• Journal of the Korea Organic Resources Recycling Association
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• v.28 no.1
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• pp.65-72
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• 2020

The aims of this study were to compare the biomethanation of CO₂ through specific methanogenic activity (SMA) test which was inoculated with four different types of mixed microbial culture obtained from full-scale anaerobic digestion (AD) plants. The experimental results showed that CH₄ conversion was the highest in the samples inoculated by seed sludge taken from ADs of food waste and brewery; under this condition, the produced biomethane contains 89.3-91.9% of CH₄. Meanwhile, the lowest level was obtained in the sample from sewage sludge. The measured ratio of CH₄ production rate to CO₂ consumption rate in all reactors was higher than the theoretical value (1) in the middle of the period and soon dropped to 0.7-0.8. It might be due to changed metabolic pathways in the reactor by the degradation of residual organic matter and the increased activity of homoacetogenic bacteria.

• Journal of the Korea Concrete Institute
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• v.24 no.5
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• pp.585-596
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• 2012

In this study, the flexural characteristics of reinforced polymer concrete T-beams strengthened with GFRP, typically used for bridges and parking structures, are investigated. A method to determine the flexural failure mode of reinforced polymer concrete T-beams comprised of compression failure (CF), tension failure (TF), and fiber sheet failure (FF) for different levels of GFRP strengthening is proposed. Moreover, the present study provides a formula to calculate the design flexural strength for each failure mode. In reinforced polymer concrete T-beams strengthened with GFRP, an ideal failure mode can be achieved when the failure occurs in the following order: 1) yield of steel reinforcement, 2) failure of GFRP, and 3) compression failure of concrete. In the case of FF mode, due to GFRP failure before the polymer concrete crushing in compression region, a concept of equivalent rectangular block based on the ultimate limit state of concrete should not be used. Thus, this study suggests an idealized stress-strain curve for polymer concrete and finds parameters for stress block, ${\alpha}$ and ${\beta}$ based on the strain distribution in polymer concrete. Furthermore, the present study suggests an aspect ratio of 2.5 by examining the compressive stress distribution and design flexural strength characteristics for different aspect ratio of T-beams. This study also provides a design flexural strength formula, and validates its acceptability based on experiment and theoretical analysis.

• KDI Journal of Economic Policy
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• v.13 no.4
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• pp.141-153
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• 1991

The optimal choice of the tax rate and the inflation rate framework is extended to yield relevant interpretations for the optimal fiscal and monetary policy regime in Korea. To study the relationship between the government budget and monetary growth in different environments of policy coordination, two models assuming different degrees of fiscal dominance are developed. By modelling differing institutional arrangements of the fiscal and the monetary authority from an optimal government finance viewpoint, we find the optimal relationship among some important fiscal and monetary variables. By testing the existence of the relationship empirically, we find the characteristics of the optimal policy-mix regime in Korea. The first model-the strong from of fiscal dominance-studies the optimal collection of seigniorage in a period-by-period optimization with standard assumptions on the income velocity of money, deriving a general testable result: the optimal inflation/tax rate ratio co-vary with the marginal revenue ratio. The second model-the weak form of fiscal dominance-studies an implication of the inflationary bias of discretionary monetary policy in the presence of fiscal side distortions. This model shows that the tax rate and the inflation rate can have a positive correlation. Empirical tests of the theoretical results are done for the Korean economy for 1972-1989 period. The test results show that the macroeconomic policy regime in Korea can be characterized by the strong form of fiscal dominance, implying the importance of the government budget in explaining money growth and inflation.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.28 no.1
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• pp.115-121
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• 1983

This experiment was conducted to investigate the growing process, nitrogen content of leaves and grain weight of the tillers of three wheat and one barley cultivars under space planting condition. The rates of the ear-bearing tillers were highest in the main stem (MS) and followed by the Ist, 2nd, 3rd tiller of the first order tiller. The leaf emergencies on main stem and tillers of barley were found simmilar results to synchronously emerging leaf theory reported by katayama, however, one or more leaves were emerged from the tillers of wheat comparing to the theoretical numbers. The orders of the ear primordia development were MS 1st 2nd 3rd tiller. The differences of ear development between main stem and tillers were greatter in wheat than in barley. Total nitrogen content in leaf decreased accompanying with growth and the highest content were found on the higher ordered tillers. The order of the proportion of each stem grain weight to the grain yield per unit area was MS > 1st≒2nd > 3rd tiller.

