• The Journal of the Korea Contents Association
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• 제17권7호
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• pp.93-100
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• 2017

Recently, demands for high-performance flash-based storage devices (i.e., flash SSD) have rapidly grown in social network services, cloud computing, super-computing, and enterprise storage systems. The industry and academic communities made the NVMe specification for high-performance storage devices, and NVMe-based flash SSDs can be now obtained in the market. In this article, we evaluate performance of NoSQL databases that social network services and cloud computing services heavily adopt by using NVMe-based flash SSDs. To this end, we use NVMe SSD that Samsung Electronics recently developed, and the SSD used in this study has performance up to 3.5GB/s for sequential read/write operations. We use WiredTiger for NoSQL databases, and it is a default storage engine for MongoDB. Our experimental results show that log processing in NoSQL databases is a major overhead when high-performance NVMe-based flash SSDs are used. Furthermore, we optimize components of log processing and optimized WiredTiger show up to 15 times better performance than original WiredTiger.

• Communications of the Korean Mathematical Society
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• 제11권2호
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• pp.377-383
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• 1996

For a given separable space X which contains no copy of $C_0$ and a weakly compact T, we show that a Dunford integrable function $f : [a,b] \to X$ is intrinsically-separable valued if and only if f is McShane integrable. Also, for a given separable space X which contains no copy of $C_0$, a weakly compact T and a Dunford integrable function f we show that if there exists a sequence $(f_n)$ of McShane integrable functions from [a,b] to X such that for each $x^* \in X^*, x^*f_n \to x^*f$ a.e., then f is McShane integrable. Finally, let X contain no copy of $C_0$. If $f : [a,b] \to X$ is McShane integrable, then F is a countably additive on $\sum$.

• Speech Sciences
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• 제4권1호
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• pp.35-46
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• 1998

In this paper production and perception data were examined to discover what acoustic features are used in distinguishing wh-questions and yes/no-questions. Production data show that the two question types are distinguished by different accentual phrasing, pitch ranges in wh-phrases, and initial lenis stop voicing of the first syllable in verb phrases. Perception data by synthetic intonation show that the two question types are distinguished by the width of pitch ranges between the first and the second syllable in wh-phrases. Initial lenis stop voicing of the first syllable in verb phrases produces a strong effect on the perceptual discrimination of the two question types.

• Progress in Superconductivity and Cryogenics
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• 제4권2호
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• pp.63-67
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• 2002

In this study, the performance of the Stirling type orifice Pulse tube refrigerator (OPTR) with a linear compressor was investigated by experiment. The dynamic pressures at three points and a temperature at the cold heat exchanger are measured to explore the dependency of the orifice on the performance of the OPTR. The experimental results show that the opening of the orifice has significant effects on the no load temperature and cool down characteristics. The Pressure amplitude in Pulse tube decrease as the opening of the orifice increase, but the mass flow rate through the orifice and the electric input Power to the compressor increase. The results show that the operating frequency and charging Pressure does not affect on the no load temperature. The pressure amplitude in pulse tube decrease as the operating frequency increase or the charging Pressure decreased.

• East Asian mathematical journal
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• 제30권3호
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• pp.303-310
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• 2014

We study the existence of regular polygons and regular solids whose vertices have integer coordinates in the three dimensional space and study side lengths of such squares, cubes and tetrahedra. We show that except for equilateral triangles, squares and regular hexagons there is no regular polygon whose vertices have integer coordinates. By using this, we show that there is no regular icosahedron and no regular dodecahedron whose vertices have integer coordinates. We characterize side lengths of such squares and cubes. In addition to these results, we prove Ionascu's result [4, Theorem2.2] that every equilateral triangle of side length $\sqrt{2}m$ for a positive integer m whose vertices have integer coordinate can be a face of a regular tetrahedron with vertices having integer coordinates in a different way.

• Bulletin of the Korean Mathematical Society
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• 제61권2호
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• pp.421-431
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• 2024

In this paper, we characterize amphicheiral 2-bridge knots with symmetric union presentations and show that there exist infinitely many amphicheiral 2-bridge knots with symmetric union presentations with two twist regions. We also show that there are no amphicheiral 3-stranded pretzel knots with symmetric union presentations.

• Journal of the Korean Mathematical Society
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• 제42권3호
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• pp.599-619
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• 2005

We define the convolutions of Fourier hyperfunctions and show that every strongly decreasing Fourier hyperfunction is a convolutor for the space of Fourier hyperfunctions and the converse is true. Also we show that there are no differential operator with constant coefficients which have a fundamental solution in the space of strongly decreasing Fourier hyperfunctions. Lastly we show that the space of multipliers for the space of Fourier hyperfunctions consists of analytic functions extended to any strip in $\mathbb{C}^n$ which are estimated with a special exponential function exp$(\mu|\chi|)$.

• 한국연소학회:학술대회논문집
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• 한국연소학회 1997년도 제15회 KOSCO SYMPOSIUM 논문집
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• pp.13-21
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• 1997

Excitations of eight pumping transitions for nitric oxide fluorescence imaging are analyzed under equivalent experimental conditions to determine the detection. Frequency mixed dye laser pumping, 1st anti-Stokes $H_2$ Raman of KrF excimer laser pumping and ArF excimer laser pumping show good sensitivities.

• Journal of applied mathematics & informatics
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• 제26권3_4호
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• pp.531-540
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• 2008

We discuss the decomposition problems on circuit graphs and triangular graphs, and show how they can be applied to obtain results on spanning trees or hamiltonian cycles. We also prove that every circuit graph containing no separating 3-cycles can be extended by adding new edges to a triangular graph containing no separating 3-cycles.

• Communications of the Korean Mathematical Society
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• 제14권2호
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• pp.365-371
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• 1999

In this paper, we prove that the range of homomorphism from a C\ulcorner-algebra A into a commutative Banach algebra B whose radical is nil contains no non-zero element of the radical of B. Using this result we show that there is no non-zero homomorphism from a C\ulcorner-algebra into a commutative radical nil Banach algebra.