scholarly journals Research on the specific movement of the head in tennis strokes

2020 ◽  
Vol 28 (80) ◽  
pp. 16-19
Author(s):  
Manuel Fernández López
Keyword(s):  
Tennis Player ◽  
Effective Technique ◽  
The Gaze ◽  
Impact Phase ◽  
Player Performance ◽  
The Impact

Technique is one of the aspects that has the most relevant influence on tennis player performance. Searching for more efficient and effective technique, by means of the application of biomechanical laws, is a constant among coaches and researchers. This article deals with a very concrete subject in tennis technique: the position of the head during the impact phase of tennis strokes. Biomechanical aspects of the strokes will also be considered, as well as other relevant aspects such as fixing the gaze during the stroke and the stretching-shortening cycle.

scholarly journals The Effects of Repetitive Drop Jumps on Impact Phase Joint Kinematics and Kinetics

2011 ◽  
Vol 27 (2) ◽  
pp. 108-115 ◽  
Author(s):  
Joshua T. Weinhandl ◽  
Jeremy D. Smith ◽  
Eric L. Dugan
Keyword(s):  
Energy Absorption ◽  
Plantar Flexion ◽  
Knee Extension ◽  
Joint Kinematics ◽  
Knee Extensors ◽  
Initial Contact ◽  
Drop Jumps ◽  
Impact Phase ◽  
The Impact ◽  
Kinematics And Kinetics

The purpose of the study was to investigate the effects of fatigue on lower extremity joint kinematics, and kinetics during repetitive drop jumps. Twelve recreationally active males (n= 6) and females (n= 6) (nine used for analysis) performed repetitive drop jumps until they could no longer reach 80% of their initial drop jump height. Kinematic and kinetic variables were assessed during the impact phase (100 ms) of all jumps. Fatigued landings were performed with increased knee extension, and ankle plantar flexion at initial contact, as well as increased ankle range of motion during the impact phase. Fatigue also resulted in increased peak ankle power absorption and increased energy absorption at the ankle. This was accompanied by an approximately equal reduction in energy absorption at the knee. While the knee extensors were the muscle group primarily responsible for absorbing the impact, individuals compensated for increased knee extension when fatigued by an increased use of the ankle plantar flexors to help absorb the forces during impact. Thus, as fatigue set in and individuals landed with more extended lower extremities, they adopted a landing strategy that shifted a greater burden to the ankle for absorbing the kinetic energy of the impact.

scholarly journals Violence and Surveillance: Some Unintended Consequences of CCTV Monitoring within Mental Health Hospital Wards

2010 ◽  
Vol 8 (1) ◽  
pp. 84-92 ◽  
Author(s):  
Suki Desai
Keyword(s):  
Mental Health ◽  
Vulnerable Populations ◽  
Unintended Consequences ◽  
England And Wales ◽  
The Gaze ◽  
Hospital Wards ◽  
The Impact ◽  
Mental Health Hospital ◽  
Health Hospital

Since 2005, CCTV cameras have featured as a tool for managing safety within mental health hospital wards in England and Wales. However this piece argues that the efficacy of cameras to control and manage violence within psychiatric wards remains inconclusive due to a lack of research, and there has been very little discussion of the impact that they might have on the vulnerable populations under the gaze of the camera.

A passive dynamic walking model with Coulomb friction at the hip joint

Robotica ◽  
2013 ◽  
Vol 31 (8) ◽  
pp. 1221-1227 ◽  
Author(s):  
Wenhao Guo ◽  
Tianshu Wang ◽  
Qi Wang
Keyword(s):  
Hip Joint ◽  
Coulomb Friction ◽  
Basins Of Attraction ◽  
Swing Phase ◽  
Dynamic Equations ◽  
Two Dimensional ◽  
Dynamic Walking ◽  
Passive Dynamic Walking ◽  
Impact Phase ◽  
The Impact

SUMMARYThis paper presents a modified passive dynamic walking model with hip friction. We add Coulomb friction to the hip joint of a two-dimensional straight-legged passive dynamic walker. The walking map is divided into two parts – the swing phase and the impact phase. Coulomb friction and impact make the model's dynamic equations nonlinear and non-smooth, and a numerical algorithm is given to deal with this model. We study the effects of hip friction on gait and obtain basins of attraction of different coefficients of friction.

The Impact of Natural Disasters: A Brief Analysis of Characteristics and Trends

1986 ◽  
Vol 2 (1-4) ◽  
pp. 221-223 ◽  
Author(s):  
Debarati Guha-Sapir ◽  
Michel F. Lechat
Keyword(s):  
Natural Disasters ◽  
Structural Damage ◽  
Mortality And Morbidity ◽  
Tectonic Force ◽  
Rescue Treatment ◽  
Essential Services ◽  
Global Statistics ◽  
Impact Phase ◽  
The Impact ◽  
Snow Storms

Most natural disasters that occur frequently may be classified into four main categories: floods, earthquakes, cyclones and famine. Other catastrophic events, such as land slides, avalanches, snow storms, fires occur at rarer occasions and threaten smaller proportions of the populated world. The destructive agents in the above categories are wind, water (a lack or excess thereof) and tectonic force. While all of these cause structural damage, their mortality and morbidity effects are varied both between them and over time. The disaster cycle can be differentiated into five main phases, extending from one disaster to the next. The phases are: the warning phase indicating the possible occurrence of a catastrophe and the threat period during which the disaster is pending; the impact phase when the disaster strikes; the emergency phase when rescue, treatment and salvage activities commence; the rehabilitation phase when essential services are provided on a temporary basis; the reconstruction phase when a permanent return to normality is achieved. The disaster-induced mortality and morbidity differ between these phases and are also a function of the prevailing health and socioeconomic conditions of the affected community. As a result of this, global statistics on disasters seem to indicate a significantly higher frequency of natural disasters in the developing countries than in the industrialized world.

