Suppression of DC-link voltage unbalance in three-level neutral-point clamped converters     

Mario Porru  Alessandro Serpi  Ignazio Marongiu  Alfonso Damiano 《Journal of The Franklin Institute》2018,355(2):728-752

Two different control approaches for suppressing DC-link voltage unbalance in Three-Level Neutral-Point Clamped Converters (NPCs) are presented in this paper. They both guarantee DC-link voltage equalization over any NPC operating conditions, i.e. when the NPC feeds or is supplied by the main AC grid at different active and/or reactive power rates. The proposed control approaches consist of either a hysteresis or a proportional regulator, each of which synthesizes the most suitable control action based on the actual DC-link voltage unbalance. Particularly, two different PWM techniques have been developed in order to achieve DC-link voltage equalization successfully, preserving NPC voltage and current waveforms at the same time. The performances achievable by means of both the proposed control approaches have been compared to each other through an extensive simulation study in order to highlight their most important advantages and drawbacks, as well as their effectiveness over any operating conditions. Particularly, both control approaches are validated in the Matlab-Simulink environment referring to DC-link voltage equalization of an NPC that represents the point of common coupling between a DC microgrid and the main AC grid.  相似文献   

Common WISC-III examiner errors: Evidence from graduate students in training     

Vincent C. Alfonso  Annemarie Johnson  Lilia Patinella  Damon E. Rader 《Psychology in the schools》1998,35(2):119-125

Sixty WISC-III protocols, administered by graduate students in training, were examined to obtain preliminary data on the frequency and types of administration and scoring errors that examinees commit. Results were compared with previous studies that have evaluated examiner errors on the Wechsler scales. In general, the present results were consistent with those of previous studies that have illustrated that a large number of scoring errors are committed by graduate students as well as by other professional groups. The majority of errors committed by participants in this study were general errors. That is, errors were not specific to a particular subtest. The five most frequent errors included failure to query, failure to record responses verbatim, reporting Full Scale IQ incorrectly, reporting Verbal IQ incorrectly, and adding individual subtest scores incorrectly. However, the traditional difficult to score Verbal subtests were not as troublesome for examiners in this study as they were for examiners in previous studies. In addition, significant decreases in the mean number of errors per protocol and in the number of most frequently occurring errors per protocol were noted. © 1998 John Wiley & Sons, Inc.  相似文献   

WIAT subtest and composite predicted-achievement values based on WISC-III verbal and performance IQs     

Dawn P. Flanagan  Vincent C. Alfonso 《Psychology in the schools》1993,30(4):310-320

Critical values tables for determining significant differences between Wechsler IQs and WIAT subtests and composites based on a predicted-achievement method are provided in the WIAT manual for the Full Scale IQ and have been constructed recently for Verbal and Performance IQs (Flanagan & Alfonso, 1993). In order to use these tables, however, a predicted achievement score(s) is required. The process of calculating predicted-achievement scores is time-consuming and may result in errors, especially when more than one ability-achievement comparison is warranted. The present paper provides tables of WIAT subtest and composite predicted-achievement standard scores based on WISC-III Verbal and Performance IQs. These tables allow examiners to determine quickly ability-achievement discrepancies based on WISC-III Verbal or Performance IQs when they are used in conjunction with the critical values tables provided in our earlier article. These tables are most useful for the accurate assessment and diagnosis of learning disabilities.  相似文献   

Effects of movement velocity and training frequency of resistance exercise on functional performance in older adults: a randomised controlled trial     

Darren L. Richardson  Michael J. Duncan  Alfonso Jimenez  Paul M. Juris  Neil D. Clarke 《European Journal of Sport Science》2019,19(2):234-246

Objectives: To investigate the effects that high-velocity, low-load (HVLL) and low-velocity, high-load (LVHL) resistance exercise, performed once or twice-weekly, have on indices of functional performance (primary outcome), maximal strength, and body composition (secondary outcomes) in older adults.

Methods: In a randomised, controlled, multi-armed, parallel design, 54 moderately-highly active, but resistance exercise naïve older adults (aged 60–79 years), attended baseline and post-10-week intervention assessment sessions. Physical and functional assessments were completed, and predicted one-repetition maximums (1-RM) were obtained for eight exercises. Participants were then randomised into one of five conditions: HVLL once-weekly (HVLL1: n?=?11) or twice-weekly (HVLL2: n?=?11), LVHL once-weekly (LVHL1: n?=?10) or twice-weekly (LVHL2: n?=?11), no-exercise control condition (CON: n?=?11). The HVLL conditions completed 3 sets of 14 repetitions at 40% 1-RM and the LVHL conditions, 3 sets of 7 repetitions at 80% 1-RM. In total, 50 participants completed all testing and were included in analyses.

