• 전기학회논문지
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• 제63권4호
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• pp.476-483
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• 2014

This paper describes the operational analysis results of the bipolar DC distribution system coupled with the distributed generators. The energy management for AC/DC power trade and the operational principle of distributed generators and energy storages were first analyzed by computer simulation with PSCAD/EMTDC software. After then a hardware simulator for the bipolar DC distribution system was built, which is composed of the grid-tied three-level inverter, battery storage, super-capacitor storage, and the voltage balancer. Various experiments with the hardware simulator were carried out to verify the operation of bipolar DC distribution system. The developed simulator has an upper-level controller which operates in connection with the controllers for each distributed generator and the battery energy storage based on CAN communication. The developed hardware simulator are possible to use in designing the bipolar DC distribution system and analyzing its performance experimentally.

• 전기학회논문지
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• 제63권8호
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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.

• Journal of Power Electronics
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• 제18권1호
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• pp.56-69
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• 2018

In this paper, an improved Space Vector Modulation (SVM) based fault tolerant operation on a nine-level Cascaded H-Bridge (CHB) inverter with an additional backup circuit is proposed. Any type of fault in a power converter may result in a power interruption and productivity loss. Three different faults on H-bridge modules in all three phases based on the SVM approach are investigated with diagrams. Any fault in an inverter phase creates an unbalanced output voltage, which can lead to instability in the system. An additional auxiliary unit is connected in series to the three phase cascaded H-bridge circuit. With the help of this and the redundant switching states in SVM, the CHB inverter produces a balanced output with low harmonic distortion. This ensures high DC bus utilization under numerous fault conditions in three phases, which improves the system reliability. Simulation results are presented on three phase nine-level inverter with the automatic fault detection algorithm in the MATLAB/SIMULINK software tool, and experimental results are presented with DSP on five-level inverter to validate the practicality of the proposed SVM fault tolerance strategy on a CHB inverter with an auxiliary circuit.

• Advances in nano research
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• 제12권4호
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• pp.387-403
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• 2022

Silica nanoparticles, which have a broad range of sizes and specific surface features, have been used in many industrial applications. This study was conducted to synthesize monodispersed silica nanoparticles directly from tetraethyl orthosilicate (TEOS) with an alkaline catalyst (NH₃) based on the sol-gel process and the Stöber method. A central composite design (CCD) is used to build a second-order (quadratic) model for the response variables without requiring a complete three-level factorial experiment. The process was then optimized to achieve the minimum particle size with the lowest concentration of TEOS. Dynamic light scattering and scanning electron microscopy were used to analyze the size, dispersity, and morphology of the synthesized nanoparticles. After optimization, a confirmation test was carried out to evaluate the confidence level of the software prediction. The results revealed that the predicted optimization is consistent with experimental procedures, and the model is significant at the 95% confidence level.

• 한국안전학회지
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• 제39권1호
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• pp.70-81
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• 2024

With heavy rainfall due to extreme weather causing increasing damage, the importance of urban flood forecasting continues to grow. To forecast urban flooding accurately and promptly, a sewer network and surface grid with appropriate detail are necessary. However, for urban areas with complex storm sewer networks and terrain structures, high-resolution grids and detailed networks can significantly prolong the analysis. Therefore, determining an appropriate level of network simplification and a suitable surface grid resolution is essential to secure the golden time for urban flood forecasting. In this study, InfoWorks ICM, a software program capable of 1D-2D coupled simulation, was used to examine urban flood forecasting performance for storm sewer networks with various levels of simplification and different surface grid resolutions. The inundation depth, inundation area, and simulation time were analyzed for each simplification level. Based on the analysis, the simulation time was reduced by up to 65% upon simplifying the storm sewer networks and by up to 96% depending on the surface grid resolution; further, the inundation area was overestimated as the grid resolution increased. This study provides insights into optimizing the simplification level and surface grid resolution for storm sewer networks to ensure efficient and accurate urban flood forecasting.

• 한국소프트웨어감정평가학회 논문지
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• 제17권2호
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• pp.11-17
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• 2021

본 연구에서는 감정사례 및 판례를 분석하여, 기존 소프트웨어 완성도 감정으로 분류되어 수행된 완성도감정, 기성고감정, 하자감정 및 비용감정의 문제점을 적시하고, 그 해결 방안을 제시한다. 판례와 법률적 관점에서 완성도와 기성고율은 큰 차이를 가지고 있다. 완성도는 개발프로세스가 종료된 소프트웨어를 대상으로 전제하는 반면, 기성고율 감정은 미완성된 소프트웨어의 개발진척도를 평가하기 때문이다. 종종 소프트웨어 기성고와 관련된 판례에서는 소프트웨어 공학 개발 절차에 따른 단계별 가중치를 인정하여 전체 기성고 또는 완성도를 산정하는 것을 볼 수 있는데, 감정에서는 대부분 기능의 구현-작동여부 만을 완성도 비율 산정의 척도로 삼고 있는 문제도 존재한다. 또한 기존 소프트웨어 완성도 감정사례에서 다루지 않았던 문제 중 하나는 소프트웨어 하자에 대한 책임 소재 분석 및 감정이 언급되지 않고 있는데 반하여, 판례에서는 분쟁이 발생한 원인을 찾아 책임소재를 다투고 있다. 본 논문에서는 위 제기된 문제를 체계적으로 분류하여 소프트웨어 완성도감정과 소프트웨어 기성고감정을 분리할 것을 제안하고 감정 방안을 제시한다.

