• Macromolecular Research
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• v.15 no.7
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• pp.646-655
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• 2007

To achieve targeted drug delivery for chemotherapy, a ligand-mediated nanoparticulate drug carrier was designed, which could identity a specific receptor on the surfaces of tumor cells. Biodegradable poly(ethylene oxide)/poly$({\varepsilon}-caprolactone)$ (PEG/PCL) amphiphilic block copolymers coupled to biotin ligands were synthesized with a variety of PEG/PCL compositions. Block copolymeric nanoparticles harboring the anticancer drug paclitaxel were prepared via micelle formation in aqueous solution. The size of the biotin-conjugated PEG/PCL nanoparticles was determined by light scattering measurements to be 88-118 nm, depending on the molecular weight of the block copolymer, and remained less than 120 nm even after paclitaxel loading. From an in vitro release study, biotin-conjugated PEG/PCL nanoparticles containing paclitaxel evidenced sustained release profiles of the drug with no initial burst effect. The biotin-conjugated PEG/PCL block copolymer itself evidenced no significant adverse effects on cell viability at $0.005-1.0{\mu}g/mL$ of nanoparticle suspension regardless of cell type (normal human fibroblasts and HeLa cells). However, biotin-conjugated PEG/PCL harboring paclitaxel evidenced a much higher cytotoxicity for cancer cells than was observed in the PEG/PCL nanoparticles without the biotin group. These results showed that the biotin-conjugated nanoparticles could improve the selective delivery of paclitaxel into cancer cells via interactions with over-expressed biotin receptors on the surfaces of cancer cells.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2007.04a
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• pp.639-644
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• 2007

The accurate peak response estimation of a seismically excited structure with frictional damping system(FDS) is very difficult since the structure with FDS shows nonlinear behavior dependent on the structural period, loading characteristics, and relative magnitude between the frictional force and the excitation load. Previous studies have estimated that by replacing a nonlinear system with an equivalent linear one or by employing the response spectrum obtained based on nonlinear time history and statistical analysis. In the case that on earthquake load is defined with probabilistic characteristics, the corresponding response of the structure with FDS has probabilistic distribution. In this study, nonlinear time history analyses were performed for the structure with FDS subjected to artificial earthquake loads generated using Kanai-Tajimi filter. An equation for the probability density function (PDF) of the displacement response is proposed by adapting the PDF of the normal distribution. Finally, coefficients of the proposed PDF is obtained by regression analysis of the statistical distribution of the time history responses. Finally, the correlation between PDFs and statistical response distribution is presented.

• Journal of the Society of Naval Architects of Korea
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• v.51 no.5
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• pp.429-434
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• 2014

The main objective of the present study is to elucidate a correlation between ship resistances from computational fluid dynamics (CFD) and brake horse powers (BHP) from towing tank in container carriers. The tests were conducted for a range of combinations of trim conditions and speeds. To achieve this goal, 295 cases of numerical simulation have been performed using Star-CCM+ which had been statistically verified to predict ship resistances (Lee & Lee, 2014). Based on the normal distribution of resistance errors in all cases of the 4 container carriers, the confidence interval of numerical error was estimated as [-2.33%,+2.42%] with 95% confidence. The correlation coefficients between the ship resistances of CFD and the brake horse powers of the experiments were higher than 0.93. As a result, the numerical calculation of ship resistances is able to be utilized in order to provide a quick guidance in selection of the optimum loading condition.

• Journal of the Korean Wood Science and Technology
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• v.36 no.5
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• pp.56-65
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• 2008

In this paper experimental results are presented for the rheological behavior of high-solids saccharification of mixed northeast hardwood as a model feedstock. The experimental determination of the viscosity, shear stress, and shear rate relationships of the 10 to 20 percent slurry concentrations with constant enzyme concentrations were performed under variable rotational speed of a viscometer (2.0 to 200 RPM) at combined temperatures (50 to $30^{\circ}C$) for the initial four hours. The viscosities of saccharification slurries observed were in the ranges of 0.024 to 0.028, 0.401 to 0.058, and 0.840 to 0.087 Pa s for shear rates up to 100 reciprocal seconds at 10, 15, and 20 percent initial solids (w/v) respectively. The fluid behavior of the suspensions was modeled using the power-law, the Herschel-Bulkley, the Casson, and the Bingham model. The results showed that broth slurries were pseudoplastic with a yield stress. The model slope increased and the model intercept decreased with increasing fermentation time at shear rates normal for the fermentor. The broth slurries exhibited Newtonian behavior at high and low shear rates during initial saccharification process. The solid particle size ranged from 57.8 to $70.0{\mu}m$ for $40^{\circ}C$ and from 44.0 to 57.5 11m for combined temperatures at 10, 15, and 20 percent initial solids (w/v) respectively.

• Journal of the Korean Society for Advanced Composite Structures
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• v.2 no.3
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• pp.36-41
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• 2011

This study proposes a experimental method to evaluate bonding strength of FRPs used for retrofitting concrete structures. Specimens are designed so that debonding failure of FRPs can be induced from reinforced concrete beams retrofitted with two layers of carbon and glass FRPs. And three-point loading tests are performed to see if debonding failure with proper debonding strength is observed from the specimens. The test results show that the tested beams are failed due to debonding of FRPs, therefore, the proposed test method is capable of evaluating debonding strength of FRPs using relatively small normal strength concrete beams.

