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A theoretical paper based on chiral micropolar effective‐medium theory suggested the possibility of unusual roton‐like acoustical‐phonon dispersion relations in 3D elastic materials. Here, as a first novelty, the corresponding inverse problem is solved, that is, a specific 3D chiral elastic metamaterial structure is designed, the behavior of which follows this effective‐medium description. The metamaterial structure is based on a simple‐cubic lattice of cubes, each of which not only has three translational but also three rotational degrees of freedom. The additional rotational degrees of freedom are crucial within micropolar elasticity. The cubes and their degrees of freedom are coupled by a chiral network of slender rods. As a second novelty, this complex metamaterial is manufactured in polymer form by 3D laser printing and its behavior is characterized experimentally by phonon‐band‐structure measurements. The results of these measurements, microstructure finite‐element calculations, and solutions of micropolar effective‐medium theory are in good agreement. The roton‐like dispersion behavior of the lowest phonon branch results from two aspects. First, chirality splits the transverse acoustical branches as well as the transverse optical branches. Second, chirality leads to an ultrastrong coupling and hybridization of chiral acoustical and optical phonons at finite wavevectors. [ABSTRACT FROM AUTHOR]

Summary: A model predictive cascade controller is proposed in this article to resolve the actuator saturation problem of underwater human‐occupied vehicle (HOV) trajectory tracking. For the kinematic model, a grasshopper optimization‐based model predictive control (MPC) is developed to obtain control velocities with small fluctuations in allowable regions. Based on the desired velocities obtained from the improved kinematic control, the HOV dynamic model is used to generate the corresponding torques and forces using sliding mode control. With the control velocities and forces given by the cascade control strategy, the elimination of actuator saturation during the HOV trajectory tracking can be realized. The proposed controller is verified by simulations using a numerical example based on a four degrees of freedom (4‐DOFs) HOV. [ABSTRACT FROM AUTHOR]

In a daily environment, several vibration energies have low amplitude and broad range of frequencies, and it is crucial to harvest them efficiently in a single triboelectric nanogenerator (TENG). Here, a multi‐degree of freedom (DOF) vibration system is coupled with TENG to make several resonant frequencies in a single device. When the number of DOF increases in the system, the number of resonant frequencies also increases. These resonant frequencies are calculated by MATLAB software using the masses and spring constant of DOF vibration system. With the masses of 20 g and the spring constant of 82.712 N m−1, it is found that 1‐DOF has one resonant frequency (20.47 Hz), 2‐DOF has two resonant frequencies (12.63 and 33.17 Hz), and 3‐DOF has three resonant frequencies (9.12, 25.55, and 36.87 Hz). At each resonant frequency, the displacement of all weight layers increases due to the constructive interference of resonance, resulting in higher output than other frequencies at the frequency sweep experiment. In addition, the magnitude and phase of output signals obtained in friction regions are evaluated through COMSOL simulation. A self‐powered wireless sensor module with 3‐DOF TENGs to detect the humidity/temperature and transmit the data every 30 min by harvesting vibration energy is demonstrated. [ABSTRACT FROM AUTHOR]

