Biological Evaluation of Graphene based Electrode Specimen Implanted on Rat Cerebral Cortex

Hyerin JEONG,Kyungtae KIM,Gaeun KIM,Minji KIM,Euiyoung KIM,Sangwon LEE,Kyu Il LEE,Sunggu YANG,ByoungKwan KIM 한국생물공학회 2023 한국생물공학회 학술대회 Vol.2023 No.10

Influence of Si/Al Ratio and Curing Temperature of Geopolymer Waste Forms on Immobilization of Radioactive Borate Waste

Byoungkwan Kim,Jaehyuk Kang,Younglim Shin,Tae-min Yeo,Wooyong Um 한국방사성폐기물학회 2022 한국방사성폐기물학회 학술논문요약집 Vol.20 No.1

Immobilization of radioactive borate waste containing a high boron concentration using cement waste form has been challenged because the soluble borate phase such as boric acid reacts with calcium compounds, hindering the hydration reaction in cement waste form. Metakaolin-based geopolymer waste form which has a pure aluminosilicate system without calcium can be a promising alternative for the cement; however, secondary B-O-Si networks are formed by a reaction between borate and silicate, resulting in poor mechanical characteristics such as low compressive strength and final setting retardation. Thus, it is important to optimize the Si/Al molar ratio and curing temperature which are critical parameters of geopolymer waste form to increase borate waste loading and enhance the durability of geopolymer. Here, metakaolin-based geopolymer waste form to immobilize simulant radioactive borate waste was fabricated by varying the Si/Al molar ratio and curing temperature. The 7 days-compressive strength results reveals that the Si/Al molar ratio of 1.4 and curing at 60°C is advantageous to achieving high waste loading (30wt%). In addition, geopolymer waste forms with the highest borate waste loading exceeded the 3.445 MPa after the waste form acceptance criteria such as thermal cycling, gamma irradiation, and water immersion tests. The leachability index of boron was 7.56 and the controlling leaching mechanism was diffusion. The thermal cycling and gamma irradiation did not significantly change the geopolymer structure. The physically incorporated borate waste was leached out from geopolymer waste form during leaching and water immersion tests. Considering these results, metakaolin-based geopolymer waste form with a low Si/Al ratio is a promising candidate for borate waste immobilization, which has been difficult using cement.

Compressive Strength Properties of Geopolymers from Pond Ash and Possibility of Utilization as Synthetic Basalt

Kim, Byoungkwan,Lee, Bokyeong,Chon, Chul-Min,Lee, Sujeong The Korean Ceramic Society 2019 한국세라믹학회지 Vol.56 No.4

Pond ash is a mixture of mostly coarser fly ash and bottom ash. The recycling rate of pond ash is low because pond ash is mixed with seawater and deposited in ponds. The pond ash is also subjected to natural weathering over a period of time. In this study, we investigated whether pond ash can be used as a raw material of geopolymers, without any purification process or through a minimal purification process. In addition, we investigated whether synthetic basalt made by adding foaming agent to geopolymer or casting it into a mold can show the surface of the natural basalt as it is. The highest 7-day compressive strength in geopolymers from pond ash without purification process was 26 MPa. The highest 7-day compressive strength in geopolymers from pond ash with impurities removed through dry sieve analysis was found to improve to 80 MPa. On the other hand, synthetic basalt made with geopolymer was shown to be more advantageous aesthetically when produced by casting it in a silicone mold rather than by adding a foaming agent. Non-purified pond ash can be made into geopolymers having low strength. Pond ash purified by sieving can, without use of an aggregate, be made into geopolymer having high-strength. Also, it is possible to produce synthetic basalt with the same appearance as natural basalt and sufficient strength for commercialization. This process will contribute to the mass consumption and recycling of pond ash.

Review on characteristics of metakaolin-based geopolymer and fast setting

Kim Byoungkwan,Lee Sujeong 한국세라믹학회 2020 한국세라믹학회지 Vol.57 No.4

The setting of metakaolin-based geopolymer depends on the raw materials and mix proportions. Setting, when material is cured at room temperature, takes about 1 day and is longer than setting time of Portland cement. For the fast setting of geopolymers, some studies increased the curing temperature or used raw materials with high CaO content. Also, Ca 2+ and Mg 2+ compounds were used as additives. Setting can be easily controlled and accelerated by adding Ca 2+ compounds. However, it has been reported that knowledge of the reaction mechanism and fi nal products between Ca 2+ and geopolymers is still limited. In this study, we investigated the characteristics of metakaolin-based geopolymers and methods for fast setting of geopolymers, and made hypotheses about the reaction mechanism between Ca 2+ and geopolymers.

Recent Advances in Geopolymer Waste Forms to Immobilize Radioactive Wastes

Byoungkwan Kim,Wooyong Um 한국방사성폐기물학회 2023 한국방사성폐기물학회 학술논문요약집 Vol.21 No.2

The immobilization of low- and intermediate-level radioactive waste (LILW) is crucial for its final disposal in repositories. While cementitious waste forms have conventionally been used for immobilizing various LILWs, they suffer from several issues, including poor durability, low resistance to leaching, and limited waste loading capacity. As an alternative, alkali or acid-activated geopolymer waste forms have garnered global attention. Unlike cementitious waste forms, geopolymer waste forms exhibit excellent physicochemical characteristics due to their three-dimensional amorphous structure and low calcium content. In this work, we provide an overview of geopolymer waste form research being conducted in countries such as Japan, the United Kingdom, the European Union, and South Korea. We specifically focus on the immobilization of soil waste, spent ion exchange resins, organic liquid waste, and evaporator concentrate (borate waste). We also identify the factors influencing the physicochemical characteristics of geopolymer waste forms and their immobilization performance. We propose a guide for optimizing the molar mixing formulations of geopolymer waste forms, including the selection of appropriate precursor materials. Additionally, we discuss the future prospects and significant challenges in the field of geopolymer waste forms that need to be addressed for their application in radioactive waste management.

