• 대한전기학회:학술대회논문집
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• 대한전기학회 1998년도 하계학술대회 논문집 C
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• pp.1073-1075
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• 1998

This paper presents the method of parameter estimation of diffusion model for monitoring Demand-Side Management Program. Bass diffusion model was applied in this paper, which has different values according to parameters ; coefficients of innovation, imitation and potential adopters. Though it is very important to estimate three parameter, there are no empirical results in practice. Thus, this paper presents the method of parameter estimation in case of few data with constraints to reduce the possibility of bad estimation. The constraints are empirical results or expert's decision. Case studies show the diffusion curves of high-efficient lighting and also forecasting of the peak value for power demand considering diffusion of high-efficient lighting, the feedback and least-square parameter estimation method used in this paper enable us to evaluate the status and forecasting of the effect of DSM program.

• Ocean Systems Engineering
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• 제10권1호
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• pp.49-65
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• 2020

In this study, the effects of inclined shaft angle on the hydro-acoustic performance of cavitating marine propellers are investigated by a numerical method developed before and Brown's empirical formula. The cavitating blades are represented by source and vortex elements. The cavity characteristics of the blades such as cavitation form, cavity volume, cavity length etc., are computed at a given cavitation number and at a set advance coefficient. A lifting surface method is applied for these calculations. The numerical lifting surface method is validated with experimental results of DTMB 4119 model benchmark propeller. After calculation of hydrodynamic characteristics of the cavitating propeller, noise spectrum and overall sound pressure level (OASPL) are computed by Brown's equation. This empirical equation is also validated with another numerical results found in the literature. The effects of inclined shaft angle on thrust coefficient, torque coefficient, efficiency and OASPL values are examined by a parametric study. By modifying the inclination angles of propeller, the thrust, torque, efficiency and OASPL are computed and compared with each other. The influence of the inclined shaft angle on cavity patterns on the blades are also discussed.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 춘계학술대회논문집B
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• pp.198-203
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• 2001

This paper discusses an experimental method for measuring the insertion loss (IL) performance of a double panel that are used in vehicles. Instead of two adjacent reverberation chambers which are generally used to measure the transmission loss (TL) of the large sound isolation materials, air-borne sound insulation tester was utilized to determine the IL and articulation index (AI) of standardized deadening materials. In comparison to reverberation chamber method, air-borne sound insulation tester method is more space-saving, more time-saving and more simple to the automotive acoustics. From the empirical results, it is verified that the performance of deadening materials is closely connected with thickness of panels, type of filling material that is filled into a double panel, and area ratio of double panel.

• 대한화학회지
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• 제55권4호
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• pp.581-589
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• 2011

넓은 범위의 온도와 조성 하에 있는 벤젠-톨루엔, 벤젠- 페놀, 벤젠- p-자일렌의 이성분계 기체 혼합물에 대한 점도와 확산계수를 반실험적 반전 방법을 사용하여 예측하였다. 점도와 확산계수에 대한 정확도는 각각 3%와 4% 이내이다.

• 한국군사과학기술학회지
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• 제2권2호
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• pp.70-82
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• 1999

During the aircraft conceptual design stage, rapid aerodynamic analyses over various configurations are required. Hence, empirical and analytical methods play important roles in predicting the aero-dynamic characteristics. In this study, total drag estimation method based on empirical and analytical approaches is developed. By comparing with the results of the wind tunnel experiment and existing prediction methods, it is demonstrated that the developed method is accurate and useful in predicting total drag for the whole Mach number range.

• Smart Structures and Systems
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• 제2권2호
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• pp.171-188
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• 2006

This paper deals with damage detection using active Lamb waves. The wavelet transform and empirical mode decomposition methods are discussed for measuring the Lamb wave's arrival time of the group velocity. An experimental system to diagnose the damage in the composite plate is developed. A method to optimize this system is also given for practical applications of active Lamb waves, which involve optimal arrangement of the piezoelectric elements to produce single mode Lamb waves. In the paper, the single mode Lamb wave means that there exists no overlapping among different Lamb wave modes and the original Lamb wave signal with the boundary reflection signals. Based on this optimized PZT arrangement method, five damage localizations on different plates are completed and the results using wavelet transform and empirical mode decomposition methods are compared.

• 대한조선학회논문집
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• 제52권4호
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• pp.338-348
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• 2015

In this study, the added resistance of ships in short waves is systematically studied by using two different numerical methods - Rankine panel method and Cartesian grid method – and existing asymptotic and empirical formulae. Analysis of added resistance in short waves has been preconceived as a shortcoming of numerical computation. This study aims to observe such preconception by comparing the computational results, particularly based on two representative three-dimensional methods, and with the existing formulae and experimental data. In the Rankine panel method, a near-field method based on direct pressure integration is adopted. In the Cartesian grid method, the wave-body interaction problem is considered as a multiphase problem, and volume fraction functions are defined in order to identify each phase in a Cartesian grid. The computational results of added resistance in short waves using the two methods are systematically compared with experimental data for several ship models, including S175 containership, KVLCC2 and Series 60 hulls (C_B = 0.7, 0.8). The present study includes the comparison with the established asymptotic and empirical formulae in short waves.

• 터널과지하공간
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• 제3권2호
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• pp.163-166
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• 1993

To improve the applicability of the Ho-Brown's empirical failure theory to field problems, transformation of failure coefficients was suggested in this study. This method was tested on the published data and good results were obtained. It seemed that this method be more reasonable than traditional method of modifying the coefficients by RMR or Q values.

• 한국항공우주학회지
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• 제44권6호
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• pp.520-529
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• 2016

본 연구의 목적은 중고도-장기체공 무인기의 성능을 역설계를 통해 분석하는 것이며, 역설계를 위한 모델로 RQ-1 Predator를 선정하였다. CATIA 프로그램을 사용하여 RQ-1 Predator의 외형에 대한 형상과 중량 분포를 생성하였다. RQ-1 Predator의 공력특성은 주로 와류격자법과 경험식을 조합하여 수행하였으며, 추진 성능은 Howe의 경험식을 통해 수행되었다. 상승률, 실용상승한도, 항속 거리, 그리고 체공 시간에 대한 역설계를 수행하였으며, 역설계 결과가 참고문헌과 잘 일치함을 확인하였다.

• 한국지반공학회논문집
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• 제26권8호
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• pp.59-66
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• 2010

본 연구에서는 동다짐 공법을 적용할 시 개량심도와 진동영향 예측을 유한요소해석을 통해 그 적용성을 규명하였다. 동다짐 공법이 적용된 기존 현장 조건에 따라 지반을 모델링하였으며, 동적하중 모델은 rigid body force를 적용하였다. 개량심도는 심도별 최대 연직 입자 가속도로 예측을 하여 기존 경험식과 비교 분석하였으며, 진동영향은 진동원으로부터 거리별 연직 최대 입자 속도를 도출하여 기존 경험식에 의한 값과 비교 분석하였다. 수치해석 결과, 개량심도의 경우 기존의 경험식과 비슷한 양상을 띄고 있으며, 진동영향의 경우는 기존 식과 특정 구간에서 차이를 보이고 있으나, 어느 정도 소요이격거리를 예측 할 수 있었다. 이들 해석결과는 경험적인 방법과 더불어 동다짐 설계의 신뢰도 향상을 위한 기초적인 자료가 될 것으로 보인다.