Background: Current commercially available hybrid magnetic resonance linear accelerators (MR‐Linac) use 2D+t cine MR imaging to provide intra‐fractional motion monitoring. However, given the limited temporal resolution of cine MR imaging, target intra‐frame motion deterioration effects, resulting in effective time latency and motion artifacts in the image domain, can be appreciable, especially in the case of fast breathing. Purpose: The aim of this work is to investigate intra‐frame motion deterioration effects in MR‐guided radiotherapy (MRgRT) by simulating the motion‐corrupted image acquisition, and to explore the feasibility of deep‐learning‐based compensation approaches, relying on the intra‐frame motion information which is spatially and temporally encoded in the raw data (k‐space). Methods: An intra‐frame motion model was defined to simulate motion‐corrupted MR images, with 4D anthropomorphic digital phantoms being exploited to provide ground truth 2D+t cine MR sequences. A total number of 10 digital phantoms were generated for lung cancer patients, with randomly selected eight patients for training or validation and the remaining two for testing. The simulation code served as the data generator, and a dedicated motion pattern perturbation scheme was proposed to build the intra‐frame motion database, where three degrees of freedom were designed to guarantee the diversity of intra‐frame motion trajectories, enabling a thorough exploration in the domain of the potential anatomical structure positions. U‐Nets with three types of loss functions: L1 or L2 loss defined in image or Fourier domain, referred to as NNImgLoss‐L1, NNFloss‐L1 and NNL2‐Loss were trained to extract information from the motion‐corrupted image and used to estimate the ground truth final‐position image, corresponding to the end of the acquisition. Images before and after compensation were evaluated in terms of (i) image mean‐squared error (MSE) and mean absolute error (MAE), and (ii) accuracy of gross tumor volume (GTV) contouring, based on optical‐flow image registration. Results: Image degradation caused by intra‐frame motion was observed: for a linearly and fully acquired Cartesian readout k‐space trajectory, intra‐frame motion resulted in an imaging latency of approximately 50% of the acquisition time; in comparison, the motion artifacts exhibited only a negligible contribution to the overall geometric errors. All three compensation models led to a decrease in image MSE/MAE and GTV position offset compared to the motion‐corrupted image. In the investigated testing dataset for GTV contouring, the average dice similarity coefficients (DSC) improved from 88% to 96%, and the 95th percentile Hausdorff distance (HD95) dropped from 4.8 mm to 2.1 mm. Different models showed slight performance variations across different intra‐frame motion amplitude categories: NNImgLoss‐L1 excelled for small/medium amplitudes, whereas NNFloss‐L1 demonstrated higher DSC median values at larger amplitudes. The saliency maps of the motion‐corrupted image highlighted the major contribution of the later acquired k‐space data, as well as the edges of the moving anatomical structures at their final positions, during the model inference stage. Conclusions: Our results demonstrate the deep‐learning‐based approaches have the potential to compensate for intra‐frame motion by utilizing the later acquired data to drive the convergence of the earlier acquired k‐space components. [ABSTRACT FROM AUTHOR]

With the rapid development of information and communication technology, intelligent wireless systems have a huge demand for devices with multi‐function integration and multi‐degree of freedom electromagnetic control. In this paper, a multifunctional folded transmitarray antenna (MFTA) using a reconfigurable metasurface is proposed to achieve simultaneous and independent modulation of beam and polarization. The beam scanning, arbitrary wave generator, and polarization conversion functions can be achieved only by adjusting the PIN diode bias on the reconfigurable metasurface. In order to prove the feasibility of the proposed method, a prototype is fabricated and verified by experiments. Both simulated and measured results verify the excellent performance of the MFTA. This work opens a door to multi‐functional integration and multi‐degree of freedom electromagnetic manipulate devices, which have great prospects in areas such as radar detection and wireless communication. [ABSTRACT FROM AUTHOR]

With the development of miniaturization and integration, multifunctional optical devices are necessary. However, its practical realization is a critical challenge due to the lack of simple structures with multiple functionalities. Here, a multimode metasurface is proposed by simply placing polymer nanocubes on the lithium niobate (LN) thin film. The intriguing properties of the integrated structure include high‐quality (Q) factors and different spectral characteristics, associated with quasi‐guide modes (GM) and Mie modes, respectively. The experiment demonstration reveals that Q factors of four modes are larger than 1000 and a second harmonic generation (SHG) enhancement factor of 25.4 is obtained, featuring strong light‐matter interaction. Importantly, the abundant spectral characteristics greatly boost three degrees of freedom, i.e., polarization, incident angle, and slot, to realize multifunctional designs. The results provide a sophisticated platform for developing high‐performance LN metasurfaces with the advantages of simplified fabrication processes and multifunctionality. The strategy can also be extended to other material systems, enabling the flexibility of metasurface‐inspired subwavelength engineering. [ABSTRACT FROM AUTHOR]

