• Nuclear Engineering and Technology
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• v.23 no.2
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• pp.183-199
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• 1991

Transient response of temperature distributions in a Pressurized Water Reactor (PWR) pressurizer vessel wall for the Inadvertent Auxiliary Spray transient has been analyzed with conservatism accounted for the resulting thermal stresses in the regions of the vessel wall which are wetted by the spray water droplets. In order to determine the forced convective heat transfer coefficient at the inner boundary surface of vessel wall where the droplets impinge on and flow down, the transient temperatures of spray droplets when they reach the inner surface of the vessel wall after travelling from the spray nozzle through the pressurizer interior space occupied with the saturated steam-noncondensable hydrogen gas mixture have been predicted. The transient temperature distributions in the vessel wall have been obtained by using the finite element method, and the typical results have been provided. It has been shown that the results of thermal analysis are consistent with representation of the input transient and have plausible physical meaning.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.27 no.12
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• pp.652-658
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• 2015

The Bubble Jet Loop Heat Pipe (BJLHP) is designed to operate in the horizontal orientation. The motion of the bubble generated by boiling working fluid on a heater surface in the evaporating section of the BJLHP helps the working fluid transfer heat to the condensing portion. In this study, we changed the position of the heater in the evaporating section from concentric to eccentric. The concentric heater is located at the center of the tube in the evaporating part, and the eccentric heater is located at the bottom of the inner surface of the same tube. We used R-134a as the working fluid, and the charging ratio was 50%vol. We measured the temperatures of the evaporating and condensing sections by changing the input electric power from 50 W to 200 W, measuring every 50 W. The results of the experiment show that the effective thermal conductivity of BJLHP using an eccentric heater is four times higher than the BJLHP obtained using a concentric heater. Additionally, we conducted a visualization experiment on the evaporating portion of BJLHP to determine why the effective thermal conductivity was higher. The working fluid was water, and we took pictures of the flow visualization for BJLHP. Nucleate boiling with the eccentric heater was more intense and generated more bubbles. Therefore, the eccentric heater was more saturated by the liquefied working fluid.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.27 no.12
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• pp.1069-1074
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• 2016

This paper presents a V-band two-stage power amplifier integrated circuit using TSMC 65 nm CMOS process. The simple input, output, and inter-stage matching networks based on passive components are integrated. By compensating for power gain characteristics using a pre-distortion technique, the linearity of the power amplifier was improved. The implemented two-stage power amplifier showed a power gain of 10.4 dB, a saturated output power of 9.7 dBm, and an efficiency of 20.8 % with a supply voltage of 1 V at the frequency band of 58.8 GHz.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.22 no.3
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• pp.380-388
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• 2011

In this paper, we developed the X-band 63 watt pulsed SSPA(Solid State Power Amplifier) by using HMIC(Hybrid Microwave Integrated Circuits). The pulsed SSPA consists of power supply and 3-stage amplifier modules : pre-amplifier stage, driver-amplifier stage, final-amplifier stage. The developed pulsed SSPA provides more than 63 watts of output power with a short pulse width and the duty cycle of up to 1.2 % at $70^{\circ}C$. The fabricated module offers great than 37 dB of saturated gain across the operating band. Input and output VSWR is <1.5:1. This module has an average current of 400 mA typical and operates at a +28 $V_{dc}$ supply. The developed SSPA in this paper can apply to pulsed Doppler radar with high speed operation.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.22 no.4
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• pp.67-72
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• 2022

This study presents the design of power amplifier (PA) in 60 nm GaN/Si HEMT technology. A customized transistor model enables the designing circuits operating at W-band. The all matching network of the PA was composed of equivalent transformer circuit to reduce matching loss. And then, equivalent transformer is several advantages without any additional inductive devices so that a wideband power characteristic can be achieved. The designed die area is 3900 ㎛ × 2300 ㎛. The designed results at center frequency achieved the small signal gain of 15.9 dB, the saturated output power (Psat) of 29.9 dBm, and the power added efficiency (PAE) of 24.2% at the supply voltage of 12 V.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.48 no.2
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• pp.74-79
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• 2011

HDR(high dynamic range) imaging techniques supports wider dynamic range than normal images captured from general still camera. These usually need several shots to obtain LDR(low dynamic range) images, causing ghosting artifacts. Accordingly, this paper suggests a method to generate new LDR images from a single Bayer image using Exposure LUT(look-up table) by considering channel dependency. We prior construct exposure LUT for each RGB channel, showing the relationship between input and average output luminance values. In the process, by applying the average luminance of input image and current exposure to LUT, new exposures which are determined by user choice are first estimated. Next, LDR images which are corresponded to new exposures are generated based on each LUT. Saturated areas are improved by considering channel dependency in the last procedure. In the experimental comparison, high PSNR values are obtained between estimated and captured images. Also, we have similar appearance on displayed images.

• Journal of Korean Tunnelling and Underground Space Association
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• v.26 no.3
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• pp.191-208
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• 2024

In this study, a hydro-mechanical-damage coupled analysis model was developed to evaluate the structural safety of radioactive waste disposal structures. The Mazars damage model, widely used to model the fracture behavior of brittle materials such as rocks or concrete, was coupled with conventional hydro-mechanical analysis and the developed model was verified via theoretical solutions from literature. To derive the numerical input values for damage-coupled analysis, uniaxial compressive strength and Brazilian tensile strength tests were performed on concrete samples made using the mix ratio of the disposal concrete silo cured under dry and saturated conditions. The input factors derived from the laboratory-scale experiments were applied to a two-dimensional finite element model of the concrete silos at the Wolseong Nuclear Environmental Management Center in Gyeongju and numerical analysis was conducted to analyze the effects of damage consideration, analysis technique, and waste loading conditions. The hydro-mechanical-damage coupled model developed in this study will be applied to the long-term behavior and stability analysis of deep geological repositories for high-level radioactive waste disposal.

