광탄성실험 Hybrid 법에 의한 일정한 변형율을 받는 O-Ring 의 응력해석

권오성(O-Sung Kwon),황재석(Jai-Sug Hawong),남정환(Jeong-Hwan Nam),한송령(Song-Ling Han),박성한(Sung-Han Park) 대한기계학회 2006 대한기계학회 춘추학술대회 Vol.2006 No.11

In this research, stresses of O-ring with uniform deformation ratio in upper and lower direction are analyzed by photoelastic experimental hybrid method. The O-ring is made from rubber and is used to sealing of the high pressure vessel. The compressive deformation ratios of O-ring are 10% and 20%. Stress components (σ<SUB>xx</SUB>, σ<SUB>yy</SUB>, τ<SUB>xy</SUB>) of O-ring uniform ratios obtained from the photoelastic experimental hybrid method are almost identical to those from Hertz’s theory. Therefore, stress freezing method and photoelastic experimental hybrid method are effective applied to the stress analysis of O-ring made from rubber and with uniform ratios. The loading device developed in this research is used to produce the uniform deformation ratio of O-ring and as loading device of stress freezing. Stress distributions results from the upper contact surface of O-ring are almost identical to those from the lower contact surface of O-ring without regard to squeeze deformation ratio.

RF-O₂ Plasma 처리한 MgO 박막의 스퍼터링 수율 측정

정원희(W. H .Jeoung),정강원(K. W. Jeong),임연찬(Y. C. Lim),오현주(H. J. Oh),박철우(C. W. Park),최은하(E. H. Choi),서윤호(Y. H. Seo),김윤기(Y. K. Kim),강승언(S. O. Kang) 한국진공학회(ASCT) 2006 Applied Science and Convergence Technology Vol.15 No.3

RF-O₂ plasma 처리한 MgO 박막의 스퍼터링 수율을 집속이온빔 장치를 이용하여 측정하였다. 가속 전압 10 ㎸의 Ga 이온빔을 주사했을 때 plasma 처리하지 않은 MgO 박막의 스퍼터링 수율은 0.33 atoms/ion, RF-O₂ plasma 처리한 MgO 박막의 스퍼터링 수율은 0.20 atoms/ion 으로 RF-O₂ plasma 처리한 경우 스퍼터링 수율이 낮아졌다. 또한 XPS, AFM을 통해 plasma 처리로 인한 MgO 표면의 변화를 관찰하였다. MgO 박막에 RF-O₂ plasma 처리 한 후 XPS O 1s spectra의 binding energy와 FWHM 값이 각각 2.36 eV와 0.6167 eV 작아졌고 표면거칠기의 RMS 값 또한 0.32 ㎚ 작아졌다. We measured sputtering yield of RF O₂-plasma treated MgO protective layer for AC-PDP(plasma display panel) using a Focused Ion Beam System(FIB). A 10 ㎸ acceleration voltage was applied. The sputtering yield of the untreated sample and the treated sample were 0.33 atoms/ion and 0.20 atoms/ion, respectively. The influence of the plasma-treatment of MgO thin film was characterized by XPS and AFM analysis. We observed that the binding energy of the O 1s spectra, the FWHM of O 1s spectra and the RMS(root-mean-square) of surface roughness decreased to 2.36 eV, 0.6167 eV and 0.32 ㎚, respectively.

Excluded vertex-minors for graphs of linear rank-width at most k

Jeong, J.,Kwon, O.j.,Oum, S.i. Academic Press 2014 European journal of combinatorics : Journal europ& Vol.41 No.-

Linear rank-width is a graph width parameter, which is a variation of rank-width by restricting its tree to a caterpillar. As a corollary of known theorems, for each k, there is a finite obstruction set O<SUB>k</SUB> of graphs such that a graph G has linear rank-width at most k if and only if no vertex-minor of G is isomorphic to a graph in O<SUB>k</SUB>. However, no attempts have been made to bound the number of graphs in O<SUB>k</SUB> for k≥2. We show that for each k, there are at least 2<SUP>Ω(3^k)</SUP> pairwise locally non-equivalent graphs in O<SUB>k</SUB>, and therefore the number of graphs in O<SUB>k</SUB> is at least double exponential. To prove this theorem, it is necessary to characterize when two graphs in O<SUB>k</SUB> are locally equivalent. A graph is a block graph if all of its blocks are complete graphs. We prove that if two block graphs without simplicial vertices of degree at least 2 are locally equivalent, then they are isomorphic. This not only is useful for our theorem but also implies a theorem of Bouchet (1988) stating that if two trees are locally equivalent, then they are isomorphic.

