• Proceedings of the KSME Conference
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• 2004.11a
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• pp.1499-1504
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• 2004

The effects of absorbing materials on the characteristics of supersonic jet noise were experimentally investigated using a convergent-divergent nozzle with a design Mach number of 2.0. Overall sound pressure levels (OASPL) and noise spectra were obtained at far-field locations. Schlieren optical system was used to visualize the flow-fields of supersonic jets. In order to investigate the effect of absorbing materials, baffle plates of different materials (metal, grass wool and polyurethane foam) were installed at the exit of the nozzle. Experiment was carried out over a wide range of nozzle pressure ratios from 2.0 and 18.0, which corresponds to over- and under-expanded conditions. The results obtained show that the screech tone amplitude and the overall sound pressure level reduce by using the baffle plates of absorbing materials, compared with the metal baffle plate. It is also found that the characteristics of supersonic jet noise are strongly dependent on the size of baffle plate.

• Structural Engineering and Mechanics
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• v.50 no.6
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• pp.817-834
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• 2014

An experimental program was designed in the current work to examine the structural behavior of ferrocement beams reinforced with composite materials under three point loadings up to failure. The experimental program comprised casting and testing of twelve ferrocement beams having the dimensions of 120 mm width, 200 mm depth and 1600 mm length. The twelve beams were different in the type of reinforcements; steel bars, traditional wire meshes (welded and expanded wire meshes) and composite materials (fiberglass wire meshes and polypropylene wire meshes). The flexural performances of the all tested beams in terms of strength, ductility, cracking behavior and energy absorption were investigated. Also all the tested beams were simulated using ANSYS program. The results of the experimental tests concluded that the beam with fiber glass meshes gives the lowest first crack load and ultimate load. The ferrocement beam reinforced with four layers of welded wire meshes has better structural behavior than those beams reinforced with other types of wire meshes. Also the beams reinforced with metal wire meshes give smaller cracks width in comparing with those reinforced with non-metal wire meshes. Also the Finite Element (FE) simulations gave good results comparing with the experimental results.

• Journal of the Korean Ceramic Society
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• v.48 no.2
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• pp.173-177
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• 2011

Decomposition promoting factors and decomposition mechanism in the zinc decomposition process of waste hard metals which are composed mostly of tungsten carbide and cobalt were evaluated. Zinc volatility amount was suppressed and zinc valatilization pressure was produced in the reaction graphite crucible inside an electric furnace for ZDP. Reaction was done for 2 h at $650^{\circ}C$, which 100 % decomposed the waste hard metals that were over 30 mm thick. As for the separation-decomposition of waste hard metals, zinc melted alloy formed a liquid composed of a mixture of ${\gamma}-{\beta}1$ phase from the cobalt binder layer (reaction interface). The volume of reacted zone was expanded and the waste hard metal layer was decomposed-separated horizontally from the hard metal. Zinc used in the ZDP process was almost completely removed-collected by decantation and volatilization-collection process at $1000^{\circ}C$.

• Journal of Sensor Science and Technology
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• v.14 no.3
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• pp.137-143
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• 2005

Research in the field of biosensor has enormously increased over the recent years. The metal-oxide semiconductor field effect transistor (MOSFET) type protein sensor offers a lot of potential advantages such as small size and weight, the possibility of automatic packaging at wafer level, on-chip integration of biosensor arrays, and the label-free molecular detection. We fabricated MOSFET protein sensor and proposed the gold-black electrode as the gate metal to improve the response. The experimental results showed that the output voltage of MOSFET protein sensor was varied by concentration of albumin proteins and the gold-black gate increased the response up to maximum 13 % because it has the larger surface area than that of planar-gold gate. It means that the expanded gate allows a larger number of ligands on same area, and makes the more albumin proteins adsorbed on gate receptor.

• Proceedings of the Korean Radioactive Waste Society Conference
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• 2018.11a
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• pp.379-379
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• 2018

MXenes are a new family of 2D transition metal carbide nanosheets analogous to graphene (Lv et al., 2017; Sun et al., 2018). Due to the easy availability, hydrophilic behavior, and tunable chemistry of MXenes, their use in applications for environmental pollution remediation such as heavy metal adsorption has recently been explored (Li et al., 2017). In this study, three-dimensional (3D) MXene ($Ti_3C_2T_x$) films with high adsorption capacity, good mechanical strength, and high selectivity for specific radionuclide from aquose solution were successfully fabricated by a polymeric precursor method using vacuum-assisted filtration. The highest removal efficiency on the films was 99.54%, 95.61%, and 82.79% for $Sr^{2+}$, $Co^{2+}$, and $Cs^+$, respectively, using a film dosage of 0.06 g/ L in the initial radionuclide solution (each radionuclide concentration = 1 mg/L and pH = 7.0). Especially, the adsorption process reached an equilibrium within 30 min. The expanded interlayer spacing of $Ti_3C_2T_x$ sheets in MXene films showed excellent radionuclide selectivity ($Cs^+$ and/or $Sr^{2+}/Co^{2+}$) (Simon, 2017). Besides, the MXene films was not only able to be easily retrieved from an aqueous solution by filtration after decontamination processes, but also to selectively separate desired target radionuclides in the solutions. Therefore, the newly developed MXene ($Ti_3C_2T_x$) films has a great potential for radionuclide removal from aqueous solution.

