• 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 Ocean Engineering and Technology
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• v.3 no.2
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• pp.535-535
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• 1989

• Proceedings of the Optical Society of Korea Conference
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• 2007.07a
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• pp.319-320
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• 2007

We report on the fabrication of two-dimensional Silicon On Insulator (SOI) photonic crystal (PhC) superprism. To optimize the design of 2-D SOI PhC superprism, the photonic band structures (TE-polarization) for triangular lattices and the dispersion surfaces were calculated and analyzed by the plane wave expansion method. Dense 2-D SOI PhC superprism nanostructures with taper input and output waveguide microstructures were successfully fabricated by nanoimprint lithography, followed by inductively coupled plasma (ICP) etching.

• 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.

• Korean Journal of Crystallography
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• v.12 no.3
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• pp.141-144
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• 2001

From the reaction of Na[Ga(N₃)₄] with PPh₃, an ionic compound [Ph₃P(OH)]/sup +/[N₃]/sup -/ (1) was isolated. Compound 1 was characterized by spectroscopy (¹H-NMR, /sup 13C{¹H}-NMR, and IR) and X-ray diffraction. Crystallographic data for 1 : orthorhombic space group P2₁2₁2₁, a = 10.491 (4) Å, b=11.603(5)Å, c=13.149(5)Å, Z=4, R(wR₂)=0.0547(0.0978).

• Journal of applied mathematics & informatics
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• v.14 no.1_2
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• pp.405-413
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• 2004

Rational parameterization of curves and surfaces is one of the main topics in computer-aided geometric design because of their computational advantages. Pythagorean hodograph (PH) curves and Minkowski Pythagorean hodograph (MPH) curves have attracted many researcher's interest because they provide for rational representation of their offset curves in Euclidean space and Minkowski space, respectively. In [10], Kim presented the characterization of the PH curves in the Euclidean space and analyzed the relation between the class of PH curves and the class of rational curves. In this paper, we extend the characterization of PH curves in [10] into that of MPH curves in the general Minkowski space and consider some generalized MPH curves satisfying this characterization.

• Journal of Korea Foundry Society
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• v.5 no.3
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• pp.13-18
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• 1985

Decarburization phenomena were investigated at $800^{\circ}C$ by the $PH_2O/PH_2$ + Ar gas mixture in the case iron range which contains Si, Mn and Cr as an alloying elements. Dissociation of cementite in a matrix which contains graphitizer as Si begins at the carbon rich cementite dendrite arms. Several primary austenite $({\gamma})$ skeletons are surrounded by those nucleated graphite nodules, and that forms a limited area of nucleation region. Decarburization reactions at $800^{\circ}C$ in Fe-C, Fe-Mn-C and Fe-Cr-C alloy are followed by parabolic rate law under the gas mixture of $PH_2O/PH_2=0.01$ and the modified rate const. ${\kappa}$ were in the range of $1{\sim}6{\times}10^{-10}cm^2/s$.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.29 no.1
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• pp.41-46
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• 2006

본 논문에서는 재시도와 완전입력 규칙을 갖는 BMAP/PH/N/0 대기시스템에 대한 주요 성능평가척도와 시스템의 정상상태 조건을 제시한다. 고려되는 시스템은 모든 서버가 서비스를 하고 있을 경우 도착이 이루어지는 배치도착은 모두 손실되며, 반대의 경우 도착하는 배치는 서비스를 받기 위해 시스템에 들어가게 된다. 만약 쉬고 있는 서버의 수가 불충분하여 배치의 일부가 즉각 서비스를 받을 수 없다면, 일단 오빗으로 이동하고 표준 재시도 대기 시스템의 규칙에 따라 후에 서비스를 받게 된다. 본 논문에서는 배치 마코프도착과정, 단계 서비스분포 및 유한버퍼를 갖는 다중서버 재시도 대기 시스템에 대한 수리모형을 제시한다. 제시된 시스템의 정상상태 분포 존재를 위한 충분조건을 유도하고, 이 분포를 계산하기 위한 알고리즘이 제시된다. 끝으로 완전입력규칙을 갖는 시스템에 대한 손실확률을 계산하기 위한 식이 유도하고, 수치 예제들을 제시한다.

• Journal of Powder Materials
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• v.9 no.4
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• pp.211-217
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• 2002

It is well known that the powder injection molding(PIM) process can overcome the shape limitations of traditional powder compaction, the costs of machining, the productivity limits of isostatic pressing and slip casting, and the defect and tolerance limitations of conventional casting. Increasing demands from industry for not only the dimensional accuracy nut mechanical strength in PIMed parts have had much effort focused on the investigation of mechanical properties of mechanical strength in PIMed parts have had much effort focused on the investigation of mechanical properties of sintered parts formed with high-strength metallic powders. The 17_4 PH $10\mu{m}$ were injection-molded into flat tensile specimens. Sintering of the compacts was carried out at the various temperatures ranging from 900 to $1350^{\circ}C$. Sintering behavior of the compacts and tensile properties of sintered specimens were investigated.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2003.05a
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• pp.160-163
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• 2003

In this study, intrinsic dynamic fracture toughness of 17-4PH casting steel is evaluated from the apparent dynamic fracture toughness of notched specimen. Notch radius of notched specimen is manufactured from 0.1mm to 4mm. The results shows that dynamic fracture toughness decreases with decreasing of notch root radius above critical notch roof radius. The true dynamic fracture toughness can be predicted from test results of apparent dynamic fracture toughness measured by using notched specimen.