Elliptical Trajectory Research Articles

A novel UAV-integrated deep network detection and relative position estimation approach for weeds

This paper aims at presenting a novel monocular vision–based approach for drones to detect multiple type of weeds and estimate their positions autonomously for precision agriculture applications. The methodology is based on classifying and detecting the weeds using a proposed deep neural network architecture, named fused-YOLO on the images acquired from a monocular camera mounted on the unmanned aerial vehicle (UAV) following a predefined elliptical trajectory. The detection/classification is complemented by a new estimation scheme adopting unscented Kalman filter (UKF) to estimate the exact location of the weeds. Bounding boxes are assigned to the detected targets (weeds) such that the centre pixels of the bounding box will represent the centre of the target. The centre pixels are extracted and converted into world coordinates forming azimuth and elevation angles from the target to the UAV, and the proposed estimation scheme is used to extract the positions of the weeds. Experiments were conducted both indoor and outdoor to validate this integrated detection/classification/estimation approach. The errors in terms of misclassification and mispositioning of the weeds estimation were minimum, and the convergence of the position estimation results was short taking into account the affordable platform with cheap sensors used in the experiments.

Development of a rotary-percussive ultrasonic drill using a bolt-clamped type piezoelectric actuator

Obtaining rock samples by drilling is an important method of asteroid detection. Due to the strict restrictions on the weight, volume, and weight on bit, conventional drilling devices are difficult to meet the requirements of drilling on an asteroid that has a weak gravitational field. This article proposed a rotary-percussive ultrasonic drill using a bonded-type piezoelectric actuator that can output harmonic vibration and elliptical trajectories simultaneously. The configuration and operation principle of the RPUD is presented and analyzed. Mode shape of the actuator and motions of the driving tips are verified by modal analysis and transient analysis, separately. Ultimately, a prototype of the RPUD is fabricated and experimentally investigated for its output characteristic and drilling performance. The test results indicate that the developed actuator can achieve the maximum no-load rotary speed of 119.2 r/min when the excitation frequency is 17.79 kHz. Furthermore, the maximum torque is 35 mNm, and the corresponding driving speed is about 20 r/min. The maximum drilling rate of the prototype to the sandstone is 7 mm per minute under a weight on bit of 5 N. The experimental results confirm that the proposed RPUD is feasible to drill rocks under a low weight on bit, which has the potential to obtain rock samples on an asteroid.

Polaron Dynamics in a Quasi-Two-Dimensional Bose–Einstein Condensate

The concept of polaron quasiparticles was first introduced in the pioneering papers by Landau and Feynman in the 1930s and 1940s. It describes the phenomenon of an external particle producing a bound state in an embedded medium. Since then, the study of polaron quasiparticles has been an active area of research in condensed matter physics, with a wide range of applications in magnetic phenomena and lattice deformation properties. In this paper, we provide a comprehensive review of the polaron quasiparticle phenomenon, including its historical origins, theoretical developments, and current research. We also study the various applications of polaron quasiparticles in condensed matter physics, including in magnetic phenomena and lattice deformation properties. The review concludes with an outlook on future directions of research in this field. In particular, we study the motion of external embedded particles in a quasi-two-dimensional Bose–Einstein condensate confined by the quantum harmonic oscillator. We found that the dynamics of attracting particles with static Bose–Einstein condensate exhibit circular and precessional elliptic trajectories due to centripetal force. Polaron-forming embedded particles in the condensate lead to a strongly nonlinear trajectory of the polaron and dynamics of condensate depending on the initial parameters of the condensate and polaron.

A U-shaped and alternately driven ultrasonic motor using three bending coupled modes

Most of ultrasonic motors (USMs) using non-isomorphic hybrid modes have resonance deviation which are easy to produce frequency decoupling, and conventional USMs can only drive rotor once in a working cycle. To overcome these problems, a surface-bonded type of U-shaped USM is proposed in this paper. At the same frequency, three isomorphic fourth-order bending vibration modes can be excited simultaneously and the resonance deviation between modes is eliminated, thus reducing the effect of frequency decoupling. In addition, a fourth-order bending vibration mode on horizontal beam of the U-shaped structure is used to provide pressing force at driving feet, and bending vibration modes on two vertical beams generate driving forces. Under the excitation of orthogonal signals, alternately driven elliptical trajectories are generated at driving feet. Besides, the surface-bonded type USM is more convenient to realize miniaturization and flexible structure. The USM is analyzed by using finite element method. The prototype is fabricated to evaluate performance of the USM. The experimental results show that velocity of the USM is 89.03 mm s−1 when excitation voltage is 180 VP-P and frequency is 86 kHz. The feasibility of working principle is proved by the experimental results.

