• Proceedings of the Korean Vacuum Society Conference
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• 2012.02a
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• pp.233-233
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• 2012

나노입자가 가지는 고유한 특성이 부각되면서 이를 소자 특성 향상에 응용하고자 하는 연구가 집중적으로 이루어지고 있다. 박막에 포함된 나노입자는 메모리, 고효율 박막형 태양전지 등에 이용될 수 있는 가능성을 보여주었으며, 나노입자에 기반 하는 소자 제조에 관한 연구가 이루어지면서 플라즈마 내 발생하는 나노입자를 이용하여 패터닝 등에 적용하고자 하는 연구가 국내외에서 활발히 이루어지고 있다. 특히 플라즈마에서 발생하는 나노입자는 플라즈마 내 전기적 및 화학적 특징으로 인해 다른 입자 제조 공정과 달리 응집이 없는 균일한 입자를 제조할 수 있다. 이러한 플라즈마 내 발생 입자를 응용하기 위해서는 각각의 응용 분야에 적합한 입경 분포 제어가 요구된다. 하지만 입자 합성 시 크기분포 특성에 관한 연구는 기존의 포집 및 전자현미경을 이용한 방법으로 실시간으로 분석하기에는 한계가 있다. 따라서 본 연구에서는 저압에서 실시간으로 나노입자 분포를 측정할 수 있는 PBMS (particle beam mass spectrometer)를 이용하여, PECVD (plasma enhanced chemical vapor deposition)의 입자 생성 조건에 따라 continuous, pulse, dual pulse로 분류되는 공정 조건에서 생성되는 입자의 크기 분포를 측정하였다. 또한 그 결과를 기존의 동일한 조건에서 포집 후 SMPS (scanning mobility particle sizer)와 전자 현미경을 이용하여 분석한 결과와 비교하였다. 실리콘 나노 입자의 측정은 PBMS 장비의 전단 부분을 PECVD 장치 내부에 연결하여 진행하였다. PECVD를 이용한 실리콘 나노입자 형성의 주요 변수는 RF pulse, 가스(Ar, SiH4, H2)의 유량, Plasma power, 공정 압력 등이 있으며 각 변수를 조절하여 공정 환경을 구성하였다. 결론적으로 본 연구를 통하여 PECVD를 이용해 각각의 공정 환경에서 생성되는 실리콘 나노입자의 실시간 입경 분포 분석을 PBMS로 수행하는 것에 신뢰성이 있음을 알 수 있었으며, 그 경향을 확인할 수 있었다. 추후 지속적 연구에 의해 변수에 따른 나노입자 생성을 데이터베이스화 하여 요구되는 응용분야에 적합한 특성을 가지는 나노입자를 형성하는 조건을 정립 하는데 중요한 역할을 할 것을 기대할 수 있다.

• Journal of the Korea institute for structural maintenance and inspection
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• v.18 no.2
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• pp.47-53
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• 2014

The paper investigates the limit state of deflection for short and medium span steel girder bridges. Deflection depends on stiffness of steel girders and integrity of the reinforced concrete slab (composite action). Load and resistance parameters are treated as random variables. A probabilistic model is developed for prediction of the deflection. The structural performance can be affected by deterioration of components, in particular corrosion of steel girders. In addition, the creep of concrete can greatly influence the deflection of composite structures. Therefore, the statistical models for creep and corrosion of structural steel are incorporated in the model. Structures designed according to the AASHTO LRFD Code are considered. Load and resistance models are developed to account for time-variability of the parameters. Monte Carlo simulations are used to estimate the deflections and probabilities of serviceability failure. Different span lengths and girder spacing are considered for structures designed as moment-controlled and deflection-controlled. A summary of obtained results is presented.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2021.05a
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• pp.35-37
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• 2021

Analyzing and predicting foreign tourists' demand is a crucial research topic in the tourism industry because it profoundly influences establishing and planning tourism policies. Since foreign tourist data is influenced by various external factors, it has a characteristic that there are many subtle changes over time. Therefore, in recent years, research is being conducted to design a prediction model by reflecting various external factors such as economic variables to predict the demand for tourists inbound. However, the regression analysis model and the recurrent neural network model, mainly used for time series prediction, did not show good performance in time series prediction reflecting various variables. Therefore, we design a foreign tourist demand prediction model that complements these limitations using a convolutional neural network. In this paper, we propose a model that predicts foreign tourists' demand by designing a one-dimensional convolutional neural network that reflects foreign tourist data for the past ten years provided by the Korea Tourism Organization and additionally collected external factors as input variables.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.19 no.2 s.72
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• pp.203-212
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• 2006

