• Korean Journal of Remote Sensing
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• v.39 no.5_3
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• pp.1009-1029
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• 2023

Urban trees play a vital role in urban ecosystems,significantly reducing impervious surfaces and impacting carbon cycling within the city. Although previous research has demonstrated the efficacy of employing artificial intelligence in conjunction with airborne light detection and ranging (LiDAR) data to generate urban tree information, the availability and cost constraints associated with LiDAR data pose limitations. Consequently, this study employed freely accessible, high-resolution multispectral satellite imagery (i.e., Sentinel-2 data) to estimate fractional tree canopy cover (FTC) within the urban confines of Suwon, South Korea, employing machine learning techniques. This study leveraged a median composite image derived from a time series of Sentinel-2 images. In order to account for the diverse land cover found in urban areas, the model incorporated three types of input variables: average (mean) and standard deviation (std) values within a 30-meter grid from 10 m resolution of optical indices from Sentinel-2, and fractional coverage for distinct land cover classes within 30 m grids from the existing level 3 land cover map. Four schemes with different combinations of input variables were compared. Notably, when all three factors (i.e., mean, std, and fractional cover) were used to consider the variation of landcover in urban areas(Scheme 4, S4), the machine learning model exhibited improved performance compared to using only the mean of optical indices (Scheme 1). Of the various models proposed, the random forest (RF) model with S4 demonstrated the most remarkable performance, achieving R² of 0.8196, and mean absolute error (MAE) of 0.0749, and a root mean squared error (RMSE) of 0.1022. The std variable exhibited the highest impact on model outputs within the heterogeneous land covers based on the variable importance analysis. This trained RF model with S4 was then applied to the entire Suwon region, consistently delivering robust results with an R² of 0.8702, MAE of 0.0873, and RMSE of 0.1335. The FTC estimation method developed in this study is expected to offer advantages for application in various regions, providing fundamental data for a better understanding of carbon dynamics in urban ecosystems in the future.

• The Journal of the Korea institute of electronic communication sciences
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• v.8 no.1
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• pp.181-189
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• 2013

This study was conducted to provide basic data in establishing a method for helping adolescents form the concept of correct oral health knowledge, by searching for their misconceptions about oral health knowledge and figuring out relevant factors. Results showed that they had appropriate knowledge on a relatively large number of questions regarding the level of oral health knowledge, but they also had misconceptions about the toothbrush grip, how to use medicines for gum diseases, and the project of fluorine concentration adjustment in water. It was shown that the score of oral health knowledge turned out to be 10.78 on average as a whole and the mean difference was within the error range. As for the correlations of misconceptions about oral health knowledge by group, it was noted that there were no differences in gender and education level, but those who completed oral health education had more appropriate concepts than those who did not (p < 0.001). In terms of the paths that they obtained oral health knowledge, the Internet and mass media (35.4%) had the highest rate and school (9.6%) had the lowest rate. With regards to the level of oral health knowledge, school had 10.56, which was the lowest score. In this regard, in order for adolescents to form adequate oral health knowledge, the following should be done. therefore, it would be necessary to activate school oral health education so as for adolescents to exercise adequate oral health behavior and to train many oral health educators so as for them to be provided with more educational opportunities.

• Journal of Korea Water Resources Association
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• v.45 no.5
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• pp.495-503
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• 2012

It is necessary to perform the precise analysis of unsteady flow for effective design of the side-weir detention basin installed in the river. Generally, the HEC-RAS program, which is a 1D unsteady numerical model, is mostly used to simulate the unsteady flow for rivers. However, it is difficult to have confidence of unsteady flow results simulated by HEC-RAS due to the lack of experimental data and field monitoring data for the channel with a side-weir detention basin. Therefore, the purpose of this study is to validate or verify the simulation results calculated by HEC-RAS through the experiments for the open channel with a side-weir detention basin using specially-designed unsteady discharge-supply system. The experimental cases included unsteady flows in the straight channel with and without a side-weir detention basin. Especially, for the case with a detention basin, the experiment was performed to consider only the free flow condition over the side-weir. The study results showed that values of water level and discharge obtained from HEC-RAS coincided reasonably with experimental results with the maximum error of 3% for water level and 1% for discharge in the case of the flow without the side-weir detention basin and 4% for water level and 2% for discharge with the side-weir detention basin.

• 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 the Korean Association of Geographic Information Studies
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• v.9 no.2
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• pp.79-90
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• 2006

The partitioning level of a catchment becomes an issue if the calculated results from different levels show the same performance regardless of the levels. This study aims to identify the proper processing level of spatial resolution for the SWMM model application in an urban area. Using GIS overlaying technique, the division of subcatchments as a hydrologic similarity unit (HSU) is achieved with a comprehensive consideration of surface slope conditions, flow directions of storm sewers, and current land cover situation. Three surface-sewer alternatives are made on the basis of three different levels of surface divisions as well as the number of sewer connections and used as runoff simulation fields for the application of SWMM. As the result, it is found that the effect of a spatial resolution on the surface runoff results is not significant. On the other hand, the accumulated pollution load from an unit subcatchment, which is built by aggregation of several unit subcatchments consisting of various land cover conditions is reduced through the deterioration of surface spatial resolution. Although overall runoff pattern and accumulated runoff are little affected by spatial resolution, the simulated runoff from sewer outlet shows slight difference at the peak appearance time. The gap between surface pollution load accumulated and it discharged from the sewer outlet in a surface-sewer alternative during runoff period is monitored but the level of error is less than 5-10% except the lowest spatial resolution case.

