• Journal of Korean Academy of Oral and Maxillofacial Radiology
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• v.20 no.2
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• pp.289-297
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• 1990

The purpose of this study was to assess the resolution and focal spot size of dental X-ray machines. Fifty dental X-ray machines were selected for measuring resolution and focal spot size. These machines were used in general dental clinics. The time of installation of the X-ray machine varies from 1 year to 10 years. The resolution of these machines was measured with the test pattern. The focal spot size of these machines was measured with the star test pattern. The following results were obtained: 1. The resolution of dental intraoral X-ray machines was not significantly changed in ten years. 2. The focal spot size of dental intraoral X-ray machines was not significantly increased in ten years. The statistical analysis between the mean focal spot size and nominal focal spot size was significant at the 0.05 level about the more than 3 years used machines.

• Research in Community and Public Health Nursing
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• v.15 no.2
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• pp.277-288
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• 2004

Purpose: This study was to provide basic information for preventing high school students from smoking by examining their actual smoking condition and their knowledge and attitude about smoking. Method: The subjects were 515 students selected from six(6), high schools in Jecheon. Data were collected using a questionnaire from the 1st to the 17th of December 2002. The author prepared the tool by modifying the scale of knowledge and attitude about smoking developed by Moon(2001). Data were analyzed with SPSS/WIN program using frequencies, percentages, $x^2$-test, t-test, ANOVA. Duncan test and Pearson's correlation coefficient. Result: 1. The percentage of ex-smoking students was 29.9% of male students and 18.6% of female ones. The percentage of currently smoking students was 23.9% of male students and 3.0% of female ones. The percentage of non-smoking students was 46.2% of male students and 78.4% of female ones, 2. There were not significant differences in smoking knowledge according to smoking status in male and female students. 3. There were significant differences in smoking attitude according to smoking status in male(F=32.70, p=.000) and female(F=11.15, p=.000) students. 4. In smoking status according to general characteristics, there were significant differences according to the type of school($x^2$=32.93, p=.000), grade($x^2$=11.91, p=.018), educational level of the father($x^2$=30.52, p=.000) and the mother($x^2$=14.23, p=.027), monthly allowance($x^2$=17.19, p=.028), harmony of family members($x^2$=15.23, p=.019), school life($x^2$=26.96, p=.00l) and school record($x^2$=30.24, p=.000). 5. In smoking status according to smoking-related characteristics, there were significant differences according to experience in cigarette purchase($x^2$=150.04. p=.000), experience in errands for cigarette($x^2$=20.00, p=.000), knowledge of cigarette price($x^2$=72.52, p=.000), close friends' smoking($x^2$=107.41. p=.000) and smoking of brothers and sisters($x^2$=16.97, p=.002). 6. There were significant correlation between knowledge and attitude about smoking in the whole students(r=.337. p=.000), ex-smokers(r=.324. p=.000), non-smokers(r=.369. p=.000) but there was not a significant correlation between knowledge and attitude about smoking in current smokers(r=.128. p=.30l). Conclusion: Smoking prevention education should considered students' smoking status. Current smokers need smoking prevention education aiming to change their attitude toward smoking in order for them to reduce smoking and to practice smoking cessation.

• Journal of IKEEE
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• v.18 no.3
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• pp.435-441
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• 2014

The V2X cooperative communication system is fusion technology which makes vehicle manuver safer. To evaluate and anticipate effect of these kind of technology, it requires real-car based road construction, implementation of communication devices, hiring inspection specialized personnel. For this reason, many laboratories and universities experience difficulties to test their technology results. Also, the need of implementing reliable testbed for testing vehicle safety applications and V2X communication technology is increasing as V2X device development is being accelerated. In this paper, we implemented a system which synchronizes traffic and network simulators via developing External interface to set simulation based testing environment in order to solve the difficulties.

• KSCI Review
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• v.15 no.1
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• pp.203-207
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• 2007

본 논문에서는 비디오의 분할을 위하여 먼저 기존에 제안되었던 차이 값 추출방법들의 단점들을 극복하고 장점을 최대한 활용할 수 있으며 급진적 장면전환부터 점진적 장면전환까지 모두 예측할 수 있는 강건하고 복합적인 차이 값 추출방법에 대해서 제안한다. 이 방법은 지역적 $X^2$-테스트로서 기존의 컬러 히스토그램과 $X^2$-테스트를 결합한 방법이다. 본 논문을 위하여 기존의 히스토그램 기반 알고리즘과 비교하여 좋은 성능을 보여주는 $X^2$-테스트를 변형하였고, 컬러 값의 세분화 작업에 따른 검출효과를 높이기 위하여 명암도 등급에 따른 가중치를 적용한 지역적 $X^2$-테스트를 이용하였다. 이 방법은 복잡하고 다양한 시세계의 영상 변화를 가장 일반적이고 표준화된 방법으로 분석하고 분할하며 표현할 수 있는 방법이다. 기존의 $X^2$-테스트와 제안된 지역적 $X^2$-테스트 방법의 비교는 실험을 통해 입증되었다.

