• The Transactions of The Korean Institute of Electrical Engineers
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• v.68 no.1
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• pp.98-101
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• 2019

In this paper, we propose the power-based pipelined-forwarding MAC protocol which can select relay nodes according to the residual power and energy harvesting rate in EH-WSN (energy-harvesting wireless sensor networks). The proposed MAC follows a pipelined-forwarding scheme in which nodes repeatedly sleep and wake up in an EH-WSN environment and data is continuously transmitted from a high-level node to a low-level node. The sleep interval is adaptively controlled so that nodes with low energy harvesting rate can be charged sufficiently, thereby minimizing the transmission delay and increasing the network lifetime. Simulation shows that the proposed MAC protocol improves the balance of residual power and network lifetime.

• Proceedings of the Korean Nuclear Society Conference
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• 2005.05a
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• pp.259-260
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• 2005

• Journal of KSNVE
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• v.10 no.2
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• pp.221-228
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• 2000

In this paper, analytical study is performed to reduce residual vibration in seeking mode of optical pick-up. The conditions for acceleration adn deceleration time in trapezoidal velocity profile to reduce residual vibration are derived for undamped vibration system. To verify the validity of conditiosn two example studies are carried out. Numerical and experimental implementations for flexible arm system attached to moving part show that residual vibration is effectively reduced by calculated velocity profile. In addition, simulation study for optical pick-up reveals that by changing natural frequency to resonance frequency the conditions derived assuming undamped system can be applied to obtain velocity profile for minimum residual energy in damped vibration system.

• Journal of the Korean Society for Precision Engineering
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• v.17 no.12
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• pp.195-200
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• 2000

In order to find a residual stress in the micro-machined beam, first natural frequency of the beam that has the residual stress inside is analyzed using the Rayleigh's energy method. Micro gold electroplated structure is fabricated by surface micro-machining process. The made structure is clamped-clamped beam and its 1st natural frequency is measured by resonance method. For the better estimation of the residual stress, an equivalent length of micro-machined beam to ideal beam is calculated by FEM. The residual stress is estimated from the equivalent length and the measured natural frequency.

• Computers and Concrete
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• v.24 no.1
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• pp.63-71
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• 2019

Thermal energy from high temperatures can cause concrete damage, including mechanical and chemical degradation. In view of this, the residual mechanical properties of high-strength fiber reinforced concrete with a design strength of 75 MPa exposed to $400-800^{\circ}C$ were investigated in this study. The test results show that the average residual compressive strength of high-strength fiber reinforced concrete after being exposed to $400-800^{\circ}C$ was 88%, 69%, and 23% of roomtemperature strength, respectively. In addition, the benefit of steel fibers on the residual compressive strength of concrete was limited, but polypropylene fibers can help to maintain the residual compressive strength and flexural strength of concrete after exposure to $400-600^{\circ}C$. Further, the load-deflection curve of specimen containing steel fibers exposed to $400-800^{\circ}C$ had a better fracture toughness.

• International Journal of Korean Welding Society
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• v.3 no.1
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• pp.17-22
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• 2003

During the laser welding, weldments are suddenly heated and cooled by laser beam of high density energy. This phenomenon gives an occasion to complex welding residual stresses, which have a great influence on structural instability, in laser welds. However, relevant researches on this field are not sufficient until now and residual stress measurements have experimental and practical limitations. From these reasons, a numerical simulation may be attractive in order to solve the residual stress problem. For clarifying the distribution of heat and welding residual stresses in laser welds with the nail-head shape, authors conduct the finite element analysis (two-dimensional unstationary heat conduction & thermal elastic and plastic analysis). From the results, we can confirm the stress concentration occurs at the place of melting line shape changed in laser welds with the nail-head shape.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.17 no.6
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• pp.1706-1727
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• 2023

