• 제목/요약/키워드: non-linear least squares

검색결과 81건 처리시간 0.022초

Closed-form optimum tuning formulas for passive Tuned Mass Dampers under benchmark excitations

  • Salvi, Jonathan;Rizzi, Egidio
    • Smart Structures and Systems
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    • 제17권2호
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    • pp.231-256
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    • 2016
  • This study concerns the derivation of optimum tuning formulas for a passive Tuned Mass Damper (TMD) device, for the case of benchmark ideal excitations acting on a single-degree-of-freedom (SDOF) damped primary structure. The free TMD parameters are tuned first through a non-linear gradient-based optimisation algorithm, for the case of harmonic or white noise excitations, acting either as force on the SDOF primary structure or as base acceleration. The achieved optimum TMD parameters are successively interpolated according to appropriate analytical fitting proposals, by non-linear least squares, in order to produce simple and effective TMD tuning formulas. In particular, two fitting models are presented. The main proposal is composed of a simple polynomial relationship, refined within the fitting process, and constitutes the optimum choice. A second model refers to proper modifications of literature formulas for the case of an undamped primary structure. The results in terms of final (interpolated) optimum TMD parameters and of device effectiveness in reducing the structural dynamic response are finally displayed and discussed in detail, showing the wide and ready-to-use validity of the proposed optimisation procedure and achieved tuning formulas. Several post-tuning trials have been carried out as well on SDOF and MDOF shear-type frame buildings, by confirming the effective benefit provided by the proposed optimum TMD.

Debye Polarization을 이용한 흡음재 모델링에 대한 연구 (An Approach for Modeling of Sound Absorbing Material using Debye Polarization)

  • 박규칠;;윤종락
    • 한국정보통신학회논문지
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    • 제16권7호
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    • pp.1391-1396
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    • 2012
  • 본 연구에서는 해저의 반사면이나 흡음재와 같이 주파수에 따라 다른 특성을 가지는 매체를 수치적으로 모델링하였다. 기존의 흡음재 해석 등가회로 모델에 용량성 성분을 부가하기 위해 Debye polarization 기법을 적용하여 흡음재의 모델링을 하였다. 이 모델의 파라미터를 추정하기 위해 폴리우레탄이라는 흡음재의 흡음 주파수 특성을 이용하였다. 파라미터의 추정에는 non-linear least squares라는 비선형 최적화 기법을 사용하였다. 먼저 두께 25 mm의 폴리우레탄의 흡음재의 파라미터를 추정하였으며, 이 파라미터를 이용해 50 mm의 폴리우레탄의 특성을 모델링하는 것이 가능하였다. 이를 바탕으로 흡음재의 주파수에 따른 흡음 특성을 하나의 간단한 모델로 모델링하는 것이 가능함을 보였다.

가중 최소자승 필터링과 색 표현 모델을 결합한 넓은 동적 영역 이미지 표현 (High Dynamic Range Image Display Combining Weighted Least Squares Filtering with Color Appearance Model)

  • 박미선;이경준;위승우;정제창
    • 방송공학회논문지
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    • 제21권6호
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    • pp.920-928
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    • 2016
  • 최근 넓은 동적 영역 이미지 기술은 컴퓨터 그래픽 분야에서 화제다. 본 논문에서는 가중 최소자승(가중회귀분석) 최적화 체계에 기반하여 넓은 동적 영역 이미지를 처리하는 톤매핑 알고리듬을 제안한다. 제안하는 방법은 시각적 후광 현상을 피하는 동시에 기존의 디스플레이에서 더 지각적인 넓은 동적 영역 이미지들을 보여주기 위해 가중 최소자승 필터링과 iCAM06모델을 결합한다. 제안된 알고리듬은 먼저 넓은 동적 영역 이미지를 base layer와 detail layer로 나눈다. Base layer는 큰 규모의 변화량을 가지고 있으며 가중 최소자승 필터링을 사용하여 얻어지고 iCAM06 모델을 포함한다. 다음으로, 인간의 시각 체계에 따라 base layer는 적응적으로 압축된다. 압축 시에는 base layer만 대비를 줄이고 detail layer을 보존한다. 본 논문에서는 객관적 화질 평가와 주관적 화질 평가를 통하여 제안하는 알고리듬을 적용한 이미지가 기존의 알고리듬을 적용한 이미지들에 비해 원본 넓은 동적 영역 이미지에 더 유사하다는 것을 보여준다.

가우시안 포락선 선형 첩 신호의 순시 주파수 추정을 통한 원전 내 계측 케이블의 고장점 진단 연구 (Instantaneous Frequency Estimation of the Gaussian Enveloped Linear Chirp Signal for Localizing the Faults of the Instrumental Cable in Nuclear Power Plant)

  • 이춘구;박진배;윤태성
    • 전기학회논문지
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    • 제62권7호
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    • pp.987-993
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    • 2013
  • Integrity of the control and instrumental cables in nuclear power plant is important to maintain the stability of the nuclear power plants. In order to diagnose the integrity of the cables, the diagnostic methods based on reflectometry have been studied. The reflectometry is a non-destructive method and it is applicable to diagnose the live cables. We introduce a Gaussian enveloped linear chirp reflectometry to diagnose the cables in the nuclear power plants. In this paper, we estimate the instantaneous frequency of the Gaussian enveloped linear chirp signal by using the weighted robust least squares filtering to localize the impedance discontinuities in the class 1E instrumental cable.

