• Tribology and Lubricants
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• 제22권4호
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• pp.218-224
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• 2006

The sludge oils were produced necessarily in the ships operation, so that it will be the best way to manage the sludge oils inside ship itself from a viewpoint of the prevention of marine oil pollution. The ultra-sonic breaking system which recycle the sludge oil from ship into usable oil to be brunt is recognized as a most possible recycling device. In this regards, the purpose of this study is to examine erosion damage,on the SS400 specimen by cavitation and the effect of impact pressure generated from the demolition of the cavity of ultrasonic vibration in the marine sludge oil environment.. The erosion damage of specimen was investigated mainly on weight loss, weight loss rate and maximum erosion rate with variation of the oil temperature as well as the change of space between transducer hem and specimen. The experimental results showed that as the space between ultrasonic vibrator horn and specimen disk increased, the weight loss and weight loss rate decreased and the values were larger in SFO than in SLO. The experimental results can be useful to the development of sludge oil disposing systems and to consider a countermeasure for the prevention of erosion damages by cavitation.

• 전산구조공학
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• 제2권3호
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• pp.77-84
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• 1989

본 논문의 내용은 철근콘크리트 보-기둥 접합부가 지진 하중을 받을 때의 거동에 대하여 관찰한 것이다. 똑같이 제작된 두개의 시험체에 정적 반복하중과 동적 반복하중을 가하여 하중-처짐 곡선이나 파괴 성상 등에 관하여 차이점을 기록하였다. 동적하중을 받는 시험체의 거동은 내진설계 규준에서 일반적으로 쓰여지는 정적하중 하에서의 시험체의 거동과는 판이한 양상을 보여주었다. 시험체가 동적하중을 받을 때에는 정적하중을 받을 때 보다 1. 극한하중이 20-25% 증가하고 2. 높은 취성을 보이며 3. 균열이 집중되고 4. 휨파괴 보다는 전단파괴현상을 나타내었다.

• 대한기계학회논문집A
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• 제20권12호
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• pp.3847-3855
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• 1996

In order to study the relationship between static and cynamic behaviors of silion caride, both quasi-static indentaiton and impact experiments of spherical particle have been conducted. The difference inmaterial behavior when using the two mehtods suggests a loading rate difference in the damate pattrern and fracture strength of silicon carbide. This investigation showed some difference in damage pattern according to particla property, especially inthe case of particle impact. There was no differences in deformation behaviors according to the loading rate when the crater profiles were compared with each other at the same contact radius. From the result of residual strength evaluation, it was found that the strength degradation began at the initiation of ring crack and its behavior was colsely related to morphologies of the damage developed which was also dependent upon the extent of deformation atthe loaidng point. In the case of static indentation, there didnot exist the particle property effects onthe strength degradation behavior.

• Structural Engineering and Mechanics
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• 제34권6호
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• pp.755-778
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• 2010

Near-fault ground motion with directivity or fling effects is significantly influenced by the rupture mechanism and substantially different from ordinary records. This class of ground motion has large amplitude and long period, exhibits unusual response spectra shapes, possesses high PGV/PGA and PGD/PGA ratios and is best characterized in the velocity and the displacement time-histories. Such ground motion is also characterized by its energy being contained in a single or very few pulses, thus capable of causing severe damage to the structures. This paper investigates the characteristics of near-fault pulse-like ground motions and their implications on the structural responses using new proposed measures, such as, the effective frequency range, the energy rate (in time and frequency domains) and the damage indices. The paper develops also simple mathematical expressions for modeling this class of ground motion and the associated structural responses, thus eliminating numerical integration of the equations of motion. An optimization technique is also developed by using energy concepts and damage indices for modeling this class of ground motion for inelastic structures at sites having limited earthquake data.

• KCI Concrete Journal
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• 제13권2호
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• pp.26-32
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• 2001

A simple expected damage cost model is developed and a systematic approach to evaluate the economic effects of seismic hazards to reinforced concrete structures is presented. An expected damage cost function during a specific lifetime is modeled by a Poisson's process with uniform continuous cash flow assumption. It is possible that the proposed method can decouple the damage cost effect from random earthquake events. Thus, expected damage cost function can be formulated as a combination of three independent terms; a present worth factor of Poisson's process, a damage cost interpolation function and a mean occurrence rate of earthquake intensity. The validity of the proposed method is demonstrated by a comparative study of LCC evaluations with the previous study.

• Structural Engineering and Mechanics
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• 제10권2호
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• pp.139-156
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• 2000

This paper concerns the development of a computational model for the damage evolution of engineering materials under dynamic loading. Two models describing the anisotropic damage evolution of a material are presented; the first is based on a power function of the effective equivalent stress and the second on the damage strain energy release rate. The methods for computing the damage accumulated in structural components and their implementation in a finite element programme are presented together with some numerical results. The dynamic response of a damaged structural component and the dynamic behaviour of a damaged material have been studied numerically. This study shows that the frequency spectrum of a damaged structure is down-shifted, while the damping ratio of damaged materials becomes higher, the amplitude of the response significantly increases and the resonance ensuing from the damage growth still occurs in a damaged structure.