In the upcoming epochs, conventional energy may deplete soon. Thus, the use of conventional energy in the power industries need to be supplemented by non‐conventional energy resources. This would result in loss of synchronisms in the power grids owing to the fact that solar and wind alternate their attributes expeditiously with change in atmospheric phenomenon. To ameliorate frequency deviation within a specific range automatic generation control (AGC) implements forced allowance on system operation. A three area thermal with photovoltaic (PV), electric vehicle (EV), wind system is considered under deregulated environment to develop and to judge the efficacy of newly developed cascade fractional order hybrid controller combination of (FOTID & 3DOF‐PID). Comparing the aforementioned controller to other controllers such as the three degree of freedom proportional‐integral‐derivative (3DOF‐PID), the fractional order tilt‐integral‐derivative (FOTID) and the proportional‐integral‐derivative (PID) justifies the system's effectiveness. This assessment has been accomplished by a trendy optimization technique such as hybrid whale optimization algorithm (HWOA). However, the main intent of this write‐up is to fabricate a cascade fractional order (CC‐FO) hybrid controller that would act as the new control mechanism for the proposed system under deregulated scenario. It has been found that the suggested CC‐FO hybrid controller stabilizes the system (i.e., Under step load disruptions, frequency deviation and tie‐line power become zero) in the shortest amount of time possible. Additionally, it is seen that the recommended controller can control a wide range of nominal loading circumstances and system characteristics, demonstrating its robustness. [ABSTRACT FROM AUTHOR]

Single‐sided NMR instruments utilize inhomogeneous magnetic fields with strong gradients to nondestructively probe physical properties of materials. The sensitive region of this type of magnet is often a thin slice above the magnet's surface; measuring planar samples with high spatial resolution requires coplanarity between the sensitive region of the magnet and the sample region of interest. We developed an algorithmic approach to position flat samples coplanar with the magnet's sensitive region. The efficient and objective positioning process utilizes an adjustable stage that offers control over three degrees of freedom, and the optimal position for each sample is found with a quadtree algorithm. We show this algorithm is effective for positioning samples with various relaxation behaviors. We report resolution values that describe position optimization, acquisition constraints, and final spatial resolution for each sample. Measurements after optimized positioning had appropriate spatial resolution to distinguish physical regions of layered samples with different physical properties, namely, relaxation behavior. Our algorithmic positioning process can be implemented for planar samples in research and industrial settings to enhance spatial resolution of single‐sided NMR measurements. [ABSTRACT FROM AUTHOR]

A cart‐double pendulum system is an underactuated mechanical system that has three degrees of freedom (DOF) and has two actuators. This paper discusses the stabilizing control problem for this non‐linear mechanical system. First, an input relationship is constructed to transform the 3‐DOF cart‐double pendulum system into a 2‐DOF reduced‐order system in a fixed time. Second, a swing‐up controller is designed for the reduced‐order system to make the system infinitely approach upright equilibrium point. After that, the swing‐up controller switches to a fixed‐time balance stabilization controller, which stabilizes the cart‐double pendulum at the upright equilibrium point in a fixed time. Finally, numerical examples verify the effectiveness of this presented control strategy. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Summary: The swing characteristics of the load of ship‐mounted rotary cranes is very complicated, due to the rotation of the boom. Especially, when the crane is operating at sea, it is subject to some disturbances caused by waves, which makes the precise control of the load more difficult. We study the control problem of a four degree of freedom ship‐mounted rotary crane with continuous yaw and roll disturbances in this paper. Specifically, we propose an adaptive controller and the adaptive laws can be updated in real‐time depending on the state of the system and the disturbance. This method does not require linearization of the crane dynamic equations, therefore, the crane can get great control performance even if it is far from the equilibrium point. Comparative experiments demonstrate that the proposed method has excellent anti‐disturbance ability. [ABSTRACT FROM AUTHOR]

Direct integration methods are widely used for dynamic response computation. However, the performance of their computational accuracy significantly degrades with increasing the time step. Although machine learning methods can address this shortcoming, they require training data for dynamic response computation. This paper proposes a novel computational method to overcome these shortcomings. The proposed approach is a data‐free physics‐driven estimator, which minimizes the objective function of multi‐output least squares support vector machines for regression to model parameters subject to physical constraints introduced by the multi‐degree of freedom system's dynamic equilibrium equations and initial conditions in the feature space, bypassing the need for training data (due to the coupled physics) and for satisfying the requirement of the time step due to the built‐in optimization procedure. A new efficient step‐by‐step solver is developed to solve the optimization problem, and the solution is equivalent to a hyperplane satisfying the physical constraints in the feature space. The extension of the proposed approach for nonlinear dynamic response computation is also analyzed theoretically. The numerical results demonstrate that the proposed approach provides the solution with higher accuracy and efficiency and achieves the best performance for large time steps over classical integration methods. [ABSTRACT FROM AUTHOR]

