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김교한,허만수,김형일,황운석,高田 雄京,奧野 攻 대한치과기재학회 1999 대한치과재료학회지 Vol.26 No.4
One of the fields in which titanium(Ti) is becoming increasingly valuable is the field of biomaterials. Ti had shown its good corrosion resistance, high strength to weight ratio, and compatibility with human tissues. Such applications of Ti in this area involve replacing stainless steel and cobalt-chromium alloy implant which are used in skull, shoulder joint, spine, and dental implant. In dental field, titanium has been used as dental implant, so it becomes necessary to examine and estimate the anti-corrosion ability of Ti and its alloys at the severe conditions such as crevice corrosion and galvanic corrosion. The purposes of this study was to examine the corrosion mechanisms of the pure Ti showing good corrosion resistance under an oral corrosion environment when it is coupled with dental casting Type Ⅱ and Type Ⅳ gold alloys. These coupling corrosion mechanisms were studied in three conditions. First was by measuring the resting potential of pure Ti, when it was uncoupled and coupled with Type Ⅱ and Type Ⅳ alloys. Second was by measuring anode polarization behavior of pure Ti, Type Ⅱ and Type Ⅳ alloys, and third was by detecting dissolved ions from the pure Ti, uncoupled and coupled with Type Ⅱ and Type Ⅳ gold alloys which were immersed in 0.9% NaCl solution for 7 days. The resting potential showed a low potential value at the initial stage but increasing into a high value (to 0.18 V) with time elapse and reached a stable value. On the contrary, the potentials of Type Ⅱ and Type Ⅳ gold alloys were in their values at the initial stage of immersion, then decreased with the time and reached stable values, being higher than the value of pure Ti. When pure Ti coupled with Type Ⅱ and Type Ⅳ gold alloys, the resting potential of coupled one was between the values of each one. When Type Ⅱ and Type Ⅳ gold alloys were coupled with pure Ti, there was an increase in Ag, Cu, and Zn. Also, Zn ions released the high potential precious metal alloys, compared to the uncoupled case. Ti ion was not detected at any cases of pure Ti or coupled with gold alloys. It was thought that one of the causes of the increase in Ag, Zn, and Cu ions when Ti was coupled with dental gold alloys was that Ag, Zn, and Cu ions were selectively dissoluted from the Ag rich regions around grain boundary and the casting defects. In conclusions, the results of this study suggest that the pure Ti was very stable when coupled with the gold alloys in oral cavity.
Galvanic Coupling Effect on Corrosion Behavior of Al Alloy-Matrix Composites
Hwang, Woon Suk,Kim, Hyoun Woo 대한금속재료학회 2002 METALS AND MATERIALS International Vol.8 No.6
Galvanic coupling effect on the corrosion of SiC-reinforced aluminum alloy-matrix composites was investigated in a sodium chloride solution. The potentiodynamic polarization measurement indicated that pitting potentials of metal matrix composites (MMCs) and AA2124 matrix alloy were similar, and pitting potential of MMCs was almost same as corrosion potential, while pitting susceptibility of MMCs was higher than that of AA2124 alloy. Galvanic current by formation of galvanic couple between SiCw and matrix reveals very low value because of large cathodic polarization of SiC. However, by increasing potential of matrix to pitting potential by this galvanic couple and thus, forming pits easily at the weak passive film near SiC reinforcing phase preferentially, it is concluded that pitting susceptibility of MMCs increases highly than AA2124 alloy of matrix composition.
