법랑질에 대한 total etching과 self-etching 접착제의 산부식 효과와 미세인장결합강도

오선경,허복,김현철 大韓齒科保存學會 2004 Restorative Dentistry & Endodontics Vol.29 No.3

The purpose of this study was to evaluate the etching effects and bond strength of total etching and self-etching adhesive system on unground enamel using scanning electron microscopy and microtensile bond strength test. The buccal coronal unground enamel from human extracted molars were prepared using low-speed diamond saw. Scotchbond Multi-Purpose (group SM), Clearfil SE Bond (group SE), or Adper Prompt L-Pop (group LP) were applied to the prepared teeth, and the blocks of resin composite (Filtek Z250) were built up incrementally. Resin tag formation was evaluated by scanning electron microscopy, after removal of enamel surface by acid dissolution and dehydration. For microtensile bond strength test, resin-bonded teeth were sectioned to give a bonded surface area of 1㎟. Microtensile bond strength test was perfomed. The results of this study were as follows. 1. A definite etching pattern was observed in Scotchbond Multi-Purpose group. 2. Self-etching groups were characterized as shallow and irregular etching patterns. 3. The results (mean) of microtensile bond strength were SM; 26.55 MPa, SE; 18.15 MPa, LP; 15.57 MPa. SM had significantly higher microtensile bond strength than SE and PL (p〈0.05), but there was no significant difference between SE and PL.

Cryptococcal 뇌막염이 병발된 수막 암종증 1예

안병철,고지영,이현옥,최진영,권오상,박용욱 중앙대부설한국의과학연구소 1990 한국의과학 Vol.22 No.1

세가지 니켈 티타늄 파일의 휨과 비틀림 조건에서의 응력 분포에 관한 3차원 유한요소 연구

김태오,이찬주,김병민,박정길,허복,김현철 大韓齒科保存學會 2008 Restorative Dentistry & Endodontics Vol.33 No.4

이 연구의 목적은 세가지 니켈-티타늄 파일의 휨과 회전 조건 하에서의 응력 분포를 유한요소 모형을 이용하여 비교하는 것이다. ProFile .06/#30, ProTaper와 ProTaper Universal의 F3파일을 마이크로컴퓨터 단층촬영을 하고 reverse engineering을 통하여 세 니켈 티타늄 파일의 구조를 얻고 삼차원 유한요소모형을 제작하였다. 니켈 티타늄 합금의 비선형적인 물리적 성질을 반영하고 ABAQUS 프로그램을 이용하여 휨과 회전 조건 하에서의 기계적인 움직임을 수학적으로 예측 분석하였다. U-형태의 단면 구조를 가진 ProFile이 모형 가운데 가장 좋은 휨 성질을 나타냈다. 동일한 휨량 조건에서는 볼록한 삼각형 단면의 ProTaper가 다른모형보다 많은 힘을 필요로 하였으며, 반면에 가장 높은 von Mises 응력은 ProTaper Universal의 단면에서 움푹 파인 부위에 집중되었다. ProFile 모형은 동일한 크기의 회전력에 대해 가장 큰 응력 집중을 U-형 구 부위에 나타냈다. ProTaper 모형은 다른 모형에 비해 동일량을 비틀기 위해 더 많은 힘을 필요로 하였으며, 반면에 동량의 비틀림에서는 가장 높은 von Mises 응력이 ProTaper Universal의 단면에서 움푹 파인 부위에 집중되었다. Flexibility and fracture properties determine the performance of NiTi rotary instruments. The purpose of this study was to evaluate how geometrical differences between three NiTi instruments affect the deformation and stress distributions under bending and torsional conditions using finite element analysis. Three NiTi files (ProFile .06 / #30, F3 of ProTaper and ProTaper Universal) were scanned using a Micro-CT. The obtained structural geometries were meshed with linear, eight-noded hexahedral elements. The mechanical behavior (deformation and von Mises equivalent stress) of the three endodontic instruments were analyzed under four bending and rotational conditions using ABAQUS finite element analysis software. The nonlinear mechanical behavior of the NiTi was taken into account. The U-shaped cross sectional geometry of ProFile showed the highest flexibility of the three file models. The ProTaper, which has a convex triangular cross-section, was the most stiff file model. For the same deflection, the ProTaper required more force to reach the same deflection as the other models, and needed more torque than other models for the same amount of rotation. The highest von Mises stress value was found at the groove area in the cross-section of the ProTaper Universal. Under torsion, all files showed highest stresses at their groove area. The ProFile showed highest von Mises stress value under the same torsional moment while the ProTaper Universal showed the highest value under same rotational angle.

