• 한국세라믹학회지
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• 제44권3호
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• pp.162-168
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• 2007

Silica wet gels were prepared ken water glass ($29\;wt%\;SiO_{2}$) by using Amberlite as a ion exchange resin. After washing in distilled water, the wet gels were further aged in a solution of TEOS/EtOH to strengthen of 3-dimensional network structure. As increase TEOS content in aging solution, BET surface area and porosity of the ambient dried silica aerogels were significantly decreased, and average pore diameter was also decreased 30 nm to -10 nm. Also, higher density and compressive strength were obtained in case of higher TEOS content. This is due to precipitation of $SiO_{2}$ nano particles by TEOS. Hence, TEOS addition plays an important role of both strengthening and stiffness of silica wet gel network. By adding over 30 vol% TEOS, a crack-free monolithic silica aerogel tiles were obtained and its density, compressive strength, and thermal conductivity were shown $0.232g/cm^{3}$, 7.3 MPa, and 0.029 W/mk, respectivly.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2004년도 학술대회 논문집 정보 및 제어부문
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• pp.723-725
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• 2004

An iterative robust control design for PZT using Gaussian wavelet networks is proposed. A Gaussian wavelet network with accurate approximation capability is employed to approximate the nonlinear hysteresis dynamics of PZT systems by using an iterative control algorithm. Depending on the finite number of wavelet basis functions which results in unavoidable approximation errors, a robust control law is provided to guarantee the stability of the closed-loop nano positioning system. Finally, the effectiveness of the robust control approach is illustrated through comparative simulations on a PZT.

• 한국생물공학회:학술대회논문집
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• 한국생물공학회 2000년도 춘계학술발표대회
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• pp.442-445
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• 2000

Amphiphilic polyurethane(APU) particle is a polymeric surfactant, and could increase the solubility of 2-methylnaphthalene significantly. 2-Methylnaphthalene was recovered by the precipitation of APU particles and was degraded by Acinetobacter sp. K2-2. APU particle was recovered and reused after treatment of triethylamine.

• 정보와 통신
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• 제30권6호
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• pp.40-46
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• 2013

본고에서는 무선인체센서내트워크의 개념을 정립하고, WBAN (Wireless Body Network)의 표준화 동향, 문제점 그리고 향후 지속 가능한 연구 방향에 대하여 고찰하였다. 클라우드 컴퓨팅 환경은 인체센서 노드에서 고성능 슈퍼 컴퓨터에 이르는 다양한 범위의 서로 다른 장치를 연결하여 컨텐트 중심의 서비스를 제공하게 될 것이며 이에 대한 이슈와 연구방향을 진단하였다. 나노기술로 인하여 나노미터 수준의 장치를 개발할 수 있을 것으로 예상되며, 이러한 나노장치 간 정보교환은 의료, 환경 및 군사 분야에서 떠오르는 나노 응용기술로 발전하게 되었다. 나노장치 사이의 정보전송을 전기자기학적(EM) 나노통신 및 분자레벨 나노통신으로 구분할 수 있으며 이들의 연구 방향을 통신 이론적 관점에서 고찰하고 분석하였다.

• 한국지반환경공학회 논문집
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• 제17권2호
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• pp.5-11
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• 2016

다층벽탄소나노튜브(MWCNT)와 titanium(IV) butoxide(TNB) 그리고 silver nitrate($AgNO_3$)를 이용하여 졸-겔법으로 $MWCNT-TiO_2$ 복합체와 $Ag-MWCNT-TiO_2$ 복합체를 제조하였다. 복합체에서의 Ag의 분산 및 구조를 주사전자현미경(SEM)과 투과전자현미경(FE-TEM)으로 관찰하였다. X선 회절 분석기(XRD)를 이용하여 복합체의 패턴을 보았을 때 anatase 결정구조를 확인할 수 있었다. 에너지 분광 분석기(EDX)로 원소성분을 분석한 결과 주요 원소인 C, Ti, O 그리고 Ag가 확인되었다. $TiO_2$ 입자는 MWCNT에 균일하게 분산되었고, Ag 입자는 튜브 표면에 고정되었다. 또한 UV 조사 시간에 따른 메틸렌블루의 분해를 통하여 광촉매 활성평가를 하였다. $Ag-MWCNT-TiO_2$ 복합체는 $MWCNT-TiO_2$ 복합체보다 높은 광분해능을 보였다. Ag의 높은 전도성이 $MWCNT-TiO_2$ 복합체의 광활성을 향상 시킨다는 결과를 나타냈다.