장기 저장연료의 열안정성 및 연료접촉 고무오링의 수명예측 연구

정근우(K. W. Chung),홍진숙(J. S. Hong),김영운(Y. W. Kim),한정식(J. S. Han),정병훈(B. H. Jeong),권태수(T. S. Kwon),서동욱(D. O. Suh),성민준(M. J. Sung),권영일(Y. I. Kwon) 한국트라이볼로지학회 2018 한국윤활학회지(윤활학회지) Vol.34 No.5

Thermal deterioration of fuel due to long-term storage influences engine performance and causes malfunctions. Fuel stability is usually evaluated via heat resistance and thermal stability during a brief heat shock at high temperature; storage stability in this scenario means that there is very little change in the quality of the fuel during long-term storage. In addition, rubber-based products such as oil seals, O-rings, and rubber hoses can influence the quality of the fuel. When these rubber products are in contact with fuel, they can swell, mechanically weaken, and occasionally crack, thus leaking low molar weight rubber and additives including plasticizer and antioxidant into the fuel to degrade its properties and shorten its useful lifetime. This study determines the thermal stabilities of three kinds of synthetic fuels by evaluating their low temperature kinematic viscosities, chemical composition changes via GC analyses, gross heat of combustion, and color changes. We evaluate the compression set of O-rings by immersing one NBR and two FKM rubber O-rings in the three synthetic fuel samples in airtight containers at variable storage temperatures for six months; from this, we estimate the lifetimes of the O-rings using the Power law model. There were very little changes in the chemical compositions and gross heat of combustion after six months of the experiment. The lifetimes are thus dependent on the materials of the rubber products, and in particular, the FKM O-ring was calculated to have a theoretical lifetime of 200 to 5,700 years. These results indicate that the synthetic fuels maintain their physical properties even after long-term storage at high temperatures, and the FKM O-ring is suitable for long-term sealing of these fuels.

<tex> ${\rm TmBa}_{2}{\rm Cu}_{3}{\rm O}_{7-{\rm x}}$</tex> Superconducting Thin Films Grown by Pulsed Laser Deposition

Rock-Kil Ko,O-Jong Kwon,Kyu-Jeong Song,Ahmad, D.,Chan Park,Joon-Ho Lee,Seung-Su An,Nam-Jin Lee,Sang-Soo Oh,Young-Cheol Kim Institute of Electrical and Electronics Engineers 2007 IEEE transactions on applied superconductivity Vol.17 No.2

<P>TmBa<SUB>2</SUB>Cu<SUB>3</SUB>O<SUB>7</SUB> <SUB>-</SUB> <SUB>x</SUB> films which is one of the (Rare earth)Ba<SUB>2</SUB>Cu<SUB>3</SUB>O<SUB>7</SUB> <SUB>-</SUB> <SUB>x</SUB> high temperature superconductors with small ionic radius of rare earth element, were deposited on STO (100) single crystal substrates and Y<SUB>2</SUB>O<SUB>3</SUB>/YSZ/CeO<SUB>2</SUB> buffered metal substrates by pulsed laser deposition. The J<SUB>c</SUB> (77 K) and the value of onset of Tc TmBCO thin film on STO substrate was 4.5 MA/cm<SUP>2</SUP> and 86 K, respectively. The of J<SUB>c</SUB> TmBCO coated conductor on metal substrate was 1 MA/cm<SUP>2</SUP> . In-field property measurement was carried out at temperatures between 10 K and 77 K in magnetic filed up to 6 T in PPMS system. This is the first report, to the best of our knowledge, of TmBCO thin films and coated conductors with TmBCO film as the superconducting layer which have critical current densities at 77 K of 4.5 MA/ cm<SUP>2</SUP> and 1 MA/cm<SUP>2</SUP> , respectively. The superconducting properties of TmBCO films and the possibility of using TmBCO film as the superconducting layer of the HTS coated conductor, were investigated.</P>

