• Journal of Mechanical Science and Technology
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• 제19권9호
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• pp.1773-1780
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• 2005

The process of mould design in the foundry industry has been based on the intuition and experience of foundry engineers and designers. To bring the industry to a more scientific basis the design process should be integrated with scientific analysis such as heat transfer. The production by foundry techniques is influenced by the geometry configuration, which affects the solidification conditions and subsequent cooling. Numerical simulation and/or experiments make possible the selection of adequate materials, reducing cycle times and minimizing production costs. The main propose of this work is to study the heat transfer phenomena in the mould considering the phase change of the cast-part. Due to complex geometry of the mould, a block unstructured grid and a generalized curvilinear formulation engaged with the finite volume method is described and applied. Two types of boundary conditions, diffusive and Newtonian, are used and compared. The developed numerical code is tested in real case and the main results are compared with experimental data. The results showed that the solidification time is about 6 seconds for diffusive boundary conditions and 14.8 seconds for Newtonian boundary conditions. The use of the block unstructured grid in combination with a generalized curvilinear formulation works well with the finite volume method and allows the development of more efficient algorithms with better capacity to describe the part contours through a lesser number of elements.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2002년도 학술대회지
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• pp.55-58
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• 2002

Parallel finite element code has been recently developed for the analysis of the incompressible Wavier-Stokes equations using domain decomposition method. Metis and MPI libraries are used for the domain partitioning of an unstructured mesh and the data communication between sub-domains, respectively. For unsteady computation of the incompressible Navier-Stokes equations, 4-step splitting method is combined with P1P1 finite element formulation. Smagorinsky and dynamic model are implemented for the simulation of turbulent flows. For the validation performance-estimation of the developed parallel code, three-dimensional Laplace equation has been solved. It has been found that the speed-up of 40 has been obtained from the present parallel code fir the bench mark problem. Lastly, the turbulent flows around the MIRA model and Tiburon model have been solved using 32 processors on IBM SMP cluster and unstructured mesh. The computed drag coefficient agrees better with the existing experiment as the mesh resolution of the region increases, where the variation of pressure is severe.

• Communications for Statistical Applications and Methods
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• 제31권2호
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• pp.179-189
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• 2024

In multivariate regression with a high-dimensional response Y ∈ ℝ^r and a relatively low-dimensional predictor X ∈ ℝ^p (where r ≥ 2), the statistical analysis of such data presents significant challenges due to the exponential increase in the number of parameters as the dimension of the response grows. Most existing dimension reduction techniques primarily focus on reducing the dimension of the predictors (X), not the dimension of the response variable (Y). Yoo and Cook (2008) introduced a response dimension reduction method that preserves information about the conditional mean E(Y | X). Building upon this foundational work, Yoo (2018) proposed two semi-parametric methods, principal response reduction (PRR) and principal fitted response reduction (PFRR), then expanded these methods to unstructured principal fitted response reduction (UPFRR) (Yoo, 2019). This paper reviews these four response dimension reduction methodologies mentioned above. In addition, it introduces the implementation of the mbrdr package in R. The mbrdr is a unique tool in the R community, as it is specifically designed for response dimension reduction, setting it apart from existing dimension reduction packages that focus solely on predictors.

• 대기
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• 제27권4호
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• pp.377-384
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• 2017

The effective management of call centers under special circumstances is critical to improve customer satisfaction. In order to effectively respond to call center counseling demand, this paper aims to identify factors having the greatest impact on the number of Korea Meteorological Administration (KMA) call center counseling. To do so, we propose to combine call center data with severe weather announcement data and investigate how the severe weather announcement affects the number of KMA call center counseling. A time lag analysis is conducted and it is found that the severe weather announcement takes about an hour to be reflected in the number of KMA call center counseling. Based on the result of the time lag analysis, we conduct a comparative analysis according to time and season using the data collected from 1 January 2012, to 29 June 2016. The results show that the number of KMA call center counseling increases at lunchtime and decreases during nighttime, and the average rate of change in call center counseling demand tends to be larger under the severe weather announcement. For the comparative analysis according to the season, there are significant differences in the effect of severe weather announcement on the number of KMA call center counseling in spring, fall and winter.

• 여성건강간호학회지
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• 제26권3호
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• pp.205-212
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• 2020

Purpose: This study aimed to identify the components of preterm birth (PTB) through women's personal narratives and to visualize clinical symptom expressions (CSEs). Methods: The participants were 11 women who gave birth before 37 weeks of gestational age. Personal narratives were collected by interactive unstructured storytelling via individual interviews, from August 8 to December 4, 2019 after receiving approval of the Institutional Review Board. The textual data were converted to PDF and analyzed using the MAXQDA program (VERBI Software). Results: The participants' mean age was 34.6 (±2.98) years, and five participants had a spontaneous vaginal birth. The following nine components of PTB were identified: obstetric condition, emotional condition, physical condition, medical condition, hospital environment, life-related stress, pregnancy-related stress, spousal support, and informational support. The top three codes were preterm labor, personal characteristics, and premature rupture of membrane, and the codes found for more than half of the participants were short cervix, fear of PTB, concern about fetal well-being, sleep difficulty, insufficient spousal and informational support, and physical difficulties. The top six CSEs were stress, hydramnios, false labor, concern about fetal wellbeing, true labor pain, and uterine contraction. "Stress" was ranked first in terms of frequency and "uterine contraction" had individual attributes. Conclusion: The text network analysis of narratives from women who gave birth preterm yielded nine PTB components and six CSEs. These nine components should be included for developing a reliable and valid scale for PTB risk and stress. The CSEs can be applied for assessing preterm labor, as well as considered as strategies for students in women's health nursing practicum.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2006년도 추계 학술대회논문집
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• pp.151-154
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• 2006

