Maximum Ball Research Articles

Multi-scale pore network modelling of fluid mass transfer in nano-micro porous media

It is widely accepted that pore size distribution and spatial pore connectivity directly impact on the macroscopic porous medium transport properties. Therefore it is indispensable to characterize nano-micro porous media like shale with multi-scale pore structure to accurately assess fluid transport properties. In this study, we propose a multi-scale pore network model to estimate the fluid transport properties. A 3D binary inorganic porous structure model is constructed from a section of scanning electron microscopy (SEM) image which only images large scale inorganic pores and its corresponding inorganic pore network is extracted by the maximal ball fitting method. The nano-porous organic matter is treated as the virtual throat which is embedded in series or parallel connection with the inorganic throat on the original inorganic pore network. Three parameters namely the ratio of total amount of the virtual throat to the total amount of the inorganic throat, the proportion of virtual throat in parallel connection with the inorganic throat and average organic pore radius inside the organic matter are applied to analyze the impact of multi-scale pore structure characteristic on fluid transport properties. The constructed multi-scale pore network model accounts for the organic matter distribution, organic matter total volume, organic pore size, inorganic pore structure and connectivity characteristic between organic and inorganic system all together. Nano-micro scale fluid transport mechanisms are considered in modelling fluid mass transfer. Key analysis results indicate that the fluid mass transfer in nano-micro porous media is influenced by the nano-porous organic matter distribution pattern and it’s local volume. The series connection of nano-porous organic matter and the increase of virtual throat amounts significantly decrease the fluid transport ability. Furthermore, the established multi-scale pore network model is used to interpretate laboratory pressure pulse decay response curve.

Determination of pore types in coquinas carbonates and their effects on formation factors and porosity exponents

ABSTRACT Calculation of the saturation of carbonates with various pore types and complicated pore structures in electrical resistivity models requires data on pore types and their effects on electrical resistivity. Therefore, the objectives are to determine the pore types and to investigate their effects on electrical resistivity. The pore types of three coquinas samples were determined by the distributions of experimental porosities and porosity exponents in the cross-plot of the dual porosity model and pore visualization from X-ray computerized tomography. A process-based method was applied to reconstruct the pore-scale models with different pore types. Their pore networks and electrical resistivity were extracted and calculated by the maximal ball and finite element methods, respectively. Fracture reduced the formation factor and porosity exponent. Connected vug increased the pore space that swept by the electrical current to reduce the formation factor while increasing the porosity exponent. Isolated vug undermined the pore space to increase the formation factor and porosity exponent. The effects of the tiny vug were much more obvious than the effects of the large one. This investigation will help to classify the pore types and propose electrical resistivity models that correspond to specific pore types and vug sizes in carbonate reservoirs.

Using Computer Simulation to Investigate Which Joint Angle Changes Have the Most Effect on Ball Release Speed in Overarm Throwing

Efficient throwing mechanics is predicated on a pitcher’s ability to perform a sequence of movements of body segments, which progresses from the legs, pelvis, and trunk to the smaller, distal arm segments. Each segment plays a vital role in achieving maximum ball velocity at ball release. The perturbation of one joint angle has an effect on the ball release speed. An eight-segment angle-driven simulation model of the trunk, upper limbs and ball was developed to determine which joint angle changes have the most influence on ball release speed in overarm throwing for an experienced pitcher. Fifteen overarm throwing trials were recorded, and the joint angle time histories of each trial were input into the simulation model. Systematically replacing each joint angle time history with a constant value showed that overarm throwing was sensitive (≥5 m/s effect on ball release speed) to trunk extension/flexion and upper arm external/internal rotation, and very sensitive (≥10 m/s effect) to forearm extension/flexion. Computer simulation allows detailed analysis and complete control to investigate contributions to performance, and the key joint angle changes for overarm throwing were identified in this analysis.

