딥러닝 회귀/분류 문제에서 변수 선택의 영향

이승재,장대흥 한국품질경영학회 2020 한국품질경영학회 학술대회 Vol.2020 No.-

예측분석에서는 회귀분석시 설명변수 사이의 다중공선성 문제를 해결하기 위하여 전통적인 변수선택 방법이나 벌점회귀를 주로 사용한다. 본 연구에서는 실제 자료를 통한 딥러닝 회귀 및 분류문제에서 이러한 변수선택 방법이나 벌점회귀를 사용할 때 모형 평가 측도나 컴퓨터 계산 속도에 어떠한 영향을 주는지를 평가하였고 자료나 입력변수의 크기에 따라 변수선택의 영향이 어떻게 달라지는지 비교하였다.

사회적재난(화재)시 대피시설(피난사다리)에 대한 강화 필요성 검토

이승재,Lee, Seungjea 한국공간구조학회 2022 한국공간구조학회지 Vol.22 No.1

Radiation Exposure of Hands and Feet from $^{18}F$-FDG in Radio-technologists

이승재,정석,서수현,박용성,박훈희,오신현,임한상,김재삼,이창호,Lee, Seung-Jae,Jeong, Seok,Seo, Soo-Hyun,Park, Yong-Sung,Park, Hoon-Hee,Oh, Shin-Hyun,Lim, Han-Sang,Kim, Jae-Sam,Lee, Chang-Ho The Korean Society of Nuclear Medicine Technology 2011 핵의학 기술 Vol.15 No.2

방사선 작업 종사자들의 손 및 작업화의 방사선 오염 정도를 분석하여 외부 방사선 오염과 피폭의 위험도를 예상해 보고, 방사선 작업 종사자들의 점차적인 수적 증가와 장기근무화 되고 있는 것을 고려하여, 손 및 작업복으로 인한 방사선 오염 방지를 위한 대책을 강구 하기 위하여 본 연구를 실시하였다. 2010년 8월 4일부터 2011년 1월 14일까지 세브란스병원 핵의학과 PET/CT 검사실에 근무하는 방사선사 6명의 손 및 작업화의 방사선 오염 선량을 8시(아침), 12시(점심), 16시(저녁)에 각각 측정하였다. 통계적 분석은 SPSS 17을 이용하여 프리드만 검정, 양측꼬리검정, 윌콕슨 (표본비교) 검정을 실시하였다. 8시에 측정한 손과 작업화의 오염 선량은 다른 시간대의 선량과 비교하여 통계학적 유의성이 있었다. 특정한 경우, 측정된 선량값이 다른 시간대인 12시 16시의 선량보다 훨씬 높게 나타났다. 손에 대한 감마선의 영향을 알아보기 위해 오염되기 전의 선량을 예상하였으나 작업화의 선량은 예상이 쉽지 않아서 시행되지 않았다. 방사선 작업 종사자의 수적 증가와 장기 근무화 현상을 고려할 때 작은 양의 방사능 오염도 피폭의 축적을 가져옴으로 개인 피폭, 오염 관리에 신경 써야 할 것이다. 비록 손과 작업화의 오염 선량이 관련된 권고안 보다 낮게 나타났음에도 불구하고, 방사능 오염을 방지하기 위한 작업은 반드시 필요하다. 따라서 방사선사들은 방사능 오염을 방지하기 위하여, 보다 방사능 피폭 관련 모니터링을 정기적, 주기적으로 실시하는 등의 적절한 피폭 방지 대책을 강구하여야 한다. Purpose: The radiation exposure from radioisotope at the hands and foots of radiation workers who works in PET/CT part at the department of nuclear medicine was investigated in this study. Materials and Methods: From 4th August 2010 to 14th January 2011, 6 radio-technologists' radiation on hands and feet were measured. All radio-technologist have been examined around 8; morning, 12; afternoon, and 16 o'clock; evening, respectively. SPSS version 17 was used for statistical analysis. Results: The statistical significances were calculated in several ways. The radiation from both hands and feet in the Morning was lower than Afternoon and Evening. In some cases, the detected radiation showed extremely high values in data. In order to find the effect of the ${\gamma}$-ray on the hand, the estimated doses were presumably calculated, however, the exposure dose on feet were unmeasured. Conclusion: Even if the radiation exposure from the radioisotope at the hands and feet were under the limitations, it is definitely needs to prevent the radiation-contamination. Therefore, the radio-technologists need to have a proper radiation-dealing-procedure of their own, and must try to prevent a radiation exposure by themselves.

Conjugate Gradient 기법을 이용한 관측교통량 기반 통행수요 추정

이승재,이헌주(Hum Ju Lee) 대한교통학회 2003 대한교통학회 학술대회지 Vol.44 No.-

관측교통량으로 OD행렬을 추정하는 일반적인 형태는 엔트로피 최대화 방법(Entropy Maximizing), 일반화 최소자승법(Generalized Least Squares), 베이지안 추론기법(Bayesian Inference) 등이 있다. 이러한 기법들을 이용한 모형들은 일반적으로 2단계(bi-level)형태를 이루고 있다.

한국 산업인력구조의 변화와 주조산업계 대응방안

이승재,조인성,Lee, Seung-Jae,Cho, In-Sung 한국주조공학회 2018 한국주조공학회지 Vol.38 No.2

The lack of industrial manpower that Korean companies have been suffering in 21st century is largely responsible for the low-fertility phenomenon. This research suggests an alternative solution with a program for fostering foreign laborers with technical skills in casting industry. Industrial manpower growth is feasible through accepting migrants who have had official education on the fundamental industrial technologies provided by Korean government. These technically trained migrants who can keep economical self-perpetuating ability are can help to effectively address the problem of the declining working-age population and the decreasing potential growth rate in Korea.

