• ETRI Journal
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• v.43 no.6
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• pp.966-977
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• 2021

Filterbank multicarrier with offset quadrature amplitude modulation (FBMC-OQAM) is an attractive alternative to the orthogonal frequency division multiplexing (OFDM) modulation technique. In comparison with OFDM, the FBMC-OQAM signal has better spectral confinement and higher spectral efficiency and tolerance to synchronization errors, primarily due to per-subcarrier filtering using a frequency-time localized prototype filter. However, the filtering process introduces intrinsic interference among the symbols and complicates channel estimation (CE). An efficient way to improve the CE in FBMC-OQAM is using a technique known as windowed frequency domain averaging (FDA); however, it requires a priori knowledge of the window length parameter which is set based on the channel's frequency selectivity (FS). As the channel's FS is not fixed and not a priori known, we propose a k-nearest neighbor-based machine learning algorithm to classify the FS and decide on the FDA's window length. A comparative theoretical analysis of the mean-squared error (MSE) is performed to prove the proposed CE scheme's effectiveness, validated through extensive simulations. The adaptive CE scheme is shown to yield a reduction in CE-MSE and improved bit error rates compared with the popular preamble-based CE schemes for FBMC-OQAM, without a priori knowledge of channel's frequency selectivity.

• Journal of the Korea Society of Computer and Information
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• v.28 no.2
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• pp.55-62
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• 2023

Radio waves must pass through the unstable atmosphere for successful wireless data transmission from space to ground stations. Data link algorithms required by the International Space Data Systems Advisory Committee (CCSDS) must be capable of detecting and resynchronizing cryptographic and receiver-side errors. However, error recovery is not part of the CCSDS requirements. This paper proposes an algorithm that enables robustness and error recovery against various noises. We experimented with environments such as Gaussian, Salt, Pepper, and S&P noise through noise reduction filters, filters that improve sharpness, and EDSR. In addition, we compare similar algorithms SES Alarmed and DSES Alarmed.

• Journal of information and communication convergence engineering
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• v.21 no.1
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• pp.90-97
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• 2023

Digital holographic microscopy (DHM) is a three-dimensional (3D) imaging technique that uses the phase information of coherent light. In the reconstruction process of DHM, a narrow region around the positive or negative sideband from the Fourier domain is windowed to avoid noise due to the DC spectrum of the hologram spectrum. However, the limited size of the window also degrades the high-frequency information of the 3D object profile. Although a large window can have more detailed information of the 3D object shape, the noise is increased. To solve this trade-off, we propose phase difference averaging (PDA). The proposed method yields high-frequency information of the specimen while reducing the DC noise. In this paper, we explain the reconstruction algorithm for this method and compare it to various conventional filtering methods including Gaussian, Wiener, average, median, and bilateral filtering methods.

• The Journal of the Korea institute of electronic communication sciences
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• v.18 no.6
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• pp.1291-1298
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• 2023

Surveillance reconnaissance sensor network is used for surveillance in wartime and area of operation. In this paper, we propose a target localization method using the detection signal strength of seismic sensors. Relay equipment calculates the target location using coordinate information and detection signal strength of the seismic sensors. Target localization error deviation due to environmental factors was minimized by subtracting the dynamic offset when calculating the target location. Field test shows improvement of target localization through reduction of errors. The average error was decreased to 3.62m. Up to 62% improved result was obtained compared to weighted centroid localization method.