Simulation based improved seismic fragility analysis of structures

  • Ghosh, Shyamal;Chakraborty, Subrata
    • Earthquakes and Structures
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    • 제12권5호
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    • pp.569-581
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    • 2017
  • The Monte Carlo Simulation (MCS) based seismic fragility analysis (SFA) approach allows defining more realistic relationship between failure probability and seismic intensity. However, the approach requires simulating large number of nonlinear dynamic analyses of structure for reliable estimate of fragility. It makes the approach computationally challenging. The response surface method (RSM) based metamodeling approach which replaces computationally involve complex mechanical model of a structure is found to be a viable alternative in this regard. An adaptive moving least squares method (MLSM) based RSM in the MCS framework is explored in the present study for efficient SFA of existing structures. In doing so, the repetition of seismic intensity for complete generation of fragility curve is avoided by including this as one of the predictors in the response estimate model. The proposed procedure is elucidated by considering a non-linear SDOF system and an existing reinforced concrete frame considered to be located in the Guwahati City of the Northeast region of India. The fragility results are obtained by the usual least squares based and the proposed MLSM based RSM and compared with that of obtained by the direct MCS technique to study the effectiveness of the proposed approach.

Efficient wind fragility analysis of RC high rise building through metamodelling

  • Bhandari, Apurva;Datta, Gaurav;Bhattacharjya, Soumya
    • Wind and Structures
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    • 제27권3호
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    • pp.199-211
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    • 2018
  • This paper deals with wind fragility and risk analysis of high rise buildings subjected to stochastic wind load. Conventionally, such problems are dealt in full Monte Carlo Simulation framework, which requires extensive computational time. Thus, to make the procedure computationally efficient, application of metamodelling technique in fragility analysis is explored in the present study. Since, accuracy by the conventional Least Squares Method (LSM) based metamodelling is often challenged, an efficient Moving Least Squares Method based adaptive metamodelling technique is proposed for wind fragility analysis. In doing so, artificial time history of wind load is generated by three wind field models: i.e., a simple one based on alongwind component of wind speed; a more detailed one considering coherence and wind directionality effect, and a third one considering nonstationary effect of mean wind. The results show that the proposed approach is more accurate than the conventional LSM based metamodelling approach when compared to full simulation approach as reference. At the same time, the proposed approach drastically reduces computational time in comparison to the full simulation approach. The results by the three wind field models are compared. The importance of non-linear structural analysis in fragility evaluation has been also demonstrated.

FUZZY REGRESSION MODEL WITH MONOTONIC RESPONSE FUNCTION

  • Choi, Seung Hoe;Jung, Hye-Young;Lee, Woo-Joo;Yoon, Jin Hee
    • 대한수학회논문집
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    • 제33권3호
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    • pp.973-983
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    • 2018
  • Fuzzy linear regression model has been widely studied with many successful applications but there have been only a few studies on the fuzzy regression model with monotonic response function as a generalization of the linear response function. In this paper, we propose the fuzzy regression model with the monotonic response function and the algorithm to construct the proposed model by using ${\alpha}-level$ set of fuzzy number and the resolution identity theorem. To estimate parameters of the proposed model, the least squares (LS) method and the least absolute deviation (LAD) method have been used in this paper. In addition, to evaluate the performance of the proposed model, two performance measures of goodness of fit are introduced. The numerical examples indicate that the fuzzy regression model with the monotonic response function is preferable to the fuzzy linear regression model when the fuzzy data represent the non-linear pattern.

최우도 모형을 이용한 수위-유량곡선식 개발 (Development of Rating Curves Using a Maximum Likelihood Model)

  • 김경훈;박준일;신찬기
    • 환경위생공학
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    • 제23권4호
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    • pp.83-93
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    • 2008
  • The non-linear least squares model(NLSM) has long been the standard technique used by hydrologists for constructing rating curves. The reasons for its adaptation are vague, and its appropriateness as a method of describing discharge measurement uncertainty has not been well investigated. It is shown in this paper that the classical method of NLSM can model only a very limited class of variance heterogeneity. Furthermore, this lack of flexibility often leads to unaccounted heteroscedasticity, resulting in dubious values for the rating curve parameters and estimated discharge. By introducing a heteroscedastic maximum likelihood model(HMLM), the variance heterogeneity is treated more generally. The maximum likelihood model stabilises the variance better than the NLSM approach, and thus is a more robust and appropriate way to fit a rating curve to a set of discharge measurements.

방위센서를 이용한 배열 형상 추정기법 (Array Shape Estimation Method Using Heading Sensors)

  • 조요한;서희선;조치영
    • 소음진동
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    • 제10권5호
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    • pp.886-891
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    • 2000
  • In this paper, an iterative array shape estimation technique is presented, which is based on the use of the least squares polynomial fitting to the data from heading sensors. The estimated polynomial shape model is then used for calculating the hydrophone positions on the assumption that the arc distances between sensors are constant. In order to verify the applicability of the proposed algorithm, numerical simulations are performed using two types of non-linear array shapes. In addition the noise effects of heading sensors on the array shape estimation results and the performance of beamformer are also investigated.

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비선형 최소자승법을 이용한 성장곡선 모형의 매개변수 추정시 초기값 설정 방법에 관한 연구 (Determination of starting values in estimating growth curves by using non-linear least squares)

  • 염세경;홍승표;강회일;김지수;전치혁
    • 산업공학
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    • 제14권2호
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    • pp.190-197
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    • 2001
  • Growth curves including Logistic and Gompertz functions are widely used in forecasting the market demand. To estimated the parameters of those functions, we use the non-linear least square method. However, it is difficult to set up the starting points for each parameter. If a wrong starting point is selected, the result reveals the local optimum or does not converge to a certain value. The purpose of this paper is to resolve the problem of selecting a starting point. Especially, rescaling the market data using the national economic index make it possible to figure out the range of parameters and to utilize the grid search method. Applications to some real data are also included.

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