• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2011년 춘계학술대회논문집
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• pp.605-607
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• 2011

A Study on the flow-structure characteristics of a 3/2 way pneumatic valve is essential for optimizing the performance of ship engines. It is important for the valve to have desirable safety factor am reduced weight from the safety and economic point of view. In this study, we capture flow-structure characteristics of 3/2 way pneumatic valve. This is optimized based on the proper design criteria. The air at a pressure of 30 bar is the working fluid which is made to fill in the tack in short time. This time is defined as the filling time. The flow and structure analysis is performed for three cases under maximum stress and safety factor. In optimum design, considering the flow-structure characteristics, we model twenty seven cases by using DOE(design of experiments) method Here, analysis for each cases is performed and then metamodels are created We obtain optimized parameters and then analysis is repeated to compare with the initial model. Finally, the feasibility of the optimum design is verified.

• 한국멀티미디어학회논문지
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• 제22권4호
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• pp.443-454
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• 2019

In recent years, there has been active research on a recommender system that considers three or more inputs in addition to users and goods, making it a multi-dimensional array, also known as a tensor. The main issue with using tensor is that there are a lot of missing values, making it sparse. In order to solve this, the tensor can be shrunk using the tensor decomposition algorithm into a lower dimensional array called a factor matrix. Then, the tensor is reconstructed by calculating factor matrices to fill original empty cells with predicted values. This is called tensor reconstruction. In this paper, we propose a user-based Top-K recommender system by normalized PARAFAC tensor reconstruction. This method involves factorization of a tensor into factor matrices and reconstructs the tensor again. Before decomposition, the original tensor is normalized based on each dimension to reduce overfitting. Using the real world dataset, this paper shows the processing of a large amount of data and implements a recommender system based on Apache Spark. In addition, this study has confirmed that the recommender performance is improved through normalization of the tensor.

• Geomechanics and Engineering
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• 제28권4호
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• pp.397-404
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• 2022

Accurate prediction of the undrained shaft resistance is essential for robust design of bored piles in undrained condition. The undrained shaft resistance is calculated using the undrained adhesion factor multiplied by the undrained cohesion of the soil. However, the available correlations to predict the undrained adhesion factor have been developed using simple regression techniques and the accuracy of these correlations has not been thoroughly assessed in previous studies. The lack of the assessment of these correlations made it difficult for geotechnical engineers to select the most accurate correlation in routine designs. Furthermore, limited attempts have been made in previous studies to use advanced data mining techniques to develop simple and accurate correlation to predict the undrained adhesion factor. This research, therefore, has been conducted to fill these gaps in knowledge by developing novel and robust correlation to predict the undrained adhesion factor. The development of the new correlation has been conducted using the multi-objective evolutionary polynomial regression analysis. The new correlation outperformed the available empirical correlations, where the new correlation scored lower mean absolute error, mean square error, root mean square error and standard deviation of measured to predicted adhesion factor, and higher mean, a20-index and coefficient of correlation. The correlation also successfully showed the influence of the undrained cohesion and the effective stress on the adhesion factor. Hence, the new correlation enhances the design accuracy and can be used by practitioner geotechnical engineers to ensure optimized designs of bored piles in undrained conditions.

• 대한디지털의료영상학회논문지
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• 제6권1호
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• pp.24-30
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• 2003

평판 digital x-선 검출기는 차세대 x-ray system으로 최근 연구와 개발이 활발하게 진행되고 있는 system이다. 본 연구는 환자의 피폭 및 작업 종사자의 피폭을 최소화 할 수 있고 의료장비의 디지털화에 발맞추어 PACS 등에 사용 가능한 a-Se을 이용한 직접방식의 digital x-선 검출기 구현에 관한 것이다. Prototype digital x-선 검출기는 TFT층과 a-Se층으로 이루어져 있다. Digital x-선 검출기센서 증착과 정의 최적화 수행 결과를 참고문헌1)-4)과 비교했을 때 매우 유사함을 확인하였다. 제작된 검출기의 pixel pitch는 $139{\mu}m$였고, fill factor는 86%, 전체 검출기의 검출면적은 14"${\times}$8.5"였다. Digital 영상의 해상력을 고려하기 위해 손과 test 패턴영상을 얻었고, 58%, 3.0lp/mm의 높은 MTF를 얻을 수가 있었다. 이러한 결과로 a-Se 기반의 Digital X선 검출기가 구현되었으며 본 연구결과를 토대로 향후 digital X선 검출기 개발기술의 발전과 성능향상을 가져올 것으로 기대된다.

