• 대한기계학회논문집A
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• 제34권3호
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• pp.291-298
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• 2010

본 논문은 자동차 디젤엔진의 EGR 시스템에 사용되는 EGR 냉각기의 열교환 효율에 관한 것으로 배기가스의 냉각수 사이의 열교환을 촉진시키기 위한 방법으로 딤플형 EGR 냉각기를 설계 및 그 성능을 평가하였다. 개발초기 단계에서 딤플형 EGR 냉각기의 성능을 평가하기 위하여 기존 스파이럴 타입의 EGR 냉각기와 딤플형 EGR 냉각기의 전열면적을 비교하였으며, 균질화 기법을 이용한 유한요소해석을 통하여 딤플형 EGR 냉각기의 구조 건전성을 평가하였다. 또한, 딤플형 열교환 튜브의 생산공정-딤플성형, edge bending, center v-notch bending, 압착, 플라즈마 용접-을 체계화하였다. 최종적으로 본 연구를 통하여 딤플형 EGR 냉각기를 개발하였으며, 그 성능을 검증하였다.

• Corrosion Science and Technology
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• 제16권2호
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• pp.49-58
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• 2017

Many research efforts on the effect of nitrogen on the corrosion resistance of stainless steels have been reported, but little research has been conducted on the effect of nitrogen for the weldment of stainless steels by the seal-weld method. Therefore, this work focused on the determining the corrosion resistance of tube/tube sheet mock-up specimen for sea water condensers, and elucidating the effect of shielding nitrogen gas on its resistance. The pitting corrosion of autogenously welded specimen propagated preferentially along the dendritic structure. Regardless of the percent of shielding nitrogen gas, the analyzed nitrogen contents were very much lower than that of the bulk specimen. This can be arisen because the nitrogen in shielding gas may partly dissolve into the weldment, but simultaneously during the welding process, nitrogen in the alloy may escape into the atmosphere. However, the pitting resistance equivalent number (PREN) of the interdendrite area was higher than that of the dendrite arm, regardless of the shielding gas percent; and the PREN of the interdendrite area was higher than that of the base metal; the PREN of the dendrite arm was lower than that of the base metal because of the formation of (Cr, Mo) rich phases by welding.

• 한국지반공학회논문집
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• 제18권5호
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• pp.261-269
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• 2002

본 논문에서 고함수비 슬러지나 퇴적물들의 탈수에 지오텍스타일 튜브들의 이용이 연구되었고, 튜브들의 사용에 대한 실용성과 영향을 미치는 요인들도 평가되었다. 개조된 실험기를 사용하여 고함수비물질들과 두종류의 woven지오텍스타일 튜브에 대해서 압력여과시험들이 실험되었다. 실험결과, 1) 지오텍스타일 튜브안쪽에 형성된 필터케익이 튜브안에서 세립자 유지의 주 원인이며, 또한 튜브의 투수율 감수의 원인이고, 2) 필터케익형성을 조정해서 토사유지율과 투수율사이의 균형을 얻는것이 성공적인 지오텍스타일 튜브사용에 가장 중요한 것이며, 3) 지오텍스타일, 슬러지 특성, 여과압력등이 탈수효과 및 탈수율에 영향을 미침을 알 수 있었다

• Korean Journal of Ophthalmology
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• 제32권6호
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• pp.433-437
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• 2018

Purpose: Various absorbable anti-adhesion agents have been used to prevent postoperative synechia formation after endonasal surgery. The purpose of this study was to evaluate the anti-adhesion effects of HyFence and Mediclore after endonasal dacryocystorhinostomy (DCR) compared to a mixed solution of hyaluronic acid and sodium carboxymethylcellulose (Guardix-Sol). Methods: In this retrospective study, endonasal DCR and silicone tube intubation were performed on 198 eyes of 151 patients. Three different anti-adhesion adjuvants were applied to the osteotomy site in the nasal cavity after standard endonasal DCR procedures. The subjects were classified into three respective groups: group A (71 eyes, Guardix-Sol 1.5 g), group B (89 eyes, HyFence 1.5 mL), and group C (38 eyes, Mediclore 1 cc). The three groups were evaluated by asking patients about subjective symptoms and by performing lacrimal irrigation tests and endoscopic examinations. Results: There were no statistically significant differences in age, sex, timing of tube removal, or follow-up period among the three groups. There were no statistically significant differences in success rates among the three groups (p = 0.990, 91.5% [65 / 71], 92.1% [82 / 89], and 92.1% [35 / 38], respectively). Conclusions: HyFence and Mediclore are safe and effective adjunctive modalities following endonasal DCR compared to Guardix-Sol. Therefore, these agents can be considered good alternatives to Guardix-Sol to increase the success rate of endonasal DCR in treating patients with poor prognosis.

