• Journal of electromagnetic engineering and science
• /
• v.18 no.3
• /
• pp.206-211
• /
• 2018

In this paper, we proposed a two-level feature vector fusion technique to improve the performance of target classification. The proposed method combines feature vectors of the early-time region and late-time region in the first-level fusion. In the second-level fusion, we combine the monostatic and bistatic features obtained in the first level. The radar cross section (RCS) of the 3D full-scale model is obtained using the electromagnetic analysis tool FEKO, and then, the feature vector of the target is extracted from it. The feature vector based on the waveform structure is used as the feature vector of the early-time region, while the resonance frequency extracted using the evolutionary programming-based CLEAN algorithm is used as the feature vector of the late-time region. The study results show that the two-level fusion method is better than the one-level fusion method.

• Journal of Power Electronics
• /
• v.12 no.2
• /
• pp.285-293
• /
• 2012

Multilevel inverters have gained attention in high-power applications due to their numerous advantages in comparison with conventional two-level inverters. In this paper a simplified Space-Vector Modulation (SVM) algorithm for a three-level Neutral-Point Clamped (NPC) inverter is implemented on a Freescale$^{(R)}$ DSP56F8037. The algorithm is based on a simplification of the space-vector diagram for a three-level inverter so that it can be used with a two-level inverter. Once the simplification has been achieved, calculation of the dwell times and the switching sequences are carried out in the same way as for the two-level SVM method. Details of the hardware design are included. Experimental results are analyzed to validate the performance of the simplified algorithm.

• Journal of Electrical Engineering and Technology
• /
• v.13 no.1
• /
• pp.263-269
• /
• 2018

In this study, a selective inverter operation between a 2-level voltage source converter (VSC) and a 3-level T-type VSC (3LT VSC) is proposed to improve the efficiency of a 3LT VSC. The 3LT VSC topology, except for its neutral-point switches, has similar operations as that of the 2-level VSC. If an operation mode is changed according to efficiency, the efficiency can be improved because efficiencies of each methods are depending on current and MI (Modulation Index). The proposed method calculates the power losses of the two topologies and operates as the having lower losses. To calculate the losses, the switching and conduction losses based on the operation mode of each topology were analyzed. The controller determined the operation mode of the 2- or 3-level VSC based on the power loss calculated during every cycle. The validity of the proposed control scheme was investigated through simulation and experiments. The waveform and average efficiency of each method were compared.

• Nuclear Engineering and Technology
• /
• v.55 no.7
• /
• pp.2407-2418
• /
• 2023

Internal replaceable electronic module substitutions can impact EMC (ElectroMagnetic Compatibility) qualification testing and results if EMC testing is conducted at the cabinet level. The impact of component substitutions on EMC qualification results therefore should be evaluated. If a qualitative evaluation is not adequate to ensure that the modified product will not impact the cabinet level EMC qualification results, a new qualification testing should be conducted. Component level retesting should be conducted under electromagnetically equivalent conditions with the cabinet level test. This paper analyzes the propagation of conducted susceptibility test waveforms in a representative cabinet and evaluates the impact of component substitutions on cabinet level EMC qualification results according to the location of the replacement items. A guideline for a qualitative evaluation of the impact of component substitutions is described based on the propagation of the conducted susceptibility test waveforms. A module level test method is also described based on an analysis of the shielding effectiveness of the cabinet.

• 한국전산유체공학회:학술대회논문집
• /
• 2009.11a
• /
• pp.1-1
• /
• 2009

In this presentation, I talk about various fluid simulation methods that have been developed for computer graphics special effects since 1996. They are all based on CFD but sacrifice physical reality for visual plausability and time. But as the speed of computer increases rapidly and the capability of GPU (graphics processing unit) improves, methods for more physical realism have been tried. In this talk, I will focus on four aspects of fluid simulation methods for computer graphics: (1) particle level-set methods, (2) particle-based simulation, (3) methods for exact satisfaction of incompressibility constraint, and (4) GPU-based simulation. (1) Particle level-set methods evolve the surface of fluid by means of the zero-level set and a band of massless marker particles on both sides of it. The evolution of the zero-level set captures the surface in an approximate manner and the evolution of marker particles captures the fine details of the surface, and the zero-level set is modified based on the particle positions in each step of evolution. (2) Recently the particle-based Lagrangian approach to fluid simulation gains some popularity, because it automatically respects mass conservation and the difficulty of tracking the surface geometry has been somewhat addressed. (3) Until recently fluid simulation algorithm was dominated by approximate fractional step methods. They split the Navier-Stoke equation into two, so that the first one solves the equation without considering the incompressibility constraint and the second finds the pressure which satisfies the constraint. In this approach, the first step introduces error inevitably, producing numerical diffusion in solution. But recently exact fractional step methods without error have been developed by fluid mechanics scholars), and another method was introduced which satisfies the incompressibility constraint by formulating fluid in terms of vorticity field rather than velocity field (by computer graphics scholars). (4) Finally, I want to mention GPU implementation of fluid simulation, which takes advantage of the fact that discrete fluid equations can be solved in parallel.

