Large Ball Research Articles

Nature's All-in-One: Multitasking Robots Inspired by Dung Beetles.

Dung beetles impressively coordinate their 6 legs to effectively roll large dung balls. They can also roll dung balls varying in the weight on different terrains. The mechanisms underlying how their motor commands are adapted to walk and simultaneously roll balls (multitasking behavior) under different conditions remain unknown. This study unravels the mechanisms of how dung beetles roll dung balls and adapt their leg movements to stably roll balls over different terrains for multitasking robots. A modular neural-based loco-manipulation control inspired by and based on ethological observations of the ball-rolling behavior of dung beetles is synthesized. The proposed neural-based control contains a central pattern generator (CPG) module, a pattern formation network (PFN) module, and a robot orientation control (ROC) module. The integrated control mechanisms can control a dung beetle-like robot (ALPHA) with biomechanical feet to perform adaptive (multitasking) loco-manipulation (walking and ball-rolling) on various terrains (flat and uneven). It can deal with different ball weights (2.0 and 4.6kg) and ball types (soft and rigid). The control mechanisms can serve as guiding principles for solving sensory-motor coordination for multitasking robots. Furthermore, this study contributes to biological research by enhancing the understanding of sensory-motor coordination for adaptive (multitasking) loco-manipulation behavior in animals.

The Effects of Constraints on the Variability of Throwing Patterns in Young Children

This research examined how changes in task constraints impacted the throwing patterns of children. The study involved 24 children, with an equal number of males and females, aged 5 and 6. The primary task constraints were the orientation of the target (horizontal or vertical hoops) and the size of the ball (diameters of 6 cm or 12 cm). We observed throwing patterns and analyzed kinematic changes in the preferred throws’ components. Initially, some children transitioned from using two hands to using one hand, and from underhand to overarm throws, particularly when using the larger balls. However, the preferred pattern for most children was one-hand overarm throwing. The kinematic analysis revealed that the participants adapted their throwing technique based on the size of the ball and the orientation of the hoop. The most significant adjustments occurred in the forearm component in response to changes in the target orientation. Notably, when aiming for a vertical hoop, distinct modifications were observed, including elevating the humerus and pulling the hand backward. These findings support the dynamical systems theory, which explains how movement patterns vary during motor development. The study also discussed the potential benefits of using constraints for skill acquisition in physical education settings.

Topological Edge Spectrum Along Curved Interfaces

Abstract We prove that if the boundary of a topological insulator divides the plane into two regions, each containing arbitrarily large balls, then it acts as a conductor. Conversely, we construct a counterexample to show that topological insulators that fit within strips do not need to admit conducting boundary modes. This constitutes a new setup where the bulk-edge correspondence is violated. Our proof relies on a seemingly paradoxical and underappreciated property of the bulk indices of topological insulators: they are global quantities that can be locally computed.

Head size in Delta ceramic-on-ceramic total hip arthroplasty: a comparative registry study.

Optimal bearing size in total hip arthroplasty (THA) has not been clearly ascertained, but large diameter ceramic balls may improve function and implant stability, with minimal concerns for wear. Delta ceramic-on-ceramic (COC) THA were stratified based on head diameter (32, 36 and 40mm), aiming to assess: 1) survival rates, reasons for revision and hazard ratios for failure; 2) survival rates and hazard ratios for aseptic loosening, dislocation/primary instability, liner failure. A regional arthroplasty registry was enquired about Delta COC THA performed for primary osteoarthritis, stratified by head size. 13,161 primary cementless THAs were included in the study, with a mean follow-up of 5.7years (range: 0-17): 3980 (30.2%) 32mm balls, 8327 (63.3%) 36mm heads, 854 (6.5%) 40mm heads. The three cohorts achieved similar survival rates (p = 0.99) and adjusted hazard ratios (p > 0.05). No revisions for head breakage or metallosis occurred. When revision for cup aseptic loosening was the endpoint, the survival rates of three cohorts (p = 0.08) and the adjusted hazard ratios (p > 0.05) were similar. The three cohorts achieved comparable survival rates when revision for dislocation/primary instability was the endpoint (p = 0.08). When the endpoint was revision for liner breakage, 32mm cohort showed higher rates of revision (p = 0.01). No liner failure was detected in the 40mm cohort. 32mm, 36mm and 40mm provided similar 10-year survival rates in Delta COC THA. 40mm heads emerged as safe options but did not lower the revisions for dislocations/primary instability. IV (therapeutic study).

