• Ocean Systems Engineering
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• 제7권3호
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• pp.299-318
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• 2017

The paper aims at illustrating several key issues and ongoing efforts for development of a reliable fully-Lagrangian particle-based solver for simulation of hydroelastic slamming. Fluid model is founded on the solution of Navier-Stokes along with continuity equations via an enhanced version of a projection-based particle method, namely, Moving Particle Semi-implicit (MPS) method. The fluid model is carefully coupled with a structure model on the basis of conservation of linear and angular momenta for an elastic solid. The developed coupled FSI (Fluid-Structure Interaction) solver is applied to simulations of high velocity impact of an elastic aluminum wedge and hydroelastic slammings of marine panels. Validations are made both qualitatively and quantitatively in terms of reproduced pressure as well as structure deformation. Several remaining challenges as well as important key issues are highlighted. At last, a recently developed multi-scale MPS method is incorporated in the developed FSI solver towards enhancement of its adaptivity.

• 한국수산과학회지
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• 제53권5호
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• pp.665-671
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• 2020

The chemical and rheological properties of fucoidan and alginate prepared from different parts of Undaria pinnatifida (sporophyll, frond, stipe) were investigated. The algal materials were extracted with HCl (pH 2.0, 3 h at 70℃) to prepare fucoidan, and the remaining solid was continuously re-extracted with Na₂CO₃ (pH 10.0, 70℃, 3 h) to prepare alginic acid. The fucoidan and alginic acid contents in the sporophyll, frond, and stipe were 11.14%, 3.84%, and 1.73% and 22.04%, 37.14%, and 31.74%, respectively. The content of fucoidan and alginate depends on the part extracted. The fucoidan extracted from the sporophyll mainly consists of fucose and galactose, but the fucoidan extracted from frond and stipe contains mannose in addition to fucose and galactose. Fourier-transform infrared spectroscopy analysis of fucoidan and alginate suggests the presence of sulfate groups (1261 and 840 cm^-1) and carboxyl groups (1626 and 1419 cm^-1), respectively. Alginate solutions (5%) had a low viscosity of 10.84-31.63 mPa·s. The activation energies of fucoidan and sodium alginate were 14.45-18.38 kJ/mol and 18.61-22.06 kJ/mol, respectively. The D-mannuronic acid/L-guluronic acid (M/G) ratios of alginate showed a relatively high (frond, 3.72; stipe, 2.88; and sporophyll, 1.80).

• 한국표면공학회지
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• 제49권5호
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• pp.439-446
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• 2016

In 2015, a fin tube (Cu-Ni 70/30 alloy) of package type heat exchanger for navy vessel was perforated through the wall which led to refrigerant leakage. This failure occurred after only one year since its installation. In this study, cause of the failure was determined based on available documents, metallographic studies and computational fluid dynamics simulation conducted on this fin tube. The results showed that dimensional gap between inserted plastic tube and inside wall of fin tube is the cause of the swirling turbulent stream of sea water. As a result of combination of swirling turbulence and continuing collision of hard solid particles in sea water, erosion corrosion has begun at the end of inserted plastic tube area. Crevice corrosion followed later in the crevice between the outer wall of plastic tube and inner wall of fin tube. It was found that other remaining tubes also showed the same corrosion phenomena. Thorough inspection and prompt replacement will have to be accomplished for the fin tubes of the same model heat exchanger.

• 상하수도학회지
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• 제20권2호
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• pp.245-255
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• 2006

Dissolved air flotation is a solid-liquid separation system that uses fine bubbles rising from bottom to remove particles in water. In order to enhance the flotation velocity and removal efficiency of flocs in the flotation process, we tried to obtain pretreatment conditions for the optimum DAF process operation by comparing and evaluating features of actual floc formation and flotation velocity etc, according to coagulant types and conditions for flocculation mixing intensity by using PIA, PDA, and FSA. Accordingly, generating big flocs that have low density at low flocculation mixing intensity may reduce treatment efficiency. In addition, generating small flocs at high flocculation mixing intensity makes floc-bubbles smaller, which reduces flotation velocity, In this study, it was found that high flocculation mixing intensity could not remove the remaining micro-particles after flocculation, which had negative effects on treated water quality, Therefore, in order to enhance treatment efficiency in a flotation process, flocculation mixing intensity around $50sec^{-1}$ is effective.

