Fabrication of transparent Y₂O₃ ceramics with record-high thermal shock resistance

Zhu, Lin-Lin,Park, Young-Jo,Gan, Lin,Kim, Ha-Neul,Ko, Jae-Woong,Kim, Hai-Doo Elsevier 2018 Journal of the European Ceramic Society Vol.38 No.11

<P><B>Abstract</B></P> <P>Sintering-additive-free fine-grained highly transparent Y<SUB>2</SUB>O<SUB>3</SUB> ceramics featuring record-high thermal shock resistance were fabricated using commercial powders via vacuum pre-sintering (1375–1550 °C) followed by hot-isostatic pressing (1450 °C). The sample pre-sintered at 1450 °C provides the optimum microstructure for post HIPing, which resulted in a grain size of 0.64 μm. The transmittance, microhardness and fracture toughness of the thus HIPed sample are 80.8% at 1100 nm and 65.5% at 400 nm (1.2 mm thick), 8.0 ± 0.02 GPa and 1.00 ± 0.06 MPa m<SUP>1/2</SUP>, respectively. The thermal conductivity increases from 13.1 to 16.5 W/m/K with increasing vacuum pre-sinterin Proc. SPIE-Int. Soc. Opt g temperature from 1450 to 1550 °C. This hybrid sintering method realized high thermal conductivity and high strength simultaneously. Consequently, the thermal shock resistance of the HIPed specimen vacuum pre-sintered at 1450 °C in this work is the highest ever reported to the best of our knowledge, which makes the developed material a promising candidate for high-power laser host and IR dome.</P>

Enhancement of the thermal shock resistance of transparent Y₂O₃ ceramics by reducing the content of sintering additive

Zhu, Lin-Lin,Park, Young-Jo,Gan, Lin,Kim, Ha-Neul,Ko, Jae-Woong,Lee, Jae-Wook,Kim, Hai-Doo Elsevier 2018 Ceramics international Vol.44 No.14

<P><B>Abstract</B></P> <P>It is known that 1.0 at.% is the lowest amount of ZrO<SUB>2</SUB> which can be used for the sintering of well-balanced Y<SUB>2</SUB>O<SUB>3</SUB> ceramics to ensure both transparency and strength. In this work, a highly transparent Y<SUB>2</SUB>O<SUB>3</SUB> ceramic material doped with a reduced amount of ZrO<SUB>2</SUB> (0.5 at.%) was fabricated by means of a hot-press sintering method at a temperature as low as 1600°C using commercial powders. The in-line transmittance of the 0.5 at.% ZrO<SUB>2</SUB>-doped Y<SUB>2</SUB>O<SUB>3</SUB> sample (2 mm thick) is 80.8% at 1100 nm and 72.2% at 400 nm with an average grain size of 1.06 μm. By reducing the ZrO<SUB>2</SUB> content from 1.0 to 0.5 at.%, the thermal conductivity is increased by 18.2% with only a slight decline in the strength and the band gap becomes broader. Consequently, the Hasselman mild-thermal-shock figure of merit of the developed specimen increases by 13.0% overall. These results indicate that this Y<SUB>2</SUB>O<SUB>3</SUB> ceramic has potential for use as a laser host or an infrared window material used on Mach-speed applications.</P>

Fabrication and characterization of highly transparent Y₂O₃ ceramics by hybrid sintering: A combination of hot pressing and a subsequent HIP treatment

Zhu, Lin-Lin,Park, Young-Jo,Gan, Lin,Kim, Ha-Neul,Ko, Jae-Woong,Kim, Hai-Doo Elsevier 2018 Journal of the European Ceramic Society Vol.38 No.9

<P><B>Abstract</B></P> <P>We succeeded in the optimization of highly transparent Y<SUB>2</SUB>O<SUB>3</SUB> ceramics with a submicrometer grain size approximately 0.6 μm by hot pressing (1300–1550 °C) and a subsequent HIP (1450 °C) treatment using commercial Y<SUB>2</SUB>O<SUB>3</SUB> powders as starting powders and ZrO<SUB>2</SUB> as a sintering additive. The optimum microstructure for the HIP treatment was prepared by hot pressing at a temperature as low as 1400 °C for 3 h with a relative density of 99.3%. The thus HIP-treated specimen showed the best transmittance (2 mm thick) ever reported of 83.4% and 78.3% at 1100 and 400 nm, respectively. Specifically, the transmittance using this hybrid sintering method improved substantially in the visible range compared to that of the counterpart using hot pressing only. A simulation of the transmittance based on the Beer-Lambert law and Mie scattering theory has proved that this improvement is mainly due to the elimination of nanopores below 15 nm in size.</P>

