• Journal of Positioning, Navigation, and Timing
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• v.10 no.4
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• pp.315-333
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• 2021

Due to the Global Navigation Satellite System (GNSS) modernization, recently launched GNSS satellites transmit signals at various frequency bands such as L1, L2 and L5. Considering the Korean Positioning System (KPS) signal and other GNSS augmentation signals in the future, there is a high probability of applying more complex communication techniques to the new GNSS signals. For the reason, GNSS receivers based on flexible Software Defined Radio (SDR) concept needs to be developed to evaluate various experimental communication techniques by accessing each signal processing module in detail. This paper proposes a novel SDR-based A-GNSS receiver capable of processing multi-GNSS/RNSS signals at multi-frequency bands. Due to the modular structure, the proposed receiver has high flexibility and expandability. For real-time implementation, A-GNSS server software is designed to provide immediate delivery of satellite ephemeris data on demand. Due to the sampling bandwidth limitation of RF front-ends, multiple SDRs are considered to process the multi-GNSS/RNSS multi-frequency signals simultaneously. To avoid the overflow problem of sampled RF data, an efficient memory buffer management strategy was considered. To collect and process the multi-GNSS/RNSS multi-frequency signals in real-time, the proposed SDR A-GNSS receiver utilizes multiple threads implemented on a CPU and multiple NVIDIA CUDA GPGPUs for parallel processing. To evaluate the performance of the proposed SDR A-GNSS receiver, several experiments were performed with field collected data. By the experiments, it was shown that A-GNSS requirements can be satisfied sufficiently utilizing only milliseconds samples. The continuous signal tracking performance was also confirmed with the hundreds of milliseconds data for multi-GNSS/RNSS multi-frequency signals and with the ten-seconds data for multi-GNSS/RNSS single-frequency signals.

• Journal of the Korean Society for Precision Engineering
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• v.22 no.9 s.174
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• pp.107-114
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• 2005

With the recent progress in flexible manufacturing systems (FMS) in industry, increasing attention has been given to Automatic Guided Vehicle (AGV) systems. An AGV is a self-powered unit for transporting materials between stations without needing to be controlled by an operator. Such a system has several sensors to recognize the external state, and it is designed to travel between stations automatically without external assistance. To manage each device automatically in real time it requires a distributed controller with a main computer as the host, as well as a number of micro-controllers. In this study, an AGV system with dual motor drive was constructed. A Pentium 4 personal computer was set up as the main host for the distributed control, and this communicated with other micro-controllers in the management of the motor. The speed of each motor was also controlled by a micro-controller.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.63 no.8
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• pp.1046-1054
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• 2014

In this paper, a hardware prototype for the 10kVA 11-level MMC was built and various experimental works were conducted to verify the operation algorithms of MMC. The hardware prototype was designed using computer simulation with PSCAD/EMTDC software. After manufactured in the lab, the hardware prototype was tested to verify the modulation algorithms to form the output voltage, the balancing algorithm to equalize the sub-module capacitor voltage, and the redundancy operation algorithm to improve the system reliability. The developed hardware prototype can be utilized for analyzing the basic operation and performance improvement of MMC according to the modulation and redundancy operation scheme. It also can be utilize to analyze the basic operational characteristics of HVDC system based on MMC.

• The Korean Journal of Applied Statistics
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• v.21 no.6
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• pp.997-1006
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• 2008

This paper proposes a new model by combining an infinite-server queueing model for multi-task processing software system with a perfect debugging model based on Markov process with two types of faults suggested by Lee et al. (2001). We apply this model for module and integration testing in the testing process. Also, we compute several measure, such as the expected number of tasks whose processes can be completed and the task completion probability are investigated under the proposed model.

• 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.

