Twist Mode Research Articles

The Impact of Backspin Release Modes on Basketball Spin Axis Alignment

Background: Ball backspin is created during a basketball's final release. The complex nature of the hand-ball interaction at the moment of release can result in spin axis (SA) misalignment, which decreases shooting accuracy.Aims: This study is the first to analyze distinct backspin modes, such as hand orientation, twist, and push location, and how each mode contributes to overall SA misalignment.Methods: Three-dimensional ball backspin, hand orientation, hand position, and ball twist before release were measured for 20 male basketball athletes. The multiple linear regression test analyzed SA misalignment about the vertical axis (ey) and side SA misalignment (ez).Results: The multiple linear regression for SA misalignment about the vertical axis (ey) found that the orientation of the fingers and twist modes were equally important while the push location was insignificant (f2 = 1.9, R2 = 0.63, F = 17.0, p 0.001). For side SA misalignment (ez), all three modes contributed to ez misalignment (f2 = 3.3, R2 = 0.77, F = 18.1, p 0.001), with both the orientation of the palm and twist modes contributing equally and the vertical push location having a smaller contribution.Conclusion: This study demonstrates that five different backspin modes—two for ey and three for ez—each have distinct effects and combine to produce the final SA alignment after the ball is released. Knowing how each mode contributes to the final SA misalignment will allow coaches to identify necessary changes in individual players' shooting techniques to improve their release and increase accuracy.

Mechanical response of double-stranded DNA: Bend, twist, and overwind.

We employed all-atom molecular dynamics simulations to explore the mechanical response of bending, twisting, and overwinding for double-stranded DNA (dsDNA). We analyzed the bending and twisting deformations, as well as their stiffnesses, using the tilt, roll, and twist modes under stretching force. Findings indicate that the roll and twist angles vary linearly with the stretching force but show opposite trends. The tilt, roll, and twist elastic moduli are considered constants, while the coupling between roll and twist modes slightly decreases under stretching force. The effect of the stretching force on the roll and twist modes, including both their deformations and elasticities, exhibits sequence-dependence, with symmetry around the base pair step. Furthermore, we examined the overwinding path and mechanism of dsDNA from the perspective of the stiffness matrix, based on the tilt, roll, and twist modes. The correlations among tilt, roll, and twist angles imply an alternative overwinding pathway via twist-roll coupling when dsDNA is stretched, wherein entropic contribution prevails.

Modelling of aero-mechanical response of wind turbine blade with damages by computational fluid dynamics, finite element analysis and Bayesian network

Computational Fluid Dynamics and Finite Element Analysis structural models are developed for generation of large datasets of high-fidelity aerodynamic loading, displacement and stress for the NREL 5 MW wind turbine blade. Based on the datasets, analysis of structural responses of the turbine blade and their possible shifts with respect to a change in the operating conditions, e.g. rotor plane tilting and yawing, are performed. A Bayesian Network model is trained to produce ranges of values and likelihoods of occurrence of abnormal structural response or the most likely damage in the blade from inputs of operating conditions. The numerical analysis showed that yawing and tilting of rotor plane has very strong influence on the performance of a wind turbine. The out-of-plane bending is the dominant mode of the rotor blade while twisting and other complex modes of displacement could be more significant during some operating conditions such as at high tilt and yaw angles. The Bayesian Network is capable of computing probability mass functions of mechanical stress or displacement of the blade given a rotor rotation speed and a type of damage or vice versa, identifying a type of damage given a measured stress distribution level.

