• 대한수의학회지
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• 제35권2호
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• pp.279-285
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• 1995

To characterize non-adrenergic non-cholinergic(NANC) nerve mediated contractile responses in circular smooth muscle of bovine reticular groove, we investigated NANC relaxation and contraction induced by electric field stimulation to enteric nerves. In the presence of atropine($1{\mu}M$) and guanethidine($50{\mu}M$), electric field stimulation at frequency of 1 to 16Hz(square pulses, 0.5ms duration, 70V) evoked clear-cut relaxations through stimulations. Transient 'rebound contraction' was occured when the stimulus was switched off. All of the responses (relaxation and rebound contraction) were dose-dependently blocked by Nw-nitro-$_{\small{L}}$-arginine methyl ester(L-NAME), an inhibitor of nitric oxide synthesis, and methylene blue, and inhibitor of soluble guanylate cyclase. Tetraethyl ammonium(TEA), a potassium channel blocker, did not block the NANC relaxations.

• 전자공학회논문지A
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• 제32A권12호
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• pp.130-135
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• 1995

GaAs power MESFET's with 0.5 .mu.m gate length using a conventional UV lithography and angle evaporations are fabricated and then DC and RF characteristics are measured and carefully analyzed. The 0.5$\mu$m GaAs power MESFET's are fabricated on epi-wafers which have an undoped GaAs layer inbetween n+ and n GaAs layers grown by MBE, and by the processes such as an image reversal(IR), air-bridge, and our developed 0.5 .mu.m gate fabrication techniques. The total gate widths of the fabricated 0.5$\mu$m GaAs power MESFETs are 0.6-3.0 mm, the current saturation of them 80-400 mA, the maximum linear and RF output power of them 60-265 mW. The current gain cut-off frequencies for the 0.5$\mu$m GaAs power MESFETs varies 13-16 GHz. For the test frequency of 10 GHz the maximum unilateral transducer power gains and the power added efficiencies of the GaAs power devices are 7.0-2.5 dB and 35.68-30.76 %, respectively.

• 전기학회논문지
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• 제56권12호
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• pp.2184-2188
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• 2007

We developed a novel method of partial discharge(PD) location based on the fact that the waveform of PD signal propagate along the GIB (Gas Insulated Bus) is composed of several modes of electromagnetic wave with different group velocities and cut-off frequencies. From the PD waveform, measured at a broadband PD sensor attached on the GIB, we could derive arrival time and frequency components of different modes using the short term Fourier transform or etc. After the group velocities of different modes are calculated, the location of the PD source could be estimated. To show the effectiveness of this new locating method in a real on site application, we used this method to locate the position of a PD source at a 76 m long 345 kV GIB substation. The estimated location of the PD source using the method proposed above was in good agreement with the actual location found from the inspection result of internal component in the GIB with 2.4% of the estimation error.

• 한국항행학회논문지
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• 제15권4호
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• pp.571-577
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• 2011

본 논문은 차동 모드로 동작하는 메타 재질 구조를 바탕으로 평형 필터 설계를 제안한 것이다. 이 메타 재질 구조는 차동 모드 동작에서는 Composite Right/Left-Handed(CRLH) 메타 재질로 동작하여 필터 특성을 갖지만, 공통 모드에서는 통과대역이 차단되는 성질을 갖는 평형 CRLH 단위 셀로 구성되었다. 이러한 차동모드 특성을 갖는 단위 셀을 직렬로 4단을 연결하여 필터를 구성하였으며, 제안된 메타 재질의 특성은 차동 모드 평형 필터로 동작하고, 공통 모드에서는 차단되는 특성을 실험 결과를 통하여 확인하였다. 메타 재질을 이용한 평형 필터는 대역폭이 960 MHz~1000 MHz, 4.1dB의 삽입손실을 갖는 특성을 얻었다.

• 전력전자학회논문지
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• 제17권2호
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• pp.93-98
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• 2012

A precise measurement of the grid voltage is one of the essential techniques, which is required to connect a renewable energy to the grid. In general, when a filter is used to eliminate unnecessary harmonics and noises, a signal is distorted by phase delay, amplitude attenuation, and other distortions. And the response characteristic of a controller is directly affected by bandwidth of cut-off frequency of the filter. To alleviate this problems, we propose an effective algorithm based on DFT(Discrete Fourier Transform) instead of approaching the filter application. The proposed algorithm ensures high precise measurement of the grid voltage because it can extract the fundamental and harmonics from the raw signal without any distortions. The high performance of the proposed algorithm is verified by PSIM simulation and experiments of Grid-Connected VSI.

