Interferometric SAR observation of the 2021 Mount Nyiragongo Eruption In Congo using Sentinel-1 data

Arip Syaripudin Nur,Muhammad Fulki Fadhillah,Suci Ramayanti,Chang-Wook Lee 대한지질학회 2021 대한지질학회 학술대회 Vol.2021 No.10

On May 22, 2021, Mount Nyiragongo erupted in the Democratic Republic of the Congo, threatening the nearby city of Goma and neighboring towns. As a result, 32 people were reported killed, and more than 400,000 people were forced to be evacuated. Therefore, monitoring the 2021 Nyiragongo eruption is required, including mapping surface deformation, lava flows, and damaged buildings. The use of point-based interferometric synthetic aperture radar (InSAR) time series analysis continues to grow, such as PSI and StaMPS. However, persistent scatter, which is more sensitive to urban and rocky conditions, has limitations in applying mountainous areas with vegetated areas. In this study, we used an enhanced combination method of interferometric scattering with the optimal point scattering method (ICOPS) after the eruption of Mount Nyiragongo to generate time series deformations and mean deformation maps. SAR data from the Sentinel-1 satellite for 2020-2021 were used in this study. For comparison, we used the StaMPS method based on persistent scatterer to study the deformation of Mount Nyiragongo. And the initial results show an increase in the coverage of measurement points (MP) using the ICOPS method. In addition, the use of optimized hotspot analysis (OHSA) on MP can provide additional insight in deformation analysis by exploiting the advantages of spatial clustering on MP. This study is an initial overview showing promising performance for the application of ICOPS in deformation studies. In addition, we generated a damage proxy map (DPM) derived from temporal changes in the InSAR coherence to identify anomalous changes that indicated earthquake damage. The DPM shows a loss of coherence in the urban area near Goma airport, which may have been caused by several earthquakes after the eruption. Compared to image analysis from UNOSAT, DPM revealed areas damaged by lava flows south of Mount Nyiragongo. Rapid assessment after an eruption followed by an earthquake can help with evacuation planning and mitigation to reduce disaster risk.

Mapping of Post-Wildfire Burned Area Using KOMPSAT-3A and Sentinel-2 Imagery: The Case of Sokcho Wildfire, Korea

( Arip Syaripudin Nur ),( Sungjae Park ),( Kwang-jae Lee ),( Jiyoon Moon ),( Chang-wook Lee ) 대한원격탐사학회 2020 大韓遠隔探査學會誌 Vol.36 No.6

On April 4, 2019, a forest fire started in Goseong County and lasted for three days, burning the neighboring areas of Sokcho. The strong winds moved the blaze from one region to another region and declared the worst wildfire in South Korea in years. More than 1,880 facilities, including 400 homes, were burnt down. The fire burned a total area of 529 hectares (1,307 acres), which involved 13,000 rescuers and 16,500 military troops to control the fire occurrence. Thousands of people were evacuated, and two people are dead. This study generated post-wildfire maps to provide necessary data for evacuation and mitigation planning to respond to this destructive wildfire, also prevent further damage and restore the area affected by the wildfire. This study used KOMPSAT-3A and Sentinel-2 imagery to map the post-wildfire condition. The SVM showed higher accuracy (overall accuracy 95.29%) compared with ANN (overall accuracy of 94.61%) for the KOMPSAT-3A. Moreover, for Sentinel-2, the SVM attained a higher accuracy (overall accuracy of 91.52%) than the ANN algorithm (overall accuracy 90.11%). In total, four post-wildfire burned area maps were generated; these results can be used to assess the area affected by the Sokcho wildfire and wildfire mitigation planning in the future.

코로나19 팬데믹 기간의 서울의 사회적 거리두기 단계 변화와 The Suomi National Polar-Orbiting Partnership (S-NPP) 위성 영상을 이용한 Nighttime Light (NTL) 간의 상관관계

( Arip Syaripudin Nur ),이슬기 ( Seulki Lee ),( Suci Ramayanti ),한주 ( Ju Han ) 대한원격탐사학회 2021 大韓遠隔探査學會誌 Vol.37 No.6

