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Estimation of Fracture Toughness Using Flat‑Ended Cylindrical Indentation
Woojoo Kim,Seunghun Choi,Junyeong Kim,Seung‑won Jeon,Min‑Jae Choi,Dongil Kwon 대한금속·재료학회 2021 METALS AND MATERIALS International Vol.27 No.9
A method is proposed to predict the fracture toughness of in-service structures using the instrumented indentation test. Whileprevious studies have attempted to predict fracture toughness using spherical indenters, we propose the method to predictfracture toughness using flat-ended cylindrical indenters. Using the geometric similarity of a cylindrical indentation testand the Cracked Round Bar (CRB) fracture toughness test, fracture toughness values were derived from a single indentationtest by assuming that the load–depth curve of the indentation test is the same as the load–displacement curve of the CRBfracture toughness test. To determine the crack initiation point, the concept of limit load in CRB testing is adopted, and anew load–depth curve is obtained using a suggestion in the standard of fracture toughness test. In order to apply the proposedmethod directly to in-service structures, the model uses mechanical parameters that can be obtained by indentation testing. The model was verified on metallic materials primarily used in nuclear power plants.
Evaluation of Comprehensibility of Newly Introduced Water-sport Prohibitive Signs in Korea
( Woojoo Kim ),( Yohana Siswandari ),( Shuping Xiong ) 한국감성과학회 2014 춘계학술대회 Vol.2014 No.-
The aim of this study is to evaluate the comprehensibility of newly introduced water-sport prohibitive signs issued by The Ministry of Knowledge Economy (MKE, later merged into The Ministry of Trade, Industry and Energy) of Korea, and to redesign poorly comprehended signs based on participants`feedback and ergonomic design principles. Comprehensibility tests of fourteen water-sport prohibitive signs were conducted with forty Korean participants. In session I, each participant was asked to guess the meaning of each sign verbally in an open-ended test, whereas in session II, each participant was encouraged to give opinion on each sign`s features and ideas for design improvement. Experimental results showed that only two out of fourteen signs have reached the comprehension rate (67%) recommended by the ISO standard, indicating that the recently introduced water-sport prohibitive signs by MKE still need to be improved.
Evaluation of comprehensibility of newly introduced water-sport prohibitive signs in Korea
Woojoo Kim,Yohana Siswandari,Shuping Xiong 대한인간공학회 2014 대한인간공학회 학술대회논문집 Vol.2014 No.5
The aim of this study is to evaluate the comprehensibility of newly introduced water-sport prohibitive signs issued by The Ministry of Knowledge Economy (MKE, later merged into The Ministry of Trade, Industry and Energy) of Korea, and to redesign poorly comprehended signs based on participants’ feedback and ergonomic design principles. Comprehensibility tests of fourteen water-sport prohibitive signs were conducted with forty Korean participants. In session I, each participant was asked to guess the meaning of each sign verbally in an open-ended test, whereas in session II, each participant was encouraged to give opinion on each sign’s features and ideas for design improvement. Experimental results showed that only two out of fourteen signs have reached the comprehension rate (67%) recommended by the ISO standard, indicating that the recently introduced water-sport prohibitive signs by MKE still need to be improved. The identified poorly comprehended signs were also redesigned. The results of this study may serve as a useful input for water-sport sign designers in creating easy-to-comprehend safety signs.
Woojoo Kim,Yohana Siswandari,Shuping Xiong 대한인간공학회 2015 大韓人間工學會誌 Vol.34 No.1
Objective: The goal of this study is to evaluate the comprehensibility of the newly introduced water-sport prohibitive signs by the Ministry of Knowledge Economy (MKE, later merged into the Ministry of Trade, Industry and Energy) among Koreans and westerners, and to check whether the comprehensibility is affected by cultural differences. Background: The Ministry of Knowledge Economy had newly introduced fourteen water-sport prohibitive signs at the end of 2011 to alert people to potentially dangerous situations. However, no studies had been found so far to review or assess their comprehensibility. Method: Comprehensibility tests of fourteen water-sport prohibitive signs were conducted with forty Koreans and forty Westerners in two sequential sessions. In session I, participants were asked to guess the meaning of each sign verbally in an open-ended test. In session II, participants were encouraged to provide feedback for each sign after its intended meaning was given. Results: Only two out of fourteen signs satisfied the comprehension rate (67%) recommended by ISO standard for both groups (Koreans and Westerners). Cultural difference between Koreans and westerners significantly affect the comprehension rates of the investigated signs, and Westerners exhibit better overall comprehension than Koreans. Five poorly comprehended signs for both Korean and Western groups were identified. Conclusion: The recently introduced water-sport prohibitive warning signs by MKE still need a lot of improvements in order to be implemented nationally or internationally. There were significant differences in the signs" comprehensibility between Koreans and westerners. Application: The findings may serve as a useful input for researchers and watersport sign designers in creating easy-to-comprehend safety signs.
