Publications by authors named "Young-Wook Park"

Article Synopsis
  • The study investigates the effects of removing one submandibular gland on the size of the opposite gland in patients who had oral cancer surgeries between 2008 and 2023.
  • Using 3D imaging, researchers found that the volume of the remaining gland increased significantly after the excision, suggesting a compensatory adaptation.
  • The findings highlight the importance of considering this volume change in post-operative care and surgical planning to improve treatment outcomes for oral cancer patients.
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We selectively improved the viewing angle characteristics and light extraction efficiency of blue thermally activated delayed fluorescence (TADF) organic light-emitting diodes (OLEDs) by tailoring a nanofiber-shaped SiN layer, which was used as an internal scattering layer. The diameter of the polymer nanofibers changed according to the mass ratio of polyacrylonitrile (PAN) and poly(methyl methacrylate) (PMMA) in the polymer solution for electrospinning. The SiN nanofiber (SNF) structure was fabricated by etching an SiN film using the PAN/PMMA nanofiber as a mask, making it easier to adjust parameters, such as the diameter, open ratio, and height, even though the SNF structure was randomly shaped.

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Luminous efficiency is a pivotal factor for assessing the performance of optoelectronic devices, wherein light loss caused by diverse factors is harvested and converted into the radiative mode. In this study, we demonstrate a nanoscale vacuum photonic crystal layer (nVPCL) for light extraction enhancement. A corrugated semi-transparent electrode incorporating a periodic hollow-structure array was designed through a simulation that utilizes finite-difference time-domain computational analysis.

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We report the electroluminescence (EL) characteristics of blue ultra-thin emissive layer (U-EML) phosphorescent (PH) organic light-emitting diodes (OLED) and thermally activated delayed fluorescence (TADF) OLED. A variety of transport layer (TL) materials were used in the fabricated OLEDs. The well-known FIrpic and DMAC-DPS were used with a thickness of 0.

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Article Synopsis
  • This study explores the impact of different diffuser designs on the electroluminescence (EL) performance of blue phosphorescent organic light-emitting diodes (PHOLEDs) with ultra-thin emission layers (EMLs).
  • Various diffuser parameters, such as shape, size, distribution, and packing, were systematically tested and analyzed to determine their effects on efficiency and viewing angle.
  • The findings revealed that the largest diffuser (75 μm hemisphere) significantly enhanced the external quantum efficiency (EQE), increasing it from 16.6% to 24.3% and broadening the viewing angle by 5.1%.
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This study investigates the application of scattering structures to the metal layer in a DMD (Dielectric/Metal/Dielectric) configuration through plasma treatment. The purpose is to enhance the light extraction efficiency of organic light-emitting diodes (OLEDs). Different plasma conditions were explored to create scattering structures on the metal layer.

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In this study, we demonstrated organic light-emitting diodes (OLEDs) outcoupling with a flexible polydimethylsiloxane (PDMS) film with a micro-convex structure using the breath figure (BF) method. We can easily control the micro-convex pattern by adjusting the concentration of polystyrene and the humidity during the BF process. As process conditions to fabricate the micro-convex structure, polymer concentrations of 10, 20, 40, and 80 mg/mL and 60, 70, and 80% relative humidity were used.

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Background: This study aimed to analyze the accuracy of the output of three-dimensional (3D) customized surgical guides and titanium implants in a rabbit model, and of mandibulectomy, reconstructive surgery, and surgical outcome; additionally, the correlation between surgical accuracy and surgical outcomes, including the differences in surgical outcome according to surgical accuracy, was analyzed.

Results: The output of implants was accurately implemented within the error range (- 0.03-0.

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We present a micro-sphere PDMS film to improve the external quantum efficiency (EQE) in OLEDs. The micro-sphere PDMS film was fabricated with the breath figure (BF) and replica molding process. The polymer template was prepared through stabilization of the water droplets at the polymer/water interface.

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In this study, we fabricated a random nanostructure (RNS) external light extraction composite layer containing high-refractive-index nanoparticles through a simple and inexpensive solution process and a low-temperature mask-free process. We focused on varying the shape and density of the RNSs and adjusted the concentration of the high-refractive-index nanoparticles to control the optical properties. The RNSs fabricated using a low-temperature mask-free process can use the distance between the nanostructures and various forms to control the diffraction and scattering effects in the visible light wavelength range.

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Article Synopsis
  • - This study focuses on improving the light extraction efficiency of organic light-emitting diodes (OLEDs) by using a micro-nano hybrid structure as an external light extraction layer.
  • - Researchers utilized a reactive ion-etching process with O and CHF plasma to create various micro-nano hybrid structures, which were then analyzed for efficiency both experimentally and theoretically.
  • - The results showed that the newly developed hybrid structure can boost light extraction efficiency by up to 38% and enhance the viewing angle, providing a practical approach to improve OLED performance through optimized structure design.
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Background: Many studies on maintaining the condyle in a normal or anatomical position during orthognathic surgery have been conducted to stabilize surgical outcomes and prevent iatrogenic temporomandibular joint complications. The aim of this study is to evaluate the changes in condylar positions after orthognathic surgery using virtual surgical planning via the balanced orthognathic surgery (BOS) system.

