• Title/Summary/Keyword: Hwang Doyeon

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Synthesis of the Ni-doped ternary compound Ba(Fe1-xNix)2Se3

  • Park, Hyeon Beom;Shin, Soohyeon;Jung, Soon-Gil;Hwang, Doyeon;Lee, Hyoyoung;Park, Tuson
    • Progress in Superconductivity and Cryogenics
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    • v.17 no.4
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    • pp.30-33
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    • 2015
  • We report the synthesis of Ni-doped $BaFe_2Se_3$ single crystals by using a flux method. X-ray diffraction (XRD) of $Ba(Fe_{1-x}Ni_x)_2Se_3$ shows a gradual peak shift with an increase in the nominal Ni-doping rate, x = 0, 0.05, and 0.10, due to a decrease in unit-cell volume. All samples show a spin glass transition, and temperature dependence of magnetic susceptibility shows a negligible change in the spin-glass transition temperature ($T_g$) with Ni concentration x. The temperature dependence of electrical resistivity for $BaFe_2Se_3$ shows an insulating behavior, and the resistivity value at 295 K and the activation energy ($E_a$) obtained from the Arrhenius plot decrease with increasing x. These results suggest that the Ni doping can be effectively worked as a dopant for electron charge carriers, but is less efficient in controlling the magnetic property, such as spin glass transition, in the $BaFe_2Se_3$ compound.

Reaction Characteristics of New Oxygen Carrier for 0.5 MWth Chemical Looping Combustion System at High Temperature and High Pressure Conditions (0.5 MWth 케미컬루핑 연소 시스템 적용을 위한 신규 산소전달입자의 고온·고압 반응 특성)

  • KIM, JUNGHWAN;LEE, DOYEON;NAM, HYUNGSEOK;JO, SUNG-HO;HWANG, BYUNG WOOK;BAEK, JEOM-IN;RYU, HO-JUNG
    • Transactions of the Korean hydrogen and new energy society
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    • v.29 no.5
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    • pp.473-482
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    • 2018
  • To check applicability of recently developed new oxygen carrier for 0.5 MWth chemical looping combustion system, reactivity tests were carried out at high temperature and high pressure conditions. Pressure, temperature, gas velocity, $CH_4$ flow rate, and solid height were considered as operating variables. The new oxygen carrier (N016-R4) showed not only high fuel conversion but also high $CO_2$ selectivity within all the operating conditions in this study. The reactivity of N016-R4 particle was compared with previous oxygen carriers. The N016-R4 particle represented outstanding reactivity among 10 oxygen carriers in terms of fuel conversion and $CO_2$ selectivity.

Hydrodynamics and Solid Circulation Characteristics of Oxygen Carrier for 0.5 MWth Chemical Looping Combustion System (0.5 MWth 케미컬루핑 연소시스템 적용을 위한 산소전달입자의 수력학 특성 및 고체순환 특성)

  • RYU, HO-JUNG;KIM, JUNGHWAN;HWANG, BYUNG WOOK;NAM, HYUNGSEOK;LEE, DOYEON;JO, SUNG-HO;BAEK, JEOM-IN
    • Transactions of the Korean hydrogen and new energy society
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    • v.29 no.6
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    • pp.635-641
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    • 2018
  • To select the operating condition of 0.5 MWth chemical looping combustion system, minimum fluidization velocity, transition velocity to fast fluidization and solid circulation rate were measured using mass produced new oxygen carrier (N016-R4) which produced by spray drying method for 0.5 MWth chemical looping combustion system. A minimum fluidization velocity decreased as the pressure increased. The measured transition velocity to fast fluidization was 2.0 m/s at ambient temperature and pressure. The measured solid circulation rate increased as the solid control valve opening increased. We could control the solid circulation rate from 26 to $93kg/m^2s$. Based on the measured minimum fluidization velocity and transition velocity to fast fluidization, we choose appropriate operating conditions and demonstrated continuous solid circulation at high pressure condition (5 bar-abs) up to 24 hours.

