90 resultados para Three Body Problem


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An abdominal profile index (API) was developed for pink-footed geese Anser brachyrhynchus as a measure of body condition. On basis of carcass analysis of 56 adult geese with known API prior to collection, we found significant linear relationships between API against body mass, abdominal fat and total energy content. Hence, changes in API reflect net energy intake rates. As an example of the applicability of the calibration, we compared APIs of individually marked geese before and after long migration episodes and estimated the cost of flight at 8.9 kJ/km. In addition we estimated gain rates at three major staging sites along the spring flyway indicating an increase in fueling rates with latitude. Calibration of APIs and energy contents offers new opportunities for field studies of waterfowl energetics.

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The objective of this study was to examine the effect of self-reported breakfast size, daily eating, and other health habits on body mass index (BMI). We hypothesized that a consumption of a substantial breakfast compared with skipping or small breakfasts would be associated with lower BMI. Three independent, cross-sectional, screening surveys were conducted by Sydney Adventist Hospital in 1976, 1986, and 2005 in the surrounding community. The archived survey forms of 384 men and 338 women in 1976, 244 men and 229 women in 1986, and 270 men and 62 women in 2005 were randomly selected. Body mass index was determined from height and weight measured by hospital staff. The reported amount consumed at breakfast was one of several eating habits that predicted BMI for men but not women. It explained 5% to 6% of the variance in male BMI in all 3 years examined. As the reported breakfast amount increased, men's BMI decreased. Lifestyle confounders including vegetarianism and physical activity did not affect this relationship. However, the consumption of breakfast was significantly positively associated with consumption of cereals, bread, fruit, and spreads, while coffee consumption was significantly associated with smaller breakfasts or breakfast skipping. The consumption of relatively large breakfasts may influence BMI in men, and its promotion may help reduce the prevalence of obesity in Australia and elsewhere.

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This paper uses finite element upper and lower bound limit analysis to produce chart solutions for three-dimensional (3D) natural slopes for both short- and long-term stability. The presented chart solutions are convenient tools that can be used for preliminary design purposes. The rigorous limit analysis results in this paper were found to bracket the true factor of safety within ±10% or better, which can be used as a benchmark for the solutions from other methods. The depth of the slip surfaces is observed to be generally shallow for most analyzed cases, particularly for the long-term slope stability problem. In addition, it was found that using a two-dimensional (2D) analysis may lead to significant differences in estimating safety factors, which can differ by 2%–60% depending on the slope geometry and soil properties. Therefore, great care and judgement are required when applying 2D analyses to 3D slope problems.

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Load-induced strains applied to bone can stimulate its development and adaptation. In order to quantify the incident strains within the skeleton, in vivo implementation of strain gauges on the surfaces of bone is typically used. However, in vivo strain measurements require invasive methodology that is challenging and limited to certain regions of superficial bones only such as the anterior surface of the tibia. Based on our previous study [Al Nazer et al. (2008) J Biomech. 41:1036–1043], an alternative numerical approach to analyse in vivo strains based on the flexible multibody simulation approach was proposed. The purpose of this study was to extend the idea of using the flexible multibody approach in the analysis of bone strains during physical activity through integrating the magnetic resonance imaging (MRI) technique within the framework. In order to investigate the reliability and validity of the proposed approach, a three-dimensional full body musculoskeletal model with a flexible tibia was used as a demonstration example. The model was used in a forward dynamics simulation in order to predict the tibial strains during walking on a level exercise. The flexible tibial model was developed using the actual geometry of human tibia, which was obtained from three-dimensional reconstruction of MRI. Motion capture data obtained from walking at constant velocity were used to drive the model during the inverse dynamics simulation in order to teach the muscles to reproduce the motion in the forward dynamics simulation. Based on the agreement between the literature-based in vivo strain measurements and the simulated strain results, it can be concluded that the flexible multibody approach enables reasonable predictions of bone strain in response to dynamic loading. The information obtained from the present approach can be useful in clinical applications including devising exercises to prevent bone fragility or to accelerate fracture healing.

