further away from the canal will probably elicit a larger reflexive eye movement. This is exactly what is required to compensate the larger change in viewing angle, and it corresponds to experimental findings. Two fictitious forces (d'Alembert forces), the centrifugal force and the Euler force, cause the rotation centre-dependency of the canal stimulation. Implications for (pre)clinical eccentric rotation experiments are discussed.

Comment on “On the account of surface tension nonlinearity under of nano-plate bending”

Examples of solving a nonlinear one-dimensional problem on bending, compressive buckling, and free transverse vibrations of a nano-film, considered in the commented article, have shown primarily the effect of the linear part of surface tension, where it is main, whereas its quadratic terms make a small contribution. In the present paper was considered postbuckling of the nano-film, when the known von Kármán-type models of nano-plate bending reduce to a linear problem and allow only the critical Euler force to be determined. The proposed model allows to describe post-buckling fully, in particular to build the load-deflection ratio.

STUDY OF THE STRAIN STATE AND MOVEMENTS OF A FLEXIBLE ROD WITH INITIAL CURVATURE

Abstract. Aim. The possibility of obtaining the regressive part of the elastic (regressiveprogressive) characteristic under axial loading in the initial period is studied by applying an elastic rod having an initial curvature under vertical compressive load. The objective of the study is to determine the static characteristics of such a rod without taking the resistance forces into account. Method. To solve the problem, the elliptic parameters method was used to make a comparison with a solution obtained using the finite element method in the ANSYS engineering simulation software. Results. A technique was developed for assessing the strain state and displacements of a flexible rod with initial curvature in order to study the regression-progressive characteristic of various elastic systems having initial curvature for their effective use in determining oscillations. Conclusion. The obtained technique can be used to determine the deformed state of an elastic flexible rod having initial curvature and displacement of the point of application of force. At the same time, by setting various initial parameters of the flexible rod in order to obtain a regressive-progressive characteristic, significant displacements can be obtained in the subcritical region when the axial load does not exceed the Euler force for this flexible rod

Multi-objective optimization and linear buckling of serial chain of a medical robot tool for soft tissue surgery

<p>The slender structures of a medical robot may have a tendency to buckling when a force equal to the critical Euler force and an additional disturbance will work on their structures. In this work, eigenvalue problem that describes the linear buckling is under consideration. The main goal of the article is to check when linear buckling phenomenon appears in construction of a medical robot with serial chain due to the fact that for safety reasons of a robot’s work, it is necessary to answer the question, whether the buckling may occur in the robot’s structure. For this purpose, a numerical calculation model was defined by using the finite element method. The values of load factor coefficients that are eigenvalue are determinated and also the eigenvectors that have shapes of deformation for the next eigenvalues are presented. The multi-criteria optimization model was determined to aim for the minimum mass of the effector and the buckling coefficient, from which the Euler force results, for the maximum. The solution was obtained on the basis of Pareto fronts and the MOGA genetic algorithm.</p>