Formulation of justifiable wind loading distributions up tall buildings derived from HFFB measurements

For the general case of non-linear and combined sway and twist mode shapes, analysis of HFFB measurements gives rise to serious challenges and various techniques have been developed using significant assumptions. This is because it is not possible to directly obtain the distribution of varying fluctuating wind loads throughout the height of tall buildings. This paper proposes a straightforward HFFB-based wind load/twist distribution approach in the time domain to predict the wind-induced dynamic response of tall buildings. Using this framework, it is possible to overcome the deficiencies of mode shape correction factor approach, and the complexity and impracticality of alternative approaches for tall buildings. Two 1:300 scale rigid models of benchmark tall buildings, IAWE Buildings A and B, have been selected to perform a detailed wind tunnel investigation as subjects to evaluate this proposed HFFB approach study. Building A has complex 3D mode shapes combining sway and twist, whereas the simpler Building B has uncoupled linear mode shapes in sway and twist. The high frequency pressure integration (HFPI) wind tunnel technique was utilised to measure surface pressure information in separate tests to obtain the reference wind loading for validation of the HFFB predictions. Furthermore, a commonly used HFFB mode shape correction factor approach was used to estimate the dynamic wind responses which were compared to those from the proposed approach. From the comparison between the aerodynamic and dynamic wind results from proposed HFFB approach and reference HFPI results, it is found that the proposed HFFB approach can predict the vertical distributions of the wind forces and torque (wind loads) with acceptable accuracy for carrying out the conceptual stage of tall building design.

Compact Micro-Coriolis Mass-Flow Meter with Optical Readout.

This paper presents the first nickel-plated micro-Coriolis mass-flow sensor with integrated optical readout. The sensor consists of a freely suspended tube made of electroplated nickel with a total length of 60 mm, an inner diameter of 580 µm, and a wall thickness of approximately 8 µm. The U-shaped tube is actuated by Lorentz forces. An optical readout consisting of two LEDs and two phototransistors is used to detect the tube motion. Mass-flow measurements were performed at room temperature with water and isopropyl alcohol for flows up to 200 g/h and 100 g/h, respectively. The measured resonance frequencies were 1.67 kHz and 738 Hz for water and 1.70 kHz and 752 Hz for isopropyl alcohol for the twist and swing modes, respectively. The measured phase shift between the two readout signals shows a linear response to mass flow with very similar sensitivities for water and isopropyl alcohol of 0.41mdegg/h and 0.43 mdegg/h, respectively.

Giant tridimensional power responses in a T-shaped magneto–mechano–electric energy harvester

We present a T-shaped MME-EH that enables collaborative twisting or bending operation modes for tridimensional responses. The device produces a peak–peak output power of 98.5 mW at 60 Hz, which is 262% higher than the state-of-the-art results.

Fuzzy super twisting mode control of a rigid-flexible robotic arm based on approximate inertial manifold dimensionality reduction.

The control of infinite-dimensional rigid-flexible robotic arms presents significant challenges, with direct truncation of first-order modal models resulting in poor control quality and second-order models leading to complex hardware implementations. To address these issues, we propose a fuzzy super twisting mode control method based on approximate inertial manifold dimensionality reduction for the robotic arm. This innovative approach features an adjustable exponential non-singular sliding surface and a stable continuous super twisting algorithm. A novel fuzzy strategy dynamically optimizes the sliding surface coefficient in real-time, simplifying the control mechanism. Our findings, supported by various simulations and experiments, indicate that the proposed method outperforms directly truncated first-order and second-order modal models. It demonstrates effective tracking performance under bounded external disturbances and robustness to system variability. The method's finite-time convergence, facilitated by the modification of the nonlinear homogeneous sliding surface, along with the system's stability, confirmed via Lyapunov theory, marks a significant improvement in control quality and simplification of hardware implementation for rigid-flexible robotic arms.

Robust Nonlinear Trajectory Controllers for a Single-Rotor UAV with Particle Swarm Optimization Tuning

This paper presents the utilization of robust nonlinear control schemes for a single-rotor unmanned aerial vehicle (SR-UAV) mathematical model. The nonlinear dynamics of the vehicle are modeled according to the translational and rotational motions. The general structure is based on a translation controller connected in cascade with a P-PI attitude controller. Three different control approaches (classical PID, Super Twisting, and Adaptive Sliding Mode) are compared for the translation control. The parameters of such controllers are hard to tune by using a trial-and-error procedure, so we use an automated tuning procedure based on the Particle Swarm Optimization (PSO) method. The controllers were simulated in scenarios with wind gust disturbances, and a performance comparison was made between the different controllers with and without optimized gains. The results show a significant improvement in the performance of the PSO-tuned controllers.

