• Journal of the Korean Ceramic Society
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• v.20 no.2
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• pp.115-122
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• 1983

There has been many controversies about the effects of additive in sintering of SiC But no prior systematic work has been reported about the difference between the effects of B and $B_4C$ as additive. The sintering behavior of SiC and its strength are studied and the optimum concentrations of additives and sintering conditions for SiC are determined. The effects of B and $B_4C$ have same effects on reactive sintering of SiC except the easiness of transport via vapor phase for uniform distribution in case of B. The strength of sintered SiC without exaggerated grain growth is limited by surface flaws and is nearly independent of temperature up to 140$0^{\circ}C$.

• Journal of the Korean Recycled Construction Resources Institute
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• v.9 no.2
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• pp.177-184
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• 2021

In this study, the effects of ground granulated blast furnace slag(GGBFS) and expansive additive(EA) on early strength mortar were examined for the purpose of reducing carbon and improving cement performance. As a result, ealry strength Portland cement(EPC) tended to decrease in flow compared to ordinary Portland cement(OPC), but binder with EPC and GGBFS was possible to obtain higher liquidity than OPC. EPC showed higher compressive strength and shrinkage than OPC. The compressive strength of specimen with EPC and GGBFS was reduced proportionally to the replacement ratio of GGBFS. The replacement ratio of GGBFS above the compressive strength equivalent to OPC was higher under low temperature conditions. The use of GGBFS resulted in high shrinkage compared to OPC, and this characteristic was even greater under low temperature conditions. The shrinkage of specimen with EA was decreased in early ages, but was higher than the OPC in long-term ages.

• Journal of the Korea Institute of Building Construction
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• v.12 no.5
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• pp.468-477
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• 2012

This study aimed to mix and test mortar incorporating activated Hwangtoh to improve the Hwangtoh brick bond strength of brick structures. To do this, the bond strength correlation of mortar was analyzed by means of materials and experiment factors and levels, and the optimum conditions were suggested after analyzing the physical properties of brick and the mix ratio of mortar and additive. Furthermore, the compressive strength and bond strength were found to be in inverse proportion, and in terms of the materials and mixing level, W/C ratio, substitution ratio of activated Hwangtoh, and fine aggregate grading were shown to have a considerable influence on the strength. In conclusion, the optimum mixing conditions to improve the bond strength are found to set W/C ratio at 65% and replacmenet ratio of activated Hwangtoh at 10%.

• KEPCO Journal on Electric Power and Energy
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• v.7 no.1
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• pp.129-135
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• 2021

Recently, additive manufacturing (AM) technology such as powder bed fusion (PBF) and directed energy deposition (DED) are actively attempted as consumers' needs for parts with complex shapes and expensive materials. In the present work, the effect of processing parameters on the mechanical properties of 316L stainless steel coupons fabricated by PBF and DED AM technology was investigated. Three major mechanical tests, including tension, impact, and fatigue, were performed on coupons extracted from the standard components at angles of 0, 45, 90 degrees for the build layers, and compared with those of investment casting and commercial wrought products. Austenitic 316L stainless steel additively manufactured have been well known to be generally stronger but highly vulnerable to impact and lack in elongation compared to casting and wrought materials. The process-induced pore density has been proved the most critical factor in determining the mechanical properties of AM-built metal parts. Therefore, it was strongly recommended to reduce those lack of fusion defects as much as possible by carefully control the energy density of the laser. For example, under the high energy density conditions, PBF-built parts showed 46% higher tensile strength but more than 75% lower impact strength than the wrought products. However, by optimizing the energy density of the laser of the metal AM system, it has been confirmed that it is possible to manufacture metal parts that can satisfy both strength and ductility, and thus it is expected to be actively applied in the field of electric power section soon.

• Journal of the Korean Chemical Society
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• v.54 no.1
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• pp.105-109
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• 2010

HEMA (2-hydroxyethyl methacrylate), EGDMA (ethylene glycol dimethacrylate) and propylene glycol was copolymerized in the presence of AIBN (azobisisobutyronitrile) initiator in a mould. The physical properties of the contact lens were measured. The water content of 37.06~38.71%, refractive index of 1.492~1.432, visible transmittance of 89.4~91.5%, tensile strength of 0.1416~0.2302 kgf, and contact angle of $38.60{\sim}53.53^{\circ}$ were obtained. Therefore, the contact lens material produced using propylene glycol as an additive satisfied the basic physical properties required for contact lenses application. It is interesting to note that an increase in wettability and tensile strength while having no significant changes in water content.

