• Applied Chemistry for Engineering
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• v.17 no.6
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• pp.604-608
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• 2006

Polymer composites for measuring the radioactive contamination are prepared by coating ZnS(Ag) powders as a scintillator on polysulfone base layer. The composites consist of the active layer for a scintillation reaction with radioactive wastes and the transparent support layer for transmittance of light photons emitted by scintillation in the active layer. The binding of the active layer, including ZnS(Ag), on the support layer is proceeded via coating with polysulfone as a binder, without any extra adhesive. The coating was obtained by either casting via a Doctor Blade as applicator or screen printing. The prepared composites feature a monolithic structure, resulting in the complete adhesion between two layers. The composite prepared by the casting technique using an applicator holds a good detection efficiency in measuring the alpha radionuclide, but its structure becomes fragile because of warping in morphology. On the contrary, the composite prepared by the screen printing shows a good detection capacity as well as a good stability in a mechanical shape.

• Journal of the Korean Society of Marine Environment & Safety
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• v.18 no.2
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• pp.145-152
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• 2012

As the problems of global warming are brought up recently, many skillful solutions for developing new renewable energy are suggested. One of the most remarkable things is ocean energy. Korea has abundant ocean energy resources owing to geographical characteristics surrounded by sea on three sides, thus the technology of commercialization about tidal current power, wave power is demanded. Especially, Tidal energy conversion system is a means of maintaining environment naturally. Tidal current generation is a form to produce electricity by installing rotors, generators to convert a horizontal flow generated by tidal current into rotating movement. According to rotor direction, a tidal current turbine is largely distinguished between horizontal and vertical axis shape. Power capacity depends on the section size crossing a rotor and tidal current speed. We therefore investigated three dimensional flow analysis and performance evaluation using commercial ANSYS-CFX code for an 100 kW class horizontal axis turbine for low water level. Then We also studied three dimensional flow characteristics of a rotating rotor and blade surface streamlines around a rotor. As a result, We found that torque increased with TSR, the maximum torque occurred at TSR 3.77 and torque decreased even though TSR increased. Moreover we could get power coefficient 0.38 at designed flow velocity.

• Journal of Korean Society of Environmental Engineers
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• v.37 no.1
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• pp.23-33
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• 2015

This study was carried out for the purpose of minimizing the area of rapid flow inside the water tank. And the shape of incurrent canal was improved, and then the characteristics of fluid flow occurring inside the water tank was analyzed by using the Computational Fluid Dynamics (CFD) simulation method. better multiple hoe screw nozzle incurrent canal was used instead of conventional drop current canal used for the water tank. And according to the results of analyzing the characteristics of fluid flow, in case a screw blade was installed inside the nozzle, fluid flow was sprayed wide. And wide fluid flow was shown inside the cylindrical water tank too. Besides, a tracer simulation was carried out, in case of installing 1 and 2 multiple hoe screw nozzle incurrent canals at the cubic water tank. As a result, MODAL, MODAL index value was close to 1, in case of installing 2 canals. Therefore, it was possible to obtain the results of being close to the characteristics of plug flow.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2017.05a
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• pp.248-250
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• 2017

The Mar-M-247 alloy is one of the most widely used materials for gas turbine components in aerospace filed and it shows excellent high temperature strength properties. Hot section parts, such as turbine nozzle and blade, are difficult to manufacture because of their complicated shape. So, the joining process usually applies to them. In this study, the high-temperature behavior of Mar-M-247 alloy at liquid diffusion bonding was investigated. Thus, we performed the diffusion bonding at $1,121^{\circ}C$ for 7 minutes, and observed changes in high temperature strength. As a result, the strength of the bonded specimens decreased by about 70% at $649^{\circ}C$, 60% at $825^{\circ}C$, and 45% at $1,000^{\circ}C$ compared to the base metal. As a result of observing the strength change with bonding time, the specimen bonded for 720 minutes showed a similar strength with the base metal at $649^{\circ}C$. Inferring this result, the joint is considered to be the one-body part.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2008.03a
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• pp.25-34
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• 2008

In this paper, three-dimensional multiblade row unsteady Navier-Stokes simulations at a hot streak temperature ratio of 2.0 have been performed to reveal the effects of rotor tip clearance on the inlet hot streak migration characteristics in low pressure stage of a Vaneless Counter-Rotating Turbine. The hot streak is circular in shape with a diameter equal to 25% of the high pressure turbine stator span. The hot streak center is located at 50% of the span and the leading edge of the high pressure turbine stator. The tip clearance size studied in this paper is 2.0mm(2.59% high pressure turbine rotor height, and 2.09% low pressure turbine rotor height). The numerical results show that the hot streak is not mixed out by the time it reaches the exit of high pressure turbine rotor. The separation of colder and hotter fluid is observed at the inlet of low pressure turbine rotor. Most of hotter fluid migrates towards the rotor pressure surface, and only little hotter fluid migrates to the rotor suction surface when it convects into the low pressure turbine rotor. And the hotter fluid migrated to the tip region of the high pressure turbine rotor impinges on the leading edge of the low pressure turbine rotor after it goes through the high pressure turbine rotor. The migration of the hotter fluid directly results in very high heat load at the leading edge of the low pressure turbine rotor. The migration characteristics of the hot streak in the low pressure turbine rotor are dominated by the combined effects of secondary flow and leakage flow at the tip clearance. The leakage flow trends to drive the hotter fluid towards the blade tip on the pressure surface and to the hub on the suction surface, even partial hotter fluid near the pressure surface is also driven to the rotor suction surface through the tip clearance. Compared with the case without rotor tip clearance, the heat load of the low pressure turbine rotor is intensified due to the effects of the leakage flow. And the numerical results also indicate that the leakage flow effect trends to increase the low pressure turbine rotor outlet temperature at the tip region.

