• Journal of Microbiology and Biotechnology
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• v.22 no.11
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• pp.1457-1466
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• 2012

Antimicrobial peptides (AMPs) exert antimicrobial activity against Gram-positive and Gram-negative bacteria, fungi, and viruses by various mechanisms. AMPs commonly possess particular characteristics by harboring cationic and amphipathic structures and binding to cell membranes, resulting in the leakage of essential cell contents by forming pores or disturbing lipid organization. These membrane disruptive mechanisms of AMPs are possible to explain according to the various structure forming pores in the membrane. Some AMPs inhibit DNA and/or RNA synthesis as well as apoptosis induction by reactive oxygen species (ROS) accumulation and mitochondrial dysfunction. Specifically, mitochondria play a major role in the apoptotic pathway. During apoptosis induced by AMPs, cells undergo cytochrome c release, caspase activation, phosphatidylserine externalization, plasma or mitochondrial membrane depolarization, DNA and nuclei damage, cell shrinkage, apoptotic body formation, and membrane blebbing. Even AMPs, which have been reported to exert membrane-active mechanisms, induce apoptosis in yeast. These phenomena were also discovered in tumor cells treated with AMPs. The apoptosis mechanism of AMPs is available for various therapeutics such as antibiotics for antibiotic-resistant pathogens that resist to the membrane active mechanism, and antitumor agents with selectivity to tumor cells.

• CELLMED
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• v.5 no.2
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• pp.9.1-9.14
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• 2015

The so-called "Needham's Grand Question" (NGQ) can be formulated as why modern science was developed in Europe despite the earlier successes of science and technology in ancient China. Numerous answers have been proposed. In this review, it will be pointed out that traditional Chinese natural philosophy (TCNP) and traditional Chinese medicine (TCM) are in fact dealing with problems of highly complex dynamical systems of Nature and human beings. Due to the lack of mathematical machinery in dealing with such complex phenomena, a holistic approach was taken by ancient Chinese instead. It was very successful for the first eighteen centuries. In the recent three centuries, however, the reductionist and mechanistic viewpoints of Western natural philosophy, sciences, and medicine have been prevalent all over the world up to now. The main obstacle in preventing the advancement of TCM, TCNP and its sciences is actually the lacking of proper mathematical tools in dealing with complex dynamical systems. Fortunately, the tools are now available and a "chaotic wave theory of fractal continuum" has been proposed recently. To give the theory an operational meaning, three basic laws of TCNP are outlined. These three laws of wave/field interactions contrast readily with those of Newton's particle collisions. Via the proposed three laws, TCM, TCNP and its sciences can be unified under the same principles. Finally, an answer to NGQ can be accurately given. It is hoped that this review will help promoting a genuine understanding of natural philosophy, sciences, and medicine in an ecumenical way.

• Nuclear Engineering and Technology
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• v.52 no.12
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• pp.2743-2759
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• 2020

A detailed computational fluid dynamics (CFD) simulation analysis model was developed using ANSYS CFX 16.1 and analyzed to simulate the basic design and internal flow characteristics of a 180 MW small modular reactor (SMR) with a natural circulation flow system. To analyze the natural circulation phenomena without a pump for the initial flow generation inside the reactor, the flow characteristics were evaluated for each output assuming various initial powers relative to the critical condition. The eddy phenomenon and the flow imbalance phenomenon at each output were confirmed, and a flow leveling structure under the core was proposed for an optimization of the internal natural circulation flow. In the steady-state analysis, the temperature distribution and heat transfer speed at each position considering an increase in the output power of the core were calculated, and the conceptual design of the SMR had a sufficient thermal margin (31.4 K). A transient model with the output ranging from 0% to 100% was analyzed, and the obtained values were close to the T_hot and T_cold temperature difference value estimated in the conceptual design of the SMR. The K-factor was calculated from the flow analysis data of the CFX model and applied to an analysis model in RELAP5/MOD3.3, the optimal analysis system code for nuclear power plants. The CFX analysis results and RELAP analysis results were evaluated in terms of the internal flow characteristics per core output. The two codes, which model the same nuclear power plant, have different flow analysis schemes but can be used complementarily. In particular, it will be useful to carry out detailed studies of the timing of the steam generator intervention when an SMR is activated. The thermal and hydraulic characteristics of the models that applied porous media to the core & steam generators and the models that embodied the entire detail shape were compared and analyzed. Although there were differences in the ability to analyze detailed flow characteristics at some low powers, it was confirmed that there was no significant difference in the thermal hydraulic characteristics' analysis of the SMR system's conceptual design.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.21 no.1
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• pp.153-164
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• 1997

