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This study developed an innovative active vibration canceling (AVC) system designed to mitigate non-periodic vibrations during road driving to enhance passenger comfort. The macro-fiber composite (MFC) used in the system is a smart material that is flexible, soft, lightweight, and applicable in many fields as a dual-purpose sensor and actuator. The target vibrations are road vibration data that were collected while driving on standard urban (Seoul) and highway roads at 40 km/s. To predict and cancel the target vibration accurately before passing it, we modeled the vibration prediction algorithm using a long short-term memory recurrent neural network (LSTM RNN). We regenerated vibrations on Seoul and highway roads at 40 km/s using MFCs and measured the displacements of the measured, predicted, and AVC vibrations of each road condition. To evaluate the vibration, we computed the root mean squared error (RMSE) and compared standard deviation (SD) values. The accuracies of LSTM RNN vibration prediction algorithms are 97.27% and 96.36% on Seoul roads and highway roads, respectively, at 40 km/s. Although the vibration ratio compared with the AVC results are different, there was no difference between the values of the AVC vibrations. According to a previous study and the principle of the AVC system, the target vibrations decrease by canceling the inverse vibration of the MFC actuator. [ABSTRACT FROM AUTHOR]

Landslides are one of the riskiest disasters combining excessive rainfall and unstable slope that a wetness index can quantify. The wetness index generated by water infiltration considering the rainfall pattern such as cumulated rainfall, rainfall duration and rainfall intensity should be estimated for the slope stability analysis. Even though the infiltration capacity of soils has been largely focused to evaluate the slope stability, the temporal patterns of rainfall have commonly been ignored or assumed as a steady state for the prediction of the slope failure in the previous studies. Thus, this study focuses more on evaluating the influence of various rainfall patterns on the slope stability, and compares it with an actual landslide incident that occurred in 2011, in Korea. The factor of safety (FS) considering the time-dependent wetness index variation is used to determine the slope stability. For the various rainfall designs, the uniform rainfall distribution, Yen and Chow, Mononobe, alternating block and second quartile Huff models are adopted. Thereafter, the FS variations from five models are compared with an actual landslide incident in Seoul, Korea. Among the rainfall designs, the models that consider the abrupt rainfall intensity capture the landslide time with an FS < 1. Therefore, the appropriate adoption of a rainfall distribution model should be highlighted for landslide prediction. [ABSTRACT FROM AUTHOR]

Purpose: Whether prior radiotherapy (RT) affects the response of EGFR-mutated non-small cell lung cancer (NSCLC) to EGFR tyrosine kinase inhibitor (TKI) remains elusive. Methods: Patients with EGFR-mutated NSCLC treated with EGFR TKIs who recurred after curative treatment at Asan Medical Center, Seoul, Korea were included. The progression-free survival (PFS) and overall survival (OS) from the initiation of EGFR TKI in patients who recurred after definitive RT were analyzed and compared to the outcomes of RT-naïve patients with advanced NSCLC treated with EGFR TKIs from previously reported prospective clinical trial results. Results: A total of 60 patients who recurred after definitive RT were included. The median age was 70 years (range, 38–88), with 24 patients (40.0%) being males. Among the 60 patients, 52 patients (86.7%) had exon 19 deletion or L858R mutation, with 49 patients (81.7%) receiving gefitinib as the first-line EGFR TKI. The median PFS and OS from the initiation of EGFR TKI were 10.4 months (95% confidence interval [CI], 7.4–13.2) and 21.3 months (95% CI, 13.4–28.8), respectively. Conclusion: The EGFR TKI efficacy in EGFR-mutated patients with NSCLC who recurred after RT was comparable with that in historic controls of RT-naïve patients with advanced NSCLC treated with EGFR TKIs, indicating that RT may not affect EGFR TKI efficacy. [ABSTRACT FROM AUTHOR]

