• The Journal of the Acoustical Society of Korea
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• v.21 no.5
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• pp.478-484
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• 2002

Linear towed arrays (LTA) have a nonlinear shape due to tow vessel motion, ocean swells and currents. By reasons of nominally linear shape, various towed array shape estimation techniques have been developed since the perturbed shape cause the error in target detection. In this paper,, we propose the beamforming method for the perturbed LTA with simple structure. The proposed method linearizes a nonlinear phase of steering vector with position information measured by two reference sensors. It can be proved using some properties of Markov transition matrix, and iteration number of linearization process is decided by variance of cross phase difference. As a result of computer simulation in the ocean environment, beampattern of the proposed method is almost same with the ideal case in my type of array shape. In the signal-to-noise ratio (SNR) performance simlation, the DOA estimation performance of the proposed beamforming method is evaluated, and the comparison with Bartlett beamformer of the LTA shows that the proposed method can estimate. the spatial characteristic of sources more accuracy.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.10 no.6
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• pp.1186-1190
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• 2009

In this paper, we studied on a characteristic of movement of charged particle in equal electric field. In order to fabricate a panel, we used positive charged toner particles of black and negative one of yellow. Panel was biased rectangle pulse without any overshoot. Also, panel's optical characteristics with contrast ratio and viewing angle is measured with RT-200. Response time was measure by using incident laser and detective photodiode. The distribution of m/q of particles by driving in panel throughout the contrast ratio and response time. As a results, driving voltage, contrast ratio, and response time are decided by m/q of charged particles and when m/q of charged particles in panel have regular distribution, it is induce improvement driving characteristics.

• Journal of Korea Water Resources Association
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• v.46 no.4
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• pp.389-400
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• 2013

In this study, a conventional pipeline unsteady friction model has been integrated into Levenberg Marquardt method to calibrate friction coefficient in a pipeline system. The method of characteristics has been employed as the modeling platform for the frequency dependant model of unsteady friction. In order to obtain Hessian and Jacobian matrix for optimization, the direct differentiation of pressure to friction factor was calculated and sensitivities to friction for heads and discharges were formulated for implementation to the integration constant in the characteristic method. Using a hypothetical simple pipeline system, time series of pressure, introduced by a sudden valve closure, were obtained for various Reynolds numbers. Convergency in fiction factors were evaluated both in steady and unsteady friction models. The comparison of calibration performance between the proposed method and genetic algorithm indicates that faster and stabler behaviour of Levenberg Marquardt method than those of evolutionary calibration.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.21 no.12
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• pp.1447-1453
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• 2010

In this paper, the design and the fabrication of dual-band bandpass filter using two dual-mode resonators is presented. Dual-mode resonator using a short stub is miniaturized by inter-digital capacitor and stepped impedance. Two dual mode resonators are designed to have different resonant frequencies, one for the lower passband and the other for the upper passband. Transmission zero is positioned at low or high rejection bands with a sharp skirt characteristic. Dual-band operation can be achieved using dual feeding structure. For WLAN, the proposed filter at 2.45/5.25 GHz is designed and fabricated. The size of the filter is as compact as 1$10.83\;mm{\times}5.3\;mm$.

• Korean Journal of Materials Research
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• v.21 no.6
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• pp.314-319
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• 2011

Melt foaming method is one of cost-effective methods to make metal foam and it has been successfully applied to fabricate Mg foams. In this research, AZ31 Mg alloy ingot was used as a metal matrix, using AlCa granular as thickening agent and $CaCO_3$ powder as foaming agent, AZ31 Mg alloy foams were fabricated by melt-foaming method at different foaming temperatures. The porosity was above 41.2%~73.3%, pore size was between 0.38~1.52 mm, and homogenous pore structures were obtained. Microstructure and mechanical properties of the AZ31 Mg alloy foams were investigated by optical microscopy, SEM and UTM. The results showed that pore structure and pore distribution were much better than those fabricated at lower temperatures. The compression behavior of the AZ31 Mg alloy foam behaved as typical porous materials. As the foaming temperature increased from $660^{\circ}C$ to $750^{\circ}C$, the compressed strength also increased. The AZ31 Mg alloy foam with a foaming temperature of $720^{\circ}C$ had the best energy absorption. The energy absorption value of Mg foam was 15.52 $MJ/m^3$ at a densification strain of 52%. Furthermore, the high energy absorption efficiencies of the AZ31 Mg alloy foam kept at about 0.85 in the plastic plateau region, which indicates that composite foam possess a high energy absorption characteristic, and the Vickers hardness of AZ31 Mg alloy foam decreased as the foaming temperature increased.

• Journal of Korea Water Resources Association
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• v.44 no.5
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• pp.351-362
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• 2011

The soil moisture measurements and correlation analysis are presented to improve understanding the hydrological process at the hillslope scale. The rainfall events is a main driver of soil moisture variation, and its stochastic characteristic need to be properly treated prior to the correlation analysis between soil moisture measurements. Using field measurements for two designated periods during the late summer and autumn seasons in 2007 obtained from the Bumrunsa hillslope located at the Sulmachun watershed, prewhitened correlation analysis were performed for 8, 14, 7 and 7 relationships representing the vertical, lateral, recharge and return flows, for two designated periods, respectively. The analysis indicated both temporal and spatial variation patterns of hydrological processes, which can be explained by the relative contribution of matrix and macropore flows and the impact of transect topography, respectively.

