• Transactions on Electrical and Electronic Materials
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• v.16 no.2
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• pp.99-102
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• 2015

Thin film transistors (TFTs) with amorphous 2 wt% silicon-doped zinc tin oxide (a-2SZTO) channel layer were fabricated using an RF magnetron sputtering system, and the effect of post-annealing treatment time on the structural and electrical properties of a-2SZTO systems was investigated. It is well known that Si can effectively reduce the generation of oxygen vacancies. However, it is interesting to note that prolonged annealing could have a bad effect on the roughness of a-2SZTO systems, since the roughness of a-2SZTO thin films increases in proportion to the thermal annealing treatment time. Thermal annealing can control the electrical characteristics of amorphous oxide semiconductor (AOS) TFTs. It was observed herein that prolonged annealing treatment can cause bumpy roughness, which led to increase of the contact resistance between the electrode and channel. Thus, it was confirmed that deterioration of the electrical characteristics could occur due to prolonged annealing. The longer annealing time also decreased the field effect mobility. The a-2SZTO TFTs annealed at 500℃ for 2 hours displayed the mobility of 2.17 cm²/Vs. As the electrical characteristics of a-2SZTO annealed at a fixed temperature for long periods were deteriorated, careful optimization of the annealing conditions for a-2SZTO, in terms of time, should be carried out to achieve better performance.

• Proceedings of the KIEE Conference
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• 2011.07a
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• pp.1507-1508
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• 2011

본 논문에서는 전기장이 염료감응형 태양전지 광전극의 산화반도체($TiO_2$)에 미치는 영향에 대해 설명하고 DSC의 효율과 밀접한 관련이 있는 산화반도체의 결정구조 개선에 초점을 맞추어 효율을 향상시키고자 하였다. DSC의 광전극 제조에서 FTO 기판에 doctor-blade 방법을 통해 $TiO_2$ paste 도포 한 후 소성 직전 전기장을 인가하여 입자의 결정화를 돕는다. 이때 인가 전압과 전압을 인가하는 시간을 변화시키면서 실험하였다. 그 후 $450^{\circ}C$에서 30분 동안 소성하였다. FE-SEM으로 $TiO_2$의 형태를 보고 전기장이 $TiO_2$ 결정화에 미치는 영향을 확인하였고, current-voltage 특성 분석을 통해 에너지 변환 효율과 각 요소들을 비교하였다. UV-vis spectrophotometer, EIS 측정으로 각 DSC의 광 흡수율과 $TiO_2$/염료/전해질 영역에서의 저항을 분석하였다. 그 결과 전기장이 가해진 $TiO_2$의 결정이 더 잘 배열된 것을 확인하였고, 그로인해 에너지 변환 효율이 7.09%에서 8.65%로 증가한 것을 알 수 있었다.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.4
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• pp.657-663
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• 2018

In this study, shape optimization was performed to improve the vibration isolation capability of an anti-vibration rubber assembly, which is used in the field option cabin of agricultural tractors. A uniaxial tension test and biaxial tension test were performed to characterize the hyper-elastic material properties of rubber, and the data were used to calibrate the material model used in the finite element analyses. A field test was performed to quantify the input excitation from the tractor and the output response at the cabin frame. To account for the nonlinear behavior of rubber, static analyses were performed and the load-displacement curve of rubber was derived. The stiffness of the rubber was calculated from this curve and input to the harmonic analyses of the cabin. The results were verified using the test data. Taguchi's parameter design method was used to find the optimal shape of the anti-vibration rubber assembly, which indicated a shape with reduced stiffness. The vibration of the cabin frame was reduced by the optimization by as much as 35% compared to the initial design.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.28 no.6
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• pp.379-383
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• 2015

Some insulating materials are organized and analyzed with variables to obtain the optimized profile of encapsulated three phase of epoxy barrier which is applied to gas compartment and supporting conductors for high voltage GIS (gas insulated switchgear). The high voltage GIS is used in electrical power system and operating reliability. In this paper, optimization possibility of barrier shape including both electrical insulation performance and mechanical strength, premised on that condition minimizing volume and light weight should be kept for high voltage GIS, could be achieved by analysis simulation. As a result, filling material which is lower permittivity such as $SiO_2$ instead of $Al_2O_3$ properly to the epoxy material, can be improved to increase the electrical insulation performance and mechanical strength for an optimized profile barrier of a high voltage GIS.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.18 no.4 s.119
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• pp.372-378
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• 2007

This paper presents an improvement of field uniformity in a reverberation chamber with QRDs(Quadratic Residue Diffuser) and also shows the optimal dimension of the QRDs. The QRD is designed for $1{\sim}3\;GHz$ frequency band and the FDTD(finite-Difference Time-Domain) method is used to analyze the field characteristics. At 2 GHz, the standard deviation of test volume in the reverberation chamber is the smallest when the QRD has $30{\sim}60\;%$ coverage of one side of the reverberation chamber and the field uniformity is worsened when the coverage of the QRD is either below 20 % or above 70 % of the area of the side wall. Particularly, the standard deviation of test volume in the reverberation chamber with 30 % coverage of QRD is improved by 1.53 dB compared to that of the reference chamber with no QRDs.