• Imaging Science in Dentistry
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• 제51권1호
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• pp.73-80
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• 2021

Purpose: The purpose of this study was to evaluate the cone-beam computed tomographic (CBCT) imaging and histopathological characteristics of osteoradionecrosis(ORN) and medication-related osteonecrosis of the jaw(MRONJ). Materials and Methods: Ten surgical specimens from segmental mandibulectomy (3 ORN and 7 MRONJ) were analyzed using CBCT. The CBCT parameters were as follows: high-resolution mode (tube voltage, 90.0 kV; tube current, 4.00 mA; rotation time, 16.8 s; field of view, 56 mm×56 mm; thickness, 0.099 mm). Histopathological characteristics were evaluated using histological slides of the surgical specimens. The Pearson chi-square test was used to compare ORN and MRONJ in terms of CBCT findings(internal texture, sequestrum, periosteal reaction and cortical perforation) and histopathological characteristics(necrotic bone, inflammatory cells, reactive bone formation, bacteria, Actinomyces, and osteoclasts). A P value less than 0.05 was considered to indicate statistical significance. Results: MRONJ showed periosteal reaction on CBCT more frequently than ORN (7 of 7 [100%] vs. 0 of 3 [0%], P<0.05). Regarding histopathological characteristics, MRONJ showed osteoclasts more frequently than ORN (6 of 7 [85.7%] vs. 0 of 3 [0%], P<0.05). Conclusion: This study evaluated the CBCT imaging and histopathological characteristics of ORN and MRONJ, and the findings suggest that CBCT could be useful for the evaluation of ORN and MRONJ.

• 한국발생생물학회:학술대회논문집
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• 한국발생생물학회 2003년도 제3회 국제심포지움 및 학술대회
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• pp.110-110
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• 2003

The high incidence of polyspermic fertilization is one of the major causes lowering the overall efficiency of porcine IVF. The common procedure for IVF involves the co-culture of both gametes in the medium drop, which increases sperm concentration and incidence of polyspermy. Therefore, the present study was carried out to increase the efficiency of porcine IVF by reducing polyspermy using a modified swim-up method. This method modifies conventional swim-up washing by placing oocytes directly at the time of washing. Sperm pellet was prepared in the tube and mature oocytes were placed on cell strainer with $70 \mu m$ pore size (Falcon 2350) at the top of the tube. After insemination, the oocytes were stained for examination. Also, the developmental potential of fertilized embryos was measured to evaluate for the feasibility of this method. While having similar penetration rates in both methods ($86.67 \pm 2.36% to 83.33 \pm 1.36%$), there was a significant reduction of polyspermy in modified swim-up method ($17.50 \pm 1.60%$) compare to the control ($44.1 \pm 3.70%$ (p<0.05). Subsequent culture showed higher rate of blastocyst formation in modified swim-up method (20.44$\pm$0.99%) than the control ($15.73 \pm 3.26%$) (P<0.05), even though there was no significant difference. These results suggest that, by controlling the number of spermatozoa reaching the oocytes, porcine oocytes might be protected from polyspermy in vitro. Also, the developmental potential of the fertilized embryos using this method could be improved by increasing the pool of spermatozoa with better quality. Further optimization of the procedure required to implicate this method in routine porcine IVF.

• 문화기술의 융합
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• 제9권3호
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• pp.221-237
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• 2023

본 연구의 목적은 급격한 미디어 산업 변화의 중심에 있는 개인 미디어 환경에 관심을 가지고, 특히 어디서든 접속, 시청, 제작 가능한 모바일 미디어 환경을 선도하는 1인 혹은 소수 미디어 크리에이터들의 활동 영역을 탐구하여 크리에이터들과 시청자들 간의 상호 생태계를 면밀히 살피는 단계적 연구의 일환으로 진행되었다. 특히 전문 유튜버 영역의 확장 가능성이 날로 진화하는 콘텐츠 서비스 사용자들의 욕구 및 수요 형태의 변화에 맞닥뜨린 상황에 주목하고, 전문 유튜버의 평판이 시청자의 충성도와 구독의도에 미치는 영향, 그리고 진정성이 이들 관계에서 형성하는 조절효과를 살펴보고자 하였으며, 이러한 관계 형성 과정을 구체적 자료를 통해 실증하는 것이 본 연구의 목적이다. 결론 부분에 연구결과를 토대로 유추할 수 있는 시사점과 향후 추가 연구를 위한 제언 등을 제시하였다.

