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Yujin Hwang,이창건,최영민,정성일,Doohyun Kim,Kwangho Lee,이재근,김수형 대한기계학회 2011 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.25 No.11
Various carbon-based particles such as graphite, carbon black, graphite nanofibers and carbon nanotubes were dispersed in mineral oil to systematically examine the effect of the size and shape of particles on the properties of friction performance. As the results of friction tests using a disc-on-disc tribotester, the friction coefficient of a disc specimen was significantly reduced when nano-sized spherical particles were suspended in mineral oil. This was attributed to the presence of spherical nanoparticles, which prevented direct contact between frictional surfaces. However, the fibrous nanoparticles with high aspect ratios deteriorated the lubrication performance between friction surfaces due to a higher degree of agglomeration.
Lubricant-Added Conductive Composite for Direct Writing of a Stretchable Electrode
Hwang, Yujin,Lee, Jeong Hwan,Kim, Young Heon,Jeong, Sunho,Lee, Su Yeon,Jung, Jaebong,Kim, Ji Hoon,Choi, Youngmin,Jung, Sungmook American Chemical Society 2019 ACS APPLIED MATERIALS & INTERFACES Vol.11 No.51
<P>Stretchable electrodes, which are essential components of next-generation electronic devices, should be highly conductive under multiaxial tensile strain, durable under repetitive stretching, and patternable for integrating stretchable devices. Herein, a lubricant-added stretchable conductive composite of a polydimethylsiloxane-based elastomer containing silver flakes is reported. The added lubricant minimizes changes in conductivity during stretching and maximizes elastic durability by reducing friction. The conductivity varies from 1933.3 S·cm<SUP>-1</SUP> at 0% strain to 307.5 S·cm<SUP>-1</SUP> at 300% uniaxial stretching and 1264.1 S·cm<SUP>-1</SUP> at 50% biaxial stretching. Furthermore, the composite exhibits high durability, even after 1000 cycles of stretching at 200%, and the conductive composite paste can be applied to fine-linewidth direct writing.</P> [FIG OMISSION]</BR>
YUJIN HWANG,안영철,SEONGIR CHEONG,KEUNHO JIN,JAEKUEN LEE 대한설비공학회 2010 International Journal Of Air-Conditioning and Refr Vol.18 No.3
There are many attempts to use a fuel cell system as a residential power generation system. The purpose of this study is to investigate the optimal design of a water tank for a hot water system when the fuel cell co-generation system is combined with a domestic hot water supply system. The demands of hot water supply per month per home for 76–168 m2 of acreage are investigated in Busan for a year. It showed somewhat large differences between the actual demand and the designed demand of hot water, but the actual capacity of hourly averaged hot water demands is analyzed as 60 ℓ/h in this study based on the actual demand. The experiments are performed in the various inlet and outlet locations of nozzles in the hot water tank, and the hot water consumption rates. The experimental results showed that the optimal capacity of the water tank is 200 ℓ when the thermal efficiency, the storing capacity of hot water and the space for installation are considered.
