문항반응이론에서 피험자 능력 및 문항모수 추정 알고리즘 개발

최항석,차경준,김성훈,박정,박영선,Choi, Hang-Seok,Cha, Kyung-Joon,Kim, Sung-Hoon,Park, Chung,Park, Young-Sun 한국통계학회 2008 Communications for statistical applications and me Vol.15 No.3

Item response theory(IRT) estimates latent ability of a subject based on the property of item and item parameters using item characteristics curve(ICC) of each item case. The initial value and another problems occurs when we try to estimate item parameters of IRT(e.g. the maximum likelihood estimate). Thus, we propose the asymptotic approximation method(AAM) to solve the above mentioned problems. We notice that the proposed method can be thought as an alternative to estimate item parameters when we have small size of data or need to estimate items with local fluctuations. We developed 'Any Assess' and tested reliability of the system result by simulating a practical use possibility.

다양한 형상의 덕트내 난류유동 및 스칼라 전달현상의 특성

최항석(Choi Hang Seok) 한국산업응용수학회 2011 한국산업응용수학회 학술대회 논문집 Vol.6 No.1

덕트(duct)나 채널(channel)내의 난류유동(turbulent flow)은 각각의 형상에 따라 다양한 난류의 조직구조(coherent structure)를 형성한다. 이러한 난류의 조직구조는 벽면 근방에서 주로 발생하며, 이로 인해 유동의 모멘텀(momentum) 및 스칼라(scalar)량의 전달현상(transport phenomena)에 중요한 영향을 끼친다. 본 연구에서는 바닥면이 파형을 갖는 덕트, 가로-세로비가 다른 사각 덕트 및 곡면이 있는 사각 덕트 내의 난류유통을 LES(large eddy simulation)를 이용하여 전산 해석하여, 각각의 덕트 내부에서 발생하는 난류의 조직구조 및 이로 인한 스칼라량의 전달 특성에 관해 살펴보았다.

토목구조물에서 적용할 수 있는 효율적인 신재생에너지 활용 기술인 에너지파일(Energy Pile)이란 무엇입니까?

최항석(Hang-Seok Choi),정경식(Kyoung-Sik Jung) 대한토목학회 2013 대한토목학회지 Vol.61 No.6

풀-브릿지 영전압 영전류 컨버터의 소신호 모델링

최항석(Hang-seok Choi),조보형(B. H. Cho) 대한전기학회 1999 대한전기학회 학술대회 논문집 Vol.1999 No.7

수직 밀페형 지증 열교환기용 뒤채움재의 열전도 및 점도특성 연구

최항석(Choi, Hang-Seok),이철호(Lee, Chul-Ho),길후정(Gil, Hu-Jeong),최효범(Choi, Hyo-Pum),우상백(Woo, Sang-Baik) 한국신재생에너지학회 2007 한국신재생에너지학회 학술대회논문집 Vol.2007 No.11

In order to characterize the thermal conductivity and viscosity of grout materials used for backfilling ground heat exchangers, nine bentonite grouts and cement grouts being adapted in the United State have been considered in this study. The bentonite grouts indicate that the thermal conductivity and viscosity increase with the content of bentonite or filler (silica sand). In addition, material segregation can be observed when the viscosity of grout is relatively low. The saturated cement grouts appear to possess much higher thermal conductivity than the saturated bentonite grouts, and the reduction of thermal conductivity in the cement grouts after drying specimens is less than in case of the bentonite grouts. Maintaining the moisture content of grouts is a crucial factor in enhancing the efficiency of ground heat exchangers.

