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61.
Robert B. Anderson Julius A. Marshall Andrea L’Afflitto 《Journal of The Franklin Institute》2021,358(12):6281-6308
In classical model reference adaptive control (MRAC), the adaptive rates must be tuned to meet multiple competing objectives. Large adaptive rates guarantee rapid convergence of the trajectory tracking error to zero. However, large adaptive rates may also induce saturation of the actuators and excessive overshoots of the closed-loop system’s trajectory tracking error. Conversely, low adaptive rates may produce unsatisfactory trajectory tracking performances. To overcome these limitations, in the classical MRAC framework, the adaptive rates must be tuned through an iterative process. Alternative approaches require to modify the plant’s reference model or the reference command input. This paper presents the first MRAC laws for nonlinear dynamical systems affected by matched and parametric uncertainties that constrain both the closed-loop system’s trajectory tracking error and the control input at all times within user-defined bounds, and enforce a user-defined rate of convergence on the trajectory tracking error. By applying the proposed MRAC laws, the adaptive rates can be set arbitrarily large and both the plant’s reference model and the reference command input can be chosen arbitrarily. The user-defined rate of convergence of the closed-loop plant’s trajectory is enforced by introducing a user-defined auxiliary reference model, which converges to the trajectory tracking error obtained by applying the classical MRAC laws before its transient dynamics has decayed, and steering the trajectory tracking error to the auxiliary reference model at a rate of convergence that is higher than the rate of convergence of the plant’s reference model. The ability of the proposed MRAC laws to prescribe the performance of the closed-loop system’s trajectory tracking error and control input is guaranteed by barrier Lyapunov functions. Numerical simulations illustrate both the applicability of our theoretical results and their effectiveness compared to other techniques such as prescribed performance control, which allows to constrain both the rate of convergence and the maximum overshoot on the trajectory tracking error of uncertain systems. 相似文献
62.
A multidisciplinary approach is implemented to model and analyse the performance of Olympic rowing boats. A reduced-order model that couples rowers motions with the hull, oars and hydrodynamic and hydrostatic forces is detailed. This model is complemented with a sensitivity analysis carried out by means of a non-intrusive polynomial chaos expansion. Sensitivity analysis results for two different boat classes, namely, a lightweight single scull and a coxless four are presented and discussed. This analysis contrasts, for both classes, the effects of varying forces exerted by the rowers, weights of rowers and cadence of motions on the boat performance. 相似文献
63.
Vandermoere F Blanchemanche S Bieberstein A Marette S Roosen J 《Public understanding of science (Bristol, England)》2011,20(2):195-206
In spite of great expectations about the potential of nanotechnology, this study shows that people are rather ambiguous and pessimistic about nanotechnology applications in the food domain. Our findings are drawn from a survey of public perceptions about nanotechnology food and nanotechnology food packaging (N = 752). Multinomial logistic regression analyses further reveal that knowledge about food risks and nanotechnology significantly influences people's views about nanotechnology food packaging. However, knowledge variables were unrelated to support for nanofood, suggesting that an increase in people's knowledge might not be sufficient to bridge the gap between the excitement some business leaders in the food sector have and the restraint of the public. Additionally, opposition to nanofood was not related to the use of heuristics but to trust in governmental agencies. Furthermore, the results indicate that public perceptions of nanoscience in the food domain significantly relate to views on science, technology, and nature. 相似文献
64.
The European university landscape: A micro characterization based on evidence from the Aquameth project 总被引:2,自引:0,他引:2
Cinzia Daraio Andrea BonaccorsiAldo Geuna Benedetto LeporiLaurent Bach Peter BogetoftMargarida F. Cardoso Elena Castro-MartinezGustavo Crespi Ignacio Fernandez de LucioHarold Fried Adela Garcia-AracilAnnamaria Inzelt Ben JongbloedGerhard Kempkes Patrick LlerenaMireille Matt Maria OlivaresCarsten Pohl Tarmo RatyMaria J. Rosa Cláudia S. SarricoLéopold Simar Stig SlipersaeterPedro N. Teixeira Philippe Vanden Eeckaut 《Research Policy》2011,40(1):148-164
This paper provides a new and systematic characterization of 488 universities, from 11 European countries: Finland, France, Germany, Hungary, Italy, Netherlands, Norway, Portugal, Spain, Switzerland and UK. Using micro indicators built on the integrated Aquameth database, we characterize the European university landscape according to the following dimensions: history/foundation of university, dynamics of growth, specialization pattern, subject mix, funding composition, offer profile and productivity. 相似文献
65.
