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승용 디젤 엔진에서 엔진 주요 변수가 EGR cooler fouling에 미치는 영향 평가
박상준(Sangjun Park),이영복(Youngbok Lee),송순호(Soonho Song),전광민(Kwang Min Chun),민선기(Sunki Min),정도영(Doyoung Chung),정종화(Chonghwa Chung) 한국자동차공학회 2012 한국자동차공학회 부문종합 학술대회 Vol.2012 No.5
EGR technology is one of the method to achieve NOx reduction from diesel engine. Cooled EGR system has been used to meet the strict emission regulation. However, when using this system for a long period of time, a fouling phenomenon defined by deposition of PM on cooler wall. As a result, the performance of the engine and NOx reduction rate was deteriorated. In this study, the effects of various variables (coolant temperature, flow rate, BMEP) on EGR cooler fouling were evaluated using engine exhaust partial flow at steady-state. In addition, in order to evaluate the diesel oxidation catalyst effect on EGR cooler fouling, the experiment was carried out about the diesel oxidation catalyst when it was installed before the EGR cooler. The effectiveness drop of the EGR cooler became larger as the coolant temperature decreased. But flow rate did not affect the fouling phenomenon. Furthermore, the effectiveness of the EGR cooler was improved with diesel oxidation catalyst.
CMUT-based resonant gas sensor array for VOC detection with low operating voltage
Park, Sangjun,Yoon, Inug,Lee, Sungwoo,Kim, Hyojung,Seo, Ji-Won,Chung, Yoonyoung,Unger, Alexander,Kupnik, Mario,Lee, Hyunjoo J. Elsevier 2018 Sensors and actuators. B Chemical Vol.273 No.-
<P><B>Abstract</B></P> <P>With the anticipation for a more connected world through the Internet of Things, there is still a strong demand for miniaturized chemical sensors. Here, we report on a miniaturized resonant chemical sensor based on a Capacitive Micromachined Ultrasonic Transducer (CMUT) with a low operating voltage suitable for portable gas sensor applications. Previously reported CMUT chemical sensors required a DC operating voltage (16∼50 V) higher than the supply voltages of common circuits (<I>e.g.,</I> 1.8–5 V). Thus, additional circuitry such as a charge pump circuit often was required as a part of the sensor interface circuits to supply the DC voltage to CMUT. This resulted in additional power consumption and a larger footprint. In this work, the vacuum gap of the CMUT which determines the operating voltage was reduced to 50 nm through the development of a double oxidation process with a high wafer-level yield. We achieved a significantly smaller pull-in voltage (<10 V) for a 500-nm-thick CMUT resonant sensor. The CMUT was operated at approximately 80% of the pull-in voltage (∼8 V) which does not require additional voltage supply to that of the real-time read-out circuitry. Based on the resonant frequency of 6.7 MHz, the theoretical sensitivity of the fabricated CMUT resonant sensor was 0.8 Hz/fg. By coating four different chemically-sensitive polymer layers, we confirmed the operation of the CMUT with low operating voltage as a chemical sensor. Frequency shifts due to the chemical reaction of volatile organic compounds were observed and analyzed through principal component analysis. This work demonstrates the potential of the developed CMUT with low bias voltage as a key component of a portable chemical sensor system.</P> <P><B>Highlights</B></P> <P> <UL> <LI> CMUT-based resonant gas sensors with low operating voltage (<8 V) were fabricated. </LI> <LI> The low-voltage CMUT sensor functionalized with PEO exhibited 0.54 Hz/ppm sensitivity to toluene. </LI> <LI> Four CMUT sensors functionalized with different polymers were evaluated against multiple VOCs. </LI> <LI> Discrimination among gases were demonstrated through the use of multiple CMUT sensors. </LI> </UL> </P>
Kim, Sangjune,Park, Do-Young,Lee, Dohyun,Kim, Wanil,Jeong, Young-Hun,Lee, Juhyun,Chung, Sung-Kee,Ha, Hyunjung,Choi, Bo-Hwa,Kim, Kyong-Tai American Society for Microbiology 2014 Molecular and cellular biology Vol.34 No.4
<P>Misfolding of proteins containing abnormal expansions of polyglutamine (polyQ) repeats is associated with cytotoxicity in several neurodegenerative disorders, including Huntington's disease. Recently, the eukaryotic chaperonin TRiC hetero-oligomeric complex has been shown to play an important role in protecting cells against the accumulation of misfolded polyQ protein aggregates. It is essential to elucidate how TRiC function is regulated to better understand the pathological mechanism of polyQ aggregation. Here, we propose that vaccinia-related kinase 2 (VRK2) is a critical enzyme that negatively regulates TRiC. In mammalian cells, overexpression of wild-type VRK2 decreased endogenous TRiC protein levels by promoting TRiC ubiquitination, but a VRK2 kinase-dead mutant did not. Interestingly, VRK2-mediated downregulation of TRiC increased aggregate formation of a polyQ-expanded huntingtin fragment. This effect was ameliorated by rescue of TRiC protein levels. Notably, small interference RNA-mediated knockdown of VRK2 enhanced TRiC protein stability and decreased polyQ aggregation. The VRK2-mediated reduction of TRiC protein levels was subsequent to the recruitment of COP1 E3 ligase. Among the members of the COP1 E3 ligase complex, VRK2 interacted with RBX1 and increased E3 ligase activity on TRiC <I>in vitro</I>. Taken together, these results demonstrate that VRK2 is crucial to regulate the ubiquitination-proteosomal degradation of TRiC, which controls folding of polyglutamine proteins involved in Huntington's disease.</P>