• Journal of the Korea Concrete Institute
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• v.22 no.5
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• pp.719-725
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• 2010

The analysis and experimental program of reinforced concrete (RC) structures for resistance against such extreme loads as earthquake, blast, and impact have been carried by many researchers and designers. Under the extreme loads, a large amount of energy is suddenly exerted to the structure, hence if the structure fails to absorb the impact energy, catastrophic collapse may occur. To prevent catastrophic collapse of structures, reinforced concrete must have adeguate toughness or it needs to be strengthened. The FRP strengthening method and SFRC are studied widely in resistance of impact load because of their high energy absorption capacity. In this study, drop weight impact tests were implemented to evaluate the impact resistance of SFRC and FRP strengthened RC beam while the total steel fiber volume fractions was fixed at 0.75% carbon FRP flexural strengthened RC beams. Futhermore, to prevent the shear-plug cracks when the impact load strikes the beams, additional FRP shear strengthening method are applied. The experimental, results showed that the FRP strengthened RC SFRC beams has high resistance of shear-plug cracks and crack width and SFRC has high resistance of concrete spalling failure compared to normal RC beams. The FRP flexural and shear strengthening RC beams has weakness in the spalling failure because the impact load concentrated the concrete face which is not strengthened with FRP sheets.

• Journal of Life Science
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• v.31 no.7
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• pp.677-685
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• 2021

Cannabis sativa L. belongs to the Cannabaceae family and is an annual herbaceous flowing plant. The plants can be classified into narcotic marijuana and nonnarcotic hemp. Different parts of C. sativa L. have been used as food, medicine, cosmetics, fiber and textile. However, the use of leaf, flower, and seed of C. sativa L was forbidden in Korea in January 1977 as a result of the Cannabis Control Act due to the narcotic properties. The plant's mature stems have limited uses for the production of fiber and sheets. Recently, various cannabinoids, terpenes and essential fatty acids were identified from C. sativa L., and their safety and useful bio-activities, such as neuroprotective, anti-inflammation, antithrombosis, antiepileptic, and antimicrobial activities, and the relief of pain, have been highlighted. Furthermore, the process of reduction of tetrahydrocannabinol, a representative narcotic compound, and the isolation of cannabidiol, a nonnarcotic active compound in C. sativa L., have been determined. These findings resulted in the legalization of C. sativa L. in Korea for medical use in December 2018 and the exclusion of C. sativa L. from the narcotic list of the UN Commission on Narcotics Drugs (UNCND) in December 2020. Therefore, developments of various high-value added products have commenced worldwide. Additionally, in 2021, the Korean government deregulated special zones based on hemp. In this study, the current status and the prospect of the hemp industry, as well as essential techniques for developing new hemp products, are provided for the activation of the Korea Green-Rush.

• Journal of the Korea institute for structural maintenance and inspection
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• v.19 no.2
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• pp.151-159
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• 2015

In this study, experimental research was carried out to evaluate and improve the seismic performance of reinforced concrete beam-column joint regions using strengthening materials (CFRP sheet, AFRP sheet, embedded CFRP rod) in existing reinforced concrete structure. Therefore it was constructed and tested seven specimens retrofitting the beam-column joint regions using such retrofitting materials. Specimens, designed by retrofitting the beam-column joint regions of existing reinforced concrete structure, were showed the stable failure mode and increase of load-carrying capacity due to the effect of crack control at the times of initial loading and confinement of retrofitting materials during testing. Specimens LBCJ-CRUS, designed by the retrofitting of CFRP Rod and CFRP Sheet in reinforecd beam-column joint regions were increased its maximum load carrying capacity by 1.54 times and its energy dissipation capacity by 2.36 times in comparison with standard specimen LBCJ for a displacement ductility of 4 and 7. And Specimens LBCJ-CS, LBCJ-AF series were increased its energy dissipation capacity each by 2.04~2.34, 1.63~3.02 times in comparison with standard specimen LBCJ for a displacement ductility of 7.

• Korean Journal of Plant Resources
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• v.23 no.5
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• pp.465-479
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• 2010

This study was carried out to classify the regional folk plants in the inland of Gyeongsangbuk-do. According to the survey results from 582 survey sheets of 126 residents at 85 places of 17 counties and cities from March to October, 2009, the folk plants in the inland of Gyeongsangbuk-do consisted of a total 254 taxa; 76 families, 207 genera, 225 species, 2 subspecies, 26 varieties, and 1 form. The use by its usage was: 216 taxa; edible, 82 taxa; medicinal, 30 taxa; dye, 3 taxa; aroma, 4 taxa; spice, 4 taxa; ornamental, 1 taxa; fiber, 2 taxa; oil, 1 taxa; starch, 5 taxa; fuel, 9 taxa; others, respectively, so the edible use is the highest. The most useful part was the leaf, followed by stem and root. The folk plants of 3 head families from Yeongyang and Cheongsong were 42 taxa. The consistency comparison between the scientific name and the local name were the highest in the 50's and the lowest in 80's.

