• 대한의용생체공학회:의공학회지
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• 제20권3호
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• pp.307-314
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• 1999

M-wave 는 신경전도 연구에 있어서 후기반응 현상 중 직접적인 반응으로, 반응 후 일정시간내에 정보가 존재하는 단발 반응의 특성을 가지고 있다. 이러한 M-wave 는 신경계통의 질환을 진단하기 위한 유용한 요소이며, 따라서 M-wave 의 형태 및 시간에 관한 정보가 간단히 표현될 수 있다면 신경질환 연구에 많은 도움이 될 것이다. 따라서 본 연구에서는 Ar 모델링 방법이 이러한 M-wave 의 정보 압축에 있어서 효과적임을 증명하였다. 이로 인해 먼저 실제로 측정된 M-wave 신호에서 Ar 파라메터를 추정하였으며, 추정된 파라메터를 가지고 근사화한 곡선과 최근의 M-wave의 정보압축에 관한 연구인 Hermite 변환을 이용한 방법에 따른 근사화 곡선을 비교하였다. 제안된 방법의 구체적인 검증을 위해 실신호와 근사화 곡선의 정규화 평균자승오차(NMSE)를 구하여 비교하였다. 결론적으로 M-wave 의 정보를 압축하는데 있어 Hermite 변환은 30개의 파라메터가 필요한 반면, 본 연구에서 제시한 AR 모델링방법은 3개의 파라메터만 가지고도 효과적으로 M-wave 의 특징을 압축할 수 있음을 보였다.

• 대한설비공학회:학술대회논문집
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• 대한설비공학회 2008년도 동계학술발표대회 논문집
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• pp.227-232
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• 2008

The present study was investigated the local heat transfer characteristics and temperature distribution on the louver fin by using the expansion model. Heat transfer rate, frost mass and temperature distribution of the louver fin under frosting condition were experimentally investigated. Local heat transfer rate and heat flux on the louver were analyzed by the conduction heat transfer between top and lower part of the louver. The experimental key parameter was brine inlet temperature(-5, -10, $-15^{\circ}C$). The heat transfer performance and frost mass at brine temperature of $-15^{\circ}C$ were increased by maximum 3 time than the brine temperature of $-5^{\circ}C$. At all experimental case, local heat transfer rate and heat flux of the louver were almost symmetry at the louver number of 6. Especially, local heat transfer rate and heat flux were maximum increased on the louver number of 4 and 8.

• 예술인문사회 융합 멀티미디어 논문지
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• 제9권4호
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• pp.1-10
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• 2019

이 연구는 수업모델로서 메이커 교육을 대학원수업 사례에 두고 탐색하는데 있다. 학습자중심으로 교육 패러다임이 변화되면서 대학원교육에서도 수업혁신을 위한 한 방법으로 모델중심 수업에 대한 관심이 증가하고 있다. 메이커 교육은 학습자를 적극적인 아이디어 생산자이면서 창조자이자 발명가로서의 개인 및 동료들 간의 자발적 공유와 나눔 활동에 주목하여 메이커 활동이 지닌 교육적 가치를 탐색하고 있다. 메이커운동이 가지는 개인적 가치(자기주도성, 창의력, 자신감, 즐거움 등)와 환경적 가치(IT 활용, 민주적 접근성, 소통, 공유, 공감 등)가 복합적으로 확인됨에 따라 이러한 메이커 운동이 가지는 교육적 의미와 가치를 반영한 교수학습 방법이 요구된다. 이러한 맥락에서 본 연구는 대학원 학생들이 개인 연구역량 향상을 위해 수행한 메이커 교육에 대한 과정의 경험을 융합연구 과정의 글쓰기에 초점을 두고 개별 프로젝트를 수행하였으며, 이를 통해 연구역량과 개인적 경험을 내용 분석하였다. 메이커 교육을 통해 창작자로서 자신의 글쓰기가 변화되는 과정을 성찰하였으며, 동료와의 공유와 비평을 통해 연구역량을 강화할 수 있었다는 점을 긍정적 학습경험으로 평가하고 있다.

• Nuclear Engineering and Technology
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• 제55권6호
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• pp.2230-2245
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• 2023

KANT (KAIST Advanced Nuclear Tachygraphy) is a PWR core simulator recently developed at Korea Advance Institute of Science and Technology, which solves three-dimensional steady-state and transient multigroup neutron diffusion equations under Cartesian geometries alongside the incorporation of thermal-hydraulics feedback effect for multi-physics calculation. It utilizes the standard Nodal Expansion Method (NEM) accelerated with various Coarse Mesh Finite Difference (CMFD) methods for neutronics calculation. For thermal-hydraulics (TH) calculation, a single-phase flow model and a one-dimensional cylindrical fuel rod heat conduction model are employed. The time-dependent neutronics and TH calculations are numerically solved through an implicit Euler scheme, where a detailed coupling strategy is presented in this paper alongside a description of nodal equivalence, macroscopic depletion, and pin power reconstruction. For validation of the steady, transient, and depletion calculation with pin power reconstruction capacity of KANT, solutions for various benchmark problems are presented. The IAEA 3-D PWR and 4-group KOEBERG problems were considered for the steady-state reactor benchmark problem. For transient calculations, LMW (Lagenbuch, Maurer and Werner) LWR and NEACRP 3-D PWR benchmarks were solved, where the latter problem includes thermal-hydraulics feedback. For macroscopic depletion with pin power reconstruction, a small PWR problem modified with KAIST benchmark model was solved. For validation of the multi-physics analysis capability of KANT concerning large-sized PWRs, the BEAVRS Cycle1 benchmark has been considered. It was found that KANT solutions are accurate and consistent compared to other published works.