Although composite construction has many mechanical advantages over noncomposite construction, the design of noncomposite construction for skew bridges with large skew angels has been often checked because composite construction caused large stresses in the bridge deck. But there is somewhat difficulty to apply noncomposite construction in the field because of the structural problem such as the slip at the interface between the concrete deck and steel girders. In this study, the validity of the application of the composite construction to skew angles with large skew angles is investigated by analyzing effects of two interactions such as composite and noncomposite actions between the concrete deck and steel girders on the behavior of skew bridges. A series of parametric studies for the total 27 simply supported skew bridges was conducted with respect to parameters such as girder spacing, skew angle, and deck aspect ratio. The improvement of the behavior of composite skew bridges was examined by using the concept of the stiffness adjustment of bearings which I suggested in previous research. Results of analyses show that a more desirable behavior of skew bridges can be obtained from composite construction instead of noncomposite construction and the method of the stiffness adjustment of bearings results in a more rational and economical design of composite skew bridges and substructures.

• Journal of Intelligence and Information Systems
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• v.16 no.4
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• pp.67-84
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• 2010

In terms of business, forecasting is a work of what is expected to happen in the future to make managerial decisions and plans. Therefore, the accurate forecasting is very important for major managerial decision making and is the basis for making various strategies of business. But it is very difficult to make an unbiased and consistent estimate because of uncertainty and complexity in the future business environment. That is why we should use scientific forecasting model to support business decision making, and make an effort to minimize the model's forecasting error which is difference between observation and estimator. Nevertheless, minimizing the error is not an easy task. Case-based reasoning is a problem solving method that utilizes the past similar case to solve the current problem. To build the successful case-based reasoning models, retrieving the case not only the most similar case but also the most relevant case is very important. To retrieve the similar and relevant case from past cases, the measurement of similarities between cases is an important key factor. Especially, if the cases contain symbolic data, it is more difficult to measure the distances. The purpose of this study is to improve the forecasting accuracy of case-based reasoning approach using fuzzy relation and composition. Especially, two methods are adopted to measure the similarity between cases containing symbolic data. One is to deduct the similarity matrix following binary logic(the judgment of sameness between two symbolic data), the other is to deduct the similarity matrix following fuzzy relation and composition. This study is conducted in the following order; data gathering and preprocessing, model building and analysis, validation analysis, conclusion. First, in the progress of data gathering and preprocessing we collect data set including categorical dependent variables. Also, the data set gathered is cross-section data and independent variables of the data set include several qualitative variables expressed symbolic data. The research data consists of many financial ratios and the corresponding bond ratings of Korean companies. The ratings we employ in this study cover all bonds rated by one of the bond rating agencies in Korea. Our total sample includes 1,816 companies whose commercial papers have been rated in the period 1997~2000. Credit grades are defined as outputs and classified into 5 rating categories(A1, A2, A3, B, C) according to credit levels. Second, in the progress of model building and analysis we deduct the similarity matrix following binary logic and fuzzy composition to measure the similarity between cases containing symbolic data. In this process, the used types of fuzzy composition are max-min, max-product, max-average. And then, the analysis is carried out by case-based reasoning approach with the deducted similarity matrix. Third, in the progress of validation analysis we verify the validation of model through McNemar test based on hit ratio. Finally, we draw a conclusion from the study. As a result, the similarity measuring method using fuzzy relation and composition shows good forecasting performance compared to the similarity measuring method using binary logic for similarity measurement between two symbolic data. But the results of the analysis are not statistically significant in forecasting performance among the types of fuzzy composition. The contributions of this study are as follows. We propose another methodology that fuzzy relation and fuzzy composition could be applied for the similarity measurement between two symbolic data. That is the most important factor to build case-based reasoning model.