Continuous measurements of aerosol extinction coefficient (σext) from the High Spectral Resolution Lidar (HSRL) in Seoul from 2016 to 2018 were used to investigate the diurnal variation of the aerosol optical depth (AOD). Nighttime AOD displayed a larger mean and standard deviation (0.45 ± 0.47) than daytime (0.40 ± 0.29). Hygroscopic growth of aerosols under humid conditions was a key factor in the relative enhancement of nighttime AOD. Taking advantage of the HSRL's vertically resolved measurements, the contribution of aerosols within the boundary layer (BL) and free troposphere (FT) to AOD and its temporal variation were investigated. Unlike the diurnal AOD variation, AOD within the BL (AODBL) showed similar diurnal variations with the mixing layer height (MLH), displaying lower nighttime values with a peak around 14–15 local standard time. However, the low correlation between MLH and AODBL (R2 = 0.06) implied that MLH was not the sole deterministic factor of AODBL. A larger AOD of FT aerosols (AODFT) was observed during spring due to frequent elevated dust layers. Using mean σext within the BL and surface PM10 concentrations, the mass extinction efficiency (MEE) of aerosols in Seoul was estimated. The PM10 MEE showed a mean of 5.40 g m−2 and displayed significant variability by PM2.5 to PM10 ratio, season, and ambient relative humidity. The uncertainty of estimated surface PM10 concentrations was minimized when the seasonality and humidity factor in MEE were taken into account (the normalized mean bias decreased from 10.6%, using a single MEE value, to 6.2%). Plain Language Summary: The vertical distribution of aerosols and its evolution over time is important for accurately simulating near‐surface air quality, since the chemical and transport processes of aerosols vary by altitude. Understanding the optical properties of aerosols by altitude is also important when accounting for aerosol radiative and climate effects. We investigated the temporal variation of aerosol optical properties in Seoul, Korea, using 2‐year (2016–2018) High Spectral Resolution Lidar measurements. We found significant hygroscopic growth of aerosols during nighttime that led to enhanced aerosol optical depth (AOD). The diurnal variation of the AOD within the boundary layer (AODBL) resembled that of the mixing layer height (MLH), displaying maximas at 14–15 local standard time and lower values at night. However, due to daytime aerosol dilution and enhancement of aerosol extinction coefficients by hygroscopic growth during nighttime, AODBL and MLH were not necessarily correlated. Significant increases in AOD within the free troposphere (AODFT) were found during spring when long‐range transport of dust particles was frequent. Ambient relative humidity, seasons, and the vertical distribution of aerosols (i.e., the contribution of aerosols within the BL to AOD) should be considered when estimating surface particulate matter concentration from remote sensing measurements of AOD. Key Points: Hygroscopic growth of aerosols during nighttime led to significant enhancement of aerosol optical depth (AOD)Significant increases in free tropospheric AOD were found during spring when long‐range transport of dust particles was frequentAmbient relative humidity, season, and aerosol vertical distribution are key factors when estimating surface air quality from remote sensing measurements [ABSTRACT FROM AUTHOR]

Response to vaccines generally varies according to individual factors of the vaccinated subjects such as demographics and immune status. While there are various reports of factors associated with immunogenicity of mRNA COVID-19 vaccines, little is known about those of adenovirus vector vaccines. We conducted a prospective observational study to assess the relationships of antibody level with age, sex, body mass index (BMI), and adverse reactions (ARs) to an adenovirus vector vaccine, ChAdOx1 nCoV-19. Healthcare workers who planned to receive both the first and second injections of the ChAdOx1 nCoV-19 vaccine at Hanyang University Hospital, Seoul, Korea, were enrolled in the study. Seven days after each injection, participants were asked to complete an online adverse reaction survey. In addition, anti-SARS-CoV-2 spike (S) protein receptor binding domain (RBD) antibody concentration was measured 4 weeks after the second injection. All participants (n = 447, 100%) showed serologic positivity (≥ 0.8 U/mL) 4 weeks after the second injection of ChAdOx1 nCoV-19 vaccine. Furthermore, the anti-SARS-CoV-2 S protein RBD concentration was similar among groups when stratified by age, sex, BMI, or presence and severity of AR; multivariable linear regression found no associations between antibody response to the ChAdOx1 nCoV-19 vaccine and age, BMI, sex, and vaccine-induced ARs. In conclusion, age, sex, obesity, and ARs were not associated with antibody responses after two doses of ChAdOx1 nCoV-19 vaccination. [ABSTRACT FROM AUTHOR]

