• KDI Journal of Economic Policy
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• v.36 no.1
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• pp.81-106
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• 2014

This paper compares the monetary policy problem in open economies with that in closed economies. It is found that the monetary policy problems in open and closed economies are isomorphic even in the presence of distortions in a steady state and hence the optimal monetary policies have similar properties. On the other hand, the monetary policy maker in open economies has a distorted incentive to manipulate the terms-of-trade. Because of the additional distortion in open economies, there exist gains from international monetary policy cooperation even in the case of a unit intertemporal elasticity of substitution, in contrast to the literature that abstracts from distortions in a steady state. Also, it is found that in the presence of distortions inflation bias is decreasing in openness, which is line with empirical evidence. In addition, this paper presents a simple transformation so that methods in closed-economy models are easily applicable to open-economy models.

• Journal of the Korea institute for structural maintenance and inspection
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• v.22 no.2
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• pp.90-97
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• 2018

The quantities of electronic waste have been increased rapidly, and was caused variety problems such as environmental pollution or dissipation of resource. So, it needed to development of recycling technology about heavy metal in the electronic waste. Meanwhile, filler material (concrete or mortar) was used for shielding radioactive waste, however, it did not used materials that it is proved radiation shielding performance. So, there is a lack of confidence in the shielding performance. Therefore, in this paper, mechanical properties of concrete was evaluated for the applicability using electronic waste as fine aggregate of filler material. From the test results, compressive and flexural strength and elasticity modulus and the micro pore in the $1{\mu}m$ range was significantly affected by substitution of electronic waste, however, it could be improved the performance by using mineral admixture as binder. So, it is shown that the electronic waste could be applicable as fine aggregate of filler material.

• Journal of the Korean Wood Science and Technology
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• v.21 no.2
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• pp.57-65
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• 1993

The aim of this research was to manufacture sludge-particle board using paper sludge with wood particle and to investigate physical and mechanical properties of various sludge-particle boards, fabricated with ratios of sludge to particle of 10 to 90, 20 to 80, 30 to 70, 40 to 60 and 50 to 50(oven dry weight based). Sludge-particle boards were manufactured by urea-formaldehyde resin, 0.8 target specific gravity, and 10mm thickness. It was possible to manufacture sludge-particle board as the same processing in the present particleboard manufacturing system. This sludge-particle board have different properties as composition ratios of sludge and particle. And sludge-particle board made from 10 percent to 20 percent of sludge mixing ratio have similar mechanical properties compared with control particleboard. Especially, the sludge-particle board made from 10 percent to 40 percent mixing ratios of sludge have superior to control particleboard in internal bond, screw withdrawal holding strength and modulus of elasticity. In the case of dimensional stability, water absorption was increased and thickness swelling was decreased as increased with sludge mixing proportion. The sludge-particle board made of different mixing ratios of our laboratory design was able to concluded that there is possibility of partial substitution of wood particle materials.

• Computers and Concrete
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• v.24 no.3
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• pp.193-206
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• 2019

Although concrete is the most widely used construction material, its deficiency in shrinkage and low tensile resistance is undeniable. However, the aforementioned defects can be partially modified by addition of fibers. On the other hand, possibility of adding waste materials in concrete has provided a new ground for use of recycled concrete aggregates in the construction industry. In this study, a constant combination of recyclable coarse and fine concrete aggregates was used to replace the corresponding aggregates at 50% substitution percentage. Moreover, in order to investigate the effects of fibers on mechanical and durability properties of recycled aggregate concrete, the amounts of 0.5%, 1%, and 1.5% steel fibers (ST) and 0.05%, 0.1% and 0.15% polypropylene (PP) fibers by volumes were used individually and in hybrid forms. Compressive strength, tensile strength, flexural strength, ultrasonic pulse velocity (UPV), water absorption, toughness, elastic modulus and shrinkage of samples were investigated. The results of mechanical properties showed that PP fibers reduced the compressive strength while positive impact of steel fibers was evident both in single and hybrid forms. Tensile and flexural strength of samples were improved and the energy absorption of samples containing fibers increased substantially before and after crack presence. Growth in toughness especially in hybrid fiber-reinforced specimens retarded the propagation of cracks. Modulus of elasticity was decreased by the addition of PP fibers while the contrary trend was observed with the addition of steel fibers. PP fibers decreased the ultrasonic pulse velocity slightly and had undesirable effect on water absorption. However, steel fiber caused negligible decline in UPV and a small impact on water absorption. Steel fibers reduce the drying shrinkage by up to 35% when was applied solely. Using fibers also resulted in increasing the ductility of samples in failure. In addition, mechanical properties changes were also evaluated by statistical analysis of MATLAB software and smoothing spline interpolation on compressive, flexural, and indirect tensile strength. Using shell interpolation, the optimization process in areas without laboratory results led to determining optimal theoretical points in a two-parameter system including steel fibers and polypropylene.

