• 공학교육연구
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• 제13권6호
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• pp.143-151
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• 2010

본 논문은 서울과학기술대학교(구 서울산업대학교) 기계설계자동화공학부에서 16년간의 캡스톤디자인 운영경험과 개선을 바탕으로 캡스톤디자인 교과목 기반의 프로그램 학습성과의 평가 사례에 대해 서술하였다. 우선, 캡스톤디자인 교과목과 관련된 프로그램 학습성과를 소개하였고, 평가 방법 및 항목에 대해서 설명하였다. 이를 바탕으로 하여 2008년도의 학습성과 평가 결과를 도출하였고, 이를 분석한 후 개선 전략을 수립하였다. 전략으로서 학생들에게 심사 기준과 모범사례를 온라인상에 미리 공개하였고, 그 결과 2009년도에는 전반적으로 약 3.3% 개선된 학습성과 평가 결과를 얻을 수 있었다. 마지막으로 코스 임베디드 평가 개념 측면에서 캡스톤디자인 교과목을 이용한 프로그램 학습성과 평가의 타당성, 효율성, 내실성, 그리고 지속가능성에 대해서도 논의하였다.

• 한국산학기술학회논문지
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• 제16권8호
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• pp.5143-5151
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• 2015

이 연구의 목적은 예비보육교사들의 교육신념과 보육헌신이 교사효능감에 영향을 미치는 요인은 무엇인지를 알아보고자 하였다. 이러한 연구목적을 달성하기 위하여 I시에 소재한 예비보육교사 239명을 대상으로 질문지를 사용하여 실시하였다. 연구결과에 대하여 첫째, 예비보육교사들이 지각한 교육신념은 성숙주의가, 보육헌신에서는 교육애가, 교사효능감은 교수전략과 학생참여가 가장 높게 인식하는 것으로 나타났다. 둘째, 예비보육교사들의 교육신념, 보육헌신, 교사효능감에서 통계적으로 유의미한 상관관계가 있는 것으로 나타났다. 셋째, 예비유아교사들의 교육신념과 보육헌신이 교사효능감에 긍정적인 영향을 미치는 것으로 나타났다. 이러한 연구결과로 볼 때, 보육교사의 역할과 중요성을 인식하고 질 높은 보육서비스 향상을 위하여 교사효늠감이 형성될 수 있는 보육교사교육과 전문성인식에 대한 내실화를 마련하는데 다양한 연구가 진행되어야 할 것으로 사료된다.

• 한국콘텐츠학회논문지
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• 제12권2호
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• pp.505-516
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• 2012

본 연구에서는 65세 이상의 한국노인을 대상으로 노후 개념의 원형적 요인들은 무엇인지 알아보고, 그 원형의 개념 추출을 위해 511명을 대상으로 무선 표집하여 90문항의 2차 예비척도 문항 개발하였고, 2차552명을 대상으로 구성요인 확인, 3차 399명을 대상으로 구성타당도, 그리고 공인타당도, 성공적 노후척도와 성별, 연령, 학력에 따른 차이 검증을 실시하였다. 그 결과 '한국노인의 성공적 노후 척도'는 총 47문항으로 '일상적 삶의 순조로움', '자녀성공', '경제적 안정', '심리적 지지', '적극적 활동', '부부관계만족', '가족지지'와 같은 7개의 요인으로 구성됨을 확인하였다. 그리고 한국노인의 성공적 노후의 신뢰도는 .932로 높은 내적 일치도를 보였고, 탐색적 요인분석을 통해 요인과 문항 간의 관계가 통계적으로 유의미함을 확인하여 요인구조에 대한 타당도를 확인하였다.

• 대한치과보철학회지
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• 제44권4호
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• pp.414-420
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• 2006

Purpose : The purpose of this study is to use finite element analysis to predict the fatigue life of an implant system subjected to fatigue load by mastication (chewing force). The reliability and the stability of implant system can be defined in terms of the fatigue strength. Not only an implant is expensive but also it is almost impossible to correct after it is inserted. From a bio-engineering standpoint, the fatigue strength of the dental implant system must be evaluated by simulation (FEA). Material and Methods Finite element analysis and fatigue test are performed to estimate the fatigue strength of the implant system. Mesh of implant is generated with the actual shape and size. In this paper, the fatigue strength of implant system is estimated. U-fit (T. Strong, Korea, internal type). The stress field in implant is calculated by elastic-plastic finite element analysis. The equivalent fatigue stress, considering the contact and preload stretching of a screw by torque for tightening an abutment, is obtained by means of Sine's method. To evaluate the reliability of the calculated fatigue strength, fatigue test is performed. Results: A comparison of the calculated fatigue strength with experimental data showed the validity and accuracy of the proposed method. The initiation points of the fatigue failure in the implant system exist in the region of high equivalent fatigue stress values. Conclusion: The above proposed method for fatigue life estimation tan be applied to other configurations of the differently designed and improved implant. In order to prove reliability of prototype implant, fatigue test should be executed. The proposed method is economical for the prediction of fatigue life because fatigue testing, which is time consuming and precision-dependent, is not required.