Effect of Loop Seal Geometry on Solid Circulation in a Gas-Solid Fluidized Bed (기체-고체 유동층에서 루프실의 형상이 고체순환에 미치는 영향)

  • RYU, HO-JUNG;JO, SUNG-HO;LEE, SEUNG-YONG;LEE, DOYEON;NAM, HYUNGSEOK;HWANG, BYUNG WOOK;KIM, HANA;WON, YOO SEOB;KIM, JUNGHWAN;BAEK, JEOM-IN
    • Transactions of the Korean hydrogen and new energy society
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    • v.30 no.4
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    • pp.312-319
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    • 2019
  • Effect of loop seal geometry on solid circulation characteristics was investigated with two different types of upper loop seals and lower loop seals in a gas-solid fluidized bed system. Upper loop seal which has a wide gap between solid intake and outlet parts requires more fluidization gas to maintain smooth solid circulation. Moreover, the lower loop seal which has a wide gap requires more fluidization gas to achieve the same solid circulation rate. These results can be explained by results of minimum fluidization velocity in the lower loop seals. Consequently, if a loop seal has a wide gap between solid intake and outlet parts, more fluidization gases should be fed to ensure enough solid circulation rate and smooth solid circulation.

The Effect of Locally Administered Fibrinolytic Drugs Following Aneurysmal Subarachnoid Hemorrhage : A Meta-Analysis with Eight Randomized Controlled Studies

  • Jang, Kyoung Min;Choi, Hyun Ho;Nam, Taek Kyun;Park, Yong Sook;Kwon, Jeong Taik;Byun, Jun Soo;Hwang, Doyeon
    • Journal of Korean Neurosurgical Society
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    • v.64 no.2
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    • pp.207-216
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    • 2021
  • Objective : Rapid dissolution of blood clots reduces vasospasm and hydrocephalus after subarachnoid hemorrhage (SAH), and locally administered fibrinolytic drugs (LAFDs) could facilitate the dissolution. However, the efficacy of LAFDs remains controversial. The aim of this meta-analysis was to determine the efficacy of LAFDs for vasospasm and hydrocephalus and in clinical outcomes. Methods : From PubMed, EMBASE, and Cochrane database, data were extracted by two authors. Meta-analysis was performed using a random effect model. Inclusion criteria were patients who had LAFDs with urokinase-type or recombinant tissue-plasminogen activator after SAH in comparison with medically untreated patients with fibrinolytic drugs. We only included randomized controlled trials (RCTs) in this analysis. The outcomes of interest were vasospasm, hydrocephalus, mortality, and 90-day unfavorable functional outcome. Results : Data from eight RCTs with 550 patients were included. Pooled-analysis revealed that the LAFDs were significantly associated with lower rates of vasospasm (LAFDs group vs. control group, 26.5% vs. 39.2%; odds ratio [OR], 0.48; 95% confidence interval [CI], 0.32-0.73); hydrocephalus (LAFDs group vs. control group, 26.0% vs. 31.6%; OR, 0.54; 95% CI, 0.32-0.91); and mortality (LAFDs group vs. control group, 10.5% vs. 15.7%; OR, 0.58; 95% CI, 0.34-0.99). The proportion of 90-day unfavorable outcomes was lower in the LAFDs group (LAFDs group vs. control group, 32.7% vs. 43.5%; OR, 0.55; 95% CI, 0.37-0.80). Conclusion : This meta-analysis with eight RCTs indicated that LAFDs were significantly associated with lower rates of vasospasm and hydrocephalus after SAH. Thus, LAFDs could consequently reduce mortality and improve clinical outcome after SAH.

Diagnostic Performance of On-Site Automatic Coronary Computed Tomography Angiography-Derived Fractional Flow Reserve

  • Doyeon Hwang;Sang-Hyeon Park;Chang-Wook Nam;Joon-Hyung Doh;Hyun Kuk Kim;Yongcheol Kim;Eun Ju Chun;Bon-Kwon Koo
    • Korean Circulation Journal
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    • v.54 no.7
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    • pp.382-394
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    • 2024
  • Background and Objectives: Fractional flow reserve (FFR) is an invasive standard method to identify ischemia-causing coronary artery disease (CAD). With the advancement of technology, FFR can be noninvasively computed from coronary computed tomography angiography (CCTA). Recently, a novel simpler method has been developed to calculate onsite CCTA-derived FFR (CT-FFR) with a commercially available workstation. Methods: A total of 319 CAD patients who underwent CCTA, invasive coronary angiography, and FFR measurement were included. The primary outcome was the accuracy of CT-FFR for defining myocardial ischemia evaluated with an invasive FFR as a reference. The presence of ischemia was defined as FFR ≤0.80. Anatomical obstructive stenosis was defined as diameter stenosis on CCTA ≥50%, and the diagnostic performance of CT-FFR and CCTA stenosis for ischemia was compared. Results: Among participants (mean age 64.7±9.4 years, male 77.7%), mean FFR was 0.82±0.10, and 126 (39.5%) patients had an invasive FFR value of ≤0.80. The diagnostic accuracy, sensitivity, specificity, positive predictive value, and negative predictive value of CT-FFR were 80.6% (95% confidence interval [CI], 80.5-80.7%), 88.1% (95% CI, 82.4-93.7%), 75.6% (95% CI, 69.6-81.7%), 70.3% (95% CI, 63.1-77.4%), and 90.7% (95% CI, 86.2-95.2%), respectively. CT-FFR had higher diagnostic accuracy (80.6% vs. 59.1%, p<0.001) and discriminant ability (area under the curve from receiver operating characteristic curve 0.86 vs. 0.64, p<0.001), compared with anatomical obstructive stenosis on CCTA. Conclusions: This novel CT-FFR obtained from an on-site workstation demonstrated clinically acceptable diagnostic performance and provided better diagnostic accuracy and discriminant ability for identifying hemodynamically significant lesions than CCTA alone.

