• 한국지하수토양환경학회지:지하수토양환경
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• 제20권7호
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• pp.112-120
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• 2015

Statistical trend analysis using the data from the National Groundwater Quality Monitoring Network (NGQMN) of Korea was conducted to establish a new groundwater quality management framework. Sen’s test, a non-parametric statistical method for trend analysis, was used to determine the linear trend of the groundwater quality data. The analysis was conducted at different confidence levels (i.e., at 70, 80, 90, 95, and 99% confidence levels) for three of groundwater quality parameters, i.e., nitrate-nitrogen, chloride, and pH, which have sufficient time series of the NGQMN data between 2007 and 2013. The results showed that different trends can be determined for different depths even for the same monitoring site and the numbers of wells having significant trends vary with different confidence levels. The wells with increasing or decreasing trends were far less than the wells with no trend. Chloride had more wells with increasing trend than other parameters. On the other hand, nitrate-nitrogen had the most wells with increasing trend and concentration exceeding 75% of the threshold values (TVs). Based on the methodology used for this study, we suggest including groundwater TVs and trend analysis to evaluate groundwater quality and to establish an advanced groundwater quality management framework.

• 한국해안·해양공학회논문집
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• 제29권3호
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• pp.129-138
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• 2017

연안의 파랑환경은 해안지형의 변화, 해양생물의 서식조건, 해양구조물의 설계 등에 직접적인 영향을 미치는 매우 중요한 인자이다. 최근 기후변화로 인한 파랑환경의 변화도 예상되고 있는 상황에서, 가용한 자료를 이용한 파랑환경의 추세분석이 요구된다. 본 연구에서는 한국 연안 6개 지점(덕적도, 외연도, 칠발도, 마라도, 포항, 울릉도) 평상파랑의 부이관측 자료를 이용하여 장기 변화양상을 분석하였다. 먼저, 국내 기상청 해양기상부이 관측 자료의 이상치를 제거하기 위해 Rosner 방법을 사용하였으며, 이를 ECMWF 재해석 자료와 피어슨 상관분석을 수행하였다. 그 결과, 해양기상부이와 ECMWF 자료간의 상관성은 0.849~0.938로 나타났다. 한편, 맨-캔달 검정법을 이용하여 평상파랑의 장기변동 양상을 검토하였으며 그 결과, 덕적도, 외연도, 칠발도 지점은 변동이 없는 것으로 나타났지만, 마라도, 포항, 울릉도 지점은 증가하는 경향을 보였다.

• 대한토목학회논문집
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• 제28권1B호
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• pp.65-77
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• 2008

본 연구에서는 지리 및 지형적 특성과 도시화에 따른 기후변화가 기준증발산량에 미치는 영향을 파악하기 위하여 FAO P-M 기준증발산식을 이용하여 연별 및 각 월별 기준증발산량과 기준증발산식의 에너지항 및 공기동력항 변화추세를 분석하였다. 추세분석을 위하여 전국 21개 연구지역에서 일별 기후자료를 수집하여 Spearman 순위상관분석, Sen분석(Sen's estimator of slope) 그리고 실제변화율분석과 선형회귀분석 등을 실시하였다. 또한 도시지역 특성에 따라 21개 연구지역을 군집화하였고, 각 군집에 따른 기준증발산과 기준증발산식의 에너지항 및 공기동력항의 변화를 분석하였다. 연구결과에 의하면 도시화정도는 기준증발산, 에너지항 및 공기동력항의 변화추세 및 크기에 밀접한 영향이 있으나, 변화추세 정도(Sen's slope)에는 큰 영향이 없는 것으로 나타났다. 에너지항의 경우 해안지역에서는 주로 증가추세를 보이는 반면, 내륙지역에서는 일부 월을 제외하고 감소추세를 보이고 있다. 또한 지역 경사도는 에너지항보다는 공기동력항 변화추세 정도(Sen's slope)에 더 큰 영향력을 보이는 것으로 판단된다. 공기동력항의 경우 해안 및 내륙지역에서 증가추세를 보이고 있고, 내륙지역이 해안지역보다 더 큰 공기동력항의 증가추세를 보이고 있다.

• 해양환경안전학회:학술대회논문집
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• 해양환경안전학회 2017년도 추계학술발표회
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• pp.43-43
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• 2017

• 한국군사과학기술학회지
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• 제14권5호
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• pp.859-870
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• 2011

The purpose of this paper is to develop reliability analysis procedures for repairable systems with interval failure time data and apply the procedures for assessing the storage reliability of a subsystem of a certain type of guided missile. In the procedures, the interval failure time data are converted to pseudo failure times using the uniform random generation method, mid-point method or equispaced intervals method. Then, such analytic trend tests as Laplace, Lewis-Robinson, Pair-wise Comparison Nonparametric tests are used to determine whether the failure process follows a renewal or non-renewal process. Monte Carlo simulation experiments are conducted to compare the three conversion methods in terms of the statistical performance for each trend test when the underlying process is homogeneous Poisson, renewal, or non-homogeneous Poisson. The simulation results show that the uniform random generation method is best among the three. These results are applied to actual field data collected for a subsystem of a certain type of guided missile to identify its failure process and to estimate its mean time to failure and annual mean repair cost.