• Journal of the Korea institute for structural maintenance and inspection
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• v.14 no.6
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• pp.153-161
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• 2010

Numerous past studies have shown that safety and serviceability of many concrete infrastructures and buildings built in 1970's have far less strength capacities than their original intended design capacities, thereby requiring repair and strengthening. Currently, aged concrete structures are being repaired using various methods developed in the past. Unfortunately, these methods do not consider the specific conditions that these members are under, but they merely attach repairing materials on the external surface for random strength improvements. Therefore, in order to improve repair and strengthening methods by considering composite behavior between repairing material and structural member, enhanced construction methodologies are needed. Also, the enhanced repairing and strengthening methods must be able to be implemented on structural members constructed using high performance concrete to meet the present construction demand of building mammoth structures. Therefore, in this study, a repairing and strengthening method for retrofitting high strength concrete (HSC) columns that can effectively improve column performance is developed. A square HSC column's cross-sectional shape is converted to an octagonal shape by attaching precast members on the surface of the column. Then, the octagonal column surface is surface wrapped using Carbon Fiber Sheets (CFS). The method allows maximum usage of confinement effect from externally jacketing CFS to improve strength and ductility of repaired HSC columns. The research results are discussed in detail.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.31 no.6A
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• pp.457-464
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• 2011

An experimental study was performed to evaluate the possibility of using stiff type PolyUrea(PU) on RC slab as a strengthening material. Stiff type PU(STPU) was sprayed on the bottom surface of the slab specimens, which were then attached with CFRP or GFRP sheets. Also the evaluation of the bond capacity, the single most influential parameter on strengthening of RC structures, was carried out the flexural capacity evaluation test results showed that the load carrying capacity of the PU specimen was greater and less than the unstrengthened and FRP sheet attached specimens, respectively. The STPU specimens showed a ductile flexural behavior in the plastic displacement range. With respect to bond capacity, the bond strength of all of the specimen exceeded the code required bond strength of 1.5 MPa. Also, the STPU sprayed specimen without using epoxy resin did not peel off when the tensile grip was applied for testing. The stability of the PU bond failure indicate a good bond strength of PU when applied to concrete.

• Korean Journal of Plant Resources
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• v.25 no.5
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• pp.523-542
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• 2012

This study was carried out to clarify the regional folk plants in the southern inland area of Gyeonggi-do Province. According to the survey results, derived from 1,229 sheets of 90 residents at 35 places from 9 counties and cities between October 2009 and December 2010, the folk plants in the inland southern area of Gyeonggi-do consisted of a total of 259 taxa; 82 families, 200 genera, 221 species, 4 subspecies, 32 varieties, and 2 forma. The classification of the plants by its usage was; 214 as edible, 119 as medicinal, 34 as ornamental, 18 as timber, 12 as dye, 5 as oil, 3 as spice, 2 as fiber, 2 as aroma, and 22 as others uses. So, the edible and medicinal uses are higher than other uses. The most useful part was the leaf, followed by fruit, stem, root, and flower. The collection season was focused on spring and summer, because the leaf was mainly collected in an edible condition during those seasons. Traditional knowledge of folk plants was mostly passed down orally. The consistency comparison between the standard common name and the local name was the highest in the people in 50s and the lowest in those in 80s.

• Korean Journal of Plant Resources
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• v.24 no.4
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• pp.379-394
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• 2011

This study was carried out to classify the folk plants in southern region of Gangwon-do. According to the survey results from 1,103 survey sheets of 83 residents at 32 places of 9 counties and cities from March to October, 2010, the folk plants in the southern region of Gangwon-do consisted of a total 311 taxa; 92 families, 222 genera, 274 species, 2 subspecies, 29 varieties, and 6 form. The use by its usage was: 227 taxa; Edible, 174 taxa; Medicinal, 14 taxa; Ornamental, 5 taxa; Oil, 5 taxa; Spice, 4 taxa; Dye, 1 taxa; Fiber, 1 taxa; Aroma, 1 taxa; Fuel, 32 taxa; Others, respectively, so the edible use is the highest. The most useful part was the leaf, followed by root and fruit. The consistency comparison between the scientific name and the local name were the highest in the 50's and the lowest in 80's.