• Journal of the Korean earth science society
• /
• v.41 no.3
• /
• pp.222-237
• /
• 2020

A heavy (93 mm hr^-1) rainfall event accompanied by lightning occurred over Gangneung in the Yeongdong region of South Korea on August 6, 2018. This study investigated the underlying mechanism for the heavy rainfall event by using COMS satellite cloud products, surface- and upper-level weather charts, ECMWF reanalysis data, and radiosonde data. The COMS satellite cloud products showed rainfall exceeding 10 mm hr^-1, with the lowest cloud-top temperature of approximately -65℃ and high cloud optical thickness of approximately 20-25. The radiosonde data showed the existence of strong vertical wind shear between the upper and lower cloud layers. Furthermore, a strong inversion in the equivalent potential temperature was observed at a pressure altitude of 700 hPa. In addition, there was a highly developed cloud layer at a height of 13 km, corresponding with the vertical analysis of the ECMWF data. This demonstrated the increased atmospheric instability induced by the vertical differences in equivalent potential temperature in the Yeongdong region. Consequently, cold, dry air was trapped within relatively warm, humid air in the upper atmosphere over the East Sea and adjacent Yeongdong region. This caused unstable atmospheric conditions that led to rapidly developing convective clouds and heavy rainfall over Gangneung.

• Journal of the Korean Recycled Construction Resources Institute
• /
• v.1 no.1
• /
• pp.98-107
• /
• 2005

In other to recycle the waste concrete produced in stiu on the construction and management in highway, the recycled aggregates were experimentally examined in a practical application for anti-freezing layer and lean concrete base course. From the results, the mobile impact crusher and the eccentric-mounted cone and jaw were superior to the others for the graded aggregates. In the case of anti-freezing layer, the recycled one was easily controlled since the dry densities, contrary to natural one, were not largely changed with the moisture contents. It was found that the 7days compressive strengths of lean concrete were above the 10MPa regardless of the crushing types. From the result of testing the bearing capacity of anti-freezing layer, it was found that when the recycled aggregates mixed with natural sand would be within the required gradations, the layer meets the requirements of limitation and the percentage to passing 2-20mm sieve increased by 5~13% because the flimsy mortars on aggregate were re-crushed by vibrated-roller compactor. Although the compressive strength of lean concrete was 71~85% of the natural coarse aggregate, the recycled aggregates are applicable to the lean concrete because they largely exceeded the required strength, 5.8MPa.

• Korean Chemical Engineering Research
• /
• v.57 no.4
• /
• pp.512-518
• /
• 2019

To develop a membrane electrode assembly (MEA) with lower Pt loading and higher performance in proton exchange membrane fuel cells (PEMFCs), it is an important research issue to understand interfacial structure of Pt/C catalyst and ionomer and design the catalyst layer structure. In this study, we prepared short-side-chain Nafion-based ionomer dispersion using propylene glycol (PG) as a solvent instead of water which is commonly used as a solvent for commercially available ionomers. Cathode catalyst layers with different ionomer content from 20 to 35 wt% were prepared using the ionomer dispersion for the fabrication of four different MEAs, and their fuel cell performance was evaluated. As the ionomer content increased to 35 wt%, the performance of the prepared MEAs increased proportionally, unlike the commercially available water-based ionomer, which exhibited an optimum at about 25 wt%. Small size micelles and slow evaporation of PG in the ionomer dispersion were effective in proton transfer by inducing the formation of a uniformly structured catalyst layer, but the low oxygen permeability problem of the PG-based ionomer film should be resolved to improve the MEA performance.

• Journal of the Korea Institute of Construction Safety
• /
• v.6 no.1
• /
• pp.12-18
• /
• 2024

High-rise, large-scale, and diversification of buildings are possible, and the reduction of concrete cross-sections reduces the weight of the structure, thereby increasing or decreasing the height of the floor, securing a large number of floors at the same height, securing a large effective space, and reducing the amount of materials, rebar, and concrete used for designating the foundation floor. In terms of site construction and quality, a low water binder ratio can reduce the occurrence of dry shrinkage and minimize bleeding on the concrete surface. It has the advantage of securing self-fulfilling properties by improving fluidity by using high-performance sensitizers, making it easier to construct the site, and shortening the mold removal period by expressing early strength of concrete. In particular, with the rapid development of concrete-related construction technology in recent years, the application of ultra-high-strength concrete with a design standard strength of 100 MPa or higher is expanding in high-rise buildings. However, although high-rise buildings with more than 120 stories have recently been ordered or scheduled in Korea, the research results of developing ultra-high-strength concrete with more than 130 MPa class considering field applicability and testing and evaluating the actual applicability in the field are insufficient. In this study, in order to confirm the applicability of ultra-high-strength concrete in the field, a preliminary experiment for the member of a reduced simulation was conducted to find the optimal mixing ratio studied through various indoor basic experiments. After that, 130 MPa-class ultra-high-strength concrete was produced in a ready-mixed concrete factory in a mock member similar to the life size, and the flow characteristics, strength characteristics, and hydration heat of concrete were experimentally studied through on-site pump pressing.

