• Journal of the Korean Institute of Telematics and Electronics B
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• v.33B no.2
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• pp.88-94
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• 1996

In this paper, we present a half rate speech coder using trellis excitation. The coder combines code-excited linear prediction (CELP) system and trellis quantization method using the codebook expansion, and it produces higher speech quality than the typical CELP coder for the same transmission rate. A subjective comparison with 3~8 bit .$\mu$-law PCM indicates that the half rate coder provides speech quality between 5-bit and 6-bit $\mu$-law PCM .

• Proceedings of the Korea Concrete Institute Conference
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• 2000.10a
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• pp.379-382
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• 2000

In this paper, we evaluated the suitability of converter slag as concrete aggregate by measuring physical and chemical characteristics of converter slag. The converter slag mainly contains SiO₂and CaO as the chemical composition. The reaction with water and a little of free CaO in the slag causes slag's volume to expanse. Therefore, we used several aging method in order to decrease the characteristics of slag volume expansion. Then the compressive strength of concrete with the converter slag aggregate is measured.

• Proceedings of the Korea Concrete Institute Conference
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• 2000.10a
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• pp.801-809
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• 2000

Until recently as a method of repairing leaking problem, generally urethane series were used for many structures as subway, box culvert etc. However the lacking of sufficient penetration capacity have made it difficult to repair such structures completely. Now, we could achieve enhanced quality of repairing work by using new material which was compounded of urethane series and cement series properly. This material can penetrate concrete structure efficiently and move interactively with the structure in case of the thermal expansion. Besides of this, we could prevent expecting leakage through several improvements on the aspects of design, materials and site implementation.

• Journal of applied mathematics & informatics
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• v.5 no.3
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• pp.669-690
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• 1998

In this paper we develop a new theory of adjoint and symmetric method in the class of general implicit one-step fixed-stepsize methods. These methods arise from simple and natral def-initions of the concepts of symmetry and adjointness that provide a fruitful basis for analysis. We prove a number of theorems for meth-ods having these properties and show in particular that only the symmetric methods possess a quadratic asymptotic expansion of the global error. In addition we give a very simple test to identify the symmetric methods in practice.

• Coupled systems mechanics
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• v.7 no.1
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• pp.61-77
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• 2018

This paper establish a high concentration ratio approximation of linear elastic properties of materials with periodic microstructure with cubic inclusions. The approximation is derived using first few terms of power series expansion of the solution of the equivalent eigenstrain problem with a homogeneous eigenstrain approximation. Viability of the approximation at high concentration ratios is proved by comparison with a numerical solution of the homogenization problem. To this end some theoretical result of symmetry properties of the homogenization problem are given. Using these results efficient numerical computation on a reduced computational domain is presented.

• Journal of the Korean Institute of Telematics and Electronics
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• v.27 no.6
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• pp.921-928
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• 1990

A multivariable equalizer is designed which compensates transmission distortion for coaxial transmission line. The characteristic transfer function with bilateral parameter domain is approximated using the expansion method of orthonormal function and Gram Schmidt orthogonal function, but the parameter domain of approximated function is limited to unilateral. To solve that problem, Bode type transfer function is used to give bilateral variable characteristic to approximated function. The multivariable equalizer in this paper can be substituted for the current equalizer which consist of a fixed equalizer and a variable equalizer.

• Proceedings of the Optical Society of Korea Conference
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• 2007.07a
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• pp.319-320
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• 2007

We report on the fabrication of two-dimensional Silicon On Insulator (SOI) photonic crystal (PhC) superprism. To optimize the design of 2-D SOI PhC superprism, the photonic band structures (TE-polarization) for triangular lattices and the dispersion surfaces were calculated and analyzed by the plane wave expansion method. Dense 2-D SOI PhC superprism nanostructures with taper input and output waveguide microstructures were successfully fabricated by nanoimprint lithography, followed by inductively coupled plasma (ICP) etching.

• Journal of the Korean Ceramic Society
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• v.33 no.10
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• pp.1147-1155
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• 1996

• Journal of the Korean Ceramic Society
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• v.22 no.5
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• pp.66-70
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• 1985

This study was to investigate physical properties of the system $Ca(Mg_{1-x}Al_x) (Si_{2-x}Al_x)O_6$ by quenching method. This system $\chi$=0.1 to 0.3 had same crystal phase microstructure and similar properties. Bulk density microhardness thermal expansion coefficient and modulus of rupture of these solid solutions were 2.87~2.95g/cm3 850~900kg/$mm^2$, $7.5~7.8{\times}10^{-6}$/$^{\circ}C$ and 1950~1980kg/$cm^2$ respectively.

• Proceedings of the Korea Electromagnetic Engineering Society Conference
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• 2001.11a
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• pp.319-324
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• 2001

An anatomical head and a multi-layered spherical head with a half-wave handset antenna have been analysed and compared using the Finite-Difference Time-Domain (FDTD) and the Eigenfuntion Expansion Method (EEM), respectively. The analysis shows that results from a simple spherical head with a half-wave antenna can be used to predict the main antenna radiation patters as well as estimates of the peak SAR in a handset user's head. Various representative design data are presented using a six-layered spherical head with a half-wave antenna at 900 MHz