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이두호,전병열,이창복,김범수,Lee, Doo-Ho,Jeon, Byeong-Yeol,Lee, Chang-Bok,Kim, Bum-Soo 한국해양학회 1999 바다 Vol.4 No.1
발전소 가동에 따른 퇴적물내 중금속원소의 오염 가능성을 알아보기 위하여 삼천포화력발전소와 영광원자력 발전소 주변해역의 표층퇴적물을 대상으로 중금속 함량 분석을 실시하였으며 선정된 일부 퇴적물에 대해서는 화학적 존재형태를 파악하기 위해 연속추출분석을 실시하였다. 퇴적불 중의 금속원소 함량 분포는 대체적으로 평균입도에 의해 조절되고 있으며 탄산염 함량 및 유기불 함량에 의해서도 영향을 받고 있는 것으로 나타났다. 또한 화학적 존재형태별 분석에서도 Mn을 제외한 대부분의 중금속이 잔류상으로 존재하고 있어 인위적인 오염에 의해서라기 보다는 자연적인 분산에 의해 존재하고 있는 것으로 나타났다. In order to examine the degree of heavy metal pollutions around Samcheonpo and Youngkwang power plants, marine sediment samples were analyzed to determine heavy metal contents. Some of these sediment samples were also analyzed by using of a sequential extraction technique to know geochemical forms of the metals. The results showed that the spatial distribution of heavy metals coincided very well with those of mean grain size, carbonates and organic matters. The chemical speciation data using sequential extraction analysis also showed that a considerable amount of heavy metals except for Mn were bounded in the residual fraction, which mode of occurrence of heavy metals was generally interpreted as being the result of the lithogenic origin.
온도와 물성의 불확실성을 고려한 고무 마운트의 동특성 해석
이두호,황인성,Lee, Doo-Ho,Hwang, In-Sung 한국전산구조공학회 2011 한국전산구조공학회논문집 Vol.24 No.4
본 논문에서는 통계적인 방법을 이용하여 점탄성 제진재인 합성고무의 물성에 대한 변동성을 평가하는 방법을 제안하고 측정데이터를 이용하여 합성고무에 대한 평가를 수행하고 합성고무로 이루어진 고무 마운트에 대한 동특성 해석을 수행하였다. 고무 물성의 불확실성 인자로는 외기 온도의 변화와 실험 데이터의 오차 및 점탄성 물질모델의 오차를 고려하였다. 고무는 분수차 미분모델로 표현되었고, 온도의 영향은 비선형 이동계수모델을 도입하여 복소계수로 나타내어 동강성과 감쇠를 표현하였다. 이러한 물성모델을 바탕으로 고무에 대한 물성 실험데이터와 물성계수의 확률밀도함수 사이에 정의된 우도함수를 최대화하는 통계적 보정방법을 이용하여 물성모델의 물질계수들에 대한 변동성을 추정하였다. 합성고무로 이루어진 제진용 고무 마운트에 대하여 유한요소모델을 이용하여 동특성을 계산하였다. 동특성의 계산시 추정된 물성의 통계값을 적용하고 몬테카를로 해석을 통하여 동강성의 변동성을 살펴서 그 변동성이 매우 큼을 확인하였다. In this paper, a statistical calibration method is proposed in order to identify the variability of complex modulus for a rubber material due to operational temperature and experimental/model errors. To describe temperature- and frequency-dependent material properties, a fractional derivative model and a shift factor relationship are used. A likelihood function is defined as a product of the probability density functions where experimental values lie on the model. The variation of the fractional derivative model parameters is obtained by maximizing the likelihood function. Using the proposed method, the variability of a synthetic rubber material is estimated and applied to a rubber mount problem. The dynamic characteristics of the rubber mount are calculated using a finite element model of which material properties are sampled from Monte Carlo simulation. The calculated dynamic stiffnesses show very large variation.
이두호(Lee, Doo-Ho),김봉기(Kim, Bong-Ki),변정우(Byun, Joung-Woo),김현실(Kim, Hyun-Sil) 한국소음진동공학회 2011 한국소음진동공학회 논문집 Vol.21 No.5
An empirical formula proposed by Petersson and Plunt(PP's formula) and finite element analysis for impedance calculation of ship equipment foundations are investigated by comparing the analysis results with those of experimental results. The PP's formula well estimates resonant frequency of the foundations and impedance level except around the resonant region although the impedance level around the resonant frequency is heavily dependent upon the assumed loss factor. The results show that the PP's formula and finite element models can be complementarily used to estimate the impedance characteristics of various types of foundation of ships in design stage.
A Note on the Inter-Loss Time Distribution of an M/G/1/1 Queuing System
Doo Ho Lee(이두호) 한국경영과학회 2016 韓國經營科學會誌 Vol.41 No.3
This note discusses the inter-loss time ofan M/G/1/1 queuing system. The inter-loss time is defined as the time duration between two consecutive losses of arriving customers. In this study, we present the explicit Laplace transform of the inter-loss time distribution of an M/G/1/1 queuing system.
점탄성 물질의 온도와 주파수 의존성을 고려한 구속형 제진보의 최대 손실계수 설계
이두호(Lee, Doo-Ho) 한국소음진동공학회 2008 한국소음진동공학회 논문집 Vol.18 No.2
Optimal damping layout of the constrained viscoelastic damping layer on beam is identified with temperatures by using a gradient-based numerical search algorithm. An optimal design problem is defined in order to determine the constrained damping layer configuration. A finite element formulation is introduced to model the constrained layer damping beam. The four-parameter fractional derivative model and the Arrhenius shift factor are used to describe dynamic characteristics of viscoelastic material with respect to frequency and temperature. Frequency-dependent complex-valued eigenvalue problems are solved by using a simple re-substitution algorithm in order to obtain the loss factor of each mode and responses of the structure. The results of the numerical example show that the proposed method can reduce frequency responses of beam at peaks only by reconfiguring the layout of constrained damping layer within a limited weight constraint.
이중투과체 및 VIP복합 단열재 적용 평판 집열기의 성능 향상에 대한 연구
이두호(Doo Ho Lee),장한빈(Han Bin Jang),김용학(Young Hak Kim),도규형(Kyu Hyung Do),이광섭(Kwang Seob Lee),류남진(Nam Jin Lyu) 대한설비공학회 2016 설비공학 논문집 Vol.28 No.11
The purpose of this research is to improve the thermal effiency of solar collector and to quantitatively analyze its performance. Solar thermal systems have been limited to water heating systems mainly using low-temperature range. However, through diverse developments, the application has been extended to medium- and high-temperature fields such as solar heating, solar air conditioning, and solar thermal industrial process. Among the diverse research, this research is specially focusing on enhancement of the thermal performance by minimizing the heat loss coefficient of flat plate solar collectors. In order to do it, a front-side glazing material and a back-side insulation material with high insulated structure is proposed and based on computational analysis, the performance of energy collecting volume of the proposed solar collector is analyzed. The research shows that the proposed structure has the excellent performance at medium- and high-temperature range. therefore, it is expected that the proposed structure can easily replace existing technologies.
Doo Ho Lee(이두호) 한국경영과학회 2017 韓國經營科學會誌 Vol.42 No.4
This note presents the recursive relations of the queue length moments in the discrete-time Geo/Geo/1 queue and finite buffer Geo/Geo/1/B queue, respectively. With the local balance equations governing the system, we provide an alternative and simple approach to derive the queue length moments instead of taking the derivatives of the probability generating function.