• Asian Journal of Atmospheric Environment
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• 제7권3호
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• pp.161-168
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• 2013

In this study, an investigation was conducted to assess the washout mechanism of Asian dust particles through both laboratory-scale experiment and model calculation. To artificially simulate Asian dust particle, $CaCO_3$ particles were generated inside an experimental chamber. They were then scavenged by the artificial rain drops. The abundant $CaCO_3$ particles scavenged on a rain drop were successively identified by SEM observation. The concentrations of Ca in residual $CaCO_3$ particles on individual droplet were quantified by PIXE analysis. There was a tendency toward a high accumulation of Ca on a relatively small drop (e.g., <1.0 mm diameter). It is thus suggested that smaller rain drops can effectively scavenge a significant amount of Asian dust particles in ambient atmosphere. The numerical estimation can account for 92.1% and 83.2% of Ca that were measured in small (<1.0 mm diameter) and large (>2.0 mm diameter) size drops, respectively.

• 대한토목학회논문집
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• 제44권4호
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• pp.465-482
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• 2024

The global use of groundwater in coastal areas has increased. Events such as seawater intrusion (SWI) are expected to increase along with the acceleration of natural disasters owing to environmental changes such as climate change, resulting in large-scale damage worldwide. Current trends in the research of coastal groundwater and related natural disasters include testing and verifying technologies using major case studies from individual countries. We identified global research trends in coastal groundwater, related these trends to changing environments and climate, and confirmed the qualitative and quantitative growth of these studies. This study describes the theoretical background and techniques for coastal groundwater analysis and details regional-scale SWI indicators based on analytical and numerical studies. This review highlights recent technologies that consider uncertainty and promotes discussions on field data obtained using new technologies. Finally, the research findings and trends for a regional coastal aquifer in Korea are discussed to describe recent SWI approaches for groundwater resources.

• 정보처리학회논문지C
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• 제8C권6호
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• pp.639-639
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• 2001

본 논문에서는 거대한 PCN망에서 HLR의 오버헤드 트래픽을 줄이기 위한 분산위치관리기법을 제안한다. 제안된 기법은 수학적 분석과 시뮬레이션 분석을 통하여 복제하는 위치 정보가 작은 PCN망에서도 효율적이고 적합하다는 것을 보여준다. 또한 위치관리의 오버헤드 트래픽을 더욱 줄이기 위하여 계층환경으로 구성하여 거대한 PCN망의 규모로 확장할 수 있다. 분석 결과를 통해서 제안된 분산위치관리기법이 표준 IS-41기법보다 우수하다는 것을 보인다.

• 정보처리학회논문지C
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• 제8C권6호
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• pp.839-846
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• 2001

본 논문에서는 거대한 PCN망에서 HLR의 오버헤드 트래픽을 줄이기 위한 분산위치관리기법을 제안한다. 제안된 기법은 수학적 분석과 시뮬레이션 분석을 통하여 복제하는 위치 정보가 작은 PCN망에서도 효율적이고 적합하다는 것을 보여준다. 또한 위치관리의 오버헤드 트래픽을 더욱 줄이기 위하여 계층환경으로 구성하여 거대한 PCN망의 규모로 확장할 수 있다. 분석 결과를 통해서 제안된 분산위치관리기법이 표준 IS-41기법보다 우수하다는 것을 보인다.

• Geomechanics and Engineering
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• 제14권2호
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• pp.115-129
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• 2018

This paper presents a set of results of plate load tests that imposed incremental cyclic loading to a sandy soil bed containing multiple layers of granulated rubber-soil mixture (RSM) at large model scale. Loading and unloading cycles were applied with amplitudes incrementally increasing from 140 to 700 kPa in five steps. A thickness of the RSM layer of approximately 0.4 times the footing diameter was found to deliver the minimum total and residual settlements, irrespective of the level of applied cyclic load. Both the total and residual settlements decrease with increase in the number of RSM layers, regardless of the level of applied cyclic load, but the rate of reduction in both settlements reduces with increase in the number of RSM layers. When the thickness of the RSM layer is smaller, or larger, settlements increase and, at large thicknesses may even exceed those of untreated soil. Layers of the RSM reduced the vertical stress transferred through the foundation depth by distributing the load over a wider area. With the inclusion of RSM layers, the coefficient of elastic uniform compression decreases by a factor of around 3-4. A softer response was obtained when more RSM layers were included beneath the footing damping capacity improves appreciably when the sand bed incorporates RSM layers. Numerical modeling using "FLAC-3D" confirms that multiple RSM layers will improve the performance of a foundation under heavy loading.

