• Journal of the Korea Institute of Military Science and Technology
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• v.24 no.1
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• pp.50-60
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• 2021

For conventional AESA radars, DC-DC power modules using 300 Vdc have low efficiency, high volume, heavy weight, and high price, which have problems in modularity with T/R module groups. In this paper, to improve these problems, we propose a distributed DC-DC power module with high-voltage 800 Vdc and high-efficiency Step-down Converter. In particular, power requirements for modern and future marine weapons systems and sensors are rapidly evolving into high-energy and high-voltage power systems. The power distribution of the next generation Navy AESA radar antenna is under development with 1000 Vdc. In this paper, the proposed highvoltage, high-efficiency DC-DC power modules increase space(size), weight, power and cooling(SWaP-C) margins, reduce integration costs/risk, and reduce maintenance costs. Reduced system weight and higher reliability are achieved in navy and ground AESA systems. In addition, the proposed architecture will be easier to scale with larger shipboard radars and applicable to other platforms.

• Journal of Power Electronics
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• v.17 no.4
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• pp.1037-1047
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• 2017

The Differential Power Processing (DPP) converter is a promising multi-module photovoltaic inverter architecture recently proposed for photovoltaic systems. In this paper, a DPP converter architecture, in which each PV-panel has its own DPP converter in shunt, performs distributed maximum power point tracking (DMPPT) control. It maintains a high energy conversion efficiency, even under partial shading conditions. The system architecture only deals with the power differences among the PV panels, which reduces the power capacity of the converters. Therefore, the DPP systems can easily overcome the conventional disadvantages of PCS such as centralized, string, and module integrated converter (MIC) topologies. Among the various types of the DPP systems, the feed-forward method has been selected for both its voltage balancing and power transfer to a modified H-bridge inverter that needs charge balancing of the input capacitors. The modified H-bridge multi-level inverter had some advantages such as a low part count and cost competitiveness when compared to conventional multi-level inverters. Therefore, it is frequently used in photovoltaic (PV) power conditioning system (PCS). However, its simplified switching network draws input current asymmetrically. Therefore, input capacitors in series suffer from a problem due to a charge imbalance. This paper validates the operating principle and feasibility of the proposed topology through the simulation and experimental results. They show that the input-capacitor voltages maintain the voltage balance with the PV MPPT control operating with a 140-W hardware prototype.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.25 no.1
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• pp.50-55
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• 2021

Multi-path system is a system in which utilizes various networks simultaneously. It is expected that multi-path system can enhance communication speed, reliability, security of network. In this paper, we focus on path selection in multi-path system. To select optimal path, we propose deep reinforcement learning algorithm which is rewarded by the round-trip-time (RTT) of each networks. Unlike multi-armed bandit model, deep Q learning is applied to consider rapidly changing situations. Due to the delay of RTT data, we also suggest compensation algorithm of the delayed reward. Moreover, we implement testbed learning server to evaluate the performance of proposed algorithm. The learning server contains distributed database and tensorflow module to efficiently operate deep learning algorithm. By means of simulation, we showed that the proposed algorithm has better performance than lowest RTT about 20%.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.38 no.2
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• pp.115-120
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• 2014

In this study, a module is developed for modeling and analyzing dynamic behavior of a wind turbine using RecurDyn, which is a commercial multi-body dynamics software developed by FunctionBay, Inc. The wind turbine consists of tower, nacelle, hub and blades. Tower and blades are regarded as flexible bodies for considering elastic effect using beam theory and spring force. In this paper, a constant speed wind was assumed and aerodynamic force is modeled using BEM theory. Dynamic analysis applying this aerodynamic force is carried out. To verify the validity of analysis results, these results are compared to those of GH-Bladed which is a commercial software for analyzing wind turbine system distributed by Garrad Hassan.

• Journal of the Korean Society for Precision Engineering
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• v.20 no.9
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• pp.142-150
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• 2003

MDO is one of the efficient methods for huge and multi -functional system design. This paper describes a design collaboration framework with MDO in networked design environment. A prototype of web -based integrated design system was implemented to show sharing and exchange of models and analysis information between MDO modules and collaborative design stations. Server System consists of MDO modules for optimization and modeling module for 3D modeling operation. Client system provide user with graphic interface for shape modeling and system operation. We believe that the proposed approach can be extended to solve real complex multidisciplinary design problems.

