• Transactions of the Korean Society of Mechanical Engineers B
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• v.21 no.5
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• pp.650-658
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• 1997

Analysis and control of intake charge motion such as swirl and tumble are very important factors in improving the gasoline engine performance. In this paper, single-frame PTV (particle tracking velocimetry) is used to investigate intake tumble patterns in a steady flow test rig of gasoline engine with dual-intake-valve and pent-roof combustion chamber. Intake tumble pattern is quantified in accordance with blockage ratio of TIV (tumble intensifying valve) with single- frame PTv.The view of the instantaneous 2-D velocity field gives a realistic understanding of in-cylinder flow field. Thus it is confirmed that PTV is a effective tool in engine design. In conventional port, two tumble structures appear clearly, and the larger one is observed under the exhaust valve side and the smaller is right below the intake valve side. The larger vorticity is observed in TIV port, thus it is concluded that TIV have an effect on intensified tumble motion in cylinder flow.

• The Transactions of the Korean Institute of Power Electronics
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• v.26 no.2
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• pp.150-157
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• 2021

Nowadays, a DC microgrid that can link various distributed power sources is gaining much attention. Accordingly, research on fault situations, such as line-to-line and line-to-ground faults of the DC microgrid, has been conducted to improve grid reliability. However, the blackout of an AC system and the oscillation of a DC bus voltage have not been reported or have not been sufficiently verified by previous research. In this study, a 20 kW DC microgrid testbed using a power HIL simulation technique is proposed. This testbed can simulate various fault conditions without any additional grid facilities and dangerous experiments. It includes the blackout of the DC microgrid caused by the AC utility grid's blackout, a drastic load increment, and the DC bus voltage oscillation caused by the LCL filter of the voltage source converter. The effectiveness of the proposed testbed is verified by using Opal-RT's OP5707 real-time simulator with a 3 kW prototype three-port dual-active-bridge converter.

• Journal of Korea Port Economic Association
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• v.39 no.3
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• pp.141-153
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• 2023

Recently, conflict management has emerged as a major issue. Among them, public conflicts that occur in the process of promotion public policies can have negative social effects, so it is very important to manage conflicts effectively. Therefore, this study aimed to examine the characteristics of public conflicts related to ports in order to lay the foundation for the smooth promotion of public policies related to ports. The significance of this study is that it collected and categorized conflict cases in the port sector through various channels to examine the characteristics of port-related conflicts more closely. The results of this study are summarized as follows. First, this study categorized port-related public conflicts by considering the characteristics of actors, life cycles, and issues, which confirmed that conflicts over ports have various issues. Second, we found that many port-related public conflicts have been resolved in a highly coercive manner. Third, it is necessary to explore non-coercive approaches to induce conflict resolution. Fourth, it is necessary to establish a dual system of proactive and reactive measures to manage port-related public conflicts.

• Journal of the Korea Society of Computer and Information
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• v.27 no.3
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• pp.71-77
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• 2022

In this paper, we propose 1×2 array antenna with dual linear polarization characteristics for mmWave band operation. The proposed antenna is designed two microstirp feeding structure and FR-4 substrate, which is thickness 0.4 mm, and the dielectric constant is 4.3. The size of 1×2 array antenna is 2.33 mm×2.33 mm, and total size of array antenna is 13.0 mm×6.90 mm. From the fabrication and measurement results, bandwidths of 1.13 GHz (28.52~29.65 GHz) for port 1 and 1.08 GHz (28.45~29.53 GHz) for port 2 were obtained based on the impedance bandwidth. Cross polarization ratios are obtained from 7.68 dBi to 16.90 dBi in case of vertical polarization, and from 7.46 dBi to 15.97 dBi in case of horizontal polarization for input port 1, respectively. Also, cross polarization ratios are obtained from 8.59 dBi to 13.72 dBi in case of vertical polarization and from 9.03 dB to 14.0 dB in case of horizontal polarization for input port 2, respectively.

