• Journal of Korean Ophthalmic Optics Society
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• v.9 no.2
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• pp.361-370
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• 2004

The purpose of this study was to evaluate the outcome and Factors that influence the quantity of Phoria in the low correction and perfect correction. Also the coincidence with the opticenter and the pupillary distance was a principal factor that influence the quantity of Phoria. Thereupon, this study is attributed to promote the perfect Phoria test. The subjects for this study were 120 persons(240 eye) in myopic refractive errors. ISP/WIN program was used for the data analysis. The collected data was analyzed by descriptive statistics and Spearman's correlation coefficient. The results of this study were as follows: 1. The prism pattern was difference between low correction and perfect correction in the Phoria test. The proportion of orthophoria was changed from 10.0% to 12.5%, exophoria was changed from 67.5% to 62.5%, and esophoria was changed from 22.0% to 32.5%, respectively. 2. The average of optical center distance and pupillary distance were 31.70mm and 31.49 mm, respectively. 3. Among the 120 myopic glasses wearers, the distance between optical centers was coincided with the pupillary distance in 37.5%, and discrepant in 62.5%. 4. For the patients who were coincided with the pupillary distance, the proportion of exophoria decreased 53.33%, esophoria increased 20.0%. 5. For the changing of the quantity of Phoria in the low correction, the degree of exophoria decreased 1.11 prism diopters in the perfect correction, esophoria increased 0.39 prism diopters.

• Korean Journal of Remote Sensing
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• v.36 no.3
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• pp.425-439
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• 2020

Through the operations of advanced geostationary meteorological satellite such as Himawari-8 and GK2A, higher resolution and frequency of AOD (Aerosol Optical Depth) data have become available. In this study, we analyzed the characteristics of Himawari-8/AHI (Advanced Himawari Imager) aerosol properties using the recent 4 years (2016~2019) of Sun photometer data observed at the five stations(Seoul National University, Yonsei University, Hankuk University of Foreign Studies, Gwangju Institute of Science and Technology, Anmyon island) which is a part of the AERONET (Aerosol Robotic Network). In addition, we analyzed the causes for the AOD differences between Himawari AOD and Sun photometer AOD. The results showed that the two AOD data are very similar regardless of geographic location, in particular, for the clear condition (cloud amount < 3). However, the quality of Himawari AOD data is heavily degraded compared to that of the clear condition, in terms of bias (0.05 : 0.21), correlation (0.74 : 0.64) and RMSE (Root Mean Square Error; 0.21 : 0.51), when cloud amount is increased. In general, the large differences between two AOD data are mainly related to the cloud amount and relative humidity. The Himawari strongly overestimates the AOD at all five stations when cloud amount and relative humidity are large. However, the wind speed, precipitable water, height of cloud base and Angstrom Exponent have been shown to have no effect on the AOD differences irrespective of geographic location and cloud amount. The results suggest that caution is required when using Himawari AOD data in cloudy conditions.

• Korean Journal of Remote Sensing
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• v.36 no.5_1
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• pp.785-791
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• 2020

The radiance measured from satellite has noise due to atmospheric effect. Atmospheric correction is the process of calculating surface reflectance by removing atmospheric effect and surface reflectance is calculated by the Radiative Transfer Model (RTM)-based Look-Up Table (LUT). In general, studies using a LUT make LUT for each channel with the same atmospheric and geometric conditions. However, atmospheric effect of atmospheric factors do not react sensitively in the same channel. In this study, the LUT for each channel of Korea Multi-Purpose SATellite (KOMPSAT)-3/3A was made under the same atmospheric·geometric conditions. And, the accuracy of the LUT was verified by using the simulated Top of Atmosphere radiation and surface reflectance in the RTM. As a result, the relative error of the surface reflectance in the blue channel that sensitive to the aerosol optical depth was 81.14% at the maximum, and 42.67% in the NIR (Near Infrared) channel.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.42 no.8
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• pp.692-700
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• 2014

In this work, satellite FE (finite element) model updating for the prediction of the effect of micro-vibration is described. In the case of satellites launched in low earth orbit, high agility and more mission accomplishments are required by the customer in order to procure many images from satellites. To achieve the goal, many mechanisms, including high capacity wheels and antennas with multi-axis gimbals have been widely adopted, but they become a source of micro-vibration which could significantly deteriorate the quality of images. To investigate the effect due to the micro-vibration in orbit on the ground, a prediction is conducted through an integrated model coupling the measured jitter sources with FE (finite element) model. Before prediction, the FE model is updated to match simulation results with the modal survey test. Subsequently, the quality of FE model is evaluated in terms of frequency deviation error, the resemblance of mode shapes and FRFs (frequency response functions) between test and analysis.

• Journal of Korean Society of Environmental Engineers
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• v.28 no.4
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• pp.447-452
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• 2006

The remote sensing technique was applied to enhance the water qualify model validation in a large water body. Since the satellite image usually covers the wide surface area of a large water body, it can compensate for the lark of measured data points required for model calibration and verification. This paper describes the analysis of Landsat FTM+images collected on April 29th and September 4th in year 2000 to evaluate surface water temperature of Lake Paldang. The water temperature data obtained from the satellite image were compared with model results by estimating three different methods of error criteria. The residual ratios on April 29th and September 4th were 0.13 and 0.04 respectively. This showed that the model result accords with the data obtained from the process of satellite image. Without considering atmospheric interference, however, transformation process of satellite image causes relatively large residual ratio in the surface water temperature distribution pattern on April 29th. In the future study, therefore, the atmospheric properties of image acquisition point needs to be considered for the application of radiance transformation model.

