• The Journal of Korean Institute of Communications and Information Sciences
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• v.39A no.7
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• pp.372-379
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• 2014

When a hand-held device with limited battery transmits and receives data using short-range wireless communication systems, such as WLAN(Wireless Local Area Network) or high speed WPAN(Wireless Personal Area Network), instead of mobile communication systems, the device is able to reduce the power consumption due to the reduced transmission distance. However, if there are many WLAN or high speed WPAN systems around the device, non-negligible power may be consumed by receiving and decoding the packets which have nothing to do with the device. In this paper, we propose a scheme reducing the power consumption by including physical-layer ID in WLAN or WPAN packets and avoiding unnecessary packet receptions. Also, we describe a method to determine the optimum number of physical-layer IDs.

• Journal of Environmental Science International
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• v.9 no.2
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• pp.115-123
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• 2000

The dynamics of water quality and phytoplankton population had examined by monthly sampling from the upper to the lower part of watergate in an artificial Shihwa Reservoir in which situated near newly cities and incustrial complex on the west coast of Korea from January 1997 to December 1998. Among environmental factors, yearly average concentration of chl-a, TN and TP seemed to eutrophic or hypertrophic conditions that ranged 146.4~245.8 $\mu\textrm{g}$/$\ell$, 1.6~2.7 mg N/$\ell$, 258~448 $\mu\textrm{g}$ P/$\ell$, 26.9~80.7 $\mu\textrm{g}$/$\ell$, 1.0~2.4 mgN/$\ell$ and 74~239 $\mu\textrm{g}$P/$\ell$ respectively. Water quality was extremely deteriorated to consistently accumulation into inner reservoir by load of pollutants from autochthonous and allochthonous until early July 1997 after embankment. Water pollution of Shihwa Reservoir was remarkble on the biological condition with largely persistent bloom of phytoplankton and increase rate of standing crops was 2.4/yr. The development trend of phytoplankton in water ecosystem were closely related to increse and decrease of physico-chemical factors and those scale seemed to control by nutrient contents. Inflow of seawater into reservoir to object of repair of water quality. As to see dominant species, composition of those composed to mostly freshwater algae before inflow of seawater such as Selenastrum capricornutum of green algae, cyclotella atomus, C. meneghiniana of diatom and Microcystis spp. of blue-green algae and the other hand brackish algae were dominated after inflow of seawater such as Chaetoceros dicipiens, Skeletonema costatum of diatom, Dinophysis acuminata, Gymnodinium mikimotoi, G. sanguineum, Gyrodinium spirale, Prorocentrum minmum of dinoflagellate and Eutreptiella gymnastica of euglenoid. Moreover, small flagellates including Chroomonas spp. of cryptomonad were abundant throughout the year. The cause of water deterioration during fill of the freshwater were complexly supported with extra and intra parameters. The variation pattern of phytoplankton were related to water temperature and salinity by inflow of seawater based to plentiful nutrients. The dynamics of phytoplankton were assessed to ecosystem that clearly condition of dominant by unique or a few angel species seasonally.

• Journal of Institute of Control, Robotics and Systems
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• v.22 no.3
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• pp.199-203
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• 2016

A brain-computer interface or BCI provides an alternative method for acting on the world. Brain signals can be recorded from the electrical activity along the scalp using an electrode cap. By analyzing the EEG, it is possible to determine whether a person is thinking about his/her hand or foot movement and this information can be transferred to a machine and then translated into commands. However, we do not know which information relates to motor imagery and which channel is good for extracting features. A general approach is to use all electronic channels to analyze the EEG signals, but this causes many problems, such as overfitting and problems removing noisy and artificial signals. To overcome these problems, in this paper we used a new optimization method called the Fruit Fly optimization algorithm (FOA) to select the best channels and then combine them with CSP method to extract features to improve the classification accuracy by linear discriminant analysis. We also used particle swarm optimization (PSO) and a genetic algorithm (GA) to select the optimal EEG channel and compared the performance with that of the FOA algorithm. The results show that for some subjects, the FOA algorithm is a better method for selecting the optimal EEG channel in a short time.