• Journal of the Korea Safety Management & Science
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• v.11 no.4
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• pp.169-176
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• 2009

Many researches and projects are implemented about u-IT according to changes of ubiquitous environments in the world. Especially, there are benefits to raise lifestyle and we can develop industry by applying ubiquitous regionally. Also it makes citizen feel comfortable directly. There are many projects to regionally adopt ubiquitous services like u-City model for getting this advantages. RFID technology must be suited to each environment because each RFID tag has different characteristics according to frequency band. We need to integrate bands of RFID to overcome limitations and provide more detail information and services. In this study, we develop the dual band RFID Manager needed adopting u-Zone service for both 13.56MHz and 2.45GHz. The RFID Manager, application software for base station of u-Zone, delivers the information from readers to integrated u-Zone server system.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.17 no.8 s.111
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• pp.707-712
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• 2006

In this paper, dual bias control circuit and PBG(Photonic BandGap) structure have been employed to improve PAE(Power Added Effciency) of the Doherty amplifier on Input power level. The gate and drain bias voltage has been controlled with the envelope of the input RF signal and PBG structure has been employed on the output port of Doherty amplifier. The proposed Doherty amplifier using dual bias controlled circuit and PBG has been improved the average PAE by 8%, $IMD_3$ by -5 dBc. And proposed Doherty amplifier has a high efficiency more than 30% on overall input power level, respectively.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.13 no.1
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• pp.19-25
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• 2002

This paper presents novel architectures for power amplifier (PA) relying on 3rd harmonic-tuning technique and dual feeding antenna structure for the isolation of the Tx and the Rx ports. Active integrated antenna (AIA) with power amplifier makes the problem of the isolation between the Tx and the Rx ports occur So, this paper suggests dual feeding and dual resonant structures of the AIA with PA are possible to obtain the high isolation between the Tx and the Rx signals. Dual resonant triangular microstrip antenna, which can replace power amplifier tuning circuit, with slots-loaded and characteristic of the isolation between the Tx and the Rx ports using inset microstrip line feeding and probe feeding methods is proposed and experimentally studied for the case of thin substrate.

• Korea Trade Review
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• v.44 no.5
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• pp.65-92
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• 2019

The purposes of this study are to examine the impact of LMX on psychological empowerment, job engagement, and customer orientation, and to analyze the dual mediation effect of psychological empowerment and job engagement. To conduct this study, we used 333 questionnaires collected by members of domestic companies and organizations. Analyses results are as follows: First, LMX has no positive effect on customer orientation. Second, in the relationship between LMX and customer orientation, psychological empowerment and job engagement play a mediating role. Third, in the relationship between LMX and customer orientation, psychological empowerment and Job Engagement play a dual mediating role. The results of this study suggest the following implications. The theoretical implication is that this study once again confirmed behavior patterns such as cognition, emotion, attitude, and behavior of members in the organization. In addition, this study contributes to the literature by explaining that these behavior patterns by way of social exchange theory. The practical implication is that this study confirmed that members in the management field need to utilize a customer orientation in order to achieve the organization's goal efficiently and effectively.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2016.05a
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• pp.98-99
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• 2016

The aim of study is to develop a dual driven ship berthing/deberthing system with $360^{\circ}$ steerability. A large ship used bow thruster, side thruster and pod propulsor etc. when approaching to a pier. But as marine leisure boats become large-scaled, the number of accidents is recently increasing what caused a ship to crash into a ship and a ship to crash into mooring facilities during berthing/deberthing on a marina. To solve the problem, the control responsiveness of a joystick connected with two motors and a propeller was checked and torque was increased by the electromagnetic design of magnetic gear. A sea trial test was carried out to investigate a performance of the developed system in the real sea.

• Journal of Advanced Marine Engineering and Technology
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• v.35 no.2
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• pp.288-294
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• 2011

In this paper, the FPGA-based SoC board (Xilinx Virtex-4 ML401 EVM) is adopted to control electrical power inverter system. For marine application, its performance is shown on PC-based system for monitoring electrical characteristics of a power inverter using by the NMEA 2000 protocol. This power inverter system is achieved in Real-Time monitoring and control by dual micro-processor operation on embedded FPGA-based SoC board. One micro processor is for control (Control processor) electrical power inverter using by PWM signal. And the other microprocessor (Communication processor) is for communication with PC-based monitoring system. The two-processor is communicating each other using by dual-port ram (DPRAM). PC-based system user can control and monitor information of the electrical power inverter via NMEA 2000 based communication processor. Control and monitoring information includes the inverter status and configuration. SoC board converts this information to Parameter Group Numbers (PGNs) in the NMEA 2000 protocol. This system can be applied to marine power electronics for distributed power generation, transmission or regulation systems on the ship.