• The Journal of the Acoustical Society of Korea
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• v.37 no.6
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• pp.396-403
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• 2018

In this paper, a high-performance and low-noise centrifugal fan is developed for cooling automotive seats which provide a driver with pleasant driving environment. First, the flow characteristics of the existing fan unit was analyzed using a fan performance tester and CFD (Computational Fluid Dynamics) simulations. The analysis of the predicted flow field indicated vortex flow near the tip of fan hub and stagnation flow on the top of fan hub. Two design points are devised to reduce the vortex flow and the stagnation flow observed in the existing fan unit. First, the cut-off clearance which is the minimum distance between the fan blade and the fan housing is increased to reduce the vortex strength and, as a result, to reduce the overall sound pressure level. Second, the hub shape is more modified to eliminate the stagnation flow. The validity of proposed design is confirmed through the numerical analysis. Finally, a prototype is manufactured with a basis on the numerical analysis result and its improved flow and noise performances are confirmed through the P-Q curves measured by using the Fan Tester and the SPL (Sound Pressure Level) levels measured in the anechoic chamber.

• Journal of Industrial Convergence
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• v.21 no.2
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• pp.93-101
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• 2023

In this study, the physical and chemical fiber damage caused by knives, scissors, and chemicals was analyzed and used as technical data to determine the cause of the damage. Using 4 types of knives, 5 types of scissors and 4 types of chemicals(Sulfuric Acid, Hydrochloric Acid, Sodium Hydroxide, Potassium Hydroxide) physical and chemical to Cotton, Wool, Polyester, Rayon, T/C (Polyester 50%, Cotton 50%), T/W (Polyester 50%, Wool 50%) Damages were created and analyzed for damage caused by tools and chemicals. For penetrating damage caused by knives and scissors, 'V' type damage was generally seen when the blade part was penetrated, 'T', 'ㅁ', ''C' type damage was found, and in the case of scissors, 'Y' ' This type of damage was common. Fiber damage caused by chemicals showed various damage such as remanent trace, corrosion, degraded, contracting, and color changes. Physical damage of fibers showed differences in characteristics according to the shape characteristics of tools, and chemical damage showed differences in characteristics according to chemicals and types of fibers.

• Korean Journal of Plant Taxonomy
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• v.34 no.2
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• pp.97-118
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• 2004

A comparative anatomical and ultrastructural study was undertaken to investigare on the leaf epidermis by light microscopy (LM) and scanning electron microscopy (SEM). On the basis of results from this study, it was grasped major characters of taxa and variation range of each character on the level of species, section and subgenus respectively. The shape of leaf epidermal cell was oblong to linear, which was varied by each taxon. Epidermal cell of taxa in sects. Microscordum, Anguinum, and Rhizirideum, which had wide leaf blade, oblong instead of linear shape in others examined taxa in this study. The leaf of taxa in sect. Anguinum was hypostomatic, while the rest of taxa had amphistomatic leaf. This was also one of characters which could discriminate taxa of sect. Anguinum from others. The guard cell in investigated taxa had not so much variation in the respect of its size. The number of stomata per unit area reduced by increasing size of epidermal cell, the fewest number of stomata per unit area was found in the taxa of sect. Anguinum. The type of stomatal apparatus of observed all taxa was anomocytic. It was found to know ultrastructural variation in the epidermal cell, like as patterns of sculpture on the cell wall, and features of deposition of wax by SEM. There were no depositions of wax in the taxa of sect. Microscordum and Anguinum, but fine thread-like structures which were parallel or cross to axis was found on the surface of epidermal cell respectively. The patterns of sculpture on the cell were prominent straight in sects. Recticulato-bulbosa and Rhizirideum, discontinuous line in the sect. Oreiprason. The epicuticular wax had been deposited on the surface of its epidermal cell in all taxa except sects. Microscordum and Anguinum.

• Korean Journal of Materials Research
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• v.8 no.12
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• pp.1165-1169
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• 1998

A single crystal cast blade was manufactured by CMSX 6, one of the first generarion nickel based single crystal superalloys by the selector method in a vacuum furnace. The single crystal has been grown with cooling rate of 2.5 mm/min, after pouring the molten alloy of 163$0^{\circ}C$ to the mold heated to 150$0^{\circ}C$. The cast structure could be classified into matrix (dendrite) and eutectic regions in ${\gamma}$'shape and size. The eutectic region showed higher Ti content. As the additional results of ${\gamma}$'precipitates by EPMA and CBED analysis the ${\gamma}$'size was less than 0.5~0.7$\mu\textrm{m}$, showing the chemical composition close to Ni$_3$Al of Ll$_2$ lattice structure. But ${\gamma}$'size has increased to bigger than 1.0$\mu\textrm{m}$, being near to eutectic region, changing its shape to bar or huge block types. These showed the chemical structure near to Ni$_3$Ti of D $O_{24}$ lattice structure. Therefore, ${\gamma}$'morphology of dendrite and eutectic regions depends absolutely on its chemical composition and lattice structure.