Solidification of Borate Waste Using Metakaolin-Based Geopolymer Waste Form

Byoungkwan Kim,Juhyeok Lee,Jaehyuk Kang,Younglim Shin,Won-Seok Kim,Wooyong Um 한국방사성폐기물학회 2020 한국방사성폐기물학회 학술논문요약집 Vol.2020 No.12

국내 커뮤니케이션 연구의 통계분석방법의 현황과 문제점: 지난 10년간 〈한국언론학보〉게재 논문의 내용분석

이병관(Byoungkwan Lee),김재민(Jaemin Kim),김주환(Juhwan Kim),장다연(Dayeon Jang),권나현(Nahyun Gwon) 한국언론학회 2020 한국언론학보 Vol.64 No.5

Although statistical analysis methods are essential tools for quantitative researchers, controversy has persisted over the objectivity of inference through statistical procedures. The purpose of this study is to review the use and trends of statistical analysis methods in quantitative research papers published between 2010 to 2019 in the Korean Journal of Journalism and Communication Studies and to discuss its practices and problems of statistical use in communication research in Korea. For this purpose, 612 quantitative research papers using statistical analysis methods were content-analyzed out of a total of 845 papers published across 10 years. In this 612 quantitative research, the basic characteristics of the study, as well as the reliability between coders, the number of coders, and power for experimental design, were reviewed according to the methodology used. This study also checked for the use of null hypotheses and multi-item measures, and more specific details including the statistical packages, the basic assumptions of statistical analysis methods used in individual studies, such as t-test and regression, and the description of statistical results. Research papers were collected, reviewed, and analyzed by four graduate students majoring in advertising and public relations. The inter-coder reliability was measured by Kripendorff alpha, and the reliability for each item was between 0.71 and 1, thus ensuring a stable level of reliability. As a result of the analysis, research using surveys was the most common among the research methods, and regression was the most frequently used statistical method except for descriptive statistics. The most commonly used statistical package was SPSS. The current study found problems of over-reliance on a specific statistical package, erroneous interpretation of statistical analysis results, and misuse of statistical methods for yielding contrived results. In particular, over-reliance on a specific statistical package was related to over-reliance of specific statistical analysis methods such as partial eta squared and cronbach alpha. At the same time, in most studies, wrong practices were also found. For example, important information regarding the processes and results of statistical analysis was not provided, such as basic statistical assumptions and correlation between major variables, and neither was information on confidence intervals as supplementary indicators of null hypothesis significance testing. Given that this study empirically identified the criticisms and discussions that have been continuously raised about statistical analysis methods and reporting, this study holds implications. Through this study, it is hoped that future Korean communication researchers will actively carry out research on various problems and alternatives raised in individual statistical analysis methods, thereby enriching academic discussions.

자동차용 핀 부싱 베어링의 응력해석에 대한 연구

이병관(Byoungkwan Lee),김도현(Dohyun Kim),심종현(Jonghyun Shim),김청균(Chungkyun Kim),이일권(Il Kwon Lee) 한국트라이볼로지학회 2008 한국트라이볼로지학회 학술대회 Vol.2008 No.11

The connecting rod is the tribological part of automobile's engine. Since it is operated under several loads such as a compressive force, tensile force, bending force and high heat, it has proper strength and hardness. The pin-bushing bearing is a part is used at the small end of a connecting rod. It has a two part, Copper alloy and beck metal. As It contacts with a piston pin, it has good strength, lubricating ability. So in this paper, we analyze the strength safety of a pin-bushing bearing by a finite element method.

Homogeneity Test of Cesium and Cobalt Loaded Ion Exchange Resins in Polymer Waste Form

Jueun Kim,Byoungkwan Kim,Bhupendra Kumar Singh,Wooyong Um 한국방사성폐기물학회 2020 한국방사성폐기물학회 학술논문요약집 Vol.2020 No.12

Virtual Bus 개념의 CAN-Ethernet 게이트웨이 설계

김병관(Byoungkwan Kim),신봉걸(Bongkeol Shin),장주욱(Ju wook Jang) 한국자동차공학회 2014 한국자동차공학회 부문종합 학술대회 Vol.2014 No.5

The Controller Area Network (CAN) is a commonly used technology for connecting electronic control units (ECUs) in the vehicles. However the number of ECUs in vehicle is increasing and data traffic is increasing suddenly by real time service like Topview. Therefore Ethernet backbone is proposed to solve this problem, and CAN-Ethernet gateway becomes crucial. In AUTOSAR 4.1, they proposed CAN-Ethernet gateway which has First In First Out (FIFO) queues for storing messages before transmitting them. However, FIFO queues are not guarantee that priority of messages when low priority message is arrive faster than high priority message. In this paper we propose new CAN-Etehrnet gateway to which is applied a Virtual Bus. This scheme is guarantee that priority of messages and decrease transmisson delay of high priority messages.