• Korean journal of applied entomology
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• v.38 no.3
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• pp.231-240
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• 1999

The long-term tend an pattern changes of Chilo suppressalis(Walker) occurrence in Suwon were analyzed and the forecasting models for spring emergence of C. suppressalis in Suwon were developed. From 1965 to 196, the population dynamics of C. suppressalis in Suwon shows a cyclic fluctuation with one large peak an one small peak, and its periodicity was ca. 36 generations(18 years). C. suppressalis population dynamics in Suwon was characterized as controlled by the endogenous dynamics dictated by the 1st order negative feedback mechanism (fast density dependence). The dynaics mechanism of C. suppressalis populations was not changed although its population density decreased drastically over the years. Using th dta of C. suppressalis spring occurrence in Suwon, forecasting models for spring emergence of C.supressalis were developed based on temperature-dependent development model or degree days. In general, these models well described the C. suppressalis spring emergence pattern in Suwon. Also, forecasting problems in spring moth emergence related with C. suppressalis population dynamics were discussed.

• The Bulletin of The Korean Astronomical Society
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• v.43 no.1
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• pp.66.1-66.1
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• 2018

Turbulence is a phenomenon which largely determines the density and velocity fields in molecular clouds. Turbulence can produce density fluctuation which triggers a gravitational collapse, and it can also produce a non-thermal pressure against gravity. Therefore, turbulence controls the mode and tempo of star formation. However, despite many years of study, the properties of turbulence remain poorly understood. As part of the Taeduk Radio Astronomy Observatory (TRAO) Key Science Program (KSP), "apping Turbulent properties In star-forming MolEcular clouds down to the Sonic scale (TIMES; PI: Jeong-Eun Lee)", we have mapped two star-forming clouds, the Orion A and the ${\rho}$ Ophiuchus molecular clouds, in 3 sets of lines (13CO 1-0/C18O 1-0, HCN 1-0/HCO+ 1-0, and CS 2-1/N2H+ 1-0) using the TRAO 14-m telescope. We aim to map entire clouds with a high-velocity resolution (~0.05 km/s) to compare turbulent properties between two different star-forming environments. We will present the preliminary results using a statistical method, Principal Component Analysis (PCA), that is a useful tool to represent turbulent power spectrum.

• Journal of Wetlands Research
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• v.12 no.3
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• pp.57-65
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• 2010

This study was conducted to present primary data on the change of the physical characteristics of reservoir sediments for understanding the sedimentation. The records of the annual summation of the precipitation of >50mm per day (AP50) were compared with changes of bulk density, organic matter, mean grain-size, and sand ratio in sediment cores sampled from three reservoirs without dredging record. Reservoir sediments, characterized by mineral soil, contained organic matters originated from the debris of terrestrial plants, and changes of organic matter were related to changes of grain-size flowing into reservoirs when sediments of fine sandy loam showed 10% of organic matter contents. Rapid changes of grain-size and sand ratio in the sediment cores were associated with the increase and decrease of precipitation, and fluctuation of water level and water flow in reservoirs might have influenced on the formation of sediments in reservoirs. Records of AP50 suggested that sediments could accumulate more than about 30 within the short period of 10 years. The accumulated sediments in a short time can reflect the effect of natural and anthropogenic events on the physical characteristics of sediments.

• Journal of the Korean Geographical Society
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• v.45 no.6
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• pp.788-805
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• 2010

The present USN (Ubiquitous Sensor Networks) node deployment practices have many limitations in terms of positional connectivity. The aim of this research was to minimize a redundancy of USN route nodes, by integrating spatially weighted parameters such as visibility, proximity to cell center, road density, building density and cell overlapping ratio into a comprehensive GIS database. This spatially weighted approach made it possible to reduce the number of route nodes (11) required in the study site as compared to that of the grid network method (24). The field test for RSSI (Received Signal Strength Indicator) indicates that the spatially weighted deployment could comply with the quality assurance standard for node connectivity, and that reduced route nodes do not show a significant degree of signal fluctuation for different site conditions. This study demonstrated that the spatially weighted deployment can be used to minimize a redundancy of USN route nodes in a routine manner, and the quantitative evidence removing a redundancy of USN route nodes could be utilized as major tools to ensure the strong signal in the USN, that is frequently encountered in real applications.

• Journal of the Korean Society of Propulsion Engineers
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• v.18 no.6
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• pp.34-41
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• 2014

A feasibility study of thrust control of hybrid propulsion system for lunar exploration is presented. The thrust control experiments were performed by controlling the oxidizer mass flow rate where the thrust modulation is carried by using a ball valve and a stepping motor. The gaseous oxygen (GOX) and the HDPE (High Density PolyEthylene) were used for the oxidizer and solid fuel, respectively. It was found that the thrust levels were stable without much fluctuation during the modulation period, and that the thrust was exactly controlled with target thrust modulation ratio of 53% and 32%.

