• Journal of the Korea institute for structural maintenance and inspection
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• v.23 no.7
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• pp.58-65
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• 2019

Polymer concrete is expected to be widely used as a building material because it has a shorter hardening time and excellent compression, tensile, bending, bond strength, frictional resistance and abrasion loss compared to general concrete. The polymer concrete has excellent vibration damping performance and research on the use of various reinforcing materials is being conducted. However, in order to completely replace the general concrete and the general anti-vibration reinforcement, such polymer concrete requires an overall review of vibration reduction performance considering physical properties, dynamic properties, productivity and field applicability. In this study, the physical and dynamic properties of polymer concrete by epoxy mixing ratio were compared with those of general concrete. It was appeared that compression, tensile, bending and bond strengths of polymer concrete by epoxy mixing were significantly higher than those of general concrete. Especially, the tensile strength was more than 4 ~ 6.5 times. Based on the basic physical properties of polymer concrete, the damping ratio, which is a dynamic characteristic according to the epoxy mixing ratio, was derived through analytical models and experiments. As a result, the dynamic stiffness of polymer concrete was 20% higher than that of general concrete and the loss rate was about 3 times higher.

• Polymer(Korea)
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• v.33 no.5
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• pp.501-508
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• 2009

The thermal degradation experiment of sodium salt of poly (${\gamma}$-glutamic acid) (PGGNa) has been carried out in both its solid phase and solution phase at the range of $57{\sim}120^{\circ}C$ and their molecular weight decreasing effect was analyzed as a function of time by means of viscometry and light scattering. Based on the solid phase degradation results, it was supposed that the bond scission rate in a polymer chain kept constant and that the bond scission was occurred on a randomly located position in a polymer chain. For the degradation in solution phase, it was also found that all data at various temperatures were dropped on a single master curve when the reduced time $t/t^*$ was used in the plot of the reciprocal intrinsic viscosity (or molecular weight). This degradation curve in solution phase could be expressed as the sum of a single exponential and a linear equation and especially, the single exponential character appeared only at the beginning stage. The activation energy was measured as $107{\sim}115$ kJ/mol in this study and agreed with the literature values.

• Current Photovoltaic Research
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• v.9 no.3
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• pp.75-83
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• 2021

The tunnel oxide passivated contact (TOPCon) structure got more consideration for development of high performance solar cells by the introduction of a tunnel oxide layer between the substrate and poly-Si is best for attaining interface passivation. The quality of passivation of the tunnel oxide layer clearly depends on the bond of SiO in the tunnel oxide layer, which is affected by the subsequent annealing and the tunnel oxide layer was formed in the suboxide region (SiO, Si₂O, Si₂O₃) at the interface with the substrate. In the suboxide region, an oxygen-rich bond is formed as a result of subsequent annealing that also improves the quality of passivation. To control the surface morphology, annealing profile, and acceleration rate, an oxide tunnel junction structure with a passivation characteristic of 700 mV or more (V_oc) on a p-type wafer could achieved. The quality of passivation of samples subjected to RTP annealing at temperatures above 900℃ declined rapidly. To improve the quality of passivation of the tunnel oxide layer, the physical properties and thermal stability of the thin layer must be considered. TOPCon silicon solar cell has a boron diffused front emitter, a tunnel-SiO_x/n⁺-poly-Si/SiN_x:H structure at the rear side, and screen-printed electrodes on both sides. The saturation currents J_o of this structure on polished surface is 1.3 fA/cm² and for textured silicon surfaces is 3.7 fA/cm² before printing the silver contacts. After printing the Ag contacts, the J_o of this structure increases to 50.7 fA/cm² on textured silicon surfaces, which is still manageably less for metal contacts. This structure was applied to TOPCon solar cells, resulting in a median efficiency of 23.91%, and a highest efficiency of 24.58%, independently. The conversion efficiency of interdigitated back-contact solar cells has reached up to 26% by enhancing the optoelectrical properties for both-sides-contacted of the cells.

