•Compared with the existing results, both the attacker and the defender are considered under a game-theoretic framework. Besides, the energy constraints are introduced to limit the attack times and ...encryption rank, respectively.•Different from the related works, the worst-case attack schedules and parameters are designed collaboratively to maximize the impact of the stealthy attacks.•The proposed optimal encryption strategies increase the difficulty of launching stealthy attacks and diminish the impact of attacks simultaneously.
This paper investigates the problem of encryption strategy for cyber-physical systems based on the Stackelberg game theoretic model with a stealthy attacker and a defender. In order to defend against the attacker who can inject false data without being detected by the detector, an encryption mechanism is proposed. Different from the existing results, the energy constraints are introduced to limit the attack times of attacker and encryption rank of defender, respectively. Under the framework of Stackelberg game, the optimal encryption strategies against worst-case stealthy attacks are designed for accumulative and terminal estimation performance, which increase the difficulty of launching stealthy attacks and diminish the impact of attacks on system performance simultaneously. Finally, simulation examples are provided to demonstrate effectiveness of the proposed strategy.
The tactical formation has been shown to influence the match performance of professional soccer players. This study aimed to examine the effects of in-game changes in tactical formation on match ...performance and to analyze coach-specific differences. We investigated three consecutive seasons of an elite team in the German Bundesliga which were managed by three different coaches, respectively. For every season, the formation changes that occurred during games were recorded. The match performance was measured on a team level using the variables “goals,” “chances,” and “scoring zone” entries (≙successful attacking sequence) for the own/opposing team. Non-parametric tests were used to compare the 10 min before with the 10 min after the formation change, as well as games with and without formation change. In the 10 min after the formation change, the team achieved more goals/chances/scoring zone entries than in the 10 min before the formation change (mean ES = 0.52). Similarly, the team conceded fewer opposing goals/chances/scoring zone entries in the 10 min after the formation change (mean ES = 0.35). Furthermore, the results indicate that the success of the respective formation change was dependent on the responsible coach. Depending on the season, the extent of the impacts varied (season 1: mean ES = 0.71; season 2: mean ES = 0.26; and season 3: mean ES = 0.22). Over all three seasons, the formation changes had a positive effect on the match performance of the analyzed team, highlighting their importance in professional soccer. Depending on the season, formation changes had varying impacts on the performance, indicating coach-specific differences. Therefore, the quality of the formation changes of the different coaches varied. The provided information can support coaches in understanding the effects of their in-game decisions.
The aims of this study were to analyze the peak physical demands in elite futsal by quantifying the most demanding scenarios of match play and to identify the differences between playing positions ...(defenders, wingers, and pivots) and the seasonal trend for five different rolling average time windows (30, 60, 120, 180, and 300 s). The most demanding scenarios of external load from distance, speed, acceleration, and deceleration variables were obtained from 14 elite futsal players using a local positioning system during 15 official matches in the premier Spanish Futsal League (2018-2019 season). The results showed an extremely large effect of the time window for all dependent variables in all positional groups. Another important finding of this study was that, in regard to the seasonal trend, only defenders reported clear moderate-large positive trends for high-speed running (>18 km⋅h
) efforts, high-acceleration efforts, and high-deceleration efforts. Finally, moderate-large individual differences in player means for all dependent variables and clear differences between games for most dependent variables were found, suggesting how likely contextual factors may exert an influence on how "demanding" the most demanding scenarios are. The findings of this study provide coaches and strength and conditioning coaches further knowledge of the peak physical demands in elite futsal competition. This valuable information may lead to a more precise position-specific training prescription.
Sampling frequency of microsensors that measure the position of the players in team sports is a variable that could affect the accuracy of the measurement. The aim of the present study was to assess ...the impact of the sampling frequency on the measurement of a collective tactical behaviour variable: the total area (TA). Sixteen young U16 male soccer players participated in the study. They carried out three controlled tasks. Tactical variable was measured by a radio ultra-wide band technology (IMU; WIMU PROTM, RealTrack Systems, Almeria, Spain). For TA different sampling frequencies were applied (i.e. 1 Hz, 2 Hz, 4 Hz and 10 Hz). Trivial differences (p 0.05) were found between the TA values across the different amounts of inserted data per second across Task 1 (ES= 0.04-0.08), Task 2 (ES= 0.01-0.09) and Task 3 (ES= -0.03-0.04). Also High to perfect ICCs (0.91-1) and linear correlations (r= 0.961-1; p 0.01) were found among the TA values obtained through all sampling frequencies. The sampling frequency (i.e. 1 Hz, 2 Hz, 4 Hz and 10 Hz) does not affect the measurement of total area during tactical behaviour analysis but does significantly affect the change in centroid position measurement. Thus, it is recommended the use of 1 Hz to measure TA, but further studies should analyse the impact of lower than 1 Hz and greater than 10 Hz sampling frequencies to measure this collective tactical behavior.
