• 대한기계학회논문집A
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• 제38권2호
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• pp.121-127
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• 2014

단층 그래핀 시트(Single layer graphene sheet, SLGS)의 찢어짐 모드(모드 III) 파괴 예측을 위한 원자 기반 미세결합요소모델이 개발되었다. 이 모델은 그래핀 시트의 최대 변형률 관계를 예측하기 위해 수정된 모스포텐셜을 사용한다. 면외 전단하중 조건에서 그래핀의 모드 III 파괴를 광범위한 분자역학(Molecular mechanics, MM) 시뮬레이션으로 조사하였다. 분자역학은 원자의 균열선단 근처 원자의 변위를 설명하기 위해 사용되었고, 선형탄성파괴역학은 이 영역 바깥의 영역을 설명하기 위해 사용되었다. 해석 결과 분자역학 방법이 SLGS의 전단 물성 계산뿐만 아니라 armchair 및 zigzag 방향 모드 III 파괴인성 연구에도 단순하면서도 신뢰할만하다는 것을 보여준다. SLGS 의 모드 III 파괴인성은 zigzag 방향에 대해 $0.86MPa{\sqrt{m}}$, armchair 방향에 대해 $0.93MPa{\sqrt{m}}$로 예측되었다.

• 한국초전도학회:학술대회논문집
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• 한국초전도학회 1999년도 High Temperature Superconductivity Vol.IX
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• pp.75-82
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• 1999

TE$_{01\;{\delta}}$ mode Cavity Resonators with a low loss dielectric rod and YBa$_2Cu_3O_{7-{\delta}}$ (YBCO) endplates were prepared and their microwave properties were studied at temperatures above 30 K. Both sapphire and rutile were used as the dielectrics. The TE$_{01\;{\delta}}$ mode Q$_0$ of the resonator, designed to work as a tunable resonator with variations in the gap distance (s) between the dielectric rod and the top YBCO, was more than 1000000 at s = 0 mm and at 30 K and .the resonant frequency of 19.56GHz when a sapphire rod was used for the dielectric. The TE$_2Cu_3O_{7-{\delta}}$ mode resonant frequency (f$_0$) appeared to decrease as the temperature is raised. Meanwhile, the temperature dependence of the TE$_2Cu_3O_{7-{\delta}}$ mode f$_0$ of the rutile-loaded resonator appeared different with f$_0$ increasing according to the temperature and Q$_0$ more than 300000 at 30 K and f$_0$ = 8.56 CHz. Comparisons were made between the microwave properties of the sapphire-loaded and the rutile-loaded resonators. Also, applications of the TE$_2Cu_3O_{7-{\delta}}$ mode cavity resonator for a tunable resonator with a very high Q$_0$ as · well as a characterization tool for surface resistance measurements of HTS films are described.

• Journal of Korean Neurosurgical Society
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• 제51권1호
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• pp.24-30
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• 2012

Objective : This study was conducted to assess the clinical significance of traumatic brain stem injury (TBSI) reflected on Glasgow Coma Score (GCS) and Glasgow Outcome Score (GOS) by various clinical variables. Methods : A total of 136 TBSI patients were selected out of 2695 head-injured patients. All initial computerized tomography and/or magnetic resonance imaging studies were retrospectively analyzed according to demographic- and injury variables which result in GCS and GOS. Results : In univariate analysis, mode of injury showed a significant effect on combined injury (p<0.001), as were the cases with skull fracture on radiologic finding (p<0.000). The GCS showed a various correlation with radiologic finding (p<0.000), mode of injury (p<0.002), but less favorably with impact site (p<0.052), age (p<0.054) and skull fracture (p<0.057), in order of statistical significances. However, only GOS showed a definite correlation to radiologic finding (p<0.000). In multivariate analysis, the individual variables to enhance an unfavorable effect on GCS were radiologic finding [odds ratio (OR) 7.327, 95% confidence interval (CI)], mode of injury (OR; 4.499, 95% CI) and age (OR; 3.141, 95% CI). Those which influence an unfavorable effect on GOS were radiologic finding (OR; 25.420, 95% CI) and age (OR; 2.674, 95% CI). Conclusion : In evaluation of TBSI on outcome, the variables such as radiological finding, mode of injury, and age were revealed as three important ones to have an unfavorable effect on early stage outcome expressed as GCS. However, mode of injury was shown not to have an unfavorable effect on late stage outcome as GOS. Among all unfavorable variables, radiological finding was confirmed as the only powerful prognostic variable both on GCS and GOS.

• Composites Research
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• 제28권4호
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• pp.191-196
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• 2015

본 연구에서는 접착제로 체결된 구조물의 접착 조인트에서의 파괴인성을 조사하기 위하여 알루미늄 폼으로 제작한 Mode III 형 DCB 시험편들에 대하여 정적 해석 및 실험을 수행하였다. 정적 해석에서의 경우, 각 시험편 모델들은 강제 변위가 약 5 mm 진행되었을 때 최대 반력을 보였으며, 이 때 각 시험편 모델들의 최대 반력은 두께가 35 mm인 모델이 약 0.25 kN, 두께가 45 mm인 모델이 약 0.28 kN, 두께가 55 mm인 모델이 약 0.5 kN으로 나타났다. 이 해석 결과들을 입증하기 위하여 정적 실험의 경우에서 두 개의 시험편들을 택하였다. 정적 실험에서의 경우, 각 시험편들은 강제 변위가 약 5~6 mm 진행되었을 때 최대 반력을 보였으며, 각 시험편들의 최대 반력은 두께가 35 mm인 시험편이 약 0.22 kN, 두께가 45 mm인 시험편이 약 0.3 kN으로 나타났다. 도출된 결과값들을 비교하였을 때 해석과 실험의 데이터들 간에 큰 차이가 없음을 알 수 있었고, 따라서 별도의 실험과정 없이 해석을 통해서도 그 연구 데이터들을 확보할 수 있을 것으로 판단되며, Mode III 형 DCB 접합구조물에서의 기계적 특성들을 체계적으로 분석할 수 있을 것으로 사료된다.

