• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2002년도 하계종합학술대회 논문집(2)
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• pp.61-64
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• 2002

We have optimally designed and implemented by a monolithic microwave integrated circuit(MMIC) the low noise amplifier(LNA) of 5.8GHz band composed of receiver front-end(RFE) in a on-board equipment system for dedicated short range communication using a depletion-mode GaAs MESFET. The LNA is provided with two active devices, matching circuits, and two drain bias circuits. Operating at a single supply of 3V and a consumption current of 18㎃, The gain at center frequency 5.8GHz is 13.4dB, Noise figure(NF) is 1.94dB, Input 3rd order intercept point(lIPS) is 3dBm, and Input return loss(5$_{11}$) and Output return loss(S$_{22}$) is -l8dB and -13.3dB, respectively. The circuit size is 1.2$\times$O.7$\textrm{mm}^2$.EX>.>.

• 한국결정성장학회지
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• 제6권2호
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• pp.155-165
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• 1996

Growth of $LiNbO_3$ single crystal by Czochralski method was carried out to study the piezoelectric effects. Piezoelectric coefficients and elastic compliances of the $LiNbO_3$ single crystal were determined by the resonance method of length-extentional mode of bar resonator from the room temperature up to $100^{\circ}C$. Two dielectric constants of $LiNbO_3$ were also determined by measuring the capacitance of the plate specimen. Measured constants were piezoelectric coefficients $d_{15},d_{22},d_{31},d_{33}$ elastic compliances $s^E_{11},s^E_{33},2s^E_{13}+2s^E_{44},s^E_{14}$ and dielectric constants $K^T_{11},K^T_{33}$. As temperature increased, elastic compliances changed very slowly while piezoelectric coeffiecients and dielectric constant $K^T_{33}$ changed very rapidly. Electromechanical coupling constant of zyw ($45^{\circ}C$)-bar was as high as 0.51 in room temperature and nearly constant up to $1000^{\circ}C$. The increase of piezoelectric coefficients was mainly due to the increase of dielectric permittivity.

• ETRI Journal
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• 제39권5호
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• pp.737-745
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• 2017

A 6-GHz-to-18-GHz monolithic nonuniform distributed power amplifier has been designed using the load modulation of increased series gate capacitance. This amplifier was implemented using a $0.25-{\mu}m$ AlGaN/GaN HEMT process on a SiC substrate. With the proposed load modulation, we enhanced the amplifier's simulated performance by 4.8 dB in output power, and by 13.1% in power-added efficiency (PAE) at the upper limit of the bandwidth, compared with an amplifier with uniform gate coupling capacitors. Under the pulse-mode condition of a $100-{\mu}s$ pulse period and a 10% duty cycle, the fabricated power amplifier showed a saturated output power of 39.5 dBm (9 W) to 40.4 dBm (11 W) with an associated PAE of 17% to 22%, and input/output return losses of more than 10 dB within 6 GHz to 18 GHz.

• Geomechanics and Engineering
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• 제35권1호
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• pp.13-27
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• 2023

The model production for large-scale (lateral length ≥ 2.0 m) capillary barrier (CB) model tests is time and cost-intensive. To address these limitations, the framework of a small-scale CB (SSCB) model test under the lateral no-flow condition has been established. In this study, to validate the experimental methodology of the SSCB model test, a series of seepage analyses on the SSCB model test and engineered slopes in the same and additional test conditions was performed. First, the seepage behavior and diversion length (L_D) of the CB system were investigated under three rainfall conditions. In the seepage analysis for the engineered slopes with different slope angles and sand layer thicknesses, the L_D increased with the increase in the slope angle and sand layer thickness, although the increase rate of the L_D with the sand layer thickness exhibited an upper limit. The L_D values from the seepage analysis agreed well with the results estimated from the laboratory SSCB mode test. Therefore, it can be concluded that the experimental methodology of the SSCB model test is one of the promising alternatives to efficiently evaluate the water-shielding performance of the CB system for an engineered slope.

• 한국자동차공학회논문집
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• 제13권3호
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• pp.102-109
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• 2005

Wheel-slip control systems are able to control the braking force more accurately and can be adapted to different vehicles more easily than conventional ABS systems. But, in order to achieve the superior braking performance through the wheel-slip control, real-time information such as the tire braking force is required. For example, in the case of EHB (Electro-Hydraulic Brake) systems, the tire braking force cannot be measured directly, but can be approximated based on the characteristics of the brake disk-pad friction. The friction characteristics can change significantly depending on aging of the brake, moisture on the contact area, heat etc. In this paper, a wheel slip The proposed wheel slip control system is composed of two subsystems: braking force monitor and robust slip controller In the brake force monitor subsystem, the tire braking forces as well as the brake disk-pad friction coefficient are estimated considering the friction variation between the brake pad and disk. The robust wheel slip control subsystem is designed based on sliding mode control methods and follows the target wheel-slip using the estimated tire braking forces. The proposed sliding mode controller is robust to the uncertainties in estimating the braking force and brake disk-pad friction. The performance of the proposed wheel-slip control system is evaluated in various simulations.

