• Journal of Korea Society of Digital Industry and Information Management
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• v.7 no.4
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• pp.119-131
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• 2011

In this paper, we explore the application of 2-D dual-tree discrete wavelet transform (DDWT), which is a directional and redundant transform, for image coding. DDWT main property is a more computationally efficient approach to shift invariance. Also, the DDWT gives much better directional selectivity when filtering multidimensional signals. The dual-tree DWT of a signal is implemented using two critically-sampled DWTs in parallel on the same data. The transform is 2-times expansive because for an N-point signal it gives 2N DWT coefficients. If the filters are designed is a specific way, then the sub-band signals of the upper DWT can be interpreted as the real part of a complex wavelet transform, and sub-band signals of the lower DWT can be interpreted as the imaginary part. The quincunx lattice is a sampling method in image processing. It treats the different directions more homogeneously than the separable two dimensional schemes. Quincunx lattice yields a non separable 2D-wavelet transform, which is also symmetric in both horizontal and vertical direction. And non-separable wavelet transformation can generate sub-images of multiple degrees rotated versions. Therefore, non-separable image processing using DDWT services good performance.

• Journal of the Society of Naval Architects of Korea
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• v.45 no.4
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• pp.403-410
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• 2008

This paper describes the optimization of the rudder section by the genetic algorism based on VLM(Vortex Lattice Method) and panel method. The developed propeller-rudder analysis program has been validated by comparing with experimental data. The research extends to optimize the anti-erosion rudder section of the large container ship. The object function is the amount of pressure at leading edge of rudder which is closely related with erosion phenomena. The optimized rudder has been compared with conventional rudder with NACA 0021 section by analyzing with the developed program. The finally optimized section has low and mild pressure distribution in comparison with the NACA rudder. The experiments is expected to be carried out for the validation of the present optimization and more parametric study of section geometry is also expected to be conducted in the near future.

• Clean Technology
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• v.14 no.3
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• pp.153-159
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• 2008

The solubility of triclosan, an anti-acne agent was measured in supercritical carbon dioxide ($scCO_2$) with a variable volume view cell at 313.15, 323.15, and 333.15 K and at pressures between 10 and 40 MPa. We successfully correlated triclosan solubility in $scCO_2$ using the quasi-chemical nonrandom lattice fluid (QLF) equation of state. Triclosan was micronized using the rapid expansion of supercritical solutions (RESS) process. The effects of temperature and pressure on particle size were investigated using phase behavior data and correlated results from the QLF model.

• Transactions of the Korean hydrogen and new energy society
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• v.14 no.2
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• pp.97-104
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• 2003

The structural transitions of the matrix and the second phases of $Ti_{1.0}Mn_{0.9}V_{1.1}$ and $Ti_{1.0}Cr_{1.5}V_{1.7}$ alloys upon hydrogenation have been investigated at 293K. The effect of hydrogen isotope on their crystal structures has been also discussed. The crystal structures, Phase abundance and lattice parameters of the hydrides were determined by the Rietveld method using X-ray diffraction data. At the experimental temperature, the $Ti_{1.0}Mn_{0.9}V_{1.1}$ alloy and $Ti_{1.0}Cr_{1.5}V_{1.7}$ alloy revealed different structural transition processes upon hydrogenation although the crystal structures of these two alloys are both BCC at room temperature. The second phases such as Ti-rich phase with $NiTi_2$ structure and $\alpha$-Ti with HCP structure absorbed hydrogen at relatively low hydrogen pressures and the phase abundance remained almost constant. This means that it is desirable to decrease the amount of the second phases as far as possible in order to increase the effective hydrogen storage capacities of the alloys. The crystal structures of corresponding isotope hydrides, the phase abundance and the lattice parameters did not depend on the kind of hydrogen isotope, but only on the hydrogen content.

• Progress in Superconductivity and Cryogenics
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• v.20 no.2
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• pp.24-28
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• 2018

To understand the effects of Cd substitution for Cu, $(Pb_{0.5}Cu_{0.5-x}Cd_x)Sr_2(Ca_{0.7}Y_{0.3})Cu_2O_z$ (x = 0 ~ 0.5) compounds were synthesized and the structural and superconducting properties of the compounds were characterized. Resistivity data revealed that superconducting transition temperature rises initially up to x = 0.25 and then decreases as the Cd doping content increases. Room-temperature thermoelectric power decreases at first up to x = 0.25 and then increases with higher Cd doping content, indicating that the change in $T_c$ is mainly caused by the change in the hole concentration on the superconducting planes by the Cd doping. The non-monotonic dependence of the lattice parameters and the transition temperature with Cd doping content is discussed in connection with the possible formation of $Pb^{+2}$ ions and the removal of excess oxygen caused by Cd substitution in the charge reservoir layer. A correlation between transition temperature and c/a lattice parameter ratio was observed for the $(Pb_{0.5}Cu_{0.5-x}Cd_x)Sr_2(Ca_{0.7}Y_{0.3})Cu_2O_z$ system.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.59 no.11
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• pp.2108-2113
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• 2010