New Records of Two Filamentous Brown Algae, Acinetospora asiatica and Botrytella reinboldii from Korea

Antony Otinga Oteng’o,Jose Avila-Peltroche,So Young Jeong,Boo Yeon Won,Tae Oh Cho 한국환경생물학회 2018 환경생물 : 환경생물학회지 Vol.36 No.3

Acinetospora asiatica and Botrytella reinboldii are reported as two new records from S. Korea based on morphological studies and molecular analyses. A. asiatica is mainly characterized by the presence of sparsely branched uniseriate filaments with diffused meristematic zones, the formation of crampons at right angles, and the formation of plurilocular sporangia on both prostrate and erect filaments. B. reinboldii is characterized by the presence of irregularly alternating branched uniseriate filaments attached by rhizoids, and single or clustered plurilocular sporangia with a single opening. Molecular analyses of rbcL gene revealed that A. asiatica and B. reinboldii are placed within each clade of Acinetospora and Botrytella, respectively.

Aspergillus fumigatus에 대한 단핵구의 항진균 작용에서 Interleukin-15의 역할

조정호,장경희,김효열,송영구,김창오,박윤수,홍성관,허애정,염준섭,김준명 대한의진균학회 2001 대한의진균학회지 Vol.6 No.2

Background : Despite recent advances in antifungal chemotherapy, invasive aspergillosis remains an important cause of morbidity and mortality in immunocompromised patients. Interleukin-15 (IL-15) is a cytokine that is known to enhance antifungal activities of monocytes against Candida albicans. Objective: The purpose of this study is to investigate the potentials of IL-15 to enhance antifungal activities of monocytes against Aspergillus fumigatus. Methods: Peripheral blood monocytes from healthy adults were incubated with 0,1,10,100 ng/ml of IL-15 for 1, 2, and 4 days. Then, the ability of IL-15 to elicit the production of superoxide anion, the damage of hyphae by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyletrazolium bromide assay, and the killing ability of Aspergillus fumigatus conidia was investigated. Results: Incubation of peripheral blood monocytes with 100 ng/ml of IL-15 enhanced hyphal damage after 2 days (p<0.05), condicidal activity from the first day (p<0.05), and increased the production of superoxide anion (O2-) in response to phorbol myristate acetate. Conclusion: Our results indicate that IL-15 augments the microbicidal activity of human monocytes against Aspergillus fumigatus .[Kor J Med Mycol 6(2): 64-69]

Fabrication of fluorine-doped diamond-like carbon stamps for UV nanoimprint lithography

Altun, A O,Jeong, J H,Rha, J J,Choi, D G,Kim, K D,Lee, E S IOP Pub 2006 Nanotechnology Vol.17 No.18

<P>Two fluorine-doped diamond-like carbon (F-DLC) stamps with sub-100 nm line patterns were fabricated using a direct etching method. These were applied successfully to ultraviolet (UV) nanoimprint lithography without requiring an anti-adhesion layer coating. Tests were performed to determine the optimum fluorine concentration for the F-DLC stamps. The ideal stamp material consisted of 25 at.% F-DLC with a contact angle of 85°, UV transmittance of 16.4–26.8%, and hardness of 4.5 GPa. The O<SUB>2</SUB> plasma etch rate of the DLC was increased considerably by the fluorine doping, making it comparable to the etch rate of polymethyl methacrylate (PMMA). Thus, only PMMA was used as the etch mask in the fabrication of the stamps. </P>

Would Romanian Style Revolution be Possible in North Korea?

