• Fire Science and Engineering
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• v.31 no.4
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• pp.43-51
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• 2017

In this study, new design fire curves were suggested for the utilization in fire simulations. Numerical simulations with the Fire Dynamics Simulator (FDS) were performed for the n-octane and n-heptane pool fires in the ISO 9705 compartment to evaluate the prediction performance of the previous quadratic, exponential design fire curves and newly suggested ones. The numerical results were compared with the experimental temperature and concentrations of $O_2$ and $CO_2$. The numerical results with the previous quadratic and exponential curves showed slow increase and decrease trend than experiments. However, the numerical results with the newly suggested 2 design fire curves showed more similar variation trend in temperature, $O_2$ and $CO_2$ concentrations than the quadratic and exponential curves. It was found that the newly suggested design fire curves can be possibly used in the numerical simulation of fires in a practical respect.

• Journal of the Korea Society of Computer and Information
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• v.17 no.2
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• pp.23-29
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• 2012

To recently, light of the sun and fuel cell etc. which is new and renewable energy is developed with the direct current energy source mostly. And it is necessary that the utilization plan which does supply it properly. In this case, the direct current illumination system can be a typical alternative of it. The system similar to the development system is composed of type which connects to each other the photovoltaic pannel, the charge kit, and the battery bank. I develop all-in-one system which the power supply system and photovoltaic pannel which can charge and use efficiently. Additionally, I exploit the DC lamp module of three wave which can separate the electronic ballasts from the module. Developed the DC Lamp module of all-in-one which can turn on or can turn off, by operation of ON/OFF button. It can be used semipermanently by changing just only electronic ballasts.

• Journal of Korean Society for Quality Management
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• v.46 no.4
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• pp.899-910
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• 2018

Purpose: Generally, since the population density is lower in suburban areas, the distance to school is inevitably long. Therefore, schools in suburban areas often operate school buses to improve student welfare. However, since school buses are usually used only during going to and from school, the utilization rates are relatively low. Therefore, this study aims to establish integrated operation plan of public school bus covering all schools. Methods: It is necessary to decide which school buses will serve the specific demand node which want to go to certain school in order to design an integrated operation plan for school buses. Therefore, a mathematical model is developed for minimizing the total number of vehicles and the distance of transportation by reflecting the characteristics of school buses and students as constraints. To solve the proposed mathematical model, CPLEX, a commercial solver, is applied. Results: To validate and to confirm the proposed process, numerical example is designed with the comparison between before and after integrated operations of school buses in terms of total operation cost. The result shows that the integrated operation can lead the reduction of the number of school buses as well as the decreasing of the fuel cost. Conclusion: This study provides the quantitative method to perform the integrated operation of school buses in suburban areas. The optimal operation strategy is required because there are more complex decision-making elements considering the integrated operation. It is expected to apply this research result at real situation to expand this services based on an optimal operation.

• Journal of the Korean Wood Science and Technology
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• v.32 no.4
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• pp.46-51
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• 2004

The objective of this study was to evaluate the applicability of high temperature drying to pitch pine (Pinus rigida) lumber, especially intended for use as lamina of structural glued laminated timber (glulam), to enhance the efficient utilization and provide added-value to that species. The high temperature schedule and drying procedures utilized were shown to be reasonable for drying glulam lamina due to the occurrence of small moisture gradients, minimal residual drying stress, and low warpage. Through preliminary tests, it was confirmed that residual resin at lamina surfaces did not adversely affect the gluing process. However, quantitative analysis of resin is required for developing a method to constrain the occurrence of pitch trouble with respect to decreasing long-term adhesive and finish durability of glulam in use after manufacturing. The final moisture content of high temperature dried lamina was much lower than target moisture content and discoloration was more severe than anticipated. In a further study, it will be necessary to determine the optimal drying conditions, such as temperature, humidity, drying time, and top load restraint level, which could best control discoloration, warpage, and moisture content of the lamina, while minimizing fuel expense.

• Journal of the Korean Society of Propulsion Engineers
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• v.25 no.2
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• pp.119-143
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• 2021

Selecting liquid methane as fuel is a prevailing trend for recent rocket engine developments around the world, triggered by its affordability, reusability, storability for deep space exploration, and prospect for in-situ resource utilization. Given years of time required for acquiring a new rocket engine, a national-level R&D program to develop a methane engine is highly desirable at the earliest opportunity in order to catch up with this worldwide trend towards reusing launch vehicles for competitiveness and mission flexibility. In light of the monumental cost associated with development, fabrication, and testing of a booster stage engine, it is strategically a prudent choice to start with a low-thrust engine and build up space application cases.

• Journal of the Korean Wood Science and Technology
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• v.32 no.1
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• pp.88-95
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• 2004

The purpose of this study is to identify the species of wood members used in the Keunjungjeon Hall, main building of the Kyungbok palace in Seoul. The total 144 samples consist of 52 from pillars and 92 from other wood members. Only two species were identified, which were Abies holophylla Max. (needle fir) and Pinus densiflora Sieb. et Zucc. (Japanese red pine). For the pillars, A. holophylla were more abundantly used than P. densiflora. Among 20 outer pillars ('Pyeongju'), 11 were A. holophylla, and 9 were P. densiflora. Among 12 inner pillars ('Naejinkoju'), 7 were A. holophylla, and 5 were P. densiflora. Among 4 inner corner pillars ('Gwikoju'), 3 were A. holophylla and 1 was P. densiflora. For 92 other wood members, only 2 purlins were A. holophylla and the others were all P. densiflora. The results suggest that the common opinion 'Palace buildings of Korea are made from red pine woods' should be corrected. We think that fir logs might be used for the pillars instead of pines because long and straight pines were not available during 1860s due to heavy utilization of pines as construction and fuel materials in the late Chosun period.

