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Smart conducting polymer composites having zero temperature coefficient of resistance.
Chu, Kunmo,Lee, Sung-Chul,Lee, Sangeui,Kim, Dongearn,Moon, Changyoul,Park, Sung-Hoon RSC Pub 2015 Nanoscale Vol.7 No.2
<P>Zero temperature coefficient of resistance (TCR) is essential for the precise control of temperature in heating element and sensor applications. Many studies have focused on developing zero-TCR systems with inorganic compounds; however, very few have dealt with developing zero-TCR systems with polymeric materials. Composite systems with a polymer matrix and a conducting filler show either a negative (NTC) or a positive temperature coefficient (PTC) of resistance, depending on several factors, e.g., the polymer nature and the filler shape. In this study, we developed a hybrid conducting zero-TCR composite having self-heating properties for thermal stability and reliable temperature control. The bi-layer composites consisted of a carbon nanotube (CNT)-based layer having an NTC of resistance and a carbon black (CB)-based layer having a PTC of resistance which was in direct contact with electrodes to stabilize the electrical resistance change during electric Joule heating. The composite showed nearly constant resistance values with less than 2% deviation of the normalized resistance until 200 C. The CB layer worked both as a buffer and as a distributor layer against the current flow from an applied voltage. This behavior, which was confirmed both experimentally and theoretically, has been rarely reported for polymer-based composite systems.</P>
Chu, Won-Shik,Jeong, Suk-Yong,Pandey, Jitendra Kumar,Ahn, Sung-Hoon,Lee, Jae-Hoon,Chi, Sang-Cheol Korean Society for Precision Engineering 2008 International Journal of Precision Engineering and Vol.9 No.2
The Rapid Prototyping (RP) technology has advanced in many application areas. In this research, two different types, cylinder and scaffold, of implantable Drug Delivery System (DDS) were fabricated using Nano Composite Deposition System (NCDS), one of the RP systems. The anti-cancer drug (5-fluorouracil, 5-FU), biodegradable polymer (PLGA(85: 15)), and bio ceramic (Hydroxyapatite, HA) were used to form drug-polymer composite material. Both types of DDS were evaluated in vivo environment for two weeks. For evaluation, the cumulative drug release and shape stability were measured. Test results showed that the scaffold DDS provide higher cumulative drug release and has better stability than cylinder DDS.
Exploitation of the Endocytic Pathway by Orientia tsutsugamushi in Nonprofessional Phagocytes
Chu, Hyuk,Lee, Jung-Hee,Han, Seung-Hoon,Kim, Se-Yoon,Cho, Nam-Hyuk,Kim, Ik-Sang,Choi, Myung-Sik American Society for Microbiology 2006 Infection and immunity Vol.74 No.7
<B>ABSTRACT</B><P><I>Orientia tsutsugamushi</I>, a causative agent of scrub typhus, is an obligate intracellular bacterium that requires the exploitation of the endocytic pathway in the host cell. We observed the localization of <I>O. tsutsugamushi</I> with clathrin or adaptor protein 2 within 30 min after the infection of nonprofessional phagocytes. We have further confirmed that the infectivity of <I>O. tsutsugamushi</I> is significantly reduced by drugs that block clathrin-mediated endocytosis but not by filipin III, an inhibitor that blocks caveola-mediated endocytosis. In the present study, with a confocal microscope, <I>O. tsutsugamushi</I> was sequentially colocalized with the early and late endosomal markers EEA1 and LAMP2, respectively, within 1 h after infection. The colocalization of <I>O. tsutsugamushi</I> organisms with EEA1 and LAMP2 gradually disappeared until 2 h postinfection, and then free <I>O. tsutsugamushi</I> organisms were found in the cytoplasm. When the acidification of endocytic vesicles was blocked by treating the cells with NH4Cl or bafilomycin A, the escape of <I>O. tsutsugamushi</I> organisms from the endocytic pathway was severely impaired, and the infectivity of <I>O. tsutsugamushi</I> was drastically reduced. To our knowledge, this is the first report that the invasion of <I>O. tsutsugamushi</I> is dependent on the clathrin-dependent endocytic pathway and the acidification process of the endocytic vesicles in nonprofessional phagocytes.</P>
Fabrication of micro parts using nano composite deposition system
Chu, Won-Shik,Kim, Sung-Geun,Jung, Woo-Kyun,Kim, Hyung-Jung,Ahn, Sung-Hoon MCB UNIVERSITY PRESS 2007 RAPID PROTOTYPING JOURNAL Vol.13 No.5
<B>Purpose</B> - The purpose of this research, is to develop a nano composite deposition system (NCDS) to fabricate three dimensional functional nano composite parts. <B>Design/methodology/approach</B> - The NCDS is a hybrid system in which material removal process by mechanical micro machining and/or the deposition process is combined. <B>Findings</B> - Hybrid RP technology showed higher precision than those made by casting or deposition process. Tensile strength of the hydroxyapatite-acrylic composite was about four times higher than that of resin-only specimen while MWCNT composite did not show much improvement. <B>Originality/value</B> - The paper illustrates new approaches for rapid prototyping techniques with various materials and high precision.