• Journal of the Korean Wood Science and Technology
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• v.50 no.2
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• pp.134-147
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• 2022

The objective of this study is to determine the effect of fiber direction arrangement and layer composition of hybrid bamboo laminate boards on the physical and mechanical properties. The raw material used was tali bamboo (Gigantochloa apus (J.A. & J.H. Schultes) Kurs) rope in the form of flat sheets (zephyr) and falcata veneer (Paraserianthes falcataria (L) Nielsen). Zephyr bamboo was arranged in three layers using water-based isocyanate polymer (WBPI) with a glue spread rate of 300 g/m². There were variations in the substitution of the core layer with falcata veneers (hybrid) as much as two layers and using a glue spread rate of 170 g/m². The laminated bamboo board was cold-pressed at a pressure of 22.2 kgf/cm² for 1 h, and the physical and mechanical properties were evaluated. The results showed that the arrangement of the fiber direction significantly affected the dimensional stability, modulus of rupture, modulus of elasticity, shear strength, and screw withdrawal strength. However, the composition of the layers had no significant effect on the physical and mechanical properties. The bonding quality of bamboo laminate boards with WBPI was considered to be quite good, as shown by the absence of delamination in all test samples. The bamboo hybrid laminate board can be an alternative based on the physical and mechanical properties that can meet laminated board standards.

• Advances in concrete construction
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• v.16 no.6
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• pp.303-316
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• 2023

Using industrial wastes and construction and demolition (C&D) wastes is potentially advantageous for concrete production in terms of sustainability improvement. In this paper, a sustainable Self-Compacting Concrete (SCC) made with industrial wastes and C&D wastes was proposed by considerably replacing natural counterparts with recycled coarse aggregates (RCAs) and supplementary cementitious materials (SCMs) (i.e., Fly ash (FA), ground granulated blast furnace slag (GGBS) and silica fume (SF)). A total of 12 SCC mixes with various RCAs and different combination SCMs were prepared, which comprise binary, ternary and quaternary mixes. The mechanical properties in terms of compressive strength and static elasticity modulus of recycled aggregates (RA-SCC) mixes were determined and analyzed. Microstructural study was implemented to analyze the reason of improvement on mechanical properties. By means of life cycle assessment (LCA) method, the environmental impacts of RA-SCC with various RCAs and SCMs were quantified, analyzed and compared in the system boundary of "cradle-to-gate". In addition, the comparison of LCA results with respect to mechanical properties was conducted. The results demonstrate that the addition of proposed combination SCMs leads to significant improvement in mechanical properties of quaternary RA-SCC mixes with FA, GGBS and SF. Furthermore, quaternary RA-SCC mixes emit lowest environmental burdens without compromising mechanical properties. Thus, using the combination of FA, GGBS and SF as cement substitution to manufacture RA-SCC significantly improves the sustainability of SCC by minimizing the depletion of cement and non-renewable natural resources.

• KDI Journal of Economic Policy
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• v.13 no.2
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• pp.41-67
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• 1991

Local autonomy of Korea's lower-level local council has been reinstated following elections last March for the first time in thirty years. Last June, we had elections for the upper-level local council. Mayors, governors, and administrative chiefs of cities, provinces and other local government bodies are slated for elections in the first half of next year. The impacts of local autonomy are taking effect in not only the political sphere, but also the administrative and economic spheres. In fact, it seems that some modification of all economic policy making and administration is inevitable. Since the initiation of local autonomy, in order to make the economy work more efficiently, it has become quite important to examine the impact of local autonomy on the national economy. The areas of local autonomy include independent legislative power, administrative power, organizational power, and most important of all, the independent public financial power of the local governments. The purpose of this paper is to examine the effects of local autonomy on the national economy and ways of enhancing the role of local public finance to facilitate settlement and development of the local autonomy system. Local autonomy will contribute to the continuous growth of our economy, allow balanced development, and generate greater efficiency. However, local autonomy can also incur economic costs causing at times short-term price instability, inefficient resource allocation, through tax competition and tax exporting, and insolvency of local government due to abusive fiscal operation. To reduce these side effects, different alternatives must be considered. Local autonomy systems generally provide more efficient resource allocation than centralization. But in the model used in Chapter 3 of this paper, the relative efficiencies of both local autonomy and centralization are determined by comparing the elasticity of substitution between national public goods and local public goods. If the elasticity of substitution is bigger than one, centralization provides a more efficient resource allocation. The development of local autonomy could be attained through democratization of the local public finance system including the following three propositions. I) The independence of public financial power of local governments should be established over central government. Furthermore, a democratically operated scheme of intergovernmental fiscal coordination is especially necessary. 2) In the operation of local finance, direct democracy is needed to induce the voluntary participation of local residents. The residents can take part in planning both the local budget and the development of the community. To attain this goal, all the results of local finance operations should be made public. 3) Among economic ill-effects of the local autonomy system, the most serious one is the possibility of insolvency of local governments. Therefore, measures to limit abusive spending by the local governments should be introduced, such as the fiscal restraints system adopted in the United States.

