• 산업경영시스템학회지
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• 제36권4호
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• pp.64-70
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• 2013

Estimation approaches for casual relation model with high-order factors have strict restrictions or limits. In the case of ML (Maximum Likelihood), a strong assumption which data must show a normal distribution is required and factors of exponentiation is impossible due to the uncertainty of factors. To overcome this limitation many PLS (Partial Least Squares) approaches are introduced to estimate the structural equation model including high-order factors. However, it is possible to yield biased estimates if there are some differences in the number of measurement variables connected to each latent variable. In addition, any approach does not exist to deal with general cases not having any measurement variable of high-order factors. This study compare several approaches including the repeated measures approach which are used to estimate the casual relation model including high-order factors by using PLS (Partial Least Squares), and suggest the best estimation approach. In other words, the study proposes the best approach through the research on the existing studies related to the casual relation model including high-order factors by using PLS and approach comparison using a virtual model.

• Structural Engineering and Mechanics
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• 제61권4호
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• pp.551-561
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• 2017

As FGM (functionally graded material) bars which vibrate in axial or longitudinal direction have great potential for applications in diverse engineering fields, developing a reliable mathematical model that provides very reliable vibration and wave characteristics of a FGM axial bar, especially at high frequencies, has been an important research issue during last decades. Thus, as an extension of the previous works (Hong et al. 2014, Hong and Lee 2015) on three-layered FGM axial bars (hereafter called FGM bars), an enhanced spectral element model is proposed for a FGM bar model in which axial and radial displacements in the radial direction are treated more realistic by representing the inner FGM layer by multiple sub-layers. The accuracy and performance of the proposed enhanced spectral element model is evaluated by comparison with the solutions obtained by using the commercial finite element package ANSYS. The proposed enhanced spectral element model is also evaluated by comparison with the author's previous spectral element model. In addition, the effects of Poisson's ratio on the dynamics and wave characteristics in example FGM bars are numerically investigated.

• 한국측량학회지
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• 제12권1호
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• pp.95-106
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• 1994

지오이드 모델링에 필요한 기준면으로 사용되는 여러가지 지오포텐셜모델들을 시험하여 한반도 주변의 최적기준면을 결정하고자 하였다. 시험은 지오포텐셜모델들로부터 계산된 중력이상과 실제측정한 중력 이상의 차를 검토하였으며, 지오포텐셜모델들간의 중력이상과 지오이드고의 차를 비교·검토하였다. 또한 GPS 측량데이타로부터 계산된 지오이드고와 지오포텐셜모델로부터 계산된 지오이드고를 검토하였다. 시험결과 OSU91A 모델이 한반도 주변에서의 기준면으로 적합하다는 것을 알 수 있었다.

• 한국과학교육학회지
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• 제15권3호
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• pp.284-290
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• 1995

This study examined the effects of the learning cycle model by learner's characteristics such as I.Q., cognitive levels, inquiry skins, cognitive style, activity, reflectiveness. To see the effects of the learning cycle model, nonequivalent control group pretest-posttest multiple treatment designs was used in the study. 99 middle school second-graders(female) were divided into two groups. One group was selected as the experimental group (n=50), the other served at the comparison group(n=49). During the eight-month period, the students in the experimental group were instructed according to the learning cycle model, while the students in the comparison group were instructed according to the traditional instruction methods. Achievement data from science achievement test were analyzed by an ANOVA technique. The results of the study are as follows : 1. Science knowledge achievement. For the lower level students of activity, the learning cycle model is superior to the traditional approaches in science knowledge achievement. 2. Science inquiry skills. For the upper level students of I.Q., cognitive levels, inquiry skills, cognitive style and reflectiveness, the learning cycle model is superior to the traditional approaches in science inquiry skills. 3. Attitudes toward science. For the lower level students of I.Q., cognitive levels, inquiry skills, cognitive style, activity and reflectiveness, the learning cycle model is superior to the traditional approaches in attitudes toward science.

• 한국관개배수논문집
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• 제14권1호
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• pp.41-49
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• 2007

In this study, Kajiyama equation and SWAT model were used to estimate the available water resources from 1967 to 2003 at the small scale watershed, located in Dongnae-Myeon, Chunchen, Gangwon. The annual average streamflow for dry years estimated using the Kajiyama equation and the SWAT model were $2,593,779m^3$ and $2,579,162m^3$. The annual average streamflow for wet years were $7,223,804m^3$ and $7,035,253m^3$, respectively. The annual arrange streamflow for the entire 36 year period were $14,868,601m^3$ and $14,214,292m^3$, respectively. The coefficient of determination ($R^2$) and the Nash-Sutcliffe coefficient for comparison between Kajiyama and SWAT were 0.90 and 0.79, respectively. The comparison indicates that the Kajiyama equation and the SWAT model can be used to estimate the streamflow at th study watershed with reasonable accuracy, although the estimated values were not compared with measured streamflow data, which is not available at the small scale study watershed. However, the Kajiyama equation is recommended for estimating available water resources at Dongnae-Myeon watershed because of its ease-of-use and reasonable accuracy compared with the SWAT model, requiring numerous model input and expensive GIS software in operating the model

• 한국초전도ㆍ저온공학회논문지
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• 제22권2호
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• pp.38-43
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• 2020

This paper presents comparative research on characteristics of air-cored and iron-cored high-temperature superconductor (HTS) field winding synchronous motors. The 100 kW air-cored model is designed analytically by Spatial Harmonic Method, and based on this model, the iron-cored model having the same output power is designed for comparison. Due to the substantial difference of permeability property between air and iron-core, there is a difference of magnetic field magnitude and angle with respect to the HTS tape c-axis, resulting in a different critical current of the field winding considering the anisotropic property of HTS tape. For a detailed comparison between two models, the following key motor characteristics are calculated through the Finite Element Method (FEM) simulation: 1) critical current; 2) HTS wire length; and 3) torque characteristics. From the simulation results, it can be confirmed that the critical current value of the iron-cored model increases by 33 %. Also, in the case of the superconducting wire consumption, those of the iron-cored and air-cored models are 95.3 m and 815.6 m, respectively. So the wire usage can be reduced to about 88 % by using iron core. However, in terms of torque characteristics, the torque ripple of the iron-cored model is about twice as large as that of the air-cored model, which may be a disadvantage on vibration and acoustic noise.

