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"Lee, Sang Min"
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Analysis of Activation Process of Carbon Black Based on Structural Parameters Obtained by XRD Analysis
by
Lee, Sang-Min
,
Lee, Sang-Hye
,
Roh, Jae-Seung
in
Activated carbon
,
activation
,
Activation analysis
2021
In the present study, carbon black activated by CO2 gas was examined through XRD analysis, especially with regard to changes in its structural parameters. Based on the results, its activation process was thoroughly analyzed. The activation process was controlled by isothermally activating the carbon black inside a reaction tube through which CO2 gas flowed. With this approach, the degree of activation was varied as desired. At an early stage of the activation process, the amorphous fraction on the carbon black surface was preferentially activated, and later the less-developed crystalline carbon (LDCC) region inside the carbon black particles started to be activated. The latter process was attributable to the formation of pores inside the carbon black particles. As the activation process proceeded further, the more-developed crystalline carbon (MDCC) region started to be activated, thereby causing the pores inside the carbon black particles to grow larger. At the last stage of the activation process, La was found to be decreased to about 40 Å. This implied that the edges of the graphite crystals had been activated, thus causing the internal pores to grow and coalesce into larger pores. Activated conductive Super-P with enhanced pore properties is expected to have wide applications.
Journal Article
Heat Stress Changes over East Asia under 1.5° and 2.0°C Global Warming Targets
2018
This study provides a first quantification of possible benefits of global warming mitigation through heat stress reduction over East Asia by comparing projection results between low-emission and high-emission scenarios, as well as between 1.5° and 2.0°C target temperature conditions. Future changes in summer heat stress over East Asia were examined based on the wet-bulb globe temperature (WBGT) using CMIP5 multimodel simulations. Changes in the intensity, frequency, and duration of heat stress were analyzed in terms of area fraction across RCP2.6, RCP4.5, and RCP8.5 scenarios and also between two selected model groups representing 1.5°-and 2.0°C-warmer worlds. Severe heat stress, exceeding the 50-yr return value of the present-day period, is expected to become very frequent, occurring every second year over the large part of East Asia by the 2040s, irrespective of RCP scenarios. The frequency of extreme daily heat stress events is predicted to increase in a similar speed of expansion, with signals emerging from the low latitudes. The WBGT signal emergence is found to be much faster than that of corresponding temperature alone due to the smaller variability in WBGT, supporting previous findings. The 1.5°C-warmer world would have about 20% reduction in areas experiencing severe heat stress over East Asia, compared to the 2.0°C-warmer world, with significant changes identified over the low latitudes. Further, compared to the transient world, the equilibrium world exhibits larger increases in heat stress over East Asia, likely due to the warmer ocean surface in the northwestern North Pacific. This suggests an important role of ocean warming patterns in the regional assessment of global warming mitigation.
Journal Article
A Comprehensive Review of Degradation Prediction Methods for an Automotive Proton Exchange Membrane Fuel Cell
by
Lee, Sang-Min
,
Yu, Sangseok
,
Nguyen, Huu-Linh
in
Automobiles, Electric
,
Automotive materials
,
Carbon
2023
Proton exchange membrane fuel cells (PEMFCs) are an alternative power source for automobiles that are capable of being cleaner and emission-free. As of yet, long-term durability is a core issue to be resolved for the mass production of hydrogen fuel cell vehicles that requires varied research in the range from sustainable materials to the optimal operating strategy. The capacity to accurately estimate performance degradation is critical for developing reliable and durable PEMFCs. This review investigates various PEMFC performance degradation modeling techniques, such as model-based, data-driven, and hybrid models. The pros and cons of each approach are explored, as well as the challenges in adequately predicting performance degradation. Physics-based models are capable of simulating the physical and electrochemical processes which occur in fuel cell components. However, these models tend to be computationally demanding and can vary in terms of parameters between different studies. On the other hand, data-driven models provide rapid and accurate predictions based on historical data, but they may struggle to generalize effectively to new operating conditions or scenarios. Hybrid prediction approaches combine the strengths of both types of models, offering improved accuracy but also introducing increased computational complexity to the calculations. The review closes with recommendations for future research in this area, highlighting the need for more extensive and accurate prediction models to increase the reliability and durability of PEMFCs for fuel cell electric vehicles.
