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Youngsu Lim,Gi-Taek Oh,Bolam Kim,Jinseob Kim,Juhui Park,Seoungju Lee,Gyuhyeon Kim,Min-Woo Lee,Dae sung Lee 한국방사성폐기물학회 2023 한국방사성폐기물학회 학술논문요약집 Vol.21 No.1
A low- and intermediate-level radioactive waste repository contains different types of radionuclides and organic complexing agents. Their chemical interaction in the repository can result in the formation of radionuclide-ligand complexes, leading to their high transport behaviors in the engineered and natural rock barriers. Furthermore, the release of radionuclides from the repository can pose a significant risk to both human health and the environment. This study explores the impact of different experimental conditions on the transport behaviors of 99Tc, 137Cs, and 238U through three types of barrier samples: concrete, sedimentary rock, and granite. To assess the transport behavior of the samples, the geochemical characteristics were determined using X-ray diffraction (XRD), X-ray fluorescence (XRF), Fouriertransform infrared spectroscopy (FTIR), scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM-EDS), and Brunauer-Emmett-Teller (BET) analysis. The adsorption distribution coefficient (Kd) was used as an indicator of transport behavior, and it was determined in batch systems under different conditions such as solution pH (ranging from 7 to 13), temperature (ranging from 10 to 40°C), and with the presence of organic complexing agents such as ethylenediaminetetraacetic acid (EDTA), nitrilotriacetic acid (NTA), and isosaccharinic acid (ISA). A support vector machine (SVM) was used to develop a prediction model for the Kd values. It was found that, regardless of the experimental parameters, 99Tc may migrate easily due to its anionic property. Conversely, 137Cs showed low transport behaviors under all tested conditions. The transport behaviors of 238U were impacted by the order of EDTA > NTA> ISA, particularly with the concrete sample. The SVM models can also be used to predict the Kd values of the radionuclides in the event of an accidental release from the repository.
Youngsu Lim,Juhui Park,Dae Sung Lee 한국방사성폐기물학회 2022 한국방사성폐기물학회 학술논문요약집 Vol.20 No.2
Low- and intermediate-level radioactive wastes have been disposed of in the first-phase deep underground silo disposal at Gyeongju in South Korea. These radioactive wastes contain harmful radionuclides such as Uranium-238 (238U), which can pose long-term and deleterious effects on humans and the natural environment. Ethylenediaminetetraacetic acid and isosaccharinic acid, which can be formed via cellulosic waste degradation under high alkaline conditions might considerably enhance the transport behavior of 238U with the intrusion of rainwater and groundwater. In this study, the engineered barriers (concrete and grout) and natural barriers (sedimentary rock and granite) were used to investigate the 238U transport behavior in artificial cementitious porewater of State I (pH 13.3) and State II (pH 12.5) based on groundwater or rainwater. The surface properties and geochemical compositions of barrier samples were characterized using XRD, XRF, SEM-EDX, and BET. The transport behaviors of 238U in various solution conditions were observed by sorption distribution coefficient (Kd) at a range of initial chelating agents concentration (10-5-10-2 M). The sorption behavior of 238U was retarded more in the engineered rock barriers than in the natural rock barriers. The mobility enhancement of 238U was more significant in State I than in State II. In comparison with the absence of chelating agents, negligible changes in the Kd values of 238U were observed at less than initial chelating agent concentrations of 10-4 M. However, the Kd values of 238U were significantly reduced at initial chelating agent concentrations higher than 10-3 M. Therefore, these experimental findings show that the transport behavior of 238U into the geo- and bio-sphere could be accelerated by the presence of chelating agents and the type of cement degradation states.
개방형 및 비개방형 리더십과 마케팅역량이 기업성과에 미치는 영향: 소상공기업의 비대면서비스사용성을 중심으로
임영수(YoungSu Lim),김영균(YoungKyun Kim) 한국산업정보학회 2022 한국산업정보학회논문지 Vol.27 No.3
소상공기업의 특성상 경영자의 리더십과 마케팅역량의 따라서 상이한 기업성과가 나타났다. 특히 경영자의 비대면서비스사용성의 인식을 통한 기업성과의 유무를 확인하였다. 소상공기업의 임원들을 대상으로 설문을 진행한 결과, 소상공기업 경영자의 개방적리더십과 마케팅역량은 기업성과에 영향을 보이는 것으로 나타났으며 또한 비대면서비스사용성의 편리성에 영향을 미치는 것으로 나타났다. Due to the nature of small businesses, different corporate performance was found according to the leadership and marketing capabilities of managers. In particular, the presence or absence of corporate performance was confirmed through the manager"s perception of the usability of non-face-to-face services. As a result of conducting a survey of executives of small businesses, it was found that the open leadership and marketing capabilities of small business managers had an effect on corporate performance and also had an effect on the convenience of non-face-to-face service use.
