• JSTS:Journal of Semiconductor Technology and Science
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• 제15권2호
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• pp.184-193
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• 2015

This paper proposes a cost-efficient and automatic method for large data acquisition from a test chip without expensive equipment to characterize random process variation in an integrated circuit. Our method requires only a test chip, a personal computer, a cheap digital-to-analog converter, a controller and multimeters, and thus large volume measurement can be performed on an office desk at low cost. To demonstrate the proposed method, we designed a test chip with a current model logic driver and an array of 128 current mirrors that mimic the random process variation of the driver's tail current mirror. Using our method, we characterized the random process variation of the driver's voltage due to the random process variation on the driver's tail current mirror from large volume measurement data. The statistical characteristics of the driver's output voltage calculated from the measured data are compared with Monte Carlo simulation. The difference between the measured and the simulated averages and standard deviations are less than 20% showing that we can easily characterize the random process variation at low cost by using our cost-efficient automatic large data acquisition method.

• Smart Structures and Systems
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• 제21권5호
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• pp.591-600
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• 2018

The probabilistic characterization of wind field characteristics is a significant task for fatigue reliability assessment of long-span railway bridges in wind-prone regions. In consideration of the effect of wind direction, the stochastic properties of wind field should be represented by a bivariate statistical model of wind speed and direction. This paper presents the construction of the bivariate model of wind speed and direction at the site of a railway arch bridge by use of the long-term structural health monitoring (SHM) data. The wind characteristics are derived by analyzing the real-time wind monitoring data, such as the mean wind speed and direction, turbulence intensity, turbulence integral scale, and power spectral density. A sequential quadratic programming (SQP) algorithm-based finite mixture modeling method is proposed to formulate the joint distribution model of wind speed and direction. For the probability density function (PDF) of wind speed, a double-parameter Weibull distribution function is utilized, and a von Mises distribution function is applied to represent the PDF of wind direction. The SQP algorithm with multi-start points is used to estimate the parameters in the bivariate model, namely Weibull-von Mises mixture model. One-year wind monitoring data are selected to validate the effectiveness of the proposed modeling method. The optimal model is jointly evaluated by the Bayesian information criterion (BIC) and coefficient of determination, $R^2$. The obtained results indicate that the proposed SQP algorithm-based finite mixture modeling method can effectively establish the bivariate model of wind speed and direction. The established bivariate model of wind speed and direction will facilitate the wind-induced fatigue reliability assessment of long-span bridges.

• 한국정보전자통신기술학회논문지
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• 제8권6호
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• pp.483-490
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• 2015

소프트웨어의 디버깅과정에서 오류 발생의 시간을 기반으로 하는 많은 소프트웨어 신뢰성 모델이 제안되어 왔다. 무한고장 모형과 비동질적인 포아송 과정에 의존한 소프트웨어 신뢰성 모형을 이용하면 모수 추정이 가능하다. 소프트웨어를 시장에 인도하는 결정을 내리기 위해서는 조건부 고장률이 중요한 변수가 된다. 무한 고장 모형은 실제 상황에서 다양한 분야에 사용된다. 특성화 문제, 특이점의 감지, 선형 추정, 시스템의 안정성 연구, 수명을 테스트, 생존 분석, 데이터 압축 및 기타 여러 분야에서의 사용이 점점 많아지고 있다. 통계적 공정 관리 (SPC)는 소프트웨어 고장의 예측을 모니터링 함으로써 소프트웨어 신뢰성의 향상에 크게 기여 할 수 있다. 컨트롤 차트는 널리 소프트웨어 산업의 소프트웨어 공정 관리에 사용되는 도구이다. 본 논문에서 NHPP에 근원을 둔 로그 포아송 실행시간 모형, 즉,Musa-Okumo 모형과 파우어 로우(Power-law) 모형의 평균값 함수를 이용한 통계적 공정관리 차트를 이용한 제어 메커니즘을 제안하였다.

