• Journal of Korean Society for Geospatial Information Science
• /
• v.23 no.2
• /
• pp.39-48
• /
• 2015

Lately, Unmanned Aerial Vehicles(UAV), Unmanned Aerial Systems(UAS) or also often known as drones, as a data acquisition platform and as a measurement instrument are becoming attractive for many photogrammetric surveying applications, especially generation of the high density point clouds(HDPC). This paper presents the performance evaluation of a low-cost rotary wing quadrocopter UAS for generation of the HDPC in a test bed environment. Its performance was assessed by comparing the coordinates of UAS based HDPC to the results of Network RTK GNSS surveying with 62 ground check points. The results indicate that the position RMSE of the check points are ${\sigma}_H={\pm}0.102m$ in Horizonatal plane, and ${\sigma}_V={\pm}0.209m$ in vertical, and the maxium deviation of Elevation was 0.570m within block area of ortho-photo mosaic. Therefore the required level of accuracy at NGII for production of ortho-images mosaic at a scale of 1:1000 was reached, UAS based imagery was found to make use of it to update scale 1:1000 map. And also, since this results are less than or equal to the required level in working rule agreement for airborne laser scanning surveying of NGII for Digital Elevation Model generation of grids $1m{\times}1m$ and 1:1000 scale, could be applied with production of topographic map and ortho-image mosaic at a scale of 1:1000~1:2500 over small-scale areas.

• Atmosphere
• /
• v.21 no.1
• /
• pp.57-67
• /
• 2011

Aerosol lidar ratio (extinction-to-backscatter ratio) at 532 nm was determined using 4-year measurements of elastic-backscatter lidar and sky radiometer at Seoul National University of Seoul, Korea. The mean lidar ratio (with standard deviation) based on 4 years of measurements is found to be $61.7{\pm}16.5$ sr, and weak seasonal variations are noted with a maximum in JJA ($68.1{\pm}16.8$ sr) and a minimum in DJF ($57.2{\pm}17.9$ sr). The lidar ratios for clean, dust, and polluted conditions are estimated to be $45.0{\pm}9.5$ sr, $51.7{\pm}13.7$ sr, and $62.2{\pm}13.2$ sr, respectively. While the lidar ratio for the polluted condition is appears to be consistent with previous studies, clean and dust conditions tend to have larger ratios, compared to previous estimates. This discrepancy is thought to be mainly due to the anthropogenic aerosols existing throughout the year around Seoul, which may cause increased lidar ratios even for clean and dust conditions.

• Journal of Energy Engineering
• /
• v.29 no.2
• /
• pp.1-9
• /
• 2020

In recent days, fuel cell has received attention from the world as an alternative power source to hydrocarbon used in automobile engines. With the industrial advances of fuel cell, There have been a lot of researches actively conducted to find a way of generating hydrogen. Among many hydrogen production methods, Solid Oxide Electrolysis Cell(SOEC) is not only a basic way but also environment-friendly method to produce hydrogen gas. Solid Oxide Electrolysis Cell has lower electrical energy demands and high thermal efficiency since it is possible to operate under high temperature and high pressure conditions. For these reasons, experimental researches as well as studies on numerical modeling for Solid Oxide Electrolysis Cell have been under way. However, studies on numerical modeling are relatively less enough than experimental accomplishments and have limited performance prediction, which mostly is considered as a result from inadequate effects of electrochemical properties by temperature and pressure. In this study, various experimental studies of commercial Membrane Electrode Assembly (MEA) composed of Ni-YSZ (40wt%, Ni-60 wt% YSZ)/8-YSZ (TOSOH, TZ8Y)/LSM (La_0.9Sr_0.1MnO₃) was utilized for improving effectiveness of SOEC model. After numerically analyzing effects of electrochemical properties according to operating temperature, causing the largest deviation between experiments and simulation are that Charge Transfer Coefficient (CTC), exchange current density, diffusion coefficient, electrical conductivity in SOEC. Analyzing temperature effect on parameter used in overpotential model is conducted for modeling of SOEC. cross-validation method is adopted for application of various MEA and evaluating feasibility of model. As a result, the study confirm that the numerical model of SOEC based on structured process of effectiveness evaluation makes performance prediction better.