• Journal of the korean academy of Pediatric Dentistry
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• v.51 no.2
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• pp.109-131
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• 2024

This review aims to examine safety concerns in pediatric dental care and underscore the need for comprehensive patient safety initiatives within the Korean Academy of Pediatric Dentistry. Drawing insights from the prevailing patient safety policies of the American Academy of Pediatric Dentistry, case reports, and systematic reviews, this review elucidates issues such as dental fires during sedation, ocular complications from local anesthesia, and surgical emphysema. This review highlights the significance of safety toolkits encompassing infection control, medical error reduction, dental unit waterline infection, and nitrous oxide safety in pediatric dental settings, underscoring the need to foster a safety culture. Furthermore, this study explores the curriculum for pediatric dentistry residency programs, emphasizing concepts such as high-reliability organizations and mortality and morbidity conferences. The study suggests the need for initiatives to enhance patient safety, including establishing safety committees, expanding reporting systems, policy development, and supporting research related to patient safety. In conclusion, this study underlines key messages, emphasizing the utmost priority of patient safety, acknowledging the inevitability of human error, promoting effective communication, and cultivating a patient safety culture. These principles are vital for advancing patient safety in pediatric dental care and improving outcomes among pediatric patients.

• Journal of Environmental Science International
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• v.10 no.1
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• pp.21-25
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• 2001

The Keum river has been utilized for drinking water supply of several city including Kunsan city and is deepening pollution state due to numerous municipal and industrial discharges. The concentration BOD in river is affected by the organic loading from a tributary and the algae biomass that largely happen to under eutrophication state. In the eutrophic water mass such as the Keum river, the autochthonous BOD was very important part for making a decision of water quality management, because it was accounted for majority of the total BOD. The predict of water quality has important meaning for management of water quality pollution of the Keum river. The purpose of this study will manage and predict water quality of the Keum river using QUAL-2E model considering the autochthonous BOD. The estimation of autochthonous BOD represented that the relationship between BOD and chlorophyll a. The regression equation was shown to be autochthonous BOD=$\beta$(sub)5$\times$chlorophyll a. The results of this study may be summarized as followed; The QUAL-2E model was calibrated with the data surveyed in the field of the study area in June, 1998. The calculated value by QUAL-2E model are in good agree to measured value within relative error of 7.80~20.33%. Especially, in the case of the considering autochthonous BOD, the calculated value of BOD were fairly good coincided with the observed values within relative error of 15%. But the case of not considering autochthonous BOD, relative error of BOD was shown to be 43.2%. In order to attain II grade of water quality standard in Puyo station which has a intake facility of water supply, we reduced to the pollutants loading of tributaries. In the case of removed 100% BOD of tributaries, the BOD of Puyo station was 4.07mg/$\ell$, belong to III grade of water quality standard. But in the case of removed 88% nutrient of tributaries, it was satisfied to II grade of water quality standard as below 3mg/$\ell$ of BOD. For estimation of autochthonous BOD in Keum river, we are performed simulating in accordance with reduction of nutrient load(50~100%) under conditions removal 90% organic load. Occupancy of autochthonous BOD according to nutrient loading reductions were varied from 25.97~79.51%. Occupancy of autochthonous BOD was shown to be a tendency to increasing in accordance with reduction of nutrient loading. Showing the above results, the nutrient that one of the growing factor of algae was important role in decision of BOD in the Keum river. For the water quality management of the Keum river, therefore, it is necessary to considering autochthonous BOD and to construction of advanced sewage treatment plant for nutrient removal.

• Journal of the Korean Society of Radiology
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• v.17 no.1
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• pp.1-9
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• 2023

For optimal image quality of computer tomography angiography (CTA), different iodine concentrations and scan parameters were applied to quantitatively evaluate the image quality characteristics of filtered back projection (FBP), hybrid-iterative reconstruction (hybrid-IR), and deep learning reconstruction (DLR). A 320-row-detector CT scanner scanned a phantom with various iodine concentrations (1.2, 2.9, 4.9, 6.9, 10.4, 14.3, 18.4, and 25.9 mg/mL) located at the edge of a cylindrical water phantom with a diameter of 19 cm. Data obtained using each reconstruction technique was analyzed through noise, coefficient of variation (COV), and root mean square error (RMSE). As the iodine concentration increased, the CT number value increased, but the noise change did not show any special characteristics. COV decreased with increasing iodine concentration for FBP, adaptive iterative dose reduction (AIDR) 3D, and advanced intelligent clear-IQ engine (AiCE) at various tube voltages and tube currents. In addition, when the iodine concentration was low, there was a slight difference in COV between the reconstitution techniques, but there was little difference as the iodine concentration increased. AiCE showed the characteristic that RMSE decreased as the iodine concentration increased but rather increased after a specific concentration (4.9 mg/mL). Therefore, the user will have to consider the characteristics of scan parameters such as tube current and tube voltage as well as iodine concentration according to the reconstruction technique for optimal CTA image acquisition.

