• Membrane Journal
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• v.15 no.3
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• pp.247-254
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• 2005

Chitosan film has potential applications in agriculture, food, and pharmacy. However, films made only from chitosan lack gas barrier and have poor mechanical properties. For enhanced gas barrier and mechanical properties, chitosan/clay nanocomposites have been prepared with montmorillonite (MMT) which is a layered structure of clays and chitosan. The cationic biopolymer, chitosan is intercalated into $Na^+-montmorillonite$ through cationic exchange and hydrogen bonding process. Diluted acetic acid is used as solvent f3r dissolving and dispersing chitosan. Chitosan was intercalated or exfoliated in MMT and it was confirmed by X-ray diffraction method. D-spacing of the characteristic peak from MMT plate in chitosan/clay nanocomposites was moved and diminished. The thermal stability and the mechanical properties of the nanocomposites are measured by TGA and Universal Testing Machine. Gas permeability through the chitosan/clay nanocomposites films decreased due to increased tortuosity made by intercalation of clay in chitosan.

• Journal of the Korea Concrete Institute
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• v.17 no.4 s.88
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• pp.613-620
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• 2005

There are some problems in utilizing recycled concrete aggregate go structural use because of the difficulties concerning about quality control and durability. It seems to be possible to utilize recycled concrete aggregate for making concrete products because quality control of concrete products is easier than ready-mixed concrete, but there are little studies about the properties of the steam-cured recycled aggregate concrete. In this study, various tests were performed such as compressive strength, flexural strength, splitting tensile strength, bonding strength and chloride ion penetration test to evaluate the effect of substitution of recycled concrete aggregate. The results of strength test showed that the concrete strength decreased with the increase of the substitution ratio of recycled concrete aggregate, but it was in the reasonable range and almost equal to that of normal concrete below the substitution ratio of $50\%$. On the other hand, strength test of furnace slag cement concrete shows that the strength of recycled concrete with furnace slag cement under curing condition lower than that of recycled concrete with ordinary portland cement under same condition. From the result of this study, it can be concluded that recycled concrete aggregate is able to be utilized for structural use but substitution ratio should be decided with care in each case. The result of this study could be used as the basic data for the structural use of recycled concrete aggregate.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.35 no.1
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• pp.15-22
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• 2022

This paper introduces research on the hinge joint of modular structure joints using finite element analysis. The modular structure has a characteristic in that it is difficult to expect the integrity of columns and beams between unit modules because the construction is carried out such that the modules are stacked. However, the current modular design ignores these structural characteristics, considers the moment transmission for the lateral force, and analyzes it in the same manner as the existing steel structure. Moreover, to fasten the moment bonding, bolts are fastened outside and inside the module, resulting in an unreasonable situation in which the finish is added after assembly. To consider the characteristics that are difficult to expect, such as unity, a modular structure system using hinge joints was proposed. This paper proposed and reviewed the basic theory of joints by devising a modified scissors model that is modified from the scissors model used in other research to verify the transmission of load when changing from the existing moment junction to a hinge junction. Based on the basics, the results were verified by comparing them with Midas Gen, a structural analysis program. Additionally, the member strength and usability were reviewed by changing the modular structure designed as a moment joint to a hinge joint.

• Korean Journal of Heritage: History & Science
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• v.56 no.1
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• pp.100-116
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• 2023

The Sinamsa Temple was built in the late Goryeo Dynasty and a gilt-bronze seated Buddha is enshrined in Geungnakjeon hall in the precinct. Various damages occurred in the gilt layer of the Buddha, such as peeling of the gilt layer and deteriorating gloss. In the study, the conservation conditions of the inside and outside on the statue were accurately investigated, and the making technique was interpreted through the material characteristics and non-destructive diagnosis of the statue. As a result, it is estimated that gold-gilding layer is pure gold, coloration pigment of black is carbon, green is malachite, atacamite and verdigris, red is red lead and cinnabar, respectively. In the deterioration evaluation, peeling, cracking, break out and exfoliation of the gilt layer are confirmed as damages, but the conservation condition is relatively wholesome. However, the gloss of the gilt layer is calculated to be wider in the poorer part than the maintenance part. The ultrasonic velocity of the statue was calculated to be 1,230 to 3,987 (mean 2,608) m/s and showed a relatively wide range. In infrared thermography, peeling was not confirmed, and no special bonding marks were found. In endoscope, some biological damage and corrosion were observed on the surface of the internal metal, and sealed artifacts were identified. Manufacturing technique based on the study, it is considered that the gilt-bronze seated Buddha was cast at once, and the mold was inverted to inject molten metal.

