• Nuclear Engineering and Technology
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• v.2 no.3
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• pp.163-178
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• 1970

Deformation modes at room temperature and the interaction between slip lines and ${\gamma}$' precipitate particles in heat treated Rene 41 were studied by means of replica techniques in an electron microscope. The alloy had been deformed by compression after aging for times up to 9300 hr at 76$0^{\circ}C$ and 87$0^{\circ}C$. The slip structure observed was similar to that of o brass, i.e., consisting of single slip lines occurred on the｛111｝<110> system. The slip structure was also correlated with aging conditions. Slip lines appeared to pass through ${\gamma}$' particles, shearing them with the matrix even after a prolonged heat treatment. It was concluded on the basis of comparison with previously published data that ${\gamma}$' particles remain at least partially coherent with the matrix even in a greatly overaged condition.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.13 no.10
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• pp.777-784
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• 2003

Acoustic response control of a corner-pinned plate using piezoelectric wafers was studied, both theoretically and experimentally Three different sizes of aluminum alloy plates were used and available ball joints were employed to hold the plate at the four corners. The plate with the largest aspect ratio showed the largest and most clear responses to the acoustic excitation in the range of frequencies (0∼200 Hz), and sound pressure levels (80∼100 dB) as predicted. The reduction of the acoustic response of the plate by piezoelectric actuator was very significant, more than expected, but abatement of the sound transmission through the plate was only slightly altered by the piezoelectric actuator. This work is an original work extending earlier work with doors excited by acoustic fields. The important difference is the used of ball joints to simulate the joints.

• The Journal of Engineering Geology
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• v.14 no.4 s.41
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• pp.381-390
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• 2004

This study was performed to relate the weathering properties of Oyaish tuff from Japan to mechanical properties of rocks in terms of mineralogical alteration and chemistry. The tuff is composed of clinoptilolite, quartz, feldspars, mordenite, opal C-T, and smectite. Since fresh tuff contains approximately $30\~50\%$ zeolite, it is expected that the rock is subjected to weathering process ascribed to water contents on earth surface, significantly reducing mechanical strength of tuff. It is also anticipated that weathering process and properties may be different even in the same rock mass, due to the differences in local mineralogy, chemistry and microtextures in tuff.

• 연구논문집
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• s.29
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• pp.131-139
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• 1999

The effect of ball milling conditions in the milling of aluminium foil scraps was studied. Initial foil thickness, ball size. content of oleic acid. weight ratio of mineral spirits/foil. charged amount of foil were varied in wet ball milling process. It is impossible to make flake powders by milling of foil scraps with thickness $120 \mum$. As foil thickness decreases from $60\mum$ to $6.5\mum$, Mean size of powder milled for 30 h decreases from 107 µm to 17 µm. Bigger ball is slightly beneficial for milling of foils to the flake powders due to the larger impact energy produced by them. It is impossible to mill the foil without oleic acid to fabricate the flake powder. As content of oleic acid increases from 1.5 % to 5 %, mean size of flake powder milled for 30 h is drastically decreased. For the mineral spirits content below 50 %, foil scrap was not milled because sliding motion of balls by lubricant effect between balls and wall of container. As weight ratio of mineral spirits and foil increase over 100 %, foils were milled powders with mean powder size 15 - 20 때 irrespective of mineral spirits content due to reduced lubricant effect. As charged amount of foil decreases, mean powder size decreases due to increased collision frequency between ball and foil.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.264.2-264.2
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• 2014

