• Title/Summary/Keyword: Monolithic

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Silica aerogels for potential sensor material prepared by azeotropic mixture (공비혼합물로 제조된 다공성 센서재료용 실리카 에어로젤)

  • Shlyakhtina, A.V.;Oh, Young-Jei
    • Journal of Sensor Science and Technology
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    • v.16 no.6
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    • pp.395-400
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    • 2007
  • Ambient drying sol-gel processing was used for monolithic silica ambigels in the temperature range of $130-250^{\circ}C$. A new method of mesopore ambigels, which mean the aerogels prepared by ambient pressure drying process synthesis, is suggested at first. This method includes two important approaches. The first point is that $SiO_{2}$ surface modification of wet gel was performed by trimethylchlorosilane in n-butanol solution. This procedure is provided the silica gel mesopore structure formation. The second point is a creation of the ternary azeotropic mixture water/n-butanol/octane as porous liquid, which is effectively provided removing of water such a low temperature by 2 step drying condition under ambient pressure. The silica aerogels, which were prepared by ambient pressure drying from azeotropic mixture of water/n-butanol/octane, are transparent, crack-free and mesoporous (pore size ${\sim}$ 5.6 nm) with surface area of ${\sim}$ $923{\;}m^2/g$, bulk density of $0.4{\;}g/cm^3$ and porosity of 85 %.

A Magneto-Optic Waveguide Isolator Using Multimode Interference Effect

  • Yang, J.S.;Roh, J.W.;Lee, W.Y.;Ok, S.H.;Woo, D.H.;Byun, Y.T.;Jhon, Y.M.;Mizumoto T.;Lee,S.
    • Journal of Magnetics
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    • v.10 no.2
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    • pp.41-43
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    • 2005
  • We have investigated an optical waveguide isolator with a multimode interference section by wafer direct bonding, operating at a wavelength $1.55\;{\mu}m$. In order to fabricate the device for monolithic integration, the wafer direct bonding between a magnetic garnet material as a cladding layer and a semiconductor guiding layer has been achieved. We found that wafer direct bonding between InP and GGG $(Gd_3Ga_5O_{12})$ is effective for the integration of a waveguide optical isolator. The isolation ratio was obtained to be 2.9 dB in the device.

Synthesis of Nano-Sized Cu Powder by PVA Solution Method and Thermal Characteristics of Sintered Cu Powder Compacts (PVA 용액법을 통한 나노 Cu 분말합성 및 소결체의 열적 특성)

  • Oh, Bok-Hyun;Ma, Chung-Il;Lee, Sang-Jin
    • Korean Journal of Materials Research
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    • v.30 no.2
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    • pp.93-98
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    • 2020
  • Effective control of the heat generated from electronics and semiconductor devices requires a high thermal conductivity and a low thermal expansion coefficient appropriate for devices or modules. A method of reducing the thermal expansion coefficient of Cu has been suggested wherein a ceramic filler having a low thermal expansion coefficient is applied to Cu, which has high thermal conductivity. In this study, using pressureless sintering rather than costly pressure sintering, a polymer solution synthesis method was used to make nano-sized Cu powder for application to Cu matrix with an AlN filler. Due to the low sinterability, the sintered Cu prepared from commercial Cu powder included large pores inside the sintered bodies. A sintered Cu body with Zn, as a liquid phase sintering agent, was prepared by the polymer solution synthesis method for exclusion of pores, which affect thermal conductivity and thermal expansion. The pressureless sintered Cu bodies including Zn showed higher thermal conductivity (180 W/m·K) and lower thermal expansion coefficient (15.8×10-6/℃) than did the monolithic synthesized Cu sintered body.