• Advances in concrete construction
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• 제14권1호
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• pp.57-70
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• 2022

The spiral case concrete (SCC) used in the underground powerhouse of large hydropower stations is complex, difficult to pour, and has high requirements for temperature control and crack prevention. In this study, based on the closed-loop control theory of "multi-source sensing, real analysis, and intelligent control", a new intelligent cooling control system (ICCS) suitable for the SCC is developed and is further applied to the Wudongde large-scale underground powerhouse. By employing the site monitoring data, numerical simulation, and field investigation, the temperature control quality of the SCC is evaluated. The results show that the target temperature control curve can be accurately tracked, and the temperature control indicators such as the maximum temperature can meet the design requirements by adopting the ICCS. Moreover, the numerical results and site investigation indicate that a safety factor of the spiral case structure was sure, and no cracking was found in the concrete blocks, by which the effectiveness of the system for improving the quality of temperature control of the SCC is verified. Finally, an intelligent cooling control procedure suitable for the SCC is proposed, which can provide a reference for improving the design and construction level for similar projects.

• 마이크로전자및패키징학회지
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• 제28권4호
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• pp.47-50
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• 2021

Nanoimprint lithography (NIL) has revolutionized the fabrications of electronics, photonics, optical and biological devices. Among all the NIL processes, roll-to-roll nanoimprinting is regarded best for having the attributes of low cost, continuous, simple, and energy-efficient process for nanoscale device fabrication. However, large-area printing is limited by the master mold deformation. In this study, a finite element model (FEM) has been constructed to assess the deformation of the roll mold adhesively wrapped on the carbon fiber reinforced material (CFRP) base roll. This study also optimizes the deformations in the metallic roll mold with respect to nip-forces applied in the printing process of nano-fabrication on large scale. The numerical simulations were also conducted to evaluate the deflection in roll mold assembly due to gravity. The results have shown decreasing trend of the deformation with decreasing nip-force. Also, pressure uniformity of about 40% has been optimized by using the current numerical model along with an acceptable deflection value in the vertical axis due to gravity.

• 한국음향학회지
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• 제43권1호
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• pp.95-102
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• 2024

기술 발전에 힘입어 고속열차의 운항속도는 증가하고 있으며, 고속열차 외부 유동장으로부터 발생하는 공력소음은 설계 단계에서 매우 중요한 고려 대상이 되어왔다. 이러한 고속열차의 유동기인소음을 정확하게 예측하기 위해서는 근거리 음향장에서 고해상도의 음원 발생과 원거리 음향장에서 수치적 소산이 적은 소음 전파가 요구된다. 이는 실제 고속열차의 구성요소 별로 시공간 스케일을 모두 적절하게 고려할 수 있는 수치격자 및 시간해상도가 동반되어야 한다. 이러한 도전점을 극복하기 위해, 본 연구는 실제 크기 및 실제 운행속도의 고속열차 5차량의 외부 유동장 및 음향장을 3차원 압축성 대와류모사(Large Eddy Simulation, LES) 기법을 이용하여 동시 계산하였다. 수치해석의 검증을 위해 벽면압력섭동 측정 결과와 수치해석 결과를 비교하였다. Ffowcs Williams and Hawkings 방정식을 이용하여 고속열차로부터 방사되는 음향파워를 예측하고 주행속도간 결과를 비교분석하였다. 본 연구는 고속열차의 공력소음 발생 메커니즘 분석을 바탕으로 한 소음 저감에 기여할 것으로 사료된다.

• 한국콘텐츠학회논문지
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• 제13권3호
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• pp.428-434
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• 2013

빈발하고 있는 대규모 홍수와 자연재해는 정확도가 높은 하천 흐름 수치해석 모델에 대한 관심의 증대로 이어지고 있다. 현재 하천에서 발생하는 일반적인 흐름은 기존에 개발된 여러 형태의 천수방정식을 지배방정식으로 하는 수치기법에 의해 해석되고 있으나, 연속적이지 않은 형태의 흐름을 해석하거나 매우 정확한 해석을 필요로 하는 경우에는 기존의 수치해석기법은 많은 한계를 보여 주고 있다. 본 연구에서는 불연속 갤러킨 기법 기반의 흐름 모델을 개발하고, 이를 이용하여 전통적으로 1차원 천이류로 분류되는, 댐 붕괴파, 둔덕위 흐름 모의에 적용하여 기존의 수치해와 대체로 잘 일치함을 확인하였다.

• Geomechanics and Engineering
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• 제7권1호
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• pp.105-131
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• 2014

In this paper, the effects of variability of smear zone characteristics induced by installation of prefabricated vertical drains on the preloading design are investigated employing analytical and numerical approaches. Conventional radial consolidation theory has been adopted to conduct analytical parametric studies considering variations of smear zone permeability and extent. FLAC 2D finite difference software has been employed to conduct the numerical simulations. The finite difference analyses have been verified using three case studies including two embankments and a large-scale laboratory consolidometer with a central geosynthetic vertical drain. A comprehensive numerical parametric study is conducted to investigate the influence of smear zone permeability and extent on the model predictions. Furthermore, the construction of the trial embankment is recommended as a reliable solution to estimate accurate smear zone properties and minimise the post construction settlement. A back-calculation procedure is employed to determine the minimum required waiting time after construction of the trial embankment to predict the smear zone characteristics precisely. Results of this study indicate that the accurate smear zone permeability and extent can be back-calculated when 30% degree of consolidation is obtained after construction of the trial embankment.