• Journal of Korea Water Resources Association
• /
• v.48 no.5
• /
• pp.367-377
• /
• 2015

ADCPs have been highlighted so far for measuring steramflow discharge in terms of their high-order of accuracy, relatively low cost and less field operators driven by their easy in-situ operation. While ADCPs become increasingly dominant in hydrometric area, their actual measurement accuracy for velocity and bathymetry measurement has not been sufficiently validated due to the lack of reliable bench-mark data, and subsequently there are still many uncertain aspects for using ADCPs in the field. This research aimed at analyzing inter-comparison results between ADCP measurements with respect to the detailed ADV measurement in a specified field environment. Overall, 184 ADV points were collected for densely designed grids for the given cross-section that has 6 m of width, 1 m of depth, and 0.7 m/s of averaged mean flow velocity. Concurrently, ADCP fixed-points measurements were conducted for each 0.2m and 0.02m of horizontal and vertical spacing respectively. The inter-comparison results indicated that ADCP matched ADV velocity very accurately for 0.4~0.8 of relative depth (y/h), but noticeable deviation occurred between them in near surface and bottom region. For evaluating the capacity of measuring bathymetry of ADCPs, bottom tracking bathymetry based on oblique beams showed better performance than vertical beam approach, and similar results were shown for fixed and moving-boat method as well. Error analysis for velocity and bathymetry measurements of ADCP can be potentially able to be utilized for the more detailed uncertainty analysis of the ADCP discharge measurement.

• Journal of Korean Society for Geospatial Information Science
• /
• v.22 no.2
• /
• pp.25-32
• /
• 2014

The river plan executes the role for prevention of disaster and protection of environment, and requires the surveying results with high accuracies for managing river, dam, reservoir which will be the major infrastructures. The purpose of this study is for comparing and analyzing the results of river surveying which is used widely for disaster management and construction industry support. The results are gathered by using LiDAR which is being used in Korea recently and by using Total station. Study area is chosen at upper area of Bukhan River which is located at Gangwon-do. Total 2 cross-sections of the two methods are extracted from the study area. The standard deviation of land part is about 0.017m which shows little difference between two methods, but the Airborne LiDAR results cannot survey the heights of the points accurately at the singular points with vertical structure and water body part. To overcome the problems through this study, there should be ways to survey the bottom river through transmission of water level within the same margin scope as land part and to survey detailed facilities used by laser exactly through continuous research and experiment. When implementation stage comes, this study expect that this document will be utilized variously for making decision in the area of planning and drawing of business and engineering not just for river regarding the major area or the area that people cannot access.

• The Journal of the Korea Contents Association
• /
• v.16 no.12
• /
• pp.124-131
• /
• 2016

This study was conducted to serve as a basis for education by identifying the correlation of college admission type, college-life satisfaction and academic achievement of radiologic science students. Data were collected from 2 universities and 2 colleges located in Gyeonggi Provice, North Chungcheong Province, North Gyeongsang Province. A total of 371 questionnaires were collected, 363 of which were included in this study. The results showed that there were no differences in academic achievement according to the type of college admission. It could be able to interpret that since department of radiologic science is popular, students with high academic records applies the department of radiologic science and there are less deviation of academic records among students. A correlation analysis of academic achievement showed learning attitude is a statistically valid factor. Learning attitudes can be changed by exposure to the environment. This will require a variety of program development for improving learning attitudes. In addition, academic achievement of radiologic science students is associated with license acquisition. It need to be made together research on determinants and development of learning method to improve the learning attitude.

• Journal of Korean Society of Forest Science
• /
• v.108 no.4
• /
• pp.592-599
• /
• 2019

This study aimed to develop an equation for estimating stem volume for Larix kaempferiin South Korea using independent variables, diameter at breast height (DBH), and height as being closely associated with stem volume. Analysis was conducted on the growth performance of 2,840 Larix kaempferi samples across South Korea after felling them and gleaning diameter data according to both stem height and stem analyses. In order to test the fitness of six different stem taper equations, empirical assessment was conducted for fitness index (FI), bias, mean, and absolute deviation (MAD), and coefficient variation (%CV). The two selectedmodels found to be optimal were the following: model one (V=a+bDBH²), established by employing DBH only; and model four (V=a+bDBH²H), established by utilizing DBH and height, respectively. The findings of non-linear regression indicated statistical significance (p < 0.05) in a and b, which were the coefficients for the intercepts and slopes of the models. The FI of the models ranged between 94% and 99%, and the bias was close to zero, while MAD ranged from 0.01 to 0.05, and %CV from 5.97 to 14.43, indicating a high level of fitness. Thus, using the suggested models, the basic information necessary for forest management was obtained, and an estimation of the stem volume was effected without delay soon after effecting DBH and height measurements.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.35 no.11
• /
• pp.1127-1131
• /
• 2011

We report on a pumpless cell culture chip in which a constant medium perfusion rate is maintained by balanced droplet dispensing. Previous chips had a decreasing perfusion rate due to the decreasing hydraulic-head difference ${\Delta}h$ between the inlet and drain. However, the present chip maintains a constant medium perfusion rate due to the constant ${\Delta}h$ between the inlet and drain maintained by balanced droplet dispensing. The perfusion rate Q was measured to be 0.1-$0.3{\mu}l$/min with a maximum deviation and error of 9.96% and 6.92%, respectively. In the perfusion culture (Q = 0.1-$0.3{\mu}l$/min), the maximum growth-rate of H358 cells was measured to be $57.8%{\pm}21.1%$ per day, which is 1.9 times higher than that of a static culture. The perfusion culture also resulted in higher cell viability than a static culture. The present chip offers a favorable environment with a high growth-rate and viability and thus has potential for use in the integrated cell culture system.