Journal Article
Effect of prone positioning on oxygenation and static respiratory system compliance in COVID-19 ARDS vs. non-COVID ARDS
by
Lee, Hong Yeul
,
Park, Jimyung
,
Lee, Jinwoo
in
Acute respiratory distress syndrome
,
Care and treatment
,
Compliance
2021
Background
Prone positioning is recommended for patients with moderate-to-severe acute respiratory distress syndrome (ARDS) receiving mechanical ventilation. While the debate continues as to whether COVID-19 ARDS is clinically different from non-COVID ARDS, there is little data on whether the physiological effects of prone positioning differ between the two conditions. We aimed to compare the physiological effect of prone positioning between patients with COVID-19 ARDS and those with non-COVID ARDS.
Methods
We retrospectively compared 23 patients with COVID-19 ARDS and 145 patients with non-COVID ARDS treated using prone positioning while on mechanical ventilation. Changes in PaO
2
/FiO
2
ratio and static respiratory system compliance (Crs) after the first session of prone positioning were compared between the two groups: first, using all patients with non-COVID ARDS, and second, using subgroups of patients with non-COVID ARDS matched 1:1 with patients with COVID-19 ARDS for baseline PaO
2
/FiO
2
ratio and static Crs. We also evaluated whether the response to the first prone positioning session was associated with the clinical outcome.
Results
When compared with the entire group of patients with non-COVID ARDS, patients with COVID-19 ARDS showed more pronounced improvement in PaO
2
/FiO
2
ratio [adjusted difference 39.3 (95% CI 5.2–73.5) mmHg] and static Crs [adjusted difference 3.4 (95% CI 1.1–5.6) mL/cmH
2
O]. However, these between-group differences were not significant when the matched samples (either PaO
2
/FiO
2
-matched or compliance-matched) were analyzed. Patients who successfully discontinued mechanical ventilation showed more remarkable improvement in PaO
2
/FiO
2
ratio [median 112 (IQR 85–144) vs. 35 (IQR 6–52) mmHg,
P
= 0.003] and static compliance [median 5.7 (IQR 3.3–7.7) vs. − 1.0 (IQR − 3.7–3.0) mL/cmH
2
O,
P
= 0.006] after prone positioning compared with patients who did not. The association between oxygenation and Crs responses to prone positioning and clinical outcome was also evident in the adjusted competing risk regression.
Conclusions
In patients with COVID-19 ARDS, prone positioning was as effective in improving respiratory physiology as in patients with non-COVID ARDS. Thus, it should be actively considered as a therapeutic option. The physiological response to the first session of prone positioning was predictive of the clinical outcome of patients with COVID-19 ARDS.
Journal Article
A cooperative biphasic MoOx–MoPx promoter enables a fast-charging lithium-ion battery
2021
The realisation of fast-charging lithium-ion batteries with long cycle lifetimes is hindered by the uncontrollable plating of metallic Li on the graphite anode during high-rate charging. Here we report that surface engineering of graphite with a cooperative biphasic MoO
x
–MoP
x
promoter improves the charging rate and suppresses Li plating without compromising energy density. We design and synthesise MoO
x
–MoP
x
/graphite via controllable and scalable surface engineering, i.e., the deposition of a MoO
x
nanolayer on the graphite surface, followed by vapour-induced partial phase transformation of MoO
x
to MoP
x
. A variety of analytical studies combined with thermodynamic calculations demonstrate that MoO
x
effectively mitigates the formation of resistive films on the graphite surface, while MoP
x
hosts Li
+
at relatively high potentials via a fast intercalation reaction and plays a dominant role in lowering the Li
+
adsorption energy. The MoO
x
–MoP
x
/graphite anode exhibits a fast-charging capability (<10 min charging for 80% of the capacity) and stable cycling performance without any signs of Li plating over 300 cycles when coupled with a LiNi
0.6
Co
0.2
Mn
0.2
O
2
cathode. Thus, the developed approach paves the way to the design of advanced anode materials for fast-charging Li-ion batteries.
Fast-charging of lithium-ion batteries is hindered by the uncontrollable plating of metallic Li on the graphite anode during cycling. Here, the authors demonstrate the fast chargeability and long cycle lifetimes via surface engineering of graphite with a cooperative biphasic MoO
x
–MoP
x
promoter.
