• 한국광학회:학술대회논문집
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• 한국광학회 2006년도 하계학술발표회 논문집
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• pp.363-364
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• 2006

We developed 60 GHz analog optical transmitter modules for radio-over-fiber (RoF). They were consisted of an electroabsorption modulator (EAM), impedance matching circuit, and amplifier. The characteristics of fabricated modules were investigated by measuring the signal-to-noise ratio and the noise figure of the 60 GHz RoF link.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2002년도 추계학술대회 논문집 전기물성,응용부문
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• pp.228-229
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• 2002

접지설계시, 과도상태와 정상상태의 접지진단을 위해서는 무엇보다도 접지전류의 분류상태를 정확히 측정하는 기술의 확립이 필요하며, 필드측정의 타당성 검증을 위해서는 시뮬레이션이 병형되어야 한다. 따라서, 본 논문에서는 접지임피던스 및 접지전류 분류율 계산을 정확하게 실행하여 필드측정치에 대한 검증과 접지설계의 안정성과 경제성을 도모하기 위한 효과적인 프로그램을 개발하였다.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2000년도 추계학술대회논문집
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• pp.232-236
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• 2000

To provide model parameters for servo control system design, dynamic characteristics of a piezoelectric microactuator for hard disk drive(HDD) were investigated. At first frequency response characteristics was measured and a second order model was proposed. Here the amplitude dependent dynamic characteristics such as low frequency gain and damping ratio were studied. In addition, the load current and equivalent impedance of the piezoelectric actuator were measured by varying excitation voltage and frequency. At last, the super-harmonic resonance of the piezoelectric actuator was discussed.

• 전기화학회지
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• 제1권1호
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• pp.33-39
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• 1998

본 연구에서는 전자-선 증발법으로 제조된 비정질의 텅스텐 산화물 박막과 전해질 계면에서 진행되는 전기화학반응을 1 M $LiCLO_4/PC$유기 전해질 계면에서 비정질의 텅스텐 산화물 박막 내부로 삽입된 리튬의 양론 값과 박막 전위의 변화에 대하여 연구하였다. 특히 복소수 임피던스 스펙트럼으로부터 제안된 박막과 전해질 계면의 등가 회로는 리튬의 층간 반응 기구가 텅스텐 산화물 박막/유기 전해질 계면에서 리튬 이온의 전하 전달 현상, 텅스텐 산화물 박막에 리튬의 흡착현상 및 박막 내부로의 리튬의 흡수 및 확산 현상으로 구성되어 있다는 것을 알 수 있었다. 또한 CNLS fitting법에 의하여 시뮬레이션된 $R_{ct},\;C_{dl},\;D$, 및 $\sigma_{Li}$ 등의 열역학 및 속도론적 변수 값 등의 상관 관계로부터,비정질의 텅스텐 산화물 박막의 소. 발색 특성은 이들 변수값과 관련이 있었으며, 특히 $Li_y,WO_3$, 박막 내의 리튬의 몰비 y=0.167및 전극 전위 E=2.25 V(vs. Li)에서 전기 발색의 한계값을 갖는 것으로 조사되었다.

• 한국지반공학회논문집
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• 제34권2호
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• pp.33-42
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• 2018

본 연구에서는 소형 압전소자의 전기-역학적 임피던스를 이용하여 모래의 단위중량이나 강도를 평가하였다. 다짐 몰드 내 크기가 다른 세 종류의 미고결 낙동강모래를 느슨하거나 조밀하게 성형한 다음 내부에 직경 20mm 원형모양의 납작한 압전소자를 설치하고 임피던스를 측정하였다. 또한, 가는 낙동강모래에 시멘트비 4, 8, 12, 16%로 직경 50mm, 높이 100mm의 고결 공시체를 6층으로 다져서 제작하였다. 고결 공시체의 3층 내부에 압전소자를 수평방향으로 설치한 다음 3일 동안 임피던스 신호를 측정하였으며, 측정 후 일축압축시험을 실시하였다. 미고결 모래의 단위중량이 증가함에 따라 공진주파수는 102kHz에서 105kHz까지 약간 증가하였으며, 공진주파수 발생 시 컨덕턴스는 감소하였다. 고결 모래의 양생시간과 시멘트비가 증가함에 따라 공진주파수는 129kHz에서 266kHz까지 크게 증가하였으며, 공진주파수 발생 시 컨덕턴스는 반대로 감소하는 경향을 보였다. 고결 모래의 일축압축강도는 시멘트비에 따라 289-1,390kPa 정도이며, 공진주파수와는 뚜렷한 정비례 관계를 보이지만 공진주파수 발생 시 컨덕턴스와는 반비례 관계를 보였다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1999년도 하계학술대회 논문집 D
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• pp.1680-1682
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• 1999

In this study, three kinds of Mn-Zn ferrite/Ni-Zn ferrite/$Ni_2Y$ ferroxplana prepared by the coprecipitation method were compounded with the silicon rubber, and the ring-shaped specimens with various compositional ratio were made. The material constant of ferrite/rubber composite absorbers was obtained by the 2-port method. The material constants of the ferrite/rubber composite microwave absorber made of three kinds of ferrite with various compositional ratio were utilized in design the matching conditions (frequency and thickness) on the impedance matching map. We were able to predict the matching condition from the matching map. On all three kinds of ferrite/rubber composite microwave absorber with less than compositional ratio 60[wt.%] of ferroxplana, we have found that the reflection losses were over than 20[dB] at the S-Band $(2\sim4[GHz])$ and C-Band$(4\sim8[GHz])$.

