• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.23 no.9
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• pp.1019-1024
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• 2012

In this paper, a UWB antenna using a SIR(Step Impedance Resonator) that eliminate signal interference at 5 GHz WLAN as the first rejection band and adjust the second rejection band is proposed. Unlike the unit impedance resonator, the second harmonic of SIR is decided according to step impedance. Therefore, To adjust the second rejection band, SIR is applied to UWB antenna. Also, the equivalent circuit of the antenna at first rejection band is presented and the equivalent modeling values of the SIR and the coupling value is obtained. The proposed antenna is satisfied to cover full UWB band with return losses less than -10 dB and has band rejection characteristic in 5 GHz WLAN band. The radiation patterns show +y directivity characteristics in H-plane and the group delay variations are within 1.0 ns.

• Korean Journal of Materials Research
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• v.21 no.2
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• pp.111-114
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• 2011

As a growth-template of ZnO nanorods (NR), a hexagonal $\beta-Ni(OH)_2$ nanosheet (NS) was synthesized with the low temperature hydrothermal process and its microstructure was investigated using a high resolution scanning electron microscope and transmission electron microscope. Zinc nitrate hexahydrate was hydrolyzed by hexamethylenetetramine with the same mole ratio and various temperatures, growth times and total concentrations. The optimum hydrothermal processing condition for the best crystallinity of hexagonal $\beta-Ni(OH)_2$ NS was determined to be with 3.5 mM at $95^{\circ}C$ for 2 h. The prepared $Ni(OH)_2$ NSs were two dimensionally arrayed on a substrate using an air-water interface tapping method, and the quality of the array was evaluated using an X-ray diffractometer. Because of the similarity of the lattice parameter of the (0001) plane between ZnO (wurzite a = 0.325 nm, c = 0.521 nm) and hexagonal $\beta-Ni(OH)_2$ (brucite a = 0.313 nm, c = 0.461 nm) on the synthesized hexagonal $\beta-Ni(OH)_2$ NS, ZnO NRs were successfully grown without seeds. At 35 mM of divalent Zn ion, the entire hexagonal $\beta-Ni(OH)_2$ NSs were covered with ZnO NRs, and this result implies the possibility that ZnO NR can be grown epitaxially on hexagonal $\beta-Ni(OH)_2$ NS by a soluble process. After the thermal annealing process, $\beta-Ni(OH)_2$ changed into NiO, which has the property of a p-type semiconductor, and then ZnO and NiO formed a p-n junction for a large area light emitting diode.

• The Korean Journal of Nuclear Medicine
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• v.38 no.1
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• pp.21-29
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• 2004

Purpose: Much evidence suggests long-term cigarette smoking alters coronary vascular endothelial response. On this study, we applied nonnegative matrix factorization (NMF), an unsupervised learning algorithm, to CO-less $H_2^{15}O-PET$ to investigate coronary endothelial dysfunction caused by smoking noninvasively. Materials and methods: This study enrolled eighteen young male volunteers consisting of 9 smokers $(23.8{\pm}1.1\;yr;\;6.5{\pm}2.5$ pack-years) and 9 nonsmokers $(23.8{\pm}2.9 yr)$. They do not have any cardiovascular risk factor or disease history. Myocardial $H_2^{15}O-PET$ was performed at rest, during cold ($5^{\circ}C$) pressor stimulation and during adenosine infusion. Left ventricular blood pool and myocardium were segmented on dynamic PET data by NMF method. Myocardial blood flow (MBF) was calculated from input and tissue functions by a single compartmental model with correction of partial volume and spillover effects. Results: There were no significant difference in resting MBF between the two groups (Smokers: 1.43 0.41 ml/g/min and non-smokers: $1.37{\pm}0.41$ ml/g/min p=NS). during cold pressor stimulation, MBF in smokers was significantly lower than 4hat in non-smokers ($1.25{\pm}0.34$ ml/g/min vs $1.59{\pm}0.29$ ml/gmin; p=0.019). The difference in the ratio of cold pressor MBF to resting MBF between the two groups was also significant (p=0.024; $90{\pm}24%$ in smokers and $122{\pm}28%$ in non-smokers.). During adenosine infusion, however, hyperemic MBF did not differ significantly between smokers and non-smokers ($5.81{\pm}1.99$ ml/g/min vs $5.11{\pm}1.31$ ml/g/min ; p=NS). Conclusion: in smokers, MBF during cold pressor stimulation was significantly lower compared wi4h nonsmokers, reflecting smoking-Induced endothelial dysfunction. However, there was no significant difference in MBF during adenosine-induced hyperemia between the two groups.

