• Korean Journal of Materials Research
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• v.22 no.5
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• pp.253-258
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• 2012

Activated magnetite ($Fe_3O_{4-{\delta}}$) was applied to reducing $CO_2$ gas emissions to avoid greenhouse effects. Wet and dry methods were developed as a $CO_2$ removal process. One of the typical dry methods is $CO_2$ decomposition using activated magnetite ($Fe_3O_{4-{\delta}}$). Generally, $Fe_3O_{4-{\delta}}$ is manufactured by reduction of $Fe_3O_4$ by $H_2$ gas. This process has an explosion risk. Therefore, a non-explosive process to make $Fe_3O_{4-{\delta}}$ was studied using $FeC_2O_4{\cdot}2H_2O$ and $N_2$. $FeSO_4{\cdot}7H_2O$ and $(NH_4)_2C_2O_4{\cdot}H_2O$ were used as starting materials. So, ${\alpha}-FeC_2O_4{\cdot}2H_2O$ was synthesized by precipitation method. During the calcination process, $FeC_2O_4{\cdot}2H_2O$ was decomposed to $Fe_3O_4$, CO, and $CO_2$. The specific surface area of the activated magnetite varied with the calcination temperature from 15.43 $m^2/g$ to 9.32 $m^2/g$. The densities of $FeC_2O_4{\cdot}2H_2O$ and $Fe_3O_4$ were 2.28 g/$cm^3$ and 5.2 g/$cm^3$, respectively. Also, the $Fe_3O_4$ was reduced to $Fe_3O_{4-{\delta}}$ by CO. From the TGA results in air of the specimen that was calcined at $450^{\circ}C$ for three hours in $N_2$ atmosphere, the ${\delta}$-value of $Fe_3O_{4-{\delta}}$ was estimated. The ${\delta}$-value of $Fe_3O_{4-{\delta}}$ was 0.3170 when the sample was heat treated at $400^{\circ}C$ for 3 hours and 0.6583 when the sample was heat treated at $450^{\circ}C$ for 3 hours. $Fe_3O_{4-{\delta}}$ was oxidized to $Fe_3O_4$ when $Fe_3O_{4-{\delta}}$ was reacted with $CO_2$ because $CO_2$ is decomposed to C and $O_2$.

• Rapid Communication in Photoscience
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• v.3 no.4
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• pp.70-72
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• 2014

Visible-light irradiation of MeCN solution containing di(hydroxo)metallo(tetraphenyl)porphyrin complex $(tppM(OH)_2$: 1a; $M=Sb(V)^+Br^-$, 1b; $M=P(V)^+Cl^-$, 1c; M=Ge(IV)) and 2-mercaptoethanol (2-ME) as a substrate under aerated condition gave bis(2-hydroxyethyl)disulfide (2-HEDS) as an oxidative product of 2-ME. It is indicated that the oxidation of 2-ME should proceed with a photocatalytic process by 1, because the turn over number (TON) for the formation of 2-HEDS was over unit. The TON was determined to be 642 as a maximum value when 1a was used as a sensitizer. The formation of 2-HDES was extremely slow under argon atmosphere. The fluorescence of 1 was not quenched by 2-ME at all, and the free energy change (${\Delta}G$) with electron transfer (ET) from 2-ME to excited triplet state of $1(^31^*)$ was estimated as a negative value. The quenching rate constant ($k_r$) of $^31^*$ by 2-ME, obtained by the kinetics for the formation of 2-HEDS, strongly depends on ${\Delta}G$. These findings indicate that 1-sensitized oxidation was initiated by photoinduced ET from 2-ME to $^31^*$ to generate both radical cation of 2-ME ($2-ME^{+\bulle}$) and porphyrin radical anion ($1^{-\bulle}$), resulting that the formation of 2-HEDS can be proceeded by the dimerization of $2-ME^{+\bulle}$, and through a catalytic cycle due to returning to 1 by the ET from $1^{-\bulle}$ to molecular oxygen.