Wave effects on the hydroelastic response of a surface-piercing hydrofoil. Part 2. Cavitating and ventilating flows

The objective of this paper is to understand the effects of waves and vaporous cavitation upon the hydrodynamic and hydroelastic responses of a flexible surface-piercing hydrofoil, adding to the subcavitating results presented in Part 1. In general, the presence of a sufficiently large vaporous cavitation bubble facilitated the formation of a ventilated cavity, substantially reducing the angle of attack or speed required to induce fully ventilated flow, relative to subcavitating conditions. A new co-analysis procedure was used to isolate synchronous hydrodynamic modes and structural operating deflection shapes. Significant dynamic load amplification occurred when the resonant frequencies of the first twisting and second bending modes coalesced in both fully wetted and partially cavitating flows. The presence of waves did not diminish the effect of frequency coalescence, but did encourage intermittent lock-in with both leading edge cavity shedding and trailing edge vortex shedding at certain speeds. Partial cavity shedding typically had a negligible impact on the power spectral densities of structural motions because of incoherent cavity shedding. However, lock-in between the cavity shedding frequency and modal coalescence frequency led to shifting of the primary frequency peak, as well as amplified harmonics and interactions between the cavity shedding frequency and vortex shedding frequency. The transition from partially cavitating to fully ventilated flow caused sudden and large drops in the mean hydrodynamic loads and deformations, as well as substantial reductions in the intensity of the fluctuations.

Nonlinear terahertz control of the lead halide perovskite lattice.

Lead halide perovskites (LHPs) have emerged as an excellent class of semiconductors for next-generation solar cells and optoelectronic devices. Tailoring physical properties by fine-tuning the lattice structures has been explored in these materials by chemical composition or morphology. Nevertheless, its dynamic counterpart, phonon-driven ultrafast material control, as contemporarily harnessed for oxide perovskites, has not yet been established. Here, we use intense THz electric fields to obtain direct lattice control via nonlinear excitation of coherent octahedral twist modes in hybrid CH3NH3PbBr3 and all-inorganic CsPbBr3 perovskites. These Raman-active phonons at 0.9 to 1.3 THz are found to govern the ultrafast THz-induced Kerr effect in the low-temperature orthorhombic phase and thus dominate the phonon-modulated polarizability with potential implications for dynamic charge carrier screening beyond the Fröhlich polaron. Our work opens the door to selective control of LHP's vibrational degrees of freedom governing phase transitions and dynamic disorder.

Inelastic Neutron Scattering Study of Phonon Dispersion Relation in Higher Manganese Silicides

We report inelastic neutron scattering (INS) measurements of the phonon dispersion relation in higher manganese silicides (HMSs). A large ingot of HMS is synthesized using a slow cooling method, which is found to have Mn15Si26 as the primary phase. The sample is composed of highly oriented crystallites as confirmed by a neutron pole-figure study and thermal conductivity data. Our INS results are mostly consistent with earlier experimental and theoretical phonon studies in HMS, including the presence of a low-lying twisting mode. However, some discrepancies are also observed. Most notably, a 5 meV gap at the zone center and the softer dispersion relation of the low-lying twisting mode. We discuss the potential origins of these observations and their implications for the thermal properties of HMS.

