• 한국광학회:학술대회논문집
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• 한국광학회 2002년도 하계학술발표회
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• pp.18-19
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• 2002

1950년 Norman Ramsy는 시간적으로 분리된 두 진동 자장을 사용한 마이크로파 전이 방법을 개발했다 이 방법을 사용할 경우 그림1과 같이 넓은 선폭을 가지는 공진선 ("Rabi pedestal") 위에 좁은 선폭의 분광 신호("Ramsey fringe")를 얻을 수 있다. 램지 방법은 정밀한 분광 측정에 많이 사용되고 있으며, 특히 원자 시계를 구현하기 위한 기본 기술이 되고 있다. (중략)

• 반도체디스플레이기술학회지
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• 제8권4호
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• pp.21-24
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• 2009

We investigated a nanoscale inertia sensor based on telescoping carbon nanotubes, using classical molecular dynamics simulations. The position of the telescoping nanotubes is controlled by the centrifugal force exerted by the rotation platform, thus, position shifts are determined by the capacitance between carbon nanotubes and the electrode, and the operating frequency of the carbon nanotube oscillator. This measurement system, tracking oscillations of the carbon nanotube oscillator, can be used as the sensor for numerous types of devices, such as motion detectors, accelerometers and acoustic sensors.

• 한국진공학회지
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• 제5권1호
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• pp.33-38
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• 1996

The induced linewidth, frequency shift and absorption spectrum for a molecular dipole in the vicinity of a phase -conjugate mirror have been investgated within a classical phenomenological model, with particularreference to the technique of optical phase conjugation by a surface. While the shifts and the widths show similar characteristics as those obtained recently by Bochove who considered the problem within the context of four-wave mixing, the results obtained in the present model can be defined uniquely with the possibility of an infinite lifetime for the excited admolecule . Furthermore, the absorption lineshape obtained here some interesting features which depend on both the magnitude and the phase of the complex reflectivity of the mirror.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2001년도 하계학술대회 논문집 D
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• pp.2606-2609
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• 2001

We propose a robust channel equalization algorithm. which is called a 1-tap additional coefficient decision feedback equalizer(ACDFE), to improve the Doppler shift performance for the OFDM receiver. The algorithm is based on the frequency domain DFE with additional coefficients which are independent of the OFDM subcarriers. Test results on OFDM-16QAM signals confirm that the proposed ACDFE is robust against fading channel due to Doppler shifts and outperforms the conventional DFE in terms of SER, MSE, and convergence speed.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2004년도 하계종합학술대회 논문집(1)
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• pp.217-220
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• 2004

This paper presents design simulation, implementation, and measurement of a miniaturized GPS/K-PCS dual-band LTCC chip antenna for mobile communication handsets. The dimension of LTCC chip antenna is $9mm{\times}15mm{\times}1.2mm$. The lower meander type antenna is to be tuned to the lower frequency (GPS) band and the upper meander antenna with via hole connection is to contribute the higher frequency (K-PCS) band. In order to lowering the resonant frequency for GPS band, two printed modified meander antenna with gap stub is used to integrate with PCS band operation. The measured resonant frequency at GPS band shifts to lower frequency about 100MHz. The measured impedance bandwidth(VSWR $\leq$ 2) are 55MHz and 120MHz at the resonant frequency. respectively.

• ETRI Journal
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• 제36권3호
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• pp.510-513
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• 2014

A Q-band pHEMT image-rejection low-noise amplifier (IR-LNA) is presented using inter-stage tunable resonators. The inter-stage L-C resonators can maximize an image rejection by functioning as inter-stage matching circuits at an operating frequency ($F_{OP}$) and short circuits at an image frequency ($F_{IM}$). In addition, it also brings more wideband image rejection than conventional notch filters. Moreover, tunable varactors in L-C resonators not only compensate for the mismatch of an image frequency induced by the process variation or model error but can also change the image frequency according to a required RF frequency. The implemented pHEMT IR-LNA shows 54.3 dB maximum image rejection ratio (IRR). By changing the varactor bias, the image frequency shifts from 27 GHz to 37 GHz with over 40 dB IRR, a 19.1 dB to 17.6 dB peak gain, and 3.2 dB to 4.3 dB noise figure. To the best of the authors' knowledge, it shows the highest IRR and $F_{IM}/F_{OP}$ of the reported millimeter/quasi-millimeter wave IR-LNAs.

