Specific Degrees Of Freedom Research Articles

Fundamental role of nonlocal orders in 1D extended Bose-Hubbard model.

Nonlocal order parameters capture the presence of correlated fluctuations between specific degrees of freedom, in otherwise disordered quantum matter. Here, we provide a further example of their fundamental role, deriving the ground state phase diagram of the filling one extended Bose-Hubbard model, exclusively in terms of their ordering. By means of a density matrix renormalization group numerical analysis, we show that in addition to the (even) parity order characteristic of the Mott insulating phase and the string order nonvanishing in the Haldane insulator, the recently proposed odd parity order completes the picture, becoming nonvanishing at the transition from the normal superfluid to the paired superfluid phase. The above three nonlocal parameters capture all the distinct phases, including the density wave phase, in which the local order is seen as the simultaneous presence of correlated fluctuations in different channels. They provide a unique tool for the experimental observation of the full phase diagram of strongly correlated quantum matter, by means of local density measurements.

Design and analysis of parallel six-dimensional force sensor based on near-singular characteristics

The high sensitivity six-dimensional force sensor is the core component of intelligent robot force feedback perception, which is related to the structure of the sensor. This paper proposes a new modeling method to chain the near singular eight-branch Stewart mechanism, which indicates the relationship between structural parameters and sensitivity. The new method gains 16 new configurations by innovating the traditional Stewart institution. A configuration with high sensitivity in Fz, Mx and My directions is selected for further study. The theoretical stiffness model and force mapping model show that the sensitivity of the new structure can be amplified by 4 times in specific degrees of freedom. The results show that the nonlinear error and coupling error are 2.77% and 2.26%, respectively. The proposed method can be widely applied in the field of parallel six-dimensional force sensors.

Do Bernstein's Stages of Learning Apply after Stroke? A Scoping Review on the Development of Whole-Body Coordination after Cerebrovascular Accidents.

Stroke is one of the leading causes of disability around the world, presenting unique challenges in motor development during the rehabilitation process. Based on studies in movement and sports science, thorough knowledge has accumulated on the development of movement skills. Through the works of Nikolai Bernstein, it has been established that when learning new skills, people tend to first simplify coordination by 'freezing' their degrees of freedom, after which they start building efficiency by 'releasing' specific degrees of freedom. If a similar pattern of development can be established post-stroke, it would imply that lessons learned in sports skill acquisition can also be implemented to optimize stroke rehabilitation. The current scoping review aims to assess whether the Bernsteinian freezing-to-releasing stages of learning also apply to developing whole-body movement skills after stroke. To this end, we systematically screened the existing literature for studies involving a longitudinal measure of whole-body coordination after a stroke. Only five articles met the criteria for inclusion, indicating a gap in research on this topic. Based on the observations within these articles, we could neither confirm nor reject whether the freezing-to-releasing process can apply after a stroke. We could, however, hypothesize a detailed description of the freezing-to-releasing process, which can be assessed in future works.

A comprehensive code-to-code comparison study with the modified IEA15MW-UMaine Floating Wind Turbine for H2020 HIPERWIND project

An extensive code-to-code comparison among DIEGO, DLW and HAWC2 has been performed on a floating wind turbine (modified version of UMaine floater with IEAWIND 15MW wind turbine). In total, 10 cases are compared, and a few key results of this comparison are reported in this paper. From the comparisons, it is clearly seen that the results predicted by the three codes are generally agreed well despite some differences in specific degrees of freedom like roll, sway and yaw for the extreme load case, which requires additional investigations.

Nonstatistical Photoinduced Processes in Gaseous Organic Molecules.

