• Journal of the Korean Institute of Intelligent Systems
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• v.25 no.1
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• pp.15-21
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• 2015

In support vector machine, the values of parameters included in kernels affect strongly generalization ability. It is often difficult to determine appropriate values of those parameters in advance. It has been observed through our studies that the burden for deciding the values of those parameters in support vector regression can be reduced by utilizing ensemble learning. However, the straightforward application of the method to large scale problems is too time consuming. In this paper, we propose a method in which the original data set is decomposed into a certain number of sub data set in order to reduce the burden for parameter tuning in support vector regression with large scale data sets and imbalanced data set, particularly.

• 한국신재생에너지학회:학술대회논문집
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• 2005.06a
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• pp.42-46
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• 2005

In spite of fast growing of prediction codes, there is still not negligible uncertainty in their results. This uncertainty affects on the turbine structural design and power production prediction. With the growing size of wind turbine, reducing this uncertainty is becoming one of critical issues for high performance and efficient wind turbine design. In this respect, there are international efforts to evaluate and tune prediction codes of wind turbine. As the reference data for this purpose, field test data is not appropriate because of its uncontrollable wind characteristics and its inherent uncertainty. Wind tunnel can provide controllable wind. For this reason, NREL has done the full scale test of the 10m turbine at NASA-Ames. With this reference data, a blind comparison has been done with participation of 18 organizations with 19 modeling tools. The results were not favorable. In Europe, a similar project is going on. Nine organizations from five countries are participating in the MEXICO project to do full scale wind tunnel tests and calculation with prediction codes. In this study. these two projects were reviewed in respect of wind tunnel test and its contribution. As a conclusion, it is suggested that scale model wind tunnel tests can be a complementary tool to calculation codes which were evaluated worse than expected.

• Journal of the Korea Institute of Military Science and Technology
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• v.10 no.4
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• pp.20-29
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• 2007

The engagement control software embedded in the weapon control computer of the fire control center for air defense missile system is large-scale real-time software. The use of typical software development methodologies is not appropriate to develop such large-scale embedded software in terms of reusability, reliability, and productivity for the reason that it is significantly complicated, and highly dependent on hardware platforms and developers. In this paper, a model-based software architecture using components based on UML 2.0 for the engagement control software is presented in order to solve these problems. This software architecture is verified using the black-box test, the scenario-based test, and the Ethernet packet monitoring test methods. The results demonstrate that the developed software architecture can be employed to enhance reusability, maintainability, and productivity of large-scale embedded software.

• Transactions of the Korean Society of Mechanical Engineers
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• v.7 no.2
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• pp.193-203
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• 1983

The mixed convective heat transfer problems are characterized by the relatively significant contribution of buoyancy force to the transport processes of momentum and heat. Past analytical studies on this kind of problems have been carried out by employing either the conventional R-.epsilon. turbulence model which includes constant turbulent Prandtl number .sigma.$_{+}$ 1 or an extended R-.epsilon. turbulence model which takes account of the buoyancy effect in appropriate length scale equations. But in the latter case, the temperature variance .the+a.$^{2}$ over bar is approximated by a model under local equilibrium condition and the time scale ratio between velocity and temperature is assumed to be constant. These approximation is known to break down when the buoyancy effect is dominant. The present study is aimed at development of new computational turbulence closure level which can be applied to this rather complex turbulent process. The temperature variance is obtained directly by solving its dynamic transport equation and the time scale ratio which is variable in space is computed by a solution of a dynamic equation for the rate of scalar dissipation .epsilon.$_{\thetod}$ It was found that the computational results are in good agreement with available experimental data of wide range of unstable conditions.

• Interaction and multiscale mechanics
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• v.4 no.3
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• pp.187-206
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• 2011

Accurate estimations of pre-failure deformations and post-failure responses of geostructures require that the simulation tool possesses at least three main ingredients: 1) a constitutive model that is able to describe the macroscopic stress-strain-strength behavior of soils subjected to complex stress/strain paths over a wide range of confining pressures and densities, 2) an embedded length scale that accounts for the intricate physical phenomena that occur at the grain size scale in the soil, and 3) a computational platform that allows the analysis to be carried out beyond the development of an initially "contained" failure zone in the soil. In this paper, a two-scale micropolar plasticity model will be used to incorporate all these ingredients. The model is implemented in a finite element platform that is based on the mechanics of micropolar continua. Appropriate finite elements are developed to couple displacement, micro-rotations, and pore-water pressure in form of $u_n-{\phi}_m$ and $u_n-p_m-{\phi}_m$ (n > m) elements for analysis of dry and saturated soils. Performance of the model is assessed in a biaxial compression test on a slightly heterogeneous specimen of sand. The role of micropolar component of the model on capturing the post-failure response of the soil is demonstrated.