• Environmental Analysis Health and Toxicology
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• v.29
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• pp.12.1-12.8
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• 2014

Objectives Cohort studies of associations between air pollution and health have used exposure prediction approaches to estimate individual-level concentrations. A common prediction method used in Korean cohort studies is ordinary kriging. In this study, performance of ordinary kriging models for long-term particulate matter less than or equal to $10{\mu}m$ in diameter ($PM_{10}$) concentrations in seven major Korean cities was investigated with a focus on spatial prediction ability. Methods We obtained hourly $PM_{10}$ data for 2010 at 226 urban-ambient monitoring sites in South Korea and computed annual average $PM_{10}$ concentrations at each site. Given the annual averages, we developed ordinary kriging prediction models for each of the seven major cities and for the entire country by using an exponential covariance reference model and a maximum likelihood estimation method. For model evaluation, cross-validation was performed and mean square error and R-squared ($R^2$) statistics were computed. Results Mean annual average $PM_{10}$ concentrations in the seven major cities ranged between 45.5 and $66.0{\mu}g/m^3$ (standard deviation=2.40 and $9.51{\mu}g/m^3$, respectively). Cross-validated $R^2$ values in Seoul and Busan were 0.31 and 0.23, respectively, whereas the other five cities had $R^2$ values of zero. The national model produced a higher cross-validated $R^2$ (0.36) than those for the city-specific models. Conclusions In general, the ordinary kriging models performed poorly for the seven major cities and the entire country of South Korea, but the model performance was better in the national model. To improve model performance, future studies should examine different prediction approaches that incorporate $PM_{10}$ source characteristics.

• Korean Journal of Agricultural and Forest Meteorology
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• v.9 no.3
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• pp.179-187
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• 2007

This study was conducted to develop site index equations for some pine species by climatic zones based on the relationships between site index and environmental factors. The selected pine species were Pinus densiflora Sieb. et. Zucc., Pinus densiflora for, erecta, and Pinus thunbergii. A total of 28 environmental factors were obtained from a digital forest site map. The influence of 28 environmental factors on site index was evaluated by multiple regression analysis. Four to eight environmental factors were selected in the final site index equation for pine species by climatic zones. The site index equations developed in this study was then verified by three evaluation statistics such as model's estimation bias, model's precision and mean square error type of measure. We concluded that the site index equations for the pine species by climatic Bones were capable of estimating forest site productivity. Based on these site index equations, the amount of productive areas for the species by climatic zones was estimated by applying the GIS technique to digital forest maps.

• Journal of Environmental Impact Assessment
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• v.26 no.1
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• pp.11-26
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• 2017

Approximate empirical equations obtained by measuring overall noise levels at different distances have been used to evaluate environmental influence of the railway noise though the accurate prediction of noise levels is important. In this paper, a noise prediction model considering the frequency characteristics of noise sources and propagation was suggested to improve the accuracy of noise prediction. The railway noise source was assorted into track, wheel, traction and aerodynamic components and they were characterized with the source strength and speed coefficient at each octave-band frequency. Correction terms for the acoustic roughness and the track/bridge condition were introduced. The sound attenuation from a source to a receiver was calculated taking account of the geometrical divergence, atmospheric absorption, ground effect, diffraction at obstacles and directivity of source by applying ISO 9613-2. For obtaining the source strength and speed coefficients, the results of rolling noise model, numerical analysis and measurements of pass-by noise were analyzed. We compared the predicted and measured noise levels in various vehicles and tracks, and verified the accuracy of the present model. It is found that the present model gives less error than the conventional one, so that it can be applied to make the accurate prediction of railway noise effect and establish its countermeasures efficiently.

• The Journal of the Korea Contents Association
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• v.18 no.2
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• pp.468-475
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• 2018

The current system of making course evaluations mandatory in universities in Korea in order to supplement low participation levels is a major hindering factor for the validity of the evaluation results due to students' insincere responses. This study points out the problems in course evaluations that are in the form of surveys and instead proposes a sample course evaluation system that utilizes a sample mean to deduce a population mean, attempting to prove through simulation that this is statistically significant. Thus, small, medium, and large scale courses as well as cyber courses that were available in S University in the fall 2016 semester were set as the population, and each course's evaluation average grade was set as the population mean. Furthermore, we used the average grade and standard deviation of the same courses from the previous year in order to decide the sample number, the reliability level was set as 95%, and the margin of error was set as ${\pm}0.25$. As a result of carrying out a simulation using the data analysis tool R, all the courses (small scale, medium scale, large scale, and cyber) showed to have a reliability level close to 95% including the population mean, and consequently practicality of the representative sample course evaluation system was proven.

• Journal of Astronomy and Space Sciences
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• v.21 no.4
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• pp.399-416
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• 2004

The FIMS (Far-ultraviolet IMaging Spectrograph), the main payload onboard the first Korean science satellite STSAT-1, has performed various observations since its launch on September 2003. It has been found that the attitude informations provided by spacecraft bus system have a time offset problem, and the problem has been extensively studied. After the time offset correction, boresight offsets between FIMS fields of view, of long and short wavelength bands, respectivley, and spacecraft attitude systems, which are mainly due to alignment error between the FIMS and spacecraft mechanical systems, were calculated through the observations of well known calibration targets. Monthly status and precision of the attitude information are also described. Correction methods for spatially variable exposure, intrinsic to FIMS data, are discussed. These results are essential to the FIMS data analysis, and will be used as references for subsequent studies on more accurate attitude corrections.