Processes that proceed in femtoseconds are usually referred to as being ultrafast, and they are investigated in experiments that involve laser pulses with femtosecond duration in so-called pump probe schemes, where a light pulse triggers a molecular process and a second light pulse interrogates the temporal evolution of the molecular population. The focus of this review is on the reactivity patterns that arise when energy is not equally distributed on all the available degrees of freedom as a consequence of the very short time scale in play and on how the localization of internal energy in a specific mode can be thought of as directing a process toward (or away from) a certain outcome. The nonstatistical aspects are illustrated with examples from photophysics and photochemistry for a range of organic molecules. The processes are initiated by a variety of nuclear motions that are all governed by the energy gradients in the Franck–Condon region. Essentially, the molecules will start to adapt to the new electronic environment on the excited state to eventually reach the equilibrium structure. It is this structural change that is enabling an ultrafast electronic transition in cases where the nuclear motion leads to a transition point with significant coupling between to electronic states and to ultrafast reaction if there is a coupling to a reactive mode at the transition point between the involved states. With the knowledge of the relation between electronic excitation and equilibrium structure, it is possible to predict how the nuclei move after excitation and often whether an ultrafast (and inherently nonstatistical) electronic transition or even a bond breakage will take place. In addition to the understanding of how nonstatistical photoinduced processes proceed from a given excited state, it has been found that randomization of the energy does not even always take place when the molecule takes part in processes that are normally considered statistical, such as for example nonradiative transitions between excited states. This means that energy can be localized in a specific degree of freedom on a state other than the one that is initially prepared. This is a finding that could kickoff the ultimate dream in applied photochemistry; namely light excitation that leads to the rupture of a specific bond.

Online Estimation Techniques for Natural and Excitation Frequencies on MDOF Vibrating Mechanical Systems

An online algebraic estimation technique for natural and forcing frequencies for a class of uncertain and lumped-parameter vibrating mechanical systems with n degrees of freedom is described. In general, realistic vibrating systems can be affected by unknown exogenous excitation forces with multiple and independent frequency harmonic components. Hence, natural frequencies as well as excitation force frequencies can be simultaneously computed from an algebraic approach into a small interval of time during online operation of the mechanical system. Measurements of an available output signal, associated with some specific degree of freedom, are only required for frequency estimation in time-domain. Information on mass, stiffness and damping matrices are not necessary for multifrequency estimation algorithms. Some analytical, numerical and experimental results on a cantilever Euler–Bernoulli beam are described to show and validate the acceptable estimation of multiple frequencies in forced multiple degrees of freedom vibrating systems.

VD-PQ; A Velocity-Dependent Viscous Damping Model for Wave-Structure Interaction Analysis

For the analysis and design of coastal and offshore structures, viscous loads represent one of the most influential parameters that dominate their response. Very commonly, the potential flow theory is used for identifying the excitation wave loads, while the viscous damping loads are taken into consideration as distributed drag type loads and/or as linear and quadratic damping loads approximated with the use of motion decay curves of the structure in specific degrees of freedom. In the present paper, is developed and proposed a numerical analysis method for addressing wave-structure interaction effects through a velocity-dependent viscous damping model. Results derived by a computational fluid dynamics model are coupled with a model that uses the boundary element method for the estimation of the viscous damping loads iteratively in every time-step of the analysis. The computational fluid dynamics model solves the Navier–Stokes equations considering incompressible flow, while the second model solves the modified Cummins Equation of motion of the structure in the time domain. Details about the development of the coupling method and the velocity-dependent viscous damping (VD-PQ) are presented. The coupling between the different models is realized through a dynamic-link library. The proposed coupling method is applied for the case of a wave energy converter. Results derived with the use of the developed numerical analysis method are compared against experimental data and relevant numerical analysis predictions. The importance of considering the instantaneous velocity of the structure in estimating the viscous damping loads is demonstrated. The proposed numerical analysis method for estimating the viscous damping loads provides good accuracy compared to experimental data and, at the same time, low computational cost.

Influence of the main operating parameters on the DRPSA process design based on the equilibrium theory

Among the adsorption-based separation processes for gaseous mixtures, those exploiting pressure variations, so-called Pressure Swing Adsorption (PSA) processes, are the most popular. In this work, we focus on the specific PSA configuration known as Dual Reflux-Pressure Swing Adsorption (DR-PSA) given its ability to achieve sharp separations. In the case of binary mixtures, an analytical approach based on Equilibrium Theory has been proposed to identify the operating conditions for complete separation under the assumption of linear isotherms. This same approach is not available when the separation is not complete. Accordingly, in this work we study the features of non-complete separations by solving numerically a general DR-PSA model with parameter values suitable to approach equilibrium conditions (no mass transport resistances, no axial mixing, isothermal conditions and no pressure drop), thus reproducing the analytical solution when complete separations are examined. Even for non-complete separations, triangularly shaped regions at constant purity can be identified on a plane whose axes correspond to suitable design parameters. Moreover, we found a general indication on how to select the lateral feed injection position to limit the loss in product purities when complete separation is not established, whatever is the composition of the feeding mixture. Finally, a sensitivity analysis with respect to pressure ratio, light reflux ratio and heavy product flowrate is proposed in order to assess how to recover product purities according to the specific degrees of freedom of a DR-PSA apparatus.

