• Title/Summary/Keyword: General linear model

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IS CALCIUM II TRIPLET A GOOD METALLICITY INDICATOR OF GLOBULAR CLUSTERS IN EARLY-TYPE GALAXIES?

  • CHUNG, CHUL;YOON, SUK-JIN;LEE, SANG-YOON;LEE, YOUNG-WOOK
    • Publications of The Korean Astronomical Society
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    • v.30 no.2
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    • pp.489-490
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    • 2015
  • We present population synthesis models for the calcium II triplet (CaT), currently the most popular metallicity indicator, based on high-resolution empirical spectral energy distributions (SEDs). Our new CaT models, based on empirical SEDs, show a linear correlation below [Fe/H] ~ -0.5, but the linear relation breaks down in the metal-rich regime by converging to the same equivalent width. This relation shows good agreement with the observed CaT of globular clusters (GCs) in NGC 1407 and the Milky Way. However, a model based on theoretical SEDs does not show this feature of the CaT and fails to reproduce observed GCs in the metal-rich regime. This linear relation may cause inaccurate metallicity determination for metal-rich stellar populations. We have also confirmed that the effect of horizontal-branch stars on the CaT is almost negligible in models based on both empirical and theoretical SEDs. Our new empirical model may explain the difference between the color distributions and CaT distributions of GCs in various early-type galaxies. Based on our model, we claim that the CaT is not a good metallicity indicator for simple stellar populations in the metal-rich regime.

Estimating dose-response curves using splines: a nonparametric Bayesian knot selection method

  • Lee, Jiwon;Kim, Yongku;Kim, Young Min
    • Communications for Statistical Applications and Methods
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    • v.29 no.3
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    • pp.287-299
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    • 2022
  • In radiation epidemiology, the excess relative risk (ERR) model is used to determine the dose-response relationship. In general, the dose-response relationship for the ERR model is assumed to be linear, linear-quadratic, linear-threshold, quadratic, and so on. However, since none of these functions dominate other functions for expressing the dose-response relationship, a Bayesian semiparametric method using splines has recently been proposed. Thus, we improve the Bayesian semiparametric method for the selection of the tuning parameters for splines as the number and location of knots using a Bayesian knot selection method. Equally spaced knots cannot capture the characteristic of radiation exposed dose distribution which is highly skewed in general. Therefore, we propose a nonparametric Bayesian knot selection method based on a Dirichlet process mixture model. Inference of the spline coefficients after obtaining the number and location of knots is performed in the Bayesian framework. We apply this approach to the life span study cohort data from the radiation effects research foundation in Japan, and the results illustrate that the proposed method provides competitive curve estimates for the dose-response curve and relatively stable credible intervals for the curve.

A GENERAL FORMULATION OF COMBUSTION INSTABILITY FOR RAMJETS AND AFTERBURNERS

  • Hyun-Gull Yoon
    • Proceedings of the Korean Society of Propulsion Engineers Conference
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    • 1996.11a
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    • pp.119-133
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    • 1996
  • A wave equation and a comprehensive linear combustion model are developed for ramjet and afterburner combustion instability predictions. Modal analysis is used to develop general results for frequencies and damping factors and examples of their applications are given.

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Stick-slip Friction Modeling and Performance Comparison of a Precise Linear Actuator (정밀 직선구동 액츄어에이터의 스틱슬립 마찰 모형화 및 성능특성 비교)

  • Kim, Sang-Chae;Kim, Soo-Hyun
    • Journal of the Korean Society for Precision Engineering
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    • v.18 no.4
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    • pp.64-71
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    • 2001
  • In general, precise linear actuators using piezoelectric element are driven by friction force. Exact understanding of friction plays an important role in analysis and control of a motor. In this research, we designed a precise linear actuator using piezoelectric elements and observed its dynamic characteristics. By varying phase angle difference and amplitudes of the sinusoidal waves that are driving inputs, we can know that it is possible to control moving direction and distance of the slider. As preload is increased, its moving distance is decreased. And also, we have modeled a precise linear actuator using stick slip friction models such as classical, Karnopp. and reset integrator. Finally, by comparing the results of simulation and experiment, it was verified that the model is well designed.

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Linear Programming Model Discovery from Databases Using GPS and Artificial Neural Networks (GPS와 인공신경망을 활용한 데이터베이스로부터의 선형계획모형 발견법)

  • 권오병;양진설
    • Journal of the Korean Operations Research and Management Science Society
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    • v.25 no.3
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    • pp.91-107
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    • 2000
  • The linear programming model is a special form of useful knowledge that is embedded in a database. Since formulating models from scratch requires knowledge-intensive efforts, knowledge-based formulation support systems have been proposed in the Decision Support Systems area. However, they rely on the assumption that sufficient domain knowledge should already be captured as a specific knowledge representation form. Hence, the purpose of this paper is to propose a methodology that finds useful knowledge on building linear programming models from a database. The methodology consists of two parts. The first part is to find s first-cut model based on a data dictionary. To do so, we applied the General Problem Solver(GPS) algorithm. The second part is to discover a second-cut model by applying neural network technique. An illustrative example is described to show the feasibility of the proposed methodology.

