• Nuclear Engineering and Technology
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• 제38권3호
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• pp.201-210
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• 2006

This article presents a brief overview of an important area of neutron scattering: the general principles and techniques of elastic, quasielastic and inelastic scattering from a system composed predominately of incoherent scatterers. The methodology is then applied to the study of water, specifically when it is confined in nanometer-scale environments. The confined water exhibits uniquely anomalous properties in the supercooled state. It also nourishes biological functions, and supports essential chemical reactions in living systems. We focus on recent investigations of water encapsulated in nanoporous silica and carbon nanotubes, hydrated water in proteins and water or hydroxyl species incorporated in nanostructured minerals. Through these scientific examples, we demonstrate the advantages derived from the high sensitivity of incoherent neutron spectroscopy to hydrogen atom motions and hydrogen-bond dynamics, aided by rigorous data interpretation method using molecular dynamics simulations or theoretical modelling. This enables us to probe the inter-/intramolecular vibrations and relaxation/diffusion processes of water molecules in a complex environment.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2004년도 춘계 학술발표회 제16권1호
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• pp.584-587
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• 2004

This research investigates the rheological behavior and the confined water ratio of the cement paste and binder condition in order to predict mix design proportion of the high flowing concrete. The purpose of this study is to determine the optimum replacement ratio of binders including fly ash, and lime stone powder by the cement weight. For this purpose, belite cement, blast furnace slag cement and ordinary portland cement are selected. As test results, the confined water ratio shows the following range ; OPC>blast furnace slag cement>belite cement. Therefore, belite cement is proved very excellent cementitious materials in a view point of the flowability. The optimum replacement ratio of lime stone powder is shown over $30\%$ in case of belite cement and about $10\%$ in case of slag cement type. Also, the optimum replacement ratio of fly ash is shown $30\%$ by the cement weight considering the confined water ratio and deformable coefficient of the paste condition.

• 대한조선학회논문집
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• 제48권4호
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• pp.317-324
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• 2011

When a ship proceeds in confined water, like canal, the water ahead of ship is pushed by hull. This pushed water returns to the side and under the hull, and this returned water will make fluid velocity higher at the side and under the hull, compared to the case in the infinite water depth. Due to the higher velocity, the pressure under the hull will decrease, resulting in the ship drop. This phenomenon is called "ship squat" and ship squat will result in various marine accidents. In this paper, for predicting ship squat, numerical calculation was carried out using commercial CFD code, FLUENT. To confirm wave pattern profile around the ship, VOF(Volume of Fluid) method was applied. The calculated results were compared with other paper's results and empirical methods.

• Journal of Mechanical Science and Technology
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• 제19권8호
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• pp.1582-1596
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• 2005

Groundwater flow and behavior have to be investigated based on heterogeneous subsurface formation since the homogeneity assumption of this formation is not valid. Over the past twenty years, stochastic approach and Monte Carlo technique have been utilized very efficiently to understand the groundwater flow behavior. However, these techniques require lots of computational and numerical efforts according to the various researchers' comments. Therefore, utilizing new techniques with much less computational efforts such as Artificial Neural Network (ANN) in the prediction of the stochastic behavior for the groundwater based on heterogeneous subsurface formation is highly appreciated. The current paper introduces the ANN technique to investigate and predict the stochastic behavior of a well draw down in a confined aquifer based on subsurface heterogeneous hydraulic conductivity. Several ANN models are developed in this research to predict the unsteady two dimensional well draw down and its stochastic characteristics in a confined aquifer. The results of this study showed that ANN method with less computational efforts was very efficiently capable of simulating and predicting the stochastic behavior of the well draw down resulted from the continuous constant pumping in the middle of a confined aquifer with subsurface heterogeneous hydraulic conductivity.

• Smart Structures and Systems
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• 제30권5호
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• pp.433-446
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• 2022

Despite efforts to reduce unexpected accidents at confined construction sites, choking accidents continue to occur. Because of the poorly ventilated atmosphere, particularly in long, confined underground spaces, workers are subject to dangerous working conditions despite the use of artificial ventilation. Moreover, the traditional monitoring methods of using portable gas detectors place safety inspectors in direct contact with hazardous conditions. In this study, a long-range (LoRa)-based wireless safety monitoring system that features the network organization, fault-tolerant, power management, and a graphical user interface (GUI) was developed for underground construction sites. The LoRa wireless data communication system was adopted to detect hazardous gases and oxygen deficiency within a confined underground space with adjustable communication range and low power consumption. Fault tolerance based on the mapping information of the entire wireless sensor network was particularly implemented to ensure the reliable operation of the monitoring system. Moreover, a sleep mode was implemented for the efficient power management. The GUI was also developed to control the entire safety-monitoring system and to manage the measured data. The developed safety-monitoring system was validated in an indoor testing and at two full-scale water pipeline construction sites.

