Rotational Degrees Of Freedom Research Articles

Performance Comparison of Guided Mortar Projectiles with Fixed and Moving Fins

Guidance munition has become one of the popular subjects in both the theoretical and applicable studies since they could find a wide field of use in recent years because of their high performance and lower collateral damage capabilities as per the improving defence concept. The use of smaller and lighter guided munition makes the stated advantages increase without relinquishing the effectiveness. In this study, the design of a guidance kit which makes the mortar projectiles become guided when released from aerial platforms and the relevant computer simulations performed upon a selected projectile model are investigated. Here, two different configurations are considered based on the rotational degree of freedom of a pair of fins mounted on a rotary ring. In the simulations in which it is assumed that the guided projectile is released from an unmanned aerial vehicle, the different values of the fin deflection, autopilot switching duration, and side wind are considered for both of the mentioned geometries. Finally, the final miss distance and time of flight values obtained for all the designated cases are compared.

GMLS-based numerical manifold method in mechanical analysis of thin plates with complicated shape or cutouts

We proposed a generalized moving least squares (GMLS) based numerical manifold method (NMM) and applied to investigate mechanical behaviors of thin plates with various shape and cutouts. The influence domains of nodes in generalized moving least squares (GMLS) interpolation are employed to construct the mathematical cover, which is specifically fitted for the fourth-order problems with rotational degrees of freedom. Moreover, the GMLS-based NMM can naturally treat plates with arbitrary complex geometry and openings without resorting to those complicated criteria and tailored operations while simplifying the physical cover generation process. In numerical study, a suitable mass lumping scheme is formulated and advised for transverse vibration analysis. Bending, vibration and buckling behaviors of thin plates with different shapes and cutouts are studied. Numerical results manifest that GMLS-based NMM can accurately model transverse mechanical behaviors.

The body‐point model and its application to describe the motion of an electron near the nucleus of a hydrogen atom

AbstractWe consider the motion of a body‐point near an attracting center. The body‐point is defined as a particle with the following properties. (a) The body‐point occupies zero volume in space like a point mass. (b) The body‐point has both translational and rotational degrees of freedom like a rigid body. (c) The body‐point is characterized by a larger number of moments of inertia than an ordinary rigid body. Due to the additional moments of inertia, the body‐point acquires dynamic properties that are fundamentally different from the dynamic properties of an ordinary rigid body. We show that the trajectory of the body‐point moving near the attracting center is a spatial curve, and not a flat one, as it would be in the case of a point mass or a rigid body. We study in detail a special case of the body‐point motion, in which the magnitude of the momentum vector remains constant. We show that, in this special case, the region of space where the trajectory of the body‐point is located can be interpreted as the orbital of an electron in a hydrogen atom. Assuming that the body‐point models the electron in the ground energy state, we determine the parameters of our model. We emphasize that the problem of the body‐point motion near an attracting center is considered for the first time, and therefore all theoretical results presented in this paper are novel. Also, for the first time, the model of the body‐point in a central potential field is used to describe the behavior of an electron in a hydrogen atom.

Necessary and Sufficient Condition for Organic Room‐Temperature Phosphorescence from Host–Guest Doped Crystalline Systems

AbstractControlling and predicting the long‐lived room‐temperature phosphorescence (RTP) from organic materials are the next challenges to address for the realization of new efficient organic RTP systems. Here, a new approach is developed to reach these objectives by considering host–guest doped crystals, as well‐suited model systems in that they allow the comprehensive understanding of synergetic structural interactions between crystalline host matrices and emitting guest molecules, one of the key parameters to understand the correlation between the solid‐state organization and crystal RTP performances. Two series of σ‐conjugated donor/acceptor (D‐σ‐A) carbazole‐based matrices and isomeric 1H‐benzo[f]indole‐based dopants are designed, capable of exploring a wide variety of conformations thanks to large rotational degrees of freedom provided by the σ‐conjugation. By correlating the results of single‐crystal X‐ray diffraction analysis and photoluminescence properties, a necessary and sufficient condition for RTP is established that paves the way for the development of new long‐lived RTP host–guest doped systems.

