• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2008년도 춘계 학술발표회 초청강연 및 논문집
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• pp.575-586
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• 2008

The main objective of this paper is to develop an improved model for the analysis of liquefaction potential and to predict excess pore pressure (EPP) using the proposed model that can simulate behavior of saturated sand under earthquake loading conditions. The damage concept is adopted for the development of the proposed model. For the development of the model, a general formulation based on experimental results and damage potential using cumulative absolute velocity (CAV) is proposed for a more realistic description of dynamic responses of saturated sand. Undrained dynamic triaxial tests are conducted using earthquake loading conditions. Based on test results, the NCER-NCW function in terms of $w_d$ and CAV is developed. Procedure for the evaluation of EPP and determination of model parameters for the proposed model is presented as well. For the determination of initial liquefaction, the minimum curvature method using the NCS-NCW curve is proposed. It is observed that predicted initial liquefaction using the proposed method agrees well with measured initial liquefaction. From results of additional undrained dynamic triaxial tests, it is seen that predicted EPP generation using the proposed model agrees well with measured results for earthquake loading cases.

• 방송공학회논문지
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• 제18권5호
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• pp.730-737
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• 2013

본 논문은 정합 오차 기준을 확장한 제한된 1비트 변환 (Constrained One-Bit Transform : C1BT) 기반의 움직임 예측 알고리즘을 제안하였다. 제한된 1비트 변환 기반의 움직임 예측 알고리즘에서는 정합 오차 기준으로 기존의 움직임 예측 방법인 전역 탐색 알고리즘 (Full Search Algorithm: FSA)에서 사용되는 SAD (Sum of Absolute Differences) 대신 NNMP (Number of Non-Matching Points)를 사용하여 하드웨어 구현을 용이하게 하고 연산량을 크게 줄였으나 움직임 예측의 정확도를 감소시켰다. 이 점을 개선하고자 이 논문에서는 제한된 1비트 변환의 정합 오차 기준을 확장하여 움직임 예측의 정확도를 높이는 알고리즘을 제안하였고 이는 기존의 알고리즘과 비교한 결과 PSNR (Peak Signal to Nosie Ratio) 측면에서 더 우수한 성능을 보였다.

• 한국멀티미디어학회논문지
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• 제25권2호
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• pp.440-449
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• 2022

In recent years, the air pollution and Air Quality Index (AQI) has been a pivotal point for researchers due to its effect on human health. Various research has been done in predicting the AQI but most of these studies, either lack dense temporal data or cover one or two air pollutant elements. In this paper, a hybrid Convolutional Neural approach integrated with recurrent neural network architecture (CNN-LSTM), is presented to find air pollution inference using a multivariate air pollutant elements dataset. The aim of this research is to design a robust and real-time air pollutant forecasting system by exploiting a neural network. The proposed approach is implemented on a 24-month dataset from Seoul, Republic of Korea. The predicted results are cross-validated with the real dataset and compared with the state-of-the-art techniques to evaluate its robustness and performance. The proposed model outperforms SVM, SVM-Polynomial, ANN, and RF models with 60.17%, 68.99%, 14.6%, and 6.29%, respectively. The model performs SVM and SVM-Polynomial in predicting O3 by 78.04% and 83.79%, respectively. Overall performance of the model is measured in terms of Mean Absolute Error (MAE), Mean Absolute Percentage Error (MAPE) and the Root Mean Square Error (RMSE).

• Nuclear Engineering and Technology
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• 제55권4호
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• pp.1342-1349
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• 2023

The planning accuracy of charged particle therapy (CPT) is subject to the accuracy of stopping power (SP) estimation. In this study, we propose a method of deriving a pseudo-triple-energy CT (pTECT) that can be achievable in the existing dual-energy CT (DECT) systems for better SP estimation. In order to remove the direct effect of errors in CT values, relative CT values according to three scanning voltage settings were used. CT values of each tissue substitute phantom were measured to show the non-linearity of the values thereby suggesting the absolute difference and ratio of CT values as parameters for SP estimation. Electron density, effective atomic number (EAN), mean excitation energy and SP were calculated based on these parameters. Two of conventional methods were implemented and compared to the proposed pTECT method in terms of residuals, absolute error and root-mean-square-error (RMSE). The proposed method outperformed the comparison methods in every evaluation metrics. Especially, the estimation error for EAN and mean excitation using pTECT were converging to zero. In this proof-of-concept study, we showed the feasibility of using three CT values for accurate SP estimation. Our suggested pTECT method indicates potential clinical utility of spectral CT imaging for CPT planning.

