Complete loss distribution model of GaN HEMTs considering the influence of parasitic parameters

Shengwei Gao,Jinrui Tian,Xiaoyu Fu,Yongxiao Li,Bo Wang,Lixia Zhao 전력전자학회 2024 JOURNAL OF POWER ELECTRONICS Vol.24 No.1

When compared with Si-based devices, Gallium Nitride High Electron Mobility Transistors (GaN HEMTs) possess the advantages of lower junction-to-case thermal resistance, smaller on-state resistance, faster switching velocity, and higher switching frequency. These advantages make them a promising power semiconductor device. However, with the enhancement of switching frequencies, the influence of parasitic parameters on switching ringing and the losses of GaN HEMTs are increasingly severe. Thus, it is necessary to predict the loss distribution by establishing an accurate loss model of the switching process. On the premise of considering parasitic inductance, nonlinear junction capacitance, and reverse transfer characteristics, this article proposes a precise switching loss model of GaN HEMTs to predict the loss distribution in the switching process. In addition, it verifies results based on the double pulse test (DPT) circuit, which validates the accuracy of the proposed model. Ultimately, based on the above-mentioned loss model, this article discussed the influence of parasitic capacitance and inductance on the output capacitance loss (Eqoss), the reverse conduction loss (ESD), the opening V-I overlap loss (Eopen), the closing V-I overlap loss (Eclose), and the total loss (Etotal). Then, this article produces an optimizing method to enhance the conversion efficiency of GaN HEMTs in accordance with laboratory findings.

Oxymatrine inhibits the pyroptosis in rat insulinoma cells by affecting nuclear factor kappa B and nuclear factor (erythroid-derived 2)-like 2 protein/heme oxygenase-1 pathways

Jingying Gao,Lixia Xia,Yuanyuan Wei 대한약리학회 2022 The Korean Journal of Physiology & Pharmacology Vol.26 No.3

As the mechanism underlying glucose metabolism regulation by oxymatrine is unclear, this study investigated the effects of oxymatrine on pyroptosis in INS-1 cells. Flow cytometry was employed to examine cell pyroptosis and reactive oxygen species (ROS) production. Cell pyroptosis was also investigated via transmission electron microscopy and lactate dehydrogenase (LDH) release. Protein levels were detected using western blotting and interleukin (IL)-1β and IL-18 secretion by enzyme-linked immunosorbent assay. The caspase-1 activity and DNA-binding activity of nuclear factor kappa B (NF-κB) and nuclear factor (erythroid-derived 2)-like 2 protein (Nrf2) were also assessed. In the high glucose and high fat-treated INS-1 cells (HG + PA), the caspase-1 activity and LDH content, as well as Nod-like receptor family pyrin domain containing 3, Gsdmd-N, caspase-1, apoptosis-associated specklike protein containing a CARD, IL-1β, and IL-18 levels were increased. Moreover, P65 protein levels increased in the nucleus but decreased in the cytoplasm. Oxymatrine attenuated these effects and suppressed high glucose and high fat-induced ROS production. The increased levels of nuclear Nrf2 and heme oxygenase-1 (HO-1) in the HG + PA cells were further elevated after oxymatrine treatment, whereas cytoplasmic Nrf2 and Keleh-like ECH-associated protein levels decreased. Additionally, the elevated transcriptional activity of p65 in HG + PA cells was reduced by oxymatrine, whereas that of Nrf2 increased. The results indicate that the inhibition of pyroptosis in INS- 1 cells by oxymatrine, a key factor in its glucose metabolism regulation, involves the suppression of the NF-κB pathway and activation of the Nrf2/HO-1 pathway.

Mechanism analysis on fluidelastic instability of tube bundles in considering of cross-flow effects

Jiang Lai,Lei Sun,Lixia Gao,Pengzhou Li 한국원자력학회 2019 Nuclear Engineering and Technology Vol.51 No.1

Fluidelastic instability is a key issue in steam generator tube bundles subjected in cross-flow. With a lowflow velocity, a large amplitude vibration of the tube observed by many researchers. However, themechanism of this vibration is seldom analyzed. In this paper, the mechanism of cross-flow effects onfluidelastic instability of tube bundles was investigated. Analysis reveals that when the system reachesthe critical state, there would be two forms, with two critical velocities, and thus two expressions for thecritical velocities were obtained. Fluidelastic instability experiment and numerical analysis were conductedto obtain the critical velocity. And, if system damping is small, with increases of the flow velocity,the stability behavior of tube array changes. At a certain flow velocity, the stability of tube array reachesthe first critical state, a dynamic bifurcation occurs. The tube array returns to a stable state with continuesto increase the flow velocity. At another certain flow velocity, the stability of tube array reachesthe second critical state, another dynamic bifurcation occurs. However, if system damping is big, there isonly one critical state with increases the flow velocity. Compared the results of experiments to numericalanalysis, it shows a good agreement.

