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Efficiency of planted and unplanted vertical flow aerated filters in treatment of young landfill leachate
Full text linkABSTRACT: Young landfill leachate, produced by the passage of water through operating sites at a municipal landfill, is highly concentrated in organic matter, ammonia and metals, and is typically treated using intensive, conventional systems. Studies have demonstrated efficient treatment of low-strength old leachate, produced by capped sites at a landfill, by nature-based systems such as treatment wetlands. Few studies have investigated the use of similar systems to treat young leachate. The objectives of this study were to 1) determine if vertical flow planted and unplanted aerated filters could efficiently treat young leachate COD, BOD5, TSS, NH4 and p-cresol; 2) determine the suitability and effect of two plant species on treatment efficiency; 3) quantify the denitrification capacity achieved in pre-anoxic filters; and 4) determine full-scale design criteria (hydraulic and organic loading rates and space requirements) for 1500 m3/d of young leachate. Five 430 L water-saturated vertical flow pilot-scale filters with forced aeration and 10 to 20 mm granite gravel media were operated in parallel in a greenhouse for 42 weeks total during fall 2020 and spring through fall 2021. Each filter was fed with an average of 16.4 L m−2 d−1 of anaerobically pretreated young leachate spiked with 3340 μg/L of p-cresol for an organic loading rate of 3.5 g BOD5 m−3 d−1 to each filter. Two filters were planted with Salix miyabeana ‘SX67’, two were planted with Sporobolus michauxianus and one was left unplanted. Two planted filters (one with each plant species) had pre-anoxic filters for denitrification. Results indicated that planted and unplanted filters offered similar treatment, with average removal efficiencies of 74 % for COD, 98 % for BOD5, 96 % for TSS, 100 % for NH4 and 100 % for p-cresol. Young leachate treatment negatively impacted plant health and their chlorophyll fluorescence. Systems with pre-anoxic filters were able to achieve a higher total nitrogen removal efficiency of 70 % compared to 60 % on average for systems without pre-anoxic filters. The high removal efficiency achieved suggests that filter systems were operated below the treatment capacity of the microorganisms. Unplanted aerated filters are a promising technology for treatment of young landfill leachate and p-cresol
Enabling beam-scanning antenna technologies for terahertz wireless systems: a review
Full text linkABSTRACT: Due to the exponentially growing global mobile data of wireless communications evolving from 5 G to 6 G in recent years, research activities of leveraging terahertz (THz) waves to obtain larger channel capacities have shown an ever-increasing pace and reached an unprecedented height than before. Historically, the past few decades have already witnessed much progress in THz generation and detection technologies, which have been recognized for a long time as the bottleneck preventing the THz waves from being tamed by human beings. However, the importance of developing advanced components such as antennas, transmission lines, filters, power amplimers, etc., which constitute the basic building blocks of a THz wireless system, should not be overlooked for the sake of exploiting the THz spectra for future advanced wireless communications, sensing and imaging applications. While producing a scannable highly-directive antenna beam proves to be indispensable in the period of microwaves, the significance of such functionality is more critical in the THz era, considering that THz waves have more intractable challenges such as the severity of free-space propagation losses, the susceptibility to atmospheric environments, and the unavailability of efficient signal sources. This article is structured under this background, which is dedicated to reviewing several enabling beam-scanning antenna concepts, structures, and architectures that have been developed for THz wireless systems. Specifically, we divide these THz beam-scanning solutions into four basic groups based on different mechanisms, i.e., mechanical motion, phased array, frequency beam-scanning, and reconfigurable metasurfaces
CABBA: Compatible Authenticated Bandwidth-efficient Broadcast protocol for ADS-B
Full text linkABSTRACT: The Automatic Dependent Surveillance-Broadcast (ADS-B) is a surveillance technology mandated in many airspaces. It improves safety, increases efficiency and reduces air traffic congestion by broadcasting aircraft navigation data. Yet, ADS-B is vulnerable to spoofing attacks as it lacks mechanisms to ensure the integrity and authenticity of the data being supplied. None of the existing cryptographic solutions fully meet the backward compatibility and bandwidth preservation requirements of the standard. Hence, we propose the Compatible Authenticated Bandwidth-efficient Broadcast protocol for ADS-B (CABBA), an improved approach that integrates TESLA, phase-overlay modulation techniques and certificate-based PKI. As a result, entity authentication, data origin authentication, and data integrity are the security services that CABBA offers. To assess compliance with the standard, we designed an SDR-based implementation of CABBA and performed backward compatibility tests on commercial and general aviation (GA) ADS-B in receivers. Besides, we calculated the 1090ES band’s activity factor and analyzed the channel occupancy rate according to ITU-R SM.2256-1 recommendation. Also, we performed a bit error rate analysis of CABBA messages. The results suggest that CABBA is backward compatible, does not incur significant communication overhead, and has an error rate that is acceptable for Eb/No values above 14 dB
A hybrid recommendation system using association rule mining, i-ALS algorithm, and SVD++ approach: a case study of a B2B company
Full text linkABSTRACT: In the field of recommendation systems, collaborative filtering is a widely used technique. It provides recommendations to active users based on the ratings provided by similar users. However, this method may reduce the accuracy of user preference predictions and lead to lower-quality recommendations in cases of high data sparsity. This issue is often observed in the Business-to-Business (B2B) context, where user-generated reviews are often sparse. To overcome this challenge, we present a novel hybrid approach that explores product taxonomies and association rule mining combined with an advanced method for initialization. Our approach first involves generating a new explicit taxonomy based solely on textual product descriptions and extending the user–product matrix using association rule mining results. Second, complementary items are added to the user–item matrix based on users’ purchasing behaviors, as emphasized by the extracted association rules. Finally, we use the implicit Alternating Least Squares (i-ALS) algorithm and initialize the latent factor matrices with values obtained through the singular value decomposition approach (BLS-SVD++). This hybrid approach is tested and compared with conventional approaches, considering a real-world case study of a distributor located in Quebec. The results obtained from feedback implicitly inferred from sales data demonstrated improved RS performance compared to conventional approaches
An efficient solution methodology for the airport slot allocation problem with preprocessing and column-and-row generation
No full textDelineation of the thermal plume associated with a standing column well system in a fractured aquifer using numerical modeling
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