Based on multiple linear regression (MLR) models, we estimated the PM2.5 at Seoul using a number of aerosol optical depth (AOD) values obtained from ground-based and satellite remote sensing observations. To construct the MLR model, we consider various parameters related to the ambient meteorology and air quality. In general, all AOD values resulted in the high quality of PM2.5 estimation through the MLR method: mostly correlation coefficients >~0.8. Among various polar-orbit satellite AODs, AOD values from the MODIS measurement contribute to better PM2.5 estimation. We also found that the quality of estimated PM2.5 shows some seasonal variation; the estimated PM2.5 values consistently have the highest correlation with in situ PM2.5 in autumn, but are not well established in winter, probably due to the difficulty of AOD retrieval in the winter condition. MLR modeling using spectral AOD values from the ground-based measurements revealed that the accuracy of PM2.5 estimation does not depend on the selected wavelength. Although all AOD values used in this study resulted in a reasonable accuracy range of PM2.5 estimation, our analyses of the difference in estimated PM2.5 reveal the importance of utilizing the proper AOD for the best quality of PM2.5 estimation. [ABSTRACT FROM AUTHOR]

• Location selection issue for smart mobility hubs in urban areas needs addressal. • Methodology to select optimal locations for integrated mobility hub is proposed. • It includes airspace obstacle analysis and AHP-based selection criteria and weights. • 177 spots capital region of Korea were selected and ranked based on scores. • 5 spots, including bus terminals and a transit garage, were the best locations. This study suggests a systematic approach for selecting the optimal locations for mobility hubs in urban areas, which serves as transfer centers for various modes of transport—including buses, metros, and emerging smart mobility services that operate underground, on the ground, and in low-altitude airspace. The emerging smart mobility services covered in this study include personal mobility, car sharing, demand-responsive transit, automated shuttles, and urban air mobility. This study establishes a two-step location selection approach: the first step uses vertiport obstacle analysis to exclude locations that could not support urban air mobility takeoff and landing requirements, and the second step employs an analytical hierarchy method to provide selection criteria and weights for the purpose of prioritization. The approach is applied for the selection of the location of mobility hub in Seoul Metropolitan Area. This two-step approach proposed in this study provides a practical method for selecting the location of a mobility hub where various mobility services with unique operational requirements exist, and ultimately it could be an excellent reference for urban mobility planners and engineers concerned with identifying and selecting the mobility-hub locations. [ABSTRACT FROM AUTHOR]

This study examines cirrus cloud top and bottom heights (CTH and CBH, respectively) and the associated optical properties revealed by ground-based lidar in Seoul (SNU-L), Korea, and space-borne Cloud–Aerosol Lidar with Orthogonal Polarization (CALIOP), which were obtained during a three-year measurement period between July 2006 and June 2009. From two selected cases, we determined good agreement in CTH and CBH with cirrus cloud optical depth (COD) between ground-based lidar and space-borne CALIOP. In particular, CODs at a wavelength of 532nm calculated from the three years of SNU-L and CALIOP measurements were 0.417±0.394 and 0.425±0.479, respectively. The fraction of COD lower than 0.1 was approximately 17% and 25% of the total SNU-L and CALIOP profiles, respectively, and approximately 50% of both lidar profiles were classified as sub-visual or optically thin such that COD was <0.3. The mean depolarization ratio was estimated to be 0.30±0.06 for SNU-L and 0.34±0.08 for CALIOP. The monthly variation of CODs from SNU-L and CALIOP measurements was not distinct, whereas cirrus altitudes from both SNU-L and CALIOP showed distinct monthly variation. CALIOP observations showed that cirrus clouds reached the tropopause level in all months, whereas the up-looking SNU-L did not detect cirrus clouds near the tropopause in summer due to signal attenuation by underlying optically thick clouds. The cloud layer thickness (CLT) and COD showed a distinct linear relationship up to approximately 2km of the CLT; however, the COD did not increase, but remained constant when the CLT was greater than 2.0km. The ice crystal content, lidar signal attenuation, and the presence of multi-layered cirrus clouds may have contributed to this tendency. [ABSTRACT FROM AUTHOR]