• 한국세라믹학회지
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• 제50권6호
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• pp.510-517
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• 2013

In this study, the properties of blue inorganic nano-pigments with a spinel structure were systematically investigated. We report the preparation of a blue ceramic nano-pigment and the Co and Ni substitutional effects on the blue color. $MgAl_2O_4$ was selected as the crystalline host network for the synthesis of cobalt and nickel-based blue ceramic nano-pigments. Various compositions of $Co_xMg_{1-x}Al_2O_4$ and $Ni_xMg_{1-x}Al_2O_4$ ($0{\leq}x{\leq}1$) powders were prepared using apolymerized complex method. The obtained powder was preheated at $400^{\circ}C$ for 5 h and then calcined at $1000^{\circ}C$ for 5 h. XRD patterns of the (Co,Mg)$Al_2O_4$ and (Ni,Mg)$Al_2O_4$ samples showed a single phase of the spinel structure in all compositions. TEM results indicated nano-sized pigments for (Co,Mg)$Al_2O_4$ and (Ni,Mg)$Al_2O_4$ with a particle size ranging from 20 to 50 nm. The characteristics of the color tones of (Co,Mg)$Al_2O_4$ and (Ni,Mg)$Al_2O_4$ were analyzed by CIE $L^*a^*b^*$ measurements. In addition, the thermal stability and the binding characteristics of (Co,Mg)$Al_2O_4$, (Ni,Mg)$Al_2O_4$ are discussed in terms of the TG-DSC and FT-IR results, respectively.

• 디지털콘텐츠학회 논문지
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• 제13권1호
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• pp.129-139
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• 2012

최근 소형화, 저가격, 저전력 기술의 발달에 힘입어 무선 통신이 가능한 스마트 센서 기술이 발전하고 있다. 특히 스마트 센서의 소형화 기술인 MEMS (micro-electro-mechanical system) 및 NEMS(nano-electro mechanical system) 기반의 센서 기술을 바탕으로 무선 센서 네트워크에 대한 연구가 활발하게 진행되고 있다. 그러나 무선 센서 네트워크는 각종 물리적 자원에 대한 제약이 심하기 때문에 네트워크 보안을 유지하기 어렵다. 본 논문에서는 무선 센서 네트워크 환경에서 제한된 자원으로 안전한 키 확립하는 방법과 센싱된 정보의 암호화를 위해 사용할 수 있는 키 관리 메커니즘 및 키 관리 프로토콜, 보안 기술을 위한 제안한다.

• 한국생산제조학회지
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• 제19권1호
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• pp.94-100
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• 2010

Nowadays, several nontraditional machining(NTM) processes are widely used to machine a complex and accurate shape part of hard materials, such as titanium, ceramics, high strength temperature resistant and refractory materials which are difficult to machine and having high strength, hardness, toughness. Machining of these complex shapes in such materials by traditional machining processes are very difficult. The NTM processes is important in the areas of micro- and nano scale machining, where high accuracy and superior surface characteristics are required, which can only be achieved using these NTM processes. So, for effective selection of different NTM processes, careful decision making for a given NTM application is often necessary. An appropriate NTM process for a given material and shape condition is very difficult for the novice engineers. In this paper, an expert system based on an analytic network process(ANP) is suggested for a best selection of NTM process in a NTM application considering an prior interdependency effect among various factors.

• 한국분말재료학회지
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• 제9권5호
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• pp.346-351
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• 2002

Pure and fine, two-component titanate powders (barium titanate, calcium titanate etc.) were synthesized by an ethylene glycol method. Titanium isopropoxide and other metal ionic salts were dissolved in liquid-type ethylene glycol without any precipitation. In non-aqueous system, the amount of ethylene glycol affected the solubility and homogeneity of metal cation sources in the solution. At the optimum amount of the polymer, the metal ions were dispersed effectively in solution and a homogeneous polymeric network was formed. Most of the synthesized powders had sub-micron or nano-size primary particles after calcination and the agglomerated calcined powders were easily ground by ball milling process. All synthesized titanate powders had stable crystallization behavior at low temperature and high specific surface area after ball milling. The crystallization behavior and the microstructures of the calcined powders were affected on the ethylene glycol content.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2004년도 전력전자학술대회 논문집(2)
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• pp.858-861
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• 2004

This paper presents a wavelet-based neural network technology for the detection and classification of the various types of power quality disturbances. Power quality phenomena are short-time problems and of many varieties. Particularly, the transients happen during very short durations to the nano- and microsecond. Thus, a method for detecting and classifying transient signals at the same time and in an automatic combines the properties of the wavelet transform and the advantages of neural networks. Especially, the additional feature extraction to improve the recognition rate is considered. The configuration of the hardware of WN (PQ-DAS) and some case studies are described.