Nyquist Plot Parametrization for Quantitative Analysis of Vibration of the Vocal Folds

ObjectivesThe Nyquist plot provides a graphical representation of the glottal cycles as elliptical trajectories in a 2D plane. This study proposes a methodology to parameterize the Nyquist plot with application to support the quantitative analysis of voice disorders. MethodsWe considered high-speed videoendoscopy recordings of 33 functional dysphonia (FD) patients and 33 normophonic controls (NC). Quantitative analysis was performed by computing four shape-based parameters from the Nyquist plot: Variability, Size (Perimeter and Area), and Consistency. Additionally, we performed automatic classification using a linear support vector machine and feature importance analysis by combining the proposed features with state-of-the-art glottal area waveform (GAW) parameters. ResultsWe found that the inter-cycle variability was significantly higher in FD patients compared to NC. We achieved a classification accuracy of 83% when the top 30 most important features were used. Furthermore, the proposed Nyquist plot features were ranked in the top 12 most important features. ConclusionsThe Nyquist plot provides complementary information for subjective and objective assessment of voice disorders. On the one hand, with visual inspection it is possible to observe intra- and inter-glottal cycle irregularities during sustained phonation. On the other hand, shaped-based parameters allow quantifying such irregularities and provide complementary information to state-of-the-art GAW parameters.

Development of a three-degree-of-freedom piezoelectric actuator.

Multi-degree of freedom piezoelectric actuators are strongly needed for industrial applications, especially when manipulating a large and heavy mirror or lens in an optical system. A novel three-degree-of-freedom piezoelectric actuator, which is driven by two pairs of piezo-stack actuator with spatial compliant mechanisms designed to guide the motion and preload the piezo-stack actuators, is herein proposed. The structure and working principle of the proposed actuator are illustrated and its kinematic characteristic is analyzed. The stiffness of the spatial compliant mechanisms is modeled, and the dynamic characteristics are analyzed, Finite Element method is utilized to validate the correctness of the stiffness modeling and the free vibration analysis of the proposed actuator. A prototype actuator is fabricated and its output performances have been tested. Working space of X ranging from -7.1 to 5.6μm, Y ranging from -6.2 to 8.2μm and Z ranging from -2.3 to 2.1μm, displacement resolutions of 15/16/21nm along X-/Y-/Z-axis and average velocities of 52.3, 82.8 and 29.5 µm/s along X-axis, Y-axis, and Z-axis with carrying load up to 2kg and driving frequency of 500Hz have been achieved by the prototype actuator. The method of waveform generating for the proposed actuator has been developed with the inverse hysteresis compensation, and test results indicate that the positioning accuracy of the prototype actuator in the open loop has been improved from 0.94 to 0.23μm for a circular trajectory tracking, from 0.48 to 0.29 μmm for an elliptical trajectory tracking, and from 0.61 to 0.32μm for a rectangular trajectory tracking with the compensated waveform of driving voltage.

2D PIV/PTV–3D uRANS RSM Investigation on the Combined Effect of Iron Filings Filtering Techniques in a Backward Facing Step Flow

The presence of suspended particles in liquid fluids is one of the main reasons for hydraulic system failure. Metallic impurities in particular increase the presence of toxic substances in wastewater; therefore, it is vital to study and address the behaviour of such particles in water flows. The current literature lacks studiees approaching the combined effect of different filtering techniques in backward-facing step (BFS) flows. This work aims to analyse the behaviour of iron filings within a BFS system, making use of a combined experimental 2D PIV/PTV–3D uRANS computational approach. Experiments and computations are performed at a Reynolds number mathrm{{Re}}_{H} = 3684.63. Computational measurements are performed in several planes whereas the experimental campaign is focused on the dynamics of the particles through the streamwise middle plane. A half plane reattachment length of X_{rm{r}} = 11.73h is measured for an inlet flow turbulence intensity of about 1%. The trajectories of the iron filings under the influence of an external magnetic field are examined. A comparison with their paths under the influence of no attractive forces elucidates that the presence of an external magnetic field alters their elliptical trajectories. Moreover, a more forward magnet placement reveals greater trajectory disruptions.

