• Journal of the Korean Geotechnical Society
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• v.24 no.1
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• pp.71-80
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• 2008

This paper presents the reusults of wide width tensile tests under sustained and cyclic loads with vairous loading rate on geogrids. A seires of modified wide width tensile tests were conducted to investigate the effect of tensile strain rate on the deformation behavior of the geogrids. In addition, residual deformation characteristics of a geogrid under sustained or cyclic tests were also investigated. The results indicated that the residual deformation of a geogrid is strongly related to the viscous behavior of the geogrid, and the residual deformation can be well described by a hyperbolic curve. Also revealed was that residual deformation of a geogrid when subject to sustained or cyclic load should be described with the framework of viscous behavior.

• Journal of the Korean Geotechnical Society
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• v.23 no.6
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• pp.5-21
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• 2007

Despite a number of advantages of reinforced earth walls over conventional concrete retaining walls, there exit concerns over long-term residual deformation when they are subjected to repeated and/or cyclic loads, especially when used as part of permanent structures. In view of these concerns, in this paper time-dependant deformation characteristics of geosynthetic reinforced modular block walls under sustained anuor repeated loads were investigated using reduced-scale model tests. The results indicated that a sustained or repeated load can yield appreciable magnitude of residual deformation, and that the residual deformations are influenced not only by the loading characteristics but by the mechanical properties of geogrid. It is also found that the preloading technique can be effectively used in controlling residual deformations of reinforced soils subjected to sustained and/or repeated loads.

• Journal of the Korean Geosynthetics Society
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• v.10 no.4
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• pp.105-112
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• 2011

This paper presents the numerical modelling technique for modeling the time-dependent behavior of geosynthetic reinforced soil wall under a sustained load. The applicability of power law-based creep models for modeling the creep deformations of geogrid and reinforced soil was first examined. The modeling approach was then used to simulate the long-term performance of a geosynthetic reinforced soil wall used in a bridge abutment. The results indicated that the power law-based models can be effectively used for modelling the long term behavior of geosynthetic reinforced walls under sustained loading. In addition, it was shown that, when using creep deformation susceptible backfill soils, the abutment wall and the sill beam may experience deformations exceeding allowable limits. Practical implications of the findings from this study are discussed in great detail.

• Journal of Pharmaceutical Investigation
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• v.29 no.4
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• pp.309-313
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• 1999

This study was prepared to develop the sustained release dosage form of phenylpropanolamine hydrochloride (PPA) by complexation with cation exchange resin(CER). The PPA-CER complex was confirmed by differential scanning calorimetry(DSC) thennogram, indicating a relative shift of an endometric peak of PPA to higher temperature. The loading efficiency was increased as the amount of PPA was increased as well as the time of fractional exchange was advanced as the temperatures were increased. Loading efficiency, fractional exchange, reaction rate constant and activation energy were highly dependent on the temperature and drug : resin ratio. The optimal ratio of PPA and resin was estimated to be 10: 10 for the sustained release.

• Steel and Composite Structures
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• v.35 no.1
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• pp.93-109
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• 2020

Developed from conventional concrete filled steel tubular (CFST) members, concrete-encased CFST has attracted growing attention in building and bridge practices. In actual construction, the inner CFST is erected prior to the casting of the outer reinforced concrete part to support the construction preload, after which the whole composite member is under sustained service load. The complex loading sequence leads to highly nonlinear material interaction and consequently complicated structural performance. This paper studies the full-range behaviour of concrete-encased CFST columns with initial preload on inner CFST followed by sustained service load over the whole composite section. Validated against the reported data obtained from specifically designed tests, a finite element analysis model is developed to investigate the detailed structural behaviour in terms of ultimate strength, load distribution, material interaction and strain development. Parametric analysis is then carried out to evaluate the impact of significant factors on the structural behaviour of the composite columns. Finally, a simplified design method for estimating the sectional capacity of concrete-encased CFST is proposed, with the combined influences of construction preload and sustained service load being taken into account. The feasibility of the developed method is validated against both the test data and the simulation results.

• Journal of Korea Technical Association of The Pulp and Paper Industry
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• v.32 no.1
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• pp.1-9
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• 2000

This study was carried out to improve the opacity of printing paper. Conventional filler loading enhanced the opacity of paper, but subsequently caused reduction of paper strength of paper. We try to seek a new filler loading method so-called beater loading that enhances opacity of paper as well as sustained desire strength. In our experiment, comparing to direct loading method, the beater loading method enhanced 0.8% of opacity and 0.2% of brightness. This also decreased the rates of strength reduction of paper. Therefore, the results obtained in this study indicated that beater loading was a very effective method to improve the opacity of paper while not to decreased so much of paper strength.

