• Economic and Environmental Geology
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• v.30 no.1
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• pp.51-60
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• 1997

The high radon (Rn222) potentials of soil, groundwater, hotspring and indoor environments in the Taejon city area were delineated by use of an EDA RDA-200 radon detector. The U and Th contents were also analysed using a Multi Channel Analyzer to illustrate the sources of the radon potentials. The average U concentrations in Taejon vary according to the type of granites such as $4.14{\pm}2.36ppm$ in schistose granite (SG), $3.13{\pm}1.70ppm$ in biotite granite (BG) and $3.01{\pm}1.95ppm$ in two mica granite (TG). The U contents in the granites are closely related with the amounts of uraniferous minerals. However, the U contents in the soil are found to be $5.05{\pm}4.75ppm$ in TG, $4.07{\pm}1.69ppm$ in BG and $3.87{\pm}1.91ppm$ in SG which are mainly explained by the different cation exchange capacities (CEC) of the soils from various granites. The levels of soil radon are $552{\pm}656pCi/l$ in SG, in which levels at two locations exceed the level of 1,350 pCi/l established as guideline for follow-up action by the U.S. Environmental Protection Agency (EPA), $443{\pm}284pCi/l$ in TG and $224{\pm}115pCi/l$ in the BG. The soil radon concentrations are found to be proportional to the U content and hardness of the soils. The groundwater radon concentrations in the domestic wells of - 30~-100 m depth show that $6,907{\pm}4,665pCi/l$ in TG, $5,503{\pm}6,551pCi/l$ in SG and $2,104{\pm}1,157pCi/l$ in BG which are positively related with U contents in soils. The radon levels of six groundwater wells in TG and two in SG are greater than guideline for drinking water level, 10,000 pCi/l by EPA (1986). Average radon contents of hotsprings and public bathes in the TG area are $7,071{\pm}1,942pCi/l$ and $1,638{\pm}709pCi/l$, respectively, which are below the EPA standard for remedial action value of the 10,000 pCi/l. The mean indoor radon concentrations of the TG and SG areas are $1.60{\pm}1.20pCi/l$ and $1.60{\pm}0.70pCi/l$, respectively. The elevated indoor radon levels of 5.6 pCi/l and 6.7 pCi/l are found to be particularly in TG area, which exceeds 4 pCi/i guideline, correlating positively with the U contents in the soil and radon concentration in the groundwater.

• Food Science of Animal Resources
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• v.26 no.2
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• pp.245-251
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• 2006

This study was performed to investigate the changes of vitamin A, vitamin E, vitamin $B_l$ and vitamin $B_2$ contents in cow's raw milk collected from dairy farms in Chungcheong-do and Jeolla-do for a year. The contents of fat soluble vitamin A and E were changed as seasonal effect, but water soluble vitamin $B_l$ and $B_2$ contents were not changed as seasonal effect. Vitamin A content in cow's raw milk was as follows [minimum ${\sim}$maximum (mean), ug/100 mL]; $35.1{\sim}59.0$ (44.4) in spring, $36.7{\sim}65.6$ (50.0) in summer, $28.7{\sim}61.2$ (46.8) in autumn and $29.9{\sim}57.8$ (43.1) in winter. In case of vitamin E was as follows [minimum${\sim}$maximum (mean), ug/100 mL]; $28.3{\sim}59.2$ (45.8) in spring, $39.6{\sim}69.9$ (58.8) in summer, $35.0{\sim}62.8$ (46.2) in autumn and $26.0{\sim}55.4$ (41.5) in winter. In case of vitamin $B_l$ was as follow [minimum${\sim}$maximum (mean), ug/100 mL]; $27.7{\sim}57.9$ (42.84) in spring, $32.4{\sim}66.1$ (49.39) in summer, $34.1{\sim}63.7$ (46.69) in autumn and $20.6{\sim}61.4$ (43.20 in winter. The amounts of vitamin $B_2$ in cow's raw milk was as follows [minimum${\sim}$maximum (mean), ug/100 mL]; $150{\sim}182$ (160 in spring, $145{\sim}185$ (163) in summer, $149{\sim}180$ (166) in autumn and $148{\sim}190$ (167) in winter.

• Journal of the Korean Mathematical Society
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• v.44 no.1
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• pp.1-10
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• 2007

The purpose of this paper is to define generalized twisted q-Bernoulli numbers by using p-adic q-integrals. Furthermore, we construct a q-analogue of the p-adic generalized twisted L-functions which interpolate generalized twisted q-Bernoulli numbers. This is the generalization of Kim's h-extension of p-adic q-L-function which was constructed in [5] and is a partial answer for the open question which was remained in [3].

• Communications of the Korean Mathematical Society
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• v.10 no.1
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• pp.109-113
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• 1995

For a Hilbert space H, let L(H) denote the algebra of all bounded operators on H. For an $n \in N$, it is well known that any element $T \in L(\oplus^n H)$ is expressed as an $n \times n$ matrix each of whose entries lies in L(H) so that T is written as $$ (1) T = (T_{ij}), i, j = 1, 2, ..., n, T_{ij} \in L(H), $$ where $\oplus^n H$ is the direct sum Hilbert space of n copies of H.

