• 한국자기학회지
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• 제23권6호
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• pp.193-199
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• 2013

NiFe/Cu/NiFe/IrMn/NiFe/Cu/NiFe 이중구조 GMR-SV 박막의 열처리 조건에 의존하는 자기등방성 영역분포 특성을 조사하였다. 진공 챔버내에서 이중구조 GMR-SV 박막을 후열처리 온도를 조절하여 면상에서 강자성체 층의 자화용이축 회전을 유도하였다. 자유층과 고정층의 자화용이축 방향에 의존하는 이중구조 GMR-SV 박막의 자기저항곡선은 외부자기장의 각도를 $0^{\circ}$에서 $360^{\circ}$까지 변화시킨 후 외부자기장의 세기에 따라서 측정하였다. 후열처리 온도가 $107^{\circ}C$일 때, 외부자기장의 방향이 $0^{\circ}$에서 $90^{\circ}$까지 영역에서 자장감응도가 약 1.52 %/Oe인 자기등방성 특성을 보였다. 이러한 특성은 고정층과 자유층을 형성하는 강자성층들이 면상에서 서로 직교한 결과임을 나타내며, 자기등방성 GMR-SV 박막 소자는 임의 방향으로 자화된 마이크로 자성비드를 검출할 수 있는 고감도 바이오센서로 사용할 가능성을 제시하였다.

• 대한수학회논문집
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• 제13권2호
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• pp.345-358
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• 1998

Let (p/q,n) denote the orbifold with its underlying space $S^3$ and a rational knot or link p/q as its singular set with a cyclic isotropy group of order n. In this paper we shall show the geometrical realization for the case (7/3,n) for all $n \geq 3$.

• 대한수학회논문집
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• 제14권1호
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• pp.211-216
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• 1999

We study the anti-linear involutions on a real algebraic vector bundle with bundle with a compact real algebraic group action.

• Kyungpook Mathematical Journal
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• 제52권3호
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• pp.271-278
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• 2012

We study some functions defined on the unit tangent space, which are formed with the second fundamental form of submanifolds of a real space form. These give an exact expression of isotropy of submanifolds in a real space form and a relationship between intrinsic invariants and extrinsic ones.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2003년도 ICCAS
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• pp.2066-2071
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• 2003

In this paper, we identify the isotropic configurations of an omnidirectional mobile robot with three caster wheels, depending on the selection of actuated joints. First, We obtain the kinematic model of a caster wheeled omnidirectional mobile robot(COMR) without matrix inversion. For a given task velocity, the instantaneous motion of each wheel is decomposed into two orthogonal instantaneous motions of the steering and the rotating joints. Second, with the characteristic length introduced, we derive the isotropy conditions of a COMR having $n({\ge}3)$ actuated joints, which are imposed on two Jacobian matrices, $A{\in}R^{n{\times}3}$ and $B{\in}R^{6{\times}6}$. Under the condition of $B{\propto}I_6$, three caster wheels should have identical structure with the length of the steering link equal to the radius of the wheel. Third, depending on the selection of actuated joints, we derive the conditions for $A^t$ $A{\propto}I_3$ and identify the isotropic configurations of a COMR. All possible actuation sets with different number of actuated joints and different combination of rotating and steering joins are considered.

• 대한기계학회논문집B
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• 제20권8호
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• pp.2650-2669
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• 1996

A new low Reynolds number nonlinear second moment turbulence closure was introduced to analyze a square sectioned 180.deg. bend flow. Inclusion of nonlinear return to isotropy term and cubic mean pressure strain term has brought out a marked improvement in the level of agreement with measured velocity profiles. Optimization of present closure was performed by comparison of computed velocity profiles with the experimental ones with variation of nonlinear return to isotropy term and quadratic and cubic pressure-strain model. Progressive vortex breakdown due to the interaction of primary and secondary flows was well captured by using the optimized second moment turbulence closure.

