Variable training: effects on velocity and accuracy in the tennis serve     

Hector Hernández-Davo  Tomás Urbán  Jose Manuel Sarabia  Casto Juan-Recio  Francisco Javier Moreno 《Journal of sports sciences》2013,31(14):1383-1388

Abstract

Variable practice has been shown to be an effective strategy to improve open motor skills. However, the usefulness of this procedure in closed motor skills remains controversial. The following study has the objective of analysing the effects of variability practice in the improvement of a closed skill. The skill studied has been the tennis serve. Thirty young tennis players (13 ± 1.52 years), divided in two groups, took part in this study. One group practiced in variable conditions and the other group in consistency conditions. Both groups performed 12 training sessions (60 serves/session). The variable practice group improved their accuracy significantly compared with the consistency group (F_3.25 = 3.078; P = 0.035). The velocity of serve increased after training in both groups (F_3.25 = 15.890; P = 0.001). The practice in variable conditions seems to be effective in improving the performance of the tennis serve.  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   

The interdependence of language and translational math skills among bilingual hispanic engineering students     

Jose P. Mestre  William J. Gerace  Jack Lochhead 《科学教学研究杂志》1982,19(5):399-410

The performance of 43 Hispanic engineering and science majors on a task that consists of reading a sentence describing a mathematical relationship between two variables, and then writing an equation describing the relationship, is investigated in both English and Spanish. Results are compared with grade point average and with language proficiency. Comparison of the bilingual group to a monolingual group consisting of 52 engineering and science students shows that performance, as measured by either the mathematical translation task or grade point average, is more strongly correlated with language proficiency for the bilingual group. Clinical interviews conducted with samples from each group reveal large differences in the interpretation of the mathematical task between Hispanics and monolinguals. Suggestions are made for the improvement of the technical education of Hispanics.  相似文献   

The Evolution of the Concept of Capacitance Throughout the Development of the Electric Theory and the Understanding of Its Meaning by University Students     

Jenaro Guisasola  Jose L. Zubimendi  Jose M. Almudí  Mikel Ceberio 《Science & Education》2002,11(3):247-261

There are few didactic studies concerning the difficulties met by students inunderstanding the meaning of capacitance in a charged body. However, theunderstanding of capacitance can be a good indicator of the Students' learningof electrostatic theory in general. To describe Students' difficulties in learningthis concept we have considered, on the one hand, that individuals constructmental representations in order to help their understanding of the way a physicalsystem works under varied circumstances. On the other hand, a critical study ofthe history and epistemology of science is likely to enlighten us teachers andresearchers about the presence of qualitative leaps in the evolution of a concept.Thus, the consideration by teachers of these `discontinuities between meaningsfor the same concept, may lead them to understand Students' difficulties on learningit. We developed a historical study of the development of the capacitance conceptand an empirical study with students to identify historical and learning difficulties.The results obtained seem to show that most of the students who reason aboutaspects related to the charge of bodies and capacitance feel more comfortablewhen they talk in terms of charge than in terms of electric potential in a similarway to the first explanations of the early electric theories.  相似文献   

Perceptual learning transfer in an appetitive Pavlovian task     

Antonio A. Artigas  Jose Prados 《Learning & behavior》2017,45(2):115-123

In two experiments, rats were given intermixed or blocked preexposure to two similar compound stimuli, AX and BX. Following preexposure, conditioning trials took place in which AX (Experiment 1) or a novel compound stimulus NX (Experiment 2) was paired with a food-unconditioned stimulus in an appetitive Pavlovian preparation. Animals that were given alternated preexposure showed lower generalization from AX to BX (Experiment 1) and from NX to a new compound, ZX (Experiment 2), than animals that were given blocked preexposure, a perceptual learning and a perceptual learning transfer effect, respectively.  相似文献   

Which firms want PhDs? An analysis of the determinants of the demand     

Jose Garcia-Quevedo  Francisco Mas-Verdú  Jose Polo-Otero 《Higher Education》2012,63(5):607-620

PhD graduates hold the highest education degree, are trained to conduct research and can be considered a key element in the creation, commercialization and diffusion of innovations. The impact of PhDs on innovation and economic development takes place through several channels such as the accumulation of scientific capital stock, the enhancement of technology transfers and the promotion of cooperation relationships in innovation processes. Although the placement of PhDs in industry provides a very important mechanism for transmitting knowledge from universities to firms, information about the characteristics of the firms that employ PhDs is very scarce. The goal of this paper is to improve understanding of the determinants of the demand for PhDs in the private sector. Three main potential determinants of the demand for PhDs are considered: cooperation between firms and universities, R&D activities of firms and several characteristics of firms, size, sector, productivity and age. The results from the econometric analysis show that cooperation between firms and universities encourages firms to recruit PhDs and point to the existence of accumulative effects in the hiring of PhD graduates.  相似文献   

