• International Journal of Human Ecology
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• 제4권2호
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• pp.77-87
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• 2003

This paper tried to construct statistical and econometric models on the basis of economic theory in order to discuss the issue of statistical efficiency and unbiasedness including the sample selection bias correcting problem. Comparative analytical tool were one stage Tobit of Maximum Likelihood estimation and Heckman's two-step Tobit of Ordinary Least Squares. The results showed that the adequacy of model for the analysis on demand and choice, we believe that there is no big difference in explanatory variables between the first selection model and the second linear probability model. Since the Lambda, the self- selectivity correction factor, in the Type II Tobit is not statistically significant, there is no self-selectivity in the Type II Tobit model, indicating that Type I Tobit model would give us better explanation in the demand for and choice which is less complicated statistical method rather than type II model.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 1998년도 하계종합학술대회논문집
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• pp.465-468
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• 1998

For porous silicon layer to be used as active layer in various devices, it is necessary to be formed locally along with a designed pattern on the wafer. However, there is still no suitable masking layer to withstand against the high concentration of HF for a time of some minutes up to some hours during the anodic process effectively. In this work, we investigated the property of selectivity between p$^{+}$ and n layers to form localized porous silicon even without a mask by the difference of the anodic I-V characteristics on the doping level and doping type. The width of the pattern made in the sample was 2mm, and the formed porous silicon layer was observed by SEM to see the morphology on the cross section below the surface. As the results, it was found that the selectivity was reasonable for the pattern size over 100.mu.m.m.

• 말소리와 음성과학
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• 제6권2호
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• pp.65-71
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• 2014

The purpose of this study was to investigate whether young children with cleft palate differ from those of noncleft typically developing children in terms of expressive vocabulary size, phonological characteristics and lexical selectivity. A total of 12 children with cleft palate and 12 noncleft children who were matched by age and gender participated in the study. The groups were compared by size of expressive vocabulary reported on Korean version of MacArthur-Bates Communicative Development Inventories and the number of different words, consonant inventory, the percentage of words beginning with obstruents and vowels, nasal, and glottal sounds, and the percentage of words which do not include obstruents in a language sample. Also, correlation analysis were performed to examine the relationship between measures on size of expressive vocabulary and phonological characteristics. The results showed that expressive vocabulary size and consonant inventory for children with cleft palate produced significantly smaller than those for noncleft children. Children with cleft palate produced significantly more words beginning with vowel or which do not include obstruents, and fewer words beginning with obstruents than noncleft children. The two groups showed different results on significant correlations between measures on size of expressive vocabulary and phonological characteristics indicating that children with cleft palate show different lexical selectivity from their noncleft peers. The results suggest that children with cleft palate aged 18-30 months demonstrate a slower rate of lexical and phonological development compared with their noncleft peers and they develop lexical selectivity reflecting cleft palate speech. The results will have a clinical implication on speech-language intervention for young children with cleft palates.

• 한국연초학회지
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• 제29권2호
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• pp.132-139
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• 2007

This study was performed to apply the more rapid and accurate sample preparation, and the high selectivity and sensitivity of the analyte detection by gas chromatography-triple quadrupole mass spectrometry (GC-MS/MS). QuEChERS (quick, easy, cheap, effective, rugged and safe) method was validated for 49 agrochemicals in the CORESTA Agrochemical Advisory Committee guide and amenable to GC-MS/MS determination. In QuEChERS method, the effects of sorbents (PSA, $C_{18}$ and GCB) and matrix of the analytes in tobacco types (flue-cured, burley and oriental) were investigated. MS/MS acquisition provided high specificity and selectivity for agrochemicals and low limit of quantification. QuEChERS by using PSA alone and the matrix-matched standards gave good recoveries and RSD values in three types of tobaccos. QuEChERS method was no needed to be complex clean-up procedure and would be used as the fast and easy method for agrochemical residue analysis in tobacco.