• Proceedings of the KIEE Conference
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• 1995.07c
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• pp.1326-1329
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• 1995

An influences of gap clearance, pressure and applied voltage shape on breakdown characteristics are investigated by using a rod-to-plane electrode in $SF_6$ gas. In case of D.C and A.C, a corona stabilization effect increases the breakdown voltage remarkably for lower pressure than 0.2MPa, whereas incase of negative D.C this effect exists independently of gas pressure. This suggests that an insulation optimization in a pratical apparatus is needed to prevent a corona appearance through the removal of local field enhancement.

• Journal of Biomedical Engineering Research
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• v.13 no.3
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• pp.217-224
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• 1992

A new three-channel surface gradient coil obtained by using numerical optimization and its application to MR computerized nomography are presented. The new surface gradient coil pro aided linear field gradient region more than twice wider compared with the t'irst surface gradi encl coil, removed torque and field offset, and reduced coupling between the surface gradient coil and combined surface rf coil. We realized the new surface gradient coil set with $30{\times}60{cm^2}$2 size, which generated more tharl 4G/cm with 100 amperes over a $4{\times}4{\times}4{cm^3}$ region with good linearity. The optimal geometries of the three-channel surface gradient coil and volun teer's high-resolution in wiuo spinal cord Images obtained by using the optimized surface gradi ent coil set are presented.

• Journal of the Korean Society of Industry Convergence
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• v.24 no.5
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• pp.531-536
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• 2021

As artificial intelligence technology advances, it is being applied to various application fields. Artificial intelligence is performing well in the field of image recognition and classification. Chip design specialized in this field is also actively being studied. Artificial intelligence-specific chips are designed to provide optimal performance for the applications. At the design task, memory component optimization is becoming an important issue. In this study, the optimal algorithm for the memory size exploration is presented, and the optimal memory size is becoming as a important factor in providing a proper design that meets the requirements of performance, cost, and power consumption.

• Structural Engineering and Mechanics
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• v.45 no.4
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• pp.471-494
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• 2013

In this paper, identification of isotropic and orthotropic linear elastic material constitutive parameters has been demonstrated by a FEA-free energy-based inverse analysis method. An important feature of the proposed method is that it requires no finite element (FE) simulation of the tested material. Full-field displacements calculated using digital image correlation (DIC) are used to compute DIC stress fields enforcing the equilibrium condition and DIC strain fields using interpolation functions. Boundary tractions and displacements are implicitly recast into an objective function that measures the energy residual of external work and internal elastic strain energy. The energy conservation principle states that the residual should be zero, and so minimizing this objective function inversely identifies the constitutive parameters. Synthetic data from simulated testing of isotropic materials and orthotropic composite materials under 2D plane stress conditions are used for verification of the proposed method. When identifying the constitutive parameters, it is beneficial to apply loadings in multiple directions, and in ways that create non-uniform stress distributions. The sensitivity of the parameter identification method to noise in both the measured full-field DIC displacements and loadings has been investigated.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2010.06a
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• pp.337-337
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• 2010

갈륨-질화물 (GaN) 기반의 고 전자 이동도 트랜지스터 (High Electron Mobility Transistor, HEMT)는 GaN의 큰 밴드갭 (3.4~6.2 eV), 높은 항복전계 (Ec~3 MV/cm) 및 높은 전자 포화 속도 (saturation velocity $-107\;cm{\cdot}s-1$) 특성과 AlGaN/GaN 등과 같은 이종접합구조(Heterostructure )로부터 발생하는 높은 면밀도(Sheet Concentration)를 갖는 이차원 전자가스(Two-Dimensional Electron Gas, 2DEG) 채널로 인해 차세대 고출력/고전압 소자로서 각광받고 있다. 하지만 드레인 쪽의 게이트 에지부분에 집중되는 전계로 인한 애벌린치 할복현상(Breakdown)이 발생하는 문제점이 있다. 따라서 AlGaN/GaN HEMT의 항복전압 향상을 위한 방법으로 필드플레이트(Field-Plate) 구조가 많이 사용되고 있다. 본 논문에서는 2D 시뮬레이션을 통한 AlGaN/GaN HEMT의 필드플레이트 구조 최적화를 수행하였다. 이를 위해 ATLASTM 전산모사 프로그램을 이용하여 필드플레이트 길이, 절연체 증류 및 두께에 따른 전류 전압 특성 및 전계 분산효과에 대한 전산모사를 수행하여 그 결과를 비교, 분석 하였다, 이를 바탕으로 기존의 구조에 비해 약 300%이상 향상된 항복전압을 갖는 AlGaN/GaN HEMT의 최적화된 필드 플레이트 구조를 제안하였다.