• Journal of Korean Home Economics Education Association
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• v.30 no.3
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• pp.151-173
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• 2018

The purposes of this study was to identify the magnitude and direction of the effects of Practical Reasoning Instruction (PRI) on students' achievements in Home Economics classes using the meta-analysis method and to examine whether the effects of PRI vary across publication status, study design, year of the studies, school level, gender of students, type of students' achievements, content area, location where the interventions of PRI were conducted, and duration. Thirty-four primary studies with 44 effect sizes were analyzed with calculation method of Becker(1988). A funnel plot method result revealed no publication bias. The results of this meta-analysis are as follows. First, PRI was more effective than traditional instruction on students' achievements. A summary statistic was 0.60 with a standard error of .074, which means that an increase of about two-third of a standard deviation beyond what would be expected from traditional instruction was gained from PRI intervention. Second, categorical and regression analyses were employed to find the sources of variance and moderators that predict the effects of PRI. The moderator analyses revealed no statistically significant effects of publication status, study design, school level, gender of students, type of students' achievements, and duration. Content area, location where the interventions of PRI were revealed to be moderators. It was concluded that PRI was effective in improving students' achievements regardless of publication status, study design, year of the studies, school level, gender of students, type of student achievement, and duration.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.47 no.5
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• pp.153-164
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• 2010

A program consumes energy by executing its instructions. The amount of cosumed power is mainly proportional to algorithm complexity and it can be calculated by using complexity information. Generally, the complexity of a S/W is estimated by the microprocessor simulator. But, the simulation takes long time why the simulator is a software modeled the hardware and it only provides the information about computational complexity quantitatively. In this paper, we propose a complexity estimation method of analysis of S/W on source code level and produce the complexity metric mathematically. The function-wise complexity metrics give the detailed information about the calculation-concentrated location in function. The performance of the proposed method is compared with the result of the gate-level microprocessor simulator 'SimpleScalar'. The used softwares for performance test are $4{\times}4$ integer transform, intra-prediction and motion estimation in the latest video codec, H.264/AVC. The number of executed instructions are used to estimate quantitatively and it appears about 11.6%, 9.6% and 3.5% of error respectively in contradistinction to the result of SimpleScalar.

• Korean Journal of Cognitive Science
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• v.25 no.2
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• pp.91-107
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• 2014

The syllable frequency effect is defined as the inhibitory effect that words starting with high frequency syllable generate a longer lexical decision latency and a larger error rate than words starting with low frequency syllable do. Researchers agree that the reason of the inhibitory effect is the interference from syllable neighbors sharing a target's first syllable at the lexical level and the degree of the interference effect correlates with the number of syllable neighbors or stronger syllable neighbors which have a higher word frequency. However, although the syllable frequency can be classified as the syllable type and token frequency, previous studies in visual word recognition have used the syllable frequency without the classification. Recently Conrad, Carreiras, & Jacobs (2008) demonstrated that the syllable type frequency might reflect a sub-lexical processing level including matching from letters to syllables and the syllable token frequency might reflect competitions between a target and higher frequency words of syllable neighbors in the whole word lexical processing level. Therefore, the present study investigated their proposals using word naming tasks. Generally word naming tasks are more sensitive to sub-lexical processing. Thus, the present study expected a facilitative effect of high syllable type frequency and a null effect of high syllable token frequency. In Experiment 1, words starting with high syllable type frequency generated a faster naming latency than words starting with low syllable type frequency with holding syllable token frequency of them. In Experiment 2, high syllable token frequency also created a shorter naming time than low syllable token frequency with holding their syllable type frequency. For that reason, we rejected the propose of Conrad et al. and suggested that both type and token syllable frequency could relate to the sub-lexical processing.

• Journal of the Korea Society of Computer and Information
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• v.15 no.3
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• pp.65-72
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• 2010

We propose the asymmetric 2.5Gbps/622Mbps PON(Passive Optical Network) in order to reduce the bandwith of filter at receiver with inverse RZ(Return to Zero) code coded downstream and NRZ(Non Return to Zero) upstream re-modulation. I theoretically analyze BER(Bit Error Rate) performance and the power sensitivity with the optimal threshold level by performing simulation with MATLAB according to the types of downstream data. The results have shown that the optimal threshold level at the optical receiver could be saturated at 0.33 as the optical received power increase more than -26dBm to keep $10^{-12}$ of BER to a minimum. Also the power sensitivity is more improved by about 3dB by fixing the threshold level at 0.33 than the conventional receiver. The proposed system can be a useful technology for optical access networks with asymmetric upstream and downstream data rates because the optical receiver can be used without controlling threshold levels and that does not require a light source in optical network unit (ONU) and its control circuits in the optical line termination (OLT).

• Journal of Korean Society of Forest Science
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• v.89 no.3
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• pp.405-413
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• 2000

This study was conducted to develop an on-line monitoring system for a forest hydrological environment and its meteorological condition, such as temperature, wind direction and speed, rainfall and water level on V-notch, electrical conductivity(EC), potential of hydrogen(PH) by the motor drive sensor unit and measurement with a single-chip microprocessor as controller. These results are summarized as follows ; 1. The monitoring system consists of a signal process unit, motor drive sensor unit, radio modem unit and power supply. 2. The motor drive sensor unit protects the sensor from swift current or freezing and can constantly maintain fixed water level during measurements. 3. This monitoring system can transfer the data by radio modem. Additionally, this system can monitor hydrological conditions in real time. 4. The hardware was made of several modules with an independent CPU. They can be mounted, removed, repaired and added to. Their function can be changed and expanded. 5. These are the result of an accuracy test, the values of temperature, EC and pH measured within an error range of ${\pm}0.2^{\circ}C$, ${\pm}1{\mu}S$ and ${\pm}0.1pH$ respectively. 6. This monitoring system proved to be able to measure various factors for a forest hydrological environment in various experimental stations.