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This paper presents new capabilities of the virtual-human Santos™ introduced last year. Santos™ is an avatar that has extensive modeling and simulation features. It is a digital human model with over 100 degrees-of-freedom (DOF), where the hand model has 25 DOF, direct optimization-based method, and real-human like appearance. The newly developed analysis includes (1) a 25-DOF hand model that is the first step to study hand grasping; (2) posture prediction advances such as multiple end-effectors (two arms, two arms + head + legs), real-time inverse kinematics for posture prediction for any points, vision functionality; (3) dynamic motion prediction with external loads; and (4) musculosteletal modeling that includes determining muscle forces, and muscle stress.

Simulating human motion is a complex problem due to redundancy of the human musculoskeletal system. The concept of task-based motion prediction using single- or multi-objective optimization techniques provides a viable approach for predicting intermediate motions of digital humans. It is shown that task-based motion prediction is in fact a numerical optimal control problem. Alternative formulations for simulation of human motion are possible and can be solved by modern nonlinear optimization methods. Three techniques based on state variable elimination, direct collocation and differential inclusion are presented and compared. The basic idea of the formulations is to treat different combinations of the state variables, such as the joint profiles and torques or their parametric representations as independent variables in the optimization process.

A new engine piston incorporating heat pipe cooling technology is under development for improved thermal-tribological. performance. Due to the particular structure of the engine piston, curved heat pipes should be employed. The objective of this paper is to study fluid impingement inside curved pipes for curved heat pipe design. Experimental studies of fluid impingement using different curved transparent pipes are performed on an engine-heat pipe apparatus to determine the correlation between the heat pipe design parameters and minimum cranking frequency, or critical impingement frequency. Experimental results show that pipe curvature has little influence on the critical impingement frequency if the non-dimensional offset value of curved pipes is less than 0.3. The critical impingement frequency is higher for the pipe with a longer length and smaller diameter.