Motional Degrees Of Freedom Research Articles

Development of naoe-FOAM-SJTU solver based on OpenFOAM for marine hydrodynamics

A CFD solver naoe-FOAM-SJTU (The abbreviation naoe stands for naval architecture and ocean engineering) is developed based on the open source platform OpenFOAM with the purpose of simulating various marine hydrodynamic problems. In the present paper, self-developed modules, i.e., wave generation and absorption, 6 degrees of freedom motion, mooring system, dynamic overset grid, fluid-structure interaction, unsteady actuator line model, implemented on the open source platform OpenFOAM are introduced to illustrate the development of the marine hydrodynamics CFD solver. Furthermore, extensive simulations of marine hydrodynamic problems using the developed modules are conducted and validated by available experimental data. It has been proved that the CFD solver naoe-FOAM-SJTU is suitable and reliable in predicting the complex viscous flow around ship and offshore structures. Efficiency and accuracy need to be focused in the future development of the present CFD solver.

Development and Testing of a Prototype for 3D Radial Pulse Image Measurement and Compatible With 1D Pulse Wave Analysis

This study proposes the prototype of a wrist pulse acquisition device with three-dimensional pulse image (3DPI) obtained at the radial artery. The proposed prototype is designed with mechanical and electronic circuit hardware as well as the control and data acquisition software to have fourteen degrees of movement freedom against the sophisticated geometry of the wrist radial artery for accurate pulse-taking. Three robot fingers with nine degrees of movement freedom and a wrist fixer with two degrees of rotation freedom and one degree of manual movement freedom are designed to mimic the fine pulse-taking skill of a Chinese medicine physician. The customer-designed array sensors with $5\times5$ -1 sensing elements in an array are attached on the robot fingertips to get 3DPI with spatial information for direct translation of pulse feeling patterns in Chinese medicine texts, in addition to being compatible with 1D pulse wave analysis. To check reliability of the prototype, adopted is SphygmoCor with pulse data correlation. Consequently, the prototype passes safety tests and has high correlation of pulse data (waveform and peripheral augmented index) with those obtained by SphygmoCor. The automatic multi-depth pulse-taking with robot fingers attached array sensors on their tips can get acceptably repeatable pulse data with coefficient of variation less than 10%. By simultaneous pulse-taking at Cun-Guan-Chi positions, 3DPIs demonstrate great different stereoscopic waveshapes against almost unchanged single temporal pulse waveshape. Hence, the proposed prototype may be a useful tool to perform array pulse-taking for Chinese medicine pulse diagnosis and pulse wave analysis for cardiovascular examination.

Oral function analysis with six degrees of freedom motion and synchronization measurement of the EMG

Oral function analysis with six degrees of freedom motion and synchronization measurement of the EMG

Hydrodynamic Analysis and Power Conversion for Point Absorber WEC with Two Degrees of Freedom Using CFD

Point absorber wave energy device with multiple degrees of freedom (DOF) is assumed to have a better absorption ability of mechanical energy from ocean waves. In this paper, a coaxial symmetric articulated point absorber wave energy converter with two degrees of freedom is presented. The mechanical equations of the oscillation buoy with power take-off mechanism (PTO) in regular waves are established. The three-dimensional numerical wave tank is built in consideration of the buoy motion based upon the CFD method. The appropriate simulation elements are selected for the buoy and wave parameters. The feasibility of the CFD method is verified through the contrast between the numerical simulation results of typical wave conditions and test results. In such case, the buoy with single DOF of heave, pitch and their coupling motion considering free (no PTO damping) and damped oscillations in regular waves are simulated by using the verified CFD method respectively. The hydrodynamic and wave energy conversion characteristics with typical wave conditions are analyzed. The numerical results show that the heave and pitch can affect each other in the buoy coupling motion, hydrodynamic loads, wave energy absorption and flow field. The total capture width ratio with two coupled DOF motion is higher than that with a single DOF motion. The wave energy conversion of a certain DOF motion may be higher than that of the single certain DOF motion even though the wave is at the resonance period. When the wave periods are high enough, the interaction between the coupled DOF motions can be neglected.