• 한국독성학회:학술대회논문집
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• 한국독성학회 2006년도 추계학술대회
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• pp.65-74
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• 2006

Modem drug discovery requires rapid pharmacokinetic evaluation of chemically diverse compounds for early candidate selection. This demands the development of analytical methods that offer high-throughput of samples. Naturally, liquid chromatography / tandem mass spectrometry (LC-MS/MS) is choice of the analytical method because of its superior sensitivity and selectivity. As a result of the short analysis time(typically 3-5min) by LC-MS/MS, sample preparation has become the rate- determining step in the whole analytical cycle. Consequently tremendous efforts are being made to speed up and automate this step. In a typical automated 96-well SPE(solid-phase extraction) procedure, plasma samples are transferred to the 96-well SPE plate, internal standard and aqueous buffer solutions are added and then vacuum is applied using the robotic liquid handling system. It takes only 20-90 min to process 96 samples by automated SPE and the analyst is physically occupied for only approximately 10 min. Recently, the ultra-high flow rate liquid chromatography (turbulent-flow chromatography)has sparked a huge interest for rapid and direct quantitation of drugs in plasma. There is no sample preparation except for sample aliquotting, internal standard addition and centrifugation. This type of analysis is achieved by using a small diameter column with a large particle size(30-5O ${\mu}$m) and a high flow rate, typically between 3-5 ml/min. Silica-based monolithic HPLC columns contain a novel chromatographic support in which the traditional particulate packing has been replaced with a single, continuous network (monolith) of pcrous silica. The main advantage of such a network is decreased backpressure due to macropores (2 ${\mu}$m) throughout the network. This allows high flow rates, and hence fast analyses that are unattainable with traditional particulate columns. The reduction of particle diameter in HPLC results in increased column efficiency. use of small particles (<2 urn), however, requires p.essu.es beyond the traditional 6,000 psi of conventional pumping devices. Instrumental development in recent years has resulted in pumping devices capable of handling the requirements of columns packed with small particles. The staggered parallel HPLC system consists of four fully independent binary HPLC pumps, a modified auto sampler, and a series of switching and selector valves all controlled by a single computer program. The system improves sample throughput without sacrificing chromatographic separation or data quality. Sample throughput can be increased nearly four-fold without requiring significant changes in current analytical procedures. The process of Bioanalytical Method Validation is required by the FDA to assess and verify the performance of a chronlatographic method prior to its application in sample analysis. The validation should address the selectivity, linearity, accuracy, precision and stability of the method. This presentation will provide all overview of the work required to accomplish a full validation and show how a chromatographic method is suitable for toxirokinetic sample analysis. A liquid chromatography/tandem mass spectrometry (LC-MS/MS) method developed to quantitate drug levels in dog plasma will be used as an example of tile process.

• 산업식품공학
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• 제21권3호
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• pp.191-200
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• 2017

There have been great efforts to develop a rapid and sensitive detection method to monitor the presence of pathogenic bacteria in food. While a number of methods have been reported for bacterial detection with a detection limit to a single digit, most of them are suitable only for the bacteria in pure culture or buffered solution. On the other hand, foods are composed of highly complicated matrices containing carbohydrate, fat, protein, fibers, and many other components whose composition varies from one food to the other. Furthermore, many components in food interfere with the downstream detection process, which significantly affect the sensitivity and selectivity of the detection. Therefore, isolating and concentrating the target pathogenic bacteria from food matrices are of importance to enhance the detection power of the system. The present review provides an introduction to the representative sample preparation strategies to isolate target pathogenic bacteria from food sample. We further describe the nucleic acid-based detection methods, such as PCR, real-time PCR, NASBA, RCA, LCR, and LAMP. Nucleic acid-based methods are by far the most sensitive and effective for the detection of a low number of target pathogens whose performance is greatly improved by combining with the sample preparation methods.

• Journal of Radiation Protection and Research
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• 제24권1호
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• pp.9-15
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• 1999

칼슘을 함유한 방사성 환경시료 용액으로부터 스트론튬을 분리하기 위한 방법으로 함침형 액막을 제조하여 그 분리특성을 고찰하였다. 운반체로 사용된 DC18C6과 DNNS의 농도에 따라 금속이온 투과도와 스트론튬 선택도에 영향을 미쳤으며, 특히 0.1M DC18C6과 25mM DNNS을 함침시켜 제조한 액막의 경우에서 93.3%의 스트론튬 선택도를 얻을 수 있었다. 모의용액의 스트론튬에 대한 칼슘의 함량비가 1 : 25 - 1 : 50일 때 스트론튬 선택성이 90% 이상으로 나타났으며, 따라서 본 연구에서 제조한 액막은 스트론튬 측정을 위한 해수 환경시료의 전처리에 적용 가능할 것으로 생각된다.

