Motion Of Point Research Articles

OPTIMIZATION OF THE PROCESSES OF MOVEMENT AND ACCELERATION OF THE OVERHEAD CRANE TROLLEY IN THE MODE OF DAMPING UNCONTROLLED LOAD OSCILLATIONS

The paper deals with the modeling and optimization of the processes of movement and acceleration of a bridge crane trolley in the mode of damping uncontrolled oscillations of the load. For the dynamic system of a flat pendulum with vibration damping, which describes the oscillations of a bridge crane load on a flexible rope suspension in a separate vertical plane, it is proposed to use third-order time splines that model the motion and acceleration of the load suspension point in the horizontal direction of the trolley's movement. To determine the time dependence of the angle of deviation of the crane from the gravitational ver-tical, it is proposed to use the methods of classical calculus of variations (Euler-Poisson equation), which allow optimizing (minimizing) the value of this angle in the process of accelerating a trolley with a load sus-pended from the ropes of an overhead crane. An analytical solution to the problem of damping residual uncontrollable oscillations of the overhead crane load, which usually occur after full acceleration or braking of the load suspension point on the trolley, is obtained. To derive the dependencies, an analytical approach was used to calculate the value of the angle of deviation of the overhead crane's cargo rope from the gravitational vertical, depending on the acceleration and displacement of the load suspension point. The problem of loosening of a load moved by an overhead crane is considered and solved in a new way that allows to completely avoiding pendulum spatial oscillations of the load on a rope suspension. The mathematical apparatus of linear algebra (Kramer's rule, in particular) is used, which allows us to establish analytically the law of time motion of a rope with a load, the angle of deviation of which from the vertical takes minimum values in the process of acceleration of the cargo trolley.

About tautochronic movements

It is shown that a material point, under the influence of an attractive linear force and a repulsive force inversely proportional to the cube of the distance from the center of attraction, performs a periodic motion, the period of which does not depend on the initial data (tautochronic motion). The problem is reduced to a nonlinear autonomous second-order equation, the general solution of which is expressed in terms of elementary functions. It has also been proven that for other power laws of repulsive force, except for degrees 0, 1 and –3, the movement of a material point is not tautochronous.

Translational Tomography with the Wide-field Imager for Parker Solar Probe (WISPR). II. Refinements to the Method

We present progress on the translational tomography technique for measuring the three-dimensional structure of the corona from near-perihelion Wide-field Imager for Parker Solar Probe (WISPR) image sequences. Translational tomography makes use of noncircular motion of a camera to extract three-dimensional information from an optically thin subject. Parker Solar Probe (PSP) presents a special case both because of the particular structure of the corona and because of the nonlinear motion of the vantage point. We show improvements to a previous direct analytic method (described in Paper I of this series) and an alternative inversion pathway using a synthetic sequence of WISPR images. The newer method successfully reconstructs the correct locations of modeled coronal rays in a synthetic WISPR image sequence, with curvilinear camera motion modeled on the PSP orbit. We present the refined methodology and validation study, and show that the technique is ready for application to actual WISPR data.

Research on circulation control mechanisms based on Lagrangian dynamics

Circulation control technology greatly improves an aircraft's aerodynamic efficiency by employing high-speed jets at the wing's trailing edge, which generates the Coanda effect. This paper analyzes and reveals the mechanism of circulation control from the perspective of Lagrangian dynamics. First, simulate the circulation control airfoil using the shear stress transport turbulence model to obtain instantaneous flow field data under various jet momentum coefficients (Cμ) and angles of attack. Subsequently, from the perspective of Lagrangian dynamics, the mixing, material transport, and momentum transfer processes between the jet and the trailing-edge separation zone are analyzed using attracting Lagrangian Coherent Structures (aLCSs) under different jet momentum coefficients. Next, through the perspective of particle motion in the Lagrangian framework, the study reveals the accelerating effect of the Coanda jet on the low-speed fluid over the upper wing surface. Additionally, repelling Lagrangian Coherent Structures are used to characterize the downward movement of the leading-edge stagnation point after applying circulation control, and the impact of this movement on the flow state is analyzed. Finally, the analysis using aLCSs assesses the flow control effectiveness of Coanda jets as “virtual aerodynamic flaps.” This analysis helps to further understand the advantages of the “virtual rudder surface” formed by Coanda jet.