Dynamic Analysis of Linke Hofmann Busch Coach and Determination of its Sensitive Design Parameters Considering Suspended Equipments

This study aims at dynamic behaviour of a Linke Hofmann Busch coach and its sensitive parameters against track irregularities considering various suspended equipment. The randomly distributed track irregularities characterized in terms of Indian Rail Road PSD standard are considered main source of excitation that produces undesired vibrations. The coach body and bogie frame subjected to 4 degree of freedom motions (bounce, lateral, roll and pitch) are modelled using finite element methodology where system matrices such as mass, stiffness and damping matrices are obtained for eigenvalue solution. Using modal parameters obtained as above and PSD of track irregularities, both vertical and lateral mean square acceleration responses (MSAR) are determined at various points of concern on coach body. It is observed that the vertical peak responses occur in low frequency range (0-10 Hz) which is caused by long wavelength irregularities of track that causes discomfort. It is also observed that constant peak lateral responses occur at still lower frequency as compared to vertical response which again causes discomfort to vehicle riders. This concludes that there is a further scope of improvement in comfort level with minor adjustments of suspended equipment of a LHB coach. A sensitivity analysis based on the partial derivatives against FRF displacement is conducted and most sensitive design parameters are obtained for optimization to improve ride comfort. It is suggested that if the mass of bio toilet tanks and relative position of battery box + transformer unit i.e. most sensitive parameters of suspended equipment are changed then the ride comfort can be improved

A New Decoupled RotLin Motor With Fuzzy Sliding Mode Control

In this paper, a new rotary-linear switched-reluctance motor with a magnetic decoupled structure is introduced. The rotational motion of the motor, managed by a sliding-mode controller, is coordinated with the proportional-derivation linear motion by using a fuzzy logic block. Consequently, both rotational and linear motions can be realized simultaneously. In addition, the decoupled magnetic paths of the motor in two directions are analyzed by finite-element method, with the force and torque measurements suggesting the feasibility of the motor. Both the simulation and experimental results show that the motor is totally decoupled in the linear and rotary directions. The linear movement and the rotation at the same time validate the effectiveness of the motor design and the proposed control method, with highly accurate responses for the two degrees of freedom movement.

Effects of Degrees of Motion Freedom on Free-Fall of A Sphere in Fluid

Free-fall of a sphere in fluid is investigated at a Galileo number of 204 by direct numerical simulations (DNS). We mainly focus on the effects of different degrees-of-freedom (DOFs) of the sphere motion during free-fall. The characteristics of free-fall are compared with those of flow past a fixed sphere. Additional numerical tests are conducted with constraints placed on the translational or rotational DOFs of the sphere motion to analyze different DOFs of sphere motion. The transverse motion contributes significantly to the characteristics of free-fall; it results in the retardation of the vortex shedding, leading to the decrease of the Strouhal number. In addition, the transversal sphere motion exhibits the tendency to promote the sphere rotation. On the contrary, the effects of the sphere rotation and vertical oscillations during free-fall are negligible.

Unconditional Steady-State Entanglement in Macroscopic Hybrid Systems by Coherent Noise Cancellation.

The generation of entanglement between disparate physical objects is a key ingredient in the field of quantum technologies, since they can have different functionalities in a quantum network. Here we propose and analyze a generic approach to steady-state entanglement generation between two oscillators with different temperatures and decoherence properties coupled in cascade to a common unidirectional light field. The scheme is based on a combination of coherent noise cancellation and dynamical cooling techniques for two oscillators with effective masses of opposite signs, such as quasispin and motional degrees of freedom, respectively. The interference effect provided by the cascaded setup can be tuned to implement additional noise cancellation leading to improved entanglement even in the presence of a hot thermal environment. The unconditional entanglement generation is advantageous since it provides a ready-to-use quantum resource. Remarkably, by comparing to the conditional entanglement achievable in the dynamically stable regime, we find our unconditional scheme to deliver a virtually identical performance when operated optimally.

