• 한국자기학회지
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• 제3권3호
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• pp.221-228
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• 1993

고밀도기록용 박막재료로서의 충족조건은 높은 보자력, 높은 포화자화, 생산성, 그리고 화학적 안정성으로써 수직자기기록매체 CoCrMo 자성박막을 RF 스퍼터링 방법으로 제조한 후, 부식 특성을 전기화학적 측정, acceleration corrosion test 및 부식후 박막의 표면분석을 통하여 조사 하였다. CoCrMo 박막의 부식특성은 스퍼터링 조건에 따라서 다르게 나타났으며, Mo의 함량이 증가 할수록 내식성은 향상되었다. 전기화학부식실험 결과 박막의 Mo 함량이 증가할수록 뚜렷한 활성- 불활성 전이를 나타내었으며 부동태전류밀도의 감소를 나타내었다. Accelerated corrosion test에 서 CoCrMo 박막의 부식은 전기화학반응에 의하여 일어났으며 Mo첨가에 따라 부식이 일어난 곳의 수는 감소하였다. AES분석결과 부식 장소에는 많은 양의 $Cl_{-}$ 이온이 존재하였고, Cr의 고갈이 부식의 원인이었다.

• Journal of electromagnetic engineering and science
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• 제6권4호
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• pp.235-243
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• 2006

In this paper, the fractal shape is applied to microstrip band pass filters and integrated on a high-resistivity Si substrate to solve conventional $2^{nd}$ harmonic problem. Conventional microstrip coupled line filters are popular in RF front ends, because they can be easily fabricated and integrated with other RF components. However, they typically have large second harmonics that can cause unwanted interference in interested frequency bands. Without any additional filters, the proposed Koch shape filters have suppressed the $2^{nd}$ harmonics by about -40 dB, so they can be used in systems such as direct conversion receiver with stringent harmonic suppression requirements.

• 한국표면공학회지
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• 제41권4호
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• pp.134-141
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• 2008

We have developed a numerical model for a remote ICP(inductively coupled plasma) system in 2D and 3D with gas distribution configurations and confirmed it by plasma diagnostics. The ICP source has a Cu tube antenna wound along a quartz tube driven by a variable frequency rf power source($1.9{\sim}3.2$ MHz) for fast tuning without resort to motor driven variable capacitors. We investigated what conditions should be met to make the plasma remotely localized within the quartz tube region without charged particles' diffusing down to a substrate which is 300 mm below the source, using the numerical model. OES(optical emission spectroscopy), Langmuir probe measurements, and thermocouple measurement were used to verify it. To maintain ion current density at the substrate less than 0.1 $mA/cm^2$, two requirements were found to be necessary; higher gas pressure than 100 mTorr and smaller rf power than 1 kW for Ar.

• Journal of electromagnetic engineering and science
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• 제9권1호
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• pp.25-31
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• 2009

This paper describes CMOS VCO circuit design procedures and techniques for multi-band/multi-standard RF transceivers. The proposed techniques enable a 4 GHz CMOS VCO to satisfy all requirements for Quad-band GSMIEDGE and WCDMA standards by achieving a good trade-off among important specifications, phase noise, power consumption, modulation performance, and chip area efficiency. To meet the very stringent GSM T/Rx phase noise and wide frequency range specifications, the VCO utilizes bond-wire inductors with high-quality factor, an 8-bit coarse tune capbank for low VCO gain(30$\sim$50 MHz/V) and an on-chip $2^{nd}$ harmonic noise filter. The proposed VCO is implemented in $0.13{\mu}m$ CMOS technology. The measured tuning range is about 34 %(3.17 to 4.49 GHz). The VCO exhibits a phase noise of -123 dBc/Hz at 400 kHz offset and -145 dBc/Hz at 3 MHz offset from a 900 MHz carrier after LO chain. The calculated figure of merit(FOM) is -183.5 dBc/Hz at 3 MHz offset. This fully integrated VCO occupies $0.45{\times}0.9\;mm^2$.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2008년도 하계학술대회 논문집 Vol.9
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• pp.473-474
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• 2008

This paper proposes that the relative transmittance and emission intensity measured via optical emission spectroscopy (OES) is a useful for fault detection of reactive ion etch process. With the increased requests for non-invasive as well as real-time plasma process monitoring for fault detection and classification (FDC), OES is suggested as a useful diagnostic tool that satisfies both of the requirements. Relative optical transmittance and emission intensity of oxygen plasma acquired from various process conditions are directly compared with the process variables, such as RF power, oxygen flow and chamber pressure. The changes of RF power and Pressure are linearly proportional to the emission intensity while the change of gas flow can be detected with the relative transmittance.

