The Effect of Wood Type on the Reflection of a Table Tennis Ball

The table tennis game table can be made of any material with certain bounce height requirements according to ITTF regulations. Wood as the main material for the table is found in Indonesia. Various types of wood have the potential to be a dining table material. This study was conducted to determine the effect of the type of wood on the bounce of a table tennis ball. Experiments were carried out on 9 types of wood, namely hardwoods (teak, sono, coconut), medium hardwoods (meranti, plywood and jackfruit) and soft woods (waru, randu and sengon). The height of the falling ball is determined to be 30 cm for the ball's bounce recorded by the camera. The ball used is a ball with a weight of 24 grams and 30 grams. Camera recording data is processed with Kinovea 08.15 to get the reflection height. The bounce height is used as a reference for ITTF standard compliance. The initial height and reflection height were then used to calculate the coefficient of restitution (COR). Data collection was carried out 5 times and the average value was calculated. The level of wood hardness is influenced by its specific gravity. Hard wood has a relatively high specific gravity. Teak wood which is relatively hard has a specific gravity value of 0.59 – 0.82 gr/cm3

A Bayesian computational model to investigate expert anticipation of a seemingly unpredictable ball bounce

During dynamic and time-constrained sporting tasks performers rely on both online perceptual information and prior contextual knowledge to make effective anticipatory judgments. It has been suggested that performers may integrate these sources of information in an approximately Bayesian fashion, by weighting available information sources according to their expected precision. In the present work, we extended Bayesian brain approaches to anticipation by using formal computational models to estimate how performers weighted different information sources when anticipating the bounce direction of a rugby ball. Both recreational (novice) and professional (expert) rugby players (n = 58) were asked to predict the bounce height of an oncoming rugby ball in a temporal occlusion paradigm. A Bayesian computational model, based on a partially observable Markov decision process, was fitted to observed responses to estimate participants’ weighting of online sensory cues and prior beliefs about ball bounce height. The results showed that experts were more sensitive to online sensory information, but that neither experts nor novices relied heavily on contextual priors in this task. Experts, but not novices, were observed to down-weight contextual priors in their anticipatory decisions as later and more precise visual cues emerged, as predicted by Bayesian and active inference accounts of perception.

Dynamics Test Research of Bounce of Carrier-Based Aircraft Arresting Hook

The test of arresting hook bounce is one of the most essential technologies in the design and research of arresting hook. In order to research the dynamic performance of the hook after touchdown and impacting with the deck when the aircraft is arrested, an approach for a certain type of aircraft arresting hook bounce test is proposed in this paper. Solutions to critical technique issues arising in the test process such as aircraft sinking velocity control, aircraft horizontal velocity simulation, and simulation of the performance of the damper are derived and verified by the bounce test of the arresting hook. The bounce height, bounce distance, stroke length of the arresting hook damper after the hook is impacted are measured by the test. The test method proposed can be used for researching the bounce of arresting hook and providing reliable test data for the design of carrier-based aircraft and arresting hook.

Fabrication of Bionic Linear Actuator and Application Study Based on 3D Printing

In this manuscript, a bionic linear actuator was developed base on the ionic actuator: ionicpolymer metal composites, and the mainly fabrication method was presented in the currentinvestigation. Subsequently, a bionic robot was developed using 3D printing technique to fabricatethe skeleton structure and the presented Bi-IPMC(assembled by two segmented IPMC strip) linearactuator as the driving power. After a mathematical model of bionic robot, a experimented bionicrobot was manufactured to investigate. The results founded that our bionic robot behaved a maximumbounce height arrived at 22mm under applied 5V direct current, and the bounce height can keep onthe values of 18mm over the applied voltage of 4V.

Bouncing Vibration and Complete Tracking Conditions of a Contact Recording Slider Model on a Harmonic Wavy Disk Surface

An extended study of the general characteristics of the bouncing vibrations of a contact recording head slider was done for a single-degree-of-freedom slider model bouncing on a harmonic wavy disk surface with linear contact stiffness and damping. The relationship between bounce height and waviness frequency and the role of a top contact point necessary for stable bouncing vibrations are discussed. Since the dynamic contact force increases to ten times the static slider load even when the bounce height is only one nanometer, the importance of complete tracking without separation is discussed. Then the complete tracking conditions of disk surface waviness under disturbances of ten nanometer bounce height are calculated for various design parameter values, including the waviness phase. It is also shown that a collision model can predict almost the same complete tracking zones as an elastic contact model.