Enhanced Sliding Mode Control and Online Estimation of Optimal Slip Ratio for Railway Vehicle Braking Systems

Jianfeng Liu,Qing Peng,Zhiwu Huang,Weirong Liu,Heng Li 한국정밀공학회 2018 International Journal of Precision Engineering and Vol.19 No.5

This paper proposes an optimal anti-locking control scheme so as to improve the braking performance of railway vehicles. The controlling effect of sliding mode control is improved, and the optimal slip ratio is achieved by extreme seeking algorithm. Firstly, a substitute function for the conventional sign function is proposed. Secondly, a closed loop observer for braking systems is used to enhance the estimation value of adhesion force, which can also be used for calculating reference speed. Finally Sliding Mode Controlbased controller needs to be entered a reference slip ratio called optimal slip ratio, which is searched by extreme seeking algorithm from the functional relationship between slip ratio and friction coefficient. Thus, the maximum adhesion is achieved despite wheel/ rail surface changes. The simulation result demonstrates the effect of real-time adjustment for braking torque, which guarantees the braking performance.

Long non-coding RNA T-cell leukemia/lymphoma 6 serves as a sponge for miR-21 modulating the cell proliferation of retinoblastoma through PTEN

Tao, Sisi,Wang, Weidong,Liu, Pengfei,Wang, Hua,Chen, Weirong The Korean Society of Pharmacology 2019 The Korean Journal of Physiology & Pharmacology Vol.23 No.6

Retinoblastoma (Rb) is one of the most common eye malignancies occur in childhood. The crucial roles of non-coding RNAs, particularly long non-coding RNAs (lncRNAs) and microRNAs (miRNAs), have been widely reported in Rb progression. In the present study, we found the expression of lncRNA T-cell leukemia/lymphoma 6 (TCL6) was significantly downregulated in Rb tissues and cell lines. Knockdown of lncRNA TCL6 promoted cell proliferation while reduced cell apoptosis in Rb cells. Moreover, lncRNA TCL6 serves as a sponge for miR-21, a previously-reported oncogenic miRNA in Rb, by direct targeting to negatively regulated miR-21 expression, therefore modulating Rb proliferation through miR-21. TCL6 overexpression inhibited Rb cell proliferation while miR-21 overexpression exerted an opposing effect; the effect of TCL6 overexpression was partially attenuated by miR-21 overexpression. PTEN/PI3K/AKT signaling pathway was involved in lncRNA TCL6/miR-21 axis modulating Rb cell proliferation. Taken together, lncRNA TCL6 serves as a tumor suppressor by acting as a sponge for miR-21 to counteract miR-21-mediated PTEN repression.

An Energy-Based Nonlinear Pressure Observer for Fast and Precise Braking Force Control of the ECP Brake

Yingze Yang,Lu Xiong,Weirong Liu,Kai Gao,Zhiwu Huang 한국정밀공학회 2018 International Journal of Precision Engineering and Vol.19 No.10

The inconsistent braking force will result in collision compacts between adjacent freight cars of heavy haul train, which utilizes ECP as brake system. Moreover, the rigid connection mode aggravates the negative effect. In practical applications, the brake pipe (BP) pressure sensor is used as the feedback in the closed loop brake force control of the ECP brake, but there is no sensor in the brake cylinder (BC), whose pressure is the control target, and these factors will contribute the longitudinal impacts among the freight cars. Therefore, an accurate and fast braking force control is extremely important for ECP brake. Firstly, as for the highly nonlinear ECP system of heavy haul train, an energy-based globally stable pressure observer for ECP brake is proposed. And then, according to the pressure of BC estimated by the observer, an enhanced sliding-mode control algorithm is applied to realize the fast and precise braking force control. Finally, experimental results are presented to demonstrate and validate effectiveness of the proposed observer and control algorithm.

Low Frequency Current Ripple Mitigation of Two Stage Three-Phase PEMFC Generation Systems

Deng, Huiwen,Li, Qi,Liu, Zhixiang,Li, Lun,Chen, Weirong The Korean Institute of Power Electronics 2016 JOURNAL OF POWER ELECTRONICS Vol.16 No.6

This paper presents a two stage three-phase proton exchange membrane fuel cell (PEMFC) generation system. When the system is connected to a three-phase load, it is very sensitive to the characteristics and type of the load. Especially unbalanced three-phase loads, which result in a pulsating power that is twice the output frequency at the inverter output, and cause the dc-link to generate low frequency ripples. This penetrates to the fuel cell side through the front-end dc-dc converter, which makes the fuel cell work in an unsafe condition and degrades its lifespan. In this paper, the generation and propagation mechanism of low frequency ripple is analyzed and its impact on fuel cells is presented based on the PEMFC output characteristics model. Then a novel method to evaluate low frequency current ripple control capability is investigated. Moreover, a control scheme with bandpass filter inserted into the current feed-forward path, and ripple duty ratio compensation based on current mode control with notch filter is also proposed to achieve low frequency ripple suppression and dynamic characteristics improvement during load transients. Finally, different control methods are verified and compared by simulation and experimental results.

