• Journal of Korean Society of Industrial and Systems Engineering
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• v.24 no.62
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• pp.1-10
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• 2001

The electronics industry is fast growing segment of manufacturing and service industries. It is important that the manufacturer develops a product with adequate life cycle, high quality, and low failure rate in the specified time period. Environmental Stress Screening(ESS) and burn-in are widely used in the electronic industry to assist in the elimination of early failure. In this research, we construct optimal cost model of combined ESS and burn-in under various warranty policy and establish optimal testing times for given environments. Also we conduct sensitivity analysis on various parameter. The results of this study are summarized as follows. Comparing free warranty policy to rebate warranty policy, optimal ESS time is longer under free warranty policy, and optimal burn-in time is longer under rebate warranty policy. Free warranty policy higher than rebate warranty policy in total cost.

• Journal of Forest and Environmental Science
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• v.20 no.1
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• pp.51-57
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• 2004

Some effective management schemes have been drawn up by reviewing the function and role of the forest in the viewpoint of groundwater. It is desirable for us to seek an model combined with existing green dam and under dam. Another model combined with under dam and divergent dam is also considered to be necessary depending on its geology. These can be an effective means in the present situation where large dam is not easy to be constructed in spite of growing demand of securing additional water resources.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.04a
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• pp.449-452
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• 2008

This study is to manufacture HSCC (High flowing Self-Compacting Concrete) be able to construction without vibration & hardening, and it is stable according to the change of the surface number of aggregate and to examine the factor of reduction occurred before after hardening through the indoor experiment. It is essential to use of the thickener to increase the viscosity in the combined HSCC. In this result, it make more bubbles than HSCC of pulverulent body. The result of study has shown, through the surface air bubble by not passed air bubbles within concrete after hardening, It has bad effect in not only appearance of structures but strength & duration. It is the experiment for air bubble of concrete according to the types of aggregate (fine aggregate), mixing time of concrete, exfoliation, material of model form and so that reduce the air bubble of combined HSCC. Experiments have shown, the effect of exfoliation was bigger than the effect of form for the performance of surface finishing of combined HSCC after hardening according to the exfoliation or material of model form and the opaque guris has good condition of finishing.

• Journal of Magnetics
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• v.16 no.2
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• pp.114-119
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• 2011

This paper presents a magnetization modeling method combined with material sensitivity information to identify the unknown magnetization distribution of a hull and improve the accuracy of the predicted fields. First, based on the magnetization modeling, the hull surface was divided into three-dimensional sheet elements, where the individual remanent magnetization was assumed to be constant. For a fast search of the optimum magnetization distribution on the hull, a material sensitivity formula containing the first-order gradient information of an objective function was combined with the magnetization modeling method. The feature of the proposed method is that it can provide a stable and accurate field solution, even in the vicinity of the hull. Finally, the validity of the method was tested using a scale model ship.

• Journal of Science Education
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• v.42 no.2
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• pp.132-147
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• 2018

The goal of this research is to suggest a theoretical process-centered assessment model based on Learning Progressions of key competencies in the context of STEAM instructions. The "Process-Products Combined Module-type (P2CM) STEAM Assessment Model (P2CM STEAM Assessment Model, hereafter) can be used both as an instructional model and as an assesment model, applicable for various STEAM topics and instructional types. consists of 3 axes. The first X axis stands for 4C competencies that should be emphasized through STEAM instruction. The second Y axis stands for the types and the hierarchy of STEAM instructions. The third Z axis stands for the assessment standards based on LP. We also exemplified an assessment module combined creativity competency with creativity-based instruction based on . Based on the research results, we suggested elaboration of assessment models based on Korean LP research outcomes, development and supply of formative assessment models through field-based in-depth research, modification of formative assessment models with the participation of teacher communities and in-service teachers, and the necessity of further research on assessment models for tracking LP.

• Journal of Power Electronics
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• v.18 no.1
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• pp.129-136
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• 2018

An accurate state-of-charge (SOC) estimation ensures the reliable and efficient operation of a lithium-ion battery management system. On the basis of a combined electrochemical model, this study adopts the forgetting factor least squares algorithm to identify battery parameters and eliminate the influence of test conditions. Then, it implements online SOC estimation with high accuracy and low run time by utilizing the low computational complexity of the unscented Kalman filter (UKF) and the rapid convergence of a particle filter (PF). The PF algorithm is adopted to decrease convergence time when the initial error is large; otherwise, the UKF algorithm is used to approximate the actual SOC with low computational complexity. The effect of the number of sampling particles in the PF is also evaluated. Finally, experimental results are used to verify the superiority of the combined method over other individual algorithms.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.27 no.6
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• pp.669-678
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• 2009

Real-time image georeferencing technologies are required to generate spatial information promptly from the image sequences acquired by a multi-sensor system. We thus derive a sequential adjustment algorithm based on the combined adjustment model. By adopting the sequential adjustment model, we develop a sequential AT(Aerial Triangulation) algorithm to georeference image sequences in real-time. The proposed algorithm enables to perform AT rapidly with the minimum computation at the current stage by using the results computed at the previous stage whenever a new image is added. Experiments with simulated data were conducted to verify the effectiveness of the proposed algorithm. The results of the experiments show that the georeferencing of each image took very short time and its accuracy was determined within ${\pm}4cm$ on the ground control points comparing to the results of the existing simultaneous AT.

• Fibers and Polymers
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• v.3 no.1
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• pp.31-37
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• 2002

Most fibers are irregular, and they are often subjected to combined loading conditions during processing and enduse. In this paper polyester and wool fibers under the combined tensile and torsional loads have been studied for the first time using the finite element method (FEM). The dimensional irregularities of these fibers are simulated with sine waves of different magnitude and frequency. The breaking load and breaking extension of the fibers at different twist or torsion levels are then calculated from the finite element model. The results indicate that twist and level of fiber irregularity have a major impact on the mechanical properties of the fiber and the effect of the frequency of irregularity is relatively small.

• Journal of Advanced Navigation Technology
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• v.27 no.2
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• pp.214-220
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• 2023

Because there exist a region in the rotational speed and torque map that the a particular combination of a motor and an ESC (Electronic Speed Control) can maintain its peak efficiency, identifying this region is important for designing an efficient system. Firstly the accuracy of the measurement device is verified using the published propeller measurement data. And then, the combined motor-ESC efficiencies of an individual propeller are measured at a wide range of rotational speeds. With measurements obtained from a large number of different propellers, efficiency contours are obtained. It is shown that there exist a significant difference between the measured combined efficiency and the motor efficiency computed using a simple model. In addition, with the same motor, the combined efficiency can have a meaningful variation depending on the model of the ESC. The efficiency contours derived from this study will be useful for the design and optimization of electric propulsion systems of an aircraft where propulsion efficiency is critical.

• Journal of the Korean Society of Safety
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• v.15 no.1
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• pp.19-27
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• 2000

This paper numerically deals with combined heat transfer in a enclosure with a block. The block affected by hot wall is located centrally in the enclosure with a radiating gray gas. The discrete ordinate method(DOM) was used for solving the radiative transfer equation. Both laminar and turbulent cases were investigated for various Rayleigh number and standard k-$\varepsilon$ model was adopted to turbulent case. The effects of optical thickness, wall emissivity and fluid-solid thermal conductivity ratio are investigated on the flow and temperature fields. This study shows that as the wall emissivity decreases, the temperature distribution gradually becomes uniform and the heat transfer is reduced in enclosure. It is expected that this study can help to design the energy system related to the combined heat transfer and operate it safely.