• Smart Structures and Systems
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• v.29 no.4
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• pp.589-598
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• 2022

Timber structures are susceptible to structural damages caused by variations in moisture content (MC), inducing severe durability deterioration and safety issues. Therefore, it is of great significance to detect MC levels in timber structures. Compared to current methods for timber MC detection, which are time-consuming and require bulky equipment deployment, Lead Zirconate Titanate (PZT)-enabled stress wave sensing combined with statistic machine learning classification proposed in this paper show the advantage of the portable device and ease of operation. First, stress wave signals from different MC cases are excited and received by PZT sensors through active sensing. Subsequently, two non-baseline features are extracted from these stress wave signals. Finally, these features are fed to a statistic machine learning classifier (i.e., naïve Bayesian classification) to achieve MC detection of timber structures. Numerical simulations validate the feasibility of PZT-enabled sensing to perceive MC variations. Tests referring to five MC cases are conducted to verify the effectiveness of the proposed method. Results present high accuracy for timber MC detection, showing a great potential to conduct rapid and long-term monitoring of the MC level of timber structures in future field applications.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.30 no.12 s.255
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• pp.1211-1217
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• 2006

This study is focused on oxidation prevention of STS430, which is generally used as solid oxide fuel cell(SOFC) interconnect at intermediate operating temperatures with oxidation-proof coatings. Inconel, $La_{0.6}Sr_{0.4}CoO_3(LSCo)$ and $La_{0.6}Sr_{0.4}CoO_3(LSCr)$ were chosen as coating materials. Using a radio frequency magnetron sputtering method, each target material was deposited as thin film on STS430 and was analyzed to find out favorable conditions. In this study, LSCr-coated STS430 can reduce electrical resistance to 1/3 level, compared with uncoated STS430. Also, long-term durability test at $700^{\circ}C$ for 1000 hours tells that LSCr thin layer performs an important role to prohibit serious degradations. Superior oxidation-resistant characteristic of LSCr-coated STS430 is attributed to the inhibition of spinel structure formation such as $MnCr_2O_4$.

• Corrosion Science and Technology
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• v.21 no.6
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• pp.514-524
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• 2022

Carbon emissions from fuel consumption have been pointed by scientists as the cause of global warming. In particular, fossil fuels are known to emit more carbon when burned than other types of fuels. In this regard, International Maritime Organization has announced a regulation plan to reduce carbon dioxide emissions. Therefore, recently, Liquefied Natural Gas propulsion ships are responding to such carbon reduction regulation. However, from a long-term perspective, it is necessary to use carbon-free fuels such as hydrogen and ammonia. Nitrogen oxides might be generated during ammonia combustion. There is a possibility that incompletely burned ammonia is discharged. Therefore, rather than being used as a direct fuel, Ammonia is only used to reduce NO_X such as urea solution in diesel vehicle Selective Catalyst Reduction. Currently, LPG vehicle fuel feed system studies have evaluated the durability of combustion injectors and fuel tanks in ammonia environment. However, few studies have been conducted to apply ammonia as a ship fuel. Therefore, this study aims to evaluate corrosion damage that might occur when ammonia is used as a propulsion fuel on ships.

• Journal of Chest Surgery
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• v.43 no.4
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• pp.441-446
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• 2010

The ideal graft requires acceptable size, less tissue toxicity, resistance to infection, and long-term durability. Great saphenous veins are gaining popularity as acceptable graft conduits, but they require time to grow in caliber. We report 2 cases of graft bypass and reconstruction using superficial femoral veins to acheive immediate high-flow patency.

• Journal of the Korea Concrete Institute
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• v.24 no.2
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• pp.103-109
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• 2012

Micro-cracks with a width less than 0.1 mm in precast concrete panels do not cause structural problem, but they can cause problems in long term durability and concrete surfaces aesthetic, requiring additional repair costs. In this paper, polymer cement concrete is used to increase flexural tensile strength and to prevent micro-cracks due to construction loads on LB-DECK panels. Using 5% polymer-cement ratio, the panel crack moment is increased by improving flexural tensile strength and controlling visible micro-cracks during construction stage of LB-DECK.

• Pediatric Gastroenterology, Hepatology & Nutrition
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• v.7 no.2
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• pp.197-207
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• 2004

