• International Journal of Reliability and Applications
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• 제15권2호
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• pp.125-150
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• 2014

Accelerated life tests (ALTs) are extensively used to determine the reliability of a product in a short period of time. Test units are subject to elevated stresses which yield quick failures. ALT can be carried out using constant-stress, step-stress, progressive-stress, cyclic-stress or random-stress loading and their various combinations. An ALT with linearly increasing stress is ramp-stress test. Much of the previous work on planning ALTs has focused on constant-stress, step-stress, ramp-stress schemes and their various combinations where the stress is generally increased. This paper presents an optimal design of ramp soak-stress ALT model which is based on the principle of Thermal cycling. Thermal cycling involves applying high and low temperatures repeatedly over time. The optimal plan consists in finding out relevant experimental variables, namely, stress rates and stress rate change points, by minimizing variance of reliability function with pre-specified mission time under normal operating conditions. The Burr type XII life distribution and time-censored data have been used for the purpose. Burr type XII life distribution has been found appropriate for accelerated life testing experiments. The method developed has been explained using a numerical example and sensitivity analysis carried out.

• 대한간호학회지
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• 제28권3호
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• pp.550-562
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• 1998

The purpose of this study was to test the Theory of Planned Behavior in the prediction of contraceptive behavior among married women. This study used a descriptive correlational design to examine the relationships among the study variables. Eighty married women in Seoul and Kyungki-do participated in this study, Research instruments used were the tool for measuring TPB variables search as attitude toward contraception, subjective norm, perceived behavioral control, and intention ; and the tool for measuring contraceptive behavior. The former was modified by the researcher according to Ajzen & Fishbein(1980)'s guidelines for tool development and Jee (1993)'s tool. The latter was developed by the researcher Data was collected from July 20, 1996 to October 25, 1996. The results are as follows ; The three factors, attitude, subjective norm and perceived behavioral control of contraception can explain 30% of the variance in contraceptive intention. Inspection of path coefficient for each of the three predictor variables revealed that subjective norm and perceived behavioral control were the predictor variables on intention, while attitude was not. ; and intention and percevied behavioral control factors can explain 42% of the variance in contraceptive behavior. Inspection of path coefficient for each of the two predictor variables revealed that intention and perceived behavioral control were the predictor variables on behavior. In conclusion, this study identified that Theory of Planned Behavior was a useful model in the prediction of contraceptive behavior, and the contraceptive service program based on the TPB variables would be an effective nursing intervention for the change in contraceptive behavior.

• Asian-Australasian Journal of Animal Sciences
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• 제22권7호
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• pp.923-930
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• 2009

This study was conducted to compare three models: two random regression models with and without considering heterogeneity in the residual variances and a lactation model (LM) for evaluating the genetic ability of Holstein cows in Korea. Two datasets were prepared for this study. To apply the test-day random regression model, 94,390 test-day records were prepared from 15,263 cows. The second data set consisted of 14,704 lactation records covering milk production over 305 days. Raw milk yield and composition data were collected from 1998 to 2002 by the National Agricultural Cooperative Federation' dairy cattle improvement center by way of its milk testing program, which is nationally based. The pedigree information for this analysis was collected by the Korean Animal Improvement Association. The random regression models (RRMs) are single-trait animal models that consider each lactation record as an independent trait. Estimates of covariance were assumed to be different ones. In order to consider heterogeneity of residual variance in the analysis, test-days were classified into 29 classes. By considering heterogeneity of residual variance, variation for lactation performance in the early lactation classes was higher than during the middle classes and variance was lower in the late lactation classes than in the other two classes. This may be due to feeding management system and physiological properties of Holstein cows in Korea. Over classes e6 to e26 (covering 61 to 270 DIM), there was little change in residual variance, suggesting that a model with homogeneity of variance be used restricting the data to these days only. Estimates of heritability for milk yield ranged from 0.154 to 0.455, for which the estimates were variable depending on different lactation periods. Most of the heritabilities for milk yield using the RRM were higher than in the lactation model, and the estimate of genetic variance of milk yield was lower in the late lactation period than in the early or middle periods.

