• 설비공학논문집
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• 제27권4호
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• pp.187-194
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• 2015

This paper describes the PI controller design based on a practical transfer function model for centrifugal water chillers. The rotational speed of a compressor and the opening angle of an electronic expansion valve were simultaneously regulated as manipulated variables to maintain temperature reference and to ensure high efficiency of the chiller. The COP according to the change in each variable was investigated by performing some static experiments, and it was reflected in the PI controller design to accomplish the high efficiency control. Especially, the practical transfer function model of the chiller was built based on the dynamic experimental data considering the strong inherent non-linearity and complexity of the chiller system. The validity of the designed PI controller was proven by some experimental results using the test facility and the results were also compared to the conventional evaporating pressure control results.

• 한국해안해양공학회지
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• 제9권4호
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• pp.176-181
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• 1997

토목환경공학분야의 응용을 위하여 실용적이고 사용이 간편한 자료수집기를 개발하였다. 이 기기는 PC의 병렬포트를 이용하여 자료를 획득·전송하고 비전문가라 하더라도 실내 및 현장실험에 손쉽게 응용할 수 있도록 설계되었다. 통상의 자료수집기는 저장용량이 작아 불편한 점을 감안하여 컴퓨터의 저장장치를 그대로 이용하여 문제를 해결하였다. 또한 PC의 고급 프로그래밍 언어를 직접 이용하여 복잡한 자료수집계획을 손쉽게 수행할 수 있도록 하였다. 방화대교 건설현장에서 각종 센서와 GPS를 이용하여 행한 실제 현장시험을 통하여 개발된기기의 실용성을 입증하였다.

• 실천공학교육논문지
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• 제9권2호
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• pp.119-124
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• 2017

사출성형 시 유압실린더의 힘으로 스크류가 앞으로 전진하는 동안, 금형의 러너시스템은 성형품 형상의 캐비티 내를 충진시키는 유로로 용융된 수지의 충진, 패킹과정에 관계되며, 이는 스프루(sprue), 러너(runner), 게이트(gate)에 의해서 성형품의 외관, 수지의 물성, 치수 정밀도 및 성형 사이클 등에 큰 영향을 준다. 러너, 게이트 설계가 잘못된 피드시스템은 다양한 성형불량을 일으키므로 이를 방지할 수 있는 최적의 러너밸런스를 유지하는 것이 중요하다. 사출금형을 제작하는 업체에서 응용할 수 있는 실무적인 금형기술 지식을 향상시키기 위해서 기술적인 애로분야에 대한 기술지도를 바탕으로 금형기술 과정의 훈련모델을 제시한다.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2005년도 지반공학 공동 학술발표회
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• pp.639-648
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• 2005

Up to now, practical engineers applying simplicity value of rockfall block weight suggested in design manual without considering in-situ rockfall block weight which reflect joint characteristics. However, the size of rockfall block varies with joint spacing of discontinuities and influences over rockfall analysis results. In this paper, we estimate realistic rockfall block weight distribution using statistical invariances of joint spacing derived from scan-line survey result. And, we study whether this distribution is applicable in practical rockfall analysis directly. As the results of this study, rockfall analysis results that using rockfall block weight distribution estimated from scan-line survey show resonable and realistic outcomes.

• Journal of Electrical Engineering and Technology
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• 제9권6호
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• pp.1900-1908
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• 2014

This paper establishes a compact and practical model for a water-wall system comprising supercritical once-through boilers, which can be used for automatic control or simple analysis of the entire boiler-turbine system. Input and output variables of the water-wall system are defined, and balance equations are applied using a lumped parameter method. For practical purposes, the dynamic equations are developed with respect to pressure and temperature instead of density and internal energy. A comparison with results obtained using APESS, a practical thermal power plant simulator developed by Doosan Heavy Industries and Construction, is presented with respect to steady state and transient responses.