Analysis of Maximal Topologies and Their DoFs in Topological Interference Management

Topological interference management (TIM) can obtain degrees of freedom (DoF) gains with no channel state information at the transmitters (CSIT) except topological information of network in the interference channel. It was shown that TIM achieves symmetric DoF 1/2 when internal conflict does not exist among messages [7]. However, it is difficult to assure whether a specific topology can achieve symmetric DoF 1/2 without scrutinizing internal conflict. It is also hard to derive a specific topology directly from the conventional condition for symmetric DoF 1/2. Even except for the topology achieving symmetric DoF 1/2, topology achieving specific DoF less than 1/2 is not well known. With these problems in mind, we propose a method to derive all maximal topologies directly in TIM, named as alliance construction in K-user interference channel. That is, it is proved that a topology is maximal if and only if it is derived from alliance construction. Further we translate a topology design by alliance construction in the alignment-conflict graph into topology matrix and propose conditions for maximal topology matrix (MTM). Moreover, we propose a generalized alliance construction that derives topologies achieving DoF 1/n for n ≥ 3 by generalizing sub-alliances. A topology matrix can also be used to analyze topologies with DoF 1/n .

110th Anniversary: Mesoscale Complexity—To Dodge or To Confront?

This commentary briefly addresses the complexity at mesoscales of different levels, describes the limitations of traditional approaches, and introduces the preliminary principle of the potential mesoscience. It is believed that mesoscale complexity arises from collective effects, and emerges within mesoregimes. Such complexity makes the averaging approaches (based on the assumption of homogeneity) solely at the system scale (or within each computational grid) problematic while the ab initio approaches solely at the element scale are commonly unaffordable to achieving system behavior. The difficulty in finding a single-objective extremal principle and the invalidity of the homogeneity assumption indicates that the equilibrium framework might not be a good starting point to understand the behavior of systems far from equilibrium. Focusing on the specific degrees of freedom at mesoscales and revealing the corresponding multiple dominant mechanisms seemingly pave a promising way, and this methodology leads to the concept of mesoscience. Some topics closely related to chemistry have been proposed within such a framework as well.

Reducing Phase Offset Using Novel Adaptive Cyclic Prefix Based Adaptive Sub Block Correlation for BWA Networks

In this paper, a generic approach has been developed for the reduction of phase offset in BWA networks considering a novel Adaptive Cyclic Prefix (ACP) and Adaptive Sub Block (ASB) correlation computation for both WiMAX and LTE networks. The successive design steps along with practical assumptions and mathematical derivations are incorporated in developing the ACPASB algorithm. In comparison to the conventional Fixed Sub Block (FSB) mechanism, the ACPASB algorithm improves the correlation among the subcarriers by drastic reduction of phase offset, leading to maximum removal of Inter Symbol Interference (ISI). The index for reduction of phase offset is evaluated in terms of increased estimated correlation factor (η) for which the correlation threshold (ηth) has been determined using Pearson Product Moment formula and specific degree of freedom (df). Estimated ηth serves as an indicator of maximum ISI free region. The estimation of phase offset is accomplished by the measurement of Error Vector Magnitude (EVM) and Relative Constellation Error (RCE) with the help of Vector Signal Analyzer (VSA) incorporated in the model of WiMAX/LTE transceiver. The data transmission with such minimum ISI, guarantees the selection of highest order modulation and coding scheme (64-QAM (3/4)) even under severe degradation of the channel in a typical BWA network. It has alsobeen observed that even under severely fading channel, the selection of dynamic sub-block length inherently delivers a substantially good Raw Data Rate (RDR) under 64-QAM (3/4) modulation. Complexity analysis and simulation results show that ACPASB scheme outperforms ACPFSB thereby saving design turnaround time significantly.

Precision positioning using a novel six axes compliant nano-manipulator

In this paper, a novel micro-scale nano-manipulator capable of positioning in six degrees of freedom (DOF) is introduced. Undesired deflections, while operating in a specific DOF, are restricted by the aid of distinctive design of flexure hinges and actuators’ arrangements. The compliant mechanism is actuated by thermo-electro-mechanical actuators, as they could be integrated and exert large forces in a nanometer resolution. The actuators are bidirectional capable of applying force in both transverse and longitudinal directions. Performance of the two degrees of freedom actuator is thoroughly explored via numerical and analytical analyses, showing a good agreement. The workspace and performance of the precision positioner is studied using finite element methods. Finally, identification of forward and inverse kinematic of the nano-manipulator is performed utilizing neural network concept. A well-trained and appropriate neural network can efficiently replace the time-consuming and complex analytical and experimental methods.