• Proceedings of the Korean Geotechical Society Conference
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• 2008.03a
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• pp.1051-1060
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• 2008

The use of the coal ash for surcharge material, in a view of the environmental aspect, can decrease amount of the reclamation through recycling waste materials as well as prevent a destruction of the ecosystem attributed to sand picking. In addition, it can reduce both unit cost of material and construction expenses. In this study, new construction material as alternative surcharge material using coal ash, which is by-product from thermoelectric power plant, were developed. Mixing ratios of fly ash and bottom ash derived from the coal ash in Samchunpo thermoelectric power plants were determined. Furthermore, mixing conditions depending on the ratios of the cement and gypsum used for chemical additive were determined too. Uniaxial compression strength tests were conducted at different mixing conditions and Design graph of optimum mixing ratio at each required strength for economic efficiency is indicated in this paper.

• Journal of Ocean Engineering and Technology
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• v.22 no.4
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• pp.46-50
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• 2008

Super duplex stainless steel has along life in severe environments because of its strength and corrosion resistance. If 0.2$\sim$0.3% Nitrogen in aninterstitial solid solution is added, the austenite structure is reinforced. This improves the solid solution hardening and the anticorrosionability. In this study, the mechanical properties and structures of the super duplex stainless steel with the 0.2% N additive were investigated to determine the effect of various volume fractions on the austenite phase. The various volume fractions and distributions of the austenite structure in the applied test specimens were obtained by changing the heat treatment temperature and cycle. The characteristics by amounts of the $\sigma$ phase obtained from the precipitation heat treatment were alsoinvestigated. From the results, when the austenite volume fraction increases, the tensile strength decreases and elongation increases. And the $\sigma$ phase was rapidly increased by increasing the heat treatment time. When the volume fraction of the $\sigma$ phase increased, tensile strength increased.

• The Research Journal of the Costume Culture
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• v.22 no.2
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• pp.339-345
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• 2014

This study analyzes and compares Hanji made with loess to Hanji made with kaolin, two yellow-based inorganic pigments, in terms of its physical properties, optical properties, and color fastness to light with the aim of using it as a fashion material. Hanji made by adding inorganic pigments showed an approximately 20% retention ratio on average. This figure was similar to those of loess and kaolin. Physical properties were analyzed, with the following results. A higher amount of additives lowered the apparent density and increased thickness and bulk. In general, inorganic pigment-added Hanji had lower tensile strength, bursting strength, and folding endurance compared to non-additive Hanji. The analysis of optical properties showed a lower brightness index for Hanji made with inorganic pigments compared to non-additive Hanji. When comparing the two inorganic pigments, the brightness of Hanji made with kaolin was higher. Regarding color fastness to light, loess showed level 4 and kaolin showed level 5 when 25% inorganic pigments on pulp were added to Hanji. Thus, Hanji made by adding inorganic pigments during the manufacturing process may perform well as materials for fashion because the additives enhanced both the color fastness to light and the bulk while maintaining the strength. In addition, Hanji dyed with inorganic pigments may have the potential to serve as materials for the fashion industry while still retaining the characteristics of Hanji.

• Journal of the Korean Society of Industry Convergence
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• v.24 no.3
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• pp.283-288
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• 2021

A tungsten material using a pressure sintering process and a titanium sintering additive was prepared to evaluate the microstructure, and mechanical properties of flexural strength and hardness. In addition, the reliability on each hardness data was evaluated by analyzing the distribution of the hardness of the tungsten material using the Weibull probability distribution. In particular, the optimal manufacturing conditions were analyzed by analyzing the correlation between the sintering temperature and the mechanical properties of the tungsten sintered body. Although the sintering density of the tungsten material was hardly changed up to 1700 ℃, but it was increased at 1800 ℃. The hardness of the tungsten sintered material increased as the sintering temperature increased, and in particular, the tungsten material sintered at 1800 ℃ showed a high hardness value of about 1790 Hv. It showed relatively excellent flexural strength at a sintering temperature of 1800 ℃.

• Computers and Concrete
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• v.29 no.4
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• pp.237-246
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• 2022

The concrete quality relies on general factors like preparation technique, uniformity of the compaction, amount and appropriateness of the additives. The current article investigates the impact of a well knows amino acid, L-arginine as an additive on water requirements, setting durations and characterization of various cement samples. Compressive strength tests of reference and L-arginine added cements at age of 2, 7 and 28 days were carried out according to TS-EN 196-1. Samples were blended by incorporating various amounts of L-arginine (25 ppm, 50 ppm and 75 ppm) in the cement water mixture which were tested with Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), thermo-gravimetric analysis (TG), scanning electron microscopy (SEM) and the energy-dispersive X-ray spectroscopy (EDS) on the 28th day. Results revealed that L-arginine does not affect the setting time, volume expansion of cement and water demands negatively; rather it imparts enhanced sustainability to the samples. It was determined that the highest value belonged to the 75L mortar with an increase of 2.6% compared to the reference sample when the compressive strengths of all mortars were compared on the 28th day. Besides, it has been observed that the development of calcium silicate hydrate or C-S-H gel, calcium hydroxide or CH and other hydrated products are associated with each other. L-arginine definitely has a contribution in the consumption of CH formed in the hydration process.