• Journal of Wetlands Research
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• v.6 no.1
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• pp.105-115
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• 2004

This study was carried out to grade and evaluate the intertidal mudflat by birds. The mudflat was graded by two methods such as the scoring and ranking. First, for the scoring of the mudflat, five factors were estimated; population size, the number of protected species, the individuals of protected birds, the number of species(or subspecies) over 1% level of the survival population, and 1% level of the domestic population. After scoring of these five factors, the grade was scored by total. Second, for the ranking, six factors were estimated; population size, the density of birds, the index of species diversity, species richness, species evenness, and population stability. After ranking of these six factors, the grade was relatively ranked. Five grade by scoring was the important mudflat for the value of international preservation, and the most mudflats of the estuary gained V grade. The higher grades by ranking were the mudflats of Nakdonggang and Mankyunggang river estuaries. And the inner mudflats were more valuable than the outer mudflats in Mankyunggang & Dongjingang river estuaries. The grading of the mudflat by birds can be used for estimating and appointing of the important mudflats, and suggested the objective of criteria for the effective preservation and management.

• International Commerce and Information Review
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• v.14 no.4
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• pp.297-315
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• 2012

In this paper, we explore the effects of export insurance on the Korea's export by using the gravity model with the data of 112 countries that Korea exports on years of 2005 and 2009. For this model, we used the Korea export as a dependent variables and real GDP, distance between the two nations, export insurance, country credit rating of the Korea's counterpart countries and FTA were used as an independent variables. The results show that the underwriting performance of the export insurance and the sovereign credit rating of the export counterpart countries have the positive impact on Korea's export. Also, the impact of the export insurance is more increasing to the Korea exportation but the importance of the economy size of the export counterpart countries decreased after 2008 global financial crisis. Particularly, the influence to the export by the sovereign credit rating has diminished in that period and this seems to be due to the export insurance has increased. These results imply that the export insurance plays an important role to promote the Korea's exportation since 2008 global recession. Especially, if the recession continues, then there will be more crippling impact to the small-mid size companies rather than large size companies. Therefore, Korea government should do their best to continuously expand the export insurance for the purpose of increasing Korea exportation, expecially to the small-mid size companies.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.34 no.4
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• pp.255-262
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• 2021

In this study, a jointless bridge that integrates the superstructure and abutment without installing an expansion joint was analyzed. An example of a jointless bridge that has been introduced in Korea since 2009. Owing to the short period of use and lack of experience in design, construction, and maintenance, there is insufficient information regarding the long-term behavior of jointless bridges. When analyzing numerous bridges, the numerical analysis model must maintain the numerical values used and ensure the convenience of model construction. In this study, sensitivity analysis was performed to select a numerical model for various types of jointless bridges using commercial finite element programs, MIDAS Civil and ABAQUS 2018. According to a solid element-based model, we analyzed the mean and maximum relative errors between structural models. Consequently, it was found that the beam element-based model exhibits a significantly small relative error in comparison to the shell element, where a relatively large error was recorded. Therefore, the optimal numerical analysis model, a practical model that maintains the similarity and precision of the displacement shape cause by relative error, was judged to be the most suitable for jointless bridges based on the shell element.

• Korean Journal of Remote Sensing
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• v.37 no.2
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• pp.211-220
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• 2021

Land Surface Temperature (LST) is one of the useful parameters to diagnose the growth and development of crop and to detect crop stress. Unmanned Aerial Vehicle (UAV)-based LST (LSTUAV) can be estimated in the regional spatial scale due to miniaturization of thermal infrared camera and development of UAV. Given that meteorological variable, type of instrument, and surface condition can affect the LSTUAV, the evaluation for accuracy of LSTUAV is required. The purpose of this study is to evaluate the accuracy of LSTUAV using LST measured at ground (LSTGround) under various meteorological conditions and growth phases of garlic crop. To evaluate the accuracy of LSTUAV, Relative humidity (RH), absolute humidity (AH), gust, and vegetation index were considered. Root mean square error (RMSE) after minimizing the bias between LSTUAV and LSTGround was 2.565℃ under above 60% of RH, and it was higher than that of 1.82℃ under the below 60% of RH. Therefore, LSTUAV measurement should be conducted under the below 60% of RH. The error depending on the gust and surface conditions was not statistically significant (p-value < 0.05). LSTUAV had reliable accuracy under the wind speed conditions that allow flight and reflected the crop condition. These results help to comprehend the accuracy of LSTUAV and to utilize it in the agriculture field.