Flame oscillation phenomena in a co-flow diffusion flame was experimentally studied with periodic fuel supply using a solenoid valve. The degree of excitation was controlled by changing the volume flux of fuel passing through the valve. Flame oscillation frequencies were measured utilizing a photodiode, a spectrum analyzer, video and high speed movies. Laser planar visualization was employed to study the correlation between the flame oscillation and the toroidal vortices. Observed are three regimes of flame oscillation, where the oscillation frequencies are for the multiples of excitation, the excitation itself and the flame natural oscillation. Both periods of natural oscillation and of excitation induced oscillation exist over one cycle of the excitation in the frequency multiplied regime. It is considered as an effect of balancing the influence of buoyancy driven vortex with that of excitation induced vortex near the excitation rate of 0.2. Flame shapes are become monotonous as increasing the excitation frequency to the range of over two fold of the natural oscillation. The flame oscillation can be modulated to the frequency of either multiples of excitation or excitation itself under certain conditions. This implies that the flame oscillation could be modulated to avoid the resonance frequency of the combustor, and shows the possibility of active control of the flame oscillation.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.11 no.12
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• pp.5199-5206
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• 2010

In this paper, we investigate the buckling analysis of laminated composite plates, using a improved assumed natural strain shell element. In order to overcome membrane and shear locking phenomena, the assumed natural strain method is used. The eigenvalues of the laminated composite plates are calculated by varying the width-thickness ratio and angle of fiber. To improve an shell element for buckling analysis, the new combination of sampling points for assumed natural strain method was applied and the refined first-order shear deformation theory which allows the shear deformation without shear correction factor. In order to validate the present solutions, the reference solutions are used and discussed. The results of laminated composite plates under the in-plane shear loading may be the benchmark test for the buckling analysis.

• Journal of Microbiology and Biotechnology
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• v.15 no.6
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• pp.1197-1206
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• 2005

Vibrio vulnificus is an opportunistic pathogen that causes a septicemia and expresses numerous virulence factors, in which luxS and smcR are genes encoding for components responsible for quorum-sensing regulation. In the present study, null mutants were constructed with lesions in each or both of these two genes from the V. vulnificus Vv$\Delta$Z strain, which is a lacZ$^{-}$ and chloramphenicol/streptomycin-resistant derivative of the wild-type ATCC29307 strain, and their phenotypes related to virulence were compared with those of the parental cells. $LD_{50}$ and histopathological findings of luxS-, smcR-, or luxS- smcR- deficient mutant were not different from those of the parent strain, a lacZ-deficient streptomycin-resistant strain in mice. However, time of death in mice was delayed, and numbers of bacteria survived in bloodstream after intraperitoneal injection in mice were decreased by mutation, especially luxS and smcR double mutant (VvSR$\Delta$ZSR). These phenomena were supported by increased serum sensitivity and delayed bacterial proliferation in both murine blood and iron-restricted medium. These results suggest that the luxS and luxR homologous genes in V. vulnificus could playa role in bacterial survival in host by enhancing proliferation and adjusting to changed environment.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.11 no.6
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• pp.2284-2291
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• 2010

In this paper, we investigate the vibration analysis of plates, using an 8-node shell element that accounts for the transverse shear strains and rotary inertia. The forced vibration analysis of plates subjected to arbitrary loading is investigated. In order to overcome membrane and shear locking phenomena, the assumed natural strain method is used. To improve an 8-node shell element for forced vibration analysis, the new combination of sampling points for assumed natural strain method was applied. The refined first-order shear deformation theory based on Reissner-Mindlin theory which allows the shear deformation without shear correction factor and rotary inertia effect to be considered is adopted for development of 8-node assumed strain shell element. In order to validate the finite element numerical solutions, the reference solutions of plates are presented. Results of the present theory show good agreement with the reference solution. In addition the effect of damping is investigated on the forced vibration analysis of plates.