Entanglement-like properties in spin–orbit coupled ultra cold atom and violation of Bell-like inequality

We show that the general quantum state of synthetically spin–orbit coupled ultra cold bosonic atoms, whose condensate was experimentally created recently by Lin et al (2011 Nature 471, 83), shows entanglement between motional degrees of freedom (momentum) and internal degrees of freedom (hyperfine spin). We demonstrate the violation of Bell-like inequality (CHSH) for such states that provide a unique opportunity to verify fundamental principles like quantum contextuality for commutating observables which are not spatially separated. We analyze in detail the Rabi oscillation executed by such an atom-laser system and how this influences quantities like entanglement entropy, the violation of Bell-like inequality, etc. We also discuss the implications of our result in testing quantum contextuality and Bell’s Inequality violation by macroscopic quantum object like Bose–Einstein condensate of ultra cold atoms.

Aerodynamics and Flight Dynamics Simulation of Basic Finner Supersonic Flight in Aeroballistic Experiment

This paper presents some results of aerodynamics and flight dynamics modeling of Basic Finner supersonic flight in an aeroballistic experiment [1]. Three dimensional surface based on the experiment description was formed. Unstructured tetrahedral volume mesh is formed after it. Aerodynamics computations were done by software package for CFD numerical computation of free form high-speed vehicle ug3D developed in the Institute for Problems in Mechanics. Obtained from CFD calculations aerodynamic coefficients became initial data for unguided Basic Finner flight dynamics calculations. Flight dynamics computations were done by developed solver MODIN for typical high speed vehicles flight dynamics calculations [2]. Six degrees of freedom motion without considering Earth rotation and form are adopted. Results of experimental and obtained numerical aerodynamic coefficients and flight parameters data comparison are also presented.

Analysis and Design of a Maglev Permanent Magnet Synchronous Linear Motor to Reduce Additional Torque in dq Current Control

The maglev linear motor has three degrees of motion freedom, which are respectively realized by the thrust force in the x-axis, the levitation force in the z-axis and the torque around the y-axis. Both the thrust force and levitation force can be seen as the sum of the forces on the three windings. The resultant thrust force and resultant levitation force are independently controlled by d-axis current and q-axis current respectively. Thus, the commonly used dq transformation control strategy is suitable for realizing the control of the resultant force, either thrust force and levitation force. However, the forces on the three windings also generate additional torque because they do not pass the mover mass center. To realize the maglev system high-precision control, a maglev linear motor with a new structure is proposed in this paper to decrease this torque. First, the electromagnetic model of the motor can be deduced through the Lorenz force formula. Second, the analytic method and finite element method are used to explore the reason of this additional torque and what factors affect its change trend. Furthermore, a maglev linear motor with a new structure is proposed, with two sets of 90 degrees shifted winding designed on the mover. Under such a structure, the mover position dependent periodic part of the additional torque can be offset. Finally, the theoretical analysis is validated by the simulation result that the additionally generated rotating torque can be offset with little fluctuation in the proposed new-structure maglev linear motor. Moreover, the control system is built in MATLAB/Simulink, which shows that it has small thrust ripple and high-precision performance.

Video-assisted thoracic surgery : Aglobal development

More than 200 years ago the first attempts at thoracoscopy were made but only after its introduction 25years ago has video-assisted thoracoscopic surgery (VATS) experienced rapid progress. Due to worldwide cooperation and international networking tremendous progress of the technique was made by thoracic surgeons on all continents developing the technique into aless invasive operating procedure on the thorax. For patients this meant improvement in the quality of life and ultimately better survival rates following lung cancer surgery. The VATS procedures are nowadays the preferred method unless the size and extent of the tumor prohibits aminimally invasive procedure. New trends in VATS are ambulatory, drainless or uniportal VATS, the latter being possible because insufflation of carbon dioxide is not necessary, allowing manipulation with multiple instruments through one small incision. The other trend is robotic-assisted thoracic surgery. The benefits of the robotics are higher degrees of freedom for movement of the instruments. The development of VATS is nowadays aglobal one with North America and Asian countries being the most active protagonists, but European countries also play an important role in shaping the future of minimally invasive surgery. Modern media help to further promote the technique.

