• Journal of Environmental Science International
• /
• v.17 no.2
• /
• pp.135-140
• /
• 2008

Steel net gabion is eco-friendly retaining wall structure showing favorable ability to overcome construction and environmental restriction and also to resist corrosion, chemical attack and degradation. This paper is dealt with the applicability of gabion metal net as a substitution of existing strengthening material. Pull out test was carried out to verify the applicability of gabion metal net. According to results, the increase of surcharge loading and horizontal load resulted in a yield of metal net. The stress at the time of yield was in the range of elasticity. Accordingly, gabion metal net can be substituted for existing geogrid and there is a need for experiment and analysis of arrangement direction and durability of gabion steel net.

• Journal of the Korean institute of surface engineering
• /
• v.43 no.6
• /
• pp.255-259
• /
• 2010

In this work, Ni-Co composites incorporated with nano-sized SiC particles in the range of 45-55 nm are prepared by electroplating. The effects of plating duration on the chemical composition, surface morphology, crystalline structures and hardness have been studied. The maximum hardness of Ni-Co-SiC composite coating is approximately 633 Hv at plating duration of 1 h. The hardness is gradually decreased with increasing plating duration, which can be attributed to the growth of crystalline size and the agglomerates of SiC nano-particles. It is therefore explained that the grain refinement of Ni-Co matrix and stable dispersion of SiC particles play an important role for strengthening, which indicate Hall-Petch relation and Orowan model were dominant for hardening of Ni-Co-SiC composite coatings.

• The Korean Journal of Food And Nutrition
• /
• v.29 no.1
• /
• pp.58-64
• /
• 2016

This study was conducted to investigate the health effects of the general components of acorns in animals. In Korea, acorns have been used as food material in the form of acorn starch. Acorns contain tannin, gallic acid, digallic acid, and gallotannin. Therefore, the health effects of acorns as functional food are actively being studied. The chemical composition of acorns may vary according to the harvest time, region, and breed. Acorns have excellent antioxidant properties and might be beneficial in controlling hyperlipidemia, obesity, cardiovascular disease, and dementia, as well as strengthening immune competence. Further study is necessary to better understand the benefits of acorns, as it is expected to represent a large part of the food industry.

• Proceedings of the Korean Institute of Building Construction Conference
• /
• 2012.05a
• /
• pp.295-298
• /
• 2012

Repair and strengthening is necessary to extend the service life of existing buildings. Polymer-modified cement mortar (PCM) has been extensively used as a high performance material particularly for finishing and repairing works in concrete building because of itsexcellent adhesion, waterproofing, resistance to chemical attack, and workability. As PCM contains organic polymer, it is necessary to clarify its properties at high temperature under fire, on which sufficient data are not available. This paper evaluated the burn-up characteristics of polymer-modified cement mortar with cone calorimeter test, non-combustibility test and flammability test with experimental parameters such as the types of polymer, unit-polymer content, polymer-cement ratio and thickness of the specimen.

• Proceedings of the Korean Powder Metallurgy Institute Conference
• /
• 2002.07a
• /
• pp.133-155
• /
• 2002

1. Quasicrystalline powders shows exotic physical and mechanical p properties 2. Applications: structural application: strengthening particles for composites C Coating application: wear resistance, low friction coefficient 3. For thermal spaying: material loss during process should be c considered to control chemical composition of deposit 4. Friction coefficient is strongly dependent on contact geometry F Friction coefficient from pin on plate: 0.1-0.2 Friction coe야icient from flat on plate: about 0.46. 5. Quasicrystalline materials show lower friction coefficient but higher w wear rate than corresponding values of $Cr_20_3$ coated layer. 6. Amorphous coating seems to be promising

• Proceedings of the Korea Concrete Institute Conference
• /
• 2006.11a
• /
• pp.161-164
• /
• 2006

Carbon fiber reinforced polymer(CFRP) strips have superior mechanical and chemical properties in comparison with conventional materials. The purpose of this study is to investigate the mechanical shear behavior of concrete structures strengthened by CFRP strips A total of 15 concrete members were made and tested. Shear span to depth ratio(a/d) and the spacing of CFRP stripswere selected as major test variables. From test results, it isshown that shear strengthening with CFRP strips can increase the first shear strength and ultimate shear strength of concrete members significantly. And the brittle shear failure mode can be changed to a ductile failure mode by CFRP strips.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2006.11a
• /
• pp.165-168
• /
• 2006

