• 한국해양공학회지
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• 제35권4호
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• pp.257-265
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• 2021

Many studies have been performed to predict a reliable and accurate stress-range distribution and fatigue damage regarding the Gaussian wide-band stress response due to multi-peak waves and multiple dynamic loads. So far, most of the approximation models provide slightly inaccurate results in comparison with the rain-flow counting method as an exact solution. A step-by-step study was carried out to develop new approximate spectral moments that are close to the rain-flow counting moment, which can be used for the development of a fatigue damage model. Using the special parameters and bandwidth parameters, four kinds of parameter-based combinations were constructed and estimated using the R-squared values from regression analysis. Based on the results, four candidate empirical formulas were determined and compared with the rain-flow counting moment, probability density function, and root mean square (RMS) value for relative distance. The new approximate spectral moments were finally decided through comparison studies of eight response spectra. The new spectral moments presented in this study could play an important role in improving the accuracy of fatigue damage model development. The present study shows that the new approximate moment is a very important variable for the enhancement of Gaussian wide-band fatigue damage assessment.

• 한국항공우주학회지
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• 제50권11호
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• pp.755-762
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• 2022

유도무기 형상에 대한 풍동시험 데이터를 다양한 반경험식 기반 코드 및 CFD해석 코드를 이용한 공력 해석 결과와 비교하였다. 주날개 형상 2종과 주날개와 꼬리날개가 일렬로 늘어선 inline 형상 및 서로 교차되는 interdigitate 형상 등 총 3가지 형상에 대해 시험결과와 비교하였으며, 형상의 특징에 따라 코드별로 차이가 있는 것을 확인하였다. 추가적으로 CFD해석결과를 유동가시화 시험결과와 비교함으로써 CFD 해석 코드가 와류의 흐름을 정확하게 예측하는 것을 확인하였다.

• 응용통계연구
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• 제18권2호
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• pp.343-354
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• 2005

데이터 마이닝에서 데이터를 효율적으로 분류하고자 할 때 많이 사용하고 있는 알고리즘을 실제 자료에 적용시켜 분류성능을 비교하였다. 분류자 생성기법으로는 의사결정나무기법 중의 하나인 CART, 배깅과 부스팅 알고리즘을 CART 모형에 결합한 분류자, 그리고 SVM 분류자를 비교하였다. CART는 결과 해석이 쉬운 장점을 가지고 있지만 데이터에 따라 생성된 분류자가 다양하여 불안정하다는 단점을 가지고 있다. 따라서 이러한 CART의 단점을 보완한 배깅 또는 부스팅 알고리즘과의 결합을 통해 분류자를 생성하고 그 성능에 대해 평가하였다. 또한 최근 들어 분류성능을 인정받고 있는 SVM의 분류성능과도 비교?평가하였다. 각 기법에 의한 분류 결과를 가지고 의사결정나무를 형성하여 자료가 가지는 데이터의 특성에 따른 분류 성능을 알아보았다. 그 결과 데이터의 결측치가 없고 관측값의 수가 적은 경우는 SVM의 분류성능이 뛰어남을 알 수 있었고, 관측값의 수가 많을 때에는 부스팅 알고리즘의 분류성능이 뛰어났으며, 데이터의 결측치가 존재하는 경우는 배깅의 분류성능이 뛰어남을 알 수 있었다.

• 대한교통학회지
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• 제31권6호
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• pp.67-89
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• 2013

본 연구는 관찰적 사전 사후 평가연구의 세 방법인 단순비교법, 비교그룹에 의한 방법 그리고 경험적 베이즈 방법에 대한 실증 분석을 수행하고, 그 결과를 비교하며, 평가연구에 적용 방안을 제시하고자 한다. 이를 위해 2005년과 2006년에 영동고속도로에서 시행된 안전진단사업의 평가를 수행하였다. 분석결과 세 가지 방법 모두 안전진단조치로 인한 개선효과가 나타나고 있으며, 단순비교법이 개선효과가 가장 크고 그 다음이 비교그룹에 의한 방법, 경험적 베이즈 방법의 순으로 나타났다. 단순비교법의 결과는 교통사고 감소추이가 반영되어 과대 추정되었으며, 비교그룹방법의 결과에는 비교그룹의 외부우연요인이 내재되어 있다. 경험적 베이즈 방법은 참조그룹의 사고예측모형에 의해 평균으로의 회귀 현상이 통제되므로, 두 방법과 비교해 결과가 비교적 정확하다. 평가연구의 수행에서, 분석가는 평가방법별 장 단점을 잘 이해하고, 관련된 모든 지역에서 사고추이의 검토를 선행한 후에 평가 분석을 수행하여야 한다.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2002년도 춘계학술대회논문집
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• pp.1071-1076
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• 2002

The purpose of this paper is to examine sound absorption characteristics of sintered Al(aluminum) plate. Comparison between experiment and theoretical analysts by using empirical formula are made. Based on comparison. it is found that Voronina model gives more reasonable explanation for sound absorption characteristics of sintered Al plates. Effect of air gap with varying the thickness of plates are also investigated, which concludes that the air gap generally increase absorption but for too thick thickness of Al plates. Al plates with air gap shows 0.85∼0.9 of NRC(Noise Reduction Coefficient) measured in reverberation room. which is comparable to glass wool. Comparison between normal and random Incident absorption shows that random incident absorption is higher than normal incident absorption.