• The Journal of Korean Association of Computer Education
• /
• v.23 no.1
• /
• pp.77-90
• /
• 2020

The purpose of the study is to provide educational implications for more effective Problem-based learning(PBL) by investigating students' learning types based on their online learning behaviors. A total of 1,341 students participated in the study, and they engaged in a six-week-long PBL program run by K University. For the study, participants' online activity data were collected. From the data, a total of 48 variables that represent their various online learning behaviors were extracted. Based on the variables, hierarchical cluster analysis was conducted to analyze learning types. Also, the differences in learning characteristics and achievements were investigated by considering types of learning. As a result, the learning types in online PBL were classified as 'high-level participation (cluster 1)', 'medium-level participation (cluster 2)', and 'low-level participation (cluster 3)'. In addition, the achievement level was found to be highest in 'high-level participation (cluster 1)' and lowest in 'low-level participation (cluster 3)'. Based on the results, the implications for improving online PBL were suggested.

• Asia Marketing Journal
• /
• v.17 no.1
• /
• pp.97-121
• /
• 2015

In this research, we examine whether and why temporal distance influences evaluations of two different types of brand extensions: concept-based extensions, defined as extensions primarily based on the importance or relevance of brand concepts to extension products; and similarity-based extensions, defined as extensions primarily based on the amount of feature similarity at the product-category level. In Study 1, we test the hypothesis that concept-based extensions are evaluated more favorably when they are framed to launch in the distant rather than in the near future, whereas similaritybased extensions are evaluated more favorably when they are framed to launch in the near rather than in the distant future. In Study 2, we confirm that this time-dependent differential evaluation is driven by the difference in construal level between the bases of the two types of extensions - i.e., brand-concept consistency and product-category feature similarity. As such, we find that conceptbased extensions are evaluated more favorably under the abstract than concrete mindset, whereas similarity-based extensions are evaluated more favorably under the concrete than abstract mindset. In Study 3, we extend to the case for a broad brand (i.e., brands that market products across multiple categories), finding that making accessible a specific product category of a broad parent brand influences evaluations of near-future, but not distant-future, brand extensions. Combined together, our findings suggest that temporal distance influences brand extension evaluation through its effect on the importance placed on brand concepts and feature similarity. That is, consumers rely on different bases to evaluate brand extensions, depending on their perception of when the extensions take place and on under what mindset they are placed. This research makes theoretical contributions to the brand extension research by identifying one important determinant to brand extension evaluation and also uncovering its underlying dynamics. It also contributes to expanding the scope of the construal level theory by putting forth a novel interpretation of two bases of perceived fit in terms of construal level. Marketers who are about to launch and advertise brand extensions may benefit by considering temporal-distance information in determining what content to deliver about extensions in their communication efforts. Conceptual relation of a parent brand to extensions needs to be emphasized in the distant future, whereas feature similarity should be highlighted in the near future.

• Journal of Elementary Mathematics Education in Korea
• /
• v.21 no.4
• /
• pp.575-598
• /
• 2017

This study aims to explore the level-specific characteristics of arithmetical thinking based on the arithmetical thinking factors and develop an arithmetical thinking level test that can identify students' arithmetical thinking levels by specifying the levels of arithmetical thinking based on the factors. In order to solve the research problems, we categorized the arithmetical thinking factors into 1~4 levels based on the literature review and constructed items of the arithmetical thinking level test considering both content and process based on the arithmetical thinking factors and the level-specific characteristics of the arithmetical thinking which conformed to the Guttman scale. To investigate the adequacy of the analysis of the arithmetical thinking levels, we reanalyzed the level-specific characteristics of the arithmetical thinking by checking that it matched the factors classified to the test developed by the Guttman scale. From the results of this research, the following conclusions were drawn. First, the arithmetical thinking factors are categorized into four levels which have different characteristics. Second, the arithmetical thinking level test of this study was developed satisfying the Guttman scale and it reflects the level-specific characteristics of the arithmetical thinking levels from 1 to 4. It is possible to determine the students' arithmetical thinking level using this test. Third, according to the results of the final application of the arithmetical thinking level test for 5th and 6th graders, teachers should provide more abundant learning experiences related to the relation level (the level 3) and the application level (the level 4) to increase students' arithmetical thinking level.

• The Korean Journal of Emergency Medical Services
• /
• v.17 no.3
• /
• pp.139-147
• /
• 2013

Purpose: The purpose of the study is to confirm the effect of ACLS program using simulations and understanding self-efficacy, practice satisfaction, learning attitude, and interest in ACLS after theory classes and simulation-based practice. Methods: A non-equivalent simulation-based practice post test design was used. The participants were 28 paramedic students. The students participated in simulation-based practice for 3 weeks and conventional instruction class for 12 weeks. Results: The students showed higher level of self-efficacy(p=.043), practice satisfaction(p<.001) and learning attitude(p=.003) compared to the conventional lecture students. Conclusion: Level of self-efficacy after simulation-based practice for ACLS was higher than that of self-efficacy after conventional instruction classes. Level of practice satisfaction was also higher. Academic achievement after simulation-based practice was higher than that in conventional instruction classes.

• School Mathematics
• /
• v.13 no.1
• /
• pp.207-227
• /
• 2011

This study developed a statistical thinking level with constructs framework from based on Jones, Thornton, Langrall, & Mooney (2000) to analyze the 6th graders' thinking level shown on their survey activities. It was modified by 5 constructs framework such as collecting, describing, organizing, representing, and analyzing and interpreting data with four thinking levels, which represent a continuum from idiosyncratic to analytic reasoning. As a result, among four levels such as idiosyncratic level (level 1), transitional level (level 2), quantitative level (level 3), and analytical level (level 4), levels of two through four are shown on statistical thinking levels in this study.