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Sentinel-2 Cloud Mask Classification Using Deep Learning Method
Ekram Mokhtar Rewehel,Jianqiang Li,Hatem M. Keshk 한국항공우주학회 2022 International Journal of Aeronautical and Space Sc Vol.23 No.3
The Copernicus Sentinel-2 mission operated by the European Space Agency (ESA) provides comprehensive and continuous multi-spectral observations of all Earth’s land surface since mid-2015. Clouds and cloud shadows significantly decrease the usability of optical satellite data especially in agricultural applications; therefore, an accurate and reliable cloud mask is mandatory for effective Earth Observation (EO) optical data exploitation. During the last years, image segmentation techniques have developed rapidly with the exploitation of neural networks capabilities. In this perspective, the KappaMask processor using U-Net architecture was developed with the ability to generate a classification mask over northern latitudes into the following classes: clear, cloud shadow, semi-transparent cloud (thin clouds), and cloud, invalid. For training, a Sentinel-2 dataset covering Northern European terrestrial area was labeled. KappaMask provides a 10 m classification mask for Sentinel-2 Level- 2A (L2A) and Level-1C (L1C) products. The total dice coefficient on the test dataset, which was not seen by the model at any stage, was 80% for KappaMask L2A and 76% for KappaMask L1C for 27 clear, cloud shadow, semi-transparent, cloud classes. Comparison with rule-based cloud mask 28 methods was then performed on the same test dataset, where Sen2Cor reached 59% dice coefficient 29 for clear, cloud shadow, semi-transparent, cloud classes, Fmask 61% for clear, cloud shadow, cloud 30 classes, and Maja 51% for clear and cloud classes. The closest machine learning open-source cloud classification mask, S2cloudless, has 63% dice coefficient providing only cloud and clear classes, while KappaMask L2A with a more complex classification schema outperformed S2cloudless by 17%.
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Basma Ekram,Bothaina M. Abd El-Hady,Abeer M. El-Kady,Sherif M. Amr,Hala Gabr,Ahmed I. Waly,Osiris W. Guirguis 한국섬유공학회 2019 Fibers and polymers Vol.20 No.4
Electrospun polycaprolactone is widely used in the medical field. Formic acid/acetic acid (FA/AA) solvent systemis one of the safest solvents used for the production of nano-range polycaprolactone (PCL) fibers, although it has a very lowstability. In the present study, the stability of PCL in FA/AA system was enhanced by sodium hydrogen carbonate (NaHCO3)addition with three different concentrations (1, 5 and 10 wt%). The resultant electrospun fiber properties were compared tothat treated by alkaline hydrolysis. The viscosity and conductivity of PCL solutions were measured before the electrospinningprocess. Moreover, the obtained electrospun PCL mats were characterized by SEM, FT-IR, XRD, contact anglemeasurements, degradability, swelling, and mechanical properties, as well as their ability to enhance the proliferation andadhesion of mesenchymal stem cells (MSCs). It was found that NaHCO3 not only enhanced the fiber properties, such ashydrophilicity, degradability and mechanical properties but also had a significant effect on the stability of polycaprolactone inFA/AA solvent system, as well as an enhanced MSCs proliferation and adhesion. Although hydrolyzed PCL showed high cellviability and adhesion, it showed much lower mechanical properties (0.7 MPa) compared to neat PCL (1.3 MPa) and PCLNaHCO3(5.1 MPa). In conclusion, the addition of NaHCO3 to PCL solution prior to the electrospinning process represents anovel and an effective approach to improve the physicochemical properties and biological behavior of electrospun PCL matsfor tissue engineering application.
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Hridoy Al-Ekram Elahee,Tipo Imrul Hasan,Sami Md. Shamsudduha,Babu Md. Ripon,Ahmed Md. Sayem,Rahman Syed Masiur,Tusher Shekh Md. Shajid Hasan,Rashid Kazi Jihadur,Naim Mohammad 대한공간정보학회 2022 Spatial Information Research Vol.30 No.1
The ongoing COVID-19 pandemic has caused unprecedented public health concern in Bangladesh. This study investigated the role of Non-Pharmaceutical Interventions on COVID-19 transmission and post-lockdown scenarios of 64 administrative districts and the country as a whole based on the spatiotemporal variations of effective reproduction number (Rt) of COVID-19 incidences. The daily confirmed COVID-19 data of Bangladesh and its administrative districts from March 8, 2020, to March 10, 2021, were used to estimate Rt. This study finds that the maximum value of Rt reached 4.15 (3.43, 4.97, 95% CI) in late March 2020, which remained above 1 afterwards in most of the districts. Containment measures are moderately effective in reducing transmission by 24.03%. The Rt was established below 1 from early December 2020 for overall Bangladesh and a gradual increase of Rt above 1 has been seen from early February 2021. The basic reproduction number (R0) in Bangladesh probably varied around 2.02 (1.33–3.28, 95% CI). This study finds a significant positive correlation (r = 0.75) between population density and COVID-19 incidence and explaining 56% variation in Bangladesh. The findings of this study are expected to support the policymakers to adopt appropriate measures for curbing the COVID-19 transmission effectively.
