More and more satellites are populating the sky nowadays in the Low Earth orbits (LEO). Most of the targeted applications are related to broadband and narrowband communications, Earth observation, synthetic aperture radar, and internet-of-Things (IoT) connectivity. In addition to these targeted applications, there is yet-to-be-harnessed potential for LEO and positioning, navigation, and timing (PNT) systems, or what is nowadays referred to as LEO-PNT. No commercial LEO-PNT solutions currently exist and there is no unified research on LEO-PNT concepts. Our survey aims to fill the gaps in knowledge regarding what a LEO-PNT system entails, its technical design steps and challenges, what physical layer parameters are viable solutions, what tools can be used for a LEO-PNT design (e.g., optimisation steps, hardware and software simulators, etc.), the existing models of wireless channels for satellite-toground and ground-to-satellite propagation, and the commercial prospects of a future LEO-PNT system. A comprehensive and multidisciplinary survey is provided by a team of authors with complementary expertise in wireless communications, signal processing, navigation and tracking, physics, machine learning, Earth observation, remote sensing, digital economy, and business models.
Aquaculture medicines, drugs, and chemicals or simply AMDC, are critical in protecting aquaculture farmers from disease in farmed animals and economic losses. The AMDC is now a well-established industry in Bangladesh, and each year, new products that benefit farmers are launched. This review examined published research information on AMDC over the last decade (2011-2020) and discovered that 41 research publications from various parts of Bangladesh were published, citing the names of 1484 AMDC products. It was discovered that 19 generic antibiotics are well established and widely used in different regions' aquaculture, including shrimp aquaculture. Although some researchers expressed concern about the use of antibiotics in aquaculture, they believe that with proper withdrawal periods and the application of small doses, farmers may avoid economic losses. However, the pathway of the antibiotic introduction in aquaculture setup in Bangladesh was unknown to the researchers, through this review, we revealed the pathway of antibiotics introduction in aquaculture. Additionally, this review revealed that various AMDC products, including oxygen suppliers, growth promoter supplements, disinfectants, raw chemicals, probiotics, pond preparation and management AMDC, and toxic gas removal AMDC, are readily available in various markets throughout Bangladesh. The observation implied that research on the efficacy of various AMDC products in Bangladesh's agro-ecological zones could be conducted, which would aid researchers in deciphering the true nature of AMDC in sub-tropical climates. Asian J. Med. Biol. Res. 2021, 7 (2), 90-106
The coastal embankment system has been gradually built during the last 40 years. The embankments were originally designed to increase agricultural production by preventing salt water intrusion not to protect against cyclonic storms. The alignment of the embankments did not consider the changing conditions in bathymetry of the sea and thalweg migration of the rivers and therefore many embankments are located under tidal water level and have severe toe and slope erosion problems during the monsoon season. The crest level and embankment cross sections have not optimized the protection of hinterland and the embankment itself and therefore the embankments typically only provide protection for the cyclones with 5-12 year return periods and the designed crest level of the sea facing coastal polder equal to the sum of normal maximum recorded water stage plus 1.50m. In this study to estimate the design crest level and side slope for sea facing embankment have been established based on maximum storm surge level, wave run-up for cyclonic wave, freeboard allowing 5 l/m/s overtopping ,potential climate change impact and land subsidence. Statistical analysis of surge level and wave run-up is carried out using Extreme Value Analysis (EVA) in MIKE Zero.
Today, a substantial portion of global trade is carried by sea. Consequently, the reliance on Global Navigation Satellite System (GNSS)-based navigation in the oceans and inland waterways has been rapidly growing. GNSS is vulnerable to various radio frequency interference. The objective of this research is to propose a resilient Multi-Frequency, Multi-Constellation (MFMC) receiver in the context of maritime navigation to identify any GNSS signal jamming incident and switch to a jamming-free signal immediately. With that goal in mind, the authors implemented a jamming event detector that can identify the start, end, and total duration of the detected jamming event on any of the impacted GNSS signal(s). By utilizing a jamming event detector, the proposed resilient MFMC receiver indeed provides a seamless positioning solution in the event of single-frequency jamming on either the lower or upper L-band. In addition, this manuscript also contains positioning performance analysis of GPS-L5-only, Galileo-E5a-only, and Galileo-E5b-only signals and their multi-GNSS combinations in a maritime operational environment in the Gulf of Finland. The positioning performance of lower L-band GNSS signals in a maritime environment has not been thoroughly investigated as per the authors’ knowledge.
A broad variety of aquaculture-related medications, drugs, and chemicals (AMDC) are extensively used in the aquaculture industry in South-Eastern Bangladesh. Fish farmers are worried about the quality of their final product, and disease outbreaks must be stopped at all costs. Farmers are sometimes one ahead of the curve when it comes to producing healthy final products by including probiotics, vitamins, and minerals into their aquaculture setups to promote early and disease-free output. However, the current study was carried out in south eastern Bangladesh, specifically in the highly dense aquaculture regions of Chandpur, Cumilla, and Feni district (17 upazilas), from November 2016 to January 2018. Questions were asked through interviews and a Focus Group Discussion (FGD) was held to gather primary data. The major target groups were aquaculture farmers, AMDC shops, pharmaceutical company employees, and hatchery owners. In this three-county area, according to the findings from the thorough research, there are a total of 33 companies that advertise 330 generics brand products via their own distributional channels. Among the available AMDC products in the study area, growth promoters were mostly abundant products among all categories while other products such as predator removal products, insecticides and ectoparasiticides, water quality and pond management, plankton producer, plankton bloom cleaner, disinfectant and disease treatment, toxic gas reducer, pH controller, oxygen supply, stress reducer, growth promoter, probiotics and antibiotics were most selling products to the farmers. The present study revealed 19 generic of antibiotics were available and prescribed by the AMDC vendors or aquaculture disease consultants (ADC) around the regions. Additionally, the research also included the dosages of AMDC and the method of administration in the aquaculture pond, which will assist both the farmers and the ADC in selecting and suggesting the appropriate medications or treatments that may be beneficial to the farmers in the long run. Asian Australas. J. Biosci. Biotechnol. 2021, 6 (2), 103-127
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