• Communications for Statistical Applications and Methods
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• v.8 no.2
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• pp.435-442
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• 2001

Bayes estimators and generalized ML estimators for reliability of a k-unit hot standby system with the perfect switch based upon a complete sample of failure times observed from an exponential distribution using noninformative, generalized uniform, and gamma priors for the failure rate are proposed, and MSE's of proposed several estimators for the standby system reliability are compared numerically each other through the Monte Carlo simulation.

• Proceedings of the KIEE Conference
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• 2009.07a
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• pp.1416_1417
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• 2009

This paper shows the characteristic of wave tail according to inductance values in 10/$350{\mu}s$ impulse circuit with crowbar switch. The PSpice was used to simulate the 10/$350{\mu}s$ current waveform and lightning current impulse generator was used to generate real current waveform. As a capacitor of condenser bank increases, a virtual front time increases and a time to half-value decreases. To get a perfect 10/$350{\mu}s$ current waveform, we should consider the combination of circuit values of the inductance, capacitance, time difference between trigger pulses and charged voltage of capacitor bank.

• Progress in Superconductivity and Cryogenics
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• v.9 no.3
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• pp.57-61
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• 2007

The current limiting characteristics of hybrid SFCL with additional power electronic devices was investigated in order to improve operation reliabilities. The hybrid SFCL developed consists of a superconducting trigger (S/T) part, a fast switch (F/S) module and a current limiting (C/L) part. Although hybrid SFCL had shown a excellent current limiting characteristics, this device was rather vulnerable to the residual arc currents which could exist during fast switch operation. This undesirable arc should be extinguished as quickly as possible in order to implement perfect fault current commutation. So, in order to eliminate the residual arcs between fast switch contacts, the power electronic devices (IGBT or GTO) were connected in series between the S/T part and the interrupter of the F/S module. According to the fault tests conducting with an input voltage of $270\;V_{rms}$ and a fault current of $5\;kA_{rms}$, The power electronic devices could perfectly remove the arc generated between the contacts of the interrupter within 4 ms after the fault occurred. From the test analysis, it was confirmed that the hybrid SFCL could enhance the operation reliability by adopting additional power electronic devices.

• Journal of the Korean Data and Information Science Society
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• v.14 no.4
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• pp.1055-1065
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• 2003

We shall propose maximum likelihood, Bayesian and generalized maximum likelihood estimation for the reliability of the two-unit hot standby system with exponential lifetime distribution that switch is perfect. Each estimation will be compared numerically in terms of various mission times, parameter values and asymptotic relative efficiency through Monte Carlo simulation.

• Journal of the Korean Data and Information Science Society
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• v.8 no.1
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• pp.31-39
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• 1997

we shall propose some Bayes estimators and some generalized maximum likelihood estimators for reliability of a two-unit hot standby system with perfect switch based upon a complete sample of failure times observed from the exponential model and compare the peformances of the proposed estimators in terms of mean squared error.

• Journal of the Korean Data and Information Science Society
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• v.15 no.1
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• pp.239-250
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• 2004

We shall propose maximum likelihood, Bayesian and generalized maximum likelihood estimation for the reliability of the two-unit hot standby system with Rayleigh lifetime distribution that switch is perfect. Each estimation will be compared numerically in terms of various mission times, parameter values and asymptotic relative efficiency through Monte Carlo simulation.

• Magazine of the Korean Society of Agricultural Engineers
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• v.37 no.1
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• pp.49-54
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• 1995

Three types of floating-type automatic inlet were developed for the purpose of reduc- ing farmer's working hours required for water management and saving irrigation water. The point of automation is to use a float within the inlet which is floated and sinked by the ponding depth of paddy field, Thus opens and closes the control gate of irrigation. Suitability of each inlet may depend on production cost, applicability to paddy field condi- tions, and feasibility to farmers, etc. The first model was composed of three parts : chamber for irrigation control gate, chamber for float controlled by ponding depth, and connection bar between the two parts. It was designed to open and close the control gate gradually as the ponding depth drops and rises to a certain level. The second model was designed to improve the weak point of the first model which is the imperfect-closing of gate when it approaches to the end of ir- rigation. A switch-spring was equipped above the connection bar for perfect opening and closing of gate when the ponding depth reaches to a certain level. The third model was designed by combining the two chambers, that is, cut in halves the inlet volume of the above two models. Magnets were equipped above the float for perfect opening and closing gate. The functional experiment for three developed inlets was successfully carried out and the rating curves were derived.

• Journal of the Korean Institute of Telematics and Electronics D
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• v.36D no.3
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• pp.1-11
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• 1999

It is now common practice to utilize the quadrature RF coils to improve the signal-to-noise ratio (SNR) in the Magnetic Resonance Imaging (MRI) System. In addition, to make such an available SNR improvement, it is mandatory to use a well-designed quadrature coupler, which facilitates a perfect 3-dB coupling and quadrature-phase shift. However, the four ports matching condition has to be well considered during the RF excitation and the signal detection period. This work investigates the effects of such a mismatching condition (especially, due to patient) from the analysis, simulation, and real implementation and firstly proposes dynamic loading technique for a quadrature coupler and transmitting/receiving switch module to minimize a patient mismatching and enhance a system reliability. Also, we designed and implemented the quadrature coupler and transmitting/receiving switch module using microstrip. As a result, the SNR of our MRI system using the microstrip quadrature coupler and transmitting/receiving switch module with dynamic load increases 3 dB compared with the old one using USA quadrature switch. Also, the power capability of quadrature coupler and transmitting/receiving switch module is 5-kw peak power. Considering power loss and reduction of size, we used a RT/duroid 6010 substrate with high permittivity and for simulation we use Compact Software.

• Proceedings of the KIEE Conference
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• 2000.11a
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• pp.76-78
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• 2000

The previous MCC's have the demerits of high cost and much manhour for rework because they are impossible for the standardization of products and have many manual connections. The customers require the products which can operate in connection with SCADA system by digitalizing the functions of the current MCC's and are systematized with capability of remote control. To solve these disadvantages and requirements, we developed the Electronic Motor Control System according to starting type for applying to fields based on this. This system has the various functions such as protection, measurement, and communication. Using these functions, it can monitor motor status through communication with the upper system and define the circuit for lower connection cost according to starting type and shorter manufacture period by program. The development of this product results in establishment of competitive structure with domestic competition and perfect automatic monitoring through linkage with SCADA system. In addition, it provides the comparable dominancy of receiving on orders in switch gear and adaptability to change of MCC market in Japan and Europe.

• Archives of design research
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• v.21
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• pp.41-52
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• 1997

The development of architecture made it possible to predict human's dream having a perfect control over his environment be fulfilled by the development of the electric engineering after the twentieth century. During a century, throgh the renovation of systems, the design concepts of its environment, dwelling space, and the relationship between human and system. By exploring any possible new idea on the basis of the technical limits of the current system, let us suggest the advanced products ahead of a century.