Stabilization and passification of distributed-order fractional linear systems using methods of preservation     

Guillermo Fernández-Anaya  José-Job Flores-Godoy  Armando-Fabian Lugo-Peñaloza  Rodrígo Muñoz-Vega 《Journal of The Franklin Institute》2013,350(10):2881-2900

This paper studies the stabilization and passification of a class of distributed-order linear time-invariant systems, by using methods of preservation in the frequency domain. Results about preservation of stability and passivity of classical linear time-invariant systems are extended to one more general family of matrix functions. Based on these results, a new approach to the problems of stabilization and passification of distributed-order linear time-invariant systems is presented. Also a result that extends the known techniques for pole placement of classical linear time-invariant systems to the new class of distributed-order linear time-invariant systems is given. Examples are given to show the validity of theoretical results.  相似文献   

A Multidimensional Analysis of the Disability Digital Divide: Some Evidence for Internet Use     

María Rosalía Vicente  Ana Jesús López 《The Information Society》2013,29(1):48-64

Over the last few years, information and communication technologies have become an essential part of daily life, affecting education, employment, and leisure, among other activities. Nonetheless, many individuals still reap few or no benefits from these technologies, and there are resilient gaps in their use. Within this larger context, the authors examine the Internet digital divide between people with and without disabilities from a multidimensional approach. Rather than analyzing the gap in terms of “haves” and “have-nots,” a range of Internet-related dimensions—affordability, motivation and attitudes, skills, usage, and others—is taken into account.  相似文献   

Generalized multistable structure via chaotic synchronization and preservation of scrolls     

E. Jiménez-López  J.S. González Salas  L.J. Ontañón-García  E. Campos-Cantón  A.N. Pisarchik 《Journal of The Franklin Institute》2013,350(10):2853-2866

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Providing metrics and automatic enhancement for hierarchical taxonomies     

Ghassan Beydoun  Francisco García-Sánchez  Cristin M. Vincent-Torres  Antonio A. Lopez-Lorca  Rodrigo Martínez-Béjar 《Information processing & management》2013

Taxonomies enable organising information in a human–machine understandable form, but constructing them for reuse and maintainability remains difficult. The paper presents a formal underpinning to provide quality metrics for a taxonomy under development. It proposes a methodology for semi-automatic building of maintainable taxonomies and outlines key features of the knowledge engineering context where the metrics and methodology are most suitable. The strength of the approach presented is that it is applied during the actual construction of the taxonomy. Users provide terms to describe different domain elements, as well as their attributes, and methodology uses metrics to assess the quality of this input. Changes according to given quality constraints are then proposed during the actual development of the taxonomy.  相似文献   

Measuring Physical Activity in Preschoolers: Reliability and Validity of the System for Observing Fitness Instruction Time for Preschoolers (SOFIT-P)     

Shreela V. Sharma  Ru-Jye Chuang  Katherine Skala  Heather Atteberry 《Measurement in physical education and exercise science》2013,17(4):257-273

The purpose of this study is describe the initial feasibility, reliability, and validity of an instrument to measure physical activity in preschoolers using direct observation. The System for Observing Fitness Instruction Time for Preschoolers was developed and tested among 3- to 6-year-old children over fall 2008 for feasibility and reliability (Phase I, n = 67) and in fall 2009 for concurrent validity (Phase II, n = 27). Phase I showed that preschoolers spent >75% of their active time at preschool in light physical activity. The mean inter-observer agreements scores were ≥.75 for physical activity level and type. Correlation coefficients, measuring construct validity between the lesson context and physical activity types with and with the activity levels, were moderately strong. Phase II showed moderately strong correlations ranging from .50 to .54 between the System for Observing Fitness Instruction Time for Preschoolers and Actigraph accelerometers for physical activity levels. The System for Observing Fitness Instruction Time for Preschoolers shows promising initial results as a new method for measuring physical activity among preschoolers.  相似文献   

‘Governmentality’ in the origins of European female PE and sport: the Spanish case study (1883–1936)     

Raúl Sánchez García  Antonio Rivero Herraiz 《Sport, Education and Society》2013,18(4):494-510

The purpose of the paper is twofold: (1) to contribute to the analysis of the origins of modern European female PE and sports from a power perspective, inspired by Foucault's work; and (2) to present a detailed analysis of female PE and sport in Spain (1883–1936) as a specific European case study. It is argued that these physical activities could be conceived in the Spanish case as part of a specific kind of ‘governmentality’ with a dual nature. On the one hand they represented disciplinary ‘technologies of power’ over the female body. Selected physical activities—dictated mainly from the hygienic-moral position of the Regeneracionistas (‘Regenerationists’)—were exerted as a kind of ‘bio-power’ for the control of the female population. On the other hand, such kind of activities (especially sports) represented certain ‘technologies of the self’ for middle and upper class women. Through participation in sports, women gained a more active and public role in the Spanish society of the era, obtaining some degree of autonomy in self-governance over their bodies and their lives.  相似文献   

Three strikes and you’re out: culture,facilities, and participation among LGBTQ youth in sports     

Alex Kulick  Laura J. Wernick  Mario Alberto V. Espinoza  Tarkington J. Newman  Adrienne B. Dessel 《Sport, Education and Society》2013,18(9):939-953

