• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.319-319
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• 2013

Even though the fabrication methods of metal oxide based thin film capacitor have been well established such as RF sputtering, Sol-gel, metal organic chemical vapor deposition (MOCVD), ion beam assisted deposition (IBAD) and pulsed laser deposition (PLD), an applicable capacitor of printed circuit board (PCB) has not realized yet by these methods. Barium Strontium Titanate (BST) and other high-k ceramic oxides are important materials used in integrated passive devices, multi-chip modules (MCM), high-density interconnect, and chip-scale packaging. Thin film multi-layer technology is strongly demanded for having high capacitance (120 nF/$mm^2$). In this study, we suggest novel multi-layer thin film capacitor design and fabrication technology utilized by plasma assisted deposition and photolithography processes. Ba0.6Sr0.4TiO3 (BST) was used for the dielectric material since it has high dielectric constant and low dielectric loss. 5-layered BST and Pt thin films with multi-layer sandwich structures were formed on Pt/Ti/$SiO_2$/Si substrate by RF-magnetron sputtering and DC-sputtering. Pt electrodes and BST layers were patterned to reveal internal electrodes by photolithography. SiO2 passivation layer was deposited by plasma-enhanced chemical vapor deposition (PE-CVD). The passivation layer plays an important role to prevent short connection between the electrodes. It was patterned to create holes for the connection between internal electrodes and external electrodes by reactive-ion etching (RIE). External contact pads were formed by Pt electrodes. The microstructure and dielectric characteristics of the capacitors were investigated by scanning electron microscopy (SEM) and impedance analyzer, respectively. In conclusion, the 0402 sized thin film multi-layer capacitors have been demonstrated, which have capacitance of 10 nF. They are expected to be used for decoupling purpose and have been fabricated with high yield.

• Journal of Sensor Science and Technology
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• v.7 no.6
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• pp.386-393
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• 1998

We have carried out the measurements of complex dielectric constants with impedance/gain-phase analyzer using capacitor method and the experiments of high temperature X-ray powder diffraction with X-ray diffractometer using ${\theta}-2{\theta}$ scan method for the KTP single crystal which has the premium nonlinear optical properties. From the results of high temperature X-ray powder diffraction experiments, we have found that KTP does not undergo structural phase transition below $900^{\circ}C$. It is clear that KTP undergoes structural phase transition around $900^{\circ}C$ and belongs to orthorhombic above $900^{\circ}C$ still. However, we have applied phenomenological relation of dielectric relaxation to the results of complex dielectric measurement and have found that relaxation mechanism of KTP well satisfies the Cole-Cole relation over the temperature range from $-78^{\circ}C$ to $200^{\circ}C$. And also the relaxation time well satisfies the Vogel-Fulcher relation. It is regarded that the hopping and thermally activated diffusion mechanism may control the conduction behavior of KTP above $200^{\circ}C$.

• Journal of Korean Physical Therapy Science
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• v.7 no.1
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• pp.321-331
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• 2000

The purpose of this study was to investigate the difference of body composition and IADL of between male elder and female elder. (This study consisted of elder male(n=10) and elder female(n=10),) The mean age of elder male and female was 67.20, 67.50 years. The data were analyzed with t-test, using SPSS PC+ program. Body composition was measured using Inbody 2.0(seoul, korea) of segmental multi-frequency impedance analyzer technique. IADL was measured with Philadelphia Geriatric Center IADL. The result of this study were the following: 1. The difference of Body composition 1) The %fat of elder female was significantly(p<0.05) higher than elder male by 11.48%. 2) The fat mass(kg) of elder female was significantly(p<0.05) higher than elder male by 6.28kg. 3) The free fat mass(kg) of elder male was significantly(p<0.05) higher than elder female by 9.03kg. 4) The muscle mass(kg) of elder male was significantly(p<0.05) higher than elder female by 8.63kg. 5) The WHR(%) elder female was no significantly higher than elder male by 0.03%. 6) The TBW(l) of elder male was significantly(p<0.05) higher than elder female by 6.321. The factor of significant difference of between elder male and female was %fat, fat mass(kg), free fat mass(kg), total body water(l). 2. The difference of IADL 1) IADL of elder male was no significantly higher than elder female by 1.20. As a result of this study, optimal body composition group was elder male group. Optimal body composition of elder had improved IADL. In addition to, this result of this study, it can suggested the consideration of the Health promotion program for elder.