Space-vector PWM Techniques for a Two-Phase Permanent Magnet Synchronous Motor Considering a Reduction in Switching Losses

Hai Lin,Fei Zhao,Byung-il Kwon 대한전기학회 2015 Journal of Electrical Engineering & Technology Vol.10 No.3

Two PWM techniques using space vector pulse-width modulation (SVPWM) are proposed for a two-phase permanent magnet synchronous motor (PMSM) driven by a two-phase eightswitch inverter. A two-phase motor with two symmetric stator windings is usually driven by a twophase four-, six-, or eight-switch inverter. Compared with a four- and six-switch inverter, a two-phase eight-switch inverter can achieve larger power output. For two-phase motor drives, the SVPWM technique achieves more efficient DC bus voltage utilization and less harmonic distortion of the output voltage. For a two-phase PMSM fed by a two-phase eight-switch inverter under a normal SVPWM scheme, each of the eight PWM trigger signals for the inverter have to be changed twice in a cycle, causing a higher PWM frequency. Based on the normal SVPWM scheme, two effective SVPWM schemes are investigated in order to reduce the PWM frequency by rearranging four comparison values, while achieving the same function as the normal PWM scheme. A detailed explanation of the normal and two proposed SVPWM schemes is illustrated in the paper. The experimental results demonstrate that the proposed schemes achieve a better steady performance with lower switching losses compared with the normal scheme.

An Improved Flux Observer for Sensorless Permanent Magnet Synchronous Motor Drives with Parameter Identification

Hai Lin,Kyu-Yun Hwang,Byung-Il Kwon 대한전기학회 2013 Journal of Electrical Engineering & Technology Vol.8 No.3

This paper investigates an improved stator flux linkage observer for sensorless permanent magnet synchronous motor (PMSM) drives using a voltage-based flux linkage model and an adaptive sliding mode variable structure. We propose a new observer design that employs an improved sliding mode reaching law to achieve better estimation accuracy. The design includes two models and two adaptive estimating laws, and we illustrate that the design is stable using the Popov hyper-stability theory. Simulation and experimental results demonstrate that the proposed estimator accurately calculates the speed, the stator flux linkage, and the resistance while overcoming the shortcomings of traditional estimators.

Enhanced (R)-2-(4-Hydroxyphenoxy)Propionic Acid Production by Beauveria bassiana: Optimization of Culture Medium and H₂O₂ Supplement under Static Cultivation

( Hai-feng Hu ),( Hai-yan Zhou ),( Xian-lin Wang ),( Yuan-shan Wang ),( Ya-ping Xue ),( Yu-guo Zheng ) 한국미생물 · 생명공학회 2020 Journal of microbiology and biotechnology Vol.30 No.8

(R)-2-(4-hydroxyphenoxy)propionic acid (HPOPA) is a key intermediate for the preparation of aryloxyphenoxypropionic acid herbicides (R-isomer). In order to improve the HPOPA production from the substrate (R)-2-phenoxypropionic acid (POPA) with Beauveria bassiana CCN-A7, static cultivation and H₂O₂ addition were attempted and found to be conducive to the task at hand. This is the first report on HPOPA production under static cultivation and reactive oxygen species (ROS) induction. On this premise, the cultivation conditions and fermentation medium compositions were optimized. As a result, the optimal carbon source, organic nitrogen source, and inorganic nitrogen source were determined to be glucose, peptone, and ammonium sulfate, respectively. The optimal inoculum size and fermentation temperature were 13.3% and 28℃, respectively. The significant factors including glucose, peptone, and H₂O₂, identified based on Plackett-Burman design, were further optimized through Central Composite Design (CCD). The optimal concentrations were as follows: glucose 38.81 g/l, peptone 7.28 g/l, and H₂O₂ 1.08 g/l/100 ml. Under the optimized conditions, HPOPA titer was improved from 9.60 g/l to 19.53 g/l, representing an increase of 2.03- fold. The results obtained in this work will provide novel strategies for improving the biosynthesis of hydroxy aromatics.