• Journal of the Korean Society of Food Science and Nutrition
• /
• v.44 no.9
• /
• pp.1311-1316
• /
• 2015

The aim of this study was to investigate the quality characteristics and antioxidant activities of herbal medicine extract granules for the comparison of commercial powder products such as adlay tea powder and roasted grain powder. The antioxidant activities of samples were estimated using reducing power, 1,1-diphenyl-2-picrylhydrazyl (DPPH) and 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) free radical scavenging activities, and total polyphenolic contents. Herbal extract granules contained $126.44{\pm}7.26mg/100g$ of total polyphenolic contents. Interestingly, the highest antioxidant activity was found in 5.5% herbal extract granules, which showed DPPH and ABTS free radical scavenging activities of 71.82% and 85.28%, respectively, at 100 mg/mL and reducing power of O.D 1.25. These results suggested that addition of herbal medicine extract had beneficial effects on the functionality of granules without any affecting on its sensory characteristics.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2008.11a
• /
• pp.341-344
• /
• 2008

Lightweight concrete is known for its advantage of reducing the self-weight of the structures, reducing the areas of sectional members as well as making the construction convenient. Thus the construction cost can be saved when applied to structures such as long-span bridge and high rise building. However, the lightweight concrete requires specific mix design method that is quite different from the typical concrete, since using the typical mix method would give rise the material segregation as well as lower the strength by the reduced weight of the aggregate. In order to avoid such problems, it is recommended to apply the mix design method of self-consolidating concrete for the lightweight concrete. Therefore experimental tests were performed as such mechanical properties(compressive strength, dry density and structural efficiency) of concrete and dry shrinkage according to ACI committee 209.

• Composites Research
• /
• v.32 no.6
• /
• pp.314-318
• /
• 2019

A simple and very flexible automatic dipping machine was constructed for producing functional multilayer films on wide substrates via the layer-by-layer (LbL) assembly technique. The proposed machine exhibits several features that allow a fully automated coating operation, such as various depositing recipes, control of the dipping depth and time, operating speed, and rinsing flow, air-assist drying nozzles, and an operation display. The machine uniformly dips a substrate into aqueous mixtures containing complementary (e.g., oppositely charged, capable of hydrogen bonding, or capable of covalent bonding) species. Between the dipping of each species, the sample is spray cleaned with deionized water and blow-dried with air. The dipping, rinsing, and drying areas and times are adjustable by a computer program. Graphene-based thin films up to ten-bilayers were prepared and characterized. This film exhibits the highly filled multilayer structures and low thermal resistance, indicating that the robotic dipping system is simple to produce functional thin film coatings with a variety of different layers.

• Korean journal of food and cookery science
• /
• v.23 no.3 s.99
• /
• pp.288-293
• /
• 2007

In this study, chunggukjang was made from soybeans and Bacillus natto. This chunggukjang was meant to be consumed as a margarine and butter substitute, to help lower trans-fatty acid (TFA) intake. A freeze-dried garlic product was used during fermentation to aid in removing the smell of the chunggukjang. Chunggukjang has a very low fluidity due to its high viscosity; therefore, we added 3%(w/w) soybean oil to improve the fluidity. We found that the TFA content of the garlic chunggukiang paste was no more than 0.02${\sim}$0.05%, which was low compared to the usual contents of margarine and butter. After 4 weeks of storage the TFA content was 0.03${\sim}$0.08%, and it remained within the limits of the permissible amount. The addition of soybean oil allowed this chunggukjang to be made with greater ease, and the freeze-dried garlic eliminated the negative inherent qualities of the chunggukjang. Therefore, this garlic chunggukjang paste could be considered reasonable for commercial production.

• 보존과학연구
• /
• s.37
• /
• pp.17-26
• /
• 2016

Mado shipwreck No.1 is where a total of 57 bamboo slips were discovered. Bamboo slips first excavated in the sea. It treated low concentration PEG vacuum freeze drying treatment refer to the method that research finding consolidation about waterlogged bamboo before. PEG 2000 and PEG 4000 used to consolidation materials but some bamboo slips that treated PEG 4000 surface color have been darken using heat gun at surface treatment. So the residual PEG on object's surface was remove steam iron. Bonding used to put 100% PEG 2000 the rayon paper in the surface for stabilization and giving a strength.

• Journal of the Society of Cosmetic Scientists of Korea
• /
• v.31 no.3 s.52
• /
• pp.227-235
• /
• 2005

Skin aging is not a disease nor an abnormal phenomenon but a collection of degenerative changes with age, characterized by skin dryness, wrinkle formation, and loss of skin elasticity. The skin wrinkles are caused by either genetically predisposed factors or environmental factors such as UV irradiation or physical/chemical stimulus. The histological manifestations of wrinkles are changes in both amount and integrity of elastic and collagen fibers. Here we report the isolation and characterization of 3 active compounds, prangenidin, 8-hydroxybergapten, and xanthotoxol from Angelica dahurica root. The anti-wrinkle activities of these compounds were also investigated.