• Journal of the Korean Society of Radiology
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• v.83 no.6
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• pp.1360-1365
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• 2022

Hutchinson-Gilford progeria syndrome (HGPS) is a rare, progressive, premature aging syndrome with early morbidity due to cardiovascular and cerebrovascular diseases. Clinical symptoms are very diverse, including non-specific symptoms such as growth retardation, scleroderma, alopecia, and osteoporosis, as well as hypertension and cardiovascular diseases that occur in childhood and adolescence due to accelerated vascular aging. In patients with HGPS, MR angiography is recommended for early diagnosis of asymptomatic stroke or vascular changes and to assess increased risk of cerebrovascular disease. We report the second domestic case of HGPS confirmed by genetic analysis in a 5-year-old child with typical clinical features, and the first English case report in Korea to present brain MR angiography findings.

• Nuclear Engineering and Technology
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• v.56 no.9
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• pp.3740-3749
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• 2024

To reduce the losses caused by aging failure of insulation gate bipolar transistor (IGBT), which is the core components of nuclear power plant rod position indicating and rod control (RPC) system. It is necessary to conduct studies on its life prediction. The selection of IGBT failure characteristic parameters in existing research relies heavily on failure principles and expert experience. Moreover, the analysis and learning of time-domain degradation data have not been fully conducted, resulting in low prediction efficiency as the monotonicity, time correlation, and poor anti-interference ability of extracted degradation features. This paper utilizes the advantages of the stacked denoising autoencoder(SDAE) network in adaptive feature extraction and denoising capabilities to perform adaptive feature extraction on IGBT time-domain degradation data; establishes a long-short-term memory (LSTM) prediction model, and optimizes the learning rate, number of nodes in the hidden layer, and number of hidden layers using the Gray Wolf Optimization (GWO) algorithm; conducts verification experiments on the IGBT accelerated aging dataset provided by NASA PCoE Research Center, and selects performance evaluation indicators to compare and analyze the prediction results of the SDAE-LSTM model, PSOLSTM model, and BP model. The results show that the SDAE-LSTM model can achieve more accurate and stable IGBT life prediction.

• 보존과학연구
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• s.33
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• pp.45-55
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• 2012

A beeswax-treated paper has no air permeability but has the water repellency compared with a general Hanji. Because of these properties, the differences of the aging factors and mechanisms between the outer partition of beeswax-treated paper that is affected by the surrounding conservation environment and the inner partition of it that is not affected are bigger than general books. In this research, we analyzed and compared the aging characteristics through the accelerated aging of the beeswax-treated paper by some air and humidity conditions. The results of the physical and optical analysis after the artificial aging, it was shown that the oxygen accelerates the aging of the beeswax-treated paper and the condition with the humidity 50% RH is more stable than the condition with the humidity 0% RH. The results of the CG/MS analysis that was conducted to figure out the decomposition charateristics of the beeswax according to the air quality and the humidity, a low molecular weight compound that the number of carbon is C9-C20 including a fatty acid such as a palmitic acid was increased as the aging was progressed. However, under the same environment, a compound that the number of carbon is C21-C36 including a hydrocarbon and a aliphatic alcohol and a high molecular weight compound that the number of carbon is more than C34 including a wax ester were decreased. A rate of change according to the air quality and the humidity was similar to the beeswax-treated papers.

• Journal of the Korean Society of Food Science and Nutrition
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• v.34 no.1
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• pp.99-106
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• 2005

Skin is continously exposed to ultraviolet (UV) radiation, the major cause of skin disorders including skin aging. Chlorophylls were well known as photosensitizer initiating subsequent chemical reactions such as photooxidative deterioration of cellular structures. This experiment was designed to elucidate the effects of $\beta$-carotene and ascorbic acid with chlorophylls on UVB-induced photooxidation in linoleic acid emulsion model system and skin homogenate of ICR mouse. In linoleic acid emulsion model system, the addition of chlorophyll and $\beta$-carotene accelerated the photooxidation, while high concentration of ascorbic acid prevented. The combination of chlorophylls, $\beta$-carotene and ascorbic acid, which concentrations are simplified from mustard leaf kimchi, prevented UVB-induced photooxidation. Although single treatment of $\beta$-caretene accelerated photooxidaiton, $\beta$-caretene acted as antioxidant in the combination with ascorbic acid. Similarly the addition of individual chlorophylls and $\beta$-carotene accelerated the UVB-induced photooxidation in skin homogenate of ICR mouse. 50 ppm of ascorbic acid did not show the any preventive effect, however 500 ppm of ascorbic acid effectively prevented the oxidation. Photooxidation was prevented in the combination of chlorophylls and $\beta$-carotene with 500 ppm of ascorbic acid and concentration rate of ascorbic acid plays an important role in the prevention of UVB-induced photooxidation.