• Korean Journal of Child Studies
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• v.32 no.2
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• pp.35-52
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• 2011

The purpose of this study was to evaluate the validity and reliability of the Penn Interactive Peer Play Scale (PIPPS) for Korean young children, with a special confirmative factor analysis. The participants were composed of 435 5-to 6-year-old children and their parents, and 42 teachers. The instruments included the 32-item exploratory PIPPS (Choi & Shin, 2008), the Preschool Behavior Questionnaire (PBQ; Park, 1992), and the PIPPS on parental reporting. The PIPPS was confirmed, and supported the following constructs resulting in the investigation of 3 factors, 'play disruption', 'play interaction', and 'play disconnection', along with 30 items similar to the PIPPS (2008). Inter-correlations between the sub-factors of PIPPS with those of criterion measures were validated by ratings from the PBQ and the parent version of the PIPPS. The reliability coefficients of the sub-factors of the PIPPS ranged from .85 to .92. In conclusion, 3 factor structure of the PIPPS was appropriate to represent the interactive peer play of Korean young children.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.26 no.1
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• pp.203-210
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• 2002

The transmission pipeline industry spends many millions of dollars annually performing inline inspections, excavating sites of possible corrosion, and repairing or replacing damaged sections of pipe. New criteria fur evaluation of the integrity of corroded pipe have been developed in recent years to help in controlling these costs. These new criteria vary widely in their estimates of integrity and the most appropriate criterion fur a given pipeline is net always clear. This paper presents an overview, comparison and evaluation of acceptability criteria for corrosion deflects in pipelines. By full scale burst tests, this paper has assessed the relative accuracy of each of theses criteria in predicting burst pressure. Many of the criteria appear to be excessively conservative and indicate that deflects must be repaired when none is needed, based upon burst test data.

• Clinical and Experimental Pediatrics
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• v.59 no.10
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• pp.414-420
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• 2016

Purpose: We investigated behavioral problems, attention problems, and cognitive function in children and adolescents born small for gestational age (SGA). Methods: Forty-six SGA children born at term and 46 appropriate for gestational age (AGA) children born at term were compared. Psychiatric symptoms were examined with reference to the Korean-Child Behavior Checklist, Korean-Youth Self Report, and Attention Deficit Hyperactivity Disorder Rating Scale (ADHD-RS). Cognitive function was estimated using the Wechsler Intelligence Scale. Sociodemographic data were recorded from interviews. Results: SGA children had high scores on delinquent behavior, aggressive behavior, and the externalizing scale, and they also showed a propensity for anxiety and depression. The SGA group had a higher mean ADHD-RS score than the AGA group ($10.52{\pm}8.10$ vs.$9.93{\pm}7.23$), but the difference was not significant. The SGA group had a significantly lower verbal intelligence quotient (IQ) than the AGA group, but the mean scores of both groups were within normal limits. Conclusion: This study indicates marked behavioral problems, such as delinquency, aggressiveness, and anxiety and depression, as well as low verbal IQ in the SGA group than in the AGA group. Even in cases in which these symptoms are not severe, early detection and proper treatment can help these children adapt to society.

• Tribology and Lubricants
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• v.24 no.6
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• pp.320-325
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• 2008

The recent industrial application requires technical methods to get the cutting fluid droplet surfaces in particular from the viewpoint of topography and micro texture. To characterize the surface topography of droplet, the combination of the confocal laser scanning microscope (CLSM) and wavelet filtering is well suited for obtaining the droplet geometry encountered in tribological research. This technique indicates a better agreement in obtaining an appropriate droplet surface obtained by the CLSM over a detail range of surface accuracy (resolution: $2{\mu}m$). And the results allow an excellent accuracy in a measurement of a droplet surface. The combination of extended focal depth measurement configured and multi-scale wavelet filtering has proven that it can construct a droplet surface in a successive and accurate way. A multi-scale approach of wavelet filtering was developed based on the decomposition and reconstruction of droplet surface by 2D wavelet transform using db9 (a mother wavelet of daubechies). Also this technique can be extended to characterize the quantification of droplet properties and other field in a wide range of scales. Finally this method is verified to be a better droplet surface modeling in a micro scale arising in a mist machining.

• Journal of Korea Technical Association of The Pulp and Paper Industry
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• v.47 no.6
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• pp.5-21
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• 2015

The common production methods of nanocellulosic (cellulosic nanofibrils, CNF) materials from wood are being reviewed, together with large scale applications and particularly papermaking applications. The high energy demand for producing CNF has been one particular problem, which has been addressed over the years and can now be considered solved. Another problem was the clogging of homogenizers/microfluidizers, and the different routes to decrease the energy demand. The clogging tendency, related to the flocculation tendency of fibres is discussed in some detail. The most common methods to decrease the energy demand are TEMPO-oxidation, carboxymethylation and mechanical/enzymatic pre-treatments in the order of increased energy demand for delamination. The rheology characteristics of CNF materials, i.e. the high shear viscosity, shear thinning and the thixotropic properties are being illuminated. CNF materials are strength adjuvants that enhance the relative bonded area in paper sheets and, hence increase the sheet density and give an increased strength of the paper, particularly for chemical pulps. At the same time papers obtain a lower light scattering, higher hygroexpansion and decreased air permeability, similar to the effects of beating pulps. The negative effects on drainage by CNF materials must be alleviated through the appropriate use of microparticulate drainage aids. The use of CNF in films and coatings is interesting because CNF films and coatings can provide paper/board with good oxygen barrier properties, particularly at low relative humidities. Some other high volume applications such as concrete, oil recovery applications, automotive body applications and plastic packaging are also briefly discussed.