• Proceedings of the Korea Technical Association of the Pulp and Paper Industry Conference
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• 2006.06b
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• pp.471-474
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• 2006

Environment-friendly shock-absorbing materials were made of wastepaper such as old corrugated containers (OCC) and old newspapers (ONP) with a vacuum forming method. The plate-like cushioning materials made of OCC and ONP respectively by vacuum forming showed superior shock-absorbing properties with lower elastic moduli compared to expanded polystyrene (EPS) and pulp mold. Even though the plate-like materials had many free voids in their fiber structure, their apparent densities (${\approx}0.1g/cm^{3}$) were a little higher than that of EPS (${\approx}0.03g/cm^{3}$) and much lower than that of pulp mold (${\approx}0.3g/cm^{3}$). However, the elastic moduli of the cushioning materials made of wastepaper were much lower than that of EPS or pulp mold. This finding implies that the cushioning materials made of OCC fibers containing more lignin than ONP show better shock-absorbing properties than ONP Moreover, the cushioning materials made of OCC and ONP respectively showed greater porosity than pulp mold. The addition of cationic starch to the cushioning materials contributed to an increase in the elastic modulus to the same level as that of EPS. Furthermore, the deterioration in fiber quality by repeated use of wastepaper played a great role in improving shock-absorbing ability.

• Composites Research
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• v.33 no.2
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• pp.76-80
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• 2020

In this study, vacuum bag hot-press (V-HP) process can be used as an out-of-autoclave (OOA) process by improving the inefficient process of the autoclave forming method with excellent physical properties and surface quality. A carbon fiber composite was molded via V-HP process and analyzed the physical properties and microstructures between composites manufactured by autoclave (AC) process and hot-press process (HP). The tensile strength of the composite materials using the V-HP process was 320.6 MPa and the AC process samples found to be substantially close to the tensile strength of 335.3 MPa. As a result of confirming the surface quality of the composite material using SEM, it was confirmed that in the V-HP process, the removal state of pores due to volatile solvent in the resin was slightly lower than that of the AC process, but it had a considerably superior surface compared to the HP process.

• Journal of the Korean Society of Food Culture
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• v.39 no.2
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• pp.119-126
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• 2024

This study was conducted to examine the microbiological quality indicators (total bacterial count and coliform count) and physicochemical quality indicators (pH, redness, volatile basic nitrogen [VBN] content) of meat according to various storage temperatures (-20~15℃) and packaging methods (wrap, vacuum). Based on these results, we proposed a safe consumption period. Redness, pH, and VBN content were not considered appropriate for setting the expiration date, as the redness and pH of the meat after spoilage were better than the standard values for both vacuum and wrap packaging (p<0.05). Additionally, the VBN content at 2 and 4℃ increased slightly (fresh level) until the initial time of spoilage (1.0×10⁶ colony-forming unit [CFU]/cm²) and then increased rapidly thereafter. Therefore, the results were not consistent with microbial spoilage. When the decay point was evaluated based on the presence of microorganisms, vacuum packaging extended the storage period approximately 2.5-fold when compared with wrap packaging, and the meat could be stored at 2 or 4℃ for 40 or 23 days, respectively. Therefore, to evaluate meat quality, microbial indicators should be considered first. The microbiological standards proposed in this study can be used for safety management during the distribution of meat. However, to ensure meat safety, additional investigations of appropriate indicators of freshness must be conducted.

• Composites Research
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• v.26 no.1
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• pp.42-47
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• 2013

In this study, an economical and effective processing technique to form multiple dimples on the surface of a composite part, which are known to be useful to improve aerodynamic performance and heat dissipation. Forming dimples on the surface using molds is an expensive processing because forming multiple tiny positive spheres on the surface of the mold requires much time and effort. In this study, plates with multiple round holes are utilized as a core to form dimples on the carbon/epoxy composite skin covering the core. A vacuum bagging process is used to apply pressure on the surface while curing. Composite parts which have multiple dimples on the surface can be utilized in the field which needs high aerodynamic performance and heat dissipation ability such as high speed sports car bodies.

• Proceedings of the Membrane Society of Korea Conference
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• 2003.07a
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• pp.133-135
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• 2003

The removal of dissolved oxygen(DO) from water was studied using a poly(vinyliene fluoride)(PVDF) hollow fiber membrane contactor(HFMC) with the vacuum degassing process(VDP), Asymmetric porous PVDF hollow fiber membranes (HFM) for membrane contactor were prepared by a wet phase inversion method. In spinning of these PVDF hollow fibers, dimethy lacetamide (DMAc), LiCl and pure water were used as a solvent, a pore-forming additive and internal/external coagulant, respectively. The characteristics of the structure(pore size, porosity etc.) of the prepared PVDF HFMs as a function of concentration of pore-forming additive in polymer dope solution were studied. Also, the removal efficiency of DO from water according to flow rates of water, using PVDF HFMC with VDP, was studied. The performance of the asymmetric porous PVDF HFMC and a symmetric porous PP HFMC commercialized were compared. As a result, the asymmetric porous PVDF HFMC showed higher removal efficiency of DO than that of a symmetric porous PP HFMC.

