Lambda Calculus for Engineers

In pure functional programming it is awkward to use a stateful sub-computation in a predominantly stateless computation. The problem is that the state of the subcomputation has to be passed around using ugly plumbing. Classical examples of the plumbing problem are: providing a supply of fresh names, and providing a supply of random numbers. We propose to use (deterministic) inductive definitions rather than recursion equations as a basic paradigm and show how this makes it easier to add the plumbing

Dynamics and diffusive-conformational coupling in polymer bulk samples and surfaces: A molecular dynamics study

The impact of free surfaces on the mobility and conformational fluctuations of model polymer chains is investigated with the help of classical molecular dynamics simulations over a broad temperature range. Below a critical temperature, T *, similar to the critical temperature of the mode coupling theory, the center-of-mass displacements and temporal fluctuations of the radius of gyration of individual chains-as a fingerprint of structural reconfigurations-reveal a strong enhancement close to surfaces, while this effect diminishes with increasing temperature and observation time. Interpreting conformational fluctuations as a random walk in conformational space, identical activation enthalpies for structural reconfigurations and diffusion are obtained within the error bars in the bulk and at the surfaces, thus indicating a coupling of diffusive and conformational dynamics. © IOP Publishing Ltd. and Deutsche Physikalische Gesellschaft

Studies supporting an upper-atmosphere chemical release program. Part I - Experimental studies on chemiluminescence. Part II - A model of releases leading to upper-atmospheric chemi-ion formation Final report, May 1965 - May 1966

Chemiluminescence of chemical compounds released in upper atmosphere and model of releases leading to upper atmospheric chemi-ionizatio

Reduction of mesh sensitivity in continuum damage mechanics

Continuum damage theories can be applied to simulate the failure behaviour of engineering constructions. In the constitutive equations of the material a damage parameter is incorporated. A damage criterion and a damage evolution law are postulated and quantified based on experimental data. The elaboration of the mathematical formulation is performed by common finite element techniques. Without special precautions the numerical results appear to be unacceptably dependent on the measure of the spatial discretization. It is shown that a simple but effective procedure leads to the conservation of objectivity

Deep Reinforcement Learning for Physics-Based Musculoskeletal Simulations of Healthy Subjects and Transfemoral Prostheses’ Users During Normal Walking

This paper proposes to use deep reinforcement learning for the simulation of physics-based musculoskeletal models of both healthy subjects and transfemoral prostheses’ users during normal level-ground walking. The deep reinforcement learning algorithm is based on the proximal policy optimization approach in combination with imitation learning to guarantee a natural walking gait while reducing the computational time of the training. Firstly, the optimization algorithm is implemented for the OpenSim model of a healthy subject and validated with experimental data from a public data-set. Afterwards, the optimization algorithm is implemented for the OpenSim model of a generic transfemoral prosthesis’ user, which has been obtained by reducing the number of muscles around the knee and ankle joints and, specifically, by keeping only the uniarticular ones. The model of the transfemoral prosthesis’ user shows a stable gait, with a forward dynamic comparable to the healthy subject’s, yet using higher muscles’ forces. Even though the computed muscles’ forces could not be directly used as control inputs for muscle-like linear actuators due to their pattern, this study paves the way for using deep reinforcement learning for the design of the control architecture of transfemoral prostheses