Motional Degrees Of Freedom Research Articles

Single-ion quantum Otto engine with always-on bath interaction

We demonstrate how the reciprocating heat cycle of a quantum Otto engine (QOE) can be implemented using a single ion and an always-on thermal environment. The internal degree of freedom of the ion is chosen as the working fluid, while the motional degree of freedom can be used as the cold bath. We show, that by adiabatically changing the local magnetic field, the work efficiency can be asymptotically made unity. We propose a projective measurement of the internal state of the ion that mimics the release of heat from the working fluid during the engine cycle. In our proposal, the coupling to the hot and the cold baths need not be switched off and on in an alternate fashion during the engine cycle, unlike other existing proposals of QOE. This renders the proposal experimentally feasible using the available tapped-ion engineering technology.

A cold-atom Fermi-Hubbard antiferromagnet.

Exotic phenomena in systems with strongly correlated electrons emerge from the interplay between spin and motional degrees of freedom. For example, doping an antiferromagnet is expected to give rise to pseudogap states and high-temperature superconductors. Quantum simulation using ultracold fermions in optical lattices could help to answer open questions about the doped Hubbard Hamiltonian, and has recently been advanced by quantum gas microscopy. Here we report the realization of an antiferromagnet in a repulsively interacting Fermi gas on a two-dimensional square lattice of about 80 sites at a temperature of 0.25 times the tunnelling energy. The antiferromagnetic long-range order manifests through the divergence of the correlation length, which reaches the size of the system, the development of a peak in the spin structure factor and a staggered magnetization that is close to the ground-state value. We hole-dope the system away from half-filling, towards a regime in which complex many-body states are expected, and find that strong magnetic correlations persist at the antiferromagnetic ordering vector up to dopings of about 15 per cent. In this regime, numerical simulations are challenging and so experiments provide a valuable benchmark. Our results demonstrate that microscopy of cold atoms in optical lattices can help us to understand the low-temperature Fermi-Hubbard model.

Hydrodynamic response simulation of Catenary mooring in the spar truss floating platform under Caspian Sea conditions

Nowadays, oil platform's moorings failure one of the most important challenges of the drilling industry in deep seas for the establishment and stability of the platform during operation. The behavior of these moorings plays an important role in the preservation of the platform with interaction by waves and environmental forces. In this regard a sample of non-classical Spar Truss platform was analyzed using Moses software in the Caspian Sea. Also hydrodynamic analysis of mooring system based on three-dimensional diffraction method was used; this analysis is based on time dependent and six degrees of freedom motion. Therefore response amplitude operator (RAO) of platform moorings was obtained by incident wave. The effect of removing a platform mooring was studied. The results indicate a high gradient change in Surge Movement. Also the results of this study can be used as a benchmark for spar platforms design in Caspian sea.

Modeling and simulation of five DOF motions for SWATH ships

To develop marine simulators of Small Waterplane Area Twin Hull (SWATH) ships and gain a better understanding of the maneuverability of the SWATH, a mathematical model with five Degree of Freedom (DOF) for SWATH has been established, in which the surge, sway, yaw, roll and pitch motions are all considered. The characteristics of the SWATH ship form and the hydrodynamic interaction among the twin bodies, twin propellers and twin rudders are taken into consideration on the basis of the three DOF maneuvering mathematical model. To verify the effectiveness of the modeling and ensure the use of the model in marine handling simulators, a detailed model is tentatively established on the basis of empirical formulas. Based on the acquired results, tests were performed to simulate the steady turning and zigzag motions of the ship. The results are in accordance with regular pattern and trend of motion of SWATH ships. This verifies the effectiveness of the mathematical model of the turning movement.

