• Korean Journal of Materials Research
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• v.22 no.11
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• pp.620-625
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• 2012

A general synthetic method to make $Fe_3O_{4-{\delta}}$ (activated magnetite) is the reduction of $Fe_3O_4$ by $H_2$ atmosphere. However, this process has an explosion risk. Therefore, we studied the process of synthesis of $Fe_3O_{4-{\delta}}$ depending on heat-treatment conditions using $FeC_2O_4{\cdot}2H_2O$ in Ar atmosphere. The thermal decomposition characteristics of $FeC_2O_4{\cdot}2H_2O$ and the ${\delta}$-value of $Fe_3O_{4-{\delta}}$ were analyzed with TG/DTA in Ar atmosphere. ${\beta}-FeC_2O_4{\cdot}2H_2O$ was synthesized by precipitation method using $FeSO_4{\cdot}7H_2O$ and $(NH_4)_2C_2O_4{\cdot}H_2O$. The concentration of the solution was 0.1 M and the equivalent ratio was 1.0. ${\beta}-FeC_2O_4{\cdot}2H_2O$ was decomposed to $H_2O$ and $FeC_2O$4 from $150^{\circ}C$ to $200^{\circ}C$. $FeC_2O4$ was decomposed to CO, $CO_2$, and $Fe_3O_4$ from $200^{\circ}C$ to $250^{\circ}C$. Single phase $Fe_3O_4$ was formed by the decomposition of ${\beta}-FeC_2O_4{\cdot}2H_2O$ in Ar atmosphere. However, $Fe_3C$, Fe and $Fe_4N$ were formed as minor phases when ${\beta}-FeC_2O_4{\cdot}2H_2O$ was decomposed in $N_2$ atmosphere. Then, $Fe_3O_4$ was reduced to $Fe_3O_{4-{\delta}}$ by decomposion of CO. The reduction of $Fe_3O_4$ to $Fe_3O_{4-{\delta}}$ progressed from $320^{\circ}C$ to $400^{\circ}C$; the reaction was exothermic. The degree of exothermal reaction was varied with heat treatment temperature, heating rate, Ar flow rate, and holding time. The ${\delta}$-value of $Fe_3O_{4-{\delta}}$ was greatly influenced by the heat treatment temperature and the heating rate. However, Ar flow rate and holding time had a minor effect on ${\delta}$-value.

• 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.

• Food Science and Preservation
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• v.22 no.4
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• pp.559-566
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• 2015

The aim of this study was to develop an analytical method for determination of T-2 toxin and HT-2 toxin level in cereals and to survey their levels using LC-MS/MS. The T-2 and HT-2 toxins were simultaneously analyzed by electrospray ionization with a positive ion mode and multiple reaction monitoring (MRM) after filteration and immuno-affinity column clean-up. A matrix-matched standard calibration used for quantification and recoveries of T-2 and HT-3 toxins were in the range of $100.6{\pm}7.2%$ and $96.8{\pm}9.4%$, respectively. Limits of detection and quantification of T-2 and HT-2 toxins were estimated to be 0.5 and $1.5{\mu}g/kg$, respectively. Each repeatability (RSRr) of T-2 and HT-2 toxins was determined to be 0.9~6.0%, and 4.9~6.1%, respectively. Total 115 samples cereals were collected from 9 types of cereals for analysis. The positive percentages of T-2 and HT-2 toxins obtained from collected samples were found to be 72% and 80%, respectively. The contamination level of T-2 toxin and HT-2 toxin in cereals were $37.1{\mu}g/kg$, and $5.4{\mu}g/kg$, respectively. Therefore, this study suggests that the developed method could be an useful analytical method to determine the T-2 and HT-2 toxin level in cereals and the present data could be used as a reference to estimate the risk assessment.

• Asia-Pacific Journal of Business Venturing and Entrepreneurship
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• v.18 no.6
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• pp.159-172
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• 2023

This study aims to empirically investigate the relative effects of business-to-business (vs. business-to-consumer) business model innovation (BMI) on innovation performance. The research examines the impact of three key components of BMI: 1. value creation, 2. value proposition, and 3. value capture, on innovation performance. The 2022 Entrepreneurship Survey data by the Korean Entrepreneurship Foundation was used to analyze 2,879 companies. An exploratory data analysis (EDA) including various categories such as industry, firm, CEO, and technology chracteristics was conducted to show the latest startup status in Korea. The results show that value creation of B2B (vs. B2C) firms has a more positive and significant impact on innovation performance. Whereas, value proposition of B2C (vs. B2B) firms was found to have a more positive and significant effect on innovation performance. Interestingly, value capture did not show any effects for either type of firms. Additionally, the study employed seemingly unrelated regression (SUR) analysis for robustness checks. These findings provide important insights about the relative effects of B2B-BMI (vs. B2C-BMI).

