• The Journal of the Korea institute of electronic communication sciences
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• v.16 no.3
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• pp.493-502
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• 2021

A Vegetative Propagation by Runner(VPR) Algorithm-based on MPPT Algorithm that can track MPP by adapting to external environmental changes is presented. VPR is an optimization algorithm that mimics the plant ecology of movement and reproduction based on vegetation organs. The VPR algorithm includes a procedure for aging and a procedure for searching the surroundings by rhizomes. Accordingly, it is possible to continuously search around the optimal point. Therefore, the VPR-based MPPT algorithm can continuously search for an optimal point by adapting the changes in the external environment in the process of executing the MPPT algorithm. In this paper, we analyzed the performance of the VPR-based MPPT algorithm by a number of simulations. In addition, the superiority of performance was compared by performance comparison in the same environment as MPPT algorithm based on PSO.

• Investigative Magnetic Resonance Imaging
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• v.25 no.2
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• pp.118-128
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• 2021

Purpose: To investigate the value of MR textural analysis, including use of diffusion-weighted imaging (DWI) to differentiate malignant from benign soft-tissue tumors on 3T MRI. Materials and Methods: We enrolled 69 patients (25 men, 44 women, ages 18 to 84 years) with pathologically confirmed soft-tissue tumors (29 benign, 40 malignant) who underwent pre-treatment 3T-MRI. We calculated MR texture, including mean, standard deviation (SD), skewness, kurtosis, mean of positive pixels (MPP), and entropy, according to different spatial-scale factors (SSF, 0, 2, 4, 6) on axial T1- and T2-weighted images (T1WI, T2WI), contrast-enhanced T1WI (CE-T1WI), high b-value DWI (800 sec/mm²), and apparent diffusion coefficient (ADC) map. We used the Mann-Whitney U test, logistic regression, and area under the receiver operating characteristic curve (AUC) for statistical analysis. Results: Malignant soft-tissue tumors had significantly lower mean values of DWI, ADC, T2WI and CE-T1WI, MPP of ADC, and CE-T1WI, but significantly higher kurtosis of DWI, T1WI, and CE-T1WI, and entropy of DWI, ADC, and T2WI than did benign tumors (P < 0.050). In multivariate logistic regression, the mean ADC value (SSF, 6) and kurtosis of CE-T1WI (SSF, 4) were independently associated with malignancy (P ≤ 0.009). A multivariate model of MR features worked well for diagnosis of malignant soft-tissue tumors (AUC, 0.909). Conclusion: Accurate diagnosis could be obtained using MR textural analysis with DWI and CE-T1WI in differentiating benign from malignant soft-tissue tumors.

• Korean Journal of Radiology
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• v.20 no.4
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• pp.569-579
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• 2019

Objective: To investigate the usefulness of computed tomography (CT) texture analysis (CTTA) in estimating histologic tumor grade and in predicting disease-free survival (DFS) after surgical resection in patients with hepatocellular carcinoma (HCC). Materials and Methods: Eighty-one patients with a single HCC who had undergone quadriphasic liver CT followed by surgical resection were enrolled. Texture analysis of tumors on preoperative CT images was performed using commercially available software. The mean, mean of positive pixels (MPP), entropy, kurtosis, skewness, and standard deviation (SD) of the pixel distribution histogram were derived with and without filtration. The texture features were then compared between groups classified according to histologic grade. Kaplan-Meier and Cox proportional hazards analyses were performed to determine the relationship between texture features and DFS. Results: SD and MPP quantified from fine to coarse textures on arterial-phase CT images showed significant positive associations with the histologic grade of HCC (p < 0.05). Kaplan-Meier analysis identified most CT texture features across the different filters from fine to coarse texture scales as significant univariate markers of DFS. Cox proportional hazards analysis identified skewness on arterial-phase images (fine texture scale, spatial scaling factor [SSF] 2.0, p < 0.001; medium texture scale, SSF 3.0, p < 0.001), tumor size (p = 0.001), microscopic vascular invasion (p = 0.034), rim arterial enhancement (p = 0.024), and peritumoral parenchymal enhancement (p = 0.010) as independent predictors of DFS. Conclusion: CTTA was demonstrated to provide texture features significantly correlated with higher tumor grade as well as predictive markers of DFS after surgical resection of HCCs in addition to other valuable imaging and clinico-pathologic parameters.

