Ball Weight Research Articles

Enclosing weighted points with an almost-unit ball

Given a set of n points with positive real weights in d-dimensional space, we consider an approximation to the problem of placing a unit ball, in order to maximize the sum of the weights of the points enclosed by the ball. Given an approximation parameter ε < 1 , we present an O ( n / ε d − 1 ) expected time algorithm that determines a ball of radius 1 + ε enclosing a weight at least as large as the weight of the optimal unit ball. This is the first approximate algorithm for the weighted version of the problem in d-dimensional space. We also present a matching lower bound for a certain class of algorithms for the problem.

Análisis de perfiles de difracción de rayos X de una aleación Cu-8% en peso de Cr obtenida por medio de aleado mecánico

El presente trabajo estudia la evolución de la estructura de una mezcla de polvos Cu-8% peso de Cr, aleada mecánicamente, por medio del análisis de perfiles de difracción de rayos X. Se encontró que al aumentar el tiempo de molienda, el tamaño de cristalitas y la energía de falla de apilamiento disminuyeron, y los valores de microdeformación y probabilidad de falla de apilamiento aumentaron. La distribución de cristalitas se desplazo hacia valores menores de tamaño de cristalitas al incrementar el tiempo de molienda. Después de 50 horas de molienda, los datos indicaron que se ha producido una solución sólida de cromo en cobre.

INTELLIGENT CONTROL OF MAGNETIC LEVITATION SYSTEM

This work investigates the design of a controller for keeping a steel ball suspended in the air. The main function of the controller is to maintain the balance between the magnetic force and the ball’s weight. A PD fuzzy controller is designed for this unstable nonlinear system to maintain the balance between the magnetic force and the ball's weight and to achieve robust stability against model uncertainties.

The Influence of Task Constraints on the Glenohumeral Horizontal Abduction Angle of the Overarm Throw of Novice Throwers

The action of the throwing arm during the development of the mature overarm throwing pattern has garnered much attention in recent years. Many of these studies have incorporated Newell’s (1986) developmental model into the description of the organismic (e.g., Halverson, Roberton, & Langendorfer, 1982; Langendorfer & Roberton, 2002) and/or environmental constraints placed upon the thrower (e.g., Thomas & French, 1985; Thomas, Michael, & Gallagher, 1994). According to Newell, three types of constraints—the organism, environment, and task—must be considered when investigating factors related to motor development and learning. These factors and their interactions are included in Newell’s triangular model as key sources of constraint when examining motor development at any age. Constraints are usually defined as facilitative channeling of movement, or limitations thereof, implying that constraints either encourage or limit motor development depending on the characteristics of the constraints (Haywood & Getchell, 2005). Organismic constraints involve the genetic makeup and an individual’s unique characteristics, such as height, limb length and mass, attentional focus, motivation, and arousal level. Because of organismic constraints, people performing the same task in identical environments may achieve various degrees of success (Haywood & Getchell, 2005). Environmental constraints include those that describe the setting in which an organism lives and thrives. For example, light, temperature, humidity level, air quality, nutritional opportunities, laws, cultural beliefs and practices, and normative views regarding acceptable behavior represent environmental constraints (Haywood & Getchell). Task constraints are controls that are placed upon the execution of the skill, such as skill criteria, equipment used, and the task itself (Haywood & Getchell). Only a few studies have accounted for the third axiom of Newell’s model, which is the task constraint (Cross, 2004; Southard, 1998). For instance, several studies have investigated how various populations of children respond to different instructional strategies when learning the skill of throwing (e.g., Goodway & Branta, 2003; Goodway, Rudisill, & Valentini, 2002; Valentini & Rudisill, 2004a, 2004b), but the majority of the studies have not reported or described the size or weight of the throwing implement. The failure to report and/or standardize task constraints, such as ball size and weight, makes comparisons across studies difficult, due to evidence that the size and weight of the ball influence the mechanics of overarm throwing (Alexander, 1991; Cross; 2004). Therefore, this study aimed to determine the influence of task constraints on the horizontal abduction angle of the overarm throw of novice throwers. Specifically, the study attempted to determine whether increasing the inertial components of the distal portion of the throwing arm forces the arm into an increased glenohumeral horizontal abduction angle. In an attempt to define the effects of task constraints on the overarm throwing motion, Alexander suggested The Influence of Task Constraints on the Glenohumeral Horizontal Abduction Angle of the Overarm Throw of Novice Throwers