Numerical investigation of the interaction between an inverse T-type fixed/floating breakwater and regular/irregular waves

This paper presents a numerical analysis of nonlinear interaction between inverse T-type free surface breakwater and regular/irregular waves using a zonal hybrid RANS/laminar method based on an improved mesh updating strategy, which divides the whole computation domain into several parts to avoid low quality mesh elements caused by the large-scale movement. Each mesh zone is specified with different degrees of motion freedom. In the stationary zone where the flow is less influenced by the body motion, the flow is assumed to be laminar to avoid energy loss during the wave propagation. The RANS turbulence model applies only to the moving zones that move with specified motion components (sway/heave/pitch). The zonal hybrid RANS/laminar method is validated by comparison with the experimental data measured under a regular wave with period Tw=1.0s and amplitude A=0.0192m. The simulated motion responses, especially the sway motion amplitudes, of the floating breakwater are agree well with the experimental measurements. The motion responses and the energy-dissipating performances of the fixed/floating inverse T-type-type breakwater under regular/irregular waves are further investigated.

Numerical Modeling and 3D Investigation of INWAVE Device

In this article, numerical studies on a tightly moored point absorber type wave energy converter called INWAVE are presented. This system consists of a buoy, subsea pulleys, and a power take off (PTO) module. The buoy is moored by three ropes that pass through the subsea pulleys to the PTO module. Owing to the counterweight in the PTO module, a constant tension, which provides a horizontal restoring force to the buoy, is constantly applied to the rope. As waves pass by, the buoy is subjected to six degrees of freedom motion, consisting of surge, heave, sway, roll, pitch, and yaw, which causes reciprocating motion in the three mooring ropes. The PTO module converts the motion of the ropes into electric power. This process is expressed as a dynamic equation based on Newtonian mechanics and the performance of the device is analyzed using time domain simulation. We introduce the concept of virtual torsion spring in order to prevent the impact error in the ratchet gear modules which convert bidirectional motion of rope drum into unidirectional rotary motion. The three-dimensional geometrical relationship between the ropes and the buoy is investigated, and the effects of the angle of the mooring rope and the direction of wave propagation are addressed to determine the interaction between the tension of the rope and the buoy. Results have shown that the mooring rope angle has a large impact on the power extraction. The simulation results present a useful starting point for future experimental work.

Large-Deformation Model of a Soft-Bodied Esophageal Actuator Driven by Air Pressure

To study the effect of food flow rheology on the human esophageal swallowing process, a biologically inspired actuator prototype has been developed. The actuator is made of silicone rubber where smooth and continuous peristaltic motion is generated by inflating air chambers distributed within its body. The soft material gives the actuator intrinsic compliance and infinite degrees of freedom in motion. Thus, it is challenging to model the behavior online by current methods. In order to investigate the large-scale deformation of the soft-bodied actuator in response to the air chamber pressures, a geometrically simplified two-dimensional (2-D) model composed of separated beam-shaped elements is proposed. It considers the mechanical properties of the material, the sophisticated geometry of the actuator as it deforms, and the distributed pressure behavior. Empirical data from the actuator prototype (captured by articulography) and the simulated results are compared to investigate the accuracy of the model. The differences of deformations between the experimental results and the theoretical model are analyzed.

Driving Simulator Development with Two Degrees of Freedom Motion for Driver Behavior Study

This paper discusses about the development of a driving simulator with 2 Degree of Freedom (DOF) motion platform as a data collection tool for driver behavior research. The simulator was installed with motion platform, steering wheel, pedals, transmission, screens, computer, simulation software and sound system to record the driving behaviors in simulated traffic environment. Data containing information such as participants' response time, vehicle speed, acceleration, braking, turn signals use and vehicle positioning were collected. This paper also discusses the benefits of driving simulator development for driver behavior research while addressing its challenge and limitation for future improvement. The paper concludes that the driving simulator development can contribute significantly to road safety research specifically in driver behavior study.

パラレルリンク機構を用いた5自由度HEM<sup>2</sup>の開発

In this paper, Haptic End-effector for Medicine and Manufacturing (HEM2) with five degree of freedom (DoF) motion is developed for safer and more intuitive robotic surgery. In resent years, multi DoF forceps robots have been studied and developed to support surgeons. However, conventional multi DoF forceps robots cannot transmit force sensation to surgeons adequately. Force sensation is important for safe and accurate teleoperation. In this paper, a master-slave five DoF HEM2 is developed as a haptic forceps robot. Five DoF motion corresponds with the motion of human hand which can realize complex tasks. By implementing acceleration based bilateral control, force sensation can be transmitted. Spherical joint driven by parallel link mechanism realizes the bending motion of the end-effector. The coaxial driving power transmission mechanism is used to decrease the weight of movable part and improve backdrivability. Besides, the mechanism is composed of rigid parts. The performance of the five DoF HEM2 is validated by experiments.

