• Title/Summary/Keyword: Direct gradient analysis

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An Analysis of Vegetation-Environment Relationships of Mt. Gyeryong and Mt. Deokyu by Detrended Canonical Correspondence Analysis (DCCA에 의(依)한 계룡산(鷄龍山)과 덕유산(德裕山)의 삼림군집(森林群集)과 환경(環境)의 상관관계(相關關係) 분석(分析))

  • Song, Ho-Kyung
    • Journal of Korean Society of Forest Science
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    • v.79 no.2
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    • pp.216-221
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    • 1990
  • Vegetational data from Mt. Gyeryong and Deokyu in central Korea were analysed in relation to 15 environmental variables. Two multivariate methods were applied : two-way indicator species analysis (TWINSPAN) for classification and detrended canonical correspondence analysis(DCCA), a recent technique which extracts ordination axes that can be related to environmental factors. The relationship between the distribution of dominant species of forest vegetation and soil condition in Mt. Gyeryong and Deokyu was investigated by analyzing elevation and soil nutrition gradient. Quercus mongolica forest was distributed in the high elevation and good nutrition area, Carpinzrs laxiflora and Fraxinus rhynclzophylla forest in the medium elevation and good nutrition area, Piszus densiflora-Quercus mongolica and Quercus variabilis forest in the medium elevation and medium nutrition area, Styrax jabozaica forest in the low elevation and medium nutrition area, and Pinus densiflora forest in the low elevation and poor nutrition area. The dominant compositional gradient related to elevation.

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Stable Path Tracking Control Using a Wavelet Based Fuzzy Neural Network for Mobile Robots

  • Oh, Joon-Seop;Park, Jin-Bae;Choi, Yoon-Ho
    • 제어로봇시스템학회:학술대회논문집
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    • 2005.06a
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    • pp.2254-2259
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    • 2005
  • In this paper, we propose a wavelet based fuzzy neural network(WFNN) based direct adaptive control scheme for the solution of the tracking problem of mobile robots. To design a controller, we present a WFNN structure that merges advantages of neural network, fuzzy model and wavelet transform. The basic idea of our WFNN structure is to realize the process of fuzzy reasoning of wavelet fuzzy system by the structure of a neural network and to make the parameters of fuzzy reasoning be expressed by the connection weights of a neural network. In our control system, the control signals are directly obtained to minimize the difference between the reference track and the pose of mobile robot using the gradient descent(GD) method. In addition, an approach that uses adaptive learning rates for the training of WFNN controller is driven via a Lyapunov stability analysis to guarantee the fast convergence, that is, learning rates are adaptively determined to rapidly minimize the state errors of a mobile robot. Finally, to evaluate the performance of the proposed direct adaptive control system using the WFNN controller, we compare the control performance of the WFNN controller with those of the FNN, the WNN and the WFM controllers.

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Stability Estimation of NATM Tunnel due to Excavation using Back Analysis (역해석기법을 통한 NATM 터널의 안정성 평가)

  • Lee, Jae-Ho;Kim, Young-Su;Jin, Guang-Ril;Park, Jin-Kyu;Park, Si-Hyun;Choi, Chil-Yong
    • Proceedings of the Korean Geotechical Society Conference
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    • 2008.03a
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    • pp.494-504
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    • 2008
  • Successful design, construction and maintenance of NATM tunnel demands prediction, control, stability estimation and monitoring of surface settlement, gradient and ground displacement with high accuracy. Back analysis using measured data and forward analysis have been and are indispensable tools to achieve this goal. Sakurai provided the hazard warning levels for assessing the stability of tunnels using the relation of critical strain and apparent Young's modulus. This paper performed the estimation of tunnel stability on construction. Firstly, the apparent Young's modulus concept and back analysis method is introduced for the assessment of tunnel safety during excavation a brief framework. Secondly, this paper deals with case study using "Apparent Young's modulus" and "Back analysis" for the purpose of estimating the stability of NATM tunnel in Korea. Finally, a general method that can be estimated the tunnel stability discussed by a flow chart.

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Microfluidic chip for the analysis of bacterial chemotaxis (박테리아 주화성 검사용 마이크로 플루이딕 칩)

  • Lee, Sang-Ho;Jeong, Heon-Ho;Kim, Ki-Young;Lee, Chang-Soo
    • Proceedings of the KIEE Conference
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    • 2009.07a
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    • pp.1521_1522
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    • 2009
  • Chemotaxis is the directed movement of cells in gradients of signaling molecules, an essential biological process that underlies morhpogenesis during development, and the recruitment of immune cells to sites of infection. Especially, bacterial chemotaxis has utilized as an important prelude to study metabolism, prey-predator relationship, symbiosis, other ecological interactions in microbial communities. Recently, novel analytical formats integrated with microfluidics were introduced to investigate the chemotaxis of the cells with the precise control of chemical gradient and small volume of cells. In this study, we present a method to detect bacterial chemotaxis by direct fluidic contacting. The developed fluidic-handling method is driven by capillary force, hydrophobic barrier and a cohesion force between fluids. We have investigated the chemotactic response of E Coli. and Pseudomonas aeruginosa to three kinds of chemoeffectors such as HEPES buffer, peptone and chloroform.