Changing trends of the guidelines for the management of thyroid nodule

Hai Lin Park 대한외과학회 2015 대한외과학회 학술대회 초록집 Vol.2015 No.11

Original Articles : A New Rat Model of Cisplatin-induced Neuropathic Pain

( Hai Lin ),( Bong Ha Heo ),( Myung Ha Yoon ) 대한통증학회 2015 The Korean Journal of Pain Vol.28 No.4

Background: Chemotherapy-induced peripheral neuropathy is a major side effect of anti-cancer drugs, and our knowledge of its mechanisms is lacking. Several models for chemotherapy-induced neuropathy have been introduced. However, the outcomes of these models differ significantly among laboratories. Our object was to create a model of chemotherapy-induced neuropathy in rats with cancer. Methods: Female Sprague-Dawley rats were used. Mammary rat metastasis tumor (MRMT-1) cells were implanted subcutaneously in rats. Chemotherapy-induced peripheral neuropathy was induced by injection of cisplatin once a day for four days. The responses to mechanical and thermal stimuli were examined using von Frey filaments, acetone, and radiant heat. Results: Cisplatin (2 mg/kg/day) produced mechanical allodynia, while it did not induce cold allodynia or thermal hyperalgesia. This dose of cisplatin could work successfully against cancer. Body weight loss was not observed in cisplatin-treated rats, nor were other abnormal behaviors noted in the same rats. Conclusions: Repeated injection of intraperitoneal cisplatin induced peripheral neuropathic pain in rats. Thus, this type of rat model has broad applicability in studies related to searching for the mechanism of cisplatin-induced mechanical allodynia and agents for the treatment of neuropathic pain. (Korean J Pain 2015; 28: 236-243)

Association of Cyclin D1 Variants with Head and Neck Cancer Susceptibility: Evidence from a Meta-analysis

Lin, Hai,Fang, Lian,Lin, Dong Asian Pacific Journal of Cancer Prevention 2014 Asian Pacific journal of cancer prevention Vol.15 No.14

Whether cyclin D1 (CCND1) gene variants increase susceptibility to head and neck cancer (HNC) is undetermined. Therefore, we performed the present meta-analysis to systematically assess any possible association between CCND1 variants (G870A and G1722C) and HNC risk. Seventeen studies for CCND1 G870A and three studies for CCND1 G1722C were included. Overall, CCND1 polymorphisms (G870A and G1722C) had no association with increased HNC risk (p>0.05). In the subgroup analysis by smoking status, significantly increased HNC risk was found among smokers under allele contrast, homozygous comparison and recessive models (p<0.05), smoking carriers of A allele and AA genotype appearing at elevated risk. In conclusion, while there was overall a lack of any association between CCND1 polymorphisms (G870A and G1722C) and HNC risk, smokers carrying the A allele and AA genotype of the CCND1 G870A polymorphism may be susceptible to HNC development.

Determination of the Kinetic Properties of Platycodin D for the Inhibition of Pancreatic Lipase Using a 1,2-Diglyceride-Based Colorimetric Assay

Hai Lin Zhao,Yeong Shik Kim 대한약학회 2004 Archives of Pharmacal Research Vol.27 No.9

A 1, 2-diglyceride-based multi-step colorimetric assay to measure the pancreatic lipase activity was applied for the determination of the kinetic profiles of the lipase inhibition with a slight modification and the validity verification. With this assay method, our study revealed that platycodin D, one of major constituents of Platycodi Radix, inhibits the pancreatic lipase activity in a competitive type, with the value of KI being 0.18±0.02 mM. In addition, PD has affected the values of Km, app and Kcat/Km in a dose- dependent manner. The results shed a meaningful light on how PD mediates lipid metabolism in the intestinal tracts. On the other hand, since the revised assay is sensitive, rapid, and does not affect the accuracy to the kinetic properties, it is applicable not only to evaluation of the kinetic properties of the pancreatic lipase, but also to highthroughput screening of pancreatic lipase activity.