• Korean journal of applied entomology
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• v.57 no.4
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• pp.361-372
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• 2018

Migratory insect pest populations migrate from the southern China to Korea through jet streams. In Korea, 5 major migratory insect species are important, i.e. Nilaparvata lugens, Sogatella furcifera, Laodelphax striatellus, Cnaphalocrocis medinalis and Mythimma separate, which are damages to the major crops, rice. This study was conducted from late July 2016 to early September 2016 and from July 2017 to August 2017 in rice paddy of Jeolla-province. C. medinalis and M. separata collected using pheromone traps, while N. lugens, S. furcifera and L. striatellus collected using 3 methods (visual surveys, sweeping surveys, sticky traps). SADIE (Spatial Analysis by Distance IndicEs) among geostatistics was used to analyze migratory insect pests. SADIE was used to analyze spatial distribution and index of aggregation $I_a$, index of clustering $V_i$, $V_j$ were used to investigate the spatial distribution. Also, the clustering indices were mapped as red-blue plot. C. medinalis and M. separata showed different distribution based on SADIE spatial aggregation analysis and red-blue plot analysis. Initial spatial distributions of L. striatellus and other planthoppers were differed for sampling location and time.

• Wind and Structures
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• v.4 no.5
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• pp.413-440
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• 2001

This paper presents an extensive analysis of unsteady wind loading data on a 18 m long and 2 m high wall in a rural environment, with the wind at a range of angles to the wall normal. The data is firstly analyzed using standard statistical techniques (moments of probability distributions, auto- and cross-correlations, auto- and cross-spectra etc.). The analysis is taken further using a variety of less conventional methods - conditional sampling, proper orthogonal decomposition and wavelet analysis. It is shown that, even though the geometry is simple, the nature of the unsteady flow is surprisingly complex. The fluctuating pressures on the front face of the wall are to a great extent caused by the turbulent fluctuations in the upstream flow, and reflect the oncoming flow structures. The results further suggest that there are distinct structures in the oncoming flow with a variety of scales, and that the second order quasi-steady approach can predict the pressure fluctuations quite well. The fluctuating pressures on the rear face are also influenced by the fluctuations in the oncoming turbulence, but also by unsteady fluctuations due to wake unsteadiness. These fluctuations have a greater temporal and spatial coherence than on the front face and the quasi-steady method over-predicts the extent of these fluctuations. Finally the results are used to check some assumptions made in the current UK wind loading code of practice.

• ETRI Journal
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• v.40 no.3
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• pp.366-375
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• 2018

Recently, techniques involving head-mounted displays (HMDs) have attracted much attention from academia and industry owing to the increased demand for virtual reality and augmented reality applications. Because HMDs are positioned near to users' eyes, it is important to solve the accommodation-vergence conflict problem to prevent dizziness. Therefore, holography is considered ideal for implementing HMDs. However, within the Nyquist region, the accommodation effect is limited by the space-bandwidth-product of the signal, which is determined by the sampling number of spatial light modulators. In addition, information about the angular spectrum is duplicated over the Fourier domain, and it is necessary to filter out the redundancy. The size of the exit-pupil of the HMD is limited by the Nyquist sampling theory. We newly propose a holographic HMD with an expanded exit-pupil over the Nyquist region by using the time-multiplexing method, and the accommodation effect is enhanced. We realize time-multiplexing by synchronizing a high-speed digital micromirror device and a liquid-crystal shutter array. We also demonstrate the accommodation effect experimentally.

• Asian Journal of Atmospheric Environment
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• v.4 no.2
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• pp.72-79
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• 2010

In this study, the ionic composition of volcanogenically derived particles and their temporal and spatial distributions have been investigated to evaluate the impact of the volcanic eruption on the local ecosystem and residents. To this end, an intensive field study was conducted to measure the size-segregated particulate matters at the east part of Sakurajima in Japan. Fractionated sampling of particles into > $PM_{10}$, $PM_{10-2.5}$, and $PM_{2.5}$ was made by a multi nozzle cascade impactor (MCI). The concentration of various ions present in the size-resolved particles was determined by Ion chromatography. The time dependent 3-dimensional Volcanic Ash Forecast Transport And Dispersion (VAFTAD) model developed by the NOAA Air Resources Laboratory (ARL) indicated that the sampling site of this work was affected by the volcanic aerosol particles plume. The temporal distributions of sulfate and $PM_{2.5}$ during the field campaign were significantly variable with important contributions to particle mass concentration. The chlorine loss, suspected to be caused by acidic components of volcanic gases, occurred predominantly in fine particles smaller than $10\;{\mu}m$.

• Proceedings of the KSRS Conference
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• v.2
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• pp.816-819
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• 2006

One of the most difficult parameters to measure in the sea is current speed and direction. Recently, efforts are being made to estimate the ocean current vectors by utilizing sequential satellite imageries. In this study, we attempted to estimated sea surface current vector (sscv) by using satellite ocean color imageries of SeaWifs around the Korean Peninsula. This ocean color image data has 1-day sampling interval and spatial resolution of 1x1 km. Maximum cross-correlation method is employed which is aimed to detect similar patterns between sequential images. The estimated current vectors are compared to the surface geostrophic current vectors obtained from altimeter of sea level height data. In utilizing the color imagery data, some limitations and drawbacks exist so that in warm water region where phytoplankton concentration is relatively lower than in cold water region, estimation of sscv is poor and unreliable. On the other hand, two current vector fields agree reasonably well in the Korean South Sea region where high concentration of chlorophyll-a and weak tide is observed. In the future, with ocean color images of shorter sampling interval by COMS satellite, the algorithm and methodology developed in the study would be useful in providing the information for the ocean current around Korean Peninsula.

