Current methods of the conversion between a rotation quaternion and Euler angles are either a complicated set of multiple sequence-specific implementations, or a complicated method relying on multiple matrix multiplications. In this paper a general formula is presented for extracting the Euler angles in any desired sequence from a unit quaternion. This is a direct method, in that no intermediate conversion step is required (no quaternion-to-rotation matrix conversion, for example) and it is general because it works with all 12 possible sequences of rotations. A closed formula was first developed for extracting angles in any of the 12 possible sequences, both "Proper Euler angles" and "Tait-Bryan angles". The resulting algorithm was compared with a popular implementation of the matrix-to-Euler angle algorithm, which involves a quaternion-to-matrix conversion in the first computational step. Lastly, a single-page pseudo-code implementation of this algorithm is presented, illustrating its conciseness and straightforward implementation. With an execution speed 30 times faster than the classical method, our algorithm can be of great interest in every aspect.
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Int J Numer Method Biomed Eng
January 2025
The Ferrara Center for Patient Safety and Clinical Simulation, New York Institute of Technology, College of Osteopathic Medicine, New York City, New York, USA.
The study findings demonstrate that the amniotic fluid plays an important role in protecting the fetus during convulsive maternal seizures. The amniotic fluid was found to be an effective buffer, significantly reducing the transfer of kinetic energy to the fetus during these events. This highlights the sufficient protection provided by the amniotic fluid in such circumstances.
View Article and Find Full Text PDFJ Chem Phys
December 2024
Department of Chemistry, Ohio State University, 100 West 18th Avenue, Columbus, Ohio 43210, USA.
A simplified theoretical description of multiple-quantum excitation and mixing for nuclear magnetic resonance of half-integer quadrupolar nuclei is presented. The approach recasts the multiple-quantum nutation behavior in terms of reduced excitation and mixing curves through a scaling of the first-order offset frequency by the quadrupolar coupling constant. The two-dimensional correlation of the static first-order anisotropic line shape to the second-order anisotropic magic-angle-spinning (MAS) line shape is utilized to transform the three-dimensional integral over the three Euler angles into a single integral over the dimensionless first-order offset parameter.
View Article and Find Full Text PDFClin Biomech (Bristol)
December 2024
Dept. of Human Movement Science, Vrije Universiteit Amsterdam, Amsterdam Movement Sciences, Amsterdam, the Netherlands.
Background: There is inconsistent evidence suggesting that people with chronic low back pain may differ in variability of repeated trunk movements compared to people without chronic low back pain. These inconsistencies may be due to low reliability and task dependence of movement variability measures, which can be addressed using multiple movement tasks and summary measures.
Methods: Participants with and without chronic low back pain were recruited.
Rev Sci Instrum
December 2024
School of Mechanical Engineering, Northeast Electric Power University, Jilin 132012, China.
This work proposes a new rotary piezoelectric energy harvester using magnetic excitation inspired by the fan blade. The configuration and operating principle of the harvester are introduced. Then, the equivalent nonlinear model of the piezoelectric beam is established based on the Euler-Bernoulli theory and the Rayleigh-Ritz method.
View Article and Find Full Text PDFNanomaterials (Basel)
November 2024
School of Materials Science and Engineering, Northeastern University, Shenyang 110819, China.
Bimodal grain structure (BGS) Mg alloys containing a high fraction of fine grains (FGs) and a low fraction of coarse grains (CGs) show a good combination of strength and plasticity. Here, taking the ZK60 alloy as an example, the influences of CG size, volume fraction, and texture intensity on mechanical properties and the hetero-deformation-induced (HDI) effect were examined using the Mori-Tanaka mean-field method combined with strain gradient theory of plasticity. The results indicate that the overall mechanical properties decrease with an increase in CG size because the limited HDI effect cannot compensate for the strength and plasticity decrease derived from larger CGs.
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