• 한국정밀공학회지
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• 제7권4호
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• pp.103-116
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• 1990

The mixed mode surface crack in finite-width plate subjected to uniform shearing has been analyzed in 3-D problem by using boundary element method. The calculations were carried out for the surface crack angles (${\alpha}$) of $0^{\circ}, 15^{\circ}, 30^{\circ}, 45^{\circ}, 60^{\circ}, and 75^{\circ}, $ and for the aspect ratio(a/c) of 0.2, 0.4, 0.6 and 1.0 to get stress intensity factors at the boundary points of the surface crack. For the aspect ratio of 1.0 and the surface crack angles, finite element method was used to check the results in this in this study. Comparison of the results from both method showed good agreement.

• 한국정밀공학회지
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• 제7권4호
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• pp.117-129
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• 1990

The mixed mode surface crack in finite-width plate subjected to uniform shearing has been analyzed in 3-D problem by using boundary element method. The calculations were carried out for the surface crack angles (${\alpha}$) of $0^{\circ}, 15^{\circ}, 30^{\circ}, 45^{\circ}, 60^{\circ}, and 75^{\circ}, $ and for the aspect ratio(a/c) of 0.2, 0.4, 0.6 and 1.0 to get stress intensity factors at the boundary points of the surface crack. For the aspect ratio of 1.0 and the surface crack angles, finite element method was used to check the results in this in this study. Comparison of the results from both method showed good agreement.

• Journal of the Optical Society of Korea
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• 제11권3호
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• pp.97-100
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• 2007

We have investigated properties of a plastic photonic crystal fiber guiding terahertz radiations, THz photonic crystal fiber. The single-mode condition and dispersion of a plastic triangular THz photonic crystal fiber are investigated by using the plane wave expansion method and the beam propagation method. The THz photonic crystal fiber can perform as a single-mode fiber below 2.5 THz when the ratio of diameter (d) and period (${\Lambda}$) of air holes is less than 0.475. The THz photonic crystal fiber with ${\Lambda}=500{\mu}m$ and $d/{\Lambda}=0.4$ shows almost zero flattened dispersion behavior, $-0.03{\pm}0.02 ps/THz{\cdot}cm$, in the THz frequency range from 0.8 to 2.0 THz.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 1998년도 추계종합학술대회 논문집
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• pp.1077-1080
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• 1998

In this paper, a simple low-power current-mode CMOS wotage reference circuit is proposed. The reference circuit of enhancement-mode MOS transistors and resistors. Temperature compensation is made by adding a current component proportional to a thermal voltage to a current component proportional to a threshold voltage. The designed circuit has been simulated using a $0.65\mu\textrm{m}$ n-well CMOS process parameters. The simulation results show that the reference circuit has a temperature coefficient less than $7.8ppm/^{\circ}C$ and a power-supply(VDD) coefficient less than 0.079%/V for a temperature range from $-30^{\circ}C$ to $130^{\circ}C$ and a VDD range from 4.0V to 12V. The power consumption is 105㎼ for VDD=5V and $T=30^{\circ}C.$ The proposed reference circuit can be designed to generate a wide range of reference voltages owing to its current-mode operation.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2008년도 제30회 춘계학술대회논문집
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• pp.244-247
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• 2008

ISL의 초폭굉 모드 램 가속기 실험을 바탕으로 하여 혼합기 강도를 조정하여 수치해석을 수행하였다 ($3.0CO_2$ 희석과 $2.5CO_2$ 희석). 계산결과 $3.0CO_2$ 희석의 경우는 초기 점화가 이루어지지 않아 탄체가 가속되지 않은 반면 $2.5CO_2$ 희석을 한 경우에는 점화가 이루어지고 높은 가속을 보임을 알 수 있었다. 이것은 탄체의 가속성능이 혼합기의 강도에 단순히 비례하지 않으며 점화가 가능한 최소한의 혼합기 강도 이상에서만 초폭굉 모드 램 가속기가 정상적으로 작동함을 알 수 있었다.

• 한국전기전자재료학회논문지
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• 제26권2호
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• pp.114-118
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• 2013

In this study, coupled mode piezoelectric devices for AE sensor application with excellent displacement and piezoelectric characteristics were simulated using ATILA FEM program, and then fabricated. Displacements and electromechanical coupling factors of the piezoelectric devices were investigated. The simulation results showed that excellent displacement and electromechanical coupling factor were obtained when the ratio of diameter/thickness was 1.0. The piezoelectric device of ${\Phi}/T$= 1.0 exhibited the optimum values of fr= 406 kHz, displacement= $6.11{\times}10^{-8}[m]$, $k_{eff}$= 0.648. The results show that the coupled vibration mode piezoelectric device is a promising candidate for the application of AE sensor piezoelectric device.