• Nuclear Engineering and Technology
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• v.55 no.8
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• pp.3030-3038
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• 2023

Nowadays, mobile robots have been used to search for uncontrolled radioactive source in indoor environments to avoid radiation exposure for technicians. However, in the indoor environments, especially in the presence of obstacles, how to make the robots with limited sensing capabilities automatically search for the radioactive source remains a major challenge. Also, the source search efficiency of robots needs to be further improved to meet practical scenarios such as limited exploration time. This paper proposes an automatic source search strategy, abbreviated as ACA: the location of source is estimated by a convolutional neural network (CNN), and the path is planned by the A-star algorithm. First, the search area is represented as an occupancy grid map. Then, the radiation dose distribution of the radioactive source in the occupancy grid map is obtained by Monte Carlo (MC) method simulation, and multiple sets of radiation data are collected through the eight neighborhood self-avoiding random walk (ENSAW) algorithm as the radiation data set. Further, the radiation data set is fed into the designed CNN architecture to train the network model in advance. When the searcher enters the search area where the radioactive source exists, the location of source is estimated by the network model and the search path is planned by the A-star algorithm, and this process is iterated continuously until the searcher reaches the location of radioactive source. The experimental results show that the average number of radiometric measurements and the average number of moving steps of the ACA algorithm are only 2.1% and 33.2% of those of the gradient search (GS) algorithm in the indoor environment without obstacles. In the indoor environment shielded by concrete walls, the GS algorithm fails to search for the source, while the ACA algorithm successfully searches for the source with fewer moving steps and sparse radiometric data.

• Convergence Security Journal
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• v.22 no.4
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• pp.17-24
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• 2022

Recently, machine learning-based cyber attack detection and classification research has been actively conducted, achieving a high level of detection accuracy. However, low-spec IoT devices and large-scale network traffic make it difficult to apply machine learning-based detection models in IoT environment. Therefore, In this paper, we propose an efficient IoT attack detection and classification method through PCA(Principal Component Analysis) and LightGBM(Light Gradient Boosting Model) using datasets collected in a MQTT(Message Queuing Telementry Transport) IoT protocol environment that is also used in the defense field. As a result of the experiment, even though the original dataset was reduced to about 15%, the performance was almost similar to that of the original. It also showed the best performance in comparative evaluation with the four dimensional reduction techniques selected in this paper.

• Proceedings of the Korean Society of Crop Science Conference
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• 2022.10a
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• pp.232-232
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• 2022

We reported in our recent studies that the combined treatment of Paenibacillus yonginensis DCY84^T (DCY84^T) and Silicon (Si) promotes initial plant growth and increases resistance to biotic and abiotic stress. To understand the molecular background of these phenotypes, Liquid Chromatography Mass Spectrometry (LC-MS) analysis was performed, and it was confirmed that unsaturated fatty acid metabolites such as oleic acid and linoleic acid decreased in response to the combined treatment of DCY84^T and Si. The stearoyl-acyl carrier protein desaturase (SACPD) introduces the cis double bond into the acyl-ACPs at C9, resulting in the production of unsaturated fatty acid. We identified OsSSI2 encoding SACPD in rice and found that the expression of OsSSI2 was reduced under DCY84^T and Si treatment. Furthermore, qRT-PCR analysis revealed that the expression of OsWRKY45, which is downstream of OsSSI2, was upregulated in response to DCY84^T and Si treatment. These results enable the speculation that activation of the salicylic acid (SA)-responsive gene, OsWRKY45, may contribute to enhancing biological stress resistance. Based on this, we propose a probable model for the rice defense pathway following DCY84^T and Si treatment. This model retains a WRKY45-dependent but NH1(NPR1)-independent SA signaling pathway.

• Journal of Internet Computing and Services
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• v.25 no.2
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• pp.1-9
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• 2024

Although federated learning is designed to be safer than centralized methods in terms of security and privacy, it still has many vulnerabilities. An attacker performing an adversarial attack intentionally manipulates the deep learning model by injecting carefully crafted input data, that is, adversarial examples, into the client's training data to induce misclassification. A common defense strategy against this is so-called adversarial training, which involves preemptively learning the characteristics of adversarial examples into the model. Existing research assumes a scenario where all clients are under adversarial attack, but considering the number of clients in federated learning is very large, this is far from reality. In this paper, we experimentally examine aspects of adversarial training in a scenario where some of the clients are under attack. Through experiments, we found that there is a trade-off relationship in which the classification accuracy for normal samples decreases as the classification accuracy for adversarial examples increases. In order to effectively utilize this trade-off relationship, we present a method to perform adversarial training by adaptively selecting a loss function depending on whether the client is attacked.

• Journal of the Korea Society for Simulation
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• v.33 no.2
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• pp.13-25
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• 2024

In the performance analysis of a weapon system, the combat effectiveness is difficult to go beyond the conceptual level in the early stages of development. This is especially true in the case of new concept of weapon system that has never existed before. In this study, with the aim of analyzing the effectiveness of small personal guided weapons, the design of the warhead and the detonation test were carried out and the results were analyzed. Afterwards, trajectory of fragments were calculated from the results, and it is applied to the anti-personnel effectiveness logic which is a part of combat simulation tool. At the same time, delivery accuracy logic was constructed from Monte-Carlo simulation with 6-DOF trajectory model. Subsequent simulated experiments were conducted with test scenarios to confirm the simulation logic reflecting the results of the warhead detonation tests for verifying the simulation approach of weapon systems, and it was confirmed that the simulation logic incorporating the results of the warhead detonation tests functioned properly.