Background: Self-expandable metal stents (SEMS) have been used as a bridging or palliative treatment for malignant colorectal obstruction. Colonic obstruction also may arise from advanced extracolonic malignancy, but the clinical outcomes of stent placement for extracolonic malignancy are unclear. This study compared the clinical outcomes of SEMS between patients with colorectal cancer and those with extracolonic malignancy. Methods: Patients who underwent endoscopic SEMS placement for a malignant colorectal obstruction were enrolled at Seoul National University Hospital from April 2005 and August 2011. Their medical records were retrospectively reviewed in terms of success rate, complications, and duration of stent patency. Results: Endoscopic SEMS placements were performed for colorectal cancer in 149 patients and for extracolonic malignancy in 60 patients. The causes of obstruction in extracolonic malignancy were advanced gastric cancer in 39 patients (65 %), pancreatic cancer in nine patients (15 %), ovarian cancer in three patients (5 %) and other causes in nine patients (15 %). The clinical success rates were similar between the two groups (92.6 vs 86.7 %; p = 0.688), and multivariate analysis showed no significant risk factor for unsuccessful endoscopic SEMS placement. Reobstruction in palliative endoscopic SEMS placement occurred for 16 patients with colorectal cancer (21.9 %) and 18 patients with extracolonic malignancy (30 %) during a median follow-up period of 90 days ( p = 0.288). The rates did not differ significantly between the two groups (4.1 vs 8.3 %; p = 0.467). The median duration of stent patency was 193 ± 42 days for the patients with colorectal cancer and 186 ± 31 days for the patients with extracolonic malignancy ( p = 0.253). The duration of stent patency was not affected by underlying malignancy, previous surgery, or palliative chemotherapy. Conclusions: Endoscopic SEMS placement is highly effective and comparable for palliation of obstruction in extracolonic malignancy and colorectal cancer in terms of clinical success, complications, and duration of patency. [ABSTRACT FROM AUTHOR]

Abstract: In this study, we investigate the transport of dust particles, its vertical distribution, and the associated meteorological conditions during an Asian dust event that was observed in Seoul, Korea on May 29–31, 2008. This study analyzes data from ground-based and space-borne 2-wavelength polarization lidars, particulate mass concentrations, and synoptic weather data. Surface meteorological station observations of dust phenomena, dust transport model, and weather maps consistently show that the dust particles were transported from the source regions (Inner Mongolia, Man-Ju, and Ordos areas) to Korea via the northeastern part of China. Network observations of the PM10 concentrations in Korea revealed that a majority of the heavy dust particles traveled across South Korea from the northwest to the southeast direction with a horizontal scale of 250–300km and a traveling speed of approximately 40kmh−1. This extraordinary dust event, in terms of its intensity and timing during the year, occurred due to the blockage of an unusually intensified low-pressure system in the northeastern part of China as well as high-pressure system centered over the Sea of Okhotsk and the Kuril Islands. The low values of the particle depolarization ratio (δ 532) (≤0.05) and color ratio (CR) during the pre-dust period indicate the presence of spherical, non-dust, and relatively small particles. The mean δ 532 value was approximately 0.123±0.069 between altitudes of ground ~2.8km, and 0.161±0.049 for near-surface dust layer (ground ~1.2km). This value is quite similar to that obtained during the 3-year SNU-Lidar measurements in Seoul (δ 532 ~0.136±0.027). The value of δ 532 during the 2nd multilayered dust episode ranged between 0.081 and 0.120 for near-surface dust layers, and between 0.076 and 0.114 for elevated dust layers. The CALIPSO measurements of β 532, δ 532, and CR also revealed the presence of dense dust aerosols along the transport route. [Copyright &y& Elsevier]

We have estimated the mixing height (MH) and investigated the relationship between vertical mixing and ground-level ozone concentrations in Seoul, Korea, by using three ground-based active remote sensing instruments operating side by side: micro-pulse lidar (MPL), differential absorption lidar (DIAL), and differential optical absorption spectroscopy (DOAS). The MH is estimated from MPL measurements of aerosol extinction profiles by the gradient method under convective conditions. Comparisons of the MHs estimated from MPL and radiosonde measurements show a good agreement (r 2=0.99). Continuous MPL measurements with high temporal and vertical resolution reveal the diurnal variations of the MH under convective conditions and the presence of a residual layer during the nighttime. Comprehensive measurements of ozone and aerosol by MPL, DIAL and DOAS during an high ozone episode (24–26 May 2000) in Seoul, Korea, reveal that (1) photochemical ozone production and advection from upwind regions (the western part of Seoul) contribute two peaks of ozone concentrations at the ground around 14:00 and 18:00 local time on 25 May 2000, respectively, and (2) the entrainment and the fumigation processes of ozone aloft in the nighttime residual layer into the ground is a major contributor of high concentrations of ground-level ozone observed on the following day (26 May 2000). [Copyright &y& Elsevier]