한국은 코로나19로 인한 감염전파를 줄이기 위해 4단계의 사회적 거리두기 기준을 설정하고 확진자 발생 비율을 기준으로 단계를 전환하여 시행하고 있다. 이러한 사회적 거리두기는 사람들의 이동 및 모임 등 사회적 접촉을 제한함으로써 시민들의 활동량에 변화를 가져왔다. 이를 직관적으로 확인할 수 있는 데이터 중 하나가 Night Time Light (NTL)이다. NTL은 인공위성에 포착된 불빛을 활용해 측정한 국가경제규모를 측정할 수 있는 변수로, 야간동안 사람의 사회 활동을 파악하는데 활용할 수 있다. NTL 자료는 수오미 위성(Suomi National Polar-orbiting Partnership, S-NPP)에 탑재된 센서인 Visible Infrared Imaging Radiometer Suite (VIIRS)에 포함된 Day-Night Band (DNB)를 통해 얻을 수 있다. 본 연구는 2019년 1월 5일부터 2021년 10월 26일까지 1023개의 Suomi 자료를 수집하고, 서울의 NTL 변화를 시계열로 생성하여 사회적 거리두기 단계와의 상관관계를 분석하였다. 그 결과 사회적 거리두기의 단계가 높아질수록 NTL의 공간적, 시간적 변화가 모두 감소된 것으로 나타났다. 이는 더 높은 단계의 사회적 거리두기 정책이 실행됨에 따라 야간 시간대의 상업 활동 및 모임 인원 제한 등과 같은 사회적 활동의 제한이 실제로 서울의 NTL 감소에 영향을 준 것으로 해석할 수 있다. 본 연구는 향후 코로나19 관련 정부의 정책을 평가하고 개선하기 위한 참고자료로 활용할 수 있을 것이다. In order to reduce the spread of infection due to COVID-19, South Korea has established a four-step social distancing standard and implemented it by changing the steps based on the rate of confirmed cases. The implementation of social distancing brought about a change in the amount of activity of citizens by limiting social contact such as movement and gathering of people. One of the data that can intuitively confirm this is Night Time Light (NTL). NTL is a variable that can measure the size of the national economy measured using lights captured by satellites, and can be used to understand people’s social activities during the night. The NTL visible data is obtained via the Visible Infrared Imaging Radiometer Suite (VIIRS) Day-Night Band (DNB) onboard the Suomi National Polar-orbiting Partnership (S-NPP) satellite. 1023 of Suomi data from 1 January 2019 until 26 October 2021 were collected to generate time series of NTL radiance change over Seoul to analyze the correlation with social distancing policy. The results show that implementing the level of social distancing generally decreased the NTL radiance both in spatial disparities and temporal patterns. The higher level of policy, limiting human activities combined with the low number of people who have been vaccinated and the closure of various facilities. Because of social distancing, the differences in human activities affected the nighttime light during the COVID-19 pandemic, especially in Seoul, South Korea. Therefore, this study can be used as a reference for the government in evaluating and improving policies related to efforts reducing the transmission of COVID-19.

Damage Proxy Map (DPM) of the 2016 Gyeongju and 2017 Pohang Earthquakes Using Sentinel-1 Imagery

( Arip Syaripudin Nur ),( Chang-wook Lee ) 대한원격탐사학회 2021 大韓遠隔探査學會誌 Vol.37 No.1

The ML 5.8 earthquake shocked Gyeongju, Korea, at 11:32:55 UTC on September 12, 2016. One year later, on the afternoon of November 15, 2017, the ML 5.4 earthquake occurred in Pohang, South Korea. The earthquakes injured many residents, damaged buildings, and affected the economy of Gyeongju and Pohang. The damage proxy maps (DPMs) were generated from Sentinel-1 synthetic aperture radar (SAR) imagery by comparing pre- and co-events interferometric coherences to identify anomalous changes that indicate damaged by the earthquakes. DPMs manage to detect coherence loss in residential and commercial areas in both Gyeongju and Pohang earthquakes. We found that our results show a good correlation with the Korea Meteorological Administration (KMA) report with Modified Mercalli Intensity (MMI) scale values of more than VII (seven). The color scale of Sentinel-1 DPMs indicates an increasingly significant change in the area covered by the pixel, delineating collapsed walls and roofs from the official report. The resulting maps can be used to assess the distribution of seismic damage after the Gyeongju and Pohang earthquakes and can also be used as inventory data of damaged buildings to map seismic vulnerability using machine learning in Gyeongju or Pohang.

