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  1. Article ; Online: Designing a Geodesic Faceted Acoustical Volumetric Array Using a Novel Analytical Method.

    Yusuf, Taofeek Ayotunde / Roh, Yongrae

    Sensors (Basel, Switzerland)

    2023  Volume 23, Issue 6

    Abstract: We present a novel analytical method as an efficient approach to design a geodesic-faceted array (GFA) for achieving a beam performance equivalent to that of a typical spherical array (SA). GFA is a triangle-based quasi-spherical configuration, which is ... ...

    Abstract We present a novel analytical method as an efficient approach to design a geodesic-faceted array (GFA) for achieving a beam performance equivalent to that of a typical spherical array (SA). GFA is a triangle-based quasi-spherical configuration, which is conventionally created using the icosahedron method imitated from the geodesic dome roof construction process. In this conventional approach, the geodesic triangles have nonuniform geometries due to some distortions that occur during the random icosahedron division process. In this study, we took a paradigm shift from this approach and adopt a new technique to design a GFA that is based on uniform triangles. The characteristic equations that relate the geodesic triangle with a spherical platform were first developed as functions of the operating frequency and geometric parameters of the array. Then, the directional factor was derived to calculate the beam pattern associated with the array. A sample design of GFA for a given underwater sonar imaging system was synthesized through an optimization process. The GFA design was compared with that of a typical SA, and a reduction of 16.5% in the number of array elements was recorded in the GFA at a nearly equivalent performance. Both arrays were modeled, simulated, and analyzed using the finite element method (FEM) to validate the theoretical designs. Comparison of the results showed a high degree of compliance between the FEM and the theoretical method for both arrays. The proposed novel approach is faster and requires fewer computer resources than the FEM. Moreover, this approach is more flexible than the traditional icosahedron method in adjusting geometrical parameters in response to desired performance outputs.
    Language English
    Publishing date 2023-03-16
    Publishing country Switzerland
    Document type Journal Article
    ZDB-ID 2052857-7
    ISSN 1424-8220 ; 1424-8220
    ISSN (online) 1424-8220
    ISSN 1424-8220
    DOI 10.3390/s23063173
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  2. Article ; Online: Design and Fabrication of a High-Sensitivity and Wideband Cymbal Hydrophone.

    Kim, Donghyun / Roh, Yongrae

    Sensors (Basel, Switzerland)

    2023  Volume 23, Issue 22

    Abstract: So far, cymbal transducers have been developed primarily for transmitting purposes, and even when used for receiving, the focus has been mostly on improving the receiving sensitivity. In this study, we developed a cymbal hydrophone with a higher ... ...

    Abstract So far, cymbal transducers have been developed primarily for transmitting purposes, and even when used for receiving, the focus has been mostly on improving the receiving sensitivity. In this study, we developed a cymbal hydrophone with a higher sensitivity and a wider bandwidth than other existing hydrophones. First, the initial structure of the cymbal hydrophone was established, and then the effects of structural variables on the hydrophone's performance were analyzed using the finite element method. Based on the analysis results, the structure having the highest sensitivity and widest bandwidth, with a receiving voltage sensitivity level above a certain threshold, was derived using optimal design techniques. A prototype of the cymbal hydrophone with the designed structure was fabricated, and its performance was measured, validating the effectiveness of the design by comparing the measurement results with the design values. The developed cymbal hydrophone is expected to be utilized in various underwater precision measurements, as it possesses a significantly broader reception frequency bandwidth when compared with other hydrophones used for the same purpose.
    Language English
    Publishing date 2023-11-10
    Publishing country Switzerland
    Document type Journal Article
    ZDB-ID 2052857-7
    ISSN 1424-8220 ; 1424-8220
    ISSN (online) 1424-8220
    ISSN 1424-8220
    DOI 10.3390/s23229086
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  3. Article ; Online: Which intervention is more effective in improving sarcopenia in older adults? A systematic review with meta-analysis of randomized controlled trials.

    Park, Seong-Hi / Roh, Younhee

    Mechanisms of ageing and development

    2022  Volume 210, Page(s) 111773

    Abstract: This systematic review aims, however, to determine which intervention is more effective. The skeletal muscle index (SMI), handgrip, and gait speed were used as indicators of improvement, and these effects were compared across six subgroups: combined ... ...