The literatures on ‘varieties of capitalism’ (VoC) and ‘national innovation systems’ (NIS) propose very similar arguments about how firms require different types of labour qualifications to pursue strategies of radical product innovation (RPI), incremental product innovation (IPI), and product imitation (PI) respectively. Despite their similar lines of reasoning, however, the VoC scholars are concerned with the skill profiles of a firm's entire workforce, whereas the NIS proponents focus on the knowledge base of scientists. Given that both literatures have developed without explicitly taking the arguments of the neighbouring discipline into account, it is thus unclear whether they explain the same, or different, phenomena. Furthermore, both literatures propose firm level arguments but test them on the basis of macro- rather than micro-level indicators. This paper therefore asks: first, does micro-level evidence support the VoC and NIS arguments that particular types of employee skills and knowledge backgrounds of scientists are needed for different competitive strategies? And, if so, do RPI, IPI, and PI firms need to employ scientists in combination with a workforce having the respective qualifications, or is it sufficient if scientists or employees alone are adequately qualified. Quantitative analyses indicate that a particular mix of scientific knowledge combined with employee skills facilitate RPI, IPI, and PI strategies. The article thus concludes that - despite their similar reasoning - the VoC and the NIS literatures indeed describe different phenomena, without being aware of the synergies created whenever adequate employee and scientific qualifications are hired together. 相似文献
66.
英国大学专利技术转移研究及其借鉴意义 总被引:1,自引:0,他引:1
英国大学不仅在研究水平方面而且在与产业界的合作方面均处于全球领先的地位.本文以英国大学专利技术转移活动为研究对象,首先介绍了英国大学专利技术转移活动在许可合同数量和收入两个方面的情况,继而提出英国大学的大学技术转移中心和国家大学技术转移协会是大学专利技术转移活动的重要组织保障,优秀的研究成果和商业化、国际化意识的培养是大学专利技术转移活动的先决条件,政府法律法规的设立和政府项目的支持是大学专利技术转移活动的指导因素.最后,提出了英国大学专利技术转移对我国大学专利技术转移活动的借鉴意义. 相似文献
67.
68.
The growing complexity of scientific challenges demands increasingly intense research collaboration, both domestic and international. The resulting trend affects not only the modes of producing new knowledge, but also the way it is disseminated within scientific communities. This paper analyses the relationship between the “degree of internationalization” of a country’s scientific production and that of the relevant citing publications. The empirical analysis is based on 2010-2012 Italian publications. Findings show: i) the probability of being cited increases with the degree of internationalization of the research team; ii) totally domestic research teams tend to cite to a greater extent totally domestic publications; iii) vice versa, publications resulting from international collaborations tend to be more cited by totally foreign publications rather than by publications including domestic authors. These results emerge both at overall and at discipline level. Findings might inform research policies geared towards internationalization. 相似文献
69.
Andrea C. Walker Rachelle Gewecke Illene N. Cupit Jeffrey T. Fox 《Journal of College Counseling》2014,17(2):131-149
This phenomenological study, based on ecological systems theory, examined the college student bereavement experience in a Christian university. Undergraduate students (N = 127) from a small Christian university provided answers to open‐ended questions about their experiences regarding college following a death loss. Results indicate that students are generally successful in adapting to bereavement and prefer an environment open to discussing death and asking difficult religious questions. Implications for counselors are provided. 相似文献
70.
It is an accepted fact that resilience is a multifaceted phenomenon which has been proven to affect the learning, growth and development of individuals. A child’s formative years are a time when resilience needs to be promoted so they can cope with the challenges of life. This paper reports some of the findings of an Australian Research Council-funded longitudinal study which investigated resilience in the context of significant transitions in the lives of children and young adults. This study explored the conditions and characteristics of resilience, looking at the educational, health, work-related or leisure interventions that support and foster resilience. Outlined in this paper are findings from the early years cohort of the study involving teachers’ pedagogy informing the practical approaches and strategies that promote and protect resilience in young children. It is argued that teachers working with young children need to be mindful of using enabling strategies in which their practice works purposively with the school environment and the building of relationships. 相似文献