• Journal of applied mathematics & informatics
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• v.22 no.1_2
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• pp.193-208
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• 2006

A modified BFGS algorithm for solving the unconstrained optimization, whose Hessian matrix at the minimum point of the convex function is of rank defects, is presented in this paper. The main idea of the algorithm is first to add a modified term to the convex function for obtain an equivalent model, then simply the model to get the modified BFGS algorithm. The superlinear convergence property of the algorithm is proved in this paper. To compared with the Tensor algorithms presented by R. B. Schnabel (seing [4],[5]), this method is more efficient for solving singular unconstrained optimization in computing amount and complication.

• Journal of radiological science and technology
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• v.45 no.1
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• pp.11-17
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• 2022

This study was purpose to quantitative assessment of the resolution characteristics by using American college of radiology(ACR) phantom for magnetic resonance imaging (MRI). The MRI equipment was used (Achiva 3.0T MRI, Philips system, Netherlands) and the head/neck matrix shim SENSE head coil were 32 channels(elements) receive MR coil. And the MRI equipment was used (Discovery MR 750, 3.0T MRI, GE medical system, America) and the head/neck matrix shim MC 3003G-32R 32-CH head coil were receive MR coil. As for the modulation transfer function(MTF) comparison result by using ACR magnetic resonance imaging phantom, the MTF value of the ACR standard T2 image in GE equipment is 0.199 when the frequency is 1.0 mm^-1 and the MTF value of the hospital T2 image in Philips equipment is 0.528. It was used efficiently by using a general sequence more than the standard sequence method using the ACR phantom. In addition it is significant that the quantitative quality assurance evaluation method for resolution characteristics was applied mutatis mutandis, and the result values of the physical image characteristics of the 3.0T MRI device were presented.

• Journal of Power Electronics
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• v.15 no.6
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• pp.1456-1467
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• 2015

This paper presents a novel close-loop control scheme based on small signal modeling and weighted composite voltage feedback for a three-phase input and single-phase output Matrix Converter (3-1MC). A small non-polar capacitor is employed as the decoupling unit. The composite voltage weighted by the load voltage and the decoupling unit voltage is used as the feedback value for the voltage controller. Together with the current loop, the dual-loop control is implemented in the 3-1MC. In this paper, the weighted composite voltage expression is derived based on the sinusoidal pulse-width modulation (SPWM) strategy. The switch functions of the 3-1MC are deduced, and the average signal model and small signal model are built. Furthermore, the stability and dynamic performance of the 3-1MC are studied, and simulation and experiment studies are executed. The results show that the control method is effective and feasible. They also show that the design is reasonable and that the operating performance of the 3-1MC is good.

• Journal of Power Electronics
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• v.19 no.1
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• pp.89-98
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• 2019

This paper analyzes the input side performance of a conventional three-phase to single-phase matrix converter (3-1MC). It also presents the input-side waveform quality under this topology. The suppression of low-frequency input current harmonics is studied using the 3-1MC plus capacitance compensation unit. The constraint between the modulation function of the output and compensation sides is analyzed, and the relations among the voltage utilization ratio and the output compensation capacitance, filter capacitors and other system parameters are deduced. For a 3-1MC without large-capacity energy storage, the system performance is susceptible to input voltage imbalance. This paper decouples the inner current of the 3-1MC using a Lyapunov function in the input positive and negative sequence bi-coordinate axes. Meanwhile, the outer loop adopts a voltage-weighted synthesis of the output and compensation sides as a cascade of control objects. Experiments show that this strategy suppresses the low-frequency input current harmonics caused by input voltage imbalance, and ensures that the system maintains good static and dynamic performances under input-unbalanced conditions. At the same time, the parameter selection and debugging methods are simple.

• The Journal of Fisheries Business Administration
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• v.38 no.3
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• pp.1-24
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• 2007

This study examines the relative competitive position of korean fisheries products market over period of 2001 to 2005 and selects strategic exported goods from its position provide against concluding FTA agreement with China and Japan. The portfolio approach is used to develope competitiveness-market share matrix. The position of each export countries on the competitiveness market share matrix will be in one of nine cells, with differing implications for their role in korean fisheries products market. Based the competitiveness market share matrix, each export countries are divided into first cell type, third cell type and ninth cell type and the items of ninth cell type are chosen as strategic exportable goods. The results of this study are summarized as follows: First, in the case of each country change aspect, China is trending to decrease quantity but shows number of item that increase gradually with high share still, and look trend that increase third cell type item too gradually, and in case of first cell type item is that competitive position is high more relatively than the Korea. In the case of Japan, ninth cell type item is falling gradually, and share does not show big change generally in case of first cell type item. Second, in the case of strategic exportable goods that analyze using domestic competitive position cell type and MCA with competitive position in domestic fisheries products market and export market, was appear by codfish(frozen), cuttle fish(frozen) etc. in case with China, and by mackerel(frozen), other sea bream(frozen), laver(dry), bathing(dry) etc. in case with Japan. And analyzed goods that have all export competitive advantages in both countries are roes of alaska pollack(frozen), other roes of fish(except frozen roes of alaska pollack), squid(frozen) etc.

