In contrast to previous studies on firm survival which tend to focus on features related to the structure of the firms and their area of activity, our aim here is to widen the perspective usually adopted in the field, taking into account a larger and more qualitative set of variables. Among these variables, features related to the individual characteristics of the entrepreneur, to the context of entrepreneurship and to the insertion in entrepreneurial networks are significant to explain the life span of new firms. The empirical material is drawn from two surveys, which provide detailed data about a group of new firms created in France in 1994 and closed down before 1997 or still running in 1997. Our empirical approach on qualitative data is based on data analysis methods (linear discriminant analysis, barycentric discriminant analysis, analysis of variance). According to the characteristics of the entrepreneur, the main explanatory factors for the survival of new firms are the fact that they are entrepreneurs who have taken over firms, that they have acquired during their previous occupational activity an experience in the same branch of activity and that they experience a successful integration into the entrepreneurial networks. These three factors show that the survival of young firms is indirectly conditioned by the existence of an initial custom, by the mastery of a job and by the know-how in the entrepreneurial function.
Although surface electromyography (sEMG) has a high correlation to muscle force, an accurate model that can estimate joint torque from sEMG is still elusive. Artificial neural networks (NN), renowned as universal approximators, have been employed to capture this complex nonlinear relation. This work focuses on investigating possible improvements to the NN methodology and algorithm that would consistently produce reliable sEMG-to-knee-joint torque mapping for any individual. This includes improvements in number of inputs, data normalization techniques, NN architecture and training algorithms. Data (sEMG) from five knee extensor and flexor muscle from one subject were recorded on 10 random days over a period of 3 weeks whilst subject performed both isometric and isokinetic movements. The results indicate that incorporating more muscles into the NN and normalizing the data at each isometric angle prior to NN training improves torque estimation. The mean lowest estimation error achieved for isometric motion was 10.461% (1.792), whereas the lowest estimation errors for isokinetic motion were larger than 20%.
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