Purpose: To evaluate the long-term therapeutic efficacy and durability of lamivudine in Korean children with chronic hepatitis B. Methods: A total of 48 children (31 male and 17 female; age, 1~18 years, mean, 8 years) with chronic hepatitis B who received lamivudine for at least six months from March 1999 to September 2004 were followed for a mean period of 29 months (8~66 months) at Department of Pediatrics, Kyungpook National University Hospital in Korea. Response to treatment was defined as the normalization of ALT and HBV DNA levels, and HBeAg seroconversion after the initiation of treatment. Results: Twenty nine (60%) among the 48 children treated with lamivudine responded and nine (19%) children lost HBsAg during therapy. ALT and HBV DNA level had normalized in 94% one year after the initiation of treatment. Kaplan-Meier estimates of cumulative HBeAg seroconversion rates over the years were 13% (0.5 year), 34% (1 year), 50% (1.5 years), 68% (2 years), 79% (2.5 years) and 90% at 3 years respectively. Above all, among the 22 children treated before the age of seven, loss of HBsAg occurred in eight (36%), which showed superior rate of HBsAg loss (p=0.002 vs age >7). Conclusion: Long-term treatment of lamivudine improved the rate of HBeAg seroconversion in Korean children with chronic hepatitis B. After three years' observation, most of treated children have sustained HBeAg clearance. We believe that lamivudine should be tried as the first therapeutic option for children with chronic hepatitis B in immune clearance phase.

• Journal of the Korean Electrochemical Society
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• v.19 no.1
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• pp.14-20
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• 2016

Vanadium redox flow battery (VRFB) is an energy conversion device in which charging and discharging are alternatively carried out by oxidation and reduction reactions of vanadium ions with different oxidation states. VRFB consists of electrolyte, electrode, ion-exchange membrane, etc. The role of ion-exchange membranes in VRFB separates anolyte and catholyte and provides a high conductivity to hydrogen ions. Recently much attention has been devoted to develop ideal ion-exchange membranes for VRFB. A number of developed ion-exchange membranes should be evaluated to find out ideal ion-exchange membranes for VRFB. Long-term durability test is a crucial characterization of ion-exchange membranes for commercialization, but is very time-consuming. In this study, the life time prediction protocol of ion-exchange membranes in VRFB cell tests was developed through short-term single cell performance evaluation (real total operation time, 87.5 hrs) at three different current densities. We confirmed a decrease in test time up to 96.2% of real durability tests (expected total operation time, 2,296 hrs) and 5~6% of relative error discrepancy between the predicted and the real life time in a unit cell.

• Journal of the Regional Association of Architectural Institute of Korea
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• v.20 no.6
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• pp.121-129
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• 2018

The present study analyzed what policies are being executed for deteriorated apartments in Japan and what characteristics each policy had in order to examine policy direction and implications for the improvement of vitalization of remodeling business of deteriorated apartments in Korea. The study results are as follows. Japan recognized social problems of deteriorated apartments and pushed forward a national level remodeling actively by preparing financial support of central government and supporting plan by city and province. First, Japan maintained initial performance of buildings through phased maintenance for deterioration of buildings and aimed to reduce environmental load and maintain asset values of buildings through enlarging durability of buildings by responding to lifestyle according to social changes. To this end, they promoted the long life of buildings through the establishment of systematic long term repair plan from the stage of moving in the buildings. Second, in order to reduce the risk of remodeling projects, they prepared an environment where business could be carried out with an easy mind in various aspects by introducing remodeling business registration system and large scale repair construction defect insurance system. Third, they reduced economic burden of main agents of remodeling business with tax preferential treatment and financial support policies. Fourth, they have established remodeling support system based on overall social issues and connected it with social effect that could be obtained through this. The remodeling policies of Japan were carried out in the direction of solving social problems and considering economic aspect rather than just improving individuals' residence environment.

• Journal of the Korea Convergence Society
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• v.11 no.11
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• pp.165-173
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• 2020

ABS and PLA are applied for restoring missing part of damaged ceramics, but are not similar to the material of ceramics, so this study conducted a research on the properties and applicability of ceramic resin. This study conducted actual restoration of ABS and ceramic resin as well as cast restoration method with experiment of properties. Results show that manufacturing of restored part showed higher precision than existing materials, which enables printing of tiny shapes showing excellent surface texture and gloss than L30 and ABS resin. As a result of measuring properties, the material showed excellent durability than existing materials with no contraction and deformation and compressive strength, but value of specific gravity and hardness can lower processability after manufacturing. Long-term monitoring, evaluation of reliability of ceramic resin applied in this study, additional researches on the restorability of the original shape when printing too thin or long restored part are needed.

• Journal of the Korean GEO-environmental Society
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• v.3 no.3
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• pp.27-36
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• 2002

Generally, it is known that urethane injection is excellent in long-term durability and environment friendly for ground improvement. However, urethane grouting has short rise time thus the penetration distance from the injection point is so short. Therefore, urethane injection cannot be used for the site where requires ground improvement in deep location from the injection point. Other injection materials such as cement cannot be alternatives when rapid hardening is required. From this study, we improve disadvantage urethane injection by developing TAS method. From the field tests, it is ascertained that TAS increases injection distance over 10m, which is further than that of original urethane grouting. In addition, TAS has relatively short Rise-time compared to cement grouting thus instantaneous improvement can be mobilized right after the injection. Short Rise-time and long penetration distance provide excellent applicability for tunnel construction.