Publications by authors named "Jae-Woong Yoon"

Article Synopsis
  • - This study investigated the metabolic effects of different antiviral treatments for chronic hepatitis B (specifically focusing on tenofovir alafenamide [TAF]) using a 15-year cohort of patients in Korea, separated into two groups: those on a single antiviral and those who switched antivirals.
  • - After applying statistical methods, the findings revealed significant changes in cholesterol levels among groups, with TAF causing an increase in total cholesterol and a notable rise in atherosclerotic cardiovascular disease (ASCVD) risk compared to other treatments.
  • - In patients who switched from tenofovir disoproxil fumarate (TDF) to TAF, there was a significant increase in total cholesterol post-switch, highlighting the potential metabolic
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We propose a topological coherent perfect absorber that enables almost ideal performance with remarkably compact device footprint and tight incident beams. The proposed structure is based on a topological junction of two guided-mode-resonance gratings. The structure provides robust systematic ways of remarkably tight lateral confinement of the absorbing resonance mode and near-perfect mode-match to arbitrary incident beams, which are unavailable with the conventional approaches.

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Nanophotonic light emitters are key components in numerous application areas because of their compactness and versatility. Here, we propose a topological beam emitter structure that takes advantage of submicrometer footprint size, small divergence angle, high efficiency, and adaptable beam shaping capability. The proposed structure consists of a topological junction of two guided-mode resonance gratings inducing a leaky Jackiw-Rebbi state resonance.

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We demonstrate a new type of multifocal and extended depth of focus (EDOF) intraocular lenses (IOLs) embedding μm-thin geometric phase (GP) lens layers. As an emerging approach for lens phase design, the GP modulated IOLs outperform conventional diffractive IOLs in multifocality while completely avoiding the clinically undesirable demand for additional surface patterns to standard monofocal IOL designs. The number of foci and light splitting ratio of the GP IOLs are adjusted by changing the number of stacked GP layers and the thickness of each layer.

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Creating micro and nano lasers, high threshold gain is an inherent problem that have critically restricted their great technological potentials. Here, we propose an inverse-cavity laser structure where its threshold gain in the shortest-cavity regime is order-of-magnitude lower than the conventional cavity configurations. In the proposed structure, a resonant feedback mechanism efficiently transfers external optical gain to the cavity mode at a higher rate for a shorter cavity, hence resulting in the threshold gain reducing with decreasing cavity length in stark contrast to the conventional cavity structures.

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According to previous studies, the increased risk of cutaneous infectious disorders in patients with atopic dermatitis (AD) is related to impaired epidermal function, abnormal systemic immune function, and lower antimicrobial peptides. In this study, we analyzed the association between AD and cutaneous infectious disorders in the real world using sequential pattern mining (SPM). We analyzed National Health Insurance data from 2010-2013 using SPM to identify comorbid cutaneous infectious diseases and the onset durations of comorbidities.

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The notion of synthetic dimensions in artificial photonic systems has received considerable attention as it provides novel methods for exploring hypothetical topological phenomena as well as potential device applications. Here, we present nanophotonic manifestation of a two-dimensional topological nodal phase in bilayer resonant grating structures. Using the mathematical analogy between a topological semimetal and vertically asymmetric photonic lattices, we show that the interlayer shift simulates an extra momentum dimension for creating a two-dimensional topological nodal phase.

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Anti-parity-time (APT) symmetry is associated with various effects beyond the fundamental limitations implied in the standard Hermitian-Hamiltonian dynamics. Here, we create an optical APT-symmetric system in a synthetic frequency domain using a conventional fiber without intrinsic gain or loss and experimentally reveal photonic APT-symmetric effects, including energy-difference conservation and synchronized power oscillation, which have not yet been confirmed experimentally in the optical domain. The optical fiber-based APT-symmetric system has a long interaction length because of its negligible loss, and the APT-symmetric Hamiltonian is precisely tunable with optical pumping density and phase mismatch.

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Scoring atopic dermatitis (AD) severity with the Eczema Area and Severity Index (EASI) in an objective and reproducible manner is challenging. Automated measurement of erythema, papulation, excoriation, and lichenification severity using images has not yet been investigated. Our aim was to determine whether convolutional neural networks (CNNs) could assess erythema, papulation, excoriation, and lichenification severity at a level of competence comparable to dermatologists.

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We propose a monolithic focus-tunable lens structure based on the dielectric-elastomer actuator (DEA) technology. In our focus-tunable lens, a soft lens and radial in-plane actuator mimicking the ocular focal-tuning mechanism are constructed in a single body of an optimized dielectric-elastomer film. We provide device fabrication methods including elastomer synthesis, structure formation, and packaging process steps.

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Crosslinked poly(dimethylsiloxane) (PDMS) has been widely used as a dielectric elastomer for electrically driven actuators because it exhibits high elasticity, low initial modulus, and excellent moldability in spite of low dielectric constant. However, further improvement in the characteristics of the PDMS elastomer is not easy due to its chemical non-reactivity. Here, we report a simple method for functionalizing the elastomer by varying content of hydridosilyl groups in PDMS acted as a crosslinker.

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This case-control study uses population-based data to examine the association of psoriasis with mental health disorders, and to identify trends in their rates of occurrence and times to onset after diagnosis of psoriasis.

