• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제55권6호
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• pp.297-301
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• 2006

In the present work, we investigate the characteristics of new composition material, chalcogenide $Ge_1Se_1Te_2$ material in order to overcome the problems of conventional PRAM devices. The Tc of $Ge_1Se_1Te_2$ bulk was measured $231.503^{\circ}C$ with DSC analysis. For static DC test mode, at low voltage, two different resistances are observed. depending on the crystalline state of the phase-change resistor. In the first sweep, the as-deposited amorphous $Ge_1Se_1Te_2$ showed very high resistance. However when it reached the threshold voltage(about 11.8 V), the electrical resistance of device was drastically reduced through the formation of an electrically conducting path. The phase transition between the low conductive amorphous state and the high conductive crystal]me state was caused by the set and reset pulses respectively which fed through electrical signal. Set pulse has 4.3 V. 200 ns. then sample resistance is $80\sim100{\Omega}$. Reset pulse has 8.6 V 80 ns, then the sample resistance is $50{\sim}100K{\Omega}$. For such high resistance ratio of $R_{reset}/R_{set}$, we can expect high sensing margin reading the recorded data. We have confirmed that phase change properties of $Ge_1Se_1Te_2$ materials are closely related with the structure through the experiment of self-heating layers.

• 한국재료학회지
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• 제23권3호
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• pp.190-193
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• 2013

Spatial distributions of alloying elements of an Fe-based amorphous ribbon with a nominal composition of $Fe_{75}C_{11}Si_2B_8Cr_4$ were analyzed through the atom probe tomography method. The amorphous ribbon was prepared through the melt spinning method. The macroscopic amorphous natures were confirmed using an X-ray diffractometer (XRD) and a differential scanning calorimeter (DSC). Atom Probe (Cameca LEAP 3000X HR) analyses were carried out in pulsed voltage mode at a specimen base temperature of about 60 K, a pulse to base voltage ratio of 15 %, and a pulse frequency of 200 kHz. The target detection rate was set to 5 ions per 1000 pulses. Based on a statistical analyses of the data obtained from the volume of $59{\times}59{\times}33nm^3$, homogeneous distributions of alloying elements in nano-scales were concluded. Even with high carbon and strong carbide forming element contents, nano-scale segregation zones of alloying elements were not detected within the Fe-based amorphous ribbon. However, the existence of small sub-nanometer scale clusters due to short range ordering cannot be completely excluded.

• 한국전자파학회논문지
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• 제12권4호
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• pp.576-585
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• 2001

본 논문에서는 광 전송 링크의 전송 성능 향상 방안으로써 표준 단일 모드 광섬유에 발생되는 색 분산과 자기 위상 변조 (SPM ; self phase modulation)에 의한 광 펄스의 왜곡을 최적으로 보상할 수 있는 광 위상 공액기(OPC ;optical phase conjugator) 에서의펌프 신호의 최적 전력을 시뮬레이션을 통한 분석적인 방법으로도 도출하고, 최적 펌프 전력 조건하에서의 안정된 수신 성능 유지를 위한 초기 입력 광 신호 전력의 범위를 살펴보았다. 본 논문에서 사용한 보상 기법은 전송 링크 중간에 광 위상 공액기를 두어 신호 왜곡을 보상하는 MSSI(mid-span spectral inversion)이고, 보상정도에 대한 평가는 EOP(eye-opening penalty)를 통해 수행하였다. 자기 위상 변조 등의 비선형 현상에 의한 신호 왜곡의 보상에 있어 전력 조절 문제가 매우 중요하기 때문에 본 연구에서 수행한 결과를 바탕으로 한 시스템 전송 거리, 속도 및 성능에 맞는 최적 펌프 전력, 신호파 초기 전력, 증폭기 간격등의 도출과 이의 적용으로 전송 능력이 매우 증대된 시스템 구현이 가능하다는 것을 입증하였다.