Reliability of Algorithms Interpreting Topological and Geometric Properties of Porous Media for Pore Network Modelling

Pore network models (PNMs) offer a computationally efficient way to analyse transport in porous media. Their effectiveness depends on how well they represent the topology and geometry of real pore systems, for example as imaged by X-ray CT. The performance of two popular algorithms, maximum ball and watershed, is evaluated for three porous systems: an idealised medium with known pore throat properties and two rocks with different morphogenesis—carbonate and sandstone. It is demonstrated that while the extracted PNM simulates simple flow (permeability) with acceptable accuracy, their topological and geometric properties are significantly different. This suggests that such PNM may not serve more complex studies, such as reactive/convective transport of contaminants or bacteria, and further research is necessary to improve the interpretation of real pore spaces with networks. Linear topology–geometry relations are derived and presented to stimulate development of more realistic PNM.

Functional Hip Characteristics and Their Relationship With Ball Velocity in College Baseball Pitchers.

Compared to shoulder and elbow functions, the hip functional characteristics of baseball pitchers have not been fully investigated. Therefore, little is known about the relationship between hip function and pitching performance. The purpose of this study was to evaluate the characteristics of hip flexibility and strength, focusing on their influences on the ball velocity in baseball pitchers. Descriptive laboratory study. Laboratory and university baseball facility. Twenty-three college baseball pitchers. Passive hip range of motion (ROM) and isometric hip muscle strength were bilaterally measured. The pitchers threw 20 fastballs at an official pitching distance. Bilateral hip ROM and strength in flexion, extension, abduction, adduction, and external and internal rotation; the maximal ball velocity. The pivot side showed smaller hip external rotation ROM (P < .01), larger hip internal rotation ROM (P = .03), and greater hip adduction strength (P = .03) than the stride side. The hip extension ROM on the stride side had a negative correlation with the maximal ball velocity (r = -.58, P < .01). The maximal ball velocity (135.3 [4.1]km/h) positively correlated with the hip extension (r = .59, P < .01), flexion (r = .57, P < .01), abduction (r = .55, P < .01), and adduction (r = .55, P < .01) strength on the pivot leg, and the hip flexion (r = .53, P = .01), abduction (r = .67, P < .01), and adduction (r = .46, P = .03) strength on the stride leg. These findings suggest that baseball pitchers do not have marked side-to-side differences in hip flexibility and strength, and that an important fitness factor for increasing ball velocity is not the hip flexibility but the hip muscle strength of both legs.

The acute effects of a short technique-intense training period on side-foot kick performance among elite female soccer players.

Previously, it was shown that elite soccer teams were 24% more likely to win matches if their passing effectiveness were increased by 1%. However, research interventions aiming to improve passing performance are scarce. The current study aimed to investigate the effect of a short technique-intense training period on side-foot kick performance among elite female soccer players. Four side-foot kick tests were completed before and after a training period: kicking a stationary ball using match-relevant (SBRS) and maximal ball speed (SBMS), passing the ball on the move using match-relevant ball speed (RBRS), and repeated side-foot kicks onto a rebound-box with continuously increasing passing distance (RRB). The players were assigned to either the intervention group or the control group. The training intervention consisted of six 55-min training sessions with five side-foot kick exercises. Within-group and between-group differences were investigated using paired-samples t-test and Mann-Whitney U test, respectively. The intervention group improved the performance in the RBRS and RRB tests (both P<0.05), but no differences were found for the SBRS and SBMS tests (both P>0.05). No improvements were found for the control group independent of test condition (all P>0.05). Significant between-group differences were found for the RBRS and RRB tests (both P<0.05), whereas no differences were found for the SBRS and SBMS tests (both P>0.05). The fundamental soccer skill of passing a moving ball was improved in elite female soccer players by a short technique-intense training period.

