• Korean Journal of Materials Research
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• v.12 no.5
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• pp.414-422
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• 2002

Three different multi-component white cast irons alloyed with Cr, V, Mo and W were prepared in order to study their as-cast and solidification structures. Three combinations of the alloying elements were selected so as to obtain the different types of carbides and matrix structures : 3%C-10%Cr-5%Mo-5%W(alloy No.1), 3%C-10%V-5% Mo-5%W(alloy No. 2) and 3%C-17%Cr-3% V(alloy No.3). The as-cast microstructures were investigated with optical and scanning electron microscopes. There existed two different types of carbides, $M_7C_3$ carbide with rod-like morphology and $M_6C$ carbide with fishbone-like one, and matrix in the alloy No. 1. The alloy No. 2 consisted of MC carbide with chunky and flaky type and needle-like $M_2C$ carbide, and matrix. The chunky type referred to primary MC carbide and the flaky one to eutectic MC carbide. The morphology of the alloy No. 3 represented a typical hypo-eutectic high chromium white cast iron composed of rod-like $M_7C_3$ carbide which is very sensitive to heat flow direction and matrix. To clarify the solidification sequence, each iron(50g) was remelted at 1723K in an alumina crucible using a silicon carbide resistance furnace under argon atmosphere. The molten iron was cooled at the rate of 10K/min and quenched into water at several temperatures during thermal analysis. The solidification structures of the specimen were found to consist of austenite dendrite(${\gamma}$), $ ({\gamma}+ M_7C_3)$ eutectic and $({\gamma}+ M_6C)$ eutectic in the alloy No. 1, proeutectic MC, austenite dendrite(${\gamma}$), (${\gamma}$+MC) eutectic and $({\gamma}+ M_2C)$ eutectic in the alloy No. 2, and proeutectic $M_7C_3$ and $ ({\gamma}+ M_7C_3)$ eutectic in the alloy No 3. respectively.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.33 no.5C
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• pp.361-370
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• 2008

NoC is adopted for data communication between processors and IPs in MPSoC system. NoC has an advantage of scalability in that system can be easily expanded just by adding switches. However, as the number of switches increases, chip area increases as well as data transfer latency. This paper proposes an architecture that can reduce the number of switches in the system by sharing network interfaces. To reduce NI area, the modules sharing network interface use a common buffer in network interface. Experimental results show that the chip area has been reduced by 46.5% and data transfer latency by 17.1%, respectively, compared to conventional architecture.

• Transactions of the Korean Society of Automotive Engineers
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• v.20 no.4
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• pp.142-149
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• 2012

The reduction characteristics of $NO_2$ to NO are experimentally studied over a platinum-based catalyst, especially at lower temperatures below about $200^{\circ}C$. In the present work, two types of steady-state experiments, engine bench and synthetic gas bench tests, are carried out in sequence. Steady-state engine bench tests with the DOC mounted on a light duty 4-cylinder 2.0 liter turbocharged diesel engine are performed and prove that CO plays a major role in $NO_2$ abatement at temperatures below the light-off temperature of CO oxidation, about $200^{\circ}C$. Synthetic gas bench tests are then performed using synthetic gas mixtures with CO, $C_3H_6$, NO, $NO_2$, $O_2$, $H_2O$ and $N_2$ in the $140{\sim}450^{\circ}C$ T-range and show that both CO and $C_3H_6$ are capable of reducing $NO_2$. It is noted that the reaction rate of $NO_2$ with $C_3H_6$ is much higher than that with CO. At temperatures below about $200^{\circ}C$, the reduction of $NO_2$ to NO is promoted with increasing CO concentration and $NO_2$/$NO_X$ ratio and with decreasing $O_2$ concentration, as well as with the presence of $H_2O$.

• Transactions of the Korean Society of Automotive Engineers
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• v.21 no.6
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• pp.64-71
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• 2013

In this study we designed a lean $NO_x$ trap (LNT) model with $GT-POWER^{TM}$ program and then the LNT model was compared to the bench flow reactor test results. This model consists of 9 kinetic reactions to represent the main steps of NO oxidation, $NO_x$ adsorption, $NO_x$ release and then its reduction. The comparison was performed on the operating conditions at the space velocity of 50,000 1/hr and 80,000 1/hr with the temperature range of $200^{\circ}C{\sim}500^{\circ}C$ with the even spaced temperature step of $50^{\circ}C$. The experimental results show that the $NO_x$ conversion efficiency was enhanced by the temperature up to $350^{\circ}C$ and then decayed at higher temperatures. The LNT model predicts the similar trend of the $NO_x$ conversion efficiency to the experimental results below $350^{\circ}C$, but overestimates above $350^{\circ}C$. This overestimation comes from the higher reduction efficiency which was obtained by the different reduction gas composition such as $C_3H_6$ in the model to replace $CH_4$, $C_2H_4$ in the bench test.

• Microbiology and Biotechnology Letters
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• v.24 no.1
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• pp.59-66
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• 1996

Virginiae butanolide C(VB-C) is one of the butyrolactone autoregulators, which triggers the productin of virginiamycin in Streptomyces virginiae. To further understand the mechanism of virginiamycin induction, we isolated three mutants from S. virginiae by N-methyl-N'-nitrosoguanidine (NTG) treatment. The characteristics of the three mutants were confirmed as follows: the mutant No. 1 delayed the production of the VB-C, receptor and antibiotics; the mutant No.3 hyperproduced receptor; the mutant No.4 failed to produce the VB-C. The addition of synthetic VB-C couldn't induce the production of antibiotics in the mutant No.1 due to delayed production of receptor, could provoke the production of larger amount of antibiotics than parental wild type strain in the mutant No.3 due to the presence of large amount of receptor, and could induce production of very small amount of antibiotics in the mutant No.4 due to the absence of VB-C. Antimicrobial spectrum and HPLC analysis of the mutant No.1 and No.3 suggested that the VB-C might have a specific ability to induce the production of virginiamycin M and S. These results imply that the VB-C has an ability to trigger the production of virginiamycin under receptor existence in S. virginiae.