Estimation of Plastic Energy Dissipation Amount of Multi-bent Spatial structure by Equivalent Linear Analysis

이승재,Lee, Seung-Jae Korean Association for Spatial Structures 2006 한국공간구조논문집 Vol.6 No.2

It is important to evaluate energy absorption capacity of frames required during a design earthquake. An inelastic computer analysis based on mathematical modelling of energy absorbing frames and elements makes it possible to evaluate required energy absorption capacity. But such an analysis sometimes consumes much computation time particularly in case of complicated structural system. This paper presents a proposal to predict energy absorption of multi-bent steel frames by simple equivalent linear method.

초대형 막구조물 지붕용 ETFE 필름 막재의 인장특성

이승재,이소라,Lee, Seung-Jae,Lee, So-Ra 한국공간구조학회 2010 한국공간구조학회지 Vol.10 No.1

ETFE is the abbreviation of Ethylen Tetra Fluoro Etylene, a sort of colorless and transparent granules. The advantage ETFE film has daylight transmission and chemical the resistance and The thickness of ETFE film is used to from $50{\mu}m$ to $300{\mu}m$ and tensile strength of ETFE film changes from 40MPa to 60MPa and the tensile strain at break can get to about 300-400%. In this paper, ETFE film carried out the tensile proprieties, such as the tensile strain at break, the tensile strength are examined. ETFE 필름 막재는 Ethylen Tetra Fluoro Etylene의 약자로, 무색의 투명한 막재료이다. ETFE 필름 막재는 내화학성이 있고 매우 가벼운 장점이 있는 것으로 알려져 있다. ETFE 필름 막재는 $50{\mu}m$에서 $300{\mu}m$의 두께가 주로 사용되며, 인장강도는 40MPa에서 60MPa 300%에서 400%정도이다. 본 연구에서는 최근 해외에서 초대형 박구조물의 박재료로 시용되는 ETFE 필름 막재에 대한 기초적 역학적 특성을 조사하기 위하여 인장시험을 수행하였다. 인장시험으로부터 인장강도, 인장연신율, 영계수(Young's Modulus) 등 건축 설계 시 필요한 기초적 자료를 제공하고자 한다.

식방풍(植防風, Peucedani Radix)의 품질표준화에 관한 연구

이승재,김호현,조형권,이광섭,강인호,함인혜,황완균,Lee, Seung-Jae,Kim, Ho-Hyun,Cho, Hyoung-Kwon,Lee, Kwang-Sup,Kang, In-Ho,Ham, In-Hye,Whang, Wan-Kyunn 한국생약학회 2001 생약학회지 Vol.32 No.4

The Radix of Peucedanum japonicum (Umbelliferae) has been used for dispelling wind-damp, headache, chills and wind cold. In order to evaluate to quality of it, the method for the quantitative determination of peujaponiside $(peucedanol\;7-O-{\beta}-D-apiofuranosyl(1{\rightarrow}6)-{\beta}-D-glucopyranoside)$ as standard compound has been developed. Peujaponiside is a major compound of Peucedani Radix. It was analyzed by HPLC using the solvent system of 15% $CH_3CN$. The amount of peujaponiside from Peucedani Radix are in the range 0.14% (n=20).

단기 창업교육이 예비창업자의 심리적 특성 변화 영향에 대한 탐색적 연구

이승재,황보윤,Lee, Seung-Jae,HwangBo, Yun 한국벤처창업학회 2010 벤처창업연구 Vol.5 No.1

This study intend to analyze effect on a change mental feature of founder received entrepreneurship short-term education called the successful foundation package. In other words, what kind of change the mental feature of founder before and after entrepreneurship education. The founder of the psychological characteristics include the locus of control, risk-taking propensity, need for achievement, ambiguity tolerance and specially new psychological trait, that is, creativity. The result of paired T-test and ANCOVA on pre-founders who received Entrepreneurship short-term education which called successful business start-up package is that need for achievement, ambiguity tolerance and creativity among pre-founders' psychological characteristics are enhanced by Entrepreneurship short-term education. However ANCOVA shows that there are no psychological characteristics changes according to age, education, the number of Entrepreneurship education.

전층각막이식수술 후 10년 경과 관찰

이승재,조은영,김만수.Seung Jae Lee. M.D.. Eun Young Cho. M.D.. Man Soo Kim. M.D. 대한안과학회 2006 대한안과학회지 Vol.47 No.7

Purpose: To evaluate clinical outcomes 10 years after penetrating keratoplasty. Methods: We analyzed 69 eyes of 68 patients who had undergone penetrating keratoplasty by one surgeon between 1994 and 1995. We evaluated long-term outcome of corneal graft and follow-up rates for 10 years after surgery. Slitlamp biomicroscopy was performed to assess the condition of grafts. Visual acuity, manifest refraction, central corneal thickness, and endothelial cell count were measured if the patient visited the clinic. The patients who did not visit the clinic were asked to subjectively assess visual acuity and gross corneal clarity to gauge the condition of the graft cornea by telephone survey. Results: The mean age was 42.5 years and the sex distribution of recipients was predominantly male (M:F=48:20). At 10 years after surgery, 28 grafts were clear, 28 grafts were known to have failed, and the status of 13 grafts remained unknown. The highest survival rate was noted in keratoconus, and the major preoperative diseases of graft failure were bullous keratopathy and infectious keratitis. Fifty percent of patients attended all follow-up visits over the 10 years. Conclusions: The graft survival rate at 10 years after keratoplasty was 50%.