• Nuclear Engineering and Technology
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• 제37권2호
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• pp.201-206
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• 2005

Fretting, which is a special type of wear, is defined as small amplitude relative motion along the contacting interface between two materials. The structural integrity of steam generators in nuclear power plants is very much dependent upon the fretting wear characteristics of Inconel 690 U-tubes. In this study, a finite element model that can simulate fretting wear on the secondary side of the steam generator was developed and used for a quantitative investigation of the fretting wear phenomenon. Finite element modeling of elastic contact wear problems was performed to demonstrate the feasibility of applying the finite element method to fretting wear problems. The elastic beam problem, with existing solutions, is treated as a numerical example. By introducing a control parameter s, which scaled up the wear constant and scaled down the cycle numbers, the algorithm was shown to greatly reduce the time required for the analysis. The work rate model was adopted in the wear model. In the three-dimensional finite element analysis, a quarterly symmetric model was used to simulate cross tubes contacting at right angles. The wear constant of Inconel 690 in the work rate model was taken as $K=26.7{\times}10^{-15}\;Pa^{-1}$ from experimental data obtained using a fretting wear test rig with a piezoelectric actuator. The analyses revealed donut-shaped wear along the contacting boundary, which is a typical feature of fretting wear.

• Carbon letters
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• 제8권2호
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• pp.95-100
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• 2007

A series of activated carbons (ACs) were derived from sugarcane bagasse under two activation schemes: steam-pyrolysis at $600-800^{\circ}C$ and chemical activation with $H_3PO_4$ at $500^{\circ}C$. Some carbons were treated at 400, $600^{\circ}C$, or for 1-3 h, and/or in flowing air during pyrolysis of acid-impregnated mass. XRD profiles displayed two broad diffuse bands centered around $2{\theta}=23$ and $43^{\circ}$, currently associated with diffraction from the 002 and 100/101 set of planes in graphite, respectively. These correspond to the interlayer spacing, Lc, and microcrystallite lateral dimensions, La, of the turbostratic (fully disordered) graphene layers. Steam pyrolysis-activated carbons exhibit only the two mentioned broad bands with enhancement in number of layers, with temperature, and small decrease in microcrystallite diameter, La. XRD patterns of $H_3PO_4$-ACs display more developed and separated peaks in the early region with maxima at $2{\theta}=23$, 26 and $29^{\circ}$, possibly ascribed to fragmented microcrystallites (or partially organized structures). Diffraction within the $2{\theta}=43^{\circ}$ is still broad although depressed and diffuse, suggesting that the intragraphitic layers are less developed. Varying the conditions of chemical activation inflicts insignificant structural alterations. Circulating air during pyrolysis leads to enhancement of the basic graphitic structure with destruction and degradation in the lateral dimensions.

• Corrosion Science and Technology
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• 제22권3호
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• pp.214-219
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• 2023

Considering the case in the United States where most nuclear power plants with an initial design life of 40 years continue to operate until 60 or 80 years after undergoing material soundness evaluation, it is time to plan a more robust long-term operation strategy for nuclear power plants in Korea. There are some reports that SRO/LRO might be formed when Alloy 690 is heat treated for 10,000 hours to 100,000 hours at 360 to 450 ℃. The possibility of LRO formation in Alloy 690 steam generator tubings of Kori nuclear power plant unit 1 (Kori-1) was investigated using existing research papers. The mechanism in which SRO/LRO occurred was also surveyed. Alloy 690 was found to be more likely to cause ordering than Alloy 600 in terms of alloy composition. The ordering could be evaluated through changes in material properties. However, it is difficult to evaluate it from a microstructural point of view. The likelihood of LRO in Alloy 690 of the Kori-1 plant operated at 320 ℃ for 19 years seemed to be low in terms of time and exposure temperature.

• 펄프종이기술
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• 제29권4호
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• pp.18-27
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• 1997

This study was performed to obtained the optimal delignified condition of exploded wood on the acid hydrolysis with sulfuric acid. Wood chips of pine wood(Pinus desiflora), oak wood(Quercus serrata) and birch wood (Betula platyphylla var. japonica) were treated with a high pressure steam (20-30kgf/$\textrm{cm}^2$, 2-6 minutes). The exploded wood was delignified with sodium hydroxide and sodium chlorite, and then hydrolyzed with sulfuric acid. The result can be summerized as follows ; In the exploded wood treated with sodium hydroxide, the optimal concentration of sodium hydroxide was 1% as content of lignin in the exploded wood. Lignin content of exploded wood treated with sodium chlorite was lower then that sodium hydroxide. The maximum reducing sugar yield of exploded wood treated with 1% sodium hydroxide was lower than non-treated exploded wood. In the case of sodium chlorite treated, the maximum reducing sugar yield was hgher than non-treated exploded wood. Sugar composition of acid hydrolysis solution was composed of xylose and glucose residue, and the rate of glucose residue was increased in high pressure condition.