• 설비공학논문집
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• 제19권6호
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• pp.457-463
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• 2007

Various correlations of saturated vapor density in a truncated power series form are tested and compared in this study. Saturated vapor density correlation can be expressed relating logarithmic reduced density to the reduced temperature. Five types of correlation has been investigated using saturated vapor density data for 22 pure substance refrigerants from ASHRAE (American Society of Heating, Reftigerating and Air-Conditioning Engineers, Inc.) property tables and NIST (National Institute of Standards and Technology) Chemistry Webbook. Correlations are fitted to the data points by least squares method. Data points are equally weighted. The best type of correlation among the five types is suggested. The results obtained indicate that the best correlations with 3, 4, and 5 terms yield average AAD's (Average Absolute Deviation) of 0.27%, 0.04%, and 0.02%, respectively, while widely used conventional correlations with 3, 4, and 5 terms yield those of 1.19%, 0.61%, and 0.17%. The suggested type of correlation could reduce the number of terms while improving performance.

• 유통과학연구
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• 제21권9호
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• pp.115-121
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• 2023

Purpose: This study aimed to deal with disputes between the seller and the buyer in connection with the Letter of Credit (LC) in a sales contract. The Contracts for the International Sale of Goods (CISG) provides the rules on the fundamental breaches which can lead to termination of the sales contract but the CISG is not enough to govern issues arising from the LC disputes when the sales contract is not clear about the payment terms. This paper tried to find some solutions to the disputes by considering international rules, such as the Principles of European Contract Law (PECL). Research design, data and methodology: The methodology applied in this study was an analysis of some court decisions and extended literature review. Results: The study revealed that in contracts for the sale of international goods, the buyer was obliged to open an LC as manner of payment. If the buyer failed to open an LC or amend the terms of the LC, the seller could avoid the contract because this could deprive the seller's expected interest. Conclusions: Few studies in Korea have been comprehensively analyzed in terms of the obligations of regarding the LC with respect to the CISG in court cases. This study suggests safeguarding the buyer and seller when the LC is considered absolute or conditional.

• 한국노년학
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• 제39권1호
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• pp.169-188
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• 2019

본 연구에서는 12개년의 종단면 시계열 자료를 활용하여 절대소득과 상대소득을 포함한 노후의 소득수준이 생활만족도에 영향을 미치는지의 여부를 검증하였다. 연구결과, 자산분위별, 지역별 및 학력기준에 따른 각 준거집단의 상대소득이 노인 자신의 절대소득보다 노후의 생활만족도에 더 큰 영향력을 미치고 있음을 확인할 수 있었다. 횡단자료를 이용한 상관관계 분석에서도 상대소득은 생활만족도와 밀접한 관련성을 갖는 것으로 나타났으며 종단자료를 이용한 패널분석모형에서 준거집단의 상대소득 수준은 노후의 생활만족도 수준결정에 있어 유의미한 영향을 보이고 있었다. 비교대상이 되는 준거집단의 소득수준보다 상대적으로 자신의 소득수준이 높을 경우에 노후의 삶의 만족도는 증가하는 것으로 확인되었다. 또한 과거 시점의 생활만족도 수준도 현재 노인의 평균 생활만족도 결정에 유의미한 영향을 미치는 것으로 나타났다. 종단자료 분석에서 나타난 이러한 분석결과는 중장기적 관점에서의 노인의 생활만족도 결정과정에서 기존의 절대소득가설보다는 상대소득가설이 보다 타당하다는 사실을 입증하고 있다. 구체적인 학문적 및 실천적 함의로는 정책당국의 경제적 지원만으로는 충분치 않으며 노인일자리를 창출·보급함으로써 노인들의 사회참여 기회를 제공하는 것이 필요하며, 다양한 형태의 비경제적 사회참여 확대 및 이를 보장하기 위한 체계적인 노력이 뒷받침되어야 할 것으로 판단된다.

