• Title/Summary/Keyword: Symmetric condition

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Multi-directionally Movable Lambda Shape Transducer for Ultrasonic Motor (초음파 모터용 람다형 다방향 변환자)

  • Do, Young-Soo;Nam, Hyo-Duk;Kim, Young-Duk
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.21 no.2
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    • pp.131-136
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    • 2008
  • The transducer for multi-directionally movable ultrasonic motor having lambda shaped vibrators has been proposed and designed. The two branches cross at a right angle with each other at the tip. FEM analyses of lambda shaped transducer were carried out to find vibration modes for ultrasonic motor. The lambda shaped transducer has one symmetric mode and two anti-symmetric modes. The symmetric mode generates the normal direction motion of the tip. The lateral and vertical direction motion of the tip are excited by two anti-symmetric modes. The normal and lateral direction motions made an lateral elliptic trajectory. And the normal and vertical direction motions made an vertical elliptic trajectory normal to previous one. The transducer with 1 mm in thickness and 25 mm in length has been fabricated and evaluated. The resonance frequencies of the transducer was 32 kHz and 103 kHz. The tangential and vertical vibration displacement of the transducer having the lateral elliptic trajectory were $1.5{\mu}m\;and\;1.1{\mu}m$, respectively at the driving voltage of 100 Vpp and frequency of 32 kHz and 103 kHz. And the tangential and vertical vibration displacement of the transducer having the vertical elliptic trajectory were $0.4{\mu}m\;and\;0.2{\mu}m$, respectively at the same driving condition.

On Generalized 𝜙-recurrent Kenmotsu Manifolds with respect to Quarter-symmetric Metric Connection

  • Hui, Shyamal Kumar;Lemence, Richard Santiago
    • Kyungpook Mathematical Journal
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    • v.58 no.2
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    • pp.347-359
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    • 2018
  • A Kenmotsu manifold $M^n({\phi},\;{\xi},\;{\eta},\;g)$, (n = 2m + 1 > 3) is called a generalized ${\phi}-recurrent$ if its curvature tensor R satisfies $${\phi}^2(({\nabla}_wR)(X,Y)Z)=A(W)R(X,Y)Z+B(W)G(X,Y)Z$$ for all $X,\;Y,\;Z,\;W{\in}{\chi}(M)$, where ${\nabla}$ denotes the operator of covariant differentiation with respect to the metric g, i.e. ${\nabla}$ is the Riemannian connection, A, B are non-vanishing 1-forms and G is given by G(X, Y)Z = g(Y, Z)X - g(X, Z)Y. In particular, if A = 0 = B then the manifold is called a ${\phi}-symmetric$. Now, a Kenmotsu manifold $M^n({\phi},\;{\xi},\;{\eta},\;g)$, (n = 2m + 1 > 3) is said to be generalized ${\phi}-Ricci$ recurrent if it satisfies $${\phi}^2(({\nabla}_wQ)(Y))=A(X)QY+B(X)Y$$ for any vector field $X,\;Y{\in}{\chi}(M)$, where Q is the Ricci operator, i.e., g(QX, Y) = S(X, Y) for all X, Y. In this paper, we study generalized ${\phi}-recurrent$ and generalized ${\phi}-Ricci$ recurrent Kenmotsu manifolds with respect to quarter-symmetric metric connection and obtain a necessary and sufficient condition of a generalized ${\phi}-recurrent$ Kenmotsu manifold with respect to quarter symmetric metric connection to be generalized Ricci recurrent Kenmotsu manifold with respect to quarter symmetric metric connection.

A Numerical Study on the Behavior of Convex and Concave Slopes in Plan View (볼록 및 오목 사면 형상에 따른 거동에 대한 수치해석 모형 연구)

  • 정우철;박형동;박연준;유광호
    • Proceedings of the Korean Geotechical Society Conference
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    • 2000.11b
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    • pp.213-220
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    • 2000
  • Numerical modeling of cut slope has some limits in simulating the real slopes. In the case of 2D analysis of slope stability, it is assumed that slope is simply straight even when it is concave or convex in plan view. In this study, 3D analysis in curved shape slopes has been conducted for the comparison with 2D analysis in terms of failure mode and factor of safety. For this, 3D analysis by FLAC3D was compared with 2D analysis in plane strain condition and axi-symmetric model condition by FLAC. It was also observed how safety factors of slopes were affected by the variation of the tensile strength and cohesion, which are important variables to decide whether the slope fails or not. 2D analysis of concave slopes under plane strain condition showed much smaller safety factors by 16-40 % errors depending on the radius of curvature of slopes, compared to the more realistic values from 3D analysis. In case of convex slopes, the lower values by 7-10 % has been reported. 2D analysis of axi-symmetric model showed also smaller safety factors by 6-10 % and by 2-4 %, in case of concave and convex slopes, respectively. Such results are expected to contribute to the better understanding of failure process and could be applied for improved design of slopes.

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GLOBAL SOLUTIONS OF SEMIRELATIVISTIC HARTREE TYPE EQUATIONS

  • Cho, Yong-Geun;Ozawa, Tohru
    • Journal of the Korean Mathematical Society
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    • v.44 no.5
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    • pp.1065-1078
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    • 2007
  • We consider initial value problems for the semirelativistic Hartree type equations with cubic convolution nonlinearity $F(u)=(V*{\mid}u{\mid}^2)u$. Here V is a sum of two Coulomb type potentials. Under a specified decay condition and a symmetric condition for the potential V we show the global existence and scattering of solutions.

