• Journal of Power Electronics
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• v.10 no.5
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• pp.572-578
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• 2010

This paper discusses a transformerless shunt static compensator (STATCOM) based on a modular multilevel converter (MMC). It introduces a new time-discrete appropriate current control algorithm and a phase-shifted carrier modulation strategy for fast compensation of the reactive power and harmonics, and also for the balancing of the three-phase source side currents. Analytical formulas are derived to demonstrate the accurate mechanism of the stored energy balancing inside the MMC. Various simulated waveforms verify that the MMC based STATCOM is capable of reactive power compensation, harmonic cancellation, and simultaneous load balancing, while controlling and balancing all of the DC mean voltages even during the transient states.

• Journal of Korean Association for Spatial Structures
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• v.20 no.3
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• pp.35-42
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• 2020

The purpose of this study is to develop precast concrete modules that can be used as a booth and a single-story building with a large space. This precast concrete module is originally designed to have a hexagonal facade when the upper and lower parts, which are symmetrical about horizontal connection line, are combined. A structural design was conducted to ensure structural safety of these precast concrete modules and to extend the slope of the inclined members as far as possible. Then the finite element analysis was performed to estimate the lateral and vertical deflection of complete precast concrete modular structures. And to verify the structural safety of these precast concrete modules, weight loading tests were conducted on the upper and lower modules respectively.

• Journal of Power Electronics
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• v.2 no.3
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• pp.212-219
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• 2002

A novel mode of parallel operation of a modular 3-phase AC-DC flyback converter for power factor correction along with tight regulation was recently analyzed and presented. The advantage of the proposed converter does not require expensive high voltage and high current devices that are normally needed in popular boost type 3-phase converter. In this paper tile detailed small signal analysis of the modular 3-phase AC-DC flyback converter is provided for control purpose and also experimental results are included to confirm the validity of the analysis.

• Journal of Industrial Technology
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• v.32 no.A
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• pp.39-45
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• 2012

In this paper the digital control scheme of interleaved PFC for 3-phase modular UPS is presented. The interleaved PFC is composed of two identical PFC connected in parallel and each PFC is controlled by the interleaved switching signals which have the same switching frequency and the $180^{\circ}$ phase difference. As a consequence of the interleaving operation, the Interleaved PFC exhibits both lower current ripple at the input side and lower voltage ripple at the outside. Therefore, the switching and conduction losses as well as EMI levels can be significantly decreased. Simulation and experimental results verify the usefulness of the interleaved PFC.

• Nonlinear Functional Analysis and Applications
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• v.28 no.1
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• pp.1-9
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• 2023

Our aim in this paper is to give some new proofs to fixed point theorems due to Abdou [1] for mappings satisfying Reich type contractions in modular metric spaces. We removed the restriction that ω satisfies the ∆₂-type condition imposed on the results of [1]. Furthermore, Lemma 2.6 of [1] which was crucial in the proofs of the results of [1] is not needed in the proofs of our results. Our method of proof is simpler and interesting.

• Proceedings of the Membrane Society of Korea Conference
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• 1997.06a
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• pp.143-158
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• 1997

Electrochemical deionization (EDI) offers continuous demineralization at higher water recovery rates (>90%), compared with mixed bed ion exchange, and without the use of chemical regenerants and the associated production of saline waste water. Although EDI technology has been used in some power generation applications, its wider application requires the satisfactory resolution of outstanding capital cost and performance issues. This paper reports on the field evaluation of a new cost-effective EDI technology in a power generation application. The E-Cell System$^{TM}$, which became commercially available in the fourth quarter of 1996, consists of a rugged, modular system, based on a new high-performance EDI stack. Starting in May 1996, a 100 gpm modular EDI pilot system, rated for operation at 100 psi, was evaluated at the TVA Brown's Ferry Nuclear Plant. The feed consisted of Reverse Osmosis (RO) permeate with a conductivity of 4-7 $\mu$S/cm. The pilot system reliably produced 17.8-18.0 M$\Omega$.cm water under design operating conditions, independent. Silica levels were reduced from ca. 50 ppb to 4 ppb, while TOC levels were reduced from ca. 120 ppb to 30 ppb.

