Publications by authors named "Wonseok Han"

We investigate the dynamics of surface plasmon (SP) lasing in Au gratings fabricated on InGaAs with a period of around 400 nm, which locates the SP resonance near the semiconductor energy gap and facilitates efficient energy transfer. By optically pumping the InGaAs to reach the population inversion required for the amplification and the lasing, we observe SP lasing at specific wavelengths that satisfy the SPR condition depending on the grating period. The carrier dynamics in semiconductor and the photon density in the SP cavity was investigated from the time-resolved pump-probe measurement and the time resolved photoluminescence spectroscopy, respectively.

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  • GaAs-on-Si templates with low-temperature (LT) and high-temperature (HT) dislocation filter layers (DFLs) were grown to study the effects of growth temperature on threading dislocation density (TDD).
  • TDD values for LT-DFL and HT-DFL were found to be 5.2 × 10^6 cm^-2 and 1.5 × 10^6 cm^-2, respectively, with HT-DFL showing a significant reduction compared to a control sample without DFLs.
  • Higher optical performance and lower leakage current were observed in devices made with HT-DFL, indicating that high-temperature growth can enhance the performance of GaAs devices on silicon substrates.
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Tobacco smoking is associated with a high global mortality rate since it is known to cause cancers and lung and heart diseases. To control and reduce annual mortality attributed to smoking, it is essential to design applicable smoke cessation programs based on realistic tobacco exposure risk assessment. In this regard, understanding the smoking habits of the smoker is crucial.

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Exposure to environmental tobacco smoke (ETS) is the reason for approximately 1% of global mortality. ETS exposure can happen either as inhalation of direct cigarette smoke (second-hand smoke) or its associated residue particles (third-hand smoke), especially when living with a smoker in the same family. This study investigated the association between the urinary cotinine levels, as biomarkers of exposure to tobacco smoke, of smokers and those exposed to second-hand and third-hand smoke while living in the same family, through a Korean nationwide survey.

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Introduction: Understanding interactions of smoking topography with biomarkers of exposure to tobacco is essential for accurate smoking risk assessments.

Methods: In this study, the smoking topography and the levels of tobacco smoke exposure urinary biomarkers of a sample of active Korean smokers were quantified and measured. The results were used to investigate the effect of daily activities and smoking time on the smoking topography.

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Objectives: The aim of the study was to investigate the correlations within the levels of biomarkers in different biological matrices, along with smoking topography variables, among active male smokers in Korea. Accordingly, we defined a transformation factor to convert level of tobacco smoke exposure and impact biomarkers from different biometrics.

Methods: We examined smoking topography of recruited volunteers using a self-reporting survey.

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We demonstrate strong modulation of the transmission around the surface plasmon polariton (SPP) resonance in metal/semiconductor hybrid nanostructures based on Ag film on top of InGaAs. The change in the real and imaginary parts of the refractive index due to photoexcited carriers in InGaAs generates a shift in the SPP resonance and enhanced transmission near the SPP resonance. Temporal evolution of the complex refractive index was traced by comparing the transient transmission with finite-difference time-domain (FDTD) simulations.

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Background: Foremost fine hairs in the frontal hairline region are critical in hair transplantation for hairline correction (HTHC) in women. However, there are few studies on a nonsurgical revisionary method for improving an unnatural foremost hairline with thick donor hairs resulting from a previous HTHC.

Objective: To investigate the efficacy and safety of using a hair removal laser (HRL) system to create fine hairs in Asian women with thick donor hairs.

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We present an optimization of spot-size converter (SSC) of waveguide photodetector (PD) for small polarization dependent loss (PDL). Beam-propagation method simulation gives responsivity for each polarization and SSC structure. From the calculated responsivity data, optimum structure of SSC is determined that can be implemented with a sufficient process tolerance.

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  • A 72-year-old woman with a history of acupuncture scars presented with shortness of breath and weakness, leading to a diagnosis of pericardial abscess caused by Staphylococcus aureus bacteremia.
  • Diagnostic tests, including echocardiography and pericardiocentesis, revealed pericardial fluid collection with the bacteria growing in both the fluid and blood.
  • Despite aggressive treatment with antibiotics and drainage, the patient unfortunately passed away just 2 days after her admission to the hospital.
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A femoral artery pseudoaneurysm (FAP) is one of the most troublesome complications following invasive procedures related to the femoral arterial access. Post-procedure FAP rarely occurs; however, its occurrence tends to increase with the more frequently antiplatelet agents, anticoagulants, and larger-sized catheter used for interventional procedures. Traditionally, surgical repair has been considered as the standard treatment modality for FAP; however, less invasive methods currently exist such as blind manual or ultrasound-guided compression repair (UGCR) as well as percutaneous thrombin injection, both of which have replaced the need for surgery.

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