Study on the Correlation between Analysis and Experiment for the Nonlinear Behavior of large Panel Precast Concrete Subassemblage (P.C 대형판 부분구조의 비선형 거동에 관한 실험과 해석 비교연구)

  • 김성호;이한선;이병해
    • Proceedings of the Computational Structural Engineering Institute Conference
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    • 1990.10a
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    • pp.47-54
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    • 1990
  • Under external loads, large panel structures behave quite differently from monolithic wall structures, because of the distinct planes of weakness in the horizontal and vertical joints between panels. Study on the ultimate load and the failure mode of the large panel structures under extream lateral loads is therefore important. The purpose of this study is to predict the nonlinear behavior of the structure using the general purpose nonlinear computer program 'ANSR' being based on the quasi-static test results of the large panel structure(full scale in two story) and to examine the distribution and change mode of the internal forces which can not be obtained in the test.

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TEM Microstructure of Al2O3/Ni Nanocomposites by Electroless Deposition (무전해코팅법으로 제조한 Al2O3/Ni 나노 Composite의 TEM 미세조직)

  • 한재길;이재영;김택수;이병택
    • Journal of Powder Materials
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    • v.10 no.3
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    • pp.195-200
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    • 2003
  • Ni coated $Al_2O_3$ composite was successfully Prepared by the electroless deposition Process. The average size of Ni particles coated on the $Al_2O_3$ matrix powder was about 20 nm. It was hard to find any reaction compound as an impurity at interface between $Al_2O_3$ and Ni particles after sintering. The characterization of microstructure crystal structure and fracture behavior of the sintered body were investigated using XRD, TEM and Victors hardness tester, and compared with those of the sintered $Al_2O_3$ monolithic body. Many dislocations were observed in the Ni phase due to the difference of thermal expansion coefficient between $Al_2O_3$ and Ni phase, and no observed microcracks at their $Al_2O_3$ and Ni interface. In the $Al_2O_3$/Ni composite, the main fracture mode showed a mixed fracture with intergranular and transgranuluar type having some ,surface roughness. The fracture toughness was slightly increased due to the plastic deformation mechanism of Ni phase in the $Al_2O_3$/Ni composite.

ANTIMICROBIAL EFFECT OF MINOCYCLINE EMBEDDED IN POLYCAPROLACTONE ON NECROTIC CANAL (괴사치수 근관에서 항생제 국소약물송달제제의 항균효과에 관한 연구)

  • Kwon, Soo-Kyoung;Yoom, Soo-Han
    • Restorative Dentistry and Endodontics
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    • v.16 no.1
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    • pp.226-235
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    • 1991
  • Therapeutic use of antibiotics in the pulpal disease should reduce the clinical symptoms and pathogenic microflora in the pulp. The purpose of this study was focused on local drug delivery into the root canal in endodontic therapy. Monolithic films from polycaprolactone and polyethylene glycol preparations with minocycline were prepared, and then the antimicrobial effect of these films on necrotic canal was tested. A total 17 necrotized pulp teeth were sampled before and 1 week after insertion of film into the pulp. Bacterial culture were performed with anaerobical condition and seeded in the 5 selective and non - selective media for 7 days in $37^{\circ}C$ of anaerobic chamber. Bacterial identification were performed with Gram staining, biochemical test, and API kit There was significantly decreased of anaerobic and aerobic microflora of 13 among 17 patients after therapy. Among the identified microflora, Streptococcus species, black - pigmented species and Fusobacterium species were significantly reduced 1 week after treatment with local delivery antibiotics. Furthermore, clinical symptoms included in pain and local swelling were continuousely reduced after therapy. These results suggest that local drug delivery with minocycline is effeicient to treat the endodontic involved teeth for releasing clinical symptoms and microbiological shifting.

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Fabrication and Mechanical Properties of Nanoquasicrystalline Phase Reinforced Ti-based Bulk Metallic Glass Matrix Composites (나노 준결정상으로 강화된 Ti계 벌크 비정질기지 복합재의 제조 및 기계적 특성 고찰)