Journal Article
Proportion and clinical features of never‐smokers with non‐small cell lung cancer
by
Lee, Chang‐Hoon
,
Choi, Sun Mi
,
Yoo, Chul‐Gyu
in
Epidermal growth factor receptor
,
Hospitals
,
KRAS
2017
Background The proportion of never‐smokers with non‐small cell lung cancer (NSCLC) is increasing, but that in Korea has not been well addressed in a large population. We aimed to evaluate the proportion and clinical features of never‐smokers with NSCLC in a large single institution. Methods We analyzed clinical data of 1860 consecutive patients who were newly diagnosed with NSCLC between June 2011 and December 2014. Results Of the 1860 NSCLC patients, 707 (38.0%) were never‐smokers. The proportions of women (83.7% vs. 5.6%) and adenocarcinoma (89.8% vs. 44.9%) were higher among never‐smokers than among ever‐smokers. Significantly more never‐smokers were diagnosed at a younger median age (65 vs. 68 years, P < 0.001) and earlier stage (stage I–II, 44.5% vs. 38.9%, P = 0.015) compared with ever‐smokers. Epidermal growth factor receptor mutations (57.8% vs. 24.4%, P < 0.001) and anaplastic lymphoma kinase rearrangements (7.8% vs. 2.8%, P < 0.001) were more common in never‐smokers, whereas Kirsten rat sarcoma viral oncogene homolog mutations (5.8% vs. 9.6%, P = 0.021) were less frequently encountered in never‐smokers than in ever‐smokers. Never‐smokers showed longer survival after adjusting for the favorable effects of younger age, female sex, adenocarcinoma histology, better performance status, early stage disease, being asymptomatic at diagnosis, received antitumor treatment, and the presence of driver mutations (hazard ratio, 0.624; 95% confidence interval, 0.460–0.848; P = 0.003). Conclusions More than one‐third of the Korean patients with NSCLC were never‐smokers. NSCLC in never‐smokers had different clinical characteristics and major driver mutations and resulted in longer overall survival compared with NSCLC in ever‐smokers.
Journal Article
Viral Load Kinetics of MERS Coronavirus Infection
by
Kim, Eui-Chong
,
Bang, Ji Hwan
,
Kim, Eu Suk
in
Coronavirus Infections - classification
,
Coronavirus Infections - virology
,
Coronaviruses
2016
Middle East respiratory syndrome coronavirus continues to circulate in the Middle East. During a recent outbreak in Korea, changes in MERS coronavirus viral load were determined during the course of illness in 17 patients.
To the Editor:
The outbreak of Middle East respiratory syndrome coronavirus (MERS-CoV) infection in South Korea involved 186 patients and resulted in 38 deaths, with four large hospital outbreaks accounting for 82% of the total cases.
1
,
2
Here, we report changes in viral load over time in patients with MERS.
We included all patients who were admitted to three Seoul National University–affiliated hospitals; the institutional review boards of these hospitals approved this study and waived the need for written informed consent on public health grounds. The patients were categorized into a group with severe disease (severe group) or a group . . .
Journal Article
Effect of high-flow oxygen versus T-piece ventilation strategies during spontaneous breathing trials on weaning failure among patients receiving mechanical ventilation: a randomized controlled trial
by
Lee, Sang-Min
,
Lee, Hong Yeul
,
Lee, Jinwoo
in
Aged
,
Airway Extubation - methods
,
Breathing exercises
2022
Background
A spontaneous breathing trial (SBT) is used to determine whether patients are ready for extubation, but the best method for choosing the SBT strategy remains controversial. We investigated the effect of high-flow oxygen versus T-piece ventilation strategies during SBT on rates of weaning failure among patients receiving mechanical ventilation.
Methods
This randomized clinical trial was conducted from June 2019 through January 2022 among patients receiving mechanical ventilation for ≥ 12 h who fulfilled the weaning readiness criteria at a single-center medical intensive care unit. Patients were randomized to undergo either T-piece SBT or high-flow oxygen SBT. The primary outcome was weaning failure on day 2, and the secondary outcomes were weaning failure on day 7, ICU and hospital length of stay, and ICU and in-hospital morality.
Results
Of 108 patients (mean age, 67.0 ± 11.1 years; 64.8% men), 54 received T-piece SBT and 54 received high-flow oxygen SBT. Weaning failure on day 2 occurred in 5 patients (9.3%) in the T-piece group and 3 patients (5.6%) in the high-flow group (difference, 3.7% [95% CI, − 6.1–13.6];
p
= 0.713). Weaning failure on day 7 occurred in 13 patients (24.1%) in the T-piece group and 7 patients (13.0%) in the high-flow group (difference, 11.1% [95% CI, − 3.4–25.6];
p
= 0.215). A post hoc subgroup analysis showed that high-flow oxygen SBT was significantly associated with a lower rate of weaning failure on day 7 (OR, 0.17 [95% CI, 0.04–0.78]) among those patients intubated because of respiratory failure (
p
for interaction = 0.020). The ICU and hospital length of stay and mortality rates did not differ significantly between the two groups. During the study, no serious adverse events were recorded.