• The Journal of Advanced Prosthodontics
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• 제7권4호
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• pp.271-277
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• 2015

PURPOSE. This study was to evaluate the marginal fit of two CAD-CAM anatomic contour zirconia crown systems compared to lithium disilicate glass-ceramic crowns. MATERIALS AND METHODS. Shoulder and deep chamfer margin were formed on each acrylic resin tooth model of a maxillary first premolar. Two CAD-CAM systems (Prettau$^{(R)}$Zirconia and ZENOSTAR$^{(R)}$ZR translucent) and lithium disilicate glass ceramic (IPS e.max$^{(R)}$press) crowns were made (n=16). Each crown was bonded to stone dies with resin cement (Rely X Unicem). Marginal gap and absolute marginal discrepancy of crowns were measured using a light microscope equipped with a digital camera (Leica DFC295) magnified by a factor of 100. Two-way analysis of variance (ANOVA) and post-hoc Tukey's HSD test were conducted to analyze the significance of crown marginal fit regarding the finish line configuration and the fabrication system. RESULTS. The mean marginal gap of lithium disilicate glass ceramic crowns (IPS e.max$^{(R)}$press) was significantly lower than that of the CAD-CAM anatomic contour zirconia crown system (Prettau$^{(R)}$Zirconia) (P<.05). Both fabrication systems and finish line configurations significantly influenced the absolute marginal discrepancy (P<.05). CONCLUSION. The lithium disilicate glass ceramic crown (IPS e.max$^{(R)}$press) had significantly smaller marginal gap than the CAD-CAM anatomic contour zirconia crown system (Prettau$^{(R)}$Zirconia). In terms of absolute marginal discrepancy, the CAD-CAM anatomic contour zirconia crown system (ZENOSTAR$^{(R)}$ZR translucent) had under-extended margin, whereas the CAD-CAM anatomic contour zirconia crown system (Prettau$^{(R)}$Zirconia) and lithium disilicate glass ceramic crowns (IPS e.max$^{(R)}$press) had overextended margins.

• 생명과학회지
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• 제22권9호
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• pp.1214-1223
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• 2012

본 연구는 진범의 in-vitro 생리활성과 진범 향이 신경생리학적으로 뇌파에 미치는 영향을 비교 분석하였다. 그 결과 진범 향 및 재조합 향 흡입 시 흡입 전에 비해 뇌파지표 absolute alpha power spectrum (AA)와 absolute theta power spectrum (AT)가 유의미하게 감소하였으며(p<0.05), 진범과 진범 재조합 향 흡입 시 출현한 파형의 유발 부위가 각각 조금씩 다른 양상을 나타내기는 하였지만, 동일하게 alpha와 theta파가 나타났으며, 증가율 역시 향 흡입 시 감소하는 동일 양상을 나타내어 뇌에 각성효과를 일으킨 것으로 판단된다. 진범의 생리활성 검증 결과 수렴효과를 제외한 DPPH, collagenase, nitric oxide 저해활성 검증에서 진범 에탄올 추출물의 활성이 열수 추출물에 비해 우수하였으며, 특히 collagenase저해활성에서 진범 에탄올 추출물 500 ppm에서 80%의 저해활성을 나타내었으며, 또한 nitric oxide 저해활성에서 진범 열수 및 에탄올 추출물 100 ppm에서 50% 이상의 NO저해활성을 나타내었다. 이러한 결과로부터 진범은 화장품 및 향료 개발의 천연소재로 사용이 가능할 것으로 판단된다.

• Computers and Concrete
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• 제11권2호
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• pp.149-167
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• 2013

The complete stress-strain behavior of steel fiber reinforced concrete in compression is needed for the analysis and design of structures. An experimental investigation was carried out to generate the complete stress-strain curve of high-performance steel fiber reinforced concrete (HPSFRC) with a strength range of 52-80 MPa. The variation in concrete strength was achieved by varying the water-to-cementitious materials ratio of 0.40-0.25 and steel fiber content (Vf = 0.5, 1.0 and 1.5% with l/d = 80 and 55) in terms of fiber reinforcing parameter, at 10% silica fume replacement. The effects of these parameters on the shape of stress-strain curves are presented. Based on the test data, a simple model is proposed to generate the complete stress-strain relationship for HPSFRC. The proposed model has been found to give good correlation with the stress-strain curves generated experimentally. Inclusion of fibers into HPC improved the ductility considerably. Equations to quantify the effect of fibers on compressive strength, strain at peak stress and toughness of concrete in terms of fiber reinforcing index are also proposed, which predicted the test data quite accurately. Compressive strength prediction model was validated with the strength data of earlier researchers with an absolute variation of 2.1%.