A Multi-Sensor Fusion MAV State Estimation from Long-Range Stereo, IMU, GPS and Barometric Sensors.

State estimation is the most critical capability for MAV (Micro-Aerial Vehicle) localization, autonomous obstacle avoidance, robust flight control and 3D environmental mapping. There are three main challenges for MAV state estimation: (1) it can deal with aggressive 6 DOF (Degree Of Freedom) motion; (2) it should be robust to intermittent GPS (Global Positioning System) (even GPS-denied) situations; (3) it should work well both for low- and high-altitude flight. In this paper, we present a state estimation technique by fusing long-range stereo visual odometry, GPS, barometric and IMU (Inertial Measurement Unit) measurements. The new estimation system has two main parts, a stochastic cloning EKF (Extended Kalman Filter) estimator that loosely fuses both absolute state measurements (GPS, barometer) and the relative state measurements (IMU, visual odometry), and is derived and discussed in detail. A long-range stereo visual odometry is proposed for high-altitude MAV odometry calculation by using both multi-view stereo triangulation and a multi-view stereo inverse depth filter. The odometry takes the EKF information (IMU integral) for robust camera pose tracking and image feature matching, and the stereo odometry output serves as the relative measurements for the update of the state estimation. Experimental results on a benchmark dataset and our real flight dataset show the effectiveness of the proposed state estimation system, especially for the aggressive, intermittent GPS and high-altitude MAV flight.

Hexapod control system and software

Hexapod is a testing device for generation of six degrees of freedom movement. Its control system is built from the National Instruments components and control application is created in the software LabVIEW. Using the real-time system to run this application requires special programming procedures because the precise timing of the control loop has to be observed. The hexapod motion control is based on its kinematic model. Equations for the six basic motions (3-axis movement and 3-axis rotation) were obtained from the kinematic model. These equations are implemented directly in the control program for basic movement and rotation control. The control system, program design and program optimization are described in this paper.

A Mechatronics Approach for Design of Multiview Image Acquisition Setup for Scene Reconstruction with Single Camera

Conventional design approach is being actively replaced by concurrent design approach in the context of interdisciplinary systems. The proposed research work intends to develop a single moving camera based stereo vision system for scene reconstruction with the intrinsic advantage of multi-directional fields of view. The conventional stereo vision setup uses two stationary passive cameras to capture images of a scene from different vantage points. The proposed system imparts varying mechanical degrees of freedom motion for both the object and the camera which aids in acquiring sequence of images which covers all the visible regions of the object of interest. This gives better detail of the scene under consideration as compared to the conventional two images based stereopsis. A mechatronics design approach has been presented which carefully integrates various elements of the system such as the mechanisms, actuators, sensors and the electronic controller. The paper clearly pin points the cues for the design of the mechanical system which are obtained from the requirements of the computer vision system. The relative pose between the camera and the scene is governed by three independent degrees of freedom namely rotation angle for the object, tilt and working distance for the camera. The selection of the aforementioned parameters is decided by the specifications such as field of view, size of the object and sensor and spatial resolution. The proposed design predicts the system to enjoy benefits of reduced cost and improved flexibility in general.

How wet should be the reaction coordinate for ligand unbinding?

We use a recently proposed method called Spectral Gap Optimization of Order Parameters (SGOOP) [P. Tiwary and B. J. Berne, Proc. Natl. Acad. Sci. U. S. A. 113, 2839 (2016)], to determine an optimal 1-dimensional reaction coordinate (RC) for the unbinding of a bucky-ball from a pocket in explicit water. This RC is estimated as a linear combination of the multiple available order parameters that collectively can be used to distinguish the various stable states relevant for unbinding. We pay special attention to determining and quantifying the degree to which water molecules should be included in the RC. Using SGOOP with under-sampled biased simulations, we predict that water plays a distinct role in the reaction coordinate for unbinding in the case when the ligand is sterically constrained to move along an axis of symmetry. This prediction is validated through extensive calculations of the unbinding times through metadynamics and by comparison through detailed balance with unbiased molecular dynamics estimate of the binding time. However when the steric constraint is removed, we find that the role of water in the reaction coordinate diminishes. Here instead SGOOP identifies a good one-dimensional RC involving various motional degrees of freedom.

