• 한국초등과학교육학회지:초등과학교육
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• 제40권3호
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• pp.390-406
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• 2021

이 연구는 화산과 지진 단원의 수업에 GeoMapApp을 활용한 학습 자료를 적용하고, 공간 능력이 서로 다른 초등학생들이 인지한 공간 개념, 표현한 공간적 표상의 도구, 지형 구조를 표현하는 데 적용한 공간적 추론을 추출하여 공간적 사고의 과정을 분석하였다. 공간 능력 상위 집단 학생들은 인지한 공간 개념 정보를 수평 거리에 따라 구간을 나누어 화산과 지진의 지형 구조에 관한 심리적 이미지를 형성하는 내적 공간 표상을 활용하거나, 인식한 공간 개념을 그대로 연결하는 공간적 추론의 사례를 보였다. 또한, 지진 자료를 보고 공간 개념을 변형하여 공간적 추론을 수행하는 예도 있었다. 공간 능력 하위 집단 학생들은 공간 개념을 직접 지형 구조로 연결하는 공간적 추론을 보이거나, 공간 개념을 부분적으로 인식하여 지형을 파악하는 공간적 추론 사례를 보였다. 연구 결과를 근거로 초등학생들이 GeoMapApp 자료에서 거리, 높이, 깊이와 같은 공간 개념을 정확히 인식해야 더 나은 공간적 사고를 구현할 수 있음을 밝혔다.

• 한국전자파학회논문지
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• 제30권1호
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• pp.23-27
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• 2019

본 논문에서는 비 침습적, 비 파괴적으로 샘플의 단층구조와 단층의 미세진동을 실시간으로 동시에 영상화하는 마이크로 바이브로 토모그라피(micro vibro tomography: MVT) 시스템 개발 및 미세진동 측정 방법을 제안한다. 제안한 방법은 광 간섭 단층촬영기술(optical coherence tomography: OCT)을 기반으로 하여, 샘플의 위상변이를 이용해 마이크로 단위의 움직임을 측정하는 알고리즘을 적용한 방법이다. 본 실험에서는 고막을 모방한 라텍스 샘플에 2~5 kHz 주파수의 음파를 인가시키고, 음파에 의한 샘플의 미세진동을 제안한 MVT 시스템을 이용하여 측정하였다. 그 결과, 고막 모방 샘플의 단층구조와 미세진동을 동시에 영상화할 수 있었고, 표면부의 미세진동을 MVT 표면 진동 이미지로 프로젝팅하여 고막 모방 샘플의 전체적인 진동 형태를 관찰할 수 있었다.

• 한국군사과학기술학회지
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• 제22권4호
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• pp.492-500
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• 2019

Equal channel angular pressing(ECAP) is a severe plastic deformation technique capable of introducing large shear strain in bulk metal materials. However, if an ECAPed material has an inhomogeneous microstructure and anisotropic mechanical properties, this material is difficult to apply as structural components subjected to multi-axial stress during use. In this study, extruded oxygen-free copper(OFC) rods with a large diameter of 42 mm are extruded through ECAP by route Bc up to 12 passes. The variations in the microstructure, hardness, tensile properties, and microstructural and mechanical homogeneity of the ECAPed samples are systematically analyzed. High-strength OFC rods with a homogeneous and equiaxed-ultrafine grain structure are obtained by the repeated application of ECAP up to 8 and 12 passes. ECAPed samples with 4 and 8 passes exhibit much smaller differences in terms of the average grain sizes on the cross-sectional area and the tensile strengths along the axial and circumferential directions, as compared to the samples with 1 and 2 passes. Therefore, it is considered that the OFC materials, which are fabricated via the ECAP process with pass numbers of a multiple of 4, are suitable to be applied as high-strength structural parts used under multi-axial stress conditions.

• Journal of the Korean Wood Science and Technology
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• 제47권1호
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• pp.8-20
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• 2019

This study was conducted to analyze the pore structure of Yellow poplar. Cross-sectional surfaces of heartwood and sapwood of Yellow poplar (Liriodendron tulipifera) were observed by SEM, and the true density of the heartwood, intermediate wood and sapwood were measured by gas pycnometery, while gas permeability and pore size of heartwood, intermediate wood and sapwood were measured by capillary flow porometery. The pores were classified as through pore, blind pore and closed pore. It was determined that the permeability was increased due to the content and size of through pore being increased although the total porosity of specimen showed slight difference from pith to bark. The content of through pore porosity was 33.754 % of heartwood and 47.810 % of sapwood, showed an increasing trend from pith to bark, however, those for the blind pore porosity and closed pore porosity were 27.890 % and 19.492 % for heartwood and 19.447 % and 4.660 % for sapwood, showed a decreasing trend from pith to bark. The max pore size of specimens was increased by about 5 times from $5.927{\mu}m$ to $31.334{\mu}m$, and mean flow pore size was increased by about 315 times from $0.397{\mu}m$ to $12.437{\mu}m$ from pith to bark.