• The Korean Journal of Pesticide Science
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• v.10 no.2
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• pp.76-83
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• 2006

In order to investigate the impacts of non-selective herbicide, glufosinate-ammonium (ammonium 4-[hydroxy(methyl)phosphinoyl] -DL-homoalaninate, GLA) to the non-target organisms, earthworm was exposed to GLA in the field soil for a month, and microbial populations in the soil were investigated after application of GLA. Simultaneously, the residues of GLA and its metabolite, 3-MPP were analyzed in the same soil. Meanwhile, to elucidate the influence of GLA to the growth of non-target crops incase of inter-furrow application, the amounts of carotenoid, chlorophyll, amino acid, proteins and sugars in the leaves of potato and chinese cabbage grown in the same field were investigated. In result, the dead earthworm was not observed during the test period, and the increasing rates of bodyweight were $9.410{\sim}11.603%$ in GLA-treated plots and 5.645% in GLA-untreated plots. The populations of fungi, bacteria and actinomycetes in the GLA-treated soils were $6.2{\times}10^4$, $1.5{\times}10^6$ and $5.7{\times}10^4$, respectively. They maintained relatively similar levels to the control which were $3.7{\times}10^4$, $3.7{\times}10^5$ and $3.7{\times}10^4$, respectively. In residue analysis, the limit of detection of GLA was 0.02 mg $kg^{-1}$, that of 3-MPP was the same level, and the half-life of GLA was 15 days in sandy clay loam soil. This result indicates that GLA was degraded very quickly in field soil. On the other hand, the amounts of physiological, biochemical components such as carotenoid, amino acid, chlorophyll, protein and sugar were ranged from 90.0 to 104.3% in potato and from 99.0 to 112.7% in chinese cabbage. Comparing with hand-weeded plots, it is indicated that GLA had not affected to the growth of non-target crops when applied at inter-furrow in crops-growing field.

• Korean Journal of Environment and Ecology
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• v.27 no.6
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• pp.765-776
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• 2013

This study was conducted to find out availability of a urban forest (Eudeungsan) as a substitute place of Mudeungsan Provincial Park (MPP) in overuse problem and to identify related factors to place substitutability. During June-August of 2012, 232 samples who have ever visited both of the two places (i.e., MPP and Euduengsan) in Gwang-ju city were selected by using convenient sampling and snowball sampling methods. Self-administered questionnaire survey was conducted, and the valid responses from 225 samples (97.0%) were used for data analysis. 24.2% of respondents had "considerably" or "very much" intention to use the substitute place, and 65.5% of respondents showed "a little" or "somewhat" 10.3% of respondents didn't have any intention to visit Eudeungsan as a substitute place of MPP. Generally, socio-demographic and visiting characteristics were not related with intention to visit Eudeungsan as a substitute place of MPP. It was only found that respondents who largely visit 'alone' to Eudeungsan tended to have higher intention to visit the substitute place than those who visit 'in group.' Three factors of reasons to visit Eudeungsan (i.e.,Challenge/self-development: ${\beta}=0.35$; Accessibility/familiarity: ${\beta}=0.27$; Adventure: ${\beta}=-0.19$) influenced intention to visit the substitute place. Relationship between reasons to visit and intention to visit the substitute place was found. No direct relationship was found between perceived similarity of the places and intention to visit substitute place, and similarity of recreation experiences showed perfect mediating effects between the two variables.

• Journal of Power Electronics
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• v.12 no.1
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• pp.164-171
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• 2012

Variable step size maximum power point trackers (MPPTs) are widely used in photovoltaic (PV) systems to extract the peak array power which depends on solar irradiation and array temperature. One essential factor which judges system dynamics and steady state performances is the scaling factor (N), which is used to update the controlling equation in the tracking algorithm to determine a new duty cycle. This paper proposes a novel stability study of variable step size incremental resistance maximum power point tracking (INR MPPT). The main contribution of this analysis appears when developing the overall small signal model of the PV system. Therefore, by using linear control theory, the boundary value of the scaling factor can be determined. The theoretical analysis and the design principle of the proposed stability analysis have been validated using MATLAB simulations, and experimentally using a fixed point digital signal processor (TMS320F2808).

