• Journal of the Korean Data and Information Science Society
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• v.15 no.1
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• pp.201-210
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• 2004

The peakedness ordering is closely related to dispersive ordering. In this paper we consider the statistical inference concerning peakedness ordering between two arbitrary symmetric distributions. Nonparametric maximum likelihood estimates of two distribution functions under symmetry and peakedness ordering are given. The likelihood ratio test for equality of two symmetric discrete distributions in the sense of peakedness ordering is studied.

• Management Science and Financial Engineering
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• v.8 no.1
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• pp.1-19
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• 2002

Ordering is used to reduce the amount of fill-ins in the Cholesky factor of a symmetric positive definite matrix. One of the most efficient ordering methods is the minimum degree ordering algorithm(MDO). In this paper, we provide a few techniques that improve the performance of MDO implemented with the clique storage scheme. First, the absorption of nodes in the cliques is developed which reduces the number of cliques and the amount of storage space required for MDO. Second, we present a modified minimum degree ordering algorithm of which the number of degree updates can be reduced by introducing the lower bounds of degrees. Third, using both the lower and upper bounds of degrees, we develop an approximate minimum degree ordering algorithm. Experimental results show that the proposed algorithm is competitive with the minimum degree ordering algorithm that uses quotient graphs from the points of the ordering time and the nonzeros in the Cholesky factor.

• Journal of Korean Institute of Industrial Engineers
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• v.34 no.1
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• pp.1-12
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• 2008

The Kanban system in Just-In-Time (JIT) production is very effective in reducing the inventories when consumption rate of the final product is relatively stable. When large fluctuations exist in the consumption rate, a new production ordering policy in which the production order quantity is determined by smoothing the demands exponentially is more suitable. This new ordering policy has not been investigated sufficiently. In this research, a multi-stage production and inventory system with stock points for materials and finished items located at each stage is considered. Approximations of average inventories at each stage in the system are derived theoretically. Numerical simulations are carried out to assess the accuracy of approximations and to evaluate the effectiveness of the new ordering policy as compared with the Kanban system. As a result, it is shown that the new ordering policy can achieve significantly lower inventory costs than the original Kanban system. The new ordering policy thus emerges as a key concept for an effective supply chain management.

• Journal of the Korean Ceramic Society
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• v.37 no.5
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• pp.491-496
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• 2000

Single phae Pb(Mg1/3Nb2/3)O3-based solid solutions, the Mg2+ of which are replaced by 20mol% of Ni2+, Zn2+, Cd2+, and the Pb2+ of which are replaced by 0∼20 mol% of La3+, were synthesized and their ordering structures of B-site cations were investigated by XRD and TEM. The B'-site cations (Mg2+, Ni2+, Zn2+, Cd2+) are disordered while these B'-site cations and the B"-site cations (Nb5+) are nonstoichiometrically 1:1 ordered within the ordered nano-domains dispersed in the Nb5+-rich disordered matrix. The charge imbalance between the B'-rich ordered nano-domains and the B"-rich disordered matrix are compensated by the doping of electron donor such as La3+, which enhances the degree of nonstoichiometric 1:1 ordering. For a given La3+ content, the degree of nonstoichiometric 1:1 ordering increases as the average ionic size difference between the B'-and B"-site cations increases, Ni2+

• Journal of Magnetics
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• v.10 no.1
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• pp.28-32
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• 2005

The magnetic properties and ordering behavior of Nb-doped FePt alloy films prepared by dc-magnetron sputtering were investigated. It was found that Nb addition retarded the ordering reaction from the disordered face-centered-cubic (fcc) Al phase to the ordered face-centered-tetragonal (fct) L1₀ phase. The tetragonality (c/a ratio) of the ordered fct L1₀ phase increased with the Nb concentration. Nb addition hampered c-axis contraction during ordering, probably because the larger Nb atoms occupy Pt sites. Consequently, the coercivity and magnetocrystalline anisotropic energy of Nb-doped FePt alloy films are lower than those of un-doped FePt film under equivalent annealing conditions.