• Journal of Wetlands Research
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• v.11 no.2
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• pp.99-106
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• 2009

Water spider(Argyroneta aquatica Clerck) is only spider that live under aquatic water. In korea, water spider distributed only in Undari Wetland, Yeochon County, Kyongii Proviance, where it is designated as Natural Monument. I counted the population density, analysed the ecological traits such as actual vegetation map, and suggested conservation strategy and eco-tourism planning for water spider. The population mean density of water spider was one individual/$m^2$ and 8,000 individuals/ha. The wetland inhabited by water spider was characterized by high water level fluctuation between rainy season and dry ones. Wetland plant community was dominated by Phragmites australis and Leersia oryzoides var. japonica with submersed plant, Utricularia japonica. It is need to supply water for inhibiting terrestial succession trend during the dry season and to connect three fragmented wetlands through ecological corridor. Also, It was suggested that ecotourism planning is important for conserving this wetland.

• The Journal of Fisheries Business Administration
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• v.49 no.4
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• pp.99-108
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• 2018

Maintaining a certain level of fisheries production is due to the increase in aquaculture production. In recent years, aquaculture plays an important role in fishery production in Korea. Nevertheless, aquaculture should be carefully managed by regulations because it also causes environmental load which can threat sustainability of aquaculture. For this reason, Korean government has regulated density of culturing facilities with the Fisheries Law and its adjective decrees. The regulatory compliance of fisheries businesses is very low because the criteria for the regulation of the density were not enacted with scientific research. Thus, this research was aimed to obtain scientific criteria for the regulation of oyster aquaculture in Jaran Bay with economic assessment. For this research, we collected the data necessary for the assessment on five investigation points in the bay for two years. With the data, simulation for the growth rate of oyster was performed and the result showed that at least 25.5% of facilities should be reduced. Also, it was revealed that removing 2 long lines would be most beneficial. The NPV of the best measurement was 35,120,300 won and IRR was 11.7%. With this research, the government will gain more accurate regulatory compliance due to the scientific approach. Moreover, fisheries businesses in oyster aquaculture can obtain flexibility to cope with market fluctuation.

• The Bulletin of The Korean Astronomical Society
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• v.46 no.2
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• pp.37.2-37.2
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• 2021

Turbulence produces the density and velocity fluctuations in molecular clouds, and dense regions within the density fluctuation are the birthplace of stars. Also, turbulence can produce non-thermal pressure against gravity. Thus, turbulence plays a crucial roles in controlling star formation. However, despite many years of study, the detailed relation between turbulence and star formation remain poorly understood. As part of the Taeduk Radio Astronomy Observatory (TRAO) Key Science Program (KSP), "mapping Turbulent properties In star-forming MolEcular clouds down to the Sonic scale (TIMES; PI: Jeong-Eun Lee)", we mapped two star-forming molecular clouds, the Orion A and the ρ Ophiuchus molecular clouds, in six molecular lines (¹³CO 1-0/C¹⁸O 1-0, HCN 1-0/HCO⁺ 1-0, and CS 2-1/N₂H⁺ 1-0) using the TRAO 14-m telescope. We applied the Principal Component Analysis (PCA) to the observed data in two different ways. The first method is analyzing the variation of line intensities in velocity space to evaluate the velocity power spectrum of underlying turbulence. We investigated the relation between the star formation activities and properties of turbulence. The other method is analyzing the variation of the integrated intensities between the molecular lines to find the characteristic correlation between them. We found that the HCN, HCO⁺, and CS lines well correlate with each other in the integral shaped filament in the Orion A cloud, while the HCO⁺ line is anti-correlate with the HCN and CS lines in L1688 of the Ophiuchus cloud.

• JSTS:Journal of Semiconductor Technology and Science
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• v.16 no.2
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• pp.185-190
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• 2016

A 70-${\AA}$ nanowire field-effect transistor (FET) for sub-10-nm CMOS technology is designed and simulated in order to investigate the impact of an oxide trap on random telegraph noise (RTN) in the device. It is observed that the drain current fluctuation (${\Delta}I_D/I_D$) increases up to a maximum of 78 % due to the single electron trapping. In addition, the effect of various trap positions on the RTN in the nanowire FET is thoroughly analyzed at various drain and gate voltages. As the drain voltage increases, the peak point for the ${\Delta}I_D/I_D$ shifts toward the source side. The distortion in the electron carrier density and the conduction band energy when the trap is filled with an electron at various positions in the device supports these results.

• Transactions of the Korean Society of Mechanical Engineers
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• v.18 no.3
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• pp.635-644
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• 1994

This study investigated mainly on the flow characteristics of a droplet in the cross region of twin spray. The velocities of the droplet were measured along the axial and radial direction, and the flow characteristics of the droplet were statistically analyzed. For the statistical analysis, the probability density of the turbulent components has been studied, and then the Reynolds shear stress, the skewness and the flatness factors were calculated, and compared with the Gaussian value. Two pressure swirl stomizers were used for the twin spray system and kerosene was employed as the working liquid. 2-D PDA(particle dynamic analyzer) was used for the purpose of the measurement of droplet size and velocities. As a result, it was found that (1) the droplets collision was taken place strongly in the cross region. So, a large momentum loss of droplets due to the loss of natural movement direction was occurred, and momentum loss of radial direction was greater than that of axial direction. (2) The axial direction skewness factor approached to zero like the Gaussian distribution in the cross region of twin spray. (3) In the cross region of twin spray, the fluctuation instability of droplet was increased because of the development of the turbulence characteristics due to the droplet collision.