• Nuclear Engineering and Technology
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• v.55 no.9
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• pp.3301-3312
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• 2023

This study incorporates a high-fidelity transient analysis solver based on multigroup CMFD in the MOC code STREAM. Transport modeling with heterogeneous geometries of the reactor core increases computational cost in terms of memory and time, whereas the multigroup CMFD reduces the computational cost. The reactor condition does not change at every time step, which is a vital point for the utilization of CMFD. CMFD correction factors are updated from the transport solution whenever the reactor core condition changes, and the simulation continues until the end. The transport solution is adjusted once CMFD achieves the solution. The flux-weighted method is used for rod decusping to update the partially inserted control rod cell material, which maintains the solution's stability. A smaller time-step size is needed to obtain an accurate solution, which increases the computational cost. The adaptive step-size control algorithm is robust for controlling the time step size. This algorithm is based on local errors and has the potential capability to accept or reject the solution. Several numerical problems are selected to analyze the performance and numerical accuracy of parallel computing, rod decusping, and adaptive time step control. Lastly, a typical pressurized LWR was chosen to study the rod-ejection accident.

• Journal of the Korea Concrete Institute
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• v.23 no.5
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• pp.551-558
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• 2011

The effect of the maximum aggregate size and substitution rate of natural sand on the mechanical properties of concrete is evaluated using 15 lightweight aggregate concrete mixes. For mechanical properties of concrete, compressive strength increase with respect to age, tensile resistance, elastic modulus, rupture modulus, and stress-strain relationship were measured. The experimental data were compared with the design equations specified in ACI 318-08, EC2, and/or CEB-FIP code provisions and empirical equations proposed by Slate et al., Yang et al., and Wang et al. The test results showed that compressive strength of lightweight concrete decreased with increase in maximum aggregate size and amount of lightweight fine aggregates. The parameters to predict the compressive strength development could be empirically formulated as a function of specific gravity of coarse aggregates and substitution rate of natural sand. The measured rupture modulus and tensile strength of concrete were commonly less than the prediction values obtained from code provisions or empirical equations, which can be attributed to the tensile resistance of lightweight aggregate concrete being significantly affected by its density as well as compressive strength.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.41 no.9
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• pp.85-95
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• 2004

As the design complexity increases, it is a major problem that the size of test pattern is large and power consumption is high in scan, especially system-on-a-chip(SoC), with the automatic test equipment(ATE). Because static compaction of test patterns heads to higher power for testing, it is very hard to reduce the test pattern volume for low power testing. This paper proposes an efficient compression/decompression algorithm based on run-length coding for reducing the amount of test data for low power testing that must be stored on a tester and be transferred to SoC. The experimental results show that the new algorithm is very efficient by reducing the memory space for test patterns and the hardware overhead for the decoder.

• Journal of the Korea Safety Management & Science
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• v.11 no.4
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• pp.221-228
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• 2009

Electronic Product Code Information Services(EPCIS) is an EPCglobal standard for sharing EPC related information between trading partners. EPCIS provides a new important capability to improve efficiency, security, and visibility in the global supply chain. EPCIS data are classified into two categories, master data (static data) and event data (dynamic data). Master data are static and constant for objects, for example, the name and code of product and the manufacturer, etc. Event data refer to things that happen dynamically with the passing of time, for example, the date of manufacture, the period and the route of circulation, the date of storage in warehouse, etc. There are four kinds of event data which are Object Event data, Aggregation Event data, Quantity Event data, and Transaction Event data. This thesis we propose an event-based data model for EPC Information Service repository in RFID based integrated logistics center. This data model can reduce the data volume and handle well all kinds of entity relationships. From the point of aspect of data quantity, we propose a formula model that can explain how many EPCIS events data are created per one business activity. Using this formula model, we can estimate the size of EPCIS events data of RFID based integrated logistics center for a one day under the assumed scenario.

• 유체기계공업학회:학술대회논문집
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• 2002.12a
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• pp.396-401
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• 2002

The purpose of this 3-D numerical simulation is evaluate the application of a commercial CFD code to predict 3-D flow characteristics of wind turbine. The experimental approach, which has been main method of investigation, appears to be its limits, the cost increasing disproportionally with the size of the wind turbines, and is hence mostly limited to observing the phenomena. Hence, the use of Computational Fluid Dynamics (CFD) techniques and Wavier-Stokes solvers are considered a very serious contender. The flow solver CFX-TASCflow is employed in all computations presented in this paper. The 3-D flow separation and the wake distribution of 2 bladed Horizontal Axis Wind Turbines (HAWTs) are compared to Heuristic model and visualized result by NREL(National Renewable Energy Laboratory). Simulated 3-D flow separation structure on the rotor blade is very similar to Heuristic model and the wake structure of the wind turbine is good agree with visualized results.