• Journal of the Korean Society of Food Science and Nutrition
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• v.41 no.9
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• pp.1253-1258
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• 2012

In the present study, we investigated the effects of Rubus coreanus Miquel (RCM) on memory ability of senescence-accelerated mice (SAM). Prone 8 strains of SAM mice (SAMP8), which is a useful animal for investigating the mechanism of brain aging and senile dementia, were fed a diet containing 100 mg/kg body weight/day of RCM for 8 weeks. Memory ability of mice was examined by using passive avoidance test and Morris water maze test. SAMP8 mice showed remarkable memory impairment compared with senescence-resistant 1 strains of SAM (SAMR1). RCM significantly improved memory ability of SAMP8 mice. In addition, acetylcholineasterase activities decreased in the brain of SAMP8 mice treated with RCM. Taken together, these results suggest that RCM may act as an acetylcholineasterase inhibitor, thereby improving senescence-related memory impairment.

• Proceedings of the KIEE Conference
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• 1999.07d
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• pp.1621-1623
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• 1999

Recently, high voltage outdoor ploymer insulators have been widely used commercially owing to their excellent electrical and mechanical properties, superior comtamination flashover performance, light weight, easy installation or handing, no maintenance during service, competitive price and so on. compared to porcelaain and glass insulators. For instance, silicone rubber(SR) for polymeric insulators specially has much superior insulating and anti-pollution performance due to its specific hydrophobicity even in severe contaminated environments. We have investigated surface discharge current characteristics of silicone rubbers(SR) for HV outdoor composite insulation specimen under accelerated aging codition using a computer measuring system. The relations of average leakage current and surface discharge current repetition rates and discharge current amplitude, the distribution of discharge current amplitude were studied to investigate electrical conduction of silicone rubber surface with the salt fog condition.

• Proceedings of the KIEE Conference
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• 2004.07c
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• pp.1679-1681
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• 2004

Class-F and B resin-rich type insulating tapes are generally used for the ground wall insulations of respective air-cooled and water-cooled stator windings in larger turbine generators. In this paper, their electrical properties coupled with aging times in higher temperature than designed one in normal condition were experimentally investigated and the results of two comparative tests were presented on the existing class-F resin-rich type tape and a developed one after curing. The resin-rich tapes currently used arc composed of six and a half 3-layer sheets that arc structured with mica paper, the top and bottom supports of it respectively, and the epoxy resin to bind them tightly. The results for breakdown voltage and strength on the cured specimens were presented, which were composed of the unaged, the aged accelerated for one, two, and three thousand hours at 180 $^{\circ}C$. The surface and volume resistivities on them were measured and the results are also presented to make a comparative test for the initial electrical characteristics.

• Proceedings of the KIEE Conference
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• 2004.07c
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• pp.1676-1678
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• 2004

Class-F resin-rich type insulating tapes are generally used for the groundwall insulations of the large turbine generators with air-cooled and hydrogen-cooled stator windings. In this paper, mechanical strength properties degraded over aging time in higher temperature than designed one in normal condition were experimentally investigated and the results of comparative tests were presented on the existing class-F resin-rich type tape and a developed one after curing. The resin-rich insulating tapes with composite material of Mica/Epoxy/support currently were used in this test. The tests for tensile and flexural strength properties were conducted with the specimens which were composed of unaged and the aged specimens accelerated for one, two, and three thousand hours at 180 $^{\circ}C$. The tensional strength was only measured for the unaged specimens and the results are also presented to make a comparative test for their initial mechanical characteristics.

• 한국신재생에너지학회:학술대회논문집
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• 2010.11a
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• pp.76.2-76.2
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• 2010

The gas diffusion layer is the key component of the proton exchange membrane fuel cell because it directly affect to the mass transport mechanism and dynamic behavior of the cell. In this study, the effects of GDL aging on the transient response of the PEM fuel cell is systematically investigated using current step transient response analysis under different stoichiometric ratios and humidity conditions. With GDLs aged by the accelerated stress test, the effects of hydrophobicity and structural changes due to carbon loss in the GDL on the transient response of PEM fuel cells are determined. The degraded GDLs that had uneven hydrophobicity distributions cause local water flooding inside the GDL and induce lower and unstable voltage responses after load changes.

• Journal of Korea Technical Association of The Pulp and Paper Industry
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• v.45 no.3
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• pp.1-8
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• 2013

Hanji has been used mainly for preservation paper because of superior mechanical properties. However, it was not used in printing for inkjet and laser printer-printed letters. In this study, machine-made Hanji was prepared with five different contents of paper mulberry 20, 40, 60, 80 and 100% and managed by same pressure calendering. By increasing of paper mulberry contents, tearing index and folding endurance of machine-made Hanji increased because of increased fiber-to-fiber bonding. Printability property of machine-made Hanji improved by decreasing of paper mulberry contents. After 20 hours accelerated aging, the initial folding endurance of machine-made Hanji was reduced by approximately one-fourth degree. Between 40 and 100% contents of paper mulberry was showed similar levels about preservation property. The machine-made Hanji of paper mulberry 60% content was suitable for permanence and printability properties using preservation paper and printer-printed letters.