• BMB Reports
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• v.38 no.1
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• pp.115-119
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• 2005

Replacement of valine by tryptophan or tyrosine at position $\alpha$96 of the $\alpha$ chain ($\alpha$96Val), located in the ${\alpha}_1{\beta}_2$ subunit interface of hemoglobin leads to low oxygen affinity hemoglobin, and has been suggested to be due to the extra stability introduced by an aromatic amino acid at the $\alpha$96 position. The characteristic of aromatic amino acid substitution at the $\alpha$96 of hemoglobin has been further investigated by producing double mutant r Hb ($\alpha$42Tyr$\rightarrow$ Phe, $\alpha$96Val$\rightarrow$Trp). r Hb ($\alpha$42Tyr$\rightarrow$Phe) is known to exhibit almost no cooperativity in binding oxygen, and possesses high oxygen affinity due to the disruption of the hydrogen bond between $\alpha$42Tyr and $\beta$99Asp in the ${\alpha}_1{\beta}_2$ subunit interface of deoxy Hb A. The second mutation, $\alpha$96Val$\rightarrow$Trp, may compensate the functional defects of r Hb ($\alpha$42Tyr$\rightarrow$Phe), if the stability due to the introduction of trypophan at the $\alpha$96 position is strong enough to overcome the defect of r Hb ($\alpha$42Tyr$\rightarrow$Phe). Double mutant r Hb ($\alpha$42Tyr$\rightarrow$Phe, $\alpha$96Val$\rightarrow$Trp) exhibited almost no cooperativity in binding oxygen and possessed high oxygen affinity, similarly to that of r Hb ($\alpha$42Tyr$\rightarrow$Phe). $^1$H NMR spectroscopic data of r Hb ($\alpha$42Tyr$\rightarrow$Phe, $\alpha$96Val$\rightarrow$Trp) also showed a very unstable deoxy-quaternary structure. The present investigation has demonstrated that the presence of the crucible hydrogen bond between $\alpha$42Tyr and $\beta$99Asp is essential for the novel oxygen binding properties of deoxy Hb ($\alpha$96Val$\rightarrow$Trp).

• Asia pacific journal of information systems
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• v.18 no.3
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• pp.21-43
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• 2008

The task network which is formed of different individuals can be recognized as a social network. Therefore, the way to communicate with people inside or outside the network has considerable influence on their outcome. Moreover, the position on which a member stands in a network shows the different effects of the information systems supporting communication with others. In this paper, it is to be studied how personal CMC (computer-mediated communication) tools affect the mission that those who work for a network perform through diverse task networks. Especially, we focused on synchronicity of CMC. On this score, the perspective of Media Synchronicity Theory was taken that had been suggested by criticizing Media Richness Theory. It is the objective, from this perspective, to find which characteristics of networks make the value of IT supporting synchronicity high. In the research trends of social networks, there have been two traditional perspectives to explain the effect of network: embeddedness and diversity ones. These differ from the aspect which type of social network can provide much more economic benefits. As similar studies have been reported by various researchers, these are also divided into the bonding and bridging views which are based on internal and external tie, respectively, Size, density, and centrality were measured as the characteristics of personal task networks. Size means the level of relationship between members. It is the total number of other colleagues who work with a specific member for a certain project. It means, the larger the size of task network, the more the number of coworkers who interact each other through the job. Density is the ratio of the number of relationships arranged actually to the total number of available ones. In an ego-centered network, it is defined as the ratio of the number of relationship made really to the total number of possible ones between members who are actually involved each other. The higher the level of density, the larger the number of projects on which the members collaborate. Centrality means that his/her position is on the exact center of whole network. There are several methods to measure it. In this research, betweenness centrality was adopted among them. It is measured by the position on which one member stands between others in a network. The determinant to raise its level is the shortest geodesic that represents the shortest distance between members. Centrality also indicates the level of role as a broker among others. To verify the hypotheses, we interviewed and surveyed a group of employees of a nationwide financial organization in which a groupware system is used. They were questioned about two CMC applications: MSN with a higher level of synchronicity and email with a lower one. As a result, the larger the size of his/her own task network, the smaller its density and the higher the level of his/her centrality, the higher the level of the effect using the task network with CMC tools. Above all, this positive effect is verified to be much more produced while using CMC applications with higher-level synchronicity. Among the a variety of situations under which the use of CMC gives more benefits, this research is considered as one of rare cases regarding the characteristics of task network as moderators by focusing ITs for the operation of his/her own task network. It is another contribution of this research to prove empirically that the values of information system depend on the social, or comparative, characteristic of time. Though the same amount of time is shared, the social characteristics of users change its value. In addition, it is significant to examine empirically that the ITs with higher-level synchronicity have the positive effect on productivity. Many businesses are worried about the negative effect of synchronous ITs, for their employees are likely to use them for personal social activities. However. this research can help to dismiss the concern against CMC tools.

