• Proceedings of the KIEE Conference
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• 2007.11c
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• pp.93-96
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• 2007

In this paper, the testing equipment for evaluating aging characteristics of outdoor silicone rubber insulator resulting from the environmental aging effect with regards to sunlight(UV) was developed. Influence of sunlight effect aging is seriously increase due to destruction of ozone layer which is occurred by consumption of fossil fuel. For this purpose, silicone rubber was aged under the artificial sunlight by exposure of xenon lamp radiation in the accelerating aging chamber and various test and analysis were performed such as breakdown strength, contact angle. And FT-IR analysis has been followed.

• Proceedings of the Korea Society for Energy Engineering kosee Conference
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• 2003.05a
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• pp.415-423
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• 2003

Korea Electric Power Research Institute(KEPRI) had worked a comprehensive Plant Lifetime Management (PLiM) project for a CANDU plant in corporation with Korea Hydro and Nuclear Power(KHNP). The project had been performed to understand the aging status of major components screened from the plant and to address provisions for the continued operation over its design life. A feasibility of the continued operation was reviewed in the aspects of technology, economics, and regulatory environments. This paper introduces general approach of aging assessment, screening of critical components and an experience of aging assessment for an example of fuel channel that is the most critical component in CANDU plant.

• Korean Journal of Materials Research
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• v.25 no.10
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• pp.516-522
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• 2015

Aging aircraft structures are inevitably exposed to environment for a long time facing many potential problems, including corrosion and wide spread fatigue damage, which in turn cause the degradation of flight safety. In this study, the environmental surface damages on aging aircraft structures induced during service were quantitatively analyzed. Additionally, S-N fatigue tests were performed with center hole specimens extracted from aging aircraft structures. From the results of quantitative analyses of the surface damages and fatigue tests, it is concluded that corrosion pits initiated during service reduce the fatigue life significantly. Finally, using the fracture mechanics and the EIFS (equivalent initial flaw size) concepts, the remaining fatigue life was predicted based on actual fatigue test results.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.27 no.12
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• pp.877-882
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• 2014

It has been confirmed that the inner defect of transformer and the perfect diagnosis for aging are closely related to safe electric power transmission system and that the detection of accident and diagnosis technique turn out to be very important issues. Since electric power machinery consists of various kinds of components, however, it is very difficult to make a diagnosis for aging by one parameter. Thus, diagnosis for aging is feasible only through the combination of various parameters. Recently, various expert systems have been developed and applied to diagnosis for aging, but they are not yet reliable enough to apply to the real system. In this paper, XLPE which is ultra high voltage cable insulator material were chosen to investigate the influence of void on insulator material using partial discharge. Obtained data have been processed by PRPD (phased resolved partial discharge) distribution function and K-means. And statistical and cluster distribution of partial discharge have been analysed and investigated.

• Osteoporosis and Sarcopenia
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• v.3 no.3
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• pp.117-122
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• 2017

Sarcopenia is the degenerative loss of muscle mass and function with aging. Recently sarcopenia was recognized as a clinical disease by the International Classification of Disease, 10th revision, Clinical Modification. An imbalance between protein synthesis and degradation causes a gradual loss of muscle mass, resulting in a decline of muscle function as a progress of sarcopenia. Many mechanisms involved in the onset of sarcopenia include age-related factors as well as activity-, disease-, and nutrition-related factors. The stage of sarcopenia reflecting the severity of conditions assists clinical management of sarcopenia. It is important that systemic descriptions of the disease conditions include age, sex, and other environmental risk factors as well as levels of physical function. To develop a new therapeutic intervention needed is the detailed understanding of molecular and cellular mechanisms by which apoptosis, autophagy, atrophy, and hypertrophy occur in the muscle stem cells, myotubes, and/or neuromuscular junction. The new strategy to managing sarcopenia will be signal-modulating small molecules, natural compounds, repurposing of old drugs, and muscle-specific microRNAs.