• The Journal of Society for e-Business Studies
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• v.24 no.3
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• pp.35-51
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• 2019

The two main goals of this study are to derive independent factors affecting the success rate of crowdfunding and to empirically analyze the variation of independent factors' effects on the success of crowdfunding by industry (Internet, culture/art, manufacturing/distribution), and funding type (stock type, bond type). To identify the success factors of crowdfunding for invigoration and strategic utilization, first, several variables were refined after interviews with experts and platform operators with investment experiences in numerous crowdfunding projects. Then, independent factors affecting project involvement were categorized as follows: a characteristic of project, participant activity, and enterprise. Also, the results derived from the influence of independent variables on crowdfunding after moderating effects were driven. Selected independent factors in this study are as follows: crowdfunding period, target amount, visual contents, minimum account money, number of comments, number of SNS followers, level of interest, financial Statement disclosure, investment attraction, venture company, intellectual property rights disclosure, and business operation period. Selected moderating factors in this study are as follows: industry (Internet, culture/art, manufacturing/distribution), and funding type (stock type, bond type). In conclusion, a discussion of the academical and practical implications and a suggestion of directions for further research are explained.

• The Journal of the Korea Contents Association
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• v.22 no.7
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• pp.443-477
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• 2022

The purpose of this study was to explore the continuing bonds experienced by adolescent victims' 15 parents of the Sewol ferry disaster. The research aim is to classify the continuing bonds into representational, functional, emotional, and relationship characteristics through contents analysis and identify them. The way dimension was found to be continuing bond through "physical objects and space," "dream and spiritual exchange," "personal memorial and ritual activities," "thoughts of deceased children," and "surviving children." In the "functional dimension," it was found that sustainable ties help families find new meanings and purposes in their lives and comfort them by making them feel they are with their children. In addition, at the emotional level, they experienced 'positive emotions' while feeling with their children, and experienced 'pain', and some research participants found it difficult to sustain the bond itself. At the level of each relationship characteristic, the relationship between parents and children was an extension of the relationship even after the child was deceased, and the relationship characteristics were reproduced. The implications for grief counseling were presented by applying a dead two-axis model to the results of this study.

• Mass Spectrometry Letters
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• v.14 no.4
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• pp.153-159
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• 2023

The copper ion, Cu(II), binding sites for amyloid fragment Aβ1-16 (=Aβ16 ) were investigated to explain the biological activity difference in the Aβ16 aggregation process. The [M+Cu+(z-2)H]^z+ (z = 2, 3 and 4, M = Aβ16 monomer) and [D+Cu+(z-2)H]^z+ (z = 3 and 5, D = Aβ16 dimer) structures were investigated using electrospray ionization (ESI) mass spectrometry (MS) and tandem mass spectrometry (MS/MS). Fragment ions of the [M+Cu+(z-2)H]^z+ and [D+Cu+(z-2)H]^z+ complexes were observed using collision-induced dissociation MS/MS. Three different fragmentation patterns (fragment "a", "b", and "y" ion series) were observed in the MS/MS spectrum of the (Aβ16 monomer or dimer-Cu) complex, with the "b" and "y" ion series regularly observed. The "a" ion series was not observed in the MS/MS spectrum of the [M+Cu+2H]⁴⁺ complex. In the non-covalent bond dissociation process, the [D+Cu+3H]⁵⁺ complex separated into three components ([M+Cu+H]³⁺, M³⁺, and M²⁺), and the [M+Cu]²⁺ subunit was not observed. The {M + fragment ion of [M+Cu+H]³⁺} fragmentation pattern was observed during the covalent bond dissociation of the [D+Cu +3H]⁵⁺ complex. The {M + [M+Cu+H]³⁺} complex geometry was assumed to be stable in the [D+Cu+3H]⁵⁺ complex. The {M + fragment ion of [M+Cu]²⁺} fragmentation pattern was also observed in the MS/MS spectrum of the [D+Cu+H]³⁺ complex. The {M + [y₉+Cu]¹⁺} fragment ion was the characteristic fragment ion. The [D+Cu+H]³⁺ and [D+Cu+3H]⁵⁺ complexes were likely to form a monomer-monomer-Cu (M-M-Cu) structure instead of a monomer-Cu-monomer (M-Cu-M) structure.