Kim, Byung Hyo,Shin, Kwangsoo,Kwon, Soon Gu,Jang, Youngjin,Lee, Hyun-Seok,Lee, Hyunjae,Jun, Samuel Woojoo,Lee, Jisoo,Han, Sang Yun,Yim, Yong-Hyeon,Kim, Dae-Hyeong,Hyeon, Taeghwan American Chemical Society 2013 JOURNAL OF THE AMERICAN CHEMICAL SOCIETY - Vol.135 No.7
<P>We present a rapid and reliable method for determining the sizes and size distributions of <5 nm-sized iron oxide nanocrystals (NCs) using matrix-assisted laser desorption/ionization time of flight (MALDI-TOF) mass spectrometry (MS). MS data were readily converted to size information using a simple equation. The size distribution obtained from the mass spectrum is well-matched with the data from transmission electron microscopy, which requires long and tedious analysis work. The size distribution obtained from the mass spectrum is highly resolved and can detect size differences of only a few angstroms. We used this MS-based technique to investigate the formation of iron oxide NCs, which is not easy to monitor with other methods. From ex situ measurements, we observed the transition from molecular precursors to clusters and then finally to NCs.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/jacsat/2013/jacsat.2013.135.issue-7/ja310030c/production/images/medium/ja-2012-10030c_0004.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/ja310030c'>ACS Electronic Supporting Info</A></P>
가산자료 모형을 이용한 정액형 입원보험 가입자의 의료이용량 실증분석
이우주 ( Woojoo Lee ),김정환 ( Jeonghwan Kim ),김영대 ( Yeongdae Kim ),고방원 ( Bangwon Ko ) 한국보험학회 2019 保險學會誌 Vol.117 No.-
이 연구에서는 정액형 입원보험에 가입한 사람들을 대상으로, 가입금액에 따른 입원일수를 가산자료 모형을 이용하여 분석하였다. 실증분석을 위해 2015년도 말 정액형 입원보험을 유지하고 있는 45세에서 64세 사이의 여성가입자를 고려하였으며, 해당년도 입원보험금이 청구된 입원일수를 취합하여 고액가입자의 의료이용 실태를 파악하고자 하였다. 분석결과 가입금액은 연령에 상관없이 입원일수와 상당한 연관성을 가지고 있었으며, 통계적인 모형화가 가능할 정도로 특징적인 패턴을 나타내는 것을 확인할 수 있었다. 물론 이러한 결과로부터 정액형 입원보험 가입자의 도덕적 해이를 속단하기에는 무리가 따르지만, 입원보험료를 산출할 때 성별이나 나이 등과 더불어 가입금액의 크기를 반영할 필요가 있다고 판단된다. 향후 관련 연구에서 대용량 가산자료를 분석하는데 활용할 수 있도록 일반화 가법모형 및 R 코드를 소개하였다. In this paper, we analyze fixed-amount-type hospital insurance data using count data models to investigate the effect of the sum insured on the number of days staying in hospital. For the empirical analysis, we gather the contract information regarding the female insureds aged from 45 to 64 at the end of year 2015, and utilize the accident statistics related to the insurance claims to see how the insured behaves as the sum insured increases. According to our empirical analysis, the sum insured exhibits a considerable association with the number of days staying in hospital irrespective of age, and the pattern was so prominent to be statistically modeled. It might be too hasty to view this as a result of the insureds’ moral hazard, but it seems necessary to reflect the amount of sum insured together with the insured’ sexuality or age for the premium calculation. For the future application of generalized additive model (GAM) to large-scale count data in insurance, we explain the GAM model and the associated R-code at the appendix.