• Asian Pacific Journal of Cancer Prevention
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• v.17 no.6
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• pp.2781-2785
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• 2016

Background: Matric metalloproteinase (MMP) 13 gene expression is increased in esophageal squamous cell carcinomas (ESCCs) and associated with increasing tumor invasion, lymph node involvement and decreased survival rates. Levels of the circulating enzyme may be elevated and used as a marker of tumor progression. In this study, clinical application of MMP-13 serum levels was evaluated for early detection, prediction of prognosis and survival time of ESCC patients. Materials and Methods: Serum levels of MMP13 were determined by ELISA in 66 ESCC patients prior of any treatment and 54 healthy controls for comparison with clinicopathological data through statistical analysis with Man Whitney U and Log-Rank tests. In addition, clinical value of MMP13 levels for diagnosis was evaluated by receiver operating characteristic (ROC) test. Results: The serum level of MMP-13 in patients (>250 pg/ml) was significantly higher than in the control group (<100 pg/ml) (p value=0.004). Also the results showed a significant correlation between MMP-13 serum levels with tumor stage (p value = 0.003), depth of tumor invasion (p value=0.008), involvement of lymph nodes (p value = 0.011), tumor size (p value = 0.018) and survival time. While there were no significant correlation with grade and location of tumors. ROC analysis showed that MMP-13 level is an accurate diagnostic marker especially to differentiate pre-invasive/ invasive lesions from normal controls (sensitivity and specificity: 100%). Conclusions: These findings indicate a potential clinical significance of serum MMP13 measurement for early detection and prognostic assessment in ESCC patients.

• Journal of agriculture & life science
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• v.43 no.4
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• pp.33-36
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• 2009

Globose to clavate base-ball sized, pear shaped, fruiting bodies were found under the Himalayan cedar, Cedrus deodora at less fertile and poor sandy poor soil in the campus of Gyeongsang National University in Jinju, Korea. The fruiting body was at first, round to club-shaped, usually with a narrow, rooting base with yellowish rhizomorphs attached to it and lack a volva and a sterile base. The peridium of fruiting body was tough and crusty. The peridioles were white pea-like capsules in a blackish matrix. The color change to darker tints of brown at the top of the exterior peridium reflected the gradual ripening of the interior gleba and peridioles, which proceeded from the top downward to become a mass of spore dust, appearing as cinnamon brown at the apex of the vertical section. At around this stage, the peridium cracked open linearly, exposing the gleba with powdery spores mass released from overmatured peridioles. Spores were more or less round, warty or spiny, 10 to $12{\mu}m$; globose, cinnamon brown in powdery mass, with spines up to $2{\mu}m$ long. The thin peridium ruptured further in response to the disintegration of the peridioles, releasing the powdery spores, which proceeded until whole fruiting body disappeared leaving the dry spore dust coats in the vicinity. The absence of a capillitium is a distinctive characteristic that distinguishes the specimen from other puff-ball fungi and from most of earthballs. Based on the above characteristics, the specimen was identified as Poslithus tinctorius.

• Polymer(Korea)
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• v.32 no.5
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• pp.458-464
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• 2008

A successful scaffold should have a highly porous structure and good mechanical stability. High porosity and appropriate pore size provide structural matrix for initial cell attachment and proliferation enabling the exchange of nutrients between the scaffold and environment. In this paper the highly porous scaffold of poly(${\varepsilon}$-caprolactone) electrospun nanofibers could be manufactured with an auxiliary electrode and chemical blowing agent (BA) under several processing conditions, such as the concentration of PCL solution, weight percent of a chemical blowing agent, and decomposition time of a chemical blowing agent. To attain stable electrospinnability and blown nanofiber mats having high microporosity and large pore, a processing condition, 8wt% of PCL solution and 0.5wt% of a chemical blowing agent under $100^{\circ}C$ and decomposition time of $2{\sim}3\;s$, was used. The growth characteristic of human dermal fibroblasts cells cultured in the mats showed the good adhesion and proliferation on the blown mat compared to a normal electrospun mat.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.19 no.3
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• pp.173-178
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• 2019

To analyze the diffraction properties of optical signals by periodic blazed 2D diffraction gratings, Toeplitz dielectric tensor is first defined and formulated by 2D spatial Fourier expansions associated with asymmetric blazed grating profile. The characteristic modes in each layer is then based on eigenvalue problem, and the complete solution is found rigorously in terms of modal transmission-line theory (MTLT) to address the pertinent boundary-value problems. Toeplitz matrix of symmetric and sawtooth profiles is derived from that of asymmetric blazed grating profile, and the diffraction properties for each profile are numerically simulated. The numerical results reveal that the asymmetric and symmetric profiles behave as anti-reflection GMR filter while the sawtooth profile works better as anti-transmission one rather than anti-reflection filter.