• Journal of Labour Economics
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• v.29 no.1
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• pp.129-152
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• 2006

The purpose in this study is to analyze the effect of expected public pension assets (or social security wealth) and retirement incentives on retirement behaviors of two wage earners households. For the purpose of the study, an empirical analysis was conducted. In the empirical step, it was found that the empirical results were significant for men, but not for women namely, statistically asymmetric if behaviors of two couples are interdependent. The cause for the statistically asymmetric results were then determined. The Bivariate Probit model was used for estimation in the first step and the KLIPS(Korean Labor and Income Panel Study) was used as data for estimation. According to the empirical analysis, the results showed statistically significant asymmetry for men, however not for women, in expected public pension assets and other retirement incentives, non-wage assets, age difference, spouse's health status, spouse's monthly wages per hour and aging of their spouse In this study, cause of statistically asymmetric result in asymmetric complementarities of leisure of couples were found, then explained through different methods of comparison from the most recent studies. First, spouse's cross wage elasticity of self leisure demand(retirement) was calculated and determined whether complementarities of leisure of couples is positive or negative. Then, the degree of complementarities of leisure was distinguished in comparison with the relative size of two cross elasticities. Thus, men have relatively strong complementarities of leisure. But for women, it may roughly cancel out due to the substitution effect and the income effect. Therefore, women have relatively weak complementarities of leisure.

• Journal of Labour Economics
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• v.40 no.1
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• pp.1-36
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• 2017

This study aimed to analyze influencing factors to increase the wage differential between large enterprise and subcontracted small-medium enterprises by using panel data composed of 19 manufacturing industries for 16 years from 1999 to 2014. According to the results of analysis, in large enterprises the elasticity of substitution between the labor inputs and the subcontracted product supplies from small-medium enterprises was significantly less than 1. So, the increase in wages of workers of large enterprises, whose degree of employment protection was relatively high, seemed to increase the share of wage cost in total cost and was resulted to decrease the cost share of subcontracted product supplies significantly. This was interpreted to be able to exert a negative influence upon the price of subcontracted product supplies and the wages of workers in subcontracted small-medium enterprises, and, therefore, to increase the wage differentials between large enterprises and subcontracted small-medium enterprises. Furthermore, it was also found that the increases in the labor union participation rate at large enterprises and the openness rate of the industry concerned were contributing to make such effects much stronger significantly. In order to mitigate the wage differentials and the polarizing trend in labor market, we can suggest to establish a certain kind of flexible wage system and to introduce co-bargaining practices with the workers of subcontracted small-medium enterprises within large enterprises, and also for the workers of small-medium enterprises, to prepare new social systems to upgrade their human resources and job skills drastically.

• Culinary science and hospitality research
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• v.18 no.4
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• pp.183-198
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• 2012

The purpose of this study is to determine potential effectiveness of sourdough starter powder (made of Korean wheat flour) in the quality characteristics of bread and in the substitution effect of a dough improver in bread baking. The bread containing sourdough starter powder was considered to be most suitable for making sourdough bread. As a result, SP 10 showed the best fermentation rate and the highest volume and specific volume. In sensory testing, SP 10 was most preferable among others. According to experimental comparison between optimal addition ratio of SP 10 and other sourdough starter powder products available in Korean domestic market, SI had the highest fermentation rate, highest volume and specific volume. Analysis of texture showed that SI was soft with the lowest hardness and the highest elasticity. Sensory test showed that SI was most preferable of all, and SP 10 was more preferable than BP. It was concluded that SP 10 was not less preferable in the aspect of preference at sensory test than other products. Hence, it is expected that sourdough starter powder made of Korean wheat flour will be possibly more popular and effective in replacing some portion of dough improver of baking.