김민재 교수

This paper proposes a soft-switched single switch isolated converter. The proposed converter is able to offer low cost and high power density in step-up application due to the following features: zero-current switching (ZCS) turn-on and zero-voltage switching (ZVS) turn-off of switch and ZCS turn-off of diodes regardless of voltage and load variation; low rated lossless snubber; reduced transformer volume compared to flyback-based converters due to low magnetizing current. Experimental results o

We report a copper-catalyzed enatiotopic-group-selective allylation of <i>gem</i>-diborylalkanes with allyl bromides. The combination of copper(I) bromide and H₈-BINOL derived phosphoramidite ligand proved to be the most effective catalytic system to provide various enantioenriched homoallylic boronate esters, containing a boron-substituted stereogenic center that is solely derived from <i>gem</i>-diborylalkanes, in good yields with high enantiomeric ratios under mild conditions. Expe

We have investigated the electronic structures and magnetic properties of a newly discovered hydrocarbon superconductor, ${\mathrm{K}}_{3}$picene, having ${T}_{c}$ $=$ 18 K. We have shown that the metal-insulator transition is driven in ${\mathrm{K}}_{3}$picene by 5% volume enhancement with the formation of the local magnetic moment. Active bands for the superconductivity near the Fermi level (${E}_{F}$) have hybridized character of LUMO and LUMO$+$1 of the picene molecule. Fermi surfaces of ${\

This paper proposes a new parallel loaded resonant converter operating in a narrow switching frequency under wide output voltage range. The proposed converter is capable of operating under zero-voltage switching turn-on of switches and zero-current switching turn-off of diodes. Also, the resonant capacitor with feasible capacitance and current rating can be selected by adjusting the turn ratio of the transformer, making the proposed converter more realizable in high power application. Further, t

We have investigated the temperature ($T$)-dependent evolution of orbital states in a typical spin-orbital-lattice-coupled $2p$ electron Mott system $\mathrm{K}{\mathrm{O}}_{2}$, based on the electronic structures obtained by the dynamical mean-field theory as well as the density functional theory. We have shown that $\mathrm{K}{\mathrm{O}}_{2}$ exhibits the orbital fluctuation feature at high $T$ due to degenerate ${\ensuremath{\pi}}_{g}^{*}$ orbitals. Upon cooling, the orbital fluctuation is s

This paper presents a new driving method for a sulfur plasma lamp in low-power applications. The newly developed magnetron power supply (MPS) is a series-resonance type with a full-bridge topology controlled by the phase shift to track the beam current of the magnetron. To drive the sulfur plasma lamp optimally, the MPS should: 1) provide peak power above a discharge condition to excite the sulfur plasma lamp, and 2) allow average power control of the light dimmer while satisfying condition 1. T

Numerous methodologies have been developed in an effort to reduce cogging torque. However, most of these methodologies have side effects that limit their applications. One approach is the optimization methodology that determines an optimized design variable within confined conditions. The response surface methodology (RSM) and the genetic algorithm (GA) are powerful instruments for such optimizations and are matters of common interest. However, they have some weaknesses. Generally, the RSM canno

The iron-based superconductor FeSe_{1-x}Te_{x} has recently gained significant attention as a host of two distinct physical phenomena: (i) Majorana zero modes that can serve as potential topologically protected qubits, and (ii) a realization of the orbital-selective Mott transition. In this Letter, we connect these two phenomena and provide new insights into the interplay between strong electronic correlations and nontrivial topology in FeSe_{1-x}Te_{x}. Using linearized quasiparticle self-consi

We report a copper-catalyzed regio-, diastereo-, and enantioselective allylic alkylation of allyl bromides using 1,1-diborylalkanes as prochiral nucleophiles. This methodology employs copper(I) bromide as a catalyst, an ( R )-BINOL-derived phosphoramidite as a ligand, and lithium benzoate as a crucial additive. The reaction affords enantioenriched homoallylic boronic esters possessing vicinal stereocenters in good yields and high diastereo- and enantioselectivity. The developed method demonstrat

This paper proposes a new symmetrical bidirectional L3C resonant converter with wide voltage range. Due to the proposed symmetrical resonant tank with notch resonant characteristic, the proposed converter is capable of not only achieving soft switching of all switches in forward and backward modes but also operating in a narrow switching frequency range even under wide voltage range. Also, due to zero gain at the notch resonant frequency, the proposed converter does not suffer from increased cur

This letter proposes a new model for the aggregate adjacent channel interference (ACI) received from nearby terminal stations (TSs) of heterogeneous wireless networks. It is well known that lognormal distribution approximates the aggregate received signal, but we found that it does not perform well for ACI-modeling among coexisting TSs. We propose a weighted sum of lognormals-based approximation (WSLA) where the probability density function (PDF) of the aggregate ACI appears in the form of a wei

To explore the origin of high N\'eel temperature $({T}_{N}=930\text{ }\text{K})$ of ${\text{KFeO}}_{2}$, which has only 4 coordination number, we have investigated electronic structures and magnetic properties of $A{\text{FeO}}_{2}$ ($A=\text{K}$ and Rb) by employing the first-principles band-structure method and the Monte Carlo simulation. We have confirmed the observed antiferromagnetic (AFM) ground state of ${\text{KFeO}}_{2}$, and obtained nearly identical electronic structures for ${\text{K

This paper proposes a single switch soft switching isolated converter. The proposed converter is able to offer low cost and high power density in high step up application due to the following features: ZCS turn on and ZVS turn off of switch and ZCS turn off of diodes regardless of voltage and load variation; simple gate driver circuit and low rated lossless snubeer; reduced transformer volume compared to flyback or forward based converters due to low magnetizing current. Experimental results on

We have investigated temperature-dependent electronic structures of ${\mathrm{Na}}_{2}{\mathrm{IrO}}_{3}$ to unravel its insulating nature. Employing the combined scheme of the density functional theory (DFT) and the dynamical mean-field theory (DMFT), we have shown that the insulating state persists even above the N\'eel temperature $({T}_{N})$, which reveals that ${\mathrm{Na}}_{2}{\mathrm{IrO}}_{3}$ is classified as a Mott-type insulator. The measured photoemission spectrum in the paramagneti

This paper proposes a new parallel loaded resonant converter with wide input and output voltage range. The proposed converter is capable of operating under zero-voltage switching (ZVS) turn-on of switches and zero-current switching (ZCS) turn-off of diodes and works in a narrow switching frequency under wide input and output voltage range. Also, proper selection of resonant capacitor is possible by adjusting the turn ratio of the transformer, making the proposed converter more realizable in high