Model analysis, simplified control and sensitivity verification of modular multilevel DC-DC converter with parallel branches

Ren, Qiang,Xiao, Fei,Ai, Sheng The Korean Institute of Power Electronics 2020 JOURNAL OF POWER ELECTRONICS Vol.20 No.2

In view of the modular multilevel topology with its uses in medium-voltage DC vessel integrated power systems, this paper deals with typical modular multilevel DC-DC converter (MMDC) topologies and AC control methods. In terms of DC control, a brief introduction is first made about a MMDC topology with parallel branches and its static characteristics. Then, an analysis is focused on the modeling of the MMDC and its model simplification. An optimal control strategy is proposed for the simplified model. Finally, the sensitivity of this system to model and parameter uncertainties is verified both theoretically and experimentally. The obtained results show that the proposed MMDC consisting of a heterogeneous full-bridge submodule and a parallel-branch structure can make the submodule voltage self-balancing and the range of output voltage wide. The use of an optimal control strategy based on a simplified model can lead the system to achieve good static and dynamic performance and robustness.

Dynamic performance of a novel hydraulically damped rubber mount with inertial track at low frequency: modeling and experimental study

Xin Liao,Lin Chengqi,Heow Pueh Lee,Renqiang Jiao 대한기계학회 2023 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.37 No.12

To suppress the vibration of the suspended cab of construction machinery, a novel passive hydraulically damped rubber mount (PHDRM) with multi-inertial tracks is designed. The two suspension system models describing single and multi-inertial tracks are proposed in different coupled relations based on the parallel combination model of rubber and fluid, considering fluid rheological behavior and compressibility. The low-frequency dynamic behaviors of the PHDRM and rubber isolator with corresponding structures under fixedfrequency and frequency-sweep excitations are investigated analytically and experimentally. It is demonstrated that the dynamic stiffness of PHDRM exhibits softening characteristics, as well as amplitude and frequency dependence, which are caused by the viscoelastic behavior of hydraulic oil and fluid-solid coupling. And the damping has a more significant amplitude and frequency dependence. The results also illustrate that PHDRM exhibits more excellent dynamic performance in suppressing vibration and resonance compared to the traditional rubber isolator. The effectiveness of the mathematical model is verified by comparing the simulation and experimental results. Further, the dynamic performances of the PHDRM with different lengths, cross sections, and numbers of inertial tracks are studied by using measured forcedisplacement loops and transmissibility, and their vibration isolation performances were compared. Experimental results show that the PHDRM with three inertial tracks has significant advantages in energy dissipation, resulting in better predictions in reducing transmissibility. The studies in this paper provide an important theoretical basis and reference value for the structural optimization design of the hydraulically damped rubber mount.

Application of the Multi-Source Data Fusion Algorithm in the Hail Identification

Yonghua Zhu,Yongqing Wang,Zhiqun Hu,Fansen Xu,Renqiang Liu 한국기상학회 2022 Asia-Pacific Journal of Atmospheric Sciences Vol.58 No.3

In this study, the canonical correlation analysis algorithm (CCA) is used to fuse the two-dimensional wind field retrieved from the single-Doppler weather radar, the three-dimensional wind field retrieved from the dual-Doppler weather radars, the observations from the ground automatic weather stations and the meteorological reanalysis data in three hail episodes (“0625” episode in Beijing, “0330” and “0801” episodes in Guangdong). During the hail episode in Beijing on June 25, 2020, an evident and long-lasting three-body scatter spike was observed, which played an important role in the hail identification and warning. In the three-dimensional wind field retrieved from the dual-Doppler weather radars, there is horizontal convergence of northeasterly and northwesterly winds and that of northwesterly and southeasterly winds in the low-level strong echo area, and there are obvious updrafts in the vertical wind field structure. Such a circulation configuration is favorable for the development and maintenance of hail storm. The multi-source data fusion of the wind fields can effectively improve the identification of the low-level convergence. The data fusion for the other two hail episodes (“0330” and “0801” episodes in Guangdong) yields the same conclusion. It is revealed that the dual-radar fusion performs better than the single-radar fusion in the identification of the meso-γ scale vortices. It can visually illustrate the characteristics of the cyclonic convergent flow fields which is more consistent with the near-surface observation. It can be concluded that the multi-source data fusion technique is practicable in the three severe convection processes.

