• 유체기계공업학회:학술대회논문집
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• 유체기계공업학회 1999년도 유체기계 연구개발 발표회 논문집
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• pp.301-308
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• 1999

The present study investigates numerically particle laden flow through compressor cascades and a rocket nozzle. Engines are affected by various particles which are suspending in the atmosphere. Especially in the case of aircraft aviating in volcanic, industrial and desert region including many particles, each components of engine system are damaged severely. That damage modes are erosion of compressor blading and rotor path components, partial or total blockage of cooling passage and engine control system degradation. Numerical prediction and experimental data, erosion rates are predicted for two materials - ceramic, soft metal - on compressor blade surface. Aluminum oxide ($Al_2O_3$) Particles included in solid rocket propelant make ablative the rocket motor nozzle and imped the expansion processes of propulsion. By the definition of particle deposition efficiency, characteristics of particles impaction are considered quantitatively Stoke number is defined over the various particle sizes and particle trajectories are treated by Lagrangian approach. Particle stability is considered by definition of Weber number in rocket nozzle and particle breakup and evaporation is simulated in a rocket nozzle.

• 한국표면공학회:학술대회논문집
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• 한국표면공학회 2003년도 추계학술발표회초록집
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• pp.118-118
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• 2003

In a rolling wire probe, a key component of an inspection apparatus for PDP electrode patterns, the electric performance of it is known to be strongly dependent on the surface condition of a collet pin, a needle pin, and a wire. However, the collet and needle pins rotate very rapidly in contact with each other, which results in the degradation of the surface by the heat and friction and finally the formation of black wear marks on the surface after a several hundred hours test. Once the black wear marks appear on the surface, the electric resistance of the probe increases sharply and so the integrity of the probe is severely damaged. In this experiment, TiN coating, which has excellent electric conductances and good wear-resistance, has been applied on the surface of collect and needle pins for preventing the surface damages. In order to achieve the homogeneous coating with a good adhesion property, special coating substrate stages and jigs were designed and applied during coating. TiN has been deposited using 99.999% Titanium target by a DC reactive sputtering method. According to the components and jigs, processing parameters, such as DC power, RF bias and the flow rate ratio of Ar and N$_2$ used as reactive gases, has been controlled to obtain good TiN films. Detailed problems and solutions for applying the new substrate stages and jigs will be discussed.

• 한국작물학회지
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• 제47권2호
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• pp.123-126
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• 2002

Lipoxygenase might be associated with seed deterioration by catalyzing the incorporation of molecular oxygen into fatty acids and generating free radicals. This study was performed to determine whether seed lipoxygenase activity would alter soybean seed longevity. In this study, germination percentage of lipoxygenase-lacking cultivar Jinpumkong2 (lx1lx1lx2lx2lx3lx3) was lower than that of Taekwangkong (Lx1Lx1Lx2Lx2Lx3Lx3). Segregation ratio for the three lipoxygenase isozymes of the F2-derived from the cross between Taekwangkong and Jinpumkong2 was fitted to 9 (Lx1Lx2Lx3) : 3 (Lx1Lx2lx3) : 3 (lxllx2Lx3) : 1 (lx1lx2lx3), suggesting the tight linkage between the Lx1 and Lx2 loci. Germination percentages varied widely but not differed among lipoxygenase isozyme types of F$_3$ seeds before and after accelerated aging. Seed coat of Jinpumkong2 was damaged severely following accelerated aging, whereas that of Taekwangkong was not. Thus, seed of lipoxygenase-lacking soybean cultivar, Jinpumkong2 showed greater deterioration compared with that of the normal Taekwangkong. However, the presence or absence of lipoxygenase activity had no effect on soybean germination.

• The Plant Pathology Journal
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• 제17권1호
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• pp.45-51
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• 2001

A root rot/vine decline disease occurred naturally on bottle gourd-stocked watermelon, melon, oriental melon and squash grown in greenhouses, but not on these plants grown in fields. Self-rooted watermelon, cucumber, pumpkin and luffa were also proven to be hosts of the pathogen by artificial inoculation in this experiment. The pathogen was identified as Monosporascus cannonballus by comparing microscopic characteristics of fungal structures with those of previously identified fungal strains. Our field investigations showed that the temperature and electric conductivity of soil in infected greenhouses were higher and the soil moisture content was lower than in noninfected greenhouses. To investigate soil-environmental factors affecting disease development, greenhouse trials and inoculation experiments were conducted. The host plants inoculated and grown under conditions of high soil temperature and electrical conductivity ($35\pm2^{\circ}$, 3.2-3.5 mS) and with low soil moisture content (pF 3.0-4.5) were most severely damaged by the fungal disease. Since plants growing in greenhouses ae usually exposed to such environmental conditions, this may be the reason why the monosporascus root rot/vine decline disease has occurred only on cucurbits cultivated in greenhouses but not in field conditions.

