• Journal of Korean Society for Atmospheric Environment
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• v.27 no.2
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• pp.133-141
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• 2011

In this study, different calibration approaches for reduced sulfur compounds (RSCs) were investigated by using thermal desorption coupled with gas chromatography (GC) and pulsed flame photometric detection (PFPD). To evaluate the effects of calibration procedures, gaseous standards of 4 RSCs ($H_2S$, $CH_3SH$, DMS, and DMDS) prepared at 10 ppm level were analyzed at 7 loading injection volumes (40, 60, 80, 100, 160, 240, and 320 ${\mu}L$). The results were then compared with calibration curves made with the Z (zero offset) and N (non-zero offset) method. The concentrations of unknown samples were then quantified by using R (ratio) method in which the slope values are compared between standards and samples. Secondly, in A (average) method, results obtained from a multi-point analysis of unknown samples were also averaged to extract representative values for each sample. Results of both experiments showed that analytical error of low molecular weight components (such as $H_2S$ and $CH_3SH$) was greatly expanded with the Z method. In conclusion, the combined application of N-A method was the more realistic approach to reduce biases in the quantification of RSCs.

• Journal of Broadcast Engineering
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• v.20 no.1
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• pp.122-139
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• 2015

Though the digital transition of terrestrial TV has been completed, the transmission system for terrestrial radio has not been determined and terrestrial radio still keeps its analog transmission. This study, under coorientation model, aims to explore the cognitive difference in recognizing important factors to be considered in deciding the digital radio transmission system between the employees of terrestrial broadcasters and then crucial issues related to the factors are driven. It has been found that the most big cognitive difference among the employees of three major terrestrial broadcasters lies in selecting frequency band for digital radio transmission. But there was little difference of opinion on simultaneous production-transmission, efficiency of frequency usage, broadcast quality and standards of service. The most disputable point in transition to digital radio broadcasting is selecting the frequency band for digital radio between the frequency bands used for FM radio broadcast (88-108MHz), terrestrial DMB (VHF Ch7~13) and FM radio adjacent broadcast band (76~88MHz: VHF Ch5~6). So, the question concludes into the selection issue between DAB+, HD-Radio, and DRM+. To improve the quality of radio broadcasting service and enhance the satisfaction of listeners, it is desirable to allow to operate both production system and transmission station, to enhance high transmission efficiency with minimum transmission facility, and to permit new entrance of broadcasters.

• Corrosion Science and Technology
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• v.7 no.6
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• pp.350-361
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• 2008

Canada's oil sands contain one of the largest reserves of oil in the world. According to recent estimates, there are nearly 180 billion barrels of oil in the Canadian oil sands trapped in a complex mixture of sand, water and clay. More than 40 companies have been currently operating or developing oil sands facilities since the first production in 1967. The process of oil sands upgrading is similar with down stream refinery, but the corrosion environment in upgrading refinery is often more severe than in the refinery because of high chlorides, mineral contents, carbonic acid, heavy viscosity and fouling, higher naphthenic acid [$NA-R(CH_{2})nCOOH$], and greater sulfur contents. Naphthenic acid corrosion (NAC) which is one of the most critical corrosion issues in up & downstream refinery plants was observed for the first time in 1920's in refinery distillation processes of Rumania, Azerbaizan (Baku), Venezuela, and California. As a first API report, the 11th annual meeting stated sources and mechanism of NAC in early 1930's. API has been developing the risk base standards, such as API RP580, 571, and Publication 581 which are based on the worst NAC damage in the world since 2000. Nevertheless not only the NAC phenomena and control in Canadian sands oil process are not much widely known but also there are still no engineering guidances for the Canadian sands oil in API standards. This paper will give NAC phenomina and materials selection guidance against NA environment in Canadian oil sands upgrading processes.

• 한국연소학회:학술대회논문집
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• 2004.11a
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• pp.141-145
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• 2004

The objective of the present study is to conduct model combustion tests for various injectors to identify their combustion stability characteristics. Three different double swirl coaxial injectors with variation of a recess length have been tested for the comparative study of CH flame structure and dynamic characteristics. Gaseous oxygen and mixture of gaseous methane and propane have been employed for simulating actual propellants used for a full-scale thrust chamber. Upon test results, the direct comparison between various types of injectors can be realized for the selection of the best design among prospective injectors.

