• 한국산학기술학회논문지
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• 제20권6호
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• pp.9-13
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• 2019

본 연구에서는 박막 패턴의 히터를 반도체 공정 기술을 이용하여 소형 백금 박막 히터를 실리콘 기판 상에 제작하고 박막히터의 인가전압, 전력, 온도의 열특성을 측정 분석하였다. 박막 패턴 히터의 온도는 전력 증가에 따라서 증가하였으나 높은 전력구간에서는 온도 증가율이 완만해지는 결과를 확인하였다. 백금 박막 패턴 히터의 고온구간의 특성은 측정 환경에 의한 영향으로서 대기분위기와 진공분위기에서 측정한 결과를 열저항 모델을 이용하여 열특성을 해석하였다. 진공분위기에서 측정한 경우가 열저항값 0.79 [K/mW]로서 대기분위기에서의 열저항 값 0.69 [K/mW]보다 높게 측정되었다. 대기분위기보다는 진공분위기에서 낮은 전력으로 박막 패턴 히터의 온도를 유지할 수 있었고 이들 결과는 박막 패턴 히터 소자의 구조 설계에 활용이 기대된다.

• Smart Structures and Systems
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• 제23권3호
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• pp.307-318
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• 2019

The frequently excessive vibrations presented in civil structures during seismic events or service conditions may result in users' discomfort, or worst, in structures failure, producing economic and even human casualties. This work contributes in proposing the synthesis of a nonlinear optimal control strategy for semiactive structural control, with the main characteristic that the synthesis considers both the structure model and the semiactive actuator nonlinear dynamics, which produces a nonlinear system that requires a nonlinear controller design. The aim is to reduce the unwanted vibrations in the response of civil structures, by means of intelligent fluid semiactive actuator such as the Magnetorheological Damper (MRD), which is a device with a low level of power consumption. The civil structures for which the proposed control methodology can be applied are those admitting a state-dependent coefficient factorized representation model, such as buildings, bridges, among others. A scaled model of a three storey building is analyzed as a case study, whose dynamical response involves displacement, velocity and acceleration of each one of the storeys, subjected to the North-South component of the September 19th., 2017, Puebla-Morelos (7.1M), Mexico earthquake. The investigation rests on comparing the structural response over time for two different conditions: with no control device installed and with one MRD installed between the first floor and the ground, where a nonlinear optimal signal for the MRD input voltage is determined. Simulation results are presented to show the effectiveness of the proposed controller for reducing the building's dynamical response.

• Nuclear Engineering and Technology
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• 제51권4호
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• pp.1091-1097
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• 2019

After the Fukushima accident in 2011, there has been increased public concern about radioactive contamination of water resources through fallout in neighboring countries. However, there is still no available initial response system that can promptly detect radionuclides. The purpose of this research is to develop the most efficient gamma spectrometer to monitor radionuclides in an aquatic environment. We chose a thallium-doped sodium iodide (NaI(Tl)) scintillator readout with a silicon photo multiplier (SiPM) due to its compactness and low operating voltage. Three types of a scintillation detector were tested. One was composed of a scintillator and a photomultiplier tube (PMT) as a reference; another system consisted of a scintillator and an array of SiPMs with a light guide; and the other was a scintillator directly coupled with an array of SiPMs. Among the SiPM-based detectors, the direct coupling system showed the best energy resolution at all energy peaks. It achieved 9.76% energy resolution for a 662 keV gamma ray. Through additional experiments and a simulation, we proved that the light guide degraded energy resolution with increasing statistical uncertainty. The results indicated that the SiPM-based scintillation detector with no light guide is the most efficient design for monitoring radionuclides in an aquatic environment.