• 지질공학
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• 제3권3호
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• pp.231-239
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• 1993

본 연구에서는 지층속도가 이방성의 일종인 횡적등방성을 갖는 지역에서의 시추공 간 탄성파 주시자료를 역산하여 속도 이상대를 규명하는 연구를 시행하였다. 등방성 및 횡적등방성이 모형지층에 대해 파선추적법으로 합성 탄성파 주시를 구한 후, 이 주시자료에 대해 이방성을 고려한 ART 역산법과 이방성을 고려하지 않은 일반적인 ART 연산법에 의해 속도 분포를 구해본 결과, 이방성을 고려한 ART법에 의하면 이방성 및 등방성 지층의 속도분포가 잘 결정되었으며 일반적 ART법에 의하면 등방성 지층의 속도는 잘 결정되나 이방성 지층의 속도에는 오차가 많이 발생하였다. 따라서 지층의 이방성 또는 횡적등방성에 대한 사전 정보가 없을 때에는 이방성을 고려한 ART법을 적용하는 것이 좋을 것이다.

• Geomechanics and Engineering
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• 제11권4호
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• pp.515-530
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• 2016

In this paper, five different quantitative parameters were proposed for the characterization of the primary roughness which is the component of surface morphology that prevails during large strike-slip faults of more than 50 m. These parameters are mostly the anisotropic properties of rock surface morphology at various scales: (i) coefficient ($k_a$) and degree (${\delta}_a$) of apparent structural anisotropy of surface; (ii) coefficient ($k_r$) and degree (${\delta}_r$) of real structural anisotropy of surface; (iii) surface anisotropy function P(${\varphi}$); and (iv) degree of surface waviness ($W_s$). The coefficient and degree of apparent structural anisotropy allow qualifying the anisotropy/isotropy of a discontinuity according to a classification into four classes: anisotropic, moderately anisotropic/isotropic and isotropic. The coefficient and degree of real structural anisotropy of surface captures directly the actual surface anisotropy using geostatistical method. The anisotropy function predicts directional geometric properties of a surface of discontinuity from measurements in two orthogonal directions. These predicted data may subsequently be used to highlight the anisotropy/isotropy of the surface (radar plot). The degree of surface waviness allows qualifying the undulation of anisotropic surfaces. The proposed quantitative parameters allows their application at both lab and field scales.

• Transactions on Control, Automation and Systems Engineering
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• 제3권4호
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• pp.217-222
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• 2001

We propose a new two-degree of freedom parallel mechanism for a haptic device and will refer to the mechanism as the SenSation. The SenSation is designed in order to improve the kinematic performanced and to achieve static balance. We use the panto graph mechanisms in order to change the location of active joints, which leads to transform a direct kinematic singularity into a nonsingularity. The direct kinematic singular configurations of the SenSation occur near the workspace boundary. Using the property that position vector of rigid body rotating about a fixed point is normal to the velocity vector, Jacobian matrix is derived. Using the vector method, two different types of singularities of the SenSation can be identified and we discuss the physical significance of each of the three types of singularities. We will compare the kinematic performances(force manipulability ellipsoid, kinematic isotropy) of the SenSation with those of five-var parallel mechanism. By specifying that the potential energy be fixed, the conditions for the static balancing of the SenSation is derived. The static balancing is accomplished by changing the center of mass of the links.

• 한국주조공학회지
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• 제30권6호
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• pp.210-216
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• 2010

The aim of this study is to characterize a thixoextruded 7075 Al wrought alloy bar in terms of its isotropic behavior through the optical microscope, mechanical test and electron back scattered diffraction. It is also discussed of the extrudability improvement for 7075 Al wrought alloy by thixoextrusion, with emphasis on controlling thixoextrusion parameters. Hot extrusion shows that the maximum extrusion pressure depends on their characteristics in terms of flow stress and hot workability. In the contrary, thixoextrusion demonstrates that the maximum extrusion pressure is almost uniform regardless of the experimental parameters, such as initial ram speed, die bearing length and thixoextrusion temperature. The hot extruded microstructures become elongated to extrusion direction, while the thixoextruded microstructures are isotropic and homogeneously distributed due to the existence of liquid phase between solid grains during the process. The grain refinement due to dynamic recrystallization during thixoextrusion has been also occurred. Subsequent recrystallization would lead to the strengthening of mechanical properties, as observed in the study. The important point is that the values of tensile, yield strength and elongation of the thixoextruded bar without plastic deformation are similar to those of the hot extruded bar with severe plastic deformation.