Bridge pressure flow scour at clear water threshold condition     

郭俊克 《天津大学学报(英文版)》2009,15(2):79-94

Bridge pressure flow scour at clear water threshold condition is studied theoretically and experimentally. The flume experiments reveal that the measured scour profiles under a bridge are more or less 2-dimensional; all the measured scour profiles can be described by two similarity equations, where the horizontal distance is scaled by the deck width while the local scour by the maximum scour depth; the maximum scour position is located just under the bridge about 15% deck width from the downstream deck edge; the scour begins at about one deck width upstream the bridge while the deposition occurs at about 2.5 deck widths downstream the bridge; and the maximum scour depth decreases with increas-ing sediment size, but increases with deck inundation. The theoretical analysis shows that: bridge scour can be divided into three cases, i.e. downstream unsubmerged, partially submerged, and totally submerged. For downstream unsubmerged flows, the maximum bridge scour depth is an open-channel problem where the conventional methods in terms of critical velocity or bed shear stress can be applied; for partially and totally submerged flows, the equilibrium maximum scour depth can be described by a scour and an inundation similarity number, which has been confirmed by experiments with two decks and two sediment sizes. For application, a design and field evaluation procedure with examples is presented, including the maximum scour depth and scour profile.  相似文献   

Development and validation of Coaches’ Interpersonal Style Questionnaire     

Juan J. Pulido  David Sánchez-Oliva  Francisco M. Leo  Jorge Sánchez-Cano  Tomás García-Calvo 《Measurement in physical education and exercise science》2018,22(1):25-37

Purpose: The objectives were to develop and validate the Coaches’ Interpersonal Style Questionnaire. The Coaches’ Interpersonal Style Questionnaire analyzes the interpersonal style adopted by coaches when implementing their strategy of supporting or thwarting athletes’ basic psychological needs. Method: In Study 1, an exploratory factor analysis was performed with 265 Spanish male athletes, between 11- and 17-years-old, to confirm the internal structure of the questionnaire. Study 2 was conducted with 430 athletes, also between 11- and 17-years-old. Both confirmatory factor analysis and exploratory structural equation modeling were used to test a set of alternative models to find the best measurement model. Results: The hierarchical exploratory structural equation modeling model showed the best fit to the data and acceptable standardized factor loadings. Concurrent validity was revealed through correlational analysis of the basic psychological need satisfaction and frustration. Conclusion: This study provides a multi-dimensional questionnaire to assess coaches’ interpersonal style perceived by athletes.  相似文献   

Associations Between Sexting Behaviors and Sexual Behaviors Among Mobile Phone‐Owning Teens in Los Angeles          下载免费PDF全文

Eric Rice  Jaih Craddock  Mary Hemler  Joshua Rusow  Aaron Plant  Jorge Montoya  Timothy Kordic 《Child development》2018,89(1):110-117

The implications of teen sexting for healthy development continue to concern parents, academics, and the general public. Using a probability sample of high school students (N = 1,208) aged 12–18, the prevalence of sexting, associations with sexting, and associations between sexing and sexual activity were assessed. Seventeen percent both sent and received sexts, and 24% only received sexts. Sending and receiving sexts were positively associated with each other and both behaviors were associated with having peers who sext. Lifetime reports of sexual intercourse, anal sex, oral sex, and recent unprotected sex were positively associated with reports of texting 300 or more times per day, only receiving sexts, and both sending and receiving sexts.  相似文献   

Associations Among Infant Iron Deficiency,Childhood Emotion and Attention Regulation,and Adolescent Problem Behaviors          下载免费PDF全文

Patricia East  Erin Delker  Betsy Lozoff  Jorge Delva  Marcela Castillo  Sheila Gahagan 《Child development》2018,89(2):593-608

This study examined whether iron deficiency (ID) in infancy contributes to problem behaviors in adolescence through its influence on poor regulatory abilities in childhood. Chilean infants (N = 1,116) were studied when there was no national program for iron fortification (1991–1996), resulting in high rates of ID (28%) and iron‐deficiency anemia (IDA, 17%). Infants (54% male) were studied at childhood (M_age = 10 years) and adolescence (M_age = 14 years). IDA in infancy was related to excessive alcohol use and risky sexual behavior in adolescence through its effect on poor emotion regulation in childhood. Attentional control deficits at age 10 were also related to both infant IDA and heightened risk taking in adolescence. Findings elucidate how poor childhood regulatory abilities associated with infant IDA compromise adjustment in adolescence.  相似文献   