• Membrane and Water Treatment
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• 제7권3호
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• pp.223-240
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• 2016

In this study, poly(vinyl-alcohol) and water insoluble ${\beta}$-cyclodextrin polymer (${\beta}$-CDP) cross-linked with citric acid, have been used as macrocyclic carrier in the preparation of polymer inclusion membranes (PIMs) for aniline (as molecule model) extraction from aqueous media. The obtained membranes were firstly characterized by X-ray diffraction, Fourier transform infrared and water swelling test. The transport of aniline was studied in a two-compartment transport cell under various experimental conditions, such as carrier content in the membranes, stirring rate and initial aniline concentration. The kinetic study was performed and the kinetic parameters were calculated as rate constant (k), permeability coefficient (P) and flux (J). These first results demonstrated the utility of such polymeric membranes for environmental decontamination of toxic organic molecules like aniline. Predictive modeling of transport flux through these materials was then studied using design of experiments; the design chosen was a two level full factorial design $2^k$. An empirical correlation between aniline transport flux and independent variables (Poly ${\beta}$-CD membrane content, agitation speed and initial aniline concentration) was successfully obtained. Statistical analysis showed that initial aniline concentration of the solution was the most important parameter in the study domain. The model revealed the existence of a strong interaction between the Poly ${\beta}$-CD membrane content and the stirring speed of the source solution. The good agreement between the model and the experimental transport data confirms the model's validity.

• 한방재활의학과학회지
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• 제32권1호
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• pp.63-72
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• 2022

Objectives This study was conducted to characterize scoliosis patients visiting Korean medicine hospital and to analyze the demands and factors affecting discomfort. Methods This retrospective study analyzed 33 scoliosis patients who visited Korean medicine hospital from March, 2021 to October, 2021. The data analysis consisted of three factors: (1) demographic characteristics, (2) characteristics of demands on Korean medicine (reasons for choosing Korean medical treatment, preferred treatment methods, most uncomfortable part, treatment priorities) and (3) discomfort factors (treatment experiences, diagnosed age and Cobb's angle). Statistical analyses were performed and a p-value≤0.05 was considered to be statistically significant. Results 43.75% of the patients chose 'effectiveness' for the reason why they preferred Korean medicine treatment. 'Chuna treatment' was the most preferred treatment method. The patients chose 'lower back' for the most uncomfortable part and 'pain' for the highest priority of improvement. The Cobb's angle of included patients was 16.02±7.65° and it is not much differ to average of Cobb's angle in Korean. Discomfort was more severe in the patients with treatment-experienced than treatment-naive. The score of discomfort in appearance and psychological were higher in the patients diagnosed in childhood or adolescent period than who were diagnosed after adult. Classification based on Cobb's angle showed no statistical difference. Conclusions Not only Cobb's angle but also other clinical factors should be considered for effective treatment in scoliosis. Also, It is necessary to pay attention to adult scoliosis patients.

• 미생물학회지
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• 제51권1호
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• pp.48-60
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• 2015

순창군에서 제조된 전통 장류로부터 612종의 다양한 미생물을 분리하였고, 612종의 미생물 중에서 생리활성 분석 및 biogenic amine 생성여부를 조사하여 최종적으로 Bacillus subtilis SCJ4를 선별하였다. 최종 선별한 균주 SCJ4의 생화학적 특성과 16S rRNA 염기서열 분석에 의해 B. subtilis SCJ4로 명명하였으며, B. subtilis SCJ4의 산업적으로 사용이 적합한 최적배지조성을 확립하기 위하여 통계학적 방법인 반응표면 분석법을 사용하였다. 실험계획법은 배지조성을 예측하기 위해 Plackett-Burman design을 사용하여 모델을 설정하였다. 실험 모델을 통하여 선별된 배지 조성으로는 tryptone, peptone, $MgSO_4$로 예측되었으며, 배지조성에 대한 농도를 설정하기 위해 중심합성계획법을 사용하여 최적화를 수행하였다. 최종 예측된 배지 조성의 농도는 tryptone 15.35 g/L, peptone 12.235 g/L, $MgSO_4$ 3.5 g/L로 예측되었다. 이때 최대 균체량은 1.07497 g/L로 예측되었으며, 모델의 검증실험을 통하여 예측된 모델과 실제 결과가 동일함을 확인하였으며, 기본배양배지와 비교하였을 때 균체량이 0.8767 g/L에서 1.1222 g/L으로 약 28%증가하였다.

