• Transactions of the Korean Society of Automotive Engineers
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• v.22 no.5
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• pp.13-19
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• 2014

Urea-SCR system is the selective catalytic reduction to reduce nitrogen oxides ($NO_x$) emitted from diesel vehicles. The objective of this study is numerical analysis of 3-dimensional unsteady melting problems of frozen urea by using an electric heater. It can be applied to determine capacity of power with respect to time and the location of the urea suction pipe in urea storage tank. The study includes the change of liquid volume fraction, temperature profiles and a influence of natural convection by using the commercial software STAR-CCM+(v7.06). The accuracy of the numerical analysis is estimated by comparisons with experimental data. After validation, a numerical analysis for freezing urea is conducted with four different heating power. From the results, it was found that relation of velocity of phase interface and amount of melting urea by increasing heating power in a container. There is also a difference in trend between velocity of phase interface and amounts of melting urea because of effect of natural convection.

• Transactions of the Korean Society of Automotive Engineers
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• v.21 no.4
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• pp.106-112
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• 2013

Compression ratio is an important factor affecting engine performance and emission characteristics since thermal efficiency of spark ignition engine can be theoretically improved by increasing compression ratio. In order to evaluate the effect of compression ratio change in HCNG engine, natural gas engine was employed using HCNG30 (CNG 70 vol%, hydrogen 30 vol%). Combustion and emission characteristics of CNG and HCNG fuel was analyzed with respect to the change of compression ratio at each operating condition. The results showed that thermal efficiency improved and $CH_4$, $CO_2$ emission decreased with the increase in compression ratio while $NO_x$ emissions were decreased at a certain excess air ratio condition. Higher thermal efficiency and further reduction of exhaust emissions can be achieved by the increase of compression ratio and the retard of spark timing.

• Journal of Mechanical Science and Technology
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• v.15 no.12
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• pp.1882-1891
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• 2001

The present paper investigated the effect of ultrasonic vibrations on the melting process of a phase-change material (PCM). Furthermore, the present study considered constant heat flux boundary conditions unlike many of the previous researches adopted constant wall temperature conditions. Therefore, in the present study, modified dimensionless parameters such as Ste* and Ra* were used. Also, general relationships between melting with ultrasonic vibrations and melting without ultrasonic vibrations were established during the melting of PCM. Experimental observations show that the effect of ultrasonic vibrations on heat transfer is very important throughout the melting process. The results of the present study reveal that ultrasonic vibrations accompany the effects like agitation, acoustic streaming, cavitation, and oscillating fluid motion. Such effects are a prime mechanism in the overall melting process when ultrasonic vibrations are applied. They enhance the melting process as much as 2.5 tildes, compared with the result of natural melting. Also, energy can be saved by applying ultrasonic vibrations to the natural melting. In addition, various time-wise dimensionless numbers provide conclusive evidence of the important role of ultrasonic vibrations on the melting phenomena.

• Korean Institute of Interior Design Journal
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• no.6
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• pp.63-66
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• 1995

Our natural desire to exuviate old theory and search for new ideas means conversion and reformation. Howev-er, the new idea of the present moment will soon become an ancient history when the next generation emerges with more advanced ideas. Naturally, we have learned to accept the past history and utilized it as a the foundation for the future. Through the repeated process of the learning method, the popula-tion cultivate themselves with proper understanding and appropriate attitude toward design. By analyzing social behaviors of the past and living conditions, we can ex-pand our imaginations beyond limits. Each society and its local condition have tremendous effects on the develop-ment and progress of artistic theories, techniques and craftsmanship, and potential design of every day use products. Today, interior design can not afford to ignore the or-ganic relationship of life style and space. Thus, the plan-ning of space means the planning of life style. Life style, as it is, has a vast definition and changes with time. That is why spaces, which consider the life style and its environment when designed, show different aspects ac-cording to its corresponding time. Interior design, in particular, differs by time and re-gion to create its unique style. The change in space is the natural result of the change in life style which again is sensitive to the change in cultural and environmental elements. Design is no longer designing of mere physical elements and environment. Design should be taken as the equivalent of creating spiritual culture.

• 한국태양에너지학회:학술대회논문집
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• 2011.04a
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• pp.256-262
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• 2011

Environmental pollution by Using of a fossil fuel, a reckless and growth-oriented development since the Industrial Revolution has caused global change of environment. An issue largest among this is a climate change. A global mean temperature since 19th century has climbed up $0.4{\sim}0.8^{\circ}C$. After The Kyoto Protocol regarding a greenhouse gas reduction goal took effect, be situations that decrease of greenhouse gas was acutely required. Interest of utilization of the new & renewable energy is increasing every day. This study shows that at first divided a country to nine range by natural geography, and second executed Meteorological data analysis of recent 30 years considering level of significance by nine range. The results of this study are that in heating load calculation of building, periodic temperature data management is required because facility capacity and cost are affected greatly by outdoor temperature, and temperature by climate range needs consideration of pertinent area. Lastly, ground temperature was assumed of the weather in region, the ground and soil.