• 한국작물학회:학술대회논문집
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• 한국작물학회 2017년도 9th Asian Crop Science Association conference
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• pp.247-247
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• 2017

Byobusan area of Aomori prefecture in Japan was a marshy sand dune and had developed for agricultural land use with a large-scale sprinkler system. Recently, it becomes an agricultural problem at this area that distinctive damage with browning maculation and fissures frequently occurs in Chinese yam tubers. Acetaldehyde is one of the factor candidates of underground part damage in plants. In this study, incidence rate of the tuber damage, and the morphological character and elemental composition of the damage parts in tubers were investigated with applications of excessive irrigation water or acetaldehyde water solution into the yam field. The incidence rate of the distinctive tuber damage increased as the input amount of irrigation water was increased. At the browning maculation parts of the tubers, many fissures and damages of cork layer were observed under scanning electron microscopy. In addition, the periderm of tubers was significantly thicker in damaged parts than in non-damaged parts. Funguses, bacterium and nematodes were not observed in the damaged part under scanning electron microscopy. The weight ratio of each constituent element in an analyzed area relative to the total weight of major essential elements was measured with energy dispersive X-ray spectrometry. The results showed that the weight ratios of boron, carbon, phosphorus, sulfur and calcium were higher in damaged parts than in non-damaged parts whereas the weight ratios of oxygen and chlorine were lower in damaged parts than in non-damaged parts. It was also shown by this spectrometry that iron, cadmium, lead and zinc were not directly involved in occurrence of the tuber damage. In this study, there was no remarkable difference of tuber appearance between non-acetaldehyde and acetaldehyde application treatments. From the above results, it is shown that the damage would be a physiological disorder induced by the input of a large quantity of water in the sandy field.

• 대한원격탐사학회지
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• 제38권6_1호
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• pp.1489-1503
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• 2022

드론(drone)과 센서(senor) 적용기술은 농업분야 작물의 성장 정보에 대한 디지털화를 가능하게 하면서 정밀농업 발전을 한층 가속화하고 있다. 이 기술은 자연재해 발생시 농작물 피해량 산정을 가능하게 하고, 현장 방문조사로 진행되고 있는 농작물재해보험 평가방법의 과학화에 기여할 수 있다. 본 연구는 콩을 대상으로 드론 기반 RGB영상을 취득하여 추출된 식생지수로 도복피해율을 산정하는 방법을 개발하고자 하였다. Support Vector Classifier (SVC) 분류 모델은 Crop Surface Model (CSM) 기반의 도복피해율에 식생지수를 추가하여 식생지수 적용성을 검토하였다. 식생지수 중 Visible Atmospherically Resistant Index (VARI), Green Red Vegetation Index (GRVI) 기반 콩의 도복피해율 분류 정확도는 각각 0.709, 0.705로 높은 분류정확도를 나타내었다. 연구 결과, 드론 기반 RGB 영상은 도복피해율 산정에 매우 유용한 도구로 활용 가능하다는 점을 확인할 수 있었다. 본 연구에서 얻어진 결과는 이상기후로 인한 광역 지역 자연재해에 대한 도복피해 산정 시 Sentinel-2, RapidEye 위성과 더불어 2025년 발사 예정인 농림업중형위성 영상과 연계해 활용 가능할 것으로 기대된다.

• 자원ㆍ환경경제연구
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• 제23권1호
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• pp.21-42
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• 2014

본 연구에서는 기후변화에 따른 해수면 상승이 우리나라 동해안 및 남해안 일대에 미치는 경제적 영향과 이를 방어하기 위한 최적 해안 방어비율을 광역시 도별로 분석하였다. 이를 위하여 FUND(The Climate Framework for Uncertainty, Negotiation and Distribution) 모형에 우리나라에 적합한 지표들을 적용하여 분석하였다. 해당 광역시 도의 면적 대비 예상 범람 지역 비율을 분석한 결과를 보면 광역시 도별로 지리적 차이가 있어 부산광역시는 시나리오에 따라 3.19% 내외로 상대적으로 높은 범람 비율로 추정되었으나 강원도는 0.1% 내외로 낮게 추정되었다. 경제적 피해비용도 광역시 도별로 차이가 있어 경제활동이 상대적으로 활발한 부산광역시, 울산광역시 및 경상남도에서의 경제적 피해비용은 매우 높게 나타났다. 그러나 최적 해안 방어비율 추정 결과를 보면 해안선의 길이가 짧고 경제적 피해비용이 큰 부산광역시와 울산 광역시는 각각 98% 내외, 92% 내외로 높게 추정되었고 경제적 피해 규모는 상대적으로 크나 해안 방어비용 또한 높게 추정된 경상남도에서는 최적해안 방어비율이 78%~79%로 추정되었다. 이에 반하여 강원도의 경우에는 경제적 피해 규모가 작아 최적 해안 방어비율이 시나리오별로 43% 내외로 추정되었다.

• Wind and Structures
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• 제19권3호
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• pp.321-337
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• 2014

This study has developed an Enhanced Remote-Sensing (ERS) scale to improve the accuracy and efficiency of using remote-sensing images of residential building to predict their damage conditions. The new scale, by incorporating multiple damage states observable on remote-sensing imagery, substantially reduces measurement errors and increases the amount of information retained. A ground damage survey was conducted six days after the Joplin EF 5 tornado in 2011. A total of 1,400 one- and two-family residences (FR12) were selected and their damage states were evaluated based on Degree of Damage (DOD) in the Enhanced Fujita (EF) scale. A subsequent remote-sensing survey was performed to rate damages with the ERS scale using high-resolution aerial imagery. Results from Ordinary Least Square regression indicate that ERS-derived damage states could reliably predict the ground level damage with 94% of variance in DOD explained by ERS. The superior performance is mainly because ERS extracts more information. The regression model developed can be used for future rapid assessment of tornado damages. In addition, this study provides strong empirical evidence for the effectiveness of the ERS scale and remote-sensing technology for assessment of damages from tornadoes and other wind events.