Quantum‐dot‐based integrated non‐linear sources

The authors report on the design and the preliminary characterisation of two active non-linear sources in the terahertz and near-infrared range. The former is associated to difference-frequency generation between whispering gallery modes of an AlGaAs microring resonator, whereas the latter is granted by parametric generation in a waveguide via modal phase matching. Both devices rely on embedded quantum-dot lasers, which allow for low-threshold currents and unconventional geometries. They also include specific degrees of freedom that open a practical route towards phase matching, either during the lithographic process or during operation.

Flux-pinning mechanisms for improving cryogenic segmented mirror performance

Although large cryogenic space telescopes may provide a means of answering compelling astrophysics questions, the required increase in the primary mirror diameter presents technical challenges. Larger primaries are more flexible, and cryogenic mirrors are typically very lightly damped—the material damping is negligible, and common damping methods break down. To address these challenges, we propose placing flux-pinning mechanisms along the edges of adjacent mirror segments. These mechanisms consist of a collection of magnets and superconductors, and like flexures, they preferentially allow motion in specific degrees of freedom. Motion in nonpreferred degrees of freedom is resisted by a force analogous to a damped spring force, and the stiffness and damping can be adjusted independently. As an example, we consider simple mechanisms consisting of an inexpensive magnet and a single superconductor. These mechanisms provide increasing resistance as the magnet and superconductor—or mirror segments attached to each—come closer to colliding. These mechanisms, with typical stiffness and damping values on the order of 5000 N/m and 5 kg/s, respectively, also provide modest improvements to the mirror performance. Greater gains can be achieved by using stronger magnets or smaller separations, or by placing nonmagnetic conductive materials near the mechanism.

Robust Identification of Three-Dimensional Thumb and Index Finger Kinematics With a Minimal Set of Markers

This study presents a methodology to determine thumb and index finger kinematics while utilizing a minimal set of markers. The motion capture of skin-surface markers presents inherent challenges for the accurate and comprehensive measurement of digit kinematics. As such, it is desirable to utilize robust methods for assessing digit kinematics with fewer markers. The approach presented in this study involved coordinate system alignment, locating joint centers of rotation, and a solution model to estimate three-dimensional (3-D) digit kinematics. The solution model for each digit was based on assumptions of rigid-body interactions, specific degrees of freedom (DOFs) at each located joint, and the aligned coordinate system definitions. Techniques of inverse kinematics and optimization were applied to calculate the 3-D position and orientation of digit segments during pinching between the thumb and index finger. The 3-D joint center locations were reliably fitted with mean coefficients of variation below 5%. A parameterized form of the solution model yielded feasible solutions that met specified tolerance and convergence criteria for over 85% of the test points. The solution results were intuitive to the pinching function. The thumb was measured to be rotated about the CMC joint to bring it into opposition to the index finger and larger rotational excursions (>10 deg) were observed in flexion/extension compared to abduction/adduction and axial rotation for all joints. While the solution model produced results similar to those computed from a full marker set, the model facilitated the usage of fewer markers, which inherently lessened the effects of passive motion error and reduced the post-experimental effort required for marker processing.

All photons are equal but some photons are more equal than others

Two photons are said to be identical if they are prepared in the same quantum state. Given the latter, there is a unique way to achieve this. Conversely, there are many different ways of preparing two non-identical photons: they may differ in frequency, polarization, amplitude, etc. Therefore, photon distinguishability depends upon the specific degree of freedom being varied. By means of a careful analysis of the coincidence probability distribution in a Hong–Ou–Mandel experiment, we can show that photon distinguishability can be actually quantified by the rate of distinguishability of photons, an experimentally measurable parameter that crucially depends on both the photon quantum state and the degree of freedom under control.

