• Journal of the Korea Institute of Information Security & Cryptology
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• v.32 no.2
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• pp.201-211
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• 2022

According to the recent change in the cybersecurity paradigm, research on anomaly detection methods using machine learning and deep learning techniques, which are AI implementation technologies, is increasing. In this study, a comparative study on data preprocessing techniques that can improve the anomaly detection performance of a GRU (Gated Recurrent Unit) neural network-based intrusion detection model using NGIDS-DS (Next Generation IDS Dataset), an open dataset, was conducted. In addition, in order to solve the class imbalance problem according to the ratio of normal data and attack data, the detection performance according to the oversampling ratio was compared and analyzed using the oversampling technique applied with DCGAN (Deep Convolutional Generative Adversarial Networks). As a result of the experiment, the method preprocessed using the Doc2Vec algorithm for system call feature and process execution path feature showed good performance, and in the case of oversampling performance, when DCGAN was used, improved detection performance was shown.

• Ocean and Polar Research
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• v.45 no.3
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• pp.103-111
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• 2023

To evaluate the impact of effluents from land-based fish farms on the coastal ocean of Wando, Korea, we analyzed inorganic nutrients, particulate organic carbon (POC), dissolved organic carbon (DOC), and colored dissolved organic matter (CDOM) in the effluent and influent of land-based fish farms during the summer (July) of 2021. The average concentrations of nutrients (Dissolved inorganic nitrogen, phosphorus, and silicate; DIN, DIP, and DSi, respectively) in the effluents of this study area were 17±3.7 μM, 1.4±0.7 μM, and 14±1.6 μM, respectively. The average concentrations of POC and DOC were 37±22 μM and 81±13 μM, respectively, with POC accounting for about 30% for total organic carbon in effluents. The Reduced Dissolved Inorganic Nitrogen/Total Dissolved Inorganic Nitrogen ratio (0.7), potential short-period index, indicates that the discharge of nutrients excreted by the fish and unconsumed feed into coastal water results in such nutrients being deposited and accumulated in the sediment. Subsequently, this continuous accumulation triggers the release of ammonium ions during organic matter decomposition, and the ammonium-enriched waters that encroach on fish farms as influent seem to be due to the diffusion of high concentrations of ammonium from bottom sediment. Furthermore, we used fluorescence indices to examine the characteristics of organic matter sources, obtaining mean values of 1.54±0.19, 1.06±0.06, and 1.56±0.06 for the humification index, biological index, and fluorescence index, respectively, in the effluent. These results indicate that the organic matters had an autochthonous origin that resulted from microbial decomposition, and such organic matters were rapidly generated and removed by biological activity, likely supplied from the sediment. Our results suggest that the effluent from land-based fish farms could be a potential source of deoxygenation occurrence in coastal areas.

• Journal of Advanced Navigation Technology
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• v.27 no.3
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• pp.293-299
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• 2023

UPRT(Upset Prevention And Recovery Training) is an accident prevention training program developed over a three-year period after the main cause of aircraft accidents in commercial aviation between 2001 and 2011 was analyzed as LOC-I(Loss Of Control Flight). In 2014, ICAO presented UPRT for fixed-wing aircraft through Doc.10011(Manual On Aeroplane Upset Prevention And Recovery Training) and recommended mandatory implementation to Contracting States from March 2019. Since naval P-3C is a major mission of maritime patrol and anti-submarine warfare, it takes a lot of time to fly at low altitude (70-600 m), and the majority of P-3C pilots have experienced spatial disorientation, so Upset prevention and recovery training is essential for naval P-3C pilots. To this end, this study intends to present measures for UPRT from limited conditions using the P-3C simulator owned by the Navy.

• Journal of Advanced Navigation Technology
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• v.25 no.6
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• pp.498-509
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• 2021

The wake turbulence at the wingtip of preceding aircraft may affect the normal operation of following aircraft. Aircraft are classified into four categories according to their maximum take-off weight, and horizontal separation is applied with this category matrix. The FAA and EUROCONTROL revealed that the magnitude and effect of preceding aircraft wake turbulence were smaller than the current distance separation minima suggest. This new information presents the opportunity for revising wake turbulence minima into seven categories (RECAT). This paper confirms the feasibility of implementing RECAT at major airports in South Korea using the draft of ICAO Doc. 10122. The paper also calculates the ultimate runway capacity of Incheon International Airport in South Korea using the Harris Model and comparatively analyzes the amount of runway capacity. As a result of the analysis, it was confirmed that the implementation of RECAT could increase the ultimate runway capacity of Incheon International Airport. This paper's calculation methods and results can be used as primary data for implementing RECAT in other airports.