Conclusions
Among patients receiving mechanical ventilation, high-flow oxygen SBT did not significantly reduce the risk of weaning failure compared with T-piece SBT. However, the study may have been underpowered to detect a clinically important treatment effect for the comparison of high-flow oxygen SBT versus T-piece SBT, and a higher percentage of patients with simple weaning and a lower weaning failure rate than expected should be considered when interpreting the findings.
Clinical trial registration
This trial was registered with ClinicalTrials.gov (number NCT03929328) on April 26, 2019.
Journal Article
Prospective, multicenter validation of the deep learning-based cardiac arrest risk management system for predicting in-hospital cardiac arrest or unplanned intensive care unit transfer in patients admitted to general wards
by
Cho, Kyung-Jae
,
Lee, Dong Hyun
,
Song, Myung Jin
in
Accuracy
,
Artificial intelligence
,
Cardiac arrest
2023
Background
Retrospective studies have demonstrated that the deep learning-based cardiac arrest risk management system (DeepCARS™) is superior to the conventional methods in predicting in-hospital cardiac arrest (IHCA). This prospective study aimed to investigate the predictive accuracy of the DeepCARS™ for IHCA or unplanned intensive care unit transfer (UIT) among general ward patients, compared with that of conventional methods in real-world practice.
Methods
This prospective, multicenter cohort study was conducted at four teaching hospitals in South Korea. All adult patients admitted to general wards during the 3-month study period were included. The primary outcome was predictive accuracy for the occurrence of IHCA or UIT within 24 h of the alarm being triggered. Area under the receiver operating characteristic curve (AUROC) values were used to compare the DeepCARS™ with the modified early warning score (MEWS), national early warning Score (NEWS), and single-parameter track-and-trigger systems.
Results
Among 55,083 patients, the incidence rates of IHCA and UIT were 0.90 and 6.44 per 1,000 admissions, respectively. In terms of the composite outcome, the AUROC for the DeepCARS™ was superior to those for the MEWS and NEWS (0.869 vs. 0.756/0.767). At the same sensitivity level of the cutoff values, the mean alarm counts per day per 1,000 beds were significantly reduced for the DeepCARS™, and the rate of appropriate alarms was higher when using the DeepCARS™ than when using conventional systems.
Conclusion
The DeepCARS™ predicts IHCA and UIT more accurately and efficiently than conventional methods. Thus, the DeepCARS™ may be an effective screening tool for detecting clinical deterioration in real-world clinical practice.
Trial registration
This study was registered at ClinicalTrials.gov (
NCT04951973
) on June 30, 2021.
Journal Article
Mortality risk and causes of death in patients with non-cystic fibrosis bronchiectasis
2019
Background
All-cause mortality risk and causes of death in bronchiectasis patients have not been fully investigated. The aim of this study was to compare the mortality risk and causes of death between individuals with bronchiectasis and those without bronchiectasis.
Methods
Patients with or without bronchiectasis determined based on chest computed tomography (CT) at one centre between 2005 and 2016 were enrolled. Among the patients without bronchiectasis, a control group was selected after applying additional exclusion criteria. We compared the mortality risk and causes of death between the bronchiectasis and control groups without lung disease. Subgroup analyses were also performed according to identification of
Pseudomonas
or non-tuberculous mycobacteria, airflow limitation, and smoking status.
Results
Of the total 217,702 patients who underwent chest CT, 18,134 bronchiectasis patients and 90,313 non-bronchiectasis patients were included. The all-cause mortality rate in the bronchiectasis group was 1608.8 per 100,000 person-years (95% confidence interval (CI), 1531.5–1690.0), which was higher than that in the control group (133.5 per 100,000 person-years; 95% CI, 124.1–143.8;
P
< 0.001). The bronchiectasis group had higher all-cause (adjusted hazard ratio (aHR), 1.26; 95% CI, 1.09–1.47), respiratory (aHR, 3.49; 95% CI, 2.21–5.51), and lung cancer-related (aHR, 3.48; 95% CI, 2.33–5.22) mortality risks than the control group. In subgroup analysis, patients with airflow limitation and ever smokers showed higher all-cause mortality risk among bronchiectasis patients. Therefore, we observed significant interrelation between bronchiectasis and smoking, concerning the risks of all-cause mortality (
P
for multiplicative interaction, 0.030, RERI, 0.432; 95% CI, 0.097–0.769) and lung cancer-related mortality (RERI, 8.68; 95% CI, 1.631–15.736).
Conclusion
Individuals with bronchiectasis had a higher risk of all-cause, respiratory, and lung cancer-related mortality compared to control group. The risk of all-cause mortality was more prominent in those with airflow limitation and in ever smokers.
Journal Article