• Proceedings of the Plant Resources Society of Korea Conference
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• 2010.05a
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• pp.12-12
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• 2010

We developed droplet-vitrification protocol, a combination of droplet-freezing and solution-based vitrification, and applied to germplasm collections of garlic, potato, lily as well as cell lines, including hairy roots, somatic embryos. To establish a garlic cryobank, four Korean garlic field collections at Danyang, Suwon, Mokpo and Namhae were cryopreserved last five years. The protocol applied consisted of preculture for 3-4 days at $10^{\circ}C$ on solid MS medium with 0.3M sucrose, loading for 40 min in liquid medium with 35% PVS3, dehydration with PVS3 for 150 min, cooling in $5{\mu}l$ droplets of PVS3 placed on aluminum foil strips by dipping these strips in liquid nitrogen, warming them by plunging the foil strips into pre-heated($40^{\circ}C$) 0.8M sucrose solution for 30s. A total of over 900 accessions of garlic were stored in liquid nitrogen for long-term conservation using unripe inflorescences, cloves or bulbils. Twelve alternative plant vitrification solutions were designed by modifying cryoprotectant concentrations from the original PVS2 and PVS3. The results suggest that PVS2-based vitrification solutions with increased glycerol and sucrose and/or decreased DMSO and EG concentrations can be applied for medium size explants which are tolerant to chemical toxicity and moderately sensitive to osmotic stress. PVS3 and variants can be used widely when samples are heterogeneous, of large size and/or very sensitive to chemical toxicity and tolerant to osmotic stress.

• Macromolecular Research
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• v.13 no.3
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• pp.167-175
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• 2005

This review explores recent works involving the use of the self-assembled nanoparticles of bile acid-modified glycol chitosans (BGCs) as a new drug carrier for cancer therapy. BGC nanoparticles were produced by chemically grafting different bile acids through the use of l-ethyl-3-(3-dimethylaminopropyl)-carbodiimide (EDC). The precise control of the size, structure, and hydrophobicity of the various BGC nanoparticles could be achieved by grafting different amounts of bile acids. The BGC nanoparticles so produced formed nanoparticles ranging in size from 210 to 850 nm in phosphate-buffered saline (PBS, pH=7.4), which exhibited substantially lower critical aggregation concentrations (0.038-0.260 mg/mL) than those of other low-molecular-weight surfactants, indicating that they possess high thermodynamic stability. The SOC nanoparticles could encapsulate small molecular peptides and hydrophobic anticancer drugs with a high loading efficiency and release them in a sustained manner. This review also highlights the biodistribution of the BGC nanoparticles, in order to demonstrate their accumulation in the tumor tissue, by utilizing the enhanced permeability and retention (EPR) effect. The different approaches used to optimize the delivery of drugs to treat cancer are also described in the last section.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.12
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• pp.50-56
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• 2017

The perimeter structure in high-rise buildings, which plays a major role in resisting lateral forces, is generally formed by the orthogonal placement of the beam and column, but currently various grid patterns are implemented. In a previous study, the adaptability of the $IsoTruss^{(R)}$ grid (ITG) as a perimeter structure was examined. In this study, a method of estimating the required cross sectional area of a member in a preliminary design is proposed. The members of the perimeter structure are placed in three planes, perpendicular (PPR), parallel (PPL) and oblique (POQ) to the lateral loading, and the stiffness of the members in the POQ was taken into account by projecting them onto the PPL or PPR. Three models are established for member size zoning through the height of the building, in order to investigate the effect of the shear and moment in the calculation of the required cross sectional area. To examine the effectiveness of this study, a 64-story building is designed and analyzed. The effect of the member size zoning was examined by comparing the maximum lateral displacement, required steel amount, and axial strength ratio of the columns. Judging from the maximum lateral displacement, which was 97.3% of the allowable limit, the proposed formula seems to be implemental in sizing the members of an ITG structure at the initial stage of member selection.

