MnO₂-Nanosheet-Modified Gold Nanocage Loaded with Chlorin e6 for Photothermal and Photodynamic Therapy

Yujie Gao,Ruijing Liang,Jintao Zhu 한국고분자학회 2016 한국고분자학회 학술대회 연구논문 초록집 Vol.41 No.2

Microstructural and magnetic studies on the Cr substituted M-type CaSrLa hexaferrite magnets

Yujie Yang 한양대학교 세라믹연구소 2017 Journal of Ceramic Processing Research Vol.18 No.3

A series of Cr substituted M-type hexaferrite Ca0.30Sr0.35La0.35CrxFe12-xO19 (0 ≤ x ≤ 1.05) magnets were prepared by theconventional solid state reaction method. The properties of the samples were characterized by X-ray diffraction (XRD), fieldemission scanning electron microscopy (FE-SEM) and a permanent magnetic measuring system. At Cr substitution (x) ≤ 0.60,XRD patterns of the magnetic powders show the M-type strontium hexaferrite phase with α-Fe2O3 as a second phase. WhenCr substitution (x) ≥ 0.60, there are magnetoplumbite phase patterns with only a small trace of α-Fe2O3 phase. The images ofthe magnets show that the hexagonal structures are formed, and the particle size keeps unchanged with increasing Crsubstitution (x). The remanence (Br) decreases with Cr substitution (x) from 0.00 to 1.05. The intrinsic coercivity (Hcj) increaseswith Cr substitution (x) from 0.00 to 1.05. While the magnetic induction coercivity (Hcb) first increases with Cr substitution(x) from 0 to 0.75 and then decreases at Cr substitution (x) ≥ 0.75.

Dynamic performance of 6.5 kV SiC MOSFET body diodes and anti‑parallel Schottky barrier diodes

Yujie Du,Xinling Tang,Xiaoguang Wei,Shuai Sun,Fei Yang,Zhibin Zhao 전력전자학회 2023 JOURNAL OF POWER ELECTRONICS Vol.23 No.6

For a silicon carbide (SiC) metal–oxide–semiconductor fi eld-eff ect transistor (MOSFET), both the body diode of the MOSFET and an anti-parallel diode can function as a freewheeling diode that carries reverse current. Selecting a suitable freewheeling method is particularly important to fully exploit the performance of high-voltage SiC MOSFET devices. In this study, based on the 6.5 kV SiC MOSFET and the Schottky barrier diode (SBD) developed by our research group, the dynamic characteristics of the MOSFET body diode, the SBD, and the parallel connection of the two are investigated. In addition, the influence of capacitive current on the dynamic characteristics is analyzed by establishing an equivalent circuit model. Test results show that when compared with the body diode, the SBD has an extremely low reverse recovery current, a lower capacitive current, and better reverse recovery temperature stability. Thus, the SBD is regarded as the most suitable freewheeling diode for the 6.5 kV SiC MOSFET. Finally, a package solution for the 6.5 kV SiC MOSFET and SBD is proposed.

Impacts of heat treatment on the microstructure and magnetic properties of LaPr-Co substituted M-type CaSr hexaferrite

Yujie Yang 한양대학교 세라믹연구소 2017 Journal of Ceramic Processing Research Vol.18 No.4

The M-type hexaferrite Ca0.4Sr0.3(La0.8Pr0.2)0.3Fe11.76Co0.24O19 was synthesized by the solid-state reaction method. The effects ofcalcination temperature and sintering temperature on the microstructural and magnetic properties have been carefullyinvestigated. The X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM) and a permanent magneticmeasuring system were used to investigate the microstructure and magnetic properties of the samples. Single-phase hexaferritepatterns are observed for the hexaferrite magnetic powders at different temperatures from 1210 to 1270 oC for 2 hrs. The FESEMimages of the magnets show that the hexagonal structures have been formed in the magnets, and the grains in themagnets are distributed evenly. With the increase of calcination temperature, the remanence (Br) and maximum energyproduct [(BH)max] increase from 1210 oC to 1270 oC, while the magnetic induction coercivity (Hcb) and intrinsic coercivity (Hcj)increase from 1210 oC to 1250 oC, and then decrease when the calcination temperature ≥ 1250 oC. With the increase ofsintering temperature, the remanence (Br) and maximum energy product [(BH)max] increase from 1180 to 1200 oC, while themagnetic induction coercivity (Hcb) and intrinsic coercivity (Hcj) increase from 1180 to 1195 oC, and then decrease when thecalcination temperature ≥ 1195 oC.

