Short-circuit and open-circuit faults monitoring of IGBTs in solid-state-transformers using collector-emitter voltage

Cao, Qiuling,Che, Yanbo,Yang, Jianxiong,Mi, Menglai,Men, Yaoyao The Korean Institute of Power Electronics 2021 JOURNAL OF POWER ELECTRONICS Vol.21 No.7

The aging and malfunction of devices with great power have been the main causes of the collapse and failure of grid systems. Since they are frequently used in grid systems, the failure of a solid-state-transformer has a great impact on the energy-saving and normal operation of network systems. Moreover, the main switching element of a solid-state-transformer is a welding type IGBT, which is also the most fragile part. First, the uneven current flow phenomenon of paralleled IGBT modules is introduced. Then, the main factors influencing solid-state-transformer failure, along with the short-circuit and open-circuit faults of IGBTs are analyzed. After the derivation V_CE, it can be seen that it is related to the short-circuit and open-circuit faults of IGBTs. After comparison and analysis, one type of solid-state-transformer should be chosen to be widely applied and with integral functions for models and simulations. The IGBTs in solid-state-transformers vary in terms of fault condition and position, which influences the internal and external electrical parameters of systems. Therefore, it is proposed that collector-emitter voltage can be used to characterize the fault conditions of solid-state-transformers. Through simulation verification and waveform observations, it can be seen that the collector-emitter voltage and V_M, which is the voltage of the primary side of the transformer in a solid-state-transformer, can be used to characterize the failure condition of the internal converter of the solid-state-transformer.

Highly Electrocatalytic Cu₂ZnSn(S_1–<i>x</i>Se_<i>x</i>)₄ Counter Electrodes for Quantum-Dot-Sensitized Solar Cells

Cao, Yuebin,Xiao, Yanjun,Jung, Jin-Young,Um, Han-Don,Jee, Sang-Won,Choi, Hye Mi,Bang, Jin Ho,Lee, Jung-Ho American Chemical Society 2013 ACS APPLIED MATERIALS & INTERFACES Vol.5 No.3

<P>Traditional Pt counter electrode in quantum-dot-sensitized solar cells suffers from a low electrocatalytic activity and instability due to irreversible surface adsorption of sulfur species incurred while regenerating polysulfide (S<SUB><I>n</I></SUB><SUP>2–</SUP>/S<SUP>2–</SUP>) electrolytes. To overcome such constraints, chemically synthesized Cu<SUB>2</SUB>ZnSn(S<SUB>1–<I>x</I></SUB>Se<SUB><I>x</I></SUB>)<SUB>4</SUB> nanocrystals were evaluated as an alternative to Pt. The resulting chalcogenides exhibited remarkable electrocatalytic activities for reduction of polysulfide (S<SUB><I>n</I></SUB><SUP>2-</SUP>) to sulfide (S<SUP>2–</SUP>), which were dictated by the ratios of S/Se. In this study, a quantum dot sensitized solar cell constructed with Cu<SUB>2</SUB>ZnSn(S<SUB>0.5</SUB>Se<SUB>0.5</SUB>)<SUB>4</SUB> as a counter electrode showed the highest energy conversion efficiency of 3.01%, which was even higher than that using Pt (1.24%). The compositional variations in between Cu<SUB>2</SUB>ZnSnS<SUB>4</SUB> (<I>x</I> = 0) and Cu<SUB>2</SUB>ZnSnSe<SUB>4</SUB> (<I>x</I> = 1) revealed that the solar cell performances were closely related to a difference in electrocatalytic activities for polysulfide reduction governed by the S/Se ratios.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/aamick/2013/aamick.2013.5.issue-3/am302522c/production/images/medium/am-2012-02522c_0007.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/am302522c'>ACS Electronic Supporting Info</A></P>

Synthesis and up-conversion emissions of $$\hbox {Yb}^{3+}{/}\hbox {Er}^{3+}$$ Yb 3 + / Er 3 + , $$\hbox {Yb}^{3+}{/}\hbox {Tm}^{3+}$$ Yb 3 + / Tm 3 + and $$\hbox {Yb}^{3+}{/}\hbox {Tm}^{3+}{/}\hbox {Gd}^{3+}$$ Yb 3 + / Tm 3 + / Gd 3 + co-doped $$\hbox {

Cao, Chunyan,Xie, An,Noh, Hyeon Mi,Jeong, Jung Hyun Springer-Verlag 2017 Bulletin of materials science Vol.40 No.6

Eu³⁺ doped lutetium molybdenum oxides: Synthesis, optical properties, thermal behavior, and LED packaging

