• East Asian mathematical journal
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• v.29 no.2
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• pp.189-205
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• 2013

Addition problems can be divided into the 'problem of quantity' which does not have the concept of object or unit, and the 'problem of number' which have the concept of object or unit. 'Additive property' is the factor which has to be considered in the former case. On the other hand, 'additive property' is not considered and meaningless in the latter case. However, this additive property is not emphasized in the elementary curriculum that mostly deals with quantitative problems, so related errors are occurred in actual life. In this study, we will investigate to the pre-service elementary teachers through the problems of deciding the additive property. The result shows that the pre-service elementary teachers' cognition of additive problems is insufficient. This study will provide focal points in the teacher education and the elementary education, and the clues for the operating programs through the information about the tendency of errors.

• Journal of the Korean Society of Clothing and Textiles
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• v.24 no.6
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• pp.819-827
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• 2000

The purpose of this study is to produce cotton fabric having improved dyeability and colorfastness as well as retaining the desirable durable press property. When cotton fabric was treated with additives, nitrogen content was increased as the additive concentration was increased. DP ratings and wrinkle recovery properties of BTCA treated cotton fabrics were greatly increased. But DP rating was lowered slightly by adding additives and wrinkle recovery property was decreased with the increase of additive concentration. Tensile strength was decreased by BTCA treatment but increased as additive concentration was increased. Various BTCA/additive treatments produced great affinity for reactive and acid dyes when dyebaths were adjusted at pH 3. It was showed that dyeability was increased as additive concentration was increased. The most effective additive for improving the dyeing properties of the crosslinked cotton was TEAㆍHCl. In case of reactive dye, there was almost no improvement on the dyeability of finished cotton by adding salt. Color fastness to washing and light of finished and dyed cotton were low except for the washfastness of reactive dye. Dyeing the BTCA/additive treated cotton fabrics with reactive dye had no effect on the physical properties.

• Corrosion Science and Technology
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• v.18 no.6
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• pp.258-266
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• 2019

The objective of this study was to evaluate corrosion resistance of additive manufactured 316L stainless steel and alloy 625 powders widely used in corrosion resistance alloys of marine industry in comparison with cast alloys. Directed Energy Deposition (DED) method was used in this work for sample production. DED parameter adjustment was also studied for optimum manufacturing and for minimizing the influence of defects on corrosion property. Additive manufactured alloys showed lower corrosion resistance in seawater compared to cast alloys. The reason for the degradation of anti-corrosion property was speculated to be due to loss of microstructural integrity intrinsic to the additive manufacturing process. Application of heat treatment with various conditions after DED was attempted. The effect of heat treatments was analyzed with a microstructure study. It was found that 316L and alloy 625 produced by the DED process could recover their expected corrosion resistance when heat treated at 1200 ℃.

• Communications of the Korean Mathematical Society
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• v.39 no.2
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• pp.313-329
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• 2024

An (additive) commutative monoid is called atomic if every given non-invertible element can be written as a sum of atoms (i.e., irreducible elements), in which case, such a sum is called a factorization of the given element. The number of atoms (counting repetitions) in the corresponding sum is called the length of the factorization. Following Geroldinger and Zhong, we say that an atomic monoid M is a length-finite factorization monoid if each b ∈ M has only finitely many factorizations of any prescribed length. An additive submonoid of ℝ_≥0 is called a positive monoid. Factorizations in positive monoids have been actively studied in recent years. The main purpose of this paper is to give a better understanding of the non-unique factorization phenomenon in positive monoids through the lens of the length-finite factorization property. To do so, we identify a large class of positive monoids which satisfy the length-finite factorization property. Then we compare the length-finite factorization property to the bounded and the finite factorization properties, which are two properties that have been systematically investigated for more than thirty years.

