New curve sprint test for soccer players: Reliability and relationship with linear sprint     

Alberto Fílter  Jesús Olivares  Alfredo Santalla  Fabio Y. Nakamura  Irineu Loturco  Bernardo Requena 《Journal of sports sciences》2020,38(11-12):1320-1325

ABSTRACT

The speed performance is involved not only in linear sprints, but also in a wide spectrum of multi-directional movements, such as curve sprinting. Curved sprint can be defined as sprint with gradual and continuous change of direction (COD). Although ~85% of the actions performed at maximum velocity in a professional soccer league are curvilinear sprints, there is not any specific test to assess this ability. This study aimed to analyse the reliability of a new curve sprint test, and compare its results with those obtained by soccer players in linear sprint. Forty experienced soccer players performed 3 attempts of curve sprint (using the penalty arc) to right and left side (17 m), and 3 linear sprints (17 m) in two different days. The ICCs (inter-session reliability) were 0.93 for sprint curve right side (CSRS) and 0.89 for sprint curve left side (CSLS), considered “acceptable”. The CVs (intra-session reliability) were 0.87% in CSRS and 1.15% in CSLS. The coefficient of determination (R²) between linear and curve sprinting was ~35%. The association between curve sides was “very large” (r = 0.878; p < 0.01). In summary, we showed that “curve sprint test” is highly reliable, and that curvilinear and linear sprints are different and independent actions.  相似文献   

高校医学学报重点号组稿模式的建立与思考——以《山东大学学报(医学版)》为例     

顾黎  陈斌  周英智 《中国科技期刊研究》2018,29(7):739-744

【目的】 总结笔者所在期刊组织专题/专刊(以下简称“重点号”)的工作模式，为高校医学学报实现规模化组稿提供参考。【方法】 比较《山东大学学报(医学版)》2016—2017年刊发的7个重点号中的约稿及同卷期自由来稿的下载频次和被引频次，分析重点号的刊出效果。回顾重点号的组织过程，总结组稿模式，归纳要点，反思不足。【结果】 重点号约稿的篇均下载频次和被引频次分别是同卷期自由来稿的2.74倍和6.00倍，基本实现预期的约稿效果。《山东大学学报(医学版)》通过两年多的实践，建立了适合自身发展的重点号组稿模式，主编和编委的办刊热情得到了有效激发，组稿达到较大规模，办刊进入良性循环。【结论】 建立的重点号组稿模式可以明显提升期刊的学术影响力，具有较强的可操作性和可复制性；高校医学学报可以通过主动建立适合自身发展的组稿模式，突破办刊困境。  相似文献   

Observer-based decentralized control of large-scale stochastic high-order feedforward systems with multi time delays     

Liang Liu  Shengyuan Xu  Xue-Jun Xie  Bing Xiao 《Journal of The Franklin Institute》2019,356(16):9627-9645

This paper investigates the problem of observer-based decentralized control for a class of large-scale stochastic high-order feedforward systems with multi time delays. By using the homogeneous domination idea and constructing the implementable observer, the decentralized output-feedback controller design scheme is firstly proposed. Then, with the aid of stochastic time delay system stability theory, the globally asymptotically stable in probability of the closed-loop system is verified by selecting an appropriate Lyapunov–Krasoviskii functional. Finally, an example is provided to demonstrate the efficiency of the proposed design method.  相似文献   

Synergetic governing controller design for the hydraulic turbine governing system with complex conduit system     

Jianzhong Zhou  Yuncheng Zhang  Yang Zheng  Yanhe Xu 《Journal of The Franklin Institute》2018,355(10):4131-4146

The hydraulic turbine governing system plays an indispensable role in maintaining the stability of electrical power system. In this paper, synergetic control theory is introduced to enhance the regulating ability of the hydraulic turbine governing system. For the purpose of describing the characteristics of objective system and deducing the synergetic control rule, a nonlinear mathematic model of a hydraulic turbine governing system with long tail race and two surge tanks is established. Furthermore, the nonlinear characteristic of the hydraulic turbine is described by six variable partial derivatives. For further investigation, the hydraulic turbine governing system is conducted to running under load condition when its coaxial generator connects to an infinite bus. Simulation experiments have been made under both load disturbance and three-phase short circuit fault conditions to compare the dynamic performances of proposed synergetic governing controller and classic PID controller. The results indicate that the proposed synergetic governing controller is an effective alternative in normal condition and a superior one in emergency. Moreover, the robustness of synergetic governing controller has also been discussed at the end of this paper.  相似文献   

New insights in stability analysis of delayed Lotka–Volterra systems     

Xu-Guang Li  Jun-Xiu Chen  Silviu-Iulian Niculescu  Arben Çela 《Journal of The Franklin Institute》2018,355(17):8683-8697

