• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 2006년 추계학술발표대회 개요집
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• pp.136-138
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• 2006

Recently a lots of problems have observed in high densified and high integrated electronic components. One of them is ion migration phenomena, which induce the electrical short of electrical circuit. Ion migration phenomena has been observed in the field of exposing the specific environment and using for a long time. Also as the RoHS restriction was started in July 1st, 2006, Pb-free solder was utilized in electronics assemblies. In this case, it is very important to compatible between components and printed circuit board(PCB), thus surface treatment materials of PCB was changed to Sn, Sn-3.0Ag-0.5Cu, Cu. Therefore these new application become to need to reevaluate the sensitivity about electrochemical ion migration. This study was evaluated the occurrence time of electrochemical ion migration using by water drop test. We utilized PCB(printed circuit board) having a comb pattern as follows 0.1, 0.318, 0.5, 1.0 mm pattern distance. Sn-3.0Ag-0.5Cu and Sn-37Pb were electroplated on the comb pattern. 6.5V and 15.0V were applied in the comb pattern and then we measured the electrical short time causing by occurring the ion migration. In these results, we evaluate the sensitivity and derived the prediction models of ion migration occurrence time depending on the pattern materials, applied voltage and pattern spacing of PCB conductor.

• 조명전기설비학회논문지
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• 제20권5호
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• pp.9-17
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• 2006

규모가 큰 제철소는 전기로와 같은 비선형 부하를 가지고 있다. 고조파 측정 결과로 고조파는 시간에 따라 변하는 특성이 관측되었다. 순시치 측정에 의한 고조파 평가는 측정 순간에 따라 고조파가 다를 수 있으므로 모호한 결과를 초래할 수 있다. 시간에 따라 변하는 고조파를 해결하기 위해 쓰이는 가장 보편적인 방법은 누적확률을 사용하는 것이다. 고조파 시뮬레이션은 사례연구 시스템의 전압 및 전류 왜곡을 평가하기 위해 이용되었다. 본 논문에서는 전기로 부하의 고조파 현장 측정, 국제 고조파 관리 기준인 IEC 61000-3-6과 IEEE Std. 519에 의한 고조파 평가, 시간에 따라 변하는 고조파의 시뮬레이션을 심도 있게 다루고자 한다. 고조파 해석 프로그램인 EDSA는 사례 연구에 시뮬레이션 도구로 사용되었다.

• 한국진공학회지
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• 제9권2호
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• pp.136-143
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• 2000

RF magnetron sputtering법으로 $SrBi_2Ta_2O_9$ (SBT)박막을 상온에서 p-type Si(100) 기판위에 증착하여 DRO 강유전체 메모리(destructive read out ferroelectric random access memory)에 사용되는 강유전체막으로 Pt/SBT/Pt/Ti/$SiO_2$/Si (MFM)구조의 응용가능성을 확인하였다. 구조적인 특징들이 열처리 시간의 변화와 Ar/$O_2$의 가스 유량비의 변화에 따라서 XRD(x-ray diffractometer)에 의해 관찰되었으며 표면 특성은 FE-SEM(field emission scanning electron microscopy)에 의해서 관찰하고 박막의 전기적 특성들은 P-V(polarization-voltage measurement)와 I-V(current-voltage measurement)를 사용하여 관찰하였다. 스퍼터링 증착시 Ar/$O_2$의 가스 유량비는 1:4에서 4:1까지 변화 시켰고 SBT박막은 상온에서 증착시켰다. XRD 측정시 박막들은 SBT의 (105), (110) peak들을 나타내었다. 상온에서 증착시킨 박막은 1시간, 2시간 동안 산소 분위기에서 $800^{\circ}C$ 열처리를 하여 결정화 시켰다. SBT 박막의 P-V곡선은 이력 곡선의 모양을 갖추었으며 비대칭적인 강유전체 특성을 나타내었다. Ar/$O_2$ 가스유량비가 1 : 1, 2 : 1인 경우에 박막의 누설 전류밀도 값이 제일 좋았으며, 그 값은 3V 5V 7V에서 각각 $3.11\times10^{-8} \textrm{A/cm}^2$, $5\times10^{-8}\textrm{A/cm}^2$, $7\times10^{-8}\textrm{A/cm}^2$ 이었다. 열처리 시간을 2시간으로 증가시킨 후, 그들의 전기적 특성과 결정화특성이 개선됨을 확인하였다. AES 분석 및 EPMA분석으로 SBT박막의 깊이 분포 및 조성을 확인하였다.

