• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.7 no.4
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• pp.622-632
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• 1995

The present numerical study is aimed to investigate time-dependent characteristics of a two-dimensional lid-driven square cavity flow of three high Reynolds numbers, $7.5{\times}10^3$, $10^4$ and $3{\times}10^4$. A conservative convection term on irregular grids was adopted by renewing the MAC type difference schemes on regular grids. Relaxation of velocity and pressure is implemented by SOLA algorithm. In case of $Re=7.5{\times}10^3$, flow behavior converges to steady state after a transient period. But for $Re=10^4$, periodic unsteady sinusoidal fluctuation of local velocity and kinetic energy is found and continuous movements of small eddies in the secondary flow regions are also discovered. Random generation of eddies and their active migrating behavior are detected for $Re=3{\times}10^4$, resulting in complete unsteady and non-linear flow characteristics. And, an organized structure similar to a Moffat vortex is also observed from the time-mean flow patterns. Furthermore, a typoon-like vortex(TLV) appears intemittently and rotates along the separation regions and boundary layers.

• Journal of the Korean Solar Energy Society
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• v.29 no.4
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• pp.58-64
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• 2009

This aim of the study is to demonstrate the effect of a photovoltaic module installed on a small wind-photovoltaic hybrid generation system. Computational fluid dynamics(CFD) is used to interpret the velocity field around the photovoltaic module and the blade areas of a wind turbine. According to the simulation results, it is obvious that x_velocity and y_velocity varies very significantly with time near the photovoltaic module. This would lead to an increase of periodic wind load caused by flow separation at the edge of the photovoltaic module. This study discusses the flow characteristics in term of velocity and frequency analysis. Moreover we suggest a distance between a photovoltaic module and a wind turbine to avoid partially the negative effect caused by the photovoltaic module.

• Bulletin of the Korean Chemical Society
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• v.24 no.10
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• pp.1485-1489
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• 2003

The gelation for di-(2-ethylhexyl) phthalate (DEHP)-plasticized poly(vinyl chloride) was studied by measuring time-resolved small-angle X-ray scattering (SAXS) and a flow of the solutions in test tube. It was found that for the gelation there were three regimes. At Regime I, the solution rapidly changed to a gel, and the SAXS intensity showed a peak and the peak intensity increased, keeping the peak angle constant. Applying the SAXS intensity to the kinetic analysis of the liquid-liquid phase separation, it was revealed that the spinodal decomposition proceeded to develop a periodic length of 29.9 nanometer in size, a hydrogen-bonding-type association in polymer rich phase followed, and then it induced fast gelation rate. At Regime II, the gelation slowly occurred and the SAXS intensity was not observed, suggesting that a homogeneous gel network was formed by a hydrogen-bonding. At regime III, the solution was a homogeneous sol.

• Korean Journal of Metals and Materials
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• v.49 no.11
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• pp.910-915
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• 2011

The microstructures and mechanical properties of roll-bonded STS439/Al1050/STS304 clad materials were investigated after an annealing process at various temperatures. Interfacial layer was developed at the STS439/Al1050 and Al1050/STS304 interfaces at $550^{\circ}C$. STS439/Al1050/STS304 clad metals fractured suddenly in a single step and the fracture decreased with increasing annealing temperatures at $450^{\circ}C$. After annealing at $550^{\circ}C$, samples fractured in three steps with each layer fracturing independently. Interfacial layers formed at $550^{\circ}C$ with a high Vickers microhardness were found to be brittle. During tensile testing, periodic parallel cracks were observed at the interfacial reaction layer. Observed micro-void between Al1050 and the interfacial layer was found to weaken the Al1050/reaction layer interface, leading to the total separation between Al1050 and the reaction layer.

• Journal of Software Assessment and Valuation
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• v.15 no.1
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• pp.109-114
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• 2019

In this paper, simulations of S-parameter and characteristic impedance for the probe pin are performed and its high-frequency performance is analyzed. The probe pins are arranged with one signal pin in the center and four ground pins on the top, bottom, left and right sides. The insertion loss and return loss of the probe pin are calculated while increasing the separation between the probe pins to 0.35 mm, 0.40 mm, and 0.50 mm, respectively. It is confirmed that the probe pin has different features of the insertion loss due to its periodic resonance phenomenon. Effect of the characteristic impedance on pitch and assignment of the probe pin is also analyzed. It is verified that there are a number of ground pins whose characteristic impedance is close to 50 Ω.

• Journal of the Microelectronics and Packaging Society
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• v.26 no.1
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• pp.9-15
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• 2019

Here, we present a facile route to fabricate a vertically stacked 3D porous structure-based triboelectric nanogenerator (TENG) that can be used to harvest energy from the friction in a repetitive contact-separation mode. The unit component of TENG consists of thin Al foil electrodes integrated with microstructured 3D foams such as Ni, Cu, and polyurethane (PU), which provide advantageous tribo-surfaces specifically to increase the friction area to the elastomeric counter contact surfaces (i.e., polydimethylsiloxane, PDMS). The periodic contact/separation-induced triboelectric power generation from a single unit of the 3D porous structure-based TENG was up to $0.74mW/m^2$ under a mild condition. To demonstrate the potential applications of our approach, we applied our TENGs to small-scale devices, operating 48 LEDs and capacitors. We envision that this energy harvesting technology can be expanded to the applications of sustainably operating portable electronic devices in a simple and cost-effective manner by effectively harvesting wasted energy resources from the environment.