• Journal of Power Electronics
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• v.18 no.2
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• pp.456-466
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• 2018

This paper introduces the development of a de-icer based on a full-bridge modular multilevel converter (FMMC). The FMMC can generate a wide range of DC voltages owing to its modularity, scalability, and redundancy, which makes it suitable for ice-melting applications. First, operating principles and voltage ranges are analyzed when FMMC is applied as a mobile de-icer. Second, two new startup strategies, constant modulation index and constant power startup strategies, are proposed. Third, the main control strategies of the de-icer are proposed. Fourth, a novel rated-current zero-power test scheme is proposed to simplify test conditions. Finally, a 10 kV 1.5 kA mobile MMC de-icer is designed and built, and experiments are carried out to validate the proposed startup, control strategies, and rated-current zero-power test scheme.

• Nuclear Engineering and Technology
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• v.56 no.7
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• pp.2641-2649
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• 2024

Effective management of slightly used nuclear fuel (SUNF) is crucial for both technical and public acceptance reasons. SUNF management, radiotoxicity risk, and associated financial investment and technological capabilities are major concerns in nuclear power production. Reducing the volume of SUNF can simplify its management, and one possible solution is utilizing small modular reactors (SMR) and advanced fuel designs like those with thorium. This research focuses on studying the neutronic performance and radionuclide inventory of three different thorium fuel configurations. The mass of fissile material in thorium-based fuel significantly impacts Kinf, burn-up, and neutron energy spectrum. Compared to uranium, thorium as a fuel produces far fewer transuranic elements and less long-lived fission products (LLFPs) at the end of the core cycle (EOC). However, certain fission product elements produced from thorium-based fuel exhibit higher radioactivity at the beginning of the core cycle (BOC). Physical separation of thorium and uranium in the fuel block, like seed-and-blanket units (SBU) and duplex fuel designs, generate less radioactive waste with lower radioactivity and longer cycle lengths than homogeneous or mixed thorium-uranium fuel. Furthermore, the SBU and duplex feel designs exhibit comparable neutron spectra, leading to negligible differences in SUNF production between the two.

• Steel and Composite Structures
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• v.30 no.2
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• pp.185-199
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• 2019

Modular construction is an emerging technology to accommodate the increasing restrictions in terms of construction period, energy efficiency and environmental impacts, since each structural module is prefabricated offsite beforehand and assembled onsite using industrialized techniques. However, some innate structural drawbacks of this innovative method are also distinct, such as connection tying inaccessibility, column instability and system robustness. This study aims to explore the theoretical and numerical stability analysis of a tenon-connected square hollow section (SHS) steel column to address the tying and stability issue in modular construction. Due to the excellent performance of composite structures in fire resistance and buckling prevention, concrete-filled steel tube (CFST) columns are also taken into account in the analysis to evaluate the feasibility of adopting composite sections in modular buildings. Characteristic equations with three variables, i.e., the length ratio, the bending stiffness ratio and the rotational stiffness ratio, are generated from the fourth-order governing differential equations. The rotational stiffness ratio is recognized as the most significant factor, with interval analysis conducted for its mechanical significance and domain. Numerical analysis using ABAQUS is conducted for validation of characteristic equations. Recommendations and instructions in predicting the buckling performance of both SHS and CFST columns are then proposed.

• Korean Journal of Construction Engineering and Management
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• v.22 no.6
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• pp.120-130
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• 2021

Recently, the government is reinforcing safety management at construction sites to prevent safety accidents in construction works, and the safety management plan of workers is an important situation. Meanwhile, modular construction is expected to be gradually expanded to middle and high-rise buildings, but active measures to ensure worker safety are insufficient. This study is a preliminary study of the development of a checklist for preventive worker safety management. The purpose of this study is to derive a checklist classification system for the safety management of workers in the field of modular construction by preceding studies, case analysis, and expert advisory opinions. The classification system consists of large categories of factory manufacturing, transportation, and on-site construction, and the sub-system consists of six sub-classes: foundation work, frame work, modular frame installation work, finishing work, and facility work. Among them, the sub-classification of modular frame installation work consists of 12 unit works, centering on module lifting and assembly module work, which are the main construction processes. And the classification system reflects the three main management factors and contents for defined safety management. It is expected that the research results of this study can contribute to efficient safety management at the modular construction site.