• Journal of the Korean Society of Marine Environment & Safety
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• v.13 no.4
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• pp.55-63
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• 2007

The Group Digital Surveillance System for Fishery Safety and Security (GDSS-F2S) is to provide the target tracking information and the target identification information in order to secure an huge aquaculture farm-field from a thief. The two information, however, is not enough to indict the thief due to the lack of lawful evidences for the crime actions. To overcome this problem, we consider the target image information as one of solutions after discussion with the effective countermeasure tools for the crime actions with scenario-based analysis according to the geological feature of aquaculture farm-field. To capture the real-time image for the trespassing targets in the aquaculture farm-field area, we developed the image capture system which is consists of ultra sensitive CCD(Charge-Coupled Device) camera with 0.0001 Lux and supplementary devices. As results from the field tests for GDSS-F2S with image capture system, the high definite images of the vehicle number plate and shape, person's actions and features are obtainable not only day time but also very dark night without moon light. Thus it is cleary known that the improved GDSS-F2S with image capture system can provide much enough lawful evidences for the crime actions of targets.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.1
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• pp.12-17
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• 2018

In order to enhance the realism of a virtual environment, a method of maximizing the stiffness of the virtual environment model is needed, which maintains the stability of the haptic system. In our previous research, we proposed a haptic system with a first order hold, instead of a zero order hold, and showed that the maximum available stiffness of a virtual spring with the first-order hold is larger than that with the zero-order hold. However, in terms of real system implementation, the zero order hold is a more common and easy method. In this paper, we propose an extrapolation method and a high frequency zero-order-hold output method in order to obtain the stability region using a zero order hold, which is equivalent to the method using the first-order-hold. The simulation results shows that the stability range of the virtual spring becomes almost the same as that of the method using the first order hold when the sampling period of the high frequency zero-order-hold method is decreased. Moreover, the stability range of the proposed method is several times to several tens of times greater than that of the method using the zero order hold only. Therefore, it is expected that the proposed method can enhance the realism of rigid bodies in a virtual environment.

• Journal of the Korean Society of Marine Environment & Safety
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• v.26 no.5
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• pp.466-473
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• 2020

A marine air drone is a new device that can be used to respond to and prevent marine casualties. Determining the districts where marine air drones can be deployed helps the government decision makers identify efficient policy. The aim of this study is to develop a model using the fuzzy-analytic hierarchy process (F-AHP) and additive ratio assessment (ARAS) method to evaluate appropriate districts for deploying marine air drones. To verify the applicability of the proposed model, a case study was performed with respect to the Korea coast guard (KCG) districts. Since the deployed marine air drones are characterized by a high degree of overlap between the evaluation attributes. the F-AHP is used to determine the weights of identified criteria. The results of this study, show that missing people from the shore was the most important criterion for deployment of the drone. For ranking the local districts of the KCG, the ARAS is applied in the case study with the single goal of 50% reduction in marine casualties. Consequently, the highest priority district was identified as Mokpo, followed by Incheon, Seogwipo, Taean, Wando, Yeosu, Pohang, Tongyeong, Gunsan, Bolyeong, Jeju, Buan, Donghae, Sokcho, Ulsan, Uljin, Busan, Changwon, and Pyeongtaeg.

• Journal of the Microelectronics and Packaging Society
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• v.23 no.4
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• pp.87-92
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• 2016

The importance of heat dissipation for the electric device modules along the thickness direction is increasing. Two types of two-layered materials, metal-metal bonding and dielectric-metal bonding, have been fabricated by roll bonding process and a thermal diffusivity of the specimens was measured along the thickness direction. The thermal diffusivity of specimens with metal-metal bonding measured by light flash analysis (LFA) showed a same value independent on the direction of heat flow. However, the thermal diffusivity of specimens with dielectric-metal bonding showed a big difference of 17.5% when the direction of heat flow changed oppositely in the LFA process. The measured thermal diffusivity of specimens when the heat flows from metal to dielectric direction showed smaller value of 17.5% compared to the value when the heat flow from dielectric to metal direction. The difference in thermal diffusivity of specimens with dielectric-metal bonding dependence on direction of heat flow is due to the electron-phonon resistance that occurred transfer process of electron energy to phonon energy near the interface.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.10
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• pp.777-784
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• 2017

Energy harvesting through a thermoelectric module normally makes use of the temperature gradient in the system's operational environment. Therefore, it is difficult to obtain the desired output power when the system is subjected to an environment in which a low temperature gradient is generated across the module, because the power generation efficiency of the thermoelectric device is not optimized. The utilization of solar energy, which is a form of renewable energy abundant in nature, has mostly been limited to photovoltaic solar cells and solar thermal energy generation. However, photovoltaic power generation is capable of utilizing only a narrow wavelength band from the sunlight and, thus, the power generation efficiency might be lowered by light scattering. In the case of solar thermal energy generation, the system usually requires large-scale facilities. In this study, a simple and small size thermoelectric power generation system with a solar concentrator was designed to create a large temperature gradient for enhanced performance. A solar tracking system was used to concentrate the solar thermal energy during the experiments and a liquid circulating chiller was installed to maintain a large temperature gradient in order to avoid heat transfer to the bottom of the thermoelectric module. Then, the setup was tested through a series of experiments and the performance of the system was analyzed for the purpose of evaluating its feasibility and validity.