• Korean Chemical Engineering Research
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• 제49권6호
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• pp.798-803
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• 2011

난황에 포함된 IgY는 포유동물에 있는 바이러스나 항원에 반응하는 항체와 같은 역할을 한다. IgY 분리를 위해 난황을 전처리한 후 3-zone SMB를 이용하여 지질단백질들로 부터 분리하는 전산모사연구를 수행하였다. 회분식 크로마토그래피와 pulse input method(PIM) 실험을 이용하여 전산모사 매개변수와 흡착 등온식을 얻었다. Aspen simulator를 이용하여 전산모사를 수행하여 IgY를 분리할 수 있는 SMB 운전조건을 다음과 같이 제시할 수 있었다. 삼각형 이론의 $m_2$와 $m_3$ 값은 각각 0.18, 1.0이고 스위칭 타임은 419 초이었다. 전산모사 결과 raffinate의 IgY 순도가 98.39%이고 두번째 싸이클에서 순도가 정상상태에 도달하였다.

• Journal of Radiation Protection and Research
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• 제42권1호
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• pp.48-55
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• 2017

Background: Simultaneous detection of neutrons and gamma rays have become much more practicable, by taking advantage of good gamma-ray discrimination properties using pulse shape discrimination (PSD) technique. Recently, we introduced a commercial CLYC system in Korea, and performed an initial characterization and simulation studies for the CLYC detector system to provide references for the future implementation of the dual-mode scintillator system in various studies and applications. Materials and Methods: We evaluated a CLYC detector with 95% $^6Li$ enrichment using various gamma-ray sources and a $^{252}Cf$ neutron source, with validation of our Monte Carlo simulation results via measurement experiments. Absolute full-energy peak efficiency values were calculated for gamma-ray sources and neutron source using MCNP6 and compared with measurement experiments of the calibration sources. In addition, behavioral characteristics of neutrons were validated by comparing simulations and experiments on neutron moderation with various polyethylene (PE) moderator thicknesses. Results and Discussion: Both results showed good agreements in overall characteristics of the gamma and neutron detection efficiencies, with consistent ~20% discrepancy. Furthermore, moderation of neutrons emitted from $^{252}Cf$ showed similarities between the simulation and the experiment, in terms of their relative ratios depending on the thickness of the PE moderator. Conclusion: A CLYC detector system was characterized for its energy resolution and detection efficiency, and Monte Carlo simulations on the detector system was validated experimentally. Validation of the simulation results in overall trend of the CLYC detector behavior will provide the fundamental basis and validity of follow-up Monte Carlo simulation studies for the development of our dual-particle imager using a rotational modulation collimator.

• 전기전자학회논문지
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• 제23권3호
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• pp.1104-1107
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• 2019

본 논문에서는 데드 타임을 줄여 전력 효율을 높이기 위해 데드 타임 제어기를 이용한 웨어러블 AMOLED 디스플레이용 DC-DC 부스트 변환기를 제안한다. 또한, 본 변환기에서는 경부하에서 전력 효율을 높이고 출력 전압 리플을 감소시키기 위해 PWM-SPWM (set-time variable pulse width modulation) 듀얼 모드를 이용한다. 제안하는 회로는 $0.18{\mu}m$ BCDMOS 공정을 이용하여 시뮬레이션을 한 결과 1 mA~70 mA의 부하 전류 범위에서 39%~96%의 전력 효율과 2 mV의 리플 전압을 가졌다. 본 회로의 전력 효율은 PWM-SPWM 방식보다 최대 2% 상승하였고, PWM 방식보다 최대 8% 상승하였다.

• 전기전자학회논문지
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• 제23권3호
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• pp.1061-1067
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• 2019

본 논문에서는 PTWS 방식을 이용한 고집적화된 AMOLED용 3-채널 DC-DC 변환기의 설계한다. 양의 전압 $V_{POS}$는 경부하에서 효율을 제고하기 위해 SPWM 듀얼모드와 PTWS 방식을 적용한 부스트 변환기로 설계한다. 음의 전압 $V_{NEG}$는 전력 손실을 줄이기 위해 PSM 방식을 적용한 0.5x 인버팅 차지펌프를 이용해 설계하고, 추가적인 전압 $V_{AVDD}$는 LDO를 이용하여 설계한다. 제안된 DC-DC 변환기는 $0.18{\mu}m$ BCDMOS 공정을 사용하여 시뮬레이션을 한 결과 부하전류 1mA~70mA에서 전력효율 56.9%~90.2%를 가지고, 양의 전압 $V_{POS}$에서 최대 5mV의 출력 리플을 가졌다.

