• Ecology and Resilient Infrastructure
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• v.3 no.1
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• pp.46-53
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• 2016

This study was conducted to analyze the effect of the different land covers of an urban park (Hyowon park) in downtown Suwon on the urban thermal variations during a hot summer. The effect of the air temperature reduction in the urban park was 4.4%-4.5% for the downtown residence (Maetan-dong). This value was about 0.8% lower than that of the outskirts residence (Sanggwanggyo-dong). The daily mean temperature, daily maximum temperature, summer day and heat wave frequency were measured under the different land covers (cement-block, grass, pine-grass, shading area and mixed forest) showed these values generally decreased under natural land cover types. Daily minimum temperature and tropical night frequency didn't seem to correlate with the land cover types. Means of thermal comfort indices (wet bulb globe temperature, heat index and discomfort index) in the shading area, mixed forest and the pine-grass types were lower than those of cement block and grass types. However the levels of those indices were equal to 'very high' or 'caution' levels in the afternoon (13:00-15:00). In the morning (06:00-08:00), thermal comfort indices of the urban park didn't correlate with land cover types. Therefore, to reduce heat stress and to improve the thermal comfort in urban parks, an increase in the area of natural land cover such as grass, forest and open spaces is required.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.12
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• pp.663-670
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• 2019

Corrective thermal performance analysis is required for power plants' turbine cycles to determine the performance status of the cycle and improve the economic operation of the power plant. We developed a sectional classification method for the main feed-water flow to make precise corrections for the performance analysis based on the Performance Test Code (PTC) of the American Society of Mechanical Engineers (ASME). The method was developed for the estimation of the turbine cycle performance in a classified section. The classification is based on feature identification of the correlation status of the main feed-water flow measurements. We also developed predictive algorithms for the corrected main feed-water through a Kernel Regression (KR) model for each classified feature area. The method was compared with estimation using an Artificial Neural Network (ANN). The feature classification and predictive model provided more practical and reliable methods for the corrective thermal performance analysis of a turbine cycle.

• The Journal of the Korea institute of electronic communication sciences
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• v.19 no.4
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• pp.763-770
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• 2024

Currently, land-based fish farms utilizing seawater have introduced and are utilizing various equipment such as real-time water quality monitoring systems, facility automation systems, and automated dissolved oxygen supply devices. Furthermore, data collected from various equipment in these fish farms produce structured and unstructured big data related to water quality environment, facility operations, and workplace visual information. The big data generated in the operational environment of fish farms aims to improve operational and production efficiency through the development and application of various methods. This study aims to develop a system for effectively analyzing and visualizing big data produced from land-based fish farms. It proposes a data visualization process suitable for use in a fish farm big data analysis system, develops big data visualization tools, and compares the results. Additionally, it presents intuitive visualization models for exploring and comparing big data with time-series characteristics.

• Journal of Environmental Impact Assessment
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• v.28 no.4
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• pp.373-386
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• 2019

In The study, is to investigate the spatial characteristics of the Miho stream, which is the main tributary of the Geum River system, and to identify the main factors influencing the water quality using water quality analysis and multivariate analysis. The survey subjects were selected as 7 main sites in the Miho stream water system, From 2012 to 2017, 16 items including weather temperature and weather data were used for multivariate analysis. As a result of the water quality analysis, the average concentration of BOD and COD for 6 years was 3grade (normal) compared with the water quality environmental standard (river) of conditions. The concentrations of nitrogen and phosphorus were highest at th upstream site, then decreased and then increased again by the hydrogeological and geomorphological effect. Cluster analysis of spatial and water quality characteristics, it was evaluated as three clusters and the pollution sources is the greatest impact. As a result of principal component analysis and factor analysis on each cluster and mainstream, three to four major components were extracted. Main stream and the Cluster 1, Cluster 3 first principal factor included nitrogen and seasonal factors,first factor of Cluster 2 included nitrogen and water temperature. Nitrogen is the principal factor which affects water quality in Miho stream.

• Land and Housing Review
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• v.14 no.4
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• pp.47-62
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• 2023

Using the dynamic panel model, this study investigates rent determinants for small and medium-sized office buildings in Korea's CBD and Gangnam areas, key business districts. The results reveal that rents for small and medium-sized office buildings in CBD and Gangnam areas are influenced by macroeconomic fluctuations and characteristics of buildings and locations, suggesting a market with both spatial consumer and investment goods attributes. There are several investment implications as follows. First, even if the location in the CBD area is advantageous, the practical limitations in renovating aging small and medium-sized office buildings must be taken into account when investing. Second, parking conditions are a key factor influencing rent prices in CBD areas, so evaluating the parking facilities and improvement potential of small and medium-sized office buildings is essential for investors. Finally, due to the high sensitivity of Gangnam's small and medium-sized office market to macroeconomic trends, it's vital to prioritize monetary policy shifts as a key factor in investment decisions.

