• KSCE Journal of Civil and Environmental Engineering Research
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• v.6 no.4
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• pp.43-52
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• 1986

With increasing of computer use, a least squares method is now widely used in the regression analysis of various data. Unreliable results of regression coefficients due to the floating point of computer and problems of ordinary least squares method are described in detail. To improve these problems, a least squares method using orthogonal function is developed. Also, Comparison and analysis are performed through an example of numerical test, and re-orthogonalization method is used to increase the accuracy. As an example of application, the optimum order of AR process for the time series of monthly flow at the Pyungchang station is determined using Akaike's FPE(Final Prediction Error) which decides optimum degree of AR process. The result shows the AR(2) process is optimum to the series at the station.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.19 no.1
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• pp.253-259
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• 2019

The wedding seating problem(WSP) is to finding a minimum loss of guest relations(sit together preference) with restricted seats of a table for complex guest relation network. The WSP is NP-hard because of the algorithm that can be find the optimal solution within polynomial-time is unknown yet. Therefore we can't solve the WSP not computer-assisted programming but by hand. This paper suggests min-cut rule theory that the two guests with maximum preference can't separate in other two tables because this is not obtains minimum loss of preference. As a result of various experimental, this algorithm obtains proper seating chart meet to the seats of a table constraints.

• Korean Journal of Head & Neck Oncology
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• v.16 no.2
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• pp.177-181
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• 2000

배경 및 목적: Theodor Kocker에 의해 일반화된 전통적인 갑상선 수술방법은 갑상선 질환의 종류 및 정도, 수술범위와 상관없이 광범위한 수술범위로 인한 조직 손상으로 인해 수술후 환자들의 여러가지 불편감은 물론 경부의 넓은 부위의 통증과 경부 피부부종, 장액종, 혈종 등과 같은 후유증을 동반할 수 있다. 최근 본 저자들은 이같은 전통적 갑상선 수술의 부작용을 최소화하기 위해 작은 피부절개($3{\sim}4.5cm$) 후 피하 피판(subplatysmal skin flap) 없이 직접 갑상선으로 접근하는 새로운 수술기법으로서 최소침습 갑상선 수술기법을 개발하였기에 그 술식을 소개하고 전통적인 갑상선 절제술에 대한 우월성을 확인하고자 본 연구를 시행하였다. 대상 및 방법: 1999년 1월 15일 부터 2000년 1월 14일까지 573예의 갑상선 수술 예 중 최소침습 갑상선절제술이 시행되었던 466예와 1998년 1월 15일부터 1999년 1월 14일까지 전통적 갑상선 수술을 시행한 549예 중 거대 종양(양성>6cm, 악성>5cm), 흉골하 선종, 국소진행암, 재발암, 측경부의 다발성 림프절 전이가 있었던 112예를 제외한 437예의 임상병리적 특성과 피부절개 길이, 수술 시간, 수술중 출혈양, 수술후 진통제 요구빈도 및 재윈기간, 수술 후 합병증 발생빈도를 비교 분석하였다. 결 과: 두 군간의 임상병리적 특성상의 유의한 차이는 없었다. 피부절개 길이($3.7{\pm}0.7cm,\;vs\;9.6{\pm}3.3cm$), 수술 시간($57.6{\pm}11.7$분 vs $85.2{\pm}32.3$분) 수술 중 출혈양($18.4{\pm}15.3ml\;vs\;43.1{\pm}21.8ml$), 수술후 재원기간($1.6{\pm}0.5$일 vs $4.3{\pm}1.6$일), 및 수술후 진통제 요구빈도가 전통적 수술군에 비해 최소침습 수술군에서 통계적으로 유의하게 감소되었으나(p<0.05), 수술후 장액종 및 혈종 형성, 일시적인 음색변화, 일시적인 저칼슘혈증과 같은 합병증의 발생빈도는 각각 4.3%(n=20)와 4.8%(n=21)로 두 군간에 유의한 차이가 없었다. 결 론: 최소침습 갑상선 수술법은 새로운 수술기구의 도입 없이도 갑상선 수술의 충분한 시야를 확보할 수 있고 안전하고 간단하게 시행할 수 있으며, 기존 수술법으로 인한 부작용을 최소화할 수 있어 전통적 인 수술법을 대치할 수 있는 새로운 방법으로 사료된다.

• Economic and Environmental Geology
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• v.50 no.6
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• pp.517-523
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• 2017

A linear relationship between two stable water isotopes, oxygen and hydrogen, has been used to understand the water cycle as a basic tool. A slope and intercept from the linear relationship indicates what kind of physical processes occur during movement of water. Traditionally, ordinary least squares (OLS) method has been utilized for the linear relationship, but total least squares (TLS) method provides more accurate slope and intercept theoretically because isotopic compositions of both oxygen and hydrogen have uncertainties. In this work, OLS and TLS were compared with isotopic compositions of snow and snowmelt collected from the King Sejong Station, Antarctica and isotopic compositions of water vapor observed by Lee et al. (2013) in the western part of Korea. The slopes from the linear relationship of isotopic compositions of snow and snowmelt at the King Sejong Station were estimated to be 7.00 (OLS) and 7.16(TLS) and the slopes of stable water vapor isotopes were 7.75(OLS) and 7.87(TLS). There was a melting process in the snow near the King Sejong Station and the water vapor was directly transported from the ocean to the study area based on the slope calculations. There is no significant difference in two slopes to interpret the physical processes. However, it is necessary to evaluate the slope differences from the two methods for studies for example, groundwater recharge processes, using the absolute slope values.