Underactuated systems are extensively utilized in practice while attracting a huge deal of attention in theoretical studies. There are few robust control strategies for general underactuated systems because of the variety of their dynamic models. A dynamic surface control strategy with a nonlinear disturbance observer is proposed in this study, to stabilize multi‐degree of freedom underactuated systems. In such systems the number of underactuated degrees of freedom is not higher compared to the actuated ones. A disturbance observer is utilized to dispose of the uncertain disturbance and cross terms in dynamic model which may cause failure to the controller. Then, a dynamic surface control strategy is presented which is not sensitive to the diversity of dynamic models. The stability of whole system is proven by Lyapunov‐based method. The control law is successfully applied to nonlinear underactuated systems in benchmark cascade form such as two‐translational oscillator with rotational actuator, crane, wheeled inverted pendulum. The effectiveness of proposed controllers are illustrated by MATLAB simulation results. Finally, comparative studies are presented to verify the superiority of the proposed method. [ABSTRACT FROM AUTHOR]

Faculty attitudes toward rhinology fellowship training: a survey of rhinology fellowship programs. Keywords: fellowships; match; otolaryngology; program evaluation; rhinology; surveys and questionnaires EN fellowships match otolaryngology program evaluation rhinology surveys and questionnaires 165 167 3 01/27/23 20230201 NES 230201 INTRODUCTION As fellowship programs in rhinology continue to develop, an understanding of the interests of fellows and fellowship directors is critical to initiate conversations about the future direction of the fellowship experience. [Extracted from the article]

Metasurfaces are ultrathin optical elements that can manipulate the light at subwavelength scale. The light input on the metasurface can be converted into output with abrupt changes of amplitude, phase, and polarization (APP) properties. However, a simultaneous and arbitrary conversion of all the three optical properties is not yet realized. In this paper, a Jones matrix with minimal number of four degrees of freedom that enables the conversion between two optical states with arbitrary APP distributions is proposed. The Jones matrix is constructed with a dielectric metasurface and is experimentally verified for various conversions of the three optical properties. This work unlocks some unknown powerful abilities of metasurface even with the minimal design degree of freedom, which can expand the scope of meta optics. [ABSTRACT FROM AUTHOR]

Paleobiologists typically exclude impossible joint poses from reconstructions of extinct animals by estimating the rotational range of motion (ROM) of fossil joints. However, this ubiquitous practice carries the assumption that osteological estimates of ROM consistently overestimate true joint mobility. Because studies founded on ROM‐based exclusion have contributed substantially to our understanding of functional and locomotor evolution, it is critical that this assumption be tested. Here, we evaluate whether ROM‐based exclusion is, as currently implemented, a reliable strategy. We measured the true mobilities of five intact cadaveric joints using marker‐based X‐ray Reconstruction of Moving Morphology and compared them to virtual osteological estimates of ROM made allowing (a) only all three rotational, (b) all three rotational and one translational, and (c) all three rotational and all three translational degrees of freedom. We found that allowing combinations of motions in all six degrees of freedom is necessary to ensure that true mobility is always successfully captured. In other words, failing to include joint translations in ROM analyses results in the erroneous exclusion of many joint poses that are possible in life. We therefore suggest that the functional and evolutionary conclusions of existing paleobiological reconstructions may be weakened or even overturned when all six degrees of freedom are considered. We offer an expanded methodological framework for virtual ROM estimation including joint translations and outline recommendations for future ROM‐based exclusion studies. [ABSTRACT FROM AUTHOR]

This article presents a time varying wavelet-based pole assignment (WPA) method to control seismic vibrations in multi-degree of freedom (MDOF) structural systems. The discrete wavelet transform is used to determine the energy content over the frequency band of the response in real time. The frequency content was implemented in the Big Bang-Big Crunch algorithm to update the optimum values of the closed-loop poles of the structural system adaptively. To calculate optimum gain matrix, a robust pole placement algorithm was used. The gain matrix is calculated online based on response characteristic in real time and must not be calculated a priori (offline) choice. The WPA is tested on a 10-story structural system subject to several historical ground motions. It is observed that the WPA has advantages in some design problems. Numerical examples illustrate that the proposed approach reduces the displacement response of the structure in real time more than conventional linear quadratic regulator (LQR) controller. [ABSTRACT FROM AUTHOR]