• Journal of the Korean Mathematical Society
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• v.46 no.3
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• pp.577-588
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• 2009

In this paper, the author studies the k-th commutators of oscillatory singular integral operators with a BMO function and phases more general than polynomials. For 1 < p < $\infty$, the $L^p$-boundedness of such operators are obtained provided their kernels belong to the spaces $L(log+L)^{k+1}(S^{n-1})$. The results of the corresponding maximal operators are also established.

• Journal of the Korean Mathematical Society
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• v.44 no.3
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• pp.733-745
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• 2007

We prove the $L^p(1 boundedness of the parabolic Marcinkiewicz integral with the kernel function $\Omega{\in}L(log^+L)^{1/2}(S^{n-1})$. The result is an improvement and extension of some known results.

• Bulletin of the Korean Mathematical Society
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• v.34 no.1
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• pp.9-17
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• 1997

Define $\bar{g}{\upsilon, \omega) = -\upsilon_1\omega_1 + \cdots + \upsilon_n\omega_n$ for $\upsilon, \omega in R^n$. $R^n$ together with this metric is called the Lorentzian n-space, denoted by $L^n$, and $R^n$ together with the Euclidean metric is called the Euclidean n-space, denoted by $E^n$. A Lorentzian surface in $L^n$ means an orientable connected 2-dimensional Lorentzian submanifold of $L^n$ equipped with the induced Lorentzian metrix g from $\bar{g}$.

• Korean Journal of Food Science and Technology
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• v.50 no.6
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• pp.572-580
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• 2018

Biologically active substances including gamma-aminobutryric acid (GABA) were added into whey by co fermentation using Bacillus subtilis HA and Lactobacillus plantarum EJ2014. The first fermentation using B. subtilis HA with 5% monosodium glutamate (MSG) and 2% glucose enhanced the production of poly-${\gamma}$-glutamic acid (PGA), resulting in higher consistency of $4.09Pas^n$ as well as whey protein peptides. After the second fermentation using L. plantarum EJ2014, the remaining MSG (3.40%) as a precursor was completely converted to 2.21% GABA. Furthermore, the lactose content in whey decreased from 6.73 to 3.68% after co-fermentation, and the tyrosine content increased from 20.47 to 38.24%. Peptides derived of whey proteins were confirmed by SDS-PAGE. Viable cell counts of B. subtilis and L. plantarum were 5.83 log CFU/mL and 9.20 log CFU/mL, respectively. Thus, co-fermentation of whey could produce the novel food ingredient fortified with biologically active compounds including GABA, ${\gamma}$-PGA, peptides, and probiotics.

• Phonetics and Speech Sciences
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• v.15 no.4
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• pp.11-16
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• 2023

The present study examines how a cognitive attention affects Korean learners of English (L2) in perceiving the English stop voicing distinction (/d/-/t/). This study tested the effect of attentional distractor on primary and non-primary acoustic cues, focusing on the role of Voice Onset Time (VOT) and fundamental frequency (F0). Using the dual-task paradigm, 28 Korean adult learners of English participated in the stop identification task carried with (distractor) and without (no-distractor) arithmetic calculation. Results showed that when distracted, Korean learners' sensitivity to VOT decreased as priorly reported with native English speakers. Furthermore, as F0 is a primary cue for a L1 Korean stop laryngeal contrast, its role in L2 English voicing distinction was also affected by a distractor, without compensating for the reduced VOT sensitivity. These findings suggest that flexible use of multiple cues in L1 is not necessarily beneficial for L2 phonological processing when coping with a adverse listening condition.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.18 no.3
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• pp.355-362
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• 2020

The corrosion behavior of the Inconel X-750 alloy was investigated for its potential application under a Cl₂-O₂ mixed gas flow in an Ar atmosphere. The corrosion rate was found to be negligible at temperatures up to 400℃ under a flow rate of 30 mL·min^-1 Cl₂ + 170 mL·min^-1 Ar, whereas an exponential increase was observed in the corrosion rate at temperatures greater than 500℃. The suppression of the corrosion reaction due to the presence of O₂ was verified experimentally at flow rates of 30 mL·min^-1 Cl₂ (4.96 g·m^-2·h^-1), 20 mL·min^-1 Cl₂ + 10 mL·min^-1 O₂ (2.02 g·m^-2 ·h^-1), and 10 mL·min^-1 Cl₂ + 20 mL·min^-1 O₂ (1.34 g·m^-2·h^-1) under a constant Ar flow rate of 170 mL·min^-1 at 600℃ for 8 h. The surface morphology analysis results revealed that porous surfaces with tunnel-type holes were produced under the Cl₂-O₂ mixed-gas condition. Furthermore, the effects of the Cl₂ flow rate on the corrosion rate were investigated, indicating that its impact was negligible within the range of 5-30 mL·min^-1 Cl₂ at 600℃.