Analytical loss model of series-resonant indirect-matrix-type power electronics transformers using MOSFETs

Hu, Yujie,Li, Zixin,Zhao, Cong,Li, Yaohua The Korean Institute of Power Electronics 2021 JOURNAL OF POWER ELECTRONICS Vol.21 No.11

A MOSFET-based series-resonant indirect-matrix-type power electronic transformer (PET) consists of line-frequency-switching folding-unfolding bridges and series-resonant dc-dc converters (SRCs), which is an attractive choice to achieve ac-ac conversion due to its high efficiency and high power density. However, the conduction losses, switching losses, and core losses in each of the high-frequency switching cycles T_s are different due to the pulsating dc voltage |ac|, which introduces difficulties in the calculation of losses. In addition, the small dc capacitors also participate in the resonance, and the resonant current shape deviates from a pure sine. Therefore, the conventional loss model is not suitable for PETs. In this paper, the time-domain analysis of SRC resonant current considering the dc capacitor is developed. Then, the analytical expression of the resonant current RMS value in grid cycle T_g is derived, which is more accurate in calculating conduction loss than the conventional model. In addition, it avoids the calculating losses in each T_s. Next, an analytical switching loss model is developed based on the curve fitting of the capacitance-voltage relationship. A simplified analytical core loss model is provided. Each part of the loss of the PET is verified by thermal simulations, and the total losses are verified by efficiency tests on an experiment prototype.

Strong adsorption of cationic dyes by cucurbit[7]uril modified magnetic carbon nanotubes: Investigation on adsorption performance, reusability, and adsorption mechanism

Yujie Hu,Changjun Zou,Tingting Xiong,Huihui Wang 한국공업화학회 2023 Journal of Industrial and Engineering Chemistry Vol.128 No.-

In this work, a facile one-pot method was used to synthesize the co-modified carbon nanotube adsorbent(CB/MMCNT) of cucurbit[7]uril and Fe3O4. A series of characterizations were utilized to confirm the successfulsynthesis of the adsorbent. VSM and separation experiments demonstrated that the adsorbentexhibited excellent magnetic separation performance and could achieve rapid separation within 30 s. BET results show that the adsorbent has excellent specific surface area (67.438 m2/g). Subsequently, threecationic dyes, namely Methylene blue (MB), Malachite green (MG), and Gentian violet (GV), were utilizedin batch adsorption experiments. A strong adsorption effect on cations is exerted by the adsorbentthrough hydrogen bonds, electrostatic interactions, p-p conjugation effects and hydrophobic interactions. Under the optimal conditions (pH = 6, T = 300 min, C0 = 1000 mg/L), the maximum adsorptioncapacity of CB/MMCNT to MB, MG, and GV was 851.5 mg/g, 720.2 mg/g, and 563.4 mg/g. The adsorptiondata could be well fitted by both the pseudo-second-order kinetic model (R2 > 0.99) and Langmuir isothermmodel (R2 > 0.99). Thermodynamic data indicated that the adsorption process was spontaneousand endothermic. Moreover, the cyclic reuse performance of CB/MMCNT was evaluated through 7 cyclesof recycling experiments, which demonstrated that it maintained a high dye removal rate (MB 84%, MG78%, GV 81%), indicating its excellent reusability. Additionally, CB/MMCNT still maintained its impressivecationic dye removal performance (MB 95.8%, MG 92.7%, GV 92.2%) when tested in practical water environments. Overall, CB/MMCNT is a promising, environmentally friendly, efficient, and sustainable adsorbentfor removing cationic dyes.