Large stroke electromagnetic redundant actuated six degrees-of-freedom parallel compliant micropositioning stage

In this paper, a novel large stroke six degrees-of-freedom (6-DOF) electromagnetic redundant actuated micropositioning stage is proposed. The 6-DOF stage adopts a configuration that is composed of eight parallel driving branch chains. Each branch chain is driven by a voice coil motor and incorporates a parallelogram flexure mechanism and a decoupling mechanism for guidance and decoupling. The positioning stage is symmetrically arranged and possesses the advantages of simple structure and easy assembly. As a result, assembly errors are significantly reduced and positioning accuracy is enhanced. The decoupling mechanism uses a large stroke flexible ball joint that increases the motion range of the positioning stage and decouples the coupled motion, thereby enhancing the stability and accuracy of the stage. To evaluate the performance of the stage, static and dynamic analytical models of the 6-DOF stage are derived based on the compliance matrix method and the Lagrangian dynamic modeling method. Additionally, the accuracy of the analytical models and the static and dynamic performances of the positioning stage are verified through finite element analysis (FEA) and experimental testing. The experimental results demonstrate that the stage realizes a workspace of 2.06 mm × 2.02 mm × 3.1 mm × 23.4 mrad × 23.1 mrad × 14.9 mrad. Finally, to verify the tracking performance trajectory of the 6-DOF positioning stage, tracking experiments are performed using a controller that combines a proportional-integral controller and a notch filter.

Scalable concept drift adaptation for stream data mining

Stream data mining aims to handle the continuous and ongoing generation of data flows (e.g. weather, stock and traffic data), which often encounters concept drift as time progresses. Traditional offline algorithms struggle with learning from real-time data, making online algorithms more fitting for mining the stream data with dynamic concepts. Among families of the online learning algorithms, single pass stands out for its efficiency in processing one sample point at a time, and inspecting it only once at most. Currently, there exist online algorithms tailored for single pass over the stream data by converting the problems of classification into minimum enclosing ball. However, these methods mainly focus on expanding the ball to enclose the new data. An excessively large ball might overwrite data of the new concept, creating difficulty in triggering the model updating process. This paper proposes a new online single pass framework for stream data mining, namely Scalable Concept Drift Adaptation (SCDA), and presents three distinct online methods (SCDA-I, SCDA-II and SCDA-III) based on that framework. These methods dynamically adjust the ball by expanding or contracting when new sample points arrive, thereby effectively avoiding the issue of excessively large balls. To evaluate their performance, we conduct the experiments on 7 synthetic and 5 real-world benchmark datasets and compete with the state-of-the-arts. The experiments demonstrate the applicability and flexibility of the SCDA methods in stream data mining by comparing three aspects: predictive performance, memory usage and scalability of the ball. Among them, the SCDA-III method performs best in all these aspects.

Inderdigitation, double twist, and topological defects in a system of hard lollipops

ABSTRACT Using hard particle Monte Carlo simulations, we studied a three-dimensional system consisting of identical, lollipop-like particles. Each lollipop was built of five identical, tangent balls placed along a line and one larger ball at one side of the particle and modelled the RM734 molecule, for which ferroelectric and splay nematics were recently discovered in the experiment. Although our model did not recreate these phases, we observed inherently polar type A and C interdigitated smectics. Moreover, an intriguing, isotropic phase consisting of double-twisted clusters joined by planar defects was formed for a moderate packing fraction and ball diameter ratio.

Using Discrete Element Method to Analyse the Drop Ball Test

The drop ball test (DBT) is a common quality control procedure used in many grinding media manufacturing units to evaluate the quality of manufactured balls. Whilst DBTs have provided reasonable data over many years, the quantitative comparison of the energy that the balls are subjected to during the DBT and in high-impact loading environments such as semi-autogenous grinding (SAG) mills remains a grey area. To that end, DBT experiments were conducted, and the discrete element method (DEM) was used to assess the grinding media collision behaviour and the extent of ball impact loading to determine the impact energy spectra of the ball collisions. The impact energy spectra data obtained were used to quantify the energy that the grinding balls are exposed to in the DBT environment. The results showed that larger balls were exposed to relatively higher energy levels and had a higher probability of fracture than smaller balls. Furthermore, early ball breakage in a grinding environment is mostly attributed to the existence of imperfections or pre-existing defaults within the ball, whilst continuous wear is a gradual consequence that deplete balls in the mill.