Methods: Postoperative changes in condylar position were retrospectively evaluated in 22 condyles of 11 patients with skeletal class III malocclusion who underwent orthognathic surgery using virtual surgical planning via the BOS system.

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Background: Compared to the conventional approach, including preoperative orthodontic preparation, the so-called surgery-first approach (SFA) seems to reduce the overall treatment time in the correction of skeletal class III dentofacial deformity. However, there have been controversies about postoperative skeletal stability with SFA. Therefore, we investigated the long-term stability and the overall treatment time after maxillomandibular surgery for skeletal class III correction with or without preoperative orthodontic preparation.

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In this study, we report highly efficient green phosphorescent organic light-emitting diodes (OLEDs) with ultra-thin emission layers (EMLs). We use tris[2-phenylpyridinato-C2,N]iridium(III) (Ir(ppy)), a green phosphorescent dopant, for creating the OLEDs. Under systematic analysis, the peak external quantum efficiency (EQE) of an optimized device based on the ultra-thin EML structure is found to be approximately 24%.

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Conventional sensors are rigid, involve complex processes and structures, and one sensor can detect only one type of stimulus. The manufacturing costs of such devices are high owing to the use of vacuum processes for the formation of thin films and electrodes and the complicated fabrication processes required to construct multiple layers. In addition, the multiple-layer design increases the risk of peeling due to mechanical movement.

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Medical devices, which enhance the quality of life, have experienced a gradual increase in demand. Various research groups have attempted to incorporate soft materials such as skin into wearable devices. We developed a stretchable substrate with high elasticity by forming a porous structure on polydimethylsiloxane (PDMS).

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Background: Pedicled buccal fat pad (PBFP) has been used for the reconstruction of small-sized maxillary defects but cannot be used without hard tissue support on the defect larger than 4 cm × 4 cm × 3 cm.

Case Presentation: A 64-year-old man had a history of squamous cell carcinoma of the left maxilla. After removal of the posterior maxilla, a complex bone defect (size, 5 cm × 4 cm × 3 cm) was immediately reconstructed using PBFP combined with a titanium mesh.

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In this study, we report the self-nanostructured growth of 4,6-bis(3,5-di(pyridin-3-yl)phenyl)-2-methylpyrimidine (B3PyMPM), which is widely used as an electron transport layer for organic light-emitting diodes (OLEDs). B3PyMPM nanostructures were formed on the surface of a substrate using vacuum thermal evaporation, and parameters such as substrate rotation speed and evaporation angle were altered to study their effect on the growth of nanostructures. Moreover, it was proven that the growth of nanostructures was dependent on the underneath materials.

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In this study, we report the effects of the substrate rotational speed on the morphological characteristics of lithium fluoride (LiF) during thermal evaporation. LiF is used as a typical material in a vacuum-level shift-based electron injection layer and can improve both the charge injection and light emission properties when inserted into the electrode/organic material interface of organic light-emitting diodes (OLEDs). In general OLED research, rotary evaporation is widely used to ensure uniformity.

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In this paper, we report on the effects of the substrate thermal evaporation process rotation speed on the electroluminescence (EL) characteristics of organic light-emitting diodes (OLEDs). In general OLED research, rotational and angle tilted deposition are widely used to maintain uniformity. However, there have been few reports on the effects of this deposition method on film characteristics.

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In the research of organic light-emitting diodes (OLEDs), the OLEDs that are fabricated via conventional doping methods have complicated structures and fabrication processes. To overcome these limitations, the ultra-thin emission layer (EML) method, which adopts a simple structure has been effectively used in the research of OLEDs. However, studies on white color OLEDs (WOLEDs) fabricated using the ultra-thin EML method are scarce.

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The viewing angle characteristics and light extraction efficiency of organic light-emitting diodes (OLEDs) with a micro-cavity structure were enhanced. This was accomplished by inserting a diffusion layer composed of nano-sized structures of a transparent polymer poly(methyl methacrylate) (PMMA) combined with a zinc oxide (ZnO) semi-planarization layer with a high refractive index (n = 2.1) into the devices.

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In this work, we report the effect of the rotation speed of the deposited substrate on the electroluminescence (EL) efficiency of the organic light-emitting diode (OLED). Because it has been reported that the deposition angle velocity affects the growth of an organic thin film, it is expected that the OLED EL characteristics must be affected depending on the substrate rotation velocity. Thus, in this work, the substrate rotation velocity was altered during the deposition of each organic material.

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The phenomenon by which the efficiency decreases rapidly with the increase in luminance or current density in organic light-emitting diodes is termed efficiency roll-off. In particular, phosphorescent organic light-emitting diodes are known to have higher efficiency, but tend to exhibit higher efficiency roll-off compared with fluorescent organic light-emitting diodes. In this study, we report the efficiency roll-off characteristics of double-dopant phosphorescent organic light-emitting diodes.

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Of the drugs developed to prevent and treat osteoporosis, bisphosphonate has played a very important role in preventing osteoporotic fractures. However, case reports describing atypical femoral fractures in patients using long-term bisphosphonates have emerged. The majority of atypical femur fractures occurs in the lateral aspect of the subtrochanteric or femur diaphysis, which is explained by accumulation of tensile stress in these areas.

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