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1.
Empirical data on the development of interaction, communication, and language in deafblind children is very rare. To fill this gap, a case study was conducted in which the interaction between a teacher and a deafblind boy age 3 years 4 months was analyzed. Sequential analysis of their interaction confirmed some general clinical impressions about interaction with deafblind children, and provided the basis for suggestions on how the interaction pattern might be changed. 相似文献
2.
Lotte L. Lintmeijer Gert S. Faber Hessel R. Kruk A. J. “Knoek” van Soest Mathijs J. Hofmijster 《European Journal of Sport Science》2018,18(7):940-946
For a valid determination of a rower’s mechanical power output, the anterior–posterior (AP) acceleration of a rower’s centre of mass (CoM) is required. The current study was designed to evaluate the accuracy of the determination of this acceleration using a full-body inertial measurement units (IMUs) suit in combination with a mass distribution model. Three methods were evaluated. In the first two methods, IMU data were combined with either a subject-specific mass distribution or a standard mass distribution model for athletes. In the third method, a rower’s AP CoM acceleration was estimated using a single IMU placed at the pelvis.Experienced rowers rowed on an ergometer that was placed on two force plates, while wearing a full-body IMUs suit. Correspondence values between AP CoM acceleration based on IMU data (the three methods) and AP CoM acceleration obtained from force plate data (reference) were calculated. Good correspondence was found between the reference AP CoM acceleration and the AP CoM accelerations determined using IMU data in combination with the subject-specific mass model and the standard mass model (intraclass correlation coefficients [ICC] >?0.988 and normalized root mean square errors [nRMSE]?3.81%). Correspondence was lower for the AP CoM accelerations determined using a single pelvis IMU (0.877?Based on these results, we recommend determining a rower’s AP CoM acceleration using IMUs in combination with the standard mass model. Finally, we conclude that accurate determination of a rower’s AP CoM acceleration is not possible on the basis of the pelvis acceleration only. 相似文献
3.
Mathijs J. Hofmijster Lotte L. Lintmeijer Peter J. Beek A. J. Knoek van Soest 《Journal of sports sciences》2018,36(18):2147-2153
Mechanical power output is a key performance-determining variable in many cyclic sports. In rowing, instantaneous power output is commonly determined as the dot product of handle force moment and oar angular velocity. The aim of this study was to show that this commonly used proxy is theoretically flawed and to provide an indication of the magnitude of the error. To obtain a consistent dataset, simulations were performed using a previously proposed forward dynamical model. Inputs were previously recorded rower kinematics and horizontal oar angle, at 20 and 32 strokes?min?1. From simulation outputs, true power output and power output according to the common proxy were calculated. The error when using the common proxy was quantified as the difference between the average power output according to the proxy and the true average power output (P?residual), and as the ratio of this difference to the true average power output (ratiores./rower). At stroke rate 20, P?residual was 27.4 W and ratiores./rower was 0.143; at stroke rate 32, P?residual was 44.3 W and ratiores./rower was 0.142. Power output in rowing appears to be underestimated when calculated according to the common proxy. Simulations suggest this error to be at least 10% of the true power output. 相似文献
4.
Abstract Rowers sit on a seat that slides relative to the boat/ergometer. If a rower lifts him or herself from this sliding seat at any time, the seat will move away from under them and the rowing action is disrupted. From a mechanical perspective, it is clear that the need for the rower to remain in contact with the sliding seat at all times imposes position-dependent constraints on the forces exerted at the oar handle and the footstretcher. Here we investigate if the mechanical power output during rowing, which is strongly related to these forces, might be improved if the contact with the sliding seat was of no concern to the rower. In particular, we examine if elimination of these constraints by strapping the rower to the sliding seat leads to an increase in performance during the start on a standard rowing ergometer. Eleven well-trained female rowers performed 5-stroke starts in normal and strapped conditions. Handle force, vertical seat force, footstretcher force, and handle kinematics were recorded, from which mechanical power and work output were calculated. Most of the relevant mechanical variables differed significantly between the normal and strapped conditions. Most importantly, mechanical power output (averaged over the 5-stroke start) in the strapped condition was 12% higher than in the normal condition. We conclude that strapping a rower's pelvis to the sliding seat allows more vigorous execution of the stroke phases, resulting in a substantial improvement in performance during the start of ergometer rowing. 相似文献
5.
Abstract In rowing, power is inevitably lost as kinetic energy is imparted to the water during push-off with the blades. Power loss is estimated from reconstructed blade kinetics and kinematics. Traditionally, it is assumed that the oar is completely rigid and that force acts strictly perpendicular to the blade. The aim of the present study was to evaluate how reconstructed blade kinematics, kinetics, and average power loss are affected by these assumptions. A calibration experiment with instrumented oars and oarlocks was performed to establish relations between measured signals and oar deformation and blade force. Next, an on-water experiment was performed with a single female world-class rower rowing at constant racing pace in an instrumented scull. Blade kinematics, kinetics, and power loss under different assumptions (rigid versus deformable oars; absence or presence of a blade force component parallel to the oar) were reconstructed. Estimated power losses at the blades are 18% higher when parallel blade force is incorporated. Incorporating oar deformation affects reconstructed blade kinematics and instantaneous power loss, but has no effect on estimation of power losses at the blades. Assumptions on oar deformation and blade force direction have implications for the reconstructed blade kinetics and kinematics. Neglecting parallel blade forces leads to a substantial underestimation of power losses at the blades. 相似文献
6.
