• 한국재료학회:학술대회논문집
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• 한국재료학회 2011년도 추계학술발표대회
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• pp.25.2-25.2
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• 2011

Recently, thin film capacitors used for vehicle inverters are small size, high capacitance, fast response, and large capacitance. But its applications were made up of liquid as electrolyte, so its capacitors are limited to low operating temperature range and the polarity. This research proposes using Ni-P alloys by electroless plating as the electrode instead of liquid electrode. Our substrate has a high aspect ratio and complicated shape because of anodic aluminum oxide (AAO). We used AAO because film thickness and effective surface area are depended on for high capacitance. As the metal electrode instead of electrolyte is injected into AAO, the film capacitor has advantages high voltage, wide operating temperature, and excellent frequency property. However, thin film capacitor made by electroless-plated Ni on AAO for full-filling into etched tunnel was limited from optimizing the deposition process so as to prevent open-through pore structures at the electroless plating owing to complicated morphological structure. In this paper, the electroless plating parameters are controlled by temperature in electroless Ni plating for reducing reaction rate. The Electrical properties with I-V and capacitance density were measured. By using nickel electrode, the capacitance density for the etched and Ni electroless plated films was 100 nFcm-2 while that for a film without any etch tunnel was 12.5 nFcm-2. Breakdown voltage and leakage current are improved, as the properties of metal deposition by electroless plating. The synthesized final nanostructures were characterized by scanning electron microscopy (SEM).

• 한국재료학회지
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• 제23권8호
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• pp.405-422
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• 2013

Atomic layer deposition(ALD) is a promising deposition method and has been studied and used in many different areas, such as displays, semiconductors, batteries, and solar cells. This method, which is based on a self-limiting growth mechanism, facilitates precise control of film thickness at an atomic level and enables deposition on large and three dimensionally complex surfaces. For instance, ALD technology is very useful for 3D and high aspect ratio structures such as dynamic random access memory(DRAM) and other non-volatile memories(NVMs). In addition, a variety of materials can be deposited using ALD, oxides, nitrides, sulfides, metals, and so on. In conventional ALD, the source and reactant are pulsed into the reaction chamber alternately, one at a time, separated by purging or evacuation periods. Thermal ALD and metal organic ALD are also used, but these have their own advantages and disadvantages. Furthermore, plasma-enhanced ALD has come into the spotlight because it has more freedom in processing conditions; it uses highly reactive radicals and ions and for a wider range of material properties than the conventional thermal ALD, which uses $H_2O$ and $O_3$ as an oxygen reactant. However, the throughput is still a challenge for a current time divided ALD system. Therefore, a new concept of ALD, fast ALD or spatial ALD, which separate half-reactions spatially, has been extensively under development. In this paper, we reviewed these various kinds of ALD equipment, possible materials using ALD, and recent ALD research applications mainly focused on materials required in microelectronics.

• 한국광물학회지
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• 제29권2호
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• pp.35-45
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• 2016

점토광물은 자연에서 쉽게 얻을 수 있고, 환경친화적이며 다양한 물리화학적 특성을 갖고 있어 인류 역사상 여러 분야에 활용되어 왔다. 최근에는 몬모릴로나이트, 카올리나이트, 세피올라이트, 금속이중층수산화물과 같은 점토 화합물에 화학적 개질을 도입하여 산업분야에 활용하고자 하는 연구가 활발히 진행되고 있다. 넓은 비표면적과 높은 측면비율, 나노수준의 입자 두께, 그리고 조절가능한 표면전하를 갖는 점토화합물에 화학적 개질을 적용하면, 고분자의 기계적 성질과 기체차단성을 개선하고, 고분자 필름에 지속적 항균성을 부여하는 충전제로 사용할 수 있다. 또한, 개질된 점토화합물은 높은 흡착능과 화학적 선택성을 지니므로, 수질이나 토양을 오염시키는 화학적, 생물학적 오염원을 효과적으로 제거하는 물질로도 활용 가능하다. 본 논평에서는 이러한 점토화합물들이 미래의 주요산업군인 식품포장재 및 환경개선 분야에 활용될 가능성에 대해 최근 연구 결과를 소개하고자 한다.