• Journal of the Korea institute for structural maintenance and inspection
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• v.26 no.3
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• pp.39-47
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• 2022

In this paper, we proposed a thickness measurement method of concrete slab using GPR, and the verification of the suggested algorithm was carried out through real-scale experiment. The thickness measurement algorithm developed in this study is to set the relative dielectric constant based on the unique shape of parabola, and time series data can be converted to thickness information. GPR scanning were conducted in four types of slab structure for noise reduction, including finishing mortar, autoclaved lightweight concrete, and noise damping layer. The thickness obtained by GPR was compared with Boring data, and the average error was 1.95 mm. In order to investigate the effect of finishing materials on the slab, additional three types of finishing materials were placed, and the following average error was 1.70 mm. In addition, sampling interval from device, the effect of radius on the shape of parabola, and Boring error were comprehensively discussed. Based on the experimental verification, GPR scanning and the suggested algorithm have a great potential that they can be applied to the thickness measurement of finishing mortar from concrete slab with high accuracy.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.37 no.3
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• pp.163-171
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• 2024

Structural health monitoring for ships and offshore structures is important in various aspects. Ships and offshore structures are continuously exposed to various environmental conditions, such as waves, wind, and currents. In the event of an accident, immense economic losses, environmental pollution, and safety problems can occur, so it is necessary to detect structural damage or defects early. In this study, structural response data of multi-linked floating offshore structures under various wave load conditions was calculated by performing fluid-structure coupled analysis. Furthermore, the order reduction method with distortion base mode was applied to the structures for predicting the structural response by using the results of numerical analysis. The distortion base mode order reduction method can predict the structural response of a desired area with high accuracy, but prediction performance is affected by sensor arrangement. Optimization based on a genetic algorithm was performed to search for optimal sensor arrangement and improve the prediction performance of the distortion base mode-based reduced-order model. Consequently, a sensor arrangement that predicted the structural response with an error of about 84.0% less than the initial sensor arrangement was derived based on the root mean squared error, which is a prediction performance evaluation index. The computational cost was reduced by about 8 times compared to evaluating the prediction performance of reduced-order models for a total of 43,758 sensor arrangement combinations. and the expected performance was overturned to approximately 84.0% based on sensor placement, including the largest square root error.

• English Language & Literature Teaching
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• no.1
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• pp.159-187
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• 1995

The purpose of this study is to investigate common errors made by Korean learners in English composition and to find out what is an effective and appropriate teaching method of English composition in Korea. For these purposes, 197 students on the third grade in high school were selected as the subjects of this research. The students were tested by way of the immediate translation of 31 simple Korean sentences into English which are supposed to be easy for those students to write without any difficulty. About 2 minutes were given for testing each sentence. The results are as follows : First. the whole sum of errors made by 197 students was 2,972 and these types of errors were classified into 13 categories by Duskova's grammatical method and James'. The errors with comparatively high frequency were prepositional errors(17.2%), verbal errors(15.4%), and the errors with low frequency were article errors(1.9%), to-infinitive errors. Second, when Korean students learn English as a target language, overgeneralization(33.6%) and reduction(17.5) influenced the learners much more greatly than language transfer(22.2) did. But the influence of language transfer including interference & overgeneralization(l5.2%) and interference & reduction(10.7%) was no less than 48.1%. The statistics shows that the learners have a tendency to analyze, systematize and regularize the target language when they start to learn a new language.