• Journal of Life Science
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• v.17 no.5 s.85
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• pp.625-633
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• 2007

We isolated a new extracellular alginate lyase-producing microorganism, which displayed alginate-depolymerizing activity in plate assays, from coastal soils in Wando, Jeollanam-do, Korea. This alginate-depolymerizing bacterium belonged to the genus Streptomyces and it was named Streptomyces sp. MET 0515. An extracellular alginate lyase(ALY1) secreted by Streptomyces sp. MET 0515, was purified to homogeneity by a combination of acetone precipitation, anion-exchange chromatography (Q-Sepharose and DEAE-Sepharose) and Sephacryl S-200 HR gel filtration chromatography. Its molecular mass was 26 kDa as determined by SDS-PACE analysis. The enzyme had an optimal temperature of $70^{\circ}C$ for its activity, and was most active at pH 7.5. The thermal and pH stability were $0-50^{\circ}C$, and pH 6.0-9.0, respectively. The enzyme activity was stimulated by 1mM $Mn^{2+}$, and inhibited by 1mM $Fe^{3+}$, 1mM EDTA and 1mM $Zn^{2+}$. Preliminary analysis of substrate specificity showed that this alginate lyase had activity on both poly-alpha 1,4-L-guluronate and poly-beta 1,4-D-mannuronate in the alginate molecule.

• The Journal of Korean Academy of Prosthodontics
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• v.52 no.4
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• pp.279-286
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• 2014

Purpose: The aim of this study was to investigate the effect of implant thread profile on the marginal bone stresses which develop during implant insertion. Materials and methods: Four experimental implants were created by placing four different thread systems on the body ($4.1mm{\times}10mm$) of the ITI standard implant. The thread types studied in this study included the buttress, v-shape, reverse buttress, and square shape threads. In order to examine the insertion stress generation, 3D dynamic finite element analysis was performed which simulated the insertion process of implants into a 1.2 mm thick cortical bone plate (containing 3.5 mm pilot hole) using a PC-based DEFORM 3D (ver 6.1, SFTC, Columbus, OH, USA) program. Results: Insertion stresses higher than human cortical bone developed around the implants. The level of insertion stresses was much different depending on the thread. Stress level was lowest near the v-shape thread, and highest near the square shaped thread. Difference in the interfacial bone stress level was more noticeable near the valley than the tip of the threads. Conclusion: Among the four threads, the v-shape thread was turned out to minimize the insertion stress level and thereby create better conditions for implant osseointegration.

• The Journal of Korean Academy of Prosthodontics
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• v.33 no.4
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• pp.780-806
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• 1995

The purpose of this study was to describe the application of 3D finite element analysis to determine resultant stresses on the bone anchored fixed prosthesis, implants and supporting bone of the mandible according to fixture numbers and load conditions. 4 or 6 fixtures and the bone anchored fixed prosthesis were placed in 3D finite element mandibular arch model which represents an actual mandibular skull. A $45^{\circ}$ diagonal load of 10㎏ was labiolingually applied in the center of the prosthesis(P1). A $45^{\circ}$ diagonal load of 20㎏ was buccolingually applied at the location of the 10mm or 20mm cantilever posterior to the most distal implant(P2 or P3). The vertical distribution loads were applied to the superior surfaces of both the right and the left 20mm cantilevers(P4). In order that the boundary conditions of the structure were located to the mandibular ramus and angle, the distal bone plane was to totally fixed to prevent rigid body motion of the entire model. 3D finite element analysis was perfomed for stress distribution and deflection on implants and supporting bone using commercial software(ABAQUS program. for Sun-SPARC Workstation. The results were as follows : 1. In all conditions of load, the hightest tensile stresses were observed at the metal lates of prostheses. 2. The higher tensile stresses were observed at the diagonal loads rather than the vertical loads 3. 6-implants cases were more stable than 4-implants cases for decreasing bending and torque under diagonal load on the anterior of prosthesis. 4. From a biomechanical perspective, high stress developed at the metal plate of cantilever-to-the most distal implant junctions as a consequence of loads applied to the cantilever extension. 5. Under diagonal load on cantilever extension, the 6-implants cases had a tendency to reduce displacement and to increase the reaction force of supporting point due to increasing the bendign stiffness of the prosthesis than 4-implants cases. 6. Under diagonal load on cantilever extension, the case of 10mm long cantilever was more stable than that of 20mm long cnatilever in respect of stress distribution and displacement. 7. When the ends of 10mm or 20mm long cantilever were loaded, the higher tensile stress was observed at the second most distal implant rather than the first most distal implant. 8. The 6-implants cases were more favorable about prevention of screw loosening under repeated loadings because 6-implants cases had smaller deformation and 4-implants cases had larger deformation.