The effect of dynamic twisting on the flow field and the unsteady forces of a heaving flat plate

Many marine animals can dynamically twist their pectoral fins while swimming. The effects of such dynamic twisting on the unsteady forces on the fin and its surrounding flow field are yet to be understood in detail. In this paper, a flat plate executing a heaving maneuver is subjected to a similar dynamic twisting. In particular, the effects of the direction of twist, non-dimensional heaving amplitude, and reduced frequency are studied using a force sensor and particle image velocimetry (PIV) measurements. Two reduced frequencies, , and , and two twisting modes are investigated. In the first twisting mode, the plate is twisted in the direction of the heave (forward-twist), and in the second mode, the plate is twisted opposite to the direction of the heave (backward-twist). Force sensor measurements show that the forward-twist recovers some of the lift that is usually lost during the upstroke of flapping locomotion. Additionally, the forward-twist maintains a near-constant lift coefficient during the transition between downstroke and upstroke, suggesting a more stable form of locomotion. PIV results show that forward-twist limits circulation and leading-edge vortex growth during the downstroke, keeping at the cost of the reduced lift. By contrast, backward-twist increases the circulation during the downstroke, resulting in large increases in both lift and drag coefficients. Force sensor data also showed that this effect on the lift is reversed during the upstroke, where the backward-twist causes a negative lift. The effects of each twisting mode are mainly caused by the changes in the shear layer velocity that occur as a result of twisting about the spanwise axis along the mid-chord. The twisting performed by forward-twist reduces the effective angle of attack through the upstroke and downstroke, resulting in a reduced shear layer velocity and lower circulation. The twisting performed by backward-twist does the exact opposite, increasing the effective angle of attack through the upstroke and downstroke and consequently increasing the shear layer velocity and circulation.

Speed-planning algorithm and super twisting control for autonomous vehicle steering system

Autonomous vehicle field has seen much development in recent years, especially with the appearance of new efficient control techniques focusing on longitudinal and lateral direction in order to follow a specified trajectory or path. This paper proposes a new systematic control technique to simultaneously generate a suitable speed profile and control the vehicle lateral motion through a predetermined path that considers different driving scenarios representing real-world driving. First, an extended-kinematic model for an autonomous vehicle is designed based on side-slip angle estimation. Then, the proposed technique uses a relationship between lateral error, heading error, and vehicle velocity to generate a suitable steering angle based on super twisting mode control. Second, a speed-planning algorithm is developed to control vehicle velocity. The algorithm uses a strategy for sharp curve identification; then it generates an adequate speed profile depending on the dynamic characteristics of these curves to ensure smooth motion of the vehicle through the whole trajectory. The obtained results from using a speed-planning algorithm with a super twisting controller prove the high performance of this control technique in terms of decreasing errors and respecting passenger comfort.

Molecular dynamics simulation of infrared absorption spectra of one-dimensional ordered single-file water

Compared with bulk water (BW), the water in nanochannels usually shows unique structural and dynamic properties, which is still unable to be effectively detected and characterized by existing experimental techniques. The spectrum is an effective technical means for studying and identifying the material composition and characteristics. In this study, the infrared absorption spectra of one-dimensional ordered single-file water (SW) confined in (6, 6) single-walled carbon nanotubes are calculated by molecular dynamics simulation. It is found that the ordered arrangement of SW results in an obvious blue shift and enhancement of the spectral peak in the 0–35 THz range relative to the bulk water. The analysis shows that this phenomenon is caused by the change of coupling weight of libration vibrations (including rock, twist and wag modes) of SW. The twist vibration mode and wag vibration mode with higher frequency are relatively easy to occur because the binding energy decreases under the single chain structure of water, which results in the blue shift and enhancement of the spectral peak. Meanwhile, the present study shows that the spectral component characteristics of SW can well predict and explain the structural and dynamic properties of SW. Further, terahertz simulation experiments show that the infrared absorption capacity of SW basically conforms with the spectral distribution characteristics.