• Journal of Life Science
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• v.23 no.11
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• pp.1342-1350
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• 2013

We examined the effect of hydrogen sulfide ($H_2S$) in chemical hypoxia-induced injury in mouse hepatocytes. Cell viability was significantly decreased by cobalt chloride ($CoCl_2$), a well-known hypoxia mimetic agent in a time- and dose- dependent manner. Sodium hydrosulfide (NaHS, a donor of $H_2S$) pretreatment before exposure to $CoCl_2$ significantly attenuated the $CoCl_2$-induced decrease of cell viability. $CoCl_2$ treatment resulted in an increase of intracellular ROS generation, which is inhibited by NaHS or N-acetyl-cysteine (NAC, a ROS scavenger), and p38 MAPK phosphorylation, which is also blocked by NaHS or NAC. The $CoCl_2$-induced increase of the Bax/Bcl-2 ratio was attenuated by NaHS, NAC, and SB 203580 (p38 MAPK inhibitor). The $CoCl_2$-induced decrease of cell viability was also attenuated by NaHS, NAC, and SB 203580 pretreatment. Additionally, NaHS inhibited the $CoCl_2$-induced COX-2. Similar to the effect of NaHS, NAC blocked $CoCl_2$-induced COX-2 expression. Furthermore, NS-398 (a selective COX-2 inhibitor) attenuated not only the $CoCl_2$-induced increase of the Bax/Bcl-2 ratio, it also decreased cell viability. Taken together, $H_2S$ protects primary cultured mouse hepatocytes against $CoCl_2$-induced cell injury through inhibition of the ROS-activated p38 MAPK cascade and the COX-2 pathway.

• The Korean Journal of Physiology and Pharmacology
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• v.2 no.4
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• pp.435-441
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• 1998

We examined effects of interleukin $1{\alpha}$ ($IL1{\alpha}$) and phorbol 12, 13 dibutyrate (PDB), an activator of protein kinase C, on mRNA for Prostaglandin H synthase (PGHS) and prostanoid production in cultured ovine meningeal fibroblasts. Immuno- and morphologically-identified fibroblasts were derived from cerebral cortex and white matter from fetal lambs (approximately 120 days gestation) and grown to confluence on glass coverslips in 12 well plates. Levels of prostaglandin $F_{2{\alpha}}$ and the stable hydrolysis product of prostacyclin (i.e., $6-keto-PGF_{1{\alpha}}$) were determined using enzyme immunoassay. Relative amounts of mRNA were determined by in situ hybridization using ovine cDNA for PGHS1. $IL1{\alpha}$ (10 ng/ml) increased mRNA levels over baseline by $62{\pm}19%$ (p＜0.05) at 60 min., $37{\pm}12%$ (NS) at 120 min., and $36{\pm}18%$ (NS) at 240 min (n=12). Levels of $6-keto-PGF_{1{\alpha}}$ were $148{\pm}18%$ pg/ml during baseline, $246{\pm}41%$ pg/ml at 60 min., $248{\pm}40%$ pg/ml at 120 min., and $259{\pm}62%$ pg/ml at 240 min (all p＜0.05) (n=12). $PGF_{2{\alpha}}$ was increased although it wasn't statistically significant. However, $IL1{\alpha}$ decreased $PGE_2$ level significantly (all p＜0.05). PDB $(10^{-6}M)$ increased mRNA levels over baseline by $25{\pm}6%$ after 30 min., $40{\pm}6%$ after 60 min., and $20{\pm}8%$ after 90 min. (n=9) (all p＜0.05). Levels of $6-keto-PGF_{1{\alpha}}$ were $200{\pm}43%$ pg/ml during baseline, $202{\pm}43%$ pg/ml after 30 min. (NS), $268{\pm}58%$ pg/ml after 60 min. (p＜0.05), and $296{\pm}60%$ pg/ml after 90 min. (p＜0.05) (n=9). Levels of $PGF_{2{\alpha}}$ were $178{\pm}26%$ pg/ml during baseline, $300{\pm}30%$ pg/ml after 30 min., $299{\pm}35%$ pg/ml after 60 min., and $355{\pm}32%$ pg/ml after 90 min (all p＜0.05) (n=6). Actinomycin-D (1 mg/ml) prevented increases in mRNA, $6-keto-PGF_{1{\alpha}}$, and $PGF_{2{\alpha}}$ at 60 min. for both $IL1{\alpha}$ and PDB. We conclude that cerebral fibroblasts are avid producers of prostanoids, and that enhanced production of PGHS is responsible for augmented $PGF_{2{\alpha}}$ and prostacyclin production in the presence of an activator of protein kinase C and for decreased $PGE_2$ and increased prostacyclin production in the presence of $IL1{\alpha}$.

