Inerter-like devices used for vibration isolation: A historical perspective

Recently, a lot of attention has been given to a mechanical device known as the inerter. It is a mechanical component that can be compared to a capacitor with two ungrounded terminals in the mechanical-electrical systems analogy. In this paper, it is shown that although the concept of an inerter as a separate mechanical element is relatively new, there are several well-established vibration isolation systems that exhibit similar behavior to a simple lumped parameter system containing an inerter. Through a review of the literature, a link is established between the old and new ideas. Furthermore, a comparison between the systems is carried out using the quantities of mechanical impedance and displacement transmissibility. The advantages and disadvantages of using the inerter in vibration isolation are discussed, and a simple way of improving the high-frequency performance without severely degrading the low-frequency performance is described.     

A longitudinal developmental analysis of students’ causality beliefs about school performance

This study examined the development of school-related causality beliefs which are children’s generalized perceptions of the utility or power of different categories of specific means in producing school outcomes. Based on the action theory perspective, we analyzed the developmental model of these beliefs as well as the trajectories of the five perceived causes of school success and failure: ability, effort, luck, teacher’s help, and unknown causes. On a 5-year longitudinal study, following a group of 63 students over an 8-year period (from the second to the ninth grades), using hierarchical linear models, intraindividual changes and interindividual differences in these changes were identified; also, factors that might account for this variability were tested. The results showed a decrease of the effectiveness attributed to the various causes, but their differentiated trajectories, and a relative independence of gender and achievement factors (engagement and school grades) in the evolution of these beliefs. School children in the lower grades value most highly ability and effort as causes of school success. Student’s beliefs about the causes of school performance become both more conservative and more differentiated along schooling, which is probably a normative general tendency. Findings from this longitudinal study corroborate, to a large extent, a consistent set of important developmental findings based on previous cross-sectional designs.     

Dimensions as Virtual Items: Improving the predictive ability of top-N recommender systems

Traditionally, recommender systems for the web deal with applications that have two dimensions, users and items. Based on access data that relate these dimensions, a recommendation model can be built and used to identify a set of N items that will be of interest to a certain user. In this paper we propose a multidimensional approach, called DaVI (Dimensions as Virtual Items), that consists in inserting contextual and background information as new user–item pairs. The main advantage of this approach is that it can be applied in combination with several existing two-dimensional recommendation algorithms. To evaluate its effectiveness, we used the DaVI approach with two different top-N recommender algorithms, Item-based Collaborative Filtering and Association Rules based, and ran an extensive set of experiments in three different real world data sets. In addition, we have also compared our approach to the previously introduced combined reduction and weight post-filtering approaches. The empirical results strongly indicate that our approach enables the application of existing two-dimensional recommendation algorithms in multidimensional data, exploiting the useful information of these data to improve the predictive ability of top-N recommender systems.     

Home advantage in judo: A study of the world ranking list

Abstract

In 2009, the International Judo Federation established a ranking system (RS) to classify athletes and to distribute the competitor quotas of the Olympic Games. However, the RS does not consider the home advantage. This issue has not been studied in judo, and its implications for the RS have not been determined. The objective was to verify the home advantage in judo in terms of winning a medal or the number of matches won. Therefore, 25 competitions that computed points for the RS in 2009 were analysed. Logistic regression analysis and the Poisson generalised linear model were used for the analyses, which included the relative quality of the athletes. The sample was composed only of athletes who had competed both at home and away. The odds ratio for winning medals was higher for athletes who competed at home for both males and females. The association between the number of matches won and competing at home was significant only for the male athletes. The home advantage was observed in the competitions that used the judo RS. Thus, it is likely that athletes from countries that host competitions using the RS have an advantage in terms of obtaining their Olympic classification.     

Active relatives and health-related physical fitness in European adolescents: The HELENA Study

Abstract

High physical fitness in childhood and adolescence is positively associated with favourable health-related outcomes. Our aim was to examine the relationship between relatives’ (father, mother, brother, sister, and best friend) physical activity engagement and encouragement on adolescents’ physical fitness. Adolescents were part of the HELENA study, a multi-centre study conducted in 10 cities from nine European countries in 2006–2008. Participants were 3288 adolescents (48% boys, 52% girls) aged 12.5–17.5 years with valid data on at least one of the three fitness variables studied: muscular strength (standing long jump), speed/agility (4×10 m shuttle run), and cardiorespiratory fitness (20 m shuttle run). The adolescents reported their relatives’ physical activity engagement and encouragement. Analysis of covariance showed that relatives’ physical activity engagement (father, mother, brother, and best friend) was positively related to cardiorespiratory fitness (P < 0.05); and mother's and sisters’ physical activity engagement were positively associated with higher muscular strength in adolescents (P < 0.05). Furthermore, father's physical activity encouragement was positively linked to physical fitness (all fitness components) in adolescents (P < 0.05). Interventions aimed at improving physical fitness in young people might be more successful when family members, particularly mothers and fathers, are encouraged to engage in physical activity and support adolescents’ physical activity.     