On the Dynamics of an Enhanced Coaxial Inertial Exciter for Vibratory Machines

Theoretical investigations into the capabilities of a coaxial inertial drive with various operating modes for vibratory conveyors and screens are conducted in the paper. The coaxial inertial exciter is designed with one asynchronous electric motor and the kinematically synchronized rotation of two unbalanced masses. Three variants of angular speeds ratios, namely ω2/ω1 = 1, ω2/ω1 = –1, and ω2/ω1 = 2, are considered. Based on these relations, the circular, elliptical, and complex motion trajectories of the working members are implemented. In the first two cases, single-frequency harmonic oscillations take place. In the latter case, the double-frequency periodic oscillations are excited. The dynamic behavior of the motor’s shaft during its running-up and running-out is considered. The influence of the inertial parameters of the unbalanced rotors and the relative phase shift angle between them on the elliptical trajectories of the vibratory system’s mass center motion is investigated. The use of forced kinematic synchronization provides the motion stability of the vibratory system for all considered working regimes.

A Symmetric-Actuating Linear Piezoceramic Ultrasonic Motor Capable of Producing a Scissoring Effect.

Conventionally, to produce a linear motion, one motor's stator is employed to drive one runner moving forward or backward. So far, there is almost no report of one electromechanical motor or piezoelectric ultrasonic motor that can directly generate two symmetrical linear motions, while this function is desired for precise scissoring and grasping in the minimally invasive surgery field. Herein, we report a brand-new symmetric-actuating linear piezoceramic ultrasonic motor capable of generating symmetrical linear motions of two outputs directly without additional mechanical transmission mechanisms. The key component of the motor is an (2 × 3) arrayed piezoceramic bar stator operating in the coupled resonant mode of the first longitudinal (L1) and third bending (B3) modes, leading to symmetric elliptical vibration trajectories at its two ends. A pair of microsurgical scissors is used as the end-effector, demonstrating a very promising future for high-precision microsurgical operations. The sliders of the prototype show the following features: (a) symmetrical, fast relative moving velocity (~1 m/s) outward or inward simultaneously; (b) high step resolution (40 nm); and (c) high power density (405.4 mW/cm3) and high efficiency (22.1%) that are double those of typical piezoceramic ultrasonic motors, indicating the full capacity of symmetric-actuating linear piezoceramic ultrasonic motor working in symmetric operation principle. This work also has enlightening significance for future symmetric-actuating device designs.

An Approach for Elliptical Trajectory Planning with Vertical Straight Line Segments of Pick‐and‐Place Robot Operation with Height Clearance

This study deals with elliptical trajectory planning with vertical straight‐line segments for pick‐and‐place robot operation with height clearance. It is significant for trajectory planning for the pick‐and‐place operation with the different height clearance between the picking point and placing point, or with the height clearance for picking and placing the product in the box. In this study, we propose an optimal asymmetric bisected elliptical path with two vertical straight line segments and a method to generate a motion profile suited to geometry of the optimal asymmetric bisected elliptical path based on the radius of curvature. The simulation result demonstrates that the proposed trajectory planning approach enables to reduce workspace and cycle period of the pick‐and‐place operation by minimizing the length and height of the path and guarantees continuity and smoothness of velocity, acceleration and jerk, and results in smoothness of working action of robot actuators.

Energy extraction performance of tandem flapping foil undergoing elliptical motion trajectory

The energy extraction performance of tandem flapping was numerically investigated by varying the flapping trajectory and position between the foils at a Reynolds number of 1173. A simple sinusoidal flapping trajectory is compared to a 2D simulation of tandem flapping foil following an elliptical trajectory. The simulation was carried out with NACA 0012 by varying the Strouhal number (St) between 0.2 and 0.5. The results show that with an elliptical motion trajectory pattern and an inter-foil spacing of 1.5 cm- 2cm (where cm is the mean chord length) between the foils would significantly enhance the energy extraction, whereas an unfavourable spacing between the forewing (fw) and hindwing (hw) foils results in unfavourable wake interaction, which reduces the energy extraction when compared to solo flapping foil. The highest energy extraction efficiency of 44% is achieved at St = 0.4. This research sheds new light on the creation of bio-mimetic devices by utilising a wake vortex to improve energy extraction efficiency.