• Journal of the Korean Institute of Gas
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• v.27 no.4
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• pp.78-84
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• 2023

Recently, the world's countries are tightening regulations on CO2 and air pollutants emission to solve them. In addition, eco friendly vehicles is increasing to replace automobiles in internal combustion engine. The government is supporting the expansion of hydrogen refueling infrastructure according to the hydrogen economy road map. In particular, refueling station is important to secure the safety that supplies high-pressure hydrogen with a wide LFL range. This paper is on guidelines for the determination safety distances to ensure worker safety from accident as jet fire. The safety distance is set according to the procedure of the EIGA doc 075/21. For accident frequency is upper 3.5E-05 per annum, safety distance is decided via consequence analysis where the risk of harm is below individual harm exposure threshold.

• Journal of Advanced Navigation Technology
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• v.28 no.3
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• pp.272-277
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• 2024

In most countries, instrument flight procedures are designed by applying one of the following standards: the International Aviation Organization's DOC 8168, Air Navigation Services and Operation Procedures (PANS-OPS), or the US Federal Aviation Administration's TERPS, Terminal Procedures. In particular, the circling approach procedure has many differences between the two standards, and the US terminal procedure (TERPS) has become more complicated since 2013 by applying expanded standards depending on altitude. The circling approach procedures are more risky than straight-in approach procedures because it involves maneuvering the aircraft close to the ground at low energy for landing. In order to accurately understand these differences, this study provides to distinguish by what criteria the circling approach procedure is designed according to individual domestic airports in Korea, to calculate the radius for the range of circling approach areas that guarantee minimum obstacle avoidance during circling approach maneuvers, and to present methods for performing safe circling approach procedures.

• Journal of Korean Society on Water Environment
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• v.40 no.5
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• pp.215-228
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• 2024

Lakes are one of major sources of methane gas due to anaerobic decomposition of organic matter in sediments. Since methane released from lakes is a greenhouse gas, it is necessary to investigate factors affecting methane production of lakes. This study conducted field and incubation experiments in Lake Asan in August and October to determine effects of thermal stratification and sediment organic matter characteristics on methane production. Field experiments measured temperature and dissolved oxygen to determine the formation of thermal stratification of lakes. Methane and organic matter characteristics were analyzed using gas chromatography, Total Organic Carbon (TOC) analyzers, and fluorescence spectroscopy. Incubation experiments under anaerobic conditions used sediment and water samples from the same site. Field results showed higher methane fluxes in August and increased Dissolved Organic Carbon (DOC) concentration closer to Asan Bay seawall. Elevated methane fluxes and DOC concentration resulted from intensified anaerobic decomposition formed by thermal stratification. Incubation results indicated that sediment organic matter characteristics influenced methane flux between sites. Statistical analysis revealed that thermal stratification could be a primary factor affecting methane production of lakes. Characteristics of sediment organic matter with respect to quantity and quality could be factors influencing methane production of lakes. Results of this study can serve as fundamental data for predicting methane emissions from lakes due to climate change and for mitigating lake's contributions to global warming.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.15 no.4
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• pp.2029-2035
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• 2014