Progress in measuring the performance of baseball and softball bats

The performance of baseball and softball bats has improved markedly over the past four decades. This has motivated many associations to develop test methods and measures to regulate bat performance. The present study reviews the progress of laboratory bat performance tests. The test involves an initially stationary bat that is allowed to recoil after being impacted by a ball. Bat performance was shown to be insensitive to changes in the way the bat was supported and sensitive to the rebound ball and bat speed. The rebound ball and bat speeds were in turn influenced by air turbulence and bat vibration, respectively. The common technique of normalizing the bat–ball coefficient of restitution (COR), by dividing it by the ball COR, was shown to overcorrect by more than the original effect of ball COR. Normalizing bat performance for the effect of ball weight, on the other hand, reduced its effect on bat performance. Measuring bat performance in the laboratory at impact speeds representative of play conditions had only a small effect on the relative performance between bats, but improved the correlation with field results. While laboratory bat performance tests are complex and experimentally challenging, they are robust and repeatable. © 2008 John Wiley and Sons Asia Pte Ltd

On weighted balls-into-bins games

We consider the well-known problem of randomly allocating m balls into n bins. We investigate various properties of single-choice games as well as multiple-choice games in the context of weighted balls. We are particularly interested in questions that are concerned with the distribution of ball weights, and the order in which balls are allocated. Do any of these parameters influence the maximum expected load of any bin, and if yes, then how? The problem of weighted balls is of practical relevance. Balls-into-bins games are frequently used to conveniently model load balancing problems. Here, weights can be used to model resource requirements of the jobs, i.e., memory or running time.

Trunk Muscle Activity During Stability Ball and Free Weight Exercises

The purpose of this investigation was to compare trunk muscle activity during stability ball and free weight exercises. Nine resistance-trained men participated in one testing session in which squats (SQ) and deadlifts (DL) were completed with loads of approximately 50, 70, 90, and 100% of one-repetition maximum (1RM). Isometric contractions during 3 stability ball exercises (quadruped (QP), pelvic thrust (PT), ball back extension (BE)) were also completed. During all exercises, average integrated electromyography (IEMG) from the rectus abdominus (RA), external oblique (EO), longissimus (L1) and multifidus (L5) was collected and analyzed. Results demonstrate that when expressed relative to 100% DL 1RM, muscle activity was 19.5 +/- 14.8% for L1 and 30.2 +/- 19.3% for L5 during QP, 31.4 +/- 13.4% for L1 and 37.6 +/- 12.4% for L5 during PT, and 44.2 +/- 22.8% for L1 and 45.5 +/- 21.6% for L5 during BE. IEMG of L1 during SQ and DL at 90 and 100% 1RM, and relative muscle activity of L5 during SQ and DL at 100% 1RM was significantly greater (P < or = 0.05) than in the stability ball exercises. Furthermore, relative muscle activity of L1 during DL at 50 and 70% 1RM was significantly greater than in QP and PT. No significant differences were observed in RA and EO during any of the exercises. In conclusion, activity of the trunk muscles during SQs and DLs is greater or equal to that which is produced during the stability ball exercises. It appears that stability ball exercises may not provide a sufficient stimulus for increasing muscular strength or hypertrophy; consequently, the role of stability ball exercises in strength and conditioning programs is questioned. SQs and DLs are recommended for increasing strength and hypertrophy of the back extensors.