( Sang Min Yoon ),( Baek-yeol Ryoo ),( So Jung Lee ),( Jong Hoon Kim ),( Ji Hoon Shin ),( Jihyun An ),( Han Chu Lee ),( Young-suk Lim ) 대한간학회 2018 춘·추계 학술대회 (KASL) Vol.2018 No.1
Aims: Patients with hepatocellular carcinoma (HCC) showing macroscopic vascular invasion (MVI) bear an extremely poor prognosis. Sorafenib is the sole treatment option for advanced stage HCC with MVI with unsatisfactory response rate and survival benefit. Combined transarterial chemoembolization (TACE) plus external beam radiotherapy (RT) has shown promising results in these patients by observational studies. Here, we report the efficacy and safety of TACE plus RT compared to sorafenib in patients with advanced HCC and MVI. Methods: This study was a randomized, open-label trial at an academic tertiary care center. Between July 2013 and October 2016, 90 treatment-naive patients with liver-confined HCC showing MVI were randomly assigned to receive sorafenib (400 mg twice-daily; n = 45; sorafenib group) or TACE (every 6 weeks) plus RT (within 3 weeks after the first TACE; n = 45; TACE+RT group). Primary endpoint was 12-week the progression-free survival (PFS) rate by intention-to-treat analysis. Radiologic response was assessed by independent review according to Response Evaluation Criteria in Solid Tumors (version 1.1). Crossover of treatment was permitted after confirming disease progression. Results: Patients were 33 to 82 years of age, and 85.6% were male. All patients had portal vein invasion of HCC and Child- Pugh class A liver function. The median maximal tumor diameter was 9.7 cm. Most (78.9%) patients had multiple lesions. At week 12, the PFS rate was significantly higher in the TACE+RT group than the sorafenib group (86.7% vs. 34.3%; P<0.001). The TACE+RT group showed significantly higher radiologic response rate (33.3% vs. 2.2% at 24 weeks; P<0.001), significantly longer median time to disease progression (31 weeks vs. 11.7 weeks; P<0.001), and significantly longer overall survival (55 weeks vs. 43 weeks; P=0.04), compared with the sorafenib group. No patients in the TACE+RT group discontinued treatment due to hepatic decompensation. Conclusions: In patients with advanced HCC showing MVI, first-line treatment with TACE+RT was well-tolerated and provided improved progression-free survival, objective response rate, time to disease progression, and overall survival, compared with sorafenib.
Design and performance evaluation of Korean traditional heating system—Ondol: Case study of Nepal
Chu, Won-Shik,Kim, Min-Soo,Lee, Kyung-Tae,Bhandari, Binayak,Lee, Gil-Yong,Yoon, Hae-Sung,Kim, Hyung-Soo,Park, Jae-Il,Bilegt, Erkhes,Lee, Jang-Yeob,Song, Ji-Hyun,Park, Gee-Hoon,Bhandari, Pratibha,Lee, Elsevier 2017 Energy and buildings Vol.138 No.-
<P><B>Abstract</B></P> <P>Poor infrastructure in developing countries, combined with challenging geographical characteristics, is associated with problems of limited access to resources, poor transportation and environmental health issues. In some developing countries, there are no heating systems during the winter season, which causes problems for both people and livestock. The most common heating source is from open fires using biomass from animal and plant residue, which are also used for cooking. Fireplaces are typically located inside the house, which can lead to respiratory health problems because of limited ventilation. Thus, heating systems with proper ventilation are desirable to mitigate health problems and improve living conditions. Here we describe the application of ‘Ondol’, a traditional Korean heating system that was redesigned for improved efficiency, in remote villages in a mountainous region of Nepal. Total 10 models of Ondol were designed and fabricated, and the temperature profile and uniformity were characterized to select the optimal design. The height and type of the ‘Gorae’ were the most important factors in determining the efficiency. The optimal design was provided to local people, who were trained to replicate and build the Ondol on their own. A post-installation survey was carried out to evaluate the effectiveness of the system.</P>
Grain Characteristics and Inheritance of Green-kerneled Rice (Oryza sativa L.)
Sang Ho Chu,Ho Hoon Lee,Su Noh Ryu,Hee Jong Koh 한국육종학회 2004 한국육종학회지 Vol.36 No.4
This study was conducted to characterize and to elucidate the inheritance mode of green-kerneled rices which were selected in rice germplasms collected in China. Three green-kerneled varieties (Hexi 41, Beijingluimi-1, and Jilinluimi-1), three regular whi
Rapid Prototyping and Testing of 3D Micro Rockets Using Mechanical Micro Machining
Chu Won-Shik,Beak Chang-Il,Ahn Sung-Hoon,Cho Tae-Hwan The Korean Society of Mechanical Engineers 2006 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.20 No.1
The trend of miniaturization has been applied to the research of rockets to develop prototypes of micro rockets. In this paper, the development of a web-integrated prototyping system for three-dimensional micro rockets, and the results of combustion tests are discussed. The body of rocket was made of 6061 aluminum cylinder by lathe process. The three-dimensional micro nozzles were fabricated on the same aluminum by using micro endmills with ${\phi}100{\mu}m{sim}{\phi}500{\mu}m$ diameter. Two types of micro nozzle were fabricated and compared for performance. The total mass of the rockets was 7.32 g and that of propellant (gun powder) was 0.65 g. The thrust-to-weight ratio was between 1.58 and 1.74, and the flight test with 45 degree launch angle from the ground resulted in $46\;m{\sim}53\;m$ of horizontal flight distance. In addition, ABS housing for the micro machined rocket was fabricated using Fused Deposition Modeling (FDM). A web-based design, fabrication, and test system for micro nozzles was proposed to integrate the distributed hardware resources. Test data was sent to the designer via the same web server for the faster feedback to the rocket designer.