• Journal of Powder Materials
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• v.14 no.4
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• pp.261-264
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• 2007

The electromagnetic wave (EM) absorption properties of various particle size have been investigated in a sheet-type absorber using the $Fe_{73}Si_{16}B_{7}Nb_{3}Cu_{1}$ alloy powder. With decreasing the average particle size, the complex permeability (${\mu}_{r}$) and permittivity (${\varepsilon}_{r}$) increased and the matching frequency is shifted toward lower frequency. The fabricated EM wave absorbers showed permeability $2{\sim}6$, permittivity $17{\sim}23$ for a $-325{\sim}+400$ mesh sample, and the calculated power absorption was as high as 80% in the frequency range over 2 GHz.

• Journal of Sensor Science and Technology
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• v.24 no.2
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• pp.119-123
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• 2015

This paper presents the inkjet-printed flexible temperature and humidity sensor(F-TH sensor) using PEDOT:PSS. The series, mesh and parallel type sensing element using PEDOT:PSS ink was printed on the overhead projector(OHP) film. The fabricated sensor of each structure has the temperature sensitivity of $140{\Omega}/^{\circ}C$, $29{\Omega}/^{\circ}C$ and $1.4{\Omega}/^{\circ}C$ with linearity, respectively. Also the fabricated sensor was not only possible to measure a temperature, but also to detect humidity. The humidity sensitivity of $400{\Omega}/%RH$, $3.4{\Omega}/%RH$ and $3{\Omega}/%RH$ with linearity, respectively. The fabricated F-TH sensor is expected for the various applications such as electronic devices, bio-healthcare, industrial field.

• Environmental Engineering Research
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• v.19 no.3
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• pp.215-221
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• 2014

Nano-sized $TiO_2$ particles were produced by a premixed flame aerosol reactor, and they were immobilized on a mesh-type substrate in form of particulate film. The reactor made it possible maintaining the original particulate characteristics determined in the flame synthetic process. The particulate morphology and crystalline phase were not changed until the particulate were finally coated on the substrate, which resulted in the better performance of the photocatalytic conversion of the volatile organic compounds (VOCs) in the ultraviolet $(UV)-TiO_2$ system. In the flame aerosol reactor, the various specific surface areas and the anatase weight fractions of the synthesized particles were obtained by manipulating the parameters in the combustion process. The performance of the $TiO_2$ particulate films was evaluated for the destruction of the VOCs under the various UV irradiation conditions. The decomposition rates of benzene and formaldehyde under the irradiation of UV-C of 254 nm in wavelength were evaluated to check the performance of $TiO_2$ film layer to be applied in air quality control system.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.15 no.10
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• pp.5968-5973
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• 2014

The gate location in injection molding has a significant influence on the quality and productivity. Therefore, injection molding CAE is used to determine the gate location. With increasing injection molding CAE and the adoption of a 3D mesh, which takes more computation time for analysis, gate location optimization in the shortest time and least resources is the most challenging issue. In this paper, we propose a methodology for optimization based on the flow length to consider the flow balance and weld line. In addition, the flow balance is obtained in the disc-type plate while the weld lines exit the slit-holes to avoid a stress concentration.

• New & Renewable Energy
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• v.8 no.3
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• pp.6-13
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• 2012

This paper describes unsteady internal flow characteristics of a cathode air blower, used for the 1 kW fuel cell system. The cathode air blower considered in the present study is a diaphragm type blower. To analyze the flow field inside the diaphragm cavity, compressible unsteady numerical simulation is performed. Moving mesh system is applied to the numerical analysis for describing the volume change of the diaphragm cavity in time. Throughout a numerical simulation by modeling the inlet and outlet valves in a diaphragm cavity, unsteady nature of an internal flow is successfully analyzed. Variations of mass flow rate, force and pressure on the lower moving plate of a diaphragm cavity are evaluated in time. The computed mass flow rate at the same pressure and rotating frequency of a motor has a maximum of 5 percent error with the experimental data. It is found that flow pattern at the suction process is more complex compared to that at the discharge process. Unsteady nature of internal flow in the cathode air blower is analyzed in detail.

• Korean Journal of Materials Research
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• v.29 no.10
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• pp.603-608
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• 2019

Plastic waste is becoming a problem in various countries because of the difficulty of natural decomposition. One type is PET plastic(Polyethylene Terephthalate), which is often used as a bottle for soft drink packaging, and LDPE(Low Density Polyethylene), which is also widely used as a food or beverage packaging material. The use of these two types of plastic continuously, without good recycling, will have a negative impact on the environment. Building material waste is also becoming a serious environmental problem. This study aims to provide a solution to the problem of the above plastic waste and building material waste by making them into a mixture to be used as bricks. Research is carried out by mixing both materials, namely plastic heated at a temperature of $180-220^{\circ}C$ and building material waste that had been crushed and sized to 30-40 mesh with homogeneous stirring. The ratios of PET and LDPE plastic to building material waste are 9 : 1, 8 : 2, 7 : 3, 6 : 4 and 5 : 5. After heating and printing, density, water absorption and compressive strength tests are carried out. Addition of PET and LDPE plastic can increase compressive strength, and reduce water absorption, porosity and density. A maximum compressive strength of 10.5 MPa is obtained at the ratio of 6 : 4.

