Rotational Degrees Of Freedom Research Articles

Design, evaluation, and optimization of a novel 3UPU-S parallel mechanism with three rotational degrees of freedom

Design, evaluation, and optimization of a novel 3UPU-S parallel mechanism with three rotational degrees of freedom

Systematic coarse-graining of sequence-dependent structure and elasticity of double-stranded DNA

Coarse-grained models have played an important role in the study of the behavior of DNA at length scales beyond a few hundred base pairs. Traditionally, these models have relied on structurally featureless and sequence-independent approaches, such as the twistable wormlike chain. However, research over the past decade has highlighted the substantial impact of DNA sequence even at the kilobase pair scale. Several robust sequence-dependent models have emerged, capturing intricacies at the base pair-step level. Here we introduce an analytical framework for coarse-graining such models to lower resolution representations while preserving essential structural and dynamic features, enabling the efficient sampling of large molecules. When considering both rotational and translational degrees of freedom, coarse-graining is shown to yield excellent results up to about one helical repeat. For scenarios where the local stretch modulus is inconsequential, this range can be significantly increased by only considering the rotational degrees of freedom, which permits faithful coarse-grained representation up to several helical repeats. Rather than providing a fully parametrized model, we present the methodology and software necessary for mapping any base pair-step model to the desired level of coarse-graining. Finally, we provide application examples of our method, including estimates of the persistence length and effective torsional stiffness of DNA in a setup mimicking a freely orbiting tweezer, as well as simulations of helically curved DNA. Published by the American Physical Society 2025

Dynamics of a single anisotropic particle under various resetting protocols

We study analytically the dynamics of an anisotropic particle subjected to different stochastic resetting schemes in two dimensions. The Brownian motion of shape-asymmetric particles in two dimensions results in anisotropic diffusion at short times, while the late-time transport is isotropic due to rotational diffusion. We show that the presence of orientational resetting promotes the anisotropy to late times. When the spatial and orientational degrees of freedom are reset, we find that a non-trivial spatial probability distribution emerges in the steady state that is determined by the initial orientation, particle asymmetry and the resetting rate. When only spatial degrees of freedom are reset while the orientational degree of freedom is allowed to evolve freely, the steady state is independent of the particle asymmetry. When only particle orientation is reset, the late-time probability density is given by a Gaussian with an effective diffusion tensor, including off-diagonal terms, determined by the resetting rate. Generally, the coupling between the translational and rotational degrees of freedom, when combined with stochastic resetting, gives rise to unique behavior at late times not present in the case of symmetric particles. Considering recent developments in experimental implementations of resetting, our results can be useful for the control of asymmetric colloids, for example in self-assembly processes.

Inverse and Forward Kinematics and CAD-Based Simulation of a 5-DOF Delta-Type Parallel Robot with Actuation Redundancy

This article introduces a novel modification of a Delta-type parallel robot. The robot has five degrees of freedom and provides its end-effector with a 3T2R motion pattern (three translational and two rotational degrees of freedom). The fifth degree of freedom (rotation) is kinematically decoupled from the other four motions, and it is controlled by two drives. Thus, the proposed robot has a redundant actuation. In this article, we present an algorithm to solve the inverse kinematics of this robot and apply it to a path modeling example of a spiral-like trajectory. Numerical simulations illustrate the algorithm and show how the actuated coordinates change along the considered trajectory. Forward kinematics follows next, and an approach is introduced to determine all end-effector configurations for the specified displacements in the actuated joints. A numerical example presents four assembly modes of the robot corresponding to four real solutions of the forward kinematic problem. Finally, this article demonstrates a computer-aided design and analysis of the proposed robot: we describe a procedure for analyzing inverse kinematics and calculating actuation torques. This study forms the basis for the future manufacturing and experimental analysis of a robot prototype.

