• 한국식품영양학회지
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• 제5권1호
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• pp.33-40
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• 1992

This research was attempted to investigate the sex bias in nutrition knowledge, food preference and food roles in the family. 152 couples living in Seoul, Cheonan in the 205∼605 were selected for this research as subjects from October 1 to December 20, 1991. The data analysis was made by way of ire quency, percentage, X2-test using SPSS package. The summarized results are as follows. 1. The survey on the sex bias in nutrition knowledge related heart disease on the subjects showed that there were no significant differences between men and women. But women had a relatively good nutrition knowledge than men. Especially women had a good nutrition knowledge that low sodium diet and exercise are efficient on preventing heart disease. 2. On the food preference, the subject showed significant difference between men and women. Men showed a relatively highest preference for protein food just as pork, fish, and tofu. Women showed a relatively highest preference for bread, fruit and vegetable. 3. On the food roles, the subjects showed that gender difference in household labor regarding food preparation still exit. Food-related activities are clearly still the domain of women in most families. Husbands and wives in younger families tended to think the husbands showed increase their efforts in food related activities.

• 한국조사연구학회지:조사연구
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• 제7권2호
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• pp.39-52
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• 2006

우리나라 대다수 조사전문기관은 지역 성 나이대 할당표본추출에 의한 전화조사를 하고 있다. 그러나 평일에는 인구사회적 속성에 따른 개인별 재택률의 차이가 심하므로 체계적 응답자선택편향(respondent selection bias)이 우려된다. 문제 해결을 위해 조사시간대를 할당변수로 추가한 '시간균형할당표본추출'(time-balanced quota sampling) 방법과 저녁시간대 할당을 부분적으로 완화한 '시간균형준할당표본추출'(time-balanced quasi-quota sampling) 방법을 제안한다. 그리고 우리나라 통계청에서 2004년에 수집한 생활시간조사 원자료를 가상적 모집단으로 설정하여 새로운 할당추출법과 기존할당추출법에 의해 얻는 몬테칼로 표본들을 비교할 것이다.

• 대한치과의사협회지
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• 제58권3호
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• pp.152-168
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• 2020

The propensity score matching method is a statistical method used to reduce selection bias in observational studies and to show effects similar to random allocation. There are many observational studies in dentistry research, and differences in baseline covariates between the control and case groups affect the outcome. In order to reduce the bias due to confounding variables, the propensity scores are used by equating groups based on the baseline covariates. This method is effective, especially when there are many covariates or the sample size is small. In this paper, the propensity score matching method was explained in a simple way with a dental example by using R software. This simulated data were obtained from one of retrospective study. The control group and the case group were matched according to the propensity score and compared before and after treatment. The propensity score matching method could be an alternative to compensate for the disadvantage of the observation study by reducing the bias based on the covariates with the propensity score.

• 한방안이비인후피부과학회지
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• 제30권3호
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• pp.166-181
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• 2017

Objectives : The study was done to verify the relation between early-onset androgenetic alopecia(AGA) and metabolic syndrome(MetS). Methods : Data were collected through electronic database including KoreaMed, National Assembly Library, KMBASE, NDSL, KCI, KERIS, Google Scholar, Pubmed, Cochrane CENTRAL and EBSCO MEDLINE. A total of 13 case-control studies related to the MetS of early-onset alopecia patients were used for the systematic review and meta-analysis. Risk of bias of included studies were assessed by RoBANS tool. RevMan5.3, CMA3 were used for the meta-analysis. Results : In 13 evaluated articles, most frequent bias was the participant selection bias that was found in 10 articles. Significant association between early-onset AGA and MetS was found in 10(76.9%) out of 13 articles in the systematic review. In meta-analysis, early-onset male AGA was associated with increased risk of metabolic syndrome(OR: 3.73, 95% CI:2.49 -5.61). Conclusions : AGA, particularly early -onset male AGA, is significantly associated with MetS. Therefore all patients with early onset male AGA should be suggested to take preventive treatment to reduce the risk of MetS and various problems associated with it.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 춘계학술대회논문집B
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• pp.164-169
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• 2001

The active magnetic bearing has many advantages - an active positioning, no contact and lubrication free motion - and is widely used in high precision motion stages. But, the conventional magnetic bearings composed of electromagnets only are power consuming due to their bias current and have the excessive heat generation, which can make the repeatability of the positioning system worse. To overcome this drawback, we developed a novel permanent magnet (PM) biased linear magnetic bearing for a high precision magnetically levitated stage. The permanent magnets provide a bias flux and generate a bias force, and the electromagnet increases or reduces a flux of the permanent magnets and gives a levitation force. This paper presents a theoretical magnetic circuit analysis, FEM analysis and experimental data from the 1-DOF tests, and compares the theoretical power consumption of the electromagnetic bearings and the PM biased linear magnetic bearings. The PM biased linear magnetic bearing presented in this paper gives better load capacity but lower power consumption than a conventional electromagnetic bearing and will be adopted in our 6-DOF high precision linear positioning maglev stage.

