• Title/Summary/Keyword: Characteristic Roots

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An Analysis of Stress Intensity Factors of Composite Materials by Boundary Element Method (BEM) (경계요소법(BEM)에 의한 복합재료의 응력확대계수 해석)

  • 이갑래;조상봉;최용식
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.15 no.1
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    • pp.179-189
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    • 1991
  • Composite materials are generally treated as anisotropic or an orthotropic materials. Unlike isotropic materials, the orthotropic materials can divided three groups depending upon the relationship of the four material constants or depending upon the characteristic roots of orthotropic materials. In particular, the fundamental solutions of two dimensional BEM for composite materials (orthotropic or anisotropic material) generally have a singularity in the conventional method when the characteristic roots are equal. In consideration of this singularity in the conventional method when the characteristic roots are equal. In consideration of this singular problems, in this paper, the fundamental solutions of BEM are systematically analysed for orthotropic materials. And the stress and displacement fields for a crack in an orthotropic materials are singular when the characteristic roots of orthotropic materials are equal. Therefore, these fields for a crack in an orthotropic materials are analysed by the analogous method to isotropic materials when the characteristic roots are equal.

Characteristic Impact Odorants of Changpo (Acorus calamus var. angustatus Bess) Root Essential Oil

  • Choi, Hyang-Sook
    • Food Science and Biotechnology
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    • v.14 no.4
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    • pp.450-455
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    • 2005
  • This study was conducted to determine firstly the composition of the essential oil from fresh changpo (Acorus calamus var. angustatus Bess) roots quantitatively and qualitatively by use of two internal standards, and secondly volatile compounds which are primarily responsible for the aroma of changpo roots. Simultaneous steam distillation and extraction method was used for essential oil extraction, and aroma extract dilution analysis (AEDA) and sniffing test by gas chromatography/olfactometry (GC/O) were used to detect the characteristic impact odorants. According to the instrumental analysis of changpo root essential oil, cis, trans-famesol (47.56 mg/kg of fresh wt), octanoic acid (23.73 mg/kg of fresh wt), trans-2-dodecenal (20.28 mg/kg of fresh wt) and trans, trans-farnesol (13.81 mg/kg of fresh wt) were the most abundant compounds. Geranyl acetate, trans-nerolidol and trans, trans-farnesyl acetate were evaluated as the characteristic impact odorants of changpo roots from results of AEDA and sniffing test. Especially, geranyl acetate was considered as the most similar odor component to changpo roots by organoleptic evaluation with GC/O.

Stability of Time Delay Systems Using Numerical Computation of Argument Principles

  • Suh, Young-Soo
    • International Journal of Control, Automation, and Systems
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    • v.1 no.1
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    • pp.127-133
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    • 2003
  • This paper proposes a new numerical method to check the stability of a general class of time delay systems. The proposed method checks whether there are characteristic roots whose real values are nonnegative through two steps. Firstly, rectangular bounds of characteristic roots whose real values are nonnegative are computed. Secondly, the existence of roots inside the bounds are checked using the numerical computation of argument principles. An adaptive discretization is proposed for the numerical computation of argument principles.

A study of fundamental solution of BEM for orthotropic materials (직교이방성 재료에 대한 경계요소법(BEM)의 기본해에 관한 연구)

  • 이갑래;조상봉;최용식
    • Journal of the korean Society of Automotive Engineers
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    • v.12 no.2
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    • pp.51-58
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    • 1990
  • According to the developments of various composite materials, it seems to be very important to evaluate the strength and fracture behavior of composite materials. When the composite material is considered as orthotropic material, the characteristic equation of orthotropic material have complex roots. If characteristic roots are equal, the fundamental solutions of BEM become singular ones. This paper analyse the fundamental solutions of the singular problem of orthotropic material using the analogous method to isotropic material.

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Performance of Roots-type Vacuum Pump with Cassini Oval Lobe Shape (Cassini 형 루츠 진공 펌프의 성능에 관한 연구)

  • Kim, H.J.;Cho, J.H.;Kim, Youn-J.
    • Proceedings of the KSME Conference
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    • 2000.04b
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    • pp.813-818
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    • 2000
  • The objective of this study is to elucidate the characteristic performance of Roots-type vacuum pump with Cassini oval lobe shape. The modelled lobe shape of Roots-type vacuum pump is two-lobe spur gear. The numerical analyses are performed fer leak flows, using 4th-order Runge-Kutta method and are compared with experimental results. Results show that for the case of involute lobe shape the total amount of the leak flow conductance is greater than that of cycloid and Cassini oval lobe shapes.

