• Journal of KIISE
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• v.41 no.12
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• pp.1090-1098
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• 2014

In this paper, an improved ACDE (Adaptive Cauchy Differential Evolution) algorithm with faster convergence speed, called ACDE2, is suggested. The baseline ACDE algorithm uses a "DE/rand/1" mutation strategy to provide good population diversity, and it is appropriate for solving multimodal optimization problems. However, the convergence speed of the mutation strategy is slow, and it is therefore not suitable for solving unimodal optimization problems. The ACDE2 algorithm uses a "DE/current-to-best/1" mutation strategy in order to provide a fast convergence speed, where a control parameter initialization operator is used to avoid converging to local optimization. The operator is executed after every predefined number of generations or when every individual fails to evolve, which assigns a value with a high level of exploration property to the control parameter of each individual, providing additional population diversity. Our experimental results show that the ACDE2 algorithm performs better than some state-of-the-art DE algorithms, particularly in unimodal optimization problems.

• Polymer(Korea)
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• v.38 no.4
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• pp.417-424
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• 2014

Reactivity and rheological behavior of highly concentrated polymer bonded explosives (PBX) simulant was studied. As a binder, thermosetting hydroxyl terminated polybutadiene (HTPB) was used. By using bimodal $CaCO_3$ (size ratio 10:1) and sugar particles (size ratio 25:1) as fillers, maximum 75 v% filling was possible during melt mixing. The relative viscosities of bimodal suspension were much lower than those of unimodal one and showed minimum values at 0.25 of fine particle fraction. In curing experiment, as curing temperature increased, the time of initiation and completeness of curing reaction became shortened, the torque kept low, and the change of internal temperature decreased.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.2 no.3
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• pp.119-127
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• 1990

Wave directional spectrum estimation methods for irregular waves were considered in this study. Until now, the Longuet-Higgins Method (LHM) initiated by Longuet-Higgins et al. (1963) has been widely used, but resolutions of the estimation were found to be low. Kobune's Maximum Entropy Method (MEM) for the estimation of wave directional spectrum, bas-ed on the entropy Principle showed higher resolutions comparing with the LHM . If the wave directional spectrum is of Delta functions, the MEM is exact in its estimation. It was also found that for a unimodal spectrum, if the Mitsuyasu's spreading coefficient is above 5, the estimation resolutions were high. In bimodal spectrum, as the angle difference between the two peaks increased, the resolution improved. The energy seems to transfer to the smoother peak in the smoothing of peak's peakedness. LHM has a tendency to estimate bimodal spectrum as a unimodal spectrum ； thus, except for its computational speed, the resolution of LHM falls far below that of MEM.

• The Korean Journal of Malacology
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• v.29 no.1
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• pp.65-76
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• 2013

We investigated the gametogenic cycle and spawning seasons of the male Chlamys (Azumapecten) farreri nipponensis by qualitative and quantitative analyses, and also the size at 50% of group sexual maturity was calculated by the data of first sexual maturity. In this study, the male gametogenic cycle of this species by qualitative analysis was divided into five successive stages: early active stage (January to March), late active stage (March to April), ripe stage (April to August), partially spawned stage (July to September), and spent/inactive stage (August to January). The male gametogenic cycle showed similar patterns with monthly changes in the gonadosomatic index and condition index. Particularly, spawning in male scallop occurred once a year from July to September, unlike the spawning period of this species (from June to August) reported by the previous researchers. In quantitative statistical analysis using an image analyzer system, the patterns of monthly changes in the percent (%) of the areas occupied by spermatogenic stages to the testis areas in males showed a maximum in June, and then sharply dropped from July to September, 2006. From these data, it is apparent that the spawning season of C. (A.) farreri nipponensis occurred once per year from July to early September, indicating a unimodal gametogenic cycle during the year. Shell heights at 50% of group sexual maturity (RM50) fitted to an exponential equation were estimated to be 49.90 mm in males (considered to be one year old), and it was 100% for male scallops over 61.0 mm (considered to be two years old).

• Polymer(Korea)
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• v.36 no.5
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• pp.593-598
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• 2012

Solution polymerization behaviors of L-lactide using single and mixed aluminium catalyst systems were studied. Triisobutylaluminium (TIBA) was a reference catalyst for mixing. For the $Al(O-i-Pr)_3$/TIBA catalytic systems, the molecular weight of the resulting polylactide (PLA) decreased as the composition of $Al(O-i-Pr)_3$ increased. The higher molecular weight shoulder was revealed in their GPC curve. At TIBA of 80 mol% a bimodal GPC curve was shown. The conversion in the trimethylaluminium (TMA)/TIBA catalysts system decreased as the composition of TMA in the mixed catalyst increased. The conversion in the trioctylaluminium (TOA)/TIBA catalysts system decreased as the composition of TOA in the mixed catalyst increased. The unimodal molecular weight distribution was observed with the TOA/TIBA catalyst systems. The Al compounds-mixed catalyst could produce a higher molecular weight shoulder in the GPC curve.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.32 no.3
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• pp.173-181
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• 2019