Influencing factors on effectiveness of reverse total shoulder arthroplasty

To summarize the influencing factors on the effectiveness of reverse total shoulder arthroplasty (RTSA), so as to provide reference for clinical treatment. The related research literature of RTSA at home and abroad was extensively consulted, and the factors that may affect the effectiveness were summarized from the aspects of surgical technique, muscle condition, general condition of patients, psychological expectation, and lifestyle. For surgical techniques, different surgical approaches have their own advantages. The glenoid notch, poor bone ingrowth, increased bone resorption, and infection would lead to the loosening of glenoid prosthesis. In addition, the neck shaft angle and inclination angle of humeral prosthesis affect the occurrence of glenoid notch and the range of motion of joint internal/external rotation after operation, respectively. For muscle condition, the quality of teres minor and deltoid muscle has an important influence on joint stability after operation. Moderate increase of deltoid muscle tension can improve joint mobility after operation, and suture repair of subscapular tendon during operation can relieve joint pain and improve function, range of motion, and strength. For the general condition of patients, gender, age, and body mass index are all related to postoperative joint function and complications, and different occupations and postoperative exercise levels affect the recovery. The patients with severe degenerative diseases, poor preoperative function, and long disease duration have lower expectations and higher satisfaction with the effectiveness, and bad lifestyle has a negative impact on the effectiveness. The effectiveness of RTSA is related to surgical technique, muscle condition, general condition of patients, psychological expectation, and lifestyle. In order to avoid the loosening of glenoid prosthesis, the operator should choose humeral prosthesis with small neck shaft angle and large glenoid ball and put them down and inclined inferiorly during operation, and choose appropriate approach to eliminate space with drainage to reduce the risk of infection. After operation, patients should avoid activities that generate high anterior and posterior shear forces. In addition, the humeral prosthesis with a inclination angle of 10°-20° can achieve the best balance between the range of internal rotation and external rotation after operation. Proper deltoid tension can maintain joint stability and good range of motion. Suture of subscapular tendon is recommended.

Cycles in graphs with geometric property (T)

We show that a sequence of graphs with uniformly bounded vertex degrees, number of vertices going to infinity, and with geometric property (T) has many small cycles. We also show that when a small part of such a sequence of graphs with geometric property (T) is changed, it still has geometric property (T), provided that it is still an expander. We use this to give an example of a sequence of graphs with geometric property (T) that has large cycle-free balls.

Effect of ball–material ratio on Cu-Bi mixed powder and self-lubricating material properties

Purpose This study aims to investigate the effects of ball–material ratio on the properties of mixed powders and Cu-Bi self-lubricating alloy materials. Design/methodology/approach Cu-Bi mixed powder was ball milled at different ball–material ratios, and the preparation of Cu-Bi alloy materials was achieved through powder metallurgy technology. Scanning electron microscopy, X-ray diffraction and Raman spectroscopy were conducted to study the microstructure and phase composition of the mixed powder. The apparent density and flow characteristics of mixed powders were investigated using a Hall flowmeter. Tests on the crushing strength, impact toughness and tribological properties of self-lubricating alloy materials were conducted using a universal electronic testing machine, 300 J pendulum impact testing machine and M200 ring-block tribometer, respectively. Findings With the increase in ball–material ratio, the spherical copper matrix particles in the mixed powder became lamellar, the mechanical properties of the material gradually reduced, the friction coefficient of the material first decreased and then stabilized and the wear rate decreased initially and then increased. The increase in the ball–material ratio resulted in the fine network distribution of the Bi phase in the copper alloy matrix, which benefitted its enrichment on the worn surface for the formation a lubricating film and improvement of the material’s tribological performance. However, a large ball–material ratio can excessively weaken the mechanical properties of the material and reduce its wear resistance. Originality/value The effects of ball–material ratio on Cu-Bi mixed powder and material properties were clarified. This work provides a reference for the mechanical alloying process and its engineering applications.

Anchored heat kernel upper bounds on graphs with unbounded geometry and anti-trees

We derive Gaussian heat kernel bounds on graphs with respect to a fixed origin for large times under the assumption of a Sobolev inequality and volume doubling on large balls. The main result is then applied to anti-trees with unbounded vertex degree, yielding Gaussian upper bounds for this class of graphs for the first time. In order to prove this, we show that isoperimetric estimates with respect to intrinsic metrics yield Sobolev inequalities. Finally, we prove that anti-trees are Ahlfors regular and that they satisfy an isoperimetric inequality of a larger dimension.

