Impulsive fixed-time observer for linear time-delay systems     

K. Langueh  G. Zheng  T. Floquet 《Journal of The Franklin Institute》2018,355(7):3354-3366

This paper presents a fixed-time observer for a general class of linear time-delay systems. In contrast to many existing observers, which normally estimate system’s trajectory in an asymptotic fashion, the proposed observer estimates system’s state in a prescribed time. The proposed fixed-time observer is realized by updating the observer in an impulsive manner. Simulation results are also presented to illustrate the convergence behavior of the proposed fixed-time observer.  相似文献   

Hierarchical linear dynamical systems for unsupervised musical note recognition     

Goktug T. Cinar  Pedro M.N. Sequeira  Jose C. Principe 《Journal of The Franklin Institute》2018,355(4):1638-1662

In this paper we develop a new framework for time series segmentation based on a Hierarchical Linear Dynamical System (HLDS), and test its performance on monophonic and polyphonic musical note recognition. The center piece of our approach is the inclusion of constraints in the filter topology, instead of on the cost function as normally done in machine learning. Just by slowing down the dynamics of the top layer of an augmented (multilayer) state model, which is still compatible with the recursive update equation proposed originally by Kalman, the system learns directly from data all the musical notes, without labels, effectively creating a time series clustering algorithm that does not require segmentation. We analyze the HLDS properties and show that it provides better classification accuracy compared to current state-of-the-art approaches.  相似文献   

Truncation error analysis in computing of SEP and SEP floor for partially coherent receiver of MPSK signals over composite fading channels     

Zvezdan M. Marjanović  Goran T. Djordjević  Gradimir V. Milovanović 《Journal of The Franklin Institute》2018,355(2):965-980

In this paper, we analyze detection of multilevel phase-shift keying (MPSK) signals transmitted over a Gamma shadowed Nakagami-m fading channel. We derive novel analytical expression, in terms of Meijer’s G function, for Fourier coefficients of the probability density function of the received signal composite phase. Under the assumption of the imperfect reference signal extraction in the receiver, which is performed from the pilot signal, the analytical expression is derived for the symbol error probability (SEP) in the form of convergent series. The existence of the error floor is identified, and expression for its computation is provided. Mathematical proofs for convergence of Fourier series are provided for both SEP and SEP floor, and novel expressions of upper bounds for truncation errors are derived in terms of elementary mathematical functions. The convergence rate of the derived expressions is examined. Numerical results are confirmed independently by Monte-Carlo simulations.  相似文献   

Joint ventures and technology adoption: A Chinese industrial policy that backfired     

Sabrina T. Howell 《Research Policy》2018,47(8):1448-1462

To spur technology transfer, emerging market policymakers often require foreign firms to form joint ventures (JVs) with domestic firms. Through knowledge spillovers, JVs may reduce technology acquisition costs for domestic firms. Yet domestic firm rents from JVs could discourage innovation through a cannibalization effect. Which force dominates is an empirical question. I address it with novel data on China's auto sector. In response to fuel economy standards requiring firms to upgrade technology or sacrifice quality, firms with JVs reduced quality and price relative to their counterparts. Consistent with cannibalization, firms with JVs drive the negative effect.  相似文献   

Vanillic Acid in Endometrial Carcinoma: A Role for Nitric Oxide?     

Salvatore Chirumbolo  Geir Bjørklund 《Indian journal of clinical biochemistry : IJCB》2018,33(2):239-240

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Relationships between highly skilled golfers’ clubhead velocity and force producing capabilities during vertical jumps and an isometric mid-thigh pull     

Jack E. T. Wells  Andrew C. S. Mitchell  Laura H. Charalambous  Iain M. Fletcher 《Journal of sports sciences》2018,36(16):1847-1851

Whilst previous research has highlighted significant relationships between golfers’ clubhead velocity (CHV) and their vertical jump height and maximum strength, these field-based protocols were unable to measure the actual vertical ground reaction force (vGRF) variables that may correlate to performance. The aim of this study was to investigate relationships between isometric mid-thigh pull (IMTP), countermovement jump (CMJ), squat jump (SJ) and drop jump (DJ) vGRF variables and CHV in highly skilled golfers. Twenty-seven male category 1 golfers performed IMTP, CMJ, SJ and DJ on a dual force platform. The vertical jumps were used to measure positive impulse during different stretch-shortening cycle velocities, with the IMTP assessing peak force (PF) and rate of force development (RFD). Clubhead velocity was measured using a TrackMan launch monitor at a golf driving range. Pearsons correlation coefficient analyses revealed significant relationships between peak CHV and CMJ positive impulse (r = 0.788, p < 0.001), SJ positive impulse (r = 0.692; p < 0.001), DJ positive impulse (r = 0.561, p < 0.01), PF (r = 0.482, p < 0.01), RFD from 0–150 ms (r = 0.343, p < 0.05) and RFD from 0–200 ms (r = 0.398, p < 0.05). The findings from this investigation indicate strong relationships between vertical ground reaction force variables and clubhead velocity.  相似文献   