Preparation and characterization of hexaferrites Ba0.40Sr0.60-xNdxFe12.00-xZnxO19 by the solid-state reaction route

Yujie Yang,Xiansong Liu,Shuangjiu Feng,Xucai Kan,Qingrong Lv,Feng Hu,Jiangli Ni,Chaocheng Liu,Wei Wang 한양대학교 세라믹연구소 2020 Journal of Ceramic Processing Research Vol.21 No.4

The microstructural, spectral, magnetic and electric properties of hexaferrites Ba0.40Sr0.60-xNdxFe12.00-xZnxO19 (0.00 ≤ x ≤ 0.30)synthesized by the solid-state reaction route have been studied. XRD results confirmed that the hexaferrites with Nd-Zncontent (x) of 0.00 ≤ x ≤ 0.24 were single M-type phase, and the hexaferrite with x = 0.30 exhibited the M-type phase andimpurity phase. The remanence (Br) increased with x from 0.00 to 0.06, and then decreased when x ≥ 0.06. The intrinsiccoercivity (Hcj) and magnetic induction coercivity (Hcb) decreased with x from 0.00 to 0.30. Br indicated a linear decreasingbehavior with increasing temperature from 20 oC to 140 oC. Hcj raised linearly with increasing temperature from 20 oC to 140oC. The value of aBr basically remained constant with Nd-Zn content (x). The value of aHcj increased with x from 0.00 to 0.12,and began to decrease when x ≥ 0.12. The electrical resitivity (ρ) presented a decreasing trend with x from 0.00 to 0.30.

Tensile Behaviors of Laser-Discrete-Quenched Substrate/Nickel Coating of Electroplated Grinding Wheel

Cong Mao,Yujie Zhong,Yongle Hu,Weidong Tang,Z. M. Bi,Zhaohong Lei,Changchun Jiang,Aimin Tang 한국정밀공학회 2022 International Journal of Precision Engineering and Vol.9 No.5

Electroplated grinding wheel has significant advantages, such as longer service life, higher removal rate, reduction of preparation work, reapplication of the wheel bub. Then it is an efficient, green and eco-friendly abrasive tool. In order to reveal the mechanism that the service life of the electroplated grinding wheel is increased by pre-quenched substrate, the tensile behavior and interfacial stresses of the laser-discrete-quenched substrate/nickel coating were studied through tensile experiment and simulation. The results show that random initial cracks appear in the nickel coating over the unquenched zone before the tensile experiment. There is an inter-diffusion region at the interface of steel substrate and nickel coating; in comparison with the unquenched zone, the size of the inter-diffusion region in the laser-quenched zone was decreased significantly (e.g., 1.2 μm in comparison with 2.6 μm). In tensile testing, the coating over the pre-quenched specimen remains bonded with the substrate firmly even the fracture occurs. In contrast, the damages in the forms of blistering, stripping and exfoliating occurred in the coating over the unquenched specimen. When a fracture occurs, there is a significant difference of the ultimate strains of quenched and unquenched zones; the ultimate strain of quenched zone is 0.0714, while that of the unquenched zone is 0.1667. At the bonding interface, the pre-quenched specimen ensured the overall shear stress and the maximum normal stress, which are lower than those of unquenched specimen. The initial cracks in pre-quenched specimen propagate during stretching, the effect of the absorbed strain energy reduces strain mismatch between the substrate and coating at the interface, and this improves the bonding strength at the interface of the laser-discrete-quenched specimen significantly.

RhoGDI2 induced malignant phenotypes of pancreatic cancer cells via regulating Snail expression

Yi Bin,Hu You,Zhu Dongming,Yao Jun,Zhou Jian,Zhang Yi,He Zhilong,Zhang Lifeng,Zhang Zixiang,Yang Jian,Tang Yuchen,Huang Yujie,Li Dechun,Liu Qiuhua 한국유전학회 2022 Genes & Genomics Vol.44 No.5