Damage Proxy Map over Collapsed Structure in Ansan Using COSMO-SkyMed Data

Nur, Arip Syaripudin,Fadhillah, Muhammad Fulki,Jung, Young-Hoon,Nam, Boo Hyun,Kim, Yong Je,Park, Yu-Chul,Lee, Chang-Wook The Korean Society of Engineering Geology 2022 지질공학 Vol.32 No.3

An area under construction for a living facility collapsed around 12:48 KST on 13 January 2021 in Sa-dong, Ansan-si, Gyeonggi-do. There were no casualties due to the rapid evacuation measure, but part of the temporary retaining facility collapsed, and several cracks occurred in the adjacent road on the south side. This study used the potential of synthetic aperture radar (SAR) satellite for surface property changes that lies in backscattering characteristic to map the collapsed structure. The interferometric SAR technique can make a direct measurement of the decorrelation among different acquisition dates by integrating both amplitude and phase information. The damage proxy map (DPM) technique has been employed using four high-resolution Constellation of Small Satellites for Mediterranean basin Observation (COSMO-SkyMed) data spanning from 2020 to 2021 during ascending observation to analyze the collapse of the construction. DPM relies on the difference of pre- and co-event interferometric coherences to depict anomalous changes that indicate collapsed structure in the study area. The DPMs were displayed in a color scale that indicates an increasingly more significant ground surface change in the area covered by the pixels, depicting the collapsed structure. Therefore, the DPM technique with SAR data can be used for damage assessment with accurate and comprehensive detection after an event. In addition, we classify the amplitude information using support vector machine (SVM) and maximum likelihood classification algorithms. An investigation committee was formed to determine the cause of the collapse of the retaining wall and to suggest technical and institutional measures and alternatives to prevent similar incidents from reoccurring. The report from the committee revealed that the incident was caused by a combination of factors that were not carried out properly.

Mapping of Post-Wildfire Burned Area Using KOMPSAT-3A and Sentinel-2 Imagery: The Case of Sokcho Wildfire, Korea

Nur, Arip Syaripudin,Park, Sungjae,Lee, Kwang-Jae,Moon, Jiyoon,Lee, Chang-Wook The Korean Society of Remote Sensing 2020 大韓遠隔探査學會誌 Vol.36 No.6

On April 4, 2019, a forest fire started in Goseong County and lasted for three days, burning the neighboring areas of Sokcho. The strong winds moved the blaze from one region to another region and declared the worst wildfire in South Korea in years. More than 1,880 facilities, including 400 homes, were burnt down. The fire burned a total area of 529 hectares (1,307 acres), which involved 13,000 rescuers and 16,500 military troops to control the fire occurrence. Thousands of people were evacuated, and two people are dead. This study generated post-wildfire maps to provide necessary data for evacuation and mitigation planning to respond to this destructive wildfire, also prevent further damage and restore the area affected by the wildfire. This study used KOMPSAT-3A and Sentinel-2 imagery to map the post-wildfire condition. The SVM showed higher accuracy (overall accuracy 95.29%) compared with ANN (overall accuracy of 94.61%) for the KOMPSAT-3A. Moreover, for Sentinel-2, the SVM attained a higher accuracy (overall accuracy of 91.52%) than the ANN algorithm (overall accuracy 90.11%). In total, four post-wildfire burned area maps were generated; these results can be used to assess the area affected by the Sokcho wildfire and wildfire mitigation planning in the future.

The dependence of microdroplet size on the parameters governing the dewetting process on circular micropillar arrays

Bambang Arip Dwiyantoro,Shiu-Wu Chau 대한기계학회 2013 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.27 No.7

We theoretically investigated the correlation among the size of microdroplet, the geometrical parameters of circular micropillars, and the parameters governing the dewetting process. Dimensional analysis is used to determine independent dimensionless groups to characterize the diameter of microdroplet, i.e., the Ohnesorge number (Oh), the capillary number (Ca), the dimensionless liquid thickness (H),and the contact angle (θ ). The simulation results show that the size of microdroplet on the top surface of micropillar depends on the parameters in the dewetting process. The dimensionless droplet diameter (d) grows with the increase of H, where d becomes saturated provided H reaches a critical value of 2.5. The decrease of Ohnesorge number results in microdroplets with large diameter. For small contact angle, the top surface of micropillar is mostly wetted, which leads to large microdroplets. When the value of the capillary number increases,the viscous force on the top surface of micropillar magnifies, and leads to the growth of droplet diameter until the value of Ca reaches a critical value. For H < 2.5, the magnitude of the critical capillary number (Cac) depends on Oh, θ, and H*, while Cac is a constant for H ≥ 2.5. The dimensionless droplet diameter (d) can be determined by the product of functions of Oh, θ, H*, and Ca*.