PERSONNEL NEEDS IN SCHOOL PSYCHOLOGY: A 10‐YEAR FOLLOW‐UP STUDY ON PREDICTED PERSONNEL SHORTAGES     

Jose M. Castillo  Michael J. Curtis  Sim Yin Tan 《Psychology in the schools》2014,51(8):832-849

Concerns regarding whether a sufficient supply of school psychologists exists have been evident for decades. Studies have predicted that school psychology would face a critical personnel shortage that would peak in 2010, but continue into the foreseeable future. The current study is a 10‐year follow‐up investigation based on previously published personnel shortage projections. Data derived from the National Association of School Psychologists 2009–2010 national study were used to examine current personnel shortages as well as to project the extent to which personnel shortages are likely to continue. Findings indicate that the field of school psychology continues to experience a personnel shortage that will continue through 2025. Additionally, greater rates of retirements are projected for the field for school psychologists who are males, who possess a doctoral degree, and for university faculty. Analyses based on the U.S. Census Regions indicate that notable differences are likely to occur in the match between the supply of and demand for school psychologists based on geographical location. Implications are discussed relating to the recruitment and retention of school psychologists and to the services they deliver.  相似文献   

Crowdsourcing interactions: using crowdsourcing for evaluating interactive information retrieval systems   总被引：1，自引：0，他引：1  

Guido Zuccon  Teerapong Leelanupab  Stewart Whiting  Emine Yilmaz  Joemon M. Jose  Leif Azzopardi 《Information Retrieval》2013,16(2):267-305

In the field of information retrieval (IR), researchers and practitioners are often faced with a demand for valid approaches to evaluate the performance of retrieval systems. The Cranfield experiment paradigm has been dominant for the in-vitro evaluation of IR systems. Alternative to this paradigm, laboratory-based user studies have been widely used to evaluate interactive information retrieval (IIR) systems, and at the same time investigate users’ information searching behaviours. Major drawbacks of laboratory-based user studies for evaluating IIR systems include the high monetary and temporal costs involved in setting up and running those experiments, the lack of heterogeneity amongst the user population and the limited scale of the experiments, which usually involve a relatively restricted set of users. In this paper, we propose an alternative experimental methodology to laboratory-based user studies. Our novel experimental methodology uses a crowdsourcing platform as a means of engaging study participants. Through crowdsourcing, our experimental methodology can capture user interactions and searching behaviours at a lower cost, with more data, and within a shorter period than traditional laboratory-based user studies, and therefore can be used to assess the performances of IIR systems. In this article, we show the characteristic differences of our approach with respect to traditional IIR experimental and evaluation procedures. We also perform a use case study comparing crowdsourcing-based evaluation with laboratory-based evaluation of IIR systems, which can serve as a tutorial for setting up crowdsourcing-based IIR evaluations.  相似文献   

Student-perceived organizational support and perceived employability in the marketing of higher education     

Irene Trullas  Oriol R. Fusalba  Angels Fito  Jose M. Sallan 《Journal of Marketing for HIGHER EDUCATION》2013,23(2):266-281

In the current context, the need for marketing in institutions of higher education is undeniable. The specification of the student not merely as a ‘customer’ means that traditional marketing no longer has sufficient capacity to explain the behavior of the student body. In this study, a four-level relationship marketing model is tested to check the influence of perceived organizational support (POS) and perceived employability on identification with the institution and the perceived price-quality ratio and how these influence student satisfaction. In addition, the constructs prior to POS and perceived employability are identified, which are explicit enough to enable specific marketing actions to be carried out. As POS is a construct defined for the labor market, its use applied to relational marketing comes up as something innovative.

To this end, Likert scales have been designed and validated to measure these constructs. The results of this test show how the perception of organizational support depends on the relationship of the student body with the administration and management of the center. Likewise, the perception of employability depends on the perceived reputation and the perception of the promotion of employability. Furthermore, it is confirmed that satisfaction is positively related to identification and the perceived price-quality ratio, which in turn are positively related to organizational support and perceived employability.  相似文献   

The measurement of production efficiency in scientific journals through stochastic frontier analysis models: Application to quantitative economics journals     

Francisco J. Ortega  Jose M. Gavilan 《Journal of Informetrics》2013,7(4):959-965

The importance of a scientific journal is usually established by considering the number of citations received by the papers that the journal publishes. In this way, the number of citations received by a scientific journal can be considered as a measure of the total production of the journal. In this paper, in order to obtain measures of the efficiency in the production process, the approach provided by stochastic frontier analysis (SFA) is considered, and econometric models are proposed. These models estimate a frontier production, which is the maximum achievable number of citations to the journal based on its resources. The efficiency can then be measured by considering the difference between the actual production and the estimated frontier. This approach is applied to the measurement of the productive efficiency of the journals of the JCR social sciences edition database, which belong simultaneously to the areas of “economics” and “social sciences, mathematical methods”.  相似文献