Evolution of central pattern generators for the control of a five-link bipedal walking mechanism

Central pattern generators (CPGs), with a basis is neurophysiological studies, are a type of neural network for the generation of rhythmic motion. While CPGs are being increasingly used in robot control, most applications are hand-tuned for a specific task and it is acknowledged in the field that generic methods and design principles for creating individual networks for a given task are lacking. This study presents an approach where the connectivity and oscillatory parameters of a CPG network are determined by an evolutionary algorithm with fitness evaluations in a realistic simulation with accurate physics. We apply this technique to a five-link planar walking mechanism to demonstrate its feasibility and performance. In addition, to see whether results from simulation can be acceptably transferred to real robot hardware, the best evolved CPG network is also tested on a real mechanism. Our results also confirm that the biologically inspired CPG model is well suited for legged locomotion, since a diverse manifestation of networks have been observed to succeed in fitness simulations during evolution.Comment: 11 pages, 9 figures; substantial revision of content, organization, and quantitative result

Simple scoring system to predict in-hospital mortality after surgery for infective endocarditis

BACKGROUND: Aspecific scoring systems are used to predict the risk of death postsurgery in patients with infective endocarditis (IE). The purpose of the present study was both to analyze the risk factors for in-hospital death, which complicates surgery for IE, and to create a mortality risk score based on the results of this analysis. METHODS AND RESULTS: Outcomes of 361 consecutive patients (mean age, 59.1\ub115.4 years) who had undergone surgery for IE in 8 European centers of cardiac surgery were recorded prospectively, and a risk factor analysis (multivariable logistic regression) for in-hospital death was performed. The discriminatory power of a new predictive scoring system was assessed with the receiver operating characteristic curve analysis. Score validation procedures were carried out. Fifty-six (15.5%) patients died postsurgery. BMI >27 kg/m2 (odds ratio [OR], 1.79; P=0.049), estimated glomerular filtration rate 55 mm Hg (OR, 1.78; P=0.032), and critical state (OR, 2.37; P=0.017) were independent predictors of in-hospital death. A scoring system was devised to predict in-hospital death postsurgery for IE (area under the receiver operating characteristic curve, 0.780; 95% CI, 0.734-0.822). The score performed better than 5 of 6 scoring systems for in-hospital death after cardiac surgery that were considered. CONCLUSIONS: A simple scoring system based on risk factors for in-hospital death was specifically created to predict mortality risk postsurgery in patients with IE

Application de la théorie linéaire de la mécanique de la rupture aux structures métalliques épaisses - Méthodes pratiques de calcul des facteurs d'intensité de contrainte

The bases of Linear Elastic Fracture Mechanics are summed up. It is shown how this theory can be applied to industrial structures and not only to simple geometries and loads, and how stress intensity factors can always be defined. The conditions under which the stress intensity factor is a fast fracture criterion are examined, as well as corrections and limitations resulting from plastic deformation. It is shown how weight functions depending only on geometrical parameters make the calculation of the stress intensity factors possible by a simple integral, for any load applied to a given body. Such weight functions are given for a long axial crack and a circumferential crack in a cylinder of revolution.On résume les fondements de la Théorie Linéaire de la Mécanique de la Rupture. On montre comment cette théorie peut être appliquée à des structures industrielles et non seulement à des géométries et des chargements simples, et comment les facteurs d'intensité de contrainte peuvent être définis dans tous les cas. On examine sous quelles conditions le facteur d'intensité de contrainte est un critère de rupture brutale, et les corrections et limitations qui résultent de la déformation plastique. On montre ensuite comment la connaissance des fonctions poids attachées à une géométrie ramène à une quadrature le calcul du facteur d'intensité de contrainte. On donne des fonctions de poids pour une longue fissure axiale et une fissure circonférentielle dans un cylindre de révolution

Using Social Network Analysis to predict online contributions: The impact of network diversity in cross-cultural collaboration

Although collaborative web-based tools are often used in blended environments such as education, little research has analysed the predictive power of face-to-face social connections on measurable user behaviours in online collaboration, particularly in diverse settings. In this paper, we use Social Network Analysis to compare users’ pre-existing social networks with the quantity of their contributions to an online chat-based collaborative activity in a higher education classroom. In addition, we consider whether the amount of diversity present in one’s social network leads to more online contributions in an anonymous cross-cultural collaborative setting. Our findings indicate that pre-existing social connections can predict how much users contribute to online education-related collaborative activities with diverse group members, even more so than academic performance. Furthermore, our findings suggest that future Web Science research should consider how the more traditionally ‘qualitative’ socio-cultural influences affect user participation and use of online collaborative tools

The Role Culture and Personality Play in an Authentic Online Group Learning Experience

Both educators and students face challenges in successful collaborative work, particularly when students come from a diverse set of backgrounds and cultures. This is especially the case at business schools, which have some of the most diverse student populations in the UK. One explanation for this could be that culture and personality influence behaviour in group work, creating mismatched expectations. This assumption has led to current research focusing upon student reflections and perceptions of these challenges, while few studies objectively explore what influences actual student behaviours in group work. Therefore, this paper describes a learning analytics study of an activity designed to replicate a group learning experience. In a lab environment, 58 students at a UK business school were placed in small groups to work with a Harvard Business School case study using an online chat to communicate with all members of their group. Student contributions were analysed and compared using Hofstede’s Cultural Dimensions (Hofstede, Hofstede, & Minkov, 2010) and the Big Five Ten Item Personality Measure (Gosling, Rentfrom, & Swann, 2003). Our analysis suggests that cultural traits in particular influences and can predict student group work behaviours