• 한국전기전자재료학회논문지
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• 제27권1호
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• pp.27-32
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• 2014

In this paper, PZT piezoelectric ceramic specimens with 4 compositions (Zr/Ti=50/50, 53/47, 56/44, 58/42) in $Pb(Zr,Ti)O_3$ system were fabricated. We studied effects of poling strength and thermal aging on the temperature characteristics of eletromechanical coupling factor k31 of the specimens, which were poled with the DC electric fields, 1.5, 2.5 and 3.5 kV/mm respectively and thermally aged for an hour at $200^{\circ}C$. The eletromechanical coupling factor k31 of the specimen with the composition Zr/Ti= 53/47, nearest to the morphotropic phase boundary decreased the most greatly, irrelevant to the intensity of poling field, due to 1st thermal aging. And the temperature coefficient of eletromechanical coupling factor k31 was (-) in the tetragonal phase composition and (+) in the rhombohedral phase composition, which is reverse in the temperature coefficient of resonance frequency. It is interesting that eletromechanical coupling factor k31 of PZT ceramics is shown to be able to increase as temperature increase in the interval $-20{\sim}80^{\circ}C$.

• 조명전기설비학회논문지
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• 제19권8호
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• pp.85-93
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• 2005

본 논문에서는 고속 드라이브를 위하여 IPMSM의 약계자 영역에서 최대 토크제어를 제시한다. 최대 토크동작을 위하여 최적 d축 전류를 결정하고 이 전류를 각 제어모드에서 사용한다. 최대 토크를 발생하기 위하여 전류 조절기의 출력인 인버터의 출력전압은 DC 링크전압을 최대로 이용한다. 제어모드의 원활한 전이는 지령신호에 기초하여 자동적으로 수행한다. 본 논문에서 제시한 최대 토크제어로 IPMSM 드라이브에 적용시험을 한다. 그리고 시험결과의 응답특성을 다양하게 분석하여 본 논문의 타당성을 입증한다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2007년도 제38회 하계학술대회
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• pp.1984-1985
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• 2007

Polyimide is widely used as a high-temperature insulating material. Space charge distributions in polyimide (PI) films strongly depend upon electric field, temperature, water content and so on. We observed space charge distributions in PI films with various water contents. When a dc field was applied to as-received PI films or water-treated PI films, positive and negative homo space charges were observed near the respective electrodes at 333 K. In dried PI films, the homo space charges were much reduced, and positive and negative hetero space charges in the bulk were clearly observed. The space charge amounts in water-treated PI films were smaller than in as-received ones, while the current density in water-treated PI film was larger than that in as-received one by two or more orders of magnitude. These suggest not only that the charge injection from the electrode is enhanced by absorbed water but also that absorbed water makes carriers mobile. The decay of space charge was also faster in water-treated PI than in as-received or dried one. This also supports the enhancement of apparent mobilities of carriers in PI by absorbed water.

• 한국인터넷방송통신학회논문지
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• 제12권1호
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• pp.165-172
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• 2012

$1.3{\mu}m$ 파장에서 동작하는 비대칭 Mach-Zehnder 간섭기에 분할전극 구조를 배열하여 전계 측정시스템의 감지부를 설계, 제작하였다. BPM 전산모사를 통해서 소자를 설계하였고, $LiNbO_3$에 Ti 확산방법으로 구현된 채널 광도파로에 집중 전극구조를 배열하여 집적광학 칩을 제작하였다. ${\pi}/2$ 위상차를 갖도록 설계된 비대칭 구조에서는 DC 0V에서 측정된 출력 광세기가 최고치에 약 1//2에 해당됨을 확인하였으며, 1KHz 전기신호를 인가해서 ${\pi}/2$ 위상차 때문에 나타나는 전기적 현상들을 확인하였다.

