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      • KCI등재

        Point-to-point motions control of an electromagnetic direct-drive gas valve

        Jiayu Lu,Siqin Chang,Liang Liu,Xinyu Fan 대한기계학회 2018 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.32 No.1

        Electromagnetic linear actuators are widely used as drives in gas regulating valve, which is the key factor to determine the performance of the gas valve. In order to improve the performance of Electromagnetic direct-drive gas valve (EMDGV), a compound controller for non-repetitive point-to-point motions was proposed in this paper, combining with the advantages of Active disturbance rejection control (ADRC), Time-optimal control (TOC) and Sliding mode control (SMC). Simulation and experimental results show that the proposed method has the characteristics of fast response and high precision, and can achieve soft landing control. The response time is less than 8 ms, the control accuracy is 0.02 mm, and the seating velocity is within 0.04 m/s. The proposed method also has strong robustness to actuator parameter variation and good anti-disturbance ability.

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        MODELING ANALYSIS ON IMPROVING CYLINDER BALANCE IN A GASOLINE ENGINE USING ELECTROMAGNETIC VALVE TRAIN

        Yaxuan Xu,Siqin Chang,Liang Liu,Tianbo Wang,Maoyang Hu 한국자동차공학회 2019 International journal of automotive technology Vol.20 No.6

        For the multi-cylinder gasoline engine, the consistency among cylinders is an important index to affect the engine emission and the engine power. In this paper, an individual cylinder air-fuel ratio (A/F) control method for a fourcylinder camless engine with the electromagnetic valve train (EMVT) was proposed to reduce the imbalance of engine torque. An individual cylinder A/F estimation algorithm with a single universal exhaust gas oxygen (UEGO) sensor based on fading Kalman filtering was introduced. Four proportional-integral feedback controllers were built to regulate the individual A/F by adjusting the intake valve closing (IVC) timing of each cylinder independently based on the EMVT. The effectiveness of the proposed estimation and control approach was validated by co-simulation of GT-Power and Simulink. The results showed that the proposed estimation method could accurately estimate the individual cylinder A/F, and the maximum estimation error under steady state condition was less than 1 %. With the feedback control, both the individual A/F imbalance and the cylinderto- cylinder torque generation imbalance were decreased.

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        Antiadipogenic Effects and Mechanisms of Combinations of Genistein, Epigallocatechin-3-Gallate, and/or Resveratrol in Preadipocytes

        Bulbul Ahmed,Siqin Liu,Hongwei Si 한국식품영양과학회 2017 Journal of medicinal food Vol.20 No.2

        Natural bioactive compounds are considered an excellent alternative strategy for developing effective, safe, and cost-effective antiobesity agents. The aim of this study was to investigate if combinations of soy bean genistein (G), green tea epigallocatechin-3-gallate (E), and/or grape resveratrol (R) at low dosages synergistically inhibit preadipocyte differentiation both in 3T3-L1 cells and human primary preadipocytes (HPAs). Our results show that combinations of G, E, and/or R additively inhibited preadipocyte differentiation (39–56% of control) both in 3T3-L1 cells at 30 μM and HPAs at 15 μM, while the individual compounds have no antiadipogenic effect at the selected concentrations. We also observed similar patterns that combinations of G, E, and/or R additively reduced protein expressions of peroxisome proliferator-activated receptor gamma (PPAR-γ) and CCAAT binding proteins alpha (C/EBP-α), the two key preadipocyte differentiation regulators, both in differentiated 3T3-L1 cells and HPAs. Moreover, combined G, E, and/or R attenuated protein expressions of fatty acid binding protein 4 and perilipin, two PPAR-γ/C/EBP-α downstream molecules in fat drop development in a very similar pattern, in inhibiting differentiation in preadipocytes. This combined antiadipogenic effect of G + E + R is additive, not synergistic according to our results and the Median-Effect Principle. In addition, we found that a lower concentration (15 μM) of G, E, and/or R is required in HPAs than the concentration (30 μM) needed in 3T3-L1 cells, to exert the combined antiadipogenic effect. These data suggest that combinations of G, E, and/or R intake or soy bean, green tea, and/or grape simultaneous consumption may prevent obesity in human being.

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