Publications by authors named "Seong-Hyun Lee"

The tunnel field-effect transistor (TFET) with surrounding channel nanowire (SCNW) structure promises better performance than the conventional planar TFET in terms of subthreshold swing (SS) and on-current (). In spite of the advantages of SCNW TFET, there are some technical issues in the aspects of a hump phenomenon in subthreshold region and a high ambipolar current () in off-state. In order to overcome these issues, a novel dual-gate SCNW TFET (DG-SCNW TFET) with differential gate work functions (WFs) and a gate-drain underlap is proposed and studied by using technology computer-aided design (TCAD) simulation.

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Background And Objectives: Noise levels and room acoustic parameters at a tertiary referral hospital, Seoul National University Hospital (SNUH) in Korea, are investigated.

Materials And Methods: Through a questionnaire, acoustically problematic rooms are identified. Noise levels in emergency rooms (ERs) and intensive care units (ICUs) are measured over about three days.

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A new concept of a tunneling oxide-free nonvolatile memory device with a deep trap interface floating gate is proposed. This device demonstrates a high on/off current ratio of 10 and a sizable memory window due to deep traps at the interface between the channel and gate dielectric layers. Interestingly, irradiation with 400 nm light can completely restore the program state to the initial one (performing an erasing process), which is attributed to the visible light-sensitive channel layer.

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We investigated the ultraviolet (UV) responses of a heterojunction Si quantum dot (QD) solar cell consisting of p-type Si-QDs fabricated on a n-type crystalline Si (p-Si-QD/n-c-Si HJSC). The UV responses were compared with a conventional n-type crystalline Si solar cell (n-c-Si SC). The external and internal quantum efficiency results of the p-Si-QD/n-c-Si HJSC exhibited a clear enhancement in the UV responses (300-400 nm), which was not observed in the n-c-Si SC.

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Artificially designed acoustic meta-surfaces have the ability to manipulate sound energy to an extraordinary extent. Here, we report on a new type of directional reflective surface consisting of an array of sub-wavelength Helmholtz resonators with varying internal coiled path lengths, which induce a reflection phase gradient along a planar acoustic meta-surface. The acoustically reshaped reflective surface created by the gradient-impeding meta-surface yields a distinct focal line similar to a parabolic cylinder antenna, and is used for directive sound beamforming.

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In this paper, the sound transmission loss (STL) of thin double plates with an air cavity between them in a rigid duct is considered using an analytical approach. The vibration motion of the plate and sound pressure field are expanded in terms of an infinite series of the modal functions. Under the plane wave condition, a low frequency solution is derived by including the first few symmetric modes.

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Background: Bisphosphonates (BPs) are the most commonly used anti-osteoporotic drugs, which have been proven to reduce the risk of osteoporotic fractures. However, use of BPs, particularly for long periods of time, is associated with an increased risk of atypical femoral fracture (AFF). Healing of BP-associated AFF is usually delayed because of suppressed bone turnover.

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A scattering matrix (S-matrix) analysis method was developed for evaluating hydrogenated amorphous silicon (a-Si:H)-based thin film solar cells. In this approach, light wave vectors A and B represent the incoming and outgoing behaviors of the incident solar light, respectively, in terms of coherent wave and incoherent intensity components. The S-matrix determines the relation between A and B according to optical effects such as reflection and transmission, as described by the Fresnel equations, scattering at the boundary surfaces, or scattering within the propagation medium, as described by the Beer-Lambert law and the change in the phase of the propagating light wave.

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Purpose: Transrectal ultrasound (TRUS)-guided biopsy of the prostate is usually safe. However, some patients are hospitalized owing to complications from TRUS biopsy. We identified the risk factors for complications and effective preventive measures for treating complications after TRUS biopsy.

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The emission enhancement of sound without electronic components has wide applications in a variety of remote systems, especially when highly miniaturized (smaller than wavelength) structures can be used. The recent advent of acoustic metamaterials has made it possible to realize this. In this study, we propose, design, and demonstrate a new class of acoustic cavity using a double-walled metamaterial structure operating at an extremely low frequency.

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Ethnopharmacological Relevence: The ginseng root has been traditionally used as a sedative in oriental countries. However, the condition "ginseng abuse syndrome" (GAS), defined as hypertension, nervousness, sleeplessness, skin eruption, and morning diarrhea, was coined as a result of a study of people who had been using a variety of ginseng preparations. However, we reported that administration of RGE increased rapid eye movement (REM) and non rapid eye movement (NREM) sleep via GABAergic systems in animals.

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It is well known that the presence of a grazing mean flow affects the acoustic impedance of an aperture, but the detailed nature and understanding of the influence is still unknown. In this paper, results from a recent theoretical analysis of the problem are compared with a new set of experimental results. The purpose is twofold.

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Although there are many analytical and empirical models for orifice impedance, the predicted acoustical performance when adopting any one of them sometimes shows a large discrepancy with the measured result in some cases. In order to obtain a new practical and precise empirical impedance model under grazing flow conditions, the acoustic impedance of circular orifices has been measured with a variation of the involved parameters under very carefully tested and controlled measurement conditions. The parameters involved in determining the acoustic impedance of an orifice are comprised of the orifice diameter, orifice thickness, perforation ratio, mean flow velocity, and frequency.

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