• Journal of Positioning, Navigation, and Timing
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• v.12 no.2
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• pp.177-184
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• 2023

In order to reserve frequency bands for stable operation of the Korean Positioning System (KPS), it must be demonstrated that the impact of interference caused by KPS on other services operating in the same bands is tolerable. The International Telecommunication Union (ITU) provides the radio regulations and a compatibility assessment methodology for the coexistence of different services in limited frequency resources. The purpose of this paper is to investigate the radio regulations regarding the compatibility issues between the KPS and other services sharing the same frequency bands. The results of the investigation show that the RNSS system can be operated in the L5-band under the condition that the Power Flux Density (PFD) and Aggregated Equivalent PFD (AEPFD) thresholds specified in the radio regulations are met. In addition, the ITU recommends that the interference-to-noise ratio (INR) protection criteria be met to prevent degradation of the performance of radar systems operating in the L2/L6-band. In the case of the S-band, coordination of allocations for RDSS space stations with respect to terrestrial services is not required if the PFD does not exceed regulated thresholds regulated by ITU.

• Journal of Environmental Impact Assessment
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• v.32 no.5
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• pp.269-278
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• 2023

The pollution status of heavy metals in the soils of children's playground was investigated for a sustainable soil environment in urban parks of Seoul. As sampling sites, 281 locations were selected from a 7 districts in the Seoul city. The overall mean concentrations of the heavy metals (Cd 0.21 mg/kg, Cu 5.97 mg/kg, As 2.40 mg/kg, Pb 7.55 mg/kg, Zn 34.08 mg/kg, Ni 4.22 mg/kg, Hg 0.02 mg/kg and Cr6+ not detected.) in the soils of the palygrounds were lower than the worrisome level in criteria for area 1 in Korea soil environment conservation act. In addition, when the soil pollution grade (SPC) was evaluated as an average value, it was found to be less than 100, the first grade, at all points in the seven autonomous districts, indicating thatthe soil was in good soil condition. However, when evaluated as the maximum value, some of the five districts showed values of 100 or more. Therefore, it was found that continuous management and interest of the local government, which is the management body of children's playgrounds, is necessary for a safe soil environment.

• Journal of the Society of Naval Architects of Korea
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• v.59 no.5
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• pp.252-261
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• 2022

The present study concerns assessing the operability of a surface combatant, based on the Percent-Time-Operable (PTO). For validation of the seakeeping analysis in the regular waves, the model test is first conducted in a towing tank. The seakeeping analysis results in the regular waves are expanded to the irregular waves, considering the wave spectra around the Korean peninsula and in North Pacific. The seakeeping criteria of the surface combatant in transit, combat, replenishment operation, and survival condition are defined by the literature review. An annual operation scenario of the surface combatant in two operation areas, i.e., advance speed and wave direction, are combined with the seakeeping analysis results to assess PTO. The main constraints of operability of the surface combatant are identified as the pitch angle and vertical velocity at the helicopter deck.

• Smart Structures and Systems
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• v.31 no.4
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• pp.365-381
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• 2023

The existing vision-based techniques for inspection and condition assessment of civil infrastructure are mostly manual and consequently time-consuming, expensive, subjective, and risky. As a viable alternative, researchers in the past resorted to deep learning-based autonomous damage detection algorithms for expedited post-disaster reconnaissance of structures. Although a number of automatic damage detection algorithms have been proposed, the scarcity of labeled training data remains a major concern. To address this issue, this study proposed a semi-supervised learning (SSL) framework based on consistency regularization and cross-supervision. Image data from post-earthquake reconnaissance, that contains cracks, spalling, and exposed rebars are used to evaluate the proposed solution. Experiments are carried out under different data partition protocols, and it is shown that the proposed SSL method can make use of unlabeled images to enhance the segmentation performance when limited amount of ground truth labels are provided. This study also proposes DeepLab-AASPP and modified versions of U-Net++ based on channel-wise attention mechanism to better segment the components and damage areas from images of reinforced concrete buildings. The channel-wise attention mechanism can effectively improve the performance of the network by dynamically scaling the feature maps so that the networks can focus on more informative feature maps in the concatenation layer. The proposed DeepLab-AASPP achieves the best performance on component segmentation and damage state segmentation tasks with mIoU scores of 0.9850 and 0.7032, respectively. For crack, spalling, and rebar segmentation tasks, modified U-Net++ obtains the best performance with Igou scores (excluding the background pixels) of 0.5449, 0.9375, and 0.5018, respectively. The proposed architectures win the second place in IC-SHM2021 competition in all five tasks of Project 2.