• 한국정밀공학회지
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• 제24권5호
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• pp.44-55
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• 2007

The method for fatigue life prediction of ball bearing is proposed applying the algorithm of contact fatigue prediction based on stress analysis. In order to do this, a series of simulation such as initial surface stress analysis, EHL analysis, subsurface stress analysis and fatigue analysis are conducted from the loading at each ball location calculated for a bearing subjected to external bearing load and contact shape function. And uniaxial fatigue tests are performed to obtain fatigue parameter of AISI 52100 steel. It was found that since stress is usually higher at the inner raceway contact than at the outer raceway contact, fatigue failure occurs on the inner raceway first. When the fatigue life calculated in the stress-based method are compared with L50 life of L-P model, Crossland criterion for the radial load increment is similar to L50 life and Dang Van criterion for the axial load increment is similar. In the case of EHL contact, there is no difference of fatigue life between dry contact and EHL contact, when maximum Hertz pressure exceeds 2.5GPa.

• 임상간호연구
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• 제25권2호
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• pp.142-150
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• 2019

Purpose: The aim of this study was to evaluate the efficiency of the Humpty Dumpty Falls Scale as one of the falls risk assessment tools, and also to evaluate risk factors as predictors of falls in pediatric patient populations. Methods: In a retrospective, case-control design with data from the electronic medical records of 13 pediatric patients who fell and 1,941 who did not fall before matching and 429 who did not fall after matching by gender, age, diagnosis, and length of stay. Results: All the variables showed no significant differences after matching. At the cutoff score of 13, sensitivity, specificity, negative and positive predictive values were 92.3%, 37.1%, 99.9%, and 0.01%, respectively. The area under the Receiver Operating Characteristics was 0.597. The results from the logistic regression showed that the pediatric inpatient population who had higher risk scores was significantly associated with falls. The odds ratios ranged from 1.31 to 4.71 with 90% confidence interval. Conclusion: The saturation impairments criterion as one of the diagnostic parameter was negatively associated with falls, but the relative risk score was higher than the other criteria. Therefore, it seems that the diagnostic parameter seems to be required to verify results through large sample studies.

• 물과 미래
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• 제23권3호
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• pp.319-328
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• 1990

2차원 하구모델의 매개변수 동정을 BF좌표계로 변환된 ADI-FDM출력 수치모형을 사용하여 수행하였다. 모형에서 기본 방정식을 동수역학식과 수송방정식이 복합된 방정식을 사용하였다. Thompson식이 지배방정식을 사각평면으로 변환 하는데 사용도이ㅓㅆ으며 Thompson의 Elliptic 격자발생기법이 BF 좌표계에서 곡선격자망을 발생하는데 사용되었다. 지배방정식에서 동정될 매개변수는 마찰계수와 분산 정수이다. 출력수치모형은 BF좌표계에서 조석평균 염도 모형이 사용되었다. 최적화 기법으로 영향계수 알고리즘을 적용하였다. 또한 Lumped 모형이 동정에 고려 되었다. 본 연구는 새로운 출력 수치모형이 하구염도 모형의 매개변수 동정에 있어 유용한가를 검토 하는데 중점을 두었다. 제안된 기법은 간단한 가상모형에 실험적인 적용을 통하여 검토되었다. 검토한 결과는 제안된 기법이 하구모형에서 매개변수 동정시 도입될 수 있음을 보여주었다.

• 한국지반공학회논문집
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• 제29권1호
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• pp.61-70
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• 2013

본 연구에서는 2차원 유한차분 해석을 이용하여 절리암반에 시공된 말뚝기초의 선단지지력을 분석하였다. 이를 위해 암반의 절리상태를 고려할 수 있는 Hoek-Brown 항복규준을 이용하여 다양한 조건의 수치해석이 수행되었다. 넓은 범위의 절리상태를 고려하기 위하여 GSI를 주 매개변수로 설정하였고 말뚝 직경, 암반의 일축압축강도, Hoek-Brown 상수 $m_0$의 매개변수 영향을 살펴보았다. 본 연구결과 매개변수들의 변화에 따른 절리 암반에 설치된 말뚝기초의 선단지지력 변화 경향을 확인하였고 이러한 결과를 토대로 매개변수 분석에 따른 선단지지력 결과를 도출하였다.