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Although dissociative symptoms have been linked with both food- and appearance-related aspects of eating disorders, the psychological mechanisms underlying these relationships remain unclear. The present study evaluated the hypothesis that the disturbances of self-identity attributed to dissociation can manifest as disturbances of body image and, in turn, undermine body-specific self-evaluations relevant to disordered eating (i.e., body comparison, body dissatisfaction, and internalization of the thin ideal). Ninety-three female university students completed self-report measures of dissociation and body-related aspects of disordered eating. In addition, the method of constant stimuli was used to experimentally derive three measures of body image disturbance: (1) accuracy of body size estimations (body image distortion), (2) ability to discriminate between different body sizes (body image sensitivity), and (3) consistency in one’s body size estimations (body image variability). The findings show that dissociation is related to symptoms of disordered eating, and that these relationships may be mediated by body image instability. Collectively, these findings support the notion that the body image attitudes and behaviours that characterize eating disorders may derive from proprioceptive deficits due to dissociation.

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During a NASA conference in the 1960s, the term cyborg was created through an amalgamation of the terms ‘cybernetics’ and ‘organism’. Coined by concert pianist Manfred Clynes and research colleague Nathan Kline to describe the internal technological modification of the body. This new term resonated within popular culture and was quickly embraced by science fiction where the cyborg became a popular character. The image of the cyborg is often hyper-physical and hyper-sexual. The super sexualised woman who can shoot bullets from her breasts is a popular comic book cyborg representation. The Replicants from Riddley Scott’s Blade Runner and Arnold Schwaznegger’s role the Terminator are other examples where the technological and physical combination produces a terrifying hyper humans. Increasingly the future of our physicality is one that is intertwined with technology. Although the image of the cyborg is often an exaggerated character it holds within it real future possibilities. Consider the portable arm wrist communicator from the scifi classic Star Trek. The watch phone communication device was once an object of the imagination but now a reality in the personal mobile phone. This paper argues that through imagined imagery of the cyborg, future possibilities can be seen.

One example of the image of the cyborg representing possible human futures is the performance work Cyborpyg. Cyborpyg is a 40-minute contemporary dance work that integrates three dimensional (3D) animation and video media within the performance. Projected 3D animated prosthetic limbs appear to extend the dancers from within. These digital limbs integrate with dancer’s bodies transforming them into cyborgs. The animations are an extreme form of aesthetic modification reflecting the possible consequences of the integration of technology within the body. Cyborpyg also explores both utopic and dystipic themes within the cyborg paradigm. The dancing hybrid bodies perform magical feats not possible with an unmodified body. Feet twist into talons and flippers, eyes extend from the head, arms transform into robotic attachments. The dancer’s bodies also appear trapped in an unrelenting environment with prosthesis that appear to torture and inflict serious harm. This paper explores the idea that the imagined image of the cyborg reflects future possibilities for the human physicality.

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Physical models and scaled prototypes of architecture play an important role in design. They enable architects and designers to investigate the formal, functional, and material attributes of the design. Understanding digital processes of realizing scaled prototypes is a significant problem confronting design practice. This paper reports on three approaches to the translation of Gaussian surface models into scaled physical prototype models. Based on the geometry of Eladio Dieste’s Gaussian Vaults, the paper reports on the aspects encountered in the process of digital to physical construction using scaled prototypes. The primary focus of the paper is on computing the design geometry, investigating methods for preparing the geometry for fabrication and physical construction. Three different approaches in the translation from digital to physical models are investigated: rapid prototyping, two-dimensional surface models in paper and structural component models using CNC fabrication. The three approaches identify a body of knowledge in the design and prototyping of Gaussian vaults. Finally the paper discusses the digital to fabrication translation processes with regards to the characteristics, benefits and limitations of the three approaches of prototyping the ruled surface geometry of Gaussian Vaults. The results of each of three fabrication processes allowed for a better understanding of the digital to physical translation process. The use of rapid prototyping permits the production of form models that provide a representation of the physical characteristics such as size, shape and proportion of the Gaussian Vault.

