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Topic Review
BDS-3 Integrity Concept
Compared to the BeiDou regional navigation satellite system (BDS-2), the BeiDou global navigation satellite system (BDS-3) carried out a brand new integrity concept design and construction work, which defines and achieves the integrity functions for major civil open services (OS) signals such as B1C, B2a, and B1I. The integrity definition and calculation method of BDS-3 are introduced. The fault tree model for satellite signal-in-space (SIS) is used, to decompose and obtain the integrity risk bottom events. In response to the weakness in the space and ground segments of the system, a variety of integrity monitoring measures have been taken. On this basis, the design values for the new B1C/B2a signal and the original B1I signal are proposed, which are 0.9 × 10−5 and 0.8 × 10−5, respectively. The hybrid alarming mechanism of BDS-3, which has both the ground alarming approach and the satellite alarming approach, is explained. At last, an integrity risk analysis and verification work were carried out using the operating data of the system in 2019. The results show that the actual operation of the system is consistent with the conceptual design, which satisfies the integrity performance promised by BDS-3 in the ICAO SAPRs.
  • 819
  • 24 Nov 2021
Topic Review
Global Marine Dissolved Organic Matter
Marine dissolved organic matter (DOM) holds ~660 billion metric tons of carbon, making it one of Earth’s major carbon reservoirs that is exchangeable with the atmosphere on annual to millennial time scales. The global ocean scale dynamics of the pool have become better illuminated over the past few decades. 
  • 818
  • 15 Sep 2021
Topic Review
Chemical Analysis of Organochlorine Pesticide in Agricultural Soils
Soil constitutes the central environmental compartment that, primarily due to anthropogenic activities, is the recipient of several contaminants. Among these are organochlorine pesticides (OCPs), which are of major concern, even though they were banned decades ago due to their persistence and the health effects they can elicit. A plethora of methods have been developed and applied for OCP analysis in environmental matrices (i.e., soil and sediment). The entire chemical analysis involves several crucial stages such as sample preparation and analyte chromatographic separation, including detection, quantification, and data analysis. Among them, the sample preparation step is considered as the most critical point to be made prior to instrumental analysis. In particular, the development of methodologies for determining pesticides in soil is a challenging task. As a result of the complexity and the physicochemical characteristics of such types of samples, two main factors should be considered: (a) the extremely low concentration of banned OCPs in soil samples. This is the reason why extremely sensitive analytical methods (including, in many cases, enrichment techniques) are required for the detection and quantification of these analytes at such levels, and (b) the strong binding of OCPs to soil.
  • 818
  • 31 May 2022
Topic Review
Central Highlands, Vietnam
Tây Nguyên, translated as Western Highlands and sometimes also called Central Highlands, is one of the regions of Vietnam. It contains the provinces of Đắk Lắk, Đắk Nông, Gia Lai, Kon Tum, Lâm Đồng. This region is sometimes referred to as Cao nguyên Trung bộ (literally "Midland Highlands"), and was referred to during the Republic of Vietnam as Cao nguyên Trung phần (literally "Central Highlands").
  • 818
  • 22 Nov 2022
Topic Review
Recent Advances in Membrane Distillation Module Configurations
Membrane Distillation (MD) is a membrane-based, temperature-driven water reclamation process. While research emphasis has been largely on membrane design, upscaling of MD has prompted advancements in energy-efficient module design and configurations. Apart from the four conventional configurations, researchers have come up with novel MD membrane module designs and configurations to improve thermal efficiency. While membrane design has been the focus of many studies, development of appropriate system configurations for optimal energy efficiency for each application has received considerable attention, and is a critical aspect in advancing MD configurations. This review assesses advancements in modified and novel MD configurations design with emphasis on the effects of upscaling and pilot scale studies. Improved MD configurations discussed in this review are the material gap MD, conductive gap MD, permeate gap MD, vacuum-enhanced AGMD/DCMD, submerged MD, flashed-feed MD, dead-end MD, and vacuum-enhanced multi-effect MD. All of these modified MD configurations are designed either to reduce the heat loss by mitigating the temperature polarization or to improve the mass transfer and permeate flux. Vacuum-enhanced MD processes and MD process with non-contact feed solution show promise at the lab-scale and must be further investigated. Hollow fiber membrane-based pilot scale modules have not yet been sufficiently explored. In addition, comparison of various configurations is prevented by a lack of standardized testing conditions. We also reflect on recent pilot scale studies, ongoing hurdles in commercialization, niche applications and energy efficiency of the MD process.
  • 817
  • 28 Jan 2022
Topic Review
E-Waste in Africa
Waste electronic and electrical equipment (e-waste) consists of used and discarded electrical and electronic items ranging from refrigerators to cell phones and printed circuit boards.
  • 816
  • 05 Sep 2021
Topic Review
A Focus on Active Chemicals in Sub-Saharan Africa
Active chemicals are among the contaminants of emerging concern that are rarely covered in regulatory documents in sub-Saharan Africa. 
  • 815
  • 31 Dec 2021
Topic Review
Greenhouse Gas Emissions from Reservoirs
Reservoirs are manmade lakes created by building dams on rivers for various purposes: flood control, electricity generation, irrigation, water supply, aquaculture, environmental services, recreational activities, navigation etc. In freshwater ecosystems, several mechanisms are involved in the natural carbon cycle. They receive carbon from terrestrial ecosystems through drainage, capture the carbon through primary production, bury the carbon in sediments, emit GHG through biomass degradation and respiration, and transport the carbon downstream to the seas or oceans. GHG emissions can be increased by human activities around the ecosystem through sewage and agricultural pollution.
  • 814
  • 03 Nov 2021
Topic Review
Environmental Nanotechnologies in Wastewater Treatment
Nanotechnologies (NTs) are nowadays well established on both private households and commercial markets. NTs are fully accepted in several sectors such as medicine and pharmacy, or in industry such as chemistry, electricity, food production, military, and other commercial branches due to their unique properties. With regard to the growing demands on environmental resources caused through still growing worldwide population, application of NTs is an extremely important new branch in the environmental sector delivering several advantages. The entry provides a comprehensive overview on current developments in environmental remediation, wastewater treatment, drinking water treatment and agriculture. More in detail, in the section environmental remediation, the application on NTs towards enhanced reductive dechlorination,  removal of heavy metals and remediation of oil spills were reviewed. Developments towards adsorption of heavy metals and persistent substances, advanced photocatalytic degradation of common wastewater pollutants, and improvements in membrane filtration processes were predominantely highlighted. On the one hand, nanotechnologies (NTs) refer to nanostructure techniques, such as nanolithography and nanomanipulation, but also to nanomaterials (NMs) on the other hand. NMs refer commonly to nanoparticles (NPs), nanotubes, nanofilms, and others. The engineered era of NTs combines different application sectors, including biological, biotechnological, chemical, medical, pharmaceutical, food and agriculture, environmental, electronic, material engineering, and other industrial processing technologies, and other branches.
  • 813
  • 01 Apr 2022
Topic Review
Carbon Footprint
A carbon footprint is “a measure of the exclusive total amount of carbon dioxide emissions that is directly and indirectly caused by the activities of an individual or is accumulated over the life stages of a product”.
  • 813
  • 11 Jan 2022
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