• 대한기계학회논문집
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• 제19권7호
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• pp.1709-1719
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• 1995

The primary objective of the paper is to obtain the basic information of the natural convection of a stratified with various parametric conditions related to rotating speed, temperature and concentration gradient. For the purpose of it, experiments are performed in a stably stratified salt-water solution with lateral heating in a stationary or rotating annulus. The experiment covers the ranges of Ar=2, Le=100, R $a_{\ta}$=2 10$^{5}$ and Ta=0, 10$^{5}$ - 2.5*10$^{8}$ . Many interesting flow phenomena are observed and rotation effects are examined. Particularly as Taylor number increases (rotation increases) at a given R $a_{\ta}$, the generation of rolls at hot wall is inhibited and the formation and merging process of layers are delayed.

• 한국경영과학회지
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• 제14권2호
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• pp.47-47
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• 1989

This paper considers the parallel machines scheduling problem characterized as a multi-objective combinatorial problem. As this problem belongs to the NP-complete problem, genetic algorithms are applied instead of the traditional analytical approach. The purpose of this study is to show how the problem can be effectively solved by using genetic algorithms with a permutation approach. First, a permutation representation which can effectively represent the chromosome is introduced for this problem . Next, a schedule builder which employs the combination of scheduling theories and a simple heuristic approach is suggested. Finally, through the computer experiments of genetic algorithm to test problems, we show that the niche formation method does not contribute to getting better solutions and that the PMX crossover operator is the best among the selected four recombination operators at least for our problem in terms of both the performance of the solution and the operational convenience.

• 한국원자력학회:학술대회논문집
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• 한국원자력학회 1997년도 추계학술발표회논문집(1)
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• pp.617-624
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• 1997

This Paper Presents an effective and simple procedure for the simulation of the motion of the solid-liquid interfacial boundary and the transient temperature field during phase change process. To accomplish this purpose, an iterative implicit solution algorithm has been developed by employing the dual reciprocity boundary element method. The dual reciprocity boundary element approach provided in this paper is much simpler than the usual boundary element method applying a reciprocity principle and an available technique for dealing with domain integral of boundary element formulation simultaneously. The effectiveness of the present analysis method have been illustrated through comparisons of the calculation results of an example with its semi-analytical or other numerical solutions where available.

• JSTS:Journal of Semiconductor Technology and Science
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• 제16권3호
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• pp.261-273
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• 2016

Reconfigurable finite impulse response (FIR) filters whose filter coefficients and filter order change dynamically during run-time play an important role in the software defined radio (SDR) systems, multi-channel filters, and digital up/down converters. However, there are not many reports on such reconfigurable designs which can support dynamic variation of filter order and filter coefficients. The purpose of this paper is to provide an architectural solution for the FIR filters to support run-time variation of the filter order and filter coefficients. First, two straightforward designs, namely, (i) single-MAC based design and (ii) full-parallel design are presented. For large variation of the filter order, two designs based on (iii) folded structure and (iv) fast FIR algorithm are presented. Finally, we propose (v) high throughput design which provides significant advantage in terms of hardware and/or time complexities over the other designs. We compare complexities of all the five structures, and provide the synthesis results for verification.

• 항공우주시스템공학회지
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• 제8권4호
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• pp.18-23
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• 2014

In preliminary design phase, the wing geometry of the civil aircraft was determined using the empirical equation and historical data. To make wing geometry more aerodynamically efficient, an aerodynamic shape optimization was conducted. For this purpose the parametric modeling, high fidelity CFD analysis and metamodel-based optimal design technique were adopted. The parametric modeling got the design process to achieve the improvement by generating the configuration outputs easily for the major design variables. The optimal design equations were formularized as the type of the multi-objective functions considering low/high speed and lift/drag coefficient. The optimal solution was explored with the help of the kriging metamodel and the desirability function, therefore the optimal wing planform was sought to be excellent at both low and high speed region. Additionally the optimal wing planform was validated that it was excellent not only at the specific AOA, but also all over the range of AOA.

• 충청수학회지
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• 제24권4호
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• pp.639-663
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• 2011

Motivated by Agarwal and O'Regan ( Boundary value problems for general discrete systems on infinite intervals, Comput. Math. Appl. 33(1997)85-99), this article deals with the discrete type BVP of the infinite difference equations. The sufficient conditions to guarantee the existence of at least three positive solutions are established. An example is presented to illustrate the main results. It is the purpose of this paper to show that the approach to get positive solutions of BVPs by using multi-fixed-point theorems can be extended to treat BVPs for infinite difference equations. The strong Caratheodory (S-Caratheodory) function is defined in this paper.

• 소성∙가공
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• 제30권4호
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• pp.186-194
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• 2021

Finite element simulation is a widely applied method for practical purpose in various metal forming process. However, in the simulation of elasto-plastic behavior of porous material or in crystal plasticity coupled multi-scale simulation, it requires much calculation time, which is a limitation in its application in practical situations. A machine learning model that directly outputs the constitutive equation without iterative calculations would greatly reduce the calculation time of the simulation. In this study, we examined the possibility of artificial intelligence based constitutive equation with the input of existing state variables and current velocity filed. To introduce the methodology, we described the process of obtaining the training data, machine learning process and the coupling of machine learning model with commercial software DEFROM^TM, as a preliminary study, via rigid plastic finite element simulation.

