• Title/Summary/Keyword: gradient structure

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Effects of Combustion Atmosphere Pressure on Non-premixed Counterflow Flame (비예혼합 대향류 화염에서 연소 분위기 압력 영향 연구)

  • Lee, Kee-Man
    • Journal of Advanced Marine Engineering and Technology
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    • v.30 no.8
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    • pp.853-862
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    • 2006
  • The present study is numerically investigated the flame structure of non-premixed counterflow jet flames using the laminar flamelet model Detailed flame structures with the fuel composition of 40% CO, 30% $H_2$. 30% $N_2$ and an oxidizer composition of 79% $N_2$ and 21% $O_2$ in a non-premixed counterflow flame are studied numerically. This study is aimed to investigate the effects of axial velocity gradient and combustion atmosphere pressure on flame structure. The results show that the role of axial velocity gradient on combustion processes is globally opposite to that of combustion atmosphere pressure. That is, chemical nonequilibrium effects become dominant with increasing axial velocity gradient, but are suppressed with increasing ambient pressure. Also, the flame strength is globally weakened by the increase of axial velocity gradient but is augmented by the increase of ambient pressure. However, flame extinction is described better on the basis of only chemical reaction and in this study axial velocity gradient and ambient pressure play a similar role conceptually such that the increase of axial velocity gradient and ambient pressure cause flame not to be extinguished and extend the extinction limit, respectively. Consequently it is suggested that a combustion process like flame extinction is mainly influenced by the competition between the radical formation reaction and the third-body recombination reaction.

A Study on Structure Analysis of Natural Forest -Vertical Growth of Stem in Natural Oak Forests- (천연림(天然林)의 임분구조(林分構造) 해석(解析)에 관(關)한 연구(硏究) -참나무천연림(天然林)의 직립생장(直立生長)-)

  • Yun, Jong Wha;Han, Sang Sup;Kim, Ji Hong
    • Journal of Korean Society of Forest Science
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    • v.71 no.1
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    • pp.50-54
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    • 1985
  • The effect of relations parameters on the declination gradient of trees was studied in natural forest of Quercus variabilis, Quercus ${\times}$ grosseserrata, Quercus aliens, and Quercus dentata grown at various slope gradient. The declination gradients of trees were effected by the species, slope gradient, and direction of slope, but not effected by density and height in all species. The species shows a superior factor effecting declination gradient of trees compared with other relations parameters, and next effective factor was slope gradient. Especially in all of slope gradient, the declination gradient of Quercus ${\times}$ grossesserrata was highest.

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Forced vibration response in nanocomposite cylindrical shells - Based on strain gradient beam theory

  • Shokravi, Maryam
    • Steel and Composite Structures
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    • v.28 no.3
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    • pp.381-388
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    • 2018
  • In this paper, forced vibration of micro cylindrical shell reinforced by functionally graded carbon nanotubes (FG-CNTs) is presented. The structure is subjected to transverse harmonic load and modeled by beam model. The size effects are considered based on strain gradient theory containing three small scale parameters. The mixture rule is used for obtaining the effective material properties of the structure. Based on sinusoidal shear deformation theory of beam, energy method and Hamilton's principle, the motion equations are derived. Applying differential quadrature method (DQM) and Newmark method, the frequency curves of the structure are plotted. The effect of different parameters including, CNTs volume percent and distribution type, boundary conditions, size effect and length to thickness ratio on the frequency curves of the structure is studied. Numerical results indicate that the dynamic deflection of the FGX-CNT-reinforced cylindrical is lower with respect to other type of CNT distribution.

RICCI-BOURGUIGNON SOLITONS AND FISCHER-MARSDEN CONJECTURE ON GENERALIZED SASAKIAN-SPACE-FORMS WITH 𝛽-KENMOTSU STRUCTURE

  • Sudhakar Kumar Chaubey;Young Jin Suh
    • Journal of the Korean Mathematical Society
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    • v.60 no.2
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    • pp.341-358
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    • 2023
  • Our aim is to study the properties of Fischer-Marsden conjecture and Ricci-Bourguignon solitons within the framework of generalized Sasakian-space-forms with 𝛽-Kenmotsu structure. It is proven that a (2n + 1)-dimensional generalized Sasakian-space-form with 𝛽-Kenmotsu structure satisfying the Fischer-Marsden equation is a conformal gradient soliton. Also, it is shown that a generalized Sasakian-space-form with 𝛽-Kenmotsu structure admitting a gradient Ricci-Bourguignon soliton is either ψ∖Tk × M2n+1-k or gradient 𝜂-Yamabe soliton.