• Microbiology and Biotechnology Letters
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• v.41 no.3
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• pp.320-326
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• 2013

In a previous study, we investigated the antioxidative and cellular protective effects of Parthenocissus tricuspidata stem extracts. In this study, we prepared nano-emulsion containing P. tricuspidata stem extract to improve skin permeation. The particle size of the nano-emulsion using the microfluidizer was 302 nm. Its loading efficiency was over 86%. The size distribution of the nano-emulsion took a monodispersed form and the nano-emulsion was more stable than typical emulsion without using microfluidizer during a 2 week period. In vitro skin permeation study of nano-emulsion containing P. tricuspidata stem extracts was carried out using Franz diffusion cell. The 1,3-butylene glycol used as a control group had 32.59% skin permeation efficiency. The skin permeation efficiency of the nano-emulsion was 42.47%. Also, we observed the antibacterial activity of the ethyl acetate fraction on skin flora for prospective applications as a natural antimicrobial. The ethyl acetate fraction had antibacterial activities higher than methyl paraben on Staphylococcus aureus, and Bacillus subtilis. These results indicate that nano-emulsion containing P. tricuspidata stem extracts could possess valued applications in cosmetic formulations for improving skin permeation. Also, based on the antibacterial activities on skin flora, antioxidative and cellular protective effects shown in our previous study, we suggest that P. tricuspidata stem extracts could be used as functional cosmetic materials.

• Explosives and Blasting
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• v.38 no.1
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• pp.30-37
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• 2020

In this study the split ring (SR) test was investigated for its applicability to the measurement of the tensile strength of rock specimen of NX size. The concept of the SR test is the same as the half ring (HR) test (Choi et al., 2019) except that the expected fracture plane is perpendicular to the loading direction. Because of this perpendicularity, however, it was believed that the SR test could be more accurate than the HR test. Like the HR specimen, the SR specimen is a curved prismatic bar with a uniform section. Appealing to a basic bending theory in strength of materials, the tensile strength for the special bar can be calculated analytically. Numerical simulations using LS-DYNA revealed, as expected, that the strength errors were 1% and 5% for the tensional and compressional SR tests, respectively, which were much lower than that (12%) of the HR test. To identify the performance of the two SR tests, laboratory experiments were conducted. The HR and Brazilian tests were also performed for comparison. The experiments showed that the ratios of the tensional and compressional SR to Brazilian strengths were 1.2~1.4 and 1.1~1.2, respectively, which are too small compared to empirical values in ordinary bend tests. Consequently, it is concluded that the SR test is not appropriate for use in tensile strength test of rock specimen of NX size. But the ratio of the HR to Brazilian strengths was within 1.7~2.0 for both the previous and present studies, showing a good consistency in their test results.

• Journal of the Society of Cosmetic Scientists of Korea
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• v.30 no.3 s.47
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• pp.295-305
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• 2004

Colloid and surface chemistry have been focused on surface area and surface energy. Local surface properties such as surface density, interaction, molecular orientation and reactivity have been one of interesting subjects. Systems of such surface energy being important would be listed as association colloid, emulsion, particle dispersion, foam, and 2-D surface and film. Such nanoparticle systems would be applied to drug delivery systems and functional cosmetics with biocompatible and degradable materials, while nanoparticles having its size of several nm to micron, and wide surface area, have been accepted as a possible drug carrier because their preparation, characteristics and drug loading have been inves-tigated. The biocompatible carriers were also used for the solubilization of insoluble drugs, the enhancement of skin absorption, the block out of UV radiation, the chemical stabilization and controlled release. Nano/micro emulstion system is classified into nano/microsphere, nano/microcapsule, nano/microemulsion, polymeric micelle, liposome according to its prep-aration method and size. Specially, the preparation method and industrial applications have been introduced for polymeric micelles self-assembled in aqueous solution, nano/microapsules controlling the concentration and activity of high concen-tration and activity materials, and monolayer or multilayer liposomes carrying bioactive ingredients.