• Journal of the Korean Institute of Landscape Architecture
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• v.31 no.1
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• pp.54-65
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• 2003

The results of the research were as follows: The entire space of the village was based on natural formation in its initial formation stage. The traditional location conditions and environment were equipped with the possibility and conditions for the development of the village. Spatial boundaries were mostly divided by natural topography. The quantify of lots diminished in spatial structural factors, while the division of roads by hierarchy in terms of size became explicit. Alleys, as the minimum hierarchial nit, were degraded. The residence unit was focused on economic efficiency. Communal use facilities showed an external relations trend as central facilities. The land, unit residence and communal facilities approached the high hierarchial roads. The communal facilities showed relatively higher independence compared to the residence units. The spatial structural changes followed traditional life style in the initial stage of village formation; however, social elements mainly impacted on the changes. Since reform opening, economic elements were major causes of changes, while construction conditions, life style, and awareness of structures impacted upon the changes. Thus, the economic element is the major change element in the Korean Villages, even though other elements will also become diverse.

• Journal of Climate Change Research
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• v.7 no.4
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• pp.421-426
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• 2016

Significant warming by anthropogenic influences over Korea is analyzed using CMIP5 projections (monthly mean, maximum and minimum temperatures) from RCP 8.5, 4.5, and 2.6 scenarios. Time of emergence (TOE) in JJA and DJF is chosen as the year when the magnitude of warming against the natural climate variability satisfies S/N>2 in 80% of the models in this study. Significant emergence in JJA is expected to appear in 2030s in three RCP scenarios, earlier than TOE in DJF. In DJF, TOE is expected to be 2040s in RCP 8.5 and is delayed in 2060s, 2080s in RCP 4.5, 2.6, respectively. Later emergence in low emission scenarios implies an importance of climate change mitigation consistent with previous studies. Maximum and minimum temperatures show similar results to the case of mean temperature. ToE is found to be affected by the amplitude of natural variability by season, variables and model spread, which requires further understanding.

• Journal of the Society of Disaster Information
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• v.15 no.3
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• pp.367-379
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• 2019

Purpose: This study aims to propose a framework for climate change risk management by analyzing characteristics of climate-induced disasters. Method: The recent global and domestic trends of loss and damage under natural disaster events and the characteristics of climate-induced disasters were analyzed to design a framework for climate change risk management. Results: In consideration of the uncertainty of climate risk and various spatio-temporal scales of climate disasters, a new framework is suggested for comprehensive climate risk management that includes risk assessment, goal setting, planning, monitoring and evaluation, learning and adjustment. The framework aims at an iterative process that is activated by stakeholder engagement. Conclusion: Pilot studies need to be conducted to revise and polish the framework in the future, and institutional arrangements should be prepared for the effective implementation of the comprehensive climate risk management.

• Korean Journal of Metals and Materials
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• v.48 no.5
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• pp.410-416
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• 2010

Studies were carried out to establish the technology for sodium-clad compatibility and to analyze the compatibility behavior of the Sodium-cooled Fast Reactor (SFR) cladding material under a flowing sodium environment. The natural circulation facility caused by the thermal convection of the liquid sodium was constructed and the 316-series stainless steels were exposed at $650{^{\circ}C}$ liquid sodium for 1458 hours. The weight change and related microstructural change were analyzed. The results showed that the quasi-dynamic facility represented by the natural convection exhibited similar results compared to the conventional dynamic facility. Selective leaching and local depletion of the chromium, re-distribution of the carbide, and the decarburization process took place in the 316-series stainless steel under a flowing sodium environment. This process decreased as the sodium flowed along the channel, which was caused by the change in the dissolved oxygen and carbon activity in the liquid sodium.

• Ocean and Polar Research
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• v.44 no.1
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• pp.69-82
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• 2022

The Ross Sea, Antarctica plays an important role in the formation of Antarctic Bottom Water (AABW) which is the densest water mass in global thermohaline circulation. Of the AABW, 25% is formed in the Ross Sea, and sea ice formation at the polynya (ice-free area) developed in front of ice shelves of the Ross Sea is considered as a pivotal mechanism for AABW production. For this reason, monitoring the Ross Sea variations is very important to understand changes of global thermohaline circulation influenced by climate change. In addition, the Ross Sea is also regarded as a natural laboratory in investigating ice-ocean interactions owing to the development of the polynya. In this article, I introduce characteristics of the Ross Sea described in previous observational studies, and investigate variations that have occurred in the Ross Sea in the past and those taking place in the present. Furthermore, based on these observational results, I outline variations or changes that can be anticipated in the Ross Sea in the future, and make an appeal to researchers regarding the importance and necessity of continuous observations in the Ross Sea.