• 품질경영학회지
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• 제48권1호
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• pp.201-214
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• 2020

Purpose: The purpose of this paper is to determine an optimal number of cycle times for the replacement under the circumstance where the system is replaced at the periodic time and the multiple number of working cycles whichever occurs first and the system is minimally repaired between the replacements if it fails. Methods: The system is replaced at periodic time () or cycle time, whichever occurs first, and is repaired minimally when it fails between successive replacements. To determine the optimal number of cycle times, the expected total cost rate is optimized with respect to the number of cycle times, where the expected total cost rate is defined as the ratio of the expected total cost between replacements to the expected time between replacements. Results: In this paper, we conduct a sensitivity analysis to find the following results. First, when the expected number of failures per unit time increases, the optimal number of cycle times decreases. Second, when the periodic time for replacement becomes longer, the optimal number of cycle times decreases. Third, when the expected value for exponential distribution of the cycle time increases, the optimal number of cycle times increases. Conclusion: A mathematical model is suggested to find the optimal number of cycle times and numerical examples are provided through the sensitivity analysis on the model parameters to see the patterns for changes of the optimal number of cycle times.

• Coupled systems mechanics
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• 제7권5호
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• pp.611-626
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• 2018

We theoretically consider a possible influence of periodic oceanic tides on non-periodic changes in the dynamics of the Earth and Moon over a long time scale. A particular emphasis will be placed on the contribution from rotating tidal waves, which rotate along the inner edge of an oceanic basin surrounded by topographic boundary. We formulate the angular momentum and the mechanical energy of the rotating tidal wave in terms of celestial parameters with regard to the Earth and Moon. The obtained formula are used to discuss how the energy dissipation in the rotating tidal wave should be relevant to the secular variation in the Earth's spin rotation and the Earth-Moon distance. We also discuss the applicability of the formula to general oceanic binary planets subject to tidal coupling.

• 대한전자공학회논문지
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• 제26권9호
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• pp.1436-1443
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• 1989

In this paper, we propose a maximum-likelihood estimation(MLE) method to obtain the location and the amplitude of the pulses in MPE( multi-pulse excitation)-LPC speech synthesis using multi-pulses as excitation source. This MLE method computes the value maximizing the likelihood function with respect to unknown parameters(amplitude and position of the pulses) for the observed data sequence. Thus in the case of overlapped pulses, the method is equivalent to Ozawa's crosscorrelation method, resulting in equal amount of computation and sound quality with the cross-correlation method. We show by computer simulation: the multi-pulses obtained by MLE method are(1) pseudo-periodic in pitch in the case of voicde sound, (2) the pulses are random for unvoiced sound, (3) the pulses change from random to periodic in the interval where the original speech signal changes from unvoiced to voiced. Short time power specta of original speech and syunthesized speech obtained by using multi-pulses as excitation source are quite similar to each other at the formants.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2003년도 추계학술대회
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• pp.682-687
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• 2003

The variations of temperature and velocity fields in a Hele-Shaw convection cell (HSC) were investigated using a holographic interferometry and 2-D PIV system with varying Rayleigh number. To measure quasisteady changes of temperature field, two different measurement methods of holographic interferometry; double-exposure method and real-time method, were employed. In the double-exposure method, unwanted waves can be eliminated effectively using digital image processing technique and the reconstruction images are clear, but transient flow structure cannot be reconstructed clearly. On the other hand, transient convective flow can be reconstructed well using the real-time method. However, the fringe patterns reconstructed by the real-time method contain more noises, compared with the double-exposure method. Experimental results show a steady flow pattern at low Rayleigh numbers and a time-dependent periodic flow structure at high Rayleigh numbers. The periodic flow pattern at high Rayleigh numbers obtained by the real-time holographic interferometer method is in a good agreement with the PIV results.

• 한국신뢰성학회지:신뢰성응용연구
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• 제18권2호
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• pp.104-113
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• 2018

Purpose: This paper proposes the non-periodic preventive maintenance policy based on the level of cumulative hazard intensity. We aim to construct a cost-effectiveness on the proposed model with relaxing the constraint on reliability. Methods: We use the level of cumulative hazard intensity as a condition variable, instead of reliability. Such a level of cumulative hazard intensity can derive the reliability which decreases as the frequency of preventive maintenance action increases. We also model the imperfect preventive maintenance action using the proportional age setback model. Conclusion: We provide a numerical example to illustrate the proposed model. We also analyze how the parameters of our model affect the optimal preventive maintenance policy. The results show that as long as high reliability is guaranteed, the inefficient preventive maintenance action is performed reducing the system operation time. Moreover, the optimal value of the proposed model is sensitive to changes in preventive maintenance cost and replacement cost.