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Study on Measurement of Flood Risk and Forecasting Model (홍수 위험도 척도 및 예측모형 연구)

  • Kwon, S.H.;Oh, H.S.
    • Journal of Korean Society of Industrial and Systems Engineering
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    • v.38 no.1
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    • pp.118-123
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    • 2015
  • There have been various studies on measurements of flood risk and forecasting models. For river and dam region, PDF and FVI has been proposed for measurement of flood risk and regression models have been applied for forecasting model. For Bo region unlikely river or dam region, flood risk would unexpectedly increase due to outgoing water to keep water amount under the designated risk level even the drain system could hardly manage the water amount. GFI and general linear model was proposed for flood risk measurement and forecasting model. In this paper, FVI with the consideration of duration on GFI was proposed for flood risk measurement at Bo region. General linear model was applied to the empirical data from Bo region of Nadong river to derive the forecasting model of FVI at three different values of Base High Level, 2m, 2.5m and 3m. The significant predictor variables on the target variable, FVI were as follows: ground water level based on sea level with negative effect, difference between ground altitude of ground water and river level with negative effect, and difference between ground water level and river level after Bo water being filled with positive sign for quantitative variables. And for qualitative variable, effective soil depth and ground soil type were significant for FVI.

Generating high resolution of daily mean temperature using statistical models (통계적모형을 통한 고해상도 일별 평균기온 산정)

  • Yoon, Sanghoo
    • Journal of the Korean Data and Information Science Society
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    • v.27 no.5
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    • pp.1215-1224
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    • 2016
  • Climate information of the high resolution grid units is an important factor to explain the phenomenon in a variety of research field. Statistical linear interpolation models are computationally inexpensive and applicable to any climate data compared to the dynamic simulation method at regional scales. In this paper, we considered four different linear-based statistical interpolation models: general linear model, generalized additive model, spatial linear regression model, and Bayesian spatial linear regression model. The climate variable of interest was the daily mean temperature, where the spatial variability was explained using geographic terrain information: latitude, longitude, elevation. The data were collected by weather stations in January from 2003 and 2012. In the sense of RMSE and correlation coefficient, Bayesian spatial linear regression model showed better performance in reflecting the spatial pattern compared to the other models.

Quantitative Frameworks for Multivalent Macromolecular Interactions in Biological Linear Lattice Systems

  • Choi, Jaejun;Kim, Ryeonghyeon;Koh, Junseock
    • Molecules and Cells
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    • v.45 no.7
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    • pp.444-453
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    • 2022
  • Multivalent macromolecular interactions underlie dynamic regulation of diverse biological processes in ever-changing cellular states. These interactions often involve binding of multiple proteins to a linear lattice including intrinsically disordered proteins and the chromosomal DNA with many repeating recognition motifs. Quantitative understanding of such multivalent interactions on a linear lattice is crucial for exploring their unique regulatory potentials in the cellular processes. In this review, the distinctive molecular features of the linear lattice system are first discussed with a particular focus on the overlapping nature of potential protein binding sites within a lattice. Then, we introduce two general quantitative frameworks, combinatorial and conditional probability models, dealing with the overlap problem and relating the binding parameters to the experimentally measurable properties of the linear lattice-protein interactions. To this end, we present two specific examples where the quantitative models have been applied and further extended to provide biological insights into specific cellular processes. In the first case, the conditional probability model was extended to highlight the significant impact of nonspecific binding of transcription factors to the chromosomal DNA on gene-specific transcriptional activities. The second case presents the recently developed combinatorial models to unravel the complex organization of target protein binding sites within an intrinsically disordered region (IDR) of a nucleoporin. In particular, these models have suggested a unique function of IDRs as a molecular switch coupling distinct cellular processes. The quantitative models reviewed here are envisioned to further advance for dissection and functional studies of more complex systems including phase-separated biomolecular condensates.

A Correction of East Asian Summer Precipitation Simulated by PNU/CME CGCM Using Multiple Linear Regression (다중 선형 회귀를 이용한 PNU/CME CGCM의 동아시아 여름철 강수예측 보정 연구)

  • Hwang, Yoon-Jeong;Ahn, Joong-Bae
    • Journal of the Korean earth science society
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    • v.28 no.2
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    • pp.214-226
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    • 2007
  • Because precipitation is influenced by various atmospheric variables, it is highly nonlinear. Although precipitation predicted by a dynamic model can be corrected by using a nonlinear Artificial Neural Network, this approach has limits such as choices of the initial weight, local minima and the number of neurons, etc. In the present paper, we correct simulated precipitation by using a multiple linear regression (MLR) method, which is simple and widely used. First of all, Ensemble hindcast is conducted by the PNU/CME Coupled General Circulation Model (CGCM) (Park and Ahn, 2004) for the period from April to August in 1979-2005. MLR is applied to precipitation simulated by PNU/CME CGCM for the months of June (lead 2), July (lead 3), August (lead 4) and seasonal mean JJA (from June to August) of the Northeast Asian region including the Korean Peninsula $(110^{\circ}-145^{\circ}E,\;25-55^{\circ}N)$. We build the MLR model using a linear relationship between observed precipitation and the hindcasted results from the PNU/CME CGCM. The predictor variables selected from CGCM are precipitation, 500 hPa vertical velocity, 200 hPa divergence, surface air temperature and others. After performing a leave-oneout cross validation, the results are compared with the PNU/CME CGCM's. The results including Heidke skill scores demonstrate that the MLR corrected results have better forecasts than the direct CGCM result for rainfall.

Investigation of the Instability of FGM box beams

  • Ziane, Noureddine;Meftah, Sid Ahmed;Ruta, Giuseppe;Tounsi, Abdelouahed;Adda Bedia, El Abbas
    • Structural Engineering and Mechanics
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    • v.54 no.3
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    • pp.579-595
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    • 2015
  • A general geometrically non-linear model for lateral-torsional buckling of thick and thin-walled FGM box beams is presented. In this model primary and secondary torsional warping and shear effects are taken into account. The coupled equilibrium equations obtained from Galerkin's method are derived and the corresponding tangent matrix is used to compute the critical moments. General expression is derived for the lateral-torsional buckling load of unshearable FGM beams. The results are validated by comparison with a 3D finite element simulation using the code ABAQUS. The influences of the geometrical characteristics and the shear effects on the buckling loads are demonstrated through several case studies.