• Nuclear Engineering and Technology
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• v.50 no.1
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• pp.35-42
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• 2018

This article presents clean core criticality calculations and control rod worth calculations for TRIGA (Training, Research, Isotope production-General Atomics) Mark II research reactor benchmark cores using Winfrith Improved Multi-group Scheme-D/4 (WIMS-D/4) and Program for Reactor In-core Analysis using Diffusion Equation (PRIDE) codes. Cores 133 and 134 were analyzed in 2-D (r, ${\theta}$) and 3-D (r, ${\theta}$, z), using WIMS-D/4 and PRIDE codes. Moreover, the influence of cross-section data was also studied using various libraries based on Evaluated Nuclear Data File (ENDF/B-VI.8 and VII.0), Joint Evaluated Fission and Fusion File (JEFF-3.1), Japanese Evaluated Nuclear Data Library (JENDL-3.2), and Joint Evaluated File (JEF-2.2) nuclear data. The simulation results showed that the multiplication factor calculated for all these data libraries is within 1% of the experimental results. The reactivity worth of the control rods of core 134 was also calculated with different homogenization approaches. A comparison was made with experimental and reported Monte Carlo results, and it was found that, using proper homogenization of absorber regions and surrounding fuel regions, the results obtained with PRIDE code are significantly improved.

• Korean Journal of Materials Research
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• v.12 no.3
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• pp.205-210
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• 2002

The HPS(High Porosity Support, 39.3%) and the LPS( Low Porosity Support, 18.7%) were fabricated to investigate the phase transformation and the chance of microstructure with porosity of alumina support. Alumina sol was made using aluminum tri-sec $butoxide(ATSB,\; Al(O-Bu)_3)$, the membrane on porous support with different porosity and the membrane without support were fabricated. The $\theta$-to ${\alpha}-A1_2O_3$ phase transformation in the membranes was investigated using thin film X-ray diffraction (XRD), and the change of microstructure was observed using scanning electron microscopy(SEM). XRD patterns showed that the membrane on LPS and HPS had 10$0^{\circ}C$, 5$0^{\circ}C$ higher $\theta$-to ${\alpha}-A1_2O_3$ transformation temperature compared to the unsupported membrane. A similar effect was also observed in microstructure of the membranes, theoritical temperature difference were 97$^{\circ}C$ and 44$^{\circ}C$ by Crapeyron equation.

• Proceedings of the Korean Nuclear Society Conference
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• 1997.10a
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• pp.481-486
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• 1997

The interfacial shear stress is experimentally investigated for co-current air-water stratified flow in inclined rectangular channels having a length of 1854mm, width of 120mm and height of 40mm at almost atmospheric pressure. Experiments are carried out in several inclinations from $0^{\circ}\;up\;to\;10^{\circ}$. The local film thickness and the wave height are measured at three locations, i.e., L/H = 8,23, and 40. According to the inclination angle, the experimental data are categorized into two groups; nearly horizontal data group ($0^{\circ}\;{\leq}\;{\theta}\;{\leq}\;0.7^{\circ}$), and inclined channel data group ($0.7^{\circ}\;{\leq}\;{\theta}\;{\leq}\;10^{\circ}$). Experimental observations for nearly horizontal data group show that the flow is not fully developed due to the water level gradient and the hydraulic jump within the channel. For the inclined channel data group, a dimensionless wave height, $\Delta$h/h, is empirically correlated in terms of $Re_{G}$ and h/H. A modified root-mean-square wave height is proposed to consider the effects of the interfacial and wave propagation velocities. It is found that an equivalent roughness has a linear relationship with the modified root-mean-square wave height and its relationship is independent of the inclination.

• Journal of the Korean Magnetics Society
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• v.4 no.4
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• pp.307-312
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• 1994

The magneto-optical Kerr effect due to the (Fe,Co)/(Pd,Pt,Cu,Ag) multilayer film is calculated considering of multiple reflection effect, and the calculated Kerr spectrum is compared to the reported experimental value. In case of Co/Pd, the reliance of composition and the variable tendency of magneto-optical Kerr rotation angle for Co thickness fully coresponds to experimantal and theoretical value. The theoretical Kerr spectrum of Fe/Cu and Fe/Ag multilayer films show the peaks near the Cu and Ag optical ansorption band in accordance with the experiment. But in case of Co/Pt, the increase tendency of Kerr rofation with decreasing wavelength reported by experiments could not be explained by the optical multiple interference. This difference of theoretical and experimental Kerr spectrum of Co/Pt film might be related with the change of electronic structure of Co and/or Pt from their bulk state.

• Journal of Welding and Joining
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• v.18 no.5
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• pp.84-89
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• 2000

Friction welding of titanium and aluminium is numerically modeled by the axisymmetric thermal elastic-plastic analysis. In titanium/aluminium friction welding, heat transfers into the titanium substrate to a distance of z=10(mm) on the side of the bondline and into the whole region of the aluminium substrate having the large thermal conductivity. Adjacent to the bondline, $^{\sigma}r\;and\;^{\sigma\theta}$ are tensile in the substrate whose thermal shrinkage is large, and are compressive in the substrate whose thermal shrinkage is small. $\sigma_z$ along the radial direction is large tensile at the periphery of the component. Plastic strain occurs only close to the bondline in the aluminium substrate. In the components of plastic strain, $\varepsilon^p_r\;and\;\varepsilon^p_{\theta}$ have positive values and $\varepsilon^p_r$ has large negative value. However, $\varepsilon^p_r$ is produced not because of the severity of the mechanical restraint condition, but on purpose to satisfy the condition of the volume constant. A plastic work is proposed as a measure to evaluate the mechanical severity. The plastic work is larger in the aluminium substrate than that in the titanium substrate. The mechanical condition is severer in the aluminium substrate.

