• Bulletin of the Korean Chemical Society
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• v.17 no.9
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• pp.794-798
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• 1996

Solid solutions of the nonstoichiometric Dy1-xSrxCoO3-y system with the compositions of x=0.00, 0.25, 0.50, 0.75, and 1.00 have been synthesized by the solid state reaction at 1000 ℃ under atmospheric air pressure. The crystallographic structures of the solid solutions are analyzed by the powder X-ray diffraction patterns at room temperature. The analyses assign the compositions of x=0.00 and 0.25 to the orthorhombic system with space group of Pbnm/D2h16, the compositions of x=0.50 and 0.75 to the tetragonal system like a typical SrCoO2.86, and the composition of x=l.00 or SrCoO2.50 to the brownmillerite type system with space group of I**a. The reduced lattice volumes increase with x value due to the larger radius of Sr2+ ion than that of Dy3+ ion. The mole ratio of Co4+ ion to total Co ion with mixed valence state between Co3+ and Co4+ ions at B sites or τ value has been determined by an iodometric titration. All the samples except for the DyCoO3 compound show the mixed valnce state and thus the composition of x=0.50 has the maximum τ value in the system. The oxygen vacancies increasing with x value are randomly distributed over the crystal lattice except for the composition of x=l.00 which have the ordering of the oxygen vacancies. The nonstoichiometric chemical formulas of the Dy1-xSrxCo3+1-τCo4+τO3-(x-τ)/2 system are formulated from the x, τ, and y values. The electrical conductivity in the temperature range of 100 to 900 K increases with τ value linearly because of positive holes of the Co4+ ions in π* band as a conducting carrier. The activation energy of the x=0.50 as Ea=0.17 eV is minimum among other compouds. Broad and high order transition due to the overlap between σ* and π* bands broadened by the thermal activation is observed near 1000 K and shows a low temperature-semiconducting behavior. Magnetic properties following the Currie-Weiss law show the low to high spin transition in the cobaltate perovskite. Especially, the composition of x=0.75 presents weak ferromagnetic behavior due to the Co3+-O2--Co4+ indirect superexchange interaction.

• Journal of Korea Port Economic Association
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• v.34 no.3
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• pp.133-158
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• 2018

The role and ratio of national vessels in the global container shipping market have reduced significantly due to the bankruptcy of Hanjin Shipping in early 2017. All import-export companies, as well as container ports in Korea, are facing a crisis. The Trump's tariff and trade battles have had a negative impact on the increase in the North American cargo. However, Chinese and Japanese container shipping companies, which merged with domestic container shipping companies, and mega carriers such as Maersk and CMA CGM have benefited from the decline in shipping supplies due to the collapse of Hanjin Shipping, the world's 10th largest container carrier in Korea. The import/export freight trade in Korea is witnessing the increasing stronghold of foreign carriers. This scenario is expected to weaken Korea's negotiation powers with overseas shipping companies in domestic ports, such as Busan and Kwangyang, thereby making it more challenging to attract shipping carriers. This study compares the global container-shipping network in 2007 and 2017 by combining the network topology of the social network analysis and the economics of the liner shipping connectivity index (LSCI) and the container port connectivity index (CPCI) analysis. The findings of this study are that the role of the ports across the world can be identified, and CPCI has a high correlation with the centrality index and freight volume data. These findings can contribute toward the utilization of the meaning of the necessary centrality index without an additional centrality analysis. This study can be applied not only to the call strategy of container carriers but also to the alliance and development strategy of Korean ports.

