• Title/Summary/Keyword: Debris Impact

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Experimental Study on the Effect of Arrangement of Cylindrical Countermeasures on Debris Flow Impact Load (원통형 대책구조물의 배치조건에 따른 토석류의 충격하중에 대한 실험적 연구)

  • Cho, Heungseok;Kim, Beomjun;Yune, Chanyoung
    • Journal of the Korean Geotechnical Society
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    • v.36 no.11
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    • pp.135-148
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    • 2020
  • In this study, to investigate the effect of the array of cylindrical baffles on debris flow impact load, a series of small-scale tests were conducted according to varying row numbers of installed baffles in the flume. After the test, the behavior of debris flow interacting with baffles during the flow process was investigated. Based on the results, the influence varying velocity and flow depth on Froude number and dynamic pressure coefficient were analyzed. Test results showed that the greatest peak impact load occurred at the second row of baffle arrays. The dynamic pressure coefficient was also estimated by suggested equation and compared with previous studies.

Strategies for Response and Mitigation of Marine Environmental Damage Caused by Plastic Debris

  • Lee, Jungsub
    • Journal of the Korean Society of Marine Environment & Safety
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    • v.27 no.3
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    • pp.439-446
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    • 2021
  • Environmental damage caused by marine plastic debris occurs and has become a major contributor to marine pollution. This study analyzed the current state of marine plastic debris pollution and proposed essential strategies to reduce damage. To assess the current state of pollution arising from marine plastic debris, this study investigated the properties of plastic debris, reviewed case studies of ecological impacts, and examined the inflow and distribution of marine plastic debris. The results of this study indicate that the major deleterious effects of marine plastics are entanglement and ingestion. In addition, the amount of plastic waste entering the sea was estimated to be 230 Mt in 2015 and may increase to 554 Mt in 2050. In this study, three key strategies were proposed to reduce damage and preserve the ecosystem, including: 1) removing plastic debris in the marine environment, 2) limiting the release of plastic debris to the marine environment, and 3) preventing damage to humans and marine life from plastic debris. To minimize the environmental damage caused by marine plastic debris, the proposed response strategies should be implemented in parallel.

Roof tile frangibility and puncture of metal window shutters

  • Laboy-Rodriguez, Sylvia T.;Smith, Daniel;Gurley, Kurtis R.;Masters, Forrest J.
    • Wind and Structures
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    • v.17 no.2
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    • pp.185-202
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    • 2013
  • The goal of this study was to investigate the vulnerability of roof tile systems and metal shutters to roof tile debris. Three phases addressed the performance of tile roof systems and metal shutters impacted by roof tile debris. The first phase experimentally evaluated the tile fragment size and quantity generated by a tile striking a tile roof system. The second phase experimentally quantified the puncture vulnerability of common metal panel shutter systems as a function of tile fragment impact speed. The third phase provided context for interpretation of the experimental results through the use of a tile trajectory model. The results provide supporting evidence that while metal panel window shutters provide significant protection against a prevalent form of windborne debris, these systems are vulnerable to tile fragment puncture in design level tropical cyclones. These findings correlate with field observations made after Hurricane Charley (2004).

Analysis of Debis Flow according to Change of Slope Angle (사면경사 변화에 따른 토석류의 거동 분석)

  • Park, Byung-Soo;Jun, Sang-Hyun;Yoo, Nam-Jae;Han, Kwang-Doo;Yoon, Young-Ho
    • Proceedings of the Korean Geotechical Society Conference
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    • 2010.03a
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    • pp.1294-1301
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    • 2010
  • This study is an experimental research for the dispersion behavior and impact characteristics of debris flow according to change of slope. Large scale experimental setup for the debris flow was established to simulate the artificial rainfall and control the ground slope. Parameters such as materials of debris flow, slope, and length of slope were used for the experiments. After the experiments, it was found that the speed of ground material components was increased about 28~47%. It was found that speed can be increased by increasing the particle size. Furthermore, maximum/final loads for ground material components were increased 89% for the coarse aggregate and 68% for the fine aggregate comparing with sand.

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Real-Time Estimation of Missile Debris Predicted Impact Point and Dispersion Using Deep Neural Network (심층 신경망을 이용한 실시간 유도탄 파편 탄착점 및 분산 추정)

  • Kang, Tae Young;Park, Kuk-Kwon;Kim, Jeong-Hun;Ryoo, Chang-Kyung
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.49 no.3
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    • pp.197-204
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    • 2021
  • If a failure or an abnormal maneuver occurs during the flight test of a missile, the missile is deliberately self-destructed so as not to continue the flight. At this time, debris are produced and it is important to estimate the impact area in real-time whether it is out of the safety area. In this paper, we propose a method to estimate the debris dispersion area and falling time in real-time using a Fully-Connected Neural Network (FCNN). We applied the Unscented Transform (UT) to generate a large amount of training data. UT parameters were selected by comparing with Monte-Carlo (MC) simulation to secure reliability. Also, we analyzed the performance of the proposed method by comparing the estimation result of MC.