• Journal of Acupuncture Research
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• 제30권3호
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• pp.51-59
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• 2013

Objectives : This study was designed to evaluate clinical evidence of acupuncture treatment for peripheral facial palsy in South Korea. Methods : All process was independently proceeded by two investigators. Literature search was performed in 9 databases from their inception to February 2013. Searched reports was twice excluded for title, abstract and body. And then, data extract and analysis was done before assessing risk of bias by Cochrane Handbook. Results : 10 randomized controlled trials(RCT) were finally included. 4 RCT handled postauricular pain with facial palsy. All articles at least used in combination with two treatments. Interventions like pharmacopuncture, electroacupuncture, scalp acupuncture etcetera were conducted as treatment to evaluate efficacy, and some study reported advantageous effects of treatment group compared to baseline or control group. Adverse events didn't referd to in any studies. In assessing risk of bias, indefinite and uncertain information made all included trials to have a high risk of bias. Conclusions : Because of methodological deficit, there is no sufficient evidence to allow any conclusion about the efficacy of acupuncture for peripheral facial palsy. Therefore, well designed trials with high quality is needed from now on.

• 한국항해항만학회:학술대회논문집
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• 한국항해항만학회 2006년도 International Symposium on GPS/GNSS Vol.2
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• pp.598-601
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• 2006

The radio signal in GNSS was intentionally designed with two frequencies in order to combat the dispersion error caused by trans-ionospheric propagation. By measuring the path delay independently at the two, widely spaced GPS frequencies, L1 & L2, the TEC along the path from satellite to receiver can be measured directly. The issue with dual frequency measurement of the ionosphere is the calibration of L1/L2 interfrequency biases. L1/L2 interfrequency biases are generated because physical electric signal paths of L1 and L2 circuits are different from each other for both satellites and receiver. Conventionally L1/L2 interfrequency bias is estimated and broadcasted by 2D ionospheric model. In this paper, we estimated IFB (interfrequency bias) by 2D & 3D ionospheric models including real time filter methods and compared the result of those and concluded the merit of 3D tomography model to recover the problem of 2D thin shell model. We confirmed our conclusion by experimental data.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2007년도 추계학술대회 논문집
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• pp.188-189
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• 2007

The etching characteristics of $Al_2O_3$ films using the inductively coupled plasma (ICP) was investigated. The etch gas was the mixture of $BCl_3$ and He. The effect of ICP source and bias powers on etch rate and etch selectivity to polycrystalline Si was investigated in the etch process of $Al_2O_3$. The etch rate of $Al_2O_3$ film was 23nm/min when the source power and bias power were 600W and 60W, respectively. The results also indicated that the etch selectivity to polycrystalline Si could not be enhanced to be higher than 1.0 by changing the ICP source power and bias power, under the experimental conditions used in the present work. Based on plasma parameters extracted from Langmuir probe data, the etching mechanism of $Al_2O_3$ film was discussed in detail.

• Transactions on Electrical and Electronic Materials
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• 제14권2호
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• pp.67-70
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• 2013

In this study, we changed the input parameters (gas mixing ratio, RF power, DC bias voltage, and process pressure), and then monitored the effect on TiN etch rate and selectivity with $SiO_2$. When the RF power, DC-bias voltage, and process pressure were fixed at 700 W, - 150 V, and 15 mTorr, the etch rate of TiN increased with increasing $CF_4$ content from 0 to 20 % in $CF_4$/Ar plasma. The TiN etch rate reached maximum at 20% $CF_4$ addition. As RF power, DC bias voltage, and process pressure increased, all ranges of etch rates for TiN thin films showed increasing trends. The analysis of x-ray photoelectron spectroscopy (XPS) was carried out to investigate the chemical reactions between the surfaces of TiN and etch species. Based on experimental data, ion-assisted chemical etching was proposed as the main etch mechanism for TiN thin films in $CF_4$/Ar plasma.

• 한국물환경학회지
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• 제23권2호
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• pp.251-259
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• 2007

In this study three log-transformed linear regression models are compared with the focus of bias correction problem. The models are the traditional simple linear regression estimator (SL), the quasi maximum likelihood estimator (QMLE) and the minimum variance unbiased estimator (MVUE). Using such models, suspended solid loads can be estimated using the discharge - suspended solid data set that has been measured by NIER Nakdong River Water Environment Laboratory. As a result, SL shows negative bias for most values of the measured discharge range. QMLE is nearly unbiased for moderate values of the measured discharge range, but shows increasingly positive bias for either large or small value of the measured discharge range. MVUE is unbiased. It is also analyzed how the estimated regression coefficient and exponent are distributed along Nakdong river main stream.