•Focusing on the micro perspective, evolutionary game theory is employed to unpack the ‘black box’ of the polycentric waste governance(PWG) at the community level.•Four potential ESS in the ...tripartite evolutionary game model have been identified after elaborating on eight equilibrium points with seven scenarios.•Transmission effect exists in the interplays among three polycentric waste governance stakeholders.•Potential dilemmas, including “tragedy of the commons” and market failure have been identified in PWG.
Polycentric waste governance (PWG) is novel approach to handling the increasing waste by embracing broader stakeholders, compared to isolated public service. This paper sought to unpack the strategic coevolution mechanism of PWG's main stakeholders at community level by evolutionary game theory. Our findings highlighted that “Recycler” ultimately chooses active participation while “Community” and “Householder” are on the fence. In addition, the transmission effect existed in the interplays among three agents. Our modeling analysis also echoed the “tragedy of the commons” and market failure in the theoretical landscape of PWG. Thus, the countermeasures, including community engagement, public perception, innovative “Government-Market” cooperation mode, etc., deserved attention. Uncovering the ‘black box’ of the PWG model, an enhanced understanding of governance actors’ strategic evolution mechanism for improving the PWG theory is obtained thus far. The research findings would expect to enlighten the practice of PWG in reality, thereby mitigating the dilemma of “waste siege.”
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The objective of this research was to analyze the importance of maintaining the net position in men’s and women’s professional padel. The data sample was drawn from 2,756 padel rallies (n = 1,434 ...men’s and n = 1,322 women’s) in matches played during the 2021 season of the World Padel Tour circuit. The results showed that there was no net exchange in 50.7% of the women’s rallies, while in 65.9% of men’s rallies, the servers kept the net. Due to their physical advantages, men servers had more opportunities to finish the rally at the net than women servers, giving them more opportunities to win the rally. However, when either men or women receivers finished the rally at the net, they had more opportunities to win the rally. In addition, both men and women tended to end the rallies with a winner when they were in the net zone and with an error when they were at the back of the court. These findings suggest that wins in padel are closely related to time spent at the net.
Characterization refers to the process of attributing character traits to narrative entities called ‘characters'. While there is a long tradition of characterization theory in literary studies, the ...topic has not been examined extensively in game research. Based on insights from literary, film, and game studies, this article creates a theoretical model of how ‘character,' or character traits, can be attributed in video games, and offers a methodological vocabulary for further character(ization) research. First, this paper synthesizes the tradition of characterization research in literary studies. Second, it identifies three participants in video game characterization (developers, actors, and players) and introduces the concept of ergodic characterization to describe those instances in which players produce nontrivial characterization efforts. Finally, the framework itself is presented through application to various game titles, and several answers to methodological problems within game characterization analysis are suggested.
Current studies have reported high accuracy in global positioning system (GPS) and recently developed ultra-wideband (UWB)-based tracking systems for monitoring time - motion patterns. The accuracy ...and reliability of both systems may be different in tactical analysis application, an aspect that has never been studied previously. The aims of the present study were: (i) to determine and compare the accuracy of GPS and UWB technologies in soccer players' positions (ii) to compare the tactical application of both systems. Following institutional ethical approval and familiarisation, 14 well-trained soccer players performed tests around five courses: (a) field perimeter, (b) halfway line, (c) centre circle, (d) perimeter of the penalty area, and (e) semicircle penalty area. Also, a small-sided game was played monitored with WIMUPRO™ to determine real and practical differences in accuracy of both systems in tactical analysis. For the GPS, the mean absolute error (N = 9445) of "x" and "y" coordinates was 41.23 ± 17.31 cm and 47.6 ± 8.97 cm, respectively. For UWB, it was 9.57 ± 2.66 cm and 7.15 ± 2.62 cm. The results of the "x" and "y" accuracy comparison were significantly lower in all cases (p < 0.05) with an ES of 0.78 and 0.95, respectively. In a real practical application, the differences of both systems reached 8.31% in typical tactical variables (ES = 0.11). In contrast to GPS-10Hz, UWB WIMUPRO™-20 Hz has been demonstrated to be an acceptable technology to estimate the position of players on the pitch with high accuracy and be a useful, automatic, and portable instrument for tactical analysis measurement.
The aim of this study was to assess center of mass (COM) acceleration and movement during change of direction (COD) maneuvers during a competitive soccer game to elucidate situation-specific demands ...of COD performance. This information can assist in developing soccer-specific tests and training methods. Fifteen elite-level female youth soccer players were tracked for one game with inertial measurement units (IMU) attached to the lower back. COD movements in combination with situational patterns were identified using high-speed video. LASSO regression was used to identify the most important predictors associated with higher vertical peak accelerations (PAv) of the COM during COD movements. COD angle, running speed, contact, and challenge from the opposition were identified as important features related to higher PAv. This study adds to the literature on the demands of COD performance in soccer match-play. The unique approach with game-specific situational data from female youth players provides increased insight into the game-demands of COD and agility performance. PAv in games was higher with larger COD angles, increased running speed, or with contact when the player was challenged by the opposition. A larger study including more games is warranted to increase confidence in using these variables as a basis for training or testing agility.
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