Aerodynamic Force and Aeroelastic Response Characteristics Analyses for the Galloping of Ice-Covered Four-Split Transmission Lines in Oblique Flows

In order to study the galloping mechanism of ice-covered four-split transmission lines in oblique flows, the aerodynamic forces and aero-elastic response characteristics of the crescent-shaped four-split ice-covered transmission lines are investigated through wind tunnel tests on rigid and aero-elastic models. According to Den Hartog and Nigel’s galloping theories, the damping coefficients are calculated based on the experimental data. The results show that the crescent-shaped ice-covered four-split transmission lines usually suffer from torsional galloping. Furthermore, based on the aero-elastic wind tunnel data, the galloping is characterized by an elliptical trajectory, negative damping ratio, and a negative strain at hanging position. In addition, the galloping appears to be more prone to occur under oblique flows, with a larger galloping amplitude and a lower critical wind speed. This might be because an out-of-plane vibration of the third-order mode is excited at a lower wind speed, leading to a coupled resonance between in-plane and out-of-plane vibrations at the third-order mode with a frequency ratio of 1:1. The experimental results in this paper can also be used to verify the fluid-structure interaction simulation method of ice-covered transmission lines.

Investigation and Analysis of EM Pulse Propagation Inside Human Head for High-Resolution UWB Elliptical SAR Imaging

In this paper, an ultra-wideband (UWB) microwave imaging system based on an elliptical synthetic aperture radar (ESAR) is proposed as a possible solution for human head imaging. The system along with the image reconstruction method operates in the time domain. We have adopted the global back-projection technique to an elliptical trajectory of data acquisition, to shape around the head. A miniaturized, low profile custom-designed, UWB patch antenna capable of operating in the proximity of the head tissues is used as a sensor. The antenna aperture impedance is matched to the head tissues to enable pumping radiating electromagnetic waves into the human head needles of any coupling liquid. The impact of operational bandwidth and radiated power on system key performance factors i.e., penetration depth, range-resolution, and safety aspects are fully investigated based on calculations as well as full-wave simulations. It is observed that by increasing the bandwidth of radiated pulse from 0.8∼2.8 GHz (which was used in most of the previous works) to 1.0∼5.2 GHz, the range resolution can be improved remarkably from 23.0 mm to 16.0 mm deep inside the head. However, further increase in operational bandwidth will not improve the resolution of the system and a significant fraction of the radiated power will be dissipated in the brain tissues. To demonstrate the system performance, a constellation of 12 antenna elements is placed in an elliptical shape directly attached to the 3D phantom to acquire the raw data using full-wave simulations. Finally, an image from a 3D MRI-derived phantom is reconstructed to validate the imaging capability of the designed system. The proposed system can be used as a tool for early diagnosis as well as for treatment monitoring while getting therapy like chemo or radiotherapies.

An Extended Control of the Input Angle for Matrix Converters Connected With the Nonunity Power Factor Loads

This article proposes a novel pulsewidth modulation (PWM) modulation algorithm for multiphase conventional matrix converters, with three inputs and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$k$</tex-math></inline-formula> outputs, using the transfer function of the load angle. The proposed approach extends the range of power angle control at the input during the operation with a maximum voltage transfer ratio. The proposed concept is based on the direct analytic voltage PWM modulation with an elliptical trajectory of reference load voltages. The proposal has been verified using the circuit simulation in PSIM software, symbolic analysis using MATLAB, and finally through an experiment.

A unique cardiac electrocardiographic 3D model. Toward interpretable AI diagnosis.

