Restoration Force Research Articles

A Study on Failure Judgement Criteria Based on Ball Joint Restoration Force of Automotive Stabilizer Links

A Study on Failure Judgement Criteria Based on Ball Joint Restoration Force of Automotive Stabilizer Links

Radiation generation from an array of magnetized anharmonic carbon nanotubes

An investigation into second-harmonic generation from magnetized anharmonic carbon nanotubes (CNTs) mounted on a silica substrate is conducted using a Gaussian laser pulse with modulated amplitude. An intense amplitude-modulated laser pulse incident on the array of CNTs displaces their electrons generating a restoration force. This restoration force is the nonlinear function of displacement of electrons, which ensures the anharmonic behavior of CNTs. Using the paraxial ray approximation, the nonlinear interaction of the incident pulse with CNTs is expressed in terms of a wave equation derived using the perturbative technique. The nonlinear current at second-harmonic frequency arises due to the perturbation of the electron density of CNTs by the ponderomotive force exerted on them by an incident pulse. Numerical outcomes validate the enhanced efficiency of the generated harmonic when considering the phenomenon of self-focusing. With the substantial optical nonlinearities of an anharmonic CNT structure, the plasmon resonance is broadened and high efficiency in generating harmonics is attained. It is seen that the augmenting of the amplitude-modulated parameter of the pulse and the external magnetic field strength enhances system nonlinearity, resulting in increased amplitude of generated second harmonics. Additionally, the effect of the heating rate of CNTs on the efficiency of the generated harmonic is also discussed.

Interaction of spatial-Gaussian lasers with the magnetized CNTs in the presence of DC electric field and enhanced THz emission

The interaction of spatial-Gaussian lasers with magnetized carbon nanotubes (CNTs) in the presence of a DC electric field is shown to broaden the surface plasmon resonance effectively. The prime feature of the interaction of lasers with magnetized CNTs is that when the electron cylinder of CNT is shifted with respect to the ion cylinder, the space charge electric field is developed in the overlapped region and results in the restoration force of the electrons. The restoration force along with the ponderomotive and magnetic forces assist to increase the nonlinear current which is further enhanced by the drift velocity acquired by the electrons of CNTs due to the applied static electric field. This action is also responsible for the enhanced THz yield at surface plasmon resonance condition where is the polarization coefficient, is the relative permittivity of the dielectric substrate, is the cyclotron frequency of CNT electrons and is the plasma frequency. The study reveals that THz generation from the magnetized CNTs may be a promising source for the detection of dangerous chemicals like royal demolition explosive (RDX), pentaerythritol tetra-nitrate (PETN), trinitrotoluene (TNT), etc.

Interaction of obliquely incident lasers with anharmonic CNTs acting as dipole antenna to generate resonant THz radiation

The present paper explores the terahertz (THz) generation by the interaction of obliquely incident laser beams with the array of vertically aligned anharmonic carbon nanotubes (CNTs) acting as dipole antennas. In the scheme, anharmonicity arises due to the nonlinear variation of restoration force on the various electrons of CNTs and it plays a key role in the enhancement of THz generation. The anharmonic CNTs help in broadening the resonance peak, which paves the way for the enhancement of the normalized THz amplitude. The laser beams incident obliquely on the close-packed array of vertically aligned anharmonic CNTs grown over the glass substrate and set oscillations in the CNTs so that each CNT act as the oscillatory dipole to generate THz radiation. The THz electric field shows enhancement at surface plasmon resonance frequency , where is the characteristic parameter of CNTs, is the relative permittivity of lattice and is the plasma frequency. This scheme is quite suitable to generate THz radiations in the milliwatt range of optimized values of the laser and CNTs parameters. We also explore the impact of polarization, S-parameter, critical angle, and length-matching effects of CNT antennas on the THz generation.

Resonant excitation of THz radiations by the interaction of amplitude-modulated laser beams with an anharmonic CNTs in the presence of static D.C. electric and magnetic fields

We proposed an alternative scheme for the generation of terahertz (THz) radiation by using the rectangular array of horizontally aligned hollow anharmonic carbon nanotubes (CNTs) embedded on the base of the dielectric surface. Two transversely amplitude-modulated filamented laser beams interact with this array of CNTs in the presence of static D.C. electric and magnetic fields acting mutually perpendicular to each other as well as to the direction of propagation of the laser beams. Due to the non-uniform density of electrons in CNTs, the restoration force on the different electrons is different and this results in anharmonicity. This anharmonicity broadens the resonance peak. The laser beams also exert space periodic ponderomotive force and beat frequency ponderomotive force on the electrons of CNTs. Space periodic ponderomotive force is well balanced by the pressure gradient force to form a transverse density ripple. Nonlinear coupling between D.C. drift velocity of electrons and electron density in the plasma of CNTs results in enhancement in the generation of THz radiation. We have found that the normalized THz amplitude increases significantly with the increase of applied electric field from 10kV/cm to 20kV/cm and magnetic field from 11.50kG to 24.50kG.