Trajectory error compensation method for grinding robots based on kinematic calibration and joint variable prediction

Trajectory accuracy, a crucial metric in assessing the dynamic performance of grinding robots, is influenced by the uncertain movement of the tool center point, directly impacting the surface quality of processed workpieces. This article introduces an innovative method for compensating trajectory errors. Initially, a strategy for error compensation is derived using differential kinematics theory. Subsequently, a robot kinematic calibration method utilizing ring particle swarm optimization (RPSO) is proposed to address static errors in the grinding robot. Simultaneously, a method for predicting robot joint variables based on a dual-channel feedforward neural network (DCFNN) is designed to mitigate dynamic errors. Finally, a simulation platform is developed to validate the proposed method. Simulation analysis using extensive data demonstrates an 89.3% improvement in absolute position accuracy and a 74.2% reduction in error fluctuation range, outperforming sparrow search algorithm (SSA), improved mayfly algorithm (IMA), multi-representation integrated predictive neural network (MRIPNN), etc. Algorithmic comparison reveals that kinematic calibration significantly reduces the average trajectory error, while joint variable prediction notably minimizes error fluctuation. Validation through trajectory straightness testing and a 3D printing propeller grinding experiment achieves a trajectory straightness of 0.2425 mm. Implementing this method enables achieving 86.1% surface machining allowance within tolerance, making it an optimal solution for grinding robots.

Dynamics of a knuckle crane carrying a load subjected to wind pressure

AbstractThe paper presents the authors’ model of a knuckle crane offshore type that takes into account the flexibility of boom and drives, which is used to analyze the effect of constant wind pressure or cyclical gusts on the dynamics of the crane and the load. The mathematical model of the crane is derived using a formalism of joint coordinates, homogeneous transformation matrices, and Lagrange equations. Using this model, the influence of wind pressure on the torques and forces in the crane drives and on the accuracy of load positioning is investigated. The results show that the influence of wind on the accuracy of load positioning should not be assessed by limiting the observation to the movement of its gravity center but by observing the movement of characteristic points, the corners of the load. Root mean squared (RMS) indicators are used to quantitatively assess this impact on the driving torque and forces, and appropriate indicators are proposed to assess the accuracy of load positioning.

Three-dimensional stagnation point motion of bioconvection nanofluid via moving stretching sheet with convective and anisotropic slip condition

The current article deals with the SM of a NFs on a 3D moving surface containing bioconvection, microorganisms, and convective conditions over anisotropic slip. This work reports describes the characteristics of bioconvection aspects of nanofluid containing microorganisms with anisotropic slip condition. The study may be important from the application point of view in microfluidic devices, antibiotics, enhanced oil recovery and many other areas. Applying the similarity variables, the basic gov. Eqs are translated to ordinary ones, and such Eqs are calculate by R-K-F fourth order programming with shooting scheme by MATLAB software. The physical parameters on the moving surface are explained in detail via graphs. We found that the temperature increases with a higher revolution and larger numerical numbers (convection parameter), while the HTR declined for various values of the SFP. The HTR enhances with surface convection, and therefore, the convection condition is helpful in reducing the viscous drag on the moving SS.

A Calculation Method of Bearing Balls Rotational Vectors Based on Binocular Vision Three-Dimensional Coordinates Measurement

