Detector Mount Design for GMTNIRS

Sangjun Kim,Chan Park,Sanghyuk Kim,Woojin Park,Heeyoung Oh,Ueejeong Jeong,Sungho Lee,Jae Sok Oh,Jae-Joon Lee,Byeong-Gon Park,Myeong-Gu Park 한국천문학회 2023 天文學會報 Vol.48 No.2

Study on the Fluidity and Strength Properties of High Performance Concrete Utilizing Crushed Sand

Park, Sangjun Korea Concrete Institute 2012 International Journal of Concrete Structures and M Vol.6 No.4

Recently, it has been difficult to get natural sand for concrete due to an insufficient supply in Korea. Crushed sand was thought as a substitute and previous research has been focused on low fluidity and normal compressive strength (24-30 MPa). Study on high performance concrete using crushed sand is hardly found in Korea. In this study it was investigated that the effect of the crushed sand on fluidity and compressive strength properties of high performance concrete. Blending crushed sand (FM: 3.98) produced in Namyangju, Kyunggido and sea sand (FM: 2.80) produced in Asan bay in Chungnam. The final FMs of fine aggregate were 3.50, 3.23, and 3.08. W/B was set as 0.25 to get high performance. With the test results an analysis of relationship was performed using a statistical program. It was shown that strength property of concrete using crushed aggregate at the very early age or after specific time was mainly affected by strength development properties of binders instead of the crushed sand.

Model-based multi-objective Pareto optimization of the BSFC and NO_x emission of a dual-fuel engine using a variable valve strategy

Park, Sangjun,Song, Soonho Elsevier 2017 Journal of natural gas science and engineering Vol.39 No.-

<P><B>Abstract</B></P> <P>Various advanced technologies, including dual-fuel combustion, have been developed to meet reinforced emission regulations in the automobile industry. In this work, natural gas (NG) was added from 0 to 30% in steps of 10% as the energy fraction of the fuel to evaluate the fundamental effects of the NG substitution ratio (NSR) on the combustion, performance and nitrogen oxides (NO<SUB>x</SUB>) emission of a dual-fuel engine. Although the NO<SUB>x</SUB> emission significantly improved because of the higher specific heat capacity of air–NG mixtures, the in-cylinder pressure decreased with increasing NG fraction because of a longer ignition delay, which also detrimentally affected the brake specific fuel consumption (BSFC) by decreasing the brake thermal efficiency (BTE) of the engine. The injection timing was optimized using a design of experiments (DoE) approach to minimize the BSFC under various load and NSR conditions. The optimal injection timing was more advanced with lower load and higher NSC conditions. Additionally, the optimal Pareto fronts for improved performance and NO<SUB>x</SUB> emission of the dual-fuel engine were obtained from a multi-objective Pareto optimization. These results suggested suitable intake and exhaust valve timing strategies to control the BSFC and NO<SUB>x</SUB> emission of a dual-fuel engine.</P> <P><B>Highlights</B></P> <P> <UL> <LI> The fundamental effects of a natural gas addition on diesel engine are investigated. </LI> <LI> NO<SUB>x</SUB> emission significantly reduced with increasing a natural gas fraction. </LI> <LI> The total BSFC of dual-fuel engine deteriorated as a natural gas fraction increased. </LI> <LI> The BSFC and NO<SUB>x</SUB> emission are minimized simultaneously by Pareto optimization. </LI> <LI> The variable valve strategies to control the BSFC and NO<SUB>x</SUB> emission are developed. </LI> </UL> </P>

Case Study of Hanford Site-specific Hydrologic Parameter Establishing Procedure

SangJune Park,Jihyang Byon,Seokyoung Ahn 한국방사성폐기물학회 2019 한국방사성폐기물학회 학술논문요약집 Vol.2019 No.10

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>

Study on the Fluidity and Strength Properties of High Performance Concrete Utilizing Crushed Sand

Sangjun Park 한국콘크리트학회 2012 International Journal of Concrete Structures and M Vol.6 No.4

Recently, it has been difficult to get natural sand for concrete due to an insufficient supply in Korea. Crushed sand was thought as a substitute and previous research has been focused on low fluidity and normal compressive strength (24?30 MPa). Study on high performance concrete using crushed sand is hardly found in Korea. In this study it was investigated that the effect of the crushed sand on fluidity and compressive strength properties of high performance concrete. Blending crushed sand (FM: 3.98) produced in Namyangju, Kyunggido and sea sand (FM: 2.80) produced in Asan bay in Chungnam. The final FMs of fine aggregate were 3.50, 3.23, and 3.08. W/B was set as 0.25 to get high performance. With the test results an analysis of relationship was performed using a statistical program. It was shown that strength property of concrete using crushed aggregate at the very early age or after specific time was mainly affected by strength development properties of binders instead of the crushed sand.