Structure-Function Relationships in Muscle Fibres: MyoRobot Online Assessment of Muscle Fibre Elasticity and Sarcomere Length Distributions.

Muscle biomechanics is set by the spacing of repetitive striation patterns of individual sarcomeres within single muscle fibres of stacked myofibrils. Sarcomere lengths (SL) are rather unequally distributed than of equal distance. This non-uniformity may affect both, force production as well as passive-elastic deformation. However, online recording of SL during axially imposed strains is cumbersome due to a lack of compact technologies. To fuse SL pattern recognition with restoration force assessments during quasi-static axial stretch, we implemented live tracking of SL distributions simultaneous to voice-coil actuated stretch and restoration force recordings in our MyoRobot 2.0 automated biomechatronics platform. Both were obtained online during stretch-relaxation cycles of murine single muscle fibres. Under quasi-static stretch conditions ( ∼1 μm/s fibre length changes), almost no apparent hysteresis was detected in single fibres. SL showed a non-uniform distribution. While mean SL varied between 2.6 μm and 3.4 μm upon 140% stretch, two populations of fibres were noticed: one showing a minor change in SL distribution with stretch, and one becoming more equally distributed upon stretch. A roughly 5% SL variability under rest either diminishes or remains almost unaltered upon elastic axial deformation. This may reflect differential impact of mostly extra-sarcomeric components to stretch in this stretch range. The augmented functionality of the MyoRobot 2.0 towards online sarcomere analyses within single fibres shall provide a valuable tool for the muscle community to study the contribution of serial elastic and force producing elements in health and disease models.

Complementary Vacuum Field Emission Transistor

A complementary vacuum field emission device structure is proposed, and its operation is analyzed by multiphysics simulation. A freely moving double-clamped cantilever, which balances the electrostatic attraction force and elastic restoration force, is used as the source electrode while the drain electrode is fixed. The electron-emitting cathode is formed on the source for the n-type device and on the drain for the p-type. Thus, complementary current–voltage characteristics are obtained only with Fowler–Nordheim tunneling electron transport. The impact of various design parameters such as vacuum gap, cantilever beam thickness, gate width, and tip offset on the drain and gate leakage currents is investigated. Inverter logic operation is verified successfully using complementary devices.

Fabrication and Characterization of Roll-to-Roll-Coated Cantilever-Structured Touch Sensors.

It is common in the field of printed electronics that polydimethylsiloxane (PDMS) be used as a dielectric layer for capacitive sensors because of its high elasticity and restoration force. However, capacitive sensors with the PDMS dielectric layer have a lower sensitivity than those with an air-gap structure that has been fabricated by the conventional micro-electromechanical system (MEMS) process. This paper presents a productive method for fabricating air-gap structures for touch sensors by roll-to-roll slot-die coating. The air-gap is formed by coating and removing a sacrificial layer. Cantilever-structured capacitive touch sensors with an air-gap are fabricated as follows: First, the bottom electrode, the dielectric layer, and the poly(vinyl alcohol) (PVA) sacrificial layer are roll-to-roll slot-die-coated on a flexible substrate. In addition, the spacer layer is spin-coated. On the sacrificial and spacer layers, the top electrode and structural layer are formed by spin-coating. Then, the air-gap and cantilever structure are made by removing the sacrificial layer in water. The cantilever-structured sensor samples are examined in terms of sensitivity, hysteresis, and repeatability. In particular, the electrical performance of the samples is compared to those with the PDMS dielectric layer. Experimental results show that the cantilever-structured sensor samples have significantly higher sensitivity compared to those with the PDMS dielectric layer.