Unconstrained Sleep Apnea Monitoring Using Polyvinylidene Fluoride Film-Based Sensor
Hwang, Su Hwan,Lee, Hong Ji,Yoon, Hee Nam,Jung, Da Woon,Lee, Yu-Jin G.,Lee, Yu Jin,Jeong, Do-Un,Park, Kwang Suk IEEE 2014 IEEE Transactions on Biomedical Engineering Vol.61 No.7
<P>We established and tested an unconstrained sleep apnea monitoring method using a polyvinylidene (PVDF) film-based sensor for continuous and accurate monitoring of apneic events occurred during sleep. Twenty-six sleep apnea patients and six normal subjects participated in this study. Subjects' respiratory signals were measured using the PVDF-based sensor during polysomnography. The PVDF sensor comprised a 4 × 1 array, and a thin silicon pad was placed over the sensor to prevent damage. Total thickness of the merged system was approximately 1.1 mm which was thin enough to prevent the subject from being consciously aware of its presence. It was designed to be placed under subjects' backs and installed between a bed cover and mattress. The proposed method was based on the standard deviation of the PVDF signals, and it was applied to a test set for detecting apneic events. The method's performance was assessed by comparing the results with a sleep physician's manual scoring. The correlation coefficient for the apnea-hypopnea index (AHI) values between the methods was 0.94 (p <; 0.001). The areas under the receiver operating curves at three AHI threshold levels (>5, >15, and >20) for sleep apnea diagnosis were 0.98, 0.99, and 0.98, respectively. For min-by-min apnea detection, the method classified sleep apnea with an average sensitivity of 72.9%, specificity of 90.6%, accuracy of 85.5%, and kappa statistic of 0.60. The developed system and method can be applied to sleep apnea detection in home or ambulatory monitoring.</P>
Hwang, Jung-Suk,Chung, Hye-Kyung,Bae, Eun-Kyong,Lee, Ah-Young,Ji, Hee-Jung,Park, Dong-Woon,Jung, Hwa-Jin,Cho, Chung-Won,Choi, Hyun-Ju,Lee, Dong-Seok,Lee, Kang-Ro,Youn, Hyun-Joo The Pharmaceutical Society of Korea 2003 Archives of Pharmacal Research Vol.26 No.4
A polysaccharide fraction, AIP1, purified from Artemisia iwayomogi was shown to have immunomodulating and anti-tumor activities in mice. In order to determine how the AIP1 fraction exhibits the immunomodulating activity, the effect of the fraction on the apoptosis of mouse spleen cells was investigated. Treatment of the mouse spleen cells with the AIP1 fraction resulted ,in the suppression of apoptotic death and an extension of cell survival in culture, indicating that the fraction might modulate the death of spleen cells. Treatment of the mice with the AIP1 fraction in vivo also resulted in less apoptosis of the spleen cells, which indicates the physiological relevance of the anti-apoptosis effect of the fraction in vitro. A mouse gene array was used to determine the profile of the gene expression change showing a pattern of up- and down-regulated genes by the AIP1 treatment. This study provides preliminary information regarding the immunomodulatory mechanism of the AIP1 fraction.
Hwang, Geon-Tae,Palneedi, Haribabu,Jung, Byung Mun,Kwon, Suk Jin,Peddigari, Mahesh,Min, Yuho,Kim, Jong-Woo,Ahn, Cheol-Woo,Choi, Jong-Jin,Hahn, Byung-Dong,Choi, Joon-Hwan,Yoon, Woon-Ha,Park, Dong-Soo,L American Chemical Society 2018 ACS APPLIED MATERIALS & INTERFACES Vol.10 No.38
<P>We report the effect of epoxy adhesion layers with different mechanical or physical property on a magnetoelectric (ME) composite laminate composed of FeBSi alloy (Metglas)/single-crystal Pb(Mg<SUB>1/3</SUB>Nb<SUB>2/3</SUB>)O<SUB>3</SUB>-Pb(Zr,Ti)O<SUB>3</SUB>/Metglas to achieve an improved ME conversion performance. Through theoretical simulation, it was revealed that the Young’s modulus and the thickness of interfacial adhesives were major parameters that influence the conversion efficiency in ME composites. In the experimental evaluation, we utilized three epoxy materials with a distinct Young’s modulus and adjusted the average thickness of the adhesion layers to optimize the ME conversion. The experimental results show that a thin epoxy layer with a high Young’s modulus provided the best performance in the inorganic-based ME conversion process. By tailoring the interfacial adhesion property, the ME laminate generated a high conversion coefficient of 328.8 V/(cm Oe), with a mechanical quality factor of 132.0 at the resonance mode. Moreover, we demonstrated a highly sensitive alternating current magnetic field sensor that had a detection resolution below 10 pT. The optimization of the epoxy layers in the ME laminate composite provided significant enhancement of the ME response in a simple manner.</P> [FIG OMISSION]</BR>