• 공업화학
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• 제9권4호
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• pp.579-584
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• 1998

자외선 경화 반응에 의해 만들어지는 고분자/액정 복합막에서 자외선 광 개시제의 농도, 복합막의 두께 및 중합에 의한 상분리 시의 온도, 전기장의 영향 등 제조 외부 조건에 따른 복합막의 전기 광학적 특성의 변화에 대하여 조사를 하였다. 광개시제나 다관능성 단량체의 농도증가에 따라 고분자 매트릭스의 가교밀도가 증가하고 상대적으로 더 작은 액정상이 형성되며 그에 따라 액정과 고분자의 계면 면적이 넓어져 복합막의 구동전압이 증가하는 것이 관찰되었다. 분자량이 서로 다른 두 종류의 diacrylate 형의 올리고머를 사용하여 만든 복합막에 있어서는 분자량이 큰 PTDA-1000을 사용한 경우 복합막의 초기 투명도는 더 올라가지만 일정한 구동전압 이상에서 투명도의 포화 상태가 일어나는 데 반하여 분자량이 적은 PTDA-250을 사용한 경우에는 필름의 초기 투명도가 훨씬 더 낮아지는 대신 60 V 이상의 전압에서도 투명도의 포화 상태가 일어나지 않는 것이 관찰되었다. 중합에 의한 상분리시 온도가 높아질수록 복합막의 초기 투명도는 높아지는 것이 관찰되었으며 이것은 액정/UV 경화 혼합물의 온도가 높아짐에 따라 점도가 낮아지고 용해도는 증가하여서 상대적으로 큰 액정상들이 복합막 내에 생기기 때문인 것으로 생각되었다. 한편 복합막의 두께가 얇을수록 구동전압은 비례적으로 낮아졌으며 중합에 의한 상분리 시에 인가되는 외부전기장의 효과는 전장이 초기 투과도 뿐 아니라 구동전압이나 응답시간에도 영향을 미치는 것이 관찰되었다.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2004년도 ICCAS
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• pp.232-237
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• 2004

In many application of DC-DC converters, loads cannot be specified in advance, i.e., their amplitudes are suddenly changed from the zero to the maximum rating. Generally, design conditions are changed for each load and then each controller is re-designed. Then, a so-called robust DC-DC converter which can cover such extensive load changes and also input voltage changes with one controller is needed. Analog control IC is used usually for the controller of DC-DC converter. Simple integral control etc. are performed with the analog control IC. However it is difficult to retain sufficient robustness of DC-DC converter by these techniques. The authors proposed the method of designing an approximate 2-degree-of-freedom (2DOF) controller of DC-AC converter. This controller has an ability to attain sufficient robustness against extensive load and DC power supply changes. For applying this approximate 2DOF controller to DC-DC converter, it is necessary to improve the degree of approximation for better robustness. In this paper, we propose a method of designing good approximate 2DOF digital controller which makes the control bandwidth wider, and at the same time makes a variation of the output voltage very small at a sudden change of resistive load. The proposed good approximate 2DOF digital controller is actually implemented on a DSP and is connected to a DC-DC converter. Experimental studies demonstrate that this type digital controller can satisfy given specifications.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2009년도 하계학술대회 논문집
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• pp.295-296
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• 2009

There are various application of liquid crystal materials to devices, especially, blue phase liquid crystal (BPLC) and nano-structured liquid crystal mixture have been studied recently because BPs existing temperature range has been expanded by polymer-stabilization and liquid crystal has been confined in room which has certain coherence length so that their particular characters, such as fast response time and optically isotropic state at no electric field, could apply to advanced liquid crystal display devices. However, there is an crucial problem which is high operating voltage from low Kerr constant and limited electric field utilization using in-plain electric field. In this paper, we will analyze cell structure in the way of using electric field and show effective electric field utilization to reduce operating voltage.

• The Korean Journal of Physiology and Pharmacology
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• 제1권6호
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• pp.741-748
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• 1997