• 센서학회지
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• 제28권3호
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• pp.198-204
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• 2019

In this study, we propose a wearable force sensor using 3D printed mold and liquid metal. Liquid metal, such as Galinstan, is one of the promising functional materials in stretchable electronics known for its intrinsic mechanical and electronic properties. The proposed soft force sensor measures the external force by the resistance change caused by the cross-sectional area change. Fused deposition modeling-based 3D printing is a simple and cost-effective fabrication of resilient elastomers using liquid metal. Using a 3D printed microchannel mold, 3D multichannel Galinstan microchannels were fabricated with a serpentine structure for signal stability because it is important to maintain the sensitivity of the sensor even in various mechanical deformations. We performed various electro-mechanical tests for performance characterization and verified the signal stability while stretching and bending. The proposed sensor exhibited good signal stability under 100% longitudinal strain, and the resistance change ranged within 5% of the initial value. We attached the proposed sensor on the finger joint and evaluated the signal change during various finger movements and the application of external forces.

• 대한금속재료학회지
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• 제46권3호
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• pp.159-168
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• 2008

Thermally-evaporated 10 nm-Ni/1 nm-Ru/(30 nm or 70 nm-poly)Si structures were fabricated in order to investigate the thermal stability of Ru-inserted nickel monosilicide. The silicide samples underwent rapid thermal anne aling at $300{\sim}1,100^{\circ}C$ for 40 seconds. Silicides suitable for the salicide process were formed on the top of the single crystal and polycrystalline silicon substrates mimicking actives and gates. The sheet resistance was measured using a four-point probe. High resolution X-ray diffraction and Auger depth profiling were used for phase and chemical composition analysis, respectively. Transmission electron microscope and scanning probe microscope(SPM) were used to determine the cross-sectional structure and surface roughness. The silicide, which formed on single crystal silicon and 30 nm polysilicon substrate, could defer the transformation of $Ni_2Si $i and $NiSi_2 $, and was stable at temperatures up to $1,100^{\circ}C$ and $1,100^{\circ}C$, respectively. Regarding microstructure, the nano-size NiSi preferred phase was observed on single crystalline Si substrate, and agglomerate phase was shown on 30 nm-thick polycrystalline Si substrate, respectively. The silicide, formed on 70 nm polysilicon substrate, showed high resistance at temperatures >$700^{\circ}C$ caused by mixed microstructure. Through SPM analysis, we confirmed that the surface roughness increased abruptly on single crystal Si substrate while not changed on polycrystalline substrate. The Ru-inserted nickel monosilicide could maintain a low resistance in wide temperature range and is considered suitable for the nano-thick silicide process.

• 한국콘텐츠학회논문지
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• 제21권4호
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• pp.67-76
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• 2021

모바일 앱으로 과제를 수행할 때에 트리-뷰 메뉴의 외적인 구조에 따라 사용성이 달라지고, 메뉴의 배열이 사용자가 기대하는 스크립트와 다를 때에 사용성이 떨어지고, 그리고 과제의 복잡성에 따라 이 둘의 효과가 달라진다는 연구가설을 검증하였다. 이를 위하여 대학생 참가자들이 기대하는 숙박 예약 스크립트를 작성하였으며, 과제완료시간과 오반응률을 종속변인으로 하는 실험을 설계하였다. 실험은 예약 시스템 프로토타입을 스마트폰에 구현하여 실시하였다. 그 결과로 과제가 복잡할 때에 수행이 전반적으로 불리한 가운데, 구획메뉴의 수월성이 과제가 복잡할 때에 두드러졌으며 복잡한 과제에서 메뉴의 배열이 기대와 일치할 때에 긍정적인 반응이 관찰되었다. 이러한 결과를 논의하여 모바일 화면에 절차적인 메뉴를 설계할 때에는 작업기억의 부담을 최소화하는 방안을 마련하고, 과제에 맞는 트리-뷰가 무엇인지를 고민하고, 그리고 복잡한 과제에서는 사용자가 기대하는 스크립트에 준하여 메뉴를 배열하여야 한다는 사실을 발견할 수 있었다.