• Journal of Advanced Marine Engineering and Technology
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• v.40 no.6
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• pp.453-457
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• 2016

In various industrial plants such as power generation plants, petrochemical plants, and unit factories, there is an increasing demand for a system that generates hot water using waste or surplus steam. Compact steam unit (CSU), which produces hot water by using steam, is a good solution considering energy reuse. In this study, as a basic study to develop a high-pressure CSU, heat transfer characteristics of a hybrid heat exchanger were investigated through experiments, in order to use the hybrid heat exchanger instead of a conventional plate heat exchanger as the core component of CSU. The experimental results are the followings. Heat balance between the hot side and cold side was satisfied within ${\pm}5%$. Overall heat transfer coefficient increased linearly as the Reynolds number increased and exceeded $5,524W/m^2K$ when the flow velocity was above 0.5 m/s. In addition, pressure drop also increased as the Reynolds number increased, and pressure drop per unit length was below 50 kPa/m.

• The Journal of Korean Academy of Prosthodontics
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• v.44 no.1
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• pp.1-9
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• 2006

Purpose: The purpose of this study was to evaluate the efficacy and substitute possibility of a newly developed flowable composite resins as a luting cement for translucent fiber post. Material & Method: Two kinds of 12 mm translucent fiber Post (D.T. Light-Post (Bisco, USA) and FRC Postec (Ivoclar vivadent, Liechtenstein) was inserted into the teflon mold (7 mm diameter, 9 mm long) and Filtek-Flow (3M ESPE. USA), a light activated flowable composite resin, was polymerized for 60 seconds through the post. Also, the post was cut from the tip to 9 mm, 6 mm, 3 mm, and Filtek-Flow was light cured according to each length. For comparison, 60 seconds light-cured and 24 hours self-cured two dual cured resin cement (Duo-cement (Bisco, USA) and 2 Panavia-F (Kuraray, Japan)) samples were prepared as control group. Also cavities (1 mm in width, 1 mm in depth and 12 mm in length) were prepared using acrylic plate and aluminum bar, and flowable composite resin was flied and light cured by the diffused light from the fiber post's side wall. The degree of polymerization was measured according to the distance from curing light using Vickers' hardness test. Result: Within the limitation of this study, the following conclusions were drawn: 1. Vickers' hardness of light cured dual cured resin cement and flowable composite resin decreased from Panavia-F, Filtek-Flow and Duo-cement accordingly (p<0.05). In the dual curing resin cement, light curing performed group showed higher surface hardness value than self cured only group (p<0.05). 2. Surface hardness ratio (light cured through fiber post /directly light cured) of D.T. Light-Post using Filtek-Flow showed about 70% in the 6 mm deep and about 50% in the 12 mm deep FRC Postec showed only 40% of surface hardness ratio. 3. Surface hardness ratio by diffused light from the post's side wall showed about 50% at 6 mm and 9 mm deep, and about 40% at 12 mm deep in D.T. Light-Post. However, FRC Postec showed about 40% at 6 mm deep, and almost no polymerization in 9 mm and 12 mm deep.

• Steel and Composite Structures
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• v.21 no.2
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• pp.249-266
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• 2016

The interest of this article lies in the proposition of using bionic method to develop a new sound absorber and analyze the efficient of this absorber in a ski cabin. Inspired by the coupling absorption structure of the skin and feather of a typical silent flying bird - owl, a bionic coupling multi-layer structure model is developed, which is composed of a micro-silt plate, porous fibrous material and a flexible micro-perforated membrane backed with airspace. The finite element simulation method with ACTRAN is applied to calculate the acoustic performance of the multi-layer absorber, the vibration modal of the ski cabin and the sound pressure level (SPL) near the skier's ears before and after pasting the absorber at the flour carpet and seats in the cabin. As expected, the SPL near the ears was significantly reduced after adding sound-absorbing material. Among them, the model 2 and model 5 showed the best sound absorption efficiency and the SPL almost reduced 5 dB. Moreover, it was most effctive for the SPL reduction with full admittance configuration at both the carpet and the seats, and the carpet contribution seems to be predominant.

• Proceedings of the KSAR Conference
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• 2003.06a
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• pp.88-88
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• 2003