Developing a Usability Testing System Using Web Standards
Youngsu Kim,Junyoung Choi,Ji Hyoun Lim 대한인간공학회 2011 대한인간공학회 학술대회논문집 Vol.2011 No.5
Objective: The aim of this study is to design and develop a UI evaluation system for smart phones using web standards. Background: The variety of past usability evaluations are based on WIMP user interfaces. However, the emergence of smart phones brought forth numerous types of operating systems and mobile browsers to the users. To evaluate interfaces on this wide array of devices, a new approach is needed in designing and developing UI evaluation systems. Method: Using web standards consisting of HTML 5, CSS 3 and ECMA Script (JavaScript), a 2-tier architecture consisting of a web/e-mail server and the application was designed to ensure interoperability between devices. To minimize data transaction and acquire safety in terms of data integrity, the application requires a single download of all required resources. The application runs on the client-side only, writes the output data into an e-mail and uses the phone's e-mail application to send the data to the server - again requiring only one upload transaction. Case Study: A smart phone user interface evaluation experiment was developed. A single URL was given to subjects to access, download and execute the web application. Experiment data were successfully collected via e-mail. Conclusion: Web standards have proved to be capable of implementing usability evaluation systems tailored for smart phones, providing to a certain limit the qualities required for valid academic experiments in the field of Us bility Engineering. Application: The design and development of the proposed system will help Usability experts perform UI evaluations with flexibility and help subject recruiting by improved interoperability and availability.
서브 나노초 상승시간의 고전압 펄스 발생용 피킹 스위치
노영수(Youngsu Roh),진윤식(Yun-Sik Jin),조주현(Chuhyun Cho),임수원(Soowon Lim) 대한전기학회 2012 전기학회논문지 Vol.61 No.9
A triaxial Blumlein pulse forming line has been designed to generate a pulse whose voltage is ∼300 ㎸, pulse duration is ∼5 ㎱, and rise time is ∼500 ㎰. It turns out, however, that the rise time of the pulse becomes much longer than 500 ㎰ due to parasitic inductances and capacitances existing inside the system. A peaking switch has been developed to shorten the rise time of the pulse from Blumlein pulse forming line. In the peaking switch, a wedge-shaped dielectric material (MC 901 nylon) is employed to surround the electrode on the antenna side. This shape inhibits an abrupt change of the output impedance, thereby minimizing the reflection of the output pulse. Experimental results show that the peaking switch is capable of improving the rise time of the pulse at a level of 500 ㎰.
Gate-Tunable and Programmable n-InGaAs/Black Phosphorus Heterojunction Diodes
Lee, Youngsu,Um, Doo-Seung,Lim, Seongdong,Lee, Hochan,Kim, Minsoo P.,Yang, Tzu-Yi,Chueh, Yu-Lun,Kim, Hyung-jun,Ko, Hyunhyub American Chemical Society 2019 ACS APPLIED MATERIALS & INTERFACES Vol.11 No.26
<P>Semiconductor heterostructures have enabled numerous applications in diodes, photodetectors, junction field-effect transistors, and memory devices. Two-dimensional (2D) materials and III-V compound semiconductors are two representative materials providing excellent heterojunction platforms for the fabrication of heterostructure devices. The marriage between these semiconductors with completely different crystal structures may enable a new heterojunction with unprecedented physical properties. In this study, we demonstrate a multifunctional heterostructure device based on 2D black phosphorus and n-InGaAs nanomembrane semiconductors that exhibit gate-tunable, photoresponsive, and programmable diode characteristics. The device exhibits clear rectification with a large gate-tunable forward current, which displays rectification and switching with a maximum rectification ratio of 4600 and an on/off ratio exceeding 10<SUP>5</SUP>, respectively. The device also offers nonvolatile memory properties, including large hysteresis and stable retention of storage charges. By combining the memory and gate-tunable rectifying properties, the rectification ratio of the device can be controlled and memorized from 0.06 to 400. Moreover, the device can generate three different electrical signals by combining a photoresponsivity of 0.704 A/W with the gate-tunable property, offering potential applications, for example, multiple logic operator. This work presents a heterostructure design based on 2D and III-V compound semiconductors, showing unique physical properties for the development of multifunctional heterostructure devices.</P> [FIG OMISSION]</BR>