• Journal of the Mineralogical Society of Korea
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• v.30 no.2
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• pp.59-70
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• 2017

$SiO_2$ is one of the most abundant constituents of the Earth's crust and mantle. Probing its electronic structures at high pressures is essential to understand their elastic and thermodynamic properties in the Earth's interior. The in situ high-pressure x-ray Raman scattering (XRS) experiment has been effective in providing detailed bonding transitions of the low-z materials under extreme compression. However, the relationship between the local atomic structures and XRS features at high pressure has not been fully established. The ab initio calculations have been used to overcome such experimental difficulties. Here we report the partial density of states (PDOS) of O atoms and the O K-edge XRS spectra of ${\alpha}-quartz$, ${\alpha}-cristobalite$, and $CaCl_2$-type $SiO_2$ phases calculated using ab initio calculations based on the full-potential linearized augmented plane wave (FP-LAPW) method. The unoccupied O PDOSs of the $CaCl_2$-type $SiO_2$ calculated with and without applying the core-hole effects present significantly distinctive features. The unoccupied O p states of the ${\alpha}-quartz$, ${\alpha}-cristobalite$ and $CaCl_2$-type $SiO_2$ calculated with considering the core-hole effect present similar features to their calculated O K-edge XRS spectra. This confirms that characteristic features in the O K-edge XRS stem from the electronic transition from 1s to unoccupied 2p states. The current results indicate that the core-hole effects should be taken in to consideration to calculate the precise O K-edge XRS features of the $SiO_2$ polymorphs at high pressure. Furthermore, we also calculated O K-edge XRS spectrum for $CaCl_2$-type $SiO_2$ at ~63 GPa. As the experimental spectra for these high pressure phases are not currently available, the current results for the $CaCl_2$-type $SiO_2$ provide useful prospect to predict in situ high-pressure XRS spectra.

• Resources Recycling
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• v.2 no.2
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• pp.27-38
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• 1993

In this study, we investigated the grinding and sedimentation(elutriation) process of the dusts for the effective separation of high purity iron and iron oxides. For characterization of the dust, particle size distribution and chemical composition, were examined. The results obtained in this study may be summarized as follows : 1. The converter CF(clarifier) dust of the Pohang 1st, 2nd steel making factory and EC(Evaporation Cooler), EP(Eltrostatic precititator) dust of the Kwangyang 2nd steel making factory are composed $\alpha$-Fe(21~50%), FeO(wustite)$Fe_3$$O_4$(magnetite), $Fe_2$$O_3$, CaO, $Al_2$$O_3$, $SiO_2$, and etc. 2. Pure iron has ductile characteristic in nature, particle size of the pure iron increase by increasing the grinding time. On the other hand, it is conformed that bo고 particles of hematite and magnetite become less than 325 mesh after 10 minutes grinding. 3. By applying the elutriation technique for the EC dust of the Kwangyang 2nd steel making factory, the iron powder of high content more than 99.17% of pure Fe was recovered with 37.8% yield at grinding time for 40 minutes. 4. By applying the elutriation technique for the CF dust of the Pohang 2nd steel making factory, the iron powder of high content more than 98.38% of pure Fe was recovered with 44.42% yield at grinding time for 40 minutes. 5. When magnetic separation was performed using plastic bonding magnet of 70 gauss, more than 98% Fe grade of iron powder was recovered in the size range +65 -200 mesh but the recovery of it was low.