Bo-Woon Kim,Young-Kyung Jo,Gyeong-Nam Kim,Jung-Yun Hwang,Mi-Yeon Hong,Won-Dug Seo,Suk-Nam Hwang 대한미생물학회 2022 Journal of Bacteriology and Virology Vol.52 No.3
This study was conducted on the incidence of CRE infection and CPE gene distribution in Ulsan to prepare basic data for preventing the spread of CRE infection by confirming the regional characteristics of CRE infection. The results of the CRE infection test from 2018 to 2021 conducted by the Ulsan Metropolitan Government Research Institute of Public Health and Environment in accordance with the experimental method of the Korea Disease Control and Prevention Agency’s SOP on CRE infection test were analyzed for the study. Through the analysis, it was confirmed that the positive rate of ‘CRE or CPE’ in the samples surveyed increased from 92.83% in 2018 to 97.62% in 2021. In the analyzed ‘CRE (including CP-CRE)’ samples, Ertapenem resistance was the most common at 94.34%, Imipenem resistance 65.37%, Meropenem resistance 63.34%, and Doripenem resistance 52.70%. Regarding the average distribution of ‘CRE (including CP-CRE)’ by genus for the four years, the genus Klebsiella was isolated the most with an average of 72.04%, followed by the genus Escherichia (10.81%), the genus Enterobacter (9.54%), and the genus Citrobacter (1.27%.). From 2018 to 2021, the proportion of ‘CP-CRE’ increased significantly from 59.07% to 68.45% and the types of genus and species identified as ‘CP-CRE’ were diversified during the same period. The distribution of the detected CPE genes were highest in KPC (89.31%), and NDM (8.53%), and the distribution of CPE gene subtypes also varied. It is expected that this study can be used as basic data for preparing suitable countermeasures against CRE infection in the community in the future
가짜뉴스 관련 국내 입법안 분석과 그 한계 위헌성 여부를 중심으로
황용석(Hwang, Yong Suk),정재관(Jeong, Jae Kwan),정다운(Jung, Da Woon) 동국대학교 사회과학연구원 2018 사회과학연구 Vol.25 No.2
2016년 미국 대선을 기점으로 가짜뉴스가 확산되며 이에 따른 정치 사회적 파장이 커짐에 따라 가짜뉴스를 규제하기 위한 방안이 모색되고 있다. 사업자의 기술적 조치와 내적 규약을 통한 자율규제방식과 더불어 법률을 통한 타율규제 또한 최근 들어 시도되고 있다. 그러나 가짜뉴스가 다양한 의미로 사용됨에 따라 개념 정의가 불명확해지고 있으며 명확성의 원칙에 위반한 규제 시도는 표현의 자유를 포함한 헌법적 가치와 상충할 우려가 있다. 이에 이 연구에서는 가짜뉴스와 연관된 법률 구조의 특성을 고찰하고 입법 과정에서 기준이 될 수 있는 헌법적 가치(표현의 자유, 사전검열 금지, 명확성의 원칙, 과잉금지원칙)에 대해 분석하였다. 가치기준에 따라 최근 발의된 개정안의 위헌성 여부를 검토하였다. 그 결과 최근 발의된 개정안들은 다음의 문제점을 내포하고 있다. 첫째로, 명확성과 과잉금지의 원칙을 위배하는 법조항이 다수 포함되어 있다. 둘째로, 정보통신서비스 제공자를 규율하여 입법 목적을 달성하는 방식을 택하는데 이는 권리침해의 문제와 국내 사업자의 역차별 문제를 야기한다. 셋째로, 법령의 목적 정당성에 위배하는 조항이 다수 있다. 마지막으로, 위축효과를 발생시킬 수 있는 규제안들을 포함하고 있다. Fake news has been an important issues in political and social agenda since 2016 U.S. presidential election. In order to reduce the fake news, both self-regulations using technological measures and internal regulation by service providers and legal restrictions are attempted. However, Conceptualization of the fake news becomes more difficult as the term is used for various purposes and situations. Regulations without clear definition may contradict with other consitutional values including freedom of expression. Therefore, this study considered characteristics of legal systems related to the fake news and analyzed the constitutional values(freedom of expression, pre-censorship, principle of disclosure, principle of proportionality) that serve as criteria during the legislation. Finally, this study examined legislation bills on fake news to see if bills may contain unconstitutional components. The results suggest as followed; first, several bills may violate principle of disclosure and principle of proportionality. Second, regulating domestic service providers may cause infringement of their rights and reverse discrimination. Third, several bills may violate objective legitimacy. Finally, some bills contain regulation generating chilling effects