• Restorative Dentistry and Endodontics
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• v.37 no.1
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• pp.16-23
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• 2012

Objectives: Present study was undertaken to investigate the crystal growth onto synthetic hydroxyapatite (HA) seeds in pH 4.3 and pH 7.0 supersaturated solutions with different fluoride concentrations. Materials and Methods: 8 groups of pH 4.3 and 7.0 calcium phosphate supersaturated solutions were prepared with different fluoride concentrations (0, 1, 2 and 4 ppm). Calcium phosphate precipitates yield crystal growth onto the HA seed surface while solutions flow. For evaluation of crystallizing process, the changes of $Ca^{2+}$, $PO{_4}^{3-}$, $F^-$ concentrations of the inlet and outlet solutions were determined. The recovered solid samples were weighed to assess the amount of minerals precipitated, and finally determined their composition to deduce characteristics of crystals. Results: During the seeded crystal growth, there were significantly more consumption of $Ca^{2+}$, $PO{_4}^{3-}$, $F^-$ in pH 4.3 solutions than pH 7.0 (p < 0.05). As fluoride concentration increased in pH 4.3 solution, $Ca^{2+}$, $PO{_4}^{3-}$, $F^-$ consumption in experimental solutions, weight increment of HA seed, and fluoride ratio in crystallized samples were increased. There were significant differences among the groups (p < 0.05). But in pH 7.0 solution, these phenomena were not significant. In pH 7.0 solutions, analyses of crystallized samples showed higher Ca/P ratio in higher fluoride concentration. There were significant differences among the groups (p < 0.05). But in pH 4.3 solution, there were not significant differences in Ca/P ratio. Conclusions: Crystal growth in pH 4.3 solutions was superior to that in pH 7.0 solutions. In pH 4.3 solutions, crystal growth increased with showed in higher fluoride concentration up to 4 ppm.

• Korean Chemical Engineering Research
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• v.43 no.2
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• pp.249-258
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• 2005

A two-column six-step pressure swing adsorption(PSA) process was to study separation of hydrogen from hydrogen and methane($60_{vol}%/40_{vol}%$) binary system onto activated carbon adsorbent. The effects of the feed gas pressure, the feed flowrate and the P/F(purge to feed) ratio on the process performance were evaluated. The cyclic steady-states of PSA process were reached to after 15 cycles. $H_2$ purity increases according as the P/F ratio and pressure increase and the feed flow rate decreases; however, $H_2$ recovery shows an opposite phenomena to the purity. PSA process simulation studied to find optimum operation condition. In the results, 22 LPM feed flowrate, 11 atm adsorption pressure and 0.10 P/F ratio might be optimal values to obtain more than 75% recovery and 99% purity hydrogen. In this study was non-isothermal and non-adiabatic model considering linear driving force(LDF) model and Langmuir-Freundlich adsorption isotherm considered to compare between prediction and experimental data.

• Particle and aerosol research
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• v.13 no.2
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• pp.79-85
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• 2017

This study identified the loss of minimum fluidization velocity and pressure in accordance with the superficial velocity of $NiO/MoO_3/MoS_2$, a rare metallic oxide and high value-added material in the lab-scale fluidized bed reactor (L=0.25 m, D=0.05 m). The average pressure loss in L/D 1, 2, and 3 of $NiO/MoO_3/MoS_2$ within the scope of superficial gas velocity between 0.07 and 0.45 m/s based on the L/D 1, 2, and 3 of the specimen was shown to be 290~1952 Pa at decreasing flux and 253~1925 Pa at increasing flux. The comparison between the theoretical value proposed by Wen and the test data showed a difference between 0.021~0.36 magnification. Based on these results, this study was able to determine the operation conditions where rare metallic oxides could be applied in real phenomena.

• Journal of Life Science
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• v.25 no.4
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• pp.441-449
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• 2015

Endlicheria anomala, a neotropical plant, is found in northern South America and the Amazon region. It is traditionally used to remove poisons and cure gangrene. According to recent data, this plant has diverse biological properties such as anti-oxidative, anti-inflammatory and anti-melanogenic properties. However, the anti-cancer effect of E. anomala and its molecular mechanisms remain unclear. In this study, we examined the anti-cancer effect and the active mechanism of methanol extract of E. anomala (MEEA) in human lung adenocarcinoma cells (A549) and human liver cancer cells (HepG2). Our data revealed that MEEA showed cytotoxic activity in a dose-dependent manner and induced apoptosis both in A549 and HepG2 cells. We verified evidences of apoptosis via formation of chromatin condensation, apoptotic body and accumulation of cells in the subG1 phase. Following observed apoptosis-related phenomena, we found that the induction of apoptosis by MEEA was associated with the increase of tumor suppressor p53 and cyclin-dependent kinase inhibitor p21 (WAF1/CIP1) expression. Furthermore, MEEA-induced apoptosis was characterized with proteolytic activation of caspase-3, degradation of poly ADP ribose polymerase (PARP), and up-regulation of pro-apoptotic Bax expression. Taken together, these findings indicate that MEEA may have potential cancer therapeutic utility in A549 and HepG2 cells.