• Journal of the Korea Institute of Building Construction
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• v.15 no.5
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• pp.515-525
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• 2015

Currently, according to the climate change, serious damage by typhoon has been occurred in the world. In this respect, the research on the prediction model to minimize the damage from various natural disaster has been conducted in several developed countries. In the case of U.S, various models to predict building damage costs have been used widely in many organizations such as insurance companies and governments. In South Korea, although studies regarding damage prediction model according to typhoon have been conducted, the scope has been only limited to consider the property of typhoon. However, it is necessary to consider various factors such as typhoon information, geography, construction environment, and socio-economy factors to predict the damages. Therefore, to address this issue, first, correlation analysis is conducted between various variables based on the data of typhoon from 2003 to 2012. Second, the damage prediction model by using regression analysis is developed based on suggested influence factors. The findings of this study can be utilized to develop the model for predicting the damage costs of buildings by typhoon like HAZUS-MH of US.

• Journal of the Institute of Electronics and Information Engineers
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• v.52 no.1
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• pp.89-101
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• 2015

This paper proposes a statistical model of 3-D positions when tracking moving targets using the uncooled infrared (IR) stereo camera system. The proposed model is derived from two errors. One is the position error which is caused by the sampling pixels in the digital image. The other is the timing jitter which results from the irregular capture-timing in the infrared cameras. The capture-timing in the IR camera is measured using the jitter meter designed in this paper, and the observed jitters are statistically modeled as Gaussian distribution. This paper derives an integrated probability distribution by combining jitter error with pixel position error. The combined error is modeled as the convolution of two error distributions. To verify the proposed statistical position error model, this paper has some experiments in tracking moving objects with IR stereo camera. The 3-D positions of object are accurately measured by the trajectory scanner, and 3-D positions are also estimated by stereo matching from IR stereo camera system. According to the experiments, the positions of moving object are estimated within the statistically reliable range which is derived by convolution of two probability models of pixel position error and timing jitter respectively. It is expected that the proposed statistical model can be applied to estimate the uncertain 3-D positions of moving objects in the diverse fields.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.19 no.1
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• pp.23-32
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• 2008

In the VHF range, active antennas are widely used for wideband applications due to their small size. Active antenna consists of antenna elements and amplifiers, which are directly connected to each other. Gain and noise-figure characteristics are very important for good sensitivity performance, because it is located at the front end of a receiving system. In this study, we developed an active dipole antenna with 5:1 bandwidth(100${\sim}$500 MHz), which consists of a dipole antenna and a P-HEMT amplifier. To obtain required performances, the antenna and the amplifier should be designed simultaneously. In order for that, we introduced an equivalent port concept to model the 1-port dipole antenna as an equivalent 2-port system. Using the proposed equivalent port, the performance of the active dipole antenna was simulated by the ADS. In order to measure the gain and noise-figure characteristics of the antenna, we utilized the same concept of the two-port equivalent impedance model. The measurement results for typical gain, NF and VSWR in the required frequency band were 8dBi, 9dB and 1.7:1, respectively. The radiation patterns at the principal planes were same as the typical radiation pattern of a dipole antenna. By comparing the simulation results with measured ones, it is confirmed that the proposed methods works well.

• Journal of Digital Convergence
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• v.12 no.5
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• pp.139-148
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• 2014

In recent years, computational models using parametric estimation method have been developed and used widely for efficient cost analysis. In this research, by applying experienced data from Guidance and Control Systems in Missile System field, the cost analysis for engineering model and commercial computational model(Price H, HL, M, S) are conducted and its result is analysed, so that the difference between two models and its grounds are apprehended. Comparing the calibrated value of computational model based on the data base of similar equipment and the cost from the engineering estimation, the two results are very close. It means that the credibility of data is enhanced through calibration. Also, for cost analysis of similar components in the future, the method for calibration of the computational models is also examined. When estimating development cost in this research, although many parts have been estimated through uncertain elements, the reliability could have been enhanced by applying computational model which secures objectivity. It is a very reasonable estimation method by utilizing calibration of the computational models based on existing accumulated development data.

• Journal of the Korea Society of Computer and Information
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• v.17 no.12
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• pp.61-69
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• 2012

This paper shows results of the precise time comparison technique based on GPS code transfer in order to determine the UTC(Universal Time Coordinated) and generate TAI(International Atomic Time). CGGTTS(CCTF Group on GNSS Time Transfer Standards) which is generated by GPS timing receivers is used as the international standard format. For geodetic receivers which provide RINEX formats as GPS time transfer results, ROB(Royal Observatory of Belgium) developed a conversion program, r2cggtts, and have distributed the program to timing laboratories participating in TAI link all over the world. Timing laboratories generate the time comparison results of GPS code transfer by the program and send them to BIPM(Bureau International des Poids et Mesures) periodically. In this paper, we introduce the delay features generated while GPS code is transferred and the calibration methods of them. Then, we introduce the tropospheric delay and analyze the results of Saastamoinen model and NATO(North Atlantic Treaty organization) model. Saastamoinen model is the representative tropospheric zenith path delay model and NATO model is applied to the legacy r2cggtts program.