• Journal of Korean Society of Forest Science
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• v.95 no.5
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• pp.591-594
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• 2006

To have better urban forests in future we are focusing on two major issues like other countries. How we could have more urban forest-quantitative approach-against the expanding of urbanization, and how we could produce better urban forest-qualitative approach-to give a chance in contact with better nature for urban people. Prime surveys on urban forests have been carried out in 6 major cities since 1991, and the city of Daegu which is located on the east southern area of Korea have been case studied for qualitative approaches during last 3 years. Major species of the remnant forests were Pinus densiflora, Pinus rigida, Pinus thunbergii and Robinia pseudoacacia. Approximately 20% of the surveyed forests were lost their structure as forests caused by illegal farming, facilities and as the bare ground by excessive visitors. Generally speaking the condition of forests for biotope was very poor in overall. From two years data of monitoring of birds, we found that wooded parkways and woodland squares had more species than street tree areas. Nests were found mainly on the branch of Zelkova serrata, Pinus densiflora and Quercus myrsinaefolia. The size of urban forests mainly determined the species richness of birds. According to the oxygen output and carbon input by photosynthesis measurement, the capability was in order of Platanus occidentalis, Zelkova serrata and Ginko biloba. Air conditioning effects of trees through transpiration measurement was found and the quality of forests also related to the reducing of urban heat-island.

• Korean Chemical Engineering Research
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• v.57 no.2
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• pp.210-218
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• 2019

Batch experiment studies were carried out on the adsorption of the major tar compound, 2-picoline, derived from the plant cell cultures of Taxus chinensis, using Sylopute while varying parameters such as initial 2-picoline concentration, contact time and adsorption temperature. The experimental data were fitted to the Langmuir, Freundlich, Temkin and Dubinin-Radushkevich isotherm models. Comparison of results revealed that the Langmuir isotherm model could account for the adsorption isotherm data with the highest accuracy among the four isotherm models considered. From the analysis of adsorption isotherms, it was found that adsorption capacity decreased with increasing temperature and the adsorption of 2-picoline onto Sylopute was favorable. The kinetic data were well described by the pseudo-second-order kinetic model, while intraparticle diffusion and boundary layer diffusion did not play a dominated role in 2-picoline adsorption according to the intraparticle diffusion model. Thermodynamic parameters revealed the exothermic, irreversible and non-spontaneous nature of adsorption. The isosteric heat of adsorption decreased as surface loading ($q_e$) increased, indicating a heterogeneous surface.

• Applied Chemistry for Engineering
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• v.32 no.4
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• pp.442-448
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• 2021

Flow field is an important parameter for polymer electrolyte membrane fuel cell (PEMFC) performance to have an effect on the reactant supply, heat and water diffusion, and contact resistance. In this study, PEMFC performance was investigated using Cu foam flow field at the cathode of 25 cm² unit cell. Polarization curve and electrochemical impedance spectroscopy were performed at different pressure and relative humidity conditions. The Cu foam showed lower cell performance than that of serpentine type due to its high ohmic resistance, but lower activation and concentration loss due to the even reactant distribution of porous structure. Cu foam has the advantage of effective water transport because of its hydrophobicity. However, it showed low membrane hydration at low humidity condition. The metal foam flow field could improve fuel cell performance with a uniform pressure distribution and effective water management, so future research on the properties of metal foam should be conducted to reduce electrical resistance of bipolar plate.

• Current Photovoltaic Research
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• v.9 no.4
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• pp.145-159
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• 2021

Light soaking (LS) stability in polymer solar cells (PSCs) has always been a challenge to achieve due to unstable photoactive layer-electrode interface. Especially, the electron transport layer (ETL) and photoactive layer interface limits the LS stability of PSCs. Herein, we have modified the most commonly used and robust zinc oxide (ZnO) ETL-interface using an organic dye molecule and a co-adsorbent. Power conversion efficiencies have been slightly improved but when these PSCs were subjected to long term LS stability chamber, equipped with heat and humidity (45℃ and 85% relative humidity), an outstanding stability in the case of ZnO/dye+co-adsorbent ETL containing devices have been achieved. The enhanced LS stability occurred due to the suppressed interfacial defects and robust contact between the ZnO and photoactive layer. Current density as well as fill factors have been retained after LS with the modified ETL as compared to un-modified ETL, owing to their higher charge collection efficiencies which originated from higher electron mobilities. Moreover, the existence of less traps (as observed from light intensity-open circuit voltage measurements and dark currents at -2V) are also found to be one of the reasons for enhanced LS stability in the current study. We conclude that the mitigation ETL-surface traps using an organic dye with a co-adsorbent is an effective and robust approach to enhance the LS stability in PSCs.

• Korean Chemical Engineering Research
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• v.60 no.2
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• pp.255-259
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• 2022

Solar membrane steam generation is a very promising technology that can harvest purified water from seawater or wastewater during the current danger of running out of pure water. However, solar Membrane steam generation had direct contact with water, making it difficult to increase the efficient amount of evaporation. Here, we propose solar membrane steam generator composed of polydimethylsiloxane (PDMS) and graphene oxide (GO) and improved evaporation through wettability control in part throughout the water-absorbing membrane. Wettability control has shown significant improvements in thermal localization and temperature rise in the area of heat exchange with sunlight. The evaporator has an evaporation rate of 1.54 kg m^-2 h^-1 under 1 sun irradiation. The results showed that Solar membrane steam evaporation can effectively harvest pure water through an increase in evaporation.

