• Journal of the Korean Statistical Society
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• v.3 no.2
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• pp.85-101
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• 1974

In a Balanced Factorial Experiments (BFE) with n factors $F_1, F_2,\cdots,F_n$ at $m_1, m_2,\cdots,m_n$ levels respectively, Shah [15] has considered the following association scheme: the two treatments are the $(P_1, P_2,\cdot,P_n)$th associates, where $p_i=1$ if the ith factor occurs at the same level in both treatments and $p_i=0$ otherwise; $\lambda_{(p_1,p_2,\cdots,p_n)}$ will denote the number of times these treatments occur together in a block. He has showed that a BFE is partially Blanced Incomplete Block(PBIB) design with repsect to the above association scheme. Kurjian and Zelan [6] have proved that factorial designs possessing a Property A (a particular structure for their matrix NN') are factorially balanced.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.24 no.5
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• pp.515-524
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• 2013

The program for dielectric ceramic waveguide filter was developed based on the direct coupled filter of ${\lambda}/2$ step impedance prototype. This developed program was called DWFD(Direct coupled Waveguide Filter Design). The filter was designed by 3-dimensional laminated type to reduce the size at the 1 GHz. S scattering matrix for this filter was calculated using the DWFD program. The width of inductive irises for laminated filter was computed by HFSS simulation tool. This waveguide filter was designed by 8 poles with bandwidth 25 MHz at the center frequency 881.5 MHz. By using a dielectric constant 35.4 and laminated type, the size of filter was reduced with width 50 mm and height 48 mm rapidly. We can see that the measured results agree well with the HFSS simulation result. Finally, this paper is shown that the design and implementation of waveguide filters can be presented by using DWFD program simply.

• Korean Journal of Crystallography
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• v.15 no.1
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• pp.24-28
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• 2004

The structure of $C_{12}H_{15}N_3O_3$ has been determined by X-ray diffraction methods. The crystal system is monoclinic, space group $P2_1/c$, unit cell constants, a = 12.9955(9) ${\AA}$, b = 7.7137(5) ${\AA}$, c = 13.4699(11) ${\AA}$, ${\beta}$ = 107.86(1)$^{\circ}$, V = 1285.2(1) ${\AA}^3$, T = 296 K, Z = 4, $D_c$ = 1.350 $Mgm^{-3}$. The intensity data were collected on an Enraf-Nonius CAD-4 Diffractometer with graphite monochromated Mo $K{\alpha}$ radiation (${\lambda}$ = 1.71073 ${\AA}$). The molecular structure was solved by direct methods and refined by full-matrix least squares to a final R = 4.19% for 1644 unique observed $F_0\;>\;4{\sigma}(F_0)$ reflections 193 parameters.

• Journal of the Korean Institute of Telematics and Electronics D
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• v.36D no.6
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• pp.52-60
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• 1999

Fabricability of phase shifted grating filters has been theoretically studied by an effective index transfer matrix method. In the optical band-pass filter with multiple ${\lambda}/4$ phase-shifts, the phase-shift error and random variation of the grating period should be suppressed such that corresponding resonance frequency lies within, the filter pass-band. The tolerance for the relative error is less than $10^3$, and is quite stringent in typical filters for WDM application. End facet reflection produces ripple in the transmission spectra and the reflectivity should be less than 1% in order to keep the ripple less than 0.25dB. Also, the effect of waveguide absorption loss is enhanced by the resonance in the filter, and the absorption should be limited to 1dB/cm for the signal loss of less than 0.2dB.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.13 no.1
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• pp.75-85
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• 2000

When applying a system identification technique, which incorporates an experimental model to a corresponding finite element model of a structure, one of the major problems is the large difference in the numbers of degrees of freedom (dof) between the two models. While there are large number of dofs in a finite element model, the number of measurement points is practically limited. So it is very difficult to incorporate them. Especially rotational dofs are hard to measure. In this study a method is presented for estimating structural dynamic responses at unmeasurable locations in frequency domain. The proposed method is tested numerically and the feasibility for practical application has been demonstrated through an example structure under moving loads, where translational and rotational dofs of beam at a center point are estimated from the partial measurements of responses at accessible points.