Mathematical models of cardiac electrical activity are one of the most important tools for elucidating information about heart diagnostics. In this paper, we present an efficient mathematical formulation for this modeling simple enough to be easily parameterized and rich enough to provide realistic signals. It relies on a five dipole representation of the cardiac electric source, each one associated with the well-known waves of the electrocardiogram signal. Beyond the physical basis of the model, the parameters are physiologically interpretable as they characterize the wave shape, similar to what a physician would look for in signals, thus making them very useful in diagnosis. The model accurately reproduces the electrocardiogram signals of any diseased or healthy heart. This new discovery represents a significant advance in electrocardiography research. It is especially useful for diagnosis, patient follow-up or decision-making on new therapies; is also a promising tool for well-performing, transparent and interpretable AI approaches.

BgRT Motion Management Maintains Target Dose Coverage for Respiratory and Non-Respiratory Motion

<h3>Purpose/Objective(s)</h3> Biology-guided radiotherapy (BgRT) uses outgoing emissions after administration of an injected radiotracer to dynamically guide the delivery of radiation treatment to PET-avid targets. In this study, we evaluated the tracking performance of FDG-guided BGRT for two potential types of motion management (respiratory and non-respiratory (gastrointestinal)) while exploring different target shapes: spherical and non-spherical. BgRT is designed to ensure target coverage while keeping organ-at-risk (OAR) doses low. <h3>Materials/Methods</h3> A large custom anthropomorphic phantom with 2 robotic articulating arms was used to place a target and organ-at-risk inside a 27-liter water filled cavity. The targets consisted of an integrated ion chamber inside a 3D printed 22 mm sphere or a small non-spherical ovoid shape filled with FDG. The hot FDG-filled OAR consisted of either a 3D printed large C-shape annulus (mimicking a heart), large ovoid (mimicking a kidney), or a 30 mm sphere, all with integrated ion chambers. Both the 3D printed target and the OAR were filled with an 8:1 concentration ratio versus the water background. Three different 10 Gy/fraction treatment plans with two different target shapes and realistic nearby OARs were created with a 5 mm margin added to the CTV to generate the PTV. 3D printed targets and OARs were loaded with EBT-XD radiographic film. A 3D elliptical motion trajectory with breathing induced hysteresis with a maximum amplitude of +/- 12 mm was used for the respiratory motion model. An asymmetric slow-moving drift waveform with long-step shifts of +13/-5mm mm was used for the non-respiratory (gastrointestinal) motion model. Dosimetric results were evaluated based on 2-dimensional comparisons between measured film and planned dose distributions for the target and OAR. BgRT must maintain a prescription dose margin greater than 2 mm on the CTV for the three different motion experiments. Also, ion-chamber point dose and maximum film dose on the OAR must be within bounds predicted by the treatment planning system. <h3>Results</h3> BgRT was able to meet minimum margin requirements (a margin loss < 3mm) and meet prescription dose coverage in both motion management scenarios while maintaining OAR dose limits within the plan predicted bounds (see Table 1). <h3>Conclusion</h3> BgRT is able to provide motion management in complex cases that is agnostic to the type of motion. BgRT is able to maintain the PTV coverage with less than 3 mm reduction from the original 5mm margin.

Study of the dynamic model of the oscillating system of vibratory feeders with an elliptical trajectory of the movement of the working body

Vibrating feed bins with electromagnetic drive are widely used in the automation of production processes in mechanical engineering and instrument engineering. They are used for feeding miniature, small, or medium-sized parts to automated production equipment. These parts must be located in a certain stable position, that is, oriented in space, when using these feeders to feed component parts to the assembly position in assembly machines. Different means of orientation may be applied, which are directly located in the bunkers of these devices, in this case. The parts must be transported without sensitive tossing on trays of vibratory feeders for reliable operation of such orientation devices. A vibratory feeders with an elliptical trajectory of vibrations of the working body should be used in this case. A vibrating feeder with independent oscillations can be used in such a case. Vertical and horizontal component oscillations are excited by separate drives in it. It is necessary to apply a device for shifting phases in the power supply system of vibration drives to obtain elliptical oscillations. However, existing designs of vibrobunker feeders with an independent oscillation system have a number of significant disadvantages. They require the presence of independent vibrators: an axial vibrator to excite vertical vibrations and two or more tangential vibrators to excite horizontal (angular) vibrations. In addition, it is necessary to have a device for shifting the phases between them. Therefore, there was a need to create a new design of a vibrating bunker feeder with a system of elliptical oscillations, which will not have the listed disadvantages. Such a vibrating hopper feeder was developed and an experimental sample of this design was made. However, for the successful implementation of such feeders, a preliminary calculation of the parameters of their oscillating system is required, the methodology of which differs from the existing one. In the presented work, a mathematical study of the dynamics of the oscillating system of such vibratory feeders was carried out and a calculation method for its calculation was developed.