Effect of type, amount and configuration of reinforcement in HSC box-girders reinforced with BFRP bars and steel stirrups under torsion-shear-bending

There has been no research on the performance of high-strength concrete (HSC) hollow members reinforced with basalt fiber reinforced polymer (BFRP) bars and steel stirrups under combined torsion (T), shear (V), and moment (M); this study examines the above scenario. Six specimens of identical size and length were constructed and tested, each having a total quantity of reinforcement of 2.5%. The supports were restrained against twisting and the load was applied at a transverse eccentricity of 1.67 m at midspan, producing the required T-V-M ratio, with torsion as the dominant action. The proportion of longitudinal to transverse reinforcement, the number and diameter of longitudinal BFRP bars, and the diameter and spacing of steel stirrups, were the factors investigated. The experimental results were evaluated in terms of strength and stiffness, deflection and angle of twist, cracking pattern, and failure modes. For the same total amount of reinforcement, the best results were achieved utilizing specimens with BFRP bars and steel stirrups of smaller diameter at closer spacings. Employing more longitudinal BFRP bars ( ρ l = 1.58 ρ t ) produced better outcomes than using more steel stirrups ( ρ t = 1.32 ρ l ), indicating that the amount of BFRP bars is as critical as or more important than the amount of steel stirrups. The experimental results of cracking torque and twist, and ultimate torque were compared to the code and other available expressions. It was found that ACI, CSA, and EC equations can be extrapolated without any modification to predict the torsional strength of HSC box-girders longitudinally reinforced with BFRP bars under combined T-V-M. In addition, a new approach was suggested, which can predict the ultimate torsional twist capacity reasonably well.

Modal properties of honeycomb wheels: A parametric analysis using response surface method

Three-dimensional finite element (FE) models of a honeycomb non-pneumatic wheel (NPW) with three different spokes configurations of varying cell angles were developed in ABAQUS software in order to investigate its modal properties under a given normal load. The validity of these wheel models was confirmed through comparisons of predicted wheel responses with available data in published studies for similar wheel material properties and components dimensions. The important vibration modes affecting the wheel responses were initially identified together with the important design factors affecting the modal properties. Response surface models relating the natural frequency of each chosen influential vibration mode with its important design factors and the two-factor interactions were subsequently developed utilizing the results of FE simulations corresponding to design points of the screening design and the experimental design based on central composite design (CCD) approach. These regression models showed good fitting accuracy of the natural frequencies obtained in CCDs together with relatively satisfactory prediction ability over the design region considered. The resulting regression models are thus considered to serve as a design guidance for realizing desired wheel modal properties. The results derived from parametric studies showed that natural frequencies of identified in-plane and out-of-plane vibration modes are significantly affected by design parameters of the spokes. These include the initial elastic modulus and thickness of the honeycomb cell-wall and the cell angle. Most of the identified vibration modes are also strongly influenced by the thickness dimensions of the core layer and the tread, while their initial elastic moduli revealed considerable effects only on the wheel Hop and Twist modes.

Chiral control of spin-crossover dynamics in Fe(II) complexes.

Iron-based spin-crossover complexes hold tremendous promise as multifunctional switches in molecular devices. However, real-world technological applications require the excited high-spin state to be kinetically stable-a feature that has been achieved only at cryogenic temperatures. Here we demonstrate high-spin-state trapping by controlling the chiral configuration of the prototypical iron(II)tris(4,4'-dimethyl-2,2'-bipyridine) in solution, associated for stereocontrol with the enantiopure Δ- or Λ-enantiomer of tris(3,4,5,6-tetrachlorobenzene-1,2-diolato-κ2O1,O2)phosphorus(V) (P(O2C6Cl4)3- or TRISPHAT) anions. We characterize the high-spin-state relaxation using broadband ultrafast circular dichroism spectroscopy in the deep ultraviolet in combination with transient absorption and anisotropy measurements. We find that the high-spin-state decay is accompanied by ultrafast changes of its optical activity, reflecting the coupling to a symmetry-breaking torsional twisting mode, contrary to the commonly assumed picture. The diastereoselective ion pairing suppresses the vibrational population of the identified reaction coordinate, thereby achieving a fourfold increase of the high-spin-state lifetime. More generally, our results motivate the synthetic control of the torsional modes of iron(II) complexes as a complementary route to manipulate their spin-crossover dynamics.

