Adaptive Backstepping Controller Design for Stochastic Jump Systems

In this technical note, we improve the results in a paper by Shi et al., in which problems of stochastic stability and sliding mode control for a class of linear continuous-time systems with stochastic jumps were considered. However, the system considered is switching stochastically between different subsystems, the dynamics of the jump system can not stay on each sliding surface of subsystems forever, therefore, it is difficult to determine whether the closed-loop system is stochastically stable. In this technical note, the backstepping techniques are adopted to overcome the problem in a paper by Shi et al.. The resulting closed-loop system is bounded in probability. It has been shown that the adaptive control problem for the Markovian jump systems is solvable if a set of coupled linear matrix inequalities (LMIs) have solutions. A numerical example is given to show the potential of the proposed techniques

The Impact of the Risk Perception of COVID-19 PANDEMIC on College Students' Occupational Anxiety: The Moderating Effect of Career Adaptability

In order to understand the changes in college students' risk perception and occupational emotion under major public health events and to explore the influencing factors of college graduates' employment guidance, 578 college students were surveyed by questionnaire to explore the impact of the risk perception of COVID-19 pandemic on college students' occupational anxiety and its internal mechanisms, and to analyze the mediating role of psychological resilience in the impact and the moderating role of career adaptability. The results showed that: (1) there is a significant positive correlation between the risk perception of COVID-19 pandemic and occupational anxiety; there is a significant negative correlation between risk perception and psychological resilience; there is a significant negative correlation between the psychological resilience and occupational anxiety. (2) Psychological resilience plays a mediating role between risk perception and occupational anxiety. (3) Career adaptability plays a negative moderating role between the risk perception of COVID-19 pandemic and occupational anxiety. These results showed that the risk perception of COVID-19 pandemic not only directly aggravates college students' occupational anxiety, but also indirectly affects occupational anxiety through psychological resilience; Career adaptability significantly alleviats the incremental effect of the risk perception of COVID-19 pandemic on college students' occupational anxiety. This paper has positive enlightenment on how to improve the employability of college students and alleviate their employment anxiety during major public health events

Coherent control of Snell's law at metasurfaces

It was recently demonstrated that the well-known Snell's law must be corrected for phase gradient metasurfaces to account for their spatially varying phase, leading to normal and anomalous transmission and reflection of light on such metasurfaces. Here we show that the efficiency of normal and anomalous transmission and reflection of light can be controlled by the intensity or phase of a second coherent wave. The phenomenon is illustrated using gradient metasurfaces based on V-shaped and rectangular apertures in a metal film. This coherent control effect can be exploited for wave front shaping and signal routing

Theoretical research of dynamic characteristics of Tc bearing of measurement while drilling

In this paper, through analyzing Tc bearing by the theory of Hydrodynamic lubrication, the unsteady Reynolds equation of Tc bearing under the dynamic-state condition is initially established. The formula of Tc bearing’s liquid-film dimensionless stiffness coefficient and damping coefficient is derived. Furthermore, two kinds of the distribution curves of Tc bearing’s liquid-film dimensionless stiffness coefficient, damping coefficient against Tc bearing’s eccentricity ratio and width-diameter ratio are displayed respectively, and the stability criterion of liquid film is worked out and the angular speed of instability of bearing shaft is calculated. Overall, conclusions are drawn: downhole system improves the entire system’s stability by enhancing the stiffness of bearing shaft itself. The improvement of the stability of bearing shaft itself, which can be done by altering the structure of Tc bearing and adopting better spiral flutes and ellipse groove can strengthen the whole system’s stability. The high width-diameter ratio of Tc bearing increases the liquid film’s stiffness coefficient and damping coefficient of Tc bearing. The rotational rate of rotary table is lower than half of that of the supporting system of Tc bearing

An ant colony optimization method for generalized TSP problem

Focused on a variation of the euclidean traveling salesman problem (TSP), namely, the generalized traveling salesman problem (GTSP), this paper extends the ant colony optimization method from TSP to this field. By considering the group influence, an improved method is further improved. To avoid locking into local minima, a mutation process and a local searching technique are also introduced into this method. Numerical results show that the proposed method can deal with the GTSP problems fairly well, and the developed mutation process and local search technique are effective

Environmental pollution liability insurance and green innovation of enterprises: Incentive tools or self-interest means?

The existing theoretical research on environmental liability insurance mainly focuses on system construction, development status and other aspects, and mainly consists of normative research, with relatively little empirical research. This paper uses empirical research methods to explore the impact of environmental liability insurance on the green innovation of enterprises and examines the driving role of environmental liability insurance in green innovation from the perspective of green governance. This paper, based on the list of enterprises purchasing environmental pollution liability insurance (EPLI) as published by the Ministry of Ecology and Environment, explores the impact of EPLI on the green innovation of enterprises. It is found that purchasing EPLI can significantly improve the green innovation of enterprises. The effect path test shows that EPLI can promote the green innovation of enterprises by relaxing financing constraints and reducing agency costs. The heterogeneity scenario test shows that compared with non-state-owned enterprises, non-heavily polluting enterprises, and enterprises in regions with a lower intensity of environmental regulation, EPLI plays a stronger role in the promotion of green innovation of state-owned enterprises, heavily polluting enterprises and enterprises in regions with a higher intensity of environmental regulation. In addition, it is found that the promotion effect of EPLI on green innovation is mainly reflected in the significant improvement of high-quality green innovation and the optimization of the structure of the green patent output. This paper affirms the positive role of EPLI on the green operations of enterprises and provides empirical evidence that green insurance serves the development of the green innovation of enterprises