Effective description of a suspended mirror coupled to cavity light: Limitations of Q enhancement due to normal-mode splitting by an optical spring

Pendulums have long been used as force sensors due to their ultimately low dissipation (high-quality factor) characteristic. They are widely used in the measurement of the gravitational constant, detection of gravitational waves, and determination of ultralight dark matter. Furthermore, it is expected that the quantum nature of gravity will be demonstrated by performing quantum control for macroscopic pendulums. Recently, we have demonstrated that quantum entanglement between two pendulums can be generated using an optical spring [D. Miki, N. Matsumoto, A. Matsumura, T. Shichijo, Y. Sugiyama, K. Yamamoto, and N. Yamamoto, arXiv:2210.13169 (2022)]; however, we have ignored that an optical spring can reduce the quality factor (Q-factor) by applying normal-mode splitting between the pendulum and rotational modes possessing relatively high dissipation. Herein, we analyze a system composed of a cylinder suspended using a beam (a suspended mirror, i.e., a pendulum) and an optical spring to consider normal-mode splitting. The reduction in Q-factor is determined only by the beam parameters: the ratio of the radius of the mirror to the length of the beam, and the ratio of the frequency of the rotational mode to the pendulum mode in the absence of cavity photons. In our analysis, we find that the reduction factor $4.38$ is reproduced, which is consistent with the experimental result in Matsumoto \textit{et al.} [N. Matsumoto, S. B. Catan$\tilde{\text{o}}$-Lopez, M. Sugawara, S. Suzuki, N. Abe, K. Komori, Y. Michimura, Y. Aso, and K. Edamatsu, Phys. Rev. Lett. 122, 071101 (2019)]. Our analysis shows that low dissipation (high quality) can be reached using an optical spring for the realistic pendulum system considering the rotational degree of freedom.

Dynamics of a 3-UPS-UPU-S Parallel Mechanism

In this paper, a parallel mechanism with two rotational degrees of freedom is proposed. It could rotate freely and continuously around the two coordinate axes at the fixed origin of the coordinate frame. The structure of the mechanism is a second-order over constraint parallel structure and the moving platform and base platform are connected by five kinematic chains. The motion characteristics of this structure are analyzed by reciprocal screw equation. Then, the kinematics and dynamics modelling are carried out systematically in a unified way. The kinematics of the mechanism is established by means of screws, the displacements and accelerations of each joint and any point on a link could be calculated by the kinematic screw equation directly. The analysis of acceleration and its mathematical expression in screw form are given, and the acceleration matrix could be applied into the dynamic analysis based on the Newton–Euler equation. All the constraint forces and torques could be obtained by a single set of Newton–Euler equations.

The development and evaluation of an in-vitro shoulder simulator with active muscle simulation

The purpose of the present study was to develop a novel active in-vitro shoulder simulator to emulate all forms of planar and non-planar glenohumeral motions with active muscle simulation on cadaver specimens or shoulder models and to critically evaluate its performance. A physiologic shoulder simulator, driven using simulated muscle force, was developed to dynamically realize accurate kinematic control in all three rotational degrees of freedom (DOF) under physiological kinetic boundaries. The control algorithm of the simulator was implemented using three parallel running independent control loops, which regulate the forces of individual muscles in the respect DOF and work asynchronously in disparate sequences adapted to specific motions (abduction, flexion/extension and rotation). Three cadaveric specimens were used to evaluate the kinematic and kinetic performance of the simulator during simulated motions. High kinematic accuracy (maximum mean deviation ≤ 2.35° and RMSE 1.13°) and repeatability (maximum and average SD of ≤ 1.21° and 0.67°) were observed in all three rotational DOF investigated. The reliabilities of all individual muscle forces actuated in the simulator during planar and non-planar motions were generally excellent, with the 95% CIs of ICC estimates of > 0.90 for most instances (30/36). A novel shoulder simulator with active muscle simulation was developed and evaluated. Its capability to reproduce kinematics and kinetics in a physiological range for all DOF was systematically evaluated for multiple kinetic and kinematic outcome variables. The presented simulator is a powerful tool for investigating the biomechanics of physiological and pathological shoulder joints and to evaluate various surgical interventions. Acquisition of reliable data in joint kinetics and translational kinematics during active motions is critical to assess shoulder pathologies and appropriate treatments. We provide a unique muscle activated physiologic shoulder simulator, which allows the comprehensive acquisition of joint kinematic and kinetic data during repeated realistic planar and non-planar motions.

Quantum Uncertainty Limit for Stern-Gerlach Interferometry with Massive Objects.

