• Tribology and Lubricants
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• v.38 no.4
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• pp.121-127
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• 2022

This study presents the development of an integrated oil purification system consisting of moisture removal, oil flushing, and oil filtering devices. In this system, the oil flushing device is combined with a micro-bubble generator. Oil purification is necessary for ensuring the high performance of the lubricant through the efficient removal of contaminants and thus enables good maintenance of mechanical systems. The developed purification system removes moisture, varnish, and solid particles. Moreover, during oil purification, the oil flushing device separates foreign materials and contaminants remaining in the lubricating oil piping or mechanical systems. The microbubble generator, which is combined with the oil flushing device, can separate harmful contaminants, such as sludge, wear particles, and rust, from piping or lubrication systems through the cavitation effect. Moisture is removed using a double high-vacuum chamber, while sludge and varnish are removed via electro-absorption using a high-voltage generator. Additionally, the total maintenance cost of the system is reduced through the use of domestically fabricated cartridge filters composed of glass fiber and cellulose. The heater, which maintains the temperature of the lubricant at 60℃, can process 41,000 L of lubricant simultaneously. Multiple tests confirmed that the proposed integrated purification system exhibits good performance in oil flushing and removal of water and varnish.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2002.05a
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• pp.181-183
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• 2002

The accurate permeability for preform is critical to model and design the impregnation of fluid resin in the composite manufacturing process. In this study, the in-plane and transverse permeability for a woven fabric are predicted numerically through the coupled flow model which combines microscopic with macroscopic flow. The microscopic and macroscopic flow which are flows within the micro-unit and macro-unit cell, respectively, are calculated by using 3-D CVFEM(control volume finite element method). To avoid checker-board pressure field and improve the efficiency on numerical computation, A new interpolation function for velocity is proposed on the basis of analytic solutions. The permeability of plain woven fabric is measured through unidirectional flow experiment and compared with the permeability calculated numerically. Based on the good agreement of the results, the relationships between the permeability and the structures of preform such as the fiber volume fraction and stacking effect can be understood. The reverse and the simple stacking are taken in account. Unlike past literatures, this study is based on more realistic unit cell and the improved prediction of permeability can be achieved. It is observed that in-plane flow is more dominant than transverse flow in the real flow through preform and the stacking effect of multi-layered preform is negligible. Consequently, the proposed coupled flow model can be applied to modeling of real composite materials processing.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.11 no.4
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• pp.170-175
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• 2001

It was possible to grow the $Al_{2}O_{3}$ based $Y_{3}A_{5}O_{12}(YAG),ZrO_{2}$ binary and ternary eutectic fibers using micro-pulling down method with a growing rate of 0.1~15 mm/min. While $Al_{2}O_{3}/ZrO_{2}$ showed cellular-lamellar structure, $Al_{2}O_{3}$/YAG and $Al_{2}O_{3}$/YAG/$ZrO_{2}$ternary eutectic fibers showed homogeneous Chinese script lamellar structures. The microstructures of $Al_{2}O_{3}/ZrO_{2}$ binary eutectic fibers changed with solidification rate from lamellar pattern to cellular structure. The interlamellar spacing agreed with the inverse-square-root dependance on pulling rate according to $\lambda$=$kv_p\;{-1/2}$. $Al_{2}O_{3}/ZrO_{2}$ binary eutectic fibers recorded the highest tensile strength of about 1560MPa at room temperature. $Al_2O_3/YAG/ZrO_2$ternary eutectic fiber showed excellent thermal stability to $1200^{\circ}C$ without significant decrease. The maximum strength of ternary eutectic fibers recorded were 1100MPa at $25^{\circ}C$ and 970MPa at $1200^{\circ}C$, respectively.