• Journal of the Society of Naval Architects of Korea
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• v.46 no.6
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• pp.675-687
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• 2009

In general, the forming process of the curved hull plates consists of sub tasks, such as roll bending, line heating, and triangle heating. In order to complement the automated curved hull forming system, it is necessary to develop an algorithm to classify the curved hull plates of a ship into standard shapes with respect to the techniques of forming task, such as the roll bending, the line heating, and the triangle heating. In this paper, the curved hull plates are classified by four standard shapes and the combination of them, or saddle, convex, flat, cylindrical shape, and the combination of them, that are related to the forming tasks necessary to form the shapes. In preprocessing, the Gaussian curvature and the mean curvature at the mid-point of a mesh of modeling surface by Coon's patch are calculated. Then the nearest neighbor method to classify the input plate type is applied. Tests to verify the developed algorithm with sample plates of a real ship data have been performed.

• Journal of Korean Association for Spatial Structures
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• v.22 no.1
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• pp.41-49
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• 2022

In the case of columns in buildings with soft story, the concentration of stress due to the difference in stiffness can damage the columns. The irregularity of buildings including soft story requires retrofit because combined load of compression, bending, shear, and torsion acts on the structure. Concrete jacketing is advantageous in securing the strength and stiffness of existing members. However, the brittleness of concrete make it difficult to secure ductility to resist the large deformation, and the complicated construction process for integrity between the existing member and extended section reduces the constructability. In this study, two types of Steel Grid Reinforcement (SGR), which are Steel Wire Mesh (SWM) for integrity and Steel Fiber Non-Shrinkage Mortar (SFNM) for crack resistance are proposed. One reinforced concrete (RC) column with non-seismic details and two columns retrofitted with each different types of proposed method were manufactured. Seismic performance was analyzed for cyclic loading test in which a combined load of compression, bending, shear, and torsion was applied. As a result of the experiment, specimens retrofitted with proposed concrete jacketing method showed 862% of maximum load, 188% of maximum displacement and 1,324% of stiffness compared to non-retrofitted specimen.

• Nuclear Engineering and Technology
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• v.53 no.5
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• pp.1483-1490
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• 2021

Many studies are undertaken into nuclear power plants (NPPs) in preparation for accidents exceeding design standards. In this paper, we analyze the applicability of various wireless communication technologies as accident countermeasures in different NPP environments. In particular, a commercial wireless communication module (WCM) is investigated by measuring leakage current and packet error rate (PER), which vary depending on the intensity of incident radiation on the module, by testing at a Co-60 gamma-ray irradiation facility. The experimental results show that the WCMs continued to operate after total doses of 940 and 1097 Gy, with PERs of 3.6% and 0.8%, when exposed to irradiation dose rates of 185 and 486 Gy/h, respectively. In short, the lower irradiation dose rate decreased the performance of WCMs more than the higher dose rate. In experiments comparing the two communication protocols of request/response and one-way, the WCMs survived up to 997 and 1177 Gy, with PERs of 2% and 0%, respectively. Since the request/response protocol uses both the transmitter and the receiver, while the one-way protocol uses only the transmitter, then the electronic system on the side of the receiver is more vulnerable to radiation effects. From our experiments, the tested module is expected to be used for design-based accidents (DBAs) of "Category A" type, and has confirmed the possibility of using wireless communication systems in NPPs.

• International conference on construction engineering and project management
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• 2009.05a
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• pp.794-799
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• 2009

The temperature control of in-place concrete is the most important factor for an early age of curing concrete. Heat stress of mass concrete caused by the heat of hydration can induce the crack of concrete, and a frost damage from cold weather casting concrete results defect on compressive strength and degradation of durability. Therefore, success and failure of concrete work is dependant on the measurement and control of concrete temperature. In addition, the compressive strength assessment of in-place concrete obtained from the maturity calculated from the history of temperature make a reduction of construction cycle time, possible. For that purpose, wireless temperature measuring system was developed to control temperature and assess strength of concrete. And, it was possible to monitor the temperature of concrete over 1km apart from site office and to take a proper measure; mesh-type network was developed for wireless sensor. Furthermore, curing control system that contains the program capable to calculate the maturity of concrete from the history of temperature and to assess the compressive strength of concrete was established. In this study, organization and practical method of developed curing control system are presented; base on in-place application case.