Stefan Mohr

Stefan Mohr
Independent Researcher · RnD Racquetsport

Dipl.-Ing. Dr.

About

15
Publications
6,305
Reads
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370
Citations
Introduction
Academic Background: Technical Physics with Diploma in Supersymmetric Quantum Field Theory / Special interests in Numerical Simulation and Modelling / PhD in simulation of surface processes in an electrochemical cell / Finite Element Analysis (Thermal and Mechanical Simulations)
Additional affiliations
Position
  • Lecturer of Physics and Technical Mechanics Applied University Dornbirn
Position
  • Sound Engineering of Tennis Rackets
Education
January 1996 - September 1999
University of Innsbruck
Field of study
  • Physics
September 1990 - September 1995
TU Wien
Field of study
  • Technical Physics

Publications

Publications (15)
Article
Full-text available
The ‘feel’ of tennis rackets is of increasing importance to manufacturers seeking product differentiation in a context where further performance enhancements are prevented by a combination of mechanical limits and regulations imposed to protect the integrity of the sport. Vibrations excited during a shot contribute greatly to the perception of ‘fee...
Article
A ball game racket according to the present invention comprises a racket head and a racket shaft, wherein the racket head comprises a stringing having transverse strings and longitudinal strings each having a vibration length. The racket head comprises a means which reduces the vibration length of a plurality of strings on both sides of the stringi...
Article
Full-text available
A finite element (FE) model of a tennis racket was created to aid in the design and development of new rackets by allowing engineers to analyse the mechanical properties of the frames without making physical prototypes. This approach saves both time and money but only if the model is an accurate representation of the manufactured racket. The FE mod...
Article
During an impact between a tennis racket and a tennis ball, mechanical oscillations are excited in the frame and stringbed. These vibrations continue after the ball has left the stringbed and have been shown to contribute greatly to the 'feel' of the racket. During this research, lightweight accelerometers were used to measure frame vibrations exci...
Chapter
Full-text available
An analysis of the vibration characteristics of a tennis racket system; frame, string-bed plus damper has been conducted. The influence of how the frequency spectrum is altered by the application of string dampers was investigated. Several experimental setups were used to determine how the vibration profile changed by varying the positioning and we...
Article
Full-text available
Femtosecond modelocked lasers using new ytterbium-doped borate crystals (Yb:Sr$_3$Y(BO$_3$)$_3$, Yb:Ca$_4$GdO(BO$_3$)$_3$ and Yb:Ca$_4$YO(BO$_3$)$_3$) are demonstrated. Pulse duration as short as 69 fs has been obtained. To modelock such lasers, fast saturable absorbers need to be used. Two different types of fast saturable absorbers have been stud...
Article
We have developed a diode-pumped Yb(3+)Sr(3)Y(BO(3))(3) (Yb:BOYS) laser generating 69-fs pulses, at a central wavelength of 1062 nm. This laser is mode locked by use of a semiconductor saturable-absorber mirror and emits 80 mW of average power at 113 MHz. This is, to our knowledge, the first mode-locked Yb:BOYS laser and the shortest duration obtai...
Article
Full-text available
We have developed a diode-pumped Yb 3 + : Sr 3 Y BO 3 3 (Yb:BOYS) laser generating 69-fs pulses, at a central wavelength of 1062 nm. This laser is mode locked by use of a semiconductor saturable-absorber mirror and emits 80 mW of average power at 113 MHz. This is, to our knowledge, the first mode-locked Yb:BOYS laser and the shortest duration obtai...
Conference Paper
We present the first diode pumped femtosecond Yb:Sr<sub>3</sub>Y(BO<sub>3</sub>)<sub>3</sub> (also called Yb:BOYS) laser. Laser materials suitable for efficient, simple and compact ultrafast laser sources should provide a broad emission bandwidth, should exhibit favorable thermal properties, and should offer the possibility to be directly diode-pum...
Article
Full-text available
We demonstrate for the first time the use of a new crystal, Yb:BOYS, in a femtosecond oscillator. Pulses as short as 69fs have been obtained at 1062nm with an average power of 80mW and with a tunability of 25nm. Higher average power Yb:BOYS mode-locked oscillators have also been studied. Pulses of 86fs with an average power of 300mW have been produ...
Article
Triethanolamine and D-gluconate both form alkali stable complexes with iron(III)- and iron(II)-ions. The redox behaviour of solutions containing one type of ligand is compared with solutions containing both ligands in excess compared with the iron(III)-concentration. Spectrophotometric investigations and experiments with cyclic voltammetry yield in...

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