• 한국안전학회지
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• 제33권4호
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• pp.105-110
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• 2018

Korea has entered to 'aged society', which the elderly people over 65 years old is over 14% of total population. This paper aims to analyze the traffic accident by aging level. In pursuing the above, this paper focuses on modeling the traffic accident severity based on three aging levels. The main results are as follows. First, the ratio of fatal and serious injured persons (FSI) is judged to increase according to increasing aging level. Second, the null hypothesis that there is no difference in FSI among three aging levels (aging, aged, and super-aged) is rejected. Four accident severity generalized linear models which are all statistically significant have been developed. Third, the common variables are analyzed to be median age, the number of hospital beds per persons, and turn signal usage ratio. Fourth, the differentiated traffic safety policies fitted to aging levels are required. The enforcement of traffic law violation and safety enhancement of motorcycle in the region of 'aging society', improvement of traffic facilities in the region of 'aged society', and expansion of transportation facilities in the region of 'super-aged society' are evaluated to be indispensable.

• 말소리와 음성과학
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• 제10권4호
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• pp.31-37
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• 2018

Pitch trajectories reflect a continuous variation of vocal fold movements over time. This study examined the pitch trajectories of English vowels produced by 139 American English speakers, statistically analyzing their trajectories using the Generalized Additive Mixed Models (GAMMs). First, Praat was used to read the sound data of Hillenbrand et al. (1995). A pitch analysis script was then prepared, and six pitch values at the corresponding time points within each vowel segment were collected and checked. The results showed that the group of men produced the lowest pitch trajectories, followed by the groups of women, boys, then girls. The density line showed a bimodal distribution. The pitch values at the six corresponding time points formed a single dip, which changed gradually across the vowel segment from 204 to 193 to 196 Hz. The normality tests performed on the pitch data rejected the null hypothesis. Nonparametric tests were therefore conducted to discover the significant differences in the values among the four groups. The GAMMs, which analyzed all the pitch data, produced significant results among the pitch values at the six corresponding time points but not between the two groups of boys and girls. The GAMMs also revealed that the two groups were significantly different only at the first and second time points. Accordingly, the methodology of this study and its findings may be applicable to future studies comparing curvilinear data sets elicited by experimental conditions.

• 천문학회보
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• 제44권1호
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• pp.79.3-79.3
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• 2019

Observational evidence for intrinsic galaxy alignments in isolated spiral pairs is presented. From the catalog of the galaxy groups identified by Tempel et al. in the flux-limited galaxy sample of the Sloan Digital Sky Survey Data Release 10, we select those groups consisting only of two spiral galaxies as isolated spiral pairs and investigate if and how strongly the spin axes of their two spiral members are aligned with each other. We detect a clear signal of intrinsic spin alignment in isolated spiral pairs, which leads to the rejection of the null hypothesis at the 99.9999% confidence level via the Rayleigh test. It is also found that those isolated pairs comprising two early-type spiral galaxies exhibit the strongest signal of intrinsic spin alignment and that the strength of the alignment signal depends on the angular separation distance as well as on the luminosity ratio of the member galaxies. Using the dark matter halos consisting of only two subhalos resolved in the EAGLE hydrodynamic simulations, we repeat the same analysis but fail to find any alignment tendency between the spin angular momentum vectors of the stellar components of the subhalos, which is in tension with the observational result. Several possible sources of this apparent inconsistency between the observational and the numerical results are discussed.

• 천문학회보
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• 제44권1호
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• pp.35.2-35.2
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• 2019

Observational evidence for intrinsic galaxy alignments in isolated spiral pairs is presented. From the catalog of the galaxy groups identified by Tempel et al. in the flux-limited galaxy sample of the Sloan Digital Sky Survey Data Release 10, we select those groups consisting only of two spiral galaxies as isolated spiral pairs and investigate if and how strongly the spin axes of their two spiral members are aligned with each other. We detect a clear signal of intrinsic spin alignment in isolated spiral pairs, which leads to the rejection of the null hypothesis at the 99.9999% confidence level via the Rayleigh test. It is also found that those isolated pairs comprising two early-type spiral galaxies exhibit the strongest signal of intrinsic spin alignment and that the strength of the alignment signal depends on the angular separation distance as well as on the luminosity ratio of the member galaxies. Using the dark matter halos consisting of only two subhalos resolved in the EAGLE hydrodynamic simulations, we repeat the same analysis but fail to find any alignment tendency between the spin angular momentum vectors of the stellar components of the subhalos, which is in tension with the observational result. Several possible sources of this apparent inconsistency between the observational and the numerical results are discussed.

