• Journal of Korean Society of Forest Science
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• v.104 no.1
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• pp.117-126
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• 2015

Forest statistics of local administrative districts have many social needs, nevertheless we have some difficulties for working out an accurate statistics because of insufficient data in small-area level. Thus, new small-area estimation method has to set aside additional data, decrease errors of statistics and consider the local forest characteristics at the same time. In this study, we researched the spatial divisions that can set aside additional data for statistics production and satisfy the major premise, which is "forest characteristics of spatial divisions have to be equal to that of small-area". And we compared synthetic estimation methods based on three different spatial divisions(provinces, neighbor districts and new expanded districts). New expanded districts were divided based on the criteria of climate, soil type and tree species composition that affects local forest characteristics. Small-area statistics were assessed in terms of the ability to estimate local forest characteristics and consistency within large-area statistics. As a result, new expanded districts synthetic estimation was assessed to calculate statistics that reflects local forest characteristics better than other two estimation methods. Moreover, this synthetic estimation method produced the statistics that was included within 95% confidence interval of large-area statistics and was the closer to large-area statistics than the neighbor districts synthetic estimation.

• Journal of the Korea Institute of Building Construction
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• v.20 no.1
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• pp.43-51
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• 2020

The main purpose of protective facility for small military unit is to provide the protection of not all the weapons system but the near-miss bullet in Korean army. In particular about the small caliber bullets, especially KM80 in Korea, there were many studies that both of the experiential and structural design methods dose not reflect enough the military threat. For that reason, a new equation to calculate effective anti-piercing depths for RC slabs against small caliber bullets is proposed in earlier research with actual shooting test. But, the test only considers the strength of concrete without the thickness of concrete, types of aggregate, the angle of yaw of bullet, high-strength concrete, etc. Therefore, this study evaluated the ballistic resistance performance by thickness and proportion of magnetic aggregate of concrete. As a result, we identified two major statistical estimations that the error of piercing depth by the angle of yaw of bullet could be cancelled by barrage and the thickness and proportion of magnetic aggregate of concrete dose not effect on the protection ability of concrete structure.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.13 no.5
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• pp.436-442
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• 2020

ESS(energy storage system) has recently become an important power source in various areas due to increased renewable energy resources. The more ESS is used, the less the effective capacity of the ESS. Therefore, it is important to manage the remaining useful lifetime(RUL). RUL can be checked regularly by inspectors, but it is common to be monitored and estimated by an automated monitoring system. The accurate state estimation is important to ESS operator for economical and efficient operation. RUL estimation model usually requires complex mathematical calculations consisting of cycle aging and calendar aging that are caused by the operation frequency and over time, respectively. A lightweight RUL estimation model is required to be embedded in low-performance processors that are installed on ESS. In this paper, a lightweight ESS RUL estimation model is proposed to operate on low-performance micro-processors. The simulation results show less than 1% errors compared to the original RUL model case. In addition, a performance analysis is conducted based on ATmega 328. The results show 76.8 to 78.3 % of computational time reduction.

• Journal of the Korean Institute of Gas
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• v.24 no.4
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• pp.62-72
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• 2020

This study presents a methodology of history matching to evaluate the productivity of shale gas reservoir with high reliability and predict future production rate in the Horn-River basin, Canada. Sensitivity analysis was performed to analyze the effect of physical properties of shale gas reservoir on productivity. Based on the results, reservoir properties were classified into 4 cases and history matching were performed considering the classified 4 cases as objective function. The blind test was conducted using additional field production data for 3 years after the history matching period. The error of gas production rate in Case 1(all reservoir parameters), Case 2(influenced parameters for productivity), Case 3(controllable parameters), and Case 4(uncontrollable parameters) were 7.67%, 7.13%, 17.54%, and 10.04%, respectively. This means that it seems to be effective to consider all reservoir parameters in early period for 4 years but Case 2 which considered influenced parameters for productivity shows the highest reliability in predicting future production. The estimated ultimate recovery (EUR) of production well predicted using the Case 2 model was estimated to be 17.24 Bcf by December 2030 and the recovery factor compared to original gas in place (OGIP) was 32.2%.

• Journal of the korean academy of Pediatric Dentistry
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• v.48 no.3
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• pp.245-254
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• 2021

The aim of this study was to evaluate the accuracy of 3 different automatic landmark identification programs on lateral cephalgrams and the clinical acceptability in pediatric dentistry. Sixty digital cephalometric radiographs of 7 to 12 years old healthy children were randomly selected. Fourteen landmarks were chosen for assessment and the mean of 3 measurements of each landmark by a single examiner was defined as the baseline landmarks. The mean difference between an automatically identified landmark and the baseline landmark was measured for each landmark on each image. The total mean difference of 3 automatic programs compared to the baseline landmarks were 2.53 ± 1.63 mm. Errors among 3 programs were not significantly different for 12 of 14 landmarks except Orbitale and Gonion. The automatic landmark identification programs showed significant higher mean detection errors than the manual method. The programs couldn't be used as the 1st tool to replace human examiners. But considering short consuming time, these results indicate that all 3 programs have sufficient validity to be used in pediatric dental clinic.

