• 한국재료학회지
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• 제22권6호
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• pp.298-302
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• 2012

Fe/$SiO_2$ core-shell type composite nanoparticles have been synthesized using a reverse micelle process combined with metal alkoxide hydrolysis and condensation. Nano-sized $SiO_2$ composite particles with a core-shell structure were prepared by arrested precipitation of Fe clusters in reverse micelles, followed by hydrolysis and condensation of organometallic precursors in micro-emulsion matrices. Microstructural and chemical analyses of Fe/$SiO_2$ core-shell type composite nanoparticles were carried out by TEM and EDS. The size of the particles and the thickness of the coating could be controlled by manipulating the relative rates of the hydrolysis and condensation reaction of TEOS within the micro-emulsion. The water/surfactant molar ratio influenced the Fe particle distribution of the core-shell composite particles, and the distribution of Fe particles was broadened as R increased. The particle size of Fe increased linearly with increasing $FeNO_3$ solution concentration. The average size of the cluster was found to depend on the micelle size, the nature of the solvent, and the concentration of the reagent. The average size of synthesized Fe/$SiO_2$ core-shell type composite nanoparticles was in a range of 10-30 nm and Fe particles were 1.5-7 nm in size. The effects of synthesis parameters, such as the molar ratio of water to TEOS and the molar ratio of water to surfactant, are discussed.

• 대한의용생체공학회:의공학회지
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• 제31권4호
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• pp.321-327
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• 2010

Most of the ear shells of hearing aids are manufactured manually, and it is one of the reasons that the cost of the custom-made hearing aids can be increased. Thus it is required to manufacture the ready-made ear shell for the purpose of easy manufacturing and decrease in cost. In this study, we extract parameters in order to manufacture the ready-made ear shell for CIC type hearing aids and simulate to reconstruct the ear shell using the extracted parameters. To parameter extraction, we set up the eleven parameters for the ready-made ear shell based on anatomical characteristics of the ear canal, and we found values of the parameters from twenty-one impressions in their 20s and twelve impressions in their 60s using aperture detection and feature detection algorithms. Classifying the parameters by size, we also determine the parameters of ready-made ear shell into three types for people in their 20s and two types for people in their 60s. Each ready-made ear shell was simulated to reconstruct using figured parameters, and evaluated the rate of agreement with unused impressions for setting parameters. To evaluate the ready-made ear shell, we calculate the volume ratio and intersection between of the each impression and ready-made ear shell, and the intersection ratio using the intersection volume and ready-made ear shell volume. As a result, the volume ratio was about 70%, and volume match ratio was also up to 70%. It means that the ready-made ear shell we simulated is the significantly matched to impression.

• 유공압시스템학회논문집
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• 제5권2호
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• pp.8-13
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• 2008

Shell-and-tube type heat exchangers are generally classified with fixed tube-sheet and floating tube-sheet heat exchangers. In this paper, we employed the fixed tube-sheet heat exchangers. We theoretically investigated the safety evaluation of our shell-tube heat exchanger by axial, bending and equivalent stress of fin tubes, tube plates, channels and shell. Design pressure ranges were chosen pressure($0.6{\sim}2\;MPa$) on tube side and 200 %(3 MPa) of Maximum pressure on shell side for safety evaluation of heat exchangers. This research will be useful for fabrication of heat exchangers to prevent against damage hazard of heat exchangers in operation.

• 한국공간구조학회논문집
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• 제12권4호
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• pp.57-69
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• 2012

This study investigated the behaviors of the gabled hyperbolic paraboloid shell structure subjected to differential settlement and the horizontal displacement due to the elongation of tie rod/beam on supports. Two types of shell structure with different roof slopes are used in study; conventional type which has perimeter beams around the shell panel, and simple type which removes the edge beams along the slab edge line. The effect of the removal of edge beam under vertical or horizontal displacement on supports, and the roof slope was compared using the finite element analysis.

• Archives of Pharmacal Research
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• 제20권4호
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• pp.324-329
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• 1997

AB-type amphiphilic copolymers (abbreviated as LE) composed of poly (L-leucine) (PLL) as the A component and poly (ethylene oxide) (PEO) as the B component were synthesized by the ring-opening polymerization of L-leucine N-carboxy-anhydride initiated by methoxy polyoxyethylene amine $(Me-PEO-NH_2)$ and characterized. Core-shell type nanoparticles were prepared by the diafiltration method. Particle size distribution obtained by dynamic light scattering was dependent on PLL composition and the size for LE-1, LE-2 and LE-3 was $369.6{\pm}267$, $523.4{\pm}410$ and $561.2{\pm}364 nm$, respectively. Shapes of the nanoparticies observed by transmission electron microscope (TEM) were almostly spherical. The critical micelle concentration (CMC) of the nanoparticles determined by a fluorescence probe technique was dependent on the composition of hydrophobic PLL, and the CMC for LE-1, LE-2 and LE-3 was $2.0{\times}10^{-6},1.7{\times}10^{-6}$ and $1.5{\times}10^{-6}(mol/l) $, respectively. Clonazepam release from core-shell type nanoparticles in vitro was dependent on PLL composition and drug loading content.

