• Tribology and Lubricants
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• v.35 no.4
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• pp.222-228
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• 2019

As rubber products such as O-rings, which are also known as packings or toric joints, come in regular, long term contact with liquid fuel, they can eventually swell, become mechanically weakened, and occasionally crack; this diminishes both their usefulness and intrinsic lifetime and could cause leaks during the steady-state flow condition of the fuel. In this study, we evaluate the lifetime of such products through compression set tests of FKM, a family of fluorocarbon elastomer materials defined by the ASTM international standard D141; these materials have great compression, sunlight, and ozone resistance as well as a low gas absorption rate. In this process, O-rings are immersed in the liquid fuel of airtight containers that can be expressed as a compression set, and the liquid fuel leakage in a flow rig tester at variable temperatures over 12 months is investigated. Using the Power Law model, our study determined a theoretical O-ring lifetime of 2,647 years, i.e. a semi-permanent lifespan, by confirming the absence of liquid fuel leakage around the O-ring assembled fittings. These results indicate that the FKM O-rings are significantly compatible for fuel tests to evaluate long-term sealing conditions.

• Journal of the Korean Society of Clothing and Textiles
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• v.46 no.5
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• pp.836-847
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• 2022

This study establishes basic data for the development of a new Chemical, Biological, and Radioactive (CBR) protective clothing by selecting the ventilation position to optimize thermal comfort on the basis of the opening and closing of each part. Participants were eight men in their 20s who had previously worn CBR protective clothing. After vigorous exercise and perspiration, the microclimate of the clothing and skin temperature was measured. Results revealed that when the ventilation zipper was opened after exercising, the skin and clothing microclimate temperatures, which had increased during the exercise, decreased in the chest and shoulder blade regions. The clothing microclimate humidity decreased in the chest area. The change was greatest in the chest region; the skin temperature decreased by 0.2℃, the clothing microclimate temperature by 2.7℃, and the clothing microclimate humidity by 3.2%RH through ventilation. Thus, the opening that allows the exchange of accumulated heat and moisture while wearing the CBR protective clothing is efficient.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.11
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• pp.595-601
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• 2020

During the safety inspection of nitrocellulose-made explosive containers stored for more than 10 years, cracks were found in the containers. Therefore, a failure cause analysis test was performed. First, the cause of failure through the failure tree analysis was conducted to select the factors that influenced failure. The changes in the properties of the container caused by the acceleration of the reaction were found to be the cause of the failure by confirming the influence on the environment and internal/external factors that may occur during storage. To confirm this, environmental tests, such as thermal shock test and vacuum thermal stability test, were performed using a naturally aged container to analyze the cause of failure, and an accelerated aging test was performed to reproduce the failure. Through this, the chemical reaction was accelerated by heat and charge, as in the result of the fault tree analysis, and it was confirmed that the physical properties of the container were changed. In addition, the service life of the container was estimated using the Arrhenius model for the storage life due to thermal aging.

• Journal of the Korea Institute of Military Science and Technology
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• v.18 no.5
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• pp.582-593
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• 2015

For military training and course-of-action analysis, OneSAF Int'l version being used in ROK Army has a limited capability to simulate NBC(nuclear, biological, and chemical) damages. For high-fidelity NBC combat simulation, it is required to visualize NBC contamination dispersion in consideration of weather conditions and terrain characteristics. However, OneSAF itself handling interaction among thousands of combat entities cannot carry out a simulation of NBC contamination dispersion because it brings about an excess burden. To resolve this problem, this research aims to design simulation federation for analysis on NBC operational effects. After examining design consideration to connect OneSAF and a NBC contamination dispersion model, we design a federation architecture that facilitates the interaction between OneSAF and a NBC contamination dispersion model. Afterwards, we implement a federation interface to share simulation data by publish-subscribe pattern and to translate them into the proprietary format for each model. We prove the possibility of federation between both models, as showing that dispersion of NBC contaminated cloud and changes in concentration are reflected in OneSAF-based engagement simulation.

• Korean Management Science Review
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• v.32 no.4
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• pp.109-133
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• 2015

This paper considers the allocation and engagement scheduling of air defense missiles by using MIP (mixed integer programming). Specifically, it focuses on developing a realistic MIP model for a real battle situation where multiple enemy missiles are headed toward valuable defended assets and there exist multiple air defense missiles to counteract the threats. In addition to the conventional objective such as the minimization of surviving target value, the maximization of total intercept altitude is introduced as a new objective. The intercept altitude of incoming missiles is important in order to minimize damages from debris of the intercepted missiles and moreover it can be critical if the enemy warhead contains an atomic or chemical bomb. The concept of so called the time window is used to model the engagement situation and a continuous time is assumed for flying times of the both missiles. Lastly, the model is extended to simulate the situation where the guidance radar, which guides a defense missile to its target, has the maximum guidance capacity. The initial mathematical model developed contains several non-linear constraints and a non-linear objective function. Hence, the linearization of those terms is performed before it is solved by a commercially available software. Then to thoroughly examine the MIP model, the model is empirically evaluated with several test problems. Specifically, the models with different objective functions are compared and several battle scenarios are generated to evaluate performance of the models including the extended one. The results indicate that the new model consistently presents better and more realistic results than the compared models.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.22 no.1
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• pp.305-312
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• 2021