• Proceedings of the KIEE Conference
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• 2003.10a
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• pp.207-210
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• 2003

가스절연개폐장치(Gas-Insulated Switchgear, GIS) 내부에서 발생하는 부분방전(Partial Discharge, PD) 신호는 1ns이하의 상승시간(rising time)을 가지므로, 이 신호를 효과적으로 측정하기 위해서는 초광대역(Ultra Wide Band, UWB)특성을 갖는 커플러가 필요하다. 본 논문에서는 이러한 UWB 특성을 구현하기 위해, 대수주기 톱니형 평면 안테나(log-periodic toothed planar antenna)와 등각 스파이럴 패치안테나(equi-angular spiral patch antenna)형태의 두 가지 초광대역 UHF 커플러를 설계 제작하였다. 제작한 커플러들의 특성을 파악하기 위해 안테나의 급전부에, 자체 설계한 매칭 회로인 발룬(balun, balance to unbalance)을 장착하여, 반사계수, 모의펄스에 의한 검출신호, 스펙트럼 둥을 측정하였다.

• 제어로봇시스템학회:학술대회논문집
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• 2005.06a
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• pp.352-355
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• 2005

This paper describes an engineering model development of a pulsed plasma thruster, which is capable of an impulse bit of 20uNs and a specific impulse of 800s. The solid fuel which is Teflon allows for a self-contained, inert and stable propellant system. And, the PPT technology makes it possible to consider a revolutionary attitude control system (ACS) concept providing stabilization and pointing accuracies previously obtainable only with reaction wheels, with reduced mass and power requirements.

• Proceedings of the KIEE Conference
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• 1998.07e
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• pp.1650-1652
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• 1998

This paper describes characteristics of electric field waveforms associated with multiple-lightning discharges. The electric field measurment system. consists of hemi-sphere antenna 30 cm in diameter. integrator and data acquisition device. The frequency bandwidth is from 200 Hz to 1.56 MHz, and the sensitivity is 0.96 mV/V/m. The detected electric field signal is digitized every 500 ns with the resolution of 12-bit and the length of 2 kilowords and is registered at a personal computer. Also parameters of the electric fields associated with multiple-lightning discharges are ststistically analyzed.

• Proceedings of the KIEE Conference
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• summer
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• pp.1184-1186
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• 2004

Focus Electrode(FE) 기능을 갖는 진행파관 증폭기(TWTA)를 구동하기 위하여 고전압 펄스전원 장치가 필요하다. 이 전원장치는 영부터 -5.0 kV TWT 캐소드 고전압 위에서 펄스 출력으로 동작되어야 한다 고전압펄스전원장치는 바이어스 전압이 영부터 -1.5 kV사이를 연속적으로 가변 할 수 있어야 하고, 펄스의 반복 주파수는 CW로 부터 1 kHz 그리고 펄스폭은 $10\;{\mu}s$부터 $500\;{\mu}s$로 선택 가능하여야 한다. 그리고 출력펄스의 상승 및 하강 시간은 150 ns 보다 작아야 한다. 턴-온 및 오프의 스윗칭 시간을 만족시키기 위하여 고전압 스위치는 직렬로 연결된 FET 모듈을 사용하였다. 본 논문에서는 이러한 고전압 펄스전원장치의 설계 및 제작원리 그리고 시험결과에 대하여 다루었다.

• Journal of Life Science
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• v.30 no.9
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• pp.749-762
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• 2020

Influenza A viruses are circulating in a variety of hosts, including humans, pigs, and poultry. Swine influenza virus is a zoonotic pathogen that can be readily transmitted to humans. The influenza viruses of the 2009 H1N1 pandemic were derived from swine influenza viruses, and it has been suggested that the 1957 H2N2 pandemic and the 1968 H3N2 pandemic both originated in pigs. Pigs are regarded as a mixing vessel in the creation of novel influenza viruses since they are readily infected with human and avian influenza viruses. We isolated three novel H1N2 influenza viruses from pigs showing respiratory symptoms on a Korean farm in 2019. These viruses were reassortants, containing PA and NP genes from those of the 2009 H1N1 influenza virus in addition to PB2, PB1, HA, NA, M, and NS genes from those of triple-reassortant swine H3N2 and classical swine H1N2 influenza viruses circulating in Korean pigs. Mice infected with the isolated H1N2 influenza virus lost up to 17% body weight and exhibited interstitial pneumonia involving infiltration of many inflammatory cells. Results suggest that close surveillance to detect emerging influenza viruses in pigs is necessary for the health of both pigs and humans.