• 전기전자학회논문지
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• 제24권4호
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• pp.921-930
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• 2020

대포병탐지레이더는 포탄의 궤적을 역으로 추적하여 화포 원점과 탄착점을 추정해 낸다. 부가적으로 추적 화포의 탄종을 식별하는 기능도 포함된다. 레이더를 통해 포탄의 궤적을 추적하는 중에는 포탄과 레이더의 위치에 따라 감지된 신호들이 다르게 나타나는 경우가 발생한다. 이는 포탄의 종류를 식별하기에는 모호한 부분이 있다. 본 논문은 레이더의 신호처리 과정 중에 산출하는 데이터를 바탕으로 퍼지이론과 인공지능을 이용하여 포탄의 종류를 구분하고 비교하였다. 연구 결과에 의하면 인공지능에 의한 정확도가 퍼지이론을 사용한 표적 식별 결과 대비 우수한 식별률이 나오는 것을 확인했다. 실험에 사용된 데이터는 포탄을 실제 발사하여 대포병탐지레이더-II로부터 얻은 것이다.

• Korean Chemical Engineering Research
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• 제59권1호
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• pp.118-126
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• 2021

폐기물로 대량 발생되는 굴껍질을 활용한 vaterite 형 탄산칼슘 제조 실험을 하였다. 굴껍질을 800 ℃의 온도에서 항량이 되도록 가열하여 산화칼슘이 주성분인 소성 굴껍질을 제조하였다. 이 굴껍질을 질산 용액에 녹여 0.1 M 질산칼슘 수용액을 만들고, 0.1 몰 라이신/1 몰 생석회가 첨가된 0.1 M 탄산나트륨 수용액과 20 ℃, 600 rpm 교반 조건에서 1시간동안 반응시켜 탄산칼슘을 제조하였다. XRD, SEM, Size 분석을 하고 vaterite 84.5%, calcite 15.5% 함유한 구형 탄산칼슘을 확인하였다. 평균 입경 범위는 6.87 ㎛ 이었고, 아미노산 분석에서 탄산칼슘 내의 라이신 함유량은 0.1%이었다.

• Journal of Mechanical Science and Technology
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• 제15권11호
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• pp.1555-1562
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• 2001

In a conventional shell-and-tube heat exchanger, fluid contacts with tubes flowing up and down in a shell, therefore there is a defect in the heat transfer with tubes due to the stagnation portions . Fins are attached to the tubes in order to increase heat transfer efficiency, but there exists a limit. Therefore, it is necessary to improve heat exchanger performance by changing the fluid flow in the shell. In this study, a highly efficient shell-and-tube heat exchanger with spiral baffle plates is simulated three-dimensionally using a commercial thermal-fluid analysis code, CFX4.2. In this type of heat exchanger, fluid contacts with tubes flowing rotationally in the shell. It could improve heat exchanger performance considerably because stagnation portions in the shell could be removed. It is proved that the shell-and-tube heat exchanger with spiral baffle plates is superior to the conventional heat exchanger in terms of heat transfer.

• 자원환경지질
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• 제52권2호
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• pp.119-128
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• 2019

국내에서는 연간 약 30만 톤 내외의 굴패각이 발생되고 있어, 이를 대규모로 활용할 수 있는 적절한 방안이 요구되고 있다. $CaCO_3$가 주성분인 굴패각을 탈황재료로 사용하는 연구들이 많이 진행되어 왔으나, 지금까지는 주로 건식탈황을 대상으로 한 것이었다. 본 연구에서는 굴패각을 소성하여 습식탈황재료로 활용하는 가능성에 대하여 고찰하였다. 이를 위하여 습식배연탈황공정의 하나인 spray type 방식의 모사탈황장치를 제작하여 소성 굴패각의 탈황특성을 석회석과 비교하였다. 연구결과, 소성 굴패각은 석회석이나 소성하지 않은 굴패각에 비하여 우수한 $SO_2$ 흡수능을 보였다. 이는 굴패각이 소성 및 수화반응을 통해 상대적으로 반응성이 높은 형태($Ca(OH)_2$)로 전환되었기 때문이다. 이로 인하여 반응잔류물 중에 석고($CaSO_4{\cdot}2H_2O$)의 함량이 다른 경우에 비하여 높게 나타났다. 본 연구의 연속탈황실험에서는 소성 굴패각이 석회석에 비하여 큰 pH 변동폭을 보였으며, 석회석과 소성 굴패각을 혼합하여 수행된 탈황실험에서도 소성 굴패각의 혼합비율이 증가됨에 따라 pH변동폭이 커지는 결과를 보였다. 이러한 현상은 소성 굴패각의 $SO_2$ 흡수 반응성이 큰 것을 잘 보여주는 것이다. 본 연구결과는 소성 굴패각을 습식탈황에 이용할 경우 탈황효율을 크게 향상시킬 수 있음도 보여준다.

• 자원리싸이클링
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• 제13권1호
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• pp.54-58
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• 2004

Wollastonite-type glass ceramics were prepared by milling and firing at various temperatures using an automobile waste glass and waste shell as starting materials. Powder mixture ground by disk-type ball mill for 3 hours was pressed into a disk. The pressed specimen was fired at $850^{\circ}C$,$950^{\circ}C$ and $1050^{\circ}C$ for 1 hour in air. From FE-SEM observation, with an increase of the firing temperature from $850^{\circ}C$ to $1050^{\circ}C$, whisker-type phase was grown to about 10 $\mu\textrm{m}$ in length. Specimen fired at $1050^{\circ}C$ showed the formation of well-crystallized whisker-type wollastonite grains and the highest compressive strength.