• The Korean Journal of Physiology and Pharmacology
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• v.12 no.3
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• pp.125-129
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• 2008

The aim of this study was to determine whether single nucleotide polymorphisms (SNPs) of matrix metallopeptidase 2 (MMP2) are associated with obesity. MMP2 is an enzyme with proteolytic activity against matrix and nonmatrix proteins, particularly basement membrane constituents. To identify the relationship between polymorphisms of MMP2 and overweight/obese, we genotyped 5 SNPs (rs17242319, rs1053605, rs243849, rs2287074, and rs10775332) of the coding region of MMP2 using the Golden Gate assay on an Illumina BeadStation 500 GX. One hundred and forty two overweight/obese ($BMI\;{\ge}\;23$) and 145 normal (BMI 18 to < 23) subjects were analyzed. SNPStats, Haploview, HapAnalyzer, SNPAnalyzer, and Helixtree programs were used for the analysis of genetic data. A linkage disequilibrium (LD) block was discovered among the 5 SNPs selected, including rs17242319, rs1053605, rs243849, and rs2287074. Of the 5 polymorphisms, 2 synonymous SNPs [rs17242319 (Gly226Gly) and rs10775332 (Phe602Phe)] were found significant associations with overweight/obese. Recently, rs1132896 replaced rs17242319 as a new number (SNP database, BUILD 129). In haplotype analysis using Haploview, a haplotype (haplotype: CCCA) containing a meaningful polymorphism (rs17242319) was found to be significantly different. The results suggest that MMP2 may be associated with overweight/obese in Korean population.

• Journal of the Korea Society of Computer and Information
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• v.21 no.11
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• pp.17-21
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• 2016

Heterogeneity assessment of tumor in oncology is important for diagnosis of cancer and therapy. The aim of this study was performed assess heterogeneity tumor region in PET image using texture analysis. For assessment of heterogeneity tumor in PET image, we inserted sphere phantom in torso phantom. Cu-64 labeled radioisotope was administrated by 156.84 MBq in torso phantom. PET/CT image was acquired by PET/CT scanner (Discovery 710, GE Healthcare, Milwaukee, WI). The texture analysis of PET images was calculated using occurrence probability of gray level co-occurrence matrix. Energy and entropy is one of results of texture analysis. We performed the texture analysis in tumor, liver, and background. Assessment textural features of region-of-interest (ROI) in torso phantom used in-house software. We calculated the textural features of torso phantom in PET image using texture analysis. Calculated entropy in tumor, liver, and background were 5.322, 7.639, and 7.818. The further study will perform assessment of heterogeneity using clinical tumor PET image.

• Wind and Structures
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• v.23 no.4
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• pp.367-383
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• 2016

The influence mechanism of mean value components, noted as $P_0$, on POD applications for complete random fields $P_C(t)$ and fluctuating random fields $P_F(t)$ are illustrated mathematically. The critical philosophy of the illustration is introduction of a new matrix, defined as the correlation function matrix of $P_0$, which connect the correlation function matrix of $P_C(t)$ and $P_F(t)$, and their POD results. Then, POD analyses for several different wind pressure fields were presented comparatively as validation. It's inevitable mathematically that the first eigenmode of $P_C(t)$ resembles the distribution of $P_0$ and the first eigenvalue of $P_C(t)$ is close to the energy of $P_0$, due to similarity of the correlation function matrixs of $P_C(t)$ and $P_0$. However, the viewpoint is not rigorous mathematically that the first mode represents the mean pressure and the following modes represent the fluctuating pressure when $P_C(t)$ are employed in POD application. When $P_C(t)$ are employed, POD results of all modes would be distorted by the mean value components, and it's impossible to identify $P_0$ and $P_F(t)$ separately. Consequently, characteristics of the fluctuating component, which is always the primary concern in wind pressure field analysis, can only be precisely identified with $P_0$ excluded in POD.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.08a
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• pp.270-270
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• 2010

4족 반도체 원소 양자점들은 원소가 가지고 있는 반도체적 성질과, 양자점에서 나타나는 quantum confinements 적인 특성 때문에 전자재료나 광학적 분야, 특히 태양전지 분야에서 그 쓰임이 대두되고 있다. 이러한 4족 반도체 원소의 양자점들을 만들기 위한 여러 방법들이 시도되고 있는데, 그 중에서 특히 절연체 박막에 4족 반도체 원소의 양자점들을 만드는 방법에는 이온주입, PVD, 그리고 CVD 를 통한 multi-layer 증착후 열처리 과정을 반드시 포함하는 Stranski- krastanov 방법이 주로 사용되고 있다. 본 실험에서는 고체원소 이온주입이라는 방법을 통해 절연체 박막의 증착과 이온주입이 한 진공용기 내에서 연속공정으로 이루어 지면서, 별도의 열처리 과정 없이 결정화된 게르마늄 양자점을 만들어 보았다. 이는 (X-ray diffraction) XRD와 Raman spectroscopy로 결정화된 게르마늄을 확인할 수 있었으며, (X-ray photoelectron spectroscopy)XPS 데이터로도 순수한 게르마늄이 표면에서 깊이 방향으로 약 $1,000\;{\AA}$ 만큼 게르마늄 양자점들이 만들어 짐을 알 수 있었다. 마지막으로 (High resolution transmittance electron microscopy) HRTEM으로 그 양자점의 크기와 분포도 그리고 결정성을 알아 보았다.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.55 no.5
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• pp.272-277
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• 2006

The present study is devoted to investigate numerically the optical characteristics of multi-layer thin film structures such as $Si/SiO_2\;and\;Ge/Si/SiO_2$ by using the characteristics transmission matrix method. The reflectivity and the absorptivity rate for thin film structures are estimated for different incident angles of rays and various film thicknesses. In addition, the influence of wavelength on optical characteristics related to complex refractive index is examined. It is found that such wave-like characteristics are observed in predicting reflectivities and depends mainly on film thickness. Moreover, the present study predicts the film thickness for ignoring wave interference effects, and it also discusses the fundamental physics behind optical and energy absorption characteristics appearing in multi-layer thin film structures.