Impacts of praseodymium substitution on structural, spectral, magnetic and electrical properties of strontium W-type hexaferrites

Yujie Yang,Xiansong Liu,Shuangjiu Feng,Qingrong Lv,Xucai Kan,Ruiwei Zhu 한양대학교 세라믹연구소 2020 Journal of Ceramic Processing Research Vol.21 No.3

Praseodymium substituted strontium W-type hexaferrites Sr1-xPrxZn0.8Co1.2Fe16O27 (0.00 ≤ x ≤ 0.40) were prepared via theconventional ceramic technique. XRD analysis of W-type hexaferrites with Pr content (x) of 0.00 ≤ x ≤ 0.24 shows the single Wtypehexaferrite phase. However, for the W-type hexaferrites with Pr content (x) ≥ 0.32, the impurity phase (α-Fe2O3) is detected. FE-SEM images show that the grains are platelet-like shapes. The saturation magnetization (Ms), remanent magnetization (Mr)and magneton number (nB) first increase with Pr content (x) from 0.00 to 0.16, and then decrease when Pr content (x) ≥ 0.16. The Mr/Ms ratio, magnetic anisotropy field (Ha), coercivity (Hc) and maximum energy product [(BH)max] increase with Pr content(x) from 0.00 to 0.40. While the first anisotropy constant (K1) increases with Pr content (x) from 0.00 to 0.16, and then decreaseswhen Pr content (x) ≥ 0.16. The DC electrical resistivity (ρ) decreases with Pr content (x) from 0.00 to 0.40.

Dark Septate Endophyte (DSE) Fungi Isolated from Metal Polluted Soils: Their Taxonomic Position, Tolerance, and Accumulation of Heavy Metals In Vitro

Yujie Zhang,Yan Zhang,Maojun Liu,Xiaodong Shi,Zhiwei Zhao 한국미생물학회 2008 The journal of microbiology Vol.46 No.6

To understand the possible role of the plant root associated fungi on metal tolerance, their role in the uptake of heavy metals and the potential transfer of these metal ions to the plant, three strains of dark septate endophytic (DSE) fungi were isolated from a waste smelter site in southwest China, and one strain was isolated from a non-contaminated site. According to molecular phylogenetic analysis of the ITS 1-5.8S rDNA-ITS 2 gene regions and morphological characteristics, one is identified as Exophiala pisciphila, and the other three are non-sporulating fungi under the experiment condition with the nearest phylogenetic affinities to the Thysanorea papuana strain EU041814. Tolerance and accumulation abilities of the three DSE strains for metals were investigated in liquid culture. Minimum inhibitory concentrations (MIC) of Pb, Zn, and Cd were determined. It was demonstrated that the tolerance of the DSE strains varied between metal species and strains. The E. pisciphila strain is able to accumulate lead and cadmium over 20% and 5% of dry weight of biomass, respectively. Partial of the sequestrated metals can be washed with CaCl2. Morphological and enzyme activity changes taking place in the presence of excessive Pb, Cd, and/or Zn also indicate that the mechanism of heavy metal tolerance and accumulation of the DSE strains would be a complex process. The findings indicated promising tolerance and accumulation of the DSE strains with potential values in metal cycling and restoration of soil and water system.

News-driven Business Cycles: Evidence from Investors’ Expectations of Future Stock Market Returns

( Yujie Zhang ),( Deokwoo Nam ) 한양대학교 경제연구소 2022 JOURNAL OF ECONOMIC RESEARCH Vol.27 No.1

This paper uses a time series of investors’ expectations of future stock market returns, which is proposed by Greenwood and Shleifer (2014), as a new proxy for expectations of future economic developments. Incorporating this measure of expectations into otherwise standard VAR models and implementing the approach of sign restrictions to identify news shocks, we provide empirical evidence in favor of the news-driven business cycles hypothesis. New shocks identified by exploiting movements in the measure of investors’ expectations are found to induce a generalized boom of the economy that is associated with delayed and permanent increases in total factor productivity, but not with its current improvements.

