Least Squares Approach to Inverse Problems in Musculoskeletal Biomechanics

Inverse simulations of musculoskeletal models computes the internal forces such as muscle and joint reaction forces, which are hard to measure, using the more easily measured motion and external forces as input data. Because of the difficulties of measuring muscle forces and joint reactions, simulations are hard to validate. One way of reducing errors for the simulations is to ensure that the mathematical problem is well-posed. This paper presents a study of regularity aspects for an inverse simulation method, often called forward dynamics or dynamical optimization, that takes into account both measurement errors and muscle dynamics. The simulation method is explained in detail. Regularity is examined for a test problem around the optimum using the approximated quadratic problem. The results shows improved rank by including a regularization term in the objective that handles the mechanical over-determinancy. Using the 3-element Hill muscle model the chosen regularization term is the norm of the activation. To make the problem full-rank only the excitation bounds should be included in the constraints. However, this results in small negative values of the activation which indicates that muscles are pushing and not pulling. Despite this unrealistic behavior the error maybe small enough to be accepted for specific applications. These results is a starting point start for achieving better results of inverse musculoskeletal simulations from a numerical point of view.

Employer Branding idag : Attraktivitet genom sociala medier

The use of social media has during the last couple of years increased and is now a major part of most of the organizations marketing strategies. But how does this fit with the Employer Branding strategies? And how does this affect the organizational attractiveness as an employer? These were two of the questions we wanted to examine and analyze. In order to answer these questions, we conducted interviews with six different companies divided into 3 subgroups. The intention of this was to get a wider perspective of how the implementation of social media in the Employer Branding could work. And could this change the recruitment process? What we could see afterwards is that more time is spent on taking references online through social media sites. Some say it is more honest than the traditional references that the candidate got to choose. Other conclusions that we could find was that it is important to use social media in todays market but it is crucial to use it in a proper way. Companies must form a strategy based on their Employee Value Proposition in order to reach the wanted receivers using social media. It is also important that the Employee Value Proposition is based on the companies’ corporate values.