• Journal of the Korean Chemical Society
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• v.27 no.3
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• pp.194-200
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• 1983

Effect of metallic salts added to the ${\alpha}-Fe_2O_3-HCl\;or\;{\alpha}-Fe_2O_3-H_2SO_4$ reaction systems were investigated by colorimetric and gravimetric determinations. While reductive salts exhibited remarkably enhanced reaction rate, non-reductive salts showed inhibitive results. We supposed that the improvement of dissolution rate of ${\alpha}-Fe_2O_3$ by the addition of $FeCl_2$, a reductive salt, to the ${\alpha}-Fe_2O_3-HCl$ system can be attributed to the formation of chloro-bridge between $Fe^{3+}\;and\; Fe^{2+}$, and therefore some partial electronic charge transfer from $Fe^{2+}\;to\;Fe^{3+}$ on the surface of ${\alpha}-Fe_2O_3$ will be easily achieved through the bridged bond. The transferred charge to the surface will reduce the positive charge of initial $Fe^{3+}$, and also result to reduce the lattice energy of that site. Assuming tothat there is a linear relationship between the lattice energy change and the change of activation energy of the reaction system, the transferred partial electronic charge to $Fe^{3+}$ of ${\alpha}-Fe_2O_3$ surface was calculated to be ca. 0.36e.

• Journal of Korean Society on Water Environment
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• v.36 no.6
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• pp.508-520
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• 2020

Dam reservoirs have been reported to contribute significantly to global carbon emissions, but unlike natural lakes, there is considerable uncertainty in calculating carbon emissions due to the complex of emission pathways. In particular, the method of calculating carbon dioxide (CO2) net atmospheric flux (NAF) based on a simple gas exchange theory from sporadic data has limitations in explaining the spatiotemporal variations in the CO2 flux in stratified reservoirs. This study was aimed to analyze the spatial and temporal CO2 distribution and mass balance in Daecheong Reservoir, located in the mid-latitude monsoon climate zone, by applying a two-dimensional hydrodynamic and water quality model (CE-QUAL-W2). Simulation results showed that the Daecheong Reservoir is a heterotrophic system in which CO2 is supersaturated as a whole and releases CO2 to the atmosphere. Spatially, CO2 emissions were greater in the lacustrine zone than in the riverine and transition zones. In terms of time, CO2 emissions changed dynamically according to the temporal stratification structure of the reservoir and temporal variations of algae biomass. CO2 emissions were greater at night than during the day and were seasonally greatest in winter. The CO2 NAF calculated by the CE-QUAL-W2 model and the gas exchange theory showed a similar range, but there was a difference in the point of occurrence of the peak value. The findings provide useful information to improve the quantification of CO2 emissions from reservoirs. In order to reduce the uncertainty in the estimation of reservoir carbon emissions, more precise monitoring in time and space is required.

• Journal of Information Technology Services
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• v.22 no.1
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• pp.75-93
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• 2023

The game industry has grown not only by combining them with various technologies also introducing new types of business models such as P2P, F2P, and P2W. Furthermore, games which implemented X2E model with blockchain technology are recently in the spotlight of the public attention. As domestic game companies have also prospect the blockchain games feasible, they are seeking ways to expand their global market share by strengthening the X2E model. Hence, by carrying this new business model out, it is expected to diversify their global revenue stream, which was previously confined to Asia region. This study analyzed the case of companies that have implemented the P2E and C2E models in order to suggest the direction of development for the game platform in Web 3.0 era. The cases of P2E game platform, which constitute of Axie Infinity and Mir 4, encompass the compensation structure, the stabilization mechanism of the in-game token economy, and future strategies regarding blockchain gaming. Likewise, the platform structure, business model, and future growth potential was discussed in terms of C2E scheme, focusing on the ZEPETO and Roblox cases. Based on the above case analysis, this study attempted to provide information on the current limitations and development directions of the P2E and C2E platforms. The current limitations in legal and industrial aspects should be addressed to facilitate the blooming of blockchain and P2E game industry. In addition, the necessity of not only social support also improvement on the technology and social stigma of full-time creators is ought to be emphasized in an effort to encourage the development of C2E platforms.

