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Cho, Youngick,Lee, Hojin,Jeong, Yoonjae,Kim, Hansung The Electrochemical Society 2018 Journal of the Electrochemical Society Vol.165 No.5
<P>A novel synthetic process was developed to synthesize nano-sized core-shell catalysts through atomic rearrangement by heat-treatment. Agglomeration of nanoparticles caused by the high-temperature heat-treatment was alleviated by using a modified protective coating method. In this method, the carbon layer formed by the carbonization of polydopamine serves as a protective coating layer, which suppresses the sintering of the catalyst particles continuously until the high-temperature heat-treatment is completed. Later, the carbonized carbon layer is removed by ozone treatment because it blocks the active site of the catalyst. Since ozone is a highly oxidative gas, it can selectively remove the carbon layer at room temperature in just 7 minutes without affecting the physical properties of the catalyst itself, which makes this method suitable for mass production. The Pt-based alloy catalyst was prepared by this unique process was proved to have a Pt-rich shell structure, and the particles can remain small (similar to 5 nm) even after high-temperature heat-treatment, thus exhibiting high oxygen reduction reaction (ORR) activity in fuel cells. (C) 2018 The Electrochemical Society.</P>
간단한 구조의 고조파 정합 네트워크를 갖는 GaN-HEMT 고효율 Doherty 전력증폭기
김윤재(Yoonjae Kim),김민석(Minseok Kim),강현욱(Hyunuk Kang),조수호(Sooho Cho),배종석(Jongseok Bae),이휘섭(Hwiseob Lee),양영구(Youngoo Yang) 한국전자파학회 2015 한국전자파학회논문지 Vol.26 No.9
본 논문에서는 long term evolution(LTE) 통신을 위한 2.6 GHz 대역에서 동작하는 고효율 Doherty 전력증폭기를 설계하였다. 2차 및 3차 고조파 임피던스를 조정하기 위한 간단한 구조의 정합 네트워크를 통해 전력증폭기의 고효율 동작을 달성하였다. Doherty 전력증폭기는 다양한 측면에서 장점을 갖는 GaN-HEMT 소자를 이용하여 제작되었으며, 10 MHz의 대역폭 및 6.5 dB 첨두 전력 대 평균 전력비(PAPR)의 특성을 갖는 LTE downlink 신호를 이용하여 측정되었다. 평균 전력 33.4 dBm에서 13.1 dB의 전력 이득, 57.6 %의 전력부가효율(PAE) 및 ?25.7 dBc의 인접채널누설비(ACLR) 특성을 갖는다. This paper presents a Doherty power amplifier(DPA) operating in the 2.6 GHz band for long term evolution(LTE) systems. In order to achieve high efficiency, second and third harmonic impedances are controlled using a compact output matching network. The DPA was implemented using a gallium nitride high electron mobility transistor(GaN-HEMT) that has many advantages, such as high power density and high efficiency. The implemented DPA was measured using an LTE downlink signal with a 10 MHz bandwidth and 6.5 dB PAPR. The implemented DPA exhibited a gain of 13.1 dB, a power-added efficiency(PAE) of 57.6 %, and an ACLR of ?25.7 dBc at an average output power of 33.4 dBm.
Single cell heterogeneity in human pluripotent stem cells
( Seungbok Yang ),( Yoonjae Cho ),( Jiwon Jang ) 생화학분자생물학회 2021 BMB Reports Vol.54 No.10
Human pluripotent stem cells (hPSCs) include human embryonic stem cells (hESCs) derived from blastocysts and human induced pluripotent stem cells (hiPSCs) generated from somatic cell reprogramming. Due to their self-renewal ability and pluripotent differentiation potential, hPSCs serve as an excellent experimental platform for human development, disease modeling, drug screening, and cell therapy. Traditionally, hPSCs were considered to form a homogenous population. However, recent advances in single cell technologies revealed a high degree of variability between individual cells within a hPSC population. Different types of heterogeneity can arise by genetic and epigenetic abnormalities associated with long-term in vitro culture and somatic cell reprogramming. These variations initially appear in a rare population of cells. However, some cancer-related variations can confer growth advantages to the affected cells and alter cellular phenotypes, which raises significant concerns in hPSC applications. In contrast, other types of heterogeneity are related to intrinsic features of hPSCs such as asynchronous cell cycle and spatial asymmetry in cell adhesion. A growing body of evidence suggests that hPSCs exploit the intrinsic heterogeneity to produce multiple lineages during differentiation. This idea offers a new concept of pluripotency with single cell heterogeneity as an integral element. Collectively, single cell heterogeneity is Janus-faced in hPSC function and application. Harmful heterogeneity has to be minimized by improving culture conditions and screening methods. However, other heterogeneity that is integral for pluripotency can be utilized to control hPSC proliferation and differentiation. [BMB Reports 2021; 54(10): 505-515]