Cao, Chunyan,Xie, Along,Zhou, Tianliang,Zhong, Haichang,Lu, Xiangjun,Xie, An,Noh, Hyeon Mi,Jeong, Jung Hyun Elsevier 2020 Journal of luminescence Vol.217 No.-

<P><B>Abstract</B></P> <P>Some lutetium molybdenum oxides were synthesized through a solid-state reaction method. By adjusting the molar ratios of raw materials of Lu<SUB>2</SUB>O<SUB>3</SUB> (Eu<SUB>2</SUB>O<SUB>3</SUB>) to MoO<SUB>3</SUB>, Eu<SUP>3+</SUP> doped lutetium molybdenum oxides Lu<SUB>2</SUB>MoO<SUB>6</SUB>, Lu<SUB>2</SUB>Mo<SUB>2</SUB>O<SUB>9</SUB>, Lu<SUB>2</SUB>(MoO<SUB>4</SUB>)<SUB>3</SUB>, and Lu<SUB>6</SUB>MoO<SUB>12</SUB> were obtained. The materials were characterized by X-ray diffraction (XRD) patterns, scanning electron microscope (SEM) images, energy-dispersive spectra (EDS), diffuse reflection (DR) spectra, photoluminescence (PL) excitation and emission spectra, luminescence decay curves, and temperature dependent integrated emission spectra. Enhanced excitation and emission spectra were recorded at high temperatures. Possible energy transfer processes were proposed to explain the excitation and emission spectra. By combining some phosphors with near ultraviolet (NUV) chips, the obtained light emitting diodes (LEDs) gave red light under forward bias current. The results suggest that the obtained Eu<SUP>3+</SUP> doped lutetium molybdenum oxides have potential applications in phosphor converted based NUV LEDs.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Eu<SUP>3+</SUP> doped Lu<SUB>2</SUB>MoO<SUB>6</SUB>, Lu<SUB>2</SUB>Mo<SUB>2</SUB>O<SUB>9</SUB>, Lu<SUB>2</SUB>(MoO<SUB>4</SUB>)<SUB>3</SUB>, and Lu<SUB>6</SUB>MoO<SUB>12</SUB> were obtained. </LI> <LI> The materials present different structures, morphologies, optical properties, and luminescece decay behaviors. </LI> <LI> Eu<SUP>3+</SUP> concentration dependent optical properties in Lu<SUB>2</SUB>MoO<SUB>6</SUB> were researched. </LI> <LI> Enhanced excitation and emission spectra were recorded under high temperatures in some materials. </LI> <LI> Red LEDs were obtained by packaging phosphors to NUV LED chips. </LI> </UL> </P>

A new silver metaniobate semiconductor of Ag_0.5La_0.5Nb₂O₆ with defect-perovskite structure

Mi, Longqing,Feng, Yongyi,Cao, Lei,Xue, Mingqiang,Huang, Yanlin,Qin, Lin,Seo, Hyo Jin Elsevier 2018 Spectrochimica acta. Part A, Molecular and biomole Vol.192 No.-

<P><B>Abstract</B></P> <P>Silver-containing lanthanum metaniobate Ag<SUB>0.5</SUB>La<SUB>0.5</SUB>Nb<SUB>2</SUB>O<SUB>6</SUB> nanoparticles were synthesized by sol-gel polymerized complex method. A typical defect-perovskite structure was confirmed by XRD Rietveld refinements. The surface characteristics of the sample were tested by SEM, TEM and EDS measurements. SEM and TEM show that the sample presents ball-like particles with the diameters of 100nm to 400nm. The sample shows both self-activated luminescence and photocatalytic activities. Ag<SUB>0.5</SUB>La<SUB>0.5</SUB>Nb<SUB>2</SUB>O<SUB>6</SUB> has a direct transition with band energy of 2.85eV. The Ag4d-O2p hybridization in the valence band contributes to the narrowed band gap. The luminescence properties of Ag<SUB>0.5</SUB>La<SUB>0.5</SUB>Nb<SUB>2</SUB>O<SUB>6</SUB> have been investigated for the first time. The luminescence is characterized by two emission centers with maximum wavelength near 460 and 530nm. The emission and excitation spectra, decay curves and the thermal quenching mechanism were discussed. Ag<SUB>0.5</SUB>La<SUB>0.5</SUB>Nb<SUB>2</SUB>O<SUB>6</SUB> shows the efficient photocatalytic activities and the photodegradation rate for methylene blue dye (MB) can reach about 95% under visible light (>420nm) irradiation in 5h. The trapped experiments for the active species were tested and discussed, which verified that OH radicals could be the major active species in photocatalysis.</P> <P><B>Highlights</B></P> <P> <UL> <LI> A new silver-containing metaniobate Ag<SUB>0.5</SUB>La<SUB>0.5</SUB>Nb<SUB>2</SUB>O<SUB>6</SUB> was synthesized. </LI> <LI> Ag<SUB>0.5</SUB>La<SUB>0.5</SUB>Nb<SUB>2</SUB>O<SUB>6</SUB> has a typical defect-perovskite structure. </LI> <LI> Ag<SUB>0.5</SUB>La<SUB>0.5</SUB>Nb<SUB>2</SUB>O<SUB>6</SUB> shows both self-activated luminescence and photocatalytic activities. </LI> <LI> The mechanisms of luminescence and photocatalysis were elucidated. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Cholinesterase inhibitory alkaloids from the rhizomes of <i>Coptis chinensis</i>