We analyze the fundamental coherence limit of a nano-object with an embedded spin in a Stern-Gerlach interferometer. This limit stems from the which-path information provided by the object's rotational degrees of freedom due to the evolution of their quantum uncertainty. We show that such interferometry is straightforward in a weak magnetic field and short duration. Large wave packet separation is made possible with proper fine-tuning over long durations. This opens the door to fundamental tests of quantum theory and quantum gravity. The results and conclusions are extendable to any type of interferometry with complex objects.

Free Vibration of Inclined Twisted Cables

This paper is aimed at simulating and investigating the coupled translational and rotational vibrations occurring simultaneously in inclined sagged cables. The three-dimensional behavior of the single-layered six wires strand stiffness results are reduced to effective one-dimensional behavior from the elasticity-based finite element behavior analyses under axial tension and torsional loads. These are directly compared with multiple one-dimensional analytical model results. The effective stiffness coefficients agreed well for the actual lay angle of the cable and at angles below 20 degrees with finite element models where internal contact was not considered. To find the cable natural frequency and corresponding modal shapes the derived primary stiffness and mass matrices are discretized over the inclined sagged cable using a finite element model where the two-node cable element has three translational and three rotational degrees of freedom. The vibration behavior is also studied using extensive experimental tests using the same cable geometry and material used in the numerical calculations. In addition to the physical experiments, the finite element model accuracy was also compared with results from a well-known analytical model available from the literature for horizontal cables, and the influence of the inclination angle variation was also investigated and compared with the computer finite element software ABAQUS for the same purpose. The results found confirm the correctness of the derived formulation, mathematical, and psychical importance of the six-degrees of freedom finite element model developed and the efficiency in evaluating the coupled cable dynamic behavior. It addition, the results highlight the fundamental dynamics of inclined cables and the role of the inclination angle, sag, and weight of the cable.

Meloxicam hydro-chloride.

The title salt, C14H14N3O4S2 +·Cl- [systematic name: 2-(4-hy-droxy-2-methyl-1,1-dioxo-1,2-benzo-thia-zine-3-amido)-5-methyl-1,3-thia-zol-3-ium chloride] is the hydro-chloride derivative of meloxicam, a drug used to treat pain and inflammation in rheumatic disorders and osteoarthritis. Although its mol-ecular structure is similar to that previously reported for the hydro-bromide analogue, both salts are not isomorphous. Different crystal structures originate from a conformational modification, arising from a degree of rotational freedom for the thia-zolium ring in the cations. By taking as a reference the conformation of meloxicam, the thia-zolium ring is twisted by 10.96 and -16.70° in the hydro-chloride and hydro-bromide salts, while the 1,2-benzo-thia-zine core is a rigid scaffold. This behaviour could explain why meloxicam is a polymorphous compound.

Kinematics analysis and simulation of 2-CRS-S' parallel mechanism

A 2-CRS-S ' parallel mechanism is proposed in this paper. The parallel mechanism consists of a static platform, two identical driving branches, a moving platform and a fixed branch, with two rotational degrees of freedom on the X and Y axes. Taking the driving branch chain in the mechanism as the research object, the inverse kinematics analysis of the parallel mechanism is carried out by using the D-H analysis method, and on this basis, the forward kinematics analysis of the structure is carried out by combining the particle swarm optimization algorithm. Finally, the Adams software is used to simulate and analyze the mechanism, and the motion angle curve of the moving platform of the mechanism is obtained, which verifies the correctness of the theoretical analysis. The obtained motion angle curves show regular periodic changes, and the curves have no breakpoints and mutations, indicating that the mechanism runs smoothly during the movement and has good kinematic performance.

Proposal for Zeeman slowing of Rb2 molecules in a supersonic beam, inducing internal cooling

We present a theoretical proposal on Zeeman slowing of a Rb2 supersonic beam, relying on transitions between rovibrational levels of the electronic ground-state and the electronic excited state. Translational cooling is induced by optical transitions from to involving P () and Q () branches. This is achieved by shaping the spectrum of broadband laser sources, in addition to two single-frequency laser sources addressing the transitions. Our Monte–Carlo simulations indicate that the velocity of the molecules can be slowed from 500 m s−1 down to a few m s−1 by a Zeeman slower with a 1.2 m length, after scattering about 150 000 photons. At the end of the slowing process, half of the molecules are internally cooled, predicted to be in the ground-state levels. A final optical pumping step transferring the population to the ground-state level could produce a molecular beam exiting the Zeeman slower which is cold in all the translational, vibrational, and rotational degrees of freedom. Such an approach could potentially be a great interest for cooling down a large class of molecular species.

