Optimizing time delay feedback for active vibration control of a cantilever beam using a genetic algorithm

Active vibration control using time delay for a cantilever beam is developed in this paper. The equation of motion of the system is developed using the discrete standard formulation, and the discrete quadratic function is used to design the controller. The original contribution in this paper is using a genetic algorithm to determine the optimal time delay feedback for active vibration control of a cantilever beam. Simulations of the beam demonstrated that the genetic algorithm correctly identified the time delay which produced the quickest attenuation of unwanted vibrations for both mode one and mode two. In terms of frequency response, the optimal time delay for both modes reduced the resonant amplitude. In a mixed mode situation, the simulation demonstrated that an optimal time delay could be identified.

Six year follow-up of students who participated in a school-based physical activity interventions : a longitudinal cohort study

Background
The purpose of this paper was to evaluate the long-term impact of a childhood motor skill intervention on adolescent motor skills and physical activity.

Methods
In 2006, we undertook a follow-up of motor skill proficiency (catch, kick, throw, vertical jump, side gallop) and physical activity in adolescents who had participated in a one-year primary school intervention Move It Groove It (MIGI) in 2000. Logistic regression models were analysed for each skill to determine whether the probability of children in the intervention group achieving mastery or near mastery was either maintained or had increased in subsequent years, relative to controls. In these models the main predictor variable was intervention status, with adjustment for gender, grade, and skill level in 2000. A general linear model, controlling for gender and grade, examined whether former intervention students spent more time in moderate-to-vigorous physical activity at follow-up than control students.

Results
Half (52%, n = 481) of the 928 MIGI participants were located in 28 schools, with 276 (57%) assessed. 52% were female, 58% in Grade 10, 40% in Grade 11 and 54% were former intervention students. At follow-up, intervention students had improved their catch ability relative to controls and were five times more likely to be able to catch: ORcatch = 5.51, CI (1.95 – 15.55), but had lost their advantage in the throw and kick: ORthrow = .43, CI (.23 – .82), ORkick = .39, CI (.20 – .78). For the other skills, intervention students appeared to maintain their advantage: ORjump = 1.14, CI (.56 – 2.34), ORgallop = 1.24, CI (.55 – 2.79). Intervention students were no more active at follow-up.

Conclusion
Six years after the 12-month MIGI intervention, whilst intervention students had increased their advantage relative to controls in one skill, and appeared to maintain their advantage in two, they lost their advantage in two skills and were no more active than controls at follow up. More longitudinal research is needed to explore whether gains in motor skill proficiency in children can be sustained and to determine the intervention characteristics that translate to subsequent physical activity.

Developmental stress and female mate choice behaviour in the zebra finch

The potential effects of early environmental conditions on adult female mate choice have been largely neglected in studies of sexual selection. Our study tested whether developmental stress affects the mate choice behaviour of female zebra finches, Taeniopygia guttata, when choosing between potential mates. In an experiment manipulating developmental condition, female zebra finches were raised under nutritional stress or control conditions. In adulthood, female preferences were assessed using extensive four-stimulus mate choice trials. Nutritional stress affected growth rates during the period of stress, with experimentally stressed females lighter than controls. During mate choice trials stressed females were almost three times less active than controls and made fewer sampling visits to the stimulus males, although we found no evidence of a direct effect of developmental experience on which males were preferred. Thus, developmental experience had a clear effect on behavioural patterns in a mate choice context. To test whether this effect is specific to a mate choice context, we also investigated the effect of developmental stress on female activity rates in three social contexts: isolation, contact with a conspecific male (a potential mate) and contact with a conspecific female. Here, female activity did not differ between the experimental treatments in any of the social situations. Overall, our findings suggest that environmental conditions during early development can have long-term context-dependent consequences for adult female mate choice behaviour, mediated by changes in activity rates.

Three year follow-up of an early childhood intervention: what about physical activity and weight status?

Fundamental movement skills are a correlate of physical activity and weight status. Children who participated in a preschool intervention had greater movement skill proficiency and improved anthropometric measures (waist circumference and BMI z scores) post intervention. Three years later, intervention girls had retained their object control skill advantage. The study purpose was to assess whether at three year follow up a) intervention children were more physically active than controls and b) the intervention effect on anthropometrics was still present.

Hormone therapy is associated with smaller achilles tendon diameter in active post-menopausal women

The effects of hormonal status and activity levels on Achilles tendon structure were examined in asymptomatic post-menopausal women. It was hypothesized that women using hormone replacement therapy (HRT) would have better tendon structure than those not using HRT and that active women would have poorer tendon structure than inactive women. Eighty-five women including 53 active women (regular golf players) and 32 controls (healthy but inactive women) recorded their HRT and menopausal history and underwent basic anthropometric measurements. Women were divided into two groups based on their hormonal status: those currently using HRT; and those who had never used HRT or ceased using HRT at least 12 months prior to the study. Achilles tendons were examined with ultrasound and categorized as normal or abnormal, and the diameter of each tendon (mm) was recorded. Active women had a greater prevalence of tendon abnormality ( P=0.10) and thicker Achilles tendons than inactive women ( P<0.05). Active women on HRT had less tendon abnormality ( P=0.056) than active women not on HRT and significantly less tendon thickness ( P<0.05). This study indicates that Achilles tendon diameter is greater in active post-menopausal women. Hormone replacement therapy appeared to ameliorate this effect in active women. A similar effect from HRT on the Achilles tendons of inactive women was not apparent.

