• Steel and Composite Structures
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• 제46권6호
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• pp.759-772
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• 2023

This manuscript presents a comprehensive mathematical model to investigate buckling stability and postbuckling response of bio-inspired composite beams with helicoidal orientations. The higher order shear deformation theory as well as the Timoshenko beam theories are exploited to include the shear influence. The equilibrium nonlinear integro-differential equations of helicoidal composite beams are derived in detail using the energy conservation principle. Differential integral quadrature method (DIQM) is employed to discretize the nonlinear system of differential equations and solve them via the Newton iterative method then obtain the response of helicoidal composite beam. Numerical calculations are carried out to check the validity of the present solution methodology and to quantify the effects of helicoidal rotation angle, elastic foundation constants, beam theories, geometric and material properties on buckling, postbuckling of bio-inspired helicoidal composite beams. The developed model can be employed in design and analysis of curved helicoidal composite beam used in aerospace and naval structures.

• Advances in nano research
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• 제13권4호
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• pp.341-350
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• 2022

The continuous elements method, also known as the dynamic stiffness method, is effective for solving structural dynamics problems, especially over a large frequency range. Before applying this method to fluid-structure interactions, it is advisable to check its validity for pure acoustics, without considering the different coupling parameters. This paper describes a procedure for taking wave propagation into account in the formulation of a Dynamic Stiffness Matrix. The procedure is presented in the context of the harmonic response of acoustic pressure. This development was validated by comparing the harmonic response calculations performed using the continuous element model with the analytical solution. In addition, this paper illustrates the application of this method to a simple compressible flow problem, since it has been applied solely to structural problems to date.

• 한국컴퓨터정보학회:학술대회논문집
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• 한국컴퓨터정보학회 2023년도 제68차 하계학술대회논문집 31권2호
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• pp.99-100
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• 2023

국립중앙박물관에서는 국공사립 박물관 및 미술관 등의 소장품을 체계적인 관리지원을 위하여 문화유산표준관리시스템을 개발 및 배포하고 있다. 문화유산표준관리시스템의 자료등록 방법은 크게 두가지로 나뉘고 있다. 첫 번째는 소장품등록의 웹페이지화면에서 할 수 있으며 두 번째는 엑셀양식을 통한 일괄등록이다. 본 논문에서는 엑셀양식을 통한 일괄등록의 경우에서 별도의 웹페이지를 작성하여 자료입력방식에서 생길 수 있는 인적오류를 최소화하는 방법을 제시한다.

• Journal of Preventive Medicine and Public Health
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• 제30권4호
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• pp.741-751
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• 1997

Measurement of blood lead (PbB) and blood zinc protoporphyrin (ZPP) are most common biological indices to identify the individual at risk for excess or the health sequences by lead exposure. Because PbB is known most important and reliable index of lead exposure, PbB is often regarded as a gold standard to detect lead exposure. But in Korea PbB is a secondary test item of detailed health check-up with positive finding of screening test in most occasion. Our lead standard requires all lead workers to take annual heath-check twice a year for investigation of their health effect due to lead exposure. Blood ZPP is one of most important index to detect high lead absorption in lead workers as a screening test. Measurement of blood ZPP is known ,well to correlate with PbB in steady state of exposure in most lead workers and is often used as a primary screening test to detect high lead absorption of lead workers with the advantage of simplicity, easiness, portability and low cost. The current cut-off criteria of blood ZPP for further detailed health check-up is $100{\mu}g/d\ell$ which is supposed to match the level of $40{\mu}g/d\ell$ of PbB according to our standard. Authors tried to investigate the validity of current criteria of cut-off level $(100{\mu}g/d\ell)$ of blood ZPP and possible another better cut-off level of it to detect the lead workers whose PbB level over $40{\mu}g/d\ell$. The subjects in our study were 212 male workers in three small scale storage battery industries. Blood ZPP, PbB and hemoglobin (Hb) were selected as the indices of lead exposure. The results were as follows. 1. The mean of blood ZPP, PbB and Hb in lead workers were $79.5{\pm}46.7{\mu}g/d\ell,\;38.7{\pm}15.1{\mu}g/d\ell,\;and\;14.8{\pm}1.2g/d\ell$, respectively. There were significant differences in blood ZPP, PbB and Hb by industry (P<0.01). 2. The percents of lead workers whose blood ZPP were above $100{\mu}g/d\ell$ in the group of work duration below 1, 1-4, 5-9 and above 10 years were 8.6%, 17.2%, 47.6%, and 50.0%, respectively. The percents of lead workers whose PbB were above $40{\mu}g/d\ell$ in those were 31.4%, 40.4%, 71.4%, and 86.4%, respectively. 3. The percents of lead workers whose PbB were below $40{\mu}g/d\ell$, $40-59{\mu}g/d\ell$ and above $60{\mu}g/d\ell$ were 54.7%, 34.9% and 10.4%, respectively. Those of lead workers whose blood ZPP were below $100{\mu}g/d\ell$, $100-149{\mu}g/d\ell$ and above $150{\mu}g/d\ell$ were 79.2%, 13.7% and 7.1%, respectively. 4. Simple linear regression of PbB on blood ZPP was statistically significant (P<0.01) and as PbB was $40{\mu}g/d\ell$, blood ZPP was $82.1{\mu}g/d\ell$. 5. While the highest sensitivity and specificity of blood ZPP test to detect lead workers with PbB eve. $40{\mu}g/d\ell$ were observed in the cut-off level of $50{\mu}g/d\ell$ and $100{\mu}g/d\ell$ of blood ZPP, respectively, the highest validity (sensitivity+specificity) of blood ZPP to detect lead workers with PbB over $40{\mu}g/d\ell$ was observed in the cut-off level of around $70{\mu}g/d\ell$ of blood ZPP. But even with optimal cut-off level of around $70{\mu}g/d\ell$ of blood ZPP, still 25.0% of false negative and 20.7% false positive lead workers were found. As the result of this study, it was suggested that reconsideration of current blood ZPP cut-off of our lead standard from $100{\mu}g/d\ell$ to somewhat lower level such as around $70{\mu}g/d\ell$ and the inclusion of PbB measurement as a primary screening test for lead workers was highly recommended for the effective prevention of lead workers.

