• Journal of the Korea institute for structural maintenance and inspection
• /
• v.19 no.1
• /
• pp.35-44
• /
• 2015

Two main parameters were examined such as CSA content and polymer-binder ratio to find effects on the strength, water absorption, chloride ion penetration depth, carbonation depth, length change and chemical resistance of polymer-modified mortar with CSA and EVA polymer powder (EVAPP). As results, compressive, flexural, tensile, adhesive strengths, and length change of the polymer-modified mortar with CSA and EVAPP increases with increasing CSA content and polymer-binder ratio, although the water absorption, chloride ion penetration depth, and carbonation depth decrease with increasing polymer-binder ratio and CSA content, and also the chemical resistance decreases. Such strength and durability development is attributed to the high tensile strength of EVA polymer and the improved bond between cement hydrates and aggregates because of the addition of EVAPP and CSA.

• International Journal of Korean Welding Society
• /
• v.2 no.2
• /
• pp.14-18
• /
• 2002

Titanium and titanium alloy are excellent in corrosion resistance and specific intensity, and also in the biocompatibility. On the other hand, the brazing is bonding method of which productivity and reliability are high, when the complicated and precise structure of the thin plate is constructed. However, though conventional titanium-based brazing filler metal was excellent in bond strength and corrosion resistance, it was disadvantageous that metal structure and mechanical property of the base metal deteriorated, since the brazing temperature ( about $1000^{\circ}C$ ) is considerably high. Authors developed new brazing filler metal which added Zr to Ti-Cu (-Ni) alloy which can be brazed at $900^{\circ}C$ or less about 15 years ago. In this paper, the development of more low-melting-point brazing filler metal was tried by the addition of the fourth elements such as Ni, Co, Cr for the Ti-Zr-Cu alloy. As a method for finding the low-melting-point composition, eutectic composition exploration method was used in order to reduce the experiment point. As the result, several kinds of new brazing filler metal such as 37.5Ti-37.5-Zr-25Cu alloy (melting point: $825^{\circ}C$) and 30Ti-43Zr-25Cu-2Cr alloy (melting point: $825^{\circ}C$) was developed. Then, the brazing joint showed the characteristics which were almost equal to the base metal from the result of obtaining metallic structure and strength of joint of brazing joint. However, the brazing filler metal composition of the melting point of $820^{\circ}C$ or less could not be found. Consequentially, it was clarified that the brazing filler metal developed in this study could be practically sufficiently used from results such as metal structure of brazing joint and tensile test of the joint.

• International Journal of Highway Engineering
• /
• v.17 no.3
• /
• pp.35-47
• /
• 2015

PURPOSES : A tack coat has been utilized to increase the bond performance between the surface layer and base course (intermediate course) at various road pavement sites. This is similarly true in other nations. Based on this connection, the objective of the present study is to evaluate the properties of hot mix asphalt (HMA) mixtures with an RSC-4 or BD-Coat and determine the application rate of the tack coat. METHODS : The HMA specimens were manufactured using superpave gyratory compaction. The HMA mixtures were composed of a 5-cm thick surface layer and a 10-cm thick base course. An impact hammer resonance test (IHRT) and a static load shear test were conducted to evaluate the performance of the HMA mixtures with a tack coat. From these tests, the dynamic moduli related to the high-frequency resistance and interlayer shear strength (ISS) of HMA could be obtained. RESULTS : The results of the dynamic moduli of HMA are discussed based on the resonance frequency (RF). To check the accuracy of the IHRT, we conducted a coherence analysis. A direct shear test using the application of a static load test was carried out to evaluate the interlayer shear strength (ISS) of HMA. CONCLUSIONS : The maximum ISS was demonstrated at an RSC-4 application rate of 462 gsm, and the maximum dynamic modulus was demonstrated at an RSC-4 application rate of 306 gsm. By averaging the results of the ISS, the maximum ISS values were obtained when a BD-Coat application rate of 602 gsm was applied.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.22 no.5
• /
• pp.31-38
• /
• 2018

The effects of polymer-binder ratio and metakaolin content on the properties of ultrarapid-hardening polymer-modified concretes using metakaolin are examined. As a result, regardless of the metakaolin content, the flexural, compressive and adhesion in tension strength of the ultrarapid-hardening polymer-modified concretes tend to increase with increasing polymer-binder ratio. Regardless of the polymer-binder ratio, the strengths of the ultrarapid-hardening polymer-modified concretes increase with increasing metakaolin content, and reaches a maximum at metakaolin content of 5%. The water absorption, carbonation depth and resistance of chloride ion penetration of the ultrarapid-hardening polymer-modified concretes decrease with increasing polymer-binder ratio. The resistance of freezing and thawing improvement is attributed to the improved bond between cement hydrates and aggregates because of the incorporation of polymer dispersion.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.18 no.3
• /
• pp.153-159
• /
• 2014

This research reviewed the joint and duration characteristics depending on the surface treatment condition and lap spliced length in the PET film jointing method using the high hardness liquid material. As a result, the corona discharge treatment was improved to the contact angle, joint tensile strength, and joint peel resistance compared to non-treatment. Particularly, a surface treatment E (Corona discharge + Primer + PU bond + Polyester fabric) turned out to the best, and especially when the lap spliced length is longer than 15mm, stable joint performance was secured under the long term deterioration treatment of 16 weeks. Thus, the joint is considered to be applicable as the water-proof material.

