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991.
Jinwon Yun Kyungin Cho Young Duk Lee Sangseok Yu 《International Journal of Hydrogen Energy》2018,43(9):4546-4562
The methane steam reforming reaction is an extremely high endothermic reaction that needs a high temperature heat source. Various fuel cell hybrid systems have been developed to improve the thermal efficiency of the entire system. This paper presents a low temperature steam reformer for those hybrid systems to maximize the utilization of energy from a low temperature waste heat source. In this study, the steam reformer has a shell and tube configuration that is divided into the following zones: the inlet heat exchanging zone, the reforming zone and the exit heat exchanging zone. Four different configurations for methane steam reformers are developed to examine the effect of heat transfer on the methane conversion performance of the low temperature steam reformer. The experimental results show that the overall heat transfer area is a critical parameter in achieving a high methane conversion rate. When the heat transfer area increases about 30%, the results showed elevated dry mole fractions of hydrogen about 3% with about 30 °C rise of reformer outlet temperature. 相似文献
992.
Ki Beom Park Young Tae Cho Yoon Gyo Jung 《Journal of Mechanical Science and Technology》2018,32(4):1569-1574
Due to their superior thermal and mechanical properties, super alloys widely used in the aerospace industry have been well-documented in terms of AdvantEdge-based analysis of cutting characteristics rather than experimental methods. However, the well-known super alloy Inconel 601 does not have any database of its material properties in AdvantEdge, which underscores the urgency to build such a database. Hence, the current study uses the Johnson-Cook equation to build a database of Inconel 601’s material properties in AdvantEdge. To that end, drawing on a room temperature tensile test, elevated temperature tensile test and orthogonal cutting test, the current study determines the Johnson-Cook constitutive equation for Inconel 601, and verifies the reliability of the determined Johnson-Cook constitutive equation by comparing the experimental values with the analytical values. 相似文献
993.
Myoung Do Seo Young Jo Kim Jong Sung Lim Jeong Won Kang 《Korean Journal of Chemical Engineering》2012,29(1):103-110
Vapor-liquid equilibrium (VLE) for binary mixtures composed of ethanol+methyl isobutyl ketone, 1-butanol+ methyl ethyl ketone,
and 1-butanol+methyl propyl ketone systems was measured using a circulation type equilibrium apparatus at atmospheric pressure.
The measured data and literature data for alcohol and ketone systems have been correlated by the UNIversal Quasi-Chemical
(UNIQUAC) model with two binary interaction parameters and the non-random lattice fluid equation of state with hydrogen bonding
equation of state (NLF-HB EoS) using a single binary interaction parameter. For the NLF-HB EoS calculations, the numbers of
proton acceptor for ketones were adjusted between 0 and 1. The calculation results with the NLF-HB EoS are better than those
with the UNIQUAC model. 相似文献
994.
Jae-hoon Choi Hyun-sik Ahn Dong-keun Lee Jong-kuk Jin Gye-yong Jang Dae-kyung Seong Min-sung Yun Hyun-seok Shin Yaung-soo Kim 《Fusion Engineering and Design》2012,87(11):1828-1833
This paper presents the current control method of thyristor converter which is applied to PF power supply in KSTAR [1]. The thyristor converter for PF superconducting coil is composed of two 6 pulse converters and each converter is connected in parallel using DC reactor to reduce voltage ripple, current rating of converter and harmonic components. For 4 quadrant operation, each 6 pulse converter has six arms of anti-paralleled thyristor device, back-to-back connection [2]. To apply this converter on KSTAR PF coil, stable coil current control is needed. Additionally, PF coil needs smooth current control without dead-time when current polarity changes and it is not easy in back-to-back thyristor converter. For this reason, zero crossing current control using circulating current and test results are introduced in this paper and it was satisfactory. 相似文献
995.
Sung Chul Jee Ho Jae Lee Young Hoon Joo 《International Journal of Control, Automation and Systems》2012,10(4):841-848
This paper addresses sensor fault detection and isolation problems for continuous- and discrete-time linear time-invariant systems. To that end, we employ a bank consisting of the same number of observers as there are sensors. Both the observer gain and the residual gain are considered. Unlike earlier work, the design conditions with H ?/H ∞ performance are derived in terms of linear, rather than nonlinear, matrix inequalities. An illustrative example is provided to show the effectiveness of the proposed methodology. 相似文献
996.