Effects of moxidectin on coprophagous insects in cattle dung pats in Japan

Effects of the antiparasitic drug moxidectin were studied in laboratory and field experiments in Hokkaido, Japan by pour-on administrations (500 μg/kg) on a target pest Haematobia irritans Linnaeus, nontarget coprophagous flies represented by Neomyia cornicina (Fabricius), and the dung beetle Caccobius jessoensis Harold. The concentration of moxidectin excreted into cattle dung was maximum at 3 days post-treatment both in the first and second trials, and then it diminished. No moxidectin was detected on or after day 21 post-treatment in the first trial, and on or after day 28 post-treatment in the second trial. Larval development of H. irritans was hampered from 1 to 7 days post-treatment. No N. cornicina pupated in dung at days 1 and 3 post-treatment, and pupation and emergence rates were reduced in the dung until 7 days post-treatment. There were no significant differences in numbers and weight of brood balls constructed by Caccobius jessoensis in dung from treated and control cattle. Adult emergence rates of C. jessoensis on days 1, 3, 7, 14 post-treatments were not significantly different between control and treated groups, and more than 90% of adult emergence rates were demonstrated in both groups. In the field study using emergence traps, 3,433 (18 families) flies emerged from dung from untreated control cattle and 1,667 (16 families) flies emerged from dung from treated cattle. Notably, the number of Sciaridae spp. (first Experiment) and Sepsis latiforceps Duda and Sphaeroceridae spp. (second Experiment) significantly decreased in dung pats of treated cattle. From 48 dung pats in the field experiments, total dry weight of major coprophagous flies that emerged was 1,741.8 mg in dung from control cattle and 1,170.0 mg in dung from treated cattle, showing 32.8% reduction in treated dung. Emergence rates of C. jessoensis from brood balls recovered from soil beneath dung pats in the field experiments were not significantly different between dung from control and treated cattle on each sampling day (1, 7, 14, and 21 days) post-treatment.

Adverse effects of ivermectin on the dung beetles,Caccobius jessoensisHarold, and rare species,Copris ochusMotschulsky andCopris acutidensMotschulsky (Coleoptera: Scarabaeidae), in Japan

Effects of the antiparasitic drug, ivermectin, on the dung beetles, Caccobius jessoensis Harold, 1867 and the rare species, Copris ochus Motschulsky, 1860 and Copris acutidens Motschulsky, 1860 were studied in laboratory and field experiments in Hokkaido, Japan. Ivermectin was detected in dung from 1 to 21 or 28 days following treatment, with a peak on the first day after treatment in two pour-on administrations (500 microg kg(-1)), although there were considerable differences between the two peaks. In C. jessoensis, brood balls constructed by the female were not reduced in the dung of treated cattle except for seven days after treatment in experiment 2. Also, there was no significant difference in the mean weight of brood balls between dung from treated and control cattle. However, the emergence rates were significantly reduced in dung 1-3 days after treatment. In the field study, brood balls constructed by C. jessoensis were more abundant in dung from treated cattle in experiment 1, but adult emergence was significantly reduced at one and seven days after treatments. Adult mortality of C. ochus Motschulsky at 90 days after the beginning of rearing was 11.1% in dung from control cattle with 22 brood balls constructed, whereas it was 84% in dung from treated cattle with no brood balls and/or ovipositioning. Also, in C. acutidens Motschulsky, adult mortality at 90 days after the beginning of rearing was 3.6% in dung from control cattle with 13 brood balls constructed, whereas it was 94.1% in dung from treated cattle with no brood balls or ovipositioning. The environmental risk in the use of ivermectin during breeding period of dung beetles in pasture is discussed.

The Influence of Ball Size and Weight on the Lag Period of the Upper Arm in Overhand Throwing

The key component to maximizing velocity in overhand throwing is proper proximal to distal sequencing of the body. It is known, however, that objects that are too heavy to be thrown in this manner will be tossed in a more simultaneous manner, eliminating the lag period between adjacent segments. Yet, there is little research on the effect of ball size and weight on the lag between segments, particularly between the shoulder and trunk, which is of critical importance in throwing mechanics. PURPOSE: To investigate the effect of different size and weighted balls on the time period between forward movement of the trunk and forward movement of the upper arm, as denned by the elbow. METHODS: Thirteen participants (m = 10, f = 3) considered experienced throwers, were asked to throw three different weighted baseballs and softballs (4oz, 7oz, 12oz) of regulation diameters (9 inch & 12 inch circumference, respectively), with the balls randomly assigned to avoid learning effects. Participants were asked to throw the ball as “hard as they could” into large net placed in front of them. The upper arm lag period was analyzed using a custom (Motion Reality Inc., Atlanta Ga) 6 camera motion capture system, with markers interspersed throughout the upper body. RESULTS: A 2 (size) x 3 (weight) within subject repeated measures ANOVA revealed a size main effect (p = .043, power = .548) and a size-weight interaction (p= 0.049, power = .559), but no main effect for weight. CONCLUSIONS: The results of this study suggest that the size of the ball has a greater effect than the weight of a ball when propelling an object in a sequential manner. This finding supports the hypothesis that experienced throwers will revert to more simultaneous (or push) motions for objects that are too large for them to throw comfortably. Thus, suggesting that grip may play a role in determining the motor program employed by the thrower.