• Transactions of the Korean Society of Mechanical Engineers
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• v.18 no.9
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• pp.2374-2385
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• 1994

SiCw/Al composite material is especially attractive because of their superior specific strength, specific stiffness, corrosion fatigue resistance, creep resistance, and wear resistance compared with the corresponding wrought Al alloy. In this study, Fatigue crack growth behavior and fatigue crack path morphology(FCPM) of SiC whisker reinforced Al 6061 alloy with 25% SiC volume fraction and Al 6061 allay were performed. Result of the fatigue crack growth test sgiwed that fatigue crack growth rate of SiCw/Al 6061 composite was slower than that of Al 6061 matrix therefore it was confirmed that Sic whisker have a excellent fatigue resistance. And Al 6061 matrix had only FCPM perpendicular to loading direction. On the other hand SiCw/Al 6061 composite had three types in fatigue crack path morphology. First type is that both sides FCPM of artificial notch are perpendicular to loading direction. Second type is that a FCPM in artifical notch has slant angle to loading direction and the other side FCPM is perpendicular to loading direction. Third type is that both sides FCPM of notch have slant angle to loading direction. It was considered that this kinds of phenomena were due to non-uniform distribution of SiC whisker and confirmed by SEM observation for fracture mechanism study.

• Journal of the Korean Society for Nondestructive Testing
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• v.22 no.3
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• pp.284-291
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• 2002

An attempt was made to evaluate the degree of aging degradation in thermally aged 2.25Cr-1Mo steel by electrical resistivity measurement. Artificial aging was performed to simulate the microstructural degradation in 2.25Cr-1Mo steel arising from long time exposure at $540^{\circ}C$. Microstructural parameter (amount of solid solution element), mechanical property (ductile-brittle transition temperature) and electrical resistivity were measured to investigate the mutual relationship among these parameters. Depletion of solid solution element(Mo and Cr) in matrix was detected after aging. The ductile-brittle transition temperature(DBTT) increased rapidly in the initial stage of aging and then saturated afterward. On the other hand, the electrical resistivity decreased rapidly in the beginning and then saturated in the later stage of aging.

• Journal of Forest and Environmental Science
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• v.30 no.1
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• pp.133-144
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• 2014

This study was carried out to review the pattern of forest stand development for six Gangwondo Baekdudaegan Mountains which experienced different type and duration of intensive legal protection. Vegetation data from point sampling method were employed to classify community types by cluster analysis on the basis of the importance values of canopy tree species for the study areas. The names of classified communities were given by the composition of dominant tree species. The communities were also compared one another in terms of stand structure by species diversity index. The results indicated that National Parks (Seoraksan and Odaesan) had greater proportion of mixed mesophytic forest type which was supposed to progress further forest succession process so as to have more complex and diversified stand structure. On the other hand, ordinary forest areas (Seokbyeongsan and Deokhangsan) had greater proportion of the forest types which was dominatively composed of Quercus mongolica and Pinus densiflora. The forest types with large amount of these two species would tend to develop for relatively short period of time of 40-50 years after artificial disturbances. Hyangnobong of Natural Protection Area and Hambaeksan of Natural Ecosystem Conservation Area showed intermediate stand development pattern in between National Parks and ordinary forest areas. The period of intensive legal protection of the forest area was positively correlated with species diversity index (R=0.736), and noted that the forest which received intensive protection regulation for longer period tended to show more complex and diversified stand structure.

• Proceedings of the Korean Society of Crop Science Conference
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• 2017.06a
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• pp.137-137
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• 2017

Rice has important role as a primary food resource in especially the Asia, Korea, China, India, Indonesia and Japan. After development and increasingly using artificial chemical fertilizer, rice is getting high quality and quantity to satisfy ever-increasing people. On the other hand, the earth environment is more polluted each day. Nowadays consumers are looking for the organic crops or foods that were grown with eco-friendly method and in pure farmland. With the immergence of this trend, it is time to development environmentally-friendly agriculture. One of the methods is growing green manure crops in winter or spring on the fields. For this reasons, growing rye and Italian ryegrass are useful to use green manure to enhance rice production without chemical fertilizers and make the property of the soil eco-friendly. To know how improve the quality and quantity of rice with green manures, rye and Italian ryegrass, first the characteristics of green manure corps were measured. Dry matter yields of the rye and Italian ryegrass were 2.21 and $1.81t\;Ha^{-1}$. And the percentages of the dry matter were 28 and 32%. And, analyzed mineral components in rye and Italian ryegrass were nitrogen, organic matter, $P_2O_5$, CaO, $C_2O$ and MgO. Specially, the percentages of the organic matter and the CaO between rye and Italian ryegrass have difference appreciably. the height of the rice on the Italian ryegrass-fertilized field was the highest among the variant fields. The height of the rice on the non-fertilized field was the lowest. Yield of the Italian ryegrass-, rye- and non-fertilized rice are 805.2, 639.9 and $415.3kg\;10a^{-1}$. At the result, Italian ryegrass is the most effective green manure among the 3 treated-fertilized.

