• Journal of The Korean Society of Agricultural Engineers
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• v.54 no.6
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• pp.101-109
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• 2012

Silt curtains are constructed for minimizing pollution of sediment dispersion in water bodies. In spite of wide uses of the silt curtains, there are few studies for analyzing the effectiveness of them with respect to their dimension and hydraulic characteristics. Currently, the market of silt curtains does not provide the various dimension of them due to the limit of information regarding its effectiveness on reducing sediment pollution. In this study, a series of experiments were conducted to investigate hydraulic characteristics around the silt curtains under the different flow conditions. For this study, a silt curtain was fabricated and an open channel with 30cm of width and 40cm of depth was used. The results indicated that the silt curtain was not effective in preventing dispersion at flow velocities over 0.5m/s in real conditions. Based on the experimental results, it is required that approaching velocity should be minimized and the weight of bottom be increased in order to reduce deformation. The results of this study will provide information required to design appropriate dimension of silt curtains in various water environment such as velocity and water depths.

• Journal of Biomedical Engineering Research
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• v.16 no.1
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• pp.67-76
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• 1995

Explosive evaporative removal process of biological tissue by absorption of a CW laser has been simulated by using gelatin and a multimode Nd: YAG laser. Because the point of maximun temperature of laser-irradiated gelatin exists below the surface due to surface cooling, evaporation at the boiling temperature is made explosively from below the surface. The important parameters of this process are the conduction loss to laser power absorption (defined as the conduction-to-laser power parameter, Nk), the convection heat transfer at the surface to conduction loss (defined as Bi), dimensionless extinction coefficient (defined as BrJ, and dimensionless irradiation time (defined as Fo). Dependence of Fo on Nk and Bi has been observed by experiment, and the results have been compared with the numerical results obtained by solving a 2-dimensional conduction equation. Fo and explosion depth (from the surface to the point of maximun temperature) are increased when Nk and Bi are increased. To find out the minimum laser power for explosive evaporative removal process, steady state analysis has been also made. The limit of Nk to induce evaporative removal, which is proportional to the inverse of the laser power, has been obtained.

• Wind and Structures
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• v.21 no.6
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• pp.597-607
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• 2015

With an increasing demand of a renewable energy, new offshore wind turbine farms are being planned in some parts of the world. Foundation installation asks a significant cost of the total budget of offshore wind turbine (OWT) projects. Hence, a cost reduction from foundation parts is a key element when a cost-efficient designing of OWT budget. Mono-piles have been largely used, accounting about 78% of existing OWT foundations, because they are considered as a most economical alternative with a relatively shallow-water, less than 30 m of seawater depth. OWT design standards such as IEC, GL, DNV, API, and Eurocode are being developed in a form of reliability based limit state design method. In this paper, reliability analysis using the response surface method (RSM) and numerical simulation technique for an OWT mono-pile foundation were performed to investigate the sensitivities of mono-pile design parameters, and to find practical implications of RSM reliability analysis.

• Nuclear Engineering and Technology
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• v.25 no.2
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• pp.215-221
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• 1993

A required initial condition for a steam explosion to occur following core meltdown accidents of a nuclear power plant is the formation of a coarse mixture of molten fuel and water. The extent of a premixing is the measure of efficiency of steam explosion that may follow. A simple one-dimensional, transient model and the flooding criteria have been applied to evaluate the fuel/coolant mixing limit. Also, both instant breakup and dynamic breakup models for the mixing process have been separately used here and compared each other. The results indicate that fuel temperature, ambient pressure, mixing diameter, water depth, and pouring diameter are the important parameters affecting the mixing behavior.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2001.04a
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• pp.100-107
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• 2001

One major problem in the model testing is the boundary effect and size effect caused by the limit in the size of the container. To overcome this problem, various types of laminar boxes are gradually manufactured and used in the shaking table test, which ideally has zero stiffness to horizontal shear. In this study, a small-scale laminar box is manufactured, which is composed of 6 thin aluminum rectangular hollow plates, and its inside dimensions are 300 mm length by 200 mm width by 350 mm depth. Shaking table tests are performed both with the laminar box and the rigid box under the same conditions, where displacements and accelerations are measured at various points of the box and model ground. As result of analyzing the measured data, during the propagation of input seismic motion from the bottom to the ground surface, the relative displacement of the model ground and the amplification of acceleration is hardly amplified in the rigid box. Because of the effect of stress waves reflecting from the rigid wall, the acceleration is slightly decreased at the edge in the rigid box. The laminar box, manufactured in this study, has a problem in that the soil behavior at the edge of ground surface is affected by the inertia force of the top layer due to its excessive self-weight.

