• Communications of the Korean Mathematical Society
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• v.15 no.1
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• pp.123-131
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• 2000

Let {X(t) : t $\geq$B 0} be a Symmetric $\alpha$ Stable and H-Self-similar process with stationary increments. We examine a.s. Holder unboundedness of S$\alpha$S H-sssi Chentsov processes and H-sssi Chentsov fields for order ${\gamma}$>H. Finally, we prove a.s. Holder continuity of S$\alpha$S H-sssi processes with ergodic seating transformations for the case of H>1/$\alpha$.

• Journal of the Korean Mathematical Society
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• v.41 no.6
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• pp.1071-1086
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• 2004

This paper is concerned with the strong consistency of the estimators of the autocovariance function and the spectral density function for the autoregressive process in the case where only an amplitude modulated process with missing data is observed. These results will give a simple and practical sufficient condition for the strong consistency of those estimators. Finally, some examples are given to illustrate the application of main result.

• Journal of Korean Society for Atmospheric Environment
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• v.32 no.6
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• pp.603-612
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• 2016

The objective of this study was to estimate the emission characteristics for PM, $PM_{10}$, and $PM_{2.5}$ in the various stationary sources. The particulate matters collected in the various stationary sources such as power plants (Coal and B-C oil), incinerators(municipal and industrial waste), and glass furnaces. The PM and $PM_{10}$, PM and $PM_{2.5}$, $PM_{10}$ and $PM_{2.5}$ samples were collected using the cyclone type $PM_{10}$, $PM_{2.5}$ samplers and 30 species(19 inorganic species, 9 ionic species, OC and EC) were analyzed by ICP, IC, and TOR/IMPROVE methods. The mass concentrations of PM, $PM_{10}$, $PM_{2.5}$ from nine stationary sources ranged $0.63{\sim}9.58mg/Sm^3$, $0.26{\sim}7.47mg/Sm^3$ and $0.13{\sim}6.34mg/Sm^3$, respectively. The level of $PM_{10}$, $PM_{2.5}$ portion in PM calculated 0.63~0.99, 0.38~0.94, respectively. In the case of emission trend for species, power plant showed high concentrations for Al, Mg, Na, Si, V and $SO_4{^{2-}}$, respectively. Also, Ca, Fe, K, Si, $Cl^-$, and $K^+$ showed high in incinerator. In the case of glass furnace, Na, Pb, K, Si, $Na^+$ and $SO_4{^{2-}}$ represented high concentrations. Power plant showed higher EC/OC concentrations than other sampling sites. These results suggest the possible role for complement establishment process of emission inventory and emission management for PM.

• KSBB Journal
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• v.25 no.3
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• pp.205-214
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• 2010

Many successive liquid-liquid extractions occur enabling purification of the crude material to occur. In high performance counter-current chromatography (HPCCC), crude material is partitioned between two immiscible layers of solvent phases. The stationary phase (SP) is retained by hydrodynamic force field effect and the mobile phase (MP) is pumped through the column. Purification occurs because of the different solubility of the components in the liquid mobile and stationary phases. There are many key benefits of liquid stationary phases such as high mass and volume injection loadings, total sample recovery, and easy scale-up. Many researchers showed that predictable scale-up from simple test is feasible with knowledge of the stationary phase retention for the planned process scale run. In this review we review the recent advances in HPCCC research and also describe the key applications such as natural products and synthetics (small or large molecules).

• Journal of Korean Society of Disaster and Security
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• v.13 no.3
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• pp.15-28
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• 2020

Hydrological data is very important in understanding the hydrological process and identifying its characteristics to protect human life and property from natural disasters. In particular, hydrological analysis are often performed assuming that hydrological data are stationary. However, recently climate change has raised the issue of climate stationary, and it is necessary to analyze the nonstationary of the climate. In this study, a method to analyze the stationarity of hydrological data was examined using the annual precipitation of 37 meteorological stations with long - term record data. Therefore, in this study, the stationary was determined by analyzing the persistence, trend, and stability using annual precipitation. Overall results showed that a trend was observed in 4 out of 37 stations, stable was investigated at 15 stations, and persistence was shown at 4 stations. In the stationary analysis using the annual precipitation data, 25 stations (67% of 37 stations) were nonstationary.