• 대한치과보철학회지
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• 제43권5호
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• pp.622-632
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• 2005

Statement of problem: Silicone Index Tooth Tray impression system which does not use gingicord has a shortcoming. It takes time to remove internal wall of Silicone Index Tooth Tray for space of wash impression material. Purpose: This study was to evaluate whether providing certain space to impression body can prevent from doing complicated laboratory work. Material and methods: After mounting metal dies with shoulder and chamfer margins arbiturarily, SITT was produced using $Blu-mousse^(R)$. In one experimental group, wash impression was taken using $Fit-tester^(R)$ without removing interior surface of SITT and in the other group, wash impression was taken using $Fit-tester^(R)$ providing 0.5mm space in the SITT and then compared the differences in two groups. Results: 1. There was no significant difference between a group which did not allow space and a group which granted equal 0.5mm space. 2. There was no significant difference between gingival diameter, occlusal diameter of metal die that has shoulder margin and gingival diameter, occlusal diameter of metal die that has chamfer margin. 3. There was no significant difference between a group which did not take pick-up impression and a group which took pick-up impression through relining method using SITT 4. There was no significant difference between a group that poured immediately after taking primary impression and a group that poured after removing poured stone die. Conclusions: When taking an impression of an abutment using SITT impression system, it is considered to obtain clinically identical results between a group that did not grant a 0.5mm space within SITT for wash impression and a group which invest a space. Furthermore, it is considered possible to produce an individual die through secondary pouring.

• The Journal of Advanced Prosthodontics
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• 제6권1호
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• pp.46-52
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• 2014

PURPOSE. The aim of this study was to evaluate the interface accuracy of computer-assisted designed and manufactured (CAD/CAM) titanium abutments and implant fixture compared to gold-cast UCLA abutments. MATERIALS AND METHODS. An external connection implant system (Mark III, n=10) and an internal connection implant system (Replace Select, n=10) were used, 5 of each group were connected to milled titanium abutment and the rest were connected to the gold-cast UCLA abutments. The implant fixture and abutment were tightened to torque of 35 Ncm using a digital torque gauge, and initial detorque values were measured 10 minutes after tightening. To mimic the mastication, a cyclic loading was applied at 14 Hz for one million cycles, with the stress amplitude range being within 0 N to 100 N. After the cyclic loading, detorque values were measured again. The fixture-abutment gaps were measured under a microscope and recorded with an accuracy of ${\pm}0.1{\mu}m$ at 50 points. RESULTS. Initial detorque values of milled abutment were significantly higher than those of cast abutment (P<.05). Detorque values after one million dynamic cyclic loadings were not significantly different (P>.05). After cyclic loading, detorque values of cast abutment increased, but those of milled abutment decreased (P<.05). There was no significant difference of gap dimension between the milled abutment group and the cast abutment group after cyclic loading. CONCLUSION. In conclusion, CAD/CAM milled titanium abutment can be fabricated with sufficient accuracy to permit screw joint stability between abutment and fixture comparable to that of the traditional gold cast UCLA abutment.

• Geomechanics and Engineering
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• 제14권4호
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• pp.307-314
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• 2018

Strength of loess that experienced cyclic freeze and thaw is of great significance for evaluating stability of slopes and foundations in loess regions. This paper takes the frequently encountered loess in the Northwestern China as the study object and carried out three kinds of laboratory tests including freeze-thaw test, direct shear test and SEM test to investigate the strength behaviors of loess after cyclic freeze and thaw, and the correlation with meso-level changes in soil structure. Results show that for loess specimens at four dry densities, the cohesion decreases with freeze-thaw cycles until a residual value is reached and thus an exponential equation is proposed. Besides, little change in the angle of internal friction was observed as freeze-thaw proceeds. This may depend on the varying of soil structure, based on which a clue can be found from the surface morphology and mesoscopic scanning of loess specimens. Clearly we observed significant changes in surface morphology of loess and it tends to aggravate at higher water contents or more cycles of freeze and thaw. Moreover, freeze-thaw cycling leads to obvious changes in the meso-structure of loess including lowering the particle aggregates and increasing both the proportion of fine particles and porosity area ratio. A damage variable dependent on the ratio of porosity area is introduced based on the continuum damage mechanics and its correlation with cohesion is discussed.