비휘발성 메모리는 전원이 공급되지 않아도 저장된 정보를 계속 유지하는 메모리로써 현재 다양한 차세대 전자소자의 집적화 구현을 위해 저전압 동작 및 저장능력의 향상 등에 대한 연구가 활발히 진행되고 있다. 이때 삽입되는 전하저장층의 경우 기존 널리 이용되는 질화막(SiNx) 외에 최근에는 산화 알루미늄(Al2O3) 등의 고유전상수 물질 뿐만 아니라, 밴드갭 조절을 통해 전하저장능력을 향상시키는 산화막(SiOx)에 대한 연구도 진행 중이다. 이번 연구에서는 전하저장능력을 향상시키기 위해 전하저장층으로 산화막을 이용할 뿐만 아니라, 기존의 평편한 구조가 아닌 표면 조절을 통해 전하저장능력을 보다 향상시키고자 한다. 또한 이번 연구에서는 비휘발성 메모리 소자의 응용을 위해 우선적으로 금속-절연체-반도체 형태의 MOOxOyS 구조를 이용하였다. 이 때 실리콘 표면적을 변화시키기 위해 이용된 실리콘 웨이퍼는 1) 평편한 실리콘, 2) 수산화암모늄, 이소프로필 알코올 및 탈이온수를 혼합한 용액에 식각시킨 삼각형 구조, 3) 불산, 질산 및 아세트산을 혼합한 용액에 식각시킨 라운드 구조이다. 정전용량-전압 측정을 통해 얻어진 메모리 윈도우는 1) 평편한 실리콘의 경우 약 5.1 V, 2) 삼각형 구조의 경우 약 5.3 V, 3) 라운드 구조의 경우 약 5.9 V를 얻었다. 이 때, 라운드 구조의 경우 가장 넓은 표면적으로 인해 상대적으로 전하트랩이 가장 많이 되어 메모리 윈도우가 가장 커지는 특성을 볼 수 있었다.

• Proceedings of the Korean Radioactive Waste Society Conference
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• 2005.06a
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• pp.194-195
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• 2005

방사선관리구역 내에서 발생되는 많은 양(발전소별 연간 약$100{\sim}700$개 정도)의 사용 후 공기정화 필터는 고체 폐기물 드럼의 단면적 보다 넓어 별도로 필터를 압축하거나 분해 작업 없이는 폐기물로 직접 처리가 곤란하다. 처리 시 많은 양의 분진이 발생하여 작업자의 내부피폭 가능성 및 많은 양의 고체 폐기물이 발생할 수 있는 잠재성이 있어 시료분석 결과 오염된 필터 내지는 바로 드럼 처리하여 내부 피폭 가능성을 미연에 방지하고 필터 프레임은 재사용을 유도하여 폐기물 저감화, 작업환경 개선 및 경제적인 이익을 창출할 수 있다. 영광 3발전소와 울진 3발전소의 경우 타 발전소에 비해 방사선관리구역 내 공기정화 처리기의 설치수량이 많아(약 700개/년) 공기정화필터가 매년 다수 발생되고 있으며, 이를 전량 드럼 처리 시 고체폐기물 드럼이 더 발생하게 되어 영구처분비용의 증가를 초래하게 된다. 발전소 전체적으로는 약 3,500개/년의 폐필터가 발생되고 있다. 이렇게 발생되는 공기정화필터의 프레임을 재사용함으로써 그 효과는 1) 알루미늄을 포함한 유리섬유를 드럼처리 시 고체방사성 폐기물드럼 생성량 감소 2) 프레임 재사용으로 인한 예산절감 효과 3) 폐필터 분해작업 시 분진에 의한 작업자 체내${\cdot}$외 피폭방지와 작업장 오염 확산 방지 및 환경 개선 4) 작업시간 단축 및 소요인력 감소 효과를 볼 수 있다.

• Composites Research
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• v.17 no.2
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• pp.34-39
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• 2004

In this paper, a modified and representative unit cell model was employed to study the tensile behaviour of closed-cell metallic foams with varying spatial density distribution as well as material imperfections. The density variation was assumed to follow a statistical probability distribution of the Gaussian type. A multiple cell finite element model, utilising the modified unit cell, was developed. The model exhibits deformation patterns similar to those observed in tensile testing. The nominal stress-strain curve obtained from quasistatic tensile of the foam was compared with experimental findings and was found to be in good agreement in the scheme of maximum strength only if the appropriate density distribution and volume fraction of internal imperfections are taken into account. Moreover, maximum tensile strength of the aluminium foam was found to be more sensitive to the volume fraction of imperfection than standard deviation of the density.