• Communications for Statistical Applications and Methods
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• v.10 no.2
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• pp.619-626
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• 2003

Given a prior guess for the unknown value of P(Y

• Journal of Korean Society of Industrial and Systems Engineering
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• v.5 no.7
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• pp.25-27
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• 1982

In most introductory statistics courses and text, the two equal tail test is presented without justification. In the present paper, the two equal tail critical region will be discussed in the light of unbiasedness with some test examples for the mean and the variance based on the random sample $X_1$, $X_2$,....$X_n$ from N($\mu$, $\delta^2$) using only elementary mathematics.

• Korean Journal of Soil Science and Fertilizer
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• v.1 no.1
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• pp.117-123
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• 1968

A simplest and best method to find out lime requirement for Korean soils is described. Twenty six top soil samples were collected from various localities and chemical characteristics were dertermined. Three different buffer curve methods were employed as the standard to find out the most reliable test for lime requirement. In addition, the lime requirement test by the Shoemaker's and Woodruff's as well as the O.R.D. kit method were compared with the most reliable buffer curve method. The results may be summarized as follows. 1. The regression equation of the most reliable lime requirement by buffer curve method, y, on percent base saturation of various soils, X, was y=9.69-0.106 X and the negative correlation coefficient r=-0.84 was statistically significant at 5% level. 2. Lime requirement test by the best, buffer curve, method was more well correlated with the sum of exchangeable hydrogen and exchangeable aluminum contents of the soil samples than the exchangeable hydrogen content only. 3. The ordinary buffer curve method for lime requirement is more reasonable than the lime requirement test by the buffer curve prepared after addition of 1 normal potassium chloride or calcium chloride solutions. 4. The lime requirement tests by the most reasonable buffer curve method, X, and by the Woodruff's, the Shoemaker's and O.R.D. kit were compared. The best method for laboratory lime requirement test was the Shoemaker's method and the O.R.D. kit method also was good enough for the field test and these two method are recommended as the unified method of lime requirement test in each soil testing laboratories throughout Korea.

• Journal of the Korean Society of Propulsion Engineers
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• v.5 no.4
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• pp.20-30
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• 2001

This study represents the Nondestructive Test about impact damage of composite materials made by different lay-up patterns and degrees. For this study, they were examined by the drop test on composite materials of two type lap-up patterns with fabric and unidirectional prepreg and examined nondestructive test of those. Nondestructive methods were X-ray test with $ZnI_2$ penetrant and Ultrasonic C-scan. The defect detectability of X-ray and Ultrasonic test was compared according to defect species. And the amounts of damage on impacted zone wert compared according to impact energy on two type test specimens. At results, Ultrasonic test was more effective to detect delamination and Penetrant X-ray test was more effective to detect matrix crack and fiber fracture. There were some differences in defect shapes and grades according to lay-up patterns and degrees, and the trend appeared that matrix crack, delamination, fiber fracture occured and increasing defects sizes according to increasing impact energy.

• Journal of ILASS-Korea
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• v.21 no.4
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• pp.200-206
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• 2016

Recently, the certification procedure for exhaust emission regulation of LDV has tested with the NEDC mode in the laboratory. But the on-road exhaust emissions exceed the standard emission limits. Therefore, it is important to analyze the real-driving emissions (RDE) with a portable emissions measurement system (PEMS). In present study, the on-road emissions were measured with a PEMS and evaluated by moving averaging window (MAW) method. Also, it was compared with the $CO_2$ and $NO_x$ emissions for real-driving and test modes from euro-6 light-duty vehicles equipped with SCR and LNT systems. In results, on-road $NO_x$ emission has been 2.3-10.0 times higher than the standard $NO_x$ emission limit on NEDC mode. The reason was that the test modes did not reflect traffic and various real-driving patterns sufficiently.

• Journal of the Korean Society of Visualization
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• v.8 no.2
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• pp.45-50
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• 2010

The objective of this study is to elucidate the feasibility of synchrotron X-ray micro CT as a non-destructive imaging method to visualize the three-dimensional morphological structures of biological and non-biological samples. The experiments were conducted in 7B2 X-ray micro CT beamline in Pohang Accelerate Laboratory (PAL). A rotational 3-axis stage was specially designed for $0^{\circ}-180^{\circ}$ scanning of test samples. Preliminary tests were performed for opaque samples including a mosquito head, a plant seed and gas diffusion layer (GDL) of polymer electrolyte fuel cell to verify the feasibility of the X-ray micro CT. It visualized clearly the internal structure of all the test samples, supporting its usefulness.