• 한국수자원학회논문집
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• 제38권9호
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• pp.737-746
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• 2005

최적화란 목적함수가 최대 또는 최소가 되도록 하는 결정변수를 찾아가는 절차이다. 기존의 많은 연구자들은 최적해의 효율적인 탐색과정에 집중한 반면 최적화의 시작점이라 할 수 있는 목적함수 구성을 위한 연구는 상대적으로 미진한 것이 사실이다. 따라서 본 연구에서는 국내외에서 빈번히 사용되고 있는 가중평균법을 사용하여 tradeoff를 고려한 목적함수와 절대우선순위를 위한 가중값을 적용한 목적함수를 구성하여 표본추계학적 동적계획법을 통해 산정한 최적운영률을 비교하였다. 그 결과 절대우선순위를 위한 가중값을 적용한 경우가 보다 실제 저수지운영과 부합하는 결과를 나타내는 것을 확인할 수 있었다. 따라서 국내 다목적댐 운영계획에 보다 적합한 목적함수를 구성하기 위해서는 절대우선순위를 위한 가중값을 부여하여 목적함수를 구성하는 것이 타당한 것으로 판단된다.

• Restorative Dentistry and Endodontics
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• 제20권1호
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• pp.261-274
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• 1995

This study aimed to evaluate the marginal microleakage of Class V cavities of All-bond 2 (Wet - bonding system), Gluma (Adhesion of resin to exposed collagen fibers), and Scotchbond Multi-purpose(Mild Etching System). Hundred extracted human teeth divided into a control and three experimental groups consisting of eight teeth. The experimental group was further subdivided into All- bond2, Gluma and Scotchbond MP groups, Vitrebond served as the control. The positive control group consisted of specimens filled with resin and with no etching, primer and bonding procesure. Polished specimens underwent temperature changed from $5^{\circ}C$ to $55^{\circ}C$ a thousand times. After thermocycling, speciemens were placed in 2 % methylene blue dye solution for 24 hours in an incubator set at $37^{\circ}C$. The teeth were sectioned buccolingually and the degree of dye penetration was observed with a stereomicroscoped(*20). The following results were obtained. 1. Both the control and the experimental group showed a lower degree of dye penetration on enamel than on dentin margins(p<0.05) 2. Gluma exhibited a statistically significant lower degree of dye penetration than All-bond 2 on enamel margins(p<0.05) Scotchbond MP also exhibited a lower degree of dye penetration than All-bone 2 but was no statistically significant. Gluma and Scotchbond MP exhibited a similar degree of dye penetration. 3. The degree of dye penetration of All-bond 2, Gluma and Scotch bond MP showed no statistically singnificance on enamel margins but was significantly lower than in the control using Vitrebond. 4. All-bond 2 exhibited a statistically significant lower degree of dye penetration than Gluma on dentin margins. All- bond 2 and Scotchbond MP showed a similar degree of dye penetration. 5. The degree of dye penetration of All-bond 2, Gluma and Scotchbond MP showed no statistically significance on dentin margins. There was neither a statistical significance with the control.

• 토지주택연구
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• 제4권4호
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• pp.349-360
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• 2013

최근 도청 이전 신도시, 위례신도시 등 두 개 이상 지자체를 포함하는 신도시(복합경계신도시) 개발이 증가하고 있다. 그러나 현행 도시개발제도는 단일 지자체 신도시를 대상으로 하고 있어, 복합경계 신도시의 개발과 관리를 위한 제도 개선이 필요하다. 다층적 거버넌스(Multi-level governance) 개념은 광역지자체와 기초지자체가 포함된 위례신도시에서 갈등이슈를 파악하고, 개발사업자와 주민까지 참여하는 협력 대안을 모색하는데 유리한 개념틀을 제공한다. 본 연구의 목적은 위례신도시를 사례로 다층적 거버넌스(Multi-level governance)의 개념틀을 활용하여 복합경계신도시의 개발과 관리 운영 과정에서 발생하는 갈등이슈를 파악하고, 협력적 관리방안을 제시하는 것이다. 이를 위해 관련자 및 전문가 인터뷰, 문헌연구, 전문가 포럼 등을 진행하였으며, 도시개발 관련 선행연구와 경제자유구역 등 유사사례로부터 시사점을 도출하였다. 본 연구의 주요 결과는 다음과 같다. 첫째, 위례신도시 개발 관리의 주요 부문을 학교 학군, 행정서비스, 공급처리시설, 도시기반시설로 구분하고, 각 부문별 갈등이슈를 분석하여 갈등구조를 파악하였다. 둘째, 위례신도시는 복합경계 신도시로서 행정구역 별 분리 관리와 통합 관리간의 대립, 광역적 관리 대 국지적 관리가 갈등의 기본축을 형성하고 있음을 확인하였다. 셋째, 위례신도시의 협력적 관리를 위해서는 최소한 지자체 행정협의회, 지자체조합, 전문관리기구의 세 가지 차원에서 Multi-level governance를 구성하여야 한다는 점을 향후 관리방안으로 제시하였다.