• Journal of Korean Society of Water and Wastewater
• /
• v.25 no.5
• /
• pp.681-689
• /
• 2011

Submerged membrane bio-reactor (SMBR) has several advantages such as high MLSS, long SRT, and low F/M ratio at wastewater treatment. So, this has widely applied over the world and many studies have been conducted. However, membrane fouling remains an inevitable problem. This study was investigated using bench-scale SMBR with three poeration modes. Raw waters were prepared by addition of starch, acetic and fibric acid to recovery water of zeolite. The efficiency of nitrification and COD were very stable as about 95% and 80%, respectively. And critical flux was 128.8L/$m^{2}$/hr. The result of biodegradability test was following values at the each mode : Ss+Xs/$C_{T}$=81.7%, 35.1% and 45.3%, $X_{I}+S_{I}/C_{T}=18.3%$, 64.9% and 54.7%. When particulate matters such as $X_{I}$ and $X_{S}$ in influent are increased, membrane fouling will take place more and more. A relative ratio of filtration resistance to the fouling occurred by the cake layer was increased when increased the portion of $X_{I}$ and polysaccharide. It was thought that the formation of cake layer was promoted due to bond between $X_{I}$ and vicid material s generated from the polysaccharide.

• Proceedings of the Korean Society of Crop Science Conference
• /
• 2022.10a
• /
• pp.232-232
• /
• 2022

We reported in our recent studies that the combined treatment of Paenibacillus yonginensis DCY84^T (DCY84^T) and Silicon (Si) promotes initial plant growth and increases resistance to biotic and abiotic stress. To understand the molecular background of these phenotypes, Liquid Chromatography Mass Spectrometry (LC-MS) analysis was performed, and it was confirmed that unsaturated fatty acid metabolites such as oleic acid and linoleic acid decreased in response to the combined treatment of DCY84^T and Si. The stearoyl-acyl carrier protein desaturase (SACPD) introduces the cis double bond into the acyl-ACPs at C9, resulting in the production of unsaturated fatty acid. We identified OsSSI2 encoding SACPD in rice and found that the expression of OsSSI2 was reduced under DCY84^T and Si treatment. Furthermore, qRT-PCR analysis revealed that the expression of OsWRKY45, which is downstream of OsSSI2, was upregulated in response to DCY84^T and Si treatment. These results enable the speculation that activation of the salicylic acid (SA)-responsive gene, OsWRKY45, may contribute to enhancing biological stress resistance. Based on this, we propose a probable model for the rice defense pathway following DCY84^T and Si treatment. This model retains a WRKY45-dependent but NH1(NPR1)-independent SA signaling pathway.

• Journal of the Korea Concrete Institute
• /
• v.19 no.5
• /
• pp.639-646
• /
• 2007

This study performed several tests for the durability of the concrete coated with nano synthesis ceramics which do not contain volatile organic compounds harmful to environment. The tests were adhesion test on dry and humid concrete, SEM test, MIP analysis, carbonation, chloride diffusion by electronic facilitation, freezing-thawing resistance, alkaline resistance, and brine resistance test. In the adhesion test on dry and humid concrete, nano synthesis ceramics coating produced the highest results among all the coatings tested. Nano synthesis ceramics adhered solidly on the concrete surface. The adhesive strength seemed to result from the hydrogen bond between nano synthesis ceramics which are inorganic and generated by hydrolysis and re-condensation reaction and the concrete's hydrates such as calcium silicate aluminate or calcium silicate hydrate. SEM test and MIP analysis results show surface structure with finest crevices pore in the nano synthesis ceramics coating applied concretes. In the carbonation, chloride diffusion, and freezing-thawing resistance tests, the concretes with nano synthesis ceramics coating indicated the best results. Based on these test results, further progress in application of nano synthesis ceramics coatings to various concrete structures including costal structures and sewerage arrangements can be expected.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.18 no.11
• /
• pp.747-754
• /
• 2017

The Concrete-Filled Tube (CFT) system was developed for its excellent structural performance, such as its good stiffness, stress and ductility, which is derived from the mechanical advantages of its composite structure. However, it is known that the flat type of reinforcing plates need stiffeners placed at a certain distance from each other to avoid buckling failure, which increases the cost accordingly. This paper investigates the contribution of the rib elements placed inside the steel tube for the purpose of increasing the bond strength between the steel and concrete and fire performance with no additional protection. The test results also demonstrate the effectiveness of the corrugated rib's shape against fire. The results of this study showed that the buckling prevention and fire resistance performance criteria were satisfied by the application of the inner surface attachment rib, due to the resulting increase in the strength of the CFT column. Therefore, it is considered that the CFT method using the corrugated rib structure reinforcement developed through this study satisfies the structural and fire resistance performance criteria without the need for a refractory coating. Future studies will be needed to make the process efficient and economical for factory production.

• The Korean Journal of Pesticide Science
• /
• v.2 no.2
• /
• pp.75-82
• /
• 1998

This study was conducted to find out the biochemical or metabolic resistance mechanism of brown planthopper (BPH) to carbofuran. Differences between resistant ($LD_{50};\;20.3{\mu}g/g$) and susceptible strains($LD_{50};\;0.3{\mu}g/g$) were shown. The amounts of carbofuran metabolite, benzofuranol, and the origin, not developed by Thin Layer Chromatography, were much more in the susceptible strain. But the mother compound, carbofuran, was much more in the resistant strain. The tendencies of metabolism one and three hours after treatment were similar in both strains except for the amounts of metabolites described above. From the study, it is supposed that hydrolytic enzyme, esterase, changes its role from cleaving the esteric bond of carbofuran to making conjugates with carbofuran. This seems to be the main resistance mechanism of BPH to carbofuran. Oxidase and transferase may play little or no role in resistance mechanism. Oxidative and transferring enzymes gave no effects on the metabolism of carbofuran in the resistant strain compared with the susceptible strain.