• Food Science of Animal Resources
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• v.44 no.2
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• pp.269-283
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• 2024

Cultured meat is one of the research areas currently in the spotlight in the agricultural and livestock industry, and refers to cells obtained from livestock that are proliferated and differentiated and processed into edible meat. These cell-cultured meats are mainly studied at the lab-scale by culturing them in flasks, and for commercial use, they are produced using scaffolds that mimic cell supports. Scaffolds are broadly divided into fiber scaffolds, hydrogels, and micro-carrier beads, and these are classified according to processing methods and materials. In particular, a scaffold is essential for mass production, which allows it to have appearance, texture, and flavor characteristics similar to meat. Because cultured meat is cultured in a state where oxygen is blocked, it may be lighter in color or produce less flavor substances than edible meat, but these can be compensated for by adding natural substances to the scaffolds or improving fat adhesion. In addition, it has the advantage of being able to express the texture characteristics of the scaffolds that make up the meat in various ways depending on the materials and manufacturing methods of the scaffolds. As a result, to increase consumers' preference for cultured meat and its similarity to edible meat, it is believed that manufacturing scaffolds taking into account the characteristics of edible meat will serve as an important factor. Therefore, continued research and interest in scaffolds is believed to be necessary.

• Steel and Composite Structures
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• v.52 no.3
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• pp.249-271
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• 2024

In this scientific work, an analytical solution for the dynamic analysis of cross-ply and angle-ply laminated composite plates is proposed. Due to technical issues during the manufacturing of composite materials, porosities and micro-voids can be produced within the composite material samples, which can carry on to a reduction in the density and strength of the materials. In this research, the laminated composite plates are assumed to have new distributions of porosities over the plate cross-section. The structure is modeled using a simple integral shear deformation theory in which the transverse shear deformation effect is included. The governing equations of motion are obtained employing the principle of Hamilton's. The solution is determined via Navier's approach. The Maple program is used to obtain the numerical results. In the numerical examples, the effects of geometry, ratio, modulus ratio, fiber orientation angle, number of layers and porosity parameter on the natural frequencies of symmetric and anti-symmetric laminated composite plates is presented and discussed in detail. Also, the impacts of the kinds of porosity distribution models on the natural frequencies of symmetric and anti-symmetric laminated composite plates are investigated.

• Journal of Adhesion and Interface
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• v.11 no.4
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• pp.149-154
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• 2010

Interfacial evaluation was investigated for single-carbon fiber/phenolic and carbon nanotube (CNT)-phenolic composites by micromechanical technique and electrical resistance measurement combined with wettability test. Compressive strength of pure phenol and CNT-phenolic composites were compared using Broutman specimen. The contact resistance of CNT-phenolic composites was obtained using a gradient specimen by two and four-point methods. Surface energies and wettability by dynamic contact angle measurement were measured using Wilhelmy plate technique. Since hydrophobic domains are formed as heterogeneous microstructure of CNT in the surface, the dynamic contact angle exhibited more than $90^{\circ}$. CNT-phenolic composites exhibited a higher apparent modulus than neat phenolic case due to better stress transferring effect. Work of adhesion, $W_a$ between single-carbon fiber and CNT-phenolic composites exhibited higher than neat phenolic resin due to the enhanced viscosity by CNT addition. It was consistent with micro-failure patterns in microdroplet test.

• Korean Journal of Optics and Photonics
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• v.15 no.4
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• pp.385-390
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• 2004

In this paper, we designed a 4-bit optical true time-delay(TTD) for phased array antennas(PAAs), which is composed of a wavelength-fixed optical source, 2 ${\times}$ 2 optical MEMS switches, and fiber-optic delay lines. A 4-bit TTD with a unit time delay difference of 6 ps for 10-GHz PAAs has been implemented. Measurement results on time delay show an error of -0.4 ps at maximum, corresponding to a radiation angle error of less than 1.63$^{\circ}$. Thus, the TTD implemented in this research performs in excellent agreement with theory. Each TTD line, composed of MEMS switches and fiber-optic delay lines, connected to the corresponding antenna element has insertion loss in between 1.36 ㏈ and 2.40 ㏈ depending upon the setup of the switches. On the other hand, the insertion loss difference between TTD lines was 0.32 ㏈ at maximum for a fixed radiation angle. The TTD structure proposed in this paper might be more reliable and economical than those previously proposed using tunable wavelength sources if proper power equalization either with gain control of RF amplifiers or variable attenuators is achieved.