• 대한간호학회지
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• 제52권6호
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• pp.582-597
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• 2022

Purpose: This study aimed to translate the Infertility Stigma Scale (ISS) into Korean and to evaluate its reliability and validity in the Korean context. Methods: Data were collected from 350 women who underwent in vitro fertilization (IVF). Data were analyzed using SPSS WIN 25.0 and AMOS 22.0. Content validity was analyzed using the item-level content validity index (I-CVI) and scale-level content validity index/averaging (S-CVI/Ave). The preliminary survey was conducted on 20 women who had experienced IVF at least once to check the level of understanding of the tool and the time required to fill out the questionnaire. Exploratory and confirmatory factor analyses were used to test construct validity. Additionally, hypothesis-testing construct validity were tested. Cronbach's α was used to assess the reliability. Results: The Korean-ISS (K-ISS) consists of 25 items, excluding two items from the original ISS questionnaire. Exploratory factor analysis identified four factors, which explained 75.6% of the total variance. The four distinct factors were infertility stigma with self-devaluation (56.8%), public stigma (8.1%), social withdrawal (6.5%), and family stigma (4.2%). In the confirmatory factor analysis, the 25 items in the four-factor structure were validated (χ² /df ≤ 3, RMSEA ≤ 10). The hypothesis-testing construct validity of K-ISS against FPI (r = .58~.71, p < .001) and FQI (r = - .49~- .65, p < .001) was tested and found to be significant. The internal consistency reliability of the K-ISS, assessed using Cronbach's α, was .97. Conclusion: The K-ISS has satisfactory construct validity and reliability; therefore, it can help minimize the negative impact of stigma by measuring the stigma associated with women experiencing infertility.

• 한국주거학회논문집
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• 제26권4호
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• pp.105-118
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• 2015

The purpose of this study was to give a suggestion for vitalizing rural area's community, with respect to the components of community; 'locality' and 'communality'. The survey was conducted at Hondong, Hodongseong-gun, Chungcheongnam-do, which was a representative area for active rural area community. For the survey, we interviewed an activist on the village in November $9^{th}$, 2014, and let 81 residents fill the questionnaires during March $7^{th}$ to $14^{th}$, 2015. Major findings were as follows. 1) As for the 'locality' factor, the motives of residents' immigration were influenced by the availability of facilities for agriculture education, living, and convenience in the area. Most of residents recognized that the area comprises their own community facility area and expanded area with concentrated facilities of 'li', minimal adminstration unit. It means that their usage pattern of community facilities influences their conceptions of the village. 2) As for the 'communality' factor, original residents and immigrant back-to-farm residents showed different pattern in communicating with neighbors and community facility usages. Residents communicated with neighbors by meeting up or using the concentrated facilities in Gatgol, and visited the Balmak library frequently. Residents' sense of belonging was high with mean 4.16 point of 5.0 in Likert scale.