Evaluating the perception of disability and the inclusive education of teachers: the Italian validation of the Sacie-R (Sentiments,Attitudes, and Concerns about Inclusive Education – Revised Scale)     

Anna Maria Murdaca  Sebastiano Costa 《欧洲特需教育杂志》2018,33(1):148-156

This study aimed to verify the factorial structure, internal validity, reliability, and criterion validity of The Sentiments, Attitudes and Concerns about Inclusive Education Revised Scale (SACIE-R) in an Italian sample. The SACIE-R is a useful tool to measure three aspects of teachers’ perceptions about inclusion, which are Sentiments, Attitudes and Concerns, providing valuable information to address the needs of teachers working with special students. A measure of this construct is currently not available in Italian, and a validation process is required. In order to provide an initial psychometric evaluation of the Italian adaptation, the SACIE-R was translated for use in Italian-speaking populations. Four hundred Italian teachers enrolled in educational teaching courses completed the SACIE-R. Confirmatory factor analyses demonstrated a good fit to the hypothesised 3-factor model, and adequate internal consistency for the scale was evidenced. A confirmatory factor analysis showed the same factor structural validity as the original instrument (although some items in the original version were deleted). Furthermore, taken together, the results showed a good level of reliability, and convergent and discriminant validity. Finally, the Italian version of the SACIE-R has good psychometric characteristics that can make it a useful measure of teacher attitude toward inclusion in the Italian educational context.  相似文献   

Contribution of limbs’ actions to the four competitive swimming strokes: a nonlinear approach     

Raul F. Bartolomeu  Mário J. Costa  Tiago M. Barbosa 《Journal of sports sciences》2018,36(16):1836-1845

The aim of our study was to assess the effect of the limbs’ actions on the nonlinear properties of the four competitive swimming strokes. Forty-nine swimmers performed all-out sprints at front-crawl, backstroke, breaststroke and butterfly, each one at full stroke (FS), only the arms’ stroke (AS), and only leg kicking (LK), in a total of 12 bouts, 6 per day. A speedo-meter cable was attached to the swimmer’s hip, to collect the speed-time raw data (f = 50Hz). Velocity, speed fluctuation, sample entropy and fractal dimension were derived from the speed-time series. Significant and moderate-strong effects were noted for both stroke and condition in all variables in the study (p ≤ 0.001; 0,560<η² < 0,952). The four competitive strokes and their three conditions exhibited nonlinear properties. The swimming pattern was less complex and more predictable for LK in comparison to AS and FS. Breaststroke and butterfly have more complex but more predictable patterns than backstroke and front-crawl.  相似文献   

Social agency and football fandom: the cultural pedagogies of the Western Sydney ultras     

Jorge Knijnik 《Sport in Society》2018,21(6):946-959

Abstract

This article addresses key questions of social agency and cultural pedagogy within the neoliberal structures of ‘modern football’ in the Australian context. It reports on a two-year ethnographic study of the Red and Black Bloc, an Australian ultras group in Western Sydney, one of the most culturally diverse areas in Australia. The origins of the Western Sydney ultras are described, along with their struggles to build their own cultural identity and to fight for social agency within a commodified football league. By combining a multifaceted theoretical model with a range of ethnographic data – including document analysis and in-depth interviews – this study reveals the processes by which the Western Sydney ultras enhance members’ social cohesion towards an increased social consciousness. The paper acknowledges the role that ultras, as authentic cultural formations, may have in the propagation of new cultural pedagogies that have the potential to enhance citizenship, communal life and participatory democracy.  相似文献   

Physical exercises for preventing injuries among adult male football players: A systematic review     

Jorge Pérez-Gómez  JoséCarmelo Adsuar  Pedro EAlcaraz  Jorge Carlos-Vivas 《运动与健康科学(英文)》2022,11(1):115-122

