• Journal of Wetlands Research
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• v.21 no.2
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• pp.173-180
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• 2019

This study was conducted to understand factors affecting TSS and heavy metals transport on the road, parking lot and roof. During storm events, heavy metals, which were mostly attached to TSS, were also transported when TSS was washed off in the road, parking lot and roof. This finding may be supported by the significant correlations between TSS load and total and soluble heavy metals load including Cr, Fe, Cu, and Pb (Pearson r value: 0.52 to 0.73; probability p value<0.01). Generation and transport of TSS and heavy metals were greater in the road and parking lot compared to the roof due to vehicular activities, slope and greater catchment areas of these sites. It was found that TSS transport during peak flows of storm events ranges from 65% to 75% implying that by controlling peak flows, TSS transportation to nearby water bodies may be decreased. Depending on the target TSS and heavy metal reduction, sizing of low impact development (LID) technologies and green infrastructures (GI) such as infiltration trench, tree box filter, and rain garden may be calculated. Future researchers were recommended to assess the limitations of the systems and determine the design considerations for these types of facilities.

• Journal of IKEEE
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• v.23 no.1
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• pp.280-288
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• 2019

In the CR-enabled MANET, routing paths can be easily destroyed due to node mobility and channel unavailability (due to the emergence of the PU of a channel), resulting in significant overhead to maintain/recover the routing path. In this paper, network caching is actively used for route maintenance, taking into account the properties of the CR. In the proposed scheme, even if a node detects that a path becomes unavailable, it does not generate control messages to establish an alternative path. Instead, the node stores the packets in its local cache and 1) waits for a certain amount of time for the PU to disappear; 2) waits for a little longer while overhearing messages from other flow; 3) after that, the node applies local route recovery process or delay tolerant forwarding strategy. According to the simulation study using the OPNET simulator, it is shown that the proposed scheme successfully reduces the amount of control messages for path recovery and the service latency for the time-sensitive traffic by 13.8% and 45.4%, respectively, compared to the existing scheme. Nevertheless, the delivery ratio of the time-insensitive traffic is improved 14.5% in the proposed scheme.

• The Journal of Korean Academy of Prosthodontics
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• v.53 no.4
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• pp.337-344
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• 2015

Purpose: The purpose of present study is to examine the correlation between the accuracy of abutment preparation and the marginal adaptation of metal coping. With this view, this study compared the correlations regard to the three different manufacturing methods of selective laser sintering technique, milling and casting. Materials and methods: Two master models were made in a different way. First model with deep chamfer margin was prepared directly by a general clinician and the second model was designed by 3-D designing software program with the same abutment preparation principle and produced by computer aided manufacturing. 12 Co-Cr alloy copings were produced respectively with three different method; SLS system, CAD/CAM milling and conventional lost wax technique from each master model. The total 72 copings fully sit on the master model were stereoscopically evaluated at 40 points along the entire circumferential margin. Results: Significant differences in the absolute marginal discrepancies of Co- Cr copings from SLS system (P=.0231) and casting method (P<.0001) were shown between hand preparation model and computer designed model. However, no significant difference was found between the two model groups from milling method (P=.9962). Conclusion: Within the limitation of this study, the effect of the accuracy of abutment preparation on the marginal adaptation of Co-Cr coping is statistically significant in SLS system and casting group. The copings produced by SLS system exhibited the lowest marginal discrepancies among all groups, and the marginal gap of this method group was influenced by the accuracy of the abutment preparation.

• Korean Journal of Remote Sensing
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• v.38 no.5_1
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• pp.497-510
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• 2022

Agricultural reservoirs are essential structures for water supplies during dry period in the Korean peninsula, where water resources are temporally unequally distributed. For efficient water management, systematic and effective monitoring of medium-small reservoirs is required. Synthetic Aperture Radar (SAR) provides a way for continuous monitoring of those, with its capability of all-weather observation. This study aims to evaluate the applicability of SAR in monitoring medium-small reservoirs using Sentinel-1 (10 m resolution) and Capella X-SAR (1 m resolution), at Chari (CR), Galjeon (GJ), Dwitgol (DG) reservoirs located in Ulsan, Korea. Water detected results applying Z fuzzy function-based threshold (Z-thresh) and Chan-vese (CV), an object detection-based segmentation algorithm, are quantitatively evaluated using UAV-detected water boundary (UWB). Accuracy metrics from Z-thresh were 0.87, 0.89, 0.77 (at CR, GJ, DG, respectively) using Sentinel-1 and 0.78, 0.72, 0.81 using Capella, and improvements were observed when CV was applied (Sentinel-1: 0.94, 0.89, 0.84, Capella: 0.92, 0.89, 0.93). Boundaries of the waterbody detected from Capella agreed relatively well with UWB; however, false- and un-detections occurred from speckle noises, due to its high resolution. When masked with optical sensor-based supplementary images, improvements up to 13% were observed. More effective water resource management is expected to be possible with continuous monitoring of available water quantity, when more accurate and precise SAR-based water detection technique is developed.