• Smart Structures and Systems
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• 제30권3호
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• pp.303-315
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• 2022

The degradation of wheel tread may result in serious hazards in the railway operation system. Therefore, timely wheel defect diagnosis of in-service trains to avoid tragic events is of particular importance. The focus of this study is to develop a novel wheel defect detection approach based on the relevance vector machine (RVM) which enables online detection of potentially defective wheels with trackside monitoring data acquired under different running-speed conditions. With the dynamic strain responses collected by a trackside monitoring system, the cumulative Fourier amplitudes (CFA) characterizing the effect of individual wheels are extracted to formulate multiple probabilistic regression models (MPRMs) in terms of multi-kernel RVM, which accommodate both variables of vibration frequency and running speed. Compared with the general single-kernel RVM-based model, the proposed multi-kernel MPRM approach bears better local and global representation ability and generalization performance, which are prerequisite for reliable wheel defect detection by means of data acquired under different running-speed conditions. After formulating the MPRMs, we adopt a Bayesian null hypothesis indicator for wheel defect identification and quantification, and the proposed method is demonstrated by utilizing real-world monitoring data acquired by an FBG-based trackside monitoring system deployed on a high-speed trial railway. The results testify the validity of the proposed method for wheel defect detection under different running-speed conditions.

• 한국측량학회지
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• 제40권3호
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• pp.207-215
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• 2022

저가형 UAV기반 사진측량의 정밀도와 정확도를 평가하기 위한 실험을 수행하였다. 높은 정확도의 지상기준점과 검사점의 3차원 좌표를 추정하고자 GNSS정지관측과 기선해석, 망조정을 수행하였고, 신뢰수준 95%에 대하여 정확도가 1cm 이내인 좌표를 확보하였다. 실험 대상지에 대한 항공 사진은 DJI Phantom 4와 이에 탑재된 FC330 카메라로 7회 반복 촬영하였고, 이를 두 가지 소프트웨어로 처리하였다. 10개 검사점에 대한 소프트웨어 자동 추출좌표와 GNSS 추정해를 비교하여 표준편차 및 RMSE를 분석하였다. 두 소프트웨어 처리 결과, 95% 신뢰수준에 대해 표준편차는 남북, 동서, 높이 방향 각각 약 1cm, 2cm, 4cm 이내, RMSE는 수평과 높이 각각 9cm, 8cm 이내였으며, 표준편차가 RMSE에 비해 현저히 작았다. 두 소프트웨어 처리 결과의 통계적 차이를 확인하고자 F-ratio 검정을 수행하였다. 정밀도에 대해서는 모든 좌표 성분에 대해 한쪽꼬리 검정의 귀무가설이 기각되었고, RMSE에 대해서는 수평에 대한 것만 기각되었다. 이에 따라, 동일한 사진 자료를 처리하더라도 소프트웨어에 따라 그 결과에 통계적 차이가 있을 수 있음에 유의할 필요가 있다.

• 한국건설관리학회논문집
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• 제25권3호
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• pp.47-57
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• 2024

본 연구의 목적은 중대재해처벌법에 따른 건설 노동자의 중대재해인지 수준과 안전의식 수준 간의 상관관계를 분석하는 것이다. 건설 노동자, 건설 관리자, 안전 관리자를 대상으로 설문조사를 실시하였다. 이 연구의 결과는 다음과 같다. 세 그룹 간의 상관관계 분석 결과, 안전 관리자가 가장 높은 상관관계를 보였으며, 그 다음으로 건설 관리자와 건설 노동자가 이어지며, 세 그룹 모두 보통 수준의 상관관계를 나타냈다. 전체 그룹에서의 상관관계 분석도 유의한 상관관계를 나타내었으며, 참가자 수가 증가함에 따라 더 높은 상관계수가 관찰되었다. 또한, 상관계수의 유의성을 검증하기 위해 p-value와 유의수준(α)을 비교하였다. 결과적으로 유의수준인 0.05보다 작은 p-value를 얻어 귀무가설을 기각하고 대립가설인 "중대재해처벌법에 대한 인지 정도와 안전의식 수준 정도는 관계가 있다"를 채택하다. 따라서, 중대재해처벌법의 인지 정도와 건설 안전의식 수준은 관련이 있다는 결론을 얻었다. 이 연구의 한계점은 주관적인 지표를 기반으로 한 설문조사에 의존하였으므로, 질문 항목의 난이도에 변동성이 존재할 수 있다는 점이다.