Erratum: Correction of Text in the Article "Prasugrel-based De-Escalation of Dual Antiplatelet Therapy After Percutaneous Coronary Intervention in Patients With STEMI"

  • You-Jeong Ki;Bong Ki Lee;Kyung Woo Park;Jang-Whan Bae;Doyeon Hwang;Jeehoon Kang;Jung-Kyu Han;Han-Mo Yang;Hyun-Jae Kang;Bon-Kwon Koo;Dong-Bin Kim;In-Ho Chae;Keon-Woong Moon;Hyun Woong Park;Ki-Bum Won;Dong Woon Jeon;Kyoo-Rok Han;Si Wan Choi;Jae Kean Ryu;Myung Ho Jeong;Kwang Soo Cha;Hyo-Soo Kim;HOST-RP-ACS investigators
    • Korean Circulation Journal
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    • v.52 no.6
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    • pp.483-484
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    • 2022

Estimation of PM10 and PM2.5 inhalation dose by travel time and respiratory volume in common transport microenvironments in Seoul, Korea (서울지역 교통수단별 이동시간과 호흡량을 고려한 미세먼지 흡입량 추정에 관한 연구)

  • Lee, Yong-Il;Jung, Wonseck;Hwang, Doyeon;Kim, Taesung;Park, Duckshin
    • Particle and aerosol research
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    • v.14 no.4
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    • pp.97-105
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    • 2018
  • Recently, people's interest in particulate matter (PM) has been increasing, due to its hazardous health effects. The purpose of this study was to investigate the concentrations and as well as the inhaled weight of PM, correlated with person's heart rate in subway, bus, vehicle and bicycle in the major public transportation (Sadang - Jamsil and Nowon - Dongdaemun) in Seoul. The concentration of $PM_{10}$ and $PM_{2.5}$ were measured from each of transportation means and calculated the average concentrations which were 87.2 and $57.8{\mu}g/m^3$ for subway, 62.8 and $42.5{\mu}g/m^3$ for vehicle, 61.5 and $36.8{\mu}g/m^3$ for bus and 53.0 and $29.4{\mu}g/m^3$ for bicycle in $PM_{10}$ and $PM_{2.5}$ respectively. Inhalation dose for $PM_{10}$ and $PM_{2.5}$ were estimated at 248.1 and $139.4{\mu}g$ for bicycle, 56.7 and $39.3{\mu}g$ for vehicle, 49.4 and $29.9{\mu}g$ for bus and 44.3 and $29.1{\mu}g$ for subway, respectively. Even though subway had the highest concentration, the highest inhalation dose was the bicycle. It was due to the long travel time-exposure and breathing rate which leads to maximum of $PM_{10}$ 5.6 and $PM_{2.5}$ with 4.8 times inhalation dose comparing with other modes of transportation. With regards to future studies, the amount of inhalation in each transportation means should be considered in risk assessments of PM.