• Mycobiology
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• v.45 no.2
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• pp.73-83
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• 2017

The ability of dead cells of endophytic Drechslera hawaiiensis of Morus alba L. grown in heavy metals habitats for bioremoval of cadmium ($Cd^{2+}$), copper ($Cu^{2+}$), and lead ($Pb^{2+}$) in aqueous solution was evaluated under different conditions. Whereas the highest extent of $Cd^{2+}$ and $Cu^{2+}$ removal and uptake occurred at pH 8 as well as $Pb^{2+}$ occurred at neutral pH (6-7) after equilibrium time 10 min. Initial concentration 30 mg/L of $Cd^{+2}$ for 10 min contact time and 50 to 90 mg/L of $Pb^{2+}$ and $Cu^{2+}$ supported the highest biosorption after optimal contact time of 30 min achieved with biomass dose equal to 5 mg of dried died biomass of D. hawaiiensis. The maximum removal of $Cd^{2+}$, $Cu^{2+}$, and $Pb^{2+}$ equal to 100%, 100%, and 99.6% with uptake capacity estimated to be 0.28, 2.33, and 9.63 mg/g from real industrial wastewater, respectively were achieved within 3 hr contact time at pH 7.0, 7.0, and 6.0, respectively by using the dead biomass of D. hawaiiensis compared to 94.7%, 98%, and 99.26% removal with uptake equal to 0.264, 2.3, and 9.58 mg/g of $Cd^{2+}$, $Cu^{2+}$, and $Pb^{2+}$, respectively with the living cells of the strain under the same conditions. The biosorbent was analyzed by Fourier Transformer Infrared Spectroscopy (FT-IR) analysis to identify the various functional groups contributing in the sorption process. From FT-IR spectra analysis, hydroxyl and amides were the major functional groups contributed in biosorption process. It was concluded that endophytic D. hawaiiensis biomass can be used potentially as biosorbent for removing $Cd^{2+}$, $Cu^{2+}$, and $Pb^{2+}$ in aqueous solutions.

• Bulletin of the Korean Chemical Society
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• v.34 no.1
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• pp.167-173
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• 2013

A series of highly efficient red phosphorescent heteroleptic iridium(III) complexes 1-6 containing two cyclometalating 2-(2,4-substitued phenyl)quinoxaline ligands and one chromophoric ancillary ligand were synthesized: (pqx)$_2Ir$(mprz) (1), (dmpqx)$_2Ir$(mprz) (2), (dfpqx)$_2Ir$(mprz) (3), (pqx)$_2Ir$(prz) (4), (dmpqx)$_2Ir$(prz) (5), (dfpqx)$_2Ir$(prz) (6), where pqx = 2-phenylquinoxaline, dfpqx = 2-(2,4-diflourophenyl)quinoxaline, dmpqx = 2-(2,4-dimethoxyphenyl)quinoxaline, prz = 2-pyrazinecarboxylate and mprz = 5-methyl-2-pyrazinecarboxylate. The absorption, emission, electrochemical and thermal properties of the complexes were evaluated for potential applications to organic light-emitting diodes (OLEDs). The structure of complex 2 was also determined by single-crystal X-ray diffraction analysis. Complex 2 exhibited distorted octahedral geometry around the iridium metal ion, for which 2-(2,4-dimethoxyphenyl)quinoxaline N atoms and C atoms of orthometalated phenyl groups are located at the mutual trans and cis-positions, respectively. The emission spectra of the complexes are governed largely by the nature of the cyclometalating ligand, and the phosphorescent peak wavelengths can be tuned from 588 to 630 nm with high quantum efficiencies of 0.64 to 0.86. Cyclic voltammetry revealed irreversible metal-centered oxidation with potentials in the range of 1.16 to 1.89 V as well as two quasi-reversible reduction waves with potentials ranging from -0.94 to -1.54 V due to the sequential addition of two electrons to the more electron-accepting heterocyclic portion of two distinctive cyclometalated C^N ligands.