In the present study, we have investigated the effect of metabolic inhibition on the inward rectifier K current ($I_{K1}$). Using whole cell patch clamp technique we applied voltage ramp from +80 mV to -140 mV at a holding potential of -30 mV and recorded the whole cell current in single ventricular myocytes isolated from the rabbit heart. The current-voltage relationship showed N-shape (a large inward current and little outward current with a negative slope) which is a characteristic of $I_{K1}$. Application of 0.2 mM dinitrophenol (DNP, an uncoupler of oxidative phosphorylation as a tool for chemical hypoxia) to the bathing solution with the pipette solution containing 5 mM ATP, produced a gradual increase of outward current followed by a gradual decrease of inward current with little change in the reversal potential (-80 mV). The increase of outward current was reversed by glibenclamide ($10\;{\mu}M$), suggesting that it is caused by the activation of $K_{ATP}$. When DNP and glibenclamide were applied at the same time or glibenclamide was pretreated, DNP produced same degree of reduction in the magnitude of the inward current. These results show that metabolic inhibition induces not only the increase of $K_{ATP}$ channel but also the decrease of $I_{K1}$. Perfusing the cell with ATP-free pipette solution induced the changes very similar to those observed using DNP. Long exposure of DNP (30 min) or ATP-free pipette solution produced a marked decrease of both inward and outward current with a significant change in the reversal potential. Above results suggest that the decrease of $I_{K1}$ may contribute to the depolarisation of membrane potential during metabolic inhibition.

• 수산해양기술연구
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• 제37권1호
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• pp.57-65
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• 2001

본 연구에서는 2차자속을 파라미터로 하는 순시토크제어법에 근거한 속도센서리스 제어방식을 제안하였고, 2차자속 정보를 이용하여 운전중 변동하는 2차저항을 속도추정과 동시에 동정할 수 있음을 제시하였다. 수치시뮬레이션을 통해 얻은 결과는 다음과 같다. 1) 2차자속을 교류를 중첩한 형태로 토크응답, 속도응답과는 독립적인 제어가 가능하다. 2) 수치실험상으로 무부하시 0[rpm]을 포함하는 저속영역에서도 양호한 속도추정이 이루어졌다. 3) 위의 속도추정을 바탕으로 수[rpm]대의 저속 영역에서 양호한 속도센서리스제어가 이루어졌다. 4) 2차저항값은 제안된 동정식을 통해 실제 2차 저항값에 수렴하는 특성을 보임으로써 2차저항의 동시동정과 속도센서리스제어가 가능함을 확인하였다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1994년도 하계학술대회 논문집 A
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• pp.535-538
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• 1994

In this paper, an isolated ZVS-PWM boost converter is proposed for single stage line conversion. For power factor correction, we used the half bridge topology at the primary side of isolation transformer permitting switching devices to operate under ZVS by using circuit parastics and operating at a fixed duty ratio near 50%. Thus the relatively continuous input current distortion and small size input filter are also achievable. The ZVS-PWM boost operation of the proposed converter can be achieved by using the boost inductor $L_f$, main switch $Q_3$, and simple auxiliary circuit at the secondary side of isolation transformer. The secondary side circuit differ from a conventional PWM boost converter by introduction a simple auxiliary circuit. The auxiliary circuit is actived only during a short switching transition time to create the ZVS condition for the main switch as that of the ZVT-PWM boost converter. With a single stage, it is possible to achieve a sinusoidal line current at unity power factor as well as the isolated 48V DC output. Comparing to the two stage schemes, overall effiency of the proposed converter is highly improved due to the effective ZVS of all devices as well as single stage power conversion. Thus, it can be operated at high switching frequency allowing use of small size input filter. Minimum voltage and current stress make it high power application possible.

• 한국전기전자재료학회논문지
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• 제17권3호
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• pp.289-293
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• 2004

PNW-PMN-PZT ceramics were fabricated with the variations of Nb$_2$O$_{5}$ addition and their microstructural and piezoelectric characteristics were investigated. When the amount of Nb$_2$O$_{5}$ increased, grain size decreased gradually. At 0.3wt％ Nb$_2$O$_{5}$ which is the same weight percent with Fe$_2$O$_3$, maximum tetragonality(c/a) and density were shown due to the complexed doping effects. Also, this composition that showed Qm of 2,041, kp of 0.55, grain size of 2.5${\mu}{\textrm}{m}$ and $\varepsilon$r of 1704 were proper for high power application. Using this composition, Rosen-type piezoelectric transformer was fabricated as the size of 1 ${\times}$ 16 ${\times}$ 5㎣ and its electrical characteristics were investigated with the variations of load resistance and driving frequency. At the resistance of 200㏀, maximum step-up ratio of 13.68 was shown. After driving PDA CCFL for 25 min using the inverter circuit, at driving frequency of 214.4KHz, input voltage of 31.78 V and input current of 21.1mA were measured at the input part of piezoelectric transformer. And then, output voltage of 293.2 V and output current of 2.2mA were shown at the output part of piezoelectric transformer. At the same time, efficiency of 96.2％ and temperature rise of 3.5$^{\circ}C$ were appeared at the piezoelectric transformer.ormer.