• Korean Chemical Engineering Research
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• v.61 no.1
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• pp.32-38
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• 2023

In this study, the electrochemical properties of dopamine coated silicon/silicon carbide/carbon(Si/SiC/C) composite materials were investigated to improve cycle stability and rate performance of silicon-based anode active material for lithium-ion batteries. After synthesizing CTAB/SiO₂ using the Stöber method, the Si/SiC composites were prepared through the magnesium thermal reduction method with NaCl as heat absorbent. Then, carbon coated Si/SiC anode materials were synthesized through polymerization of dopamine. The physical properties of the prepared Si/SiC/C anode materials were analyzed by SEM, TEM, XRD and BET. Also the electrochemical performance were investigated by cycle stability, rate performance, cyclic voltammetry and EIS test of lithium-ion batteries in 1 M LiPF₆ (EC: DEC = 1:1 vol%) electrolyte. The prepared 1-Si/SiC showed a discharge capacity of 633 mAh/g and 1-Si/SiC/C had a discharge capacity of 877 mAh/g at 0.1 C after 100 cycles. Therefore, it was confirmed that cycle stability was improved through dopamine coating. In addition, the anode materials were obtain a high capacity of 576 mAh/g at 5 C and a capacity recovery of 99.9% at 0.1 C/0.1 C.

• Applied Chemistry for Engineering
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• v.25 no.4
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• pp.418-424
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• 2014

The improved thermal stability and anti-oxidation properties of Lyocell fiber were studied based on flame retardant treatment by using NaCl/$H_3PO_4$ solution. The optimized conditions of flame retardant treatment were studied on various maxing ratio of NaCl and $H_3PO_4$ and the mechanism was proposed through experimental results of thermal stability anti-oxidation. The IPDT (integral procedural decomposition temperature), LOI (limited oxygen index) and $E_a$ (activation energy) increased 23, 30 and 24% respectively via flame retardant treatment. It is noted that thermal stability and anti-oxidation improved based on char and carbon layer formation by dehydrogenation and dissociation of C-C bond resulting the hindrance of oxygen and heat energy into polymer resin. The optimized conditions for efficient flame retardant property of Lyocell fiber were provided using NaCl/$H_3PO_4$ solution and the mechanism was also studied based on experimental results such as IDT (initial decomposition temperature), IPDT, LOI and $E_a$.

• Membrane Journal
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• v.22 no.5
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• pp.369-380
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• 2012

A one-dimensional numerical model based on the energy and mass equations have been developed to predict the trans membrane water vapor flux and thermal efficiency under various operating conditions in Direct Contact Membrane Distillation (DCMD) process. The model validation have been carried out by experimental data from literature and showed good agreement. The effect of operating parameters such as brine inlet temperature and velocity, and distillate inlet temperature and velocity to increase water vapor flux and thermal efficiency were predicted by the steady-state model. The results showed that the inlet temperature and velocity in brine side are dominant factors to control the water vapor flux and thermal efficiency because the effect of inlet temperature and velocity in brine side showed the higher water vapor flux and thermal efficiency than that of inlet temperature and velocity in distillate side. The water vapor flux was increased 3.4 times in the range of 21.22 $kg/m^2h$ to 71.26 $kg/m^2h$ and the thermal efficiency was increased 37.5% in that of 0.556 to 0.765 with increasing brine inlet temperature from $60^{\circ}C$ to $95^{\circ}C$. Meanwhile, the water vapor flux was increased 30% in that of 27.91 $kg/m^2h$ to 36.33 $kg/m^2h$ and thermal efficiency increased 7.5% in that of 0.6 to 0.646 as the brine inlet velocity was increased from 60 m/h to 300 m/h.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2017.05a
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• pp.148-153
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• 2017

During natural ageing of HTPB propellant undergoes a series of slow physico-chemical degradation reactions. By using accelerated ageing conditions it is possible to simulate the material behaviour at different time-temperature conditions especially focused on the in-service conditions. Ageing behaviour of HTPB propellant were investigated using HFC(Micro-Heat Flow Calorimeter) is universal technique for measuring the rate of slow chemical and physical processes in long-term storage.

• Journal of the Korean Society of Propulsion Engineers
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• v.22 no.5
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• pp.59-65
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• 2018

During natural aging, hydroxyl-terminated polybutadiene(HTPB) propellant undergoes a series of slow physico-chemical degradation reactions. By using accelerated ageing conditions it is possible to simulate the material behavior at different time-temperatures focusing on in-service conditions. Aging behaviors of HTPB propellant are investigated using HFC(heat flow calorimeter), a universal technique for measuring the rate of slow chemical and physical processes in long-term storage.