Derivation of SPH equations in a moving referential coordinate system

The conventional SPH method uses kernel interpolation to derive the spatial semi-discretisation of the governing equations. These equations, derived using a straight application of the kernel interpolation method, are not used in practice. Instead the equations, commonly used in SPH codes, are heuristically modified to enforce symmetry and local conservation properties. This paper revisits the process of deriving these semi-discrete SPH equations. It is shown that by using the assumption of a moving referential coordinate system and moving control volume, instead of the fixed referential coordinate system and fixed control volume used in the conventional SPH method, a set of new semi- discrete equations can be rigorously derived. The new forms of semi-discrete equations are similar to the SPH equations used in practice. It is shown through numerical examples that the new rigorously derived equations give similar results to those obtained using the conventional SPH equations

Inferring functional extinction based on sighting records

© The Author(s), 2016. This is the author's version of the work and is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Biological Conservation 199 (2016): 84-87, doi:10.1016/j.biocon.2016.04.034.The term functional extinction is used to describe a permanent failure of reproduction or recruitment in a population. Functional extinction results in a truncation of the age distribution, but this can be very difficult to detect in poorly studied populations. Here, we describe a novel statistical method for detecting functional extinction based on a sighting record of individuals of known or estimated ages. The method is based on a simple population dynamics model and simulation results show that it works well even with limited data. The method is illustrated using a sighting record of the ship sturgeon (Acipenser nudiventris) in the Danube River. The results indicate that this population is functionally extinct, most likely by 2002. Management implications of this finding are discussed.The authors also acknowledge the sponsorship provided by the Alexander von Humboldt Foundation and the Federal German Ministry for Education and Research, as well as the support by the Project No. 173045, funded by the Ministry of Education, Science and Technological Development of the Republic of Serbia.2017-05-1

ASSESSMENT OF THIGH MUSCLES MECHANICAL CAPACITIES FOLLOWING ACL RECONSTRUCTION USING THE TWO-VELOCITY METHOD

We evaluated the ability of recently proposed two-velocity method to discriminate between thigh muscle mechanical capacities of the involved and the uninvolved leg following ACL reconstruction (ACLR). 15 athletes were tested 4 and 6 months following ACLR. F-V linear relationship parameters (F intercept - F0, V intercept - V0, slope – a, and Pmax) were obtained from line drawn through 60 and 180 °/s data (the \u27two-velocity method\u27). In quadriceps, all parameters revealed between leg differences 4 and 6 months after ACLR. In addition F0 and V0 of the involved leg were higher at 6 than at 4 months after ACLR. In hamstrings, differences between legs were found only for F0 at 4 months. In conclusion, parameter of the two-velocity method could be sensitive enough to detect between-leg differences in muscle F, V, and P producing capacities following ACLR

FORCE-VELOCITY RELATIONSHIP OF LEG MUSCLES ASSESSED BY MOTORIZED TREADMILL TESTS

We aimed to explore the properties of the F-V relationship of leg muscles exerting the maximum pulling F within a wide range of V set on a standard motorized treadmill. Subjects exerted maximum horizontally pulling F while walking on a treadmill set to 8 different V (1.4 - 3.3 m/s). The obtained F-V relationships proved to be linear and strong (all R \u3e 0.84), while their parameters depicting the leg muscle capacities for producing maximum F, V, and power (i.e., the maximum product of F and V) were highly reliable (0.84 \u3c ICC \u3c 0.97; 6.4 \u3c CV% \u3c 19.3). Moreover, when obtained from only the lowest and highest V the F-V relationships revealed virtually identical outcomes. We conclude that the evaluated procedure could be developed into an ecologically valid and reliable protocol for routine testing of the F, V, and P-producing capacities of leg muscles

DOES SPECIALIZATION IN KARATE AFFECT REACTION TIME IN SPECIFIC KARATE KUMITE SITUATIONS?

The aim of this study was to investigate the effect of karate specialization on the reaction time in specific karate kumite situations. In order to maximize the ecological validity of experimental set-up, we used our recently proposed and evaluated video-based method (Mudric et al., 2015). Within this method, the reaction time is calculated from the kinematic parameters recorded on both offensive action stimuli and defensive action responses. The results obtained from three groups of subjects (i.e., karate kumite, karate kata and beginners) indicate significant differences in reaction time between the beginners and both specialized karate groups. There were also prominent but not significant differences between the karate kumite and karate kata. These findings suggest that particular sport specialization could improve reaction time of an athlete in specific sport situations

A SIMPLE METHOD FOR ASSESSMENT OF MUSCLE MECHANICAL CAPACITIES FROM FUNCTIONAL MOVEMENT TASKS

The aim of the present study was to evaluate the level of agreement between the routinely used multiple-load method and a simple two-load method based on direct assessment of the F-V relationship from only 2 external loads applied. Twelve participants were tested on the maximum performance vertical jumps, cycling, bench press throws, and bench pull performed against a variety of different loads. All four tested tasks revealed both exceptionally strong relationships between the parameters of the 2 methods (median R = 0.98) and a lack of meaningful differences between their magnitudes (fixed bias below 3.4%). Therefore, addition of another load to the standard tests of various functional tasks typically conducted under a single set of mechanical conditions could allow for the assessment of the muscle mechanical properties, such as the muscle F, V, and P producing capacities