• Coupled systems mechanics
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• v.3 no.1
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• pp.53-71
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• 2014

Accurate prognoses of the durability of concrete structures require a detailed description of the continuously running aging processes and a consideration of the complete load history. Therefore, in the framework of continuous porous media mechanics a model is developed, which allows a detailed analysis of the most important aging processes of concrete as well as a flexible coupling of different processes. An overview of the prediction model and the balance equations is given. The material dependent model equations, the consequences of coupling different processes and the solution scheme are discussed. In two case studies the aging of concrete due to hydration and chloride penetration are presented, which illustrate the capabilities and the characteristics of the developed model.

• Journal of the Korean Society of Propulsion Engineers
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• v.25 no.3
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• pp.26-41
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• 2021

Titanium hydride potassium perchlorate (THPP) has played an important role as initiators of the propulsion system. However, the 'aging' may cause performance degradation and even give rise to a failure in the total system. In this study, various hygrothermal aging conditions were considered and the aging effects on thermodynamic and ignition characteristics of THPP are provided via thermal analysis and ignition measurements. Also, physical-chemical changes were identified by morphological analysis. In conclusion, thermal aging led to E_α decrease-high reactivity due to oxidizer decomposition whereas hygrothermal aging gave rise to an opposite tendency by fuel oxidation.

• Analytical Science and Technology
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• v.36 no.2
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• pp.80-88
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• 2023

Fingerprints play a crucial role in the identification of potential suspects in criminal cases. However, determining the actual time, i.e., the time at which the fingermark was deposited, is challenging. Herein, we investigated the persistence and aging of fingerprints over time by observing the time evolution of latent fingerprints on a polystyrene box stored in a dark room. Fingerprint samples that were stored for up to two years could be detected with maximum accuracy using a black iron-oxide-based emulsion (black emulsion). To estimate the time of fingerprint deposition, fingerprint aging was studied by analyzing the lipid components of the fingerprints after their development. Cholesterol and squalene were selected as indicators of fingerprint aging, and their ratio was estimated to assess aging. In the case of fingerprint samples stored in a dark room for up to one month after deposition, the cholesterol/squalene ratio was approximately 0.01; it increased gradually to ≥ 0.1 over six months. A substantial reduction in the levels of cholesterol and squalene from the initial levels was also noted. Cholesterol and squalene were not detected after one year of storage. Thus, the extent of aging could be determined by analyzing the aging indicators for up to six months. Two cases that could cause error in the estimation of the fingerprint deposition time, namely, heating of the fingerprint sample before development and storage of the developed fingerprints in a dark room, were also investigated.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.32 no.7
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• pp.569-575
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• 2008

In this study, disk type of thermal barrier coating system for gas turbine blade was isothermally aged in the furnace changing exposure time and temperature. For each aging condition, bond tests for three samples were conducted for evaluating degradation of adhesive or cohesive strength of thermal barrier coating system. For as-sprayed condition, the location of fracture in the bond test was in the middle of epoxy which have bond strength of 57 MPa. As specimens are degraded by thermal aging, bond strength gradually decreased and the location of failure was also changed from within top coat at the earlier stage of thermal aging to the interface between top coat and TGO at the later stage due to the delamination in the coating.

• Journal of the Korean Society of Safety
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• v.15 no.1
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• pp.28-35
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• 2000

As huge energy transfer systems like a nuclear power plant, steam power plant and petrochemical plant are operated for a long time, mechanical properties are changed by degradation. The life time of the systems can be affected by the mechanical properties. So determination of the integrity of the metallic structure is required either to en4sure that failure will not occur during the service life of the components or to evaluate the lifetime extension of the structure. An automated ball indentation(ABI) method was developed as a non-destructive technique for evaluating the integrity of such metallic components. In this paper, we would like to present the aging evaluation technique by the ABI method. The five classes of the thermally aged CF8M specimens were prepared using an artificially accelerated aging method. After holding 100, 300, 900, 1800 and 3600 hours at 43$0^{\circ}C$, the specimens were cooled down using water to room temperature respectively. The tensile test, hardness test, charpy impact test, ABI test were performed. The results of the fracture test were compared with those of ABI test and the new evaluation technique of the integrity of metallic structures was developed.