The Long Term Evolution (LTE) system is based on the Orthogonal Frequency Division Multiplexing (OFDM) and relies its channel estimation on the lattice-type pilot samples in the multipath fading channel environment. The estimation of the channel frequency response (CFR) makes use of the least squares estimate (LSE) for each pilot samples, followed by an interpolation both in time- and in frequency-domain to fill up the channel estimates for subcarriers corresponding to data samples. Any interpolation scheme could be adopted for this purpose. Depending on the requirements of the target system, we may choose a simple linear interpolation or a sophisticated one. For any choice of an interpolation scheme, these is a trade-off between estimation accuracy and numerical cost. For those wireless communication systems based on the OFDM and the preamble-type pilot structure, the DFT-based channel estimation and its variants have been successfully. Yet, it may not be suitable for the lattice-type pilot structure, since the pilot samples are not sufficient to provide an accurate estimate and it is known to be sensitive to the location as well as the length of the time-domain window. In this paper, we propose a simple interpolated based on the upsampling mechanism in the multirate signal processing. The proposed method provides an excellent alternative to the DFT-based methods in terms of numerical cost and accuracy. The performance of the proposed technique is verified on a multipath environment suggested on a 3GPP LTE specification.

• International Journal of Aeronautical and Space Sciences
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• v.18 no.3
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• pp.474-484
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• 2017

This paper studies the applicability of an efficient numerical model based on artificial neural networks (ANNs) to predict the dynamic responses of the wing structure of an airplane due to atmospheric turbulence in the time domain. The turbulence velocity is given in the form of a stationary Gaussian random process with the von Karman power spectral density. The wing structure is modeled by a classical beam considering bending and torsional deformations. An unsteady vortex-lattice method is applied to estimate the aerodynamic pressure distribution on the wing surface. Initially, the trim condition is obtained, then structural dynamic responses are computed. The numerical solution of the wing structure's responses to a random turbulence profile is used as a training data for the ANN. The current ANN is a three-layer network with the output fed back to the input layer through delays. The results from this study have validated the proposed low-cost ANN model for the predictions of dynamic responses of wing structures due to atmospheric turbulence. The accuracy of the predicted results by the ANN was discussed. The paper indicated that predictions for the bending moments are more accurate than those for the torsional moments of the wing structure.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2006.06a
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• pp.180-181
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• 2006

CdSe single crystal was grown by sublimation method in the two-step vertical electric furnace. This CdSe single crustal had hexagonal structure whose lattice constants of $a_0$ and $c_0$ were measured $4.299\;{\AA}$ and $7.009\;{\AA}$ by extrapolation method, respectively. CdSe single crystal was n-type semiconductor values were measured from Hall data by Van der Pauw method in the room temperature. Mobility tends to increase in proportion to $T^{3/2}$ from 33K to 130K due to impurity scattering. but mobility tends to decrease in proprtion to $T^{-3/2}$ from 130K to 293K due to lattice scattering. CdSe thin film was made by electron beam evaporation technique had also hexagonal structure. The grain size of this thin film was grown to $1{\mu}m$ as a result of annealing in the vapor of Ar or Cd. Annealde CdSe thin film was n-type semiconductor whose carrier density had about $7{\times}10^{12}cm^{-3}$ and its mobility had about $1.6{\times}10^3cm^2/V$ sec at room temperature.

• Korean Journal of Materials Research
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• v.15 no.9
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• pp.566-576
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• 2005

This paper describes an ab Initio study on interface energies, misfit strain energies, and electron structures at coherent interfaces Fe(bcc structure)/MCs(NaCl structure M=Ti, Zr, Hf). The interface energies at relaxed interfaces Fe/TiC, Fe/ZrC and Fe/HfC were 0.263, 0.153 and $0.271 J/m^2$, respectively. It was understood that the dependence of interface energy on the type of carbide was closely related to changes of the binding energies between Fe, M and C atoms before and after formation of the interfaces Fe/MCs with the help of the DLP/NNBB (Discrete Lattice Plane/ Nearest Neighbour Broken Bond) model and data of the electron structures. The misfit strain energies in Fe/TiC, Fe/ZrC and Fe/HfC systems were 0.390, 1.692 and 1.408 eV per 16 atoms(Fe: 8 atoms and MC; 8 atoms). More misfit energy was generated as difference of lattice parameters between the bulk Fe and the bulk MCs increased.

• Bulletin of the Korean Chemical Society
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• v.14 no.1
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• pp.91-95
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• 1993

In this work we have studied the spin-lattice relaxation of $^{19}$F spins in benzotrifluoride in our quest for a reliable method of discriminating the contribution due to dipolar relaxation mechanism from that due to spin-rotational mechanism for nuclear spins located on methyl or substituted methyl group in organic molecules. Over the temperature range of 248-268 K the decay of normalized longitudinal magnetization was found to be well described by a two parameter equation of the form R(t) = exp(-st){$\frac{5}{6}$exp(-s$_1$)+$\frac{1}{6}$} which was derived under the assumption that interactions in the A3 spin system are modulated randomly and predominantly by internal rotational motions of -CF_3$ top, and it was shown that the separation of contribution due to dipolar interactions from that due to spin-rotation interaction could be successfully achieved by least-square fitting of observed data to this equation. The results indicate that the spin-rotational contribution is overwhelmingly larger than that of dipolar origin over the given temperature range and becomes more deminating at higher temperature.