• 한국광학회지
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• 제11권1호
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• pp.25-32
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• 2000

순수 N-(4-nitrophenyl)-(L)-prolinol (NPP)와 NPP를 곁가지로 갖는 poly(methyl metharcrylate) (PMMA) 및 poly(p-phenlene terephthalates) (PPT) 고분자계의 제 1차 초편극도 $\beta$를 전기장 인가 제 2고조파 발생(EFISHG)방법과 hyper-Rayleigh 산란(HRS) 방법으로 측정하여 비교하였다. 1,1,2,2,-tetrachloroethane 용액속의 순수 NPP와 NPP-PMMA 경우, 두 방법으로 구한 $\beta$측정값은 실험오차 이내에서 유사하였다. 그러나 1,1,2,2,-tetrachloroethane 용액속의 HNPP-PPT 고분자 경우 $\beta$측정 결과는 순수 NPP에 비하여 EFISHG에서는 9.7배 증대되고 HRS에서는 2.4배 증대되었다. 이 결과는 견고한 고분자 주사슬에 비선형 광 발색단을 곁가지로 갖는 고분자계에서는 직류 전기장속에서 발색단들이 고분자 2차 비선형 특성에 상호 보강적으로 기여하여 극성 고분자 사슬에서와 같이 증대된 것으로 해석하였다.

• 대한의용생체공학회:의공학회지
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• 제27권4호
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• pp.154-163
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• 2006

A 64-channel magnetocardiogram (MCG) system using low-noise superconducting quantum interference device (SQUID) planar gradiometers was developed for the measurements of cardiac magnetic fields generated by the heart electric activity. Owing to high flux-to-voltage transfers of double relaxation oscillation SQUID (DROS) sensors, the flux-locked loop electronics for SQUID operation could be made simpler than that of conventional DC SQUIDs, and the SQUID control was done automatically through a fiber-optic cable. The pickup coils are first-order planar gradiometers with a baseline of 4 em. The insert has 64 planar gradiometers as the sensing channels and were arranged to measure MCG field components tangential to the chest surface. When the 64-channel insert was in operation everyday, the average boil-off rate of the dewar was 3.6 Lid. The noise spectrum of the SQUID planar gradiometer system was about 5 fT$_{rms}$/$\checkmark$Hz at 100 Hz, operated inside a moderately shielded room. The MCG measurements were done at a sampling rate of 500 Hz or 1 kHz, and realtime display of MCG traces and heart rate were displayed. After the acquisition, magnetic field mapping and current mapping could be done. From the magnetic and current information, parameters for the diagnosis of myocardial ischemia were evaluated to be compared with other diagnostic methods.

• 한국전기전자재료학회논문지
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• 제11권2호
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• pp.111-120
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• 1998

In this paper, the $(SrPb)(CaMg)TiO_3$ ceramics with paraelectric properties were fabricated by the mixed oxide method. It was investigated that which the variation of contents of $Bi_2O_3{\cdot}3TiO_2$ effects on structural, dielectrical and electrical properties of specimens. As a result, the grain size were grown with increasing the contents of $Bi_2O_3{\cdot}3TiO_2$. The relative dielectric constants were increased up to 4[mol%] of $Bi_2O_3{\cdot}3TiO_2$, and decreased more or less at a low temperature in the specimens which had more than. But the temperature coefficient. of capacitance were showed ${\pm}25$[%]. The dielectric loss were less than 0.05 in all specimens which had more than 4[mol%] of $Bi_2O_3{\cdot}3TiO_2$. In order to investigate the behavior of charged particles, the characteristics of electrical conduction were measured. As a result, the conduction current was divided into the three steps as a function of DC electric field. The first step was Ohmic region due to ionic conduction, below 15[kV/cm]. The second step was showed a saturation which seems to be related to a depolarizing field occuring in field-enforced ferroelectric phase, between 15[kV/cm] and 40[kV/cm]. The third step was attributed to Child's law related to space charge which injected from electrode, above 40[kV/cm].