• Clinical and Experimental Pediatrics
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• 제48권8호
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• pp.886-893
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• 2005

목 적 : 가와사키병은 어린 소아에서 전신성 혈관염을 일으키는 가장 흔한 원인이다. 가와사키병이 발병한 경우 여러 혈관 성장인자들의 분비가 촉진되어 내막층의 증식과 신생 혈관 생성작용이 진행되면서 관상동맥이 재구성된다. 수년간 가와사키병의 치료제로 IVIG와 코르티코스테로이드가 사용되었으나 그 치료기전이 명확히 밝혀진 바는 없다. 이런 IVIG와 코르티코스테로이드가 가와사키병의 관상동맥합병증을 감소시키는데 어떠한 기전으로 작용하는지 알아보고자 본 연구에서는 Matrigel을 이용하여 in vitro에서 VEGF에 의해 유도된 내막세포 분화에 대한 IVIG와 methylprednisolone의 효과를 보고자 하였다. 방 법 : Matrigel을 이용하여 in vitro에서 VEGF에 의해 유도된 내막세포 분화에 대한 IVIG와 methylprednisolone의 효과를 보고자 VEGF, VEGF와 IVIG, VEGF와 VEGF antibody, VEGF와 methylprednisolone, VEGF, IVIG와 methylprednisolone을 각각 넣어주고, HUVECs를 18시간 동안 배양 후 튜브의 총 길이를 측정하였다. 결 과 : 1) IVIG의 농도를 25 mg/mL, 그리고 40 mg/mL로 증량하였을 경우 IVIG를 투여하지 않은 대조군에 비하여 통계학적으로 각각 유의한 세포수(HUVECs) 감소 효과를 관찰할 수 있었으며(P<0.001), 40 mg/mL를 처리한 경우가 25 mg/mL를 처리한 경우보다 세포수 감소 효과가 더 뚜렷하였다(P<0.05). 세포배양 시간에 따른 억제 효과는 25 mg/mL과 40 mg/mL에서 배양 후 24시간과 48시간 모두에서 대조군과 비교하여 통계학적으로 유의한 효과를 보였다(P<0.001). 2) VEGF 20 ng/mL를 처리한 군에 IVIG 40 mg/mL 또는 여러 농도의 methylprednisolone($10^{-12}M$, $10^{-9}M$ or $10^{-6}M$)을 처치해 주었을 때 튜브 형성이 유의하게 억제되었으며(P<0.05), methylprednisolone의 경우 그 억제 정도가 농도에 비례하여 일어났으나 IVIG 투여시 보다는 억제 효과가 약하였다. 한편, IVIG와 methylprednisolone와 병합투여한 경우는 methylprednisolone 농도에 상관없이 모두 튜브 형성을 잘 억제하였으며(P<0.001), IVIG만 단독 투여한 것과 통계적 차이는 없었다. 결 론 : 본 연구에서는 in vitro에서 VEGF가 HUVECs의 분화를 유도하고 분화된 내막세포의 맥관 형성이 IVIG와 methylprednisolone에 의해 저해된다는 것을 보여주었다. 이는 가와사키병의 관상동맥합병증이 생기는 기전 중 VEGF와 내막세포의 분화로 인해 일어나는 관상동맥의 재구성을 IVIG와 methylprednisolone이 억제한다는 것을 시사하며 치료 기전 중 하나로 제시될 수 있다.

• The Korean Journal of Physiology and Pharmacology
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• 제22권2호
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• pp.203-213
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• 2018