Carbon fiber reinforced polymer(CFRP) have superior mechanical and chemical properties in comparison with conventional materials. And post-tensioning method has been used for structural reinforcement of RC structures due to easy installation and good effect of resisting capacity of structures. But the higher cost of CFRP and the loss of prestressing force with time are considered the major problems to use it. In this study, CFRP Strips and external post tensioning for rehabilitation of old concrete structures were adapted and optimal combination of these methods is considered. A total of 17 concrete members were made and tested. The types and numbers of CFRP strips and post-tensioning types were selected as major test variables. From test results, it is shown that the concrete members that post tensioned and bonded CFRP strips has a pronounced effect on the strength and deformational behavior. This present study indicates that external temporally post tensioning can reduce the amount of CFRP strips required and the combination of temporally post tensioning and CFRP strips may meet the strength and ductility requirements of old structures.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.21 no.3
• /
• pp.488-496
• /
• 2020

This study was based on nitrate chemical accidents at home and abroad. Toxic gases due to adverse reactions are generated in the workplace, laboratory, hospital, container damage, and chemical misinjection. Through a case review of possible situations and safety, this study analyzed various cases of accidents, accident status, accident type, cause of the accident, location of the accidents, etc. from 2014 to 2018. The plans for improvement in education and nitrate accidents were reviewed. As a result, 36 nitrate chemical accidents were investigated, including 16 careless worker accidents, eight transportation accidents, and 12 facilities shortages. Nitrate chemical accidents are occurring continuously. Based on this, the range of toxic effects using CARIS was calculated at the worst-case scenario, and the effective response range was measured through the damage impact range. For this purpose, the impact range was predicted based on the strengthening of safety education, emergency action plan and correlation, and the quantified data was identified. In addition, the reliability of the scope of impact was reviewed based on the correlation formula that could facilitate the evacuation of residents, and it was applied to actual accident scenarios of the workplace to present the effects of the accident response and preventive measures.

• Korea-Australia Rheology Journal
• /
• v.14 no.4
• /
• pp.189-201
• /
• 2002

The interaction between hydrophobically modified hydroxyethyl cellulose (hmHEC), containing approximately 1 wt% side-alkyl chains of $C_{16}$, and an anionic sodium dodecyl sulphate (SDS) surfactant was investigated. For a semi-dilute solution of 0.5 wt% hmHEC, the previously observed behaviour of a maximum in solution viscosity at intermediate SDS concentrations, followed by a drop at higher SDS concentrations, until above the cmc of surfactant when the solution resembles that of the unsubstituted polymer, was confirmed. Additionally, a two-phase region containing a hydrogel phase and a water-like supernatant was found at low SDS concentrations up to 0.2 wt%, a concentration which is akin to the critical association concentration, cac, of SDS in the presence of hmHEC. Above this concentration, SDS molecules bind strongly to form mixed micellar aggregates with the polymer alkyl side-chains, thus strengthening the network junctions, resulting in the observed increase in viscosity and elastic modulus of the solution. The shear behaviour of this polymer-surfactant complex during steady and step stress experiments was examined In great detail. Between SDS concentrations of 0.2 and 0.25 wt%, the shear viscosity of the hmHEC-polymer complex network undergoes shear-induced thickening, followed by a two-stage shear-induced fracture or break-up of the network. The thickening is thought to be due to structural rearrangement, causing the network of flexible polymers to expand, enabling some polymer hydrophobic groups to be converted from intra- to inter-chain associations. At higher applied stress, a partial local break-up of the network occurs, while at even higher stress, above the critical or network yield stress, a complete fracture of the network into small microgel-like units, Is believed to occur. This second network rupture is progressive with time of shear and no steady state in viscosity was observed even after 300 s. The structure which was reformed after the cessation of shear is found to be significantly different from the original state.

• KSBB Journal
• /
• v.22 no.4
• /
• pp.213-217
• /
• 2007

It has been reported that hydrophobic additives generally decrease the release rate of protein drugs from drug delivery systems (DDS) and hydrophilic additives increase the release rate. In many cases, however, the addition of hydrophilic molecule is necessary for improving the stability of protein drugs. In the present work, the effects of hydrophilic additives on the release profiles, and micelle formation of protein drug formulations were investigated to develop a novel method for protein drug delivery. For model protein drug, bovine serum albumin (BSA) was employed and several hydrophilic additives were used in the release experiments. Hydrophilic additive D-sorbitol showed the lower release rates of BSA than other hydrophobic additives due to the gel strengthening ability of the additive and the optimum concentration of D-sorbitol was 3 w/v % for the retarded release rate. In addition, it was found that the addition of D-sorbitol was very effective for obtaining homogeneous and stable DDS. The results were discussed in terms of the micelle formation and the micelle structure, i.e., the differences in gel structure and the distribution of drugs in micelles.