• 치위생과학회지
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• 제16권6호
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• pp.458-463
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• 2016

본 연구는 교근비대증을 주소로 내원한 환자들을 대상으로 보툴리눔 독소 치료 과정에 이갈이 여부에 따른 최대 교합력 변화 차이와 심리 변화 차이를 파악하고자 하는데 그 목적이 있다. 연구대상은 교근비대증을 주소로 내원한 20세 이상의 여성을 대상으로 이갈이가 있는 이갈이군 10명과 이갈이가 없는 비이갈이군 10명으로 구성하였으며 대상자들에게는 보툴리눔 독소 A를 주입하였다. 주입하기 전, 주입 후 2주, 4주, 8주, 12주 동안 최대 교합력을 측정하고 심리요인 변화 정도를 확인하기 위하여 SCL-90-R을 이용하여 우울과 불안의 변화를 파악하였다. 이갈이군과 비이갈이군은 보툴리눔 독소 A의 치료에 있어 좌, 우 각각 4주째 교합력의 최대 감소 효과가 있었고 8주째부터는 원래의 교합력을 회복하는 변화를 보였다. 이갈이군은 우울과 불안에서 기간의 변화에 따른 통계적 차이를 확인할 수 있으며 우울과 불안이 가장 악화되는 8주째에 교합력도 원래의 상태로 회복하는 변화를 보여 우울과 불안으로 인한 근수축이 이악물기를 유발하여 보툴리눔 독소 A의 치료 기간을 단축시키는 것으로 생각된다. 이에 비해 비이갈이군에서 우울은 기간에 따른 변화는 있었으나 통계적으로 유의하지는 않았으며 최대 교합력의 변화도 8주째부터 회복은 하였으나 그 변화의 크기가 이갈이 집단과 달리 긴 시간을 가지고 변화하였다. 우울과 불안은 이갈이에 대한 보툴리눔 독소 A의 치료 과정에 심리 요인의 변화로 인하여 약물 치료 기간을 단축시키는 영향을 미칠 것으로 생각되며 치료에는 기능적 요소들과 함께 다면적인 심리 요인도 함께 반영하여 치료계획을 세운다면 약물에만 의존하여 무분별하게 남용되는 약물을 최소화하고 정신건강에도 도움을 줄 수 있을 것으로 생각된다.

• Annals of Clinical Neurophysiology
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• 제14권1호
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• pp.7-11
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• 2012

Polysomnography is used to diagnose many types of sleep disorders including sleep apnea, periodic limb movement disorder, REM sleep behavior disorder, parasomnias, and narcolepsy. It is a comprehensive recording of the biophysiological changes that occur during sleep. The polysomnography monitors many body functions parameters including EEG, EOG, EMG, ECG, respiratory airflow, respiratory effort, and pulse oximetry during sleep. Multiple Sleep Latency Test (MSLT) is performed for diagnosing narcolepsy and excessive daytime sleepiness. It is usually to be done after an overnight polysomnography. The test consists of four or five 20-minute nap opportunities that are scheduled two hours apart.

• 한국작물학회:학술대회논문집
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• 한국작물학회 2000년도 춘계 학술대회지
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• pp.144-145
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• 2000

• 대한수학회보
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• 제35권4호
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• pp.689-700
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• 1998

We consider an infinite dimensional dynamical system what is called Lattice Dynamical System given by a discrete nonlinear diffusion equation. By assuming the nonlinearity to be a general nonlinear function with mild restrictions, we show that as the diffusion parameter changes the stationery state of the given system undergoes bifurcations from the zero state to a bounded invariant set or a 3- or 4-periodic state in the global phase space of the given system according to the values of the coefficients of the linear part of the given nonlinearity.

• Clinical and Experimental Pediatrics
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• 제57권10호
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• pp.445-450
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• 2014

Purpose: Familial hypokalemic periodic paralysis (HOKPP) is an autosomal dominant channelopathy characterized by episodic attacks of muscle weakness and hypokalemia. Mutations in the calcium channel gene, CACNA1S, or the sodium channel gene, SCN4A, have been found to be responsible for HOKPP; however, the mechanism that causes hypokalemia remains to be determined. The aim of this study was to improve the understanding of this mechanism by investigating the expression of calcium-activated potassium ($K_{Ca}$) channel genes in HOKPP patients. Methods: We measured the intracellular calcium concentration with fura-2-acetoxymethyl ester in skeletal muscle cells of HOKPP patients and healthy individuals. We examined the mRNA and protein expression of KCa channel genes (KCNMA1, KCNN1, KCNN2, KCNN3, and KCNN4) in both cell types. Results: Patient cells exhibited higher cytosolic calcium levels than normal cells. Quantitative reverse transcription polymerase chain reaction analysis showed that the mRNA levels of the $K_{Ca}$ channel genes did not significantly differ between patient and normal cells. However, western blot analysis showed that protein levels of the KCNMA1 gene, which encodes $K_{Ca}$1.1 channels (also called big potassium channels), were significantly lower in the membrane fraction and higher in the cytosolic fraction of patient cells than normal cells. When patient cells were exposed to 50 mM potassium buffer, which was used to induce depolarization, the altered subcellular distribution of BK channels remained unchanged. Conclusion: These findings suggest a novel mechanism for the development of hypokalemia and paralysis in HOKPP and demonstrate a connection between disease-associated mutations in calcium/sodium channels and pathogenic changes in nonmutant potassium channels.