Abstract: The recurrence of focal segmental glomerulosclerosis (FSGS) in transplants is a well-known problem in pediatric renal transplantation (Tx). Recently, the race of the recipient was recognized as a major variable associated with disease recurrence. In view of this finding, we report on our single-center experience of FSGS recurrence in Korean children, an ethnically homogeneous Far East Asian population. Clinical records and renal biopsy specimens, both native and graft, were reviewed for all pediatric renal Txs (recipient age ≤ 18 yr) performed at Seoul National University Hospital from 1984 to 1999. Twenty-two children with primary FSGS received 22 allografts for renal replacement. The mean age of disease onset in these patients was 5.9 yr. The grafts were from 12 living-related, six living-unrelated, and four cadaveric donors, and all recipients were immunosuppressed with cyclosporin A (CsA)-based regimens. Post-transplant recurrence of FSGS was confirmed in nine patients (41%). Long-term graft survival in recurrent and non-recurrent groups was not significantly different. Risk factor analysis showed that patients with a disease duration shorter than 48 months (odds ratio 11.7, 95% CI 1.53–89.1) and a glomerulosclerosis percentage of < 55% by renal biopsy (odds ratio 16.0, 95% CI 1.45–176) were at greater risk of disease recurrence. These results suggest that Korean children are similar to non-African-American youngsters in the USA and Europe with respect to post-transplant recurrence of FSGS. The same may be true of other Far Eastern Asian children. [ABSTRACT FROM AUTHOR]

High-resolution meteorological information is essential for attaining sustainable and resilient cities. To elucidate high-resolution features of surface and air temperatures in high-rise building blocks (BBs), a 3-dimensional BB meteorological observation experiment (BBMEX) campaign was designed. The campaign was carried out in a central commercial area in Seoul during a heat-wave event period (5−6 August) in 2019. Several types of fixed instrument were deployed, a mobile meteorological observation cart (MOCA) and a vehicle were operated periodically. The surface temperature was determined to be strongly dependent on the facial direction of a building, and sunlit or shade by surrounding obstacles. Considerable increases in surface temperature on the eastern facades of buildings before noon, on horizontal surfaces near noon, and on the western facades in the afternoon could provide more energy in BBs than over a flat surface. The air temperatures in the BB were higher than those at the Seoul station by 0.1−2.2 °C (1.1−1.9 °C) in daytime (night-time). The MOCA revealed that the surface and air temperatures in a BB could be affected by many complex factors, such as the structure of the BBs, shades, as well as the existence of facilities that mitigate heat stresses, such as ground fountains and waterways. [ABSTRACT FROM AUTHOR]

The empirical/statistical models to estimate the surface Particulate Matter (PM2.5) concentration in Seoul from Geostationary Ocean Color Imager (GOCI) Aerosol Optical Depth (AOD) product were developed for the period of 2015. Two vertical correction methods, vertical ratio of aerosol (VRA) calculated from LIDAR vertical profile of backscattering coefficients and AOD below boundary layer extracted from planetary boundary layer height (PAOD), were effective to increase the correlation between the satellite-derived AOD and ground-observed PM2.5. In order to improve the accuracy in PM2.5 estimation, additional meteorological factors (wind speed, visibility, and air temperature, relative humidity) affecting AOD and PM2.5 relationships were considered as predictor variables in the multiple linear regression (MLR) models. Stable atmospheric state with low wind speed and high relative humidity conditions are closely associated with high PM2.5 concentrations in the morning. The estimates show a similar variation in time (day and season), and a high correlation (R=0.85) compared to observed PM2.5 concentration. The models developed in this study are applicable to the surface PM2.5 estimation using AOD retrieved from the future GK-2A and GK-2B. [ABSTRACT FROM AUTHOR]

Purpose: To identify the characteristics and causes of uveitis in Seoul, South Korea.Methods: We performed a retrospective medical record review of 602 patients diagnosed with uveitis at seven tertiary ophthalmology centers between January and December 2013.Results: The most common type of uveitis was anterior uveitis (n = 281), followed by posterior uveitis (n = 152), panuveitis (n = 126), and intermediate uveitis (n = 43). Among patients with an identified cause (n = 252), 149 and 103 had non-infectious and infectious uveitis, respectively, and ankylosing spondylitis (n = 53), Behcet disease (n = 43), and endophthalmitis (n = 25) were common identified causes of uveitis.Conclusions: Anterior uveitis was the most common type of uveitis, and the incidence of infectious uveitis was relatively high in Seoul. Ankylosing spondylitis and Behcet disease were the most common systemic diseases causing uveitis in this sample. [ABSTRACT FROM AUTHOR]