Ginsenoside Rg3 nanoparticles with permeation enhancing based chitosan derivatives were encapsulated with doxorubicin by thermosensitive hydrogel and anti-cancer evaluation of peritumoral hydrogel injection combined with PD-L1 antibody

Wu Hao,Wei Guoli,Luo Lixia,Li Lingchang,Gao Yibo,Tan Xiaobin,Wang Sen,Chang Haoxiao,Liu Yuxi,Wei Yingjie,Song Jie,Zhang Zhenhai,Huo Jiege 한국생체재료학회 2023 생체재료학회지 Vol.27 No.00

Combination of chemotherapy and immune checkpoint inhibitor therapy has greatly improved the anticancer effect on multiple malignancies. However, the efficiency on triple-negative breast cancer (TNBC) is limited, since most patients bear “cold” tumors with low tumor immunogenicity. Doxorubicin (DOX), one of the most effective chemotherapy agents, can induce immunogenic cell death (ICD) and thus initiating immune response.In this study, to maximize the ICD effect induced by DOX, chitosan and cell-penetrating peptide (R6F3)-modified nanoparticles (PNPs) loaded with ginsenoside Rg3 (Rg3) were fabricated using the self-assembly technique, followed by co-encapsulation with DOX based on thermo-sensitive hydrogel. Orthotopic tumor model and contralateral tumor model were established to observe the antitumor efficacy of the thermo-sensitive hydrogel combined with anti-PD-L1 immunotherapy, besides, the biocompatibility was also evaluated by histopathological.Rg3-PNPs strengthened the immunogenic cell death (ICD) effect induced by DOX. Moreover, the hydrogel co-loading Rg3-PNPs and DOX provoked stronger immune response in originally nonimmunogenic 4T1 tumors than DOX monotherapy. Following combination with PD-L1 blocking, substantial antitumor effect was achieved due to the recruitment of memory T cells and the decline of adaptive PD-L1 enrichment.The hydrogel encapsulating DOX and highly permeable Rg3-PNPs provided an efficient strategy for remodeling immunosuppressive tumor microenvironment and converting immune “cold” 4T1 into “hot” tumors.

Fluidelastic instability of a tube array in two-phase cross-flow considering the effect of tube material

Huantong Liu,Jiang Lai,Lei Sun,Pengzhou Li,Lixia Gao,Danping Yu 한국원자력학회 2019 Nuclear Engineering and Technology Vol.51 No.8

Fluidelastic instability of a tube array is a key factor of the security of a nuclear power plant. An unsteady model of the fluidelastic instability of a tube array subjected to two-phase flow was developed to analyze the fluidelastic instability of tube bundles in two-phase flow. Based on this model, a computational program was written to calculate the eigenvalue and the critical velocity of the fluidelastic instability. The unsteady model and the program were verified by comparing with the experimental results reported previously. The influences of void fraction and the tube's material properties on the critical velocity were investigated. Numerical results showed that, with increasing the void fraction of the two-phase flow, the tube array becomes more stable. The results indicate that the critical velocities of the tube array made of stainless are much higher than those of the other two tube arrays within void fraction ranging from 20%to 80%.

Capacitors Energy Strategy Based Cascaded H-Bridge Converter for DC Port Failures

Xu Peng,Xiaohan Liu,Guolong Yang,Xijun Liu,Lixia Gao,Xinyu Zhu 전력전자학회 2019 JOURNAL OF POWER ELECTRONICS Vol.19 No.5

In this paper, a capacitors energy strategy based Cascaded H-bridge Converter (CHBC) for steady DC link voltage is proposed, which allow the CHBC to work while DC power fails. The topology of the CHBC is analyzed to construct the proposed strategy. The capacitors energy strategy is deduced based on the principle that the DC link voltage should be steady, the switch state should be smooth and the switch frequency should be normal. Experiments based on a three-module prototype, including static experiment, start experiment and step change experiment, proves the correctness of the strategy. They also verified the excellent fault tolerance ability and good dynamic performance of the proposed strategy.