• Steel and Composite Structures
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• 제25권3호
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• pp.347-360
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• 2017

The goal of this study is to fill this apparent gap in the area about vibration analysis of multiwalled carbon nanotubes (MWCNTs) curved panels by providing 3-D vibration analysis results for functionally graded multiwalled carbon nanotubes (FG-MWCNTs) sandwich structure with power-law distribution of nanotube. The effective material properties of the FG-MWCNT structures are estimated using a modified Halpin-Tsai equation. Modified Halpin-Tsai equation was used to evaluate the Young's modulus of MWCNT/epoxy composite samples by the incorporation of an orientation as well as an exponential shape factor in the equation. The exponential shape factor modifies the Halpin-Tsai equation from expressing a straight line to a nonlinear one in the MWCNTs wt% range considered. Also, the mass density and Poisson's ratio of the MWCNT/phenolic composite are considered based on the rule of mixtures. Parametric studies are carried out to highlight the influence of MWCNT volume fraction in the thickness, different types of CNT distribution, boundary conditions and geometrical parameters on vibrational behavior of FG-MWCNT thick curved panels. Because of using two-dimensional generalized differential quadrature method, the present approach makes possible vibration analysis of cylindrical panels with two opposite axial edges simply supported and arbitrary boundary conditions including Free, Simply supported and Clamped at the curved edges. For an overall comprehension on 3-D vibration analysis of sandwich panel, some mode shape contour plots are reported in this research work.

• 한국환경복원기술학회지
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• 제3권1호
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• pp.52-61
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• 2000

Permeability is important factor in the geotechnical problems, such as seepage discharge and dissipation of excess pore water pressure. The Kozeny-Carman equation works well for graded soils but serious discrepancies are found in clays. Major factor for these discrepancies is the tortuous flow path and unequal pore size. To estimate the permeability of fine grained soils, a permeability equation in which swelling potential is coupled with Kozeny-Carman equation is proposed in this study. To verify proposed equation, a series of variable head permeability test was carried out for steel making slag and sludge mixed with bentonite. The coefficients of permeability which is measured in the laboratory is compared with the values by the proposed equation. From the comparison, it is shown that the proposed equation can predict the coefficient of permeability of clays with satisfaction. As steel making slag and sludge is industry waste, it is reused as material of road foundation and cement but the rate of use is low. It mixed sodium-bentonite with high swelling property and permeability decrease effect. Then, Admixture investigates reuse possibility as liner of waste fill.

• 대한치과교정학회지
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• 제23권4호
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• pp.735-743
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• 1993

In orthodontic field, although lots of new materials have been developed and many mechanics intro duced, we can face the case patient cooperation still remain a problem to solve. So, factors related to the compliance of 254 adolescent orthodontic patients using intraoral elastic or extraoral orthopedic appliances were under investigation. The study subjects were 11 to 18 years old and from 5 exclusive orthodontitc clinics in seoul. The subjects were asked to fill a questionnaire and compliances were evaluated by their assigned orthodontists. The questionnaire was consisted of 63 questions, and they represent 13 factors-7 psychological & 6 nonpsychological fators. The collected data were analyzed using ANOVA test between the compliance group and the factors. 1. The compliances were evenly distributed in both sex and age groups. 2. As a whole, it was found that the Attitude towards appliances ffactor affected the degree of compliance. 3. Besides that, in younger(11-12) age group, Pain and discomfort associated with treatment factor was also found to be related to the degree of compliance. 4. On the contrary, in older(16-18) age group, the degree of compliance was influenced by the factor of Achievement motivation, Role expectation, parental relationship.

• 전력전자학회:학술대회논문집
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• 전력전자학회 1999년도 전력전자학술대회 논문집
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• pp.266-269
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• 1999

Several power factor correction(PFC) circuits are presented to achieve high PF electronic ballast for both voltage-fed and current-fed electronic ballast. The proposed PFC circuits use valley-fill(VF) type DC-link stages modified from the conventional VF circuit to adopt the charge pumping method for PFC operations during the valley intervals. In voltage-fed ballast, charge pump capacitors are connected with the resonant capacitors. In current-fed type, the charge pump capacitors are connected with the additional secondary-side of the power transformer. The measured PF and THD are higher than 0.99 and 15% for all proposed PFC circuits. The lamp current CF is also acceptable in the proposed circuits. The proposed circuit is suitable for implementing cost-effective electronic ballast.