Results: Only LVHL2 improved 30-sec chair stand performance (p?=?.035; g?=?0.89), arm curls (p?=?.011; g?=?1.65) and grip-strength (p?=?.015; g?=?0.34) compared to CON. LVHL2 improved maximal strength compared to CON for 7/8 exercises (p?p?Conclusion: Possibly due to the lower intensity nature of the HVLL conditions, LVHL, twice-weekly was most beneficial for improving functional performance and strength in moderately-highly active older adults. Therefore, we recommend that exercise professionals ensure resistance exercise sessions have sufficient intensity of effort and volume, in order to maximise functional performance and strength gains in older adults.  相似文献   

Adoption and impact of a learning analytics dashboard supporting the advisor—Student dialogue in a higher education institute in Latin America     

Tinne De Laet  Martijn Millecamp  Margarita Ortiz-Rojas  Alberto Jimenez  Ricardo Maya  Katrien Verbert 《British journal of educational technology : journal of the Council for Educational Technology》2020,51(4):1002-1018

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The Mysterious Crescent-Shaped Amphitheatre Weapon: A New Interpretation     

Alfonso Manas 《国际体育史杂志》2017,34(7-8):656-675

Three Roman mosaics show a tool (a staff ending in a crescent) that has always been a mystery for researchers. Some of them make no comment at all about it when discussing those mosaics, limiting themselves to describing its shape. Others try to deduce what its function was, and propose it might be a symbol (of a corporation of venatores or of a god). A few suggest it could be a weapon for fighting the animals (bulls) that appear nearby. Here I propose that the tool might indeed be a weapon for fighting animals, especially bulls, during the venationes, its precise function being to cut the hamstring tendon of one of the hind legs of the animal. I base this hypothesis on the fact that that same tool was still used in sixteenth-century Spain for that task. Of course, this hypothesis implies accepting that the tool had continued in use in the Iberian peninsula for that same function from the times of the Romans until the sixteenth century, which seems likely, since bull fights and the breeding of bulls have been activities uninterrupted in the Iberian peninsula since the times of the Romans (as attested by evidence).  相似文献   

Movement concepts approach in studies on flamenco dancing: A systematic review     

Wanda Forczek  Irene Baena-Chicón  Alfonso Vargas-Macías 《European Journal of Sport Science》2017,17(9):1161-1176

Background: Flamenco is a highly emotional and demanding dance form. It is important to understand how the dancer’s body works in order to improve fitness levels and reduce injuries. Thus, our investigation reviewed studies on kinesiological aspects of flamenco over recent years. Methods: The review was restricted to experimental studies. Literature searches were conducted using the following databases: PubMed, Scopus, and Ebsco: SPORTDiscus with Full Text, Medline, Health Source: Nursing/Academic Edition, Health Source – Consumer Edition. After limiting the search, 180 potential articles remained for analysis. Results: A total of 27 papers on different aspects of flamenco dance were finally selected: biomechanics (14), podiatry (6), injury incidence (3), anthropometry (2), and physiology (2). These studies have applied well-established methods from sports studies. However, we noted a number of potential limitations when applied to flamenco. Conclusions: The evidence from this review shows that flamenco dancing demands high levels of effort. Further research is required to understand how the dancer’s body works in order to improve fitness levels and reduce injuries. Most of the results presented here are consistent among studies. However, there is a great scarcity of research addressing flamenco movement in a more comprehensive perspective.  相似文献   

The temporal structure of judo bouts in visually impaired men and women     

Gutiérrez-Santiago A  Prieto I  Camerino O  Anguera T 《Journal of sports sciences》2011,29(13):1443-1451

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“Prolegómenos para una gramática fílmica en clave pedagógica”     

Jesús Jimenez 《Cultura y Educación》2013,25(19-20):193-203

A partir de los paralelismos y correspondencias entre las gramáticas del lenguaje oral y del lenguaje fílmico que se analizan en el artículo, el autor propone la utilización del cine para revitalizar la enseñanza de lengua y literatura.  相似文献   

An unexpected large continental source of reactive bromine and chlorine with significant impact on wintertime air quality     

Xiang Peng  Weihao Wang  Men Xia  Hui Chen  A R Ravishankara  Qinyi Li  Alfonso Saiz-Lopez  Pengfei Liu  Fei Zhang  Chenglong Zhang  Likun Xue  Xinfeng Wang  Christian George  Jinhe Wang  Yujing Mu  Jianmin Chen  Tao Wang 《国家科学评论(英文版)》2021,8(7)

Halogen atoms affect the budget of ozone and the fate of pollutants such as hydrocarbons and mercury. Yet their sources and significances in polluted continental regions are poorly understood. Here we report the observation of unprecedented levels (averaging at 60 parts per trillion) of bromine chloride (BrCl) at a mid-latitude site in North China during winter. Widespread coal burning in rural households and a photo-assisted process were the primary source of BrCl and other bromine gases. BrCl contributed about 55% of both bromine and chlorine atoms. The halogen atoms increased the abundance of ‘conventional’ tropospheric oxidants (OH, HO₂ and RO₂) by 26%–73%, and enhanced oxidation of hydrocarbon by nearly a factor of two and the net ozone production by 55%. Our study reveals the significant role of reactive halogen in winter atmospheric chemistry and the deterioration of air quality in continental regions where uncontrolled coal combustion is prevalent.  相似文献