• Nuclear Engineering and Technology
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• 제35권5호
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• pp.369-377
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• 2003

Since Zr-2.5Nb pressure tubes have a high risk for the formation of blisters during their operation in pressurized heavy water reactors, there has been a strong incentive to develop a method for the non-destructive detection of blisters grown on the tube surfaces. However, because there is little mismatch in acoustic impedance between the hydride blisters and zirconium matrix, it is not easy to distinguish the boundary between the blister and zirconium matrix with conventional ultrasonic methods. This study has focused on the development of a special ultrasonic method, so called ultrasonic velocity ratio method for a reliable detection of blisters formed on Zr-2.5Nb pressure tubes. Hydride blisters were grown on the outer surface of the Zr-2.5Nb pressure tube using a cold finger attached to a steady state thermal diffusion equipment. To maximize a difference in the ultrasonic velocity in hydride blisters and the zirconium matrix, the ultrasonic velocity ratio of longitudinal wave to shear wave, $V_L/V_S$, has been determined based on the flight time of the longitudinal echo and reflected shear echo from the outer surface of the tubes. The feasibility of the ultrasonic velocity ratio method is confirmed by comparing the contour plots reproduced by this method with those of the blisters grown on the Zr-2.5Nb pressure tubes.

• 한국보건간호학회지
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• 제18권2호
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• pp.299-311
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• 2004

Purpose: Somatotype drawing developed by Sorensen et al.(1983) has been evaluated as a simple instrument of obesity level without real somatic measuring as height and weight. This study was designed to validate somatotype drawings for obesity assessment by bioelectrical impedance body component analysis. Method: At first questionnaire of somatotype drawing was done. Subjects were measured body component by bioelectrical impedance analysis as weight, BMI(body mass index), WHR(waist-hip ratio), body water, protein mass, mineral mass, body fat mass, skeletal muscle mass, soft lean mass, fat free mass and percent body fat. We evaluated correlations between these data and somatotype drawings and tried to grouping of somatotype drawings with the means of major body component value. Result: The data were collected from 205 college women whose height and weight were $161.2\pm4.8,\;55\pm8.3$. Spearman's correlation coefficients of somatotype drawing were 0.74 with BMI, 0.68 with weight 0.69 with body fat mass, 0.65 with WHR. 0.64 with percent body fat after adiusted age. The grade of somatotype drawings were grouped as 1-2, 3-4, 5-6. 7-9 by BMI, body fat mass, weight, 1, 2-4, 5-6, 7-9 by WHR and 1-2, 3-4, 5-9 by percent body fat(ANOVA and Duncan's method). Conclusion: So quick instrument using somatotype drawings were useful tools for evaluation of obesity level and is applicable to screen degree of body fat in self-administered questionnaire survey.

• 한국재료학회지
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• 제21권8호
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• pp.468-475
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• 2011

[ $LaMeO_3$ ](Me = Cr, Co) powders were prepared using the polymeric precursor method. The effects of the chelating agent and the polymeric additive on the synthesis of the $LaMeO_3$ perovskite were studied. The samples were synthesized using ethylene glycol (EG) as the solvent, acetyl acetone (AcAc) as the chelating agent, and polyvinylpyrrolidone (PVP) as the polymer additive. The thermal decomposition behavior of the precursor powder was characterized using a thermal analysis (TG-DTA). The crystallization and particle sizes of the $LaMeO_3$ powders were investigated via powder X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), and particle size analyzer, respectively. The as-prepared precursor primarily has $LaMeO_3$ at the optimum condition, i.e. for a molar ratio of both metal-source (a : a) : EG (80a : 80a) : AcAc (8a) inclusive of 1 wt% PVP. When the as-prepared precursor was calcined at $700^{\circ}C$, only a single phase was observed to correspond with the orthorhombic structure of $LaCrO_3$ and the rhombohedral structure of $LaCoO_3$. A solid-electrolyte impedance-metric sensor device composed of $Li_{1.5}Al_{0.5}Ti_{1.5}(PO_4)_3$ as a transducer and $LaMeO_3$ as a receptor has been systematically investigated for the detection of NOx in the range of 20 to 250 ppm at $400^{\circ}C$. The sensor responses were able to divide the component between resistance and capacitance. The impedance-metric sensor for the NO showed higher sensitivity compared with $NO_2$. The responses of the impedance-metric sensor device showed dependence on each value of the NOx concentration.

• 센서학회지
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• 제24권1호
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• pp.22-28
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• 2015

This study demonstrates a polyimide nerve cuff electrode with a conductive polymer for improving recording signal quality at peripheral nerve. The nerve cuff electrodes with platinum (Pt), iridium oxide (IrOx), and poly(3,4-ethylenedioxythiophene): p-toluene sulfonate (PEDOT:pTS) were fabricated and investigated their electrical characteristics for improving recorded nerve signal quality. The fabricated nerve cuff electrodes with Pt, IrOx, and PEDOT:pTS were characterized their impedance and CDC by using electrochemical impedance spectroscopy (EIS) and cyclic voltammetry. The impedance of PEDOT:pTS measured at 1 kHz was $257{\Omega}$, which was extremely lower than the value of the nerve cuff electrodes with IrOx ($15897{\Omega}$) and Pt ($952{\Omega}$), respectively. Furthermore, the charge delivery capacity (CDC) of the nerve cuff electrode with PEDOT:pTS was dramatically increased to 62 times than the nerve cuff electrode with IrOx. In ex-vivo test using extracted sciatic nerve of spaque-dawley rat (SD rat), the PEDOT:pTS group exhibited higher signal-to-interference ratio than IrOx group. These results indicated that the nerve cuff electrode with PEDOT:pTS is promising for effective implantable nerve signal recording.