Hypervelocity Impact Simulations Considering Space Objects With Various Shapes and Impact Angles (다양한 형상의 우주 물체와 충돌 각도를 고려한 우주 구조물의 초고속 충돌 시뮬레이션 연구)

  • Shin, Hyun-Cheol;Park, Jae-Sang
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.50 no.12
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    • pp.829-838
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    • 2022
  • This study conducts Hypervelocity Impact(HVI) simulations considering space objects with various shapes and different impact angles. A commercial nonlinear structural dynamics analysis code, LS-DYNA, is used for the present simulation study. The Smoothed Particle Hydrodynamic(SPH) method is applied to represent the impact phenomena with hypervelocity. Mie-Grüneisen Equation of State and Johnson-Cook material model are used to consider nonlinear structural behaviors of metallic materials. The space objects with various shapes are modeled as a sphere, cube, cylinder, and cone, respectively. The space structure is modeled as a thin plate(200 mm×200 mm×2 mm). HVI simulations are conducted when space objects with various shapes with 4.119 km/s collide with the space structures, and the impact phenomena such as a debris cloud are analyzed considering the space objects with various shapes having the same mass at the different impact angles of 0°, 30° and 45° between the space object and space structure. Although space objects have the same kinetic energy, different debris clouds are generated due to different shapes. In addition, it is investigated that the size of the debris cloud is decreased by impact angles.

An Evaluation of Cooling of Core Debris and Impact on Containment Transient Pressure under Severe Accident Conditions (극심한 사고시 노심 냉각 및 격납용기 과도압력에 미치는 영향)

  • Jong In Lee;Jin Soo Kim;Byung Hun Lee
    • Nuclear Engineering and Technology
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    • v.15 no.4
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    • pp.256-266
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    • 1983
  • An evaluation of containment transient pressure due to the particulate debris/water/concrete interaction under severe accident conditions is presented for a pressurized water reactor with a large dry containment building. A particulate debris/water/concrete model is developed and incorporated into the MARCH computer code. Comparisons with the existing MARCH molten debris/concrete model were performed for the TMLB' and S$_2$D sequences. The results yield a much slower concrete decomposition rate and release less gases into the containment atmosphere. Contrary to the molten debris model, the particulate debris model exhibits a strong interaction with water and causes a higher containment pressure. The effect of gas influx on the debris bed heat transfer was found to be insignificant.

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Hypervelocity Impact Analyses Considering Various Impact Conditions for Space Structures with Different Thicknesses (다양한 두께의 우주 구조물에 대한 다양한 충돌 조건의 초고속 충돌 해석 연구)

  • Won-Hee Ryu;Ji-Woo Choi;Hyo-Seok Yang;Hyun-Cheol Shin;Chang-Hoon Sim;Jae-Sang Park
    • Journal of Aerospace System Engineering
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    • v.17 no.4
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    • pp.43-57
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    • 2023
  • The hypervelocity impact simulations of space objects and structures are performed using LS-DYNA. Space objects with spherical, conical, and hollow cylindrical shapes are modeled using the Smoothed Particle Hydrodynamics (SPH). The direct and indirect impact zones of a space structure are modeled using the SPH and finite element methods, respectively. The Johnson-Cook material model and Mie-Grüneisen Equation of State are used to represent the nonlinear behavior of metallic materials in hypervelocity impact. In the hypervelocity impact simulations, various impact conditions are considered, such as the shape of the space object, the thickness of the space structure, the impact angle, and the impact velocity. The shapes of debris clouds are quantitatively classified based on the geometric parameters. Conical space objects provide the worst debris clouds for all impact conditions.

Risk Index of Debris Flow Damage for Hydro- and Geographic Characteristics of Debris Flow with Bayesian Method

  • Lee, JunSeon;Yang, WooJun;You, KwangHo;Kim, MunMo;Lee, Seung Oh
    • Proceedings of the Korea Contents Association Conference
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    • 2016.05a
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    • pp.241-242
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    • 2016
  • Recent abnormal climate change induces localized heavy rainfall and extreme disasters such as debris flow near urban area. Thus many researches have been conducted to estimate and prevent, especially in focus of physical behavior of debris flow. Even though it is hardly to consider overall related parameters to estimate the extent and degree of directly or indirectly damages due to debris flow. Those analytic restraint would be caused by the diversity and complexity of regional topographic and hydrodynamic characteristics of debris flow inside. We have utilized the Bayesian method to compensate the uncertainty due to the complex characteristics of it after analyzing the numerical results from FLO-2D and field measurement data. Revised values by field measurements will enhance the numerical results and the missing parameters during numerical simulation will be supplemented with this methodology. As a final outcome in this study, the risk index of debris flow damage will be suggested to provide quantitative estimation in terms of hazard protection including the impact on buildings, especially in inner and outer of urban area.

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Experimental Study on Laser-driven Miniflyer for Description of Space Debris with High-speed (빠른 속도의 우주먼지 모사를 위한 레이저기반의 입자가속에 관한 실험적 연구)

  • Baek, Won-Kye;Yoh, Jai-Ick
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.41 no.2
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    • pp.120-126
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    • 2013
  • Increasing numbers of space debris around the earth now pose a major threat to satellites as their impact velocity may reach up to several km/s. We use a pulse laser to accelerate a miniflyer for mimicking the space debris. The multi-layer coat on the confined medium is known to promote a higher acceleration. However, it requires some special techniques which take somewhat long time and cost to coat. Instead, we devised a simple concept to coat by the black lacquer paint on a flyer. It shows improvement in the flyer velocity by 1.5-2 times the uncoated, and the resulting velocity reached 1.42km/s with Nd:YAG laser energy under 1.4 joules. The resulting velocity is suitable for satellite vulnerability test for debris impact in the geostationary orbit.