• The Korean Journal of Ceramics
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• 제2권3호
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• pp.131-136
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• 1996

The electrical conductivity of polycrystalline TiO2 samples was measured over the temperature range 1000°-1400℃ and from 0.21 to 10-16 atm of oxygen. Based on the excellent fit observed between the theoretically derived relatin σ3=(Aσ+B)Po2-1/2+D'σ2 and the experimental conductivity data, the nonstoichimetric defect structure of TiO2 was rationalized in terms of a defect model involving quasi-free electrons and both singly and doubly ionized oxygen vacancies. The standard enthalpy of formation for the following defect reactions in TiO2. (a) OO={{{{ { 1} over {2 } }}O2(g)+VO+e'; Δ{{{{ { H}`_{o } ^{a } }}=5.15(eV) (b) OO={{{{ { 1} over {2 } }}O2(g)+VO+2e'; Δ{{{{ { H}`_{0 } ^{ a} }}=6.30(eV) (c) VO=VO+e'; Δ{{{{ { H}`_{0 } ^{a } }}=1.15(eV) were determined from the temperature dependence of A and B obtained from the above relation and from the experimental expression between the electron mobility and temperature. The electrical conductivity of TiO2 in air below approximately 950℃ appears, on the basis of this investigation, to be impurity controlled due to the presence of aluminum rather than intrinsic conduction.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1999년도 하계학술대회 논문집 D
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• pp.1916-1918
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• 1999

The electrical conductive mechanism and temperature dependence of electrical resistivity of ${\beta}-SiC+ZrB_2$ composites with $Al_2O_3+Y_2O_3$ contents were investigated. The electrical resistivity of hot-pressed composites was measured by the Pauw method from $25^{\circ}C$ to $700^{\circ}C$. The electrical resistivity of the composites showed the PTCR(Positive Temperature Coefficient Resistivity) and follow the electrical conduction model for a homogeneous mixture of two kind of particles with different conductivity. Also, the electrical resistivity versus temperature curves indicate the formation of local chains of $ZrB_2$ particles.

• Journal of Power Electronics
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• 제5권2호
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• pp.99-103
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• 2005

In this paper, a novel circuit topology of a three-winding coupling inductor-assisting a high-frequency PWM boost chopper type DC-DC power converter with a high boost voltage conversion ratio and low switch voltage stress is proposed for the new energy interfaced DC power conditioner in solar photovoltaic and fuel cell generation systems. The operating principle in a steady state is described by using its equivalent circuits under the practical condition of energy processing of a lossless capacitive snubber. The newly-proposed power MOSFET boost chopper type DC-DC power converter with the three-winding coupled inductor type transformer and a single lossless capacitor snubber is built and tested for an output power of 500W. Utilizing the lower voltage and internal resistance power MOSFET switch in the proposed PWM boost chopper type DC-DC power converter can reduce the conduction losses of the active power switch compared to the conventional model. Therefore, the total actual power conversion efficiency under a condition of the nominal rated output power is estimated to be 81.1 ％, which is 3.7％ higher than the conventional PWM boost chopper DC power conversion circuit topology.

• 대한화학회지
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• 제28권2호
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• pp.102-108
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• 1984

$ZnCe_{1+y}O_2$상에서 CO산화반응 속도가 $300{\sim}500^{\circ}C$영역에서 측정되었다. 산화반응 속도는 CO에 1차 O2에 0.5차를 나타내는 속도식에 따랐으며 격자점의 산소와 Zn 도프에 기인되어 생성된 Vo-2e' 결함이 CO 및 O2의 활성화 sites로 작용되었다. 전기전도도 데이타와 rate law로 부터 산화반응 메카니즘이 규명되었으며 율속과정이 제안되었다

• 한국진공학회:학술대회논문집
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• 한국진공학회 2016년도 제50회 동계 정기학술대회 초록집
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• pp.125.1-125.1
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• 2016

The excitonic insulator (EI), which is one of fundamental insulators, was theoretically proposed in 1967 but its material realization has not been established well. Only a few materials were proposed as EIs but their experimental evidences were indirect such as the renormalization of band dispersions or an anomaly in electrical resistivity. We conducted scanning tunneling microscopy / spectroscopy measurements and found out that $Ta_2$ $NiSe_5$, which was the most recently proposed as an EI, had a metal-insulator phase transition with the energy gap of 700 meV at 78 K. Moreover, the spatially delocalized excitonic energy level was observed within the energy gap, which could be the direct evidence of the EI ground state. Our theoretical model calculation with the order parameter of 150 meV reproduces the spectral function and the excitonic energy gap very well. In addition, experimental data shows that the band character is inverted at the valence and conduction band edges by the exciton formation, indicating that the mechanism of exciton condensation is similar to the Bardeen-Cooper-Schrieffer (BCS) mechanism of cooper pairs in superconductors.

• 대한기계학회논문집
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• 제15권1호
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• pp.323-327
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• 1991

본 연구에서는 로켓노즐로 부터 분출되는 고온의 초음속제트가 45˚로 경사진 평판으로 분사되는 경우의 열전달을 측정하였다.고온의 제트가 충돌하는 평판표면 의 고온과 열유속을 측정하는 것이 거의 불가능하므로, 국소적열전달은 국소적 준 1차 원 열전도모형을 평판표면 아래에서 측정한 온도자료에 적용하여 구하였다.