Teaching qualitative methodologies as praxis

Young Chun Kim(Young Chun Kim),Seungho Choi(Seungho Choi),Jung-Hoon Jung(Jung-Hoon Jung) 아시아질적탐구학회 2022 아시아질적탐구 Vol.1 No.1

The purpose of this article is to provide the appearance and meaning of teaching qualitative research in South Korea wherein whose academic culture has been highly influenced, if not dominated, by the West. In this respect, the authors conceptualize the experiences of teaching qualitative research to undergraduate and graduate students in South Korea. To do so, three authors have collected stories, experiences, and reflections of teaching qualitative methodologies, and then categorized their reflections of these experiences. The stories the authors tell entail five themes as follows; teaching qualitative research as (a) dangerous practice, (b) painful practice, (c) horrifying practice, (d) educative practice, and (e) brave practice. Each practice, as metaphors, illuminate the meanings of the practices of teaching qualitative research in South Korea. The authors conclude the article with questions to provoke Korean researchers to rethink and reflect on their practices of teaching and conducting qualitative research in the Korean context and beyond.

Accuracy Improvement in Cyclic Voltammetry Stripping Analysis of Thiourea Concentration in Copper Plating Baths

Choe, Seunghoe,Kim, Myung Jun,Kim, Kwang Hwan,Kim, Hoe Chul,Song, Jae Chun,Kim, Soo-Kil,Kim, Jae Jeong The Electrochemical Society 2015 Journal of the Electrochemical Society Vol.162 No.4

<P>Cyclic voltammetry stripping (CVS) has been regarded as a powerful tool for monitoring the concentrations of organic additives in plating baths. In this study, the dilution titration (DT) method of CVS was modified to improve the measurement accuracy of thiourea (TU) concentrations in Cu plating baths. The conventional DT-CVS method cannot guarantee high accuracy because the electrochemical behavior of TU is concentration and potential dependent, which can cause disturbances in the response signals. In this study, by adding polyethylene glycol (PEG) as an organic additive, the undesirable electrochemical behavior of TU was suppressed and the accuracy of DT-CVS was greatly improved. Using the improved method, the concentrations of TU and its derivatives in the plating bath were measured. The errors between the real and measured concentrations were reduced from 15.0%, 36.0%, and 15.0% using the conventional DT-CVS method to within 3.00%, 6.00%, and 6.00% for TU, N-ethyl thiourea, and N<SUP>′</SUP>,N-diethyl thiourea, respectively, using the improved method.</P>

REMOVAL OF AGGREGATES FROM MICRON-SIZED POLYMETHYL METHACRYLATE (PMMA) LATEX BEADS USING FULL FEED DEPLETION MODE OF GRAVITATIONAL SPLITT FRACTIONATION (FFD-GSF)

Lee, Seungho,Cho, Sung Kwang,Yoon, Jin Woo,Choi, Seong-Ho,Chun, Jong-Han,Eum, Chul Hun,Kwen, HaiDoo Taylor Francis 2009 JOURNAL OF LIQUID CHROMATOGRAPHY AND RELATED TECHN Vol.33 No.1

<P> Split-flow thin cell (SPLITT) fractionation (SF) provides separation of colloidal particles or macromolecules into two fractions. A gravitational SF (GSF) system was constructed and its applicability was tested for removal of aggregates from mass-produced polymethyl methacrylate (PMMA) latex beads. The full-feed depletion (FFD) mode of GSF (FFD-GSF) was found to be a simpler alternative to the conventional mode for removal of the aggregates. Unlike in the conventional mode, where two inlets are used for feeding of the sample suspension and the carrier liquid respectively, only one inlet (for the sample feeding) is used in the FFD mode, allowing easier control of the flow rate. Also the sample suspension is not diluted during FFD mode operation. Aggregated particles were found only in one of the two fractions, allowing removal of the aggregates. The sample was continuously fed into the GSF system, showing potential application to a large quantity operation for removal of the PMMA aggregates.</P>

Seismic retrofit of framed structures using a steel frame assembly

Michael Adane,Seungho Chun,Jinkoo Kim 국제구조공학회 2023 Steel and Composite Structures, An International J Vol.46 No.6