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Hridoy Al-Ekram Elahee,Tipo Imrul Hasan,Sami Md. Shamsudduha,Babu Md. Ripon,Ahmed Md. Sayem,Rahman Syed Masiur,Tusher Shekh Md. Shajid Hasan,Rashid Kazi Jihadur,Naim Mohammad 대한공간정보학회 2022 Spatial Information Research Vol.30 No.2
The ongoing COVID-19 pandemic has caused unprecedented public health concern in Bangladesh. This study investigated the role of Non-Pharmaceutical Interventions on COVID-19 transmission and post-lockdown scenarios of 64 administrative districts and the country as a whole based on the spatiotemporal variations of effective reproduction number (Rt) of COVID-19 incidences. The daily confirmed COVID-19 data of Bangladesh and its administrative districts from March 8, 2020, to March 10, 2021, were used to estimate Rt. This study finds that the maximum value of Rt reached 4.15 (3.43, 4.97, 95% CI) in late March 2020, which remained above 1 afterwards in most of the districts. Containment measures are moderately effective in reducing transmission by 24.03%. The Rt was established below 1 from early December 2020 for overall Bangladesh and a gradual increase of Rt above 1 has been seen from early February 2021. The basic reproduction number (R0) in Bangladesh probably varied around 2.02 (1.33–3.28, 95% CI). This study finds a significant positive correlation (r = 0.75) between population density and COVID-19 incidence and explaining 56% variation in Bangladesh. The findings of this study are expected to support the policymakers to adopt appropriate measures for curbing the COVID-19 transmission effectively.
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Tier-Aware Resource Allocation in OFDMA Macrocell-Small Cell Networks
Abdelnasser, Amr,Hossain, Ekram,Dong In Kim Institute of Electrical and Electronics Engineers 2015 IEEE Transactions on Communications Vol. No.
<P>We present a joint sub-channel and power allocation framework for downlink transmission in an orthogonal frequency-division multiple access (OFDMA)-based cellular network composed of a macrocell overlaid by small cells. In this framework, the resource allocation (RA) problems for both the macrocell and small cells are formulated as optimization problems. For the macrocell, we formulate an RA problem that is aware of the existence of the small cell tier. In this problem, the macrocell performs RA to satisfy the data rate requirements of macro user equipments (MUEs) while maximizing the tolerable interference from the small cell tier on its allocated sub-channels. Although the RA problem for the macrocell is shown to be a mixed integer nonlinear problem (MINLP), we prove that the macrocell can solve another alternate optimization problem that will yield the optimal solution with reduced complexity. For the small cells, following the same idea of tier-awareness, we formulate an optimization problem that accounts for both RA and admission control (AC) and aims at maximizing the number of admitted users while simultaneously minimizing the consumed bandwidth. Similar to the macrocell optimization problem, the small cell problem is shown to be an MINLP. We obtain a sub-optimal solution to the MINLP problem relying on convex relaxation. In addition, we employ the dual decomposition technique to have a distributed solution for the small cell tier. Numerical results confirm the performance gains of our proposed RA formulation for the macrocell over the traditional resource allocation based on minimizing the transmission power. Besides, it is shown that the formulation based on convex relaxation yields a similar behavior to the MINLP formulation. Also, the distributed solution converges to the same solution obtained by solving the corresponding convex optimization problem in a centralized fashion.</P>
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Ali, Md Shipon,Hossain, Ekram,Kim, Dong In Institute of Electrical and Electronics Engineers 2018 IEEE wireless communications Vol.25 No.2
<P>We outline a general framework to use CoMP transmission technology in downlink multi-cell NOMA systems considering distributed power allocation at each cell. In this framework, CoMP transmission is used for users experiencing strong received signals from multiple cells, while each cell adopts NOMA for resource allocation to its active users. After a brief review of the working principles of different CoMP schemes, we investigate their applicability and necessary conditions for their use in a downlink multi-cell NOMA system. After that, we discuss various network scenarios with different spatial distributions of users and present the formula for achievable rate of users under each of the CoMP-NOMA scenarios. To this end, a numerical performance evaluation is carried out for the proposed CoMP-NOMA systems, and the results are compared with those for conventional orthogonal multiple access based CoMP systems. The numerical results quantify the spectral efficiency gain of the proposed CoMP-NOMA models over CoMP-OMA. Finally, we conclude this article by identifying the major challenges in implementing CoMP-NOMA in future cellular systems.</P>