• Journal of the Korean Institute of Intelligent Systems
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• v.25 no.6
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• pp.529-535
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• 2015

Biological networks have been handled with the static concept. However, life phenomena in cells occur depending on the cellular state and the external environment, and only a few proteins and their interactions are selectively activated. Therefore, we should adopt the dynamic network concept that the structure of a biological network varies along the flow of time. This concept is effective to analyze the progressive transition of the disease. In this paper, we applied the proposed method to Alzheimer's disease to analyze the structural and functional characteristics of the disease network. Using gene expression data and protein-protein interaction data, we constructed the sub-networks in accordance with the progress of disease (normal, early, middle and late). Based on this, we analyzed structural properties of the network. Furthermore, we found module structures in the network to analyze the functional properties of the sub-networks using the gene ontology analysis (GO). As a result, it was shown that the functional characteristics of the dynamics network is well compatible with the stage of the disease which shows that it can be used to describe important biological events of the disease. Via the proposed approach, it is possible to observe the molecular network change involved in the disease progression which is not generally investigated, and to understand the pathogenesis and progression mechanism of the disease at a molecular level.

• Journal of the Korea Concrete Institute
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• v.20 no.2
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• pp.147-156
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• 2008

In an uniaxial compressive test of a concrete standard specimen (150$\times$300 mm) the crack initiation and extension with the stress increase are the major reason of the failure, which is similar to the breakage of the particle bonding in the simulation by using particle bonded model, especially particle flow code in 3 dimensions (PFC3D) developed by Itasca Consulting Group Inc. That is the main motive to study the possibility of an uniaxial compressive strength test simulation. It is important to investigate the relationship between the micro-parameters and the macro-properties because the 3-dimensional particle bonded model uses the spherical particles to analyze the physical phenomena. Contact bonded model used herein has eight micro-parameters and there are five macro-properties; Young's modulus, Poisson's ratio, uniaxial compressive strength and the crack initiation stress and the ratio concerning the crack propagation with the stress. To simulate the compressive test we made quantitative relationships between the micro-parameters and the macro-properties by using the fractional factorial design and various sensitivity analyses including regression analysis, which result in the good agreement with the previous studies. Also, the stress-stain curve and the crack distribution over the specimen given by PFC3D showed the mechanical behavior of the concrete standard specimen under the uniaxial compression. It is concluded that the particle bonded model can be a good tool for the analyzing the mechanical behavior of concrete under the uniaxial compressive load.

• Journal of Energy Engineering
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• v.8 no.4
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• pp.553-559
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• 1999

This study has been implemented to investigate various characteristics of coals which are imported from abroad. KIER has developed 1 T/D bench-scale unit, entrained-flow coal-slurry gasification technology to investigate the followings: 1) to assess the appropriate foreign coals for gasification. 2) to establish the data base for gasification phenomena, 3) to minimize the technical risks prior to introduction of commercial scaled IGCC power plant, 4) to develop essential key technologies and to establish operational experiences for coal gasification. The foreign coals used in the gasification are Cyprus and Alaska coals from U. S. A. Cyprus coal(bituminous) and Alaska coal (lignite) were shown about 1.29$0^{\circ}C$. The concentrations of coal-slurry for Cyprus were maintained up to 58%, 62% and 65% in order to enable to feed satisfactorily it into the gasifier without any other problems at feeding systems. However, the Alaska coal was unable to maintain slurry concentration over the 60% due to its high viscosity. During the experiments, $O_2/coal$ ratios in both coals ere maintained from 0.6~1.2, but especially Alaska coal was required excessive oxygen feed due to its high ingerent moisture contents. During the experiments with two different coals, the concentrations of syngas $(H_2+CO)$ were shown as 40~62%, and the heating value of syngas were detected as 1,400~2,050 kcal/N㎥

• Journal of the Korea Institute of Information and Communication Engineering
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• v.8 no.3
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• pp.679-685
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• 2004