Effects of Daidzein on Body Weight Gain, Serum IGF-I Level and Cellular Immune Function in Intact Male Piglets

Wang, Genlin,Zhang, Xiangying,Han, Zhaoyu,Liu, Zhaobin,Liu, Weirong Asian Australasian Association of Animal Productio 2002 Animal Bioscience Vol.15 No.7

10 male piglets at 5-6 weeks old with similar body weight (BW) were randomly assigned into the experimental (EXP) and control (CON) groups. The animals in EXP received intro-muscular injection with daidzein (DA) at the dose of 0.5 mg DA per kg start BW on day 1. The same procedures were repeated once every 3 days for eight times. The animals in CON received the injection only with same volume of control peanut oil. The animals were weighted on day 14 and 28 and the blood samples were obtained at different stages of the treatment for determining IGF-I levels and blood parameters. At the end of the experiment, the thymus and spleen from all the animals were surgically taken out and weighted. The results showed that BW and average daily gain (ADG) were not significantly different between the groups in term of the whole period, but ADG between days 14-28 was higher in EXP than in CON (p<0.05). On days 18, 21 and 25, IGF-I levels in EXP group were 20.53% (p<0.05), 15.92% (p>0.05) and 23.46% (p<0.05), respectively, higher than those in CON. The weights of thymus and spleen, the ratios of their weights to BW and red blood count (RBC) did not significantly differ between the groups at all stages. White blood count (WBC) in EXP steadily increased from day 22, reached its apex on day 24, which was higher than in CON (p<0.05) and its own levels on day 20 and 22 (p<0.01 or p<0.05), and remained higher on the later time (p=0.058). The results of percentage of T-Lymphocytes also demonstrated similar trend to WBC, but TLymphocyte transformation rate (%) appeared no significant change between the groups. In conclusion, Daidzein could stimulate male piglet growth and elevate serum IGF-I levels at certain stages of the treatment. It could also increase WBC and T-Lymphocyte rates, but had no significant impacts on RBC and T-Lymphocyte transformation rate.

Long non-coding RNA T-cell leukemia/lymphoma 6 serves as a sponge for miR-21 modulating the cell proliferation of retinoblastoma through PTEN

Sisi Tao,Weidong Wang,Pengfei Liu,Hua Wang,Weirong Chen 대한약리학회 2019 The Korean Journal of Physiology & Pharmacology Vol.23 No.6

Retinoblastoma (Rb) is one of the most common eye malignancies occur in childhood. The crucial roles of non-coding RNAs, particularly long non-coding RNAs (lncRNAs) and microRNAs (miRNAs), have been widely reported in Rb progression. In the present study, we found the expression of lncRNA T-cell leukemia/lymphoma 6 (TCL6) was significantly downregulated in Rb tissues and cell lines. Knockdown of lncRNA TCL6 promoted cell proliferation while reduced cell apoptosis in Rb cells. Moreover, lncRNA TCL6 serves as a sponge for miR-21, a previously-reported oncogenic miRNA in Rb, by direct targeting to negatively regulated miR-21 expression, therefore modulating Rb proliferation through miR-21. TCL6 overexpression inhibited Rb cell proliferation while miR-21 overexpression exerted an opposing effect; the effect of TCL6 overexpression was partially attenuated by miR-21 overexpression. PTEN/PI3K/AKT signaling pathway was involved in lncRNA TCL6/miR-21 axis modulating Rb cell proliferation. Taken together, lncRNA TCL6 serves as a tumor suppressor by acting as a sponge for miR-21 to counteract miR-21-mediated PTEN repression.

Low Frequency Current Ripple Mitigation of Two Stage Three-Phase PEMFC Generation Systems

Huiwen Deng,Qi Li,Zhixiang Liu,Lun Li,Weirong Chen 전력전자학회 2016 JOURNAL OF POWER ELECTRONICS Vol.16 No.6

This paper presents a two stage three-phase proton exchange membrane fuel cell (PEMFC) generation system. When the system is connected to a three-phase load, it is very sensitive to the characteristics and type of the load. Especially unbalanced three-phase loads, which result in a pulsating power that is twice the output frequency at the inverter output, and cause the dc-link to generate low frequency ripples. This penetrates to the fuel cell side through the front-end dc-dc converter, which makes the fuel cell work in an unsafe condition and degrades its lifespan. In this paper, the generation and propagation mechanism of low frequency ripple is analyzed and its impact on fuel cells is presented based on the PEMFC output characteristics model. Then a novel method to evaluate low frequency current ripple control capability is investigated. Moreover, a control scheme with bandpass filter inserted into the current feed-forward path, and ripple duty ratio compensation based on current mode control with notch filter is also proposed to achieve low frequency ripple suppression and dynamic characteristics improvement during load transients. Finally, different control methods are verified and compared by simulation and experimental results.