Low-Rank Representation-Based Image Super-Resolution Reconstruction with Edge-Preserving

  • Gao, Rui;Cheng, Deqiang;Yao, Jie;Chen, Liangliang
    • KSII Transactions on Internet and Information Systems (TIIS)
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    • v.14 no.9
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    • pp.3745-3761
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    • 2020
  • Low-rank representation methods already achieve many applications in the image reconstruction. However, for high-gradient image patches with rich texture details and strong edge information, it is difficult to find sufficient similar patches. Existing low-rank representation methods usually destroy image critical details and fail to preserve edge structure. In order to promote the performance, a new representation-based image super-resolution reconstruction method is proposed, which combines gradient domain guided image filter with the structure-constrained low-rank representation so as to enhance image details as well as reveal the intrinsic structure of an input image. Firstly, we extract the gradient domain guided filter of each atom in high resolution dictionary in order to acquire high-frequency prior information. Secondly, this prior information is taken as a structure constraint and introduced into the low-rank representation framework to develop a new model so as to maintain the edges of reconstructed image. Thirdly, the approximate optimal solution of the model is solved through alternating direction method of multipliers. After that, experiments are performed and results show that the proposed algorithm has higher performances than conventional state-of-the-art algorithms in both quantitative and qualitative aspects.

Analysis of Changes in the Characteristics of Urban Spatial Structure in Korea through the Population Gradient Curve (인구밀도경사함수를 이용한 우리나라 도시공간구조의 지역별.규모별 변화특성 분석)

  • Yun, Kapsik;Lee, Gabjeong
    • Journal of the Economic Geographical Society of Korea
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    • v.16 no.3
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    • pp.445-457
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    • 2013
  • This paper aims to investigate changes in the characteristics of urban spatial structure in Korea by regional groups and city size between 2000 and 2010. The characteristics of urban spatial structure is analyzed by Clark's population gradient curve in this paper. Therefore key parameters in population gradient function, such as population density gradients and population density in CBD represent the characteristics of urban spatial structure. The result shows that most of cities in Korea have experienced suburbanization rather than concentration, but small-size cities have experienced concentration during the period.

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Radiation Analysis of a Finite Microstrip Antenna Structure Using the CG-FFT Method : Volume Formulation (유한한 마이크로스트립 안테나구조에서 CG-FFT 방법을 이용한 복사 해석)

  • 손창우;이철훈김종규조영기
    • Proceedings of the IEEK Conference
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    • 1998.10a
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    • pp.343-346
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    • 1998
  • In this paper a radiation problem for a finite microstrip antenna structure is analyzed. For the analysis of finite structures we utilize the equivalent volume current. Intergral equation for the unknown equivalent volume current induced on a finite microstrip structure is derived and solved by the use of conjugate gradient-fast fourier. transform (CG-FFT) method. Some numerical examples are radiation patterns derived by the equivalent volume current solved by the conjugate gradient-fast fourier transform.

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Free vibration analysis of a three-layered microbeam based on strain gradient theory and three-unknown shear and normal deformation theory

  • Arefi, Mohammad;Zenkour, Ashraf M.
    • Steel and Composite Structures
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    • v.26 no.4
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    • pp.421-437
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    • 2018
  • Free vibration analysis of a three-layered microbeam including an elastic micro-core and two piezo-magnetic face-sheets resting on Pasternak's foundation are studied in this paper. Strain gradient theory is used for size-dependent modeling of microbeam. In addition, three-unknown shear and normal deformations theory is employed for description of displacement field. Hamilton's principle is used for derivation of the governing equations of motion in electro-magneto-mechanical loads. Three micro-length-scale parameters based on strain gradient theory are employed for prediction of vibrational characteristics of structure in micro-scale. The results show that increase of three micro-length-scale parameters leads to significant increase of three natural frequencies especially for increase of second micro-length-scale parameter. This result is according to this fact that stiffness of a micro-scale structure is increased with increase of micro-length-scale parameters.

SASAKIAN 3-MANIFOLDS ADMITTING A GRADIENT RICCI-YAMABE SOLITON

  • Dey, Dibakar
    • Korean Journal of Mathematics
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    • v.29 no.3
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    • pp.547-554
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    • 2021
  • The object of the present paper is to characterize Sasakian 3-manifolds admitting a gradient Ricci-Yamabe soliton. It is shown that a Sasakian 3-manifold M with constant scalar curvature admitting a proper gradient Ricci-Yamabe soliton is Einstein and locally isometric to a unit sphere. Also, the potential vector field is an infinitesimal automorphism of the contact metric structure. In addition, if M is complete, then it is compact.

Modified gradient methods hybridized with Tikhonov regularization for damage identification of spatial structure

  • Naseralavi, S.S.;Shojaee, S.;Ahmadi, M.
    • Smart Structures and Systems
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    • v.18 no.5
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    • pp.839-864
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    • 2016
  • This paper presents an efficient method for updating the structural finite element model. Model updating is performed through minimizing the difference between the recorded acceleration of a real damaged structure and a hypothetical damaged one. This is performed by updating physical parameters (module of elasticity in this study) in each step using iterative process of modified nonlinear conjugate gradient (M-NCG) and modified Broyden-Fletcher-Goldfarb-Shanno algorithm (M-BFGS) separately. These algorithms are based on sensitivity analysis and provide a solution for nonlinear damage detection problem. Three illustrative test examples are considered to assess the performance of the proposed method. Finally, it is demonstrated that the proposed method is satisfactory for detecting the location and ratio of structural damage in presence of noise.