Experimental investigation on the hydrodynamic performance of a quay moored jackup

Offshore platforms under construction are normally moored along the quayside during the outfitting stage. The safety of the platforms must be guaranteed during the entire process of outfitting which may last for several months. In this study, the hydrodynamic performance of a quay moored jackup is investigated by using a set of wave basin model tests. In the seakeeping model tests, the dynamic responses of the system, including the six degrees of freedom motions of the jackup and the barge, tensions on the mooring lines and the collision forces on the fenders, were measured in various sea states, and statistical analyses were conducted. Meanwhile, the dynamic responses in current-and-wind-only sea states were analysed for comparison with those in the wave conditions to assess the influence of the wind and the current. It is observed that the offshore wind plays an important role in quay mooring systems and the mooring line tensions are found to exceed the strength of the lines in offshore wind conditions. The possible reasons are discussed in detail and suggestions are proposed for optimising the mooring system performance.

Arrays of individually controlled ions suitable for two-dimensional quantum simulations.

A precisely controlled quantum system may reveal a fundamental understanding of another, less accessible system of interest. A universal quantum computer is currently out of reach, but an analogue quantum simulator that makes relevant observables, interactions and states of a quantum model accessible could permit insight into complex dynamics. Several platforms have been suggested and proof-of-principle experiments have been conducted. Here, we operate two-dimensional arrays of three trapped ions in individually controlled harmonic wells forming equilateral triangles with side lengths 40 and 80 μm. In our approach, which is scalable to arbitrary two-dimensional lattices, we demonstrate individual control of the electronic and motional degrees of freedom, preparation of a fiducial initial state with ion motion close to the ground state, as well as a tuning of couplings between ions within experimental sequences. Our work paves the way towards a quantum simulator of two-dimensional systems designed at will.

TH-AB-202-10: Quantifying the Accuracy and Precision of Six Degree-Of-Freedom Motion Estimation for Use in Real-Time Tumor Motion Monitoring During Radiotherapy

Purpose: Kilovoltage intrafraction monitoring (KIM) scheme has been successfully used to simultaneously monitor 3D tumor motion during radiotherapy. Recently, an iterative closest point (ICP) algorithm was implemented in KIM to also measure rotations about three axes, enabling real-time tracking of tumor motion in six degrees-of-freedom (DoF). This study aims to evaluate the accuracy of the six DoF motion estimates of KIM by comparing it with the corresponding motion (i) measured by the Calypso; and (ii) derived from kV/MV triangulation. Methods: (i) Various motions (static and dynamic) were applied to a CIRS phantom with three embedded electromagnetic transponders (Calypso Medical) using a 5D motion platform (HexaMotion) and a rotating treatment couch while both KIM and Calypso were used to concurrently track the phantom motion in six DoF. (ii) KIM was also used to retrospectively estimate six DoF motion from continuous sets of kV projections of a prostate, implanted with three gold fiducial markers (2 patients with 80 fractions in total), acquired during the treatment. Corresponding motion was obtained from kV/MV triangulation using a closed form least squares method based on three markers’ positions. Only the frames where all three markers were present were used in the analysis. The mean differences between the corresponding motion estimates were calculated for each DoF. Results: Experimental results showed that the mean of absolute differences in six DoF phantom motion measured by Calypso and KIM were within 1.1° and 0.7 mm. kV/MV triangulation derived six DoF prostate tumor better agreed with KIM estimated motion with the mean (s.d.) difference of up to 0.2° (1.36°) and 0.2 (0.25) mm for rotation and translation, respectively. Conclusion: These results suggest that KIM can provide an accurate six DoF intrafraction tumor during radiotherapy.