Statistical modeling of the mechanical alloying process for producing of Al/SiC nanocomposite powders

Mechanical alloying process was modeled by statistical approach for producing of Al/SiC nanocomposite powders. The process variables included two dimensionless variables TV where T and V are milling time and speed, respectively, and P1/ P2 where P1 and P2 are balls weight and powders weight, respectively. Responses of the process were crystallite size of the aluminum matrix, lattice strain of the aluminum matrix, and mean particle size of nanocomposite powders. The response variables were obtained by X-ray diffraction patterns (XRD), transmission electron microscopy (TEM), and laser particle size analyzer (LPSA). Two statistical models namely, fixed effects and regression model were developed. Analysis of variance (ANOVA) at 5% levels of significance for fixed effects model and 1% for regression model were performed. Results showed that P1/ P2 has a significant effect on the crystallite size, and lattice strain of the aluminum matrix and TV has a significant effect on the crystallite size, and lattice strain of the aluminum matrix as well as mean particle size of nanocomposite powders. ANOVA for regression model showed that the linear effects of TV and P1/ P2 variables were significant for crystallite size, lattice strain of the aluminum matrix, and mean particle size of nanocomposite powders. The final regression models were checked and accepted by residual analysis.

バスケットボールのボールの規格化に関する史的考察

The purpose of this study is to clarify the transition of the standardization of the ball used in basketball. The following conclusions can be drawn.1. Originally, the official ball was to be an ordinary Association football. This was the rule for the first few years of the game until a special ball for basketball was specified by the official rules in 1894-95. The special ball was made by the Overman Wheel Company and A. G. Spalding & Bros. Company. The price was 4 dollars.2. In 1895-96, an addition required the ball to be tightly inflated so that it could not be held by the lacing and the official rules stipulated that the ball made by the Overman Wheel Company was official. The ball was more strictly defined in 1896-97, when an addition limited its variableness. The Spalding ball became the only official ball this year. The price of this official ball was 6 dollars.3. The rules changed the ball's weight in 1909, when the manufacturers complained that they could not make a ball of the required weight that would have the required lasting qualities. In 1926-27 an air pressure measurement was first used. In the 1930s the rules committee passed several rules regarding the standardization of the ball.4. In the depression year 1930, conditions in high schools and small colleges were critical. The cost of a top grade basketball had increased in a short time from 7.50to 22.00. H. V. Porter, a member of the National Basketball Committee, was given the responsibility of negotiating with leading manufacturers and working out the details for a cheaper ball. As a result, a molded new type ball was devised in 1934-35. The new type ball and improved construction of the sewn leather ball made it possible to specify a uniform bouncing reaction.5. Today, any official ball is virtually identical to any other. This is because continuous developments in ball manufacturing have narrowed tolerance levels in all respects. The ball has always changed in the interests of greater standardization. The advances in manufacturing techniques have furthered the standardization process.

Mechanical alloying of Cu–Mo powder mixtures and thermodynamic study of solubility

A set of Cu-based powder mixtures containing up to 8 at.% Mo has been processed through mechanical alloying for a range of milling times up to 75 h. The milling operation was carried out using two types of milling media, stainless steel and tungsten carbide balls, keeping a constant powder to balls weight ratio of 10:1. The alloyed powders obtained were characterised by X-ray diffraction and scanning electron microscopy in order to determine the mean crystallite size and particles morphology after milling, respectively. The crystallite size produced after milling was quantitatively determined based on both, the Scherrer and Williamson–Hall methods. An estimate of the increased solubility of Mo in Cu, produced by the microstructural refinement during milling, was carried out through a thermodynamical analysis based on the influence of crystallite size reduction on chemical potentials.