• Journal of the Korean Operations Research and Management Science Society
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• v.4 no.1
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• pp.25-31
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• 1979

We consider the optimal ordering policy for a single-product two-stage inventory system where the main assumptions are as follows: (i) constant continuous demand only at stage 2, (ii) constant input (production) rate at stage 1, (iii) instantaneous delivery (transportation) from stage 1 to stage 2, (iv) backlogging is allowed only at stage 2, (v) an infinite planning horizon. Costs considered are ordering and linear holding costs at both stages, and linear shortage cost only at stages 2. By solving 9 different case problems, we have observed the general from of the optimal ordering policies for our model which minimizes the total cost per unit time. It is noticeable from this observation that the questionable but more often than not adopted assumption by many authors in determining the optimal potimal policy for multistage inventory systems, that the ordering (lot) sizes at each stage remain constant thruout the planning horizon, is not valid.

• Journal of applied mathematics & informatics
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• v.5 no.1
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• pp.41-50
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• 1998

There are various notions of partial ordering between life-times of systems; stochastic ordering failure rate ordering and likeli-hood ration ordering. In this paper we show that for series systems with non i.i.d. exponential lifetimes of components standby redundancy at component level is better than that at system level in failure rate or-dering and likelihood ratio ordering. We also demonstrate that for 2-component parallel systems with i.i.d. exponential lifetimes of com-ponents standby system redundancy is better than standby component redundancy in failure rate ordering and likelihood ratio ordering.

• The Korean Journal of Ceramics
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• v.2 no.3
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• pp.157-161
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• 1996

Cry structures of $Na_xWO_3$ (0.5$\leq$x$\leq$1.0) were investigated. Transmission electron microscopy (TEM) studies indicate that there is an ordering of sodium ions when x=0.75. The direction of ordering is [110] and the wavelength of ordering is twice of the interplanar distance of (110) plane. It has been confirmed that a superlattice containing eight $Na_{0.75}WO_3$ is the unit cell of ordered structure. In this unit cell, Na sites at (000) and ($\frac{2}{1}\frac{2}{1}\frac{2}{1}$) are vacant. The ordered phase was preserved after the annealing at $600^{\circ}C$ in the air. In reduced $Na_xWO_3$ with x=0.5 and 1.0, extra phases were found with the partially ordered perovskite phase. After annealing at $600^{\circ}C$, theses phases transformed to the phases found in calcined specimens.

• Applied Microscopy
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• v.34 no.2
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• pp.113-120
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• 2004

Microstructural characteristics of the Complex Perovskite (1-x) $(Li_{1/2}Sm_{1/2})TiO_3-x (Na_{1/2}Sm_{1/2})TiO_3$ (LNST) system have been investigated using the transmission electron microscopy (TEM). When $0.0{\leq}x{\leq}0.6$, the vacancy ordering forming the 1/2 (001) superlattice reflections due to the A-site cation deficiencies has apperaed. It could be confirmed by presence of ABPs. But it was difficult to form the vacancy ordering since vacancy concentration gradually lowered as the amount of the substituted Li ions decrease. Antiphase boundaries (APBs) were presented in microstructures of LNST when $0.8{\leq}x{\leq}1.0$. It was considered that these boundaries were caused by the 1:1 chemical ordering of A-site cations, Na and Sm ions. LNST had not only the antiphase tilting of oxygen octahedron but also the inphase tilting of oxygen octahedron and the antiparallel shift of cations all of them. It could be confirmed by presence of ferroelastic domains

• Journal of Magnetics
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• v.9 no.1
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• pp.9-12
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• 2004

We have investigated sintering effects on Fe/Mo ordering and magnetoresistance (MR) in double perovskite-reflection lines due to $Sr_2FeMoO_6$ (SFMO). Polycrystalline samples have been prepared by the conventional solid-state reaction by sintering in a stream of 5% $H_2/Ar$ gas. All samples are single phase and exhibit a series of superstructurecation ordering at Fe and Mo sites. As sintering temperature increases from 900 to $1300^{\circ}C$, the degree of Fe/Mo ordering increases from 82 to 92%, magnetization (15 K, 7 kOe) increases from 1.6 to 2.7 ${\mu}_B/f.u.,$ and Curie temperature increases at a rate of 4.3 K/% with the increase of Fe/Mo ordering ratio. The magnitude of MR measured at 5 K is 19% for sample prepared at $1000^{\circ}C$ with magnetic fields of 7 kOe. The observed MR is proportional to the square of magnetization indicating that the MR feature in SFMO is explained by the spin-polarized tunneling at grain boundaries.