Influence of Mn substitution on the magnetic and microstructural properties of the Sr0.75La0.25Fe12.00-x MnxO19 hexaferrites

Yujie Yang 한양대학교 세라믹연구소 2017 Journal of Ceramic Processing Research Vol.18 No.2

A series of Mn substituted M-type hexaferrites having the chemical compositions of Sr0.75La0.25Fe12.00-xMnxO19 (where 0.00 ≤x ≤ 0.60) were prepared by the conventional ceramic processing method. X-ray diffraction (XRD) was used to evaluate thehexagonal phase evolution for the M-type hexaferrite magnetic powders. The XRD results show that Mn3+ ions completelyenter into the hexaferrite structure and all magnetic powders show M-type hexagonal structure. Magnetic properties of thepowders were studied by a physical property measurement system-vibrating sample magnetometer (PPMS-VSM). Thesaturation magnetization (Ms) and remanent magnetization (Mr) first slightly increase with Mn content (x) from 0.00 to 0.24,and then decrease with Mn content (x) form 0.24 to 0.60. The coercivity (Hc) of the magnetic powders first increases with Mncontent (x) from 0.00 to 0.12, and then decrease with Mn content (x) form 0.12 to 0.36, and increases with the increase of Mncontent (x) when Mn content (x) ≥ 0.36.

Effects of Pr-Co content on the microstructural and magnetic properties of the Pr-Co substituted M-type strontium hexaferrites

Yujie Yang 한양대학교 세라믹연구소 2017 Journal of Ceramic Processing Research Vol.18 No.6

Pr-Co substituted M-type strontium hexaferrites with the chemical composition of Sr1-xPrxFe12-yCoyO19 (x = 0.00-0.50; y = 0.00-0.35) were prepared by the solid-state reaction method. Microstructures of the M-type hexaferrite samples were investigatedby the X-ray diffraction (XRD) and a field emission scanning electron microscopy (FE-SEM). The single-phase with hexagonalstructure is obtained in the M-type hexaferrites with Pr-Co content (0.00 ≤ x ≤ 0.20, 0.00 ≤ y ≤ 0.14). For the M-typehexaferrites with Pr-Co content (x ≥ 0.20, y ≥ 0.14), impurity phases are observed in the structure. The image of therepresentative magnet exhibits that the M-type hexagonal structure is formed in the magnet. A permanent magneticmeasuring system was used to measure the magnetic properties of the M-type hexaferrite magnets. The remanence (Br),maximum energy product [(BH)max] and Hk/Hcj ratios increase with the increasing substitution content of Pr (0.00 ≤ x ≤ 0.10)and Co (0.00 ≤ y ≤ 0.07), and then decrease with increasing substitution content of Pr (x ≥ 0.10) and Co (y ≥ 0.07). The intrinsiccoercivity (Hcj) and magnetic induction coercivity (Hcb) decrease with increaing Pr-Co content (0.00 ≤ x ≤ 0.30, 0.00 ≤ y ≤ 0.21),and then increase with increasing substitution content of Pr (x ≥ 0.30) and Co (y ≥ 0.21).

AN IMPROVED METHOD FOR TRANSFERRING GRAPHENE GROWN BY CHEMICAL VAPOR DEPOSITION

YUJIE REN,CHAOFU ZHU,WEIWEI CAI,HUIFENG LI,YUFENG HAO,YAPING WU,SHANSHAN CHEN,QINGZHI WU,RICHARD D. PINER,RODNEY S. RUOFF 성균관대학교(자연과학캠퍼스) 성균나노과학기술원 2012 NANO Vol.7 No.1

In this paper, we report an improved transfer of graphene by directly picking up the graphene with target substrates and the comparison of such transferred graphene samples with other graphene samples transferred by the commonly used "PMMA-based transfer" method. Raman spectroscopy studies show that this "direct transfer method" does not degrade the graphene structure and field effect transistor measurements show that it does not introduce any extra doping in graphene; in contrast, PMMA-based transfer samples have strong n-type doping. We also find that graphene samples achieved by this direct transfer method show higher mobility than graphene obtained from the PMMA-based transfer method.