• 디지털융복합연구
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• 제13권2호
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• pp.141-151
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• 2015

스마트폰 보급률이 높아지면서 모바일 결재 서비스가 더욱 확대되고 있다. 따라서 모바일 커머스 시장도 급격히 증가하고 있다. 그리고 모바일 커머스 서비스가 확대됨에 따라 고품질과 높은 신뢰성의 요구가 증가하고 있는 추세이다. 모바일 결재서비스 확대 배경으로는 시간, 공간적인 면에서 소비자에게 편리함을 제공하는 동시에 정보기술의 발전으로 제공 비용의 감소가 크게 작용하고 있다. 본 논문에서는 모바일 커머스 소프트웨어 기반 기술을 조사하고 모바일 커머스 소프트웨어의 품질시험 평가를 위해 특성을 분석하여 국제표준 규격인 ISO/IEC 12119와 ISO/IEC 9126을 기반으로 모바일 커머스 소프트웨어 품질 평가모델과 체계를 제안하였다.

• Nuclear Engineering and Technology
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• 제55권8호
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• pp.2844-2853
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• 2023

A sophisticated Bayesian multilevel model for estimating group bias was developed to improve the utility of the ASTM E900-15 embrittlement trend curve (ETC) to assess the conditions of nuclear power plants (NPPs). For multilevel model development, the Baseline 22 surveillance dataset was basically classified into groups based on the NPP name, product form, and notch orientation. By including the notch direction in the grouping criteria, the developed model could account for TTS differences among NPP groups with different notch orientations, which have not been considered in previous ETCs. The parameters of the multilevel model and biases of the NPP groups were calculated using the Markov Chain Monte Carlo method. As the number of data points within a group increased, the group bias approached the mean residual, resulting in reduced credible intervals of the mean, and vice versa. Even when the number of surveillance test data points was less than three, the multilevel model could estimate appropriate biases without overfitting. The model also allowed for a quantitative estimate of the changes in the bias and prediction interval that occurred as a result of adding more surveillance test data. The biases estimated through the multilevel model significantly improved the performance of E900-15.

• 한국수학교육학회지시리즈B:순수및응용수학
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• 제4권1호
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• pp.7-18
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• 1997

Consider an $r\;\times\;c$ contingency table under the full multinomial model in which each classification is ordered. The problem is to test the null hypothesis of independence. A number of tests have been proposed for this problem. In this article we show that all of these tests can be improved on in some sense for most cases. In fact the preceding tests sometimes are inadmissible in a strict sense. Furthermore, we show by example that in some cases improved tests can yield substantially improved power functions.

• 오토저널
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• 제9권5호
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• pp.6-18
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• 1987

Owing to remarkable development in automotive industry, vehicle performance comes close to perfection and guarantee of stability is getting emphasized in accordance with high speed trend in vehicle. In recent years, the utilization of automatic test method for research and development of automotive brake system is being propelled actively, which pursue whole automatic control from simple measurement to data acquisition. The main subject of this paper is to make a brief explanation on Micro computer controlled Automatic Test Method for Automotive Brake System which makes it possible to test with high accuracy and speed.

• 한국생활과학회지
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• 제18권2호
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• pp.465-476
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• 2009

The purpose of this study is to investigate recognition degree and acceptability of fashion trends of new consumers who live in digital era, and to determine how these factors have influence on their use of fashion trend information. The study was conducted with 696 people from 15 to 34 years old. A self-administrated questionnaire based on the results of previous researches was developed. The data were analyzed with statistical analyses such as frequency analysis, mean, factor analysis, t-test, ANOVA, correlation and regression analysis. The results are as follows: first, new digital consumer's recognition degree (RD) of fashion trends is 7.85 on the average, given that the top of scale is 20.0, it is quite low. Of fashion trend RD, fashion item RD is the highest. The female subjects recognize fashion trends better than the male subjects. Second, fashion trend acceptance of new digital generation is classified into 5 factors: 'search acceptance', 'lead acceptance', 'follow acceptance', 'non-acceptance', and 'delay acceptance'. The female subjects show higher degree in the factors of 'search acceptance', 'lead acceptance' and 'follow acceptance' of fashion trend than the males; hence it means that the females have more positive attitudes in fashion trend acceptance than the males. Third, there are significant differences between genders in the fashion information utilization. Compared to the males, the females more use fashion information on style, fabrics and color. Concludingly, their fashion trend recognition degree and acceptance made an influence in part on their utilization of fashion information.