( Yujin Kwon ),( Su-yeon Cho ),( Jaeyoung Kwon ),( Min Hwang ),( Hoseong Hwang ),( Yoon Jin Kang ),( Hyeon-seong Lee ),( Jiyoon Kim ),( Won Kyu Kim ) 생화학분자생물학회 2022 BMB Reports Vol.55 No.6
The treatment of atopic dermatitis (AD) is challenging due to its complex etiology. From epidermal disruption to chronic inflammation, various cells and inflammatory pathways contribute to the progression of AD. As with immunosuppressants, general inhibition of inflammatory pathways can be effective, but this approach is not suitable for long-term treatment due to its side effects. This study aimed to identify a plant extract (PE) with anti-inflammatory effects on multiple cell types involved in AD development and provide relevant mechanistic evidence. Degranulation was measured in RBL-2H3 cells to screen 30 PEs native to South Korea. To investigate the anti-inflammatory effects of Parasenecio auriculatus var. matsumurana Nakai extract (PAE) in AD, production of cytokines and nitric oxide, activation status of FcεRI and TLR4 signaling, cell-cell junction, and cell viability were evaluated using qRT-PCR, western blotting, confocal microscopy, Griess system, and an MTT assay in RBL-2H3, HEK293, RAW264.7, and HaCaT cells. For in vivo experiments, a DNCBinduced AD mouse model was constructed, and hematoxylin and eosin, periodic acid-Schiff, toluidine blue, and F4/80-staining were performed. The chemical constituents of PAE were analyzed by HPLC-MS. By measuring the anti-degranulation effects of 30 PEs in RBL-2H3 cells, we found that Paeonia lactiflora Pall., PA, and Rehmannia glutinosa (Gaertn.) Libosch. ex Steud. show an inhibitory activity of more than 50%. Of these, PAE most dramatically and consistently suppressed cytokine expression, including IL-4, IL-9, IL-13, and TNF-α. PAE potently inhibited FcεRI signaling, which mechanistically supports its basophil-stabilizing effects, and PAE downregulated cytokines and NO production in macrophages via perturbation of toll-like receptor signaling. Moreover, PAE suppressed cytokine production in keratinocytes and upregulated the expression of tight junction molecules ZO-1 and occludin. In a DNCB-induced AD mouse model, the topical application of PAE significantly improved atopic index scores, immune cell infiltration, cytokine expression, abnormal activation of signaling molecules in FcεRI and TLR signaling, and damaged skin structure compared with dexamethasone. The anti-inflammatory effect of PAE was mainly due to integerrimine. Our findings suggest that PAE could potently inhibit multi-inflammatory cells involved in AD development, synergistically block the propagation of inflammatory responses, and thus alleviate AD symptoms. [BMB Reports 2022; 55(6): 275-280]
< 전시-P-87 > 표준 그레이 카드를 이용한 비표준 종이의 명도(lightness)값 보정 방법 연구
황유진 ( Yujin Hwang ),정명준 ( Myung-joon Jeong ) 한국목재공학회 2019 한국목재공학회 학술발표논문집 Vol.2019 No.1
종이의 명도(lightness) 측정은 색지와 같은 일정한 색상을 유지해야 되는 종이 제품뿐만 아니라 인쇄, 포장, 위생 등 다양한 종이 분야에서 종이 외관적 성질의 하나의 지표로 활용되고 있다. 이러한 종이 명도는 산업 부분뿐만 아니라 종이 문화재 보존 분야에서도 종이의 노화를 평가하는 중요한 지표로 활용되고 있다. 특히 명도 측정 기기의 발달과 국제표준규격에서 제시하는 표준조건 충족 시 정교한 측정이 가능해졌다. 그러나 산업 부분과는 달리 종이 문화재의 경우 같은 명도의 종이를 일정 매수 이상 겹쳐 하나의 종이 패드를 형성하여 측정해야 되는 조건을 충족시키기 어렵다. 따라서 과학 기술의 발전에도 불구하고 종이 문화재 부분에서 명도 측정은 측정상 많은 오차를 발생시킨다. 본 연구에서는 이러한 문제점을 해결하고자 같은 명도의 종이 패드 대신에 백색, 그레이, 흑색의 표준판을 뒷판(backboard)으로 하여 종이 고유의 명도를 추정하고자 하였다. 1차적으로 같은 명도의 종이 매수와 각각의 표준판에 따른 명도 변화를 각각의 명도별로 평가하였으며, 표준판의 명도 영향과 불투명도와의 상관관계를 평가하였다. 최종적으로 측정 시료의 명도, 표준판의 명도, 불투명도와의 상관관계로 부터 종이 고유의 명도를 계산하였다. 그 결과 고유명도 값에 따라 최대 약 8%까지 명도 오차가 발생되었고, 시료에서 약 1% 이하의 수준으로 명도 값을 개선시킬 수 있었다. <사사> 본 연구는 한국연구재단 ‘이공분야기초연구사업(과제번호: NRF-2016R1D1A1B03933947)의 지원에 의해 수행되었습니다.