• Korean Journal of Ecology and Environment
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• v.53 no.3
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• pp.304-310
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• 2020

Smart farm is a high-tech type of plant factory that artificially makes environmental conditions suitable for the growth of plants and manages them to automatically produce the desired plants regardless of seasons or space. This study was conducted by identifying the effects of Hertz and Duty ratio on the photosynthetic rate of ginseng, a medicinal crop, to find the optimal conditions for photosynthetic responses in smart farms. The light sources consisted of a total of 10 chambers using LED system, with 4 R+B(red+blue) mixed lights and 6 R+B+W (red+blue+white) mixed lights. In addition, the Hertz of the R+B mixed light was treated at 20, 60, 180, 540, 1620 and 4860 hz respectively. The R+B+W mixed light was treated with 60, 180, 540, and 1620 hz. Afterwards, experiments were conducted with the duty ratio of 30, 50, and 70%. As a result, the photosynthetic rate of ginseng according to duty ratio and Hertz was the highest at 60 hz when duty ratio was set to 50%. On the other hand, that was the lowest when the duty ratio was 30% at the same 60 hz. In addition, the photosynthetic rates were highest in the R+B mixed light and R+B+W mixed light at 60 hz. Therefore, the condition with the highest photosynthetic rate of ginseng in smart farms is 60 hz when the duty ratio in R+B mixed light is 50%.

• Korean Journal of Environmental Biology
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• v.34 no.4
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• pp.272-280
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• 2016

Changes in land use and increase in urban energy consumption influence urban life. This study analyzed the characteristics and patterns of urban heat and presents management schemes to generate a comfortable and sustainable urban environment. The study aimed to demonstrate the positive effects of artificial ground greening on improving the microclimate through evapotranspiration using perennial herbs. We have designed a chamber that could control constant temperature and humidity, measure temperature reductions in each plant and changes in sensible heat and latent heat. This study identified Sedum kamtschaticum as the most effective plant in controlling temperature. At $22^{\circ}C$, $3.2^{\circ}C$ temperature reduction was observed, whereas four other plants showed a $1.5^{\circ}C$ reduction. At $25^{\circ}C$, $2.0^{\circ}C$ temperature reduction was observed. On the other hand, the use of Sedum sarmentosum resulted in the lowest effect. Zoysia japonica is the most commonly used ground covering plant, although the temperature reduction of Lysimachia nummularia was more effective at high temperature conditions. Sensible heat and latent heat were calculated to evaluate the thermal performance of energy. At a temperature >$30^{\circ}C$, L. nummularia and S. sarmentosum emitted high latent heat. In this study, we analyzed the thermal performance of green roof perennial plants; in particular, we analyzed the evapotranspiration and temperature reduction of each plant. Since the substrate depth and types, plant species, and seasonal change may influence temperature reduction and latent heat of green roofs, further studies are necessary.

• Journal of the Korean Society for Nondestructive Testing
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• v.22 no.5
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• pp.483-489
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• 2002

The computer simulation has been done for non-insulated and insulated pipes which are vacant or half filled with liquid. The simulation results showed that the density profile on the radiography is continuous and symmetrical around the center of pipe in the case of vacant pipe. On the other hand the density profiles are not symmetrical and depend on geometrical setting for radiography in the case of half filled pipes. Finally, experimental testing on a non-insulated carbon steel pipe with artificial notches of different depth is carried out using Ir-192 and industrial film. Comparing the measured density profile on the radiograph to the calculated one, it has been shown that it is possible to evaluate thickness variation by measuring density profile on a radiograph.