Background Light quality significantly affects plant growth and development, photosynthesis, and carbon and nitrogen metabolism. Apple (Malus domestica Borkh.) is a widely cultivated and economically important fruit crop worldwide. However, there are still few studies on the effects of different light qualities on the growth and development of apple seedlings. Results In this study, we explored the effects of blue and red light treatments on the growth and development, photosynthetic characteristics, leaf chloroplast ultrastructure, and carbon and nitrogen metabolism of apple seedlings. Blue light significantly inhibited apple plant growth and leaf extension, but it promoted the development of leaf tissue structures and chloroplasts and positively affected leaf stomatal conductance, the transpiration rate, and photosynthetic efficiency. The red light treatment promoted apple plant growth and root development, but it resulted in loosely organized leaf palisade tissues and low chlorophyll contents. The blue and red light treatments enhanced the accumulation of ammonium nitrogen in apple seedlings. Moreover, the blue light treatment significantly promoted nitrogen metabolism. Additionally, an RNA-seq analysis revealed that both blue light and red light can significantly up-regulate the expression of genes related to carbon and nitrogen metabolism. Blue light can also promote amino acid synthesis and flavonoid metabolism, whereas red light can induce plant hormone signal transduction. The expression of a gene encoding a bHLH transcription factor (MYC2-like) was significantly up-regulated in response to blue light, implying it may be important for blue light-mediated plant development. Conclusions Considered together, blue and red light have important effects on apple growth, carbon and nitrogen metabolism. These findings may be useful for determining the ideal light conditions for apple cultivation to maximize fruit yield and quality.

A real-time optimal control of parallel hybrid electric vehicles (PHEVs) with the equivalent consumption minimization strategy (ECMS) is presented in this paper, whose purpose is to achieve the total equivalent fuel consumption minimization and to maintain the battery state of charge (SOC) within its operation range at all times simultaneously. Vehicle and assembly models of PHEVs are established, which provide the foundation for the following calculations. The ECMS is described in detail, in which an instantaneous cost function including the fuel energy and the electrical energy is proposed, whose emphasis is the computation of the equivalent factor. The real-time optimal control strategy is designed through regarding the minimum of the total equivalent fuel consumption as the control objective and the torque split factor as the control variable. The validation of the control strategy proposed is demonstrated both in the MATLAB/Simulink/Advisor environment and under actual transportation conditions by comparing the fuel economy, the charge sustainability, and parts performance with other three control strategies under different driving cycles including standard, actual, and real-time road conditions. Through numerical simulations and real vehicle tests, the accuracy of the approach used for the evaluation of the equivalent factor is confirmed, and the potential of the proposed control strategy in terms of fuel economy and keeping the deviations of SOC at a low level is illustrated.

Due to the friction-induced discontinuity of the clutch torque and ICE on/off, seamless mode transition of hybrid electric vehicles (HEVs) is difficult to achieve, which has a bad influence on the vehicle ride comfort. In the face of system uncontinuity and strong nonlinearity during mode switching with ICE starting, a control strategy of torque dynamic coordination is proposed by means of sliding mode control based on disturbance compensation. Firstly, the steady-state and transient models of parts and working modes are built, which improves modeling accuracy and adaptability to transient driving cycle. Furthermore, the switching process from pure electric driving to hybrid driving is divided into three phases including internal combustion engine (ICE) starting, speed synchronization and torque redistribution. The design of according disturbance observer and sliding mode controller is described in detail. Lastly, compared with other two control strategies, the rationality and validity of the control method designed are testified not only by computer simulations but also experimental tests under the comprehensive driving cycle of local passenger vehicles. The potential of the proposed control strategy in terms of power transfer smoothness and improving riding comfort is illustrated. INDEX TERMS Hybrid electric vehicle (HEV), coordinated control, sliding mode control, mode switching.

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To improve hybrid electric vehicle (HEV) fuel efficiency further, the decision as to whether the internal combustion engine (ICE) should start or stop is important. This paper presents a novel optimization method of the ICE start-stop by using the model predictive control (MPC) based on equivalent consumption minimization strategy (ECMS). The optimization method and flow of the ICE start-stop are described in detail. Three torque-split control strategies are proposed for the comparison purpose. From the ICE operating points, the fuel consumption and the battery SOC, simulation results reveal that the transient MPC strategy with ICE start-stop has a huge potential for improving the overall fuel economy.