최재원 교수

In the cuprates, high-temperature superconductivity, spin-density-wave order, and charge-density-wave (CDW) order are intertwined, and symmetry determination is challenging due to domain formation. We investigated the CDW in the prototypical cuprate La_{1.88}Sr_{0.12}CuO_{4} via x-ray diffraction employing uniaxial pressure as a domain-selective stimulus to establish the unidirectional nature of the CDW unambiguously. A fivefold enhancement of the CDW amplitude is found when homogeneous supercon

The second layer of ^{4}He films adsorbed on a graphite substrate is an excellent experimental platform to study the interplay between superfluid and structural orders. Here, we report a rigid two-frequency torsional oscillator study on the second layer as a function of temperature and ^{4}He atomic density. For the first time, we show experimentally that the superfluid density is independent of frequency, which can be interpreted as unequivocal evidence of genuine superfluidity. The phase diagr

Phase transitions and symmetry are intimately linked. Melting of ice, for example, restores translation invariance. The mysterious hidden order (HO) phase of ${\mathrm{URu}}_{2}{\mathrm{Si}}_{2}$ has, despite relentless research efforts, kept its symmetry breaking element intangible. Here, we present a high-resolution x-ray diffraction study of the ${\mathrm{URu}}_{2}{\mathrm{Si}}_{2}$ crystal structure as a function of hydrostatic pressure. Below a critical pressure threshold ${p}_{c}\ensuremat

Abstract The omnipresence of charge density waves (CDWs) across almost all cuprate families underpins a common organizing principle. However, a longstanding debate of whether its spatial symmetry is stripe or checkerboard remains unresolved. While CDWs in lanthanum‐ and yttrium‐based cuprates possess a stripe symmetry, distinguishing these two scenarios is challenging for the short‐range CDW in bismuth‐based cuprates. Here, high‐resolution resonant inelastic x‐ray scattering is employed to uncov

The rigid double-torus torsional oscillator (TO) is constructed to reduce any elastic effects inherent to complicated TO structures, allowing explicit probing for a genuine supersolid signature. We investigated the frequency- and temperature-dependent response of the rigid double-torus TO containing solid $^{4}\mathrm{He}$ with 0.6-ppb $^{3}\mathrm{He}$ and 300-ppb $^{3}\mathrm{He}$. We did not find evidence to support the frequency-independent contribution proposed to be a property of supersoli

Objective: To elucidate the association between periodic limb movements in sleep (PLMS) and mortality. Methods: Nocturnal polysomnographic recordings of 1,344 subjects obtained from 1995 to 2008 were reviewed. The subjects were divided into four groups based on PLMS and insomnia: reference group (PLMS≤5), insomnia group (PLMS≤5 with insomnia symptoms), 5<PLMS≤15 group, and the PLMS>15 group. We searched each subject’s Identification Number in the death records from the Statistics of Korea, the n

The charge density wave in the high-temperature superconductor YBa2Cu3O7−x (YBCO) has two different ordering tendencies differentiated by their c-axis correlations. These correspond to ferro- (F-CDW) and antiferro- (AF-CDW) couplings between CDWs in neighbouring CuO2 bilayers. This discovery has prompted several fundamental questions: how does superconductivity adjust to two competing orders and are either of these orders responsible for the electronic reconstruction? Here we use x-ray diffracti

The automotive industry evaluates various success factors to achieve competitive advantage in selling products. Existing studies have predicted the success of newly launched automobiles based on an economic perspective. However, factors such as dynamic changes in consumer preferences and the emergence of numerous automobile brands pose difficulty in understanding product quality. This study proposes a method of understanding the automotive market using text mining techniques and online user opin

We reexamined the rotation-induced effect observed in solid $^{4}\mathrm{He}$ by using a rigid two-frequency torsional oscillator (TO). The previous rotation experiments reported the rotation-induced suppression of the ``nonclassical'' TO response that was interpreted as evidence of irrotational bulk superfluidity in solid $^{4}\mathrm{He}$. However, the experiment employed a nonrigid TO that could amplify the elastic contribution in the TO response. Thus, it is important to clarify if the rotat

At an early age, human infants are able to learn and build a model of the world very quickly by constantly observing and interacting with objects around them. One of the most fundamental intuitions human infants acquire is intuitive physics. Human infants learn and develop these models, which later serve as prior knowledge for further learning. Inspired by such behaviors exhibited by human infants, we introduce a graphical physics network integrated with deep reinforcement learning. Specifically

Spontaneous symmetry breaking constitutes a paradigmatic classification scheme of matter. However, broken symmetry also entails domain degeneracy that often impedes identification of novel low symmetry states. In quantum matter, this is additionally complicated by competing intertwined symmetry breaking orders. A prime example is that of unconventional superconductivity and density-wave orders in doped cuprates in which their respective symmetry relation remains a key question. Using uniaxial pr

본 연구는 자율주행차량이 혼재된 네트워크에서 실제 검증이 어려운 교통상황 중 시뮬레이션을 통 해 구현 가능한 위험 상황들을 탐색하고 이에 대응할 수 있는 전략들과 평가 방법들을 매칭하여 네트워크의 안전과 이동성을 높일 수 있도록 하는 세부적인 시나리오 개발을 목적으로 한다. V2X 를 활용하여 자율주행차량에게 상황에 대한 대응 전략을 전달하여 상황별로 대처하고자 하였고, 이를 위해 미시 시뮬레이션을 활용하여 네트워크를 구축한 뒤, 각각 상황들을 구현하고 대응 전략 과 평가지표들을 제시하여 정상 교통류 상태와 이상 상태가 발생한 총 10가지 상황에 대해 테스트 시나리오를 개발하였다. 개발된 테스트 시나리오 중 하나를 미시 시뮬레이션을 통해 수행하고 대응 전략 전후의 효과를 확인하여 활용 가능성을 확인하였다. 본 연구에서 개발된 시나리오는 자율주행 차량의 정보 송수신을 활용하여 네트워크 전체의 안정성을 효과적으로 높일 수 있을 것으로 기대된다.

목 적 : 일반스프링 매트리스에 비교하여 지지력 등을 향상시킨 컨투어 코일 매트리스가 주관적 및 객관적인 수면의질을 향상시킬 수 있는지 알아보고자 하였다. 방 법 : 건강하게 수면하는 일반인 대상자 15명을 모집하였다. 연구대상자들은 두 종류의 매트리스에서 잠을 자면서야간수면다원검사를 시행하였고 검사 전, 후 주관적인 수면의 질에 대한 자가설문지를 작성하게 하였다. 한 연구대상자가 각각 다른 매트리스에서 2일에 걸쳐 야간수면다원검사를 시행하여 얻어진 객관적인 수면변인들과 주관적인 자가설문지 변수들로 교차설계분석을 시행하였다. 결 과 : 야간수면다원검사에서 측정된 수면잠복기가 컨투어 코일 매트리스에서 잠을 잔 경우 일반스프링 매트리스에서 잠을 잔 경우보다 평균 1.9분 감소하였다. 이외에도 주관적으로 느낀 수면 중 각성횟수, 깊게 잠든 느낌 그리고 잠자리의 편안함이 컨투어 코일 매트리스가 유의하게 더 나은결과를 보였다. 결 론 : 매트리스가 종류에 따라서 주관적인 수면의 질뿐만 아니라