ABSTRACT

School-based sports and physical education play an important role in the development of youth (Jones, Edwards, et al., 2017), but participation in athletics is unequal for lesbian, gay, bisexual, transgender, and queer (LGBTQ) youth compared to their straight/cisgender peers [Greenspan, S. B., Griffith, C., & Murtagh, E. F. (2017). LGBTQ youths’ school athletic experiences: A 40-year content analysis in nine flagship journals. Journal of LGBT Issues in Counseling, 11(3), 190–200]. Sport cultures, generally, recreate dynamics of exclusion for marginalized youth. However, there are opportunities to transform these spaces into more inclusive and positive environments to support positive growth for all young people [Newman, T., Alvarez, A., & Kim, M. (2017). An experiential approach to sport-based positive youth development. Journal of Experiential Education, 40(3), 308–322]. Our study uses a data set of adolescents, collected as part of a community-based participatory action research project led by high school students in southeast Michigan, USA. Respondents reported their sexual and gender identities, as well as experiences in youth sport, as well as safety using sex-segregated facilities (i.e., bathrooms and locker-rooms). Using mediation models based on linear regression, we found evidence that LGBQ high school students play sports at a significantly lower rate compared to straight students, and among those who play sports, LGBTQ respondents felt significantly less safe compared to straight and cisgender students. Opposite to the LGBQ and trans youth in this study, straight/cisgender youth also reported feeling safer using all facilities. The mediation models suggest that these inequalities help to explain disparities in rates of sports participation and feelings of safety while participating. These findings have important implications for policy, practice, and future research.  相似文献   

Velocity profiling using inertial sensors for freestyle swimming   总被引：1，自引：1，他引：0  

Andy Stamm  Daniel A. James  David V. Thiel 《Sports Engineering》2013,16(1):1-11

The ability to unobtrusively measure velocity in the aquatic environment is a fundamental challenge for engineers and sports scientists and important in assessing the skill level. The aim of this research was to develop a method for velocity profiling in freestyle swimming utilising a purpose-built inertial sensor. Seventeen swimmers with different experience levels participated in this study performing a total of 159 laps in the velocity range from 0.79 to 2.04 m s^?1. Data were collected using a triaxial accelerometer and a tethered velocity meter. The collected acceleration data were filtered using a 0.5 Hz Hamming-windowed FIR filter to remove the gravitational acceleration before the lap velocity profiles were calculated. These calculated lap velocity profiles were then compared with the velocity profiles measured by the velocity meter using Bland–Altman analysis. The scattering follows a normal distribution with a mean skewness of 0.96 ± 0.47 and kurtosis of 2.93 ± 1.12. The results show that an inertial sensor alone can be used to determine a lap velocity profile from single point acceleration records.  相似文献   

List of Reviewers     

Coral Falco  Javier Molina-García  Octavio Álvarez  Isaac Estevan 《Sports biomechanics / International Society of Biomechanics in Sports》2013,12(4):381-382

The aim of this study was to investigate the effects of target distance on temporal and impact force parameters that are important performance factors in taekwondo kicks. Forty-nine taekwondo athletes (age = 24.5 ± 5.9 years; mass = 79.9 ± 10.8 kg) were recruited: 13 male experts, 21 male novices, 8 female experts, and 6 female novices. Impact force, reaction time, and execution time were computed. Three-way repeated measure ANOVAs revealed significant ‘distance’ effect on impact force, reaction time, and execution time (p = 0.001). Comparisons between distance conditions revealed that taekwondo athletes kicked with higher impact force from short distance (17.6 ± 7.5 N/kg) than from long distance (13.1 ± 5.7 N/kg) (p < 0.001), had lower reaction time from short distance (498 ± 90 ms) and normal distance (521 ± 111 ms) than from long distance (602 ± 121 ms) (p < 0.001), and had lower execution time from short distance (261 ± 69 ms/m) than from normal distance (306 ± 105 ms/m) or from long distance (350 ± 106 ms/m) (p = 0.003 and p < 0.001, respectively). In conclusion, target distance affected the kick performance; as distance increases, impact force decreased and reaction time increased. Therefore, when reaction to a simple visual stimulus is needed, kicking from a long distance is not recommended, as longer time is required to respond.  相似文献   

Effects of mat characteristics on plantar pressure patterns and perceived mat properties during landing in gymnastics     

Pedro Pérez-Soriano  Salvador Llana-Belloch  Gaspar Morey-Klapsing  Jose Antonio Perez-Turpin  Juan Manuel Cortell-Tormo 《Sports biomechanics / International Society of Biomechanics in Sports》2013,12(4):245-257

Shock absorption and stability during landings is provided by both, gymnast ability and mat properties. The aims of this study were to determine the influence of different mat constructions on their energy absorption and stability capabilities, and to analyse how these properties affect gymnast's plantar pressures as well as subjective mat perception during landing. Six mats were tested using a standard mechanical drop test. In addition, plantar pressures and subjective perception during landing were obtained from 15 expert gymnasts. The different mats influenced plantar pressures and gymnasts' subjective perception during landing of gymnasts. Significant correlations between plantar pressures at the medial metatarsal and lateral metatarsal zones of the gymnasts' feet with the different shock absorption characteristics of the mats were found. However, subjective perception tests were not able to discriminate mat functionality between the six mats as no significant correlations between the mechanical mat properties with the subjective perception of these properties were found. This study demonstrated that plantar pressures are a useful tool for discriminating different landing mats. Using similar approaches, ideally including kinematics as well, could help us in our understanding about the influences of different mats upon gymnast-mat interaction.  相似文献