Background:Football is the most practised sport in the world and is associated with the risk of injuries in the players.Some studies have been published that identify injury prevention programs,but there is no review of the full body of evidence on injury prevention programs for use by football coaches.The aim of this article was to carry out a systematic review of published studies on injury prevention programs for adult male footballers,identify points of common understanding and establish recommendations that should be considered in the design of injury prevention strategies.Methods:PubMed and EMBASE databases were used to identify relevant published articles using the following keywords:"soccer"AND"injury"AND"prevention".Results:A total of 2512 studies were identified initially,but only 11 studies met the inclusion criteria,and their outcomes are presented.Results revealed that injury prevention programs in football have focused on strength training,proprioceptive training,multicomponent programs(balance,core stability,and functional strength and mobility),and warm-up programs.Conclusion:Based on results from the studies analyzed,football players can lower the incidence of match and training injuries by participating in dynamic warm-up programs that include preventive exercises before games or during training sessions,and by adding strength,balance,and mobility training to the training sessions.  相似文献   

Clones identification of Sequoia sempervirens (D.Don) Endl.in Chile by using PCR-RAPDs technique     

Manuel TORAL IBAEZ  Margarita CARU  Miguel A.HERRERA  Luis GONZALEZ  Luis M.MARTIN  Jorge MIRANDA  Rafael M.NAVARRO-CERRILLO 《Journal of Zhejiang University. Science. B》2009,10(2)

A protocol of polymerase chain reaction-random amplified polymorphic DNAs (PCR-RAPDs) was established to analyse the gene diversity and genotype identification for clones of Sequoia sempervirens (D.Don) Endl.in Chile.Ten (out of 34) clones from introduction trial located in Voipir-Viilarrica,Chile,were studied.The PCR-RAPDs technique and a modified hexadecyltrimethylammonium bromide (CTAB) protocol were used for genomic DNA extraction.The PCR tests were carried out employing 10-mer random primers.The amplification products were detected by electrophoresis in agarose gels.Forty nine polymorphic bands were obtained with the selected primers (BG04,BF07,BF 12,BF13,and BF 14) and were ordered according to their molecular size.The genetic similarity between samples was calculated by the Jaccard index and a dendrogram was constructed using a cluster analysis of unweighted pair group method using arithmetic averages (UPGMA).Of the primers tested,5 (out of 60) RAPD primers were selected for their reproducibility and high polymorphism.A total of 49 polymorphic RAPD bands were detected out of 252 bands.The genetic similarity analysis demonstrates an extensive genetic variability between the tested clones and the dendrogram depicts the genetic relationships among the clones,suggesting a geographic relationship.The results indicate that the RAPD markers permitted the identification of the assayed clones,although they are derived from the same geographic origin.  相似文献   

Clones identification of Sequoia sempervirens (D. Don) Endl. in Chile by using PCR-RAPDs technique     

Manuel Toral Ibañez  Margarita Caru  Miguel A. Herrera  Luis Gonzalez  Luis M. Martin  Jorge Miranda  Rafael M. Navarro-Cerrillo 《Journal of Zhejiang University. Science. B》2009,10(2):112-119

A protocol of polymerase chain reaction-random amplified polymorphic DNAs (PCR-RAPDs) was established to analyse the gene diversity and genotype identification for clones of Sequoia sempervirens (D. Don) Endl. in Chile. Ten (out of 34) clones from introduction trial located in Voipir-Villarrica, Chile, were studied. The PCR-RAPDs technique and a modified hexadecyltrimethylammonium bromide (CTAB) protocol were used for genomic DNA extraction. The PCR tests were carried out employing 10-mer random primers. The amplification products were detected by electrophoresis in agarose gels. Forty nine polymorphic bands were obtained with the selected primers (BG04, BF07, BF12, BF13, and BF14) and were ordered according to their molecular size. The genetic similarity between samples was calculated by the Jaccard index and a dendrogram was constructed using a cluster analysis of unweighted pair group method using arithmetic averages (UPGMA). Of the primers tested, 5 (out of 60) RAPD primers were selected for their reproducibility and high polymorphism. A total of 49 polymorphic RAPD bands were detected out of 252 bands. The genetic similarity analysis demonstrates an extensive genetic variability between the tested clones and the dendrogram depicts the genetic relationships among the clones, suggesting a geographic relationship. The results indicate that the RAPD markers permitted the identification of the assayed clones, although they are derived from the same geographic origin. Project (No. CONICYT-FONDEF PROYECT D01 I 1008) supported by the National Commission of Science and Research of Chile  相似文献