• 산업경영시스템학회지
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• 제27권4호
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• pp.125-132
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• 2004

Computer simulation is widely known as a very powerful and practical tool to understand behaviors of considered systems and evaluate design alternatives. However, to use simulation technologies, one should acquire simulation languages, statistics, etc. Also, lots of resources such as time and money are necessary to develop models and analyze statistical data. These obstacles prevent one from adopting simulation tools easily. This paper presents practical guidelines for successful application of simulation. Firstly, we propose how to acquire simulation tools to help one who is going to use simulation techniques. Next guidelines are for introducing simulation software set including simulation and support softwares. Lastly, guidelines for simulation project management are presented.

• 국제학술발표논문집
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• The 6th International Conference on Construction Engineering and Project Management
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• pp.430-434
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• 2015

Safety education at the tertiary level prepares students to enter construction industry with adequate safety knowledge; then accidents can be prevented proactively. However, safety subject has not been paid adequate attention in universities and most institutional safety programs consider safety matters in isolation. Meanwhile, anatomical theory in the medicine field has been successfully adopted and proved potential advantageous in various scientific disciplines. With this regard, this study proposes a visualization based Building Anatomy Model (BAM) for construction safety education, which utilizes the anatomical theory in order to improve student's safety knowledge and practical skill. This BAM consists of two modules: 1) Knowledge Acquisition Module (KAM) aims to deliver safety knowledge to students through building anatomy models; 2) Practical Experience Module (PEM) where students safely perform construction activities by using the system to improve safety skill. The system trial is validated with virtual scenarios derived from real accidents cases. This study emphasizes the visualization based building anatomy model would be a powerful pedagogical method to provide effectively safety knowledge and practical skill for students, as a result, safety competence of students would be enhanced.

• 한국정보통신학회논문지
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• 제26권2호
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• pp.271-277
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• 2022

PBFT(Practical Byzantine Fault Tolerant)는 분산 네트워크 환경에서 비의도적·의도적 결함을 해결하여 합의를 달성할 수 있는 합의 알고리즘으로 높은 성능과 절대적 최종성을 보장할 수 있다. 하지만 합의 과정에서 반복적으로 발생하는 메시지 브로드캐스팅으로 인해 네트워크의 규모가 증가할수록 네트워크 부하도 커진다. PBFT 알고리즘의 특성상 소규모·프라이빗 블록체인에는 적합하지만, 대규모·퍼블릭 블록체인에 적용하기엔 한계가 있다. PBFT는 블록체인 네트워크의 성능에 영향을 끼치기 때문에 산업에서는 PBFT가 제품 및 서비스에 적합한지 테스트할 수 있어야 하며, 학계에서는 PBFT 성능 향상 연구를 위한 통일된 평가지표와 평가 기술이 필요하다. 본 논문에서는 PBFT 계열 합의 알고리즘을 평가할 수 있는 정량적 지표와 평가 프레임워크에 대해 연구한다. 또한 제안한 PBFT 평가 프레임워크를 사용하여 PBFT의 처리량, 지연시간, 내결함성을 평가한다.

• 건설관리
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• 제12권5호
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• pp.73-77
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• 2011

• Structural Engineering and Mechanics
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• 제20권3호
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• pp.363-380
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• 2005

The cable tension plays an important role in the construction, assessment and long-term health monitoring of cable structures. The cable vibration equation is nonlinear if cable sag and bending stiffness are included. The engineering implementation of a vibration-based cable tension evaluation is mostly carried out by the simple taut string theory. However, the simple theory may cause unacceptable errors in many applications since the cable sag and bending stiffness are ignored. From the practical point of view, it is necessary to have empirical formulas if they are simple and yet accurate. Based on the solutions by means of energy method and fitting the exact solutions of cable vibration equations where the cable sag and bending stiffness are respectively taken into account, the empirical formulas are proposed in the paper to estimate cable tension based on the cable fundamental frequency only. The applicability of the proposed formulas is verified by comparing the results with those reported in the literatures and with the experimental results carried out on the stay cables in the laboratory. The proposed formulas are straightforward and they are convenient for practical engineers to fast estimate the cable tension by the cable fundamental frequency.