Dynamic Analysis of Semi-submersible Under the Postulated Failure of Restraining System with Buoy

Coupled dynamic analyses of a deep-water Semi-submersible platform, in the South China Sea region, is carried out under postulated damage of the restraining system for both 10 and 100-years return period events. Under the combined action of wind, wave, and current loads, motion responses of Semi-submersible at 1500 and 2000 m water depths are analyzed in time-domain. Dynamic tension variations in the mooring lines are investigated for a fatigue failure using the S–N curve approach. Inclusion of a submerged buoy in the mooring system resulted in a marginal increase of the response due to a reduction in the restoration force of the mooring lines; submerged buoy also resulted in additional damping. The results of numerical studies showed an increase in tension in the mooring lines, which are adjacent to the damaged ones, causing reduced fatigue life. With the inclusion of submerged buoy in the mooring system, there is a considerable decrease in tension variation in mooring lines, increasing fatigue life. Failure of a mooring line causes an increase in tension of the adjacent mooring line, but not valid under all circumstances. It is seen from the studies that despite the postulated failure induced in a mooring, the adjoining line remains unaffected due to a steady coupling motion of the platform.

Analytical Approach to the Surface Plasmon Resonance Characteristic of Metal Nanoparticle Dimer in Dipole-Dipole Approximation

This theoretical study deals with the effect of bi-particle interaction on the surface plasmon resonance (SPR) in a dimer which includes two identical metal nanoparticles (NPs). Considering the dipole-dipole interaction in a Drude-like model, an appropriate equation is derived for the permittivity of each NP. The restoration force related to the classical confinement originating from the finite size of NPs is considered, and an appropriate adjustment coefficient is considered for this term through analyzing experimental data. Two different polarizations are considered for the laser beam electric field, and it is shown that the orientation of the electric field has an essential role in the linear optical properties of a dimer. Numerical investigation is accomplished for a dimer of gold NPs with two different diameters of 4 nm and 20 nm. For the parallel polarization, dipole-dipole interaction leads to the redshift of SPR wavelength and increase in its peak value, while for the perpendicular polarization, the absolute opposite results are derived. For all cases, it is shown that SPR wavelength functionality with respect to the geometric factor a/d (NP radius to the separation) can be presented by a cubic equation that fits better than an exponential one suggested by the earlier studies which demonstrates the dipole-dipole characteristic of the interaction. Qualitatively, our results are in good agreement with the other experimental studies.

Modified Drude model for small gold nanoparticles surface plasmon resonance based on the role of classical confinement

In this paper, we study the effect of restoration force caused by the limited size of a small metallic nanoparticle (MNP) on its linear response to the electric field of incident light. In a semi-classical phenomenological Drude-like model for small MNP, we consider restoration force caused by the displacement of conduction electrons with respect to the ionic positive background taking into account a free coefficient as a function of diameter of nanoparticle (NP) in the force term obtained by the idealistic Thomson model in order to adjust the classical approach. All important mechanisms of the energy dissipation such as electron-electron, electron-phonon and electron-NP surface scatterings and radiation are included in the model. In addition a correction term added to the damping factor of mentioned mechanisms in order to rectify the deficiencies of theoretical approaches. For determining the free parameters of model, the experimental data of extinction cross section of gold NPs with different sizes doped in the glass host medium are used and a good agreement between experimental data and results of our model is observed. It is shown that by decreasing the diameter of NP, the restoration force becomes larger and classical confinement effect becomes more dominant in the interaction. According to experimental data, the best fitted parameter for the coefficient of restoration force is a third order negative powers function of diameter. The fitted function for the correction damping factor is proportional to the inverse squared wavelength and third order power series of NP diameter. Based on the model parameters, the real and imaginary parts of permittivity for different sizes of gold NPs are presented and it is seen that the imaginary part is more sensitive to the diameter variations. Increase in the NP diameter causes increase in the real part of permittivity (which is negative) and decrease in the imaginary part.

Appearance of stagnation points in skyrmion-based STNO due to geometric asymmetries

In this work, we investigated the motion of a skyrmion on an asymmetric disk induced by an out-of-plane spin-polarized current. The appearance of two movement regimes based on disk asymmetry was reported. A tangential component is induced in the restoration force by the asymmetry, which in turn competes with the tangential component of the STT force. For a disk with low asymmetry, a precession motion was obtained and for a disk with high asymmetry, a convergent movement to points of stagnation was reported. These regimes can be understood as a result of competition between restoration forces and STT forces.

