• Applied Chemistry for Engineering
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• v.31 no.5
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• pp.502-508
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• 2020

Dual drug-eluting stents (DES) is a primary treatment method for coronary arterial diseases in current interventional cardiology practice. However, their pathological results according to the sequence of coating of drugs have not been reported yet. The peptide-dopamine dissolved in acetonitrile was coated onto the Chonnam National University Hospital (CNUH) stent using an electrospinning coating machine. For secondary coating (e.g., sirolimus coating, designated as SPS), sirolimus (SRL) and poly lactic-glycolic acid (PLGA) were mixed in tetrahydrofuran (THF), and the solution was then coated on the CNUH stent that had underwent the primary peptide coating using an electrospinning and spray technique. Next, the peptide-dopamine was coated on the SRL-PLGA coated stent (PSS). In this study, it was confirmed that endothelialization was promoted without being significantly affected by the coating order (SPS or PSS). The sequence of drug and peptide coating may affect the development of restenosis and PSS was effective in the prevention of restenosis compared to that of using SPS.

• Journal of the Korean Ceramic Society
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• v.38 no.9
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• pp.817-821
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• 2001

A new $Mg_{2-x}MN_xSnO_4$ phosphor with an inverse spinel structure was synthesized by the solid-state reaction technique. The photoluminescence properties of the $Mg_2SnO_4$:Mn phosphors were investigated under 147nm -vacuum ultraviolet ray excitation. The Mn-doped $Mg_2SnO_4$ phosphor exhibited high emission intensity with the spectrum centered at 500nm wavelength. It was explained that the green emission in $Mg_2SnO_4$:Mn phosphor has originated from energy transfer from $^4T_1$ to $^6A_1$ of $Mn^{2+}$ ion at tetrahedral site of the spinel structure. The $Mn^{2+}$ ion concentration exhibiting the maximum emission intensity under the excitation of 147nm-vacuum ultraviolet ray was 0.25mol%. And the decay time of the phosphor was shorter than 10ms.

• Spatial Information Research
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• v.14 no.2 s.37
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• pp.223-234
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• 2006

In order to examine spatio-temporal characteristics of coastal water quality, we applied GIS spatial analysis to the water quality data collected from observation points located on Korean coastal area during 1997$\sim$2004. The water quality parameters measured included: chlorophyll-a, pH, DO, COD, SS, dissolved inorganic nitrogen, dissolved inorganic phosphorous, salinity, temperature. The water quality data used in this paper was obtained only at selected sites even though they are potentially available at any location in a continuous surface. Thus, it is necessary to estimate the values at unsampled locations so as to analyze spatial distribution patterns of coastal water quality, Owing to this reason, we applied IDW(inverse distance weighted) interpolation method to water quality data and evaluated the usefulness of IDW method. After IDW interfolation method was applied, we divided the Korean coastal area into 46 sections and examined spatio-temporal patterns of each section using GIS visualization technique. As a result of evaluation, we can blow that IDW interpolation and GIS are useful for understanding spatial and temporal distribution characteristics of coastal water quality data which is collected from a wide area far many years.

• Geophysics and Geophysical Exploration
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• v.20 no.4
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• pp.232-240
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• 2017

Normal moveout correction is one of the main procedures of seismic reflection data processing and a crucial pre-processing step for AVO analysis. Unfortunately, stretch phenomenon, which is the intrinsic problem of NMO correction, degrades the quality of stack section and reliability of AVO analysis. Although muting is applied to resolve this problem, it makes far-offset traces more useful to develop an advanced NMO correction technique without stretch. In this paper, easy and detailed explanations are provided on the definition and methodology of NMO correction, and then the cause of stretch is explained with its characteristics. A graphical explanation for NMO correction is given for the intuitive understanding of stretch phenomenon. Additionally, the theoretical formulation is derived to quantitatively understand the NMO correction. Through explaining the muting process to remove NMO stretch, the limitations of conventional methods are investigated and the need for a new resolution comes to discussion. We describe a stretch-free NMO correction based on inverse theory among many different stretch-free NMO corrections. Finally, the stretch-free NMO correction is verified through synthetic example and real data.

• Journal of Korea Water Resources Association
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• v.50 no.12
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• pp.849-862
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• 2017

The increased frequency of meteorological disasters has been observed due to increased extreme events such as heavy rainfalls and flash floods. Numerous studies using high-resolution weather radar rainfall data have been carried out on the hydrological effects. In this study, a conditional merging technique is employed, which makes use of geostatistical methods to extract the optimal information from the observed data. In this context, three different techniques such as kriging, inverse distance weighting and spline interpolation methods are applied to conditionally merge radar and ground rainfall data. The results show that the estimated rainfall not only reproduce the spatial pattern of sub-hourly rainfall with a relatively small error, but also provide reliable temporal estimates of radar rainfall. The proposed modeling framework provides feasibility of using conditionally merged rainfall estimation at high spatio-temporal resolution in ungauged areas.

