• 폴리머
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• 제38권4호
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• pp.411-416
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• 2014

극성을 띠고있어 응집되는 성향이 카본블랙에 비해 강한 실리카의 분산도는 고무 복합소재의 물성을 좌우하는 중요한 요소이다. Wolff는 입자간 상호계수(${\alpha}_F$)를 도입하여 충전제간의 구조발달을 최초로 표현하였다. 하지만, 양기능성 실란의 도입에 따라 형성되는 3차원 구조발달은 표현할 수 없었다. 후에 이를 보완하기 위하여 Wolff의 표현은 복합소재 내 ${\alpha}_F$를 포함하는 구조발달 상호계수 ${\alpha}_C$로 확장되어 표현되었지만, 실험적으로 이 표현을 증명한 연구는 없었다. 이 논문은 구조발달 상호계수인 ${\alpha}_C$를 ${\alpha}_F$(실리카-실리카간 구조발달 상호계수), ${\alpha}_{FP}$(실리카-실란-고무간 구조발달 상호계수), ${\alpha}_P$(고무-고무간 구조발달 상호계수)로 고려하여 단기능성 및 양기능성 실란으로 처리된 실리카가 함유된 복합소재를 실험에 의해 최초로 표현하였다. 구조가 다른 실란들(PTES, OTES, TESPD, TESPT)을 이용하여 구조발달 상호계수 ${\alpha}_C$를 구성하는 ${\alpha}_F$, ${\alpha}_{FP}$, ${\alpha}_P$의 수치들을 측정하고 계산하였다. TESPT가 첨가된 복합소재의 ${\alpha}_C$의 값은 1.64이며, 이를 구성하고 있는 ${\alpha}_F$, ${\alpha}_{FP}$, ${\alpha}_P$는 각각 0.99, 0.31, 0.34로 나타났다.

• The Korean Journal of Ecology
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• 제23권6호
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• pp.435-438
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• 2000

Diameter distributions describe forest stand structure information. Prediction equations for percentiles of diameter distribution and parameter recovery procedures for the Weibull distribution function based on four percentile equations were applied to develop prediction system of even-aged slash pine stand structure development in terms of the number of stems per diameter class changes. Four percentiles of the cumulative diameter distribution were predicted as a function of stand characteristics. The predicted diameter distributions were tested against the observed diameter distributions using the Kolmogorov-Smirnov two sample test at the ${\alpha}$=0.05 level. Statistically, no significant differences were detected based on the data from 236 evaluation data sets. This stand level diameter distribution prediction system will be useful in slash pine stand structure modeling and in updating forest inventories for the long-term forest management planning.

• Structural Engineering and Mechanics
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• 제31권4호
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• pp.393-405
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• 2009

The Purpose of this paper is to show the applicability of a methodology, developed by the authors, with which to perform the mechanical optimization of space truss structures strongly restricted. This methodology use a parameter call "Volumetric Displacement", as the Objective Function of the optimization process. This parameter considers altogether the structure weight and deformation whose effects are opposed. The Finite Element Method is employed to calculate the stress/strain state and the natural frequency of the structure through a structural linear static and natural frequency analysis. In order to show the potentially of this simple methodology, its application on a large diameter telescope structure (10 m) considering the strongly restriction that became of its use, is presented. This methodology, applied in previous works on continuous structures, such as shell roof and fluid storage vessels, is applied in this case to a space truss structure, with the purpose of generalize its applicability to different structural topology. This technique could be useful in the morphology design of deployable and retractable roof structures, whose use has extensively spread in the last years.

• 대한토목학회논문집
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• 제35권4호
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• pp.845-852
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• 2015

파랑의 처오름높이는 항만 및 호안구조물의 마루높이 산정에 있어 주요한 설계요소이다. 본 연구에서는 TTP로 피복된 경사식구조물을 대상으로 2차원 수리실험을 수행하였으며, 실험에 적용된 실험파는 불규칙파로서 구조물 toe 위치에서 비쇄파, 쇄파 및 쇄파된 파의 조건을 포함한다. 본 실험결과를 이용하여 사면경사 1:1.5인 경사식구조물의 처오름높이를 산정할 수 있는 경험식을 쇄파 유사성 매개변수를 이용하여 제안하였다. 그리고 본 실험결과는 기존 연구결과인 van der Meer and Stam(1992)의 결과와 비교하였다.

• Structural Engineering and Mechanics
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• 제59권6호
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• pp.1037-1054
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• 2016

Structural parameter evaluation and external force estimation are two important parts of structural health monitoring. But the structural parameter identification with limited input information is still a challenging problem. A new simultaneous identification method in time domain is proposed in this study to identify the structural parameters and evaluate the external force. Each sampling point in the time history of external force is taken as the unknowns in force evaluation. To reduce the number of unknowns for force evaluation the time domain measurements are divided into several windows. In each time window the structural excitation is decomposed by orthogonal polynomials. The time-variant excitation can be represented approximately by the linear combination of these orthogonal bases. Structural parameters and the coefficients of decomposition are added to the state variable to be identified. The extended Kalman filter (EKF) is augmented and selected as the mathematical tool for the implementation of state variable evaluation. The proposed method is validated numerically with simulation studies of a time-invariant linear structure, a hysteretic nonlinear structure and a time-variant linear shear frame, respectively. Results from the simulation studies indicate that the proposed method is capable of identifying the dynamic load and structural parameters fairly accurately. This method could also identify the time-variant and nonlinear structural parameter even with contaminated incomplete measurement.