Cao, Thao Quyen,Ngo, Quynh-Mai Thi,Seong, Su Hui,Youn, Ui Joung,Kim, Jeong Ah,Kim, Junheon,Kim, Jin-Cheol,Woo, Mi Hee,Choi, Jae Sue,Min, Byung Sun Elsevier 2018 Bioorganic chemistry Vol.77 No.-

<P><B>Abstract</B></P> <P> <I>Coptis chinensis</I> has been used as a medicinal herb in traditional oriental medicine. In this study, chemical investigation of a water extract of <I>C. chinensis</I> identified two new quaternary protoberberines (<B>1</B>, <B>2</B>), a new tricyclic amide (<B>3</B>), together with five known compounds. Their chemical structures were elucidated by analysis with 1D and 2D NMR and high-resolution mass spectroscopy, as well as by comparison with those reported in the literature. Compounds <B>4</B>, <B>5</B>, and <B>7</B> showed potent inhibition against acetylcholinesterase (AChE) with IC<SUB>50</SUB> values of 1.1, 5.6, and 12.9 μM, respectively. Compounds <B>2</B> and <B>4</B> showed inhibition of butyrylcholinesterase (BChE) with IC<SUB>50</SUB> values of 11.5 and 27.8 μM, respectively. The kinetic activities were investigated to find out the type of enzyme inhibition involved. The types of AChE inhibition shown by compounds <B>5</B> and <B>7</B> were noncompetitive; BChE inhibition by compound <B>2</B> was also noncompetitive.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Two new protoberberines and a new amide were isolated from <I>Coptis chinensis</I>. </LI> <LI> Isolated compounds (<B>1−8</B>) were screened for their <I>in vitro</I> ChEs inhibitory effects. </LI> <LI> Compound <B>4</B> showed the most activity on AChE with IC<SUB>50</SUB> values of 1.1 µM. </LI> <LI> Compounds <B>2</B> showed strong inhibition of BChE with IC<SUB>50</SUB> values of 11.5 µM. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Wavelength conversion of Yb³⁺-activated Y₄CdMo₃O₁₆ from near UV-region to IR emission

Mi, Longqing,Xu, Jian,Feng, Yongyi,Cao, Lei,Xue, Mingqiang,Huang, Yanlin,Chen, Cuili,Seo, Hyo Jin Elsevier 2018 Materials chemistry and physics Vol.204 No.-

<P><B>Abstract</B></P> <P>Yb<SUP>3+</SUP> (0.5–30 mol %) activated Y<SUB>4</SUB>CdMo<SUB>3</SUB>O<SUB>16</SUB> phosphors have been prepared by the traditional solid-state reaction method. The phase formation was investigated by the XRD structural refinements. The surface properties of the powder phosphors were verified by SEM, TEM and EDS measurements. The optical properties were evaluated by the reflectance spectra, photoluminescence excitation and emission spectra, decay curves (lifetimes), and the absolute quantum efficiency (QE). Under the excitation of UV light, Yb<SUP>3+</SUP>-activated Y<SUB>4</SUB>CdMo<SUB>3</SUB>O<SUB>16</SUB> shows the efficient near-infrared (NIR) emission bands (900–1100 nm), which is ascribed to the <SUP>2</SUP>F<SUB>5/2</SUB> → <SUP>2</SUP>F<SUB>7/2</SUB> transitions of Yb<SUP>3+</SUP> ions. The NIR emission intensity shows a dependence on Yb<SUP>3+</SUP> contents, which has an optimal doping of 25 mol %. The energy transfer (ET) from MoO<SUB>4</SUB> to Yb<SUP>3+</SUP> ions in the lattices was discussed. The NIR emission around 1000 nm just corresponds to the optical response of Si-based solar cells. Consequently, the efficiency could be enhanced by arranging luminescent layers mixed with Y<SUB>4</SUB>CdMo<SUB>3</SUB>O<SUB>16</SUB>:Yb<SUP>3+</SUP> phosphors and transparent matrix in the front surface of Si solar cells.</P> <P><B>Highlights</B></P> <P> <UL> <LI> The structural refinements of the Yb<SUP>3+</SUP>-doped phosphors were completed. </LI> <LI> The charge transfer of the molybdate to Yb<SUP>3+</SUP> ions is efficient. </LI> <LI> Efficient conversion from near UV light to Yb<SUP>3+</SUP> IR emission was demonstrated. </LI> <LI> This is an excellent candidate for enhancement of spectral response of Si-based solar cells. </LI> </UL> </P>

