• Korean Journal of Agricultural and Forest Meteorology
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• v.16 no.4
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• pp.359-367
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• 2014

Drought index can be used to implement an early warning system for drought and to operate a drought monitoring service. In this study, an approach was examined to determine agricultural drought index (ADI) at high spatial resolution, e.g., 270 m. The value of ADI was calculated based on soil water balance between supply and demand of water. Water supply is calculated by the cumulative effective precipitation with the application of the weight to the precipitation from two months ago. Water demand is derived from the actual evapotranspiration, which was calculated applying a crop coefficient to the reference evapotranspiration. The amount of surface runoff on a given soil type was also used to calculate soil residual moisture. Presence of drought was determined based on the probability distribution in the given area. In order to assess the reliability of this index, the amount of residual moisture, which represents severity of drought, was compared with measurements of soil moisture at three experimental between July 2012 and December 2013. As a result, the ADI had greater correlation with measured soil moisture compared with the standardized precipitation index, which suggested that the ADI would be useful for drought warning services.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.40 no.1
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• pp.25-33
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• 2020

A drought event is characterized by duration, severity and affected area. In general, after calculating a drought index using hydro-meteorological time series at a station, a drought event is defined based on the run theory to identify the beginning and end time. However, this one-dimensional analysis has limitations for analyzing the spatio-temporal occurrence characteristics and movement paths of drought. Therefore, this study is to define a three-dimensional drought event using a simple clustering algorithm and to develop a drought map that can be used to understand the drought severity according to the spatio-temporal expansion of drought. As a result, compared with the two-dimensional monitoring information to show spatial distribution of drought index, a proposed drought map is able to show three-dimensional drought characteristics inclusing drought duration, spatial cumulative severity, and centroid of drought. The analysis of drought map indicated that there was a drought event which had the affected area less than 10 % while on occations while there were 11 drought events (44 %) which had the affected area more a than 90 % of the total area. This means that it is important to understand the relationship between spatial variation of drought affected area and severity corresponding to various drought durations. The development of drought map based on three-dimensional drought analysis is useful to analyze the spatio-temporal occurrence characteristics and propagation patterns of regional drought which can be utilized in developing mitigation measures for future extreme droughts.

• Journal of Life Science
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• v.18 no.7
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• pp.924-930
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• 2008

Community structure refers to the number of species in a community and the pattern of distribution of individuals among those species. The purpose of this paper was to describe a statistical analysis for detecting a ecological biodiversity which is valid even though the assumption at the different sampling points is not violated spatial randomness of species. Counts and cover were determined from 10 ($20\;m{\times}20\;m$) plots in five sites of the Oncheon River which is located in Busan, Korea. Total 95 taxa (85 species, 9 varieties, and one form) were identified and measured in edge sides of this river. These were a total of present in the five sites. Overall across the fragments, mean number of species per plot differed significantly among the five sites (F=7.75, p<0.01). Shannon-Wiener functions differed significantly among plots (F=4.12, p<0.05), with the St. 1 having significantly higher value (2.380) than the others (2.206 for St. 2, 2.116 for St. 3, 2.069 for St. 4, and 0.637 for St. 5). The richness indices, R1 decreased from the upper stream of the Oncheon River to the lower stream. We used a novel way of representing community structure to show that abundance within closely related pairs of co-occurring species in the Oncheon River. The differences between the distributions for of congeners and pairs of non-congeners showed at the largest difference of the cumulative fractions of the data sets (x=0.85).