• Journal of Conservation Science
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• v.38 no.4
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• pp.314-326
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• 2022

Investigation of conservation status, optical survey, infrared thermography, and ultrasonic examination were performed on Avalokitesvara Bodhisattva mural and Buddhist Monk Bodhidharma mural to determine the conservation status and physical properties. As a result of investigation of conservation status, the types of damage are largely divided into the wall and finishing layer damage, painting layer degradation, damage due to restoration materials, stains and contamination, and biological damage. As a result of the optical survey, drawing, stains, and repainted site were confirmed. Result of the infrared thermography, the delamination of the finishing layer was confirmed, and some locations and shapes of the wooden lath inside the wall were identified. The result of the 3D scanning, the deviation, and the separation of the wall was confirmed. As a result of ultrasonic examination, it was confirmed that the physical properties of the mural were identified and the ultrasonic speed was relatively low due to physical damage such as delamination and exfoliation of the finishing layer and cracking. Ultrasonic speed values were also high in some wall cracks or delamination, and it was confirmed by the infrared thermography results that the wooden lath inside the wall was located in those parts. It was possible to understand that the wooden lath inside the walls affects the ultrasonic speed during the ultrasonic examination. Therefore, management through periodic inspection of the relevant elements is necessary, and a countermeasure for damage that may occur in the future should be prepared along with intensive monitoring of the major damage identified in this diagnosis result.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.5 no.2
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• pp.77-85
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• 2000

Simulation of local external forcing and its response in the rotation table experiment has been investigated. Spatially-uniform external forcings have been applied in many experimental studies, however, based on the fact that the north-south distribution of the wind-stress curl and the existence of local maximum of the sea surface heat loss in the northern part of the East Sea, new method of combined effects of local forcings has been employed in separate experiments. Carefully designed local source or sink at the bottom of the cylindrical container can produce horizontal pressure gradient within the Ekman layer, and consequently the interior also attains the same pressure gradient that produces geostrophic interior circulation. In order to keep free surface during the local-surface cooling, a side-wall cooling method is suggested. For the various type of local forcing including the effects local cooling and the periodic change of local wind-stress curl, western-boundary flow in terms of its strength, position of separation from the boundary have been observed.

• Journal of the korean academy of Pediatric Dentistry
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• v.36 no.4
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• pp.586-590
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• 2009

Leukocyte adhesion deficiency is rare inherited defect on phagocytic function resulting lack of leukocyte cell surface expression of $\beta2$ integrin molecule that are essential for leukocyte adhesion to endothelial cells and chemotaxis. Clinical features of patients with leukocyte adhesion deficiency type I include recurrent necrotic infection of the skin mucous membranes, and intestinal tract with septicemia, and omphalitis arising from delayed umbilical cord separation. Oral manifestations are severe progressive periodontitis with alveolar bone loss, periodontal pockets, and partial and total premature loss of the deciduous and permanent dentitions. We report a case of leukocyte adhesion deficiency type I in a 5-year-old child with severe periodontitis. In order to prevent local and systemic infection, we controlled periodontal disease with periodic oral prophylaxis. Oral swabs and blood cultures were perfomed for suspected infection, so that optimal measures were taken through the use of appropriate antibiotics.

• Korean Journal of Social Welfare
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• v.40
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• pp.38-67
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• 2000

The study aims to understand the traditional context of the social policies in Germany by reviewing the course of transition of the traditional, ancient and/or medieval social policies or ideas of social policy in the country as a typical example of such transitions, which started being passed over to the modern civic society at the end of the medieval age, that is, during the 15th and 16th centuries. One of the reasons why the domestic interest in the German social policy is higher than the actual research achievements and frequently discussed seems explainable because a social security or welfare policy through a social insurance was initiated in Germany for the first time over the world in the 19th century. Notwithstanding, however, that all of us know that such a policy was not made in a day, cases are sometimes visible where focuses are easily drawn only to the periodic and economical phenomena in the 19th century and the strategic option of Preussen. Moreover, no literature which integrates thoroughly or publicly the social policies in Germany has been introduced at home, and some research books or study papers, if any, are inclined to concentrate merely on the social policies after the 19th century. Indeed, there are views, not rare, that a social policy of a national dimension was initiated along with the establishment of capitalism or an industrial society. According to such views, an industrial society or capitalism was begun to shape in the 19th century, and it is accordingly so national to lay our focuses on the social policies after the century. But from the fact that a national social policy existed much farther before the capitalism was established, it can be inferred that such policies were inevitable in all societies where a social issue existed. In the case of our country which experienced a more serious separation from the tradition than other countries by her rapid industrialization and Westernization, it is true that some traditional traces remain still regardless of their actual realization.