Tumor undergo uncontrolled, excessive proliferation leads to hypoxic microenvironment. To fulfill their demand for nutrient, and oxygen, tumor angiogenesis is required. Endothelial progenitor cells (EPCs) have been known to the main source of angiogenesis because of their potential to differentiation into endothelial cells. Therefore, understanding the mechanism of EPC-mediated angiogenesis in hypoxia is critical for development of cancer therapy. Recently, mitochondrial dynamics has emerged as a critical mechanism for cellular function and differentiation under hypoxic conditions. However, the role of mitochondrial dynamics in hypoxia-induced angiogenesis remains to be elucidated. In this study, we demonstrated that hypoxia-induced mitochondrial fission accelerates EPCs bioactivities. We first investigated the effect of hypoxia on EPC-mediated angiogenesis. Cell migration, invasion, and tube formation was significantly increased under hypoxic conditions; expression of EPC surface markers was unchanged. And mitochondrial fission was induced by hypoxia time-dependent manner. We found that hypoxia-induced mitochondrial fission was triggered by dynamin-related protein Drp1, specifically, phosphorylated DRP1 at Ser637, a suppression marker for mitochondrial fission, was impaired in hypoxia time-dependent manner. To confirm the role of DRP1 in EPC-mediated angiogenesis, we analyzed cell bioactivities using Mdivi-1, a selective DRP1 inhibitor, and DRP1 siRNA. DRP1 silencing or Mdivi-1 treatment dramatically reduced cell migration, invasion, and tube formation in EPCs, but the expression of EPC surface markers was unchanged. In conclusion, we uncovered a novel role of mitochondrial fission in hypoxia-induced angiogenesis. Therefore, we suggest that specific modulation of DRP1-mediated mitochondrial dynamics may be a potential therapeutic strategy in EPC-mediated tumor angiogenesis.

• 대한한방종양학회지
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• 제7권1호
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• pp.39-60
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• 2001

Fuzhengfangaitang is a prescript for inhibiting recurrence and metastasis of cancer. We had examined the anti-metatstastic effect of Fuzhengfangaitang. Furthermore, we performed the following experiments with ingredients of Fuzhengfangaitang. The purpose of this thesis is to study what ingredients of Fuzhengfangaitang have more valuable anti-cancer effects. And the results are listed below: 1. Cell Viability assay At the dose of 400$\mu$g/ml, most ingredients of Fuzhengfangaitang depressed viability of ECV-304. And especially, Scutellaria barbata D. DON$50{\mu}g/ml$ : 53.118%, $100{\mu}g/ml$: 49.092%, $200{\mu}g/ml$ : 43.765%, $400{\mu}g/ml$ : 12.747%), Polygonum bistorta L.($50{\mu}g/ml$ : 45.554%, $100{\mu}g/ml$ : 45.554%, $200{\mu}g/ml$ : 0.0%, $400{\mu}g/ml$ : 0.0%) and Psoralea corylifolia L.($50{\mu}g/ml$ : 86.591%, $100{\mu}g/ml$ : 81.307%, $200{\mu}g/ml$ : 24.801%, $400{\mu}g/ml$ : 3.111%) highly depressed cell viability more than the other ingredients. (${\alpha}$<0.05) 2. Cell Proliferation assay Proliferation assay with ingredients of Fuzhengfangaitang on ECV-304 showed that Crataegus pinnatifuda BGE ($50{\mu}g/ml$: 63.276%, $100{\mu}g/ml$ : 64.092%, $200{\mu}g/ml$ : 68.966% $400{\mu}g/ml$ : 38.517%, ED50=$296.974{\mu}g/ml$), Polygonum bistorta L.($50{\mu}g/ml$ : 83.981%, $100{\mu}g/ml$ : 86.997%, $200{\mu}g/ml$ : 58.780%, $400{\mu}g/ml$ : 26.408%), ED50=$266.725{\mu}g/ml$) and Psoralea corylifolia L.($50{\mu}g/ml$ : 103.037%, $100{\mu}g/ml$ : 82.529%, $200{\mu}g/ml$ : 2.829%, $400{\mu}g/ml$ : 0.998%), ED50=$177.369{\mu}g/ml$) depressed cell proliferation more than the other ingredients. 3. Tube Formation assay Compared with the control group, most ingredients of Fuzhengfangaitang did not remarkably inhibited the Tube Formation assay of ECV-304 at the dose of $100{\mu}g/ml$. But, Polygonum bistorta L. highly inhibited the tube formation of ECV -304 at the lower dose of $50{\mu}g/ml$. 4. Rat Aortic Ring assay In comparison with the control group, Scutellaria barbata D. DON., root of Polygonum bistorta L. and Psoralea corylifolia L. restricted the angiogenesis of the rat aortic ring at the dose of $100{\mu}g/ml$. And the other ingredients of Fuzhengfangaitang did not restricted the angiogenesis of the rat aortic ring at that dose. Especially, Polygonum bistorta L. highly inhibited the angiogenesis of the rat aortic ring at the lower dose of $50{\mu}g/ml$. From our research, the anti-angiogenic effects of the ingredients of Fuzhengfangaitang was proven. Moreover, it will be helpful for designing more effective prescription for anti angiogenesis.