• New & Renewable Energy
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• v.18 no.3
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• pp.1-9
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• 2022

This study analyzed the anticipated supply-and-demand of forest biomass energy (through wood pellets) until 2050, in South Korea. Comparing the utilization rates of forest resources of five countries (United Kingdom, Germany, Finland, Japan, and S. Korea), it was found that S. Korea does not nearly utilize its forest resources for energy purposes. The total demand for wood pellets in S. Korea (based on a power generation efficiency of 38%) was predicted to be 3,629 and 4,371 thousand tons in 2034 and 2050, respectively. The anticipated total wood pellet power generation ratio to target power consumption is 1.13% (5,745 GWh), 1.17% (6,336 GWh), and 1.25% (7,631 GWh) in 2020, 2030, and 2050, respectively. Low value-added forest residues left unattended in forests are called "Unused Forest Biomass" in S. Korea. From the analysis, the total annual potential amount of raw material, sustainably collectible amount, and available amount of wood pellet in 2050 were estimated to be 6,877, 4,814, and 3,370 thousand tons, respectively. The rate of contribution to Nationally Determined Contributions was up to 0.64%. Through this study, the authors found that forest biomass energy will contribute to a carbon neutral society in the near future at the national level.

• Transactions of the Korean hydrogen and new energy society
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• v.33 no.6
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• pp.845-855
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• 2022

In response to climate change, the world is continuing efforts to reduce fossil fuels, expand renewable energy, and improve energy efficiency with the goal of achieving carbon neutrality. In particular, R&D is being made on the value chain covering the entire cycle of hydrogen production, storage, transportation, and utilization in order to shift the energy supply system to focus on hydrogen energy. Hydrogen-based energy sources can produce heat and electricity at the same time, so it is possible to utilize heat energy, which can increase overall efficiency. In this study, calculation of the optimal scale for hydrogen-based cogeneration and the composition of heat sources were reviewed. It refers to a method of the optimal heat source size according to the external heat supply and heat storage to be considered. The results of this study can be used as basic data for establishing a hydrogen-based energy supply model in the future.

• Structural Engineering and Mechanics
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• v.87 no.3
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• pp.221-229
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• 2023

Urbanization and industrialization have significantly increased the amount of solid waste produced in recent decades, posing considerable disposal problems and environmental burdens. The practice of waste utilization in concrete has gained popularity among construction practitioners and researchers for the efficient use of resources and the transition to the circular economy in construction. This study employed Lytag aggregate, an environmentally friendly pulverized fuel ash-based lightweight aggregate, as a substitute for natural coarse aggregate. At the same time, fly ash, an industrial by-product, was used as a partial substitute for cement. Concrete mix M20 was experimented with using fly ash and Lytag lightweight aggregate. The percentages of fly ash that make up the replacements were 5%, 10%, 15%, 20%, and 25%. The Compressive Strength (CS), Split Tensile Strength (STS), and deflection were discovered at these percentages after 56 days of testing. The concrete cube, cylinder, and beam specimens were examined in the explorations, as mentioned earlier. The results indicate that a 10% substitution of cement with fly ash and a replacement of coarse aggregate with Lytag lightweight aggregate produced concrete that performed well in terms of mechanical properties and deflection. The cementitious composites have varying characteristics as the environment changes. Therefore, understanding their mechanical properties are crucial for safety reasons. CS, STS, and deflection are the essential property of concrete. Machine learning (ML) approaches have been necessary to predict the CS of concrete. The Artificial Fish Swarm Optimization (AFSO), Particle Swarm Optimization (PSO), and Harmony Search (HS) algorithms were investigated for the prediction of outcomes. This work deftly explains the tremendous AFSO technique, which achieves the precise ideal values of the weights in the model to crown the mathematical modeling technique. This has been proved by the minimum, maximum, and sample median, and the first and third quartiles were used as the basis for a boxplot through the standardized method of showing the dataset. It graphically displays the quantitative value distribution of a field. The correlation matrix and confidence interval were represented graphically using the corrupt method.

• Coupled systems mechanics
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• v.12 no.6
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• pp.531-537
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• 2023

Municipal solid waste landfills are unpredictable bioreactors which in cases of mishandling and bad supervision presents numerous risks. The key to municipal waste landfills is to approach them from the point of prevention of the possible consequences, which means using methods of organized waste disposal, and also utilizing landfill gas, as an unavoidable consequence with disposal of municipal solid waste with a high share of biodegradable organic matter. This paper presents an overview about problems of solid municipal waste management, type and composition of waste, and an overview of waste management condition. Further, the problem of landfill and landfill gasses is described with the calculation models of landfill production, as well as the use of the SWM GHG Calculator and LandGEM software on a specific example of gas production for the central zone at Sarajevo landfill "Smiljevici". Main focus of this thesis is the analysis of potentials of greenhouse gas emission reduction measures from the waste management. Overview of the best available techniques in waste management is presented as well as the methodology used for calculations. Scenarios of greenhouse gas emission reduction in waste management were defined so that emissions were calculated using the appropriate model. In the final section of the paper, its description of the problem of collection and utilization the landfill gas at the sanitary landfill "Smiljevici", and implementation of the system for landfill gas collection and solution suggestion for the gasification and exploitation of gas. Energy, environmental and economic benefits can be accomplished by utilizing municipal solid waste as fuel in industry and energy and moreover by utilizing energy generation from landfill gas, which this thesis emphasizes.