월수함수 단일항전개를 이용한 추적 최적제어기 설계

안두수,오현철,김민형,이재춘,이명규 成均館大學校 科學技術硏究所 1995 論文集 Vol.46 No.1

This paper presents the methode of optimal control theory and observer for time invariant system via Single Term Walsh Series. The algorithm of the optimal control theory is simulated by MATLAB.

Wilson's Disease 2예

고지영,안병철,이현옥,권오상,최진영 중앙대부설한국의과학연구소 1989 한국의과학 Vol.21 No.3

부신피질 호산성 과립세포종 1예

이성진,이호권,박철영,정인경,홍은경,오기원,김현규,김두만,유재명,임성희,최문기,유형준,박성우 대한내분비학회 2004 Endocrinology and metabolism Vol.19 No.1

저자들은 건강검진에서 시행한 복부 초음파검사상 우연히 좌측 부신 종괴가 발견되어 복부 전산화 단층 촬영검사와 호르몬검사를 시행한 후 부신피질 악성종양과의 감별 진단을 위해 부신절제술과 전자현미경검사를 포함한 병리조직학적 검사를 시행하여 부신피질호산성 과립세포종으로 진단한 증례를 경험하였기에 문헌고찰과 함께 이를 보고하는 바이다. Oncocytomas are neoplasms, histologically are composed of epithelial cells, with abundant, acidophilic and granular cytoplasm. Electron microscopic studies of oncocytomas have shown that the cytoplasm of oncocytes is packed with mitochondria. The adrenal gland is a very rare anatomical site for oncocytomas, and to the best of our knowledge, only thirty-six cases of adrenal oncocytomas have been described. Herein, a case of a large adrenal mass in a forty-year-old man, which was incidentally detected by abdominal ultrasonography, is presented. This patient demonstrated no clinical manifestation associated with adrenal hyperfunction. Hormonal studies showed no abnormal findings, except for a mild elevation of the 24-hour urinary VMA level. Abdominal computed tomography with enhancement revealed a large, well-defined left adrenal mass, measuring 5.0×4.2 ×3.0 cm. The patient underwent a left adrenalectomy, and a light microscopic examination confirmed an adrenocortical oncocytoma, with characteristic oncocytes and polygonal, abundant, eosinophilic and granular cytoplasm. The tumor cells were positive for cytokeratin and vimentin as well as S-100, but negative for chromogranin on immunohistochemical staining. An electron microscopic examination demonstrated closely packed mitochondria, containing intramitochondrial inclusions. After surgery, there was no evidence of a recurrent or distant metastatic disease at the 5 month follow-up. In summary, an extremely rare case of a man with an adrenocortical oncocytoma is reported, which was confirmed by histological examinations, including electron microscopy (J Kor Soc Endocrinol 19:82∼89, 2004).

Review of a Case of Chronic Obstructive Pulmonary Disease in Workers Exposed to Synthetic Fibers

Hyeon-cheol Oh,Chae-seong Lim,Jung-won Kim,Eun-seok Kim,Ji-eun Lee,Sang-cheol Kim 한국산업보건학회 2023 한국산업보건학회지 Vol.33 No.3

Objectives: Objectives of this study were: 1) to introduce industrial situation and health hazards of synthetic fiber, 2) to review a case of chronic obstructive pulmonary disease in a worker exposed to synthetic fiber reported to the Korea Occupational Disease Surveillance Center, and 3) to suggest supplementary measures for the occupational health system for workers exposed to synthetic fibers. Methods: Respiratory exposure, health hazards, and exposure standards for synthetic fiber dust in Korea and other countries were reviewed. In addition, a case of chronic obstructive pulmonary disease due to exposure to nylon dust reported to the Korea Occupational Disease Surveillance Center was reviewed and summarized. Results: The worker was a 53-year-old non-smoking male who had been involved in the nylon weaving process for 26 years. He had shortness of breath from three years ago. He was diagnosed with chronic obstructive pulmonary disease. PM1.0, PM2.5, and PM10 were measured at 26.6 μg/m3, 48.2 μg/m3, and 91.7 μg/m3, respectively. Fiber components estimated as nylon fiber were detected in the microscopic examination of a solid sample. Conclusions: For workers exposed to synthetic fiber dust, special health examinations of the respiratory system, regular work environment measurement, and work environment management through workplace health management should be performed. It is necessary to research on health effects of synthetic fibers.