Capacitors Energy Strategy Based Cascaded H-Bridge Converter for DC Port Failures

Peng, Xu,Liu, Xiaohan,Yang, Guolong,Liu, Xijun,Gao, Lixia,Zhu, Xinyu The Korean Institute of Power Electronics 2019 JOURNAL OF POWER ELECTRONICS Vol.19 No.5

In this paper, a capacitors energy strategy based Cascaded H-bridge Converter (CHBC) for steady DC link voltage is proposed, which allow the CHBC to work while DC power fails. The topology of the CHBC is analyzed to construct the proposed strategy. The capacitors energy strategy is deduced based on the principle that the DC link voltage should be steady, the switch state should be smooth and the switch frequency should be normal. Experiments based on a three-module prototype, including static experiment, start experiment and step change experiment, proves the correctness of the strategy. They also verified the excellent fault tolerance ability and good dynamic performance of the proposed strategy.

Glia maturation factor beta deficiency protects against diabetic osteoporosis by suppressing osteoclast hyperactivity

Shi Si,Gu Huijie,Xu Jinyuan,Sun Wan,Liu Caiyin,Zhu Tong,Wang Juan,Gao Furong,Zhang Jieping,Ou Qingjian,Jin Caixia,Xu Jingying,Chen Hao,Li Jiao,Xu Guotong,Tian Haibin,Lu Lixia 생화학분자생물학회 2023 Experimental and molecular medicine Vol.55 No.-

Excessive osteoclast activation, which depends on dramatic changes in actin dynamics, causes osteoporosis (OP). The molecular mechanism of osteoclast activation in OP related to type 1 diabetes (T1D) remains unclear. Glia maturation factor beta (GMFB) is considered a growth and differentiation factor for both glia and neurons. Here, we demonstrated that Gmfb deficiency effectively ameliorated the phenotype of T1D-OP in rats by inhibiting osteoclast hyperactivity. In vitro assays showed that GMFB participated in osteoclast activation rather than proliferation. Gmfb deficiency did not affect osteoclast sealing zone (SZ) formation but effectively decreased the SZ area by decreasing actin depolymerization. When GMFB was overexpressed in Gmfb-deficient osteoclasts, the size of the SZ area was enlarged in a dose-dependent manner. Moreover, decreased actin depolymerization led to a decrease in nuclear G-actin, which activated MKL1/SRF-dependent gene transcription. We found that pro-osteoclastogenic factors (Mmp9 and Mmp14) were downregulated, while anti-osteoclastogenic factors (Cftr and Fhl2) were upregulated in Gmfb KO osteoclasts. A GMFB inhibitor, DS-30, targeting the binding site of GMFB and Arp2/3, was obtained. Biocore analysis revealed a high affinity between DS-30 and GMFB in a dose-dependent manner. As expected, DS-30 strongly suppressed osteoclast hyperactivity in vivo and in vitro. In conclusion, our work identified a new therapeutic strategy for T1D-OP treatment. The discovery of GMFB inhibitors will contribute to translational research on T1D-OP.

Voltage balance evaluation strategy for DC-port faults in centralized aircraft ground power unit based on three-level neutral point clamped cascaded converter

Peng, Xu,Yu, Le,Gong, Kaiyue,Liu, Xiaohan,Yang, Guolong,Xu, Jiangjun,Zhou, Chao,Gao, Lixia,Zhu, Xinyu The Korean Institute of Power Electronics 2021 JOURNAL OF POWER ELECTRONICS Vol.21 No.8

An aircraft ground power unit (GPU) can replace the auxiliary power unit (APU) in an aircraft while the aircraft is parked at an airport. Therefore, the problems associated with the oil consumption and air pollution of the APU are solved. However, the GPU is faced with challenges in terms of utilization, power quality, and fault tolerance. Thus, a novel centralized aircraft GPU based on a three-level neutral point clamped cascaded converter (3LNPC-CC) is introduced in this paper to improve utilization and power quality. Furthermore, an evaluation voltage balance strategy is proposed for the DC-port fault tolerance of the 3LNPC-CC. In addition, both the modulation of the phase shift pulse width modulation (PSPWM) and the control of the double closed loop are used in the 3LNPC-CC. A simulation platform including the control, modulation, and fault tolerance of the system is established to verify the feasibility and performance of the proposed GPU. In particular, it is used to evaluate the voltage balance strategy for DC-port faults. Moreover, a prototype of the GPU and relevant experiments are completed to verify the correctness and feasibility of the system and the strategy.