• 한국항공우주학회지
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• 제40권5호
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• pp.375-384
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• 2012

본 연구에서는 초음속 비행체에 나타나는 유동 특성 해석을 위해 1988 Wilcox $\mathcal{k}-{\omega}$ 모델과 2008 Wilcox 모델의 수치 결과를 비교하였다. 충격파 - 경계층 간섭 현상과 램프 주입기 혼합 문제에 대하여 실험결과와 비교, 검토하였다. 또한, 표면 마찰 측정의 기초가 되는 평판 흐름과 전단 층 성장에 대한 상관 관계식도 비교, 분석 하였다. 램프 주입기 케이스에서 최대 주입 질량비는 1988 Wilcox 모델을 이용하였을 때 보다 신뢰성 있는 해석 결과를 예측할 수 있었다. 그러나 충격파 - 경계층 간섭 케이스에 대해서는 2008 Wilcox 모델을 적용하였을 때 더 정확한 해석 결과가 도출됨을 확인하였다.

• 대한수의학회지
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• 제44권4호
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• pp.607-613
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• 2004

Helicobacter pylori (H. pylori)-infection is an important pathogen of stomach cancer after chronic gastritis and ulceration in the stomach and duodenum. However, the virulences of H. pylori strains have not been well-defined between clinical isolates. This study was designed to establish water-immersion-restraint stress (WIRS) model in mongolian gerbil for comparison of pathogenicity of H. pylori strains. To determine an optimal duration time for WIRS model in gerbil, 5-week-old Mongolian gerbils were divided into different groups by WIRS duration time. After graded duration of WIRS, the macroscopic ulcer index (UI) was measured with the stomach and duodenum of sacrificed animal. There were no significant differences between male and female in same duration group. However, the UI increased significantly in a time-dependent fashion. The group of 6 hours-WIRS animals showed severe hemorrhage and ulceration in their stomach and duodenum. On the other hand, the very mild lesions induced in 2 hours-treated animals. Therefore, we determined an optimal duration time for WIRS model in gerbil as 4 hours. Thereafter, we evaluated whether this WIRS model in gerbil could be used as an useful tool for in vivo comparison of pathogenicity of H. pylori strains by enhancement of pathological severity in H. pylori-infected gerbils. Mongolian gerbils were divided into H. pyloriinfected and PBS-inoculated groups. Thereafter, they were divided again into 4 hours-WIRS and no WIRS subgroups. After treatment, the severity of pathological changes was evaluated in a same manner with previous duration-determining experiment. When the animals were exposed to WIRS, the UI was significantly higher in the infected group than in the uninfected group. These results suggested that the established gerbil-WIRS model in this study enhanced effectively the severity of pathogenic changes in the H. pylori-infected Mongolian gerbils and could be used as an useful tool for in vivo comparison of pathogenicity of H. pylori strains.

• 한방안이비인후피부과학회지
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• 제14권1호
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• pp.182-189
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• 2001

This study was performed to compare the effect of Ojeoksan which have extracted by varied extractor(press extractor : PE, pressless extractor : PLE, short acting extractor : SE) on model of blood stasis in rats, Except for the normal group, hydrocortisone acetate(HA;25mg/kg in ethanol. IM) to induce experimental blood stasis model for 1 weeks and each extract of Ojeaksan was administrated after 1hr following HA injection for 1week. We measured the hematocrit, the platelet count, the prothrombin time, levels of fibrinogen in rats' blood, The sample Ⅰ(Ojeoksan extracted by PE) group showed significant decrease of hematocrit. prothrombin time and significant increase of the platelet count, levels of fibrinogen in comparison with those of the control group, The sample Ⅱ(Ojeaksan) extracted by PLE) group showed significant decrease of hematocrit and significant increase of levels of fibrinogen in comparison with those of the control group. Administration of the sample Ⅲ(Ojeaksan extracted by SE) group showed significant decrease of hematocrit and significant increase of the platelet count, levels of fibrinogen in comparison with those of the control group.

• Computers and Concrete
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• 제11권6호
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• pp.541-569
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• 2013

There is a wide variety of existing Genetic Algorithms (GA) operators and parameters in the literature. However, there is no unique technique that shows the best performance for different classes of optimization problems. Hence, the evaluation of these operators and parameters, which influence the effectiveness of the search process, must be carried out on a problem basis. This paper presents a comparison for the influence of GA operators and parameters on the performance of the damage identification problem using the finite element model updating method (FEMU). The damage is defined as reduction in bending rigidity of the finite elements of a reinforced concrete beam. A certain damage scenario is adopted and identified using different GA operators by minimizing the differences between experimental and analytical modal parameters. In this study, different selection, crossover and mutation operators are compared with each other based on the reliability, accuracy and efficiency criteria. The exploration and exploitation capabilities of different operators are evaluated. Also a comparison is carried out for the parallel and sequential GAs with different population sizes and the effect of the multiple use of some crossover operators is investigated. The results show that the roulettewheel selection technique together with real valued encoding gives the best results. It is also apparent that the Non-uniform Mutation as well as Parent Centric Normal Crossover can be confidently used in the damage identification problem. Nevertheless the parallel GAs increases both computation speed and the efficiency of the method.