Although the electrophoretic deposition method has the advantage of simple processing procedure, less fabrication facilities, and easier control for deposition thickness and wire length, providing economical and technical merits, it also has the disadvantages of cracking and porosity phenomena, requiring an improved processing method for higher particle density and constant particle orientation. we have developed an optimization method to increase the particle density and to unify its orientation, and have performed a study to overcome the cracking and porosity problems in the fabricated superconductor. In order to improve the surface uniformity and the conduction properties of the fabricated YBCO thick films, a system that applies alternate voltage vertically has been developed for the first time and applied to the electrophoretic deposition process. The applied alternate electric field caused a force to be exerted on each YBCO particle and resulted in a rotation of the particle in the direction of applied electric field, accomplishing a uniform particle orientation. We name this process as the shaky-aligned electrophoretic deposition method. For commercial utilization and efficiency, in this dissertation, alternating voltage of 60 Hz and 25 ∼ 120 V/cm was proposed to apply it as a subsidiary source for shaky-flow deposition so that the fabricated thin film showed uniform surface morphology with less voids and cracks and Tc,zero of 90 K and the critical current density of 3419 A/$cm^2$.

• Korean Journal of Soil Science and Fertilizer
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• v.39 no.1
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• pp.29-37
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• 2006

In remediation of the contaminated soil, it requires to select at least more than two remediation technologies depending on the fate and transport phenomena through complicated reactions in soil matrix. Therefore, methodologies related to develop the integrated remediation technology were reviewed for agricultural soils contaminated with heavy metals. Pneumatic fracturing is necessary to implement deficiency because soil washing is not effective to remove heavy metals in the subsurface soil. But it needs to evaluate the characteristics such as essential data and factors of designated technology in order to effectively apply them in the site. In the remediation site, the important soil physical and chemical factors to be considered are hydrology, porosity, soil texture and structure, types and concentrations of the contaminants, and fate and its transport properties. However, the integrated technology can be restrictive by advective flux in the area which remediation is highly effective although both soil washing and pneumatic fracturing were applied simultaneously in the site. Therefore, we need to understand flow pathways of the target contaminants in the subsurface soils, that includes kinetic desorption and flux, predictive simulation modeling, and complicated reaction in heterogenous soil.

• Cross-Cultural Studies
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• v.25
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• pp.313-336
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• 2011

The objective of this thesis is to unfold Latin American trends overlapping with Korean contemporary novels as an interesting scene in the circle of Korea literature at the beginning of the 21st century. This study was conducted largely in two directions. One is examining how long novel A Guest of Seok-yeong HWANG, a representative realist writer in Korea, and another long novel One Hundred Years Motel (Baeknyeon Motel) of Cheol-woo IM, a writer who has expressed Korean shamanic flowering as his fictitious characteristic since the 1980s, meet and interact with the world of magic realism in long novel One Hundred Years of Solitude of G. G. Marquez born in Colombia, Latin America, and the other is discussing the fictional techniques of H. L. Borges overlapping with short stories in novel collections The Age of Twenty and Fictions of Midnight by, respectively, young writers Yeon-soo KIM and PARK Hyeong-seo who displayed a unique world of fictions in the 2000s. For these purposes, we developed the points of discussion from the viewpoint of 'the meeting of two essences' for Seok-yeong HWANG and Marquez, of 'the meeting of two 'hundred years'' for Cheol-woo IM and Marquez, of 'novel writing as the finding of the original' for Yeon-soo KIM and Borges, and of 'novel writing surrounding fictions' for Hyeong-seo PARK and Borges. Around 2000, the trend of Latin American novels emerged as a phenomenon in Korean novels. It was probably a natural consequence of contemporary writers' struggling with genres and post-genres, the overturn of the center and the periphery, and blurred boundaries. Seok-yeong HWANG, Cheol-woo IM, Yeon-soo KIM, and PARK Hyeong-seo borrowed the contents and techniques of Latin American novels, but further research is required on how continuously their works internalized the characteristic properties of Marquez-style, Borges-style or polyphonic Latin American novels and, by doing so, how much they expanded or determined their own line. This is why this study has been performed productively out of vital importance. In every age throughout history, there have been the phenomena of encountering and sympathizing, and overlapping and spreading with foreign novels. This study is meaningful in that it illuminated the aspects of Korean contemporary novels in the flow of world literature through tracing the origin and reality of the trend of Latin American novels emerging conspicuously through overlapping particularly with Korean novels published in the 2000s.