• 보존과학회지
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• 제35권1호
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• pp.33-40
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• 2019

During the conservation and maintenance of the birthplace center yard of President Asan Yoon Bosun, four porcelain enamel dishware were excavated from the central yard well. The glaze layer of excavated enamel was severely damaged; hence, the conservation process was done rapidly. In addition, scientific investigation and analysis were conducted to confirm the material properties of the glaze layer. It was confirmed that the outer surface was inverted and dried, while the inner surface was upright and fired during the glazing and drying process by measuring the film thickness. By examining the breakup phenomenon, the breaking up of the white enamel on the colored enamel was confirmed. This indicates that the colored glaze rose to the surface depending on the density of the colored glaze and white glaze. The investigation of the cross-section of the film confirmed that the lower layer formed according to the bonding properties with metal during the glazing process. Analysis of the constituents of the identified lower layer confirmed that there are differences between the specific components of the metal oxide of the lower layer and the surface color development of the upper layer.

• 한국지진공학회논문집
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• 제23권1호
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• pp.9-18
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• 2019

In 2017 Pohang Earthquake, a number of residential buildings with pilotis at their first level were severely damaged. In this study, the results of an analytical investigation on the seismic performance and structural damage of two bearing wall buildings with pilotis are presented. The vibration mode and lateral force-resisting mechanism of the buildings with vertical and plan irregularity were investigated through elastic analysis. Then, based on the investigations, methods of nonlinear modeling for walls and columns at the piloti level were proposed. By performing nonlinear static and dynamic analyses, structural damages of the walls and columns at the piloti level under 2017 Pohang Earthquake were predicted. The results show that the area and arrangement of walls in the piloti level significantly affected the seismic safety of the buildings. Initially, the lateral resistance of the piloti story was dominated mainly by the walls resisting in-plane shear. After shear cracking and yielding of the walls, the columns showing double-curvature flexural behavior contributed significantly to the residual strength and ductility.

• Earthquakes and Structures
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• 제22권4호
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• pp.331-343
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• 2022

Masonry structures are the most common structural systems that have been used almost all over the world from the earliest ages of history to the present day. These structural systems are often unfavorably affected by natural disasters such as earthquakes. The main reason for this is that they are built without sufficient engineering knowledge. On January 24, 2020, a severe earthquake occurred near the Sivrice District of Elazığ in eastern Turkey. According to the Turkish Directorate of Disaster and Emergency Management (AFAD), the magnitude of the earthquake was 6.8 and the focal depth 8 km. This earthquake caused damage and destruction to the masonry structures used extensively in the region. The Hacı Yusuf Taş (new) mosque in the Malatya city center, located about 64 km from the epicenter of the earthquake, was among the buildings affected by the earthquake. The mosque has smooth-cut stone walls and domes made of brick units. The main dome of the structure was severely damaged during the earthquake. In this study, information about the earthquake is first provided, and the damage to the mosque is then interpreted via photographs. In addition, two separate finite element models were produced, where the current state of mosque and solution suggestions are presented, and response spectrum analyses were carried out. According to these analyses and field observations, a buttress system to the main walls of the structure should be constructed in the direction which has little lateral rigidity.

