• 대한기계학회:학술대회논문집
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• 대한기계학회 2008년도 추계학술대회B
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• pp.2070-2075
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• 2008

Identification of steady-state is the first step in developing a fault detection and diagnosis (FDD) system. In a complete FDD system, the steady-state detector will be included as a module in a self-learning algorithm which enables the working system's reference model to "tune" itself to its particular installation. In this study, a steady-state detector of a residential air conditioner based on moving windows was designed. Seven representing measurements were selected as key features for steady-state detection. The optimized moving window size and the feature thresholds was suggested through startup transient test and no-fault steady-state test. Performance of the steady-state detector was verified during indoor load change test. From the research, the general methodology to design a moving window steady-state detector was provided for vapor compression applications.

• Bulletin of the Korean Chemical Society
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• 제6권2호
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• pp.91-95
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• 1985

The dynamic properties near (and at) a stable steady state are discussed, when a chemical system relaxes from the unstable steady state. The time-dependent correlation length for the fluctuating variable near a stable steady state is explicitly obtained by introducing the probability average for the variable satisfying the rate equation. The study is carried out about the effect of nonlinearity on the correlation length near (and at) a stable steady state.

• 대한수학회지
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• 제49권4호
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• pp.715-731
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• 2012

This paper considers the stability of positive steady-state solutions bifurcating from the trivial solution in a delayed Lotka-Volterra two-species predator-prey diffusion system with a discrete delay and subject to the homogeneous Dirichlet boundary conditions on a general bounded open spatial domain with smooth boundary. The existence, uniqueness and asymptotic expressions of small positive steady-sate solutions bifurcating from the trivial solution are given by using the implicit function theorem. By regarding the time delay as the bifurcation parameter and analyzing in detail the eigenvalue problems of system at the positive steady-state solutions, the asymptotic stability of bifurcating steady-state solutions is studied. It is demonstrated that the bifurcating steady-state solutions are asymptotically stable when the delay is less than a certain critical value and is unstable when the delay is greater than this critical value and the system under consideration can undergo a Hopf bifurcation at the bifurcating steady-state solutions when the delay crosses through a sequence of critical values.

• 대한설비공학회:학술대회논문집
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• 대한설비공학회 2008년도 하계학술발표대회 논문집
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• pp.282-287
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• 2008

Identification of steady-state is the first step in developing a fault detection and diagnosis (FDD) system. In a complete FDD system, the steady-state detector will be included as a module in a self-learning algorithm which enables the working system's reference model to "tune" itself to its particular installation. In this study, a steady-state detector of a residential air conditioner based on moving windows was designed. Seven representing measurements were selected as key features for steady-state detection. The optimized moving window size and the feature thresholds was suggested through startup transient test and no-fault steady-state test. Performance of the steady-state detector was verified during indoor load change test. From the research, the general methodology to design a moving window steady-state detector was provided for vapor compression applications.

• Computers and Concrete
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• 제13권1호
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• pp.117-133
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• 2014

This study presents a rapid method for determining the steady state migration coefficient of concrete by measuring the electric current. This study determines the steady state chloride migration coefficient using the accelerated chloride migration test (ACMT). There are two stages to obtain the chloride migration coefficient. The first stage, the steady-state condition was obtained from the initial electric current at the beginning of ACMT. The second stage, the average electrical current in the steady state condition was used to determine the steady state chloride migration coefficient. The chloride migration coefficient can be determined from the average steady state current to avoid sampling and analyzing chlorides during the ACMT.

• 한국데이터정보과학회:학술대회논문집
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• 한국데이터정보과학회 2002년도 춘계학술대회
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• pp.17-22
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• 2002

Availability is an important characteristic of a repairable component. Iyer(1992) obtained the 'limiting efficiency'(not the `steady state availability') of the age-dependent minimal repair model which was first considered by Block et al.(1985). However the existence of the steady state availability of the model has not been reported. In this note, the existence of the steady state availability of the model is shown and a brief remark on the importance of the property is given.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1991년도 한국자동제어학술회의논문집(국제학술편); KOEX, Seoul; 22-24 Oct. 1991
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• pp.1888-1893
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• 1991

Systematic design of a controller for a water temperature system was considered, with the intention of devising an accurate control experiment. The results of an experiment using a water temperature system based on the pole placement regulator showed water temperature oscillation and steady state error. This paper proposed a. method for eliminating both the oscillation and the steady state error. The oscillation was eliminated by a drive delay compensation technique, in which a future state value of the system was predicted through a real time computer simulation. The steady state error was eliminated by an steady state error correction technique, in which an actual steady state heatrate in the system model was replaced by an imaginary heatrate. By combining these two techniques, we obtained an experimental result for water temperature control of 0.01 (.deg. C) accuracy. Furthermore, the proposed method was evaluated relatively by comparing the experimental results using several other methods and proved to be the most accurate and convenient control method for the delay system.

• 전자공학회논문지A
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• 제30A권8호
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• pp.63-71
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• 1993

To verify validity of the steady-state Nyquist theorem and the steady-state Nyquist theorem with hot carrier effects in semiconductor devices, we calculate thermal noise in n-i-n structures using both the steady-state Nyquist theorem and the Monte-Carlo method, and compare the results from these two-methods. When the carrier temperature is not far from the lattice temperature, the results from both methods agree with each other very well, but in the hot carrier regime there are some discrepancies. Our results support the argument that for MOSFETs and MESFETs operating in the linear region, the channel thermal noise should be explained by the steady-state Nyquist theorem rather than by the existing theories.

• 천문학회보
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• 제41권1호
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• pp.44.2-44.2
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• 2016

The solar wind electrons are made of three or four distinct components, which are core Maxwellian background, isotropic halo, and super-halo (and sometimes, highly field-aligned strahl component which can be considered as a fourth element). We put forth a steady-state model for the solar wind electrons by considering both the steady-state particle and wave kinetic equations. Since the steady-state solar wind electron VDFs and the steady-state wave fluctuation spectrum are related to each other, we also investigate the complete fluctuation spectra in the whistler and Langmuir frequency ranges by considering halo- and superhalo-like model electron VDFs. It is found that the energetic electrons make important contributions to the total emission spectrum. Based on this, we complete the steady-state model by considering both the whistler and Langmuir fluctuations. In particular, the Langmuir fluctuation plays an important role in the formation and maintenance of nonthermal electrons.

• 대한기계학회논문집B
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• 제34권4호
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• pp.333-339
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• 2010

고장감지 및 진단(FDD) 시스템의 구축의 기초 연구로 정상상태 진단기에 대한 연구를 수행하였다. 정상상태에 대한 진단은 시스템 전체를 관찰하거나 몇몇 필요한 시스템 파라미터를 모니터링 함으로써 가능하다. 최적화된 정상상태 진단기를 이용하면 FDD 시스템에서 필수적인 정상운전 시의 기준모델(no fault reference model)을 자가학습을 통하여 적용할 수 있다. 본 연구에서는 가정용 열펌프가 냉방조건으로 작동할 경우에 대해 이동창을 기반으로 7개의 측정값들에 대한 표준편차를 분석함으로써 정상상태 판정을 내리도록 하였다. 정상상태 진단기의 작동의 여부는 실내부하를 조절함으로써 확인하였다. 본 연구를 통하여 열펌프 등의 증기압축 사이클 시스템에 대하여 이동창을 기반으로 한 정상상태 진단기 개발 방법을 제시하였다.