• Journal of the Institute of Electronics Engineers of Korea CI
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• v.42 no.6
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• pp.63-74
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• 2005

In Electronic Commerce, the latest most of the personalized recommender systems have applied to the collaborative filtering technique. This method calculates the weight of similarity among users who have a similar preference degree in order to predict and recommend the item which hits to propensity of users. In this case, we commonly use Pearson Correlation Coefficient. However, this method is feasible to calculate a correlation if only there are the items that two users evaluated a preference degree in common. Accordingly, the accuracy of prediction falls. The weight of similarity can affect not only the case which predicts the item which hits to propensity of users, but also the performance of the personalized recommender system. In this study, we verify the improvement of the prediction accuracy through an experiment after observing the rule of the weight of similarity applying Vector similarity, Entropy, Inverse user frequency, and Default voting of Information Retrieval field. The result shows that the method combining the weight of similarity using the Entropy with Default voting got the most efficient performance.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.45 no.4
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• pp.1-8
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• 2008

In orthogonal frequency division multiplexing (OFDM) system the time selectivity of wireless channel introduces intercarrier interference (ICI), which degrades system performance in proportion to Doppler frequency. To mitigate the ICI effect, we can generally employ a classical zero-forcing (ZF) equalizer. However, the ZF scheme requires an inverse of a large matrix, which results in prohibitively high computational complexity. In this paper, we propose a low complexity ZF equalization scheme for suppressing the ICI caused by highly time-varying channels in OFDM systems. From the fact that the ICI on a subcarrier is mainly caused by several neighboring subcarriers, the proposed scheme exploits a numerical approximation for matrix inversion based on Neumann's Series (truncated second order). To further improve performance, the partial ICI cancellation technique is also used with reduced complexity. Complexity analysis and simulation results show that the proposed scheme provides the advantage of reducing computational complexity significantly, while achieving almost the same performance as that of the classical ZF a roach.

• Korean Journal of Clinical Pharmacy
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• v.18 no.1
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• pp.60-67
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• 2008

This study aimed to compare a microparticle enzyme immunoassay (MEIA) with a liquid chromatography-tandem mass spectrometry (LC/MS/MS) technique for the measurement of tacrolimus concentrations in adult liver transplant recipients, to investigate how the assay choice influenced the population pharmacokinetics of tacrolimus and to identify patient characteristics that affected pharmacokinetic parameters in each assay. Tacrolimus concentrations from 29 liver (n=52 paired-samples) transplant recipients measured by both MEIA and LC/MS/MS were used to evaluate the performance of these methods in the clinical setting. Tacrolimus pharmacokinetics was studied independently using MEIA and LC/MS/MS data in 70 adult patients using a population approach performed with NONMEM. Patient characteristics which influenced pharmacokinetic parameters in each assay were compared. The relation between LC/MS/MS and MEIA measurements was best described by the regression equation MEIA=1.465*LC/MS/MS-1.336 (r=0.91). Multiple linear regression analysis showed significant inverse relationships between assay difference and hematocrit (Hct) (p<0.025) in liver graft recipients. In MEIA, the population estimate of tacrolimus CL/F and apparent volume of distribution (Vd/F) were found to be 10.1 L/h and 226 L, and in LC/MS/MS, 13 L/h and 305 L respectively. Neither patient's age, weight, gender, grafted hepatic weight, albumin concentration, nor markers of liver function influenced tacrolimus CL/F The final model of CL/F was found to be 10.1+(Hct/Hct mean)$^{12.0}$ in MEIA and 13+(1+Hct/578) in LC/MS/MS indicating that CL/F was influenced by hematocrit.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.64 no.4
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• pp.605-611
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• 2015

The measurement and analysis of angular change have been studied in many fields. This study developed an angle measurement technique with optical fiber and photodiode. The position and attached angle of photodiode were investigated to find the proper combination of parameter. The results showed that the increased measuring range was achieved when the position of detector was away from the center of rotation. Inverse mathematical model was used to obtain angular changes with an optical fiber. The applications of this study include in optical sensor, joint angle measurement, and sport science.

• Proceedings of the KIEE Conference
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• 1998.07c
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• pp.918-922
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• 1998

With the development of industry, the qualitical advancement of power is needed. Since it is placed in the end step of power system, the fault at the distribution system causes some users blackout directly. So if the fault occurs, quick restoration is very important subject and, for the reason, induction of the distribution automation system is now being progressed briskly. For the quick restoration of the faulted distribution system, the load shedding of the blackout-area must be followed, and the other problems like the shedded load, faulted voltage and the rest may cause other accident. Accordingly load shedding must be based on the precise calculation technique during the distribution system load flow(dist flow) calculation. In these days because of its superior convergence characteristic the Newton-Raphson method is most widely used. The number of buses in the distribution system amounts to thousands, and if the fault occurs at the distribution system, the speed for the dist flow calculation is to be improved to apply to the On-Line system. However, Newton-Raphson method takes much time relatively because it must calculate the Jacobian matrix and inverse matrix at every iteration, and in the case of huge load, the equation is hard to converge. In this thesis. matrix equation is used to make algebraical expression and then to solve load flow equation and to modify above defects. Then the complex matrix is divided into real part and imaginary part to keep sparcity. As a result time needed for calculation diminished. Application of mentioned algorithm to 302 bus, 700 bus, 1004 bus system led to almost identical result got by Newton-Raphson method and showed constant convergence characteristic. The effect of time reduction showed 88.2%, 86.4%, 85.1% at each case of 302 bus, 700 bus system 86.4%, and 1004 bus system.