排序方式： 共有62条查询结果，搜索用时 187 毫秒
51.
Igor J. Pietkiewicz 《International Journal for Educational and Vocational Guidance》2016,16(3):379-404
The aim of this study was to explore experiences of Roman Catholic clergy who relinquish the priesthood. Ten former priests participated in semi-structured interviews that were subjected to interpretative phenomenological analysis. Overall, the study found that priests experienced needs and aspirations conflicting with their social role and the expectations made of them. They found making decisions about vocational change frustrating and stressful because of concerns about breaking community norms, fear of social stigma, and disbelief in their ability to cope in lay life. Specific guidelines for supporting priests through counseling psychologists are provided. 相似文献
52.
In this work, tuning rules of the PID controller have been developed by categorizing a system's response into distinct classes. The classes are formed using the shapes of the test oscillations induced by the system under the Modified Relay Feedback Test (MRFT) produced by specific system models. It is proposed that a physical system can be categorized into one of the proposed classes and thus the tuning rules for a particular class can apply to any kind of system from this class. The idea of producing tuning rules that are based on the shape of the oscillations induced in the loop containing the process comes from the observations that oscillatory responses of physical systems reveal just a few different shapes depending on system dynamics. For applying the developed optimal tuning rules for an arbitrary system, first, certain system characteristics are determined using a priori knowledge of the class model. Then the system's response with the application of the MRFT is examined to classify the oscillation waveform/shape. In this work, such classification is carried out using a cross-correlation algorithm. Finally, a class tuning rules are applied. 相似文献
53.
I.M. Boiko N.V. Kuznetsov R.N. Mokaev E.D. Akimova 《Journal of The Franklin Institute》2021,358(1):363-383
Asymmetric self-excited periodic motions or periodic solutions which are produced by relay feedback systems that have symmetric characteristics are studied in the paper. Two different mechanisms of producing an asymmetric oscillation by a system with symmetric properties are noted and analyzed by the locus of a perturbed relay system (LPRS) method. Bifurcation between the ability to excite symmetric and asymmetric oscillation with variation of system parameters is analyzed. An algorithm of finding asymmetric solutions is proposed. 相似文献
54.
Kokot G Vilfan M Osterman N Vilfan A Kavčič B Poberaj I Babič D 《Biomicrofluidics》2011,5(3):34103-341039
We observed and measured the fluid flow that was generated by an artificial cilium. The cilium was composed of superparamagnetic microspheres, in which magnetic dipole moments were induced by an external magnetic field. The interaction between the dipole moments resulted in formation of long chains-cilia, and the same external magnetic field was also used to drive the cilia in a periodic manner. Asymmetric periodic motion of the cilium resulted in generation of fluid flow and net pumping of the surrounding fluid. The flow and pumping performance were closely monitored by introducing small fluorescent tracer particles into the system. By detecting their motion, the fluid flow around an individual cilium was mapped and the flow velocities measured. We confirm that symmetric periodic beating of one cilium results in vortical motion only, whereas asymmetry is required for additional translational motion. We determine the effect of asymmetry on the pumping performance of a cilium, verify the theoretically predicted optimal pumping conditions, and determine the fluid behaviour around a linear array of three neighbouring cilia. In this case, the contributions of neighbouring cilia enhance the maximal flow velocity compared with a single cilium and contribute to a more uniform translational flow above the surface. 相似文献
55.
Knowledge spillovers through human mobility across national borders: Evidence from Zhongguancun Science Park in China 总被引：1，自引：0，他引：1
This paper investigates the impact of returnee entrepreneurs and their knowledge spillovers on innovation in high-tech firms in China. Using panel data for 1318 high-tech firms in Beijing Zhongguancun Science Park (ZSP) we find that returnee entrepreneurs create a significant spillover effect that promotes innovation in other local high-tech firms. The extent of this spillover effect is positively moderated by the non-returnee firm's absorptive capacity approximated by the skill level of employees. Multinational enterprises’ R&D activities positively affect the innovation intensity of non-returnee firms only when these local firms possess the sufficient level of absorptive capacity. Our findings have important implications for policy-makers and practitioners. 相似文献
56.