• Journal of Distribution Science
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• v.11 no.10
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• pp.73-79
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• 2013

Purpose - This study examines the impact of oil price volatility on economic activities in Korea. The new millennium has seen a deregulation in the crude oil market, which invited immense capital inflow into Korea. It has also raised oil price levels and volatility. Drawing on the recent theoretical literature that emphasizes the role of volatility, this paper attends to the asymmetric changes in economic growth in response to the oil price movement. This study further examines several key macroeconomic variables, such as interest rate, production, and inflation. We come to the conclusion that oil price volatility can, in some part, explain the structural changes. Research design, data, and methodology - We use two methodological frameworks in this study. First, in regards to the oil price uncertainty, we use an Exponential-GARCH (Exponential Generalized Autoregressive Conditional Heteroskedasticity: EGARCH) model estimate to elucidate the asymmetric effect of oil price shock on the conditional oil price volatility. Second, along with the estimation of the conditional volatility by the EGARCH model, we use the estimates in a VECM (Vector Error Correction Model). The study thus examines the dynamic impacts of oil price volatility on industrial production, price levels, and monetary policy responses. We also approximate the monetary policy function by the yield of monetary stabilization bond. The data collected for the study ranges from 1990: M1 to 2013: M7. In the VECM analysis section, the time span is split into two sub-periods; one from 1990 to 1999, and another from 2000 to 2013, due to the U.S. CFTC (Commodity Futures Trading Commission) deregulation on the crude oil futures that became effective in 2000. This paper intends to probe the relationship between oil price uncertainty and macroeconomic variables since the structural change in the oil market became effective. Results and Conclusions - The dynamic impulse response functions obtained from the VECM show a prolonged dampening effect of oil price volatility shock on the industrial production across all sub-periods. We also find that inflation measured by CPI rises by one standard deviation shock in response to oil price uncertainty, and lasts for the ensuing period. In addition, the impulse response functions allude that South Korea practices an expansionary monetary policy in response to oil price shocks, which stems from oil price uncertainty. Moreover, a comparison of the results of the dynamic impulse response functions from the two sub-periods suggests that the dynamic relationships have strengthened since 2000. Specifically, the results are most drastic in terms of industrial production; the impact of oil price volatility shocks has more than doubled from the year 2000 onwards. These results again indicate that the relationships between crude oil price uncertainty and Korean macroeconomic activities have been strengthened since the year2000, which resulted in a structural change in the crude oil market due to the deregulation of the crude oil futures.

• Information Systems Review
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• v.18 no.2
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• pp.107-125
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• 2016

With the rapid growth of the mobile application market, mobile donation applications have emerged as a new type of application that enables users to donate without actual payments. To date, limited research has been conducted to provide guidelines on how to design new types of mobile donation applications. Using cause-related marketing theory as theoretical framework, this study aims to identify the features of mobile donation applications that increase the intention of users to use such applications. To achieve this goal, we conducted two experiments. The results of an ANOVA test in the first experiment showed that indirect mobile donation applications (i.e., applications without actual payment) have a stronger positive effect on perceived effectiveness and cause involvement than direct mobile donation applications (i.e., applications with actual payment). In addition, perceived effectiveness and cause involvement yield positive effects on the intention to use mobile donation applications. The results of the second experiment showed that indirect mobile donation applications with utilitarian functions have a greater positive effect on perceived effectiveness and cause involvement than mobile donation applications with hedonic functions. These results contribute to mobile application and donation research as well as provide guidelines for practitioners on the design of mobile donation applications.

• Journal of Forest and Environmental Science
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• v.13 no.1
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• pp.66-80
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• 1997

Pinus koraiensis is one of the major speciese which have been recently planted for ten years and consists of 31% of total plantation. Presently young stand less than 30 years consists of 87% of total forest, but tending thinning of it is hardly carried out and the desirable direction for the thinning is not established yet. The objective of the study is to introduce the optimum thinning plan and thinning method through the long-run experiment of tending thinning for the Pinus koraiensis stand. The experiments carry out to interprete its growth model on the subject of two thinning experimental plots and yield table of Pinus koraiensis. As the basic step for understanding the thinning process, a theoretical growth model which is suitable to express the growth process is required. For that purpose, three growth functions (Mitscherlich, 4 parameter Richards, 3 parameter Richards) are applied to the diameter growth of the sample trees which are taken in the two plots. The results show that 3 parameter Richards is the most suitable. It is also verified that the diameter growth, the height growth, and the decrease in the number of stocks can be estimated by this function. To estimate the growth change of single tree, growth model including parameter h which is related to the occupation area of single tree are introduced. The parameter h can be estimated by using the data of the diameter growth obtained from the established experimental plots. Therefore, if both verification and modification of the usefulness of the model suggested is made, equations which tell about the thinning effects could be drived by estimating the growth process of single tree in advance.