• Fire Science and Engineering
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• v.24 no.4
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• pp.12-17
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• 2010

The purpose of this study is to determine how effectively waste tire recycled material mixed with flame retardant work in combating fire. As discovered in the previous study, waste tire mixed with cement mortar has more insulation capacity. However, this mortar is weak against fire. Therefore flame retardant, with a specific proportional mix, will be added to increase its fire prevention capacity. Tests will be made in accordance with ISO 5657 procedures for measuring fire ignition time, flame and shape variation of test pieces at the Building Material Test Institute. The test piece will be set up with horizontal levels having a constant radiation heat of $1{\sim}5W/cm^2$. Temperature transfers and increases from the surface into the interior. Combustible gases result due to pyrolysis, and regular contact is maintained between the fire source and the center of the test piece for assessment purposes. Ignition has not been occurred without adding retardant meaning that there is almost no possibility of ignition of waste tire particle. This fact can be considered as fire load to appreciate a volume of combustion materials. Flame is not occurred due to heat-absorbing effect by adding non-organic series retardant into waste tire particle. Conclusions have been summarized as follows; 1) Combustion of building material can be decreased by adding retardant to waste tire-mixing mortar. But compressive strength and insulation capacity of the material should be measured later. 2) Firing prevention and ignition are main points of building fire. Reasonable fire engineering assessment of interior material should be made for establishing effective disaster prevention system.

• Journal of the Mineralogical Society of Korea
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• v.30 no.1
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• pp.31-43
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• 2017

This study investigated mineralogy, spectral characteristics and heavy metal contamination including Cd, Ni, Al, Fe, Mn and S for white precipitation in Miin falls based on XRF, XRD, and spectrometer. As a result, Al concentration was abnormally high at all samples, and most of the samples showed high contamination level in Cd and Ni. XRD results detected quartz, kaolinite, rhomboclase, aluminocoquimbite, and gibbsite which infers that heavy metal elements are distributed by adsorption with clay minerals. Spectral characteristics of white precipitation can be described by increasing pattern of reflectance in visible spectrum and decreasing pattern of reflectance in longer wave length including near infrared and shortwave infrared spectrum. The absorption features reveals that spectral characteristics of white precipitation is mainly controlled by kaolinite, rhomboclase, aluminocoquimbite, and gibbsite. The relationship between heavy metal concentration and absorption depth showed high positive correlation for Al concentration and absorption feature at 2202 nm of Al-OH absorption. This spectral characteristics indicates that absorption depth could be effectively used for estimation of heavy metal concentration.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.2
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• pp.7-13
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• 2019

This study aims to develop a FE Model to simulate dissimilar friction stir welding and to address its potential for fundamental analysis and practical applications. The FE model is based on Coupled Eulerian-Lagrangian approach. Multiphysics systems are calculated using explicit time integration algorithm, and heat generations by friction and inelastic heat conversion as well as heat transfer through the bottom surface are included. Using the developed model, friction stir welding between an Al6061T6 plate and an AZ61 plate were simulated. Three simulations are carried out varying the welding parameters. The model is capable of predicting the temperature and plastic strain fields and the distribution of void. The simulation results showed that temperature was generally greater in Mg plates and that, as a rotation speed increase, not the maximum temperature of Mg plate increased, but did the temperature of Al plate. In addition, the model could predict flash defects, however, the prediction of void near the welding tool was not satisfactory. Since the model includes the complex physics closely occurring during FSW, the model possibly analyze a lot of phenomena hard to discovered by experiments. However, practical applications may be limited due to huge simulation time.