• Journal of Agricultural Extension & Community Development
• /
• v.3 no.1
• /
• pp.141-155
• /
• 1996

The purpose of this study was to investigate the sole of local newspaper for community development in Korea. Specific objectives of the study were : 1) to identify the role of local newspaper in community development, 2) to analyze problems and situations on local newspapers in Korea, and 3) to suggest desirable roles of local newspaper for the community development. To attain the above objectives, this study was carried out through literature review, contest analysis of selected local newspapers, and the questionnaire survey of selected readers of local newspaper. The data were collected from 267 readers of local newspaper who participated in the farmers` training session in the Rural Development Administration, by using questionnaires developed by the researcher, and total of 263 questionnaires were analyzed. The statistical techniques used for the study were frequence, percentile, standard deviation utilizing the $SPSS/PC^+$. The major findings of the study were as follows : 1. The major roles of functions of local newspapers identified in this study were summarized as to reinforce the community consciousness, to form community opinion, to watch and to monitor community environment, to provide education and entertainment, and to contribute to the conveyance and promotion of community culture. 2. The general characteristic of local newspaper readers surveyed were; a) average distance from town to their village was 9.3 Km, b) average age was 29 years, c) about 75% of them were senior high school graduates, and d) about 96% of them participated in group activities. 3. About 45% of the respondents used television or radio for their moor sources of local news were TV or radio, while about 31% respondents used immunity newspaper for their moor sources of local news. About 67% of the respondents kept their readership over two years, and about 40% of them read community newspaper regularly at their home. 4. The results of content analysis showed drat the local newspapers were dealing with articles on cultural affairs, community consciousness, administrative and civic affairs, however, there were not enough educational news, and various kinds of general news in the community. 5. Survey also showed the most needed news were ; 1) political news including administrative and civic affairs, 2) economic news including sales and distribution, 3) social news including social problems on environmental pollution and community development works, 4) educational news including technology and information, 5) cultural news including guide to cultural and historical sites and local brief news. 6. In the evaluation of local newspaper, the readers were generally positive in valued roles of local newspaper in community relations, community development, promoting community cohesion and understanding of community members, and about 40% of the respondents were positive in predicting the bright future perspectives of local newspapers. 7. In the readers` evaluation of local newspaper, readers responded that local newspapers were very closely related to the community and residents, reflecting the current concerns of local population and recognizing the value of community media, and the contents of local newspaper were positively related to daily lives of community residents and opinions of overall community.

• Particle and aerosol research
• /
• v.16 no.2
• /
• pp.31-47
• /
• 2020

Although interest in air quality has increased due to the frequent occurrence of high-concentration fine particulate matter recently, the official fine particulate matter measuring network has failed to provide spatial detailed air quality information. This is because current measurement equipment has a high cost of installation and maintenance, which limits the composition of the measuring network at high resolution. To compensate for the limitations of the current official measuring network, this study constructed a spatial high density measuring network using the fine particulate matter simple measuring device developed by Observer, W-Station. W-Station installed 48 units on Jeju Island and measured PM_2.5 for six months. The data collected in W-Station were corrected by applying the first regression equation for each section, and these measurements were compared and analyzed based on the official measurements installed in Jeju Island. As a result, the time series of PM_2.5 concentrations measured in W-Station showed concentration characteristics similar to those of the environmental pollution measuring network. In particular, the results of comparing the measurements of W-Station within a 2 km radius of the reference station and the reference station showed that the coefficient of determination (R²) was 0.79, 0.81, 0.67, respectively. In addition, for W-Station within a 1 km radius, the coefficient of determination was 0.85, 0.82, 0.68, respectively, showing slightly higher correlation. In addition, the local concentration deviation of some regions could be confirmed through 48 high density measuring networks. These results show that if a network of measurements is constructed with adequate spatial distribution using a number of simple meters with a certain degree of proven performance, the measurements are effective in monitoring local air quality and can be fully utilized to supplement or replace formal measurements.