• Journal of Dental Rehabilitation and Applied Science
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• v.35 no.3
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• pp.132-142
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• 2019

Purpose: The purpose of this finite element analysis study is to introduce the novel Lock screw system and analyze its mechanical property to see if it can prevent abutment screw loosening. Materials and Methods: The Lock screw is a component tightened on the inside of the implant abutment which applies compressive force to the abutment screw head. To investigate the effect, modeling was done using CAD program and it was analyzed by finite element analysis under various load conditions. First, the preload was measured according to the tightening torque of the abutment screw then it was compared with the theoretical value to verify the analytical model. The validated analytical model was then divided into those with no external load and those with 178 N, and the tightening torque of the lock screw was changed to 10, 20, 30 Ncm respectively to examine the property of stress distribution on the implant components. Results: Using Lock screw under various loading conditions did not produce equivalent stresses beyond the yield strength of the implant components. In addition, the axial load was increased at the abutment-abutment screw interface. Conclusion: The use of Lock screw does not exert excessive stress on the implant components and may increase the frictional force between the abutment-abutment screw interface, thus it is considered to prevent loosening of the abutment screw.

• Journal of Life Science
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• v.29 no.8
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• pp.916-921
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• 2019

In this study, we constructed a biological system that exhibited thermotolerance, ethanol tolerance, and increased ethanol productivity using a random mutagenesis method. We attempted to isolate a thermotolerant mutant using proofreading-deficient DNA polymerase ${\delta}$ and ${\varepsilon}$ encoded by the pol3 and pol2 genes, respectively, in Saccharomyces cerevisiae. To obtain mutants that could grow at high temperatures ($38^{\circ}C$ and $40^{\circ}C$), random mutagenesis of AMY410 (pol2-4) and AMY126 (pol3-01) strains was induced. The parental strains (AMY410 and AMY126) grew poorly at temperatures higher than $38^{\circ}C$. By stepwise elevation of the incubation temperature, AMY410-Ht (heat tolerance) and AMY126-Ht strains that proliferated at $40^{\circ}C$ were obtained. These strains were further incubated in medium containing 6% and 8% ethanol and then AMY410-HEt (heat and ethanol tolerance) and AMY126-HEt strain with ethanol tolerance at an 8% ethanol concentration was obtained. The AMY126-HEt strain grew even at an ethanol concentration of 10%. Furthermore, following the addition of high concentrations of glucose (5% and 10%), an AMY126-HEt3 strain with increased ethanol productivity was isolated. This strain produced 24.7 g/l of ethanol (95% theoretical conversion yield) from 50 g/l of glucose. The findings demonstrate that a new biological system (yeast strain) showing various phenotypes can be easily and efficiently bred by random mutagenesis of a proofreading- deficient mutant.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.34 no.1
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• pp.59-69
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• 2021

Recently, large-scale offshore and coastal structures have been constructed owing to the increasing interest in eco-friendly energy development. To achieve this, precise simulations of waves are necessary to ensure the safe operations of marine structures. Several experiments are required in the field to understand the offshore wave; however, in terms of scale, it is difficult to control variables, and the cost is significant. In this study, numerical waves under various wave conditions are produced using a piston-type wavemaker, and the produced wave profiles are verified by comparing with the results from a numerical wave tank (NWT) modeled using the smoothed particle hydrodynamics (SPH) method and theoretical equations. To minimize the effect by the reflected wave, a mass-weighted damping zone is set at the right end of the NWT, and therefore, stable and uniform waves are simulated. The waves are generated using the linear and Stokes wave theories, and it is observed that the numerical wave profiles calculated by the Stokes wave theory yield high accuracy. When the relative depth is smaller than two, the results show good agreement irrespective of the wave steepness. However, when the relative depth and wave steepness are larger than 2 and 0.04, respectively, the errors are negligible if the measurement position is close to the excitation plate. However, the error is 10% or larger if the measurement position is away from the excitation location. Applicable target wave ranges are confirmed through various case studies.