• Journal of the Korean Society for Nondestructive Testing
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• v.15 no.4
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• pp.549-560
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• 1996

The purpose of this study is to investigate the usefulness of small punch(SP) test using miniaturized specimens as a method for fracture strength evaluation of CANDU pressure tube embrittled by hydrogen. According to the test results, the fracture strength evaluation as a function of hydrogen concentration at $-196^{\circ}C$ was much better than that at room temperature, as the difference of SP fracture energy(Esp) with hydrogen concentration was more significant at $-196^{\circ}C$ than at room temperature for the hydrogen concentration up to 300ppm-H. It was also observed that the peak of average AE energy, the cumulative average AE energy and the cumulative average AE energy per equivalent fracture, strain increased with the increase of hydrogen concentration. From the results of load-displacement behaviors, Esp behaviors, macro- and micro-SEM fractographs and AE test it has been concluded that the SP test method using miniaturized specimen($10mm{\times}10mm{\times}0.5mm$) will be a useful test method to evaluate the fracture strength for CANDU pressure tube embrittled by hydrogen.

• 한국연소학회:학술대회논문집
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• 1999.10a
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• pp.11-20
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• 1999

Acoustic pressure response and NO formation of hydrogen-air diffusion flames at various pressures are numerically studied by employing counterflow diffusion flame as a model flame let in turbulent flames in combustion chambers. The numerical results show that extinction strain rate increases linearly with pressure and then decreases, and increases again at high pressures. Thus, flames are classified into three pressure regimes. Such non-monotonic behavior is caused by the change in chemical kinetic behavior as pressure rises. Acoustic pressure response in each regime is investigated based on the Rayleigh criterion. At low pressures, pressure-rise causes the increase in flame temperature and chain branching/recombination reaction rates, resulting in increased heat release. Therefore, amplification in pressure oscillation is predicted. Similar phenomena are predicted at high pressures. At moderate pressures, weak amplification is predicted. Emission index of NO shows similar behaviors as to the peak-temperature variation with pressure.

• Journal of ILASS-Korea
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• v.15 no.4
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• pp.182-188
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• 2010

Significant real fluid behaviors including rapid property changes take place where high pressure combustion devices such as rocket engines. The flamelet model is the reliable approach to account for the real fluid effects. In the present study, the flamelet equations are extended to treat the general fluids over transcritical and supercritical states. The real fluid flamelet model is carried out for the gaseous hydrogen and cryogenic liquid oxygen flames at the wide range of thermodynamic conditions. Based on numerical results, the precise discussions are made for effects of real fluid, pressure, and differential diffusion on the local flame structure.

• Bulletin of the Korean Chemical Society
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• v.30 no.3
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• pp.589-594
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• 2009

We have performed DFT B3LYP/6-31G(d,p) calculations to investigate the complexation behaviors of the ethyl ester derivative of p-tert-butylcalix[6]arene (1) toward a variety of alkylammonium ions. We have studied the binding sites of these host-guest complexes focusing on the p-tert-butylcalix[6]arene pocket (endo) of 1. The smaller alkylammonium cations have the better complexation efficiency than the bulkier alkylammonium ions with the p-tert-butylcalix[6]aryl ester. The hydrogen-bonding of N-H$\ldots$O is one of the important factors for the complexation behavior of the p-tert-butylcalix[6]aryl ester, in addition to the NH-aromatic π, CH-aromatic π and electrostatic interactions, and the steric hindrance of alkylammonium cation. The hydrogen-bonded distances and angles of N-H$\ldots$O are reported for the complexes of the p-tert-butylcalix[6]aryl ester with various alkylammonium ions.

• Proceedings of the Korean Nuclear Society Conference
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• 2003.05a
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• pp.177-177
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• 2003

• Proceedings of the Korean Nuclear Society Conference
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• 2002.05a
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• pp.257.2-257
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• 2002

• Proceedings of the Korean Nuclear Society Conference
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• 2004.05a
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• pp.325-325
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• 2004

• Nuclear Engineering and Technology
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• v.45 no.2
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• pp.265-276
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• 2013

Pressure tubes made of Zr-2.5 wt% Nb alloy are important components consisting reactor coolant pressure boundary of a pressurized heavy water reactor, in which unanticipated through-wall cracks and rupture may occur due to a delayed hydride cracking (DHC). The Canadian Standards Association has provided deterministic and probabilistic structural integrity evaluation procedures to protect pressure tubes against DHC. However, intuitive understanding and subsequent assessment of flaw behaviors are still insufficient due to complex degradation mechanisms and diverse influential parameters of DHC compared with those of stress corrosion cracking and fatigue crack growth phenomena. In the present study, a deterministic flaw assessment program was developed and applied for systematic integrity assessment of the pressure tubes. Based on the examination results dealing with effects of flaw shapes, pressure tube dimensional changes, hydrogen concentrations of pressure tubes and plant operation scenarios, a simple and rough method for effective cooldown operation was proposed to minimize DHC risks. The developed deterministic assessment program for pressure tubes can be used to derive further technical bases for probabilistic damage frequency assessment.

• Korean Chemical Engineering Research
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• v.51 no.1
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• pp.136-143
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• 2013

In this study, both transient behaviors of a biofilter system with improved design and a conventional biofilter were observed to perform the treatment of waste air containing malodor and volatile organic compound (VOC). Their behaviors of removal efficiency and treated concentration of malodor and VOC were compared each other. During 1st~7th stages of improved biofilter system operation it was observed that the order of treated ethanol concentration at each sampling port was switched due to the difference of microbe-population-distribution in spite of the difference of biofilter effective height. However, at 8th stage of its operation, the order of treated ethanol concentration at each sampling port was consistent to the order of biofilter effective height at each sampling port. The same was applied to the case of hydrogen sulfide, even though the difference of switched treated-hydrogen sulfide-concentrations was less than that of switched treated-ethanol-concentrations. The ethanol-removal efficiency of the biofilter system with improved design was ca. 96%, which was greater by 2% than that of the conventional biofilter. The transient behavior of treated hydrogen sulfide concentration of both biofilters were similar to each other. However, the concentration of hydrogen sulfide treated by the biofilter system with improved design was observed lower than that by the conventional biofilter. The hydrogen sulfide-removal efficiency of the biofilter system with improved design was higher by ca. 2% than that of the conventional biofilter. Therefore, the hydrogen sulfide-removal efficiency of the biofilter system with improved design was observed to be enhanced by the same as its ethanol-removal efficiency.

• Bulletin of the Korean Chemical Society
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• v.33 no.1
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• pp.95-99
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• 2012

Two novel copper(II) complexes, [Cu(dmamhp)$(H_2O)_2(SO_4)]_n$ (1) and [Cu(dmamhp)$(NO_3)_2(H_2O)]{\cdot}H_2O$ (2) [dmamhp = 2-dimethylaminomethyl-3-hydroxypyridine] have been synthesized and structurally characterized by single crystal X-ray diffraction analysis. Compound 1 displays a double one-dimensional chains structure, in which each chain is constituted with the distorted octahedral copper(II) complex bridged through bidentate sulfate ligands resulting in a coordination polymer. The bifurcated hydrogen bonds and $\pi-\pi$ interactions play important roles in the formation of the double chains structure. On the other hand, compound 2 adopts a distorted square pyramidal geometry around copper(II) ion and exists as a discrete monomer. There are intermolecular bifurcated hydrogen bonds and $\pi-\pi$ stacking interactions between the monomeric units. The magnetic properties revealed that the paramagnetic behaviors are dominantly manifested and there are no intermolecular magnetic interactions in both compound 1 and 2.