Increased Expression of miR-146a in Children With Allergic Rhinitis After Allergen-Specific Immunotherapy

Xi Luo,Haiyu Hong,Jun Tang,Xingmei Wu,Zhibin Lin,Renqiang Ma,Yunping Fan,Geng Xu,Dabo Liu,Huabin Li 대한천식알레르기학회 2016 Allergy, Asthma & Immunology Research Vol.8 No.2

Purpose: MicroRNAs (miRs) were recently recognized to be important for immune cell differentiation and immune regulation. However, whether miRs were involved in allergen-specific immunotherapy (SIT) remains largely unknown. This study sought to examine changes in miR-146a and T regulatory cells in children with persistent allergic rhinitis (AR) after 3 months of subcutaneous immunotherapy (SCIT) and sublingual immunotherapy (SLIT). Methods: Twenty-four HDM-sensitized children with persistent AR were enrolled and treated with SCIT (n=13) or SLIT (n=11) for 3 months. Relative miR-146a and Foxp3 mRNA expression, the TRAF6 protein level, and the ratio of post-treatment to baseline IL-10+CD4+ T cells between the SCIT and SLIT groups were examined in the peripheral blood mononuclear cells (PBMCs) of AR patients using quantitative reverse transcription polymerase chain reaction (qRT-PCR), flow cytometry, and Western blot analysis, respectively. Serum levels of IL-5 and IL-10 were determined using ELISA. Results: After 3 months of SIT, both the TNSS and INSS scores were significantly decreased compared to the baseline value (P<0.01). The relative expression of miR-146a and Foxp3 mRNA was significantly increased after both SCIT and SLIT (P<0.01). The ratio of post-treatment to baseline IL-10+CD4+ T cells and the serum IL-10 level were significantly increased in both the SCIT and SLIT groups (P<0.01), whereas the TRAF6 protein level and serum IL-5 level were significantly decreased (P<0.01). No significant differences in these biomarkers were observed between the SCIT and SLIT groups. Conclusions: Our findings suggest that miR-146a and its related biomarkers may be comparably modulated after both SCIT and SLIT, highlighting miR-146a as a potential therapeutic target for the improved management of AR.

A new macro-micro dual drive parallel robot for chromosome dissection

Jin Feng,Feng Gao,Xianchao Zhao,Yi Yue,Renqiang Liu 대한기계학회 2012 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.26 No.1

This paper presents a parallel-structure system dually driven by six servo motors and six piezoelectric actuators. Due to the combination of macro and micro manipulators which are both of orthogonal structures, the proposed system possesses a concise structure as well as actuation isolation and output motion decoupling properties. By using a glass needle mounted on a six-dimensional force sensor in endpoint operating, this system can be applied to chromosome dissection that to make the whole process more efficient and automatic. The glass needle tip has a stroke of 106 mm in three linear motions and 18.7-arc-degrees in three angle motion directions, with servo motors adopted. It also has the resolution of 20 nanometers with the adoption of piezoelectric actuators. The kinematics, isotropy, decoupling and design considerations of the proposed robot are discussed. Workspace and resolution of both macro and micro manipulators are measured separately. The experiments are also conducted to show its capability in dissecting chromosomes.

Expression and Regulation of Transcription Factor FoxA2 in Chronic Rhinosinusitis With and Without Nasal Polyps

Qing Luo,Jia Zhang,Hongtian Wang,Fenghong Chen,Xi Luo,Beiping Miao,Xingmei Wu,Renqiang Ma,Xiangqian Luo,Geng Xu,Jianbo Shi,Huabin Li 대한천식알레르기학회 2015 Allergy, Asthma & Immunology Research Vol.7 No.5

Purpose: Chronic rhinosinusitis (CRS) is characterized by the excessive production of mucus. However, the molecular mechanism underlying mucin overproduction in CRS with or without nasal polyps (CRSwNP and CRSsNP, respectively) is poorly understood. This study was conducted to assess the importance of the transcription factor FoxA2 in mucin production and to investigate the targeting of FoxA2 as a potential therapeutic strategy for mucus hypersecretion in CRS patients. Methods: We enrolled 15 CRSwNP patients, 15 CRSsNP patients, and 10 normal controls in this study. The expression levels of FoxA2, MUC5AC, and MUC5B in inflamed and healthy nasal tissues were examined via immunohistochemistry and quantitative reverse transcription-polymerase chain reaction, and the levels of several proinflammatory cytokines in nasal secretions were measured via FlowCytomix analysis. In addition, the expression of MUC5AC and FoxA2 was determined in polyp-derived epithelial cells and NCI-H292 cells after in vitro stimulation. Results: FoxA2 was significantly down-regulated, and MUC5AC and MUC5B were significantly up-regulated in both the CRSwNP and CRSsNP patients compared to the controls (P<0.05), and the protein level of FoxA2 was negatively associated with the IL-6 level in the CRS patients (P<0.05). IL-6 significantly increased MUC5AC expression but inhibited FoxA2 expression in vitro (P<0.05). Transfection with a FoxA2 expression plasmid significantly decreased MUC5AC promoter activity (P<0.05) and inhibited IL-6-induced MUC5AC production (P<0.05). In addition, clarithromycin significantly alleviated IL-6-induced FoxA2 suppression and decreased MUC5AC expression in vitro (P<0.05). Conclusions: Our findings suggest that FoxA2 may be considered a therapeutic target for the modulation of mucus hypersecretion in CRS patients.