• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.9 no.6
• /
• pp.1775-1781
• /
• 2008

The effects of the type of curing agent on the swelling of the natural rubber(NR) sponge applicable to the self-sealing layer of a helicopter fuel tank were investigated. The curing systems employed were peroxide and mixed ones of sulfur and peroxide. The NR compounds were prepared in a kneader and a roll-mill. The compounds were partially cured in a press at high pressure and subsequently cured fully with expansion in another press at atmospheric pressure. The apparent density of the NR sponge was measured and the cell structure was observed with scanning electron microscopy. The swelling experiments were performed at room temperature using toluene, iso-octane, and an aircraft fuel as a solvent. More rapid volume swelling of the NR sponge cured by peroxide was achieved than cured by sulfur and peroxide with similar amount of curing agent added in rubber compounds. The apparent density and cell structure of the sponge were extremely sensitive to the amount of peroxide, which influences again the swelling behavior of the NR sponge. It is important to control properly two reactions of decomposition of foaming agent and crosslinking of NR in the mold to obtain rapid swelling of the NR sponge on contact of the fuel.

• Animal Bioscience
• /
• v.35 no.3
• /
• pp.385-398
• /
• 2022

Objective: The objective was to evaluate the influence of different dietary crude protein (CP) levels during the growth phase on reproductive characteristics and reproductive efficiency as well as the body development of adult male Japanese quail. Methods: Three hundred one-day-old male quails were distributed into five treatments with diets containing different CP levels (18%, 20%, 22%, 24%, and 26%) in a completely randomized design, with six replicates of ten birds each. The CP diets were applied only during the growth phase (1 to 35 days). At 36 days of age, the birds were transferred to 30 laying cages with three males and nine females each, and all birds received the same diet formulated to meet production-phase requirements until 96 days of age. Results: The growth rate of the birds increased linearly (p<0.01) with increasing dietary CP, but the age of maximum growth decreased (p<0.05). At growth maturity, all birds had the same body weight (p>0.05). At 35 days of age, higher weight gain was obtained (p<0.05) with diets containing 22% CP or higher. No effects on feed conversion were observed in this phase. The increase in dietary CP enhanced (p<0.01) nitrogen intake and nitrogen excretion but did not affect (p>0.05) nitrogen retention. Testis size, seminiferous tubular area, number of spermatogonia, and germinal epithelial height at 35 days of age increased linearly (p<0.05) with dietary CP, while the number of Leydig cells decreased (p<0.01). The Sertoli cell number at 60 days of age increased linearly (p<0.01) with dietary CP. Dietary CP levels did not affect cloacal gland size, foam weight, foam protein concentration, semen volume, or flock fertility at 90 days of age. Conclusion: Dietary CP concentration affected body and testicular development in male Japanese quails but did not affect reproductive efficiency.

• Journal of the Korean GEO-environmental Society
• /
• v.11 no.4
• /
• pp.33-42
• /
• 2010

The lightweight foamed concrete is used to reduce the weight of the backfill material. When it is applied, the volume is often contracted due to segregation, necessitating re-injection. In this study, it was manufactured a new lightweight foamed concrete by adding plasticizer and tested the engineering properties of the material. The tests included unconfined compressive strength test, unit weight test, flow test, pH test, and permeability test. The plasticizer is shown to have an important influence on the flow. It was shown that 2~2.4% of plasticizer was adequate. The new material was shown to have positive influence on the flow and reduction of weight when applied to the backfill of the structures.

• Korean Journal of Materials Research
• /
• v.19 no.10
• /
• pp.544-549
• /
• 2009

Activated carbon (AC) with very large surface area has high capacitance per weight. However, such activation methods tend to suffer from low yields, below 50%, and are low in electrode density and capacitance per volume. Carbon NanoFibers (CNFs) had high surface area polarizability, high electrical conductivity and chemical stability, as well as extremely high mechanical strength and modulus, which make them an important material for electrochemical capacitors. The electrochemical properties of immobilized CNF electrodes were studied for use as in electrical double layer capacitor (EDLC) applications. Immobilized CNFs on Ni foam grown by thermal chemical vapor deposition (CVD) were successfully fabricated. CNFs had a uniform diameter range from 50 to 60 nm. Surface area was 56 m$^2$/g. CNF electrodes were compared with AC and multi wall carbon nanotube (MWNT) electrodes. The electrochemical performance of the various electrodes was examined with aqueous electrolyte of 2M KOH. Equivalent series resistance (ESR) of the CNF electrodes was lower than that of AC and MWNT electrodes. The specific capacitance of 47.5 F/g of the CNF electrodes was achieved with discharge current density of 1 mA/cm$^2$.