• Korean Journal of Optics and Photonics
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• v.14 no.3
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• pp.343-348
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• 2003

Indium tin oxide (ITO) thin films (170 nm) were grown by DC magnetron sputtering deposition on Coming glass substrates without a post annealing. The electrical transport and optical properties of the films have been investigated as a function of deposition temperature $T_{s}$ (10$0^{\circ}C$$\leq$ $T_{s}$$\leq$35$0^{\circ}C$) and oxygen partial pressure $P_{o_{2}}$, (0 $P_{o_{2}}$ $\leq$ 10$^{-5}$ torr). Films were deposited from a high density (99% of theoretical density) ITO target (I $n_2$ $O_3$: Sn $O_2$= 90 wt% : 10 wt%) made of ITO nano powders. With an increase of $T_{s}$ the electrical resistivity p of ITO thin films was found to decrease, but the mobility $\mu$$_{H}$ was found to increase. The carrier density nu shows the maximum value of 6.6$\times$10$^{20}$ /㎤ at $T_{s}$ = 30$0^{\circ}C$. At fixed Is, with an increase of the oxygen partial pressure, $n_{H}$ and $\mu$$_{H}$ were found to decrease, but p was found to increase. The minimum resistivity and maximum mobility values of the ITO films were found to be 0.3 mΩ.cm and 39.3 $\textrm{cm}^2$/V.s, respectively. The visible transmittance of the ITO films was above 80%.. 80%..

• Korean Journal of Soil Science and Fertilizer
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• v.40 no.5
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• pp.405-411
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• 2007

This study was carried out to measure insoluble phosphorus fractions content fixed in different soil type and isolate a superior phosphate solublizing bacteria(PSB) producing free phosphate in citrus orchard soil. Distribution of insoluble phosphate fraction ordered Al-P>Ca-P>Fe-P in the investigated citrus orchards. Insoluble phosphate fraction such as Al-P, Ca-P, Fe-P were higher in volcanic ash than in non-volcanic ash soil. A PSB with high holo zone in PDA-P medium isolated from citrus orchard soil. This strain identificated by MIDI system as Bacillus sphaericus. The optimum growth of pH and temperature were at 4~5, $30^{\circ}C$, respectively. When Bacillus sphaericus cultured at $25^{\circ}C$, 150 rpm condition in LB broth medium included different phosphate. Bacillus sphaericus produced free phosphate in the culture broth medium from tricalcium-phosphate(207.0 ppm), aluminium phosphate(324.5 ppm) and hydroxyapatite(334.8 ppm) and Phosphatase activity of Bacillus sphaericus was higher at $35^{\circ}C$ culture condition than that of $25^{\circ}C$. Two type preparation inoculated Bacillus sphaericus made with carrier materials such as Bentonite, $CaCO_3$, Sodium alginate. Density of PSB in this preparation conserved at $10^5c.f.u.\;g^{-1}$ level during storage in different temperature condition for 7 month. It also showed that free phosphate produced at PDA-P medium.

• Journal of Animal Science and Technology
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• v.63 no.5
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• pp.1126-1141
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• 2021

Recent evidence has shown that methionine (Met) supplementation can improve milk protein synthesis under hyperthermia (which reduces milk production). To explore the mechanism by which milk protein synthesis is affected by Met supplementation under hyperthermia, mammary alveolar (MAC-T) cells were incubated at a hyperthermic temperature of 42℃ for 6 h in media with different concentrations of Met. While the control group (CON) contained a normal amino acid concentration profile (60 ㎍/mL of Met), the three treatment groups were supplemented with Met at concentrations of 10 ㎍/mL (MET70, 70 ㎍/mL of Met), 20 ㎍/mL (MET80, 80 ㎍/mL of Met), and 30 ㎍/mL (MET90,90 ㎍/mL of Met). Our results show that additional Met supplementation increases the mRNA and protein levels of BCL2 (B-cell lymphoma-2, an anti-apoptosis agent), and decreases the mRNA and protein levels of BAX (Bcl-2-associated X protein, a pro-apoptosis agent), especially at an additional supplementary concentration of 20 ㎍/mL (group Met80). Supplementation with higher concentrations of Met decreased the mRNA levels of Caspase-3 and Caspase-9, and increased protein levels of heat shock protein (HSP70). The total protein levels of the mechanistic target of rapamycin (mTOR) and the mTOR signalling pathway-related proteins, AKT, ribosomal protein S6 kinase B1 (RPS6KB1), and ribosomal protein S6 (RPS6), increased with increasing Met supplementation, and peaked at 80 ㎍/mL Met (group Met80). In addition, we also found that additional Met supplementation upregulated the gene expression of αS1-casein (CSN1S1), β-casein (CSN2), and the amino acid transporter genes SLC38A2, SLC38A3 which are known to be mTOR targets. Additional Met supplementation, however, had no effect on the gene expression of κ-casein (CSN3) and solute carrier family 34 member 2 (SLC34A2). Our results suggest that additional Met supplementation with 20 ㎍/mL may promote the synthesis of milk proteins in bovine mammary epithelial cells under hyperthermia by inhibiting apoptosis, activating the AKT-mTOR-RPS6KB1 signalling pathway, and regulating the entry of amino acids into these cells.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.31 no.4
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• pp.154-158
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• 2021