• Journal of Korean Ophthalmic Optics Society
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• v.17 no.3
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• pp.285-291
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• 2012

Purpose: This study was conducted to research any effect on visual function related to accommodation by VDT work. Methods: The refraction power, accommodative lag, accommodative facility, relative accommodation, amplitude of accommodation and blink rate were measured before and after VDT work for 2 hours on 48 university students (16 males and 32 females), without abnormal accommodative function and systemic and ocular disease, who had never undergone corrective eye surgery. All examinations were performed with distant refraction, and a survey was conducted on the items related to subjective symptoms of VDT syndrome. Results: After 2 hours of VDT work, refractive power increased by 0.23 D, the amount of change in accommodative lag were $0.17{\pm}0.42D$ in the right eye and $0.23{\pm}0.47D$ in the left eye (t=2.26, p=0.03). There were statistically significant differences. Both the accommodative facility and relative accommodation and amplitude of accommodation were decreased after work. However, blink rate were increased. After VDT work, 33.4% of the subjects showed subjective symptoms of asthenopia and 33.3% of them showed shoulder pain. Conclusions: As a result, the accommodative lag increased in response to the two hours of VDT work, and overall accommodative functions were decreased. In addition, as symptoms of providing visual strain, asthenopia showed the most prominent subjective symptoms.

• Informatization Policy
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• v.26 no.2
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• pp.24-45
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• 2019

This paper analyzes the size of direct and indirect impact of the information and communication technology(ICT) producing sector to the Korean economic growth We first divide the entire economy into the ICT producing sector and the ICT using sector, and estimate the contributions to the economic growth by each sector. We also try to answer the question on what the possible causes of the ICT producing sector's contribution are to growth. In oder to find the answer, we focus on the change in the relative prices of ICT products produced in the ICT producing sector and examine the long-term relations among the relative prices of ICT products, the ratio of ICT products used in the ICT using sector as an intermediate input, and the output of the entire economy. We find that the overall economic growth has been weakened but the ICT sector's contribution to the growth has increased. Specifically, the indirect contribution of the ICT producing sector, through the ICT using sector, to economic growth was greater than the direct contribution of the ICT producing sector itself. We also find a stable, long-term negative relation between the relative prices of ICT products produced in the ICT producing sector and the ratio of ICT products as an intermediate input in the ICT using sector. In addition, the decrease in the relative prices of ICT products produced in the ICT producing sector increases the use of ICT products in the ICT using sector and the output of the entire economy. These findings can be interpreted that the price decrease in the ICT products improves the production efficiency in other sectors and helps directly and indirectly, accelerating growth of the entire economy.

• Journal of the Korean GEO-environmental Society
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• v.16 no.4
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• pp.5-12
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• 2015

Civil engineers have taken the numerous slope monitoring data for an engineering project subjected to hazard potential of slide. However, the topics on how to deal with and draw out proper information from the data related to the slope behavior have not been widely discussed. Recently, several researchers had installed the real-time monitoring system to cope with slope failure; however they are mainly focused on the hardware system installation. Therefore, this study tries to show how the measured data could be grouped and connected each other. The basic idea of analyzing method studied in this paper came from the clustering, which is the part of data mining analysis. Therefore, at the base of classification of time series data, the authors suggest three mathematical data analyzing methods; Average Index of different displacement ($AD_{i,j}$), Difference of average relative displacement ($\overline{RD}_{i,j}$) and Coordinate system of average and relative displacement ($\overline{RD}$, AD). These analyzing methods are based on the statistical method and failure mechanism of slope. Therefore they showed clustering relationships of the similar parts of the slope which makes the same sliding mechanism.