• 한국정보통신학회:학술대회논문집
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• 한국정보통신학회 2016년도 추계학술대회
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• pp.61-62
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• 2016

본 논문에서는 ultra wide band(UWB) 대역(3.1-10.6 GHz)에서 동작하는 소형 계단형 개방 슬롯 안테나의 설계 방법에 대하여 연구하였다. 계단형 개방 슬롯 안테나의 접지면에 L형 슬롯을 추가하여 낮은 주파수에서 공진이 발생하도록 하여 소형화하고, 중간주파수 및 고주파수 대역에서 이득을 높이기 위해 스트립 도파기를 추가하였다. L형 슬롯의 길이, 도파기와 슬롯 안테나 사이의 간격 및 도파기의 길이에 따른 입력 반사계수와 이득 특성을 분석하였다. $30mm{\times}30mm$ 크기로 최적화된 안테나를 FR4 기판 상에 제작하고 특성을 실험한 결과 전압 정재파비(voltage standing wave ratio; VSWR)가 2 이하인 대역은 3.02-11.04 GHz으로 UWB 대역에서 동작함을 확인하였다.

• 전기전자학회논문지
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• 제23권3호
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• pp.917-924
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• 2019

This paper presents a wideband low noise amplifier (LNA) that is suitable for LTE-Advanced and 5G communication standards employing carrier aggregation (CA). The proposed LNA encompasses a common input stage and a dual output second stage with a buffer at each distinct output. This architecture is targeted to operate in both intra-band (contiguous and non-contiguous) and inter-band CA. In the proposed design, the input and second stages employ a gm enhancement with resistive feedback technique to achieve self-biasing, enhanced gain, wide bandwidth as well as reduced noise figure of the proposed LNA. An up/down power controller controls the single input single out (SISO) and single input multiple outputs (SIMO) modes of operation for inter-band and intra-band operations. The proposed LNA is designed with a 45nm CMOS technology. For SISO mode of operation, the LNA operates from 0.52GHz to 4.29GHz with a maximum power gain of 17.77dB, 2.88dB minimum noise figure and input (output) matching performance better than -10dB. For SIMO mode of operation, the proposed LNA operates from 0.52GHz to 4.44GHz with a maximum voltage gain of 18.30dB, a minimum noise figure of 2.82dB with equally good matching performance. An $IIP_3$ value of -6.7dBm is achieved in both SISO and SIMO operations. with a maximum current of 42mA consumed (LNA+buffer in SIMO operation) from a 1.2V supply.

• 전기전자학회논문지
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• 제23권3호
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• pp.858-864
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• 2019

본 논문에서는 센서 유틸리티 네트워크에서 센서 노드들 사이의 주파수 차이로 인한 데이터 손실을 제거하기 위한 클록 시스템이 제안된다. 각 센서 노드를 위한 제안된 클록 시스템은 버스트 클록-데이터 복원 회로, 32-위상 클록을 출력하는 디지털 위상 고정 루프, 그리고 프로그래밍 가능한 개방형 루프 분수 분할기를 사용하는 디지털 주파수 합성기로 구성된다. 첫번째 센서 노드에는 버스트 클록-데이터 복원 회로 대신 능동 인덕터를 사용하는 CMOS 발진기가 사용된다. 제안된 클록 시스템은 1.2 V 공급 전압을 이용하는 65nm CMOS 공정에서 설계된다. 센서 노드들 사이의 주파수 오류가 1%일 때, 제안하는 버스트 클록-데이터 복원 회로는 기준 클록으로 5Mbps 데이터 속도에 대해 64배 체배된 주파수를 가짐으로 4.95 ns의 시간지터를 가진다. 설계된 디지털 주파수 합성기의 주파수 변경은 100 kHz에서 320 MHz의 주파수 범위에서 출력 클록의 한 주기 내에 수행된다.

• The Korean Journal of Physiology and Pharmacology
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• 제23권3호
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• pp.219-227
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• 2019

Polycystic kidney disease 2-like-1 (PKD2L1), polycystin-L or transient receptor potential polycystin 3 (TRPP3) is a TRP superfamily member. It is a calcium-permeable non-selective cation channel that regulates intracellular calcium concentration and thereby calcium signaling. Although the calmodulin (CaM) inhibitor, calmidazolium, is an activator of the PKD2L1 channel, the activating mechanism remains unclear. The purpose of this study is to clarify whether CaM takes part in the regulation of the PKD2L1 channel, and if so, how. With patch clamp techniques, we observed the current amplitudes of PKD2L1 significantly reduced when co-expressed with CaM and $CaM{\triangle}N$. This result suggests that the N-lobe of CaM carries a more crucial role in regulating PKD2L1 and guides us into our next question on the different functions of two lobes of CaM. We also identified the predicted CaM binding site, and generated deletion and truncation mutants. The mutants showed significant reduction in currents losing PKD2L1 current-voltage curve, suggesting that the C-terminal region from 590 to 600 is crucial for maintaining the functionality of the PKD2L1 channel. With PKD2L1608Stop mutant showing increased current amplitudes, we further examined the functional importance of EF-hand domain. Along with co-expression of CaM, ${\triangle}EF$-hand mutant also showed significant changes in current amplitudes and potentiation time. Our findings suggest that there is a constitutive inhibition of EF-hand and binding of CaM C-lobe on the channel in low calcium concentration. At higher calcium concentration, calcium ions occupy the N-lobe as well as the EF-hand domain, allowing the two to compete to bind to the channel.