• Structural Engineering and Mechanics
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• 제84권2호
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• pp.167-180
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• 2022

A strategic structure when exposed to direct hit of conventional bomb/projectile are severely damaged because of large amounts of energy released by the impact and penetration of bomb. When massive concrete slabs suffer a direct hit, the energy released during impact and penetration process are able to easily break up large mass of concrete. When over stressed under such impact of bombs, the concrete structure fails showing brittle behavioural nature. This paper is intended to study and suggest the protective measures for structures used for strategic application by adopting a means to dissipate the large quantum of energy released. To quantitatively evaluate the force, displacement and energy in such scenario, a fine numerical model of the proposed layered structure of different combinations was built in ANSYS programme in which tri-nitrotoluene (TNT) explosive was detonated at penetration depth calculated for GP1000 Lbs bomb. The distinct blast mitigation effect of the proposed structure was demonstrated by adopting various layers/barriers created as protective measures for the strategic structure. The calculated result shows that the blast effect on the structure is potentially reduced due to provision of buster slab with sand cushioning provided as protective measure to the main structure. This concept of layered protective measures may be adopted for safeguarding strategic structures such as Domes, Tunnels and Underground Structures.

• Applied Microscopy
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• 제24권2호
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• pp.63-77
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• 1994

This experiment was performed to study the morphological responses of the epidermis of the rat scalp, following X-ray irradiation. Male rats were divided into normal and experimental groups. Rats anesthetized with sodium thiopental, were exposed only on their head areas with a single dose of 3,000rads or 6,000rads, respectively. Radiation was produced by Mitsubishi Linea Accelerator ML-4MV at the speed of 200rads/min. The target distance was 80cm. Animals were sacrificed on six hours, two days and six days following irradiation. By the perfusion fixation through the heart, rats were fixed with 1% glutaraldehyde-1% paraformaldehyde solution. Pieces of the tissue taken from the scalp were refixed in 2.5% glutaraldehyde-1.5% paraformaldehyde solution, followed by post-fixation with 1% osmium tetroxide, and embedded within araldite mixture. The sections were cut on a LKB-V ultratome, stained with uranyl acetate and lead citrate, and were observed with JEM 100CX-II electron microscope. The results were as follow; 1. Six hours after exposure to 3,000rads of X-ray. Disrupted intercellular spaces, within which some amorphous materials were filled, disrupted mitochondria, and vacuoles in the keratinocytes were frequently observed, but six days after exposure to 3,000rads of X-ray, Morphology of the keratinocytes was generally restored. 2. Many of the morphological changes were seen on the six days after exposure to 6,000rads of X-ray. 3. Widened intercellular spaces and thickened dense plaques of the desmosomes were frequently observed after exposure to 6,000rads of X-ray. 4. In the experimental groups, the Langerhans and the Merkel cells were damaged, similarly to the keratinocyte. Above results suggest that head irradiation with the dose of 3,000rads temporarily damaged the epidermis of the scalp, though most of the structures recover within six days, whereas with the dose of 6,000rads it severely damaged the epidermis without showing any recovering tendency.

• 대한토목학회논문집
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• 제43권6호
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• pp.883-896
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• 2023

인간 활동 영역이 산지 곳곳에 퍼져 있는 한국에서는 산불이 주거지역이나 각종 시설물을 위협하는 경우가 잦다. 따라서 산불 이후 대책 마련과 피해 복구를 위해 피해 범위를 빠르게 파악할 필요가 있으며, 이러한 경우 원격탐사가 유용한 도구가 될 수 있다. 본 연구에서는 2019년 4월에 발생한 고성·속초 산불 피해지역에 k-nearest neighbor (kNN) 알고리즘을 적용하여 피해 범위를 탐지하는 실험을 수행하였다. 다양한 인공지물을 포함하는 지표와 숲이 혼재된 지역 특성을 고려하여 적절한 공간 해상도와 시간 해상도를 제공하는 Sentinel-2 multispectral instrument (MSI) 자료를 사용하였다. Sentinel-2 MSI의 여섯 밴드와 정규식생지수(NDVI), 정규탄화지수(NBR)를 분류 특성으로 사용하였다. 산불 피해지역과 비피해 지역에서 무작위로 추출된 2,000개 지점 정보를 이용하여 kNN 분류기를 훈련시켰다. 분류 성능을 높이기 위해 데이터에서 특이값을 제거하고 임상도를 병용하였다. 다양한 이웃(neighbor) 수와 분류 특성 조합을 적용하여 산불 후 데이터를 이용한 실험과 산불 전후 데이터 차이를 이용한 실험을 수행하였다. 산불 전후 데이터 차이를 이용하였을 때 더 우수한 분류 성과를 얻을 수 있었지만, 산불 후 데이터만을 이용한 경우에도 피해지역의 범위를 파악할 수 있었다.