The rotational speed vectors of the bearing balls affect their service life and running performance. Observing the actual rotational speed of the ball is a prerequisite for revealing its true motion law and conducting sliding behavior simulation analysis. To address the need for accuracy and real-time measurement of spin angular velocity, which is also under high-frequency and high-speed ball motion conditions, a new measurement method of ball rotation vectors based on a binocular vision system is proposed. Firstly, marker points are laid on the balls, and their three-dimensional (3D) coordinates in the camera coordinate system are calculated in real time using the triangulation principle. Secondly, based on the 3D coordinates before and after the movement of the marker point and the trajectory of the ball, the mathematical model of the spin motion of the ball was established. Finally, based on the ball spin motion model, the three-dimensional vision measurement technology was first applied to the measurement of the bearing ball rotation vector through formula derivation, achieving the analysis of bearing ball rolling and sliding characteristics. Experimental results demonstrate that the visual measurement system with the frame rate of 100 FPS (frames per second) yields a measurement error within ±0.2% over a speed range from 5 to 50 RPM (revolutions per minute), and the maximum measurement errors of spin angular velocity and linear velocity are 0.25°/s and 0.028 mm/s, respectively. The experimental results show that this method has good accuracy and stability in measuring the rotation vector of the ball, providing a reference for bearing balls' rotational speed monitoring and the analysis of the sliding behavior of bearing balls.

Experimental study on mechanical and acoustic emission characteristics of red sandstone containing combined flaws of hole-fissure under biaxial compression

To investigate the mechanical behaviour and failure mechanism of flawed rock masses under biaxial stress conditions, a series of biaxial compression experiments are conducted on red sandstone specimens containing combined flaws of the circular hole and perforated symmetric fissure combined with acoustic emission (AE) technology in this work. The results show a close association between the stress-strain curve morphology and confining stress, both the biaxial compression strength and elastic modulus exhibit an upward trend with increasing fissure angle and confining stress. The maximum AE energy and cumulative AE energy both increase with higher confining stress. The crack types in the specimens are identified by analyzing the AF/RA value distribution, revealing a gradual decrease in the percentage of tensile cracks with increasing fissure angle. An AE localization algorithm based on the least absolute value method is applied to pinpoint AE events during biaxial compression, and AE events distribution is analyzed through the Kernel density estimation (KDE). The crack extension behaviour is described based on the movement of the maximum kernel density points, which initially exhibits a progression from both ends of the specimen towards the central region and subsequently from the central fissure tip towards the two ends.

Transverse vortex-induced vibration of a sphere with the application of Lorentz force at low Reynolds number

In this study, the transverse vortex-induced vibration (VIV) of an elastically mounted sphere with the application of a streamwise Lorentz force is investigated through direct numerical simulation. The research parameter range is 300 ≤ Re ≤ 1100 and −0.8 ≤ N ≤ 1, where Re is the Reynolds number and N is the interaction parameter of the Lorentz force. The dependence of sphere responses, forces, and wake structures on Re and N is illustrated in detail. Within this range, two oscillation patterns are identified: VIV and desynchronization. Three wake patterns are identified: two-sided hairpin vortex emerges in the VIV region, while one-sided hairpin vortex and double-threaded wake structures are observed in the desynchronization region. The evolution of these wake patterns is related to the motion of the rear stagnation point (RSP) and separation line (SL) on the sphere surface. A large positive or negative Lorentz force suppresses the motion of RSP and SL, leading to the one-sided hairpin vortex or double-threaded wake structures replacing the two-sided hairpin vortex. Finally, the oscillation patterns are summarized on a map of amplitude response contours in the Re-N space.

Active disturbance rejection control for spacecraft relative motion in libration point orbits subject to actuator saturation and time-delays

This paper proposes a novel active disturbance rejection control (ADRC) scheme to achieve the spacecraft relative pose synchronization in the libration orbits under the constrations of the actuator saturation and time-delays. The relative kinematics and dynamics between two spacecraft are modeled using dual quaternions to avoid singularity. A set of dimensionless variables is introduced to improve computational accuracy. An extended state observer, consisting of a time-delay predictor and an anti-windup compensator, is designed to address actuator saturation and communication time delays. A composite controller is then proposed, based on the designed observer, to mitigate the impact of total disturbances. Finally, two illustrative numerical simulations, including a spacecraft close rendezvous and docking scenario and a formation flying scenario, are provided to verify the effectiveness of the proposed ADRC scheme.