• Journal of the Earthquake Engineering Society of Korea
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• v.5 no.4
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• pp.39-49
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• 2001

In this paper, inelastic analysis procedures are presented for the seismic performance evaluation of RC bridge piers with premature termination of main reinforcement. The mechanical characteristic of cracked concrete and reinforcing bar in concrete has been modeled, considering the bond effect between reinforcing bars and concrete, the effect of aggregate interlocking at crack surface and the stiffness degradation after the crack. The smeared crack approach is incorporated. In boundary plane at which each member with different thickness is connected, local discontinuous deformation due to the abrupt change in their stiffness can be taken into account by introducing interface element. The increase of concrete strength due to the lateral confining reinforcement has been also taken into account to model the confined concrete. The proposed numerical method for seismic performance evaluation of RC bridge piers with premature termination of main reinforcement will be verified by comparison with reliable experimental results.

• Journal of Sensor Science and Technology
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• v.9 no.2
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• pp.134-140
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• 2000

Si wafer direct bonding(SDB) technology is very attractive for both Si-on-insulator(SOI) electronic devices and MEMS applications. This paper presents on pre-bonding according to HF pre-treatment conditions in Si wafer direct bonding. The characteristics of bonded sample were measured under different bonding conditions of HF concentration and applied pressure. The bonding strength was evaluated by tensile strength method. A bond characteristic on the interface was analyzed by using FT-IR, and surface roughness according to HF concentration was analyzed by AFM. Si-F bonds on Si surface after HF pre-treatment are replaced by Si-OH during a DI water rinse. Consequently, hydrophobic wafer was bonded by hydrogen bonding of Si-OH$\cdots$(HOH$\cdots$HOH$\cdots$HOH)$\cdots$OH-Si. The pre-bonding strength depends on the HF pre-treatment condition before pre-bonding. (Min : $2.4kgf/cm^2{\sim}$Max : $14.9kgf/cm^2$)

• Journal of the Korean Vacuum Society
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• v.18 no.6
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• pp.453-458
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• 2009

SiOC film was deposited by the chemical vapor deposition using BTMSM and oxygen mixed precursor. The characteristic of SiOC film varied with increasing of the gas flow rate ratios. The dielectric constant was obtained by C-V measurement using the structure of metal/SiOC film/Si. The space effect due to the steric hindrance between alkyl group at terminal bond of Si-$CH_3$ made the pores, and increased the thickness. However, the SiOC film due to the lowering of the polarization decreased the thickness and then decreased the dielectric constant. After annealing process, the dielectric constant decreased because of the evaporation of the OH or $H_2O$ sites. The thickness was related to the lowering of the dielectric constant by the reduction of the polarization and the thickness decreased with the decrease of the dielectric constant. The refractive index was in inverse proportion to thickness. The trends of the thickness and refractive index did not change after annealing.

• Journal of Korean Tunnelling and Underground Space Association
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• v.7 no.2
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• pp.143-152
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• 2005

Shotcrete for support of tunnel structures may contact with groundwater. The hazardous components in groundwater may cause corrosion of shotcrete. Also, the hazardous components may deteriorate the engineering properties of shotcrete, such as compressive strength, bond strength, flexural strength and so forth. The more the effect of the hazardous components on the shotcrete may increase, the more the stability of tunnel structure may decrease. The specimens were artificially immersed in various chemical solutions including hazardous components after the specimens were made at the tunnel construction site. It was performed to analyze the effect of the hazardous components in ground water on the engineering properties of shotcrete. The uniaxial compressive strength test, XRD, SEM were conducted to evaluate the durability and corrosion of shotcrete.