• JSTS:Journal of Semiconductor Technology and Science
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• v.7 no.4
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• pp.267-273
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• 2007

A fractional-N frequency synthesizer supports quadruple bands and multiple standards for mobile broadcasting systems. A novel linearized coarse tuned VCO adopting a pseudo-exponential capacitor bank structure is proposed to cover the wide bandwidth of 65%. The proposed technique successfully reduces the variations of KVCO and per-code frequency step by 3.2 and 2.7 times, respectively. For the divider and prescaler circuits, TSPC (true single-phase clock) logic is extensively utilized for high speed operation, low power consumption, and small silicon area. Implemented in $0.18-{\mu}m$ CMOS, the PLL covers $154{\sim}303$ MHz (VHF-III), $462{\sim}911$ MHz (UHF), and $1441{\sim}1887$ MHz (L1, L2) with two VCO's while dissipating 23 mA from 1.8 V supply. The integrated phase noise is 0.598 and 0.812 degree for the integer-N and fractional-N modes, respectively, at 750 MHz output frequency. The in-band noise at 10 kHz offset is -96 dBc/Hz for the integer-N mode and degraded only by 3 dB for the fractional-N mode.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.11 no.2
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• pp.49-54
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• 1978

The cold water mass appeared in offshore of the east coast of Korea in summer season was studied in aspect of chemical oceanography. Such a typical relationship between phosphate and dissolved oxygen as shown in the upwelling regions could not be found in the east coast except around the Kampo coast, southern part of the east coast. It is possible to isolate the North Korean Cold Water from tile proper water of tile Japan Sea by using $\sigma_t-O_2$ diagram. The origin of the cold water mass in offshore of the east coast of Korea in summer is not mainly due to the development of upwelling of the proper water of the Japan Sea but thesouthwardflolvingoftheNorthKoreanCold Water.

• Journal of the Korean Mathematical Society
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• v.47 no.5
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• pp.967-983
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• 2010

Let M be an n-dimensional complete simply connected Riemannian manifold with sectional curvature bounded above by a nonpositive constant $-{\kappa}^2$. Using the cone total curvature TC($\Gamma$) of a graph $\Gamma$ which was introduced by Gulliver and Yamada [8], we prove that the density at any point of a soap film-like surface $\Sigma$ spanning a graph $\Gamma\;\subset\;M$ is less than or equal to $\frac{1}{2\pi}\{TC(\Gamma)-{\kappa}^2Area(p{\times}\Gamma)\}$. From this density estimate we obtain the regularity theorems for soap film-like surfaces spanning graphs with small total curvature. In particular, when n = 3, this density estimate implies that if $TC(\Gamma)$ < $3.649{\pi}\;+\;{\kappa}^2\inf\limits_{p{\in}F}Area(p{\times}{\Gamma})$, then the only possible singularities of a piecewise smooth (M, 0, $\delta$)-minimizing set $\Sigma$ are the Y-singularity cone. In a manifold with sectional curvature bounded above by $b^2$ and diameter bounded by $\pi$/b, we obtain similar results for any soap film-like surfaces spanning a graph with the corresponding bound on cone total curvature.

• Macromolecular Research
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• v.13 no.3
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• pp.223-228
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• 2005

In the present work, a low-density polyethylene (LDPE) composite, filled with Zn-ion coated structural silica encapsulated with the diglycidyl ether of bisphenol-A (DGEBA), was synthesized using the conventional melt-blending technique in a sigma internal mixer. The catalytic activity of the Zn-ions (originating from the structural silica) towards the oxirane group (diglycidyl ether of bisphenol-A (DGEBA): encapsulating agent) was assessed by infrared spectroscopy. Two composites, each with a filler content of $2.5 wt\%$ were developed. The first one was obtained by melt blending the Zn-ion coated structural silica with LDPE in a co-rotating sigma internal mixer. The second one was obtained by melt blending the same LDPE, but with DGEBA encapsulated Zn-ion coated structural silica. Epoxy resin encapsulation of the Zn-ion coated structural silica resulted in its having good interfacial adhesion and a homogeneous dispersion in the polymer matrix. Furthermore, the encapsulation of epoxy resin over the Zn-ion coated structural silica showed improvements in both the mechanical and thermal properties, viz. a $33\%$ increase in the elastic modulus and a rise in the onset degradation temperature from 355 to $371^{\circ}C$, in comparison to the Zn-ion coated structural silica.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2006.05a
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• pp.571-572
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• 2006

RTP (rapid thermal pressing), one of micro-pattern replication techniques like hot embossing, is focused on achieving shorter cycle time. DFSS(Design for Six Sigma) has been applied in order to enhance the completeness of the development process for RTP system. According to DIDOV roadmap, we derived design concepts and subsequently decided the main performances, design factors, and components for RTP system. In the design process of RTP system using finite element analysis, it was realized that its structural characteristics affect large area replicability. Optimizing structural design factors, based on CAE, it was checked out that its large area replicability could be improved in a virtual test. Finally, we have a plan to validate the large area replicability of the developed RTP system, by performing micro-pattern replication tests with polymeric sheets.