Effect of Flapping Trajectory and Interfoil Distance on Propulsive Performance of a Tandem Flapping Foil

Abstract In the present research, a 2D simulation of tandem flapping foil following an elliptical trajectory, i.e., altered from a simple flapping trajectory is performed. The purpose of the research is to evaluate the influence of the trajectory motion of the tandem flapping foil on hydrodynamics characteristics and propulsive efficiency. The study is carried out with tandem foil configurations as in such position, both the foils are subjected to the same flow, which allows the flapping foil to enhance the propulsive efficiencies with proper selection of foil position as well as the foil trajectory. The 2D simulation is carried out with NACA 0012 at Re = 1173 by varying Strouhal number (St) between 0.2 and 0.5. The results show that an elliptical motion trajectory pattern and interfoil spacing of 1cm–2cm (where cm is the mean chord length) between the foils would enhance the propulsive efficiency whereas an unfavorable spacing between the foils causes unfavorable wake interaction, which reduces propulsive efficiency as compared to solo flapping foil. When the results of the current numerical investigation of elliptical trajectory are compared to the results of simple trajectory tandem flapping, the current study shows a significant increase in propulsive efficiency. This study gives new insights in the development of biomimetic propulsors, as it strives to improve propulsive efficiency through the usage of wake vortex.

Probing Our Universe’s Past Using Earth’s Geological and Climatological History and Shadows of Galactic Black Holes

In this short review, we discuss how Earth’s climatological and geological history and also how the shadows of galactic black holes might reveal our Universe’s past evolution. Specifically we point out that a pressure singularity that occurred in our Universe’s past might have left its imprint on Earth’s geological and climatological history and on the shadows of cosmological black holes. Our approach is based on the fact that the H0 tension problem may be resolved if some sort of abrupt physics change occurred in our Universe 70–150 Myrs ago, an abrupt change that deeply affected the Cepheid parameters. We review how such an abrupt physics change might have been caused in our Universe by a smooth passage of it through a pressure finite-time singularity. Such finite-time singularities might occur in modified gravity and specifically in F(R) gravity, so we show how modified gravity might drive this type of evolution, without resorting to peculiar cosmic fluids or scalar fields. The presence of such a pressure singularity can distort the elliptic trajectories of bound objects in the Universe, causing possible geological and climatological changes on Earth, if its elliptic trajectory around the Sun might have changed. Also, such a pressure singularity affects directly the circular photon orbits around supermassive galactic black holes existing at cosmological redshift distances, thus the shadows of some cosmological black holes at redshifts z≤0.01, might look different in shape, compared with the SgrA* and M87* supermassive black holes. This feature however can be checked experimentally in the very far future.

Poro-elastic and poro-elasto-plastic modeling of sandy seabed under wave action

The seabed could be liquefied due to the wave-induced accumulation of residual excess pore water pressure (EPWP), resulting in the instability of offshore and marine structures. Thus, it is of importance to consider both the buildup of EPWP and the associated deformation behavior of the seabed. In this study, a dynamic poro-elasto-plastic seabed model, integrated with a state-dependent plasticity model, is developed in COMSOL Multiphysics. The numerical model of seabed is validated against the analytical solutions and model tests. The elliptical trajectories of soil particle at different depths of the poro-elastic seabed under the progressive wave are illustrated. The ratio of the amplitude of vertical displacement to that of horizontal displacement generally decreases as the depth increases for the poro-elastic seabed. In the poro-elasto-plastic seabed, however, the soil particles tend to move following the direction of the wave propagation. Moreover, the soil particles at the shallow part of the seabed go downwards before the initial liquefaction, while the soil particles at the lower position initially go upwards and then turn to go downwards when the initial liquefaction occurs. Particularly, the surface seabed with lower relative density is more prone to lose the stability, resulting in a dramatic upward vertical displacement.