• 대한원격탐사학회지
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• 제36권4호
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• pp.573-586
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• 2020

PM (particulate matter) is of interest to everyone because it can have adverse effects on human health by the infiltration from respiratory to internal organs. To date, many studies have made efforts for the prediction of PM10 and PM2.5 concentrations. Unlike previous studies, we conducted the prediction of tomorrow's PM10 concentration for the Air Korea stations using Chinese PM10 data in addition to the satellite AOD and weather variables. We constructed 230,639 matchups from the raw data over 3 million and built an RF (random forest) model from the matchups to cope with the complexity and nonlinearity. The validation statistics from the blind test showed excellent accuracy with the RMSE (root mean square error) of 9.905 ㎍/㎥ and the CC (correlation coefficient) of 0.918. Moreover, our prediction model showed a stable performance without the dependency on seasons or the degree of PM10 concentration. However, part of coastal areas had a relatively low accuracy, which implies that a dedicated model for coastal areas will be necessary. Additional input variables such as wind direction, precipitation, and air stability should also be incorporated into the prediction model as future work.

• Bulletin of the Korean Chemical Society
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• 제34권11호
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• pp.3284-3288
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• 2013

This paper describes first development and validation of pentafluorophenylprophyl ligand-based liquid chromatography coupled to tandem mass spectrometry (PFPLC-MS/MS) method to determine metformin, a highly polar compound, in human plasma. Metformin and Phenformin (internal standard) were extracted from human plasma 50 ${\mu}L$ with a single-step protein precipitation. The chromatographic separation was performed using a linear gradient elution of mobile phase involving 5.0 mM ammonium formate solution with 0.1% formic acid (A) and acetonitrile (B) over 3.0 min of run time on a Phenomenex Luna PFP column. The detection was performed using a triple-quadrupole tandem mass spectrometer (Waters Quattro micro) with electrospray ionization in the mode of positive ionization and multiple-reaction monitoring (MRM). The developed method was validated with 5.0 ng/mL of lower limit of quantification (LLOQ). The calibration curve was linear over 5-3000 ng/mL of the concentration range ($R^2$ > 0.99). The specificity, selectivity, carry-over effect, precision, accuracy and stability of the method met the acceptance criteria. The method developed in this study had had rapidness, simplicity and ruggedness. The reliable method was successfully applied to high throughput analysis of real samples for a practical purpose of a pharmacokinetic study.

• Journal of the Korean Wood Science and Technology
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• 제37권4호
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• pp.340-348
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• 2009

본 연구에서는 소경저질재를 원료로 한 목재 파티클과 폐플라스틱 중에서도 많이 발생되고 있는 열가소성 재생폴리에틸렌을 결합제로 사용하여 복합패널을 제조하였다. 목재 파티클의 크기(1/32", 1/4", 1/2")와 재생폴리에틸렌의 혼합비(10%, 30%, 50%)에 따라 복합패널을 제조하여 물성을 조사하였다. 복합패널의 밀도는 같은 혼합비에서 목재 파티클이 클수록 다소 감소하는 경향을 나타냈다. 흡수 두께팽창률과 수분흡수율은 재생폴리 에틸렌의 혼합비가 증가할수록 감소하였으며, 재생폴리에틸렌이 30% 이상 혼합될 경우 14일간의 침지실험에서 치수안정성이 매우 우수하였다. 재생폴리에틸렌의 혼합비가 증가할수록 박리강도가 높아 졌으며, 휨강도 또한 같은 경향을 나타냈다. 습윤 휨강도 실험에서 30% 이상 재생폴리에틸렌을 혼합하여 제조된 복합패널은 기건 휨강도와 큰 차이를 보이지 않았다. SEM 사진 관찰을 통해 재생폴리에틸렌이 용융되어 목재 조직 내에 일부 침투되어 쐐기 형태의 기계적 결합을 형성하고 있었으며, 목재 파티클을 감싸는 매질(matrix)로써 결합되어 있는 것을 관찰할 수 있었다.