Extending Generalized Explicit Terms and Applying Euler–Bernoulli Beam Theory to Enhance Dynamic Response Prediction in Receptance Coupling Method

This paper presents a theoretical framework to enhance the prediction of dynamic responses in complex mechanical systems, such as vehicle structures, by incorporating both translational and rotational degrees of freedom. Traditional receptance coupling methods often neglect rotational effects, leading to significant inaccuracies at higher frequencies. Additionally, approaches that implicitly include full dynamics frequently result in redundancy of generalized coordinates, especially at connection points. To address these limitations, the generalized receptance coupling method using Frequency-Based Substructuring is extended to explicitly account for rotational dynamics resulting in a refined GRCFBS approach. This extension enhances both the understanding and prediction of system responses, which are represented through the receptance matrix or Frequency Response Function. Building on Jetmundsen’s foundational work, the proposed framework introduces a practical, generalized formulation that explicitly incorporates full translational and rotational dynamics at each substructure node. This explicit definition provides deeper insights into system behavior, particularly for complex interactions between substructures under weak and strong coupling scenarios at interface points. The Euler–Bernoulli beam theory is employed to model rotational behavior at critical points, yielding reduced-order and explicit receptance matrices for substructures in the coupling process. The methodology’s accuracy and applicability in capturing resonance and anti-resonance modes are validated through two case studies: the coupling of two flexible subsystems and the integration of flexible and rigid components. Results are benchmarked against numerical finite element analysis, and all limitations and potential improvements are discussed. By directly incorporating rotational dynamics directly, this approach enables more reliable dynamic response predictions under multi-directional loading conditions, particularly for vehicle and machinery system design. The GRCFBS method offers a versatile and reliable tool for dynamic system analysis, with significant potential for vibration analysis over a broad frequency range.

High-temperature high-k polyolefin by rational molecular design

Polymer film dielectrics are highly favored for capacitive energy storage due to the inherent advantages of high breakdown strength, low dielectric loss, and ease of processing. High-density renewables conversion and harsh-condition electrification further emphasize the need for high-temperature, high-k polymers. A unique design strategy is developed to augment high-temperature polyolefins with improved dielectric constant, via the integration of phenyl pendants hanging off the rigid bicyclic backbone. The impacts of the pendant polarizability and steric positioning on dielectric constant, bandgap, glass-transition temperature (Tg), and high-field, high-temperature dielectric characteristics have been investigated. The orientational polarization of the polar phenyl pendants with rotational degree of freedom imparts cyclic olefins with enhanced dielectric constants, while maintaining the large bandgap, and high glass-transition temperature (Tg > 170 °C). Among these synthesized polymers, m-PNB-BP stands out with a remarkable dielectric constant of 4 at a high sub-Tg temperature of 150 °C, and a high discharged density of 8.6 J/m3 at 660 MV/m. This study unveils a different path for designing high-temperature polymers with enhanced dielectric constants, particularly beneficial for capacitive energy storage.

Shell Analysis Using a Solid-Shell Approach

Shells are curved three-dimensional structures whose thickness is much smaller than their other two dimensions. They can be found in various sectors, such as aerospace, energy, naval and civil engineering. There are several structural theories in the literature to deal with this type of structure, such as Kirchhoff-Love, Reissner-Mindlin and Higher-order theories. However, these theories are based on assumptions that require rotational degrees of freedom in their kinematic description, making the problem complex, especially for geometrically nonlinear analysis, since large 3D rotations are not additive. Furthermore, in shell theories, it is usually assumed that there is no thickness stretching. In other words, the normal transversal strain is neglected, so it is not possible to use full 3D constitutive models for the analysis. With this in mind, the structural modeling in this work will be based on the solid-shell approach, which uses a 3D mesh with only one element through the thickness and does not require rotational degrees of freedom in the kinematic description, like in solid elements, but with a lower computational cost. Its formulation considers the general stress state, so a complete 3D constitutive relation is assumed. The use of this theory in structural problems results in partial differential equations whose analytical solutions are very complex or impossible to obtain, thus requiring the use of numerical methods to obtain approximate results. The presented formulation can be applied to develop isoparametric and isogeometric solid-shell elements. The performance of linear and quadratic elements is assessed using numerical examples.