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Onychomycosis (OM) is a common nail disease. Although controversial, vascular diseases are considered independent predictors of OM and vice versa. Sequential pattern mining (SPM) has not been previously used for statistical analysis in dermatology, but it is an efficient method for identifying frequent association rules in multiple sequential data sets.

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A low-temperature laser crystallization is newly devised for producing polycrystalline silicon (poly-Si) thin films of low-loss, low surface roughness enough for nanoscale patterning, applicable to practical Si metasurface elements on complementary metal-oxide semiconductor (CMOS) electronic architectures in visible lights. The method is based on dielectric encapsulation of an amorphous Si film and subsequent laser-induced local crystallization. Such poly-Si thin film yields order-of-magnitude smaller surface roughness and grain size than those obtained with the conventional laser annealing processes.

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Topological operations around exceptional points-time-varying system configurations associated with non-Hermitian singularities-have been proposed as a robust approach to achieving far-reaching open-system dynamics, as demonstrated in highly dissipative microwave transmission and cryogenic optomechanical oscillator experiments. In stark contrast to conventional systems based on closed-system Hermitian dynamics, environmental interferences at exceptional points are dynamically engaged with their internal coupling properties to create rotational stimuli in fictitious-parameter domains, resulting in chiral systems that exhibit various anomalous physical phenomena. To achieve new wave properties and concomitant device architectures to control them, realizations of such systems in application-abundant technological areas, including communications and signal processing systems, are the next step.

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Developing tunable lenses, an expansion-based mechanism for dynamic focus adjustment can provide a larger focal length tuning range than a contraction-based mechanism. Here, we develop an expansion-tunable soft lens module using a disk-type dielectric elastomer actuator (DEA) that creates axially symmetric pulling forces on a soft lens. Adopted from a biological accommodation mechanism in human eyes, a soft lens at the annular center of a disk-type DEA pair is efficiently stretched to change the focal length in a highly reliable manner.

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We propose an elastomer thin-film pressure sensor enabled by pressure-sensitive optical signals through vertical photonic tunnel-junction couplers. We provide the operation principle, design, fabrication, and test results from a 50 μm thick polydimethylsiloxane sheet accommodating embedded vertical photonic tunnel-junction couplers. The result with a 5 mm long device shows a differential optical power change that is ∼140% of the incident power under moderate external pressure of ∼40  kPa, thereby clearly demonstrating a robust pressure-sensing capability realized in a highly flexible, lightweight, transferrable, optically transparent, and bio-compatible thin-film material.

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Parity-time (PT) symmetry and associated non-Hermitian properties in open physical systems have been intensively studied in search of new interaction schemes and their applications. Here, we experimentally demonstrate an electrical circuit producing key non-Hermitian properties and unusual wave dynamics grounded on anti-PT (APT) symmetry. Using a resistively coupled amplifying-LRC-resonator circuit, we realize a generic APT-symmetric system that enables comprehensive spectral and time-domain analyses on essential consequences of the APT symmetry.

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Background: Influenza-associated myositis (IAM) is a rare and poorly recognized complication of influenza infection in children, and is characterized by acute onset of severe pain in the lower extremities and a refusal to ambulate walk. We sought to understand the association between IAM and influenza B infection and to investigate its clinical and laboratory characteristics in affected children.

Methods: Influenza B-associated myositis (IBAM) cases diagnosed in the pediatrics department of Wonkwang University Hospital from January 2010 and March 2016 were analyzed retrospectively.

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Mesenteric cysts are rare intra-abdominal lesions occurring during childhood, which were first described in 1507. Cases of mesenteric cysts have been continuously reported, but these cases were very small in number. They are often asymptomatic and incidentally found while patients are undergoing work-up or receiving treatment for other conditions such as appendicitis, small-bowel obstruction, or diverticulitis; however, patients may still have lower abdominal pain and symptoms that are frequently associated with other abdominal conditions.

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We propose a free-space electro-optic transmission modulator based on multiple p-n-junction semiconductor subwavelength gratings. The proposed device operates with a high-Q guided-mode resonance undergoing electro-optic resonance shift due to direct electrical control. Using rigorous electrical and optical modeling methods, we theoretically demonstrate a modulation depth of 84%, on-state efficiency 85%, and on-off extinction ratio of 19 dB at 1,550 nm wavelength under electrical control signals within a favorably low bias voltage range from -4 V to +1 V.

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Time-asymmetric state-evolution properties while encircling an exceptional point are presently of great interest in search of new principles for controlling atomic and optical systems. Here, we show that encircling-an-exceptional-point interactions that are essentially reciprocal in the linear interaction regime make a plausible nonlinear integrated optical device architecture highly nonreciprocal over an extremely broad spectrum. In the proposed strategy, we describe an experimentally realizable coupled-waveguide structure that supports an encircling-an-exceptional-point parametric evolution under the influence of a gain saturation nonlinearity.

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Recently, synthetic optical materials represented via non-Hermitian Hamiltonians have attracted significant attention because of their nonorthogonal eigensystems, enabling unidirectionality, nonreciprocity and unconventional beam dynamics. Such systems demand carefully configured complex optical potentials to create skewed vector spaces with a desired metric distortion. In this paper, we report optically generated non-Hermitian photonic lattices with versatile control of real and imaginary sub-lattices.

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