• Korean Journal of Ecology and Environment
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• v.40 no.2
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• pp.264-272
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• 2007

Runoff of non-point pollutants has affected bad influence to water quality of river as reaching within short time. For this reason, reducing them prior to reaching aquatic systems or treating them after collection from discharge process of pollutants are desirable for efficient treatment of pollutants. This study was carried out to develop an ecotechnological method to prevent further aggravation of water quality by non-point source through vegetation filter strips. This study has placed a focus on improving infiltration capacity of soil for the optimum condition of vegetation filter strips. Therefore, we used titled soil filter strips instead of vegetation filter strips in this study. The three types of soil tilter strips were used in a bench scale experiment before applying to the field. The reduction efficiency of pollutants in soil filter strips (SS $84.5{\sim}92.5%$, BOD $67.9{\sim}80.6%$, T-N $43.4{\sim}76.6%$, T-P $40.6{\sim}87.4%$, Cu $28.3{\sim}48.1%$ Fe $92.1{\sim}97.7%$, Pb $81.4{\sim}97.3%$) was much higher than that of the controled group. And non-point pollutants reduction efficiency by soil filter strip's forms was estimated to be distinguishing in order of bio material, mixture of sand and gravel and lastly the whole gravel. In the event, the whole reduction efficiency of pollutants on the soil filter strips disclosed good results.

• Journal of the Korea Organic Resources Recycling Association
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• v.24 no.1
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• pp.31-40
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• 2016

In this study, mesophilic anaerobic digestion of source separated food waste was carried out by leachate recirculation system and methane gas was produced. Two systems - system A and B were fabricated and placed within water bath to maintain $36^{\circ}C$. Each system was comprised of an anaerobic bioreactor and a leachate tank. Leachate in bioreactor was separated through the screen located at 30 mm above the bottom and a pump was installed to transfer collected leachate to the leachate tank. Everyday, 2.5 L of the leachate was pumped from the bioreactor to the leachate tank for 30 min and transferred leachate was pumped back to the top of the bioreactor for 30min, sequentially. Source separated food waste used for this experiment was washed by water before transferring to the laboratory. Transferred food waste was warmed to $36^{\circ}C$ before being fed to bioreactors. System A was fed to 49.1 g VS (Volatile Solids) and System B was fed to 54.0 g VS at every two weeks, respectively. $NH_4{^+}-N$ and salinity were monitored to see the inhibition toward anaerobic bioreaction and it was found that concentrations of these materials were not high enough to affect the bioreaction. Although the food waste was fed biweekly for 112 days and 140 days at system A and B, respectively, there was no sludge withdrawal from each system. Average methane productions rates were 0.439 L $CH_4/g$ VS and 0.368 L $CH_4/g$ VS for system A and B, respectively.

• Journal of Korean Society of Forest Science
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• v.101 no.2
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• pp.175-184
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• 2012

This study was conducted to develop new mattress systems with vegetation base materials for protecting stream bank and rapid rehabilitation. Vegetation base materials are primarily compounded with fine soil, organic composts and peat moss as plant fibers, a water retainer and a soil improver. Peat moss can usually provide necessary natural fibers and organic materials in soil. Especially, peat moss can absorb up to 25 times its own weight in water and is therefore valued as a water retainer to prevent drying effect of vegetation base materials which can harm the growth of vegetation in mattresses. Normally mattress systems resist the lateral earth pressures or stream power by their own weight. Therefore, filled materials must have suitable weight, compressive strength and durability to resist the loading, as well as the effects of water and weathering. In this project, 100 to 200-mm clean, hard stones were basically specified, and about 50-mm rubbles were also used. Test application of new mattress system carried out in the stream bank of a small stream in the Gwangreung experimental forest, belonging to Korea Forest Research Institute (KFRI) in December 16th, 2006. As a result of the monitoring of vegetation coverage of test application plots (each plot size is 4 by 2 m), the coverage of all plots reached 100% in the end of May, 2007 (approximately 50 days passed after the first gemination of vegetation). The coverage of the plots using big hard stones and organic composts and the plots containing peat moss increased more rapidly. The results show that peat moss is effective to retain soil moisture and establish more sound environment for vegetation gemination.