Quantifying individual muscle contribution to three-dimensional reaching tasks

We investigated the individual muscle contribution to arm motion to better understand the complex muscular coordination underlying three-dimensional (3D) reaching tasks of the upper limb (UL). The individual contributions of biceps, triceps, deltoid anterior, medius, posterior and pectoralis major to the control of specific degrees of freedom (DOFs) were examined: using a scaled musculoskeletal model, the muscle excitations that reproduce the kinematics were calculated using computed muscle control and a forward simulation was generated. During consequent perturbation analyses, the muscle excitation of selected muscles was instantaneously increased and the resulting effect on the specific DOF was studied to quantify the muscle contribution. The calculated muscle contributions were compared to the responses elicited during electrical stimulation experiments. Innovative in our findings is that muscle action during reaching clearly depended on the reaching trajectory in 3D space. For the majority of the muscles, the magnitude of muscle action changed and even reversed when reaching to different heights and widths. Furthermore, muscle effects on non spanned joints were reported. Using a musculoskeletal model and forward simulation techniques, we demonstrate individual position-dependent muscle contributions to 3D joint kinematics of the UL.

SU-E-J-31: Site Specific Setup Errors Analysis of MVCT Daily Imaging with TomoTherapy

Purpose: To analyze the variation in patient setup and anatomical changes for five different anatomical sites observed in Helical TomoTherapy (HT). Methods: 52 patients treated for five anatomical sites [brain (10), head‐neck (13), Lung (10), abdomen (9) and pelvis (10)] using a HT system were analyzed.Brain, head and neck patients were immobilized with thermoplastic orfit while Lung, abdomen and pelvis patients were immobilized with body fix. Prior to the treatment, three external fiducials per patient were used for setup, which consisted of skin tattoos for prostate and lung patients. There was a marking on mask for head‐neck and brain patients. Daily megavoltage computed tomography (MVCT) images were acquired prior to each treatment and were fused with the planning Kilovoltage Computed Tomography (KVCT) reference image to determine the daily setup errors and deformation. The setup errors were corrected before treatment and were used, along with the organ motions, to determine the planning target volume (PTV) margins. Results: Mean lateral, longitudinal and vertical shift was found more for Pelvis (1 mm), Abdomen (3.34 mm) and brain (6 mm) respectively. Results of setup error analysis are largely influenced by restricting specific degrees of freedom during image registration. If a yaw and pitch rotations exist during fusion, this will increase the lateral shift correction. If a pitch offset exist, the restriction will increase the vertical and longitudinal shift correction. The results are analyzed by restricting pitch and yaw and corrections are made for roll only. Conclusions: The setup errors are site specific and statistically significant. The data presented in this work might be useful in developing advanced radiotherapy technique. These interfractional variations if not adequately accounted for, can result in the delivery of suboptimal dose distribution. HT system used in this study, have capability of quantifying and addressing these variations.

Simulated Q-annealing: conformational search with an effective potential

We have tested a version of the generalized simulated annealing algorithm based on molecular dynamics simulations with effective potential suggested by Tsallis statistics. The generalized annealing method, termed "simulated Q-annealing (SQ)," is applied to the simulations of a synthetic 11-residue peptide segment (1AQG). In SQ, the energy barriers between local minima change as the parameter q is varied and specific degrees of freedom can be selectively heated up and annealed. Conformational dynamics obtained by ordinary simulated annealing (SA) and SQ simulations are compared in order to illustrate the effectiveness of the SQ approach in conformational searching. We show that SQ can navigate the potential energy surface efficiently with a simple annealing protocol and demonstrate that conformations sampled by SQ can represent the funnel-like free energy surface.

Dynamic Manipulation Inspired by the Handling of a Pizza Peel

This paper discusses dynamic manipulation inspired by the handling mechanism of a pizza chef. The chef handles a tool called ldquopizza peel,rdquo where a plate is attached at the tip of a bar, and he remotely manipulates a pizza on the plate. We found that he aggressively utilizes only two degrees of freedom (DOFs) from the remote handling location during manipulation: translation along the bar and rotation about the bar. From the viewpoint of a dynamic system, the inertial loads for these specific DOFs are never affected by the length of the bar. This is important for the production of quick plate motions so that the object on the plate can be dynamically and remotely manipulated. Applying this handling mechanism to a robot system, we first reveal how to make the object's motion for three DOFs by using two DOFs of plate motion. We then show that it is guaranteed to achieve an arbitrary desired set of position and orientation of the object by the proposed manipulation scheme. The proposed method has good manipulability because the translational motion of the object can be fully decoupled from the rotational motion (though not <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">vice</i> <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">versa</i> ). Finally, we show a couple of experiments that confirm the basic idea.