• Advances in nano research
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• 제10권5호
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• pp.415-422
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• 2021

Silicene, a 2D allotrope of silicon, is predicted to be a potential material for future transistor that might be compatible with present silicon fabrication technology. Similar to graphene, silicene exhibits the honeycomb lattice structure. Consequently, silicene is a semimetallic material, preventing its application as a field-effect transistor. Therefore, this work proposes the uniform doping bandgap engineering technique to obtain the n-type silicene nanosheet. By applying nearest neighbour tight-binding approach and parabolic band assumption, the analytical modelling equations for band structure, density of states, electrons and holes concentrations, intrinsic electrons velocity, and ideal ballistic current transport characteristics are computed. All simulations are done by using MATLAB. The results show that a bandgap of 0.66 eV has been induced in uniformly doped silicene with phosphorus (PSi₃NW) in the zigzag direction. Moreover, the relationships between intrinsic velocity to different temperatures and carrier concentration are further studied in this paper. The results show that the ballistic carrier velocity of PSi₃NW is independent on temperature within the degenerate regime. In addition, an ideal room temperature subthreshold swing of 60 mV/dec is extracted from ballistic current-voltage transfer characteristics. In conclusion, the PSi₃NW is a potential nanomaterial for future electronics applications, particularly in the digital switching applications.

• 한국재료학회지
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• 제31권1호
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• pp.16-22
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• 2021

In this study, quantum dot-sensitized solar cells (QDSSC) using CdSe/ZnS quantum dots (QD) of various sizes with green, yellow, and red colors are developed. Quantum dots, depending their different sizes, have advantages of absorbing light of various wavelengths. This absorption of light of various wavelengths increases the photocurrent production of solar cells. The absorption and emission peaks and excellent photochemical properties of the synthesized quantum dots are confirmed through UV-visible and photoluminescence (PL) analysis. In TEM analysis, the average sizes of individual green, yellow, and red quantum dots are shown to be 5 nm, 6 nm, and 8 nm. The J-V curves of QDSSC for one type of QD show a current density of 1.7 mA/㎠ and an open-circuit voltage of 0.49 V, while QDSSC using three type of QDs shows improved electrical characteristics of 5.52 mA/㎠ and 0.52 V. As a result, the photoelectric conversion efficiency of QDSSC using one type of QD is as low as 0.53 %, but QDSSC using three type of QDs has a measured efficiency of 1.4 %.

• Current Applied Physics
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• 제18권12호
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• pp.1571-1576
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• 2018

Recent study shows that the main reason for limiting CZTS device performance lies in the low open circuit voltage, and crucial factor that could affect the $V_{oc}$ is secondary phases like ZnS existing in absorber layer and its interfaces. In this work, the $Cu_2ZnSnS_4$ thin film solar cells were prepared by sputtering CuSn and CuZn alloy targets. Through tuning the Zn/Sn ratios of the CZTS thin films, the crystal structure, morphology, chemical composition and phase purity of CZTS thin films were characterized by X-Ray Diffraction (XRD), scanning electron microscopy (SEM) equipped with an energy dispersive spectrometer (EDS) and Raman spectroscopy. The statistics data show that the CZTS solar cell with a ratio of Zn/Sn = 1.2 have the best power convention efficiency of 5.07%. After HCl etching process, the CZTS thin film solar cell with the highest efficiency 5.41% was obtained, which demonstrated that CZTS film solar cells with high efficiency could be developed by sputtering CuSn and CuZn alloy targets.