• The Korean Journal of Ceramics
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• 제5권4호
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• pp.379-385
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• 1999

Minute boehmite crystals with high aspect rations, which were hydrothermally synthesized from gibbsite in $Ba(OH)_2$ solution, occluded Ba with the Ba/Al molar ratio of about 0.03 in their interlayers. Their surface areas were about 14$\m^2$/g. The Ba-intercalated bohemite samples were partly used for producing $BaAl_{12}O){19}$ with low sinterability by externally supplementing $Ba(OH)_2$, and for forming transient aluminas. The surface area of $BaAl_{12}O){19}$ obtained by firing at $1500^{\circ}C$ for 3 h was 5.3$\m^2$/g, which was significantly lower than 12$\m^2$/g of the sol-gel origin. While a mixture ${\gamma}$-alumina and BaO is known to from $BaAl_{12}O){19}$ at $1200^{\circ}C$, solid state reaction between η-alumina transformed from the Ba-intercalated boehmite and BaO formed from $Ba(OH)_2$ deposited on the boehmite started above $1300^{\circ}C$. This suggests that large sized $Ba^{2+}$ ion occluded in η-alumina considerably suppresses the diffusion of $Al^{3+}$ ion. The surface area of the Ba-intercalated boehmite fired at $1400^{\circ}C$ for 3h was as high as 14$\m^2$/g indicative of its potential applicability to combustion catalysts. But it was decreased to 5.0$\m^2$/g after firing at $1500^{\circ}C$ for 3 h, accompanied by abrupt formations of $\alpha$-alumina and $BaAl_{12}O){19}$ as main products. The suppression of $\alpha$-alumina formation up to $1400^{\circ}C$ also suggests the significant blocking effect of $Ba^{2+}$ ion on the diffusion of the component ions.

• 토지주택연구
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• 제2권3호
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• pp.259-268
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• 2011

Space extension and the increase of the number of households are helpful to raise business value of the remodeling through the renovation of apartment houses that is required by residents of new cities and large-scaled apartment. However, in the case of accepting this demand, it could have a bad influence on the landscape of a complex in terms of the structure of apartment houses and the safety of construction and urban planning, and a problem occurs in the aspect of fairness for reconstruction. For the study, the current status related to the remodeling system through laws, related articles since 2000 and research data was analyzed. In addition, the individual quantitative analysis was conducted in the four aspects to judge whether households expansion for remodeling is plausible:1) Statistical data to comprehend the changes of population and social structure 2) Survey data of floor space index and the building-to-land ratio of new cities at the intial stage for the review of the effect of architectural planning and urban environment 3) Surveys of experts on structural safety in order to judge whether the demand of expansion is accepted or not. 4) Quantitative analysis of each item to compare fairness with reconstruction. Therefore, this study is intended to understand problems of the remodeling system that is currently operated. Moreover, it will be further reviewed that the expansion of households is feasible through the permission of expansion and it will be discussed that the revitalization of the apartment remodeling has a positive impact on the residential environment.

• 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.

• 한국레이저가공학회지
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• 제14권2호
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• pp.8-12
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• 2011

As the aged population grows around the world, many medical instruments and devices have been developed recently. Among the devices, a drug delivery stent is a medical device which requires precision machining. Conventional drug delivery stent has problems of residual polymer and decoating because the drug is coated on the surface of stent with the polymer. If the drug is impregnated in micro hole array on the surface of the stent, the problem can be solved. Micro sized holes are generally fabricated by laser machining; however, the fabricated holes do not have an enough aspect ratio to contain the drug or a good surface finish to deliver it to blood vessel tissue. To overcome these problems, we propose a vibration-assisted machining mechanism with PZT (Piezoelectric Transducers) for the fabrication of micro sized holes. If the mechanism vibrates the eyepiece of the laser machining head, the laser spot on the workpiece will vibrate vertically because objective lens in the eyepiece shakes by the mechanism's vibration. According to the former researches, the vibrating frequency over 20kHz and amplitude over 500nm are preferable. The vibration mechanism has cylindrical guide, hollowed PZT and supports. In the cylinder, the eyepiece is mounted. The cylindrical guide has upper and low plates and side wall. The shape of plates and side wall are designed to have high resonating frequency and large amplitude of motion. The PZT also is selected to have high actuating force and high speed of motion. The support has symmetrical and rigid characteristics.