• Journal of Korean Society of Environmental Engineers
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• v.22 no.3
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• pp.575-585
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• 2000

Mass and elemental dry deposition fluxes and ambient particle size distributions were measured using dry deposition plates, a cascade impactor. and a CPS(Coarse Particle Sampler), from July to November 1998 in Seoul. Korea. Primarily anthropogenic elemental fluxes (Cu, Mn, Ni, Pb, Zn) were on average one to two orders of magnitude lower than primarily crustal elements (Al, Ca). Complete total and elemental particle size distributions showed trimodal size distributions due to the peak in particles larger than $10{\mu}m$ in diameter. A multi-step model and the Sehmel-Hodgson model were used to calculate total and cumulative deposition fluxes. The result indicated that dry deposition fluxes were extremely sensitive to the mass of particles larger than $10{\mu}m$ in diameter due to their high dry deposition velocities. The result showed that particles larger than $10{\mu}m$ in diameter dominated atmospheric dry deposition. The modeled fluxes calculated using the measured atmospheric particle size distributions and modeled deposition velocities were compared to measured ones. In general, the measured mass and elemental fluxes agreed well with the modeled ones.

• Journal of Korean Society of Environmental Engineers
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• v.27 no.3
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• pp.262-272
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• 2005

This study was undertaken to obtain design concentrations for the natural system treating stream water flowing into estuarine lake(Sapgyo). This lake has three major, so called, national-class streams: one is Gokgyo flowing through two medium-size municipal areas and the others are Muhan and Sapgyo placed in mostly rural area nested with some small towns. The results of three year's investigation showed big changes in water quality during the period between dry and wet seasons. Nitrogen concentration usually decreases as the flow rate increases. The change of phosphorus concentration in Gokgyo was the same pattern as nitrogen, but in other two streams it was inversely related with flow rates. This is probably due to the chemical property of the particles washed out from the different stream basins during wet season. It was found that about 40 to 60% of the total nitrogen are in soluble form and on average, 35% of the total phosphorus consists of dissolved-P. Representative concentration of these streams has to be separately determined based on dry and wet season. TDS and SS could be indicating parameters useful to depict and characterize a change of water quality with respect to flow rate because their measurement is easy and also includes a small analytical error. TDS values measured during dry season are related with high nitrogen concentration while during wet season, SS values effectively reflect a high concentration of phosphorus. For design purpose, cumulative concentration distribution graph presented in this paper can be directly or indirectly applied to other streams through a brief comparative and verificative study.

• 한국가스학회:학술대회논문집
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• 2005.10a
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• pp.37-43
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• 2005

The questionnaires about the safety of the urban gas have been carried out for the end users. about 8 of 10 persons said that the urban gas Is safe to use, whereas $35\%$ of them said there exists a hazard of an accident in thier residences. There cannot be found the clear evidences that the understandings on the safety of the urban gas have no relations to their ages, sex, and monthly incomes, while the safety is less confidential to the highly educated, the accident-experienced, or the mans who are poor at the safety inspections. Most of the questioned man know the inspection knacks for the gas utilities, but only $60\%$ of them carry out it. They said that they do not feel the necessity of the inspection because they are inspected routinely by the suppliers or the inspection companies. This says that the end user does not concern the safety inspections, and in order to improve the dependency of the user for the self-inspections, the inspection staff should educate the user for the necessity and the knack of inspections to encourage the self-inspection of the gas utilities.

• Korean journal of applied entomology
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• v.52 no.1
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• pp.5-12
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• 2013

The Hawaiian beet webworm (Spoladea recurvalis) is one of the serious insect pests found on red beet (Beta vulgaris var. conditiva) in Korea. The study was conducted to investigate the development period of S. recurvalis at various constant temperatures, 15.0, 17.5, 20.0, 22.5, 25.0, 27.5, 30.0, 32.5 and $35.0^{\circ}C$, with $65{\pm}5%$ RH and a photoperiod of 16L:8D. The developmental period from egg to pre-adult was 51.0 days at $17.5^{\circ}C$ and 14.6 days at $35.0^{\circ}C$. The developmental period of S. recurvalis was decreased with increasing temperature. The relationship between the developmental rate and temperature was fitted well by linear regression analysis ($R^2{\geq}0.87$). The lower developmental threshold and effective accumulative temperature of the total immature stage were $10.4^{\circ}C$ and 384.7 degree days, respectively. The nonlinear relationship between the temperature and developmental rate was well described by the Lactin model. The relationship between the cumulative frequency and normalized distributions of the developmental period for each life stage were fitted to the Weibull function with $R^2=0.63{\sim}0.87$.