Narrowing down the conditions for extinction of Pavlovian feature-positive discriminations in humans
Priya R. van Vooren Mathijs Franssen Tom Beckers Dirk Hermans Frank Baeyens 《Learning & behavior》2012,40(4):393-404
The aim of this study was to delineate the minimal conditions for extinction of Pavlovian modulation in humans. Previous experiments at our lab showed that, after X ? A+/A?C acquisition training, X?C trials did not extinguish differential X ? A+/A?C responding, while X ? A?C trials did. Additionally, X ? A?C extinction training seemed only to extinguish differential X ? A+/A?C responding, while leaving differential responding on a concurrently trained Y ? B+/B?C discrimination intact. It thus seemed that the X ? A+/A?C discrimination can only be extinguished by X ? A?C extinction trials. (Rescorla, Journal of Experimental Psychology: Animal Behavior Processes 12, 16?C24, 1986), on the other hand, found that the minimal conditions for extinction were broader in pigeons: Namely, he found that an acquired X ? A+/A?C discrimination could be extinguished by presenting the original feature X in combination with a different target (B) that was minimally trained as an exciter. We thus wanted to examine whether this was also the case in humans. We found that nonreinforced X ? B?C presentations did not abolish discriminative X ? A/A responding when target B was a nonreinforced stimulus. Nonreinforced X ? B?C trials did extinguish the X ? A+/A?C discrimination when target B had previously been trained as a target for modulation (X ? B+/B?C or Y ? B+/B?C training) or as a reinforced exciter (B+). Our results thusf parallel and extend those in nonhuman animals (Rescorla, Journal of Experimental Psychology: Animal Behavior Processes 12, 16?C24, 1986). 相似文献
7.
Lotte L. Lintmeijer Mathijs J. Hofmijster Guido A. Schulte Fischedick Patrick J. Zijlstra A. J. “Knoek” Van Soest 《Journal of sports sciences》2018,36(18):2138-2146
In rowing, mechanical power output is a key parameter for biophysical analyses and performance monitoring and should therefore be measured accurately. It is common practice to estimate on-water power output as the time average of the dot product of the moment of the handle force relative to the oar pin and the oar angular velocity. In a theoretical analysis we have recently shown that this measure differs from the true power output by an amount that equals the mean of the rower’s mass multiplied by the rower’s center of mass acceleration and the velocity of the boat. In this study we investigated the difference between a rower’s power output calculated using the common proxy and the true power output under different rowing conditions. Nine rowers participated in an on-water experiment consisting of 7 trials in a single scull. Stroke rate, technique and forces applied to the oar were varied. On average, rowers’ power output was underestimated with 12.3% when determined using the common proxy. Variations between rowers and rowing conditions were small (SD = 1.1%) and mostly due to differences in stroke rate. To analyze and monitor rowing performance accurately, a correction of the determination of rowers’ on-water power output is therefore required. 相似文献
8.
Individual behaviour change is fast becoming a kind of ‘holy grail’ to tackle climate change, in environmental policy, the environmental movement and academic literature. This is contested by those who claim that social structures are the main problem and who advocate collective social action. The objective of the research presented in this paper is to better understand why environmentally concerned citizens choose one of these two types of engagement. Our focus is on the role of experiences of and/or convictions about power in shaping this choice. Within the framework of an explorative qualitative study, we engaged in in-depth interviews with 12 young environmentally concerned citizens. On this basis, five main findings are elaborated. Firstly, powerlessness is shown to be a crucial experience, whatever the respondents’ engagement. Secondly, ‘strategy scepticism’ seems to be a more important obstacle for engagement than ‘climate scepticism’. Thirdly, many respondents express significant resistance towards being ‘conditioned’ by awareness-raising campaigns. Fourthly, a ‘gap’ is observed between respondents’ analysis and their strategy proposals. Finally, we underscore another important gap between concrete and abstract levels in respondents’ discourses. All these findings disclose paradoxical aspects of the role of power in shaping the concerned citizens’ engaged choices. 相似文献
9.
Teachers’ beliefs are crucial to the success of inclusion programmes and reform efforts for children with special educational needs (SEN). Based on this evidence, one hundred and thirty‐nine primary pre‐service teachers from one training institution in the Netherlands completed an adapted version of a measure of beliefs towards inclusive education. In contrast to previous studies on pre‐service teachers, results of this study showed participants held neutral or negative beliefs towards this matter. In addition, limited time for pupils received the highest rating as a barrier to inclusion, whereas direct teaching experience was the most preferred method of inclusion. The implications of this study for practice and indications for future research are discussed. 相似文献
10.
This paper examines how network relations between firms influence firm survival by explicitly addressing the moderating role of changing technological regimes. Using longitudinal data on 1385 developers and 190 publishers of video games in the global video game industry between 1972 and 2007, the analyses show that the effect of network ties between developers and publishers on the survival probability of developers is moderated by the level of technological turbulence in the industry. The results show that the effect of network partner failure on firm survival is dependent on the strength of ties. The failure of strongly tied network partners harms developers in stable periods and benefits them in turbulent eras, while no such relation is found for weakly tied network partners. Network partner diversity positively affects firm performance in epochs of technological turbulence, while the effect plays no significant role for firm survival in stable settings. The results indicate that the relation between interfirm network relations and firm survival are moderated by sequences of technological renewal in the video game industry which causes the industry to go through an evolution that deviates from the typical S-shaped trajectory found in industries that are characterized by strong path-dependent processes. 相似文献