Maximum ball in play demands for sub-elite Rugby Union referees in domestic club rugby

Purpose: Rugby union referee research has reported the game demands for whole game averages and comparisons between each half and 10 minute periods. No study has reported the movement game demands for the maximum ball in play time for referees. The purpose of this study was to quantify the maximum ball in play (Max BiP) demands termed “worst case scenario” (WCS) of sub-elite rugby union referees using 10Hz Global Positioning System (GPS) units. Method: Movement demands of ten (n = 10) sub-elite referees across 27 matches, played during the 2017/18 All Ireland League Division 1, was calculated using 10Hz GPS units. The total distance covered (m), relative distance (m.min -1 ), percentage time in 6 velocity zones, were reported across the whole match, 1 st half, 2 nd half, 10minute periods and the maximum ball in play time using paired sample t-tests. Cohen’s d effect sizes were reported. Results: The maximum ball in play time was reported to be 172 ± 71 sec. The relative distance during Max BiP (107.9 ± 22.54 m.min -1 ) was significantly higher (p 7.01 m.s -1 ). Conclusion: The results of this study quantifies the Max BiP movement demands for a sub-elite rugby union referee which are higher than those reported in whole game averages, 1 st & 2 nd halves and some 10min periods. These results provide sports scientists with the worst case scenario demands and can allow for these demands to be replicated in training with those experienced in matches.

Investigating the effects of pore types on the pore geometry, topology and electrical resistivity in fractured and vuggy samples using pore-scale models

ABSTRACTThe interpretation of electrical resistivity for assessing the saturation in rocks with complicated pore structures and various pore types requires the intrinsic parameters quantifying pore structures incorporated in modified resistivity models. Therefore, the objectives are to investigate pore types effect on the pore morphology and electrical resistivity and to determine the key pore morphological parameters for each pore type. The maximal ball method was applied to extract the pore networks of the reconstructed pore-scale models using a process-based method, and the pore morphology was characterized using a pore-network analysis and a random walk simulation. The resistivity was simulated using a finite element method. The key parameters determined by the Morris screening method for the fractured, isolated and connected vuggy models were the Euler number, the cross-sectional pore-to-throat area ratio (PTAR) and the pore radius, respectively. The qualitative relationships between the Euler number, the PTAR and the porosity exponent for the fractured and vuggy models were determined and validated using three Coquinas carbonates. This investigation will help to elucidate the variations of the porosity exponent and to further derive a new electrical resistivity model that correlates the pore morphology to the resistivity in fractured and vuggy carbonate reservoirs.

Effects of pore clusters on the permeability, formation factor and porosity exponent of porous media

ABSTRACTMicropore and pore evolution both severely influence pore structure and transport properties. The micropore connects isolated pores to predominate connected pore cluster while the pore evolution generates isolated pores. Therefore, investigating separate impacts of predominate and remaining pore clusters is the first step to modify the existing electrical resistivity and permeability models with consideration of the micropore and pore evolution.The main pore clusters in six porous media including sandstone and carbonate were first extracted. Then, the pore geometry, topology, electrical resistivity and permeability from the main pore cluster compared with them from all the pore clusters in the same porous medium. The calculations of pore morphological and the petrophysical properties were all based on the pore networks extracted from the porous media by maximal ball method.The predominant pore cluster mainly determined the pore geometry, electrical resistivity and permeability of the corresponded porous medium. However, the isolated pore clusters from pore evolution undermined the pore connectivity. The developments of the remaining pore clusters slightly affected the electrical resistivity and permeability while seriously impacted the porosity exponents. Therefore, the micropore could increase the pore connectivity, and then slightly increase the permeability and reduce the electrical resistivity.

Electromyographic analysis of hip adductor muscles in soccer instep and side-foot kicking

ABSTRACTA possible link between soccer-specific injuries, such as groin pain and the action of hip adductor muscles has been suggested. This study aimed to investigate neuromuscular activation of the adductor magnus (AM) and longus (AL) muscles during instep and side-foot soccer kicks. Eight university soccer players performed the two types of kick at 50%, 75% and 100% of the maximal ball speed. Surface electromyography (EMG) was recorded from the AM, AL, vastus lateralis (VL) and biceps femoris (BF) muscles of both kicking and supporting legs and the kicking motions were three-dimensionally captured. In the kicking leg, an increase in surface EMG with an increase in ball speed during instep kicking was noted in the AM muscle (p < 0.016), but not in AL, VL or BF muscles (p > 0.016). In the supporting leg, surface EMG of both AM and AL muscles was significantly increased with an increase in the ball speed before ball impact during both instep and side-foot kicks (p < 0.016). These results suggest that hip adductor muscles markedly contribute to either the kicking or supporting leg to emphasise the action of soccer kicks.