Recently, linear oscillatory actuators have been used in a wide range of applications. In particular, small linear oscillatory actuators are expected to be used in haptic devices by being extended to provide multi-degree-of-freedom motion with arbitrary acceleration. In this paper, we propose a compact two-DOF oscillatory actuator that can move in various directions on a plane. The static and dynamic characteristics of the actuator are determined by the 3D finite element method. The effectiveness of this method is shown through a comparison of the measured results with the experimental results from a prototype. [ABSTRACT FROM AUTHOR]

We present a three-degree-of-freedom planar actuator that can position a mover over a wide range of locations in the yaw and translational directions. In conventional planar actuators, which have multiple pairs of permanent magnets and armature coils, the mover cannot be displaced by large amounts unless the planar actuator has numerous armature coils. Furthermore, the movable area of conventional planar actuators in the yaw direction is quite narrow because of the interference between the different pairs of permanent magnets and armature currents that occurs due to the yaw displacements. The proposed planar actuator has only six stationary armature conductors for two sets of three-phase currents. The mover constantly faces all the armature conductors, and hence, it can be subjected to driving forces for three-degree-of-freedom movement anywhere on a plane parallel to the stator surface. Therefore, the movable area of the actuator can be easily expanded by increasing the length of the armature conductors. However, the driving forces depend on the yaw angle, and large yaw displacements impede the generation of sufficiently strong driving forces. In this paper, we present the results of experiments conducted to determine the movable area of our proposed planar actuator in the yaw direction. The experimental results indicate that sufficient torques in the yaw direction can be generated when the yaw displacement is less than 26°. The driving force acting on the mover is a function of the yaw angle and is periodic with a 90° period due to the central symmetry of the actuator. The experimental results also indicate that the mover can travel over 90° displacements in the yaw direction. Thus, we successfully demonstrate the three-degree-of-freedom large movement of the planar actuator by controlling two sets of three-phase currents. © 2011 Wiley Periodicals, Inc. Electr Eng Jpn, 177(4): 51-61, 2011; Published online in Wiley Online Library (). DOI 10.1002/eej.21208 [ABSTRACT FROM AUTHOR]

SUMMARY Redundant multi-degree-of-freedom ( MDOF) bilateral system in workspace is expected to be a key technology for the development of next-generation robots because of the variety of feasible tasks. Nowadays, four-channel bilateral structures based on acceleration control have been introduced to realize both position and force tracking in a bilateral control system. Additionally, torque observers have been implemented to facilitate force feedback without the use of torque/force sensors. However, differences in controller composition between the joint space and workspace are still unclear. In particular, observer designs in both spaces are important for a realization of torque/force sensorless bilateral control. This paper presents a performance evaluation of an MDOF force sensorless bilateral system performed by considering the design space of observers by numerical and experimental analyses. © 2013 Wiley Periodicals, Inc. Electr Eng Jpn, 186(4): 70-80, 2014; Published online in Wiley Online Library (wileyonlinelibrary.com). DOI 10.1002/eej.22481 [ABSTRACT FROM AUTHOR]

SUMMARY Recently, linear oscillatory actuators have been used in a wide range of applications. In particular, small linear oscillatory actuators are expected to be used in haptic devices by being extended to provide multi-degree-of-freedom motion with arbitrary acceleration. In this paper, we propose a compact two- DOF oscillatory actuator that can move in various directions on a plane. The static and dynamic characteristics of the actuator are determined by the 3D finite element method. The effectiveness of this method is shown through a comparison of the measured results with the experimental results from a prototype. © 2013 Wiley Periodicals, Inc. Electr Eng Jpn, 186(1): 58-65, 2013; Published online in Wiley Online Library (wileyonlinelibrary.com). DOI 10.1002/eej.22312 [ABSTRACT FROM AUTHOR]