Action Understanding Requires the Left Inferior Frontal Cortex

Numerous studies have established that inferior frontal cortex is active when hand actions are planned, imagined, remembered, imitated, and even observed. Furthermore, it has been proposed that these activations reflect a process of simulating the observed action to allow it to be understood and thus fully perceived. However, direct evidence for a perceptual role for left inferior frontal cortex is rare, and linguistic or motor contributions to the reported activations have not been ruled out. We used repetitive transcranial magnetic stimulation (rTMS) over inferior frontal gyrus during a perceptual weight-judgement task to test the hypothesis that this region contributes to action understanding. rTMS at this site impaired judgments of the weight of a box lifted by a person, but not judgements of the weight of a bouncing ball or of stimulus duration, and rTMS at control sites had no impact. This demonstrates that the integrity of left inferior frontal gyrus is necessary to make accurate perceptual judgments about other people's actions.

A Micromachined Thermal Flow Sensor Applied to A PC Mouse Device

This paper reports on a new PC mouse device by the use of the micromachined thermal flow sensors. The proposed mouse contains two small flow sensors mounted in two 10-mm-diameter and 3-mm-depth spaces in order to measure its velocity and direction. When the mouse is moved in a direction, air flow is generated because the air tends to stay where it is. Our sensors can detect the wide range flow speed which enables the mouse speed ranging from hundreds to one mm/s. A ball-type mouse is as big as one's palm because the mouse needs sufficient weight of a rubber ball to provide friction force. An optical mouse is smaller but it needs a patterned indented surface and sufficient light reflection from the surface of the desktop. The present flow mouse is as small as an optical one and it can work even on a smooth transparent glass. The results indicate that displacement can be measured with in an error ratio +/$2% at 10, 50,100 and 150 mm/s. This error ratio is good enough for this application

Ash-Melting Process Utilizing Thermite Reaction between Chromium Electroplating Sludge and Aluminum Dross

The aim of this work is to evaluate the possible application of the thermite reaction to the melting process of the municipal solid waste incineration ash (MSWI ash). The thermite agent was produced by mixing calcined chromium electroplating sludge with aluminum dross in appropriate stoichiometric proportions and then forming the mix into variously sized balls. The effect of size of the ball on the amount of melted MSWI ash, aggregation of metallic substances in the slag, and the level of environmental safety of generated slag were investigated. The reaction was initiated by heating a mix of single thermite ball and MSWI ash in a muffle furnace, and generated molten slag. The amount of MSWI ash increased with the weight of the thermite balls linearly, and its ratio was from 2.0 to 2.4. Comparative elution tests of untreated MSWI ash, MSWI slag, and thermite-derived slag show the environmental benefits of this type of approach. This paper presents the feasibility of ash melting process with thermite agent, the maximum amount of MSWI ash melted by one thermite ball, and the environmental benefits. Mixing a thermite agent with MSWI ash as an exothermic agent enhances the efficiency of the melting process, alleviates the energy consumption, and can be used to conventional melting techniques.

Effect Of Changes In Ball Weight On Shoulder Rotations During Upper Body Plyometrics