• Proceedings of the Korea Concrete Institute Conference
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• 2005.05b
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• pp.321-324
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• 2005

This paper presents a preliminary study on the influence of material ductility on diagonal tension behavior of shear-wall panels. There have been a number of previous studies, which suggest that the use of high ductile material such as ECC (Engineered Cementitious Composite) significantly enhanced shear capacity of structural elements even without shear reinforcements involved. The present study emphasizes increased shear capacity of shear-wall panels by employing a unique strain-hardening ECC reinforced with poly(vinyl alcohol) (PVA) short random fibers. Normal concrete was adopted as the reference material. Experimental investigation was performed to assess the failure mode of shear-wall panels subjected to knife-edge loading. The results from experiments show that ECC panels exhibit a more ductile failure mode and higher shear capacity when compared to ordinary concrete panels. The superior ductility of ECC was clearly reflected by micro-crack development, suppressing the localized drastic fracture typically observed in concrete specimen. This enhanced structural performance indicates that the application of ECC for a in-filled frame panel can be effective in enhancing seismic resistance of an existing frame in service.

• Journal of the Korean GEO-environmental Society
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• v.18 no.11
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• pp.27-33
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• 2017

Nonlinear dynamic analysis is performed to calculate the response of U-shaped cantilever retaining structure under seismic loading using the finite element (FE) analysis program OpenSees. A particular interest of the study is to evaluate whether the moment demand in the cantilever can be accurately predicted, because it is an important component in the seismic design. The numerical model is validated against a centrifuge test that was performed on cantilever walls with dry medium dense sand in backfill. Seismic analysis is performed using the pressure-dependent, multi-yield-surface, plasticity based soil constitutive model implemented in OpenSees. Normal springs are used to simulate the soil-structure interface. Comparison with centrifuge show that FE analysis provides good estimates of both the acceleration response and bending moment. The lateral earth pressure near the bottom of the wall is overestimated in the numerical model, but this does not contribute to a higher prediction of the moment.

• Journal of the Korean Geosynthetics Society
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• v.19 no.1
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• pp.1-9
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• 2020

This paper presents the results of experimental investigation on the effect of degree of saturation of soil on the pullout behavior of a geogrid. Different test variables were taken into account while performing the experiment including the soil physical conditions based on water content and external loading applied. The soil used was locally available weathered granite soil. The tests included variations in saturation of about 90%, 80%, 70% and 45% (optimum moisture content). The pullout tests were performed according to ASTM standard D 6706-01. The results indicate that increasing the degree of saturation in the soil decreases the pull-out capacity, which in turn decreases the interface friction angle and interaction coefficient. The decrease in the pullout interface coefficient was observed to be around 12.50% to 33.33% depending on the normal load and degree of saturation of the soil. The test results demonstrated the detrimental effect of increasing the degree of saturation within the reinforce soil on the pullout behavior of reinforcement, thus on the internal stability. The practical inferences of the outcomes are analyzed in detail.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.51 no.7
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• pp.349-361
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• 2002

Occasionally, equipment in a distribution system fails due to damage from weather, vandalism, or other causes. Failures and unexpected events do not always occur as and where expected. Therefore, a good contingency plan, multi-zone or otherwise, provides flexibility by locating switches at various strategic locations so that parts of a feeder can be picked up in the event of line outages at various places. It is possible to create feeder system layout that achieve remarkable contingency support economics, even as their normal peak loading levels approach thermal capacity, by utilizing six, seven, or even nine switchable zones per feeder. But many switchable zones per feeder are of questionable practicality and effectiveness, because of the complexity and time required for the switching operation. In practice, a zonal scheme with between three and four zones will usually provide complete contingency backup for all feeders. Line switches have both capital and maintenance costs, the planning for multi-zonal schemes is considerably more difficult than or loop or single-zone systems, and the required switching operations required during contingencies take more time. But multi-zonal schemes are used because these costs come to far less than the cost of additional capacity required for loop or single-zone. In this paper, we present the optimal number of switchable zones per feeder in Kora distribution system.

• Korean Journal of Biological Psychiatry
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• v.13 no.4
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• pp.267-272
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• 2006

Objectives : Schizophrenia is a clinically heterogenous disease with a strong genetic component. Many studies have suggested that brain-derived neurotrophic factor(BDNF) is involved in the pathophysiology of schizophrenia. This study was performed to determine whether there is an association between BDNF Val66Met polymorphism and schizophrenia. Methods : To identify any genetic predisposition to schizophrenia, we investigated the BDNF Val66Met polymorphism in 106 patients with schizophrenia and 147 normal controls with PCR-RFLP method. Statistical analyses were used to test the association between and BDNF Val66Met genotype and Schizophrenia. Results : No association was found between BDNF Val66Met polymorphism and schizophrenia. No significant differences were found comparing the BDNF genotype distributions according to the age of onset, the number of admission and familial loading in schizophrenia. Conclusion : This result indicates that BDNF Val66Met polymorphism is not associated with schizophrenia. However, further studies with a large number of subjects are needed to confirm whether the BDNF gene is related to schizophrenia.