排序方式： 共有74条查询结果，搜索用时 15 毫秒
41.
Tiago Roux Oliveira Alessandro Jacoud Peixoto Liu Hsu 《Journal of The Franklin Institute》2012,349(4):1397-1415
This paper addresses the design of a sliding mode based extremum-seeking controller for a class of single-input–single-output (SISO) uncertain nonlinear systems with unmatched and state-dependent strong nonlinearities. We demonstrate that it is possible to achieve an arbitrarily small neighborhood of the desired optimal point using only output-feedback. The key idea is the combination of a periodic switching function with a norm state observer. As an important advantage, we show that the proposed scheme achieves extremum-seeking for all initial conditions, i.e., the real-time optimization algorithm has global convergence properties. An application to a simple nonderivative optimizer illustrates the viability of the proposed approach. 相似文献
42.
As job markets have been polarizing, firms have been changing their labor inputs. By using matched employer–employee data for Portugal, we examine whether labor market polarization has occurred within or across firms and how labor input upgrades have contributed to overall productivity growth. We develop a firm taxonomy based on worker's occupational data. Firms can be focused on one task – Abstract, Manual or Routine – on a combination of tasks, or none. Results show that Abstract firms are the most productive and their share has increased over time. Manual firms, the least productive, have had a stable share throughout the period. Routine firms have seen their share decline over time. The dynamic decomposition of the estimated productivity reveals that productivity growth is propelled by increased market shares of the most productive incumbents and exiting of the least productive, especially for Abstract firms. Notwithstanding these productivity growth drivers, they fail to avert the productivity stagnation observed in Portugal between 2004 and 2009 due to the overall decline in productivity of incumbent firms, especially Routine. We discuss the policy implications of our results which are relevant to other European economies also lagging behind in terms of knowledge and innovation capabilities. 相似文献
43.
Trademarks as an indicator of innovation and industrial change 总被引：1，自引：0，他引：1
As innovation becomes an ever more central issue for the development of firms and world economies, so the need for improved assessments of innovative performance grows more urgent. This paper suggests that trademark analysis can contribute in capturing relevant aspects of innovation phenomena and the process of industrial change. We propose trademarks as a complementary indicator in the portfolio of available empirical tools of innovation studies and industrial dynamics. Our empirical exploration is based on a study of community trade marks (CTM), an intellectual property right granted in the European Union, and draws on recent research on trademarking trends in Portugal. Quantitative as well as qualitative data, including survey data from a representative sample of Portuguese manufacturing and services firms, are used to identify the advantages and limitations of this indicator. 相似文献
44.
Hugo Ribeiro Zanetti Lucas Gonçalves da Cruz Camilo Luís Monteiro Lourenço Fernando de Freitas Neves Mário Leon Silva-Vergara Edmar Lacerda Mendes 《European Journal of Sport Science》2016,16(8):1232-1239
The purpose of this study is to analyse the effect of 12 weeks of non-linear resistance training (NLRT) on anthropometry, muscle strength and inflammatory biomarkers in persons infected with human immunodeficiency virus (PIHIV). Thirty previously sedentary PIHIVs were randomized into the NLRT (n?=?15) and control (CON, n?=?15) groups. NLRT group were submitted to 12 weeks of training, whereas the CON group maintained their daily habits. At baseline and after 12 weeks, both groups underwent anthropometric evaluations and blood sampling for the analysis of inflammatory biomarkers. Analysis of covariance using preintervention values as covariate was performed to determine the effects of exercise on anthropometry, muscle strength, cytokines levels and T cells. Significance was set at p?p?p p?=?.009), blood levels of interleukin (IL)-1β (p?=?.029), IL-6 (p?=?.005), IL-8 (p?=?.010), and tumour necrosis factor (TNF)-α (p?=?.001) and an increase in muscle strength (p?p?=?.030) and CD4+ (p?=?.004) and CD8+ (p?相似文献
45.
International Trends in Health Science Librarianship Part 18: The Middle East (Iran,Qatar and Turkey) 
下载免费PDF全文
下载免费PDF全文 Kimia Zeraatkar Haleh Ayatollahi Tracy Havlin Karen Neves Mesra Şendir 《Health information and libraries journal》2016,33(2):156-160
This is the 18th in a series of articles exploring international trends in health science librarianship in the 21st century. The focus of the present issue is the Middle East (Iran, Qatar and Turkey). The next feature column will investigate trends in the Balkan States JM 相似文献
46.
Jorge E. Morais Daniel A. Marinho Raul Arellano Tiago M. Barbosa 《Sports biomechanics / International Society of Biomechanics in Sports》2019,18(1):100-114
The aim of this study was to examine the performance characteristics of male and female finalists in the 100-m distance at the 2016 European Championships in swimming (long-course-metre). The performances of all 64 (32-males and 32-females) were analysed (8 swimmers per event; Freestyle, Backstroke, Breaststroke and Butterfly). A set of start and turn parameters were analysed. In the start main outcome, male swimmers were faster in Butterfly (5.71 ± 0.14s) and females in Freestyle (6.68 ± 0.28s). In the turn main outcome, male and female swimmers were faster in Freestyle (males: 9.55 ± 0.13s; females: 10.78 ± 0.28s). A significant and strong stroke effect was noted in the start and turn main outcome, in both sexes. In the start plus the turn combined, males and females were faster in Freestyle (males: 15.40 ± 0.20s; females: 17.45 ± 0.54s). The start and the turn combined accounted almost one-third of the total race time in all events, and non-significant differences (p > 0.05) were noted across the four swim strokes. Once this research made evident the high relevance of start and turns, it is suggested that coaches and swimmers should dedicate an expressive portion of the training perfecting these actions. 相似文献
47.
48.
Sílvia Ferreira Ana M. Morais Isabel P. Neves 《International Studies in Sociology of Education》2013,23(2):137-159
The study analyses the extent to which the sociological message transmitted by the Official Pedagogic Discourse of the curriculum for Portuguese middle schools contains the ideological and pedagogical principles of its authors. The research is epistemologically and sociologically grounded, placing particular emphasis on Bernstein theory of pedagogic discourse. The ideological principles underlie broad educational aims and the pedagogical principles underlie characteristics of the pedagogic practice. Data was obtained through a semi‐structured interview with the authors and documental analysis of their publications. The results suggest that the authors were distinct in the ideological and pedagogical principles they valued and that discontinuities were evident between those principles and the curriculum message. These results are discussed and their consequences in terms of scientific learning are explored. 相似文献
49.
50.
Rodrigo R. Bini Tiago C. Jacques Felipe P. Carpes Marco A. Vaz 《Journal of sports sciences》2017,35(14):1336-1341
ABSTRACTPrevious studies have been limited to describe asymmetries during pedalling and suggest possible repercussion on performance and/or injury risks. However, few studies have presented strategies to mitigate asymmetries. The purpose of this study was to assess the effectiveness of a pedalling retraining intervention to reduce bilateral pedal force asymmetries. Twenty cyclists were assessed and 10 enrolled in a pedalling retraining method receiving visual and verbal feedback of pedal forces. The asymmetry index was computed for comparison of bilateral peak pedal forces and used during retraining (12 trials at 70% of peak power). Significantly larger asymmetry was observed for asymmetrical cyclists at the first three trials (P < 0.01 and ES = 1.39), which was reduced when post-retraining was compared to measures from symmetrical cyclists (P = 0.69 and ES = 0.18). Cyclists with larger asymmetry (>20%) in bilateral pedal forces reduce their asymmetries using sessions of pedalling retraining and achieve asymmetry indices similar to symmetrical cyclists. 相似文献