• Journal of Preventive Medicine and Public Health
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• 제42권4호
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• pp.223-230
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• 2009

Objectives : This study was conducted to validate self-reported smoking among high school students using urinary cotinine. Methods : A self report of smoking behavior was collected together with urine sample for cotinine analysis from 130 male and female students in two vocational high school students in November, 2007. Validity and agreement between self-reported smoking and urinary cotinine was analyzed with STATA 9.0 for different definitions of current smokers, and frequent and daily smokers. Urinary cotinine concentration was measured by the DRI Cotinine Assay for urine (Microgenics Corp., Fremont, CA) on Toshiba 200FR. The cut-off point of urinary cotinine was 50 ng/dl. Results : The concentrations of urinary cotinine were significantly different according to the frequency and amount of smoking. Sensitivity and specificity was 90.9% and 91.8% respectively, and the Cohen s kappa value was 0.787 among the current smokers who smoked at least one day during one month preceding the survey. The comparable high sensitivity, specificity, and kappa value were shown also among the other definitions of current smokers, that is, subjective smokers, and weekly smokers. Conclusions : The results showed the high validity of self-reported smoking among high school students. However, due to the small sample size and limitation of the participants, it is cautious to generalize the results to overall high school students.

• 전자공학회논문지A
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• 제32A권2호
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• pp.66-72
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• 1995

Using the Si/SiGe layer grown by solid source molecular beam epitaxy(SSMBE) on the LOCOS-patterned wafers, an emitter-base self-aligned hterojunction biplar transistor(HBT) with the polysilicon-emitter and the silicon germanium(SiGe) base has been fabricated. Trech isolation process, planarization process using a chemical-mechanical poliching, and the selectively implanted collector(SIC) process were performed. A titanium disilicide (TiSi$_{2}$), as a base electrode, was used to reduce an extrinsic base resistance. To prevent the strain relaxation of the SiGe epitaxial layer, low temperature (820${^\circ}C$) annealing process was applied for the emitter-base junction formation and the dopant activation in the arsenic-implanted polysilicon. For the self-aligned Si/SiGe HBT of 0.9${\times}3.8{\mu}m^{2}$ emitter size, a cut-off requency (f$_{T}$) of 17GHz, a maximum oscillation frequency (f$_{max}$) of 10GHz, a current gian (h$_{FE}$) of 140, and an emitter-collector breakdown voltage (BV$_{CEO}$) of 3.2V have been typically achieved.

• Journal of the Optical Society of Korea
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• 제19권5호
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• pp.487-493
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• 2015

A wavefront coding (WFC) technique provides an extension of the depth of field for a microscopy imaging system with slight loss of image spatial resolution. Through the analysis of the relationship between the incidence angle of light at the phase mask and the system pupil function, a mixing symmetrical cubic phase mask (CPM) applied to 5X-40X micro-objectives is optimized simultaneously based on point-spread function (PSF) invariance and nonzero mean values of the modulation transfer function (MTF) near the spatial cut-off frequency. Optimization results of the CPM show that the depth of field of these micro-objectives is extended 3-10 times respectively while keeping their resolution. Further imaging simulations also prove its ability in enhancing the defocus imaging.

• JSTS:Journal of Semiconductor Technology and Science
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• 제2권1호
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• pp.59-69
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• 2002

A semi-analytical model based on exact numerical analysis of the 2DEG channel in pseudo-morphic HEMT (PMHEMT) is presented. The exactness of the model stems from solving both Schrodinger's wave equation and Poisson's equation simultaneously and self-consistently. The analytical modeling of the device terminal characteristics in relation to the charge control model has allowed a best fit with the geometrical and structural parameters of the device. The numerically obtained data for the charge control of the channel are best fitted to analytical expressions which render the problem analytical. The obtained good agreement between experimental and modeled current/voltage characteristics and small signal parameters has confirmed the validity of the model over a wide range of biasing voltages. The model has been used to compare both the performance and characteristics of a PMHEMT with a competetive HEMT. The comparison between the two devices has been made in terms of 2DEG density, transfer characteristics, transconductance, gate capacitance and unity current gain cut-off frequency. The results show that PMHEMT outperforms the conventional HEMT in all considered parameters.

• 한국전자파학회논문지
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• 제14권11호
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• pp.1143-1148
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• 2003

CPW와 마이크로스트립선로에서 수십 피코초의 펄스 폭을 갖는 가우시안(Gaussian) 펄스 신호가 진행해 갈 때 기판 및 선로 구조에 따른 분산 및 펄스의 전파 특성을 시간 영역에서 해석하고 측정하였다. 특히, 선로에 사용된 기판의 기본 TE 모드에 대한 차단 주파수( $f_{TE}$ )의 변화에 따른 CPW와 마이크로스트립 선로간의 전송특성을 구하고 비교하였다. 이를 실험적으로 확인하기 위해 $f_{TE}$ 가 다른 기판에 두 가지 50 $\Omega$ 선로를 제작하여 수십 피코초 펄스가 진행되었을 때의 전송 특성을 시간 영역 분석기능이 내장된 VNA(Vector Network Analyzer)를 이용해서 측정하였다.