• International Journal of Fuzzy Logic and Intelligent Systems
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• 제6권1호
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• pp.33-38
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• 2006

In this paper, we propose a new architecture of Fuzzy Polynomial Neural Networks(FPNN) by means of genetically optimized Fuzzy Polynomial Neuron(FPN) and discuss its comprehensive design methodology involving mechanisms of genetic optimization, especially Genetic Algorithms(GAs). The conventional FPNN developed so far are based on mechanisms of self-organization and evolutionary optimization. The design of the network exploits the extended Group Method of Data Handling(GMDH) with some essential parameters of the network being provided by the designer and kept fixed throughout the overall development process. This restriction may hamper a possibility of producing an optimal architecture of the model. The proposed FPNN gives rise to a structurally optimized network and comes with a substantial level of flexibility in comparison to the one we encounter in conventional FPNNs. It is shown that the proposed advanced genetic algorithms based Fuzzy Polynomial Neural Networks is more useful and effective than the existing models for nonlinear process. We experimented with Medical Imaging System(MIS) dataset to evaluate the performance of the proposed model.

• 한국정보과학회논문지:시스템및이론
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• 제29권4호
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• pp.192-200
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• 2002

PC 클러스터 시스템에서 노드 사이의 데이타 교환을 위해 사용되는 TCP/IP 기반 통신 방식은 소프트웨어 부하가 크기 때문에 전체 시스템의 성능을 저하시키는 요인이 된다. 이러한 문제점을 해결하기 위해 사용자 수준 통신(user-level communication) 구조가 제안되었다. 사용자 수준 통신은 성능에 치명적인 영향을 미치는 커널을 통신 단계에서 제거함으로써 적은 지연 시간과 높은 대역폭을 제공하며, 이러한 우수한 성능은 업계 표준인 VIA(Virtual Interface Architecture)를 만들었다. 본 논문에서는 공유 메모리 기반 Interconnect의 IEEE 표준인 SCI(Scalable Coherent Interface) 네트워크에 기반하여 VIA 클러스터 시스템을 구현하였다. 본 논문의 클러스터 시스템은 메시지 패싱 및 공유메모리 프로그래밍 환경을 동시에 제공하며, 최대 84MB/s의 대역폭과 $8{\mu}s$의 지연 시간을 가진다. 또한, 본 시스템이 병렬 벤치마크 프로그램의 수행시 비교 대상 시스템들에 비해 성능이 우수함을 입증하였다.

• 대한전자공학회논문지SD
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• 제46권1호
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• pp.24-38
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• 2009

본 논문에서는 OCD(On-Chip Debugger)기반의 프로세서 디버거 구현한 것에 대해서 소개한다. 구현한 디버거는 프로세서 칩 내부에 내장에 내장해서 디버깅 기능을 하는 OCD로직과 심볼릭(Symbolic) 디버깅 기능을 지원하는 GNU 디버거 기반의 소프트웨어 디버거, 그리고 소프트웨어 디버거와 OCD를 연결해주고 고속 디버깅을 지원하는 인터페이스 & 컨트롤(Interface & Control) 블록으로 3개의 기능 블록으로 구성되어 있다. 디버거는 대상 프로세서에 OCD블록을 내장하여 소프트웨어 디버거를 이용해서 C/Assembly 레벨에서 디버깅이 가능하다. 디버깅 시스템(On-Chip Debugging System)은 FPGA로 구현된 32비트 RISC 타입 프로세서 코어에 OCD 블록을 내장해서 소프트웨어 디버거와 인터페이스 & 컨트롤 블록을 연동하여 동작을 검증하였다.

• 한국경영과학회지
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• 제20권2호
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• pp.159-178
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• 1995

Supervisory control is an approach based on formal language. it is used to model and control discrete event systems in which each discrete event process is represented as an automation. A supervisor is a generator that switches control patterns in such a way that a given discrete evenet process behaves in obedience to various constraints. A flexible manufacturing cell (FMC) is one of discrete evenet systems. Functions necessary for the operation of an FMC are characterized by operational components and informational compoments. The operational components can be modeled using the finite state machines and the informational components can be modeled using the abstract formalism which describes supporting operations of the cell controller. In this paper, we addressed function required for FMC control specification, software engineering aspects on FMC control based on supervisory control, a concept of event queue for resolving synchronization problem, and complexity reduction. Based on the mathematical model of an FMC. we synthesized the controller by integrating a supervisor for FMC with control specification that specifies event-driven operation of the cell controller. The proposed control scheme is stable mathematically so that the system always behaves on a controlled way even under the existence of uncontrollable events. Furthermore, using an event queue concept, we can solve a synchronization problem caused by the violation of instantaneity assumption of supervisory control theory in real life situation. And also, we can propotype a control software rapidly due to the modularity of the proposed control scheme.