Kim, Jae-Hyun;Kim, Gang-Phil;Ryu, Hong-Keun;Suh, Hong-Suk;Lee, Jung-Ho
Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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2008.06a
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pp.241-241
/
2008
Macrofore formation in silicon and other semiconductors using electrochemical etching processes has been, in the last years, a subject of great attention of both theory and practice. Its first reason of concern is new areas of macropore silicone applications arising from microelectromechanical systems processing (MEMS), membrane techniques, solar cells, sensors, photonic crystals, and new technologies like a silicon-on-nothing (SON) technology. Its formation mechanism with a rich variety of controllable microstructures and their many potential applications have been studied extensively recently. Porous silicon is formed by anodic etching of crystalline silicon in hydrofluoric acid. During the etching process holes are required to enable the dissolution of the silicon anode. For p-type silicon, holes are the majority charge carriers, therefore porous silicon can be formed under the action of a positive bias on the silicon anode. For n-type silicon, holes to dissolve silicon is supplied by illuminating n-type silicon with above-band-gap light which allows sufficient generation of holes. To make a desired three-dimensional nano- or micro-structures, pre-structuring the masked surface in KOH solution to form a periodic array of etch pits before electrochemical etching. Due to enhanced electric field, the holes are efficiently collected at the pore tips for etching. The depletion of holes in the space charge region prevents silicon dissolution at the sidewalls, enabling anisotropic etching for the trenches. This is correct theoretical explanation for n-type Si etching. However, there are a few experimental repors in p-type silicon, while a number of theoretical models have been worked out to explain experimental dependence observed. To perform ordered macrofore formaion for p-type silicon, various kinds of mask patterns to make initial KOH etch pits were used. In order to understand the roles played by the kinds of etching solution in the formation of pillar arrays, we have undertaken a systematic study of the solvent effects in mixtures of HF, N-dimethylformamide (DMF), iso-propanol, and mixtures of HF with water on the macrofore structure formation on monocrystalline p-type silicon with a resistivity varying between 10 ~ 0.01 $\Omega$ cm. The etching solution including the iso-propanol produced a best three dimensional pillar structures. The experimental results are discussed on the base of Lehmann's comprehensive model based on SCR width.
The wooden striker on the Divine Bell of King Seongdeok was examined to identify the species of the wood and the outdoor wood weathering caused by solar light, moisture, temperature and air. The species of the wooden striker was identified to Zelkova serrata. When observed the striker with naked eyes, the results were surface discoloration (graying), cracking and roughness. In order to examine the morphological changes according to deterioration type, the specimen were separated to three part(I, II,III-spot). The I-spot was discolored to gray and at the same time entirely covered with dust. So the observation was impossible. The II-spot was also discolored but its texture could be observed. On it could observe numerous fungal hypae and dirts like dust flown into the cell lumens. The cell wall has been so weakened by weathering that it lost the physical intensity. This have made microchecks and splits on the cell wall. Although fungal hypae covered the cell, they did not result in wood decay. The III-spot, located just 0.5 mm below the surface, was maintaining the natural red-brown color of the wood. Its cell wall was similar to that of sound wood. These changes are different from wood decay, and limited only to the surface of the striker-less than or equal to 0.5 mm below.
Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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2011.10a
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pp.782-785
/
2011
Needs for MG(Microgrid) development are increasing all over the world as a solution to the problems including the depletion problem of energy resources, the growing demand for electric power and the climatic and environmental change. Especially Photovoltaic power is one of the most general renewable energy resources. However there is a problem of the uniformity of power quality because the power generated from solar light is very sensitive to climate fluctuation (variation of insolation and duration of sunshine, etc). As a solution to the above problem, ESS(Energy Storage System) is considered generally, but it has some limitations. To solve this problem this paper suggests a hybrid estimation method of photovoltaic power generation according to two climatic factors, i.e. insolation and sunshine. This result seems to help design the appropriate capacity of ESS and estimate the proper switching time between DC and AC power in the premises power system and thus maintain the uniformity of power quality.