• 과학교육연구지
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• 제42권3호
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• pp.308-321
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• 2018

이 연구는 과학탐구 상황에서 반회의주의적 태도를 조사하는 문항을 개발하는 것이 목적이다. 문헌 연구, 전문가 검토, 통계적 타당도 검증을 거쳐 문항을 개발하고, 성별, 계열별로 점수 차이를 확인하였다. 이 연구를 위하여 363명의 고등학생들이 참여하였다. 문항 타당도 확인을 위하여 라쉬 분석, 내적 일관성 신뢰도 확인 등을 수행하였고, 성별과 계열별 반회의주의적 태도의 점수 비교를 위하여 이원분산분석을 확인하였다. 연구 결과 과학탐구상황에서 반회의주의 태도를 측정할 수 있는 23개 리커트 형태의 자기보고형 검사도구를 개발하였다. 반회의주의적 태도 측정을 위하여 과학탐구 상황을 크게 '문제 인식과 가설 생성', '실험 설계', '관찰', '설명과 해석'으로 구분하여 각 구인별로 측정할 수 있는 다수의 문항을 개발하였다. 둘째, 과학탐구상황에서 반회의주의 태도 측정 문항의 타당도와 신뢰도를 엄격한 방법을 통해 확인하였다. 라쉬 분석을 통해 다차원 부분점수모델의 분석의 적합성을 확인하였으며, 라쉬 분석을 통해 문항 적합도를 확인한 결과 23개 문항 모두 적합으로 나타났다. 다양한 신뢰도 지수도 적합한 것으로 나타났다. 남학생과 여학생, 문과계열과 이과계열별로 구분하여 반회의주의적 태도를 비교한 결과 유의미한 차이를 나타낸 비교는 실험설계에서 계열별 차이를 제외하고 없는 것으로 확인되었다. 개발된 문항들을 활용하여 과학탐구 과정에서 반회의주의적 태도를 점검하고, 과학탐구 수업의 효과를 비교하는데 활용될 수 있을 것이다.

• 대한지구과학교육학회지
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• 제8권3호
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• pp.332-345
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• 2015

Earth science is the study to explore the planet in which we live. Among these earth science geology of the area it can be the most critical and important study. However, because of the size and scope is too broad temporal spatial eurona covered in geology is true that many students find difficult about the geology field. In this study, in conjunction with landscape formation of geologic time for the concept to be among the core areas of Geology examined the concept and recognize it as the destination for high school students. Is a test tool for the analysis was adapted for use by Jolley (2010) has developed LIFT (The Landscape Identification and Formation Test). Currently we fix the strip to match the country through a validity check of the curriculum. Results of the study were as follows: First, the ability to check the landscape and formation is expected to estimate the time and the liberal arts students was higher than the natural science students. The reason for this seems to be the influence of learning geographical subjects. Second, the concept of geological time was found to lack both natural science and liberal arts students. The reason is that the students in the previous process because it deals with the concept of geologic time from the top of Earth Science Education II seems to be because there was no chance of learning about geological time. Third, the results confirm the confidence of the students surveyed in the landscape formation time natural science students was higher than liberal arts students. The research measured gender boys higher than girls. Fourth, the students on the landscape and geological time was found to have a number of misconceptions. This appears to be due to the students to feel difficulty in thinking of the concept because the need to understand the abstract geologic time. Therefore, it is necessary just to hold misconceptions about the concept of geology students have through the study of the landscape and geological time.