The optical transmittance of Mn-doped SnO₂ monolayer film increased gradually from 80.9 to 85.4 % at 550 nm wavelengths upon increasing the O₂/Ar+O₂ concentration rate from 0 to 7.9 % and the band gap energy changed from 3.0 to 3.6 eV. The resistivity tended to decrease from 3.21 Ω·cm to 0.03 Ω·cm, reaching a minimum at 2.7 %, and then gradually increased from 0.03 to 52.0 Ω·cm at higher O₂/Ar+O₂ gas concentration ratio. Based on XPS spectra analysis, the Sn 3d_5/2 peak of Mn-doped SnO₂ single layer shifted slightly from 486.40 to 486.58 and O_1s peak also shifted from 530.20 to 530.33 eV with increase the O₂/Ar+O₂ concentration ratio. Therefore, the XPS spectra results indicate that a multiphase with SnO and SnO₂ coexisted in the sputtered Mn-doped SnO₂ monolayer film.

• Journal of Korea Trade
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• v.25 no.8
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• pp.57-74
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• 2021

Purpose - This study aims to analyze the characteristics of network construction by Norwegian Air and AirAsia X, which are recognized as leading airlines in the long-haul LCC market. Based on this analysis, this study intends to provide implications for networking strategies for Korean LCCs that seek to enter the long-haul market when the aviation market stabilizes again upon the end of the COVID-19 pandemic. Design/methodology - To conduct the network analysis on long-haul low-cost airlines, the Official Airline Guide (OAG) Schedule Analyzer was used to extract long-haul data of Norwegian Air and AirAsia X. To analyze the trend of the long-haul route network, we obtained the data from 3 separate years between 2011 and 2019. The network was analyzed using UCINET 6.0 in order to examine the network structure of long-haul low-cost airlines and the growth trend of each stage. Findings - Analyzing the network of long-haul routes by visualizing the network structure of low-cost carriers showed the following results. In its early years, Norwegian Air's long-haul route network, centering on regional airports in Spain and Sweden, connected European regions, the Middle East, and Africa. As time passed, however, the network expanded and became steadily strong as the airline connected airports in other European countries to North America and Asia. In addition, in 2011, AirAsia X showed links to parts of Europe, such as London and Paris, the Middle East and India, and Australia and Northeast Asia, centering on the Kuala Lumpur Airport. Although the routes in Europe were suspended, the network continued to expand while concentrating on routes of less than approximately 7,000 km. It was found that instead of giving up on ultra-long-haul routes such as Europe, the network was further expanded in Northeast Asia, such as the routes in Korea and Japan centering on China. Originality/value - Until the COVID-19 pandemic broke out, Norwegian Air actively expanded long-haul routes, resulting in the number of long-haul routes quintupling since 2011. The unfortunate circumstance, wherein the world aviation market was rendered stagnant due to the outbreak of COVID-19, hit Norwegian Air harder than any other low-cost carriers. However, in the case of AirAsia X, it was found that it did not suffer as much damage as Norwegian Air because it initially withdrew from unprofitable routes over 7,000 km and grew by gradually increasing profitable destinations over shorter distances. When the COVID-19 pandemic ends and the aviation market stabilizes, low-cost carriers around the world, including Korea, that enter the long-haul route market will need to employ strategies to analyze the marketability of potential routes and to launch the routes that yield the highest profits without being bound by distance. For stable growth, it is necessary to take a conservative stance; first, by reviewing the business feasibility of the operating a small number of highly profitable routes, and second, by gradually expanding these routes.

