• 한국전자파학회논문지
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• 제11권2호
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• pp.186-196
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• 2000

본 논문에서는 이중통신용 안테나 시스템을 위한 변형된 사각 루프 주파수 선택 반사기를 제안하고, 그 특성 을 해석하였다 변형된 사각 루프 주파수 선택 반사기를 해석함에 있어서 유전체의 영향과 주기적 배열구조임을 고려하기 워하여 파수 영역 방법(Spectral Domain Method)과 Floquet 이론을 도입하였으며, 수치해석 방법으로 는 rooftop basis function을 이용한 모멘트법을 적용하였다 해석결과로는 기존의 사각 루프와 변형된 사각 루프 의 전송 특성플 비교하였으며. 변형된 사각 루프의 경우 입사각과 편파 변화에 따른 전송 특성도 제시하였다. 수 치해석 방법의 타당성을 검증하기 위해 변형된 사각 루프 주파수 선택 반사기를 실제 제작 및 측정하여 수치해 석 결파와 비교하였다. 측정결과는 수치해석 결과와 비교적 잘 일치함을 보였다

• 설비공학논문집
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• 제7권1호
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• pp.42-51
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• 1995

In order to establish a theoretical basis for the analyses of transient behaviors in stratified thermal storage tanks, analytical approaches to an improved one-dimensional model are made. In the present model the storage tank is treated as a finite region with an adiabatic tank exit, whereas it has been considered as a simple semi-infinite region previously. Application of the Laplace transformation and the Inversion theorem to the governing equations makes it possible to obtain an exact infinite-series solution, which is convergent only at sufficiently large time. Accordingly a complementary solution which is available for short times, i.e., the time range of this study is sought by an approximate method. The approximate solution which is rigorously validated through the examination of neglected terms in the solution procedure agrees quite well with the exact one. Moreover, it is simpler to use and more convenient to interpret the physical meaning of the solution. Comparison of the present solution with the previous ones shows relatively large difference near the tank bottom, which results from the more realistic boundary condition adopted in the present model. Some representative results by the approximate solution including effects of the Peclet number on temperature distrbutions are illustrated to show the utility of this study. In consequence, it is expected that the present results based on the improved model replace the foregoing ones as a new theoretical reference for studies of thermal stratification fields.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2005년도 추계학술대회논문집
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• pp.287-292
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• 2005

This paper presents a rational polynomial approximation method to estimate modal parameters of wind excited structures using incomplete noisy measurements of structural responses and partial measurements of wind velocities only. A stochastic model of the excitation wind force acting on the structure is estimated from partial measurements of wind velocities. Then the transfer functions of the structure are approximated as rational polynomial functions. From the poles and zeros of the estimated rational polynomial functions, the modal parameters, such as natural frequencies, damping ratios, and mode shapes are extracted. Since the frequency characteristics of wind forces acting on structures can be assumed as a smooth Gaussian process especially around the natural frequencies of the structures according to the central limit theorem (Brillinger, 1969; Yaglom, 1987), the estimated modal parameters are robust and reliable with respect to the assumed stochastic input models. To verify the proposed method, the modal parameters of a TV transmission tower excited by gust wind are estimated. Comparison study with the results of other researchers shows the efficacy of the suggested method.

• Nuclear Engineering and Technology
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• 제53권12호
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• pp.3944-3951
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• 2021

Several reasons such as no free lunch theorem indicate that there is not a universal Feature selection (FS) technique that outperforms other ones. Moreover, some approaches such as using synthetic dataset, in presence of large number of FS techniques, are very tedious and time consuming task. In this study to tackle the issue of dependency of estimation accuracy on the selected FS technique, a methodology based on the heterogeneous ensemble is proposed. The performance of the major learning algorithms of neural network (i.e. the FFNN-BR, the FFNN-LM) in combination with the diverse FS techniques (i.e. the NCA, the F-test, the Kendall's tau, the Pearson, the Spearman, and the Relief) and different combination techniques of the heterogeneous ensemble (i.e. the Min, the Median, the Arithmetic mean, and the Geometric mean) are considered. The target parameters/transients of Bushehr nuclear power plant (BNPP) are examined as the case study. The results show that the Min combination technique gives the more accurate estimation. Therefore, if the number of FS techniques is m and the number of learning algorithms is n, by the heterogeneous ensemble, the search space for acceptable estimation of the target parameters may be reduced from n × m to n × 1. The proposed methodology gives a simple and practical approach for more reliable and more accurate estimation of the target parameters compared to the methods such as the use of synthetic dataset or trial and error methods.