• Journal of Korean Society of Forest Science
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• v.101 no.1
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• pp.130-137
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• 2012

This study has conducted to develop new gabion wall systems with vegetation base materials for stream bank stability and rapid rehabilitation. Vegetation base materials are primarily compounded with fine soil, organic composts and peat moss as plant fibers, a water retainer and a soil improver. Normally gabion wall systems resist the lateral earth pressures or stream power by their own weight. Therefore, fill material must have suitable weight, compressive strength and durability to resist the loading, as well as the effects of water and weathering. In this project, 100 to 200-mm clean, hard stones are basically specified, and about 50-mm rubbles are also used. Test application of new gabion wall system carried out in the stream bank of a small stream in the Gwangreung experimental forest, belonging to Korea Forest Research Institute (KFRI) in December 16th, 2006. As a result of the analysis of hydraulic stability of new gabion wall system, gabion wall system has highest threshold shear stress when the gabion wall covered by vegetation. New gabion wall system is highly resistant to sliding and overturning because safety coefficients exceed 1.5. As a result of term of slope stability analysis of new gabion wall system by Bishop and Fellenius methods, stability of stream bank was highly increased after the construction of gabion wall. Therefore, new gabion wall system is effective to stabilize unstable stream bank.

• Coupled systems mechanics
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• v.8 no.4
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• pp.315-338
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• 2019

The numerical investigations have been carried out on reinforced concrete slab against blast loading to demonstrate the accuracy and effectiveness of the finite element based numerical models using commercial package ABAQUS. The response of reinforced concrete slab have been studied against the influence of weight of TNT, standoff distance, boundary conditions, influence of air blast and surface blast. The results thus obtained from simulations were compared with the experiments available in literature. The inelastic behavior of concrete and steel reinforcement bar has been incorporated through concrete damage plasticity model and Johnson-cook models available in ABAQUS were presented. The predicted results through numerical simulations of the present study were found in close agreement with the experimental results. The damage mechanism and stress response of target were assessed based on the intensity of deformations, impulse velocity, von-Mises stresses and damage index in concrete. The results indicate that the standoff distance has great influence on the survivability of RC slab against blast loading. It is concluded that the velocity of impulse wave was found to be decreased from 17 to 11 m/s when the mass of TNT is reduced from 12 to 6 kg. It is observed that the maximum stress in the concrete was found to be in the range of 15 to $20N/mm^2$ and is almost constant for given charge weight. The slab with two short edge discontinuous end condition was found better and it may be utilised in designing important structures. Also it is observed that the deflection in slab by air blast was found decreased by 60% as compared to surface blast.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.17 no.8
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• pp.2188-2208
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• 2023

Quality of Service (QoS) is a critical feature of Wireless Sensor Networks (WSNs) with routing algorithms. Data packets are moved between cluster heads with QoS using a number of energy-efficient routing techniques. However, sustaining high scalability while increasing the life of a WSN's networks scenario remains a challenging task. Thus, this research aims to develop an energy-balancing component that ensures equal energy consumption for all network sensors while offering flexible routing without congestion, even at peak hours. This research work proposes a Gravitational Blackhole Search Optimised splay tree routing framework. Based on the splay tree topology, the routing procedure is carried out by the suggested method using three distinct steps. Initially, the proposed GBSO decides the optimal route at initiation phases by choosing the root node with optimum energy in the splay tree. In the selection stage, the steps for energy update and trust update are completed by evaluating a novel reliance function utilising the Parent Reliance (PR) and Grand Parent Reliance (GPR). Finally, in the routing phase, using the fitness measure and the minimal distance, the GBSO algorithm determines the best route for data broadcast. The model results demonstrated the efficacy of the suggested technique with 99.52% packet delivery ratio, a minimum delay of 0.19 s, and a network lifetime of 1750 rounds with 200 nodes. Also, the comparative analysis ensured that the suggested algorithm surpasses the effectiveness of the existing algorithm in all aspects and guaranteed end-to-end delivery of packets.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.18 no.3
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• pp.801-825
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• 2024