The development of spatial orientation in children 5-6 years old with visual impairment

Relevance. At the present stage, despite a significant amount of research and various methodological developments, the problem of the development of spatial orientation in children aged 5-6 years with visual impairment remains relevant. The age period of pre-school and junior schoolchildren is called the "golden age", referring to the rate of development of coordination abilities. To develop coordination abilities, we recommend using: multicolored cubes, gymnastic sticks, ropes, balls of different colors and sizes: small, medium (including "sound balls") and large balls. When conducting classes, we recommend using methodological techniques based on motor activity.The aim is to determine the mechanisms of spatial orientation development in children with visual impairments.Organization and methods of research. Visual impairment has a negative effect on the overall physical development of children and their health. In children with visual pathology, there is a significant lag in physical development, and the ability to assess and regulate spatiotemporal and dynamic parameters is significantly reduced.The results of the study and their discussion. The main factor in the development of orientation in the classroom is the gradual dynamic introduction of more complex exercises into classes.Conclusions. When conducting classes, it is necessary to focus on the assessment of indicators of such parameters as speed of motor reaction, orientation in space, dexterity, which are most significant in the development of orientation in space.

Experimental and Simulation Investigation on Ball-Sealer Transport and Diversion Performance Aided by Machine Learning Method

Summary Ball-sealer diversion has been proven to be an effective and economical way to increase fractures and fracturing volume in multistage hydraulic fracturing and matrix acidizing treatments. However, designing and implementing a successful ball-sealer diversion treatment is still challenging. Typically, operators rely on empirical data to determine diversion parameters and need an understanding of accurate ball transport and diversion behaviors. A model for optimizing operating parameters, including fluid and ball properties, and predicting the diversion performance of ball sealers before treatment is needed for designing the fracturing process. In this work, we systematically investigated ball-sealer diversion using experimental and numerical methods. The resolved model of computational fluid dynamics (CFD) and discrete element method (DEM) is first developed to simulate the transport of a large ball in a horizontal wellbore with side holes. The experimental results validated the numerical model. The effects of the ball position in the pipe, flow ratio of the hole to pipe, injection flow rate, and ball density on the diversion performance were studied under field parameters. The results show that the ball sealer easily misses the heel-side perforation due to the inertial effect and travels to the toe side due to the large inertia and turbulent flow. The ball position and flow rate ratio are crucial for the diversion performance. There is a threshold value of the ball position under the specific condition, and the ball successfully turns to the perforation only when the threshold distance is met. A ball sealer closer to the perforation will have a larger probability of blocking the hole than the ball at the other side of the wellbore. The larger the flow rate ratio, the more the drag force on the ball, and the ball can successfully divert to the perforation despite the ball being far from the hole. The injection flow rate and ball density negatively correlate with the diversion performance due to the large inertia and gravity. The best classification result with the F1 score of 87.0% in the prediction set was achieved using the random forest (RF) algorithm. It provides new insight into developing ball sealers and adjusting fracturing parameters based on machine learning (ML) methods.

Advanced characterisation of photovoltaics for hail resistance

Climate change is intensifying severe weather events, especially in alpine environments where hailstorms are more frequent and intense. In particular, hail damage seriously affects photovoltaic systems. The severity of hailstorms as well as impact responses are important factors in mitigating loss, so the first research area that needs to be addressed is the resistance of photovoltaic modules to hail. According to IEC 61215 standard, a PV module should resist at the minimum to the impact of a hailstone of 25 mm launched at 80 km/h, while the Swiss VKF standard demands a minimum of 30 mm, practically making it 40 mm or more. The hail test stand is being enhanced to support larger diameters and higher speed, enabling module manufacturers to assess their products with adequate safety margins. Larger ice ball requires evaluating sample preparation, repeatability, representativity, and the ability to handle high speeds and masses in order to minimise uncertainty in impact energy. In this preliminary study, ice ball samples with diameters of 25, 40, and 70 mm were tested on a Hopkinson bar at speeds from 20 to 140 m/s and temperatures from −5 °C to −20 °C. The effects of impact velocity, loading rate, and impact time were examined. Finally, the first tests on PV modulus with large ice ball and high velocity are presented.

Survey and Isolation of Rice False Smut Pathogen Ustilaginoidea virens (Cooke) Takahashi

Roving survey has been conducted during first quarter of 2023 at selected paddy fields of Cauvery Delta zone (Tanjore, Perambalur) and Western zone (Coimbatore, Erode) of Tamil Nadu to assess the Percent Disease Incidence for rice false smut disease in which the maximum disease incidence was recorded in Erode district (40%). The infected spikelet were observed with the characteristic symptoms where the individual rice grains turned into large, fluffy and velvety green balls, later these balls turns hard during maturity. The pathogen Ustilaginoidea virens was isolated from the infected smut balls in potato sucrose agar medium in which the fungus appears as small white colonies after seven days of isolation.