Polarization-rotation-driven modulation of second harmonic generation in van der Waals layered ferroelectric CuInP2S6

Two-dimensional van der Waals (vdW) ferroelectrics, renowned for their spontaneous breaking of inversion symmetry and finite electric polarization, are pivotal in nonlinear optics and low-power nanoelectronics. Prior studies primarily focused on materials exhibiting out-of-plane or in-plane ferroelectric polarization, whose rotational degrees of freedom are commonly overlooked. Herein, we experimentally validate the existence of a weak yet symmetry-allowed in-plane polarization in the low-symmetry vdW ferroelectric CuInP2S6 by rigorous structural analysis and vectorial property characterizations. Remarkably, the magnitude of this in-plane polarization is tunable via an interface-induced electric field, leading to a significant contrast in second harmonic generation between oppositely polarized domains. Based on this unique rotational capability of electric polarization, we demonstrate an electrically tunable second-order optical emission in a fabricated vdW ferroelectric capacitor. Our findings highlight the intricate interplay between crystal symmetry and tensorial physical properties, providing a novel pathway for manipulating nonlinear optical functionalities in vdW layered ferroelectrics.

Ab initio description of monopole resonances in light- and medium-mass nuclei

Giant Resonances are, with nuclear rotations, the most evident expression of collectivity in finite nuclei. These two categories of excitations, however, are traditionally described within different formal schemes, such that vibrational and rotational degrees of freedom are separately treated and coupling effects between those are often neglected. The present work puts forward an approach aiming at a consistent treatment of vibrations and rotations. Specifically, this paper is the last in a series of four dedicated to the investigation of the giant monopole resonance in doubly open-shell nuclei via the ab initio Projected Generator Coordinate Method (PGCM). The present focus is on the treatment and impact of angular momentum restoration within such calculations. The PGCM being based on the use of deformed mean-field states, the angular-momentum restoration is performed when solving the secular equation to extract vibrational excitations. In this context, it is shown that performing the angular momentum restoration only after solving the secular equation contaminates the monopole response with an unphysical coupling to the rotational motion, as was also shown recently for (quasi-particle) random phase approximation calculations based on a deformed reference state. Eventually, the present work based on the PGCM confirms that an a priori angular momentum restoration is necessary to handle consistently both collective motions at the same time. This further pleads in favor of implementing the full-fledged projected (quasi-particle) random phase approximation in the future.

Cross-Shaped Peg-in-Hole Autonomous Assembly System via BP Neural Network Based on Force/Moment and Visual Information

Currently, research on peg-in-hole (PiH) compliant assembly is predominantly limited to circular pegs and holes, with insufficient exploration of various complex-shaped PiH tasks. Furthermore, the degree of freedom for rotation about the axis of the circular peg cannot be constrained after assembly, and few studies have covered the complete process from autonomous hole-searching to insertion. Based on the above problems, a novel cross-shaped peg and hole design has been devised. The center coordinates of the cross-hole are obtained during the hole-searching process using the three-dimensional reconstruction theory of a binocular stereo vision camera. During the insertion process, 26 contact states of the cross-peg and the cross-hole were classified, and the mapping relationship between the force-moment sensor and relative errors was established based on a backpropagation (BP) neural network, thus completing the task of autonomous PiH assembly. This system avoids hand-guiding, completely realizes the autonomous assembly task from hole-searching to insertion, and can be replaced by other structures of pegs and holes for repeated assembly after obtaining the accurate relative pose between two assembly platforms, which provides a brand-new and unified solution for complex-shaped PiH assembly.

