• Journal of the Korea Academia-Industrial cooperation Society
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• v.10 no.6
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• pp.1346-1352
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• 2009

Warranty cost of automobile parts varies depending on the parts failure rate in a warranty region of individual markets. Parts failure rate is significantly affected by usage-rate given that other stressors of individual markets are similar. Accordingly, warranty cost can be predicted by failure modeling which reflects usage-rate and using a stochastic process. In this paper, one-dimensional approach is used by applying accelerated failure time model on the assumption that the usage-rate is linear. Such model can explain changes in parts failure rate depending on the changes in usage-rate since it can be expressed as a function of usage-rate. Therefore, acquisition of usage-rate in a new market will automatically lead to estimate of failure rate even without warranty data and warranty cost of parts can be predicted through a renewal process in replacement cases. A case study using warranty data of two real markets is presented in the application part of this paper.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2008.03a
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• pp.218-225
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• 2008

When the heat release and acoustic pressure fluctuations are generated in the combustor by irregular combustion, these fluctuations affect the mass flow rate of the propellants injected through the injectors. Also, the variations of the mass flow rate by these fluctuations again bring about irregular combustion and furthermore that is related with combustion instability. Therefore, it is very important to identify the mass variation for the pressure fluctuation on the injector and to investigate its transfer function. So, we first have studied quantifying the variation of mass flow rate generated in simplex swirl injector by injection pressure fluctuation. To acquire the transient mass flow rate in orifice with time, we have tried to measure of the flow axial velocity and liquid film thickness in orifice. The axial velocity is acquired through theoretical approach after measuring the pressure in orifice and the flow area in the orifice is measured by electric conductance method. As results, mass flow rate calculated by axial velocity and liquid film thickness measuring in orifice accorded with mass flow rate acquired by direct measuring method in the small error range within 1 percents in steady state and within 6 percents as average mass flow rate in pulsated state. Hence this method can be used to measure the mass flow rate not only in steady state but also in unsteady state because the mass flow rate in the orifice can acquire with time and this method shows very high accuracy based on the experimental results.

• Korea Trade Review
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• v.42 no.4
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• pp.49-68
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• 2017

This paper investigates the spillover effect of the U.S. Interest on Korea's interest rate as well as the role of exchange rate in the spillover effects, by utilizing a open macro model on the determinants of long-term interest rates. According to the cointegration estimation and the Impulse response function, it is found that, across both long-term and short-term, there exist the spillover effect of the U.S. Interest on Korea's interest rate. The fiscal deficit and expected exchange rate have significantly positive relationship with the Koreas's long-term interest rate. Further, foreign exchange market intervention in Korea did not have significant effect on the spillover effect. Thus, this study suggests that exchange rate flexibility would not be enough to restrain the spillover effects of the U.S. interest rate.

• The Korean Journal of Physiology
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• v.18 no.1
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• pp.67-79
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• 1984

In an effort to elucidate the physiological characteristics in cardiopulmonary function, electromyogram(EMG), and blood chemistry in athletic high school students, an analysis of electrocardiogram(ECG) and EMG, pulmonary function test, venous blood gas analysis($Pvo_2$ and$Pvco_2$), and measurement of heart rate, blood pressure, respiratory rate, blood glucose and blood lactate were made for 16 to 19 year-old high school students who were divided into athletic (n=19) and non-athletic (n=20) group. The results obtained are summarized as follows. 1) ECG intervals in athletes were longer than in non-athletes, and the difference was significant in R-R, Q-T and T-P intervals. Resting heart rate in athletes was 56.3/min showing a bradycardia compared with 79.8/min in non-athletes. Amplitudes of R and T waves in lead $V_5$ were significantly higher than in non-athletes. 2) Pulmonary function parameters in athletes showed higher values than in non-athletes. Parameters which showed significant differences were FEV 0.5, PEF, FEF 25%, PIF and FEF $200{\sim}1.200\;ml. 3) Heart rate, blood pressure, and respiratory rate after exercise were significantly elevated from resting values. Heart rate and respiratory rate showed greater increase in non-athletes, while blood pressure showed greater increase in athletes. 4) $Pvo_2$ was lowered ana $Pvco_2$ was elevated after exercise, and there was no significant difference between two groups. 5) Blood glucose and lactate levels were elevated after exercise. The difference was significant in blood lactate, and was greater in non-athletes. 6) EMG amplitude was steadily increased with increasing load of exercise, and the increase was greater in athletes than in non-athletes.

