• Nuclear Engineering and Technology
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• v.12 no.2
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• pp.111-120
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• 1980

Nuclear physics parameters of the Wolsung CANDU-PHW reactor are computed by use of the PHWCELL computer code that is an improved version of LATREP. The PHWCELL code mainly computes cell parameters of heavy water moderated reactors, and modeling scheme of heavy water reactor cell calculations has been developed with the PHWCELL computer code. The reactor operating conditions considered in the study are cold zero power (CZP) and hot full power (HFP) with equilibrium poison. The cell parameters are also computed as a function of fuel burnup and the numerical results are compared with the results in PSR of the Wolsung unit and in the previous study.

• Journal of Power Electronics
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• v.9 no.5
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• pp.809-821
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• 2009

This paper proposes a new phase-shift full-bridge DC-DC converter by applying energy recovery circuits to a conventional full-bridge DC-DC converter in plasma display panel applications. The converter can achieve soft-switching in main-switches by an extra auxiliary resonant network even with the wide operating condition of both output load and input voltage. The un-coupled design guidelines to the main bridge-leg component parameters for soft-switching operation contribute to conduction loss reduction in the transformer primary side leading to efficiency improvement. The auxiliary switches in the resonant network also operate in zero-current switching. This paper analyzes the operation modes of the proposed scheme and presents the key design guidelines through steady state analysis. Also, the paper verifies the validity of the circuits by hardware experiments with a 1kW DC/DC converter prototype.

• Proceedings of the KIPE Conference
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• 2008.06a
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• pp.544-546
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• 2008

An improved dual-path energy recovery circuit (ERC) using a current source and a voltage source for plasma display panel (PDP) is proposed. The proposed ERC uses the voltage source to charge a panel and the current source to discharge the panel. Thus, the proposed circuit can make the panel charge to $V_S$ and discharge to 0V, fully and it is possible to achieve zero voltage switching (ZVS) of all switches in H-bridge inverter and zero current switching (ZCS) of all switches in the ERC. Moreover, it has less conduction and switching loss in ERC devices by the dual energy recovery paths for charging and discharging the panel. Furthermore, it has features of canceling the gas discharge current, high performance and the low cost ERC components. The operation principle and features of the proposed ERC are presented in detail and verified with 42-inch SD PDP.

• Proceedings of the KIPE Conference
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• 1998.10a
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• pp.270-275
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• 1998

A new single phase power factor correction rectifier/regulator with dc linked energy feedback circuit is proposed, which is capable of achieving the zero voltage switching (ZVS) of a boost rectifier stage without any auxiliary switch. The performance of the proposed rectifier/regulator is demonstrated through a 200W, 90 KHz prototype. This proposed rectifier/regulator with dc linked energy feedback circuit is particularly suited for distributed power system applications

• MALSORI
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• no.31_32
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• pp.9-22
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• 1996

This study aims to describe the acoustic characteristics of Korean nasal sounds making use of the notion of pole and zero. In case of [m], the 1st and 4th formant almost remains as the original shape respectively, on the contrary, the 2nd and 3rd formant were observed as a variable cluster together. Alveolar [n] shows that the 3rd and 4th formant make a variable cluster with their antiformant(zero), however, the 1st and 2nd formant keep the static shape of their on. Velar [$\eta$] has 4 formants below 2900 Hz and the 3rd and 4th formant constitute a variable cluster together as does the case [n]. With respect to the energy distribution in case of [n] and [$\eta$], the energy value diminishes from Fl up to F3 continuously but augments in F4. The [m] shows that in the region of Fl-F2 does the energy fall down and rise from F3 to above.

• New & Renewable Energy
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• v.18 no.4
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• pp.12-21
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• 2022

The pyrolysis characteristics of high-density polyethylene (HDPE), low-density polyethylene (LDPE), and polypropylene (PP) were analyzed numerically using a 1D plug flow reactor (PFR) model. A lumped kinetic model was selected to simplify the pyrolysis products as wax, oil, and gas. The simulation was performed in the 400-600℃ range, and the plastic pyrolysis and product generation characteristics with respect to time were compared at various temperatures. It was found that plastic pyrolysis accelerates rapidly as the temperature rises. The amounts of the pyrolysis products wax and oil increase and then decrease with time, whereas the amount of gas produced increases continuously. In LDPE pyrolysis, the pyrolysis time was longer than that observed for other plastics at a specified temperature, and the amount of wax generated was the greatest. The maximum mass fraction of oil was obtained in the order of HDPE, PP, and LDPE at a specified temperature, and it decreased with temperature. Although the 1D model adopted in this study has a limitation in that it does not include material transport and heat transfer phenomena, the qualitative results presented herein could provide base data regarding various types of plastic pyrolysis to predict the product characteristics. These results can in turn be used when designing pyrolysis reactors.