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Spatial modeling of COVID-19 transmission in Bangladesh
Sarkar Showmitra Kumar,Ekram Khondaker Mohammed Mohiuddin,Das Palash Chandra 대한공간정보학회 2021 Spatial Information Research Vol.29 No.5
The purpose of the research was to investigate and identify the demographic risk factors behind the transmission of COVID-19 in Bangladesh based on spatial and statistical modeling. Number of COVID-19 confirmed cases per thousand population as the dependent variable and nine demographic explanatory variables were considered. Different spatial (i.e., Spatial Lag and Spatial Error Model) and non-spatial (Classic Model) regression techniques were employed in the research to detect the geographical relevance of potential risk factors affecting the transmission of COVID-19. Results indicate that population density was crucial for explaining the pattern of COVID-19 transmission in Bangladesh. Spatial Auto-correlation suggests that the spatial pattern of population density were significantly clustered at a confidence interval of 95%. Again, the regression analysis also shows that population density is an influential determinant for the propagation of COVID-19 in Bangladesh, with densely populated districts like Dhaka and Narayanganj also being among the worst affected areas. The findings of this research will help the government agencies and communities for effective and well-informed decision making in order to develop and implement strategies to contain the further spread of COVID-19 in Bangladesh.
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Downlink Power Allocation for CoMP-NOMA in Multi-Cell Networks
Ali, Md Shipon,Hossain, Ekram,Al-Dweik, Arafat,Kim, Dong In Institute of Electrical and Electronics Engineers 2018 IEEE Transactions on Communications Vol. No.
<P>This paper considers the problem of dynamic power allocation in the downlink of multi-cell networks, where each cell utilizes non-orthogonal multiple access (NOMA)-based resource allocation. Also, coordinated multi-point (CoMP) transmission is utilized among multiple cells to serve users experiencing severe inter-cell interference (ICI). Under this CoMP- NOMA framework, CoMP transmission is applied to a user experiencing less distinctive channel gain with multiple base stations (BSs)/cells (i.e., severe ICI-prone user) and non-CoMP transmission (i.e., transmission without any coordination among multiple BSs) is applied to a user experiencing dominating channel gain with only one BS/cell, while NOMA is utilized at each BS to schedule CoMP and non-CoMP users over the same transmission resources, i.e., time, spectrum and space. After discussing various CoMP- NOMA models for downlink power allocation in multi-cell networks, we focus on a joint transmission CoMP- NOMA (JT-CoMP-NOMA) model. For the JT-CoMP-NOMA model, an optimal joint power allocation problem is formulated and the solution is derived for each CoMP- set consisting of multiple cooperating BSs (i.e., CoMP BSs). To avoid the huge computational complexity of the joint power optimization approach, we propose a distributed power optimization approach at each cooperating BS whose optimal solution is independent of the solution of other coordinating BSs. The distributed solution for the joint power optimization problem is validated and numerical performance evaluation is carried out for the proposed CoMP- NOMA models including JT-CoMP-NOMA and coordinated scheduling CoMP- NOMA (CS-CoMP-NOMA). The obtained results reveal significant gains in spectral and energy efficiency in comparison with conventional CoMP- orthogonal multiple access (CoMP-OMA) systems.</P>
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Perturbation analysis for spectrum sharing in cognitive radio networks
Keshavarz, Hengameh,Hossain, Ekram,Noghanian, Sima,Dong In Kim IEEE 2010 IEEE TRANSACTIONS ON WIRELESS COMMUNICATIONS Vol.9 No.5
<P>A primary ad-hoc network working in parallel with a secondary ad-hoc network is considered. The main challenge in operating cognitive ad-hoc networks is the lack of a centralized controller performing resource allocation for different users in the network. In this paper, a distributed power allocation scheme is considered for secondary users and its performance is analyzed when time average channel gains are substituted for instantaneous channel gains. In this way, it is not necessary to exchange instantaneous channel information; however, users' allocated power will be perturbed. It is of interest to analyze mathematically this perturbation and to show how it affects the network performance. In particular, an upper bound on perturbation of each user's allocated power, rate, and interference caused to a primary receivers by the secondary users is obtained. Then, it is shown that how this perturbation affects the transmission rate and the probability of interference constraint violation by the secondary users.</P>
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