• 한국자기공명학회논문지
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• 제17권2호
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• pp.86-91
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• 2013

Detailed information about the structural nature of three-coordinate borons in ${\beta}-BaB_2O_4$ is obtained through $^{11}B$ MAS NMR and $^{11}B$ single-crystal NMR. The three-coordinate $BO_3$ of the two borons B(1) and B(2) in ${\beta}-BaB_2O_4$ were distinguished. The spin-lattice relaxation time in the laboratory frame $T_1$ for B(1) and B(2) slowly decreases with increasing temperature, whereas the spin-lattice relaxation time in the rotating frame $T_{1{\rho}}$ for B(1) and B(2), which differs from $T_1$, is nearly constant. The B(1) and B(2) of the two types were distinguished by $^{11}B$ MAS NMR and $^{11}B$ single-crystal NMR.

• 대한전자공학회논문지TC
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• 제40권10호
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• pp.150-158
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• 2003

라인 소스에 의한 빔 패턴 합성 문제에서 소스 분포함수와 빔 패턴간의 관계는 푸리에 변환쌍으로 표현 될 수 있다. 본 연구에서는 원하는 lobe형 빔 패턴을 만족시키는 라인 소스 분포함수를 반복 샘플링을 통한 비선형 역변환법을 사용하여 합성하는 일반적인 방법을 제안한다. 이 방법은 유전 매질에 TE 및 TM 평면파 입사시 원하는 역산란 반사계수를 갖도록 하는 연속적으로 분포된 유전율 합성에 적용될 수 있으며, 임의 반사계수를 갖는 전송선로 합성에도 적용될 수 있는 장점을 가진다. 대역저지 공간 필터 및 분산 특성을 갖는 전송선로 필터에 적용, 분석하므로서 제안한 방법의 타당성을 보인다.

• 대한전자공학회논문지
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• 제26권6호
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• pp.71-78
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• 1989

비선형 시스템의 입출력 관계는 볼테라 급수로 나타낼 수 있으며 그것은 볼테라 커널에 의해 규명될 수 있다. 본 연구는 소수의 볼테라 급수항을 사용하여 계단 입력에 의한 고무의 힘-변위 관계를 모델링하는데 관한 것이다. 무한의 기울기를 가진 계단 입력을 가하여 얻어진 실험결과에서 일정한 압축시의 계단입력에 대한 결과를 예측한다. 비스코일레스틱 재료를 나타내는 현저한 특징중의 하나인 힘-변위 관계를 모델링하기 위해 2차와 3차 볼테라 급수 모델을 사용한다. 3차 볼테라 급수 모델이 2차 볼테라 급수 모델의 결과에 비해 더 좋은 결과가 얻어지고 있다.

• 한국정밀공학회지
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• 제8권2호
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• pp.27-35
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• 1991

We propose the crack growth rate equation which applied over three regions (threshold region, stable region, unstable region) of fatigue crack propagation. Constant stress amplitude fatigue tests are conducted for four materials under three stress ratios of R=0.05, R=0.2 and R=0.4. Materials which have different mechanical properties i.e. stainless steel, low carbon steel, medium carbon steel and aluminum alloy are used. The fatigue crack growth rate equation is given by $da/dN={\beta} (1-R)^{\delta}\({\DELTA}K-{\DELTA}K_t)^{\alpha} / (K_{cf}-K_{max})$${\alpha}, {\beta}$ , and ${\delta}$ are constants, and ${\Delta}K_t$ is stress intensity factor range at low ${\Delta}K$ region. The constants are obtained from nonlinear least square method. $K_{ef}$is critical fatigue stress intensity factor. The relation between half crack length and number of cycles obtained by integrating the crack growth rate equation is in agreement with the experimental data. It is also experimented with constant maximum stress and decreasing stress ratios, and the fatigue growth rate of each material is in accord with the proposed equation.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2010년도 추계 학술발표회
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• pp.349-356
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• 2010

In this study, a new design method of pile bent structure considering plastic hinge was proposed on the basis of the beam-column model. Based on the analysis results, it is found that the positioning of plastic hinge on the pile bent structure was influenced by nonlinear behavior of material and p-$\Delta$ effect. Moreover, concrete cracking began to occur at the joint section between the pile and column in case of pile bent structure with different cross-sections. The plastic hinge can be developed on the pile bent structure when large displacement was occurred, and pile bent structures can be maintained well only if it is developed on the column part. Therefore, in this study, the optimized cross-section ratio between column and pile was analyzed to induce the plastic hinge at the joint section between the pile and column. Based on this, the optimized diameter ratio of pile and column can be obtained below the inflection point of the bi-linear curve depending on the relations between column-pile diameter ratio($D_c/D_p$) and normalized lateral cracking load ratio($F/F_{Dc=Dp}$). And through this study, it is founded that in-depth limit($L_{As}$=0.4%) normalized by the pile length($L_P$) are proportionally decreased as the pile length($L_P/D_P$) increases up to $L_P/D_P$=17.5, and beyond that in-depth limit converges to a constant value. Finally, it is found that the proposed limit depth by taking into account the minimum concrete-steel ratio would be more economical design of the pile bent structure.