• Korean Journal of Agricultural Science
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• v.32 no.1
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• pp.29-42
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• 2005

During a long journey of agricultural products from the production area to markets, the quality of agricultural products was always affected by some degree of vibration. The vibration input during the transportation may cause serious agricultural product injury, and this damage is particularly severe whenever the vegetable inside package is free to bounce, and is vibrated at its resonant frequency. The objectives of this study were to determine the resonant frequency of the oriental melon and to investigate the relationships between resonant frequency and physical properties of the oriental melon such as mass, volume and major and minor axes. In this study vibration testing device was constructed to determine the vibration response of the oriental melon in frequency ranges of 5 to 150 Hz. The computer program for controlling the vibration shaker and the function generator and measuring the vibration characteristics of the oriental melon was developed. The ranges of resonant frequency and peak acceleration at resonance of the oriental melon were 51 to 73 Hz and 1.24 to 1.92 G-rms, respectively. The resonant frequency and the peak acceleration decreased with the increase of the sample mass, volume, major and minor axes of the oriental melon. Multiple regression models for resonant frequency and peak acceleration of the oriental melon as a function of mass, major axis and minor axis of the sample were developed and analyzed.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.13 no.5
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• pp.425-431
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• 2020

Recent advancements in industries and technologies have resulted in an increase in the volume of transportation, management, and distribution of logistics. Radio-frequency identification (RFID) technologies have been developed to efficiently manage such a large amount of logistics information. The use of RFID for management is being applied not only to the logistics industry, but also to the power transmission and energy management field. However, due to the limitation of program development capacity, the RFID device is limited in development, and this limitation is vulnerable to security because the existing strong encryption method cannot be used. For this reason, we designed a chaotic system for security with simple operations that are easy to apply to such a restricted environment of RFID. The designed system is a two-dimensional tent map chaotic system. In order to solve the problem of a biased distribution of signals according to the parameters of the chaotic dynamical system, the system has a cryptographic parameter(𝜇₁), a distribution parameter(𝜇₂), and a parameter(𝜃), which is the constant point, ID value, that can be used as a key value. The designed RFID authentication system is similar to random numbers, and it has the characteristics of chaotic signals that can be reproduced with initial values. It can also solve the problem of a biased distribution of parameters, so it is deemed to be more effective than the existing encryption method using the chaotic system.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.5
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• pp.3370-3377
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• 2015

FMECA(Failure Mode, Effects and Criticality Analysis) techniques to make quantitative evaluation of failure effects severity and criticality have been applied to systematic failure analysis for reliability improvement of train which should provide regular service and secure high level of safety as a mass transportation system. These FMECA techniques do not fully reflect the inherent train operation and maintenance circumstances because they are based on the FMECA standards devised for other industries such as automobile industry and FMECA standard dedicated to train industry has not been established yet. This paper analyzes FMECA standards for various industries, and suggests a FMECA technique dedicated to train industry which makes failure effect analysis and criticality analysis step by step and makes criticality analysis placing emphasis on the severity of the failure effect. The proposed technique is applied to FMECA of high-speed current breaker which is a core safety device of train using field failure data for 15 years of train maintenance. The FMECA results show that breakage of arc chute has the highest risk with 3rd severity class and 5th criticality class among all the components of high-speed circuit breaker. Damage and poor contact of electronic valve, and cylinder breakage with 3rd severity class and 4th criticality class are followed by. These results can be applied to improvement of design and maintenance process for high-speed circuit breaker of train.

• Journal of the Korea Organic Resources Recycling Association
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• v.27 no.2
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• pp.67-73
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• 2019

In this study, to optimize the production and utilization of biogas for organic waste resources, the precision monitoring of on-site facilities and the energy balance by facility were analyzed, and the solutions for field problems were investigated, and the design and operation guidelines for pretreatment facilities and generators were presented. Gas pre-treatment is required to solve frequent failures and efficiency degradation in operation of high quality refining facilities, and processing processes such as desulfurization, dehumidification, deoxidization, dust treatment, volatile organic compounds, etc. Since these processes are substances that are also eliminated from the high-quality process, quantitative guidelines are not presented in the gas pretreatment process, but are suggested to operate during the processing process as a qualitative guideline. In particular, dust, siloxane, and volatile organic compounds are the main cause of frequent failure of high-quality processes if they are not removed from the gas pretreatment process. Design of the biogas high-quality process. The operation guidelines provide quality standards [Methane content (including propane) of 95% or more] with 90% or more utilization of the total gas generation, two systems, and a margin of 10% or more. It also proposed installing gas equalization tank, installing thermal automatic control system for controlling equalization of auxiliary fuel, installing dehumidification device at the back of high quality for removing moisture generated in the process of gas compression, installing heat-resisting facilities to prevent freezing of facilities in winter and reducing efficiency, and installing membrane facilities in particular.

• Applied Chemistry for Engineering
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• v.33 no.2
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• pp.126-132
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• 2022

Alkaline fuel cells using liquid fuels such as hydrazine and ammonia are gaining great attention as a clean and renewable energy solution possibly owing to advantages such as excellent energy density, simple structure, compact size in fuel container, and ease of storage and transportation. However, common shortcomings including cathode flooding, fuel crossover, side yield reactions, and fuel security and toxicity are still challenging issues. Real time monitoring of fuel concentrations integrated into a fuel cell device can help improving fuel cell performance via predicting any loss of fuels used at a cathode for efficient energy production. There have been extensive research efforts made on developing real-time sensing platforms for hydrazine and ammonia. Among these, recent advancements in electrochemical sensors offering high sensitivity and selectivity, easy fabrication, and fast monitoring capability for analysis of hydrazine and ammonia concentrations will be introduced. In particular, research trend on the integration of metallic and metal oxide nanoparticles and also their hybrids with carbon-based nanomaterials into electrochemical sensing platforms for improvement in sensitivity and selectivity will be highlighted.