In the present paper, hovering performance analyses of proprotor and helicopter rotor blades were performed by using FLUENT software. As a proprotor, TRAM(Tilt Rotor Aeroacoustic Model) was selected and performance analysis was carried out with mesh adaptation for more elaborate solution. As a helicopter rotor blades, two bladed Caradonna and Tung's rotor and four-bladed BO-105 helicopter rotor blades were selected. In case of Caradonna and Tung's rotor, vortex trajectory was compared with experimental data to inspect the vortex convection capability of the present flow solver. For the final case, performance of BO-105 helicopter rotor blades was investigated and compared with experimental data. After performance analyses of proprotor and helicopter rotors, it was shown that the present solver showed reasonable vortex strength, wake geometry and thurst coefficient distributions. But power coefficient was somewhat overestimated about $10%{\sim}15%$ regard less of mesh adaptation.

• 대한공간정보학회지
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• 제4권1호
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• pp.23-29
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• 1996

본 연구에서는 토지정보체계(GIS)의 도형정보 처리를 위한 객체지향 데이타베이스를 개발하고, 이를 위하여 사용된 프로그램 개발방법을 설명하였다. 본 연구의 결과, 도형자료를 저장하고 관리하기 위한 자료모델을 개발하였으며, 개체지향 프로그래밍기법에 의한 도형자료 관리를 실현하였다. 도형자료 처리를 위한 자료모델을 개발함에 있어서, 관망해석을 하지 않는 자료관리만을 목표로 하였기 때문에 위상학적(topology) 자료구조를 갖지 않는 단순한 벡터모델을 사용하였다. 차후에 관거의 연결망을 기초로 하는 분석기능을 개발할 경우에는, 도형자료 처리를 위한 자료구조 부분에 대하여 수정 또는 추가 개발이 필요할 것이다.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제11권8호
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• pp.4133-4145
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• 2017

Advances in science and technology are driving us to the better life but also forcing us to make more investment at the same time. Therefore, the government has provided the investment to carry on the promising futuristic technology successfully. Indeed, a lot of resources from the government have supported into the science and technology R&D projects for several decades. However, the performance of the public investments remains unclear in many ways, so thus it is required that planning and evaluation about the new investment should be on data driven decision with fact based evidence. In this regard, the government wanted to know the trend and issue of the science and technology with evidences, and has accumulated an amount of database about the science and technology such as research papers, patents, project reports, and R&D information. Nowadays, the database is supporting to various activities such as planning policy, budget allocation, and investment evaluation for the science and technology but the information quality is not reached to the expectation because of limitations of text mining to drill out the information from the unstructured data like the reports and papers. To solve the problem, this study proposes a practical text mining methodology for the science and technology trend analysis, in case of aerospace technology, and conduct text mining methods such as ontology development, topic analysis, network analysis and their visualization.

• 한국치위생학회지
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• 제23권4호
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• pp.303-309
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• 2023

Objectives: According to the Korea Education Development Institute, the college admission quota is expected to exceed the number of high school graduates, leading to an anticipated expansion in the gap between them. This paper aims to conduct an empirical analysis of the variables previously studied, with a specific focus on the admission competition rate for the department of dental hygiene. Methods: The research methodology is the multiple linear regression analysis. The research data contains the structured data from academy information, and the web-based unstructured data collected over the past 3 years. Results: After conducting the analysis, it was newly discovered that the university's online recognition and its location in the metropolitan area were statistically significant factors influencing the admission competition rate for the department of dental hygiene. Conclusions: The findings of this study are expected to be helpful in formulating admission strategies for universities to attract new students and identifying the factors that influence student attraction.

• 한국기록관리학회지
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• 제23권4호
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• pp.73-89
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• 2023

본 연구에서는 텍스트 마이닝 기법을 활용하여 국내 기록관리 연구 분야의 비정형 텍스트 데이터인 국문 초록에서 사용된 키워드 빈도를 분석하여 키워드 간 거리 분석을 통해 국내기록관리 연구 동향을 파악하는 것이 목적이다. 이를 위해 한국학술지인용색인(Korea Citation Index, KCI)의 학술지 기관통계(등재지, 등재후보지)에서 대분류(복합학), 중분류 (문헌정보학)으로 검색된 학술지(28종) 중 등재지 7종 1,157편을 추출하여 77,578개의 키워드를 시각화하였다. Word2vec를 활용한 t-SNE, Scattertext 등의 분석을 수행하였다. 분석 결과, 첫째로 1,157편의 논문에서 얻은 77,578개의 키워드를 빈도 분석한 결과, "기록관리" (889회), "분석"(888회), "아카이브"(742회), "기록물"(562회), "활용"(449회) 등의 키워드가 연구자들에 의해 주요 주제로 다뤄지고 있음을 확인하였다. 둘째로, Word2vec 분석을 통해 키워드 간의 벡터 표현을 생성하고 유사도 거리를 조사한 뒤, t-SNE와 Scattertext를 활용하여 시각화하였다. 시각화 결과에서 기록관리 연구 분야는 두 그룹으로 나누어졌는데 첫 번째 그룹(과거)에는 "아카이빙", "국가기록관리", "표준화", "공문서", "기록관리제도" 등의 키워드가 빈도가 높게 나타났으며, 두 번째 그룹(현재)에는 "공동체", "데이터", "기록정보서비스", "온라인", "디지털 아카이브" 등의 키워드가 주요한 관심을 받고 있는 것으로 나타났다.