Tolerance in the Ramsey interference of a trapped nanodiamond

The scheme recently proposed in [M. Scala et al., Phys Rev Lett 111, 180403 (2013)], where a gravity-dependent phase shift is induced on the spin of a nitrogen-vacancy (NV) center in a trapped nanodiamond by the interaction between its magnetic moment and the quantized motion of the particle, provides a way to detect spatial quantum superpositions by means of spin measurements only. Here, the effect of unwanted coupling with other motional degrees of freedom is considered and we show that it does not affect the validity of the scheme. Both this coupling and the additional error source due to misalignment between the quantization axis of the NV center spin and the trapping axis are shown not to change the qualitative behavior of the system, so that a proof-of- principle experiment can be neatly performed. Our analysis, which shows that the scheme retains the important features of not requiring ground state cooling and of being resistant to thermal fluctuations, can be useful for the several schemes which have been proposed recently for testing macroscopic superpositions in trapped microsystems.

이륜 도립진자 이동로봇을 위한 강인제어기 설계

The research on two-wheeled inverted pendulum (TWIP) mobile robots has been ongoing in a number of robotic laboratories around the world. In this paper, we consider a robust controller design for the TWIP mobile robot driving on uniform slopes. We use a 2 degree-of-freedom (DOF) model which is obtained by restricting the spinning motion in a 3 DOF motion dynamic equation. In order to design the robust controller guaranteeing stability of the TWIP mobile robot driving on inclined surface, we propose a sliding mode control based on the theory of variable structure systems and design a sliding surface using the theory of the linear quadratic regulation (LQR). For simulation, the dynamic model of the TWIP mobile robot is constructed using Mathworks` Simulink and the sliding mode control is also implemented using Simulink. From simulation results, we show that the proposed controller effectively controls the TWIP mobile robot driving on slopes.

Revisiting the Thermodynamics of Water Surfaces and the Effects of Surfactant Head Group.

It is common knowledge that surfactants lower the surface tension of water. The typical textbook explanation of this phenomenon is that the force of attraction between surfactant and water molecules is less than that between two water molecules; hence the surface contraction force decreases in the presence of surfactants; however, this common description, based on the strength of intermolecular interactions, is overly simplified because it ignores an important thermodynamic function: the surface entropy of water. Here we report separate measurements of water's surface enthalpy and surface entropy in the presence of nonionic, zwitterionic, anionic, and cationic surfactants. While all of these surfactants decreased the surface enthalpy of water by 50-70%, the surface entropy of water could drop to near-zero or even negative values for ionic surfactants. Studies of this zero-entropy state of water surface using phase-sensitive sum-frequency generation (SFG) vibrational spectroscopy and molecular dynamics (MD) simulations suggested that the zero-entropy state of the water surface was associated with surfactant-induced ordering of water molecules and enhanced hydrogen bond formation at the water surface. Both effects reduce water molecules' degrees of freedom for motion and thus lower the surface entropy of water. The ability of a surfactant to decrease the surface entropy of water is in the order ionic > zwitterionic > nonionic. For all surfactant head groups surface entropy plays a critical role in determining the surface tension of water. The description of water's surface tension is not complete without considering its surface entropy.

A Prototype Device for 3D Regional, Passive Elasticity Measurements of the Murine Myocardium Using AFM

This study presents the design and implementation of a prototype device that interfaces with commercial atomic force microscopy (AFM) instruments to accurately measure ex vivo, regional, passive elasticity measurements of the murine myocardium in three-dimensions (3D). The constructed prototype has a translation stage base allows fine adjustment of planar location at the micrometer level of accuracy. Four degrees of motional freedom are allowed in total, permitting fine, independent rotations of the murine heart (oriented at right-angles with respect to its normal mode of operation) at 2–5° increments, along its two axes of symmetry. Successful mounting of the constructed prototype was realized on the AFM’s base platform, with Zpositioning maintained through the instrument’s electronics. Measurements of normal epicardial tissue elasticity in one excised male C57BL/6 heart led to a mean value (over 15 epicardial locations) of 51.8 ± 5.4 kPa. A flexible, versatile, and low-cost prototype assembly was designed, implemented, and tested to conduct epicardial elasticity measurements in a semi-automatedmanner, using AFM. The epicardial elasticity values are within expected, published ranges for the normal myocardium of 10–55 kPa. Efforts are ongoing to allow 3D regional elasticity measurements at finer resolution with potential usefulness to studies of genetically altered mice.