• Journal of the Economic Geographical Society of Korea
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• v.4 no.2
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• pp.57-77
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• 2001

The Honam region has been recognized as one of the most lagging regions in Korea. Drawing upon some decompositions oi Gross Regional Domestic Product(GRDP) per head and labor productivity, the overall trend of inequalities in Korea has been revealed and the trajectory of the Honam region's economic change has been identified by examining how the region's economic performance changed relative to that of Korea in the 1990s. There are some findings. First of all, Korea is characterized by strong divergence in the development of its region economies, in terms o\ulcorner per capita GRDP, which relies upon productivity differentials rather than differences in employment rates. Second, the Honam region has displayed poor economic performances in terms of GRDP per head except for Jeonnam. Third, the dramatic fall in cumulative population growth relative to the national average has been an important factor in the Jeonnam's overwhelming economic performance measured by per capita GRDP. Fourth, the decline in the relative productivity of the Honam region is mostly explained by falling relative regional productivity growth in construction, transport and manufacturing, although it should be noted that the latter sector has made positive contribution to raising relative regional productivity of Jeonnam. Fifth, overall the shift in employment to service sector, especially to social, personal, public, health, education, other services other than distribution, hotels, catering has tended to support relative regional productivities, along with the positive contribution being made oi agriculture, forestry and fishing to relative regional productivity growth in the Honam region.

• Korean Journal of Materials Research
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• v.23 no.4
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• pp.240-245
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• 2013

Electrochemical surface treatment is commonly used to form a thin, rough, and porous oxidation layer on the surface of titanium. The purpose of this study was to investigate the formation of nanotubular titanium oxide arrays during short anodization processing. The specimen used in this study was 99.9% pure cp-Ti (ASTM Grade II) in the form of a disc with diameter of 15 mm and a thickness of 1 mm. A DC power supplier was used with the anodizing apparatus, and the titanium specimen and the platinum plate ($3mm{\times}4mm{\times}0.1mm$) were connected to an anode and cathode, respectively. The progressive formation of $TiO_2$ nanotubes was observed with FE-SEM (Field Emission Scanning Electron Microscopy). Highly ordered $TiO_2$ nanotubes were formed at a potential of 20 V in a solution of 1M $H_3PO_4$ + 1.5 wt.% HF for 10 minutes, corresponding with steady state processing. The diameters and the closed ends of $TiO_2$ nanotubes measured at a value of 50 cumulative percent were 100 nm and 120 nm, respectively. The $TiO_2$ nanotubes had lengths of 500 nm. As the anodization processing reached 10 minutes, the frequency distribution for the diameters and the closed ends of the $TiO_2$ nanotubes was gradually reduced. Short anodization processing for $TiO_2$ nanotubes of within 10 minutes was established.

• Journal of the Korean Society of Radiology
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• v.12 no.2
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• pp.209-216
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• 2018

In the field of angiography and interventional radiology, it is said that the risk of radiation exposure to the eyes is high due to the characteristics of work, but currently divided dose assessment and management are not carried out in reality. Therefore, in this study, in order to evaluate the dose of the operator in the surgical environment and to analyze the shields, firstly, we selected the point where the operator is mainly located, evaluated the exposure dose of the eye after attaching the pocket dosimeter to the lateral angle point of the head and neck phantom, and evaluate shielding effect when wearing lead glasses that is currently commercialized. Secondly, we evaluated the tendency of the exposure dose of the eye and the shielding effect through simulation in the same geometric structure as the actual measurement. As a result, in the case of measurement using a dosimeter, the cumulative dose increased with the increase of the fluoroscopic time, and the tendency was different according to the position of the operator. Simulation results show that the dose distribution of the eye lens in the mathematical phantom is about 1.1 ~ 1.3 times higher than that of the cornea. Also, The protective effect of the lead glasses showed a shielding effect of at least 3.7 ~ 21.4% in each eye.