• Journal of fish pathology
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• v.3 no.1
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• pp.27-38
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• 1990

Hematological conditions were measured to the cultured bastard halibut classified by control group and establishments of mari-floating netcages from April 7, 1990 to May 24, 1990. The RBC, Hb, HT, MCHC, MCH and MCV values were $289{\pm}61{\times}10/^4/mm^3$, $4.8{\pm}0.9g/dl$, $22{\pm}6%$, $22.7{\pm}4.0%$, $16.9{\pm}3.3pg$ and $77{\pm}19{\mu}m^3$ respectively in the hematological conditions of control group. Relation between Hb and Ht was represented highly positive(r＝0.805, p<0.01>, and relation between MCV and MCH was represented positive (r＝0.696, p<.0.05) in the control group. In the variation of hematological conditions classified by experimental group, RBC of PVC group was returned $293{\pm}57{\times}10/mm^3$ on the 21th after locomotion to mari-floating netcages. RBC of netron group was also returned as control level on the 21th after locomotion, showed stabilization. Hb of PVC and netron group was low in the range of variation, was represented $3.9{\pm}9.6g/dl$ on the 45th after locomotion. The group that was also satabilizied variation of Ht were PVC, netron group. According to the results of hematological conditions classified by establishment of mari-floating netcages, the experiment group that were stabilized variation were in order of PVC, netron and pole-PVC group. But the other groups were extended the range of variation.

• Economic and Environmental Geology
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• v.49 no.2
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• pp.105-120
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• 2016

Most of riverside in Korea, in case of application of water curtain cultivation (WCC) technique, has been inveterately suffering from the gradual drawdown of groundwater level and related shortage of water resources during the WCC peak time. We believe that the water resources issue in these riverside areas can be effectively solved when the interaction between groundwater and nearby surface water is well understood. To investigate the connection between stream and ground water, and the influence of stream water on the nearby aquifer, this study examined the water temperature and oxygen and hydrogen stable isotopic compositions. The study area is well-known strawberry field applying the WCC technique in Sangdae-ri, Gadeok-myon, Cheongju City, and the sampling was done from February 2012 through June 2014 for stream and ground water. Some groundwater wells near stream showed big temporal variations in water temperature, and their oxygen and hydrogen stable isotopes showed similar compositions to those of adjacent stream water. This indicates that the influence of stream water is highly reflected in the stable isotopic composition of groundwater. Four cross-sectional lines from stream to hillside were established in the study area to determine the spatial differences in water quality of wells. At the late stage of WCC in February to March, groundwater of wells in line with short cross-sectional length showed the narrow range of isotopic compositions; however, those in the long cross-sectional line showed a wide compositional range. It was shown that the influence of the stream water at the late WCC stage have reached to the distance of 160 to 165 m from stream line, which is equivalent to the whole length and one-third point in each short and long cross-sectional line, respectively. Therefore, the wide compositional range in the long cross-sectional lines was not only due to the influence of stream water, but apparently resulted from the change of relative impact of each groundwater supplying from two or more aquifers. In view of stable isotopic compositions, there seems to be three different aquifers in this study area, which is competing for dominance of water quality in wells at each period of WCC.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.32 no.4
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• pp.61-66
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• 2004

The objective of the present study is to develop methodology for the assessment of combustion stability of liquid rocket injectors. To simulate actual combustion occurring inside of a thrust chamber, a fullscale injector has been employed in the study, which bums gaseous oxygen and mixture of methane and propane. The main idea of the experiment is that the mixing mechanism is considered as a dominant factor significantly affecting combustion instability in a fullscale thrust chamber. A single split triplet injector has been used with an open-end cylindrical combustion chamber. The characteristics revealed by excited dynamic pressures in gaseous combustion show degrees of relative acoustic damping depending on operating conditions. Upon test results, the direct comparison between various types of injectors can be realized for the selection of the best design among prospective injectors.