• Structural Engineering and Mechanics
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• v.39 no.3
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• pp.427-447
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• 2011

The progressive collapse phenomenon is generally regarded as dynamic. Due to the impracticality of nonlinear dynamic computations for practitioners, an interest arises for the development of equivalent static pushover procedures. The present paper proposes a methodology to identify such a procedure for sudden column removals, using energetic evaluations to determine the pushover loads to apply. In a dynamic context, equality between the cumulated external and internal works indicates a vanishing kinetic energy. If such a state is reached, the structure is sometimes assumed able to withstand the column removal. Approximations of these works can be estimated using a static computation, leading to an estimate of the displacements at the zero kinetic energy configuration. In comparison with other available procedures based on such criteria, the present contribution identifies loading patterns to associate with the zero-kinetic energy criterion to avoid a single-degree-of-freedom idealisation. A parametric study over a family of regular steel structures of varying sizes uses non-linear dynamic computations to assess the proposed pushover loading pattern for the cases of central and lateral ground floor column failure. The identified quasi-static loading schemes are shown to allow detecting nearly all dynamically detected plastic hinges, so that the various beams are provided with sufficient resistance during the design process. A proper accuracy is obtained for the plastic rotations of the most plastified hinges almost independently of the design parameters (loads, geometry, robustness), indicating that the methodology could be extended to provide estimates of the required ductility for the beams, columns, and beam-column connections.

• Journal of Communications and Networks
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• v.16 no.2
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• pp.172-182
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• 2014

In this paper, we investigate the fundamental performance limits of the cooperative sensing using energy detection by considering the unlimited number of sensing nodes. Although a lot of cognitive radio research so far proposed various uses of energy detection because of its simplicity, the performance limits of energy detection have not been studied when a large number of sensing nodes exist. First, we show that when the sensing nodes see the independent and identically distributed channel conditions, then as the number of sensing nodes N goes to infinity, the OR rule of hard decision achieves zero of false alarm Pf for any given target probability of detection $\bar{P_d}$ irrespective of the non-zero received primary user signal to noise ratio ${\gamma}$. Second, we show that under the same condition, when the AND rule of hard decision is used, there exists a lower bound of $P_f$. Interestingly, however, for given $\bar{P_d}$, $P_f$ goes to 1 as N goes to infinity. Third, we show that when the soft decision is used, there exists a way of achieving 100% utilization of secondary user, i.e., the sensing time overhead ratio goes to zero so does $P_f$.We verify our analyses by performing extensive simulations of the proposed unlimited cooperative sensing. Finally, we suggest a way of incorporating the unlimited cooperative sensing into a practical cellular system such as long term evolutionadvanced by exploiting the existing frame structure of absolute blank subframe to implement the in-band sensing.

• Journal of the Architectural Institute of Korea Structure & Construction
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• v.36 no.3
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• pp.147-157
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• 2020

With the increasing obligation to reduce greenhouse gas emissions to the building sector, the government has been gradually expanding its obligation to zero-energy buildings since 2020. Since the ZEB certification took effect in 2017, 48 preliminary and main certifications have been completed as of March 2019, and most of them are public buildings or even certified, but have earned Grade 5 of ZEB. This means that compared with the number of annual building permits registered in Korea, the figure is insignificant, and that it receives little if not mandatory. Therefore, this study investigated empirical cases of ZEB additional construction cost and conducted cost benefit analysis according to changes in ZEB additional construction cost based on a preliminary feasibility analysis project recently conducted by the KDI. In addition, considering the public buildings, the social costs were considered, and the cost-benefit analysis method was the same as the KDI's preliminary feasibility analysis method. The analysis shows that if the ratio of ZEB additional construction cost is more than 5 percent, it is analyzed that there is no economic feasibility, and considering that the ratio of additional construction cost in the cases of ZEB in Korea is 17 percent to 38 percent, it will not be easy to obtain ZEB certification in terms of cost. Finally, to narrow these differences in cost and economic aspects, the overseas low energy and ZEB incentive examples proposed measures such as the concept of subsidy payment in Illinois and the compensation of social costs to private ZEB.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.17 no.4
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• pp.1123-1146
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• 2023

In South Korea, there have been many studies on efficient building-energy management using renewable energy facilities in single zero-energy houses or buildings. However, such management was limited due to spatial and economic problems. To realize a smart zero-energy city, studying efficient energy integration for the entire city, not just for a single house or building, is necessary. Therefore, this study was conducted in the eco-friendly energy town of Chungbuk Innovation City. Chungbuk successfully realized energy independence by converging new and renewable energy facilities for the first time in South Korea. This study analyzes energy data collected from public buildings in that town every minute for a year. We propose a smart city building-energy management model based on the results that combine various renewable energy sources with grid power. Supervised learning can determine when it is best to sell surplus electricity, or unsupervised learning can be used if there is a particular pattern or rule for energy use. However, it is more appropriate to use reinforcement learning to maximize rewards in an environment with numerous variables that change every moment. Therefore, we propose a power distribution algorithm based on reinforcement learning that considers the sales of Energy Storage System power from surplus renewable energy. Finally, we confirm through economic analysis that a 10% saving is possible from this efficiency.