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Lagged Unstable Regressor Models and Asymptotic Efficiency of the Ordinary Least Squares Estimator

  • Shin, Dong-Wan;Oh, Man-Suk
    • Journal of the Korean Statistical Society
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    • v.31 no.2
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    • pp.251-259
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    • 2002
  • Lagged regressor models with general stationary errors independent of the regressors are considered. The regressor process is unstable having characteristic roots on the unit circle. If the order of the lag matches the number of roots on the unit circle, the ordinary least squares estimator (OLSE) is asymptotically efficient in that it has the same limiting distribution as the generalized least squares estimator (GLSE) under the same normalization. This result extends the well-known result of Grenander and Rosenblatt (1957) for asymptotic efficiency of the OLSE in deterministic polynomial and/or trigonometric regressor models to a class of models with stochastic regressors.

Community Structure of Arbuscular Mycorrhizal Fungi in Upo Wetland, Korea

  • Park, Hyeok;Ko, Kang-Moon;Eom, Ahn-Heum
    • 한국균학회소식:학술대회논문집
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    • 2018.05a
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    • pp.35-35
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    • 2018
  • Arbuscular mycorrhizal fungi (AMF) are one of the most widespread symbionts globally. Owing to their enhanced nutrient absorption capacity, AMF significantly contribute to the survival of individual plants and the ecosystem functioning. Community structures of AMF are affected by many environmental factors Inland wetlands have a different environment from common forest soils, therefore, plants inhabiting wetlands may have characteristic AMF communities. The purpose of this study was to compare the AMF communities in wetlands, among the species of host plants. We sampled the roots of 3 host plant species, Phragmites communis, Miscanthus sacchariflorus, and Trisetum bifidum with rhizospheres from 3 isolated areas in Upo wetland, Korea. We extracted DNA from AMF spores in rhizospheres and the roots of 3 plant species. We amplified 18S rDNA of AMF using AMF specific primer. As a result, we confirmed 9 species from 5 genera in AMF spores, and 5 species from 3 genera in plant roots. Funneliformis caledonium was the most dominant species in field soils, on the other hand, Diversispora aurantia was the most dominant species in plant roots. We confirmed that species diversity and abundance of AMF communities were different among host plant species. These results showed that the AMF community had specific to host plants in the inland wetland.

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Characteristic of Orchid Mycorrhizal Fungi from Roots of Cypripedium japonicum and C. macranthum (광릉요강꽃과 복주머니란의 뿌리에 감염된 난균근균의 특성)

  • Sim, Mi-Yeong;Youm, Jae-Young;Chung, Jae-Min;Lee, Byung-Chun;Koo, Chang-Duck;Eom, Ahn-Heum
    • The Korean Journal of Mycology
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    • v.38 no.1
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    • pp.1-4
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    • 2010
  • Orchid mycorrhizal fungi(OMF) were examined in roots of the two threatened orchid species, Cypripedium japonicum and C. macranthum. The morphological characteristics of mycorrhizal colonization in the roots of two orchid species were observed. OMF colonized in the roots of two species were identified using molecular analysis. DNA from the root was extracted and amplified internal transcribed spacer(ITS) region using basidiomycete ITS primers, ITS1-OF and ITS4-OF. Four species belonging to Tulasnellaceae in roots of C. japonicum and two species of Tulasnellaceae and one basidiomycetous species was found in roots of C. macranthum.

Analytical Evaluation of Rotor Dynamic Characteristic of Roots Type Vacuum Pump (루츠타입 진공펌프 동특성의 해석적 평가)

  • Lee, Jong-Myeong;Kim, Yong-Hwi;Ha, Jeong-Min;Gu, Dong-Sik;Choi, Byeong-Keun
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.21 no.12
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    • pp.1112-1119
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    • 2011
  • The goal of this study is the stability evaluation of a vacuum pump through modal test and rotor dynamics. Roots type vacuum pump, which is a dry vacuum pump, is necessary for the manufacturing process of the semiconductor and the display. Eigenvalue was solved by the finite-element method(FEM) using 2D and 3D models, then the modal test result was compared with the FEM result. According to the comparison, the analysis result using the 2D was more accurate than the 3D model. Therefore, rotor dynamics was performed by the 2D model. Campbell diagram and root-locus maps, which were calculated by complex-eigenvalue analysis, were used to evaluate the stability of the rotors of the vacuum pump. And displacement solved by unbalance response analysis was compared with the minimum clearance between two rotors of the vacuum pump. Thus, the vacuum pump is assumed operated under steady state through the evaluation of the rotor dynamics.