• Nuclear Engineering and Technology
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• 제52권9호
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• pp.2100-2106
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• 2020

This paper newly proposes an efficient analytic springback prediction method to predict the final dimensions of bent cylindrical tubes for a helical tube steam generator in a small modular reactor. Three-dimensional bending procedure is treated as a two-dimensional in-plane bending procedure by integrating the Euler beam theory. To enhance the accuracy of the springback prediction, mathematical representations of flow stress and elastic modulus for unloading are systematically integrated into the analytic prediction model. This technique not only precisely predicts the final dimensions of the bent helical tube after a springback, but also effectively predicts the various target radii. Numerical validations were performed for five different radii of helical tube bending by comparing the final radius after a springback.

• 한국의류학회지
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• 제24권3호
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• pp.440-447
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• 2000

The effects of DP finishing conditions including process technique and finishing agent on the mechanical properties and hand of cotton fabrics were investigated. 100% cotton fabrics were treated with NMA/DMDHEU and NMA/YF using wet-fixation and steam-fixation process. For comparison, conventional pad-dry-cure process was used with DMDHEU. After DP finishing, tensile and compressional resilience increased and bending hysteresis decreased, resulting in the improvement of dimensional stability of cotton fabric. WF and SF process rendered fabrics better shear properties, tensile energy, and compressional linearity and energy than PDC process. However, SF process produced fabrics with higher geometrical roughness than WF process. After DP finishing, primary hand values except Koshi increased, resulting in the increase of total hand value of cotton fabric.

• 한국수소및신에너지학회논문집
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• 제20권5호
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• pp.439-446
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• 2009

This paper investigates the dehydration and RDF (Refuse Derived Fuel) production of organic wastes, livestock manure and sewerage sludge with pressurized hydrothermal treatment process. The renewable technology for the organic wastes must involve short treatment time required, reusable energy source, anti-odor and viruses, low cost for the treatment, and well-fertilization. The pressurized hydrothermal treatment process promotes to evaporate moisture in the waste after being shortly treated in a reactor, which uses steam and heat supplied by an external boiler. By the pressurized steam, the cell walls of the waste break and effectively release the internal moisture. Then, the dried waste can be mixed with waste vinyls to produce RDF with a higher heating value as high as 6,700 kcal/kg.

• 한국염색가공학회지
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• 제3권3호
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• pp.6-14
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• 1991

To develop an one-bath process for weight-reduction and mercerization of polyester/cotton fabric, concentrated NaOH solution was padded and steam-treated at high temperature. Following results which can be used commercially are obtained. (1) Steaming temperature of 110-12$0^{\circ}C$ is most efficient. (2) Optimum concentration of NaOH solution is 15-20%. (3) Most favorable weight-reduction is 20% in the aspect of fabric handle, and under this treating condition, dye exhaustion onto the mercerized cotton fiber is also increased to 40% or more. From above results, we believe that the economical and concurrent weight-reduction and mercerzation of polyester/cotton fabric can be realized. Moreover, with continuous treatment by pad-steam procedure, it is expected that this is, also, advantageous for the improvement of fabric quality and productivity.

• 열처리공학회지
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• 제14권3호
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• pp.145-150
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• 2001

The effect of laser welding and surface treatment, developed as a method of repairing steam generator tubes, on the pitting corrosion resistance of alloy 690 was examined. The surfaces of some heat-treated Alloy 690 materials were melt-treated using the Nd-YAG laser beam, and then examined to characterize the microstructures. The resistance to pitting corrosion was evaluated by measuring of Ep(pitting potential) through the electrochemical tests and also by measuring the degree of pit generation through the immersion tests. The pit formation characteristics were investigated by observing microstructural changes and pit morphologies. The results show that the resistance to pitting corrosion increases in the order of the following list; solution annealed Alloy 690, thermally treated Alloy 690, and laser surface melt-treated Alloy 690. The melted region was found to have a cellular structure and fine precipitates. It was confirmed that the resistance of Alloy 690 to pit initiation and also to pit propagation was higher when it was laser treated than treated otherwise.

• Biomolecules & Therapeutics
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• 제21권5호
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• pp.405-410
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• 2013

Codonopsis lanceolata (Campanulaceae) traditionally have been used as a tonic and to treat patients with lung abscesses. Recently, it was proposed that the extract and some compounds isolated from C. lanceolata reversed scopolamine-induced memory and learning deficits. The purpose of this study was to evaluate the improvement of cognitive enhancing effect of C. lanceolata by steam and fermentation process in scopolamine-induced memory impairment mice models by passive avoidance test and Morris water maze test. The extract of C. lanceolata or the extract of steamed and fermented C. lanceolata (SFCE) was orally administered to male mice at the doses of 100 and 300 mg/kg body weight. As a result, mice treated with steamed and fermented C. lanceolata extract (SFCE) (300 mg/kg body weight, p.o.) showed shorter escape latencies than those with C. lanceolata extract or the scopolamine-administered group in Morris water maze test. Also, it exerted longer step-through latency time than scopolamine treated group in passive avoidance test. Furthermore, neuroprotective effect of SFCE on glutamate-induced cytotoxicity was assessed in HT22 cells. Only SFCE-treated cells showed significant protection at 500 ${\mu}g/ml$. Interestingly, steamed C. lanceolata with fermentation contained more phenolic acid including gallic acid and vanillic acid than original C. lanceolata. Collectively, these results suggest that steam and fermentation process of C. lanceolata increased cognitive enhancing activity related to the memory processes and neuroprotective effect than original C. lanceolata.