• Journal of Korean Society for Atmospheric Environment
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• v.21 no.2
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• pp.269-274
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• 2005

In this work, analytical bias arising from the gas chromatographic determination of sulfur compounds was evaluated by the application of direct loop injection method to the GC/PFPD detection of four sulfur compounds including H$_{2}$S, CH$_{3}$SH, DMS, and DMDS. For the proper evaluation of analytical uncertainties involved in GC calibration, we employed two comparative techniques of calibration at fxed concentration injection (CFCI) vs calibration at fixed volume injection (CFVI) method. The results of our study indicate that CFCI method exhibits very poor sensitivity due to the matrix effect with varying injection volumes. On the other hand, as CFVI method overcomes such limitation, it can be used to obtain very accurate quantification of S compounds at their high concentration levels above a few to a few tens ppb.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.644-644
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• 2013

Graphene is a two-dimensional sp2 layer material. Despite the short history in the empirical synthesis of the graphene layers, the academic/industrial unique features have brought highly significant interest in research and development related to graphene-related materials. In particular, the electrical and optical performances have been targeted towards pre-existing microelectronicand emerging nanoelectronic applications. The graphene synthesis relies on a variety of processing factors, such as temperature, pressure, and gas ratios involving H2, CH4, and Ar, in addition to the inherent selection of copper substrates. The current work places its emphasis on the role of experimental factors in growing graphene thin films. The thermally-grown graphene layers are characterized using physical/chemical analyses, i.e., four point resistance measurements, Raman spectroscopy, and UV-Visible spectrophotometry. Ultimately, an optimization strategy is proposed in growing high-quality graphene layers well-controlled through empirical factors.

• Bulletin of the Korean Chemical Society
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• v.29 no.9
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• pp.1761-1764
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• 2008

The adsorption structure and binding of maleimide (MI) and succinimide (SI) on silver nanocolloidal surfaces have been comparatively investigated by means of pH-varied surface-enhanced Raman scattering (SERS). The two molecules appeared not to adsorb onto Ag surfaces at pH values below 5. The appearance of a ring ν (CH) band at ~3100 $cm^{-1}$ denoted the standing geometry of MI’s aromatic ring on Ag. The absence or weakness of in-plane vibrational modes of MI and SI also supported a perpendicular orientation of MI and SI on Ag from the electromagnetic selection rule. Density functional theory (DFT) calculations were employed to examine the vibrational frequencies of MI’s and SI’s neutral and anionic states.

• Proceedings of the IEEK Conference
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• 2007.07a
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• pp.13-14
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• 2007

We propose HERAH(Hierarchical Energy-Aware Routing Algorithm for Heterogeneous Wireless Sensor Networks) that is the hierarchical routing algorithm in WSNs and is established on heterogeneous environment. HERAH performs CH selection by considering residual energy level and uses multi-hop communication within cluster. So, HERAH makes improvements in the energy savings and the network lifetime compared with LEACH.

• Applied Chemistry for Engineering
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• v.25 no.5
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• pp.497-502
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• 2014

The conversion reaction of methane and carbon dioxide at an atmospheric pressure plasma reactor filled with Ni-$Al_2O_3$ and Ni-$MgAl_2O_4$ catalyst was performed. Effects of various process parameters such as the applied electric power, reaction gas flow rate, reactor temperature, mixing ratio of reactants and the presence of the catalyst on the reaction between methane and carbon dioxide were analyzed. From the analysis of the contribution of the catalyst in the reaction step, even if the temperature raised to $400^{\circ}C$, there was no spontaneous catalytic conversion of methane and carbon dioxide without plasma discharges. When the catalysts for the conversion of methane and carbon dioxide would be adopted to the plasma reactor, the careful selection of suitable catalysts and process parameters should be essential.

• Asian-Australasian Journal of Animal Sciences
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• v.31 no.6
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• pp.804-811
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• 2018

Objective: Complete mtDNA D-loop sequences of four Thai indigenous chicken varieties, including Pra-dhu-hang-dam (PD), Leung-hang-khao (LK), Chee (CH), and Dang (DA) were explored for genetic diversity and relationships with their potential ancestor and possible associates to address chicken domestication in Thailand. Methods: A total of 220 complete mtDNA D-loop sequences of the four Thai indigenous chicken varieties were obtained by Sanger direct sequencing of polymerase chain reaction amplicons of 1,231 to 1,232 base pair in size. A neighbor-joining dendrogram was constructed with reference complete mtDNA D-loop sequences of Red Junglefowl (RJF) and those different chicken breeds available on National Center for Biotechnology Information database. Genetic diversity indices and neutrality test by Tajima's D test were performed. Genetic differences both within and among populations were estimated using analysis of molecular variance (AMOVA). Pairwise fixation index ($F_{ST}$) was conducted to evaluated genetic relationships between these varieties. Results: Twenty-three identified haplotypes were classified in six haplogroups (A-E and H) with the majority clustered in haplogroup A and B. Each variety was in multiple haplogroups with haplogroups A, B, D, and E being shared by all studied varieties. The averaged haplotype and nucleotide diversities were, respectively 0.8607 and 0.00579 with non-significant Tajima's D values being observed in all populations. Haplogroup distribution was closely related to that of RJF particularly Gallus gallus gallus (G. g. gallus) and G. g. spadiceus. As denoted by AMOVA, the mean diversity was mostly due to within-population variation (90.53%) while between-population variation (9.47%) accounted for much less. By pairwise $F_{ST}$, LK was most closely related to DA ($F_{ST}=0.00879$) while DA was farthest from CH ($F_{ST}=0.24882$). Conclusion: All 4 Thai indigenous chickens are in close relationship with their potential ancestor, the RJF. A contribution of shared, multiple maternal lineages was in the nature of these varieties, which have been domesticated under neutral selection.