• Progress in Superconductivity
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• 제13권1호
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• pp.1-6
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• 2011

Measurement of magnetic signals generated from electric activity of myocardium provides useful information for the functional diagnosis of heart diseases. Key technical component of the magnetocardiography (MCG) technology is SQUID. To measure MCG signals with high signal-to-noise ratio, sensitive SQUID magnetic field sensors are needed. Present magnetic field sensors based on Nb SQUIDs have field sensitivity good enough to measure most of MCG signals. However, for accurate measurement of fine signal pattern or detection of local atrial fibrillation signals, we may need higher field sensitivity. In addition to field sensitivity, economic aspect of the SQUID system is also important. To simplify the SQUID readout electronics, the output voltage or flux-to-voltage transfer of SQUID should be large enough so that direct measurement of SQUID output can be done using room-temperature preamplifiers. Double relaxation oscillation SQUID (DROS), having about 10 times larger flux-to-voltage transfers than those of DC-SQUIDs, was shown to be a good choice to make the electronics compact. For effective cancellation of external noise inside a thin economic shielded room, first-order axial gradiometer with high balance, simple structure and long-baseline is needed. We developed a technology to make the axial gradiometer compact using direct bonding of superconductive wires between pickup coil and input coil. Conventional insert has mechanical support to hold the gradiometer array, and the dewar neck has equal diameter with the dewar bottom. Boiling of the liquid He can generate mechanical vibrations in the gradiometer array due to mechanical connection structure. Elimination of the mechanical support, and direct mounting of the gradiometer array into the dewar bottom can reduce the dewar neck diameter, resulting in the reduction of liquid He consumption.

• 한국진공학회지
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• 제6권2호
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• pp.136-142
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• 1997

An/n-GaAs(100) Schottky 장벽 diode를 제작하여 변조전압($V_{ac}$) 및 dc 바이어스 전 압($V_{bias}$) 변화에 따른 electroreflectance(ER)를 측정하였다. 관측된 Franz-Keldysh oscillation(FKO) 피크로부터 이 시료의 내부 전기장($E_i$)은 $5.76\times 10^{4}$V/cm였다. $V_{ac}$를 변화시 킴에 따라 ER신호의 모양은 변화가 없고, 진폭만 선형적으로 증가하였다. 순방향 및 역방향 의 $V_{bias}$변화에 따라 ER신호의 진폭은 감소하였으며, $V_{bias}$가 -5.0~0.6V로 증가함에 따라 Ei 는 $19.3\times 10^4\sim4.39\times10^4$V/cm로 감소하였다. 그리고 $V_{bias}$변화에 대한 $E_i^2$의 그래프로부터 built-in 전압(Vbi)은 0.70V였으며, 이 값은 $V_{bias}$변화에 따른 FKO피크의 진폭 관계 그래프 에서 얻은 결과와 잘 일치하였다. 또한 이 시료의 캐리어 농도(N)와 전위장벽($\Phi$)은 300K에 서 각각 $2.4\times 10^{16}\textrm{cm}^{-3}$와 0.78eV의 값을 얻었다.

• 대한토목학회논문집
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• 제30권1C호
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• pp.37-44
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• 2010

최근 도심지 재개발, 지하철과 같은 지하공간의 시공 등과 관련하여 도심지 지반조사의 중요성이 부각되고 있으나, 지반내 전기잡음, 교통진동, 지중 매설물 등 많은 장애 요인으로 인하여 도심지 지반조사의 신뢰성은 낮을 수 밖에 없는 상황이다. 이에 본 논문에서는 전기비저항 시험을 도심지에서 수행하고자 할 때 대두되는 가장 큰 장애요인 중 하나인 전기잡음 문제를 최소화할 수 있는 유사직류 전기비저항 기법(Pseudo-DC Resistivity Survey, PDC-R)을 제시하였다. PDC-R 기법은 기존의 전기비저항 시험과는 달리 0.1~1.0Hz 범위의 저주파 교류를 입력전원으로 사용하여 전기비저항 시험을 수행하는 것으로 도심지 전기잡음 성분인 60Hz의 배수가 되는 주파수를 회피함으로써 도심지 전기잡음의 간섭을 최소화하는 것이다. 본 연구에서는 PDC-R 기법의 구현을 위해서 교류 입력전원과 관련된 영향인자, 즉, 표면효과(skin effect), 주파수 효과, 입력전류 크기 등에 대한 연구를 수행하여 최적의 시험조건을 설정하였다. 또한, PDC-R 기법을 자연 지반에 적용하여 기존 전기비저항 시험, CapSASW 시험 등과의 비교를 통하여, PDC-R 기법의 신뢰성과 실용성을 검증하였다.