Equivalent formulations of the Müntz-Szász completeness condition for systems of complex exponentials

New results pertaining to the completeness of a system of complex exponentials in L_p spaces are presented. It is shown that the well-known Müntz-Szász condition can be interpreted in terms of an equivalence relation, thereby proving that the standard Müntz-Szász formulation is equivalent with certain alternative formulations.     

正弦永磁同步电机转矩脉动抑制

为研究永磁同步电机中非正弦气隙磁链分布及其对转矩脉动的影响,用Matlab/Simulink对磁链非正弦、且存在较大齿槽转矩的永磁同步电机及其控制系统进行仿真.采用迭代学习控制算法抑制永磁同步电机转速和转矩的脉动.对转速环和转矩环下两种不同的迭代学习控制方案进行比较.仿真结果表明,两种不同的迭代学习控制方案均可以抑制转矩和转速的脉动.     

Transactional Links Between Social Anxiety Symptoms and Parenting Across Adolescence: Between- and Within-Person Associations

This 4-year longitudinal multi-informant study examined between- and within-person associations between adolescent social anxiety symptoms and parenting (parental psychological control and autonomy support). A community sample of 819 adolescents (46.1% girls; M_ageT₁ = 13.4 years) reported annually on social anxiety symptoms and both adolescents and mothers reported on parenting. Between-person associations suggested that adolescent social anxiety symptoms were associated with higher adolescent- and mother-reported psychological control and lower mother-reported autonomy support. At the within-person level, however, mothers reported lower psychological control and higher autonomy support after periods with higher adolescent social anxiety symptoms. Our findings illustrate the importance of distinguishing among between-person and within-person associations and including perceptions of both dyad members in longitudinal research concerning parenting and adolescent mental health.     

The Validity of the Interpersonal Behaviors Questionnaire (IBQ) in Sport

According to Self-Determination Theory (SDT), basic psychological needs will be influenced by other individuals’ interpersonal behaviors. The objective of the present research is to extend the validity of the Interpersonal Behaviors Questionnaire (IBQ and IBQ-Self) to the sport context. The measure was designed to assess perceptions of interpersonal behaviors of others (IBQ) or self-reports of interpersonal behaviors (IBQ-Self) in the context of SDT. This measure consists of 24 items and six subscales looking at autonomy-supportive, autonomy-thwarting (controlling), competence-supportive, competence-thwarting, relatedness-supportive, and relatedness-thwarting interpersonal behaviors. In Study 1, athletes were asked to report on their perceptions of their coaches’ interpersonal behaviors (IBQ). In Study 2, coaches were asked to report on their interpersonal behaviors when they coach their athletes (IBQ-Self). The results supported that the scale had a strong factor structure, internal consistency, and validity. Overall, the results supported the IBQ and IBQ-Self are valid measures of interpersonal behaviors in sport.     

Worldwide variation in the performance of children and adolescents: an analysis of 109 studies of the 20-m shuttle run test in 37 countries

This study is a meta-analysis of 109 reports of the performance of children and adolescents on the 20-m shuttle run test (20-mSRT). The studies were performed in 37 countries and included data on 418,026 children, tested between 1981 and 2003. Results were expressed as running speed (km x h(-1)) at the final completed stage of the 20-mSRT. Raw data were combined with pseudodata using Monte Carlo simulation. The 20-mSRT performances were expressed as z-scores relative to all children of the same age and sex from all countries. An overall "performance index" was derived for each country as the average of the age- and sex-specific z-scores for all children from that country. Factorial analysis of variance was used to compare scores among countries and regions, and between boys and girls of the same age. There was wide and significant (P < 0.0001) global variability in the performance of children. The best performing children were from the Northern European countries Estonia, Iceland, Lithuania, and Finland (0.6 - 0.9 standard deviations above the global average). The worst performing children were from Singapore, Brazil, USA, Italy, Portugal, and Greece (0.4 - 0.9 standard deviations below the global average). There is evidence that performance was negatively related to being overweight, as well as to a country's average temperature.     

