艺术生态平衡的特性及失衡现象透视

艺术生态系统是一种社会生态系统,但它与自然生态系统一样,也存在着平衡与失调的问题。艺术生态平衡的特性,表现在生态结构和生态功能的和谐性;生态系统的自维持、自调控性;生态系统的开放性;生态种类的多样性。艺术生态失衡的主要标志是,结构生态失衡和功能生态失衡。对照这种特性和标志,透视艺术结构生态和功能生态失衡状况。

论艺术生态系统的生态特征

艺术生态系统除了具有一般系统所具有的共同特征外,还具有时空概念性、群落生态性、生态演替性、自调控性、"人工性"等生态特征。研究艺术生态系统的生态特征,对于人类管理艺术生态系统、保持艺术生态系统的平衡、充分发挥艺术的生态功能具有一定的价值和意义。

艺术生态系统的平衡维护

运用生态平衡理念指导艺术的发展,尊重艺术生态系统的自维持和自调控性,保持艺术生态系统的多样性和开放性,加强管理,维护艺术生态系统的平衡。

Variation of alkaline characteristics in bauxite residue under phosphogypsum amendment

Aiming at alkaline problem of bauxite residue,this work focused variation of alkaline characteristics in bauxite residue through phosphogypsum treatment.The results demonstrated that the pH of bauxite residue reduced from initial 10.83 to 8.70 when 1.50 wt%phosphogypsum was added for 91 d.The removal rates of free alkali and exchangeable sodium were 97.94%and 75.87%,respectively.Meanwhile,significant positive correlations(P<0.05)existed between pH and free alkali,exchangeable sodium.The effect of free alkali composition was CO3^2–>OH^–>AlO2^–>HCO3^–.In addition,alkaline phase decreased from 52.81%to 48.58%and gypsum stably presented in bauxite residue which continuously provided Ca^2+to inhibit dissolution of combined alkali.Furthermore,phosphogypsum promoted formation of macroaggregate structure,increased Ca^2+,decreased Na+and Al^3+on the surface of bauxite residue significantly,ultimately promoting soil formation in bauxite residue.

Predictive current control system of PMSM based on LADRC

For a permanent magnet synchronous motor(PMSM)model predictive current control(MPCC)system,when the speed loop adopts proportional-integral(PI)control,speed regulation is easily affected by motor parameters,resulting in the inability to balance the system robustness and dynamic performance.A PMSM optimal control strategy combining linear active disturbance rejection control(LADRC)and two-vector MPCC(TV-MPCC)is proposed.Firstly,a mathematical model of a PMSM is presented,and the PMSM TV-MPCC model is developed in the synchronous rotation coordinate system.Secondly,a first-order LADRC controller composed of a linear extended state observer and linear state error feedback is designed to reduce the complexity of parameter tuning while linearly simplifying the traditional active disturbance rejection control(ADRC)structure.Finally,the conventional PI speed regulator in the motor speed control system is replaced by the designed LADRC controller.The simulation results show that the speed control system using LADRC can effectively deal with the changes in motor parameters and has better robustness and dynamic performance than PI control and similar methods.The system has a fast motor speed response,small overshoot,strong anti-interference,and no steady-state error,and the total harmonic distortion is reduced.

Linear and nonlinear control of a robotic excavator

Various control systems for a robotic excavator named LUCIE (Lancaster University Computerized and Intelligent Excavator),were investigated. The excavator is being developed to dig trenches autonomously. One stumbling block is the achievement of adequate,accurate,quick and smooth movement under automatic control. Here,both classical and modern approaches are considered,including proportional-integral-derivative (PID) control tuned by conventional Zigler-Nichols rules,linear proportional-integral-plus (PIP) control,and a novel nonlinear PIP controller based on a state-dependent parameter (SDP) model structure,in which the parameters are functionally dependent on other variables in the system. Implementation results for the excavator joint arms control demonstrate that SDP-PIP controller provides the improved performance with fast,smooth and accurate response in comparison with both PID and linearized PIP control.

Using Adaptive Gain Scheduling LQR Method Control of Arm Driven Inverted Pendulum System Based on PIC18F4431

The arm driven inverted pendulum system is a highly nonlinear model, muhivariable and absolutely unstable dynamic system so it is very difficult to obtain exact mathematical model and balance the inverted pendulum with variable position of the ann. To solve this problem, this paper presents a mathematical model for arm driven inverted pendulum in mid-position configuration and an adaptive gain scheduling linear quadratic regulator control method for the stabilizing the inverted pendulum. The proposed controllers for arm driven inverted pendulum are simulated using MATLAB-SIMULINK and implemented on an experiment system using PIC 18F4431 mieroeontroller. The result of experiment system shows the control performance to be very good in a wide range stabilization of the arm position.

Autonomy in Scaffolding as Learning in Teacher-Student Negotiation of Meaning in a University EFL Classroom

Based upon sociocultural theory, this study investigates the dynamics of the teacher＇s roles and learner autonomy in the process of scaffolding in teacher-student negotiation of meaning in an EFL classroom, The participants were 25 undergraduate students and a Chinese teacher of English at a university in China. The teacher-student dialogue was the central mechanism mediating the construction of negotiation of meaning and form in language learning. The analysis of classroom discourse and the teacher＇s retrospection from an interview illustrated the teacher＇s different roles in interaction, where scaffolding acted as a structured pedagogical tool. The study revealed that the learners were afforded assistance to progress from other- regulation to self-regulation, and consequently, the teacher exploited opportunities to enhance learner autonomy in negotiation of spaces for autonomy in classroom teaching. The study has probed into the significance of the teacher＇s capacity of controlling scaffolding effectively and generated implications for teacher development and learner training.