Structural–Parametric Synthesis of Path-Generating Mechanisms and Manipulators

This paper presents a structural–parametric synthesis of the four-link and Stephenson I, Stephenson II, and Stephenson III six-link path-generating mechanisms. The four-link path-generating mechanism is formed by connecting the output point and the base using an active closing kinematic chain (CKC) with two DOFs and a negative CKC of the type RR. The six-link path-generating mechanisms are formed by connecting the output point and the base by active, passive and negative CKCs. Active CKC has active kinematic pair, passive CKC has zero DOF, and negative CKC has a negative DOF. Active and negative CKCs impose geometrical constraints on the movement of the output point, and the geometric parameters of their links are determined by least-square approximation. Geometric parameters of the passive CKC are varied to satisfy the geometrical constraints of the active and negative CKCs. The CKCs of the active, passive and negative types, connecting the output point and the base, are the structural modules from which the different types of the path-generating mechanisms are synthesized. Numerical examples of the parametric synthesis of the four-link and six-link path-generating mechanisms are presented.

Displacement norm in the presence of an inverse-square perturbing acceleration in the reference frame associated with the radius vector

The problem of motion of a zero-mass point under the influence of attraction to the central body and a small perturbing acceleration P′ = P/r 2 is considered, where r is the distance to the attracting center, components of the vector P are assumed to be constant in a reference system with axes directed along the radius vector, the transversal and the angular momentum vector. Previously, for this problem, we found equations of motion in the mean elements and formulas for the transition from the osculating elements to the mean elements in the first order of smallness; we neglected second-order quantities. In this work, the Euclidean (root–mean–square over the mean anomaly) displacement norm ||dr||2 is obtained, where dr represents the difference between the position vectors on the osculating and mean orbit. It turned out that ||dr||2 depends only on the components of the vector P (positive definite quadratic form), the semi–major axis (proportional to the second power) and the eccentricity of the osculating ellipse. The norm ||dr||2 is obtained in the form of series in powers of the β=e/1+1-e2and in powers of the eccentricity e. The results are applied to the problem of the motion of asteroids under the influence of a perturbing acceleration inversely proportional to the square of the heliocentric distance, in particular, under the influence of the Yarkovsky effect.

Predicting the Consequences of an Emergency at a Railway Station

Purpose. The paper considers the problem of determining the size of the damage zones in the event of an emergency at a railway station due to a tanker fire. The task of forecasting is to determine the zones of thermal pollution, as well as chemical and mechanical pollution. The main objective of the study is to create numerical models for calculating the zones of mechanical and thermal pollution in the event of a fire at a railway station. Methodology. To analyze the size and intensity of zones of thermal, chemical, and mechanical environmental pollution in the event of an extreme situation at a railway station, we used the equations of heat and mass transfer and Newton's second law for modeling mechanical environmental pollution. To solve the equations, numerical methods such as Euler's method and finite difference schemes were used. On the basis of the developed numerical models, a computer code was created to conduct a computational experiment. Findings. Modern computer models for assessing the zones of chemical, thermal, and mechanical pollution in the event of an extreme situation have been developed. The results of computer modeling are presented. Originality. A set of numerical models for computer simulation of heat and mass transfer processes and dynamics of point motion has been created, which allows conducting a computational experiment to determine the contamination zones during a fire at a railway station. Practical value. A computer code was developed on the basis of the created mathematical models. This code is a tool for solving important problems in the field of environmental safety and civil protection. The computer code makes it possible to quickly determine the intensity and size of environmental pollution zones in the event of an extreme situation.

A Study on Differences in Educational Method to Periodic Inspection Work of Nuclear Power Plants

Construction work and regular inspection work at nuclear power plants involve many special tasks, unlike general on-site work. In addition, the opportunity to transfer knowledge from skilled workers to unskilled workers is limited due to the inability to easily enter the plant and various security and radiation exposure issues. Therefore, in this study, we considered the application of virtual reality (VR) as a method to increase opportunities to learn anytime and anywhere and to transfer knowledge more effectively. In addition, as an interactive learning method to improve comprehension, we devised a system that uses hand tracking and eye tracking to allow participants to experience movements and postures that are closer to the real work in a virtual space. For hand-based work, three actions, “pinch”, “grab”, and “hold”, were reproduced depending on the sizes of the parts and tools, and visual confirmation work was reproduced by the movement of the gaze point of the eyes, faithfully reproducing the special actions of the inspection work. We confirmed that a hybrid learning process that appropriately combines the developed active learning method, using experiential VR, with conventional passive learning methods, using paper and video, can improve the comprehension and retention of special work at nuclear power plants.