• Journal of Chest Surgery
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• 제54권6호
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• pp.494-499
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• 2021

Background: A recent increase in the incidental detection of ground glass nodules (GGNs) has created a need for improved diagnostic accuracy in screening for malignancies. However, surgical diagnosis remains challenging, especially via video-assisted thoracoscopic surgery (VATS). Herein, we present the efficacy of a novel electrical navigation system for perioperative percutaneous transthoracic nodule localization. Methods: Eighteen patients with GGNs who underwent electromagnetic navigated percutaneous transthoracic needle localization (ETTNL), followed by 1-stage diagnostic wedge resections via VATS between January and December 2020, were included in the analysis. Data on patient characteristics, nodules, procedures, and pathological diagnoses were collected and retrospectively reviewed. Results: Of the 18 nodules, 17 were successfully localized. Nine nodules were pure GGNs, and the remaining 9 were part-solid GGNs. The median nodule size was 9.0 mm (range, 4.0-20.0 mm); and the median depth from the visceral pleura was 5.2 mm (range, 0.0-14.4 mm). The median procedure time was 10 minutes (range, 7-20 minutes). The final pathologic results showed benign lesions in 3 cases and malignant lesions in 15 cases. Conclusion: Perioperative ETTNL appears to be an effective method for the localization of GGNs, providing guidance for a 1-stage VATS procedure.

• Tribology and Lubricants
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• 제38권4호
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• pp.121-127
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• 2022

This study presents the development of an integrated oil purification system consisting of moisture removal, oil flushing, and oil filtering devices. In this system, the oil flushing device is combined with a micro-bubble generator. Oil purification is necessary for ensuring the high performance of the lubricant through the efficient removal of contaminants and thus enables good maintenance of mechanical systems. The developed purification system removes moisture, varnish, and solid particles. Moreover, during oil purification, the oil flushing device separates foreign materials and contaminants remaining in the lubricating oil piping or mechanical systems. The microbubble generator, which is combined with the oil flushing device, can separate harmful contaminants, such as sludge, wear particles, and rust, from piping or lubrication systems through the cavitation effect. Moisture is removed using a double high-vacuum chamber, while sludge and varnish are removed via electro-absorption using a high-voltage generator. Additionally, the total maintenance cost of the system is reduced through the use of domestically fabricated cartridge filters composed of glass fiber and cellulose. The heater, which maintains the temperature of the lubricant at 60℃, can process 41,000 L of lubricant simultaneously. Multiple tests confirmed that the proposed integrated purification system exhibits good performance in oil flushing and removal of water and varnish.

• 한국결정성장학회지
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• 제24권4호
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• pp.176-182
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• 2014

상온 압축 성형 후 고상 반응 소결 공정을 통하여 $Mg_3Sb_2$ 소결체를 제조하고자 하였다. Mg과 Sb의 성분의 몰비와 반응온도에 따른 결정상의 변화를 조사하였다. 773~843 K에서 얻어진 고상반응 소결체들은 전형적인 $Mg_3Sb_2$ 결정상을 형성하였으나 소결체의 위치에 따라 약간 다른 상적 구성을 보였다. 소결체 하단 부위에서 전형적으로 얻어지는 결정상이 얻어졌으며 823 K 온도에서는 Mg : Sb = 3.15 : 1.85 조성일 때, 843 K 온도에서는 Mg의 몰 수가 3.10 이상인 모든 조성에서 ${\alpha}-Mg_3Sb_2$ 상과 정확히 일치하는 결정상이 얻어졌다. 미량 남아있는 Mg 성분은 응고 후 냉각 시 ${\alpha}-Mg_3Sb_2$ 상으로부터 석출된 것으로 보인다.

• Journal of Microbiology and Biotechnology
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• 제16권1호
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• pp.92-101
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• 2006

The bacterial diversity of the bovine rumen was examined using a PCR-based approach. 16S rDNA sequences were amplified and cloned from three fractions of rumen (solid, fluid, and epithelium) that are likely to represent different bacterial niches. A total of 113 clones were sequenced, and similarities to known l6S rDNA sequences were examined. About $47.8\%$ of the sequences had $90-97\%$ similarity to 16S rDNA database sequences. Furthermore, about $62.2\%$ of the sequences were $98-100\%$ similar to 16S rDNA database sequences. For the remaining $6.1\%$, the similarity was less than $90\%$. Phylogenetic analysis was also used to infer the makeup of the bacterial communities in the different rumen fractions. The Cytophaga-Flexibacter-Bacteroides group (CFB, $67.5\%$), low G+C Gram-positive bacteria (LGCGPB, $30\%$), and Proteobacteria $(2.5\%)$ were represented in the rumen fluid clone set; LGCGPB $(75.7\%)$, CFB$(10.8\%)$, Proteobacteria $(5.4\%)$, high G+C Gram-positive bacteria (HGCGPB, $5.4\%$), and Spirochaetes $(2.7\%)$ were represented in the rumen solid clone set; and the CFB group $(94.4\%)$ and LGCGPB $(5.6\%)$ were represented in the rumen epithelium clone set. These findings suggest that the rumen fluid, solid, and epithelium support different microbial populations that may play specific roles in rumen function.