• Journal of Space Technology and Applications
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• v.1 no.3
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• pp.356-363
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• 2021

It was common knowledge in textbooks that images acquired using mid-infrared ray were not suitable for measuring temperature near room temperature. But a recent satellite image using a mid-infrared sensor show the possibility that the result measured using the mid-infrared sensor can also measure the temperature near room temperature. In this paper, the possibility and accuracy of extraction room temperature information from satellite images with mid-infrared sensors are reviewed. The mid-infrared satellite image reviewed in this paper showed the temperature of room temperature well, and regarding the reliability as an absolute value of the measured temperature, the effect of the heat transfer amount due to the direct reflection of sunlight on the surface and the effect of the infrared absorption amount absorbed in the atmosphere can be seen as a relatively small or constant value. However, the problem of uncertainty in the radiation coefficient due to physical properties, which is the limit of the non-contact thermometer, remained a problem to be solved.

• Journal of the Microelectronics and Packaging Society
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• v.29 no.2
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• pp.19-31
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• 2022

With the advent of technologies based on big data, the trend of electronics towards high performance and high integration density continues. However, this development of electronics suffers from overheating issues, which seriously threaten the reliability of the devices. To develop effective strategies for thermal management, it is crucial to accurately evaluate the temperature distribution and design the heat dissipation path within the device in the operating condition. This paper introduces thermoreflectance microscopy that can observe the temperature distribution of a device with high spatial and temporal resolutions in a non-contact way. Specifically, the working principle and various forms of thermoreflectance microscopy are presented along with the latest research trends to improve the temperature, space, and time resolutions. We further review several examples in which thermoreflectance microscopy is applied to investigate the temperature and thermal characteristics of electronic devices.

• Journal of the Korean Institute of Gas
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• v.26 no.5
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• pp.22-27
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• 2022

Atomic Layer Deposition (ALD) is a facility that deposits an atomic layer on a wafer by causing a chemical reaction after decomposition using heat or plasma by inputting two or more gases during the semiconductor process. The main gas used at this time is NH₃ (Ammonia). NH₃ has a relatively narrow explosive range with an upper limit (UFL) of 33.6% and a lower limit (LEL) of 15%, but it can explode if a large amount suddenly gathers in one place. It is Velocity and fatal if inhaled or in contact with the skin. NH₃ (Ammonia) of ALD (Atomic Layer Deposition) facility is supplied to the chamber through the gas inlet and discharged after the reaction.

• Journal of the FoodService Safety
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• v.3 no.1
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• pp.38-44
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• 2022

This study investigated the microbiological hazards in the manufacturing processes of Naengmyeon. Sanitary indicative bacteria, such as aerobic plate counts and coliforms as well as pathogenic bacteria, were examined from raw materials, manufacturing processes, working area, 17 utensils and equipment. The aerobic plate counts for raw materials and arrowroot starch estimated as 0.77±0.68~5.02±0.28 and 5.02±0.28 log CFU/g, respectively. Coliforms were detected from wheat flour, buckwheat flour, and potato starch. Staphylococcus aureus was detected to be 0.61±1.06 log CFU/g in wheat flour and 0.20±0.35 log CFU/g in buckwheat flour. During the manufacturing process, aerobic plate counts for kneading process were 4.54±0.34 log CFU/g. But after the press out and heat process, contamination of aerobic plate counts and coliforms decreased and remained at a low level until the release process. Aerobic plate counts before washing disinfection of screw were 3.28±0.62 log CFU/100 cm², the level of which was high in utensils and equipment that had contact with employees or water. These results represent not only an important indicator for the hygienic level but also a scientific basis for analyzing biological hazards, which lead to the introduction of HACCP for the production of safe and hygienic cold noodles processed by manufacturers.

• Nuclear Engineering and Technology
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• v.55 no.7
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• pp.2534-2546
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• 2023

Gas-cooled space reactor, which adopts He-Xe gas mixture as working fluid, is a better choice for megawatt power generation. In this paper, thermal-hydraulic characteristics of He-Xe gas mixture in 2×2 rod bundle wrapped with helical wires is numerically investigated. The velocity, pressure and temperature distribution of the coolant are obtained and analyzed. The results show that the existence of helical wires forms the vortexes and changes the velocity and temperature distribution. Hot spots are found at the contact corners between helical wires and fuel rods. The highest temperature of the hot spots reach 1600K, while the mainstream temperature is less than 400K. The helical wire structure increases the friction pressure drop by 20%-50%. The effect extent varies with the pitch and the number of helical wires. The helical wire structure leads to the reduction of Nusselt number. Comparing thermal-hydraulic performance ratios (THPR) of different structures, the THPR values are all less than 1. It means that gas-cooled space reactor adopting helical wires could not strengthen the core heat removal performance. This work provides the thermal-hydraulic design basis for He-Xe gas cooled space nuclear reactor.