Experimental quantum simulation of fermion-antifermion scattering via boson exchange in a trapped ion

Quantum field theories describe a variety of fundamental phenomena in physics. However, their study often involves cumbersome numerical simulations. Quantum simulators, on the other hand, may outperform classical computational capacities due to their potential scalability. Here we report an experimental realization of a quantum simulation of fermion–antifermion scattering mediated by bosonic modes, using a multilevel trapped ion, which is a simplified model of fermion scattering in both perturbative and non-perturbative quantum electrodynamics. The simulated model exhibits prototypical features in quantum field theory including particle pair creation and annihilation, as well as self-energy interactions. These are experimentally observed by manipulating four internal levels of a 171Yb+ trapped ion, where we encode the fermionic modes, and two motional degrees of freedom that simulate the bosonic modes. Our experiment establishes an avenue towards the efficient implementation of field modes, which may prove useful in studies of quantum field theories including non-perturbative regimes.

An optimal control strategy for hybrid actuator systems: Application to an artificial muscle with electric motor assist

Humans use multiple muscles to generate such joint movements as an elbow motion. With multiple lightweight and compliant actuators, joint movements can also be efficiently generated. Similarly, robots can use multiple actuators to efficiently generate a one degree of freedom movement. For this movement, the desired joint torque must be properly distributed to each actuator. One approach to cope with this torque distribution problem is an optimal control method. However, solving the optimal control problem at each control time step has not been deemed a practical approach due to its large computational burden. In this paper, we propose a computationally efficient method to derive an optimal control strategy for a hybrid actuation system composed of multiple actuators, where each actuator has different dynamical properties. We investigated a singularly perturbed system of the hybrid actuator model that subdivided the original large-scale control problem into smaller subproblems so that the optimal control outputs for each actuator can be derived at each control time step and applied our proposed method to our pneumatic–electric hybrid actuator system. Our method derived a torque distribution strategy for the hybrid actuator by dealing with the difficulty of solving real-time optimal control problems.

Variability and stochastic simulation of power from wave energy converter arrays

A novel stochastic model has been developed which allows for the prediction of Wave Energy Converters (WECs) array power time series, based solely on knowledge of an individual WEC power time series. The model is applicable for arrays of independent WECs.The power from an array of WECs was simulated by deploying 50 individual WECs in a numerical testbed and aggregating the individual power productions. 51 differing WEC array scenarios were completed using four different WEC architectures, differing separation distances, wave directional spreading constants and device degrees of freedom. These allowed investigation into the normalized standard deviation and the frequency content relationships between the power from an individual WEC and an array of WECs. These properties were used to determine if the power from WECs within the arrays was independent.WECs are found to be independent if the separation distance is greater than 212 m. If small differences in the frequency content of the power is allowable, separation distances of 98 m with directional spreading constants (s) of 15 are allowable. WEC architecture and movement degrees of freedom were shown not to affect independence.

Counting ions and other nucleophiles at surfaces by chemical trapping.

The interfaces of membranes and other aggregates are determined by the polarity, electrical charge, molecular volume, degrees of motional freedom and packing density of the head groups of the amphiphiles. These properties also determine the type of bound ion (ion selectivity) and its local density, i.e. concentration defined by choosing an appropriate volume element at the aggregate interface. Bulk and local ion concentrations can differ by orders of magnitude. The relationships between ion (or other compound) concentrations in the bulk solvent and in the interface are complex but, in some cases, well established. As the local ion concentration, rather than that in the bulk, controls a variety of properties of membranes, micelles, vesicles and other objects of theoretical and applied interests, measurement of local (interfacial, bound) ion concentrations is of relevance for understanding and characterizing such aggregates. Many experimental methods for estimating ion distributions between the bulk solution and the interface provide indirect estimates because they are based on concentration-dependent properties, rather than concentration measurements. Dediazoniation, i.e. the loss of N2, of a substituted diazophenyl derivative provides a tool for determining the number of nucleophiles (including neutral or negatively charged ions) surrounding the diazophenyl derivative prior to the dediazoniation event. This reaction, defined as chemical trapping, and the appropriate reference points obtained in bulk solution allow direct measurements of local concentrations of a variety of nucleophiles at the surface of membranes and other aggregates. Here we review our contributions of our research group to the use, and understanding, of this method and applications of chemical trapping to the description of local concentrations of ions and other nucleophiles in micelles, reverse micelles, vesicles and solvent mixtures. Among other results, we have shown that interfacial water determines micellar shape, zwitterionic vesicle-forming amphiphiles display ion selectivity and urea does not accumulate at micellar interfaces. We have also shown that reaction products can be predicted from the composition of the initial state, even in non-ideal solvent mixtures, supporting the usefulness of chemical trapping as a method to determine local concentrations. In addition, we have analysed the mechanism of dediazoniation, both on theoretical and experimental basis, and concluded that the formation of a free phenyl cation is not a necessary part of the reaction pathway.

