• Journal of Power Electronics
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• v.9 no.4
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• pp.535-543
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• 2009

In this paper, pulse-width modulation (PWM) control strategy of various topologies of matrix converters is presented, which is based on direct duty ratio PWM (DDPWM). Because the DDPWM method has the characteristics of the inherent per-phase modular structure, it can be effectively applied to single-phase, two-phase and three-phase four-leg matrix converters as well as the common three-phase to three-phase matrix converter. Also, this paper treats command generation method in each matrix converter. The feasibility and validity of the proposed method are verified by experimental results.

• Journal of applied mathematics & informatics
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• v.28 no.5_6
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• pp.1323-1329
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• 2010

In this paper, a new fixed point theorem in cone is applied to obtain the existence of at least one positive pseudo-symmetric solution for the second order three-point boundary value problem {x" + f(t, x, x')=0, t $\in$ (0, 1), x(0)=0, x(1)=x($\eta$), where f is nonnegative continuous function; ${\eta}\;{\in}$ (0, 1) and f(t, u, v) = f(1+$\eta$-t, u, -v).

• Proceedings of the Korean Society For Composite Materials Conference
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• 2000.11a
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• pp.220-223
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• 2000

A method of calculating the natural frequency corresponding to the modes of vibration of beams and tower structures, with irregular cross sections and with arbitrary boundary conditions was developed and reported by Kim, D. H. in 1974. In this paper, the result of application of this method to the three span continuous reinforced concrete bridge with elastic intermediate supports is presented. Such bridge represents either concrete or sandwich type three span bridge on polymeric supports for passive control or on actuators for active control The concrete slab is considered as a special orthotropic plate. The influence of the modulus of the foundation and $D_{22}$, $D_{12}$, $D_{66}$ stiffnesses on the natural frequency is thoroughly studied.

• Journal of Industrial Technology
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• v.18
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• pp.343-353
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• 1998

Effective design of a database is essential for operating application systems efficiently. This paper discusses database design for a geographic information system. This goals of database design are multiple: to satisfy the information content requirements of the specified users and applications; to provide a natural and easy-to-understand structuring of the information; and to support processing requirements and any performance objectives such as response time, processing time, and storage space. Database design is a very complex process and is decomposed in three phases: conceptual, logical, and physical design. In this paper, we first collect and analyze the requirements for a geographic information system. We also perform database design for these requirements through the three design phases systematically. Our results would contribute to the effective construction of a database for a geographic information system.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.58 no.10
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• pp.1954-1961
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• 2009

This paper describes the development of a three-phase line-interactive dynamic voltage restorer with hybrid detection method, which is composed of three H-bridge inverter modules and super-capacitors. The operational feasibility was verified through computer simulations with PSCAD/EMTDC software, and experimental works with a 3kVA prototype. The developed system can compensate the input voltage sag and interruption within 2ms. The maximum allowable duration of voltage interruption is about 4 seconds. The developed system can be effectively used to compensate the voltage interruption in the sensitive load, such as computer, communication devices, and automation devices, and medical equipment. The developed system has a simple structure to be easily implemented with commercially available components, and to be highly reliable in operation.

• Proceedings of the KIEE Conference
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• 2003.07b
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• pp.810-812
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• 2003

The dynamic characteristics of a three phase induction motor which is applied by various unbalanced voltages are simulated and analyzed in this paper. The voltage equations and torque equation in the dq stationary reference frame for the three phase star connected induction motor are used in this analysis. MATLAB and SIMULINK are employed as a simulation tool. The dynamic characteristics of speed and torque are simulated for various unbalanced voltages, that is, (1) cases with the same unbalance voltage factor but different unbalanced voltages, (2) cases with only one unbalanced voltages but different degree of unbalance, and (3) cases with the same positive sequence voltage but different negative sequence voltages. The simulated results are compared and analyzed with each other, and also with the results of balanced voltage.

• Food Science and Biotechnology
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• v.14 no.3
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• pp.323-327
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• 2005

The effects of commercial marinades were evaluated for their influence on heterocyclic aromatic amine (HAA) formation and overall mutagenicity in fried beef steaks. Three different commercial marinades A, B, and C tested individually reduced the total HAA formation in fried beef steaks by 44, 38, and 40%, respectively. Three different commercial marinades were also effective in reducing the overall mutagenicity in fried beef steaks. There was, however, no significant difference in the inhibition achieved with three different commercial marinades. Reduction of overall mutagenicity was related to the decrease in HAA formation in fried beef steaks.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.18 no.10
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• pp.1-7
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• 2019

Most of people are riding on their own bicycle due to the health and environmental pollution problems. The weight must be light in order to run farther and easier by bicycle. The durability will be reduced due to the light weight of tubes and handles at bicycle. To solve this problem, the three bicycle handle models 1, 2 and 3 were compared with each other for structural analysis. The structural analysis was carried out in this study. Among three models, model 2 and model 3 had the highest and lowest strengths at the structural analysis results, respectively. At this study result, model 1 is thought to be the balanced excellent model with no defect among three models.

• Animal Systematics, Evolution and Diversity
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• v.35 no.3
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• pp.105-113
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• 2019

Feather mites comprise two superfamilies(Analgoidea and Pterolichoidea) and are highly specialized ectosymbionts of birds. To date, this group contains more than 2,500 species worldwide. Fifty-five feather mite species have been reported in Korea, and only one species of genus Alloptes has been recorded from black-tailed godwit Limosa limosa. Three new records of feather mites from the L. limosa in Korea are added in this study: Avenzoaria punctata Gaud, 1972, Bregetovia limosae (Buchholz, 1869), and Montchadskiana buchholzi (Canestrini, 1878). The genus Bregetovia Dubinin, 1951 is also new report for this country. In this paper, we provide the morphological descriptions and illustrations based on the present specimens. Additionally, we determined partial sequences of the mitochondrial cytochrome c oxidase subunit I(COI) from three feather mites as DNA barcodes.

• Journal of Multimedia Information System
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• v.9 no.3
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• pp.183-190
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• 2022

Image-based 3D object detection is one of the important and difficult problems in autonomous driving and robotics, and aims to find and represent the location, dimension and orientation of the object of interest. It generates three dimensional (3D) bounding boxes with only 2D images obtained from cameras, so there is no need for devices that provide accurate depth information such as LiDAR or Radar. Image-based methods can be divided into three main categories: monocular, stereo, and multi-view 3D object detection. In this paper, we investigate the recent state-of-the-art models of the above three categories. In the multi-view 3D object detection, which appeared together with the release of the new benchmark datasets, NuScenes and Waymo, we discuss the differences from the existing monocular and stereo methods. Also, we analyze their performance and discuss the advantages and disadvantages of them. Finally, we conclude the remaining challenges and a future direction in this field.