• Journal of the Korean Solar Energy Society
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• v.23 no.2
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• pp.71-79
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• 2003

The goal of this paper is to measure and compare the performance of solar heat pump for refrigerants. To accomplish the goal, solar heat pump with aluminum roll bond type evaporator and indoor heat exchanged(condenser) was built. The test results showed that the COP and heating capacity of HFC-32/125/134a(23/25/52 wt%, $CH_2F_2/CF_3CHF_2/CF_3CH_2F$) were higher than those of HCFC-22$(CHClF_2)$. A study proved that best conditions to use heating system that is about $40m^2$ and $80m^2$. The COP range of the whole system was from 4 to 6 according to the solar collector's area variation. Hydrochlo-rofluorocarbon HCFC-22$(CHClF_2)$ is included in the compound to be controlled. HFC-32/125/134a(23/25/52 wt%, $CH_2F_2/CF_3CHF_2/CF_3CH_2F$) is the most suitable replacement HCFC-22$(CHClF_2)$ in solar heat pump application. The solar heat pump system was designed to show the best efficiency that the room temperature make $18\sim20^{\circ}C$ and $23\sim25^{\circ}C$ in Seoul during the fall season.

• Journal of Preventive Medicine and Public Health
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• v.52 no.2
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• pp.101-108
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• 2019

Objectives: To objectively determine and compare the physical activity (PA) levels of adults newly diagnosed with type 2 diabetes (T2D) and adults without T2D in Vietnam using an accelerometer. Methods: A total of 120 participants with newly diagnosed T2D and 120 adults without T2D were recruited from a large hospital in Hanoi, the capital city of Vietnam. All participants wore an ActiGraph GT3X accelerometer for at least 5 days, including 1 weekend day. Freedson cut-off points were used to estimate different intensities of PA. In addition, comparisons between groups were made with respect to achieving the World Health Organization (WHO) and International Diabetes Federation (IDF) recommended PA guidelines. Results: Men with T2D had significantly lower levels of PA than men without T2D. The respective multivariable-adjusted mean values of daily step count, daily light-intensity, moderate-intensity, and moderate-to-vigorous-intensity PA were approximately 14%, 19%, and 22% lower in the men with T2D than in their non-T2D counterparts. However, women with T2D accumulated a greater number of steps per day than women without T2D. Only 59.2% of the adults with T2D met the minimum recommended level of PA (WHO and IDF), compared to 74.2% of adults without T2D (p<0.05). After adjusting for potential confounders, participants with T2D experienced 50.0% significantly lower odds of achieving PA recommendations. Conclusions: Vietnamese men with T2D were less physically active than those without T2D, and adults with T2D were less likely to meet PA guidelines. The results suggest a need for integrating PA into the self-management of this chronic condition.

• Asia-pacific Journal of Multimedia Services Convergent with Art, Humanities, and Sociology
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• v.8 no.8
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• pp.825-834
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• 2018

Broadcasting is a basic data communication method for interconnection networks. There are two types of broadcasting. One-to-all broadcasting is to transmit a message from one node to all other nodes and all-to-all broadcasting is to transmit a message from all the nodes that have messages to other nodes. And by the using way of the transmission port per unit time, there are two schemes of broadcasting. Single port telecommunication(SLA) is to transmit messages from one node that contains the messages to one adjacent node only and all port telecommunication(MLA) is to transmit messages from one node to all adjacent nodes within a time of unit. Matrix hypercube is that an interconnection network has improved network cost than that of hypercube with the same number of nodes. In this paper, we analyze broadcasting scheme of matirx hypercube. First, we propose one-to-all and all-to-all broadcasting algorithms of matrix hypercube. And we prove that one-to-all broadcasting times are 2n+1 and $2{\lceil}{\frac{n}{2}}{\rceil}+1$ based on the SLA and MLA models, respectively. Also, we show all-to-all broadcasting time using SLA model is $5{\times}2^{\frac{n}{2}}-2$ when n=even, and is $5{\times}2^{\frac{n-1}{2}}+2$ when n=odd.