水性レドックスフロー電池用アントラキノン系陽極液の機能化

Redox flow batteries (RFBs) are developed as grid-scale load-leveling technologies for renewable energy. Commercial RFBs use vanadium ions as active materials. However, their low energy density and high cost hinder wide deployment in electrical grids. To address these issues, 2,2′-(anthraquinone-2,6-diyldioxy)dipropionic acid (1Me) was reported as an aqueous anolyte to achieve two-electron redox capability, long cycle life, and high solubility.1 In this work, we improve the cycle stability by introducing a sterically bulkier substituent into the side chain of the anthraflavic acid derivative: 2,2′-(anthraquinone-2,6-diyldioxy)dibutyric acid (1Et; Figure 1). 1Et was synthesized by introducing methyl 2-bromobutyrate into anthraflavic acid, followed by saponification and subsequent neutralization with hydrochloric acid. Both 1Me and 1Et exhibit a redox potential of −0.68 V (vs. Ag/AgCl) in 1 mol L−1 KCl and 0.01 mol L−1 KOH aqueous solutions, indicating little influence of the substituent modification to a redox potential. Interestingly, 1Et shows higher solubility (1.73 mol L−1) than 1Me (1.54 mol L−1) despite an elongated hydrophobic alkyl side chain moiety. An ethyl group possesses a higher degree of freedom for rotation and vibration than a methyl group, resulting in larger dissolution entropy and hence higher solubility. Charge/discharge measurements using an H-type cell reveal that 1Et shows a higher capacity retention (0.029%/cycle) than that of 1Me (0.047%/cycle) (Figure 2) owing to a bulkier substituent preventing from nucleophilic attack on the side chain of anthraquinone. Levich analyses show comparable diffusion coefficients for 1Et (4.55×10−6 cm2 s−1) and 1Me (3.26×10− 6 cm2 s−1). These results demonstrate that introducing a bulkier substituent is an effective strategy to improve solubility in water and cycle stability without degrading other physical properties (e.g., redox potential and diffusivity).Reference[1] R. G. Godon, M. J. Aziz, et al., ACS Energy Lett. 2023, 8, 600. Figure 1

A kinematics-based single-actuator setup for constant-curvature bending tests in extremely large deformations

Thanks to the extreme deformability, low weight and high strength, thin elements, such as glass/carbon fiber composites shells, or chemically-strengthened glass laminae, are increasingly used for different engineering applications, ranging from deployable space structures and adaptive surfaces for architecture, to flexible electronics and wearable devices. Since an accurate design must be based on reliable values of the material strength, many research efforts have been made in recent years to propose innovative methods specifically devoted to the evaluation of the bending response of highly deformable elements. One of the most reliable procedures seems to be the clamp bending test, originally proposed for thin glass elements. The test consists in prescribing a rotation on two opposite edges of a rectangular thin plate, while adjusting the distance between the supports so to obtain a deformation into an arc of circle. If, from the analytical point of view, this is very effective because it allows to determine the material strength by using very simple formulae, from the practical point of view, its major limitation is that it requires to synchronize the motors and actuators governing the motion of translational and rotational degrees of freedom. Here, an innovative design is presented, characterized by a mechanical/kinematic interconnection between translation and rotation, so that it is possible to perform a clamp bending test in extremely large deformations by controlling just one degree of freedom, i.e., using only one actuator.

Enhanced attractive force via torsion spring as rotatable tip structure in beam-structure electrostatic chucks

This research aims to replace ball joints of beam-structure electrostatic chucks (BSESC), which are limited by issues such as structural friction and inconsistent operation, thus enhancing the applicability in industrial settings. Torsion springs are used as rotational degree-of-freedom (RDOF) mechanisms at the tip of BSESCs to reduce friction and improve repeatability, while also highlighting the positive relationship between tip rotatability and the attractive force generated. Following the law of conservation of energy, an analytical calculation was performed using a beam-spring-capacitor model to establish the correlation between tip rotatability and the maximum attractive force generated through energy system analysis. An analytical solution was derived, explicitly defining the relationship between tip rotatability and the achievable attractive force. The results were plotted using MATLAB. Experimental validations were carried out by fabricating devices that differed only in tip rotatability, and measurements of the attractive force were taken. Both analytical and experimental results clearly demonstrate a positive relationship between tip rotatability and attractive force generation in BSESCs. The use of torsion springs effectively reduces the energy concentration at the tip, delaying detachment while simultaneously increasing the attractive force, significantly improving the overall performance of BSESCs. These findings provide a foundation for future industrial applications, particularly for automated large-area manipulation of irregularly shaped targets in industries such as screen production and semiconductors.