• Restorative Dentistry and Endodontics
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• 제45권1호
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• pp.6.1-6.8
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• 2020

Objectives: This study investigated the effects of a hydrofluoric acid (HA; solution of hydrogen fluoride [HF] in water)-based smart etching (SE) solution at an elevated temperature on yttria-stabilized tetragonal zirconia polycrystal (Y-TZP) ceramics in terms of bond strength and morphological changes. Materials and Methods: Eighty sintered Y-TZP specimens were prepared for shear bond strength (SBS) testing. The bonding surface of the Y-TZP specimens was treated with 37% phosphoric acid etching at 20℃-25℃, 4% HA etching at 20℃-25℃, or HA-based SE at 70℃-80℃. In all groups, zirconia primers were applied to the bonding surface of Y-TZP. For each group, 2 types of resin cement (with or without methacryloyloxydecyl dihydrogen phosphate [MDP]) were used. SBS testing was performed. Topographic changes of the etched Y-TZP surface were analyzed using scanning electron microscopy and atomic force microscopy. The results were analyzed and compared using 2-way analysis of variance. Results: Regardless of the type of resin cement, the highest bond strength was measured in the SE group, with significant differences compared to the other groups (p < 0.05). In all groups, MDP-containing resin cement yielded significantly higher bond strength values than MDP-free resin cement (p < 0.05). It was also shown that the Y-TZP surface was etched by the SE solution, causing a large change in the surface topography. Conclusions: Bond strength significantly improved when a heated HA-based SE solution was applied to the Y-TZP surface, and the etched Y-TZP surface was more irregular and had higher surface roughness.

• 여성건강간호학회지
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• 제24권4호
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• pp.414-422
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• 2018

Purpose: To develop Korean Menstrual Symptom Scale (KMSS) for university students and test its reliability and validity. Methods: The scale was developed by intensive literature review, development of preliminary items, verification of content validity, development of secondary items, verification of construct validity, and extraction of final items. Thirty-nine items were constructed. Data for validity and reliability testing were collected with a questionnaire survey from 391 university students. Data were analyzed with descriptive statistics, factor analysis, and reliability coefficients (Cronbach's ${\alpha}$) with the SPSS program. Results: There were 37 final items which were sorted into six factors: 'negative affection (8 items)', 'change of activity level (7 items)', 'physical symptom (9 items)', 'mood change (9 items)', 'change in concentration level (4 items)', and 'body water retention (5 items)'. The cumulative percent of variance was 63.3%. Regarding the reliability of the scale, its Cronbach's ${\alpha}$ was 0.96. Cronbach's ${\alpha}$ values for these factors ranged from 0.75 to 0.91. Conclusion: The KMSS demonstrated acceptable validity and reliability. Repeated research is needed to measure menstrual symptom experienced by women of variable ages.

• 전자공학회논문지CI
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• 제47권5호
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• pp.41-49
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• 2010

휴대용 정보기기와 엔터테인먼트기기 등의 사용이 대중화 되면서 플래쉬 메모리의 수요도 급격히 증가하였다. 일반적으로 플래시 메모리는 장착되는 장치에 따라 다양한 형태의 오류 패턴을 가지며, 메모리 생산자들은 최종적인 생산과정에서 실제 장착되는 기기와 동일한 환경에서 전기적/물리적 테스트를 수행한다. 이 과정을 메모리의 응용기기 실장 테스트라고 하며, 여기에서 사용되는 장비를 메모리 실장기라 한다. 현재 여러 가지 종류의 실장기들이 제작되어 메모리 생산 환경에서 사용되고 있으나 대부분이 검수자의 청각이나 시각 등의 감각에 의존하여 메모리의 오류를 판단하고 있다. MP3 실장기의 경우 음원의 재생 기능을 이용하여 메모리 오류를 판단하는데 적절한 자동 검수 기법이 존재하지 않아 검수자가 실장기에서 재생되는 음원을 직접 듣고 오류를 판단한다. 이런 과정은 실장환경의 자동화에 있어 큰 걸림돌이 되고 있으며 인력 활용 측면에서도 비효율적이다. 본 논문에서는 MP3 장치용 플래시 메모리의 효과적인 오류 검증을 위한 음원 비교 기법을 제안한다. 제안하는 방법은 원본 파일과 MP3 장치에서 재생되는 샘플값의 분산을 활용함으로써 메모리 오류 발생 여부를 판단한다.

• 한국보건간호학회지
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• 제31권2호
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• pp.296-310
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• 2017

Purpose: The aim of this study was to develop and test the validity and reliability of the Korean version of the Pre-Menstrual Coping Measure (PMCM-K). Methods: Translation of the PMCM-K was validated using forward-backward translation methods. The study was conducted as a cross-sectional survey from March 7 to April 30, 2016 and the data from a total of 362 young adult women were used for the final analysis. The content validity, construct validity and criterion-related validity were evaluated. The internal consistency was calculated to assess the reliability. Results: The PMCM-K consisted of five factors: premenstrual coping regarding avoiding harm, awareness and acceptance of premenstrual change, self-care, communicating, and adjusting energy, which all explained 62.0% of the total variance in PMCM-K. The total score of the PMCM-K showed a positive correlation with the shortened premenstrual assessment form (r=.50). The Cronbach's alpha reliability coefficient was .94 for the overall instrument and .77-.93 for five factors. Conclusion: PMCM-K provides a valid and reliable scale for quantifying the ways of coping specific to a negative premenstrual change for Korean young adult women. The PMCM-K will play an important role as a way to gain a sense of agency in coping with premenstrual changes.