Tissue Inhibitor of Metalloproteinase-1 Enhances Eosinophilic Airway Inflammation in Severe Asthma

Cao Thi Bich Tra,Quoc Quang Luu,Yang Eun-Mi,Moon Ji-young,Shin Yoo Seob,Ryu Min Sook,최영우,Park Hae-Sim 대한천식알레르기학회 2023 Allergy, Asthma & Immunology Research Vol.15 No.4

Purpose: Severe asthma (SA) is characterized by persistent airway inflammation and remodeling, followed by lung function decline. The present study aimed to evaluate the role of tissue inhibitor of metalloproteinase-1 (TIMP-1) in the pathogenesis of SA. Methods: We enrolled 250 adult asthmatics (54 with SA and 196 with non-SA) and 140 healthy controls (HCs). Serum TIMP-1 levels were determined by enzyme-linked immunosorbent assay. The release of TIMP-1 from airway epithelial cells (AECs) in response to stimuli as well as the effects of TIMP-1 on the activations of eosinophils and macrophages were evaluated in vitro and in vivo. Results: Significantly higher levels of serum TIMP-1 were noted in asthmatics than in HCs, in the SA group than in non-SA group, and in the type 2 SA group than in non-type 2 SA group (P < 0.01 for all). A negative correlation between serum TIMP-1 and FEV1% values (r = −0.400, P = 0.003) was noted in the SA group. In vitro study demonstrated that TIMP-1 was released from AECs in response to poly I:C, IL-13, eosinophil extracellular traps (EETs) and in coculture with eosinophils. TIMP-1-stimulated mice showed eosinophilic airway inflammation, which was not completely suppressed by steroid treatment. In vitro and in vivo functional studies showed that TIMP-1 directly activated eosinophils and macrophages, and induced the release of EETs and macrophages to polarize toward M2 subset, which was suppressed by anti-TIMP-1 antibody. Conclusions: These findings suggest that TIMP-1 enhances eosinophilic airway inflammation and that serum TIMP-1 may be a potential biomarker and/or therapeutic target for type 2 SA.

Cytotoxic Activity of Compounds from Styrax obassia

Cao, Thao Quyen,Lee, Bo Mi,Jung, Yeon Woo,Nguyen, Van Thu,Kim, Jeong Ah,Min, Byung Sun NATURAL PRODUCT COMMUNICATIONS 2017 Natural product communications Vol.12 No.2

<P>Cancer is a major public health burden in both developed and developing countries. Plant-derived compounds have played an important role in the development of useful anti-cancer agents. The current study was designed to evaluate the cytotoxic activity of chemical compounds from the stem bark of Styrax obassia. Seven known compounds (1-7) were isolated and identified. Compound 2 exhibited cytotoxic activity against the breast cancer cell line MCF-7 with an IC50 of 27.9 mu M, followed by the human cervical cancer cell line Hela with an IC50 of 23.3 mu M, and the human promyelocytic leukemia cell line HL-60 with an IC50 of 47.8 mu M. Compound 7 exhibited cytotoxicity against Hela cells with an IC50 of 16.8 mu M, followed by MCF-7 cells with an IC50 of 53.5 mu M. This is the first study to investigate the significant anti-tumor properties of isolated compounds from the stem bark of S. obassia.</P>

A Primary Permanent-Magnet Linear Motor for Urban Rail Transit

Cao, Ruiwu,Cheng, Ming,Mi, Chris,Hua, Wei,Zhao, Wenxiang Journal of International Conference on Electrical 2012 Journal of international Conference on Electrical Vol.1 No.1

In this paper, a new permanent-magnet (PM) linear motor is proposed, in which both the magnets and armature windings are placed in the short mover, while the long stator consists of iron core only. Hence, this new PM linear motor can be called a primary permanent-magnet linear motor. It exhibits the advantages of robustness, low cost, high efficiency, high power factor, and high thrust force density. It is especially suitable for long stator applications such as urban rail transit. In this paper, the topology and operation principle of this motor are discussed in detail. The steady-state characteristics including field distributions, flux-linkage, back-EMF, phase inductance and thrust force are investigated. In addition, the technique of skewing stator teeth is adopted to improve the electromagnetic performance. Results from finite element method (FEM) verified the theoretical analysis results.