The COVID-19 pandemic has had a major impact on liver transplantation (LT) and living donor programs globally. In this study, we aimed to present the principles and strategies of our LT program during the pandemic period and describe its achievements. We retrospectively reviewed the outcomes of 1417 LTs performed at Asan Medical Center, Seoul, Korea, from 2020 to 2022. Of these, 216 recipients who received transplants from deceased donors were excluded, and 1201 recipients who received transplants from 1268 live donors were included in the study, including 38 children <18 years old. Among the 1201 living donor LT (LDLT) recipients, the most common indication for LT was unresectable hepatocellular carcinoma (315/1163, 27.1%) in adults and biliary atresia (29/38, 76.3%) in pediatric recipients. Emergency LDLT was performed in 40 patients (3.3%). The median model of end-stage liver disease and pediatric end-stage liver disease scores were 13.9 ± 7.2 and 13.8 ± 7.1, respectively. In-hospital mortality of recipients was higher than usual at 2.2%, but the cause of death was not related to COVID-19 infection. Of the 1268 live donors who underwent hepatectomy for liver donation, 660 (52.1%) underwent hepatectomy using a minimally invasive approach. Although 17 (1.3%) live donors experienced major complications, there were no serious life-threatening complications and no mortality. Even in a pandemic era, a team with well-established infection control protocols, patient-tailored surgical strategies, and thorough perioperative care can maintain LDLT at a similar quantitative and qualitative level as in a non-pandemic era. [ABSTRACT FROM AUTHOR]

Seasonal variations of aerosol optical properties in Seoul (polluted urban site) and Gosan (coastal background site), Korea, with an emphasis on the relative humidity were investigated using ground-based aerosol measurements and optical model calculations. The mass fraction of elemental carbon was 9–20%, but the optical contribution of these particles to light extinction was higher, up to 33–55% in Seoul. In Gosan, the contribution of non-sea-salt water-soluble aerosols on extinction was 81–93% due to the high mass fraction of these particles. Based on daily MODIS datasets, our analysis showed that the aerosol optical depths at Seoul and Gosan were highest in spring due to the influence of dust particles. The aerosol water content at Gosan, calculated using a thermodynamic equilibrium model, was higher than that at Seoul; this was attributed to the high relative humidity and high fraction of water-soluble aerosols at Gosan. At Seoul, despite abundant water vapors in summer, the possibility of hygroscopic growth of water-soluble aerosols was not more significant than that at Gosan. [Copyright &y& Elsevier]

Severe haze episodes have occurred frequently throughout megacities in East Asia, especially during winter and early spring. Although notable progress has been attained in understanding the causes of severe haze formation, the exacerbation of PM 2.5 concentration due to Asian dust has not yet been fully investigated. Here, we investigated the contribution of weak Asian dust particles to PM 2.5 concentration during early spring for an extraordinarily long-lasting high PM 2.5 episode in Seoul, Korea. PM 2.5 concentrations exceeding national criteria (35 μg m−3) were continuously observed from February 27 to March 7, 2019, and can be attributable to the transboundary transported aerosols for the Asian continent under slow eastward-migrating anticyclones. The high-frequency of PM 10-2.5 and PM 2.5 mass concentrations in the high concentration regime (PM 10-2.5 > 30 μg m−3; PM 2.5 > 80 μg m−3) suggests that Asian dust particles transported concurrently with anthropogenic pollution aerosols contributed to elevated PM 2.5 concentration during this episode. This was also evident from an elevated depolarization ratio (δ 532 : 0.06–0.13) and aerosol volume concentrations both in coarse and fine modes, which indicates the presence of non-spherical dust particles, from collocated aerosol lidar and optical particle counter measurements. Unlike severe Asian dust episodes (PM 10 > 800 μg m−3) in Korea, relatively low Asian dust particle concentrations during high PM 2.5 haze episodes have not been accurately predicted and alerted by most air quality forecasting models. This study emphasizes the need for the implementation of a series of dust emission and transport processes for better predictions of PM 2.5 concentration during winter-spring high PM 2.5 episodes. [Display omitted] • Extraordinarily long-lasting high PM 2.5 episode was studied. • Asian dust particles transported contributed to elevated PM 2.5 concentration. • Dust emission and transport processes required for better PM 2.5 predictions. [ABSTRACT FROM AUTHOR]