• Korean Journal of Remote Sensing
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• v.37 no.2
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• pp.233-243
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• 2021

Photovoltaic panels are hazardous electronic waste that has heavy metal as one of the hazardous components. Each year, hazardous electronic waste is increasing worldwide and every heavy rainfall exposes the photovoltaic panel to become the source of heavy metal soil contamination. the development needs a monitoring technology for this hazardous exposure. this research use relationships between SAR temporal baseline and coherence of Sentinel-1 satellite to detected photovoltaic panel. Also, the photovoltaic plant detection tested using the difference between that photovoltaic panel and the other difference surface of coherence. The author tested the photovoltaic panel and its environment to calculate differences in coherence relationships. As a result of the experiment, the coherence of the photovoltaic panel, which is assumed to be a permanent scatterer, shows a bias that is biased toward a median value of 0.53 with a distribution of 0.50 to 0.65. Therefore, further research is needed to improve errors that may occur during processing. Additionally, the author found that the change detection using a temporal baseline is possible as the rate of reduction of coherence of photovoltaic panels differs from those of artificial objects such as buildings. This result could be an efficient way to continuously monitor regardless of weather conditions, which was a limitation of the existing optical satellite image-based photovoltaic panel detection research and to understand the spatial distribution in situations such as photovoltaic panel loss.

• Journal of the Korean Society of Radiology
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• v.13 no.3
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• pp.481-487
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• 2019

Based on the scan conditions and algorithms that are generally applied during examinations during head CT examinations, the results of dose reduction through the application of algorithm changes were investigated through experiments. As a result, the dose reduction effect was more meaningful for the change of perfusion than for the tube voltage, and the quality evaluation using the brain phantom was relatively less reduced when the dose was reduced after the application of the Bone algorithm, especially for the application of the Bone algorithm, and the deviation of the mean CT number or Pixel value was measured relatively significantly. In other words, the conditions under which dose was reduced and quality was maintained to reduce the patient's exposure dose and obtain images of the same quality were obtained with the application of the Smooth algorithm and the resulting values of 120 kVp, 160 mA. At this point, doses were reduced by about 28%, and the mean CT number or Pixel value was also measured with relatively little error. If the results are applied to patients who visit the hospital for examination or follow-up after applying various algorithms and follow up scan conditions, the results are considered to be very useful in reducing patient exposure dose.

• Korean Journal of Remote Sensing
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• v.38 no.3
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• pp.311-326
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• 2022

The Compact Advanced Satellite 500-4 (CAS500-4) is under development to efficiently manage and monitor forests in Korea and is scheduled to launch in 2025. The National Institute of Forest Science is developing 36 types of forestry applications to utilize the CAS500-4 efficiently. The products derived using the remote sensing method require validation with ground reference data, and the quality monitoring results for the products must be continuously reported. Due to it being the first time developing the national forestry satellite, there is no official calibration and validation site for forestry products in Korea. Accordingly, the author designed a calibration and validation site for the forestry products following international standards. In addition, to install calibration and validation sites nationwide, the authors selected appropriate sensors and evaluated the applicability of the sensors. As a result, the difference between the ground observation data and the Sentinel-2 image was observed to be within ±5%, confirming that the sensor could be used for nationwide expansion.

• Journal of the Korea Society for Simulation
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• v.18 no.4
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• pp.137-148
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• 2009

The purpose of this study is to implement variable selection algorithm which helps construct a reliable linear regression model. If we use all candidate variables to construct a linear regression model, the significance of the model will be decreased and it will cause 'Curse of Dimensionality'. And if the number of data is less than the number of variables (dimension), we cannot construct the regression model. Due to these problems, we consider the variable selection problem as a combinatorial optimization problem, and apply GA (Genetic Algorithm) to the problem. Typical measures of estimating statistical significance are $R^2$, F-value of regression model, t-value of regression coefficients, and standard error of estimates. We design GA to solve multi-objective functions, because statistical significance of model is not to be estimated by a single measure. We perform experiments using simulation data, designed to consider various kinds of situations. As a result, it shows better performance than LARS (Least Angle Regression) which is an algorithm to solve variable selection problems. We modify algorithm to solve portfolio selection problem which construct portfolio by selecting stocks. We conclude that the algorithm is able to solve real problems.

• Composites Research
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• v.36 no.5
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• pp.303-309
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• 2023

In this paper, a Progressive Damage and Failure Analysis (PDFA) modeling method was developed using ABAQUS/EXPLICIT to predict in-plane damage and delamination for Open-Hole Compression (OHC) testing. The proposed PDFA model was constructed based on Hashin criteria and cohesive behavior. The strength and stiffness of OHC specimens with three types of stacking sequences [(45/-45/0₂)₃]_s , [(45/0/-45/90)₃]_s and [45/-45/0/45/-45/90/(45/-45)₂]_s were compared to comprehensively evaluate the validity of the Finite Element(FE) model of PDFA. The strength and stiffness of the OHC specimens were predicted relatively well, with less than a percentage error 10.0 %. For the numerical simulation case for each layup, the damage initiation/evolution of OHC specimens were evaluated for delamination and tension/compression matrix damage before and after failure.