    Abstract This systematic review aims, however, to determine which intervention is more effective. The skeletal muscle index (SMI), handgrip, and gait speed were used as indicators of improvement, and these effects were compared across six subgroups: combined intervention versus exercise; nutrition or control group; exercise versus nutrition; and exercise or nutrition versus control group. Out of 1596 articles, 32 studies (3063 older adults) were selected and meta-analyzed. Comparing the combined intervention with a control group, the WMD was 0.20 kg/m
    MeSH term(s) Humans ; Aged ; Sarcopenia/therapy ; Hand Strength ; Randomized Controlled Trials as Topic ; Muscle Strength ; Exercise/physiology
    Language English
    Publishing date 2022-12-16
    Publishing country Ireland
    Document type Meta-Analysis ; Systematic Review ; Journal Article ; Research Support, Non-U.S. Gov't
    ZDB-ID 183915-9
    ISSN 1872-6216 ; 0047-6374
    ISSN (online) 1872-6216
    ISSN 0047-6374
    DOI 10.1016/j.mad.2022.111773
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  4. Article ; Online: Equivalent circuit for analyzing the transmitting characteristics of multimode Tonpilz transducer.

    Pyo, Seonghun / Roh, Yongrae

    The Journal of the Acoustical Society of America

    2022  Volume 151, Issue 6, Page(s) 3594

    Abstract: Multimode Tonpilz transducers operate at longitudinal and flexural vibration modes simultaneously. Consequently, they have wider bandwidths than conventional single-mode transducers. Generally, the performance of Tonpilz transducers is analyzed using the ...

    Abstract Multimode Tonpilz transducers operate at longitudinal and flexural vibration modes simultaneously. Consequently, they have wider bandwidths than conventional single-mode transducers. Generally, the performance of Tonpilz transducers is analyzed using the finite element method (FEM), whereas the equivalent circuit method (ECM) has proven to be a fast and efficient alternative to the FEM. However, the ECM for analyzing the acoustic characteristics of multimode Tonpilz transducers has not yet been developed. To address this issue, an equivalent circuit for the multimode Tonpilz transducer is developed herein. The proposed ECM encompasses the flexural characteristics of the Tonpilz head mass, which is impossible with conventional equivalent circuits. Furthermore, a prototype of the multimode Tonpilz transducer was fabricated to verify the validity of the developed ECM. Additionally, the accuracy and compliance of the ECM were confirmed by comparing the measured performance of the transducer with that from the equivalent circuit analysis.
    Language English
    Publishing date 2022-04-05
    Publishing country United States
    Document type Journal Article
    ZDB-ID 219231-7
    ISSN 1520-8524 ; 0001-4966
    ISSN (online) 1520-8524
    ISSN 0001-4966
    DOI 10.1121/10.0011515
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  5. Article ; Online: Biomechanical Comparison between Inverted Triangle and Vertical Configurations of Three Kirschner Wires for Femoral Neck Fracture Fixation in Dogs: A Cadaveric Study.

    Heo, Seonghyeon / Lee, Haebeom / Roh, Yoonho / Jeong, Jaemin

    Veterinary sciences

    2023  Volume 10, Issue 4

    Abstract: The purpose of this study was to compare single-cycle axial load and stiffness between inverted triangle and vertical configurations of three Kirschner wires (K-wires) for femoral neck fracture fixation in small dog cadaveric models. In each of the eight ...

    Abstract The purpose of this study was to compare single-cycle axial load and stiffness between inverted triangle and vertical configurations of three Kirschner wires (K-wires) for femoral neck fracture fixation in small dog cadaveric models. In each of the eight cadavers, the basilar femoral neck fracture model was prepared on both sides of the femur. One side of the femur was stabilized with three 1.0 mm K-wires of an inverted triangle configuration (group T), and the other femur was stabilized with a vertical configuration (group V). Postoperatively, the placement of the K-wires was evaluated with radiographic and computed tomography (CT) images, and static vertical compressive loading tests were performed. The mean yield load and the lateral spread were significantly higher in group T compared to group V (
    Language English
    Publishing date 2023-04-10
    Publishing country Switzerland
    Document type Journal Article
    ZDB-ID 2768971-2
    ISSN 2306-7381 ; 2306-7381
    ISSN (online) 2306-7381
    ISSN 2306-7381
    DOI 10.3390/vetsci10040285
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  6. Article ; Online: Use of Computed Tomography and Magnetic Resonance Angiograms Combined with a 3D Surgical Guide in an Elderly Cat with an Occipital Lobe Meningioma.