Free kick goals in football: an unlikely success between failure and embarrassment     

Søren Nørgaard Sørensen  John Rasmussen 《Sports Engineering》2018,21(2):103-114

We develop and use a numerical model to investigate the window of opportunity of free kicks in association football. The planar multibody forward dynamics model comprises a two segment leg model with joint actuations, a football, a wall and the turf. Contact mechanics is defined to model the impact of the foot and the ball’s interaction with the different elements in the environment. The optimum kick is determined using the global optimization algorithm differential evolution, requiring millions of kick simulations. The sensitivity of various solutions to parameter perturbation is investigated. It is concluded that toe kicks are theoretically superior to instep kicks, but are difficult to perform reliably. The results also show that small perturbations in parameters can lead to embarrassingly failed kicks.  相似文献   

Positive environments in youth football     

Martin K. Erikstad  Tommy Haugen  Rune Høigaard 《Sportwissenschaft》2018,48(2):263-270

Derived from Basic Psychological Needs Theory (BPNT) is the notion that the social environment may promote athletes’ basic psychological needs, which are considered important for positive development and optimal motivational functioning. The present study investigated the predictive value of perceived justice and coach feedback on basic needs satisfaction in the context of youth football. Participants were Norwegian youth football players (N?=?532) participating in a national tournament. During the initial stage of the tournament, players completed the Coaching Feedback Questionnaire, Perceived Justice in Sport Questionnaire and Basic Psychological Needs in Exercise Scale under supervision. Regression analysis showed that perceived justice and positive/instructive coaching feedback positively predicted players’ needs satisfaction, while negative feedback and non-reinforcement/ignoring mistakes were not significant predictors of needs satisfaction. Together, perceptions of justice and coach feedback explained 24% of the variance in athletes’ needs satisfaction. The findings thereby indicate that athletes’ perceptions of fairness and coach feedback are important in understanding youth athletes’ needs satisfaction.  相似文献   

eSport: Vom Präfix zum Thema für den organisierten Sport!?     

T. Wendeborn  H. J. Schulke  A. Schneider 《Sportwissenschaft》2018,48(3):451-455

In an increasingly differentiated culture of movement, play and sport as well as a more and more digitized society, the topic of eSports has been intensively discussed in recent time. The objective-categorical basics of the discussion seem to be clear only at first sight. A closer look points to the need of a differentiated cross-disciplinary discussion of the topic. It becomes clear that above all the underlying understanding of sport, the content-related demarcation as well as the social positioning contribute decisively to the perception of eSport (approval/rejection). The present article takes up the discussion with reference to the heterogeneity, heteronomy and complexity of sports and provides an alternative interpretive idea on the topic.  相似文献   

Beyond health messaging: a behavioural economics approach to increasing self-selected distance during an acute bout of cycling     

Aaron T. Piepmeier  Jennifer L. Etnier  Kimberly S. Fasczewski 《European Journal of Sport Science》2018,18(9):1264-1270

The purpose of this study was to explore the effects of the perceived purpose of exercising on the self-selected distance peddled during an acute cycling task. Participants were randomly assigned to one of three groups (health, wealth, charity). All participants watched a video emphasizing the health benefits of performing at least 30?min of daily exercise. Those in the health group were not provided any additional information. Those in the wealth group were then informed that they would earn money for every two kilometres cycled. Those in the charity group were informed that they would earn money for a charity for every two kilometres cycled. Participants were not given a time/distance limit and were instructed to cycle until they chose to stop. Analyses revealed that participants in the wealth and charity group cycled significantly farther than those in the health group (approximately twice as far). Additionally, a significant sex by group interaction showed that women cycled farther for charity while men cycled farther for wealth. These results suggest that health messages used to increase exercise behaviour may benefit from exploring how paradigms from behavioural economics influence behaviors that have relevance to public health.  相似文献