토픽분석을 활용한 직장여성의 이직 원인 재탐색에 관한 연구
송현정(Hyunjung Song),조윤재(Yoonjae cho),김재욱(Jaewook Kim),윤성식(Sungsik Yoon),이석준(Sukjun Lee) 한국여성커뮤니케이션학회 2017 미디어, 젠더 & 문화 Vol.32 No.2
본 연구의 목적은 여성의 사회진출이 활발해진 현재의 시대양상에 맞춰 여성 직장인들의 주요 고민을 통해 여성 이직의 원인을 개인관련 요인과 직무관련 요인으로 분류하여 현 노동시장에서 여성 인력이 실감하는 직무 스트레스와 이직 원인, 이직 준비과정에서 느끼는 심리적 반응 및 행동을 탐색하는 것이다. 이를 위해, 여성전용 커뮤니티에 작성된 게시글들을 수집하였고, 텍스트 마이닝 기법 중 토픽분석을 수행하여 직장여성들의 주요 고민을 유형별로 분류하고 시간에 따른 고민들의 변화 추이와 연관성 분석을 통해 이직원인을 다각도로 탐색하였다. 분석결과 직장여성의 주요 고민은 개인관련 요인과 직무관련 요인 두 가지로 구분되었으며, 세부 토픽으로는 관계, 일 자체, 돈, 나이와 성별, 결혼에 의한 고민과 같이 다섯 가지 유형으로 확인되었다. 구체적인 직장여성들의 이직원인으로 직무관련요인 보다 나이, 성별 그리고 결혼과 같은 개인관련 요인이 더 영향을 미치는 것으로 파악되었다. 또한 여성들의 우선순위가 바뀌어 결혼이 늦어진다는 점과 결혼을 하게 되면 업무에 지장을 받는다는 점을 결혼과 일에 의한 고민의 연관성을 통해 확인할 수 있었다. 연구결과는 현재 직장여성들의 이직원인은 여성으로서 겪는 차별에서 기인한다는 점을 시사하며, 각종 정부정책들이 직장여성에게 유의미하지 않다는 기존의 연구와 일맥상통한다. The purpose of this study was to investigate the causes of turnover of business women through their stress by social media. The data were collected from community postings and classified major worry of business women by type using topic analysis of text mining and explored various angles of cause of turnover through changes of stress over time and correlation. Given the finding of the study, personal correlates such as age and sex, and marital status have more influence on the specific cause of turnover of business women than work-related correlates. Also, it was identified that women’s marriage is delayed because their priorities have changed and they have problems of work because they are married using correlation between marital status and work itself. The study suggest that current causes of turnover of business women is due to discrimination experienced by women. And these are consistent with previous studies which various government policies are not useful.
액체크로마토그래프-질량분석기를 이용한 정성 및 정량 오류의 확인
권진욱 ( Jinwook Kwon ),조윤제 ( Yoonjae Cho ),이규식 ( Gyuseek Rhee ) 한국환경농학회 2015 한국환경농학회지 Vol.34 No.3
BACKGROUND: To identify the sources of inaccuracy in LC/MS/MS methods used in the routine quantitation of small molecules are described and discussed. METHODS AND RESULTS: Various UPLC coupled to triple quadrupole mass spectrometer and time of flight (TOF) were used to identify the potential sources of inaccuracy and inducing the pitfalls of qualification and quntitation during the veterinary drug residue analysis. Some of stable isotope labelled veterinary drugs, which were used as internal standards, presented “cross-talk”, regardless of manufactures of mass spectrometer and types of spectrometer. Group of sulfonamides also presented inaccuracy qualification and quantitation due to the multi-residue analytical method with the same fragment ions at the close retention times. CONCLUSION: The phenomena of “cross-talk” occurring between subsequently monitored transition from stable isotope labelled and isotope non-labelled authentic chemical were identified. To prevent errors and achieve more accurate data during the analysis of small molecules by LC/MS/MS SRM method, Followings should be taken care of and kept checking; purity and concentration of stable isotope as an internal standard, prevention of carry-over during the separation in column, minimizing the ion suppression by matrix effect, identification of retention time, precursor ion and product ion, and full knowledge of data processing including smoothing and peak integration.
Lee, Myung Hyun,Lee, Yoonjae,Oh, Jung Hwan,Kim, Young Gyu,Cho, Sung Ki,Kim, Jae Jeong The Electrochemical Society 2017 Journal of the Electrochemical Society Vol.164 No.14
<P>In this study, we synthesized a leveler that contained two quaternary ammonium groups attached to hexaethylene glycol. The leveler enabled void- and seam-less Cu filling of the microvia. The convection-dependent adsorption of the leveler was assessed through electrochemical analyses such as linear sweep voltammetry and chronoamperometry on a rotating disk electrode, and the effect of convection on the adsorption of the leveler is interpreted in terms of adsorption diffusion model. In a Koutecky-Levich plot, the enhanced adsorption and inhibition of the leveler at the higher convection was clearly observed with the synthesized leveler. (c) 2017 The Electrochemical Society.</P>