This study aimed to develop a seismic retrofit technique using a steel frame which can be easily transported and assembled on site. This enables the retrofit steel frame to be easily attached to an existing structure minimizing the unwanted gap between the structure and the steel frame assembly. A one-story one-bay RC frame was tested with and without seismic retrofit using the proposed steel frame to verify the seismic retrofit effect of the proposed system, and an analysis model was developed in Opensees for seismic performance evaluation of a case study soft first-story model structure retrofitted with the developed steel frame assembly. Seismic performance of the model structure was also evaluated considering soil structure interaction effect. The experimental study confirmed that the proposed seismic retrofit system can be applied effectively to improve the seismic performance of framed structures. Time history analysis results of the model structure showed that the proposed steel frame assembly was effective in increasing the seismic load resisting capacity of the soft first-story structure. However more steel frame assemblies were required to satisfy the given performance limit state of the model structure located on weak soil due to the negative soil-structure interaction effect.

시베리아 고기압 확장시 호남 지방의 강설 분포 - 노령 산맥 서사면 지역을 중심으로 -

이승호(Lee Seungho),천재호(Jae-Ho Chun) 대한지리학회 2003 대한지리학회지 Vol.38 No.2

본 연구에서는 시베리아 고기압의 확장시 호남 지방의 강설 분포와 강설 패턴의 지역성을 파악하기 위해 호남 지방의 15개 기상관측지점의 일강설량 및 구름 자료를 분석하였다. 호남 지방의 강설은 시베리아 고기압에 의한 것이 대부분으로 북서 계절풍에 직접적으로 노출된 서해안과 노령 산맥의 서사면은 강설이 많고, 노령 산맥의 풍하측인 남해안으로 갈수록 적어진다. 특히, 노령 산맥의 서사면 지역에서는 지형적 특색에 따라 강설 분포의 패턴이 다양하여, 해안에 위치한 군산은 강설이 많고 내륙 평야에서 강설이 감소하는 경향을 보인다. 한편 내륙으로 기류가 이동하여 산지를 만나면 강제 상승하게 되어 다시 강설이 증가한다. 일반적으로 적운형 구름의 출현 빈도가 높은 지역에서 강설이 많은데, 적운형 구름은 내륙 산지, 해안, 그리고 내륙 평야 순이며, 강설 강도 또<br/> 한 내륙 산지, 해안, 내륙 평야 순으로 강하다. 특히, 정읍의 경우 배후에 노령 산맥이 가까이 있고 북서 계절풍에 대해 정면으로 노출되어 강설 강도가 가장 강하게 나타난다. 따라서, 호남 지방의 강설은 해안 지역에서의 바다 효과에 의한 강설과 내륙 산간 지역에서의 지형 효과에 의한 강설로 구분할 수 있다. This study aims to understand the patterns of spatial distribution of snowfall by Siberian High in the Honam region in Korea. In the Honam region, Siberian High induces snowfall dominantly. There is a huge amount of snowfall in the westward of the Noryung mountain ranges to the West coast in the Honam region affected by northwesterly wind directly from the Siberian High. The westward of the Noryung mountain ranges such as a heavy snowfall region has a various pattern of distribution of snowfall due to topography. The coast region has a large amount of snowfall by sea effect. And, snowfall amount is decreased from the coast to the inland plain. However, in front of mountain, snowfall is increase by reason of a forced ascending air to the mountain. In general the region where frequently appear a cumuliform cloud has a large amount of snowfall. A cumuliform cloud is frequent in the mountainous region in inland, the coast, and the inland plain in order. Snowfall is intense in the coast and the mountainous region, and weak in the inland plain. In the mountainous region, a cumuliform cloud induced by a forced ascending air by reason of topography generates snowfall mostly. This fact is the main difference with snowfall in the mountainous region and the coast region. In the<br/> result, in the Honam region, snowfall distribution and snowfall pattern are various, according to geographical climate factor such as sea and topography. The heavy snowfall region in the Honam region is divided into the coast region affected by sea effect and the mountainous region affected by topography effect.