Length-Dependent Collective Vibrational Dynamics in Alpha-Helices.

Functions of protein molecules in nature are closely associated with their well-defined three-dimensional structures and dynamics in body fluid. So far, many efforts have been made to reveal the relation of protein structure, dynamics, and function, but the structural origin of protein dynamics, especially for secondary structures as building blocks of conformation transition, is still ambiguous. Here we theoretically uncover the collective vibrations of elastic poly-alanine α-helices and find vibration patterns that are distinctively different over residue numbers ranging from 20 to 80. Contrary to the decreasing vibration magnitude from ends to the middle region for short helices, the vibration magnitude for long helices takes the minimum at approximately 1/5 of helix length from ends but reaches a peak at the center. Further analysis indicates that major vibrational modes of helical structures strongly depend on their lengths, where the twist mode dominates in the vibrations of short helices while the bend mode dominates the long ones analogous to an elastic Euler beam. The helix-coil transition pathway is also affected by the alternation of the first-order mode in helices with different lengths. The dynamic properties of the helical polypeptides are promising to be harnessed for de novo design of protein-based materials and artificial biomolecules in clinical treatments.

The topological soliton decay in a linear defect of the domain structure of twisted nematic

In this paper, the topological soliton decay in an oscillating linear defect of electroconvective structure (Williams domains) arising in π/2 twisted nematic liquid crystal are studied. In contrast to planarly oriented nematics, hydrodynamic flows in the domains of a twisted nematic have a helical character. Since, in addition to the tangential velocity component, there is also axial component, the direction of which is opposite in neighboring domains. This feature leads to the formation of stable localized extended objects — linear defects oriented normal to Williams domains. With increasing applied voltage, “zig-zag” oscillations occurs in linear defects. The boundaries between the “zig” and “zag“ states are classical dislocations. It has been found, that the dislocation, moving along the core of the defect, breaks up into an antidislocation and two dislocations. Unlike case of planarly oriented nematics, dislocations are not isolated from each other by unperturbed rolls but remain “bound” by hydrodynamic flows within the core of a linear defect. It is assumed that the splitting of the dislocation occurs as a result of the local instability of the orientational twist mode of the director n due to its strong coupling with the hydrodynamic velocity. In the framework of the sine–Gordon equation, in the presence of a dissipative term and spatial perturbations, the mechanism of a topological soliton (kink) decay into antisoliton and two solitons is considered.

Design, Fabrication, and Characterization of a Micro Coriolis Mass Flow Sensor Driven by PZT Thin Film Actuators

A micro Coriolis flow sensor accurately measures small mass flows without being affected by properties of the fluid. This paper presents a micro Coriolis mass flow sensor driven by PZT thin film piezoelectric actuators, which allows a combination of large actuation force, low power dissipation and virtually no self-heating. The sensor was fabricated using surface channel technology, resulting in a tube diameter of 40 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu \text{m}$ </tex-math></inline-formula> and a thin silicon-rich silicon nitride tube wall of 1.2 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu \text{m}$ </tex-math></inline-formula> thick, with a few additional steps to form the integrated piezoelectric actuators. The integrated actuators can actuate the sensor into both swing mode and twist mode. Both actuation modes were evaluated for different fluids and the results are presented in this paper. In the case of swing mode actuation, an optical readout was used to detect the resulting Coriolis movement, resulting in a relatively low sensitivity. In the case of twist mode actuation, a capacitive readout was used and, in comparison to previously published devices, a high mass flow sensitivity was achieved thanks to an optimized readout design. The measurement results show the read-out noise has a standard deviation of 0.15% of the full scale of 1.8 gh <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">−1</sup> when actuated in the twist mode. [2020-0392]