• Archives of Metallurgy and Materials
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• v.64 no.3
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• pp.959-962
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• 2019

This study was carried out to evaluate the aspect of microstructure and mechanical property development on additive manufactured pure Ti at elevated heat-input. For this work, pure Ti powder (commercial purity, grade 1) was selected, and selective laser melting was conducted from 0.5 to 1.4 J/mm. As a result, increase in heat-input led to the significant grain growth form 4 ㎛ to 12 ㎛, accompanying with the change of grain shape, correctly widmanstätten structured grains. In addition, Vickers microhardness was notably increased from 228 Hv to 358 Hv in accordance with elevated heat-input, which was attributed to the increased concentration of oxygen and nitrogen mainly occurred during selected laser melting process.

• Proceedings of the KIEE Conference
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• 2004.07c
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• pp.1988-1990
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• 2004

In this paper, we investigated electrical property of epoxy resin which includes elastomers to improve electrical and mechanical property, as varied to additive elastomer contents. There are four samples with 5[phr], 10[phr], 15[phr] and 20[phr]. We meIt was experimented with changing temperature($-80^{\circ}C{\sim}50^{\circ}C$) and frequency (10Hz, 60Hz, 1kHz, 10kHz) According to the experimental results, when the additive elastomer contents are increasing, the permittivity and tan${\delta}$ has very high value in particular at low frequency and high temperature. It also appears that those increasing rates relate to additive elastomer contents. That is to say, even though epoxy resin are improved in mechanical property according to elastomer contents, the elastic epoxy can has bad dielectric characteristics for electrical power application.

• Carbon letters
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• v.23
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• pp.48-54
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• 2017

This research considers the effect of added mesophase pitch (MP) as an additive during the pitch synthesis reaction of pyrolyzed fuel oil (PFO). Two effects are generated by adding MP. One is an enhancement of thermal stability due to the high thermal property of the additive; the other is that the volatile compounds that were removed by vaporization of PFO during the thermal reaction can participate in the pitch synthesis reaction ($PFO{\rightarrow}pitch$) more efficiently. The effect differs according to the amount of the additive. When the amount of the additive is less than 7 wt%, the first effect is dominant, whereas the second effect is dominant when the additive amount exceeds 10 wt%.

• Communications of the Korean Mathematical Society
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• v.37 no.3
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• pp.669-679
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• 2022

We provide a characterization of the positive monoids (i.e., additive submonoids of the nonnegative real numbers) that satisfy the finite factorization property. As a result, we establish that positive monoids with well-ordered generating sets satisfy the finite factorization property, while positive monoids with co-well-ordered generating sets satisfy this property if and only if they satisfy the bounded factorization property.

• Journal of Powder Materials
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• v.31 no.4
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• pp.302-307
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• 2024

This study explored the process-structure-property (PSP) relationships in Ti-6Al-4V alloys fabricated through direct energy deposition (DED) additive manufacturing. A systematic investigation was conducted to clarify how process variables-specifically, manipulating the cooling rate and energy input by adjusting the laser power and scan speed during the DED process-influenced the phase fractions, pore structures, and the resultant mechanical properties of the samples under various processing conditions. Significant links were found between the controlled process parameters and the structural and mechanical characteristics of the produced alloys. The findings of this research provide foundational knowledge that will drive the development of more effective and precise control strategies in additive manufacturing, thereby improving the performance and reliability of produced materials. This, in turn, promises to make significant contributions to both the advancement of additive manufacturing technologies and their applications in critical sectors.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.11a
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• pp.297-300
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• 2004

In this paper, we investigated insulation property of epoxy resin which includes elastomers to improve mechanical property, as varied to additive elastomer contents and to moisture absorption. There are four samples with 5[phr], 10[phr], 15[phr] and 20[phr]. we experimented to acquire insulation property(absorption rate, dissolution rate, apparent rate) and electrical property(perittivity, $tan\delta$, BDV) during respectively the time such as 6[h], 12[h], 18[h], 24[h] for moisture absorption. According to the experimental results, it is appeared that when the additive elastomer contents are increasing or when specimens remain more moisture, absorption rate, dissolution rate, permittivity and $tan\delta$ are slightly increasing but apparent rate and BDV(break-Down Voltage) strength are decreasing in particular, elastomer content [20]phr appeared remarkedly the more increase or decrease than others.