• Korean Management Science Review
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• v.26 no.3
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• pp.145-156
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• 2009

The probability distribution of the repair process should be determined to choose the optimal spare level of a weapon system with a queueing model. Though most weapon systems have a multi-step repair process, previous studies use the exponential distribution for the multi-step repair process. But the PH distribution is more appropriate for this case. We utilize the PH distribution on a queueing model and solve it with MGM(Matrix Geometric Method). We derive the optimal spare level using the PH distribution and show the difference of results between the PH and exponential distribution.

• Journal of Korea Society of Industrial Information Systems
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• v.9 no.3
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• pp.32-37
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• 2004

This paper investigates the mathematical model of multi-server retrial queueing system with the Batch Markovian Arrival Process (BMAP), the Phase type (PH) service distribution and the finite buffer. The sufficient condition for the steady state distribution existence and the algorithm for calculating this distribution are presented. Finally, a formula to solve loss probability in the case of complete admission discipline is derived.

• Communications for Statistical Applications and Methods
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• v.19 no.1
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• pp.169-175
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• 2012

The sensitivity of the performance measures such as the mean and the standard deviation of the queue length and the blocking probability with respect to the moments of the service time are numerically investigated. The service time distribution is fitted with phase type(PH) distribution by matching the first three moments of service time and the M/G/c retrial queue is approximated by the M/PH/c retrial queue. Approximations are compared with the simulation results.

• Journal of the Korean Operations Research and Management Science Society
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• v.22 no.1
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• pp.87-99
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• 1997

This paper considers warranty servicing for repairable products when product lifetimes are phase-type(PH) distributions. Two replace-repair strategies are analyzed based on renwal processes. The quantities of interest can be expressed in terms of the renewal function which, in general, is very difficult to evaluate. By exploiting properties of PH distributions we obtain simplification to evaluate these performance measures. Numerical examples for four different PH distributions with typical functions are presented and the results are discussed.

• Journal of the Korea Society for Simulation
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• v.33 no.1
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• pp.19-26
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• 2024

The phase-type, PH, distribution is defined as the time to absorption into a terminal state in a continuous-time Markov chain. As the PH distribution includes family of exponential distributions, it has been widely used in stochastic models. Since the PH distribution is represented and generated by an initial probability vector and a generator matrix which is called the Markovian representation, we need to find a vector and a matrix that are consistent with given set of moments if we want simulate a PH distribution. In this paper, we propose an approach to simulate a PH distribution based on distribution function which can be obtained directly from moments. For the simulation of PH distribution of order 2, closed-form formula and streamlined procedures are given based on the Jordan decomposition and the minimal Laplace transform which is computationally more efficient than the moment matching methods for the Markovian representation. Our approach can be used more effectively than the Markovian representation in generating higher order PH distribution in queueing network simulation.

• Bulletin of the Korean Chemical Society
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• v.19 no.3
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• pp.340-344
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• 1998

A facile synthesis of 4,5-(1',2'-diphenylethylenedithio)-1,3-dithiole-2-thione (dPhEDT-DTT) is carried out via a Diels-Alder type [2+4] cycloaddition reaction of 1,3-dithiol-2,4,5-trithione oligomer and t-stilbene. Molecular structure of dPhEDT-DTT is determined by x-ray crystallography: space group P1, a=11.694(3) Å, b=12.117(3) Å, c=14.688(3) Å, α=113.12(2)°, β=102.23(2)°, γ=107.02(2)°, V= 1699.1(7) Å3, Z=2. It turns out that dPhEDT-DTT crystallizes as a racemic compound consisting of (R,R) and (S,S) enantiomers. Coupling reaction of dPhEDT-DTO undergone in neat P(OEt)3 yields TTF(SEt)4 instead of ET derivative. When PR3 (R=OEt, OPh, Ph) is used in benzene, toluene or xylene, however, dPhEDT-DTO is decomposed.

• Korean journal of applied entomology
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• v.32 no.2
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• pp.208-217
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• 1993

Feeding behavior fo female brown planthoppers, Nilaparvata lugens Stal, was examined with an electrical recording technique using DC amplifier and through anatomical observation of stylet ovement in the rice plat with electrical recordings. There was six feeding patterns, type P, S, SB, O, X and Ph with the brown planthopper. Type P was a probing pattern during searching the proper feeding site. Type S appeared to be associated with the initial penetration and changing direction through the tissues, and from this type type SB pattern could be distinguished by the regularity of the large potential drops seen, and might be associated with penetration of the phloem sheath and/or salivation in the phloem sheath. The type O pattern shows none of the large voltage drops which were believed to occur when cell walls were being broken down and passes through a relatively thin layer of cells into an air space. The very constant waveform of the type X pattern could be seen during ingestion within the xylem bundle sheath area. The Ph pattern always followed an SB pattern and was associated with a marked negative voltage drop. When this pattern was seen, the brown planthopper might be ingested plant sap from phloem sheath area.

• Bulletin of the Korean Mathematical Society
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• v.53 no.4
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• pp.985-1004
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• 2016

We consider the MAP/PH/c/K queue in which blocked customers retry to get service and servers may take vacations. The time interval between retrials and vacation times are of phase type (PH) distributions. Using the method of mean drift, a sufficient condition of ergodicity is provided. A condition for the system to be unstable is also given by the stochastic comparison method.

• Mycobiology
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• v.31 no.1
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• pp.42-45
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• 2003

For transformation of Pleurotus ostreatus, two novel vectors, pPhKM1 and pPhKM2, were constructed, using the regulatory sequences of the P. sajor-caju $\beta$-tubulin gene(TUB1) and the ble gene encoding phleomycin binding protein. pPhKM1 contains ble fused to the TUB1 promoter and the Schizophyllum commune GPD terminator. pPhKM2 contains ble fused to the promoter and terminator regions of P. sajor-caju TUB1. To confirm phleomycin-resistance activity, each vector was cotrans-formed with pTRura3-2 into the P. ostreatus homokaryotic $ura^-$ strain. The transforming DNA was stably integrated into the genomic DNA. Subsequently, phleomycin resistance was conferred on wild-type dikaryotic P. ostreatus by transformation with pPhKM1 or pPhKM2. This transformation system generated stable phleomycin-resistant transformants.

• Clinical and Experimental Pediatrics
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• v.53 no.6
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• pp.688-693
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• 2010

An increase in the number of preterm infants and a decrease in the gestational age at birth have resulted in an increase in the number of patients with significant bronchopulmonary dysplasia (BPD) and secondary pulmonary hypertension (PH). PH contributes significantly to the high morbidity and mortality in the BPD patients. Therefore, regular monitoring for PH by using echocardiography and B-type natriuretic peptide (BNP) or N-terminal-proBNP must be conducted in the BPD patients with greater than moderate degree to prevent PH and to ensure early treatment if PH is present. In the BPD patients with significant PH, multi-modality treatment, including treatment for correcting an underlying disease, oxygen supply, use of diverse selective pulmonary vasodilators (inhaled nitric oxide, inhaled prostacyclins, sildenafil, and endothelin-receptor antagonist) and other methods, is mandatory.