Abstract: The diagrid nodes that are designed to be installed in the Lotte Super Tower located in Seoul, South Korea were examined experimentally. This paper aims to investigate the cyclic behavior of the diagrid nodes under lateral loads, such as wind load or seismic load and to suggest the details and welding methods of nodes for application to an actual building based on test results. Two types of specimens were developed and tested cyclically. The PA type utilized an open-section layout for the node, whereas the PB type utilized a box-section layout for the node. Based on the test results, the cyclic performance for diagrid nodes was discussed with an emphasis on the initial stiffness, strength, and welding methods. [Copyright &y& Elsevier]

Heterogeneous hydrolysis of dinitrogen pentoxide (N 2 O 5) plays an important role in nighttime nitrate (NO 3 −) formation in urban areas, and sometimes influences the occurrence of heavy PM 2.5 pollution the next day in the Seoul Metropolitan Area (SMA), Korea. Here, we discuss the heavy PM 2.5 wintertime episode of January 13–15, 2018, which was mainly induced by nighttime N 2 O 5 heterogeneous reaction in the SMA. In our case, we confirmed that nighttime N 2 O 5 hydrolysis is the most critical factor in the rapid formation of aerosol nitrate at high levels during the night, which prevailed in the morning of the next day. Our Integrated Process Rate (IPR) analysis showed that nighttime nitrate production in the episode was almost solely attributable to N 2 O 5 chemistry, with hourly mean production rates of 0.8 ± 0.4 μg/m3 per hour in SMA, which is comparable to the daytime nitrate photochemical production rates of 0.9 ± 0.5 μg/m3 per hour. We also carried out a series of assessment of N 2 O 5 –driven nitrate formation sensitivity, and relevant errors were quantified by applying different N 2 O 5 uptake coefficients in the WRF-CMAQ model. The potential errors of nighttime-average nitrate concentrations induced by N 2 O 5 uptake process were assessed from a linear perspective for the planetary boundary layer (PBL) variances caused by four different PBL parameterization schemes: YSU, ACM2, MYJ, and QNSE. The potential error ranges by N 2 O 5 uptake process were analyzed to be 2.3 to 3.5 μg/m3 (~10% relative to the nighttime-average), while biases of PBL simulations from 4 parameterization schemes were 2.3 ± 1.0 μg/m3, showing similar ranges in our episode. Although N 2 O 5 –driven heavy PM 2.5 episodes do not occur often in SMA, our findings suggest the importance of N 2 O 5 chemistry in vigorous wintertime nitrate formation and operational prediction errors of such PM 2.5 episodes, under the premise of enhanced PBL simulation capabilities. • N 2 O 5 heterogeneous chemistry was investigated by intervening the uptake coefficient (γN 2 O 5) with WRF-CMAQ. • Nighttime nitrate production rate driven by N 2 O 5 chemistrywas analyzed to be 0.8 ±0.4 μg/m3/hr in IPR analysis. • Simulations with different uptake coefficients (γN 2 O 5) indicate that improving γN 2 O 5 can contribute to better predicting fine nitrate by 10%. • Error ranges from both PBL schemes and uptake process of N 2 O 5 showed approximately ~10% relative to the nighttime-average PM 2.5. [ABSTRACT FROM AUTHOR]