• 한국광학회지
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• 제4권4호
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• pp.434-441
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• 1993

단일 통과 라만레이저에서 접속 조건에 따른 1차 Stokes 파의 출력특성을 조사하였다. 펌푸빔으로는 Q-switched Nd-YAG 레이저의 기본파인 파장 $1.06{\mu}m$의 빔을 사용하였고 매질로는 고압 메탄을 사용하엿다. 실험 결과 펌프빔을 라만셀로 집속하는 조건에 따라 큰 출력의 치이를 보였는데, 집속상수가 클수록 Stokes 출력이 증가하였다. 이러한 결과는 Stokes와 anti-Stokes의 결합에 의한 이득감소로 이해할 수 있는데, 여기서는 간단한 이론을 통해 집속 조건에 따른 Stokes와 anti-Stokes의 결합의 정도를 알아보고 이득감소 현상을 피하기 위한 집속상수의 기준을 제시하였다. 라만 산란에 수반되는 유도 Brillouin 산란을 측정한 결과 문턱에너지가 집속상수에 비례하여 증가하였고, 이론적으로 이는 다중 모드 레이저를 펌프로 사용할 때 상호작용 거리가 간석성 거리로 제한되어 나타나는 현상으로 이해할 수 있으면 간섭성 거리를 2mm라 했을 때 실험 결과와 비교적 잘 일치하였다.

• Environmental Analysis Health and Toxicology
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• 제18권4호
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• pp.305-310
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• 2003

A rapid, inexpensive enzymatic method is proposed for indirect water quality testing in terms of heavy metal toxicity. The activity of glucose-6-phosphate dehydrogenase was applied for heavy metal toxicity test as an effective criterion in water quality. The toxicity of Pb (lead) and Cd (cadmium) for water flea, Moina macrocopa, were evaluated for 2-8 days with variables of mobilization ability. And the reproduction impairment of Moina macrocopa were investigated as the parameter of chronic toxicity test for Pb and Cd. As a result, the EC$_{50}$ for immobilization of Moina macrocopa were Pb and Cd were 1.6749 and 0.4683, respectively. The values of reproductive impairment to Moina macrocopa for Pb and Cd were 9.5938 and 8.3264 in EC$_{50}$ A significant alteration of G6PDH (Glucose-6-phosphate dehydrogenase) activity of Moina macrocopa was observed when Cd and Pb were treated in media. The results obtained indicate that G6PDH activity of Moina macrocopa can be used as an indicative parameter in aquatic toxicity tests for heavy metals.als.

• Communications for Statistical Applications and Methods
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• 제14권2호
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• pp.431-442
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• 2007

In this paper, we develop the noninformative priors when the parameter of interest is the difference between quantiles of two exponential distributions. We want to develop the first and second order probability matching priors. But we prove that the second order probability matching prior does not exist. It turns out that Jeffreys' prior does not satisfy the first order matching criterion. The Bayesian credible intervals based on the first order probability matching prior meet the frequentist target coverage probabilities much better than the frequentist intervals of Jeffreys' prior. Some simulation and real example will be given.

• International journal of advanced smart convergence
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• 제1권1호
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• pp.6-13
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• 2012

An improved algorithm for image quality assessment is presented. First a simple model of human visual system, consisting of a nonlinear function and a 2-D filter, processes the input images. This filter has one user-defined parameter, whose value depends on the reference image. This way the algorithm can adapt to different scenarios. In the next step the average value of locally computed correlation coefficients between the two processed images is found. This criterion is closely related to the way in which human observer assesses image quality. Finally, image quality measure is computed as the average value of locally computed correlation coefficients, adjusted by the average correlation coefficient between the reference and error images. By this approach the proposed measure differentiates between the random and signal dependant distortions, which have different effects on human observer. Performance of the proposed quality measure is illustrated by examples involving images with different types of degradation.

• 한국산업융합학회 논문집
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• 제2권2호
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• pp.131-137
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• 1999

Package crack caused by the soldering process in the surface mounting plastic package is evaluated by applying the energy release rate criterion. The package crack formation depend on various parameters such as chip set, chip size, package thickness, package width, material properties and the moisture content etc. The effects of chip set and the other parameters were estimated during the analysis of package cracks which were located in the edge of the upper interface of the chip and the lower interlace of the die pad. From the results, it could be obtained that the more significant parameters to effect the chip set are chip width.

• 한국산업정보학회논문지
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• 제6권1호
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• pp.7-14
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• 2001

동기식 스트림 암호 시스템 적용을 위한 ZS 동기 알고리듬이 다수 제안된 바 있지만, 그 중에서 ZS-1 알고리듬은 스트림 암호 시스템 구현상의 어려움이 있고, ZS-2 알고리듬은 에러 확산이 많으며, ZS-3는 회로가 복잡해지는 단점을 갖는다. 그리고 이들 알고리듬은 적용 분야를 주의하여 선택하여야 할 필요성이 있으며, 본 논문에서는 몇 가지 파라메터 변화에 따른 결과 값의 비교를 통하여 주어진 시스템에 적합한 알고리듬을 선택하는 방향을 제시하였다.