Self-propelled ion gel at air-water interface

We report on a self-propelled gel using ionic liquid as a new type of self-propellant that generates a powerful and durable motion at an air-water interface. The gel is composed of 1-ethyl-3-methylimidazolium-bis(trifluoromethylsulfonyl)imide (EMIM-TFSI) and poly(vinylidene fluoride-co-hexafluoropropylene) (P(VDF-co-HFP)). A long rectangular ion gel piece placed on the interface shows rapid rotation motion with maximum frequency close to 10 Hz, corresponding to the velocity over 300 mms−1 at an outmost end of the piece. The rotation continues for ca. 102 s, followed by a reciprocating motion (<~103 s) and a nonlinear motion in long-time observations (>~103 s). The behaviours can be explained by the model considering elution of EMIM-TFSI to the air-water interface, rapid dissolution into water, and slow diffusion in an inhomogeneous polymer gel network. Because the self-propellants are promptly removed from the interface by dissolution, durable self-propelled motions are observed also at limited interface areas close in size to the gel pieces. A variety of motions are induced in such systems where the degree of freedom in motion is limited. As the ion gel possesses formability and processability, it is also advantageous for practical applications. We demonstrate that the gel does work as an engine.

Numerical simulations for the safe return to port of a damaged passenger ship in head or following seas

This study investigated the motion responses and flooding behavior of a damaged passenger ship model, using numerical simulations of fluid dynamics and six degrees of freedom motion. The test condition was based on the safe return to port regulations, and the numerical investigation was performed by solving unsteady Reynolds-averaged Navier–Stokes equations, using CFDShip-Iowa program and SUGGAR++ library. The selected hull form was scaled model of a passenger ship provided by the Ship Stability Research Center at the University of Strathclyde, UK. A damaged compartment was located amidships. Computed ship motions in head and following seas in regular wave train were analyzed by fast Fourier transform and the computation results of the pitch, heave, and roll motions and the advance speed were compared with experimental data in the same test condition. The pitch and heave motions by the numerical analysis agreed well with the experimental results, but the computation overpredicted roll motions at the natural roll frequency. In head seas conditions, the advance speed was overpredicted, regardless of the wave amplitude and period. In addition, flow behavior around the course-keeping model was investigated, in terms of the free-surface wave, hull wake, and flooding behavior.

Rashba Effect in a Single Colloidal CsPbBr3 Perovskite Nanocrystal Detected by Magneto-Optical Measurements.

This study depicts the influence of the Rashba effect on the band-edge exciton processes in all-inorganic CsPbBr3 perovskite single colloidal nanocrystal (NC). The study is based on magneto-optical measurements carried out at cryogenic temperatures under various magnetic field strengths in which discrete excitonic transitions were detected by linearly and circularly polarized measurements. Interestingly, the experiments show a nonlinear energy splitting between polarized transitions versus magnetic field strength, indicating a crossover between a Rashba effect (at the lowest fields) to a Zeeman effect at fields above 4 T. We postulate that the Rashba effect emanates from a lattice distortion induced by the Cs+ motion degree of freedom or due to a surface effect in nanoscale NCs. The unusual magneto-optical properties shown here underscore the importance of the Rashba effect in the implementation of such perovskite materials in various optical and spin-based devices.

Parametric feedback cooling of levitated optomechanics in a parabolic mirror trap

We demonstrate a simple and robust geometry for optical trapping in vacuum of a single nanoparticle based on a parabolic mirror and the optical gradient force, and we demonstrate rapid parametric feedback cooling of all three motional degrees of freedom from room temperature to a few mK. A single laser at 1550nm, and a single photodiode, are used for trapping, position detection, and cooling for all three dimensions. Particles with diameters from 26nm to 160nm are trapped without feedback to 10$^{-5}$mbar and with feedback engaged the pressure is reduced to 10$^{-6}$mbar. Modifications to the harmonic motion in the presence of noise and feedback are studied, and an experimental mechanical quality factor $>4\times 10^7$ is estimated.