For Internet of Things, it is more preferred to have immediate access to environment information from sensor nodes (SNs) rather than from gateway nodes (GWNs). To fulfill the goal, mutual authentication scheme between user and SNs with session key (SK) negotiation is more suitable. However, this is a challenging task due to the constrained power, computation, communication and storage resources of SNs. Though lots of authentication schemes with SK negotiation have been designed to deal with it, they are still insufficiently secure and/or efficient, and some even have serious vulnerabilities. Therefore, we design an efficient secure authentication scheme with session key negotiation (eSAS2KN) for wireless sensor networks (WSNs) utilizing fuzzy extractor technique, hash function and bitwise exclusive-or lightweight operations. In the eSAS2KN, user and SNs are mutually authenticated with anonymity, and an SK is negotiated for their direct and instant communications subsequently. To prove the security of eSAS2KN, we give detailed informal security analysis, carry out logical verification by applying BAN logic, present formal security proof by employing Real-Or-Random (ROR) model, and implement formal security verification by using AVISPA tool. Finally, computation and communication costs comparison show the eSAS2kN is more efficient and secure for practical application.

• Journal of the Earthquake Engineering Society of Korea
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• v.9 no.1 s.41
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• pp.61-70
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• 2005

Shaking table tests are carried out on a single-degree-of-freedom mass that is equipped with a hybrid base isolation system. The isolator consists of a set of four specially-designed friction pendulum systems (FPS) and a magnetorheological (MR) damper. The structure and its hybrid isolation system are subjected to various intensities of near- and far-fault earthquakes on a large shake table. The proposed fuzzy controller uses feedback from displacement or acceleration transducers attached to the structure to modulate resistance of the semi-active damper to motion. Results from several types of passive and semi-active control strategies are summarized and compared. The study shows that a combination of FPS isolators and an adjustable MR damper can effectively provide robust control of vibration for a large full-scale structure undergoing a wide variety of seismic loads.

• Journal of the Earthquake Engineering Society of Korea
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• v.9 no.2 s.42
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• pp.7-15
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• 2005

Numerical analysis model is proposed to predict the dynamic behavior of a single-degree-of-freedom structure that is equipped with hybrid base isolation system. Hybrid base isolation system is composed of friction pendulum systems (FPS) and a magnetorheological (MR) damper. A neuro-fuzzy model is used to represent dynamic behavior of the MR damper. Fuzzy model of the MR damper is trained by ANFIS (Adaptive Neuro-Fuzzy Inference System) using various displacement, velocity, and voltage combinations that are obtained from a series of performance tests. Modelling of the FPS is carried out with a nonlinear analytical equation that is derived in this study and neuro-fuzzy training. Fuzzy logic controller is employed to control the command voltage that is sent to MR damper. The dynamic responses of experimental structure subjected to various earthquake excitations are compared with numerically simulated results using neuro-fuzzy modeling method. Numerical simulation using neuro-fuzzy models of the MR damper and FPS predict response of the hybrid base isolation system very well.

• Journal of KIISE
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• v.43 no.2
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• pp.237-245
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• 2016

In this paper we introduce a novel database research area called science of databases (SoDB) and carry out a comprehensive analysis of its case studies. SoDB aims to better understand interesting phenomena observed across multiple database management systems (DBMSes). While mathematical and engineering work in the database field has been dominant, less attention has been given to scientific approaches through which DBMSes can be better understood. Scientific investigations can lead to better engineered designs through deeper understanding of query optimizers and transaction processing. The SoDB research has investigated several interesting phenomena observed across different DBMSes and provided several engineering implications based on our uncovered results. In this paper we introduce a novel scientific, empirical methodology and describe the research infrastructure to enable the methodology. We then review each of a selected group of phenomena studied and present an identified structural causal model associated with each phenomenon. We also conduct a comprehensive analysis on the case studies. Finally, we suggest future directions to expand the SoDB research.