Assessment of the Change in the Nasal Septum and Nasal Profile After Le Fort I With Cone Beam Computed Tomography.

This study aimed to determine the relationship between nasal changes and the amount of advancement, impaction, and downward movement of the maxilla after Le Fort I osteotomy. The study included 48 patients who underwent Le Fort I surgery and had pre- and postoperative cone-beam computed tomography records. Changes in the nasal septum were evaluated by measuring septal deviation angles and volumes. In addition, nasolabial angle and width of nasal and alar base were examined. Groups were determined according to the movement of point A (the deepest point on the curvature of the maxillary alveolar process), using a threshold of 1.5 mm for vertical movements and 4 mm for sagittal movements. This resulted in the comparison of 6 groups of 8 people each. Results are presented as mean and standard deviation or median and range depending on the data distribution. Significance level was accepted as P < 0.05. There were no significant differences for each group on its own septal deviation volume or angle values pre/postoperatively. Groups 3 and 5, which both had at least 1.5 mm of impaction, showed significant changes in both deviation angle and volume between the preoperative and postoperative measurements. Nasolabial angle did not show significant changes between groups. Alar base width and nasal width increase was significantly highest in Group 1, which has more than 4 mm sagittal movement and less than 1.5 mm vertical movement. Le Fort I osteotomy may lead to undesirable changes in the spatial positioning of the nasal septum. The results of this study suggest that maxillary advancement does not significantly impact septal deviation, whereas maxillary impaction increases the amount of deviation. In addition, nasal width and alar base width tended to increase, and the nasolabial angle tended to decrease slightly, regardless of the direction of movement of the maxilla after orthognathic surgery. Surgeons should consider increased nasal septal deviation risks when planning impaction of the maxilla. The soft tissue changes in the nose vary according to different directions and amounts of Le Fort I surgery.

Unsteady characteristics of supersonic base flow influenced by the exhaust jet

The supersonic base flow with an exhaust jet is significantly unsteady, whose characteristics can be influenced by the exhaust jet states. By the exhaust jet, we mean the working fluid produced by the rocket engine and exhausted by the base nozzle in supersonic velocity, which is used to generate thrust. A numerical investigation of the base flow at Mach 1.96 is carried out via the delayed detached eddy simulation. The effects of presence, expanded states, and temperature of the exhaust jet on the unsteady characteristics are analyzed. Compared with the exhaust jet off, the exhaust jet presence causes the base pressure fluctuation intensity to increase in the high-frequency band (SrD &amp;gt; 0.5) and changes the dominant mode from wake oscillation (SrD = 0.12) to the periodically expand-shrink of the exhaust jet diameter (SrD = 0.16). Compared with the underexpanded state, the overexpanded exhaust jet induces the flow separation inside the nozzle, which causes a decrease in the base pressure fluctuation intensity in the high-frequency band (SrD &amp;gt; 1.0), and the separation point movement and exhaust jet oscillation constitute the dominant mode (SrD = 0.13). Compared with the low-temperature jet, the base pressure fluctuation intensity is slightly reduced in the high-frequency band (SrD &amp;gt; 1.0) for the high-temperature jet, and the flapping motion of the jet shear layer becomes the dominant mode (SrD = 1.5).

PPLICATION OF KINEMATIC APPROACHES IN GEOMETRIC PROBLEMS

This work is devoted to the use of kinematic methods in the process of solving geometric problems. The first part of the work is devoted to solving geometric problems by considering the movements of some image points. The minimum knowledge required to apply the kinematic method in elementary geometry is briefly outlined. Then a solution to a generalized version of a well-known geometric problem is presented. The importance of studying elements of operator calculus from an interdisciplinary perspective is also presented. The next part of the article examines problems selected according to the principle of gradual complication, from high school to bachelor’s degree. In these problems, the radius of curvature at various points is determined by kinematic way. Using the result of solving a kinematic problem about a body thrown in a horizontal direction, the expression for the radius of curvature of a parabola is determined. One physical method for determining the radius of curvature of a cycloid is presented. The problem of motion, which generates the equations of an ellipse and a hyperbola, is considered, and a kinematic version of determining the radii of curvature at the points of intersection of these curves and axes of symmetry is presented. The main methodological novelty of the work lies in the development, generalization and systematic presentation of kinematic problems that bring geometric results. Some methodological guidelines and arguments are also given to substantiate the importance of the discussed kinematic approaches to solving geometric problems.