A Pilot Establishment of the Job-Exposure Matrix of Lead Using the Standard Process Code of Nationwide Exposure Databases in Korea

Park Ju-Hyun,Choi Sangjun,Koh Dong-Hee,Lim Dae Sung,Park Dong-Uk,Kim Hwan Cheol,이상길,Lee Jihye,Lim Ji Seon,Sung Yeji,Yoon Ko Kyoung 한국산업안전보건공단 산업안전보건연구원 2022 Safety and health at work Vol.13 No.4

Background The purpose of this study is to construct a job-exposure matrix for lead that accounts for industry and work processes within industries using a nationwide exposure database. Methods We used the work environment measurement data (WEMD) of lead monitored nationwide from 2015 to 2016. Industrial hygienists standardized the work process codes in the database to 37 standard process and extracted key index words for each process. A total of 37 standardized process codes were allocated to each measurement based on an automated key word search based on the degree of agreement between the measurement information and the standard process index. Summary statistics, including the arithmetic mean, geometric mean, and 95th percentile level (X95), was calculated according to industry, process, and industry process. Using statistical parameters of contrast and precision, we compared the similarity of exposure groups by industry, process, and industry process. Results The exposure intensity of lead was estimated for 583 exposure groups combined with 128 industry and 35 process. The X95 value of the “casting” process of the “manufacture of basic precious and non-ferrous metals” industry was 53.29 μg/m3, exceeding the occupational exposure limit of 50 μg/m3. Regardless of the limitation of the minimum number of samples in the exposure group, higher contrast was observed when the exposure groups were by industry process than by industry or process. Conclusion We evaluated the exposure intensities of lead by combination of industry and process. The results will be helpful in determining more accurate information regarding exposure in lead-related epidemiological studies.

Synthesis of Imidazopyridines via Copper-Catalyzed, Formal Aza-[3 + 2] Cycloaddition Reaction of Pyridine Derivatives with α-Diazo Oxime Ethers

Park, Sangjune,Kim, Hyunseok,Son, Jeong-Yu,Um, Kyusik,Lee, Sooho,Baek, Yonghyeon,Seo, Boram,Lee, Phil Ho American Chemical Society 2017 Journal of organic chemistry Vol.82 No.19

<P>The Cu-catalyzed, formal aza-[3 + 2] cycloaddition reaction of pyridine derivatives with α-diazo oxime ethers in trifluoroethanol was used to synthesize imidazopyridines via the release of molecular nitrogen and elimination of alcohol. These methods enabled modular synthesis of a wide range of <I>N</I>-heterobicyclic compounds such as imidazopyridazines, imidazopyrimidines, and imidazopyrazines with an α-imino Cu-carbenoid generated from the α-diazo oxime ethers and copper.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/joceah/2017/joceah.2017.82.issue-19/acs.joc.7b01714/production/images/medium/jo-2017-01714z_0011.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/jo7b01714'>ACS Electronic Supporting Info</A></P>

Numerical study of the performance and NO_x emission of a diesel-methanol dual-fuel engine using multi-objective Pareto optimization

Park, Sangjun,Cho, Jungkeun,Park, Jungsoo,Song, Soonho Pergamon Press 2017 Energy Vol.124 No.-

<P><B>Abstract</B></P> <P>The effect of methanol addition on the performance and NO<SUB>x</SUB> emission of a diesel engine was investigated using one-dimensional engine cycle simulation. The methanol component was injected into the intake manifold of a diesel engine at a certain energy fraction (0, 5, 10, or 15%) of the fuel. The in-cylinder pressure and temperature decreased as the methanol content increased due to the lower cetane number and lower heating value of methanol. The resulting decrease in the combustion efficiency lowered the NO<SUB>x</SUB> emission and brake thermal efficiency of the engine, and consequently deteriorated the brake specific fuel consumption (BSFC). The BSFC decreased but the NO<SUB>x</SUB> emission increased with advanced injection timing under dual-fuel operating conditions. Response surface plots of the BSFC and NO<SUB>x</SUB> emission as a function of the injection timing and exhaust gas recirculation (EGR) rate were obtained using a design of experiment method. The optimal Pareto fronts that improved both the BSFC and NO<SUB>x</SUB> emission were found. The EGR rate had a greater influence on the optimal Pareto front than the injection timing, which suggested that design parameters such as the injection timing and EGR rate could be used to control the performance and emission under various duel-fuel conditions.</P> <P><B>Highlights</B></P> <P> <UL> <LI> The performance and emission of a diesel-methanol dual-fuel engine is investigated. </LI> <LI> The BSFC of the diesel engine is deteriorated as the methanol content increased. </LI> <LI> The NOx emission of the diesel engine is reduced as the methanol content increased. </LI> <LI> Both the BSFC and NOx emission are improved by multi-objective Pareto optimization. </LI> <LI> Design parameters are suggested to control the performance of the dual-fuel engine. </LI> </UL> </P>

Optical Improvement of GaN-Based Light Emitting Diodes by Interfacial Si Treatment in InGaN/GaN Quantum Well Structure

Park, Sangjun,Lee, Sangwon,Yoo, Hongjae,Choi, Joowon,Lee, Sung-Nam Institute of Pure and Applied Physics 2012 Japanese Journal of Applied Physics Vol.51 No.9