A ROLE OF SINGLETONS IN QUANTUM CENTRAL LIMIT THEOREMS

  • Accardi, Luigi;Hashimoto, Yukihiro;Obata, Nobuaki
    • Journal of the Korean Mathematical Society
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    • v.35 no.3
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    • pp.675-690
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    • 1998
  • A role of singletons in quantum central limit theorems is studied. A common feature of quantum central limit distributions, the singleton condition which guarantees the symmetry of the limit distributions, is revisited in the category of discrete groups and monoids. Introducing a general notion of quantum independence, the singleton independence which include the singleton condition as an extremal case, we clarify the role of singletons and investigate the mechanism of arising non-symmetric limit distributions.

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Laminar Convective Heat Transfer in Vertical Square Duct with Variational Symmetric Heat Flux (비균일 대칭성 열Flux인 수직 사각 닥트내의 층류조합대류 열전달 효과)

  • 김시영
    • Journal of the Korean Society of Fisheries and Ocean Technology
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    • v.18 no.1
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    • pp.47-53
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    • 1982
  • An analysis of convection, in a fully developed laminar steady flow through the vertical square duct under the condition of variational symmetric heat flux, is considered. Finite element solution algorithm by Galerkin's method with triangular elements and linear interpolation polynominals for the temperature and velocity profiles are derived for the vertical square duct. The comparison of temperature distribution due to variational symmetric heat flux in the duct were made with available the other data when the condition of peripheral heat flux were uniform and zero. Numerical values for the dimensionless temperatures and Nusselt numbers at selected Rayleigh numbers and pressure gradient parameters were obtained at a few nodal points for the vertical square ducts and effects of corner in the duct were investigated.

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An Investigation on the Thermal Characteristics of Heat-Responsive Element of Sprinkler Head (스프링클러헤드 감열부의 열적 특성에 관한 연구)

  • You, Woo-Jun;Moon, Hyo-Jun;Youm, Moon-Cheon;Ryou, Hong-Sun
    • Fire Science and Engineering
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    • v.26 no.3
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    • pp.79-84
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    • 2012
  • In this study thermal characteristics of heat-responsive element considering conduction, convection and rate of change of element using Response Time Index (RTI) applied to sensitivity test of sprinkler head at home and aborad are theoretically investigated. Analytic solution of temperature distributions with radial direction and time is obtained form energy transport equations, non-homogeneous 2th order partial differential equation, applying to constant wall temperature and symmetric condition in order to analyze thermal characteristics of heat-responsive element for circular cylindrical geometry. Base on the results, the analytic method of this study is fundamental data to practical use for sensitivity test of sprinkler head and design of heat-responsive element.

Dynamic Stability and Semi-Analytical Taylor Solution of Arch With Symmetric Mode (대칭 모드 아치의 준-해석적 테일러 해와 동적 안정성)

  • Pokhrel, Bijaya P.;Shon, Sudeok;Ha, Junhong;Lee, Seungjae
    • Journal of Korean Association for Spatial Structures
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    • v.18 no.3
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    • pp.83-91
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    • 2018
  • In this study, we investigated the dynamic stability of the system and the semi-analytical solution of the shallow arch. The governing equation for the primary symmetric mode of the arch under external load was derived and expressed simply by using parameters. The semi-analytical solution of the equation was obtained using the Taylor series and the stability of the system for the constant load was analyzed. As a result, we can classify equilibrium points by root of equilibrium equation, and classified stable, asymptotical stable and unstable resigns of equilibrium path. We observed stable points and attractors that appeared differently depending on the shape parameter h, and we can see the points where dynamic buckling occurs. Dynamic buckling of arches with initial condition did not occur in low shape parameter, and sensitive range of critical boundary was observed in low damping constants.

A Study on the Evaluation of elastic buckling strength of Singly Symmetric I-Beams (일축대칭 I형보의 탄성좌굴강도 산정에 관한 연구)

  • Ku, So-Yeun;Ryu, Hyo-Jin;Lim, Nam-Hyoung;Lee, Jin-Ok
    • 한국방재학회:학술대회논문집
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    • 2008.02a
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    • pp.79-82
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    • 2008
  • The elastic critical moment of I-beams subjected to moment is directly affected by the following factors; loading type; loading position with respect to the mid-height of the cross section; end restraint conditions. Most design specifications usually provide buckling solutions derived for uniform moment loading condition and account for variable moment along the unbraced length with a moment gradient correction factor applied to these solutions. In order for the method in the SSRC Guide to be applicable for singly symmetric I-beams, improved moment gradient correction factors were proposed in this study. Finite element buckling analyses of singly symmetric I-beams subjected to transverse loading applied at different heights with respect to the mid-height of the cross section were conducted. Transverse loads consisting of a mid-span point load and a uniformly distributed load were considered in the investigation.

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Chemical Interaction in Downstream Flows of SNG/Air Symmetric Premixed Counterflow Flame (SNG/Air 예혼합 대향류 대칭화염의 후류 유동장에서 화학적 상호작용)

  • KANG, YEONSE;LEE, KEEMAN
    • Transactions of the Korean hydrogen and new energy society
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    • v.29 no.6
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    • pp.668-679
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    • 2018
  • Experimental and numerical data were compared through a counterflow burner for the characteristic of basic flame about SNG- C11. In order to use the numerical mechanism accurately, the validation was carried out at strain rate ($a_g=30$, $120s^{-1}$) and the UCSD model showed satisfactory results. The effective Lewis number of the extinction boundary, and the behavior of extinction for the symmetric flames of the SNG-C11, could be explained through the trend of $Le_V$, and the flame of the extinction condition was inspected by the major species, key radicals and the chemical reaction paths. The interactions phenomenon in the merged flames has chemical reaction path for producing $HO_2$ were generated at stagnation point. It can be expected the one of major factors in interaction phenomenon.