“Success stories,” i.e., cases in which mathematical problems posed in a controlled setting are perceived by the problem posers or other individuals as interesting, cognitively demanding, or surprising, are essential for understanding the nature of problem posing. This paper analyzes two success stories that occurred with individuals of different mathematical backgrounds and experience in the context of a problem-posing task known from past research as the Billiard Task. The analysis focuses on understanding the ways the participants develop their initial ideas into problems they evaluate as interesting ones. Three common traits were inferred from the participants' problem-posing actions, despite individual differences. First, the participants relied on particular sets of prototypical problems, but strived to make new problems not too similar to the prototypes. Second, exploration and problem solving were involved in posing the most interesting problems. Third, the participants' problem posing involved similar stages: warming-up, searching for an interesting mathematical phenomenon, hiding the problem-posing process in the problem's formulation, and reviewing. The paper concludes with remarks about possible implications of the findings for research and practice. 相似文献
57.
Research has often found that, when high school grades and SAT scores are used to predict first‐year college grade‐point average (FGPA) via regression analysis, African‐American and Latino students, are, on average, predicted to earn higher FGPAs than they actually do. Under various plausible models, this phenomenon can be explained in terms of the unreliability of predictor variables. Attributing overprediction to measurement error, however, is not fully satisfactory: Might the measurement errors in the predictor variables be systematic in part, and could they be reduced? The research hypothesis in the current study was that the overprediction of Latino and African‐American performance occurs, at least in part, because these students are more likely than White students to attend high schools with fewer resources. The study provided some support for this hypothesis and showed that the prediction of college grades can be improved using information about high school socioeconomic status. An interesting peripheral finding was that grades provided by students’ high schools were stronger predictors of FGPA than were students’ self‐reported high school grades. Correlations between the two types of high school grades (computed for each of 18 colleges) ranged from .59 to .85. 相似文献
58.
Igor Guisasola Iain James Ceri Llewellyn Victoria Stiles Sharon Dixon 《Sports Engineering》2009,12(2):99-109
The quasi-static testing of soils used in natural turf pitches yields key parameters in soil modelling, including elastic
moduli, Poisson’s ratio and Mohr–Coulomb parameters for shearing resistance and cohesion in soil. The bulk strength of a Sand
soil used in the construction of elite sports surfaces was found to increase initially and then decrease with increasing water
content due to apparent cohesion effects. For a Clay Loam soil, more common in recreational facilities, shear strength decreased
with water content. Reducing density resulted in a reduction of shear strength and elastic moduli in both soils due to reduced
packing of particles reducing particle–particle contact surface area. The effect of roots on the shear strength of a Sand
soil was not significant but reduced elastic moduli significantly. Horizontal forces measured during running and turning in
a biomechanics laboratory were in good agreement with forces predicted using a simple quasi-static soil model for coarse-grained
(Sand) soils although this was not the case with the Clay Loam soil. 相似文献
59.
Designing high performance controllers for multirotors is a rigorous task that is often solved by trial and error approach. Trial and error tuning usually results in non-optimal controller parameters. Tuning controllers based on the existing quadrotor models would result in poor performance of quadrotors due to simplifications and inaccuracies in the underlying models. In this paper optimal tuning rules for quadrotor attitude dynamics are designed, which guarantees near-optimal performance and robustness. A single in-flight run of the Modified Relay Feedback Test that takes only few seconds with guaranteed stability is enough to have near-optimal tuning of the controller. The designed tuning rule is tested experimentally in-flight on a custom-built quadrotor. The results showed significant advantages in performance and robustness due to the proposed approach. 相似文献
60.
Igor Mayer Geertje Bekebrede Casper Harteveld Harald Warmelink Qiqi Zhou Theo van Ruijven Julia Lo Rens Kortmann Ivo Wenzler 《British journal of educational technology : journal of the Council for Educational Technology》2014,45(3):502-527
The authors present the methodological background to and underlying research design of an ongoing research project on the scientific evaluation of serious games and/or computer‐based simulation games (SGs) for advanced learning. The main research questions are: (1) what are the requirements and design principles for a comprehensive social scientific methodology for the evaluation of SGs?; (2) to what extent do SGs contribute to advanced learning?; (3) what factors contribute to or determine this learning?; and (4) to what extent and under what conditions can SG‐based learning be transferred to the real world? In the Netherlands between 2005 and 2012, several hundred SG sessions with 12 SGs were evaluated systematically, uniformly and quantitatively to create a dataset, which comprises data on 2488 respondents in higher education or work organizations. The authors present the research model, the quasi‐experimental design and the evaluation instruments. This focus in this paper is on the methodology and dataset, which form a sound foundation for forthcoming publications on the empirical results. 相似文献