Summary A polymer electrolyte fuel cell (PEFC) is an electrochemical device that converts chemical energy directly to electrical energy, and its performance greatly depends on its operating temperature. Therefore, in this paper, a novel thermodynamic PEFC model with the airflow cooling method is firstly developed for the PEFC system. Then, a novel model predictive control (MPC) controller is designed to control the stack temperature at an optimal value by adjusting the air flow rate on the basis of the developed thermodynamic PEFC model. The thermodynamic PEFC model and the designed controlling strategies are simulated and analysed in Matlab/Simulink. Three tests are conducted to estimate the reliability of the developed controllers concerning different operating conditions: (a) typical perturbation in the current load, (b) any perturbation in the current load, and (c) variation of the ambient temperature. The simulation results demonstrate that the MPC controller can effectively control the stack temperature at the desired value. Moreover, the MPC controller shows much superior effects compared with the conventional proportional integral derivative (PID) controller. In addition, the developed coolant circuit model can be easily applied to various PEFC systems. The MPC controller shows potential also for other controlling issues of PEFC systems due to its strong robustness and fast response.

Efficient and robust control strategies can greatly contribute to the reliability of fuel cell systems, and a stable output voltage is a key criterion for evaluating a fuel cell system's reliability as a power source. In this study, a polymer electrolyte fuel cell (PEFC) system model is developed, and its performances under different operating conditions are studied. Then two different novel controllers-a proportional integral derivative (PID) controller and a model predictive control (MPC) controller-are proposed and applied in the PEFC system to control its output voltage at a desired value by regulating the hydrogen and air flow rates at the same time, which features a multi-input and single-output control problem. Simulation results demonstrate that the developed PEFC system model is qualified to capture the system's behavior. And both the developed PID and MPC controllers are effective at controlling the PEFC system's output voltage.While the MPC controller presents superior performance with faster response and smaller overshoot. The proposed MPC controller can be easily employed in various control applications for fuel cell systems.

In this work, an efficient method for frequency stabilization of a highly off-resonant laser in a spin-exchange relaxation-free atomic inertial sensor is proposed. This was accomplished via the use of an optical resonator that transferred the stability of an atomic energy level to the laser frequency. The pump laser frequency was stabilized via saturation absorption spectroscopy and was used as a reference to lock the large-detuned probe laser with a double transmission Fabry–Pérot (FP) cavity. The frequency stability and bandwidth of the entire transfer cavity frequency locking system were investigated, and the results were used to elucidate the effect of cavity length on stability. The frequency stability of the system approached 1.66 × 10−11 when the FP cavity length was 30 mm. This method can be applied to a variety of ultrasensitive atomic physics experiments, such as for precision spectroscopy and laser cooling.

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Aiming at the sales management of special steel industry, group sales management model is brought out according to the enterprise management practice and market information from the sales management design practice. This paper analyzes the sales management system structure, plans exploitation technology and system structure and designs sales management system with B/S model using data mining and distributed database (DDB) technology. The system testing applation states that the system implementation is quite effective and has important significance to special Steel Corporation, social and economic worth.