Visual servo control of endoscope-holding robot based on multi-objective optimization: System modeling and instrument tracking

In routine laparoscopic surgeries, the fatigue operation and improper chief-assistant coordination of the assistant surgeon both reduce the stability of the endoscopic field of view (EFOV) and the surgical efficiency. In contrast, the assistant endoscope-holding robot (AEHR) can stably hold the endoscope and adjust the pose of endoscopic image sensor. However, the traditional method simplifies the tracking of surgical instrument tips (SITs) to the tracking of feature points, and lacks the depth optimization of monocular endoscopic image senor. Based on them, this paper proposes a surgical instrument tracking control method based on visual tracking features (VTFs) and hand-eye coordination (HEC) with feedback of multiple sensors, which can control the depth and axial rotational degrees of freedom (DOFs) of endoscope while tracking SITs. Firstly, the motion mapping Jacobian matrix between the endoscopic image sensor and the endoscope-holding manipulator (EHM) end-effector is constructed with joint encoder feedbacks, and the VTFs of endoscopic camera feedback are extracted based on the deep segmentation model of SITs. Secondly, the position adjustment model based on VTFs and the attitude adjustment model based on HEC are established. Thirdly, a complete set of visual servo control (VSC) software and hardware system for AEHRs is designed. Finally, the correctness, effectiveness and operability of the proposed method are comprehensively verified through the simulation and experiment of surgical instrument tracking. The visual tracking distance and radius error of endoscopic image sensor frames are reduced by no less than 34.6% and 42.59% under different experimental backgrounds, respectively.

Design and development of modular magnetic bio-inspired autonomous underwater robot – MMBAUV

This paper describes the design and construction of a magnetically coupled modular bio-inspired underwater robot named the Modular Magnetic Bio-Inspired Underwater Vehicle (MMBAUV). Designed to form a traveling wave to mimic efficient Body Caudal Fin (BCF) swimming and manoeuvring, its modularity allows for flexible system setup and offers an opportunity for redundancy and cost reduction through a common design structure. The specific feature of this design presents a novel application of a permanent synchronous magnetic coupling between neighbouring modules with a rotational degree of freedom (DoF). The actuated magnetic coupling provides a reliable and low maintenance solution to the fundamental issues of water tightness of flexible underwater structures. When encountering extreme conditions, the magnetic coupling allows the safe decoupling of the modules increasing the survivability of the robotic system. Presented lab testing results demonstrate the function of the design and provide initial evidence of its thrust generation and manoeuvrability.

Activity-induced propulsion and separation of passive chiral particles in liquids

Active mechanisms such as a magnetic torque, motion of a solid or liquid boundary, and changes in pressure induce motion of chiral particles perpendicular to the plane of the flow of a base liquid endowed with rotational degrees of freedom (such as a ferrofluid).

Microfluidic rotating-target device capable of three-degrees-of-freedom motion for efficient in situ serial synchrotron crystallography.

There is an increasing demand for simple and efficient sample delivery technology to match the rapid development of serial crystallography and its wide application in analyzing the structural dynamics of biological macromolecules. Here, a microfluidic rotating-target device is presented, capable of three-degrees-of-freedom motion, including two rotational degrees of freedom and one translational degree of freedom, for sample delivery. Lysozyme crystals were used as a test model with this device to collect serial synchrotron crystallography data and the device was found to be convenient and useful. This device enables in situ diffraction from crystals in a microfluidic channel without the need for crystal harvesting. The circular motion ensures that the delivery speed can be adjusted over a wide range, showing its good compatibility with different light sources. Moreover, the three-degrees-of-freedom motion guarantees the full utilization of crystals. Hence, sample consumption is greatly reduced, and only 0.1 mg of protein is consumed in collecting a complete dataset.

Simultaneous Optical Trapping and Electromagnetic Micromanipulation of Ferromagnetically Doped NaYF4 Microparticles

Optical trapping allows the trapping and manipulation of dielectric microparticles. However, full control over all six degrees of freedom of the trapped object is challenging. Here, we use ferromagnetic iron-doped upconversion microparticles for simultaneous optical trapping and magnetic micromanipulation that allows full control over all translational and rotational degrees of freedom. These microparticles have a low absorption that allows optical trapping and a high coercivity and saturation magnetization that allow magnetic manipulation. The particles will enable micromanipulation experiments, for example, in single-molecule biophysics.