  • Park, Jin-Man;Lim, Ka-Ram;Kim, Tae-Eung;Sohn, Sung-Woo;Kim, Do-Hyang
    • Journal of Korea Foundry Society
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    • v.28 no.6
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    • pp.261-267
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    • 2008
  • In-situ quasicrystalline icosahedral (I) phase reinforced Ti-based bulk metallic glass (BMG) matrix composites have been successfully fabricated by using two distinct thermal histories for BMG forming alloy. The BMG composite containing micron-scale Iphase has been introduced by controlling cooling rate during solidification, whereas nano-scale I-phase reinforced BMG composite has been produced by partial crystallization of BMG. For mechanical properties, micron-scale I-phase distributed BMG composite exhibited lower strength and plasticity compared to the monolithic BMG. On the other hand, nano-scale icosahedral phase embedded BMG composite showed enhanced strength and plasticity. These improved mechanical properties were attributed to the multiplication of shear bands and blocking of the shear band propagation in terms of isolation and homogeneous distribution of nanosize icosahdral phases in the glassy matrix, followed by stabilizing the mechanical and deformation instabilities.

The package loading equipment development cutting both ends in the process of packaging lumber for improving the working environments (노동강도 제거 및 양끝정렬 균일화를 위한 양끝절단포장적재시스템 개발)

  • Kang, Ji-Ho
    • Proceedings of the Safety Management and Science Conference
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    • 2008.04a
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    • pp.135-147
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    • 2008
  • The package loading process of the lumbering industry is an operation that after a pair of workers bind three or six lumbers into one unit and cut both ends of the lumbers, transports the weight cargo of 30-50kg by one meter, pack and load at a height of 1.2 meters. This package loading process causes lots of noise and wood dust when workers carry out the heavy work as the above. Therefore we developed the monolithic both ends cutting package loading equipment in order to prevent from getting musculoskeletal disease. An loading bar working system of this equipment is improved from pneumatic pressure system to oil pressure system, furnished the newly designed flow dividers, and developed the new system that a both end array is loaded identically. Also we developed the safety equipment of loading bar in order to prevent workers mistake and overload from malfunction during the package loading process. The main cause of job evasion on working place could be solved by preventing the musculoskeletal disease and improving the working environments.

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A Study on the Characteristics Comparison of Single Chip and Two Chip Transceiver for the Fiber Optic Modules (광모듈용 단일 칩 및 2 칩 트랜시버의 특성비교 연구)

  • Chai Sang-Hoon;Jung Hyun-Chae
    • Journal of the Institute of Electronics Engineers of Korea SD
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    • v.43 no.5 s.347
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    • pp.48-53
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    • 2006
  • This paper describes the electrical characteristics of monolithic optical transceiver circuitry being used in the fiber optic modules. It has been designed and fabricated, and compared with two chips version transceiver when operates at 155.52 Mbps data rates. To avoid noise and interference between transmitter and receiver on one chip, layout techniques such as special placement, power supply separation, guard ring, and protection wall were used in the design. To compare the two kind of fiber optic modules using each chip, single chip version has similar properties to two chip version in the electrical characteristics as noise and others.

Self Oscillating Double Conversion Mixer for low cost mm-wave system (밀리미터파 대역에서 저가격화 시스템을 위한 Self Oscillating Double Conversion Mixer)

  • Lee, Sang-Jin;Ahn, Dan;Lee, Mun-Kyo;Kwon, Hyuk-Ja;Baek, Tae-Jong;Jun, Byoung-Chul;Park, Hyun-Chang;Rhee, Jin-Koo
    • Proceedings of the IEEK Conference
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    • 2006.06a
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    • pp.491-492
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    • 2006
  • The MMIC (Microwave Monolithic Integrated Circuit) self oscillating double conversion mixer was designed and fabricated for the V-band transmitter applications. The MMIC self oscillating double conversion mixer which dose not need external local oscillator was designed using GaAs PHEMT technology. The first self oscillating mixer use PHEMT technology. The first self oscillating mixer use PHEMT for $f_{LO}$ signal generation and $f_{IF}$ signal is applied at gate port and $f_{RF1}$ signal is generated at a drain port of first stage. The second gate mixer use PHEMT for $f_{LO}$ signal and $f_{RF1}$ signal is applied at gate port and $f_{RF2}$ signal is output at a drain port of second stage.

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