• Journal of Preventive Medicine and Public Health
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• v.49 no.4
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• pp.197-204
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• 2016

Objectives: In the context of the global decrease in mortality due to gastric cancer, previous studies have reported that the effect of chronic Helicobacter pylori (H. pylori) infection on the incidence of gastric cancer varies among regions. This systematic review was conducted to investigate H. pylori as a risk factor for gastric cancer in Korea, where the incidence of gastric cancer is among the highest in the world. Methods: A search strategy was established to identify articles published in Korean as well as in English. Ultimately, we included observational studies conducted among Korean patients that designed with an age-matched and sex-matched control group that reported the odds ratio associated with H. pylori. Gastric cancer cases were subdivided into overall (OGC), cardia (CGC), non-cardia (NGC), early (EGC), advanced, intestinal (IGC), and diffuse forms of gastric cancer. Summary odds ratios (SORs) with 95% confidence intervals (CIs) were calculated in the meta-analysis using a random-effect model. Results: Eleven case-control studies were ultimately selected. H. pylori was associated with an SOR of 1.81 (95% CI, 1.29 to 2.54) for OGC. Additionally, statistically significant risks were observed for CGC, NGC, EGC, and IGC. Conclusions: Chronic H. pylori infection was found to raise the risk of gastric cancer among Koreans, with the highest risk observed for CGC and EGC (SOR=2.88 for both). Follow-up clinical epidemiologic studies are needed to assess the effects of current treatments aimed at eradicating H. pylori infections.

• Progress in Superconductivity and Cryogenics
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• v.19 no.1
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• pp.5-8
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• 2017

A series of high gradient superconducting magnetic separator (HGMS) for kaolin has been developed. It is used for processing kaolin to increase the brightness or whiteness whether it is for paper or ceramic applications. The HGMS system mainly consists of a solenoid magnet with a zero boil-off helium cryostat, a double reciprocating canisters system, and a PLC (Process Logic Controller) fully automatic control system based on SCADA (Supervisory Control and Data Acquisition) system. We have successfully developed CGC-5.5/300 and CGC-5.0/500 HGMS systems in the recent years, and now three sets of them are on-site operation in different customers. This paper will present recent progress of the HGMS system, the results of some experiments on processing kaolin clay used HGMS, and the on-site operation.

• Journal of the Korean Society for Precision Engineering
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• v.11 no.1
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• pp.54-62
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• 1994

This paper presents active control methodologies to suppress structural deflections of a composite beam using a distributed piezoelectric-film actuator and sensor. Three types of different controllers are employed to achieve vibration suppression. The controllers are established depending upon the information on the velocity components of the structrue and on the deflection magnitudes as well. They are constant-amplitude controller(CAC), constant-gain mcontroller(CGC), and constant-amplitude-gain controller(CAGC). For the minimization of the residual vibration (chattering in a settled phase), which is the practical shortcoming of the conventional CAC dur to time delay phenomenon of the hardware system, a new control algoritym CAGCis designed by selecting switching constants in an optimal manner with respect to the initial tip deflection and the applied voltage. The experimental investigations of the transient and forced vibration control for the first vibrational mode are undertaken in order to compare the suppression efficiency of each control algorithm. Moreover, simultaneous controllability of various vibrational modes through the proposed scheme is also experimentally verified by pressenting both the transfer function and the phase.

• Polymer(Korea)
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• v.31 no.6
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• pp.497-504
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• 2007

We have prepared the dinuclear half-sandwich CGC(constrained geometry catalyst) with polymethylene bridge $[Zr(({\eta}^5\;:\;{\eta}^1-C_9H_5SiMe_2NCMe_3)Me_2)_2\;[(CH_2)_n]$ [n=6(4), 9(5), 12(6)] by treating 2 equivalents of MeLi with the corresponding dichlorides compounds. To study the catalytic behavior of the dinuclear catalysts we conducted copolymerization of ethylene and 1-hexene in the presence of three kinds of boron cocatalysts, $Ph_3C^+[B(C_6F_5)_4]^-\;(B_1),\;B(C_6F_5)_3\;(B_3)$, and $Ph_3C^+[(C_6F_5)_3B-C_6F_4-B(C_6F_5)_3]^{2-}\;(B_2)$. It turned out that all active species formed by the combination of three dinuclear CGCs with three cocatalyst were very efficient catalysts for the polymerization of olefins. The activities increase as the bridge length of the dinuclear CGCs increases. At the same time the dinuclear cocatalyst exhibited the lowest activity among three cocatalysts. The prime observation is that the dinuclear cocatalyst gave rise to the formation of the copolymers with the least branches on the polyethylene backbone.

• Polymer(Korea)
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• v.35 no.1
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• pp.77-86
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• 2011

Polymerization properties of six dinuclear constrained geometry catalysts (DCGC) were investigated. The different length bridges of three catalysts were para-phenyl (Catalyst 1), para-xylyl (Catalyst 2), and para-diethylene phenyl (Catalyst 6). The other three DCGC have the same para-xylyl bridge with the different substituents at the phenyl ring of the bridge. The selected substituents were isopropyl (Catalyst 3), n-hexyl (Cataylst 4), and n-octyl (Catalyst 5), It was found that the longer catalyst not only exhibited a greater activity but also prepared a higher molecular weight copolymer. The catalyst 3 having a bulky isopropyl substituent revealed the lower activity but formed the highest molecular weight polymer comparing with the other alkyl substituted DCGCs. These results were able to be understood on the basis of the electronic and steric characteristics of the bridge. This study confirms that the control of the bridge structure of DCGC may contribute to control the microstructure of polymers.