• 한국도로학회논문집
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• 제18권6호
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• pp.153-160
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• 2016

OBJECTIVES : The objective of this study is to develop a traffic accident model of a roundabout based on the type of land use. METHODS : The traffic accident data from 2010 to 2014 were collected from the "traffic accident analysis system (TAAS)" data set of the Road Traffic Authority. A multiple linear regression model was utilized in this study to analyze the accidents based on the type of land use. Variables such as geometry and traffic volume were used to develop the accident models based on the type of land use. RESULTS : The main results are as follows. First, the null hypothesis that the type of land use does not affect the number of accidents is rejected. Second, four accident models based on the type of land use have been developed, which are statistically significant (high $R^2$ values). Finally, the total entering and circulating volumes, area of the central island, number of speed breakers, mean number of entry lanes, diameter of the inscribed circle, mean width of the entry lane, area of the roundabout, bus stops, and number of circulatory roadways are analyzed to see how they affect the accident for each type of land use. CONCLUSIONS : The development of the accident models based on the type of land use has revealed that the accident factors at a roundabout are different for each case. Thus, more speed breakers in commercial areas and an inscribed circle of proper diameter in commercial and residential areas are determined to be important for reducing the number of accidents. Additionally, expanding the width of the entry lanes, decreasing the area of the roundabouts in residential areas, and reducing the conflict factors such as bus stops in green spaces are determined to be important.

• 통상정보연구
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• 제14권3호
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• pp.307-322
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• 2012

본 논문은 패널 단위근, 패널 공적분, 패널 인과성 검정, 패널 FMOLS(fully modified OLS) 기법을 이용하여 한국의 대 동아시아 수출 결정요인을 분석하였다. 분석결과 변수들이 패널 단위근 검정을 통하여 단위근을 가지며 1차 차분 후 안정적인 자료로 전환됨을 알 수 있었으며, 패널 공적분 통계량 모두 공적분 관계가 존재하지 않는다는 귀무가설을 기각함으로써 적어도 하나의 공적분 벡터가 존재함을 알 수 있었다. 다음으로 패널 벡터오차수정모형을 도입하여 동태적 인과성 분석을 실시하였다. GDP변동이 수출변동에 영향을 미치고 수출변동이 GDP변동에 영향을 미침으로써 수출과 GDP 간에 쌍방적 인과관계가 존재함을 알 수 있었다. 그리고 ODI변동의 오차수정항 계수가 수출변동의 오차수정항 계수보다 약 1.65배 크게 나타나 ODI의 불균형에서 균형으로 조정속도가 수출보다 1.7배 정도 빠름을 확인할 수 있었다. 이와 더불어 패널 GM FMOLS 결과 환율이 1% 상승했을 때 수출이 0.28% 감소하고, GDP가 1% 증가했을 때 수출은 0.77% 증가하고, 해외직접투자가 1% 증가했을 때 수출은 0.11% 증가함을 알 수 있었다.

• 산업경영시스템학회지
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• 제42권4호
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• pp.194-202
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• 2019

Reliability analysis of the components frequently starts with the data that manufacturer provides. If enough failure data are collected from the field operations, the reliability should be recomputed and updated on the basis of the field failure data. However, when the failure time record for a component contains only a few observations, all statistical methodologies are limited. In this case, where the failure records for multiple number of identical components are available, a valid alternative is combining all the data from each component into one data set with enough sample size and utilizing the useful information in the censored data. The ROK Navy has been operating multiple Patrol Killer Guided missiles (PKGs) for several years. The Korea Multi-Function Control Console (KMFCC) is one of key components in PKG combat system. The maintenance record for the KMFCC contains less than ten failure observations and a censored datum. This paper proposes a Bayesian approach with a Dirichlet mixture model to estimate failure time density for KMFCC. Trends test for each component record indicated that null hypothesis, that failure occurrence is renewal process, is not rejected. Since the KMFCCs have been functioning under different operating environment, the failure time distribution may be a composition of a number of unknown distributions, i.e. a mixture distribution, rather than a single distribution. The Dirichlet mixture model was coded as probabilistic programming in Python using PyMC3. Then Markov Chain Monte Carlo (MCMC) sampling technique employed in PyMC3 probabilistically estimated the parameters' posterior distribution through the Dirichlet mixture model. The simulation results revealed that the mixture models provide superior fits to the combined data set over single models.