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Objective: To assess the influence of body build on the bias and limits of agreement for estimates of body fat obtained from anthropometric prediction equations when compared with the same data obtained by dual energy X-ray absorptiometry (DEXA).

Survey design and subjects:
Ninety-one premenopausal women, aged between 20 and 54 years, were chosen to represent a range of skeletal body build (relative silting height 0.50-0.56) and body fatness [body mass index (BMI) 18-34 kg/m2]. Measurements of weight, sitting height, stature, skinfold thickness, waist, umbilical and hip circumference and total body resistance and reactance were made on all subjects by standard techniques after an overnight fast. A DEXA measurement of total body fat, fat-free soft tissue and total body bone mineral mass was also obtained within 2 weeks of the anthropometric assessment.

Results:
At the group level the mean difference (bias) between DEXA and the anthropometric estimates of body fat was similar for all three anthropometric estimates ranging from 2.7 kg with impedance to 1.8 kg with skinfold thickness. The 95% limits of agreement were also similar, ranging from ±5.3 kg with body mass index to ±4.1 kg with impedance. Umbilical circumference, BMI and the amount of bone mineral expressed as a proportion of the fat-free soft-tissue mass were all significantly (P < 0.01) correlated with the level of bias between DEXA and the anthropometric estimates of body fat. This was not the case for relative sitting height or measures of body fat distribution. Regression equations which included BMI or umbilical circumference in combination with the predicted estimates of body fat essentially eliminated the association between the level of bias in predicted body fat and the level of body fatness. They also reduced the 95% limits of agreement between DEXA and the anthropometric estimates of body fat.

Conclusions:
Using DEXA estimates of body fat as the standard of reference our results suggest that the comparability and precision of body fat estimates derived from age- and/or sex-specific anthropometric prediction equations based on skinfolds and BMI, but not impedance, can be improved by adjusting for differences in BMI and umbilical circumference respectively.

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The learning experiences of first-year engineering students to a newly implemented engineering problem-based learning (PBL) curriculum is reported here, with an emphasis on student approaches to learning. Ethnographic approaches were used for data collection and analysis. This study found that student learning in a PBL team in this setting was mainly influenced by the attitudes, behaviour and learning approaches of the student members in that team. Three different learning cultures that emerged from the analysis of eight PBL teams are reported here. They are the finishing culture, the performing culture and the collaborative learning culture. It was found that the team that used a collaborative approach to learning benefited the most in this PBL setting. Students in this team approached learning at a deep level. The findings of this study imply that students in a problem-based, or project-based, learning setting may not automatically adopt a collaborative learning culture. Hence, it is important for institutions and teachers to identify and consider the factors that influence student learning in their particular setting, provide students with necessary tools and ongoing coaching to nurture deep learning approaches in PBL teams.

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This paper addresses the problem of markerless tracking of a human in full 3D with a high-dimensional (29D) body model Most work in this area has been focused on achieving accurate tracking in order to replace marker-based motion capture, but do so at the cost of relying on relatively clean observing conditions. This paper takes a different perspective, proposing a body-tracking model that is explicitly designed to handle real-world conditions such as occlusions by scene objects, failure recovery, long-term tracking, auto-initialisation, generalisation to different people and integration with action recognition. To achieve these goals, an action's motions are modelled with a variant of the hierarchical hidden Markov model The model is quantitatively evaluated with several tests, including comparison to the annealed particle filter, tracking different people and tracking with a reduced resolution and frame rate.