Under Water Sensor Networks (UWSN) has gained attraction among various communities for its potential applications like acoustic monitoring, 3D mapping, tsunami detection, oil spill monitoring, and target tracking. Unlike terrestrial sensor networks, it performs an acoustic mode of communication to carry out collaborative tasks. Typically, surface sink nodes are deployed for aggregating acoustic phenomena collected from the underwater sensors through the multi-hop path. In this context, UWSN is constrained by factors such as lower bandwidth, high propagation delay, and limited battery power. Also, the vulnerabilities to compromise the aquatic environment are in growing numbers. The paper proposes an Energy-Efficient standalone Intrusion Detection System (EEIDS) to entail the acoustic environment against malicious attacks and improve the network lifetime. In EEIDS, attributes such as node ID, residual energy, and depth value are verified for forwarding the data packets in a secured path and stabilizing the nodes' energy levels. Initially, for each node, three agents are modeled to perform the assigned responsibilities. For instance, ID agent verifies the node's authentication of the node, EN agent checks for the residual energy of the node, and D agent substantiates the depth value of each node. Next, the classification of normal and malevolent nodes is performed by determining the score for each node. Furthermore, the proposed system utilizes the sheep-flock heredity algorithm to validate the input attributes using the optimized probability values stored in the training dataset. This assists in finding out the best-fit motes in the UWSN. Significantly, the proposed system detects and isolates the malicious nodes with tampered credentials and nodes with lower residual energy in minimal time. The parameters such as the time taken for malicious node detection, network lifetime, energy consumption, and delivery ratio are investigated using simulation tools. Comparison results show that the proposed EEIDS outperforms the existing acoustic security systems.

• Clean Technology
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• v.24 no.2
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• pp.119-126
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• 2018

This study introduced a treatment process that was developed to treat Indonesian low-rank coal with high-ash content, which has the same characteristics as residual coal from the biosolubilization process. The treatment process includes separation of ash, solid-liquid separation, pelletizing, and drying. To reduce the ash content, flotation was performed using 4-methyl-2-pentanol (MIBC) as frother, and kerosene, waste oil, and cashew nut shell liquid (CNSL) as collectors. The increasing amount of collector had an effect on combustible coal recovery and ash reduction. After flotation, a filter press, extruder, and an oven drier were used to make a dried coal pellet. Then another coal pellet was made using asphalt as a binder. The compressive strength and friability of the coal pellets were tested and compared.

• ETRI Journal
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• v.44 no.3
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• pp.389-399
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• 2022

Wireless sensor networks (WSNs) are one of the basic building blocks of Internet of Things (IoT) systems. However, the wireless sensing nodes in WSNs suffer from energy constraint issues because the replacement/recharging of the batteries of the nodes tends to be difficult. Furthermore, a number of realistic IoT scenarios, such as habitat and battlefield monitoring, contain mobile sensing elements, which makes the energy issues more critical. This research paper focuses on realistic WSN scenarios that involve mobile sensing elements with the aim of mitigating the attendant energy constraint issues using the concept of radio-frequency (RF) energy extraction. The proposed technique incorporates a cluster head election workflow for WSNs that includes mobile sensing elements capable of RF energy harvesting. The extensive simulation analysis demonstrated the higher efficacy of the proposed technique compared with the existing techniques in terms of residual energy, number of functional nodes, and network lifetime, with approximately 50% of the nodes found to be functional at the 4000th, 5000th, and 6000th rounds for the proposed technique with initial energies of 0.25, 0.5 and 1 J, respectively.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.25 no.4
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• pp.253-257
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• 2016

The effects of re-peening on the compressive residual stress and fatigue life of Al7075-T6 were investigated. The compressive residual stress induced on the surface of components by shot peening is known to increase the fatigue life. However, the fatigue load relaxes the compressive residual stress of components. Re-peening is a technique to again induce the relaxed compressive residual stress and increase the total fatigue life of components. In this study, the re-peening process was applied to fatigue-loaded specimens. The compressive residual stress and fatigue life were examined for re-peened specimens with fatigue ratios of 30%, 50%, and 70%. The results showed that the compressive residual stress of the specimens was relaxed under the fatigue load. The re-peening process significantly increases the compressive residual stress and total fatigue life.