• Journal of Navigation and Port Research
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• v.45 no.6
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• pp.276-283
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• 2021

The capital structure of the shipping business, which is characterized by its capital intensity and extreme market volatility, is closely related to long-term stability. Research in this area has been conducted mostly in the form of deriving the determinants of capital structure from company-wise financial ratios. This research, on the other hand, has a different approach to the topic. It identifies the relationship between actual cash profit and loss and other variables - i.e. actual vessel prices, interest rates and leverage ratio - by employing historical simulation. The result demonstrates that the P anamax cash profit shows 0 (break-even point) when the debt weight reaches 64.38% (debt ratio 180.74%) and the Cape, 73.04% (debt ratio 270.92%). Additionally, the ships of different types show a divided pattern for the pre- and post-'Super Boom'. It indicates that the business area and the market cycle should be considered when a leverage strategy is established. This research benefits shipping companies set a rational leverage strategy as well as delivers a reasonable guideline to government authorities for the development of a sound policy on shipping finance.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.3
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• pp.29-34
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• 2019

Silicon carbide is considered to be a potentially useful material for high-temperature electronic devices, as its large energy band gap and the p-type and/or n-type conduction can be controlled by impurity doping. Particularly, electric conductivity of porous n-type SiC semiconductors fabricated from ${\beta}-SiC$ powder at $2000^{\circ}C$ in $N_2$ atmosphere was comparable to or even larger than the reported values of SiC single crystals in the temperature region of $800^{\circ}C$ to $1000^{\circ}C$, while thermal conductivity was kept as low as 1/10 to 1/30 of that for a dense SiC ceramics. In this work, for the purpose of decreasing sintering temperature, it was attempted to fabricate porous reaction-sintered bodies at low temperatures ($1400-1600^{\circ}C$) by thermal decomposition of polycarbosilane (PCS) impregnated in n-type ${\beta}-SiC$ powder. The repetition of the impregnation and sintering process ($N_2$ atmosphere, $1600^{\circ}C$, 3h) resulted in only a slight increase in the relative density but in a great improvement in the Seebeck coefficient and electrical conductivity. However the power factor which reflects the thermoelectric conversion efficiency of the present work is 1 to 2 orders of magnitude lower than that of the porous SiC semiconductors fabricated by conventional sintering at high temperature, it can be stated that thermoelectric properties of SiC semiconductors fabricated by the present reaction-sintering process could be further improved by precise control of microstructure and carrier density.

• Journal of the Microelectronics and Packaging Society
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• v.26 no.2
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• pp.15-21
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• 2019

We investigated the structural, electrical and optical properties of zinc oxide (ZnO) ultra-thin films grown at $150^{\circ}C$ by atomic layer deposition (ALD). Diethylzinc and deionized water were used as metal precursors and reactants, respectively, for the deposition of ZnO thin films. The growth rate per ALD cycle was a constant 0.21 nm/cycle at $150^{\circ}C$, and samples below 50 cycles had amorphous properties due to the relatively thin thickness at the initial ALD growth stage. With the increase of the thickness from 100 cycles to 200 cycles, the crystallinity of ZnO thin films was increased and hexagonal wurtzite structure was observed. In addition, the particle size of the ZnO thin film increased with increasing number of ALD cycles. Electrical properties analysis showed that the resistivity value decreased with the increase of the thin film thickness, which is correlated with the decrease of the grain boundary concentration in the thicker ZnO thin film due to the increase of grain size and the improvement of the crystallinity. Optical characterization results showed that the band edge absorption in the near ultraviolet region (300 nm~400 nm) was increased and shifted. This phenomenon is due to the increase of the carrier concentration with the increase of the ZnO thin film thickness. This result agrees well with the decrease of the resistivity with the increase of the thin film thickness. Consequently, as the thickness of the thin film increases, the stress on the film surface is relaxed, the band gap decreases, and the crystallinity and conductivity are improved.