• Korean Journal of Environmental Agriculture
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• v.14 no.3
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• pp.263-271
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• 1995

Chemical assessment of soil pollution with heavy metals was made by analyzing the changes in pH, ionic strength, cationic concentration and chemical species in the soil solution. Saturated pastes of the unpolluted soils were made by adding solutions containing Cu or Cd and the final Cu or Cd concentrations were in the range of 0 to 400 mg/kg. After equilibrating for 24 hours at $25^{\circ}C$, the soil solution was extracted from the saturated pastes by the vacuum extraction method and analyzed for pH, electrical conductivity, Cu, Cd, cations and inorganic ligands. Chemical species in soil solution were calculated by the GEOCHEM-PC program employing the input variables of pH, ionic strength(${\mu}$), molar concentrations of cations and ligands. Increasing Cu or Cd additions lowered pH of the soil solution but increased concentrations of Ca, Mg and K resulting in increases of ${\mu}$ of the soil solution. Effects of Cu on lowering pH and increasing ${\mu}$ were greater than those of Cd. Concentrations of Cu or Cd in soil solution were relatively very low as compared to those of additions, but increased linearly with increasing additions representing that concentrations of Cu were higher than those of Cd. At 400 mg/kg additions, concentrations of Cu were in the range of 0.51 to 11.70 mg/L but those of Cd were 34.4 to 88.5 mg/L. Major species of Ca, Mg and K were free ions and these species were equivalent to greater than 95 molar % of the existing respective molar concentrations. These cationic species were not changed by Cu or Cd additions. Major species of Cu in lower pH soils such as SiCL and SL were free $Cu^{2+}$ (>95 molar %), but those in LS having a higher pH were free $Cu^{2-}$ and Cu-hydroxide complex. At 100 mg Cu/kg treatment, $Cu^{2+}$ and Cu-hydroxide complex were equivalent to 73 and 22.4 molar %, respectively. These respective percentages were decreased and increased correspondingly with increasing Cu treatments. Major species of Cd in soil solution were free $Cd^{2+}$ and Cd-chloride complex, representing 79 to 85 molar % for $Cd^{2+}$ and 13 to 20% for Cd-chloride complex at 10 mg Cd/kg treatment. With increasing Cd additions to 400 mg/kg, $Cd^{2+}$ species decreased to $40{\sim}47%$ but Cd-chloride complexes increased to $53{\sim}60$ molar %. These results demonstrated that soil contamination with heavy metals caused an adverse effect on the plant nutritional aspects of soil solution by lowering pH, increasing cations temporarily, and increasing free metal concentrations and species enough to be phytotoxic.

• Journal of the Institute of Electronics Engineers of Korea CI
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• v.45 no.2
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• pp.1-9
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• 2008

As the security requirements of mobile phones have been increasing, there have been extensive researches using one biometric feature (e.g., an iris, a fingerprint, or a face image) for authentication. Due to the limitation of uni-modal biometrics, we propose a method that combines face and iris images in order to improve accuracy in mobile environments. This paper presents four advantages and contributions over previous research. First, in order to capture both face and iris image at fast speed and simultaneously, we use a built-in conventional mega pixel camera in mobile phone, which is revised to capture the NIR (Near-InfraRed) face and iris image. Second, in order to increase the authentication accuracy of face and iris, we propose a score level fusion method based on SVM (Support Vector Machine). Third, to reduce the classification complexities of SVM and intra-variation of face and iris data, we normalize the input face and iris data, respectively. For face, a NIR illuminator and NIR passing filter on camera are used to reduce the illumination variance caused by environmental visible lighting and the consequent saturated region in face by the NIR illuminator is normalized by low processing logarithmic algorithm considering mobile phone. For iris, image transform into polar coordinate and iris code shifting are used for obtaining robust identification accuracy irrespective of image capturing condition. Fourth, to increase the processing speed on mobile phone, we use integer based face and iris authentication algorithms. Experimental results were tested with face and iris images by mega-pixel camera of mobile phone. It showed that the authentication accuracy using SVM was better than those of uni-modal (face or iris), SUM, MAX, NIN and weighted SUM rules.

• Journal of the Korean Geotechnical Society
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• v.35 no.11
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• pp.7-14
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• 2019

The compacted bentonite buffer is one of the major components of an engineered barrier system (EBS) for the disposal of high-level radioactive waste (HLW), and it is considered the best candidate for the buffer material. The buffer is located between disposal canisters and near-field rock mass, and it interrupts the release of radionuclide from disposal canisters and protect them from the penetration of groundwater. At initial disposal condition, degree of saturation of the compacted bentonite buffer decreases because of high thermal quantities released from the disposal canisters. However, the degree of saturation of the compacted bentonite buffer gradually increases caused by inflow of groundwater. The saturated and unsaturated behavior of the buffer is a very important input data since it can determine the safety performance of EBS. Therefore, this paper investigated water retention capacity (WRC) for the Korean compacted bentonite buffer. The WRC of the compacted bentonite buffer was derived by measuring volumetric water content and water suction when temperature variation was between 24℃~125℃ considering decrease of degree of saturation with respect to temperature increase. The WRC was also derived with the same volumetric water content under the room temperature condition, and it showed 1~15% larger water suction than high temperature condition.