• Proceedings of the Korea Society for Simulation Conference
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• 2005.05a
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• pp.129-133
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• 2005

This paper describes the methodology of connecting MASTER (Multi-purpose Analyzer for Static and Transient Effects of Reactors) to simulator system, system configuration, and previous test. The actual simulator environment for Youngkwang Unit1 has been developed. It is impossible for the simulator server to execute MASTER code by limitation of computer performance. So, environment of distributed system was developed, and it had a synchronization task. As MASTER and simulator module should be synchronized in different device, the connection of communication was tested and verified.

• Journal of IKEEE
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• v.24 no.1
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• pp.178-185
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• 2020

This paper proposes precise time synchronization-based synchronized sampling structure applied HW/SW platform for LAN-based protection of future digital substations. The integrated software of the proposed platform includes IEC 61850 protocol, IEEE 1588 precision time protocol and synchronized sampling structure. The proposed platform expected to provide a basis of an application of future distributed sensing data-based protection and control methods by providing synchronized measurement among IEDs. The implementation of the proposed HW/SW platform technique was performed using TMDXIDK572 multi-core/multi-processor evaluation module and its time synchronization performance and synchronized sampling function were confirmed through the performance tests.

• Journal of the Korean Society for Precision Engineering
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• v.9 no.4
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• pp.36-43
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• 1992

This paper presents a hierarchical real-time operation control and monitoring scheme of the FMS/CIM center which has been implemented at the Automation and Systems Research Institute of Seoul National University. The hierarchical structure of the whole scheme consists of three lavers. The upper layer is in charge of on-line scheduling, computer network control, shop-floor monitoring and command generation for AGV dispatching, machining, assembly, inspection, set-up, etc. The middle layer has six modules, which are installed in the FMS host computer with the upper layer and run on the multi-tasking basis. Each module is connected to one of six cell controllers distributed in the FMS model plant and transfers operation command down to each cell controller through the Ethernet/TCP-IP local area network. The lower layer is comprised of six cell control software modules for machining cell, assembly cell, inspection cell, set-up stations. AS/RS and AGV. Each cell controller reports the status of the manufacturing facilites to the middle layer as well as ecxecuting the appropriate sequence control of the manufacturing processes.

• Journal of Korea Multimedia Society
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• v.3 no.5
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• pp.506-515
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• 2000

In this paper a web-based real-time education system, which is able to support education through multimedia, is suggested for the expansion of learner's creative ability in the school. This system is designed so that it can support three things: 1) a real time interaction between interaction between instructors and learners, 2) individual learning through such an interaction, and 3) a coercive distribution of display by instructions for preventing the deviation of learners from learning. Also, the system, which UML is applied to, makers efficient interaction possible through the module for the real-time exchange and management of messages even in the multi-user environment. Through this system, not only the simulation by learners can be made for experiments and practices, but also questions and respondence can be supported on the procedure of experiments and the analysis of their results. This system is bulit on constructivism, and aimed at helping the learning progress and knowledge formation of learners.

• Journal of Korea Multimedia Society
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• v.9 no.6
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• pp.742-749
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• 2006

In the network-based game where it uses the Internet infrastructure, the implementation is possible with the various methods. Such Applications are developed in the multi-tired architecture. There are many cases for the server to be separated from the hardware or the software. In this case, a lot of applications make the distributed process possible and are made as the multi-tiered architecture to develop the reusability of the existing software module. Especially, it is mostly general to separate for the case of a database server to a new tier. One of the important points of multi-tiered server side applications is security and because of this, it is difficult to share the related data about the design skill. Using design patterns, it gives help in reusing the existing written-code for the design of the game that needs a lot of money and time. Design Patterns are related to the software reuse. For the development of more efficient games, if well-defined design patterns are provided to the developers, then it would make more easy advanced game API and make possible the framework for the game development based on the API Through the analysis of the general network-based game currently servicing in the Internet, in this paper, we discuss how to implement a business logic tier using database system among the server side architectures. The main objective of this article is to show an efficient APIs(Application Programming Interfaces) design method which can be used to manage the data that must be saved to the database system among the packets that client/server have to be exchange.