본 연구는 배란후 48시간째 회수된 난소로부터 황체세포를 체외배양 후 progesterone 분비에 대한 LH, IGF-1 및 TGF$\beta$첨가효과에 대해 검토하였다. 축산기술연구소에서 사육중인 돼지(체중 145$\pm$kg) 12두로부터 발정을 유도시켜 배란후 약 48시간째 도축하여 난소를 회수하였다. 회수된 난소로부터 황체를 분리하여 세절한 후 0.25% collagenase용액(0.025mg DNase, 50mM EDTA, 50mM Dithiothreitol)으로 37$^{\circ}C$의 진탕수조에서 30분간 배양하여 황체세포를 분리 회수하였다. 회수된 황체세포는 D-MEM 용액(GIBCO, 10% FCS와 antibiotics 첨가)으로 2회 세정하여 1$\times$$10^{6}$live cell/$m\ell$이 되도록 희석한 후 24 well culture plate(Coming, New Tork 14831)에 분주하여 $CO_2$ 배양기($CO_2$: 5%)에서 12시간 간격으로 배양액을 회수하였으며 48시간까지 배양하였다. 배양액 1$m\ell$당 LH, IGF-I 및 TGF$\beta$1을 단독 혹은 공배양하여 회수된 배양액내의 progesterone 농도를 RIA법으로 분석하였다. 돼지황체세포는 배양후 24시간째에 높은 농도의 progesterone이 측정되었으며 LH를 첨가한 대조구에 비해 유의적으로 높은 progesterone이 측정되었다. 또한 IGF-1 과 TGF$\beta$1을 첨가한 군에서도 높은 농도의 progesterone이 측정되었다 그러나 TGF$\beta$ 혹은 IGF-I 단독으로는 대조구의 결과와 큰 차이가 없었다 따라서 돼지 황체세포에서의 progesterone 분비는 TGF$\beta$ 및 IGF-I 그리고 LH의 황체세포의 progesterone 분비기능을 촉진하는 것으로 나타났다.

• Interaction and multiscale mechanics
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• v.2 no.3
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• pp.321-332
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• 2009

Recent development in composites containing phase-transforming particles, such as vanadium dioxide or barium titanate, reveals the overall stiffness and viscoelastic damping of the composites may be unbounded (Lakes et al. 2001, Jaglinski et al. 2007). Negative stiffness is induced from phase transformation predicted by the Landau phase transformation theory. Although this unbounded phenomenon is theoretically supported with the composite homogenization theory, detailed stress analyses of the composites are still lacking. In this work, we analyze the stress distribution of the Hashin-Shtrikman (HS) composite and its two-dimensional variant, namely a circular inclusion in a square plate, under the assumption that the Young's modulus of the inclusion is negative. Assumption of negative stiffness is a priori in the present analysis. For stress analysis, a closed form solution for the HS model and finite element solutions for the 2D composite are presented. A static loading condition is adopted to estimate the effective modulus of the composites by the ratio of stress to average strain on the loading edges. It is found that the interfacial stresses between the circular inclusion and matrix increase dramatically when the negative stiffness is so tuned that overall stiffness is unbounded. Furthermore, it is found that stress distributions in the inclusion are not uniform, contrary to Eshelby's theorem, which states, for two-phase, infinite composites, the inclusion's stress distribution is uniform when the shape of the inclusion has higher symmetry than an ellipse. The stability of the composites is discussed from the viewpoint of deterioration of perfect interface conditions due to excessive interfacial stresses.

• Food Science of Animal Resources
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• v.30 no.5
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• pp.804-810
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• 2010

This study was performed to select protease-producing Bacillus sp. as a potential probiotic starter for fermented meat products. In order to isolate protease-producing bacterium from meju, measured the diameter of the clear zone on agar plate (TSA, 1% (w/v) skim milk) and analyzed for intracellular protease activity, then 10 Bacillus-like strains were isolated. Three Bacillus-like strains (P19, P27, and P33) among 10 strains were able to tolerate in acidic condition (TSB, pH 2.5, 2 h incubation). These 3 strains were showed antimicrobial activity against food-borne pathogenic bacteria. These vegetative cells of 3 strains were showed a survival rate of 0.04% to 0.08% under the artificial gastric acidic condition (TSB, pH 2.5 with 1% (w/v) pepsin), but spore-forming cells were 56.29% to 84.77%. Vegetative cells of 3 strains were the least bile-resistant, while spore-forming cells of 3 strains showed higher survival rate more than 76% under artificial bile condition (TSB, 0.1% (w/v) oxgall bile). In these strains, P27 strain was finally selected as a good probiotic strain. P27 strain was tentatively identified as Bacillus amyloliquefaciens by API CHB kit and 16S rDNA sequence analysis. The results of this study suggest that B. amyloliquefaciens P27 can be used as a potential probiotic starter for fermented meat product.

• Journal of Advanced Marine Engineering and Technology
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• v.37 no.8
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• pp.893-904
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• 2013

In this paper, a Kriging metamodel-based multi-objective optimization strategy in conjunction with an NSGA-II(non-dominated sorted genetic algorithm-II) has been employed to optimize the valve-plate shape of the axial piston pump utilizing 3D CFD simulations. The optimization process for minimum pressure ripple and maximum pump efficiency is composed of two steps; (1) CFD simulation of the piston pump operation with various combination of six parameters selected based on the optimization principle, and (2) applying a multi-objective optimization approach based on the NSGA-II using the CFD data set to evaluate the Pareto front. Our exploration shows that we can choose an optimal trade-off solution combination to reach a target efficiency of the axial piston pump with minimum pressure ripple.