    Byun, Pillmoo / Roh, Yoonho / Lee, Haebeom / Jeong, Jaemin

    Veterinary sciences

    2023  Volume 10, Issue 4

    Abstract: We present a case of occipital lobe meningioma resection in an elderly cat. The surgery was performed with the goal of avoiding major bleeding. An 11-year-old castrated indoor-only male Persian Chinchilla (5.5 kg) was presented with a month-long history ... ...

    Abstract We present a case of occipital lobe meningioma resection in an elderly cat. The surgery was performed with the goal of avoiding major bleeding. An 11-year-old castrated indoor-only male Persian Chinchilla (5.5 kg) was presented with a month-long history of progressive tetraparesis for a left occipital lobe meningioma. Magnetic resonance imaging revealed a T2-weighted heterogeneously hyperintensity and a T1-weighted well-contrast enhancing extradural mass in the left occipital lobe of the brain. Cerebral angiographic data were obtained using magnetic resonance (MRA) and computed tomography angiography (CTA). Advanced angiograms and virtual reconstruction of images revealed that the tumor was surrounded by the caudal parasagittal meningeal vein. A left caudal rostrotentorial craniotomy and en bloc resection of the tumor were performed, and histopathology revealed a meningioma. Complete neurological recovery was achieved within 10 days after surgery. To the best of our knowledge, this is the first case report describing CTA and MRA findings and favorable clinical outcomes after surgical management of a brain meningioma without severe perioperative complications.
    Language English
    Publishing date 2023-03-29
    Publishing country Switzerland
    Document type Case Reports
    ZDB-ID 2768971-2
    ISSN 2306-7381 ; 2306-7381
    ISSN (online) 2306-7381
    ISSN 2306-7381
    DOI 10.3390/vetsci10040264
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  7. Article ; Online: Revealing the Loss Mechanism of Chemically-Induced Hot Electron Transport.

    Roh, Yujin / Jin, Yeonghoon / Jeon, Beomjoon / Park, Yujin / Yu, Kyoungsik / Park, Jeong Young

    Nano letters

    2024  Volume 24, Issue 11, Page(s) 3490–3497

    Abstract: Hot electrons are crucial for unraveling the intrinsic relationship between chemical reactions and charge transfer in heterogeneous catalysis. Significant research focused on real-time detection of reaction-driven hot electron flow (chemicurrent) to ... ...

    Abstract Hot electrons are crucial for unraveling the intrinsic relationship between chemical reactions and charge transfer in heterogeneous catalysis. Significant research focused on real-time detection of reaction-driven hot electron flow (chemicurrent) to elucidate the energy conversion mechanisms, but it remains elusive because carrier generation contributes to only part of the entire process. Here, a theoretical model for quantifying the chemicurrent yield is presented by clarifying the contributions of hot carrier losses from the internal emission and multiple reflections. The experimental chemicurrent yield verifies our model with a reliable mean free path of hot electrons, emphasizing the importance of comprehensive consideration of the transport process besides hot electron generation. Moreover, Pt nanoparticles (NPs)-decorated Au/TiO
    Language English
    Publishing date 2024-03-11
    Publishing country United States
    Document type Journal Article
    ISSN 1530-6992
    ISSN (online) 1530-6992
    DOI 10.1021/acs.nanolett.4c00330
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  8. Article: Radiographic Characteristics of the Femoral Nutrient Artery Canals in Total Hip Arthroplasty using Cementless Femoral Stem.

    Roh, Y H / Yoo, S J / Choi, T H / Nam, K W

    Malaysian orthopaedic journal

    2023  Volume 17, Issue 1, Page(s) 124–132

    Abstract: Introduction: Accurate diagnosis of undisplaced periprosthetic femoral fracture (PFF) after hip arthroplasty is crucial, as overlooked PFF may affect its treatment and prognosis. The undisplaced PFF is often difficult to distinguish from radiolucent ... ...