초등ㆍ중등교사들의 다문화교육을 위한 운영 방안 연구

최항석(Choi, Hang-Seok),차미정(Cha, Mi-Jeung) 한국다문화교육연구학회 2010 다문화교육 Vol.1 No.3

이 논문은 현장교사의 운영 방안을 연구하기 위해 초등ㆍ중등교사들에 대하여 다문화교육 중요성 인식과 다문화적 효능감에 관련된 상황을 알아보고, 효과적인 지도방안을 위한 실제지도와 자녀지도를 위한 교사들의 태도에 관해 알아보았다. 연구문제에서는, 초등ㆍ중등교사들 의 다문화교육에 관한 인식조사를 통해 학교 교육을 담당하고 있는 교사의 다문화적 역량을 알아보고자 초등ㆍ중등 교사의 다문화교육 중요성에 관한 인식에는 어떤 차이가 있는가? 교사들은 학교 현장에서 필요한 다문화교육의 효율적인 지도방안은 무엇이라고 생각하는가?를 파악하였다. 결과에서는 첫째, 초등ㆍ중등교사들의 경우 교사경력 별, 다문화가정 자녀의 지도 유ㆍ무에는 다문화교육에 관한 인식과 다문화적 효능감에는 영향을 미치지 못하는 것으로 나타났다. 둘째, 초등교사의 경우 교사연수 유ㆍ무에는 영향이 없었지만, 중등교사의 경우는 교사연수 유ㆍ무가 다문화교육에 관한 인식과 다문화적 효능감에 큰 영향을 준 것으로 나타났다. 셋째, 다문화가정 자녀의 지도에 대해서는 담임교사의 역할이 큰 것으로 나타났으며 만일 전담교사로 적합한 사람을 선정한다변, 다문화가정에 대해 관심과 이해도가 높은 자원봉사자로 확인 할 수 있었다. 넷째, 다문화가정 자녀를 위한 행ㆍ재정적 지원을 위해서는 다문화가정 자녀에게 알맞은 교재ㆍ교수 학습자료 개발과 지원이 필요하며, 다문화가정 자녀를 위해서는 학교에 적응하고 친구를 만들 수 있는 방법들이 교육과정에 포함되어 있어야 한다는 것을 알 수 있었다. This paper includes a research of how teachers(elementary and middle) recognize the importance of multi-cultural education. The research result also states several ways to efficiently prepare the multi-cultural society and the most desired way of education. This paper made a diagnosis of teachers' current recognition of multi-cultural education in order to get a thorough view of the current situation. This includes checking the instructors' awareness of the possible clash between children of a multi-culture family and a children from a local family, which cannot be ignored for a successful multi-cultural education process. This paper also analyzed the difference of recognition between instructors experienced of multi-cultural education and not. Most teachers were not experienced of getting education of multi-cultural education, but they showed a thorough recognition and a high potential efficiency. The research showed that the teacher in charge of the class is the most important instructor for foreign children. An appropriate teacher in charge for such students appeared to be instructors who deeply understands and cares multi-cultural education and families. In order for students from other culture to adapt well, the education system must not exclude such students, and should provide not only administrative but also financial support. The education system should prepare appropriate textbooks, teaching materials, and especially the plans to help make harmony between local and foreign students. Foreign students must be guaranteed of easy access of such support, and moreover the system should give the instructors more chance to get educated of multi-cultural teachings. The teachers need education first in order for them to teach better. Also, for Korean society to adjust itself well to a multi-cultural society, the government, the educator, and the citizens must understand multi-culture well and they all must work as a team. This requires sustaining support from the government. Teachers must get educated before they educate, and the government and the citizens as one should form a respectful atmosphere for foreigners.

기포 유동층 반응기내 목질계 바이오매스의 급속열분해 특성

최항석(Hang Seok Choi) 한국전산유체공학회 2011 한국전산유체공학회지 Vol.16 No.2

The fast pyrolysis characteristics of lignocellulosic biomass are investigated for a bubbling fluidized bed reactor by means of computational fluid dynamics (CFD). To simulate multiphase reacting flows for gases and solids, an Eulerian-Eulerian approach is applied. Attention is paid for the prim my and secondary reactions affected by gas-solid flow field. From the result, it is scrutinized that fast pyrolysis reaction is promoted by chaotic bubbling motion of the multiphase flow enhancing the mixing of solid particles. in particular, vortical flow motions around gas bubbles play an important role for solid mixing and consequent fast pyrolysis reaction. Discussion is made for the time-averaged pyrolysis reaction rates together with time-averaged flow quantities which show peculiar characteristics according to local transverse location in a bubbling fluidized bed reactor.