• 한국재료학회:학술대회논문집
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• 한국재료학회 2012년도 춘계학술발표대회
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• pp.88.1-88.1
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• 2012

Silicon nanowires (SiNWs), due to their unusual quantum-confinement effects that lead to superior electrical and optical properties compared to those of the bulk silicon, have been widely researched as a potential building block in a variety of novel electronic devices. The conventional means for the synthesis of SiNWs has been the vapor-liquid-solid method using chemical vapor deposition; however, this method is time consuming, environmentally unfriendly, and do not support vertical growth. As an alternate, the electroless etching method has been proposed, which uses metal catalysts contained in aqueous hydrofluoric acids (HF) for vertically etching the bulk silicon substrate. This new method can support large-area growth in a short time, and vertically aligned SiNWs with high aspect ratio can be readily synthesized with excellent reproducibility. Nonetheless, there still are rooms for improvement such as the poor surface characteristics that lead to degradation in electrical performance, and non-uniformity of the diameter and shapes of the synthesized SiNWs. Here, we report a facile method of SiNWs synthesis having uniform sizes, diameters, and shapes, which may be other than just cylindrical shapes using a modified nanosphere lithography technique. The diameters of the polystyrene nanospheres can be adjustable through varying the time of O2 plasma treatment, which serve as a mask template for metal deposition on a silicon substrate. After the removal of the nanospheres, SiNWs having the exact same shape as the mask are synthesized using wet etching technique in a solution of HF, hydrogen peroxide, and deionized water. Different electrical and optical characteristics were obtained according to the shapes and sizes of the SiNWs, which implies that they can serve specific purposes according to their types.

• 플랜트 저널
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• 제8권3호
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• pp.49-54
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• 2012

현재 운영 중인 발전소 전동기의 고정자 권선 고장 실제사례를 토대로 전동기에서 발생하는 자속 데이터의 고주파 영역 스펙트럼을 분석함으로써 결함이 있는 전동기와 건전한 전동기의 자속 특성 및 변화추이를 분석하였다. 전동기 자속스펙트럼의 고주파 영역을 분석한 결과 결함이 있는 전동기는 고정자 슬롯 주파수 대비 고정자 슬롯 사이드밴드 주파수의 상대적 크기 비율이 건전한 전동기에 비해 매우 높음을 확인하였다. 또한 결함이 있는 전동기는 시간이 지날수록 고정자 슬롯 주파수 대비 고정자 슬롯 사이드밴드 주파수의 상대적 크기 비율 크기도 더욱 커지는 현상도 확인하였다. 그리고 결함이 있는 전동기의 자속 데이터는 불시 고장 1개월여 전부터 결함 상태를 인식할 수 있는 신호를 나타냄으로써 전동기 고정자 권선 결함에 대한 사전 예측능력이 매우 탁월함을 확인하였다.

• 한국컴퓨터정보학회논문지
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• 제12권1호
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• pp.219-229
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• 2007

본 연구는 코스닥시장에서 합병기업을 대상으로 연구의 결과 첫째, 합병공시효과검증에서는 공시시점에서 정(+)의 누적초과수익률로서 기업가치증가로 해석할 수 있으나, 장기간에서는 상반된 결과가 도출되었다. 둘째, 합병으로 인해 일반기업의 가치증가가 벤처기업보다 높다고 볼 수 있다. 셋째, 과거성과가 높은 glamour 기업보다 과거 성과가 좋지 않은 value기업이 합병 후 성과가 높아진다는 성과추정가설이 성립한다. 넷째, 소규모기업의 누적초과수익률이 대규모기업의 누적초과수익률을 초과함으로서 합병으로 인한 규모효과(size effect)가 존재하는 것으로 해석할 수 있다. 다섯째, 운영성과 검증에서는 합병시점에서는 대부분의 변수가 정(+)의 값이나 합병 후 음(-)의 값을 보였다. 이런 결과는 코스닥 시장에서의 합병이 경제적 논리보다는 재무적 논리에 바탕을 두고 있다고 평가함으로서 기업가치가 하락하는 것으로 추정된다.