    Abstract Introduction: Accurate diagnosis of undisplaced periprosthetic femoral fracture (PFF) after hip arthroplasty is crucial, as overlooked PFF may affect its treatment and prognosis. The undisplaced PFF is often difficult to distinguish from radiolucent lines of nutrient artery canal (NAC) of the femur present on post-operative radiographs. We aimed to identify the radiographic features of NAC to distinguish them from PFFs.
    Materials and methods: In this retrospective radiological study, a total of 242 cases in 215 patients with hip arthroplasty were analysed using pre-operative and post-operative anteroposterior (AP) and translateral (TL) radiographs. Interobserver agreement of the measurements was assessed by two independent experienced orthopaedic surgeons. The kappa value ranged from 0.83 to 0.87, indicating strong agreement according to the Landis and Koch criteria.
    Results: The NACs were found pre-operatively in 94 (39.8%) cases on AP views and in 122 cases (50.4%) on TL views. The radiolucent lines were observed post-operatively in 42 (17.4%) on AP views and 122 (50.4%) on the TL views. three cases (1.2%) had a fracture around the stem that were detected on radiographs. One case with PFF presented simultaneously with NAC on the immediate post-operative radiographs. All patients were treated by conservative measures, and the radiolucent lines did not appear on follow-up radiographs.
    Conclusion: It is not easy to differentiate undisplaced PFFs that can occur after hip arthroplasty operation from NACs. However, accurate diagnosis is possible through careful observation and comparison of pre-operative and post-operative radiologic images.
    Language English
    Publishing date 2023-04-08
    Publishing country Malaysia
    Document type Journal Article
    ZDB-ID 2621480-5
    ISSN 1985-2533
    ISSN 1985-2533
    DOI 10.5704/MOJ.2303.015
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  9. Article ; Online: Identification of Chemical and Structural Characteristics of Acrylic Paint Layer Using Terahertz Metasurfaces.

    Kim, Taeyeon / Im, Jaeryong / Roh, Yeeun / Lee, Geon / Seo, Minah

    Analytical chemistry

    2023  Volume 95, Issue 41, Page(s) 15302–15310

    Abstract: The precise investigation and monitoring of the internal structural change within complex layered systems are crucial, as the emergence of undesirable defects or formation of secondary internal structures significantly exerts a profound influence on the ... ...

    Abstract The precise investigation and monitoring of the internal structural change within complex layered systems are crucial, as the emergence of undesirable defects or formation of secondary internal structures significantly exerts a profound influence on the overall properties of the system. We demonstrate an advanced sensing platform utilizing terahertz metasurfaces, allowing chemical detection and precise identification within an acrylic paint layer with a noticeable sensitivity, reaching down to several hundreds of nanometers, in nondestructive and noncontact manners. The identification of solid and mixed paint samples was achieved by analyzing their optical properties, including the refractive index and absorption coefficient. Notably, the presence of internal pore defects within the mixed acrylic paint led to geometric distortions, affecting the state of the overall system. Intriguingly, even in cases where acrylic paint exhibited identical colors perceptible under visible light, distinct discrimination and identification of chemical compositions were successfully proposed.
    Language English
    Publishing date 2023-09-28
    Publishing country United States
    Document type Journal Article
    ZDB-ID 1508-8
    ISSN 1520-6882 ; 0003-2700
    ISSN (online) 1520-6882
    ISSN 0003-2700
    DOI 10.1021/acs.analchem.3c02727
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  10. Article ; Online: Selection of a Potting Material and Method for Broadband Underwater Cymbal Arrays.

    Wang, Wenbo / Shim, Hayeong / Roh, Yongrae

    Sensors (Basel, Switzerland)

    2022  Volume 22, Issue 21

    Abstract: Cymbal transducers are often used in arrays for underwater communication and detection systems. The working environment of a cymbal array is underwater; therefore, waterproofing, salt-corrosion prevention, and impact resistance are necessary for stable ... ...

    Abstract Cymbal transducers are often used in arrays for underwater communication and detection systems. The working environment of a cymbal array is underwater; therefore, waterproofing, salt-corrosion prevention, and impact resistance are necessary for stable operation of the array. Hence, we simulated potting a cymbal array with 15 different rubber and epoxy materials available in the market, using the finite element method, and analyzed their effect on the transmitting voltage response spectrum of the array. From the analysis results, we selected the material that would achieve the widest frequency bandwidth, while preserving the structural stability of the array. A potting method corresponding to the selected material was suggested as well. This study provides guidelines for the selection of a potting material for use in underwater transducer arrays.
    Language English
    Publishing date 2022-10-30
    Publishing country Switzerland
    Document type Journal Article
    ZDB-ID 2052857-7
    ISSN 1424-8220 ; 1424-8220
    ISSN (online) 1424-8220
    ISSN 1424-8220
    DOI 10.3390/s22218324
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