• Geophysics and Geophysical Exploration
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• v.24 no.4
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• pp.180-193
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• 2021

The complex resistivity method is an exploration technique that can obtain various characteristic information of underground media by measuring resistivity and phase in the frequency domain, and its utilization has recently increased. In this paper, a three-dimensional inversion algorithm for the CR data was developed to increase the utilization of this method. The Poisson equation, which can be applied when the electromagnetic coupling effect is ignored, was applied to the modeling, and the inversion algorithm was developed by modifying the existing algorithm by adopting comlex variables. In order to increase the stability of the inversion, a technique was introduced to automatically adjust the Lagrangian multiplier according to the ratio of the error vector and the model update vector. Furthermore, to compensate for the loss of data due to noisy phase data, a two-step inversion method that conducts inversion iterations using only resistivity data in the beginning and both of resistivity and phase data in the second half was developed. As a result of the experiment for the synthetic data, stable inversion results were obtained, and the validity to real data was also confirmed by applying the developed 3D inversion algorithm to the analysis of field data acquired near a hydrothermal mine.

• Journal of Satellite, Information and Communications
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• v.11 no.1
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• pp.6-11
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• 2016

In this paper, we have analyzed the effects of co-channel, adjacent-channel, and the human shield(Body Blockage) for wideband WLAN based on the IEEE802.11n 40MHz channel bandwidth required for high speed digital signage service. Simulation results show that wideband WLAN can be operated with 78 interferers over 63m distance in co- channel, 80 interferer over 61m distance in adjacent channel. By applying the mitigation method for reducing the interference, we have confirmed that protection distance is improved to 51m using beamforming, and 40m using cognitive radio in co-channel interference. Also body blockage interference is reduced using adaptive channel bandwidth, C/I ratio, beamforming, power control mitigation methodology.

• Journal of Advanced Navigation Technology
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• v.18 no.4
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• pp.347-352
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• 2014

In this paper, we propose a Markovian queueing model(M/M/1)-based call admission control to reduce forced terminating rate of non-real secondary user's call for Multi-services Cognitive Radio Networks. A existing control has a problem that the forced terminating rate increases because of adopting a policy of spectrum priority allocation to real calls. In our scheme the rate can be reduced as the call that has no useful spectrum waits in a queue until getting an available spectrum. Our scheme use a neural-net based prediction of primary user's reappearance. Through the simulation, we analysis the call forced terminating rate, access delay and spectrum utilization efficiency, and then show that our scheme can more reduce the forced terminating rate of the call, compared to that of the existing algorithm.

• Journal of KIISE:Databases
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• v.29 no.3
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• pp.193-206
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• 2002

In this paper, we design and implement an efficient bulk-loading algorithm for CIR-Tree. Bulk-loading techniques increase node utilization, improve query performance and reduce index construction time. The CIR-tree has variable size of internal node entries since it only maintains minimal dimensions to decriminate child nodes. This property increases fan-out of internal nodes and improves search performance. Even though several bulk-loading algorithms for multi/high-dimensional index structures have been proposed, we cannot apple them to CIR-tree because of the variable size of internal node entries. In this paper, we propose an efficient bulk- loading algorithm for CIR-tree that improves the existing bulk-loading algorithm and accomodates the property of CIR-tree. We also implement it on a storage system MiDAS-III and show superiority of our algorithm through various experiments.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.38B no.6
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• pp.446-453
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• 2013

Clustering schemes have been adopted as an efficient solution to prolong network lifetime and improve network scalability. In such clustering schemes cluster ratio is represented by the rate of the number of cluster heads and the number of total nodes, and affects the performance of clustering schemes. In this paper, we mathematically analyze an optimal clustering ratio in wireless sensor networks. We consider a multi-hop to one-hop transmission case and aim to provide the optimal cluster ratio to minimize the system hop-count and maximize packet reception ratio between nodes. We examine its performance through a set of simulations. The simulation results show that the proposed optimal cluster ratio effectively reduce transmission count and enhance energy efficiency in wireless sensor networks.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.25 no.10
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• pp.1062-1068
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• 2014

In this paper, a novel approach estimating target's rotation velocity(RV) is proposed for inverse synthetic aperture radar(ISAR) cross-range scaling(CRS). Scale invariant feature transform(SIFT) is applied to two sequently generated ISAR images for extracting non-fluctuating scatterers. Considering the fact that the distance between target's rotation center(RC) and SIFT features is same, we can set a criterion for estimating RV. Then, the criterion is optimized through the proposed method based on particle swarm optimization(PSO) combined with exhaustive search method. Simulation results show that the proposed algorithm can precisely estimate RV of a scenario based maneuvering target without RC information. With the use of the estimated RV, ISAR image can be correctly re-scaled along the cross-range direction.