• 한국정보통신학회논문지
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• 제20권1호
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• pp.117-122
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• 2016

본 논문에서는 차량 추돌 방지 단거리 레이더용 24-GHz CMOS 고주파 전력 증폭기 (RF power amplifier)를 제안한다. 이러한 회로는 클래스-A 모드 증폭기로서 단간 (inter-stages) 공액 정합 (conjugate matching) 회로를 가진 공통-소스 단으로 구성되어 있다. 제안한 회로는 TSMC $0.13-{\mu}m$ 혼성신호/고주파 CMOS 공정 ($f_T/f_{MAX}=120/140GHz$)으로 설계하였다. 2볼트 전원전압에서 동작하며, 저전압 전원에서도 높은 전력 이득, 낮은 삽입 손실 및 낮은 음지수를 가지도록 설계되어 있다. 전체 칩 면적을 줄이기 위해 넓은 면적을 차지하는 실제 인덕터 대신 전송선(transmission line)을 이용하였다. 설계한 CMOS 고주파 전력 증폭기는 최근 발표된 연구결과에 비해 $0.1mm^2$의 가장 작은 칩 크기, 40mW의 가장 적은 소비전력, 26.5dB의 가장 높은 전력이득, 19.2dBm의 가장 높은 포화 출력 전력 및 17.2%의 가장 높은 최대 전력부가 효율 특성을 보였다.

• Journal of Electrical Engineering and Technology
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• 제13권3호
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• pp.1251-1264
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• 2018

The systematic and effective design method of a Class-D current-source resonant inverter for use in an induction cooker with zero-ripple line current is presented. The design procedure is based on the principle of the Class-D current-source resonant inverter with a simplified load network model that is a parallel equivalent circuit. An induction load characterization is obtained from a large-signal excitation test-bench based on parallel load network, which is the key to an accurate design for the induction cooker system. Accordingly, the proposed scheme provides a systematic, precise, and feasible solution than the existing design method based on series-parallel load network under low-signal excitation. Moreover, a zero-ripple condition of utility-line input current is naturally preserved without any extra circuit or control. Meanwhile, a differential-mode input electromagnetic interference (EMI) filter can be eliminated, high power quality in utility-line can be obtained, and a standard-recovery diode of bridge-rectifier can be employed. The step-by-step design procedure explained with design example. The devices stress and power loss analysis of induction cooker with a parallel load network under large-signal excitation are described. A 2,500-W laboratory prototype was developed for $220-V_{rms}/50-Hz$ utility-line to verify the theoretical analysis. An efficiency of the prototype is 96% at full load.

• Bulletin of the Korean Chemical Society
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• 제30권4호
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• pp.913-916
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• 2009

Femtosecond vibrational spectroscopy was used to probe the dynamics of CO rebinding to hemoglobin (Hb), denatured by 4.0 M GdnHCl in $D_2O# at 283 K, after photolysis of HbCO. The stretching mode of $^{13}CO$ bound to the denatured $Hb^{13}CO$ showed a single band centered at 1922 $cm^{-1}$, indistinguishable from that of denatured $Mb^{13}CO$. Geminate rebinding of CO to the denatured Hb was accelerated more than 1000 times, suggesting that the native structure of the Hb is required to suppress efficient geminate rebinding of CO, as is the case in Mb. The geminate yield and rate for CO rebinding are almost the same in both the denatured Hb and Mb. Similarity in the equilibrium spectrum and rebinding dynamics of CO indicates that the state of the denatured Hb is very similar to that of the denatured Mb. In the denatured Hb, quaternary contact of the protein is likely severed, with the denatured protein existing as an independent subunit much like Mb.

• 한국자동차공학회논문집
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• 제7권7호
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• pp.15-23
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• 1999

In recent years, environmental damage to urban area becomes serious problem due to the exhaust emissions by increasing the number of vehicle . Especially, diesel particulate matters(DPM) are hazardous air pollutant s to human health and environment. The reduction technologies of exhaust emissions from diesel engines are improvement of engine combustion, fuel quality and development of diesel exhaust aftertreatment. In this study, a diesel oxidation catalyst(DOC) that is one of diesel exhaust aftertreatments was made for performance evaluation . It was tested for NA and turbocharged engine by D-13 mode that currently be used for regulation driving test mode in Korea Scanning mobility particle sizer (SMPS) was used for the analysis of the particle size distribution with and w/o DOC. As the results , for NA and tubochartged engine, CO, THC, DPM was respectively reduced 85.7, 40.7,3.3% and 79.1, 53.1, 11.6% by DOC. Test results of particle size distribution was showed that particle number is 107 ~108per ㎤ , 2 $\times$105 ~5$\times$105$\mu\textrm{g}$/㎥ for weight concentration and 100~200nm for particle mean size in diesel engine and there is no effect to reduce the particle concentration by the DOC.

• 디지털융복합연구
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• 제13권8호
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• pp.221-234
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• 2015

독일의 강소기업에 대한 이해를 바탕으로 국내에서도 중앙정부나 지방자치단체를 중심으로 강소기업 육성을 위해 다양한 정책이 추진되고 있다. 그러나 국내 강소기업은 독일과는 상당히 다른 특성을 가지며, 연구와 정책개발을 위해서는 그 차이에 대한 이해가 선행되어야 할 것이다. 첫째, 전반적 특성과 전략적 행동 및 성과 측면에서 지역의 강소기업은 독일 기업에 비해 업력이 현저히 짧고 특정 분야에의 전문화 정도는 오히려 낮으며, 특히 원가경쟁력과 세계화 등의 측면에서는 약점을 보이는 것으로 나타났다. 둘째, 기술개발 방법에 있어서, 독일의 강소기업은 자체 연구개발을 통한 기술개발과 경쟁력 확보에 초점을 두는 반면, 지역의 성공적 중소기업은 협력적 기술개발, 특히 기술제휴를 적극적으로 활용하는 것으로 나타났다. 이러한 분석을 바탕으로, 연구의 기여와 정책적 시사점에 대해 논의하고, 연구의 한계와 향후 연구방향을 제시하였다.