In this study, we conducted the adsorption equilibrium and batch experiments of dissolved organic carbon (DOC) in the wastewater by granular activated carbon (GAC). The components of organic compound were Beef extract (1.8 mg/L), Peptone (2.7 mg/L), Humic acid (4.2 mg/L), Tannic acid (4.2 mg/L), Sodium lignin sulfonate (2.4 mg/L), Sodium lauryle sulfate (0.94 mg/L), Arabic gum powder (4.7 mg/L), Arabic acid (polysaccharide) (5.0 mg/L), $(NH_4)_2SO_4$ (7.1 mg/L), $K_2HPO_4$ (7.0 mg/L), $NH_4HCO_3$ (19.8 mg/L), $MgSO_4{\cdot}7H_2O$ (0.71 mg/L), The adsorption characteristics of DOC in synthetic wastewater was described using the mathematical model through a series of isotherm and batch experiments. It showed that there was linear adsorption region in the low DOC concentration (0~2.5 mg/L) and favorable adsorption region in high concentration (2.5~6 mg/L). The synthetic wastewater used was prepared using known quantities of organic and/or inorganic compounds. Adsorption modelling isotherms were predicted by the Freundlich, Langmuir, Sips and hybrid isotherm equations. Especially, hybrid isotherm of Linear and Sips equation was a good adsorption equilibrium in the region of the both the low concentration and high concentration. In applying carbon adsorption for treating water and wastewater, hybrid adsorption equation plus linear equation with Sips equation will be a good new adsorption equilibrium model. Linear driving force approximation (LDFA) kinetic equation with Hybrid (linear+Sips) adsorption isotherm model was successfully applied to predict the adsorption kinetics data in various GAC adsorbent amounts.

• Korean Journal of Soil Science and Fertilizer
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• v.40 no.4
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• pp.311-325
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• 2007

The concept of metal bioavailability, rather than total metal in soils, is increasingly becoming important for a thorough understanding of risk assessment and remediation. This is because bioavailable metals generally represented by the labile or soluble metal components existing as either free ions or soluble complexed ions are likely to be accessible to receptor organismsrather than heavy metals tightly bound on soil surface. Consequently, many researchers have investigated the bioavailability of metals in both soil and solution phases together with the key soil properties influencing bioavailability. In order to study bioavailability changes various techniques have been developed including chemical based extraction (weak salt solution extraction, chelate extraction, etc.) and speciation of metals using devices such as ion selective electrode (ISE) and diffusive gradient in the thin film (DGT). Changes in soil metal bioavailability typically occur through adsorption/desorption reactions of metal ions exchanged between soil solution and soil binding sites in response to changes in environment factors such as soil pH, organic matter (OM), dissolved organic carbon (DOC), low-molecular weight organic acids (LMWOAs), and index cations. Increasesin soil pH result in decreases in metal bioavailability through adsorption of metal ions on deprotonated binding sites. Organic matter may also decrease metal bioavailability by providing more negatively charged binding sites, and metal bioavailability can also be decreases as concentrations of DOC and LMWOAs increase as these both form strong chelate complexeswith metal ions in soil solution. The interaction of metal ions with these soil properties also varies depending on the soil and metal type.

• Korean Journal of Soil Science and Fertilizer
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• v.41 no.1
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• pp.55-64
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• 2008

A detailed understanding and appreciation of the important mechanisms operating at the soil:root interface, commonly identified as the rhizosphere, is critical for evaluating the potential for particular plant species to be successfully used as part of a phytoremediation technique. For specific plants, mechanisms may exist to overcome the inherit limitation of the phytoremediation technique when poorly mobile soil metals are of interest. In the present study, the influence of root exudates on the rhizosphere chemistry of soil and consequential metal uptake were investigated following culture of vetiver grass (Vetiveria zizanioides), recognized as a promising plant for land stabilization, in three different long-term contaminated soils and one non-contaminated control soil. The soil solution pH increased (0.3-1.1 units) following vetiver grass culture and dissolved organic carbon (DOC) also significantly increased in all soils with the highest increase in PP02 (23 to $173mg\;L^{-1}$). Chemical changes are contributed to root exudation by vetiver grass when exposed to high concentration of heavy metals. Chemical changes, consequently, influenced metal (Cd, Cu, Pb, and Zn) solubility and speciation in the rhizosphere. The highest solubility was observed for soil Ko01 (eg. 2091 and $318{\mu}g\;L^{-1}$ for Cd and Pb, respectively). Initial heavy metal solubility in soils varied with soil and either increased or decreased following vetiver grass culture depending on the soil type. An increase in pH following plant culture generally resulted in a decrease in metal solubility, while elevated DOC due to root exudation resulted in an increase in metal solubility via the formation of metal-DOC complexes. Donnan speciation demonstrated a significant decrease in free Cd and Zn in the rhizosphere and the concentration of Cd, Pb, and Zn in vetiver grass shoot was highly correlated with soluble concentration rather than total soil metal concentration.