浅谈物理教学中学生提问能力的培养

物理教学中学生提出问题能力的培养很重要,我们应从改变教学模式,启迪问题思维,激发学生兴趣发现问题,塑造自由氛围,鼓励学生提问等方面着手。     

Exertional Heat Stroke of Max Gilpin; A Preventable Death

ABSTRACT

Exertional heat stroke (EHS) is a medical emergency whose likelihood in sport settings is often contingent on environmental factors, team policies, coaching strategies, and broader cultural expectations. Moreover, when it occurs, it requires immediate recognition, proper management, and care to optimize chances of survival or recovery without long-term sequelae. Max Gilpin, a secondary school American football player from Louisville, Kentucky, suffered an EHS during a football practice in August 2008, an event that resulted in his death. The purpose of this article is to use interdisciplinary methods to identify key factors that contributed to this tragedy so that similar situations do not happen again. It concludes that within a culture of inclusive gender norms and care, efforts should be made to have appropriate onsite medical expertise available to develop and implement best practices for the prevention, management, and treatment of EHS, along with coaching education specific to medical emergencies in sport and physical activity (such as EHS). This will create an environment that promotes health and safety for all student athletes participating in sport at the secondary school level.     

Home advantage in judo: A study of the world ranking list

Abstract

In 2009, the International Judo Federation established a ranking system (RS) to classify athletes and to distribute the competitor quotas of the Olympic Games. However, the RS does not consider the home advantage. This issue has not been studied in judo, and its implications for the RS have not been determined. The objective was to verify the home advantage in judo in terms of winning a medal or the number of matches won. Therefore, 25 competitions that computed points for the RS in 2009 were analysed. Logistic regression analysis and the Poisson generalised linear model were used for the analyses, which included the relative quality of the athletes. The sample was composed only of athletes who had competed both at home and away. The odds ratio for winning medals was higher for athletes who competed at home for both males and females. The association between the number of matches won and competing at home was significant only for the male athletes. The home advantage was observed in the competitions that used the judo RS. Thus, it is likely that athletes from countries that host competitions using the RS have an advantage in terms of obtaining their Olympic classification.     

Lunar spacecraft powered descent control using higher-order sliding mode techniques

Robust performance of a flight control system in the presence of parametric uncertainty and external disturbances is of paramount importance to a successful planetary exploration program. The present research is concerned with the design of an autopilot that uses high-order sliding mode (HOSM) control principles so as to enhance the robustness properties of a lunar landing vehicle during the approach phase of powered descent. The design technique is applied to a high-fidelity simulation of the Apollo Lunar Module (LM). The design efficiently utilizes both the reaction control system (RCS) actuators and the severely rate-limited gimbal drive actuator (GDA) to effect smooth detection and compensation of sensed angular acceleration disturbances about the vehicle's control axes. The integration of a HOSM control law for the RCS effectors with a HOSM disturbance observer is shown to provide performance comparable to that of the heritage autopilot and may also avoid some difficulties encountered in the Apollo flights. Performance is maintained with the controller implemented in discrete time in the presence of a realistic vehicle and sensor model, demonstrating a unique application of sliding mode control to a complex aerospace system.     

Coordinated decentralized sliding mode MRAC with control cost optimization for a class of nonlinear systems

In this paper, we develop an approach for solving the problem of sliding mode decentralized adaptive state-feedback tracking with continuous control actions for a class of uncertain nonlinear dynamical systems. In addition to the traditional asymptotic zero error tracking specification in the sliding mode decentralized model reference adaptive control (MRAC) problem formulation, here an additional requirement is specified explicitly in the problem statement. The tracking objective is described by a set of admissible reference trajectories, called a performance tube. The input signal to the reference model, selected within specified bounds, is used as a design parameter. The best reference trajectory is found by solving an additional optimization problem whose criterion penalizes the variance of the control signal.     

Quadrotor vehicle control via sliding mode controller driven by sliding mode disturbance observer

Over the last decade, considerable interest has been shown from industry, government and academia to the design of Vertical Take-Off and Landing (VTOL) autonomous aerial vehicles. This paper uses the recently developed sliding mode control driven by sliding mode disturbance observer (SMC-SMDO) approach to design a robust flight controller for a small quadrotor vehicle. This technique allows for a continuous control robust to external disturbance and model uncertainties to be computed without the use of high control gain or extensive computational power. The robustness of the control to unknown external disturbances also leads to a reduction of the design cost as less pre-flight analyses are required. The multiple-loop, multiple time-scale SMC-SMDO flight controller is designed to provide robust position and attitude control of the vehicle while relying only on knowledge of the limits of the disturbances. Extensive simulations of a 6 DOF computer model demonstrate the robustness of the control when faced with external disturbances (including wind, collision and actuator failure) as well as model uncertainties.     

Launch vehicle attitude control using sliding mode control and observation techniques

In determining flight controls for launch vehicle systems, several uncertain factors must be taken into account, including a variety of payloads, a wide range of flight conditions and different mission profiles, wind disturbances and plant uncertainties. Crewed vehicles must adhere to human rating requirements, which limit the angular rates. Sliding mode control algorithms that are inherently robust to external disturbances and plant uncertainties are very good candidates for improving the robustness and accuracy of the flight control systems. Recently emerging Higher Order Sliding Mode (HOSM) control is even more powerful than the classical Sliding Mode Controls (SMC), including the capability to handle systems with arbitrary relative degree. This paper proposes sliding mode launch vehicle flight controls using classical SMC driven by the sliding mode disturbance observer (SMDO) and higher-order multiple and single loop designs. A case study on the SLV-X Launch Vehicle studied under a joint DARPA/Air Force program called the Force Application and Launch from CONtinental United States (FALCON) program is shown. The intensive simulations demonstrate efficacy of the proposed HOSM and SMC-SMDO control algorithms for launch vehicle attitude control.     

Emotional and motivational relationship of elementary students to mathematical problem-solving: a person-centered approach

European Journal of Psychology of Education - Recent literature has shown that achievement emotions, their regulation, and perceived competence play a compelling role in mathematics learning and...