Background: Rho GDP dissociation inhibitor 2 (RhoGDI2) has been shown to contribute to the aggressive phenotypes of human cancers, such as tumor metastasis and chemoresistance. Objective: This study aimed to assess the effects of RhoGDI2 on tumor progression and chemoresistance in pancreatic cancer cells. Methods: The expression of RhoGDI2 in pancreatic cancer cells was detected by Western blot analysis. Gain-of-function and loss-of-function approaches were done to examine the malignant phenotypes of the RhoGDI2-expressing or RhoGDI2-depleting cells. The correlation between RhoGDI2 and Snail was also analyzed. Results: Differential expression of RhoGDI2 protein in pancreatic cancer cell lines was identified. Gain-of-function and loss-of-function experiments showed that RhoGDI2 induced the malignant phenotypes of pancreatic cancer cells, including proliferation, migration, invasion, and gemcitabine (GEM) chemoresistance. The upregulation of RhoGDI2 stimulated the expression of Snail, resulting in the altered expression of epithelial marker E-cadherin and mesenchymal marker Vimentin, which were characteristics of the tumorigenic activity of epithelial-mesenchymal transition. The expression of RhoGDI2 and Snail was upregulated in clinical tumor samples, and higher expression of RhoGDI2 or Snail was significantly associated with poor patient survival in pancreatic ductal adenocarcinoma (PDAC). Conclusion: The findings indicated that RhoGDI2 promoted GEM resistance and tumor progression in pancreatic cancer and that RhoGDI2 might be a potential therapeutic target in patients with PDAC.

Frequency-Domain Transformation Approaches to Develop the d-q Synchronous-Frame Models of Three-Phase Symmetrical Networks and Applications in Modeling of PWM Power Converters

Xiaoyu Wang,Jinjun Liu,Yuji Meng,Jinku Hu,Chang Yuan 전력전자학회 2007 ICPE(ISPE)논문집 Vol.- No.-

Although state-space averaging small-signal modeling techniques are successfully established in DC-DC converters and three-phase sinusoidal PWM converters, these approaches are limited only to low-order systems, and the modeling process is very complex. This paper proposes two equivalent approaches in frequency domain to develop the d-q synchronous-frame models from stationary-frame models for arbitrary three-phase symmetrical circuits. The first modeling approach is illustrated with frequency transformation, by which the target synchronous-frame models could be easily obtained by frequency transformation of the prototype stationary-frame models. The second modeling approach is based on the reactive elements substitutions. These two approaches can be proven to be equivalent, and the first approach is suitable for input-output models, while the second approach is preferable for state-space models. As illustrative examples, these approaches are applied to develop the synchronous-frame models of large three-phase systems with PWM converters. They are proven valid with the comparison with current published models.

Sertad1 Induces Neurological Injury after Ischemic Stroke via the CDK4/p-Rb Pathway

Jianxiong Li,Bin Li,Yujie Bu,Hailin Zhang,Jia Guo,Jianping Hu,Yanfang Zhang 한국분자세포생물학회 2022 Molecules and cells Vol.45 No.4

SERTA domain-containing protein 1 (Sertad1) is upregulated in the models of DNA damage and Alzheimer’s disease, contributing to neuronal death. However, the role and mechanism of Sertad1 in ischemic/hypoxic neurological injury remain unclear. In the present study, our results showed that the expression of Sertad1 was upregulated in a mouse middle cerebral artery occlusion and reperfusion model and in HT22 cells after oxygen-glucose deprivation/reoxygenation (OGD/R). Sertad1 knockdown significantly ameliorated ischemia-induced brain infarct volume, neurological deficits and neuronal apoptosis. In addition, it significantly ameliorated the OGD/R-induced inhibition of cell viability and apoptotic cell death in HT22 cells. Sertad1 knockdown significantly inhibited the ischemic/hypoxic-induced expression of p-Rb, B-Myb, and Bim in vivo and in vitro. However, Sertad1 overexpression significantly exacerbated the OGD/R-induced inhibition of cell viability and apoptotic cell death and p-Rb, B-Myb, and Bim expression in HT22 cells. In further studies, we demonstrated that Sertad1 directly binds to CDK4 and the CDK4 inhibitor ON123300 restores the effects of Sertad1 overexpression on OGD/R-induced apoptotic cell death and p-Rb, B-Myb, and Bim expression in HT22 cells. These results suggested that Sertad1 contributed to ischemic/hypoxic neurological injury by activating the CDK4/p-Rb pathway.