• Proceedings of the KIPE Conference
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• 2011.11a
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• pp.267-268
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• 2011

In order to increase the efficiency of the PV solar can get maximum power output from a control is up. But MPPT request Converter since Solar module always work MPP about out condition. This paper study of 170W stand-alone PV MPPT system for charge and discharge control system of the battery. The proposed system is a way of Flyback converters, and controls the algorithm used P&O control method and ATmega128.

• Proceedings of the KIPE Conference
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• 2003.07a
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• pp.204-207
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• 2003

PV model is presented based on the shockley diode equation. The simple model has a photo-current source, an single diode junction and a series resistance and includes temperature dependences. An accurate PV module electrical model is presented, matching with boost converter MPPT strategy and demonstrated in Matlab for a typical general purpose solar cell. Given solar insolation and temperature, the model returns current vector and MPP.

• Proceedings of the Korean Institute of Intelligent Systems Conference
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• 2000.11a
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• pp.484-488
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• 2000

병렬 컴퓨터를 사용하는 경우 하드웨어만으로 모든 것이 해결되지 않으며 병렬처리 기법의 도입이 불가피하다. 효과를 극대화하기 위하여서는 각 병렬 컴퓨터의 하드웨어적인 특징을 극대화할 수 있는 병렬 알고리즘과 병렬 프로그램 등 소프트웨어 개발이 필수적이다. GMRES(Generalized Minimal residual) 방법은 아주 큰 대칭 또는 비대칭 선형시스템의 해를 구하는 반복법 중의 하나로 일반적으로 많이 사용되고 있다. 서로 직교인 벡터를 하나씩 구하는 대신에 선형인 s개의 벡터를 구하고 각 그룹간에는 직교가 되게하는 s-step GMRES 알고리즘은 병렬적 성질을 더 많이 가지고 있다. 이 병렬 알고리즘의 전반부는 이미 개발된 s-step Arnoldi 알고리즘을 이용할 수 있다. s-step GMRES 알고리즘은 message passing 병렬 시스템에서 모든 프로세서들 사이의 자료 교환 시간을 줄임으로써 기존의 GMRES 방법에 비해 훨씬 더 병렬성을 증가시킨다. 본 논문에서는 초병렬 시스템(MPP)인 Cray T3E에서 많은 프로세서를 이용할 경우 개발된 s-step 알고리즘이 기존의 알고리즘에 비하여 얼마나 더 효과적으로 빨리 수행될 수 있는지 분석한다.

• Proceedings of the Korean Institute of Intelligent Systems Conference
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• 2000.11a
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• pp.480-483
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• 2000

공학의 많은 응용분야에서 큰 회소 행렬(Large Sparse Matrices)에 대한 가장 작거나 또는 가장 큰 고유치(Eigenvalues)들을 요구하게 되는데, 이때 많이 이용되는 것은 Krylov Subspace로의 Projection방법이다. 대칭 행렬에 대해서는 Lanczos방법을, 비대칭 행렬에 대해서는 Biorhtogonal Lanczos방법을 이용할 수 있다. 이러한 기존의 알고리즘들은 새롭게 제안되는 병렬처리 시스템에서 효과적이지 못하다. 많은 프로세서를 가지는 병렬처리 컴퓨터 중에서도 분산 기억장치 시스템(Distributed Memory System)에서는 프로세서들 사이의 Data Communication에 필요한 시간을 줄이도록 해야한다. 본 논문에서는 기존의 Lanczos 알고리즘을 수정함으로써, 알고리즘의 동기점(Synchronization Point)을 줄이고 병렬화를 위한 입상(Granularity)을 증가시켜서 MPP인 Cray T3E에서 Data Communication에 필요한 시간을 줄인다. 많은 프로세서를 사용하는 경우 수정된 알고리즘이 기존의 알고리즘에 비해 더 나은 speedup을 보여준다.