• Journal of Broadcast Engineering
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• v.16 no.6
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• pp.927-940
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• 2011

In this paper, we improve a time-domain channel estimation algorithm with multi-input multi-output (MIMO) systems for the next-generation digital television (DTV). The conventional algorithm use orthogonal codes for separating channels from the time-domain orthogonal frequency division multiplexing (OFDM) symbols. However. it has the disadvantage of reduced data-rate because of many pilots. The improved algorithm shows better performance than the conventional one even with reduced number of pilots. The improved algorithm is evaluated by computer simulations.

• Proceedings of the Korea Concrete Institute Conference
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• 2001.11a
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• pp.117-122
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• 2001

Recently, epoxy-coated re-bar used to the structure partly and put to practical use step, but not economical and appeared to the defect of deterioration of long term bond strength between concrete. The method for complement the defect of epoxy coated re-bar, study of polymer cement slurry coated re-bar started and basic properties appeared to excellent, but study of bond properties embedded in concrete specimens insufficient until now. This study attempts to examination of using possibility for bond strength of polymer cement slurry coated re-bar between concrete specimens compare to ACI Code and KS Code through pull-out test of 15cm$\times$15cm$\times$15cm specimens with polymer cement slurry coated re-bar as polymer cement ratio 50%, 100%, 150%, coating thickness 250${\mu}{\textrm}{m}$, 440${\mu}{\textrm}{m}$ and curing age. In the results of this study, the bond strength of polymer cement slurry coated re-bar compare to plain re-bar, epoxy coated re-bar decreased St/BA-modified polymer cement slurry coated re-bar, but bond strength of PA-modified polymer cement slurry coated re-bar appeared to excellent results. The bond properties of polymer cement slurry coated re-bar between concrete will be obtain more precise results according to compressive strength change of concrete and re-bar diameter size.

• Journal of Mechanical Science and Technology
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• v.18 no.11
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• pp.2009-2020
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• 2004

A parametric study of the factors controlling static and dynamic denting, as well as local stiffness, has been made on simplified panels of different sizes, curvatures, thicknesses and strengths. Analyses have been performed using the finite element method to predict dent resistance and panel stiffness. A parametric approach is used with finite element models of simplified panels. Two sizes of panels with square plan dimensions and a wide range of curvatures are analysed for several combinations of material thickness and strength, all representative of auto-motive closure panels. Analysis was performed using the implicit finite element code, LS-NIKE, and the explicit dynamic code, LS-DYNA for the static and dynamic cases, respectively. Panel dent resistance and stiffness behaviour are shown to be complex phenomena and strongly interrelated. Factors favouring improved dent resistance include increased yield strength and panel thickness. Panel stiffness also increases with thickness and with higher curvatures but decreases with size and very low curvatures. Conditions for best dynamic and static dent performance are shown to be inherently in conflict ; that is, panels with low stiffness tend to perform well under impact loading but demonstrate inferior static dent performance. Stiffer panels are prone to larger dynamic dents due to higher contact forces but exhibit good static performance through increased resistance to oil canning.

• Transactions of the Korean Society of Pressure Vessels and Piping
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• v.9 no.1
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• pp.62-69
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• 2013

A probabilistic assessment code, PRO-LOCA ver. 3.7 which was developed in an international co-operative research program, PARTRIDGE was evaluated by conducting sensitivity analysis. The effect of some variables such as simulation methods (adaptive sampling, iteration numbers, weld residual stress model), crack features(Poisson's arrival rate, maximum numbers of cracks, initial flaw size, fabrication flaws), operating and loading conditions(temperature, primary bending stress, earthquake strength and frequency), and inspection model(inspection intervals, detectable leak rate) on the failure probabilities of a surge line nozzle was investigated. The results of sensitivity analysis shows the remaining problems of the PRO-LOCA code such as the instability of adaptive sampling and unexpected trend of failure probabilities at an early stage.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.1C
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• pp.20-25
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• 2006

In this paper, the performance of Tree-LDPC code is presented based on the min-sum algorithm with scaling and the asymptotic performance in the water fall region is shown by density evolution. We presents that the Tree-LDPC code show a significant performance gain by scaling with the optimal scaling factor which is obtained by density evolution methods. We also show that the performance of min-sum with scaling is as good as the performance of sum-product while the decoding complexity of min-sum algorithm is much lower than that of sum-product algorithm. The Tree-LDPC decoder is implemented on a FPGA chip with a small interleaver size.