• 대한공업교육학회지
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• v.30 no.1
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• pp.133-148
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• 2005

This research attempts to establish a strategy through which to secure the introduction of the KEM 2.0 system. Another aim of this research is to eventually establish a service system which can be used to automatically generate and provide the metadata information contained in the Cylearn system. in order to facilitate Korean vocational high school students access to teaching-learning materials. The main research tasks associated with this research were: 1) To establish the components of the file server system while taking into consideration the environment in which each educational organization operates; 2) To utilize the KEM 2.0 in order to optimize the configuration of the Cylearn system and the related software. To do so, the KEM 2.0. should be applied in close coordination with Edunet: The results of this research can be summarized as follows: First, a strategy to introduce the KEM 2.0 was established. To achieve this, the researcher analyzed the characteristics of the sequencing and presentation methods and suggested teaching-learning materials based on the KEM 2.0.s sequencing system. Second, the file server was constructed using the KEM 2.0. The established file server took into account the environmental conditions in which the Edunet system operates so as to facilitate the creation of a network system with Edunet. Third, the Cylearn service system was linked to Edunet. The researcher developed a module using the KEM 2.0. that could be used to transmit the metadata related to teaching-learning materials to Edunet. To achieve this, an input device and a databank which could be used to transfer the generated metadata to Edunet were developed. The input device and databank developed using the KEM 2.0. were used to transfer the metadata to Edunet by linking the Cylearn system to the Edunet system.

• Journal of the Korean Operations Research and Management Science Society
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• v.41 no.4
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• pp.55-73
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• 2016

Marketing activities play an important role in determining sales performances for B2B companies; however, prior research implies that the effect of marketing activities in the industrial market cannot be inferred from findings in the consumer market due to their differences such as types of customers or products. We further note that B2C companies (i.e. B2B client companies) serve individual consumers, and thus, B2B sales performance can be better understood as consumer market contexts are also taken into account. In this research, we study B2B marketing activities and B2C market contexts, and their effects on B2B sales performance. To this end, we focus on three factors : sales calls conducted by B2B companies, and market commercialization and social interactions in regions where B2C companies operate. Our empirical analyses provide the following results. First, B2B sales performance improves in proportion to sales calls. When sales calls serve as the means to provide product information, they help client companies understand product benefits and make purchases accordingly. Second, B2B sales performance increases as B2C markets become more commercialized, but the effect of sales calls on B2B sales declines. Commercialized markets are more attractive to individual consumers and thus, lead to greater sales in the consumer market. However, the role of sales calls as information sources weakens as B2C companies share product information themselves and develop expertise in commercialized markets. Finally, B2B sales are greater in urban markets compared to suburbs. However, the effect of sales calls on B2B sales increases in suburban markets compared to the urban counterpart. Cohesive social interactions in suburbs hinder information diffusion among B2C companies, which in turn strengthens the role of sales calls as information sources. We theoretically contribute to the B2B marketing literature and managerially suggest strategies to improve B2B sales performance.

• Journal of Korean Society on Water Environment
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• v.20 no.5
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• pp.488-493
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• 2004

The effects were examined from several conditions of $TiO_2$ photocatalysis reaction to phenols degradation by changing it's reacting conditions such as phenol concentration, pH, $TiO_2$ concentration, $H_2O_2$ concentration, flow rate, and intensity of ultraviolet rays. Phenol degradation was more efficient in low concentration of phenol, neutral pH. Phenol degradation appeared to increase as concentration of $TiO_2$ photocatalyst, that of $H_2O_2$ and intensity of ultraviolet rays increased. As $TiO_2$ dosage increased, initial rate constant k linearly increased. When $H_2O_2$ was injected more than optimum, phenol removal rate didn't increase in proportional to the change of $H_2O_2$ concentration as OH radicals was being consumed. When flow rate is less than $4.75m^3/m^2$ day, phenol removal efficiency appeared to decrease as ultraviolet rays transmission rate becomes low by $TiO_2$ suspension coated in photo reaction column. Meanwhile, initial rate constant according to light intensity change in less than $25mW/cm^2$ appeared to be in proportion to light intensity ($mW/cm^2$) Removal efficiency decreased about 12% after 180 minutes of reaction time while showed stable removal efficiency of 100% after 300 minutes when using regenerated $TiO_2$.