• 한국전문물리치료학회지
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• 제22권1호
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• pp.1-8
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• 2015

The purpose of this study was to compare the change in electromyography (EMG) activity in the gluteus maximus (G-max) and the gluteus medius (G-med) in subjects with and without chronic ankle instability (CAI) during three functional postures. Twenty four females were recruited for this study. Subjects were assigned into two groups: with CAI ($n_1=12$) and without CAI ($n_2=12$). The assessment postures were rotational squat, one leg stand above a gradient and crossed leg-sway. Electromyographic activities of the G-max and the G-med were recorded using surface EMG and was normalized using the maximal voluntary isometric contraction elicited using a manual muscle testing. Independent t-test was used to determine the statistical differences between two groups during the three functional postures. The comparisons of the three posture between two groups were performed using a one-way repeated analysis of variance. A Bonferroni adjustment used for post hoc analysis. The activation of EMG on G-max performing the one leg stand above a gradient and crossed leg-sway in subjects with CAI is significantly higher than normal group (p<.05). The activation of EMG on the G-max during the rotational squat was significantly increased, compared to those of the one leg stand above a gradient and crossed leg-sway (p<.05). The activation of EMG on G-med performing three exercise at CAI is significantly higher than normal group (p<.05). The activation of EMG on the G-med during the crossed leg-sway was significantly increased, compared to the rotational squat (p<.05). This study provides valuable information for clinician who research CAI.

• 방송공학회논문지
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• 제2권2호
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• pp.146-155
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• 1997

본 논문은 MPEG-4와 같이 객체 및 내용 기반 영상 부호화에 필요한 동영상의 자동 영역 분할 알고리즘을 제안한다. 통계적 가설 검증(statistical hypothesis test)을 사용하여 영상 시퀀스내에 포함된 비디오 객체들(video objects)을 움직임 물체(moving objects)와 배경 (background)으로 자동 분할하는 새로운 영상 분할 알고리즘을 제안한다. 기존 방법들이 두 개의 연속된 영상을 사용하는 반면에, 제안된 방법은 3개의 연속된 영상을 사용하여, 2개의 차영상의 평균값을 비교하여 가설검증을 행함으로써 잡음에 강한 특성을 나타낸다. 그리고 제안된 방법은 기존 방법과는 달리 참분산(true variance)을 사전에 알고 있을 필요가 없는 장점을 갖고 있다[18]. 또한 시간정보만을 이용한 변화 검출 방법의 문제점인 불규칙하고 부정확한 영역의 경계를 공간정보를 이용하여 보정하는 새로운 방법을 제안한다. 시험 결과에서 주어진 것처럼 제안된 시공간정보를 이용한 영상 분할 알고리즘이 시각적으로 의미있는 분할 결과를 제공함을 알 수 있고, 정확한 영역 경계를 추출할 수 있기 때문에 MPEG-4와 같은 객체 기반 영상 부호화에 적용할 경우에 영역 경계에서 상당히 우수한 재생 화질을 얻을 수 있다.

• 한국농림기상학회지
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• 제21권4호
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• pp.307-316
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• 2019

농업 분야 온실가스 발생은 토양환경, 기상환경, 작물 생장 등 모든 생태계 변화와 인위적인 영농활동의 상호작용에 따라 변화하여 배출량 변동성의 크기가 매우 크므로 배출량 자료에 대한 신뢰구간 확보가 필요하다. 이에 온실가스 배출량 및 흡수량에 대한 신뢰구간을 정의하는 불확도 평가가 필요하지만 불확도 평가 방법에 대한 연구는 부족한 실정이다. 따라서 본 연구에서는 밭토양에서 발생하는 N₂O 배출량 저감 효과의 유의성을 불확도 추정기법을 통하여 판정하고자 하였다. 질소 비료 시비효과 증진 및 N₂O 배출량 감소를 위한 요소분해효소 억제제 NBPT 함유 원예용 비료, 표준시비, 무시비 등 5처리 집단들의 신뢰구간에 차이가 있는지를 불확도 평가를 통해 확인하였으며, N₂O 배출량 개별 자료들의 변동성을 모두 고려한 신뢰구간을 찾아내어 분석한 결과로 신뢰성 있는 저감 효과(처리간 차이)의 유무를 판정할 수 있었다. 또한 고추와 배추 재배지에서 요소분해효소 억제제 NBPT 함유 원예용 비료를 시용하면 표준시비와 같은 생육상황에서 온실가스 저감효과를 볼 수 있는 것으로 확인되었다.