This study examines the damage to the submarine's escape trunk hatch spring through microstructure analysis. The cause of the escape trunk's damage during the submarine's construction and its improvement measures were reviewed. To determine the cause of breakage of the escape trunk spring, samples were taken from the damaged product and analyzed for chemical composition, hardness, and microstructure. In particular, the breakage part of the spring was analyzed in-depth by using a scanning electron microscope to determine the cause of corrosion destruction. Finally, a spring shape design method was proposed through the investigation of the cause of spring breakage. In addition, a newly improved spring was produced by applying a nylon coating with excellent corrosion resistance and abrasion resistance. Applying to an actual submarine trunk hatch revealed that the coating peeling phenomenon due to the contact between the springs is significantly improved when the hatch is opened or closed compared to the existing products.

• Korean Journal of Optics and Photonics
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• v.28 no.3
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• pp.116-121
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• 2017

In this paper, a Raman spectrometer is designed to detect chemicals contaminating the ground. The system is based on Raman spectroscopy, which is spectral analysis of scattered light from chemicals, induced by a laser. The system consists of a transmitting-optics module with a laser to induce Raman-scattered light from the sample, a receiving-optics module to collect the scattered light, and a spectrograph to separate the collected light into a wavelength spectrum. The telescope, a part of the receiving-optics module, is designed to produce a focal spot in the same position for variable measurement distances using the code V simulator, considering the distance change between the system and the road. The Raman spectra of 12 chemicals on a glass surface and on a concrete sample were measured. Intensity differences between the Raman spectra acquired on a glass surface and on a concrete sample were observed, but the characteristics of the spectra according to the chemicals on them were similar. Additionally, the Raman spectrum of PTFE (polytetrafluoroethylene) was measured at various distances. The measured and simulated optical throughputs were similar. In conclusion, it is confirmed that with this system the Raman spectrum can be measured, irrespective of the distance change.

• Bulletin of the Korean Chemical Society
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• v.33 no.3
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• pp.855-861
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• 2012

A pioneering version of an on-line management system for high-energy molecules (MS-HEMs) was developed by the ADD and BMDRC in Korea. The current system can manage the physicochemical and explosive properties of virtual and existing HEMs. The on-line MS-HEMs consist of three main routines: management, calculation, and search. The management routine contains a user-friendly interface to store and manage molecular structures and other properties of the new HEMs. The calculation routine automatically calculates a number of compositional and topological molecular descriptors when a new HEM is stored in the MS-HEMs. Physical properties, such as the heat of formation and density, can also be calculated using group additivity methods. In addition, the calculation routine for the impact sensitivity can be used to obtain the safety nature of new HEMs. The impact sensitivity was estimated in a knowledge-based manner using in-house neural network code. The search routine enables general users to find an exact HEM and its properties by sketching a 2D chemical structure, or to retrieve HEMs and their properties by giving a range of properties. These on-line MS-HEMs are expected be powerful tool for deriving novel promising HEMs.

• Journal of Nutrition and Health
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• v.30 no.7
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• pp.803-812
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• 1997

The influences of dietary supplements of vitamin E on hepatocellular chemical carcinogenesis have been studied, Placental glutathione S-transferase(GST-P) positive foci area, antioxidant enzymes(superoxide dismutase(SOD), catalase, glutathione reductase, glutathione peroxidase, glutathione S-transferase(GST)), glucose 6-phosphatase(G6Pase) activities, and lipid peroxidation of mecrosomes(thiobarbituric acid reactive substances(TBARS) contents) were investigated. For is purpose , we used the murine chemical hepatocardinogenic procedure induced by modified Ito model, which consists of 200mg/kg body weight diethylinitrosamine (DEN) injection, 0.01% 2-acethlaminoflurene(2-AAF) feeding for 6 weeks, and partial hepatectomy on week 3. Weanling Sprague-Dawley male rats were fed pulverized Purina rat chow with 15, 000IU/kg diet vitamin E from initiation or promotion stages. We found that vitamin E supplement decreased the area of GST-P positive foci. Catalase, glutathione peroxidase, glutathione reductase. GST activities, and TBARS contents were decreased. On the other hand G6Pase activities were increased by vitamin E supplement. It seemed that vitamin E supplements helped endogenous defense systems against carcinogenesis by decreasing TBARS contents, $H_2O$$_2$ and organic peroxides. So, vitamin E seemed to protect cell from free radical damage in carcinogenesis. Anticarcinogenic effects of vitamin E were more effective at intiation that at promotion stage. These results suggest that vitamin E has suppressive effects on hepatocellular chemical carcinogenesis, probably through antioxidant effects against TBARS contents $H_2O$$_2$ and orgainc peroxides.

• Proceedings of the Materials Research Society of Korea Conference
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• 2008.11a
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• pp.19.2-19.2
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• 2008