Labour market regulation and team performance: The Victorian Football League's Coulter Law, 1930–1970

The Coulter Law was a set of Victorian Football League (VFL) recruiting and payment rules that operated from 1930 to 1970 and set maximum wages for individual players. Testing of the conventional view – that most VFL clubs breached these rules to maximise the utility derived from winning games – is hampered by the unavailability of individual wage data. We develop a model that observes connections between player turnover and team performance at three VFL clubs. The ways that clubs managed team payrolls in a regulated labour market are not sufficient to explain variations in team performance. Clubs lost experienced players to minor leagues, regardless of whether they complied with the Coulter Law. The ability of clubs to develop replacement players had a stronger influence on team performance.     

The effect of directive tutor guidance in problem-based learning of statistics on students’ perceptions and achievement

In this study directive tutor guidance in problem-based learning (PBL) of statistics is investigated. In a quasi experiment in an educational setting, directive guiding tutors were compared with tutors in a more traditional role. Results showed that the subjective perceptions of the students with regard to the course, the tutor, and the discussions in the tutorial meetings were more positive in the guided condition. The quality of the problems used in the meetings and general tutor functioning were evaluated as equal in both conditions. Achievement was marginally higher in the guided condition. It can be concluded that directive tutor guidance is an effective addition to PBL of statistics.     

Energy Cost of Disco Dancing

Abstract

The purpose of this study was to evaluate the energy cost of dancing in the conditions that prevail in disco clubs. To avoid any hindrance in the movements of the dancers, oxygen uptake was assessed by retroextrapolating the 0₂ recovery curve to time zero of recovery. Males and females required a similar energy cost for disco dancing, that is 30.1 ± 10.3 ml 0₂ · kg_-1 · min^-1 for a fundamental music rhythm of 135.0 ± 7.7 bpm (X ± SD = for 15 university students). Males, being heavier than females, have a higher absolute energy expenditure (X ± SD = 48.5 ± 15.2 and 31.7 ± 13.7 kj · min^-1). Heart rate was 134.5 ± 13.4 bpm. Total energy expenditure for a dancing evening (90 min of active time) was estimated to be 4350 and 2850 kJ for the males and the females respectively. At approximately 60 and 70% [Vdot]O₂ max for the males and females respectively, disco dancing could be efficient for improving aerobic fitness and for controlling excess body fat. In this respect, and from the literature, disco dancing (rock and roll, hustle, twist, disco) appears almost twice as strenuous as square dancing and most other traditional dances (rumba, fox trot, waltz). The above figures are averages, and intra-individual variations of 3.0 ml kg^-1 min^-1 (average difference between two trials) and inter-individual variations of 10.3 ml · kg^-1 · min^-1 (standard deviation) suggest caution before applying the average scores to any individual. Results reported above did not appear to be affected by the music rhythm, at least not for the range observed in this study (120–150 bpm). Indeed the energy cost of dancing on two music rhythms (128.0 ± 8.9 and 140.0 ± 9.8 bpm) was not significantly different; furthermore, the correlation between the rhythm and the oxygen uptake was only r = 0.1.     

Parenting Support and the Role of Society in Parental Self‐Understanding: Furedi's Paranoid Parenting Revisited

The publication of Frank Furedi's Paranoid Parenting in 2001 was trend‐setting in the sense that it addresses parents directly in a way that is intended to be both critical and supportive, by helping parents to look through a sociological lens at their alleged predicament. Furedi's hope is that this will lead to the restoration of parental self‐confidence, which he claims to be sorely lacking in contemporary (Western?) society. I argue that such a project would be more likely to succeed if one were to hold a less dim view of the way both parents and other individuals are connected with their own society. By introducing a cultural‐hermeneutical perspective on human agency, based on a specific reading of Heidegger and Taylor, I suggest a more constructive way to reconnect parents with the ongoing conversations in their communities and to conceptualise parenting support.