Design and optimization of novel transceiver device for one‑way single‑wire power transfer

Yang Li,Taocheng Hu,Xueliang Wang,Yujie Zhai,Yao Li,Wenxin Huang,Zhigang Lou 전력전자학회 2023 JOURNAL OF POWER ELECTRONICS Vol.23 No.10

The further development of wireless power transfer technology is hindered by the limiting relationship between transmission distance, transmission efficiency, and size of the coupling mechanism. Thus, a feasible solution was provided by one-way single-wire power transfer. First, a horn-type mode conversion device was proposed in this study by analyzing the principle of one-way single-wire power transfer. Second, the system structure was designed to save materials and reduce the volume of space. The transmission efficiency of the system was improved, and the operating frequency was reduced by optimizing the parameters of the mode conversion device. Finally, the feasibility and structural applicability of the one-way single-wire power transfer method proposed in this study were proved by the experimental results.

PIL5, a phytochrome-interacting bHLH protein, regulates gibberellin responsiveness by binding directly to the GAI and RGA promoters in Arabidopsis seeds.

Oh, Eunkyoo,Yamaguchi, Shinjiro,Hu, Jianhong,Yusuke, Jikumaru,Jung, Byunghyuck,Paik, Inyup,Lee, Hee-Seung,Sun, Tai-ping,Kamiya, Yuji,Choi, Giltsu American Society of Plant Physiologists 2007 The Plant cell Vol.19 No.4

<P>Previous work showed that PHYTOCHROME-INTERACTING FACTOR3-LIKE5 (PIL5), a light-labile basic helix-loop-helix protein, inhibits seed germination by repressing GIBBERELLIN 3beta-HYDROXYLASE1 (GA3ox1) and GA3ox2 and activating a gibberellic acid (GA) catabolic gene (GA2ox2). However, we show persistent light-dependent and PIL5-inhibited germination behavior in the absence of both de novo GA biosynthesis and deactivation by GA2ox2, suggesting that PIL5 regulates not only GA metabolism but also GA responsiveness. PIL5 increases the expression of two GA repressor (DELLA) genes, GA-INSENSITIVE (GAI) and REPRESSOR OF GA1-3 (RGA/RGA1), in darkness. The hypersensitivity of gai-t6 rga-28 to red light and the suppression of germination defects of a rga-28 PIL5 overexpression line show the significant role of this transcriptional regulation in seed germination. PIL5 also increases abscisic acid (ABA) levels by activating ABA biosynthetic genes and repressing an ABA catabolic gene. PIL5 binds directly to GAI and RGA promoters but not to GA and ABA metabolic gene promoters. Together, our results show that light signals perceived by phytochromes cause a reduction in the PIL5 protein level, which in turn regulates the transcription of two DELLA genes directly and that of GA and ABA metabolic genes indirectly.</P>

Frequency Characteristics of the Synchronous-Frame Based D-Q Methods for Active Power Filters

WANG Xiaoyu,LIU Jinjun,HU Jinku,MENG Yuji,YUAN Chang 전력전자학회 2008 JOURNAL OF POWER ELECTRONICS Vol.8 No.1

The d-q harmonic detecting algorithms are dominant methods to generate current references for active power filters (APF). They are often implemented in the synchronous frame and time domain. This paper researches the frequency characteristics of d-q synchronous transformations, which are closely related to the analysis and design issues of control system. Intuitively, the synchronous transformation is explained with amplitude modulation (AM) in this paper. Then, the synchronous filter is proven to be a time-invariant and linear system, and its transfer function matrix is derived in the stationary frames. These frequency-domain models imply that the synchronous transformation has an equivalent effect of frequency transformation. It is because of this feature, the d-q method achieves band-pass characteristics with the low pass filters in the synchronous frame at run time. To simplify these analytical models, an instantaneous positive-negative sequence frame is proposed as expansion of traditional symmetrical components theory. Furthermore, the synchronous filter is compared with the traditional bind-pass filters based on these frequency-domain analytical models. The d-q harmonic detection methods are also improved to eliminate the inherent coupling effect of synchronous transformation. Typical examples are given to verify previous analysis and comparison. Simulation and experimental results are also provided for verification.