Development of a Genome-Wide Random Mutagenesis System Using Proofreading-Deficient DNA Polymerase δ in the Methylotrophic Yeast Hansenula polymorpha

( Oh Cheol Kim ),( Sang Yoon Kim ),( Dong Hyeon Hwang ),( Doo Byoung Oh ),( Hyun Ah Kang ),( Oh Suk Kwon ) 한국미생물 · 생명공학회 2013 Journal of microbiology and biotechnology Vol.23 No.3

The thermotolerant methylotrophic yeast Hansenula polymorpha is attracting interest as a potential strain for the production of recombinant proteins and biofuels. However, only limited numbers of genome engineering tools are currently available for H. polymorpha. In the present study, we identified the HpPOL3 gene encoding the catalytic subunit of DNA polymerase δ of H. polymorpha and mutated the sequence encoding conserved amino acid residues that are important for its proofreading 3`→5` exonuclease activity. The resulting HpPOL3* gene encoding the error-prone proofreading-deficient DNA polymerase δ was cloned under a methanol oxidase promoter to construct the mutator plasmid pHIF8, which also contains additional elements for site-specific chromosomal integration, selection, and excision. In a H. polymorpha mutator strain chromosomally integrated with pHIF8, a URA3- mutant resistant to 5-fluoroorotic acid was generated at a 50-fold higher frequency than in the wild-type strain, due to the dominant negative expression of HpPOL3*. Moreover, after obtaining the desired mutant, the mutator allele was readily removed from the chromosome by homologous recombination to avoid the uncontrolled accumulation of additional mutations. Our mutator system, which depends on the accumulation of random mutations that are incorporated during DNA replication, will be useful to generate strains with mutant phenotypes, especially those related to unknown or multiple genes on the chromosome.

반응표면법을 이용한 커버 플라스틱 적층 구조의 내 충격 특성 평가

오현철(Hyeon-Cheol Oh),신창민(Chang-Min Shin),정누리(Nu-Ri Cheong),김근영(Keun-Young Kim),이병채(Byung-Chai Lee) (사)한국CDE학회 2013 한국 CAD/CAM 학회 학술발표회 논문집 Vol.2013 No.1

This study aims to perform the finite element analysis for the laminated structure including cover-plastic materials and evaluate variations in impact resistance properties using the response surface methodology. Recently launched smart devices use the tempered glass as a cover, which has drawbacks such as high prices, manufacturing problems and heavy weight. Cover-plastic materials with high hardness were developed to overcome those and to carry out impact test and process design improvements are needed in order to evaluate impact resistance of the prototype when designing it using that materials. Finite element analysis with impact load was performed for the primary design variables and they were evaluated in view of the cost and the effectiveness. Also aspects of the impact resistance were analyzed by constructing the response surface model.

비국가행위자의 사이버공격에 관한 국제법적 연구

오현철(Oh, Hyeon Cheol) 국제법평론회 2016 국제법평론 Vol.0 No.45

Cyberspace will become a main front in both irregular and traditional conflicts. Enemies in cyberspace will include both states and non-state actors and will range from the unsophisticated amateur to highly trained professional hackers. Through cyberspace, enemies will target industry, academia, government, as well as the military in the air, land, maritime, and space domains. One of most prominent features of the global Issue is the significant surge in numbers and importance of non-state actors. The rise of these non-state actors and their growing involvement in world politics challenges the assumptions of traditional approaches to international relations which assume that states are the only important unites of the international system. Traditionally, the principal actors of war and conflict on the would stage were nation-states. Nation-states, or states, have a legally recognized status among the international community, Non-state actors, on the other hand, lack such legal status. Nevertheless, since World War Ⅱ, the world has experienced a significant increase in non-state actors becoming actors in world politics and war. Today, the cyber warfare from non-state actors currently dominates the cyber battlefield. With an increasing number of cyber attacks originating from sophisticated cyber criminals, hackivists, and State-sponsored patriotic hackers, a new era of cyber warfare is emerging. This article argues that existing international laws of war are inadequate and need to be adjusted and clearly defined to include cyber attacks involving state and non-state actors.