PURPOSE To determine differences in shoulder kinematics with 3 different weighted balls during an upper body plyometric exercise. METHODS This study was conducted on 5 males (age 32±7 yrs) using standard 2, 6, & 12lb medicine balls. Subjects performed a plyometric chest pass with both arms against a rebounder for 10 consecutive trials. Each subject was instrumented with 23 retroreflective markers modified from Aguinaldo (2004). 3D motion data was collected with 8 cameras (Motion Analysis Corp.) at 240Hz. Joint centers were calculated with virtual markers within EvaRT (Motion Analysis Corp.). Marker trajectories were then exported to Matlab to calculate shoulder joint angles using the Joint Coordinate System method. ROM for each trial was calculated from the max. & min. angles from each shoulder rotation. A repeated measures ANOVA was utilized to determine the effect of ball weight on each dependent variable. RESULTS Shoulder flex/ext, abd/add & int/ext ROM were all significantly increased when the ball weight was increased (main effect of ball p<0.001, p<0.01, and p<0.01). There were NS differences in side-to-side measures from each shoulder joint rotation. Post-hoc analysis revealed significant change in shoulder flex ROM from each increase in weight (p<0.05). However, abd/add ROM was significantly increased only from the 2 to 6lb weight while int/ext rotation was significantly increased only from the 6 to 12lb weight. The reliability, intraclass correlation coefficient (ICC[3,1]), of the measurements was high (average over 3 weights: shoulder flex r=0.789, abd r=0.884 & int/ext r=0.912).TableCONCLUSIONS Increasing ball weight affected shoulder abd/add and int/ext rotation differently. Changes in abd/add occurred at low weight, while changes in int/ext rotation required higher loads. Therefore, when developing an upper extremity plyometric program, the patient's individual injury and resultant “at-risk” movements must be considered prior to deciding on a progression of weight.

Effect Of Changes In Ball Weight On Shoulder Rotations During Upper Body Plyometrics

Effect Of Changes In Ball Weight On Shoulder Rotations During Upper Body Plyometrics

Forearm Injury-Gymnastics

HISTORY A 17-year-old junior elite gymnast sustained a forearm injury during a grip-lock maneuver after a release technique during a high bar exercise. Patient underwent a mid-shaft ulna and radius fracture reduction at the emergency room by the emergency room physician. Patient was released from the emergency room with a splint as the patient did not have significant swelling and pain. Patient's father followed-up with orthopaedic surgeon next day by phone previous to office visit. Patient's father reported that his son is complaining of numbness, tingling, swelling and pain of all fingers. Patient was scheduled to be seen at the surgery center that day. PHYSICAL EXAMINATION Examination revealed severely swollen hand and fingers with severe tenderness to palpation. Tenderness with attempts at passive range of motion of all fingers was noted. After splint removal significant forearm swelling was noted mainly in the volar aspect. Distal vasculature was intact with a 2+ radial pulse. Instability at the fracture site with gross motion of forearm bones was noted. Patient had intact light touch sensation in his fingertips and thumb. DIFFERENTIAL DIAGNOSIS Right ulna and radius shaft fracture. Right forearm compartment syndrome TESTS AND RESULTS Forearm radiographs: -Radius and Ulna mid to distal shaft fracture with comminution and evidence of instability at fracture site. FINAL WORKING DIAGNOSIS -Right both-bone forearm fracture with compartment syndrome TREATMENTS AND OUTCOMES Right both-bone forearm fracture open reduction with internal fixation using plates. Fasciotomy of volar flexor and dorsal extensor compartments with debridement of non-viable muscle tissue. Proximal 80% of volar incision was left open with rubber band stapled in criss-cross manner forming a lattice to not allow the skin to retract. Prophylactic oral antibiotics Whirlpool, wet-to-dry dressing changes, elbow, wrist and hand ROM exercises and home program instruction daily until full skin closure. Right forearm open wound irrigation and muscle debridement with skin closure 6 days after initial surgery. The more proximal 5-cm of dorsoulnar aspect was left open as there would be too much tension on the skin edges. Repeated radiographs of radius and ulna fractures at 5 days, 3 weeks, and 8 and 12 weeks after initial injury showed well-aligned both-bone forearm fracture with hardware in place. 3-cm wound closure 3 weeks later. Plastic surgery to close remaining 2-cm open wound with flap and graft. Strengthening exercises progressing to medicine ball plyometrics and weight bearing activities by 4 months.

Cavitation in a Lubrication Flow between a Moving Sphere and a Boundary

A heavy sphere is free to move inside a rotating horizontal cylinder filled with viscous liquid. The steady motion is essentially Stokesian, and the sphere rotates at a fixed location with a lubrication layer between the ball and the wall. The symmetry of the flow field suggests there will be no force to balance the normal component of the ball's weight. However, we show that a normal force can arise when a cavitation bubble is present. The bubble size was measured as a function of the cylinder rotation rate and agrees well with a model which uses the force and torque balances on the sphere.