• Nuclear Engineering and Technology
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• v.52 no.6
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• pp.1156-1163
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• 2020

Fuel temperature coefficient (FTC) of PuO₂+ZrO₂ (ROX) fueled LWR cell is analyzed neutronically with reactor- and weapons-grade plutonium fuels in comparison with a U-free PuO₂+ThO₂ (TOX), and a conventional MOX fuel cells. The FTC value of a ROX fueled LWR is smaller compared to a TOX or a MOX fueled LWRs and becomes extremely positive especially, at EOL. This is because when fuel temperature is increased, thermal neutron spectrum is shifted to harder, which is extreme at EOL in ROX fuel than that in TOX and MOX fuels. Consequently at EOL, ²³⁹Pu and ²⁴¹Pu contributes to positive fuel temperature reactivity (FTR) in ROX fuel, while they have negative contribution in TOX and MOX fuels. The FTC problem of ROX fuel is mitigated by additive ThO₂, UO₂ or Er₂O₃. In ROX-additive fuel, the atomic density of fissile Pu becomes more than additive free ROX fuel especially at EOL, which is the main cause to improve the FTC problem. The density of fissile Pu is more effective to decrease the thermal spectrum shifts with increase the fuel temperature than additive ThO₂, UO₂ or Er₂O₃ in ROX fuel.

• Nuclear Engineering and Technology
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• v.52 no.6
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• pp.1110-1119
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• 2020

The Floating Absorber for Safety at Transient (FAST) is a safety device used in the innovative Sodium-cooled Fast Reactor (iSFR). The FAST insert negative reactivity under transient or accident conditions. However, behavior of the FAST is still unclear under transient conditions. Therefore, the existing Floating Absorber for Safety at Transient Analysis Code (FASTAC) is improved to analyze the FAST movement by considering the reactivity and temperature distribution within the reactor core. The current FAST system is simulated under a single control rod withdrawal accident condition. In this investigation, the reactor thermal power does not return to its initial thermal power even if the FAST inserts negative reactivity. Only a 9 K of coolant temperature margin, in the hottest fuel assembly at EOL, can lead to unnecessary insertion of the negative reactivity. On the other hand, the FASTs cannot contribute to controlling the reactivity when normalized radial power is less than 0.889 at BOL and 0.972 at EOL. These simulation results suggest that the current FAST design needs to be optimized depending on its installed location. Meanwhile, the FAST system keeps the fuel, cladding and coolant temperatures below their limit temperatures with given conditions.

• Geomechanics and Engineering
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• v.23 no.4
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• pp.301-311
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• 2020

In this study, shear strength behavior of fine-grained soils was investigated under unsaturated conditions. The samples in the unsaturated state were subjected to a net normal stress (σ-u_a) of 40 kPa and different matric suctions (u_a-u_w) of 50, 100 and 150 kPa. The matric suction values applied in the triaxial tests were selected according to the bubbling pressures determined from the SWC curves. The study was carried out on prepared re-constituted cylindrical samples by uniaxial consolidation of soil slurries. First, consolidated drained (CD) triaxial compression tests were performed on the saturated samples and the cohesion and angle of internal friction were determined. After that, drained triaxial compression tests under matric suctions were performed on the unsaturated samples. In order to obtain unsaturated test results, cohesion and internal friction angle values of saturated samples were used. The nonlinear surface representing the shear strength surface was approximated consisting of two planes (double planar surface). The reason for the nonlinear behavior of some soils is that the amount of sand content contained in it is relatively high and the bubbling pressure/permanent water content value is relatively low.

• The Bulletin of The Korean Astronomical Society
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• v.37 no.2
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• pp.83.2-83.2
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• 2012

Type I AGNs are classified by the presence of broad emission lines while Type II AGNs show narrow emission lines only. All-sky surveys such as SDSS provide large AGN samples for statistical studies. However, the AGN samples suffer selection bias due to the incomplete selection criteria. To investigate the missing Type I AGNs in optical spectroscopic surveys, we start with a sample of SDSS Type II AGNs at 0.02 < z < 0.05, using the MPA-JHU SDSS DR7 catalog. We search for the hidden broad $H{\alpha}$ component with both visual inspection and the multi-component spectral decomposition method. Out of 1383 Type II AGNs, we find a total of 62 missing Type I AGNs (~4.5%). The sample has mean black hole mass, log $(M_{BH}/M_{SUN))=6.48{\pm}0.53$, and luminosity, log $(L_{H{\alpha}}/ergs^{-1})=40.52{\pm}0.33$, with Eddington ratio, log $(L_{bol}/L_{Edd})=-1.51{\pm}0.41$. We will describe the sample and present the $M_{BH}-{\sigma}_*$, and $M_{BH}-M_*$ relations of the sample in the context of the BH-galaxy coevolution.