• Structural Engineering and Mechanics
• /
• v.65 no.4
• /
• pp.491-504
• /
• 2018

Because of sandwich structures with low weight and high stiffness have much usage in various industries such as civil and aerospace engineering, in this article, buckling and free vibration analyses of coupled micro composite sandwich plates are investigated based on sinusoidal shear deformation (SSDT) and most general strain gradient theories (MGSGT). It is assumed that the sandwich structure rested on an orthotropic elastic foundation and make of four composite face sheets with temperature-dependent material properties that they reinforced by carbon and boron nitride nanotubes and two flexible transversely orthotropic cores. Mathematical formulation is presented using Hamilton's principle and governing equations of motions are derived based on energy approach and applying variation method for simply supported edges under electro-magneto-thermo-mechanical, axial buckling and pre-stresses loadings. In order to predict the effects of various parameters such as material length scale parameter, length to width ratio, length to thickness ratio, thickness of face sheets to core thickness ratio, nanotubes volume fraction, pre-stress load and orthotropic elastic medium on the natural frequencies and critical buckling load of double-bonded micro composite sandwich plates. It is found that orthotropic elastic medium has a special role on the system stability and increasing Winkler and Pasternak constants lead to enhance the natural frequency and critical buckling load of micro plates, while decrease natural frequency and critical buckling load with increasing temperature changes. Also, it is showed that pre-stresses due to help the axial buckling load causes that delay the buckling phenomenon. Moreover, it is concluded that the sandwich structures with orthotropic cores have high stiffness, but because they are not economical, thus it is necessary the sandwich plates reinforce by carbon or boron nitride nanotubes specially, because these nanotubes have important thermal and mechanical properties in comparison of the other reinforcement.

• Journal of the Society of Cosmetic Scientists of Korea
• /
• v.18 no.1
• /
• pp.1-41
• /
• 1992

A new and unique class of nonionic surfactants was synthesized by reacting biological a-tocopherol with ethylene oxide for functional cosmetics. The structures were confirmed by Hl-UMR, FT-lR, TLC and elemental analysis. POV and conjugated diene value study for EPO showed POE(n)TE had antioxidative effect similar to tocopheryl acetate Protective effect on cell membrane in photohemolysis of POE(5)TE, POE(10)TE and POE(18)TE were slightly lower than tocopherol but higher than nonoxynol-12, and POE(10)TE had UV absorption power comparable with tocopherol and homosalate. Biological activity of the hydrophobic group of the new surfactants make them unique and different from those of conventional nonionic surfactants Systematic safety evaluations of POE(n)TEs on the skin and eye proved that they are as safe as tocopherol. The results of physicochemical study showed POE(10)TE had the lowest CMC value, POE(18)TE had the maximum surface tension reduction and the highest foam volume and POE(n)TEs had various HLB values by the degree of ethoxylation. The test resul Is of technological and practical applications of these surfactants for cosmetics showed some POE(n)TEs were superior to conventional surfactants. POE(5)TE in W/O emulsions, POE(10)TE and POE(12)TE in O/W emulsions, POE(12)TE in dispersions, POE(18)TE in solubilizations and POE(50)TE in gelations were shown to be excellent which was considered due to the structural characteristic and formation of liquid crystals of POE(n)TEs. By the development and applications of these excel lent multi-functional surfactants, innovative functional cosmetics were successfully formulated.