박정오(Park, Jeong O) 한국외국어대학교 동유럽발칸연구소 2012 동유럽발칸연구 Vol.30 No.-

Similarities between Romanian and North Korean dictatorship can be understood at the level of common sense even though we do not mention in details. Because among many dictators on earth, Ceauşescu imitated directly the North Korean-style dictatorship. But I would like to suggest that some differences between these two systems can be found clearly. Although the Romanian clan dictatorship took North Korea as a model, I think that it was just an imitation of the dictatorship of North Korea. And I also believe that the clan dictatorship of North Korea including individual idolatry had some limits to put down roots in Romania. In other words, the soil of Romania and North Korea was different. North Koreans have oriental sentiments and values, while Romanians have strong characteristics of European individualism. Therefore, there are some differences between these two peoples ruled by communism under similar absolute dictatorships. Usually, comparing North Korea and Romania, most of people just examine the political system of these two countries. But it is also important to examine how are these two peoples ruled by the nation's system. My opinion is that there are some clear differences between these two peoples who accept the communist dictatorship in their country. Although the censorship has been carried out during Ceauşescu's dictatorship, personal freedoms including religion has been largely recognized and some Romanian writers published their works which criticized indirectly Ceauşescu's dictatorship. Compared to other Eastern European nations, social resistance movements in Romania led by dissidents and dissident groups almost did not exist. This kind of situation also can be found in North Korea. By the way, regarding this, there are also some differences between Romania and North Korea. In case of North Korea, there are very few activities of dissidents. In contrast, activities of dissidents were very weak in Romania compared to other Eastern European countries, even though they had existed. Around the World War II, Romania was richer than Greece. So Romanians could compare 'good life in the past' and 'hardscrabble life' of the late '80s, figuring it out as the consequence of Ceauşescu's dictatorship. In contrast, North Korean people are just living resignedly because they have never got previous experiences of rich life. Therefore, when we are examining carefully the dictatorship of North Korea compared to Romania, they seem to be similar on a larger scale but we can also find some differences. North Koreans might tremble with horror due to the powerful politics of fear in their country that exterminate a family of a whole three generations, but in accepting the idolatry for Jeong-il Kim and his clan dictatorship it seems to be a little bit different than Romania's situation. 차우셰스쿠는 지구상의 많은 독재자들 중에서 북한식의 독재체제를 직접 모방했기 때문에, 루마니아와 북한의 공통점은 일일이 언급하지 않아도 우리가 생각하는 상식적인 수준에서 이해할 수 있다. 그런데 두 체제간의 차이점도 있다. 루마니아 족벌독재체제는 북한을 모델로 삼긴 했지만 ‘북한의 아류’에 불과했던 것으로 생각되고 또 우상숭배를 포함한 북한식의 족벌독재체제가 루마니아에서 뿌리를 내리기에는 한계가 있었던 것으로 생각된다. 한마디로 북한식의 강력한 족벌독재체제가 루마니아에 뿌리를 내리는데 루마니아라는 토양과 북한의 토양이 많이 달랐다고 생각된다. 즉 북한 주민들은 동양의 정서와 가치관을 가진 반면에 루마니아인들은 유럽인 특유의 개인주의 성향이 강하다고 볼 수 있는데, 이 말은 비슷한 독재체제하에서 공산주의의 지배를 받는 두 나라 국민들 간에 차이가 있다는 말이다. 보통 루마니아와 북한을 비교할 때, 대개는 두 국가의 체제만을 비교해서 보는데, 체제의 지배를 받는 국민들이 어떤가도 아주 중요하다. 즉 공산주의 독재 체제를 받아들이는 루마니아인과 북한 주민들 사이에 차이가 있어 보인다. 차우셰스쿠 집권시절, 종교를 포함한 개인의 자유가 상당부분 인정되었고 또 검열제가 실시되었지만 루마니아 일부 작가들은 차우셰스쿠 독재체제를 우회로 비판하는 작품들을 출판하기도 했다. 다른 동유럽 국가에 비해 루마니아에서 반체제 인사와 단체의 활동’이 거의 없는 것은 북한과 닮은 점이다. 그런데 반체제 인사와 단체의 활동과 관련해서도 루마니아와 북한 사이에는 조금의 차이는 있어 보인다. 북한의 경우, 반체제 인사와 단체의 활동이 거의 없는데 반해, 루마니아는 있었지만 다른 동유럽 국가에 비해 아주 미약했다고 언급할 수 있다. 제2차 세계대전 전후 루마니아는 유럽에서도 잘 사는 나라에 속했다. 실제로 당시 루마니아는 그리스보다 잘 사는 나라였다. 그래서 루마니아인들은 ‘살기 힘든 현재’와 ‘잘살았던 과거’를 비교하게 되고 또 그 이유를 공산주의 체제 혹은 차우셰스쿠 독재 때문이라는 해답을 쉽게 찾을 수 있는데 반해, 잘살아본 경험이 없어 살기 힘든 현재를 배교할 곳이 없는 북한 주민들은 그냥 체념하듯이 살고 있는 것으로 생각된다. 1960년대 루마니아는 농업국으로 전락시키려는 소련 흐루시초프 정책에 반 대해 중공업 위주의 스탈린식 경제체제 통한 국가발전 도모하였다. 루마니아가, 농업국으로 전락시키려는 소련 흐루시초프 정책에 반대하여 중공업 위주의 경제발전을 도모한 것은 차우셰스쿠 이전의 대통령인 게오르게 게오르기우-데지(Gheorghe Gheorghiu-Dej) 시대로 거슬러 올라간다. 그런데 차우셰스쿠 시대에 와서 루마니아 공산당은, 루마니아 3대 주력산업(철강업, 기계공업 그리고 중화학공업)을 선정하여 과도하게 발전시켰다. 당시 경공업이 완전히 도외시되었고 또 3대 주력산업은 아무런 시장조사 없이 자의적으로 즉 루마니아 공산당 마음대로 선정하였다. 시장경제 원칙을 무시하다보니 루마니아 경제정책은 당연히 실패했고 결국 80년대 말 루마니아 경제는 파국으로 치달았다. 결국 루마니아와 북한의 독재체제를 살펴보면 큰 틀에서는 비슷하지만 분명‘정도의 차이’는 있어 보인다. 그리고 3대 멸족이라는 북한식의 강력한 공포정치로 인한 두려움 때문인지 모르겠지만 어쨌든 김정일 우상숭배와 족벌독재정치를 받아들이는 북한 주민들의 태도는 루마니아인들과는 차이가 있어 보인다.

