• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.30 no.1
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• pp.31-38
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• 2012

The geo-referencing accuracy of the images acquired by a UAV based multi-sensor system is affected by the accuracy of the mounting parameters involving the relationship between a camera and a GPS/INS system as well as the performance of a GPS/INS system. Therefore, the estimation of the accurate mounting parameters of a multi-sensor system is important. Currently, we are developing a low altitude multi-sensor system based on a UAV, which can monitor target areas in real time for rapid responses for emergency situations such as natural disasters and accidents. In this study, we suggest a system calibration method for the estimation of the mounting parameters of a multi-sensor system like our system. We also generate simulation data with the sensor specifications of our system, and derive an effective flight configuration and the number of ground control points for accurate and efficient system calibration by applying the proposed method to the simulated data. The experimental results indicate that the proposed method can estimate accurate mounting parameters using over five ground control points and flight configuration composed of six strips. In the near future, we plan to estimate mounting parameters of our system using the proposed method and evaluate the geo-referencing accuracy of the acquired sensory data.

• Ecology and Resilient Infrastructure
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• v.8 no.1
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• pp.22-31
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• 2021

Surface image velocimetry (SIV) is a noncontact velocimetry technique based on images. Recently, studies have been conducted on surface velocity measurements using drones to measure a wide range of velocities and discharges. However, when measuring the surface velocity using a drone, reference points must be included in the image for image correction and the calculation of the ground sample distance, which limits the flight altitude and shooting area of the drone. A technique for calculating the surface velocity that does not require reference points must be developed to maximize spatial freedom, which is the advantage of velocity measurements using drone images. In this study, a technique for calculating the surface velocity that uses only the drone position and the specifications of the drone-mounted camera, without reference points, was developed. To verify the developed surface velocity calculation technique, surface velocities were calculated at the Andong River Experiment Center and then measured with a FlowTracker. The surface velocities measured by conventional SIV using reference points and those calculated by the developed SIV method without reference points were compared. The results confirmed an average difference of approximately 4.70% from the velocity obtained by the conventional SIV and approximately 4.60% from the velocity measured by FlowTracker. The proposed technique can accurately measure the surface velocity using a drone regardless of the flight altitude, shooting area, and analysis area.

• Journal of Aerospace System Engineering
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• v.16 no.4
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• pp.28-34
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• 2022

In 2021, Virgin Orbit converted a 747-400 aircraft into an air launch platform, and successfully launched it twice in February and July. Compared to the existing ground launch, interest in the air launch is increasing due to its great utility, such as its independence from the launch location or weather, cost reducing factor, shorter launch preparation time, and its benefit pursuant to altitude and speed. Additionally, as small satellites have similar performance to mid/large satellites in the past due to the miniaturization and precision of electronic equipment, small satellite launches are expected to dominate in the future. In this paper, institutional certification methods such as domestic, overseas, civilian and military airworthiness certification regulations/procedures are reviewed to ensure flight safety of aerial projectiles using large domestic civil aircraft, and applicable civil and military airworthiness certification technology standards are reviewed and analyzed. Additionally, we will review and suggest effective airworthiness certification application plans that reflect the reality, and present airworthiness certification standards (draft) for aerial launch vehicles, by analyzing applicable airworthiness certification technical standards when remodeling aerial launch vehicles.

• Geophysics and Geophysical Exploration
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• v.25 no.1
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• pp.26-37
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• 2022

Recently, multiple methods using small aircraft for geophysical exploration have been suggested as a result of the development of information and communication technology. In this study, we introduce the hybrid unmanned aircraft electromagnetic system of the Korea Institute of Geosciences and Mineral resources, which is under development. Additionally, data processing and interpretation methods are suggested via the analysis of datasets obtained using the system under development to verify the system. Because the system uses a three-component receiver hanging from a drone, the effects of rotation on the obtained data are significant and were therefore corrected using a rotation matrix. During the survey, the heights of the source and the receiver and their offsets vary in real time and the measured data are contaminated with noise. The noise makes it difficult to interpret the data using the conventional method. Therefore, we developed a recurrent neural network (RNN) model to enable rapid predictions of the apparent resistivity using magnetic field data. Field data noise is included in the training datasets of the RNN model to improve its performance on noise-contaminated field data. Compared with the results of the electrical resistivity survey, the trained RNN model predicted similar apparent resistivities for the test field dataset.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.40 no.1
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• pp.1-14
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• 2022

In order to conduct rapid, accurate and safe surveying at the excavation site, In this study, the possibility of underground facility survey using drones and the expected effect of 3D visualization were obtained as follows. Phantom4Pro 20MP drones have a 30m flight altitude and a redundant 85% flight plan, securing a GSD (Ground Sampling Distance) value of 0.85mm and 4points of GCP (Groud Control Point)and 2points of check point were calculated, and 7.3mm of ground control point and 11mm of check point were obtained. The importance of GCP was confirmed when measured with low-cost drones. If there is no ground reference point, the error range of X value is derived from -81.2 cm to +90.0 cm, and the error range of Y value is +6.8 cm to 155.9 cm. This study classifies point cloud data using the Pix4D program. I'm sorting underground facility data and road pavement data, and visualized 3D data of road and underground facilities of actual model through overlapping process. Overlaid point cloud data can be used to check the location and depth of the place you want through the Open Source program CloudCompare. This study will become a new paradigm of underground facility surveying.