• ALGAE
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• v.24 no.3
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• pp.149-161
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• 2009

Characteristics of benthic microalgae and sediment properties were investigated for the intertidal flats of Kwangyang Bay, Korea. Sampling stations were selected every 100 m in the intertidal flats from land-side to open ocean at two different sampling sites. Samples were collected in June 2004, July, September, November, February and May 2005. Sediments properties were measured including temperature, water contents, sediment bulk density, nutrient concentrations in porewater. Chlorophyll a concentrations in surface sediment (0.5 cm) were measured and relationships between the chlorophyll a and various sediment properties were analyzed to identify major mechanisms regulating biomass of benthic microalgae in the intertidal flats using simple linear regression analysis. Sediment chlorophyll a concentrations were maximum during winter and minimum during warm seasons ranging from 4.4 mg $m^{-2}\;to\;81.2\;mg\;m^{-2}$. No clear spatial variations were observed for the sediment chlorophyll a in the study sites. Results from regression analysis suggested that benthic microalgae biomass was affected by sediment temperature and nutrients especially ammonium and silicate. Grazing effect was estimated using chlorophyll: pheopigments ratio, indirect indicator of grazing activity, and the positive correlation of the ratio and chlorophyll a implied that microalgae biomass is affected by grazing of zoobenthos although direct measurement of grazing activity is required to determine the importance of top-down controls in the benthic microalgae dynamics.

• Proceedings of the Korean Society for Agricultural Machinery Conference
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• 2000.11b
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• pp.236-245
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• 2000

The feasibility of precision farming for small sized fields was studied by determining fertilizing amount of nitrogenous and calcareous to a cite specific region. A detailed soil survey at three experimental fields of 672㎡, 300㎡ and 140㎡ revealed a considerable spatial variation of the pH and organic matter(OM) levels. Soil organic matter was measured using Walkley-Black method and soil pH was measured with a pH sensor. Soil sample was obtained by Grid Node Sampling Method. The soil sampling depth was 10 - 20 cm from the soil surface. To display soil nutrient variation, a soil map was made using Geographic Information System (GIS) software. In soil mapping, soil data between nodes was interpolated using Inverse Distance Weighting (IDW) method. The variation was about 1 - 1.8 in pH value and 1.4 -7 % in OM content. Fertilizing Amount of nitrogenous and calcareous was determined by the fertilizing equation which was proposed by National Institute of Agricultural Science and Technology.(NIAST). The variation of fertilizing amount was about 3 - 11 kg/10a in nitrogenous and 70 - 140 kg/10a in calcareous. The results showed a feasibility of precision fertilizing for small size fields.

• Economic and Environmental Geology
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• v.25 no.1
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• pp.73-77
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• 1992

This paper compares numerical quadrature techniques for computing an inverse Fourier transform integral in two-dimensional resistivity modeling. The quadrature techniques using exponential and cubic spline interpolations are examined for the case of a homogeneous earth model. In both methods the integral over the interval from 0 to ${\lambda}_{min}$, where ${\lambda}_{min}$, is the minimum sampling spatial wavenumber, is calculated by approximating Fourier transformed potentials to a logarithmic function. This scheme greatly reduces the inverse Fourier transform error associated with the logarithmic discontinuity at ${\lambda}=0$. Numrical results show that, if the sampling intervals are adequate, the cubic spline interpolation method is more accurate than the exponential interpolation method.

• Journal of Biosystems Engineering
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• v.25 no.3
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• pp.241-250
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• 2000

The feasibility of precision fertilizing for small size fields was studied by determining fertilizing amount of nitrogenous and calcareous to a cite specific region. A detailed soil survey at three experimental fields of $672m^2$, $300m^2$ and $140m^2$ revealed a considerable spatial variation of the pH and organic matter(OM) levels. Soil organic matter was measured using Walkley-Black method and soil pH was measured with a pH sensor. Soil sample was obtained by Grid Node Sampling Method. The soil sampling depth was 10∼20 cm from the soil surface. To display soil nutrient variation, a soil map was made using Geographic Information System (GIS) software. In soil mapping, soil data between nodes was interpolated using Inverse Distance Weighting (IDW) method. The variation was about 1∼1.8 in pH value and 1.4∼7% in OM content. Fertilizing Amount of nitrogenous and calcareous was determined by th fertilizing equation which was proposed by National Institute of Agricultural Science and Technology(NIAST). The variation of fertilizing amount was about 3∼11 kg/10a in nitrogenous and 70∼140 kg/10a in calcareous. The results showed a feasibility of precision fertilizing for small size fields.

• Journal of the Institute of Convergence Signal Processing
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• v.10 no.2
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• pp.127-131
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• 2009

In the digital waveguide theory, traveling waves are represented by general solution to the wave equation that is second-order linear partial differential equation. The movement of these waves can be implemented using only delay lines. An unit delay in the general digital waveguide describes a sampling time interval. However, in the space-based digital waveguide the unit delay implies the spatial sampling distance. In consideration of these differences between two models, it is known that the space-based digital waveguide model is adequate to synthesize pitch-shifted sounds such as vibrato because the propagation distance can be directly control. In this paper, the time-based digital waveguide model which also synthesizes pitch-shifted sounds is proposed and compared with space-based digital waveguide.