• 한국지역지리학회지
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• 제13권1호
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• pp.43-53
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• 2007

삼각주연안 사주섬과 주변의 간석지로 이루어진 낙동강 하류지역의 삼각주 해안은 사주섬을 중심으로 지형변화가 활발하게 진행되고 있다. 퇴적환경의 특성은 삼각주연안 사주섬의 형태변화를 유발하는 원인이 된다는 측면에서 삼각주연안 사주섬 지형변화를 이해하기 위한 중요한 요소가 된다. 이 연구에서는 낙동강 삼각주연안 사주섬 표층퇴적물의 입도특성과 공간적 분포를 살펴보았다. 현재 낙동강 하구역 삼각주 해안을 형성하고 있는 진우도와 신자도, 도요등의 입도분석 결과, 평균입도의 분포는 외해 쪽에서 내륙 쪽 방향으로 조립화하는 경향을 보이고 조류의 이동이 진행되는 조수통로 부근에서 조립질이 분포하였다. 분급의 분포는 세 사주섬에서 양호한 분급을 고르게 나타나고 있음을 파악하였다. 연구지역 표층퇴적뭍의 왜도는 대체로 조립질 쪽으로 악간 치우친 음성 왜도가 주로 나타나지만 세립질 쪽으로 악간 치우친 양성 왜도의 경우도 조수통로 부근에서 분포하는 경향이 나타났다. 사주섬의 퇴적물 특성과 지형변화를 관련하여 살펴보면 지형변화가 진행되고 있는 지역을 중심으로 조립질 퇴적물과 양호한 분급도, 음성 왜도와 부분적으로 약한 양성 왜도가 나타나고 있는데 이것은 다른 지역에 비해 상대적으로 강하고 규칙적인 에너지가 도달하고 있으며 이동과정에서 상대적으로 조립질 퇴적물이 선별적으로 이동하는 과정에서 나타나는 결과로 해석된다.

• 한국음향학회지
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• 제34권6호
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• pp.423-431
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• 2015

한국해양과학기술원과 한양대학교에서 공동으로 진행한 해양음향 실험이 2013년 5월에 경기만 태안반도 서쪽에 위치한 천해에서 실시되었다. 본 논문에서는 측정된 중주파수(6~16 kHz) 해저면 반사손실 결과를 제시하고, 수평입사각 $17{\sim}60^{\circ}$ 범위에서 레일리 반사계수 모델과 비교분석한다. 실험해역 지질은 다중 퇴적층으로 구성되어 있었으며, 표층 퇴적물이 다양한 구성성분(평균 입도 $5.9{\phi}$)으로 이루어져 있는 지역이었다. 분석 결과에 의하면 표층 퇴적물의 평균 입자를 고려한 모델결과는 측정된 반사손실과 다소 차이를 보였으며, 퇴적층의 지음향 정보를 역산한 결과 약 $4{\phi}$ 평균입도에서 측정치와 비교적 잘 일치하는 것으로 나타났다. 이러한 차이의 원인은 표층 퇴적물 입도의 표준 편차가 $4.3{\phi}$로 다른지역에 비해 상당히 컸기 때문일 것으로 추측된다. 상부 퇴적층은 역산 결과로부터 얻어진 지음향 파라미터를 사용하고 하부 퇴적층은 $1.3{\phi}$의 평균입도로부터 예측된 지음향 파라미터를 사용하였을 때, 모델결과는 측정된 반사손실 결과와 전체적으로 일치하는 경향을 나타냈다.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2008년도 추계학술대회 논문집
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• pp.38-41
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• 2008

To investigate the evolution of microstructure and texture in AZ31 Mg alloy, direct/indirect extrusion process was carried out at $300^{\circ}C$ with various extrusion speeds. The distribution of grain size depends on extrusion method and extrusion speed. More homogeneous grain site can be obtained at higher extrusion speed of indirect extrusion process. Extrusion speed does not affect significantly texture evolution during extrusion process regardless of extrusion method. ODF section is more useful to understand texture evolution during extrusion process compared with pole figure.

• 한국분말재료학회지
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• 제5권4호
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• pp.258-264
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• 1998

The initial sintering behaviour of the powder injection molded (PIMed) W-l5wt%Cu nanocomposite powder was investigated. The W-Cu nanocomposite powder was produced by the mechanochemical process consisting of high energy ball-milling and hydrogen reduction of W blue powder-CuO mixture. Solid state sintering of the powder compacts was conducted at $1050^{\circ}C$ for 2~10 hours in hydrogen at mosphere. The sintering behaviour was examined and discussed in terms of microstructural developments such as W-Cu aggregate formation, pore size distribution and W grain growth. The volume shrinkage of PIM specimen was slightly larger than that of PM(conventional PM specimen), being due to fast local densification in the PIM. Remarkable decrease of carbon and oxygen in the PIM enhanced local densification in the early stage of solid state sintering process with eliminating very fine pores less than 10 nm. In addition, such local densiflcation in the PIM is presumably responsible for mitigating of W-grain growth in the initial stage.

• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2008년도 International Meeting on Information Display
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• pp.957-960
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• 2008

The influences of silicon and MgO seed particle on the reconstruction characteristics of MgO protective layer were investigated to clarify the mechanism of reconstruction and exaggerated grain growth (EGG) in AC-PDP. The reconstruction and EGG are closely correlated with the driving force for nucleation and growth, interface energy and initial size distribution of MgO protective layer in plasma space during discharge in AC-PDP.

• 한국세라믹학회지
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• 제29권3호
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• pp.211-215
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• 1992

Crack free PbTiO3 ceramics were produced by sol-gel processing using alkoxide, which has not been reported to be successful. The PbTiO3 gels were prepared from Ti alkoxide and lead acetate without any dopants. They were calcined at $600^{\circ}C$ and miled to produce fine PbTiO3 powder. It was pressed into discs and they were sintered at 110$0^{\circ}C$ for a few hours. The sintered ceramics were relativley hard and dense as having about 96% of theoretical density of PbTiO3. Fabrication of pure PbTiO3 ceramics by sol-gel processing is possibly due to their small grain size and uniform distribution of residual stress created during cubic-tetragonal transition over large number of small grains in fine grain PbTiO3 ceramics.

• 한국세라믹학회지
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• 제26권4호
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• pp.493-498
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• 1989

High purity, submicron BaTiO3 powder was prepared by a hydrothermal technique using Ba(OH)2.8H2O, TiCl4 and NH4OH as starting raw materials. The submicron BaTiO3 powder was synthesized at 130~23$0^{\circ}C$ for 2.5h to yield highly crystalline particles with a narrow particle distribution. The mole ratio of Ba(OH)2.8H2O/TiO(OH)2 was 1.5. It is possible to obtain BaTiO3 with Ba : Ti=1.00$\pm$0/01. The samples densified well at 13$25^{\circ}C$, showing a uniform and fine grain structure. The grain size ranged between 0.3 and 0.5${\mu}{\textrm}{m}$. The products obtained by hydrothermal treatment at various temperatures from 130 to 23$0^{\circ}C$ were characterized by XRD, DTA, BET and SEM etc.

• 소성∙가공
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• 제6권2호
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• pp.102-109
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• 1997

The multistage deformation and stress relaxation were carried out to investigate the strain induced precipitation by torsion tests in the range of 1000~80$0^{\circ}C$, 0.05~5/sec for V-microalloyed steel. The starting temperature and time for the initiation of precipitation were determined by stress relaxation tests. The distribution of precipitates increased, as the strain rate increased and the mean size of precipitates was found to be about 10~30nm. The precipitation starting time$(P_s)$ decreased with increasing strain rate and the amount of pre-strain. The effect of deformation conditions on the no-recrystallization temperature$(T_nr)$ was also determined in the multistage deformation. $T_nr$ Tnr decreased with increasing the strain and strain rate. In the controlled rolling simulation, grain refinement and precipitation hardening effects could be achieved by the alternative large pass strain at the latter half pass stage under the condition of low temperature and high strain rate.

• Nuclear Engineering and Technology
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• 제53권1호
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• pp.172-177
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• 2021

The microstructure and texture of three 316L foils of 25 ㎛ thickness, which were subjected to different manufacturing process, were systematically characterized using advance analytical techniques. Then, the electrochemical property of the 316L foils in simulated pressurized water reactor (PWR) solution was analyzed using potentiodynamic polarization. The results showed that final rolling strain and annealing temperature had evident effect on grain size, fraction of recrystallization, grain boundary type and texture distribution. It was suggested that large final rolling strain could transfer Brass texture to Copper texture; low annealing temperature could limit the formation of preferable orientations in the rolling process to reduce anisotropy. Potentiodynamic polarization test showed that all samples exhibited good corrosion performance in the simulated primary PWR solution.

• Fisheries and Aquatic Sciences
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• 제4권2호
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• pp.51-57
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• 2001

Polychlorinated dibenzo-p-dioxins (PCDDs) and dibenzofurans (PCDFs) were measured in sediment samples from 19 stations in the coastal areas of Korea from February to July 2000. PCDDs and PCDFs were detected in all sediment samples. The concentrations of these con­taminants ranged from 18.2 to 804.0 pg/g dry weight and I-TEQ concentrations varied from 0.1 to 5.5 pg/g dry weight. Examination of homologue groups showed that octachlorinated dibenzo-p-dioxin (OCDD) was predominant congener in Korean coast. This pattern was similar to homologue profiles of marine sediments in which the main source of PCDDs/DFs was derived from the atmospheric deposition of particulate matters generated from various industrial activities. Grain size and total organic carbon (TOC) distribution are one of the important factors governing PCDDs/DFs concentration in this study.