To estimate probabilistic distribution function from experimental data, kernel density estimation(KDE) is mostly used in cases when data is insufficient. The estimated distribution using KDE depends on bandwidth selectors that smoothen or overfit a kernel estimator to experimental data. In this study, various bandwidth selectors such as the Silverman's rule of thumb, rule using adaptive estimates, and oversmoothing rule, were compared for accuracy and conservativeness. For this, statistical simulations were carried out using assumed true models including unimodal and multimodal distributions, and, accuracies and conservativeness of estimating distribution functions were compared according to various data. In addition, it was verified how the estimated distributions using KDE with different bandwidth selectors affect reliability analysis results through simple reliability examples.

• Journal of Environmental Science International
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• v.30 no.9
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• pp.727-739
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• 2021

Measurements on mass size distribution of roadside aerosols were obtained in downtown Jeju City from July 2018 to May 2020 using an 8-stage cascade impactor sampler and the compositions of aerosols were analyzed. The mass size distribution of total aerosols was bimodal with aerosols existing in both the fine and coarse modes. The mass size distributions of Na⁺, Mg²⁺, Ca²⁺, Cl^-, NH₄⁺ and SO₄^2- were unimodal, whereas that of K⁺ was bimodal. For NO₃^-, the size distribution in winter and spring was bimodal with the peaks in both fine and coarse modes, whereas for summer and autumn the distribution was unimodal with a peak in the coarse mode. NH₄⁺ was found to co-exist with SO₄^2- in the fine mode with an average molar ratio of [NH₄⁺]/[SO₄^2-] equal to 2.05. Good correlation was observed between NO₃^- and NH₄⁺ in the fine mode particles in spring and winter. Based on the value of the marine enrichment factor for Cl^-, Mg²⁺, K⁺, Ca²⁺ and SO₄^2-, it may be inferred that a major part of the roadside aerosols in downtown Jeju City was largely contributed by terrigenous sources, although the influence of sea salt was normally present.

• Journal of Environmental Health Sciences
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• v.30 no.4
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• pp.320-328
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• 2004

A number of health hazards are generated in welding processes. In this paper, the characteristics of fumes and some other hazardous agents in welding are reviewed. Fumes in welding are generated by complex mechanism like physical ejection of particles, oxidation-enhanced vaporization, vaporization-condensation-oxidation, and spatter contribution. Fume generation rates could be described as a power function in a given process. Most of fume constituents was originated from consumables rather than base metal. The mass distribution for the welding fumes is unimodal and very small to penetrate respiratory system. So, almost fractions of fumes are classified into the respirable particulate mass. Total chromium contents in FCAW were similar to those from SMAW whereas hexavalent chromium concentrations in fume were similar to those produced from MIG welding fume. Hexavalent chromium was mostly soluble which was similar to the characteristic solubility of fume hexavalent chromium from SMAW.

• Architectural research
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• v.13 no.4
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• pp.19-30
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• 2011

This investigation, based on empirical research, examined the role of complexity and order in the aesthetic experience of architectural forms. The basic assumption of this study was that perception in architectural form is a process of interpreting a pattern in a reductive way. Thus, perceptual arousal is not determined by the absolute complexity of a configuration. Rather, the actual perceived complexity is a function of the organization of the system (order). In addition, complexity and order were defined and categorized into four variables according to their significant characteristics; simple order, complex order, random complexity, and lawful complexity. The series of experiments confirmed that there is a point on the psychological complexity dimension which is optimal. By demonstrating that consensual and individual aesthetic preference can be measured to have a unimodal function of relationship with complexity, the results of the experiments indicated that complexity and orderliness are effective design factors for enhancing aesthetics of a building facade. This investigation offered a conceptual framework that relates the physical (architectural form) and psychological factors (complexity and order) operating in the aesthetic experience of building facades.

• Proceedings of the IEEK Conference
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• 2000.06d
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• pp.43-46
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• 2000

In this paper, we propose a fast adaptive diamond search algorithm(FADS) for block matching motion estimation. Fast motion estimation algorithms reduce the computational complexity by using the UESA (Unimodal Error Search Assumption) that the matching error monotonically increases as the search moves away from the global minimum error. Recently many fast BMAs(Block Matching Algorithms) make use of the fact that the global minimum points in real world video sequences are centered at the position of zero motion. But these BMAs, especially in large motion, are easily trapped into the local minima and result in poor matching accuracy. So, we propose a new motion estimation algorithm using the spatial correlation among the adjacent blocks. We change the origin of search window according to the spatially adjacent motion vectors and their MAE(Mean Absolute Error). The computer simulation shows that the proposed algorithm has almost the same computational complexity with UCBDS(Unrestricted Center-Biased Diamond Search)〔1〕, but enhance PSNR. Moreover, the proposed algorithm gives almost the same PSNR as that of FS(Full Search), even for the large motion case, with half the computational load.