• International Journal of Computer Science & Network Security
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• 제24권3호
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• pp.196-200
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• 2024

Weather forecasting is considered to be of utmost important among various important sectors such as flood management and hydro-electricity generation. Although there are various numerical methods for weather forecasting but majority of them are reported to be Mechanistic computationally demanding due to their complexities. Therefore, it is necessary to develop and build models for accurately predicting the weather conditions which are faster as well as efficient in comparison to the prevalent meteorological models. The study has been undertaken to forecast various atmospheric parameters in the city of Bangalore using Naïve Bayes algorithms. The individual parameters analyzed in the study consisted of wind speed (WS), wind direction (WD), relative humidity (RH), solar radiation (SR), black carbon (BC), radiative forcing (RF), air temperature (AT), bar pressure (BP), PM₁₀ and PM_2.5 of the Bangalore city collected from Air Quality Monitoring Station for a period of 5 years from January 2015 to May 2019. The study concluded that Naive Bayes is an easy and efficient classifier that is centered on Bayes theorem, is quite efficient in forecasting the various air pollution parameters of the city of Bangalore.

• 디지털콘텐츠학회 논문지
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• 제2권2호
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• pp.103-115
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• 2001

본 논문은 퍼지지식베이스에서 러프 집합과 요인공간이론을 적용하여 최소 결정규칙 생성과 근사추론 연산을 수행하는 두 개의 알고리듬을 제안한다. 최소 결정규칙의 생성은 속성요인에 관련한 상관분석과 베이지안 정리를 응용한 데이터의 분류기법과 리덕트에 의해 수행된다. 이 결정규칙으로 이루어진 최소지식 베이스의 탐색공간에서 소속함수와 t-norm의 합성 연산을 정의한 근사추론 방식에 의해 특정 객체를 검색한다. 본 연구의 러프와 퍼지연산 모듈을 수행하는 제안 알고리듬 기법을 객체및 속성수를 증가시키는 시뮬레이션을 통해 다른 검색이론 및 합성연산 방식과 비교하였다. 그 결과 다른 제 방법보다 본 연구에서 제안하는 기법이 특정 객체를 추출하기 위한 검색연산 시간에 있어 보다 빠르게 검색됨을 입증하였다.

• 한국항공우주학회지
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• 제44권5호
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• pp.391-398
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• 2016

본 연구에서는 난류 유입조건을 갖는 수평축 풍력터빈 블레이드의 공력 하중에 대해 초점을 맞추어 연구하였다. 난류모델은 풍속과 방향에 대한 변동을 포함하며, 그 특성은 난류 강도와 표준편차로 표현된다. IEC61400-1에서는 정상 난류 모델과 정상 풍속 측면도에 대해서 피로해석을 수행하도록 규정하고 있다. 이를 위해 공력 최적설계 절차를 통해 얻어낸 MW급 수평축 풍력터빈 블레이드 허브와 저속 회전축에 대한 공력하중 해석을 수행한다. 공력하중 성분은 수치적인 절차를 통해 얻어내며 이를 블레이드 회전 특성을 고려하여 해석적으로 검토하였다. 난류 조건을 고려했을 때의 최대 추력과 토크의 변동치는 난류 조건을 고려하지 않았을 때의 값들에 비해 5~8 배 더 큰 값을 보였다. 따라서 난류 조건을 반영한 하중 해석은 풍력터빈 블레이드의 구조설계에 있어서 필수적임을 확인하였다.

• 한국융합학회논문지
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• 제10권1호
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• pp.205-214
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• 2019