• Korean Chemical Engineering Research
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• v.53 no.2
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• pp.236-242
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• 2015

We present two data-driven modeling methods, partial least square (PLS) and artificial neural network (ANN), to predict the major operating and performance variables of a polymer electrolyte membrane (PEM) fuel cell stack. PLS and ANN models were constructed using the experimental data obtained from the testing of a 30 kW-class PEM fuel cell stack, and then were compared with each other in terms of their prediction and computational performances. To reduce the complexity of the models, we combined a variables importance on PLS projection (VIP) as a variable selection method into the modeling procedure in which the predictor variables are selected from a set of input operation variables. The modeling results showed that the ANN models outperformed the PLS models in predicting the average cell voltage and cathode outlet temperature of the fuel cell stack. However, the PLS models also offered satisfactory prediction performances although they can only capture linear correlations between the predictor and output variables. Depending on the degree of modeling accuracy and speed, both ANN and PLS models can be employed for performance predictions, offline and online optimizations, controls, and fault diagnoses in the field of PEM fuel cell designs and operations.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.14 no.4
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• pp.233-241
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• 2014

This paper suggests a fast minimum spanning tree algorithm which simplify the original graph to 2-edge connected graph, and using the cycling property. Borůvka algorithm firstly gets the partial spanning tree using cycle property for one-edge connected graph that selects the only one minimum weighted edge (e) per vertex (v). Additionally, that selects minimum weighted edge between partial spanning trees using cut property. Kruskal algorithm uses cut property for ascending ordered of all edges. Reverse-delete algorithm uses cycle property for descending ordered of all edges. Borůvka and Kruskal algorithms always perform |e| times for all edges. The proposed algorithm obtains 2-edge connected graph that selects 2 minimum weighted edges for each vertex firstly. Secondly, we use cycle property for 2-edges connected graph, and stop the algorithm until |e|=|v|-1 For actual 10 benchmark data, The proposed algorithm can be get the minimum spanning trees. Also, this algorithm reduces 60% of the trial number than Borůvka, Kruskal and Reverse-delete algorithms.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.36 no.5
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• pp.438-447
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• 2008

This study is focused on reliability based design optimization (RBDO) using moving least squares. A response surface is used to derive a limit-state equation for reliability based design optimization. Response surface method (RSM) with least square method (LSM) or Kriging will be used as a response surface. RSM is fast to make the response surface. On the other hand, RSM has disadvantage to make the response surface of nonlinear equation. Kriging can make the response surface in nonlinear equation precisely but needs considerable amount of computations. The moving least square method (MLSM) is made of both methods (RSM with LSM+Kriging). Numerical results by MLSM are compared with those by LMS in Rosenbrock function and six-hump carmel back function. The RBDO of engine duct of smart UAV is pursued in this paper. It is proved that RBDO is useful tool for aerospace structural optimal design problems.

• Journal of the Korea Society of Computer and Information
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• v.17 no.10
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• pp.155-165
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• 2012

This paper suggests traveling salesman problem algorithm that have been unsolved problem with NP-Hard. The proposed algorithm is a heuristic with edge-swap method. The classical method finds the initial solution starts with first node and visits to mostly adjacent nodes then decides the traveling path. This paper selects minimum weight edge for each nodes, then perform Min-Min method that start from minimum weight edge among the selected edges and Min-Max method that starts from maximum weight edges among it. Then we decide tie initial solution to minimum path length between Min-Min and Min-Max method. To get the final optimal solution, we apply previous two-opt to initial solution. Also, we suggest extended 3-opt and 4-opt additionally. For the 7 actual experimental data, this algorithm can be get the optimal solutions of state-of-the-art with fast and correct.

• Fire Science and Engineering
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• v.27 no.5
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• pp.64-69
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• 2013

The autoignition temperatures (AITs) of solvent mixture was important index for the safe handling of flammable liquids which constitute the solvent mixtures. This study measured the AITs and ignition delay time for n-propanol and formic acid system by using ASTM E659 apparatus. The AITs of n-Propanol and Formic acid which constituted binary system were $435^{\circ}C$ and $498^{\circ}C$, respectively. The experimental AITs of n-propanol and formic acid system were a good agreement with the calculated AITs by the proposed equations with a few A.A.D. (average absolute deviation). And n- Propanol and formic acid system was shown the minimum autoignition temperature behavior (MAITB).

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.41 no.4
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• pp.275-283
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• 2013

In this paper, the structural optimum design method of composite rotor blade cross-section was investigated with the genetic algorithm. An auto-mesh generation program was developed for iterative calculations of optimum design, and stresses in the blade cross-section were analyzed by VABS (variational asymptotic beam sectional analysis) program. Minimum mass of rotor blade was defined as an object function, and stress failure index, center mass and blade minimum mass per unit length were chosen as constraints. Finally, design parameters such as the thickness and layup angles of a skin, and the thickness, position and width of a torsion box were determined through the structural optimum design method of composite rotor blade cross-section presented in this paper.