• Proceedings of the Korea Information Processing Society Conference
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• 2016.10a
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• pp.459-460
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• 2016

국방 소프트웨어는 다양한 플랫폼(OS, H/W)에서 개발된다. 대부분의 국방소프트웨어는 플랫폼 종속적으로 개발되기 때문에 서로 다른 플랫폼 간 개발된 모듈의 재사용성이 떨어진다. 본 논문은 멀티 플랫폼 환경에서 재사용 가능한 모듈을 개발할 수 있는 개발 환경 구축과 구축된 개발 환경에서 멀티 플랫폼 모듈 개발 및 시험에 대한 내용을 설명한다.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.4 no.1
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• pp.5-24
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• 2010

Data fusion is an attractive technology because it allows various trade-offs related to performance metrics, e.g., energy, latency, accuracy, fault-tolerance and security in wireless sensor networks (WSNs). Under a complicated environment, each sensor node must be equipped with more than one type of sensor module to monitor multi-targets, so that the complexity for the fusion process is increased due to the existence of various physical attributes. In this paper, we first investigate the process and performance of multi-attribute fusion in data gathering of WSNs, and then propose a self-adaptive threshold method to balance the different change rates of each attributive data. Furthermore, we present a method to measure the energy-conservation efficiency of multi-attribute fusion. Based on our proposed methods, we design a novel energy equilibrium routing method for WSNs, viz., multi-attribute fusion tree (MAFT). Simulation results demonstrate that MAFT achieves very good performance in terms of the network lifetime.

• Proceedings of the Korea Institute of Applied Superconductivity and Cryogenics Conference
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• 2002.02a
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• pp.135-137
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• 2002

In the favor of adjusting microwave signal, Hairpin type Filter, which delay microwave signal enough to several nanosecond, is a key component. One of the main advantage in using Hairpin type Filter is a conveniency for equipping with Delay Module, and because of having a wide bandwidth, Hairpin type Filter can be designed to satisfy the most applications. In this work, we attempted to estimate the delay time in a superconductive hairpin type filter A software to synthesize even and odd order equiripple hairpin type filter has been developed. This software arbitrarily locate its transfer zeros making symmetric of asymmetric amplitude response and equalizing group delay. Borland C++ compiler has been used. The program was designed to run under MS-DOS, Window 98, Window 2000. The program optimizes the position of the transfer function zeros in order to fulfill the group delay specification masks. We designed and fabricated a hairpin type HTS 2-pole microstrip bandpass filter to operate at 5.8Ghz. The fabrication method was pulsed laser deposition and YBCO films were deposited on sapphire substrates with a Ce$O_{2}$ thin layer as a buffer layer. We also developed a new style hairpin type filter by using interdigitide inner-pole. Compared to the same size regular hairpin type filters, our filters had a lower center frequency.

• Proceedings of the KIEE Conference
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• 2000.07b
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• pp.1381-1383
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• 2000

A multi-train operation simulation software is under development, in this G7 Project for a High Speed Train System, to simulate the running performance, power consumption, signalling and operation. In the first stage, a Train Performance Simulation (TPS) software is introduced in this paper. This is a core module of whole system and gives some parameters of a train, e.g., its position, speed traction and braking power and electric power system state, etc. In this paper, calculation technique was used for voltage drop at the train's positions and major posts along the catenary line. The final program will be used as an evaluation tool for system performance in constructing a new line or introducing a new train system.

• IE interfaces
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• v.7 no.3
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• pp.213-225
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• 1994

For the implementation of CE(Concurrent Engineering), the TDMS(Technical Document Management System) which integrates design and manufacuring information, is required. In this paper a drawing information management system, one of the essential modules for the TDMS has been developed. The system is operated in SUN SPARC II workstations. A CAD software called CIMCAD-2D is used for the storage and management of drawings. Relational DBMS ORACLE is used for the development of information data bases concerned with drawings. As an integration tool, the multi-media software called LINKAGE is used. Various functions for drawings and concerned information have been developed with the internal language CIMSHELL and SQL $^*PLUS$.