• Microbiology and Biotechnology Letters
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• v.3 no.3
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• pp.123-134
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• 1975

Out of 96 yeast strains isolated from various natural habitats, five strains were screened based on their ability to ferment agricultural biproducts such as rice-, barley-and wheat-bran, and sawdust. These were identified as Hansenula anomala var anomala, Candide utilis, C. pelliculosa, Debaryomyces hansenii, and Irpex lacteus. Using these yeasts the above mentioned agricultural biproducts were fermented in various combinations. The fermented product was fed to 180 male Starcroses for eight weeks and obtained a body weight increase of 15.1g a day, while the unfermented control feed increased 10.5g a day.

• The Journal of the Korea institute of electronic communication sciences
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• v.9 no.12
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• pp.1345-1352
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• 2014

Bus architecture of SoC has been replaced by NoC in recent years. Noc uses the multi-clock domains to transmit and receive data between neighbor network interfaces and they have same frequency, but a phase difference because of clock skew. So a synchronizer is used for a mesochronous frequency in interconnection between network interfaces. In this paper the metastability is defined and analyzed in a D latch and a D flip-flop to search the possibilities that data can be lost in the process of sending and receiving data between interconnects when a local frequency and a transmitted frequency have a phase difference. 180nm CMOS model parameter and 1GHz are used to simulate them in HSpice. The simulation results show that the metastability happens in a latch and a flip-flop when input data change near the clock edges and there are intermediate states for a longer time as input data change closer at the clock edge. And the next stage can lose input data depending on environmental conditions such as temperature, processing variations, power supply, etc. The simulation results are very useful to design a mescochronous synchronizer for NoC.

• Journal of the Korean Chemical Society
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• v.39 no.6
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• pp.440-445
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• 1995

The chemical compositions and stability constants, thermodynamic parameters for the neodymium(Ⅲ) complexes of substituted benzo-1,4,7,10,13-pentaoxacyclopentadecane(B15C5) have been determined by spectrophotometry and conductometry in methanol solution at various temperatures. As substituents, CH3, Br, CHO, NO2, and 3,4-(NO2)2 were used. In methanol solution the ratios of neodymium(Ⅲ) to the ligands in the complexes are 1 : 1. The stability constants were increased in order of B15C5-3,4-(NO2)2 < B15C5-NO2 < B15C5-CHO < B15C5-Br < B15C5 < B15C5-CH3. This observation can be explained in terms of the substituent effect. The order of stability constants was dimethylsulfoxide < acetone < acetonitrile in solution and the magnitudes were found to be inversely proportional to the solvents donicities. These results could be understood in terms of solvent basicity, ligand basicity, solvation of the cation, and entropy changes of complex formation.

• Journal of Energy Engineering
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• v.8 no.2
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• pp.279-284
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• 1999

Thermal analyses were conducted in a thermogravimetric analyzer by isothermal technique in order to characterize the Korean anthracites-nitrogen oxides reaction. The tested coal sample was Dogae anthracites and compared with SP-1 graphite. Carbon-NO and carbon-N$_2$O reactions were carried out with respect to isothermal reaction temperatures (550$^{\circ}C$-900$^{\circ}C$) and reactant gas partial pressures (5 kPa∼20 kPa). In NO reaction, measured reaction orders of NO concentration and activation energy were 0.45∼0.96 and 39∼l12 kJ/mol, respectively. In N$_2$O reaction, measured reaction orders of N$_2$O concentration and activation energy were 0.62∼0.87 and 190∼215.3 kJ/mol, respectively. Compared the Korean anthracites-nitrogen oxides reaction with the combustion reaction, the reaction rate in the oxidation below 700$^{\circ}C$ decreases in the order O$_2$>NO>N$_2$O. But above 700$^{\circ}C$, the reaction rate of N$_2$O is faster than that of NO.

• Archives of Pharmacal Research
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• v.22 no.1
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• pp.48-54
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• 1999

These studies were designed to examine the differential effect of nitric oxide (NO) and cGMP on glutamate neurotransmission. In primary cultures of rat cerebellar granule cells, the glutamate receptor agonist N-methyl-D-aspartate (NMDA) stimulates the elevation of intracellular calcium concentration ($[Ca^{2+}]_i$), the release of glutamate, the synthesis of NO and an increase of cGMP. Although NO has been shown to stimulate guanylyl cyclase, it is unclear yet whether NO alters the NMDA-induced glutamate release and ${[Ca^{2+}]}_i$ elevation. We showed that the NO synthase inhibitor, NG-monomethyl-L-arginine (NMMA), partially prevented the NMDA-induced release of glutamate and elevation of ${[Ca^{2+}]}_i$ and completely blocked the elevation of cGMP. These effects of NO on glutamate release and [Ca2+]i elevation were unlikely to be secondary to cGMP as the cGMP analogue, dibutyryl cGMP (dBcGMP), did not suppress the effects of NMDA. Rather, dBcGMP slightly augmented the NMDA-induced elevation of ${[Ca^{2+}]}_i$ with no change in the basal level of glutamate or ${[Ca^{2+}]}_i$. The extracellular NO scavenger hydroxocobalamine prevented the NMDA-induced release of glutamate providing indirect evidence that the effect of NO may act on the NMDA receptor. These results suggest that low concentration of NO has a role in maintaining the NMDA receptor activation in a cGMP-independent manner.