Relationship of Glove Arm Kinematics With Established Pitching Kinematic and Kinetic Variables Among Youth Baseball Pitchers.

Background:While the kinematics of the pitching arm, trunk, and pelvis have been described and studied, glove arm kinematics remain an understudied portion of the pitching motion. Baseball pitchers seek to achieve maximum ball velocity in a fashion that does not place the arm at risk of injury.Purpose:To assess the relationship between glove arm shoulder horizontal abduction and elbow flexion and pitching arm kinematics and kinetics among youth pitchers to determine whether recommendations can be made toward a safer pitching motion.Study Design:Descriptive laboratory study.Methods:Thirty-three right-handed youth male baseball pitchers (mean ± SD: age, 13.6 ± 2.0 years; height, 169.4 ± 14.3 cm; weight, 63.5 ± 13.0 kg; experience, 7.3 ± 3.0 years) threw 3 fastballs to a catcher while kinematic data were collected with an electromagnetic tracking system. The Spearman rank-order test was used to identify relationships between glove arm horizontal abduction and glove arm elbow flexion and various kinematics and kinetics found at maximum shoulder external rotation (MER) and ball release for the fastest fastball delivered by each participant.Results:At MER, there were significant relationships found between a more flexed glove arm elbow and increased pitching arm elbow valgus force (rs[31] = –0.52, P = .002), increased pitching arm shoulder anterior force (rs = –0.39, P = .024), and decreased hip velocity (rs[31] = –0.45, P = .009). Additionally, there were significant relationships between greater glove arm horizontal abduction at MER and increased pitching arm humeral velocity (rs[31] = 0.52, P = .002) and increased trunk rotational velocity (rs[31] = 0.40, P = .022) at MER.Conclusion:A more extended glove arm elbow and more horizontally abducted glove arm shoulder at MER could prove to be more advantageous for performance and possibly be a safer motion for the baseball thrower.Clinical Relevance:The orthopaedic community can dictate safer biomechanics when communicating with pitchers, trainers, and pitching coaches.

Knee Angle and Stride Length in Association with Ball Speed in Youth Baseball Pitchers.

The purpose of this study was to determine whether stride length and knee angle of the leading leg at foot contact, at the instant of maximal external rotation of the shoulder, and at ball release are associated with ball speed in elite youth baseball pitchers. In this study, fifty-two elite youth baseball pitchers (mean age 15.2 SD (standard deviation) 1.7 years) pitched ten fastballs. Data were collected with three high-speed video cameras at a frequency of 240 Hz. Stride length and knee angle of the leading leg were calculated at foot contact, maximal external rotation, and ball release. The associations between these kinematic variables and ball speed were separately determined using generalized estimating equations. Stride length as percentage of body height and knee angle at foot contact were not significantly associated with ball speed. However, knee angles at maximal external rotation and ball release were significantly associated with ball speed. Ball speed increased by 0.45 m/s (1 mph) with an increase in knee extension of 18 degrees at maximal external rotation and 19.5 degrees at ball release. In conclusion, more knee extension of the leading leg at maximal external rotation and ball release is associated with higher ball speeds in elite youth baseball pitchers.

3D pore network extraction in granular media by unifying the Delaunay tessellation and maximal ball methods

In this study, a novel method for pore network extraction in the weakly consolidated media is reported, which unifies both the Delaunay tessellation (DT) and maximal ball (MB) methods in a complementary way. This unified method retains the advantages of both methods, and most importantly, eliminates the disadvantages when either the DT or the MB method is used individually. As a result of such a combination, the merging process of the Delaunay tetrahedra can be carried out in an objective way by utilizing the clustering results of maximal balls. Furthermore, the problems generated in using the maximal balls method, e.g., underestimating the throat size and producing tiny and incorrect throats, can be eliminated by incorporating the Delaunay tessellation, which enables precisely partition the pore space and accurately defining the throat size. Examination of this unified method, based on the results of pore network extraction on a sample (with a periodic boundary) before and after the triaxial shearing using DEM simulation, verifies that this method is objective and effective. The associated morphology of the pore space therefore can be accurately described in terms of the pore size, throat size and the associated distributions. This unified method also has the potential to characterize another dimension of fabric in granular media, i.e., the throat-based fabric.