Junghyun Kim Joon Hyuk Suh Hyun-Deok Cho Wonjae Kang Yong Seok Choi 《Food additives & contaminants. Part A, Chemistry, analysis, control, exposure & risk assessment》2016,33(3):420-432
A multi-class, multi-residue analytical method based on LC-MS/MS detection was developed for the screening and confirmation of 28 veterinary drug and metabolite residues in flatfish, shrimp and eel. The chosen veterinary drugs are prohibited or unauthorised compounds in Korea, which were categorised into various chemical classes including nitroimidazoles, benzimidazoles, sulfones, quinolones, macrolides, phenothiazines, pyrethroids and others. To achieve fast and simultaneous extraction of various analytes, a simple and generic liquid extraction procedure using EDTA-ammonium acetate buffer and acetonitrile, without further clean-up steps, was applied to sample preparation. The final extracts were analysed by ultra-high-performance liquid chromatography coupled with tandem mass spectrometry (UHPLC-MS/MS). The method was validated for each compound in each matrix at three different concentrations (5, 10 and 20 ng g–1) in accordance with Codex guidelines (CAC/GL 71-2009). For most compounds, the recoveries were in the range of 60–110%, and precision, expressed as the relative standard deviation (RSD), was in the range of 5–15%. The detection capabilities (CCβs) were below or equal to 5 ng g–1, which indicates that the developed method is sufficient to detect illegal fishery products containing the target compounds above the residue limit (10 ng g–1) of the new regulatory system (Positive List System – PLS). 相似文献
997.
Seokmin Hong Jaemin Song Min-Chul Kim Kwon-Jae Choi Bong-Sang Lee 《Metals and Materials International》2016,22(2):196-203
The effects of microstructural changes in heavy-section Mn-Mo-Ni low alloy steel on Charpy impact properties were investigated using a 210 mm thick reactor pressure vessel. Specimens were sampled from 5 different positions at intervals of 1/4 thickness from the inner surface to the outer surface. A detailed microstructural analysis of impact-fractured specimens showed that coarse carbides along the lath boundaries acted as fracture initiation sites, and cleavage cracks deviated at prior-austenite grain boundaries and bainite lath boundaries. Upper shelf energy was higher and energy transition temperature was lower at the surface positon, where fine bainitic microstructure with homogeneously distributed fine carbides were present. Toward the center, coarse upper bainite and precipitation of coarse inter-lath carbides were observed, which deteriorated impact properties. At the 1/4T position, the Charpy impact properties were worse than those at other positions owing to the combination of elongated-coarse inter-lath carbides and large effective grain size. 相似文献
998.
999.
The effects of 8-h annealing at 960 °C on the gaseous phase hydrogen storage and electrochemical properties of partial-Ni substituted Zr8Ni21 alloys were studied. The substituting elements included Mg, Al, Sc, V, Mn, Co, Sn, La, and Hf. Only the main phase of the annealed Sn-substitution remained Zr8Ni21-structured while those of other substitutions turned into Zr7Ni10 or Zr2Ni7. The observed trend in maximum gaseous phase hydrogen storage capacity followed the increasing order of B/A ratio of the main phase as orthogonal Zr7Ni10 > tetragonal Zr7Ni10 > Zr8Ni21 > Zr2Ni7. After annealing, due to the increase in abundance of the main phase, the maximum gaseous phase hydrogen storage capacities of alloys with higher capacities before annealing increased while others decreased. The full discharge capacity also improved in the same increasing order of B/A ratio in the main phase. Hf-substitution showed the highest electrochemical discharge capacity at 200 mAh g−1. After annealing, all alloys with the same main phase as the as-cast alloys showed degradation in full electrochemical capacity due to the reduction in both number and abundance of the catalytic secondary phases. All supplements assisted in improving surface exchange current from the base binary Zr8Ni21 alloy. Except for La- and Hf-substitutions, annealing reduced the surface exchange current density. The bulk hydrogen diffusion coefficient decreased with most of the supplements except for V- and Sn-substitutions. All supplements, except for Sc, showed improvement in the bulk diffusion after annealing. Furthermore, the maximum gaseous phase hydrogen storage capacity showed a strong correlation to the full electrochemical discharge capacity. Among all alloys in this study, the as-cast Hf-substituted Zr8Ni21 alloy demonstrated the best overall gaseous hydrogen storage and electrochemical properties. 相似文献
1000.
Lee Jae Hoon Park Eunju Jin Hyue Ju Lee Yunjeong Choi Seung Jun Lee Gyu Whan Chang Pahn-Shick Paik Hyun-Dong 《Food science and biotechnology》2017,26(5):1371-1377
Food Science and Biotechnology - The purpose of this study was to evaluate the anti-inflammatory and anti-genotoxic activity of branched-chain amino acids (BCAAs) in lipopolysaccharide (LPS)... 相似文献