Nonlinear laser absorption over a dielectric embedded with nanorods

AbstractAn analytical formalism of laser absorption in a nanorod embedded dielectric surface has been developed. Nanorods lie in the plane of the dielectric, in the form of a planar array. A laser, impinged on them with an electric field perpendicular to the lengths of the nanorods, imparts oscillatory velocity to nanorod electrons. As the free electrons of a nanorod are displaced, a space charge field is developed in the nanorod that exerts restoration force on the electrons and their drift velocity shows a resonance at ${\rm \omega} = {\rm \omega} _{\rm p}/\sqrt 2 $, where ωp denotes the plasma frequency of free electrons inside the nanorod. It is inhibited by collisions and nanorod expansion. At the resonance, the electrons are efficiently heated by the laser and laser energy is strongly absorbed, resulting in significant reduction in laser transmissivity. The transmissivity decreases with laser intensity.

Biomechanical behaviour of bulk-fill resin composites in class II restorations

The aim of this study was to evaluate the biomechanical properties expressed by shrinkage stress, cuspal strain, fracture strength and failure mode in molars with large class II mesio-occlusal-distal restorations. Sixty-four human caries-free third molars were selected and distributed randomly into four groups: Z100 restorative material (Z100), Tetric N-Ceram Bulk-Fill (TNC), Filtek Bulk-Fill (FBF) and Aura Ultra Universal (ABF). The bulk-fill materials were inserted in one singular bulk increment and the conventional composite resin in three ones. Polymerisation shrinkage stress was evaluated by optical Fibre Bragg Gratings (FBG) sensors (n = 6). The cuspal deformation was measured using an extensometer during three moments: restorative procedure, axial compressive loading and at fracture (n = 10). The fracture strength was evaluated on a universal machine. The failure mode was analysed by Scanning Electron Microscopy (SEM). Data were analysed using one-way ANOVA tests with Tukey's posthoc test (α = 5%). Data of the failure mode were submitted to a likelihood ratio chi-square test. Z100 presented the highest mean value for the shrinkage stress (p < 0.05) by FBG evaluation, whereas bulk-fill resin groups presented low polymerisation stress mean value, especially the TNC (p < 0.05). The cuspal deformation test showed that Z100 presented a significant difference mean value compared to the other groups (p < 0.01) during the restoration and compressive axial force; however, load until the fracture presented a difference only between TNC and FBF (p < 0.05). The fracture strength of TNC was statistically different from Z100 (p < 0.01). The failure mode was not statistically different in all the groups (p > 0.05). Bulk-fill composites promoted less polymerisation shrinkage stress than conventional microhybrid composite during and after the light curing process in class II posterior resin composite restorations.

Nonlinear absorption and harmonic generation of laser in an assembly of CNT's

An analytical formalism is developed to study the nonlinear propagation of a high power laser through an array of parallel carbon nanotubes and generation of second and third harmonics. The array is mounted on a planar surface, and a laser propagates perpendicular to the lengths of the tubes. The nonlinearity arises through the electrostatic restoration force on the displaced electron cylinder with respect to the ion cylinder by the laser. The effect is resonantly enhanced near the surface plasmon resonance. For typical powers of the laser and areal density of nanotubes of radius 2 × 10−8 m, the attenuation length turns out to be 5 cm. The second harmonic conversion efficiency is of the order of 1.4 × 10−2, while the third harmonic conversion efficiency is 0.9 × 10−2.

Electrocaloric effect in ferroelectric ceramics with point defects

The electrocaloric effect has drawn much attention due to its potential application in cooling devices. A negative electrocaloric effect is predicted to be induced in defect-doped ferroelectrics by computational results [A. Grünebohm and T. Nishimatsu, Phys. Rev. B 93, 134101 (2016) and Ma et al., Phys. Rev. B 94, 094113 (2016)], but it need to be confirmed by experimental results. In this work, we prepared a 1 mol. % Mn-doped Pb(Zr0.2,Ti0.8)O3 ceramics (Pb((Zr0.2,Ti0.8)0.99,Mn0.01)O3), and the electrocaloric effect of the defect-containing ferroelectric ceramics has been investigated by both direct and indirect methods. The indirect method shows a similar negative electrocaloric effect signal as the computational results predicted, while the direct method gives a positive electrocaloric effect. The absence of the negative electrocaloric effect obtained by the direct method may originate from: (a) the unavailability and the improper prediction of the Maxwell relation, (b) an improper assumption of fixed defects in the computational models, and (c) the offset of heat loss due to the application of a large electric field. In addition, we find a giant positive electrocaloric effect of 0.55 K at room temperature in the aged ceramics where no phase transition takes place. We attribute this abnormal electrocaloric effect to the restoration force of the defect dipoles. Our results not only provide insights into the origin of the negative electrocaloric effect, but also offer opportunities for the design of electrocaloric materials.

