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981.
L. Luque-Vega B. Castillo-Toledo Alexander G. Loukianov 《Journal of The Franklin Institute》2012,349(2):719-739
This paper presents the design of a controller based on the block control technique combined with the super twisting control algorithm for trajectory tracking of a quadrotor helicopter. A first order exact differentiator is used in order to estimate the virtual control inputs, which simplifies the control law design. In addition, the wind parameter resulting from the aerodynamic forces is also estimated in order to ensure robustness against these unmatched perturbations. The stability and finite time convergence of the exact differentiator have been recently proved by means of Lyapunov functions, and therefore the stability analysis of the proposed controller has been carried out along the same lines. The performance and effectiveness of the proposed controller are tested in a simulation study taking into account external disturbances. 相似文献
982.
Appropriate intellectual property protection and economic growth in countries at different levels of development 总被引:1,自引:0,他引:1
This paper examines how the role of patents and utility models in innovation and economic growth varies by level of economic development. Using a panel dataset of over 70 countries, we find that patent protection is an important determinant of innovation and that patentable innovations contribute to economic growth in developed countries, but not in developing. Instead, in developing economies, a minor form of intellectual property rights (IPRs) - namely utility models - is conducive to innovation and growth, controlling for other factors. Using Korean firm level data as a case study, we find that utility model innovations contribute to firm performance when firms are technologically lagging and that those minor innovations can be a learning device and thus a stepping stone for developing more patentable inventions later on. Upon reaching higher levels of technological capabilities, firms become more reliant upon patents and less on utility models. Thus the lesson here is that patent protection enhances innovation and economic growth in countries where the capacity to conduct innovative research exists. Where this capacity is weaker, a system that provides incentives to conduct minor, incremental inventions is more conducive to growth. The significance of this paper is to emphasize the importance not just of the strength of IPRs but of the appropriate type of IPRs for economic development. 相似文献
983.
Firms’ genetic characteristics and competence-enlarging strategies: A comparison between academic and non-academic high-tech start-ups 总被引:1,自引:0,他引:1
Massimo G. Colombo Evila Piva 《Research Policy》2012,41(1):79-92
This paper argues that academic high-tech start-ups exhibit peculiar “genetic characteristics” that leave an enduring imprint on firm development. We formulate a series of hypotheses on the effects of such genetic characteristics on the post-entry strategies that academic high-tech start-ups adopt to enlarge their initial competence endowments. In the empirical section, we use matched-pair statistical techniques and run several regressions to test the theoretical hypotheses. Our findings contribute to the literature on the antecedents of the strategies adopted by academic high-tech start-ups. They also allow us to derive implications for academic entrepreneurs, university managers and policy makers. 相似文献
984.
环境社会学与自然资源社会学是关于社会与自然界相互关系的两个主要研究传统。目前关于这两个分支学科的讨论主要是局限在美国学术界内,而其对于其它国家环境和社会研究学科建设的借鉴作用尚未引起足够的重视,这正是本文在中国的学术背景中提出环境社会学与自然资源社会学相互融合问题的原因所在。环境社会学在中国正处于重要的学科建设阶段,垮学科的中国环境与资源社会学在投身中国"资源节约型、环境友好型"社会的建设中完全有希望实现环境社会学与自然资源社会学的实质融合。 相似文献
985.
Williams G Irwin G Kerwin DG Newell KM 《Sports biomechanics / International Society of Biomechanics in Sports》2012,11(1):20-33
The purpose of this study is to provide evidence of technique changes during learning a sports-specific skill, the looped bar longswing (LLS). Thirteen male participants with no previous high bar experience took part in a training study. Kinematic data were collected using a CODA motion analysis system (200 Hz) during eight weekly testing sessions. Analyses focused on the amplitude of swing and the functional phase (FP) actions, defined by the rapid flexion to extension of the shoulders and extension to flexion of the hips as the performer passed through the lower vertical. Three groups were identified based on the number of sessions it took each participant to perform the LLS (G1: most successful, G2: intermediate, and G3: least successful). All participants were able to significantly increase swing amplitude over the training period (p < 0.05). For each participant the hip FP started significantly: later for G1, earlier for G2, and did not change for G3. Extension actions at the shoulders were dissimilar to those reported for elite gymnasts performing the longswing. The FP of the hips provides a mechanism to distinguish between the learners of different skill levels. The study has provided support for a single-subject design when investigating technique changes during learning. 相似文献
986.