• Korean Chemical Engineering Research
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• 제60권3호
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• pp.414-422
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• 2022

본 연구의 목적은 국내 대표적인 농경잔류물인, 볏짚과 보릿짚을 이용하여 헤미셀룰로오스 부분의 최대 가용화를 위한 산 촉매 열수 분별공정의 타당성을 조사한 것이다. 1.2-2.9 범위의 반응가혹도(CS; Combined reaction severity)에서 다양한 분별 조건들을 사용하여 초기 반응조건 기준을 설정했다. 볏짚의 경우, 160 ℃의 반응온도, 0.75%(w/v)의 H₂SO₄, 20분의 반응시간, 그리고 1:15의 고체/액체 비율을 가진 반응 조건에서 56.6%의 헤미셀룰로스 당 수율을 얻을 수 있었으며, 보릿짚의 경우, 150 ℃ 반응온도, 0.75%(w/v) H₂SO₄, 15분의 반응시간, 1:10의 고체/액체 비율에서 83.0%의 헤미셀룰로스 당 수율을 얻었다. 따라서, 볏짚과 비교하여 보릿짚의 경우 산촉매 열수분획을 효과적으로 수행할 수 있었다. 분별과정 후 남은 분획된 고형분은 볏짚과 보릿짚에서 각각 48.5%와 57.5%였다. 분별된 볏짚과 보릿짚의 XMG(Xylan+Mannan+Galactan) 함량은 17.3% 및 17.6%에서 6.0% 및 2.6%로 각각 감소하였으며, 이는 원료 짚 기준으로 각각 16.7% 및 8.5%에 해당한다. 또한, 보리 짚의 산촉매 열수분별 과정에서 과도한 분해로 인해 셀룰로오스 및 XMG의 5.6% 및 8.5%만 손실된 반면, 볏짚의 셀룰로오스 및 XMG 손실은 6.4% 및 26.6%이었다. 볏짚의 헤미셀룰로스 당은 산 촉매 열수 분별공정중, 다소 높은 반응가혹도로 인해 심하게 과분해된 것에 기인한다.

• Journal of Yeungnam Medical Science
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• 제16권1호
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• pp.94-100
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• 1999

본 연구는 신보존수술의 임상적 가치를 알아보기 위해, 반대측 신장이 기능적으로 정상인 작은 크기의 고형 신종양 환자를 대상으로 신보존수술을 이용한 환자의 임상 경과를 후향적인 조사를 통하여 알아보고자 하였다. 21례의 환자중 술전 방사선 영상 소견상 신세포암으로 추정된 15례의 환자는 술후 병리조직학적 검사 결과 14례에서 신세포암($T_1N_0M_0$ : 14례)으로, 1례에서 호산성과립세포종으로 진단되었다. 신혈관지방종으로 추정된 4례는 역시 신혈관지방종으로 진단되었고, 또한 신세포암과 구별하기 어려웠던 2례는 선혈관지방종 및 해면상혈관종으로 각각 밝혀졌다. 신세포암의 재발, 원격 전이 및 신세포암으로 인한 사망 등은 추척 관찰 기간(평균 18.6개월, 1-103개월) 중 관찰되지 않았고 양성 신종양 환자군에서도 종양의 재발은 관찰되지 않았다(평균 추척 관찰 기간 : 43.8개월, 7-97개월). 신보존수술의 합병증으로는 1례의 신세포암에서 wedge resection을 시행한 후 술후 10일에 신출혈로 인한 육안적 혈뇨 및 혈압 저하의 소견이 나타나 근치적 신적출술을 시행하였고, 그 외 다른 환자에서는 요낭종, 후복막혈종 및 폐 색전증 등과 갈은 합병증은 관찰되지 않았다. 이상의 결과에서, 대측 신장의 기능이 정상인 작은 표기(4cm 이하)의 단일 고형 신종양 환자일 경우 신기능을 보존하기 위하여 신보존수술은 좋은 치료법으로 생각되며 일차적인 치료법으로 사용되어도 유익하리라 기대되나, 향후 보다 장기적인 추적 관찰이 필요하리라 생각된다.