우리나라 정부 당국은 주로 최저가낙찰제도를 이용하여 조달을 시행해왔으나, 과거 일정 시기 동안은 제한적 평균가 낙찰제 경매방식(일명 부찰제)을 이용하여 시설공사부문 조달을 실시했다. 부찰제란 각 입찰자들이 서로 모르게 공급가격을 적어 내면 그 가격을 평균하여 그 평균값에 가장 가까우면서 평균값보다는 낮은 공급가격을 부른 사람이 승자가 되며, 그가 부른 가격에서 낙찰가가 결정되는 제도이다. 본 논문은 제한적 평균가낙찰제 경매방식을 자원배분기구설계(mechanism design)의 관점에서 정형화하고, 고려할 문제를 제시한다. 나아가 ?명의 일반적 상황 하에서 사적 정보를 가지고 있는 입찰자들의 전략을 일양 분포 가정과 선형전략의 가정을 도입하여 구하고, 이를 통해 부찰제 경매방식의 균형을 제시한다. 또한 이러한 균형전략을 최저가낙찰제도와 비교함으로써 우리나라에서 자주 사용되는 두 제도의 효율성과 기대수입의 측면을 살펴본다. 끝으로 부찰제를 실시하는 경매인(정부)의 현실적 목적성이 어느 정도 달성되고 있는가를 비판적으로 고찰한다.

• 한국간호교육학회지
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• 제27권3호
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• pp.227-239
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• 2021

Purpose: This study used an exploratory sequential approach (mixed methods) design to explore essential meaning through comparing and analyzing the experiences of nursing students in virtual simulation practice and high fidelity simulation practice education in parallel. Methods: The study participants were 20 nursing students, and data were collected through focus group meetings from July 17 to August 5, 2020, and via online quantitative data from November 10 to November 15, 2020. The qualitative data were analyzed using Giorgi's phenomenological method, and the quantitative data were analyzed using descriptive statistics, the Mann-Whitney U test, Kruskal-Wallis H test analysis of variance and Spearman's ρ correlation. Results: The comparison between the two simulation training experiences was shown in five contextual structures, as follows: (1) reflection of the clinical field, (2) thinking theorem vs. thinking expansion, (3) individual-centered learning vs. team-centered learning, (4) attitudes toward participating in practical training, (5) metacognition of personal competency as a prospective nurse, and (6) revisiting the method of practice training. There was a positive correlation between satisfaction with the practice and the clinical judgment ability of high fidelity simulation, which was statistically significant (r=.47, p=.036). Conclusion: Comparing the experiences between virtual simulation practice training and high fidelity simulation practice training, which has increased in demand due to the Coronavirus Disease-2019 pandemic, is meaningful as it provides practical data for introspection and reflection on in-campus clinical education.

• 한국운동역학회지
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• 제16권3호
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• pp.1-7
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• 2006

The Primary type of swinging motion in human movement is that which is characteristic of a pendulum. The two types of pendulums are identified as simple and compound. A simple pendulum consist of a small body suspended by a relatively long cord. Its total mass is contained within the bob. The cord is not considered to have mass. A compound pendulum, on the other hand, is any pendulum such as the human body swinging by hands from a horizontal bar. Therefore a compound pendulum depicts important motions that are harmonic, periodic, and oscillatory. In this paper one discusses and compares two algorithms of Newton's method(F = m a) and Euler's method (M = $I{\times}{\alpha}$) in compound pendulum. Through exercise model such as human body with weight(m = 50 kg), body length(L = 1.5m), and center of gravity ($L_c$ = 0.4119L) from proximal end swinging by hands from a horizontal bar, one finds kinematic variables(angle displacement / velocity / acceleration), and simulates kinematic variables by changing body lengths and body mass. BSP by Clauser et al.(1969) & Chandler et al.(1975) is used to find moment of inertia of the compound pendulum. The radius of gyration about center of gravity (CoG) is $k_c\;=\;K_c{\times}L$ (단, k= radius of gyration, K= radius of gyration /segment length), and then moment of inertia about center of gravity(CoG) becomes $I_c\;=\;m\;k_c^2$. Finally, moment of inertia about Z-axis by parallel theorem becomes $I_o\;=\;I_c\;+\;m\;k^2$. The two-order ordinary differential equations of models are solved by ND function of numeric analysis method in Mathematica5.1. The results are as follows; First, The complexity of Newton's method is much more complex than that of Euler's method Second, one could be find kinematic variables according to changing body lengths(L = 1.3 / 1.7 m) and periods are increased by body length increment(L = 1.3 / 1.5 / 1.7 m). Third, one could be find that periods are not changing by means of changing mass(m = 50 / 55 / 60 kg). Conclusively, one is intended to meditate the possibility of applying a compound pendulum to sports(balling, golf, gymnastics and so on) necessary swinging motions. Further improvements to the study could be to apply Euler's method to real motions and one would be able to develop the simulator.