Michael J. Shoemaker Amy B. Curtis Eric Vangsnes Michael G. Dickinson 《Cardiopulmonary Physical Therapy Journal》2012,23(3):5-15
Purpose
The purpose of the present review was to use existing, published data to provide an estimate of the amount of change in six-minute walk test distance (Δ6MWT) that represents a clinically meaningful change in individuals with chronic heart failure (CHF).Methods
The present review included two separate literature searches of the CINAHL and Medline databases for articles that: (1) reported the intraclass correlation coefficient (ICC) of the 6MWT in individuals with CHF, and (2) used the 6MWT along with either aerobic capacity or health-related quality of life (HRQL) as study endpoints in randomized controlled trials (RCTs) of exercise-based intervention for individuals with CHF. The ICCs were used to calculate the minimum detectable difference (MDD) at the 95% confidence interval for each included study. The Δ6MWT associated with aerobic capacity and HRQL within-group effect sizes for the intervention and control groups in each included RCT was analyzed using receiver operating characteristic (ROC) curves.Results
Thirteen articles reported the ICC for the 6MWT. The mean (standard deviation) MDD calculated based on these data was 43.1(16.8) m. Eighteen RCTs measured the 6MWT and either aerobic capacity and/or HRQL. A Δ6MWT of 40–45 m was associated with at least moderate aerobic capacity and HRQL effect sizes in the intervention groups. The Δ6MWT thresholds that discriminated between intervention and control groups using ROC curves revealed the following sensitivity/specificity for the respective thresholds: 19 m, 94.4/83.3%, 32 m, 83.3/94.4%, and 48 m 44.4/100% (AUC = .935, p = .009, CI95% .855, 1.015).Conclusions
A Δ6MWT of approximately 45 m appears to exceed measurement error and be associated with significant changes in either aerobic capacity and/or HRQL.Key Words: heart failure, six-minute walk test, clinically meaningful change, minimum detectable difference 相似文献987.
Delphinus EM Sayers MG 《Sports biomechanics / International Society of Biomechanics in Sports》2012,11(2):212-222
Putting proficiency is a key determinant of golfing success and yet minimal biomechanical research has been published on this important skill. Little is known about the motion and coordination of the pelvis and trunk during the putting motion. The purpose of this study was to present detailed three-dimensional (3D) kinematic profiles of the pelvis and trunk during the putting motion, and to determine if differences in kinematics exist between proficient and non-proficient golfers. A 3D analysis (100 Hz) was conducted on 10 single figure handicap golfers using a six-camera motion capture system. Participants completed 18 putts (2 m) towards a cup in an indoor facility and were subsequently divided into two groups based on putting proficiency (Proficient: >79%; Non-proficient: <79%). Variables assessed were the linear movements of the centre of mass (COM) and head, and the angular movements of the pelvis and trunk. Effect size statistics showed that the Proficient putters tended to move predominantly in the frontal plane (towards the target), while the non-proficient putters moved more sagittally. In addition, the Non-proficient putters recorded greater movement variability. The implications of this study suggest that putting proficiency is enhanced when the COM moves towards the target. 相似文献
988.
新年伊始,先给各位读者拜个晚年,祝读者们在新的一年里步步高升,心想事成!
除了平常的1V1外,2V2赛事也引起了许多war3爱好者的关注,一些赛事例如一周一赛的双打杯,每周都有许多玩家自行组队‘基’情参赛,而在职业圈里也有Beiieve这位韩国大神参加,这也让比赛不缺乏亮点,而每周的皇冠录像中更是频频出现精彩的2V2录像,这也使得2V2比赛得到了广大玩家进一步的关注,也让War3所带给大家的魅力得以传承。 相似文献
989.
本次经典回顾为大家带来的是06年时的一场天王对决,比赛双方分别是巫妖王Sweet和兽王Grubby。在那个剑圣还没有被开发出来的年代里,兽人部落的首发英雄多半都是当时的领袖FS(先知),其独有的幽灵狼在前期能给予对手强有力的压制效果,而第二技能闪电链则是部落仅有的AOE神技之一,在当时配合上老牛的冲击波,威力十足,不过在当时几近无敌的吹风流和Sky一波流面前,兽人部落的抬头之日还没有到来。另一边亡灵当时的情况则是 相似文献
990.