Prasugrel-based De-Escalation of Dual Antiplatelet Therapy After Percutaneous Coronary Intervention in Patients With STEMI

  • You-Jeong Ki;Bong Ki Lee;Kyung Woo Park;Jang-Whan Bae;Doyeon Hwang;Jeehoon Kang;Jung-Kyu Han;Han-Mo Yang;Hyun-Jae Kang;Bon-Kwon Koo;Dong-Bin Kim;In-Ho Chae;Keon-Woong Moon;Hyun Woong Park;Ki-Bum Won;Dong Woon Jeon;Kyoo-Rok Han;Si Wan Choi;Jae Kean Ryu;Myung Ho Jeong;Kwang Soo Cha;Hyo-Soo Kim;HOST-RP-ACS investigators
    • Korean Circulation Journal
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    • v.52 no.4
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    • pp.304-319
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    • 2022
  • Background and Objectives: De-escalation of dual-antiplatelet therapy through dose reduction of prasugrel improved net adverse clinical events (NACEs) after acute coronary syndrome (ACS), mainly through the reduction of bleeding without an increase in ischemic outcomes. Whether the benefits of de-escalation are sustained in highly thrombotic conditions such as ST-elevation myocardial infarction (STEMI) is unknown. We aimed to assess the efficacy and safety of de-escalation therapy in patients with STEMI or non-ST-segment elevation ACS (NSTE-ACS). Methods: This is a pre-specified subgroup analysis of the HOST-REDUCE-POLYTECH-ACS trial. ACS patients were randomized to prasugrel de-escalation (5 mg daily) or conventional dose (10 mg daily) at 1-month post-percutaneous coronary intervention. The primary endpoint was a NACE, defined as a composite of all-cause death, non-fatal myocardial infarction, stent thrombosis, clinically driven revascularization, stroke, and bleeding events of grade ≥2 Bleeding Academic Research Consortium (BARC) criteria at 1 year. Results: Among 2,338 patients included in the randomization, 326 patients were diagnosed with STEMI. In patients with NSTE-ACS, the risk of the primary endpoint was significantly reduced with de-escalation (hazard ratio [HR], 0.65; 95% confidence interval [CI], 0.48-0.89; p=0.006 for de-escalation vs. conventional), mainly driven by a reduced bleeding. However, in those with STEMI, there was no difference in the occurrence of the primary outcome (HR, 1.04; 95% CI, 0.48-2.26; p=0.915; p for interaction=0.271). Conclusions: Prasugrel dose de-escalation reduced the rate of NACE and bleeding, without increasing the rate of ischemic events in NSTE-ACS patients but not in STEMI patients.

Differential Prognostic Implications of Pre- and Post-Stent Fractional Flow Reserve in Patients Undergoing Percutaneous Coronary Intervention

  • Jinlong Zhang;Doyeon Hwang;Seokhun Yang;Chee Hae Kim;Joo Myung Lee;Chang-Wook Nam;Eun-Seok Shin;Joon-Hyung Doh;Masahiro Hoshino;Rikuta Hamaya;Yoshihisa Kanaji;Tadashi Murai;Jun-Jie Zhang;Fei Ye;Xiaobo Li;Zhen Ge;Shao-Liang Chen;Tsunekazu Kakuta;Bon-Kwon Koo
    • Korean Circulation Journal
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    • v.52 no.1
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    • pp.47-59
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    • 2022
  • Background and Objectives: The influence of pre-intervention coronary physiologic status on outcomes post percutaneous coronary intervention (PCI) is not well known. We sought to investigate the prognostic implications of pre-PCI fractional flow reserve (FFR) combined with post-PCI FFR. Methods: A total of 1,479 PCI patients with pre-and post-PCI FFR data were analyzed. The patients were classified according to the median values of pre-PCI FFR (0.71) and post-PCI FFR (0.88). The primary outcome was target vessel failure (TVF) at 2 years. Results: The risk of TVF was higher in the low pre-PCI FFR group than in the high pre-PCI FFR group (hazard ratio, 1.82; 95% confidence interval, 1.15-2.87; p=0.011). In 4 group comparisons, the cumulative incidences of TVF at 2 years were 3.8%, 4.1%, 4.8%, and 10.2% in the high pre-/high post-, low pre-/high post-, high pre-/low post-, and low pre-/low post-PCI FFR groups, respectively. The risk of TVF was the highest in the low pre-/low post-PCI FFR group among the groups (p values for comparisons <0.05). In addition, the high pre-/low post-PCI FFR group presented a comparable risk of TVF with the high post-PCI FFR groups (p values for comparison >0.05). When the prognostic value of the post-PCI FFR was evaluated according to the pre-PCI FFR, the risk of TVF significantly decreased with an increase in post-PCI FFR in the low pre-PCI FFR group, but not in the high pre-PCI FFR group. Conclusions: Pre-PCI FFR was associated with clinical outcomes after PCI, and the prognostic value of post-PCI FFR differed according to the pre-PCI FFR.