Development of Rail Camera for Bridge inspection with Attitude Control using Thrust of Rotors

A lot of concrete structures are deteriorating to dangerous levels throughout Japan. These concrete structures need to be inspected regularly to ensure they are safe enough to be used. According to national standards, a visual inspection of the bridge is required once every five years. In the visual inspection, the worker checks the bridge with their own eyes directly. So, it is necessary to set up scaffolding to access the bridge's underside for visual inspection. Alternatively, it is an essential aerial work platform. However, setting up of scaffolding and aerial work platforms is not economical in time and money. So, we developed an inspection device for the check of bridges called a Rail camera. This inspection device connects a rod and a rail and the connection has a rotational degree of freedom. Rotors are attached to the tip of the rod and it can be attitude controlled by thrust of rotors. So, half of the device's weight is lifted by the thrust of the rotors. And it can be taken with a camera mounted on an electric slider on the rail. The worker on the bridge can check the underside of the bridge safely by holding the rod with one hand and operating the rail camera with another hand. The rail camera developed had a rail length of 2 m and a weight of 2.5 kg. Magnesium was used for the rail and rod to reduce weight. Coaxial rotors were used to cancel the counter-torque caused by the rotation of the propeller. To verify the performance, a visual inspection was performed on the bridge. As a result, it was confirmed that the horizontal attitude was maintained by the rotor thrust.

The Interior Contact-Aided Rolling Element

Abstract This work introduces an interior contact-aided rolling element (I-CORE) compliant mechanism that draws upon the concepts used for the contact-aided rolling element, cross-axis flexural pivot, and pre-curved flexible beam. The I-CORE incorporates a bilinear compressive stiffness response with an initial tailorable stiffness governed by the flexural geometry, followed by a stiffness curve governed by the material stiffness at the contact point. The I-CORE mechanism can achieve one or two degrees of rotational freedom as well as a single degree of translational freedom. The purpose of the present work was to introduce the I-CORE mechanism, as well as a pseudo-rigid-body replacement model (PRBM) of the I-CORE mechanism which was subsequently validated using both finite element analysis and benchtop mechanical testing. A pseudo-rigid body model was created for the I-CORE to simplify the rapid adaptation of this mechanism to different design applications. This model was validated using both finite element analysis and benchtop mechanical testing under both compression and rotation loading conditions. Additionally, multiple configurations of the device were created and evaluated in order to test its sensitivity to certain design features including the flexure width, flexure thickness, and the radius of the rounded contact surfaces. It was found that the model is sensitive to the thickness of the flexures and that despite some limitations, the pseudo-rigid body model is sufficiently accurate for initial design work. Some possible applications of the mechanism are proposed.

Pyrazolo-Pyrimidinones with Improved Solubility and Selective Inhibition of Adenylyl Cyclase Type 1 Activity for Treatment of Inflammatory Pain.

Adenylyl cyclase isoform 1 (AC1) is considered a promising target for treating inflammatory pain. Our group identified the pyrazolyl-pyrimidinone scaffold as potent and selective inhibitors of Ca2+/CaM-mediated AC1 activity; however, the molecules suffered from poor aqueous solubility. The current study presents a strategy to improve aqueous solubility of the scaffold by reduction of crystal packing energy and increasing rotational degrees of freedom within the molecule. Structure-activity and property relationship studies identified the second generation lead 7-47A (AC10142A) that demonstrated and AC1 IC50 value of 0.26 μM and aqueous solubility of 74 ± 7 μM. After in vitro ADME characterization, the scaffold advanced to in vivo pharmacokinetic evaluation, demonstrating adequate levels of exposure. Finally, 7-47A exhibited antiallodynic efficacy in a rat complete Freund's adjuvant model for inflammatory pain showing improvement over previous iterations of this scaffold. These results further validate AC1 inhibition as a viable therapeutic strategy for treating chronic and inflammatory pain.

Comment on: “Analytical solutions to the Schrödinger equation for a generalized Cornell potential and its applications to diatomic molecules and heavy mesons”

We analyze a recent calculation of the energy levels of some quantum-mechanical models derived from the so-called generalized Cornell potential. We argue that the authors obtained essentially the same spectrum for potentials with considerably different spectra. We show that the authors obtained negative eigenvalues in the case of a positive-definite potential. The reason is due to the approximation used in the solution of the Schrödinger equation. We point out that the omission of the sum over the rotational degrees of freedom in the canonical partition function leads to incomplete expressions for the thermodynamic functions.