• Polymer(Korea)
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• v.27 no.1
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• pp.9-16
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• 2003

Ipriflavone (IP) stimulates proliferation and differentiation of osteoblast and also enhances calcitonin secretion in the presence of estrogen. Poly(lactide-co-glycolide) (PLCA) due to its controllable biodegradability and relatively good biocompatibility is one of the most significant candidates for the study of drug controlled release system. In this study, IP-loaded PLGA microspheres (MSs) was prepared by using conventional O/W solvent evaporation method. The size of MSs was in the range of 5~200 $mu extrm{m}$. The morphology of MSs was characterized by SEM. And, in vitro release amounts of IP were analyzed by HPLC. The highest encapsulation efficiency were obtained by using gelatin and polyvinyl alcohol (PVA) as emulsifiers. The morphology, size distribution, and in vitro release pattern of MSs were changed by several preparation parameters such as molecular weights (8, 20, 33 and 90 kg/mol), polymer concentrations (2.5, 5, 10 and 20%), emulsifier types (PVA, gelatin and Tween 80), initial drug loading amount (5, 10, 20 and 30%) and stirring speed (250, 500 and 1000 rpm). The release of IP in vitro was more prolonged over 30 days, with close to zero-order pattern by controlling the preparation parameters. The physicochemical properties of IP-loaded PLGA MSs were investigated by XRD and DSC.

• Explosives and Blasting
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• v.39 no.3
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• pp.15-23
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• 2021

Ventilation shafts are pathways in mines and tunnels for the removal of dust or smoke during underground space construction and operation. In mines, blasting with long blast holes is preferred for the excavation of a ventilation shaft in the 10~20m long crown pillar section. In this case, the bottom part of the blast hole is completely drilled in order to determine the drilling error, and this causes a problem of lowering the explosive charge and blasting efficiency. It is possible to solve the problem of explosive loading and to increase the blast efficiency by covering the curb of the blasthole by using stemming material. In this study, simulations for the blasting of a ventilation shaft were performed with various stemming lengths and the blasthole diameters(45, 76mm) using AUTODYN 2D SPH(Smooth particle hydrodynamics) analysis technique. Also the optimal bottom stemming column was derived by checking the size of the boulder and burden line according to blasting. Analysis result, blasting efficiency is lessened in case of stemming length less than 30cm and the optimal length of the stemming material should be 30cm or higher to achieve high efficiency of blasting.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.42 no.6
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• pp.825-836
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• 2022

Micropiles can be used to support additional load in extended building structures. However, their use brings about a risk of exceeding the bearing capacity of existing piles. In this study, pre-compression was applied to distribute the load of an existing building to micropiles, and an indoor loading test was performed to confirm the structural applicability of a wedge-type anchorage device designed to improve its capacity. According to the test results, the maximum strain of the anchorage device was 0.63 times that of the yield strain, and the amount of slip generated at the time of anchorage was 0.11 mm, satisfying structural standards. In addition, using MIDAS GTS, a geotechnical finite element analysis software, the effect of the size of the pre-compression, the thickness of the soil layer, and the ground conditions around the tip on the reaction force of the existing piles and micropiles were analyzed. From the numerical analysis, as the size of the pre-compression load increased, the reaction force of the existing pile decreased, resulting in a reduction rate of up to 36 %. In addition, as the soil layer increased by 5 m, the reduction rate decreased by 4 %, and when the ground condition at the tip of the micropile was weathered rock, the reduction rate increased by 14 % compared with that of weathered soil.

• Journal of the Korean Society of Marine Environment & Safety
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• v.29 no.2
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• pp.230-237
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• 2023

Due to the COVID-19 pandemic and climate change, shortages of essential commodities and resources continue to occur globally. To address this problem, trade volume demand suddenly increased, driving up the freight rate of container ships sharply. The size of container vessels progressively increased from 1,500 TEU (twenty-foot equivalent unit) in the 1960s to 24,400 TEU in 2021. As the improvement of container loading capacity is closely related to the enlargement of the lashing bridge structure, it is necessary to design a structure effective for good container securing and safe under the various external loads that occur during voyage. Major classification societies have recently issued structural-analysis-based guidelines to evaluate the structural safety of lashing bridges, but their acceptance criteria and evaluation methods are different, causing confusion among engineers during design. In this study, the strength change characteristics are summarized by variations in the main variables (modeling range, opening consideration, mesh size) likely to affect the results. Based on this result, the authors propose a reasonable structural-analysis-based evaluation that is expected to serve as a reference in the next revision of classification standards.