• The Journal of the Convergence on Culture Technology
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• v.10 no.4
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• pp.397-403
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• 2024

North Korea's rapidly advancing drone development and operational capabilities have become a significant threat to South Korea's security. The drone incursions by North Korea in 2014, 2017, and 2022 demonstrate the technological advancement and provocative potential of North Korean drones. This study aims to closely analyze the military threats posed by North Korean drones and seek effective countermeasures. The research examines the development level of North Korean drone technology, its military applications, the characteristics and patterns of recent drone incursions, the adequacy and limitations of South Korea's current response systems, and future countermeasures. For this purpose, domestic and international research literature and media reports were reviewed, and specific North Korean drone incursion cases were analyzed. The results indicate that North Korea's small drones possess technological features such as small size, low altitude, low-speed flight, long-duration flight, and reconnaissance equipment. These drones pose threats that can be utilized for reconnaissance, surveillance, surprise attacks, and terrorism. Additionally, South Korea's current response systems reveal limitations such as inadequate detection and identification capabilities, low interception success rates, lack of an integrated response system, and insufficient specialized personnel and equipment. Therefore, this study suggests various technical, policy, and international cooperative countermeasures, including the development of drone detection and identification technologies, the utilization of diverse drone neutralization technologies, the establishment of legal and institutional foundations, the construction of a cooperative framework among relevant agencies, and the strengthening of international cooperation. The study particularly emphasizes the importance of raising awareness of the North Korean drone threat across South Korean society and unifying national efforts to respond to these threats.

• Economic and Environmental Geology
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• v.57 no.4
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• pp.353-362
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• 2024

This study examined the spectral characteristics of sediments according to moisture content using an unmanned aerial vehicle (UAV)-based hyperspectral sensor and evaluated the efficiency of moisture content detection at different flight altitudes. For this purpose, hyperspectral images in the 400-1000nm wavelength range were acquired and analyzed at altitudes of 40m and 80m for sediment samples with various moisture contents. The reflectance of the sediments generally showed a decreasing trend as the moisture content increased. Correlation analysis between moisture content and reflectance showed a strong negative correlation (r < -0.8) across the entire 400-900nm range. The moisture content detection model constructed using the Random Forest technique showed detection accuracies of RMSE 2.6%, R² 0.92 at 40m altitude and RMSE 2.2%, R² 0.95 at 80m altitude, confirming that the difference in accuracy between altitudes was minimal. Variable importance analysis revealed that the 600-700nm band played a crucial role in moisture content detection. This study is expected to be utilized in efficient sediment moisture management and natural disaster prediction in the field of environmental monitoring in the future.

• Journal of the Korean Academy of Child and Adolescent Psychiatry
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• v.10 no.2
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• pp.201-211
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• 1999

Objectives：This study investigated the characteristics of detained delinquent adolescents and variables related to the repeated crime during 6 months after release. Methods：The socio-demographic and crime-related characteristics of 73 detained adolescents were evaluated by semi-structured interviews and police records, and the psychological characteristics of them measured by the MMPI. We also compared the characteristics between subjects with and without repeated crime during 6 months after release. Results：1) Most of detained adolescents had families with low socioeconomic status(77%) and broken families(48%). Sixty-six percent of them were dropped out of school. The most frequent crime pattern was theft(49%), and with accomplice(77%). Seventy-five percent of total subjects had the records of previous conviction. Of the previous convictions, seventy-eight percent was same with the present crimes. 2) Subjects with repeated crime during 6 months after release were younger and had higher T-score on Pa scale of MMPI than the subjects without repeated crime. More adolescents with repeated crime had broken families than those without repeated crime. They also showed the crime-related characteristics of higher percent of theft among crime patterns, higher incidence of previous conviction, younger age of the first crime, and shorter crime-free duration from the last to present crime. Conclusion：These results of present study suggest that the development and the persistence of adolescent delinquency would be resulted from interaction of factors of individual, family, school, and community. By the comparison between subjects with and without repeated crime, it was found that familial dysfunction, younger age at first crime, presence of previous conviction might be the risk factors for repeated delinquency. To prevent repeated crime of delinquent adolescents more effectively, early therapeutic intervention and the development of programs to help adaptation in school and community would be essential.

• Journal of the Korean Society of Propulsion Engineers
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• v.16 no.5
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• pp.58-66
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• 2012

The IR signature and radiative base heating from an aircraft plume have been important factors for aircraft survivability in modern battle fields. In order to enhance the aircraft survivability and reduce the base heating, infrared signatures emitted from an aircraft exhaust plume should be determined. In this work, therefore, IR signatures and radiative base heating characteristics are examined in the plume exhausted from the aircraft with operating at altitude of 5 km in M=0.9 and 1.6, respectively. As a result, it is found that the particular wavelength IR signature has high spectral characteristics because of $H_2O$ and $CO_2$ gases in the plume, and the radiative heat flux coming into the base plane increases with higher Mach number and shorter distance.

• The Journal of the Korea Contents Association
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• v.16 no.8
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• pp.729-742
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• 2016

The purpose of this study is to investigate the influence of parenting and peers on youth engagement to pornography media, the fourth year data of the fourth-grade panel (first year at middle school) and the fourth-year data of the eighth-grade panel (first year at high school) were analyzed. The number of cases investigated for this panel study were 2,378 subjects among the fourth-year panel of the fourth grade and 2,361 subjects among the fourth-year panel of middle schoolers. But this study, the total of 720 subjects that the response were made in the pornography items are analyzed. The result of this study reveals that male students were more likely to be addicted to pornography than female students. Also, inconsistency and excessive intervention among the parenting attitudes and peer attachment and numbers of delinquent friens among the peer factors were shown to have influence on youth addiction to pornography. Based on such results, a proposal that a plan to increase the parental education and strengthen peer relationships is important ahead of the Controlled intervention in the meantime was made.