The Effects of Microdimple Texture on the Friction and Thermal Behavior of a Point Contact

This study investigates the effects of the microdimple texture on the friction and surface temperature performances of a ball-on-disk contact, operating under the speed and load ranges that cover typical gearing applications. Circular-shaped microdimple arrays with different dimple center distances and dimple depths are implemented on the ball surface to quantify the impacts of these two parameters on the friction coefficient and the maximum ball surface temperature. In addition, the contacts of three surface texture combinations, namely microdimpled and polished ball surface versus polished disk surface, polished ball surface versus polished disk surface, and ground ball surface versus ground disk surface, are compared to demonstrate any beneficial or detrimental effect of microdimples in heavily loaded high-speed applications. This study adopts a thermal mixed EHL point contact model, whose capability and accuracy have been well demonstrated by comparing to the experimental measurements, to quantify the deterministic tribological behavior within the contact, allowing the exploration of the underlying mechanism that governs the role of microdimples in the elastohydrodynamic lubrication (EHL).

Side-to-side difference in dynamic unilateral balance ability and pitching performance in Japanese collegiate baseball pitchers.

[Purpose] To evaluate the side-to-side difference in dynamic unilateral balance ability and to determine the correlation of the balance ability with pitching performance in collegiate baseball pitchers. [Subjects and Methods] Twenty-five Japanese collegiate baseball pitchers participated in this study. Dynamic balance ability during a unilateral stance was bilaterally evaluated using the star excursion balance test (SEBT). The pitchers threw 20 fastballs at an official pitching distance; the maximal ball velocity and pitching accuracy (the number of strike/20 pitches × 100) were assessed. Side-to-side difference in scores of SEBT was assessed using a paired t-test. Correlations between SEBT scores and pitching performance were evaluated for both legs using a Pearson’s correlation analysis. [Results] The pivot side showed significantly higher score of the SEBT in the anteromedial direction than the stride side. On the other hand, the SEBT scores in the pivot and stride legs did not have significant correlations with maximal ball velocity and pitching accuracy. [Conclusion] These findings suggest that marked side-to-side difference does not exist in the dynamic unilateral balance ability of collegiate baseball pitchers and that the dynamic unilateral balance ability of each leg is not directly related to maximal ball velocity and pitching accuracy.

Kicking ability and kicking deficit in young elite soccer players

Kicking ability in soccer has been evaluated predominantly by the maximum ball velocity. The kicking deficit (KD) may be defined as the percentage of the difference between the maximum ball velocity each player achieved by the non-preferred leg kick in relation to the preferred leg kick. This study aimed to compare: side-to-side kicking velocity, vertical jumps and anthropometrics between the younger (G-14) and older (G+14) than 14 years soccer players. An additional aim was to investigate associations among these variables. Participants were 92 young elite soccer players from the development programme of a top Spanish division club. They were divided into two age groups according to their growth and motor development stages (10.80-13.55 years, n=46; 14.02-16.39 years, n=46). Student’s t-test showed that the maximum kicking velocity with the preferred and non-preferred leg, jumping performance, and all anthropometric measurements were significantly (p&amp;lt;.01) higher in G+14 compared with G-14. In contrast, KD values remained stable (15.31%- 15.83%) without significant differences between the groups. Pearson’s correlation analysis revealed that vertical jump tests and anthropometric measurements correlated with kicking ball velocity produced by the preferred and non-preferred leg. Our results demonstrate that kicking skills are still not consolidated and power factors may be determinant for kicking performance in young soccer players. In addition, the KD may be a constant element for both the under and above 14 years soccer players and could result from an unequal and greater use of the preferred leg in comparison with the non-preferred leg.