• 항공우주기술
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• 제10권2호
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• pp.82-86
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• 2011

본 논문에서는 통신해양기상위성의 TM 안테나[2.290 GHz]에 의해 발생된 RF가 발사체 PROTON M/Breeze M long 패어링 안에서 형성되는 전기장의 세기를 예측한다. 위성이 TM을 내보내기 위해 의도적으로 방사하는 전기장의 세기는 PROTON M / BREEZE M 패어링의 특성을 고려함으로써 예측될수 있다. 다른 정지궤도 발사체는 PROTON의 패어링과 유사한 특성을 갖기 때문에, 예측된 결과가 다른 발사체에도 적용될 것이라 예상된다. 해석결과로써, 패어링내의 전기장의 세기는 위성 본체와는 전자파 적합성 요구사항을 만족하나, 발사체 PROTON M/Breeze M과는 전자파 적합성 요구사항을 만족하지 못한다.

• The Journal of Asian Finance, Economics and Business
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• 제8권5호
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• pp.167-178
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• 2021

This study aims to identify the influence of paradoxical leadership on proactive work behavior mediated through psychological safety in the hotel industry. This study employs survey data of five-star deluxe hotels in South Korea using convenience sampling. The number of 270 cases was used for analysis and the hypotheses were analyzed with structural equation modeling and AMOS 20. Paradoxical leadership includes five sub-variables of self-centeredness with other-centeredness (SO) distance and closeness (DC), uniformly and individualization (UI), work requirements and flexibility (RF), and decision control and autonomy (CA). The results indicate that DC, UI, and CA positively influence psychological safety. Further, RF and CA make a positive impact on proactive work. Psychological safety fully mediates the effect of DC and UI on proactive work behavior and partially mediates the effect of CA on it. The findings of this study suggest that the impact of paradoxical leadership on proactive work behavior can be strengthened when this relationship is accompanied with psychological safety and other mediation variables for the relationship need to be further investigated. This study suggests how hotel managers enhance the level of proactive work behavior by training themselves to be paradoxical leaders and making psychologically safe environment.

• Journal of Astronomy and Space Sciences
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• 제37권4호
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• pp.219-228
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• 2020

A CubeSat platform has become a popular choice due to inexpensive commercial off-the-shelf (COTS) components and low launch cost. However, it requires more power-efficient and higher-data rate downlink capability for space applications related to remote sensing. In addition, the platform is limited by the size, weight and power (SWaP) constraints as well as the regulatory issue of licensing the radio frequency (RF) spectrum. The requirements and limitations have put optical communications on promising alternatives to RF communications for a CubeSat platform, owing to the power efficiency and high data rate as well as the license free spectrum. In this study, we analyzed the performance of optical downlink communications compatible with CubeSat platforms in terms of data rate, bit error rate (BER) and outage probability. Mathematical models of BER and outage probability were derived based on not only the log-normal model of atmospheric turbulence but also a transmitter with a finite extinction ratio. Given the fixed slot width, the optimal guard time and modulation orders were chosen to achieve the target data rate. And the two performance metrics, BER and outage data rate, were analyzed and discussed with respect to beam divergence angle, scintillation index and zenith angle.

• International Journal of Aerospace System Engineering
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• 제9권1호
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• pp.1-15
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• 2022

Pyrotechnic initiators provide a source of pyrotechnic energy used to initiate a variety of space mechanisms. Pyrotechnic systems build in electromagnetic environment that may lead to critical or catastrophic hazards. Special precautions are need to prevent a pulse large enough to trigger the initiator from appearing in the pyrotechnic firing circuits at any but the desired time. The EMC verification shall be shown by analysis or test that the pyrotechnic systems meets the requirements of inadvertent activation. The MIL-STD-1576 and two range safeties, AFSPC and CSG, require the safety margin for electromagnetic potential hazards to pyrotechnic systems to a level at least 20 dB below the maximum no-fire power of the EED. The PC23 is equivalent to NASA standard initiator and the 1EPWH100 squib is ESA standard initiator. This paper verifies the two safety margins for electromagnetic potential hazards. The first is verified by analyzing against a RF power. The second is verified by testing against a DC current. The EMC safety margin requirement against RF power has been demonstrated through the electric field coupling analysis in differential mode with 21 dB both PC23 and 1EPWH100, and in common mode with 58 dB for PC23 and 48 dB for 1EPWH100 against the maximum no-fire power of the EED. Also, the EMC safety margin requirement against DC current has been demonstrated through the electrical isolation test for the pyrotechnic firing circuits with greater than 20 dB below the maximum no-fire current of the EED.

• 농촌계획
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• 제28권4호
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• pp.105-117
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• 2022

This study tested SVM(support vector machine), RF(random forest), and ANN(artificial neural network) machine-learning models that can predict net irrigation water requirements in paddy fields. For the Jeonju and Jeongeup meteorological stations, the net irrigation water requirement was calculated using K-HAS from 1981 to 2021 and set as the label. For each algorithm, twelve models were constructed based on cumulative precipitation, precipitation, crop evapotranspiration, and month. Compared to the CE model, the R² of the CEP model was higher, and MAE, RMSE, and MSE were lower. Comprehensively considering learning performance and learning time, it is judged that the RF algorithm has the best usability and predictive power of five-days is better than three-days. The results of this study are expected to provide the scientific information necessary for the decision-making of on-site water managers is expected to be possible through the connection with weather forecast data. In the future, if the actual amount of irrigation and supply are measured, it is necessary to develop a learning model that reflects this.