• Proceedings of the Korea Water Resources Association Conference
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• 1991.07a
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• pp.88-101
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• 1991

충주댐 및 소양강댐 유역에 대해 현재 한국수자원공사에서 개발 사용되고 있는 저류함수 유출모형에 최적화 기법을 적용하여 모형을 효율적으로 자동보정 하기위함이 본 연구의 목적이다. 최적화 기법으로는 다양한 조건하에서도 해의 안정성이 Gradient-Based 방법보다 우수한 직접 탐색법(Direct Search Method)의 하나인 Pattern-Search법으로 선정하였으며 목적함수로는 산정된 유출과 관측치의 편차의 제곱에 대한 누계치로 정의하였다. 합성유입량(Synthetic Inflow)을 이용한 민감도 분석에 의해 매개변수 5개(유역 저류상수 및 지체시간, 포화우량, 하도의 지체시간)를 결정변수로 선정하였다. 또한 실시간 모형의 보정을 위하여 최적화 모형의 수렴조건을 분석한 결과 P-S 법의 증분 감소횟수 2회가 합리적으로 나타났다. 본 모형을 충주댐 및 소양강댐의 과거 홍수사상에 대해 적용하였으며 댐지점에서 전체유역을 일괄 보정하는 방법과 댐 상류 수위국을 기준으로 나눈 중유역별로 일괄 보정하는 방법을 채택하여 분석하였다. 실시간 보정된 모형의 예측기능을 시험한 결과 상당한 오차발생의 여지가 충분하며 중유역별 매개변수의 보정은 대유역 일괄보정에 비해 예측에 따른 오차를 줄일 수 있는 방법의 하나이다. 또한 최적화 기법에 의한 매개변수의 자동 보정은 시행착오에 의한 수동보정의 경우보다 시간 및 노력면에서 효율적이며 보다 신뢰성 있는 보정을 실시 할 수 있다.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.23 no.8
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• pp.2113-2119
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• 1998

The optimization problem of BDDs plays an improtant role in the area of logic synthesis and formal verification. Since the variable ordering has great impacts on the size and form of BDD, finding a good variable order is very important problem. In this paper, a new variable ordering scheme called incremental optimization algorithm is presented. The proposed algorithm reduces search space more than a half of that of the conventional sifting algorithm, and computing time has been greatly reduced withoug depreciating the performance. Moreover, the incremental optimization algorithm is very simple than other variable reordering algorithms including the sifting algorithm. The proposed algorithm has been implemented and the efficiency has been show using may benchmark circuits.

• Journal of Korean Society of Steel Construction
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• v.24 no.5
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• pp.521-534
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• 2012

In this research, we carry this study into effect on the basis of utilizing character of composite beam and developing applicable section to some of high strength steel. We evaluated flexural capacity of composite beam that is a unit member through experiments. The existing nominal strength formula of Composite Beam which is a previous method was reviewed and the experiment had been progressive by using each composite members as main variables though the result. Capacity evaluation of U-shape Hybrid Forming Beam(HyFo Beam) which is a new shape show as follow from the result. First, it is resonable to resist demand moment by couple moments which are occurred in concrete compressive-strength and steel tensile-strength. Second, the capacity was stably increased in proportion to the depth of beams and the thickness of steel plates. The last, HyFo Beam was showed as ductile behavior.

• Journal of KIISE
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• v.44 no.9
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• pp.986-991
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• 2017

In this paper, we present a method for synthesizing imperative programs from input-output examples. Given (1) a set of input-output examples, (2) an incomplete program, and (3) variables and integer constants to be used, the synthesizer outputs a complete program that satisfies all of the given examples. The basic synthesis algorithm enumerates all possible candidate programs until the solution program is found (enumerative search). However, it is too slow for practical use due to the huge search space. To accelerate the search speed, our approach uses code optimization and avoids unnecessary search for the programs that are syntactically different but semantically equivalent. We have evaluated our synthesis algorithm on 20 introductory programming problems, and the results show that our method improves the speed of the basic algorithm by 10x on average.

• Journal of the Korea Concrete Institute
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• v.27 no.5
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• pp.501-510
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• 2015

Composite construction of precast concrete and cast-in-place concrete is currently used for the modular construction. In this case, the use of steel fiber reinforced concrete (SFRC) could be beneficial for precast concrete. However, the shear strength of such composite members (SFRC and cast-in-place concrete) is not clearly defined in current design codes. In the present study, steel fiber composite beam tests were conducted to evaluate the effect of steel fibers on the composite members. The test variables are the area ratio of SFRC and shear reinforcement ratio. The test results showed that when minimum horizontal shear reinforcement was used, the shear strength of composite beams increased in proportion to the area ratio of steel fiber reinforced concrete. However, because of the steel fiber, the composite beams were susceptible to horizontal shear failure. Thus, minimum horizontal shear reinforcement is required for SFRC composite beams.