• 지질공학
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• 제2권1호
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• pp.58-69
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• 1992

피압대수층에 있어서 피압층을 관통하는 시추공에는 대기압의 변화에 따라 수위변화가 이루어지며, 그들의 관계는 대기압이 상승하면 수위는 하강하고, 대기압이 하강하면 수위는 상승하는 반비례의 관계를 갖는다. 이러한 대기압이 압력변화를 수위로 환산한 후 수위변화량과 기압변화량과의 비율을 대기압효율이라 한다. 본역 경상계 퇴적층에 있어 주 대수층은 파쇄대, 절리면, 층리면과 지역적으로 분포하는 marl층내에 분포하는 용해공극 등에 의해 이루어진다. 본역내 대기압 효율의 분포는 8-90%로서 지역적 특성에 따라 Confinde, Unconfinde, Semi-Confined Aqifer 가 분포함을 알 수 있다. 대기압효율은 저류계수와 반비례함으로 양수시험 이전의 대수층 특성파악을 위한 경제적인 방법이기도 하다.

• 상하수도학회지
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• 제22권6호
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• pp.681-687
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• 2008

It is well known that the water infiltration rate depends on soil properties such as soil water content, water head, capillary suction, density, hydraulic conductivity, and porosity. However, most of proposed infiltration models assume that the air phase is continuous and in equilibrium with the atmosphere or air compression and air entrapment on infiltration was not considered. This study presents experimental results on unsaturated water infiltration to relate air entrapment and hydraulic conductivity function based on soil air properties. The objectives of this study were to measure change of soil air pressure ahead of wetting front under air drain and air confined condition to find the confined air effect on infiltration rate, to reduce the entrapped air volume related with soil air pressure to increase the soil permeability, and to make a basis of infiltration process model for the purpose of improvement of infiltration rate in the homogeneous soil column. The results of the work show that soil air pressure increases according to increasement of the saturated soil depth rather than the wetting front depth during infiltration process.

• Steel and Composite Structures
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• 제21권2호
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• pp.411-427
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• 2016

While the cyclic behaviour of fiber-reinforced polymer (FRP)-confined columns is studied rather extensively, the cyclic response especially the energy dissipation of FRP-confined damaged and undamaged square RC columns is not yet fully understood. In this paper, an experimental and numerical investigation was conducted to study the cyclic behavior of two different types of Carbon FRP (CFRP)-confined square RC columns: strengthened and repaired. The main variables investigated are initial damage, confinement of CFRP, longitudinal steel reinforcement ratio. The experimental results show that lower initial damage, added confinement with CFRP and longitudinal reinforcement enhance the ductility, energy dissipation capacity and strength of the columns, decrease the stiffness and strength degradation rates of all CFRP-confined square RC columns. Two hysteretic constitutive models were developed for confined damaged and undamaged concrete and cast into the non-linear beam-column fiber-based models in the software Open System for Earthquake Engineering Simulation (OpenSees) to analyze the cyclic behavior of CFRP-confined damaged and undamaged columns. The results of the numerical models are in good agreement with the experiments.

• Tribology and Lubricants
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• 제19권5호
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• pp.245-250
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• 2003

Water is known to playa crucial role on friction of moving parts in nanoscale contact. Little is, however, known about the tribological behavior of a solid surface that is covered with water adsorption layer. The objective of this study is to investigate the nanotribological behavior of the water layer in relation to water affinity of the surface and relative humidity. This paper presents an examination of the frictional behavior of water adsorption layer as 'confined liquid film'. It is shown that the friction is inversely proportional to the hydrophilicity of surface and relative humidity. On the other hand, friction of hydrophobic surface is not influenced by relative humidity. A model is proposed for the water-mediated contact in which it is shown that the water layer between two hydrophilic surfaces with high relative humidity behaves as a lubricant.

• 한국수자원학회:학술대회논문집
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• 한국수자원학회 1983년도 제25회 수공학 연구발표회 논문초록집
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• pp.80-83
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• 1983