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This paper focuses on the problem of tracking people through occlusions by scene objects. Rather than relying on models of the scene to predict when occlusions will occur as other researchers have done, this paper proposes a linear dynamic system that switches between two alternatives of the position measurement in order to handle occlusions as they occur. The filter automatically switches between a foot-based measure of position (assuming z = Q) to a head-based position measure (given the person's height) when an occlusion of the person's lower body occurs. No knowledge of the scene or its occluding objects is used. Unlike similar research [2, 14], the approach does not assume a fixed height for people and so is able to track humans through occlusions even when they change height during the occlusion. The approach is evaluated on three furnished scenes containing tables, chairs, desks and partitions. Occlusions range from occlusions of legs, occlusions whilst being seated and near-total occlusions where only the person's head is visible. Results show that the approach provides a significant reduction in false-positive tracks in a multi-camera environment, and more than halves the number of lost tracks in single monocular camera views.

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This paper is a conceptual and methodological review of the literature on the impact of TV on preschoolers' weight status. A systematic search, of papers published between January 1995 and January 2010, identified twenty-six relevant studies. Fifteen of these were cross-sectional in design and eleven adopted a prospective design; a positive association between hours of TV and child adiposity was found in all but three studies. Although assessed in a limited number of studies, diet may mediate the relationship between TV viewing and BMI. Another likely mediator may be the content of TV programs watched; only three studies examined this association and findings were inconsistent. Our review revealed that research examining mediating effects is limited, focusing more on simple cross-sectional or prospective relationships between TV habits and child body mass index. Further investigation of the mechanisms by which TV viewing affects preschool weight gain is needed.

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We assessed intergenerational differences in food, physical activity, and body size perceptions among refugees and migrants from the Horn of Africa living in Victoria, Australia. We used a qualitative design and obtained data from 48 participants (18 individual interviews; 3 semistructured focus groups). Three major themes emerged: (a) food and physical activity, (b) preference of body size and social expectations, and (c) perceived consequences of various body sizes. For parents, large body size was perceived to equate with being beautiful and wealthy; slimness was associated with chronic illness and poverty. Parents adopted strategies that promoted weight gain in children. These included tailored food practices and restricting children’s involvement in physical activity. For young people, slimness was the ideal body size endorsed by their peers, and they adopted strategies to resist parental pressure to gain weight. Obesity-prevention programs in this subpopulation need to adopt a multigenerational approach.

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We administered a paper-and-pencil questionnaire to 133 female and 99 male Japanese high school students 13–18 years old (M = 15.9, SD = 1.57) from the Kansai area to examine cultural influences on their body image and body change behaviours. Our aim was to ascertain the independent and combined influences from traditional Japanese, modern Japanese, and Western values. Cluster analyses identified four ‘acculturative’ groups: ‘anti-modern’, ‘traditional’, ‘pro-modern/anti-traditional’, and ‘pro-Western/anti-Japanese’. Pro-modern and pro-Western adolescents were most dissatisfied with their bodies, and pro-Western adolescents were also most likely to attempt weight loss. The results demonstrate the value of assessing cultural interactions in Japan along three dimensions.

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 Problem based learning has been implemented as a pedagogical tool world-wide across a range of health professions since its inception at McMaster University, Canada, in 1969 (Neville & Norman, 2007). In addition to enhancing knowledge and understanding it is also claimed that PBL develops communication skills, encourages teamwork, sharing of information and respect for others, furthers problem solving skills, and allows students to assume responsibility for their own learning (Wood, 2003). However, the cognitive outcomes of PBL and traditional pedagogy (based on didactic teaching) are similar and hence widespread adoption of PBL has been questioned (see Colliver, 2000). Criticisms of PBL include its resource hungry nature, requiring, as it does, experienced tutors to facilitate .learning across several clusters of students dealing with the same problem. Given the actual and anticipated increase in numbers of medical students in Australia other strategies that retain the advantages of PBL, while minimising the demands on faculty, should now be explored. This paper reports our experience with a modification of the traditional PBL approach, termed PBLplus. This innovation was trialled in a regional clinical school, attached to a hospital, with a group of 19 graduate entry students, who had completed an integrated Year 1 / 2 of the MBBS. PBLplus involved allocating students from the whole class to three task directed groups. Groups had specified assignments to complete to facilitate learning across the whole class. A tutor listened to student presentations and provided an interactive presentation. Hence use of tutors was made more efficient, and faculty input was more specialised.