• Biotechnology and Bioprocess Engineering:BBE
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• v.3 no.2
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• pp.103-108
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• 1998

A hydrophobic substrate triolein was hydrolyzed by lipase in a mono-phase reaction system containing cyclodextrin(CD) as emulsifier. The triolein was transformation to an emulsion-like state in the CD containing reaction system in contrast to the oil-droplet like state without CD due to the formation of an inclusion complex between the lipids and CDs. The hydyrolysis reaction increased substantially in the CD containing reaction system, and the optimum reaction conditions including the amount of lipase, ${\beta}$-CD concentration, and mixing ratio of triolein and ${\beta}$-CD, were determined. The performance of the enzyme reaction in a mono-phase reaction system was compared with that of a two-phase reaction system which used water immiscible hexane as the organic solvent. The role of a CD in the mono-phase reaction system was elucidated by comparing the degree of the inclusion complex formation with triolein and oleic acid, Km and Vmax values, and product inhibition by oleic aicd in aqueous and CD containing reaction systems. The resulting enhanced reaction seems to be caused by two phenomena; the increased accessibility of lipase to triolein and reduced product inhibition by oleic acid through the formation of an inclusion complex.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2001.05a
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• pp.668-674
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• 2001

An experimental study was performed for two types of co-axial cylindrical shell structures in order to establish the relationship between in-air dynamic characteristics and in-water ones and to observe hydrodynamic mass effects on their mode shapes when submerged. The outer cylinders are prepared with two kinds to get more insights on the fluid-structure interaction phenomena: one is flexible, which means that the outer cylinder has almost same stiffness as the inner one, and the other is a rigid one whose stiffness is more than ten times of the inner one's(it might be regarded as the scaled-down model of the reactor internals). The finite element. analyses were also implemented to support the experimental results. The results show that the natural frequencies of a co-axial cylindrical shell structure in water are remarkably lower than those in air due to the fluid mass effects. In case of the flexible-to-flexible cylinders, there exist in-phase and out-of-phase mode shapes and they are affected by the annular gap between the. co-axial cylinders. For the in-phase mode the in-water natural frequency decreases exponentially as the gap increases, while it slightly increases in case of the out-of-phase mode due to the squeezing effect of the gap fluid. In the flexible-to-rigid case, the normalized natural frequency(in-water frequency/in-air one) of the inner cylinder(core barrel model) ranges between in-phase and out-of-phase mode frequencies of the flexible-to-flexible co-axial cylindrical structure having identical dimensions. Also the normalized natural frequency of the inner cylinder of the flexible-to-rigid one moves from near of the in-phase mode frequency into the out-of-phase mode value of the flexible-to-flexible case as circumferential mode number(n) increases.

• Journal of Korean Society of Rural Planning
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• v.24 no.1
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• pp.113-127
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• 2018

This study comprehends that the landscape of Ipsan Village is the accumulated output of the landscape management and social behavior by the historic personages through the reference research and field surveys. And the study sorted out the over-layered landscape characteristics of Ipsan Village by analyzing the dispersed landscape elements as follows. First, right before the start of Japanese invasions to Korea(1592-98), Tamjin(耽津) An(安) Family moved into Ipsan and started establishing the a single clan village. At a site with mountain background and facing the water(背山臨水), the village used to be a typical farming one with an organically planned road-system and housing area following the traditional order. However, the landscape has changed drastically since the 20th century with the construction of banks, roads and readjustment of arable land etc. Second, the original landscape, which can be figured out through the 'Gosanjaesibyukgyeong(高山齋十六景)' in the 18th century, shows its harmony with natural landscape: mountain & valley, stream & field, traditional trees, etc, cultural landscape: village, well, spring, etc, and momentary landscape: seasons, time, weather phenomena, sound, behavior, etc. Third, based on the second, 16 natural landscape elements: mountain & stream, planting, etc. and 25 cultural landscape elements: housing spaces, self-cultivation & ceremony spaces, community spaces and modern education & enlightenment spaces were selected and interpreted as landscaping meanings. Fourth, the over-layered landscape which stems from the compositive functions and inter-connectivity of landscape elements which consists Ipsan Village is regarded as 'Natural geographical and Fungsu landscape', 'Rural production and livelihood landscape', 'Confucian ceremony and symbolic landscape' and 'Modern education and enlightenment landscape.'