High-speed non-invasive measurement of tibial rotation during the impact phase of running

Ergonomics ◽  
2005 ◽  
Vol 48 (11-14) ◽  
pp. 1623-1637 ◽  
Author(s):  
C. J. Digby ◽  
M. J. Lake ◽  
A. Lees
Keyword(s):  
High Speed ◽  
Tibial Rotation ◽  
Non Invasive ◽  
Impact Phase ◽  
The Impact ◽  
Invasive Measurement

Inductive Sensor with Sintered Magnetic Core to Evaluate the Performances of the Table Tennis Players

2011 ◽  
Vol 672 ◽  
pp. 105-108 ◽  
Author(s):  
Gabriel Ioan Mangra ◽  
Sorin Vasile Savu ◽  
Danut Savu
Keyword(s):  
Performance Evaluation ◽  
Magnetic Core ◽  
Experimental Results ◽  
Tennis Player ◽  
Table Tennis ◽  
Tennis Players ◽  
The Impact ◽  
Contact Sensors ◽  
Reaction Speed

The reaction speed of the tennis player and the speed of the ball after the impact to the tennis blade, they both are important elements of the performance evaluation of a tennis player. The determination of those parameters is possible by using specialized contact sensors. Permanent ceramic magnets can be used to process such sensors and the paper presents the experimental results concerning the processing of such magnets of barium hexaferritte powders

ICP Etching of 4H-SiC Substrates

2013 ◽  
Vol 740-742 ◽  
pp. 825-828 ◽  
Author(s):  
Jerome Biscarrat ◽  
Jean François Michaud ◽  
Emmanuel Collard ◽  
Daniel Alquier
Keyword(s):  
Process Parameters ◽  
Plasma Etching ◽  
Inductively Coupled Plasma ◽  
Etch Rate ◽  
Effective Technique ◽  
Working Pressure ◽  
Inductively Coupled ◽  
Icp Etching ◽  
High Etch Rate ◽  
The Impact

Due to its inert chemical nature, plasma etching is the most effective technique to pattern SiC. In this paper, dry etching of 4H-SiC substrate in Inductively Coupled Plasma (ICP) has been studied in order to evaluate the impact of process parameters on the characteristics of etching such as etch rate and trenching effect. Key process parameters such as platen power and ICP coil power prove to be essential to control the SiC etch rate. On the other hand, the ICP coil power and the working pressure mainly master the trenching effect. Our results enlighten that high etch rate with minimal trenching effect can be obtained using high ICP coil power and low working pressure.

Overtrawlability and Mechanical Damage of Pipe-in-Pipe

2013 ◽  
Vol 81 (3) ◽  
Author(s):  
Zheng Jiexin ◽  
Andrew Palmer ◽  
Paul Brunning
Keyword(s):  
Finite Element ◽  
Static Analysis ◽  
Standard Method ◽  
Mechanical Damage ◽  
Static Indentation ◽  
Indentation Tests ◽  
Offshore Industry ◽  
Impact Phase ◽  
High Level ◽  
The Impact

A pipeline on the seabed may be struck by moving trawl gear, and that may damage the pipeline. Trenching can be a useful but expensive way to protect the pipeline. Pipe-in-pipe and bundled pipeline systems are widely used in the offshore industry recently because of their high level of thermal insulation and because they lend themselves to rapid and economical installation. However, there is no clearly specified standard method to analyze the overtrawlability of pipe-in-pipe systems. If we apply the same method as for the single wall pipe, it is likely to result in a conservative design for the pipe-in-pipe. The objective of this paper is to investigate the overtrawlability of pipe-in-pipe, especially in the impact phase, and to fill this gap. In this study, the authors demonstrate that a quasi-static analysis can replace a dynamic analysis to some extent because the overall response does not show a big difference. The demonstration is based on both quasi-static indentation tests and impact tests for single wall pipe and pipe-in-pipe, as well as the corresponding finite element (FE) models. The FE models not only help to compare the responses but also offer a way to analyze the overtrawlability of the pipe-in-pipe. The quasi-static FE models are used for a further comparison between a pipe-in-pipe and a 406.4 mm (16 in.) single wall pipe to illustrate the overtrawlability of the pipe-in-pipe.

Impact of Opponents’ Clothing and Body Language on Impression Formation and Outcome Expectations

2005 ◽  
Vol 27 (1) ◽  
pp. 39-52 ◽  
Author(s):  
Iain Greenlees ◽  
Richard Buscombe ◽  
Richard Thelwell ◽  
Tim Holder ◽  
Matthew Rimmer
Keyword(s):  
Nonverbal Communication ◽  
Impression Formation ◽  
Interactive Effect ◽  
Outcome Expectations ◽  
Body Language ◽  
Tennis Player ◽  
Tennis Players ◽  
The Impact ◽  
Tennis Match

The aim of this study was to examine the impact of a tennis player’s body language and clothing (general vs. sport-specific) on the impressions observers form of them. Forty male tennis players viewed videos of a target tennis player warming up. Each participant viewed the target player displaying one of four combinations of body language and clothing (positive body language/tennis-specific clothing; positive body language/general sportswear; negative body language/tennis-specific clothing; negative body language/general sportswear). After viewing the target player, participants rated their impressions of the model’s episodic states and dispositions and gave their perceptions of the likely outcome of a tennis match with the target player. Analyses of variance revealed that positive body language led to favorable episodic impressions and low outcome expectations. Analysis also indicated that clothing and body language had an interactive effect on dispositional judgments. The study supports the contention that nonverbal communication can influence sporting interactions.

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