• Macromolecular Research
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• v.15 no.5
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• pp.430-436
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• 2007

The dinuclear half-sandwich CGCs (constrained geometry catalyst) with a polymethylene bridge, $[Ti({\eta}^5 : {\eta}^1-indenyl)SiMe_2NCMe_3]_2(CH_2)_n]$[n = 6 (1) and 12 (2)], have been employed in the copolymerization of ethylene and norbornene (NBE). To compare the mononuclear metallocene catalysts; $Ti({\eta}^5 : {\eta}^1-2-hexylindenyl)SiMe_2NCMe_3$ (3), $(Cp^* SiMe_2NCMe_3)$Ti (Dow CGC) (4) and ansa-$Et(Ind)_2ZrCI_2$ (5), were also studied for the copolymerization of ethylene and NBE. It was found that the activity increased in the order: 1 < 2 < 3 < 5 < 4, indicating that the presence of the bridge between two the CGC units contributed to depressing the polymerization activity of the CGCs. This result strongly suggests that the implication of steric disturbance due to the presence of the bridge may playa significant role in slowing the activity. Dinuclear CGCs have been found to be very efficient for the incorporation of NBE onto the polyethylene backbone. The NBE contents in the copolymers formed ranged from 10 to 42%, depending on the polymerization conditions. Strong chemical shifts were observed at ${\delta}$42.0 and 47.8 of the isotactic alternating NBE sequences, NENEN, in the copolymers with high NBE contents. In addition, a resonance at 47.1 ppm for the sequences of the isolated NBE, EENEE, was observed in the $^{13}C-NMR$ spectra of the copolymers with low NBE contents. The absence of signals for isotactic dyad at 48.1 and 49.1 ppm illustrated there were no isotactic or microblock (NBE-NBE) sequences in the copolymers. This result indicated that the dinuclear CGCs were effective for making randomly distributed ethylene-NBE copolymers.

• Review of KIISC
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• v.28 no.2
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• pp.33-42
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• 2018

머신러닝 및 인공지능 기술의 발전은 다양한 분야 활용되고 있고, 이는 보안 분야에서도 마찬가지로 로그 분석이나, 악성코드 탐지, 취약점 탐색 및 대응 등 다양한 분야에서 자동화를 위한 연구가 진행되고 있다. 특히 취약점 탐색 및 대응 분야의 경우 2016년 데프콘에서 진행된 CGC를 필두로 바이너리나 소스코드 내의 취약점을 정확하게 탐색하고 패치하기 위해 다양한 연구가 시도되고 있다. 이에 본 논문에서는 취약점을 탐색 및 대응하기 위해 각 연구 별 탐색 기술과 대응 기술을 분류 및 분석한다.

• Proceedings of the Polymer Society of Korea Conference
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• 2006.10a
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• pp.159-160
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• 2006

We developed novel catalyst, PHENICS composed of the combination of a cyclopentadienyl group to perform a high catalytic activity and a bulky phenoxy group, which performs the production of high molecular weight polyolefin. The polymerization activity of PHENICS at high temperature is higher than well-known CGC catalyst. PHENICS showed the excellent ability of comonomer incorporation into polymer chain. The obtained copolymer had a high molecular weight. The PHENICS catalyst is also active to the copolymerization of ethylene and several vinyl comonomers such as styrene, norbornen, and conjugated dienes. We will discuss new cocatalysts for PHENICS to improve activity and the ability of molecular weight control.

• Proceedings of the Polymer Society of Korea Conference
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• 2006.10a
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• pp.223-223
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• 2006

A Suzuki-coupling route is developed for preparation of ortho-phenylene-bridged Cp/amido complexes, one of which shows higher activity, higher 1-hexene incorporation, and higher molecular weight than the silylene-bridged standard CGC $[Me_{2}Si({\eta}^{5}-Me_{4}Cp)(N^{t}Bu)]TiCl_{2}$.

• Journal of Pharmaceutical Investigation
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• v.38 no.6
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• pp.365-372
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• 2008

The aim of this study was to investigate the frequency of the SNPs on MDR1 exon 12, 21 and 26 in Korean population and to analyze haplotype frequency on MDR1 exon 12, 21 and 26 in Korean population. A total of 426 healthy subjects was genotyped for MDR1, using polymerase chain reaction-based diagnostic tests. Haplotype was statistically inferred using an algorithm based on the expectation-maximization (EM). MDR1 C1236T genotyping revealed that the frequency for homozygous wild-type (C/C), heterozygous (C/T) and for homozygous mutant-type (T/T) was 20.19%, 46.48% and 33.33%, respectively. MDR1 G2677T/A genotyping revealed that the frequency for homozygous G/G, heterozygous G/T, homozygous T/T, heterozygous G/A, heterozygous T/A and for homozygous A/A type was 30.75%, 42.26%, 9.86%, 7.51 %, 7.04% and 2.58%, respectively. MDR1 C3435T genotyping revealed that the frequency for homozygous wild-type (C/C), heterozygous (C/T) and for homozygous mutant-type (T/T) was 38.73%, 50.24% and 11.03%, respectively. Twelve haplotypes were observed. Of the three major haplotypes identified (CGC, TTT and TGC), the CGC haplotype were mainly predominant in the Korean populations and accounted for 29.96% of total haplotype in Korean.