A preliminary biomechanical assessment and user perceptions of a motorized lifter for patient transfer

ABSTRACT A “no-lift” policy in healthcare discourages manual patient lifting to reduce worker injuries. This study explores modifications to a floor lift (NEAR-1) to align with this policy. NEAR-1 features a shorter lower lifting arm and a redesigned sling, enabling patients to (a) transfer in a sitting position, unlike a floor lift’s semi-reclining position, and (b) feel more in control by removing the sling’s rotational degree of freedom and letting the patient’s feet rest on the lifter base. The device also reduced patient weight-bearing, compared to sit-to-stand lifts. Biomechanical analysis was done to map the risk to the nurses and capture the patient’s experience with the modified lift (NEAR-1). Thirteen subjects carried out patient transfer tasks using both the NEAR-1 and the manual transfer approach, and this comparison will provide the baseline data for future systematic reviews. From the results, NEAR-1 significantly reduced the L5-S1 compression, the mediolateral shear forces, and the anteroposterior shear forces, with the exception of the muscle activities in the lower back, the shoulder, and the biceps. Moreover, patients felt safer and more comfortable with the device. Overall, the NEAR-1 lifter presents a biomechanically beneficial and user-friendly option for patients with limited weight-bearing capability.

Curved Three‐Director Cosserat Shells with Strong Coupling

AbstractContinuum‐based shell models are an established approach for the simulation of thin deformables in computer graphics. However, existing research in physically‐based animation is mostly focused on shear‐rigid Kirchhoff‐Love shells. In this work we explore three‐director Cosserat (micropolar) shells which introduce additional rotational degrees of freedom. This microrotation field models transverse shearing and in‐plane drilling rotations. We propose an incremental potential formulation of the Cosserat shell dynamics which allows for strong coupling with frictional contact and other physical systems. We evaluate a corresponding finite element discretization for non‐planar shells using second‐order elements which alleviates shear‐locking and permits simulation of curved geometries. Our formulation and the discretization, in particular of the rotational degrees of freedom, is designed to integrate well with typical simulation approaches in physically‐based animation. While the discretization of the rotations requires some care, we demonstrate that they do not pose significant numerical challenges in Newton's method. In our experiments we also show that the codimensional shell model is consistent with the respective three‐dimensional model. We qualitatively compare our formulation with Kirchhoff‐Love shells and demonstrate intriguing use cases for the additional modes of control over dynamic deformations offered by the Cosserat model such as directly prescribing rotations or angular velocities and influencing the shell's curvature.

Study of chemiluminescence of methane–air flame stabilized on a flat porous burner

In this work, the spatial distribution and spectral characteristics of the chemiluminescence of chemically excited species, OH∗ and CH∗, are experimentally and numerically studied by using a stationary premixed methane–air flame stabilized on the surface of a flat porous burner for various equivalence ratio and normal pressure. Numerical simulations are carried out using detailed reaction mechanisms, and the experimental study includes high-resolution spatial and spectral optical measurements. Despite the data reported in the literature, it is found that (i) the rotational degrees of freedom of OH∗ and CH∗ are not in thermal equilibrium with the surrounding gas and therefore cannot be used to measure flame temperature; (ii) there is no direct correlation between the heat release rate and the distribution of OH∗ and CH∗; (iii) the detailed reaction mechanisms not only quantitatively, and also qualitatively differ in description of the OH∗ and CH∗ concentrations. Since the chemically excited species are well localized in a direction normal to the flame surface, they are demonstrated to be a very accurate markers of flame location. The shape of the combustion front can be reconstructed and resolved up to the accuracy of tens of microns, which is very important for estimation of blow-off critical parameters and measurement of the laminar burning velocity.Novelty and significance statementCurrently, there is a growing interest in the development of sensors for combustion control systems, including active control and suppression of instabilities, in combustion chambers of various devices and engines based on chemiluminescence of excited reaction species. The possibility of non-invasive determination of parameters such as flame temperature, stoichiometry, heat release rate location, etc. using this technique is discussed. We have found that most of these parameters cannot be estimated either due to fundamental limitations or insufficient knowledge of the reaction kinetics involved in the production of these species. Nevertheless, since OH* and CH* are well localized in the direction normal to the flame surface, they can be used as very accurate markers of flame shape and position, allowing us to reconstruct the flame surface to within tens of microns resolution, which is very important for estimating blow-off critical parameters and measuring laminar burning velocity.