Combinação de força

Tipos

Biomechanical force matching –A subject’s maximum voluntary contraction (MVC) is recorded and used to normalize both reference forces and results between subjects. During the test subjects are assisted in producing a reference force using various types of feedback (static weight or visual display of force generated). This is followed by an attempt of the subject to generate the reference force without assistance. The duration for both reference and matching tasks is usually four seconds. Results are taken as a mean value of force generated over a time interval set by the researcher. Time intervals are generally one second long and near the end of the attempt. Reference forces are typically set as a percentage of a subject’s MVC while error is typically reported as a percentage of a subject’s MVC.Atomic force matching – It is one of the effective research method to obtain realistic classical interatomic potential or force field for molecular dynamics simulation with high degree of transferability for systems which the first principles or ab initio method is capable of treating. This method is based on fitting the forces on individual atoms in a number of reference structures, cohesive energies and stresses on unit cell obtained from first principles calculation with those obtained from classical interatomic potential. The target of the computational fitting is to determine unknown coefficients in classical interatomic potential function. This method is developed by F. Ercolessi, and J. B. Adams during 1992 and 1993 at Department of Material Science and Engineering at the University of Urbana-Campaign. The enormous number of reference structures, which can reach several thousand values, makes it possible to fit large number of parameters needed for potential in binary and ternary systems.

Para o potencial de Lennard-Jones:

V LJ = 4 ε [ ( σ r ) 12 − ( σ r ) 6 ] , {\displaystyle V_{\text{LJ}}=4\varepsilon \left[\left({\frac {\sigma }{r}}\right)^{12}-\left({\frac {\sigma }{r}}\right)^{6}\right],}

Onde ε é a profundidade do poço potencial, σ é a distância finita na qual o potencial entre partículas é zero, r é a distância entre as partículas. Esses dois parâmetros desconhecidos podem ser ajustados para reproduzir dados experimentais ou dados precisos obtidos dos primeiros cálculos de princípio. A diferenciação do potencial de L-J em relação a r fornece uma expressão para a força inter-molecular líquida entre 2 moléculas. Essa força inter-molecular pode ser atraente ou repulsiva, dependendo do valor de r. Quando R é muito pequeno, as moléculas se repelem. No método de correspondência de força, as forças do potencial clássico

F LJ = − d V LJ d r = 4 ε [ ( 12 r ) ( σ r ) 12 − ( 6 r ) ( σ r ) 6 ] {\displaystyle F_{\text{LJ}}=-{\frac {dV_{\text{LJ}}}{dr}}=4\varepsilon \left[\left({\frac {12}{r}}\right)\left({\frac {\sigma }{r}}\right)^{12}-\left({\frac {6}{r}}\right)\left({\frac {\sigma }{r}}\right)^{6}\right]} are compared with reference force F 0 {\displaystyle F^{0}} calculated from ab initio method to determine σ {\displaystyle {\sigma }} and ε {\displaystyle {\varepsilon }} .

Formulários

A correspondência da força biomecânica tem sido usada pelos pesquisadores para descrever a precisão das contrações musculares sob várias condições. Observou -se que o polegar é mais preciso na correspondência de força do que os dedos. O comprometimento do extensor Pollicis longus não produziu uma diminuição na precisão da correspondência de força do flexor Pollicis longus.