• 환경영향평가
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• 제4권3호
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• pp.1-8
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• 1995

In generally speaking, the purpose of Environmental Impact Assessment(EIA) is to give the environment its due place in the decision-making process by clearly ealuating the environmental consequence of a proposed activity before action is taken. The introduction of conventional EIA is to be seen as an end product of a very long evolutionary process, starting with rudimentary but evolving pollution control measures for air, water, noise, land and chemicals, each governed by separate, and separately administered pieces of legislation. In EIA process, the measures of status, scoping, proposed mitigation and communication have not been very quantitative in their significancy. Of course, the determinations have uncertainity in the implications for significant impacts. To improve the determination of significant impacts, some more comprehensive methodologies of EIA has been proposed with the concepts of risk analysis in the proposed projects. The concepts of risk analysis has been introduced to the expression of human health impairment due to environmental pollutants since the early 1980's. The risk analysis being meant by the statistical significance of impact has a process quantitatively considering uncertainities and importances of ecological systems and human health as well. The process of risk analysis shows assessment, doseresponse in toxicity, exposure assessment and risk characterization. With the risk assessment, it could be suggested for the proper measurements against their anticipated risk in the EIA. This paper deals the priciples developing process and application of the risk-based analysis in EIA.

• 대한안전경영과학회지
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• 제15권4호
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• pp.145-152
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• 2013

The purpose of this study was to investigate the effect of risk awareness on injury experience in quick delivery service workers. Risk awareness has complicate characteristics such as its level of worker and worker's decision about the level of other's risk perception. Data were collected by interview survey with structured questionnaire about injury experience, risk perception, work characteristics, and socio-demographic characteristics of quick delivery service workers by cross sectional survey design in 2012. The sample size was 120 respondent of quick delivery service workers. Statistical method for this study was hierarchical logistic regression method with 3 different models using socio-demographic characteristics and work characteristics and risk perception, etc. The difference between the level of risk perception of quick delivery service and other's was statistically significant effect on the experience of injury. Especially the higher the level of risk perception of quick delivery service workers is than other's, the lower the injury experience of quick delivery service worker is. The limitation of this study can be found in survey design. The future study for investigation of mechanism of the combined effect of risk perception of quick delivery service workers and others on injury experience.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2012년도 제43회 하계 정기 학술대회 초록집
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• pp.362-362
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• 2012

Graphene-based materials have been gaining the unprecedented academic and industrial applications, due to the unique charge transport as a new kind of 2-dimensional materials. The applications incorporate electronic devices, nonvolatile memories, batteries, chemical sensors, etc. based on the electrical, mechanical, structural, optical, and chemical features newly reported. The current work employs thermal chemical vapor deposition involving H2 and CH4, in order to synthesize the 2-dimensional graphene materials. The qualitative/quantitative characterizations of the synthesized graphene materials are evaluated using Raman spectroscopy and Hall Measurements, In particular, the effect of processing variables is systematically investigated on the formation of graphene materials through statistical design of experiments. The optimized graphene materials will be attempted towards the potential applications to flat-panel displays.

• 대한화학회지
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• 제51권2호
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• pp.115-124
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• 2007

α, β-불포화 케톤 유도체를 실리카-황산 촉매 하에서 비용매 교차 알돌 응축 반응법을 이용하여 합성하였다. 합성 수율은 90% 이상이었으며, 사용된 촉매는 회수 가능하였다. 합성돤 화합물들의 물리화학적인 특성은 IR, NMR, Mass 등의 분광학적 분석 방법을 이용하여 결정하였다. 케톤 생성물에 미치는 치환기 효과는 측정된 분광 데이터와 Hammet 치환기 상수간의 상관관계로 표현되는 다중 상관계수 방정식에 의하여 잘 설명될 수 있었다.