Convexity of the radial sum of a star body and a ball

AbstractWe investigate the convexity of the radial sum of two convex bodies containing the origin. Generally, the radial sum of two convex bodies containing the origin is not convex. We show that the radial sum of a star body (with respect to the origin) and any large centered ball is convex, which produces a pair of convex bodies containing the origin whose radial sum is convex.We also investigate the convexity of the intersection body of a convex body containing the origin. Generally, the intersection body of a convex body containing the origin is not convex. Busemann’s theorem states that the intersection body of any centered convex body is convex. We are interested in how to construct convex intersection bodies from convex bodies without any symmetry (especially, central symmetry). We show that the intersection body of the radial sum of a star body (with respect to the origin) and any large centered ball is convex, which produces a convex body with no symmetries whose intersection body is convex.

Structural optimization of pitch bearings for offshore wind turbines

Pitch bearings are key components for the pitch system of wind turbines, and their reliability is closely associated with normal operation of wind turbines. In this paper, to solve the low efficiency problem of the GH Bladed and MATLAB software in design and analysis due to its operation in a single-user, stand-alone and single-key mode, GH bladed and MATLAB were combined based on Python for the integrated load spectrum calculation of pitch bearings through the full life cycle. Based on theories of contact strength analysis and fatigue life, finite element analysis and sub-modelling refinement techniques are established to investigate the relation between structural parameters and raceway stress of the bearings. Based on the Artificial Fish Swarm Algorithm (AFSA), the structural parameters are optimized to minimize the maximum contact stress on the bearing raceways and maximize the fatigue life of the bearings. The results show that the maximum contact load and the maximum contact stress on the pitch bearing raceways are significantly reduced and the bearing fatigue life is notably increased by 8.7%. The method proposed in the present study applies not only to pitch bearings, but also to other large four-point contact ball bearings.

Narrow escape in composite domains forming heterogeneous networks

Cellular networks are often composed of thin tubules connecting much larger node compartments. These structures serve for active or diffusion transport of proteins. Examples are glial networks in the brain, the endoplasmic reticulum in cells or dendritic spines. In this latter case, a large ball forming the head is connected to the dendrite by a narrow passage. In all cases, how the transport of molecules, ions or proteins is regulated determines the time scale of chemical reactions or signal transduction. In the present study, based on modeling diffusion in three dimensions, we compute the mean time for a Brownian particle to reach a narrow target inside such a composite network made of tubules connected to spherical nodes. We derive asymptotic formulas by solving a mixed Neumann–Dirichlet boundary value problem with small Dirichlet part. We first consider the general case of a network domain organized in a 2-D lattice structure that consists of spherical ball compartments connected via narrow cylindrical passages. For a single target located on the boundary of one of the spherical domains, we derive a sparse linear system of equations for each Mean First Passage Time (MFPT) averaged over the different compartments. We then consider a composite domain consisting of a spherical head-like domain, with narrow absorbing targets on its boundary, that is connected to a large cylinder via a narrow cylindrical neck. For Brownian particles starting within the neck, we derive an asymptotic formula for the MFPT. When diffusing particles can be absorbed upon hitting additional absorbing boundaries of the large cylindrical compartment, we derive asymptotic formulas for the splitting probability and conditional MFPT to reach a target on the spherical head. We compare these formulas with numerical solutions of the mixed boundary value problem and with Brownian simulations, allowing to explore geometrical parameter ranges. To conclude, the present analysis reveals that the mean arrival time, driven by diffusion in heterogeneous networks, is controlled by the targets and tubules sizes, as well as the size of the nodal compartments.

Multidimensional Analysis of Precursor Information of Rockburst during Loading and Unloading of Deep Diorite

At present, rockburst disasters cannot be predicted accurately, and the prevention and control of deep underground engineering disasters are significantly challenging. To explore the evolution law of precursory information of rockburst instability, the rockburst test of diorite was conducted with high confining pressure and different unloading rates (0.1 MPa/s, 0.3 MPa/s, 0.5 MPa/s, 0.7 MPa/s, and 0.9 MPa/s). Multidimensional analysis is carried out by evaluating deformation features, fast Fourier transform (FFT), energy entropy, singular spectrum entropy, and power spectrum entropy. The results show that Poisson’s ratio is hook-shaped before rockburst, the elastic modulus is in the shape of a step, ringing count and energy surge after a quiet period, three-dimensional law of 0.98 σ c ~ σ c stress location space shows a large red ball distribution along the shear plane, b value fluctuates in the low-value range, and low-frequency high amplitude and high-frequency low amplitude fluctuate in a large range after 300 s, with frequent abnormal fluctuations of the energy spectrum entropy, the singular spectrum entropy, and the power spectrum entropy curve. The above research results can be considered the evolution law of rockburst precursor information, which enriches the theoretical method of explosion disaster prediction.