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Application of the first-order perturbation method to optimal structural design

  • Lee, Byung Woo;Lim, O Kaung
    • Structural Engineering and Mechanics
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    • v.4 no.4
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    • pp.425-436
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    • 1996
  • An application of the perturbation method to optimum structural design with random parameters is presented. It is formulated on the basis of the first-order stochastic finite element perturbation method. It also takes into full account the stress, displacement and eigenvalue constraints, together with the rates of change of the random variables. A method for calculating the sensitivity coefficients in regard to the governing equation and the first-order perturbed equation has been derived, by using a direct differentiation approach. A gradient-based nonlinear programming technique is used to solve the problem. The numerical results are specifically noted, where the stiffness parameter and external load are treated as random variables.

Structural Optimization Using Stochastic Finite Element Second-Order Perturbation Method (확률 유한요소 이차섭동법을 사용한 구조물 최적설계)

  • 임오강;이병우
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.19 no.8
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    • pp.1822-1831
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    • 1995
  • A general formulation of the design optimization problem with the random parameters is presented here. The formulation is based on the stochastic finite element second-order perturbation method ; it takes into full account of the stress and displacement constraints together with the rates of change of the random variables. A method of direct differentiation for calculating the sensitivity coefficients in regard to the governing equation and the second-order perturbed equation is derived. A gradient-based nonlinear programming technique is used to solve the problem. The numerical results are specifically noted, where the stiffness parameter and external load are treated as random variables.

Ecological Consideration for Restoration of the Degraded Urban River

  • Lee, Chang-Seok;You, Young-Han
    • 한국생태학회:학술대회논문집
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    • 2002.08a
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    • pp.113-118
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    • 2002
  • Vegetation and riverine structures were compared among urban and several semi-natural rivers by applying direct gradient analysis and ordination method. Urban rivers showed different species composition from the semi-natural ones. Species composition of semi-natural rivers depended on the geographical positions, such as the upstream, midstream, and downstream and on micro-topographies, such as the waterside, flooding bed, and embankment. Semi-natural rivers showed gentle change in micro-topography, whereas urban one did not so. Our restoration plan to improve the ecological quality of the degraded urban river by imitating semi-natural river was prepared based on those data.

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Structural damage detection including the temperature difference based on response sensitivity analysis

  • Wei, J.J.;Lv, Z.R.
    • Structural Engineering and Mechanics
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    • v.53 no.2
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    • pp.249-260
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    • 2015
  • Damage detection based on a reference set of measured data usually has the problem of different environmental temperature in the two sets of measurements, and the effect of temperature difference is usually ignored in the subsequent model updating. This paper attempts to identify the structural damage including the temperature difference with artificial measurement noise. Both local damages and the temperature difference are identified in a gradient-based model updating method based on dynamic response sensitivity. The sensitivities of dynamic response with respect to the system parameters and temperature difference are calculated by direct integration method. The measured dynamic responses of the structure from two different states are used directly to identify the structural local damages and the temperature difference. A single degree-of-freedom mass-spring system and a planar truss structure are studied to illustrate the effectiveness of the proposed method.

Ecological Consideration for Restoration of the Degraded Urban River

  • Lee, Chang-Seok;Yon, Young-Han
    • The Korean Journal of Ecology
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    • v.25 no.4
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    • pp.247-252
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    • 2002
  • Vegetation and riverine structures were compared among urban and several semi-natural rivers by applying direct gradient analysis and ordination method. Urban rivers showed different species composition from the semi-natural ones. Species composition of semi-natural rivers depended on the geographical positions, such as the upstream, midstream, and downstream and on micro-topographies, such as the waterside, flooding bed, and embankment. Semi-natural rivers showed gentle change in micro-topography, whereas urban one did not so. Our restoration plan to improve the ecological quality of the degraded urban river by imitating semi-natural river was prepared based on those data.

CHARACTERISTICS OF BIOHYDROGEN PRODUCTION AND MICROBIAL COMMUNITY AS A FUNCTION OF SUBSTRATE CONCENTRATION

  • Youn, Jong-Ho;Shin, Hang-Sik
    • Environmental Engineering Research
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    • v.10 no.1
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    • pp.7-14
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    • 2005
  • The feasibility of hydrogen production with a raw seed sludge through direct acclimation of feedstock was investigated at acidogenic stage, and methane was harvested at followed methanogenic stage in an anaerobic two-stage process. Hydrogen content was higher than 57% at all tested organic loading rates (OLRs) and the yield of hydrogen ranged from 1.5 to 2.4 mol H2/mol hexose consumed and peaked at 6 gVSl-1day-1. Normal butyrate and acetate were main volatile fatty acids (VFAs), whereas the concentration of propionate was insignificant. The hydrogen-producing bacteria, Clostridium thermosaccharolyticum, was detected with strong intensity at all tested organic loading rates (OLRs) by denaturing gradient gel electrophoresis (DGGE) of the polymerase chain reaction (PCR) analysis. From COD balance in the process, the fraction of the feed-COD converted to the hydrogen-COD at acidogenic stage ranged from 7.9% to 9.3% and peaked at 6 gVSl-1day-1, whereas the fraction of feed-COD converted to the methane-COD at methanogenic stage ranged from 66.2% to 72.3% and peaked at 3 gVSl-1day-1.