• Nuclear Engineering and Technology
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• v.46 no.3
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• pp.291-298
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• 2014

This paper concerns estimating uncertainties of the core neutronics design parameters of power reactors by direct sampling method (DSM) calculations based on the two-step McCARD/MASTER design system in which McCARD is used to generate the fuel assembly (FA) homogenized few group constants (FGCs) while MASTER is used to conduct the core neutronics design computation. It presents an extended application of the uncertainty propagation analysis method originally designed for uncertainty quantification of the FA FGCs as a way to produce the covariances between the FGCs of any pair of FAs comprising the core, or the covariance matrix of the FA FGCs required for random sampling of the FA FGCs input sets into direct sampling core calculations by MASTER. For illustrative purposes, the uncertainties of core design parameters such as the effective multiplication factor ($k_{eff}$), normalized FA power densities, power peaking factors, etc. for the beginning of life (BOL) core of Yonggwang nuclear unit 4 (YGN4) at the hot zero power and all rods out are estimated by the McCARD/MASTER-based DSM computations. The results are compared with those from the uncertainty propagation analysis method based on the McCARD-predicted sensitivity coefficients of nuclear design parameters and the cross section covariance data.

• Aerospace Engineering and Technology
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• v.2 no.1
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• pp.80-88
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• 2003

The present analysis quantifies the particulate contamination of KOMPSAT-2 satellite until in orbit life. Assumptions are defined about integration and test conditions and durations, then a budget is drawn. As KOMPSAT-2 activities are carried out in good cleanliness conditions, the particulate contamination budgets for satellite and instrument surfaces at BOL is fair. To summarise, in the baseline launch conditions (class 10,000) the contribution of satellite AIT and launch activities adds 500 PPM to MSC and STA apertures (telescope mirrors ; front lens ; baffle), 20,000 PPM to MSC and STA outer surfaces, 14 000 PPM to plate-form horizontal surfaces, 1400 PPM to plate-form vertical surfaces, 1000 PPM to plate-form radiators and less than 300 PPM to solar arra.

• Journal of The Korean Astronomical Society
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• v.55 no.4
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• pp.131-138
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• 2022

We report the discovery of four quasars with M₁₄₅₀ ≳ -25.0 mag at z ~ 5 and supermassive black hole mass measurement for one of the quasars. They were selected as promising high-redshift quasar candidates via deep learning and Bayesian information criterion, which are expected to be effective in discriminating quasars from the late-type stars and high-redshift galaxies. The candidates were observed by the Double Spectrograph on the Palomar 200-inch Hale Telescope. They show clear Lyα breaks at about 7000-8000 Å, indicating they are quasars at 4.7 < z < 5.6. For HSC J233107-001014, we measure the mass of its supermassive black hole (SMBH) using its C _IV λ1549 emission line. The SMBH mass and Eddington ratio of the quasar are found to be ~10⁸ M_⊙ and ~0.6, respectively. This suggests that this quasar possibly harbors a fast growing SMBH near the Eddington limit despite its faintness (L_Bol < 10⁴⁶ erg s^-1). Our 100% quasar identification rate supports high efficiency of our deep learning and Bayesian information criterion selection method, which can be applied to future surveys to increase high-redshift quasar sample.

• Journal of Ocean Engineering and Technology
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• v.26 no.2
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• pp.58-67
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• 2012

Recently, both the integration of product data during design and production and the effective management of information during full lifecycles have attracted attention from shipyards and ship owners as a result of recycling regulations and a desire for efficient operations. Generally, PLM (Product Lifecycle Management) supports a collaborative environment during the BOL (Beginning of Life) stage, while an ALM (Asset Lifecycle Management) system provides all of the information required to maintain, overhaul, and discard/recycle all or part of a vessel during the MOL (Middle of Life) and EOL (End of Life) stages. The main goal of this paper is to suggest the fundamental configuration of a PALM (Product Asset Lifecylce Management) system and a method that can be used to utilize a marine vessel's lifecycle information during the MOL, emphasizing the maintenance information during the middle of life. The authors also suggest a PALM system configuration in which lifecycle information can be collected by a PEID (Product Embedded Information Device) integrating a microcomputer, sensors, and wireless network communication. Through a prototype PALM system, the suggested features and PALM system configuration are implemented.

• Korean Journal of Ichthyology
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• v.26 no.3
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• pp.239-242
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• 2014

A single specimen (196.4 mm standard length) of the scorpaenid Hozukius emblemarinus was collected by a bottom trawl from the coastal waters off Ulsan, East Sea, Southern Korea. The specimen is characterized by a deep oblong body, three spines on the lower margin of the eye, a dorsal fin with 12 spines, a head mostly covered with various sizes of scales, and a truncate posterior margin of the caudal fin. This is the first record of H. emblemarinus in Korea; we therefore add the species to the Korean fish fauna and propose the new Korean name, "Dong-hae-keun-nun-bol-rak" for this species.

• Journal of Digital Convergence
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• v.17 no.9
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• pp.279-290
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• 2019

The purpose of this study was to explore communication experiences with doctors experienced by nurses in clinical settings, to resolve communication difficulties, and to identify ways to communicate effectively. "What is communication with a physician experienced by a nurse? The focus of the discussion was performed with questions. The study was a qualitative study of 21 nurses with different clinical experiences using interview methods and analyzed data using the criteria of Downe-Wam bol dt. 12 Themes were reclassified to derive 4 Themes clusters. In conclusion, it is necessary to create an atmosphere of respect for doctors and nurses, and each department should be able to quickly identify and deal with communication problems. Based on the research, It is suggested that the training of communication skills be strengthened to be possible.