Yeom, Ahram;Kim, Hong Seung;Jang, Nak Won;Yun, Young;Ahn, Hyung Soo
Journal of the Korean Institute of Electrical and Electronic Material Engineers
/
v.33
no.3
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pp.214-218
/
2020
In this study, MgxZn1-xO thin films, which can be applied not only to active layers of light-emitting devices (LEDs), such as UV-LEDs, but also to solar cells, high mobility field-effect transistors, and power semiconductor devices, are fabricated using the sol-gel method. ZnO and Mg0.3Zn0.7O solution synthesized by the sol-gel method and the thin film were grown by spin coating on a Si (100) substrate and sapphire substrate. The solutions are synthesized by dissolving precursor materials in 2-methoxyethanol (2-ME) solvent, and then monoethanolamine (MEA) was added to the mixed solution as a sol stabilizer. Zinc acetate dihydrate is used as a ZnO precursor, while Mg nitrate hexahydrate and Mg acetate tetrahydrate are used as an MgO precursor. Then, the optical and structural characteristics of the fabricated thin films are compared. The molar concentration of the Zn precursor in the solvent is fixed at 0.3 M, and the amount of the Mg precursor is 30% of Mg2+/Zn2+. The optical characteristics are measured using an UV-vis spectrophotometer, and the transmittance of each wavelength is measured. Structural characteristics are measured using X-ray diffraction (XRD) and transmission electron microscopy (TEM). Composition analyses are performed using energy dispersive X-ray spectroscopy (EDS). The Mg0.3Zn0.7O thin film was well formed at the ratio of the Mg precursor added regardless of the type of Mg precursor, and the c-axis of the thin film was decreased, while the band gap was increased to 3.56 eV.
Journal of the Korean Society of Environmental Restoration Technology
/
v.13
no.6
/
pp.39-48
/
2010
The purpose of this study was to analyze air temperature decreasing effects by shading and ventilation at micro-scale experiment plots, especially focused on the Wet Bulb Globe Temperature (WBGT) in outdoor spaces. To monitor the time-serial changes of Dry-bulb Temperature (DT), Globe Temperature (GT) and Relative Humidity (RH) in the wind blocking and shading conditions, Two hexahedral steel frames were established on the open grass field, the dimension of each frame was 1.5m(W)${\times}$1.5m(L)${\times}$1.5m(H). Four vertical side of one frame was covered by transparent polyethylene film to prevent wind passing through (Wind break plot; WP). The top side of the other frame was covered with shading curtain which intercept 95% of solar light and energy (Shading plot; SP). And, Another vertical steel frame without any treatment preventing ventilation and sunlight was set up, which represents natural conditions (Control plot; CP). The major findings were as follows; 1. The average globe temperature (GT) was highest at WP showing $50.94^{\circ}C$ and lowest at SP showing $34.58^{\circ}C$. The GT of natural condition (SP) was $42.31^{\circ}C$ locating the midst between WP and SP. The difference of GT of each plot was about $8-16^{\circ}C$, which means the ventilation and shading has significant effect on decreasing the temperature. 2. WP showed the highest average dry-bulb temperature (DT) of $38.41^{\circ}C$ which apparently differ from SP and CP showing $31.94^{\circ}C$ and $33.15^{\circ}C$ respectively. The DT of SP and CP were nearly the same. 3. The average relative humidity (RH) was lowest at WP showing 15.21%, but SP and CP had similar RH 28.79%, 28.02% respectively. 4. The average of calculated WBGT were the highest at the WP ($27.61^{\circ}C$) and the lowest at the SP ($23.64^{\circ}C$). The CP ($25.49^{\circ}C$) was in the middle of the others. As summery, compared with natural condition (CP), the wind blocking increased about $2.11^{\circ}C$ WBGT, but the shading decreased about $1.84^{\circ}C$ WBGT. So It can be apparently said that the open space with much shading trees, sheltering furnitures and well-delivered wind corridor can reduce useless and even harmful energy for human outdoor activity considerably in outdoor spaces.
Hong, Gi Hoon;Cho, Sunghyun;Kang, Hoon;Park, Jeongpil;Kim, Tae-Ok;Shin, Dongil
Journal of the Korean Institute of Gas
/
v.19
no.2
/
pp.74-82
/
2015
Carbon dioxide was designated as one of greenhouse gases that cause global warming. Among various ways to solve the $CO_2$ emission issue, the 3rd-generation biomass (algae) production is considered as a viable method to reduce $CO_2$ in the atmosphere. In this research, we propose a design of an innovative sustainable production system by utilizing the 3rd generation biomass in the environment of floating production storage and offloading (FPSO). Existing biomass production systems depend on the solar energy and they cannot continue producing biomass at night. Electricity produced from offshore wind farms also need an efficient way to store the energy through energy storage system (ESS) or deliver it real-time through power grid, both requiring heavy investment of capital. Thus, we design an offshore grid structure harnessing LED lights to supply the necessary light energy, by using the electricity produced from the wind farm, resulting in the maximized production of biomass and efficient use of wind farm energy. The final design integrates the biomass production system enhanced by LED lights with a wind power generation. The suggested NLP model for the optimal design, implemented in GAMS, would be useful for designing improved offshore biomass production systems combined with the wind farm.