In this study, we contrasted major secondary inorganic species and processes responsible for submicron particle formation (SPF) events in the boundary layer (BL) and free troposphere (FT) over the Korean Peninsula during Korea-United States Air Quality (KORUS-AQ) campaign (May–June 2016) using aircraft observations. The number concentration of ultrafine particles with diameters between 3 nm and 10 nm (N CN3 – 10) during the entire KORUS-AQ period reached a peak (7606 ± 12,003 cm−3) at below 1 km altitude, implying that the particle formation around the Korean Peninsula primarily occurred in the daytime BL. During the BL SPF case (7 May 2016), the SPF over Seoul metropolitan area was more attributable to oxidation of NO 2 rather than SO 2 -to-sulfate conversion. From the analysis of the relationship between nitrogen oxidation ratio (NOR) and temperature or relative humidity (RH), NOR showed a positive correlation only with temperature. This suggests that homogeneous gas-phase reactions of NO 2 with OH or O 3 contributed to nitrate formation. From the relationship between N CN3 – 10 (> 10,000 cm−3) and the NOR (or sulfur oxidation ratio) at Olympic Park in Seoul during the entire KORUS-AQ period, it was regarded that the relative importance of nitrogen oxidation was grown as the N CN3 – 10 increased. During the FT SPF case (31 May 2016) over the yellow sea, the SO 2 -to-sulfate conversion seemed to influence SPF highly. The sulfate/CO ratio had a positive correlation with both the temperature and RH, suggesting that aqueous-phase pathways as well as gas-phase reactions might be attributable to sulfate formation in the FT. In particular, FT SPF event on 31 May was possibly caused by the direct transport of SO 2 precursors from the continent above the shallow marine boundary layer under favorable conditions for FT SPF events, such as decreased aerosol surface area and increased solar radiation. [Display omitted] • Submicron particle formation (SPF) events around the Korean Peninsula primarily occurred in the boundary layer (BL). • BL SPF case (7 May 2016) was primarily attributable to gas-phase oxidation of NO 2. • As the number of nucleation-mode particles increased, the relative importance of nitrogen oxidation was enhanced. • The SO 2 -to-sulfate conversion seemed to highly influence SPF in free troposphere (FT; 31 May 2016). • FT SPF event was possibly caused by the direct transport of SO 2 precursors. [ABSTRACT FROM AUTHOR]

The serious degradation of regional air quality is a critical social issue in East Asia despite continuous efforts to reduce the emission of pollutants and their precursors. To better understand high-pollution events in this region, the synoptic weather patterns associated with springtime non-dust high PM 10 (High PM 10) events and Asian Dust events in Seoul, South Korea, are examined for the 2001–2018 period. It is shown that the two high-pollution events accompany different atmospheric circulations. While High PM 10 events are associated with weak surface cyclonic circulations over the Southeast China, Asian Dust events are characterized by strong cyclones over Northeast China. Composite weather maps show that mid-tropospheric circulation anomalies are exactly the opposite between the two events with anticyclonic anomalies over the Korean Peninsula for High PM 10 events but cyclonic anomalies for Asian Dust events. The cluster analyses further reveal that High PM 10 events are not determined by a single dominant weather pattern. They are associated with surface cyclonic circulations from southeastern China to the Sea of Okhotsk, anticyclonic circulations around the Korean Peninsula or their mixtures. This result is in contrast with the Asian Dust events which are primarily driven by vertically well-organized continental cyclones. • Both High PM 10 and Asian Dust events exhibit a distinct seasonality over the last 18 years. • Synoptic weather patterns of High PM 10 and Asian Dust events, observed in Seoul, South Korea, are quite different. • High PM 10 events are related to pollutant transport from external sources and accumulation of local pollutants. • All of Asian Dust events are characterized by well-developed synoptic-scale cyclones. [ABSTRACT FROM AUTHOR]

In January 2018, PM2.5 warnings have been issued for three days across the Koreapeninsular, when it was increased up to 106 μg/m3. The rapid increase of PM2.5 mass wasassociated with increase in nitrate by 10 μg/m3 and NO2 by 103 ppbv within 3 hours from10:00 and 13:00. In Seoul, the maximum NO2 is usually found around 9 am. Whilethe PM2.5 mass was best correlated with ammonium (r= 0.95), the increase insulfate was insignificant. Therefore, it is critical to understand the rapid conversionmechanism of nitrate and the plausible pathways. The contribution of HNO3 is veryunlikely under overcast conditions in winter (average cloud coverage of almost around10). In fact, the calculated HNO3 was not sufficient to explain the observed NO3concentration. It might be possible that N2O5 was heterogeneously converted intoHNO3 in liquid droplets during nighttime and mixed with surface air rich in NH3during the daytime, leading to NH4NO3 formation. However, it is quite not likelybecause of the low temperature (minimum surface temperature of -2.5 ∘C) and low O3concentration (maximum O3 of 40 ppbv). The ceilometer and LIDAR measurementsreveal the shallow thin cloud and boundary layer height during the night, whichstarted expanding around 9 10 am. Therefore, we suggest that the vertical mixingplayed a key role in increase of nitrate, which was enriched in cloud droplets (icecrystal) aloft. Regarding ammonium, it is not clear if it was combined with NO3 orpartitioned into aerosol after being mixed with surface air, which will be furtherinvestigated. [ABSTRACT FROM AUTHOR]