• Journal of Korean Society of Steel Construction
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• v.11 no.2 s.39
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• pp.131-142
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• 1999

The general behavior of the curved girder including the warping effects can be presented as the series of differential equations developed by Vlasov. Generally, bending moment is the most important factor for engineer to decide the section of the girder. In order to accommodate easiness of the structural analysis for the curved girder bridge, this paper suggest the ratios of bending moment of curved gilder to that of straight girder. These ratios are presented by an approximate formula setting central angle ${\theta}(L/R)$ as a variable. The approximate formula of the maximum bending moment ratios and influence lines of all stress resultants can be used to design the three-span curved girder bridges.

• Journal of the Korean Solar Energy Society
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• v.21 no.3
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• pp.33-41
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• 2001

This paper showed the a numerical analysis of the thermal and fluid flow in solar concentration absorber with tilt angle, and the purpose of this study is to obtain the optimum tilt angle of the absorber. The boundary conditions of a numerical model were assumed as flows : (1) The heat source is located at the center of absorber (3) The bottom wall is opened and adiabatic. (3) The top, right and left walls are cooled wall. The parameters for the numerical analysis are tilt angles and Rayleigh numbers i.e., tilt angle $\theta=0^{\circ},\;15^{\circ},\;30^{\circ},\;45^{\circ},\;60^{\circ},\;75^{\circ},\;90^{\circ}$ and 101 $\leq$ Ra $\leq$ 103. The velocity vectors and isotherms were dense at wall side and the heat source. The mean Nusselt number had a maximum value at $\theta=0^{\circ}$ and showed a low value as the tilt angles were increased. Finally, the decrease rate of mean Nusselt number was appeared small with tilt angle when Rayleigh numbers were increased.

• The Korean Journal of Physiology and Pharmacology
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• v.3 no.3
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• pp.245-250
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• 1999

The effects of an antipsychotic, chlorpromazine, on the electroencephalogram (EEG) were observed while rats were awake but immobile. The time course and the dose-dependency of the EEG changes were examined. The method of the power spectrum analysis was used to examine the EEG changes by the drug. The bands were divided into delta $(1{\sim}3.5\;Hz),$ theta $(3.5{\sim}8\;Hz),$ alpha $(8{\sim}13\;Hz),$ beta1 $(13{\sim}21\;Hz),$ beta2 $(21{\sim}30\;Hz)$ and gamma $(30{\sim}50\;Hz).$ In rats, the low dose of chlropromazine (1 mg/kg, i.p.) produced a significant increase in the power of the beta1 band. The higher doses (5, 10 mg/kg, i.p.) produced a significant increase in the power of the delta, theta, alpha and beta1 bands, and the decrease in the power of the gamma band. The powers of the bands changed dose-dependently. Then, the authors discussed whether the EEG effects produced by a drug are associated with the accompanying behavioral changes specifically.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.8 no.1
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• pp.120-139
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• 1996

Experiment was performed to study the heat transfer characteristics in 27 kinds of 15 : 1 scale models of multi-louverred fin heat exchangers with a wide range of variables(R $e_{Lp}$ =100~1, 800, $L_p$/F$p$=0.3~0.9, $\theta$=20$^{\circ}$~40$^{\circ}$). Thermofoil heaters were used to heat the louver fins and the local average Nusselt number for each louver in the louver array was obtained at constant wall temperature conditions. Correlations are developed to predict the heat transfer characteristics and drag coefficients. Generally, the heat transfer characteristics in the multi-louvered fins is shown to be similar to those of the laminar heat transfer on a flat plate. As the Reynolds number, the louver pitch to fin pitch ratio$L_p$/F$p$and the louver angle($\theta$) increase respectively, the average Nusselt number increases, but the variation of average Nusselt number as a function of the louver angle is smaller than that as a function of the louver pitch to fin pitch ratio. In case of$L_p$/F$p$ <0.5, the average Nusselt number of the 3rd louver is especially lower than the others, it is expected that it is due to the flow structure such as a recirculation flow and a flow separation.

• Proceedings of the IEEK Conference
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• summer
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• pp.181-184
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• 2004

In this paper, we propose the dual band(2.4GHz and 5GHz) antenna for access point of WLAN(Wireless Local Area Network) which has similar radiation patterns for each band. Simulation results by using HFSS(High Frequency Structure Simulator) for the proposed antenna are presented. The electrical characteristics of the proposed antenna are measured with HP 8510C network analyzer and included. And radiation patterns are measured with rectangular anechoic far field antenna chamber. Measured results show that $S_{11}$ is less than - 14dB and VSWR(Voltage Standing Wave Ratio) is less than 1.5 for all frequency bands of interest. The measured maximum gain for elevation pattern at 2.40GHz is about 2.46dBi at $theta=-78^{\circ}$ and maximum gain for 5.825GHz is about 2.70dBi at $theta=-80^{\circ}.$ And the implemented antenna has good radiation pattern characteristic, therefore, we expect that the implemented dual band antenna is applicable for access point of WLAN.