• Korean Journal of Adult Nursing
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• v.22 no.3
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• pp.342-351
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• 2010

Purpose: The purpose of this study was to determine an increase in the number of younger and middle-aged people who have a stroke and the differences in their recovery experience compared with older people. Methods: The research question for this study was "What is the recovery experience of young adults and middle-aged people who suffer a stroke?". In order to answer the question, the grounded theory method was utilized. The data was collected through individual in-depth interviews of six participants, their age ranged from 36 to 45 years old. Results: After comparative analysis, the core category was "standing up for oneself with limit". The experience process were categorized into four stages: 'Facing Reality stage', 'Motivation stage', 'Desire Recovery stage', 'Self-Overcoming stage'. Conclusion: Most of the research for the recovery process was prognostic in nature and the results. This study was demonstrated certain indicators which can be useful in further research.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.19 no.12
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• pp.1078-1084
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• 2006

Impurity contamination induced by $CF_4\;and\;HBr/Cl_2/O_2$ plasma etching on Si surface was examined by using surface spectroscopes. XPS(x-ray photoelectron spectroscopy) surface analysis showed that F of 0.4 at % exists in the surface layer in the form of Si-F bonding but Br and Cl are below the detection limit $(0.1{\sim}1.0%)$ of the spectroscope. Static-SIMS(secondary ion mass spectrometry) surface analysis showed that the etched Si surface was contaminated with etching gas elements such as H, F, Cl and Br, and they existed to the depth of about $20{\sim}40nm$. The etched Si surface was treated with three different methods that were HF dip, thermal oxidation followed by HF dip and oxygen-plasma oxidation followed by HF dip. They showed an effect in reducing the impurity contamination and the oxygen-plasma oxidation followed by HF dipping method appears to be a little bit more effective.

• ALGAE
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• v.22 no.1
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• pp.17-21
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• 2007

Sargassum filicinum Harvey, a brown alga (Phaeophyceae) native to Northeastern Asia, has been recently reported from the coast of Southern California (USA). Here we report the occurrence and range extension of this introduced species, as we found the alga at La Jolla and Rancho Packard in Todos Santos Bay, Baja California, Mexico. The first collections of S. filicinum correspond to several immature plants, found on September 8, 2005, drifting in the intertidal zone at La Jolla. Later on November 9, 2006, we found a well-established population in Rancho Packard in the middle intertidal zone to 2 m depth. Since S. filicinum is an annual monoecious species with air bladders, the risk there is a high risk of spreading rapidly along the Pacific, as in the case for S. muticum. The population in Rancho Packard extends 500 m along the coast, consisting mainly of young plants with an average length of 30 cm and a density of 5 thallus/m2. This is the first record of this invasive species for the Mexican Pacific coast, and it represents the southern limit along the Pacific coast of North America. This finding suggests that this invasive species has successfully colonized the Pacific coast of North America and its distributional range is still expanding.

• Geomechanics and Engineering
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• v.15 no.4
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• pp.947-955
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• 2018

In this study, we propose a three-dimensional simplified slope stability analysis using a hybrid-type penalty method (HPM). In this method, a solid element obtained by the HPM is applied to a column that divides the slope into a lattice. Therefore, it can obtain a safety factor in the same way as simplified methods on the slip surface. Furthermore, it can obtain results (displacement and strain) that cannot be obtained by conventional limit equilibrium methods such as the Hovland method. The continuity condition of displacement between adjacent columns and between elements for each depth is considered to incorporate a penalty function and the relative displacement. For a slip surface between the bottom surface and the boundary condition to express the slip of slope, we introduce a penalty function based on the Mohr-Coulomb failure criterion. To compute the state of the slip surface, an r-min method is used in the load incremental method. Using the result of the simple three-dimensional slope stability analysis, we obtain a safety factor that is the same as the conventional method. Furthermore, the movement of the slope was calculated quantitatively and qualitatively because the displacement and strain of each element are obtained.

• Computers and Concrete
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• v.14 no.1
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• pp.19-40
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• 2014

Reinforced concrete deep beams are structural beams with low shear span-to-depth ratio, and hence in which the strain distribution is significantly nonlinear and the conventional beam theory is not applicable. A strut-and-tie model is considered one of the most rational and simplest methods available for shear strength prediction and design of deep beams. The strut-and-tie model approach describes the shear failure of a deep beam using diagonal strut and truss mechanism: The diagonal strut mechanism represents compression stress fields that develop in the concrete web between diagonal cracks of the concrete while the truss mechanism accounts for the contributions of the horizontal and vertical web reinforcements. Based on a database of 406 experimental observations, this paper proposes a new strut-and-tie-model for accurate prediction of shear strength of reinforced concrete deep beams, and further improves the model by correcting the bias and quantifying the scatter using a Bayesian parameter estimation method. Seven existing deterministic models from design codes and the literature are compared with the proposed method. Finally, a limit-state design formula and the corresponding reduction factor are developed for the proposed strut-andtie model.