바이오매스 급속열분해 반응기내 열전달 특성

최항석(Hang Seok Choi) 한국전산유체공학회 2010 한국전산유체공학회지 Vol.15 No.1

The characteristics of flow and heat transfer in a bubbling fluidized bed are investigated by means of computational fluid dynamics (CFD). To simulate two-phase flow for the gas and solid flows, Eulerian-Eulerian approach is applied. Attention is paid for a heat transfer from the wall to fluidized bed by bubbling motion of the flow. From the result, it is confirmed that heat transfer is promoted by chaotic bubbling motion of the flow by enhancement of mixing among solid particles. In particular, the vortical flow motion around gas bubble plays an important role for the mixing and consequent heat transfer. Discussion is made for the time and space averaged Nusselt number which shows peculiar characteristics corresponding to different flow regimes.

해양 지중저장층내 초임계 CO₂ 유동에 대한 전산모사

최항석(Hang Seok Choi) 大韓環境工學會 2011 대한환경공학회지 Vol.33 No.4

이산화탄소의 해양 지중저장에 대한 전산모사를 위해 실제 이산화탄소가 저장되는 해양 지중 저장층에 대한 3차원 전산모형을 개발하였다. 특히, 실제 저장층의 3차원 구조를 모사하기 위하여 공극의 크기를 불규칙(random)적으로 부여하는 수치적 방법을 고안하여 3차원 전산모형을 구성하였고, 이를 균일한 공극 구조의 경우와 비교하였다. 이렇게 구성된 3차원 공극모형 내의 초임계 이산화탄소 유동을 시뮬레이션하기 위하여 전산유체역학을 사용하였다. 이러한 초임계 이산화탄소의 시뮬레이션에는 실제 저장층의 환경 즉 온도 및 압력을 동일하게 모델링하여 적용하였다. 공극 구조가 CO₂의 유동에 미치는 영향을 살펴보기 위해, 세 가지 형태의 3차원 전산모형의 공극 구조 내부를 흐르는 초임계 이산화탄소 유동에 대한 수치해석을 수행하였으며, 특히 3차원 전산모형의 내부유동에 대한 압력강하 및 투수율을 계산하여 본 모형이 해양 지중저장의 전산모사에 적합한지를 판단하고, 이산화탄소 유량 증가에 따른 초임계 이산화탄소 유동의 특성을 살펴보았다. In the present study, a 3-dimensional (3D) numerical model was developed to mimic the micro porous structure of a geological CO₂ storage reservoir. Especially, 3D modeling technique assigning random pore size to a 3D micro porous structure was devised. Numerical method using CFD (computational fluid dynamics) was applied for the 3D micro porous structure to calculate supercritical CO₂ flow field. The three different configurations of 3D micro porous model were designed and their flow fields were calculated. For the physical conditions of CO₂ flow, temperature and pressure were set up equivalent to geological underground condition where CO₂ fluid was stored. From the results, the characteristics of the supercritical CO₂ flow fields were scrutinized and the influence of the micro pore configuration on the flow field was investigated. In particular, the pressure difference and consequent CO₂ permeability were calculated and compared with increasing CO₂ flow rate.

평생교육으로서의 다문화주의: 평생학습사회에서의 다문화교육을 위한 교육자본화 논고(論考)

최항석 ( Hang Seok Choi ),한진상 ( Jin Sang Han ) 성결대학교 다문화평화연구소 2014 다문화와 평화 Vol.8 No.3

The purpose of this study was to propose the invigoration of the educational capital for developing practical theories of multicultural education to actualize in lifelong learning society. In the 21st century, multicultural education will be the key to achieve the successful edutopia. But until now, the researches of multicultural education was not enough to analysis of the practical researches for the future. The erudition was the instirnct of human-being. Therefore, the erudition was the power of reformatting pernonal and social lives. To achieve the erudition, it is necessary to establish the invigoration of educational capital that inter-related among the human capital, social capital, and educational capital. To invigorate the educational capital, we must focus on the multicultural person as one of the most important hunan capitals. In addition to this, we need to integrate among spaces, political relationships, and program development for the invigoration of educational capltal. These should be the ``Expect`` to promise the future development of Korean Society.