• Journal of Advanced Navigation Technology
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• v.13 no.1
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• pp.41-47
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• 2009

In this paper, a band pass filter with a rejection band is proposed for UWB(Ultra Wide Band) communication system. First, low pass filter accessed cut off frequency of 10.2 GHz was designed using structure stepped impedance. And high pass filter accessed cut of frequency of 3.2 GHz was designed using parallel short-stub. There was implemented composite connection of designed low pass filter and high pass filter. The relative dielectric constant, the height, the loss tangent of the PCB substrate were ${\varepsilon}_r$=2.2, h=0.508 mm and loss tangent = 0.0009 respectively. The fabricated band pass filter shows a compact size of 3 cm. The fabricated band pass filter was characterized using 37169A VNA(Vector Network Analyzer). And measured result were obtained 7.5 GHz of bandwidth and -10 dB of return loss and -3 dB of insertion loss from pass band. The result of the research can be used for the UWB communications and MIC/MMIC, RFIC system.

• Journal of the East Asian Society of Dietary Life
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• v.20 no.1
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• pp.175-186
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• 2010

This study was conducted to investigate the body weight control, attitudes, lifestyles and dietary habits according to the obesity index of elementary school students. This study utilized questionnaires and body composition measurements collected with a bio- electrical impedance analyzer(Inbody 4.0). Specifically, differences between the underweight group, normal group, and overweight group were tested by a $x^2$-test or ANOVA and Duncan's multiple range test. The subjects consisted of 571 elementary school students residing in Chonbuk Province. The average age, height, weight, and BMI of the male subjects was 11.5 years, 150.0 cm, 45.2 kg and $20.0\;kg/m^2$, respectively. The average age, height, weight, and BMI of the female subjects was 11.5 years, 152.2 cm, 46.1 kg and $19.8\;kg/m^2$, respectively. Twenty percent of the subjects were in the underweight group, 52.2% were in the normal weight group, and 27.8% were in the overweight group according to the Korean Pediatrics Society standards. A total of 50.2% of the subjects were dissatisfied with their body weight, while 36.8% of underweight, 42.3% of normal weight, and 81.1% of overweight subjects were dissatisfied with their weight. Fifty two percent of the subjects had attempted to reduce their body weight, including 50% of the normal weight group. The main reason for wanting to reduce body weight was to maintain health. The percentage of subjects who had received body weight control education was 41.3%, but 77.6% of the subjects thought it was necessary. Poor time management, lack of physical activity, portion size of meals, unbalanced diet, frequent consumption of convenience foods, and frequent snacking all affected the obesity index. Overall, the results of this study indicate that it is necessary to develop weight control programs for all elementary school students who are underweight, normal weight, and overweight.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2010.06a
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• pp.328-328
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• 2010

압전 세라믹스는 엑츄에이터 및 센서 등의 다양한 응용분야로 인하여 많은 연구가 진행되어왔다. 최근 친환경 무연 압전계인 Bi층상구조 (BNT) 및 알칼리 니오븀산화물계 (KNN)에 대한 연구가 집중되고 있다. 한편, 소형화 및 고성능의 압전소자에 대한 요구 증가로 고가의 내부전극인 Ag, Ag-Pd합금으로 이루어진 적층압전소자에 대한 연구개발이 진행되어 왔다. 본 연구에서는 Ni이나 Cu를 내부전극으로 사용하는 적층압전소자의 개발가능성을 타진하고자 Ni의 산화를 억제할 수 있는 환원분위기 소결시에 압전소재의 상변화 및 내환원성 정도를 조사하였다. 압전소재인 BNT 및 KNN를 공기중에서 합성한 후, 환원분위기의 영향을 조사하고자 샘플을 디스크 형태로 성형하여 $1000{\sim}1200^{\circ}C$에서 2 시간 동안 공기, 중성 (N2) 와 환원 분위기 (3 % H2 - 97 %의 N2) 에서 소결한 후 미세구조와 전기적 특성을 SEM, EDS, XRD, impedance analyzer로 조사였다. 환원분위기에서 소결된 BNT 샘플은 페롭스카이트 상이 관찰되지 않았으며, SEM/EDS 분석결과 시편의 표면에 Bi의 석출이 관찰되었다. KNN의 경우에는 공기중에서 소결 시편뿐만 아니라 환원분위기에서 소결된 시편에서도 페롭스카이트 구조를 보였으며, EDS분석결과 K 및 Na의 휘발이 비교적 적었다.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.23 no.3
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• pp.206-210
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• 2010