Breakdown of isochronal superpositioning of [formula omitted]- and [formula omitted]-relaxation times in the van der Waals system – Loratadine

In this paper, high-pressure (HP) dielectric studies on the van der Waals active pharmaceutical ingredient (API) - loratadine (LOR) were carried out. It was found that, surprisingly, the secondary (β) relaxation, which, according to the Coupling Model (CM) predictions, was classified as a Johari-Goldstein (JG) process, separates from the structural (α)-mode with compression (although the shape of the α-peak is invariant to the thermodynamic conditions at constant τα). Consequently, there is a breakdown of the isochronal superpositioning of α- and β- relaxation times (τα and τβ) in this system, which is a typical behavior for the secondary process with intermolecular character. Based on these findings, two possibilities concerning the origin of the β-relaxation in LOR have been proposed: 1) it is a non-JG process (probably originating from fluctuations within cyclic rings of the API molecule), which, however, satisfies the CM predictions; or 2) it is a JG-process, which similarly to a few earlier examined H-bonded compounds (e.g., probucol and sorbitol) is characterized by a different sensitivity to compression when compared to the α-process. Moreover, it was found that the activation entropy for the β-process takes negative values, irrespective of the pressure conditions. That may be interpreted as a result of conformational variation or the loss of translational and rotational degrees of freedom, leading to increased order in API due to densification. The results presented herein give a new insight into the relationship between the structural and secondary relaxations in the close vicinity of the glass transition temperature. Furthermore, they show that HP studies are crucial in elucidating the correlation between these processes.

Vortex-induced vibrations of two tandem rigidly coupled circular cylinders with streamwise, transverse, and rotational degrees of freedom

This paper numerically investigates the effects of rigid coupling and the vibration degrees of freedom on the vortex-induced vibrations (VIV) of two tandem circular cylinders for a spacing ratio L/D = 4 at a Reynolds number of 150. Two (translational vibration) and three (translational and rotational vibration) degrees of freedom (RC-2DOF and RC-3DOF, respectively) cases are considered and compared with the case of two freely vibrating cylinders (FC). The dynamic response characteristics, flow structures, and vortex dynamics are analyzed. The results show that the rigid coupling has a significant effect on VIV. Compared with FC, the maximum transverse amplitude of the downstream cylinder decreases by 30% for RC-2DOF and approximately 15% for RC-3DOF. The lock-in region narrows by 40% for RC-2DOF, while it widens by 80% for RC-3DOF. Reattachment and co-shedding regions are observed for FC and RC-3DOF, whereas only the co-shedding region exists for RC-2DOF. We further explore flow forces and fluid–structure-interaction mechanisms in the lock-in region for RC-3DOF. The rotation of the twin-cylinder system triggers some unique vibration characteristics, such as two transverse amplitude peaks of the upstream cylinder and a prominent streamwise amplitude at Vr = 7–9. The vortex-to-vortex and vortex-to-cylinder interactions are complicated and changeable with reduced velocity for RC-3DOF.

The pore of the KcsA channel, including the entire cavity up to the selectivity filter, participates in selectivity, rectification, and ion transport.

Quantum calculations on the pore of the KcsA channel from gate to selectivity filter (SF) show how the motion of the K+ ions requires a coordination through states as a contact ion pair (CIP) just beyond the gate, then a solvent separated ion pair (SSIP) in the cavity, then again a CIP, as the ion approaches the selectivity filter (SF). Also, results on the hydration/resolvation by protein of the ion at the SF suggest a mechanism for rectification that depends on the water hydrogen bonded to the conserved threonines. K+ loses hydration water, switching to protein solvation at the SF; Na+ cannot move forward to the SF because of inability to lose hydration water to protein, so is selected out. Water confined in the cavity loses translational and rotational degrees of freedom, altering the competition between ion and protein for hydrating water. Calculations (seven positions, single ion, four positions, ion pairs) show limited barriers for a cluster with a pair of K+ ions, but large barriers for a single ion; it does not form exactly a similar SSIP at the entrance to the selectivity filter, but a SSIP at the cavity center and at the selectivity filter. Charge transfer as the ion moves through the pore can change the charge on the ion up to 0.03 q. Rectification occurs at the entrance to the SF, where the conserved threonine hydroxyls plus methyls interact with the ion near the first SF position, forming an effective ratchet and pawl that effects rectification, preventing an ion in the lowest SF position from reclaiming water in the cavity. Water–protein competition is a recurring theme as the ion moves through the pore.