Tibial Baseplate Migration Is Not Associated with Change in Patient-Reported Outcome Measures and Clinical Scores After TKA: A Secondary Analysis of 5 Radiostereometric Analysis Studies with 10-Year Follow-up.

Radiostereometric analysis (RSA) provides highly accurate data about the migration of a total knee arthroplasty (TKA) component. However, patient-reported outcome measures (PROMs) reflect the patients' perspective of their functional status, pain, and overall health after TKA. The aim of this study was to evaluate the association between tibial implant migration and change in postoperative PROMs and clinical scores, using data pooled from long-term follow-up RSA studies. Individual implant migration data were collected from 5 randomized RSA studies, including a total of 300 patients with 6 distinct TKA implant designs (all Stryker). Tibial implant migration (maximum total point motion [MTPM]) was evaluated with RSA at 3 months, 1 year, and 2, 5, 7, and 10 years postoperatively. The Knee Society Score (KSS)-Knee and KSS-Function and Knee Injury and Osteoarthritis Outcome Score (KOOS) subscales were collected in all studies at the same follow-up times. Linear mixed-effects models, with adjustment for TKA implant design and patient characteristics, were used to analyze the data. The 3-month follow-up visit was used as the baseline to assess the association between implant migration and PROMs across the 10-year follow-up. No association between tibial implant migration and change in KSS-Knee (p = 0.384), KSS-Function (p = 0.737), KOOS-Symptoms (p = 0.398), KOOS-Pain (p = 0.699), KOOS-Activities of Daily Living (p = 0.205), KOOS-Sport and Recreation (p = 0.702), or KOOS-Quality of Life (p = 0.368) was found across the entire follow-up. Similar results were found when using the 2-year follow-up as the baseline, after which both cemented and uncemented implants are expected to have stabilized. Tibial baseplate migration was not associated with postoperative worsening in PROMs or clinical scores in patients who underwent TKA. These findings suggest that implant migration, as measured with RSA, measures a different parameter (i.e., implant-bone fixation) than PROMs (i.e., patient perception) and clinical scores. Therefore, to assess the performance and safety of TKA implant designs, RSA and PROMs cannot be used interchangeably during the postoperative follow-up of patients and evaluation of the fixation of knee implants. Prognostic Level III . See Instructions for Authors for a complete description of levels of evidence.

Gangguan Perkembangan Bahasa pada Anak Usia 4 Tahun

The schipeaking in general can be interpreted as conveying one person's intentions or ideas, thoughts, concepts or contents of one's heart to another person using spoken language so that the intention can be understood by other people. Language development is the stage where children are starting to be able to convey the desired message in the form of a sequence of sounds of two or three words. Good language development, especially in speaking, enables children to express their thoughts and feelings intelligently according to the context and situation when they are speaking. This study aims to describe the condition of speech disorders experienced by 4 year old children. And investigate the factors that influence language development in early childhood. The results of the observations and analysis carried out refer to psycholinguistic studies related to language disorders. One of the symptoms in children of language and speech disorders is that there are pronunciation errors both in the mechanism of movement of the articulation points and in pronunciation. The research results show that genetic factors play a role in the speed and ability of children's language development, a social environment that is rich in interaction and language stimulation has a positive impact including the quality of conversation, vocabulary and role playing. Treatment that can be done for children who experience language and speech disorders is by doing speech therapy, oral motor, and melodic intonation. Parental education is also important in providing appropriate language stimulation. And limited language stimulation and lack of parental support can hinder children's language development. This research highlights the importance of involving active parental support to support early childhood language development.