Development of a seismic retrofit system made of steel frame with vertical slits

Hyungoo Kang,Michael Adane,Seungho Chun,Jinkoo Kim 국제구조공학회 2022 Steel and Composite Structures, An International J Vol.44 No.2

In this study, a new seismic retrofit scheme of building structures is developed by combining a steel moment frame and steel slit plates to be installed inside of an existing reinforced concrete frame. This device has the energy dissipation capability of slit dampers with slight loss of stiffness compared to the conventional steel frame reinforcement method. In order to investigate the seismic performance of the retrofit system, it was installed inside of a reinforced concrete frame and tested under cyclic loading. Finite element analysis was carried out for validation of the test results, and it was observed that the analysis and the test results match well. An analytical model was developed to apply the retrofit system to a commercial software to be used for seismic retrofit design of an example structure. The effectiveness of the retrofit scheme was investigated through nonlinear time-history response analysis (NLTHA). The cyclic loading test showed that the steel frame with slit dampers provides significant increase in strength and ductility to the bare structure. According to the analysis results of a case study building, the proposed system turned out to be effective in decreasing the seismic response of the model structure below the given target limit state.

Seismic retrofit system made of viscoelastic polymer composite material and thin steel plates

Mohammad Seddiq Eskandari Nasab,Seungho Chun,Jinkoo Kim 국제구조공학회 2022 Steel and Composite Structures, An International J Vol.43 No.2

In this study, a series of cyclic loading tests were performed on viscoelastic dampers (VED) composed of viscoelastic polymer composite material and thin steel plates to observe the variation of the mechanical properties under different loading conditions. A mathematical model was developed based on the Kelvin–Voigt and Bouc–Wen models to formulate the nonlinear force-displacement relationship of the viscoelastic damper. The accuracy of the proposed mathematical model was verified using the data obtained from the tests. The mathematical model was applied to analyze a reinforced concrete framed structure retrofitted with viscoelastic dampers. Nonlinear dynamic analysis results showed that the average maximum inter-story drift ratios of the retrofitted structure met the target limit state after installing the VED. In addition, both the maximum and residual displacements were significantly reduced after the installation of the VED.

Experimental study on steel hysteretic column dampers for seismic retrofit of structures

Mohammad Mahdi Javidan,Seungho Chun,Jinkoo Kim 국제구조공학회 2021 Steel and Composite Structures, An International J Vol.40 No.4

In this research, the seismic performance of a steel column damper is evaluated using cyclic loading tests of two one-story one-bay reinforced concrete (RC) frames before and after retrofit. The theoretical formulation and design procedure of the damper are explained first and then the details of the tests are described. The seismic performances of the test frames are evaluated in terms of hysteretic behavior, energy dissipation, crack pattern, failure mechanism, and damper behavior. The analytical model of the damper is established and verified using the experimental data. In order to further investigate the applicability of the developed damper for seismic retrofit, a case-study structure is chosen and retrofitted using the proposed damper. The seismic performance of the structure is evaluated and compared before and after retrofit in detail using pushover, nonlinear time-history, and fragility analyses. The results show that the presented damper can efficiently reduce inter-story drifts and damage of the structure. The details of modeling techniques and simulations given in this study can provide guidelines and insight into nonlinear analysis and retrofit of RC structures.

알코올 증기 유발 친수성 표면에서의 액적 되튐 연구

정종수(Jongsu Jeong),김승호(Seungho Kim),김경천(Kyung Chun Kim) 대한기계학회 2023 대한기계학회 춘추학술대회 Vol.2023 No.5

Elution Behavior of Protein and Pullulan in Asymmetrical Flow Field-flow Fractionation (AsFlFFF)

Eunsun Ji,최성호,윤국로,Jong-Han Chun,Seungho Lee* 대한화학회 2006 Bulletin of the Korean Chemical Society Vol.27 No.9

An AsFlFFF channel was designed and built, and then tested for analysis of pullulans and proteins. Pullulans and proteins having various nominal molecular weights were injected at various conditions of the cross-flow rate (Fc) and the channel-out flow rate (Fout). The retention (measured by the retention ratio R) and the zone broadening (measured by the plate height H) were measured, and then compared with theory. When the incoming flow rate, Fin (and thus Fout) was varied with Fc fixed at 2.5 mL/min, the plate height measured for the pullulan with nominal molecular weight (M) of about 100,000 showed the trend expected by the longitudinal diffusion theory (H decreases with increasing flow rate). In contrast, when Fout was varied with the flow rate ratio, Fc/Fout, fixed constant at 5, the plate height measured for the same sample showed the trend expected from the non-equilibrium theory (H increases with increasing flow rate). Calibration plots (log D vs. log M) obtained with pullulans and proteins were not coincide, probably due to the difference in molecular conformation, suggesting the analysis of pullulans and proteins using AsFlFFF requires independent calibration. It was found that the linearity of the protein-calibration plot was improved by using a buffer solution as the carrier.