• Journal of the Korean Ceramic Society
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• v.24 no.2
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• pp.123-132
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• 1987

Yttria-stabilized zirconia with erbia-lanthana were investigated with respect to the amount of Ln2O3 (Ln; Er, La) addition in the range of 0.5∼5 mol% to the base composition of 8 mol% yttriazirconia. Following analysis and measurement were adopted for the characterization of synthesizes of solid electrolyte; phase transformation, lattice parameter, crystallite size, relative density, chemical composition and SEM/EDS. Electrical conductivity by two-probe method versus temperature from 350$^{\circ}C$ to 800$^{\circ}C$ and frequency in the range of 5Hz∼13MHz by complex impedance method was also conducted together with the determination of oxygen ion transference number by EMF method for the evaluation of their electrical properties. The results were as followsing; Electrical conductivity were decreased with increase in Ln2O3 content, but their activation energies increased. In the case of La2O3 addition, espicially, its electrical conductivity was decreased owing to the segregation of second phases at the grain-boundary. Grain-boundary conductivity of the specimen contained 0.5 mol% Er2O3 exhibited a maximum conductivity among thecompositions experimented. However, their bulk conductivities decreased in both case. Oxygen ion transference number was also reduced with decrease in oxygen partial pressure. For example, in the case of Er2O3 addition it retained value in the range of 0.97∼0.94 abvove 4.74${\times}$10-2in oxygen partial pressure. With the increase in the quantities of the evaporation of additive components, the crystallite size of stabilized zirconia decreased, and their relative density also reduced owing to the formation of porosity in their matrices. In the case of La2O3 the sinterbility was improved in the limited amount of addition up to 0.5 mol%, in the same range of addition the strength of sintered bodies were improved perhaps owing to the precipitation of metastable tetragonal phase in the fully stabilized zirconia.

• The Korean Journal of Ecology
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• v.15 no.3
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• pp.311-328
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• 1992

In other to classify calcicoles and calcifuges and calcifuges within plant communities occurring on limestone and granite soils in chungbuk province, korea, soil propertile, constancy for species by prsence or absence, and ratios of soluble to insoluble $Ca^{2+}$ and $Mg^{2+}$ were investigated. In the limestone soils ph values and $Ca^{2+}$ and $Mg^{2+}$ content, ranging 7.26 ~7.48, 5.32~7.37 mg $Ca^{2+}/g$ and 0.42~0.62 mg $Mg^{2+}/g$, respectively, were higher than those in the granite soil with ph 5.76, 1.03mg $Ca^{2+}/g$ and 0.24mg $Mg^{2+}/g$. species with high constancy in the 5 communities were classified into three groups; species group a(29~36% of total number of species) was composed of species occuring on the granite soil; group c(16~24%) is commonly distributed throughout both soils. Ratios of soluble to insoluble $Ca^{2+}$ and $Mg^{2+}$ ranged from 0.1 to 81.3 in the group a, 0.2 to 0.8 in the group b and 0.2 to 8.7 in the group c. species within each group can be divided into two groups based on the values of the ratio, below or above 1.0. consequently, each of the group a and c was classified again into two groups; the group a1 and c1 with the ratio of above 1.0 and the group a2 and c2 withbelow 1.0 but the ratio could not further subdivide the group b. from these results it was proposed that plants of the group a1 were termed as obligate calcicoles, the group b as obligate calcifuges, the group c1 as facultative calcicoles, the group c2 as facultative calcifuges and the group a2 as avoiding calcifuges.

• Economic and Environmental Geology
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• v.29 no.2
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• pp.105-117
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• 1996

The Baegjeon Au-Ag and Sb deposits, small of disseminated-type gold deposits are formed as a result of epithermal processes associated a shallow-seated Cretaceous Yeogdun granitoids intrusion. The orebodies are formed by the replacement of carbonate minerals in thin-bedded oolitic limestone beds favorable for mineralization within the upper-most Cambrian Pungchon Limestone Formation. The mineralization can be recognized one stage, ore minerals composed of base metal sulfides, electrum, AgSb-S, Ag-Cu-S, and Sb-S minerals. Gold-bearing minerals consist of electrum and submicroscopic invisible gold in pyrite and arsenopyrite. The composition of electrums ranges from 33.58 to 63.48 atomic % Ag. Fluid inclusion studies reveal that ore fluids were low saline $NaCl-CO_2-H_2O$ system. Temporary fluid mixing and boiling occured in later stage. Fluid inclusion data indicates the homogenization temperatures and salinities of NaCl eqivalent wt% were 176 to $246^{\circ}C$ and from 0.0 to 4.8 wt%, respectively. And $-logfs_2$, of mineralization obtained by thermodynamic considerations as 12.4 to 13.8 atm. The ${\delta}^{34}S_{H_2S}$, values of hydrothermal sulfides were calculated to be 6.8 to 10.2‰ which was of sedimentary origin. The ${\delta}^{18}O_{H_2O}$ and ${\delta}^{13}C_{CO_2}$, range from -3.9 to 9.6‰, from -1.1 to -2.2‰, and ${\delta}D$ range from -89 to -118‰, respectively. The Au deposition during mineralization seems to have occurred as a result of decrease of temperature, $fs_2$, $fo_2$, and pH probably due to oxidation by meteoric water mixing, which destabilized original $Au(HS)^-{_2}$. The mineralization of the Baegjeon deposits is similar to the Carlin-type deposits characterized by sediments-hosted epithermal bedding replacement disseminated gold deposits.