Knowledge and Risk Perceptions of Occupational Infections Among Health-care Workers in Malaysia

Ganesh Chidambar Subramanian,Masita Arip,Saraswathy Subramaniam 한국산업안전보건공단 산업안전보건연구원 2017 Safety and health at work Vol.8 No.3

Health-care workers are at risk of exposure to occupational infections with subsequent risk of contracting diseases, disability, and even death. A systematic collection of occupational disease data is useful for monitoring current trends in work situations and disease exposures; however, these data are usually limited due to under-reporting. The objective of this study was to review literature related to knowledge, risk perceptions, and practices regarding occupational exposures to infectious diseases in Malaysian health-care settings, in particular regarding blood-borne infections, universal precautions, use of personal protective equipment, and clinical waste management. The data are useful for determining improvements in knowledge and risk perceptions among health-care workers with developments of health policies and essential interventions for prevention and control of occupational diseases.

Knowledge and Risk Perceptions of Occupational Infections Among Health-care Workers in Malaysia

Subramanian, Ganesh Chidambar,Arip, Masita,Subramaniam, T.S. Saraswathy Occupational Safety and Health Research Institute 2017 Safety and health at work Vol.8 No.3

Health-care workers are at risk of exposure to occupational infections with subsequent risk of contracting diseases, disability, and even death. A systematic collection of occupational disease data is useful for monitoring current trends in work situations and disease exposures; however, these data are usually limited due to under-reporting. The objective of this study was to review literature related to knowledge, risk perceptions, and practices regarding occupational exposures to infectious diseases in Malaysian health-care settings, in particular regarding blood-borne infections, universal precautions, use of personal protective equipment, and clinical waste management. The data are useful for determining improvements in knowledge and risk perceptions among health-care workers with developments of health policies and essential interventions for prevention and control of occupational diseases.

Eco-environmental assessment in the Sembilan Archipelago, Indonesia: its relation to the abundance of humphead wrasse and coral reef fish composition

Amran Ronny Syam,Mujiyanto,Arip Rahman,Imam Taukhid,Masayu Rahmia Anwar Putri,Andri Warsa,Lismining Pujiyani Astuti,Sri Endah Purnamaningtyas,Didik Wahju Hendro Tjahjo,Yosmaniar,Umi Chodrijah,Dini Pur The Korean Society of Fisheries and Aquatic Scienc 2023 Fisheries and Aquatic Sciences Vol.26 No.12

The Sembilan Archipelago is famous for its great biodiversity, in which the humphead wrasse (Cheilinus undulatus) (locally named Napoleon fish) is the primary commodity (economically important), and currently, the environmental degradation occurs due to anthropogenic activities. This study aimed to examine the eco-environmental parameters and assess their influence on the abundance of humphead wrasse and other coral reef fish compositions in the Sembilan Archipelago. Direct field monitoring was performed using a visual census throughout an approximately one km transect. Coral cover data collection and assessment were also carried out. A coastal water quality index (CWQI) was used to assess the water quality status. Furthermore, statistical-based analyses [hierarchical clustering, Pearson's correlation, principal component analysis (PCA), and canonical correspondence analysis (CCA)] were performed to examine the correlation between eco-environmental parameters. The Napoleon fish was only found at stations 1 and 2, with a density of about 3.8 Ind/ha, aligning with the dominant composition of the family Serranidae (covering more than 15% of the total community) and coinciding with the higher coral mortality and lower reef fish abundance. The coral reef conditions were generally ideal for supporting marine life, with a living coral percentage of about > 50% in all stations. Based on CWQI, the study area is categorized as good and excellent water quality. Of the 60 parameter values examined, the phytoplankton abundance, Napoleon fish, and temperature are highly correlated, with a correlation coefficient value greater than 0.7, and statistically significant (F < 0.05). Although the adaptation of reef fish to water quality parameters varies greatly, the most influential parameters in shaping their composition in the study area are living corals, nitrites, ammonia, larval abundance, and temperature.