Wellposedness and regularity of a nonlinear variable-order fractional wave equation

We prove the wellposedness of a nonlinear variable-order fractional wave differential equation that describes the vibration of a single particle attached to a viscoelastic material. We then prove that the high-order regularity of its solution depends on the behavior of the variable orders α(t) and β(t) of the fractional damping terms at t=0. In particular, we prove that the solution to the model recovers full regularity when the fractional damping terms exhibit (the physically relevant) elastic restoration force and integer-order damping at the initial time t=0, which, thus, eliminates the incompatibility between the nonlocal differential operators and the locality of classical initial condition.

Thrust actuator with passive restoration force for wide gap magnetic bearings

Abstract Active thrust magnetic bearings provide an axial force to balance the moving parts of machines. However, most devices produce null or unbalancing passive forces. Furthermore, reported designs usually feature very small axial and radial gaps. This paper presents a thrust actuator for wide axial gaps that produces both passive and active restoring axial forces. It features a long biconical rotor and a stator housing a single winding and two permanent magnets. Simulations are done using finite-element-analysis (FEA) and compared to magnetic circuit analysis and experimental results from a prototype with a diameter of 48 mm and 20 mm axial displacement.

Cervical Open-Door Laminoplasty by Hydroxyapatite Implant Insertion Without Suturing.

ObjectiveTo assess the efficacy of cervical open-door laminoplasty by hydroxyapatite implant insertion between the lamina and the lateral mass without suturing. MethodsAll patients who underwent cervical open-door laminoplasty with C2/C7 undermining and insertion of hydroxyapatite implants from C3 to C6 were retrospectively evaluated for surgical time and neurological outcomes according to the Japanese Orthopaedic Association (JOA) score. To assess the alignment of the cervical spine and postoperative cervical pain, the C2–7 angle and a visual analogue scale score were used, respectively. ResultsThe population consisted of 102 women and 222 men ranging in age from 32 to 90 years. The average surgical time was 86 minutes. Fourteen of 1,296 hydroxyapatite implants were kept in place with sutures due to a weak restoration force of the hinge during surgery. No hydroxyapatite implant dislocation was detected on cervical computed tomography at 1 year after surgery. The average JOA score was 10.2±2.5 before surgery and 14.6±2.8 at 1 year after surgery. The average recovery rate was 61.8%. The average C2–7 angle at the neutral position was 7.1°±6.2° before surgery and 6.5°±6.3° at 1 year after surgery. ConclusionThis method enabled us to achieve minimal exposure of the lateral mass, prevention of lateral mass injury and dural injury, and a shorter surgical time while maintaining acceptable surgical outcomes. The idea that firm suture fixation is needed to prevent spacer deviation during cervical open-door laminoplasty may need to be revisited.

Cardiac Muscle-cell Based Actuator and Self-stabilizing Biorobot - PART 1.

Biological machines often referred to as biorobots, are living cell- or tissue-based devices that are powered solely by the contractile activity of living components. Due to their inherent advantages, biorobots are gaining interest as alternatives to traditional fully artificial robots. Various studies have focused on harnessing the power of biological actuators, but only recently studies have quantitatively characterized the performance of biorobots and studied their geometry to enhance functionality and efficiency. Here, we demonstrate the development of a self-stabilizing swimming biorobot that can maintain its pitch, depth, and roll without external intervention. The design and fabrication of the PDMS scaffold for the biological actuator and biorobot followed by the functionalization with fibronectin is described in this first part. In the second part of this two-part article, we detail the incorporation of cardiomyocytes and characterize the biological actuator and biorobot function. Both incorporate a base and tail (cantilever) which produce fin-based propulsion. The tail is constructed with soft lithography techniques using PDMS and laser engraving. After incorporating the tail with the device base, it is functionalized with a cell adhesive protein and seeded confluently with cardiomyocytes. The base of the biological actuator consists of a solid PDMS block with a central glass bead (acts as a weight). The base of the biorobot consists of two composite PDMS materials, Ni-PDMS and microballoon-PDMS (MB-PDMS). The nickel powder (in Ni-PDMS) allows magnetic control of the biorobot during cells seeding and stability during locomotion. Microballoons (in MB-PDMS) decrease the density of MB-PDMS, and enable the biorobot to float and swim steadily. The use of these two materials with different mass densities, enabled precise control over the weight distribution to ensure a positive restoration force at any angle of the biorobot. This technique produces a magnetically controlled self-stabilizing swimming biorobot.