산소 첨가된 Cobalt(Ⅲ) 착물에 의한 2,6-di-tert-butylphenol의 산화반응

오정근,임채평,최용국,O, Jeong Geun,Im, Chae Pyeong,Choe, Yong Guk 대한화학회 2002 대한화학회지 Vol.46 No.3

메탄올 용액에서 산소 첨가된 Co(III) 착물을 촉매로 사용하여 흡광광도법에의한 2,6-di-tert-butylphenol(DTBP)의 산화반응에 대하여 알아보았다. 산화반응의 결과로서 주 생성물은 2,6-di-tert-butylbenzoqu-inone(BQ)였고 산소 첨가된 착물의 촉매 활성은 [Co(III)2(SMPD)2(Py)2]2O2가 [Co(III)2(SPPD)2(Py)2]2O2보다 더 컸으며 속도상수(K)는 4.55∼2.12${\times}$10-3/s의 값으로 주어졌다. 또한 산화반응은 촉매, 산소분자 및 기질의 노도에 1차 반응임을 확인하였으며 활성화 에너지(Ea)가 10.38kJ/mol로 주어져 Arrhenius의 특성에서 벗어는 결과를 보였다. The oxidation reaction between 2,6-di-tert-butylphenol (DTBP) and oxygen adducted Co(III) complexes as a catalysis has been studied by UV-visible spectrophtometry. According to the results, main product is 2,6-di-tert-butylbenzoquinone(BQ) and the activity of the complexes is bigger in [Co(III)2(SMPD)2(Py)2]2O2 than in [Co(III)2(SPPD)2(Py)2]2O2. The rate constant is 4.55~2.12${\times}$10$-3}$s. It was found that the oxidation reaction is primary reac-tion or concentration of catalysis, O2 molecule and substance. The reasult is far from Arrhenius properties because acti-vationenergy is 10.38 kJ/mol.