Representative elementary volume (REV) of cementitious materials from three-dimensional pore structure analysis

The representative elementary volume (REV) is a fundamental property of a material, but no direct measurements exist for cementitious materials. In this paper, the REV of cement pastes with supplementary cementitious materials (GGBS, PFA, SF) was determined by analysing the three-dimensional pore structure (>0.2μm) using laser scanning confocal microscopy (LSCM). The effect of axial distortion inherent to LSCM on 3D pore structure was also investigated. A range of 3D pore parameters was measured using skeletonisation, maximal ball and random walker algorithms. Results show that axial distortion has insignificant effects on most parameters except Euler connectivity, average pore and throat volumes and directional diffusion tortuosities. Most pore parameters become independent of sampling volume at ≈603μm3 except diffusion tortuosities and formation factor. The REV for porosity calculated based on a statistical approach at eight realisations and 5% relative error was found to be ≈1003μm3.

A study of correlation between permeability and pore space based on dilation operation

CO 2 and fracturing liquid injection into tight and shale gas reservoirs induces reactivity between minerals and injected materials, which results in porosity change and thus permeability change. In this paper, the dilation operation is used to simulate the change of the porosity and the corresponding change of permeability based on Lattice-Boltzmann is studied. Firstly we obtain digital images of a real core from CT experiment. Secondly the pore space of digital cores is expanded by dilation operation which is one of basic mathematical morphologies. Thirdly, the distribution of pore bodies and pore throats is obtained from the pore network modeling extracted by maximal ball method. Finally, the correlation between network modeling parameters and permeabilities is analyzed. The result is that the throat change leads to exponential change of permeability and that the big throats significantly influence permeability. Cited as : Zha, W., Yan, S., Li, D., et al. A study of correlation between permeability and pore space based on dilation operation. Advances in Geo-Energy Research, 2017, 1(2): 93-99, doi: 10.26804/ager.2017.02.04

Reconstruction of porous structure and simulation of non-continuum flow in shale matrix

Distribution and connectivity of pores in shale is difficult to characterise due to their nano-micro multiscale characteristics. Flow in the porous structure is correspondingly controlled by multiple mechanisms and thus it is challenging to estimate the flow properties of shale gas. In view of this, the pore network was employed in this study to represent the porous structure and carry out flow simulation in an organic-rich shale matrix. A self-similarity based stochastic method, which combines the advantages of μ-CT and SEM, was used to characterise the porous structure with a resolution of 10 nm. A pore network of size of 10 × 10 × 10 μm3 was constructed by the maximum ball algorithm and the multi-physics flow (including the wide range non-continuum bulk flow and surface diffusion) was simulated in the reconstructed network. The simulation results show that the apparent gas permeability increases by a factor of 3.16, with 36% contribution arising from surface diffusion when the downstream pressure depletes from 9 MPa to 2 MPa. Sensitivity analyses imply that the apparent gas permeability is dependent on the size and shape of throats, compressibility factor of gas, Langmuir adsorption parameters and reservoir conditions.

UJI PREDIKSI UMUR KEANDALAN OPERASI RADIAL BALL BEARING PADA MOTOR DIESEL SINGLE CYLINDER DENGAN PENDEKATAN AMBANG BATAS KEAUSAN

Factually where the bearingss are not functioning properly makes the performance of the entire system will decrease or can not work properly. In this study, the wear test data that will be used is the data for the operating hours of 100 hours, 200 hours, 300 hours, 400 hours and 500 hours and the first converted into a linear function to obtain a threshold of wear of each specimen. In accordance with the objectives to be achieved in this study was to determine the relationship between the limits hours of operation and wear limit set maximum ball bearings manufacturer. The data used in this study is through the mechanism of experimental tests on Diesel engines Yanmar 15 HP, 1700 RPM using 3 specimens to be validated. Furthermore, these data will be generated from a particular distribution which will provide an overview wear limit as a function of operating hours.