• Journal of Biomedical Engineering Research
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• v.16 no.3
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• pp.367-375
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• 1995

Ampicillin sodium (AMP-Na) was loaded Into fibrin glue (FG) in two different ways and was tried to achieve sustained release from FG. One was loading of AMP-Na in a simple mixing and the other was loading of bovine serum albumin (BSA) microspheres which contained ANP-Na. In case of simple mixing, the release control of AWP-Na from FG was tried by variation of FBNG concentration, but failed. However, the loading of BSA mlcrosphere containing ANP-Na into FG showed sustained re- lease of AMP-Na, especially when microsphere was crosslinked with glutaraldehyde (tO.9 : 33hr). The maximum adhesive strength of FG showed at concentration of FBWG and thrombin, 5.0 % and 25-50 NIHU/ml, respectively. The concentration of Factor Xlll (0-500 U/1g of FBNG) did not affect the adhesive strength of FG. The optimal incubation time was 60 min. The AMP-Na or BSA microsphere which was loaded into FG had no significant effect on the adhesive strength of FG.

• Proceedings of the Korea Concrete Institute Conference
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• 1999.10a
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• pp.779-782
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• 1999

This study was carried out to estimate the effects of the loading conditions on the corrosion of reinforcing bars and permeation of chloride ion. The permeation of chlorides depends not only on the transfer properties in concrete but also on the load applied in the case of reinforced concrete structures. Recent studies reported that the loading conditions affected the corrosion rate of the reinforcing bars under existence of an external current supply. But it was not reported that loading conditions affected corrosion of reinforcing bar caused by the characteristics of permeation and the process of cracking. In this experiment, it was shown that the corrosion of reinforcing bars and the characteristics of permeating were greatly affected by the loading conditions.

• Macromolecular Research
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• v.8 no.6
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• pp.253-260
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• 2000

Biodegradable wafers were prepared with poly (hydroxybutyrate-co-hydroxyvalerate) (PHBV;5, 10, and 15 mole% for 3-hydroxyvalerate) by simple heat pressing method for the sustained release of antibiotic agent, gentamicin sulfate (GS) to investigate the possibility of the treatment for osteomyelitis. The effects of hydroxyvalerate (HV) content, thickness of wafers, various types of additives such as sodium dodecyl sulfate (SDS), microcrystalline cellulose, polyvinylpyrrolidone, and hydroxypropylcellulose (HPC), and different initial drug loading ratio on the release profile have been investigated. In vitro release studies showed that different release patterns and rates could be achieved by simply modifying factors in the preparation conditions. PHBV wafers with 3 mm thickness, 10% of GS initial loading, 15% of HV content and addition of 5% of SDS and HPC were free from initial burst and a near-zero-order sustained release was observed for over 30 days. It might be suggested that the mechanisms of G5 release may be more predominant simple dissolution and diffusion of GS than erosion of PHBV in our system.

• Archives of Pharmacal Research
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• v.18 no.3
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• pp.183-188
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• 1995

Polymeric reinforcement and coatings of alginate beads were carried out to control the release rate of drug from alginate beads. A poorly water-soluble ibuprofen (IPF) was selected as a model drug. A commercially available $Eudragit^{\circledR}$ RS100 was also used as a polymer. Effects of polymeric contents, the presence of plasticizers and amount of drug loading on the release rate of drug were investigated. The release rate of drug from alginate beads in the simulated gastric fluid did not occur within 2 h but released immediately when dissolution media were switched to the simulated intestinal fluid. No significant difference of release rate from polymer-reinforced alginate bead without plasticizers was observed when compared to plain (simple) beads. However, the release rate of drug from polymer-reinforced alginate beads was further sustained and retarded when aluminium tristearate (AT) as a plasticizer was added to polymer. However, polyethylene glycol 400 (PEG400) did not change the release rate of drug from alginate beads although PEG400 was used to improve dispersion of polymer and sodium alginate, and plasticize $Eudragit^{\circledR}$ RS100 polymer. The presence of plasticizer was crucial to reinforce alginate gel matrices using a polymer. As the amount of drug loading increased, the release rate of drug increased as a result of decreasing effects of polymer contents in matrices. The significantly sustained release of drug from polymer-coated alginate beads occurred as the amount of polymer increased because the thickness of coated membrane increased so that cracks and pores of the outer surface of alginate beads could be reduced. The sustained and retarded action of polymer-reinforced and coated beads may result from the disturbance of swelling and erosion (disintegration) of alginate beads. From these findings, polymeric-reinforcement and coatings of alginate gel beads can provide an advanced delivery system by retarding the release rate of various drugs.