• Journal of the Korean Society for Precision Engineering
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• v.29 no.9
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• pp.946-957
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• 2012

The objective of this paper is to investigate into the development of a thin flat panel photo-bioreactor case with characteristics shapes. The thin flat panel photo-bioreactor case was designed to be manufactured from a plastic thermoforming process. A proper design with a relatively high rigidity was obtained through the structural analyses for different designs of the photo-bioreactor case. The thermoforming analyses were performed. From the results of the thermoforming analyses, a proper forming condition and the formability of the designed plastic photo-bioreactor case were estimated. The thermoforming moulds for the flat panel photobioreactor cases were manufactured. The thermoforming experiments were performed to examine the manufacturability of the designed flat panel photo-bioreactor cases. From the results of the thermoforming experiments, it was shown that thin flat panel photo-bioreactor cases with characteristic shapes can be manufactured from the designed thermoforming mould and process.

• Journal of the Korean Society for Precision Engineering
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• v.30 no.6
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• pp.567-572
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• 2013

In many electro-devices, the vacuum process is used as the manufacturing process. However, the vacuum process has a problem, it is difficult to apply to a continuous process such as a R2R(roll to roll) printing process. In this paper, we propose an ESD (electro static deposition) printing process has been used to apply an organic solar cell of thin film forming. ESD is a method of liquid atomization by electrical forces, an electrostatic atomizer sprays micro-drops from the solution injected into the capillary with electrostatic force generated by electric potential of about several tens kV. The organic solar cell based on a P3HT/PCBM active layer and a PEDOT:PSS electron blocking layer prepared from ESD method shows solar-to-electrical conversion efficiency of 1.42% at AM 1.5G 1sun light illumination, while 1.86% efficiency is observed when the ESD deposition of P3HT/PCBM is performed on a spin-coated PEDOT:PSS layer.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.08a
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• pp.307-307
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• 2012

In this study, we investigated that the resistance switching characteristics of Al-doped MgOx films with increasing Al doping concentration and increasing film thickness. The Al-doped MgOx based ReRAM devices with a TiN/Al-doped MgOx/Pt/Ti/SiO2 were fabricated on Si substrates. The 5 nm, 10 nm, and 15 nm thick Al-doped MgOx films were deposited by reactive dc magnetron co-sputtering at $300^{\circ}C$ and oxygen partial ratio of 60% (Ar: 16 sccm, O2: 24 sccm). Micro-structure of Al-doped MgOx films and atomic concentration were investigated by XRD and XPS, respectively. The Al-doped MgOx films showed set/reset resistance switching behavior at various Al doping concentrations. The process voltage of forming/set is decreased and whereas the initial current level is increased with decreasing thickness of Al-doped MgOx films. Besides, the initial current of Al-doped MgOx films is increased with increasing Al doping concentration in MgOx films. The change of resistance switching behavior depending on doping concentration was discussed in terms of concentration of non-lattice oxygen of Al-doped MgOx.

• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.175.1-175.1
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• 2016

In recent, tract infections such as atopic dermatitis, allergic rhinitis and a respiratory disease are increasing, giving rise to the atmospheric pollution, inflow of micro-size dust and side effect of humidifier disinfectant. In this context, the environment-friendly technology is required to eliminate airborne pathogens. We propose solution of the previous problems, making use of Radical Mist Generator (RMG). Existing technologies of air purification using a gas discharge produce harmful substances such as ozone, NOx, etc. However, the RMG uses a pure water as a plasma forming material. The RMG sprays the water mist, which contains reactive radicals to sterilize microorganisms. RMG is comprised of a power supply, plasma electrodes and a nozzle. In order to analyze the electrical characteristic and concentrations of reactive radicals, we employ an oscilloscope and a titration method. To test the sterilization effect of RMG, we used E.coli. We confirmed that E.coli was killed over 90%. Eventually, we expect that RMG can be promising tool for a purified system.

• International Journal of Precision Engineering and Manufacturing
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• v.2 no.3
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• pp.47-53
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• 2001

This paper investigates the characteristics of interlaminar fracture toughness of foam core sandwich structures under opening mode by using the double cantilever beam (DCB) specimens which are Carbon/Epoxy and foam core composites. Instead of using a DCB specimen of symmetric geometry, a non-symmetric DCB specimen was used to calculate the interlaminar fracture toughness. Three approaches for calculating the energy release rate(G$\sub$IC/) were used and fracture toughness of foam core sandwich structures made by autoclave, vacuum bagging and hotpress were compared. Experiment, analysis using nonlinear beam bending theory, and numerical work by FEM methods were performed. Bonding surface compensation and equivalent moment of inertia were used to calculate the energy release rate in nonlinear analytical work. Conclusions of experimental, nonlinear analytical and FEM methods were compared. It is, also, shown that the vacuum bagging forming can substitute the method of autoclave without serious loss of Mode I energy release rate(G$\sub$I/).