A user-centred approach to the design of an expert system for training

This paper reports the objectives, design approach and first results of a research project that aims to develop an intelligent computer-based learning environment for industrial applications. Jonas , an expert system, is part of a modelling/simulation environment which enables shopfloor workers to test and to put new philosophies of work into practice in the context of manufacture. Our approach is focused on three main ideas: the Intelligence Augmentation paradigm, user-centred system design and the constructionist theory of learning. The architecture of the modelling environment and the main features of Jonas are presented as an illustration of the design ideas discussed in the paper.     

Parental Behavior,Cognitive Appraisal,and Motivation in Young Athletes

Purpose: This study tested two hypotheses relating young athletes’ sports motivations to parental behaviors and cognitive appraisal: (1) young athletes’ motivation in sports is related to their parents’ behavior; and (2) this relationship is mediated by cognitive appraisal, even after controlling for competitive level and sports records. Method: This cross-sectional study included 673 young athletes and it measured the athletes’ perceptions of parental behaviors, cognitive appraisal, and sports motivation. Results: Structural equation modeling confirmed Hypothesis 1–the mother’s behaviors accounted for 15 to 16% of the variance in sports motivation, and the father’s behaviors accounted for 12 to 21% of the variance. The correlation patterns differed according to whether the athletes were evaluating the mother’s or father’s behaviors. Hypothesis 2 also was confirmed, for cognitive appraisal partially mediated the relationship between the perception of parental behaviors and sports motivation (34% of the variance was accounted for by the perception of the mother’s behavior; 30% by the father’s). The mediating model did not vary with competitive level or sports records. Conclusion: Parental behaviors and cognitive appraisal need to be taken into account to understand young athletes’ sports motivations.     

Effects of resistance training in HIV-infected patients: A meta-analysis of randomised controlled trials

The relative effects of resistance training (RT) upon muscle fitness and immune function among HIV-infected patients are uncertain. The purpose of this study was to perform a meta-analysis to determine the effects of RT upon muscle strength, muscle mass and CD4 cells count and to identify potential moderators of those outcomes in HIV-infected patients. Meta-analyses use random or fixed-effects model depending on the heterogeneity of effect sizes, complemented with Hedge’s g correction factor. Thirteen trials were meta-analysed. Overall, RT increased muscle strength (35.5%, P < 0.01) and CD4 cell count (26.1%, P = 0.003) versus controls (P < 0.03), but not muscle mass (P = 0.051). Meta-regression followed by subgroup moderator analysis showed that gains in muscle strength followed a dose–response pattern with largest increase detected among trials with longer (24 weeks; 49.3%) than shorter intervention (<12 weeks; 39%), higher (Physiotherapy Evidence-Based Database [PEDro] scale = 6; 38.3%) than lower (PEDro = 5; 28.1%) quality, and longer (12 months; 59.7%) than shorter time under highly active antiretroviral therapy (HAART) (<6 months; 37.1%), (P < 0.01). RT appears to be efficacious to improve muscular strength (~35.5%) and CD4 cell count (~26.1%), but not muscle mass of HIV-infected patients. Effects upon strength were greater in studies with higher quality and among trials with longer RT and HAART.     

ACCURACY AND ERROR IN ELECTORAL FORECASTS: THE CASE OF MEXICO

Forecast errors in preelectoral polls are common. Since theNicaraguan Election in 1990, a common assumption is that wheredemocratic practices are not equal to those of the developedcountries (authoritarian, in transition, etc.), the errors inpredicting electoral outcomes with the help of pre-electoralpolls result mostly from contextual effects related to the authoritariannature of the political systems. Forecast errors in developeddemocracies have been explained by flaws in sampling (GreatBritain), last minute changes in preferences (Spain, UnitedStates, and France) and a social desirability bias in the UnitedStates. The intention of this paper is to show that in Mexicoboth the accuracy and the sources of error in predicting electoralresults are very similar to those confronted by pollsters elsewhere:mostly sampling and allocation of nonrespondents and those whoare undecided. An extensive data set of pre-electoral pollsconducted in Mexico shows an average error in the order of 3–5percentage points. Some of this error could be related to sociallydesirable answers derived from contextual effects, but thiseffect is small and must not be generalized.     

How adults contribute to the development of early referential communication?

The study focuses on the organization of prelinguistic «referential» communication routines and their effects on infant’s progressive mastery of protoreferential communication. Routines are defined here as exchanges where turn-taking and/or topic are repetead and conventionalized. The design compares an experimental group and a control group in a pretest/post test format. In the experimental group, routinized exchanges about a poster are encouraged. Three «training» sessions are devoted to the establishment of routines. The sample was composed of 13 infants aged 12 to 13 months and their mothers. Comparisons between the pretest and the postest for the E group infants show an increase in the time devoted to referential behavior, in the number of infant initiations of dialogue on the poster and in the use of pointing. For the mothers, results show that, during the three «training» sessions, E group mothers, produce more points than C group mothers and tend to «confirm» infants’ pointing plus vocalization as though it was a complete reference. Findings are discussed in terms of conventionalization of protoreferential gestures and vocalizations.