Most of the reported Lotka–Volterra examples have at most one stability interval for the delay parameters. Furthermore, the existing methods fall short in treating more general case studies. Inspired by some recent results for analyzing the stability of time-delay systems, this paper focuses on a deeper characterization of the stability of Lotka–Volterra systems w.r.t. the delay parameters. More precisely, we will introduce the recently-proposed frequency-sweeping approach to study the complete stability problem for a broad class of linearized Lotka–Volterra systems. As a result, the whole stability delay-set can be analytically determined. Moreover, as a significant byproduct of the proposed approach, some Lotka–Volterra examples are found to have multiple stability delay-intervals. To the best of the authors’ knowledge, such a characterization represents a novelty for having some insights in the population dynamics: in some situations, a longer maturation period of species is helpful for the stability of a population system.  相似文献   

Technology adoption,consumer inattention and heuristic decision-making: Evidence from a UK district heating scheme     

Andrew Burlinson  Monica Giulietti  Giuliana Battisti 《Research Policy》2018,47(10):1873-1886

This paper contributes to the debate on the energy efficiency paradox according to which consumers fail to adopt cost-effective, energy efficient technologies over less efficient technologies and therefore fail to reduce energy consumption. Both traditional and behavioural theories are used to investigate the decision-making process of residential consumers with empirical evidence based upon a specially designed quasi-experimental survey of 784 households on the decision to connect to a district-heating system, a more energy efficient alternative to individual heating systems. The results suggest an internal discount rate of around 36 per cent for homeowners, a signal that consumers undervalue future energy costs. We also find the household’s decision to be negatively affected by years of payback up to around 7–8 years. Our findings suggest that neglecting consumer inattention and heuristics can lead to biases which cast doubt on the existence of the energy efficiency paradox. We believe that these results help to explain why some consumers are unlikely to invest in energy efficient technology, particularly those on low incomes.  相似文献   

Corrigendum to “Crossing the innovation threshold through mergers and acquisitions” [Res. Policy 44 (2015) 698–710]     

Elena Cefis  Orietta Marsili 《Research Policy》2018,47(9):1870

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A new sensor selection scheme for Bayesian learning based sparse signal recovery in WSNs     

Bo Xue  Linghua Zhang  Weiping Zhu  Yang Yu 《Journal of The Franklin Institute》2018,355(4):1798-1818

In this paper, we address the issue of sparse signal recovery in wireless sensor networks (WSNs) based on Bayesian learning. We first formulate a compressed sensing (CS)-based signal recovery problem for the detection of sparse event in WSNs. Then, from the perspective of energy saving and communication overhead reduction of the WSNs, we develop an optimal sensor selection algorithm by employing a lower-bound of the mean square error (MSE) for the MMSE estimator. To tackle the nonconvex difficulty of the optimum sensor selection problem, a convex relaxation is introduced to achieve a suboptimal solution. Both uncorrelated and correlated noises are considered and a low-complexity realization of the sensor selection algorithm is also suggested. Based on the selected subset of sensors, the sparse Bayesian learning (SBL) is utilized to reconstruct the sparse signal. Simulation results illustrate that our proposed approaches lead to a superior performance over the reference methods in comparison.  相似文献   

Nonlinear optimal control with disturbance rejection for asteroid landing     

Shen Kang  Jianan Wang  Chaoyong Li  Jiayuan Shan 《Journal of The Franklin Institute》2018,355(16):8027-8048

This paper presents an optimal solution to asteroid soft landing problem, on the base of $\theta ?D$ control technique and disturbance rejection mechanism. The control objective is to drive a probe to reach the surface of an asteroid with a desirable line-of-sight angle and zero velocity, eliminating the influence of external disturbance. Firstly, elementary $\theta ?D$ technique is applied in the absence of disturbance to tackle the nonlinear optimal control problem. Secondly, the disturbance is estimated in the fast-estimation framework with explicitly bounded estimation error. Afterwards, an integrated control protocol is presented in a feed-forward structure by the aid of an additional variable-structure term to ensure stability under time-varying disturbance. Simulation results of the proposed approach compared with the results of elementary $\theta ?D$ method and robust $\theta ?D$ method are presented at the end of this paper, demonstrating the effectiveness of the proposed control protocol.  相似文献   

Chattering-free full-order recursive sliding mode control for finite-time attitude synchronization of rigid spacecraft     

Zhuoyue Song  Chao Duan  Jianan Wang  Qinghe Wu 《Journal of The Franklin Institute》2019,356(2):998-1020

This paper investigates a quaternion-based finite-time cooperative attitude synchronization and tracking of multiple rigid spacecraft with a virtual leader subject to bounded external disturbances. Firstly, the communication network between followers is assumed to be an undirected graph and every follower can get a direct access to the virtual leader, by using two neighborhood attitude error signals, a novel chattering-free recursive full-order sliding mode control algorithm is proposed such that all follower spacecraft synchronize to the virtual leader in finite time. In the proposed algorithm, the sliding mode surface is constructed by two layers of sliding mode surfaces, which are called as the outer and the inner sliding mode surfaces. To achieve finite-time performance of sliding mode dynamics, the outer sliding mode surface is designed as a terminal sliding mode manifold, and the inner one is designed as a fast nonsingular terminal sliding mode manifold, respectively. Then, to reduce the heavy communication burden, a distributed recursive full-order sliding mode control law is designed by introducing a distributed finite-time sliding mode estimator such that only a subset of the group members has access to the virtual leader. Finally, a numerical example is illustrated to demonstrate the validity of the proposed results.  相似文献