• 터널과지하공간
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• 제31권4호
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• pp.211-220
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• 2021

한국의 대심도 (>40m 깊이) 터널 공사 시에 터널 붕괴 사고가 종종 일어나고 있으며, 도심지 지하공간의 얕은 심도에 인공적으로 조성된 지반에는 자연 공동뿐만 아니라 상수도관, 하수도관, 전력구 및 지하철 건설로 인한 인위적인 공동들이 복잡하게 분포되어 있다. 대심도 터널 굴착을 위해서는 이러한 다공질의 특성을 보이는 다양한 지반의 특성 및 지질구조가 지반의 안전에 미치는 영향을 이해하여야 한다. 본 연구는 국내외 사례를 바탕으로 한국의 대심도 굴착에서 암반의 위험 산정을 위한 위험 인자를 분석하였다. 연구결과, 대심도 터널 굴착시 지반의 안정성에 영향을 주는 총 7개의 카테고리들과 총 38개의 인자들이 도출되었다. 가중치가 상대적으로 높은 인자들은 단층 및 단층점토, 차응력, 암종, 지하수 및 머드 유입, 암석의 일축압축강도, 터널 단면의 크기, 터널 상부 암반의 두께, 카르스트 및 계곡지형, 습곡, 석회암의 협재, 지하수위 변동, 터널 심도, 암맥, RQD, 절리 특성, 이방성, 암반파열(rockburst) 등으로 나타났다.

• 한국해양공학회지
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• 제35권4호
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• pp.266-272
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• 2021

Mooring systems are among the most important elements employed to control the motion of floating offshore structures on the sea. Considering the use of polymer material, a new method is proposed to address the creep characteristics rather than the method of using a tension load cell for measuring the tension of the mooring line. This study uses a synthetic mooring rope made from a polymer material, which usually consists of three parts: center, eye, and splice, and which makes a joint for two successive ropes. We integrate the optical sensor into the synthetic mooring ropes to measure the rope tension. The different structure of the mooring line in the longitudinal direction can be used to measure the loads with the entire mooring configuration in series, which can be defined as SMART (Smart Mooring and Riser Truncation) mooring. To determine the characteristics of the basic SMART mooring, a SMART mooring with a diameter of 3 mm made of three different polymer materials is observed to change the wavelength that responds as the length changes. By performing the longitudinal tension experiment using three different SMART moorings, it was confirmed that there were linear wavelength changes in the response characteristics of the 3-mm-diameter SMART moorings. A 54-mm-diameter SMART mooring is produced to measure the response of longitudinal tension on the center, eye, and splice of the mooring, and a longitudinal tension of 100 t in step-by-step applied for the Maintained Test and Fatigue Cycle Test is conducted. By performing a longitudinal tension experiment, wavelength changes were detected in the center, eye, and splice position of the SMART moorings. The results obtained from each part of the installed sensors indicated a different strain measurement depending on the position of the SMART moorings. The variation of the strain measurement with the position was more than twice the result of the difference measurement, while the applied external load increased step-by-step. It appears that there is a correlation with an externally generated longitudinal tensional force depending on the cross-sectional area of each part of the SMART mooring.

• 여성건강간호학회지
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• 제27권4호
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• pp.307-317
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• 2021

Purpose: The purpose of this study was to develop and test the validity and reliability of the Korean version of the Perinatal Infant Care Social Support (K-PICSS) for postpartum mothers. Methods: This study used a cross-sectional design. The K-PICSS was developed through forward-backward translation. Online survey data were collected from 284 Korean mothers with infants 1-2 months of age. The 19-item K-PICSS consists of functional and structural domains. The functional domain of social support measures infant care practices of postpartum mothers. Exploratory factor analysis (EFA) and known-group comparison were used to verify the construct validity of the K-PICSS. Social support and postpartum depression were also measured to test criterion validity. Psychometric testing was not applicable to the structural social support domain. Results: The average age of mothers was 32.76±3.34 years, and they had been married for 38.45±29.48 months. Construct validity was supported by the results of EFA, which confirmed a three-factor structure of the scale (informational support, supporting presence, and practical support). Significant correlations of the K-PICSS with social support (r=.71, p<.001) and depression (r=-.40, p<.001) were found. The K-PICSS showed reliable internal consistency, with Cronbach's α values of .90 overall and .82-.83 in the three subscales. The vast majority of respondents reported that their husband or their parents were their main sources of support for infant care. Conclusion: This study demonstrates that the K-PICSS has satisfactory construct validity and reliability to measure infant care social support in Korea.