Journal of the Korean Association of Geographic Information Studies
/
v.21
no.4
/
pp.26-49
/
2018
The purpose of this study was to verify the reliability of the solar radiation model and discuss its applicability to the urban area of Seoul for summer heat stress mitigation. We extended the study area closer to the city scale and enhanced the spatial resolution sufficiently to determine pedestrian-level urban radiance. The domain was a $4km^2$ residential area with high-rise building sites. Radiance modelling (SOLWEIG) was performed with LiDAR (Light Detection and Ranging)-based detailed geomorphological land cover shape. The radiance model was evaluated using surface energy balance (SEB) observations. The model showed the highest accuracy on a clear day in summer. When the mean radiation temperature (MRT) was simulated, the highest value was for a low-rise building area and road surface with a low shadow effect. On the other hand, for high-rise buildings and vegetated areas, the effect of shadows was large and showed a relatively low value of mean radiation temperature. The method proposed in this study exhibits high reliability for the management of heat stress in urban areas at pedestrian height. It is applicable for many urban micro-climate management functions related to natural and artificial urban settings; for example, when a new urban infrastructure is planned.
Kim, Wonkook;Roh, Sang-Hyun;Moon, Yongseon;Jung, Sunghun
Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
/
v.37
no.3
/
pp.167-175
/
2019
Water color analysis allows non-destructive estimation of abundance of optically active water constituents in the water body. Recently, there have been increasing needs for light-weighted multispectral cameras that can be integrated with low altitude unmanned platforms such as drones, autonomous vehicles, and heli-kites, for the water color analysis by spectroradiometers. This study performs the preprocessing of the Micasense Rededge-M camera which recently receives a growing attention from the earth observation community for its handiness and applicability for local environment monitoring, and investigates the applicability of Rededge-M data for water color analysis. The Vignette correction and the band alignment were conducted for the radiometric image data from Rededge-M, and the sky, water, and solar radiation essential for the water color analysis, and the resultant remote sensing reflectance were validated with an independent hyperspectral instrument, TriOS RAMSES. The experiment shows that Rededge-M generally satisfies the basic performance criteria for water color analysis, although noticeable differences are observed in the blue (475 nm) and the near-infrared (840 nm) band compared with RAMSES.
Journal of the Korean Applied Science and Technology
/
v.36
no.2
/
pp.531-540
/
2019
Hydrophilic and hydrophobic nanosilica and tetraethyl orthosilicate (TEOS) as a coupling agent was used to form a coarse spike structure as well as an excellent reactive hydroxyl groups on the glass surface. Then, a second treatment was carried out using a trichloro-(1H,1H,2H,2H)perfluorooctylsilane(TPFOS) solution for ultimate water repellent glass surface formation. The formation of hydrophobic coating layer on glass surface using silica aerosol, which is hydrophobic nanosilica, was not able to form a durable hydrophobic coating layer due to the absence of reactive -OH groups on the surface of nanosilica. On the other hand, a glass surface was first coated with a coating liquid prepared with hydrophilic hydroxyl group-containing nanosilica and hydrolyzed TEOS, and then coated with a TPFOS solution to introduce a hydrophobic surface on glass having a water contact angle of $150^{\circ}$ or more. The sliding angle of the coated glass was less than $1^{\circ}$, which meant the surface had a super water-repellent property. In addition, as the content of hydrophilic nanosilica increased, the optical transmittance decreased and the optical transmittance also decreased after 2nd coating with the TPFOS solution. The super-hydrophobic property of the coated glass was remained up to 50 times of rubbing durability test, but only hydrophobic property was shown after 200 times of rubbing durability test. Conclusively, the optimal coating conditions was double 1st coatings with the HP3 coating solution having a hydrophilic nanosilica content of 0.3 g, and subsequent 2nd coating with the TPFOS solution. It is believed that the coating solution thus prepared can be used as a surface treatment agent for solar cells where light transmittance is also important.
Kim, Youngsear;Chae, Hyun-Byung;Seo, Jae-Soon;Chae, Soo-Kwon
Journal of the Korean Society for Environmental Technology
/
v.19
no.6
/
pp.576-585
/
2018
Systematic management during the whole life cycle from construction to operation and maintenance is very important for the seven underground pipelines (waterworks, sewerage, electricity, telecommunications, gas, heating, oil including waterworks and sewerage). Especially, it is the construction process that affects the whole life cycle of underground buried pipeline. In order to construct a new city or to maintain different underground pipes, it is always necessary to dig the ground and carry out construction and related work. There is a possibility that secondary and tertiary breaks frequently occur in the pipeline construction process after the piping constructed first in this process. To solve this problem, a system is needed which can monitor damage in real time. However, the supply of electric power for continuous operation of the system is limited according to the environment of underground buried pipelines, so it is necessary to develop a stable electric power supply system using natural energy rather than existing electric power. In this study, we developed a system that can operate the pipeline monitoring system for long time (24 hours and 15 days) using natural energy using wind and solar light.
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