• Structural Monitoring and Maintenance
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• 제9권2호
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• pp.107-127
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• 2022

Structural health monitoring (SHM) has been related to damage identification with either operational loads or other environmental loading playing a significant complimentary role in terms of structural safety. In this study, a non-parametric method of time frequency analysis on the measurement is used to address the time-frequency representation for modal parameter estimation and system damage identification of structure. The method employs the wavelet decomposition of dynamic data by using the modified complex Morlet wavelet with variable central frequency (MCMW+VCF). Through detail discussion on the selection of model parameter in wavelet analysis, the method is applied to study the dynamic response of both steel structure and reinforced concrete frame under white noise excitation as well as earthquake excitation from shaking table test. Application of the method to building earthquake response measurement is also examined. It is shown that by using the spectrogram generated from MCMW+VCF method, with suitable selected model parameter, one can clearly identify the time-varying modal frequency of the reinforced concrete structure under earthquake excitation. Discussions on the advantages and disadvantages of the method through field experiments are also presented.

• Smart Structures and Systems
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• 제29권5호
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• pp.747-755
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• 2022

Hierarchical structure parameters, proposed in She-Leveque model, are investigated for velocity components obtained from different flow types over a large range of Reynolds numbers 255 < Re_𝜆 < 720. The values of intermittency parameter 𝛽, with respect to a fixed velocity component, are observed nearly same for all four types of turbulence. The parameter 𝛾, for streamwise velocity components is nearly the same but significantly different for vertical components in different flows. It is also observed that for both parameters, an obvious relation between the longitudinal and transverse components 𝛽_T < 𝛽_L (and 𝛾_T < 𝛾_L) always holds. However, the difference between 𝛽_L and 𝛽_T is found very small in all types of turbulent flows, we studied here. It is evidenced that at low Reynolds numbers, the deviations from K41 scaling are mainly due to the most intense structures and slightly because of more heterogeneous hierarchy of fluctuation structures. However, at higher Reynolds numbers the deviations seem as a consequence of the most intense structures only. Over all, the study suggests that the hierarchy parameter 𝛽 may be consider as a universal constant.

• 해양환경안전학회지
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• 제14권1호
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• pp.21-27
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• 2008

삼각형상 구조물은 바다에서 풍요로운 어장을 만들기 위해 용승류를 발생시키기 위한 인공용승구조물의 기본적인 형태로 이용되고 있다. 인공용승류는 많은 양의 영양염류를 포함하고 있는 저층의 바닷물을 해저로부터 표층으로 끌어 올리는 작용을 한다. 이 연구의 목적은 여러 가지 성층계수에 따른 삼각형상 수중구조물 주위의 유동특성을 규명하는 것이다. 회류수조 내에서 삼각형상 구조물 모델을 대상으로 유동특성을 조사하기 위하여 유동가시화 방법을 이용한 실험적 연구를 수행하였고, 입자영상유속계(PIV)를 이용하여 수중구조물 주위의 유동장을 계측하였다. 실험결과 구조물 후상부 영역에서의 용승효과는 수심이 구조물 높이의 2배이고, 성층계수가 약 3.0일 때 가장 좋은 결과가 나타났다. 이러한 정량적인 데이터는 인공용승구조물의 기능적 효율을 결정하는 데에 유용하게 이용될 수 있을 것이다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1998년도 추계학술대회 논문집 학회본부 B
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• pp.648-650
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• 1998

This paper proposes a constructive algorithm for generating the Takagi-Sugeno type fuzzy model through the sequential learning from training data set. The proposed algorithm has a two-stage learning scheme that performs both structure and parameter learning simultaneously. The structure learning constructs fuzzy model using two growth criteria to assign new fuzzy rules for given observation data. The parameter learning adjusts the parameters of existing fuzzy rules using the LMS rule. To evaluate the performance of the proposed fuzzy modeling approach, well-known benchmark is used in simulation and compares it with other modeling approaches.

• 한국지능시스템학회:학술대회논문집
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• 한국퍼지및지능시스템학회 1998년도 추계학술대회 학술발표 논문집
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• pp.433-439
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• 1998

In this paper, we present an approach to the structure identification based on the input space partition methods and to the parameter identification by hybrid learning method in neuro-fuzzy system. The structure identification can automatically estimate the number of membership function and fuzzy rule using grid partition, tree partition, scatter partition from numerical input-output data. And then the parameter identification is carried out by the hybrid learning scheme using back-propagation and least squares estimate. Finally, we sill show its usefulness for neuro-fuzzy modeling to truck backer-upper control.