Body-segmental dynamics

Human limbs are modeled as chains of rigid body segments their movements relative to each other are defined by actuator states [27-40]. The complexity of a body-segment dynamic model depends on the number and types of body segments assumed (Figure 24.14). 

In this section we delve further into the molecular dynamics of the amorphous phase. For a different case study than PLLA, we focus on PDS in this section. Since PDS has a Tg below body temperature, segmental dynamics will surely play a role in diffusion of biologically active compounds from the implanted polymer. In order to observe whether crystallization influences the segmental dynamics in PDS, as was found for PLLA in the previous section, a series of investigations were conducted. Informative aspects of those studies are summarized and highlighted in the section that follows. 

Anthropometry can be divided into two types physical anthropometry, which deals with basic dimensions of the human body in standing and sitting positions (see, e.g.. Tables 1 and 2), and functional anthropometry, which is task oriented. Both physical and functional anthropometry can be considered in either a static or dynamic sense. Static analysis implies that only the body segment lengths in fixed position wiU be considered in workplace design. Dynamic analysis requires that acceptability of design be evaluated with respect to the need to move the body from one position to another, as well as the reach and clearance considerations. 

The body will be in a static equilibrium state when at rest or dynamic equilibrium when in motion with constant velocity. The translational equilibrium (first condition) of the body (segment) is present when the vector sum of all the forces acting on a body simultaneously is zero ( F = 0). The rotational equilibrium (second condition) of the body is present when the sum of moments about joint is zero ( M = 0). In other words, for the body to be at rest (zero velocity), the sum of all clockwise moments must be equal to the sum of all counterclockwise moments. 

Dynamic contraction — the output of muscles moving body segments [Kroemer, 1991]. 

Permits dynamic testing of most major body segments especially useful for stronger movements most devices provide good stabilization measures reciprocal muscle contractions widespread clinical acceptance also records angular data, work, power, and endurance-related measures provides a number of different reporting options also used as exercises devices... 

Different methods are available to derive the dynamical equations of motion for a motor task. In the Newton-Euler method (Pandy and Berme, 1988), free-body diagrams are eonstructed to show the external forces and torques acting on each body segment. The relationships between forces and... 

Twenty anthropometric parameters were taken for each of the subjects in order to calculate the body segment parameters will be finally be used in the inverse dynamics analysis [19][20]. Sixteen passive reflective markers were... 

The ATB model is based on the rigid body dynamics which uses Euler s equations of motion with constraint relations of the type employed in the Lagrange method. The model has been successfully used to study the articulated human body motion under various types of body segment and joint loads. The technology of robotic telepresence will provide remote, closed-loop, human control of mobile robots. 

The dynamic behavior of the ATB model is determined by classical methods of analysis. (See Fleck and Butler [8].) The body segments are coupled to form an open chain of interconnected rigid bodies. For an arbitrary segment n, the translational dynamic equation is... 

Figure 3 Calculated X-ray diffuse scattering patterns from (a) a full molecular dynamics trajectory of orthorhombic hen egg white lysozyme and (b) a trajectory obtained by fitting to the full trajectory rigid-body side chains and segments of the backbone. A full description is given in Ref. 13.

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