• Nuclear Engineering and Technology
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• 제54권11호
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• pp.4134-4145
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• 2022

The collimator is one of the high-heat-flux components used to avoid a series of vacuum and thermal problems. In this paper, the heat load distribution throughout the collimator is first calculated through experimental data, and a transient thermodynamic simulation analysis of the original model is carried out. The error of the pipe outlet temperature between the simulated and experimental values is 1.632%, indicating that the simulation result is reliable. Second, the model is optimized to improve the heat transfer performance of the collimator, including the contact mode between the pipe and the flange, the pipe material and the addition of a twisted tape in the pipe. It is concluded that the convective heat transfer coefficient of the optimized model is increased by 15.381% and the maximum wall temperature is reduced by 16.415%; thus, the heat transfer capacity of the optimized model is effectively improved. Third, to adapt the long-pulse steady-state operation of the experimental advanced superconducting Tokamak (EAST) in the future, steady-state simulations of the original and optimized collimators are carried out. The results show that the maximum temperature of the optimized model is reduced by 37.864% compared with that of the original model. The optimized model was changed as little as possible to obtain a better heat exchange structure on the premise of ensuring the consumption of the same mass flow rate of water so that the collimator can adapt to operational environments with higher heat fluxes and long pulses in the future. These research methods also provide a reference for the future design of components under high-energy and long-pulse operational conditions.

• International Journal of Computer Science & Network Security
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• 제24권6호
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• pp.200-206
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• 2024

Laser induced breakdown spectroscopy (LIBS) technique has been used for the elemental composition of the soils. In this technique, a high energy laser pulse is focused on a sample to produce plasma. From the spectroscopic analysis of such plasma plume, we have determined the different elements present in the soil. This technique is effective and rapid for the qualitative and quantitative analysis of all type of samples. In this work a Q-switched Nd: YAG laser operating with its fundamental mode (1064 nm laser wavelength), 5 nanosecond pulse width, and 10 Hz repetition rate was focused on soil samples using 10 cm quartz lens. The emission spectra of soil consist of Iron (Fe), Calcium (Ca), Titanium (Ti), Silicon (Si), Aluminum (Al), Magnesium (Mg), Manganese (Mn), Potassium (K), Nickel (Ni), Chromium (Cr), Copper (Cu), Mercury (Hg), Barium (Ba), Vanadium (V), Lead (Pb), Nitrogen (N), Scandium (Sc), Hydrogen (H), Strontium (Sr), and Lithium (Li) with different finger-prints of the transition lines. The maximum intensity of the transition lines was observed close to the surface of the sample and it was decreased along the axial direction of the plasma expansion due to the thermalization and the recombination process. We have also determined the plasma parameters such as electron temperature and the electron number density of the plasma using Boltzmann's plot method as well as the Stark broadening of the transition lines respectively. The electron temperature is estimated at 14611 °K, whereas the electron number density i.e. 4.1 × 10¹⁶ cm^-3 lies close to the surface.

• 한국산학기술학회논문지
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• 제17권6호
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• pp.715-720
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• 2016

본 논문에서는, 휴대기기를 위한 PWM(Pulse Width Modulation), 전압모드 DC-DC 승압형 컨버터를 제안한다. 제안하는 컨버터는 현재 소형화 되어가고 있는 휴대기기 시장에 적합하도록 1 MHz의 스위칭 주파수를 사용하여 칩 면적을 줄였다. 제안하는 DC-DC 컨버터는 전력단과 제어단으로 이루어지며 전력단은 인덕터, 출력 커패시터, MOS 트랜지스터 등으로 구성되며 제어단은 연산증폭기, 밴드갭 회로, 소프트 스타트 블록, 히스테리시스 비교기와 비겹침 드라이버로 구성된다. 설계된 회로는 히스테리시스 비교기와 논오버랩 드라이버를 사용하여 낮은 전압에서 구동되는 휴대기기의 잡음의 영향을 줄이고 출력전압 리플을 감소시켰다. 제안하는 회로는 1-poly 6-metal CMOS 매그나칩/하이닉스 $0.18{\mu}m$ 공정을 사용하여 레이아웃을 진행하였다. 설계된 컨버터는 입력 전압 3.3 V, 출력전압 5 V, 출력전류 100 mA 출력전압 대비 1%의 출력 전압 리플과 1 MHz의 스위칭 주파수의 특성을 갖는다. 본 논문에서 제안하는 승압형 DC-DC 컨버터는 PDA, 휴대폰, 노트북 등 휴대용 전자기기 시장에 맞는 고효율, 소형화 컨버터로서 유용하게 사용 될 것으로 사료된다.