• 한국정보과학회논문지:데이타베이스
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• 제30권5호
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• pp.464-475
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• 2003

웹상의 이미지 데이타베이스들은 자치성과 이질성이라는 두 가지 다른 특성을 갖고 있다. 즉 독립적으로 만들어지고 유지되며 질의 처리 방법이 서로 다르다. 분산된 이미지 데이타베이스들에 대한 내용기반 검색에서, 메타 서버의 유사성 측정함수에 대하여 서로 다른 지역 유사성 측정 함수를 갖는 데이터베이스들로부터 주어진 질의 객체와 유사한 객체들을 찾는 능력을 갖는 것은 중요하다. 현재까지, 동일한 유사성 측정 함수들을 사용하는 이미지 데이타베이스들을 선택하는 방법에 대하여 많은 연구가 진행되었으나 이미지 데이타베이스들이 다른 유사성 측정함수를 사용하는 경우에 대한 연구는 없었다. 본 논문에서는 웹상의 많은 이질적인 이미지 데이타베이스들 중 질의에 유사한 객체들을 보다 많이 가지고 있는 데이타베이스들을 찾는 문제를 다룬다. 데이타베이스들의 순위는 이미지 데이타베이스들의 압축된 히스토그램 정보와 적은 수의 표본 객체들을 사용하는 복합 추정에 기반을 두고 있다. 구형 영역 질의에 대한 선택률을 추정하기 위하여 히스토그램 정보를 사용하며, 유사성 측정 함수의 차이로 인한 선택률 오차를 보정하기 위하여 표본 객체들을 이용한다. 많은 수의 이미지 데이타에 대한 상세한 실험은 제안된 방법이 이질적인 분산 환경에서 효율적임을 보여준다.

• Applied Microscopy
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• 제32권4호
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• pp.311-317
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• 2002

입자 크기에 따라 상전이 경로가 달라지며 매우 큰 응집체로 존재하는 gibbsite 분말과 같은 재료의 정량적인 전이 구조 분석의 전제로서 입자 크기가 선택적인 TEM 시편의 준비가 절실히 요구된다. 입자 크기 선택성을 실현한 TEM 시편 준비의 방법론을 확립하기 위한 방안으로서 본 실험이 전개되었다. 약 1 wt%의 gibbsite 원료 분말을 에탄올 용매에 혼합 한 뒤, ball-milling에 의해 조분쇄 처리를 하고 증류수에 1 : 19의 비로 희석된 분산 조제, Darvan C, 0.25 vol%의 첨가와 함께 ultrasonic 처리를 하여 gibbsite suspension을 만들었다. 제조된 gibbsite suspension의 누적 농도 변화 관찰에 의한 침강 시간의 조정 후 정적 침강 분리에 의해 nm 크기별로 분리된 TEM 시편을 만들 수가 있었다. 시편의 전체적인 양상은 SEM으로 관찰하였고 개개 입자들의 morphology 는 TEM으로 분석하였다. 또한, 공정 과정 중의 상변화 가능성을 검토하기 위해 XRD 분석을 실시하였다.

• 노동경제논집
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• 제26권3호
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• pp.77-114
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• 2003

본 연구에서는 National Longitudinal Survey of Youth와 Panel Study of Income Dynamics 표본으로부터 구축된 특별한 형태의 데이터에 근거하여 노동시장이 과연 분단되어 있는가를 검증한다. 분석 결과 대부분의 기존 연구들이 사용하여 왔던 조사 시점에서 추출된 임금률은 장기근속자들을 선택하는 성향으로 말미암아 경기역행적인 방향으로 편의를 보이고 있으며, 이 경기역행적 선택성(countercyclical selectivity)은 저임금 산업보다는 고임금 산업에서 더 크게 나타난다. 이러한 선택성 문제를 통제하고 추정한 결과 기존 연구 결과와는 달리 실질임금은 저임금 산업보다 고임금 산업에서 훨씬 더 경기순응적(procyclical)으로 움직임이 밝혀진다. 현 연구 결과는 실질임금이 여성보다는 남성에게 있어서 훨씬 더 경기순응적이라는 기존의 연구결과들과 일치한다. 그것은 여성과 비교하여 남성은 내구재 제조업, 건설업 등 경기순응성이 높은 고임금 산업에 과다분포(over-represented)되어 있는 반면 남성과 비교하여 여성은 소매업, 서비스업 등 경기변동에 덜 민감한 저임금 산업에 과다분포되어 있기 때문이다. 보다 중요하게는 현 연구 결과는 실질임금이 이차부문에서는 상당히 경기순응적인 데에 반해 일차부문에서는 다소 경직적이라는 분단노동시장 가설들의 공통적인 예측을 기각한다.