Active surface shaping for artificial skins

Artificial skins exhibit different mechanical properties in compare to natural skins. This drawback makes physical interaction with artificial skins to be different from natural skin. Increasing the performance of the artificial skins for robotic hands and medical applications is addressed in the present paper. The idea is to add active controls within artificial skins in order to improve their dynamic or static behaviors. This directly results into more interactivity of the artificial skins. To achieve this goal, a piece-wise linear anisotropic model for artificial skins is derived. Then a model of matrix of capacitive MEMS actuators for the control purpose is coupled with the model of artificial skin. Next an active surface shaping control is applied through the control of the capacitive MEMS actuators which shapes the skin with zero error and in a desired time. A simulation study is presented to validate the idea of using MEMS actuator for active artificial skins. In the simulation, we actively control 128 capacitive micro actuators for an artificial fingertip. The fingertip provides the required shape in a required time which means the dynamics of the skin is improved.

A parent-based intervention to promote healthy eating and active behaviours in pre-school children: evaluation of the MEND 2-4 randomized controlled trial.

BACKGROUND: There is a paucity of studies evaluating targeted obesity prevention interventions in pre-school children. OBJECTIVES: We conducted a randomized controlled trial to evaluate the efficacy of a parent-based obesity prevention intervention for pre-schoolers - MEND (Mind, Exercise, Nutrition … Do It!) 2-4 on child diet, eating habits, physical activity/sedentary behaviours, and body mass index (BMI). METHODS: Parent-child dyads attended 10 weekly 90-min workshops relating to nutrition, physical activity and behaviours, including guided active play and healthy snack time. Assessments were conducted at baseline, immediately post-intervention, and 6 and 12 months post-intervention; child intake of vegetables, fruit, beverages, processed snack foods, fussiness, satiety responsiveness, physical activity, sedentary behaviour and neophobia were assessed via parent proxy report. Parent and child height and weight were measured. RESULTS: Two hundred one parent-child dyads were randomized to intervention (n = 104) and control (n = 97). Baseline mean child age was 2.7 (standard deviation [SD] 0.6) years, and child BMI-for-age z-score (World Health Organization) was 0.66 (SD 0.88). We found significant positive group effects for vegetable (P = 0.01) and snack food (P = 0.03) intake, and satiety responsiveness (P = 0.047) immediately post-intervention. At 12 months follow-up, intervention children exhibited less neophobia (P = 0.03) than controls. CONCLUSION: Future research should focus on additional strategies to support parents to continue positive behaviour change. ACTRN12610000200088.

A web-based, social networking physical activity intervention for insufficiently active adults delivered via Facebook app: randomized controlled trial

BACKGROUND: Online social networks offer considerable potential for delivery of socially influential health behavior change interventions. OBJECTIVE: To determine the efficacy, engagement, and feasibility of an online social networking physical activity intervention with pedometers delivered via Facebook app. METHODS: A total of 110 adults with a mean age of 35.6 years (SD 12.4) were recruited online in teams of 3 to 8 friends. Teams were randomly allocated to receive access to a 50-day online social networking physical activity intervention which included self-monitoring, social elements, and pedometers ("Active Team" Facebook app; n=51 individuals, 12 teams) or a wait-listed control condition (n=59 individuals, 13 teams). Assessments were undertaken online at baseline, 8 weeks, and 20 weeks. The primary outcome measure was self-reported weekly moderate-to-vigorous physical activity (MVPA). Secondary outcomes were weekly walking, vigorous physical activity time, moderate physical activity time, overall quality of life, and mental health quality of life. Analyses were undertaken using random-effects mixed modeling, accounting for potential clustering at the team level. Usage statistics were reported descriptively to determine engagement and feasibility. RESULTS: At the 8-week follow-up, the intervention participants had significantly increased their total weekly MVPA by 135 minutes relative to the control group (P=.03), due primarily to increases in walking time (155 min/week increase relative to controls, P<.001). However, statistical differences between groups for total weekly MVPA and walking time were lost at the 20-week follow-up. There were no significant changes in vigorous physical activity, nor overall quality of life or mental health quality of life at either time point. High levels of engagement with the intervention, and particularly the self-monitoring features, were observed. CONCLUSIONS: An online, social networking physical activity intervention with pedometers can produce sizable short-term physical activity changes. Future work is needed to determine how to maintain behavior change in the longer term, how to reach at-need populations, and how to disseminate such interventions on a mass scale. TRIAL REGISTRATION: Australian New Zealand Clinical Trials Registry (ANZCTR): ACTRN12614000488606; https://www.anzctr.org.au/Trial/Registration/TrialReview.aspx?id=366239 (Archived by WebCite at http://www.webcitation.org/6ZVtu6TMz).

Searching Baxter's URDF robot joint and link tree for active serial chains

Teleoperation is integral to society's uptake of modern robotic systems. Given the wide array of readily available robots, ranging from simple mobile platforms and UAVs to advanced humanoid robots such as ASIMO and PR2, teleoperation is required in many different forms. The recent advances in virtual reality systems, interactive input controls and even haptic devices facilitate a wide range of new approaches to teleoperation control. This paper considers a dynamic user interface for improving the operator's ability to teleoperate heterogeneous robotic systems in dynamic and challenging environments. In order to achieve the proposed dynamic user interface the robot(s) comprising the heterogeneous robotic system and their active components need to be categorized. The recent uptake of ROS means that many robots are now represented within the standardized Unified Robot Descriptive Format (URDF), and this paper proposes a method for searching the URDF for active serial chains in individual robot systems. Results demonstrate the ability of the approach to determine active serial chains and associated kinematic information for the Baxter torso robot.