• Korean Journal of Crystallography
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• v.15 no.2
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• pp.93-98
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• 2004

The structure of C_{28}H_{41}N_4O_4Br\;{\cdot}\;2H_2O$ has been determined by X-ray deffraction methods. The crystal system is triclinic, space group Pl, unit cell constants, a=9.000(1) $\AA$, b=9.312(3) $\AA$, c=9.344(2) $\AA$, $\alpha=89.37(20)^{\circ},\;\beta=68.81(3)^{\circ},\;\gamma=84.70(4)^{\circ},\;V=726.7(8){\AA},\;T=298K,\;Z=1,\;D_c=1.402Mgm^{-3}$. The intensity data were collected on an Enraf-Nonius CAD4 Diffractometer with graphite monochromated $MoK\alpha$ radiation $(\lambda=0.71073\;{\AA}$. The molecular structure was solved by direct methods and refined by full-matrix least squares to a final $R=5.95\%$ for 2521 unique observed $F_0>4\sigma(F_0)$reflections and 370 parameters.

• Korean Journal of Materials Research
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• v.1 no.3
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• pp.115-124
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• 1991

In this study, the relationship between mechanical properties and the effects of second phase in tri-phase steel which was composed of ferrite-martensite-bainite was investigated. In order to obtain different microstructure of ferrite+martensite(DP), ferrite+bainite(F+B), and ferrite+martensite+bainite(TP, different heat treatment has been accomplished. The effects of volume fraction and microstructure of each specimen were studied on tensile property, Charpy impact energy and stretch-flangeability. As the bainite content in triphase steels increased, the tensile strength, and yield strength decreased as well as the reduction of area and strength-uniform elongation increased. However, ferrite-bainite steel had high yield ratio and yield point elongation. The Charpy impact energy of TP and F+B steel was higher than that of DP steel. In addition, the characteristics of hole expanding limit($\lambda$) of TP steel and F+B steel were higher than that of DP steel. These mechanical properties of tri-phase steel have been improved, because bainite could be deformed easily within ferrite matrix. The effect of bainite on ductility in tri-phase steel has been found to be favorable. In this experiment, tri-phase steel contained within 27% bainite volume fraction had good nechanical properties and superior stretch-flangeability.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.24 no.2
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• pp.316-323
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• 2000

A nonlinear low-Reynolds-number heat transfer model is developed to predict turbulent flow and heat transfer in separated and reattaching flows. The $k-{\varepsilon}-f_{\mu}$ model of Park and Sung (1997) is extended to a nonlinear formulation, based on the nonlinear model of Gatski and Speziale (1993). The limiting near-wall behavior is resolved by solving the $f_{\mu}$ elliptic relaxation equation. An improved explicit algebraic heat transfer model is proposed, which is achieved by applying a matrix inversion. The scalar heat fluxes are not aligned with the mean temperature gradients in separated and reattaching flows; a full diffusivity tensor model is required. The near-wall asymptotic behavior is incorporated into the $f_{\lambda}$ function in conjunction with the $f_{\mu}$ elliptic relaxation equation. Predictions of the present model are cross-checked with existing measurements and DNS data. The model preformance is shown to be satisfactory.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.7 no.1
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• pp.43-52
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• 1996

Nonreciprocal twin-toroid ferrite phase shifter is designed, fabricated, and tested. ABCD matrix method is used to design the phase shifter and to compute its optimum dimen- sions. Quarter-wave two-section impedance matching transformers are utilized in order to match the impedance of the empty guide to that of the ferrite-loaded guide. Driving circuit controls the current needed to drive the phase shifter. Measured insertion loss and VSWR characteristics within the operaring band(9.1GHz ~ 9.5GHz) are less than 1.2dB and 1.15, respectively. After temperature compensation technique is appied to the phase shifter, the measured phase error of the phase shifter is less than $\pm4$ between $-10^{\circ}C\;and\;+60^{\circ}C$.

• Journal of Korea Foundry Society
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• v.8 no.4
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• pp.437-445
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• 1988

The effect of interlamellar spacing on microstructural stability at high temperature was studied for unidirectionally solidified ternary $Ni\;/\;Ni_3Al-Ni_3$ Nb and binary $Ni-Ni_3Nb$ eutectic composite. The interlamellar spacing of both alloy systems were varied with the growth rate according to $"{\lambda}^2R=constant"$ relationship. As a result of isothermal heat treatments at high temperature it was considered that coarsening of lamellar structure was due to concentration gradient between the tip with a relatively small radius of curvature and the side of the thick lamellae with a larger radius of the opposite sign. Fault density was increased as the interlamellar spacing decreased. Therefore it is also considered that the higher coarsening rate of the specimen with the smaller interlamellar spacing was due to higher fault density. And the diference of coarsening rate between $Ni\;/\;Ni_3Al-Ni_3Nb$ and $Ni-Ni_3Nb$ eutectic composites was not observed when the interlamellar spacing was similar in size. This means that the presence of ${\gamma}'$ in ${\gamma}\;/\;{\gamma}'\;-{\delta}$ eutectic had no b arrier effect to diffusion through the ${\gamma}$ matrix.