• Proceedings of the Korean Society for Quality Management Conference
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• 1998.11a
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• pp.277-286
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• 1998

This paper investigates the problem of determining optimal replacement policies for equipment subject to failures with cyclic rates. In many situations, the system failures depend on the operating environmental conditions that vary on time, usually with periodical manners. We use nonhomogeneous Poisson processes whose rate functions exhibit cyclic behavior as well as a long-term evolutionary trend to model the stochastic process of the failures when the rate of occurrence of the failures varies periodically, for example from day to day or between seasons. In this study, we compare optimal policies under the nonhomogeneous process with/without a cyclic component in the failure rate function. The analytical results for various situations are presented along with numerical examples using simulated data.

• 제어로봇시스템학회:학술대회논문집
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• 2003.10a
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• pp.1945-1950
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• 2003

Conceived to acquire personal information for an electronic medical record, the clinical interview contains probing questions. The number and type of inquiries are assumed to fulfill medical protocols, and therefore are deemed essential for treatment - but the rate can and should be controlled. High rates of inquiry merely intimidate the patient and affect replies. The purpose of this paper is to mathematically formulate permissible rates of clinical interviews held during telehomecare virtual visits and designed to avoid patient anxiety. Mental stress is derived as a function of the weight of importance assigned by the patient, virtual visit duration, and the rate of questioning in the direction of greater sensitivity. Two operations are of interest: Collecting and recording information by the provider, and maintaining synchrony of questions and answers by the patient. The Lorentz transformation yields the patient’s view of the operational rates. Conservation of information momentum is postulated and applied before and after replies are recorded. It is shown that the weight of importance designated by the patient to collecting and recording personal information is driven by a singularity that depends on the rate of questioning. The findings should serve as a guideline in interviewer training programs.

• Corrosion Science and Technology
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• v.7 no.2
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• pp.130-133
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• 2008

Corrosion of silver by outgassed sulfur species from rubber has been investigated by means of quartz crystal microbalance technique (QCM) and cathodic reduction technique. Silver specimens were placed together with a rubber of predefined quantity in an enclosed environment. Corrosion progressed linearly with time and silver sulfide was found as the corrosion product during all the tests. No significant dependence on RH was observed, while the corrosion rate increased as temperature rose. Furthermore the corrosion rate increased logarithmically with the quantity of the rubber placed in the exposure environment. It may be suggested that the corrosion rate of silver is determined by the amount of outgassed sulfur species which is a function of temperature and the quantity of rubber contained in the exposure environment.

• Journal of the Korean Institute of Telematics and Electronics B
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• v.30B no.12
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• pp.51-58
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• 1993

This paper presents a design of the fuzzy decision maker which infers set value for fuel rate in the rotary kiln of making CaO. The fuzzy decision maker proposed are divided into two groups whose functions are different each other. The one operates when production demand is constant. The other deals with the status of varying production demand. We have chosen several variables used for composing condition and action part by investigating ingerent features of the rotary kiln and skilled operators`manual method of inferring fuel rate. Membership function of each variable was designed by analyzing experimental data and field data collected during two months. On-line operation with fuzzy rules suggested was done safely like human operators' action.

• Structural Monitoring and Maintenance
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• v.3 no.4
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• pp.335-347
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• 2016

One of major errors in flow rate measurement for two-phase flow using an Electrical Capacitance Sensor (ECS) concerns sensor sensitivity under temperature raise. The thermal effect on electrical capacitance sensor (ECS) system for air-water two-phase flow monitoring include sensor sensitivity, capacitance measurements, capacitance change and node potential distribution is reported in this paper. The rules of 12-electrode sensor parameters such as capacitance, capacitance change, and change rate of capacitance and sensitivity map the basis of Air-water two-phase flow permittivity distribution and temperature raise are discussed by ANSYS and MATLAB, which are combined to simulate sensor characteristic. The cross-sectional void fraction as a function of temperature is determined from the scripting capabilities in ANSYS simulation. The results show that the temperature raise had a detrimental effect on the electrodes sensitivity and sensitive domain of electrodes. The FE results are in excellent agreement with an experimental result available in the literature, thus validating the accuracy and reliability of the proposed flow rate measurement system.

• Journal of the Korean Ceramic Society
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• v.56 no.6
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• pp.601-605
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• 2019

This work reports the preparation of ceramic hybrid films with illite-polyethylene composites analyzed as a function of concentration of added illite in polyethylene. The enhancement of oxygen and water-vapor transmission rate of illite-polyethylene film was evaluated to determine its influence on the freshness in fruit packaging. Particle size of illite materials was controlled in the range of 1~10 ㎛ and then mixed with LDPE to form the masterbatch. Ceramic hybrid films were prepared through a blown film making process. To determine the dispersity and abundancy of illite materials in the polyethylene matrix, various characterizations of illite-PE hybrid masterbatch and films were performed using SEM, TGA, and FT-IR. The oxygen and water-vapor transmission rate of illite-polyethylene film was found to be two times higher than that of LDPE film.