• Wind and Structures
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• 제1권1호
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• pp.77-109
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• 1998

An evaluation and comparison of seven of the world's major building codes and standards is conducted in this study, with specific discussion of their estimations of the alongwind, acrosswind, and torsional response, where applicable, for a given building. The codes and standards highlighted by this study are those of the United States, Japan, Australia, the United Kingdom, Canada, China and Europe. In addition, the responses predicted by using the measured power spectra of the alongwind, acrosswind and torsional responses for several building shapes tested in a wind tunnel are presented and a comparison between the response predicted by wind tunnel data and that estimated by some of the standards is conducted. This study serves not only as a comparison of the response estimates by international codes and standards, but also introduces a new set of wind tunnel data for validation of wind tunnel-based empirical expressions.

• 유통과학연구
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• 제17권5호
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• pp.39-50
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• 2019

Purpose - The purpose of our study is to provide an understanding of the relationships among consumer attention to social comparison information (ATSCI), consumer ethnocentrism (CET), national identity (NI), and consumer purchase intention to domestic brands (PIDB). Drawing on the social comparison theory (SCT) and social identity theory (SIT), we developed a model that is empirically testable and explains consumer behavior of domestic brands and products. Research design, data, and methodology - The conceptual framework was tested with primary data collected through a survey in China. Structural equation modeling was employed to test hypotheses. Results - The results from empirical analyses indicated that the ATSCI positively influenced CET and NI, and CET and NI affect consumer PIDB. In addition, the mediating effects of CET and NI on the relationship between ATSCI and PIDB were identified. Nonetheless, little direct impact of ATSCI on PIDB was reported. Conclusions - We suggested that international marketers use given information to attract consumer attention and develop appropriate promotions, especially for Chinese young generations that would pay much attention to social comparison information in their purchase decisions. Our study originally connected one socio-psychological antecedent, ATSCI, with CET and NI and estimated the relationships among the three antecedents and their effects on PIDB in order to predict consumer behavior in China.

• 화약ㆍ발파
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• 제37권3호
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• pp.1-12
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• 2019

폭발 해석 모델의 해석 방법은 직접적 해석과 간접적 해석으로 구별되며, 간접적 해석으로는 반경험적 해석 방법과 수치 해석적 방법으로 나뉜다. 본 연구에서는 반경험적 모델 해석의 프로그램인 ELS 폭발 해석 프로그램의 적용성을 평가하기 위해, 단순 해석 모델을 선정하고 다양한 반경험적 해석 프로그램인 AT-Blast, RC-Blast와 Kinney와 Graham의 경험식을 이용하여 자유 공중 폭발과 지표면 폭발에서의 폭발 하중 특성을 검토하였다. 단순 해석 모델에 대해 환산거리와 입사각에 대한 폭발 압력을 해석한 결과, 자유 공중 폭발 해석에서 환산거리의 범위는 $0.3{\sim}0.461m/kg^{1/3}$이고, 지표면 폭발 해석에서 환산거리의 범위는 $0.378{\sim}0.581m/kg^{1/3}$ 일 때 적합한 해석을 수행할 수 있으며, 입사각의 경우에는 $45^{\circ}$ 이내에서 해석한 결과가 적합한 것으로 판단된다.

• Ocean and Polar Research
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• 제39권3호
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• pp.233-244
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• 2017

This study seeks to analyze the needs of biotechnology companies in relation to their entry into the marine biotechnology industry and to discuss the policy implications associated with empirical tasks based on issues raised from empirical results gathered from a survey data of 200 biotechnology companies in Korea. This study made a comparison between marine and non-marine biotechnology companies and analyzed non-marine biotechnology companies' needs related to their entry into the marine biotechnology companies by using Social Network Analysis (SNA). Empirical results indicate that 23.5% of biotechnology companies produce goods using marine bio-resources. Once the utility of marine bio-resources is established, 58.8% of non-marine biotechnology companies intend to enter the marine biotechnology industry. This study also shows that non-marine biotechnology companies need technical support, information sharing, and the acquisition of raw materials to enter the marine biotechnology industry. The findings in this study provide important pointers for the direction of policies and future research in the area of marine biotechnology industry.

• 대한기계학회논문집A
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• 제26권8호
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• pp.1552-1564
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• 2002

Meter-in, meter-out and bleed-off circuits are widely utilized in order to adjust the speed of a hydraulic actuator by using a flow control valve and in order to regulate the pressure of a hydraulic volume by using a simple on-off valve. In these circuits, a relief valve serves either to maintain constant system pressure or to protect the system from over-pressure loading. The relief valve of a bleed-off circuit is the second case frequently undergoing on-off action during operation. It makes the analysis of the pressure control characteristics of the circuit highly difficult. In this paper, steady-state flow rate, pressure, heat loss and efficiency of the three circuits are reexamined and basic experiments far obtaining the characteristics of a pump and relief valve are conducted. Finally, simple empirical first-order dynamic models of decreasing and increasing pressure were separately proposed and verified by comparison with experiment. As the result, the basis for the theoretical analysis of the pressure control characteristics of a bleed-off circuit using a simple on-off valve is established.