• Structural Engineering and Mechanics
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• v.85 no.4
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• pp.531-543
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• 2023

The existing concrete bridges are time-varying working systems, where the maintenance strategy should be planned according to the time-varying performance of the bridge. This work proposes a time-dependent residual capacity assessment procedure, which considers the non-stationary bridge load effects under growing traffic and non-stationary structural deterioration owing to material degradations. Lifetime bridge load effects under traffic growth are predicated by the non-stationary peaks-over-threshold (POT) method using time-dependent generalized Pareto distribution (GPD) models. The non-stationary structural resistance owing to material degradation is modeled by incorporating the Gamma deterioration process and field inspection data. A three-span continuous box-girder bridge is illustrated as an example to demonstrate the application of the proposed procedure, and the time-varying reliability indexes of the bridge girder are calculated. The accuracy of the proposed non-stationary POT method is verified through numerical examples, where the shape parameter of the time-varying GPD model is constant but the threshold and scale parameters are polynomial functions increasing with time. The case study illustrates that the residual flexural capacities show a degradation trend from a slow decrease to an accelerated decrease under traffic growth and material degradation. The reliability index for the mid-span cross-section reduces from 4.91 to 4.55 after being in service for 100 years, and the value is from 4.96 to 4.75 for the mid-support cross-section. The studied bridge shows no safety risk under traffic growth and structural deterioration owing to its high design safety reserve. However, applying the proposed numerical approach to analyze the degradation of residual bearing capacity for bridge structures with low safety reserves is of great significance for management and maintenance.

• Honam Mathematical Journal
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• v.27 no.2
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• pp.301-315
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• 2005

Let $\{A_u,\;u=0,\;1,\;2,\;{\cdots}\}$ be a sequence of coefficient matrices such that ${\sum}_{u=0}^{\infty}{\parallel}A_u{\parallel}<{\infty}$ and ${\sum}_{u=0}^{\infty}\;A_u{\neq}O_{m{\times}m}$, where for any $m{\times}m(m{\geq}1)$, matrix $A=(a_{ij})$, ${\parallel}A{\parallel}={\sum}_{i=1}^m{\sum}_{j=1}^m{\mid}a_{ij}{\mid}$ and $O_{m{\times}m}$ denotes the $m{\times}m$ zero matrix. In this paper, a functional central limit theorem is derived for a stationary m-dimensional linear process ${\mathbb{X}}_t$ of the form ${\mathbb{X}_t}={\sum}_{u=0}^{\infty}A_u{\mathbb{Z}_{t-u}}$, where $\{\mathbb{Z}_t,\;t=0,\;{\pm}1,\;{\pm}2,\;{\cdots}\}$ is a stationary sequence of linearly positive quadrant dependent m-dimensional random vectors with $E({\mathbb{Z}_t})={{\mathbb{O}}$ and $E{\parallel}{\mathbb{Z}_t}{\parallel}^2<{\infty}$.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.21 no.4
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• pp.525-540
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• 1997

The effect of mold rotation on the transport process and resultant macrosegregation pattern during solidification of an Al-Cu alloy contained in a vertical axisymmetric annular mold cooled from the inner wall is numerically investigated. The mold initially at rest starts to rotate at a prescribed angular velocity simultaneously with the beginning of cooling. Computed results for a representative case show that the mold rotation essentially suppresses the development of both thermal and solutal convections in the melt, creating distinct characteristics such as the liquidus front, flow pattern and temperature distribution from those for the stationary mold. Thermal convection which develops at the early stages of cooling is soon extinguished by the rotating flow induced during spin-up, and thus does not effectively remove the initial superheat from the melt. On the other hand, solutal convection, though it weakens considerably and is confined within the mushy zone, still predominates over the solute redistribution process. With increasing the angular velocity, the solute transport in the axial direction is enhanced, whereas that in the radial direction is reduced. The final macrosegregation formed in the mold rotating at moderate angular velocities appears to be favorable in comparison with the stationary casting, in that not only relatively homogenized composition is achieved, but also a severely positive-segregated channel is restrained.

• Journal of Electrochemical Science and Technology
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• v.9 no.4
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• pp.320-329
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• 2018

Natural graphite is obtained from an abandoned open-cast mine and purified by a simple, eco-friendly and affordable beneficiation process including ball milling and flotation process. Both raw graphite (55 wt %) and its concentrate (85 wt %) were electrochemically tested in order to evaluate these materials as anode materials for Li-ion and Na-ion batteries. It was found that both raw and purified graphites exhibit good electrochemical activities with respect to lithium and sodium ions through completely different reaction mechanisms. The encouraging results demonstrated in this work suggest that both raw and graphite concentrates after flotation could be used respectively for stationary and embedded applications. This strategy would help in developing local electrical storage systems with a significantly low environmental footprint.

• Journal of Korean Institute of Industrial Engineers
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• v.8 no.1
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• pp.22-28
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• 1982

Under a continuous-review inventory system, the inventory position process was proved to be asymptotically independent of the general renewal demand processes, when the two processes form an asymptotic unimodel joint distribution. The analytical technique implemented through this work seems to be more like general, and so the periodic-review system can be similarly investigated. In conclusion, the results may be evaluated to direct to the analytical analyses of some inventory systems which have been treated under some restrictions on demand processes.