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51.
The independence of processes in queueing systems is generally assumed when developing queueing models. However, real systems often involve several process dependencies, and failure to take these into consideration can lead to serious underestimation of the performance measures. We consider herein a single server queueing system with a Markov renewal process (MRP) for its arrival process and a general service time distribution, and derive the distribution function and correlation coefficient of the departure process. Since the departure process also often corresponds to an arrival process in downstream queues, the results obtained here can be used to derive a better approximation of the performance measures of a non-product form general queueing network. 相似文献
52.
In order to endow the expansion-based stochastic formulation with the capability of representing the characteristic behavior of stochastic systems, i.e., the non-linear dependence of the response variability on the coefficient of variation of the stochastic field, a Monte Carlo simulation-compatible stochastic field is suggested. Through a theoretical comparison of displacement vectors in the Monte Carlo method and an expansion-based scheme, it is found that the stochastic field adopted in the expansion-based scheme is not compatible with that appearing in the Monte Carlo simulation. The Monte Carlo simulation-compatible stochastic field is established by means of enforcing the compatibility between the stochastic fields in the expansion-based scheme and the Monte Carlo simulation. Employing the stochastic field suggested in this study, the response variability is reproduced with high precision even for uncertain fields with a moderately large coefficient of variation. Furthermore, the formulation proposed here can be used as an indirect Monte Carlo scheme by directly substituting the numerically simulated random fields into the covariance formula. This yields a pronounced reduction in the computation cost while resulting in virtually the same response variability as the Monte Carlo technique. 相似文献
53.
JS Chang DY Noh IA Park MJ Kim H Song SH Ryu PG Suh 《Canadian Metallurgical Quarterly》1997,57(24):5465-5468
Phospholipase C-gamma1 (PLC-gamma1) mediates signals from various extracellular origins to evoke cellular events such as mitogenesis. Previously, we reported that PLC-gamma1 was highly expressed in colorectal cancer and familial adenomatous polyposis, suggesting that PLC-gamma1 might be oncogenic. In this study, we have established rat 3Y1 fibroblasts that overexpress whole PLC-gamma1 and src homology 2 (SH2)-SH2-SH3 domain of PLC-gamma1. These cells showed a transformed phenotype and were tumorigenic when transplanted into nude mice. These results indicate that overexpression of PLC-gamma1 could transform rat fibroblasts, and the transformation is mediated by SH2-SH2-SH3 domain of PLC-gamma1. 相似文献
54.
Seung-Beom Cho Jun-Seok Noh Sang-Jun Park Dae-Young Lim Sang-Heul Choi 《Journal of Materials Science》2007,42(13):4877-4886
Acicular magnetite (Fe3O4) powders were synthesized through new glycothermal dehydration by using crystalline α-FeOOH as precursor and glycols as solvent.
When ethylene glycol was used as solvent, the phase was in-situ transformed from acicular α-FeOOH to α-Fe2O3 and finally to Fe3O4 at 270 °C for 6 h without morphological change. When water was added as a co-solvent in glycothermal reaction, Fe3O4 powders were synthesized through dissolution–recrystallization process at 230 °C for 3 h. The volume ratio of ethylene glycol
to water (E/W) in the reaction has a strong effect on the morphology of the synthesized Fe3O4 particles. The particle shape of Fe3O4 particles changed from needle to sphere when the water content in E/W volume ratio increased from 0.5 to 1 mL in mixed glycothermal
condition. When the water were added by more than 10 ml, the particle shape of Fe3O4 changed from sphere to octahedron truncated with the {100} faces and finally distinct octahedron with only {111} faces. Also,
it is demonstrated that the size of Fe3O4 particles can be controlled from 1–2 μm to 100–200 nm by varying the reaction conditions such as the volume ratio of water
to ethylene glycol and additive in glycothermal reaction. 相似文献
55.
Roman V. Ivanov Vladimir I. Lozinsky Seok Kyun Noh Sung Soo Han Won Seok Lyoo 《应用聚合物科学杂志》2007,106(3):1470-1475
A new type of cryogel was prepared through a reaction of high‐molecular‐weight polyacrylamide (viscosity‐average molecular weight ≈ 3 × 106 Da) with glutaraldehyde in a moderately frozen aqueous medium. The influence of the crosslinking agent concentration and temperature of the reaction on the gel fraction yield, swelling characteristics, and morphology of the cryogels was investigated. The dependence of the gel fraction yield on the reaction temperature was bell‐shaped. The recognized regularities of the formation of this new type of polyacrylamide cryogel based on a high‐molecular‐weight precursor were very similar to those observed earlier for polyacrylamide cryogels synthesized through the cryopolymerization of monomeric precursors. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007 相似文献
56.
Seo-Young Noh Author Vitae Shashi K. Gadia Author Vitae 《Journal of Systems and Software》2008,81(11):1931-1943
Starting from mid 1980s, there has been a debate about what data model is most appropriate for temporal databases. A fundamental choice one has to make is whether to use intervals of time or temporal elements to timestamp objects and events with the periods of validity. The advantage of using interval timestamps is that Start and End columns can be added to relations for treating them within the framework of classical databases, leading to quick implementation. Temporal elements are finite unions of intervals. The advantage of temporal elements is that timestamps become implicitly associated with values, tuples, and relations. Furthermore, since temporal elements, by design, are closed under set theoretical operations such as union, intersection and complementation, they lead to query languages that are natural. Here, we investigate the ease of use as well as system performance for the two approaches to help settle the debate. 相似文献
57.
Corrosion properties of three different Sn‐Ag lead free solder alloys have been investigated in 0.3 wt% Na2SO4 solution as corrosive environment. As cast solder alloy was analyzed by X‐ray diffraction (XRD) and scanning electron microscopy (SEM). Volume fractions of the Ag3Sn in the solders were determined by image analysis technique. Pitting potential and corrosion potential for the alloys were determined by potentiodynamic tests. Electrochemical impedance spectroscopy (EIS) was carried out to measure the film and charge transfer resistance. Alloys with lower Ag content have been found as better corrosion resistance material. 相似文献
58.
Dong Kyun YimIn-Sun Cho Chan Woo LeeJun Hong Noh Hee Suk RohKug Sun Hong 《Optical Materials》2011,33(7):1036-1040
Novel whitish-blue phosphors based on a phosphate host matrix, γ-KCaPO4: Eu2+, were prepared by a conventional solid-state reaction method using slightly phosphorus deficient conditions and their photoluminescence properties were investigated. The concentration quenching process, temperature dependence of the luminescence and decay curve were also investigated. The γ-KCaPO4: Eu2+ phosphor was efficiently excited by UV-Visible light at wavelengths of 200-450 nm and exhibited a bright whitish-blue emission with a maximum peak wavelength of 473 nm. All of these characteristics suggest that the γ-KCaPO4: Eu2+ phosphors combined with red phosphors could be applicable to near UV-based white LEDs, i.e., only two kinds of phosphor powders are needed for the formation of white light. 相似文献
59.
A novel composite nanofiber of poly(lactic acid) (PLA) incorporated with the nanocomponent of bioactive glass was exploited using an electrospinning method. Small concentrations of the bioactive glass phase added up to 10% facilitated the generation of a nanofibrous matrix with hundreds of nanometers in diameter without a formation of beads. The addition of the bioactive glass phase greatly enhanced the in vitro apatite formation on the nanofiber surface under a body simulating medium. Osteoblastic cells were demonstrated to adhere well on the composite nanofiber and grow actively with culturing time, suggesting its usefulness as a supporting matrix for the hard tissue regeneration. 相似文献
60.