• Korean Journal of Optics and Photonics
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• v.7 no.2
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• pp.142-149
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• 1996

In non-saturation region, we measured the degenerate four wave mixing spectra of $X^2\;{\Pi}(v=0){\to}A^2{\Sigma}^+(v'=0)$ transition for OH in counterflow burner, which exists transiently in combustion reaction. We used forward box type geometry for phase matching. Calculating the population of each rotational level from the line intensities of R$_1$band and comparing it with Boltzmann distributions, we could obtain the temperatures of the flame at several points. Corrected for the absorption of incident laser fields, the final temperatures coincided with those measured by coherent anti-Stokes Raman Scattering within error $\pm$60 K near 2000 K. We also measured the concentration distribution of OH radical and it was compared to that measured by laser induced fluorescence.

• Journal of Magnetics
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• v.16 no.2
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• pp.173-176
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• 2011

Fe-Cr alloys with different Cr contents were prepared by an arc melting technique. The alloys were isochronally aged in the range from $400^{\circ}C$ to $900^{\circ}C$ with $50^{\circ}C$ steps with a holding time of 100 hours. The ageing produced embrittlement in the alloys due to either the formation of a Cr-rich ${\alpha}'$ phase or a $\sigma$ phase at high temperatures. Magnetic Hysteresis Loop (MHL) and Micro-Vickers hardness were measured at each step to correlate the magnetic and mechanical properties. Coercivity and hardness of the alloys were increased and remanence decreased up to 500-$550^{\circ}C$ due to formation of a Cr-rich ${\alpha}'$ phase. Beyond 500-$550^{\circ}C$ range, the coercivity and hardness decreased and remanence increased due to the coarsening or dissolution of the Cr-rich ${\alpha}'$ phase. In the Fe-48% Cr alloy, formation of the $\sigma$ phase at $700^{\circ}C$ reduced the maximum induction of the alloy significantly.

• Advanced Composite Materials
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• v.16 no.2
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• pp.151-166
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• 2007

High-cycle fatigue characteristics of quasi-isotropic carbon fiber reinforced plastic (CFRP) laminates [-45/0/45/90]s up to $10^8$ cycles were investigated. To assess the fatigue behavior in the high-cycle region, fatigue tests were conducted at a frequency of 100 Hz, since it is difficult to investigate the fatigue characteristics in high-cycle at 5 Hz. Then, the damage behavior of the specimen was observed with a microscope, soft X-ray photography and a 3D ultrasonic inspection system. In this study, to evaluate quantitative characteristics of both transverse crack propagation and delamination growth in the high-cycle region, the energy release rate associated with damage growth in the width direction was calculated. Transverse crack propagation and delamination growth in the width direction were evaluated based on a modified Paris law approach. The results revealed that transverse crack propagation delayed under the test conditions of less than ${\sigma}_{max}/{\sigma}_b$ = 0.3 of the applied stress level.

• Nuclear Engineering and Technology
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• v.25 no.1
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• pp.102-109
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• 1993

A PC-computer program RADAP has been developed in this study to perform a quick real-time analysis of dose assessment following an accident in a nuclear facility. RADAP uses an interactive LKagrangian puff model in simulating the transport and diffusion of radioactive plume in the atmosphere. For real-time analysis, RADAP treats one or multiple puffs of ground-level releases, simultaneously. It is assumed to maintain a Gaussian distribution within the puff and the diffusion coefficients are computed using the USNRC's normal sigma curve method. The program, however, does not consider the spatial variations but the temporal variations in wind conditions. Whole body and thyroid doses for 3$\times$31 grid are directed to output files, and they are also displayed through computer graphics on VGA or EGA color monitor. The results show that RADAP can be an excellent tool for quick estimation of accidental doses.

• Industrial Engineering and Management Systems
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• v.1 no.1
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• pp.87-92
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• 2002

A stochastic process {$A_n$, n = 1, 2, ...} is an arithmetic process (AP) if there exists some real number, d, so that {$A_n$ + (n-1)d, n =1, 2, ...} is a renewal process (RP). AP is a stochastically monotonic process and can be used for modeling a point process, i.e. point events occurring in a haphazard way in time (or space), especially with a trend. For example, the vents may be failures arising from a deteriorating machine; and such a series of failures id distributed haphazardly along a time continuum. In this paper, we discuss estimation procedures for an AP, similar to those for a geometric process (GP) proposed by Lam (1992). Two statistics are suggested for testing whether a given process is an AP. If this is so, we can estimate the parameters d, ${\mu}_{A1}$ and ${\sigma}^{2}_{A1}$ of the AP based on the techniques of simple linear regression, where ${\mu}_{A1}$ and ${\sigma}^2_{A1}$ are the mean and variance of the first random variable $A_1$ respectively. In this paper, the procedures are, for the most part, discussed in reliability terminology. Of course, the methods are valid in any area of application, in which case they should be interpreted accordingly.