• Journal of Korean Society on Water Environment
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• v.24 no.4
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• pp.423-429
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• 2008

Microfiltration (MF) and ultrafiltration (UF) processes for removal of particulate materials (i.e., turbidity, microorganisms and viruses) have been used to produce drinking water with higher quality. As membrane filtration technique has become widely applied for drinking water treatment, the importance of membrane integrity test (MIT) has also been increasingly emphasized. The results of pressure decay test (PDT) were presented in the paper to monitor membrane integrity. In this paper the PDT was carried out with deliberately-defected membrane fibers to evaluate the sensitivity of PDT on membrane fiber damage. Variation of pressure decay rate and removal rate were investigated to evaluate the impact of defection (defection ratio) and pore size of membrane. The membrane integrity could be successfully monitored by the PDT. The pressure decay rate varied from $0.002{\sim}0.189kg_f/cm^2hr$ with the initial pressure ranged from 0.2 to $1.0kg_f/cm^2hr$. Higher initial pressure which provided with higher pressure decay rate was preferred to evaluate the defection of membrane fiber. As for the particle removal rate, the Log Removal Rate (LRV) of kaolin solution decreased significantly from 3.78 to 2.31 when one fiber out of 3,200 fibers was cut. The membranes with different pore size were tested to evaluate virus removal efficiency. The virus removal rate of the MF membrane ($0.1{\mu}m$) was about 30% although the poliovirus was smaller than the pore size of the MF membrane, indicating that the removal rate was much lower than Korea Water Works Association (KWWA) certificate LRV of 1.5.

• Journal of the Korea Institute of Building Construction
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• v.24 no.2
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• pp.203-213
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• 2024

This study delves into the mechanical properties of fiber-reinforced cement composites(FRCC) concerning the dispersion method of multi-walled carbon nanotubes(MWCNTs). MWCNTs find utility in industrial applications, particularly in magnetic sensing and crack detection, owing to their diverse properties including heat resistance and chemical stability. However, current research endeavors are increasingly directed towards leveraging the electrical properties of MWCNTs for self-sensing and smart sensor development. Notably, achieving uniform dispersion of MWCNTs poses a challenge due to variations in researchers' skills and equipment, with excessive dispersion potentially leading to deterioration in mechanical performance. To address these challenges, this study employs ultrasonic dispersion for a defined duration along with PCE surfactant, known for its efficacy in dispersion. Test specimens of FRCC are prepared and subjected to strength, drawing, and direct tensile tests to evaluate their mechanical properties. Additionally, the influence of MWCNT dispersion efficiency on the enhancement of FRCC mechanical performance is scrutinized across different dispersion methods.

• Membrane Journal
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• v.24 no.3
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• pp.194-200
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• 2014

The purpose of this study was to evaluate the performance of newly developed Large Pore Micro-Filtration (LPMF) membrane in Lab size for the application of water treatment, and to find its problems with solutions. The out-to-inside filtration hollow fiber LPMF membrane of which average pore size was $5{\mu}m$ was used at this study and its material was the PET braid reinforced PVDF. Filtration tests were done through gravity with 30 cm water head difference or pressure below 1.5 bar, and the backwash was done instantaneously with the filtrate after pressurizing it to about 4 bar. The water flux of the LPMF membrane with 0.2 bar TMP (Trans Membrane Pressure) was 2 times higher than $0.4{\mu}m$ MF membrane with $0.05{\mu}m$ UF filtrate of the tap water and it was measured also with 20~30 cm water head difference which showed over 800 LMH at 30 cm water head difference. And Time-To-Filter (TTF) was performed by using $5{\mu}m$ filter paper to optimize coagulants and dosage which enhanced filtrate's turbidity and stabilized filtration flux. When the LPMF was operated with 30 cm gravity with very high dose of inorganic coagulants, the flux was maintained over 80 LMH with 93.5~99.5% turbidity removal. Especially, the filtration was maintained stably in the flux and about 97% of the recovery rate by instantaneous pressurized backwash with about 4 bar of the filtrate when the packing density was about 19%. But there was instability in filtration, since the TMP was continuously going up by inefficient backwash when the packing density was 43%.