• 한국산학기술학회논문지
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• 제17권3호
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• pp.231-240
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• 2016

최근 발생한 원전부품 시험성적서 위변조 사건은 국민들에게 많은 충격을 가져왔다. 또한 케이블 제조회사들은 부당한 이득을 취득할 목적으로 시험 데이터를 위조했으며 군수분야에서도 시험성적서를 위조하여 불량부품을 납품한 사례도 발견되었다. 성적이 위조된 부품은 무기체계 운용에 심각한 영향을 미칠 수 있으며, 이는 국가안보에 직결된다는 점에서 매우 중요한 사안이다. 본 연구에서는 군수업체의 시험데이터 위조 가능성을 검출할 수 있는 통계적 이론 기반의 방법론을 확립하고 이를 엑셀 툴을 활용하여 유효성 검증 툴을 개발하였다. 또한 군수업체 시험시스템의 전반적인 개선을 목적으로 기존의 시험시스템 요구사항들을 반영한 체크리스트 기반의 검증 도구 역시 개발하였다. 본 유효성 검증 툴을 활용하여 위조된 시험 성적서의 검출 및 검증을 통해 불량부품 사용을 사전에 차단함으로써 군수품 품질보증에 중요한 역할을 할 것으로 기대된다.

• 대한조선학회논문집
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• 제51권2호
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• pp.122-129
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• 2014

Identification of the whipping response out of the combined wave-vibration response of a flexible sea going vessel is one of the most interesting research topic from ship designer's point of view. In order to achieve this goal, a novel methodology based on the wavelet cross-correlation technique was proposed in this paper. The cross-correlation of the wavelet power spectrum averaged across the frequency axis was introduced to check the similarity between the combined wave-vibration response and impulse response. The calculated cross-correlation of the wavelet power spectrum was normalized by the auto-correlation of the each spectrum with zero time lag, eventually providing the cross-correlation coefficient that stays between 0 and 1, precisely indicating the existence of the impulse response buried in the combined wave-vibration response. Additionally, the weight function was introduced while calculating the cross-correlation of the two spectrums in order to filter out the signal of lower frequency so that the accuracy of the similarity check becomes as high as possible. The validity of the proposed methodology was checked through the application to the artificially generated ideal combined wave-vibration signal, together with the more realistic signal obtained by running 3D hydroelasticity program WISH-Flex. The correspondence of the identified whipping instances between the results, one from the proposed method and the other from the calculated slamming modal force, was excellent.

• 한국재난정보학회 논문집
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• 제19권2호
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• pp.363-371
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• 2023

연구목적: 본 연구는 BCMS의 정량적 평가체계 도입을 위해 BCMS 분야의 국제표준인 ISO 22301 (2019)의 PDCA(Plan-Do-Check-Act) 요구항목 중 Plan- '조직의 이해' part의 평가지표를 개발하는 것을 목적으로 한다. 연구방법: 20명의 BCMS 분야 전문가 그룹에 수정 델파이 기법을 활용하여 ISO 22301의 Plan- '조직의 이해'의 세부요건의 타당성을 검토하고, 평가지표의 상대적 중요도를 조사하였다. 연구결과: 효과적인 BCMS 역량평가가 가능하도록 상대적 중요도가 포함된 12개의 평가지표를 개발하여 제안하였다. 결론: BCMS의 정량적인 평가체계 도입을 위해서는 효과적인 평가가 가능하도록 상대적 중요도가 포함된 평가지표를 선별하여야 한다는 결론을 도출하였다.

• 대한기계학회논문집A
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• 제28권10호
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• pp.1603-1611
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• 2004

The validity of 'modified overlay model' to describe the cyclic behavior of annealed 316L stainless steel at room temperature was investigated. Material parameters(~f$_{i}$, m$_{i}$b, η, E) fur the model were obtained through constant strain amplitude test. The strain amplitude dependency of elastic limit and cyclic hardening, which were the characteristics of this model, were considered. Eight subelements were used to describe the nonlinearity of the hysteresis loops. The calculated hysteresis curve in each condition (0.5％, 0.7％, 0.9％ train amplitude test) was very close to the experimental one. Two tests, incremental step test and 5-step test, ere performed to check the validity of 'modified overlay model'. The elastic limit was saturated to the one of the highest strain amplitudes of the block in the incremental step test, so it seemed to be Masing material at the stabilized block. Cyclic hardening was successfully described in the increasing sequence of the strain amplitude in 5-step test. But, the slight cyclic softening followed by higher strain amplitude would not be able to simulate by'modified overlay model'. However, the discrepancy induced was very small between the calculated hystereses and the experimental ones. In conclusion,'Modified overlay model'was proved to be appropriate in strain range of 0.35％~ 1.0％..0％.