• Journal of Information Technology Services
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• v.19 no.6
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• pp.97-117
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• 2020

Five years have passed since the introduction of the smart factory amid the new opportunities for growth and job creation in relation to domestic manufacturing companies. Nevertheless, there is a lack of analysis on SMEs introduction smart factories. This study empirically analyzed the effects on the introduction of smart factories of domestic metal processing SMEs by distinguishing the characteristics of enterprises In this study, 103 companies which introduced smart factories and another 106 companies which did not introduce them were sampled. The Introduction of the Smart Factory was analyzed by four categories such as the Company characteristics (R&D capability, product production capability, organizational change), entrepreneur characteristics (risk sensitivity), relational characteristics (trust, dependence, cooperation, Influence), and structural characteristics (competition). As a result of the research, we found out product production capacity, risk sensitivity, trust and cooperation, Influence, and competition are statistically significant in the introduction of smart factory. But competition was characterized by a negative (-) sign opposite to the hypothesis. This study is meaningful in that the scope of the analysis has been expanded by analyzing whether smart factory was introduced or not considering the characteristics of the company. And there should be continuous research on its utilization as well as the introduction of smart factory.

• Wind and Structures
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• v.35 no.3
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• pp.213-227
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• 2022

The design of a building is a complex process that encompasses different fields: one of the most relevant is nowadays the energetic one, which has led to the introduction of new typologies of building envelopes. Among them, the Permeable Double Skin Façades (PDSF) are capable to reduce the solar impact and so to improve the energetic performances of the building. However, the aerodynamic characterization of a building with a PDSF is still little investigated in the current literature. The present paper proposes an experimental study to highlight the modifications induced by the outer porous façade in the aerodynamics of a building. A dedicated wind tunnel study is conducted on a rigid model of a prismatic high-rise building, where different façade configurations are tested. Specifically, the single-layer façade is compared to two PDSFs, the former realized with perforated metal and the latter with expanded metal. Outcomes of the tests allow estimating the cladding loads for all the configurations, quantifying the shielding effects ascribable to the porous layers that are translated in a significant reduction of the design pressure that could be up to 50%. Moreover, the impact of the PDSFs on the vortex shedding is investigated, suggesting the capability of the façade to suppress the generation of synchronised vortices and so mitigate the structural response of the building.

• The Journal of the Korea Contents Association
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• v.20 no.3
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• pp.687-694
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• 2020

Styrofoam is one of the most commonly used materials in everyday life, such as various packaging containers, toys, and buoys, and is likely to be found in crime scenes. However, due to the structural characteristics of Styrofoam, fingerprints cannot be deposited well. According to previous researches, powdering or cyanoacrylate fuming method was applied for developing fingerprints on Styrofoam. The purpose of this study was to investigate the effect of MMD I through comparative experiments of powdering. As a result of applying powder method and MMD I, MMD I was more effective than powder method on styrofoam.

• Analytical Science and Technology
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• v.23 no.3
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• pp.295-303
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• 2010

In this study, the wastewater-based reference material (RM) was prepared and certified for 7 trace metal elements with evaluation of uncertainties. The RM was distributed to 25 laboratories for the interlaboratory comparison testing. The certified values and expanded uncertainties were derived using ISO guideline 35 and the standard uncertainties for homogenieties were 0.43~2.67% of certified values. The analytical results from the interlaboratory comparison testing showed normal distributions and the robust means from the interlaboratory comparison testing were higher than the certified values of the RM for all analytes.

• Journal of the Korean Society of Marine Environment & Safety
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• v.19 no.6
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• pp.681-687
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• 2013

This study analyzed characteristics of 240 W high power LED lamps by comparing with those of traditional metal halide lamps. In addition, it analyzed the propriety of LED lamps as a source of light, considering seawater transmission characteristics. When Applying white LED package with the color temperature color temperature of 6500K, a 240W-LED fishing lamp has a characteristics of the luminous angle to be expanded to ${\pm}45^{\circ}$, the illumination change was improved to 0.8, as well as the luminance efficiency was improved to 98.8lm/W. As results of comparison between one 1,500W-metal halide lamp and four 240W-LED lamp with considering a seawater transmission and a luminous efficiency of scotopic vision, the radiant flux of two lamps were almost equal level at 50m depth and the luminous flux was 5% higher LED lamp than metal-halide lamp even if only applying the luminous efficiency of scotopic vision. As the luminous flux of LED lmap was 14% higher than that of metal-halide lamp with applying the luminous efficiency of scotopic vision to radiant flux at 50m depth, so LED fishing lamp was verified to alternative possibility of metal-halide lamp.