$BaTiO_3$ dielectric ceramics are widely used to multi-layer ceramic capacitor. The $BaTiO_3$ powder was synthesized at $950^{\circ}C$ by using a solid state reaction and grinded by using a high-energy mill. And then, 2.53 wt% glass frit was added to the synthesized $BaTiO_3$ powders for lowering the sintering temperature. The mixed powders were sintered at various temperatures of $1170^{\circ}C$, $1200^{\circ}C$, $1230^{\circ}C$. Microstructures of the sintered $BaTiO_3$ ceramics were inspected by SEM and crystal structures were analyzed by XRD method. The relative dielectric constant was measured by using a impedance/gain phase analyzer. The synthesized $BaTiO_3$ powder had the tetragonal perovskite structure without secondary phase and the particle size was below 200 nm. The relative densities measured at the samples sintered at the temperature above $1200^{\circ}C$ were about 95%. The relative dielectric constant showed maximum value of 2310, which was measured in the specimen sintered at $1200^{\circ}C$. From these results, we could know that the added glass frit had effects on both lowering the sintering temperature and improving the dielectric property.

• Korean Journal of Materials Research
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• v.21 no.8
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• pp.444-449
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• 2011

Nano-sized $Y_2O_3$ powders were prepared via a sol-gel method starting with $Y(NO_3)_3{\cdot}6H_2O$ (Yttrium(III) nitrate hexahydrate) and water with ethanol as a cosolvent. $Y_2O_3$ is an important rare earth oxide and has been considered for use in nuclear applications, such as ceramic materials, due to its excellent optical and refractory characteristics. It has been used as a chemically stable substrate, a crucible material for melting reactive metals, and a nozzle material for jet casting molten rare earth-iron magnetic alloys. Oxalic acid ($C_2H_2O_4$) has been adopted as a chelating agent in order to control the rate of hydrolysis and polycondensation, and ammonia was added in order to adjust the base condition. The synthesized $Y_2O_3$ powder was characterized using TG/DTA, XRD, FE-SEM, BET and Impedance Analyzer analyses. The powder changed its properties in accordance with the pH conditions of the catalyst. As the pH increases according to the FE-SEM, the grain grew and it showed that the pore size decreased while confirming the effect of the grain size. The nano-material $Y_2O_3$ powders demonstrated that the surface area was improved with the addition of oxalic acid with ammonium hydroxide.

• Proceedings of the KIEE Conference
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• 2002.07c
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• pp.1524-1526
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• 2002

본 논문에서는 $1.62{\times}1.0{\times}0.88mm^3$ 크기의 C-type과 $1.58{\times}0.82{\times}0.94mm^3$ 크기의 H-type RF 칩 인덕터를 제작하고 그들의 고주파 특성을 비교하였다. 본 연구에서는 저손실 $Al_2O_3$ 코아 물질과 직경 $40{\mu}m$의 구리(Cu) 코일을 사용하였다. 권선수를 $2{\sim}14$회로 하여 인덕턴스(L), 품질계수(Q), 임피던스의 크기와 위상, 커패시턴스(C)를 HP4291B Impedance/Material Analyzer로 측정하였다. 10회 권선시 C-type은 55nH, H-type은 67nH, 14회 권선시 C-type은 100nH, H-type은 122nH 정도로 측정되었다. 실험 결과 H-type이 C-type보다 동일 권선수에 대하여 높은 인덕턴스와 높은 자기공진주파수(SRF)를 나타냄을 확인하였다. 또한 최대 품질계수는 두 형태가 거의 비슷한 값($55{\sim}87$)을 가짐을 관찰하였다. 따라서 H-type이 C-type보다 우수한 성질을 나타냄을 알 수 있다.

• Journal of the Korean Electrochemical Society
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• v.11 no.1
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• pp.16-21
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• 2008

The key component of a direct methanol fuel cell (DMFC) is the membrane electrode assembly (MEA), which comprises a polymer electrolyte membrane and catalyst layers (anode and cathode electrode). Generally the catalyst layer is coated on the porous electrode supporter (e.g. carbon paper or cloth) using various coating methods such as brushing, decal transfer, spray coating and screen printing methods. However, these methods were disadvantageous in terms of the uniformity of catalyst layer thickness, catalyst loss, and coating time. In this work, we used bar-coating method which can prepare the catalyst layer with uniform thickness for MEA of DMFC. The surface and cross-section morphologies of the catalyst layers were observed by SEM. The performances and resistance of the MEAs were investigated through a single cell evaluation and impedance analyzer.