• 한국전기전자재료학회논문지
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• 제13권5호
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• pp.402-410
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• 2000

The electrical properties and stability of Pr$_{6}$/O$_{11}$-based ZnO wvaristors consisting of ZnO-Pr$_{6}$/O$_{11}$-CoO-Dy$_{2}$/O$_{3}$ based ceramics were investigated in the Dy$_{2}$/O$_{3}$ additive content range o 0.0 to 2.0 mol%. The density was nearly constant 5.62 g/cm$^3$corresponding to 97% of theoretical density as Dy$_{2}$/O$_{3}$ additive content increases up to 0.5 mol%. However the density decreased as Dy$_{2}$/O sub 3/ additive content is further additive content. Pr$_{6}$/O$_{11}$-based ZnO varistors doped with 0.5mol% Dy$_{2}$/O$_{3}$ exhibited a good nonlinearity, which is 37.76 in the nonlinear exponent and 5.36 $mutextrm{A}$ in the leakage current. And they exhibited very stress (0.80 V$_{1mA}$/9$0^{\circ}C$/12h)+(0.85 V$_{1mA}$/115$^{\circ}C$/12h)+(0.95 V$_{1mA}$/1$25^{\circ}C$/12h). Consequently it was estimated that ZnO-0.5 mol% Pr$_{6}$/O$_{11}$-1.0 mol% CoO-0.5 mol% Dy$_{2}$/O$_{3}$ based ceramics will be sufficiently used as a basic composition to develop the advanced Pr$_{6}$/O$_{11}$-based ZnO varistors in the future.he future.uture.he future.

• Elastomers and Composites
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• 제52권4호
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• pp.303-308
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• 2017

In this study, finite element modeling and material property tests are performed for the finite element analysis of rubber isolator parts which support the engine and isolate the vibration. As a result of the P direction analysis of the rubber isolator parts, the static stiffness in the P direction was 44.2 kg/mm, which is well within the error of 5% as compared with the test result of 46.1 kg/mm. The static stiffness of the rubber isolator parts in the Q direction was calculated to be 7.9 kg/mm, which is comparable to the test result of 8.6 kg/mm, with an error of less than 8%. As a result of the analysis on the Z direction, the static stiffness was calculated as 57.7 kg/mm, and the test results were not available. Through this study, it is expected that the time and cost for prototype development can be reduced through nonlinear finite element analysis for rubber isolator parts.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2004년도 춘계 학술발표회 제16권1호
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• pp.520-523
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• 2004

The finite element method(FEM) models were developed for the reinforced concrete flexural walls and analysed under constant axial and monotonic lateral load using ABAQUS. The major objective of the present study is to determine if the ABAQUS finite element program can be used to accurately model the post-cracked mode of failure in plastic regions of walls, and, if so, to develop practical failure criteria in the plastic range of the material response. The research comprises constitutive models to represent behavior of the materials that compose a wall on the basis of experimental data, development of techniques that are appropriate for analysis of reinforced concrete structures, verification, and calibration of the global model for reinforced concrete walls of increasing complexity. Results from the analyses of these FEM models offers significant insight into the flexural behavior of benchmark data.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2005년도 추계 학술발표회 제17권2호
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• pp.73-76
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• 2005

This paper discussed finite element method(FEM) models of the reinforced concrete frame retrofitted with cast-in plate infilled shear wall and analysed under constant axial and monotonic lateral load using ABAQUS. Detailed finite element models are created by studying the monotonic load response of the designed connection of reinforced concrete frame and cast-in plate infilled shear wall. The developed models account for the effect of material inelasticity, concrete cracking, geometric nonlinearity and bond-slip of steel, frame and infilled shear wall. In order to verify the proposed FEM, this study behaved analysis considered a diagonal reinforced steel. The analytical results compared with the experimental results.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1999년도 하계학술대회 논문집 A
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• pp.253-255
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• 1999

In this paper, a shape optimization algorithm of superconducting magnet using finite element method is presented. Since the superconductor loses its superconductivity over the critical magnetic field and critical current density, this material property should be taken into account in the design process. Trial and error approach of repeating the change of the design variables costs much time and it sometimes does not guarantee an optimal design. This paper presents a systematic and efficient design algorithm for the superconducting magnet. We employ the sensitivity analysis based on finite element formulation. As for optimization algorithm, the inequality constraint for the superconducting state is removed by modifying the objective function and the nonlinear equality constraint of constant volume is satisfied by the gradient projection method. This design algorithm is applied to an optimal design problem of a solenoid air-cored superconducting magnet that has a design objective of the maximum energy storage.