• Transactions of the Korean hydrogen and new energy society
• /
• v.32 no.4
• /
• pp.245-255
• /
• 2021

Various studies about metallic bipolar plates have been conducted to improve fuel cell performance through flow field design optimization. These research works have been mainly focused on fuel cells for vehicle, but not fuel cells for building. In order to reduce the price and volume of fuel cell stacks for building, it is necessary to apply a metallic flow field, In this study, for a metallic flow field applied to a fuel cell for building, the effect of a change in the flow field shape on the performance of a polymer electrolyte membrane fuel cell was confirmed using a model and experiments with a down-sizing single cell. As a result, the flow field using a metal foam outperforms the channel type flow field because it has higher internal differential pressure and higher reactants velocity in gas diffusion layer, resulting in higher water removal and higher oxygen concentration in the catalyst layer than the channel type flow field. This study is expected to contribute to providing basic data for selecting the optimal flow field for the full stack of polymer electrolyte membrane fuel cells for buildings.

• Applied Chemistry for Engineering
• /
• v.29 no.6
• /
• pp.753-758
• /
• 2018

Surface activities including CMC, surface tension, foaming power etc. of the rhamnolipid (RL), a biosurfactant fermented by microorganism were investigated. Both the RL and liquid detergent contained RL showed a good surface activity. For the detergency test, the liquid detergent with RL showed a slightly better performance than that of using an fatty acid. However for the foaming profile, the liquid detergent with RL exhibited a lot of foam volume and the suppression of the rinsing and foaming during rinsing cycles with the RL was not seen. Therefore it can be concluded that RL can be used as a main surfactant or co-surfactant in liquid detergents without functions of foaming suppression or rinse-aid.

• Asia-Pacific Journal of Business
• /
• v.11 no.1
• /
• pp.145-165
• /
• 2020

Purpose - The purpose of this study is to suggest strategies and solutions for entering China in the tariff and non-tariff sectors of the cosmetic industry. Design/methodology/approach - This study analyzed the import tariff rate of cosmetics in China, and analyzed the export cost by actually interviewing the exporting companies to derive the economic effect of non-tariff measures. Findings - First, We proposed the use of the FTA business model (basic cosmetics), the use of Korea-China FTA tariffs (foam cleansing, toothpaste), and the use of APTA tariffs (perfume). Second, We proposed cooperation between the governments to facilitate customs clearance procedures and improvement of FTA awareness among corporate practitioners. Third, We proposed the expansion and support of the AEO MRA system and the expansion of Korea-China MOU conclusions regarding the certification system, and the international standardization of domestic licensing system and technical conditions. Fourth, We proposed the use of government-supported projects related to obtaining overseas certifications and overseas expansion through collaboration with the same industry. Research implications or Originality - HS3304 products excluded from the Korea-China FTA should take full advantage of the FTA business model. In addition, the non-tariff measure costs are fixed costs per year, so the ratio decreases as the number of exports and export volume increases.

• Journal of Korea Water Resources Association
• /
• v.52 no.10
• /
• pp.743-752
• /
• 2019

The flow in the meandering channel is characterized by the spiral motion of secondary currents that typically cause the erosion along the outer bank. Hydraulic structures, such as spur dike and groyne, are commonly installed on the channel bottom near the outer bank to mitigate the strength of secondary currents. This study is to investigate the effects of submerged vanes installed in a $90^{\circ}$ meandering channel on the development of secondary currents through three-dimensional numerical modeling using the hybrid RANS/LES method for turbulence and the volume of fluid method, based on OpenFOAM open source toolbox, for capturing the free surface at the Froude number of 0.43. We employ the second-order-accurate finite volume methods in the space and time for the numerical modeling and compare numerical results with experimental measurements for evaluating the numerical predictions. Numerical results show that the present simulations well reproduce the experimental measurements, in terms of the time-averaged streamwise velocity and secondary velocity vector fields in the bend with submerged vanes. The computed flow fields reveal that the streamwise velocity near the bed along the outer bank at the end section of bend dramatically decrease by one third of mean velocity after the installation of vanes, which support that submerged vanes mitigate the strength of primary secondary flow and are helpful for the channel stability along the outer bank. The flow between the top of vanes and the free surface accelerates and the maximum velocity of free surface flow near the flow impingement along the outer bank increases about 20% due to the installation of submerged vanes. Numerical solutions show the formations of the horseshoe vortices at the front of vanes and the lee wakes behind the vanes, which are responsible for strong local scour around vanes. Additional study on the shapes and arrangement of vanes is required for mitigate the local scour.