• 수면정신생리
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• 제7권2호
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• pp.96-101
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• 2000

목 적 : 본 연구는, 교대근무자에 있어 세 교대근무간의 수면양상과 자율신경계활동성을 비교함으로써, 근무자들은 어떤 근무시에 가장 적합하다고 느끼는지 그리고 교대근무자의 심리적, 신체적 문제점의 특성은 무엇인지를 알아보고자 하였다. 또한 본 연구는 근무자들이 교대근무에 좀 더 효과적으로 적응하는데 도움을 주고자 기획되었다. 방 법 : 3일 정도 연속적으로 한 교대근무를 한 후 1일 휴무, 그 다음에 다른 교대로 넘어가는 빠른 순환주기의 교대근무자 51명이 연구에 참여하였다. 각 대상은 수면일기를 작성하였으며 수면잠복기, 수면기간시간, 수면 중 깨어난 횟수를 세 교대근무간에 비교하였다. Epworth 졸음척도와 시각아날로그척도를 사용하여 졸음을 평가하였으며 기분상태는 기분상태척도로 평가하였다. 심박수변동성과, 스트레스 호르몬(아드레날린, 노르아드레날린) 및 그 대사산물을 측정하여 자율신경계 활동성을 살펴보았다. 심박수변동성에는 저주파영역의 스펙트럼 파워, 고주파영역의 스펙트럼 파워, 저주파영역의 파워와 고주파영역의 파워간의 비가 포함되었다. 결 과 : 수면기간시간은 오후근무시 가장 길었고 수면잠복기는 밤근무시 가장 짧았다. 깨어났을 때의 각성도는 오전근무시 가장 저하되었고 작업 중의 각성도는 밤근무 중 가장 떨어지는 것으로 나타났다. 밤근무시 근무자들은 신체적인 피곤감과 인지기능의 저하를 호소하였다. 심박수변동성의 비교를 통해 오후근무시 부교감신경계가 가장 활성화된다는 것을 알 수 있었으며 아드레날린 및 노르아드레날린 분비도 통계적인 의미는 없었지만 오후근무시 가장 감소하였다. 결 론 : 본 연구결과 오후근무가 교대근무자에게 가장 적합한 것으로 나타났다. 오전근무시에는 빛을 아침에 투여하고 밤근무시에는 근무 중에 빛을 투여하면 교대근무에의 적응이 촉진될 것으로 생각된다.

• Bulletin of the Korean Chemical Society
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• 제30권4호
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• pp.803-809
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• 2009

Notable blue shifts of the ν2 $C{\equiv}N$ stretching, $_{v4}$ C-C stretching and $_{v8}$ CCN deformation bands of $CD_3CN$ are observed upon solvation of $InCl_3$, resulting from the donor-acceptor interaction. The Raman spectrum in the $_{v2}$ region shows further details; at least two new bands emerge on the blue side of the $_{v2}$ band of free $CD_3CN$, whose relative intensities vary with concentration, suggesting that there exist at least two different cationic species in the solution. The strong hydrogen bonds formed between the methyl group and ${InCl_4}^-$ result in a large band appearing on the red side of the ν1 $CD_3$ symmetric stretching band. The solvation number of $InCl_3$, determined from the Raman intensities of the $C{\equiv}N$ stretching bands for free and coordinated $CD_3CN$, increases from $\sim$1.5 to $\sim$1.8 with decreasing concentration.

• 한국분무공학회지
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• 제28권2호
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• pp.62-67
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• 2023

Recently, the global automobile industry is aiming for a transition from internal combustion locomotives to zero-emission vehicles. Electric vehicles powered by battery energy can operate at peak performance and improve fuel economy by applying multiple motors or multi-speed transmissions. In order to design a two-speed transmission, it is necessary to evaluate and analyze the application system and performance of electric vehicles. In this study, control performance optimization of a twostage battery electric vehicle equipped with an AMT-based automatic transmission was performed and performance according to control pattern changes was analyzed. In order to improve the operating efficiency of the motor, the shift control that sets the optimal operating point according to the vehicle speed and required torque was derived from the motor efficiency map. The performance of battery energy consumption and transmission loss energy according to the hysteresis interval was analyzed and optimized. The hysteresis interval applied to the optimal shift map acted as a factor in reducing the frequency and loss of shifts. It has been shown that keeping the hysteresis interval at about 4 km/h can reduce energy consumption while reducing the number of shifts.

• 천문학회지
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• 제48권5호
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• pp.277-284
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• 2015

We present our efforts for extending the simultaneous multi-frequency receiver system of the Korean Very Long Baseline Interferometry (VLBI) Network (KVN) to global baselines in order to measure the frequency-dependent position shifts in Active Galactic Nuclei (AGN) jets, the so called core shift effect, with an unprecedented accuracy (a few micro-arcseconds). Millimeter VLBI observations with simultaneous multi-frequency receiver systems, like those of the KVN, enable us to explore the innermost regions of AGN and high precision astrometry. Such a system is capable of locating the frequency dependent opacity changes accurately. We have conducted the feasibility test-observations with the interested partners by implementing the KVN-compatible systems. Here we describe the science case for measuring the core shift effect in the AGN jet and report progress and future plans on extending the simultaneous multi-frequency system to global baselines.